US2123921A - Refrigeration - Google Patents

Description

July 19, 1938.

S. W. E. ANDERS SON REFRIGERATION Filed Dec. 19, 1934 5 Sheets-Sheet l V INVENTOR.

Jaw W XW ATTORNEY.

INVENTOR.

Mia/3d I MATTORNEY.

July 19, 1938. s. w. E. ANDERSSON 2,123,921

' REFRIGERATION Filed Dec. 19, 1934 5 Sheets-Sheet 5 INVENTOR.

Mia/Gm A ATTORNEY.

Patented July 19, 1938 by mesne assignments, to Servel, Inc; Dover, Del., a corporation of Delaware Application December 19, 1934, Serial No. 758,195

26 Claims.

I My invention relates to refrigeratioi'nand more particularly to control of refrigeration Systems of a continuous absorption type.

It is an object of my invention to provide a control device whereby'defrosting of a refrigerator of the continous absorption type can be instigated at will and the defrosting is terminated automatically. My present invention involves an improvement of a device of this character dieclosed in my earlier application Serial No.

My invention, together with the objects and advantages thereof,'will be understood upon consideration of the following description and the accompanying drawings forming part of this specification and of which: Fig. 1 is a brokenview in front elevation of a refrigerator provided with a device embodyin my invention;

Fig. 2 is a side view, partly in vertical section,-

of the refrigerator shown in Fig. 1;

Fig. 3 is a sectional view of a control device embodying my invention and adapted for use in the refrigerator illustrated in Figs. 1 and 2;

Fig. 4 is a section taken on line 4-4 in Fig. 3;

Fig. 5 isa detail view from line 5-5 in Fig. 3;

Fig. 6 is anelevational view of the casing the device shown in Fig. 3; and

Fig. '7 is a plan view of the casing shown in Fig. 6. v

Referring to Figs. 1 and 2 of the drawings, a refrigerator cabinet i0, shown in broken view. is of a known type having an upper heat insulated chamber or food storage compartment, ac-

cessible by means of a door i2, and a lower apparatus compartment l3 from which apassage 14 extends upwardly at the back of the refrigerator in the rear of the storage compartment Ii. In the cabinet is mounted an absorption refrigera- 4 tion apparatus of a pressure equalized continuous type. Briefly, such an apparatus comprises an evaporator or cooling element in which refrigerant fluid, such as ammonia, evaporates and diil'uses into an inert pressure equalizing gas, such 45 as hydrogen. The resulting gas mixture flows into an absorber where the refrigerant is absorbed by a suitable liquid absorbent, such as water. The inert gas returns to the evaporator and enriched absorption liquid is conducted t a 50 generator. The refrigerant is expelled from solution by heating in the generator. The weakened absorption liquid is again conducted through the absorber. The expelled refrigerant is condensed and returned to the evaporator.

55 thus completing the cycle.

Referring again to Figs. 1 and 2, the apparatus, of which only the parts necessary. for this description are shown, is mounted in the cabinet with a cooling element or evaporator l5 located in the storage compartment II, and 'a generator 5 i6 located principally, in the lower apparatus compartment i3- (Fig. 2). The other parts of the apparatus are located either in the apparatus compartment l3 or the vertical passage I4. The enerator and is heated by a gas burner l8 arranged so that the burner flame is directed into the lower end of the. flue l1. Gas is supplied to the burner 18 from a conduit l8 through a suitable gas filter 20 and a control device 2! respectively. 15

The construction and operation'of the control device 2| may best be understood by reference to Figs. 3 .to 7. with more particular reference to Fig. 3, the control device 2| comprises a casing 22 providing a diaphragm chamber 23 and a valve 20 chamber 24. A bushing 25 is threaded into the open end of the valve chamber 24 and provides a valve passage 26 between the diaphragm chamber 23 and the valve chamber 24. The form of the casing 22 may be better understood by.also 25 referring toFigs. 6 and '7 which are respectively elevational and plan views of the casing alone. Bosses 21 and 28 on opposite sides of the casing 22 are drilled and threaded for gas inlet and outlet connections respectively. A passage 29 ex- 30 tends from the inlet in boss 21 to the valve chamber 24. A passagev 30 extends from the diaphragm chamber 23 to the outlet in boss 28. During operation of the device; as hereinafter described, gas flows from the inlet in boss Ti 35 through the passage 29 into the valve chamber 24, through the valve passage 26 into the diaphragm chamber 23. and through the passage 30 to the outlet in boss 28.

