GB2180336A - Securing ducts to damper housings - Google Patents

Abstract

The spigot 16 of a fluid damper 10 is provided with an annular channel 28 for receiving the end 18 of a duct 20 and with a number of duct-gripping assemblies 34 whose grip on the duct 20 increases if any force is applied to separate the damper spigot and the duct once the duct end has been pushed into the channel. Each assembly 34 includes a spragged blade 38 of springy metal which bears on the external surface of the duct end 18 and which bites more deeply into the metal of the duct end if any force is applied to separate the damper spigot and the duct. <IMAGE>

Description

SPECIFICATION Damperiduct connection means This invention relates to means for connecting a fluid damper to a duct, and is especially applicable to fluid dampers having a spigot on each side for connection to respective duct ends in ventilation systems. The invention will be described below With particular reference to fire dampers having a spring-loaded retractable metal curtain but it is to be understood that it is applicable to fluid dampers generally such as air control dampers and smoke dampers. Further, the invention is not restricted to dampers having a metal curtain.

It is usual for damper manufacturers to produce dampers having spigots which are of slightly reduced outer section in comparison with the inner section of the ducts to which the dampers are connected. This then permits each spigot to be inserted into the end of its respective duct in overlapping relationship. It is generally left to the installer of the equipment or engineers acting on his instructions to decide on the means for sealing each damper spigot to its respective duct and preventing them from coming apart. Various connecting means have been used hitherto, one of the most popular being the attachment of companion flanges to the duct and the damper with the flanges then being secured together by bolts or welding.Sealing systems have also varied but, in general, problems appear to exist at the corners of rectangular ducts which ever sealing system is used, especially as few sealing systems have positive continuous seals.

A further drawback of existing connecting means between the damper spigot and its respect duct end is that they demand some form of tooling in order to make a successful joint, whether it be for forming, drilling, rivetting, screwing, welding, bolting or clenching one or more parts forming the joint.

The aim of the present invention therefore is to provide a means of connection between a damper spigot and its respective duct end which can be factory-fitted to the damper, which requires no loose parts, and which requires no tooling on site beyond a hammer to produce a strong air-tight joint between the spigot and the duct end.

With this aim in view, the invention is directed primarily to a fluid damper having a spigot for attaching it to a duct end, in which the spigot is provided with a channel for receiving the duct end and with a number of duct-gripping members whose grip on the duct increases if any force is applied to separate a damper spigot and the duct once the duct end has been pushed into the channel.

Preferably, the duct-gripping members comprise spragged blades of springy metal which bear hard on the external surface of the duct end and which bite more deeply into the metal of the duct end if any force is applied to separate the damper spigot and the duct.

In order to provide fluid-tightness between the damper spigot and the duct end, a sealing medium such as a continuous mastic bead is injected into the channel on the spigot.

In order that the invention may be thor oughly understood, a specific example of a damper in accordance with it will now be de scribed with reference to the accompanying drawings, in which: Figure 1 is a perspective view of the dam per with a duct to be connected to the spigot of the damper; Figures 2-4 are perspective views illustrating details of the damper spigot shown in Figure 1; Figure 5 is an exploded perspective view of one of the duct-gripping assemblies provided on the damper spigot; Figure 6 is an enlarged side view of the duct-gripping assembly shown in Figure 5; Figure 7 is a front view, on an even larger scale, of the duct-gripping assembly of Figure 6; and Figures 8-11 are detail views of modifica tions to the damper.

The damper 10 shown in Figure 1 com prises an outer casing 12 of generally rectan gular construction within which are housed various means (not shown) for mounting, op erating and controlling a retractable curtain 14 made up of interlocking metal strips or plates.

This curtain 14 is normally held in a retracted position-with the individual strips of the cur tain pushed together-in an upper internal compartment of the casing 12 so that air or other fluid is free to flow through the damper.

When, however, a heat-sensitive detector in corporated in the damper senses that the tem perature has risen, thereby signifying that a fire has probably broken out, it initiates the release of the curtain from its retracted posi tion so that it moves into its extended posi tion as shown in Figure 1 under the power of a strong spring (also not shown). The damper thereby acts as a fire damper automatically in the event of fire.

In order that the damper 10 may be fitted in the ducting of a ventilation system, each side of the damper casing is provided with a hollow spigot 16, only one being visible in Figure 1. This spigot is designed to mate with the end portion 18 of a respective duct 20 so as to provide a firm air-tight joint between them.

As already indicated, it has generally been left to the installer of ventilation equipment to decide the particular form of connection to be made between each damper spigot and its re spective duct end, and various systems are used at the present time. In the case of the damper 10 shown in the drawings, however, the spigot 16 on the damper is provided with factory-fitted duct-gripping means which do not require any tooling on site beyond a hammer in order to make a strong air-tight joint between the spigot and its respective duct end. Further, the duct-gripping means on the spigot do not involve the use of any loose parts.

The spigot 16 is accordingly provided with a surrounding Z-section strip 22 having a front edge 24 which is only slightly set back from the front edge 26 of the spigot 16. An annular channel 28 to receive the front edge 18 of the duct 20 is thus provided right round the spigot 16. As shown in Figure 6, the Z-section strip 22 is spotwelded at points 30 round its circumference to the opposing parts of the spigot 16.

