GB2203530A

GB2203530A - Shut-off damper

Info

Publication number: GB2203530A
Application number: GB08807654A
Authority: GB
Inventors: Robert John Magill; David John Gaiger
Original assignee: Actionair Equipment Ltd
Current assignee: Actionair Equipment Ltd
Priority date: 1987-03-31
Filing date: 1988-03-31
Publication date: 1988-10-19
Anticipated expiration: 2008-03-31
Also published as: GB8807654D0; GB2203530B; GB8707692D0

Abstract

A hollow aerofoil section blade for use in a shut-off damper comprises two elongate strips (10, 12) of bowed or curved section which form the outer skin of the blade, the blade having an internal metal reinforcement (18) composed of two identical channel-section members (20, 22) which are spot-welded, rivetted or otherwise connected together over their opposed mating portions (24, 26) so that bending and twisting of the blade during use is reduced to a minimum. <IMAGE>

Description

Shut-off Damper This invention relates to shut-off dampers and more especially to the blades used therein. It has particular reference to those shut-off dampers which comprise a line of blades supported in a surrounding frame for rotary motion about substantially parallel axes to open or close an opening in the frame.

Shut-off dampers of the construction described above are shown in our prior British Patents Nos. 1,598,564 and2,O39,36lB. These dampers have hollow aerofoil-shaped blades each provided with fluid sealing means which extend along one of their edges so that a seal is formed between adjacent blades when the blades are in their closed positions. Additional fluid sealing means are also provided at the ends of the blades to seal those ends with respect to the surrounding frame.

In some large shut-off dampers of the construction outlined above, the length of each blade may be as much as one metre or even two metres. This gives rise to the problem that the blade may bend or twist during operation - which will, in turn, adversely affect the seal between adjacent blades when they are in their closed positions.

It is therefore an aim of the present invention to ensure that any such undesirable bending or twisting of the blades in a shut-off damper is reduced to an acceptable limit.

With this aim in view, the present invention is directed to a blade for a shut-off damper comprising an outer skin of bowed or curved cross-section on both sides of the blade, the blade having an internal metal reinforcement in the hollow space of the blade, preferably throughout its length.

The reinforcement can comprise two channelled members which are fastened together face-to-face with the outer skin of the blade being formed of two opposing strips of curved or bowed cross-section which sandwich the internal metal reinforcement between them. The two opposing strips are preferably provided with bent-over longitudinal edges so as to grip on to corresponding edges of the internal metal reinforcement.

It will be normal for the blade to have fluid sealing means along one or both of its longitudinal edges.

For this purpose the blade can have a longitudinal groove formed at its trailing and/or leading edge to receive the root portion of a sealing strip. Retainers or other such members at the ends of the blade will close the hollow space within the blade.

As will be understood, the invention extends to shut-off dampers incorporating a plurality of the blades described above.

Two examples of shut-off damper blades in accordance with the invention are shown in the accompanying drawings, in which Figure 1 is an exploded perspective view of one end portion of one of the blades; Figure 2 is a cross-section through the blade; Figure 3 is a part-sectional plan view of the end portion of the blade shown in Figure 1 to illustrate the way in which the various parts thereof fit together; Figure 4 is a section on a reduced scale through three blades in their closed positions as installed in a damper; and Figures 5 - 8 are views corresponding to Figures 1 - 4 respectively of the second form of damper blade in accordance with the invention.

The blade shown in Figures 1 - 3 is designed for use in shut-off dampers to prevent fluid flow through a duct or other passage containing such a damper. Dampers for this purpose generally comprise a line of blades supported in a surrounding frame for rotary motion about substantially parallel axes to open or close an opening in the frame. It is also usual for such shut-off dampers to be provided with sealing means along one or both of their longitudinal edges.

The blade of the present invention has been designed particularly for use in dampers where the blades are comparatively long - for exmaple, one or two metres long, although it is to be understood that the invention can be applied quite as well to blades of any length. In long blades it is, however, necessary to prevent bending and twisting of the blades, and it is for this reason that the blade of the present invention has an internal reinforcement which reduces bending and twisting of the blade to an acceptable level.

As shown in Figures 1 and 2, the blade accordingly comprises two elongate strips 10 and 12 of identical construction which are of bowed or curved section and which have bent-over longitudinal edges 14 and 16. These two strips 10 and 12 form the outer skin of the blade which is of hollow aerofoil section. Sandwiched between the two strips 10 and 12 is an internal metal reinforcement 18 composed of two identical channel-section members 20 and 22 which are spot-welded, rivetted or otherwise connected together over their opposed mating portions 24 and 26 (see Figure 2).By reason of the channels formed in the two members 20 and 22, a central passage 28 of roughly hexagonal section is formed within the hollow portion of the blade, with the two strips 10 and 12 forming the outer skin of the blade being arranged to make contact with portions 30 of the reinforcement 18 bounding or partially defining the hexagonal-section passage 28.

As shown in Figure 2, the bent-over longitudinal edges 14 and 16 of the two strips 10 and 12 grip the longitudinal edges 32 and 34 of the two channel-section members 20 and 22 forming the internal reinforcement 18.

