US2524913A

US2524913A - Expansion valve for refrigerating systems

Info

Publication number: US2524913A
Application number: US532773A
Authority: US
Inventors: Harold F Lathrop
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1944-04-26
Filing date: 1944-04-26
Publication date: 1950-10-10
Anticipated expiration: 1967-10-10

Description

0d. 10, 1950 H, LATHRQP 2,524,913

, EXPANSION VALVE FOR REFRIGERATING SYSTEMS Filed April 26, 1944 :s sheets-sheet 1 Inventor- Harold F. Labhrop,

His AttornegL Oct. 10, 1950 H. F. LATHROP EXPANSION VALVE FOR REFRIGERATING SYSTEMS Filed April 26. 1944 Sheets-Sheet 2 D l O r EM 0 a bL n 2 5 5 1 O W T Hm M a w ,u H \D W M W n74 a, F ww m 5 M. 7. J a WW 0 7 M 0 m cd u W m 5 Ill/ g F a n M M 4, LL

H i s Attorney.

Filed April 26, 1944 3 Sheets-Sheet 3 Gen. 10, 1950 H. F. LATHROP 2,524,913

EXPANSION VALVE FOR REFRIGERATING SYSTEMS nnrIMM/ Inventor: Harold F. Lathrop His Abba-neg.

Patented Oct. 10, 1950 v EXPANSION VALVE FOR REFRIGERATING SYSTEMS Harold F. Lathrop, Grabill, Ind., assignor to Genggal Electric Company, a corporation of New ork i Application April 26, 1944, Serial No. 532,773

21 Claims. (or 62-8) This invention relates to refrigerating systems and particularly to such systems which are operated at very low temperatures.

In the conventional thermostatic expansion valve there is provided an actuating member responsive to the pressure within the evaporator and which is opposed by an actuating member responsive to the temperature of the refrigerant in the suction line. The pressure responsive member tends to open the valve upon a reduction in pressure and, consequently, when the refrigerating machine is started after an idle period the valve will be opened as soon as the operation of the compressor has reduced the pressure sufficiently to actuate the pressure responsive member. In my copending application, Serial No. 532,772, filed concurrently herewith, and which has now matured into Patent Number 2,497,677 and assigned to the same assignee as the present invention, there is described and claimed a thermostatic expansion valve actuated in response to the difference between the suction line temperature and saturation temperature in the evaporator of the refrigerating system. I

When a thermostatic expansion valve is constructed as described in the above mentioned copending application, the member responsive to the saturation temperature of the liquid refrig erant tends to close the valve upon a rise in temperature, and should there be no liquid refrigerant in the evaporator when the machine is started, there would be no reduction in temperature sufficient to cool the feeler bulb of the saturation temperature responsive member and open the valve. In my aforesaid copending ap-' plication an' arrangement is described for insuring the presence of liquid refrigerant in the vicinity of the saturation temperature responsive control bulb and thereby insuring the opening of the valve when the operation of the system is started. It is an object of my present invention to provide a refrigerating system having a thermostatic expansion valve controlled by the temperature of the suction gas and the saturation temperature of the liquid refrigerant in the evaporator and provided with an improved arrangement for assuring opening of the valve and, operation of the system even though theliquid refrigerant in the evaporator should have been removed prior to starting.

It is another object of my invention to provide a refrigerating system having a thermostatic expansion valve actuated by temperature responsive elements and including an improved arrangement for controlling the amount of superheat maintained by operation of the valve.

Further objects and advantages of my invention will become apparent as the following description proceeds, and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

For a better understanding of this invention reference may be had to the accompanying drawings in which Fig. 1 illustrates diagrammatically a compression type refrigerating system provided with a control embodying my invention; Fig. 2 is an enlarged sectional view of the thermostatic expansion valve shown in Fig. 1; Figs. 3 and 4 illustrate enlarged sectional views similar to Fig. 2 of thermostatic expansion valves embodying modifications of my invention; Fig. 5 is a diagrammatic view of a portion of a refrigerating system illustrating the manner in which the valves of Figs. 3 and 4 are connected in the system; and Fig. 6 is a diagrammatic view of a system provided with an electrically operated valve embodying my invention.

Briefly, the refrigerating systems disclosed in the accompanying drawings comprise compression refrigerating machines provided with thermostatic expansion valves for controlling the flow of refrigerant from the condensing apparatus or the high pressure side of the system to the evaporator or low pressure side of the system. Instead of employing the conventional thermostatic expansion valve, a valve is employed which is provided with two temperature controlled membersone responsive to the temperature of the vaporized refrigerant withdrawn from the evaporator and the other responsive to the saturation temperature of the liquid refrigerant in the evaporator. When the system is not in operation the control member responsive to the saturation temperature tends to keep the valve closed, and on starting the system this valve can be opened only if there is liquid refrigerant adjacent the feeler bulb of the valve to cool the bulb when the pressure in the evaporator isreduced. Should there be no liquid refrigerant in the evaporator this temperature control element cannot normally open the valve and start the operation of the system. An arrangement is therefore provided for modifying the operationof the valve on starting the refrigerating system to insure opening of the valve regardless of the pressures prevailing in the normal control devices.

