Metal working – Method of mechanical manufacture – Assembling or joining
Reexamination Certificate
1999-05-12
2001-04-17
Hughes, S. Thomas (Department: 3726)
Metal working
Method of mechanical manufacture
Assembling or joining
Reexamination Certificate
active
06216331
ABSTRACT:
BACKGROUND
The present invention relates to a setting head and to a method for the insertion of elements consisting of head and shaft parts into pre-apertured workpieces, and is concerned, above all, but not exclusively, with the insertion of bolt elements into sheet metal parts, with the bolt elements being secured to the sheet metal parts via a riveted connection. Such rivetable bolt elements are known and can be classified into two different categories depending on whether the riveted connection arises in the region of the transition between the shaft and the head part or at the end face of the head facing away from the shaft part.
The present invention is concerned principally with the setting of bolt elements of the first named category in which the riveted connection arises in the region of the transition between the shaft part and the head part. However, it can be modified so that it can be used for bolts of the second category. The setting head is however in principle also suitable for the introduction or for the setting of hollow fastener elements such as rivetable nuts, above all when these have an elongated shape.
An example for a modern rivetable bolt which can be inserted into a sheet metal part or into a plate part by means of the setting head of the invention, or by means of the method of the invention, can be found in the German patent application P 44 20 475.8 of the present Applicants filed on Mar. 25, 1994. The element which is claimed there and which can be inserted into a sheet metal part comprises a shaft part and a unitary head part formed thereon and is characterized in that the element has concave peripherally closed fields or pockets at its underside serving as the contact surface, with the fields or pockets being partly bounded by ribs which extend outwardly away from the shaft part. The shaft side ends of the ribs extend in raised form along the shaft part and merge at their ends remote from the head part into at least one recess which is spirally arranged around the shaft part. During the setting process the metal of the sheet metal part is deformed into the fields and into the recess. This results in a form-fitted connection between the element and the sheet metal part. In this way, not only a rotational security of the element is present but also a connection which prevents the loss of the element from the sheet metal part prior to and during the mounting of the counter-element which has to be secured by the element to the sheet metal part.
Setting heads for the insertion of fastener elements onto bolt elements are likewise known and are frequently inserted into presses in order to rivet the fastening elements with sheet metal parts during the manufacture or shaping of the sheet metal parts.
By way of example a setting head can be found in DE-PS 34 47 006 which is suitable for the insertion of bolt elements which are riveted to the sheet metal part at the end face of the head facing away from the shaft part. In this respect the threaded part of the bolt is received over its full length within a bore of the plunger so that a high quality alignment of the bolt element is ensured as a result of the excellent mechanical guidance of the plunger.
The problem of ensuring a precise alignment of the bolt element within the setting head and during the insertion of the bolt element exists above all with bolt elements which are riveted to sheet metal parts in the region of the transition between the shaft part and the underside of the bolt head.
SUMMARY OF THE INVENTION
The object of the present invention is thus to provide a setting head for the insertion of fastener elements, principally, but not however exclusively. This invention is particularly adapted for bolt elements which are riveted to a sheet metal part in the region of the transition between the shaft part and the head. An excellent alignment of the fastener element prior to and during the setting process is ensured with a simple inexpensive compact manner of construction and problem-free operation, and indeed an alignment which is not impaired by machine vibrations or jolts.
In order to satisfy this object provision, the invention teaches that the respective element to be inserted can be held in the setting head by at least three holding fingers. Each holding finger initially centers, aligns and positions the element in the setting direction both at the head part and also at a distance from the head along the shaft part.
The corresponding method for the insertion of the element is accordingly characterized in that the elements are introduced between at least three holding fingers. The fingers respectively hold the element initially both at the head part and also at a spacing from it at the shaft part so that it is centered, aligned and positioned in the setting direction. During subsequent closing movement of the setting head, the holding fingers still hold the respective element during the initial introduction of the shaft part into the aperture of the workpiece, which is aligned above a matrix or die button. The fingers only pivot. outwardly after the guidance of the shaft part has been taken on by the guide bore of the matrix, but also guide the head part in a centered manner during this pivotal movement and during at least a part of the setting movement of the plunger, until the head part of the element contacts the workpiece or approaches the latter; and in that the element is connected in form-locked manner to the workpiece by means of the setting plunger and the matrix.
Since the respective element to be inserted is held by at least three holding fingers, both at the head part and also at an axial distance along the shaft part, it is ensured, in accordance with the invention, that the longitudinal axis of the fastener element adopts a predetermined position concentric to the setting plunger and cannot tilt. This security against tilting would for example not be generated in trouble-free manner with only two holding fingers, but could however be achieved with more holding fingers which however represent an additional mechanical complication and are actually unnecessary. The use of three holding fingers also has the advantage that adequate space is available for the introduction of the fastener element between the three holding fingers.
Since the holding fingers also hold the fastener element at the head part it is ensured that the fastener element adopts a precisely predetermined axial position along the longitudinal axis of the setting plunger, so that the working movements of the setting head or of the setting plunger and the course of the setting method can be predetermined in the most precise manner. The fastener element is however not only aligned and positioned by the holding fingers but rather also precisely centered, so that tight tolerances can be observed with respect to the positioning of the corresponding aperture of the lower lying sheet metal part. The premanufactured aperture of the sheet metal part can have a diameter which is only fractionally larger than the outer diameter of the shaft part of the fastener element. In this way a reliable riveted connection is achieved without having to fear that the shaft part will be damaged on introduction through the hole by the surrounding metal of the sheet metal part due to inaccuracies in positioning.
Since the way of holding the fastener elements in the setting head in accordance with the invention also precludes a tilting of the element the danger of damage to the tool or to the workpiece on insertion of the fastener element is largely precluded, so that undesired disturbances of the sequence of operation are minimized.
The movements of the pivotally arranged holding fingers are synchronized with one another in accordance with the invention which ensures that the desired centered alignment of the fastener element with the axial direction of the setting plunger is always given.
The synchronized means preferably comprises a sleeve with oblique surfaces for the control of the pivotal movement of the holding fingers during the worki
Cozart Jermie E.
Howard & Howard
Hughes S. Thomas
Profil Verbindungstechnik GmbH & Co. KG
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