# Patent

## Title
Air compressor with inlet control mechanism and automatic inlet control mechanism

## Abstract

An automatic inlet control mechanism and air compressor unit include a valve cavity and valve outlet. The valve cavity includes a valve control chamber and valve inlet chamber. A valve piston assembly is positioned between the valve control chamber and the valve inlet chamber to prevent the flow of air between therebetween. The valve outlet allows air to flow from the valve inlet chamber into the compressor unit. The valve piston assembly prevents air from flowing from the valve inlet chamber to the valve outlet when the compressor unit is not drawing air. A vent passageway allows air to flow between the valve control chamber and the compression cylinder inlet when compression is begun at the start-up of the compressor unit or at the loading of the idling compressor unit. A vent orifice restricts the flow of air from the valve control chamber to the compression cylinder inlet.

## Background
This application takes priority from U.S. provisional application 60/464,466 filed Apr. 22, 2003, which is incorporated herein by reference.


BACKGROUND
Portable reciprocating air compressor units are commonly used in a variety of applications to produce pneumatic pressure from mechanical energy that is generated from a conventional energy source such as gasoline or electricity. Such an air compressor unit normally includes a compressor pump having a reciprocating piston located within a compression cylinder, a power plant such as a motor or engine that supplies mechanical energy to the piston to cause it to reciprocate and an air reservoir for storing compressed air. The compression cylinder is configured to draw air from the environment surrounding the compressor unit and to compress the drawn air that is discharged into an air reservoir, creating a supply of air pressure having a predeterminable magnitude. A motor, engine, or other power plant is normally connected to the compressor pump to drive the reciprocating piston within a compression cylinder.
During operation of the compressor unit, a rotating crankshaft, flywheel, or other assembly connected to the reciprocating piston stores a sufficient amount of angular momentum to substantially reduce the amount of high speed torque that must be exerted by the power plant to cause the piston to reciprocate. This allows the compressor pump to devote more of the total torque output of the power plant to drawing air into the compression cylinder, compressing the air and discharging the air into the air reservoir.
However, prior to operation, the crankshaft does not rotate and therefore has no angular momentum. The power plant must therefore contend with a substantially increased low speed torque requirement to overcome the combined inertial and compression loaded resistance of the piston and other components of the compressor pump until operating speed is achieved. This increased low speed torque requirement can result in adverse system effects on the power plant such as stalling, overloading, or premature wear. It can also require that a larger or more sophisticated power plant be used to overcome the initial starting torque of the compressor unit, even if such a power plant is not actually needed to sustain reciprocation of the piston after the compressor has attained an operating speed. It follows that if the compression loaded resistance of the piston can be reduced prior to the compressor pump reaching its full operating speed, it becomes possible for the power plant to devote more total torque output to overcoming inertial resistance. This in turn can minimize the adverse effects of combined inertial and compression loading, can allow for the use of a smaller or less powerful and/or less sophisticated power plant or starting system, and can therefore lead to substantial reductions in energy usage by the compressor unit.
SUMMARY
The invention is an automatic inlet control mechanism and an air compressor unit having both a piston reciprocating within a compression cylinder and a compression cylinder inlet for which the automatic inlet control mechanism is a component. The air compressor unit includes a power plant such as a motor or engine to reciprocate the piston and an air reservoir to store compressed air. The control mechanism itself includes a mechanism body having a valve inlet, a valve cavity and a valve outlet. The valve cavity is divided into a valve control chamber and a valve inlet chamber. A valve piston assembly is positioned between the valve control chamber and the valve inlet chamber and is constructed to prevent the flow of air between the two chambers. The valve inlet allows air to flow from the atmosphere surrounding the compressor unit into the valve inlet chamber. The valve outlet allows air to flow from the valve inlet chamber to the compression cylinder inlet and has a size that allows a sufficient amount of air to flow into the compressor unit to allow the compressor unit to produce compressed air at a predetermined rate of production.
The valve piston assembly includes a valve piston that is configured to reciprocate within the valve cavity. In some embodiments, the valve piston assembly includes a diaphragm that is positioned to prevent airflow between the valve control chamber and the valve inlet chamber. A biasing member provides a force that moves the valve piston assembly to a position within the inlet control mechanism that prevents air from flowing from the valve inlet to the valve outlet when the compressor unit is not drawing air through the valve outlet. This occurs, by way of example, when a compressor unit is shut down or when a continuously running compressor unit is unloaded and is idling.
A vent passageway allows air to flow between the valve control chamber and the compression cylinder inlet when compression is begun at the start-up of a compressor unit or at the loading of an idling compressor unit, as the case may be. The vent passageway is at least one source of air to the compressor cylinder inlet at this time and for a period of time after the compressor unit begins to draw air through the compression cylinder inlet, following the movement of the valve piston assembly to a position which prevents air from flowing from the valve inlet chamber and through the valve outlet to the compression cylinder inlet. A vent orifice restricts the flow of air from the valve control chamber to the compression cylinder inlet. The vent orifice has a size that allows the air to be drawn by the compressor unit from the valve control chamber to the compressor cylinder at a preselected rate which causes the compressor unit to produce compressed air at less that its predetermined rate of production.
The valve control chamber has a volume that enables air to be drawn through the vent orifice into the compression cylinder inlet for a preselected period of time, until the air within the control chamber is at a sufficiently reduced pressure level to allow the valve inlet chamber to overcome the force of the biasing member sufficiently to move the valve piston assembly away from the position at which air is prevented from flowing between the valve inlet chamber and the compression cylinder inlet.
During the preselected period of time, the absence of air flow from the valve inlet chamber to the compression cylinder inlet allows the power plant to dedicate more of its torque output on inertial rather than compression loading. Thus, during this preselected period of time, the compressor unit increases its operating speed without subjecting the full combined load of inertial and compression loading on the power plant. This removal of initial operating torque when compression is started can allow for a substantial reduction in power plant wear or allow for a reduction in the power plant size to that which is necessary to maintain the reciprocation of the piston under load when the compressor has attained its operating speed.
By the time that the compressor unit achieves an operating speed, the valve piston assembly has moved away from a position that prevents air from flowing between the valve inlet chamber and compression cylinder inlet. Air then flows unobstructed from the environment surrounding the compressor into the compression cylinder, allowing the compressor to produce air at its predetermined rate of production.
Those skilled in the art will realize that this invention is capable of embodiments that are different from those shown and that details of the structure of the disclosed inlet control mechanism can be changed in various manners without departing from the scope of this invention. Accordingly, the drawings and descriptions are to be regarded as including such equivalent inlet control mechanisms as do not depart from the spirit and scope of the invention.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1. is a partial cross sectional view of an air compressor unit having an automatic inlet control mechanism according to one embodiment of the invention;
FIG. 2A is a side cross sectional view of the automatic inlet control mechanism of FIG. 1 in a fully closed position;
FIG. 2B is a side cross sectional view of the automatic inlet control mechanism of FIG. 1 in an intermediate position;
FIG. 2C is a side cross sectional view of the automatic inlet control mechanism of FIG. 1 in an open position;
FIG. 3 is an exploded perspective view of the automatic inlet control mechanism of FIGS. 2A–C;
FIG. 4 is a partial cross sectional view of an air compressor unit having an automatic inlet control mechanism according to one embodiment of the invention;
FIG. 5 is a partial cross sectional view of an air compressor unit having an automatic inlet control mechanism according to one embodiment of the invention;
FIG. 6A is a side cross sectional view of the automatic inlet control mechanism according to one embodiment of the invention in a fully closed position;
FIG. 6B is a side cross sectional view of the inlet control mechanism of FIG. 6A in an intermediate position;
FIG. 6C is a side cross sectional view of the inlet control mechanism of FIG. 6A in an open position;
FIG. 7A is a side cross sectional view of an automatic inlet control mechanism according to one embodiment of the invention in a fully closed position;
FIG. 7B is a side cross sectional view of the inlet control mechanism of FIG. 7A in an intermediate position;
FIG. 7C is a side cross sectional view of the inlet control mechanism of FIG. 7A in an open position;
FIG. 8A is a side cross sectional view of an automatic inlet control mechanism according to one embodiment of the invention in a fully closed position;
FIG. 8B is a side cross sectional view of the inlet control mechanism of FIG. 8A in an intermediate position;
FIG. 8C is a side cross sectional view of the inlet control mechanism of FIG. 8A in an open position;
FIG. 9A is a side cross sectional view of an automatic inlet control mechanism according to one embodiment of the invention in a fully closed position;
FIG. 9B is a side cross sectional view of the inlet control mechanism of FIG. 9A in an intermediate position;
FIG. 9C is a side cross sectional view of the inlet control mechanism of FIG. 9A in an open position;
FIG. 10A is a side cross sectional view of an automatic inlet control mechanism according to one embodiment of the invention in a fully closed position;
FIG. 10B is a side cross sectional view of the inlet control mechanism of FIG. 10A in an intermediate position;
FIG. 10C is a side cross sectional view of the inlet control mechanism of FIG. 10A in an open position;
FIG. 11A is a cross sectional view of an automatic inlet control mechanism according to one embodiment of the invention in a closed position;
FIG. 11B is a cross sectional view of the inlet control mechanism of FIG. 11A in an open position;
FIG. 12A is a cross sectional view of an automatic inlet control mechanism according to one embodiment of the invention in a closed position;
FIG. 12B is a cross sectional view of the inlet control mechanism of FIG. 12A in an open position;
FIG. 13A is a cross sectional view of an automatic inlet control mechanism according to one embodiment of the invention in a closed position;
FIG. 13B is a cross sectional view of the inlet control mechanism of FIG. 13A in an open position;
FIG. 14A is a side cross sectional view of an automatic inlet control mechanism according to one embodiment of the invention at a LOW setting;
FIG. 14B is a side cross sectional view of the inlet control mechanism of FIG. 14A at a MEDIUM setting;
FIG. 14C is a side cross sectional view of the inlet control mechanism of FIG. 14A at a HIGH setting;
FIG. 15A is a side cross sectional view of an automatic inlet control mechanism according to one embodiment of the invention at a LOW setting;
FIG. 15B is a side cross sectional view of the inlet control mechanism of FIG. 15A at a MEDIUM setting;
FIG. 15C is a side cross sectional view of the inlet control mechanism of FIG. 15A at a HIGH setting;
FIG. 15D is a magnified view of the inlet control mechanism of FIG. 15A at the LOW setting;
FIG. 16A is a side cross sectional view of an automatic inlet control mechanism according to one embodiment of the invention at a low setting;
FIG. 16B is a side cross sectional view of the inlet control mechanism of FIG. 16A at an intermediate setting;
FIG. 16C is a side cross sectional view of the inlet control mechanism of FIG. 16A at a high setting;
FIG. 16D is a magnified view of the adjustment mechanism of FIG. 16A;
FIG. 17A is a side cross sectional view of an automatic inlet control mechanism according to one embodiment of the invention in a closed position;
FIG. 17B is a side cross sectional view of the inlet control mechanism of FIG. 17A in an intermediate position;
FIG. 17C is a side cross sectional view of the inlet control mechanism of FIG. 17A in an open position;
FIG. 18A is a partial cross sectional view of an air compressor unit having an automatic inlet control mechanism according to one embodiment of the invention;
FIG. 18B is a magnified side cross sectional view of the automatic inlet control mechanism of FIG. 18A;
FIG. 19A is a partial cross sectional view of an air compressor unit having an automatic inlet control mechanism according to one embodiment of the invention;
FIG. 19B is a magnified side cross sectional view of the automatic inlet control mechanism of FIG. 19A;
FIG. 20A is a side cross sectional view of an automatic inlet control mechanism according to one embodiment of the invention in a closed position;
FIG. 20B is a side cross sectional view of the inlet control mechanism of FIG. 20A in a closed, intermediate position;
FIG. 20C is a side cross sectional view of the inlet control mechanism of FIG. 20A in an open position;
FIG. 21A is a side cross sectional view of an automatic inlet control mechanism according to one embodiment of the invention in a fully closed position;
FIG. 21B is a side cross sectional view of the inlet control mechanism of FIG. 21A in a closed, intermediate position;
FIG. 21C is a side cross sectional view of the inlet control mechanism of FIG. 21A in a fully open position;
FIG. 22A is a side cross sectional view of an automatic inlet control mechanism according to one embodiment of the invention in a fully closed position;
FIG. 22B is a side cross sectional view of the inlet control mechanism of FIG. 22A in a fully open position;
FIG. 23A is a side cross sectional view of an automatic inlet control mechanism according to one embodiment of the invention in a fully closed position;
FIG. 23B is a side cross sectional view of the inlet control mechanism of FIG. 23A in a fully open position;
FIG. 24A is a side cross sectional view of an automatic inlet control mechanism according to one embodiment of the invention in a fully closed position;
FIG. 24B is a side cross sectional view of the inlet control mechanism of FIG. 24A in a fully open position;
FIG. 25A is a front perspective view of an individual labyrinth restrictor of FIGS. 24A and B;
FIG. 25B is a rear view of the labyrinth restrictor of FIG. 25A;
FIG. 25C is a rear perspective view of the labyrinth restrictor of FIG. 25A;
FIG. 25D is a side view of the labyrinthine restrictor of FIG. 25A;
FIG. 26A is a side cross sectional view of an automatic inlet control mechanism according to one embodiment of the invention in a fully closed position;
FIG. 26B is a magnified side cross sectional view of the restriction in the vent passageway of the inlet control mechanism of FIG. 26A;
FIG. 26C is a side cross sectional view of the inlet control mechanism of FIG. 26A in a fully open position;
FIG. 27A is a side cross sectional view of an automatic inlet control mechanism according to one embodiment of the invention in a fully closed position;
FIG. 27B is a magnified side cross sectional view of the restriction in the vent passageway of the inlet control mechanism of FIG. 27A;
FIG. 27C is a side cross sectional view of the inlet control mechanism of FIG. 27A in a fully open position;
FIG. 28A is a side cross sectional view of an automatic inlet control mechanism according to one embodiment of the invention at a closed position;
FIG. 28B is a side cross sectional view of the inlet control mechanism of FIG. 28A at an intermediate position;
FIG. 28C is a side cross sectional view of the inlet control mechanism of FIG. 28A at an open position;
FIG. 29A is a side cross sectional view of a compressor pump having an automatic inlet control mechanism according to one embodiment of the invention in a closed position;
FIG. 29B is a side cross sectional view of the compressor pump of FIG. 29A in an open position;
FIG. 30A is a side cross sectional view of a compressor pump having an automatic inlet control mechanism according to one embodiment of the invention in a closed position; and
FIG. 30B is a side cross sectional view of the compressor pump of FIG. 30A in an open position.



