GB2213286A

GB2213286A - Throttle valve

Info

Publication number: GB2213286A
Application number: GB8828044A
Authority: GB
Inventors: Wilhelm Strache; Werner Foller
Original assignee: Gestra AG
Current assignee: Gestra AG
Priority date: 1987-12-04
Filing date: 1988-12-01
Publication date: 1989-08-09
Anticipated expiration: 2008-12-01
Also published as: FR2624245B1; GB2213286B; DE3741120A1; GB8828044D0; FR2624245A1; IT1235160B; IT8848617A0

Description

IZ7 1 ' 'L_ U U 1 Title: THROTTLE VALVE This invention relates to throttle

valves and is particularly concerned with throttle valves of the type having a valve housing; throttling means arranged in the valve housing and comprising a valve seatingy a longitudinal duct and a group of radial throttling ducts; and a closing means which comprises a sliding element arranged so as to reciprocate in the longitudinal duct in the region of the throttling ducts and a sealing face arranged to mate with the valve seating.

Throttle valves of this type are used for controlling and regulating flows of media when large pressure differences exist. A larger or smaller number of the radial throttling ducts of the throttling means are cleared for the passage of medium, according to the respective stroke position of the closing means. This allows sensitive control or regulation of the quantity. It is known, for example from U.S. Patent Specification No. 3514074, that one or more abrupt, energy- consuming changes of direction can be provided in the throttling ducts to reduce the pressure in the traversing medium. For the same purpose, it is also known, for example, that one or more successive constrictions with interposed release chambers can be arranged in the throttling ducts.

The pressure difference determines the number of throttling measures required in a throttling duct and therefore influences the radial dimensions of the throttling means. In the known throttle valves, throttling means having a relatively large diameter are required if the pressure differences are very great. This, in turn, necessitates very bulky, heavy and expensive valve housings.

The present invention aims to provide a throttle valve of the type mentioned at the outset, for which a relatively compact valve housing can be used, even in the case of very high pressure differences.

Accordingly, the present invention provides a throttle 10 valve having a valve housing; throttling means arranged in the valve housing and comprising a valve seating, a longitudinal duct and a group of radial throttling ducts; and a closing means which comprises a sliding element arranged so as to reciprocate in the longitudinal duct in the region of the throttling ducts and a sealing face arranged to mate with the valve seating; wherein the throttling means comprises at least one additional group of radial throttling ducts, the or at least two of the throttling duct groups being spaced in succession, when viewed in the longitudinal direction of the throttling means; the closing means comprises at least one additional sliding element arranged so as to reciprocate in the longitudinal duct in the region of the or each additional throttling duct group; an inner annular chamber is provided between the sliding elements in the longitudinal duct; an outer annular chamber surrounding the throttling means in the region of a throttling duct group is provided; and at least one radial through duct is provided between the inner annular chamber and the outer annular chamber.

3 - r 4 At least two groups of throttling ducts are arranged in succession in the longitudinal direction of the throttling means. The radial dimensions of the throttling means are therefore kept relatively small.

The overall valve housing is substantially more compact in construction despite the greater length of the throttling means. It is therefore lighter and more economical. The additional sliding element in the throttling means ensures that an adequate number of throttling ducts is cleared in each group of throttling ducts and that perfect control/ regulation of the flow of medium is thus achieved.

In throttle valves of this type, a radial clearance between the sliding element of the closing means and the throttling means, though only small, is unavoidable. For this reason, medium is able to f low between the sealing face of the closing means and the valve seating when the sealing face of the closing means is raised slightly from the valve seating - i.e.

before the longitudinal duct of the throttling means is cleared up to the radial throttling ducts located closest to the valve seating. If there is a very large pressure difference between the inlet and outlet duct of the throttle valve, very high flow rates occur in the narrow gap between the valve seating and the sealing face of the closing means. These can cause wear due to erosion.

