GB2082095A - Pallet for workpieces - Google Patents

Abstract

A pallet for conveying and storing workpieces, and intended for use with automatic workpiece handling and loading facilities of machine tools comprises an elongated metal frame 1 in which plastics inserts 2 are disposed. Each insert 2 is formed with one or more apertures 3 for receiving the workpieces. Frame 1 is formed with a longitudinal guide channel 7 which co- operates with a guide rail or bar of the workpiece loading facility. <IMAGE>

Description

SPECIFICATION Pallet for workpieces This invention relates to a pallet for conveying and storing workpieces, more particularly for automatic workpiece feeders of machine tools.

Swiss Patent Specification No. 570,237 discloses a facility for supplying and removing workpiece pallets of this kind. The workpieces in this facility are positioned with a particular orientation depending on production engineering requirements and are supplied on the pallet in this orientation to the loading and unloading device of a machine tool. One workpiece at a time is removed from the pallet, treated, then returned to the pallet at the same place and in the same orientation. The pallets are placed parallel to one another and at uniform intervals on a conveyor and are advanced stepwise by means of a timer. The facility has automatic gripping means for removing the individual pallets from the conveyor and for pushing the pallet down from a guide bar.

Means are also provided to supply the pallet to the loading and unloading device of the machine tool, for cycling the pallet through the device and for returning the workpiece-containing pallet to the conveying element or the guide rail or bar thereon.

The pallet disclosed by Swiss Patent Specification No. 570,237 is a solid member made of a wearresistant plastics. A high degree of resistance to wear is necessary more particularly because of the severe stressing to which the workpiece-receiving apertures are subject, such apertures having to withstand a number of workpiece-introducing cycles. To obviate or at least greatly reduce distortion of plastics pallets in production as, indeed, with all plastics products, wall thicknesses must as far as possible be identical and there must be no accumulation of plastics material in any particular part of the pallet.However, since the workpiece-receiving apertures vary in size considerably, pallets must be produced for each individual aperture size and it is necessary for pallets with different aperture sizes to differ from one another not only as regards these apertures, but also in wall thicknesses etc. in other regions, i.e. the pallets must be formed with the necessary material recesses, to avoid distortion of the pallets in production. It is therefore not sufficient to utilise an injection mould having interchangeable inserts to define different workpiece-receiving apertures and, when a pallet with different apertures is reqiured, to change only those inserts of the injection mould which are necessary for the workpiecereceiving apertures. Instead, a separate injection mould is required for each pallet. The production of such injection moulds is very expensive.

It is an object of the invention to obviate these disadvantages i.e. the expensive process of producing injection moulds for whole pallets and the unavoidable risk of distortion of the pallet so moulded.

In accordance with the invention, there is provided a pallet for conveying and storing workpieces, the pallet comprising an elongated metal frame and, disposed therein, plastics inserts formed with apertures for receiving workpieces, the frame being formed along its length with a guide groove.

An embodiment of the invention is described below by way of example with reference to the accompanying drawings wherein: Figure 1 is a perspective view partly exploded of a pallet embodying the invention, Figure 2 is a side elevation view, partly in section, of the pallet of Figure 1, Figure 3 is a view in section on the line A-A of Figure 2, Figure 4 is a plan view of the pallet, Figure 5 is a side elevation view of one of the plastics inserts incorporated in the pallet, Figure 6 is an end elevation view of the plastics insert of Figure 5, and Figure 7 is a plan view of the plastics insert.

In the embodiment to be described with reference to the drawings, the pallet is adapted to receive along its length a single row of workpieces each arranged in a predetermined position and orientation. The pallet comprises a frame 1 and, in a number which depends upon the pallet length, plastics inserts 2 each formed with an aperture 3 adapted to the workpiece concerned; in the present case each aperture 3 is square. The apertures 3 all have exactly the same orientation since they are intended for an oriented positioning of the workpieces. For the workpieces to be returned to the pallet in the same orientation as that in which they left it, the machine tool loading and unloading device must return the workpieces to the pallet in their original orientation.The frame 1 has the general form of an inverted channel-section member, providing a generally horizontal top wall and parallel longitudinal side walls extending downwardly therefrom.

The between-centres intervals T of the inserts 2, i.e. of the apertures 3, lengthwise of the pallet are determined by workpiece shape and diameter. The frame 1 is formed in at least one of its two longitudinal sides with grooves 4 which can, for example, be vertical grooves which are V-shaped in cross section and which enable the pallets to be engaged by corresponding gripping means of the machine tool for cyling the pallets through the workpiece loading and unloading station or for supplying and removing the pallets.For the sake of co-operation with other pallet moving and cycling facilities, the frame 1 can be formed at a suitable place on one of the two longitudinal sides or on both such sides or on the underside with additional recesses 5 which have a different shape from the grooves 4 e.g. which take the form of rectangular notches in the lower edge of the respective side wall, with each notch providing a vertical abutment surface 6 facing in the longitudinal direction. The spacing of the notches 5 can be the same as the spacing of the grooves 4 - i.e. it can coincide with the centre lines through the apertures 3; however, the spacings of the grooves 4 and notches 5 can be other than the spacing T of the apertures 3.

The frame 1, which to obviate distortion is made of a rigid material such as metal sheet or plate, diecast metal or the like, provides on its underside a longitudinal downwardly open groove or channel 7 which serves as a guide in movement of the pallet in a very wide variety of different facilities used for supplying such pallets to and removing such pallets from a machine tool and for moving such pallets through a machine tool.

