GB2185307A - Improvements in or relating to a damper - Google Patents

Abstract

A fire and smoke control damper has a plurality of blades, each blade having a rounded leading edge and a trailing edge formed by two inwardly directed free lips adapted to engage the rounded leading edge of the next adjacent blade. The blades are driven by a linkage which passes through spring biassed over centre condition to bias the blades in a closed condition (see Figure 4). A coil spring arrangement provides a bias on at least one damper blade (see Figures 1 and 6). <IMAGE>

Description

SPECIFICATION Improvements in or relating to a damper The present invention relates to a damper and more particularlyto a damper such as may be utilised in airflow ductwork in a building. Such dampers may be used to prevent the spread of a fire or smoke through the ductwork in the event of a fire breaking out,orto control theflowof airthroughthe ductwork.

Prior art devices are known which comprise a plurality of damper blades mounted within aframe to allowthe blades each to rotate about its own axis between an open and a closed position. The damper blades are commonly retained in the open position by means of a fusible link, which is an elementwhich fuses or melts when subjected to a predetermined temperature, and the blades are spring biassed towards the closed position. Thus, if a fire should break out and hot gases pass along the ductworkthe fusible linkwill melt and the blades will then move, under the spring bias, to the closed position.In the presently described prior art device the blades are mounted within the frame so that as the blades move to the closed position alternate blades rotate in opposite senses, and the leading edge of each blade engages with the trailing edge of the next adjacent blade to form a seal which prevents the passage of smoke orfire. The damper blades of the described prior art damper have a substantially rigid structure forthe leading edge of the blade and an open fish-tail structure for the trailing edge. Whilst this may provide a good seal when the blades are new, should either edge of the blade become distorted or mis-sha pen then this wil I obviously have a detrimental effect on the seal provided.The open fish-tail structure is not aerodynamically ideal and thus the blades, even when in the open condition, provide a considerable resistenceto airflowing through the ducting. Also, if any dirt accumulates on the leading edge of a blade, that blade may not make an adequate seal with the trailing edge ofthe adjacent blade when the damper closes.

One object of the present invention is to provide an improved damper blade seal. Further objectives of the present invention include providing an improved mechanism for biassing and moving the blades towards the closed position in the event of a fire and the inclusion of a mechanism to allowthe blades to be set to intermediate positions between the open and the closed position, so that the damper may be used as a flow control damper, as well as being used as a fire and smoke damper.

According to one aspect of this invention there is provided a bladeforguiding orterminating aflowof air, said blade comprising an outer surface defining an aerofoil section, means for pivotally mounting the blade for pivotal movement about a longitudinal axis ofthe blade, said aerofoil section having a leading and atrailing edge, said leading edge being rounded and said trailing edge being formed by two inwardly directed free lips adapted to engage with the rounded leading edge of a second such blade to form a seal along the joint between the two said blades.

Preferably the said two inwardly directed free lips are unequal in width.

Conveniently the free edge ofthe first said lip, which is the wider lip, lies adjacentthe inner surface of the said aerofoil section, and the free edge of the other lip lies adjacent the outer surface of said first lip.

Advantageously the first said lip is approximately twice the width of the second said lip and the free edge of the second lip lies adjacent the outer surface of said first lip at a position approximately one third along the length of said first lip.

Preferably the lips are resiliently retained in position in such a way that when the blade engages said second blade the lips are resiliently biassed into contact with the second blade.

Conveniently said lips are formed from a resilient material which permits a degree of movement of said lips.

According to another aspect of this invention there is provided a linkage mechanism for converting a linearmotiontoa rotary motion aboutapluralityof parallel axes comprising a drive member constrained to move linearly; means for moving said drive member; at least two rotatable members mounted for rotation about said axes; a connection between said drive member and said rotatable members which connection is adapted to pass an over dead centre condition when said rotatable members have been rotated to a predetermined position, the arrangement being such that the linear movement ofthe drive member in one direction causes the rotatable members initiallyto rotate in opposite rotational directions towards said predetermined position where said connection connecting the drive member with said rotatable members is positioned in a dead centre condition, a small further movement ofthe drive member in the same direction being possible, this movement causing the connection to move past the dead centre condition.

