US2133968A - Control for two-temperature refrigerators - Google Patents

Description

Oct. 25, 1938. w. M. VAN SCIVER ET AL 2,133,968

CONTROL FOR TWO-TEMPERATURE REFRIGERATORS Original Filed Oct. 51, 1936 m m: a RNG d Y mam R mu m mw mWm o m? M LY n wR & u Y B M N n .W W60 4 Patented Oct. 25, 1 938 CONTROL FOR TWO-TEMPERATURE BE- FRIGERATORS Walter M. Van Sciver, Lansdowne, and Raymond J. Ridge, Yeadon, Pa., assignors to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application October 31, 1936, Serial No. 108,520

' Renewed January 15, 1938 7 Claims,

A further object of our invention is to provideimproved apparatus for controlling refrigeration of high and low temperature zones of a refrigerator wherein the high temperature zone is automatically refrigerated in preference to the low temperature when both require refrigeration, with provisions for manually effecting refrigeration of the low temperature zone in preference to the higher temperature zone.

A still further object of the invention is to normally refrigerate the food storage chamber of a refrigerator in preference to the freezing chamber thereof and to manually effect, at will, refrigeration of the freezing chamber in preference to the food storage chamber with provisions for reestablishing normal control of refrigeration of the chambers automatically in response to a predetermined temperature within the freezing chamber.

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

The single figure of the drawing discloses, diagrammatically, a two temperature refrigerating system controlled in accordance with our invention.

Referring to the drawing, we show a two-temperature refrigerator generally indicated at 10, and including relatively high and low temperature chambers II and I2, respectively. Evaporators l3 and I4 are disposed within the respective chambers II and I2, for abstracting heat therefrom. The high temperature evaporator I3 operates, primarily, to cool articles of food stored in the chamber l l and the low temperature evaporator I4 operates to congeal fluid within containers shown at l and to maintain the temperature of the air in the chamber l2 at a relatively .low value. icles to be maintained in a frozen condition or at a low temperature are stored in chamber 12 as is well understood.

The evaporators l3 and I4 define elements of a refrigerating system having a common condensing unit l5 and including a compressor l6 driven by an electric motor l1. The condensing unit l5 includes a condenser l3 cooled in any suitable manner as by a fan l3 and receives compressed refrigerant gas from the compressor through a conduit 2|.

Liquid refrigerant is conveyed to the evaporators l3 and 14 through a branched conduit, 22 and vaporized refrigerant is withdrawn from the evaporators l3 and through conduits 23 and 24, respectively. The refrigerating system which we have shown is of the well known flooded evaporator type having low side floats shown at 25 and 26 for controlling the admission of condensed refrigerant to the evaporators I3 and l4,-in accordance with the levels of the liquid therein. A valve structure generally shown at 21 communicates with the suction conduits 23 and 24 and with the suction side of the compressor by means of a conduit 28. The valve structure 21 is selectively operated to efiect communication between the conduit 23 and either conduit 23 and 24 depending upon which evaporator is being refrigerated.

As shown, the valve structure 21 includes inlet chambers 3| and 32 to which the suction conduits 23 and 24 are connected, and an outlet chamber 33 communicating with the suction conduit 23 of the compressor. Valve members 34 and 35 control communication between the chamber 3| or 32 and the outlet chamber .33. A solenoid 36 actuates the valve members 34 and 35 in such manner that, when the solenoid is energized, communication between the conduits 24 and.23 is established and the evaporator I4 is thereby rendered active. When the solenoid 26 is deenergized, the valves 34 and 35 move to their lowermost position or the position shown in the drawing and communication is established between the conduits 23 and 23 for rendering the evaporator l3 active. y

During operation of the condensing unit l5,

vaporized refrigerant is withdrawn by the compressor from either evaporator l3 or 14 through conduit 23 depending upon whether the solenoid 36 is energized or deenergized. The withdrawn gas is compressed to a relatively high pressure in the condenser I3 and is cooled and condensed. Liquid refrigerant is admitted to the evaporators I3 and I4 through their associated float valves 25 and 26 and is maintained at a substantially constant level in the evaporators. The .compressor maintains the pressure of the refrigerant in the active evaporator at a relatively low value so that the refrigerant vaporizes at low temperature and abstracts heat from the evaporators in a well known manner. 3 a

The foregoing defines a conventional refrigerating system having a. pair of flooded evapora-, tors operating at different temperatures'and connected to a common condensing unit in such manner that they are selectively operated. Our improved control apparatus will now be applied. to

The chamber u, cooled by the high aspm- 1 ture evaporator II, is maintained between predetermined temperature limits preferably by means of a gas-type thermostat, generally indicated at 38. The thermostat 38 includes an expansible bellows 3! connected to a bulb 4| by means of a tube 42. As is well understood, thermostats of this type have a volatile fluid contained in the bulb 4|, the pressure of which is a function of the temperature of the bulb. Accordingly, the bellows ll expands and contracts as the evaporator l3 and bulb 4| increase and decrease in temperature, respectively. In this connection, it will be understood that the thermostat 38 may be made responsive to the temperature of the air in the chamber ll instead of the temperature of the evaporator It by disposing the bulb 4| in the air within the chamber l l.

