US2069772A - Refrigeration - Google Patents

Description

Feb. 9, 1937. G Q PEARCE 2,069,772

REFRIGERATION Filed sept. 29, 1932 Patented Feb. 9, 1937 UNITED STATES PATENT OFFICE REFRIGERATION Application September 29, 1932, Serial No. 635,391

21 Claims.

This invention relates to refrigeration, and more particularly to refrigerating systems of the character which operate continuously without stopping for temperature adjustments in an object being cooled. Such systems are stopped a relativelyy few times compared with the stopping operations of the usual intermittently operating refrigerating system which stops for temperature adjustments in the object being cooled. In the continuously operating systems or in those systems which are designed to operate substantially continuously and stop only for defrosting, repairs or the like, or when the atmospheric temperature drops below the normal range, the period of idleness is extremely long, so that the refrigerant pressure in the system will become substantially equalized throughout the system. Because of this, these systems need not, and generally are not, provided with special unloaders for the compressor, and 4therefore are likely to fail to restart if an attempt is made to restart them relatively soon after they have been stopped. It may occur, in the operation of these systems, that the line current, or source of electrical energy, may fail for a relatively short period of time, due to an electrical storm or the like, and it is desirable that the refrigerating system should restart automatically and safely after such a temporary failure of the linelcurrent.

It is among the objects of this invention to provide a control for the electric motor which drives the refrigerating system which is capable of automatically starting the motor when the current is turned on by the user, and which is capable of restarting the system safely if the line current, or source of electrical energy should be turned off temporarily and then be turned on before the refrigerantv pressure has equalized sufficiently to permit the motor to start.

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

In the drawing:

Fig. l is a diagrammatic representation of a system embodying the features of my invention;

and

Fig. 2 is a diagrammatic representation of a 7.0 slightly modified system.

A refrigerating system embodying features of this invention is designed to operate continuously during the normal atmospheric temperature range maintained in a dwelling Without stopping for cabinet temperature adjustments, and is of such a character and capacity, that it automatically maintains proper temperature conditions in the object to be cooled, notwithstanding such continuous operation. Such a system has been more fully described in the copending application, Serial No. 599,239, led March 16, 1932, to which reference is hereby made for a further disclosure of such a system.

Briefly, such a system includes a compressor I0, a condenser II, an evaporator I2. The com- 10 presser discharges the compressed refrigerant to the condenser I I which in turn discharges liqueed refrigerant through the expansion device I3 to the evaporator I2 where the refrigerant is evaporated and returns through the line Il to the 15 compressor Ill. The expansion device I3 may be of any suitable character, but preferably is of the elongatedmriiice type which maintains a fixed, and continuously open orifice, so calibrated as to length and cross-sectional area, that it o maintains the evaporator I2 at the proper tem- 0 perature to maintain the object being cooled at a substantially constant temperature notwith` standing variations in the surrounding atmosphere. In such a system, the elongated orifice in the expander I3 permits a continuous passage 25 of refrigerant therethrough, and should the compresser I0 stop temporarily, this iiow through the orifice continues and in a relatively short time equalizes the pressures throughout the refrigerating system, so that if the compressor should be 30 restarted after such a short time, it. starts with substantially no load.

Under ordinary conditions, such a system is stopped only for the purpose of defrosting the n evaporator I2 and this defrosting operation is performed only once or twice a month and is not of the type of stopping operation which is intended to maintain temperature conditions in the object being cooled. On the contrary, such a stopping operation generally permits the object being cooled to warm above the desired temperature, 'but the operation is performed because of the large accumulation of frost on the evaporator and because of its undesirable inconvenience. After such a stopping operation and because of 'its long duration, the compressor starts under no load characteristics and hence the compressor need not be provided with unloading mechanism, other than the expander I3 itself. I5 for driving the compressor may be of the split phase type which is provided with a starting winding I6 and a running winding IT, and, as is usual with this type oi' motor` theV starting torque is small. Such a motor compresser unit The motor 50 4should. fail to start.

is capable of startingy only if the entire refrigeration system has become substantially equalized as to pressure throughout, or if the unit isv provided with an automatic unloader for removing the pressure differential load during the starting period. In this particular system, no unloader need be used, as it is possible to permit the system to equalize during the infrequentstops which may be necessary.

