IE51783B1 - Construction of damper - Google Patents

Abstract

A damper (10) for use with a chimney flue (11) or outlet of a combustion appliance consists of a plate (12) curved into a shape that can nest against the inner wall (13) of the flue (11) in an open condition of the damper (10), the plate (12) having a periphery which in the closed condition of the damper (10) blocks the flue (11) by virtue of having a geometrical projection in the direction of the main axis of the flue (11) that is congruent with the flue cross-section or as much thereof as it is desired to block. The damper (10) is adjustably and pivotally mounted within the flue (11) by means of a damper control device which includes an adjustably rotatable shaft (17) disposed adjacent to the perimeter of the flue (11) either internally or externally thereof, dependent on the shape of the damper (10).

Description

This invention relates to an improved construction of damper. In particular, the invention relates to a construction of damper for use with a chimney flue or outlet of a combustion appliance of circular or elliptical cross-section.

It is often beneficial and, indeed, necessary to the performance of a combustion appliance to restrict the flue-way or appliance outlet opening by use of a damper, viz a blade or shutter,which substantially reduces the open, cross-sectional area of the flue or outlet. The cross-section of such a flue or outlet may be square or rectangular but is more usually circular or elliptical. The present invention is primarily concerned with flues or outlets (hereinafter referred to as flues) of circular or elliptical cross-section.

Conventional dampers for such flues are essentially of two types. The first type of damper consists of a flat, suitably shaped baffle which is adapted to move in and out at right angles to the main axis of the flue through a slot in the wall of said flue. The baffle is so shaped that there is a minimum open area for the passage of combustion products at all times. There are a number of disadvantages associated with the use of such a damper, notably air leakage through the slot which results in a loss of draught. Furthermore, use of such a damper is often impractical in a given location and such dampers-are considered by many to be unsightly and to detract from the appearance of a room or combustion appliance, as the case may be. - 3 The second, and most widely used, type of damper consists of a circular baffle mounted on an axis which spans the flue at the centre line thereof. A segment is removed from the baffle so as to provide the requisite free area for the egress of combustion products. Such damper is commonly referred to as a butterfly damper. This type of damper does not have the disadvantages of the sliding damper referred to above, however, it does have the disadvantage of preventing the passage of a cleaning brush.

It is an object of the present invention to provide a construction of damper which is efficient in operation and which does not have any of the disadvantages of the two conventional types of damper discussed above.

Accordingly, the invention provides a damper for a flue having a curved cross-section, wherein the damper comprises a plate within the flue pivotally mounted for rotation about an axis transverse the main axis of the flue between open and closed positions respectively, wherein the plate has an inherent curvature which permits the plate to nest snugly against the inside curved surface of the flue when the damper is open, and wherein the plate has a periphery such that when the damper is closed the geometrical projection of the curved plate in the direction of the main axis of the flue blocks all or at least a major part of the cross-section of the flue.

Preferably the flue is circular or elliptical in cross-section.

The plate is preferably adjustably and pivotally mounted within the flue by means of a damper control device which includes a shaft disposed adjacent the perimeter of the flue, either internally or externally thereof.

Further, preferably, the plate is shaped so that it forms a half cylinder which has a substantially circular projection in the main axis of the flue and is semi-circular in longitudinal section when the damper is in the closed condition. With such a construction, the damper lies in a plane which is parallel to the direction of the main axis of the flue when the damper is in its open condition, while the periphery of the damper nests against the perimeter of the flue so as to allow the passage of a cleaning brush up or down the length of the flue.

The damper according to the invention may be further defined as a flue-pipe baffle for a cylindrical flue pipe, the shape of which baffle may be notionally generated by: a) slicing a hollow metal cylinder along its axis to yield two half cylinders; the cylinder being a snug sliding fit Inside the flue; b) taking one of the half cylinders, placing it curved side upwards on a flat horizontal surface, and cutting vertically downwards through it with a tubular saw centered to intersect the cylindrical axis, the internal diameter of the tubular saw being that of the cross-section of the flue pipe to be baffled.

The invention will be understood from the following description of embodiments thereof given by way of example only with reference to the accompanying drawings in which: Fig. 1 is an end elevation in section of a flue fitted with a first embodiment of a damper according to the invention.

Fig. 2 is a plan view of the damper of Fig. 1 in the 25 closed condition.

Fig. 3 is a plan view of the damper of Fig. 1 in the open condition; Fig. 4 is an end elevation in section of a flue fitted with a second embodiment of a damper according to the invention; - 5 Fig. 5 ls a plan View of the damper of Fig. 4 ln the closed condition; and Fig. 6 is a plan view of the damper of Fig. 4 ln the open condition.

Referring to Figs. 1-3 of the drawings, there is illustrated a first embodiment of a damper according to the invention indicated generally at 10, for use in a flue of circular cross-section. The damper 10 consists of a plate 12 curved to a cylindrical contour such that the plate 12 can nest against the inner wall 13 of the flue 11 and the danger 10 is in the open condition (Fig. 3). The open condition of the damper 10 is also indicated in dotted outline in Fig. 1. The curved plate has a periphery which, in the closed condition of the damper 10, yields a circle by geometrical projection onto a cross-section of the flue 11, in the direction of the flue cylindrical axis.

The curved plate 12 has fastened thereto a pair of brackets 14 which are provided at their free end 15a,15b with holes 16 for fixedly receiving the shaft 17 of a substantially L-shaped damper operating control 18 which is pivotally mounted In a housing 19 located externally of the flue 11.

