GB2118293A - Fluid damper - Google Patents

Abstract

A fluid damper comprises a line of blades which are supported in a surrounding frame for rotary movement about substantially parallel axes between positions in which they open and close a fluid opening in the frame, and a blade drive mechanism which comprises at least one longitudinally moveable drive rod, bar or other element (23) having square holes 23a receiving round-section pins 22a associated with the blades, the drive mechanism being totally enclosed. <IMAGE>

Description

SPECIFICATION Fluid damper This invention relates to a fluid damper comprising a line of blades which are supported in a surrounding frame for rotary motion about substantially parallel axes between positions in which they fully open and fully close a fluid opening in the frame.

In a number of prior British and foreign Patent Applications, we have described different dampers which are constructed as described above. Thus, for example, in British Patent Application No. 26387/77 filed on 23rd June, 1977, corresponding U.S. Patent Application Serial No. 916,357 filed on 16th June, 1978, in the name of R. J. Magill etal, and corresponding Canadian Patent Application Serial No. 305,812 filed on 20th June, 1978, we have described a combination smoke and fire shield damper which is effective as a barrier against both smoke and fire and which incorporates the "movable blade" construction outlined above.In that particular form om damper the blades are provided with "opened-out" trailing edges so that the leading edge of each blade interlocks with the trailing edge of an adjacent blade when the blades are in their fully-closed positions.

In another British Patent Application and its corresponding U.S. and Canadian Applications (British Application No. 53581/76 filed on 22nd December, 1976; U.S. Application Serial No. 862,920 filed on 21st December, 1977, in the name of Sydney J. Field; and Canadian Application Serial No. 293,354 filed on 19th December, 1977), we have described a control damper for controlling the flow of air or other gaseous fluid through a duct which likewise makes use of the movable blades described above, the blades being movable at will to intermediate positions between their fully-open and fully-closed positions and being of aerofoil shape.

Further, in the single Complete Specification filed on our cognate British Patent Applications Nos.

6184/77 of 15th February, 1977, and 10895/77 of 29th April, 1977, we have described a shut-off damper which again has movable blades as described above with the trailing edges of such blades comprising fluid sealing means extending along those edges so that a seal is formed between adjacent blades when the latter are in their fully-closed positions. This shut-off damper is also described in the corresponding U.S. Patent Application Serial No. 877,185 filed on 13th February, 1978, in the name of R. J. Magill et al, and in Canadian Patent Application Serial No.

297,107 filed on 14th September, 1978.

Reference has been made to all these earlier Applications because the present invention is applicable to the different forms of fluid damper shown in them. In short, therefore, the present invention is applicable to control dampers, shut-off dampers, smoke dampers, fire shield dampers and to combination smoke and fire shield dampers, All the prior Patent Applications specifically mentioned above show blade drive means for rotating the blades about their parallel axes in the form of intermeshing gear wheels, one for each blade, which are rotatable in unison to cause corresponding swinging movement of the blades between their fully-open and fully-closed positions. Such gear wheels have been found to be entirely satisfactory in operation but they give rise to backlash between the intermeshing teeth of the gear wheels.The greater the number of gear wheels, the greater the backlash, and this mitigates against precise blade control. In addition, such gear wheels have to be made carefully if undesirabie torque "stiffness' in the blade drive means is to be avoided.

With this consideration in mind, the present invention is directed to an improved form of blade drive mechanism in which undesired torque stiffness or backlash is greatly reduced or substantially avoided.

To this end, a fluid damper in accordance with the invention comprises a line of blades which are supported in a surrounding frame for rotary movement about substantially parallel axes between positions in which they open and close a fluid opening in the frame, and a blade drive mechanism for effecting rotary movement of the blades about their parallel axes, in which the blade drive mechanism comprises at least one longitudinally moveable drive rod, bar or other element connected to drive more than one blade by means of reduced friction pin-and-hole connections.

The use of reduced friction pin-and-hole connections reduces the possibility of mechanical seizure.

