This invention is concerned with improvements in or relating to blind riveting and is especially concerned with tools for use in setting rivets in pull-through blind riveting.
The expression "pull-through blind riveting" is used herein to denote a procedure in which a shank of a tubular rivet having a head at one end, assembled on a stem of a mandrel which has a head which is too large to pass through the rivet shank without deforming it, is inserted in a hole in a workpiece from one side, in such a manner that the rivet head abuts the workpiece at said one side and the shank projects from the workpiece at the other side, and the rivet is set by pulling the mandrel stem at said one side of the workpiece while holding the head of the rivet against the workpiece whereby the mandrel head effects radial expansion of the rivet shank at the other side of the workpiece and is thereafter pulled right through the rivet.
It is customary in pull-through blind riveting to use a rivet-setting tool which has a nosepiece which serves as an abutment to engage the rivet head, and a mandrel with a long stem on which a number, for example 25, rivets are assembled, the rivets being set one after another upon reciprocation of the mandrel and forward feeding of the rivets successively through the nosepiece and up to the mandrel head. After all the rivets on the mandrel have been set, the mandrel is removed from the tool and the same, or another, mandrel loaded with fresh rivets is inserted in the tool.
To enable the rivets to pass forwardly along the mandrel stem through the nosepiece of a tool as just referred to, the nosepiece is constituted by two abutment members which separate, one on each side of a plane which includes the axis of the mandrel stem, thus allowing each rivet in turn to pass between the two members. In some pull-through blind riveting operations the members of the nosepiece close into abutting engagement with one another after a rivet has passed between them, the shape of the members and of the rivets permitting them so to do; in others, the members do not abut one another but close into engagement with the shank of the next following rivet on the mandrel stem. In some blind riveting operations, sufficient engagement with the rivet head in blind riveting is afforded by nosepiece members which engage only a peripheral margin of the rivet head, so far as permitted, if the members are surrounding the shank of the next rivet; in others it is important that the members closely surround the mandrel stem (as, for example, when carrying out blind riveting as described in the above-cited U.S. Patent Application Ser. No. 700,909).
It is also desirable that the mandrels of pull-through blind riveting tools can be rapidly changed when the supply of rivets on a mandrel has run out.
It is necessary for rivet-advancing means to be provided in a pull-through blind-riveting tool of the kind which has a mandrel with a number of rivets on its stem for feeding the rivets forwardly along the stem between riveting operations. Such means has customarily involved a stop device mounted on the mandrel stem and arranged to advance step by step therealong, a spring being interposed between the stop and the rearmost rivet. Such means has to be dismantled after all the rivets on a mandrel have been used to enable a fresh supply to be loaded onto it.