US2041511A

US2041511A - Refrigerating apparatus

Info

Publication number: US2041511A
Application number: US618007A
Authority: US
Inventors: George C Pearce
Original assignee: Motors Liquidation Co
Current assignee: Motors Liquidation Co
Priority date: 1932-06-18
Filing date: 1932-06-18
Publication date: 1936-05-19
Anticipated expiration: 1953-05-19

Description

L G. c. PEARCE v 2,941,511

REFR IGERAT IN G APPARATUS Filed June 18, 1932 --3 Sheets-Sheet i May 19, 1936.

G.- c. PEARCE REFR lGERAT ING APPARATUS Filed June 18, 1952' 3 Sheets-Sheet 2 Q6 7 75 33 4e 45 67 1 J09 May 19 1936; I G, Q E 2,041,511

I REFRIGERATINGAPPARATUS Filed June 18, 19 32 s Sheets-Sheet s RESET ON 4 OFF 2 3 NORMAL Patented May 19, 1936 UNITED STATES PATENT OFFICE 2,041,511 t REFRIGERATING APPARATUS George C. Pearce, Dayton, Ohio, assignor, by

mesne assignments, to General Motors Corporation, a corporation of Delaware Application June 18, 1932, Serial No. 618,007

8 Claims.

This invention relates to refrigerating apparatus, and more particularly to control mechanisms for use with such apparatus and other general purposes.

In the use of a mechanically cooled refrigerator, frost collects on the evaporator or cooling unit due to the fact that the temperature thereof is normally below 32 F. To efficiently operate such apparatus. it is necessary to remove this 10 frost occasionally and heretofore this has been accomplished by providing mechanism in conjunction with the apparatus for preventing the operation thereof and thereby permitting the temperature of the cooling unit to rise above 15 32 F. to melt the frost and ice therefrom. Such mechanism has heretofore included means for automatically resetting the refrigerating apparatus to normal operation'after completion of the defrosting cycle.

20 Such mechanisms have had the disadvantage that it was impossible to restore the system to normal operation after a defrosting cycle had begun until the completion of the defrosting cycle. This made it inconvenient when there was 25 a particular demand for refrigeration, such as for freezing ice cubes.

It is therefore an object of my invention to provide a control mechanism which may be manually initiated to preventthe operation of a refrigerat- 30 ing system in order to provide for defrosting and which will automatically restore the system to normal operation after a defrosting period or cycle but which may be restored to normal opera?- ticn any time during the defrosting cycle if it is 35 desired to do so.

It is also customary to provide an overload means for opening an electric circuit, such as the electric motor circuit of a refrigerating system, when a dangerous temperature condition 4 arises, and to provide a manually operable means for resetting the overload means. However, with such an apparatus when the trouble causing the dangerous temperature condition is uncorrected,

the electric motor will start and run for a short 45 period of time and then the overload means will again open the circuit. This, ifrepeated a sufficient number of times, will injure the apparatus sought to be protected by the overload means.

An even more destructive possibility is that the 50 operator, not knowing of the consequences, might held the manually operable means in resetting position so as to prevent the tripping of the overload means regardless of the dangerous tem perature condition. 55- It is therefore another object of my invention to provide a means for holding open the electric circuit which is necessarily operative when the overload means is being reset.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred form of the present invention is clearly shown. 1

In the drawings:

Fig. 1 is a view in elevation of my improved 1 control mechanism together with a diagrammatic representation of the remaining elements of a compression refrigerating system;

Fig. 2 is a sectional view along the line 2-2. of Fig. 1;

Fig. 3 is a side view of the control mechanism shown in Fig. 1;

Fig. 4 is a sectional view taken along the line 4-4 of Figs. 2 and 3, and

Fig. 5 is a top view of the control mechanism, the indicating plate attached.

Referring to the drawings and more particularly to Fig. 1 there is shown for the purpose of illustrating my invention a refrigerating system comprising a compressor 20 for compressing the refrigerant and for forwarding the compressed refrigerant to the condenser 2| where the refrigerant is liquefied and collected in the receiver 22. From the receiver 22 the liquid refrigerant is forwarded through a supply conduit 23 through the expansion valve 24 or cooling unit 25. In theevaporator the liquid refrigerant vaporizes under a reduced pressure and the resulting vapors are returned to the compressor through the return conduit 26. The compressor 20 is driven by an electric motor 21 through a suitable pulley and belt means 28.

