US2719408A - Lubricant return in refrigerating apparatus - Google Patents

Description

at. 1955 M. P. PENN LUBRICANT RETURN IN REFRIGERATING APPARATUS 2 Sheets-Sheet 1 Filed March 1, 1954 JNVENTOR. Melvin 1? Penn His Arramey @Cill. 4, M. PENN 2,719,408

LUBRICANT RETURN IN REFRIGERATING APPARATUS Filed March 1, 1954 2 Sheets-Sheet 2 @W N e w F m J m P Q, m a V mm I a m DA m x Y E B m z. m NM: NW N W m v. Wm h L M IE :lm mm His Armmey United States Patent Ofiice 2,719,408 Patented Oct. 4, 1955 LUBRICANT RETURN 1N REFRIGERATIN G APPARATUS Melvin P. Penn, Dayton, Ohio, assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application March 1, 1954, Serial No. 413,167

3 Claims. (Cl. 62-117.7)

This invention relates to refrigerating systems and particularly to a motor-compressor located in a sealed casing forming a part of a refrigerant translating unit for such systems.

The advent of locating both an electric motor and a compressor in a single sealed casing in a refrigerating system, of reducing the temperature of the motor by cool refrigerant fluid returning to the compressor from the evaporator of the system and of properly lubricating operating parts of the compressor and its direct driving connection with the motor has created difficulties. More serious of these difficulties occur in refrigerating systems wherein the system may be frequently shut down for a considerable length of time or where the system may, for some reason or another, have an abnormally long idle of off cycle. For example, a refrigerating system in or on a railway passenger car for cooling and conditioning air therein or a refrigerating system in or on a refrigerated produce railway car or the like may be rendered inoperative at the end of a run of the passenger car or at the end of a run of the produce car and while unloading produce therefrom. The shut down of the refrigerating system causes the pressure between the high pressure and low pressure sides thereof to substantially equalize and oil miscible or admixed with refrigerant in the system continues, for a considerable length of time after the shut down of the system and prior to equalization of pressures therein, to return from the evaporator to the sealed casing. The oil and refrigerant accumulates in the form of a body thereof in the lower portion of the casing. This is normally desirable because the oil is returned to a reservoir in the system where it is needed and utilized to lubricate operating parts of the compressor. However when the car is again put into service and operation of the refrigerating system is started low pressure is suddenly created within the sealed casing in which the body of oil and refrigerant is located, by suction of the compressor, and the body of liquid in the casing flashes or explodes into a mass of froth or foam therein. During the initial or early phase of an operating cycle of the compressor, after such a shut-down period as described, this foamy mass of oil and refrigerant will be quickly drawn into the compressing portion of the compressor and the reservoir is exhausted of its oil content by the compressor pumping this oil to other parts in the closed system. Operating parts of the compressor are thus robbed of lubrication and continued operation of the compressor, under this condition, will score or burn bearings and other parts thereof. In addition to the compressor operating without lubrication all the oil in the system is circulated to other elements thereof and a substantial amount of oil is contained in the evaporator. Consequently the mixture of oil and refrigerant within the evaporator is also in the form of a foamy mass and the bubbles of this mass blanket walls of the evaporator and render it less effective for transferring or removing heat from the space to be cooled thereby. While-the condition aforesaid may correct itself after a prolonged continuous operation of the compressor, since oil will then be gradually returned with refrigerant from the evaporator to the casing to establish a body of liquid in the casing reservoir, operating parts and bearings of the compressor may have already been burnt or damaged. I contemplate the construction of a refrigerating system wherein provision is made for trapping a body of refrigerant and lubricant in the compressor actuating compartment of a sealed casing containing an electric motor and a compressor driven thereby at least during the initial or early phase of a running or operating cycle of the compressor to isolate this liquid body from other parts of the system and to insure ample lubrication of operrating parts of the compressor.

An object of my invention is to prevent a sudden reduction of pressure on the body of liquid refrigerant and oil in a reservoir of a sealed motor-compressor casing containing an actuating mechanism for the compressor.

Another object of my invention consists of a new method of preventing oil admixed with a lubricant in a reservoir of a sealed casing of a refrigerating system containing an electric motor and a compressor driven thereby from being withdrawn from the reservoir at least during the begining or early phase of an operating cycle of the compressor.

A further object of my invention is to provide a refrigerating system with means associated with a sealed casing thereof having a dividing wall partitioning the interior of the easing into a motor compartment and a compressor compartment for permitting communication between the compartments during certain periods of effectiveness of the system and for trapping a body of oil and refrigerant in the compressor compartment of the casing to isolate oil from other parts of the system.

