US2440534A

US2440534A - Selecting valve for two-temperature refrigerating systems

Info

Publication number: US2440534A
Application number: US720255A
Authority: US
Inventors: Leonard W Atchison
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1947-01-04
Filing date: 1947-01-04
Publication date: 1948-04-27
Anticipated expiration: 1965-04-27

Description

April 27, 1948. i ATCHISQN 2,440,534

- SELECTING VALVE FOR TWO-TEPERATURE REFRIGERA'I'ING SYSTEMS med Jan. 4, 1947 Z 24 Fig.2, 6

\\ j i z,

36 37 41 -32 a; 45 33 $5 ,/Z9 as :4

Fig 3 Fig4 III Inventor:

- Leonard WA'bc hison;

Patented Apr. 27, 1948 ssmc'rmc VALVE Fort TWO-EMERA- ruaa Barman-name sys'rsus Leonard W. Atchison, Erie, Pa... alsignor General Electric Company, a corporation of York Application January 4, 1947, Serial No. 720,255

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

Some refrigerators, particularly those intended to accommodate substantial quantities of frozen foods, include separate compartments operating at different temperatures. Where separate evaporators are provided for these compartments it is desirable that the flow of refrigerant through the evaporators be controlled in a manner which will insure the 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 provide a two-temperature refrigerating system including an improved arrangement for controlling the operation of twoevaporators in accordance with pressures existing in the refrigerating system.

It is a further obj ect of my invention to provide a two-temperature refrigerating system including a unitary pressure-responsive device for selectively connecting one or another of two evaporators to the suction side oi a compressor in accordance with the pressures existing in the evaporators.

It is still another object of my invention to provide a two-temperature refrigerating system including a pressure diiferential device for connecting one or another of two evaporators to the suction side of a compressor and including an auxiliary element for controlling the action of the pressure differential device.

Further objects and advantages of my invention willbecome apparent as the following descriptlon 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 better understanding of my invention, reference may be had to the accompanyiny drawing in which Fig. 1 illustrates schematically a two-temperature refrigerating system embodying my invention; Fig. 2 is an enlarged view showing details of the pressure responsive device for controlling the flow of refrigerant in the system of Fig. 1; and Figs. 3 and 4 are fragmentary views of the device of Fig. 2 showing the refrigerant flow-directing element in different positions of operation.

Referring now to Fig. 1, I have shown a two- 10 Claims. (Cl. 62-3) temperature refrigerating system which includes a low temperature evaporator I and a higher temperature evaporator 2. Liquid refrigerant is supplied to the evaporators by a condensing unit, including a compressor 3 and a condenser 4, through a restricting tube 5. The vaporized refrigerant is withdrawn from the evaporators by the compressor through a suction line 6.

Between the evaporators I and 2 and the suction line 6 there is interposed a pressure-responsive device 'I for controlling the flow of vaporized refrigerant from the two evaporators to maintain a pressure diiferential between the evaporators. The pressure-responsive device I is connected to the evaporators I and 2 by two branch suction conduits 8 and 9 respectively, in

order to place the suction line 6 in communication with one or the other of the evaporators.

The evaporator 2 is provided with a header Ill v to which the conduit 8 is connected for the removal of vaporized refrigerant from this evaporator. In order to direct liquid refrigerant to the low temperature evaporator I a restricting tube II is connected to the header III for receiving liquid refrigerant therefrom. The'low temperature evaporator I is provided with a header I2 from which the vaporized refrigerant is withdrawn through the conduit 8. v

In order to control the starting and stopping of the compressor, a conventional control. device, such as that illustratedin Fig. 1, may be employed. In this device a thermostat bulb I3 is placed in heat exchange relationship with the low temperature evaporator I and is connected by a suitable tube ii to a bellows I5. Power is supplied to a motor II which drives thecompressor fromany suitable source through lines I I, and the bellows I5 is arranged to control a switch I8 in the power lines for starting and stopping the motor. when a predetermined low temperature is reached in the evaporator I, the bellows I5 contracts to open the switch II and stop the operation of the compressor. Conversely, when the temperature of the evaporator I reaches a predetermined maximum, the bellows closes the switch to start the compressor.