In order to control the temperature of the evaporator 25 I provide a thermostatically controlled switch means generally designated by the reference character 30 which is connected in series with the electric motor circuit 29 for controlling the operation of the electric motor and compressor.

This switch means has a housing 3| formed of insulatingmaterial, such as hard rubber or a. phenol condensation product, to which is attached a generally c-shaped sheet metal framework 32, the bottom portion 33 of which is forked to receive the lower end of a sylphon bellows 34 I which is clamped to the forked bottom portion 33 by a nut 35. The interior of the bellows is connected by means of aconduit 36 to a theme static bulb 31 which is located 'near the evaporator 25. The c-shaped member is connected to the insulated member 3| by a pair of ears I86 and I81. The (I-shaped member 32 has a projecting portion 38 provided with a pair of knife edges 39 which pivotally support one end of the bellows followeror main lever 48. The bellows follower 48 consists of an irregularly shaped plate member having notches 4| which receive projections 42 of the projecting portion 38 to hold the bellows follower 48 from lateral displacement. The bellows follower 48 has a turned down projection 43 which rests upon the top plate 44 of the bellows 34. The top plate 44 is guided in its vertical movement by a pair of vertical pins 45 which are fixed to the bottom plate 48 of the bellows 34. The bellows follower 48 has an upturned projection 41 upon which rests a spring retainer 48 which supports the bottom of the main adjustment spring 49. At the top of the main adjusting spring 49 is an upper spring retainer which is threaded upon the main adjusting screw 5|. The upper spring retainer 58 has a lug 52 at one side which rides within a vertical groove 53 in the insulated housing 3|. At the top of the main adjusting screw 5| there is provided a cold control knob 54 to provide a customers adjustment to vary the average temperature of the evaporator.

At one side of the bellows follower 48 is a T- shaped lug 55 which projects through a slot or aperture 56 in a differential plate 51. The differential plate 51 is provided with an upper aperture 58 through which projects a pin 59' which is fixed to a c-shaped metal member 32. At the upper end of the differential plate 51 there is connected a differential spring 59 which is suspended from a differential adjustment member 88 threaded upon a differential adjusting screw 6|. The differential adjustment member 68' has a depending portion 62 which bears against the wall of the insulated housing member 3| to pre vent its rotation. The diiferential adjustment spring 59 is held under tension at all times by a differential adjustment member 68. so as to hold the differential plate 51 in its upper position in which the pin 59' engages the lower edge of the aperture 58 to prevent further upward movement.

Upon the projecting portion 84 of the bellows follower 48 there is provided member of insulating material which extends through an aperture 68 in the side wall 81 of the insulated housing 3|. This insulated member 55 has a forked end provided by the notch 68 and the prongs 69 and 18 which have V-shaped recesses 1| and 12 respectively formed on their inner sides which receive the knife edges 13 formed upon the ends of the U-shaped sheet metal secondary lever 14. The U-shaped sheet metal secondary lever 14 is held against the knife edges by the toggle spring 15 which has one end connected to a T-shaped member 16 which passes through an aperture in the metal portion of the secondary lever 14. The open endof the toggle spring 15 is connected to 'an upstanding car 11 which projects between the prongs 89 and 18 of the insulating member 65.

This ear 11 forms a part of an irregularly shaped switch contact member generally designated by the reference character 18. This member 18 has a pair of rearwardly turned ears 19 and 88 pivotally mounted upon the pivot pin 8| which has its end fixed in a rear Wall 82 of the insulated housing 3|. The irregularly shaped member 18 has one arm 83 extending horizontally which terminates in the above mentioned upstanding ear 11. One portion 84 of the arm 83 is bent up so as to provide a stop for the free end of the secondary lever 14. The irregular shaped member 18 has a lip 85 projecting so as to form another stop member for the free end of the secondary lever 14 to limit its upper movement. Another arm 81 extends downwardly and has a switch contact bar 88 riveted to its lower end. The lower end of this arm 81 has a pair of pro jections 89 formed thereon which rest against the contact bar 88 forming guides to hold it in place and prevent rotation upon the single rivet 98. The switch contact bar 88, when in closed position, bridges the contacts 9| and 92 which are fixed to the bottom wall 93 of the housing 3|. The irregularly shaped member 18 also has another arm 94 extending upwardly which has a bent portion at its upper end for a purpose hereinafter to be described.

