GB2325965A - Apparatus and method for manufacturing a brush seal - Google Patents

Abstract

A method of manufacturing a brush seal draws together bristle elements to be used in the seal in the form of a bundle 12 of such elements and forces an end of the bundle against the raised portion 18 of a nominally flat surface 16 so that the bristle elements divide and splay out along the flat surface. The splayed-out bristle elements are then clamped in a seal housing 20 and cut to a suitable length to form the seal. The surface may be circular, the seal housing annular and the bundle cylindrical so as to form a circular brush seal; alternatively, these geometric figures may be radially truncated to form a semicircular or other part-circular seal. In one embodiment the bristle elements are splayed out, temporarily clamped at the ends by rings 36 and the bundle or temporary clamp rotated so as to angle the bristle elements relative to a radial direction of the bristle elements. The seal housing is then applied to provide a permanent clamp for the bristle elements in which the bristle elements are set at, for example, the normal 45‹ configuration employed in a shaft seal, or similar.

Description

APPARATUS AND METHOD FOR MANUFACTURING A BRUSH SEAL The invention concerns a method of manuflicturing a brush seal and apparatus for the carrying out of such a method.

Brush seals are commonly used to seal a surface against the leakage of a fluid, e.g.

a gas, such as in a gas turbine, or a lubricant, such as used on a rotating shaft. Such seals are often circular in form with the bristles set at an angle of approximately 45" to a tangent to the circular bristle holder.

A number of techniques for the manufacture of brush seals are known, including, for example, the technique disclosed in US patent number 4,884,850, in which the bristle elements are laid in an aligning member having a surface containing a series of oblique grooves around its circumference, the bristles being placed in these grooves, then clamped between opposing annular plates and finally cut at an appropriate point. Finally, the aligning member is removed to provide a circular brush seal in which the bristles are laid at the aforementioned 45" angle.

A major drawback with this method is that different aligning members would be required for different-sized seals. There is also fairly significant wastage of bristle material and the problem that the gap which necessarily exists between the grooves can lead to undesirable gaps in the bristle population of the seal.

A more common manufacturing technique is to wind a continuous filament around one or more mandrels and then to cut the filament to create one or more brush seals. Such a system is disclosed in, for example, US patent number 4,730,876, United Kingdom patent application 2,001,400A and United Kingdom patent application 2,253,800.

In accordance with the present invention there is provided a method of manufacturing a brush seal having a plurality of bristle elements, comprising the steps of: (a) forming a bundle of said bristle elements; (b) bringing said bundle into contact with a surface such as to cause said bristle elements to splay out against said surface; (c) clamping said bristle elements at a splayed-out point thereof, and (d) cutting said bristle elements at a given distance from said clamping point.

Step (c) may be performed using opposing halves of a bristle-element holder, said holder halves being brought to bear against said bristle elements from opposite sides thereof.

Step (c) may comprise the steps of: (c') temporarily clamping using temporary clamping means said splayed-out bristle elements approximate a splayed-out end-portion thereof; (c") permanently clamping said splayed-out bristle elements between opposing halves of a bristle-eEment holder at a point intermediate said end-portion and a point of action of said bundle on said surface, said temporary clamping operation being subsequently terminated.

A part of said surface may be substantially flat and said bundle in step (a) may be brought into contact with said sure along an axis substantially normal to said substantially flat part of said surface. Subsequent to step (c') and prior to step (e ") a relative rotation of said temporary clamping means and said bundle about said axis may be effected, an angle of said rotation determining an angle of orientation of said bristle elements in said holder following said step (c").

In step (d) the bristle elements clamped in said holder may be cut at a radially outer point relative to said housing thereby to form an external brush seal.

In step (d) the bristle elements clamped in said holder may be cut at-a radially inner point relative to said housing thereby to form an internal brush seal.