Preferably said connection comprises two links of equal length, said two links each being pivotally connected at one end thereofto a common point on the drive member, said two links each being pivotally connected atthe other end thereof to a point spaced from the centre of a respective rotatable member, the drive member passing between said rotatable members.

Conveniently a plurality of said rotatable members are provided, divided into two sets of alternate members, the members of the first set being interconnected to co-rotate and the members of the second set being interconnected to co-rotate.

Advantageously the rotatable members of each set are interconnected by means of a connecting rod which is pivotally connected to each memberofthe set at a point spaced from the centre thereof.

Preferably the mechanism forms part of a damper comprising a plurality of blades mounted in a frame, the blades being rotationally movable between open and closed conditions, each rotatable member being drivingly associated with a respective blade.

Conveniently the blades are biassed to a closed position, and when moving to the closed position underthe bias move said connection towards the dead centre condition, a continuing movement of the drive membercausing the connection to pass through the dead centre condition.

Preferably each damper blade is a blade according to the first aspect of the invention.

According to another aspect ofthis invention there is provided a damper, said damper comprising a frame, a plurality of damper blades extending across the frame and movable rotationally abouttheir longitudinal axes between open and closed positions, the damper incorporating a spring arrangementto exert a biassing torque on a rotatable member on which a damper blade is mounted, said spring arrangement comprising a coil spring, means for attaching one end of said coil spring to said rotatable member, a member suitable for receiving the windings of said coil spring and means for attaching said windings of said coil spring to said receiving member.

Preferably said receiving member is in the form of a rotatable drum and substantially all of said coil spring is wound on said drum.

Conveniently the outermost winding of said coil spring on said drum orthe drum itself, incorporates a projection, and a peg orthe like is provided for engaging with the projection when the rotatable member reaches a predetermined point in order to reduce the torque applied to said member.

Advantageously each damper blade is a blade according to the first aspect ofthe invention Conveniently the damper blades are interconnected so that one said spring arrangement biasses all the damper blades to the closed position.

Preferably the damper blades are interconnected by and driven by a linkage according to said another aspect of the invention.

In orderthatthe present invention may be more readily understood and so thatfurtherfeatures thereof may be appreciated a damper in accordance with the present invention will now be described by way of example and with reference to the accompanying figures in which: Figure 1 is a perspective view of a damper according to the present invention; Figure is a perspective view of a damper blade which forms part of the damper shown in Figure 1; Figure 3 is an end view of a plurality ofdamper blades moving into the closed position; Figure4 is an end view on the damperframe looking in the direction ofarrowAin Figure 1 showing the drive system; Figure 5is a sectional view taken on the line V-V in Figure 1 showing the spring mechanism.

Figure 6 is a partial end view looking on the right hand end ofthe dampershown in Figure 1, showing the spring mechanism.

Referring to the drawings, Figure 1 shows a dampercomprising a rectangularframe 1 defining an aperture 2. The frame 1 is adapted to form part of an airflow duct so that air,flowing through the duct, flows through the aperture 2. A plurality of parallel blades 3 are mounted on the frame 1 extending across the aperture 2.

The frame 1 is formed of frame members of U-section, each frame member having c base portion4andtwo upstanding wall members5.The base portions 4 of the frame members thatform the vertical sides of the frame 1 are each provided with a plurality of holes 6 spaced at equal intervals along thevertical axis positioned centrally betweenthe two upstanding wall members 5. The number of holes 6 provided in the base portion 4 of each ofthe vertical sides of the rectangularframe 1 corresponds to the number of blades 3 provided in the damper.

The holes 6 are each formed in a manner which leaves a portion 7 of the base 4 of the frame 1 immediately surrounding the hole projecting outwardlyfrom the base 4. The upstanding wall members 5 of one of the vertical sides of the frame 1 are provided with two aligned slots 8 through which a linkage9 may be inserted.Theframe 1 maybe formed either from one piece of material which is bent to form the fourframe members and joined at oneofthecornersoftheframeorfrom a plurality of separateframe members which are joined atthe corners of the frame. The upstanding wall members 5 may be provided with appropriately located apertures to enable the damperto be bolted to the adjacent lengths of duct.

