US2555005A - Reciprocating compressor with unloading and capacity modulating control - Google Patents

Description

y 1951 R. c. WARNEKE 2,555,005

RECIPROCATING COMPRESSOR WITH UNLOADING AND CAPACITY MODULATING CONTROL Filed Jan. 51, 1948 Inventor":

, Rcman C. Warneke,

His Attorney.

Patented May 29, 1951 RECIPROCATING COMPRESSOR WITH UN- LOADING AND CAPACITY MODULATING CONTROL Roman C. Warneke, Fort Wayne, Ind., assignor to General Electric Company, a corporation of New York Application January 31, 1948, Serial No..5,653

This invention relates to gas compressors of the reciprocating type and particularly to devices for selectively controlling the loading of such compressors and for providing modulation of the compressor capacityv In the operation of refrigerant compressors such 'as those employed, for example, in air conditioning systems, it is frequently desirable to vary the capacity of the compressor in order to control the system in accordance with the load demands thereon. Preferably this variation of capacity is effected over a relatively wide range gradually or in small steps. Accordingly it is an object of this invention to provide a capacity modulating device for compressors of the reciprocating type for controlling the loading of the compressor and which shall be of simple construction and readily controllable.

It is another object of thi invention to provide a compressor of the reciprocating type including an improved capacity modulating control employing a sleeve valve surrounding the piston.

Further objectsand advantages of the invention will become apparent as the following de,

scription proceeds, and the features of novelty which characterize the invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

For a better understanding of the invention reference may be had to the accompanying drawing in which Fig. 1 is a diagrammatic view illustrating an air cooling system provided with a refrigerant compressor embodying the invention; Fig. 2 is an enlarged sectional view of the compressor shown in Fig. 1; and Fig. 3 is an end elevation view of the compressor.

Briefly, the compressor illustrated in the draw ings is provided with a capacity modulating control including a sleeve valve surrounding the piston and mounted for axial movement on a cylinder sleeve within which the piston is reciprocated. The sleeve valve is actuated to control a by-pass around the compressor intake valve and thereby control the loading of the compressor. A compressor and control of this general type wherein a sleeve valve is employed for effecting capacity modulation is disclosed and broadly claimed in an application of Dean C. Rinehart, [Serial No. 5,645, filed concurrently herewith and assigned to the same assignee as the present invention. The present invention is directed to a compressor wherein the piston is reciprocated within a fixed cylinder or sleeve and no features disclosed in herein.

2 Claims. (01. 230-24) Referring now to the drawings, the air cooling system shown in Fig. 1 comprises a refrigerant evaporator 4 arranged in a duct 5 through which air to be cooled is circulated by operation of a suitable blower (not shown). Liquid refrigerant in the evaporator is vaporized by the absorption of heat from the air circulated through the duct, and the vaporized refrigerant is withdrawn through a, suction line 6 by operation of a reciprocating compressor 1 driven through a belt 8 by an electric motor 9. The refrigerant is compressed and discharged from the compressor and conducted to an air cooled condenser Ill having an air circulating fan ll driven by a motor I2. The hot compressed refrigerant is cooled in the condenser and liquefied and flows to a liquid receiver I3 from which it is returned to the evaporator through a liquid line l-ll'under control of a thermostatic expansion valve l5. The valve I5 is provided with a temperature responsive bulb or feeler element l5a secured in heat exchange with the suction line 6 and operates to maintain a predetermined amount of superheat in the vaporized refrigerant withdrawn from the evaporator. During the operation of the air cooling system it is desirable that the motor-compressor unit be operated at a relatively high coefficient of performance. The coeflicient of performance may be improved by preventing short cycling of the motor '9, that is, by operating the compressor at a capacity such that under low load conditions, for example, it will operate over an extended period to maintain the desired pressures in the system rather than operating at high capacity for short periods. Short cycling is objectionable because frequent starting and stopping of the electric motor tends to overheat the motor. In the system shown in Fig. 1 a control l6 responsive to the head pressure of the compressor 1 is arranged to actuate a solenoid valve I! and vary the capacity of the compressor in a manner to be described below.

