GB2253800A

GB2253800A - Manufacturing brush seals

Info

Publication number: GB2253800A
Application number: GB9210819A
Authority: GB
Inventors: Stuart Apsley Bridges
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 1988-04-05
Filing date: 1992-05-21
Publication date: 1992-09-23
Also published as: GB9210819D0

Abstract

This invention provides an apparatus for and method of manufacturing a brush seal. The apparatus comprises an annular former 22 having a radially outer 24 and a radially inner 30 portion radially separated from each other by an amount G and held relative to each other by locating means 32, and further includes a travelling wire electro discharge machining device and a guide tube. A brush seal is wound onto the former in the usual manner and the filament material 38 cut in the region of the gap G by the travelling wire 44. The wire is inserted between the filaments by first inserting a tube 52 therebetween and passing the wire 44 therethrough. Machining of the filament material is achieved by traversing the wire around the gap G. <IMAGE>

Description

APPARATUS FOR AND METHOD OF MANUFACTURING BRUSH SEALS This invention relates to an apparatus for, and method of, manufacturing brush seals. it relates particularly, but not exclusively, to brush seals produced by the winding technioue.

Brush seals are already well known per-se and are therefore not described in detail herein. Briefly, however, they comprise a pair of generally annular sideplates and a plurality of closely packed metallic bristles. The bristles are sandwiched between the sideplates and extend radially therefrom. The free ends of the bristles act against a relatively rotating component to effect a seal.

The production of brush -seals bo-winding is already well knows and is described in detail in UK Patent No. 200140DB. Briefly, however, the process involves winding a filament of wire onto an annular former having two seal sideplates incorporated therein and sandwiching the wire between 2 second pair of sideplates. Each of the two sideplates on either side of the former are then integrally joined to the wire situated therebetween hv for example welding or brazing. The otherwise free ends of the wire is then cut away from the former to allow the two seals to be separated therefrom. Final finishing of the wire, or rather bristle, may be achieved b' grinding.

One well known method of grinding makes use of a centreless grinding technique. This method is time consuming, expensive and lacks accuracy. Furtller to this, it has been found that the bristle elements bend away from the grinding -.?heel and make accurate machining difficult.

It is an object of the present invention to reduce and possibly eliminate the disadvantages of the above mentioned method of manufacture by providing an apparatus for and method of manufacture brush seals which makes use of the advantages of electro discharge machining, is simple, accurate and which lends itself to both automation and batch processing.

The present invention will now be described by way of example only with reference to the accoranying drawings, in which: Figure 1 is a cross sectional view of a brush seal, Figure 2 is a general view of a portion of an annular former onto which the -brlstle elements of the brush seal are wound, Figure 3 is a cross sectional view of the annular former shown in Figure 2 having bristle elements wound thereon and an ED wire cutting apparatus inserted therein, and Figure 4 is an expended view of part of the cutting apparatus.

Referring to Figure 1, a brush seal 10 generally comprises one long and one short annular sideplate 1?,14 and a plurality of bristle elements 16 which are sandwiched therebetween and which extend generally radially therefrom. The bristles shown extend generally radially inwards and their free ends iS act against a rotating component such ar for ex2r,ple a shaft 20 to effect a seal therebetween.

Turning now to Figure 2, the annular former of the present invention 22 comprises a first radially outer portion 24, having a pair of annular sideplates 12 situated in recesses 26,28 provided on either side thereof and a second inner portion 30. The second inner portion 30 is spaced radially from the outer portion 24 by a predetermined amount G, and held relative thereto by a plurality of pins 32 which locate in holes 34,36 provided in both portions 24,30.

A filament of bristle material 38 is wound onto the annular former 22 in the conventional manner. It will, however, be appreciated that the filament 38 will lie oaTer the gap G on both sides of the former 22 as shown in figure 3. The outer annular sideplates 14 are then applied to the outer surface of the wound filament adjacent their associated sideplates 12. The joining operation is then performed by for example welding the two pairs of sideplates 12,14 to each other and the bristle material 38 sandwiched therebetween and any surplus material removed bv for example grinding.

Prior to machining the internal diameter of the brush seal 10, the outer 24 and if necessary the inner 30 portions of the former are supported in fixtures 40 and 42 respectivel > r. The cutting wire 44 from a travelling wire electro discharge machining apparatus 46 is passed between the layers of the bristle material 38 in the region of the gap G and connected for operation to the apparatus /6 via machining heads 48,50 respectively.In order to facilitate the passing of the wire 44 through the mass of bristle material 38 it may he necessary to employ a tube 52 which is inserted between the bristle material prior to passing the wire 44 theYethrouGh. Preferably, the tube is provided with a chamfered end 54 (best seen in Figure 4) and a slot 56 along its length L. The chamfered end aids the passage thereof through the bristle material 38, whilst the slot 56 provides an outlet for the wire & during machining or allows the tube 52 te be removed prior to machining The filament material 38 is cut to size by passing a machining current through the cutting wire 44 and moving it in a circle along the gap G. It will be appreciated that the wire will cut though the filament material as it is so traversed together with any locating pins 32. It will be further appreciated that an accurate circular form may be machined by for example rotating the support means 40,42 and hence the seal 10 about a central axis of rotation R. Once all the filament material has been cut, the wire 44 may be removed and the two finished seals separated from the former 22.

