US2253623A - Refrigerating apparatus - Google Patents

Description

26, 1941; F. w. JORDAN REFRIGERATING APPARATUS Filed May 18, 1937 INVENTOR FRANK W. Jonnn'u ATTORNEZ I WITNESSES:

. r l I I Patented Aug. 26, 1941 REFRIGERATIN G APPARATUS Frank W. Jordan, San Francisco, Calif., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application May 18, 1937, Serial No. 143,215 3 Claims. '(Cl. 230-206) receives more than its share of oil, the oil level My invention relates to refrigerating apparatus comprising a plurality of compressors, more particularly a plurality of compressors connected in parallel to a common suction line, and it has for an object to provide improved means for eflecting-proper distribution of lubricating oil to the several compressors.

In the operation of a refrigerating system, the refrigerant passing through the compressor .entrains some of the oil used for lubricating the compressor. The refrigerating system is arranged, so that this oil is carried by the refrigerant completely through the refrigerating system and returned to the compressor by the suction gas. Such return of oil is depended upon to maintain the proper supply of oil in each compressor. When a plurality of compressors are connected in parallel in a refrigerating system,

as where there is a common suction line,the oil is not returned to the several compressors in the proper proportions. It is necessary, therefore, to provide some arrangement for equalizing or distributing the quantity, of 011 among the several compressors.

Heretofore, such equalization has been effected by an equalizing passage connected to the bottom of the crankcase of each compressor, the object being that the oil level in the crankcase of the compressor receiving more than its share of oil will rise and cause gravity flow of oil to the other crankcases until a common level and .proper distribution of oil is obtained. It has I been found, however, that the pressures of the several crankcases arenot always equal; the

pressure in the crankcase of a compressor that is in operation being lower than the pressure of a crankcase that is idle. The higher pressure in the'idle compressor caused flow of oil through the connecting passage to the operating compressor to such an,,gextent as to substantially empty the crankcase of the idle compressor.

When the idle compressor was started, there was found to be insumcient oil for proper lubrication thereof. 1 g

It is an object of my invention, therefore,to arrange the oil equalizing passage in such a way that onlythe quantity of oil in excess of the normal quantity in one compressor may flow through the equalizing passage to another compressor, so that sliflicient oil is retained in each a compressor for operation thereof.

In accordance with my invention, I connect the w oil equalizing passage to the crankcase or oil sump of each compressor at substantially the normal oil level therein. When one compressor rises above the normal level so that the oil may flow through the equalizing passage to another compressor. The normal quantity of oil for the compressor is disposed below the connection with I the equalizing passage so that it cannot flow I the reciprocating type.

therethrough, and thus a suflicient quantity of oil is retained in each compressor for operation thereof notwithstanding unequal pressure differences tending to cause flow into another compressor.

I prefer also to provide a second pressure equalizing passage connected to the crankcases or oil sumps of the several compressors above the oil level therein, so as to facilitate pressure equalization and gravity flow of oil for equalization.

The above and-other 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:

The single figure is a diagrammatic view of apparatus embodying my invention.

Referring to the drawing in detail, I show three compressors, I I, I2 and it connected to a common refrigerating system and disposed at the same level. The discharge outlets H of the several compressors are connected through branch conduits l5 to a common discharge line 16, and the suction inlets ll of the several compressors are connected through branch conduits IE to a common suction line l9. The discharge line I 6 is connected to a condenser 2| which in turn is connected to a liquid receiver 22. A liquid line 23 connects the liquid receiver with tors forms no part of the present invention, it

is not further described herein. The several evaporators'are connected at their outlet ends to the common suction line 19.

The compressors shown on the drawing are of Each includes a crankcase 3|, which provides an oil sump or reservoir for thecompressor. Each compressor also includes a motor 32 which, in the present embodiment has a casing common with the compressor thereby providing a hermetically sealed motor compressor unit.

Each crankcase is maintained at suction pressure by means of a passage 33 communicating between the crankcase and the suction inlet IT. This passage also permits oil returned by the suction line through the inlet l1 to drain by gravity into the crankcase. Such arrangements are well known in the art.

The bottom of the crankcase serves as a reservoir or sump for oil for lubricating the compressor. The normal liquid level is indicated at 34. The compressor is lubricated in any suitable manner, as by an oil pump, by oil from the crankcase. Inasmuch as the particular form of lubrication-system is not a part of the present invention, it is not further described herein. An oil equalizing conduit 35 is connected, through branch conduits 35 to the several crankcases at substantially the normal liquid level therein. The connection is preferably disposed so that the bottom of the opening into the crankcase is at the normal liquid level. A shut-off valve 31 may be provided in each branch conduit 36 to permit isolation of the compressor. The oil equalizing conduit 35 and the branch conduits 35 may extend downwardly as shown on the drawing, but, in order to assure gravity flow of oil therethrough, should not at any point extend above the conneotons with the several crankcases. I prefer, also, to provide a pressure equalizing conduit 38 connected through branch conduits 35 to the several crankcases at a level sufficiently high to be above the oil level in the several crankcases at all times. The branch conduits 39 may also be provided with shut-ofl valves 40.

