Patent GB-850441-A (GB)
Title: Improvements in or relating to fastener driving tools
IPC: B25C1/14
Filed: 1958-06-17
Abstract: 850,441. Stud firing tools. OLIN MATHIESON CHEMICAL CORPORATION. June 17, 1958 [May 21, 1958], No. 19343/58. Classes 9(1) and 119. Relates to a stud firing tool of the type in which a driving piston, slidably carried in the barrel bore, is acted upon by the explosive gases to drive the stud into a workpiece. According to the invention the piston is deformable and retaining means, provided at the muzzle of the barrel, is adapted in the event of excess penetration of the stud into the workpiece to retain the piston and deform it into retaining engagement with the stud, thereby to halt both the piston and stud. The retaining means may be a unitary draw die member screw threadedly'attached as a muzzle plug which on excess penetration retains and deforms the piston by a swaging action but as shown applied to the stud firing tool described in Specification 799,561 the retaining means comprises two pivotally mounted jaws 74, 75 Fig. 6 which in the closed operative positions form a die orifice which deforms and retains the piston 2. The jaws 74, 75 which have the form shown in Figs. 6, 20 are slotted at 83, 84 to receive pins 72, 73 located in holes 80 in the arms of a channel member 71 fixed on a tube 70 mounted on the barrel 22 and urged forwardly by a spring 26. An enlarged and tapered muzzle 25 of the barrel passes through an aperture 79 in the channel member and on pressing the tool against the workpiece to bring it to the ready-to-fire position, the muzzle 25 engages in recesses 85, 86 of the jaws 74, 75 to cam the jaws into the closed operating position in which the peripheral portions 88, 89 form a die orifice. For holding a fastener one end of the piston 2 is recessed at 5 and for reversibility, the other is similarly recessed at 6. Assuming that the workpiece offers normal resistance to penetration, then the piston 2 will be halted before it reaches the jaws 74 and 75, no deformation will take place and on re-opening of the jaws the piston can be extracted for re-use. If however excess penetration occurs as shown in Fig. 4, the piston 2 will pass through the die opening together with the rear end 3 of the fastener and the resultant deformation closes the recessed end 6 of the piston to form a. grip 10 with the fastener. The excess energy is dissipated in further deformation 11 and the piston 2 with the fastener 3 is then halted by the undeformed heel 12. Under continual usage a piston will in time be bulged at each end. For this reason the barrel bore is provided with a restriction 28 forming a piston sizing throat which resists this bulging by an ironing action as shown in Fig. 8 during transit of the piston through the throat 28. A breech plug 560 Fig. 23 provides the cartridge chamber which has a slotted extension for porting the bore of the plug to thereby prevent stud driving in the absence of the piston, since the gases passing through the slots will by-pass the rear end of the stud. Various studs for use in the tool are described with reference to Figs. 11 - 15 (not shown). Specifications 722,109 and 788,055 also are referred to.