GB2223942A

GB2223942A - Fire damper

Info

Publication number: GB2223942A
Application number: GB8821880A
Authority: GB
Inventors: Neville Preston
Original assignee: GILBERTS
Current assignee: GILBERTS
Priority date: 1988-09-07
Filing date: 1988-09-07
Publication date: 1990-04-25
Also published as: GB8821880D0

Abstract

A fire damper for location in ducting, having a metal shutter mounted in a housing, normally retained in a folded condition but loaded towards an extended condition across the housing, has an operating mechanism for folding the shutter after release, operable externally of the housing. Thus, re-folding of the shutter after maintenance testing is facilitated. In one embodiment the operating mechanism comprises a winding handle 41, for winding a shaft 42 on which are mounted a ratchet wheel 48 and two reels 50, 52, for steel bands 54, 56 secured to the leading element of the shutter. In an emergency condition a pawl is disengaged from the ratchet wheel 48 if a fusible device 80 releases it. For maintenance testing the engineer may lift the pawl from the ratchet wheel 48 to test the shutter release operation, and replace it prior to operating the winding handle 41 to re-fold the shutter. <IMAGE>

Description

FIRE DAMPER This invention relates to a fire damper of the type comprising a metal housing open on both sides to define an opening through the housing. The housing contains a metal shutter made up of metal elements hinged together, the shutter normally being held, against a powerful spring or springs, in a folded condition in which the damper is open to the flow of air, but being releasable to adopt an extended condition in which it closes the opening through the housing. Such a damper is employed in ducting, for example air conditioning ducting, the shutter being released, to adopt its extended condition, in the event of fire. Commonly, the shutter is released to adopt its extended condition when a fusible retaining element within the housing fails, or when a latch within the housing is released electrically, for example on external sensing of smoke and/or flames.

It is necessary for such fire dampers to be tested periodically, by releasing the shutter. The shutter then requires to be re-folded ready for use. The shutter is released and re-folded manually. The refolding operation can, however, be hazardous to the maintenance engineer. Access to the shutter is through an access door in the ducting and it may be difficult for the engineer to grip the shutter through the access door, and re-fold, against the strong spring force. There i.; an attendant risk of the shutter extending, trapping the engineer's fingers between the shutter and the bottom of the housing.

According to the present invention there is provided a fire damper of the kind comprising a metal shutter mounted in a housing, the shutter being capable of being folded into a folded (damper open) condition in which it is retained in place, but being loaded towards an extended (damper closed) condition, the fire damper comprising an operating mechanism for causing the shutter to fold into the folded condition, operable externally of the housing.

Preferably, the operating mechanism is mounted externally of the housing, suitably on a wall of the housing, and preferably adjacent the shutter, with reference to the shutter in its folded condition.

Preferably, the operating mechanism is such as to act to retain the shutter in the folded condition, other than in the event of fire or testing. Preferably, moreover, the operating mechanism is such as to act to prevent the shutter unfolding from a partly-folded position. Thus, in the event of the maintenance engineer interrupting the folding operation before folding is complete, the shutter will be retained in a partly folded condition ready for completion of the folding operation. Suitably, these features are realised by use of a ratchet and pawl, the shutter being coupled to the ratchet and the pawl being disengaged from the ratchet for release and unfolding of the shutter. However, it should be noted that the shutter may be retained in place by means alternative or additional to the operating mechanism.

The shutter may be released, in the event of fire, by any conventional means, for example by use of a fusible device which retains the shutter in place, or of an electro-magnetic device releasing the shutter in response to local and/or remote heat and/or smoke detection.

Preferably, the operating mechanism comprises a flexible, elongate metal element, for example a band or chain secured to the leading element of the shutter, and means for winding the elongate element onto a reel, such means preferably comprising a manual winding handle.

Although a single elongate element may be employed if secured centrally to the leading element, it is preferred that the operating mechanism comprises two such elements, one secured to one side of the leading element of the shutter and one secured to the other side.

