Abstract:
A solenoid valve has a housing defining a first axis and second axis, a solenoid which produces a magnetic field along the first axis, a valve shaft movable between open and closed positions along the second axis, and a manifold mounted to the housing. The shaft is biased toward the closed position by a spring and mechanical forces sufficient to overcome the force of the spring are transferred from the solenoid to the shaft by a lever to displace the shaft and then hold a first poppet valve open. The first poppet valve, which interacts with a portion of the housing to close the first valve, and a second poppet valve, which interacts with portions of the manifold to route fluid to the desired port, are mounted to the shaft. An electronic circuit controls delivery of current to the solenoid to shift and hold the shaft in the open position.

Description:
CROSS-REFERENCED TO RELATED APPLICATIONS 
     Not applicable 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable 
     BACKGROUND OF THE INVENTION 
     I. Field of the Invention 
     The present invention relates to solenoid valves. More specifically, the present invention relates to solenoid valves that have minimal power requirements. 
     II. Related Art 
     Valves are commonly used to control the flow of fluids in a hydraulic or pneumatic system. Valves are used to turn flow on or off, modulate flow or to direct flow along alternative paths. Two-port valves, for example, are used to turn flow on or off or to modulate the amount of flow past the valve. Valves with more than two ports typically have (a) either one pressure (inlet) port and multiple outlet ports, or (b) one outlet port and multiple inlet ports. In the first case, the valve is used to connect the inlet port to a selected output port to permit fluid to flow from the inlet to the selected outlet. In the second case, the valve is used to connect the outlet port to a selected input port to permit flow from the selected input port to the output port. 
     Solenoid valves have two main components, the valve and the solenoid. The solenoid is a helical coil of insulated wire in which an axial magnetic field is established by the flow of electric current through the coil. Many solenoid valves have a plunger and a spring arranged along the axial magnetic field produced by the solenoid. The spring biases the plunger toward a position which closes the valve. Application of current to the solenoid creates a magnetic field sufficient to overcome the force of the spring and open the valve. 
     A problem with solenoid valves known in the prior art is that substantial amounts of electricity are required to overcome the force of the spring to move the plunger and then retain the plunger in the open position. This adds to the cost of operation and also makes solenoid valves unacceptable for use in a variety of environments. There is a real need for an efficient solenoid type valve which can operate at low power. 
     SUMMARY OF THE INVENTION 
     Solenoid valves made in accordance with the subject invention typically include a housing, an electromagnet, an electronic circuit, a valve assembly and a lever. The housing surrounds the other aforementioned components and defines a first axis and a second axis laterally spaced from and parallel to the first axis. The housing also has a flow path. The flow path has both an inlet and outlet. The outlet is centered on the second axis of the housing. 
     The electromagnet includes a core and coil assembly. The core is preferably made of a soft magnetic material as opposed to an ordinary mild steel. One example of such a soft magnetic material is an alloy comprising more than 45% nickel and more than 45% iron. The core is positioned within the housing along the first axis. The coil assembly includes at least one helical coil surrounding the core. The coil assembly is electrically coupled to the electronic circuit. The electronic circuit is adapted to apply both a shifting voltage and a holding voltage to the coil assembly. Application of either of such voltages creates a magnetic field along the first axis. 
     The valve assembly includes a shaft extending between a first end and a second end along the aforementioned second axis. The shaft is movable along the second axis between a first position and a second position. A spring is coupled to the shaft and biases the shaft toward the first position. At least two valves are coupled to and move with the shaft. More specifically, a first poppet valve is coupled to the shaft intermediate the first and second ends of the shaft and a second poppet valve is coupled to the shaft intermediate the first poppet valve and the second end. 
     The lever also comprises an alloy of soft magnetic material. As is the case with the core, an example of a suitable material for the lever is an alloy comprising more than 45% nickel and more than 45% iron. The lever has a receiver and a plate. When positioned in the housing with the other components, the receiver is mated with the first end of the valve assembly&#39;s shaft and the plate extends from the receiver over the electromagnet. The plate has an engagement surface facing the electromagnet. The engagement surface of the plate has two end portions, a center portion and a recessed portion between each of the two end portions and the center portion. 