Referring now to the drawings, the refrigerating system illustrated in Fig. 1 includes a compressor l driven by an electric motor 2 arranged to supply hot compressed refrigerant to a condenser 3. The condenser 3 is cooled by water circulated through a receiver or Jacket 4 and the compressed refrigerant is liquefied and flows to a liquid receiver 5. The liquid refrigerant from the receiver 5 is supplied to a multiple conduit evaporator 6 through a liquid line I by operation of a thermostatic expansion valve 8. The evaporator 6 comprises a plurality of parallel conduits connected to an outlet connection 9 of the valve 8 by a refrigerant distributor In which divides the refrigerant equally among the several conduits. The evaporator 6 is arranged in an air duct I! through which air is circulated to be cooled. The refrigerant in the evaporator absorbs heat from the air to be cooled and is vaporized, and the vaporized refrigerant is returned to the compressor I through a suction line l2 manifolded to the several evaporator conduits. The compressor is operated in accordance with the temperature of the cooled air as determined by a thermostat |3 arranged in the duct II which closes upon a demand for cooling and connects the motor 2 across supply lines l4, thereby starting the operation of the refrigerating system.

The expansion valve 8, the internal construction of which is shown in Fig. 2, is provided with a temperature responsive device l5 including an expansible chamber or bellows H5. The interior of the bellows is in communication through a tube I l with a feeler bulb or temperature responsive element l8 secured to the suction line l2 so that it is responsive to the temprature of the vaporizd refrigerant withdrawn from the evaporator. The valve 8 is also provided with an expansible chamber device l9 arranged in opposed relation to the device l5 and comprising a bellows 20 forming an expansible chamber which is in communication through a tube 2| with a temperature feeler bulb 22. The feeler bulb 22 is secured in heat exchange relation with a liquid collecting sump 24 secured in communication with the lowermost conduit of the evaporator indicated at 25. The sump 24 during the normal operation of the evaporator, contains liquid refrigerant, and the device I9 is, therefore, actuated in accordance with the saturation temperature of the liquid refrigerant in the sump 24. The liquid refrigerant in the sump 24 is at the pressure of the refrigerant in the evaporator so that the temperature of the sump is the saturation temperature of the liquid refrigerant in the r evaporator. In some constructions there may be a substantial pressure drop between the inlet end of the evaporator conduits and the suction line l2; and, in such cases, the sump 24 may be located nearer the outlet end of the evaporator conduit so that the pressure in the sump is the same as the suction line pressure and the temperature of the liquid refrigerant in the sump is the saturation temperature of the refrigerant at the pressure in the suction line.

The temperature responsive devices l5 and I9 are connected in opposed relation within the body of the valve 8 by a link 26 and

springs

21 and 28 between the link and the bellows l8 and 20, respectively. The pressure on'the outside of the bellows, that is, on the sides within the valve body, is the pressure of the liquid refrigerant under high pressure admitted to the interior of the valve body at the inlet 29. The external pressures on the two elements are, therefore, equalized and the link 26 is moved only in accordance with the difiference between the internal pressures in the members l5 and I9, that is, the pressures determined by the temperatures of the feeler bulbs l8 and 22. The valve 8 is provided with a valve member 30 for controlling communication between the inlet 28 and the outlet 3| from which the refrigerant flows to the connection 9 and thence to the evaporator. The valve member 30 is biased to its closed position by a spring 32, the force of which may be adjusted by removing a cap 33 and adjusting a screw member 34. The movement of the link 26 is transmitted to the valve 30 by a lever 35 which is pivoted on the valve body at 36 and has an open slot at one end engaging a pin 31 on the link 26 and a slot 38 intermediate the ends and on the other side of the pivot 36 for engaging a pin 39 on the valve stem 38.

Under normal conditions of operation the control devices l5 and I8 cooperate to maintain a value of superheat of the vaporized refrigerant in the suction line |2 determined by the setting of the spring adjusting screw 34; and during normal operation increased pressure in the element I5 tends to open the valve while increased pressure in the element l8 tends to close the valve. It is apparent, therefore, that on an increase in temperature of the feeler bulb 22 the control device |9 tends to close the valve. If for any reason the temperature of the bulb 22 is abnormally high and there is no liquid refrigerant in the sump 24 to cool the element 22, it would be impossible to open the valve automatically if some arrangement other than the controls as just described were not provided.

