Swage type fastener with optimized lock grooves and crests and method of designing same

#The present invention relates to a two piece, swage type fastener including a pin and a collar with the collar adapted to be swaged into lock grooves on the pin and more particularly to swage type fasteners that have an optimized lock groove and crest design for use in a plurality of applications with a plurality of collars of different materials and strength. The optimized lock groove and crest design can be used in a plurality of applications due to the lock grooves and crests being able to receive swaged materials from collars made of different materials and strength during swage. A method of designing a fastener is also provided that has a lock groove and crest geometry that is optimized and is provided as a uniform construction for use in the plurality of applications with collars of different materials and strength.

#Swage fasteners can be of a pull type or stump type. A typical swage type fastener includes a pin and a collar with the pull type fastener having a pin shank having a locking portion with lock grooves and a pull portion with pull grooves. The pull grooves are adapted to be gripped by matching teeth in chuck jaws of an installation tool having a swage anvil adapted to engage the collar whereby a relative axial force can be applied between the pin and collar to move the anvil over the collar to swage it into the lock grooves.

#With respect to swage fasteners of the pull type, the pull portion is connected to the lock groove portion via a breakneck groove of reduced strength which is adapted to fracture at a preselected magnitude of axial tensile force greater than required to swage the collar whereby the pull portion, or pintail, will be severed and removed from the pin shank after completion of swaging. The breakneck groove is of sufficient strength to withstand the high tensile load for swaging and the pull grooves must be similarly of sufficient strength to accept the relative axial pull load applied by the engaged teeth of chuck jaws of the installation tool. This routinely requires that the pull portion be of a relatively large diameter so as to have sufficient material to provide the necessary size and strength for the breakneck groove and also to inhibit fracturing of the pull grooves instead of the breakneck groove.

#FIG. 1 is a longitudinal view with some portions shown in section and others shown broken away of a fastener of the present invention in assembly relationship with a portion of a tool shown as applied to the fastener prior to installation and for securing workpieces;

#FIG. 2 is a view similar to that of FIG. 1 showing the fastener securing workpieces at a minimum grip of the tool and with the swage anvil of the tool shown in the engaged, installed condition;

#FIG. 3 is a view similar to that of FIG. 2 showing the fastener securing workpieces at a maximum grip of the tool and with the swage anvil of the tool shown in the engaged, installed condition;

#Looking now to FIGS. 1 and 2, a fastener 10 is shown to include a pin member 12 and tubular collar 14. Pin member 12 has an elongated shank 15 which extends through aligned openings 16 and 17 in a pair of workpieces 18 and 20, respectively, to be secured together. An enlarged protruding head 22 at one end of shank 15 engages one side of workpiece 18. Adjacent the head 22, the shank 15 has a straight portion 24 which is adapted to be received within aligned bores 16 and 17 with a slight clearance fit or interference fit. Following the straight portion 24 is a plurality of circumferentially extending, annular lock grooves 26. A transition portion 28 smoothly connects the lock grooves 26 with straight shank portion 24.

#A breakneck groove 40 is located adjacent the lock grooves 26 and defines the weakest portion on the shank 15. A straight land 42 is located between the breakneck groove 40 and a plurality of pull grooves 44. The land 42 is of a reduced diameter relative to the shank portion 24, the lock grooves 26 and the pull grooves 44. The pull grooves 44 are adapted to be gripped by a tool 48 which is actuable to set the fastener 10. The tool 48 can be generally constructed in a manner known to those skilled in the art and therefore is only partially shown for purposes of simplicity. Briefly, the tool 48 has a plurality of jaws 50 adapted to grip the pin 12 at pull grooves 44. Jaws 50 are located in a tubular collet assembly 52 which is slidably supported in an anvil housing 54 which terminates at one end in a swage anvil portion 56.

#The symmetrically shaped, tubular collar 14 is adapted to be located over the pin shank 15 and, with the workpieces 18, 20 pulled together, will be in radial alignment with some of the lock grooves 26. With actuation of the tool 48, a relative axial force is exerted between the pin 12 and collar 14 resulting in swage anvil portion 56 swaging the collar 14 into the lock grooves 26 of pin 12. Upon completion of the swaging, the shank 15 will be severed at the breakneck groove 40, as shown in FIG. 2. Subsequently, upon further actuation of the tool 48, a collar ejector member 58 will be urged forwardly to eject the swaged collar 14 from the anvil portion 56 thus completing the installation. FIG. 3 depicts the fastener 10 in an engaged, installed position with workpieces 18 and 20 of a maximum grip with workpieces 18 and 20 being of a maximum total thickness of the fastener 10. The workpieces 18 and 20 can vary in thickness by ⅛ inch and can still be fastened together with the fastener 10 of the present invention because the fastener 10 has a double grip range. Such an approach increases the versatility of the fastener 10 in securing workpieces 18 and 20 of varying thickness.