DETAILED DESCRIPTION
Referring to the drawings, similar reference numerals are used to designate the same or corresponding parts throughout the several embodiments and figures. In some drawings, some specific embodiment variations in corresponding parts are denoted with the addition of lower case letters to reference numerals.
FIG. 1 depicts a typical wheeled portable reciprocating air compressor unit 32a. The compressor unit 32a includes a compressor pump 48a mounted on an air reservoir 50 that forms a structural chassis to support the various components of the compressor unit 32a. The compressor unit 32a is supported with one or more legs 52 and wheels 54 that are positioned near the ends of the air reservoir 50. A handle 56 allows one end of the compressor unit 32a to be lifted off of its legs 52 to enable the compressor unit 32a to be moved about on its wheels 54.
An electric motor 58 and pressure switch 60 are also mounted on the air reservoir 50. Although FIG. 1 depicts an electric motor, it will be appreciated that other types of power plants can be similarly implemented and are within the contemplated scope of the invention. The electric motor 58 is connected to draw electrical current from an electrical circuit (not shown) when the pressure switch 60 assumes an ON position. When the pressure switch 60 assumes an ON position, the motor 58 drives a pulley 34 connected to a crank shaft 62 on the compressor pump 48a with a drive belt 65. Although the crank shaft 62 is depicted as being belt driven in FIG. 1, it will be appreciated that the invention can be similarly implemented into a direct drive system in which rotational energy is transferred directly from a motor or other power plant to the crankshaft of a compressor pump through a shaft, gear, or other connective mechanism. In some embodiments, the pulley 34 can also function as a flywheel or, alternatively a separate flywheel (not shown) can be connected to the crankshaft 62. The pressure switch 60 is configured to be responsive to air pressure within the air reservoir 50 and to allow operation of the electric motor 58 when the magnitude of the pressure within the air reservoir 50 falls below a predetermined magnitude. A screen guard 66 encloses the drive belt 65 and pulley 34.
Although FIG. 1 depicts an air compressor unit 32a having basic compressor components arranged in a typical single reservoir configuration, it will be appreciated that other portable compressor unit configurations are also possible. Such compressor units include those having upright standing, pancake, spherical or multiple air reservoirs and/or liftable, all legged, tailored, wheelbarrow, or sliding chassis configurations. Other similar variations are also possible and are contemplated to be included within the types of portable reciprocating air compressor units that are suitable for use with the invention.
FIG. 1 includes a partial cross sectional view of internal components within the compressor pump 48a to further illustrate their relation to the rest of the compressor unit 32a. An automatic inlet control mechanism 36a is connected to a threaded inlet port 40a of a compression cylinder inlet 38a. The inlet control mechanism 36a and compression cylinder inlet 38a allow air to enter the compressor pump 48a during each reciprocation of a piston 42 that is located within a compression cylinder 44. The inlet port 40a is positioned to channel air from the inlet control mechanism 36a to a cylinder inlet chamber 46a which receives air before the air is channeled into the compression cylinder 44 through a cylinder inlet valve 64 positioned within a cylinder inlet hole 66. The cylinder inlet hole 66 and cylinder inlet valve 64 can be included as part of a valve plate 68 that is positioned between the cylinder inlet chamber 46a and compression cylinder 44. The cylinder inlet valve 64 is unidirectional in that it only allows air to flow through the cylinder inlet hole 66 from the cylinder inlet chamber 46a when, during an intake stroke (downward as depicted in FIG. 1) of the piston 42, the piston 42 draws air into the compression cylinder 44. During a compression stroke (upward as depicted in FIG. 1) of the piston 42, the cylinder inlet valve 64 closes to prevent air from flowing from the compression cylinder 44, through the cylinder inlet hole 66 and back into and through the cylinder inlet chamber 46a. 
The electric motor 58 effects reciprocation of the piston 42 by turning the pulley 34 and crankshaft 62 of the compressor pump 48a with the drive belt 65. The crankshaft 62 in turn causes reciprocation of a piston shaft 70 which drives the piston 42, the piston shaft 70 being connected to the piston 42 with a piston pin 72. The amount of work that the electric motor 58 must perform to cause the reciprocation of the piston 42 ultimately depends on the amount of air that is drawn through the compression cylinder inlet 38a during each piston reciprocation. This is due to the fact that the amount of air that is drawn through the compression cylinder inlet 38a ultimately determines the amount of air that the piston 42 can draw into the compression cylinder 44 and compress during each reciprocation. Thus, the amount of energy that the electric motor 58 must exert to run the compressor unit 32a is directly dependent on the amount of air that is permitted to pass through the automatic inlet control mechanism 36a during each reciprocation.
A compression cylinder outlet 74a is positioned to receive air that has been compressed in the compression cylinder 44 and to channel air from the compression cylinder 44 out of the compressor pump 48a during each compression stroke of the piston 42. The compression cylinder outlet 74a includes a cylinder outlet chamber 76a for receiving air that has been compressed in the compression cylinder 44, an outlet port 78, and a unidirectional cylinder outlet valve 80 located in a cylinder outlet hole 82 for channeling air into the cylinder outlet chamber 76a. The cylinder outlet hole 82 and cylinder outlet valve 80 can be included as part of the valve plate 68 that is positioned between the compression cylinder 44 and cylinder outlet chamber 76a. The cylinder outlet valve 80 is unidirectional in that it only allows air to flow through the cylinder outlet hole 82 and into the cylinder outlet chamber 76a when, during a compression stroke of the piston 42, the piston 42 expels air from the compression cylinder 44. During an intake stroke of the piston 42, the cylinder outlet valve 80 closes to prevent air from flowing from the cylinder outlet chamber 76a back through the cylinder outlet hole 82 and into the compression cylinder 44.
A discharge tube 84 is connected to the outlet port 78 to channel compressed air from the compressor pump 48a to the air reservoir 50. A check valve 86 is positioned at the end of the discharge tube 84 to allow air to flow from the discharge tube 84 into the air reservoir 50 while preventing backflow from the reservoir 50 into the discharge tube 86 and to prevent loss of air pressure from within the reservoir 50.
The pressure switch 60 is connected to the electric motor 58 and is mounted at a location that allows the pressure switch 60 to sense the pressure of air contained within the air reservoir 50. As air is forced into the air reservoir 50, pressure in the air reservoir 50 increases. When the air pressure within the air reservoir 50 reaches a predetermined maximum magnitude of pressurization, the pressure switch 60 assumes an OFF position since additional air compression is not necessary. Once the air pressure within the air reservoir 50 falls below a minimum predetermined magnitude, the pressure switch 60 assumes an ON position, allowing the electric motor 58 to cause the compressor pump 48a to add compressed air to the air reservoir 50 until the air pressure within the air reservoir 50 rises to the predetermined maximum magnitude at which time the pressure switch 60 returns to an OFF position. However, the amount of air that is compressed, and consequently the amount of work that is performed by the electric motor 58 with each reciprocation of the piston 42, will continue to depend on the amount of air that is permitted to enter the compression cylinder through the compression cylinder inlet 38a 
Since it is the electric motor 58 that is responsible for turning the drive belt 65 and pulley 34 to effect reciprocation of the piston 42, the electric motor 58 must also provide sufficient energy to contend with additional loads resulting from combined inertial and compression loaded resistance of the piston 42 and other components of the compressor pump 48a. Thus, if air is permitted to freely enter the compression cylinder 44 through the compression cylinder inlet 38a, the electric motor 58 must contend with an increased starting torque that includes both with the compression loaded resistance of the piston 42 and the combined inertial resistance of the piston 42 and other components of the compressor unit 32a. If air is restricted from entering the compression cylinder 44 through the compression cylinder inlet 38a, the electric motor 58 need only contend with the combined inertial resistance of the piston 42 and other components of the compressor unit 32a once air is removed from the compression cylinder inlet 38a and compression cylinder 44.
During operation, the rotating crankshaft 62, pulley 34, drive belt 65, and other components of the compressor unit 32a rotate at an operating speed and therefore store a sufficient amount of angular momentum to substantially reduce the amount of high speed torque that must be exerted by the electric motor 58 to maintain the reciprocating motion of the piston 42. This allows the compressor pump 48a to devote more of the total torque output of the electric motor 58 to drawing air into the compression cylinder 44, compressing the air, and discharging the air into the air reservoir 50.
However, prior to operation, the crankshaft 62, pulley 34, and other components do not rotate at an operating speed and therefore do not provide angular momentum that to assist the electric motor 58 in causing the reciprocation of the piston 42 while the piston is compression loaded. Therefore, in order to reduce the total torque output required from the electric motor 58 at the start of operation, i.e. in order to reduce the starting torque, it is necessary to temporarily remove the compression loaded resistance of the piston 42 until the motor 58 overcomes the inertial resistance of the compressor pump 48a, allowing the compressor pump 48a to first reach a full operating speed and restore angular momentum to the crankshaft 62, pulley 34, and other components of the compressor unit 32a. 
The automatic inlet control mechanism 36a is configured to allow for the temporary removal of piston compression loading until the compressor pump 48a reaches a full operating speed. FIG. 1 depicts the inlet control mechanism 36a connected to the inlet port 40a of the compressor unit 32a, the inlet control mechanism 36a being shown in a closed position. A magnified view of the inlet control mechanism 36a of FIG. 1 is depicted in FIG. 2A. An exploded view depicting the components of the inlet control mechanism is depicted in FIG. 3.
Comparing FIGS. 1, 2A, and 3, the control mechanism 36a includes a mechanism body 88a having a valve cavity 90a that is divided into a valve control chamber 92a and a valve inlet chamber 94a. The mechanism body 88a can include an inlet segment 87a and a control segment 89a that can be detached from each other prior to assembly to allow for the installation of a valve piston assembly 96a and/or other mechanism components into the valve cavity 90a. A male connector 91 on the inlet segment 87a allows for engagement with a female connector 93 on the control segment 89a, the male connector 91 and female connector 93 being snap connected when the mechanism body 88a is assembled. When the mechanism body 88a is assembled, the valve piston assembly 96a is positioned between the valve control chamber 92a and valve inlet chamber 94a and is configured to reciprocate within the valve cavity 90a while preventing air from flowing directly between the valve control chamber 92a and valve inlet chamber 94a. 
A valve inlet 98a extends through the mechanism body 88a and allows air to flow from the atmosphere surrounding the compressor unit 32a into the valve inlet chamber 94a. The valve inlet 98a can include a filter 100 to remove impurities from air that passes through the valve inlet 98a before the air enters the valve inlet chamber 94a. A valve outlet 102a includes a valve outlet hole 104a positioned to allow air to flow from the valve inlet chamber 94a into the compression cylinder inlet 38a. The valve outlet 102a is threaded to allow for connection to the inlet port 40a of the compression cylinder inlet 38a. The valve outlet hole 104a is sized to allow a sufficient amount of air to flow from the inlet control mechanism 36a to the compression cylinder inlet 38a to allow the compressor unit 32a to produce air at its predetermined rate of production. The valve outlet hole 104a can further include a tapered portion 103a. 
The valve piston assembly 96a includes a valve piston 108a, a diaphragm 106, a valve stem 110a, and a valve stem seal 116a that are configured to reciprocate within the valve cavity 90a along a valve axis 112. Within the valve cavity 90a, the diaphragm 106 forms a seal between the inside surface of the mechanism body 88a and the rest of the valve piston assembly 96a to prevent air from moving directly between the valve control chamber 92a and valve inlet chamber 94a. A spring biasing member 114a produces a force that biases the valve piston assembly to move toward the valve inlet chamber 94a and away from the valve control chamber 92a to a position within the inlet control mechanism 36a in which the valve stem seal 116a contacts the inside surface of the mechanism body 88a to prevent air from flowing from the valve inlet chamber 94a through the valve outlet 102a. 
A vent passageway 118a extends through the valve stem 110a, opening to the valve control chamber 92a and allowing for the communication of air between the valve control chamber 92a and valve outlet 102a or compression cylinder inlet 38a through a stem hole 120. An orifice 122a forms a restriction to air that flows through the vent passageway 118a, delaying the rate at which air can communicate between the valve control chamber 92a and valve outlet 102a or compression cylinder inlet 38a. 
The valve stem 110a also includes a sliding surface 124 on which the valve stem seal 116a reciprocates in response to the movement of the valve stem 110a with the valve piston assembly 96a and/or the air pressure differential between the compression cylinder inlet 38a and valve inlet chamber 94a. The valve stem seal 116a can be constructed of rubber, teflon, a resilient polymer, or any other material that allows for sliding or reciprocation of the valve stem seal 110a along the sliding surface 124 while also allowing for the creation of a seal between the sliding surface of the valve stem 110a and the inside surface of the mechanism body 88a when the piston assembly is in a position within the valve cavity 90a that prevents air from flowing from the valve inlet chamber 94a to the compression cylinder inlet. A lip 126 and an expanded radius 128 are positioned at opposite ends of the sliding surface 124 to restrict the reciprocating movement of the valve stem seal 116a. 
To better understand the operation of the automatic inlet control mechanism 36a, consider the air compressor unit 32a prior to operation, as depicted in FIGS. 1 and 2A. Electric current from an electric circuit (not shown) is not connected to the pressure switch 60 since the compressor unit 32a is either not in use (power OFF) or is instead in use (power ON) but air pressure within the air reservoir 50 is greater than a predetermined minimum magnitude. In either case, the pressure switch 60 does not permit electric current to flow to reach the electric motor 58. The electric motor 58 does not cause rotation of the drive belt 65, pulley 34, and drive shaft 62. Therefore, the piston 42 does not reciprocate within the compression cylinder 44 and air is neither drawn through the cylinder inlet valve 64 nor forced through the cylinder outlet valve 80 in the compressor pump 48a. The spring biasing member 114a forces the valve piston assembly 96a away from the valve control chamber 92a and toward the valve inlet chamber 94a. The valve stem seal 116a, having a larger diameter than part of the tapered portion 103a of the valve outlet 102a, seals between the valve outlet 102a and sliding surface 124 of the valve stem 110a as the expanded radius 128 forces the valve stem seal 116a against the tapered portion 103a under the force of the spring biasing member 114a. The resulting seal between the valve stem 110a and valve outlet 102a prevents air from the atmosphere surrounding the air compressor unit from 32a entering the compression cylinder 44 through the valve inlet chamber 94a. 
Now consider the compressor unit 32a when electric current is initially connected to the pressure switch 60 (power ON) and/or when pressure within the air reservoir 50 falls below a predetermined minimum magnitude while power is ON. The pressure switch 60 senses the low air pressure within the air reservoir 50 and in response connects the electric motor 58 to electric current from the electrical circuit. The motor 58 begins to rotate the drive belt 65, pulley 34, and drive shaft 62 to initiate reciprocation of the piston 42. However, the motor 58 must contend with the inertial resistance of each of these components. In addition, the motor 58 must also contend with any air that is present within the compressor pump 48a or discharge tube 84. However, the valve stem 10a and valve stem seal 116a prevent air from the atmosphere surrounding the compressor unit 32a from entering the compressor pump 48a through the inlet control mechanism 36a. 
As the piston 42 begins to reciprocate, remaining air is quickly drawn out of the cylinder inlet chamber 46a and forced through the cylinder outlet valve 80 into the cylinder outlet chamber 76a and discharge tube 84. During a very short time interval, the speed of the initial rotation of the drive belt 65, pulley 34, and drive shaft 62 and the speed of reciprocation of the piston 42 is very low. During this very short interval, the electric motor 58 must bear the combined inertial and compression loaded resistance of the piston 42 and other components. Thus, during this short interval, the combined loads cause the electric motor 58 to experience a high current draw or “current spike.”
However, after a very small number of piston reciprocations, most of the air initially present in the cylinder inlet chamber 46a is removed by the reciprocating piston 42. Most of the air is removed from the cylinder inlet chamber 46a while the piston 42 reciprocates at a very low relative speed. Since the valve stem 110a and valve stem seal 116a prevent additional amounts of air from entering the compressor pump 48a from the atmosphere through the valve inlet 98a of the inlet control mechanism 36a, air drawn through the vent passageway 118a from the valve control chamber 92a becomes the primary source of air to the compression cylinder inlet 38a as the speed of the electric motor 58 and the reciprocation rate of the piston 42 begin to increase.
The air drawn through the vent passageway 118a from the valve control chamber 92a continues to be the primary source of air to the compression cylinder inlet 38a as long as the valve piston assembly 96a is in a position that prevents air from flowing from the valve inlet chamber 94a to the compressor cylinder inlet 38a. However, the orifice 122a forms a restriction that limits the rate at which air can be drawn into the compression cylinder inlet 38a through the vent passageway 118a. As a result of this restriction, the amount of air that can be drawn into the compression cylinder inlet 38a from the valve control chamber 92a during a given time interval is very small compared to the amount of air that can be drawn from the valve inlet chamber 94a when the valve piston assembly 96a is in a position that does not prevent air from flowing between the valve inlet chamber 94a and compression cylinder inlet 38a. Consequently, compression loading of the piston 42 is greatly reduced as long as the valve control chamber 92a remains the primary source of air to the compression cylinder inlet 38a. This reduction in compression loading of the piston 42 allows the electric motor 58 to devote more total torque output to overcoming inertial resistance as the speed of the motor 58 and reciprocation rate of the piston 42 increase. Since compression loading of the piston 42 is reduced, the compressor unit 32a produces compressed air at less than its predetermined rate of production. However, the reduction in initial compression loading can be effective in significantly reducing wear of the electric motor 58 and/or can allow the motor 58 to be reduced in size to only that which is necessary to maintain the reciprocation of the piston 42 once the piston has achieved an operating speed. This can in turn allow for a substantial reduction in wear, component cost, or energy usage.
As the speed of the motor 58 and the reciprocation rate of the piston 42 continue to increase, air continues to be drawn through the vent passageway 118a, orifice 122a, and stem hole 120 from the valve control chamber 92a into the cylinder inlet chamber 46a. This reduces the amount of air pressure that is present within the valve control chamber 92a. Atmospheric pressure within the valve inlet chamber 94a is maintained by air communication through the valve inlet 98a. The sealed separation between the valve inlet chamber 94a and valve control chamber 92a created by the diaphragm 106 results in a pressure differential between the chambers that begins to force the diaphragm 106 and the rest of the valve piston assembly 96a, against the force of the spring biasing member 114a and toward the valve control chamber 92a to an intermediate position within the valve cavity 90a. 
FIG. 2B depicts the inlet control mechanism 36a in which the valve piston assembly 96a is located at such an intermediate position within the valve cavity 90a. As the valve stem 110a moves toward the valve control chamber 92a, very little pressure continues to occupy the compression cylinder inlet 38a though atmospheric pressure continues to exist within the valve inlet chamber 94a. This creates a pressure differential that continues to force the valve stem seal 116a against the tapered portion 103a of the valve outlet 102a. As the valve stem 110a moves with the rest of the valve piston assembly 96a toward the valve control chamber 92a, the valve stem seal 116a slides against the sliding surface 124 of the valve stem 110a, maintaining the seal between the valve stem 110a and the inside surface of the mechanism body 88a while continuing to prevent air from flowing from the valve inlet chamber 94a and compression cylinder inlet 38a. The valve stem 110a is normally configured so that the valve stem seal 116a continues to seal between the valve stem 110a and mechanism body 88a until the electric motor 58 and compressor unit 32a achieve an operating speed.
As the piston 42 continues to draw air from the valve control chamber 92a, the pressure differential between the valve inlet chamber 94a and compression cylinder inlet 38a continues to force the valve stem seal 116a against the tapered portion 103a of the valve outlet 102a until the valve stem seal 116a, sliding across the sliding surface 124, contacts the lip 126 of the valve stem 110a. The lip 126 forces the valve stem seal 116a away from the tapered portion 103a of the valve outlet 102a. The valve piston assembly 96a continues to move toward the valve control chamber 92a until the air in the valve control chamber 92a is at a sufficiently reduced pressure level that enables atmospheric pressure in the valve inlet chamber 94a to overcome the force of the spring biasing member 114a sufficiently to move the valve piston 108a to contact the mechanism body 88a as shown in FIG. 2C. This movement creates an air space 130a allowing air from the valve inlet chamber 94a and atmosphere to enter the compression cylinder inlet 38a. However, by the time that the valve stem seal 116a moves away from the mechanism body 88a, the electric motor 58 and compressor unit 32a will normally have achieved an operating speed and are therefore better equipped to deal with additional compression loading against the piston 42.
