GB2287668A

GB2287668A - Apparatus for trimming a workpiece

Info

Publication number: GB2287668A
Application number: GB9402253A
Authority: GB
Inventors: Jonathan Charles Weaver; James Ralph Weaver
Original assignee: WINDMILL SERVICES Ltd
Current assignee: WINDMILL SERVICES Ltd
Priority date: 1994-02-05
Filing date: 1994-02-05
Publication date: 1995-09-27
Also published as: GB9402253D0

Abstract

Apparatus for trimming flash from a welded plastics window frame comprises a milling cutter 12 and a pneumatic ram 14 for moving the milling cutter 12 along. The milling cutter 12 is hingedly connected to two parallel spaced links 20, 22 which are of equal length and are hingedly connected to the ram 14 and to two other rams 16, 18 which respectively control the angle and downwards pressure of the milling cutter 12. A depth stop comprising a shoe 26 in channel form is provided, the arms of the shoe 26 being disposed laterally of the direction of movement of the tool. A ram is provided to raise and lower the milling kit 24 in relation to the shoe 26. Flash can thus be accurately removed from a chamfered surface by the apparatus. <IMAGE>

Description

APPARATUS FOR TRIMMING A WORKPIECE The invention relates to apparatus for trimming a workpiece and particularly, but not exclusively, to apparatus for trimming welding flash from a welded plastics window frame.

Plastics window frames are commonly welded together from a number of extruded plastics profiles. Flash is produced at the weld junctions and this must be removed to finish the frame. The frame may have a main flat surface with chamfers on either side. A known apparatus will trim the main flat surface with a blade. The window frame is held horizontally by the apparatus and a knife is moved horizontally across the main flat surface to remove the flash. The flash at the chamfer junctions cannot be removed in this way, however, and is often removed by hand using a craft knife.

According to one aspect of the invention there is provided apparatus for trimming a plastics workpiece comprising a trimming tool, means for moving the trimming tool in a direction and means for adjusting the angle of the trimming tool.

In this way, angled surfaces can be trimmed by the apparatus.

The tool may take any suitable form and may be a blade, for example. In a preferred embodiment, however, the tool is a milling cutter. The angle of a milling cutter to a surface is particularly important to achieve a good finish efficiently.

Preferably, the tool is mounted by two spaced links which are hingedly attached to the tool and mounting means. The spaced links enable convenient adjustment of the angle of the tool by relative movement of the links. Preferably, the links are parallel and preferably the links are the same length. The links may thus form a parallelogram arrangement in which a full range of adjustment of the angle of the tool can be achieved. Moreover, where the direction in which the tool is urged is not the perpendicular to the angle of the tool, the tool will be retained at a same angle as it is moved.

The moving means may act on the mounting means. The adjusting means may act on the mounting means.

The moving means may comprise a ram and the adjusting means may comprise a ram.

The apparatus conveniently includes means for holding a workpiece.

The workpiece is preferably a window frame.

In following a chamfered workpiece surface, it has previously been a problem to maintain the trimming tool at the appropriate height.

According to another aspect of the invention there is provided apparatus for trimming a welded plastics workpiece comprising a depth stop and a trimming tool, the trimming tool being arranged to move forwards to trim the workpiece and the depth stop being disposed laterally of the direction of movement of the tool, the apparatus including means to alter the height of the depth stop in relation to the trimming tool, in use.

The conventional position for a depth stop would be in advance of the trimming tool, but as the flash is uneven this could not be done. By placing the depth stop laterally in relation to the trimming tool, the inventor has assured that the depth stop will follow a flat surface, clear of the welding flash and has incorporated height adjustment for the depth stop to compensation for different angles of chamfer on the surface.

Preferably, two depth stops are provided, disposed laterally on either side of the tool. The depth stops may be integral and may comprise the arms of a downwardly facing channel section member.

The apparatus suitably includes means for holding a workpiece.

Preferably, the altering means acts automatically to alter the height of the depth stop so that a change in chamfer can be accommodated. The altering means may operate in any suitable way and preferably operates pneumatically.

The trimming tool may be of any suitable type and may be a milling cutter.

Preferably, the tool is not movable laterally.

