GB2050215A

GB2050215A - Manufacture of articles of substantially annular cross-section

Info

Publication number: GB2050215A
Application number: GB7918729A
Authority: GB
Original assignee: Cross Manufacturing Co 1938 Ltd
Current assignee: Cross Manufacturing Co 1938 Ltd
Priority date: 1979-05-30
Filing date: 1979-05-30
Publication date: 1981-01-07
Also published as: FR2457738A1; FR2457738B1; IT8067849A0; JPS6339367B2; JPS55164430A; GB2050215B; DE3020578C2; DE3020578A1; IT1128786B; US4398078A

Description

1 GB2050215A 1

SPECIFICATION

Improvements in the manufacture of articles of substantially annular cross-section This invention relates to improvements in the manufacture of articles of substantially annular cross-section, for example, rings, cylinders and the like, and the invention relates in particular but not exclusively to the manufacture of annular seals such as brush seals. The term 'annular" as used herein is intended to extend to shapes bound by two similar concentric curviform figures, such as elipses, as well as truly circular shapes bound by two concentric circles. More particularly, the invention is concerned with an improved method of and means for rotating an annular article such as a seal, for the purpose of allowing the removal of material from either the internal diameter of the external diameter of the article, without the necessity of having to hold the article in a jig or chuck for rotation in a lathe, grinding machine or the like gener- ally according to widely known and used methods. The annular article may be a component required to have a substantially constant radial wall thickness, such as a seal adapted for insertion between a rotatable member and a housing therefor.

According to one aspect of this invention, there is provided a method of holding and rotating an annular article to allow the machining thereof to a substantially constant radial wall thickness, in which method the article is held by at least one pair of rollers the axes of which are substantially parallel, one of which rollers is spatially fixed and provides a reference surface engaging the inner or outer diameter of the articl6 to be machined, and the other of which rollers is biassed in a direction normal to its axis of rotation to engage the article and urge that article into engagement with the reference surface of the one roller, and power driving at least one of the rollers thereby to effect rotation of a held article about its axis. Machining - for example by grinding, turning or using an electro-discharge apparatus - may then be accomplished relative to the reference surface provided by the spatially fixed roller, to obtain an article of substantially constant radial wall thickness. The article may further be guided and supported by freely rotatable guide rollers suitably positioned around the article. Such further rollers are especially required should the article be in the form of a split annulus that is to say, having a radially-extending split or cut at some point on the periphery thereof, for example if the annulus is formecLfrom a length of material, such as wire, suitably shaped.

The method of this invention is particularly useful in the production of an annular article of circular cross-sectional shape, such as a brush seal as referred to in British Patent Specification No. 1450553 as well as in our co-pending British Patent Application No. 7917830 (Serial No 2021518), claiming the priority of our earlier pending British Patent Application No. 78-24737, filed 31st May, 1978. Brush seals of this type tend to have a relatively thin axial thickness and also a relatively thin radial wall thickness, and as a consequence it is difficult to maintain true circularity during the manufacture thereof, but provided that the seal is manufactured with a substantially constant wall thickness, the seal may then take up a true circular form when assembled in a housing, for sealing against a rotatable member. The member of this invention advantageously is used to produce the substantially constant radial wall thickness, in a finishing operation for the seal.

Using the invention, articles having walls of various sections can be produced. The walls may thus have grooves machined or otherwise formed therein, or may have a rectangular, square, circular or curved cross section; fur- ther possibilities include the production of walls with flanges projecting therefrom. Moreover, an article being held and rotated in accordance with this invention may itself have a true circular overall cross-sectional shape, or may have for example an eliptical overall cross-sectional shape.

According to another aspect of the invention, apparatus for holding and rotating an annular article comprises at least one pair of rollers the axes of which are substantially parallel, one of the rollers being spatially fixed to provide a reference surface for engaging the article and the other roller being mounted for movement in a direction normal to its axis of rotation and biased in such a direction for engaging the annular article and urging that article into engagement with the reference surface of the one roller, there being powerdrive means for at least one of the rollers to effect rotation of the held article about its axis, whereby the fixed roller provides a reference surface to which a machining operation may relate. Further guide rollers may be provided as required to assist the guiding and supporting of a held article, especially where the annulus is in the form of a split ring or the like.