According to a further aspect of the invention there is provided an apparatus for the manufacture of a brush seal, which seal cornprises a plurality of bristle elements and a bristleelement holder in which said bristle elements are secured, the apparatus comprising a bristle elernent moving means and a bristle-element splay-out means, said bristleelement moving means being adapted to move a bundle of said bristle elements along a longitudinal axis towards said bristleelement spla,-out means thereby to effect splaying-out of said bristle elements, said apparatus comprising also a bristleelement clamping means for clamping said bristle elements at a splayed-out point thereof, and a bristleelement cutting means for cutting said clamped bristle elements at a given distance from the clamping point.

The bristleelement splay-out means may comprise a surface having a portion substantially normal to said longitudinal axis and a raised portion which, in use, is brought into engagement with an end of said bundle such as to initiate splaying-out of said bristle elements.

The substantially normal surface portion may be annular and the raised portion may be approximately conical in form and disposed at a centre of said annular portion, said apparatus being suitable for the manufacture of a circular brush seal. Alternatively, the substantially normal surface portion may have the form of an incomplete annulus and the raised portion may have the form of a correspondingly incomplete approximate cone, said apparatus being suitable for the manufacture of a part-circular brush seal.

The apparatus may comprise a clamping ring for temporarily clamping splayed-out end-portions of said bristle elements.

Rotation means may also be provided for effecting relative rotation of said clamping ring and said bundle, thereby to set said bristle elements in said holder at an angle to a radial direction of said bristle elements relative to said longitudinal axis.

The apparatus may comprise a cylindrical member extensive along said longitudinal axis at a centre of said bundle, said cylindrical member in use coming into contact with an apex of said approximately conical, or incomplete approximately conical, raised portion. The cylindrical member may be hollow at an end thereof which, in use, comes into contact with said apex, an internal diameter of said hollow end being greater than a diameter of said apex.

The bristleelement moving means may comprise a means for moving said bundle and said tube towards said approximately conical, or incomplete approximately conical, portion until said apex engages with said hollow end, and for thereafter continuing movement of said bristle elements only towards said annular or part-annular surface.

The apparatus may comprise means for disposing said bristle elements around said tube to form said bundle.

The substantially normal surface portion may be a flat surface portion.

An embodiment of the invention will now be described with reference to the drawings, it being understood that the embodiments given are exemplary only and not to be construed as being in any way limiting on the invention. The drawings show: Figure 1 - a perspective view of an apparatus for manufacturing a brush seal in accordance with the invention; Figure 2 - a plan view of the apparatus of Figure 1 showing the seal bristles in a splayed-out state; Figure 3 - a detail of Figures 1 or 2 showing the disposition of a two-part seal holder in relation to the bristles; Figure 4 - an equivalent detail to that of Figure 3 in which the seal holder is in one piece; Figure 5- a detail of a seal-making apparatus according to the invention allowing the manufacture of seals of non-radially inclined bristles; Figure 6 - a bristle bundle incorporating a central rod; Figures 7(a)-(e) - various stages in the splaying-out process of the present invention; Figure 8 - a detail of an apparatus for the manufacture of a brush seal in accordance with the invention incorporating a guide ring for the deterrnination of bristle thickness.

Figure 9 - a plan view of an apparatus for the manufacture of a non-circular brush seal in accordance with the invention; Figures 10(a) and (b) - views of a non-planar brush seal, and Figures 11 - a perspective view of an apparatus for the manufacture of the brush seal illustrated in Figure 10.

With reference to Figure 1, a number of bristle elements ("bristles") 10, which may be composed of a metal or a synthetic material, depending on application, are gathered together aligned longitudinally to form a bundle or "loom" 12 and are then moved in a direction indicated by an arrow 14 towards a bristleelement splaying means 15. The splaying means 15 comprises a flat circular plate 16 in the centre of which is disposed a conical or approximately conical protrusion 18. The bundle of bristles 10 moving towards the splaying means strikes the protrusion 18 which acts as a spike forcing the bristles to splay apart and move down the sides of the protrusion 18 until they reach the flat surface of the plate 16, upon which they continue to splay out further along the plate surface. The plate thus acts as a "spreader" plate, serving to spread out the bristles at the end of the bundle.