Expansion of the bellows 39 is opposed by a spring 43, the bias of which may be adjusted by an adjusting member 43a, whereby the temperatures at -which the thermostat" operates is varied. A movable member or arm 44, pivoted at 45, is actuated by the bellows 39 as it expands and contracts and actuates a switch 46 having stationary and movable contact members 41 and 48, respectively. A quick make and break mechanism 49 of any suitable type may be interposed between the switch 46 and the movable member 44. As shown, the quick make and brake mechanism' 49 includes a pivoted arm 5| carrying the movable contact 48 and connected by a tension spring 52 to the movable arm 44.

As the center of the spring 52 passes upwardly beyond the pivot point of the arm 5| due to expansion of the bellows, the arm 5| is snapped upwardly about its pivot by the tension of the spring 5|. Accordingly, the contacts 48 and 41 are engaged and ,the switch structure 48 is in its closed position. Contraction of the bellows lowers the spring," below the pivot point of the arm 5| so that the army 5| snaps downwardly to open the switch, 4l.- The function of the switch 48 will be referred to in detail hereinafter.

The temperature of the air in the chamber II and of the evaporator I4 is controlled by a thermostat, generally indicated at 55, and similar in type tothe thermostat 38. The thermostat bl includes a bellows 56 connected by a tube 51 to a bulb 58 containing volatile fluid and disposed within the chamber l2, preferably in contact with the evaporator l4. Expansion of the bellows 56 is opposed by a spring 564, the bias of which may be adjusted by an adjusting screw 58b. The thermostat it includes a pivoted member or arm 6. actuated by the bellows 56 and operating a switch 59 by means of a quick acting mechanism II. The switch 59 is opened and closed as the bellows 5i contracts and expands, respectively. The. operaiton of the thermostat 55 is similar to the described operation of the thermostat ll.

The thermostat 38 is adjusted to maintain the temperature of the air within the chamber II at a higher value than the-temperature maintained in the chamber H by the thermostat 55. Both thermostats control the operation of the condensing unit I! and vaporization of refrigerant in the evaporators l3 and I4 in a selective manner.

operation of the condensing unit I! In accordance with our invention, the food storage chamber H is normally refrigerated in preference to the freezing chamber I! when both require refrigeration in order to preclude an undue rise in the temperature of the food products in the chamber II when a high heat load is impressed upon the low temperature evaporator I 4 such as, by placing a relatively large quantity of water in the trays II for freezing. There are times, however, when it is desirable to operate the low temperature evaporator for rapidly producing ice cubes or for congealing desserts, and, in order that this operation may be effected, we provide a mechanism for manually adjusting the control, so that the temperature of the low temperature evaporator may be depressed to a relatively low value, after which normal control is established. The manually adjustable mechanism is so arranged that it may be manually rendered inactive prior to the time that normal control is automatically reestablished or, in other words, prior to depressing the temperature to the value at which normal control is automatically established.

The manually actuated mechanism is shown generally at I! as an accessory to the low temperature thermostat 5i and preferably includes a member 43 pivoted at 64 to a flxed portion of the thermostat structure. A tension spring is attached to the member 63 and to a flxed portion of the thermostat structure 5. The spring I defines an accentuating device for biasing the member 63 in an upper or a lower position depending upon whether the center of the spring 85 is above or below the pivot point. 84. The pivoted member 63 is manually actuated by a rod 44 having a handle or knob 61, accessible to the operator. The rod I preferably carries the movable element of an electric switch 64 that is respectively opened and closed when the rod 48 and the member 63 are in their upper and lower positions. I

During periods when the mechanism 42 is inactive, or when the member I3 is in the lower position, the thermostat ll operates in the manner described for maintaining the evaporator l4 or chamber l2 at the temperature determined by the adjustment li During periods when the evaporator I4 is to be operated in preference to the evaporator 13 or, in other words, during quick freezing operations, the knob 61 is pressed for moving the member I upwardly into engagement with the movable arm 40. The arrangement is such that the member 63, when actuated to its upper position, eflects suflicient movement of the arm ll to close the switch I. As described hereinafter, this operation effects and refrigeration of the chamber l2.