A still further and more specific object of my invention is to provide a sealed casing containing a motor and a compressor of a refrigerating system with a dividing wall separating the easing into compartments which are at one time closed off from each other and at other times placed in communication with one another by a passageway in this wall controlled by a pressure operated check valve to overcome the difficulty aforesaid and render the refrigerating system more efiicient in operation.

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

In the drawings:

Figure 1 is a diagrammatic illustration of a refrigerating system having my nivention embodied in a sealed casing thereof; I

Figure 2 is a View partly in section and partly in elevation of a sealed casing forming a portion of the refrigerant translating unit of the refrigerating system disclosed in Figure l; and

Figure 3 is an enlarged fragmentary sectional view of a check valve associated with the compartment partitioning wall of the sealed casing.

Referring to the drawings I have shown in Figure 1 thereof a diagrammatic illustration of a. closed refrigerating system including a horizontally elongated sealed casing 15, having my invention embodied therein, containing an electric motor and a compressor driven thereby. Casing 15 has an outlet connected, by a pipe 16, to a condenser 17, cooled in any suitable or conventional manner, having a connection with a receiver 18. Casing 15 forms one part of a refrigerant translating unit while the condenser 17 and receiver 18 form the other parts thereof. Receiver 18 has a pipe connection 19 with a suitable or conventional expansion valve 21 having its actuating temperature responsive bulb 22 secured to an evaporator 23 near the outlet end thereof. Evaporator 23 is mounted in a compartment or the like to be refrigerated and walls of this compartment are indicated by the dot-dash lines 24. The outlet end of evaporator 23 is connected to an inlet of the sealed motor-compressor containing casing by pipe 26. A control generally represented by the reference numeral 28, of any suitable or conventional construction, forms means for energizing the motor of the refrigerant translating unit to cyclically operate the compressor thereof in response to demands for refrigeration in the space or compartment 24. In other words the motor and compressor of the translating unit of the system has idle or off cycles and running or operating cycles in accordance with the setting of control 28. Control 28 includes a snap-acting electric switch 29 which closes or opens contacts 31 and 32 interposed in an electric circuit, wires 33 and 34, leading to the motor of the refrigerant translating unit. Switch 29 is actuated by a movable bellows 36 having its movable end connected to the pivotally mounted arm 37 of control 28. The bellows 36 has a pipe connection 38 with a bulb 39 located within the space or compartment 24 to be refrigerated. Bulb 39, pipe 26, and bellows 36 are sealed and contain a volatile fluid so as to provide a temperature responsive means for actuating the control 28 as is well known in the art. When control 28 closes the contacts 31 and 32 of switch 29, in response to expansion of bellows 36 and a demand for refrigeration in compartment 24, the electric circuit through wires 33 and 34 is completed to energize and start the motor of the refrigerant translating unit in motion. The motor drives the compressor and this compressor withdraws refrigerant from evaporator 23 by way of pipe 26 and conveys it into casing 15, to reduce the pressure in evaporator 23 and cause the same to produce a refrigerating effect in compartment 24 to chill this compartment. The cool substantially evaporated refrigerant, being withdrawn from evaporator 23, enters casing 1.5 in the vicinity of the electric motor therein and is utilized to cool this motor. The withdrawn refrigerant flows from the motor within casing 15 through a suitable port or ports provided in this casing, as will be hereinafter described. to the compressing portion of the compressor whereby it is compressed and discharged from casing 15 into the condenser 17 by way of pipe 16. Compressed refrigerant is cooled and liquefied in condenser 17 and this liquid refrigerant is accumulated in the receiver 18 of the refrigerant translating unit. Liquid refrigerant is conveyed to evaporator 23 by way of pipe 19 and its entrance into the evaporator is controlled by the expansion valve 21. Elements of a closed refrigerating system as herein called for and their respective functions are well known to those skilled in the art and no further description of the system is believed necessary.

