The present invention relates to cutter devices, and more particularly to cutter devices for cutting board or sheet material of card, paper, or plastics, or laminates of card or paper with a plastics core.

Foam core board, which consists of a laminate of thin card outer layers which sandwich a foam plastics core, is often used as a lightweight, but rigid, substrate onto which posters or photographs may be mounted. Conventionally, foam core board is cut to size using a hand held knife and a straight edge as existing mechεnical cutting machines tend to apply excessive localised pressure to the board which results in crushing of the core. Similar problems arise with core flute board formed from a plastics such as polypropylene. ^" Core flute board can be cut satisfactorily with a guillotine, but

guillotines capable of handling large size sheets, typically 8ft by 4ft, are very expensive and would be beyond the reach of most small businesses of the type which usually handle mounting of photographs and posters.

A requirement accordingly exists for a relatively inexpensive and simple mechanical cutter device for cutting sheets of foam core and other board having low compressive strength.

According to the present invention there is provided a cutter device for cutting sheet material, comprising a support surface fcr the sheet material, a substantially rigid clamping plate mounted for movement relative to the support surface between a position remote from the support surface and a position adjacent the support surface to clamp sheet material against the support surface, a rectilinear guide extending substantially parallel to the support surface at least when the clamping plate is in its clamping position, and a cutter head movable along the guide whereby to cut sheet 'material clamped by the clamping plate.

In one embodiment, the clamping plate and the guide form part of a clamping assembly which is movable relative to the support surface. The clamping assembly is in the form of a clamping bar supported at each end by pivotal links to form one arm of a parallelogram linkage whereby the bar is movable parallel to itself towards and away from the support surface. The bar is retained in its clamping position under the weight of the clamping assembly, with movement of the bar being effected manually. In another embodiment, the clamping plate is displaceable towards and away from the support

surface by fluid-operated means, for example pneumatic cylinders. In this latter embodiment, the cutter head may be driven along the guide by fluid-operated means, for example a rodless pneumatic cylinder.

Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings in which:-

Figure 1 is a side view of the cutter device in accordance with the first embodiment of the invention;

Figure 2 is a part sectional view along line A-A of Figure 1;

Figure 3 is a side view of the cutter device in accordance with the second embodiment of the invention;

Figure 4 is a part sectional view along line B-B of Figure 3;

Figure 5 is a fragmentary, enlarged, side view of a clamping bar of the device of Figure 3;

Figure 6 is a pneumatic circuit used in the device of Figure 3;

Figure 7 is a first side view of a modified form of cutting head;

Figure 8 is a second side view of the cutting head shown in Figure 7;

Figure 9 is a first side view of another modified form of cutting head; ' and

Figure 10 is a second side view of the cutting head shown in Figure 9.

The cutter device shovyn in Figures 1 and 2 of the drawings comprise a planar support surface 10 above which is a clamping bar 12. The clamping bar 12 has at its underside an elongate planar clamping

plate 14 parallel to the support surface 10 and extending across the support surface. The clamping bar 12 is supported at each end by parallel pivotal links 16a, 16b each hinged at a lower end to structure rigid with the support surface and at an upper end to the clamping bar 12. The clamping bar 12 thereby forms one arm of a parallelogram linkage and can move parallel to the clamping plate 14 from a first, raised, position remote from the support surface 10 to a second, lowered, position adjacent to the support surface 10. Such movement is effected manually by the means of a handle 15 attached to one end of the bar. The movement cf the bar from its first, remote, position to its second, clamping, position effects pivotal movement of the links 16a, 16b from a stable position in which the bar is supported away from the support surface 10, through a centre position, to a clamping position in which the self weight of the bar applies the clamping pressure through the clamping plate 14.