The temperature of the chamber I 2 is depressed to a predetermined value preferably lower than the value at which the thermostat I! normally terminates refrigeration of the chamber II. This is brought about due to the fact that the spring I! is above. the pivot point 84 and biases the member ll andthe arm 6. upwardly in opposition to thebias of the spring Ila. Accordingly, the temperature and pressure of the fluid in the bulb ll must be depressed .to a lower than normal value before the bellows 56 contracts sufficiently to effect opening of the switch I9, during which operation, the mechanism 82 is returned by the arm 6| to its inactive position or the position shown in the drawing. Closure of the switch ll reestablishes normal automatic'control wherein preference of refrigeration is returned to the high temperature evaporator l8.

The mechanism 82 may be manually returned to its inactive position at any time by manually moving the adjusting knob 81 to the position shown.

The source of power for the motor I1 and solenoid 38 is represented by the line conductor L1 and L2. As shown, one terminal of the solenoid 88 is connected to the line conductor La and its other terminal is connected by a conductor ll, controlled by the switch 88, to one terminal of the motor II, the opposite terminal of the motor I! being connected to the line conductor L1. The switches 48 and "are connected in series in a conductor I2 extending from the line conductor L2 to the conductor 'll whereby a parallel circuit for the energization of the motor I I is formed. The parallel circuit including the conductor 12 defines a shunt across the solenoid so that it will be apparent that when all switches 48, 88 and 88 are closed, the solenoid 88 is deenergized due to said shunt. This condition prevails during normal automatic operation when both of the chambers II and I! require refrigeration. Accordingly, the valves 84 and 85 are in the position shown so that the evaporator l3 receives refrigerant and the chamber II is refrigerated in preference to the chamber l2.

Operation As shown in the drawing, the switches 48 and it of the thermostats are open which indicates that neither of the chambers II and I! require refrigeration. Assume a rise in temperature in the chamber l l to the value at which its thermostat 38 closes the switch 48. The motor I1 is energized by the circuit including line conductor La, conductor I2, the closed switches 48 and 68, conductor ll, motor l1 and line conductor L1. As the solenoid 38 is deenergized the valves 34 and 35 are in the position shown and the suction conduit 28 communicates with the conduit 28. Vaporous refrigerant is withdrawn from the evaporator It bythe compressor and the float 25 operates to admit condensed refrigerant to the evaporator l3 for vaporization. Refrigeration of the evaporator l3 and' chamber II is eifected as is well understood.

As the temperature of the chamber II and evaporator I3 is depressed to the desired value, the thermostat 38 opens the switch 48 and the motor I! is deenergized. Accordingly, refrigeration of the chamber II is terminated.

Assume a rise in temperature in the chamber I! to the value at which the thermostat 55 closes the switch 59. The motor I! is energized by the circuit including the line conductor La, the solenoid 36, conductor II, and closed switch 59, the

motor I! and line conductor L1. Energization of v the solenoid 38 actuates the valves 34 and- 35 upwardly for providing communication between the suction conduit 28 and conduit 24. Accordingly, the motor I! operates the condensing unit ii to circulate refrigerant through the evaporator I4 until the temperature thereof is depressed to the value at which the thermostat 55 opens its switch 59 for terminating operation of the condensing unit I. v

Assume now that both chambers I l and I! require refrigeration and that the thermostatic switches 48 and 58 are closed, the motor I! is energized by the circuit including conductor I2 andswitches 48 and 88. 'The' solenoid 86 is deenergized because of the shunt-formed thereacross by the conductor 12 and the closed switches 48 and 68. Accordingly, the conduits 28 and 88 are communicating and refrigerant circulated by the con densing unit I is vaporized in the evaporator II for refrigerating the chamber IL.

It wfll now be assumed that the operator manually actuates the mechanism 82 to its active position wherein the member 88 engages the arm 60, as described heretofore. The switch 88 is opened and the shunt circuit referred to in the foregoing is opened. As the switch 58 is closed the motor I1 and solenoid areenergized for the circulation of refrigerant through the low temperature evaporator l4. As the conductor 12 is opened by the switch 68, it will be apparent that the switch 46 is'ineflective to control the motor I'l. Accordingly, refrigeration of the low temperature chamber I 2 progresses. until the temperature therein is reduced to the value at which the thermostat 55 operates to open the switch 58 and to close the switch 68 as described heretofore. Closure of the switch 68 reestablishes normal automatic control of refrigeration of the chambers wherein the higher temperature chamber ll receives refrigeration in preference to the lower temperature chamber l2 when both demand refrigeration.