The amount of time required for the valve piston assembly 96a to move to a position, such as that depicted in FIG. 2C, that does not prevent air from flowing from the valve inlet chamber 94a through the valve outlet 102a into the compression cylinder inlet 38a depends on the rate at which air can be drawn by the piston 42 from the valve control chamber 92a, which in turn depends on the size of the orifice 122a. Thus, the amount of time during which the automatic inlet control mechanism 36a removes compression loading on the piston depends on the size or effective size of the vent restriction of air flowing through the vent passageway 118a. This amount of time can be preselected by incorporating an orifice or other restriction having a size or effective size that corresponds to the rate of allowed air flow allowing for sufficient time for the compressor unit 32a to achieve a desired operating speed while unloaded.
It will be appreciated that the invention can be similarly implemented in continuously operated compressor units. Referring now to FIG. 4, an air compressor unit 32b is depicted in which a pilot valve 132b takes the place of a pressure switch to enable the electric motor 58 to run continuously without continuously causing the compressor pump 48b to add compressed air to the air reservoir 50. The pilot valve 132b is positioned on the air reservoir 50 and is configured to be responsive to the magnitude of air pressure that is contained within the air reservoir 50. The pilot valve 132b communicates pneumatically through a pilot tube 134 with an inlet unloader 136 that is positioned on the compressor pump 48b. The inlet unloader 136 includes an unloader pin 138 that is positioned to extend to and retract from the inlet unloader 136 to interfere with the operation of the cylinder inlet valve 64 and to prevent further reservoir pressurization when the reservoir 50 is fully pressurized to a predetermined maximum magnitude of pressurization.
Consider the air compressor unit 32b when, due to usage of air pressure by devices connected to the compressor unit 32b, the magnitude of air pressure contained within the air reservoir 50 falls below a predetermined minimum magnitude. The electric motor 58 will be at an idle speed, as explained below. The pilot valve 132b senses low pressure within the reservoir 50 and assumes an OFF condition. In response, the pilot valve 132b pneumatically communicates the OFF condition to the inlet unloader 136 by removing a pneumatic pressure signal from the pilot tube 134. In turn, the inlet unloader 136 retracts the unloader pin 138 away from the inlet valve 64, allowing the inlet valve 64 to operate to permit air to be drawn from the cylinder inlet chamber 46b and through the cylinder inlet hole 66 and into the compression cylinder 44 during each intake stroke of the piston 42, while preventing air from being expelled from the compression cylinder 44 back through the cylinder inlet chamber 46b during each compression stroke of the piston 42. The pilot valve 132b will continue to prevent the inlet unloader 136 from interfering with the inlet valve 64 as long as air pressure within the reservoir 50 remains below a predetermined maximum magnitude which is larger than the predetermined minimum magnitude.
Since the motor 58 runs continuously, the amount of air that is compressed with each reciprocation of the piston 42 and the amount of torque output required to continue reciprocation of the piston 42 will continue to depend on the amount of air that is permitted by the automatic inlet control mechanism 32b to enter the compression cylinder inlet 38b. When the pilot valve 132b initially removes the pneumatic pressure signal from the pilot tube 134 to cause retraction of the unloader pin 138, the valve piston assembly 96b is normally in a position in which the valve stem seal 116 prevents air from moving from the valve inlet chamber 94b through the valve outlet 102b and into the cylinder inlet chamber 46b. Air from the valve control chamber 92b becomes the primary source of air to the compression cylinder 44 for an interval of time until which the valve piston assembly 96b moves to a position that allows for air to move from the valve inlet chamber 94b through the valve outlet 102b into the cylinder inlet chamber 46b. Since during this interval, the amount of air that can flow from the valve control chamber 92b into the compression cylinder inlet 38b is restricted by the orifice 122b, there is a substantial reduction in the amount of compression loading of the piston 42.
As the piston 42 continues to reciprocate, the valve piston assembly 96b gradually moves from an intermediate position that does not permit air to flow between the valve inlet chamber 94b and valve outlet 102b to an intermediate position that does permit airflow between the valve inlet chamber 94b and valve outlet 102b, and then continues to move to a fully open position that allows greater air flow to the compression cylinder inlet 38b. This has the effect of allowing full compression loading to be reached gradually rather than suddenly. Although the compressor unit 32b is a continuous-run system, such smooth operation can nevertheless substantially reduce wear, and can allow for the use of a smaller or less powerful power plant due to the more gradual compression loading. This further allows for reductions in both apparatus cost and energy consumption.
Now consider the same air compressor unit 32b when, due to the compression of air by the piston 42, the magnitude of air pressure contained within the reservoir 50 rises above the predetermined minimum magnitude. The pilot valve 132b continues to pneumatically communicate the OFF condition to the inlet unloader 136 until the air pressure within the air reservoir 50 rises above the predetermined maximum magnitude. When the air pressure contained within the reservoir 50 rises above the predetermined maximum magnitude, the pilot valve 132b senses that the reservoir 50 is fully pressurized and assumes an ON condition. In response, the pilot valve 132b pneumatically communicates the ON condition to the inlet unloader 136 by adding a pneumatic pressure signal through the pilot tube 134. In turn, the inlet unloader 136 extends the unloader pin 138 to contact the inlet valve 64 and to prevent the inlet valve 64 from closing during each compression stroke of the piston 42. Although the open inlet valve 64 allows air to be drawn from the valve inlet chamber 94b and cylinder inlet chamber 46b through the inlet hole 66 into the compression cylinder 44 during each intake stroke of the piston 42, the piston 42 also expels air from the compression cylinder 44 back through the inlet hole 66 into the cylinder inlet chamber 46b and valve inlet chamber 94b, valve inlet 98b, and into the environment during each compression stroke as long as the inlet unloader 136 prevents the cylinder inlet valve 64 from closing.
Since the open inlet valve 64 prevents the piston 42 from removing air pressure from the cylinder inlet chamber 46b and valve outlet 102b, air is no longer drawn from the valve control chamber 92b through the vent passageway 118b and orifice 122b. Consequently, the spring biasing member 114b is free to force the valve piston assembly 96b back toward the valve outlet 102b. Moreover, since air pressure is restored within the valve outlet 102b and compression cylinder inlet 38b, air is free to return to the valve control chamber 92b as the valve piston 108b moves toward the valve inlet chamber 94b. This continues until the valve piston assembly 96b returns to a position that prevents air from moving from the valve inlet chamber 94b to the valve outlet 102b. However, the piston 42 continues to be prevented from drawing significant amounts of air from the valve control chamber 92b as long as the unloader pin 138 prevents the inlet valve 64 from closing during each compression stroke of piston 42.
The motor 58 then runs continuously at an idle speed, as explained below. However, the compressor pump 48b will be prevented from adding air pressure to the reservoir 50, regardless of the amount of electric current drawn by the motor 58 from the electrical circuit, the amount of air that is permitted by the automatic inlet control mechanism 36b to enter through the compression cylinder inlet 38b, or the amount of torque output that is available from the electric motor 58, until the pilot valve 132b again senses that reservoir pressure is below the predetermined minimum magnitude and accordingly removes its pneumatic pressure signal from the pilot tube 134.
It will be further appreciated that the invention can be implemented into compressor units having different types of power plants. For example, FIG. 5 depicts a continuous drive compressor unit 32c having a gasoline engine 140 configured to effect reciprocation of the piston 42 by rotating the pulley 34 and crankshaft 62 with the drive belt 65. Being configured for continuous operation, the compressor unit 32c includes a pilot valve 132c and pilot tube 134 that control the operation of an inlet unloader 136. The pilot tube 134 is connected to an air cylinder 142 which is itself connected to effect adjustment of the engine throttle control 146 through a conduit 144.
In operation, when air pressure within the reservoir 50 exceeds a predetermined maximum magnitude, the pilot valve 132c assumes an ON condition reflecting the fully pressurized condition of the reservoir 50. The pilot valve 132c allows a limited amount of the pressure within the reservoir 50 to effect movement of a throttle piston (not shown) located within the air cylinder 142 to an IDLE position. The throttle piston is connected to a wire linkage (not shown) located within the conduit 144. The wire linkage is connected directly to the to throttle control 146 and causes the throttle control to move to an IDLE position when the throttle piston is in the IDLE position.
The pilot valve 132c simultaneously communicates an ON condition to the inlet unloader 136 which in turn extends the unloader pin 138 to open the cylinder inlet valve 64 and prevent compression loading of the piston 42. Since compression loading of the piston is therefore at least partially removed, it is only necessary for the engine 140 to exert sufficient torque output to maintain the inertial rotation of the pulley 34, crankshaft 62, and other compressor components. Movement by the wire linkage of the throttle control 146 to the IDLE position lowers the engine speed of the gasoline engine 140 to an idle speed, that is a level that is sufficient to maintain the inertial rotation of compressor components in the absence of compression loading of the piston 42, thereby increasing the overall efficiency of the engine 140.
When air pressure within the reservoir 50 falls below a predetermined minimum magnitude, the pilot valve 132c assumes an OFF condition reflecting the low air pressure contained within the reservoir 50. The pilot valve 132c removes air pressure from the air cylinder 142 accordingly. Spring returns (not shown) within the air cylinder 142 return the throttle piston to a FULL position, which in turn forces the wire linkage within the conduit 144 to move the throttle control to a FULL position allowing the engine 140 to resume operating speed. The pilot valve 132c simultaneously communicates an OFF condition to the inlet unloader 136 which retracts the unloader pin 138 to allow for the continued compression of air by the compressor pump 48c. 
It will be appreciated that variations in the construction of the automatic inlet control mechanism are possible and within the contemplated scope of the invention. For example, FIGS. 6A–C depict an embodiment inlet control mechanism 36d having open valve inlets 98d. A filter surrounding the control mechanism 36d is omitted to maximize the intake of air into the valve control chamber once the valve piston assembly 96d moves from a closed position, as depicted in FIG. 6A, past an intermediate position, as depicted in FIG. 6B, to a position that permits air to flow from the valve inlet chamber 94d through the valve outlet 102d to the compressor pump, as shown in FIG. 6C.
Other embodiments of the invention having open valve inlets may incorporate filter components at other locations within a mechanism body. For example, FIGS. 7A–C depict an embodiment automatic inlet control mechanism 36e having a valve passageway filter 150 located adjacent the orifice 122e on the valve stem 110e. The valve passageway filter 150 prevents foreign particles from entering the control chamber 92e. 
To effect sealing between the valve stem 110e and mechanism body 88e, the valve stem 110e is divided into an expanded radius portion 154e and a reduced radius portion 152e. FIG. 7A, depicts the inlet control mechanism 36e in a closed position in which the piston assembly 96e prevents air from flowing between the valve inlet chamber 94e and valve outlet 102e. The piston assembly 96e is biased to this position with the spring biasing member 114e. When the piston assembly 96e is this position, the reduced radius portion 152e inserts into a non-tapered portion 156e of the valve outlet 102e. An edge 148e of the expanded radius portion 154e of the valve stem 110e contacts the tapered portion 103e of the valve outlet 102e. In this position, the clearance between the reduced radius portion 152e of the valve stem 110e and non-tapered portion 156e of the valve outlet 102e is sufficiently small to prevent air from flowing between the valve inlet chamber 94e and valve outlet 102e. The contact between the edge 148e of the expanded radius portion 154e and the tapered portion of the valve outlet 102e acts to further block the flow of air.
In operation, the piston 42 draws air from the control chamber 92e through the vent passageway 118e while creating a pressure differential between the vent inlet chamber 94e and valve outlet 102e, separated by the close proximity of the reduced radius portion 152e of the valve stem 110e to the non-tapered portion 156e of the valve outlet 102e. As air continues to be drawn from the valve control chamber 92e, atmospheric pressure in the valve inlet chamber 94e causes the piston assembly 96e to move against the force of the spring biasing member 114e and toward the valve control chamber 92e, though the reduced radius portion 152e of the valve stem 110e continues to be in close proximity to the non-tapered portion 156e of the valve outlet 102e. FIG. 7B depicts the piston assembly 96e that has moved to an intermediate position in which the reduced radius portion 152e of the valve stem 110e remains in close proximity to the non-tapered portion 156e of the valve outlet 102e. As the valve stem 110e moves, as long as the reduced radius portion 152e remains in close proximity to the non-tapered portion 156e of the valve outlet 102e, air continues to be blocked from entering the compression cylinder inlet from the valve inlet chamber 94e. 
FIG. 7C depicts the piston assembly 96e after the force of the pressure differential between the valve inlet chamber 94e and valve control chamber 92e sufficiently overcomes the bias of the spring biasing member 114e to move the piston assembly 96e to an open position in which the reduced radius portion 152e of the valve stem 110e clears the non-tapered portion 156e of the valve outlet 102e. This creates an air space 130e through which air can move from the environment surrounding the inlet control mechanism 36e and from the valve inlet chamber 94e to the valve outlet 102e. The amount of time required for the piston assembly 96e to move to a position that allows air to move from the valve inlet chamber 94e to the valve outlet 102e depends on the rate at which air can be drawn though the vent passageway 118e from the valve control chamber 92e as permitted by the vent restriction that is created by the orifice 122e. It follows that the amount of time in which the control mechanism 36e removes piston compression loading depends on the amount of time that the reduced radius portion 152e of the valve stem 110e remains in close proximity to the non-tapered portion 156e of the valve outlet 102e, as permitted by the vent restriction created by the orifice 122e. 
FIG. 8A depicts an automatic inlet control mechanism 36f in which the valve outlet 102f does not include a tapered portion. The valve stem 110f includes an expanded radius portion 154f and a reduced radius portion 152f, the expanded radius portion 154f being dimensioned to allow for insertion into the valve outlet 102f without a substantial amount of clearance.
FIG. 8A depicts the inlet control mechanism 36f in a closed position in which the piston assembly 96f, due to its insertion into the valve outlet 102f, prevents air from flowing between the valve inlet chamber 94f and valve outlet 102f. The piston assembly 96f is biased to this position with the spring biasing member 114f. In this position, the clearance between the expanded radius portion 154f of the valve stem 110f and the valve outlet 102f is sufficiently small to prevent air from flowing between the valve inlet chamber 94f and valve outlet 102f. Guides 160 restrict lateral movement of the valve stem 110f and center the valve stem 110f as it reciprocates along the valve axis 112.
In operation, the piston 42 draws air from the control chamber 92f through the vent passageway 118f while creating a pressure differential between the vent inlet chamber 94f and valve outlet 102f, separated by the close proximity of the expanded radius portion 154f of the valve stem 110f to the valve outlet 102f. As air continues to be drawn from the valve control chamber 92f, atmospheric pressure in the valve inlet chamber 94f causes the piston assembly 96f to move against the bias of the spring biasing member 114e and toward the valve control chamber 92f, though the expanded radius portion 154f of the valve stem 110f continues to be in close proximity to the valve outlet 102f. 
FIG. 8B depicts the piston assembly 96f that has moved to an intermediate position in which the expanded radius portion 154f of the valve stem 110f remains in close proximity to the valve outlet 102f. As the valve stem 110f moves, it continues to block air from entering the compression cylinder inlet from the valve inlet chamber 94f as long as the expanded radius portion 154f remains in close proximity to the valve outlet 102f. 
FIG. 8C depicts the piston assembly 96f after the force of the pressure differential between the valve inlet chamber 94f and valve control chamber 92f sufficiently overcomes the bias of the spring biasing member 114f to move the piston assembly 96f to an open position in which the expanded radius portion 154f of the valve stem 110f has cleared the valve outlet 102f. This creates an air space 130f through which air can move from the environment surrounding the inlet control mechanism 36f through the valve inlet chamber 94f to the valve outlet 102f. The amount of time required for the piston assembly 96f to move to a position that allows air to move from the valve inlet chamber 94f to the valve outlet 102f depends on the rate at which air can be drawn though the vent passageway 118f from the valve control chamber 92f as permitted by the vent restriction created by the orifice 122f. It follows that the amount of time in which the control mechanism 36f removes piston compression loading depends on the amount of time that the expanded radius portion 154f of the valve stem 110f remains in close proximity to the valve outlet 102f, as permitted by the vent restriction created by the orifice 122f. 
Some embodiments having non-tapered valve outlets also allow for the use of sliding valve stem seals to restrict air flow. FIGS. 9A–C depict an inlet control mechanism 36g having a valve stem seal 116g positioned to reciprocate along a reduced radius portion 152g of a valve stem 110g. Lost sliding motion of the valve stem seal 116g is restricted with a stem clip 158g that is positioned along the length of the reduced radius portion 152g and the edge 148g of an expanded radius portion 154g of the valve stem 110g. Guides 160 restrict lateral movement of the valve stem 110g and center the valve stem 110g as it reciprocates along the valve axis 112.
FIG. 9A depicts the control mechanism 36g in a closed position in which the spring biasing member 114g biases the piston assembly 96g away from the valve control chamber 92g. The edge 148g of the expanded radius portion 154g contacts the valve stem seal 116g which seals against the mechanism body 88g. This prevents air from moving from the valve inlet chamber 94g to the valve outlet 102g and creates a pressure differential as air is drawn through the valve outlet hole 104g. 
As air is drawn through the vent passageway 118g, the piston assembly 96g, including the valve stem 110g, moves against the force of the spring biasing member 114g toward the valve control chamber 92g. However, the pressure differential between the valve inlet chamber 94g and valve outlet 102g continues to force the sliding seal 116g against the mechanism body 88g, the reduced radius portion 152g of the valve stem 110g sliding through the valve stem seal 116g. This continues until the piston assembly 96g moves to an intermediate position in which the stem clip 158g contacts the valve stem seal 116g. This intermediate position is depicted in FIG. 9B.
The time required for the piston assembly 96g to move to the intermediate position depicted in FIG. 9B depends on the rate at which air can be drawn from the valve control chamber 92g as permitted by the vent restriction created by the orifice 122g. If, from the intermediate position depicted in FIG. 9B, the piston assembly 96g continues to move toward the valve control chamber 92g, the stem clip 158g pulls the valve stem seal 116g away from the mechanism body 88g. This causes the inlet control mechanism 36g to assume an open condition as depicted in FIG. 9C, creating an air space 130g that allows air to flow between the valve inlet chamber 94g and valve outlet 102g. Thus, the time required for the piston assembly 96g to move past the intermediate position depicted in FIG. 9B determines the preselected amount of time during which air from the environment is prevented from flowing from the valve inlet chamber 94g to the compression cylinder inlet.
It will be further appreciated that the automatic inlet control mechanism can be constructed to operate without the use of a diaphragm. FIGS. 1A–C depict an inlet control mechanism 36h having a valve piston 162 that is integrated into the structure of the valve stem 110h. The valve piston 162 has a diameter that is sufficient to extend fully across the valve cavity 90h as the valve piston assembly 96h reciprocates along the valve axis 112. As it reciprocates with the valve piston assembly 96h, the valve piston 162 seals against the inside surface of the mechanism body 88h with a piston seal 164, preventing air from flowing directly between the valve control chamber 92h and valve inlet chamber 94h. The piston seal 164 can be constructed of rubber, teflon, a resilient polymer, or any other material that allows for sliding or reciprocation of the valve piston 162 against the inside surface of the mechanism body 88h, eliminating the need for a diaphragm positioned between the valve stem 110h and valve piston 162. In operation, the valve stem seal 116h prevents air from flowing between the valve inlet chamber 94b to the valve outlet 102h until the valve piston assembly 96h moves to an intermediate position as shown in FIG. 10B. As air is withdrawn from the valve control chamber 92h through the vent passageway 118h and orifice 122h, atmospheric pressure in the valve inlet chamber 94h forces the piston assembly 96h toward the valve control chamber 92h. Once the piston assembly moves past the intermediate position to an open position, such as that shown in FIG. 10C, the sliding seal 116h clears the tapered portion 103h to create an air space 130h, allowing air to flow from the valve inlet chamber 94h to the valve outlet 102h. 
Although the invention has been shown and described as having an automatic inlet control mechanism where the mechanism body is external to the compressor pump, it will be appreciated that in some embodiments, the inlet control mechanism can be integrated directly into the structure of the compressor pump. For example, FIG. 11A depicts a compressor pump 48i having an automatic inlet control mechanism 36i that includes a mechanism body 88i integrated into the structure of the compressor pump 48i. The mechanism body 88i includes a removable portion 168i that is threaded and sealed with an enclosure seal 174 to allow for installation of components of the inlet control mechanism 36i in the compressor pump 48i. An external filter 166 is attached to a valve inlet 98i leading to a valve inlet chamber 94i located below a valve control chamber 92i. A valve outlet partition 170 includes a valve outlet 102i having a tapered portion 103i and valve outlet hole 104i. The valve piston assembly 96i includes a piston 108i, valve stem 110i, and vent passageway 118i configured to reciprocate vertically along a vertical valve axis 172. When assuming a fully closed position, as shown in FIG. 11A, the valve stem 110i extends fully through the valve outlet hole 104i so that the stem hole 120 extends through the compression cylinder inlet 38i and enters the compression cylinder inlet chamber 46i. The valve stem seal 116i prevents air from the atmosphere from flowing between the valve inlet chamber 94i through the valve outlet hole 104i to the valve outlet 102i. 