A further problem in prior apparatus has been to maintain a cutter at an appropriate angle when the workpiece to be operated on is not flat or cannot conveniently be held so that the part of the workpiece to be trimmed is in the desired plane.

According to a further aspect of the invention there is provided apparatus for trimming a plastics workp ece comprising a trimming tool hingedly connected to two parallel spaced links which are of equal length and are hingedly connected to mounting means, the apparatus further comprising means for moving the mounting means in a direction.

Because of the parallel linkage for the tool, the movement of the tool permitted by the link hinge connections will maintain the trimming tool always at the same angle.

Preferably, means is provided for urging the trimming tool towards the workpiece. In this way, the trimming tool will not ride over difficult obstructions. The urging means may comprise a pneumatic ram. In this way, the ram may provide a constant resistance to lifting of the trimming tool. The urging means may act on one of the links and preferably acts on an extension to one of the links. Conveniently, the extension may be substantially at 900 to the main part of the link. This provides a good leverage arrangement.

The apparatus preferably includes a depth stop. In this way, the trimming tool will only remove material which is above a certain height from the surface to be trimmed. The depth stop is particularly suitable for use where urging means is provided and the urging means ensures contact of the depth stop with the workpiece. The depth stop is preferably disposed laterally of the direction of movement of the tool.

The moving means may comprise a ram.

Preferably, adjusting means is provided for adjusting the mounting means to adjust the relative positions of the hinge connections to the links and hence the angle of the trimming tool. The adjusting means may also comprise a ram.

An embodiment of the invention will now be described by way of example and with reference to the accompanying drawings, in which: Fig. 1 is a perspective view of the apparatus of the embodiment with the bed in partial cross-section; Fig. 2 is a perspective view of the apparatus without the bed and in partial cross-section; Fig. 3 is a side elevation of the embodiment in partial cross-section; Fig. 4 is a detail end elevation of the trimming tool of the apparatus ascending a chamfered surface; Fig. 5 is a detail end elevation of the trimming tool of the apparatus descending a chamfered surface; Fig. 6a to 6f are schematic side elevations showing the sequence of movement of the apparatus; Fig. 7 is a diagram of the pneumatic circuit of the apparatus; and, Fig. 8 is a perspective view in fragmentary detail of the movement of the tool over a chamfered workpiece.

Fig. 1 shows the apparatus 10 of the embodiment. The apparatus 10 comprises a trimming tool 12 and three rams 14,16,18 connected to the tool 12 through parallel links 20,22.

The trimming tool 12 is a milling cutter which is mounted upright and includes a ram 22 for raising and lowering the milling bit 24 in'relation to a shoe 26 which is disposed about the milling bit 24. The tool 12 also includes a motor 25 for rotating the milling bit 24. As best shown in Figs. 3, 4 and 5, the shoe 26 is a channel section member. The ends of the arms 28 of the shoe 26 are rounded. The body 30 of the tool 12 is hingedly connected to two pairs of links 20, 22. The lower pair of links 20 are hingedly connected to the arm 32 of a lower ram 14 which is fixedly mounted in the apparatus. The upper links 22 are L-shaped and comprise a main part and an extension at 90e to the main part.The main part of each link 22 extends parallel to the links 20 and is hingedly connected to the arm 34 of a middle ram 16 arranged above the ram 14 so that the distance between the hinge connection to the tool 12 and to the arm 34 of the ram 16 is the same as the distance of the link 20 between the hinge connection to the tool 12 and the hinge connection to the arm 32 of the ram 14. The ends of the extension are connected to the arm 36 of an upper ram 18 arranged above the middle ram 16. The rams 14,16,18 are mounted horizontally and lie one above the other. The ram 14 is mounted to a bed 38 of the apparatus. The rams 16 and 18 are hingedly mounted at their ends to a pair of plates 40. The plates are disposed laterally of the rams 16,18 and extend forwards to alongside the connection of the upper links 22 to the arm 34 of the ram 16.That connection is by way of a pin 42 which passes through apertures in the links 22 and passes through an eye at the end of the arm 34. The ends of the pin 42 are received in a part circular slot 44 in between two resilient stops 46. Each plate 40 also mounts a further pin 48 which extends through apertures in the lower links 20 and through an eye at the end of the arm 32 of the lower ram 14. Each plate 40 also includes an outwardly extending flange 50 which is received in a guideway 52 mounted on the bed 38.