In order to insure opening of the valve upon starting the operation of the refrigerating system, there is provided a temperature responsive device including a bellows 40 and a feeler element 4| connected by a pressure transmitting capillary tube 42. The feeler bulb 4| is secured in heat exchange with the liquid sump 24 and is surrounded by a thermally insulated enclosure 43, and within the enclosure is also arranged a small electric heater 44. This heater is connected across the terminals of the motor 2 so that it is energized whenever the thermostat l3 calls for cooling and energizes the motor 2. The heater 44 is required to supply only a very small amount of heat and this heat is absorbed during normal operation by vaporization of liquid refrigerant in the sump 24. Furthermore, during normal operation when there is liquid in the sump, the feeler bulb 4| is at a low temperature and the bellows 48 is contracted. Should there be no liquid refrigerant in the sump 24, the temperature of the feeler bulb 4| increases to a predetermined high value under influence of the heater 44, and the increased pressure in the bellows 40 expands I the bellows until the end of the bellows engages an end portion 45 of the lever 35. When the pressure is sufllcientlyhigh in the bellows 40, it overcomes the pressure in the device l9 and opens the valve 38. Liquid refrigerant is then admitted to the evaporator and some of the liquid flows to the sump 24 thereby cooling the feeler bulb 4| and contracting the bellows 40; however, the liquid refrigerant admitted to the sumo also cools the bulb 22 and restores the system to normal operation under control of the temperature r sponsive devices 5 and 9.

During the operation of the refrigerating system illustrated in Fig. 1, when there is a demand for cooling, the thermostat l3 closes nd energizes the motor 2 and also the heater 44. This starts the com ressor and refrigerant is condensedin the condenser 3 and collects in the liquid receiver 5. If liquid refrigerant is present in the evaporator 6 when the compressor is started, this ment 22 and the resulting high pressure in the device l9; however, since the heater 44 has been energized simultaneously with the starting of the motor 2, this heat is supplied to the feeler bulb 4| and increases the pressure in the bellows 46 to open the valve and admit liquid refrigerant to the evaporator, thereby restoring the system to normal operation.

In Fig. 3 there is illustrated a sectional view of a thermostatic expansion valve comprising a body or assembly 46 and temperature responsive expansible chamber devices "and 48 connected in the same manner as the devices I5 and I9 to operate a link 49; during normal operation of the valve, movement of the link 49 determined by the diflerence in pressure between the two opposed devices 41 and 46 is employed to actuate a valve 56 for controlling the passage of refrigerant through the valve body 46 from its inlet, indicated at 5|, to its outlet, indicated at 52. The manner in which the valve assembly 46 is connected in the refrigerant circuit is the same as that employed in connecting the valve 6 in the circuit of Fig. l; and, in Fig. 5, the valve 46 is shown connected in the refrigerant circuit with corresponding parts designated by the same numerals as employed in Fig.1. The temperature responsive device 41 is connected through a tube 41a with a feeler bulb (not shown) which is arranged to be responsive to the temperature of the suction line in the same manner as the thermal bulb l8 in Fig.1. The valve 46 is so constructed that an additional temperature responsive device corresponding to the device 46 of Fig. 2 is not required, and the temperature responsive device 48, which corresponds in function to the device IS in Fig. 1, is connected through a tube 480. with a thermal bulb 53; the bulb is secured in heat exchange with the sump 24 within the insulated housing 43 so that it is subject to the operation of the heater 44. It will be apparent from consideration of the operation of the system of Fig. 1 that the temperature of the feeler bulb 53 is determined in a manner similar to the temperature of the feeler bulb 4| and this temperature corresponds to the saturation temperature of the liquid refrigerant during I normal operation of the system but is increased to a predetermined high value by the heater 44 whenever there is no liquid refrigerant in the sump 24. The excess pressure produced in the device 48 by this increased temperature is employed to open the valve in the event there is no liquid refrigerantin the evaporator when operation of the sump is started.

In order to employ excessive pressure in the device 48 to open the valve 56, two pivoted levers 54 and 55 are provided within the valve body 46. The lever 54 is pivoted at 56 on the upper side of the link 49, and the lever 55 is pivoted at 51 on the lower side of the link 49. The link 49 is provided with a pin 58 engaging a slot 59 in the lever 54, and the lever 54 is pivotally connected to the valve 56 through a leaf spring 66 secured to the lever at its upper end 6| adjacent the link 49. When the lever 54 moves in a counterclockthe valve 56, whereas movement in the clockwise direction need not necessarily move the valve since the spring can bend away from the lower end of the lever. The lever 55 engages the lever 54 at a point 62 along the axis of the link 49 adlacent the pin 58 and is connected to the valve 56 by a leaf spring 63 similar to the spring 66 and secured to the lever 55 at 64. The

springs

66 and 63 are pivoted together on the valve stem 56 at 65 to permit limited movement of the springs with respect to one another and with respect to the valve stem. counterclockwise movement of the lever 55 which is produced by movement of the link 49 toward the left on a decrease in pressure in the expansible chamber device 48 tends to open the valve since the lower'end of the lever presses against the spring 63 and the force is transmitted to the valve stem 56; however, movement of this lever ina clockwise direction need not result in valve movement since the spring can move away from the lower end of the lever. Since the levers are pivoted on opposite sides of the link 49 movement of the link moves the lower ends of the levers in opposite directions, so that on movement of the link 49 to the right, the lower ends of the levers tend to move apart and on movement to the left they tend to move toward one another. The arrangement of the

leaf springs

66 and 63 makes this opposite relative movement of the two lower ends of the levers possible, and it will be evident that only one of the levers controls the operation of the valve at a time because only one of the levers can be moving in a counterclockwise direction against its corresponding leaf spring. The return movement of the valve 56 toward its seat is produced by a spring 66 whichis 'similar in function to the spring 32 in Fig. 2 and may be adjusted to determine the amount of superheat maintained by operation of the valve 56.