At four places along its length, the Z-section strip 22 is partially broken by notches 32 (see Figure 3) which help to accommodate four duct-gripping assemblies 34 mounted on the spigot 16. As will be seen from Figures 5-7, each of these duct-gripping assemblies 34 comprises a gripper body 36, a spragged duct-gripping blade 38 and a cover member 40. The gripper body 36 has a base portion 42 which rests on the outer surface of the spigot 16 and is connected thereto as shown in Figure 6 by a spot-weld or rivet 44. The base portion 42 curls round at 46 to form a recess 48 adapted to receive a small length of the front edge 18 of the duct 20. The curledround portion 46 of the gripper body 38 then leads into an upright portion 50 which serves as a mounting support for the spragged blade 38 as shown in Figure 6.In order that the blade 38 may be correctly positioned on the support 50, a horizontal shoulder 52 is formed on the latter and the upper edge of the blade 38 rests against this shoulder.

The gripper body 36, the blade 38 and the cover 40 are tightly secured together by a rivet 54 as shown in Figures 5 and 6.

The spragged blade 38 is made of springy steel or other springy metal and is free to yield at its lowermost portion-see Figure 6~where it is clear of the gripper body 36 and the cover 40.

When it is desired to fit the spigot 16 and the duct 20 together, all that an engineer needs to do is to introduce the front edge 18 of the duct 20 into the channel 28 on the spigot 16. The introduction of the front edge 18 of the duct into the channel 28 will also bring certain small lengths of the front edge 18 into contact with the respective lower ends of the spragged blades 38 on the four duct-gripping assemblies 34. If now the engi neer applies a piece of wood to the rear end 56 of the duct 20 and taps the piece of wood with a hammer, the front edge 18 of the duct will be forced beneath and past the lower ends of the spragged blades 38 until the front edge 18 of the duct meets the far end of the recess in the curled-round portion 46 of each gripper body 36~see the brokenline position of the front edge 18 of the duct 20 shown in Figure 6.With the front edge 18 of the duct thus engaged in the channel 28 of the spigot and in the curled round portion 46 of each gripper body 36, any force tending to separate the spigot from the duct will cause the lower edge of each spragged blade 38 to bite yet more deeply into the metal of the duct 20. In other words, it will not be possible to separate the spigot from the duct 20 once they have been brought together unless an exceptionally large force is used, i.e., a force greatly in excess of that which would be encountered in practice.

Once the duct and spigot have been brought together in the fashion described above, a continuous mastic bead previously injected into the channel 28 and into the groove in the gripper body 36 forms an air-tight seal between the duct and spigot. This is illustrated in Figure 2 of the drawings.

Although the invention has been described above in relation to ducts and spigots of rectangular section, it is to be understood that the invention is equally applicable to ducts and spigots of different section-for example, circular section, or oval section. It will also be appreciated that the number of duct-gripping assemblies 34 provided on each spigot will be determined by the particular dimensions of the duct and spigot being fitted together. Thus, a small fire damper such as that shown in the drawings need have only four duct-gripping assemblies 34 with each one being arranged on one side of the spigot and displaced to a small extent from a corner of the spigot. In larger diameters there will be more duct-gripping assemblies 34 on each spigot so that the distance between adjacent duct-gripping assemblies will not generally be less than 25cm.

Figures 8-10 show a modified gripper body 36a wherein the upright portion 50 extends upwards from a corner portion of a larger base portion 42a than that shown in Figure 5.

The larger base portion 42a facilitates spotwelding or rivetting of the base-portion to the spigot 16 in that the weld or rivet location 44a is offset laterally from the upright portion 50. Further, entry of the front edge 18 of the duct 20 into the channel 28 of the spigot and into the curled round portion of the gripper body 36a is assisted by this form of construction.

Yet another improvement to facilitate such entry of the front edge 18 of the duct is to turn the front edge of the Z-section strip slightly outwards as shown at 24a on the Z section strip 22a in Figure 11.

Claims (10)

1. A fluid damper having a spigot for at taching it to a duct end, in which the spigot is provided with a channel for receiving the duct end and with a number of duct-gripping mem bers whose grip on the duct increases if any force is applied to separate a damper spigot and the duct once the duct end has been pushed into the channel.

2. A fluid damper according to claim 1, in which the duct-gripping members comprise spragged blades of springy metal which bear hard on the external surface of the duct end and which bite more deeply into the metal of the duct end if any force is applied to separate the damper spigot and the duct.

3. A fluid damper according to claim 1 or claim 2, in which, in order to provide fluidtightness between the damper spigot and the duct end, a sealing medium such as a continuous mastic bead is injected into the channel on the spigot.

4. A fluid damper according to any one of claims 1-3, in which the duct-receiving channel on the spigot is formed by a surrounding Zsection strip having a front edge which is set back from the front edge of the spigot, an annular channel thereby being provided right round the spigot.

5. A fluid damper according to claim 4, in which the Z-section strip is spot-welded or otherwise connected at points round its circumference to the opposing parts of the spigot.

6. A fluid damper according to claim 4 or claim 5, in which the front edge of the Zsection strip is turned outwards to facilitate entry of the duct into the channel on the spigot.

7. A fluid damper according to any one of claims 4-6, in which the Z-section strip is partially broken by spaced-apart notches to accommodate the duct-gripping members.

8. A fluid damper according to an preceding claim, in which each duct-gripping member is supported on a respective gripper body having a base portion which rests on the outer surface of the spigot and is spot-welded, rivetted or otherwise connected thereto.

9. A fluid damper according to claim 8, in which the base portion of the gripper body curls round to form a recess adapted to receive a small length of the front edge of the duct, the curled-round portion of the gripper body being joined to an upright portion which serves as a mounting support for the respective duct-gripping member.

10. A fluid damper substantially as described herein with reference to Figures 1-7 or as modified by Figures 8-10 and/or Figure 11 of the accompanying drawings.