US2218944A

US2218944A - Refrigerating apparatus

Info

Publication number: US2218944A
Application number: US172881A
Authority: US
Inventors: Edward R Wolfert
Original assignee: Westinghouse Electric and Manufacturing Co
Current assignee: CBS Corp
Priority date: 1937-11-05
Filing date: 1937-11-05
Publication date: 1940-10-22
Anticipated expiration: 1957-10-22
Also published as: GB518055A; DE695391C; FR845348A; CH208233A

Description

Oct 22. 1 E. R. WOLFERT ,2 44

REFRIGERATING APPARATUS Filed NOV. 5, 1957 ESSES: INVENTOR EDWARD RWoLF'ER-r.

Patented Oct. 22, 1940 UNITED STATES PATENT OFFICE REFRIGERATING APPARATUS Pennsylvania Application November 5, 1937, Serial No. 172,881

' and has for an object to provide improved apparatus of this kind.

Another object of the invention is to provide an improved refrigerating system of the compression type which may be operated without unloading during the starting operation.

A further object of the invention is to prevent the starting of a refrigerant compressor during periods when the pressure difierence between the gas inlet and the outlet thereof exceeds a predetermined value.

A still further object of the invention is to provide an improved protective device for a refrigerant compressor wherein operation of the latter is terminated in response to an excessive head pressure and to a relatively low section pressure, and wherein starting of the compressor is prevented when the difference between the head and suction pressures exceeds a predetermined value.

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

The single figure of the drawing is a diagrammatic view of a refrigerating system controlled in accordance with my invention.

Reference will now be had to the drawing, wherein I have shown a refrigerating system including an evaporator H) for abstracting heat from the media to be refrigerated, a compressor II and a condenser l2, the latter being cooled in any suitable manner such as, for example, by water. The compressor ll may be directly driven by an electric motor l3 and is preferably of the enclosed type; the motor l3 being enclosed by a casing l4 secured to the compressor ll.

Refrigerant vaporized at relatively low pressure in the evaporator I0 is withdrawn through a conduit l5 by the compressor II and is compressed to a relatively high pressure and delivered to the condenser l2 through a conduit Hi. The compressed vapor is cooled by a water cooled coil l1 and is condensed. The cooling water enters the coil at l8 and is discharged at IS. A valve 20 may be disposed in the water circuit for controlling the flow of cooling water and may be controlled in any well known manner. Preferably, the flow of cooling water is controlled in accordance with head or condens-' ing pressure.

condenser 12 to the evaporator l0 through a conduit 2| having a suitable expansion device 22 connected therein for reducing the pressure of the refrigerant to the value at which it is vaporized. Preferably, the device 22 is a conventional thermostatic expansion valve and controls the flow of refrigerant to the evaporator ID in response to a predetermined value of the superheat in the vapor discharged from the evaporator III. From the foregoing description, it will be apparent that the system operates in the well known compressor-condenser-expander cycle so that no further description of the operation is deemed necessary.

The refrigerating system disclosed may be employed for cooling any medium, but the evaporator which I have disclosed is employed for cooling a gas such as air and is provided with fins 23 for increasing its heat transfer surface. A fan 24 may be used for effecting forced circulation of the air over the evaporator l0.

Protection against excessive head pressure and abnormally low evaporating pressure during operation is provided by a device diagrammati cally shown at 25, which also functions in accordance with my invention, to prevent starting of the motor l3 at times when the pressure differential between the high and low pressure sides of the system exceeds a predetermined value. Starting of the motor and compressor is, therefore, effected only when the load is at or below a predetermined value. Accordingly, the system may be operated without an unloader and without providing a driving motor having a capacity greater than that necessary for running. A description of the control device 25 will now be given.

The device 25 includes a normally closed switch 26, that is actuated by either of a pair of pressure responsive bellows 21 and 28. The bellows 21 is connected by a tube 29 to the pressure conduit l6 defining a portion of the high side of the system and the bellows 28 is connected by a tube .3l to the low side of the system and preferably to the suction conduit IS. The switch 26 may include a pivoted arm 32 connected by a snap acting spring 33 to a pivoted switch arm 34, the latter carrying a movable contact 35 that engages a stationary contact 38 in the closed position of the switch. A stop 31 limits movement of the switch arm 34 in opening direction. The main pivoted arm 32 is biased in switch closing direction by a spring 38 and a stop 39 is provided for limiting movement of the arm 32 in this direction.

