GB2090946A

GB2090946A - Butterfly valve

Info

Publication number: GB2090946A
Application number: GB8138528A
Authority: GB
Original assignee: Dienes Werk fur Maschinenteile & Co KG GmbH
Current assignee: Dienes Werk fur Maschinenteile & Co KG GmbH
Priority date: 1981-01-02
Filing date: 1981-12-22
Publication date: 1982-07-21
Also published as: DE3100008A1; FR2497553A1; GB2090946B

Abstract

A butterfly valve, for use in an intake conduit of a compressor, has a closure disc (1) and operating shaft (2) provided with transverse passages (4, 5) which, as a function of operating pressure differences or manually, are uncovered to a greater or lesser extent by means of pistons (6, 14), to regulate leakage past the disc. <IMAGE>

Description

SPECIFICATION Butterfly valve The invention relates to a butterfly valve for use in an intake conduit of a compressor, the valve having a closure member which is carried on a shaft supported in a valve housing whereby the shaft projects out through a bearing passage provided in the housing and is provided at its projecting end with an operating member for rotating the shaft to open and close the valve, and the valve having a passage for providing leakage when the valve is closed.

When it is in the closed position, the butterfly valve should exhibit a certain degree of leakage, which principally depends upon the nominal output of the associated reciprocating compressor. In the case of butterfly valves of the type described above, such leakage is usually obtained by providing a passage which passes perpendicularly through the valve closure disc. The diameter of the passage is selected so as to correspond to the nominal output of the reciprocating compressor with which it is associated. For a range of nominal outputs, it is consequently necessary to provide closure discs having passages of varying sizes, and these must be held in stock.

In order to overcome this disadvantage in accordance with the invention, in a butterfly valve of the type referred to above, a plurality of the leakage passages extend radially through the shaft which is hollow; and a regulating piston, which operates in the hollow shaft in the region of the passages and is capable of closing the passages, is loaded in a direction to open the passages by a spring to a limiting position where a part of the piston abuts against an adjusting screw which is screwed into a female thread in the projecting end of the hollow shaft.

As the regulating screw is screwed further into the hollow shaft of the valve, the number of radial leakage passages which are closed off by the regulating piston increases, leading to a corresponding reduction in the remaining amount of leakage when the valve closure member is in the closed position. Such regulation of the leakage can additionally be carried out externally when the butterfly valve is installed, in contrast to the case of known butterfly valves.

The valve may also be provided with a control piston which operates in the hollow shaft in the region of further radial leakage passages and with a helical compression spring urging the control piston in a direction to close the further passages, the opposite end face of the control piston from the further passages being in communication via a blind hole through the hollow shaft with the suction side of the valve. By this means, additional radial passages which extend through the hollow shaft are available when the pressure difference between the opposite sides of the closed butterfly valve increases. This results in automatic regulation of leakage as a function of the induction power of each particular associated reciprocating compressor.

The regulating piston may be arranged to communicate with the pressure side of the adjoining compressor through a leak-off connection arranged between its outer end face and the adjusting screw, the leak-off connection passing through the wall of the shaft and the bearing of the shaft to the outside. By this means it is made possible, in the case of partial or transitory closing of the butterfly valve, for regulation purposes, for the leakage passages to remain closed off and only to be opened when the drive to the adjoining reciprocating compressor has been switched off, so that preparations are made for the no-load starting up of the compressor assembly.In a preferred arrangement for this purpose, a peripheral annular groove is provided in the hollow shaft and communicates both with an external connector in the housing and with a space behind the piston whereby the piston can be moved away from the adjusting screw against the spring loading upon application of fluid pressure through the connector.

An example of a valve constructed in accordance with the invention is illustrated diagrammatically in the accompanying drawings, in which: Figure 1 is a view, in the direction of flow, with the valve open; Figure 2 is a section taken on the line Il-li in Figure 1 , with the shaft and inner part of the closure member shown after rotation through 900; Figure 3 is a view, corresponding to that shown in Figure 1, but with the valve closed position; and, Figure 4 is a section taken on the line lV-IV in Figure 3.

The valve has a closure disc 1 which is joined to a hollow shaft 2 which passes diametrically through it and is carried at both ends in a flange housing 3. The complete valve installed in the flange is built into the intake pipe of a compressor in a known manner which is not shown. An open end of the hollow shaft 2, which is shown in the Figures at the right hand side, extends out from a right hand bearing passage of the flange 3 and is provided at its projecting end with an operating member which is not shown, for rotating the shaft and closure disc to open and close the valve.

The disc 1 and the hollow shaft 2 are provided with aligned radial passages 4, 5 which extend perpendicularly to the plane of the disc. A regulating piston 6 operates in the region of the passages 4, the piston being urged, into a position where it uncovers the radial passage 4 to a greater or lesser extent, by means of a helical compression spring 7, which is supported at its inner end by an inner shoulder 8 on the hollow shaft 2, up to a position where a piston rod 10 abuts against an adjusting screw 9, which is screwed to a greater or lesser extent into a female thread provided at the open projecting end of the shaft 2.

In the region of the piston rod 10, a peripheral groove 11 in the hollow shaft 2 communicates with a screw connection 1 2 in the flange 3, to provide a connection to the pressure side of the adjoining compressor. By this means, the regulating piston 6 can, during operation and when the closure disc 1 is opened to a greater or lesser extent, be pushed to its inner position where it closes off the passages 4, so that the resistance to flow during operation is exclusively and unequivocally dependent upon the extent of rotation of the disc 1, which improves exact output control.

When the drive to the adjoining compressor is switched off, the pressure at the output from the compressor and, consequently, at the outer end face of the regulating piston 6, drops, so that it takes up the position which can be seen in Figure 2 and allows non-load starting up of the compressor unit when the valve is closed.

A control piston 14 which is urged into a closing position with respect to the radial passages 5 by means of a helical compression spring 13, communicates with its right hand end face, as seen in the drawings, with the external outside pressure through at least one radial passage 5, and with its left hand end face communicates, via a blind passage 1 5 through the hollow shaft 2 and the side of the disc 1 which is directed towards the compressor, with the subatmospheric intake pressure of the compressor unit. As a result of this, an automatic regulation of leakage is achieved as a function of the particular power of the associated compressor unit.

Claims

1. A butterfly valve for use in an intake conduit of a compressor, the valve having a closure member which is carried on a shaft supported in a valve housing whereby the shaft projects out through a bearing passage provided in the housing and is provided at its projecting end with an operating member for rotating the shaft to open and close the valve, and the valve having a passage for providing leakage when the valve is closed, characterised in that a plurality of the leakage passages extend radially through the shaft which is hollow; and a regulating piston, which operates in the hollow shaft in the region of the passages and is capable of closing the passages, is loaded in a direction to open the passages by a spring to a limiting position where a part of the piston abuts against an adjusting screw which is screwed into a female thread in the projecting end of the hollow shaft.

2. A valve according to claim 1, characterised in that a peripheral annular groove is provided in the hollow shaft and communicates both with an external connector in the housing and with a space behind the piston whereby the piston can be moved away from the adjusting screw against the spring loading upon application of fluid pressure through the connector.

3. A valve according to claim 1 or claim 2, characterised by a control piston which operates in the hollow shaft in the region of further radial leakage passages and by a helical compression spring urging the control piston in a direction to close the further passages, the opposite end face of the control piston from the further passages being in communication via a blind hole through the hollow shaft with the suction side of the valve.

4. A valve according to claim 1, substantially as described with reference to the accompanying drawings.