The starting control for such a system includes a device or relay |8 for maintaining a ow 'of current from the source of electrical supply A through the starting winding during the starting period and for stopping the now of said current at the termination o'f the starting period. 'Ihe control also includes devices for rendering the means or relay I8 safely reoperative after a temporary failure of the source of electrical energy and for preventing too frequent a starting and stopping of the motor after such failure of such source of electrical energy if the compressor should fail to permit the motor to start. To this end the relay I8 may' include a solenoid I8 in series with the running winding I1 whichv actuates the contact 20 for energizing the starting winding I6. 'I'he construction is such that the surgecurrent running through the running winding during the starting period is sufcient to pull the contact 20 against gravitational forces, or against a magnetic force, during the starting period of the motor so that the starting winding I8 is energized during such period; but the solenoid I9 is not of sufficient strength-to hold the contact 2D in closed position after the current through the winding |1 drops to the normal running value at the termination of the starting period.

An overload relay 2| is provided which prevents the surge current from running through the motor for `too long a period of time if the motor Thus means are provided for opening the electrical circuit if the motor fails to start after a predetermined period. To this end an overload relay 2| is provided in the formr of a resistance 22 which heats the thermostatic strip 23 yto open the contact 24 with a snap action against a resistance such as the permanent magnet 25. 'I'hus if the motor should fail to start after a predetermined period, the resistance 22 becomes heated and'causes the thermostatic strip 23"to maintain the circuit open until the resistance 22 and the thermostatic strip 23 become cooled. 'I'his control may be so constructed that f the heating and cooling period maybe of' any ing the heating and cooling'of the relay 2|, the

refrigerant continuously iiows through the expander I3, and reduces the refrigerant pressure diilerential in the compressor, so that the compressor offers less starting resistance to the motor I 5 after the expiration of such four minutes, when the circuit is again closed, and the motor once again -attempts to start. If unsuccessful again, the control 2| heats again and thus permits another four minute period to lapse before the third attempt is made to restart the motor.

It sometimes occurs that in the repeated starting attempts above described, the motor becomes overheated and it is therefore desirable to provide a long period of rest to permit the motor to cool and to insure that the refrigerating system has become thoroughly equalized before again'attempting to start the motor. To this end another control 26 is provided. This control requires a longer period of time before it becomes operative than is required by the control 2| and also maintains the circuit open for a longer period after such failure to start than the period maintained by the control 2|. Thus the control 2| may cycle several times before the control 26 becomes operative. This may be accomplished by mounting the thermostatic strip 21 on the motor casing 28. This strip 21 actuates the contact 29 against a resistance such as the permanent magnet 30 to open the circuit with a snap action after the strip 21 has been heated to a predetermined temperature. The length of time required to heat the strip 21 to this temperature is much longer than that required to heat the strip 23, because the casing 28 contains more metal than is contained in the resistance `22 and therefore heats or cools much more slowly. The

strip 21 is adapted to close the contact29 after the casing 28 has cooled to a predetermined temperature, and this cooling period is much greater in length than the cooling period of the resistance 22. A start after several attempts have been initiated by the control 2|, the control 26 opens the circuit and maintains it open for a major period of time which is much longer than the minor periods of rest maintained by the control 2|.

A manual control for stopping and starting the system by the user for defrosting, or the like, may be provided. Conveniently one of the contacts already provided may be used. Thus a stop 3| may be provided on the rod 32, which rod may be slidably connected with strip 23 in such a manner that the contact 24 may be opened without disturbing the strip 23. A snap acting, manually operated, lever construction 33 is provided to engage the hook 34 which forms an extension of the rod 32. Thus the user may operate the lever construction 33 to open the contact 24 or may operate it to permit the contact 24 to be governed by the control 2|.

In the modification shown in Fig. 2, means are provided which require a manual reset if the motor fails to start after a repeated number of starting attempts after a temporary line failure. To this end the control 26 of Fig. 1' is replaced by a manual reset control 48 shown in Fig. 2. The remaining portion of the system, having numerals similar to this Fig. 1, but with the suflix a attached, may be the same as the system shown in Fig. 1. The manual reset control 40 may include a spring member 4| tending to open the contact .42 whichin turn opens the electric circuit leading to the motorl |0a. The spring 4| is prevented from opening the 'contact 42 by means of a hook l43 which is,in engagement with the ratchet wheel 44. The ratchet wheel 44 is soldered to-the stationary shaft 45 mounted on the motor casing 28a by means of low melting point solder. After repeated attempts to start the motor by means of the automatic control 2| a, the motor casing 28a becomes overheated and melts the solder which holds the ratchet wheel 44 stationary on the shaft 45. When the solder is melted, the ratchet wheel turns and permits the spring 4| to open the contact 42, and thus opens the circuit to the motor |5a. The circuit remains open, until the button 46 is manually operated to close the contact 42 and to engage the hook 43 in the ratchet 44 after the casing Thus if the motor l5 fails to 28a has cooled sumciently to permit the-solder to 7'5 solidify and again prevent the ratchet 44 from turning.

