US3294314A - Lifting device for compressor valves - Google Patents

Description

Dec. 27, 1966 J. OTT ETAL LIFTING DEVICE FOR COMPRESSOR VALVES Filed March 22, 1966 W F W United States Patent LIFTENG DEVll CE FOR CUMPRESSQR VALVES Josef Ott, Schongau, Lech, Germany, and Friedrich Bauer,

Vienna, Austria, assignors to Hoerhiger Ventiiwerke Aktiengesellschaft, Vienna, Austria Filed Mar. 22, 966, Ser. No. 536,377 Claims priority, appiication Austria, Mar. 24, 1965, A 2,650/65 1% Claims. (Cl. 230-24) The invention relates to a lifting device for compressor valves serving for the infinitely variable control of the delivery volume of piston-type compressors, comprising lifting pins preferably guided in the valve seat and connected by means of lifting springs with a pressure plate pressing against an adjusting drive.

It is the purpose of conventional lifting devices used in piston-type compressors for the control of the delivery volume to retard the closing of the suction valve as a result of which the piston will push part of the medium contained in the cylinder back into the suction pipe during the compression stroke, the elements of the lifting device resting upon the valve plate working like the valve plate itself in accordance with the stroke cycle of the compressor. In order to keep the stresses in the valve plate and in the lifting device, particularly of high-speed pistontype compressors, as low as possible, it is desirable to reduce the mass of the lifting device following the stroke cycle to the minium. In conventional lifting devices of the type hereabove described this aim is achieved to a considerable extent by the provision of comparatively short lifting pins connected with the pressure plate only by means of lifting springs. Since the pressure plate does not follow the stroke motions, this design permits of a substantial reduction of the moving mass as compared with other conventional devices comprising so-called rigid lifting grippers guided in coaxial relation inside the valve and loaded by means of a single spring arranged between the lifting gripper and the adjusting drive.

However, experience goes to show that with various kinds of piston-type compressors, and in particular those operating within a regulating range below 70 percent of their full delivery volume, in spite of a substantial reduction of the masses of the elements of the lifting device following the stroke cycle of the compressor, breakage of the suction valve plates is liable to occur already after a few hours of operation. This may be caused by the fact that under the influence of the frequently substantial closing forces exerted by the medium flowing back into the suction pipe, the valve plates impinge upon the valve seats with considerable speed. The remedy usually tried in such cases, consisting in a reduction of the valve stroke and a reinforcement of the valve plate, was not always conducive to satisfactory results, apart from the fact that as a result of these problematic measures the cross-sectional area of flow of the valve is greatly reduced and the mass of the valve plate increased which is particularly objectionable in the case of high-speed piston-type compressors.

It is the object of the invention to provide an efficient remedy while avoiding the drawbacks inherent in the reduction of the stroke and in the reinforcement of the valve plate, considering that by providing an appropriate relationship between the masses of the elements moving in the valve on the one hand, and the structural features of the valve and the operational data of the compressor ice lifting pins acting on the valve plate, lifting springs and a pressure plate pressing against an adjusting drive, the lifting springs connecting the lit ing pins with the pressure plate, wherein the lifting pins are provided with adjusting weight detachably placed thereupon for the purpose of adapting the masses of the lifting pins to the operating conditions of the compressor, in particular with regard to speed, pressure and valve stroke. By means of this simple expedient it is possible to adapt the lifting device to existing operating conditions merely by changing the adjusting weights without altering the basic structure of the lifting device. It will therefore, not be necessary to manufacture a separate device adapted to given operating conditions. Furthermore, the invention offers an additional advantage insofar as the increase of the masses of the lifting pins is effective with throttled operation only, so that when the compressor operates at full delivery volume, where the stresses in the valve plate are known to be substantially less than in controlled operation, the moving masses of the valve are not increased.

Preferably the adjusting weights consist of sleeves inserted between the lifting springs and the spring caps provided on the top of the lifting pins. The sleeves are pressed against the spring caps by means of the lifting springs and it is therefore, not necessary to provide special means of attachment for the sleeves which greatly facilitates their fitting. Moreover, the sleeves may on compass the lifting springs over a considerable section of their length, thereby providing appropriate protection for the lifting springs and preventing broken springs or parts of same from dropping out into the valve.