. Referring again more particularly to Fig. 3, 40 means is provided for controlling flow of gas through the valve passage 26 and comprises a valve member 3| in the valve chamber 24 having a substantially triangular valve stem 32 which ex- .tends through the valve passage 26 into the diaphragm chamber 23. The valve member 3| is urged toward its closed or seated position on the bushing 25 by a load spring 33. It may be said that the valve member 3| is loaded or biased to its'closed position. p

The open side of the diaphragm chamber 23 in the valve casing 22 is closed by a flexible diaphragm 34 which is secured at its periphery between a suitable gasket 34a onthe edge of; the

, valve casing 22 and the edge of a cover plate 35. I

I6 is provided with a heating flue i1 10 An expansible diaphragm 36 is located in the diaphragm chamber 23 and mounted centrally of the flexible diaphragm 34 by means of a member 31 which will be referred to as a diaphragm stud.

Referring now to Figs. 3, 4, and 5, a member that will be referred to as a yoke 38 is located in the diaphragm chamber 23 and also mounted on the flexible diaphragm 34 by means of the stud 31'. The yoke 38 is secured to the stud 31 between the flexible diaphragm 34 and the expansible diaphragm 36, and extends around and somewhat beyond the expansible diaphragm. Between the expansible diaphragm 36 and the end of the valve stem 32 are levers 39 and 40, both pivoted at one end; and to one side of the center of the expansible diaphragm 36, on a cross piece 38a of the yoke 38 at the pivot 4|. This pivot is therefore fixed with respect to the position of the expansible diaphragm 36. A member which will be referred to as a catch 42 is pivoted at the other end of the lever 39 in a manner to engage the other end of the lever 40. A substantially hairpin shaped spring 43 is constructed and arranged in a manner to urge the levers 39 and 40 apart and at the same time urge the catch 42 into engagement with the end of the lever 40 to prevent the levers 39 and 46 from actually moving apart. The lever 39 overlies the center of the expansible diaphragm 36 and is provided with a small set screw 44 to form'a contact between the center of the expansible diaphragm 36 and the lever 39. The set screw is adjusted during fabrication of the device and then preferably sealed by a drop of solder or the like. The lever 40 overlies and contacts the stem 32 of the valve member 3|. It will now be understood that contraction and expansion of the expansible diaphragm 36 causes closing and opening movements respectively of the valve member 3|, the motion being transmitted by the levers 39 and 40 which areretained in their fixed positions with respect to each other by the catch 42 and the spring 43 as previously described, thereby substantially acting as a single lever or substantially rigid motion transmitting linkage.

The diaphragm mounting stud-.31 is provided with a passage 45 open at one end within the expansible diaphragm 36 and open at the other end outside of the sealing diaphragm 34. One end of a capillary tube 46 is connected to the outer end of the diaphragm stud passage 45, as may be seen in Fig. 3, and the other end of the capillary tube 46 is connected to a thermostat bulb 41 located in thermal contact with the cooling element 5 of the refrigerator, as may be seen in Figs. 1 and 2. The bulb 41, capilliary tube 46, and expansible diaphragm 36 consitute what is referred to as an expansible fluid thermostat which is fllled with a suitable fluid which expands upon increase'in temperature and becomes reduced in volume upon decrease in temperature.

It will now be understood that the expansible diaphragm 36 expands upon increase of temperature of the refrigerator cooling element l5 and.

contracts upon decrease intemperature of the cooling element, thereby operating the valve 3|, as previously described, to control the flow of gas to the burner responsive to temperature of the cooling element; The capillary tube 46 is formed in aloop adjacent its end which is connected to the diaphragm stud 31 so as to afford considerable flexibility and not appreciably affect movement of the stud 3! during adjustment of the thermostat as hereinafter described.

' -The cover plate 35 is provided centrally with an inset bushing 48 which is internally threaded to receive Inthreaded engagement a thermostat adjusting assembly comprising a sleeve 49, a pin 60, a cap member 5|, and a retaining nut 52. The pin 50 is provided near its inner end with a circular flange 53 so that, when the pin 50, the sleeve 49, and cap member 5| are assembled, they may be secured together as a unit by the retaining nut 52 which is threaded on the outer end of the pin 56 and tightened down against the cap 5|. A central teat 54 on the inner end of the pin 50 forms an abutment for the diaphragm mounting stud 31. It will now be understood that screwing the adjusting assembly in one direction or the other moves the center of the flexible diaphragm 34 inwardly or outwardly and changes the relative position of the expansible diaphragm 36 with respect to the valve I member 3 the cap member. 5| of the adjustment assembly the thermostat as described.