Some examples of fluid dampers in accordance with the invention are shown in the accompanying drawings, in which: Figure 1 is a perspective view of one form of damper with a small portion shown in section; Figure 2 is an exploded view in perspective of part of the damper shown in Figure 1; Figure 3 is an exploded view in perspective of another part of the damper shown in Figure 1; Figure 4 is an exploded view in perspective of part of a second form of damper; Figures 5 and 6 are both front views of caps and drive bars forming parts of the dampers shown in Figures 1 to 4; Figure 7 is a perspective view of the caps and drive bars shown in Figures 5 and 6; Figure 8 is a slightly-enlarged section through one of the caps shown in Figures 5 to 7; and Figure 9 is a reduced-size perspective view of a third form of damper which is designed to be installed within a duct.

The damper shown in Figures 1 to 3 is a combination smoke and fire shield damper, but it could equally well be another form of fluid damper as mentioned above. it comprises a roll-formed galvanised sheet steel outer frame 10 of flanged channel section and a sheet steel channel-section inner frame 12. The outer frame 10 has continuouslywelded corners and has outwardly-extending flanges 14 adapted to enter the ends of two air ducts arranged end-to-end but with a gap between them to receive the damper, which is normal practice in the United Kingdom. The attachment by welding, bolting, rivetting, or other means of the inner and outer frames together produces a double-skin air-tight casing of high rigidity and substantial strength.

As will be seen from Figure 2, the inner frame 12 has a series of circular holes 16 punched in its two vertical sides. The holes 16 support the shafts 18 of blade-bearing components 19 which fit into and onto the open ends of blades 20 which are thus mounted for rotary movement in the frame about parallel axes. The blades 20 are low-profile aspect ratio aerofoil stainless steel blades to provide low resistance to air or other gaseous fluid flowing through the damper, especialiy when the blades are in their fully-open positions (i.e., the positions of the blades shown in Figure 1 of the drawings). The aerofoil section of the blades also reduces turbulence and noise and provides excellent protection against corrosion resuling from the presence of corrosive particles in the air stream.Another advantage is that the narrow blade width readily permits the withdrawal of the complete damper from a duct, regardless of the positions of the blades within the damper casing, without materially disturbing the flow of air through the duct frame as a whole.

Rotation of the blades about their respective axes is effected through smooth-rimmed, punched-out metal caps or discs 22, there being a respective cap or disc 22 for each blade 20. As will be seen from Figure 2, the shaft 78 of each blade bearing componet 19 has a keyed end 24. The shafts 18 on one side of the damper have their keyed ends 24 arranged to enter rectangular-section central holes 26 in the caps or discs 22 (see Figure 7) which are arranged in rim-to-rim engagement and disposed in a line vertically of the damper. The caps or discs 22 rotate in unison due to the fact that each one is pivotally attached by a respective pivot pin 22a to one of two parallel connecting bars or rods 23.

Longitudinal displacement of the bars or rods 23 in the same direction will thus cause all the blades 20 to move together about their respective axes.

However, as shown by the arrows in Figure 2, alternate caps or discs 22 will rotate in opposite senses so that adjacent pairs of blades 20 will likewise rotate in opposite senses or directions to open or close the central passage through the damper.

The caps or discs 22, or, alternatively, the bars or rods 23, are acted on, directly or indirectly, by one or more springs or other resilient means so as to urge the blades 20 towards their closed positions. This can be done in various ways, using various forms of spring. In this particular instance, two of the caps or discs 22 are rotatably fast with two spring-loaded drive wheels 28 (see Figure 3), each of the wheels 28 being acted on by a coiled spring 30 which is connected at one end to the periphery of its respective wheel 28 by a pin 32 and is supported on a pin 34 in a control box 36 having a removable cover 38. The two drive wheels 28 have stub-shafts 40 projecting from each side, and these enter circular holes 46 in the control box cover 38. The positions of the wheels 28 and the coiled springs 30 in the control box 36 are shown in broken lines in Figure 3.

The effect of the springs 30 on the wheels 28 is to urge the latter to rotate in opposite senses or directions as shown by the arrows in Figure 3.

Because the two wheels 28 are rotationally fast with two adjacent caps or discs 22 (by, for example, coupling the stub shafts 40 passing through the holes 42 to the shafts 18 which enter those caps or discs, or by connecting the ends of those stub shafts 40 direct to the respective caps or discs 22), all the caps or discs 22 will be urged to rotate in such directions that the blades 20 are urged into their fully-ciosed positions so as to completely close the central passage formed by the frames 10 and 12 of the damper.

