GB2141818A - Indicating closure of fire dampers - Google Patents

Abstract

An indicator is provided for indicating whether or not the air shut-off curtain or blade assembly (12) of a fire damper in an air ventilation system is in its closed position. When a fusible link (16) is released mechanically or by heat from a fire one or more rotary indicators in housings (18) are rotated as a result of the curtain or blade assembly striking an actuating element (38) for the indicator as the curtain or blade assembly reaches its closed position. Each housing (18) has apertures (20) through which fluorescent red labels are viewed when the curtain is closed. <IMAGE>

Description

SPECIFICATION Damper indicating means This invention relates to indicating means for indicating whether or not the air shut-off curtain or blade assembly of a damper, especially a fire damper, is in its closed position.

After a damper has been fitted in a duct of an air-ventilation system, it is necessary to have some way of telling whether the shut-off curtain or blade assembly has indeed moved into its closed position when the damper is operated - for example, during regular test inspections. Various forms of indicating means have been used in the past, quite a number of these being electrical in form. They are not, however, entirely satisfactory in operation, and the aim of the present invention is to provide a new form of mechanical indicating means which give various advantages over those used hitherto.

According to the invention, damper indicating means for indicating whether or not the air shut-off curtain or blade assembly of a damper is in its closed position comprise a rotary indicator arranged to rotate through an angular distance as a result of the curtain or blade assembly striking an actuating element for the indicator as the curtain or blade assembly reaches its closed position.

Preferably duplicate rotary indicators are provided on both sides of the damper casing, the indicating means on each side including an externallymounted thimble or other small container for the respective rotary indicator, which thimble has one or more sight apertures through which the rotary indicator can be seen. In addition, each rotary indicator is urged by a spring - preferably a torsion spring - into a position of rest corresponding to the "open" position of the damper curtain or blade assembly. This means that the rotary indicator is automatically re-set when the curtain or blade assembly is moved back from its closed position to its open position. Moreover, this re-setting will take place irrespective of the orientation of the damper, i.e., whether it is disposed horizontally, vertically or in any other position.

An example of a fire damper incorporating indicating means in accordance with the invention is shown in the accompanying drawings, in which: Figure lisa perspective view from above of the fire damper with parts broken away; Figure 2 is an exploded perspective view from below of the indicating means in the damper; Figure 3 is a simplified section through the lower part of the damper; Figure 4 is a front view of the indicating means; Figure 5 is another simplified section through the lower part of the damper with the curtain or blade assembly thereof in its closed position; Figure 6 is another front view of the indicating means; Figure 7 is an enlarged section through the indicating means; Figure 8 is another enlarged section through a different part of the indicating means; and Figure 9 is an exploded perspective view through an alternative form of indicating means.

The fire damper shown in Figure 1 comprises a frame-like metal casing 10 having athrough-opening which can be closed entirely by the metal curtain 12.

This is the position in which the curtain is shown in Figure 1. When the curtain is in its normal position of rest wherein it permits air to flow freely through the damper, it occupies the space in the compartment 14 of the casing and is kept there by a fusible link 16 which extends across the opening to the compart ment. Release of the fusible link - either mechanical ly during test inspections or by the heat of a fire - will accordingly allow the curtain to move into the Figure 1 position under the influence of a strong spring. In this particular instance the curtain is composed of pivotally linked together metal blades.

In order that a visual indication may be given on the outside of the casing that the curtain has indeed moved into its closed position on release of the fusible link 16, two thimbles 18 are mounted externally on both sides of the casing 10 as shown in Figures 3 and 5. Each thimble has a pair of sighting apertures 20 and contains a closely-fitting lens 22 (see Figure 2). Within this lens is arranged a frusto-conical rotary indicator 24 which is mounted for rotation on a spigot or shaft 26 one end of which is received in a hole 28 in the respective thimble 18.