Referring now to Figure 2 of the drawings the horizontally elongated sealed casing 15 comprises a metal casting 41 having metal end plates 42 and 43 and a cast metal head 46 bolted or otherwise rigidly secured thereto. A wall 47, formed integrally with casting 41, provides a partitioning means for dividing the interior of the sealed casing 15 into side by side compartments 48 and 49. Wall 47 has a central hole therethrough forming a bearing 51 for a shaft 52. A second bearing 53 is provided in end plate 42 for the shaft 52. The portion of shaft 52 within compartment 49 has a rotor 56 of an electric motor mounted thereon and thus compartment 49 forms a motor compartment having a stator 57 of the electric motor housed therein. Motor stator 57 is spaced from the bottom wall of compartment 49, as at 55, to permit refrigerant and oil miscible therewith at the one end of the electric motor to How therefrom to the opposite end thereof toward wall 47. The portion of shaft 52 extending through the bearing 51, into the other compartment 48 of the side by side compartments, has off-set integral crank sections formed thereon so as to provide a crankshaft for parts employed to actuate a compressor in the casing and thus compartment 48 forms a compressor compartment. The compressor within casing 15 includes the substantially vertical disposed cylinders 58 each having a suitable piston 59 therein connected to the crank sections on the crankshaft 52 by connecting straps or rods 61. A plate 62, clamped under the head 46 of casing 15, is provided with suitable inlet ports and outlet ports, each controlled by a conventional spring pressed reed valve or the like, for admitting refrigerant to the cylinders 58, above the pistons 59, and for preventing refrigerant compressed by the compressor from backing into the cylinder respectively as is well known in the art. The head 46 may have a longitudinal wall therein dividing the space therein above plate 62 into a suction chamber and a discharge chamber. The inlet ports and valves controlling the same are of course exposed to the suction chamber along the one side of the head 56 while the outlet ports and their controlling valves are exposed to the compression discharge chamber on the other side of the dividing wall in head 46. Refrigerant having oil admixed therewith returns from evaporator 23 and enters the sealed casing 15 of the refrigerant translating unit or device of the refrigerating system by way of a screened inlet port 64 provided in the upper wall of motor compartment 49. This returning refrigerant and oil is cool and flows over and through portions of the electric motor within compartment 49 of casing 15 to keep its temperature down. Motor rotor 56 has holes 66 provided therein for permitting the refrigerant entering casing 15, by way of port 64, to flow therethrough toward wall 47 to the inner side of compartment 49. A port hole 68 provided in casing 15 communicates with the upper portion of motor compartment 49 and extends upwardly through a wall of the casing at one side of the cylinders 58 to the suction chamber in the compressor head 46 and to the valved inlet ports of the compressor cylinders 58. Suction port hole 68 bypasses refrigerant around the other compartment 48 in its flow from motor compartment 49 directly into the compressing portion or inlet port of the compressor.

The bottom portion of each compartment 48 and 49 within casing 15 forms or provides a sump or reservoir for a body of liquid refrigerant and oil placed in the system for lubricating operating parts thereof. Liquid from this lubricating body is circulated by a pump 70, contained in a passageway provided in end plate 42, and having an apertured operating link or drive connection 71 fitted over an eccentric '72 formed on one end of shaft 52. A piston pump is operated by rotation of shaft 52 and draws liquid upwardly from the reservoir in compartment 48 therethrough and discharges the liquid into a chamber 73 at the eccentric end 72 of shaft 52. Suitable passageways are cut in shaft 52 to convey the pumped liquid from chamber 73 through shaft 52 to bearings of the connecting rods 61 and to the shaft bearing 51 in divid ing wall 47 so that oil in this liquid will lubricate these elements as is conventional. While I have disclosed a reciprocating piston type pump 70 of any suitable construction or arrangement it is to be understood that other pumps such as a gear pump may be incorporated in the casing if desired to circulate the lubricating fluid as described. Liquid seeping out of the connecting rod bearings flows back into the reservoir of compartment 48. A small amount of liquid may seep out of shaft bearing 51 into the motor compartment 49 but most of the lubricating liquid is conducted away from bearing 51 back into compartment 48 by a return passage 74 provided in wall 47. Such a lubricating arrangement is well known to those skilled in the art.

It will be noted that the compressor compartment 48 and motor compartment 49 in the present disclosed sealed casing 15 are substantially closed off from communication with one another by the wall 47. However in accordance with my invention I provide means for permitting communication between the compartments 48 and 49 and particularly the liquid sump or reservoir thereof at certain times. At the bottom of compartment partitioning wall 47 I provide an opening or passageway 76 therethrough below the normal level of liquid in the reser voir of compartments 48 and 49. Opening 76 is controlled by a check valve generally represented by the numeral 75 and including a floating disc or the like 77, held in association with a seat 78 formed on a pipe fit ting 79, by a webbed cage 81 brazed or otherwise suitably secured to fitting 79 (see Figure 3). Disc 77 of valve 75 is raised off its seat 78 to open or permit communication between compartments 48 and 49 and is returned to its seat to close off such communication therebetween in response to pressure differentials between these compartments for a purpose and at such times as will be presently described in order to accomplish the objects of this invention.

