Abstract:
Hydraulic actuator. An actuator body includes an inlet, an outlet, a port communicating with a pre-charged diaphragm tank, and a port communicating with a pressure switch. The actuator body includes a movable member which, in a first position, closes the inlet port and provides fluidic communication with the pressure switch port while allowing pressure equalization between the inlet and an interior of the actuator body. In a second position, the movable body opens the inlet port and seals the pressure switch port. A spring is disposed within the actuator body to urge the movable member toward the first position. The invention eliminates the need for multiple springs as shown in one prior art design and eliminates the need for reliance on a hydrostatic force differential to move the movable member.

Description:
This application is a continuation-in-part of U.S. patent application Ser. No. 09/382,869, filed Aug. 25, 1999, which is a continuation-in-part of U.S. patent application Ser. No. 09/090,723, now U.S. Pat. No. 5,947,690, filed Jun. 4, 1998, and also claims priority to U.S. Provisional Application No. 60/049,234, filed Jun. 9, 1997. The entire contents of each of these applications is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     Electrically operated pumps are used to supply water from wells and to boost the pressure of municipal water systems. Such pumps are operated by electric motors under the control of a pressure sensitive switch. Some prior art systems operate by keeping a reservoir tank substantially filled with water. In such a system, the pump motor turns on when pressure drops below a pre-set value and turns off when the pressure reaches another higher pre-set value. The duty cycle for the electric motor in such a system is high, with numerous transitions from off to on and off again. 
     Alternative systems are known in which the pump runs when there is a demand for water and is off when the demand ceases. U.S. Pat. Nos. 5,190,443 and 5,509,787 are directed to actuators which control a pump based on demand. In these two patents, the interplay of hydrostatic and hydrodynamic forces moves a shuttle member which alternately opens and closes a passageway to allow pressure to communicate with a pressure-activated switch for controlling the pump motor. Another design as set forth in U.S. Pat. No. 3,871,792 utilizes a combination of hydrodynamic forces and spring forces to control a switch operate the pump motor. In particular, the configuration set forth in the &#39;792 patent requires two springs, one to control the moving member of a poppet valve and another spring to control the motion of a flexible diaphragm. The design is also complicated by first and second internal auxiliary passageways to provide for pump motor control. 
     SUMMARY OF THE INVENTION 
     In one aspect, the invention is a hydraulic actuator comprising an actuator body which includes an inlet, at least one outlet, a port communicating with a pre-charged diaphragm tank, and a port communicating with a pressure switch. The actuator body includes a movable member which, in a first position, fills the inlet port and provides fluidic communications with the pressure switch. In a second position, the movable member opens the inlet&#39;s port and seals the pressure switch port. The actuator further comprises a spring disposed within the actuator body, which urges the movable member towards the first position. The movable member includes a bypass which provides fluidic communication between the inlet and interior of the actuator body when the movable member is in the first position. The actuator may include a check valve assembly, which, in an open position, allows fluidic communication from the pressure switch to the actuator valve. 
     In a preferred embodiment, the movable member comprises a lubricious material or a lubricous coating. The lubricious material or coating may be a fluoropolymer such as Teflon™ or an acetal such as Delrin™. Other appropriate fluoropolymers include fluorinated ethylene propylene, perfluoroalkoxy copolymers, and ethylene-tetrafluoroethylene copolymers. Other appropriate lubricious coatings include diamond, diamond-like coatings, silver, metal oxides and fluorides, molybdenum sulfide, tungsten sulfide, carbon, graphite, titanium nitride, nickel alloys, parylenes, poly(vinylpyrrolidone), silicone, boron nitride, polyimides, or plasma vapor deposited polymers. 