During operation of the valve assembly 46 to maintain the desired amount of superheat during normal operating conditions in the refrigerating system, movement of the valve 56 is determined by the movement of the lever 55, an increase in pressure in the device 41 corresponding to rise in superheat temperature opening the valve and an increase in the pressure in device 48 corresponding to an increase in temperature \of the liquid in the sump 24 allowing the valve to be closed by the spring 66.

Should the refrigerating system be started when there is no liquid in the sump 24, the temperature of the feeler bulb 53 will be raised by the energization of the heater 44 and the excess pressure in the device 48 will move the link 49 sufficiently far to the right to bring the lower end of the lever 54 against the spring 66 and force the valve 56 to its open position, thereby allowing the liquid refrigerant from the liquid line 1 to flow through the outlet 52 to the evaporator. As soon as liquid refrigerant flows into the sump 24,

the vaporization of the liquid will cool the feeler 85 bulb 53 and restore the system to its normal operation so that the desired amount of superheat will be maintained by the automatic operation of the valve 46.

The thermostatic valve illustrated in Fig. 4

is similar to that illustrated in Fig. 3 in that it requires only two temperature responsive control devices. The valve in Fig. 4, indicated generally as the valve body 61, is provided with an inlet 68 communicating with the'liquld line I and an outlet 69 communicating with the outlet connection 9. The connections of this valve in the refrigerating system are essentially the same as those of the valve in Fig. 3 and the arrangement of the system may, therefore, be considered in connection with Fig. 5. Communication between the inlet and the outlet 69 may be provided by the opening of either of two valves indicated at I and II. Both of these valves are biased to their closed positions by a spring I2. Actuation 01' the valves is obtained by movement of a yoke 13 connected between opposed temperature responsive actuating members I4 and I5 at the top and bottom, respectively, of the valve body 61!. The actuating member I4 is connected to transmit movement from a bellows or expansible chamber I6 to the yoke 13 through a spring 11. Changes in pressure in the device I5 actuate an expansible chamber or bellows I8 which transmits the'force to the yoke I3 through a spring I9. The valve I0 is provided with a rod or stem 80 which is slidably engaged in a recess 8| in"the yoke I3, the valve being opened whenever the yoke I3 moves down sufficiently far to engage the upper end of the rod 80 and press the valve I0 downward against the pressure of the spring I2. The actuating member I4 corresponds to the member 41 of Figs. 3 and 5 and tends to open the valve I0 upon an increase in temperature of the vaporized refrigerant in the suction line, the corresponding pressure change being transmitted through the tube 41a. The device I5 corresponds to the actuating member 48 of the valve in Fig. 3 and on an increase in pressure caused by a rise in saturation temperature of the liquid as transmitted from its feeler bulb (not shown) through the tube 48a, the yoke I3 moves upward allowing the spring I2 to close the valve 10.

Throughout the normal operation of the refrigerating system the valve II remains closed. This valve is provided with a rod or stem 82 similar to the stem 80 and slidably engaging the yoke I3 in a recess 83. During normal operation of the system, the end of the rod 82 does not reach the bottom of the recess 83; however, should excess pressure exist in the actuating member 15, the yoke I3 will be forced upwardly until it engages the rod 83 and opens the valve II. This arrangement can, therefore, be employed with the insulated chamber and heater unit described above so that the feeler bulb of the member I5 (not shown) corresponding to the bulb 53 is raised to a predetermined high temperature when there is no liquid refrigerant in the sump 24. When this high temperature is reached the pressure in the member I5 raises the yoke I3 to open the valve II to admit liquid refrigerant to the sump 24 so that the feeler bulb of the actuating member I5 is cooled and the system restored to maintain the desired value of superheat. In order to vary the superheat adjustment of the valve, the yoke I3 is biased upwardly by a spring 84 arranged between a shoulder on the yoke and an adjustable shoulder 85. The shoulder 85 may be moved up and down by rotation of a bevel gear 86 meshed with a gear 81 which is turned by a shaft 88 after removing a cap 89.

