GB2230726A

GB2230726A - Supporting rotatable work during machining

Info

Publication number: GB2230726A
Application number: GB9009086A
Authority: GB
Inventors: Roy Douglas Liggins
Original assignee: EMI MEC Ltd
Current assignee: EMI MEC Ltd
Priority date: 1989-04-22
Filing date: 1990-04-23
Publication date: 1990-10-31
Also published as: GB9009086D0; GB8909205D0

Abstract

A collet 16 grips and rotates a workpiece 18. A bush 20 supports the end of the workpiece 18 remote from the collet 16 and a tool 10 machines the workpiece. The tool 10 can be replaced by another tool sliding a saddle 28 away from the workpiece and bringing in another tool from the side of the saddle. The bush 20 remains in place whilst tools are being changed, and the bush is movable along the workpiece e.g. by engagement of the bush with an abutment 34 on the saddle 28 or by other means. <IMAGE>

Description

IMPROVEMENTS IN AND RELATING TO MACHINING WORKPIECES The present invention relates to machining apparatus and to a method of machining a workpiece and in particular, although not exclusively, to multiple-tool lathes and the like machines where several turning and boring operations can be effected sequentially on work stock.

Historically, such multiple-tool machines have been cam operated, combining relatively low machine costs and short and highly efficient work cycles. More recently there have been evolved machines operated with numerical control that provide highly accurate and flexible machining operations.

Thus, there are machines where a number of different tools are provided on an indexable turret, providing extreme accuracy and flexibility, but with the disadvantage in terms of work cycle consequent upon the time inevitably lost when the turret is withdrawn from the work stock and indexed to bring a second (or further) cutting tool into contact with the work stock.

As an alternative to machines with indexable turrets, there are platen-type machines, where a number of cutting tools are provided on a flat plate mounted on a crossslide to enable linear movement of the plate transversely to the axis of the work stock to bring a required tool into contact with the work stock. Such machines enjoy the benefit of lower costs than indexable turret machines, and in connection with components short in length in comparison with their diameter, have the advantage of minimising non-productive times during the work cycle consequent upon the rapidity that the flat plate can be subjected to a linear transverse movement to bring a second (or further) cutting tool into contact with the work stock.The disadvantage of known platen-type machines is the difficulty of accommodating the production of long slender parts, where a bush or other means needs to be provided to support the leading end of the work stock. With platen-type machines, such a bush cannot be fixed in relation to the work stock, and must be moved longitudinally with the platen. Consequently, retraction of the platen to enable a change of tool would cause the bush to pass over an already machined part of the work stock with the serious risk of ingress of swarf into the bush that could damage the work stock or the bush.

Consequently, there is a limit with such machines on the number of tools that can be provided for longitudinal turning. Only two such tools can be provided, one of which must serve as a parting tool.

An object of the present invention is to attempt to overcome the difficulties mentioned above in platen-type machines.

According to one aspect of the present invention, machining apparatus includes drive means arranged to rotate a workpiece, a support for a workpiece when rotated by the drive means, the support being spaced from the drive means, and a workpiece machining station located on the opposite side of the support to the drive means, the machining station being arranged to machine a workpiece rotated by the drive means, the support and the drive means being moveable relative to each other, and the machining station being moveable relative to the support.

The machining station may include a plurality of tools each of which may be moveable in an axial direction relative to the rotational axis of the drive means and in a direction transverse to the axial direction. The tools may be constrained to move simultaneously in the axial or transverse direction,. or simultaneously in both directions.

When at least one of the tools is being moved in an axial direction towards the drive means, a part of the machining station may be arranged to abut a part of the support in order to move the support towards the drive means during at least part of the movement of the tool in the axial direction. The abutment at the part of the machining station with the part of the support during axial movement of the machining station towards the drive means may be arranged to maintain a predetermined distance between the door and the support.