     In another aspect, the invention is a hydraulic actuator comprising an actuator body which includes an inlet, at least one outlet, a port communicating with a pre-charged diaphragm tank, a port communicating with a pressure switch, and a passageway communicating with the port which communicates with the pressure switch and an interior of the actuator body. The actuator body includes a movable member which seals the inlet port and provides fluidic communication with the pressure switch when it is in a first position. In a second position, the movable member opens the inlet port and seals the pressure switch port. The actuator further comprises a spring disposed within the actuator body which urges the movable member toward the first position. The movable member includes a bypass which provides fluidic communication between the inlet and an interior of the actuator body which the movable member is in the first position. The actuator may further include a support member which includes a transverse passageway in fluidic communication with an axial passageway, wherein the axial passageway communicates with the port which communicates with the pressure switch. The support member may include plurality of spaced apart seals. The movable member may include a passageway which enables fluidic communication between the interior of the actuator body and the port in communication with the pressure switch when the movable member is in the first position. 
     The bypass may comprise at least one groove oriented longitudinally with respect to the movable member, which is cut into a surface of the movable member, or the by-pass may comprise at least one channel drilled through a base portion of the movable member. The movable member may include an axial passageway which enables fluid communication between the port which communicates with the pressure switch and the interior of the actuator body when the movable member is in the first position. When the movable member is in the first position, it may be seated in a recess in the actuator body and may seal the inlet port by means of an o-ring seated in the recess. A flow rate of greater than 2.5 gal/min through the inlet may exert a force on the movable member greater than that exerted by the spring. The minimum flow rate to overcome the force of the spring may be 2, 1.5, 1, or 0.5 gal/min. The actuator may further include a support member which guides the movable member in a sliding motion. The support member may include a transverse passageway which is in fluidic communication with an axial passageway, which in turn communicates with the port communicating with the pressure switch. The movable member may include a passageway which enable fluidic communication between the transverse passageway and the interior of the actuator body when the movable member is in the first position. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a cross-sectional view, partly exploded, of the actuator valve of the invention along with a pressure switch. 
     FIGS. 2A,  2 B, and  2 C are cross-sectional views of the actuator valve in different states of operation. 
     FIG. 3A is a cross-sectional view of the movable member of the actuator valve. 
     FIG. 3B is an end-on view of the movable member of the actuator, showing the low-flow bypass. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference first to FIG. 1, an actuator system  10  includes an actuator body portion  12 . The body portion  12  includes an inlet connection portion  14  which is adapted to be connected to a pump (not shown). As will be appreciated by those skilled in the art, the pump is connected to a source of water such as a well or a municipal water supply. The actuator body  12  also includes an outlet port  16  from which water is discharged as, for example, through a faucet (not shown). There may be additional outlet ports. A pressure switch assembly  18  includes an electrical switch which, when closed, turns on a pump and which, when opened, turns off a pump. The pressure switch assembly  18  is connected to a port  20  which communicates with the pressure switch  18 . A port  22  is connected to a pre-charged diaphragm tank assembly  24 . The tank assembly  24  includes an outer enclosure  26  and an inner diaphragm  28 . Water fills the diaphragm  28  which expands against air entrapped between the diaphragm  28  and the enclosure  26  to pressurize the water. If tank assembly  24  is a cold water expansion tank, the maximum working temperature should be 200° F. 
     The actuator assembly  10  will now be described in more detail in conjunction with FIG.  2 . Disposed within the actuator body  12  is a movable member  30  which is guided in its sliding motion by a fixed support  33 . As shown in the figure, the movable member  30  seats within a recess portion  32  and is in sealing relation by virtue of an o-ring seal  34 . Because movable member  30  slides against fixed support  33 , it is desirable that movable member  30  be manufactured from a lubricious material, or, alternatively, have a lubricious coating. In a preferred embodiment, movable member  30  is fabricated from a fluoropolymer, such as Teflon™ (polytetrafluoroethylene), fluorinated ethylene propylene, perfluoroalkoxy copolymers, or ethylene-tetrafluoroethylene copolymers. An acetal such as Delrin™ would also be appropriate. Alternatively, the movable member  30  can be fabricated from a material and then coated with a lubricious coating. Exemplary coatings include diamond, diamond-like coatings, silver, metal oxides and fluorides, carbon, graphite, titanium nitride, various nickel alloys, parylenes such as poly(vinylpyrrolidone), silicone, boron nitride, polyimides, and plasma vapor deposited polymers. Materials such as molybdenum sulfide, tungsten sulfide, and titanium nitride can either be used as coatings or added to a resin matrix which is used to coat the moveable member  30 . Where the movable member number  30  is seated in recessed portion  32 , the base of the movable member is tapered (FIG.  3 A). The angle, n, of the taper may be 15°, and the distance x over which the taper extends may be 0.015 in. (0.38 mm). The support member  33  includes spaced apart o-ring seals  36  and  38 . The fixed support  33  includes a transverse passageway  40  which is in fluid communication with an axial passageway  42 . The axial passageway  42  communicates with the port  20  leading to the pressure switch  18  (FIG.  1 ). 