The refrigerating system shown in Fig. 6 employs a solenoid operated expansion valve in the liquid line instead of the usual thermostatic expansion valve. The solenoid valve is controlled so that it operates to perform the function of a thermostatic expansion valve and maintain a tions in which a plurality of evaporators are sup plied from a single refrigerant condensing unit. The system is arranged to cool a storage chamber or other refrigerated area enclosed by a thermally insulated wall 90. A multiple conduit evaporator 9I is arranged within the chamber and is supplied with liquid refrigerant from a liquid line 92 by operation of a solenoid valve 93, the refrigerant being distributed equally among the several conduits of the evaporator by a refrigerant distributor 94. The vaporized refrigerant is withdrawn from the evaporator through a suction line 95. The compressor and condensing equipment have not been illustrated; however, the same general type of equipment may be employed as is shown in Fig. 1. Upon a demand for cooling in the space enclosed by the wall 90, a thermostat 96 closes its contacts and energizes the solenoid 93 provided that a switch 91 in the solenoid line has been closed. The actuation of the swItch 91 is controlled in accordance with the superheat in the suction line 95 by operation of opposed actuating

members

99 and 99. The switch 91 includes a switch arm I00 which is moved in accordance with changes in the diflerence of the pressures in the

members

98 and 99. The switch arm I00 is pivoted at its lower end to a stationary pivot IM and the movement produced by the

actuating members

98 and 99 is translated into pivotal movement of the arm I00 through coupling members I02 and I03 and a pantograph constructed of links I04, I05, I06 and MI. The links I04 and I 01 are pivoted together on the coupling I02; and links I05 and I06 are similarly pivoted on the coupling I03; the lower ends of the links I04 and I05 are pivoted at ml; and the upper ends of the links I06 and I0! are pivoted together and their pivot is slidably mounted in a slot I08 in the arm I00. The couplings I02 and I03 are held apart and in engagement with actuating rods 98' and 99' of the

devices

98 and 99, respectively, by a suitable compression spring I09. The movement of the pantograph and resulting pivotal movement of the arm I00 is determined by the difference between the forces of the

opposed devices

98 and 99. The switch 91 includes front and back contacts H0 and III, respectively. The arm I00 under normal operating conditions is biased by a superheat adjusting spring II2 to a position intermediate the contacts H0 and II I so that the solenoid valve is not energized when the amount of superheat is below a predetermined value. When the superheat rises a contact II3 on the arm I00 engages the contact H0 and closes the circuit of the solenoid 93 thereby opening the valve and admitting more refrigerant to the evaporator and lowering the amount of superheat to the predetermined desired value. Actuation of the control by operation of the

devices

98 and 99 is effected in a manner similar to the actuation of the controls of Figs. 1 to 5, inclusive; the device 98 is provided with a temperature responsive feeler bulb I I4 secured to the suction line 95 and the device 99 is provided with a temperature responsive feeler bulb II5 secured to be responsive to the temperature of liquid refrigerant in a sump H6 in communication with the lowermost conduit of the evaporator 9I. The sump H6 is supplied with heat by an electric heater III which is energized on closing of the thermostat 96; the feeler bulb H5, and heater I together with the lower portion of the sump II6 are enclosed in an insulated casing II8, this construction being essentially the same as that illustrated in Figs.

' 1 and 5. It will readily be apparent that should there be, no liquid refrigerant in the sump IIO when the thermostat 96 closes its contacts on a call for cooling that the feeler bulb will be heated directly by the heater III and the pressure in the device 99 will rise to a high value. The arrangement of the switch arm I00 is such that when this high value of pressure prevails in the device 99, the arm is rotated about the pivot IOI so that a contact II9 engages the back contact III and energizes the solenoid valve 03 to open the valve thereby admitting liquid refrigerant to the evaporator and placing the system in condition for normal operation to maintain the desired amount of superheat.

The superheat characteristics of the system" may further be improved by providing a pressure compensating device I directly connected with the suction line through a tube I2I and arranged to bias the switch arm I00 in a clockwise direction so that the bellows I20 tends to keep the switch contacts H0 and H3 out of engagement until a predetermined low pressure has been attained in the evaporator. The superheat setting is then determined by the suction line pressure, which is transmitted to the pressure responsive element I20 in addition to the setting of the adjustable spring II2. This arrangement provides compensation of the superheat setting with pressure changes and results in a more constant value of superheat over a wide range of operating temperatures. that a valve provided with this additional control may be made to maintain superheat within a range of less than 5 F. over a range of evaporator temperatures from 0 F. to -120 F.

During the operation of the refrigerating sys- It has been found.

tem illustrated in Fig. 6, liquid refrigerant may i be available at all times .in the liquid line 92 at the solenoid 93 however, the evaporator is supplied with refrigerant only on demand determined by the thermostat 98'which is responsive to the temperature within the space to be cooled. Upon a demand for cooling, the operation of the valve; 99 and its associated control mechanism is such that a predetermined value of superheat is maintained in the suction line 95. Should all the liquid refrigerant in the evaporator have been vaporized during a period when there is no demand for cooling, then the excessive pressure created in the control device 99 by the heater I I1 upon startingrotates the arm I00 to close contacts III and H9. This energizes the solenoid valve 93 and insures admission of sumcient liquid refrigerant to the evaporator to enable the control to take up its normal operating functions. Claims to the modification shown in Fig. 6 have been presented in my copending application Serial No. 781,143, filed October 21, 1947 and assigned to the same assignee as the present invention.

