US2169554A - Refrigerating apparatus - Google Patents

Description

Aug. l5, 1939. B, M, BUHANAN- 2,169,554

' RFRIGERATING APPARATUS Filed Oct. 26, 1937 Fxca. 1.

INVENTOR Ltsu: B.M.BucHANAN.

' I BY ATTOR Y Patented Aug. 15, 1939 REFRIGERATIN G APPARATUS Leslie B.- M. Buchanan, Springfield, Mass., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application October 26, 1937, Serial No. 171,018

8 Claims. (Cl. (i2-115) My invention relates to refrigerating apparatus and has for an object to provide improved apparatus of this character. l

A further object of the invention is to provide improved means for relieving a refrigerant compressor of a substantial portion of its load during the starting thereof and to load the same thereaften A further object of the invention is to progressively load a refrigerant compressor subsequent to the starting thereof.

It is another object of the invention to provide improved refrigerating apparatus of the compression type employing a capillary expansion device, wherein the condensing pressure is prevented from building up rapidly during the acceleration of the compressor.

A still further object of the invention is to provide an improved organization of the elements of a refrigerating system including a motor driven compressor having load 1elieving means and overload protection means.

These andother objects are effected by my .invention as will be apparent from the following description and claims'taken in connection with the accompanying drawing, forming a part of this application, in which:

refrigerating system employing a. compressor controlled in accordance with my invention; and,

Fig. 2 is a. diagram of the connections of the electrical elements employed in the structure shown in Fig. 1.

Reference will now be had to the drawing wherein I have shown, generally at I0, a motor driven compressor employed for the circulation of refrigerant in a refrigerating system including a condenser II, an expansion device I2 of fixed ow area, hereinafter referred to as a capillary tube, and an evaporator I3, the latter being disposed for abstracting heat from a chamber I4. As is well understood, the condenser II forms a part of the high pressure side of the system and the evaporator I3 a part of the low pressure side thereof, the expansion device or capillary tube I2 functioning to reduce the pressure of the condensed refrigerant in the condenser to the pressure of vaporization in the evaporator I3. Cooling of the compressed refrigerant in the-condenser II may be effected in any suitable manner such as, for example, by a fan I5.

YThe motor-compressor unit III lmay be of any suitable type but, preferably, includes a reciprocating type compressor I6, driven by an elecing through the casing I8, as shown. Fig. 1 is a View, partially diagrammatic, of a tric motor II, and a casing I8 for hermetically enclosing the same. A frame I9 is secured within the casing I8 and provides a support for the motor and compressor. The motor I1 is of any suitable type and includes a stator 2l supported bythe frame I9 and a rotor 22, carried by a shaft 23 that is journaled in the frame I9. The electrical conductors for the motor are not shown in Fig. l, but extend through the casing II) in any manner well understood in the art.

The compressor I6 includes a cylinder 24 that is supported by the 'frame I9 and in which a piston 25 is reciprocated. The piston 25 is actuated, preferably, by a connecting rod 26 and crank pin 21 that is eccentrically carried by the-shaft 23. The cylinder 24 includes a head structure 28 enclosing the usual inlet and exhaust valves (not shown) for controlling the flow of refrigerant gas to and from the cylinder 24. A refrigerant gas inlet passage ,29 is formed in the head structure 28 and provides a passage for the flow of gas from the interior of the casing I8 to theinlet valve of the compressor. Gas is compressed to a relatively high pressure in the compressor I6 and is discharged to the condenser I I through a conduit 3I, the latter pass- The refrigerant vaporized in the evaporator I3 is conducted to the interior of the casing I8 by means of aconduit 32.