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 refrigerating system including a compressor, condenser and evaporator in a closed refrigerant cycle, an electric motor for driving said compressor, said motor having a starting Winding and a running winding, a source of electrical energy, a starting control switch for maintaining the iiow of current from said source through said starting Winding during a starting period and for stopping the ow of said current at the termination of said starting period, means for rendering said starting control switch temporarily inoperative after failure of said electric motor to restart after a temporary failure of said source of electrical energy, and a continuously open expansion device between said-condenser and evaporator.

2. `A refrigerating system including a compressor, condenser and evaporator in a closed refrigerant cycle, anelectric motor for driving said compressor, said motor having a starting Winding and a running Winding, a source of electrical energy, a starting control switch for maintaining the ow o f current from said source through said starting winding during a starting period and for stopping the flow of said current at the termination of said starting period, means for rendering said starting control switch temporarily inoperative after failure of said electric motor to restart after a. temporary failure of said source of electrical energy, a continuously open expansion device between said condenser and evaporator, and means responsive to temperature of said motor for rendering said starting control switch inoperative while said motor is over-heated.

3. Refrigerating apparatus including a compressor, condenser, and evaporator connected in a closed circuit, said closed circuit having a continuously open restricted connection between the condenser and evaporator for controlling the iiow of refrigerant to the evaporator during the operation of the compressor, and for equalizing pres- A.Sures 'within the system to unload the compressor when the compressor is idle, an electric motor having a starting circuit and a running circuit for driving the compressor, means for connecting the starting circuit to a source of electric energy, and means for opening the motor circuit and for preventing the energization of said first mentioned means when the pressures in the closed refrigerant circuit have not equalized sufiiciently to permit starting of the electric motor, said opening means including means for reclosing the motor circuit after a period of rest.

e. Refrigerating apparatus. including a compressor, condenser, and evaporator connected in a closed circuit, said closed circuit having a continuously open restricted connection between the condenser and evaporator for controlling the flow of refrigerant to the evaporator during the operation of the compressor, and for equalizing pressures Within the system to unload the compresso-r when the compressor is idle, an electric motor having a starting circuit and a running circuit for di iving the compressor, means for connecting the starting circuit to a source of electric energy, and means for opening the motor circuit when said ilrst mentioned means is ineffective to start the electric motor, said opening means after a period of rest being effective to reclose the motor circuit.

5. In a refrigerating apparatus, the combination of a compressor, a condenser, a constantly open liquid refrigerant control device, and an evaporator in a closed refrigerant circuit, an electric motor for driving said compressor having a starting torque insuiicient to start the compressor against pressure differences of the order existing thereacross during normal operation of the apparatus, said motor having a starting winding and a running winding, a first circuit controller for controlling the starting winding, a second circuit controller for controlling at least the running winding, means adapted to open the first circuit controller when the motor approaches running speed after starting, and means for opening the second circuit controller upon the flow of excessive current and for automatically closing theA second circuit controller after an interruption of the flow of current to the running winding.

6. In a refrigeratlng apparatus, the combination of a compressor, al condenser, a constantly open liquid refrigerant control device, and an evaporator in a closed refrigerant circuit, an electric motor for driving said compressor having a starting torque insufficient to start the compressor against pressure dierences of the order existing thereacross during normal operation of the apparatus, said motor having a starting winding and a running winding, a rst circuit controller for controlling the starting winding, a second circuit controller for controlling both windings, means adapted to open the first circuit controller when the motor approaches running speed after starting, and means for opening the second circuit controller upon the iiow of excessive current and for automatically closing the second circuit controller after an interruption of .the flow of current to the running winding.