Movement of the main arm 32 upwardly and downwardly effects opening and closing of the switch 26 in a snap acting manner as the spring 33 passes the pivot of the switch arm 34. Upward movement of the main pivoted arm 32 is eiTected by a rod 4| connected to a bell crank 42 that is actuated by the bellows 28. A lost motion connection is provided between the rod 6| and lever 32 and may include a projection 43 on the lever 32 disposed within a slot 44 in the rod 4|. Normally or during periods when the evaporator pressure is above a predetermined value the rod 4| may move upwardly and downwardly without actuating the switch 26 but when the pressure is depressed to an abnormally low value, the rod 4| is raised sufllciently to cause the projection 43 to be engaged and lifted by the rod 4|, whereby the switch 26 is opened.

Operation of the switch 26 is also effected by the high side bellows 21. A second rod 45 includes a slot 46 within which a second projection 41 on the lever 32 is disposed. The rod 45 is connected to a bell crank 48 that is actuated by the bellows 21. Normally the switch 26 is unaffected by movement of the bellows 21 due to the lost motion provided by the connection between the projection 41 and slot 46. However, when the head pressure increases to abnormally high value the projection 41 is engaged by the rod 45 and the switch is moved to its open position. As described hereinafter, opening of the switch 26 due to abnormally high head pressure or low evaporator pressure stops operation of the compressor. Adjustment of the pressures at which the bellows 21 and 28 operate the switch 26 may be provided by adjustable springs 5| and 52 which oppose movement of their respective bellows.

A second switch 53 is provided in the device and is actuated conjointly by the bellows 21 and 28 and which is closed only when the difference in pressures between the high and low sides is below a predetermined value. The switch includes relatively movable contacts 54 and 55, the first of which moves with movement of the bellows 21 and the second of which is actuated by the bellows 28. The contact 54 is carried by a support 56 that may be secured to the bell crank 48 and movable therewith. The contact 55 is carried by a spring 51 forming a part of the pivoted lever 58 that is actuated by the bellows 28 and bell crank 42. One end 59 of the lever 58 is held in engagement with the bell crank 42 by means of a spring 6| that biases the lever 58 in clockwise direction. 4 g

The various elements that actuate the contacts 54 and 55 are so proportioned that the contacts are separated when the pressure differen- -tial between the high and low sides of the system exceeds a predetermined value, such as for example, 50 lbs. When the difierential is depressed to 50 lbs., due to contraction of the bellows 21 or expansion of the bellows 28 or both, the contacts 54 and 55 engage. Of course, when the pressure difierential is below 50 lbs. the contacts 54 and 55 are engaged; the contact carrying spring 51 being deflected due to the depressed position of the contact 54. As described hereinafter, the motor |3 may be started only when'the contacts 54 and 55 of the switch 53 are engaged.

The

switches

26 and 53 are connected in series in a control circuit including a conductor 53 energized from a suitable power source represented by line conductors Ll and L2. Preferably the conductors L-| and L2 define a power source of relatively low potential. The conductor 63 is connected to the operating coil 64 of a relay 65, the latter including a main switch 66 and a control switch 61 that is connected in parallel with the switch 53 by a conductor 68. Energization of the coil 64 eiTects closing of the

switches

66 and 61, and, conversely, deenergization of the same effects opening of the

switches

66 and 61. The switch 65 is connected in the motor circuit 1| that is energized from a suitable source of relatively high potential power represented by the terminals T-3 and T--4.

Starting and stopping of the compressor motor l3 may be effected by a master switch 12 preferably thermostatically operated and conneeted in the control conductor 63. When thermostatically actuated, the switch 12 may be operated in response to the temperature of the media being refrigerated or to the temperature of the evaporator l6 in a manner well understood in the art. In the present embodiment it will be assumed that the master switch 12 is closed and opened in response to predetermined high and Operation As shown in the drawing, the master switch 12 is open, so that the compressor and motor |3 are inactive. The switch 26 is closed as the head pressure and the evaporator pressure are respectively below and above the values at which this switch 26 is opened, The switch 53 is closed which indicates that the pressure differential between the high and low sides of the system is below 50 lbs. Accordingly, the system is in condition for operation when called upon by the master switch 12.