The operation of this portion of the apparatus will now be described. As the temperature of the evaporator increases, the volatile liquid in the thermostat bulb 31 vaporizes and causes an increase in pressure within the bellows 34. This increase in pressure within the bellows 34 exerts -a force upon the bellows follower 48 against the tension of the main adjusting spring 49. This pressure gradually moves the bellows follower upwardly against the tension of the main adjusting spring 48 thereby causing the double toggle mechanism to be tripped. The double toggle mechanism is tripped by the moving of the pivot point of the secondary lever by the bellows follower above the center line of the toggle spring thereby causing the secondary lever 14 to move quickly from its extreme upper position to the extreme lower position thereby rotating the irregularly shaped contact member 18 counterclockwise to bridge the main switch contacts 81 and 92. The bridging of the main switch contacts 9| and 92 permits electric energy to flow through the electric circuit to the driving motor 21 to operate'the compressor which will then lower the temperature of the evaporator 25. The lowering of the pressure in the evaporator 25 will reduce the pressure within the thermostat bulb 31 and the bellows 34 causing a retraction of the bellows follower 48 under the pressure of the main adjusting spring 49. As the bellows follower 48 moves downwardly in a clockwise direction about the knife edges 39 a predetermined distance,'the T-shaped boss 55 upon the bellows follower 48 will strike the bottom of the diiferential plate 51 causing the differential plate 51 to move downwardly along with the bellows follower against the tension of the differential spring 59. This will provide the additional resistance of the adjustable tension of the diiierential spring to the downward movement of the bellows follower 48 and in this way, a differential adjustment is provided for varying the pressure at which the main spring contacts HI and 92 will be opened and closed.

In order to defrost the evaporator, I provide a manual control member I81 which has its upper portion projecting through the top wall I82 of the insulated member 3| and which has its lower portion of a semi-circular shape pivotally mounted upon a pin |83 which is supported by an insulated boss I84. The boss 184 is fastened to the top wall I82 of the insulated member 3| by a screw I85. At one corner of the sen1i-circular portion of a manual control member l8! there is provided a pin I88 which is fastened therein. A toggle spring I89 has one end con-- nected to the pin I08 and has its opposite end connected by means of a pin IIO to the side wall III of the insulated housing 3I. This toggle spring normally holds the manual control member in ineffective or run position. Extending downwardly from the pin I08 is a link I I2 which has a lost motion slot H3 at its lower end. The lost motion slot H3 is connected by means of a pin II4 to the insulated member 65 which forms a part of the bellows follower 40.

When the manual control member IIII is in the position shown in Fig. 1, namely the run or ineffective position, the defrosting mechanism is ineffective and the pin II4 moves freely within the lostmotion slot II3. At this time the. toggle spring I09 holds the manual control member and the link I I2 in the position shown in Fig. 1. However, when the manual. control member IOI is moved to defrosting position, the upper end of the lost motion slot bears upon the pin II4 under tension of the toggle spring I09 which then has its center line beneath the pivot pin I03. The force of the toggle spring I09 acting through the link II2 on the bellows follower causes the bellows follower to be moved downwardly against the pressure within the bellows 34 to cause the double toggle switch mechanism to move the switch contact member I8 into open circuit position as shown in Fig. 1.

Since the switch contacts are thus placed in open position, the temperature of the evaporator will rise above the freezing point to cause the frost to melt from the evaporator or cooling unit 4 25. This will increase the pressure within the thermostatic bulb 31 and the bellows 34 and this pressure will finally become great enough to overcome the resistance of the main adjusting spring 49 and the tension of the defrosting toggle spring I09 to cause the switch contact member I8 to finally move to closed circuit position, thereby causing the electric motor 21 to start and operate the compressor 20. During this operation, the pin II4 which bears against the upper end of the slot I3 will move the link I I2 upwardly to return the manual control member IOI to normal running position. The manual control member IOI, however, at any time during the defrosting period, may be returned to normal running position by reason of the lost motion slot I I3, thereby removing the tension of the defrosting toggle spring from the bellows follower 40 and thus revert the switch mechanism to normal control.

It should be understood that the temperature of the evaporator 25 must rise toa temperature of from 40 to F. in order to provide suflicient pressure within the thermostatic bellows 34 to return the manual control member IOI to normal running position to terminate the defrosting cycle. It will thus be seen that the defrosting mechanism is at all times under the control of the housewife and may be initiated or terminated at will; but even if the defrosting cycle is initiated by the housewife, the frosting mechanism will be returned to ineffective position after a predetermined pressure is exerted within the interior of the bellows 34.