Alternatively or additionally separate moving means may be arranged to cause axial movement of the support either away from or towards the drive means or both.

Those moving means may comprise screw feed means, or hydraulic or pneumatic means.

The machining station and the support may be slidably mounted on a common guide extending parallel to the intended axis of rotation of the drive means.

Selectively operable connection means may be provided, such as latch means, which, when operated, enable relative axil movement of the machining station away from the drive means to cause relative axial movement of the support away from the drive means.

The support may comprise a support bush.

According to a further aspect of the present invention, a method of operating machining apparatus comprises rotating a workpiece with drive means, supporting the workpiece with a support at a location remote from the drive means, machining the workpiece on the opposite side of the support to the drive means with a tool, causing relative movement of the tool towards the drive means, causing relative movement of the support towards the drive means, and causing relative movement of the tool away from the drive means without causing simultaneous relative equal movement of the support away from the drive means.

The method may comprise the steps of rotating the workpiece, then machining the workpiece, then moving the tool relative to the drive means away from the drive means without causing relative equal movement of the support away from the drive means.

The method may comprise leaving the distance between the support and the drive means unaltered when the tool is moved relative to and away from the drive means.

The method may comprise simultaneously moving the support and the tool relative to the drive means towards the drive means during at least a part of that movement by the drive means, and the support may be caused to move by abutment with a portion of the tool.

The method may comprise using different tools to machine the workpiece. The method may comprise changing tools to machine the workpiece by moving a first tool which has partially machined the workpiece relative to and away from the drive means, and moving the first tool away form the axis of rotation, and moving a second tool towards the axis of rotation and relative to and towards the drive means.

The method may comprise removing an at least partially machined section of the workpiece and machining the remaining workpiece whilst the support remains between the portion of the workpiece being machined and the drive means.

The method may comprise subsequently moving the support relative to the drive means away from the drive means, which relative movement may be arranged to occur at the end of a particular machining operation on a workpiece.

The present invention also includes a method of operating machining apparatus when using such apparatus as herein referred to.

According to another aspect the present invention, a platen-type lathe or the like comprises a head stock with a collet to grip and rotate a projecting portion of work stock, a cross-slide mounted for longitudinal movement axially of the work stock, a tool-supporting plate mounted on the cross-slide for transverse movement in relation to the axis of the work stock, and a support bush located between the head stock and the cross-slide, said support bush being mounted for longitudinal movement axially of the work stock as the cross-slide is advanced towards the head stock, and such that it remains stationary when the cross-slide is retracted to permit transverse movement of the tool-supporting plate to effect a tool change.

A first benefit of the invention is that by avoiding a retraction of the bush as the cross-slide is retracted, there is the elimination of any possibility of swarf entering the bush, and any desired number of tools for longitudinal turning operations can be provided on the tool-support plate within the limitations of its length.

Whilst the primary intention of the invention is to permit the production of longer slender components in a platen-type machine, there is a second benefit to be enjoyed in terms of considerably reduced work cycles when relatively short components are to be produced. By providing a support bush for the leading end of the work stock, work stock of a length to produce a multiple number of short components can be advanced through the head stock collet and into the support bush. therefore, the machining operations for each short component can be completed with the support bush advancing with the crossslide, and remaining stationery as the cross-slide is withdrawn for a tool change, and the component parted from the work stock, followed by the machining of the next component, and so on.It will immediately be recognised that in contrast with conventional platen-type machines where the work stock is advanced by the length of the a single component and when the time required to open the head stock collet, advance the work stock, and close the collet, must be allotted to each component, with the invention, the lost time can be apportioned across the multiple number of components that can be produced, and when the work cycle attributed to each individual component is significantly reduced.

To enable movement of the support bush, seperate drive means can be provided to advance the support bush as the cross-slide is advanced and to hold the support bush stationary as the cross-slide is retracted to enable a tool change. Thus, a relatively simple screw feed means can be provided, but it will be understood that hydraulic or pneumatic drives can be employed. In a form of construction of noticeable simplicity the support bush can be mounted by bracket means on one or more slide bars, to be pushed by the cross-slide as it is advanced, and when the bush remains stationary when the cross-slide is retracted.