Preferably, the or each elongate elelment has portions secured together by a fusible connection, for example a fusible rivet, preferably located adjacent the end of the elongate element which is connected to the leading element of the shutter. Such connection(s) may comprise the sole fusible part of the fire damper, but may be employed, as a safeguard, in addition to the fusible or other release device(s) described previously.

Thus, should, on release of such device(s) the shutter failed to extend to close the damper, due perhaps to damage to or snagging of the elongate element(s), the shutter may be released on fusing of the connection(s).

The operating mechanism suitably comprises a shaft rotatably mounted, externally of the housing, on a wall of the housing adjacent the shutter, with reference to the shutter in its folded position, the shaft having fixed to it a ratchet wheel and the or each elongate element which acts upon the leading element of the shutter, the shaft being coupled to the winding handle.

It may be convenient in certain circumstances of difficult access for the above-mentioned winding handle to drive the shaft of the operating mechanism through a bevel gear.

In many fire dampers, the leading edge of the leading element of the shutter is bent to form a lip which is entrapped, in the extended condition of the shutter, behind abutments on the housing, to prevent any return movement of the shutter in the event of failure of the spring or springs. In the preferred aspect, the present invention provides, to facilitate the return of the shutter to its folded condition, means operable externally of the housing, for moving the leading element of the shutter to a position in which it is clear of such abutments, ready to be folded. Such means preferably comprise one or more push rods projecting through a wall of the housing.The or each such push rod is pushable against a spring bias from a position in which it permits the lip to remain behind an abutment to a position in which it has pushed the lip past the abutment, in which position the or each push rod may be secured against retraction. Preferably, two such push rods are provided, one located towards one side of the leading element and the other located towards the other side.

The invention will now be further described, by way of example, with reference to the accompanying drawings, in which : Figure 1 is a perspective view of a fire damper of the type to which the present invention may be applied (without showing the parts which effect release and refolding of the shutter); Figure 2 is a plan view of a fire damper in accordance with the invention; Figure 3 is a cross-section along the line A-A in Figure 2; Figure 4 is a cross-section along the line B-B in Figure 2; Figure 5 is a cross-section along the line C-C in Figure 2; and Figure 6 is a cross-section of an alternative fusible device not shown in the other drawings.

Figure 1 shows a fire damper 2 having a metal housing 4 which is open on both sides to define an opening through the housing. From opposite sides of a rectangular-section central part 8 of the housing 4 extend aligned, rectangular-section projecting parts 10 and 12, intended for engagement in ducting. The central part 8 extends beyond the projecting parts 10 and 12 on all sides. Mounted on the internal surface of one such side 16 of the central part 8, the top wall in use, is a metal shutter 18. The shutter is formed of a plurality of steel shutter elements 20, hinged together along hinges 22. The leading shutter element 24 has secured to each of its lateral sides a band spring 26 (of which one is seen in Figure 1). Each band spring 26 is secured at one of its ends to the leading shutter element 24, its other end being secured to parts 28 mounted on the internal surface of the lower wall 30 of the housing.

The springs bias the shutter towards the lower wall 30.

Normally the shutter is retained in a folded condition adjacent the top wall 16 but in the event of fire it is released, being drawn by the springs into its extended condition, in which it closes the opening, with the leading edge 34 of the leading element 24 engaging the lower wall 30.

Each part 28 comprises an inclined edge 36 which the leading edge 34 of the leading element contacts during the unfolding of the shutter. In the fully extended condition of the shutter, a lip 40 on the leading edge 34 is engaged behind abutments 38 at the lower end of the edges 36.

As shown in Figure 2, mounted on the top wall 16 of the housing is an operating mechanism which comprises a winding handle 41 driving a shaft 42 which runs in bearings 44, 46. The bearings are mounted on the top wall 16. Fixed to the shaft are a ratchet wheel 48 and reels 50, 52. To the spool of each reel is secured a steel band, 54, 56. Each band is connected to the leading element of the shutter.