The result is that bending and twisting of the blade during use is reduced to a minimum Open grooves 36 are thus formed along the longitudinal edges of the blade, and these grooves serve to receive the T-section root portions 38 of sealing strips 40 provided along both the leading and trailing edges of the blade. These sealing strips comprise a synthetic rubber extrusion having a hollow D-section portion 42 as well as the T-section root portion 38. The T-section root portion 38 of each sealing strip is therefore adapted to be gripped very firmly between the opposed bent-over edges 14 and 16 of the strips 10 and 12 forming the outer skin of the blade.

Bearing means for the blade are provided at each of its ends, and one such bearing means is illustrated in Figure 1. It comprises two opposed halves 44 which are rivetted, spot-welded or otherwise attached at 46 and 48 to the internal reinforcement 18.

Each end of the blade is closed by a retainer 52 as shown in Figure 1. The retainer is attached to the respective end of the blade by pins or rivets 54 which extend through holes 56 in the retainer and enter locking holes 58 in the joined-together bearing halves 44 with the flat joined-together spigots 50 of the bearing halves 44 projecting through a corresponding slot 60 in the retainer 52. It is to be understood that each end of the blade is identical in this respect.

In order to seal the ends of the blade effectively against leakage of fluid past those ends, each retainer 52 has a sealing member 62 arranged on its inner surface and a further sealing member 64 arranged on its outer surface.

The internal sealing member 62 is located in a shallow recess 70 on the inner surface of the retainer (see Figure 3) and has holes 66 for the passage therethrough of the pins or rivets 54 which secure the retainer to the respective bearing means. There is also a slot 68 in the sealing member 62 for the passage therethrough of the flat joined-together spigots 50 of the bearing means. The external sealing member 64 lies in a deep recess 71 on the outer surface of the retainer 52 and is provided with a hole 72 to permit rotation of a shaft (not shown) to which the joined-together spigots 50 are connected when the blade is mounted in a shut-off damper. In its final assembled form, each end of the blade will then appear as shown in Figure 3, with the outer sealing member 64 adapted to make good sealing contact with the frame 74 of the damper on which the blade is mounted.

The metal out of which the blade is made can be chosen according to the requirements of different customers. For example, the strips 10 and 12 forming the outer skin of the blade will normally be made of stainless steel, while the internal reinforcement 18 and the bearing means 44 will normally be made of mild steel, galvanised steel or a steel alloy. The invention is not however to be seen as being restricted to particular metals for different parts of the blade.

It is to be understood that the invention is directed not only to the form of blade described above but also to a damper incorporating such blades. A damper of this construction is shown diagrammatically in Figure 4 as having three identical blades 76, 78 and 80 of the form shown in Figures 1 - 3, the blades being shown in their closed positions. This means that the edge sealing strips 40 on the middle blade 78 sealingly engage the opposed edge sealing strips 40 on the two outer blades 76 and 80, while the outermost sealing strips 40 on the latter two blades sealingly engage the frame 74 of the damper.

In order to facilitate rotation of the blade, a coating of PTFE is applied to the outer flat surface of each sealing member 64 so as to reduce friction between that surface and the surrounding frame 74 of the damper.

Figures 5 - 8, which correspond to Figures 1 - 4, show a second form of blade and blade arrangement. Many parts of the two blades are of the same or similar construction, and the same reference numerals have been used to designate like parts. The main difference between the two blades lies in the precise construction of the internal reinforcement 18 which, in the blade shown in Figures 5 - 8, has a plurality of longitudianlly-extending corrugations 82 in place of the hexagonal-section central portion 28 shown in Figure 2. These parallel corrugations 82 - which are joined at lines 84 so that closed passages 86 are formed - give additional stiffness to the reinforcement. In addition, the bearing halves 44 are of stronger construction in Figure 5, while the root portion of each sealing strip 40 is of arrow-section in Figure 6 rather than of T-section as in Figure 2.

Claims

1. A blade for a shut-off damper comprising an outer skin of bowed or curved cross-section on both sides of the blade, the blade having an internal metal reinforcement in the hollow space of the blade.

2. A damper blade according to claim 1, in which the internal metal reinforcement extends substantially throughout the length of the blade.

3. A damper blade according to claim 1 or claim 2, in which the internal metal reinforcement comprises two channelled members which are fastened together face-toface.

4. A damper blade according to any one of claims 13, in which the outer skin of the blade is formed of two opposing strips of curved or bowed cross-section which sandwich the internal metal reinforcement between them.

5. A damper blade according to claim 4, in which the two opposing strips of bowed or curved cross-section are provided with bent-over longitudinal edges so as to grip on to corresponding edges of the internal metal reinforcement.

6. A damper blade according to any preceding claim having a longitudinal groove formed at its trailing and/or leading edge which receives the root portion of a sealing strip.

7. A damper blade according to any preceding claim having retainers or other such members at the ends of the blade to close the hollow space within the blade.

8. A damper blade according to claim 7 having separate sealing means both on the inner and outer surfaces of each retainer.

9. A damper blade according to any preceding claim, in which the internal metal reinforcement is provided with a plurality of longitudinally-extending corrugations to stiffen the reinforcement.

10. A damper blade substantially as described herein with reference to Figures 1 - 4 or Figures 5 - 8 of the accompanying drawings.

11. A shut-off damper incorporating a plurality of blades as claimed in any preceding claim, the blades being arranged for rotary motion about substantially parallel axes to open or close an opening in a surrounding frame on which the blades are supported, the longitudinal edges of adjacent blades being arranged to make sealing contact with each other and with the frame when the blades are in their closed positions.