The bristles are then, in a first example of the present manufacturing method (see plan view of Figure 2), clamped at a splayed-out point between two halves of a bristle holder 20 and the bristles cut either at a point 22 downstream of the holder in terms of bundle movement or at a point 24 upstream thereof to form, respectively, an external or internal brush seal. In practice, where an internal seal is being made, the holder 20 is applied at as near the ends of the bristles as possible in order to minimize bristle wastage, it being otherwise necessary to trim off a significant portion of the bristles downstream of the holder in the case of an internal seal. Likewise, where the seal is to be an external seal, the cut 22 is also made as near to the ends of the bristles as possible similarly to reduce wastage. In either event, care is taken to ensure that the minimum amount of bristle is moved down and across the surface of the plate 16 commensurate with the required length of the bristles and the radial depth of the the holder 20. Thus, the holder is all times be positioned as near to the outer circumference of the plate 16 as possible so that, in the case of an external seal, the bristles upstream of the holder can be severed from the holder as close to the holder and to the plate circumference as possible, and in the case of an internal seal the required cut 24 can take place also as close to the plate circumference as possible. In this way bristle usage is minimised.

Figure 3 is a partial view of a circular internal seal in which the two halves 30, 32 of a bristle holder 20 are shown clamping the splayed-out ends of the bristles 10. The seal is separated from the remaining (upstream) portion of the bristles by cutting along the cut line 24. As already mentioned, the cut line 24 is preferably located as close to the outer circumference of the spreader plate 16 as possible to minimise waste.

An alternative realisation of such an intemal seal is illustrated in Figure 4 in which, instead of using a holder having two halves, a single "U'-section holder 34 is employed which is closed at its downstream end such as to form a pocket for the bristles to be clamped into. The holder 34 is simply fitted onto the ends of the bristles, which may require to be initially trimmed in order to form a regular circle, and its open end then closed under pressure. The bristles are subsequently cut along the upstream cut line 24 as before.

The seals so far described in connection with the invention have been seals with radially oriented bristles, i.e. the bristles form an angle of 90" to a tangent to the circular holder. An important variant of this basic manufacturing scheme allows the production of seals having the bristles inclined at different angles to the holder, e.g. the 45" commonly required in many applications. This is achieved in the present invention by first clamping the splayed-out bristles not in the holder itself but in a temporary clamping means, then allowing the bundle of bristles 12 and the seal holder to be rotated relative to each other, then clamping the holder to the bristles at some point upstream of the temporary clamping rneans.

This arrangement is shown in Figure 5, in which the temporary clamping means - the clamping rings 36 - is first clamped against an end-portion of the splayed-out bristles 10, the holder 20 with its two halves-is positioned loosely at a suitable point upstream of the clamping rings and then either the clamping rings 36 or the bundle 12, or both, are rotated so that the splayed-out bristles are held taut and at a non-radial angle. Clearly, for a given direction of inclination of the bristles the clamping rings 36 will be rotated in one direction or the bundle will be rotated in the opposite direction, or possibly both items could be counter-rotated simultaneously. The last-mentioned arrangement is hinted at in Figures 1 and 5 with the arrows 17 and 19.

This embodiment of the invention very conveniently allows the creation of either an internal or an external seal since, as shown in Figure 5, the final cut of the bristles can be carried out either at a point A to form an external seal, or at a point B to form an internal seaL Indeed, it is possible to manufacture a seal which has at the same time both an external and an internal sealing function simply by cutting at the two points A and B, though this assumes that the equipment in which the seal is to be used would be able adequately to support such a seaL Of course, the earlier observations regarding the minimisation of bristle usage also apply here, so that in practice for an external seal the bristles would be cut as close to the radially inner face 38 of the holder as possible and the distance r, between this face and the outer circumference of the spreader plate 16 kept to a minimum commensurate with ease of cutting, while for an internal seal the cut line at B would be as close to the plate 16 as possible and the holder 20 would be as close to the clamping rings 36 as possible (distance r2 at a minimum), again allowing enough room for cutting to take place.

The angle of orientation of the bristles in the holder is determined in the method just described by the angle of rotation of the bundle and clamping rings 36 relative to each other.

