EP0155619B1 - Method for connecting metal sheets together - Google Patents

Description

The invention relates to a clinching method in which two sheets lying flat on top of one another are connected to one another by cutting, pressing through sheet metal material and extruding the pressed material behind the incisions. Regarding the term "enforcement", DIN 8593, Part 5, Section 4.5.2.11. to refer.

A method according to the preamble of claim 1 is known from GB-A-2 104 430.

A clinching device for joining sheet metal lying flat on top of one another, comprising a die with a central anvil part and with support parts projecting outward from the anvil and provided with cutting edges at their free end and projecting over an anvil work surface, and a punch which is passed through the die relative to the die Sheets can be moved towards the anvil work surface is disclosed in EP-B-0 077 932; with it, for example, the joint connection can be made in accordance with the aforementioned DIN sheet.

In the known device, the stamp or the stamps have a counter cutting edge for each die cutting edge, in the preferred case two parallel cutting edges and two counter cutting edges. The stamp cuts through both sheets along congruent lines, and the material pressed through on the die side is squeezed. - This known device has the advantage of very small dimensions relative to the thickness of the sheets to be connected, and both the punch and the die are very easy to manufacture.

Although, as practice has shown, the strength of the "joining point" produced with the known device is by far sufficient in most cases, there was nevertheless a need to increase the strength of the connection, and it is the object of the present invention to provide a clinching method to create, in which the joining strength is increased compared to the values achievable with the known devices.

This object is achieved by the method according to claim 1.

In comparative measurements, it has been shown in a highly surprising manner that the strength of a joining point produced according to the invention exceeds that of joining points which were produced with the known method under otherwise identical conditions by at least 50% and up to 75%; the joint connection was subjected to shear loads parallel to the sheet surface and tensile loads perpendicular to it.

When the invention is used, there is the further advantage that the non-cut sheet remains fluid-tight at the joint, and also coatings such as galvanizing or plating are not cut through, so that a generally desired corrosion protection is generally maintained.

The type of joint connection obtained according to the invention is known per se in the prior art, but is produced in a different way:

A group of publications describes methods or devices in which one sheet is cut and the other sheet is pressed through by means of a first press stroke, then the semi-finished joint connection is pressed out of the die and finished by means of a second press stroke. A-1 446 095 and GB-A-2 104 430, the latter also disclosing that the one sheet is only cut, not perforated.

Joining processes in which the joining point remains tight are known from DE-A-3 106 313. According to the teaching of this document, two sheets lying flat on top of one another are connected to one another in that a limited section of one sheet is pressed by means of a blunt stamp through the other sheet, which is also supported by a blunt die, after which both sheets pressed through are behind the first sheet facing away from the first Side of the second sheet are extruded laterally. For this purpose, two parts of the die can rebound laterally. The pressed-through and extruded material portion of the sheet facing the die does not contribute to the joining strength; on the contrary, the material of this sheet hinders the extrusion of the material pushed through by the stamp-side sheet, so that poorer strength is to be expected. In addition, the jointed surfaces of the joint are all rounded, which should further deteriorate the strength of both Scherals and tensile load. These considerations, based on the subject matter of the invention and the prior art, are of course based on the assumption of otherwise identical conditions (material quality and thickness, dimension of the joint, working pressure and working stroke).

In an apparatus for carrying out the invention, it has proven to be advantageous to make the edges delimiting the working surface of the stamp in a deliberately blunt manner by selecting an edge angle of more than 90 ° and / or rounding the edges. On the other hand, it must also be ensured that the sheet on the die side is really cut, and that the process of extrusion is also carried out in the desired manner. For the most important applications, it has turned out to be a useful compromise to design the stamp starting from its working surface in the shape of a truncated cone or truncated pyramid (depending on the shape of the cutting edges) with a cone or pyramid tip angle of 30..50 °, the definition being made by Thickness and quality of the material of the sheets is determined. An angle of 40 ° has proven itself for steel sheets of the same thickness.

The invention is also applicable to devices in which a die is used Stamp with multiple work surfaces, such as a double stamp, is assigned. The invention can also be implemented with matrices in which the support parts can be exchanged to adapt to different material qualities and / or material thicknesses.

A particularly simple embodiment of the device is obtained if the die has only two support parts with cutting edges that are parallel to one another. In addition, this embodiment has the advantage that the alignment of the die and punch in the press used only has to be carried out with high accuracy in the direction perpendicular to the cutting edges, while the alignment across is less critical.