In order to properly protect the electric motor, I provide an improved thermal overload mechanism. After the electric current passes from the contact 9I across the contact bar 88 to the contact 92, it passes through an electric heater I I6 formedof a serpentine-shaped section of nickel chromium wire which is connected at one end to the switch contact 92 and at the otherend to the overload contact I II. In close proximity to the electric heater H1 is a bi-metallic strip 8 which has one end fastened within a pivot blockmember I I9 of insulating material which is pivotally mounted upon a pin I20 fixed to the insulated-housing 3|. A second bi-metallic strip I2I has its one endfixed within the insulated pivot member II9. This second strip extends outwardly from the pivot block member at an angle of approximately 60 to the bi-metal strip I Ill. The outer end of the bi-metal strip I2I is held against an adjusting pin I22 which has a threaded upper end I23 which is threadedly mounted within the side wall III of the insulated member 3|. The upper end of the adjusting pin I22 is provided with a slot for a screw driver to adjust the position of the bi-metal strip II8. In order to hold the outer end of the bi-metal strip I2I against the end ofthe adjusting end I22, there is provided a movable pin I24. The pin I24 has one end slidably mounted within the boss I25 which projects from the rear wall 82 of the insulated member 3|. At the opposite end of the pin I24, there is a collar I26 which is held in place by the snap ring I21. Between the collar I28 and the box I25 there is a compression spring I28 which presses against the collar I26 for holding The bi-metal strip I8 and the bi-metal-strip I2I are both affected by room temperature to the same degree. for compensating the bi-metal strip II8 from changes inroom temperature. The bi-metal strip I2I compensates the bi-metal strip II8 by moving the pivot block member II9 about the pivot pin I20 a sufficient amount to compensate for the bending of the bi-metal strip caused by changes in room temperature.

The outer end of the bi-metal strip II8 has a shoulder portion I30 of an overload contact member I3I resting against it. The overload contact member is provided with a pair of ears I32 which are pivotally mounted upon a pin I33 which is fixed to the rear wall 82 of the insulated housing 3|. The overload contact member I3I is held in yielding engagement with the end of the bimetal strip II 8 by the overload spring I34 which has one end connected to a pin I35 fixed to the rear wall 82 of the insulated housing member 3I and its opposite end connected to a connecting member I36 upon the overload contact member I3I. At the lower end of the overload contact member I3I there is provided an overload contact bar I 31 which is fixed to the end of a pin I38 which extends through a lower projecting por- "is given off by the heater IIS and will affect the, bi-metai strip H8, causing it to bend downwardly, thereby releasing the shoulder portion I30 from engagement with the bi-metal strip I I8. This will permit the overload contact member I3I to rotate counter-clockwise under the tension of the overload spring I34 to separate the The bi-metal strip I2I is provided 1 A small compression spring I40 urges overload contact bar I01 from the overload contacts Ill and I42 to open the electric motor circuit 29. In this connection the spring mounting of the overload contact bar I31 will cause an abrupt removal of the contact bar from the overload contacts, thereby preventing excessive arcing.

A manual reset member I50 which has one portion projecting through the top wall I02 of the insulating member 3I and which has its lower semi-circular portion mounted upon the pin I03, is provided for re-setting the over-load contacts to closed circuit position. The manual re-set member I50 normally is resiliently held in on position by a tension spring I5I. Upon the tripping of the overload contact member I3I, the upper end I52 thereof will engage the one end I53 of the manually re-set member I50 and move the re-set member to oil position. In re-setting the overload contact member, the manual reset member I50 is moved to resetting position against the tension of the spring I5I, thereby causing the shoulder I53 to engage the end portion I52 of the overload contact member I3I. This will rotate the contact member I3I in a. clockwise direction to cause the contact bar I3'I to engage the overload contacts II! and I42 which will close the electric circuit 29 and permit the bi-metal strip IIB to again move into engagement with the shoulder portion I30 of the overload contact member I3I.

At the same time, the lug I54 will engage the upper arm 94 of the main switch contact member to move the main contact bar to opencircult position during the time the overload contact bar I31 is closing the overload switch contact. This will prevent the arcing of the overload contact when returning them to closed circuit position and in addition will prevent the starting of the electric motor until the overload mechanism is reset and held in closed circuit position by the bi-metal strip H8. If the bi-metal strip is too warm, the electric motor circuit 29 can therefore not be closed. This also prevents the housewife from forcibly holding the electric circuit closed and forcing the electric motor to run under a dangerous condition which might materially injure or destroy the electric motor.

