Proportional control value

A proportional control valve has inlet and outlet solenoids controlling the pressurization and evacuation of a chamber between two pistons in a control valve of the rack and pinion opposed-piston type. The control valve can be maintained in fully open, fully closed, or intermediate positions by selectively energizing and de-energizing the solenoids. The solenoids can be of the normally open or normally closed solenoid poppet types depending on whether the control valve is to open, close or maintain its current state in the event of a power failure.

BACKGROUND OF THE INVENTION 
This invention relates to a proportional control valve for operating a 
larger main valve. More specifically, the invention provides for opening 
or closing a control valve in varying degrees and maintaining the control 
valve in a fixed partially open state, in addition to being able to fully 
open and fully close the control valve. 
It is known in the art to open and close a main valve by mounting, on its 
actuator, a control valve of the rack and pinion opposed-piston type. In 
such control valves, each of two pistons is provided with a rack that 
engages one or more coaxially mounted pinion gears. As the pistons are 
translated away from one another, their racks rotate the pinion gears in 
one direction. As the pistons approach one another they rotate the pinion 
gear in the opposite direction. An example of such a control valve is sold 
under the logo Dynamite F-790. 
Movement of the pistons is accomplished by applying positive air pressure 
to a space between the pistons to force them apart while relieving the 
pressure outside the region between the pistons. Conversely, the pistons 
can be forced to move toward one another by relieving the pressure between 
them and increasing the pressure in the region outside the space between 
the pistons. 
Prior art control valves are operated in a fully open or fully close state 
depending upon whether the chamber between the pistons is pressurized or 
evacuated. Such prior art control valves cannot reliably be used to 
partially open a main valve to a predetermined degree and maintain the 
degree of openness once achieved. 
SUMMARY OF THE INVENTION 
The aforementioned problems of the prior art are overcome by the instant 
invention which provides for a control valve for fully opening or closing 
a main valve or maintaining the main valve in a partially open state by 
employing two solenoids to control the inlet and outlet of pressurized air 
to and from a chamber between the pistons in a rack and pinion 
opposed-piston control valve. One of the solenoids is an inlet solenoid 
which can be opened to allow pressurized air from a pressure source to 
enter the region between the pistons, and closed to interrupt the 
application of pressurized air to the region between the pistons. 
The other of the solenoids is an outlet or exhaust solenoid which can be 
opened to allow pressurized air in the region between the pistons to 
escape, and closed to entrap pressurized air in the chamber between the 
pistons in order to prevent the valve from closing further. 
Two partially compressed main springs, one provided between each piston and 
the wall of the housing in which the pistons are slidably mounted, urge 
the pistons toward one another. 
It is therefore an object of the invention to provide a proportional 
control valve of the rack and pinion opposed-piston type wherein the 
control valve can be operated in fully open, fully closed and at fixed 
partially open states. 
Another object of the invention is to provide a proportional control valve 
which can be maintained in a partially opened state without application of 
external energy to the valve. 
Still another object of the invention is to provide a proportional control 
valve which can be controlled by two solenoids each of which need only be 
operated in a fully open or fully closed disposition for operating the 
control valve in a fully open, fully closed or partially open state. 
A further object of the invention is to provide a proportional control 
valve which can respond to a power outage by automatically closing, 
opening or maintaining its current state at the time of the outage. 
Other and further objects of the invention will be apparent from the 
following drawings and description of a preferred embodiment of the 
invention in which like reference numerals are used to indicate like parts 
in the various views.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to FIG. 1 of the drawings there is shown a proportional 
control valve 1 having a housing 3 in which there is disposed a central 
rotatable shaft connectable to the shaft of a main valve to be controlled. 
Mounted on and integral with the central shaft of the control valve 1 is a 
pinion gear 5 having teeth 7 meshing with the teeth 9 of a first rack 11 
connected to a first piston 15 and teeth 10 of a parallel second rack 13 
connected to a second piston 17. The pistons 15, 17 are slidably snugly 
mounted in a cylinder 19 within the housing 3. The interior of the housing 
cylinder 19 is divided into three chambers, one interior chamber 18 
between the two pistons 15, 17 and a respective exterior chamber 21, 23 
between each one the two pistons 15, 17 and a corresponding cylinder end 
wall 20, 22. Each of the pistons 15, 17 is surrounded with a 
circumferential seal 25, 27 to prevent leakage between the three chambers 
18, 21, 23. Disposed within each of the external chambers 21, 23 is a 
compressed main coil spring 29, 31 which urges its respective piston 
toward the other piston. 
