GB2131522A

GB2131522A - Fluid flow control valve

Info

Publication number: GB2131522A
Application number: GB08330672A
Authority: GB
Inventors: Harold Hughes; Andrew Williams
Original assignee: DRALLIM IND
Current assignee: DRALLIM IND
Priority date: 1982-11-24
Filing date: 1983-11-17
Publication date: 1984-06-20
Also published as: GB8330672D0

Abstract

In a fluid flow control valve a closure member 18 of deformable material is secured to or forms part of a carrier 17 rotatably connected to a valve stem 7 mounted for rotation and longitudinal movement within the valve body so that, upon rotation of the stem 7, the carrier 17 is caused to rotate with the stem 7 and move longitudinally until the closure member 18 engages a wall 6 of the bore whereupon continued movement of the valve stem causes the closure member 18 to move longitudinally without rotation to seal deformably into contact with the end wall 6. The closure member 18 may be complementary with the bore 3, and may be of plastics, rubber or other elastomers. Various ways of connecting the carrier 17 with the stem 7 are described. <IMAGE>

Description

SPECIFICATION Fluid flow control valve This invention relates to fluid flow control valves.

Many fluid flow control valves do not provide an unobstructed flow path for the fluid and create a pressure drop even when fully open. Types of valve which have been developed to minimise these disadvantages include tapered plug valves and ball valves. However, to achieve a tight shutoff with the known valves requires the manufacturer to perform machining operations on the closure member and/or the seats to close tolerances and accordingly such valves are relatively costly to manufacture.

An object of the present invention is to provide an improved fluid flow control valve which is inexpensive to manufacture, has a minimum number of operating parts, and which provides a reliable seal when closed.

A fluid flow control valve according to the invention comprises a valve body formed with a transverse bore having a solid end wail, a fluid passageway defining inlet and outlet ports in the side wall of the bore, a closure member of deformable material secured to or forming part of a carrier rotatably connected to a valve stem, the valve stem being mounted for rotation and longitudinal movement within the valve body whereby upon rotation of the stem the carrier of the closure member is caused to rotate with the stem and move longitudinally until the closure member engages a wall of the bore whereupon continued movement of the valve stem causes the closure member to move longitudinally without rotation and into contact with the end wall of the bore and to deform to seal the ports.

The use of a closure member of deformable material makes it unnecessary to machine seats in the valve body or on the closure member which is a substantial advantage in terms of reducing manufacturing costs. The deformation of the closure member within the passageway is a particularly simple and inexpensive way of providing a reliable seal. The closure member is preferably tapered but can be of any desired shape capable of deforming sufficiently to seal the passageway. The closing force exerted by the closure member need be sufficient only to cause the material to deform sufficiently to enter into sealing engagement with the passageway.

The fact that the closure member initially rotates with the valve stem and that, upon contact being made between the closure member and the valve body, the closure member moves longitudinally without rotation into sealing engagement with the passageway, provides unique advantages over known valves which include simliar deformable closure members.

Initial rotation ensures that the portions of the closure member aligned with the passageway vary on use of the valve thereby minimising the possibility of permanent distortion of the member; subsequent longitudinal movement of the closure member without rotation minimises wear of the closure member occasioned through relative movement between the member and the valve body.

Further, because in order to provide a seal, a valve in accordance with the invention does not rely upon contact between machined seats on members of a hard material, such as metal, the reliability of the seal is assured and the valve has been found particularly suitable for use in vacuum applications.

The invention will now be described by way of .example with reference to the accompanying diagrammatic drawings in which: Figure 1 is a side elevational view in section of a fluid flow valve in accordance with the invention; and Figure 2 is a side elevational view in section of an alternative fluid flow valve in accordance with the invention.

Referring to Figure 1, the fluid flow control valve shown comprises a valve body 1 having a through flow passage 2 for the fluid to be controlled. A transverse bore 3 in the valve body 1 intersects the fluid passageway 2 such that ports 4 and 5 are formed in side walls of the bore 3.

The bore 3 has a solid end wall 6 recessed into the valve body.

