IE45240B1 - Improvements in or relating to vacuum shut-off valves - Google Patents

Abstract

The invention relates to a control valve for fluid and in particular for vacuum installation. The valve comprises a rotating element 8 inside a body 1, each of the elements 8 and body 1 having openings 2, 3 can be aligned; the element 8 carries sealing elements 16, 17 which can close the openings 2, 3 of the body 1 and a mechanism 14, 15 to move said elements 16, 17 away from said openings 2, 3 by means of which any friction between the elements 16, 17 and the inside of the valve body is practically eliminated during the operation of the valve. The mechanism 14, 15 is, in one embodiment, constituted by pneumatically or hydraulically actuated bellows.

Description

The present invention relates to rotary vacuum shutoff valves.

Vacuum shut-off valves should ideally require little or no maintenance and should, particularly when used in high vacuum systems, be free from leakage problems. Conventional vacuum shut-off valves generally include sealing members which are always in intimate contact with the interior of the valves, so that when the valves are operated friction occurs between the sealing members and the interior surface of the valves.

The sealing members and the interior surfaces of the valve therefore have to be made of carefully selected, compatible material, but even so rapid deterioration of the sealing members occurs. Thus generally the reliability of such valves is poor, they have a short working life between maintenance periods, and their range of applications is small. In addition, because of the need to minimise leakage rates and frictional forces in the valves, the passage area in these valves is usually very small in comparison with the overall size of the valves. Vesselevacuation rates using such valves are therefore in general low».

A need exists therefore for vacuum shut-off valves, which do not possess these disadvantages.

An object of the present invention is to provide a vacuum shut-off valve, in which friction between the sealing members and the interior of the valve during operation of the valve is substantially eliminated. ίθ According to the present invention there is provided a vacuum shut-off valve comprising an outer body having inlet and outlet ports, a rotatable inner body having ports adapted to communicate with the inlet and outlet ports when the valve is in an open condition, sealing members mounted on the inner body and arranged to register with the inlet and outlet ports of the outer body when the valve is in a closed condition, the sealing members being displaceable laterally with respect, to the axis of rotation of the Ιθ inner body, and means for bringing the sealing members into intimate contact, wi.h the peripheries of the inlet and outlet ports of the outer body to effect a fluid-tight seal when the valve is in a closed condition, wherein the outer body includes at least one opening through which the interior IS of the valve can be evacuated, which opening(s) is not closable by operation of the valve, Xn a preferred form of the invention, the means for brining the sealing members into intimate contact with the peripheries of the inlet and outlet ports comprises bellows units arranged to effect the lateral displacement of the sealing members. The bellows units can be actuated either hydraulically or pneumatically. Alternatively, the sealing members can be moved mechanically.

Since friction between the sealing members and the interior of the valve body operation of the valve is substantially eliminated, it is not essential to select the material for these parts with a view only to reducing the friction between them. The range of applications of the present valves is therefore very large.

The valve according to the invention can be made of an all-metal construction so as to enable the valve to be subjected to high temperatures, as for example in the practice of high vacuum technology, to drive off adsorbed or absorbed materials. If it is not required that the valve should be capable of withstanding high temperatures, for example if it is to be used in connection with onlylow vacua, then the sealing members can include seals made of a flexible synthetic raaterial such as that known as Viton11 (Registered Trade Mark} or a silicone rubber. Furthermore, the passage area of the valve can be freely Chosen in accordance with the requirements of the system in which the valve is used without constraints being imposed thereon arising from the problem of friction in the valve.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which:Figure 1 is a cross-sectional view of a first embodiment of the invention, Figure 2 is a longitudinal sectional view of the embodiment of Figure 1 taken on the lines 2-2, and Figure 3 is a longitudinal sectional view of a second embodiment of the invention, The two embodiments of the valves of the present invention will be described hereinafter with particular reference to their use as high vacuum shut-off valves in a vesselevacuation system. Other fields of use involving air or other gases in which the valves of the present invention can be used will, however, be obvious to those skilled in the art.

Referring to Figures 1 and 2, the vaive consists of a cylindrical outer body 1 which has an irlet port 2 for connection to a vessel to be evacuated and an outlet port 3 for connection to a pumping system, which is not shown. Ports 4 in the cylindrical wall of the outer body 1 and ports Sa and 5b in end pieces 6 and 7, respectively, of the outer body 1 enable spaces within it to be evacuated regardless of the condition of the valve. An elongate hollow inner body S is mounted in bearings 9 and 10 within the outer body 1 su that its longitudinal axis is coincident with that of the outer body 1. The inner body 8 has an open structure, two faces 12 and 13 of which carry bellows units 14 and 15, respectively. These bellows units are connected through the outer body to means (not shown) so that they can be operated remotely.

