GB2355402A

GB2355402A - Fire damper with telltale

Info

Publication number: GB2355402A
Application number: GB9924576A
Authority: GB
Inventors: Patrick Joseph Nolan
Original assignee: Advanced Air Technologies Inc
Current assignee: Advanced Air Technologies Inc
Priority date: 1999-10-19
Filing date: 1999-10-19
Publication date: 2001-04-25
Anticipated expiration: 2019-10-19
Also published as: GB2355402B; GB9924576D0

Abstract

A curtain fire damper has a tell-tale to indicate whether or not the damper is open or closed. The damper 60 comprises: a housing 116 and a curtain 125 movable from a retracted state in which the housing has an opening 108 for fluid flow through the damper 60 to an extended state in which the opening is closed to block flow. A tell-tale 70 in the housing moves under action of the curtain to provide an indication visible from outside the housing through the port 88 (not shown) as to whether or not the curtain 125 is blocking the damper 60. The tell-tale 70 moves across the port 88 in the direction of the moving curtain 125 when the curtain closes to provide a visible indication that the curtain is blocking the damper.

Description

2355402 Curtain Fire Damper with Tell-Tale The present invention relates

to curtain f ire damper with a tell-tale to indicate whether or not the damper is open or closed.

Curtain fire dampers are a requirement in many heating and ventilation installations. Such a damper normally has a housing, which has an opening f or air flow through the damper. The damper may also have f langes for attachment in-line with a duct. The damper has a fire resistant curtain that is retained in a retracted state within the housing when the damper is open.

The damper has means by which the curtain can be moved to block the opening through the housing. This may be necessary if there is a fire. The curtain is usually of metal or fire resistant fabric and may be retained in a roll, or concertina folds. A spring under tension is 2D usually used to provide a motive force for extending the curtain to block the opening. A retainer mechanism, such as a solenoid operated latch or a soldered linkage, then keeps the curtain retracted. A fire alarm system may then release the solenoid, or an elevated temperature in the damper may cause the soldered linkage to break, so releasing the curtain which then automatically blocks the damper to help prevent the spread of fire.

After the damper has been blocked, it is necessary for the curtain to be manually retracted and the retention mechanism set to keep the curtain in the retracted position. The curtain is normally fully concealed within the housing and by any adjoining ducting. If there are a large number of dampers, or if it is not certain in which dampers the blocking curtain may have been activated, then it can be quite inconvenient to have to access every 2405A4 18/10/99 single damper in order to see if the curtain has been extended. Therefore it is desirable if the damper has a tell-tale to indicate whether or not the damper is blocked by the curtain. In one type of curtain fire damper, the damper has an elongate cylindrical tube in clear plastic that extends from an external surface of the housing. A brightly coloured rod-like tell-tale is provided that is seated in the tube. A spring wire projects inside the housing from the rod-like tell-tale which is moved by the curtains as this moves to block the damper. As a result, the rod-like tell-tale is pushed further outwards into the clear tube. When the curtain retracts, the spring wire pulls the tell-tale out of the clear tube.

Problems have been noted with this tell-tale system. The rod-like telltale has to be at least partially inserted in the clear projecting tube at all times or else it may not insert correctly as the spring wire is pushed by the closing curtain. However, the visual indication is he degree to which the rod is projected outwards inside the tube. If the wire mechanism is not correctly set, then the tell-tale may be left partially projecting into the clear tube, in which case it is not clear whether or not the tell-tale is indicating that the damper is blocked by the curtain. Such a tell-tale also comprises a relatively large number of separate components, which adds to manufacturing costs. If it is desired to have tell-tales visible on both the inlet and outlet sides of the damper, then two such tell-tales are needes, which further adds to manufacturing costs.

It is an objet of the present invention to provide a more convenient curtain fire damper with a tell-tale indicating whether or not the curtain is blocking the damper.

240SA4 18/10/99 Accordingly, the invention provides a curtain fire damper, comprising: a housing; a curtain within the housing, the curtain being movable from a retracted state in which the housing has an opening therethrough for fluid flow through the damper to an extended state in which the opening is closed to block fluid flow through the damper; a viewing port in the housing; and a movable tell-tale within the housing, the tell-tale moving under action of the curtain to provide an indication visible from outside the housing through the port as to whether or not the curtain is blocking the damper; in which the tell-tale moves across the port in the direction of the moving curtain when the curtain closes to provide- a visible indication that the curtain is blocking the damper.