In the operation of a system of the compressor-condenser-expander type, as shown, having a capillary tube as the expansion element, gas

^ at relatively low pressure is Withdrawn from the to the evaporator until the pressures in the condenser and evaporator are substantially equalized,

When operation of the compressor is initiated,

-the pressures at the inlet and outlet thereof are substantially equal. However, the pressure in the condenser rapidly builds up during the rst few revolutions of the motor and effects a relatively high load on the motor prior to its attaining full speed. It is an object of my invention to reduce the load on the motor at this time by preventing the pressure in the condenser from building up too rapidly during the acceleration of the motor and compressor. By attaining this object, I am enabled to employ a smaller and less expensive motor, as its starting: duty is reduced, the necessary capacity thereof being determined mainly by its running duty.

In accordance with the invention, I provide a valve 33 for closing the inlet 29 of the compressor I6 during inactive periods of the compressor, which valve 33 is progressively opened subsequent to the starting of the compressor. The valve 33 may include a valve member 34 that cooperates with a valve seat 35 formed on the head structure 28. 'I'he valve member 34 may be carried and actuated by a thermal responsive member, such as, a bimetallicelement 36. The latter is heated by a heating element 31 supported in any suitable manner such as, for example, by the `cylinder 24. During inactive periods of the compressor, I6, the bimetal element 36 is cool and is in a position wherein the valve 33 is closed. When thev compressor I6 is started, the'heater 31 is energized so that the bimetal element 36 delects to the position shown in the drawing in which the valve33 is open. Movement of the bimetal element 36 may be in a snap-acting manner if desired or it may be gradual, as shown, so that the valve 33 is progressively moved to its open position. 1

The heater 31 is energized simultaneously with the energization of the motor I1 and is, preferably, connected in series with a winding 38 of the motor I1, as shown in Fig. 2. Energization of the winding 38 and heater 31 may be controlled by a suitable master switch 39 which may be manually or thermostatically operated inlanymanner well understood in the art.

Overload and thermal protection for the motor I1 may be provided by a thermal responsive overload device 4I preferably secured to the portion of the casing I8 which supports the motor I1. The device 4I is best shown diagrammatically in Fig. 2 and includes a snap-acting bimetallic disk 42 carried in heat transfer relation with the casing by a stud 43. The disk 42 is disposed also in heat transfer relation with a heater 44 which is energized with the motor I1 and is heated in f proportion to the current drawn by the motor I1. Preferably, the heater 44 is connected in series with the motor winding 38 as shown. The disk 42 bridges stationary contacts 45 and denes therewith a normally closed switch structure 46.

During normal operation, or when the current in the motor I1 and heater 44 is below apredetermined value, the switch 46 is closed. How-- ever, when an abnormal condition causes an increase in motor current to a predetermined value, the heater 44 heats the disk 42 vsuiiciently to open the switch 46. Accordingly, the heater 44 and motor I1 are deenergized. The disk 42'cools and, when its temperature is reduced to a predetermined value, it effects closure of the switch 46 and automatically energizes the motor I1 and heater 44. If the abnormal condition still exists, the switch 46 is again opened. This operation continues until the abnormal condition is corrected. lAn abnormally high temperature of the motor I1 due to some conditions other than high current also operates the switch 46 as the disk l 42 is subjected to the heat of the motor. The disk 42 responds, therefore, to the combined current and thermal conditions of the rmotor I1.

It will be apparent thatv the switch 46 also controls energization of the heater 31 of the Valve mechanism.

'Operation As shown in the drawing, theswitches 39 and H46 are closed and the valve 33 is open so that the compressor unit I0 is operated. Circulation l f is substantially equalized. During inactive period of the compressor I6, the bimetal element 36 cools and closes the valve 33.

Closure of the switch 39 in response to a demand for refrigeration effects energization of the motor I1 and heater 31 simultaneously. As the valve 33 is closed, flow of vapor from the interior of the casing I8 to the inlet chamber 29-is prevented or substantially reduced at this time. Accordingly, downward movement of the piston 25 withdraws vapor from the inlet chamber 29 and depresses the pressure therein. The volume of the chamber 29 is preferably large enough to prevent the compressor from reducing the pressure therein below a predetermined value during closure of the valve 33' and is small enough to prevent high density vapor from filling the cylinder 24 during the first few strokes of the piston 25. Accordingly, the density of the vapor in the cylinder 24 at the beginning of the compression stroke is lower than the density of the vapor in the casing I8. The amount of vapor discharged to the condenser is relatively small so that the pressure builds up slowly in the condenser during acceleration of the compressor.

