GB2044643A - Positioning jig - Google Patents

Abstract

A positioning jig, particularly suited to holding a squeegee whose blade (22) needs to be reshaped or dressed by a tool (14), comprises a support member (16) arranged to travel linearly past a guide (12), with locating studs (25,26) in the support member which receive and align the squeegee relative to the tool. The tool (14) and/or guide (12) can be advanced in step increments. <IMAGE>

Description

SPECIFICATION Positioning jig This invention relates generally to positioning jigs for use in presenting a workpiece in the correct attitude to a shaping tool.

The present invention has particular application to the dressing of squeegees, such as are used in screen printing and in the production of printed circuits. The positioning jig of the present invention is particularly, although not exclusively, adapted for use with dressing apparatus such as described in my UK patent specification 1566547.

In reshaping the blade of a squeegee for example, it is necessary to pass the squeegee between a guide member on the one hand and a reshaping tool, such as a grinding wheel, on the other hand. In the case of a squeegee, it is necessary to sharpen the blade edge at intervals in order to produce a sharp clean edge. In the case of other workpieces it may be necessary to grind, cut, reprofile or otherwise shape a surface or edge of the workpiece, again by passing it through a passage between a guide on the one hand and a shaping tool on the other hand. Although the description given hereinafter is concerned particularly with squeegees, it should be understood that the invention is generally applicable to other workpieces which need to be reshaped.

In the case of a squeegee or other workpiece which has two accurately parallel faces, then there is normally no particular problem in feeding such a workpiece between a guide and a shaping tool without the need for any special positioning jig or carrier.

However, problems arise in producing an accurately finished edge or surface on a workpiece, such as a squeegee, which is not symmetrical, or sufficiently symmetrical, in its dimensions.

It is an object of the present invention to provide a positioning jig designed to be used with a workpiece, such as a squeegee, to enable the workpiece to be presented to a reshaping tool in a supported and controlled attitude.

It is a further object of the present invention to provide a positioning jig which will hold a workpiece in a correct attitude relative to datum points on the workpiece for presentation of the workpiece at the correct attitude to a reshaping tool.

It is a further object of the present invention to provide a positioning jig which will accept any shape of workpiece, such as a squeegee, and present it in a standard manner two a reshaping tool, such as a grinding wheel.

In accordance with the present invention there is provided a positioning jig comprising a support member having a straight edge which is adapted to travel past guide means to effect linear travel of said edge, and locating means mounted on the support member and adapted to receive a workpiece thereon, the arrangement being such that the workpiece can be mounted on the support member to enable an edge or surface of the workpieceto be presented in a predetermined attitude to a reshaping tool past which the workpiece is arranged to move as the support member moves past the guide means.

Preferably, the edge or surface of the workpiece which is to be reshaped is arranged to overhang the support member.

According to a preferred feature of the invention the support member is mounted on a bearing slide to enable itto be moved past the guide means and the reshaping tool with reduced friction.

Also in accordance with the present invention there is provided squeegee dressing apparatus comprising a base on which a squeegee is arranged to be placed, cutting means mounted on the base, a guide which is mounted on the base, the cutting means and guide being relatively movable and a positioning jig also mounted on the base and com prising a support member having a straight edge arranged to travel past the guide to effect linear travel of said edge, and locating means on the support member carrying the squeegee thereon, the guide defining a rectilinear surface which abuts the jig and exerts a pressure thereon in a direction to urge the blade of the squeegee against the cutting means, a space between the cutting means and said guide surface defining a path for the jig and squeegee which is substantially at right-angles to said direction.

In order that the invention may be fully understood a number of embodiments of jig in accordance with the invention will now be described by way of example and with reference to the accompanying drawings, in which: Fig. 1 is a schematic end elevation of a first embodiment illustrating a hand squeegee; Fig. 2 is a schematic end elevation of a second embodiment using a machine squeegee, with offset; Fig. 3 is a schematic end elevation of a third embodiment using a machine squeegee, but without offset; Fig. 4 is a schematic view illustrating a further embodiment of positioning jig in accordance with the invention; and, Fig. 5 shows a modified guide system for use with a positioning jig in accordance with the invention.

In the drawings, the same elements in the various views are indicated by the same reference numerals.