Most usually, the fluid flow through the damper will be an air flow, although such a damper may be used to control the flow of other gasses or liquids.

Because the tell-tale moves in the same direction as the moving curtain, the construction of the tell-tale can be simplified. Compared with a telltale that moves at right angles to the direction of the moving curtain, the positioning of the tell-tale can be made more repeatable and reliable, even if the curtain fire damper is activated many times.

The viewing port may be a window in a wall of the housing, in which case the tell-tale has a surface which moves within the housing across the window. Such a surface may be parallel and closely spaced with the window, and brightly coloured so that the tell- tale provides a clear indication of the state of the damper.

In a preferred embodiment of the invention, the retracted curtain is provided inside the housing on a first side of 2405A4 18/10/99 the opening, and the tell-tale is provided inside the housing on an opposite second side of the opening. The tell-tall can then be spring biased towards the first side of the opening when the tell-tale is moved by the extended curtain. Then when the curtain is reset to the retracted position, the tell-tale automatically moves back to a position indicating that the damper is not blocked by the curtain.

The tell-tale may comprise a sheet with a first portion secured to the second side of the housing and with a second portion free to move under the action of the curtain. If the second portion ramps away from the second side of the housing when the curtain is retracted, then this portion will be moved towards the second side of the housing when the curtain is extended.

The sheet may have a third portion which extends across the port transverse to the second portion. This third portion can then have a surface which provides a visible indication through the port as to whether or not the damper is blocked by the curtain. In particular, the sheet third portion may extend in plane parallel with the direction of motion of the curtain as the curtain closes the opening.

The invention will now be described in further detail, by way of example with reference to the accompanying drawings, in which:

Figure 1 is a perspective view of a prior art curtain fire damper between inlet and outlet air ducts; Figure 2 is a is perspective view in more detail of the curtain fire damper of Figure 1, showing an external frame around a curtain casing and with a 2405A4 18/10/99 projecting prior art tell-tell centred along one lower edge of the frame; Figure 3 is a perspective view of a the curtain casing without the surrounding frame, shown with the curtain extended and the prior art tell-tell projecting to indicate that the curtain is blocking the damper; Figures 4 and 5 are enlarged perspective views of the prior art tell-tale, with the tell-tale indicating respectively that the damper is open and blocked; Figures 6 and 7 are perspective views of a curtain fire damper according to the invention; Figures 8 and 9 are respectively top and side views of the tell-tale of the fire damper of Figure 7; and Figure 9 is an enlarged end view of thetell-tell seated in a surrounding curtain frame.

Figure 1 shows a conventional curtain fire damper 1 set into a brick f ire break wall 2, only part of which is shown for clarity. A square cross-section inlet duct 4 is on one side of the damper 1, and a similar square crosssection outlet duct 6 is on the opposite side of the damper 4. The outlet duct 6 is shown partially cut away to reveal a square cross-section opening 8 through the damper.

Figures 2 and 3 show the conventional curtain fire damper 1 in more detail. The damper 1 comprises an outer casing 10 formed in two similar halves. Each half of the casing 10 has f langes 12 which f orm a close f it with interior walls 14 of each of the ducts 4,6. In Figure 2, one corner 2405A4 18/10/99 of the casing 10 is shown cut away to reveal part of an inner frame 16.

The f rame 16 is shown in more detail in Figure 3, and has a square or rectangular external prof ile with a top edge 18, parallel side edges 19 and a bottom edge 20. Each edge 18,19,20 is formed from a similar inwardly directed Csection in plated steel or stainless steel. This forms a rectangular channel that extends continuously around the inside of the frame 16, with a top channel 22, two parallel side channels 23 and a bottom channel 24. The channels 22,23,24 retain a fire proof curtain 25 formed from several elongate slats or blades 26 in plated or stainless steel. The frame channels 22,23,24 and surrounding casing 10 therefore form a housing for the curtain 25.

Each blade 26 has along its long parallel edges either a knuckle 27 or a socket 28, with the knuckle of one blade being pivotably retained within the socket 28 of an adjacent blade. One end blade 29 is permanently secured inside the upper channel 22 and opposite end blade 30 is f ree to move, so that the curtain 25 can be extended as shown in Figure 3 to block the opening 8 and so close the damper 1.

In Figures 1 and 2, the opening 8 is not blocked by the curtain 25. In this case, the curtain 25 is folded in concertina fashion upwards against the upper side 18 of the frame. A flat bar link 32 is then strapped underneath the concertina blades 26 to hold the blades up. The flat bar link is formed from two pieces of steel held together with a low melting point solder. Usually, the solder will melt when it reaches a temperature of 72 'C, although other melting point solders are commonly available up to about 180 OC.

