A METHOD FOR PUNCHING AND A PUNCH DIE

Abstract: The invention relates to a method of punching one or more holes in a two-wall workpiece having mutually facing walls where one or more holes is/are to be punched in at least one wall. According to the method, there is inserted in the space between the walls a punch die that has a thickness corresponding essentially to the distance between the walls. The die includes one or more punch cavities. A punch tool having one or more punches is activated on the ouside of the wall subsequent to having moved the punch die to a position in which a punch cavity is located opposite its respective punch. The invention also relates to a punch die (8) for use when carrying out the method. The punch die (8) includes one or more punch cavities (7) and is adapted for insertion into the space between the wall (2, 3) of the two-wall workpiece (1).

Description: A METHOD FOR PUNCHING AND A PUNCH DIE According to one aspect, the present invention relates to a method of the kind defined in the preamble of Claim 1, and according to a second aspect to a punch die for use when carrying out the method. Holes can normally be punched in a workpiece with no difficulty, provided that the holes shall be punched through a part of the workpiece where both sides of said are freely accessible from outside the workpiece, for instance when holes are to be punched in sheet material. The sheet, plate or strip is then laid against a fixed support surface that includes punch cavities and a punch-carrying tool is positioned with the punches opposite the punch cavities and pressed down against the sheet and therewith punch-out the holes . However, problems arise when holes are to be punched in a two-wall workpiece where the walls are spaced apart. An anvil surface for co-action with the punch tool during a punching operation cannot be easily achieved with a workpiece of this nature, due to the fact that the workpiece rests on one of its opposing walls. When attempting to punch holes in a workpiece of this nature, it is difficult to avoid deformation of the wall in which the holes are being punched,. This problem is, of course, dependent on the material from which the workpiece is comprised. Deformation is considerable in the case of certain soft metals, such as aluminium. It has therefore generally been considered impossible to punch holes in such two-wall workpieces made of certain soft metals, such as aluminium. The object of the present invention is to endeavour to overcome this problem and to provide a method which will enable holes to be punched in two-wall workpieces regardless of the material from which they are made. This object has been achieved in accordance with the invention with a method of the kind defined in the preamble of Claim 1 and comprising the method steps set forth in the characterising clause of said Claim. The insertion of a die between the two walls of the workpiece provides an anvil means which fills out the space between said walls and provides support for the wall as it is met by the punch. The anvil means enables the hole or holes to be punched without deforming the wall. Although the method can be applied for punching-out a single hole, it is primarily advantageous for use when punching-out a plurality of holes simultaneously in the wall of the workpiece. This constitutes a preferred embodiment of the inventive method. According to one preferred embodiment of the invention where holes are to be punched in both walls of the workpiece, punching of the holes is carried out in two stages, wherein the holes are punched in the second wall after having removed the die. When punching holes in the second wall of the workpiece, the punches move down through the holes made in the first wall. These embodiments and other advantageous embodiments of the inventive method are set forth in the Claims appended to Claim 1. According to a second aspect of the invention, the aforesaid object is achieved with a punch die constructed in accordance with Claim 4. The inventive die enables the inventive method to be carried out. The invention will now be described in more detail with reference to preferred embodiments thereof and also with reference to the accompanying drawings, in which Fig. 1 is a perspective view of a workpiece in which holes have been punched in accordance with the invention; Fig. 2 illustrates the problem addressed by the present invention; Fig. 3 is a cross-sectional view of a workpiece and illustrates a first step of an inventive method; Fig. 4 is a cross-sectional view corresponding to Fig. 3 and illustrating a second step of an inventive method; Fig. 5 is a sectional view of the workpiece shown in Fig. 3, taken perpendicular to the section in Fig. 3; and Fig. 6 illustrates a measure taken between the steps illustrated in Figs. 3 and 4. Shown in Fig. 1 is a workpiece 1 in the form of a two-wall elongated strip having a bottom wall 2 and a top wall 3 in which respective rows of holes 10, 4 have been punched. The illustrated workpiece may be made of aluminium, for instance. Fig. 2 illustrates the difficulty of punching holes in such a workpiece. If the workpiece is simply clamped to the work table of the punching machine, the upper wall 3 will not be supported and the punch 5 will deform the wall 3 as it punches holes therein. The disc punched from the workpiece will remain on the bottom wall and present an obstacle to continued punching. Figs. 3 and 5 illustrate the manner in which holes are punched in the upper wall 3 of the workpiece 1 in accordance with the invention. A die 8 is inserted in the space between the two walls 2, 3, so as to support the upper wall 3. The upper side of the die 8 is provided with punch cavities 7a, 7b etc., and the die is positioned so that the punch cavities are located centrally of respective punches 5a, 5b etc. The die thus functions as an effective anvil means, therewith enabling the holes 4 to be punched readily in the upper wall 3. In this case, the length of stroke of the punches must be limited in the first punching operation, so that the discs punched from the workpiece will not be pressed firmly into the die cavities and become fixed therein. If holes are also to be punched in the bottom wall 2 of the workpiece, the die 8 is withdrawn form the workpiece 1 in the direction of the arrow A shown in Fig. 6. Holes can now be punched in the bottom wall, wherewith a punch moves down through a respective hole that has already been punched in the upper wall 3. Prior to carrying out a corresponding operation on a following workpiece, the discs punched from the holes 7a, 7b etc., are removed from the die 8, for instance with the aid of compressed air, and the die 8 then inserted into the new workpiece . Withdrawal and insertion of the die 8 may, of course, be controlled automatically or effected purely manually. In the illustrated example, there is used a punch die that is common for all holes to be punched in the upper wall 3. It is also conceivable, however, to use two (or more) shorter units and to insert a die into the workpiece from each direction. Although the invention is primarily conceived for punching holes in a workpiece of the illustrated appearance, it will be apparent that the invention can also be applied with work- pieces that have lateral extensions in two directions where the holes are distributed over one surface instead of along a strip. The invention can also be applied in respect of work- pieces in which only one hole shall be punched in its upper wall, and in respect of workpieces where holes shall be punched solely in one of the two walls. The illustrated example can be readily modified for use when the two walls are angled to one another, i.e. not parallel. Neither is the inventive method restricted to square profiles, but can also be applied to U-profiles or to a double-wall workpiece in which the two walls are joined together solely at certain places .