Referring now to Fig. 2, the pressure-responsive device I includes a housing It which is proto ant.

refrigerant is withdrawn by the compressor 3.

A flow-directing element or piston 26 is slidably mounted within the chamber 26 to direct the vaporized refrigerant from the evaporators to the suction line. The piston 26 is mounted on. a shaft -21 which is adapted to reciprocate within a recess 28 provided in the plug 2|. A second piston 23 is provided within the chamber 20 and is connected to the piston 26 by a shaft 36. The

' piston 29 is provided with bumpers 3| of suitable resilient material, such as rubber, in order to cushion any impact with the closed end 32 of the chamber 20' and to provide a space between the piston 23 and the end of the chamber.

Vaporized refrigerant from the low temperature evaporator is conducted to the chamber 20 on one side of the piston 26 through the passage 23. Vaporized refrigerant from the higher temperature evaporator is conducted to the chamber 20 on the other side of the piston 26 through the passage 24. The piston 26 is therefore acted upon by the pressure differential between the pressure ofv the higher temperature evaporator on one side'and the pressure of the low temperature evaporator on the other side, and its position within the chamber is dependent on these pressures. The piston is biased toward the left by a spring 33 which fits about the shaft 21 and presses against the plug 2|.

. In addition to the piston assembly described above, the pressure-responsive device includes additional controlling apparatus which modifies the operation of the piston assembly to maintain the required difference in pressures between the evaporators. In other words, overall operation of the pressure-responsive device to maintain the required pressure differential between the evaporators is a result of a combination of the piston assembly and the modifying apparatus now tobe described. A passage 34 is provided in the closed end32 of thechamber, and a valve seat 35 is formed on the surface 32 surrounding this passage. A valve 36 is placed within the passage 34 and is arranged to cooperate with the valve seat. It will be notedthat the valve 36 projects beyond the surface 32, and the bumpers 3| are made of sufllcient size to keep the piston 23 from striking the endof'the valve 36,. The position of the valve 36 is controlled by a flexible member or bellows 31 which is mounted in one end of the housing 19. fluid, preferably a gas, such as air, which is noncondensible with the range of temperatures and pressures involved. Space for the bellows 31 is provided within a hollow cap 38 which is assembled in screw-threaded relation with the housing IS. A gasket 33 is included to prevent leakage.

of refrigerant.

In order to provide a by-pass for higher pressure refrigerant from the higher temperature evaporator to the passage 23 which receives low pressure refrigerant from the low temperature evaporator, a duct 46 is provided between the passage 34 and the passage 23. In order to permit flow of the higher pressure refrigerant to the lefthand end of chamber 23, the piston 26 is,pro-

vided with a groove or passage 4|. The valve 36 is controlled by the bellows 31 in response to the pressure of refrigerant in the higher temperature evaporator which acts on the bellows 31. The flow of refrigerant through the by-pass duct 46 and hence the substantial equalization of pressure on the two sides of piston 26 is thus con-' trolled by the valve 36 in response to the pressure acting on the bellows 31.

The valve 36 is provided with a portion 42 of reduced diameter between shoulders 43 and 44, and the end of the bellows moves along this reduced portion as it expands and contracts. Any suitable seal may be employed between the portion 42 and the bellows to prevent leakage of gas from the bellows. The valve 34 is opened when the bellows expands against shoulder 43 and moves the valve to the right upon the occurrence of a predetermined low pressure in the higher temperature evaporator. Conversely, the valve is closed when the bellows contracts against the shoulder 44 and moves the valve to the left upon the occurrence of a predetermined high pressure The bellows is charged with any suitable in the higher temperature evaporator. The higher temperature evaporator will, therefore, operate over a range of pressures, and hence a corresponding range of temperatures, from a predetermined maximum to a predetermined minimum. The extent of the range can be varied by changing the length of the portion 42 of the valve.