     When the shaft of the valve assembly is in its first position, there is a gap between the core and the center portion of the engagement surface of the plate. Application by the electrical circuit of the aforementioned shifting voltage to the coil assembly draws the center portion into contact with the core of the electromagnet thereby moving the shaft of the valve assembly from the first position to the second position. The current may then be reduced to a holding current, i.e. a current sufficient to hold the shaft of the valve assembly in the second position. 
     A manifold is coupled to the housing, i.e., either by integrally forming the manifold with the housing or attaching the manifold to the housing. In either case, the manifold has a pressure path in communication with the inlet of the flow path of the housing as well as both a port path and an exhaust path, which are selectively in communication with the outlet of the flow path of the housing. When the solenoid valve is fully assembled, the first poppet valve seats against a portion of the housing when the shaft is in the first position to seal the flow path and the second poppet valve seals against a portion of the manifold when the shaft is in the second position to seal the exhaust path. 
     Various other features may be included. For example, the coil assembly may have first and second coils. In such a case, the electronic circuit may be adapted to supply a shifting current to the first coil and a holding current to the second coil. To reduce the current necessarily supplied to the solenoid valve, the electronic circuit may include a charging capacitor which, when discharging, supplies the shifting current. The electronic circuit may also provide a step down of the voltage supplied to the circuit. In most cases, the electronic circuit will provide to the coil a shifting current to overcome the force of the spring and move the shaft to the second position and a holding current to retain the shaft in the second position. The shifting power will typically be higher than the holding power. 
     The voltages provided to the electronic circuit may vary. For example, the circuit may be adapted to operate at DC voltages in the range of between about 6 volts and 30 volts. Alternatively, the circuit may be adapted to operate at voltages as low as 24 volts direct current to as high as 240 volts alternating current. This enables the solenoid valve to be adapted to accommodate the available power at the location where the valve is to be employed. The electronic circuit ensures that only the minimum power required for operation of the valve is actually employed. 
     A complete understanding of the invention will be obtained from the following description when read in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded view of a solenoid valve made in accordance with the present invention; 
         FIG. 2  is an exploded side view of the solenoid valve of  FIG. 1 ; 
         FIG. 3  is an alternative exploded perspective view of the solenoid value of  FIG. 1 ; 
         FIG. 4  is a partial cross-sectional view of the solenoid valve of  FIG. 1 ; 
         FIG. 5  is a bottom view showing the engagement surface of the lever of the solenoid valve of  FIG. 1 ; 
         FIG. 6  is a schematic diagram showing a first embodiment of the electronic circuit of the solenoid value of  FIG. 1 ; and 
         FIG. 7  is a second embodiment of the electronic circuit. 
     
    
    
     DETAILED DESCRIPTION 
     This description of the preferred embodiment is intended to be read in connection with the accompanying drawings, which are to be considered part of the written description of this invention. In the description, relative terms such as “lower”, “upper”, “horizontal”, “vertical”, “above”, “below”, “up”, “down”, “top”, and “bottom”, as well as derivatives thereof (e.g., “horizontally”, “downwardly”, “upwardly”, etc.) should be construed to refer to the orientation as then described or as shown in the drawings under discussion. These relative terms are for convenience of the description and do not require that the apparatus be constructed or operated in the orientation shown in the drawings. Further, terms such as “connected”, “connecting”, “attached”, “attaching”, “joined”, and “joining” are used interchangeably and refer to one structure or surface being secured to another structure or surface or integrally fabricated in one piece, unless expressly described otherwise. 
     The solenoid valve  10  shown in the drawings includes a housing comprising a base  12  and a cover  14 . A separate manifold  16  is also shown. The manifold  16  may alternatively be integrally formed with the base  12 . 
     The housing defines a first axis represented by line  18  in  FIG. 4  and a second axis represented by line  20  in  FIG. 4 . In addition to containing the other components of the valve described below, the housing also contains a flow path  21  having an inlet  22  and an outlet  24 , as best shown in  FIG. 3 . The manifold  16  has pressure port  26  coupled to and in communication with the inlet  22 . The manifold also has an exhaust path  28  axially aligned with the outlet  24  and a port path  30 . The exhaust path  28  and the port path  30  are selectively in communication with the outlet  24  of the flow path of the housing by operation of the valve  10 . 