Each steel band comprises an elongate upper part, wound onto the appropriate reel 50, 52 when the shutter is in its folded condition, and a short lower part 58 in the form of a loop (Figure 5). Each loop is engaged around a respective bar 60,61 carried at the leading edge of the leading element, the leading element being cut away and the ends of the bars being retained by the lip 40 at the leading edge. The two parts of each steel band are connected together by a fusible rivet 62, 63.

As shown in Figure 3, coupled to the ratchet wheel 48 is a pawl 64. The pawl is pivoted at 66 to side walls 68 (Figure 2) which embrace the ratchet wheel 48, and is connected by a rod 70 to a fusible device 72 which is mounted on the upper wall of one of the projecting parts 10, 12.

When integral, the fusible device 72 acts upon the rod 70, and thus the pawl 64, to permit rotation of the ratchet wheel only in the direction in which it causes the bands 54, 56 to be wound onto the reels 50, 52, and the shutter to be folded.

When fused, the device 72 causes the pawl 64 to lift from the ratchet wheel, whereby the shutter is drawn by the springs 26 into its extended (damper closed) condition.

The fusible device comprises an internallythreaded collar 74 welded to the upper wall of the projecting part 10, and an externally threaded part 80 screwed into the collar. The part 80 has a through bore enclosing the lower part of the rod 70 and soldered to the lower end of the part 80 is a disc 76. The disc is apertured and the lower end of the rod 70, having been passed through the aperture, has a portion 78 which bears against the lower surface of the disc. The bore of the part 80 has an internal shoulder and a spring 82 is retained, in compression, between the shoulder and the upper surface of the disc 76.

In the event of fire, on melting of the solder the spring 82 acts to push the disc 76 down, drawing the rod 70 down. The pawl 64 is thereby pivoted to lift out of engagement with the ratchet wheel 48.

In order to be able to disengage the lip 40 from the abutments 38 from outside the housing a pair of push rods 84 are provided (Figure 4), one adjacent each abutment. Each push rod passes through an aperture in the bottom of the housing, and through a guide bracket 86 mounted on the bottom wall of the projecting part 10.

Each push rod carries a transverse pin 88 which is slidable within a slot in the respective guide bracket.

Each rod further carries a helical spring 90 engaged between the knurled head 92 of the push rod and a wall of the bracket.

When it is desired to re-fold the shutter each push rod is operated as follows : the rod is pushed, against the bias of the spring, until the pin 88 has left its slot in the guide bracket. At this point the lip has been pushed beyond the abutment 38. The rod is turned, to cause the pin to engage the end wall of the bracket, and restrain the push rod against return movement under the action of the spring.

When both push rods have been thus operated the shutter is ready to be folded.

Once the shutter is folded the push rods are again turned, to bring the pins into engagement with the slots, whereby the push rods retract, under the spring force.

An engineer testing the operation and the shutter manually releases the pawl 64 and, when provided, the additional device 94. The shutter should then adopt its extended (damper closed) condition. To return the damper to its folded (damper open) condition, the engineer pushes the two push rods 84 and turns them to keep them in the position in which they keep the lip 40 on the leading element of the shutter beyond the abutments 38; and then simply turns the winding handle 41, until folding is complete. Should the engineer have to interrupt winding before folding is complete, the ratchet and pawl prevent re-extension of the shutter.

Figure 6 relates to an alternative embodiment having latching type fusible device 94. The device has a bracket 96 secured to the undersurface of the top wall of one of the projecting part 10, 12. Mounted for latching movement within the bracket is a latch bolt 98, in the form of a latch head 100, having an inclined face 102 and a yoke part 104 which carries the head 100. The yoke part 104 has walls which embrace the head 100 in a close fit; and by means of solder the two parts are joined together. Further, the two parts are pivoted together by a pivot 106.