It is to be understood that many other forms of spring-loading could be used to obtain the desired effect- namely, to urge the blades resiliently into their fully-closed positions. For example, one or more of the caps or discs 22 could be provided with a torsion spring, or a tension spring could be attached to a peripheral portion of one or more of the caps or discs, or to the two connecting bars or rods 23.

Because the particular damper shown in Figures 1-3 has to serve both as a smoke damper and as a fire shield damper, the caps or discs 22, the connecting bars or rods 23, the drive wheels 28 and the blade bearing components 19 are preferably all made of metal, but it may be acceptable in certain instances for these particular parts to be made partially or entirely of a synthetic plastics material instead. Whatever the material used, such caps or discs, connecting bars or rods, drive wheels and bearings are totally enclosed and completely shut off from the air stream through the damper by the outer and inner frames 10, 12 and by the control box 36. This ensures that the said components do not become dirty or contaminated with impurities in the air stream.

The extent to which the blades can be rotated about their respective axes can be varied to suit the requirements of different customers. Normally they will be rotatable through at least 90 and, in many cases, through 180 .

To seal the leading edge of the uppermost blade, the trailing edge of the lowermost blade and the ends of all the blades, springy-metal sealing strips 64 are arranged along the inner surfaces of the inner frame 12 as shown in Figure 2. Each sealing strip 64 is here made of springy steel and is of arched section. The two horizontal strips 64 at the top and bottom of the damper lie in the channels of the inner frame, while the two vertical strips 64 at the sides of the damper lie between the blade bearing components 19 and the opposing surfaces of the inner frame. For this purpose, the vertical strips 64 have holes 66 formed in them to allow for the passage therethrough of the shafts 18. The arched form of the strips 64 not only helps to reduce the leakage of fumes and smoke through the damper when the blades are in their fully-closed positions but allows the strips to yield as the blades expand due to the heat of a fire.

As will be appreciated, the blades 20 must be held in their fully-open positions to allow for the passage of air through the damper during normal use of the air duct or ducts in which the damper is installed.

This means that a device needs to be provided which will hold the blades open against the action of the springs 30 but which will allow those springs to shut the blades, i.e., bring them into their fully-closed positions, should fire break out. The best form of device is therefore one which is sensitive to a rise in temperature, and the damper shown in the drawings is accordingly provided with a temperature-sensitive all-stainless steel spring-operated removable cartridge 68 carrying a replaceable fusible element 70 rated, say, at 72" C (162 F), the element 70 having a very low thermal capacity so as to be extremely sensitive to temperature rise. The cartridge 68 is easily removable from the inner casing 12, without the use of tools, by simply unscrewing it from the latter.The fusible element 70, which lies prominently in the airstream (see Figure 1), can likewise be readily replaced in the event of fire or damage by unscrewing the captive end of the cartridge. Fusing of the element 70 or removal of the fusible element or the cartridge as a whole provides the fail-safe feature of instant blade closure.

The control box 36 shown in Figure 3, besides housing the drive wheels 28 and the springs 30, also supports and partially contains a sliding operating member 72 which acts on the spring-loaded drive wheels 28 so as to rotate them into a position where the blades 20 are held in their fully-open positions. It should be mentioned, incidentally, that the torque available from either spring 30 is more than sufficient to close all the damper blades, thus providing a fail-safe feature in the unlikely event of failure of one of the two springs. Thus, linear movement of the operating member 72 to its completely extended position shown in Figure 2, either by hand or by a motor (not shown), causes two shoulders 74 on the member 72 to engage two pins 76 on the drive wheels 28, the pins being located in holes 78 and arcuate peripheral grooves 80 in the drive wheels.

Figure 4 shows, in perspective view, part of a shut-off damper which, like the damper shown in Figures 1-3, makes use of the caps and drive bars illustrated in Figures 5-8 to open and close rotatable blades 20. The shut-off damper of Figure 4 is basically of the same construction as the damper shown in Figures 1-3 except that it has additional sealing means to provide an even more tight seal when the blades are in their fully-closed positions.

