US3572378A - Compressor valve unloading device - Google Patents

Abstract

A SUCTION VALVE UNLOADER FOR RECIPROCATING COMPRESSORS TO SELECTIVELY HOLD OPEN THE SUCTION VALVES TO UNLOAD THE COMPRESSOR. THE DEVICE INCLUDES AN UNLOADER PIN MECHANICALLY BIASED TO FORCE OPEN AND HOLD THE SUCTION VALVE AND A MECHANICALLY BIASED WEDGE FOR LOCKING THE PIN IN THIS POSITION TO RESIST FLUID FORCES AGAINST THE VALVE HELD IN OPEN POSITION. CONTROL AIR PRESSURE IS USED TO MOVE THE WEDGE TO UNLOCKED POSITION AND TO RAISE THE UNLOADER PIN SO THAT THE VALVES MAY RESUME NORMAL OPERATION. IN A PREFERRED EMBODIMENT, FAILURE OF THE CONTROL AIR PRESSURE WILL CAUSE THE UNLOADER PIN TO ASSURE ITS LOCKED POSITION TO UNLOAD THE COMPRESSOR.

Description

March 23, 1971 w, HARTWICK ET AL 3,572,378

- COMPRESSOR VALVE UNLOADING DEVICE Filed Jan. 5, 1970 TITS-l- INVENTORS: WILLIAM F HAHTWICK.

BFDUTT [F.MIBKLE. v

ATTYs.

United States Patent 3,572,378 COMPRESSOR VALVE UNLOADING DEVICE William F. Hartwick, Mount Vernon, and Scott C. Mickle, Fredericktown, Ohio, assignors to Cooper Industries, Inc., Mount Vernon, Ohio Filed Jan. 5, 1970, Ser. No. 644 Int. Cl. F161: 31/524 U.S. Cl. 137-523 9 Claims ABSTRACT OF THE DISCLOSURE A suction valve unloader for reciprocating compressors to selectively hold open the suction valves to unload the compressor. The device includes an unloader pin mechanically biased to force open and hold the suction valve and a mechanically biased wedge for locking the pin in this position to resist fluid forces against the valve held in open position. Control air pressure is used to move the wedge to unlocked position and to raise the unloader pin so that the valves may resume normal operation. In a preferred embodiment, failure of the control air pressure will cause the unloader pin to assume its locked position to unload the compressor.

This invention relates to a device for unloading piston type reciprocating fluid compressors by holding open the suction valve on each of the compression cylinders so that the fluid being acted upon is alternately forced to flow between the suction manifold and cylinder and cannot be compressed and discharged.

More specifically, this invention relates to a pneumatically controlled valve unloader for reciprocating compressors which includes a positive locking device to hold the valves in open, unloaded position against the forces exerted by the fluid being compressed and also, in the preferred form, has a fail-safe feature which will unload the compressor in the event that the control air supply should fail.

Unloading devices for valves of reciprocating compressors which are pneumatically actuated by control air have been known for many years. One such device is disclosed in U.S. Pat. 1,833,613. Such devices, while suitable in some installations, encounter difficulty when used with compressors capable of extremely high compression because the valves, when unloaded, are exposed to force or drag from the fluid being compressed which tends to close the valve against the force of the valve unloader. While devices for mechanically locking the valves in an unloaded position, such as that disclosed in U.S. Pat. 2,795,238 are known in the art, the present invention is superior to such prior art devices in that it utilizes a control air pressure for initiating the unloading of the valve, mechanically locks the valve in open position and, in the preferred embodiment, includes the fail-safe feature which unloads the compressor upon failure of the control air supply.

In addition, the device of this invention can be readily adapted for use with existing equipment, is relatively simple and can be used with compressors wherein the unloaded valves are subjected to high drag forces from the fluid being compressed because the valves are mechanically locked in the unloaded position. Other objects and advantages of the invention will be apparent to those skilled in the art from the following description of a preferred embodiment of the invention, with reference being made to the accompanying drawing in which:

FIG. 1 is a cross sectional view in elevation showing the compressor valve unloading device of this invention associated with a portion of the suction valve manifold of a compressor, showing the unloader holding the valve "Ice plates in open position so that the cylinder is unloaded; an

FIG. 2 is a cross sectional view in elevation similar to FIG. 1 and showing the valve unloader in its position remote from the valve plate so that the cylinder of the compressor may operate normally.

