Refrigeration System Incorporating Temperature Responsive Wax Element Valve Controlling Evaporator Outlet Temperature

Abstract

The compressor provides hot refrigerant gas to the condenser and flow from the condenser to the evaporator is regulated by the thermostatic expansion valve, the sensing point of which is located in the return line betweeen the evaporator outlet and the wax element actuated suction line valve. A wax element actuated suction line valve is incorporated in the refrigeration system to respond to evaporator outlet temperature and thereby maintain evaporator temperature above a value which would permit frost accumulation on the evaporator. Since the evaporator temperature is controlled, the evaporator pressure is, to some lesser extent, controlled since the two are related. The wax element motor has an inherent temperature lag due to the thermal inertia of the wax and this tends to smooth out or stabilize the system and thus prevent or minimize hunting. The valve remains open as long as the temperature is above the set temperature regardless how low the pressure falls. This, then, enhances fast pulldown of the system. The wax element must be located completely upstream of the valve so as to be unaffected by refrigerant expansion as the valve throttles flow. Thus the wax element is located totally within the temperature to be sensed. In the principal embodiment the valve member is carried directly by the wax element housing and cooperates with the seat which also supports the spider or yoke supporting and guiding the wax element. Another variation incorporates a bellows assembly which functions to seal the wax element from the refrigerant and thus prevent any adverse effect on the elastomers normally incorporated in the wax element motor. In some cases there is no elastomer incorporated in the design with the bellows functioning to contain the wax medium while permitting flexure and, hence, operation of the valve.

Description

CROSS-REFERENCE TO RELATED APPLICATION

The combination valve shown in FIG. 1 is claimed in copending application Ser. No. 276,676, filed July 31, 1972.

BACKGROUND OF THE INVENTION

Wax element actuators have heretofore been used in automotive environments sensing high temperatures and in an environment quite different from refrigeration systems. In undertaking to adapt such valves to a refrigeration system it has been found necessary to incorporate new approaches in order to obtain the desired operating characteristics over a satisfactory service life.

Prior Art

The thermostatic expansion valve portion of the combination valve shown in FIG. 1 is shown in U.S. Pat. No. 3,537,645.

SUMMARY OF THE INVENTION

With the construction described in the Abstract of the invention it is possible to confine the response of the wax motor assembly to the temperature to be controlled and conversely to insulate or isolate the motor from false response due to the expanding refrigerant through the valve which would cause cooling of a motor located downstream of the valve. Rapid pulldown of the refrigeration system is insured since the valve is unaffected by the pressure at its sensing point and responds only to temperature. The wax motor, with its inherent thermal inertia, offers advantages in smoothing out the refrigeration cycle, thus minimizing hunting effects.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical section through a combination valve incorporated in a refrigeration system and incorporating a wax element actuated suction line control valve made according to this invention.

FIG. 2 is a vertical section through FIG. 1 on line 2--2.

FIG. 3 is a vertical section through an alternate design of the refrigerant control valve and incorporating a a bellows assembly to seal the wax element motor, and particularly the elastomer therein, from the refrigerant.

FIG. 4 is a vertical section through another valve also incorporating a bellows seal.

FIG. 5 is a vertical section through still another valve but not having any elastomers therein and utilizing a bellows for containing the wax within the motor assembly.

FIG. 6 is another version incorporating a bellows to contain the wax.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIG. 1 the compressor P delivers hot compressed refrigerant to the condenser C and the liquid refrigerant leaving the condenser may optionally go to a receiver but eventually goes into conduit 10 in the valve body 12. Flow from inlet 10 to outlet 14 is regulated by the thermostatic expansion valve which in this case comprises the ball-type valve 16 biased in the closing direction by spring 18 supported in the closure member 20 which is threaded into the body and is sealed by means of O-ring 22. The valve is moved in the opening direction by push pin 24 which is actuated by the rider pin 26 actuated by diaphragm 28. The rider pin is hollow so that the space 30 can communicate with the charged space 32 above the diaphragm. Thus the sensing for the chamber above the diaphragm is the temperature in space 30 inside the rider pin 26. The restricter 34 minimizes migration of liquid slugs from the space 30 to the diaphragm chamber 32 even if the valve is inverted. The rider pin 26 is partially insulated by the plastic sleeve 36 to reduce hunting effects in the valve operation.

The body outlet 14 is connected to the inlet of the evaporator E and the refrigerant leaving the evaporator enters port 38 and passes over the hollow rider pin. Thus the temperature sensed by the hollow rider pin and the charge therein is the temperature in the return flow line and the outlet of the evaporator E. The pressure at this point can communicate with the underside of the diaphragm 28 and thus the actuation of valve 16 is influenced by the temperature and pressure surrounding the rider pin. Complete details of construction of this type of valve may be found in U.S. Pat. No. 3,537,645.

