US2133967A - Control for refrigerating apparatus - Google Patents

Description

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ATTORN CONTROL FOR REFRIGERATING APPARATUS foci. 25, 193s..

WITNESSES 2 the accompanying drawing, forming a part of vaporized in the evaporator I2 at relatively low mensa oci, 2s, 193s y l i, V2,133,967

UNITED STATES PATENT OFFICE CONTROL Fon REFRI'GERATING APPA- nATUs Leslie B. M. Buchanan, Springfield, Mass., alsignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation oi' Pennsylvania Application August 18, 1937, Serial No. 159,858 '10 Claims. (Cl. 62f-4') My invention relates to refrigerating apparatus sponse to a predetermined low temperature of and has for an object to provide an improved aIlOther zone. control therefor, Reference will now be had to the drawing A further object of my invention is to control wherein I have disclosed a cabinet structure I the operation of a refrigerating machine in re- OImed Of insulating Wells and Clening e Cham- 5 sponse to the temperaturesor different zones ber II for articles to be refrigerated. An evapobeing cooled, rator I2 of any suitable type is disposed in heat A further object of the invention is to limit transfer relation with the air in the chamber II the maximum temperature of a cooling element and may include means fOI SUDDOrtinE trays I3 of a refrigeraung machine and the 'minimum in which media to be concealed Or maintained 10 temperature of the media coded thcrebic at sub-freezing temperatures may be disposed.

A still further object of the invention is to Circulation of refrigerant through the evapoprovide an improved thermostatic control for a ratOr l2 iS effected by a refrigerant condensing refrigerator that responds to temperature conunit generally Shown at M and Preferably in ditions inaplurality of remotely disposed regions. olndng a Compressor '5 driven by. on oloomo 15 These `md other Objects are effected by my motor i6, and a condenser II, the latter being invention as will be apparent from the following cooled 1n any Won known manner suon as for description and claims taken in connection with example by moans of o fan -w- Refrigerant this appiicaticn in which: pressure and temperature by heat abstracted Fig i is a diagrammatic viow of a refrigerator irom the air 1n thechainber II and the media mechanism controlled in accordance with my inm tno trays 3 lo Withdrawn from the evaporator vention; and I2 through a suction conduit I9 by the com- Fig 2 is a sectional View taken along the iine pressor I5. The withdrawn vapor is compressed H H of a detail shown in Fig i. to a relatively high pressure by the compressor I have Chosen to show my invention oopiiod I5 and is delivered through a conduit 2| to the to a conventional single evaporator refrigerator oondonser 7 Wnerein'it is Cooled and o.ondonsrd' of the domestic type but it is to be understood Liqmd refrigerant passes from the cndenser n that other forms of refrigoroting apparatus may to the evaporator. I2 through aconduit 22 having be controlled equally well including two temperaa suitable expanslon device Such as' for example 30 ture machines wherein a plurality of evaporate a conventional capillary tube 23 connected thereare employed and Operatm at different tempera ln. The pressure of the refrigerant is reduced as tures The present ,invetion denes an im it passes through the tube 23 so that vaporization at relatively low temperature may be efprovement over the control shown and claimed eoted in the evaporator L The system de 35 in my oopending application Serial No- 159:6571 scribed heretofore operates on the well known led August 18, and assigned t0 the assignee compressolmcondenser-expander cycle but 0f the present applicatiOn. In this CODending be understood that other forms of refrigerating application, I have disclosed a. control of the gensystems may be employed and controlled in ac- 40 eral type vshown in the present application apcordance with the invention. 40

plied to various forms of refrigerators including In practicing my invention, I provide a cona form wherein two different temperatures are tr01 mechanism generally ShOWl'l at 25 fOr inimaintaincd in dicrcni; cbamberstiating and terminating operation of the con- The control disoicsod in the present ar,oiioiaf densing unit I4 in accordance with temperature tion operates in a similar manner to the control flditmns il digemi zmes of the cmrl H c of the aforementioned copending application but zo larxa; llnbe znccon lrgtso aldec is an improvement thereover lin that Ithe minimunicating with a plurality of reservoirs zo and mum temperature maintained m the higher tem" 29 for containing a volatile uid. The reservoirs peraturo zone may be in err-cess of the maximum 28 and 29 may be of any suitable construction 50 temperature of the low temperature zone. In but as shown, are defined by bulbs communi. both the present and the copending applications, gating with the tube 21, operation of the compressor is initiated lin re- The charge of fluid in the system dened by sponse to a predetermined high temperature of the bellows 26, the tube 21, and the reservoirs 29 one zone being cooled and is terminated in reand 29 is such that liquid is present in one of u the reservoirs 23 or 29 while the remaining reservoir, the tube 2 and the bellows 26 contain gas. The pressure in a thermal responsive system charged in this manner will always correspond to the lowest temperature to which anypart of the system is subjected. The reason for this operation is because the fluid collects in the region of lowest temperature and, therefore, vthe pressure of vaporization is determined by thertembe apparent, therefore, that normally the resere'vaporator i2 or ina zone of low temperature is the lowest temperature portion! of the thermal responsive system and contains the liquid. Ac-