It will be appreciated that the effect of the inner portion 3Q is to locate the ends of the filaments of bristle material 38 not sandwiched between the sideplates 1,14 (the otherwise free ends) in order to facIlitate the machining operation. It will be further appreciated that the above mentioned method of machining may be used on brush seals 10 not produced by a winding technique 1r the otherwise free ends of said seals 10 are similarly constraIned by a locating means and a similar gap C provided between the annular sideplates 12,14 of said seal 10 and said locating means. Machining of the bristle elements 18 in the region cf the gap mar he achieved in the same manner as described above.

It will be still further appreciated that both the above described methods may be adopted for batch processing by stacking a number of seals 10 on top of each other such that the gaps G are in line with each other and bv using the same cutting wire 44 to cut through all the bristle filaments 38 in the region of all the gaps in one operation.

Claims

1 An apparatus for manufacturing a brush seal including a pair of sideplates having a plurality of filaments of bristle material sandwiched therebetween and projecting therefrom, the apparatus comprising: (a) support means for supporting at least one pair of sideplates with the filaments projecting radially therefrom; (b) a travelling wire electro discharge machining apparatus having a machining wire for cutting the filaments; and (c) moving means for moving at least one of the support means and machining wire relative to the other for cutting the filaments.

2 An apparatus as claimed in claim 1 wherein a plurality of pairs of sideplates are supported on a stack in the support means, and the machining wire cuts the filaments in the stack of sideplates.

3 An apparatus as claimed in claim 1 or 2 wherein the sideplates are annular, and one of the support means and the machining wire moves circularly relative to the other.

4 An apparatus as claimed in any preceding claim further comprising locating means for constraining free ends of the filaments, and the machining wire is located in a gap between the sideplates and the locating means.

5 An apparatus as claimed in any preceding claim wherein the moving means moves the machining wire relative to the support means.

pair of sideplates having a plurality of filaments of bristle material sandwiched therebetween and projecting therefrom, the method comprising the steps of: (a) supporting at least one pair of sideplates with the filaments projecting radially therefrom; and (b) moving at least one pair of sideplates and a machining wire of a travelling wire electro discharge machining apparatus relative to the other to cut the filaments.

7 A method as claimed in claim 6 wherein the step of supporting includes the step of stacking a plurality of pairs of sideplates for simultaneously cutting the filaments in the stack of sideplates.

8 A method as claimed in claim 6 or 7 wherein the sideplates are annular and one of the sideplates and the machining wire moves circularly relative to the other.

9 A method as claimed in any one of claims 6 to 8 further comprising the steps of constraining free ends of the filaments by a locating mechanism spaced from the sideplates by a gap, and locating the machining wire in the gap.

10 A method as claimed in any one of claims 6 to 9 wherein the machining wire is moved.

11 An apparatus for manufacturing a brush seal of the type which comprises a pair of annular sideplates having a plurality of filaments of bristle material 38 sandwiched therebetween and projecting radially therefrom, the apparatus comprising a means for locating the otherwise free ends of the bristle material which is spaced from the annular sideplates by a predetermined amount, thereby to define a gap.

12 An apparatus for manufacturing a brush seal of the type which comprise a pair of annular sideplates having a plurality of filaments of bristle material sandwiched therebetween and projecting radially therefrom and which is produced by winding onto an annular former, the apparatus comprising an annular former having a first radially outer portion having a recess formed on either side thereof for the receival of a pair of annular sideplates, and a second inner portion spaced radially from the outer portion by a predetermined amount, thereby to define a gap, and held relative thereto by locating means.

13 An apparatus according to claim 12 in which there is further provided a means for cutting the filament material in the region of the gap.

14 An apparatus according to claim 13 in which the means comprises a travelling wire electro discharge machining apparatus having the machining wire inserted through the filament material in the region of the gap.

15 An apparatus according to either claim 13 or claim 14 in which there is provided a means for enabling the machining wire to be passed through the filament material which comprises a tube.

16 An apparatus according to claim 15 in which the tube is provided with a slot along its length and a chamfered end.

17 An apparatus according to any one of claims 11 to 16 in which the locating means comprises a plurality of locating pins which locate in holes provided in the outer and inner portions of the annular former.

18 An apparatus substantially as herein described with reference to Figures 1 to 4 of the accompanying drawings.

19 A method of manufacturing a brush seal of the type which comprises a pair of annular sideplates having a plurality of filaments of bristle material sandwiched therebetween, and which is produced by winding onto an annular former having a first radially outer portion having a recess formed on either side thereof for the receival of a pair of annular sideplates and a second inner portion spaced radially from the outer portion by a predetermined amount, thereby to define a gap, and held relative thereto by locating means, the method including the step of cutting the filaments of bristle material in the region of the gap, thereby to release the seal from the former.

20 A method as claimed in claim 19 in which the machining wire of a travelling wire electro discharged machining apparatus is used to cut the filaments of bristle material.

21 A method as claimed in claim 20 in which the machining wire is passed through the filaments of bristle material by first inserting a tube through said filaments and then passing said machining wire therethrough.

22 A method as claimed in claim 20 or claim 21 in which the machining wire cuts through the filaments of bristle material and the locating means as it is traversed around the gap.

23 A method as claimed in claim 22, in which the machining wire is traversed around the gap by rotating the seal about its axis of rotation.

24 A method substantially as herein described with reference to figures 1 to 4of the accompanying drawings.