Referring first to Fig. 1, this shows a base plate 10 on which is mounted a guide member 12 and a grinding wheel 14 which here constitutes a reshaping tool. A support member or carrier 16 is positioned on the base 10. The carrier comprises a rectangular element which has one longer edge abutting a rectilinearface of the guide 12. A squeegee 18 comprising a stock 20 and a blade 22 is positioned on the carrier 16. The squeegee stock 20 is bored through its thickness at at least two positions along its length to receive the shank of a bolt 24. A retaining nut 26 is fitted in use on the upper end of the bolt so that it can be tightened down against the squeegee to hold it firmly in place on the carrier.A spacer 28 is provided between the squeegee stock 20 and the carrier 16 and is preferably shaped to match the profile of the stock in order to provide good support for it.

In use, the squeegee or other workpiece is appropriately positioned on the carrier so that it takes up the correct attitude relative to the grinding wheel 14 and is then fixedly held in place by tightening the retaining nuts 26. The jig with the squeegee mounted on it can then be advanced through the passage between the guide 12 and the grinding wheel to reshape the face of the blade 22.

Fig. 2 shows a machine squeegee 18 where the positioning jig is in two parts. The jig comprises a rectangular base plate 1 6a which abuts the guide 12 and rests on the base 10, and also a wedge-shaped block 16b which is carried on the support blade 16a and which has the squeegee 18 mounted thereon. By the use of this two-part jig one can introduce a degree of offset, which may be adjustable.

Fig. 3 shows the use of a machine squegee but without any offset. Here, as in the embodiment shown in Fig. 1, the jig comprises a rectangular plate 16 with the squeegee 18 mounted directly on it.

Fig. 4 shows an arrangement very similar to Fig. 3.

One can here see the provision of two handles 30 by means of which the jig and squeegee can be advanced past the grinding wheel. Two locating bolts are shown, one adjacent to each end of the squeegee stock, the left-hand bolt 25 being shown projecting up from the surface of the stock, and the right-hand bolt being shown with its retaining nut 26 in place.

Provision is preferably made for stepwise advancement of the guide and/or grinding wheel towards each other, so that the distance between the guide and the grinding wheel can be reduced in predetermined steps to produce a controlled depth of feed advance, i.e. cut on the blade.

If the guide 12 is movable, then one can arrange that the guide has one end mounted on a fixed pivot, and its other end is provided with stepping means so that the guide can be advanced in steps towards the cutter in an arcuate path in order to provide a controlled depth of cut. The guide is then also provided with clamping means to clamp it to the base 10 after the correct positioning of the workpiece between the cutter and the guide. For this purpose the base 10 is provided with arcuate slots matched to the arcuate path of movement of the guide and which serve to receive a part of the clamping means.

Fig. 5 shows an alternative arrangement of movable guide 12 in which the guide rests on the base 10 and has its longitudinal axis substantially at rightangles to two slots 48 which are cut th rough the base plate. The slots are straight and parallel to each other and extend under the respective ends of the guide 12.

One end of the guide 12, i.e. the left-hand end as shown in Fig. 5, includes a pivot mounting, at the upper end of which is a locking knob 40. The pivot and locking mechanism operates in association with the slot 18 by having a rod extending down through the slot and terminating in a clamping plate beneath the base plate 10 which can be drawn up into contact with the underside of the base to lock the pivot in any desired position along the length of the slot 18.

The other end of the guide 12, i.e. the right-hand end as shown in Fig. 5, is provided with two control knobs. It is at this end of the guide that a stepping mechanism is fitted within the guide in order to be able to advance this end of the guide towards the grinding wheel 14 in predetermined increments after the pivot at the other end of the guide has been locked in position. One knob 42 is a feed adjustment knob which is linked with the stepping mechanism, and the other knob 44 is a locking knob which again operates in association with clamping means extending through the slot 18 beneath the guide.

By making the pivot end of the guide movable in the same way as the other end of the guide which carries the stepping mechanism one achieves greater flexibility, and a greater capacity for adjustment.