7. In a refrigerating apparatus, the combination of a compressor, a condenser, a constantly open liquid refrigerant control device, and an evaporator in a closed refrigerant circuit, an electric motor for driving said compressor having a starting torque insufficient to start the compressor against pressure differences of the order existing thereacross during 4normal operation of the apparatus, said motor having a starting winding and a running winding, a first circuit controller for controlling the starting winding, a second circuit controller for controlling at least the running winding, means adapted to open the iirst circuit controller when the 'motor approaches running speed after starting, and means for opening the second circuit controller upon the flow of excessive current and for automatically closing the second circuit controller after an interruption of the iiow of current to the running winding, said last named means including time delay means for preventing maintenance of the second circuit controller in closed position until a predetermined time has elapsed after the occurrence of an excessive current flow in the motor.

8. In a refrigerating apparatus, the combination of a compressor, a. condenser, a constantly open liquid refrigerant control device, and an evaporator in a closed refrigerant circuit, an electric motor for driving said compressor having a starting torque insufficient to start the cornpressor against pressure diierences of the order existing thereacross during normal operation of the apparatus, said motor having a starting Windingand a running Winding, a first circuit controller for controlling the starting vvinding, a second circuit controller for controlling both windings, means adaptedto open the iirst circuit controller when the motor approaches running speed after starting, and means for opening the second circuit controller upon theV flow of excessive current and for automatically closing the second circuit controller' after an interruption of the flow of current to the runningv Wind- Acompressor' being constantlyexposed to the pressures existing in the evaporator and condenser,v

an electric motor Afor driving said compressor having a starting torque insufficient to start the compressor against pressure differences of the order existing thereacross during normal operation of the apparatus, said motor having a starting winding .and a running winding, 'a rst circuit controller for controlling the startingwinding, a second circuit controller for controlling at least the running winding, means adapted to lopen the first circuit controller when the motor approaches running speed after starting, and

means for opening the second circuit controller upon the flow of excessive current and for auto matically closing the second circuit controller after an interruption of the flow of current to.

the running winding.

10. In a refrigerating apparatus, the combination'of a compressor, a condenser, a constantly open liquid refrigerant control device, and an evaporator in a closed refrigerant circuit. said compressor being constantly exposed to the pressures existing in theevaporator and condenser,

an electric motor for driving said compressor having. a starting torque insufcient to startthe compressor against pressure differences of the order existing thereacross during normal-operationof the apparatus, said motor having a starting winding a'nd a running winding, a` first circuit controller for controlling the starting winding, a second circuit controller for controlling at least the 'rlmning winding, means adapted to open the first circuit controllenwhen the motor approaches running speed; after starting, and

means for opening the second circuit controller upon the owof excessive current and for automatically closing the second circuit controller after an interruption of the .now of current to the running winding, said last named means including time delay means for preventing main#- tenance of the `second circuit controller in closed position until a predetermined time has elapsed after the occurrence ofen 'excessive current flow in the motor.

11. In a refrigeratingappsrstus. the combination of a compressor, ,s condenser, a constantly' open' liquid refrigerant .control device. and an evaporator. in a closed refrigerant circuit,- said compressor being constantly expgsed' to the pres- A sures existing inthe evaporator and condenser, an electricmotor for driving said compressor having a starting torque insuillcicnt to start' the compressor against 'pressure differences of. the

order' existing thereacross during normal opera.-A

tion ofthe apparatus, said motor having a startcuit controller for controlling the starting winding, a second circuit controller for controlling at least the running winding, means adapted to open the rst circuit controller when the motor approaches running speed afterstarting, and means for opening the second circuit controller upon the flow of excessive current.

- 12. In 'a refrigerating apparatus, the combination of a compressor, a condenser, a constantly open liquid refrigerant control device, and an evaporator in a closed refrigerant circuit, said compressor being constantly exposed to the pres-l sures existing in the evaporator and condenser, an electric motor for driving said compressor having a starting torque insuillcient to .start the compressor against pressureV differences of the order existing thereacross during normal operation of the apparatus, said motor having a starte pressor, a first circuit controller f or controlling the starting winding, a second circuit controller vfor controlling' at least the running winding,

means adapted to open'th first circuit controller when` the motor approaches running speed after I evaporator in a. closed refrigerant circuit, said I refrigerant vsystem comprising a compressor, condenser, and evaporator, an electric motor having a starting circuit and a running circuit for drivingl the compressor to circulate refrigerant and to create a pressure difference in the system on either side of. the compressor, said system being provided wlthmeans for reducing the pressure dierential across the compressor when the com- V for opening the motor circuit for preventing-the energization of the electric motor when the pressure dlllerential across'the compressor has vnot been reduced sumcientlyto permitstarting of the electric motor, said opening means including means for reclosingthe motor circuit after a. period o: rest,

denser, and evaporator, an electric motor having starting circuit and a running` circuit for driving 15. Rerrigersuns apparatus including 'a dosed refrigerant system'comprising-a compressor, conthe compressor -to circulate refrigerantk and to vcreate s pressure dierenceA in the systemen -either side of Athe compresso said'. system provided". with means' for reducing the pressure Vdifferential across the compressor when the com- ,p1-essor isidle to unload. the compressor, means for connecting the startingcircuitto-a source of electric energy@ startthe compressor, land means responsiverto the electric' motor current and to electric motor for preventing the 75 energization of the electric motor under dangerous conditions.

