EP0396714A1 - Seals for gas isolators - Google Patents

Seals for gas isolators

Info

Publication number
EP0396714A1
EP0396714A1 EP19890912651 EP89912651A EP0396714A1 EP 0396714 A1 EP0396714 A1 EP 0396714A1 EP 19890912651 EP19890912651 EP 19890912651 EP 89912651 A EP89912651 A EP 89912651A EP 0396714 A1 EP0396714 A1 EP 0396714A1
Authority
EP
European Patent Office
Prior art keywords
seal
leaf spring
deflection
spring
initial
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP19890912651
Other languages
German (de)
French (fr)
Inventor
Anton Frederick Squirrell
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Grovag Grossventiltechnik AG
Original Assignee
Grovag Grossventiltechnik AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Grovag Grossventiltechnik AG filed Critical Grovag Grossventiltechnik AG
Publication of EP0396714A1 publication Critical patent/EP0396714A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
    • F16K1/00—Lift valves or globe valves, i.e. cut-off apparatus with closure members having at least a component of their opening and closing motion perpendicular to the closing faces
    • F16K1/16—Lift valves or globe valves, i.e. cut-off apparatus with closure members having at least a component of their opening and closing motion perpendicular to the closing faces with pivoted closure-members
    • F16K1/165—Lift valves or globe valves, i.e. cut-off apparatus with closure members having at least a component of their opening and closing motion perpendicular to the closing faces with pivoted closure-members with a plurality of closure members

Definitions

  • This invention relates to seals for gas isolators, and in particular provides a low stress bias spring seal with improved damping.
  • GB-1308801 describes a seal for a gas isolator which comprises a cantilever leaf spring to be attached to a fixed frame or a movable member of the isolator and a bias spring acting on the leaf spring to tension the leaf spring so as to curve the latter when the seal is not in the sealing position, the bias spring being itself tensioned to press the leaf spring flat against a seating when the seal is in the sealing position.
  • GB-2060824 provides a seal for a gas isolator which comprises a cantilever leaf spring to be attached to a fixed frame or a movable member of the isolator and a bias spring acting on the leaf spring, wherein the leaf spring is bent or curved when unstressed and wherein in the non-sealing position of the seal the bias spring makes only touch contact with the leaf spring, so that the leaf spring is unstressed in the said non-sealing position, whereby in the sealing position of the seal the stress induced in the bias spring will be the same as that induced in the leaf spring where the leaf spring and the bias spring have the same section modulus per unit length of seal.
  • the amount of differential expansion which can be accommodated is limited by the width of the support bar under the seal.
  • This bar has the dual function of clamping the seal to the blade or frame member and to prevent flutter of the seal when it is in the non-sealing position.
  • Merely to shorten the support bar under the seal is not acceptable in the case of the low stress bias spring seal according to GB-2060824. because only touch contact exists between the bias spring tip and the seal itself providing a minimal damping effect.
  • the bias spring seal depicted in GB-1308801 in which the seal is flat in the unloaded condition, provides a high contact force in the free position thus providing a high damping effect.
  • the present invention aims to combine these features in such a way as to attain an optimum combination of properties.
  • the seal is given an initial curvature corresponding to an initial deflection of, for example, half the final free deflection. It can be demonstrated that the maximum stress in the bias spring amounts to 1.5 times that corresponding to that induced by the free deflection of the seal.
  • the present invention provides a seal for a gas isolator, comprising a cantilever leaf spring to be attached to a fixed frame or a movable member of the isolator and a bias spring acting on the leaf spring, wherein the seal is given an initial curvature corresponding to an initial deflection of 10% to 90% of the final free deflection, preferably 25% to 75% thereof, more preferably 40 to 60% thereof.
  • the edge of the member to which the seal is fixed can be brought forward. In the free position, should the seal start to flutter, this extension causes a shortening in length in the upward part of the vibration cycle, thus providing additional damping effect.
  • the increased damping effect obtained by the seal according to the present invention may be considered as follows, in the general case.
  • the deflection of the leaf spring from its flat position may be denoted x, said deflection being measured in the direction perpendicular to the plane of the leaf spring in its flat position, and at the point where the tip of the bias spring contacts the leaf spring.
  • said deflection of the leaf spring is equal to x-fx, or x(l-f). where f is in effect a damping factor.
  • the perpendicular distance from the tip of the bias spring to the plane of the leaf spring in its flat position is equal to x+fx, or x(l+f). If the damping factor f is set equal to 1. then the seal according to GB-1308801 is obtained. If f is set equal to 0, then the seal according to GB-2060824 is obtained.
  • f is set equal to 0.1 to 0.9. and preferably equal to 0.25 to 0.75, more preferably from 0.4 to 0.6, and still more preferably about 0.5.
  • Figure la, lb and lc illustrate the calculation of the above-mentioned damping factor, wherein figure la illustrates the free position of the seal, figure lb the unloaded position of the leaf spring alone, and figure lc the unloaded position of the bias spring alone;
  • Figure 2 shows a seal according to the invention, wherein the edge of the member to which the seal is fixed is brought forward.
  • the deflection of the leaf spring is equal to x-fx, or x(l-f), where f is in effect a damping factor.
  • the damping factor f is set equal to 1, then the seal according to GB-1308801 is obtained. If f is set equal to 0, then the seal according to GB-2060824 is obtained.
  • f is set equal to 0.1 to 0.9, preferably 0.25 to 0.75. more preferably 0.4 to 0.6.
  • a seal according to the invention comprising a leaf spring 1 and a bias spring 2 acting thereon is fixed to a member 5.
  • Numerals 6 and 7 indicate support bars which have the dual function of clamping the seal to the member 5 and of preventing fluttering of the seal in its non-sealing position.
  • the member 5 may be a movable member (blade) of the isolator or a fixed frame of the isolator.
  • the edge of the member 5 is extended or brought forward by a distance d from the position which it would conventionally occupy. As a result, in the free position, should the seal start to flutter, this extension causes a shortening in length in the upward part of the vibration cycle, thus providing an additional damping effect.

