US1939424A - Variable volume control mechanism for compressors - Google Patents

Description

H. C. WASSON Dec. 12, 1933.

VARIABLE VOLUME CONTROL MECHANISM FOR COMPRESSORS Filed June 23. 1931 2 SheetsSheet 1 NVENT OR. Harry C Wasson A T TORNE Y.

H. C. WASSON Dec. 12. 1933.

VARIABLE VOLUME CONTROL MECHANISM FOR COMPRESSORS 1931 2 Sheets-Sheet 2 Filed June 23 INVENTOR. Harry 6." 14/0550 r h g g E b Q Eu v 3 A sfi n 1 E A TTORNEY.

Patented Dec. 12, 1933 PATENT OFFICE VARIABLE VOLUME CONTROL MEC HANISM FOR COMPRESSORS Harry 0. Wasson, Franklin, Pa., assignor to Chicago Pneumatic Tool Company, New York, N. Y., a corporation of New Jersey Application June 23, 1931. Serial No. 546,225

Claims.

This linvention relates to air and. gas compressors with particular reference to automatic regulation of output in response to the demand thereon. More particularly it is concerned with I the unloading and loading of compressors in well defined steps or stages, as for example in the conventional five-step regulation which comprises full load, three-quarter load, half, load,

quarter load and no load. Y

Among the objects of the invention are to secure balanced operation at all loads, to reduce the requisite fly wheel effect to a minimum and in general to improve prior apparatus of this general character by securing smoother operation, eliminating vibration, reducing weight, etc.

The invention involves the provision of a plurality of clearance pockets at each end of the compressor cylinder. 15y preference the pockets are of suitable number and size and are arranged so that balanced operation may be conveniently secured at all stages in five-step regulation. Three pockets, each capable of accommodating one-quarter of the fluid delivered atone end of the cylinder makes a satisfactory arrangement provided that inlet valves are still available for total unloading. When the number of inlet valves is limited/to three as is frequently'the case in high pressure cylinders, the clearance pocketsmay be limited to two, one being twice the size of the other. This arrangement leaves one of the inlet valves for total unloading and a special control isprovided to manipulate the two pockets to secure the efiect of three pockets. Each pocket, whether in'a high or. a low pressure cylinder, has an inlet valve between it and the cylinder bore, and a suitable admission valve between it and the intake pipe. When the pocket is not operating to unload the compressor, the admission valve stands widelopen and the inlet valve performs its normal function. Hence the air or gas passes through thepocket as freely as if there were no pocket at all. In order to make the pocket operative it is only necessary to hold the inlet valve open and to closethe admission valve. At no load all of the valves must be held open and to produce this effect upon'the admission valves without disturbing the inlet valves, special vent or control valves are provided. In order to illustrate the invention and the manner of its operation one embodiment thereof is disclosed in the accompanying drawings, in which:

Fig. 1 is a plan view largely diagrammatic in character disclosing the control arrangement for a two-stage double-acting duplex compressor,

the prime mover and its connections being omitted; V

Fig. 2 is a transverse sectional view on an enlarged scale through the compressor shown in Fig. 1, certain parts being necessarily omitted and the connections being largely diagrammatic in character; and

Fig. 3 is a group arrangement showing the control valves in a typical sequential arrangement, the valves being individually shown in vertical section but on a greatly enlarged scale as compared with Figs. 1 and 2.

y In the diagrammatic disclosures in Figs. 1 and 2 L indicates the low pressure cylinder and H the high pressure cylinder, R is the conventional five-step regulator of any suitable or desired type for unloading the compressor in five steps, such for example, as that disclosed in U. S. Patent 1,685,781, issued October 2, 1928 to L. F. Hoffman, inventor. As shown in Fig. 2 the chamber 4 immediately surrounding the piston chamber for low pressure cylinder L and the chamber 5 for high pressure cylinder H is for cooling fluid, such as water. Opening into the lower side of low pressure cylinder L is air inlet chamber 6 while corresponding thereto at the top is discharge chamber 7 which communicates through a conventional intercooler connection (not shown) with inlet chamber 8 at the top of high pressure cylinder H. The corresponding discharge chamber 9 on the lower side of high pressure cylinder H leads to the air receiver. Outwardly of the inlet and discharge chambers 6 and '7 the walls of low pressure cylinder L at each end'thereof'provide a series of clearance pockets or chambers PLI, PL2, PL3, each of which is of a size to receive one-quarter of the volume of air displaced by the piston at one end of its stroke. These pockets communicate with the piston chamber through openings. controlled by unloading inlet valves ILl, 1L2 and IL3 respectively and with inlet 6 through openings controlled by admission valves ALI, AL2 and AL3 respectively. All these valves are duplicated at each end of the cylinder. In addition there are unloading inlet valves 1L4 (Fig. 1)' which connect inlet 6 directly with the piston chamber.