The machining operation for removing material from an annular article held and rotated by the apparatus of this invention may be accomplished using any of a variety of known techniques - for example, by grinding, turning or using an electro-discharge machine.

By way of example only, two specific em- bodiments of apparatus of this invention and arranged to perform the article holding and rotating method also of this invention will now be described in detail, reference being made to the accompanying drawings in which:- Figure 1 shows the important parts of an 2 GB2050215A 2 electro-discharge machine, arranged to con form with this invention; Figure 2 shows a plan view through a centreless bore-grinding machine also ar ranged to conform with the method of this 70 invention; and Figure 3 shows a vertical section through the bore grinding machine of Fig. 2.

The invention will be described hereinafter with reference to the finishing of a brush seal such as is described in our co-pending Patent Application No. 79-, claiming the pri ority of our earlier Patent Application No.

78-24737, filed 31st May, 1978 Such brush seals are annular with a substantially circular cross-sectional shape, and are finished to a substantially constant radial wall thick ness by employing the method of this inven tion.

Referring now to Fig. 1, there is shown a centreless electro-discharge machine adapted for machining the metal bristles 10 of an annular brush seal 11 having one root plate 12 generally of Z-section, and another root plate 13 of generally flat shape, the bristles projecting inwardly of the seal. The seal 11 is supported between a fixed position driving roller 14 rotatably mounted on the machine frame 15, and a further driving roller 16 which is urged by means of a spring 17 towards the roller 14. Guide rollers 18 are disposed around a support plate 19 also mounted on the machine frame 15, to sup port and assist movement of the seal 11. The rollers 14 and 16 are both driven by a motor (not shown) through suitable gearing (also not shown) so as to effect rotation of the seal 11 about its axis. The machine includes an elec tro-discharge head 20 having a circular rota bable electrode 21, the head being appropri ately mounted on the machine frame for movement both vertically and parallel to the axis of rotation of the eictrode 21. A tank (not shown) surrounds the part of the machine where the discharge takes place, for curtain ing an appropriate dielectric liquid.

In operation, the brush seal 11 is rotated by driving the rollers 14 and 16, whilst the bristles are machined by the rotating electrode 21. As the seal rotates, the electrode 21 is caused to reciprocate about its own axis, whilst the spark gap automatically is servo controlled by vertical movement of the head.

It is preferred to position the general plane of the seal 11 at an angle to he horizontal - such as at 45', as shown - in order to help the servo-action of the cutting electrode in sensing the bore of the seal as the seal is rotated. Normally the cutting electrode will be immersed in a dielectric liquid, a suitable electrode being made, for example of carbon, copper or a copper alloy. The outer diameter of the seal may be machined in a generally similar manner, as may seals having root plates of shapes other than those shown in 130 tion.

Fig. 1.

Referring now to Figs. 2 and 3, there is shown-a vertical centreless bore grinding machine being used to finish the bristles of a seal 30 generally similar to seal 11 shown in Fig. 1. The seal is carried by three support rollers 31 (only one of which can be seen in Fig. 3), idler rollers 32 running on the periphery of the seal to hold it in the required position. A drive roller 33 is urged into engagement with the periphery of the seal, and is power-driven by means of a motor 34 operating through a suitable gear train 35. A control wheel 36 is rotatably mounted on a sub-frame 37 urged by a spring loading mechanism 38 towards the drive roller 33, the control wheel engaging an internal face of the seal root plate to urge the seal into engagement with the drive roller 33, so that the seal will be rotated about its axis on operation of the machine.

A grinding head 39 including a powerdriven grinding wheel 40 is mounted on the machine, for vertical movement relative to the supported seal 30. In operation, the seal is rotated by driving the roller 33 whilst the grinding wheel 40 is rotated and the grinding head 39 is reciprocated vertically. In this way, the internal bore can be ground accurately, so that the radial thickness of the seal is substan- tially constant.

Claims

1. A method of fipishing an annular article to provide a substantially constant radial wall thickness, which comprises holding the article between at least one pair of rotatable members, driving at least one of the rotatable members to cause the article to be rotated, and removing unwanted material from the article during rotation thereof by a machining device appropriately juxtaposed to the path of the rotating article, the axes of the said pair of rotatable members being substantially parallel and one of the members being spatially fixed and engaging the inner or outer circumference of the article, the other rotatable member being biassed in a direction normal to its axis of rotation to urge said other member towards the spatially fixed rotatable member and to engage the article, said spatially fixed rotatable member providing a reference surface to which the machining operation is related.