cordingly, expansion of the bellows is responsive to the temperature of the reservoir 23 and the evaporator 62. Should the temperature of the reservoir 28 be heated to a value in excessoi the temperature of the reservoir 29 which is normally higher in temperature than the reservoir 28, the iiuid vaporized in the reservoir 23 would condense in the reservoir 29 and, therefore, movement of the bellows 23 would be in accordance with the temperature of the reservoir 29. As the rese-voir 29 responds to the temperature of the air in the chamber li, movement of the bellows would bein accordance with the temperature of the air in the chamber ii or higher temperature zone.

the bellows may be transferred from the low cient heat is imparted to the reservoir 28 to elevate its temperature above that of the reservoir 23. This may be accomplished in any suitable manner but, preferably, I employ the heat of the condensed liquid for this purpose. Accordingly, a portion'of the conduit 22 is disposed in heat transfer relation with the evaporator I2 and the reservoir 23, as shown at 3i. During operation of the compressor I5, the circulated refrigerant heats the reservoir 28 so that control is efected by the reservoir 29 and during inactiveperiods of the compressor when circulation of refrigerant and heating of the reservoir 28 is substantially terminated, the reservoir 23becomes the controlling element. Further reference to the transfer of control of the expansion oi the bellows 23 will be madehereinafter.

The construction oi the thermostat 25 will now be described in detail. A frame member 32 provides a support for the various elements of the thermostat mechanism 25 and has the bellows 23 secured thereto in any suitable manner. Movement of the bellows 26 is imparted to a lever 33 that swings about a fixed pivot 34. Aspring 35 biases the bellows 26 in opposition to the pressure therein and bears against an adjusting screw, shown at 33. Upward and downward movement and 38 which are adjustable as shown.

A second lever 39 may be carried by the pivot 345 and is actuated by the lever 33 through a lost motion connection preferably including a spring di secured to the lever 33 and engaging the lever 39 as best shown in Fig. 2. The spring is moved by the bellows 23 and the Alever 33 and eiects movement of the lever 39 through frictional engagement therewith. Upwardand downward movement of the lever 39 is limited by stops 42 and 43, respectively, which may be made adjustable as shown. The angular movement of the lever 33 is greater than the angular movement of the lever 39 so that the lost motion connection dened by perature of said low temperature region. It will voir 28 being in heat transfer relation, with the In order that the control of the movement of temperature reservoir 28 to thereservoir 29, sufof the lever 33 is limited by respective stops 3l the spring 3i and lever 39 permits' overtravel of the lever 33' with respect to the lever 39 during a movement of these members and subsequent to the engagement of the lever 39. with one of its stops 52 and 33.

A switch mechanism generally indicated at 44 is actuated by the lever 39 and includes a stationary contact shown diagrammatically at Q and a movable contact d3, the latter being carried bya movable support 37 pivoted at i8 to the. frame. An over-center spring i3 connects the lever '39 to the support di and eiiects a snap-action of the latter in a switchclosing and opening direction as the center ofthe spring passes the center of the pivot 33. Downward movement ofthe contact support di is limited by a stop 5i. The switch mechanism 34 which I have shown defines one'form that may be employed', but it will be understood 'that `any suitable form oi switch mechanism may be used.

The compressor motor i6 is energized from a suitable power source represented by line conductors Lr-Lz under control of the switch 35i. Closing and opening of the switch initiates and terminates operation of the motor i5 and the compressor i3.

Operation v .As shown in the drawing, the switch i4 is open as the temperature oi the evaporator i2 is below the value at which operation of the compressor is started., Circulation of condensed refrigerant in heat transfer relation with the thermal element or reservoir 28 is not effected at this time so that this reservoir is colder than the reservoir 23 and, therefore, controls expansion of the bellows 23. The pressure in the bellows 26 is relatively low so that thelever 33 engages the stop 38.