In order to assist the splaying-out process, a number of ancillary features may also be employed in addition to the basic features outlined above. Firstly, it is conceivable that the movement of a bundle of bristles, in which the bundle constituted as it were a cylinder having bristles all the way from its centre to its outer periphery, directly onto the conical portion 18 of the splaying-out means could result in tangling of the bristles at the radial centre of the bundle. To avoid this, the invention provides for the incorporation of a hollow, or partially hollow, tube 40 situated at the core of the bundle. This is illustrated in Figure 6. In use, the bundle with the tube at its centre is held in a bristle-moving means 42 (see Figure 7(a)) which in one particular form may comprise a first arm 44 supporting the tube 40 and a second arm 46 covering and abutting the upper end-face of the bundle 12 and able to slide along the tube 40. The bundle and tube are initially held clear of the protrusionl8 (Figure 7(a)), but the arms 44 and 46 are then moved downwards bringing- the bundle and tube nearer to the protrusion 18 until the hollow end of the tube locates over the apex of the protrusion 18 (Figure 7(b)). The arm 46 then alone continues its downward movement, forcing the bristles 10 over the conical or nearconical surface of the protrusion 18, the bristles in the process separating and splaying out (Figures 7(c) and (d)). Once the splayedout ends 48 of the bristles are of a length adequate for the subsequent operations of clamping, angling (where necessary) and cutting, movement of the arm 46 ceases and these operations are carried out.

In order for the bristles 10 to be able to slide readily over the tube 40, the tube is preferably made of a material having a low coefficient of friction, e.g. PTFE. The tube may, in practice, be a solid rod over most of its length, becoming hollow only at its lower end which is destined to engage with the protrusion 18.

Also required in connection with the bundle 12 is a means of maintaining a regular geometric shape of the bundle both when it is descending towards the protrusion 18 and when it is being splayed out over the surface of the protrusion. One way of achieving this is to employ one or more guides, of which one - designated 50 - is shown in Figure 1, along the path of the bundle. Such a guide will also have the additional function of ensuring concentricity of the bundle and the protrusion. An alternative measure is to fit one or more resilient sleeves around the bundle which will maintain the cylindricality of the bundle in regions above the protrusion 18, but readily expand when the bundle moves over the surface of the protrusion. Such a resilient seal may take the form of a number of discrete elastic rings surrounding the bundle, or a single elastic sleeve over the length thereof.

Once the seal has been made, the resilient sleeve(s) - where such are employed -may be removed from the residual part of the bundle in readiness for the manufacture of the next seal, the arms 44 and 46 being to this end lifted in preparation for the attachment of the next bundle to the arm 44. Alternatively, it is possible to employ a bundle of such length as to allow the manufacture of a number of seals consecutively, in which case after one seal has been made the arm 46 is simply lowered further to drive the long bundle again over the protrusion 18 for the manufacture ofthe next seal, and so on. In this realisation the resilient sleeve may be arranged to extend over substantially the whole length of the bundle, the sleeve being cut after each seal is made.

Further possible ancillary features are the inclusion of a vibration means (not shown) for encouraging each bristle to assume a uniform position relative to its neighbour. Thus the plate 16, or the plate 16 and the moving means 42 together, may be attached to a vibrator.

This presupposes that the means used to maintain the geometric form of the bundle does not overly restrict movement of the bristles.

In addition to, or in place of, vibration means to promote evenness of bristle thickness on the spreader surface 16, a guide ring 51 may be employed at the base of the protrusion 18 (see Figure 8). This guide ring is disposed at a suitable distance from the flat surface of the plate and is configured such as to form an open mouth 52 with the start of the protrusion 18 so as to facilitate the passage of the bristles 10 under the ring 51 and onto the flat plate surface. The distance between the underside 54 of the ring 51 and the flat surface 56 of the plate helps to determine the eventual thickness of the bristle layer in the seal. This feature may work in conjunction with the loose application of the holder rings 20 to the bristles downstream of the spreader plate, as shown in Figure 2. In the latter case the rings 20 are kept apart at a distance which determines the local thickness of the bristles within the seal, the rings 20 being finally brought together in their afore-mentioned clamping action.

