Metal working – Means to assemble or disassemble – Overedge assembling means
Reexamination Certificate
2001-05-11
2003-11-25
Hong, John C. (Department: 3726)
Metal working
Means to assemble or disassemble
Overedge assembling means
C029S238000, C029S522100, C029S521000, C072S354200
Reexamination Certificate
active
06651300
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a jointing device for producing a clinching connection between a first workpiece and a second workpiece by means of a plunger which is insertable from above into the recess of a die whose peripheral wall has stationary wall sections which extends substantially parallel to the pressure direction. Moreover, the invention concerns a clinching method in which a first workpiece and a second workpiece with areal portions are placed atop one another at least with partial overlap and the first workpiece is indented from above such that it is imparted with a cup-shaped formed portion which presses into the second workpiece in the downward direction and deforms the latter without cutting, wherein the formed portion of the first workpiece forms an undercut with the second workpiece limited to predetermined peripheral areas of the formed portion. Finally, the invention relates to a clinching connection wherein a first workpiece has a formed portion which engages a formed portion of a second workpiece and forms with the second workpiece an undercut that is limited to predetermined peripheral areas.
2. Description of the Related Art
Such a clinching device, a clinching method, and a clinching connection are known from U.S. Pat. No. 5,230,136. The die has a cylinder-shaped formed portion from which radial channels extend. A plunger which has a somewhat smaller diameter than the formed portion produces during lowering into two stacked workpieces first a cup-shaped formed portion of the two workpieces wherein in the area of the channels the material of the workpieces can be forced slightly outwardly. By doing so, between the material of the upper workpiece and the material of the lower workpiece a slight undercut can be formed, while the formed portion of the lower workpiece has substantially vertically extending wall sections at the exterior.
In the process of clinching, two workpieces are connected to one another by partial deformation. This can be carried out without supplying heat, which is required, for example, for welding or soldering, and without auxiliary means such as adhesives or auxiliary connecting parts (screws or bolts).
The two workpieces must have areal portions for this purpose which must overlap at least partially with one another and which must rest parallel on one another. It is also possible to connect more than two workpieces with one another. For the subsequent explanation it is assumed that the first and the second workpieces are the outer workpieces. Alternatively, each workpiece can form an undercut with the next workpiece.
In connection with the clinching method, a single step method and a double step method are to be differentiated. In the single step method, the clinching connection is generated in a single working step. In the simplest case, a plunger is lowered into a die. By doing so, cup-shaped formed portions result in the two workpieces and are seated in one another with great friction force. Such a connection has a high shearing resistance but only minimal head-on tensile strength.
In order to increase the head-on tensile strength, dies are used in which, for example, the peripheral wall of the recess is formed by lamellas which are secured with respect to their position by an annular spring, for example, an elastomer ring. When the plunger produces the formed portions and is pressed farther with a sufficiently large force into the die, the two workpieces will deform radially outwardly and will accordingly press the lamellas outwardly so that an undercut of the first workpiece is formed in the second workpiece. In this configuration, the head-on tensile strength is substantially increased. However, the die is a relatively complex component. The lamellas must be manufactured with high precision.
An even better head-on tensile strength results during clinching with a cutting component. For this purpose, two cuts are provided at least in the workpiece facing the die. The other, upper workpiece is then deformed such that it penetrates at least partially the cuts. When applying an even higher pressure, the material is then forced through the cuts to the exterior and forms again an undercut. In this connection it is also required to provide the die with lamellas which are pulled or pressed inwardly by means of a spring force. The clinching connection with cutting component has the advantage of a high head-on tensile strength. However, it has the disadvantage that the workpieces must be cut so that it is no longer possible to provide gas and liquid tightness. This disadvantage can be prevented in that the clinching operation is employed with a reduced cutting component, according to which only the workpiece facing the die is provided with cuts. In both cases, the connection is however generally not suitable for dynamically loaded parts because notch effects result due to the cuts.
In addition to the single step method, two-step clinching methods are known which provide improved head-on tensile properties even without a cutting component. However, in this connection it is necessary to transport the workpieces from one tool to the next or, in reverse, to position a second tool on the required position on the workpiece. Both working steps require a relatively high precision during positioning which makes manipulation more difficult.
DE-A-39 23 182 A1 shows a device for connecting plate-shaped components by means of a die which is comprised of two parts connected at their lower end by a tension spring. The die has at its upper end a recess which conically widens in the downward direction. When a plunger, with interposition of two workpieces, is moved into the die, a clinching connection is produced which has an undercut over its entire periphery, i.e., an undercut between the first and the second workpieces and an undercut on the exterior side. For removing the connected workpieces, it is therefore required to pull apart the two die parts. Since this pulling apart is carried out against the force of the spring, there is the risk that the lower workpiece is scratched or damaged.
GB-A-2 069 394 describes a method for jointing plate-shaped workpieces and a device therefor. The device has a die which is formed by four springy portions which in the peripheral direction adjoin one another and surround a recess. The recess widens conically in the downward direction. In the recess, a counter member to a plunger is arranged which is moved downwardly counter to the force of a spring, when a plunger is moved into the die, with interposition of two workpieces. The movement of the counter member stops shortly before the plunger has reached its greatest stroke. By doing so, the two workpieces are pressed together at the end of the clinching process so that the material is forced radially outwardly in order to form undercuts. When removing the connected workpieces, the portions forming the die must be bent away again. Here, there is also the risk that the connected workpieces will become scratched or will be damaged in other ways.
DE-A-44 31 849 describes a clinching method and a clinching tool in which the plunger elements and die elements are arranged on oppositely positioned and synchronously rotating wheels. This allows to produce clinching connections in a continuous process.
SUMMARY OF THE INVENTION
It is an object of the invention to provide durable clinching connections which can be realized in a simple way.
This object is solved for a clinching device of the aforementioned kind in that the peripheral wall of the recess has movable wall sections between the stationary wall sections which moveable wall sections are arranged on levers wherein the levers are moveable by pressure from above into a working position and can be secured therein and form undercut areas and, by movement of the connected workpieces in the upward direction, are moved into a release position in which the undercut areas are completely released.
With such a clinching device one obtains first of all a relatively simple configura
Dalex-Werke Niepenberg GmbH & Co. KG
Hong John C.
Kueffner Friedrich
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