The several expansible chamber actuating devices illustrated in the foregoing embodiments of my invention may be charged with any suitable liquid or gaseous medium which will provide the required operating characteristics. For example, it may be desirable to charge both the suction temperature responsive device and the saturation temperature responsive device with a high pressure gas such as ethane; however, in order to obtain other characteristics it may be desirable to charge one of the devices with one gas and the other with a different gas or one or both of the devices with a vaporizable liquid Likewise, the bellows or exzpansible chambers iii of the suction temperature responsive device and the saturation temperature responsive device may be made of unequal effective areas, and in this way change the forces available for operating the valve, for the purpose of modifying the superheat characteristic. It may also be desirable for some systems to fill the two devices with varying amounts or pressures of gas in order to bias the valve to a closed position during shutdown periods. and delay opening until one of the temperature responsive elements is cooled to a predetermined degree.

It is readily apparent from the foregoing that I have provided an effective arrangement for insuring normal operation of a refrigerating system controlled by a valve responsive solely to temperatures in the system so that even though there is no liquid refrigerant on the low pressure side of the system the expansion valve will open to admit liquid refrigerant to the evaporator and permit normal operation of the system.

While I have illustrated my invention in conneotion with the compression type refrigerating systems, other applications will be apparent to those skilled in the art and I do not, therefore, desire my invention to be limited to the particular constructions shown and described, and I intend by the appended claims to cover all modifications within the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. In a refrigerating system including a high pressure side and a low pressure side and means for withdrawing refrigerant from said low pressure side and returning it to said high pressure side, means including an expansion valve for controlling the flow of refrigerant from said high pressure side to said low pressure side, said controlling means being dependent upon the presence of liquid in said low pressure side for opening said valve, and means dependent upon a predetermined high temperature of a portion of said low pressure side for admitting liquid refrigerant to said portion of said low pressure side regardless of the condition of operation of said controlling means.

2. In a refrigerating system including a condenser and an evaporator and means for withdrawing refrigerant from said evaporator and returning it to said condenser, an expansion valve for controlling the flow of refrigerant from said condenser to said evaporator, control means including a temperature responsive device arranged to be responsive to the temperature of liquid refrigerant in said evaporator for actuating said valve, said device tending to close said valve on an increase in said temperature, a liquid trap associated with said evaporator, and means including a temperature responsive element associated with said trap for supplying refrigerant to said trap regardless of the condition of operation of said first mentioned temperature responsive device.

3. In a refrigerating system including a condenser and an evaporator and means for with drawing vaporized refrigerant from said evaporator and returning it to said condenser, an expansion valve for controlling the flow of refrigerant from said condenser to said evaporator, control means including a temperature responsive device for actuating said valve, said device including a temperature responsive element arranged adjacent a portion of said evaporator normally containing liquid refrigerant to be respon- 1 l sive to the temperature of liquid refrigerant in said evaporator, said device tending to close said valve on an increase in temperature, and means dependent upon the absence of liquid refrigerant in said evaporator for opening said valve.

4. In a refrigerating system including a condenser and an evaporator and means for withdrawing refrigerant from said evaporator and returning it to said condenser, an expansion valve for controlling the flow of refrigerant from said condenser to said evaporator, control means including a temperature responsive device arranged to be responsive to the temperature of liquid refrigerant in said evaporator for actuating said valve, said device tending to close said valve on an increase in temperature, a liquid trap associated with said evaporator, and means including a temperature responsive element associated with said trap for opening said valve when the liquid refrigerant has been removed from said trap re-- gardless of the condition of operation of said first mentioned temperature responsive device.

5. In a refrigerating system including a condenser and an evaporator and means for withdrawing vaporized refrigerant from said evaporator and returning it to said condenser, an expansion valve for controling the flow of refrigerant from said condenser to said evaporator, control means including two temperature responsive devices one responsive to the temperature of vaporized refrigerant withdrawn from said evaporator and the other responsive to the temperature of liquid refrigerant in said evaporator for actuating said valve to maintain a predetermined amount of superheat in the refrigerant withdrawn from said evaporator, said other temperature responsive device tending to close said valve upon an increase in temperature, and means dependent upOn the absence of liquid refrigerant in said evaporator for opening said valve regardless of the condition of operation of said control means. I

6. In a refrigerating system including a condenser and an evaporator, means including an electrically driven compressor for withdrawing vaporized refrigerant from said evaporator and returning it to said condenser, an electric circuft for energizing said compressor, an expansion valve for controlling the flow of refrigerant from said condenser to said evaporator; control means including a temperature responsive device for actuating said valve, said device including a temperature feeler element arranged adiacent a portion of said evaporator normally containing liquid refrigerant to be responsive to the temperature of the liquid refrigerant in said evaporator, said device tending to close said valve on an increase intemperature, means including a. heater arranged to be energized upon energization of said electric circuit for supplying heat to said temperature responsive element during energization of said compressor whereby a relatively high pressure is produced in said temperature responsive device in the event that no liquid refrigerant is present in said portion of said evaporator to cool said feeler element, and means dependent upon said relatively high pressure for opening said valve.