The damper blade 3, shown in Figure 2, comprises an outer skin 10 formed to define a hollow aerofoil section with a rounded leading edge 1 1.The trailing edge 12 ofthe blade 3 is defined by the inwardly folded ends of the outer skin 10 of the blade 3 which form lips 13,14. The ends ofthe outer skin 1 0 are folded inwardlytoform one lip 13 longerthanthe other lip 14. The lip 13 is folded inwardly so thatthe edge 15 ofthe lip 13 lies adjacent the innersurface 16 of the hollow aerofoil section defined by the outer skin 10. The lip 14 is folded inwardly so thatthe end 17 of the lip 14 lies adjacent the outside surface ofthe lip 13.The lips 13 and 14 are resilient or are resiliently connected to the rest of the blade 3, so that each lip can move slightly, against a resilient bias, in a substantially pivotal manner. The free edges of the lips are not connected to any other part of the blade, so thatthe lips can move relatively freely in the manner described above.

A hollow axle or tube 18 runs approximately through the centre ofthe hollow aerofoil section defined by the outer skin 10 and is fixed to the outer skin 10 by means of rivets, spot welds or any other suitable means. The tube 18 is longer in length than the blade 3 and thus has portions 19, 20 projecting beyond the edges of the blade 3.The projecting portions 19,20 of the tube 18 are designed to be inserted through the holes 6 in the vertical walls of the frame 1 so that the blade 3 is free to rotate about a longitudinal axis passing through the centre of the tube 18when mounted in position intheframe 1.The blades 3 are designed so that when a plurality of blades, mounted within the frame 1, are moved to the closed position (as shown in Figure 1), the leading edge 11 of each blade 3 cooperates with the trailing edge 12 of an adjacent blade3toform a seal.

The lips 13, 4 of the trailing edge 12 are pushed aparttoform a seal along the leading edge 11 of an adjacent blade 3 when the lips 13, 14 come into engagement with the leading edge 11 of an adjacent blade 3, in that both lips are independently biassed into engagement with the leading edge ofthe adjacent blade. Thus a two point seal is formed along the entire length of the blade 3.

Figure 3 shows how the leading edge 11 and the trailing edge 12 of adjacent blades 3 come into engagement as the blades 3 approach the closed position. As the blades complete the illustrated movement to the closed position the uppermost blade and the lowermost blade illustrated will rotate anti-clockwise, whilst the central blade will rotate clockwise. As the blades move to the final closed position, firstly the leading edge 11 of a blade 3will engage with one ofthe lips 13, l4ofthetrailing edge 12 of an adjacent blade 3 andthis engagementwill tend to push the lips 13,14 apart and open outthe trailing edge 12slightlyastheblades3 movefurther towards the closed position.The leading edge 11 of theblade3will remainincontactwiththefirst engaged lip of the trailing edge 12 ofthe adjacent blade 3 and will subsequently engage the other lip of thetrailing edge 12 of the adjacent blade 3 which will similarly tend to push the lips 13, further apart and open out the trailing edge 12 as the blades 3 move into the closed position. The inherent resilience of the material from which the trailing edge 12 is formed will actto try and push the lips 13,14 back together again, thus ensuring firm engagement of the lips 1 3, 1 4with the leading edge 11 ofthe adjacent blade 3.At least the greater part of the flexing movement which occurs as the lips 13,14 engage the leading edge 11 of the adjacent blade takes place in the region of the outer skin 10 ofthe blade adjacent the lips 13,14. This design of cooperating leading and trailing edges ensures that a good seal is achieved over the entire length ofthe blades 3, since both lips of one blade are independently biassed into contact with the leading edge of the next adjacent blade.