There is a knife 53 mounted on the plate 40 which moves horizontally to remove flash from a horizontal surface of a workpiece.

It will thus be seen that movement of middle ram 16 will tilt the trimming tool 12 backwards and forwards by means of the hingedly mounted parallel links 20,22.

The movement is limited by the steps 46. Movement of the lower ram 14 will pull the trimming tool over a workpiece with the flange 50 sliding in the groove 52 in the bed. The upper ram 18 can be used to raise and lower the trimming tool 12 or to apply downwards pressure onto a workpiece.

Fig. 6 shows the sequence of movements of the rams in milling of a workpiece 54 which has a rising chamfered surface 56 leading to a horizontal surface 58 and a descending chamfered surface 59. Fig. 6a shows that the middle ram 16 is extended to tilt the trimming tool 12. The stop 46 is arranged so that the ram extends to give the desired angle of tilt of the trimming tool 12. The upper ram 18 is retracted so that the trimming tool 12 is clear of the workpiece initially while the middle ram 16 is being set up to arrange the trimming tool 12 at the correct angle.

The upper ram 18 is then extended to lower the cutter 24 of the milling tool into contact with the workpiece 54. The lower ram 14 is then retracted and at the same time the upper ram 18 is put under pressure to extend. This situation is shown in Fig. 6b. The arms 28 of the shoe 26 are in contact with the workpiece 54 and, as the tool 12 is drawn forwards by retraction of the ram 14, the trimming tool 12 will be lifted as it rides up the chamfered surface 56 against the pressure applied by the ram 18 which is sufficient to keep the shoe 26 in contact with the chamfered surface 56.

When the chamfered surface 56 has been milled, as shown in Fig. 6c, the upper ram 18 is retracted to lift the tool 12 away from the workpiece 54. The middle ram 16 is retracted to bring the pin 42 into contact with the stop 46 so that the trimming tool 12 is at an opposite angle to the vertical and at the appropriate angle for the downwards chamfered surface 59. The lower ram 14 continues to be retracted and the upper ram 18 is extended to lower the trimming tool 12 into contact with the downwardly chamfered surface 59 and to apply pressure to keep the arms 28 of the shoe 26 in contact with the surface as the milling cutter 24 cuts down the surface 59.

The pneumatic control system for the apparatus is shown in Fig. 7. A start valve 60 is provided and is connected through a line 62 to a valve 64 for the lower ram 14 and through a line 66 to a valve 68 for the upper ram 18. When the valve 60 is depressed, compressed air is supplied along the line 62 and 66 and the valves 64 and 68 are operated. The valve 64 operates to switch the compressed air supply from behind to in front of the plunger of the ram 14 so that the ram is retracted. The valve 68 operates in the opposite way so that the ram 18 is extended. This is the situation shown in Figs. 6b and 6c. The valve 68 also supplies compressed air through a line 69 to the motor drive 25 for the milling cutter bit 24. The arm 32 of the ram 14 includes two projections 74,76 which operate two further valves 76,78 sequentially.

As the arm 32 is retracted, firstly the projection 74 contacts the valve 78 and actuates it. The valve 78 supplies compressed air along a line 82 to a valve 84 which retracts the middle cylinder 16 to move the trimming tool 12 to the opposite angle. The valve 84 also supplies air along a line 86 to a ram 88 which raises the height of the milling cutter 24 in relation to the shoe 26. As the ram 14 continues to retract, the pressure exerted by the ram 18 keeps the shoe in contact with the chamfered surface of the workpiece as the milling cutter 24 travels down the surface removing the flash to a constant depth. When the cutter reaches the end of the chamfered surface the projection 76 will have reached the valve 80 and will actuate it. Actuation of the valve 80 connects compressed air through lines 90,92 and 94 to reset the valves 64,68 and 84. Resetting of valve 84 also connects compressed air to the ram 23 to raise the milling cutter height again. Return of the valve 68 cuts off the supply of compressed air to the milling cutter motor.

