Patent Publication Number: US-2005121636-A1

Title: Memory wire actuated control valve

Description:
This is a continuation of U.S. patent application Ser. No. 10/640,746, filed Aug. 14, 2003, now U.S. Pat. No. 6,843,465, the contents of which is hereby incorporated herein by reference in its entirety. Priority to the aforementioned application is hereby expressly claimed in accordance with 35 U.S.C. §120 and any other applicable statutes. 
    
    
     FIELD OF THE INVENTION  
      The present invention relates generally to the field of electrically operated devices, and more specifically to an improved fluid control valve and method of manufacturing and using the same. Such valves have application in a variety of fields for controlling fluid flow, including irrigation, automotive, and industrial applications.  
     BACKGROUND OF THE INVENTION  
      Fluid control valves are typically comprised of a valve assembly and an actuator which applies a motive force to a plunger rod or other coupling device of the valve assembly to open and close the valve. The most common actuator used with fluid control valves is a solenoid device. A solenoid actuator generally consists of an electrical coil which when energized with an electrical potential, produces an electromagnetic field that is utilized to apply a motive force to a magnetized work element such as a plunger.  
      Many fluid control valves have been previously disclosed. For example, U.S. Pat. No. 5,979,482, the disclosure of which is incorporated herein by reference in its entirety, discloses a solenoid actuated pilot valve assembly specially adapted for use in irrigation systems. The pilot valve comprises a solenoid device having a cylindrical housing enclosing an electrical coil. The electrical coil surrounds a ferrous plunger which is operatively coupled to a valve sealing cap of the pilot valve. When the coil of the solenoid is energized, the plunger retracts thereby allowing the valve sealing cap to retract from its valve seat and opening the pilot valve.  
      The solenoid actuated fluid control valve suffers from several drawbacks. For one, a solenoid is relatively heavy and bulky because it requires an electrical coil and a magnetizable plunger element. In addition, solenoid devices have fast actuation times which can result in excessive water hammer.  
      Accordingly, there is a need for an actuator and fluid control valve which overcome the drawbacks of previous designs.  
     SUMMARY OF THE INVENTION  
      The present invention provides an improved fluid control valve assembly and methods of manufacture and use of the same. The improved valve assembly is especially useful under dirty, contaminated or salt water conditions. The fluid control valve assembly comprises a particularly innovative memory wire actuator which may be operatively coupled to any type of valve which can be actuated by a linear or rotational motive force. For example, the memory wire actuator may be operatively coupled to a typical pilot valve via a plunger rod.  
      The memory wire actuator includes a housing defining an interior cavity. The housing has an interface which may be operably coupled to a fluid control valve. The interior cavity of the housing encloses an electrical platform assembly, an activation wire and a transfer mechanism. The electrical platform assembly is mounted in the interior cavity of the housing. The activation wire is formed of a shape memory alloy. Such wires are often referred to as “memory wires” or “muscle wires.” The activation wire exhibits a property known as “shape memory effect.” This “effect” simply means that at a specific transition temperature a deformed piece of such a shape memory alloy will return to its shape prior to being deformed. In the case of a memory wire, the wire is stretched while it is below the transition temperature and when the wire is heated above its transition temperature it contracts to its unstretched length. A common method of heating a memory wire is to simply conduct electrical current through the wire by applying an electrical potential across the wire causing electrical current to conduct through the wire. The activation wire is electrically connected to the electrical platform and is also mechanically anchored to the electrical platform.  
      The transfer mechanism converts the force generated by the activation wire into a force which can be used to actuate a valve coupled to the memory wire actuator. The transfer mechanism is coupled to the activation wire such that energizing or de-energizing the activation wire actuates the transfer mechanism. The transfer mechanism may include a biasing device which exerts a force on the activation wire to stretch the activation wire when it is in the de-energized state. Alternatively, the biasing device may be provided on a fluid control valve adapted for use with the memory wire actuator. The transfer mechanism also comprises an output device which may be operably coupled to a fluid control valve such that actuation of the transfer mechanism acts to adjust the fluid control valve.  
      In a further aspect of the present invention, the memory wire actuator is operably coupled to a pilot valve. The pilot valve may be removably attached to the housing of the memory wire actuator, or alternatively, the pilot valve may be integral to the actuator or permanently attached to the actuator. The pilot valve has a plunger operably coupled to the transfer mechanism of the memory wire actuator through a plunger rod. The pilot valve may include the biasing device and may comprise a coil spring which engages the plunger. The force of the compressed spring pushes the plunger toward a valve seat. A seat seal is mounted on the plunger and engages the valve seat when the pilot valve is in the closed position. When the memory wire actuator is activated to open the pilot valve, the transfer mechanism pulls the plunger and seat seal away from the valve seat thereby opening the pilot valve.  