From the foregoing it will be apparent that we have provided an improved control system for a two-temperature refrigerator wherein the food storage and low temperature zones thereof are maintained at relatively high and low temperatures, respectively, wherein the food storage zone is refrigerated in preferenoeto the low temperature zone during normal operation with provisions for manually effecting refrigeration of the low temperature zone in preference to the higher temperature food storage zone and wherein normal automatic operation is reestablished manually or automatically when the temperature of the lower temperature zone has been depressed to a predetermined value.

While we have shown our improved control system applied to a refrigerating system of the compressor-condenser-expander type it will be understood that it is equally applicable to'other forms of refrigerating systems. Furthermore, it. will be understood that the controlling instruments per se which we have employed have been shown byway of example and that other types ofcontrolling instruments may be used.

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

What we claim is:

1. The method of controlling the operation of a refrigerating machine having relatively high.

and low temperature evaporators, which comprises automatically and selectively effecting refrigeration by the low and higher temperature evaporators inv response to demands for cooling thereon and in such manner that the higher temperature evaporator preferentially effects refrigeration when there is a cooling demand on both evaporators, manually eflecting refrigeration by the low temperature evaporator in preference to the higher temperature evaporator, at will, and re-establishing automatic control of the evaporators in response to a predetermined low temperature of the low temperature evaporator subsequent to an operation thereof that was manually effected.

2. The method of controlling the operation of a refrigerating machine having relatively high and low temperature evaporators, which comprises automatically and selectively effecting refrigeration by the low and higher temperature evaporators in response to demands for cooling thereon and in such manner that the higher temperature evaporator preferentially effects refrigeration when there is a cooling demand on both evaporators, manually effecting refrigeration by the low temperature evaporator in preference to the higher temperature evaporator at will, and establishing automatic control of the evaporators manually, or automatically in response toa predetermined low temperature of the low temperature evaporator subsequent to an operation thereof that was manually eil'ected.

3. In apparatus for controlling the operation of a refrigerating system having first and second zones to be refrigerated, the combination of first means responsive to the temperature in the first zone for controlling refrigeration thereof, second means responsive to the temperature of the second zone for controlling refrigeration of the second zone, said first and second temperature responsive means beingso arranged that'refrigeration of the first zone is effected in preference to the second zone when both require refrigeration, and means manually operated at will, to a position wherein refrigeration of the second zone is eil'ected in preference to the first zone, said manually operated means being movable automatically or manually to a second position in which automatic control of refrigeration of both zones is returned to said first and second temperature responsive means. I

4. The combination as claimed in claim 3 wherein said temperature responsive means are provided with adjusting means for varying the temperatures at which they operate.

5. In apparatus for controlling the operation of a refrigerating system having relatively high and low temperature zones to be refrigerated, the combination of means responsive to predetermined high and low temperatures in the high temperature zone for, respectively, initiating and terminating refrigeration thereof, means responsive to predetermined high and low temperatures in the low temperature zone for respec-- tively initiating and terminating refrigeration thereof, means for selectively effecting refrigeration of the higher temperature zone in preference to the low temperature zone when both require refrigeration, means manually operable at will, for effecting refrigeration of the low temperature zone in preference to the higher temprature Bone, and means responsive to a'predetermined low temperature in -the low temperature zone for rendering said manually operable means inactive, whereby automatic control of refrigeration of the zones is returned to the two first-mentioned temperature responsive means.

6. In apparatus for controlling the operation 01 a refrigerating system having high and low temperature zones to berefrigerated, the combination of relatively high and low temperature evaporators for refrigerating the respective high and low temperature zones, means for selective-' ly circulating refrigerant through the evaporators, a first thermostat responsive to the temperature within the high temperature zone for controlling the circulation of refrigerant through its respective evaporator, a second thermostat responsive to the temperature within the low temperature zone for controlling the circulation of refrigerant through the low temperature evaporator, said thermostats being so constructed and arranged that during normal operation, the second thermostat is rendered inactive when the first thermostat operates to, eifect circulation of refrigerant through the high temperature evaporator, means for manually adjusting said secondthermostat so that it effects circulation of refrigerant through the low temperature evaporator and whereby the first thermostat is rendered inactive and means for rendering the manually adjusting means inactive and for reestablishing normal control by the thermostatsin response to a predetermined low temperature within the low temperature zone.

- 7. The method of controlling the operation of a refrigerating machine having relatively high and low temperature evaporators, which method comprises normally effecting selective refrigeration by the low and high temperature evaporators in response to demands for cooling there- -on and in such manner that the high temperature evaporator preferentially eflects refrigeration when there is a cooling demand on both evaporators, manually effecting refrigeration by the low temperature evaporator in preference to the high temperature evaporator at will andreestablishing normal control of the evaporator in response to a predetermined low temperature of 'the low temperature evaporator subsequent to an operation thereof that was manually effected.

WALTER M. VAN SCIVER. RAYMOND J. RIDGE.

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