US2454537A

US2454537A - Two-temperature refrigerating system

Info

Publication number: US2454537A
Application number: US745940A
Authority: US
Inventors: Leonard W Atchison
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1947-05-05
Filing date: 1947-05-05
Publication date: 1948-11-23
Anticipated expiration: 1965-11-23

Description

NOV. 23, 1948. w, c so 2,454,537

TWO TEMPERATURE REFRIGERATING SYSTEM Filed May 5, 1947 Fi gl.

Inventor"; Leonard W. Acchrson,

T'hs Attovney.

Patented Nov. 23, 1948 TWO-TEMPERATURE BEFBIGEBATING SYSTEM Leonard W. Atchison, Erie, Pa., auignor to General Electric Company,

York

a corporation of New Application May 5, 1947, Serial No. 745,840

4 Claims.

My invention relates to refrigerating systems and particularly to systems employing a plurality of evaporators for operation at different temperatures.

Some refrigerators, particularly those intended to accommodate substantial quantities of frozen foods, include separate compartments operating at different temperatures. Where separate evaporatorr. are provided for refrigerating these compartments it is desirable that the flow of refrigerant through the evaporators be controlled in a manner which will enable maintenance of the proper temperature in each evaporator.

It is an object of my invention to provide a two-temperature refrigerating system employing two evaporators and including an improved arrangement for controlling the flow of refrigerant through the evaporators.

It is another object of my invention to control the flow of vaporized refrigerant from the evaporators in such a manner that one evaporator at a time will be automatically connected to the suction line of the system.

It is a further object of my invention to provide a two-temperature refrigerating system employing two evaporators wherein the connection of one evaporator to the suction line is dependent on the closing of the passage from the other evaporator to the suction line.

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

For a betterunderstanding of my invention reference may be had to the accompanying drawing in which Fig. 1 illustrates schematically a two-temperature refrigerating system incorporating an embodiment of my invention; and Fig. 2 shows details of a check valve forming part of the system.

Referring now to Fig. 1 I have there shown a two-temperature refrigerating system which includes a compressor i, a condenser 2, a low temperature evaporator 3, and a higher temperature evaporator 4. The compressor may be driven by an electric motor 5, which is connected to the compressor in any suitable manner.

Liquid refrigerant is supplied to the system from the condenser through a restricting tube 6.

vaporized refrigerant is withdrawn from the system by the compressor through a suction line I which is connected by means of two branch conduits 8 and 9 to the low temperature evaporator I and the higher temperature evaporator 4 respectively. In order to provide additional cooling for the liquid refrigerant in the restricting tube i and to vaporize any liquid refrigerant withdrawn through the suction line I, the liquid line and the suction line are placed in heat exchange relation through a portion of their lengths, as indicated at II in the drawing.

The liquid refrigerant supplied through the restricting tube I is conducted to the higher temperature evaporator 4. This evaporator is provided with a header II from which vaporized refrigerant may be withdrawn and from which liquid refrigerant is supplied to the low temperature evaporator 3. Liquid refrigerant is supplied to the low temperature evaporator 3 through a second restricting tube l2 which is connected to the header II at the normal liquid level of the refrigerant therein. The low temperature evaporator I is provided with a header it from which the vaporized refrigerant is withdrawn through the conduit i.

My arrangement for controlling the operation of the refrigerating system to provide for the operation of the evaporators at different temperatures includes the provision of suitable pressureinfluenced devices in the branch suction conduits l and 9 which provide passages for vaporized refrigerant from the evaporators to the suction line I.