Claims: CLAIMS 1. A method of punching one or more holes in a two-wall workpiece where said walls are mutually interspaced, wherein the hole/holes is/are punched through at least the first of said walls, characterised by inserting between the walls a die whose thickness corresponds essentially to the distance between the walls, and activating a punch tool that carries one or more punches such as to punch a hole or holes in the first wall, subsequent to having moved the die to a position in which a punch cavity is located centrally opposite its respective punch. 2. A method according to Claim 1, in which a plurality of holes are punched simultaneously in said first wall, wherein the die has a plurality of punch cavities and the punch tool has a corresponding number of punches. 3. A method according to Claim 1 or 2 , in which the workpiece is an elongated metal strip of box-like cross- section, wherein the die is inserted into the box-like profile in the longitudinal direction of the strip. 4. A method according to any one of Claims 1-3, in which holes are also punched in the second of said walls, wherein subsequent to having punched the hole/holes in said first wall, the die is removed from said interspace and the hole/holes are punched in the second wall in a second punching operation in which the punch/punches moves/ move through the hole/holes punched in the first wall. 5. A punch die for use in a method according to any one of Claims 1-4, characterised in that the punch die is an element separate from a punch machine and is adapted for insertion into the space between the walls (2, 3) of a two-wall workpiece (1) in which a hole or holes (4) is/are to be punched, wherein the die (8) includes one or more punch cavities ( 7 ) . 6. A punch die (8) according to Claim 5, which has the form of an elongated rod of rectangular cross-section provided with a plurality of punch cavities (7) disposed along one of the long sides of said rod.

Inventors: CARLSSON PERVI, CARLSSON, PERVI
Applicants: CARLSSON PERVI, PM TEKNIK HB, CARLSSON, PERVI, PM TEKNIK HANDELSBOLAG
Application year: 1998
Main classification: B21D28
IPC codes: B21D28, B26F1