If desired, a suitable form of control mechanism may be provided for automatically controlling the operation of the several compressors. For example, a bellows 4| may be connected through a tube 42 to the suction line I9. The bellows 4| is arranged to close switches 43, 44, and 45 successively upon successive increases in suction pressure and vice versa. The switches 43 to 45 control circuits 46, 41, and 48, which supply current to the motors of the compressors II, I! and I3, respectively.

Operation The refrigerating system operates in the usual manner of such apparatus. Refrigerant is compressed by any compressor in operation and discharged under high pressure through the branch conduit l5 into the discharge line l5. It is condensed in the condenser 2| and collected in the liquid receiver 22. The liquid refrigerant is conveyed through the liquid line 23 to the evaporators whose valves 21 are open. The flow of refrigerant to each evaporator is regulated by the expansion valve 28 as well understood in the art. The refrigerant is evaporated in the evaporator and then returned through the suction line iii to such compressor or compressors as are in operation.

The bellows 4| controls the several compressors in response to the suction pressure in the suction line l9. Upon successive increases in suction pressure, the switches 43, 44, and 45 are.

successively closed and, upon successive decreases in pressure, the-switches are successively opened in the reverse order, all as will be apparent and readily understood by one skilled in the art.

The compressed refrigerant discharged from any compressor in operation carries a certain amount of entrained lubricating oil-therewith.

ing system and returned through the suction line l9. It will be apparent that the suction line l9 will not necessarily return the oil to the several compressors by the same amounts that oil is removed therefrom. Therefore, an oil equalizing passage, such as the conduit 35, is provided. When all the compressors are idle, the pressures in the several crankcases may readily equalize, this being facilitated by the pressure equalizing conduit 33. If one crankcase has a surplus quantity of oil, raising its oil level above the normal, the excess quantity may flow through the equalizing conduit 35 to the other crankcase or crankcases, so as to provide substantially normal oil level in each crankcase and to provide sumcient oil for operation of each munication with the crankcase of the compressor. ll through the suction line I3 and the pressure equalizing passage 38,, nevertheless, it is found that the pressures in the crankcases of the idle compressors l2 and iii are appreciably higher than the pressure in the crankcase of the operating compressor H, due to the pressure drop through the connecting conduits. Where the oil equalizing conduits have been connected to the bottom of each crankcase. such pressure difference has resulted in forcing substantially allof the oil from the crankcase of ,an idle compressor to the crankcase of a compressor in operation. This possibility is avoided by the present invention by connecting the oil equalizing conduit 35 substantially at the normal liquid level. Therefore, only the quantity of oil in the crankcase in excess of the normal quantity therein can flow through the equalizing passage to another crankcase. The normal quantity of oil in the crankcase is below the connection and therefore will not flow through the connection to the oil equalizing passage, regardless of pressure conditions in the several crankcases.

While I have shown my invention in connectionv with a refrigerating system comprising a common condenser and several evaporators exhausting into a common suction line, it is to be understood that such system is to be taken as exemplary and not as limiting. The invention is applicable to a wide variety of systems having refrigerant-containing means common to several compressors, so that the oil from the several compressors is intermingled and proper distribution 3 the several compressors is necessary. It is ore particularly applicable to refrigerating systems in which there is common refrigerant-containing means in the low pressure side of the system and wherein the compressors operate at substantially the same evaporator or suction pressure.

While I have shown my invention in but one erant compressors connected to a common refrigerant-containing means and each having an oil sump, one 01 said compressors being adapted to be operated while another is idle, of conduit means providing a passage, open at all times that any compressor is in operation, for flow of oil from one sump to another, said conduit means being connected to each sump at a level such that sumcient oil remains in the sump below the connection for operation of the compressor.

' 2. In refrigerating apparatus, the combination of a plurality of -refrigerant compressors connected to a common refrigerant containing means and having oil sumps disposed at a common level, one of said compressors being adapted to be onerated while another is idle, and an oil equalizing art passage connected to each oil sump at substantially the normal liquid level therein, whereby flow of oil from one 011 sump to another to the extent of depriving said one oil sump of a sumcient supply of oil is avoided, said passage being open and permitting flow of oil therethrough at all times that any compressor is in operation.

3. The combination with a plurality of refrigerant compressors connected to a common refrigerant-containing means ande'ach having an oil sump, one of said compressors being adapted I to be operated while another is idle, of an .oil

equalizing passage connected to each oil sump at such a level that there is sufllcient oil in the sump below the connection for operation of the compressor, and means providing communication between the several oil' sumps abovethe normal liquid level to provide pressure equalization.

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