Cutting tool for a punching machine, method for producing said cutting tool and punching machine

A cutting tool (1) for a punching machine has a punching body (8) on which a plurality of punching tool elements (5) which are located parallel to each other are provided. The puncing body (8) consists of a double-layered metal sheet (2, 12). Essentially longitudinal openings (7) are advantageously punched out of a sheet metal plate (2 and 12) symmetrically about an axis (6), these longitudinal openings (7) being situated parallel to each other, respectively. The sheet metal plate (2, 12) is then folded about the axis (6) in order to form the double-layered punching tool elements (5). This allows the use of more simple punching machines and enables a punching machine to be produced from just a few individual parts.

FIELD OF THE INVENTION

The invention relates to a cutting blade for a punching machine, having a punching body on which a multiplicity of punching blade elements arranged parallel to one another are provided.

BACKGROUND OF THE INVENTION

Such a punching blade has been disclosed by WO 93/24289. In this case, the lengths of the punching elements are provided in groups of different length, so that in each case only a restricted number of punching elements have to pass simultaneously through a document to be punched, as a rule a number of sheets.

These punching blades work satisfactorily. However, their high price is disadvantageous, since the requisite punching thicknesses of, for example, 3 millimeters require machines which have a fine-punching mechanism and which have to be able to produce a pressure force of, for example, 800 tonnes. This is a price-raising factor for the punching machines to be used during the production.

A further disadvantage of the punching machine according to the prior art lies in the multiplicity of parts of a punching machine using such a punching blade, in which case, in particular, it is also always necessary to additionally provide a rake.

BRIEF SUMMARY OF THE INVENTION

Based on this prior art, the object of the invention is to specify a punching blade of the type mentioned at the beginning which can be produced in a considerably more cost-effective manner and in addition can be used in a machine consisting of few parts.

This object is achieved according to the invention in that the punching body consists of a double-layered metal sheet.

A method of producing the punching blade comprises the features of punching out essentially elongated openings symmetrically about an axis from a sheet-metal plate, the elongated openings in each case being arranged parallel to one another, and of folding the sheet-metal plate about said axis.

In an advantageous method of producing a punching blade, the step of cutting off sections at the folding line for producing a desired cutting contour is added.

An advantageous punching device having a punching blade according to the invention then has merely four parts, in which case these are all produced from metal sheet which is at most only 1.5 millimeters thick.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1shows the punching blade1according to the invention. This punching blade1consists of a bottom sheet-metal plate2and a top sheet-metal plate12which lie essentially congruently above one another. Two apertures3are punched in these plates2and12, said apertures3being intended for the subsequent movement of the punching blade1. A multiplicity of parallel punching blade elements5are shown in the punching blade region4, the punching blade elements5in each case being cut off in a wavelike manner relative to an axis6, so that all the punching blade elements5do not in each case pass simultaneously through paper to be punched. The punching blade elements5are otherwise elongated in cross section and are in particular rectangular. Thus U-shaped punching recesses7are arranged between each two punching blade elements5. In other configurations, the punching blade elements5and punching recesses7may be constructed with side edges which are not parallel to one another; the punching blade elements5then taper toward the punching body8and/or are curved. Provided on that end of the punching body8which is opposite the punching blade elements5is a comb10having a multiplicity of teeth11, which each project at right angles from the plate8. The distance between the teeth11corresponds to the distance between the punching blade elements5. The teeth11have preferably been punched out of the bottom base sheet2and then bent upward by an angle of 90°. Of course, the teeth11may also be punched out of the top base sheet12.

The advantage of the punching blade1according to the invention lies in particular in the fact that the intermediate spaces7between the punching blade elements5are punched out with the metal sheet “unfolded”; i.e., in the exemplary embodiment according toFIG. 1, rectangular elongated punched-out portions have been produced symmetrically to the axis6of the original metal sheet. In the process, the rake10with the teeth11can be punched out in the same working step. At a thickness of 1.5 millimeters, conventional punching tools of 300 tonnes capacity can be used. Thus there are no costs involved with regard to complex punching tools, which is to be used in the case of sheet thicknesses of 3 millimeters.

It is advantageous to use a galvanized sheet, since, during the cutting, the zinc coating is pulled down with the cutting blade at the cut-off side edges and these cutting edges are thus sealed. This sealing is retained when the two sheet-metal layers2and12are placed one on top of the other by folding.

FIG. 2shows a punching machine in which the punching blade1according toFIG. 1may be advantageously used. The punching blade1with the rake10rests on the base body20, which is of trapezoidal design. At its narrowed end, the base body20has a comb21which has teeth which interact with the teeth11of the rake10. A paper support with integrated stripper and blade guide is designated by30and can better be seen inFIG. 3. Finally, a single lever40is provided which at the same time forms the drive for the punching and binding. Provided on the lever40are control pins which engage in the aperture3of the punching blade1, and thus this punching blade1with the punching blade elements5, for the punching, is driven through the paper support30and through the paper50. At the same time, it is thus possible for paper51which has already been punched to be bound with binder backs inserted between rake10and comb21. Thus a very simple machine is constructed in a very advantageous manner, and this machine only consists of four individual parts, the punching blade1, the base body20, the paper support and the blade guide30, and the lever40. Advantageously fastened beneath the body20is a scrap container52, i.e. a base which catches the paper residues falling into the interior space of the base frame20. The four bodies may be made of sheet metal and in particular of the same sheet metal material, but base body20or blade guide30or lever40may be made of plastic and in particular by injection molding.

Finally,FIG. 3shows a partly sectioned view of the punching machine according toFIG. 2. The same features are in each case provided with the same reference numerals. The trapezoidal base frame20with die22, through which the punching blade elements5pass, can be seen. The engagement element41with which the punching blade1can be moved on the surface23of the base frame20relative to the comb21can be seen on the lever40.

The paper support30is, for example, U-shaped and has two rows of holes which interact with the die22. In this case, the paper support30at the same time forms the integrated stripper and a blade guide.

The parts in each case advantageously consist of galvanized sheet and are therefore very simple to process. Simple punching tools can be used due to the small sheet thickness of only 1.5 millimeters. In order to achieve the thickness of the punching blade elements5of, for example, 3 millimeters, which is required for forming the holes, the punching blade1is produced by folding a pre-punched metal sheet and is merely reworked after the folding.

FIG. 4shows an advantageous exemplary embodiment of the tip of a punching blade5. The latter, as inFIG. 1, consists of two layers2,12of a metal sheet, the latter, before it has been folded, having also been provided with a punched contour in the tip region31of each punching blade5. In the exemplary embodiment shown inFIG. 4, this involves two sides32and33or34and35, respectively, of an isosceles triangle, the third side being parallel to the axis6and forming the folding axis. Thus it is possible in a very simple manner, in particular with the same punching step, to produce a three-dimensional cutting edge. This permits smaller cutting forces when each punching blade5passes through the material to be perforated. In addition, the specification of a contour in accordance with the punching blade5according toFIG. 1is also possible, but is not a requirement.