According to a preferred embodiment of the invention, therefore, the throttling means comprises an additional valve seating in the region of the additional throttling duct group and the closing means comprises an additional sealing face arranged to mate with the additional valve seating in the region of the additional sliding element. Pref erably, the two sealing faces of the closing means are reciprocable to a limited extent with respect to one another. The sliding elements are desirably each located upstream of the respective valve seating so that checking occurs at two successive, with respect to the flow of medium, positions. In order to open the throttle valve, only one closing means sealing face preferably the upstream sealing face when viewed in the direction of flow - is initially raised from its valve seating. The other closing means sealing face remains in the closed position due to the relative movability of the two sealing faces. A flow of medium which causes wear due to erosion cannot therefore be formed. A closing means sealing face is not raised from its valve seating until the other closing means sealing face is sufficiently remote from its valve seating to avoid the risk of erosion. This may be the case, for example,. if the cross-section for flow between the firstly raised closing means sealing face and its valve seating is a multiple of the radial clearance between the sliding elements and the throttling means. The throttling means therefore has a checking position which is substantially protected from wear by erosion and consequently provides a reliable seal.

V.' one sliding element of the closing means may be provided with a receiving bore which is open toward the other sliding elementf said other sliding element having a connecting shaft which extends into the receiving bore and which is provided with a stroke entrainer inside the receiving bore and an abutment for the stroke entrainer being provided in the receiving bore. A spring is desirably arranged in the receiving bore for urging the connecting shaft in the valve closing direction. The spring produces an additional sealing force at the second checking position. In the open position of the valve, it prevents undesirable movement of the second sliding element against the action of the dynamic forces of the medium.

The influence of the pressure prevailing in the inner annular chamber on the actuating force can be substantially reduced if a release piston is connected to the upstream sliding element and a pressure chamber which contains the release piston is connected to the inner annular chamber and whose internal pressure is arranged to load the release piston in the valve closing direction. Pressure variations occurring in the inner annular chamber do not adversely affect the opening movement of the throttle valve. This applies, in particular, to throttle valves whose actuating shaft has a relatively large diameter for reducing the closing force produced by the pressure. Undesirable, abrupt travel of the closing means is avoided even if the throttle valve is actuated via an elastic element (for example a pneumatic driving arrangement).

- 6 According to a particularly advantageous embodiment of this arrangement# the actuating shaft of the throttle valve forms the release piston. Thus, the release piston can comprise a thickened portion of an actuating shaft located at the high pressure end of the closing means, the actuating shaft further having a thinner shaft portion remote from the closing means, the end face of the thickened shaft portion remote from the closing means being located in the pressure chamber, a pressure-tight lead-through for the thickened shaft portion being provided at one end of the pressure chamber and a pressure-tight lead-through for the thinner shaft portion being provided at the other end of the pressure chamber.

A reliable peripheral seal for the throttling means in the valve housing between the two groups of throttling ducts can be achieved if a seating ring is arranged between two groups of throttling ducts, the valve seating for the closing means being provided on the inner edge of said seating ring and said seating ring being provided at its outer edge with an annular recess in which a seal is located; a housing wall radially surrounding the seating ring and the seal; a spacer sleeve, which rests with one end on the seal, surrounds the throttling means at one end and comprises radial throttling ducts; and holding-down means are arranged to act on the end of the spacer sleeve and the remainder of the throttling means. Since the holding-down means act simultaneously on the spacer sleeve and the rigid throttling means, the compression of the seal is limited to a defined value.

c 1.

Overloading of the seal is prevented. The spacer sleeve also has a throttling effect on the traversing medium. This additional function is beneficial to the overall volume.

The checking position can be protected from coarse particles of dirt if the throttling ducts in the spacer sleeve and the throttling ducts in the adjacent portion of the throttling means are mutually offset laterally and if the spacer sleeve surrounds the throttling means with a radial clearance which is smaller than the internal diameter of the throttling ducts. As the throttling ducts of the spacer sleeve and of the throttling means are completely offset from one another, the radial annular gap existing between these two parts forms the narrowest cross-section for flow and prevents relatively large particles of dirt from reaching the checking position.