The evaporator outlet temperature is regulated by the wax element actuated valve assembly 40 which functions to regulate movement of valve 42 relative to seat ring 44 in accordance with the temperature sensed at the wax element power head 46. The power head contains a wax charge 48 which, when it expands, deflects diaphragm 50 to push against piston 52 which fits within guide 54 and seats against the calibrating screw 56 threadably mounted in boss 58 carried in the center of the seat ring 44. Valve disc 42 fits over the right-hand end of the guide 54 against flange 60 and is staked in that position as at 62. Thus the valve disc moves with the guide. Spring 64 is compressed between the valve disc and yoke 66 which, in turn, has ends projecting through the seat ring and staked to the seat ring at 68. The outer edge of the seat ring is clamped between the combination valve body and the retaining member 70. Therefore, seat ring 44 and yoke 66 are fixed relative to the combination valve assembly and spring 64 urges the valve disc towards the seat ring. If the wax charge 48 is solid and, hence, at its minimum volume, valve 42 can seat against the seat ring but when the critical temperature or set temperature is reached, the wax charge expands considerably. Since the piston cannot move relative to the fixed calibrating spring 56, the wax element pushes itself and valve 42 away from the seat ring 44. In normal operation the valve would be open but when the set low temperature is reached, the wax would solidify and cause the valve to close.

From the foregoing it will be apparent the wax element valve can function to regulate the temperature at the evaporator outlet or, put another way, at the power head 46. The power head is located a substantial distance upstream of valve 42 and, hence, is unaffected by expansion occuring past valve 42 during throttling action of the valve. When valve 42 is closed, flow to the compressor is not shut off completely since the valve disc, which is a simple stamping, is provided with a plurality of bleed notches 72 which allow a small amount of flow past the valve even though it is closed. This provides limited refrigerant flow to the compressor to prevent compressor damage.

As noted above, the present design functions to control the temperature at the sensing point and will be unaffected by the pressure at that point. This, then, makes it possible to achieve rapid pulldown of a refrigeration system upon start-up. This pulldown will be more rapid than possible with a control valve responsive to pressure. Due to the obvious thermal lag of the heat motor assembly there is a smoothing effect and hunting is minimized.

It will be noted that the seat ring is a simple stamping having the central aperture receiving boss 58. Ports 74 permit flow past the seat ring when the valve is open. The valve disc is a simple stamping and the notches for bleed flow purposes can be formed at the same time as the disc is stamped. The yoke 66 is also fabricated by a simple stamping operation. The yoke serves two functions, to guide the piston guide 54 and to serve as a seat for spring 64.

In the foregoing description it will be noted that the heat motor assembly incorporates an elastomer diaphragm 50 which can be adversely affected by contact with refrigerant over a long period of time. With a view towards minimizing that effect, the construction shown in FIG. 3 may be used. In this arrangement the heat motor assembly 80 is fixed within a valve member 82 by rolling the left-hand edge of the valve member over the heat motor assembly as at 83. The valve member has an exterior shoulder 84 which is adapted to seat against the inwardly converging seat portion 86 of support 88. The motor assembly includes the customary guide portion 90 with piston 92 projecting therefrom and received within pad 94 seated inside bellows 96 hermetically sealed to the valve member 82 at 98. The right-hand end of the bellows, in turn, is received in the seat 100 having a threaded stem 102 passing through the threaded boss 104 carried by support 88 to permit calibration. The valve and heat motor assembly, being an integral unit, are biased to the valve closed position, i.e. seated on seat 86, by spring 106 compressed between the heat motor and valve and the open inlet end of the support 88, the spring seat at that end being formed by turning in portions of the inlet of support 88 as indicated at 108. With this arrangement it will be noted that the wax 110 in the motor portion 112 is still well upstream of the valve and seat and, hence, will be unaffected by the throttling action of the valve. The refrigerant flowing through the system cannot contact the piston 92 or pass between the piston and the guide 90 to reach the elastomer diaphragm and the like within the wax element actuator assembly. It will be appreciated, of course, that the assembly illustrated in FIG. 3 is mounted in the return line from the evaporator to the compressor and, with a slight modification to the combination valve shown in FIG. 1, may be mounted in that assembly. The flow in this instance is through the interior of the support 88 past valve 84 to the outlet ports 114 in the side of the element 88 downstream of the valve. The system pressure acting on the bellows has minimal effect since the force developed by the wax element motor is so large.

FIG. 4 shows another method for providing a bellows seal between what might be considered a conventional wax element actuator 120 and the refrigerant flowing through the system. In this embodiment the flow would be from right to left on the drawing. Here the wax element interior is isolated from the refrigerant by bellows 122, one end of which is fixed to sleeve 124 threaded on the piston guide 126. The closed end of the bellows is captured between the headed end of piston 128 and the enlarged head 130 of the calibrating screw 132 threaded through seat ring member 134. The configuration of this seat ring is comparable to that shown in FIG. 1 and it also serves to support the yoke 136, the inturned portion 138 of which serves as a guide and as a seat for spring 140 compressed between the yoke and the valve member 142. The left portion of the valve member is provided with an outturned flange 144 which functions as a valve cooperating with seat portion 146 of the seat ring. The right-hand end of the valve member is provided with an inturned flange 148 and the spring force tends to move this flange against the shoulder 150 of the wax motor assembly with the gasket 152 sandwiched therebetween to prevent flow at this point which would, of course, bypass the valve. Thus, when the wax is solid and, hence, at its smaller volume, the valve 144 seats on seat 146. The periphery of the valve can be notched to provide for bleed flow. When the wax expands in the actuator, the actuator assembly has to move relative to piston 128 since the piston 128 has no place to go. This, then, causes the actuator assembly to pick up the valve member 142 and to pull the valve 144 away from seat 146 against the bias of spring 140. This construction is similar to FIG. 3 in that the bellows functions to prevent refrigerant contact with what might be termed a conventional heat motor assembly incorporating an elastomer diaphragm alone or in combination with an elastomer plug. This can simplify the choice of elastomers and/or increase the service life of the elastomers.