It will be understood that the pulley 55 may be .replaced by a suitable control knob or dial. However, in the refrigerator illustrated, it is preferred to have the control knob in the upper part of the refrigerator cabinet on the front of the cooling element, as shown in Figs. 1 and 2 where the adjusting knob is indicated by the reference character 51. The adjustment knob 51 is provided with a suitable fixed dial or index plate 58 and is mounted on the end of a rod 59 (Fig. 2) which extends from the front of the cooling element |5 through the rear wall of the storage compartment into the vertical passage l4 where it is provided with a grooved pulley 60 similar to' the pulley 55 on the control device 2|. The pulleys 55 and 60 are operatively connected 'by a flexible wire belt 6| provided with a guide tube casing 62. Turning the knob 51 on the front of the cooling element l5 causes rotation of rod 54, pulley 60, and pulley 55, whereby the adjustment of the control thermostat is varied as previously described. For a purpose which will hereinafter appear, the arrangement just described is so constructed that only a half .turn of the adjustment knob51 and the parts operated thereby is utilized to obtain full range adjustment of the thermostat.

Referring again to Fig. 3, the diaphragm stud 31 is formed with a spiral cam 63 which extends not more than half-way around the periphery of the stud. The adjusting pin 60 is formed with a short arm 64 located in a manner to ride on the cam 63 only when the pin 56 is given more than a half turn. When the arm 64 rides up on the cam 63, the diaphragm stud 31 and the parts attached thereto, as described above, are displaced an abnormal distance, that is, a distance -which is greater than the corresponding pitch A grooved-pulley 55 is mounted on with said thermostat and the other lever being the catch 42. The adjustment knob 51 is now returned to itsdesired setting on the lower half of the scale58, thereby disengaging the arm 64 from the cam 63. The levers 40 and 39 are now closer together due to the lever 40 being engaged in the notch 65, thereby effecting a different operative relation between the exparisible diaphragm 36 and the gas valve 3i so that a given expan sion of the diaphragm 36 does not now produce the same operation of the valve 3|. Therefore, the expansible diaphragm 36 will not open the gas'valve 3| until an abnormally high temperature is reached in the cooling element l5. This high temperature should be somewhat above the freezing point of water. When the valve 3| is closed, heating of the generator of the refrigera tion apparatus is decreased, permitting the temperature of the cooling element l to rise. When the temperature of the cooling element l5 has risen above the. freezing point of water, frost that may have accumulated on the cooling element l5 will melt and become deposited in a suitable receptacle, not shown, provided for the purpose. As the temperature of the cooling element l5 rises, the diaphragm 36 expands in the valve opening direction. Since the valve 3| is not opened until an abnormally high temperature is reached, the diaphragm 36 expands an abnormal distance. The abnormal expansion of the diaphragm 36 carries the lever 39 and catch 42 such a distance that a short arm 66 on the catch 42 is engaged by a stop 61 on the yoke cross piece 38a. As the lever 39 continues to move under the expansion of the diaphragm 36, the catch 42 is revolved around its pivot on the lever 39 and against the tension of the hairpin spring 43 in a direction such that the end of the lever 49 is released from the notch 65 to its normal position. Upon return of-the lever 40 to its normal position, the gas valve 3! will not be closed until the temperature of the cooling element l5 returns to its normal value. or value for which the thermostat is adjusted by the setting of the adjustment knob 51. Therefore, the generator will be heated until the cooling element I5 is again re duced to such normal value. Then, the thermostat continues normal control of the generator heating burner l8 responsive to temperature of the cooling element l5 until the above described abnormal or defrosting operation is again instigated by turning the adjustment knob 51 to the Defrost position and immediately returning to the desired setting.

It will be understood that. various changes may be made within the scope of my invention which, therefore, is not limited to that which is shown in the drawings and described in the specification but only as indicated in the following claims.

