GB2092177A

GB2092177A - Jig for holding workpieces

Info

Publication number: GB2092177A
Application number: GB8039937A
Authority: GB
Original assignee: PENN ANODISING CO Ltd
Current assignee: PENN ANODISING CO Ltd
Priority date: 1980-12-12
Filing date: 1980-12-12
Publication date: 1982-08-11

Abstract

A jig for holding workpieces to be subjected to a treatment process, which comprises an elongate bar (1) having at least one channel (2) formed therein in its longitudinal direction, removable carrier pins (3) extending transversely from the bar for holding workpieces, the carrier pins having their one ends (5) adapted to be able to slide along the channel formed in the bar, and removable spacers (4a, 4b) for separating adjacent carrier pins and also being adapted to slide along the channel formed in the bar. The jig is particularly intended to be used for conveying workpieces to be subjected to an aluminium anodising process. <IMAGE>

Description

SPECIFICATION Jig for holding workpieces The present invention relates to a jig for holding workpieces, and is particularly intended for use for holding workpieces which are to be subjected to an aluminium anodising process.

It is well known to anodise aluminium to deposit an oxide coating thereon for the purpose of protecting the metal against corrosion by a process which generally comprises degreasing the aluminium, treating the aluminium with an etching solution (predominantly composed of caustic soda), followed by rinsing, anodising with sulphuric acid to deposit the oxide layer, and sealing.

It is conventional to convey the workpieces being subjected to the anodising process through the various treatment solutions by means of a jig which essentially comprises a vertically depending aluminium bar, usually of square cross-section, having a series of generally horizontally extending pins tightly press-fitted into holes formed in the bar, the workpieces being suspended from these pins. The pins themselves are usually arranged in pairs and have a certain amount of resilience in order to accommodate workpieces of different sizes.

However, a jig of this type has a number of disadvantages. It is difficult and relatively expensive to accurately drill in the bar the holes in which the pins are to be frictionally held.

Furthermore, the pins fitted into the bar tend to lose their resilience after a period of use.

The present invention aims to overcome these disadvantages by providing a jig for holding workpieces which is more adaptable and flexible to the requirements of the anodising process.

The present invention in one aspect provides a jig for holding workpieces to be subjected to a treatment process, which comprises an elongate bar having at least one channel formed therein in its longitudinal direction, a plurality of removable carrier pins extending transversely from the bar for holding workpieces, the carrier pins having their one ends adapted to be able to slide along the channel formed in the bar, and a plurality of removable spacers for separating adjacent carrier pins and also being adapted to slide along the channel formed in the bar.

The cost of manufacturing such a jig is reduced compared with the conventional jig previously described because it is merely necessary to cut extruded lengths of the various components comprising the jig, i.e. bar, pins and spacers, to the required length. In particular it is possible to produce spacers of various lengths so that the distances between carrier pins can be easily adjusted by simply sliding out from the bar the pins and spacers and reinserting the pins and new spacers.

The jig is particularly intended for use in an aluminium anodising process as described above, in which case the carrier pins will usually be arranged in pairs with a spacer of relatively short length arranged between the pins of each pair and a longer spacer arranged between adjacent pairs of pins. The facing surfaces of the pins of each pair may suitably each have a V-shaped groove formed therein for assisting retention of a workpiece therebetween. In this particular application the bar, carrier pins and spacers will usually all be made of aluminium.

Accordingly, the invention in another aspect provides a process for anodising aluminium, wherein workpieces to be treated are conveyed by means of a jig according to the invention, the workpieces being suspended from the carrier pins thereof.

The bar of the jig is preferably of square crosssection with channels formed in each of two opposite faces thereof, and carrier pins and spacers fitted into each of the two channels so that the pins extend in two diametrically opposite directions from the bar.

The or each channel formed in the bar is preferably of trapezium-shaped cross-section with the two non-parallel sides thereof tapering towards the open side of the channel. The spacers have a cross-section corresponding to that of the channel, and the carrier pins have their one ends also of a corresponding, i.e trapezium-shaped, cross-section. The main lengths of the carrier pins are preferably of square cross-section.

If the jig is to be used for holding small workpieces, then the bar of the jig may have channels formed in each of the four faces thereof, carrier pins extending from all four channels, the dimensions of the bar, carrier pins and spacers all being smaller than those of jigs for holding larger workpieces.

In use the bar is suspended from a flight bar attached to an overhead transporter so that the bar hangs vertically for carriage through the steps of the treatment process. The bottom of the bar is fitted with a clamp for retaining the carrier pins and spacers and maintaining the pins and spacers tightly pressed against each other.