Theyvalve 33 may be constructed to -provide a pressed too low. In this connection, itwill be apparent ,that Vthe valve 33 may be inexpensively constructed as it is not necessary to provide a uid-tight structure as is necessary in aconventional unloader valve. Accordingly, a saving in the manufacturing cost of a refrigerating system is effective by my invention.

The small amount of work expended in depressing the pressure in the inlet chamber is regained on the compression stroke and, as the density of the gas in the condenser is substantially the same as in the casing I8, the work expended in discharging the gas from the cylinder is that necessary to overcome friction in the conduit 3i and theoutlet 4valve of the the compressor. Accordingly, during the initial strokes of the piston 25, the load on the motor I1 is `relatively low so that a motor having high starting torque l or a capacity substantially in excess of the run? ning capacity is not required. l

As 'the motor I1 accelerates, j the valve 33 isV opened by the heater 31 and morevgas is admitted to'theinlet chamber 29. By proper coordinating of*the"elements described heretofore, the load n sponsive element 36 gradually opens'thevalve 33 or doesl so in a snap-acting manner. In the latter case, a higher vacuum maybe effected iny the inlet chamber 29 than in the caseof the gradual acting member, but, in b'oth cases, the pressure build-up in the condenser is retarded, which is the primary result sought.

Operation of the' compressor unit I0 is terminated by opening the master switch 39 when the demand for refrigeration is satised. When the system includes the thermal or overload responsive element 4|, it is desirable that the thermal element 36 close the valve 33 before the disk 42 closes its switch 46, subsequent to opening thereof by an overload condition. The reason for this operation is to insure that the compressor is relieved of the starting load when the device 4| starts operation after an abnormal condition. This operation may be effected by predetermining the relative rates of cooling of the elements 42 and 36.

From the foregoing, it will be apparent that I have provided an improved refrigerating system of the compression type wherein the density of the vapor in the compressor cylinder during the rst of the compression strokes is controlled, so that the head or condensing pressure progressively increases during acceleration of the motor and compressor. Accordingly, the load is pro-l gressively applied to the compressor during starting periods thereof.' The capacity of the motor for driving the compressor may, therefore, be determined mainly by its running duty and need not be increased substantially because ofr high starting'loads. The use of an inexpensive valve of the type described in place of a conventional unloader mechanism having a ground valve and seat represents a saving in the cost of manufacture.

While my invention is particularly adaptable to refrigerating systems employing an expansion device of the fixed flow area type, it will bev understood that it is not so limited and may be applied to other forms of compression refrigerator systems wherein equalization of the pressures in the high and low sides of the system is not effected during shut down periods.

While I have shown my invention in but one form, it will be obvious to those lskilled in the art that it is not so limited, but is susceptible of various changes 4and modifications without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are imposed by the prior art or as are specifically set forth in the appended claims.

What I claim is:

1. In refrigerating apparatus, the combination of a condenser, an evaporator and a compressor for translating refrigerant through the condenser and evaporator, a motor for actuating the compressor, a valve for controlling the flow of refrigerant from the evaporator to the compressor which is normally closed during inactive periods of the compressor, a thermal responsive element for progressively opening the valve when heated, a heater associated with said element, and means for energizing the motor and said heater.

2. In refrigerating apparatus, vthe combination of a condenser, an evaporator, a. compressor for translating refrigerant through the condenser and evaporator, a casing for enclosing the compressor, a motor for driving the compressor, a valve disposed Within the casing for controlling communication between the evaporator and the compressor, which valve is-normally closed during inactive periods of the compressor, and means for progressively actuating said valve to its open position subsequent to the starting of the Y time required for said valve to close subsequent 'to the deenergization of the motor.