In the description which follows, itv will be assumed that the compressor is started in respense to a predetermined maximum evaporator temperature of 30 F. and stopped when the temperature of the air in the space i! has been depressed to 42 F.- The maximum temperature of the air in the space il at the time of starting the compressor and the minimum temperature of the.

evaporator l2 at 4the time of stopping the compressor will vary, depending upon their respective heat loads. In the description which follows, it will be assumed that the. temperature of the air in the space ii increases to 45 F. during the inactive periods oi the compressor and that the minimum temperature of the evaporator l2 is 24 F.

The stop 33 is adjusted to limit downward movement of the lever 33 and contraction of the bellows when the pressure in the bellows corresponds to a temperature somewhat lower than 30 F., say 29v F. The other stop 37 limits upward movement of the lever 33 and expansion of the bellows 23 when the pressure corresponds to .a

43 F. The amount of movement oi the lever 39 permitted by the stops d2 and 43 is just sufiicient to permit operation of the switch 44 and is of less angular extent than the amount of movement 'of the lever 33.

temperature somewhat in excess oi 42 F., such as As operation of the compressor has just been 1 terminated by the opening of the switch as, the temperature'of the air in the chamber ii is 42 F. and the temperature of the evaporator is 24 F. Heating of the reservoir 28 by the warm condensed refrigerant is terminated so that the reservoir 28 becomes colder than the reservoir 29 and, therefore, becomes the controlling factor for determining pressure in thebellows 26. As the nsv vals

alsace? lever 33. Upward movement of the lever 39 is also enected, belng'frictionally engaged with the spring Il. When the temperature of the evaporator is increased toa value of 30 F., the lever 39 will have been moved suiiiciently to eiect engagement of the contacts 43 and 48. The motor I9 is therefore energized and circulation of refrigerant by the compressor I5 is started. Heating of the reservoir 23 is initiated so that vcontrol of the pressure in the bellows is transferred t-o the reservoir 29. As the reservoir 29 is subjected to a relatively high temperature of air in the space Il, the pressure in the bellows rapidly increases. At this time, the temperature of the air in the space Il is relatively high, for example, 45 F.

The rapid increase in pressure in the bellows 26 eects upward movement of the lever 33 until it engages the stop 3l. Upward movement of the lever 39 is prevented, however, by the stop 42 and, therefore, overtravel of the lever 33 with respect to. the lever 39 is permitted by the lost motion connection defined by the spring 4l of the lever 39. Operation of the compressor `l5 effects a reduction in temperature of-the evaporator i2 and the air within the space Il. The pressure within the bellows 2S is progressively decreased but contraction of the bellows is not effected at temperatures above 43 F. as the bias of the spring 35 is insuiiicient to overcome the pressure in the bellows. When the temperature of the air has been depressedv to 43, the bias of the spring 35 is sufficient to overcome the pressure in the bellows 26 and initiates downward movement of the lever 33 so that it is moved out of engagement with the stop 3l.

As the spring 4| engages the lever 39, the latter moves downwardly with the lever 33 and out of engagement with the stop I2. When the temperature of the air within the space II has been depressed to 42 F., the lever 39 will have been moved suiilciently to effect opening of the switch 44. Accordingly, operation of the compressor and heating of the reservoir 23 are terminated and the reservoir 23 again becomes lthe controlling factor for determining the pressure within the bellows 28.

As the temperature of the reservoir 23 is relatively low or at a value of 24 F. at this time, the pressure in the bellows is rapidly reduced Aand the bellows, therefore, contracts until the lever 33 engages the stop 39 which as mentioned hereinbefore occurs when the pressure within the bellows 2B corresponds to temperatures of 29 F. and below. The complete cycle of operation has now been described. v

From the foregoing description, it will be apparent that I have provided an improved control for a refrigerator wherein the minimum temperature of the air in the refrigerated zone and the maximum temperature of the evaporator are maintained at predetermined values by a single control mechanism. Accordingly, the evaporator may be operated at sub-freezing temperatures for preserving frozenarticles or may be operated so that its maximum temperature is about 32' F.

whereby defrosting during each cycle is effected.

