US2251658A - Refrigeration apparatus - Google Patents

Description

g 1941- L B. M. BUCHANAN REFRIGERATION APPARATUS Filed Feb. 21, 1940 WITNESSES:

INVENTOR M. Buchanan Leslie, 5

ATTORNZZQ Patented Aug. 5, 1941 REFRIGERATION APPARATUS Leslie B. M. Buchanan, Springfield, Mass, assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application February 21, 1940, Serial No. 320,050

11 Claims.

My invention relates to refrigerating apparatus and particularly to an improved control therefor.

It is an object of myinvention to provide an improved compensated control for refrigerating apparatus.

It is a further object of my invention to render the compensating means for a compensated control at least partially ineffective in response to abnormal temperature conditions of the media surrounding the zone to be refrigerated.

It is another object of my invention to provide an improved defrosting control for refrigerating apparatus.

It is still another object of my invention to provide an improved control for refrigerating apparatus wherein the control is compensated for changes in outside temperature and wherein defrosting is insured at those times when intermittent defrosting is automatically or manually initiated. j

These and other objects are effected by my invention as will be apparent from the following description and claims taken in accordance with the accompanying drawing, forming a part of this application, in which:

Fig. l is a diagrammatic view of a refrigerator and control therefor illustrating my invention; and,

Fig. 2 is a fragmentary view of a manuallyadjustable refrigerator control.

Referring specifically to the drawing for a detailed description of my invention, numeral ll designates generally a refrigerator cabinet having walls l2 with heat insulation l3 therebetween, which walls surround a chamber or zone H to be refrigerated. A cooling element or evaporator 55 is disposed within the zone 54 to abstract heat therefrom. Vaporous refrigerant is withdrawn from the evaporator l5 through a. suction conduit l6 and is compressed by a compressor H. The compressed refrigerant is conveyedto a condenser l8 through a conduit l9 and the refrigerant is cooled and liquefied in the condenser l8. Liquid refrigerant is conveyed to the evaporator preferably through a capillary tube flow-restricting device 2| and a liquid line 22. The liquid line is larger in internal diameter than the capillary tube 2| and contains refrigerant at s bstantlally the temperature of the evaporator IS. The liquid line 22, therefore,

substantially constant value, a temperature control device, generally indicated at 23, is provided. The temperature-control device comprises a bulb 24, having a volatile refrigerant therein, connected through a conduit 25 to a bellows 26, so that changes in the temperature of the zone M will evaporate or condense more or less refrigerant in the bulb 24 and conduit 25 and cause the bellows 2'6 to expand or contract. A spring 21 Opposes theforce of the bellows 26' anda switch-operating arm 28 is disposed between the spring 21 and the bellows 26. the bellows 26, spring 21 and operating arm 28 are disposed in the atmosphere surrounding the refrigerator cabinet ii. The operating arm 28 is pivoted at 29 on a pin it. The pin 3! is free to move vertically in a slot in a supporting member 33. Upward movement or the arm 23 closes a pair of contacts 37 through a snap-acting device 38, and downward movement of the arm 28 opens the contacts 37 through the snap acting device. Th contacts 3! are connected to conductors 4i and 42, which conductors connect an electric motor 43, which drives the compressor ii, to a source or power L1, L2. A cam 34 engages pivoted end 30 of the operating arm 28 and moves it vertically, thus providing a temperature adjust ment, the operating arm 2t being guided by the plum and slot 32. A shaft 35 is attached to the cam 34 and, as shown in Fig. 2, the end of the shaft is provided with a manually-operated temperature adjusting knob 36. Rotation of the cam 34 lowers or raises the pivoted end of the arm 28, thus requiring more or less pressure in the bellows 26 to open and close contacts 3'5, so that the average temperature of the zone It at which the contacts open and close to control operation of motor 43 and compressor ll, is varied.

