GB2101719A - Slide valve - Google Patents

Abstract

A slide valve comprises a valve plate 14 which slides in a slot in the housing 4 between positions where it blocks and opens a passage through the housing, the opposite edges of the plate 14 being guided in interrupted fluid channels formed by spaced projections 16 on the inner walls of the valve housing. The use of these projections instead of a guide groove reduces the build up of deposits. The plate 14 has a sealing strip 22 around its outside edge and this is retracted with the plate 14 through the stuffing box 34. <IMAGE>

Description

SPECIFICATION Slide valve The present invention relates to slide valves, that is to say valves comprising a sliding valve plate in a slot'in a housing, the plate being slidable in and out, through the slot, to block and open a passage through the housing.

Known slide valves have a U-shaped groove, machined in the valve housing, into which is inserted a sealing strip. The U-shaped groove also serves to guide the closure plate. The edge of the plate presses against the U-shaped sealing strip when the valve is closed. In order to provide a seal around the whole of the passage through the housing, the sealing strip also extends in the slot across the face of the plate. The sealing strip is accordingly continuous around the passage.

Although conventional slide valves are sufficient in many applications, there are probiems associated with using valves of this type, particularly when valving powdery, erosive substances, e.g. coal dust. The sealing strip is permanently in contact with the erosive substance flowing past the strip. This causes rapid wear of the sealing strip and subsequent deterioration in the efficiency of the valve.

In addition in valves having a U-shaped groove machined into the valve housing, it is possible for the erosive powdery substances to become lodged in the machined groove, particularly where the seal has been eroded and pitted. This may cause the closure, guided by the groove, to jam during operation and, if the substance is inflammable there is a risk of an explosion.

Furthermore in conventional valves the closure plate is exposed when withdrawn from the valve housing and is therefore subject to possible damage and contamination. This results in the closure plate jamming when it is returned to the valve housing.

According to the present invention there is provided a slide valve comprising a sliding valve plate in a slot in a housing, the plate being slidable in and out, through the slot, to block and open a passage through the housing, the plate having a sealing strip around its edge and the plate with the sealing strip through sealing means in the slot, whereby the sealing means and sealing stripform an uninterrupted seal around the passage when the plate is in the blocking position.

The invention will be described in more detail, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a front elevation of an embodiment of the invention showing the valve plate half-open, Fig. 2 is a side elevation of the embodiment of Fig.

1, and Fig. 3 is a fragmentary sectional view taken on line B-B in Fig. 1, showing the guide assembly and valve plate, with sealing strip attached. The guide assembly and closure plate are shown separated for clarity.

A valve housing 4 of a slide valve, formed by bolting together a cylindrical valve housing insert 6 and valve housing halves8 and 10, has a bore 12 through the insert 6.

Avalve plate 14 has parallel side edges 24 and a curved bottom edge 26 and slides in a slot formed in part by a channel in the housing half 10 and in part by a slot through the top of the insert 6. Within the insert, segments 7 of the housing haives 8 and 10 continue the line of the edges of the slot, whereby a U-shaped periphery is formed matching the shape of the valve plate.

The two valve housing halves 8 and 10 join at a plane co-extensive with one side of the plate 14; thus only one valve housing half 10 is machined to accommodate the plate 14.

The plate is guided within the bore 12 by rows of projections 16 on the segments 7 which, as is apparend from Figs. and 3, form interrupted channels guiding the edges 24 of the plate 14 as the plate moves into and out of the bore 12.

A continuous sealing strip 22, of Nitrile rubber for example, extends round the side edges 24 and base edge 26 of the valve plate 14. The strip is trapped in a groove formed by a rebate in a clamping strip 25 which is shown only in Fig. 3 and is held in place by machine screws (not shown). The edges of the rebates are formed with lips 30 which trap the strip 22 in its groove. The sealing strip 22 can also extend along the top edge of the closure plate 14 and be clamped thereagainst by plates 32.

A conventional stuffing box is used to form a seal in the slot around the plate 14 and includes a gland 34 which is tightened on to sealing material using bolts 36.

Atopworks housing 38, secured to the top of the valve housing 4 by bolts 40, comprise a pair of vertical side plates 42 spanned by a series of welded-in struts 44 spaced vertically and extending transversely between the plates 42. Windows 46 are arranged between the plates 42 and secured to the struts 44 so as to form a protective casing around the valve plate 14. The windows 46 allow the position of the valve plate 14 to be seen without removing the topworks housing 38.

Furthermore, it is easy to see if the stuffing box needs attention. If it becomes leaky, escaping material will be visible in thetopworks housing.

The top of the topworks housing 38 is formed by a universal adaptor plate 48, secured by bolts 50 to flanges on the side plates 42. The plate 48 is used to support the actuator device (not shown) and is predrilled to accept a variety of manual, hydraulic, pneumatic and/or electrical actuators. By way of example, Figs. 1 and 2 show the piston rod 20 of a hydraulic actuator connected to the valve plate by a clevis 18.

In operation, the substance passing through the slide valve is controlled by raising or lowering the valve plate 14. Although the plate is shown halfopen, with this type of valve, the plate is normally eitherfully closed or fully open.

On opening the valve fully, the plate 14 and its associated sealing strip 22 are lifted clear of the erosive substance flowing through the valve bore 12.

Since the sealing strip 22 is not in the path of the erosive substance when the valve is fully open, its working life is prolonged.

In addition, since the sealing strip 22 is secured to the valve plate 14, it is not necessary to machine a groove for the sealing strip in the valve housing 4.

Thus any powdery, erosive substance cannot become lodged and subsequent jamming of the valve plate 14 does not occur.

The projections 16, used to guide the valve plate 14, are adapted to ensure that there is only a minimum deposit of the erosive substance present during operation of the valve and effectively increase the area of the bore 12. Since the erosive substance cannot lodge in the guide projections 16, the risk of jamming in the valve plate 14 and also of explosion of retained inflammable material is reduced.

Claims (1)

1. A slide valve comprising a sliding valve plate in a slot in a housing, the plate being slidable in and out, through the slot, to block and open a passage through the housing and being guided by a plurality of spaced projections on the inner walls of the valve housing arranged, on each side of the valve plate, so as to form an intermittent guide channel about each of the opposite side edges of the valve plate.