Figure 4 is an end view on the frame 1 looking in the direction of arrow A shown in Figure 1 and shows details of the drive system for positioning the blades 3 to any desired setting between the open and closed positions. The drive system incorporates a plurality of discs 21. A first set of alternate discs (i.e. every second disc) are connected together by means of a connecting rod 22, and a second set of alternate discs (i.e. the remaining discs) are connected together by means of a connecting rod 23.A drive linkage 9 is provided which comprises a horizontal drive member 24 which is pivotally connected to two connecting links 25,26 which form a scissor link adjacent the free end of the horizontal member 24 and which have their free ends connected to points adjacent the peripheries of two adjacent discs 21, thus connecting these discs to the horizontal drive member 24.

The discs 21 are each of a circular shape, and are flat, with a centrally located bore 27 within a raised portion 28. The bore 27 is designed to accommodate the projecting portions 19,20ofthetube 18which runs through the hollow section ofthe blade 3, the raised portion 28 of the disc 21 serving to allow the disc 21 to be fixed, by means of rivets orthe like, which pass through the portion 28 to the portion of the tube 18 which extends beyond the frame 1.

Alternatively the discs may be mounted on the tube 18 in many alternative ways. For example, the end of each tube 18 may be provided with a plurality of deformable lugswhich can be passed through appropriately located slots in the disc, the lugsthen being bent over to hold the disc in position.

The linkage and connecting rods are arranged so that adjacent discs 21 will rotate in opposite directions when the drive member 24 is moved in a horizontal direction. Thus, it will be appreciated that two sets of alternate, similarly rotating discs can be distinguished. Thus the discs ofthe first set rotate in one direction, and the discs of the second set rotate in the other direction when the damper closes. Of course, the discs ofthe first set rotate in a direction opposite to said one direction, and the discs ofthe second set rotate in a direction opposite to said other direction when the damper opens.

Each disc21' in the first set of alternate discs has a small bore 29 positioned close to the outer edge of the disc. The connecting rod 22 has similar small bores at positions along its length corresponding to the positions of the bores 29 in the first set of discs 21', so that pin joints can be formed between the connecting rod 22 and the discs 21 '.

The discs 21 " in the second set of alternate discs are similarly joined to the connecting rod 23 by means of pin joints through bores 30, the bores 30 being offset by an angle of approximately 90" relative to the bores 29 in thefirstsetofdiscs 21', when the device is in the fully closed position as illustrated in Figure4.

Two adjacent discs 21 also each possess an additional small bore 31,32 positioned close to the outer edge of the disc. The connecting links 25,26 have small bores at each end,which allows one end of each linkto be joined, by means of a pin to one of the adjacent discs 21. The other ends ofthe connecting links 25,26 are connected at the same point with the drive member 24, so as to form a scissor link. The drive member24isretained in position within slots 8 formed in the upstanding walls 5 of the vertical sides of the frame 1. The scissor link arrangement allows horizontal movement ofthe drive member 24 to be translated to a rotary movement of the two adjacent discs 21 connected to the drive member 24 by means ofthe connecting links 25,26. This rotary movement is transferred to the remaining discs 21 by the connecting rods 22,23.

Movement of the blades 3 to any desired setting may take place either manually by means of a mechanical connection with the drive member 24 or may be controlled remotely, with an electrical or pneumatic device generating the required movement of the drive member 24. The drive member 24 may also contain fusible link (not shown) designed to break the connection between the drive member24 and the prime mover should the ambienttemperature exceed a given level. When this connection is brokenthe blades3withintheframe 1 will move into the closed position underthe action of the spring arrangement 33 shown in Figures 1, and 6.

The spring arrangement 33 comprises a coil spring 34 connected between two adjacent blade tubes 18.

The majority of the flat coil spring 34 is wound on a circular drum 35 which is fitted on the end of the lower blade tube 18 as shown in Figure 5. Itwill be appreciated thatalternativeforms oftorque drum 35 may be used, for example, the drum 35 may be in the form of a ring with a separate diametral component serving to form the engagement with a suitably adapted blade tube 18. The end of the coil spring 34 is connected with the drum 35 by means of the tapped fixing 36. The free end of the coil spring 34 is fixed onto an end cap 37 which in turn is fixed to the upper bladetube 18, as shown in Figure 5, by means of rivets 38.Alternatively the free end of the spring 34 may be connected to an extensiontubewhich projects from insidethe upper blade tube 18 (this embodiment not being shown in the drawings). The connection between the blade tube 18 and the extension tube may be an interference fit. As shown more clearly in Figure6,thetension in the coil spring 34 makes the spring want to coil around the lower bladetube 18. This results in an anti-clockwise torque being exerted on the upper blade tube 18. An anti-clockwise rotation of the upper blade tube 18 corresponds to a movement of the blade 3 connected to this bladetube 18 towards the closed position.