According to another embodiment of the invention, the adjusting weights are formed by rings provided in the valve in coaxial relation to same and interconnecting at least part of the lifting pins. In addition to augmenting the masses, the said rings provide better guidance of the valve plate by the lifting pins, while permitting proper adaptation of the lifting device to the motion of the valve plate within certain limits, such as when the valve plate is placed in an oblique position. Another advantage of this design resides in the fact that according to the invention, at least part of the lifting springs may be so arranged as to rest upon the rings interconnecting the lifting pins in staggered relation to thelifting pins in such a manner that for example, each lifting spring is located between two adjacent lifting pins. This arrangement permits of accomodating a larger number of lifting springs than had been possible with conventional designs, without, however, increasing the number of pins.

In such cases where the lifting pins are concentrically arranged on at least two circles, the lifting pins located on each circle can be provided with a ring of their own, thereby preserving the mobility of the lifting device and the adaptability of the same to the motions of the valve plate, in addition to preventing the rings from impeding the proper flow of the medium in the suction chamber in front of the valve seat. Furthermore, the lifting pins and the lifting springs are preferably inserted with their ends in bores of the rings in order to achieve a firm hold for the extremities of the springs. In addition, the rings may be provided with sleeve-shaped extensions around the bores for the lifting springs to be inserted therein with their extremities, so as to prevent fragments of broken springs from dropping out.

According to another embodiment of the invention, the lifting pins extend in a manner known per se over and above the lifting springs and through the pressure plate, while the adjusting weights, preferably at least one ring interconnecting a plurality of lifting pins, is located on top of the lifting pins above the lifting springs.

This particular design is applicable in such cases where the arrangement of adjusting Weights between the pressure plate and the valve seat is undesirable or impossible. Since with this arrangement the lifting pins extend entirely through the lifting springs, fragments of a broken lifting spring are prevented from falling out.

Finally, according to the invention, the adjusting weights may be so arranged on the lifting pins as to ensure their axial mobility, an elastic damping member, such as a spring, preferably a cup spring, or a disc made of some elastic material, being provided between the adjusting weights and the lifting pins. By the provision of damping elements stresses due to the action of the lifting pins upon the valve plate are attenuated, so that the increase of masses due to the presence of adjusting weights will not produce any objectionable effect in this respect either.

Further details of the invention are explained hereafter with reference to the accompanying drawing in which:

FIG. 1 shows a sectional view of a lifting device according to the invention as incorporated in a compressor valve;

FIG. 2 represents a plan view of a detail of same;

FIGS. 3 to illustrate three different embodiments of the invention featuring adjusting weights located on the top of the lifting pins.

The valve illustrated in FIG. 1 comprises a valve seat 1 and a valve guard 2 mounted on the valve seat 1 by means of a central screw spindle 3 and a nut 4 screwed thereon. Between the valve seat 1 and the valve guard 2 a guide ring 5 is provided for the guidance of the valve plate 6 and of a spring plate 7. By means of a distance sleeve 8 the valve seat 1 is tightly held against a seating 9 of the cylinder 10 which is closed outwardly by the valve cover 11.

Inside the valve seat 1 guided lifting pins 12 are provided, by means of which the controlling forces are transmitted to the valve plate 6. On the side facing away from the valve plate 6 the lifting pins 12 are provided with spring caps 13 for the lifting springs 14, the other extremities of which are supported by a pressure plate 15. For the purpose of securing the spring ends to the pressure plate 15, guide bolts 16 are screwed into same. The pressure plate is attached to a bushing 17 supported by a cylindrical guide means 18 formed by an extension of the nut 4 so as to be slidable in the direction of the valve axis. The bushing 17 is subject to the action of an adjusting drive formed by a pneumatic or hydraulic cylinder, for example, and acting upon the bushing 17 by means of a pushrod 19 located in a guide bushing 20 in the cover 11. However, the controlling forces may also be transmitted to the bushing 17 mechanically by means of a spring or the like. A helical spring 21 serves to restore the pressure plate 15 to its initial position and a bolt 22 is provided for the purpose of preventing rotation of the pressure plate 15 and to limit its stroke.