The space between the faces 12 and 13 of the inner body 8 constitutes a passageway for the gases being removed from the vessel to be evacuated, the ends of the passageway being in the form of ports adapted to communicate with the inlet, and outlet ports 2 and 3 of the outer body 1 when the vale is in an open condition.

From Figure 1 it will be seen that the outer body 1 of the valve is of a double walled construction. Whilst port 5a and 5b lead into the centre of the valve body, ports 4 lead into the interspace between the two walls of the outer body 1 so that evacuation of this interspace can take place as a safety measure should a leak develop in the innermost wall. Additionally a heating or cooling fluid could be circulated via ports 4 into this interspace for heating or cooling the valve.

In the embodiment being described, the ports 2 and 3 have a non-circular cross-section and the bellows units include sealing members 16 and 17 which conform to the S S 4 0 - 6 shape of the ports 2 and 3. Each of the sealing members and 17, has a groove 18 machined in it, the shape of which conforms to that of the peripheries of the ports 2 and 3. Positioned in the grooves 18 are metal vacuum seals 19 of the type known as Helicoflex seals. Xt is the seals 19 which actually form the vacuum seal when the valve is closed. Both the inner surface of the outer body and the contacting surfaces of the sealing members 16 and have a high surface finish and are honed and lapped together.

In order that fche valve can be subjected to bake-out procedures as are well-known in the high vacuum art, the entire valve is made of a high nickel-content alloy such as that known as Inconel (Registered Trade Mark). Alternatively, stainless steel can be used. In circumstances where it is not desired that the valve should be capable of withstanding high temperatures, the seals 19 can be made of one of the synthetic materials, such as silicone rubber, which are used for such purposes in the vacuum art.

In use, to close off the valve, the bellows units 14 and 15 are evacuated so that the sealing members l6 and 17 are withdrawn out of contact with the inner surfaces of the outer body 1, the inner body 8 is then rotated by the mechanism 11 until the seals 19 are in register with the peripheries of the ports 2 and 3· The bellows units 14 and 15 are then pressurised to bring the sealing members 16 and 17 into intimate contact with the peripheries of the ports 2 and 3, the final vacuum seal being made by the seals 19. Whilst the valve is closed off, the inner region is continuously evacuated via one or more of the ports 4, 5a or 5b provided in the outer body to prevent any leakage of air or vapour into whatever vessel is connected to the inlet port 2. To open the valve, the bellows units 14 and 15 are evacuated again and the inner body 8 is rotated 53 4 0 through a right angle by the mechanism 11 until the open sides of the body 8 are in registei· with the ports 2 and 3. If desired, the bellows units 14 and 15 can then be re-pressurised again to bring the sealing members into intimate contact with the inner surfaces of the outer body 1. for high temperature use, it is necessary to pressurise the bellows units pneumatically, whilst for low-temperature use, they can be pressurised hydraulically.

Figure 3 shows another embodiment of the invention in which the bellows units 14 and 15 are replaced by a toggle mechanism 30 actuated by a driving mechanism (not shown). In all other respects the second embodiment is the same as the first embodiment. Other mechanical devices for moving the sealing member l8 and 19 into and out of contact with the inner body 1 are wedges, or face cams.

Claims (6)

1. A vacuum shut-off valve comprising an outer bodyhaving inlet and outlet ports, a rotatable inner body having ports adapted to communicate with the inlet and outlet ports when the valve is in an open condition, sealing members mounted on the inner body and arranged to register with the inlet and outlet ports of the outer body when the valve is in a closed condition, the sealing members being displaceable laterally with respect to the axis of rotation of the inner body, and means for bringing the sealing members into intimate contact with the peripheries of the inlet and outlet ports of the outer body to effect a fluid-tight seal when the valve is in a closed condition, wherein the outer body includes at least one opening through v/hich the interior of the valve can be evacuated, which opening(s) is not closable by operation of the valve.

2. A valve as claimed in claim 1 wherein the means for bringing the sealing members into intimate contact with the peripheries of the inlet and outlet ports comprises bellows units arranged to effect the lateral displacement of the sealing members.

3. A valve as claimed in claim 2 wherein the bellows units are actuated pneumatically.

4. A valve as claimed in claim 2 wherein the bellows units are actuated hydraulically.

5. A valve as claimed in claim 1 or claim 2 wherein the sealing members are moved mechanically.

6. A valve as claimed in claim 1 substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.