WO1980001406A1

WO1980001406A1 - Slide valve

Info

Publication number: WO1980001406A1
Application number: PCT/DK1980/000001
Authority: WO
Inventors: J Sorensen; M Broe
Original assignee: Borma Armatur As
Priority date: 1979-01-05
Filing date: 1980-01-07
Publication date: 1980-07-10
Also published as: GB2050581B; GB2050581A; SE8006193L; DK4879A

Abstract

Slide valve with a valve body (3) which is movable in a valve spindle housing (5) and arranged to sealingly engage the wall of the flow channel (2) via a first sealing means (18) in the closed position of the valve, a second sealing means (10) being provided to prevent flow between the flow channel (2) and the valve spindle housing (5) said second sealing means (10) being firmly fitted in the valve spindle housing (5) and sealingly engaged with the sides of the valve body (3).

Description

Slide Valve - - - - - - - - - - -

The invention relates to a slide valve with a valve body which by means of either a valve spindle, pneumatic actuation means or the like is movable transversely to a fluid flow channel between a first position in which the valve is closed, and a second position in which the valve is open with the valve body located in a valve body housing. The valve contains sealing means, such as packings which are arranged to seal between mutually movable parts in the valve. The invention will be explained below by way of an example, it being assumed that the actuation means of the valve body are a spindle mechanism in which case said valve body housing is normally referred to as a spindle housing.

It is a well-known problem in respect of valves of the present type that they may stick, especially after having been open for an extended period of time. The problem is particularly pronounced when the valve is mounted with the spindle extending vertically downwards, as is often the case in installations in service corridors. In the past, this drawback was caused by the spindle housing acting as a large dirt pocket so that impurities might be deposited in the threads of the spindle. This cause, has been obviated e.g. by the valve disclosed in the German Auslegeschrift 1209 384, the valve body of said valve being provided with an annular packing ring which is arranged to engage with the interval wall of the spindle housing.

The latter, known valve, however, may also stick, which is now caused by a. dirt pocket with the shape of a ring chamber that is defined by the internal wall of the spindle housing, the valve body and said packing. Owing to lime or rust the valve body may become firmly attached direct to the spindle housing by "putty effect", and in less pronounced cases the packing may stick. When the valve is forced to a closed position the packing will be torn loose and be destroyed partly as a consequence of it being torn loose and partly because of the passage up the incrusted, rough spindle housing wall.

The object of the invention is to provide a slide valve having a smooth passage, i.e. essentially no dirt pockets so that a valve will be obtained in which the packings remain, intact irrespective of position of mounting and no matter how long the valve has been in the open or closed positions.

This object is achieved by constructing the valve as specified in the characterizing portion of claim 1. As depositing of impurities in dirt pockets is importantin the open position of the valve, the valve of the invention offers the fumdamental advantage over known valves that the part of the valve body which is to slide on the second sealing means when the valve is to be closed again after having been open for an extended period of time, has been present in the spindle housing in which there are no impurities from the flowing fluid thanks to the endless packing ring, so that the valve body is smooth and does not destroy the packing ring. As the packing ring essentially conforms to the bottom of the valve body, the lower edge of the valve body may, in the open position of the valve, extend very close to the packing ring, to thereby minimize the possibility of dirt pockets.

The thrust ring mentioned in claim 2 serves not only to distribute the thrust on the packing ring in the closed position of the valve, but is also arranged to press, e.g. by means of screws in the spindle housing, the packing ring against a seat in the spindle housing with a predetermined abutment force so that the packing ring abuts around the valve body with a predetermined force and friction dependent of said force.

The cross-section of the flow channel may have various shapes, e.g. the bottom of the valve body may be wedge-shaped, but preferably the cross-section of the fluid flow channel is rectangular, which partly allows a simplified construction and partly results in a smaller height of the spindle housing. Thus, the packing ring may in simple manner be caused to be located very close to the flow channel itself so that the dirt pockets, if any, will be as small as possible.

Usually, slide valves have in addition to the sealing means already mentioned a packing ring on the valve body around its edge for engagement with the wall of the flow channel in the closed position of the valve. When the flow channel has a shape like the one defined in claim 3, it may be difficult to achieve a sufficiently large abutment pressure between the second packing ring and the channel walls which are essentially parallel with the direction of movement of the valve body. The abutment pressure may be increased by means of the thrust pads mentioned in claim 4 which may extend right up to point on a level with the closed packing ring and serve as part of an engagement shoulder in the closed position of the valve.

The invention will be explained more fully below in the following description of an embodiment with reference to the drawing, in which

fig. 1 is a longitudinal section of a slide valve according to the invention, while

fig. 2 is a transverse view of the valve of fig. 1, seen towards the valve body, partly in section.

The embodiment shown in fig. 1 of the slide valve of the invention comprises a valve housing 1 which a flow channel 2 for a fluid extends through. The valve housing 1 has attached thereto a valve mechanism comprising a valve body 3 and a valve spindle 4 which is fitted in a spindle housing 5. The spindle 4 extends through the spindle housing 5 and is at the top connected to a handwheel 6.