7. In a refrigerating system including a condenser and an evaporator and means for withdrawing vaporized refrigerant from said evaporator and returning it to said condenser, an expansion valve for control ing the flow of refrigerant from said condenser at said evaporator, control means including a temperature responsive device for actuating said valve, said device including a temperature responsive element arranged adjacent a portion of said evaporator normally containing liquid refrigerant to be responsive to the temperature of liquid refrigerant in said evaporator, said device tending to close said valve on an increase in temperature, and means including a second temperature responsive device having a feeler element responsive to the temperature of liquid refrigerant in said evaporator for opening said valve upon a rise in temperature dependent upon the absence of liquid refriger'ant in said evaporator regardless of the condition of operation of said first mentioned device.

8. In a refrigerating system including a condenser and an evaporator and an electric motor driven compressor for withdrawing vaporized refrigerant from said evaporator and returning it to said condenser, an electric circuit for energizing the motor of said compresso an expansion valve for controlling the flow of refrigerant from said condenser to said evaporator, means including a temperature responsive device having a temperature feeler element arranged adjacent said evaporator to be responsive to the temperature of the liquid refrigerant therein for actuating said valve, said device tending to close said valve on an increase in temperature and normally maintaining said valve closed when said system is not in operation, and means including a heater associated with said electric circuit and arranged to provide a relatively high temperature in a portion of said evaporator in the absence of liquid refrigerant for opening said valve upon energization of said compressor.

9. In a refrigerating system including a condenser an evaporator and an electrically driven compressor for withdrawing vaporized refrigerant from said evaporator and returning it to said condenser, an electric circuit for energizing said compressor, an expansion valve for controlling the flow of refrigerant from said condenser to said evaporator, said valve tending to remain closed when said evaporator is above a predetermined temperature, said evaporator including a sump for collecting liquid refrigerant, and means dependent upon the temperature at said sump and including a heater associated with said electric circuit for opening said valve upon energization of said compressor when no liquid refrigerant is present in said sump.

10. In a refrigerating system including a condenser and an evaporator and means for withdrawing vaporized refrigerant from said evaporator and returning it to said condenser, a therinostatic expansion valve for controlling the flow of refrigerant from said condenser to said evaporator, said valve including a first actuating element responsive to the temperature of refrigerant withdrawn from said evaporator and a second actuating element arranged to be responsive to the saturation temperature of liquid refrigerant in said evaporator and tending to close said valve on a rise in temperature, and means dependent upon the absence of liquid refrigerant in a portion of said evaporator for modifying the operation of said valve to open said valve upon a predetermined rise in temperature at said portion of said evaporator,

11. An expension valve for refrigerating systems and the like comprising a valve body having an inlet and an outlet, a valve in said body for controlling the passage of fluid from said inlet to said outlet, two temperature responsive devices arranged in opposed relation to actuate said valve within a predetermined range of operating temperatures, one of said devices tending to overcome the other and close said valve on an increase in the temperature to which it is responsive, and a third temperature responsive device arranged to modify the operation of said two opposed devices and to open saidvalve when the temperature to which said third device is responsive reaches a predetermined high value.

12. An expansion valve for refrigerating systems and the like comprising a valve body having an inlet and an outlet, a valve in said body for controlling the passage of fluid from said inlet to said outlet, means including two temperature responsive devices arranged in opposed relation for actuating said valve within a predetermined range of operating temperatures, one of said devices tending to overcome the other and close said valve on an increase in thetemperature to which it is responsive, and a third temperature responsaid third device being constructed and arranged to engage said actuating means and modify the levers cooperating with said biasing means to actuate said valve within a predeterminedrange of operating temperatures, one of said devices being arranged to move said one lever to open said valve upon a decrease in the temperature to which it is responsive, and the other of said levers being arranged to open said valve upon movement of said link produced by an excessive rise of the temperature to which said one device is responsive. 1

16. An expansion valve for refrigerating systems and the like, comprising a valve body having an inlet and an outlet for fluid, a valve in said body for controlling the passage of fluid from said inlet to said outlet, means biasing said valve to its closed position, two expansible chamber temoperation of said opposed devices only when the 13. An expansion valve for refrigerating systems and the like, comprising a valve body having an inlet and an outlet for fluid, a valve in said body for controlling the passage of fluid from said inlet to said outlet, means including two temperature responsive devices arranged in opposed relation to actuate said valve within a predetermined range of operating temperatures, said last mentioned means including a lost motion connection between said valve and said devices, said valve tending to close upon movement of one of said devices in a direction resulting from an increase in the temperature to which said one device is responsive, and means dependent upon excessive movement of said one device in said direction for opening a path of communication between said inlet and said outlet.