Within an outer cylindrical wall 33 of the housing 3, in communication with 
the interior chamber 18, there is an opening 37 for introduction of air 
under positive pressure into the interior chamber 18 and evacuation of air 
from within the interior chamber 18 to the outside of the housing 3. An 
opening 39 is also provided within the outer cylindrical wall 33 of the 
housing 3 for bleeding air from chambers 21 and 23 when the springs 29 and 
30 are compressed and for admitting air into chambers 21 and 23 when the 
springs 29 and 30 expand. 
Mounted over the openings 37 and 39 within the control valve housing wall 
33 is a valve body 41 having a bore 43a leading from the opening in a 
valve seat 47 to a chamber surrounding a valve seat 57 which is in fluid 
communication with an air outlet port (not shown) through which air 
exiting the chamber 18, between the pistons 15, 17, can be exhausted to 
the atmosphere as will be hereinafter explained. Also formed in the valve 
body 41 is a bore 43b leading from the chamber surrounding the valve seat 
57 to the opening 37 which is in fluid communication with the interior 
chamber 18. A bore 45 in communication with an exhaust port (not shown) 
within the valve body 41, provides a bleed channel leading from the 
opening 39 which is in fluid communication with chambers 21 and 23, and a 
path for expelling air which passes through the opening in the valve seat 
57 when an outlet solenoid 59 is open. 
A normally closed inlet solenoid 49 has a plunger 48 made of ferromagnetic 
material which can be selectively attracted toward a pole piece or plug 
nut 46 surrounded by a coil winding 44 for exposing the opening in the 
valve seat 47 as will be known to those skilled in the art. An electrical 
current can be applied to the winding 44 for selectively opening and 
sealing the opening in the valve seat 47 in order to achieve a desired 
position for the control valve shaft as will be explained below. A bias 
spring 42 urges the plunger 48 toward its closed position for causing a 
resilient member 40 mounted on the end of the plunger 48 distal from the 
plug nut 46 to engage and seal the opening in the valve seat 47 controlled 
by the solenoid 49 when the solenoid 49 is not energized. 
An air inlet port (not shown) is in fluid communication with a chamber 
surrounding the valve seat 47. A source of pressurized air is connected to 
the inlet port for creating a pressure drop across the opening in the 
valve seat 47 when the inlet solenoid 49 is opened, i.e., when it is 
energized, at which time the magnetic force exerted by the plug nut 46 
lifts the valve member 40 away from the valve seat 47 thereby enabling air 
from the source to flow through the opening in the valve seat 47, through 
bore 43a, into the chamber surrounding valve seat 57, through bore 43b 
and, through the opening 37, into the interior pressure chamber 18 between 
the pistons 15 and 17. The resulting increase in pressure within the 
interior chamber 18 urges the pistons 15 and 17 apart so that the interior 
chamber 18 enlarges and the exterior chambers 21, 23 are reduced, thereby 
causing the racks 11, 13 to rotate the pinion 5 in a counterclockwise 
direction as viewed in the drawings. As the pistons 15 and 17 move apart, 
air can be bled from the chambers 21 and 23 through the opening 39 and 
channel 45 and out the exhaust port. 
The opening in the valve seat 57 is selectively opened and sealed under the 
control of the outlet solenoid 59. The outlet solenoid 59 is a normally 
open solenoid. It has a plunger 58 made of ferromagnetic material which 
can be selectively attracted toward a pole piece or plug nut 56 surrounded 
by a coil winding 54. An electrical current can be applied to the winding 
54 for selectively exposing and sealing the opening in the valve seat 57 
in order to achieve a desired position for the control valve shaft in 
cooperation with the inlet solenoid 49 as will be explained below. A bias 
spring 52 urges the plunger 58 toward an open position for urging a 
resilient main valve member 50 mounted on the end of the plunger 58 away 
from the outlet opening in the valve seat 57. Air can then be evacuated 
from the chamber 18 following a path through the opening 37, channel 43b, 
and the opening in the valve seat 57 which is controlled by the outlet 
solenoid 59, and out through the exhaust port (See FIG. 3). The resulting 
decrease in pressure within the interior chamber 18 allows the main 
springs 29, 31 to urge the pistons 15, 17 toward one another thereby 
causing them to rotate the pinion 5 in a clockwise direction as viewed in 
the drawings. 
When the normally open outlet solenoid 59 is energized, the plunger 58 
moves the member 50 toward and into sealing engagement with the opening 57 
thereby preventing air under pressure in the interior chamber 18 between 
the pistons 15, 17 from being evacuated to the outside of the housing 3. 
