US3537645A - Bulbless expansion valve - Google Patents

Description

Nov. 3, 1970 c. F. TREDER 3,537,645

1 BULLEss EXPANSION VALVE Filed Jan. 16, 1969 :fm1/maw' (Zar/es .7.' '//rmfer @WAL MM Patented Nov. 3, 1970 3,537,645 BULBLESS EXPANSION VALVE Charles F. Treder, Brookfield, Wis., assignor to Controls Company of America, Melrose Park, Ill., a corporation of Delaware Filed Jan. 16, 1969, Ser. No. 791,626 Int. Cl. Fb 41/04 U.S. Cl. 236--92 8 Claims ABSTRACT OF THE DISCLOSURE The thermostatic expansion valve controls refrigerant ilow to the evaporator in accordance with the pressure acting below the diaphragm and the temperature influencing the temperature responsive charged space above the diaphragm. The pressure is derived from the return conduit through the upper part of the body leading from the evaporator outlet to the compressor inlet. The rider pin connecting the diaphragm to the valve is hollowed out so that the bottom of he hole in the rider pin is in the refrigerant return flow path. This permits the charge to condense in the area of the system of refrigerant ow and respond to this temperature. Since the temperature in the return flow path is lower than the temperature ambient to the charged head, the condensed refrigerant will always be in the pin. A restrictor is placed in the upper end of the rider pin to prevent migration of condensed refrigerant to the head chamber in the event the valve is mounted upside down. A sleeve of low thermal conductivity positioned around the rider pin where it passes through the return conduit damps temperature changes and reduces valve hunting.

BACKGROUND OF INVENTION In Orth and Treder application Ser. No. 672,079, now Pat. No. 3,450,345 a valve broadly of the present type is shown but has a solid rider pin and the temperature of the head chamber is inuenced principally by conduction of heat through the upper wall of the valve body to the diaphragm support cup. The heat sink effect of the heavy upper wall damped the response but problems were encountered if the valve was mounted upside down and it was felt that the large mass of material in some cases adversely affected the response characeristics.

SUMMARY OF INVENTION The present expansion valve directly senses the temperature conditions sought to be controlled. This has been accomplished by provision of the hollow rider pin to allow the refrigerant charge in the diaphragm systemi to condense in the coldest spot and respond to the temperature at that spot, mainly in the return ow path. This locates the temperature sensing element on the location to be controlled. This arrangement is so sensitive that rapid fluctuations can lead to valve hunting. Therefore, the rider pin is surrounded by a material of low thermal conductivity to damp the response. Another feature of the invention is the provision of a restrictor in the upper portion of the hollowed out rider pin to prevent condensed refrigerant from migrating (by gravity) to the warmer head chamber when the valve is mounted upside down. If the refrigerant were to migrate into the warmer head it would flash into a gas and then recondense in the colder DESCRIPTION OF PREFERRED EMBODIMENT The lower portion of valve body 10 is provided with inlet 12 and outlet 14 separated by a partition through which port 16 is provided to supply refrigerant to the space below the partition. Ball type valve 18 cooperates with seat 20 to control flow from the inlet to the outlet. The ball is centered on cage 22 which is urged in the valve closing direction by spring 24 compressed between the cage and carrier 26 threaded into the end of the valve body and adjustable to change the spring force. The end of the valve body is sealed by cap nut 28 and an O-ring.

Valve 18 is actuated by push pin 30 which, in turn, is actuated by diaphragm rider pin 32 fixed to diaphragm pad 34 and having an end projection projecting through the pad and diaphragm 36 to communicate with head chamber 38. Pin 30 has a close sliding lit in bore 40 to minimize leakage along this portion since any such leakage would constitute a bypass.

In the upper portion of the valve body, there is a return conduit including inlet 42 connected to the outlet of the evaporator E while outlet 44 is connected to inlet of compressor C. It will be appreciated that, as usual, the output of the compressor is fed into condenser K and thence to recevier R which is conducted to the inlet 12 of the valve body 10. Pressure within the return conduit can communicate with chamber 46 below the diaphragm through port 48 in the upper wall of the valve body. From this it will be clear that the tolerance between diaphragm rider pin 32 and the upper wall is not of great concern since a little leakage here will hurt nothing. Diaphragm 36 is mounted between domed head 54 and support cup 50 threaded into the upper end of the valve body and sealed with respect thereto by means of O-ring 52. Head chamber 38 is charged with a temperature responsive charge through capillary tube 56 which is then sealed off.

