Blind fastener assembly

A blind fastener assembly for installation in a workpiece having an accessible and an inaccessible surface and an opening therebetween, said assembly comprising:

• a mandrel having an enlarged head at one end thereof, an elongated shank portion and means on said shank portion adapted for advancement of said mandrel in a direction along its longitudinal axis;
• expander means having an enlarged head at one end thereof formed to bear upon the accessible workpiece surface, a cylindrical tail section extending from the other end thereof, a tapered surface varying in radial thickness in a longitudinal direction from a minimum radial thickness at a point adjacent said cylindrical tail section to a maximum radial thickness at a location spaced from said other end, and a shank portion intermediate said enlarged head and said tapered surface, said shank portion having an outer surface formed to be placed in the workpiece opening, and an internal bore extending through said expander means carrying said mandrel shank portion;
• expandable sleeve means carried on said mandrel shank portion proximate said enlarged head, said sleeve means including a first portion of greater radial thickness adjacent one end thereof facing said enlarged head and a second portion of reduced radial thickness adjacent the other end thereof facing said expander means other end, said sleeve means having a discontinuity in the inside surface thereof between said first portion and said second portion, said portion having an inner diameter substantially equal to the outer diameter of said cylindrical tail section and having a length which is greater than that of said cylindrical tail section, said second portion being adapted to be advanced along said expander means cylindrical tail section and tapered surface and expanded thereover upon advancement of said mandrel toward the inaccessible workpiece surface, said sleeve means forming a radially outwardly extending bulb at a location axially spaced from the inaccessible workpiece surface at approximately said inside surface discon tinuity prior to contacting the inaccessible workpiece surface, said other end of said sleeve means ultimately contacting the inaccessible workpiece surface causing said outwardly extending bulb to expand radially and to propagate axially in a ripple manner toward the inaccessible workpiece surface and finally bear thereagainst over a selected area radially spaced from the area of contact of said sleeve means other end;
• and
• locking means operatively arranged between said expander means and said mandrel for locking said mandrel and said expander means together to eliminate relative motion therebetween in one direction.