GB2049503A - Pallet presenting apparatus - Google Patents

Abstract

An apparatus is provided for cyclically presenting pallets for the performance of operations on workpieces carried by the pallets comprising a pallet carrier, indexing drive means arranged to advance the pallets on the carrier stepwise such that the pallets follow the same endless path and are brought successively to a transfer position on the path, and a shuttle mechanism operative to carry the pallets individually between the transfer position and a machining region. Operation of the shuttle mechanism is synchronised with the indexing of the drive means such that, in use, each pallet will in turn be moved along said path by the drive means to said transfer position, be displaced to said machining region and subsequently returned to said transfer position by the shuttle mechanism in both cases, and then continue to be moved along said path by the indexing drive means. <IMAGE>

Description

SPECIFICATION Pallet presenting apparatus This invention relates to apparatus for cyclically presenting pallets for the performance of operations on workpieces thereon, and is intended to be used in particular, though not exclusively, in conjunction with a machine tool, so asto presentworkpieces to a selected tool in the driving spindle of the machine tool.

According to the invention there is provided apparatus for cyclically presenting pal lets for the performance of operations on workpieces thereon, comprising a carrier arrangement on which the pallets may be carried in a succession of positions,.

indexing driving means arranged to advance the pallets on the carrier stepwise such that the pallets follow the same endless path and are brought one-by-one by the stepwise advancements to a transfer position on the path, and a shuttle mechanism operative to carry the pallets individually between the transfer position and a region in which the workpiece on the pallet concerned can be machined, the operation of the shuttle mechanism being-synchronised with the indexing of the drive means such that, in use, in a plurality of stepwise advancements, each pallet will in turn be moved along said path by the drive means to said transfer position, be displaced to said machining region and subsequently returned to said transfer position by the shuttle mechanism in both cases, and then continue to be moved along said path by the indexing drive means.

In one construction, the carrier arrangement comprises a horizontal base table structure, on which the pallets can run, guided by rails on the table structure so as to follow said path, and an indexing plate mounted above said table for rotation about an upright axis and formed about its peripheral edge with cut-outs for respectively accommodating the pallets so that as, in use, the plate is rotated stepwise about said upright axis by the drive means, the plate in turn advances the pallets stepwise along said path. Conveniently, the drive means takes the form of a reversing drive and a one-way clutch connected between the reversing drive and the indexing plate.

The reversing drive can comprise a double-acting cylinder slidably mounted on a stationary piston rod and linear-to-rotary drive means for converting the reciprocating action of the cylinder to a reversing rotary drive to the clutch.

For a better understanding of the invention and to show how the same may be carried into effect.

Reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a plan view of a machine tool provided with apparatus for cyclically presenting pallets for machining of workpieces thereon; Figure 2 is a side elevation in the direction indicated by the arrow II in Figure 1; Figures 3 and 4 are partial vertical sectional views, on an enlarged scale, taken along the lines lli-lil and lV-lV, respectively, of Figure 1; and Figure 5 is an underside view of a pallet.

Referring to Figures 1 and 2, there is shown a machine tool comprising a base structure 1 and upstanding.tower 2 carrying on one side thereof a magazine 3 for storing in individual storage posi tions a plurality of different machining tools 4, a powered machining spindle 5 which can be lowered relatively to the tower for carrying out machining operations on the workpieces, and tool transfer means, including a transfer arm 6 and tool change arm 7, for individually transferring any selected tool in the magazine to the machining spindle (when in an upper, tool change, position) while simultaneous ly returning the tool previously in the spindle to a vacant position in the magazine.

The machinatool is provided with apparatus for cyclically presenting the pallets to the machine tool in a machining region to enable workpieces on the pallets to be machined by selected tools in the machining.spindle 5. This pallet presenting appar atus is indicated generally at 8 and comprises a bed 9 which can be part of, or be secured to, the base structure 1, this bed extending generally parallel to the axis of the spindle-5. Supported above the bed 9 on supports 10 is a stationary horizontal base table structure 11which is circular and.has supported.

thereon several bail castors 38 (Fi.gures 1 and 4) on which circular pallets 14 can run, the movement of the pallets being guided by inner and outer rails 12, 13, - so that the pallets can all travel along the same circular path about the upright central axis of the.

