US2555004A

US2555004A - Reciprocating compressor with unloading and capacity modulating control

Info

Publication number: US2555004A
Application number: US5645A
Authority: US
Inventors: Dean C Rinehart
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1948-01-31
Filing date: 1948-01-31
Publication date: 1951-05-29
Anticipated expiration: 1968-05-29

Description

y 1951 D. c. RINEHART RECIPRQCATING COMPRESSOR WITH UNLOADING AND CAPACITY MODULATING CONTROL Filed Jan. :51, 1948 Fig.1.

r 4 Invehtpr: Dean C.Rineh ar't l-lis Attorney.

Patented May 29, 1951 RECIPROCATING COMPRESSOR WITH UN- LOADING AND CAPACITY MODULATING CONTROL Dean 0. Rinehart, Fort Wayne, Ind., assignor to General Electric Company, a. corporation of New York Application January 31, 1948, Serial No. 5,645

This invention relates to gas compressors of the reciprocating type and particularly to devices for unloading such compressorsand for providing modulation of the compressor capacity.

In the operation of refrigerant compressors, for example, such as those employed in air conditioning systems, it is frequently desirable to provide a control which makes it possible to vary the capacity of the compressor in accordance with the demands of the system, and preferably such variation is effected over a relatively wide range in gradual steps. It is also desirable that a simple and effective unloading device be provided so that the compressor may be started under no-load conditions. Accordingly, it'is an object of this invention to provide a compressor of the reciprocating type including an improved arrangement for unloading the compressor and for modulating the capacity thereof.

It is another object of the invention to provide a capacity modulating device for compressors of the reciprocating type which shall be of simple construction and readily controllable.

Further objects and advantages of thisinvention will become apparent as the following 8 Claims. (Cl. 230-24) description 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.

The air cooling system shownin Fig. 1 comprises a refrigerant evaporator 4 arranged in a duct 5 through which air to be cooled is cir-' culated 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 II driven by a motor I2. The hot compressed refrigerant is cooled in the condenser .and liquefied and. flows to a liquid receiver l3 from which it is returned to the evaporator through a liquid line 4. u d ntro is; a Penman? e p??? c V 2 sion valve 15. The valve I5 is provided with a temperature responsive bulb or feeler element [511 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 coeflicient of performance. The coefficient 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-loadconditions, 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 It responsive to the head pressure of the compressor 1 is arranged to actuate a solenoid valve l1 and vary the capacity of the compressor in a manner to be described below. The details of construction of the'compres'sor and the arrangement of the capacity modulating and unloading device are clearly shown in Figs. 2 and 3. The compressor comprises a cylinder block I8 mounted on a crankcase l9. Cylinders 20 are formed within the block i8 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 vertically slidable within the cylinders and within which pistons 25 are reciprocated by operation of a crankslfift 26 journaled in bearings in the crankcase I9, the right-hand bearing being mounted in a removable end plate 21. The valve plate 2| is provided with intake valves including flexible disks ZB'and discharge valves including flexible disks 29 for controlling intake ports 30 and discharge ports 3| respectively. The intake valve disks 28 are provided with suitable openings 28a so that the discharge ports 3| communicate directly with the cylinder space within the sleeves 24. The intake ports 30 are connected in communication with the suction line 6 through annular intake passages 32 formed between the sleeves 24 and the block l8 and connected to the passages 30 by upright passages 33 formed as grooves in the sleeves 24'. The annular passages 32 are formed by grooves 34 in the walls of the cylinders 20 and annular grooves 35 in the external walls of thesleevesz l. The lower ends 3 36 of the sleeves 24 are of reduced external diameter and cooperate with the walls of the cylinders 2|] to form annular chambers 31 which are closed by collars 38 rigidly secured in the lower ends of the cylinders 20 by retaining rings 39. The annular chambers 31 are sealed by upper and lower resilient rings or gaskets 40 and4l. The upper gasket 40 is seated on a downwardly facing shoulder 42 formed by the reduced portion of the sleeve 24, and the lower gasket is seated on the collars 38. The gaskets are pressed apart and retained in sealing engagement with the cylinder walls by a helical spring 43 surrounding the sleeve, the gaskets being provided with annular grooves forming seats for the spring.

In the drawing the cylinder sleeves 24 have been shown in engagement with sealing rings or gaskets 44 embedded in the lower sideof the valve plate 2|. The sleeves are held in this position by fluid pressure within the chambers 3'! which opposes the force of a plurality of springs 45 arranged in rings around the sleeves and seated in recesses 41 in the valve plate and in recesses 46 in the sleeves. Only two of the springs 45 have been shown in the drawing, it being unnecessary for an understanding or the invention that the remaining springs be illustrated The combined force of the springs 45 is such that these springs overcome the springs 43 and bias the sleeves 24 to their lower position so that bypasses are provided around the'intake valves at the tops of the sleeves and the compressor is normally unloaded. The lowermost position of the sleeves is determined by stop rings 48 formed as internal flanges on th collars 38.

