The object of the invention is a cutter comprising two blades movable with respect to each other, the cutting edge of the first blade forming the arc of a circle, and the second blade being basically straight, and which blades form a cutting jaw between which the sheet to be cut is positioned, cutting thus taking place in such a way that the cutting edge of the first blade, shaped like the arc of a circle, revolves with respect to the cutting edge of the second blade, in the direction of the cutting edge.

Cutters are usually intended for cutting relatively thin sheets. However, depending on the structure of the cutter, the sheet to be cut may be of almost any type and thickness, from thin paper to thick metal plates.

One known sheet cutter is the so-called shearing cutter which comprises two knife-like blades which are in contact with each other and form an acute angle. The sheet to be cut is positioned between the blades and cutting is performed as with shears. The cutting movement can be effected by moving either both blades or only one blade. The knife-like blades may be straight, as in common hand scissors. One or both of the blades may, however, also be curved which facilitates the cutting of curved forms on the sheet.

Another known cutter is the disc cutter, in which one of the cutting blades is a sharp-edged, round disc. The other blade is usually straight. The sheet positioned between the blades is cut by moving the round disc blade in the direction of the straight blade. The disc blade thus begins to rotate as it revolves against the other blade. In this cutter, the disc blade is not rotated independently, but the rotating movement is caused by the effect of friction between the blades.

However, the cutters described above have their disadvantages. A cutter provided with knife-like blades cannot be used to cut curved shapes very easily. On the other hand, thicker sheets cannot be cut using the cutter equipped with a disc blade, as the disc blade does not rotate properly when the shearing resistance increases. Furthermore, it is not possible to cut a hole in the centre of a sheet with any of the known cutters.

The aim of this invention is to eliminate the above problems and to provide a new cutter without the above drawbacks.

It is characteristic of the cutter relating to the invention that a recess is formed in the cutting edge of the first blade, shaped like the arc of a circle, so that a gap remains between the cutter (10) blades, when the first blade is turned to such a position that the recess is facing towards the second blade.

The invention provides an efficient cutter, with which it is also possible to cut holes in the centre of sheets. The other characteristics of the invention are specified in the claims below.

The invention is described in the following by way of examples, with reference to the appended drawings in which

Figure 1 shows the cutter relating to the invention as seen from the side.

Figure 2 corresponds to figure 1 and shows the cutter blade in a different position. Figure 3 shows a sectional view of figure 1 taken along line III-III. Figure 4 shows the cutter blade as seen from the side. Figure 5 corresponds to figure 4 and shows a second embodiment of the cutter blade. Figure 6 corresponds to figure 1 and shows a second

embodiment of the cutter. Figure 7 corresponds to figure 1 and shows a third embodiment of the cutter. Figure 8 corresponds to figure 4 and shows a third embodiment of the cutter blade.

Figure 9 shows a diagrammatic view of the round blade and the straight blade of the cutter, as seen from above.

Figure 1 shows the cutter 10 relating to the invention as seen from the side. The cutter 10 comprises a rotating blade 11 and a fixed blade 12. The rotating blade 11 is basically round and the fixed blade 12 is straight. Blades 11 and 12 are arranged to be moved with respect to each other by means of a fixed toothed bar 14 attached to the frame 13 of the cutter 10 and a toothed wheel 15 matching the toothed bar is attached to the rotating blade 11.

The cutting movement between blades 11 and 12 is achieved by turning lever 16. When, as in figure 1, the lever 16 is turned anticlockwise, the toothed wheel 15 and the blade 11 rotating with it revolve to the left in figure 1. The movement of the rotating blade 11 is mechanically controlled so that, in addition to rotating, it is only able to move horizontally. For the purposes of this control, a needle bearing 18 is connected to the shaft 17 of the rotating blade 11, the bearing being able to move between the parallel guides 19a and 19b formed in the frame 13 of the cutter 10.

The sheet to be cut is positioned in the cutting jaw 20 of the cutter of figure 1, and the lever 16 is turned anticlockwise, in figure 1. Thus also the rotating blade 11 turns and moves at the same time to the left in the figure. The blades 11 and 12 then cut the sheet in the cutting jaw 20.

Figure 2 shows the rotating blade 11 of the cutter 10 in

its other extreme position, that is, on the left in figure 2, at the mouth 28 of the cutting jaw 20. The figure shows that the gap of the cutting jaw 20 is open over its entire length. This is due to the fact that the rotating blade 11 incorporates a straight segment part 21, which is at the cutting jaw 20 in the situation shown in figure 2. When the rotating blade 11 is in this position, the sheet to be cut can be pushed to the end 27 of the cutting jaw 20, and cutting can be started by turning the lever 16 clockwise as in figure 2. The rotating blade 11 will then advance to the right in figure 2 , and cutting starts from the centre of the sheet instead of the edge of the sheet as shown in figure 1.