In order to control the flow of vaporized refrigerant from the higher temperature evaporator 4, a flow-controlling device or valve M, which is responsive to the pressure in the higher temperature evaporator, is provided. .The valve il includes a housing composed of two parts l5 and i8 between which a bellows supporting ring I! is clamped. The two-part housing and the bellows supporting ring are maintained in assembled relationship by welding or in any other suitable manner. A bellows I8 is sealed to the bellows supporting ring i1, and the bellows defines with the upper part I! of the housing a closed chamber which is charged with any suitable noncondensable gas, such as nitrogen. A slide valve assembly is located in the lower part it of the housing. This valve assembly includes a valve guide is I which is secured to the part It and extends through an opening in this part. In order to control the flow of refrigerant the valve guide I9 is provided with a plurality of laterallyextending passages 20, and a valve element 2i, which is disposed within the guide IS in sliding relationship therewith, is provided with a plurality of laterally-extending passages 22 arranged for cooperation with the corresponding passages or the guide. In order to provide a passage for flow of refrigerant through the valve a longiarms 26 and 21 by rivets or any other suitable fastening devices. The length of the leaf spring 28 between its clamping points on the arms 28 and 21 is greater than the straight line distance therebetween, so that the spring is forced into a bowed condition. In order that the valve will operate between its open and closed positions with a snap action, the valve element 2| is mounted on the central portion of the bowed spring 28. In order to limit the movement of the central portion of the spring 28 in on'edirection of motion so as to secure a snap action, a stop pin 28 is mounted on a support 88 which is secured-to the guide l8. To limit the movement of the central portion of the spring 28 in the opposite direction the valve guide I8 is provided with a shoulder 8| which acts as a stop for the valve element 2| at one extreme limit of the motion of the valve.

In operation the structure described causes a snap action of the valve to the open and closed positions and prevents the valve from occupyin a throttling position. In the position shown in the drawing the pressure of the vaporized refrigerant from the higher temperature evaporator 4 is such that the bellows has expanded against the pressure of the noncondensable gas. When the 4 temperature and hence the pressure of the higher temperature evaporator 4 is reduced, the bellows is compressed and the valve operating arm 24 moves downwardly. Since the valve and hence the central portion of the bowed spring 28 are prevented from further motion by the shoulder 8| on the guide I8, the ends of the bracket ultimately move beyond the center of the spring 28, carrying with them the ends of the spring 28. This condition, which occurs when'the predetermined low temperature has been reached in the evaporator 4, results in a snap action of the spring 28 to its opposite bowed position. This moves the valve element 2| upwardly against the stop pin 28 and moves the passages 22 of the valve element out of registry with the corresponding passages 28 of the hollow cylinder to discontinue flow of vaporized refrigerant from the evaporator 4. Conversely, as the temperature and hence the pressure of the evaporator 4 increases above the predetermined minimum the bellows is caused to expand, carrying with it the valve operating arm 24 and the bracket 25. Further motion of the central portion of the leaf spring 28 is prevented by the stop pin 29, and, when the predetermined maximum temperature is reached, the leaf spring 28 snaps over center to open the valve and allow flow of vaporized refrigerant from the evaporator 4. Since the pressure existing in the evaporator bears a definite relation to the temperature, this arrangement will maintain a predetermined range of temperatures in the ev porator 4.

The speciflc valve structure described above is not part of the present invention but is described and claimed in my copending application Serial No. 759,556, filed July 8, 1947, and assigned to the same assignee as the present invention.

In the conduit 8 a check valve 82 is provided, and this check valve is arranged to allow flow of vaporized refrigerant from the low temperatureevaporator 8 upon the occurrence of a predetermined low pressure in the suction line I and the intake of the compressor I.

The check valve 82, shown in detail in F18. 2, includes a housing 88 and an internal valve body The valve body 84 is provided with a port 88 and a valve seat 88. A resilient strip 81 which is arranged to lift to open the valve upon the occurrence oi predetermined low pressure in the suction line 1 is mounted in the valve body 84 in engagement with the valve seat 88. A suitable stop 88 is provided to limit the upward movement of the strip 81.

In order to provide a lower limit of temperature for the evaporator 8 a thermostatic bulb 88 is placed in heat exchange relation with a portion of this evaporator. This bulb is adapted to stop the operation of the compressor upon the occurrence of a predetermined low temperature in the evaporator 8 and to start the compressor when the temperature in the evaporator 8 rises above a predetermined maximum. The starting and stopping of the compressor is controlled by a bellows 48, which expands or contracts in ac-' cordance with the temperature of the thermostatic bulb 38. The bellows 48 is arranged to operate a switch 4| for governing the supply of .power to the motor 8, which drives the compressor i'.