During the controlling operation the lifting springs 14 are loaded by the appropriate adjustment of the common pressure plate 15 in such a manner that the lifting pins 12 press against the valve plate 6. The lifting pins 12 keep the valve plate 6 open for part of the compression stroke of the compressor piston against the restoring force of the spring plate 7 and the closing forces exerted thereupon by the backfiowing medium. As soon as the closing forces acting upon the valve plate 6 exceed the forces exerted by the lifting springs 14, the valve plate 6 occupies its closing position on the valve seat 1 which it impinges upon with great speed as a result of the considerable forces exerted upon it by the compressing medium. The force of the impact can be attenuated by adapting the masses of the lifting pins 12 following the motions of the valve plate 6 in accordance with the stroke cycle of the compressor to the operating conditions of the compressor. For the purpose, the lifting pins 12 are topped by detachable adjusting weights which are readily exchanged in accordance with any given operating conditions.

In the embodiment shown in FIG. 1 the adjusting weights are formed by rings 23 and 24 arranged coaxially inside the valve and interconnecting the lifting pins 12 arranged on two concentric circles. The two rings 23, 24 are arranged concentrically and present bores 25 with an inwardly projecting collar 26 as shown in FIG. 2. The bores 25 present lifting pins 12 inserted therein from below and lifting springs 14 inserted from above, the collar 26 of each bore 25 being located between the spring cap 13 and the extremity of the lifting spring 14 so that the rings 23, 24 are maintained in close connection with the lifting pins 12. As appears likewise from FIG. 2, additional bores 27 are provided in the ring 24 in a peripheral direction between the bores 25, additional lifting springs 28 being inserted in the said bores 27 as shown in FIG. 1, and supported by the pressure plate '15 by means of guide bolts 16. Consequently, the rings 23 and 24 offer the additional advantage of providing accommodation for a greater number of lifting springs 14, 28 in the valve without increasing the number of lifting pins 12. Furthermore, the rings 23, 24 provide for the approximately parallel guidance of the valve plate 6 as achieved by the use of so-called rigid grippers and occasionally desirable, even if the medium is being delivered under adverse conditions of fiow.

According to the embodiment of the invention illustrated in FIG. 3 the adjusting weights comprise sleeves 29 which are placed on the top of the lifting pins 12 instead of the rings 23, 24. Each sleeve 29 is maintained in position between the spring cap 13 and the extremity of the lifting spring 14 with an inwardly protruding collar 30. Furthermore, the length of the sleeves 29 can be relatively great in the area close to the pressure plate 15 so as to encompass the lifting springs 14 over a substantial section of their overall length, thereby providing appropriate protection for the lifting springs and preventing fragments of broken springs from dropping out. In a similar manner, as shown in FIG. 1, the rings 23 and 24 may present sleeve-shaped extensions around the bores 25 and 27, the extremities of the lifting springs being inserted in the said extensions.

The variants of the invention illustrated in FIGS. 4 and 5 differ from the embodiment shown in FIGS. 1 and 3 chiefly insofar as the lifting pins 12 extend on top over and above the lifting springs 14 and through the pressure plate 15. Thus the lifting springs 14 are securely maintained in position over their entire length. In that case, the adjusting weights are placed on top of the lifting pins 12 somewhere above the lifting springs 14 and the pressure plate 15, and are, in the embodiments of the invention illustrated in the drawings, formed by rings 31 interconnecting a number of lifting pins 12. In the embodiment of the invention shown in FIG. 5 the ring 31 is furthermore supported by the upper extremity of the lifting pin 12 in such a manner as to be movable in the direction of the axis of the said lifting pin, an elastic damping means consisting of a cup spring 32 being provided between the ring 31 and the lifting pin 12. Another type of spring or a disc made of some elastic material, such as rubber or plastics, may be substituted for the said cup spring.