Figure 3 shows a cross-section of the cutter of figure 1. A fixed blade 12 is attached to the frame 13 of the cutter

10, the position of which blade can be adjusted by means of a spacer plate 22. The rotating blade 11 is secured by screws 23 to a unit formed by the toothed wheel 15, the shaft 17, the needle bearing 18 and the lever 16, which unit is moved horizontally by means of the toothed bar 14, between guides 19a and 19b of the frame 13.

Figure 4 shows the rotating blade 11 belonging to the cutter 10 of figure 1. The blade 11 is a round disc, one section of the curved edge 24 of which forms a straight segment 21. The purpose of this segment part 21 is to form an open gap in the cutting jaw 20 of the cutter 10, when this part 21 of the blade is turned to the cutting jaw 20.

Figure 5 shows a second embodiment lib of the rotating blade of the cutter 10. Deviating from the embodiment of figure 4, this embodiment of the rotating blade has three straight segment parts 21 at equal distances, that is, at a distance of 120 degrees. The advantage of this type of blade is that the blade lib can be placed in three different positions, as only one of the curved parts 24a-

curved part 24a has become blunt, the blade is turned by 120 degrees and the next sharp curved part 24b is turned to the cutting position.

Figure 6 shows a second embodiment of the cutter 10, in which the toothed wheel 15 and the toothed bar 14 shown in figure 1 have been replaced by a wire cable 25. In this case, the round blade 11 is attached to a cylindrical part 26, around which the cable wire 25, attached to the frame 13 at both ends, is wound. When the lever 16 is turned, the cylindrical part 26, and with it the rotating blade 11, advance in the guides 19a and 19b.

Figure 7 shows a third embodiment of the cutter 10, which differs from the embodiment of figure 1 in that the guides 19c and 19d are curved. In this case the rotating blade 11 moves along a curved path, in accordance with the guides 19c and 19d. In this case the toothed bar 14b must obviously also be curved in a corresponding manner. The blade 11 can now be completely round, without the segments described above.

The purpose of the curved path is to lift the rotating blade 11 off the straight blade 12 when it is at one end of its path. In the cutting jaw 20 is thus formed a corresponding open gap such as was produced in figure 1 by means of the straight segment part 21 formed on the round blade 11.

The solution shown in figure 7 can obviously also be realised using the wire cable shown in figure 6, without a toothed wheel and toothed bar.

Figure 8 shows a third embodiment of the round blade 11 of the cutter. The cutting edge 24 of the blade 11 forms the arc of a circle, a part of which has been removed. In the removed part of the cutting edge 24 of the blade 11 is a recess, which incorporates a straight segment part 21

without a sharp cutting edge. At one end of the segment 21, the straight part ends so that a notch 29 is formed between the segment part 21 and the cutting edge 24, shaped like the arc of a circle, beside which notch the cutting blade 24 ends in a sharp tip 30. The purpose of the tip 30 is that when cutting is started, the tip part 30 is pressed into the sheet to be cut first, which means that cutting starts precisely.

Figure 9 shows a diagrammatic top view of the round blade 11 and the straight blade 12 of the cutter relating to the invention, adjacent each other. The sheet is cut between these blades 11 and 12. In the embodiment shown in figure 9, the end 31 of the straight blade 12, which is usually the lower blade, is bevelled to a wedgelike shape so as to allow the piece to be cut to be turned into different positions about the sharp tip 32 of the straight blade 12.

A practical problem is presented, for example, when cutting a sheet bent to a right angle. Cutting a V-shaped or wedgelike notch extending to the bent angle of the sheet is possible only if the end 32 of the straight lower blade 12 of the cutter is bevelled to a wedgelike shape, as shown in figure 9. In a cutter equipped with this type of blade 12, a sheet bent to a right angle can be turned about the sharp tip 32 into different positions.

By way of an example, figure 9 shows, as broken lines, directions 33a and 33b which are at an angle of 90° to each other. If the sheet to be cut is turned in accordance with these directions 33a and 33b, a 90° wedgelike notch extending to the corner of the sheet can be cut into a sheet bent correspondingly to a right angle. Making a notch of this kind is often necessary, as after notching, the sheet can be bent at the notch to form a 90° angle so that the edges of the notch come into contact with each other. In this manner, a right-angled profile can be bent to a 90° angle.

In figure 9, the end 31 of the straight blade 12 is bevelled to form the angle α, which is 45° in the given example. Similarly, the cutting edge of the round blade 11 forms an angle β, which is preferably 5° - 30°.

It is obvious to a person skilled in the art that the different embodiments of the invention may vary within the scope of the claims presented below.