When the temperature of the bulb 24, rises to a predetermined value, depending upon the position of the cam 34, the bellows 26 expands and forces the arm 28 upwardly to close the contacts 31 and efiect operation of the motor 43, which in turn drives the compressor and effects a flow of refrigerant through the evaporator l5. When the temperature of the volatile refrigerant in the bulb 24 and conduit 25 is reduced sufliciently, the bellows 26 contracts and drops the arm 28, whereupon the contacts 3! are opened, thus deenergizing the motor 43 and stopping the flow of refrigerant through the evaporator l5. 7 i

In order to compensate for changes in the temperature of the media surrounding the cabinet ll so as to maintain a substantially constant temperature in the zone I4, a heat-conducting clip 44 is connected between the liquid line 22 and the conduit'25 extending between the bulb 24 and bellows 26. In a control system partially filled with a volatile refrigerant, the point of the bulb 24 and conduit 25 which is at the coldest temperature will be the controlling point and, when sufliciently cold, the pressure of the volatile refrigerant corresponding thereto causes the bellows 26 to contract and open the contacts 31.

After the refrigerant-circulating mechanism has been started by the volatile liquid in the bulb 24 rising to a predetermined pressure, the refrigerant inlet conduit 22 is decreased in temperature, substantially assuming the temperature of the evaporator l 5. Because of heat transfer through the heat-conducting clip 44, a point 45 on the conduit 25 where the clip 44 contacts it becomes colder than the bulb 24. The point 45, therefore, becomes the controlling point of the bellows system, and when point 45 is sufiiciently reduced in temperature, the bellows 26 will contract to open the contacts 31 and thus stop the circulation of the refrigerantcirculating mechanism.

However, the liquid line 22, clip 44 and'conduit 25 are all of relatively small mass and are embedded in the heat insulation l3 of the cabinet II. The heat leakage from the media surrounding the cabinet ll, therefore, quickly heats up the parts of small mass so that the temperature at the point 45 rises above the temperature of the bulb 24. The controlling point then shifts to the bulb 24 and, as soon as the temperature in the zone l4 reaches a sufficiently high value, the pressure of the vaporizable refrigerant in the bulb 24 and bellows 26 rises sufficiently to again close the contacts 31.

As the temperature of the media surrounding the cabinet ll rises, more heat will leak into the liquid line 22, clip 44 and portion 45 of the conduit 2! so that a lower temperature in the liquid line 22 is required to contract the bellows 26 sufiiciently to open the contacts 21. The motor 43, therefore, drives the compressor I! for a longer period of time, thus compensating for changes in outside temperature. Furthermore, as the outside temperature changes, more heat leaks into the chamber l4 and the temperature and pressure of the vaporizable refrigerant in the bulb 24 is, therefore, increased more rapidly, so that the bellows 26 is expanded and the contacts 31 are closed sooner. Compensation is similarly effected when warm foods, for example, are placed in the zone l4. At lower outside temperatures, the reverse of this operation occurs, so that the refrigerating mechanism operates less than with warmer outside temperatures.

The foregoing control system is completely described and claimed in the copending application of R. E. Tobey, Serial No. 228,072, filed September 2, 1938, now matured into Patent No. 2,192,- 850, dated March 5, 1940, for Refrigerating apparatus and assigned to the assignee of the present application. I

'As shown in Fig. 2, the various positions of the manually-adjustable knob 36 are preferably marked in degrees Fahrenheit. as a, control of this type will maintain the temperature of the air in the zone I 4 within a very; small range.

A portion 40 of the contour of the cam 34 is so arranged that it will drop the pivot point 29 of thearm 26 sufllciently. that relatively high temperatures in the zone I4 are required to close the contacts 31. At this time, under normal conditions, the motor 43 drives the compressor ll very infrequently and, as a result, the evaporator I5 rises suificiently in temperature so that any frost which has accumulated thereon will melt. The adjusting knob 36 is provided with a position marked D corresponding to portion 40 on the cam 34 and when the adjusting knob is moved to this position, the evaporator 15 is defrosted. Such defrosting is necessary for eflicient operation of the refrigerator, and while I have shown a manually-operable defrosting mechanism, it is clear that other well-known modes of defrosting are contemplated by my invention. For example, those defrosting devices known in the art as semi-automatic" or full automatic are also contemplated.

It has been found, however, in applying a defrosting device to a compensated control, that when the temperature of the media surrounding the cabinet ll reaches relatively high values, the evaporator 15 does not defrost even though the control is set at the defrosting position. This is because the compensating means tends to effect more frequent and longer operation of the motor 43 and refrigerant is, therefore, supplied to the evaporator l5 in such quantities that it does not defrost even though the pivoted end 29 of the arm 28 of the control is dropped to the position where defrosting would normally occur.