Referring now specifically to FIG. 1 of the drawings, the proportional 
control valve 1 of the invention is shown just as it is reaching its fully 
open state. The normally closed inlet solenoid 49 has been opened to admit 
pressurized air into the interior chamber 18 between the pistons 15, 17 to 
force them apart. At the same time, the normally open outlet solenoid has 
been closed to prevent evacuation of the air from the interior chamber 18. 
The pressure of the air in the interior chamber 18 applies to the pistons 
15, 17 a force greater than the return force of the main springs 29, 31 
thereby causing the main springs 29, 31 to be compressed as the pistons 
15, 17 reach the outer limit of their travel. As the pistons 15, 17 travel 
toward their maximum open position, the rack attached to each piston 
rotates the pinion 5 which is mounted on the control valve shaft, thereby 
turning the control valve shaft to its fully open position. The main valve 
has a shaft coupled to the control valve shaft and is, hence, also fully 
opened. 
The present invention also provides for the control valve 1 and, hence the 
main valve, to be fixed in a partially opened position as can be seen in 
FIG. 2. There, while the control valve 1 is in a partially open 
disposition intermediate fully opened and fully closed, the inlet solenoid 
49 is deenergized and the outlet or exhaust valve 59 is energized so that 
both solenoids, 49, 59 are closed. With both solenoids closed, the volume 
of air in the interior chamber 18 and the pressure exerted on the pistons 
15, 17 is constant, that is, air can neither enter into nor escape from 
the interior chamber 18. At this time the forces exerted by the main 
springs 29, 31 which urge the pistons 15, 17 toward one another and the 
resisting force exerted by the air in the interior chamber 18 are in 
equilibrium. 
When it is desired to open the valve further and maintain it in another 
intermediate disposition between fully open and its prior disposition, the 
inlet solenoid 49 is energized for reopening it while the outlet solenoid 
59 is energized for keeping it closed. The incoming supply of air to the 
interior chamber 18 causes the control valve 1 to begin to open further as 
the pistons 15, 17 are forced further apart. Once the valve has been 
further opened by a desired degree, the inlet solenoid 49 can again be 
deenergized for closing it and, thereby, maintaining the control valve 1 
in a fixed disposition corresponding to the new equilibrium position of 
the pistons 15, 17. 
Referring now to FIG. 3, in the event that it is desired to partially close 
the control valve 1 relative to its current intermediate disposition, the 
outlet solenoid 59 can be reopened by de-energizing it while the normally 
closed inlet solenoid 49 remains de-energized and, therefore, closed. Air 
can then escape from the interior chamber 18 through the opening 37 and 
through channel 43b under pressure exerted by the main springs 29, 31 on 
the pistons 15, 17 until partial closure of the control valve 1 has 
reached the desired degree. At that time, the normally open outlet 
solenoid 59 can be energized and closed to maintain the control valve 1 
fixed at its current state. 
Referring to FIG. 4, in order to fully close the control valve 1, the inlet 
solenoid 49 is deenergized and closed and the exhaust outlet valve 59 is 
deenergized and opened. At this time, the pressure of the main springs 29, 
31 forces the pistons 15, 17 toward one another with the opposing the air 
in the interior chamber 18 being forced through the opening 37 and 
expelled through channel 43b to the exhaust port. The closed inlet 
solenoid 49 prevents further air from entering the interior chamber 18 to 
oppose the closing force of the main springs 29, 31 on the pistons 15, 17. 
During closing, the racks 11, 13 rotate the pinion 5 clockwise to its 
fully closed position. 
It is to be appreciated that the foregoing is a description of a preferred 
embodiment of the invention to which variations and modifications may be 
made without departing from the spirit and scope of the invention. Various 
safety configurations can be realized in accordance with the preferred 
embodiment of the invention by selecting the inlet solenoid 49 and/or 
output valve 59 to be normally opened or normally closed. For example, if 
it is desired to have the control valve 1 fully close the main valve in 
the event of an electrical power failure, the inlet solenoid 49 can be 
selected to be a normally closed valve and the outlet solenoid 59 can be a 
normally open valve as described above. Hence during a power failure, the 
control valve 1 would assume the state shown in FIG. 4 with the pistons 
15, 17 being able to fully retract toward one another and turn the pinion 
5 to its fully closed position. 
Alternatively, it may be desirable to maintain the valve in a its current 
fixed position upon power failure, in which case both the inlet solenoid 
49 and outlet solenoid 59 could be chosen to be of the normally closed 
type. In this situation, during a power failure, the control valve 1 with 
assume the state shown in FIG. 2. 
If it is desired to maintain the control valve 1 and main valve fully open 
in the event of power failure, the inlet valve 49 can be a normally open 
valve and the outlet solenoid 59, a normally closed one. In the latter 
case, upon failure of power, the control valve 1 will assume the state 
shown in FIG. 1.