Referring first to FIG. 1, a portion of a compressor intake manifold 10 is shown with a port 11 leading to the cylinder and a lateral passage 12 connected to the supply of fluid being compressed. Between the port 11 and passage 12 is a suction valve, generally designated by reference numeral 13, which includes fluid passages 14 and a valve plate 15 biased upwardly by plate springs 16. As will be apparent to those skilled in the art, when the valve plate 15 is in its uppermost position, as shown in FIG. 2, no fluid can pass from the passage 12 to the port 11. Under normal operation, on the suction stroke of the piston, fluid is drawn from the passage 12 through the valve 13, into the port 11 and thus into the cylinder, with the valve plate 15 being opened by force of this fluid. On the compression or discharge stroke of the piston, fluid pressure and the valve spring 16 quickly close the valve plate 15 by moving it upwardly against the lower surface of the member forming the passages 14 so that the fluid cannot pass through this valve 13 and is compressed and moved to the discharge valve of that cylinder.

It is the function of the valve unloader device to hold the valve plate 1.5 in its lower, open position so that the fluid, on the compression and discharge strokes of the piston, can freely pass through the valve 13 between the port 11 and the passage 12. With the valve plate 15 held in its lower, open position, the compression cycle is interrupted as the fluid is forced back and forth between the port 11-and passage 12, t0 thus unload the compressor.

The unloading device of this invention includes an unloading pin 17 extending axially above the valve 13 and having its lower end resting upon an annular spider 18 which has fingers 19 extending downwardly through the fluid passages 14. The ends of the fingers 19 rest upon the upper surface of the valve plate 15 to hold it in open position when the valve unloader is in operation. The entire spider 18 with its fingers 19 is biased upwardly against the end of the unloading pin 17 by a spring 20 compressed between the end of an internal socket 21 0f the spider 18 and a fixed pin 22 in the suction valve 13.

The upper end of the unloading pin 17 has an enlarged portion 23 which is journaled for reciprocation within a portion of the unloader housing 24 secured to the manifold 10. The enlarged portion 23 has an upper inclined surface adapted to slidingly engage a locking wedge 25 which is positioned for reciprocation within a transverse passage 26 formed in the upper part of the housing 24. The locking wedge 25 includes an enlarged end 27 and a piston 28 at its other end which reciprocates within an enlarged piston chamber 29. A spring 30 bears against the piston 28 and wedge 25 to urge them to the right, as shown in FIG. 1, and a threaded fastener 31 extends through the piston 28 and into the end of the locking wedge 25.

The locking wedge 25 is bifurcated or slotted to allow passage of axially extending shaft 32 from the enlarged portion 23 of the unloading pin 17. The shaft 32 extends through an aperture in the upper portion of the housing 24 and supports an enlarged disk 33. Above the disk 33 is a pressure responsive flexible diaphragm 34 held between the upper portion of the housing 24 and a cover 35 which forms a pressure responsive chamber 36 below the diaphragm 34. Above the diaphragm is a push rod 37 and an enlarged head 38 which is urged upon the diaphragm 34 by a spring 39. In the absence of fluid pressure in the chamber 36, the force from the spring 39 pushes the diaphragm 34 downwardly, as shown in FIG. 1, pushes the disk 33 and its shaft 32 downwardly, and pushes the enlarged portion 23 and unloading pin 17 downwardly to urge the spider 18 to its lower position at which the valve plate 15 is held down to unload the compressor cylinder.

The right end of the chamber 29' is supplied with control air through a line 40. A control air passage 41 connects the chamber 36 below the diaphragm 34 with the chamber 29 in which the piston 28 reciprocates. It will be seen that when the locking wedge 25 and piston 28 are moved to the left, as shown in FIG. 2, control air pressure from the line 40 will flow through the passage 41 and into the chamber 36 below the diaphragm 34. The area of the diaphragm exposed to this air pressure is sufficient such that relatively low control air pressure is sufficient to move the diaphragm upwardly, along with the push rod 3-7 and its head 38, against the bias of the spring 39. With these elements moved to their upper position as shown in FIG. 2, the spring 20 will move the spider 18 and unloading pin 17 to their upper positions, to release the valve plate 15 for normal operation.

Operation of the unloader device thus described is briefly as follows. Referring to FIG. 2, with control air pressure supplied through line 40 to the chamber 29, the locking wedge 25 is moved to the left against the spring 30 and the chamber 36 is under the control air pressure through the passage 41 to move the diaphragm 34 upwardly, thus permitting the spring 20* to move the spider 18 away from the valve plate 15 so that the valves operate in their normal manner as previously described. When it is desired to unload the compressor, the control air is released, by manual or automatic movement of an air vent (not shown), so that the pressure within the chambers 29- and 36 drops to atmospheric value. At this time, the spring 30 starts to move the locking wedge 25 to the right and the spring 39 pushes the push rod 37 and its head 38 downwardly upon the diaphragm 34, upon the disk 33 and shaft 32 which urges the enlarged portion 23 of the unloading pin 17 downwardly to push the spider 18 down upon the valve plate 15 to hold it open. As the enlarged portion 23 of the unloading pin 17 moves downwardly, the locking Wedge 25 moves to the right to its position shown in FIG. 1 so that the unloading pin 17 and spider 18 are mechanically locked in their lowermost position. Thus as shown in FIG. 1, fluid drag from the fluid being compressed cannot raise the valve plate 15 against the spider 18 which is mechanically locked in its lowermost position.