In each of the embodiments of the invention shown the adjusting weights are easily removable and exchangeable for other adjusting weights, so that the lifting device can be used, depending on given requirements, either without any adjusting weight or with such adjusting weights as have been adapted to suit given operating conditions. preferably adjusting weights with different masses are made available for use if and as required, so that the masses of the members of the lifting device following the motions of the valve plate of the controlled suction valve in accordance with the stroke cycle can be readily adapted to the operating conditions of the compressor.

We claim:

1. A lifting device for compressor valves serving for the infinitely variable control of the delivery volume of piston-type compressors, comprising lifting pins acting on a valve plate, lifting springs and a pressure plate pressing against an adjusting drive, the lifting springs connecting the lifting pins with the pressure plate, wherein the lifting pins are provided with adjusting weights detachably placed thereupon for the purpose of adapting the masses of the lifting pins to the operating conditions of the compressor, in particular with regard to speed, pressure and valve stroke.

2. A lifting device as claimed in claim 1, wherein the adjusting weights consist of sleeves inserted between the lifting springs and spring caps provided on the top of the lifting pins.

3. A lifting device as claimed in claim 2, wherein the sleeves encompass the lifting springs over a substantial portion of the length of the said springs.

4. A lifting device as claimed in claim 1, wherein the adjusting weights are formed by rings in coaxial relation to the valve plate and interconnecting at least part of the lifting pins.

5. A lifting device as claimed in claim 4, wherein at least part of the lifting springs are supported by the said rings interconnecting the lifting pins at points on the adjusting rings where lifting pins are omitted.

6. A lifting device as claimed in claim 4, wherein the lifting pins are concentrically arranged on at least two circles, the lifting pins located on each circle being provided with a ring of their own.

7. A lifting device as claimed in claim 4, wherein the said rings are provided with bores, the lifting pins and the lifting springs are insestcd with their extremities in said bores.

8. A lifting device an claimed in claim 7, wherein the rings are provided with sleeve-shaped extensions around the said bores wherein the lifting springs are inserted with their extremities.

9. A lifting device as claimed in claim 1, wherein the lifting pins extend over and above the lifting springs and through the pressure plate, the adjusting weights being located on top of the lifting pins above the lifting springs.

10. A lifting device as claimed in claim 1, wherein the adjusting weights are so arranged on the lifting pins as to ensure their axial mobility, an elastic clamping member being provided between the adjusting weights and the lifting pins.

References Cited by the Examiner UNITED STATES PATENTS 1,928,678 10/1933 Sjolander 123-188 2,526,922 10/1950 Aldinger 23024 2,673,025 3/1954 Labus et a1. 23025 2,742,054 4/1956 Poundstone 137-522 MARK NEWMAN, Primary Examiner.

W. I. KRAUSS, Assistant Examiner.

Claims (2)

1. A LIFTING DEVICE FOR COMPRISING VALVES SERVING FOR THE INFINITELY VARIABLE CONTROL OF THE DELIVERY VOLUME OF PISTON-TYPE COMPRESSORS, COMPRISING LIFTING PINS ACTING ON A VALVE PLATE, LIFTING SPRINGS AND A PRESSURE PLATE PRESSING AGAINST AN ADJUSTING DRIVE, THE LIFTING SPRINGS CONNECTING THE LIFTING PINS WITH THE PRESSURE PLATE, WHEREIN THE LIFTING PINS ARE PROVIDED WITH ADJUSTING WEIGHTS DETACHABLY PLACED THEREUPON FOR THE PURPOSE OF ADAPTING THE MASSES OF THE LIFTING PINS TO THE OPERATING CONDITIONS OF THE COMPRESSOR, IN PARTICULAR WITH REGARD TO SPEED, PRESSURE AND VALVE STROKE.

2. A LIFTING DEVICE AS CLAIMED IN CLAIM 1, WHEREIN THE ADJUSTING WEIGHTS CONSIST OF SLEEVES INSERTED BETWEEN THE LIFTING SPRINGS AND SPRING CAPS PROVIDED ON THE TOP OF THE LIFTING PINS.

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