16. Refrigerating' apparatus including a closed refrigerant system comprising a compressor, condenser, and evaporator, an electric motor having a starting circuit and a running circuit for driving the compressor to circulate refrigerant and to create a pressure difference in the system on either side of the compressor, said system being provided with means for reducing the pressure differential across the compressor when the compressor is idle to unload the compressor, means for connecting the starting circuit to a source of electric energy to start the compressor, and means responsive to the electric motor current and toi` electric motor temperature for opening the electric motor circuit under dangerous conditions and thereafter closing the circuit automatically when the condition has improved.

17. A refrigerating system including a compressor, a condenser and an evaporator in a closed refrigerant circuit, an electric motor for driving said compressor, said motor having a starting winding and a running Winding, a source of electrical energy, means for maintaining the ow of current from said source through said starting Winding during a starting period and for stopping the ilow of said current at the termination of said starting period, means for rendering said rst named means reoperative after a temporary interruption in the supply of electrical energy, means for preventing the flow of current through said windings for a predetermined period of time if said temporary interruption should prove to be of insufiicient duration to unload said refrigerating system, said period of time being longer than said starting period, and means for equalizing refrigerant pressures in said system during said predetermined period.

1S. A refrigerating system including a compressor, a condenser and an evaporator in a closed refrigerant circuit, an electric motor for driving said compressor, said motor having a starting winding and a running Winding, a source of electrical energy, means for maintaining the fiow of current from said source through said sarting winding during a starting period and for stopping the flow of said current at the termination of said starting period, means for rendering said rst named means reoperative after a ternporary interruption in the supply of electrical energy, means for preventing the flow of current through said windings for a predetermined period of time if said temporary interruption should prove to be of insufficient duration to unload said refrigerating system, said period of time being longer than said starting period, and a continuously open expansion device between said condenser andy evaporator for equalizing refrigerant pressures in said system during said predetermined period.

19. A refrigerating system including a compressor, a condenser and an evaporator in a closed refrigerant circuit, an electric motor for driving said compressor, said motor having a starting winding and a running winding, a source of electrical energy, means for maintaining the flow of current from said source through said starting winding during a starting period and for stopping the ow of said current at the termination -of said starting period, means for rendering said rst named means reoperative after a temporary interruption in the supply of electrical energy, means for preventing the flow of current through said windings for a predetermined period of time if said temporary interruption should prove to be of insucient duration to unload said refrigerating system, and means for equalizing refrigerant pressures in said system during said predetermined period.

20. A refrigerating system including a compressor, a condenser and an evaporator in a closed refrigerant circuit, an electric motor for 'driving said compressor, a hermetically sealed casing enclosing said motor and compressor, said compressor being constantly subjected to the pressure difference between the condenser and the evaporator, said motor having a starting winding and a.running winding, a source of electrical energy, means for maintaining the flow of current from said source through said starting winding during a starting period and for stopping the ow of said current at the termination of said starting period, means for rendering said first named means reoperative after a. temporary interruption in the supply of electrical energy, means for preventing the ilow of current through said Windings for a predetermined period of time if said temporary interruption should prove to be of insuliicient duration to unload said refrigerating system, said period of time being longei` than said starting period, and means for equalizing refrigerant pressures in said system during said predetermined period.

21. A refrigerating system including a compressor, a condenser and an evaporator in a closed refrigerant circuit, an electric motor for driving said compressor, a hermetically sealed casing enclosing said motor and compressor, said compressor being constantly subjected to the pressure difference between the condenser and the evaporator, said motor having a starting winding and a running winding, a source of electrical energy, means for maintaining the flow of current from said source through said starting winding during a starting period and for stopping the flow of said current at the termination of said starting period, means for rendering said rst named means reoperative. after a temporary interruption in the supply of electrical energy, means for preventing the flow of current through said windlings for a predetermined period of time if said

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