It will be apparent that the system thus described is fail-safe in that a failure of control air pressure will cause the valve to become unloaded as previously described. It will also be apparent to those skilled in the art that the above described system can be modified by reversing the slope of the locking Wedge 25 and by admitting control air pressure to the space above the diaphragm 34 so that the control air pressure will be used to move the locking pin 17 and spider 18 to its locked position, with the absence of control air pressure automatically unlocking these members so that the valves would operate normally. In some installations, such a system may have certain advantages over that previously described as a preferred embodiment. The valve unloading device previously described can be modified for use with other types of compressor suction valves and other modifications may be made to the device thus described and will be apparent to those skilled in the art without departing from the spirit and scope of the following claims.

We claim:

1. A suction valve unloader for reciprocating compressors having suction valves associated with each cylinder thereof which, when held in open position, prevent compression and discharge of fluid from their associated cylinders to thus unload said compressor, said valve un- 4 loader comprising, in combination, an unloader pin positioned adjacent said suction valve in each cylinder and movable from a first position remote from said suction valve which permits normal operation thereof to a second position at which said valve is held open to unload said compressor cylinder, means urging said unloader pin towards said second position, a locking mechanism movable from a remote position away from said unloader pin to a locked position where said unloader pin is held in its second position to unload said cylinder and pneumatic control means effective to move said unloader pin and locking mechanism between their first and second and remote and locked positions, respectively.

2. The suction valve unloader of claim 1 wherein said locking mechanism is a reciprocating wedge having an inclined face positioned to bear against an adjacent position of said unloader pin whereby, when said wedge is in its said locked position, said inclined face bears against said unloader pin portion to hold it in its said second position to hold open said suction valve.

3. The suction valve unloader of claim 1 wherein said unloader pin and said locking mechanism are both spring biased towards their second and locked positions, respectively, and said pneumatic control means, when actuated, is effective to move said unloader pin and locking mechanism against said spring bias whereby failure of air pressure to said pneumatic control means will cause said spring bias to move said unloader pin and said locking mechanism to their said second and locked positions, respectively, to unload said cylinder.

4. The suction valve unloader of claim 3 wherein said locking mechanism is a reciprocating wedge having an inclined face positioned to bear against an adjacent portion of said unloader pin such that movement of said wedge to its locking position will cause said inclined face to bear against said unloader pin portion to lock it in its said second position.

5. The suction valve unloader of claim 1 wherein said pneumatic control means includes a pressure actuated diaphragm secured to said unloader pin which, when exposed to fluid pressure, moves said unloader pin against said spring bias to its first, remote position and means operated by movement of said locking mechanism to its said locked position to reduce fluid pressure on said diaphragm to thereby cause said spring bias to move said unloader pin to its said second position.

6. The suction valve unloader of claim 5 which further includes a spring biasing said locking mechanism in its said locking position and wherein said pneumatic control means further includes a means for applying fluid pressure upon said locking mechanism and effective to move it to said remote position against said spring bias.

7. A suction valve unloader for reciprocating compressors having suction valves normally opened and closed by pressure of the fluid being compressed, said unloader comprising, in combination, and unloader pin movable from a first remote position to a second position at which said suction valves are held open to prevent compression and discharge of fluid from said compressor, a spring urging said unloader stem towards said second position, a first fluid pressure responsive means which, when under control air pressure, will move said unlocking pin against said spring bias to its first remote position, a reciprocating locking wedge having an inclined face adjacent a portion of said unloader pin and adapted to reciprocate across the axis of said unloader pin such that movement to a remote position will release said pin and movement to a locked position will lock said pin in its second position to unload said compressor, a spring urging said locking wedge towards said locked position, a second fluid pressure responsive means which, when under control air pressure, will move said locking wedge against its spring to said unlocked position, means operated by movement of said locking wedge to its locked position to reduce control air pressure on said first pressure responsive means to cause said spring bias to move said unloader pin to its said second position, and means for selectively applying and removing control air pressure to said second pressure responsive means.

8. The suction valve unloader of claim 7 wherein the position of said inclined face of said locking wedge relative to its said remote and locked positions may be ad justed to compensate for wear on said inclined face.

9. The suction valve unloader of claim 7 wherein said means operated by movement of said locking wedge to reduce control air pressure on said first pressure responsive means comprises a fluid passage from said first pressure reponsive mean connected to control air pres sure only when said locking wedge is in said first remote position.

References Cited LAVERNE D. GEIGER, Primary Examiner 10 W. H. WRIGHT, Assistant Examiner US. Cl. X.R.

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