      The memory wire actuator and fluid control valve of the present invention has numerous applications, including industrial machinery, commercial and residential water systems, and is particularly well-suited to irrigation systems. In a common irrigation system, a main water supply line feeds into a plurality of control valves which may be opened or closed to control the flow of water to the outlet of the control valves. The outlet of the control valves are connected to a line feeding one or more sprinkler units. The control valves are commonly actuated by a pilot valve which when opened provides pressurized water to a diaphragm that applies a force to actuate the control valve. One such control valve is described in U.S. Pat. No. 5,979,482, the disclosure of which is hereby incorporated by reference in its entirety.  
      Accordingly, the present invention provides an improved fluid control valve assembly and methods of manufacturing and using such valve. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a cross-sectional view of a memory wire actuated control valve in a valve closed position according to the present invention.  
       FIG. 2  is a cross-sectional view of a memory wire actuated control valve in a valve open position according to the present invention.  
       FIG. 3  is a top view of the frame for the memory wire actuated control valve of  FIG. 1 .  
       FIG. 4  is a side view of the frame for the memory wire actuated control valve of  FIG. 1 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      Embodiments of the invention will now be described with reference to the accompanying Figures, wherein like numerals refer to like elements throughout. The terminology used in the description presented herein is not intended to be interpreted in any limited or restrictive manner, simply because it is being utilized in conjunction with a detailed description of certain specific embodiments of the invention. Furthermore, embodiments of the invention may include several novel features, no single one of which is solely responsible for its desirable attributes or which is essential to practicing the inventions herein described.  
      Referring now to the drawings,  FIG. 1  is a cross-sectional view of a memory wire actuated control valve  50  according to the present invention. The wire actuated control valve  50  comprises a memory wire actuator assembly  52  operably coupled to a pilot valve assembly  17 . The memory wire actuator assembly  52  may be removably attached to the pilot valve assembly  17  by threads so that the pilot valve assembly screws onto the memory wire actuator assembly  52 .  
      The memory wire actuator assembly  52  comprises a housing  1  which may be made of any suitable material including a variety of plastics such as PVC, polyethylene or polypropylene. The housing  1  may have a cylindrical shape which defines an interior cavity  54  a portion of which comprises an air chamber  25 . Within the interior cavity  54  encloses an electrical platform assembly  12 , an activation wire  11  and a transfer mechanism  56 .  
      The electrical platform assembly  12  is inserted into the interior cavity  54  and  12  bears on a shoulder of the housing  1 . The electrical platform assembly  12  includes a frame  58  which is shown in detail in  FIGS. 2 and 3 . The frame  58  has a round base  60 , a cylindrical pull rod guide  23  and four rods  62  extending out from the base  60 . The four rods  64  are used to support and position resistor  14 . The base  60  has two radial slots  21 . The electrical platform assembly  12  further includes a pair of connectors  13  affixed to the frame  58  along the slots  21 . The connectors  13  may be anchored to the frame  58  by any suitable means, including epoxy, adhesive, or mechanical attachment. One end of an activation wire  11  is connected to one of the connectors  13  and the other end of the activation wire is connected to the other connector  13 . The connectors  13  may be moved radially along the slots  21  before being fixed to the frame  58  in order to allow adjustment to eliminate slack in the activation wire  11 . Once they are properly adjusted, the connectors  13  are fixed in place on the frame  58 . A resistor  14  is also mounted on the electrical platform and is electrically connected to one of the lead wires  15  and to one of the connectors  13 . A cylindrical pull rod guide  23  is also provided on the frame which slidably receives a pull rod  10 .  
      The activation wire  11  is formed of a shape memory alloy and is often referred to as a “memory wire” or “muscle wire.” As described above, the activation wire  11  will contract in length upon application of an electrical potential across the wire causing sufficient current to conduct through the wire such that the temperature of the wire rises above its transition temperature. Conversely, upon removal of the electrical current, the activation wire  11  will cool to below the transition temperature and will expand in length. The contraction and expansion of the activation wire  11  is used to exert a force that actuates and de-actuates a transfer mechanism  56  which in turn opens and closes the pilot valve  17 .  
      The transfer mechanism  56  is coupled to the activation wire  11  by way of a pull rod  10  of the transfer mechanism  56 . The activation wire  11  is threaded through a hole in the pull rod  10  such that the pull rod  10  is in contact with the activation wire  11  at about the midpoint of the length of the activation wire  11 . In this case, the pull rod  10  is preferably made from an electrically non-conductive material, such as polymer with a high melt temperature. It should be understood that the activation wire may be two or more wire segments each connected to connectors  13  on the platform  60  pull rod  10 . The upper end of the pull rod  10  is slidably received in the pull rod guide of the frame  58 . The bottom end of the pull rod  10  couples to the particular device being actuated by the actuator  52 , in this example, the pilot valve  17 . In the embodiment of  FIG. 1 , the bottom end of the pull rod  10  is received in a bore of a vent cap  9 . The tip of the bottom end of the pull rod  10  does not quite reach the bottom surface of the bore in the vent cap such that there is a bias gap  16 . This ensures that there is a positive bias seating the seat seal  2  to the pilot valve seat  26 , as described in detail below.  
