GB2037120A

GB2037120A - Moving a drawing scanning or other working device over the surface of a work piece

Info

Publication number: GB2037120A
Application number: GB7937640A
Authority: GB
Original assignee: Aristo Graphic Systeme GmbH and Co KG
Current assignee: Aristo Graphic Systeme GmbH and Co KG
Priority date: 1978-11-04
Filing date: 1979-10-31
Publication date: 1980-07-02
Also published as: SE7908795L; DE2847977C2; DE2847977A1; JPS5573595A; NL7907634A; FR2440247A1

Abstract

A workpiece in sheet of foil form is supported on a work table 2 shaped as a segment of a hollow cylinder. A drawing, engraving, cutting, milling, scanning or other working device 6 is carried on the end of swivel arm 4 which extends radially of a cross arm 3, this cross arm in turn extending along the axis of the work table. Rotation of the swivel arm about the cylindrical axis and bodily movement of the swivel arm along the axis provide the required displacement of the working device in respective coordinate directions. The swivel arm may be replaced by an axially adjustable optical system, the transmitting and/or receiving light beam effectively forming the swivel arm. The workpiece is held on the table by suction nozzles. <IMAGE>

Description

SPECIFICATION Method and apparatus for moving a drawing scanning or other working device over the surface of a work piece The invention relates to working machines wherein the working element has to be moved in two coordinate directions, usually at right angles to one one another, over a workpiece in the form of sheet or foil. Examples of such machines are coordinatographs and similar drawing machines, as well similarly constructed engraving and cutting devices, scanning devices, plotters and the like.

High working speed are always required for such devices. Whereas the relative movements between the working tools and the surface of the workpiece to be worked were orginally produced solely by movement of the working tool in the appropriate coordinate directions with the workpiece stationary, an attempt is at present being made to increase the working speed by additionally moving the workpiece in one coordinate direction. Thus drum devices have already been proposed, for example, in which the workpiece is moved according to the one coordinate direction in the machine frame by engagement with marginal perforations in the workpiece. Here it is a disadvantage, however, that the workpiece has to take up considerable forces which reduce the working accuracy.

It is the object of the present invention to provide a new method and a new apparatus of the kind referred to above which render it possible to work with very high working speeds involving for example accelerations of the order of magnitude of 4g, with fixed workpieces.

According to one aspect to the present invention, there is provided a method for the two-dimensional movement of a drawing, scanning or other working device over the surface of a workpiece in sheet or foil form carried by a working table, characterised in that the workpiece in the form of sheet or foil is stretched over a part hollow cylindrical working table and that the working device receives its guiding in a first coordinate direction through a swivel arm pivotable about the axis of the hollow cylindrical table surface and its guiding in a second coordinate direction through an axial adjustment of the swivel arm along the axis of the hollow cylindrical table surface.

In another aspect, the present invention consists in apparatus for carrying out the method, characterised in that the surface of the work table is a segment of a hollow cylinder and that a cross arm mounted for pivoting coaxially with the axis of the hollow cylinder and extending over the width of the table comprises a swivel arm which is longitudinally movble exclusively in it and is directed radially to the table surface.

Although the workpiece normally stands still during the working, the apparatus according to the invention and the method according to the invention can be modified so that workpieces can be worked, the dimension of which, in one direction, considerably exceeds the dimension of the table. If, according to further features of the invention, unwinding and winding devices, are disposed in front of the behind the hollow cylindrical table plane, the workpiece can be moved on intermittently.

The holding of the workpiece on the work table is preferably effected by a reduced pressure produced in the table surface, which can be caused to act preferably by appropriate nozzle arrangements. If paper conveying is intended, an air cushion can also be produced with blowing nozzles.

Preferred forms of embodiment of the invention are explained in more detail below with reference to the accompanying drawings, in which: Figure 1 shows a diagrammatic perspective view of a drawing machine according to the invention, Figure 2 shows a cross-section through a modified drawing apparatus, wherein unwinding and winding devices are disposed in front of and behind the table surface, Figure 3 shows a diagrammatic cross-section through the crossarm and the swivel arm of the apparatus of Fig. 1, Figure 4 shows a detail of the cross arm movement drive illustrated in section,.