It is thus seen that in one cycle of the apparatus 10, the apparatus will mill the flash from the chamfered surfaces 56,59 of a workpiece 54 and cut flash from the horizontal surface 58. The workpiece 54 may be a window frame made from uPVC, for example, and the flash may be present at a welded corner joint.

Claims

1. Apparatus for trimming a plastics workpiece comprising a trimming tool, means for moving the trimming tool in a direction and means for adjusting the angle of the trimming tool.

2. Apparatus as claimed in claim 1, wherein the tool is a milling cutter.

3. Apparatus as claimed in claim 1 or claim 2, wherein the tool is mounted by two spaced links which are hingedly attached to the tool and mounting means.

4. Apparatus as claimed in claim 3, wherein the links are parallel.

5. Apparatus as claimed in claim 3 or claim 4, wherein the links are the same length.

6. Apparatus as claimed in claim 3, 4 or 5, wherein the moving means acts on the mounting means.

7. Apparatus as claimed in any of claims 3 to 6, wherein the adjusting means acts on the mounting means.

8. Apparatus as claimed in any preceding claim, wherein the moving means comprises a ram.

9. Apparatus as claimed in any preceding claim, wherein the adjusting means comprises a ram.

10. Apparatus as claimed in any preceding claim, wherein the apparatus includes means for holding a workpiece.

11. Apparatus as claimed in any preceding claim, wherein the workpiece is a window frame.

12. Apparatus for trimming a welded plastics workpiece comprising a depth stop and a trimming tool, the trimming tool being arranged to move forwards to trim the workpiece and the depth stop being disposed laterally of the direction of movement of the tool, the apparatus including means to alter the height of the depth stop in relation to the trimming tool, in use.

13. Apparatus as claimed in claim 12, wherein two depth stops are provided, disposed laterally on either side of the tool.

14. Apparatus as claimed in claim 13, wherein the depth stops are integral.

15. Apparatus as claimed in claim 14, wherein the depth stops comprise the arms of a downwardly facing channel section member.

16. Apparatus as claimed in any of claims 12 to 15, wherein the apparatus includes means for holding a workpiece.

17. Apparatus as claimed in any of claims 12 to 16, wherein the altering means acts automatically to alter the height of the depth stop so that a change in chamfer can be accommodated.

18. Apparatus as claimed in any of claims 12 to 17, wherein the altering means operates pneumatically.

19. Apparatus as claimed in any of claims 12 to 18, wherein the trimming tool is a milling cutter.

20. Apparatus as calmed in any of claims 12 to 19, wherein the tool is not movabie lateraily.

21. Apparatus for trimming a plastics workpiece comprising a trimming tool hingedly connected to two parallel spaced links which are of equal length and are hingedly connected to mounting means, the apparatus further comprising means for moving the mounting means in a direction.

22. Apparatus as claimed in claim 21, wherein means is provided for urging the trimming tool towards the workpiece.

23. Apparatus as claimed in claim 22, wherein the urging means comprises a ram which is arranged to provide a constant resistance to lifting of the trimming tool.

24. Apparatus as claimed in claim 22 or claim 23, wherein the urging means comprises a pneumatic ram.

25. Apparatus as claimed in claim 22, 23 or 24, wherein the urging means acts on one of the links.

26. Apparatus as claimed in claim 25, wherein the urging means acts on an extension to one of the links.

27. Apparatus as claimed in claim 26, wherein the extension is substantially at 90 to the main part of the link.

28. Apparatus as claimed in any of claims 21 to 27, wherein the apparatus includes a depth stop.

29. Apparatus as claimed in claim 28, wherein the depth stop is disposed laterally of the direction of movement of the tool.

30. Apparatus as claimed in any of claims 21 to 29, wherein the moving means comprises a ram.

31. Apparatus as claimed in any of claims 21 to 30, wherein adjusting means is provided for adjusting the mounting means to adjust the relative positions of the hinge connections to the links and hence the angle of the trimming tool.

32. Apparatus as claimed in claim 31, wherein the adjusting means comprises a ram.

33. Apparatus substantiaily as described herein with reference to the accompanying drawings.