After the refrigerating system herein disclosed has been shut down or rendered inoperative for a considerable period of time like, say, for example, over night or longer the pressure between the high pressure side of the system and low pressure side thereof will finally become equalized. For some time after such shut down period refrigerant continues to evaporate from evaporator 23 and refrigerant and oil admixed therewith flows into the motor compartment 49 of sealed casing 15. At the beginning or early phase of this shut down period, prior to equalization of pressure between the two sides of the system, the suction pressure in compartment 49 is slightly or infinitesimally greater than the pressure within compartment 48. At this time the pressure differential between the compartments or this lower pressure in compartment 49 will cause disc 77 of the check valve 75 to open and permit communication between the compartments 48 and 49 whereby refrigerant and oil admixed therewith and returned to compartment 49 will flow, through the wall 47, by way of opening or passageway 76, pipe fitting 79 and disc 77 of valve 75', since this disc 77 will be raised off seat 78, into compartment 48. As soon as the suction pressure in compartment 49 diminishes and the pressure therein reaches or equals the pressure in compartment 48, after shut down of the refrigerating system, the level of liquid in the sealed casing will be substantially the same on opposite sides of wall 47 in the side by side compartments 48 and 49. If the refrigerating system is now rendered operative, under the control of the thermostatically actuated control 28, to cause energization of the electric motor and operation of the compressor driven thereby the suction side of the compressing portion of the compressor immediately reduces the pressure within motor compartment 49 far below the pressure in compartment 48 and disc 77 of valve 75 will tightly engage its seat 78. In this manner refrigerant and oil admixed therewith within compartment 48 is isolated from the low suction pressure in motor compartment 49 and is trapped in compartment 48. While refrigerant and oil in motor compartment 49 may flash or explode into a foamy mass therein and will enter the compressing portion of the compressor, by way of the bypass hole 68, the body of liquid refrigerant and oil trapped in compartment 48 will remain relatively quiet and prevent a reduction in its level in this latter compartment to a dangerous point. Thus an ample supply or body of lubricating liquid in compartment 48 is insured for properly lubricating actuating parts of the compressor in sealed casing 15 at and/or during the beginning of a running cycle or during the early phase of operation of the compressor. Some of the fluid in compartment 48 may seep pass shaft bearing 5'1 into motor compartment 49 as the compressor continues to operate but this seepage is minute and insufiicient to materially effect the pressure differential between the compartments 48 and 49. By trapping and isolating the body of liquid refrigerant and oil within compartment 48 back flow or return thereof to compartment 49 is prevented and a high level of lubricating fluid is maintained therein. Refrigerant being vaporized from or boiling off the body of liquid in compartment 48 at this time is retarded and/or controlled so as not to permit the suction of the compressor to cause a sudden flashing or exploding of the liquid mixture within compartment 48. The small amount of seepage of fluid past bearing 51 and vaporization of refrigerant therefrom, upon being exposed to the suction pressure in compartment 49, creates a fluid mixture within compartment 48 which is high in oil content and of better lubricating properties. Trapping of refrigerant and oil in compartment 48, as described, in addition to preventing the liquid from being flushed out of the compartment also permits motor compartment 49 to be substantially dry or free of a body of liquid during operation of the motor-compressor.

When a running cycle of the motor-compressor has been completed, and is stopped, by control 28 causing opening of the contacts 31 and 32 of switch 29, refrigerant and oil admixed therewith in motor compartment 49, having been in open communication with or exposed to the suction pressure of the compressor, will increase at a much faster rate than pressure in compartment 48 and will quickly tend to reach the pressure in compartment 48 or to become equal thereto. This causes refrigerant and oil to be pushed past valve over into compartment 48 to replenish or reestablish the normal body of liquid therein. The off cycle of the motor-compressor is not usually of such duration to permit the pressure in compartments 48 and 49 to again entirely equalize. The replenishing of the body of liquid and oil in compartment 48, by the pressure differential between compartments 48 and 49 at the time the motor compressor is stopped for a normal off cycle as just described, insures an adequate supply or high level of liquid in compartment 48 to permit proper lubrication of actuating parts of the compressor when the motor is again energized to drive the compressor upon a subsequent operating or normal running cycle. Thus the amount of refrigerant absorbed by the oil in casing 15 under this condition is not in as great a proportion as when the motor-compressor is shut down for a long period of time. During ordinary off cycles of the motor-compressor the pressure differential between compartments 48 and 49 remains in substantially uniform relationship in accordance with the operating temperatures of the refrigerating system. Also under ordinary cycling operations the compressor cannot circulate abnormal amounts of oil. This not only increases the efiiciency of the compressor itself but also the efliciency of the evaporator of the refrigerating system.