table structure 11. Centred on this axis is a horizontal indexing plate 15-which is mounted for rotation about a vertical bearing column 16 and is formed with substantlaljy semicircular cut-outs around. its peripheral edge so as to accommodate in each cut-out a pallet 14. A gear quadrant 17 is connected, via a one-way clutch 18, so that it can rotatably drive the indexing plate 15, the gear quadrant being in operative. engagement with a gear rack 19 secured along the side of a double-acting hydraulic cylinder 20 which slides on a stationary piston rod 21 and is mounted within the table structure 11.Afull stroke of the cylinder in one direction indexes the plate 15 through 90 , a hydralically-operated shot pin 22 (Figure 4) being used for precise control of the end position of the. indexing plate 1 as it completes each rotational advancement. Of course, during each stroke of the cylinder 20 in the opposite direction, the clutch freewheels.

The pallet presenting apparatus 8 additionally incorporates a shuttle carriage 26 which runs on rails 27 on the bed 9 so that the carriage can be moved towards and away from the tower 2. In one possible arrangement, carriage displacement can be brought about by a double-acting hydraulic piston/cylinder arrangement (not shown).

The carriage supports a horizontal table 28 whose angular position about an upright axis 29 can be adjusted to a desired new position as the carriage is moved along.the rails. 27. Conveniently, when using a piston/cylinder arrangement to displace the shuttle carriage, any desired rotation of the table 28 can be brought about by engaging a clutch-operated drive which-incorporates a drive sprocket permanently in engagement with a stationary rack.extending para llel to the rails 27. Once the carriage has been displaced sufficiently to bring about the desired change in angular position of the table 8, the clutch is disengaged.

Extending upwardly from the table 28 is a central column 30 to which is secured a piston 31, around which is slidably mounted a double-acting cylinder 32. The upper part of this cylinder is provided with shaped portions serving as arcuate slide rails 37 on which the pallet 14 can slide.

Referring now to Figures 3, 4 and 5, it can be seen that each pallet has on its underside two guide portions 23 which provide arcuate lateral guide surfaces 24 which are centred about a common axis.

The radii of curvature of the guide surfaces 24 correspond respectively to the inner and outer radii of the inner and outer slide rails 37 respectively on the carriage to enable the pallets 14to run on the rails. The pallets are held captive on these rails by means of radially positioned clampling plates 25 which project beyond the edges of the guide surfaces 24. The edge faces of the clamping plates serve as guide faces 39 to guide the pallets along the rails 12, 13 on the table structure. The significance this arrangement is that it enables any pallet to be removed from the rails 12, so as to permit a desired pallet to replace the removed pallet.

As is clearly shown in Figure 3, when the cylinder 32 is in its lowermost position, upstanding pegs 33 on the table 28 are located within appropriately shaped apertures 34 in the clamping plate 25 so as to clamp the pallet 14 to the table 28. In the uppermost cylinder position, however, the pallet 14 is positioned with its clamping plates 25 well clear of the pegs 33.

Facility is also provided for the table 28 to be rigidly clamped to the carriage 26. A suitable clamping device involves the use of concentrically mounted gear wheels having facing teeth, one of which is rigidly fixed to the carriage 26 and the other of which is secured to the underside of the table 28 and can be brought into engagement with the fixed teeth.

When the carriage is at the end of its travel, so as to be farthest away from the tower 2 or machining tool in the spindle 5, the rails 27 supporting the pallet 14 are aligned with the rails on the base table 11. The pallet 14 on the carriage is then in a pallet transfer position. By advancing the carriage away from the transfer position along the rails 27, the workpiece on the pallet can be brought into a machining region so that the machining tool in the spindle 5, when in a lowered machining position towards the bottom of its travel, will perform the required machining operation on the workpiece.

Operation of the pallet presenting apparatus will now be readily apparent. For convenience of explanation the sequence of events following the point in the operating cycle shown in Figure 1 will now be described, in which the indexing plate 15 has just indexed a pallet 14 into the pallet transfer position.

At this stage the table 28 is clamped to the shuttle carriage and the cylinder 32 is fully raised. Then, the cylinder 32 is lowered to clamp the pallet to the table 28 which is then released from the carriage, following which the carriage 26 is displaced along the rails 27 towards the machine tool and into the machining region. If need be, the angular position of the carriage 28 is adjusted during the carriage displacement in the manner described above. Of course, irrespective of this, it is essential that the table 28 be clamped to the shuttle carriage at least before the machining operation takes place.