Whereas the protrusion 18 has been largely assumed to be conical in shape (see, e.g., Figure 1), it may advantageously deviate from this form, in particular where the protrusion meets the flat plate surface. This feature is shown in Figure 8, where the protrusion 18 can be seen to merge into the flat surface, and indeed is shown to be integral with it. Merging of the protrusion and flat surface in this manner greatly facilitates the splaying-out process of the bristles as the bundle descends. The protrusion can be either a separate member secured in some suitable way to the spreader plate, or, as already mentioned in connection with Figure 8, it may be of one piece with it.

As well as being able to produce internal or external seals, the present method is capable of producing seals of a range of sizes simply by allowing the use of spreader plates of various diameters, which in turn allows holders of correspondingly slighty greater diameters to be used. In addition, the moving means 42 can be arranged to accommodate a variety of bundles containing different numbers of bristles which, in turn, may be of varying diameters. The bristle material may also, of course, differ from seal to seal.

An additional step in the above described manufacturing technique is, where metal bristles are used in, for example, gas-tight seals and where a holder in the form of a pair of rings is employed, to weld together the bristles clamped in the seal holder and the two halves of the holder itself. This may be done while the seal is still attached to the rest of the apparatus and after rotation of clamping rings 36 and/or bundle 12 has been performed and the two halves of the holder have been brought tightly together. Alternatively, welding can be carried out after separation of the seal from the residual bristles, provided the bristles are reliably clamped in the holder.

In a further embodiment of the invention the circular spreader plate 16, conical or approximately conical protrusion 18 and cylindrical bundle 12 are replaced by corresponding items which are non-circular/non-conical, etc, or partially circulaconical, etc. This is shown in Figure 9 which is a modified version of the plan view of Figure 2. Here the spreader plate 160 and holder 200 are semicircular, the protrusion 180 is half of an approximate cone and the bundle (not shown) is half a cylinder with the tube, where such is used, situated roughly centrally in the bundle. This arrangement is suitable for the manufacture of semicircular brush seals, or seals of some other part-circular or irregular form.

A final variant of the present invention allows the production of seals which, while perhaps circular or particular in one elevation, do not lie in one plane in another elevation.

An example is shown in Figure 10, where a seal which is circular in a front elevation (Figure 10(a)) is irregularly shaped in a side elevation (Figure 10(b)). Such a seal could conceivably be required by virtue of the design of the surface to be sealed. The present invention can easily cater for such an irregular configuration by simply allowing the spreader plate 16 itself to follow a surface contour matching the required irregularity. In the case of the Figure 10 seal the plate would have the shape shown in Figure 11, the plan view thereof (not shown) being circular.

Where seals having bristles oriented at 450 or some other angle are made, the manufacturing apparatus will include means for rotating either the clamping rings 36 or the bundle 12 or both In the forrner case the rings may be disposed on a turntable arrangement driven by, for example, an electric motor, and in the latter case the arm 46 (see Figure 7(a)) may include some form of geared drive serving to rotate that end of the arm which contacts the upper end-face of the bundle 12. This presup- loses that the bundle is secured to the arm 46 instead of being merely moved along the tube - ) by means of it, and indeed this may be preferred whether the bundle is rotated or not.

It should be noted that the form of moving means 42 illustrated in Figure 7 is exemplary only and movement of the bundle towards the protrusion 18 may take place by any other suitable means.

Claims (19)

1. A method of manufacturing a brush seal having a plurality of bristle elements, comprising the steps of: (a) forming a bundle of said bristle elements; (b) bringing said bundle into contact with a surface such as to cause said bristle elements to splay out against said surface; (c) clamping said bristle elements at a splayed-out point thereof, and (d) cutting said bristle elements at a given distance from said clamping point.

2. Method as claimed in Claim 1, wherein step (c) is performed using opposing halves of a bristleelement holder, said holder halves being brought to bear against said bristle elements from opposite sides thereof.