The details of construction of the compressor and the arrangement of the capacity modulating and unloading device are clearly shown in Figs. 2 and 3. The compressor comprises a cylinder block l8 mounted on a crankcase l9. Cylinders 20 are formed within the block l8 and are closed by a compressor head structure including a valve plate 2| and a head 22 secured to the block by bolts 23. Within the cylinders 20 there are mounted cylinder sleeves 24 which are fitted into seats 25 in the block l8 at the lower ends of the cylinders 20 and are rigidly held between the seats 25 and the valve plate 2|, the usual gasket 26 being arranged between the valve plate and the block IB and also engaging the tops of the sleeves 24. Pistons 21 are mounted for vertical Sliding movement within the sleeves 24 and are reciprocated by operation of a crankshaft '28 journaled in bearings in the crankcase |9. The right-hand crankshaft bearing is mounted in a removable end plate 29 which, when removed, provides an access opening for the withdrawal of the crankshaft after the connecting rods indicated at 30 have been removed. The valve plate 2| is provided with intake valves including flexible disks 3| and discharge valves including flexible disks 32 for controlling intake ports 33 and discharge ports 34 respectively. The intake valvedisks 3| are provided with suitable openings 35 so that the discharge ports 34 communicate directly with the cylinder spaces within the sleeves 24. The intake ports 33 are connected in communication with the suction line 6 through annular intake passages 31 formed as annular grooves in the walls of the cylinders surrounding the sleeves 24 and which are connected to the passages 33 by upright passages 38 formed as vertical grooves in the sleeves 24. The lower ends of the sleeves 24 are of reduced external diameter so that an annular chamber is formed between each sleeve 24 and the cylinder wall 20 between a downwardly facing shoulder 39 formed at the top of the reduced portion of the sleeve and an upwardly facing shoulder 40 in the wall of the block l8 adjacent the bottom of the cylinder 20. Within this annular chamber about each sleeve and surrounding the piston there is mounted a sleeve valve 4| which is slidable vertically within the annular chamber about the sleeve and is urged downwardly by a compression spring 42 engaging the shoulder 39 about a reduced portion of the sleeve valve and a shoulder 43 at the lower end of this reduced portion. The annular space below the sleeve valve 4| is sealed by a resilient gasket 44 so that a closed pressure chamber 45 is formed about the lower end of the cylinder sleeve 24. Fluid pressure within this chamber 45 may. be increased to oppose the springs 42 and force the sleeve valves 4| against the shoulders 39 in a manner to be described below. When the sleeve valves 4| are in their upper positions, as shown in the drawing, they close a plurality of ports 45 opening through the cylinder sleeves 24 into the cylinder spaces, these ports in each cylinder being in open communication with the cylinder space when the piston has moved to a position below the ports. It will thus be apparent that during a. portion of each stroke of each of the pistons it is possible to provide open cornmunication between the annular intake chambers 31 and the interior of the cylinders and thus bypass the intake valves during the first portion of the stroke and partially unload the cylinder.

A body of lubricating oil 4'! is maintained in a sump formed by the bottom of the crankcase l9 and is circulated from the sump through a conduit 48 and a connection is to a gear pump comprising a gear 50 mounted on the end of the crankshaft 2B and a meshing gear 5|, these gears being arranged in a housing to provide a gear pump in a manner well known in the art. The pump discharges the oil through a duct 52 to oil circulating passages indicated generally by dotted lines in the crank 28 and the connecting rod 30. The lubricant is also employed as the pressure fluid for actuating the sleeve valves 4|, and although the same pump may be employed it is preferred, as shown in the drawing, to provide a separate pump comprising intermeshing gears 53 and 54, the gear 53 being connected directly on the stub shaft 55 to the gear 5|. Oil from the conduit 48 enters the second pump through a connection 56 and, by operation of the gears 53 and 54, is pumped through a discharge conduit 51 and enters branch conduits 58 and 59 leading to the annular chambers 45 of the left-hand and right-hand cylinders respectively. The valve I1 is arranged to control the flow of oil through the branch conduit 58. This valve is normally open but may be closed by energization of a solenoid 6G to cut off the supply of oil under pressure to the left-hand chamber 45. Bleeder passages 6| are provided in the walls of the sleeves 24 between the chambers 45 and the inside walls of the cylinder sleeves so that a minimum flow of oil is permitted and provides some of the lubrication for the pistons. A minimum opening may be provided in the valve ll so that even when the valve is in its closed position there is a flow of oil through bleeders 6| for lubricating purposes. In accordance with the usual practice both pumps preferably are provided with suitable pressure regulating devices (not shown). These bleeder passages also tend to limit the discharge pressure on the gear pump.