When machining has been completed, the carriage returns along the rails 27 to the position shown in Figure 1 (any necessary adjustment in the angular position of the table 28 being made during the return travel of the carriage) and then the cylinder 32 is raised to align the rails 37 with the rails 12, 13 on the base table 11. Next the indexing plate 15 advances through 90to move the used pallet off the carriage and bring the next pallet into the pallet transfer position. The above-described sequence of operational steps then follows for the new pallet.

During each dwell period ofthe indexing plate 15, the other pallets can be prepared ready for machining by clamping workpieces to them in the appropriate positions or by replacing pallets with further pallets containing new workpieces.

The whole sequence of operational steps, and in particular the synchronisation between the indexing of the plate 15 and the shuttle movement of the carriage (all in relation to the operating cycle of the machine tool) are controlled by a suitable control unit, for example a computer (not shown).

It is to be noted that as the outsides of the pallets are round, rotation of the pallets on the shuttle carriage can start to take place as soon as the pallet is clamped to the table 28 and this accordingly minimises any loss of capacity.

Claims (11)

1. Apparatus for cyclically presenting pallets for the performance of operations on workpieces positioned on the-pallets, which apparatus comprises (1) a carrier arrangement on which the pallets may be carried in a succession of positions, (2) indexing drive means arranged to advance the pallets on the carrier stepwise such that the pallets follow the same endless path and are brought one-by-one by the stepwise advancements to a transfer position on the path, and (3) a shuttle mechanism operative to carry the pallets individually between the transfer position and a region in which the workpiece on the pallet concerned can be machined, the apparatus being adapted so that operation of the shuttle mechanism is synchronised with the indexing of the drive means such that, in use, in a plurality of stepwise advancements, each pallet will in turn be moved along said path by the drive means to said transfer position, be displaced to said machining region and subsequently returned to said transfer position by the shuttle mechanism in both cases, and then continue to be moved along said path by the indexing drive means.

2. Apparatus as claimed in claim 1, wherein the carrier arrangement comprises (a) a horizontal base table structure, on which the pallets can run, guided by rails on the table structure so as to follow said path, and (b) an indexing plate mounted above said table for rotation about an upright axis and formed about its periphery with cut-outs for accommodating the pallets, the indexing plate being operatively engaged, in use, by the indexing drive means so that as the plate is rotated stepwise about said upright axis by the drive means, the plate in turn advances the pallets stepwise along said path.

3. Apparatus as claimed in claim 2, wherein the indexing drive means comprises a reversing drive and a one-way clutch connected between the'reversing drive and the indexing plate.

4. Apparatus as claimed in claim 3, wherein the reversing drive comprises a double-acting cylinder slidably mounted on a stationary piston rod and linear-to-rotary drive means for converting the reciprocating action of the cylinder to a reversing rotary drive to the clutch.

5. Apparatus as claimed in claim 2,3 or 4, wherein the apparatus includes (a) a magazine for housing a plurality of different machining tools, and (b) a machining spindle and tool transfer means for individually transferring any selected tool in the magazine to the machining spindle while simultaneously returning the tool previously in the spindle to a vacant position in the magazine.

6. Apparatus as claimed in claim 2,3,4 or 5, wherein the base table structure is circular and the endless path followed by the pallets is also circular.

7. Apparatus as claimed in claim 6, wherein the indexing drive means is arranged to advance the pallets through 90 of their circular path at each of the stepwise advancements.

8. Apparatus as claimed in any preceding claim, wherein the shuttle mechanism includes a shuttle carriage running on rails, the carriage displacement being effected by a double-acting hydraulic piston/ cylinder arrangement.

9. Apparatus as claimed in claim 8, wherein the shuttle carriage supports a horizontal table whose angular position about an upright axis can be adjusted by the action of a clutch-operated drive which incorporates a drive sprocket permanently in engagement with a stationary rack extending para llel with said rails, the said horizontal table serving to carry a respective one of the pallets between the transfer position and the machining region of the apparatus.

10. Apparatus for cyclically presenting pallets for the performance of operations on workpieces posi tioned on the pallets, substantially as hereinbefore described with reference to, and as illustrated in, Figures 1 to 4 of the accompanying drawings.

11. A pallet for use with apparatus as claimed in any preceding claim, the pallet being substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.