These additional sealing means comprise rubber linings 64a on the two vertical springy sealing strips 64 and hollow D-section rubber seals 20a along the trailing edges of the blades 20. In addition, the damper of Figure 4 has somewhat different mechanism to drive the caps 22 and the bars 23, the said mechanism involving the provision of two, but only two, meshing gear wheels 81 which serve to drive a selected one, or at most two, of the caps 22 from a shaft 81a driven by a motor (not shown) or turned by hand.

Figures 5-8 show the caps 22 and the bars 23 in a little more detail. The anguiar positions of the caps 22 and the longitudinal positions of the bars 23 shown in Figure 5 correspond to the fully-open positions of the blades 20, while their positions illustrated in Figure 6 correspond to the fully-closed positions of the blades.Figure 7 shows how the caps and bars are pivotally connected together, it being noted that circular metal bushes 18a are fitted over selected blade bearing shafts 18 to act as stops in controlling the movement of the bars 23 so that the overall angle of blade rotation, which would otherwise be from 0 to about 115 or more, is precisely from 0 (which is the completely open blade position wherein the blades offer minimum resistance to flow) to 900 which is the fully closed position wherein the blades provide the absolute lowest flow leakage, there being also the choice of any intermediate blade position to suit operating requirements.

The caps or discs 22 are made very simply by being pressed out from sheet metal with their extruded rectangular holes 26 providing accurate blade bearing shaft alignment. As will be seen from Figure 8, the caps 22 each have a circular peripheral indent or flange 22b to reduce friction and ensure stability throughout the total operating arc. It will also be noted that a raised radial rib 22c is formed in each cap so as to reduce friction between the caps and the bars 23. The production of such caps does not give rise to the same manufacturing tolerance difficulties as precision-made gear wheels.

The drive bars or rods 23 are equally simple to make from sheet metal and have pre-punched square holes 23a for minimum contact area with the round pins 22a, thus reducing friction and the possibility of mechanical seizure.

As already indicated, the damper illustrated in Figures 1-3 is designed to be inserted in a duct by arranging for the flanges 14 of the outer casing 10 to be inserted in the opposing ends of two duct portions. In other words, the damper is inserted in a "break" in a duct so that the inner frame 12 is substantially flush with the internal surfaces of the duct. However, in certain countries- particularly the United States of America - it is customary to position dampers entirely within a duct. Figure 9 illustrates a damper having a frame 82 which permits this to be done. The frame 82 is, in effect, the same as the inner frame 12 in Figure 2 except that the frame 82 has flanges 84 which lie against the inner surface of a duct 86. The duct 86 itself therefore forms an outer frame for the damper so that the outer frame 10 of Figures 1 and 2 is no longer needed. The remaining parts of the damper shown in Figure 4 are essentially the same as those shown in Figures 1-3.

It will be seen, therefore, that the blade drive mechanism described above does not call for the precision-made gear wheels, one for each blade, used in the blade drive mechanisms of the dampers shown in the earlier Patent Applications referred to above. Further, by means of the present invention, the problem of backlash and undesirable torque stiffness in operation of the mechanism is overcome.

Claims (1)

1. Afluid damper comprising a line of blades which are supported in a surrounding frame for rotary movement about substantially parallel axes between positions in which they open and close a fluid opening in the frame, and a blade drive mechanism for effecting rotary movement of the blades about their parallel axes, in which the blade drive mechanism comprises at least one longitudinal moveable drive rod, bar or other element connected to more than one blade by means of reduced friction pin-and-hole connections.

New claims or amendments to claims filed on Superseded claims all.

CLAIM A fluid damper having a line of blades which are supported in a surrounding frame for rotary movement about substantially parallel axes between positions in which they open and close a fluid opening in the frame, and a blade drive mechanism comprising a drive element provided with holes which receive pins associated with the blades so that the drive element is connected to the blades via pin-and-hole connections, in which the drive element is in the form of a longitudinally-movable element having pin-receiving holes provided with straight edges while the pins are of round-section so that the contact between the pins and the drive element is minimal, and in which the blade drive mechanism is totally enclosed to prevent it becoming clogged with dirt or impurities in the fluid stream passing through the damper.