A valve stem 7 is threadedly mounted in the outer end of the bore 3. A carrier 8 is threadedly mounted within the stem 7, by screw threads of opposite hand to the screw threads on the stem 7 and the bore 3, and carries a valve closure member 9. The closure member 9 is in the form of a plug of a deformable material. The valve is shown in the drawing with the closure member 9 in a position intermediate the fully closed and fully open position. Operation of the valve is achieved by rotating the valve stem in the appropriate direction. Closure is obtained by rotating the valve stem 7 to cause it to advance into the bore 3 towards the end wall 6. The carrier 8 and closure member 9 rotate with the stem.When the closure member 9 contacts the end wall 6 of the bore 3 it will cease to rotate because of the frictional forces between the member 9 and the wall 6, and further rotation of stem 7 will cause the carrier 8 to travel further into the bore 3 by means of the opposite hand threads. Since the valve closure member cannot move further axially, the material thereof will deform to take up the profile of the bore without scuffing and tearing, since it is no longer rotating, the material being under compression at this time. The valve closure member 9 is thus forced in compression against the ports 4 and 5, sealing the ports and preventing flow of fluid through the passageway 2.

The opening of valve proceeds in reverse sequence. When fully open, the closure member 9 is lifted to a position where it does not project into the passageway 2 so that unobstructed through flow of fluid is achieved.

The bore 3, and specifically the region thereof which contains the ports 4 and 5, and the valve closure member 9, are shaped to provide the condition that the material of the valve closure member 9 deforms so as to close the passageway 2 is satisified. As shown, the bore 3 is tapered in the vicinity of the ports 4 and 5, and the closure member 9 is a frusto conical tapered plug.

Tapering of the plug ensures minimal contact between any previously extruded portion of the plug which has yet to return to its original location and the bore wall as the plug is withdrawn.

The closure member 9 can be of any material that will deform to meet the requirements of this invention. Plastics, rubber and other elastomers are suitable materials. The hardness of the material should be such that it will deform sufficiently to provide a seal upon the application of a desired closing force; generally this condition will be satisfied when the closing force causes the material to extrude a small distance into the ports 4 and 5 in the closed position of the valve. If the material is too hard, satisfactory sealing may not be obtained. Conversely, if it is too soft, the material may squash down below the ports. The hardness of the material is a function of the shape and size of the closure member 9 and the bore 3, and of the ports 4 and 5, and those skilled in the art will have no difficulty in selecting a suitable material for use in a given configuration.

If desired a stop (not shown) may be provided to prevent excessive forces developing upon closure of the valve.

The fluid flow control valve illustrated in Figure 2 is similar in many respect to that illustrated in Figure 1 and like integers to those illustrated in Figure 1 have been given the same reference numerals. Thus the control valve illustrated in Figure 2 comprises a valve body 1 having a passageway 2 for the flow of fluid to be controlled. A transverse bore 3 in the valve body intersects the fluid passageway 2 such that ports 4 and 5 are formed in the side walls of the bore.

The bore 3 has a recessed solid end wall 6, the sides of the recessed portion 6 being generally parallel and normal to the lower boundary of the passageway.

A valve stem 7 is threadedly mounted in the outer end of the bore 3 and the bore is closed by an internally threaded cap 12.

Dependant from the under side of the valve stem 7 is a stem 1 3 formed with a neck portion 14 and supporting a spherical nodule 1 5 which is embraced by a complementary shaped recess or cup 1 6 set in the adjacent end of a metal carrier 1 7 of a valve closure member 18 manufactured from a suitable deformable material. The carrier 1 7 is preferably manufactured from stainless steel and includes a stem 19 which carries the closure member 18. The closure member 18 may be secured to the stem 19 in a number of ways.

Thus the material of the member 18 may be bonded or moulded in situ onto the stem; alternatively the stem may be threaded, the closure member being forced onto the stem and retained in place by the stem threads.