14. An expansion valve for refrigerating systems and the like, comprising a valve body having an inlet and an outlet for fluid, a valve in said body for controlling the passage of fluid from said inlet to said outlet, means including two temperature responsive devices arranged in opposed relation and a link connecting said devices to actuate said valve within a predetermined range of operating temperatures, said valve tending to close upon movement of one of said devices in a direction resulting from an increase in the temperature to which said one device is responsive, a lost motion connection between saicl link and said valve, and means dependent upon excessive movement of said one device in said direction for opening said valve.

15. An expansion valve for refrigerating systems and the like, comprising a valve body having an inlet and an outlet for fluid, a valve in said body for controlling the passage of fluid from said inlet to said outlet, means biasing said valve to its closed position, two temperature responsive devices having a link therebetween and. arranged in opposed relation, two levers associated with said link and having portions arranged to move in opposite directions upon movement of said link, lost motionconnections between said portions 01' said levers and said valve, one or said rerature responsive devices and a link connecting said devices in opposed relation, two pivoted levers associated with said link and having end portions arranged to move in opposite directions upon movement of said link, leaf springs connecting said levers and said valve, each of said springs affording movement of said valve independently of its respective lever in one direction and eifecting movement of said valve with its respective lever in the other direction, one of said levers and the spring connected therewith coopcrating with said biasing means to actuate said valve within a predetermined range of operating temperatures, one of said devices being arranged normally to move said one lever to open said valve upon a decrease in pressure within the ex-- pansible chamber of said device and the other of said levers cooperating with its respectivespring to open said valve upon movement of said link produced by excessive pressure in said expansible chamber of said one device.

17. An expansion valve for refrigerating systems and the like comprising a valve body having an inlet and an outlet for fluid, two valves in said body each providing communication be tween said inlet and said outlet, means biasing said valves to their closed positions, two expansible chamber devices and a link therebetween for connecting said devices in opposed relation, and lost motion connections between said valves and said link and arranged to afford operation of one of said valves in accordance with the diflerence between the pressures in said expansible chamber devices within a predetermined range of operating pressure differences, one of said expansible chamber devices tending to open said one valve upon a decrease in pressure in the expansible chamber of said device, and the other one of said valves being connected to be opened by movement of said link upon the occurrence of a predetermined excessive pressure in said one expansible chamber device.

18. An expansion valve for refrigerating systems and the like comprising a valve body having an inlet and an outlet for fluid, two independently operating valves in said body each providing communication between said inlet and said outlet, means biasing said valves to their closed positions, two temperature responsive devices and a link connecting said devices in opposed relation, and lost motion connections between said valves and said link, one of said valves being actuated by a difference in the temperatures of said devices producing a resultant force in one direction under one range of temperatures,

and the other of said valves being actuated by a difference in the temperatures of said devices producing a resultant force in the opposite direction under a different range of temperatures.

denser and an evaporator and means for withdrawing vaporized refrigerant from said evaporatorand returning it to said condenser, a valve for controlling the flow of refrigerant from said condenser to said evaporator, said valve tending to remain closed during the inactive portion of the refrigerating cycle of said system, and means for detecting the absence of liquid refrigerant in said evaporator at the beginning of the active portion of the refrigerating cycle, said means including a temperature responsive device having a feeler element adjacent a portion of said evaporator normally containing liquid refrigerant and a heater element adjacent said feeler element and said portion of said evaporator, said heater element being arranged to be energized upon the starting of the refrigerating cycle of said system.

,20. In a refrigerating system including a condenser and an evaporator and means for withdrawing vaporizedrefrigerant from said evaporator and returning it to said condenser, means for controlling the operation of said system, and means dependent upon the absence of liquid refrigerant in said evaporator for modifying the operation of said control means, said modifying means including a sump for collecting liquid refrigerant adjacent the inlet of said evaporator, a temperature responsive devicehaving a feeler element adjacent said sump, a heater element adjacent said feeler element, and means for energizing said heater.

21. An expansion valve; for refrigerating systems and the like comprising a valve body having an inlet and an outlet, a valve in said body for controlling the passage of fluid from said inlet to said outlet, a plurality of temperature responsive devices, means connecting a first and a second one of said devices in opposition for actuating said valve, said first device tending to close said valve on a rise in temperature and said second device tending to open said valve on a rise in temperature, and means dependent upon a predetermined high temperature of one of said plurality of devices and opposing said first device for positively providing communication between said inlet and said outlet.

HAROLD F. LATHROP.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,060,589 Otto Nov; 10, 1936 2,098,914 Gorrie Nov. 9, 1937 2,112,344 Otto Mar. 29, 1938 2,303,891 Moore Dec. 1, 1942 2,319,005 Lum May 11, 1943 2,342,579 Hagemann Feb. 22, 1944 2,410,795 Dillman Nov. 5, 1946