GB2180745A

GB2180745A - Fusible element mounting mechanism

Info

Publication number: GB2180745A
Application number: GB08622043A
Authority: GB
Inventors: Robert John Magill; David John Gaiger; Eric J Wightman; Eric J Wallbank
Original assignee: Actionair Equipment Ltd
Current assignee: Actionair Equipment Ltd
Priority date: 1985-09-13
Filing date: 1986-09-12
Publication date: 1987-04-08
Anticipated expiration: 2006-09-12
Also published as: GB2180745B; GB2224440B; GB2223676B; GB8522702D0; GB8622043D0; GB2224440A; GB2223676A; GB8918643D0; GB8918642D0; GB8920143D0; GB8920144D0

Abstract

A fusible element mounting mechanism can be releasably latched e.g. by a retainer spring to the spigot (12) of a damper. So that the whole mechanism can be removed from the damper for the replacement of the fusible element outside the duct in which the damper is located. The fusible element is preferably designed as a latch with one or more latch jaws adapted to engage the retractable metal curtain (18) of the damper so as to hold it in its retracted position against the action of a spring in the damper. The mounting mechanism may include a permanent thermal link, in addition to, or in replacement of, a fusible link in the mechanism. <IMAGE>

Description

SPECIFICATION Fusible element mounting mechanism This invention relates to a fusible element mounting mechanism for attachment to one of the spigots on a fluid damper which has a spigot on each side to permit it to be fastened to the ends of respective ducts. The invention is especially applicable to fire dampers and smoke dampers which require a fusible element of some kind in order to release a metal curtain, movable blades or some other form of barrier to prevent the passage of air or other fluid through the damper on the outbreak of fire in the building where the damper is installed.

Once a damper has been positioned in a duct of say, a ventilation system, the curtain of the damper needs to be inspected from time to time in order to check that it is still operable and will act properly in the event of fire breaking out. To reach the curtain and the fusible element assembly, it is usual for an inspection hatch to be provided in one of the ducts adjacent the damper so that an engineer can put his arm through the hatch opening to move the metal curtain or other barrier back into the position where it allows free flow of air through the damper after he has tested the damper. This also enables him to replace any defective parts of the assembly should that be necessary.Also, if a fire has actually occurred in the building so that the fusible element has melted to initiate operation of the damper, the above construction will allow an engineer to replace the "spent" fusible element with a new one.

Hitherto, the construction of fusible element assemblies as used in fire dampers has been such that it is not always easy for an engineer to move the metal curtain or other barrier back into its retracted position and then hold it there until he has refastened the fusible element assembly, particularly as the steel curtain or other barrier is acted on by a strong spring. Further, the replacement of the fusible element itself often proves to be quite a tricky operation and an engineer cannot always be certain that he has inserted a new fusible element correctly.

With these considerations in mind, the present invention is directed-in one of its aspects-to a fusible element mounting mechanism which can be releasably latched or otherwise removably secured to the spigot of a damper. This has the advantage that the whole mechanism can be removed from the damper for the replacement of the fusible element outside the duct.

From another aspect, the invention is directed to a novel form of fusible element which is itself designed as a latch with one or more latch jaws adapted to engage the steel curtain or other barrier so as to hold it in a retracted position.

From yet another aspect, the invention is directed to a release/stop latch spring, preferably of generally U-shape, which holds the fusible latch in its curtain-engaging position but which can be operated to allow the jaw or jaws of the fusible latch to release the metal curtain for test purposes.

The invention also concerns-from still another aspect-the use of a permanent thermal link in addition to, or in replacement of, the fusible link in the assembly. Where a thermal link is provided in addition to a fusible link dual fail-safe operation is ensured.