The shaft 17 is provided with a pair of stop plates 21a and 21b and a tooth (not shown) adjacent to stop plate 21b and which tooth is adapted for releasable engagement in conventional manner with a plurality of slots forming part of a device associated with an aperture (not shown) in wall 25 of the housing 19 through which the the shaft 17 passes. A helical spring 20 is wound on the shaft 17 intermediate the housing 19 and the stop plate 21a.

The shaft 17 is unable to rotate whilst the tooth engages a slot of the aperture in the wall 25 of the housing 19.

To rotate the damper 10 to a desired position, handle 22 of - 6 of the damper operating control 18 is moved in a direction towards the housing 19 so that the spring 20 is compressed between said housing 19 and the stop plate 21a. The stop plate 21b is accordingly moved away from the housing 19 and the tooth disengages from a given slot in the housing 19.

The handle 22 is then free to be turned until the damper 10 is in a selected position. The handle 22 can then be released and the spring 20 will bias the stop plate 21b against the housing 19. A small additional rotational adjustment of the handle 22 may be required so that the tooth on the shaft 17 will engage with a given slot in the housing 19. The number and size of slots in the housing 19 will determine the number of positions which the damper 10 may adopt within the flue 11 .

Referring to Fig. 2 it will be observed that a clearance indicated at 23, is provided between the periphery of the damper 10 and the inner wall 13 of the flue 11 when the damper 10 is in the closed condition and which clearance 23 ensures that the damper 10 never completely blocks the flue 11. Rotating the handle 22 upwardly through 90° from the position shown in Fig. 2, causes the damper 10 to rotate into its open, flue-nesting position depicted in Fig. 3.

Regerring to Figs. 4-6 of the drawings, there is illustrated a second embodiment of a damper according to the invention.

The damper 10' of this embodiment differs from the damper 10 of the first embodiment in that the curved plate 12' is cut to a shape so that it can be pivotally mounted within the perimeter of the flue 11'. In the closed position of the damper 10' (Fig. 5) the curved plate 12' has a periphery which yields a circle, with a segment removed, by geometrical projection onto a cross-section of the flue 11' in the direction of the main axis of the flue.

The damper 10' is rotatably mounted within the flue 11' by - 7 means of a pair of tubular bearings 24a,24b located in opposed relationship one on either side of the flue 11' and which bearings 24a and 24b are adapted to receive a pair of shafts 26a,26b connected to the plate 12*. The shaft 26a forms an extension of a shaft 17' of a damper operating control 18*. The shaft 17’ has a tooth (not shown) for engagement with an internal spur gear (not shown) housed in an extension 27 of the bearing 24a. A stop plate 21' is mounted on the shaft 17* and a spring 20* is provided in10 termediate said stop plate 21* and the extension 27 of the bearing 24a.

In use, to rotate the damper 10' to a selected position, handle 22' of the operating control 18' is moved in a direction towards the bearing 24a, thereby compressing the spring 20*. When the handle 22' moves a given distance, the tooth on the shaft 17' disengages from the internal spur gear in the extension 27 of the bearing 24a. The handle 22' and consequently the shaft 17* may then be rotated until the damper 10' is in the required position.

On releasing the handle 22' the spring 20' is decompressed and biases the tooth against the internal spur gear in conventional manner so as to prevent further rotation of the damper 10 *.

Claims (8)

1. CLAIMS :1. A damper for a flue having a curved cross-section, wherein the damper comprises a plate within the flue pivotally mounted for rotation about an axis trans5 verse the main axis of the flue between open and closed positions respectively, wherein the plate has an inherent curvature which permits the plate to nest snugly against the inside curved surface of the flue when the damper is open, and wherein the plate has a periphery such that 10 when the damper is closed the geometrical projection of the curved plate in the direction of the main axis of the flue blocks all or at least a major part of the cross-section of the flue.

2. A damper according to claim 1, wherein the flue 15 has a circular or elliptical cross-section.

3. A damper according to claim 1 or 2, wherein the plate may be adjustably positioned between its open and closed positions by a damper control device located externally of the flue and which includes a shaft disposed 20 adjacent the perimeter of the flue, the shaft being adjustably rotatable for selective positioning of the plate.

4. A damper according to claim 3, wherein the plate is provided with a pair of juxtaposed support brackets 25 which extend through the perimeter of the flue and are adapted to receive at their respective free ends, externally of the flue and within a housing, the shaft of the damper control device, said shaft being spring-loaded externally of the housing and having a tooth for releas30 able engagement with a plurality of co-operating slots of a device associated with an aperture in a wall of the housing through which the shaft passes and which together with the spring-loading ensures that the damper remains set at any selected angle determined by said damper control device.

5. A damper according to claim 4, wherein the plate 5 has a substantially circular projection in the main axis of the flue when the damper is closed and a substantially semi-circular side elevation.

6. A damper according to claim 3, wherein the plate has a periphery which in the closed condition of the 10 damper yields a circle with a segment removed by geometrical projection onto a cross-section of the flue in the direction of the main axis thereof.

7. A damper according to claim 6, wherein the plate is provided at its straight edge with a pair of tubular 15 bearings disposed one on either side of the flue, the shaft of the damper control device being received in one of said tubular bearings, said shaft being spring-loaded and being provided with a tooth for engagement with a spur gear associated with said one tubular bearing, such 20 that the damper may be positioned at any selected angle determined by said damper control device.

8. A damper according to claim 1, substantially as hereinbefore described with reference to and as illustrated in Figs. 1-3 and Figs. 4-6 of the accompanying drawings.