     The operation of the actuator  10  of the invention will now be described in conjunction with FIGS. 2A-C. When the movable member  30  is fully seated within the recess  32 , the inlet port  14  is closed while the port  40  is in fluidic communication with fluid within the actuator body  12  via passageway  41 . Thus, the pressure switch  18  responds to pressure within the actuator body  12  through the passageways  40  and  42 . The diaphragm  28  is distended by being filled with water; pressure is provided by air compressed between the diaphragm  28  and the enclosure  26 . A low flow bypass  62  in movable member  30  enables pressure equalization between the fluids in the actuator body  12  and the inlet connection  14 . FIG. 3B depicts bypass  62  as two longitudinal grooves in movable member  30 . The bypass may also only comprise one groove or may comprise a channel or hole which is cut through the base or bottom of movable member  30 . The bypass may also comprise a combination of channels and grooves, depending on the desired pressure within the actuator body  12 . Because o-ring  34  is seated in recess  32 , when the movable member  30  is seated within the recess, the inlet port  14  is not completely sealed from the interior of actuator  12  but rather enjoys a finite amount of fluidic communication with the interior of the actuator  12  via the bypass  62 . 
     When a faucet is opened, water will be discharged from the pre-charged diaphragm tank  24  through the outlet port  16 . For example, the pre-charged tank may exhibit a pressure of approximately 50 psi. As water flows through the outlet port  16 , pressure will decrease as the diaphragm  28  decreases in volume. The pressure decrease will be communicated through the unsealed passageway  40  to the pressure switch  18 . The pressure switch  18 , as will be appreciated by those skilled in the art, is adjusted to have a cut-in pressure setting, for example, 30 psi, below which the switch activates a pump motor and a cut-out pressure setting which deactivates the pump motor. Thus, when the pressure falls the pump motor will be activated, causing fluid to flow through the inlet port  14 . Pressure generated by the pump will cause the movable member  30  to move out of the recess  32  by overcoming the force of a spring  44  which urges the movable member downwardly. Under the influence of the pump, the movable member  30  moves upwardly as shown in FIGS. 2B and 2C. The spring  44  is not shown in FIGS. 2A-C for clarity. Hydrodynamic forces arising from the flow of water through the inlet port  14  keep the movable member in the upward position against the force of the spring  44 . Thus, water continues to flow through the output port  16 . Of course, the cross-sectional area of the grooves and channels contributing to bypass  62  will reduce the force inserted on the movable member  30  by a given flow rate of water. It is important to note that when the movable member  30  is in its upward position as shown in FIG. 2C, the transverse passageway  41  is above the o-ring seal  38  so that the passageway  40  is now sealed off from, and cannot respond to, fluid pressure changes in the actuator body  12 . Therefore, the pump will remain running as long as fluid is flowing through the outlet  16 . When, however, a faucet is turned off, flow through the outlet port  16  will stop. For a while, flow will continue through the port  22  into the diaphragm  28 . As the flow slows, the pressure in the tank will gradually increase so that the hydrodynamic force holding the movable member  30  open will be less than the downward force exerted by spring  44 . The movable member  30  will then reverse its path along fixed support  33 , moving downwardly as shown in FIG.  2 B and finally all the way downwardly into its resting position in the recess  32  as shown in FIG.  2 A. When the member  30  is in the downward position shown in FIG. 2A, the passageway  41  is now beneath the o-ring seal  38  and in fluidic communication with the fluid within the actuator body  12  via port  40  so that the passageway  40  is unsealed and “feels” the pressure in the body  12 . This high pressure is communicated to the pressure switch  18  which shuts off the pump motor. For example, a flow rate of 2 gal/min may be enough to hold up the movable member  30  against the force of spring  44 , but if the flow rate decreases to less than ½ gal/min, the force will not be sufficient, and the pump will shut off. When a faucet is once again opened, the process just described is repeated with an activation of the pump motor for as long is fluid is flowing through the outlet  16  and a deactivation of the motor once fluid flow ceases. 