An example of a fusible element mounting mechanism in accordance with the invention is illustrated in the accompanying drawings, in which Figure 1 is a perspective view, with parts broken away, of a typical fire damper having a steel- curtain and provided with a pair of spigots one of which is used to support the fusible element mounting mechanism; Figure 2 is a diagrammatic section through the damper shown in Figure 1 showing the steel curtain in its retracted position; Figure 3 is a side view of the fusible element mounting mechanism; Figure 4 is a vertical section through the Usection body of the mounting mechanism prior to its attachment to the spigot of the damper; Figure 5 is a view similar to Figure 4 showing the body of the mounting mechanism after it has been fitted on the damper spigot; Figure 6 is a plan view from above of the mounting mechanism;; Figure 7 is a vertical section through the mounting mechanism at right-angles to the view shown in Figure 3; Figure 8 is a front view of the fusible latch forming part of the mechanism; Figure 9 is a side view of the latch shown in Figure 8; Figure 10 is a plan view of the latch shown in Figures 8 and 9; Figure 11 is a view similar to Figure 7 but with certain parts removed to show the incorporation of a thermal link in the mechanism; Figure 12 is a view similar to Figure 11 illustrating the operation of the thermal link which causes the latch to release the metal curtain of the damper; and Figures 13 and 14 and Figure 15 are views of two other forms of mounting mechanism.

The fire damper shown in Figures 1 and 2 comprises a casing 10 provided with a hollow spigot 12 on each side to permit the damper to be fitted to respective ducts 14 and 16.

To permit the damper to shut off the flow of air or other fluid through the duct in the event of fire, it is provided with a metal curtain 18 composed of interfitting blades or strips which is acted on by a strong spring. Normally, the metal curtain 18 lies within an upper internal compartment 20 of the casing 10 in a foldedup condition (see Figure 2) so as to permit the free flow of air or other fluid through the ducts 14 and 16, but in the event of fire the curtain is released by heat-sensitive means so as to take up an extended position in which it closes the through-opening in the damper. Figure 1 shows the curtain at a point where it is just about to close off the passage through the damper.

It is usual in fire dampers for the metal curtain or other barrier 18 to be held in its retracted position by a fusible element assembly. It is however necessary for the operation of the damper to be tested at times, and for this purpose it is necessary that the fusible element assembly be released other than by melting of the fusible element to permit the metal curtain or other barrier to move into its extended position. It has been found however that, after such tests have taken place, it is frequently difficult for an engineer to move the metal curtain back to its retracted position and to hold it there while he resets the fusible element assembly. The same difficulty also arises when the fusible element needs to be replaced-for example after a fusible element has fused as a result of a fire in the building.

In order to overcome these problems, the fusible element assembly shown in the accompanying drawings comprises a mounting mechanism 22 (see Figure 3) having a U-section body 24 within which is pivotally carried a fusible latch 26. The central part 28 (see Figures 4 and 5) of the U-section body 24 carries a support retainer spring 30 which is attached atone end to the body 24 by a rivet or pin 32. An intermediate portion of the support retainer spring 30 is formed with a projection or nose portion 34 which extends upwards through a hole 36 in the central portion 28 of the body 24.When therefore the body 24 is pushed on to the support bracket 38 shown in Figure 4 in the direction of the arrow, the nose or projection 34 of the retainer spring 30 will be pushed down by a support bracket until the body 24 reaches the position shown in Figure 5, whereupon the nose or projection 34 on the spring 30 will snap up into a hole 40 formed in the bracket 38. The fusible element mounting mechanism is now therefore held securely on the support bracket 38 but in a removable or releasable fashion.

All that is necessary for the mounting mechanism to be released from the bracket 38 is for the end portion 42 of the retainer spring 30 to be deflected in the direction of the arrow shown in Figure 5 so as to cause the nose or projection 38 on the spring to come out of the hole 40 in the bracket 38. The body 24 of the mechanism can then be slid off the suppport 38 in the opposite direction to that illustrated in Figure 4. It will be understood that the bracket 38 is either an integral part of one of the spigots 12 on the damper or is a separate part attached to that spigot.

