GB2153973A

GB2153973A - Non-return valve

Info

Publication number: GB2153973A
Application number: GB08428226A
Authority: GB
Inventors: Gerhard Potrykus
Original assignee: Deutsche Babcock Werke AG
Current assignee: Deutsche Babcock Werke AG
Priority date: 1984-02-11
Filing date: 1984-11-08
Publication date: 1985-08-29
Also published as: DE3404982C2; GB2153973B; GB8428226D0; JPS60175877A; DE3404982A1

Abstract

A non-return valve comprises a valve cone (8) connected with a piston (12) which is guided in a liner (13) of a damping cylinder during the entire piston stroke. The piston (12) is provided with a throttle bore (17) and with further passages (16) which, in the closed setting of the valve, are disposed within the liner (13) and, in the open setting of the valve, within a space (14) which adjoins the liner (13) and is of enlarged diameter. <IMAGE>

Description

SPECIFICATION Non-return valve The present invention relates to a non-return valve.

In a non-return valve described in DE-PS 10 43 737, a damping cylinder with a piston is placed externally on a valve housing. The bore of the damping cylinder is connected with the interior of the valve housing by way of a groove which is so cut into a piston rod of the piston that in the closed setting the groove end at the side of the piston, and in opened setting the other groove end, are disposed in the region of a wall separating the damping cylinder from the valve housing. In such an arrangement, the outflow cross-sections can be arranged to be only small so that the course of the damped closing movement of a valve cone of the valve can hardly be influenced.

The non-return valve is held in open setting through the force of a fluid flow against the valve cone. Should the flow reverse in the event of a fault, for example due to a fracture in a feed duct, then the arising pressure gradient causes the valve to close the damaged duct automatically and in a short time so as to keep the quantity of fluid flowing back as small as possible. However, the delay of the fluid flow may not be too great in such a rapid closure of the valve cone, because in that case there is a risk that pressure shocks occur and the valve cone hits too hard on the valve seat. These risks are avoided through the damping of the closing movement of the piston.

In a non-return valve disclosed in DE-AS 27 57 352, the piston of the damping equipment enters into the damping cylinder only on the start of the second phase of the closing travel.

An annular gap is disposed between the inside wall of the damping cylinder and the piston so that the piston is movable in the damping cylinder free of contact until reaching its end position. However, a gap between the piston and the damping cylinder impairs the damping of the closing movement.

It would thus be desirable to provide guidance of the piston in the damping cylinder with a small gap over the entire stroke range, an effective damping being obtained with a rapid closing movement.

According to the present invention there is provided a non-return valve comprising a valve housing defining a flow duct and a freely movable control element which is operable to close the duct on return flow therethrough and which comprises a valve body co-operable with a valve seat in the duct and a piston connected by a rod to the valve body and movable in a damping cylinder in the housing between a first and a second end position in which the valve body is respectively engaged with and disengaged from the seat, the cylinder comprising a first portion defined by wall means guiding the piston throughout said movement thereof and a second portion of greater diameter than the first portion and the piston being provided with at least one flow constricting passage interconnecting the cylinder regions at either end of the piston and with at least one further passage so arranged as to open into the second portion of the cylinder for interconnection of said cylinder regions when the piston is in its second end position and to be closed by said wall means during movement of the piston into its first end position.

In a non-return valve embodying the invention, the piston remains guided in the damping cylinder over its entire stroke range, whereby the play between the piston and the cylinder wall means can be kept small such as to enable effective damping of the closing movement. The passages in the piston can be given a cross-sectional shape which is adapted to the particular requirements. As a result, different regulating characteristics can be executed for the course of the closing speed.

An embodiment of the present invention will now be more particularly described by way of example with reference to the accompanying drawing, the single figure of which is a longitudinal sectional view of a non-return valve embodying the invention, the valve being shown in open setting in the righthand half of the figure and in closed setting in the lefthand half.

Referring now to the drawing , there is shown a rapidly closing non-return valve comprising a valve housing which defines a flow duct and which has a casing 1, an inlet stub pipe 2, an outlet stub pipe 3 and a valve seating surface 4 in the flow duct. A cover 5 is fastened by means of screws 6 on the casing 1.