The clamping bar 12 has, above, and parallel to, the clamping plate 14 a rectilinear guide track 17 for a cutter head 18, the head 18 being mounted from movement along the track 17 by suitable bearings. The cutter head 18 is fitted with a knife blade 20 which sits in a seat in a base plate of the head. The seat is magnetised to allow for easy relocation of the knife blade 20. The knife blade 20 is rigidly, but removably, supported in the cutter head 18 by a bolted plate, with a cutting edge of the blade 20 projecting downwardly past an adjacent longitudinal edge of the clamping plate 14 which defines a cutting line. The support surface 10 directly below the knife blade 20 is slotted to

receive the lower end portion of the knife blade 20 in the lowered position of the clamping bar.

In readiness for a cutting operation, a piece of sheet material such a foam core board is positioned on the support surface beneath the clamping bar 12 with the bar in its stable raised position, and the board is adjusted relative to the longitudinal edge of the clamping plate 14. The clamping bar 12 is lowered by means of the handle 15 so that the clamping plate 14 moves downwardly onto the sheet material and clamps the material across its width, the self weight of the clamping bar 12 being sufficient to retain the sheet in position during the cutting operation. The cutter head 18 is then manually driven along the track 17 and the knife blade 20 travels across the sheet thereby cutting the sheet. The clamping bar 12 is fitted with stops 22a, 22b at either end of the track 17 to limit the travel of the cutting head 18. The ur.derside of the clamping plate 14 may be faced with a felt or other soft material to prevent scratching of the sheet being cut and part of the plate may be transparent to facilitate accurate placement of the sheet.

The clamping bar 12 applies via the clamping plate 14 a uniform clamping pressure across the sheet which is sufficient to hold the sheet during cutting but does not damage the structure of the sheet. Likewise, the knife blade 20 with inclines downwardly and rearwardly in the direction of travel cuts the sheet without damage. Fine adjustment of the position of the sheet prior to cutting can be made by reducing the clamping pressure by slightly raising the clamping bar.

The knife blade 20 may be replaced by a roller cutting wheel to cut paper and photographic sheet. The roller cutting wheel co-operates with an edge of the slot in the support surface to provide a scissor action, the edge being of hardened steel for this purpose. The cutter wheel is attached to the cutter head by a screw fitting which passes through the centre of the wheel and into the head to support the wheel for rotation about a substantially horizontal axis.

The device thus described can be constructed with a clamping bar of any length so as to be usable with any required width of sheet.

The embodiment of the cutter device shown in Figures 3 to 6 comprises a support surface 30 above which is mounted a clamping bar 32 having an elongate planar clamping plate 34 at its underside, the plate normally being parallel to the support surface 30. The clamping bar 32 is mounted at each end in vertical guides 36 for movement between a raised position in which the clamping plate 34 is spaced from the support surface 30 and a lowered clamping position is which the clamping plate 34 is adjacent to the support surface 30. Movement of the clamping bar 32 is effected by means of fluid cylinders 35 (Figures 5 and 6) attached to fixed structure beneath the support surface 30, each cylinder being located adjacent to one of the guides 36 with its piston rod 35a extending vertically and being attached to the adjacent end of the clamping bε.r 32.

A power-driven cutter head 38 is mounted for movement along a rectilinear guide track fixedly mounted above the support surface 30 and the clamping plate 34, the track being parallel to the support surface and to an adjacent longitudinal edge of the

clamping plate 34. The cutter head 38 carries a knife blade 40 which projects downwardly past the adjacent edge of the clamping plate 34, the lower end of the blade 40 engaging in a slot 42 in the support surface in the lowered position of the clamping bar 32 . The cutting edge of the blade 40 is rearwardly inclined and the blade mounting is as described in connection with the previous embodiment.

Preferably, the track for the cutter head 38 is formed by the body of a rodless fluid cylinder 41 mounted on fixed structure above the support surface 30, the cutter head 38 being attached to a shuttle movable along the cylinder body upon actuation of the cylinder 41.