Figures 6-10 illustrate in more detail the construction of the fusible latch 26 which is shown partially in Figure 3. As will be seen from these Figures, the latch comprises two U-section parts 44 and 46 which are fused together at their central portions 48 and 50 as shown in Figure 8. The inner one of the two U-section parts, i.e., the part 44, has two latch jaws 52 which serve to engage the lower edge of the metal curtain when it is in its retracted position so as to hold the curtain within the upper compartment 20 of the dam per as shown in Figure 2. In other words, the fusible element also acts as a latch and does not actuate a separate latching member. It will be seen that the fusible latch 26 is pivotally mounted at 54 on the body 24 and, as ex plained below, is held in a position so as to be urged into firm engagement with the lower end of the metal curtain.The pivotal mounting for the latch 26 here takes the form of a split pin but it is to be understood that any other kind of suitable pivotal mounting could be used instead.

If therefore the temperature rises above a certain level, the fusible metal joining the cen tral portions 48 and 50 of the two parts 44 and 46 of the latch will melt so that the two parts become freed from each other. The strong spring acting on the metal curtain 18 will then be able to force the curtain down wards into its extended position without any hindrance from the latch jaws 52 of the fusi ble latch.

When, however, it is desired to test the operation of the damper without fusing the fusible latch 26, it is necessary only for a release/stop latch spring 58 (see Figure 7) to be moved into the position shown in Figure 12 in order to allow the fusible latch 26 to yield against the force of the spring acting on the metal curtain 18. As will be seen from Figure 7, the release/stop latch spring 58 has two elbow portions or shoulders 60 which normally lie above and abut against the upper surfaces 62 on the outer part 46 of the fusi ble latch 26 (see Figure 9). By compressing the release/stop latch spring 58 in the manner illustrated in Figure 12, its two elbow portions 60 are moved inwardly of the surfaces 62 on the fusible latch 26 with the result that the latch is no longer able to resist the spring of the metal curtain.

As shown in Figure 7, the body 24 of the mounting mechanism has a lower bracket 64 which gives rigidity to the body 24. Projecting through overlapping parts of the body 24 and the lower bracket 64 are a pair of pins 66 and 68 which can be pressed towards one another against the spring pressure of the re lease/stop latch spring 58 so as to bring the latter into the position shown in Figure 12. It is also possible for this operation to be car ried out from a remote position using a Bowden cable 74 or other such means as shown in Figures 11 and 12. Surrounding the pins 66 and 68 are two helically-coiled memory metal springs 70 and 72 respectively which, at normal temperatures, take up the position shown in Figure 11 where they do not compress the release/stop latch spring 58.When, however, the temperature rises to about 72"C, they expand as shown in Figure 12 so as to compress the release/stop latch spring 58. That will cause release of the damper curtain. It therefore follows that the provision of a thermal link in the form of two memory metal springs 70 and 72 provides a dual fail-safe facility on the mechanism. The fusible latch 26 will therefore operate at around 200"C while the memory metal springs 70 and 72 will operate at about 72"C or at some other predetermined temperature below that at which the latch 26 fuses.

It is to be understood that the two memory metal springs 70 and 72 could be replaced by equivalent means which move in some way in response to a rise in temperature. For example, a bi-metal strip could be used in place of the two memory springs, and it would also be possible to use a single memory metal tension spring which extends between the two limbs of the release/stop latch spring 58 so as to pull them together if a rise of temperature takes place.

In some it may be acceptable for a fusible element to be dispensed with altogether and to rely solely on the memory metal springs 70 and 72 (or their equivalent) for the operation of the damper in the event that a fire breaks out. In that case the two parts 44 and 46 of the fusible latch 26 will be welded together or otherwise permanently fastened to one another.

When an engineer releases the latch 26 from engagement with the lower end of the metal curtain in order to test the operation of the damper, it is convenient for the latch 26 to be held in such a position that it latches onto the lower end of the metal curtain when the lower end is retracted again. With this consideration in mind, a small spring 56 is mounted at the top of the body 24 (see Figure 7) so as to hold the latch 26 in a position where it is ready to receive and latch onto the lower end of the metal curtain.