When the compressor is at a standstill there is no oil pressure in the chambers 45 and the valves 4| are pressed downwardly by the springs 42 to uncover the ports 46, this being the partially unloaded position. When the compressor is started, oil pressure is gradually built up in both chambers 45, the valve I! being normally open, and when a predetermined speed has been reached the pressure is sufficient to force the sleeves 4| to their uppermost positions and maintain them in this position to seal off the by-pass and load the compressor. As the conditions 01' operation change it may become desirable to decrease the total compressor capacity and this may .be done by closing the valve I1 to open the by-pass in the left-hand cylinder, and partially unload that cylinder. In order to control the valve l'l the control [6 is arranged to actuate a snap-acting switch 62 upon expansion of a bellows 63 connected through a duct 34 in communication with the discharge chamber in the head 22 of the compressor. When the head pressure reaches a predetermined high value the bellows expands and moves the switch 62 to its closed position thereby energizing the solenoid 60 and closing the valve I1. This cuts off the main supply of oil to the left-hand chamber 45 and unloads the left-hand cylinder by allowing the spring 42 to move the sleeve 24 away from its seat. The actuation of the control I6 to effect partial loading and unloading of the left-hand cylinder provides modulation of the capacity of the compressor, the cylinder being loaded again as soon as the head pressure falls to a predetermined value at which the snap-acting switch 62 is moved to its open position and deenergizes the solenoid. Whenever the compressor is stopped the oil pressure falls because of the stopping of the operation of the oil pumps, and the pressure in the chambers 45 drops to allow the springs 42 to force both sleeve valves 4| downwardly and uncover the ports 46 and unload the compressor to the extent determined by the position of the ports 46. Obviously the control I6 may be actuated accordance with any condition of operation of the refrigerating system which is indicative of the required compressor capacity so that modulation of the compressor may be efiected in accordance with changes in the selected condition, the control in response to head pressure having been selected merely as an example. It is also obvious that although a two: cylinder compressor has been illustrated the invention is applicable to compressors regardless of the number of cylinders and that, with more than two cylinders, the modulating control may be arranged for successive operation of the by-pass control of the cylinders, a plurality of the cylinders being provided with valves for controlling the flow of oil thereto.

Although this invention has been described in connection with a two-cylinder compressor having capacity modulation in both cylinders, various modifications will occur to those skilled in the art. It is not, therefore, desired that the invention be limited to the particular details illustrated and described and it is intended by the appended claims to cover all modifications within the scope and spirit of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A compressor of the reciprocating type comprising a cylinder block having a cylinder therein, a cylinder sleeve mounted in said cylinder, a portion of the walls of said sleeve and said cylinder being spaced apart to provide an annular chamber between said sleeve and the wall of said cylinder, means providing an intake passage about said cylinder sleeve in communication with said chamber, a piston mounted for reciprocation in said sleeve, means providing a head having intake and exhaust valves therein communicating with the interior of said sleeve, said sleeve having ports therein providing communication between said chamber and the interior of said sleeve, said ports when open providing a by-pass around said intake valve, a sleeve valve movably mounted in said chamber to control said ports, means for urging said sleeve valve toward its position for maintaining said ports open, and means for moving said sleeve valve toward its port closing position to close said ports and control the loading of the compressor, said last mentioned means including a portion of said annular chamber at the end of said sleeve valve remote from 6 said ports for receiving fluid under pressure to actuate said sleeve valve.

2. A compressor of the reciprocating type comprising a cylinder block having a cylinder therein, a cylinder sleeve rigidly mounted on said block within said cylinder and having a portion of reduced cross-section providing an annular chamber between said sleeve and the wall of said cylinder, said block having an annular intake passage formed therein in the wall of said cylinder in communication With said chamber, a piston mounted for reciprocation in said sleeve, means providing a head having intake and exhaust valves therein communicating with the interior of said sleeve, a sleeve valve within said annular chamber and surrounding said piston and movable between open and closed positions, said sleeve valve in its open position providing a bypass around said intake valve between said intake passage and the interior of said sleeve, means for urging said sleeve valve toward its open position, and means for moving said sleeve valve toward its closed position to close said by-pass and control the loading of the compressor.

ROMAN C. WARNEKE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,122,395 Iversen Dec. 29, 1914 1,481,358 Dwyer Jan. 22, 1924 1,683,617 Hennessy Sept. 11, 1928 2,129,073 Schoene Sept. 6, 1938 2,251,783 Davis Aug. 5, 1941 2,282,562 Cole May 12, 1942 2,329,931 Neeson Sept. 21, 1943 2,338,486 Bixler Jan. 4, 1944 2,387,117 Buehler Oct. 16, 1945 FOREIGN PATENTS Number Country Date 434,016 Great Britain 1935

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