     Centered on the first axis  18  is a magnet channel  31  adapted to hold an electromagnet  32  and a circuit board  40 . The electromagnet  32  has a core  34  also centered on the first axis  18 . Preferably, the core will be made of a soft magnetic material as opposed to ordinary mild steel. One such soft magnetic material is a metal alloy comprising more than 45% nickel and more than 45% iron. This nickel/iron alloy material is physically durable and reacts well to the cycling of power on and off to the coil(s) such that a substantial magnetic field is only present when electrical energy is applied to the coils. This alloy may be prohibitively expensive in some applications in which case other soft magnetic materials may be employed which have similar characteristics in terms of physical durability and reaction to cycling power on and off. Surrounding core  34  is a coil assembly  36  comprising at least one coil winding  38 . A second coil winding  39  may also be provided on the core  34 . The core  34  is preferably made of soft magnetic material. An example of such a soft magnetic material is an alloy containing more that 45% nickel and more than 45% iron. One such alloy is available from Carpenter Technology Corporation of Reading, Pa. This alloy is 48% nickel, 0.5% manganese, 0.35% silicon, 0.02% carbon and the remainder of the composition is iron. Other soft magnetic materials suitable for use include a silicon iron or a ferritic stainless steel. 
     An electronic circuit board  40  is shown in  FIGS. 1-4 . Two embodiments of the circuit contained on the circuit board  40  are shown in  FIGS. 6 and 7 . These circuits will be discussed in greater detail below after the mechanical features of the valve are described. 
     A valve assembly  50  ( FIG. 4 ) comprises a shaft  52  having a first end  54  and a second end  56 . A coil compression spring  58  surrounds the shaft  52 . The spring has a first spring end  60  and a second spring end  62  ( FIG. 2 ). When the valve assembly  50  is positioned in a channel  51  in the housing base  12 , the second end  56  of shaft  52  is able to pass from above through the exhaust  28  of the manifold. The diameter of the spring  58  is larger than the outlet  24  such that the portion of the base  12  of the housing surrounding outlet  24  acts as a stop  63  against the second end  62  of spring  58 . Adjacent the first end  54  of the shaft  52  is a e-clip catching recess  64  which cooperates with a washer  66  and e-clip  68  to couple the first end  60  of spring  58  to the shaft  52 . More specifically, the washer  66  is sandwiched between the first end  60  of the spring  58  and the spring clip  68 . The e-clip  68  fits into the clip catching recess  64  such that the e-clip  68  is securely affixed to the shaft  52 . In this fashion, the compression spring  58  is coupled to the shaft  52  between the stop  63  that surrounds outlet  24  and the washer  66 . The force of the spring  58  against the washer  66  and the portion of base  12  surrounding outlet  24  biases the shaft  52  upwardly toward a first position. 
     Several other significant features are associated with shaft  52 . First, a poppet valve or seal  70  surrounds the shaft  52  intermediate the first end  54  and the second end  56  of the shaft  52 . As shown in the drawings, the poppet valve  70  is proximate the second end  56  of the shaft  52 . Second, a further poppet valve or seal  72  surround the shaft  52  intermediate the first end  54  of the shaft  52  and the poppet valve  70 . In the drawings, the poppet valve  72  is proximate the poppet valve  70 . A shaft seal  74  may also be provided between the first end  54  of the shaft and the poppet valve  72 . 
     The spacing of these three seals along the shaft  52  is dictated by the geometry of the base  12  and manifold  16 . Specifically, the first poppet valve  72  must be able to fully engage and seal against the wall surrounding outlet  24  of the base  12  of the housing when the shaft is in the first position, i.e., the position caused by the biasing force of the spring  58 . Further, when the shaft  52  is forced down into a second position by energization of the solenoid coil  32 , the second poppet valve  70  must seal against the wall surrounding the exhaust path  28  of the manifold  16 . Further still and with reference to  FIG. 4 , the shaft seal  74  must at all times be above the location where the channel from the inlet  22  of the base  12  intersects the channel in which the shaft  52  resides so that flow is direct from inlet  22  to outlet  24  and fluids do not pass through the other portions of the housing. The shaft seal  74  engages a wall section  75  of the base  12  between the stop  63  and the flow path  21  which partially defines the channel  51  in which the shaft  52  resides. 