It should be apparent from the foregoing that I have, in addition to preventing starving the compressor of oil and insuring ample lubrication at all times of operating parts of the compressor, particularly at the beginning of running cycles thereof, reduced to a minimum the amount of oil required to be placed in a refrigerating system. The advantage of increasing the efficiency of the evaporator of a refrigerating system is due to the fact that an evaporator, of a refrigerating system having my invention incorporated therein will contain less oil than an evaporator of a conventional refrigerating system and this reduces foaming of fluid therein to a minimum and permits substantially lubricant free refrigerant to contact Walls of the evaporator for more effectively removing heat from the space or compartment to be cooled by the evaporator. My improvement prevents operation of a compressor without sufficient or proper lubrication and thereby eliminates scoring or burning of its bearings and other frictional engaging operating parts of the compressor.

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 as may come Within the scope of the claims which follow.

What is claimed is as follows:

1. A refrigerating system including an evaporator and a refrigerant translating unit, said unit comprising a sealed casing having a dividing wall therein partitioning the interior thereof into a motor compartment and a compressor compartment, a motor in said motor compartment, refrigerant compressing means in said compressor compartment driven by said motor, said compressing means having an inlet port and an outlet port, means for conveying refrigerant and lubricant admixed therewith from said evaporator to said motor compartment over portions of said motor therein for cooling the same, means for by-passing refrigerant received in said motor compartment around said compressor compartment and delivering the same directly to said inlet port of said compressing means, a passageway in said partitioning wall for conveying lubricant from said motor compartment into said compressor compartment, a check valve controlling said passageway for substantially preventing return flow of lubricant from said compressor compartment to said motor compartment of the sealed casing, said check valve providing the sole means of communication between said compartments whereby said compressor compartment is maintained at a higher pressure than said motor compartment at least during the early phase of operation of the motor, and said valve being actuated in response to equalization in pressure within said compartments for placing the compartments in open communication with one another.

2. A refrigerating system including an evaporator and a refrigerant translating unit, said unit comprising a horizontally elongated sealed casing having a dividing wall therein partitioning the interior thereof into side by side compartments, an electric motor in one of said compartments having a shaft extending through said dividing wall into the other of said compartments, said unit also including a compressor having a refrigerant compressing portion and an actuating portion therefore, said actuating portion of said compressor being located in said other compartment of said sealed casing and connected to said motor shaft extension, said motor compartment having an inlet adjacent one end thereof for receiving refrigerant and oil admixed therewith from said evaporator, the refrigerant of said mixture received in said motor compartment being directed over portions of said motor there in for cooling the same, said motor compartment also having an outlet by-passing refrigerant received therein around said other compartment directly into said compressing portion of said compressor, means for controlling said motor to cyclically operate said compressor, a

passageway in the lower part of said dividing wall for conveying oil from said motor compartment into said compressor actuating portion compartment, an unbiased check valve controlling said passageway for substantially preventing return flow of oil from said other compartment to said motor compartment of the sealed casing, said unbiased check valve providing the sole means of communication between said compartments whereby the pressure in said other compartment is maintained above the pressure in said motor compartment at least during the early phase of operation of the motor, and said unbiased check valve being actuated in response to equalization in pressure within said compartments for placing the cornpartments in open communication with one another through said passageway.

3. A closed refrigerant system including an evaporator, a refrigerant translating unit and conduit connections therebetween, said unit comprising a hermetically sealed casing having a dividing wall therein partitioning the interior thereof into a motor compartment and a compressor compartment, an electric motor in said motor compartment, refrigerant compressing means in said compressor compartment driven by said motor, said motor compartment having an inlet for receiving refrigerant and oil admixed therewith from said evaporator, said inlet being located adjacent the end of said motor compartment fartherest away from said dividing wall whereby refrigerant incoming to said motor compartment is circulated entirely through said motor therein over portions thereof for cooling same prior to its flow to said compressing means, means for by-passing refrigerant received in said motor compartment around said compressor compartment and delivering the same directly to said compressing means, a passageway in said partitioning wall for conveying lubricant from one to the other of said compartments, a check valve for controlling said passageway, said check valve substantially preventing flow of lubricant from said compressor compartment to said motor compart ment and maintaining said compressor compartment at a higher pressure than said motor compartment at least during the early phase of operation of said motor, and said valve being actuated in response to equalization in pressure within said compartments for placing them in open communication with one another.

References Cited in the file of this patent UNITED STATES PATENTS 1,955,958 Greenwald Apr. 24, 1934 2,085,355 Greenwald June 29, 1937 2,343,514 McCormack Mar. 7, 1944

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