• Fig. 1 zeigt in Teilseitenansicht eine erste Ausführungsform, während die zu verbindenden Bleche im Schnitt gezeichnet sind,
• Fig. 2 stellt analog zu Fig. 1 die Teile nach Beendigung des Fügevorgangs dar,
• Fig. 3 zeigt perspektivisch im Teilschnitt eine mit der Vorrichtung nach Fig. 1 und 2 gefügte Verbindung, Fig. 4 ist eine Darstellung analog Fig. 3, jedoch in Richtung der Pfeile 4 - 4 in Fig. 3 gesehen,
• Fig. 5 ist eine Draufsicht auf die Fügestelle nach Fig. 3, 4,
• Fig. 6, 7 und 8 zeigen Draufsichten auf die Matrizen weiterer Ausführungsformen von Vorrichtungen,
• Fig. 9 stellt in Seitenansicht einen Stempel einer weiteren Ausführungsform dar,
• Fig. 10 zeigt in zu Fig. 1 analoger Darstellung eine Matrize abweichender Konstruktion, und
• Fig. 11 ist eine Ansicht auf die Matrize nach Fig. 10 in Richtung des Pfeiles 11.

Embodiments of devices for carrying out the invention are explained in detail below with reference to the accompanying drawings. The drawings are largely schematic and limited to the essentials.

• Fig. 1 shows a partial side view of a first embodiment, while the sheets to be connected are drawn in section,
• 2 shows, analogously to FIG. 1, the parts after the joining process has ended,
• 3 shows a perspective partial section of a connection made with the device according to FIGS. 1 and 2, FIG. 4 is an illustration analogous to FIG. 3, but seen in the direction of arrows 4 - 4 in FIG. 3,
• 5 is a plan view of the joint according to FIGS. 3, 4,
• 6, 7 and 8 show top views of the matrices of further embodiments of devices,
• 9 shows a side view of a stamp of a further embodiment,
• FIG. 10 shows, in a representation analogous to FIG. 1, a die of a different construction, and
• 11 is a view of the die of FIG. 10 in the direction of arrow 11.

The press or press arrangement, in which the respectively associated and interacting parts of the punch, on the one hand, and the die, on the other hand, are installed in alignment with one another, are not shown in the drawings. The direction of action of the press results from the summary of FIGS. 1 and 2, which show the two possible relative positions of the punch and die at the beginning and at the end of the press stroke.

First, reference is made to FIGS. 1 to 5.

The die comprises a stationary anvil 10 supported on its underside in the press with an essentially elongated, rectangular plan; Fig. 1 shows the side view on the narrow side. Support parts 12 extend along the broad sides of the anvil and can extend laterally (FIG. 2) and whose free edges facing the anvil are designed as cutting edges. The plane defined by the two cutting edges is one dimension higher than the somewhat convexly curved working surface 16 of the anvil, which is smaller than the sum of the thickness of both sheets 18, 20, but greater than the thickness of the sheet 18 facing it.

The punch 22 has a working surface 24 which, as shown in FIG. 1, is clearly narrower than the distance between the two cutting edges of the die. Starting from this working surface, the cross section of the stamp increases so that it has the shape of a truncated pyramid with a rectangular base, the area penetrating into the sheets, the angle of inclination of the pyramid sides relative to the stamp axis being approximately 20 °; this corresponds to a tip angle of 40 °. The extent to which the working surface 24 is narrower than the cutting edge distance depends on the thickness of the sheets, in particular on the thickness of the sheet 20 facing it, and is preferably dimensioned (for which a few attempts are sufficient) that this sheet 20 during joining is no longer cut. The edge delimiting the working surface 24 is rounded, in the example with a radius of the order of 0.5 mm, and polished. The side faces of the truncated pyramid-shaped stamp section are designated by 26. The contour of the stamp on the sides extending perpendicular to the cutting edges is not shown in FIGS. 1 and 2, but can be seen in FIG. 9, which shows a stamp which is nothing more than a doubling of the stamp from FIGS. 1 and 2. It should be noted that here too the contour has approximately the same apex angle of the truncated pyramid as on the sides parallel to the cutting edge.

While Fig. 1 shows the state before joining, Fig. 2 shows the result that is present at the end of the press stroke (it should be noted that either the press pressure or the press stroke is specified):

The sheet 18 has been cut along the cutting edges 14, which extend perpendicular to the plane of the drawing, by the interaction of the same with the stamp 22, and the web 30 which has remained between the cuts has been pushed through to the working surface 16 of the anvil. By further pressure (and thus stroke) of the punch 22, the pressed-through area 32 of the sheet 20, which has not been cut, is extruded so that its material is plastically deformed behind the cut edges 34 with firm anchoring to them. The pressed-through web 30 remains with its ends 36 hanging on the sheet metal, since an incision has been made there. 3 to 5 show the addition generated in this way.