The length of the deformable closure member exceeds that of the carrier stem to define a hollow 20 in the free end of the closure member. The depth of this hollow determines the extent to which the closure member can be moved downwardly following initial contact between the member 1 8 and the recessed end wall 6, contact between the lower end of the carrier stem and the end wall providing a positive stop to movement of the closure member. In this connection it is important that the extent of travel of the threaded valve stem 7 within the valve body is sufficient to ensure that the end of the carrier stem can contact the end wall 6 upon closure of the valve.

Thus the permitted longitudinal travel of the valve stem should always be greater than the distance between the end of the carrier stem and the base of the recessed end wall 6.

The lower portion of the closure member 18 is tapered to enable the closure member to be lifted away from its seating with no or minimal contact between those portions of the member which were previously extruded into the passageway and which may not immediately return to their original locations within the closure member.

The presence of the recess 6 provides an efficient and complete seal between the ports and the passageway when the valve is closed.

In an alternative unillustrated embodiment the carrier is formed with a nodule or ball which is embraced within a complementary shaped recess or cup formed in the underside of the stem 7.

Thus a ball and socket joint is formed between the carrier and the valve stem. In a further unillustrated embodiment the carrier and valve stem are connected through a separable link formed at each end with a ball or nodule which is embraced within complementary recesses or cups formed in the carrier and valve stem.

The valve stem may be manufactured from any suitable material these including a metal such as stainless steel or a plastics material.

Other alternatives and modifications will readily occur to those skilled in the art.

Claims

1. A fluid flow control valve comprising a valve body formed with a transverse bore having a solid end wall, a fluid passageway defining inlet and outlet ports in the side wall of the bore, a closure member of deformable material secured to or forming part of a carrier rotatably connected to a valve stem, the valve stem being mounted for rotation and longitudinal movement within the valve body whereby upon rotation of the stem the carrier of the closure member is caused to rotate with the stem and move longitudinally until the closure member engages one wall of the bore whereupon continued movement of the valve stem causes the closure member to move longitudinally without rotation into contact with the end wall of the bore and to deform to seal the ports.

2. A valve as claimed in Claim 1 wherein the end wall of the bore is recessed below the lower boundary of each port to provide a seating for the abutting end of the valve closure member.

3. A valve as claimed in claim 1 wherein the carrier includes a stem about which is secured or formed the deformable closure member.

4. A valve as claimed in Claim 2 wherein the closure member is moulded in situ about the stem or is bonded or secured mechanically thereto.

5. A valve as claimed in Claim 3 or Claim 4 wherein the closure member is cylindrical in shape and wherein the length of the carrier stem is less than that of the closure member, the closure member being unsupported over a portion of its length.

6. A valve as claimed in Claim 5 wherein the distance between the free end of the valve stem and the solid end wall of the bore is less than the permitted longitudinal travel of the valve stem within the valve body.

7. A valve as claimed in any one of the preceeding claims wherein the closure member is tapered.

8. A valve as claimed in any one of the preceeding claims wherein the connection between the carrier of the closure member and the valve stem comprises a ball and socket joint which permits rotation of the carrier and closure member with the valve stem until engagement of the closure member with one wall of the bore.

9. A valve as claimed in Claim 8 wherein the carrier is formed with a protrusion or nodule which is embraced within a complementary shaped recess set in the adjacent end of the valve stem.

10. A valve as claimed in Claim 8 wherein the valve stem is formed with a protrusion or nodule which is embraced within a complementary shaped recess set in the adjacent end of the carrier.

11. A valve as claimed in any one of Claims 1 to 7 wherein the carrier of the closure member is threadedly connected to the valve stem, the respective screw threads of the carrier and the valve stem being of opposite hand whereby upon rotation of the stem the carrier is caused to rotate with the stem and move axially until the closure member engages one wall of the bore whereupon continued rotation of the valve stem causes the closure member to move longitudinally without rotation and subsequently to deform so as to close the passageway.

12. A fluid flow control valve substantially as herein described and as described with reference to Figure 1 of the accompanying drawings.

1 3. A fluid flow control valve substantially as herein described with reference to Figure 2 of the accompanying drawings.