When the temperature of the air being treated and circulated by the fan 24 has increased to predetermined value, the thermostatically operated master switch 12 is closed and thereby energizes the control circuit including the line con ductor L--|, the switch 12, the conductor 63, the engaged contacts and 36 of the normally closed switch 26, the closedcontacts 54 and 55' of the switch 53, the operating coil 64 of the relay 65 and line conductor L2. Accordingly, the

switches

66 and 61 of the relay 65 are closed, the former energizing the main circuit including terminal T-3, switch 66, conductor 1|, the motor 3 and the terminal T-4. Operation of the compressor II and its driving motor I3 is therefore initiated. Closing of the switch 61 energizes the conductor 68 which defines a shunt across the switch 53 for a purpose to be described hereinafter.

Operation of the compressor depresses the pressure and temperature of the refrigerant in the low side of the system including the evaporator 23 and the suction conduit l5. The pressure in the high side of the .system is raised, which high side includes the pressure conduit I6, condenser l2 and the liquid supply conduit 2|. Evaporation of refrigerant is effected in the evaporator 23 under control 01' the thermostatically operated expansion valve 22 so that the air translated by the fan 24 is depressed in temperature.

The increase in the head pressure expands the bellows 21 in opposition to the bias of the spring 5| and moves the contact 54 upwardly in .8 direction away from the contact 55. Likewise,

the reduction in pressure on the low side of the system contracts the bellows 28 so that the bell crank 42 is moved counter-clockwise and the lever 58 is moved clockwise by the bias of the spring 6 I. The contact is therefore moved downwardly and away from contact 54. Opening of the switch 53 does not affect deenergizing of the control circuit as the latter is maintained closed by the switch 61. Operation of the compressor H continues until the temperature of the media being cooled has been depressed to a predetermined value at which time the master switch 12 is opened for deenergizing the control circuit. Accordingly, the relay 65 opens its main switch 66 and control switch 61 so that operation of the compressor H and its driving motor l3 are terminated.

During the inactive period of the compressor II the evaporator pressure rises and the head pressure or condensing pressure is depressed.

- Accordingly, the contacts 54 and 55 are moved in closing direction and, when the pressure difi'erential between the high and low sides has been depressed to 50 lbs. the contacts 54 and 55 are engaged for conditioning the system for the starting operation. I

Starting of the compressor is prevented if the thermostat l2 closes during an inactive period of the compressor and before the pressure differential between the high and low sides of the system has decreased to50#, due to the fact that the switch 53 is maintained open by the high pressure difierential. In this event, the relay remains deenergized and its

switches

66 and 61 remain open so that the compressor motor I3 is not energized by the closing of the thermostat I2. Starting of the compressor II is effected when the pressure differential is depressed to 50# at which time the switch 53 closes and energizes the relay 65. Accordingly, the

switches

66 and 61 are closed and the motor I3 is energized for driving the compressor as described heretofore.

The foregoingdescription of the operation of the system relates to a normal cycle of operation wherein the switch 26 remained closed due to the fact that the condensing pressuredid not exceed is diagrammatically shown for the sake of clearthe pressure at which the bellows 21 effects opening of the switch 26 and the evaporating pressure remained above the low value at which the belly high value during operation, the amplitudesof'the bellows 21 is sufficient to-open the switch' 26' and, therefore, terminate operation of the motor l3. This terminating'operati'on of the motor I3 is also effected by the opening of the switch 26 if the evaporator pressure is decreased to a predetermined low value. When the head pressure decreases" and the .Ievaporator pressure increases to normal value,'the switch ZG is automatically closed by the spring 38.,

As the differential in pressure between the and low sides ofthe system mustbebelow a predetermined value during starting, 1 the system may be operated without an unloading device and without providing a motor having a capacity substantially .above the capacity necessary for running operation. In systems operated without an unloa'der,-it has heretofore been-the practice to provide'a larger and more expensive motor ness and certain refinements usually found in control instruments of this character have been omitted. Preferably, the protection device 25 is constructed as a unit and employs the same pressure responsive elements for actuating both switch

structures

26 and 53. I have shown the switch 26 actuated by both bellows 21 and 28 but it will be understood that these pressure responsive elements may operate switching means other than that shown at 26.