      The transfer mechanism  56  may further comprise a biasing device which exerts a force on the pull rod  10  in a direction which stretches the activation wire  11 . The biasing device ensures that when the actuator  52  is de-energized, the pull rod  10  is pulled downward into the de-activated position and the activation wire  11  returns to its stretched length. In the present exemplary embodiment of this invention, the biasing device is provided in the pilot valve assembly  17 .  
      The pilot valve assembly  17  includes a plunger rod  5  which is mechanically coupled to the pull rod  10 , for example by press fitting the plunger rod  5  into a bore in the end of the pull rod  10  or by mating threads on the respective parts. The plunger rod  5  is connected to a plunger  3  which houses a seat seal  2 . The plunger  3  sits in a cavity  66  in which a plunger biasing spring  8  is also housed. One end of the plunger biasing spring  8  is seated on a shoulder of the plunger  3  and the other end bears on the surface of the cavity  66 . The plunger biasing spring  8  exerts a force tending to push the plunger rod  5  and pull rod  23  into their de-activated actuator position thereby seating the seat seal  2  in the valve closed position (see  FIG. 1 ).  
      The flow circuit of the pilot valve assembly  17  comprises a pilot valve seat  26 , flow orifices  18   a  and  18   b  and a flow path between flow orifices  18   a  and  18   b.  As can be seen in  FIG. 1 , when the seat seal  2  is in the valve closed position, the seat seal  2  bears against the valve seat  26  and blocks the flow orifice  18 . In the valve open position shown in  FIG. 2 , the seat seal  2  is moved away from the valve seat  26 , thereby opening the pathway between valve orifices  18   a  and  18   b.    
      In order to seal the actuator  52  from the flow paths of the pilot valve assembly  17  several O-rings and related components are provided. First, an O-ring  4  is inserted into an O-ring groove of the pilot valve assembly  17 . In addition, a pair of O-rings  6  are installed around the plunger rod  5 . An O-ring retainer  7  holds the O-rings  6  in place. The external surface of the O-ring  6   a  seats in a bore of the vent cap  9 . Finally, a vent port  19  runs from the cavity housing the O-ring retainer  7  to the exterior of the pilot valve assembly  17  to allow venting of any leakage of fluid past the O-ring  4  and O-ring  6   b.  This prevents high pressure from being applied to O-ring  6   a  and contaminating cavity  54  with fluid.  
      The operation of the memory wire actuated control valve  50  is straightforward. Referring to  FIG. 1 , in the de-actuated state, i.e. with no electrical current conducting through the actuator  52 , the pilot valve  17  is in the valve closed position. In the valve closed position: the activation wire  11  is in its stretched state; the pull rod  10 , plunger rod  5  and plunger are pushed to their downward position by the plunger biasing spring  8 ; and the preceding assembly is holding the seat seal  2  in its closed position against the pilot valve seat.  
      Upon activation of the control valve  50  by application of an electrical potential across the lead wires  15 , electrical current conducts through the activation wire  11  thereby heating the wire above its transition temperature. This causes the activation wire  11  to contract which pulls the pull rod  10 , the plunger rod  5  and the plunger upward against the force of the plunger biasing spring. In turn, the seat seal  2  is moved upward away from the pilot valve seat  26 . As shown in  FIG. 2 , the valve  17  is now in the valve open position.  
      To close the valve  17  again, the electrical potential is removed and the activation wire  17  cools to below its transition temperature. This allows the activation wire  11  to stretch helped by the force exerted by the plunger biasing spring  8  through the plunger  3 , the plunger rod  5  and the pull rod  10 . The seat seal  2  is thereby moved onto the valve seat  26  and the valve is again in the valve closed position shown in  FIG. 1 .  
      It should be understood that the use of directional terms such as “downward” and “upward” in the description of the present invention are only based on the orientation of the memory wire actuated control valve as shown in the Figures, and is in no way limiting of the present invention. In addition, it should be appreciated that the memory wire actuated control valve  50  can easily be configured to close the valve  17  upon actuation of the actuator  50  and open the valve  17  upon de-actuation of the actuator  50 . This may be especially useful in applications where the valve  17  is normally open. Accordingly, the terms “actuation” and “de-actuation” simply refer to opposite operational positions of the actuator and are interchangeable throughout the description and claims.  
      Thus, it can be seen that the present invention provides an improved fluid control valve assembly. While the above description contains many specifics, these should not be construed as limitations on the scope of the invention, but rather as examples of particular embodiments thereof. Many other variations are possible.  
      Accordingly, the scope of the present invention should be determined not by the embodiments illustrated above, but by the appended claims and their legal equivalents. The present invention provides an improved fluid control valve assembly and methods of manufacture and use of the same. The fluid control valve assembly comprises a particularly innovative memory wire actuator which may be operatively coupled to any type of valve which can be actuated by a linear or rotational motive force. For example, the memory wire actuator may be operatively coupled to a typical pilot valve via a plunger rod.