When air is drawn by the piston 42 from the control chamber 92i through the valve passageway 118i and cylinder inlet chamber 46i, the valve piston assembly 96i moves upward along the vertical valve axis 172 as depicted in FIG. 11B. This upward movement creates an air space 130i between the valve stem seal 116i and tapered portion 103i allowing air to enter the compression cylinder inlet 38i from the valve inlet chamber 94i. 
While the invention has been shown in various embodiments having vent passageways that extend though valve stems, it will be appreciated that appropriate vent passageways can be configured in alternate positions as well. FIG. 12A depicts an embodiment compressor pump 48j having an externally positioned inlet control mechanism 36j. A vent passageway 118j extends outside of the inlet control mechanism 36j and compressor pump 48j and is connected to the valve control chamber 92j with a control chamber coupling 176 and connected to the cylinder inlet chamber 46j with an inlet chamber coupling 178. A vent orifice 122j is positioned in the vent passageway 118j near the control chamber coupling 176 to restrict the flow of air from the valve control chamber 92j into the cylinder inlet chamber 46j. The valve stem 110j is solid along its length, preventing air from moving directly between the valve control chamber 92j and valve outlet 102j. 
When the piston 42 reciprocates within the compression cylinder 44 while the valve piston assembly 96j is in the position shown in FIG. 12A, air is drawn through the externally mounted vent passageway 118j from the valve control chamber 92j which becomes the primary source of air to the compression cylinder 44 and which loses air pressure as air is progressively drawn by the piston 42. The rate at which air is drawn through the vent passageway 118j depends on the size of the orifice 122j. The valve control chamber 92j continues to be the primary source of air to the compression cylinder 44 until atmospheric pressure within the valve inlet chamber 94j forces the valve piston assembly 96j to the open position shown in FIG. 12B, creating an air space 130j through which air can enter the compression cylinder 44 from the environment.
It will be further appreciated that in some embodiments, the period of time required for a valve piston assembly to move from a fully closed to a fully open position can also be controlled by changing the relative size of the inlet control mechanism and/or valve control chamber. For example, FIG. 13A depicts an embodiment compressor pump 48k having an enlarged control segment 89k of the mechanism body 88k that effectively increases the size of the valve control chamber 92k. In operation, the increased size of the valve control chamber 92k increases the amount of time that is required for the piston 42 to draw a sufficient amount of air through the vent passageway 118k, to produce a pressure differential between the valve inlet chamber 94k and valve control chamber 92k sufficient to overcome the force of the biasing spring 114k to effect movement of the valve piston assembly 96k. Thus, the increased size of the valve control chamber 92k allows the vent passageway 118k to continue to comprise the primary source of air to the compression cylinder inlet 38k for a period of time after the piston 42 begins to draw air into the compression cylinder 44 without requiring lost mechanical motion by the valve stem seal 116k or other components of the inlet control mechanism 36k. 
Referring now to FIG. 13B, the piston assembly 96k moves to an open position once a sufficient amount of air has been drawn through the orifice 122k and vent passageway 118k to create a pressure differential between the valve inlet chamber 94k and valve control chamber 92k sufficient to overcome the force of the biasing spring 114k, creating an air space 130k that allows air to flow from the valve inlet chamber 94k to the valve outlet 102k. However, it will be appreciated that, depending on the requirements of a given specific embodiment, it may be necessary to construct the inlet control mechanism 36k to have a valve control chamber 92k that is significantly larger than corresponding control mechanisms incorporating lost mechanical motion of internal components to achieve a comparable period of delay before opening. It will be further appreciated that in some embodiments, a comparable period of delay can be achieved by adjusting the size of an orifice in a vent passageway to affect the rate at which air can be drawn from the valve control chamber. In addition, it is possible to control the period of delay by combining changes in both the orifice and control chamber sizes.
In some embodiments, the extent to which the piston assembly moves from the fully closed position can be manually limited, allowing for manual restriction of air flow between the atmosphere and compression cylinder. FIGS. 14A–C depict an embodiment inlet control mechanism 36l having a stem restrictor 178l that extends through the control segment 89l of the mechanism body 88l. The stem restrictor 178l is configured to reciprocate along the valve axis 112 and includes restrictor legs 180l positioned to engage and limit the movement of the valve stem 110l toward the valve control chamber 92l. An adjustment cam 182l is connected to rotate on the stem restrictor 178l with a pivot 184. The adjustment cam 182l includes a low cam surface 186l, a medium cam surface 188l, and a high cam surface 190l that are each positioned to contact the control segment 89l of the mechanism body 88l on its outside surface. The stem restrictor 178l is spring biased to move along the valve axis 112 toward the valve inlet chamber 94l and is locked in place by the adjustment cam 182l with the pivot 184.
A cam lever 192 allows the adjustment cam 182l to be manually rotated to selectively position the low, medium, or high cam surface 186l, 188l, or 190l in contact with the mechanism body 88l. The inlet control mechanism 36l is depicted in the LOW position in FIG. 14A, the low cam surface 186l being positioned adjacent the mechanism body 88l. The low cam surface 186l is located a relatively small distance from the pivot 184, allowing the adjustment cam 182l to lock the stem restrictor 178l against its spring bias at a position that is relatively close to the valve inlet chamber 94l. This in turn places the restrictor legs 180l in a position that restricts the valve stem 110l to move no further than an open position that creates a relatively small air space 130l between the valve stem 110l and tapered portion 103l of the valve outlet 102l, allowing a maximum amount of air to pass from the valve inlet chamber 94l that is less than when the control mechanism 36l is in the MEDIUM or HIGH positions.
The inlet control mechanism 36l is depicted in the MEDIUM position in FIG. 14B, the medium cam surface 188l being positioned adjacent the mechanism body 88l. The medium cam surface 188l is located a medium distance from the pivot 184, allowing the adjustment cam 182l to lock the stem restrictor 178l against its spring bias at a position that is a medium distance from the valve inlet chamber 94l. This in turn places the restrictor legs 180l in a position that restricts the valve stem 110l to move no further than an open position that creates a medium sized air space 130l between the valve stem 110l and tapered portion 103l of the valve outlet 102l, allowing a maximum amount of air to pass from the valve inlet chamber 94l that is less than when the control mechanism 36l is in the HIGH position but greater than when the control mechanism 36l is in the LOW position.
The inlet control mechanism 36l is depicted in the HIGH position in FIG. 14C, the high cam surface 190l being positioned adjacent the mechanism body 88l. The high cam surface 190l is located a relatively large distance from the pivot 184, allowing the adjustment cam 182l to lock the stem restrictor 178l against its spring bias at a position that is relatively far away from the valve inlet chamber 94l. This in turn places the restrictor legs 180l in a position that restricts the valve stem 110l to move no further than an open position that creates a relatively large air space 130l between the valve stem 110l and tapered portion 1031 of the valve outlet 102l, allowing a maximum amount of air to pass from the valve inlet chamber 94l that is greater than when the control mechanism 36l is in the LOW or MEDIUM positions.
FIGS. 15A–D depict an embodiment inlet control mechanism 36m having a stem restrictor 178m that extends through a resilient ring 194 positioned within the control segment 89m of the mechanism body 88m. The stem restrictor 178m is configured to reciprocate along the valve axis 112 and includes restrictor legs 180m positioned to engage and limit the movement of the valve stem hOrn toward the valve control chamber 92m. A low adjustment notch 196, medium adjustment notch 198, and high adjustment notch 200 are located along the length of the stem restrictor 178m. The low, medium, and high adjustment notches 196, 198, and 200 are each positioned to compress and engage the resilient ring 194 to lock the stem restrictor 178m against the mechanism body 88m. A magnified cross sectional view of the engagement of the resilient ring 194 by the stem restrictor 178m is depicted in FIG. 15D in the LOW position.
A restrictor handle 202 allows the stem restrictor 178m to be manually adjusted to selectively compress and engage the resilient ring 194 with the low, medium, or high adjustment notches 196, 198, or 200. The inlet control mechanism 36m is depicted in the LOW position in FIG. 15A, the low adjustment notch 196 being positioned in engagement with the resilient ring 194 to lock with the mechanism body 88m. The low adjustment notch 196 is located a relatively small distance from the restrictor legs 180m. This allows the restrictor legs 180m to assume a position that restricts the valve stem 110m to move no further than an open position that creates a relatively small air space 130m between the valve stem 110m and tapered portion 103m of the valve outlet 102m, allowing a maximum amount of air to pass from the valve inlet chamber 94m that is less than when the control mechanism 36m is in the MEDIUM or HIGH positions.
The inlet control mechanism 36m is depicted in the MEDIUM position in FIG. 15B, the medium adjustment notch 198 being positioned in engagement with the resilient ring 194 to lock with the mechanism body 88m. The medium adjustment notch 198 is located a medium distance from the restrictor legs 180m. This allows the restrictor legs 180m to assume a position that restricts the valve stem 110m to move no further than an open position that creates a medium sized air space 130m between the valve stem 110m and tapered portion 103m of the valve outlet 102m, allowing a maximum amount of air to pass from the valve inlet chamber 94m that is greater than when the control mechanism 36m is in the LOW position but less than when the control mechanism 36m is in the HIGH position.
The inlet control mechanism 36m is depicted in the HIGH position in FIG. 15C, the high adjustment notch 200 being positioned in engagement with the resilient ring 194 to lock with the mechanism body 88m. The high adjustment notch 200 is located a relatively large distance from the restrictor legs 180m. This allows the restrictor legs 180m to assume a position that restricts the valve stem 110m to move no further than an open position that creates a relatively large sized air space 130m between the valve stem 110m and tapered portion 103m of the valve outlet 102m, allowing a maximum amount of air to pass from the valve inlet chamber 94m that is greater than when the control mechanism 36m is in the LOW or MEDIUM positions.
FIGS. 16A–D depict an embodiment inlet control mechanism 36n having a threaded stem restrictor 178n that extends through a threaded portion 204 of the control segment 89n of the mechanism body 88n. The stem restrictor 178n is configured to rotate about and reciprocate along the valve axis 112 and includes restrictor legs 180n that are positioned to engage and limit the movement of the valve stem 110n toward the valve control chamber 92n. A magnified cross sectional view of the threaded portion 204 of the mechanism body 88n and the stem restrictor 178n is depicted in FIG. 16D.
A restrictor knob 206 allows the stem restrictor 178n to be manually rotated to adjust the maximum distance that the valve stem 110n and valve piston assembly 96n can move toward the valve control chamber 92n. The inlet control mechanism 36n is depicted in a position in FIG. 16A that restricts the valve stem 110n to move no further than an open position that creates a relatively small air space 130n between the valve stem 110n and tapered portion 103n of the valve outlet 102n, allowing a maximum amount of air to pass from the valve inlet chamber 94n that is of a relatively small magnitude.
The inlet control mechanism 36n is depicted in a position in FIG. 16B that restricts the valve stem 110n to move no further than an open position that creates an intermediate sized air space 130n between the valve stem 110n and tapered portion 103n of the valve outlet 102n, allowing a maximum amount of air to pass from the valve inlet chamber 94n that is of an intermediate magnitude.
The inlet control mechanism 36n is depicted in a position in FIG. 16C that restricts the valve stem 110n to move no further than an open position that creates a relatively large air space 130n between the valve stem 110n and tapered portion 103n of the valve outlet 102n, allowing a maximum amount of air to pass from the valve inlet chamber 94n that is of a relatively large magnitude.
Some embodiments of the invention also allow for continuous operation of the compressor unit without requiring the use of an inlet unloader for actuation of the cylinder inlet valve. FIGS. 17A–C depict an inlet control mechanism 154o having an equalization valve 208o positioned within the control segment 89o of the mechanism body 88o. The equalization valve 208o is connected through a pilot tube 134 to a pilot valve (not shown) mounted on the air reservoir of a compressor unit. The equalization valve 208o includes an equalization piston 210 that is configured to reciprocate along an equalization valve axis 212 in a piston chamber 216. The equalization piston 210 includes a piston ring 211 that allows the equalization piston 210 to seal against the walls of the piston chamber 216 during operation. The equalization piston 210 is connected to an equalization rod 214 that extends from the piston chamber 216 through a rod passage 222 into a ball chamber 220 where the equalization rod 214 engages a ball 218. The rod passage 222 is sufficiently large to allow air to pass freely from the piston chamber 216 past the equalization rod 214 toward the ball chamber 220.
The equalization piston 210 is biased with an equalization spring 226 to move to a position that is away from the ball chamber 220 (upwards as depicted in FIGS. 17A–C). The ball 218 also reciprocates along the equalization valve axis 212 within the ball chamber 220 and is biased with a ball spring 228 to move in the same direction as the equalization piston 210. The ball 218 is sized to allow air to pass freely around between the ball 218 and ball chamber walls 230 but to seal against the upper taper 231 of the ball chamber 220 when pressed against the upper taper 231 by the ball spring 228, preventing air flow from the rod passage 222 to the ball chamber 220. An equalization inlet 232 allows air to freely enter the piston chamber 216 from the environment to maintain atmospheric pressure within the piston chamber 216. A control inlet 234 allows for the free passage of air between the ball chamber 220 and control chamber 92o. 
When used with a continuously running air compressor unit, the inlet control mechanism 36o operates according to pneumatic signals received from the pilot valve. During operation, as long as air pressure contained within the air reservoir of the compressor unit remains above a predetermined minimum magnitude, the pilot valve assumes an ON condition. In turn, the pilot valve sends a pressure signal to the equalization valve 208o through the pilot tube 134. The pressure signal forces the equalization piston 210 against the bias of the equalization spring 226, forcing the equalization rod 214 to push the ball 218 against the bias of the ball spring 228 and away from the upper taper 231 of the ball chamber 220. This position is depicted in FIG. 17A and allows air from the environment to freely enter the ball chamber 220 by way of the equalization inlet 232 piston chamber 216, and rod passage 222. This also allows air from the environment to freely enter the control chamber 92o through the control inlet 234 and maintain atmospheric pressure within the control chamber 92o as long as the ball 218 remains away from the upper taper 231 of the ball chamber 220.
Air pressure within the control chamber 92o remains at atmospheric pressure as long as the pilot valve continues to send a pressure signal to the equalization valve 208o. The orifice 122o has a relative size that allows air to pass at a much slower rate than air can pass through the open equalization valve 208o from the environment. Although the compressor unit operates continuously, air cannot be drawn through the vent passageway 122o of the valve stem 110o as quickly as it is supplied by the open equalization valve 208o. As a result, no pressure differential exists between the valve control chamber 92o and valve inlet chamber 94o as long as the pressure signal continues and the inlet control mechanism 36o does not open to allow air from the atmosphere to flow though the valve outlet 102o to the compression cylinder.
When air pressure within the air reservoir falls below the predetermined minimum magnitude, the pilot valve assumes an OFF condition. In turn, the pilot valve removes the pressure signal from the equalization valve 208o through the pilot tube 134. With the pressure signal removed, the bias of the equalization spring 226 forces the equalization piston 210 away from the ball spring 228, drawing the equalization rod 214 away from the ball 218. The bias of the ball spring 228 forces the ball 218 against the upper taper 231 of the ball chamber 220. This position is depicted in FIG. 17B and prevents air from the environment from entering the ball chamber 220 by way of the equalization inlet 232, piston chamber 216, and rod passage 222. This also prevents air from the environment from entering the control chamber 92o through the control inlet 234.
Since the ball 218 blocks the flow of air from the environment into the control chamber 92b, air pressure contained within the control chamber 92b begins to drop as air is drawn through the vent passageway 118o and orifice 122o. This creates a pressure differential between the valve control chamber 92o and valve inlet chamber 94o that forces the piston assembly 96o toward the valve control chamber 92o, eventually opening the control mechanism 36o to the position depicted in FIG. 17C.
Once the inlet control mechanism 36o is in the position depicted in FIG. 17C, the air compressor begins to add pressure to the air reservoir. This continues until the pressure within the air reservoir returns to a predetermined maximum magnitude that is greater than the predetermined minimum magnitude. When the air pressure within the reservoir reaches the predetermined maximum magnitude, the pilot valve again assumes an ON condition to restore the pressure signal to the equalization valve 208o, removing the pressure differential between the valve inlet chamber 94o and valve control chamber 92o and returning the inlet control mechanism 36o to the position depicted in FIG. 17A.
Although FIGS. 17A–C depict an equalization valve 208o mounted within the mechanism body of the inlet control mechanism, it is also possible to mount an equalization valve externally. FIGS. 18A and B depict a compressor unit 32p having an externally mounted equalization valve 208p attached to the control segment 89p of the mechanism body 88p. The externally mounted equalization valve 208p can be mechanically similar to the equalization valve 208o positioned within the mechanism body 88o in FIGS. 17A–C, the externally mounted equalization valve 208p of FIGS. 18A and 18B being configured to allow air to be drawn from the environment through an equalization inlet 232p to a control inlet 234p leading to the control chamber 92p. A magnified cross sectional view of the inlet control mechanism 36p of FIG. 18A is depicted in FIG. 18B.
Referring again to FIG. 18A, the compressor unit can also include a combination valve 236p that combines the functions of a check valve, pilot valve, air cylinder, and a discharge unloader valve, the combination valve 236p, being connected to the discharge tube 84 from the compressor pump 48p, the pilot tube 134p, air reservoir 50, and the conduit 144 leading to the throttle control 146 of the gasoline engine 140. In this combined configuration, the discharge unloader valve is responsive to the pilot valve and is configured to allow air that is compressed with the compressor pump 48p to be channeled to the surrounding atmosphere through a discharge port 237 on the combination valve 236p rather than into the air reservoir 50 when the pilot valve assumes an ON condition. This occurs as the pilot valve sets the engine control throttle 146 to idle through the conduit 144 with the air cylinder 241.
The automatic inlet control mechanism 36p allows for a substantial size reduction in the discharge unloader valve compared to that which is required for a comparable compressor unit that does not have an inlet control. Consider the compressor unit 32p of FIGS. 18A and B when the pilot valve of the combination valve 236p assumes on ON condition. The equalization valve 208p responds to the pilot valve by allowing air to pass from the control chamber 92p through the equalization inlet 232p to the environment, removing the pressure differential between the valve inlet chamber 94p and valve control chamber 92p. The piston assembly 96p moves to a position that is depicted in FIGS. 18A and B that prevents air from moving from the valve inlet chamber 94p to the valve outlet 102p and compression cylinder inlet 38p. As the piston 42 continues to reciprocate, the valve control chamber 92p continues to be the primary source of air to the compression cylinder 44, the air being drawn through the vent passageway 118p and vent orifice 122p. Although the pressure within the valve control chamber 92p remains commensurate with atmospheric pressure, the amount of air that is drawn through the vent passageway 118p is substantially restricted by the orifice 122p. Thus, the amount of air that must be discharged by the discharge unloader vale in the combination valve 236p is also substantially reduced.
Due to this substantial reduction in the amount of air that must be discharged, the structural size of the discharge unloader valve can also be substantially reduced. In some embodiments, the unloader opening of the valve can be reduced by an order of ten or more, significantly reducing apparatus cost.
Similar inlet control mechanisms can be implemented in electrically operated continuous drive compressor units as well. FIGS. 19A and B depict a compressor unit 32q having an electric motor 58 and a combination valve 236q that combines the functions of a check valve and pilot valve, being connected to the discharge tube 84 from the compressor pump 48q, the pilot tube 134q, and air reservoir 50. FIG. 19B depicts a magnified cross sectional view of the inlet control mechanism 36q which is similar to the inlet control mechanism 36p of FIGS. 18A and B.
In some embodiments of the invention, the reciprocating motion of the piston assembly can be used to operate and/or actuate other components of the compressor unit. For example, FIGS. 20A–C depict an automatic inlet control mechanism 36r in which the piston assembly 96r includes an actuation pin 238 mounted on the valve stem 110r and positioned to reciprocate through a pin space 240 in the guide 160. The actuation pin 238 allows the piston assembly 96r to function as an actuator, the actuation pin 238 being sufficiently long to engage the venting stem 242 of a vent valve 244 positioned within the inlet segment 87r of the mechanism body 88r when the piston assembly 96r is in the closed position as depicted in FIG. 20A. The vent valve 244 includes a stem seal 246 that is connected to reciprocate with the venting stem 242 and is biased with a stem spring to seal against the stem seat 248 when the actuation pin 238 is not in engagement with the venting stem 242 as shown in FIG. 20C. The vent valve 244 connects the valve inlet chamber 94r to a vent passage 252 that can allow the attachment of a vent line 254. The vent line 254 can itself be linked to a discharge tube or other component of the compressor unit that requires the release of air pressure when the compressor unit is not compressing air and when the inlet control mechanism 36r is in the closed position, as shown in FIG. 20A.
