US2072767A - Refrigeration - Google Patents

Description

March 2, 1937. G. c. PEARCE 2,072,767

REFRIGERATION Original Filed Sept. 29, 1932 Patented Mar. 2, 1937 UNITED STATES PATENT OFFICE REFRIGERATION Application September 29, 1932, Serial No. 635,390

Renewed May 2, 1936 16 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 obu ject being cooled. Such systems are stopped a relatively few times compared with the stopping operations of the usual intermittently operating refrigerating system which stops for temperature adjustments in the objects being cooled. In the 10 continuously operating systems or in those systems which are designed to operate substantially continuously with and stop only for defrosting, repairs or the like, or when the atmospheric temperature drops below the normal range, the pe- 15 riod 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 go the compressor, and therefore 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 en- 35 ergy, 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 line current.

30 It is among the objects of this invention to provide an improved 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 also 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 refrigerant 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.

5 In the drawing:

automatically maintains proper temperature conditions in the object to be cooled, notwithstanding such continuous operation. Such a system has 55 been more fully described in the cope'nding application, Serial No. 599,239, filed March 16, 1932, to which reference is hereby made for a further disclosure of such a system.

Briefly, such a system includes a compressor ill, a condenser l I, an evaporator I2. The com- 5 pressor discharges the compressed refrigerant to the condenser H which in turn discharges liquefied refrigerant through the expansion device l3 to the evaporator l2 where the refrigerant is evaporated and returns through the line [4 to the compressor ID. The expansion device [3 may be of any suitable character, but preferably is of the elongated orifice type which maintains a fixed, and continuously open orifice, so calibrated as to length and cross-sectional area, that it maintains l5 the evaporator l2 at the proper temperature to maintain the object being cooled at a substantially constant temperature notwithstanding variations in the surrounding atmosphere. In such a system, the elongated orifice in the expander I3 permits a continuous passage of refrigerant therethrough, and should the compressor l0 stop temporarily, this flow through the orifice continues and in a relatively short time equalizes the pressures throughout the refrigerating systom; so that if thecompressor should be 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 0 evaporator l2 and this defrosting operation is performed only once or twice a month and is not of the type of stopping operation which is in-\ tended to maintain temperature conditions in the object being cooled. On the contrary, such 5 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 l3 itself. The motor [5 for driving the compressor may be of the split phase type which is provided with a starting winding I6 and a running winding l1, and, as is usual with this type of motor the starting torque is small. Such a motor compressor unit is capable of starting only if the entire refrigeration system has become substantially equalized as to pressure throughout, or if the unit is 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 by a sufliciently long period of idleness during the infrequent stops which may be necessary.

The control for the motor includes starting contacts W for controlling the flow of electric current to the starting winding and running contacts l9 for controlling the flow of electric current to the running windings. A starting control 20 is provided for the contacts l8 and a running control ii is provided for the contacts 09. The control 29 includes a thermostat in the form of a bi-metallic strip 22 heated by a resistance 23 in an electric circuit between the source of electrical energy 2% ,and the motor it which passes through the resistance 23. The bimetallic strip 22 opens the contacts l8 by moving the rod lBa carrying the movable contact upwardly against the magnet resistance 25 by va snap action in the well-known manner. The running control it includes a thermostat in the form of a bi-rnetallic strip 26 heated by a resistance 2? through which an electric circuit passes from the source of electrical energy 26 to the motor id. The stripZS opens the contacts Ed by moving the rod lQa. carrying the movable contact upwardly by a snap action against the magnet resistance 28.

The construction and calibration is such that the thermostat 28) opens the contacts it after the motor 65 has attained its running speed and maintains the contacts open so long as the motor continues'to operate normally. The control M is constructed and calibrated so that the contacts l9 remain closed so long as the motor runs normally but will open if the motor should become overloaded sumciently to overheat the thermostat 2i and cause it to open the contacts it. Also the construction is such that the thermostats automatically reclose their respective contacts when they have cooled either because the current has been turned ofi intentionally or accidentally. To this end the resistances 231 and 2,7 are placed in the circuit leading to the running winding ill, so that both thermostats 20 and M are responsive to the current flowing to the running winding. However, the thermostat 2i! isconstructed so that it heats quickly and opens the contacts l8 before the contacts ill can be opened and is of such construction that the contacts l8 are opened after a predetermined period of time sumcient to normally permit the motor IE to attain its running speed.

A manual control for stopping and starting the system may be provided and this may include a snap acting levermechanism 36 adapted to engage the hook 3! which is an extension of the contact rod i911. which controls the opening and closing of the contacts 89. The rod Ha'may have a sliding engagement with the strip 2a with a stop 33 attached to the rod Na in such a manner that the rod i911 may be moved upwardly without disturbing bi-m'etal 26. Thus the man ual control to may be operated to open the contacts l9 by moving hook 3i and therefore the rod I90 upwardly without disturbing the bimetal 26, and if the manual control 30 is placed in the closed. position, it permits the rod llBa to move downwardly and be actuated by the bimetal 26 acting through the stop 33 independently of the manual control.