The use of a positioning jig or carrier is necessary with many types of squeegee, particularly those used on automatic and semi-automatic printers, so that the squeegee is held with the blade at the correctangle and in the correct positional relationship with respect to the holes for example by means of which it is mounted on the printer. The positioning jig of the present invention will accept any shape of squeegee and present it in a standard manner to the grinding wheel. The use of the positioning jig of the present invention means that only a small amount of material is removed from the squeegee blade during the dressing operation. This is of great importance and value to the use of an automatic printer because the printing machine does notthen need to be reset each time the squeegee blade is dressed.

With the positioning jig of the present invention the workpiece to be reshaped is supported at its critical dimension points so that all angles are in their correct relationship to these points. The positioning jig holds the workpiece, such as the squeegee, in the correct attitude relative to the datum points on it, such as the machine fixing holes, the clamping points, etc., and will also hold the workpiece at the desired angle relative to a vertical centre line.

Although not shown in the drawings, it is desirable to provide means to reduce the friction between the surfaces of the guide, the base and the carrier. This is a particular problem with iong and/or heavy squeegees when the friction can make it difficult for some operators to achieve an even feed speed past the grinding wheel. This problem can be reduced or overcome bythe provision of bearing means between the components. In the case of a fixed guide 12 one can fit a precision bali-race track to which the carrier 16 is attached. A ball-bearing precision slide can be used to carry the jig and the squeegee along the guide 12.

Claims (16)

1. A positioning jig comprising a support member having a straight edge which is adapted to travel past guide means to effect linear travel of said edge, and locating means mounted on the support member and adapted to receive a workpiece thereon, the arrangement being such that the workpiece can be mounted on the support member to enable an edge or surface of the workpiece to be presented in a predetermined attitude to a reshaping tool past which the workpiece is arranged to move as the support member moves past the guide means.

2. A positioning jig as claimed in claim 1, in which the edge or surface of the workpiece which is to be reshaped is arranged to overhang the support member.

3. A positioning jig as claimed in claim 1 or 2, in which the support member is mounted on a bearing slide to enable itto be moved pastthe guide means and the reshaping tool with reduced friction.

4. A positioning jig as claimed in any preceding claim, in which the locating means comprises two elongate elements projecting from the support member and arranged to fit through two holes spaced along the length of the workpiece.

5. A positioning jig as claimed in any preceding claim, in which the support member has a plurality of relatively movable parts, one carrying the workpiece and the or an other contacting the guide means.

6. Apparatus for reshaping a workpiece comprising a positioning jig as claimed in any preceding claim, a workpiece mounted on the support member, and a tool positioned to contact an edge or surface of the workpiece.

7. Apparatus as claimed in claim 6, in which the guide means and/or reshaping tool is/are movable in stepwise increments to change the gap therebetween.

8. Apparatus as claimed in claim 7, in which the guide is movable towards and away from the tool, the guide being mounted at or adjacent to one end on a pivot which is itself movable and lockable in chosen positions.

9. Apparatus as claimed in claim 8, in which the guide is mounted on a base which has a linear slot associated with said movable pivot, and clamping means extending through the slot enables the pivot to be locked in a desired position.

10. Apparatus as claimed in claim 9, in which the base is provided with two linear parallel slots relative to which the guide moves.

11. Apparatus as claimed in any of claims 6 to 10, in which the workpiece is a squeegee.

12. Apparatus as claimed in claim 11, which includes a spacer between the stock of the squeegee and the support member.

13. Squeegee dressing apparatus comprising a base on which a squeegee is arranged to be placed, cutting means mounted on the base, a guide which is mounted on the base, the cutting means and guide being relatively movable and a positioning jig also mounted on the base and comprising a support member having a straight edge arranged to travel past the guide to effect linear travel of said edge, and locating means on the support member carrying the squeegee thereon, the guide defining a rectilinear surface which abuts the jig and exerts a pressure thereon in a direction to urge the blade of the squeegee against the cutting means, a space between the cutting means and said guide surface defining a path for the jig and squeegee which is substantially at right-angles to said direction.

14. Apparatus as claimed in claim 13, in which the guide is movable towards and away from the cutting means, the guide being mounted at or adjacent to one end on a pivot which is itself movable and lockable in chosen positions.

15. A positioning jig substantially as hereinbefore described with reference to any of Figs. 1 to 4 of the accompanying drawings.

16. Apparatus for reshaping the blade of a squeegee substantially as hereinbefore described with reference to any of Figs. 1 to 5 of the accompanying drawings.