Landscapes

  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Sealing Devices (AREA)
  • Springs (AREA)

Abstract

Joint d'étanchéité pour un dispositif d'isolation de gaz comprenant un ressort à lames (1) en porte-à-faux, à fixer à un cadre fixe ou à un élément mobile d'un dispositif d'isolation, ainsi qu'un ressort de sollicitation (2) agissant sur le ressort à lames. On a donné audit joint d'étancheité une courbure initiale correspondant à une déflexion initiale de 10 % à 90 % de la déflexion libre finale, de préférence 25 % à 75 % de cette dernière et idéalement 40 à 60 % de ladite déflexion.Gasket for a gas isolation device comprising a cantilever leaf spring (1), to be fixed to a fixed frame or to a mobile element of an isolation device, as well as a bias spring (2) acting on the leaf spring. Said seal was given an initial curvature corresponding to an initial deflection of 10% to 90% of the final free deflection, preferably 25% to 75% of the latter and ideally 40 to 60% of said deflection.

Description

SEALS FOR GAS ISOLATORS
This invention relates to seals for gas isolators, and in particular provides a low stress bias spring seal with improved damping.
GB-1308801 describes a seal for a gas isolator which comprises a cantilever leaf spring to be attached to a fixed frame or a movable member of the isolator and a bias spring acting on the leaf spring to tension the leaf spring so as to curve the latter when the seal is not in the sealing position, the bias spring being itself tensioned to press the leaf spring flat against a seating when the seal is in the sealing position.
An alternative form of seal is described in GB-2060824 which provides a seal for a gas isolator which comprises a cantilever leaf spring to be attached to a fixed frame or a movable member of the isolator and a bias spring acting on the leaf spring, wherein the leaf spring is bent or curved when unstressed and wherein in the non-sealing position of the seal the bias spring makes only touch contact with the leaf spring, so that the leaf spring is unstressed in the said non-sealing position, whereby in the sealing position of the seal the stress induced in the bias spring will be the same as that induced in the leaf spring where the leaf spring and the bias spring have the same section modulus per unit length of seal.
The increasing size of gas turbines is creating a need for larger isolating equipment. One of the main problems which confronts the designer of such equipment is that of the differential expansion which occurs between the fixed frame and the moving blade member.
The amount of differential expansion which can be accommodated is limited by the width of the support bar under the seal. This bar has the dual function of clamping the seal to the blade or frame member and to prevent flutter of the seal when it is in the non-sealing position. Merely to shorten the support bar under the seal is not acceptable in the case of the low stress bias spring seal according to GB-2060824. because only touch contact exists between the bias spring tip and the seal itself providing a minimal damping effect.
The bias spring seal depicted in GB-1308801, in which the seal is flat in the unloaded condition, provides a high contact force in the free position thus providing a high damping effect.
The present invention aims to combine these features in such a way as to attain an optimum combination of properties. The seal is given an initial curvature corresponding to an initial deflection of, for example, half the final free deflection. It can be demonstrated that the maximum stress in the bias spring amounts to 1.5 times that corresponding to that induced by the free deflection of the seal.
The present invention provides a seal for a gas isolator, comprising a cantilever leaf spring to be attached to a fixed frame or a movable member of the isolator and a bias spring acting on the leaf spring, wherein the seal is given an initial curvature corresponding to an initial deflection of 10% to 90% of the final free deflection, preferably 25% to 75% thereof, more preferably 40 to 60% thereof.
For the seal in GB-1308801 the maximum stress would be 2 times that induced by the free deflection of the seal, whilst for the seal in GB-2060824 the stress would be equal to that induced by the free deflection of the seal.
By varying the initial curvature the maximum stress and the damping effect can be varied at will.
In a preferred embodiment the edge of the member to which the seal is fixed can be brought forward. In the free position, should the seal start to flutter, this extension causes a shortening in length in the upward part of the vibration cycle, thus providing additional damping effect.
The increased damping effect obtained by the seal according to the present invention may be considered as follows, in the general case.
In the free position of the seal, where the bias spring acts on the leaf spring, the deflection of the leaf spring from its flat position may be denoted x, said deflection being measured in the direction perpendicular to the plane of the leaf spring in its flat position, and at the point where the tip of the bias spring contacts the leaf spring.
In the unloaded position of leaf spring alone, said deflection of the leaf spring is equal to x-fx, or x(l-f). where f is in effect a damping factor.
In the unloaded position of the bias spring alone, the perpendicular distance from the tip of the bias spring to the plane of the leaf spring in its flat position is equal to x+fx, or x(l+f). If the damping factor f is set equal to 1. then the seal according to GB-1308801 is obtained. If f is set equal to 0, then the seal according to GB-2060824 is obtained.
According to the present invention, f is set equal to 0.1 to 0.9. and preferably equal to 0.25 to 0.75, more preferably from 0.4 to 0.6, and still more preferably about 0.5.
The invention will be further described, by way of example, only with reference to the accompanying drawings, wherein:
Figure la, lb and lc illustrate the calculation of the above-mentioned damping factor, wherein figure la illustrates the free position of the seal, figure lb the unloaded position of the leaf spring alone, and figure lc the unloaded position of the bias spring alone; and
Figure 2 shows a seal according to the invention, wherein the edge of the member to which the seal is fixed is brought forward.
In the free position of the seal, as shown in figure la, where a bias spring 2 acts on a leaf spring 1, the deflection of the leaf spring from its flat position is denoted x, in the direction perpendicular to a theoretical flat plane 3 of the leaf spring, and at the point 4 where the tip of the bias spring contacts the leaf spring.
In the unloaded position of the leaf spring alone, as shown in figure lb, the deflection of the leaf spring is equal to x-fx, or x(l-f), where f is in effect a damping factor.
In the unloaded position of the bias spring alone, as shown in figure lc, the perpendicular distance from the tip of the bias spring to the theoretical plane 3 of the leaf spring is equal to x+fx. or x(l+f).
As mentioned above, the damping factor f is set equal to 1, then the seal according to GB-1308801 is obtained. If f is set equal to 0, then the seal according to GB-2060824 is obtained.
According to the present invention, f is set equal to 0.1 to 0.9, preferably 0.25 to 0.75. more preferably 0.4 to 0.6.
As shown in figure 2, a seal according to the invention comprising a leaf spring 1 and a bias spring 2 acting thereon is fixed to a member 5. Numerals 6 and 7 indicate support bars which have the dual function of clamping the seal to the member 5 and of preventing fluttering of the seal in its non-sealing position. The member 5 may be a movable member (blade) of the isolator or a fixed frame of the isolator. According to a preferred embodiment of the present invention as shown in figure 2, the edge of the member 5 is extended or brought forward by a distance d from the position which it would conventionally occupy. As a result, in the free position, should the seal start to flutter, this extension causes a shortening in length in the upward part of the vibration cycle, thus providing an additional damping effect.