What is claimed is:

l. Refrigeration apparatus of a continuous absorption type including a cooling element, a generator, a gas burner for heating said generator,

and a control device comprising a valve for controlling flow of gas to said burner, an expansible fluid. thermostat operative responsive to temperature of said cooling element, means for adjusting the position of said thermostat, linkage operatively connecting said thermostat and said valve comprising a pair of levers, each pivoted at one end on a pivot fixed with respect to the position of said thermostat, a spring arranged to urge said-levers apart, a catch on one of said levers constructed and arranged to engage the other lever to prevent said levers from moving apart,

one of said levers being operatively associated operatively associated with said valve, means whereby said levers are urged toward each other upon predetermined adjustment of said thermostat, said catch being constructed and arranged to detain said levers in a second position in which they are closer together, and means for operating said catch to release said levers to their normal position upon predetermined expansion of said thermostat. g

2. Refrigeration apparatus of a continuous absorption type including a cooling element, a generator, a heater for said generator, a device for regulating said heater, a thermostat operative responsive to temperature of said cooling element, means for adjusting said thermostat, linkage operatively connecting said thermostat and regu-' catchbeing constructed and arranged to detainv said levers in a second position in which they are,

closer together, and means for operating said catch to release said levers to their normal position upon predetermined operation of said thermostat responsive to increase in'temperature.

3. Refrigeration apparatus of a continuous absorption type including a cooling element, a generator, a gas burner for heating said generator, and .a control device including a valve for controlling flow. of gasto said burner an expansibie fluid thermostat operative responsive to temperature of said cooling element, linkage operatively connecting said thermostat and said valve comprising a pair ofv levers each pivoted at one end, a spring arranged to urge said levers apart, a catch on one of said' levers constructed and arranged to engage the other lever to prevent said levers from moving apart, one of said levers being operatively associated with said thermostat and the other lever being operatively associated with said valve, means to move said levers toward each other against the action of said spring, said catch being constructed and arranged to detain said levers in a second position in which they are closer together, and means for operating said catch to release said levers to their normal position upon predetermined expansion of said thermostat. v

4. Refrigeration apparatus of a continuous absorption type including a cooling element, a generator,'a heater for said generator, 9. device for regulating said heater, a thermostat operative responsive to a temperature condition affected by said cooling element, structure operatively asretain said parts in a second position in which they are closer together, and means for operating said catch to release said-parts to their normal position upon abnormal expansion of said thermostat.

5. Refrigeration apparatus of a continuous ab- .sorption type including a cooling element, a gen- Y maintaining said temperature condition substantially constant, said structure being adjustable to place said parts in an abnormal space relation with respect to each other whereby said expansion of the thermostat produces a different operation of said heater regulator to cause a change in said temperature condition, and means whereby said parts are returned to said normal space relation upon movement of said thermostat responsive to said change in temperature condition.

6. Refrigeration apparatus of a continuous absorption type including a cooling element, a generator, a gas burner for heating said generator, a valve for controlling flow of gas to said burner, a thermostat operative responsive to a temperature condition affected by said cooling element, structure operatively associating said thermostat and valve including parts normally retained in. a certain space relation with respect to each other so that a certain expansion of said thermostat produces a certain operation of said valve 7 in maintaining said temperature condition substantially constant, said structure being adjustv able to place said parts in an abnormal space relation with respect to each other whereby said expansion of the thermostat produces a different operation of said valve to cause a change in said temperature condition, and means whereby said parts are returned to said normal space relation upon movement of said thermostat responsive to said change in temperature condition.

'7. Refrigeration apparatus of a continuous ab-' sorption type including a cooling element, a generator, a gas burner for heating said generator, a. valve for regulating the flow of gas to said burner, a thermostat operative responsive to a temperature condition aifected. by saidcooling element and normally ,operatively associated with said valve so that a certain expansion of said'thermostat upon increase in temperature produces a certain operation of said valve in maintaining said'temperature condition substantially constant, and means for changing the operative relation between said thermostat and valve so that said expansion of the thermostat produces'a different operation of said valve to permitincrease in said temperature condition, and means to return said thermostat and valve to said normal operative relation upon said in,- crease in temperature condition.

