US2319993A

US2319993A - Refrigerating apparatus

Info

Publication number: US2319993A
Application number: US363072A
Authority: US
Inventors: Daniel L Kaufman
Original assignee: Motors Liquidation Co
Current assignee: Motors Liquidation Co
Priority date: 1940-10-28
Filing date: 1940-10-28
Publication date: 1943-05-25
Anticipated expiration: 1960-05-25

Description

May 25, 1943. D. L. KAUFMAN y i REFRIGERATING APPARATUS Fild oct. 28, 1940 1Nv NTOR. y

ATT NEYs Patented May 25, 1943 REFRIGERATIN G APPARATUS Daniel L. Kaufman, Dayton,

Ohio, assignor to General Motors Corporation, Dayton, Ohio, a

corporation of Delaware Application October 28, 1940, Serial No. 363,072

Claims.

This invention relates to refrigerating apparatus and moreparticularly to evaporator control means.

Ordinarily, expansion valves are controlled by pressure of the refrigerant in the evaporator and the temperatureadjacent the outlet of the evaporator. Such a valvetends to maintain the evaporator filled with refrigerant at a substantially constant temperature. This is satisfactory as long as the environment temperature remains constant and the evaporator operates above freezing temperatures. When the evapo-A rator operates below freezing temperatures it is desirable to defrost the evaporator periodically in order to remove the which acts as insulation upon the evaporator and reduces the rate of heat transfer. Various schemes have been proposed from time for doing this.

It is an object of my invention to provide upon an ordinary expansion valve in the refrigerating system an additional snap acting control which will be operated periodically to positively close the valve for a period sumcient to defrost the evaporator after which the expansion valve and the refrigerating system is returned automatically to normal operation.

It is another object of my invention to provide an ordinary expansion valve with asnap acting control which is controlled by evaporator temperature and/or the temperature of the air or medium cooled by the evaporator.

It is another object of my invention to provide an expansion valve vwith an improved simplified form lof pressure or-temperature operated snap acting control.

In installations Where frosting of the evaporating means is not a problem, it is sometimes desirable to cylically control the flow of refrigerant to each evaporating means individually according ,to the temperature of the medium cooled thereby.

It is, therefore, another object of my invention to close the expansion valve of anevaporating means when the temperature of the medium cooled thereby reaches a predetermined low limit and to open the expansion valve when the temperature of the medium reaches a predetermined higher limit.

, Further objects and advantages ofthe present invention will be apparent from the following description, referenceV being had to the accompanying drawing, wherein a preferred form of the present invention is clearly shown. In the drawing:

Fig. 1 is a diagrammatic illustration of a refrigerating system together with an expansion valve, in section, disclosing one form of my invention; 'and coating offrost Fig. 2 is a fragmentary view showing a detail of the expansion valve.

Briefly, I have shown an expansion valve having a valve needle retained in place by a spring means. This valve is provided with a snap acting control, operated through a pressure system which is thermostatically controlled by evaporator temperature and the temperature of the medium cooled. Thus, when the temperature of the thermostatic control is lowered sufficiently, the snap acting mechanism is operated to positively close the valve until the evaporator defrosts. The rise in temperature of the evaporating means above defrosting temperature operates a snap acting means to remove from valve closing position in order to allow the valve to open and operate normally.

Referring now to the drawing, there is shown a motor-compressor unit including an electric motor 20 for driving a compressor 22 which withdraws refrigerant from the evaporating means 24 through the suction conduit 2S and discharges the compressed refrigerant into the condenser 28. The compressed refrigerant is liquefied in the condenser 28 and collected in the receiver 30. From the receiver 3D, the liquid is supplied through the liquid supply conduit 32 to' an expansion valve 34 which controls the flow of liquid refrigerant into the evaporating means 213. The electric motor 2D, which drives the compressor 22, may be controlled manually or by low pressure or thermostatic control. While only a single evaporating means is shown connected to thecompressor, the invention may also be applied toy multiple systems wherein its advantages are increased and are even more irnportant.

