GB2028128A - Air damper - Google Patents

Abstract

An air damper for use as a fire damper has a reversely folding shutter formed by hinged elements 3. The shutter is normally retained in a compacted form in its frame 2 by a fusible link. The fusible link 14 has a headed pin at each end. The pins 13 are retained in respective catches 9 in which they are rotatable. A handle loop may be pivoted to the bottom shutter element to enable it to be freed from locking devices when the shutter has been extended. <IMAGE>

Description

SPECIFICATION Air dampers The present invention relates to air dampers of the kind which comprise a holding shutter composed of reversely folding hinged shutter elements which are normally held in a compact stack by means including a fusible link such that in the event of a temperature rise to a predetermined value, the fusible link parts and the shutter is opened out under its own weight and/or by springs to close the duct, thereby opposing the spread fire along the duct.

In accordance with the present invention, the means for retaining the folded shutter in its compact condition comprises a fusible link having each end releasably secured in a respective catch carried by a frame defining the opening which is closable by the shutter, the catches being on opposite sides of the opening. With this arrangement, the fusible link can be conveniently replaced simply by operating the catches. Preferably the catches are of the self operating kind which will automatically engage and hold the respective end of the fusible link when this end is moved into engagement with its catch. The catches may be remotely releasable, for example by means of a Bowden cable.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings, in which Figure 1 is a perspective view of part of a fire damper, parts of the later being broken away to show details of the fusible link and its catches, Figure 2 is a perspective view of a an attachment for one of the catches to enable the catch to be operated remotely, and Figure 3 is a perspective view of the lower part of the damper shown in Fig. 1 with parts broken away, seen from the opposite side.

The fire damper shown in Fig. 1 may be of the general kind disclosed in patent specification No. 1,114,215 having a rectangular frame 1 formed of channel-section sheet metal stock and a shutter assembly 2 formed of a set of rolled sheet stainless steel shutter elements 3. The shutter elements 3 have hinge formations 4 and 5 along each of their edges, the formation 4 of each element fitting within the formation 5 of an adjacent element so that the elements 3 together form a reversely folding shutter assembly. The upper most element 3 is securely fixed to the frame 2.

A sheet metal strap member 6 is rivetted to the frame 1 and has a portion 7 extending down each side of the shutter stack 2 to end in a flange 8 having a catch assembly 9 rivetted to it at 1 0.

Each catch assembly 9 comprises a sheet metal frame 11 of inverted channel form, the bottom and two side walls of the channel having a cut out 1 2 to receive a pin 1 3 on the respective end of a fusible link 14, the spacing between the two pins 1 3 being equal to the spacing between the two cut outs 1 2.

Each catch 9 includes a latch member 1 5 pivotally mounted on a pin 1 6 in the catch frame 11. Each latch 1 5 has a latching cam nose 1 7 and a finger tab 1 8 whereby an operator can retract the nose 1 7 from the cut out slot 1 2 to release the pin 1 3. When the pin 1 3 is pushed into the slot, it will displace the cam nose 1 7 pivoting the latch 1 5 about the pin 1 6 until the pin is past the cam nose 1 7 and a spring (not shown) can then return the latch 1 5 so that the cam nose 1 7 holds the pin 1 3 captive in the cut out slot 1 2.

Accordingly, with both pins 1 3 engaged in their catches 9, the fusible link 14 will hold the shutter 2 in its compacted reversely folded position. If the fusible link 14 parts in re sponse to high temperature, each half of the fusible link can pivot about its pin 13, allow ing the shutter 2 to open out to close the opening through the frame 1.

The fusible link 14 may be of the well known construction comprising two identical metal strips secured together in the central part of the fusible link by a low melting point alloy. Each of the pins preferably has a shank portion of diameter to fit easily into the cutout 1 2 and a head which is of sufficiently large diameter to prevent its sliding through the base portion of the cutout in which the shank portion of the pin 1 3 is retained by the cam nose 1 7. The shank portion of the pin 1 3 must of course be free to rotate in the catch in the event of the fusible link parting.

Fig. 2 shows an attachment which may be mounted on each of the catches to enable them to be remotely operated by means of a Bowden cable 20 having an outer sleeve 21 and an inner wire cable 22 slidable in the sleeve 21. A bracket plate 23 is rivetted at 24 to the catch frame 11 and has a bent up end portion 25 serving as an abutment for the sleeve 21 while being slotted to accommodate the cable 22 which is secured in a lug 26 on one arm of a bell crank lever 27 which is pivotted on the bracket 23. The other arm 28 of the bell crank lever 27 is curved to provide a convex camming surface 29 to act on the latch member 1 5 when the cable 22 is pulled into the sleeve 21 by a control member (not shown) at the other end of the cable 20 for example at a conveniently excessible part of the duct work.With constructions shown in Figs. 1 and 2, when it is required to refit the link 14 or to fit a new link (in the event of the original link having parted), this can be done with one hand-the operative inserting his hand (holding the link) through an adjacent access opening in the ductwork, refolding the shutter and then inserting the pins 1 3 in their latches 9.

The bottom 31 of the frame (Fig. 3) carries a pair of ramp elements 32 having locking noses 33 to retain the bottom formation 4 of the lowermost 34 of the elements 3. To enable the shutter to be refolded after a test operation, the formation 4 on the element 34 must first be freed from the nose 33. This is normally done from an acess opening to the rear of the shutter as seen in Fig. 3 by pushing on the element 34 but to enable this to be done also from the front as seen in Fig.

3, a ring 35 is pivoted in a strap 36 riveted to the front face of the element 34 and enables the element 34 to be pulled free from the noses 33.

Claims (6)

1. An air damper of the kind which comprise a floding shutter composed of reversely folding hinged shutter elements which are normally held in a compact stack by means including a fusible link, wherein the fusible link has each end releasably secured in a respective catch carried by a frame defining the opening which is closable shutter, the catches being on opposite sides of the opening.

2. A damper according to claim 1 wherein the catches are of the self-operating kind which will automatically engage and hold the respective end of the fusible link when this end is moved into engagement with its catch.

3. A damper according to claim 1 or 2 wherein the catches are remotely releasable.

4. A damper according to any of the preceding claims and including locking means on the frame for the end most shutter element, wherein the end most shutter element carries a handle.

5. A damper according to claim 4 wherein the handle comprises a folding loop.

6. An air damper substantially as hereinbefore described with reference to the accom panying drawings.