This invention relates to machines for cutting card, board, and like materials. An example of the application of the invention is to cutting apparatus for providing hand-powered guided cutting or shearing of sheet materials, in which a sheet of material to be cut is offered up to the apparatus and a guided cutter is caused to travel lengthwise of guide means to effect cutting. Certain aspects of the invention relate particularly to the cutting of hardboard. Other aspects relate to such cutters for cutting other materials also.

In the case of such cutting apparatus for cutting or shearing hardboard, previous proposals for cutting this material include heavy duty guillotines, saws and the use of a fixed shearing edge cooperating with a series of progressively diverging shearing wheels defining a progressive shear path for the cut hardboard material.

The shortcomings of these prior proposals in relation to the cutting of hardboard are considerable. Thus, guillotines tend to be expensive and have limitations on their cut length. Moreover, they can be dangerous. On the other hand, saws create dust, tend to be noisy, and produce a cut edge which may not be satisfactory. However, perhaps the most significant disadvantage of these proposals lies in the fact that hardboard tends to be fractured and partially shattered at at least one of the edges when it is sheared, and this produces a very imperfect finish at the cut edges.

Accordingly, there is a considerable need for improvements in relation to these prior proposals, and an object of the present invention is to provide a method and apparatus offering such improvements in relation to one or

more of these matters, or generally.

According to the invention there is provided cutting apparatus as defined in claim 1 of the accompanying claims.

Turning now to a further aspect of the present invention, we consider the guidance of the travelling carriage in cutting apparatus of this kind.

Previous proposals for the guidance for travelling cutter carriages include the use of twin wedge arrangements. These however are subject to the significant shortcoming that the twisting effect of the cutting load generated in use, and the effect of manual loads applied to the carriage during use has the result that the carriage itself tends to twist and jam.

Other shortcomings of the prior art include difficulties in providing for adjustment of the clearances between the carriage and its guides, the need to be able to take up manufacturing tolerances in the guide members themselves, and a requirement for improvements generally.

An object of this aspect of the present invention is to provide cutting or shearing apparatus offering improvements in relation to one or more of the matters discussed above, or generally.

According to the invention there is provided cutting apparatus as defined in claim 1 of the accompanying claims.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which :

Fig 1 shows a side elevation view of cutting apparatus

according to the invention; and

Fig 2 shows a section through the apparatus of Fig 1 on the line II-II.

As shown in the drawings, cutting apparatus.10 is for providing hand-powered guided cutting or shearing of sheet materials, such as hardboard. The apparatus is of the kind in which a sheet of material to be cut is offered up to the apparatus 10, and a guided cutter 12 is caused to travel lengthwise of guide means 14 to effect cutting. Sheet materials support means 16 is provided for supporting a sheet of material to be cut in a desired reference position while cutting proceeds. This support means is indicated only diagrammatically since the general structure and arrangement of such means is well known in the art. It is intended that the apparatus of the present invention will be mounted so that the sheet material being cut lies in an upwardly extending plane, and the cutter 12 moves, and is guided, in an upwardly and downwardly extending direction. For example, the support means may be generally triangular in front elevation view, and adapted to be mounted on a wall at a location where material to be cut can easily be offered up to it. The guide means 14 extends vertically from the horizontal base of the triangle to its apex.

Cutter 12 comprises a travelling carriage 18 having cutting or shearing means 20 thereon. Guide means for carriage 18 comprises the guide means 14 which is connected to the sheet material support means 16 forming a stationary assembly with the carriage 18 travelling vertically with respect to it.

Guide means 14 comprises first and second guide means 22, 24 which are laterally spaced apart with respect to the lengthwise direction of cut "C".

First guide means 22 comprises a cylindrical block of ultra high molecular weight (UHMW) "polyfine" which is a low friction polymer. The block 26 is a free sliding fit within a corresponding cylindrical guide member 28 forming part of fixed guide means 14. The guide means is formed as an aluminium extrusion 30 on which carriage 18 is freely slidable. Tie rods 32 extend lengthwise of the primary guide means 14.

Cylindrical guide block 26 and guide 28 have a common axis 34 extending parallel to the direction of cut C.

A handle 36 is mounted on carriage 18 to apply cutting forces manually thereto.

Second guide means 24 is provided by planar surfaces 38 and 40 provided on a recessed portion 42 of guide means 14 and a bearing member 44 position-adjustably mounted on the outer portion 46 of carriage 18. Position adjustment ^" of bearing member 44 can be achieved by screw-threaded means (not shown) .

A bolt 48 having a knurled nut 50 mounts shearing means 20 on carriage 18. The bolt extends through a spacer 52 and is threadedly received in a mounting plate 54 forming part of carriage 18. A laterally extending flange 56 on plate 54 has a generally C-shaped integral end fitting 58 to receive a threaded rod 60 on which cylindrical bearing block 26 is a sliding fit. Threaded adjusters (not shown) enable the block 26 to be axially squeezed, whereby its polymeric material is distorted-to take up any clearances or manufacturing tolerances which arise.

Bearing member 44 may be of the same polymeric material as cylindrical bearing 26.

Cutter 12 comprises a pair of cooperating rotatable cutting or shearing wheels 62, 64 carried on a mounting plate 66 depending from carriage 18. The mounting plate is formed with a slot 68 extending in the direction of the already cut material away from the wheels 62, 64. A link portion 70 of plate 66 connects the mounting portions 72, 74 thereof which are separated by the slot. The link portionis arranged in use to pass through the slit cut in the hardboard. Link portion 70 is cranked so that the mounting portions 72, 74 are on opposite sides of the line of cut of the wheels 62, 64.

The cutting wheels are formed with bevelled edges 76, 78 whereby in use forces exerted on the wheels by the material being cut acts, in each case, in a direction towards the other wheel. Upper wheel 62 is axially position-adjustable against the action of a coiled spring 80. Both wheels are journaled on suitable bearings 82 carried on plates 66.

Lower cutting wheel 64 is located within an extruded aluminium channel 84 having tie rods 86, and connected to fixed guide means 14.

In use, carriage 18 is manually propelled lengthwise of guide means 14 while cutting wheels 62, 64 shear the hardboard material, the latter being deflected by only from 5 degrees to 15 degrees upwardly and downwardly as it passes over link portion 70 of mounting plate 66 connecting the wheels. Forces tending to separate the cutting wheels are directly and easily resisted by the direct connection between them provided by mounting plate 66. Accordingly, the degree of overlap between these wheels needs only to lie in the range of 4% to 9% of their respective equal diameters. In the embodiment, the diameter of the cutter

wheels is 3.5 centimetres with an overlap of from 1.5 to 3 millimetres, preferably about 1.5 millimetres.

Loads applied to handle 36 during use may tend to cause pivoting of carriage 18 about the axis of rod 60, in a generally clockwise direction as seen in Fig 2. Such pivotal movement is resisted by engagement of bearing member 44 with recessed portion 42 of guide means 14. It will be noted that the confronting sliding surfaces between these two members extend generally laterally and almost at right angles with respect to the line of action of the forces concerned, whereby the tendency to jam, arising in prior art proposals, is substantially eliminated.

Interestingly, in the above-described embodiment, the disadvantages of prior art shearing or cutting mechanism for hardboard are avoided by the adoption of a twin wheel cutting system in which the deflection of the hardboard is minimised by virtue of the limited overlap of the cutting wheels which itself is a direct result of the direct connection between those wheels. Free sliding guided movement of the cutting carriage is permitted by the cylindrical bearing surfaces provided on one side with a simple face-to-face sliding contact on the other.