PULL-OUT BLANK IN A SHEET METAL CABINET WALL

Abstract: A pull-out blank for creating an opening in a cabinet wall (1) is composed of a pair of parallel-running score lines (2, 3) surrounding the blank proper. The strip (4) defined by the score lines (2, 3) is transversely scored in at least one place (5), providing a weak spot that may be punched with a pointed tool in order to force one end of the strip (4) away from the sheet metal (1). A pair of pliers may be used to pull the strip (4) out of the cabinet wall (1), whereby the blank proper is also removed.

Description: " Pull-out Blank for a Cabinet Wall The invention relates to a form of tear-out opener wherein two areas of sheet metal are separated from each other by tearing out an interjacent strip in the same material and wherein the material is provided with score lines along the longitudinal edges of the strip, primarily by deformation. Lids using this principle are known from tin cans manufactured from tin plate. In previous designs the strip is provided with a grip or handle part at the nlace where it is designed to be pulled first. An object of the present invention is to provide an opener of the said kind which is not limited to tin plate, but which works with sheet metal. The opener is characterised in that the interjacent strip is provided with at least one score line across the longitudinal direction. Such an opener, which is not provided with a grip or handle part, can be opened by first striking the area of the strip adjacent to the transverse score line with a pointed tool, e.g. a chisel, thereby separating the strip from the surrounding metal and providing an end which can be gripped with a set of pliers. Subsequently it is possible to tear out and wind up the strip from the other side of the plate. This pre-supposes that there is free access to both sides of the plate. A tear-out opener of this kind can, therefore, be used, for example, in steel cabinets for electrical installations which are designed with a series of pull-out blanks, enabling holes to be created for lead-in connections, depending on the application and mode of installation. This provides for a simple method of opening the holes necessary for a certain installation, the remaining holes staying closed and sealed, with no parts protruding. In an embodiment of this invention the opener is made of metal or other material which yields by deformation and the sheet metal may be partly pre-cut to facilitate opening. The special advantage of this embodiment is that it makes it possible to produce a pull-out blank in thicker sheet metal; firstly, because such a material can be partly pre-cut with great accuracy and secondly, because it will be easy to tear off the remaining part of the material in the cut by means of pliers, even though the material is several times thicker than in existing tear-out openers in thin tin plate. The decisive factor is that the strip which is used can be held firmly by means of the pliers and, since the surrounding material is several times thicker than the material in the cut, it provides good support for leverage of the pliers and at the same time ensures a perfect tear. The invention will be further described in the following with reference to the accompanying drawing, in which: Fig. 1 shows an area of sheet metal provided with a circular pull-out blank according to the invention, Fig. 2 shows a section along the line II- II in Fig. 1, Fig. 3 shows a section along the line III- III in Fig. 1, and Fig. 4 shows a similar section to that in Fig. 3, but according to another embodiment of the invention. Fig. 1 shows an area of sheet metal 1 which may constitute part of the wall in a cabinet. In plate 1 there are two concentric circular pre-cut curves 2 and 3 which limit a tear-out strip 4. In the embodiment shown, the pre-cut curves 2 and 3 are formed by means of a partial cut or incomplete punching along the curves 2 and 3, as shown in Fig. 3. However, there is nothing to prevent the pre-cut curves from being obtained in any other well-known manner for making grooves in a material. The strip itself is provided with a score line along the line 5, as shown in Fig. 2. The embodiment shown in Figs. 1, 2 and 3 works in the following way. If a circular opening is desired in plate 1 along the outer pre-cut curve, strip 4 should be cut at line 5 by means of a chisel, until one end of strip starts to protrude on the other side of the plate. Strip 4 can then be twisted and pulled out by means of pliers, until the whole of the circular plate is free. As mentioned above, the invention is not limited with regard to score lines of a special design. A different example is shown in Fig. 4. It is obvious that the holes may have any shape suited to the purpose in question. If, for instance, it is not a requirement that the walls of a cabinet be sealed when no blank has been pulled out, then the deformation along the line 5 made at the time of manufacture may be so large that the ends to be gripped by pliers already sufficiently protrude. By having these ends disposed on the inside of the cabinet wall, one may obtain the double advantage of only having to grip and pull in order to obtain an opening and of enabling aligned openings to be made in cabinets already mounted side by side by pulling out blanks from the respective insides of the adjacent cabinets. In other words, since access to the outside of the cabinets is not required, it is not necessary to once again remove a whole cabinet to provide aligned openings. Pull-out blanks can, according to this invention, be made in steel plate which is more than 0.5 mm thick. The tear-out method of removing the pull-out blank works well for plates that are 1.5 mm thick. Naturally, the opener can also be used for plates thinner than this.

Claims: Claims: 1. A pull-out blank in relation to two areas in sheet metal (1) being separated by tearing out an interjacent strip (4) in the same material, this material being cro- vided with score lines along the longitudinal edges (2,3) of the strip (4), primarily by deformation, c h a r a c t e r i s e d in that the interjacent strip (4) is provided with at least one score line (5) across the longitudinal direction. 2. A pull-out blank as claimed in claim 1, primarily made of metal or another material which yields by deformation, c h a r a c t e r i s e d in that the score lines along the longitudinal edges (2,3) of the strip (4) are made by partially cutting the material.

Inventors: JUST, KRISTIAN
Applicants: AKTIESELSKABET LAUR. KNUDSEN  NORDISK ELEKTRICITETS SELSKAB
Application year: 1979
Main classification: B21D28
IPC codes: B21D51, H02G3, B21D28