The valve body 3 consists of several parts, which are also shown, partly in section, in fig. 2. The lower end of the valve spindle 4 is threaded for cooperation with a spindle nut 7, which is secured in the valve body against axial movement by means of a bridge 8 and a thrust pad 9 for acting on a first packing ring 10 according to the invention via a clamping ring 11. A second thrust pad 12 is mounted transversely to and connected to the thrust pad 9 and has a central hole 13 for receiving two bushings (of which the bushing 14 can be seen in figs. 1 and 2). The bushings serve as spacers between a first and a second valve plate 15 and 16, respectively, which constitute the part of the valve body 3 that may be moved down into the flow opening 2 for obstructing flow of fluid through it. The valve plates are clamped together by means of screws (17 on fig. 2), and along the edge a second packing ring 18 is fitted between the valve plates 15 and 16 which is arranged to sealingly engage the walls of the flow channel in the closed position of the valve by clamping means, which will be described later. According to the invention the packing ring 10 is firmly mounted in the spindle housing 5, it being clamped between a seat 19 and the clamping ring 11 by means of screws, of which the screws 20, 21 can be seen in fig. 1. This construction allows the abutment pressure of the packing ring 10 on the valve plates 15, 16 to be adjusted by means of the screws 20, 21 so that the packing ring 10 is in sealing engagement all the way round the valve plates, but not harder than that said plates are sufficiently movable when the valve body is reciprocated by turning the handwheel 6.

When the valve is. in the closed position as shown in the figure, the thrust pad will compress the packing ring 10 additionally via the clamping ring 11 which has bores for the screws 21, 20 so that the packing ring 10 is in effective sealing engagement with the valve plates 15, 16 and prevents flow of fluid via the interior of the spindle housing 5.

As will be explained later the cross-section of the flow opening 2 is preferably rectangular, and in order for the second packing ring 18 to sealingly engage the vertical sides of the flow channel 2 in all conditions, two thrust keys 23 and 24 are provided in the valve body 3 which are acted on by the respective sides and bottom 22 of the wedge-shaped thrust pad 12. Owing to the wedge shape of the thrust pad 12 the thrust keys 23, 24 will exert an even, uniformly distributed thrust along their respective halves of the packing ring 18. The thrust keys 23, 24 may extend so high that they serve (at 25 in fig. 2) as an engagement shoulder for the packing ring 10 in the space between the valve plates 15, 16.

When the valve is in the described, closed position no impurities will be deposited in the interrupted flow of fluid, and the valve plates 15, 16 will accordingly remain clean, apart from a possible layer of corrosion which may be prevented by a protective layer, e.g. teflon on the valve plates. Depositing of impurities have till now been significant with the valve in the open position, and especially when the valve is located with the handwheel 6 facing downwards. Depositing takes place as a consequence of dirt pockets which in the valve of the invention are very small or non-existent owing to the essentially smooth passage which is achieved by the invention. When the valve is in the fully open position, the bottom of the valve body may either be flush with the underside of the packing ring 10 or be flush with the upper wall of the flow channel 2. In the first case, a dirt pocket will be produced with a depth corresponding to the height of the seat 19, but it is observed that the impurities cannot be deposited between mutually movable faces, the packing ring 10 being in sealing engagement around the valve plates 15, 16. In the second case a dirt pocket will be produced between the valve plates and the seat 19, but thanks to the rectangular cross-section of the flow channel 2 the sealing ring 10 may be located very close to the flow channel 2 so that the depth of the dirt pocket can be made very small, depending upon the required thickness of the seat 19. Alternatively, the packing ring 10 may have an annular, downwardly extending lip (not shown in the figure) so that no dirt pockets will be produced at all and so that a completely smooth passage will be provided.

Even though the valve of the invention is open for an extended period of time, there is no risk of such an accumulation of impurities that the valve body will stick. When the valve is to be closed again, the packing ring 10 slides on the surface of the valve plates 15, 16 which in the open position were present in the spindle housing 5 in which they are protected against impurities. The invention is not restricted to the square flow opening which is shown in the figures, but is also useful with other cross-sectional configurations, it being possible to maintain the smooth passage and the sealing engagement between the flow channel and the valve housing when the packing ring 10 conforms to the bottom of the valve body.

Claims

P a t e n t C l a i m s : - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

1. A slide valve with a valve body which is movable transversely to a fluid flow channel between a first position in which the valve body obstructs the flow of fluid, and a second position in which the entire valve body is located in a valve body housing, first and second sealing means being provided for fluid sealing engagement with the internal wall of the flow channel and the valve housing, respectively, ch a r a c t e r i z e d in that the second sealing means comprise a closed packing ring firmly fitted in the valve body housing essentially conforming with the bottom of the valve body and arranged for unbroken engagement with the valve body both in its first and second positions.

2. A slide valve according to claim 1, wherein the valve body has a thrust pad for acting on the packing ring perpendicularly to its plane in the first position of the valve body, c ha r a c t e r i z e d in that the thrust pad acts on the packing ring via a thrust ring which is movable towards the packing ring and is arranged to press the packing ring against a seat in the valve body housing with a predetermined force.

3. A slide valve according to claim 1 or 2, c har a c t e r i z e d in that the cross-section of the fluid flow channel is essentially rectangular so that the two opposite channel walls are parallel with the direction of movement of the valve body.

4. A slide valve according to claim 3, wherein the first sealing means comprise a second packing ring fitted on the valve body so that in the first position of said valve body it abuts on three of the internal walls of the flow channel, c h a r a c t e r i z e d in that second thrust pads are provided in the valve body which in the first position of the valve body are arranged to act on the second packing ring in directions which each have components perpendicular to two of the said channel walls adjoining each other.