It will be noted that rider pin 32 is provided with a blind hole 58 which terminates approximately at the midpoint of the return flow path through the upper portion of the Valve body. The blind hole, in effect, provides a small temperature sensing chamber 60 inside the rider pin and located in the system return path. Pin chamber 60 will always be colder than head chamber 38 and therefore the refrigerant charge will tend to condense in chamber 60 and the control point will be at this point which is ideally situated. Since there is not much mass involved in the rider pin the response of the valve as thus far described, would be quite rapid and subject to fluctuation on any transient temperature changes. This, of course, would result in hunting. To damp out the hunting effect low conductivity sleeve 62 is mounted over the rider pin where the pin passes through the return flow path. This sleeve can well be Delrin which, in addition to low thermal conductivity, provides a self-lubricating factor to insure free movement of the rider 32. The thickness determines the degree of damping.

In order to make the valve mountable in all positions, capillary restrictor 64 is fitted in the upper end of the rider pin. This then provides a very small capillary hole connecting rider pin chamber 60 to head chamber 38. This is adequate for transfer of pressure changes but will minimize migration of any condensed refrigerant charge in chamber 60 to the head chamber should the valve be mounted upside down. Without this restrictor there could be such migration with the result that the liquid refrigerant migrating to the head chamber (which is warmer) would ash to a gas (increasing the pressure) and then promptly be recondensed in chamber 60. This, of course, would induce hunting in the system. With the restrictor the hunting is minimized.

The hollowed out rider pin creating chamber 60 in the return flow path achieves outstanding response characteristics since it is positioned directly in the return flow path at the very point where the temperature should be controlled. Low conductivity sleeve 62 damps the 3 response characteristics and keeps the chamber 60 at an average temperature while the restrictor 64 allows the valve to be mounted in any position without hurting the response characteristics by reason of unwanted migration of condensed refrigerant from chamber 60 to head chamber 38.

I claim:

1. A thermostatic expansion valve comprising:

a valve body having a supply conduit therethrough with a valve and valve seat positioned therein whereby the valve regulates flow through the conduit to an evaporator, said valve body having a return conduit therethrough for receiving ow from the evaporator;

a diaphragm and means mounting the diaphragm on the valve body to define a pressure chamber having fluid communication with the return conduit;

means cooperating with the diaphragm to dene a head chamber;

a rider pin connecting the diaphragm to the valve for actuating the valve in accordance with movement of the diaphragm, said rider pin being hollowed out with the interior thereof in open communication with the head chamber and with the hollowed out portion of the pin being positioned in the return conduit being subjected to the temperature thereof; and

a temperature responsive charge within the hollowed out rider pin and the head chamber.

2. A thermostatic expansion valve according to claim 1 including means partially insulating the rider pin from the temperature within the return ow path to render the temperature of the charge in the pin more stable.

3. A thermostatic expansion valve according t0 claim 2 including a restriction between the pin and the head chamber to minimize ow of liquid from the pin tothe head chamber when the valve is mounted upside down.

4. A thermostatic expansion valve according to claim 1 including a restriction between the pin and the head chamber to minimize ow of liquid from the pin to the head chamber when the valve is mounted upside down.

5. A temperature responsive valve comprising:

a valve body having a conduit therethrough;

a diaphragm and diaphragm chamber carried by the body;

a pin connected to the diaphragm and extending into said conduit;

a hole in the pin extending from the diaphragm chamber into the portion of the pin positioned within the conduit to form a small chamber in the pin connected to the diaphragm chamber;

a temperature responsive charge in both of said charnbers; and

means actuated by the pin.

6. A valve according to claim 5 in which the side of the diaphragm opposite the diaphragm chamber is subjected to the pressure inthe conduit.

7. A valve according to claim 6 including means surrounding the pin within the chamber to retard the temperature change within the pin chamber.

8. A valve according to claim 5 in which the means actuated by the pin includes another valve controlling ow through another conduit in the body.

References Cited UNITED STATES PATENTS MEYER PERLIN, Primary Examiner U.S. Cl. XR. 62-204, 210, 224

UNITED STATES PATENT OFFICE CERTIFICATE 0F CORRECTION Eacent No. 3,537,645 Dated November 34, 1970 Invent0r(s) Charles F. Treder It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 4, line 22, "chamber" should read conduit g line 25, "another" should read a Signed and sealed this 14th day of November 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents ORM IDO-1050 (1D-69) USCOMM-DC 008764169