The piston 26 is illustrated in Fig. 2 in the position wherein it causes the suction line 6 to be placed in communication with the passage to the higher temperature evaporator. In this position of the piston communication between the suction line and the low temperature evaporator is prevented. In Fig. 3, the piston 26 is illustrated in a position wherein communication between the suction line 6 and the higher temperature evaporator is blocked, and the suction line 6 is connected for communication with the low temperature evaporator. In Fig. 4, there is illustrated an intermediate position in which the piston 26 allows flow-of refrigerant from both the low temperature evaporator and the higher temperature evaporator tothe suction line. The'central flat portion 45 of the piston 26 is narrower than the diameter of the passage 25, and this permits both the low temperature and the higher temperature evaporators to communicate with the suction line in this intermediate position of the piston. On each side of this central flat portion, the piston is provided with a tapered portion 46 in order to reduce shock as the piston opens communication between the suction line and either of the evaporators or, conversely, as it closes to block communication with either of the evaporators. The tapered construction allows the flow of refrigerant to increase or decrease gradually and thereby avoids the shock resulting from an abrupt starting or stopping of the flow.

The operationof the system will be discussed from two standpoints: (1) when the compressor is started after a prolonged shutdown sufllcient for equalization of pressures throughout the system, and (2) when the compressor starts during will be substantially equalized because of leakage,

andthe piston 2i, because'of the bias of the spring 33. will be; at the extreme left end of its travel, providing communication between the low temperature evaporator and the suction line. As the pressure in the low temperature evaporator is reduced, the pressure differential on the piston 26 will gradually'build up to exceed the force of thespring 33 and the piston 2 8 will move toward the right to place the suction line in, communication with the higher temperature evaporator. During this phase the piston 28 may at some time occupy a position in which refrigerant will be drawn from both the low and the higher temperature evaporators, When the pressure of the higher temperature evaporator has been suiiiciently reduced, the bellows llfwill expand to open the valve 36. This will allow a substantial equalization-of pressure on the" two sides of the piston because of leakage through the by-pass l0, and the spring I! will again force the piston 26 to the extreme left of its travel to 36 may be either open or closed depending on' the temperature and corresponding pressure existing in the higher temperature evaporator. For example, if the temperature of higher temperature evaporator should at the time be within its predetermined range,the valve 36 will be open and the full referigerating capacity of the apparatus during the complete operating cycle of the compressor may be concentrated on the low temperature evaporator. should the temperature in the higher temperature evaporator be above a predetermined value, the valve 36 will be closed and the pressure differential on the piston 2! will cause a positioning of the piston for connection of the higher temperature evaporator to the suction line; When the requirement of the high temperature evaporator has been satisfied, the valve 38 will be opened by the bellows 31 and the piston 28 will shift to connect the low temperature line to the suction line 6, At diflerent times during the operation of the refrigerating apparatus, one or the other of the evaporators may require the major portion of the refrigerating capacity of the apparatus. By my invention, the refrigerating capacity of the apparatus is automatically. concentrated on the particular evaporator which the higher temperature evaporator, and the refrigerating capacity will be concentrated on the low temperature evaporator after the requirement of the higher temperature evaporator has been satisfied.

While I have described my invention in connection with a specific two-temperature refrigerating system, I do not desire my invention to be limited to the particular 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 low tempera- 7 ing means to said withdrawing means. a Rim 5 a On the other hand} providing communication between one of said ture evaporator, a higher temperature evaporator, means for withdrawing vaporized refrigerant from said evaporators. means for maintaining rators for selectively connecting one or nother of saidevaporators to said withdrawing means,

and means responsive to a condition of one of said evaporators for modifying the operation of said pressure-responsive means.