Figure 5 shows a diagrammatic plan view of the work table and the crossarm with swivel arm present above it and Figure 6 shows an illustration similar to Fig.

3 of a cross arm which carries an axially adjustable optical system as a swivel arm, the light beam of which replaces part of the swivel arm.

Although reference is made to a drawing machine or a coordinatograph in the following description, it is here expressly mentioned that the invention can likewise be used for other working devices in which similar movements have to be produced, such as cutting devices, milling devices, scanners and plotters.

As Fig. 1 shows, the drawing machine accommodated in a machine housing 1 consists essentially of a table surface 2 curved into hollow cylindrical form and a crossarm 3 in which a swivel arm 4 is mounted for longitudinal displacement. The pivot axis X of the crossarm concides with the axis of the hollow cylindrical table surface 2. Inside the crossarm 3, the swivel arm 4 extending substantially radially in relation to the table surface 2 is movable only in the axial direction.

From the illustration of Fig. 1 it can be seen that pivoting of the crossarm 3 and hence of the swivel arm 4 about the axis X causes a movement of the device 6 fitted at the outer end of the swivel am 4 in the X-coordinate direction. If the swivel arm 4 is moved in the axial direction along the crossarm 3, with the crossarm 3 stationary, the device carrier 6 executes a movement in the direction of the X-coordinate axis.

Since the table surface 2 is concave in construction, unless the workpiece to the stretched over the table surface 2 is placed under compressive stress in the direction of the Taxis (Fig. 1), a separate device must be provided to hold the workpiece on the table surface 2. How this is done is shown by the diagrammatic illustration of Fig. 2. Here suction nozzles 20 are disposed under the table surface 2 and are connected to a source of reduced pressure. The workpiece is firmly held on the table surface 2 by the resulting reduced pressure. It is a particular advantage to provide an unwinding device 21 and a winding device 22 in front of and behind the table surface 2 in a tangential position. In this manner, workpieces of any length can be worked on the table 2.Some of the suction nozzles 20 may appropriately be able to be charged with an air blast in order to produce an air cushion on which the workpiece is supported for floating during the movement from the unwinding reel 21 to the winding reel 22.

As Fig. 3 shows, the swivel arm 4 can be moved precisely parallel and without rotation in the crossarm 3 by ball bearings 5. The swivel arm 4 projecting radially in relation to the working surface 2 preferably consists of carbonfibre reinforced plastics material. Such plastics materials, on the one hand have a very low weight and on the other hand very great rigidity so that even with very high working speeds and great acceleration of the swivel arm 4 in relation to the table surface 2, no substantial deformation can occur which would impair the drawing accuracy. At the outer end of the swivel arm 4 there is a tool holder 6 in which various tools can be inserted selectively. For example, such a tool may be a drawing unit, a milling head, a cutting device working with knives or a flowing medium, a miller or a scanning head.

The diagrammatic plan view shown in Fig.

5 shows the apparatus disposed above the work table with crossarm and swivel arm. The crossarm 3 is mounted in the machine frame 1 with bearings 11. On the crossarm 3 there are bearings 1 2 for a screw spindle 13, the associated spindle nut of which is disposed in the foot portion of the swivel arm 4. If the motor 14 disposed in the end of the crossarm 3 is actuated, the spindle 1 3 turns and moves the swivel arm 4 in the axial direction. The bearings 5 illustrated in Fig. 3 prevent tilting or radial movement of the swivel arm in relation to the crossarm.

As the said Fig. 5 shows in conjunction with Fig. 4, the outer end of the crosarm 3 carries a circular segment, preferably a segment of a wormwheel 7 in which a worm 9 mounted at 8 engages without clearance and can be moved by the drive motor 1 0.

The worm drive 7/9 and the screw spindle drive 1 3 can, of course, also be replaced by any other linear drive, for example a drive through cables or racks. In all cases the coaxial construction ensures that the linear movement produced by a motor leads to a proportional linear movement at the front end of the swivel arm despite the repeated reversing.

