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.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described in more detail with reference to the attached exemplary embodiments. In the drawings:
FIG. 1 shows a punching blade according to the invention,
FIG. 2 shows a punching machine with a punching blade according to FIG. 1 and a punched product,
FIG. 3 shows a partly sectioned perspective view of the machine according to FIG. 2, and
FIG. 4 shows the tip of a punching element in a punching blade according to an exemplary embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows the punching blade 1 according to the invention. This punching blade 1 consists of a bottom sheet-metal plate 2 and a top sheet-metal plate 12 which lie essentially congruently above one another. Two apertures 3 are punched in these plates 2 and 12, said apertures 3 being intended for the subsequent movement of the punching blade 1. A multiplicity of parallel punching blade elements 5 are shown in the punching blade region 4, the punching blade elements 5 in each case being cut off in a wavelike manner relative to an axis 6, so that all the punching blade elements 5 do not in each case pass simultaneously through paper to be punched. The punching blade elements 5 are otherwise elongated in cross section and are in particular rectangular. Thus U-shaped punching recesses 7 are arranged between each two punching blade elements 5. In other configurations, the punching blade elements 5 and punching recesses 7 may be constructed with side edges which are not parallel to one another; the punching blade elements 5 then taper toward the punching body 8 and/or are curved. Provided on that end of the punching body 8 which is opposite the punching blade elements 5 is a comb 10 having a multiplicity of teeth 11, which each project at right angles from the plate 8. The distance between the teeth 11 corresponds to the distance between the punching blade elements 5. The teeth 11 have preferably been punched out of the bottom base sheet 2 and then bent upward by an angle of 90°. Of course, the teeth 11 may also be punched out of the top base sheet 12.
The advantage of the punching blade 1 according to the invention lies in particular in the fact that the intermediate spaces 7 between the punching blade elements 5 are punched out with the metal sheet “unfolded”; i.e., in the exemplary embodiment according to FIG. 1, rectangular elongated punched-out portions have been produced symmetrically to the axis 6 of the original metal sheet. In the process, the rake 10 with the teeth 11 can 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 layers 2 and 12 are placed one on top of the other by folding.
FIG. 2 shows a punching machine in which the punching blade 1 according to FIG. 1 may be advantageously used. The punching blade 1 with the rake 10 rests on the base body 20, which is of trapezoidal design. At its narrowed end, the base body 20 has a comb 21 which has teeth which interact with the teeth 11 of the rake 10. A paper support with integrated stripper and blade guide is designated by 30 and can better be seen in FIG. 3. Finally, a single lever 40 is provided which at the same time forms the drive for the punching and binding. Provided on the lever 40 are control pins which engage in the aperture 3 of the punching blade 1, and thus this punching blade 1 with the punching blade elements 5, for the punching, is driven through the paper support 30 and through the paper 50. At the same time, it is thus possible for paper 51 which has already been punched to be bound with binder backs inserted between rake 10 and comb 21. Thus a very simple machine is constructed in a very advantageous manner, and this machine only consists of four individual parts, the punching blade 1, the base body 20, the paper support and the blade guide 30, and the lever 40. Advantageously fastened beneath the body 20 is a scrap container 52, i.e. a base which catches the paper residues falling into the interior space of the base frame 20. The four bodies may be made of sheet metal and in particular of the same sheet metal material, but base body 20 or blade guide 30 or lever 40 may be made of plastic and in particular by injection molding.
Finally, FIG. 3 shows a partly sectioned view of the punching machine according to FIG. 2. The same features are in each case provided with the same reference numerals. The trapezoidal base frame 20 with die 22, through which the punching blade elements 5 pass, can be seen. The engagement element 41 with which the punching blade 1 can be moved on the surface 23 of the base frame 20 relative to the comb 21 can be seen on the lever 40.
The paper support 30 is, for example, U-shaped and has two rows of holes which interact with the die 22. In this case, the paper support 30 at 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 elements 5 of, for example, 3 millimeters, which is required for forming the holes, the punching blade 1 is produced by folding a pre-punched metal sheet and is merely reworked after the folding.
FIG. 4 shows an advantageous exemplary embodiment of the tip of a punching blade 5. The latter, as in FIG. 1, consists of two layers 2, 12 of a metal sheet, the latter, before it has been folded, having also been provided with a punched contour in the tip region 31 of each punching blade 5. In the exemplary embodiment shown in FIG. 4, this involves two sides 32 and 33 or 34 and 35, respectively, of an isosceles triangle, the third side being parallel to the axis 6 and 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 blade 5 passes through the material to be perforated. In addition, the specification of a contour in accordance with the punching blade 5 according to FIG. 1 is also possible, but is not a requirement.
Patent Grant
6994010