The expansion valve A33 and the evaporating meansf24 are located within aninsulated compartment 36 so that the evaporating means 23 may cool the air therein so as to keep the compartment at a desirable refrigerating temperature. The liquid refrigerant, which is supplied to the expansion valve 34 through the liquid supply conduit 32, enters the valve by a connection 38 which is connected by a passage 40 extending diagonally upwardly to the central axis of the valve where it connects to a. down'- wardly extending passage which receives the threaded valve seat bushing 42. This valve seat bushing 42 opens into a cylindrical chamber 4S provided in the body of the valve.

'I'he upperl portionof this cylindrical chamber 4l connects to an outlet passage 46 provided with a connection 4,8 to the evaporator means 24. This passage 46 is connected by a small vertical passage 50 extendingwithin theinterior of a metal bellows member 52 provided in the head of the valve. The end plate of this bellows 52 is connected by three symmetrically positioned vertical pins 54 with a valve guide member 58 which is slidable vertically. within the lcylindrical .chamber 44. The valve guide member 58 carries a valve needle v58 which'is adapted to enter into and close the passage provided in the valve seat bustling 42 lto 'close the valve. The valve needle 58 is provided with an integral tapered 'collar `80 which is normally held against a' comple.

mentary seat provided in the valve guide 55 by a very light spring 82. At the bottom of the valve needle 58 there is provided an extension 64 in form of an operating pin.

The bottom of the valve guide '8 is provided with a spring retainer 86 whichreceives the upper end of a compression type coil spring 68 for applying a closing pressure upon the valve needle 58. The lower end of thi'scoil spring 58 is supported by a spring retainer 10, threaded upon an adjusting screw 12 which in turn is rotatably mounted in a bushing 14, threaded into the cylindrical chamber 44 of the valve body. The shank ofl theiadjusting screw 12 is sealed by an adjustable packing gland 15. The ad- `perature -of the l ing the heat transfer and vthe eliiciency of .the evaporator 24. This causes .a reduction in temevaporator 2| by reason of the reduced rate of the 'temperature of the air inthe immediate .vicinity f of the evaporator 24 but increases the justing screw 12 is'provided with a square head 18 for adjustment. A cap nut 80 encloses the head of the adjusting screw 10.

Thevbellows 52 at Vthe head end is enclosed by a cup-shaped sheet metal member 82 which, like -thelower periphery ofthe bellows 52, is'sealed to a nange. 84 providedJon. the head of the valve. This provides a chamber 'bf the valve 86 between the bellows and the cup-shaped member 82. l The chamber 88 is connected by a -tube 88 with the thermostat bulb 90 which is pro- `vided adjacent. the outlet of the evaporatmg means 24. This bulb, mountedin this way, is preferably charged with .a suitable grade of activated charcoal or some other suitable absorbing 4material. The. chamber 86,J the tube Vlili and the bulb 90 are also preferably charged at a suitable pressure with carbondioxideor some vother suitable gas non-condensible at operating temperatures above pressure at which it operates. Under this arrangement the pressure -within the vchamber 86 is Varied according to the temperature of the thermostatic bulb 90 by absorption and evolution of the carbon dioxide into and out of the activated charcoalin the bulb 90. This pressure tends to keep the valve open sufficiently to allow the liquid .refrigerant to approach the point at which the thermostatic bulb 90 is located. -This point,however,may be adjusted .by the adjusting-screw 18. This aol-- iustment, however, will alsochange the evaporating temperature and pressure within the evaporator 24. The bellows 52 is also responsive to the pressure within evaporator 24 through the passage which'connects with the chamber 40 within the bellows 52. l v

With such an arrangement, 'after thevalve is adjusted, the evaporator is kept substantially filled with liquid refrigerant so that the liquid refrigerant approaches. the thermostat bulb 90. The refrigerant will also evaporate at a substantially constant pressure within the evaporator means 24 by reason of the pressure control in the expansion valve. In order to keep the air in thecompartment 35- suflciently cold with the smallest-possible size of evaporator it is desirable to operate' theevaporator normally below freezing temperatures and to adjust the-expansion valve and tocontrol the operation oflthe electric motor accordingly. This entails a deposit of frost upon the evaporator means 24, which in turn 4acts as insulation, thereby reductemperature in the-remaining portions of fthe compartment 35'.