2. In a refrigerating system, a low temperature evaporator, a higher temperature evapo-' rator,-means for withdrawing vaporizedflrefrigerant from said evaporators, means for maintaining said evaporators at different pressures, said lastmentioned means including means responsive to the difference of pressure between said evaporators forselectively connecting one-"or another of said evaporators to said withdrawing means, and means responsive to the pressure of one of said evaporators for modifying the operation of saidflrst pressure-responsive 'means.

3. In a referigerating system, a low temperature evaporator, a higher temperature evaporator, means for withdrawing vaporized refrigerant from said evaporators, means for maintaining said evaporators at different pressures, said lastmentioned means including means responsive to the difference of pressure between said evaporators for selectively connecting one or another of said evaporators to said withdrawing means, and means including a bypass providing communication between said evaporators for modifying the operation of said pressure-responsive means. y

4. In a refrigerating system, a low temperature evaporator, a higher temperature evaporator, a

suction line for each or said evaporators, means 4 for withdrawing vaporized refrigerant from said evaporators through said suction lines, means for maintaining said evaporators at different pressures, said last-named means including means responsive to the difference of pressure between said evaporators for selectively connecting one or another of said suction lines to said withdrawing means, and means dependent on a condition of one of said evaporators for modifying the operation of said pressure-responsive means A 5. In a refrigerating system, a low temperature evaporator, a higher temperature evaporator, a

suction line for each of said evaporators, meansfor withdrawing vaporized refrigerant from said evaporators through said suction lines, means for maintaining said evaporators at different pressures, said last-named means including means responsive to the difierence of pressure between said evaporators for controlling communication between said suction lines and said withdrawing means, and means including a bypass between said suction lines for modifying the operation of said pressure-responsive means.

6. In a refrigerating system, a low temperature evaporator, a higher temperature evaporator, means for withdrawing vaporized refrigerant from said evaporator, means for maintaining said evaporators at different pressures including means evaporators and said withdrawing means, means providing communication between the other of said evaporators and said withdrawing means, means responsive to the difierence of pressure between said evaporators for selectively connecting said one or said other of said communicatbetween said two communicating means, and

means for controlling said bypass to modify the operation of said pressure-responsive means.

7. In a refrigerating system; a low temperature evaporator, ahigher temperature-evaporator, a suction line for each of said evaporators, means for withdrawing vaporized refrigerant from said evaporators through said' suction lines, means for maintaining said evaporators at different pressures including means responsive to the difference of pressure between said evaporators for controlling communication between said suction lines and said withdrawing means, and a bypass between said suction lines, said bypass being controlled in response to the pressure of one of said evaporators for' modifying the operation of said pressure-responsivemeans.1

8. In a refrigerating apparatus, a low temperature evaporator, a higher temperature evaporator,- means for withdrawing vaporized refrigerant from said evaporators, means for connecting said evaporators to said withdrawing means, means for maintaining said evaporators at diflerent pressures including means responsive to the "difference of pressure between said evaporators for controlling communication between said evaporators and said withdrawing means, a bellows I evaporator or said higher temperature evaporator in communication with said withdrawing means.

I said pressure-responsive device including a chamher and a piston movable in said chamber in re-' sponse to the pressure differential between said low temperature evaporator and said higher tem-'-' perature evaporator, and means responsive-to the pressure of said higher temperature evaporator for modifying the movement or said piston.

-10. In a refrigerating apparatus, a low'temperature evaporator, a higher temperature evaporator, means for withdrawing vaporized refrigerant from said evaporators, means for maintaining said evaporators at diflerent pressures ineluding a pressure responsive device for selectively connecting either said low temperature evaporator or said higher temperatureevaporator in communication with said withdrawing means,

said pressure responsive device including a chamher and a piston movable in said chamber in response to the pressure differential between said evaporators, means including a bypass for reducing the pressure differential acting on said piston,

' and a bellows responsive to the pressure of said higher temperature evaporator for controlling said by-pass to modify the movement of said V piston.

LEONARD w. ATCHISON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,133,957 Harshberger Oct. 25, 1938 2,222,701 Fletcher Nov. 26, 1940