At the end of the work cycle for a single long, slender component, or the work cycles of a number of short components, the support bush must be withdrawn. When drive means are provided, a simple reversal of the drive is to be provided for, and when the support bush is slidably mounted, a latch means can be provided and activated at the end of the working cycle or cycles, to lock the support bush to the cross-slide, whereby it can be withdrawn with the cross-slide, and then unlatched ready for the commencement of the next working cycle.

The present invention may be carried into practice in various ways but one embodiment will now be described, by way of example and with reference to the accompanying schematic drawings in which: Figure 1 is inside view of the machine after a first tool 10, has completed a machining operation; Figure 2 is a view similar to Figure 1 after a second tool 12, has completed a machining operation, and Figure 3 is a view similar to Figure 1 after a third tool 14, has completed its operation on a workpiece.

The machine includes a head stock collet 16, which is arranged to grip and rotate an elongated workpiece 18. A support bush 20, is slidably mounted on a guide 22, such that it can move towards or away from the collet. The bush provides support for that end of the workpiece 18, remote from the collet.

The tools 10, 12 and 14 are each mounted on respective housings 24, which are themselves mounted on a platen 26. Platen 26 can be slid in a horizontal direction perpendicular to the direction of rotation of the workpiece, and the platen 26, is mounted on a saddle 28, which saddle is able to slide towards or away from the collet along the guide 22.

In use, the bush 20, supports the remote end of the rotating workpiece adjacent to that part of the workpiece which is to be machined by the first tool 10. The first tool 10 is brought in to contact with the workpiece and performs a machining operation either from the end face 30 of the workpiece or from the side 32 of the workpiece by suitable radial and axial movement of the tool achieved by the sliding of the saddle on the guide or the platen on the saddle.

Once the first tool 10, has finished its machining operation the platen 26, is then slid away from the axial extent of the workpiece by sliding the platen in a radial direction on the saddle, and the next tool 12, (as shown in Figure 2) is then brought in to axial alignment with the workpiece on its associated platen 26. In an alternative embodiment (not shown) a number of different tools may be mounted on a common platen. As the second tool 12, is advanced towards the collet 16, an abutment 34, on the saddle extending towards the collet just above the guide 22, abuts the support for the bush 20, and pushes the bush towards the collet. When the saddle is retracted, away from the collet, the bush remains in position and does not retract with the saddle. In an alternative embodiment (not shown) the bush may be advanced manually or by means other than the abutment 34, either at the same as the saddle is advanced, or before or af.ter that advancement. The alternative means of advancing the bush may comprise a screw drive means or hydraulic or pneumatic drive means. When the bush is required to be moved away from the collet, for instance when the piece or pieces have been machined and taken off the workpiece 18, the drive means can be reversed, or the support bush can be attached to the saddle by means (not shown) which enable the support bush to be withdrawn as the saddle is withdrawn.

Claims

1. Machining apparatus including drive means arranged to rotate a workpiece, a support for a workpiece rotated by the drive means, the support being spaced from the drive means, and a workpiece machining station located on the opposite side of the support to the drive means, the machining station being arranged to a machine a workpiece rotated by the drive means, the support and the drive means being moveable relative to each other, and the machining station being moveable relative to the support.

2. Apparatus as claimed in Claim 1 including a plurality of tools, each of which is moveable in an axial direction relative to the rotational axis at the drive means and in a direction transverse to the axial direction.

3. Apparatus as claimed in Claim 2 in which the tools are constrained to move simultaneously in the axial direction.

4. Apparatus as claimed in Claim 2 or Claim 3 in which the tools are constrained to move simultaneously in a direction transverse to the axial direction.