In orderjto periodically melt the frost off the evaporator 24 plied an additional control to the expansion' valve. In so doing I have provided a diaphragm lchamber |0| at the side of the expansion -valve which contains the diaphragm |03 which is clamped at itsedges to the flange |05 surrounding the diaphragm chamber |0| by a flange provided on the housing |01. Thishousing |01'is .clamped 'to the valve body of the valve 34 byscrews or some'cther means, not shown. Clamped to 'op' posite sides of .this exible metal' diaphragm |0| are lever arms |09 and forming'a simple lever which employs the diaphragm for its pivot point. The arm |09 extends intothe cylinder .445 beneath 'the operating the valve needle 58. A cavity is provided in the valve-guide 56 for receiving the arm |08. The

other end of the lever, namely the armv surrounds-a thimble H3. This end ofthe arm is vprovided with 'a notch which receives a toggle pin ||5 provided within a 'spring retaining cup ||1 which is mountedwithin the lever ||9 pivoted upon the pin |2| fixed to the housing |01 'at a suitablepoint. A compression type coil spring |23 bears against the lever ||3` and surrounds the cup-shaped spring retainer ||1.

In order to operate the snap acting mechanism', .the -thimble ||3 is provided with upper and lower anges which engage the mounted projections |3| provided on the arm Within the thimble ||3 there is provided a compression type coil spring |33 having its lower end resting upon the lower flange. o f the thimble 3 and having its upper end supported by an adjusting screw |35 threaded into a bushing |31 provided in the housing |01. The threaded passage isclosed by the cap screw |39. The lower ed ofthe thimble ||3 is held by the spring |33 against the closed end of the lziellovvs |4| which hasits open end sealed to a .ange |43 provided on -the housingv |01. .Also fastened to this flange |43 is a cup-shaped member |45 which sur-- rounds the bellows |4I. This provides an operating chamber |41 between the bellowsv |44| and the cup-shaped member |45.

This operating chamber |41 .is connected by tubing |49 with the thermostat bulb |5| which is preferably mounted upon the portion of the 'evaporating means 24 where the frost disappears last upon defrosting. Frequently, this is in the central portion of the evaporating means. The tubing |49 also connects to a second bulb |53 located adjacent the evaporating means 24. Thesebulbs'll and |53 preferably contain either the same or different grades of activated charcoal.' The bulbs connecting .tubing and operat-v ring chamber |41 preferably are charged with carbondidxide or some other suitable-gas at a pressure sufliciently low to prevent condensation at any point. By this system, pressure within the heat transferand also reduces in a simple manner I have ap-4 pin projection 84 of operating chamber |41 is controlled in accordance with the temperatures of the two bulbs. If desired, either of these bulbs may be omitted and the control accomplished by a single bulb.

The tension of the coil spring |33 is so adjusted that when the evaporating means 24 as a 'f result of the accumulation of frost thereon lowers its temperature, the temperature of the bulbs and |53 will be.lowered suiliciently to allow ,the spring |33 to move the thimble H3 and the bellows |4| 'downwardly to carry the lever |09 and and its toggle pin |I5 across dead-center position so that the arm |09 engages the operating projection 5.4 and the valve needle to move the valve needle 58 to closed position .regardless of the position of the valve guide 56 and its operating bellows 52. This movement normally [will move the collar 60 away from its seat, thereby compressing the spring 62. This will stop the supply of refrigerant tothe evaporating means 24 allowing it to warm up 'and causing the frost to be melted therefrom.