Under ordinary operation, the manual control 30 is moved to ,release the rod l9a downwardly to close the contacts l9 and this initiates a starting cycle inwhich electric current flows through both windings l6 and ii and both re sistances 2 3 and 27. After a length of time sufficient to permit the motor to start, the contacts is are opened by an upward movement of the rod we thus opening the circuit 36 leading to the starting winding after which the motor l5 will be operated only by the running winding. Should the source of electrical energy, or line, temporarily fail and be reenergized before the refrigerant pressure in the system has equalized sufficiently to unload the compressor, upon the re turn of electrical energy the motor l5 probably will fail to start either because the resistance 23 has not had time to cool and close contacts l8 or will fail to start because the pressure differential in the compressor and therefore its starting torque is too great for the motor. In either case, the running thermostat 2! will become overheated and the contacts is will be opened. When these contacts are open, the flow of current through the resistances 23 and H stops and permits the thermostats 2E and M to cool, thus reclosing the contacts l8 and us. When these contacts are reclosed, a starting cycle is initiated which if successful will permit the motor it to run as long as desired, but it unsuccessliul, will re-initiate another overload and restarting cycle until such time as compressor is unloaded sufiiciently to permit the motor E5 to start.

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 comprising a compressor, condenser, a constantly open liquid refrigerant control device and evaporator in a closed refrigerant flow circuit, an electric motor for driving said compressor having a starting torque insuflicient 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, starting contacts for controlling an electric circuit through said starting winding, a starting thermostat responsive to current flow through said running winding for opening said contacts, running contacts for controlling an electric circuit through said running winding, :2. running thermostat responsive to current flow through said running winding for opening said running contacts, said thermostats being adjusted to open said starting contacts only after the motor has attained a speed sufilcient normally to insure operation on the running winding, and to open said running contacts only when said motor is overloaded.

2. A refrigerating system comprising a compressor, condenser, a constantly open liquid re- .frigerant control device and evaporator in a closed refrigerant flow circuit, an electric motor for driving said compressor having a' starting torque insumcient 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, starting contacts for controlling an electric circuit through said starting winding, a starting thermostat responsive to current fiow through said running winding for open-- ing said contacts, running contacts for controlling an electric circuit through said running winding,

a running thermostat responsive to current flow 2,072,767 through said running winding for opening said running contacts, said thermostats being adjusted to open said starting contacts only after the motor has attained a speed sufiicient normally to insure operation on the running winding, and to open said running contacts only when said motor is overloaded, said thermostats automatically reclosing their respective contacts when the respective thermostats have cooled.

3. A refrigerating system comprising a compressor, condenser, a constantly open liquid refrigerant control device and evaporator in a closed refrigerant flow 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 normal operation of the apparatus, said motor having a starting winding and a running winding, starting contacts for controlling an electric circuit through said starting winding, a starting thermostat responsive to current flow through said running winding for both opening and closing said contacts automatically, running contacts for controlling an electric circuit through said running winding, a running thermostat responsive to current flow through said running winding for opening said running contacts, said thermostats being adjusted to open said starting contacts only after the motor has attained a speed suificient normally to insure operation on the running winding, and to open said running contacts only when said motor is overloaded, the opening of said running contacts initiating a cooling period in said thermostats.

4. A refrigerating system comprising a compressor, condenser, a constantly open liquid refrigerant control device and evaporator in a closed refrigerant flow 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 normal operation of the apparatus, said motor having a starting winding and a running winding, starting contacts for controlling an electric circuit through said starting winding,

a starting thermostat responsive to current flow through said running winding for opening said contacts, running contacts for controlling an electric circuit through said running winding, a running thermostat responsive to current flow through said running winding for opening said running contacts, said thermostats being adjusted to open said starting contacts only after the motor has attained a speed suflicient nor-' mally to insure operation on the running winding, and to open said running contacts only when said motor is overloaded, said thermostats automatically reclosing their respective contacts when the respective thermostats have cooled.

5. A refrigerating system comprising a compressor, condenser, a constantly open liquid refrigerant control device and evaporator in a closed refrigerant flow 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 normal operation of the apparatus, said motor having a starting winding and a running winding, starting contacts for controlling an electric circuit through said starting winding, a starting thermostat responsive to flow of electric current to said motor for opening said starting contacts, running contacts for controlling an electric circuit through said running winding, a running thermostat responsive to the flow of electric current to said motor for opening said running contacts, said thermostats being adjusted to open said starting contacts only after the motor has attained a speed sufficient normally to insure operation on the running winding, and to open said running contacts only when said motor is overloaded, said thermostats automatically reclosing their respective contacts when the respective thermostats have cooled.

