GB2211733A - Fire damper - Google Patents

Abstract

A fire damper is intended for use in a ventilating duct. The damper comprises a plurality of blades 3 inter-connected concertina fashion, adapted to extend across the ventilation duct to seal it. The blades 3 are retained in a retractive position by a transverse link 6. Retaining means 12, 13 releasably engage at least one end of the link 6. The retaining means 12 13 incorporate an element of memory material 23 adapted to change from one configuration to another configuration when subjected to a high temperature. When the element of memory material 23 changes configuration the retaining means 12, 13 release the transverse link 6, and so the damper can move to the extended position in which it seals the ventilating duct. <IMAGE>

Description

DESCRIPTION OF INVENTION ImDrovements in or relating to a fire damper THE PRESENT INVENTION relates to a fire damper.

It has been proposed previously to provide a fire damper to be mounted in a ventilation duct, the fire damper comprising a plurality of hingedly interconnected blades which are folded into a retracted position, concertina fashion, and are retained in that position by means of a fusible link. The fusible link is adapted to break when exposed to a high temperature, thus permitting the blades to move, either under gravity or a spring biass, to an extended position in which the blades substantially seal the ventilation duct in which the damper is mounted.

Various dampers of this type have been proposed previously but reference may be made to British Patent No. 2028128B which discloses a damper of this type in which the fusible link is retained in manually operable catches, located at either end of the link, to permit the link to be removed from its position in which the damper blades are retained in the retracted position.

This enables the operation of the damper to be tested.

The present invention relates to an improvement in a damper arrangement of this general type, but embodiments of the invention may comprise dampers of very different design.

According to this invention there is provided a fire damper arrangement for use in conjunction with a ventilating duct, said damper comprising a plurality of blades interconnected concertina fashion, adapted to extend across the ventilation duct substantially to seal the ventilation duct, the blades being retained in a retracted position by means of a transverse link element, there being retaining means releasably engaging at least one end of said link, said retaining means incorporating an element of memory material adapted to change from one configuration to another configuration when the temperature to which it is exposed rises above a predetermined limit, the arrangement being such that when said element of memory material changes configuration, the condition of said retaining means is altered to ensure release of said transverse link and thus the release of the damper to the extended position.

Conveniently said link is a fusible link.

Advantageously at least one end of the said link is retained by a releasable catch which comprises part of said retaining means.

Preferably said element of memory material is adapted to release the link from the catch when the temperature to which the damper is exposed rises above said predetermined limit.

Conveniently the catch comprises a housing defining a slot into which a stud at one end of the link may be inserted, and a latching lever movable between the latching position in which part of the latching lever engages and retains the stud within the housing, and a release position in which the stud may leave the housing, the element of memory material being positioned and adapted to move said latching lever from the latched position to the release position as the element of memory material changes its configuration.

Preferably the said element memory material is an element of memory metal.

In order that the invention may be more readily understood, and so that further features thereof may be appreciated, 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 damper arrangement in accordance with the invention, and FIGURE 2 is an enlarged view of part of the arrangement shown in Figure 1.

Referring now to the drawings it is to be understood that the embodiment of the invention illustrated in Figure 1 is very similar to the fire damper described in British Patent No. 2028128, and the reader is directed to the specification of that Patent.

The presently described embodiment of the invention comprises a damper which consists of a generally inverted "U" casiing 1 which is adapted to be mounted on a ventilating duct, the casing containing a shutter 2 in the form of a plurality of individual damper blades 3 which are hingedly interconnected at their adjacent ends 4, 5. The blades 3 are folded into a retracted position within the casing 1 in a "concertina" form.

The shutter 2 is maintained in the retracted position by means of a fusible link 6 which consists of two plates 7, 8 interconnected in a central region 9 by solder. Each plate 7, 8 has a projecting stud 10, 11, the studs being at the two opposed ends of the link, and on opposite sides of the link. The studs 10, 11 are adapted to be retained by manually operable catches 12, 13 which are each mounted on the underside of an outwardly directed flange 14 provided at the base of the side wall 15 of the casing 1. Each catch 12, 13 resembles a conventional gate catch and consists of a housing 16 defining a slot 17 into which a stud, such as the stud 10 may be inserted.Pivotally mounted within the housing, by means of a pivot pin 19 is a pivotally movable latching lever 20, which is operable by means of a finger plate 21 to be moved pivotally between a latching position and an unlatching position. When the latching lever is in the latching position a projecting portion 22 of the latching lever extends across the slot 17 defined by the housing 16 to engage and retain the stud 10, but when the latching lever is in the unlatching position the stud may be inserted into or removed from the slot 17.