In the first embodiment described so far, two parallel incisions were made in the sheet 18; the die and the stamp have a very simple, inexpensive to manufacture shape. If there are special requirements for the appearance of the joints an embodiment of the device, as indicated in FIGS. 6 to 8, may be preferred. These embodiments are only shown as a top view of the die. The anvil 10 '(FIG. 6) or 10 "(FIG. 7) has the shape of a cylinder, and the support parts 12' or 12" have cutting edges which extend the sheet metal facing them along four (FIG. 6) or Cut three (Fig. 7) arcs with the same radius and common center. Between each of the incisions there remains a web, which has the function of the webs 36 from FIG. 3. The working surface of the associated punches is indicated at 24 'or 24 "; the contour of these punches is then frustoconical with a tip angle of preferably 40 ° analogous to FIG. 1.

Finally, in the embodiment according to FIG. 8, four supporting parts 12 "'are arranged around an anvil 10"', which has a square outline; the webs then remain in the corner area. It should be noted that under certain circumstances it is also possible to dispense with standing webs. This would result in a closed circular incision shape in FIGS. 6 and 7, in FIG. 8 a closed square incision shape, with the result that a plate with a corresponding outline would be punched out from the sheet metal facing the die. The appearance of the joint would be very similar to a rivet head, but care would have to be taken to ensure that the punched-out plate is ejected from the die after each operation.

The stamp according to FIG. 9 is designed as a double stamp, in that two stamps according to FIG. 1 are arranged side by side and are made in one piece. One can see the two working surfaces 24a, 24b and the respectively assigned flanks 28, which extend perpendicular to the cutting edges and also define an apex angle of 40 °. The cutting edges of the associated die are simply designed to be correspondingly longer, so that two adjacent joints are produced with one press stroke.

10 and 11 show a die in which the support parts are interchangeable.

The die comprises a base 118 with a flat support surface 120 parallel to a press table (not shown) and a flat clamping surface 122 extending perpendicular thereto. A threaded bore 124 is machined into the base perpendicular to the clamping surface 122.

The support members 126, 128 and anvil 130 are separately manufactured components. The anvil 130 is a steel stamped part, and the support parts are stamped and in the area of their cutting edges 132, both on their side facing the anvil and on its side facing away from them, the support parts are provided with a cutting edge, specially hardened or hard-coated and ground. The anvil and support parts have through holes which are aligned with the threaded bore 124 in the assembled state, the forces acting on the joining being transmitted to the base in that the support parts and anvil are supported on the support surface 120.

On the side of the support part 126 facing away from the clamping surface 122, a clamping disk 134 is provided, likewise provided with an aligned through hole. The entire assembly is held together by a clamping screw 136. In Fig. 10 the clamping screw is not yet tightened so that you can see that it is convexly curved outwards and thus acts as a spring washer. With its lower edge, it also lies on the support surface 120.

This embodiment has the advantage that the support parts can first be turned over when their cutting edges wear and, if the second pair of cutting edges is blunt, can be replaced. The anvil is also interchangeable. Experience has shown that there is no wear on the anvil, but this enables the joining of sheets of different thickness, which in turn requires a change in the distance between the cutting edges 132 and the anvil working surface 138.

The upper edge 140 of the clamping washer is at the same height as the upper edge 142 of the clamping surface 122, so that the same clamping conditions are present for both support parts.

As can be seen from FIG. 11, the support parts have a contour with lateral cutouts, so that the bending stress during lateral rebound is distributed as uniformly as possible over the length of the support parts.

Claims (2)

1. A through-joining method, in which two metal sheets (18, 20) positioned flat one on top of the other are joined together by slitting, pressing through sheet material and flow-forming the pushed-through material behind the slits, wherein only one of the metal sheets (18) is provided with slits, and the pushed-through material on the side of the slit metal sheet remote from the other metal sheet (20) is flow-formed between an anvil part (10) and a punch (22, 28), characterized in that at least two slits having first predetermined spacings from each other are made by means of the punch (22, 28) in co-operation with cutting blades (12, 14) that are arranged laterally with respect to the anvil part (10), extend beyond the working face thereof and yield resiliently outwards with respect to the anvil part (10) and are provided at their free ends with cutting edges (14), the punch boundaries facing towards the cutting blades (12, 14) have second predetermined spacings from one another that in accordance with the thickness of the metal sheet (20) not to be cut right through are less than the first spacings, and the cutting blades (12, 14) are allowed to yield resiliently outwards during the flow-forming, with the result that the joint is effected by means of a single pressing stroke.

2. A through-joining method according to claim 1, characterized in that a metal sheet (18) is provided with two straight slits parallel with one another.

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