2405A4 18/10/99 Alternatively, it is known to use other types of breakable links, such as an electro-thermal link, a solenoid driven link or an electro-magnet retained link.

In the event of a fire, elevated temperatures within the duct will cause the flat bar link 32 to separate so that the curtain 25 is free to drop and block the damper 1. Although the curtain 25 is arranged so that gravity assists its fall, a stainless steel coil tension spring 34 is provided in each C-channel 23 so that the curtain 25 is pulled positively downwards until the lower most blade 30 sits securely against a base surface 36 of the lower Cchannel 24. The damper I is then blocked by the extended curtain 25 as shown in Figure 3.

The curtain fire damper I can be reset manually, for example by an operator opening an air duct access hatch 37, pulling the curtain 25 back up, and then fitting a new bar link 32.

Figures 2 and 3 also show a conventional tell-tale 38 which indicates whether or not the curtain 25 has been extended to block the opening 8. The prior art tell-tale

38 is shown in more detail in Figures 4 and 5. A clear plastic tubular envelope 39 protrudes from the casing 10 in a direction at right angles to the direction in which the curtain 25 extends. A brightly coloured rodlike indicator 40 has a tip 41 which in Figure 4 extends partly into the clear envelope 39 and which in Figure 5 extends fully into the envelope 39. The envelope 39 has an extension 42 which protrudes inside the casing 10 in order to keep the indicator rod 40 aligned with the clear envelope 39. A spring wire 43 is connected at one end to the rod and at another end to a bracket 44 above the envelope 39. A spring wire 43 has an upper section 45 that 2405A4 18/10/99 extends into the frame 16 above the lower channel 24 in such a position that it is pressed downwards by the extending curtain 25. As shown in Figure 5, this causes the spring wire 43 to push the indicator rod 40 fully into the clear protrusion 39 in order to indicate that the curtain 25 is extended to block the damper 1.

A problem has been noted with this prior art tell-tale 38. If the spring wire 43 becomes bent, or if it is not correctly set during manufacture, then indicator rod 40 can protrude partly into the clear envelope 39. This can give a false indication that the damper has been blocked by the curtain 25. In addition, the prior art tell-tale 38 comprises about eight distinct components which adds to manufacturing cost for the curtain fire damper 1.

Figures 6 and 7 show a curtain fire damper 60 according to the invention. Not shown for clarity is a surrounding casing which is essentially the same as that shown in Figures 1 and 2. Components in the curtain fire damper 60 that are the same as those in the prior art damper 1 are indicated with reference numerals corresponding to those in the prior art damper 1 but incremented by 100. The operation of the curtain fire damper 60 is essentially the same as that described above, and so will not be repeated.

The curtain fire damper 60 according to the invention has a tell-tale 70 in the form of a unitary member, made from an elongate plate folded sheet steel, a portion of which 72 is riveted to the base surface 136 of the lower C-channel 124. When the curtain 125 is retracted up against the upper edge 118 of the frame 116, the tell-tale has a movable main portion 74 which ramps upwards from the base surface 36 towards a free end 76 away from the riveted portion 72. When the curtain 125 drops 78, the lowermost blade 130 strikes the free end 76 causing this 2405A4 18/10/99 and the tell-tale main portion 74 to rotate 80 downwards about the riveted portion 72 until the tell-tale main portion 74 comes up against the base surface 136 of the lower C-channel 124. The tell-tale main portion 74 5 therefore provides a contact portion for the curtain 125.

The tell-tale 70 is shown in more detail in Figures 8, 9 and 10. The telltale 70 is elognate and essentially T-shaped with the stem of the T forming the riveted portion 72. The arms of the T extend across nearly the full width of the lower C-channel 124, and terminate towards the f ree end 76 in a pair of upstanding f lags 62. In one preferred embodiment, the main portion 74 extends across the full width of the lower C-channel 124 from close to a junction 84 with the riveted portion 72. This provides a maximum contact area for the lower most blade 130, and also supplies the greatest spring restoring force to return the tell-tale main portion 74 to an upwardly ramping orientation when the curtain 125 is raised.