Advantageously, the two fluid cylinders 35 which effect the vertical movement of the clamping bar 32 are individually controllable so that one end of the clamping plate 34 can be lowered into a clamping position while the other end remains raised. In this condition, the plate 34 lightly clamps an edge of the sheet to permit adjustment of the position of the sheet relative to the cutting line. When the sheet is in its correct position for cutting, the other cylinder is actuated so as to lower the other end of the clamping plate 34 whereby the plate firmly clamps the sheet against the support surface prior to cutting. To permit this differential movement of the two ends of the clamping plate 34, the piston rods 35a cf the two cylinders 35 are coupled to the clamping bar 32 by swivel couplings 35d (Figure 5), the separate actuation of the two cylinders causing the clamping bar 32 to move with a swivelling motion about a horizontal axis at the point of connection of the piston rod 35a to the

bar. The ends of the clamping bar 32 in the guides 36 are curved in order to accommodate this swivelling movement as shown schematically in Figure 5.

In an alternative embodiment, differential movement of the ends of the clamping plate 34 is produced by mounting the end portions of the clamping plate 34 in lifting blocks. The lifting blocks are grooved on their top face so as to be able to engage the underside of the clamping plate 34 and the bottom face of each lifting block is adapted to couple with the piston rod of the cylinder 35. The coupling between each piston rod and each lifting block is such that it enables differential movement of each end of the clamping plate 34 to achieve the effects described above.

When the sheet has been accurately clamped, a switch 50 is actuated by the operator in order to actuate the rodless driving cylinder 41 whereby.the cutter head 38 is driven along the track from a starting position adjacent to one end of the clamping bar to a position adjacent the other end of the bar, the knife 40 cutting the sheet material beneath the clamping plate 34 during this movement. Upon reaching the other end of the bar, the head engages a microswitch 52 which acts to reverse the fluid flow to the rodless cylinder to return the head 38 to its starting position.

Preferably, the fluid cylinders 35 controlling the clamping bar 32. and the rodless cylinder 41 driving the cutter head 38 are pneumatic cylinders which may be operated by a self-contained compressor unit built into the cutter device. A suitable pneumatic circuit for these components are shown in Figure 6. In this Figure, individual manual

controls for the clamping bar cylinders are designated 56a, 56b. The circuit is so arranged that the switch 50 cannot actuate the cylinder 41 until both clamping bar cylinders 35 have been actuated to lower the clamping bar 32 into full clamping engagement with the sheet being cut.

Figures 7 to 10 illustrate modified cutter heads 38 for use with the cutter device shown in Figures 3 to 6. Figure 7 shows a cutter head 38 wherein the rearwardly inclined knife blade 40 sits in a milled seat. The knife blade 40 is rigidly, but removably, held in position by slide plate 60. Slide plate 60 is secured to the cutter head 38 by a bolt 62 which when loosened can slide within horizontal groove 64. This enables the slide plate 60 to be slid away from the knife blade 40 to thereby allow access to the knife blade 40. The knife blade 40 projects through safety plate €6 which is secured to the underside of the cutter head. Safety plate 66 prevents contact with the knife blade 40 when the cutter head 38 is mounted for use on the shuttle of the cylinder 41.

Figure 8 illustrates t cutter head 38 with a rotary cutting wheel for cutting paper and other thin sheet material. The rotary cutting wheel is mounted for rotating on stud 68 and comprises cutting wheel 70 and rubber pressure roller 72. Cutting wheel 70 co-operates with the hardened edge 44 of the slot 42 to provide a scissor cutting action for cutting paper and other thin sheet material. Rubber pressure roller 72 runs along the upper surface of the clamping plate 34 during the cutting operation to apply localised increased pressure ensuring that the

I sheet being cut does not move. The cutting wheel 70

and rubber pressure roller 72 project through the safety plate 66. The cutter heads 38 shown in Figures 7 and 8 can be used interchangeably on the cutting device by simply mounting the cutter heads 38 to the shuttle of the rodless cylinder 41 as shown schematically in Figure 4.

This embodiment of the invention provides a relatively inexpensive power-driven cutting device for cutting foam board and other board and sheet material. The device can be fabricated with a clamping bar of any required length in order to accommodate available widths of sheet or board.