Bonded or otherwise attached to the conical surface of the rotary indicator 24 are a pair of fluorescent red display labels 30. Two off-centre bores 32 and 34 are provided in the larger diameter end of the rotary indicator or label carrier 24, one bore 32 being adapted to receive one end of a torsion spring 36 and the other bore 34 serving to receive one end of an actuating element 38 in the form of a trip wire. The spigot or shaft 26 as well as the trip wire 38 pass through a T-shaped opening 40 in the casing 10, while the other end of the torsion spring 36 is hooked through the opening 40 and is retained there as shown in Figure 8.

The far end of the trip wire 38 is arranged to operate the rotary indicator of the other thimble 18.

In other words, identical indicating means having a common actuating member 38 are provided on both sides of the damper casing 10.

When the curtain 12 lies entirely within the compartment 14, the rotary indicator 24 in each thimble or cover 18 will be urged by its respective torsion spring 36 into the angular position shown in Figure 7. The red labels 30 will not, in this position, be visible through the sighting apertures 20. If, now, the fusible link 16 is released, the curtain will move (see Figure 3) into the position shown in Figure 5 where its lower edge strikes the trip wire 38. This causes the trip wire to move through a small distance determined by the longer limb of the T-shaped opening 40 in the casing 10. This movement is illustrated in Figure 8 and by comparing the position of the trip wire 38 in Figures 3 and 5.The consequence of this is that the trip wire rotates the rotary indicators or label carriers 24 in the two thimbles or covers 18 through an angular distance such that the red display labels 30 now coincide with the sighting apertures 20 as shown in Figures 5 and 6. The rotary indicators 24 therefore give plain indication, on both sides of the casing 10, that the curtain 12 is indeed in its closed position.

After the curtain has been moved back to its normal position in the compartment 14, the torsion springs 36 in the two thimbles or covers 18 will act to restore the rotary indicators to their positions of rest, i.e. the position shown in Figure 7. This will also cause the trip wire 38 to move back to the position shown in Figure 3. Such re-setting of the rotary indicators 24 and the trip wire 38 will occur irrespective of the orientation of the casing 10.

To prevent undesirable leakage of air through the T-shaped openings 40 in the casing 10, a synthetic plastics gasket 42 is provided in each thimble or cover 18.

Figure 9 shows an alternative form of indicating means in which each rotary indicator 24 has a tapered spigot 44 in place of the bore 34 shown in Figure 2. The spigot is inserted in one of two eyelets 46 provided at the ends of the actuating element 48.

By giving the spigot 44 a length of between 6 and 7 mm, there is then no risk that it will become disengaged from the respective eyelet 46.

It will therefore be seen that the invention provides a mechanical form of visual indicating means which meets test requirements in an efficient manner.

Claims (7)

1. Damper indicating means for indicating whether or not the air shut-off curtain or blade assembly of a damper is in its closed position, comprising a rotary indicator arranged to rotate through an angular distance as a result of the curtain or blade assembly striking an actuating elementfor the indicator as the curtain or blade assembly reaches its closed position.

2. Damper indicating means according to claim 1 having duplicate rotary indicators on both sides of the damper casing, the indicating means on each side including an externally-mounted thimble or other small container for the respective rotary indicator, which thimble has one or more sight apertures through which the rotary indicator can be seen.

3. Damper indicating means according to claim 1 or claim 2, in which the rotary indicator, or each such indicator, is urged by a spring into a position of rest corresponding to the "open" position of the damper curtain or blade assembly so that the rotary indicator is automatically re-set when the curtain or blade assembly is moved back from its closed position to its open position.

4. Damper indicating means according to claim 2, in which each thimble contains a closely-fitting lens within which is arranged a frusto-conical rotary indicator mounted for rotation on a spigot or shaft one end of which is received in a hole in the respective thimble.

5. Damper indicating means according to claim 4, in which one or more fluorescent labels are bonded or otherwise attached to the conical surface of each rotary indicator.

6. Damper indicating means according to claim 4 or claim 5, in which the larger-diameter end of each rotary indicator has a bore to receive one end of a torsion spring as well as means forming a connection with one end of an actuating element in the form of a trip wire.

7. Damper indicating means substantially as described herein with reference to Figures 1 - 8 or Figure 9 of the accompanying drawings.