GB2350808A

GB2350808A - Chuck dog with randomly distributed protrusions to engage workpiece

Info

Publication number: GB2350808A
Application number: GB9913306A
Authority: GB
Inventors: Fred Ransome
Original assignee: David Brown Hydraulics Ltd
Current assignee: David Brown Hydraulics Ltd
Priority date: 1999-06-09
Filing date: 1999-06-09
Publication date: 2000-12-13
Also published as: GB9913306D0

Abstract

A turning device comprises means 50 for transferring rotational movement from a driving chuck 44 to a workpiece 20, the means 50 comprising a plurality of randomly arranged protrusions 42 on a face 40 of the means 50 which engage with a face of the workpiece 20. The means 50 may be integrally formed with the chuck 44 or may comprise a collar attached thereto. The protrusions 42 may be spread evenly across the whole of the face 40 or may be arranged as a plurality of sub-faces 70. The protrusions 42 may be a granular material with an average particle size in the range of 30 to 50 microns and may be formed from synthetic diamond, borozon, aluminium oxide or chilled iron. The protrusions 42 may be applied to the face 40. If the means 50 comprises a collar attached to the chuck 44 it may be a conical collar. The face 40 is preferably substantially perpendicular to the axis of rotation 10.

Description

2350808 A TURNING APPARATUS AND METHOD

Field of the Invention

The present invention relates to a turning apparatus and method such as a lathe, and in particular to means for transferring rotational movement of a driving chuck in such a turning apparatus to an article to be turned.

Background to the Invention

A turning apparatus, typically a lathe, is an apparatus for producing articles or pieces, for example cylindrical, flat or tapered articles or pieces. Conventionally, articles are turned on a lathe to a specified shape by rotating the article about a central is axis at high speed and bringing a cutting implement up to the rotating article to cut it. Typically, rotation is applied to the article by a driving chuck which rotates about a central longitudinal axis, the article to be turned being located with respect to the driving chuck also along the central longitudinal axis. For example, prior to turning, the article is clamped in position along the axis between a driving chuck and a corresponding support clamp. It is important that the piece is accurately located on the longitudinal axis.

One way of achieving this is a pointed locating spigot positioned centrally on the driving chuck and the cooperating clamp to engage corresponding recesses in the piece to be turned.

Alternatively, a service piece may be provided at one end of the article to be turned. Typically, it is cast as 2 part of the article to be turned. The service piece can be clamped to the turning apparatus, for example to the chuck, to locate the article ready for turning. Af ter the article has been turned, the service piece is then removed to provide a finished product or a product ready for a next processing stage.

The use of service pieces is undesirable because of the extra step of removing these at the end of turning and also the difficulties in ensuring that rotation occurs, albeit within a certain tolerance, as accurately as possible about the central longitudinal axis of the lathe.

A preferred conventional method is one in which the article to be turned engages with the driving chuck of the turning apparatus directly. This method is known as "face-driving". Face-driving comprises the use of one or more metal knives arranged in a predetermined pattern about and protruding from a face rotating with the driving chuck for engaging a face of the article. Face driving can be used in conjunction with a pointed locating spigot on the chuck which locates the piece to be turned along the central axis of the driving chuck.

Although the use of knives is sufficient to rotate most metal articles, and indeed other materials such as plastic and wood, it can be problematic to turn articles made from hard metals e.g. those metals of a hardness of 60Rc such as case-hardened or through-hardened steel. This is because the knives are not capable of digging 3 into the article sufficiently, if at all, to rotate the article. This can cause the article to rotate untrue, that is, not to rotate along the central axis of the driving chuck, or not to rotate at all. This results in the non-uniform turning of the article, and an increase in defect pieces unfit for their specified purpose.

It is, therefore, an object of the present invention to alleviate the problems described above.

Suimary of the Invention Accordingly, the invention provides a turning apparatus comprising a driving chuck rotatable about a central axis; means for locating an article to be turned with respect to the driving chuck, the article being substantially aligned along said axis; and in which means for transferring rotational movement from the driving chuck to the article are provided comprising a randomly arranged multiplicity of protrusions on a face rotating with the driving chuck for engaging a face of the article.

In a second aspect of the invention, there is provided a method of turning an article comprising transferring rotation from a driving chuck to an article to be turned by engaging a randomly arranged multiplicity of protrusions on a face rotating with the driving chuck with a face of the article.