In order to overcome the aforementioned difficulty without affecting the operation of the control under normal temperature conditions, I have provided a bi-metal temperature-responsive member 46 disposed in the media surrounding the cabinet II, which is bent to the shape shown in Fig. 1 and provided with a stop 41. The bimetal member 46 and stop 41 are so positioned that the arm 28 cannot contact the bi-metal strip 46 in any of the normal operating positions thereof. However, when the cam 34 and adjusting knob 36 are moved to the defrosting position and the pivoted end 29 of the lever 26 is dropped, the opposite end of the lever 28 rises. If the temperature of the media outside the cabinet II is at a normal'value, the bi-metal strip 46 is not expanded sufficiently to touch the arm 28,. and defrosting is effected in a normal way. However, if the temperature of the media surrounding the cabinet II is at a relatively high value, for example, F. or above. the bi-metal strip 46 expands so that it contacts the switch end of the lever 28 and adds bias thereto. It is, therefore, necessary for the temperature in the chamber H to rise a greater amount to exert sufficient pressure in the bellows to overcome the combinedv action of the spring 21 and the bimetal strip 46. This increase in temperature will insure defrosting of the evaporator l5 regardless of the temperature of the media surrounding the cabinet II.

From the foregoing it will be apparent that I have provided an improved compensated control device wherein defrosting is effected and wherein defrosting is insured regardless of the temperature of the media surrounding the zone to be refrigerated. I have, furthermore, in a broader sense, provided an improved compensated control wherein the compensating means is rendered at least partially ineffective in response to abnormal temperature conditions of the media surrounding the zone to be refrigerated.

While I have shown my invention in but one form, it will be obvious to those skilled in the parting from the art that it is not so limited, but is susceptible of various changes and modifications without despirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are specifically set forth in the appended claims.

What I claim is:

1. In refrigeration apparatus, the combination of an insulated zone to be refrigerated, a cooling element for abstracting heat from the zone, a temperature-responsive means for controlling the temperature ,in the zone, means for compensating the temperature-responsive means in response to changes in the temperature of the media surrounding said zone, and means for at least partially rendering the compensating means ineffective in response to abnormal temperature conditions of the media surrounding said zone, said compensating means being entirely effective under normal temperature conditions of the media surrounding said zone.

2. In refrigeration apparatus, the combination of an insulated zone to be refrigerated, a cooling element for abstracting heat from the zone, a temperature-responsive means for controlling the temperature in the zone, means for compensating the temperature-responsive means in response to changes in the temperature of; the media surrounding said zone, means for effecting intermittent defrosting of the cooling element and means for insuring said defrosting regardless of the temperature of said media surrounding the zone.

3. In refrigeration apparatus, the combination of an insulated zone to be refrigerated, acooling element for abstracting heat from the zone, a, temperature-responsive means for controlling the temperature in the zone, means for compensating the temperature-responsive means in response to changes in the temperature of the media surrounding said zone, means for effecting intermittent defrosting of the cooling element and means for insuring said defrosting when the temperature of the media surrounding the zone is at a value which would normally compensate the controlling means to such an extent to prevent defrosting.

4. In refrigeration apparatus, the combination of an insulated zone to be refrigerated, a cooling element for abstracting heat from the zone, means for circulating refrigerant through the cooling element, temperature-responsive means for controlling the operation of the refrigerantcirculating means and, therefore, the temperature in the zone, means for compensating the temperature-responsive means in response to changes in the temperatureof the media surrounding the zone, means for effecting intermittent defrosting-of the cooling element and means for insuring said defrosting when the media surrounding the zone is at a value which would normally compensate the controlling means to such an extent that operation of the refrigerant-circulating means would be increased sufficiently to prevent defrosting.

5, In refrigeration apparatus, the combination of an insulated zone to be refrigerated, a cooling means at least a portion of which abstracts heat from the zone, means for circulating refrigerant through the cooling means, temperature-responsive means for controlling the temperature in said zone comprising means for rendering said refrigerant-circulating means active primarily in response to the temperature of the media in said zone and inactive primarily in accordance with the temperature of a portion of the cooling means as modified by the temperature of the media surrounding said zone, whereby the controlling means is compensated in response to the temperature of the surrounding media and the active and inactive periods of the refrigerant-circulating means are varied, means for effecting intermittent defrosting of the cooling element and means for insuring defrosting of the cooling element when the media surrounding the zone is at a value which would normally increase the active periods of the refrigerant-circulating means sufficiently to prevent defrosting.