     However, the consumer may not always turn on a faucet to its maximum flow. There are many situations in which full flow is not necessary and lower flow is preferred. In case a faucet is not completely opened, it will take longer for the diaphragm  28  to empty, the pressure in the interior of the actuator body  12  to decrease, and the pressure switch to open. However, the total flow through the actuator body will not be very high. If the flow rate is low enough, the water may not exert enough pressure on movable member  30  to move it all the way up to the top of support  33 . FIG. 2B shows the movable member  30  partially elevated in accordance with this example. Despite the low flow, passageway  41  is above o-ring  38 , sealing passageway  40  between o-rings  38  and  36  and preventing fluidic communication of the pressure switch with the interior of the actuator body  12 . The bypass  62  in movable member  30  enables increased flow from inlet connection  14  to outlet  16  even though movable member  30  is not completely elevated. Thus, the pump is able to operate, and the pressure switch will not cut off, at flows of a given flow rate, e.g., 2.5 gal/min. The minimum flow required to keep movable member  30  elevated can be reduced by decreasing the force constant of the spring  44  or increasing the total cross-sectional area of bypass  62 . In alternative embodiments, the minimum flow rate to elevate movable member  30  may be 2, 1.5, 1, or 0.5 gal/min. When the faucet is turned off and water is no longer being used, water flows slowly from inlet  14  through the bypass  62  into the interior of actuator body  12  until the pressure exerted by the diaphragm  28  and the water flowing through inlet  14  is the same, further slowing the flow rate. At this point, as in the full flow example, movable member  30  will again move downwardly and be seated in recess  32 . Passageway  40  will be in fluid communication with the interior of actuator body  12  via passageway  41  and will be able to communicate that pressure to the pressure switch via passageway  42 . The pressure switch will thus cut out. 
     For applications where the consumer desires even lower flow, on the order of ½ gal/min or less, water will flow out of the diaphragm, and the pump will not come on until a significant amount of water has been drawn by the consumer. At this point, the pump will come on, not so much to further provide water to the consumer as to repressurize the diaphragm. 
     Also shown in FIG. 2A is a check valve assembly  60 . The check valve assembly allows communication from the pressure switch port to the actuator body. When the valve  60  opens, the high pressure of the pressure switch port is relieved to the actuator body, assuring that the pressure switch will cut in. 
     Those skilled in the art will appreciate that the embodiments disclosed herein may be made of any suitable materials such as metals or plastics or a combination thereof. The embodiments disclosed herein have several advantages over prior art designs based on hydrostatic/hydrodynamic principles. In U.S. Pat. No. 5,509,787 discussed above, the area on one side of the movable member had to be smaller than that on the other side so that hydrostatic forces would re-seat the movable member. In the present invention, the areas may be equal since a spring is used to re-seat the movable member  30 . Importantly, only the single spring  44  is required to provide pressure switch control, unlike the dual spring design in U.S. Pat. No. 3,871,792. In the present invention, the spring  44  need only overcome the sliding friction of the movable member  30  over the fixed support  33  and no other spring is required. 
     It is intended that all modifications and variations of the present invention be included with the scope of the appended claims.