The normal operation of the refrigerating systern is as follows. The liquid refrigerant is supplied to the higher temperature evaporator 4 is vaporized in evaporator 4 due to the absorption of heat, the vaporized refrigerant is withdrawn by the compressor through the conduit 8 and the,

suction line 1. During this period the pressure in the suction line is sufliciently high that,

under the pressure conditons normally prevailing in evaporator 3, the strip 31 is retained against its seat by its natural resilience, and flow of vaporized refrigerant through the branch suction conduit 8 is prevented. Hence there is substantially no refrigeration in the evaporator 3 and the full capacity of the compressor is utilized to produce refrigeration in the higher temperature evaporator 4. When the temperature, and the corresponding pressure, of the higher temperature evaporator 4 have been reduced to the predetermined minimum, the bellows i8 contracts to close the valve l4 and stop the flow of vaporized refrigerant through the conduit 9. As the compressor continues to operate the closing of the valve [4 and the resulting stoppage'of the flow of vaporized refrigerant to the intake of the compressor will result in a lowering of the pressure at the intake of the compressor and in the suction line 1. This lowering of the pressure in the suction line 1 also results in a reduction of the pressure acting on the suction line side of the strip 31. The

strip 31 is then forced from its seat by the pressure higher temperature evaporator l is blocked by the valve I4, and the full capacity of the compressor is utilized to produce refrigeration in the low temperature evaporator 3. The restricting tube I2 is arranged, as previously described, at the normal liquid level of the refrigerant in theheader ll, so that, during the operation of the low temperature evaporator, the liquid refrigerant flowing through the restricting tube 6 builds up the liquid level in the header H and is conducted through the tube i2 to the low temperature evaporator I. The compressor continues to operate, withdrawing vaporized refrigerant from the low temperature evaporator with the resultant reduc tion in the temperature thereof until a predetermined low temperature is reached in this evaporator. The thermostatic bulb 39 then causes the switch 4| to open, breaking the circuit to the motor 5 and stopping the operation of the compressor I.

While I have shown a particular embodiment of my invention incorporated in a two-temperature refrigerating system, I do not desire my invention to be limited to the specific construction shown and described and I intend in the, appended claims to cover all modifications within the spirit and scope of my invention.

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

1. In a refrigerating system, a plurality of evaporators adapted to operate at different temperatures, means for supplying refrigerant to said evaporators, means for withdrawing refrigerant from said evaporators, means responsive to the pressure in one of said evaporators for controlling the flow of vaporized refrigerant'from said one of said evaporators to said withdrawing means,

' and means for, controlling the flow of vaporized responsive device being dependent on the pressure in one of said evaporators for controlling communication between said one evaporator and said suction line through said one branch line, and means in the other of said branch lines for controlling communication between the other of said evaporators and said suction line, said last-named means being efiective to provide communication between said other evaporator and said suction line upon the blocking of said one branch line by said pressure-responsive device.

3. In a refrigerating system, a plurality of evaporators adapted to operate at different temperatures, means for supplying liquid refrigerant to said evaporators, means for withdrawing vaporized refrigerant from said evaporators, a pressure-responsive device for controlling flow of vaporized refrigerant from one of said evaporators to said withdrawing means, a pressure-responsive device for controlling flow of vaporized refrigerant from the other of said evaporators to said withdrawing means, said second pressure-responsive device being adapted to open for flow of vaporized refrigerant on the blocking of the flow of vaporized refrigerant from said one of said ,,evaporators by said first pressure-responsive desponse to the-blocking of flow of vaporized redevice inone ofsaid branch lines, said pressure I REFERENCES crrEn" The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Da Number Y te Briggernan et al. Jan. 25. use