, 8. Refrigeration apparatus of a continuous absorption type including a cooling element, a generator, a heater for said generator, a device for regulating said heater, a thermostat operative responsive to a temperature condition aflected by said cooling element and normally operatively associated with said heater regulator so that a certain expansion of said-thermostat upon increase in temperature produces a certain operation of said regulator in maintaining said temperature condition substantially constant,.and means for changing the operative relation between said thermostat and heater regulator so that said expansion of the thermostat produces a different operation of said regulator to permit increase in said temperature condition, and means to return said thermostat and regulator to said normal operative relation upon said increase in temperature condition. I

9. Refrigeration apparatus of a continuous absorption type including a cooling element, a generator, a gas burner for heating said generator, a valve for controlling flow of gas to said burner, a thermostat having a single expansible element operative responsive to a temperature condition affected by said cooling element, a member associating said expansible element and valve in a normal operative relation to maintain substantially a desired temperature condition, means for adjusting said member to alter the operative relation between said expansible element and valve so that said valve is opened only upon abnormal increase in said temperature condition and'abnormal expansion of said element, and means for re-adjusting said member to resume said normal operative relation between said expansible element and valve upon said abnormal expansion of the expansible element. v

10. Refrigeration apparatus of continuous absorption type including a cooling element, a generator, a heater for said generator, a device for regulating said heater, a thermostat having a single expansible element operative responsive to. a temperature condition aiiected by said cooling element, a member associating said expansible element and heater regulator in a normal operative relation to maintain substantially a desired temperature condition,means for adjusting said member to alter the operative relation between said expansible element and heater regulator to cause an abnormal increase in said temperature condition and abnormal expansion of said element, and means for re-adjusting said-member to resume said normal operative relation between said expansible element and heater regulator upon said abnormal expansion of the expansible element.

11. Refrigeration apparatus of a continuous absorption type including a cooling element, a

generator, a heater for said generator, a device for regulating said heater, a thermostat operative responsive to a temperature condition affected by said cooling element, a member associating said thermostat and heater regulator in a normal operative relation, means for adjusting a dimension of said member to alter said operative relation, and means for terminating said altered operative relation responsive to abnormal change 'in said temperature condition.-

y 12. A temperatureregulator for refrigeration apparatusincluding a thermostat, a device for controlling operation of the apparatus, a member connecting said thermostat and control device in a normal operative relation, means for adjusting said member to shorten or lengthen the connection between said thermostat and control device to alter the operative relation between said thermostat and device, and means to terminate said altered operative relation responsive to an' abnormal change in temperature.

13. A temperature regulator for refrigeration apparatus including a device for controlling op- 1 with said control device in a normal operative relation to maintain substantially a desired temperature condition affected by said refrigeration apparatus, said thermostat being expansible and also bodily movable, means for altering said normal operative relation between the thermostat and control device by bodily movement of the thermostat, and means for restoring said normal operative relation responsive to abnormal expansion of said thermostat.

14. A temperature regulator for refrigeration apparatus including a device for controlling operation of the apparatus, a thermostat operative responsive to a temperature condition affected by said apparatus, a member connecting said thermostat and control device in a normal operative relation to maintain substantially a desired temperature condition, means for adjusting said member to shorten or lengthen the connection between said thermostat and control device to change said operative relation between the thermostat and control device to cause an increase in said temperature condition, and means for restoring said normal operative relation by said member responsive to said increase in temperamove the operating element from said one engaging surface to said other engaging surface to give the catch and operating element a second relative position, and means responsive to temperature of said cooling element representing defrosted condition to restore said'first relative position.

16. In an absorption refrigeration apparatus including acooling element, a generator, and a source of heat for said generator, a control device including a control element for controlling supply to said source of heat, an operating element for actuating the control element, a catch having two engaging surfaces of which one is operative to hold the operating element in a first given position relative to the catch, manual means to move the operating element from said one engaging surface to said other engaging surface to give the catch andoperating element a second relative position, and means automatically responsive to temperature of said cooling element representing defrosted condition to restore said first relative position.

1'7. In' an absorption refrigeration apparatus including a cooling element, agenerator, and a source of heat for said generator, a control device including a control element for controlling supply to said source of heat, an operating elestore said first relative position, said manual means including a cam, a pulley for turning the cam, a second pulley, a rod adjacent said cooling element for turning said second pulley, and

operative to hold the operating element in a first given position relative to the catch, means to move the operating element from said one engag-g ing surface to said other engaging surface to give.

the catch and operating element a second relative position, a spring urging the operating element into said first position of engagement between the catch and operating element, and means responsive to temperature ofsaid cooling element representing defrosted condition to restore said first relative position.