In high pressure cylinder H there are two clearance pockets H11 and PH2 at each end, the first having a capacity of one-quarter of thedisplacement of the piston at one end of the stroke and the second having twice that capacity. These pockets communicate with the piston chamberthrough openings controlled by unloading inlet valves 1H1 and H12 respectively and have openings extending to inlet chamber 8 under control of admission valves AHl and AH2 respectively. These pockets and valves, of course, are duplicated at the opposite ends of high pressure cylinder H as is indicated in Fig. 1. In addition there are unloading inlet valves 1H3 which control openings from inlet 8 directly into the piston chamber.

As clearly indicated in Fig. 2 the admission or poppet control valves ALI, AL2 and AL3 of cylinder L and AHI and AH2 of cylinder H are normally open so that the pockets controlled thereby during full load operation of the compressor merely form extensions of inlet chambers 6 and 8 so that the air or gas to be com-' pressed reaches the inlet valves in the respective cylinders as freely as if the pockets did not'exist. During the unloading steps, howevenit is necessary to close the admission valves'in order" that the clearance pockets may function to unload the compressor. To this end auxiliary control or vent valves are provided VL-1, VL2' and VL3 respectively for admission valves AL1, AL2, and 'AL3 of cylinder L. For cylinder H three auxiliary vent valves VH1, VHl and VH2 are provided in connection with admission valve AHl while a single vent valve VH2 is provided for admission valve AH2. I

With the arrangement as heretofore briefly described, it is possible to open pockets simultaneously in each end of each cylinder thereby keeping the effective capacity of each end of the cylinder the same and causing the torque developed thereby to be very uniform atall capacities. Regulator R (Fig. 1) has conduits 1a, 2a, 3a and 4a extending therefrom (Figs. 1 and 2) communicating with piping systems (1) (2) (3) (4) corresponding to the four unloading steps in fivestep regulation, namely three-quarter 1oad,'on'ehalf load, one-quarter load and no load which systems connect with the inletyad'mission and vent valves, as indicated by the numerals at the ends of the symbols for'such valves.

The various types of valves and their method of operation will be apparent from the detailed disclosure of Fig. 3. Inlet valve I, which corresponds to all valves in cylinders L and H having the leading symbol I is illustrative of a conventional unloading inlet valve of the disc or plate type wherein pressure fluid admitted through a pipe in connecting for example with conduit system (1) is effective through diaphragm 10 and head 11 secured thereto to operate valve lifter 12 carrying a series of plungers 12a for depressing'and maintaining plate valves 13 01f their seats. When the pressure is relieved above diaphragm 10, valve lifter 12 is forced upwardly by a series of springs 14 so that plate valves 13 may resume their normal function. The particular valve I here show is intended for use in high pressure cylinder '11 and is. provided with a second diaphragm 15 to prevent a building up of pressure beneath diaphragm 10 which would interfere'with the actuation of the unloading mechanism. For the inlet valves in low pressure cylinder L diaphragm 15, is omitted. I

A suitable admission valve is indicated at A (Fig. 3)' and corresponds to all valves in cylinders L and H having the leading symbol A. As shown, the valve is of the poppet type. The valve a proper forms apart of a pistona .recipr'ocable in a cylinder a2 formed by cover a3. A coil spring a4 yieldingly maintains valve plunger ain open position while pressure admitted through a pipe y will operate on piston a to overcome spring; a4 and movevalve'proper a toclosed position.- The operation of valve A is controlled by auxiliary or vent valve V which corresponds to all valves for cylinders L and H having the leading symbol V. This valve has an inlet connection at for pressure fluid, an outlet connection y leading to valve A and a vent opening 16. The double ended valve plunger 1'7 has restricted movement between a seat 18 on the valve casing and a seat 19 on guide member 20 within the casing. A spring 21 yieldingly maintainsplunger 17 against seat 18 so that there is normally an open connection beiween the pipe 12: and y. Plunger 17 has a stem 17a secured to a diaphragm 22 beneath which fluid pressure may be admitted by pipe z. A spring 23 may bear against diaphragm 22 to assist spring 21 in holding valve plunger 17 against seat 18. On admission of pressure fluid beneath diaphragm 22 it will be apparent that springs 23 and 21 will be overcome and valve plunger 17 will be moved against seat 19 whereupon pipe y leading from valve A will be placed in communication with vent 16'.