In yet a third aspect of the invention, there is provided a collar for a turning apparatus comprising a randomly 4 arranged multiplicity of protrusions on a face at the end of the collar for transferring rotational movement from a driving chuck to an article by engaging with a face of the article.

Preferably, the protrusions form point contacts with the article. The protrusions may be evenly distributed over a fraction or the whole of the face.

Preferably, the protrusions cover the whole of the face. The face may comprise a plurality of sub-faces, each subface comprising protrusions. The sub-faces may be arranged substantially symmetrically on the face about the central axis.

is Preferably, the protrusions comprise granular material. The granules may be of a size in the range of 30 to 50tM. The protrusions may comprise synthetic diamond, borozon, aluminium oxide or chilled iron. The protrusions on the face may comprise a material that is harder than the material of the article.

Preferably, the protrusions are applied to the face. The protrusions, typically in the form of grains, may be situated on the face in a single layer. Preferably, the protrusions are packed as tightly as possible. Preferably the shape of the protrusions, typically grains, is irregular.

Preferably, the protrusions are coated on the face. The protrusions may be spray coated onto the face.

Preferably, the protrusions are embedded in a layer of nickel.

Preferably, the plane of the face is substantially perpendicular to the central axis of the driving chuck. The plane of the face may be perpendicular to said central axis of the driving chuck within +/- 1.0'. Preferably, the plane of the face may be perpendicular to said central axis of the driving chuck +/ 0.1' or even +/o. OS 0.

Preferably, the face is located on a collar provided mounted on or integral with the driving chuck. The face is may be located at an end face of the collar.

Preferably, the turning apparatus or collar comprises a first member on one of the driving chuck or the collar arranged to engage with a corresponding second member on the other of the driving chuck or the collar whereby rotation is transferred from the chuck to the collar when the chuck rotates. Preferably, a pointed locating spigot is provided on one of the driving chuck or the collar arranged to engage with a corresponding recess on the other of the driving chuck or the collar.

Preferably, the collar is substantially conical.

Preferably, the plane of the face is substantially parallel to the rear face of the collar.

6 Brief Description of the Drawings

The invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 is a cutaway side view of a turning apparatus according to the invention engaging a piece to be turned; and Figure 2a is a cutaway side view of a collar, and Figures 2b-e are front views of varying faces of the collar for engaging a face of an article according to the invention.

Detailed Description of the Drawings

Referring now to both Figures 1 and 2, a driving chuck 2 of a turning apparatus 100 rotates about a central longitudinal axis 10. An article 20 to be turned is located with respect to the driving chuck 2 along the central longitudinal axis 10 ready for turning, as indicated by the arrow in Figure 1. Typically, article is clamped between driving chuck 2 and a clamp also located on axis 10 (not shown). A cone-shaped locating spigot 4 is provided on the driving chuck 2 to locate the article 20 by engaging with a corresponding recess 62 opposing face 60 of article 20. Article 20 to be turned is rotated at high speed, typically at 300 m/min, and a cutting implement 30 is brought up to the rotating article 20 to cut it, as indicated by the arrow in figure 1.

Rotational movement is transferred from the driving chuck 7 2 to the article 20 by a randomly arranged multiplicity of protrusions 42 on a face 40 rotating with the driving chuck 2 that engages a face 60 of the piece 20.

The protrusions 42 can be randomly arranged to cover the whole of the face 40, as illustrated in Figure 2b. A variety of facial arrangements is possible. For example, the protrusions can also be randomly arranged to cover a fraction, or sub-face 70, of the face 40, as illustrated in Figure 2c. A plurality of sub-faces 70 can be arranged substantially symmetrically on the face 40 about the central axis 10, as shown in Figure 2d. Likewise, a plurality of discrete faces 40 can be arranged about the central axis, as shown in Figure 2e. A symmetrical arrangement of sub-faces 70 or indeed of face 40 about the central axis 10 is advantageous in that torque is symmetrically distributed about the central axis.

Indeed, if the protrusions are substantially evenly distributed, the torque is also substantially equal on opposite sides of the central axis. This reduces stresses at the face 40-face 60 interface, which could result in nonuniform rotation of article 20 about central axis AA1.

Whilst it is preferred if face 40 is arranged so that all parts of the face with the protrusions 42 are equidistant from central axis AA1, this is less important than ensuring that face 40 is perpendicular to central axis AA1. The plane of the face 40 or sub-faces 70 is substantially perpendicular to the central axis of the driving chuck 2 within a tolerance of +/- 1.0', and 8 preferably in use within a tolerance of +/0.10 and also preferably in use within a tolerance of 0.05'. The tolerances described allow article 20 to be accurately located on the longitudinal axis 10 using locating spigots 4 and 4a positioned centrally on the driving chuck 2 to engage a corresponding recess in the article 20 to be turned, the article 20 being turned substantially about the central longitudinal axis 10 of the lathe.

