Abstract:
An improved modulating expansion valve includes a housing having a high pressure side, a low pressure side and a piston reciprocally mounted in a portion positioned centrally therebetween. A manifold is sealingly mounted above the piston, and a high pressure control passageway extends from the valve inlets, through the manifold, to a chamber on top of the piston. A low pressure passageway extends from the chamber through the manifold to the valve outlet. A pair of electrically operated solenoids open and close the high and low pressure passageways to operate the valve. Substantially infinite control of the solenoids provide for modulating control of the valve in a semi-hermetically sealed expansion valve.

Description:
This application claims priority based upon Provisional Application Ser. No. 60/072,376, filed Jan. 9, 1998 and entitled “Modulating Expansion Valve.” 
    
    
     The invention relates generally to expansion valve utilized in refrigeration systems and, more particularly, to an expansion valve for a refrigeration system controlled by a pair of electrically operated solenoid valves. 
     BACKGROUND OF THE INVENTION 
     Refrigeration systems consist of a refrigerant utilized in a cycle including a compressor, a condenser, an expansion valve and evaporator. While an expansion valve may potentially be as simple as an orifice, modern day refrigeration systems usually monitor the entire refrigeration cycle to optimize efficiency. Optimizing the efficiency in the condenser and in the evaporator entails providing an expansion valve having not only open and closed positions, but also a variety of partially open positions and a means for providing the correct optimum flow of refrigerant through the expansion valve. Presently known control apparatus used to operate a modulating expansion valve includes the use of an electric motor having an annular stator positioned on top of the valve and an armature positioned inside the hollow interior of the stator having a shaft in the center thereof which turns through a worm gear to raise and lower a regulating piston through the valve port. This type of motorized operator requires the use of shaft seals between the motor and the piston and thus provides an additional leak path to the atmosphere from the refrigeration system. 
     A need has arisen for an improved expansion valve for use in a refrigeration system that avoids the complexities of a motor operated expansion valve while providing simplicity of operation and a semi-hermetic seal between the valve and the atmosphere. 
     SUMMARY OF THE INVENTION 
     The invention resides in a modulating valve for use in controlling flow in a fluid system. The valve comprises a housing including a high pressure fluid inlet, a low pressure fluid outlet and a movable valve body positioned between the inlet and outlet. The valve body is adapted to move to open and close the valve and is biased in one of the open or closed positions. The invention further includes means having a first electrically operated pilot valve therein for providing controlled flow of fluid from the high pressure inlet of the housing to a portion of the valve body (above the piston) tending to move that valve body in a direction opposite its biased position. The invention further resides in means including a second electrically operated pilot valve for providing a control flow of fluid from the valve body (above the piston) to the low pressure outlet of the housing. This allows the valve body to move in a direction toward its biased position. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features of the present invention which are believed to be novel are set forth in the attached claims. The invention may best be understood by reference to the following description taken in conjunction with the accompanying drawings in which like numerals refer to like parts and in which: 
     FIG. 1 is a diagrammatic view of a refrigeration system utilizing the modulating expansion valve of the present invention; and 
     FIG. 2 is a vertical sectional view of the modulating expansion valve constructed in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1, a typical refrigeration system includes a closed cycle of flowing refrigerant  10 , which passes through a compressor  11  into the high pressure side of the refrigeration cycle. From the compressor  11 , the refrigerant passes through a condenser  12  and from there the refrigerant passes through the expansion valve, generally indicated at  13 , constructed in accordance with the present invention, to regulate the flow of the fluid from higher pressure to lower pressure. After the expansion valve  13 , the refrigerant is in the low pressure side of the refrigeration cycle and passes through the evaporator  14  or water chiller and thereafter back to the compressor to complete the cycle. 
