Apparatus for mechanical joining

Details Apparatus for mechanical joining Apparatus for mechanical joining

1999-11-19

2001-09-11

Watson, Robert C. (Department: 3725)

Metal working

Means to assemble or disassemble

Overedge assembling means

Reexamination Certificate

active

06286193

ABSTRACT:

The invention relates to an apparatus for mechanical joining.
Known apparatuses for mechanical joining essentially comprise a punch, a die and often also a holding-down means. As is known from U.S. Pat. No. 5,581,860, the holding-down means serves for applying a pre-selected contact-pressure force in the immediate area of a joining operation which is to be carried out and for acting as a stripper at the end of a joining operation, in order to strip the punch from the metal sheets. In this case, the force of the holding-down means is produced by a spring-pressure device with a central spring, for example in the form of a helical spring. The disadvantage here is that strippers which utilise helical springs involve large outputs and are prone to failure.
An object of the invention is thus to provide an apparatus for mechanical joining in which the holding-down means allows high production outputs.
The present invention provides an apparatus for mechanically joining metal sheets which lie flat one upon the other, having a tool set comprising at least one punch and one die which bounds a cavity in which the joining operation takes place, the punch displacing sheet-metal material out of a sheet-metal plane and upsetting it, and at least one tool part being arranged, for this purpose, on a displaceable tool carrier which has a holding-down means supported in a spring-prestressed manner adjacent to the tool part, characterized in that, for the spring-prestressing of the holding-down means, the tool carrier has a cylinder cavity in which there is guided a piston which acts on the holding-down means and on the head side bounds, with volume-changing action, a pressure chamber which can be subjected to the action of a fluid pressure medium.
An apparatus for mechanical joining according to the invention has holding-down means which do not include metallic springs and utilizes the compressibility of suitable gaseous or liquid media which are introduced in each case into a pressure chamber which is integrated in the displaceable tool carrier and is bounded with volume-changing action by a piston which acts on the holding-down means. The production outputs are increased to a considerable extent by such a spring-pressure device. In addition, constant spring forces are achieved over the relatively long service life.
The spring characteristic is flatter, with the result that high contact-pressure forces can be applied even initially. The manner and extent of the pressure-medium action also allow the spring characteristic and the maximum spring force to be set, as a result of which adaptation to a respective joining task is possible. This is important, in particular for the joining of aluminium since, in this case, relatively high stripper forces are required in order for the metal sheet, which more can stick on the punch, to be stripped off.
Further advantages reside in the considerably smaller amount of installation space in relation to prior-art spring-pressure devices. Maintenance is simplified since repair is possible by exchanging individual installation elements and renewed pressure-medium introduction.
Further configurations of the invention can be gathered from the following description and the claims.


REFERENCES:
patent: 4409720 (1983-10-01), Boudreau
patent: 5581860 (1996-12-01), Sawdon
patent: 3131301 (1983-02-01), None
patent: 3210956 (1983-09-01), None

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