TOOL AND PROCEDURE FOR JOINING OF OVERLAPPING PLATES BY PIERCING

The object of the invention is a tool and a procedure for the clamping of overlapping plates.

Overlapping plates are frequently clamped together by drilling holes in the overlapping parts of the plates and fastening them with screws, rivets or by spot-welding. In some plating works, such as false ceilings, roofing, and other internal and external architectural works (such as precision-electronic housing, etc.), holes must be bored on site, as it is difficult to know beforehand where the plates will overlap or, from an aesthetical point of view, where it will be practical to position the fastening elements. It is recommendable to first fasten the overlapping plates temporarily and fasten them later permanently with screws. The clamping device depicted in patent description DE 44 24 493, used for the clamping of two, at least partially overlapping plates, is a tool made up of two tool shanks fastened to each other and rotating around a pin; one clamp shank has a prick with a cylindrical body and a conical piercing end, and the other shank is provided with a counterpart with a borehole against the prick. The diameter of the borehole is larger than the diameter of the piercing prick. The piercing prick moves in the cylindrical hole coaxial Iy to the borehole, in a straight line, and enters the borehole with a radial play. The tool pierces the plates to be clamped after a local-tangential elongation process, and presses the rim of the hole into the borehole, thereby clamping the plates (with their own material). The fastening power of this method is relatively weak and is easily undone.

For certain plating works, mostly when using thin flexible plates, it is not necessary and not even practical to use rivets or screws for fastening, but they also require long-lasting and reliable clamping.

The purpose of this invention is the creation of a tool and a procedure for the clamping of overlapping plates that enables us to create a relatively strong, durable fastening method in a simple, easy and fast manner.

The invention is based on the perception that if a hand tool is provided with a proper piercing end and a borehole opposite it, then it is able to clamp together thin steel or plastic plates in two steps by placing the overlapping plates between the jaws of the tool and pressing the jaws together in the first step, thereby (by over-elongation) perforating the plates, and then in a second step pressing the plates with the tool in the same point from the other side. By doing this, the pieces of the plates bent and during the perforation made in the first step and now protruding from the plates will interlace and fasten the plates.

According to the invention, the task is solved with a tool made up of two tool parts, fastened to each other and rotating around a pin; both tool parts consist of a clamp shank projecting from the pin in one direction and a jaw reaching from the pin in the other direction; the first jaw has a prick towards the second jaw with a cylindrical body that comes to a conical piercing end, and in the second jaw, against the prick there is a borehole whose diameter is

larger than the diameter of the cylindrical body. The tool object of the invention has the characteristic that the cylindrical body of the prick is connected to the second jaw via a base part, and the diameter of the base part at its connection with the cylindrical body is identical to the diameter of the cylindrical body; the base part is gradually widened from the cylindrical body to the second jaw, and its diameter at the connection to the second jaw is larger than the diameter of the borehole.

According to a preferable version of the tool, the base part is of truncated conical shape.

The bending of the lower rim or collar achieved through the truncated conical shape ensures the proper direction of back-pressing.

According to another preferable version of the invention, the borehole is produced as a cylindrical opening of a ring, sleeve, shear plate or any other similar counterpart on the first jaw.

According to another preferable version of the invention, the collar of the borehole is chamfered with respect to the shape of the base part.

The invention also implies a procedure for the clamping of overlapping plates with the use of the tool object of the invention. During the procedure, the plates to be clamped together are fitted together, the overlapping part is inserted between the tool jaws, the piercing end of the prick is focused on a single clamping point, and by squeezing the clamp shanks of the tool the plates are punched through; then the tool is opened, and the plates are removed. After the removal of the punched plates, the tool or the plates are turned upside down, and the piercing end of the prick is inserted into the opening produced at the clamping point from the other side, and then by closing the tool again the plates are permanently clamped together in their own material.

The invention is further detailed in the attached drawings. The drawings include: Figure 1 shows a lateral sketch, partly segmented, of a preferable version of the invented tool. Figure 2 shows the positioning step of the invented procedure. Figure 3 shows the elongation step. Figure 4 shows the perforation step. Figure 5 shows the back-chamfering step. Figure 6 shows the back-bending step. Figure 7 shows the back-pressing step.