Although the jig has been generally described with reference to its use in an aluminium anodising process, it is envisaged that it will find many other applications, in particular in other types of metal finishing, for example electrostatic or other painting or electrobrightening.

The invention will be further described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a length of a jig according to the invention; Figures 2, 3 and 4 are cross-sections of the bar, a carrier pin and a spacer respectively of the jig shown in Figure 1; Figure 5 is a cross-section of a bar of a jig for holding small workpieces; Figure 6 is a cross-section of a different form of carrier pin, particularly for use with the bar shown in Figure 5; and Figure 7 is a cross-section of a further different form of carrier pin.

The jig shown in Figures 1 to 4 of the drawings comprises an elongate bar 1 of square crosssection having formed in each of the opposite faces thereof a longitudinally extending channel 2 of trapezium-shaped cross-section, the nonparallel walls of the channel tapering towards the open side of the channel.

In one of the channels 2 are fitted a plurality of carrier pins 3, arranged in pairs, and a plurality of spacers 4, the spacers 4a between the pins of each pair being of relatively short length compared with the spacers 4b arranged between adjacent pairs of pins. The spacers 4 are of trapeziumshaped cross-section corresponding to the shape of the channel 2, as also are the ends 5 of the pins 3 which are fitted into the channel. The main lengths of the pins 3 are of square cross-section.

It can be seen that the pins 3 and spacers 4 can be easily inserted into and removed from the channel 2 of the bar 1 by sliding them along the channel. As described above, the arrangement of the carrier pins can be thus varied by inserting spacers of different length.

Also as described above, the bar 1 is hung vertically and transported through a treatment process, with the carrier pins extending horizontally and supporting workpieces to be treated suspended therefrom.

Figure 5 shows another embodiment of a bar 11 of a jig to be used for holding small workpieces, the bar 11 being of square crosssection and having formed in each of the four faces thereof a longitudinally extending channel 12 of trapezium-shaped cross-section. In this embodiment carrier pins may be fitted into each of the four channels 12.

Figures 6 and 7 show other forms of carrier pin.

The carrier pin 13 shown in Figure 6 has a pair of prongs 1 3a which together form substantially a V-shape and between which a workpiece to be treated may be held. The carrier pin 13 may be suitably used with the bar 11 shown in Figure 5.

The carrier pin 23 shown in Figure 7 is generally U-shaped as shown and may be used in particular for supporting tubular workpieces to be treated, such a workpiece being fitted over the bend of the pin and being retained by the resilience between the two limbs of the pin.

The carrier pins 13 and 23 shown in Figures 6 and 7 have ends 15 and 25 respectively of trapezium-shaped cross-section for fitting into a channel of the bar of a jig.

Claims

1. A jig for holding workpieces to be subjected to a treatment process, which comprises an elongate bar having at least one channel formed therein in its longitudinal direction, a plurality of removable carrier pins extending transversely from the bar for holding workpieces, the carrier pins having their one ends adapted to be able to slide along the channel formed in the bar, and a plurality of removable spacers for separating adjacent carrier pins and also being adapted to slide along the channel formed in the bar.

2. A jig as claimed in Claim 1 , wherein the said bar is of square cross-section.

3. A jig as claimed in Claim 1 or 2, wherein a said channel is formed in each of two opposite faces of the said bar.

4. A jig as claimed in any of Claims 1 to 3, wherein the or each said channel is of trapeziumshaped cross-section with the two non-parallel sides thereof tapering towards the open side of the channel.

5. A jig as claimed in each of Claims 1 to 4, wherein the main length of each of the carrier pins is of square cross-section.

6. A jig as claimed in any of Claims 1 to 5, wherein the said spacers form at least two groups of different length.

7. A jig as claimed in any of Claims 1 to 6, wherein the bar, the carrier pins and the spacers are each made of aluminium.

8. A jig according to Claim 1, substantially as herein described with reference to, and as shown in, Figures 1 to 4, Figure 5, Figure 6 or Figure 7 of the accompanying drawings.

9. A process for anodising aluminium, wherein workpieces to be treated are conveyed by means of a jig as claimed in any of Claims 1 to 8, the workpieces being suspended from the carrier pins thereof.

10. A process as claimed in Claim 9, wherein the carrier pins are arranged in pairs with a spacer of relatively short length arranged between the pins of each pair and a longer spacer arranged between each adjacent pair of pins.

1 A process as claimed in Claim 10, wherein the facing surfaces of the carrier pins of each pair have a V-shaped groove formed therein.