The protrusions 42 on face 40 could be distributed in several ways. For example, the protrusions 42 can be spatially separated so that each protrusion is either not in contact with neighbouring protrusions, or in contact is with only a f ew. Alternatively, the protrusions may be closely packed so that each is in contact with a number of neighbouring protrusions or even completely surrounded. A preferred arrangement is one in which the protrusions are packed as tightly as possible in a single layer.

The protrusions comprise one or more granular materials. Reference to a relative term such as granular material means a material comprising particles or grains, typically, but not necessarily, having an irregular shape. Typically, the particles have a grain size of around 30 to 5Ogm. In a preferred embodiment, the grains are approximately equidimensional. Thus, most of the grains are able to contact the article to be turned and so contribute to the transfer of rotating force from the driving chuck to the article. The protrusions may be 9 made from a material that is harder than the material of the piece to be turned. Examples of suitable material for the protrusions include synthetic diamond, borozon, aluminium oxide and chilled iron. The apparatus 100 according to the invention is particularly suited, therefore, to hard- turning, that is, to the turning of articles made from materials having a hardness of around or greater than 700 Vickers. Such materials include case-hardened and throughhardened steels. Conversely, the apparatus 100 is also suitable for turning less hard articles such as wooden and plastic articles.

The protrusions of the present invention can be applied to the face by methods such as dipping, coating and spray-coating to provide an even and/or uneven distribution of randomly arranged protrusions 42. It can be also envisaged that the protrusions can be built into the face 40 by pre-lining a mould for casting the face 40 with protrusions 42, so that when the face 40 is cast, the protrusions 42 are cast within the face 40. Indeed, a plurality of randomly located recesses in the mould which fill with molten metal during casting can also be envisaged so that the protrusions are cast with the face 40. In one embodiment of the invention, a layer of nickel is applied to the face. The protrusions are situated on the face typically embedded in the layer of nickel. The protrusions are typically fixed firmly in the layer of nickel. Whilst it can envisaged that the protrusions can be embedded in the layer of nickel prior to the application of the layer of nickel to the face, the protrusions could also be embedded in the layer of nickel after the layer of nickel has been applied to the f ace.

The protrusions 42 can be provided on a face of the driving chuck for engaging the face 60 of the article 20.

However, the protrusions 42 can be provided at an end face 40 of a collar 50 mounted on the driving chuck 2 of a turning apparatus 100. The plane of face 40 is parallel to the rear face 52 of the collar 50 typically within a determined range, ensuring that rotation occurs about the central longitudinal axis of the lathe within the necessary tolerances for the turning operation as previously described.

is Rotational movement is transferred from driving chuck 2 to the collar 50 by a peg 22 or the like on the driving chuck 2 that engages with a corresponding recess 44 in the collar. Alternatively or in addition a similar peg 22 may be provided on the collar 50 and a recess 44 in the driving chuck 2. The collar 50 is thus mounted on the driving chuck 2 as a sliding fit and is detachable from the driving chuck 2 by sliding the collar 50 from the driving chuck 2. Advantageously, a detachable collar allows for quick and easy repair of defect collars, as well as re-application of protrusions to the face of the collar. Whilst the collar 50 is detachable from the driving chuck 2, the collar 50 may be dispensed with altogether or may be integral with the driving chuck 2.

The collar 50 is substantially conical and continuous about the driving chuck 2, however it can be envisaged that the collar may be of any size or shape so as to transfer rotational movement from the driving chuck 2 to the article 20 by the provision of protrusions 42 randomly arranged on the end face of the collar 50 for engaging a face of the article 20. For example, the collar may comprise a plurality of arms, each arm having protrusions 42 on its end face for engaging a face 60 of an article 20. For example, in Figure 2e, sub-faces 70 may be end faces of such arms. Such arms may be connected together about axis AA1 either to form a collar or on driving chuck 2.

The use of randomly arranged protrusions 42 on a face 40 rotating with the driving chuck 2 provides a large number of contact points for engaging a face 40 of the article 20. Each contact point acts over a smaller area than, say, the blade of a knife providing a greater pressure driving the protrusions into the piece for a given force than, say, with knives.