Consider the inlet control mechanism 36r either before or at the start of operation of a compressor unit. The inlet control mechanism 36r is in a closed position as depicted in FIG. 20A with the valve stem 110r preventing the flow of air between the valve inlet chamber 94r and valve outlet 102r. The actuation pin 238 pushes the venting stem 242 against the bias of the stem spring 248 to pull the stem seal 246 away from the stem seat 250, allowing air to pass from the valve inlet chamber 94r through the vent passage 252 to the vent line 254. Since the compressor unit has not yet begun to compress air, the discharge tube leading from the compressor pump to the air reservoir does not yet need to be pressurized. The vent line 254 can be connected to the discharge tube to allow pressure contained therein to escape through the vent valve 244 to the valve inlet chamber 94r, valve inlet 98r, and back into the atmosphere. As the piston assembly 96r moves toward the valve control chamber 92r, the actuation pin 238 disengages the venting stem 242 and allows the stem seal 246 to seal against the stem seat 250 under the force of the stem spring 248, as depicted in FIG. 20B. By the time the piston assembly 96r moves to a position that allows air to move from the valve inlet chamber 94r to the valve outlet 102r such that the compressor unit begins to compress air, as depicted in FIG. 20C, the vent valve 244 prevents air from being discharged to the atmosphere through the valve inlet chamber 94r, allowing compressed air to instead flow into the air reservoir.
Although the invention has been shown and described as having a vent passageway having an air restriction that comprises an orifice, it will be appreciated that many types of restrictions can be appropriately implemented. FIGS. 21A–C depict an inlet control mechanism 36s in which the restriction is formed by a reduced diameter segment 256 of the vent passageway 118s. Due to the extremely small relative diameter of the reduced diameter segment 256, the segment 256, like an orifice, greatly restricts the rate at which air can flow from the valve control chamber 92s through the vent passageway 118s to the valve outlet 102s, thereby restricting the speed at which the piston assembly 96s can move from the closed positions of FIGS. 21A and B toward to the open position of FIG. 21C.
FIGS. 22A and B depict an inlet control mechanism 36t in which the vent passageway 118t has a restriction comprising multiple orifices 122t positioned in a series along the length of the valve stem 110t. Each orifice 122t of the configuration is identical to the other and each creates a successive air flow restriction reducing the downstream air pressure by roughly one order of magnitude. Thus the successive multiple orifices can be used to substantially increase the amount of time that is necessary for the valve piston assembly 96t to move from a closed position, as depicted in FIG. 22A, to a position that allows air to move from the valve inlet chamber 94t to the valve outlet 102t, as depicted in FIG. 22B.
FIGS. 23A and B depict an inlet control mechanism 36u in which the vent passageway 118u has a restriction comprising a porous metal restrictor 258 that is press fitted within the valve stem 110u. The porous metal restrictor 258 is air permeable and allows a limited amount of air to pass therethrough, restricting airflow and reducing downstream air pressure accordingly. The effective magnitude of the restriction created can depend on the thickness or number of restrictors incorporated into the control mechanism 36u and/or the exact type or permeability of the material used. Thus, the placement of the porous metal restrictor 258 can be used to substantially increase the amount of time that is necessary for the valve piston assembly 96u to move from a closed position, as depicted in FIG. 23A, to a position that allows air to move from the valve inlet chamber 94u to the valve outlet 102u, as depicted in FIG. 23B.
FIGS. 24A and B depict an inlet control mechanism 36v in which the vent passageway 118v has a restriction comprising a labyrinth restrictor 260 that is press fitted into the vent passageway 118v of the valve stem 110v. Four different views of the labyrinth restrictor 260 are depicted in FIGS. 25A–D. The labyrinth restrictor 260 includes a plurality of flutes 264 extending along a reduced radius portion 262, the reduced radius portion 262 being sized to allow for press fitting into a reduced diameter portion 266 of the vent passageway 118v. When positioned within the reduced diameter portion 266 of the vent passageway 118v, the flutes 264 and the inside walls of the vent passageway 118v together form fluted passages allowing for the passage of air between the reduced diameter portion 266 and an expanded diameter portion 268 of the vent passageway 118v. 
The labyrinth restrictor 260 also includes an expanded radius portion 270 that is sized to allow a slight air clearance 272 to exist with the walls of the expanded diameter portion 268 of the vent passageway 118v when installed within the valve stem 110v. The expanded radius portion 270 of the restrictor 260 includes multiple grooves 274 that are incrementally spaced and positioned around the diameter of the expanded radius portion 270. The flutes 264 of the reduced radius portion 266 of the restrictor 260 are open to the air clearance 272 with the walls of the expanded diameter portion 268 of the vent passageway 118v to allow air to bypass the restrictor 260 when it is installed within the valve stem 110v. However, the close proximity of the expanded radius portion 270 of the restrictor 260 to the walls of the expanded diameter portion 268 of the vent passageway 118v creates a restriction for passing air that has a restriction size allowing air to be drawn by the compressor unit at a preselected rate to cause the compressor unit to produce compressed air at less than its predetermined rate of production. Each groove 274 creates an air expansion space with the walls of the expanded diameter portion 268 of the vent passageway 118v. As a result, each successive groove 274 creates a further, successive reduction in downstream air pressure. Where each successive groove 274 is of approximately equal size, each successive reduction in downstream air pressure will be of approximately one order of magnitude. Thus, the amount of time that is necessary for the valve piston assembly 96v to move from a closed position, as depicted in FIG. 24A, to a position that allows air to move from the valve inlet chamber 94v to the valve outlet 102v, as depicted in FIG. 24B, can be determined by the respective size, shape/orientation, or number of grooves 274 that are included on the expanded radius portion 270 of the restrictor 260.
FIGS. 26A–C depict an inlet control mechanism 36w of the invention having a restriction comprising a restriction ball 276 positioned adjacent a diagonal orifice 278. The restriction ball 276 is sized to allow air to pass between the restriction ball 276 and a ball chamber 279 of the vent passageway and allows a substantially greater amount of air to move between the vent passageway 118w and valve control chamber 92w than does the diagonal orifice 278 when the restriction ball 276 is not in contact a passageway cone 282. The restriction ball 276 is biased with a ball spring 280 located within the ball chamber 279 to engage and seal against the passageway cone 282. FIG. 26A depicts the inlet control mechanism 36w in a closed position that prevents air from moving from the valve inlet chamber 94w to the valve outlet 102w. FIG. 26B depicts a magnified view of the restriction when in the closed position depicted in FIG. 26A.
Consider the inlet control mechanism 36w prior to or at the start of operation of a compressor unit. As air begins to be drawn through the vent passageway 118w, the combined biasing force of the ball spring 280 and the suction force of the compressor unit through the vent passageway 118w force the restriction ball 276 against the passageway cone 282, preventing the movement of air from the control chamber 92w past the restriction ball 276 within the vent passageway 118w. The suction force of the compressor unit does draw air through the diagonal orifice 278. However, a comparatively small amount of air is permitted to move between the vent passageway 118w and valve control chamber 92w with the restriction ball 276 sealing against the passageway cone 282 due to the relatively small size of the diagonal orifice 278. The diagonal orifice 278 continues to restrict the rate at which air can be drawn from the valve control chamber 92w as the inlet control mechanism 36w moves to an open position, such as the position depicted in FIG. 26C.
Now, referring to FIG. 26C, consider the inlet control mechanism 36w as the compressor unit ceases operation. The valve inlet chamber 94w, being open to the environment surrounding the compressor unit, allows air from the atmosphere to enter the vent passageway 118w through the stem hole 120. Atmospheric pressure in the vent passageway 118w forces the restriction ball 276, against the bias of the ball spring 280, to move away from the passageway cone 282. Since the restriction ball 276 is sized to allow for a substantially greater amount of air to move between the vent passageway 118w and valve control chamber 92w than does the diagonal orifice 278, the movement of the restriction ball 276 away from passageway cone 282 allows air to enter the valve control chamber 92w relatively quickly. This further allows the valve control chamber 92w to quickly return to atmospheric pressure as the piston assembly 96w moves back toward the valve inlet chamber 94w under the force of the spring biasing member 114w, eventually returning the inlet control mechanism 36w to a closed position as depicted in FIG. 26A.
FIGS. 27A–C depict an inlet control mechanism 36x of the invention having a restriction comprising a reciprocating orifice 284 positioned within an orifice chamber 286 that forms a segment of the vent passageway 118x. The reciprocating orifice 284 is biased to rest against passageway seals 288 with an orifice spring 290. Air passages 292 allow for the unobstructed flow of air between the orifice chamber 286 and valve control chamber 92x. The reciprocating orifice 284 is sized to allow a substantially smaller amount of air to pass through the vent passageway 118x to the valve control chamber 92x when the reciprocating orifice 284 is resting against the passageway seals 288 than when the force of air pushes the reciprocating orifice 284 against its bias away from the passageway seals 288. FIG. 27A depicts the inlet control mechanism 36x in a closed position that prevents air from moving from the valve inlet chamber 94x to the valve outlet 102x. FIG. 27B depicts a magnified view of the restriction when in the closed position depicted in FIG. 27A.
Consider the inlet control mechanism 36x prior to or at the start of operation of a compressor unit. As air begins to be drawn through the vent passageway 118x into the compression cylinder of the compressor unit, the combined biasing force of the orifice spring 290 and the suction force of the compressor unit through the vent passageway 118x force the reciprocating orifice 284 against the passageway seals 288, restricting the movement of air from the control chamber 92x to the vent passageway 118x through the reciprocating orifice 284. However, due to the sizing of the reciprocating orifice 284, the amount of air that is permitted to move through the reciprocating orifice 284 between valve control chamber 92x and the vent passageway 118x is substantially less than the amount that would be permitted if the reciprocating orifice 284 were withdrawn from contact with the passageway seals 288. The reciprocating orifice 284 continues to restrict the rate at which air can be drawn from the valve control chamber 92x as the inlet control mechanism 36x moves to an open position, such as the position depicted in FIG. 27C.
Now, referring to FIG. 27C, consider the inlet control mechanism 36x as the compressor unit ceases operation. The valve inlet chamber 94x, being open to the environment surrounding the compressor unit, allows air from the atmosphere to enter the vent passageway 118x through the stem hole 120. Atmospheric pressure in the vent passageway 118x forces the reciprocating orifice 284, against the bias of the orifice spring 290, to move away from the passageway seals 288. Since a substantially greater amount of air can move between the vent passageway 118x and valve control chamber 92x when the reciprocating orifice 284 is not in contact with the passageway seals 288 than when air is limited to movement through the reciprocating orifice 284, air enters the valve control chamber 92x from the vent passageway 118x relatively quickly. This further allows the valve control chamber 92x to quickly return to atmospheric pressure as the piston assembly 96x moves back toward the valve inlet chamber 94x under the force of the spring biasing member 114x, eventually returning the inlet control mechanism 36x to a closed position as depicted in FIG. 26A 27A.
The invention can also be constructed to incorporate multiple, separately reciprocating members that act in concert to reduce compression loading. For example, FIGS. 28A–C depict an inlet control mechanism 36y having a reciprocating tapered section 294 that is positioned to reciprocate within the valve inlet chamber 94y and valve outlet 102y. A separate piston assembly 96y reciprocates between the valve inlet chamber 94y and valve control chamber 92y, the piston assembly 96y including a valve stem 110y that extends to the valve outlet 102y. When the inlet control mechanism 36y is in a closed position such as that depicted in FIG. 28A, the valve stem 110y extends through the valve outlet hole 104y. The valve stem 110y also extends through a section hole 296 located at the narrow end of the reciprocating tapered section 294. A section clip 298 is positioned to reciprocate with the valve stem 110y and is configured to engage the narrow end of the reciprocating tapered section 294 near the section hole 296 when the inlet control mechanism 36y is at a closed, intermediate position that is depicted in FIG. 28B. The section clip 298 is further configured to cause the reciprocating tapered section 294 to move with the valve piston assembly 96y as it continues to mover toward the valve control chamber 92y to the open position depicted in FIG. 28C. The section clip 298 includes clip holes 300 that allow air to pass in a restricted manner through, the section clip 298 from the valve inlet chamber 94y to the valve outlet 102y when the section clip 298 is in engagement with the reciprocating tapered section 294.
Consider the inlet control mechanism 36y prior to or at the start of operation of a compressor unit. As air begins to be drawn through the vent passageway 118y from the valve control chamber 92y into the compression cylinder of the compressor unit, the atmospheric pressure in the valve inlet chamber 94y begins to force the piston assembly 96y toward the valve control chamber 92y. Air is removed by the compressor pump from the valve outlet 102y while atmospheric pressure from the valve inlet chamber 94y is prevented from entering the valve outlet 102y by the reciprocating tapered section 294, the valve stem 110y, and the valve stem seal 116y. Although there is a resulting pressure differential that exists between the valve inlet chamber 94y and the valve outlet 102y, the reciprocating tapered section 294 does not move further toward the valve outlet hole 104y past the position depicted in FIG. 28A since such movement is restricted by a section seat 302 positioned on the inside surface of the inlet segment 87y. 
As the piston assembly 96y continues to move toward the valve control chamber 92y, the valve stem seal 116y, moving along the sliding surface 124, continues to prevent air from moving from the valve inlet chamber 94y to the valve outlet 102y until the lip 126 of the valve stem 110y withdraws the valve stem seal 116y from its contact with the reciprocating tapered section 294. Referring to FIG. 28B, this creates an air space 130y between the valve stem seal 116y and reciprocating tapered section 294. The section clip 298 contacts the reciprocating tapered section 294 near the section hole 296, but allows air to pass from the section hole 296 to the valve outlet 102y through clip holes 300. Air is therefore permitted to flow from the valve inlet chamber 94y to the valve outlet 102y when the inlet control mechanism 36y is in the position depicted in FIG. 28B, the amount of air permitted to pass depending on the size and number of clip holes 300.
As the piston assembly 96y continues to move toward the valve control chamber 92y, the section clip 298 forces the reciprocating tapered section 294 to withdraw from its contact with the section seat 302 toward the position depicted in FIG. 28C. As the piston assembly 96y and reciprocating tapered section 294 move toward the valve control chamber 92y, the movement is further restricted by the rate at which air is permitted to move through the clip holes 300, increasing the amount of time required for the inlet control mechanism 36y to move to the position depicted in FIG. 28A. Movement to this position opens the valve inlet chamber 94y to the valve inlet 98y, thereby opening the valve outlet 102y to atmospheric pressure and allowing air from the environment to enter the compressor pump for compression. Thus, there is sequential opening of the sealing action that is created both by the valve stem seal 116y and by the reciprocating tapered section 294 and section clip 298.
By incorporating the additional actuation and reciprocation of the reciprocating tapered section 294, the load of actuation is divided into smaller portions, distributing the total load more evenly through the stroke range of the valve piston assembly 96y. This is due to the elimination of a need for a large pressure differential-created force at a single point in the stroke range of the valve piston 108y. As a result, the inlet control mechanism 36y can have a relatively small construction while performing the equivalent compression unloading of larger inlet control mechanisms.
It will be further appreciated that some embodiments of the invention allow for incorporation of an inlet control mechanism in which the valve inlet chamber, valve control chamber, portions of the valve cavity and/or other components are located in positions that are not located along a common valve axis. For example, FIGS. 29A and B depict a compressor pump 48za of the invention having an automatic inlet control mechanism 36za that includes a mechanism body 88za integrated into the structure of the compressor pump 48za. 
The mechanism body 88za includes a removable portion 304za that is threaded to allow for removal and installation of components of the inlet control mechanism 36za in the compressor pump 48za. An external filter 166 is attached to a valve inlet 98za leading to a valve inlet chamber 94za. The valve inlet chamber 94za is part of a valve cavity 90za that extends from the valve inlet 98za to a valve outlet hole 104za and further includes a valve control chamber 92za, vent passageway 308, and atmosphere chamber 310za. The atmosphere chamber 310za is connected to the environment surrounding the inlet control mechanism 36za with an atmosphere inlet 316 that is sufficiently large to maintain atmospheric pressure within the atmosphere chamber 310za. The vent passageway 308 provides a route for the flow of air between the valve control chamber 92za and valve outlet 102za and includes an orifice 122za to restrict airflow therein.
A valve piston assembly 96za is positioned to reciprocate along a valve axis 312 and includes a valve piston 108za, valve stem 110za, and diaphragm 106. The valve stem 110za has an elongated cylindrical section 319za that is sufficiently long to extend through a reduced diameter portion 318 of the valve cavity 90za to a location that is between the valve inlet chamber 94za and valve outlet 102za. The elongated cylindrical section 319za has a cylindrical shaped, reduced dimensional portion 320 that creates an air gap 322 with the adjacent valve cavity 90za. The air gap 322 extends 360 degrees around the reduced dimensional portion 320 along a segment of the valve axis 312. The valve piston 108za and diaphragm 106 separate the valve control chamber 92za from the atmosphere chamber 310za, the diaphragm 106 forming a movable seal that prevents air from moving directly between the two chambers. The valve piston 108za and valve piston assembly 96za are biased with a biasing spring 314 to a closed position that is depicted in FIG. 29A. In this closed position, the valve stem 110za extends between the inlet chamber 94za and valve outlet 102za to block the flow of air therebetween.
Consider the inlet control mechanism 36za and compressor pump 48za before or at the start of reciprocation of the piston 42. As the piston 42 begins to reciprocate, air is quickly removed from the valve outlet 102za and the cylindrical extension 319za of the valve stem 110za restricts air from the environment from entering the valve outlet 102za from the valve inlet chamber 94za. Air is drawn from the valve control chamber 92za through the vent passageway 122za and becomes the primary source of air to the compression cylinder 44, though the amount of air that can be drawn is substantially restricted by the orifice 122za, substantially reducing compression loading of piston 42.
As air is drawn from the valve control chamber 92za a pressure differential between the valve control chamber 92za and atmosphere chamber 310za forces the piston assembly 96za away from the atmosphere chamber 310za toward the open position depicted in FIG. 29B. However, the valve stem 110za continues to restrict atmospheric pressure from the valve outlet 102za from entering the valve inlet chamber 94za until the reduced radius portion 320 of the valve stem 110za moves to a position that opens the air gap 322 to both the valve inlet chamber 94za and valve outlet 102za. 
Once the valve stem 110za moves to an open position, such as the position depicted in FIG. 29B, air is permitted to flow 360 degrees around the reduced radius portion 320 of valve stem 110za, through the air gap 322, to the valve outlet 102za, restoring compression loading to the piston 42. The biasing spring 314 returns the valve piston assembly 96zb to the position depicted in FIG. 29A once the piston 42 ceases reciprocating within the compression cylinder 44.
FIGS. 30A and B depict a compressor pump 48zb of the invention having an automatic inlet control mechanism 36zb that includes a valve stem 110zb having an air bore 324 extending through the elongated cylindrical extension 319zb that allows air to pass through the valve stem 110zb only when the inlet control mechanism 36zb is in an open position. Before or at the time the piston 42 begins to reciprocate, the valve stem 110zb is biased with the biasing spring 314 to the closed position depicted in FIG. 30A. In this position, the air bore 324 is not open to either the valve inlet chamber 94zb or the valve outlet 102zb, the cylindrical extension 319zb of the valve stem 110zb blocking the flow of air from the environment to the compression cylinder inlet 38zbHowever, as the piston 42 begins to reciprocate and draws air from the vent control chamber 92zb through the vent passageway 308 and orifice 122zb, the piston assembly 96zb moves toward an open position, such as that depicted in FIG. 30B. In an open position, the air bore 324 moves to a location that is adjacent and open to both the valve inlet chamber 94zb and the valve outlet 102zb, allowing air to pass through the air bore 324 from the environment to the compression cylinder inlet 38zb for compression. Once reciprocation of the piston 42 ceases, the biasing spring 314 moves the valve stem 319zb back to the closed position depicted in FIG. 30A.
Those skilled in the art will recognize that the various features of this invention described above can be used in various combinations with other elements without departing from the scope of the invention. Thus, the appended claims are intended to be interpreted to cover such equivalent air compressor units as do not depart from the spirit and scope of the invention.

