ISOLATION DAMPER

Abstract: A slide type isolation damper for a gas duct wherein the damper blade is relatively thin and flexible so that it deforms under gas pressure to enter in sealing engagement with support bars positioned across the duct. The support bars provide structural integrity to the damper blade which would otherwise be excessively deformed by the gas pressure.

Description: ISOLATION DAMPER TECHNICAL FIELD The present invention relates to an isolation damper fo gas ducts and more particularly to an isolation damper of th slide type. BACKGROUND ART Isolation dampers are used to close off a gas duct. A valve member of some type in the damper is brought into sealing engagement with the seat of the damper, or some othe sealing element, to form a gas tight seal preventing gas leakage past the damper. Conventional dampers are of three types viz., the poppet type wherein a flexible sheet of stee is deformed onto the seat of the damper under system pressur or negative pressure; the slide type in which an inflexible steel plate is slid across the duct and into sealing engagement with sealing means on the damper seat and the butterfly type in which two pivotably connected inflexible plates are folded into or out of sealing engagement with the sealing means on the damper seat. The poppet type valve cannot be conveniently used as an isolation damper intermediate the ends of a gas duct. The slide type suffers from the disadvantages that, firstly, a secondary seal system, which is susceptible to wear, is required to make sealing contact with the slide and, secondly, a housing is required to hold the plate when it has been withdrawn from the duct which is both unsightly and expensive to build. DISCLOSURE OF INVENTION The present invention is directed to a slide type isolation damper which does not have the disadvantages of known slide type dampers while having the advantage of the poppet type valve. The present invention consists in an isolation damper for a gas duct comprising a damper blade, a pair of guide members adapted to guide the damper blade along a path transverse to the gas duct, and means to move the damper OMPI blade along the said path between a first position in which the damper blade extends across the duct and a second position in which it is substantially withdrawn from the duct, the arrangement being characterised in that the damper blade is relatively thin and flexible such that when in the first position and under an applied gas pressure it can elastically deform to enter into sealing engagement with the guide members and in that there is disposed intermediate the guide members, and in close uxtapostion with at least one side of the path of the damper blade, a plurality of support elements against which the damper plate can bear when pressure is applied to the face of the damper blade distal t the support elements. The use of a thin, flexible damper blade allows the blade to be elastically deformed onto the guide members, which constitute the damper seat, without the need for a secondary sealing system. The flexibility of the blade also allows the blade to follow a .non-linear path as it is introduced into, and drawn out of, the duct. The blade could, for instance lie in a plane parallel to and slightly above the gas duct and be turned through 90° just before entering the duct. In this way the isolation damper could b made more cheaply and would be less unsightly. The damper blade is preferably formed of a material suc as stainless steel and preferably has a thickness of no more than 5 mm. , preferably no more than 3 mm. The use of such a thin damper, blade facilitates the movement of the blade into and out of the duct as the thin blade can cut through any duct accumulation which occurs in the guide means. The support elements preferably comprise an array of parallel bars or rods, however a grid of such bars or a perforate plate could also be used provided that the flow of gas through the duct is not unduly impeded. The support elements are preferably provided on each side of the damper blade path such that the damper blade will be supported against undue deformation upon the application of a positiv pressure to either of its faces. BRIEF DESCRIPTION OF DRAWINGS Hereinafter given by way of example only is a preferre embodiment of the invention described with reference to the accompanying drawings in which: - Fig. 1 is vertical sectional view through an isolation damper according to this invention, and Fig. 2 is a view along A-A of Fig. 1. BEST MODE OF CARRYING OUT THE INVENTION The isolation damper 10 is mounted in a gas duct 11, t gas moving through the duct in the direction of the arrow B of Fig. 1. The damper comprises a damper blade 12, a frame surrounding the duct 11 which frame includes a pair of channel shaped side members 14 constituting guide members f the damper blade 12, and drive means 15 to move the damper blade 12 into and out of the duct 11. The damper blade 12 comprises a sheet of stainless ste 3 mm. thick which is connected at its end remote from the duct to the drive means 15 as hereinafter described. The blade extends horizontally at the point of its connection to the drive means 15, it then turns through 90° before entering the guide slots 16 defined by side members 14. The frame 13, in addition to the side members 14, includes a base member 17 and a top member 18. The base member 17 includes a longitudinally extending slot 19 in alignment with slots 16 in the side members 14, and into which the lower end of the damper blade 12 slides when the damper is fully closed. A flap 20 is hingedly connected to the underside of the base member 17 and can be opened to release dust which has lodged in the frame. A plurality of support bars 21 extends between the base member 17 and the top member 18 on either side of the path traversed by the damper blade 12. The bars 21 are formed of mild steel or erosion resistant steel and may have an aerodvnamically - A - efficient cross sectional shape if desired. The top member 18 may be formed with a removable top cover 22 such that the slot 23 in the top member through which the damper blade 12 is introduced into the frame 13 ma be closed when the damper blade 12 is completely removed fro the frame 13. The drive means 15 comprises a reversible motor 24 whic drives a pair of endless chains 25 about drums 26. The chains are connected to the free end of the damper blade 12. Upon actuation of the motor 24 the damper blade 12 can be moved into or out of the duct 11. If the damper blade 12 is introduced fully into the duc 11 and a force applied to one side of the blade 12 it will b elastically deformed against the edges of the slots 16, 19 and 23 of the frame 13 and will sealingly engage therewith i view of the relatively thin, flexible, nature of the damper blade 12. As the blade 12 is forced against the edges of th slots it will similarly be forced against the support bars 2 on the side of the slots opposite the direction from which the force is applied to the blade 12. The support bars 21 give to the damper blade 12 the structural integrity lacking due to its flexible nature. O PI

Claims: The claims defining the invention are as follows: - 1. An isolation damper for a gas duct comprising a damper blade, a pair of guide members adapted to guide the damper blade along a path transverse to the gas duct, and means to move the damper blade along the said path between a first position in which the damper blade extends across the duct and a second position in which it is substantially withdraw from the duct, the arrangement being characterised in that the damper blade is relatively thin and flexible such that when in the first position and under an applied gas pressur it can elastically deform to enter into sealing engagement with the guide members and in that there is disposed intermediate the guide members, and in close juxtapostion with at least one side of the path of the damper blade, a plurality of support elements against which the damper plate can bear when pressure is applied to the face of the damper blade distal to the support elements. 2. An isolation damper for a gas duct as claimed in claim in which the guide members define a non-planar path along which the damper blade travels when moved between the first and second positions. 3. An isolation damper as claimed in claim 1 or claim 2 in which the damper blade is formed of stainless steel having a thickness of no more than 5mm. 4. An isolation damper as claimed in claim 3 in which the damper blade has a thickness of no more than 3 mm. 5. An isolation damper as claimed in any one of claims 1 t 4 in which support elements are provided on both sides of th path of the damper blade. 6. An isolation damper as claimed in any one of claims 1 t 5 in which the support elements comprise an array of paralle bars or rods. 7. An isolation damper as claimed in claim 5 in which each of the bars or rods has an aerodyna ically efficient cross sectional slope. 8. An isolation damper substantially as he einbefore described with reference to the accompanying drawing.

Inventors: STEPHENSON R
Applicants: JAMES HOWDEN PTY LTD, STEPHENSON R
Application year: 1981
Main classification: F16K3
IPC codes: F16K3, F23L13, F24F13