The operation of the apparatus is as follows. When the compressor is operating atfull load all of'the inlet valves operate normally and all of the admission or poppet valves are wide open, as indicated in" Fig. 2. When the pressure in the receiver reaches a predetermined value regulator R operates to: admit pressure fluid to'pipe' 1a and into pipe system (1). Pressure fluid then passes to hold open inlet valves I'Ll at the opposite ends of thelow pressure cylinder and at the same time to auxiliary vent valves VLl to close admission or poppet valves ALI whereupon pockets PLl receive one-quarter of the volume displaced by the piston at each stroke; The eifect on the valves is illustrated in Fig. 3 wherein valve 1 is shown with diaphragm 10' forced down to hold inlet valves 13 off their seats and auxiliary valve V is passing pressure fluid to admission or poppet valve A to close the latter and to hold it in closed position. In the high pressure piston, pressure fluid passes from piping system 1) through auxiliary or vent valve VH1 to open inlet valves IHl on. opposite ends of the cylinder and through auxiliary or vent valve VH1 to" close admission or poppet valves AHl whereupon both' ends of the high pressure cylinder are one-"quarter unloaded.

If the receiver pressure rises still further, regulator Rf'moves to half load position and admits pressure fluid through pipe 2a to pipe system (2) whereupon pressure fluid passes to the 2 series valves causing clearance pockets PL2 at opposite ends of the' low pressure cylinder'to come into operation. 'In the high pressure cylinder, motive fluid actuates the valves to put double size clearance pockets PHZ into operaion while rendering pockets PHI inoperative. This last is accomplished by passing mo'tivefluid through auxiliary or vent valve'VH2 to'the diaphragm side of auxiliary valve VH1 so that the latter vents the connection to valves'II-Il and to admission or poppet valves AHl through auxiliary or vent valve VH1.

For one-quarter load, regulator R admits pressure fluid to pipe system (3) whereupon clearance pockets PL3 -of the low pressure cylinder are brought into operation. In the highpressure cylinder motive fluid now passes to the diaphragm side of auxiliary or vent valve VH2 whereupon the diaphragm side of auxiliary valve VH1 is vented and the pressure fluid in pipe system 1) acts immediately to bring clearance pockets PHI back into operation.

For complete unloadingof the compressor regu the remaining inlet valves 1L4 and at the same time to pass motive fluid to the diaphragm sides of auxiliary or vent valves VLl, VL2 and VL3 with the result that the admission valves controlled by the latter are vented and move to the open position shown in Fig. 2. The inlet valves 1L1, 1L2 and IL3 continue to be held open by the pressure fluid systems (1) (2) and (3). In the high pressure cylinder inlet valves 1H3 are, opened (Fig. 1) while motive fluid is passed to the diaphragm sides of auxiliary or ventvalves VH2 and VH1 thereupon venting admission or poppet valves AIM and AH2 so that the latter move to open position (Fig. 2). Thus the admission or poppet valves all move to open position while all the inlet valves continuev to be held open and the air is swept by the pistons back to the intake passages with' out being compressed. The step-by-step loading of the compressor will be the reverse of the above.

From the above it will be apparent that the herein described arrangement for capacity regulation provides balanced operation of the compressor at all loads, thereby insuring smooth operation at all times and reducing the required fly wheel effect to a minimum. When the compressor is electrically operated with the motor built into the crank shaft no fiy wheel effect is required additional tothatsupplied by the rotor of the electric motor.

While the invention has been herein shown and described in what is now considered to be its preferred form, it is to be understood that the invention is not limited to the specific details thereof but covers all changes, modifications and adaptations within the scope of the appended claims.

I claim as my invention:

1. In a double acting variable volume .compressor,.a compressor cylinder having a plurality of clearance pockets at each end, a normally open admission valve for each pocket, an inlet valve between each pocket and the compressor cylinder, and means for controlling simultaneously the the valves of corresponding pockets at opposite ends'of the compressor so as to effect balanced loading and unloading of the same.