Claims

CLAIMS :
1. A seal for a gas isolator, comprising a cantilever leaf spring (1) to be attached to a fixed frame or a movable member of an isolator and a bias spring (2) acting on the leaf spring, characterized in that the seal is given an initial curvature corresponding to an initial deflection of 10% to 90% of the final free deflection.
2. A seal as claimed in claim 1, characterized in that the seal is given an initial curvature corresponding to an initial deflection of 25% to 75% of the final free deflection.
3. A seal as claimed in claim 2, characterized in that the seal is given an initial curvature corresponding to an initial deflection of 40% to 60% of the final free deflection.
4. A seal as claimed in any of claims 1 to 3, characterized in that the edge of the member (5) to which the seal (1, 2) is fixed is extended or brought forward by a distance (d) relative to said seal.
EP19890912651 1988-11-25 1989-11-20 Seals for gas isolators Withdrawn EP0396714A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB888827561A GB8827561D0 (en) 1988-11-25 1988-11-25 Seals for gas isolators
GB8827561 1988-11-25

Publications (1)

Publication Number Publication Date
EP0396714A1 true EP0396714A1 (en) 1990-11-14

Family

ID=10647462

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19890912651 Withdrawn EP0396714A1 (en) 1988-11-25 1989-11-20 Seals for gas isolators

Country Status (5)

Country Link
EP (1) EP0396714A1 (en)
JP (1) JPH03503306A (en)
GB (1) GB8827561D0 (en)
IN (1) IN174058B (en)
WO (1) WO1990006460A1 (en)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB9201762D0 (en) * 1992-01-28 1992-03-11 Wes Technology Inc Seals for gas isolators

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB463363A (en) * 1936-06-15 1937-03-30 Frederick Otto Horstmann Improvements in taps or valves for controlling the flow of fluids
US3620242A (en) * 1970-01-05 1971-11-16 Babcock & Wilcox Co Self-cleaning damper assembly
US3894481A (en) * 1972-04-03 1975-07-15 American Warming Ventilation Multi-blade damper

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9006460A1 *

Also Published As

Publication number Publication date
WO1990006460A1 (en) 1990-06-14
IN174058B (en) 1994-09-03
JPH03503306A (en) 1991-07-25
GB8827561D0 (en) 1988-12-29

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