Fastening system including segmented self releasing anvil

Claim 1

In a device for swaging a stump type fastener for clamping a plurality of workpieces together and including a pin and a tubular member adapted to be swaged onto the pin, said device swaging the tubular member onto the pin substantially by applying a force solely onto the tubular member, said device comprising a housing having a tapered opening at one end, anvil means located within said opening for relative movement therein, said anvil means comprising a plurality of separate anvil segments, said anvil segments together defining an outer frusto-conical surface having a contour complementary with that of said tapered opening, said outer frusto-conical surface and said tapered opening being at an angle providing a self releasing taper, said anvil segments together defining an inner swaging surface comprising an outer outwardly flaring bell mouth portion communicating with a reduced diameter straight cylindrical portion, said inner swaging surface selected to swage the tubular member a preselected amount to provide a desired clamping force on the workpieces via the set fastener, said inner swaging surface being of a length to confiningly embrace the tubular member for substantially its entire swaged length with said tubular member being swaged over a substantial portion by said straight cylindrical portion, a stop pin supported in said housing and having an enlarged head portion for supporting said anvil segments in their non-actuated position spaced from said tapered opening, spring means operative between said housing and said anvil segments for normally biasing said anvil segments axially outwardly against said head portion at a preselected preload, said anvil segments upon application on the tubular member being movable axially inwardly into said tapered opening with said outer frusto-conical surface engaging said tapered opening, anvil stop means cooperating with said housing and said anvil segments for limiting the axially inward movement of said anvil segments, said stop pin located at a preselected location to engage the fastener upon completion of the swaging at a position precluding said device from directly engaging the confronting one of the workpiece, said anvil segments having confronting side surfaces on adjacent ones of said anvil segments tapering radially inwardly away from each other whereby a slight axially extending gap occurs between adjacent ones of said anvil segments, said side surfaces terminating at their radially inner ends in axially extending edges which are radiused, said gaps receiving limited amounts of material from the tubular member upon swaging but providing readily visible lines extending axially for the length of the swage on the tubular member to provide observable inspection markings.