     Based on the foregoing description, it should be clear that when the shaft  52  is raised by action of the compression spring  58  into the first position, the first poppet valve  72  seals against the portion of the base  12  surrounding the outlet  24  and shaft seal  74  seals against the wall section  75 . Thus, flow from the pressure port  26  and inlet  22  is blocked. Likewise, when the force of spring  58  is overcome and the shaft is move downwardly into the second position, the first poppet valve  72  unseals, the second poppet valve seals against the wall of the manifold surrounding the exhaust path  28 , and the shaft seal  74  still is sealed against the wall section  75 . Thus, fluids are able to flow along a path from the pressure port  26  of the manifold, through the inlet  22 , the flow path  21  and the outlet.  24  of the housing and out the port path  30  of the manifold. The shaft seal  74  prevents flow into other portions of the housing and the second poppet valve  70  prevents flow out the exhaust port  28 . 
     Of course, some mechanism must be provided to overcome the force of spring  58  (a) to move the shaft  52  from its first elevated position to its second position seen in  FIG. 4  and (b) then hold the shaft  52  in its second position. In the embodiment illustrated in the drawings, this mechanism comprises the electromagnet  32  working in conjunction with a lever  80 . 
     The lever  80 , illustrated in  FIG. 5 , is made of a material which is the same or similar to the soft magnetic material of the core. The material must be physically durable to prevent flaking and erosion of the lever  80  and core  32 . The lever  80  has a receiver  82 . The receiver  82  has a recess  84  which receives and mates with the first end  54  of the shaft  52 . The lever also includes a plate  86  extending from the receiver  82 . The plate  86  has an engagement surface  88  which faces the electromagnet  32 . The engagement surface  88  has two end portions  90  and  92 , a center portion  94  and two recessed portions  96  and  98 . Recessed portion  96  is located between the center portion  94  and the end portion  90 . Recessed portion  98  is located between the center portion  94  and the end portion  92 . 
     When assembled, the engagement surface  88  of the plate  86  is over and in the face-to-face relation with the electromagnet  32 . More specifically, the center portion  94  of the plate  86  resides over the core  34  of the electromagnet  32  and the recessed portions  96  and  98  reside over the coil assembly  36 . Cover  14  is adapted to hold end portion  90  of lever  80  in constant contact with the core  34  to reduce the effective air gap. Further, the first end  54  of shaft  52  resides in the recess  84  of receiver  82 . When the electromagnet  32  is not sufficiently energized to overcome the force of spring  58 , such that the shaft is urged by spring  58  to its first position, the shaft  52  holds the engagement surface of the plate  86  away from the upper end of electromagnet  32  such that there is a gap between the top of the core  34  and the center portion  94  of the lever  80 . When the electromagnet  32  is energized, a magnetic field is created which attracts the plate  86  down until the center portion  94  comes into contact with the core  34 . In this fashion, the lever  80  and the electromagnet  32  cooperate to apply a downward force to the shaft  52  sufficient to overcome the force of spring  58 , thereby moving the shaft  52  from its first position to its second position. When power to the electromagnet  32  is shut off (or reduced below the level required to hold the shaft  52  in the second position), the spring  58  returns the shaft  52  to the shaft&#39;s first position. 
     Application of power to the electromagnet  32  is controlled by the circuitry on circuit board  40 .  FIGS. 6 and 7  show two alternative circuit arrangements. Both circuits are designed to provide a first shifting current to the electromagnet  32 . When this first shifting current is applied, the electromagnet  32  and lever  80  cooperate to shift the shaft  52  from its first position to its second position. Both of these circuits are also able to provide a second holding current to electromagnet  32 . The second holding current is less than the first shifting current. While this second holding current is applied, the electromagnet  32  and the lever  80  cooperate to hold the shaft  52  in its second position. When the shaft  52  is to be returned to its first position, power to the electromagnet  32  is cut off by the circuits  FIGS. 6 and 7 . 
     The circuits may further provide additional functions. For example, if the coil assembly has a first coil  38  and a second coil  39 , the circuit can supply the first shifting current to the first coil and then the second holding current to the second coil. Alternatively, currents can be supplied to both coils  38  and  39  for shifting the shaft  52  from the first position to the second position. Then, the current to one of coils  38  and  39  can be turned off with the current still supplied to the other coil and being sufficient to hold the shaft  52  in the second position. 