In the case of the a photodrawing unit or a plotter or scanner working optically, the swivel arm 4 can be shortened very considerably by disposing an optical system 23 instead of a swivel arm at the part moveable transversely in translation on the crossarm 3, the transmitting and/or receiving light beam of which optical system forms part of the swivel arm 4.

It may also be mentioned that fundamentally the table surface 2 may also be considerably larger in the peripheral direction than shown in Fig. 1. In view of a satisfactory possibility for observing the workpiece, however, it is an advantage if too great a proportion of the workpiece is not covered by the crossarm so that an arc length of about 90 is perferable for the table surface. The radius of curvature of the table surface 2 preferably amounts to 60 to 90 cm, but may also be greater depending on the drawing accuracy required and the masses to be set in motion.

Claims

1. A method for the two-dimensional movement of a drawing, scanning or other working device over the surface of a workpiece in sheet or foil form carried by a working table, characterised in that the workpiece in the form of sheet or foil is stretched over a part hollow cylindrical working table and that the working device receives its guiding in a first coordinate direction through a swivel arm pivotable about the axis of the hollow cylindrical table surface and its guiding in a second coordinate direction through an axial adjustment of the swivel arm along the axis of the hollow cylindrical table surface.

2. An apparatus for carrying out the method as claimed in Claim 1, characterised in that the surface of the work table is a segment of a hollow cylinder and that a cross arm mounted for pivoting coaxially with the axis of the hollow cylinder and extending over the width of the table comprises a swivel arm which is longitudinally movable exclusively in it and is directed radially to the table surface.

3. An apparatus as claimed in Claim 2, characterised in that the length of the swivel arm corresponds substantially to the radius of the hollow cylindrical table surface and a holder for a working device is disposed at the end of the swivel arm close to the table surface.

4. An apparatus as claimed in Claim 2, characterised in that at least a substantial part of the swivel arm is formed by a radially directed light beam of a light transmitter and/or receiver.

5. An apparatus as claimed in any one of Claims 2 to 4, characterised in that winding and unwinding devices extending transversely to the table surface are provided respectively in front of and behind the work table.

6. An apparatus as claimed in any one of Claims 2 to 5, characterised in that the table surface is provided with a plurality of suction and/or blast nozzles which hold the workpiece bearing against the table surface.

7. An apparatus as claimed in Claim 6, characterised in that the bores of the nozzles are so directed that an air cushion can be produced enabling the work piece to float on the table surface.

8. An apparatus as claimed in any one of Claims 2 to 7, characterised in that the table surface extends over an arc of about 90 which ends substantially horizontally at the lower end.

9. An apparatus as claimed in any one of Claims 2 to 8, characterised in that the swivel arm is movable with a screw spindle which is mounted for rotation on the crossarm and the drive motor of which is carried by the end of the crossarm.

10. An apparatus as claimed in any one of Claims 2 to 9, characterised in that a circular segment is secured to the end of the crossarm and a drive working linearly acts on its periphery.

11. An apparatus as claimed in Claim 10, characterised in that the crossarm segment is a segment of a wormwheel, in which a motordriven worm engages.

12. An apparatus as claimed in any one of Claims 2 to 8, characterised in that cable drives are provided for moving the swivel arm and crossarm.

1 3. An apparatus as claimed in any one of Claims 2 to 12, characterised in that the drive motors are constructed in the form of stepping motors.

14. An apparatus as claimed in any one of Claims 2 to 13, characterised in that the supporting parts of the swivel arm consist of carbon-fibre reinforced plastics materials.

1 5. A method for the two dimensional movement of a drawing, scanning or other working device over the surface of a workpiece in sheet or foil form carried by a working table, substantially as hereinbefore described with reference to the accompanying drawings.

1 6. Apparatus for moving a drawing, scanning or other working device in two dimensions over the surface of a workpiece in sheet or foil form carried by a working table, substantially as hereinbefore described with reference to and as shown in the accompanying drawings.