As the minimum air temperature is maintained at a predetermined value, variations-of the mean temperature thereof are relatively small during relatively wide variations in the ambient or room temperature. The maximum cabinet air temperature will vary with variations in ambient temperature but the variations in the mean temperature are substantially reduced over a conventional control in which the circulation of refrigerant is under control of the temperature of the evaporator. In the latter case, the mean temperature is subject to wide variation whenthe ambient temperature varies as the cabinet air exerts substantially no control over the refrigerating machine.

In the present system, the temperature diierential of the evaporator will vary with different ambient temperatures although the maximum evaporator temperature is maintained substantially constant. When the ambient temperature is high, the compressor is operated for longer periods in order to depress the cabinet air ternperature to 42 F. and, therefore, the minimum evaporator temperature may be depressed to vaiues below 24 F. The minimum evaporator temperature therefore is reduced as the temperature of theA ambient or room atmosphere increases. The maximum evaporator temperature is maintained substantially constant for varying ambient temperature but the temperature differential of the evaporator varies inversely with variations in ambient temperature.

In control systems wherein the temperature of the cabinet air controls the refrigerating machine, a substantially constant mean air temperature may be obtained but the temperature of the evaporator will vary so that it may operate above and below a freezing' temperature at different times depending upon the temperature of the ambient atmosphere.

It will be apparent that my improved control provides for the selection of various temperatures of .the different zones being cooled and that the minimum temperatures of the higher temperature switch M is opened or closed may be varied, and

, the mean temperatures of the evaporator and of the cabinet air may, therefore, be varied relative to each other.

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

What I claim is:

1. In refrigerating apparatus, the combination of means defining relatively low and high y temperature zones to be refrigerated, evaporator means for abstracting heat from both zones,

, means for circulating refrigerant through the during inactive periods of the circulating means, means effective during active periods of the circulating means for transferring control of the switch to the element responsive to the temperature of the higher temperature zone whereby said element is rendered eiective to open the switch and means for transmitting movement of the thermostatic device to the switch and providing for overtravel of the device with respect to the switch so that movement is imparted to the switch during the first portion of a movement of the thermostatic device and relative movement between the thermostatic device and the switch is permitted during the remaining portion of the movement of the thermostatic device.

2. In refrigerating apparatus, the combination oi means defining relatively low and high temperature zones to be refrigerated, evaporator means for abstracting heat from both zones, means for circulating refrigerant through the .evaporator means, a switch for initiating and terminating operation of the circulating means, a bellows for actuating the switch, first and second elements communicating with the bellows switch and eective to operate the switch during the iirst portion of a movement of the bellows and to permit overtravel of the bellows with respect to the switch during the remaining portion of the movement of the bellows, and means effectiveduring operating periods oi the circulating means for raising the' temperature o" the element associated with low temperature zone to a value in excess ci the temperature oi the element associated with the higher temperature zone. y

3. In a refrigerating apparatus, the combination of means dening relatively low and high temperature zones to be refrigerated, evaporator means for abstracting heat from both zones, means for circulating refrigerant through the evaporator means, a switch for initiating and terminating operation of the circulating means, a thermostatic device including a bellows and iirst and secondthermal responsive elements communicating with the bellows and containing an expansible uid, said iirst-ancl second elements being disposed in heat transfer relation with'the respective low and high temperature zones, a switch for initiating and terminating operation ci the refrigerant circulating means, adjustable means for determining the range oi movement of the bellows, means for transmitting movement of the bellows to the switch and providing for overtravel oi the bellows subsequent to an operation of the switch, said thermal responsive element associated with the low temperature zone being effective during inactive periods of the circulating means for determining the movement of the bellows, and means for rendering the thermal responsive elementassociated with the high vtemperature :tone eective for controlling the movement of the bellows during active periods of the circulating means.

4. In reirigerating apparatus, the combination of means deilnlng relatively low and high temperature zones to be refrigerated, evaporator means for abstracting heat from both zones, means for circulating refrigerant through the evaporator means, a switch for initiating and terminating operation of the circulating means,

a thermostatic device including a bellows and rst and second thermal responsive elements communicating with the bellows and containing a lvolatile fluid, said first and second elements being disposed in heat transfer relation with the respective low and high temperature zones, said thermal responsive element associated with the low temperature zone determining the pressure in the bellows during inactive periods of the circulating means, means ror increasing the temperature of the element associated with the low temperature zone to a value in excessl of the temperature of the other thermal responsive element during active periods of the circulating means whereby said other element determines the pressure of the fluid in the bellows, adjustable means for limiting the range of movement of the bellows, a switch for initiating-and termihating operation of the circulating means, a movable member for actuating the switch, means for determining the range of movement of the movable member and means for transmitting movement of the bellows to the movable member and providing for overtravel of the bellows with respect to the movable member subsequent to an operation of the switch.