This movementtowardsthe closed position is transferred to all the other blades 3 by the disc and linkage connection shown in Figure 4. As the blade tube 18 acted on by the spring 34 rotates, so all the other blades in the same set of alternate blades will rotate simultaneously in the same sense. The scissor link 25,26, initially to the right of the position illustrated in Figure4will move to the left,thus causing the other set of alternate blades to rotate in the opposite sense.

In orderto preventthe blades3from coming tog ether too rapidly into the closed position the spring 34 may incorporate a projecting portion 39 designed to engage a protruding peg 40 which is connected to the base portion 4 of the vertical side wall ofthe frame 1. The intention is that the projecting portion 39 should merely slow down the motion of the blades 3 as they come into engagement and should not stop their movement compieteiy. Thus the projecting portion 39 ofthe spring 34 is designed to engage the protruding peg 40 but also to pass inside the peg 40 underthe action ofthetension inthe spring 34.

When the blades 3 are moved to the closed position underthe action ofthe coil spring 34 the drive system may adopt the position shown in Figure 4. It is to be understoodthatthe blades initially close when the mid-point of the scissor link 25,26 is to the right of the illustrated position. However, when the fusible link has fused (or if a subscribed force is applied to the drive link 24) when the damper reaches the initially closed position the drive link 24 will still have its own momentum and will continue to move to the left.Thus, in reaching the position shown in Figure4the connecting links 25,26 and the drive link 24 have passed through a dead centre position in which the connecting links 25,26 would stand vertically. The leading and trailing edges 11,12 of adjacent blades 3 are pressed moretighty together when the links 25,25 are in the dead centre position but still provide an adequate seal when the links have moved past the dead centre position underthe action of the coil spring 34 due to the resilience of the material used to form the blades 3.

This over dead centre arrangement ofthe linkage has the advantage of making it more difficultforthe blades 3 to be blown open,for example, by a firestorm within a ductwork on one side of the blades since the blades must be closed more tightly (to enablethe linkage to pass again through the dead centre condition) before the blades can open.

It will be appreciated that the present invention can incorporate any number of blades desired with only the frame and the connecting rods 22,23 needing to be extended. It will also be appreciated that the present invention may be used as a smoke, fire, air flow control damper or any combination thereof, and that many modifications may be made to the specific embodiment described without departing from the scope ofthe invention. For example, the drive link 24 and the connecting links 25,26 may be positioned on the underside of the discs 21 with the connecting rods 22,23 being located above the discs 21.

Claims (26)

1. Abladeforguiding orterminatingaflowofair, said blade comprising an outer surface defining an aerofoil section, means for pivotally mounting the blade for pivotal movement about a longitudinal axis ofthe blade, said aerofoil section having a leading and atrailing edge, said leading edge being rounded and said trailing edge being formed by two inwardly directed free lips adapted to engage with the rounded leading edge of a second such blade to form a seal along the joint between the two said blades.

2. A blade according to claim 1 wherein the said two inwardly directed free lips are unequal in width.

3. A blade according to claim 2 wherein the free edge of the first said lip, which is the wider lip, lies adjacent the inner surface of the said aerofoil section, and the free edge of the other lip lies adjacent the outer surface of said first lip.

4. A blade according to claim 3 wherein the first said lip is approximately twice the width ofthe second said lip and the free edge of the second lip lies adjacent the outer surface of said first lip ata position approximately one third along the length of said first lip.

5. A blade according to any one of the preceding claims, wherein the lips are resiliently retained in position in such a way that when the blade engages said second blade the lips are resiliently biassed into contact with the second blade.