5. Apparatus as claimed in any preceding Claim in which, when a tool is being moved in an axial direction towards the drive means, a part of the machining station is arranged to abut a part of the support in order to move the support towards the drive means during at least part of the movement of the tool in the axial direction.

6. Apparatus as claimed in Claim 5 in which the abutment of the part of the machining station with the part of the support during axial movement of the machining station towards the drive means is arranged to maintain a predetermined distance between the tool and the support.

7. Apparatus as claimed in any preceding Claim including separate moving means arranged to cause axial movement of the support away from the drive means.

8. Apparatus as claimed in any preceding Claim including moving means arranged to cause axial movement of the support towards the drive means.

9. Apparatus as claimed in Claim 7 or 8 in which the moving means comprise screw feed means.

10. Apparatus as claimed in Claim 7 or 8 in which the moving means comprises hydraulic means.

11. Apparatus as claimed in Claim 7 or Claim 8 in which the moving means comprises pneumatic means.

12. Apparatus as claimed in any preceding Claim including selectively operable connection means which, when operated, are arranged to enable relative axial movement of the machining station away from the drive means to cause relative axial movement of the support away from the drive means.

13. Apparatus as pending Claim 12 in which the selectively operable connection means comprises latch means.

14. Apparatus as claimed in any preceding Claim in which the support comprises a support bush.

15. Machining apparatus substantially as herein described the reference to, and as shown in the accompanying drawings.

16. A method of machining a workpiece comprising rotating the workpiece with drive means, supporting the workpiece with a support at a location remote from the drive means, machining the workpiece on the opposite side of the support to the drive means with a tool, causing relative movement of the tool towards the drive means, causing relative movement of the support towards the drive means, and causing relative movement of the tool away from the drive means without causing simultaneous relative equal movement of the support away from the drive means.

17. Method as claimed in Claim 16 comprising the steps of rotating the workpiece, then machining the workpiece, then moving the tool relative to the drive means away from the drive means without causing relative equal movement of the support away from the drive means.

18. A method as claimed in Claim 16 or 17 comprising leaving the distance between the support and the drive means unaltered when the tool is moved relative to and away from the drive means.

19. A method as claimed in any of Claims 16 to 18 comprising simultaneously moving the support and the tool relative to the drive means towards the drive means during at least a part of that movement by the drive means.

20. A method as claimed in Claim 19 in which the support is caused to move relative to the drive means towards the drive means by abutment of a portion of the tool with the support.

21. A method as claimed in any Claims 16 to 20 comprising using different tools to machine the workpiece.

22. A method as claimed in Claim 21 comprising changing tools to machine the workpiece by moving a first tool which has partially machined the workpiece relative to and away from the drive means, and moving the first tool away from the axis of rotation, and moving a second tool towards the axis of rotation and relative to and towards the drive means.

23. A method as claimed in any Claims 16 to 22 comprising removing an at least partially machined section of the workpiece and machining the remaining workpiece whilst the support remains between the portion of the workpiece being machined and the drive means.

24. A method as claimed in any Claims 16 to 23 comprising subsequently moving the support relative to the drive means away from the drive means.

25. A method as claimed in Claim 24 in which the relative movement of the support away from the drive means is arranged to occur at the end of a particular machining operation on a workpiece.

26. A method of operating machining apparatus substantially as herein described with reference to, and as shown in the accompanying drawings.

27. A method of operating machining apparatus as referred to in any of Claims 16 to 26 when using apparatus as planned in any of Claims 1 to 15.

Amendments to the claims have been filed as follows 1. Machining apparatus including drive means arranged to rotate a workpiece, a support for a workpiece rotated by the drive means, the support being spaced from the drive means, and a workpiece machining station located on the opposite side of the support to the drive means, the machining station being arranged to machine a workpiece rotated by the drive means, the support being moveable relative to the drive means and the machining station and the machining station being moveable relative to the support and the drive means.