An advantage of using removable split pin or cotter pin 34 for mounting a latch 26 is that it makes replacement of the latch a very simple operation, and the engineer does not even need a tool to do such work.

Although the nose or projection 34 on the spring 30 engages positively in the hole 40 on the support brackets 38, it is convenient to provide a pair of downwardly-projecting locking lugs 76 (see Figures 3 to 6) which receive the front edge 78 of the support bracket 38 when the assembly is correctly mounted on that bracket as shown in Figure 5.

Figure 13 and 14 are views corresponding to Figures 11 and 12 to illustrate a modified construction wherein a generally L-shaped single-limb latch spring 58a is used in place of the double-limb spring 58. Only one memory spring (spring 70) is therefore provided in this form of mechanism. Similarly, Figure 15 shows another modification where a doublelimb latch spring 58b is used but in which only one memory spring (spring 72) is provided.

Claims

1. A fusible element mounting mechanism for attachment to one of the spigots on a fluid damper which has a spigot on each side to permit it to be fastened to the ends of respective ducts, in which the fusible element mounting mechanism is adapted to be releasably latched or otherwise removably secured to the spigot of a damper so that the whole mounting mechanism can be removed from the damper for the replacement of the fusible element outside the duct.

2. A fusible element mounting mechanism for attachment to one of the spigots on a fluid damper which has a spigot on each side to permit it to be fastened to the ends of respective ducts, in which the mounting mechanism supports a fusible element designed as a latch with one or more latch jaws adapted to engage a metal curtain or other barrier of the damper so as to hold it in a retracted position.

3. A fusible element mounting mechanism according to claim 2, in which a release/stop latch spring is arranged to hold the fusible latch in its curtain-engaging position but is operable to allow the jaw or jaws of the fusible latch to release the metal curtain for test purposes.

4. A fusible element mounting mechanism for attachment to one of the spigots on a fluid damper which has a spigot on each side to permit it to be fastened to the ends of respective ducts, in which the mouning mechanism includes a permanent thermal link, in addition to, or in replacement of, a fusible link in the mechanism.

5. A fusible element mounting mechanism according to any preceding claim, in which the mounting mechanism comprises a U-section body the central part of which carries a support retainer spring formed with a projection or nose portion which extends upwards through a hole in the central portion of the body so that, when the body is pushed onto a support on the damper spigot, the nose or projection of the retainer spring snaps into a hole formed in the support.

6. A fusible element mounting mechanism according to claim 2 or any claim appendant thereto, in which the latch comprises two U section parts which are fused together at their central portions with the inner one of the two U-setion parts having the latch jaw or jaws.

7. A fusible element mounting mechanism according to claim 3 or any claim appendant thereto, in which the release/stop latch spring has one or more elbow portions or shoulders which normally abut against one or more "hold" surfaces on the fusible latch but which-on compression or tension of the release/stop latch spring-are movable away from the said surfaces on the fusible latch with- the result that the latch is no longer able to resist the force of a spring in the damper.

8. A fusible element mounting mechanism according to claim 7, in which compression or tension of the release/stop latch spring to release the latch is effected by one or more operating pins or by a Bowden cable.

9. A fusible element mounting mechanism according to claim 3 or any claim appendant thereto, in which the mechanism includes at least one memory spring which, at normal temperatures, takes up a position where it does not act on the release/stop latch spring but which-if the temperature rises-expands to compress or tension the release/stop latch spring.

10. A fusible element mounting mechanism according to claim 2 or any claim appendant thereto, in which a spring is provided to hold the latch in a position where it is ready to receive and latch onto the lower end of a metal curtain in a fire damper.

11. A fusible element mounting mechanism according to claim 2 or any claim appendant thereto, in which the latch is pivotally mounted on a removable split pin or cotter pin to facilitate replacement of the latch.

12. A fusible element mounting mechanism substantially as described herein with reference to Figures 1-10, Figures 11 and 12, Figures 13 and 14, or Figure 15 of the accompanying drawings.