The invented tool is made up of two tool parts fastened to each other and rotating around a pin (1). Both tool parts are provided with a clamp shank (2, 3) projecting from the pin (1) in one direction and with a jaw (4, 5) reaching from the pin (1) in the other direction. The first jaw (4) is provided with a borehole (6) whose diameter is d1. On the second jaw (5), against the borehole (6) and towards the first jaw (4) there is a prick (7) with a cylindrical body (9) ending in a piercing end (8). The diameter d2 of the cylindrical body (9) of the prick (7) is smaller than the diameter of the d1 of the borehole (6). Since the borehole (6) and the prick (7) are equally distanced from the pin (1), they move around the same radius when the clamp shanks (2, 3) are

pressed together and, due to the difference in d1 and d2, the cylindrical body (9) of the prick (7) enters the borehole (6) with a radial play. When using the tool, this play permits the entrance of the plates' punched material.

Between the cylindrical body (9) and the second jaw (5), the prick (7) is provided with a base part (10). The base part (10) is gradually widened from the cylindrical body (9) to the second jaw (5), and is preferably of a truncated conical shape. The diameter of the base part (10) at the connection to the cylindrical body (9) is the same as the diameter d2 of the cylindrical body (9), and at the connection to the second jaw (5) its diameter is d3. Diameter d3 is larger than the diameter d1 of the borehole (6).

In another preferable version of the tool, the borehole (6) on the first jaw (4) is produced as a cylindrical opening of a ring, sleeve, shear plate or any other similar counterpart. Correspondingly, the collar of the borehole (6) is chamfered with respect to the shape of the base part.

In another preferable version of the tool, its geometric parameters are: d1 = 2.8-4.2 mm, preferably 3.5 mm; d2 = 0.8-2.8 mm, preferably 1.5 mm; and d3 = 2.9-8.0 mm, preferably 4 mm; the height of the base part (10) is 0.5-4 mm, preferably 1 mm; the height of the cylindrical body (9) is 1.5-5.0 mm, preferably 2 mm, whereas the height of the piercing end (8) is 0.2-5.0 mm, preferably 1 mm.

Aforementioned geometrical parameters are determined depending on the collective thickness of the plates to be clamped together in such a way that the difference in diameter between the d2 diameter of the cylindrical body (9) and the d1 diameter of the borehole (6) shall allow for the back-chamfering of more than twice the collective thickness of the plates to be clamped.

In another preferable version of the tool, the piercing end (8) is of hemispherical shape.

According to the invented procedure, the plates (11 , 12) to be clamped together are fitted together, the overlapping parts are fastened by hand, by vice or by any other tool for this purpose, and are inserted between the tool jaws (4, 5) provided with borehole (6) and prick (7). This is the initial situation for the procedure described in the invention (Figure 2).

The piercing end (8) of the prick (7) is focused on a single clamping point, and the clamp shanks (2, 3) of the tools are squeezed together, thereby moving and pressing the jaws (4, 5) against each other. This is an intermediate step in the procedure, i.e. the elongation step, depicted on Figure 3.

Upon pressing of the tool shanks, the prick (7) punches the plates and the rim or chamfer of the hole is pressed into the space between the borehole (6) and the cylindrical body (9) of the prick (7) (perforation step, Figure 4).

The tool is then opened and the plates are removed, though still held together to prevent slipping, and the tool or the plates are turned upside down, so that according to Figure

5 the piercing end (8) of the prick (9) may be positioned into the opening at the clamping point to perform the back-chamfering.

The tool is pressed together once again (this procedure has another intermediate step, back-bending, shown on Figure 6), while bending the rim created during the punching with the base part (10) of the prick (7) that broadens towards the second jaw (5), and thereby permanently fastening the plates to each other. Figure 7 shows the tool pressed together to the maximum, in-between the clamped plates. After opening the tool, the clamped plates are removed from the prick (7), and from between the jaws (4, 5).

The tool object of the invention is simple, cheap and easy to handle. The tool and the procedure ensure fast and easy, relatively strong and long-fasting clamping. It does not require preparation, it is sufficient to grab the plates with one hand, and use the tool with the other.

The invented procedure is not only applicable to the hand tool described in detail above, but also to any other tool - even tools guided by microprocessor - provided with the jaw types described above.

The tool and the procedure are easily applied for the construction of models, toys, at school workshops and for the elaboration of visual aids, preferably made of thin steel or plastic plate, or even cans or bottles.