Fastener for multi metal stack-ups

A fastener device for holding together multiple layers of material wherein there is a cylindrical hole having a cylindrical wall and comprising substantially axially aligned holes extending through the layers of material, said fastener device comprising a pre-assembly including a circumferentially continuous sleeve and a fastening means, said sleeve having outer and inner surfaces, one of said surfaces comprising a sleeve bore and one of said surfaces being cylindrical throughout its length, the exterior of said sleeve having a size adapted to provide an initial sliding fit in said hole, said fastening means comprising a shaft with a head at one end and a fastener portion at the opposite end with clamping means thereon, said head having a circumferentially continuous annular bearing area, the outside diameter of the shaft between the head and said fastener portion comprising a gentle tapered portion varying from a size adjacent the head relatively larger than the initial diameter of the adjacent end of said bore to a size at the opposite end smaller than said adjacent end of said bore, said shaft having a pre-assembled press fit in the bore with the sleeve partially expanded sufficient to close maximum allowable tolerances between the interior surface of the sleeve and the tapered portion of the shaft and with part of the tapered portion of the shaft adjacent the head exposed, part of the fastener portion being exposed and part of the fastener portion being located within the bore, said sleeve having a varying wall thickness which is smallest at the end adjacent the head of the fastening means and which expands progressively toward the other end, the rate of expansion being substantially uniform throughout the length of the sleeve, a first portion of the sleeve surrounding the tapered portion of the shaft in pre-assembled press fit condition having a final reduced cylindrical shape and the second portion of the wall of the sleeve which initially surrounds the fastener portion being in position deflected inward from the cylindrical shape but having a reduced compensating thickness whereby to provide expansion of said second portion to a position wherein the exterior thereof is cylindrical and alignment with the cylindrical first portion of the sleeve.

A sleeve bolt assembly for both a tension and shear fatigue critical joint comprising multiple layers of material of different hardness, yield strength, and modulus of elasticity wherein there is a common substantially cylindrical hole as long as the aggregate thickness of said layers which is the aggregate of substantially axially aligned individual holes extending through the layers of material, and wherein the capability is an interference fit of the sleeve bolt assembly in the cylindrical hole of between about 0.002 inc. and 0.025 inc. per inch diameter, said sleeve bolt assembly comprising a pre-assembly of a bolt and a circumferentially continuous sleeve, said bolt comprising a shaft having a head at one end and a thread at the opposite end, said head having a circumferentially continuous annular bearing area transverse to the bolt axis, a portion of the shaft having a gentle taper of between 0.200 to 0.300 in. per foot of length, said sleeve having a tapered bore corresponding to the taper of the shaft, an exterior portion substantially cylindrical throughout its length except for a reduced thickness compensating portion which overlies the threads, said reduced thickness having the same taper as said shaft and said sleeve, a hardness different from the hardness of at least one of said layers, and a length substantially equal to the length of the cylindrical hole, the diameter of a first portion of the shaft adjacent the head being larger than the diameter of the large end of the bore when the shaft is drawn into the bore a distance of about 0.096 in. to an initial partially expanded condition wherein the sleeve is expanded in an amount exceeding the maximum tolerance of the sleeve fit with the shaft, the length of the tapered portion of the shaft being substantially equal to the length of the sleeve, the exterior of the sleeve when in initial partially expanded condition on the shaft having a reformed cylindrical exterior portion of reduced diameter less than the initially expanded diameter and adapted to provide a sliding fit in said cylindrical hole, and means adapted to engage the thread on the shaft and draw said shaft into the bore until the head is in a position adjacent the corresponding end of the sleeve and the sleeve is in final expanded condition to create the required interference fit and joint clamp-up simultaneously with seating of the head, a portion of the shaft between the head and the adjacent end of the sleeve being exposed when in said initial partially expanded condition and adapted to provide a sleeve with an exterior in said final expanded condition cylindrical throughout its length and having a diameter expanded in size by an amount of between 0.002 in. and 0.025 in. per inch diameter of the shaft within a tolerance of .+-.0.0005 throughout the entire length of the sleeve.

A high strength fastener device for holding together multiple layers of materials through an aligned hole comprising,

• a two-piece pre-assembly including a circumferential continuous metallic sleeve and a metallic fastening means,
• said sleeve having outer and inner surfaces, said inner surface comprising a sleeve bore being uniformly tapered and said outer surface being cylindrical throughout the greater of its length,
• the exterior of said sleeve having a size adapted to provide an initial sliding fit into said hole,
• said head having a substantially radially extending, circumferentially continuous annular bearing formed to said shaft by an annular fillet portion,
• the outside diameter of the shaft between said fillet portion and said holding portion comprising a tapered portion varying uniformly in diameter from a large size adjacent to said head relatively larger than the largest diameter of the sleeve bore, which is at the adjacent end of said bore, to a smaller size at the opposite end adjacent said sleeve bore,
• the taper on the shaft being substantially the same as the taper of the sleeve bore,
• said shaft having a pre-assembled pressed fit in the bore with the sleeve partially expanded radially sufficient to remove all tolerances between the tapered outside diameter of the shaft and the tapered inside diameter of said sleeve,
• the length of said sleeve being less than the combined length of said tapered portion and said holding portion of the shaft with a first part of the holding portion extending beyond the other end of the sleeve, and a second part of the holding portion being located within the sleeve bore,
• the holding portion having a diameter less than the smallest diameter of said tapered sleeve whereby the portion of the sleeve overlying the holding portion is not expanded,
• the expansion of the sleeve over the tapered portion of the shaft is linear throughout the length of the sleeve, the first portion of the sleeve surrounding the tapered portion of the shaft in pre-assembled pressed fit condition having a final cylindrical exterior which has been reduced in diameter after pre-assembly,
• and a second portion of the sleeve surrounding a part of the holding portion having a wall which has been reformed to define a reduced compensating thickness having a taper substantially equal to the taper on said shaft and said sleeve for the unexpanded portion of the sleeve, whereby to provide expansion of said second portion to a position wherein the exterior diameter is cylindrical and in alignment with the cylindrical first portion of the sleeve when the sleeve is fully expanded.