3. Method as claimed in Claim 1, wherein step (c) comprises the steps of: (c') temporarily clamping using temporary clamping means said splayed-out bristle elements proximate a splayed-out end-portion thereof; (c") permanently clamping said splayed-out bristle elements between opposing halves of a bristleelement holder at a point intermediate said end-portion and a point of action of said bundle on said surface, said temporary clamping operation being subsequently terminated.

4. Method as claimed in Claim 3, wherein a part of said surface is substantially flat and said bundle in step (a) is brought into contact with said surface along an axis substantially normal to said substantially flat part of said surface, and wherein subsequent to step (c') and prior to step (c") a relative rotation of said temporarily clamping means and said bundle about said axis is effected, an angle of said rotation determining an angle of orientation of said bristle elements in said holder following said step (c").

5. Method as claimed in Claim 4, wherein in step (d) the bristle elements clamped in said holder are cut at a radially outer point relative to said housing thereby to form an external brush seal.

6. Method as claimed in Claim 4, wherein in step (d) the bristle elements clamped in said holder are cut at a radially inner point relative to said housing thereby to form an internal brush seal.

7. Apparatus for the manufacture of a brush seal, which seal comprises a plurality of bristle elements and a bristleelement holder in which said bristle elements are secured, the apparatus comprising a bristleelement moving means and a bristleelement splay-out means, said bristle-element moving means being adapted to move a bundle of said bristle elements along a longitudinal axis towards said bristleelement splay-out means thereby to effect splaying-out of said bristle elements, said apparatus comprising also a bristleelement clamping means for clamping said bristle elements at a splayed-out point thereof, and a bristleelement cutting means for cutting said clamped bristle elements at a given distance from the clamping point

8. Apparatus as claimed in Claim 7, wherein said bristle-element splay-out means comprises a surface having a portion substantially normal to said longitudinal axis and a raised portion which, in use, is brought into engagement with an end of said bundle such as to initiate splaying-out of said bristle elements.

9. Apparatus as claimed in Claim 8, wherein said substantially normal surface portion is annular and said raised poruon is approximately conical in form and disposed at a centre of said annular portion, said apparatus being suitable for the manufacture of a circular brush seal.

10. Apparatus as claimed in Claim 8, wherein said substantially normal surface portion has the form of an incomplete annulus and said raised portion has the form of a correspondingly incomplete approximate cone, said apparatus being suitable for the manufacture of a part-circular brush seal.

11. Apparatus as claimed in Claim 9 or Claim 10, comprising a clamping ring for temporarily clamping splayed-out end-portions of said bristle elements.

12. Apparatus as claimed in Claim 11, comprising rotation means for effecting relative rotation of said clamping ring and said bundle, thereby to set said bristle elements in said holder at an angle to aradial direction of said bristle elements relative to said longitudinal axis.

13. Apparatus as claimed in any one of Claims 9 to 12, comprising a cylindrical member extensive along said longitudinal axis at a centre of said bundle, said cylindrical member in use coming into contact with an apex of said approximately conical, or incomplete approximately conical, raised portion.

14. Apparatus as claimed in Claim 13, wherein said cylindrical member is hollow at an end thereof which, in use, comes into contact with said apex, an internal diameter of said hollow end being greater than a diameter of said apex.

15. Apparatus as claimed in Claim 14, wherein said bristle-element moving means comprises a means for moving said bundle and said tube towards said approximately conical, or incomplete approximately conical, portion until said apex engages with said hollow end, and for thereafter continuing movement of said bristle elements only towards said annular or part-annular surface.

16. Apparatus as clamped in any one of Claims 13 to 15, comprising means for disposing said bristle elements around said tube to form said bundle.

17. Apparatus as claimed in any one of Claims 8 to 16, wherein said substantially normal surface portion is a flat surface portion.

18. Method of manufacturing a brush seal substantially as hereinbefore described with reference to Figures 1, 2, 3, 4, 5, 6, 7, 8 or 9 of the drawings.

19. Apparatus for the manufacture of a brush seal substantially as shown in, and/or as hereinbefore described with reference to, Figures 1, 2, 3, 4, 5, 6, 7, 8 or 9 of the drawings.