The toggle spring |23 is so adjusted that when the thermostat bulbs |5| and |53 reach a temperature indicating that the frost has completely cycle for intermittently removing the frost fromthe evaporating means. It ls obvlousjthat in multiple systems a snap acting expansion valve like this may be applied to e'ach evaporator in.

the system which operates at freezing temperatures. Thus by this small additional control applied to the expansion valve, defrosting is lndividually accomplished intermittently for each frigerant in the evaporating means and to the temperature at the outlet of the evaporating means for normally controlling the valve opening, said expansion valve including an independent additional snap acting control for closing the valve with a snap action independent of said normal control means, said additional control including a Ysecond thermostatic means responsive to the temperature of themedium and a third thermostatic means responsive to the temperature of the evaporating means.

2. Refrigerating apparatus including a medi'- um to be cooled, an evaporating means for cooling the medium, an expansion valve for controlling-the flow of refrigerant into the evaporating means, said expansion valve including normal control means-effectively responsive to the pressure of the refrigerant in the'evaporatingV means and to the temperature at the outlet of the evaporating means for normally controlling the valve controlV means', and a direct means for directly applying the force of the snap'action control upon the valve for holding the valve in closed position.

3. Refrigerating apparatus including a medium to be cooled-an evaporating means for cooling' the medium, an expansion valve for controlling the ilow of refrigerant into the evaporating means, said expansion valve including means effectively responsive to thepressure of the re-.

frigerant in the evaporating means and to thetemperature of the refrigerant adjacent the outlet 4portion of. the evaporatlngmeans for norof the evaporating means.

v-evaporator according to the rate at which it collects frost. y

While I have illustrated my improved-control operating upon a defrosting cycle, it may also be Vused to operate upon a cycle responsive to the medium cooled or to evaporator temperature.

Where the evaporating means is used i'orl cooling water, the control may cycle according tewater temperature. In such a case. both bulbs [5| and |53 may be used, providing a control according to water and evaporatortemperature,V or the,

bulb lilvmay be omitted, providing a control according to water temperature alone.y The evaporating means may be used forcooling air at nonfrosting temperatures or for other mediums providing a control according to the Itemperature lof the medium and/or evaporator temperature.

While the form of embodiment ofthe invention as herein disclosed, constitutes .a preferred form, it is to be understood that other forms might be adopted, all coming within the scope 'of' ing the medium, Aan expansion valve for oontrolling thetlow of refrigerant into evapoiraung ineens, said expansion valve-including thermostatic and pressure normal control'nieans elective'ly to the ofthe rea. 'inedi- :luid motor.

4. Refrigerating apparatus including a medium to 1be'cooled, an evaporating means -for cooling the medium, an expansion valve for controlling the flow o f refrigerant into the evaporating means,- saldexpansion valve including means effectively responsive to the pressure of the refrigerant in the evaporating means a'nd'to the temperature of the'refrigerant adjacent the outlet portion of the evaporating means for normally controlling the valve opening, and an additional control for overcoming the normal control of the.

valve opening to positively close Asaid expansion valve, said additional control including means responsive to the temperature of the medium, and

means responsive to the temperature of the evaporating means;

5. Refrigerating apparatus Iincluding a medium to be cooled, an evaporating means for cooling the medium, a valve needle for controlling the iiow of refrigerant into the evaporating means, a iluidmotor responsive to the pressure of the refrigerant in the evaporating'means for controlling the opening of the valve needle, and 'a snap-acting control acting independently-of said fluid motor directly upon said valve needle for holding the valve 'needle in closed position. sald valve needle having a lost motion connection withsaid fluid motor allowing the valve needleto be held closed bytsaid snap-acting'means inan d position of the dependently of the action DANIEL L, KAUFMAN.