     Further, the circuit may include a charge capacitor which accumulates the necessary shifting voltage. Discharge of the capacitor shifts the shaft  52 . The circuit then continues to supply the lower holding power. This arrangement is advantageous if the current supplied to circuit board  40  would otherwise be inadequate to shift the shaft  52  from its first position to its second position. Likewise, when the voltage supplied to circuit board  40  exceeds the requirements for shifting and/or holding, the circuit of circuit board  40  may provide a step down of the voltage. The circuit may also include components which filter and/or rectify the current to convert an AC input into a DC output. Further still, the circuit can operate in DC voltage ranges as low as between about 6 volts and 30 volts. Alternatively, the electronic circuit can be adapted to operate at voltages as low as 24 volts direct current to as high as 240 volts alternating current. 
       FIG. 6  and  FIG. 7  show two alternative circuit arrangements. The circuit of  FIG. 6  is employed when a single coil is used. The circuit of  FIG. 7  is employed when two coils are used. 
     In  FIG. 6 , input voltage signals are supplied to the circuit at solder connections  100  and  101 . The voltage is then filtered by an EMI filter  102 . Voltage then is applied to an AC to DC bridge rectifier  103 . Depending on the particular application, the voltage from the rectifier  103  may be quite high (over 60 v. AC) so it is passed through a stepdown circuit  104  comprising MOSFETS designed to step down the voltage so the voltage at the terminal labeled “vcoil” is in the range of about 55 to 60 volts. The circuitry in box  105  is essentially a 5 volt power supply for the internal electronics. 
     An op amp current source is illustrated in box  106 . The current source circuitry in box  106  ensures the current output to the coil of the electromagnet is consistent through the entire voltage range. 
     The circuitry in box  110  initially changes the current source in box  106  to a higher current level which provides a higher current to the coil assembly  36  necessary for shifting the shaft  52  of the valve from the first position to the second position. The circuitry in box  110  then changes the current source in box  106  to a lower current level after a time delay determined by C 6  and R 15  which provides a lower current to the coil assembly  36  to hold the shaft  52  in the second position. The coil  38  of the coil assembly  36  is connected to the circuit at P 1  and P 2  in box  112 . The capacitor  114  stores current pulses from step-down circuit  104  when voltage is low to power the circuit. 
     The alternative circuit of  FIG. 7  is designed to be used with a dual coil electromagnet  32  having both coils  38  and  39 . The circuit of  FIG. 7  is coupled to an input signal source via connections  120  and  121 . An EMI filter is provided in box  122  and an AC to DC bridge rectifier is provided in box  124 . The MOSFET switches and capacitors in box  126  are provided to supply power to shift the coil. Voltage detector  128  detects the voltage VC on the capacitors of box  126 . The voltage detector has a gate  129  to provide a time delay via R 6  and C 11  to make sure VDD is stabilized before Vc is connected to the shift coil. The flip-flop  130  controls the on/off state of MOSFET switches Q 3  and Q 4 . The circuitry in box  132  comprises a second voltage detector which turns on the chips. Box  134  is a voltage regulator which supplies 5.35v to the hold coil  39 . Switch Q 3  controlled by flip-flop  130  turns circuit  136  on to deliver current to the “shift” coil  38  until Q 3  turns off by the time delay provided by C 12  and R 7 . Q 4  in box  140  ensures power is delivered to the “hold” coil via circuit  138  until the power to the circuit shuts off. The circuit  140  makes sure Q 1  switch transistor in box  126  is shut off whenever Q 4  is on. As such, the circuit of  FIG. 7  centrally supplies a “hold” current to the first coil  39  until the power to circuit shuts off and turns on the shift coil  38  only when necessary to move the shaft  52  from its first position to second position. 
     Various modifications may be made without deviating from the invention. For example, the valve has been described as “open” when the shaft is in its first position and “closed” when in its second position. The opposite may be the case. Likewise, the shaft  52  has been described and shown as being on the outlet side of the flow path  21 . The shaft  52  could also be placed on the inlet side of the flow path  21 . The foregoing description is intended to explain, but not limit the invention as defined by the following claims.