6. In refrigeration apparatus, the combination of an insulated zone to be refrigerated, a cooling means at least a portion of which abstracts heat from the zone, means for circulating refrigerant through the cooling means, temperature-responsive means for controlling the temperature in said zonecomprising means for rendering said refrigerant-circulating means active primarily in response to the temperature of the media in said zone and inactive primarily in accordance with the temperature of a portion of the cooling means as modified by the temperature of the media surrounding said zone, whereby the controlling means is compensated in response to the temperature of the surrounding media and the active and inactive periods of the refrigeraant-circulating means are varied, means for effecting intermittent defrosting of the cooling element and means for insuring defrosting of the cooling element when the media surrounding the zone is at a value which would normally increase the active periods of the refrigerantcirculating means sufficiently to prevent defrosting, said last means comprising temperature-responsive means which is only effective when the temperature of the surrounding media reaches the aforesaid value.

'7. In refrigeration apparatus, the combination of an insulated zone to be refrigerated, a cooling means at least a portion of which abstracts heat from the zone, means for circulating refrigerant media surrounding said zone, whereby the controlling means is compensated 'in response to the temperature of the surrounding media and the active and inactive periods of the refrigerant-circulating means are varied, means for effecting intermittent defrosting of the cooling element and means for insuring defrosting of the cooling element when the media surrounding the zone is at a value which would normally increase the active periods of the refrigerantcirculating means sufficiently to prevent defrosting, said temperature-responsive controllin means including an arm movable with changes in temperature and said means for insuring defrosting including a temperature-responsive device for biasing the movement of the arm in one direction.

8. In refrigeration apparatus, the combination of an insulated zone to be refrigerated, a cooling means at least a portion of which abstracts heat from the zone, means for circulating refrigerant through the coolingmeans, temperature-responsive means for controlling the temperature in said zone comprising means for rendering said refrigerant-circulating means active primarily in response to the temperature of the media in said zone and inactive primarily in accordance with the temperature of a portion of the cooling means as modified by the temperature of the media surrounding said zone, whereby the controlling means is compensated in response to the temperature of the surrounding media and the active and inactive periods of the refrigerant-circulating means are varied, means for effecting intermittent defrosting of the cooling element and means .for insuring defrosting of the cooling element when the media surrounding the zone is at a value which would normally increase the active periods of the refrigerant-circulating mean sufficiently to prevent defrosting, said temperature-responsive controlling means including an arm movable with changes in temperature and said means for insuring defrosting including'a temperature-responsive device for biasing the movement of the arm in one direction only when said surrounding media has risen in temperature to said value.

9. In refrigeration apparatus, the combination of a zone to be refrigerated, a cooling element for abstracting heat from said zone, a temperature control apparatus for controlling the temperature in the zone, means for compensating the temperature control apparatus in response to changes in refrigeration load, and means for rendering said compensating means at least partially ineffective in response to abnormal tern: peratures of the media surrounding said zone, said compensating means being entirely effective under normal temperature conditions of the media surrounding said zone.

10. In refrigeration apparatus, the combination of a zone to be refrigerated, a cooling element for abstracting heat from said zone, a temperature control apparatus for controlling the tem perature in the zone, means for compensating the temperature control apparatus in response to changes in refrigeration load, and means for rendering said compensating means at least partially ineffective in response to abnormal temperatures of the media surrounding said zone without effecting the compensating means under normal temperature conditions of the media surrounding said zone, said compensating means being entirely effective under normal temperature conditions of the media surrounding said zone.

11. In refrigeration apparatus, the combination of a zone to'be refrigerated, a cooling element for abstracting heat from said zone, a temperature control apparatus for controlling the temperature in the zone, means for compensating the temperature control apparatus in response to changes in refrigeration load, and means for rendering said compensating means at least partially ineffective in response to abnormal temperatures of the media surrounding said zone, said last means comprising a device for adding bias to said temperature control means only when the temperature of the media surrounding the zone reaches an abnormal value and said compensating means being entirely effective under normal temperature conditions of the media surrounding said zone.

LESLIE B. M. BUCHANAN.

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