6. A refrigerating system comprising a compressor, condenser, a constantly open liquid refrigerant control device and evaporator in a closed refrigerant flow 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 normal operation of the apparatus, said motor having a starting winding and a running winding, starting contacts for controlling 'an electric circuit through said starting winding,

a starting thermostat responsive to flow of electric current to said motor for both opening and closing said starting contacts automatically, running contacts for controlling an electric current through said running winding, a running thermostat responsive to the flow of electric current to said motor for opening said running contacts, said thermostats being adjusted to open said starting contacts only after the motor has attained a speed sufficient normally to insure operation on the running winding, and to open said running contacts only when said motor is overloaded, the opening of said running contacts initiating a cooling period in said thermostats.

'7. A refrigerating system comprising a compressor, condenser, a constantly open liquid refrigerant control device and evaporator in a closed refrigerant flow 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 normal operation of the apparatus, said motor having a starting winding and a running winding, starting contacts for controlling an electric circuit through said starting winding, a starting thermostat responsive to flow of electric current to said motor for opening said starting contacts, running contacts for controlling an electric circuit throughsaid running winding, a running thermostat responsive to the flow of electric current to said motor for opening said running contacts, said thermostats being adjusted to open said starting contacts only after the motor has attained a speed sufiicient normally to insure operation on the running' winding, and to open said running contacts only when said motor is overloaded, said thermostats automatically reclosing their respective contacts when the respective thermostats have cooled, the opening of saidrunning contacts initiating a cooling period in said thermostats.

8. A refrigerating system comprising a compressor, condenser, a constantly open liquid refrigerant control device and evaporator in a closed refrigerant flow circuit, an electric motor for driving said compressor having a starting torque insufiicient 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, starting contacts for controlling an electric circuit through said starting winding, a starting thermostat responsive to current flow to said motor for opening said contacts, an automatic overload control responsive to an overload in the running winding of said motor and controlling the flow of current to said motor, said starting thermostat being adjusted to open said starting contacts only after the motor has attained a speed sufficient normally to insure, operation on the running winding, and said overload control being adjusted to prevent the flow of electric current to said motor only when said motor is overloaded, said thermostat and overload control automatically reclosing after a predetermined period. I

9. 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 compremor having a starting torque insumcient 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, thermal current means adapted to open the first circuit controller when the motor approaches running speed after starting, and current responsive 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 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, an electric motor for driving said compressor having a starting torque insufiicient 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, thermal current means adapted to open the first circuit controller when the motor approaches running speed after starting, and thermal current responsive means for opening the second circuit controller upon the flow of excessive current and forautomatically closing the second circuit controller after an. interruption of the flow of current to the running winding. i

. 11. 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 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, thermal current means adapted to open the first circuit controller when the motor approaches running speed after starting, and current responsive 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 flow 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.

12. In a refrigerating apparatus, the combination of a compressor, a condenser, a constantly proaches running speed after starting, and thermal current responsive 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 flow 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.

13. 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 difierences 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 both motor windings, thermal current means adapted to open the first circuit controller when the motor approaches running speed after starting, and current responsive 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 flow of current to the running winding.

14. 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 normal operation of the apparatus, said motor having a starting winding and a running winding, a first circuit controller for controlling the startingv winding, a second circuit controller for controlling both motor windings, thermal current means adapted to open the first circuit controller when the motor approaches running speed after starting, and thermal current responsive means for opening the second circuit controller upon the flow of excessive current and for automaticallly closing the second circuit controller after an interruption of the flow of current to the running winding.

15. Refrigerating apparatus including a closed refrigerating system comprising a compressor, a condenser, and an evaporator, an electric motor connected to the compressor for driving the compressor, said electric motor including starting and running windings, said electric motor being supplied with electric energy through an electric circuit, said compressor being driven by said electric motor for circulating refrigerant in the closed refrigerant system by creating a pressure difference on opposite sides of the compressor, said closed refrigerant system being provided with means for reducing the pressure difference on opposite sides of the compressor when the compressor is idle to unload the compressor, starting contacts in series with the starting winding to control the energization of the starting winding, a starting thermostat for controlling the opening of said contacts, and a self-resetting overload device responsive to the overloading 'of the electric motor for opening the electric motor circuit for preventing the energization of the electric motor when the pressure difference on opposite sides of the compressor has not been reduced sufiicient- 1y to permit starting oi the electric motor, said self-resetting overload device being provided with means for re-closing the motor circuit after an interval.

l6. Refrigerating apparatus including a sealed casing containing a compressor and an electric motor connected to the compressor for driving the compressor, said electric motor including starting and running windings within the sealed casing, said windings being supplied with electric energy through an electric circuit, a refrigerant condenser and a refrigerant evaporator connected in closed refrigerant circuit with said compressor, said compressor being driven by said electric motor for circulating refrigerant in the system by creating a pressure difference on opposite sides of the compressor, and a single thermostat located outside the sealed casing for controlling both the energization and the de-energization of the starting winding independently of the running winding.

GEORGE C. PEARCE.

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