A body of lubricating oil 49 is maintained in a sump formed by the bottom of 'the crankcase I9 and is circulated from the sump through a conduit 50 and a connection to a gear pump comprising a gear 52 mounted on the end of the crankshaft 25 and a meshing gear 53, these gears being arranged in a housing to provide a gear pump in a manner well knownin the art and which discharges the oil through a duct 54 to oil circulating passages indicated generally by dotted lines in the crank 26 and'in the connecting rods indicated at 55. The lubricant is also employed as the pressure fluid for actuating the sleeves 24, and although the same pump maybe employed it is preierr'ed,'as shown in the drawing, to provide'a separate pump comprising

intermeshing gears

56 and 51, the gear 56 being connected directly by'a stub shaft'58 to thegear 53. Oil from the conduit 50 enters the second pump through a connection55 andbybperation of the

gears

56 and 51, is pumped through adi'scharge conduit 60 and entersbra'nc h' conduits Bl and 52 leading to the annular "chambers'3l of the left-hand'and right-hand cylinders respectively. The valve 11 is arranged to controlthe flow of oil through the branch conduit 61 This valve is normally open but may be'clo'sed by energization of a solenoid '63 to cutoff the supply of oil under pressure to the left-hand chamber 31. Bleeder passages 84 are provided in the walls of the sleeves '24 'betweenthe'passa'ges "3'1 and the inside walls 'of the cylinderjsleeves 'so that a minimum fiow of oil is permitted and provides lubrication for the pistons. A minimum opening may be provided in the valve l1 so that even when the valve is injitsfclosed position'there is a flow of oil'through bleede'rs 64for'lubricat ing purposes. These bleeder passages'al'so limit the back pressure on the g'ear pump. v

When the compressor is at astandstill' there is 4 no oil pressure in the chambers 31 and the sleeves 24 are pressed downwardly by the springs 45 to open the bypasses over the tops of the sleeves, this being the unloaded position. When the com pressor is started, oil pressure is gradually built up in both chambers 31, the valve I! being normally open, ahd when a predetermined speed has been reached the pressure is sufficient to force the sleeves against the gaskets 44 and maintain them in this position to seal oil the bypass and load the compressor. As the conditions of operation change it may become desirable to decrease the total compressor capacity and this may be done by closing the valve ll to open the bypass in the left-hand cylinder and unload that cylinder. In order to control the valve ll the control [5 is arranged to actuate a snap-acting switch 65 upon expansion of a bellows 66 connected through a duct 67 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 55 to its closed position thereby energizing the solenoid 63 and blosing the valve ll. This cuts off the main supply of oil to the left-hand chamber 37 and unloads the left-hand cylinderby allowing the springs 45 to move the sleeve 24 away frornits seat. The actuation of the control Hi to efiect loading andunloading of the left-hand cylinder provides modulation of the capacity of the compressor, the cylinder being loaded aga'in as soon as the head pressure falls to a predetermined value at which the snap-acting switch is moved to its open position and deenergizes the solenoid. Whenever the compressor is stopped the oil pressure falls becauseof the stopping of theoperation of the oil pumps, and the pressure in the chambers 31 drops to allow the springs 45 to force both cylinder sleeves 24 away from their seats and unload 'the compressor. Obviously the control l5 may 'be actuated in'accordance with any condition of operation of the refrigerating system which is indicativeof the required cornpressor capacity so that modulation of thecompressor may be efiecte'd. in accordance with changes in the selectedcondition, the control in response to head pressure having been selected merely by way of illustration. It is also obvious that althougha two-cylinder compressor hasbeen illustrated the invention is applicable to multicylinder compressors regardless of the number of cylinders and thatwith "more than twocylinders the modulating control may be arranged for successive operation of the bypass control of the cylinders, a pluralityof the cylinders being 'provided with valves forcontrollihgthe flow-ofoil thereto.

Although this invention has been described in connection with a twoecylinder compressor having capacity modulation control of-on'ly one of the cylinders, various modifications will occur to those skilled in thea'rt. It is not,'therefore, de sired 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 spirit and scope-of --the invention.

What I claim as new and desire tosecure'by Letters Patent of the United Statesis:

1. A compressor of thereciprocating typecomprising a cylinder block having a cylinder-therein, a piston mounted'forreciprocation in said cylinder, intakeandex "valves forsaid cylinder, a sleeve valve siir Qounding said piston and movable between open and closed positions, saidsleeve valve in its open position providing a bypassaround said intake valve, means biasing said sleeve valve toward its open position, meansincluding an annular shoulder on said sleeve valve for forming an annular chamber surrounding said piston whereby said chamber expands upon movement of said sleeve valve toward its closed position, and means for supplying to said chamber a fluid under pressure for expanding said chamber and moving said sleeve valve toward its closed position toclose said bypass and control the loading of said cylinder.

2. 'A compressor of the'reciprocating type coni prising a cylinder block, means providing a head for said block, a cylinder sleeve cooperating with said head to form a closed cylinder and mounted in said block for movement toward and away from said head, a piston in said cylinder, means for driving said piston, intake and exhaust valves for said cylinder, an annular seat on said head for limiting the movement of said sleeve toward said head and for sealing said cylinder, means for urging said sleeve away from said seat to provide a bypass around said intake valve, an expansible chamber device for moving said sleeve toward said seat, and means including a pump driven by said driving means for supplying fluid under pressure to said device to move said sleeve toward said seat and close said bypass to control the loading of said cylinder.