While I'have shown my invention in but one form, it will be obvious to those skilled in the art that it is not so limited but is susceptible of various changes and 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. Refrigerating apparatus comprising a high pressure and a low pressure side, means for circulating refrigerant through the high and low pressure sides and means responsive to a predetermined high differential in pressure between the high and low pressure sides for rendering said circulating means incapable of being started, said diiferential pressure responsive means being inefiective to control the circulating means during active periods thereof.

2. Refrigerating apparatus comprising an evaporator, a condenser, means for circulating refrigerant through the evaporator and condenser, a motor for driving the circulating means and means responsive to a predetermined high difference in pressure between the condenser and evaporator for rendering the motor incapable of being started, said last-mentioned means being ineffective to terminate operation of themotor during operating periods thereof.

3. Refrigerating apparatus comprisinga condenser and evaporator defining portions of the. high and low pressure sides of the apparatus respectively, a compressor for translating refrigerant through thehigh and low pressure sides, a motor for driving the compressor, a switch for controlling energizationof the motor, means redeenergization and the energization .of the motor respectively." 1

4. Refrigerating apparatus comprising a condenser and evaporator defining. portions of the high and low pressure sides of the apparatus, respectively, a compressorffor translating refrigmotor for driving, the compressor a switch adapted to prevent energization ofnthe motor while it is'dee'nergized, means operable in response to. a predetermined maximum difference .70 erant through the high and low pressure sides, a

between the pressures in said high and lowpressure sides to render said switch effective to prevent energization of said motor, and means for rendering said switch ineffective to terminate energization of the motor while the latter is energized.

5. Refrigerating apparatus comprising a high pressure side and a low pressure side, means for translating refrigerant through the high and low pressure sides, means responsive. to predetermined high and low pressures in the high and low sides, respectively, for rendering the refrigerant translating means inactive and means effective during inactive periods of the translating means and responsive to a predetermined high difference in pressure between the high and low sides for preventing the starting of the translating means.

6. Refrigerating apparatus comprising high and low pressure sides, means for translating refrigerant through the high and low pressure sides, electrical means for actuating the refrigerant translating means, means responsive to predetermined high and low pressure in the high and low sides, respectively, for deenergizing the electricaI means and means responsive to a predetermined high difference in pressure between the high and low pressure sides for preventing energization of the electrical means during inactive periods thereof.

7. In refrigerating apparatus, the combination of refrigerant evaporating means, means for withdrawing refrigerant vaporized in the evaporating means, electrical means for actuating the refrigerant withdrawing means, means for condensing the withdrawn vaporous refrigerant, means for conveying the condensed refrigerant to the evaporating means, a master switch for controlling the energization of the electrical means, means responsive to a predetermined high pressure of the condensed refrigerant for rendering the electrical means inactive, means responsive to a predetermined low pressure of the evaporated refrigerant for rendering the electrical means inactive and means responsive to a predetermined high differential in pressure between the condensed and evaporated refrigerant for preventing energization of the electrical means during its inactive periods.

8. Refrigerating apparatus comprising high and low pressure sides, a compressor for translating refrigerant through the high and low pressure sides, a motor for driving said compressor, switching means for controlling energization of the motor, means responsive to predetermined high and low pressures of the high and low sides, respectively, for opening the switching means, a second switch controlling energization of the motor, means responsive to a predetermined high difference in pressure between the high and low sides for opening .said second switch, and means effective during operating periods of the motor for rendering said second switch incapable ofcontrolling energization of the motor.

9. In refrigerating apparatus, the combination of an evaporator, afcompressor for compressing refrigerantvaporized in the evaporator atrelatively low pressure, a condenser for liquefying the compressed refrigerant at relatively high mined high and low pressures of the compressed and vaporized refrigerant, respectively, a switch connected in series with said switching means and opened in response to a predetermined high difference in pressure between the compressed and vaporized refrigerant, and means for shunting said switch during periods when the motor is energized.

10. In refrigerating apparatus, the combination of an evaporator, a compressor for compressing refrigerant vaporized in the evaporator at relatively low pressure, a condenser for liquefying the compressed refrigerant at relatively high pressure, a motor for driving the compressor, a switch for controlling energization of the motor and opened in response to predetermined high and low pressures of the compressed and vaporized refrigerant, respectively, a second switch connected in series with said first mentioned switch and opened in response to a predetermined high difference in pressure between the compressed and vaporized refrigerant, and a third switch connected in parallel with the second switch and closed during periods when the motor is energized.