## Claims

1. An automatic inlet control mechanism for connection to a compression cylinder inlet of a reciprocating air compressor unit which produces compressed air at a predetermined rate of production through the use of a piston that reciprocates within a compression cylinder, said inlet control mechanism comprising:
a mechanism body having a valve cavity, said valve cavity having a valve control chamber and a valve inlet chamber, a valve piston assembly positioned between said valve control chamber and said valve inlet chamber and constructed to prevent air flow between said valve control chamber and said valve inlet chamber;
a valve inlet positioned to allow air to flow from the atmosphere surrounding the compressor unit and into said valve inlet chamber;
a valve outlet having a valve outlet hole positioned to allow air to flow from said valve inlet chamber to the compression cylinder inlet, said valve outlet hole having a size sufficient to enable the compressor unit to produce compressed air at its predetermined rate of production;
said valve piston assembly including a valve piston, said valve piston assembly being positioned to reciprocate within said valve cavity, a biasing member having a force which moves said valve piston assembly to a position within said inlet control mechanism which prevents air from flowing from said valve inlet chamber through said valve outlet when the compressor unit is not drawing air through said valve outlet;
a vent passageway allowing air to flow between said valve control chamber and the compression cylinder inlet;
said vent passageway comprising at least one source of air to the compression cylinder inlet for a period of time after the compressor unit begins to draw air through the compression cylinder inlet, following the movement of said valve piston assembly to a position which prevents air from flowing from said valve inlet chamber through said valve outlet;
said vent passageway including a vent orifice which restricts the flow of air from said valve control chamber to said compression cylinder inlet; and
said vent orifice having an orifice size which allows air to be drawn, by the compressor unit, from said valve control chamber to the compression cylinder at a preselected rate which causes the compressor unit to produce compressed air at less than its predetermined rate of production, said valve control chamber having a volume which enables air to be drawn through said orifice from said valve control chamber by the compressor unit over a preselected time period until air within said valve control chamber is at a reduced pressure level which enables atmospheric pressure on said valve piston assembly from within said valve inlet chamber to overcome the force of said biasing member sufficiently to move said valve piston assembly away from the position at which said valve piston assembly prevents air from flowing from said valve inlet chamber and through said valve outlet to enable the compressor unit to produce compressed air at its predetermined rate of production.

2. The automatic inlet control mechanism of claim 1 wherein said valve piston assembly includes a diaphragm positioned between said valve control chamber and said valve inlet chamber, said diaphragm being constructed to prevent air flow between said valve control chamber and said valve inlet chamber, said diaphragm being positioned to move toward said valve control chamber when air pressure within said valve inlet chamber is greater than air pressure within said valve control chamber, said diaphragm being positioned to move toward said valve inlet chamber when air pressure within said valve control chamber is greater than the air pressure within said valve inlet chamber.

3. The automatic inlet control mechanism of claim 1 wherein said vent passageway is included within said valve piston assembly, said vent orifice being located at a position in said valve piston assembly to enable said vent orifice to restrict the flow of air from said valve control chamber to the compression cylinder inlet as said valve piston assembly reciprocates within said inlet control mechanism.

4. The automatic inlet control mechanism of claim 1 wherein said valve piston assembly includes a valve stem, said vent passageway being included within said valve piston assembly and extending through said valve stem, said vent orifice being located at a position in said valve piston assembly to enable said vent orifice to restrict the flow of air from said valve control chamber to the compression cylinder inlet as said valve piston assembly reciprocates within said inlet control mechanism.

5. The automatic inlet control mechanism of claim 1 wherein said valve outlet includes a valve outlet hole having a tapered portion, said tapered portion having at least a first inner diameter and a second inner diameter, said first inner diameter of said tapered portion being larger than said second inner diameter and being located at a position that is closer to said valve inlet chamber than said second inner diameter when said mechanism is installed, said second inner diameter being sufficiently small to form an air restriction against said valve piston assembly when said valve piston assembly is at a position within said inlet control mechanism which prevents air from flowing from said valve inlet chamber through said valve outlet, said first inner diameter of said tapered portion being sufficiently large to allow air to pass between said tapered portion of said valve outlet and said valve piston assembly when said valve piston assembly is at a position within said inlet control mechanism which allows air to flow from said valve inlet chamber through said valve outlet.

6. The automatic inlet control mechanism of claim 1 wherein said valve piston assembly includes a valve stem and a sliding seal mounted to reciprocate along at least a portion of said valve stem to contact said valve outlet to cause said valve piston assembly to prevent air from flowing from said valve inlet chamber through said valve outlet when the compressor unit is not drawing air through said valve outlet, the movement of said valve piston assembly away from the position at which said valve piston assembly prevents air from flowing from said valve inlet chamber and through said valve outlet to the compression cylinder inlet causing said sliding seal to move away from said valve outlet to allow air to flow to the compression cylinder inlet.

7. The automatic inlet control mechanism of claim 1 wherein said valve inlet includes a filter to remove impurities from air that passes through said valve inlet and enters said valve inlet chamber.

8. The automatic inlet control mechanism of claim 1 wherein said valve piston assembly includes a valve stem and a sliding seal mounted to reciprocate along at least a portion of said valve stem to contact said valve outlet to cause said valve piston assembly to prevent air from flowing from said valve inlet chamber through said valve outlet when the compressor unit is not drawing air through said valve outlet, the movement of said valve piston assembly away from the position at which said valve piston assembly prevents air from flowing from said valve inlet chamber and through said valve outlet to the compression cylinder inlet causing said sliding seal to move away from said valve outlet to allow air to flow to the compression cylinder inlet, said valve inlet including a filter to remove impurities from air that passes through said valve inlet and enters said valve inlet chamber.

9. The automatic inlet control mechanism of claim 1 wherein the compression cylinder inlet includes a cylinder inlet chamber for receiving air from the compression cylinder inlet before the air enters the compression cylinder, said vent passageway being positioned to allow for air to flow, outside said valve piston assembly, directly between said valve control chamber and the cylinder inlet chamber.

10. The automatic inlet control mechanism of claim 1 wherein:
the compression cylinder inlet includes a cylinder inlet chamber for receiving air from the compression cylinder inlet before the air enters the compression cylinder, said vent passageway being positioned to allow for air to flow, outside said valve piston assembly, directly between said valve control chamber and the cylinder inlet chamber; and
said valve piston assembly includes a valve stem and a sliding seal mounted to reciprocate along at least a portion of said valve stem to contact said valve outlet to cause said valve piston assembly to prevent air from flowing from said valve inlet chamber through said valve outlet when the compressor unit is not drawing air through said valve outlet, the movement of said valve piston assembly away from the position at which said valve piston assembly prevents air from flowing from said valve inlet chamber and through said valve outlet to the compression cylinder inlet causing said sliding seal to move away from said valve outlet to allow air to flow to the compression cylinder inlet.

11. The automatic inlet control mechanism of claim 1 wherein the compression cylinder inlet includes a cylinder inlet chamber for receiving air before the air from the compression cylinder inlet enters the compression cylinder, said automatic inlet control mechanism being located at least partially within the cylinder inlet chamber.