Face 40 can be easily and quickly replenished with protrusions 42 by, say, coating as compared to knives which need to be embedded into the driving face to an appropriate depth in an appropriate arrangement. Indeed, the pressure which causes protrusions 42 of the invention to engage article 20 also causes protrusions 42 to engage face 40 more securely. Therefore protrusions 42 even when newly coated on face 40 run little risk of becoming detached.

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Claims

Claims:

1. A turning apparatus comprising:

a driving chuck rotatable about a central axis; means for locating a piece to be turned with respect to the driving chuck, the piece being aligned substantially along said axis; and in which means for transferring rotational movement from the driving chuck to the piece are provided comprising a randomly arranged multiplicity of protrusions on a face rotating with the driving chuck for engaging a face of the piece.

2. A method of turning a piece comprising:

transferring rotation from a driving chuck to a piece to be turned by engaging a randomly arranged multiplicity of protrusions on a face rotating with the driving chuck with a face of the piece.

3. A collar for a turning apparatus comprising a randomly arranged multiplicity of protrusions on a face at the end of the collar for transferring rotational movement from a driving chuck to a piece by engaging with a face of the piece.

4. An apparatus, method or collar according to claims 1,2 or 3 in which the protrusions form point contacts with the article.

5. An apparatus, method or collar according to any preceding claim in which the protrusions are evenly 13 distributed over a fraction or the whole of the face.

6. An apparatus, method or collar according to any preceding claim in which the protrusions cover the whole 5 of the face.

7. An apparatus, method or collar according to any preceding claim in which the face comprises a plurality of sub-faces, each sub-face comprising protrusions.

8. An apparatus method or collar according to claim 7 in which the subfaces are arranged substantially symmetrically on the face about the central axis.

9. An apparatus, method or collar according to any preceding claim in which the protrusions comprise granular material.

10. An apparatus, method or collar according to claim 9 in which grains or particles of the granular material are of a size in the range of 30 to 50 gm.

11. An apparatus, method or collar according to any preceding claim in which the protrusions comprise synthetic diamond, borozon, aluminium oxide or chilled iron.

12. An apparatus, method or collar according to any preceding claim, in combination with a piece to be turned in which the protrusions on the face comprise a material that is harder than the material of the piece.

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13. An apparatus, method or collar according to any preceding claim in which the protrusions are applied to the face.

14. An apparatus, method or collar according to any preceding claim in which the protrusions are situated on the face in a single layer.

15. An apparatus, method or collar according to any preceding claim in which the protrusions are closely packed.

16. As apparatus, method or collar according to claim 15 in which the protrusions are packed as tightly as possible.

17. An apparatus, method or collar according to any preceding claim in which the protrusions are coated on the face.

18. An apparatus, method or collar according to claim 17 in which the protrusions are spray coated onto the face.

19. An apparatus, method or collar according to any preceding claim in which the protrusions are embedded in a layer of nickel.

20. An apparatus, method or collar according to any preceding claim in which the plane of the face is substantially perpendicular to the central axis of the driving chuck.

21. An apparatus, method or collar according to any preceding claim in which the plane of the face is perpendicular to said central axis of the driving chuck within +/- 1.0' or +/- 0.10 or +/- 0.050.

22. An apparatus or method according to any preceding claim in which the face is located on a collar provided mounted on or integral with the driving chuck.

23. A apparatus or method according to claim 21 or collar according to any preceding claim in which the face is located at an end face of the collar.

is

24. A turning apparatus or collar according to claim 22 or 23 comprising a first member on one of the driving chuck or the collar arranged to engage with a corresponding second member on the other of the driving chuck or the collar whereby rotation is transferred from the chuck to the collar when the chuck rotates.

25. An apparatus, method or collar according to claim 24 in which a protrusion is provided on one of the driving chuck or the collar arranged to engage with a corresponding recess on the other of the driving chuck or the collar.

26. An apparatus, method or collar according to any preceding claim in which the collar is substantially conical.

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27. An apparatus, method or collar according to any preceding claim in which the plane of the face is substantially parallel to the rear face of the collar.

28. A hard-turning apparatus substantially as described herein with reference to and/or as illustrated in Figures 1 to 2 of the accompanying diagrams.

29. A method of turning a piece substantially as described herein with reference to and/or as illustrated in Figures 1 to 2 of the accompanying diagrams.

30. A collar substantially as described herein with reference to and/or as illustrated in Figures 1 to 2 of the accompanying diagrams.