METHOD AND TOOL FOR PUNCHING HOLES

Abstract: When punching holes and objects (12), respectively, in non-metallic sheet-like material, a hitherto unknown quality and working speed can be achieved by letting a cutting tool (10, 13) from either the top side and/or the under side of the material (1) press in to a point leaving a non-cut ring of a thickness of eg. 0.01 mm. The material (12) can then be removed from the surrounding material (1) either by means of a generally known pressing-out tool or for instance by means of the compressed air inlet while the cutting tool (10, 13) is in the skin (1) or after its removal. For operating the cutting edges (10, 13) these may be mounted on a top and a bottom linear motor (4, 2 and 14, 15) which may furthermore control the pressing-out means (11). This will permit a fully automatic control of the tools.

Description: METHOD AND TOOL FOR PUNCHING HOLES • The invention relates to a method for punching holes in non-metallic sheet-like materials and a punching tool for performing the method. When making objects in eg. skin and leather, a punch- ing tool with an annular cutting edge the size and shape of which correspond to the outer shape and the shape of the hole, respectively, of the end product is generally used. This cutting tool is either manual¬ ly or mechanically pressed through the material from one side and towards an underlying backstop, a socal- led punching plate. After the punching the tool is withdrawn leaving a hole the cut object being wedged in the cutting edge from where it may be subsequently pressed out. This known method does not give the object and the hole, respectively, a cutting surface which is at right angles to the surface because the cutting edge must have a certain bevelling or free edge to avoid being jammed in the material. The bevelling side faces are particularly inconvenient for thick materials and a subsequent trimming is often required for obtaining a straight side face which is substantially at right angles to the surface. It is moreover necessary to have a punching plate which must be moved for each punch and also must be replaced after abt. 25 punches. This is highly time consuming and increases costs for the whole method. For remedying these drawbacks as much as possible, the cutting tool must have the smallest possible wall thickness which will reduce the tool's strength and so its life at the same time while the requirements to the nature of the punching plate are increased. Add to this that such an object and hole, respective- ly, will often have burrs on one side namely the under¬ side which will also require a subsequent trimming if such remnants of material are to be removed for being trimmed on both sides. To sum up it may be established that particularly in connection with heavy materials a finishing is re¬ quired where a perpendicular clean cut with uniform edges on both sides of the object and the hole, respectively, is desired. If by using the usual methods with punching tool and plate, there are to be made objects or holes in eg. skins having been treated in solid or liquid composi¬ tion salt or having been softened in liquids, this will give both technical and hygienic problems. It is the object of the invention to remedy these drawbacks by the known methods and this is achieved by a method where from the top side and under side, respectively, of the material a cutting tool is pres¬ sed through the material until the cutting edges almost touch whereupon the cut out material is re¬ moved in a manner known per se by pressing out. The result is first and foremost that the opposite cutting tools are evenly pressed in to a point around the - middle of the material. This will mean an optimum utilization of the pressing power and will at the same time halve the cutting depth of the individual cutting edges. Furthermore, the cut will be clean since burrs will not so easily occur due to the effective counter-pressure in the material. The cut objects and holes, respectively, will moreover be uniform on both sides just as the cut side edges will be substantially at right angles to the surface so that the trimming process can be completely avoid¬ ed. Advantages in relation to time consumption and work are therefore obtained. This method will leave almost no burr and if any it will be situated in the middle of the object and so rarely cause any incon¬ venience. Add to this that it is a very careful method because the cutting edges are not pressed into a backstop so that these edges are spared and their life therefore substantially increased. Finally, it is often advantageous that the pressed out object can be subsequently removed since the object will be left hanging in the non-cut ring in the middle of the material so that the object or objects can be removed from the material at a later time. In that way it is possible to make preparations for the pressing out of eg. a number of holes at a later date according to requirements just as it will be possible to adapt objects/holes by a suitable punching pattern. By using the method disclosed in claim 2 where the object is removed by pressing out while the tool is in the material, a substantially completely clean cut is obtained since any burrs will be cut off when passing one of the cutting edges. By using the tool disclosed in claim 3 with cutting edges being reciprocated from the top and/or under side, it is possible to carry out a mechanical punch¬ ing in a simple and economic manner. Finally, it is advantageous to provide one of the cut¬ ting edges with a pressing-out means as disclosed in claim 4, since it is possible to press out the object of the material when the cutting edges are in the material. By suitable removal means the object or objects can be removed from the working point in an effective and careful manner. The invention will be further described in the fol- lowing with reference to the drawing, wherein Fig. 1 shows the cutting tool pressed into the material, and Fig. 2 shows the tool with the pressing-out means in its forward position. The drawing shows an example of the method according to the invention where the punching tool is mounted in two holders 18 and 19 which may be secured to a not shown bracket. For small tools the holders may be manually operated. In these two holders there are mounted two sets of cutting tools comprising the cutting edges 10, 13 proper. In the shown embodiment there are two circular cutting edges which can therefore punch a circular hole and an object having the shape of a circular disc 12 in a piece of material 1 being eg. skin or leather. The cutting tools are each secured to a support con¬ nected to a piston 4, 14 in a working cylinder 2, 15. By a suitable admission of pressure medium such as air or liquid through pipes 8, 17, the cutting tools may be pressed into the leather 1 to a point, see Fig. 1, where the cutting edges almost meet by the centre in¬ side the leather. At this point the cylinders 4, 14 will impinge on the cylinder bottom and prevent fur¬ ther progression. At this time there is formed a circular groove on both sides of the leather for forming a disc 12 which merely hangs on to the surrounding leather by a ring having a thickness of eg. between 0.01 and 0.02 mm. By means of a pressing out piston 11 being rigidly connected to a further piston 3 in an overlying cyl¬ inder, the piston may be carried towards to disc 12, as shown in Fig. 2, by admission of the pressure medium to the cylinder via a pipe 6. The pressure medium is then fed to the opposite sides of the pis¬ tons via other pipes 9, 16, and the pistons 4, l4 move backwards and so out ot the leather. In this manner the disc 12 may be pressed out and removed from the leather and if desired be collected in a container or the like be means of net shown guide means. The disc may be pressed out by means of compressed air and the shown pressing-out device may be left out. The whole method can be controlled fully automatically so that the punching is effected quickly and precisely. Instead of the shown moving devices in the form of working cylinders any other known form of working motors may be used. For instance the returning of the cutting tools may take place by means of spring power from springs mounted between cylinder bottom and piston. Alternatively, electromagnetic motors may be used for moving the cutting edges either in both directions or in one direction and as mentioned above returning by means of springs. Moreover the movements may be performed by an electric motor moving the tools in a similar manner by means of suitable cam discs via arms. Where the punching of eg. a row of holes is required, a corresponding number of tools may be secured in a common holder with the possibility of a selective actuation of the tool or tools forming the prefixed hole pattern. The present specification merely mentions skins and leather but the method may advantageously be used for making objects and/or holes in veneer, plastic, cork, packing material, paper, cardboard, textiles, rubber. The method is particularly suitable for long-fibre materials which have hitherto caused problems by pre¬ viously known punching tools. Finally, the method and the tool are suitable for work¬ ing materials which have been moistened by chemical liquids. :..-..:A- " -