12. The automatic inlet control mechanism of claim 1 wherein: the compression cylinder inlet includes a cylinder inlet chamber for receiving air before the air from the compression cylinder inlet enters the compression cylinder, said automatic inlet control mechanism being located at least partially within the cylinder inlet chamber; and
said valve piston assembly includes a valve stem and a sliding seal mounted to reciprocate along at least a portion of said valve stem to contact said valve outlet to cause said valve piston assembly to prevent air from flowing from said valve inlet chamber through said valve outlet when the compressor unit is not drawing air through said valve outlet, the movement of said valve piston assembly away from the position at which said valve piston assembly prevents air from flowing from said valve inlet chamber and through said valve outlet to the compression cylinder inlet causing said sliding seal to move away from said valve outlet to allow air to flow to the compression cylinder inlet.

13. An automatic inlet control mechanism for connection to a compression cylinder inlet of a reciprocating air compressor unit which produces compressed air at a predetermined rate of production through the use of a piston that reciprocates within a compression cylinder, said inlet control mechanism comprising:
a mechanism body having a valve cavity, said valve cavity having a valve control chamber and a valve inlet chamber, a valve piston assembly positioned between said valve control chamber and said valve inlet chamber and constmcted to prevent air flow between said valve control chamber and said valve inlet chamber;
a valve inlet positioned to allow air to flow from the atmosphere surrounding the compressor unit and into said valve inlet chamber;
a valve outlet having a valve outlet hole positioned to allow air to flow from said valve inlet chamber to the compression cylinder inlet, said valve outlet hole having a size sufficient to enable the compressor unit to produce compressed air at its predetermined rate of production;
said valve piston assembly including a valve piston, said valve piston assembly being positioned to reciprocate within said valve cavity, a biasing member having a force which moves said valve piston assembly to a position within said inlet control mechanism which prevents air from flowing from said valve inlet chamber through said valve outlet when the compressor unit is not drawing air through said valve outlet;
a vent passageway allowing air to flow between said valve control chamber and the compression cylinder inlet;
said vent passageway comprising the primary source of air to the compression cylinder inlet for the period of time after the compressor unit begins to draw air through the compression cylinder inlet following the movement of said valve piston assembly to the position which prevents air from flowing from said valve inlet chamber through said valve outlet; said vent passageway including a vent orifice which restricts the flow of air from said valve control chamber to said compression cylinder inlet; and
said vent orifice having an orifice size which allows air to be drawn, by the compressor unit, from said valve control chamber to the compression cylinder at a preselected rate which causes the compressor unit to produce compressed air at less than its predetermined rate of production, said valve control chamber having a volume which enables air to be drawn through said orifice from said valve control chamber by the compressor unit over a preselected time period until air within said valve control chamber is at a reduced pressure level which enables atmospheric pressure on said valve piston assembly from within said valve inlet chamber to overcome the force of said biasing member sufficiently to move said valve piston assembly away from the position at which said valve piston assembly prevents air from flowing from said valve inlet chamber and through said valve outlet to said compressor chamber inlet to enable the compressor unit to produce compressed air at its predetermined rate of production.

14. The automatic inlet control mechanism of claim 13 wherein said valve piston assembly includes a diaphragm positioned between said valve control chamber and said valve inlet chamber, said diaphragm being constructed to prevent air flow between said valve control chamber and said valve inlet chamber, said diaphragm being positioned to move toward said valve control chamber when air pressure within said valve inlet chamber is greater than air pressure within said valve control chamber, said diaphragm being positioned to move toward said valve inlet chamber when air pressure within said valve control chamber is greater than the air pressure within said valve inlet chamber.

15. The automatic inlet control mechanism of claim 13 wherein said vent passageway is included within said valve piston assembly, said vent orifice being located at a position in said valve piston assembly to enable said vent orifice to restrict the flow of air from said valve control chamber to the compression cylinder inlet as said valve piston assembly reciprocates within said inlet control mechanism.

16. The automatic inlet control mechanism of claim 13 wherein said valve piston assembly includes a valve stem, said vent passageway being included within said valve piston assembly and extending though said valve stem, said vent orifice being located at a position in said valve piston assembly to enable said vent orifice to restrict the flow of air from said valve control chamber to the compression cylinder inlet as said valve piston assembly reciprocates within said inlet control mechanism.

17. The automatic inlet control mechanism of claim 13 wherein said valve outlet includes a valve outlet hole having a tapered portion, said tapered portion having at least a first inner diameter and a second inner diameter, said first inner diameter of said tapered portion being larger than said second inner diameter and being located at a position that is closer to said valve inlet chamber than said second inner diameter when said mechanism is installed, said second inner diameter being sufficiently small to form an air restriction against said valve piston assembly when said valve piston assembly is at a position within said inlet control mechanism which prevents air from flowing from said valve inlet chamber though said valve outlet, said first inner diameter of said tapered portion being sufficiently large to allow air to pass between said tapered portion of said valve outlet and said valve piston assembly when said valve piston assembly is at a position within said inlet control mechanism which allows air to flow from said valve inlet chamber through said valve outlet.

18. The automatic inlet control mechanism of claim 13 wherein said valve piston assembly includes a valve stem and a sliding seal mounted to reciprocate along at least a portion of said valve stem to contact said valve outlet to cause said valve piston assembly to prevent air from flowing from said valve inlet chamber though said valve outlet when the compressor unit is not drawing air through said valve outlet, the movement of said valve piston assembly away from the position at which said valve piston assembly prevents air from flowing from said valve inlet chamber and through said valve outlet to the compression cylinder inlet causing said sliding seal to move away from said valve outlet to allow air to flow to the compression cylinder inlet.

19. The automatic inlet control mechanism of claim 13 wherein said valve inlet includes a filter to remove impurities from air that passes through said valve inlet and enters said valve inlet chamber.

20. The automatic inlet control mechanism of claim 13 wherein said valve piston assembly includes a valve stem and a sliding seal mounted to reciprocate along at least a portion of said valve stem to contact said valve outlet to cause said valve piston assembly to prevent air from flowing from said valve inlet chamber through said valve outlet when the compressor unit is not drawing air through said valve outlet, the movement of said valve piston assembly away from the position at which said valve piston assembly prevents air from flowing from said valve inlet chamber and through said valve outlet to the compression cylinder inlet causing said sliding seal to move away from said valve outlet to allow air to flow to the compression cylinder inlet, said valve inlet including a filter to remove impurities from air that passes through said valve inlet and enters said valve inlet chamber.

21. The automatic inlet control mechanism of claim 13 wherein the compression cylinder inlet includes a cylinder inlet chamber for receiving air before the air from the compression cylinder inlet enters the compression cylinder, said automatic inlet control mechanism being located at least partially within the cylinder inlet chamber.

22. The automatic inlet control mechanism of claim 13 wherein:
the compression cylinder inlet includes a cylinder inlet chamber for receiving air before the air from the compression cylinder inlet enters the compression cylinder, said automatic inlet control mechanism being located at least partially within the cylinder inlet chamber; and
said valve piston assembly includes a valve stem and a sliding seal mounted to reciprocate along at least a portion of said valve stem to contact said valve outlet to cause said valve piston assembly to prevent air from flowing from said valve inlet chamber through said valve outlet when the compressor unit is not drawing air through said valve outlet, the movement of said valve piston assembly away from the position at which said valve piston assembly prevents air from flowing from said valve inlet chamber and through said valve outlet to the compression cylinder inlet causing said sliding seal to move away from said valve outlet to allow air to flow to the compression cylinder inlet.

23. An automatic inlet control mechanism for connection to a compression cylinder inlet of a reciprocating air compressor unit which produces compressed air at a predetermined rate of production through the use of a piston that reciprocates within a compression cylinder, said inlet control mechanism comprising:
a mechanism body having a valve cavity, said valve cavity having a valve control chamber and a valve inlet chamber, a valve piston assembly positioned between said valve control chamber and said valve inlet chamber and constructed to prevent air flow between said valve control chamber and said valve inlet chamber, said valve piston assembly including a diaphragm positioned between said valve control chamber and said valve inlet chamber, said diaphragm being constructed to prevent air flow between said valve control chamber and said valve inlet chamber, said diaphragm being positioned to move toward said valve control chamber when air pressure within said valve inlet chamber is greater than air pressure within said valve control chamber, said diaphragm being positioned to move toward said valve inlet chamber when air pressure within said valve control chamber is greater than the air pressure within said valve inlet chamber;
a valve inlet positioned to allow air to flow from the atmosphere surrounding the compressor unit and into said valve inlet chamber;
a valve outlet having a valve outlet hole positioned to allow air to flow from said valve inlet chamber to the compression cylinder inlet, said valve outlet hole having a size sufficient to enable the compressor unit to produce compressed air at its predetermined rate of production;
a valve piston and a valve stem included in said valve piston assembly, said valve piston assembly being positioned to reciprocate within said valve cavity, a biasing member having a force which moves said valve piston assembly to a position within said inlet control mechanism which prevents air from flowing from said valve inlet chamber through said valve outlet when the compressor unit is not drawing air through said valve outlet;
a vent passageway included in said valve piston assembly, said vent passageway allowing air to flow between said valve control chamber and the compression cylinder inlet;

said vent passageway comprising at least one source of air to the compression cylinder inlet for a period of time after the compressor unit begins to draw air through the compression cylinder inlet, following the movement of said valve piston assembly to a position which prevents air from flowing from said valve inlet chamber through said valve outlet to the compression cylinder inlet;
a valve outlet hole having a tapered portion included in said valve outlet, said tapered portion having a first inner diameter and a second inner diameter, said first inner diameter of said tapered portion being larger than said second inner diameter and being located at a position that is closer to said valve inlet chamber than said second inner diameter when said inlet control mechanism is installed, said second inner diameter being sufficiently small to form an air restriction against said valve piston assembly when said valve piston assembly is at a position within said inlet control mechanism which prevents air from flowing from said valve inlet chamber through said valve outlet, said first inner diameter of said tapered portion being sufficiently large to allow air to pass between said tapered portion of said valve outlet hole and said valve piston assembly when said valve piston assembly is at a position within said inlet control mechanism which allows air to flow from said valve inlet chamber through said valve outlet;
said vent passageway including a vent orifice which restricts the flow of air from said valve control chamber to said compression cylinder inlet; and
said vent orifice having an orifice size which allows air to be drawn by the compressor unit from said valve control chamber to the compression cylinder at a preselected rate which causes the compressor unit to produce compressed air at less than its predetennined rate of production, said valve control chamber having a volume which enables air to be drawn through said orifice from said valve control chamber by the compressor unit over a preselected time period until air within said valve control chamber is at a reduced pressure level which enables atmospheric pressure on the valve piston assembly from within the valve inlet chamber to overcome the force of said biasing member sufficiently to move said valve piston assembly away from the position at which said valve piston assembly prevents air from flowing from said valve inlet chamber through said valve outlet to enable the compressor unit to produce compressed air at its predetermined rate of production.

24. The automatic inlet control mechanism of claim 23 wherein said valve piston assembly includes a valve stem and a sliding seal mounted to reciprocate along at least a portion of said valve stem to contact said valve outlet to cause said valve piston assembly to prevent air from flowing from said valve inlet chamber through said valve outlet when the compressor unit is not drawing air through said valve outlet, the movement of said valve piston assembly away from the position at which said valve piston assembly prevents air from flowing from said valve inlet chamber and through said valve outlet to the compression cylinder inlet causing said sliding seal to move away from said valve outlet to allow air to flow to the compression cylinder inlet.

25. The automatic inlet control mechanism of claim 23 wherein said valve inlet includes a filter to remove impurities from air that passes through said valve inlet and enters said valve inlet chamber.

26. The automatic inlet control mechanism of claim 23 wherein said valve piston assembly includes a valve stem and a sliding seal mounted to reciprocate along at least a portion of said valve stem to contact said valve outlet to cause said valve piston assembly to prevent air from flowing from said valve inlet chamber through said valve outlet when the compressor unit is not drawing air through said valve outlet, the movement of said valve piston assembly away from the position at which said valve piston assembly prevents air from flowing from said valve inlet chamber and through said valve outlet to the compression cylinder inlet causing said sliding seal to move away from said valve outlet to allow air to flow to the compression cylinder inlet, said valve inlet including a filter to remove impurities from air that passes through said valve inlet and enters said valve inlet chamber.

27. An automatic inlet control mechanism for connection to a compression cylinder inlet of a reciprocating air compressor unit which produces compressed air at a predetermined rate of production through the use of a piston that reciprocates within a compression cylinder, said inlet control mechanism comprising:
a mechanism body having a valve cavity, said valve cavity having a valve control chamber and a valve inlet chamber, a valve piston assembly positioned between said valve control chamber and said valve inlet chamber and constructed to prevent air flow between said valve control chamber and said valve inlet chamber, said valve piston assembly including a diaphragm positioned between said valve control chamber and said valve inlet chamber, said diaphragm being constructed to prevent air flow between said valve control chamber and said valve inlet chamber, said diaphragm being positioned to move toward said valve control chamber when air pressure within said valve inlet chamber is greater than air pressure within said valve control chamber, said diaphragm being positioned to move toward said valve inlet chamber when air pressure within said valve control chamber is greater than the air pressure within said valve inlet chamber;
a valve inlet positioned to allow air to flow from the atmosphere surrounding the compressor unit and into said valve inlet chamber;
a valve outlet having a valve outlet hole positioned to allow air to flow from said valve inlet chamber to the compression cylinder inlet, said valve outlet hole having a size sufficient to enable the compressor unit to produce compressed air at its predetermined rate of production;
a valve piston and a valve stem included in said valve piston assembly, said valve piston assembly being positioned to reciprocate within said valve cavity, a biasing member having a force which moves said valve piston assembly to a position within said inlet control mechanism which prevents air from flowing from said valve inlet chamber through said valve outlet when the compressor unit is not drawing air through said valve outlet;
a vent passageway included in said valve piston assembly, said vent passageway allowing air to flow between said valve control chamber and the compression cylinder inlet;
said vent passageway comprising the primary source of air to the compression cylinder inlet for a period of time after the compressor unit begins to draw air through the compression cylinder inlet, following the movement of said valve piston assembly to a position which prevents air from flowing from said valve inlet chamber through said valve outlet to the compression cylinder inlet;
a valve outlet hole having a tapered portion included in said valve outlet, said tapered portion having a first inner diameter and a second inner diameter, said first inner diameter of said tapered portion being larger than said second inner diameter and being located at a position that is closer to said valve inlet chamber than said second inner diameter when said inlet control mechanism is installed, said second inner diameter being sufficiently small to form an air restriction against said valve piston assembly when said valve piston assembly is at a position within said inlet control mechanism which prevents air from flowing from said valve inlet chamber through said valve outlet, said first inner diameter of said tapered portion being sufficiently large to allow air to pass between said tapered portion of said valve outlet hole and said valve piston assembly when said valve piston assembly is at a position within said inlet control mechanism which allows air to flow from said valve inlet chamber through said valve outlet;
said vent passageway including a vent orifice which restricts the flow of air from said valve control chamber to said compression cylinder inlet; and
said vent orifice having an orifice size which allows air to be drawn by the compressor unit from said valve control chamber to the compression cylinder at a preselected rate which causes the compressor unit to produce compressed air at less than its predetermined rate of production, said valve control chamber having a volume which enables air to be drawn through said orifice from said valve control chamber by the compressor unit over a preselected time period until air within said valve control chamber is at a reduced pressure level which enables atmospheric pressure on the valve piston assembly from within the valve inlet chamber to overcome the force of said biasing member sufficiently to move said valve piston assembly away from the position at which said valve piston assembly prevents air from flowing from said valve inlet chamber through said valve outlet to enable the compressor unit to produce compressed air at its predetermined rate of production.

28. The automatic inlet control mechanism of claim 27 wherein said valve piston assembly includes a valve stem and a sliding seal mounted to reciprocate along at least a portion of said valve stem to contact said valve outlet to cause said valve piston assembly to prevent air from flowing from said valve inlet chamber through said valve outlet when the compressor unit is not drawing air through said valve outlet, the movement of said valve piston assembly away from the position at which said valve piston assembly prevents air from flowing from said valve inlet chamber and through said valve outlet to the compression cylinder inlet causing said sliding seal to move away from said valve outlet to allow air to flow to the compression cylinder inlet.

29. The automatic inlet control mechanism of claim 27 wherein said valve inlet includes a filter to remove impurities from air that passes through said valve inlet and enters said valve inlet chamber.

30. The automatic inlet control mechanism of claim 27 wherein said valve piston assembly includes a valve stem and a sliding seal mounted to reciprocate along at least a portion of said valve stem to contact said valve outlet to cause said valve piston assembly to prevent air from flowing from said valve inlet chamber through said valve outlet when the compressor unit is not drawing air through said valve outlet, the movement of said valve piston assembly away from the position at which said valve piston assembly prevents air from flowing from said valve inlet chamber and through said valve outlet to the compression cylinder inlet causing said sliding seal to move away from said valve outlet to allow air to flow to the compression cylinder inlet, said valve inlet including a filter to remove impurities from air that passes through said valve inlet and enters said valve inlet chamber.