2. A method as claimed in claim 1, in which the article is additionally supported by freely rotatable guide rollers positioned about the periphery of the article during the machining thereof.

3. A method as claimed in either of the preceding claims, in which the article is sub- jected to a centreless bore grinding machining operation.

4. A method as claimed in claim 1 or in claim 2, in which the article is subjected to a centreless electro-discharge machining opera- 3 GB2050215A 3

5. A method as claimed in claim 4, in which an electro-discharge machine is used having an electro-discharge head provided with a substantially circular electrode rotatable about its own axis, the head being mounted on a frame for movement both substantially vertically and substantially parallel to the axis of rotation of the electrode, the electro-discharge head being actuated as the article is rotated.

6. A method as claimed in claim 5, in which the head is moved in a reciprocating manner along an axis parallel to the axis of rotation of the electrode as the machining progresses, and the electro-discharge spark gap is automatically servo- controlled by effecting substantially vertical movement of the head as appropriate during the machining operation.

7. A method as claimed in any of the preceding claims, in which the article is held for rotation with the axis thereof at an angle part-way between horizontal and vertical.

8. A method as claimed in any of the preceding claims, in which the finished article is a component for use as a seal between a rotatable element and a housing.

9. A method as claimed in claim 8, wherein the finished article forms a brush seal having a plurality of sealing bristles, the ma- 95 chining operation being performed on the bristles.

10. A method as claimed in any of the preceding claims, in which the said article is annular but with a generally radially extending split at the point on the periphery thereof.

11. A method of finishing an annular arti cle to a substantially constant wall thickness substantially as hereinbefore described with reference to the accompanying drawings.

12. Apparatus for removing material from the inner or outer circumference of an annular article comprising, in combination, means adapted to hold and to permit rotation of the article which means has at least one pair of rotatable members the axes of which are substantially parallel, one of the rotatable members being spatially fixed to provide a reference surface and the other having biass ing means to urge said other member in a direction normal to its axis of rotation gener ally towards the spatially fixed rotatable mem ber whereby the article, when placed between the rotatable members is held thereby, means to drive at least one of the rotatable members and machining means adapted and arranged with reference to the spatially fixed rotatable member for removal of material from the inner or outer circumference of the article when held and rotated by the pair of rotatable members.

13. Apparatus as claimed in claim 12, wherein there are provided freely rotatable rollers located to guide and support the annu lar article when held between the rotatable members.

14. Apparatus as claimed in claim 12 or claim 13, wherein the matching means is a centreless bore grinding machine.

15. Apparatus as claimed in claim 12 or claim 13, wherein the machining means is a centreless electro-discharge machine.

16. Apparatus as claimed in claim 15, wherein the electro-discharge machine has an electro-discharge head having a substantially circular electrode mounted for rotation about its own axis, the head being mounted on a frame for movement both generally vertically and generally parallel to the axis of rotation of the electrode.

17. Apparatus as claimed in claim 15, wherein there is provided servocontrol means automatically to control the vertical movement of the head thereby to control the spark gap between the article and the rotatable electrode, when in operation.

18. Apparatus as claimed in any of claims 12 to 17, wherein the pair of rotatable members is arranged to hold the annular article with the axis thereof at an angle part-way between horizontal and vertical.

19. Apparatus as claimed in any of claims 12 to 18, wherein the apparatus is adapted to machine an annular brush seal component for use as a seal between a rotatable element and a housing, the machining means being located and arranged to remove excess length from bristles of the brush seal.

20. Apparatus for removing material from the inner or outer circumference of an annular article substantially as hereinbefore described and with reference to and as illustrated in the accompanying drawings.

2 1. A brush seal whenever made by a method according to any of claims 1 to 11.

Printed for Her Majesty's Stationery Office by Burgess & Son (Abingdon) Ltd.-1 980Published at The Patent Office, 25 Southampton Buildings, London, WC2A 1AY, from which copies may be obtained.