6. A blade according to claim 5, wherein said lips are formed from a resilient material which permits a degree of movement of said lips.

7. A linkage mechanism for converting a linear motion to a rotary motion abouta plurality of parallel axes comprising a drive member constrained to move linearly; means for moving said drive member; at least two rotatable members mounted for rotation about said axes; a connection between said drive member and said rotatable members which connection is adapted to pass an over dead centre condition when said rotatable members have been rotated to a predetermined position, the arrangement being such that a linear movement of the drive member in one direction causes the rotatable members initially to rotate in opposite rotational directions towards said predetermined position where said connection connecting the drive memberwith said rotatable members is positioned in a dead centre condition, a small further movement of the drive member in the same direction being possible, this movement causing the connection to move past the dead centre condition.

8. A linkage mechanism according to claim 7, wherein said connection comprises two links of equal length, said two links each being pivotally connected atone end thereoftoacommon pointon the drive member, said two links each being pivotally connected at the other end thereof to a point spaced from the centre of a respective rotatable member, the drive member passing between said rotatable members.

9. A linkage mechanism according to claim 7 or 8, wherein a plurality of said rotatable members are provided, divided into two sets of alternate members, the members of the first set being interconnected to co-rotate and the members ofthe second set being interconnected to co-rotate.

10. A linkage mechanism according to claim 9, wherein the rotatable members of each set are interconnected by means of a connecting rod which is pivotally connected to each member of the set ate point spaced from the centre thereof.

11. A linkage mechanism according to any one of the preceding claims, wherein the mechanism forms part of a damper comprising a plurality of blades mounted in a frame, the blades being rotationally movable between open and closed conditions, each rotatable member being drivingly associated with a respective blade.

12. A linkage mechanism according to claim 11, wherein the blades are biassed to a closed position, and when moving to the closed position underthe bias move said connection towards the dead centre condition, a continuing movement of the drive member causing the connection to pass through the dead centre condition.

13. Alinkage mechanism according to claim 11 or claim 12, wherein each damper blade is a blade according to anyone of claims 1 to 6.

14. A damper, said damper comprising a frame, a plurality of damper blades extending across the frame and movable rotationally abouttheir longitudinal axes between open and closed positions, the damper incorporating a spring arrangement to exert a biassing torque own a rotatable member on which a damper blade is mounted, said spring arrangement comprising a coil spring, means for attaching one end of said coil spring to said rotatable member, a member suitable for receiving thewindings of said coil spring and meansforattaching said windings ofsaid coil spring to said receiving member.

15. Adamperaccording to claim 14, wherein said receiving member is in the form of a rotatable drum and substantially all of said coil spring is wound on said drum.

16. Adamperaccordingto claim 15,whereinthe outermost winding of said coil spring on said drum, or the drum itself incorporates a projection, and a peg or the like is provided for engaging with the projection when the rotatable member reaches a predetermined point in order to reduce thetorque applied to said member.

17. A damper according to any one of claims 14 to 16, wherein the damper blades are blades according to any one of claims 1 to 6.

18. A damper according to any one of claims 14 to 17, wherein the damper blades are interconnected so that one said spring arrangement biasses all the damper blades to the closed position.

19. Adamperaccordingto claim 18,whereinthe damper blades are interconnected by and driven by a linkage according to any one of claims 7 to 13.

20. A blade substantially as described herein with reference to and as shown in Figures 1,2 and 3 oftheaccompanying drawings.

21. Alinkagearrangementsubstantiallyas described herein with reference to and as shown in Figures 1 and 4 of the accompanying drawings.

22. A damper incorporating a spring arrangement substantially as described herein with reference to and as shown in Figures 1,5 and 6 ofthe accompanying drawings.

23. A damper incorporating a blade substantially as described herein with reference to and as shown in Figures 1,2 and 3 ofthe accompanying drawings.

24. A damper incorporating a linkage arrangement substantially as described herein with reference to and as shown in Figures 1 and 4 ofthe accompanying drawings.

25. A damper substantially as described herein with reference to and as shown in the accompanying drawings.

26. Any novel feature or combination offeatures disclosed herein.