19. In an absorption refrigeration apparatus including a cooling element, a generator, and a source of heat for said generator, a control device including a control element for controlling supply to said source of heat, a pivoted operating element for actuating the control element, a-pivoted catch having two engaging surfaces of which one is operative to hold the operating element in a first given position relative to the catch, manual means to move the operating element from said one engaging surface to said other engaging surface to ,give the catch and operating element a second relative position, means urging the catch into said second'position of engagement between the catch and operating element, means urging the operating element into said first position of engagement between'the catch and operating element, and automatic means responsive to temperature of said cooling element representing defrosted condition to restore said first relative position.-

20. In valve mechanism of the character described, a valve, a valve operating element, a catch having two engaging surfaces of which one is operative to hold the operatingelement in a first given position relative to the catch, means to move the operating element from said one engaging surface to said other engaging surface to give the catch and operating element a second relative position, and means responsive to tem-' perature to restore said first relative position.

21. In'valve mechanism of the character described, a valve, a pivoted valve operating element, a pivoted catch having two engaging surfaces of which one is operative to hold the operating element in a first given position relative to the catch, means to move the operating element from said one engaging surface and permit turning of the catch for said other engaging surface to hold the operating element in a second given position relative to the catch, means responsive to temperature to turn the catch to release the operating element from said other engaging sur-v face to restore said first relative position, and

spring means urging the operating element into said first position of engagement between the catch and operating element.

22. In a refrigerator, a cabinet having an apparatus' compartment and an insulated compartment, an absorption refrigeration apparatus including a generator in said apparatus compart ment and a cooling element in said insulated compartment, means for supplying heat to said generator, and a control element for normally coning respectively, and means to bodily move said expansible element to change said parts from normal control status to defrosting status.

23. In a refrigerator, a cabinet having an apparatus compartment and an insulated compartment, an absorption refrigeration apparatus in-.- cluding a generator in said apparatus compartment, and a cooling element in said insulated compartment, means for supplying heat to said generator, and a control element for normally controlling the supply of heat, an egrpansible element, a thermal element connected to said expansible element responsive to changes of temperature of said cooling element, parts operatively connecting said normal control element and expansible element and having different relative positions for normal control and defrosting respectively, and means to bodily move said expansible element in one direction to change said parts from normal control status to defrosting status and to move said expansible element back bodily while retaining the. parts in defrosting status and to automatically change said parts from defrosting status to normal control status when the temperature of the cooling element rises to a value representing defrosted condition.

24. In a refrigerator, a cabinet having an apparatus compartment and an insulated compart ment, an absorption refrigeration apparatus including a generator in said apparatus compartment and a cooling element in said insulated compartment, means for supplying heat to said generator, and a controlelement for normally controlling the supply of heat, an expansible element, a thermal element connected to said expansible element responsive to changes of temperature of said cooling element, parts operatively connecting said normal control element and expansible element and having different relative positions for normal control and defrosting respectively and including a spring pressed operating lever to actuate said control element and a spring pressed catch lever for holding the operating element ina given position, and means to bodily move said expansible element to change said parts from normal control status to defrosting status.

25. In a refrigerator, a cabinet having an apparatus compartment and an insulated compart ment, an absorption refrigeration apparatus including a generator in said apparatus compartment and a cooling element in said insulated compartment, means for supplying heat tosaid generator, and a control member for normally controlling the supply of heat, an expansible element, a thermal element connected to said expansible element responsive to changes of temperature of said cooling element, and parts operatively connecting said normal control member and expansible element and having different relative positions for normal control and defrosting respectively, and means to bodily move said expansible element to change said parts from normal control status to defrosting status including a cam and remote control mechanism for turning said cam. I

26. In a refrigerator, a cabinet having an apparatus compartment and an insulated compartment, an absorption refrigeration apparatus including a generator in said apparatus compartment and a cooling element in said insulated compartment, means for supplying heat to said generator, and a control member for normally controlling the supply of heat, an expansible element, a thermal element connected to said expansible element responsive to changes of temperature of said cooling element, parts operatively connecting said normal control member and said expansible element and having different relative positions for normal control and defrosting respectively, and means to bodily move said expansible element to change said parts from normal control status to defrosting status and including a turnable rod adjacent said cooling element, a

pulley turnable with said rod, a second pulleynear the expansible element, and operating mech- 45 anism between said pulleys.

SVEN W. E. ANDERSSON.

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