Reliable axial support and an end seal for the throttling means in the valve housing can be achieved by a preferred arrangement according to the invention in which a base ring is arranged at the end of the throttling means and is provided at its outer edge with an annular recess in which a seal is located; the or a housing wall radially surrounds the seal and the base ring and has an axial abutment for the base ring; and a spacer sleeve extends between the seal of the base ring and the seating ring and surrounds, with radial clearance, the portion of the throttling means axially held between the two rings. The seal is also protected from excessive deformation in this case. In addition, the spacer sleeve protects the housing wall from wear due to the jets.

Preferably, the base ring has the additional valve seating for the clo. sing means on its inner edge.

if the throttling means are constructed in several parts, it is advantageous if the portions of the throttling means which have a group of throttling ducts each consist of a set of nesting tubes with radial throttling ducts. If the throttling ducts appropriately distributed round the periphery of tube, it is possible to vary both the throughput the characteristic curve of the s troke- throughput to adapt them to the respective requirements using and the same set of tubes, by twisting the tubes.

are the and and one The invention will now be further described, by way of example, with reference to the drawings, in which:- Fig. 1 is a section through one embodiment of a 20 throttle valve according to the invention having two mutually fixed sliding elements; Fig. 2 shows, as a development, a detail of the throttling means in the valve shown in Fig. 1; Fig. 3 is a section through a second embodiment of a throttle valve according to the invention with two sliding elements which reciprocate relative to one another to a limited extent; and z k Fig. 4 is a section through a further embodiment of a throttle valve according to the invention with two sliding elements which reciprocate relative to one another to a limited extent.

In the drawings, like parts are denoted by like reference numerals.

Reference will first be made to Fig. 1 of the drawings in which the throttle valve comprises a valve housing 1 having an inlet duct 2, an outlet duct 3 as well as an inner chamber 4. A multi-stage throttling means which is surrounded by a housing wall 5 over a proportion of its length, with its outlet end resting on an axial abutment 6 of the valve housing 1, is arranged in the inner chamber 4. A holding-down means 7, which holds the individual parts of the throttling means in the proposed assembly position, acts upon the inlet end of the throttling means.

A reciprocating closing means 9 which has, at its end close to the inlet duct 2, an actuating shaft 10 projecting from the valve housing 1, is located in a central longitudinal duct 8 of the throttling means. A seal 11 provides.a pressure-tight lead- through to the exterior for the actuating shaft 10.

At its outlet end, the throttling means has a base 25 ring 12 resting on the axial abutment 6. A first set of nesting tubes 13 having radial throttling ducts 14 in several planes rests on this base ring 12. A spacer ring 16 provided with radial through ducts 15 rests on the ends of the tubes 13, and a seating ring 17, having a valve seating 18 on its inner edge, rests in turn on the spacer.ring 16. The seating ring 17 and the spacer ring 16 can, if desired, be combined in a single part. A second set of nesting tubes 19 which comprise radial throttling ducts 20 in several planes rests on the seating ring 17. The seating ring 17 as well as the base ring 1 2 are provided with respective annular recesses 21, 22 in which are located respective seals 23, 24. A spacer sleeve 25 extends between the seating ring 17 and the seal 23 of the base ring 12. This spacer sleeve 25, the seals 23, 24 and the two rings 12, 17 are closely surrounded radially by the housing wall 5. An outer annular 15 chamber 26 surrounds the outer tube 13 of the first set of tubes and the spacer ring 16. The outer tube 19 of the second set of tubes is surrounded by a spacer sleeve 28, forming an annular gap 27, the spacer sleeve 28 comprising radial throttling ducts 29 20 and resting with one end on the seal 24 on the seating ring 17. The holding down means 7 acts upon the other end of the spacer sleeve 28 and simultaneously on the end face of the tubes 19. The tubes 19, the seating ring 17, the spacer ring 16, the tubes 13 and the base 25 ring 12 are therefore pressed firmly against one another and are held in their assembled position. The seals 23, 24 are at the same time compressed to a predetermined extent by the spacer sleeves 25, 28, so that they rest with a radial seal against the housing 30 -wall 5 and the seating ring 17 or base ring 12 respectively.

