Patent GB-961311-A (GB)
Title: Cartridge-operated tool for driving fasteners into hard materials
IPC: B25C1/14
Filed: 1960-12-09
Abstract: 961,311. Cartridge operated tools and fasteners fired thereby. ANSTALT FUR MONTAGETECHNIK. Dec. 9, 1960 [Dec. 11, 1959], No. 42374/60. Headings F3A and F3C. [Also in Division B4] Relates to a tool in which a cartridge plunger carrying a cartridge at its forward end is propelled forwardly to detonate the cartridge by impact with a drive plunger carrying a fastener at its forward end, which latter plunger is driven forward by the explosion of the cartridge to drive the fastener into a workpiece. According to the invention, the cartridge and drive plungers are slidably mounted for movement in a guide tube which itself is axially slidable in the tool housing which carries a splinter guard, the arrangement being such that in all positions in which the open forward end of the guide tube projects in front of the splinter guard, firing of the tool is prevented until application of the tool against the workpiece causes the guide tube to tension a spring and reach a position in which its end face lies in the end plane of the splinter guard. The invention is applicable to tools in which a trigger mechanism initiates the impact of a previously cocked cartridge plunger and to those in which impact is caused by a blow on the rear end of the cartridge plunger. In one form, Figs. 2, 3, the guide tube 2 is slidably mounted in the housing 1 which is provided with a grip sleeve 10 and the cartridge plunger 5 is formed with a replaceable cartridge carrier 6 adapted to engage in a recess in the drive plunger 4 so that the cartridge 13 engages a striker 12 therein. For the escape of combustion gases, axial grooves 14 are provided in the inner wall of the guide tube 2 and emerge through the part of the wall which in the firing position (Fig. 3) is inside the splinter guard 3 which is axially slidable by its tubular shank 32 between the guide tube 2 and the grip sleeve 10, a coil spring (not shown) urging the guard forwardly. The cartridge plunger 5 has a central bore 18 receiving a cocking spring 7 and a tubular head part 8 locked by a bayonet fastening 19 to the housing 1 contains buffer springs 21. A spring-urged knob 9 is mounted on the end of the head part 8. A cylindrical sleeve 25 with a stepped inner wall is fitted on the open end 24 of the guide tube 2, and the opening 28 therein permits passage of the forward end of 29 of the drive plunger 4 but not of widened rear portion of the plunger. A spring-urged two-arm lever 38 mounted on the guide tube 2 is formed with a stop 39 which holds the cartridge plunger 5 in the cocked position, Fig. 3. In this position and in this position only an aperture 44 in the housing 1 is opposite the lever 38 so that by depression of a trigger pawl 41 mounted on the sleeve 10, the pawl end 43 engages through the opening 44 to press the lever 38 and release the plunger 5. To prevent firing without the splinter guard, a pawl 46 mounted inside the sleeve 10 is spring- urged to engage behind a step on the guide tube 2 to block inward movement thereof unless the splinter guard is fitted so that its shank 32 keeps the pawl 46 disengaged. A further safety device prevents firing of the tool if the bayonet fastening 19 between the housing 1 and housing head 8 is not completely locked. In another embodiment, Figs. 9, 10, impact of the cartridge plunger 113 against the drive plunger 105 is caused by a blow on the head 114 of the plunger 113. The guide tube 103 slidable in the housing 101 is held in the position shown in Fig. 9 by means of a coil spring 110. The drive plunger 105 is secured against rotation with respect to the tube 103 by engagement of one or more axial ribs on its guide part 106 in gas discharge grooves which extend over the centre length of the tube 103. A ring of teeth 123, 124 is provided respectively on the adjacent parts of the cartridge and drive plungers and are so constructed that they can engage with one another only in a certain relative rotary position, and only in this position can the forward end of the cartridge plunger penetrate into the drive plunger sufficiently to enable the striker 122 to act on the end 119 of the cartridge. This rotation is effected by pressing the tool against the workpiece against the action of the spring 110 and by co-operation of a cam 126 on the outside of the guide tube 103 with a slide guide 127 formed in the housing 101. The construction of the guide 127, Figs. 13, 14 (not shown), is such that if the tool falls on the striking head 114, this rotation is not affected and no detonation takes place. Washers 27, Fig. 2, for retaining the pin 23 centred in the opening 28, are formed of a brittle hardened plastic and have the shapes shown in Figs. 5, 6 to ensure their destruction under impact of the head of the anchoring pin. Specification 961,312 is referred to.