The overload mechanism is also used as a means for shutting down the refrigerating system. When the manual reset member I50 is moved to oif position the lug I 54 engages the compensating bi-metal strip I2I to move the bimetal strip II8 counter-clockwise to disengage the outer end of the bi-metal strip II8 from the shoulder port-ion I30 of the overload contact member I3I to permit the contact member I3I to move to open circuit position. The overload contact member I3I will then remain in open circuit position to prevent operation of the electric motor and the refrigerating system until the overload mechanism is reset.

While the form of embodiment of the 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 the claims which follow.

What is claimed is as follows:

1. A circuit controlling apparatus including pressure responsive means for opening and closing an electric circuit for providing open and closed cycles according to certain pressures, a manually controllable means having an efliective and an ineffective position, said manually controllable means being movable at will from effective to ineffective position and from ineffective to effective position, and means operatively connecting said pressure responsive means and the manually controllable means when in effective position for applying an additional force upon the pressure responsive means to provide a prolonged cycle, said manually controllable means being movable to ineffective position during a prolonged cycle to terminate prematurely a prolonged cycle, said connecting means being also operated by said pressure responsive means to return said controllable means from effective to ineifective position.

2. A circuit controlling apparatus including pressure responsive means for opening and closing an electric circuit responsive to pressures to provide open and closed circuit cycles, a manual control member and snap acting means including spring means for resiliently urging the manual control member into either of two positions, a dial cooperating with said manual control member for indicating an effective and an ineii'ective position, the manual control member being movable at will from effective position to ineffective position, said manual control member when in effective position only being effective to cause said spring means to exert a force upon said pressure responsive means for providing a prolonged cycle, said manual control member being movable at will during the prolonged cycle from the effective position to the ineffective position to move the spring means to ineffective position and to remove said force upon the pressure responsive means to terminate at will the prolonged cycle, said pressure responsive means being efiective during the prolonged cycle to move the manual control member to ineffective position automatically to return the apparatus to normaloperation.

3. A circuit controlling apparatus including a pressure responsive means for opening and closing a set of contacts in an electric circuit, a set of overload contacts in said electric circuit in series with said pressure operated contacts, yielding means for moving said overload contacts to open position, a temperature responsive latch means for preventing the yielding means from moving said overload contacts to open position, said latch means being tripped at a predetermined temperature to permit the overload contacts to be opened by said yielding means, a manual control member for opening and closing the overload contacts and for resettingthe overload contacts to closed position, and means actuated by said manual control member when resetting the overload contacts to closed position for holding open said pressure operated contacts.

4. A refrigerator switch including pressure responsive means for opening and closing an electrio circuit according to certain pressures, a snap acting means including a manual control member movable to effective and ineffective positions, said snap acting means and said manual control means being movable into and out of the effective and ineffective positions as a unit, said snap acting means when moved to effective position having means movable into the path of the pressure responsive means to act upon the pressure responsive means to change the pressure at which the pressure responsive means operates, said pressure responsive means being operative upon cooperating with said manipulative device for resiliently holding said manipulative device in any one of. a plurality of positions, one of said devices having means for engaging the pressure responsive means when the finger manipulative device is in one of its positions to resist the movement of the pressure responsive means, said pressure responsive means being effective to move the finger manipulative device from one position to another.

6. A control including pressure responsive means means for controlling a means to be operated, a finger manipulative toggle device having an operative and inoperative position, said device including means effective when in operative position for controlling the movement of the pressure responsive means, said pressure responsive means being effective to move said device from one position to another, said finger manipulative toggle device being freely movable at will as a'unit to and from the operative position to control or remove its control from the pressure responsive means whenever desired.

7. A circuit controlling apparatus including a set of switch contacts in an electric circuit, pressure responsive means for opening and closing said contacts, a set oi overload switch contacts in said electric circuit in series with said pressure operated contacts, temperature responsive means for opening the overload contacts, a manual control member for resetting the overload contacts to closed position, and means actuated by force derived from the manual control member when resetting the overload contacts to closed position for holding open said pressure operated contacts.

8. A circuit controlling apparatus including a set of switch contacts in an electric circuit, pressure responsive means for opening and closing said contacts, a set of overload switch contacts in' said electric circuit in series with said pressure operated contacts, means responsive to an excessive flow: of current through said electric circuit for opening the overload contacts, means responsive to the environment temperature for compensating said current responsive means, a manual control member forresetting the overload contacts to closed position, and means actuated by force derived from the manual control member when resetting the overload contacts to closed position for holding open said pressure operated contacts.

GEORGE C. PEARCE,