Claims: PATENT CLAIMS 1. Method for punching holes in non-metallic sheet¬ like materials, c h a r a c t e r i s e d i n that a cutting tool (10, 13) is pressed through the mate¬ rial from the top side and under side, respectively, of the material (1) until the cutting edges almost touch whereupon the cut out material (12) is removed in a manner known per se by pressing out. 2. Method according to claim 1, c h a r a c t e r - i s e d i n that the cut out material (12) is re¬ moved by pressing out through one of the cutting tools (10, 13) while these tools (10, 13) are in the mate- rial (1). 3. Punching tool for performing the method according to claims 1 and 2, c h a r a c t e r i s e d i n that one or each of the cutting tools comprises a cutting edge (10, 13) mounted on a reciprocating device (4,2 and 14, 15). M. Punching tool according to claim 3, c h a r a c ¬ t e r i s e d i n that one of the cutting edges (10) is furthermore provided with an internally embedded pressing-out means (11) which means is movable from a backward position (Fig. 1) in the tool to a forward position (Fig. 2) by means of a moving device (3, 2).

Inventors: BORGQUIST NIELS ERIK, BORGQUIST, NIELS, ERIK
Applicants: TEKNOLOGISK INST, TEKNOLOGISK INSTITUT
Application year: 1984
Main classification: B26F1
IPC codes: B26D7, B26F1, C14B5