'and heater.

compressor and for retaining said valve in open position' during normal operation of the compressor.

3. In refrigerating apparatus, the combination of a condenser, an evaporator, a refrigerant compressor for withdrawing refrigerant vapor from the evaporator and for translating it to the compressor at relatively high pressure, a motor for driving the compressor, a valve for controlling the flow of vapor from the evaporator to the compressor which is normally closed ,during inactive periods ofthe compressor, means for controlling the energization of .the motor, means for operating said valve and providing for time intervals between the energization of the motor and the 15 opening of thev valve and between the deenergization of the motor and the closing of the valve, an overload responsive switch for controlling energizaltion off the motor and movable to its open position in response to a predetermined load on the motor, said switch being closed automatically after a predetermined period of time has elapsed after'the opening thereof, which period of time is longer in duration than the period of 4. In refrigerating apparatus, the combination of a condenser, an evaporator, a refrigerant comf pressor for withdrawing vapor from the evaporator and for translating it to the condenser at relatively high pressure, a motor for driving the compressor, a valve for controlling the flow of vapor to the compressor from the evaporator and normally closed during inactive periods of the compressor, electrically operated means for operating said valve and providing for time intervals between its energization and the complete opening of the valve and between its deenergization and the closing of the valve, means for simultaneously controlling energization and deenergization of the motor and the electrically operated means, an overload responsive switch for controlling energization of the motor and the electrically operated means and movable to its open position in response to a predetermined load on the motor, said switch being closed automatically after a predetermined period of time has elapsed after the opening thereof, which period of time is longer in duration than the period of time required for said valve to close 'after the deenergization of the electrically operated means.

5. In refrigerating apparatus, the combination of an evaporator, a condenser,.a compressor for translating refrigerant through the evaporator and condenser, a motor for driving the compressor, a valve for controlling the ow of gas from the evaporator to the compressor and normally closed during inactive periods of the compressor, a bimetallic element for actuating the `valve in opening direction when heated, a heater disposed in heat transfer relation with the bimetallic element, and means for simultaneously controlling the energization and deenergizatlon of the motor 6. The combination as claimed in claim 5 including an overload responsive switch for deenergizing the motor and heater simultaneously in response to a predetermined high load on the motor and for energizing the same automatically 70 after a predetermined period of time has elapsed after the opening of the switch. f

vice lhaving* a passage of xed ow area conf trolling the flow of refrigerant from the condenser to the evaporator, a compressor for Withdrawing vaporous refrigerant from the evaporator and for translating it to the condenser at relatively high pressure, a motor for driving the compressor, a valve for controlling the passage of vaporous refrigerant from the evaporator to the compressor and normally closed during the inactive periods thereof, electrical means for progressively actuating the valve to its open position and providing a time interval between the energization of the electrical means and the full opening of the valve, and means for energizing' said motor'and said electrical means.

8. In a refrigerating system, the combination of a. condenser, an evaporator, an expansion device having a passage of xed flow area controlling the flow of refrigerant from the condenser to the evaporator, a compressor for withdrawing vaporous refrigerant from the evaporator and for translating it to the condenser at relatively high pressure, a motor for driving the compressor, a valve' for controlling the passage of vaporous refrigerant from the evaporator to the compressor and normally closed during the inactive periods thereof, electrical means for operating the valve and providing for time intervals between its energization and the full opening of the valve and between its deenergization and the closing of the valve, and a switch movable to its open position for deenergizing thev motor and said electrical means in response to a predetermined high load on the motor, said switch being automatically closed for energizing the motor and the electrical means after a predetermined period of time has elapsed subsequent to the opening of the switch, said last-mentioned period.l

ottime being longer in duration than said time interval between the deenergization of the electrical means and the closing of the valve.

LESLIE B. M. BUCHANAN.

Images