Aerpat A.g.

Advel Limited

Albert C Francis

Frederick A Summerlin

Raymond D Lacey

Michael Woodrow

A blind, self-plugging rivet assembly for securing together two members (42, 43) is of the type comprising a tubular shell (13) with an enlarged head (14) at one end, and a stem (12) which extends through the bore (15) of the shell, the stem having an enlarged head (38) beyond the tail end (18) of the shell. The shell has a weakened zone (19) formed by three slits (22) extending along part of the shell shank and spaced apart equiangularly around it. The stem head (38) lies beyond the shell tail end, and has an underhead surface (39) which is slightly convex and is bounded by a sharp edge (40). The stem has a pulling portion (32) connected by a breakneck to a plugging portion (31) which is an interference fit in the shell bore. Adjacent the breakneck the plugging portion has a cylindrical skirt which, when the rivet has been installed, can be deformed outwardly to lock the plugging portion to the shell. A bead on the stem guides the tool for deforming the skirt.

Blind rivet assembly

A blind bolt is of the type comprising a tubular shell 14 through which extends a stem 13 with an enlarged head 12 at one end which, in installation of the bolt, is pulled into the shell 14 to expand it and form a blind head. The stem 11 is provided with two opposed deformations 19 to prevent the shell falling off the stem before installation. Each deformation has a relatively shallow sloping profile with its higher end towards the shell, and the width of the deformation is a maximum at the bottom end of the slope and a minimum at its higher end. The deformations are formed by pinching up portions of the stem between two opposed dies, the shape of the bite between the dies being tapered in the direction along the stem.

Blind fastener and method of manufacture thereof

A mandrel for a blind rivet is made by first forming a mandrel blank from wire stock in a series of cold heading operations which include forming an enlarged head at one end of an elongate stem, and then scraping material from the peripheral surface of part of the head adjacent to the stem and moving the material in a direction away from the stem so as to leave a core and to form a circumferential flange-like boss from the scraped material. The mandrel blank thus produced is then subjected to a rolling operation in which the mandrel blank is rolled between contoured mandrel-rolling dies and thereby formed into a finished mandrel. In particular, the contours of the rolling dies are such as to form a breaker groove at the junction between the head and stem of the blank and to cause the material of the flange-like boss to flow over the scraped surface of the core of the head and towards the stem and form a skirt peripherally of the core while confining the material of the boss so that it does not flow across the breaker-groove. Pulling grooves are rolled in the mandrel stem and the external surface of the skirt is rolled to a cylindrical shape with, optionally, a peripheral groove therein.

Growing community of inventors

Stevenage, United Kingdom

Albert C Francis