3. A compressor of the reciprocating type comprising a cylinder block, means providing a head for said block, a cylinder sleeve cooperating with said head to form a closed cylinder and mounted in said block for movement toward and away from said head, a piston in said cylinder, means for driving said piston, intake and exhaust valves for said cylinder, an annular seat on said head for limiting the movement of said sleeve toward said head and for sealing said cylinder, means for urging said sleeve away from said seat to provide a bypass around said intake valve, means providing an annular chamber expansible longitudinally of said cylinder for moving said sleeve toward said seat, and means including a pump driven by said driving means for supplying a fluid under pressure to said chamber to move said sleeve toward said seat and close said bypass to control the loading of said cylinder.

4. A compressor of the reciprocating type comprising a cylinder block having a cylinder therein, a head for said block arranged to close said cylinder, a cylinder sleeve slidably mountedin said cylinder for movement toward and away from said head, a piston mounted in said sleeve, said sleeve being formed with an external annular shoulder facin away from said head and forming an annular chamber between said sleeve and the wall of said cylinder, annular closure means spaced from said shoulder for closing said chamber, intake and discharge valves communicating with the interior of said sleeve, means for urging said sleeve away from said head to provide a bypass around said intake valve, and means for admitting fluid under pressure to said chamber for moving said sleeve toward said head to close said bypass and control the loading of the compressor.

5. A compressor of the reciprocating type comprising a cylinder block having a cylinder therein, a head for said block arranged to close said cylinder, a cylinder sleeve slidably mounted in said cylinder for movement toward and away from said head, a piston mounted in said sleeve,

said sleeve being formed with an external-annular shoulder facing away from saidheadand forming an annular chamber between said sleeve and the wall of said cylinder, annular closure means spaced from said shoulder for closing said chamber, a pair of resilient annular gaskets one seated against said-shoulder and th other seated against said closure means, a spring engaging said gaskets for urging said gaskets apart and for maintaining said gaskets seatedon said shoulder and closure means regardless of movement of said sleeve, intake and discharge valves communicating with the interior of said sleeve, means for urging said sleeve away from said head to provide a bypass around said intake valve, and means for admittin fluid under pressure to said chamber for moving said sleeve toward said head to close said bypass and control the loading of the compressor.

6. A compressor of the reciprocating type comprising a cylinder block having a cylinder therein, a valve plate for closing said cylinder, a cylinder sleeve slidably mounted in said cylinder for movement toward and away from said plate, a piston mounted in said sleeve, means providing an intake passage for said compressor extending about said sleeve, intake and exhaust valves in said plate communicating with the interior of said sleeve, said plate having a passage therein connecting said intake valve and said intake passage, means for urging said sleeve away from said valve plate to provide a bypass around said intake valve, and fluid pressure means for moving said sleeve toward said valve plate to control said bypass and effect the loading and unloading of the compressor.

'7. A compressor of the reciprocating type comprising a cylinder block having a cylinder therein, a head for said block arranged to close said cylinder, a cylinder sleeve slidably mounted in said cylinder for movement toward and away from said head, a piston mounted in said sleeve, said sleeve being formed with an external annular shoulder facing away from said head and forming an annular chamber between said sleeve and the Wall of said cylinder, annular closure means spaced from said shoulder for closing said chamber, intake and discharge valves communicating with the interior of said sleeve, means for urging said sleeve away from said head to provide a bypass around said intake valve, means for retaining a body of liquid lubricant for the compressor, a pump for supplying lubricant under pressure Irom said body to said annular chamber, and means dependent upon the load on the compressor for controlling the supply of lubricant to said chamber to close said bypass and eifect the loading of the compressor.

8. A compressor of the reciprocating type comprising a cylinder block having a cylinder therein, a head'for said block arranged to close said cylinder, a cylinder sleeve slidably mounted in said cylinder for movement toward and away from said head, a piston mounted in said sleeve, said sleeve being formed with an external annular shoulder facing away from'said head and forming an annular chamber between said sleeve and the wall of said cylinder, annular closure means spaced from said shoulder for closing said chamber, intake and discharge valves communicating with the interior of said sleeve, means for urging said sleeve away from said head to provide a bypass around said intake valve, means for retaining a body of liquid lubricant for the 7 compressor, a pump for supplying liquid lubri-e DEA-N C. RINEHART REFERENCES CITED The fb'll'dwing referefices' are of redrd in tfi file of this patent:

8 12mm sums PATENTS mfi f 1,668,195 1,709,906 2,074,9'fl 2,129,073 2:29am 2,338,486 21387-11? Numpe;

Ndfii I iiie Aikman May 3, i928 Faifiief Apr. 23; I929 Hull Mar. 1937 Shdfi sept. 6', i933 NeS'o'fi Sept. 21, 1943 Bi'idgi" Jan. 4, 1944 Buc'hler" oct. 16, 1945 FOREIGN PATENTS- Country Date Great; Britain 1935