- 11 The closing means 9 comprise two sliding elements 30, 31 at a fixed axial distance from one another. One sliding element 30 is arranged upstream of the valve seating 18 in the inner tube 19. On its end face, it is provided with a sealing face 32 mating with the valve seating 18. The other sliding element 31 is arranged in the inner tube 13. The longitudinal central duct 8 of the throttling means 12-29 forms an inner annular chamber 33 between the two sliding elements 30, 31.

The throttling ducts 29, 20 of the spacer sleeve 28 and the outer tube 19 are all mutually offset laterally (Fig. 2). The radial gap 27 between the sp-acer sleeve 28 and the outer tube 19 is substantially smaller than the internal diameter of the throttling ducts 29. The throttling ducts 20 of the tubes 19 are offset from those of their respectively adjacent tube or tubes 19 by a proportion of their internal diameter (Fig. 2). Throttling positions with interposed release positions are thus formed at the contact faces between the tubes 19. The same applies to the tubes 13 and their throttling ducts 14.

For the closing process, the sealing face 32 of the sliding element 30 comes to rest on the valve seating 18. At the same time, the sliding element 30 covers all of the throttling ducts 20 of the inner tube 19, at least in the region adjacent to the seating ring 17, while the sliding element 31 covers all of the throttling ducts 14 of the inner tube 13 at least in the region adjacent to the base ring 12.

For the opening process, the sealing face 32 of the sliding element 30 is raised from the valve seating 18. Depending on the respective stroke position, the simultaneously moved sliding elements 30, 31 clear an adequate number of throttling ducts 20, 14 both in the tubes 19 and in the tubes 13. The medium initially flows through the throttling ducts 29 in the spacer sleeve 28 and is throttled there in the first instance. It then passes into the annular gap 27 which retains undesirable impurities owing to its small width. From there, the medium continues flowing through the throttling ducts 20 cleared by the sliding element 30 and is throttled in several stages therein. The path of flow then leads through the inner annular chamber 33, the through ducts 15 and the outer annular chamber 26 into the throttling ducts 14 of the tubes 13 cleared by the sliding element 31. The medium is throttled again in several stages therein and only then flows into the outlet duct 3.

Very effective multi-stage throttling is achieved with a throttling means of relatively small diameter. The small diameter of the throttling means allows an economical valve housing which is relatively small in overall volume and.mass. In the case of extreme pressure differences, it is even possible to arrange three or more sets of tubes in the longitudinal direction of the throttling means and a corresponding number of sliding elements on the closing means.

The throttle valve according to Fig. 1 can also be 30 traversed in the direction opposed to the direction shown, if necessary.

c 13 - The throttle valve shown in Fig. 3 is substantially identical in construction to the one shown in Fig. 1. However, in Fig. 3, a second valve seating 34 is provided which is located on the base ring 12. The sliding element 30 has a sealing face 35. The two sliding elements 30, 31 of the closing means 9 are each arranged upstream of their respective valve seatings 18, 34 and are capable of travelling to a limited extent with respect to one another. For this purpose, the upstream - as viewed in the direction of flow - sliding element 30 has a receiving bore 36 which is open towards the downstream sliding element 31. The downstream sliding element 31 is provided with a connecting shaft 37 which extends into the receiving bore 36 and which is provided at its end with a stroke entrainer 38. The entrainer 38 is maintained in the receiving bore 36 in the sliding element 30 by an abutment 39 which is arranged downstream of the stroke entrainer 38 toward the sliding element 31. A spring 40 which acts upon the entrainer 38 and hence upon the connecting shaft 37 in the valve closing direction is arranged in the receiving bore 36.