A valve cone 8 provided with a sealing surface 7 is arranged to be axially displaceable in the casing 1. The valve cone 8 has a portion 9 projecting relative to a sealing surface 7 thereof. The valve cone 8 is fastened, on its side remote from the pipe 2, to a spindle 10 guided in a guide bush 11. The spindle 10 at its other end carries a piston 12, which is slidingly guided in a damping cylinder.

The damping cylinder consists of the bore of a liner 1 3 and an adjuining space 14 of increased diameter. The liner 1 3 represents a prolongation of the guide bush 11 and is formed integrally therewith. The liner 1 3 is held between a shoulder in the casing 1 and in the cover 5. The cover 5 is provided on its inside with a recess which forms the space 14 above the liner 1 3.

The piston 1 2 is inserted into the damping cylinder in such a manner that it is guided in the liner 1 3 with a very small play relative to the wall of the liner 1 3 during its entire stroke. Relief grooves 15, which produce a labyrinth effect, are provided in the upper part of the piston 1 2.

The piston 1 2 has an annular skirt at its end portion closer to the valve cone 8. Passages 16 are provided in the skirt and are so arranged that in one end setting of the piston 12 (righthand side) they are disposed in the space 14 above the liner 1 3 and in the other end setting (lefthand side) within the liner 1 3.

Preferably, the passages 1 6 have a constant cross-section only in their lower part, which cross-section narrows upwardly, for example in the form of a triangle.

The piston 1 2 is penetrated in axial direction by one or more throttle bores 1 7.

Equally, the liner 1 3 is provided in axial direction with one or more bores 18, by which a connection is produced between the flow duct in the valve housing and the space 14 above the piston 1 2.

The valve cone 8 is held in open setting (righthand side) by the force of medium flowing in through the stub pipe 2. A return seal 1 9 of the valve cone 8 bears against the guide bush 11. At the same time, the greater part of the piston 1 2 is disposed above the liner 1 3 in the space 14. Should the flow reverse in the event of a fault, for example fracture of a duct connected to the stub pipe 2, then the valve cone 8 due to the arising pressure gradient closes the damaged duct automatically and in short time. The closing movement of the valve cone 8 is initially undamped. The more deeply the piston 1 2 is drawn into the liner 1 3 in the course of the closing movement, the greater the reduction in height and width of the cross-sections of the passages 1 6. As a result, there is a reduction in the quantity of the medium which can escape through the passages 1 6 from the cylinder space underneath the piston 1 2.

After the complete overlapping of the passages 16 by the liner 13, the medium can escape only through the throttle bore 1 7. The closing movement is thus increasingly damped. Through changes in the shape of the passages 16, different regulating characteristics can be obtained for the course of the closing speed.

Claims

1. A non-return valve comprising a valve housing defining a flow duct and a freely movable control element which is operable to close the duct on return flow therethrough and which comprises a valve body co-operable with a valve seat in the duct and a piston connected by a rod to the valve body and movable in a damping cylinder in the housing between a first and a second end position in which the valve body is respectively engaged with and disengaged from the seat, the cylinder comprising a first portion defined by wall means guiding the piston throughout said movement thereof and a second portion of greater diameter than the first portion and the piston being provided with at least one flow constricting passage interconnecting the cylinder regions at either end of the piston and with at least one further passage so arranged as to open into the second portion of the cylinder for interconnection of said cylinder regions when the piston is in its second end postion and to be closed by said wall means during movement of the piston into its first end position.

2. A valve as claimed in claim 1, wherein the valve body comprises a sealing surface engageable with the valve seat and a portion projecting relative to the sealing surface at a side of the body remote from the rod.

3. A valve as claimed in either claim 1 or claim 2, wherein the piston comprises a skirt and the or each further passage is provided by an aperture in the skirt.

4. A valve as claimed in claim 3, wherein the cross-section of at least part of the or each aperture increases in size in a direction corresponding to the direction of movement of the piston from its second to its first end position.

5. A valve as claimed in any one of the preceding claims, wherein the housing is provided with a passage connecting the duct to the second portion of the cylinder.

6. A valve as claimed in claim 5, wherein said housing passage is provided by a bore in a liner defining the wall means, the bore extending substantially parallel to the axis of the cylinder.

7. A valve as claimed in any one of the preceding claims, wherein the piston is provided at its circumference with relief grooves.

8. A non-return valve substantially as hereinbefore described with reference to the accompanying drawings.