GB2146557A - Centering device - Google Patents

Abstract

Apparatus for centering an article so that it is correctly positioned for a subsequent operation comprises a vacuum chuck (2) for attachment to a plane surface of the article, a rotatable annular platen (1) coaxial with the chuck (2), the chuck (2) passing through an aperture (3) in the platen (1) and the platen (1) being arranged for movement between a first position in which it lies below that of the head of the chuck (2) and a second position in which the plane of its upper surface is substantially coplanar with that of the head of the chuck (2), the platen having a plurality of equi-spaced non-radial slots (9) through each of which extends an upstanding pin (10) carried on a pivoted link 11 for movement along the slot (9) on rotation of the platen (1), rotation of the platen (1) in opposite directions moving the pins (10) inwardly and outwardly respectively by the cam action of the edges of the slot (9) on the pin (10). <IMAGE>

Description

SPECIFICATION Centering device This invention relates to apparatus for handling articles having a planer surface and more especially to apparatus for accurately centering an article with a planer surface so that it is correctly positioned for a subsequent operation.

According to the invention an article centering apparatus comprises a vacuum chuck for attachment to a plane surface of the article, a rotatable annular platen coaxial with the chuck, the chuck passing through the aperture in the platen and the platen being arranged for movement between a first position in which the plane of its upper surface lies below that of the head of the chuck and a second position in which the plane of its upper surface is substantially coplanerwith that of the head of the chuck, the platen having a plurality of equi-spaced non-radial slots extending through its thickness, each slot extending from a point towards the edge of the platen to a point towards the central aperture of the platen, there being an upstanding pin extending through each slot and mounted beneath the platen for movement along the slot on rotation of the platen, rotation of the platen in one direction moving the pins inwardly by the cam action of one edge of the slot on its associated pin and rotation of the platen in the opposite direction moving the pins outwardly by the cam action of the other edge of the slot on the pin, means for moving the platen between the first and second positions and means for rotating the platen in both clockwise and anticlockwise directions.

To allow movement of the pins across the surface of the disc, the pins may be resiliently mounted, for example, on springs or, preferably, the pins are carried on a pivoted link arranged at such a position and of such length that the pins are constrained to move along the slots in similar mannerto the Iris of a camera.

The number of pins is not critical, although there must be at least three. There will normally, however, be somewhat more than three pins so that the device can be used for centering articles that are not completely circular, for example, articles having flat sections or notches or the like on their periphery.

In operation of the apparatus an article is placed on the vacuum chuck and held thereon by application of suction. The platen is raised with the pins in the outer most position and the platen is then rotated to cause the pins to move inwardly bringing them into contact with the article and sliding it over the surface of either the platen orthe chuck until it is centered thereon. In this position the vacuum chuck is again activated and the platen is moved to its lower position and rotated in the opposite direction to move the pins to their outer most position again.

When the article being handled is susceptible to damage if its underside contacts the surface of the platen, the top of the vacuum chuck is formed with a non-damaging surface and the platen is raised only to a level of which the pins can contact the periphery of the article, but the surface of the platen itself does not contact the article.

The apparatus is particularly adapted for the handling of substantially circular articles or, articles which have an upstanding circular feature. The apparatus may, for example, be used for centering articles of pottery or the like for accurate positioning of transfers or other decorative features, but it is of especial use in the centering of silicon wafers to enable them to be accurately positioned in mounting frames so that they can be transferred to cutting saws and other stages in the preparation of individual silicon chips.

Preferably the apparatus also includes a second vacuum chuck operating to engage the opposite surface of the article from that engged by the first chuckto enable the article to be lifted off the first chuck and transported away from the device.

The apparatus of the invention may, for example, be used in conjunction with the frame handling apparatus described in our Patent Application No:8225357 and provides a means for accurately transferring silicon wafers to the adhesive film carried on the frame.

The invention will now be described in greater detail by way of example with reference to the drawings in which Figure 1 is a plan view of one form of device according to the invention and Figure 2 is a side elevation of the device shown in Figure 1.

With reference to the drawings the centering device of the invention comprises an annular platen 1 and vacuum chuck 2 which passes through the aperture 3 in the centre of the annular platen. The vacuum chuck 2 is connectable by a vacuum line 4 to a source of vacuum (not shown). The platen, which is mounted for rotation in both clockwise and anti-clockwise directions by drive means (not shown) is supported on a fixed plate 5 having raised edge portions 6 which abut the underside of the platen 1 leaving a cavity 7 between the top of the plate 5 and the underside of the platen 1. The plate 5 is carried by a ram 8 for vertical movement.

The platen 1 has six slots 9 extending through its thickness. Each slot 9 extends along a cord of the platen 1 from a point towards the circumference of the platen 1 to to terminate at a point towards the centre of the platen. In each slot 9 is a slidable pin 10 carried on a pivoted arm 11. The pivoted arm are mounted on the top surface of the plate 5 in the cavity 7 between the plate 5 and the platen 1. On rotation of the platen 1 relative to the fixed plate 5 the pins 10 are constrained to move along the slots 9, the movement being towards the centre of the platen 1 on clockwise rotation.

In operation of the device an article is fed on to the vacuum chuck 2 and held there by applied suction.

The plate 5 and platen 1 are then raised until the top surface of the platen 1 is slightly below the top of the vacuum chuck 2. The suction of the vacuum chuck 2 is then switched off. The platen 1 is then rotated clockwise bringing the pins 10 towards the centre of the platen. The pins contact the edge of the article, which is merely resting on the chuck, and move it to a position in which it is accurately centred on the chuck. When the article is accurately centred, rotation is stopped, suction is re-applied to the vacuum chuck, the plate 5 and the platen 1 are retracted, optionally after anti-clockwise rotation of the platen to return the pins 10 to their outer most position and the article is in a desired position for further steps in a process which require accurate location of the article.

Preferably, the device to the platen is torque limited so that the pins cannot be forced so hard against the periphery of the article that they damage the article.

Claims (5)

1. Article centering apparatus comprising a vacuum chuck for attachment to a plane surface of an article, a rotatable annular platen coaxial with the chuck, the chuck passing through an aperture in the platen and the platen being arranged for movement between a first position in which the plane of its upper surface lies below that of the head of the chuck and a second position in which the plane of its upper surface is substantially coplaner with that of the head of the chuck, the platen having a plurality of equi-spaced non-radial slots extending through its thickness, each slot extending from a point towards the edge of the platen to a point towards the central aperture of the platen, there being an upstanding pin extending through each slot and mounted beneath the platen for movement along the slot on rotation of the platen, rotation of the platen in one direction moving the pins inwardly by the cam action of one edge of the slot on its associated pin and rotation of the platen in the opposite direction moving the pins outwardly by the cam action of the other edge of the slot on the pin, means for moving the platen between the first and second positions and means for rotating the platen in both clockwise and anticlockwise directions.

2. Apparatus according to claim 1, wherein the pins are carried on a pivoted link arranged at such a position and of such length that the pins are constrained to move along the slots in similar manner to the iris of a camera.

3. Apparatus according to Claim 1 or Claim 2, which includes a second vacuum chuck arranged to engage the opposite side of the article from that engaged in the first chuck to enable the article to be lifted from the first chuck and transported to a further processing step.

4. Apparatus according to any one of Claims 1 to 3, wherein rotation of the platen is effected by a torque-limited drive.

5. Apparatus according to Claim 1, substantially as described herein with reference to the drawings.