5. In reirigerating apparatus, the combination of means defining first and second zones to be refrigerated at dierent temperatures, evaporator means for abstracting heat from both zones, means for circulating refrigerant through the evaporator means, control means for initiating and terminating operation of the circulation i means, thermal-responsive means for actuating the controlmeans and responsive to a Apredeter- I mined temperature of the low temperature Zone for initiating operationv of the circulating means and responsiveto a predetermined temperature of the higher temperature zone for terminating operation of the same,l said zones being maintained between diiierent high and low temperatures and the low temperature of the high temperature zone being of higher value than the high temperature of the low temperature zone.

d. in refrigerating apparatus, the combination of means defining rst and second zones tovbe refrigerated at different temperatures, evaporator means for abstracting heatfrom both zones, means for circulating refrigerant through the evaporator means,`a switch for energizing and deenergizing the refrigerant circulating means, a

movable member actuated in response to the temperature of the low temperature zone during periods when the circulating means is deenergized and actuated in response to the temperature of. the high temperature zone during periods when the circulating means is energized, means for limiting the movement of the movable member, a mechanism for imparting movement of the movable member to the switch and including a connection permitting overtravel of the movable member subsequent to an operation ofthe switch, and means for adjusting the amount of overtravel permitted by said connection.

7. ln refrigerating apparatus, the combination of means defining a chamber to be refrigerated, an evaporator for abstracting heat from said chamber, means for circulating refrigerant through the evaporator, a switch for energizing and deenergizing the circulating means, thermal- Ily operated means for actuating said switch and ment of the thermally operated means to the switch and providing for overtravel of the. mechanism subsequent to an operation of the switch and means for adjusting the amount of overtravel oi the mechanism whereby the temperatures at which the switch is opened or closed may be varied. l

8. In refrigerating` apparatus, the combination of means deilnlng a chamberI to be refrigerated, an evaporator for abstracting heat from said chamber, means for circulating -refrigerant through the evaporator, a switch for energizing and deenergizing the circulating means, an expansiblel bellows for having thermal elements communicating therewith and disposed respectively in heat transfer relation with the evaporatoi andthe media cooled thereby, said elements and bellows enclosing an expansible iluid, a lever for actuating said switch, means deilning a connection between said bellows and said lever and providing for overtravel of the bellows with respect to the lever, means for adjusting the amount of said overtravel whereby the temperature at which the switch is opened or closed may be raised. and means for transferring control from one of said thermal elements to another so that the element associated with the evaporator is effective during inactive periods of the circulating means and the element associated with the media being cooled is elective during active periods thereof..

,9. In refrigerating apparatus, the combination of means defining a chamber to be refrigerated, an evaporator for abstracting -heat from said chamber, means for circulating refrigerant through the evaporator, a switch for energizing and deenergizing the circulating. means, an expansible bellows for having thermal elements communicating therewith and disposed respectively in heat transfer relation with the evaporator and the media cooled thereby, said elements and bellows enclosing an expansible iluid, means for selectively rendering the thermal elements effective to control expansion oi the bellows so that the element associated with the evaporator is active during deenergized periods of the circulating means and the element associated with the media cooled by the evaporator is eiiective during energized periods of the circulating means, means for limiting the amplitudes of the bellows, a lever for actuating the switch, means for limiting the movement of the lever and defining a range of movement therefor and a frictional connection between the bellows and said lever whereby movement of the bellows is imparted to the lever when the latter is intermediate the limits of its range of movement and movement of the bellows relative to the lever is permitted when said lever is at one of the limits of its range.

10. In refrigerating apparatus, the combination of means defining a zone to be cooled, an evaporator for abstracting heat from the media in said zone, means for circulating refrigerant through the evaporator, means for controlling the operation of the circulating means and movable to rst and second positions wherein the circulating means is active and inactive, respectively, means for actuating the controlling means and including elements responsive, respectively, to the temperature of the evaporator and the media cooled thereby, means for selecting the element which is to actuate the controlling means and means dening a lost motion connection between fthe actuating means and -the controlling means and providing for overtravel ofthe actuating means with respect to the controlling means subsequent tooperating the controlling means.

LESLIE B. M. BUCHANAN.

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