Depending on the downward force exerted by the curtain 125 when this is extended, and the spring bias force needed to return the tell-tale main portion 74 to an upwardly ramping orientation, a tell-tale 70 may optionally have a narrower profile between the upstanding flags 82 and riveted portion 72, as shown by the dashed lines 86 in Figure B. Referring now to Figures 9 and 10,as the tell-tale 70 is rotated 80 downwards, the flag portions 82 move across corresponding viewing ports 88 in opposite side walls 90 of the lower C- channel 124. Each viewing port 88 is covered with a clear plastic window 92 which, as shown in Figure 9, is aligned with its corresponding flag 82 only when the tell-tale main portion 74 is rotated 80 downwards against the C-channel lower surface 136.

2405A4 18/10/99 Although not illustrated, each flag 82 has on an outward facing surface 94 a brightly coloured coating, for example red paint. The outward facing surface 94 is parallel with the C-channel side wall 90 and viewing port 88, so that as the tell-tale main portion 74 is rotated 80 downwards, the brightly coloured surface 94 is moved across the viewing port 88.

The tell-tale 70 according to the invention as described above is very inexpensive to manufacture and easy to install in a curtain fire damper 60. This tell-tale 70 readily provides an unambiguous indication of whether or not the curtain fire damper 60 is blocked by the curtain 125. Furthermore, this indication is visible on both an inlet side and an outlet side of the curtain fire damper 60 without the need to duplicate the tell-tale mechanism on both sides of the damper. The invention therefore provides an economic and convenient curtain fire damper with a tell-tale to indicate whether or not the damper is open or blocked.

2405A4 18/10/99

Claims

1. A curtain fire damper, comprising: a housing; a curtain within the housing, the curtain being movable from 5 a retracted state in which the housing has an opening therethrough for fluid flow through the damper to an extended state in which the opening is closed to block fluid flow through the damper; a viewing port in the housing; and a movable telltale within the housing, the tell-tale moving under action of the curtain to provide an indication visible from outside the housing through the port as to whether or not the curtain is blocking the damper; in which the tell-tale moves across the port in the direction of the moving curtain when the curtain closes o provide a visible indication that the curtain is blocking the damper.

2. A curtain fire damper as claimed Claim 1, in which the viewing port is a window in a wall of the housing, the tell-tale having a surface which moves within the housing across the window.

3. A curtain f ire damper as claimed in Claim 1 or Claim 2, in which the retracted curtain is provided inside the housing on a first side of the opening, and the tell-tale is provided inside the housing on an opposite second side of the opening, the tell- tall being spring biased towards the first side of the opening when the tell-tale is moved by the extended curtain.

4. A curtain fire damper as claimed in any preceding claim, in which the retracted curtain is provided inside the housing on a first side of the opening, and the telltale is provided inside the housing on an opposite second side of the opening, in which the tell-tale comprises a sheet with a first portion secured to the second side of 2405A4 18/10/99 the houing and with a second portion f ree to move under the action of the curtain, the second portion ramping away from the second side of the housing when the curtain is retracted and being moved towards the second side of the 5 housing when the curtain is extended.

5. A curtain fire damper as claimed in Claim 4, in which the sheet has a third portion which extends across the port transverse to the second portion.

6. A curtain fire damper as claimed in Claim 5, in which the sheet third portion extends in plane parallel with the direction of motion of the curtain as the curtain closes the opening.

7. A curtain fire damper as claimed in any preceding claim, in which the tell-tale is a unitary member.

8. A curtain fire damper as claimed in any preceding claim, in which the housing has a pair of viewing ports, one port being visible on an inlet side of the housing, and the other port being visible on an opposite outlet side of the housing, both ports providing a visible indication of whether or not the curtain is blocking the damper from the same tell-tale.

9. A curtain fire damper as claimed in Claim 8, in which the tell tale comprises an elongate plate secured at one end to the housing and free to move at an opposite end, the opposite end having: a contact portion which is contacted by the curtain when the curtain is extended to block the damper; and at least one upstanding flag that extends transverse to the contact portion and which crosses the port when the curtain is extended to provide the visible indication as to whether or not the curtain is blocking the damper.

2405A4 18/10/99

10. A curtain fire damper as claimed in Claim 9, in which there is a pair of upstanding flags each of which crosses a corresponding port when the curtain is extended to provide the visible indication as to whether or not the curtain is blocking the damper.

11. A curtain f ire damper as claimed in Claim 9 or Claim 10, in which the tell-tale is T-shaped, the stem of the T being the end of the tell-tale that is secured to the housing, and the upstanding flags being provided at the ends of the arms of the T.

12. A curtain fire damper substantially as herein described, with reference to or as shown in Figures 6 to 10 of the accompanying drawings.

2405A4 18/10/99