When the shutter is refolded after testing, towards the end of the refolding operation the shutter engages the inclined face 102 and the complete latch bolt 98 is pushed against the force of a spring 108, to a position permitting the shutter to pass it. Once it has done so, the latch bolt returns, under the force of the spring, to its rest position, in which the latch bolt prevents unfolding of the shutter.

In the event of fire, the solder melts and the parts 100 and 104 no longer act as one part; instead, the latch head 100 pivots about the yoke part 104, the latch head 100 presents an inclined face to the shutter and the shutter, drawn down by a strong spring force, causes retraction of the device.

In this embodiment a winding handle is provided but not a ratchet and pawl device, so that re-folding of the shutter after testing must be effected without interruption.

The invention is not restricted to the details of the foregoing embodiment. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings).

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings) may be combined in any combination, except combinations where at least some of such features are mutually exclusive.

Claims

1. A fire damper comprising a metal shutter mounted in a housing, the shutter being capable of being folded into a folded (damper open) condition in which it is retained in place, but being loaded towards an extended (damper closed) condition, the fire damper comprising an operating mechanism for causing the shutter to fold into the folded condition, operable externally of the housing.

2. A fire damper as claimed in Claim 1, wherein the operating mechanism is mounted externally of the housing.

3. A fire damper as claimed in Claim 2, wherein the operating mechanism is mounted on a wall of the housing, adjacent the shutter in its folded condition.

4. A fire damper as claimed in any preceding claim, wherein the operating mechanism is such as to act to retain the shutter in the folded condition, other than in the event of fire or testing.

5. A fire damper as claimed in any preceding claim, wherein the operating mechanism is such as to act to prevent the shutter unfolding from a partly-folded condition.

6. A fire damper as claimed in any preceding claim, wherein the operating mechanism comprises a ratchet and pawl, the ratchet being coupled to the shutter.

7. A fire damper as claimed in any preceding claim, comprising a fusible link which, when fused, releases the shutter.

8. A fire damper as claimed in any preceding claim, wherein the operating mechanism comprises a flexible elongate metal element coupled to the leading element of the shutter and means for winding the elongate element onto a reel, in order to cause the shutter to fold into its folded condition.

9. A fire damper as claimed in Claim 8, wherein the operating mechanism comprises two flexible elongate metal elements, one coupled to one side of the leading element of the shutter and the other coupled to the other side.

10. A fire damper as claimed in Claim 8 and 9, wherein the or each elongate element has portions engaged together by a fusible connection.

11. A fire damper as claimed in Claim 8, 9 or 10, when dependent upon Claim 6, wherein the operating mechanism comprises a shaft rotatably mounted, externally of the housing, on a wall of the housing adjacent the shutter, in its folded condition, the shaft having fixed to it a ratchet wheel and the or each elongate element which acts upon the leading element of the shutter, the shaft being coupled to a winding handle.

12. A fire damper as claimed in any preceding claim, wherein the leading edge of the leading element of the shutter is formed with a lip which is engaged, in the extended condition of the shutter, behind abutments on the housing, to prevent any return movement of the shutter in the event of failure of the spring or springs, the fire damper further comprising means operable externally of the housing, for moving the leading element of the shutter to a position in which it is clear of such abutments, ready to be folded.

13. A fire damper as claimed in Claim 12, wherein the means for moving the leading element of the shutter comprises one or more push rods projecting through a wall of the housing, the or each push rod being pushable against a spring bias from a position in which it permits the lip to remain behind an abutment to a position in which it has pushed the lip past the abutment, in which position the or each push rod may be secured against retraction.

14. A fire damper as claimed in Claim 13, wherein two push rods are provided, one located towards one side of the leading element and the other located towards the other side.

15. A fire damper substantially as hereinbefore described with reference to the accompanying drawings.