     Referring to FIG. 2, the modulating expansion valve, generally indicated at  13 , constructed in accordance with the present invention, is shown in more detail to include a housing  13   a , constructed from a casting used for a typical globe valve, a high pressure inlet side defined by an inlet port  15  identified on the outside of the valve housing by annular inlet flange  16  therearound, a low pressure outlet port  17  identified outwardly on the valve housing  13   a  by annular outlet flange  18  therearound and an S-shaped path from the inlet port  15  to the outlet port  17 . A circular port aperture or valve seat  20  is horizontally positioned through an S-shape dividing wall  21 . Positioned between the inlet  15  and the outlet  17 , a central or top annular housing portion  22  rises vertically as an annular flange from the center portion of valve housing  13   a  and includes a central bore  23  therein in which the top end of a cylindrical piston  24  is reciprocally mounted. Bottom annular end or skirt  25  of piston  24  is reciprocally received within the circular port  20  and divides the high pressure valve inlet from the low pressure valve outlet. Piston  24  is biased in an upward or open position by spring  27  mounted between the piston skirt  25  and a plug  28  positioned at the bottom of housing  13   a . The annular sleeve  25  of piston  24  includes a plurality of triangulated cutout portions, one being typically shown at  29 , which provide increased area for fluid to flow though port  20  as the piston  24  is raised and conversely provide decreasing flow area from the valve inlet to the valve outlet as the piston is lowered, until the piston is fully lowered to the point where the top of triangulated cutouts  29  are below port  20 . At the top of port  20  is positioned an angular valve seat  31   a  that matingly sealingly engages an annular shoulder or valve seat  31   b  extending around a piston  24  when the piston is in its bottom-most position closing fluid flow through the valve  13 . 
     The improvement of the present invention resides partly in a cap shaped cylindrical manifold  32 , mounted on top of the annular central portion  22  of housing  13   a  and, also in an inlet electrical solenoid, generally indicated at  33 , mounted on the high pressure side of the valve manifold  32 , and in an electrical outlet solenoid, generally indicated at  34 , mounted on the low pressure side of the manifold  32 . The high pressure side of the annular central portion  22  of housing  13   a  also includes fluid passageway  36  extending from the high pressure inlet at  37  to the bottom of the manifold  32 . The high pressure passageway continues in manifold  32  at passageway  38  which extends upwardly to the top of manifold  32 . A continuation of the high pressure passageway  38  extends downwardly from the top of manifold  32  at passageway  40  which extends into the hollow piston chamber  41  beneath the manifold. 
     A low pressure fluid passageway from the piston chamber  41  extends through passageway  42  to the top of the low pressure side of manifold  32 . The passageway then continues at passageway  42   a  down to the top of the low pressure side of the central annular portion  22  of housing  13   a . A passageway  43  extends downwardly through the central housing portion  22  until it exits to the low pressure valve outlet at  44 . 
     The high pressure or inlet electric solenoid  33  includes a housing  44  having an annular coil  45  positioned around it. Coil  45  is energized by electricity passing through it. The hollow central core  47  of solenoid  33  includes a metal core or plunger  48  which moves in a upward direction or open position when energized by the coil  47  and is biased in a downward or closed direction by a spring  46 . The plunger  48  includes a working bottom end  50  which is sized to matingly engage an annular sealing ring  51  positioned at the top of high pressure passageway  40 . Since the piston chamber  41  is of larger area than the port  20 , flow through passageways  36 ,  38  and  40  moves the piston downwardly until the annular seat  31   b  on piston  24  sealingly engages annular seat  31   a , thus closing the valve. Working bottom end  50 , when seated cuts off refrigerant flow between high pressure passageway  38  and high pressure passageway  40 . When there is no current through coil  45 , the plunger  48  closes and moves downwardly in the hollow central core  47  to shut off high pressure fluid flow through passageway  36 ,  38  and  40  into the piston chamber  41 . 
     The low pressure side of the expansion valve of the present invention is controlled by the low pressure electric solenoid  34  which like solenoid  33  includes an annular coil  55  energized by electricity through it. A hollow central core  57  in solenoid  34  includes a metal plunger  58  reciprocally mounted therein which has a lower working end  60  which sealingly engages annular sealing ring  61  positioned at the top of low pressure passageway  43 . When plunger  58  is de-energized in its downward position, it seals and cuts off low pressure fluid flow between passageways  42 ,  42   a  and  43 , thus preventing any movement upwardly of the piston  24  through the chamber  41 . As solenoid  34  is energized, the plunger  58  moves upwardly and allows movement of fluid through passageway  42 ,  42   a ,  43  and out  44  to the low pressure side of the valve outlet  17 . Energization of solenoid  34  allows the piston  24  to move upwardly because of the bias from spring  27 , and opens the expansion valve by increasing the opening area defined by the Y-shaped cutouts  29  in the skirt  25  of piston  24 . 