Both sealing faces 32, 35 of the closing means 9 rest on their valve seatings 18, 34 in the closed position of the throttle valve shown in Fig. 3. An axial clearance is provided between the stroke entrainer 38 and the abutment 39. During the opening process, only the upstream sliding element 30 with the sealing face 32 is initially raised from the valve seating 18. The downstream sliding element 31 meanwhile continues resting with the sealing face 35 on the valve seating 34 under the influence of the spring 40 and the pressure in the annular chamber 33. No medium can f low out of the outlet duct 3 at this stage because the sealing face 35 is still seated on the valve seating 34. The abutment 39 comes to rest on the stroke entrainer 38 only as th.e opening process progresses so that the sealing face 35 of the downstream sliding element 31 is then also raised from its valve seating 34. With the flow of medium which is now being adjusted, the flow rate expected between the sealing face 32 and the valve seating 18 lies below the value which might cause wear due to erosion on the said sealing face 32 and valve seating 18. As the closing means 9 continues lifting, throttling ducts 14, 20 in the tubes 13, 19 are cleared and this takes place simultaneously in both sets of tubes.

Wear due to erosion is reliably prevented by the mutually delayed opening and closing of the sealing faces 32 and 35 on the respective valve seatings 18 and 34 which are arranged in succession in the direction of flow.

The throttle valve shown in Fig. 4 differs from the one shown in Fig. 3 in that the actuating shaft 10 of the closing means 9 has a thicker shaft portion 41 in the vicinity of the closing means and a thinner shaft portion 42 remote from the closing means. A pressure chamber 43 through which the actuating shaft 10 extends is also provided. The end of the thicker shaft portion 41 remote from the closing means is -1 k m located inside the pressure chamber 43. Pressure-tight lead-throughs 44, 45 for the thicker or thinner shaft portion 41, 42 are provided at the ends of the pressure chamber 43. The pressure chamber 43 communicates via a duct 46 with the inner annular chamber 33.

The diameter of the thicker shaft portion 41 is somewhat smaller than the outer diameter of the valve seating 18. The pressure on the inlet side therefore invariably exerts a closing force on the sliding element 30, but this closing force is relatively small in comparison with the pressure on the inlet side. This is beneficial to the size of the actuating arrangement. The pressure prevailing in the inner annular chamber 33 exerts an opening force on the sliding element 30. However, this opening force is substantially compensated by the pressure acting in the pressure chamber 43 on the free end face of the thicker shaft portion 41, as this pressure is invariably equal to the pressure in the inner annular chamber 33. The thicker shaft portion 41 therefore acts as a release piston.

As soon as the second sliding element 31 comes to rest with its sealing face 35 on the valve seating 34 during the closing process, the pressure on the inlet side is adjusted in the inner annular chamber 33. It also prevails there immediately after the first sliding element 30 comes to rest with the sealing face 32 on the valve seating 18. Thereafter, however, for example as the enclosed medium is cooled, the pressure can drop in the inner annular chamber 33.

16 - If the throttle valve is opened when the pressure is reduced in the inner annular chamber 33, then the pressure rises in the inner annular chamber 33 to the value on the inlet side as the sealing face 32 is lifted from the valve seating 18. However, the resultant increase in the opening force acting on the sliding element 30 is substantially compensated by means of the pressure chamber 43 and the thicker shaft portion 41. The actuating force required for lifting the sliding element 30 does not therefore change significantly so that, for example, even when a pneumatic actuating arrangement is used, the opening movement progresses steadily and an undesirable sudden opening movement is avoided.