31. A reciprocating air compressor unit which produces compressed air at a predetermined rate of production through the use of a piston that reciprocates within a compression cylinder, said air compressor unit comprising:
an automatic inlet control mechanism for connection to said compression cylinder inlet, said automatic inlet control having a mechanism body having a valve cavity, said valve cavity having a valve control chamber and a valve inlet chamber, a valve piston assembly positioned between said valve control chamber and said valve inlet chamber and constructed to prevent air flow between said valve control chamber and said valve inlet chamber;
a valve inlet positioned to allow air to flow from the atmosphere surrounding said compressor unit and into said valve inlet chamber;
a valve outlet having a valve outlet hole positioned to allow air to flow from said valve inlet chamber to said compression cylinder inlet, said valve outlet hole having a size sufficient to enable said compressor unit to produce compressed air at its predetermined rate of production;
said valve piston assembly including a valve piston and a valve stem, said valve piston assembly being positioned to reciprocate within said valve cavity, a biasing member having a force which moves said valve piston assembly to a position within said inlet control mechanism which prevents air from flowing from said valve inlet chamber through said valve outlet when said compressor unit is not drawing air through said valve outlet;
a vent passageway allowing air to flow between said valve control chamber and said compression cylinder inlet; said vent passageway comprising at least one source of air to said compression cylinder inlet for a period of time after said compressor unit begins to draw air though said compression cylinder inlet, following the movement of said valve piston assembly to a position which prevents air from flowing from said valve inlet chamber though said valve outlet to the compression cylinder inlet;
said vent passageway including a vent orifice which restricts the flow of air from said valve control chamber to said compression cylinder inlet; and said vent orifice having an orifice size which allows air to be drawn, by the compressor unit, from said valve control chamber to said compression cylinder at a preselected rate which causes said compressor unit to produce compressed air at less than its predetermined rate of production, said valve control chamber having a volume which enables air to be drawn though said orifice from said valve control chamber by said compressor unit over a preselected time period until air within said valve control chamber is at a reduced pressure level which enables atmospheric pressure on said valve piston assembly from within said valve inlet chamber to overcome the force of said biasing member sufficiently to move said valve piston assembly away from said position at which said valve piston assembly prevents air from flowing from said valve inlet chamber and through said valve outlet to said compression cylinder inlet enable said compressor unit to produce compressed air at its predetermined rate of production.

32. The reciprocating air compressor unit of claim 31 wherein said valve piston assembly includes a diaphragm positioned between said valve control chamber and said valve inlet chamber, said diaphagm being constructed to prevent air flow between said valve control chamber and said valve inlet chamber, said diaphragm being positioned to move toward said valve control chamber when air pressure within said valve inlet chamber is greater than air pressure within said valve control chamber, said diaphragm being positioned to move toward said valve inlet chamber when air pressure within said valve control chamber is greater than the air pressure within said valve inlet chamber.

33. The reciprocating air compressor unit of claim 31 wherein said vent passageway is included within said valve piston assembly, said vent orifice being located at a position in said valve piston assembly to enable said vent orifice to restrict the flow of air from said valve control chamber to said compression cylinder inlet as said valve piston assembly reciprocates within said inlet control mechanism.

34. The reciprocating air compressor unit of claim 31 wherein said valve piston assembly includes a valve stem, said vent passageway is included within said valve piston assembly and extends through said valve stem, said vent orifice being located at a position in said piston assembly to enable said vent orifice to restrict the flow of air from said valve control chamber to said compression cylinder inlet as said piston assembly reciprocates within said inlet control mechanism.

35. The reciprocating air compressor unit of claim 31 wherein said valve outlet includes a valve outlet hole having a tapered portion, said tapered portion having at least a first inner diameter and a second inner diameter, said first inner diameter of said tapered portion being larger than said second inner diameter and being located at a position that is closer to said valve inlet chamber than said second inner diameter, said second inner diameter being sufficiently small to form an air restriction against said valve piston assembly when said valve piston assembly is at a position within said inlet control mechanism which prevents air from flowing from said valve inlet chamber through said valve outlet, said first inner diameter of said tapered portion being sufficiently large to allow air to pass between said tapered portion of said valve outlet and said valve piston assembly when said valve piston assembly is at a position within said inlet control mechanism which allows air to flow from said valve inlet chamber through said valve outlet.

36. The reciprocating air compressor unit of claim 31 wherein said valve piston assembly includes a valve stem and a sliding seal mounted to reciprocate along at least a portion of said valve stem to contact said valve outlet to cause said valve piston assembly to prevent air from flowing from said valve inlet chamber through said valve outlet when the compressor unit is not drawing air through said valve outlet, the movement of said valve piston assembly away from the position at which said valve piston assembly prevents air from flowing from said valve inlet chamber and through said valve outlet to said compression cylinder inlet causing said sliding seal to move away from said valve outlet to allow air to flow to said compression cylinder inlet.

37. The reciprocating air compressor unit of claim 31 wherein said valve inlet includes a filter to remove impurities from air that passes through said valve inlet and enters said valve inlet chamber.

38. The reciprocating air compressor unit of claim 31 wherein said valve piston assembly includes a valve stem and a sliding seal mounted to reciprocate along at least a portion of said valve stem to contact said valve outlet to cause said valve piston assembly to prevent air from flowing from said valve inlet chamber through said valve outlet when the compressor unit is not drawing air through said valve outlet, the movement of said valve piston assembly away from the position at which said valve piston assembly prevents air from flowing from said valve inlet chamber and through said valve outlet to said compression cylinder inlet causing said sliding seal to move away from said valve outlet to allow air to flow to said compression cylinder inlet, said valve inlet including a filter to remove impurities from air that passes through said valve inlet and enters said valve inlet chamber.

39. The reciprocating air compressor unit of claim 31 wherein said compression cylinder inlet includes a cylinder inlet chamber for receiving air before the air from said compression cylinder inlet enters said compression cylinder, said automatic inlet control mechanism being located at least partially within said cylinder inlet chamber.

40. The reciprocating air compressor unit of claim 31 wherein:
said compression cylinder inlet includes a cylinder inlet chamber for receiving air before the air from said compression cylinder inlet enters said compression cylinder, said automatic inlet control mechanism being located at least partially within said cylinder inlet chamber; and
said valve piston assembly includes a valve stem and a sliding seal mounted to reciprocate along at least a portion of said valve stem to contact said valve outlet to cause said valve piston assembly to prevent air from flowing from said valve inlet chamber through said valve outlet when the compressor unit is not drawing air through said valve outlet, the movement of said valve piston assembly away from the position at which said valve piston assembly prevents air from flowing from said valve inlet chamber and through said valve outlet to the compression cylinder inlet causing said sliding seal to move away from said valve outlet to allow air to flow to said compression cylinder inlet.

41. A reciprocating air compressor unit which produces compressed air at a predetermined rate of production through the use of a piston that reciprocates within a compression cylinder, said air compressor unit comprising:
an automatic inlet control mechanism for connection to said compression cylinder inlet, said automatic inlet control having a mechanism body having a valve cavity, said valve cavity having a valve control chamber and a valve inlet chamber, a valve piston assembly positioned between said valve control chamber and said valve inlet chamber and constructed to prevent air flow between said valve control chamber and said valve inlet chamber;
a valve inlet positioned to allow air to flow from the atmosphere surrounding said compressor unit and into said valve inlet chamber;
a valve outlet having a valve outlet hole positioned to allow air to flow from said valve inlet chamber to said compression cylinder inlet, said valve outlet hole having a size sufficient to enable said compressor unit to produce compressed air at its predetermined rate of production;
said valve piston assembly including a valve piston and a valve stem, said valve piston assembly being positioned to reciprocate within said valve cavity, a biasing member having a force which moves said valve piston assembly to a position within said inlet control mechanism which prevents air from flowing from said valve inlet chamber through said valve outlet when said compressor unit is not drawing air through said valve outlet;
a vent passageway allowing air to flow between said valve control chamber and said compression cylinder inlet; said vent passageway comprising the primary source of air to said compression cylinder inlet for a period of time after said compressor unit begins to draw air through said compression cylinder inlet following the movement of said valve piston assembly to a position which prevents air from flowing from said valve inlet chamber through said valve outlet to the compression cylinder inlet;
said vent passageway including a vent orifice which restricts the flow of air from said valve control chamber to said compression cylinder inlet; and said vent orifice having an orifice size which allows air to be drawn, by the compressor unit, from said valve control chamber to said compression cylinder at a preselected rate which causes said compressor unit to produce compressed air at less than its predetermined rate of production, said valve control chamber having a volume which enables air to be drawn through said orifice from said valve control chamber by said compressor unit over a preselected time period until air within said valve control chamber is at a reduced pressure level which enables atmospheric pressure on said valve piston assembly from within said valve inlet chamber to overcome the force of said biasing member sufficiently to move said valve piston assembly away from said position at which said valve piston assembly prevents air from flowing from said valve inlet chamber and through said valve outlet to said compression cylinder inlet to enable said compressor unit to produce compressed air at its predetermined rate of production.

42. The reciprocating air compressor unit of claim 41 wherein said valve piston assembly includes a diaphragm positioned between said valve control chamber and said valve inlet chamber, said diaphragm being constructed to prevent air flow between said valve control chamber and said valve inlet chamber, said diaphragm being positioned to move toward said valve control chamber when air pressure within said valve inlet chamber is greater than air pressure within said valve control chamber, said diaphragm being positioned to move toward said valve inlet chamber when air pressure within said valve control chamber is greater than the air pressure within said valve inlet chamber.

43. The reciprocating air compressor unit of claim 41 wherein said vent passageway is included within said valve piston assembly, said vent orifice being located at a position in said valve piston assembly to enable said vent orifice to restrict the flow of air from said valve control chamber to said compression cylinder inlet as said valve piston assembly reciprocates within said inlet control mechanism.

44. The reciprocating air compressor unit of claim 41 wherein said valve piston assembly includes a valve stem, said vent passageway is included within said valve piston assembly and extends through said valve stem, said vent orifice being located at a position in said piston assembly to enable said vent orifice to restrict the flow of air from said valve control chamber to said compression cylinder inlet as said piston assembly reciprocates within said inlet control mechanism.

45. The reciprocating air compressor unit of claim 41 wherein said valve outlet includes a valve outlet hole having a tapered portion, said tapered portion having at least a first inner diameter and a second inner diameter, said first inner diameter of said tapered portion being larger than said second inner diameter and being located at a position that is closer to said valve inlet chamber than said second inner diameter, said second inner diameter being sufficiently small to form an air restriction against said valve piston assembly when said valve piston assembly is at a position within said inlet control mechanism which prevents air from flowing from said valve inlet chamber through said valve outlet, said first inner diameter of said tapered portion being sufficiently large to allow air to pass between said tapered portion of said valve outlet and said valve piston assembly when said valve piston assembly is at a position within said inlet control mechanism which allows air to flow from said valve inlet chamber through said valve outlet.

46. The reciprocating air compressor unit of claim 41 wherein said valve piston assembly includes a valve stem and a sliding seal mounted to reciprocate along at least a portion of said valve stem to contact said valve outlet to cause said valve piston assembly to prevent air from flowing from said valve inlet chamber through said valve outlet when the compressor unit is not drawing air through said valve outlet, the movement of said valve piston assembly away from the position at which said valve piston assembly prevents air from flowing from said valve inlet chamber and through said valve outlet to said compression cylinder inlet causing said sliding seal to move away from said valve outlet to allow air to flow to said compression cylinder inlet.

47. The reciprocating air compressor unit of claim 41 wherein said valve inlet includes a filter to remove impurities from air that passes through said valve inlet and enters said valve inlet chamber.

48. The reciprocating air compressor unit of claim 41 wherein said valve piston assembly includes a valve stem and a sliding seal mounted to reciprocate along at least a portion of said valve stem to contact said valve outlet to cause said valve piston assembly to prevent air from flowing from said valve inlet chamber through said valve outlet when the compressor unit is not drawing air through said valve outlet, the movement of said valve piston assembly away from the position at which said valve piston assembly prevents air from flowing from said valve inlet chamber and through said valve outlet to said compression cylinder inlet causing said sliding seal to move away from said valve outlet to allow air to flow to said compression cylinder inlet, said valve inlet including a filter to remove impurities from air that passes through said valve inlet and enters said valve inlet chamber.

49. The reciprocating air compressor unit of claim 41 wherein said compression cylinder inlet includes a cylinder inlet chamber for receiving air before the air from said compression cylinder inlet enters said compression cylinder, said automatic inlet control mechanism being located at least partially within said cylinder inlet chamber.

50. The reciprocating air compressor unit of claim 41 wherein:
said compression cylinder inlet includes a cylinder inlet chamber for receiving air before the air from said compression cylinder inlet enters said compression cylinder, said automatic inlet control mechanism being located at least partially within said cylinder inlet chamber; and
said valve piston assembly includes a valve stem and a sliding seal mounted to reciprocate along at least a portion of said valve stem to contact said valve outlet to cause said valve piston assembly to prevent air from flowing from said valve inlet chamber through said valve outlet when the compressor unit is not drawing air through said valve outlet, the movement of said valve piston assembly away from the position at which said valve piston assembly prevents air from flowing from said valve inlet chamber and through said valve outlet to the compression cylinder inlet causing said sliding seal to move away from said valve outlet to allow air to flow to said compression cylinder inlet.

51. A reciprocating air compressor unit which produces compressed air at a predetermined rate of production, said reciprocating air compressor unit comprising:
an automatic inlet control mechanism including a mechanism body having a valve cavity, said valve cavity having a valve control chamber and a valve inlet chamber, a valve piston assembly positioned between said valve control chamber and said valve inlet chamber and constructed to prevent air flow between said valve control chamber and said valve inlet chamber, said valve piston assembly including a diaphragm positioned between said valve control chamber and said valve inlet chamber, said diaphragm being constructed to prevent air flow between said valve control chamber and said valve inlet chamber, said diaphragm being positioned to move toward said valve control chamber when air pressure within said valve inlet chamber is greater than air pressure within said valve control chamber, said diaphragm being positioned to move toward said valve inlet chamber when air pressure within said valve control chamber is greater than the air pressure within said valve inlet chamber;
a valve inlet positioned to allow air to flow from the atmosphere surrounding said compressor unit and into said valve inlet chamber;
a valve outlet having a valve outlet hole positioned to allow air to flow from said valve inlet chamber to said compression cylinder inlet, said valve outlet hole having a size sufficient to enable said compressor unit to produce compressed air at its predetermined rate of production;
a valve piston and a valve stem included in said valve piston assembly, said valve piston assembly being positioned to reciprocate within said valve cavity, a biasing member having a force which moves said valve piston assembly to a position within said mechanism body which prevents air from flowing from said valve inlet chamber to said valve outlet when the compressor unit is not drawing air through said valve outlet;
a vent passageway included in said valve piston assembly, said vent passageway allowing air to flow between said valve control chamber and said compression cylinder inlet;
said vent passageway comprising the primary source of air to the compression cylinder inlet for a period of time after the compressor unit begins to draw air through said compression cylinder inlet following the movement of said valve piston assembly to a position which prevents air from flowing from said valve inlet chamber through said valve outlet;.
a valve outlet hole having a tapered portion included in said valve outlet, said tapered portion having a first inner diameter and a second inner diameter, said first inner diameter being larger than said second inner diameter, said first inner diameter of said tapered portion being located at a position that is closer to said valve inlet chamber than said second inner diameter of said tapered portion, said second inner diameter of said tapered portion being sufficiently small to form an air restriction against said valve piston assembly when said valve piston assembly is at a position within said mechanism body which prevents air from flowing from said valve inlet chamber through said valve outlet, said first inner diameter of said tapered portion being sufficiently large to allow air to pass between said tapered portion of said valve outlet hole and said valve piston assembly when said valve piston assembly is at a position within said mechanism body which allows air to flow from said valve inlet chamber through said valve outlet;
said vent passageway including a vent orifice which restricts the flow of air from said valve control chamber to said compression cylinder inlet; and
said vent orifice having an orifice size which allows air to be drawn by said compressor unit from said valve control chamber to said compression cylinder at a preselected rate which causes the compressor unit to produce compressed air at less than its predetermined rate of production, said valve control chamber having a volume which enables air to be drawn through said orifice from said valve control chamber by said compressor unit over a preselected time period until air within said valve control chamber is at a reduced pressure level which enables atmospheric pressure on the valve piston assembly from within said valve inlet chamber to overcome the force of said biasing member sufficiently to move said valve piston assembly away from the position at which said valve piston assembly prevents air from flowing from said valve inlet chamber through said valve outlet to enable said compressor unit to produce compressed air at its predetermined rate of production.

52. The reciprocating air compressor unit of claim 51 wherein said valve piston assembly includes a sliding seal mounted to reciprocate along at least a portion of said valve stem to contact said valve outlet to cause said valve piston assembly to prevent air from flowing from said valve inlet chamber through said valve outlet when said compressor unit is not drawing air through said valve outlet, the movement of said valve piston assembly away from the position at which said valve piston assembly prevents air from flowing from said valve inlet chamber and through said valve outlet to said compression cylinder inlet causing said sliding seal to move away from said valve outlet to allow air to flow to said compression cylinder inlet.

53. The reciprocating air compressor unit of claim 51 wherein said valve inlet includes a filter to remove impurities from air that passes through said valve inlet and enters said valve inlet chamber.

54. The reciprocating air compressor unit of claim 51 wherein said valve piston assembly includes a sliding seal mounted to reciprocate along at least a portion of said valve stem to contact said valve outlet to cause said valve piston assembly to prevent air from flowing from said valve inlet chamber through said valve outlet when said air compressor unit is not drawing air through said valve outlet, the movement of said valve piston assembly away from the position at which said valve piston assembly prevents air from flowing from said valve inlet chamber and through said valve outlet to said compression cylinder inlet causing said sliding seal to move away from said valve outlet to allow air to flow to said compression cylinder inlet, said valve inlet including a filter to remove impurities from air that passes through said valve inlet and enters said valve inlet chamber.