     The position of the piston  24  in the valve  13  and hence the refrigeration flow through it is controlled by operating the inlet solenoid  33  and the outlet solenoid  34 . The inlet solenoid controls the passage  36 ,  38 ,  40  connecting the inlet of the main high pressure side of the valve to the chamber  41  above the regulating piston  24 . The outlet solenoid  34  controls the passage  42 ,  42   a ,  43  and  44  connecting the chamber  41  at the top of the regulating piston  24  to the outlet  17  of the valve  13 . The refrigerant flow through valve  13  is a function of the position of the regulating piston  24  in the valve bore  41 . As the piston  24  moves upwardly in the bore  23 , the characterized open area  29  available for flow increases, and as a result, the refrigerant flow rate goes up. The flow reduces as the piston  24  moves down. The downward motion of the piston  24  can be effected by the opening the inlet solenoid  33  while leaving the outlet solenoid  34  closed. This causes the refrigerant to flow from the inlet  15  of the valve to the chamber  41  at the top of the piston  24 . Because the area of the bore  23  is greater than the port area  20 , higher inlet pressure acting on top of piston  24  causes the piston to start moving downward, thereby reducing the flow. Opening the inlet solenoid  33  with the outlet solenoid  34  closed will eventually lead to closing of the valve as the piston  24  at the lowermost point of its downward stroke will seal against the port  20 . The piston  24  can be made to hold position at any point between wide open (topmost position) to completely shut (bottommost position) thus regulating or modulating the flow rate. This can be effected by controlling the amount of time that the inlet and outlet solenoids are open and hence prevent the piston  24  from moving in the upward or downward direction. This control or modulation can be effected by commercially available controllers. For example, a rapidly moving flip flop will excite solenoids  33  and  34  as desired, to position the piston  24  in bore  23  wherever one wants. The reaction time of the valve can be controlled by the size of the orifices included in the inlet and outlet solenoid valve as shown in FIG.  2 . The larger the orifice, the faster is the reaction time and vice versa. Reaction time refers to the time required by the piston  24  to traverse a certain distance within the bore  23 . Desired reaction times can be obtained by selecting the appropriate orifice size. The regulating piston  24  is provided with spring loaded teflon seals at  62 - 63  to seal against the bore  23  and thus prevent a leak path from the chamber  41  at the top of the piston  24  to the outlet  17  of the valve  13 . A leak path from the chamber  41  at the top of the piston to the outlet of the valve  17  will prevent the valve from closing. 
     In the event of a power failure with plungers  48  and  58  closing their respective passageways, a tiny passageway  24   a  in piston  24  bleeds refrigerant from high pressure inlet  15  to chamber  41  and causes piston  24  to slowly move downward and shut off the valve as a fail safe position. Alternatively, one of the solenoid valves can be of the normally open variety rather than normally closed. Depending upon which solenoid is normally open, a power failure can cause the expansion valve to fail in either the closed or open position. 
     Thus, a typical chiller application has been shown in which the modulating expansion valve of the invention has been shown. This invention enables controlling the flow rate through the condenser and thus effectively accounts for system load changes. The inlet and outlet solenoids  33 ,  34 , respectively, being integral with the valve  13 , can be controlled by any commercially available controllers or typical plant computers. 
     The advantages that this modulating control valve  13  has is that it is semi-hermetic in construction and minimizes leak paths to the atmosphere. Also, it is simpler and less complex than presently available motor operators mounted on similar valves that open and close the valve with a shaft having seals. Thus, an improved modulating expansion valve has been shown and described in connection with the present invention. 
     It will be understood by those skilled in the art that changes and modifications may be made without departing from the true spirit and scope of the present invention. It is the intent of the appended claims to cover all such changes and modifications which fall within the true spirit and scope of the invention.