11. In refrigerating apparatus, the combination of an evaporator, a compressor for compressing refrigerant vaporized in the evaporator at relatively low pressure, a condenser for liquefying the compressed refrigerant at relatively high pressure, a motor for driving the compressor, first and second pressure responsive elements responding, respectively, to the pressures of the compressed and vaporized refrigerant, switching means for controlling energization of the motor and actuated by either of said first and second elements to its open position in response to predetermined high and low pressures of the compressed and vaporized refrigerant, respectively, a second switch connected in series with said switching means and actuated conjointly by the pressure responsive elements to its open position in response to a predetermined high difference in pressure between the compressed and vaporized refrigerant and a third switch connected in parallel with the second switch and opened and closed during periods when the motor is deenergized and energized, respectively.

12. Refrigerating apparatus comprising an evaporator, a compressor for withdrawing relatively low pressure vapor from the evaporator and for compressing the same to a relatively high pressure, a condenser for liquefying the high pressure vapor, a motor for driving the compressor, a normally closed switch for controlling energization of the motor, an element responsive to the pressure of the compressed refrigerant and connected to said switch for opening the same in response to a predeterminedhigh pressure of the compressed refrigerant, a second element responsive to the pressure of the low pressure vapor and connected to said switch for opening the same in response toa predeterminedlow pressure of the low pressure vapor, a second switch connected in series with the first switch, and actuated conjointly by both of said pressure responsive elements, said second switch being open when the difference in pressures between the high and low pressure vapor exceeds a predetermined value, and a third switch connected in parallel with the second switch and opened and closed in response to deener'gization and energization of the motor respectively.

13. In refrigerating apparatus or the like, the combination 'of a motor compressor unit including a compressor for. translating fluid from a; region oflow pressure to a region of high pressure and an electric motor for driving the compressor.

a first switch for normally controlling energization of the motor, a second switch adapted to prevent energ'ization of the motor independently of the action of the first switch, means responsive to a high difference between the pressures in said high and low pressure regions for controlling said second switch to prevent energization of the motor, and means for rendering said second switch inefiective to control energization of the motor while the unit is in operation.

14. In a refrigerating apparatus or the like, the combination of a motor compressor unit including a compressor for translating fluid from a region of low pressure to av region of high pressure and an electric motor for driving the compressor, first means for normally controlling the starting and stopping of the motor compressor unit, and second means operable in response to-a predetermined maximum diflerence between the pres-' sures in said high and lowpressure regions to prevent starting of the unit, independently of the action of said first means, but permitting starting in response to a lower diflerence in said pressures and permitting the unit to continue to operate, once it is started, to provide a pressure difference greater than said predetermined max imum pressure difference.

15. The method of controlling the operation of a motor compressor unit including a compressor operable to translate fluid from a region of low pressure toa region of high pressure and an electric motor for driving the compressor, which method comprises normally controlling energization of the motor in response toa load condition of the unit but delaying starting ofthe unit, when the unit is idle and the diflerence between the pressures in said high and low pressure regions is high, until said difference is reduced to a predetermined low value, continuing operation of the motor compressor unit, once it is started, independently of increase in said pressure difference above said predetermined'low value, and terminating operation of the unit in response to said load condition.

16. In refrigerating apparatus or the like, the combination of a motor compressor unit including a compressor for translating fluid from a region of low pressure to a region of high pressure and an electric motor for driving the compressor, and means operable in response to a predetermined maximum difference between the pressures in said high and low=pressure regions to prevent starting of the unit but permitting starting in response to a lower difference in said pressures and permitting the unit to continue to operate, once it is started, to,provide a pressure diflerence greater than said predetermined maximum pressure difference.

17. In refrigerating apparatus or the like, the combination of a motor compressor unit including a compressor for translating fluid from a region of low pressure to a region of high pressure and an electric motor for driving the compressor, first and second elements responsive to the pressures in said high and low-pressure regions, respectively, means controlled by one 01' said pressure-responsive elements and arranged to prevent operation of the unit when the pressure imposed on the associated pressure-responsive element reaches a predetermined value, and means actuated conjointly by both of said pressure-responsive elements for eil'ecting a control of the operation of the unit in response to the difference between the pressures imposed on said pressure-responsive elements.

EDWARD R. WOIJERT.