The inserts 2 are made of a low-wear plastics, so that, because the plastics is particularly resistant to abrasion, the apertures 3, which are subject to heavy abrasion as a resultoftheworkpieces being moved in and out of them frequently, have a long working life - i.e. their dimensions remain satisfactory for a prolonged period of time. The initial costs for an injection mould for such a plastics insert are, because of the reduced dimensions thereof, much lower than the initial cost of an injection mould for a complete plastics pallet.

To receive the plastics inserts 2, the frame 1 is formed with appropriately shaped apertures 11 each, in effect, formed by removal of portions of the top wall and longitudinal sides of the inverted channel memberwhichformstheframe 1. Each aperture 11 is bounded by end edge surfaces 8 and 9 and by bottom edge surfaces 10. Each surface 8, 9 has a tongue 12 projecting therefrom as an extension of the top wall of the frame and which tongue co-operates with a part of the respective plastics insert 2 to form a snap fastening and preventthe insert from dropping out.

Each insert has two parallel vertical side walls which define opposite sides of the respective rectangular aperture, and has two opposing vertical end walls each spanning the space between the side walls and defining a respective end of the respective aperture 3. The side walls, at their opposite ends, project slightly beyond the respective end walls, to define, at opposite ends of the insert, respective recesses for the respective tongue 12.

Each insert is open at the bottom, i.e. the apertures 3 extend right through the inserts.

For minimum distortion of the inserts 2 during manufacture, they should be of a size and design such that the thickness M and N of the end and side walls respectively are equal to one another over the whole extent of the apertures 3, a feature which can best be seen in Figure 7.

The inserts 2 have a shape exactly mating with the apertures 11 in frame 1. End surfaces 13 and 14 of inserts 2 each have a triangular, barb-like projection 15 which, when the insert 2 is pressed into the frame 1, from above, is pressed back by the respective tongue 12, to spring back after the insert 2 has been pressed right in and engage behind the respective tongue 12. The projections 15 engage, via abutment surfaces 16 thereof, with abutment surfaces 17 of the respective tongues 12 when the inserts are fully inserted. This is how the inserts 2 are retained in the frame 1. As a rule, no provision is made for removing the inserts 2 from the frame 1 once they have been fitted therein; however, should this be necessary, a tool such as pliers could be used to disengage the projections 15 from the projections 12.

Disposed on the underside of each insert 2 are two webs 18 which are formed as downward extensions of the end walls and which are an exact fit between the longitudinal side walls of the frame 7, i.e. the webs 18 span the channel 7 in frame 1 and their end faces engage with the inner sides of the longitudinal walls of frame 1. Each insert 2 is therefore secured transversely of the frame 1. The webs 18, which extend downwardly into groove 7 in frame 1, also serve as a support member for engagement with the rails of the guiding means of a machine used for supporting and moving the pallets. Consequently, the surfaces most subject to abrasion when the pallets are moved take the form of a low-friction and wear-resistant combination of metal and plastics.

To obviate excessive local accumulations of plastics material on the insert 2, parts 19 shown in chain-dotted lines can be omitted.

The apertures 3 in the inserts 2 are continuous apertures which extend to groove 7 in frame 1. This is necessary to enable all dirt to discharge, more particularly when the pallets are being cleaned. So that the workpieces introduced into the inserts 2 do not drop through but can take up an axially located position, each insert 2 has two lugs 20 which extend into the apertures 3 from the respective end walls.

When the workpieces to be received are of reduced diameter, the inserts 2 can be formed with two or more workpiece-receiving apertures; this feature is not shown in the drawings.

Claims (15)

1. A pallet for conveying and storing workpieces, the pallet comprising an elongated metal frame and, disposed therein, plastics inserts formed with apertures for receiving workpieces, the frame being formed along its length with a guide groove.

2. A pallet according to claim 1, in which the plastics inserts are a snap-in fit in respective recesses in the frame.

3. A pallet according to claim 2, in which the inserts have projections which engage behind associated projecting parts on the frame, said projections and the associated projecting parts forming snap fastenings.

4. A pallet according to claim 1, which has formations engageable by handling means for handling the pallet.

5. A pallet according to claim 4, in which said formations comprise transverse grooves in the metal frame.

6. A pallet according to claim 4 or claim Sin which said formations comprise recesses in the metal frame.

7. A pallet according to claims 4, 5 or 6 in which said formations comprise abutments on the metal frame.

8. A pallet according to any preceding claim, in which each insert has at the bottom thereof, at least one web which extends into the longitudinal groove in the frame, the web being adapted to bear, as a low-friction and wear-resistant element, on a guide rail or bar for the pallet.

9. A pallet according to any preceding claim, in which each insert is formed with a plurality of workpiece-receiving apertures.

10. A pallet according to any preceding claim, in which the frame is made of metal sheet or plate.

11. A pallet according to any of claims 1 to 9 in which the frame is a die-casting.

12. A pallet according to any preceding claim, in which the inserts are formed with recesses in the material to obviate accumulations of material.

13. A pallet according to any preceding claim, in which the workpiece-receiving apertures in the inserts are continuous and extend to the longitudinal groove in the frame, each said aperture having at least one lug extending into the apertures to form a bottom support for an introduced workpiece.

14. A pallet for conveying and storing workpieces, substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.

15. Any novel feature or combination of features described herein.