It will be understood that when the stud 10 and the stud 11 have been engaged by the respective catches 12, 13, the shutter 2 will be retained in a retracted position unless the temperature rises to such a degree that the solder holding the plates 7 and 8 of the fusible link 6 together melts, at which time the fusible link will break, permitting the blades 3 of the shutter 2 to move to an operative position in which they extend across the ventilation duct, thus substantially sealing the ventilation duct. The shutter 2 may also be moved to the operative position by manually releasing one or both of the catches 12 or 13 and thus these catches may be utilised to test the operation of the described damper. The catches 12 or 13 may also be remote controlled.

The damper, as thus far described, is substantially identical to the damper of British Patent 2028128. However, the present invention provides an additional heat-sensitive means to permit the shutter to move to the operative position. It is to be noted that the catch 12 as shown in Figure 1 is provided with an element 23 in the form of a substantially "U" shaped clip formed of memory metal. Memory metal is known per se. An element of memory metal may have a specific configuration at ordinary temperatures, but may "remember" an alternative configuration that it adopts when the temperature of the memory metal element exceeds a specific predetermined threshold temperature.

The two free ends of the clip 23 are each retained, by means of retaining tabs 24 formed in the housing of the catch 12, with the arcuate base of the clip being located immediately adjacent the fingerplate 21.

The clip is formed of memory metal, and is such that, at ordinary temperatures, the clip is located adjacent the undersurface of the fingerplate 21. However, the clip is such that when the temperature to which the clip is exposed exceeds a predetermined limit, the metal of the clip moves to a pre-determined condition that the metal has "remembered" and in moving to that position the arcuate portion of the clip engages the undersurface of the fingerplate 21, thus moving the latching lever 20 to such a position that the portion 22 of the latching lever 20 is moved out of the channel 17, thus permitting the stud 10 to be disengaged from the latch 12.

Memory metal is, of course, known per se and the skilled man will readily be able to make a clip to perform the function as described.

It will be appreciated, therefore, that in the described embodiment of the invention the predetermined temperature at which the memory metal clip assumes its "remembered" shape may be chosen to be less than, greater than, or equal to the temperature at which the solder retaining together the plates 7 and 8 of the fusible link 6 is intended to melt. Thus the provision of the clip 23 may serve as added precaution to ensure that the shutter 2 will move to the operative position when the temperature to which the damper is subjected reaches a predetermined limit.

The casing 1 and the associated equipment is received within an outer frame 24 which can be mounted in the ducting across which the damper is to extend.

It is to be appreciated that in a modified embodiment of the invention the fusible link 6 may be replaced by a solid bar, the release function for the shutter thus being provided solely by the memory metal clip. In such an embodiment it may be preferred to provide a memory metal clip on each of the catches 12, 13, rather than on just one catch as shown in the illustrated embodiment of the invention.

Whilst reference has been made to a clip of memory metal it is to be appreciated that other memory materials may alternatively be utilised.

Whilst the memory metal clip has been shown as positively actuating a catch to release the link that holds the shutter in the retracted position it is to be appreciated that the memory material may form part of the catch itself, so that when the memory material reaches the appropriate pre-determined temperature, the configuration of one or more elements of the catch may alter thus permitting the part of the link retained by the catch to be released.

Claims (5)

CLAIMS:

1. A fire damper arrangement for use in conjunction with a ventilating duct, said damper comprising a plurality of blades interconnected concertina fashion, adapted to extend across the ventilation duct substantially to seal the ventilation duct, the blades being retained in a retracted position by means of a transverse link element, there being retaining means releasably engaging at least one end of said link, said retaining means incorporating an element of memory material adapted to change from one configuration to another configuration when the temperature to which it is exposed rises above a predetermined limit, the arrangement being such that when said element of memory material changes configuration, the condition of said retaining means is altered to ensure release of said transverse link and thus the release of the damper to the extended position.

2. An arrangement according to claim 1 wherein said link is a fusible link.

3. An arrangement according to claim 1 or claim 2 wherein at least one end of the said link is retained by a releasable catch which comprises part of said retaining means.

4. An arrangement according to claim 3 wherein said element of memory material is adapted to release the link from the catch when the temperature to which the damper is exposed rises above said predetermined limit.

5. An arrangement according to claim 4 wherein the catch comprises a housing defining a slot into which a stud at one end of the link may be inserted, and a