-1 1

Claims

1. A throttle valve having a valve housing, throttling means arranged in the valve housing and comprising a valve seating, a longitudinal duct and a group of radial throttling ducts; and a closing means which comprises a sliding element arranged so as to reciprocate in the longitudinal duct in the region of the throttling ducts and a sealing face arranged to mate with the valve seating; wherein the throttling means comprises at least one additional group of radial throttling ducts, the or at least two of the throttling duct groups being spaced in succession, when viewed in the longitudinal direction of the throttling means; the closing means comprises at least one additional sliding element arranged so as to reciprocate in the longitudinal duct in the region of the or each additional throttling duct group; an inner annular chamber is provided between the sliding elements in the longitudinal duct; an outer annular chamber surrounding the throttling means in the region of a throttling duct groupAs provided; and at least one radial through duct is provided between the inner annular chamber and the outer annular chamber.

2. A throttle valve according to Claim 1, wherein the throttling means comprises an additional valve seating in the region of the additional throttling duct group and the closing means comprises an additional sealing face arranged to mate with the additional valve seating in the region of the additional sliding element.

18 -

3. A throttle valve according to claim 2, wherein the two sealing faces of the closing means are reciprocable to a limited extent with respect to one another.

4. A throttle valve according to Claim 3, wherein one sliding element of the closing means is provided with a receiving bore which is open toward the other sliding element, said other sliding element having a connecting shaft which extends into the receiving bore and which is provided with a stroke entrainer inside the receiving bore and an abutment for the stroke entrainer being provided in the receiving bore.

5. A throttle valve according to Claim 4, wherein a spring is arranged in the receiving bore for urging the connecting shaft in the valve closing direction.

6. A throttle valve according to any one of the preceding claims, wherein a release piston is connected to the upstream sliding element and a pressure chamber which contains the release piston is connected to the inner annular chamber and whose internal pressure is arranged to load the release piston in the valve closing direction.

4

7. A throttle valve according to Claim 6, wherein the releas.e piston comprises a thickened portion of an actuating shaft located at the high pressure end of the closing means, the actuating shaft further having a thinner shaft portion remote from the closing means, the end face of the thickened shaft portion remote from the closing means being located in the pressure chamber, a pressure-tight lead-through for the thickened shaft portion being provided at one end of the pressure chamber and a pressure-tight lead-through for the thinner shaft portion being provided at the other end of the pressure chamber.

8. A throttle valve according to any one of the preceding claims, wherein a seating ring is arranged between two groups of throttling ducts, the valve seating for the closing means being provided on the inner edge of said seating ring and said seating ring being provided at its outer edge with an annular recess in which a seal is located; a housing wall radially surrounds the seating ring and the seal; a spacer sleeve, which rests with one end on the seal, surrounds the throttling means at one end and comprises radial throttling ducts; and holding-down means are arranged to act on the end of the spacer sleeve and the remainder of the throttling means.

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9. A throttle valve according to Claim 8, wherein the throttling ducts in the spacer sleeve and the throttling ducts in the adjacent port ion of the throttling means are mutually offset laterally and wherein the spacersleeve surrounds the throttling means with a radial clearance which is smaller than the internal diameter of the throttling ducts.

10. A throttle valve according to claim 8 or claim 9, wherein a base ring is arranged at the end of the throttling means and is provided at its outer edge with an annular recess in which a seal is located; the or a housing wall radially surrounds the seal and the base ring and has an axial abutment for the base ring; and a spacer sleeve extends between the seal of the base ring and the seating ring and surrounds, with radial clearance, the portion of the throttling means 10 axially held between the two rings.

11. A throttle valve according to Claim 10, wherein the base ring has the additional valve seating for the closing means on its inner edge.

12. A throttle valve according to any one of the preceding claims, wherein the portions of the throttling means which have a group of throttling ducts each consist of a set of nesting tubes with radial throttling ducts.

13. A throttle valve substantially as described herein with reference to the drawings.

Published 1989 at The Patent Office. State House. 66 71 High Holborn, Londor.

IWCIR4TP FurMeTcOPIes InkYbe obtained from The PatentOffice Sales Branch. St Mary Cray. Orpingtor- Ken, BR5 3RD. Printed by ML2tiplex tecbzuques ltd. St Mary Cray. Rent, Con- 1187 -11