2. In a double acting variable volume compressor, a compressor cylinder having a plurality of clearance pockets at each end, a normally open admission valve for each pocket, an inlet valve between each pocket and the compressor cylinder, means for controlling simultaneously the valves of corresponding pockets at opposite ends of the compressor so as to effect balanced loading and unloading of the same, and means for opening all said admission valves for total unloading of the compressor.

3. In a double acting compressor, cylinder walls having a series of independent passages leading from the inlet to the opposite ends of the piston chamber, means for cutting on. portions of said passages to provide opposed pockets of substantially the same volume, and means for controlling the formation of said pockets simultaneously in opposed pairs so as to effect balanced unloading and loading of the compressor.

4. In a double acting compressor, a cylinder having three clearance pockets of substantially equal size at each end thereof and means for simultaneous and progressive control of said pockets in pairs to efiect five step capacity regulation ofsaid compressor and to maintain th balance of the compressor at each step.

5. In a double acting compressor, a cylinder having two clearance pockets-at each end thereof, one pocket beingsubstantially twice the sizeof the other pocket at the same end, the pockets forming opposed pairs of substantially equal capacity, and means for controlling said pockets to effect progressive-loading and unloading of the compressor in five well defined steps and to maintain thecompressor in balance at each step.

6. In' a double acting compressor, a cylinder having two clearance pockets at each end there of, one pocket at each end having the capaclty of one-fourth of the output of said end and the other pocket having twice the capacity of the first pocket, and regulating means for controlling the operation of said pockets simultaneously in pairs to efiect five step regulation in quarter capacity steps while maintaining the compressor in balance at all steps.

7. In a duplex double acting compressor, each cylinder having a series of independent passages leading from the inlet to the opposite ends of the piston chamber, means for cutting off from the inlet portions of said passages to provide opposed pockets of substantially the same capacity, and means for controlling the formation of said pockets simultaneously in both cylinders in opposed pairs so as to effect balanced unloading and loading of the compressor.

8. In a duplex double acting compressor, means providing clearance pockets in the opposite ends of each of said cylinders, the number of clearance pockets in the ends of one of said cylinders being greater than those in the other cylinder, and means for simultaneously controlling the operation of the pockets in both ends of both cylinders so as to efiect balanced unloading and loading of the compressor.

9. In a duplex double acting compressor, means providing clearance pockets in the opposite ends of each of said cylinders, the number of clearance pockets in the ends of one of said cylinders being greater than those in the other cylinder, and means for controlling the operation of the pockets of both said cylinders to unload and to load the same progressively in well defined steps and to maintain a balanced condition in both said cylinders during all said steps.

10. In a duplex double acting compressor, means providing clearance pockets in both ends of both cylinders in opposed pairs of substantially equal capacity, there being two opposed pairs in one cylinder and three opposed pairs in the other cylinder, and means for simultaneously controlling said pockets to secure five step regulation of said compressor and a balanced eifect in said compressor at each step.

unloading inlet valve controlling the opening from said passage into the piston chamber of the compressor, a normally open admission valve in said passage in spacedrelation to said inlet valve, and means for simultaneously opening said inlet valve and closing said admission valve to provide a clearance pocket in said passage for unloading said compressor.

12. A compressor having an inlet passage, an unloading inlet valve controlling the opening from said passage into the piston chamber of the compressor, a normally open admission valve in said passagein spaced relation to said inlet valve, and means for simultaneously opening said inlet valve and closing said admission valve to provide a clearance pocket in said passage for partly unloading said compressor, and means for of said compressor.

13. A compressor having an inlet passage,

I an unloading inlet valve controlling the openfrom said passage into the piston chamber of the v opening said admission valve 101. total unloading compressor, a normally open admission valve in said passage in spaced relation to said inlet valve,

and fluid pressure means for simultaneously opening said inlet valve and closing said admission valve to provide a clearance pocket in said passage forpartially unloading said compressor, and means for venting the presure fluid to said admission valve to permit opening of the same and secure total unloading of the compressor.

15. In a double acting compressor, a cylinder having a plurality of clearance pockets in each end, an intake connectable to the cylinder through said pockets, a normally open admission valve between each pocket and the compressor intake,

and an automatic intake valve between each pocket and the compressor cylinder.

HARRY C. WASSON.

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