FIELD OF INVENTION

This invention relates to the stretching or expansion of sheet material that has formed therein a pre-determined array of slots, slits or other cut-outs.

BACKGROUND ART

For the sake of convenience, the invention will be described with reference to the stretching of an aluminium extrusion that consists of a plurality of spaced apart ribs inter-connected by and projecting either side of a web portion to provide a repeating H section pattern. However, it is to be understood that this is by way of example only and it is not to be construed as a limitation upon the scope of the invention.

DISCLOSURE OF THE INVENTION

It is an object of this invention to provide an improved machine for expanding pre-cut or slotted work- pieces such as aluminium extrusions which should ensure a regular expansion of the work-piece across the direction of expansion of the work-piece.

According to the invention there is provided a machine for expanding a pre-cut or slotted work-piece having a plurality of ribs spaced apart by web portions, said machine comprising a work table, expanding means mounted for movement across the work table and including expander bars adapted to engage selected ribs of the work-piece and means for expanding the expander bars from an initial position in which the expander bars are close enough together so that the work-piece can be located on the work table with the

expander bars positioned between adjacent ribs of the work¬ piece to a final position in which the expander bars have expanded the work-piece to a pre-determined extent.

According to another aspect of the invention there is provided a machine for expanding a work-piece comprising: (i) a frame, (ii) a work table supported by the frame, (iii) a fixed cross-bar mounted on the frame adjacent a longitudinal extent of the work table, (iv) a fixed claw mounted on the fixed cross-bar adapted to engage and hold one longitudinal extent of the work-piece, (v) a movable cross-bar mounted for transverse move¬ ment across the work table, (vi) a movable claw mounted on the movable cross-bar adapted to engage and hold the other . longitudinal extent of the work-piece, (vii) linkage means connected between the fixed and movable cross-bars and supporting a plurality of expander bars adapted to engage the work-piece at pre-selected positions thereacross, and, (viii) drive means for moving the movable cross-bar away from the fixed cross-bar so as to cause the linkage means to expand whereby the expander bars expand the work-piece.

Preferably, the machine has a plurality of fixed and moving claws which are arranged opposite one another so that the respective edges of the work-piece are gripped at pre¬ determined aligned locations. Furthermore, the linkage means may be supported on the work table by nylon stilts located beneath the point of connection of each expander bar with the linkage means.

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In a preferred embodiment of the invention, the fixed and moving claws are slidable along their respective cross¬ bars and the drive means includes an endless chain drive to which the movable cross-bar is adjustably connected. The linkage means may be in the form of a series of inter¬ connected pivotal levers which form a scissors set or lazy tongs.

In order that the invention may be more readily under¬ stood and put into practical effect, reference will now be made to the accompanying drawings in which:-

Fig. 1 is a diagrammatic plan view of a machine for expanding a work-piece according to one embodiment of the invention with the work-piece expanded. Fig. 2A is a view taken along line IIA of Fig. 1 with the work-piece in its unexpanded disposition.

Fig. 2B is a view similar to Fig. 2A with the work¬ piece in its expanded disposition. Fig. 3A is a plan view of the linkage means and expander bars of the machine shown in Fig. 1 when the work-piece is to be loaded onto the machine.

Fig. 3B is a view similar to Fig. 3A with the linkage means fully extended. Fig. 4A is a diagrammatic view showing the loading of a work-piece onto the expander bars, Fig. 4B is a view similar to Fig. 4A showing the unloading of an expanded work-piece from the expander bars. Fig. 5 is a partial side view of the mounting arrange¬ ment of the fixed claw on the fixed cross-bar, Fig. 6 is a partial side view showing the support arrangement for the expander bars and the linkage means on the work table, and. Fig. 7 is a partial perspective view of the machine shown in Figs. 1 to 6.

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As indicated in Figs 1, 2A and 2B, the machine for expanding a pre-slotted work-piece includes a main frame having legs 10, 10a interconnected by a bar 11 and which support a work table 12. The main frame carries a drive motor 13 having a driven sprocket 14 around which passes a chain drive 15. Adjacent leg 10a there is an idler sprocket 16 around which the chain 15 also passes.

Above the leg 10a there is a fixed cross-bar 17 which will be described with reference to Fig. 5. A movable cross-bar 18 is adjustably mounted on the chain 15 by connectors 19. The fixed cross-bar 17 has a fixed claw 20 and the movable cross-bar 18 has a movable claw 21 mounted thereon. The claws 20, 21 are pivotted by means of cylinders 22, 23 to engage and disengage the edges of a work-piece situated on the work table 12.

Extending between the cross-bars 17, 18 is a plurality of linkage means 24 each of which consists of a series of pivotally interconnected levers 24a which form a scissors set. The ends of the linkage means 2-4 are connected to mounting plates 25, 26 on the cross-bars 17, 18. At each pivot point, the linkage means is connected to a series of upstanding parallel expander bars 27 and at appropriate points there are downwardly depending nylon stilts 28 which support the linkage 24 on the work table 12.

In the initial position of the movable cross-bar 18, the linkage 24 is closed so that the expander bars 27 are close together as shown in Figs 3A and 4A. When the movable cross-bar 18 is moved away from the fixed cross-bar 17 by the chain drive 15, the linkage 24 opens to separate the expander bars 27 as shown in Figs 3B, 4B and 6.

In this instance, the work-piece 30 consists of a plurality of ribs 31 spaced apart by web portions 32 which define a repeating H-section pattern. The other extremities

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of the ribs 31 have beads 33 which can be shaped to help retain the work-piece 30 on the expander bars 27. The work- piece 30 has formed therein an array of slots 34 which when the work-piece 30 is expanded become openings 35 as shown in Figs 1 and 4B.

As can be seen in Fig. 5 in the case of the fixed claw 20, the claws 20, 21 are slidably mounted on their cross¬ bars 17, 18. The cross-bar 17 has a rail 40 on which is mounted a carriage 41 that is locked thereto by locking bolt 42. The carriage 41 has a pivotal mounting 43 for the claw 20. At the opposite side of the carriage 41 there is a cylinder 22 mounted at an axis 44 which is arranged to raise and lower the jaw 45 of the claw 20 out of and in to engage with the rib 31 of the work-piece 30.

Appropriate control systems are provided to regulate the movement of the cross bar 18 and these include limit switches 50, 51 which are operated by abutments 52, 53 on the chain 15. A brake is associated with the chain drive to prevent over-run at the end of a stroke of the cross bar 18.

Various modifications may be made in details of design and construction without departing from the scope and ambit of the invention.

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