In the construction shown in FIG. 5 the elastomer has been eliminated from the heat motor. In this arrangement the seat ring 160 is formed much as in the other designs but the central boss 162 serves to receive the threaded end of the calibrating rod 164, the enlarged head of which seats against the flat end 166 of bellows 168, the open end of which is hermetically sealed to the outer casing 170 and the guide disc 172. The heat responsive wax 174 is contained in the space between the bellows and casing 170. The casing is guided by yoke 176 staked to the seat ring at 178. The casing is biased to the seat ring by spring 180 and, therefore, the left end of the casing functions as a valve moving relative to the seat ring. The yoke, of course, allows flow past the yoke and, if the valve is open, past the valve and then through ports 182 in the seat ring.

In this instance it will be noted the wax charge is contained within casing 170 and the bellows 168 and no elastomer is used to translate the expansion and contraction of the wax to linear motion of the piston 164 or, as in this case, to linear motion of the casing 170. It is simply the expanding and contracting volume of the wax within the bellows which causes the movement. When the wax is hot and, hence, expanded, the casing 170 will be forced to move to the right against the bias of spring 180 to thereby move the valve portion relative to the seat ring, thus allowing flow. When the set temperature is reached, the wax shrinks and solifies. When the wax cools, the bellows are actually extending, having been compressed by the heating and thus there is no stress placed on the bellows. This, then, assures long life of the bellows.

In FIG. 6 still another design is shown. In this case the wax 190 is contained within the bellows 192 instead of outside the bellows and, as will be more clear hereinafter, this has the disadvantage of stressing the bellows upon solidifying the wax. Thus when the wax is cooling, the bellows is being contracted and may be stressed adversely with a consequent shortening of bellows life. Hence, this design is not as desirable. In any event, the bellows assembly is fixed to head 194 of threaded calibrating rod 196 received in boss 198 carried by seat ring 200 which also supports yoke 202, the apertured end of which receives the intermediate yoke 204, the center of which supports the end of the bellows 190. The yoke arms are staked at 206 to the valve 208 which is centrally apertured to fit over and, therefore, be guided by rod 196. Spring 210 is compressed between head 194 and the valve 208. Thus, in the contracted or solid wax state, the valve is pushed onto the seat 200. When the wax is heated and expands, it causes the bellows to elongate and carry yoke 204 and, hence, valve 208 with the right end of the bellows, thus opening the valve.

In all of the foregoing designs the wax element sensor itself is located well away from and upstream of the valve so as to be unaffected by the expansion of refrigerant flowing through the valve. This is extremely important in a refrigeration system. All of the embodiments incorporate very simple parts making provision for bleed flow when closed and all having the virtue of the inherent thermal lag of a wax element motor which in a refrigeration system functions to smooth out the cycle, which is another way of saying hunting is minimized.

Claims

I claim:

1. The combination with a refrigeration system in which a thermostatic expansion valve regulates flow from a compressor to an evaporator, of a valve assembly for regulating evaporator outlet temperature above a predetermined value to thereby prevent frosting of the evaporator,

said temperature regulating valve assembly being located in the return line from the evaporator to the compressor and being positioned close to the evaporator outlet,

said regulating valve assembly including a valve movable relative to a valve seat and actuated by a motor device including a wax charge which melts and expands considerably at temperatures in excess of said predetermined value, the motor device being connected to the valve to actuate the valve relative to the seat,

said wax element motor device being located completely between the valve and the evaporator outlet so as to be unaffected by changes in state of the refrigerant downstream of the valve.

2. The combination of claim 1 in which the seat is fixed in the return line and is apertured to provide flow therethrough,

said motor device being supported by said seat and being connected to the valve,

spring means biasing the valve to the closed position when the wax is solid.

3. The combination of claim 2 including means in the valve providing a limited flow when the valve is seated.

4. The combination of claim 3 in which a yoke is connected to the seat and supports the distal portion of the motor device,

and calibrating means connecting the central portion of the seat to the motor device.

5. The combination according to claim 4 including a bellows sealing the interior of the motor device from contact with refrigerant in the system.

6. The combination according to claim 4 in which the motor device includes a sealed chamber, one wall of which is a bellows which expands and contracts, the wax being contained in the chamber.

7. The combination according to claim 6 in which the bellows expands as the wax contracts.

8. The combination according to claim 6 in which the bellows contacts as the wax contracts.