Patent GB-1424591-A (GB)
Title: Tools employing propellant cartridges
IPC: B25C1/14
Filed: 1973-02-07
Abstract: 1424591 Cartridge-actuated fastener driving tools GUNNEBO BRUKS AB 7 Feb 1973 [7 Feb 1972] 6114/73 Heading B4C The Specification describes a cartridgeactuated fastener driving tool and the claims are concerned with the escape of exhaust gas. General arrangement.-The tool shown consists of a body 1, Fig. 1, having a handle part 2, a forward part 3 carrying a barrel guide jacket 4, and a rearward housing 6 for a trigger mechanism 7. A tubular liner 9 through which the barrel 68 slides has a cut-away middle portion 8, a forward portion extending through the jacket 4 and terminating in a flange 10, and a rearward portion which extends through the housing 6 and held by the screwthreads 11 of an end cap 12. The handle is covered by a rubber or plastics shock absorbing member 14. The barrel 68 has at its rear end a cartridge chamber 69 in which a cartridge is detonated by a firing pin 22 to drive a striker piston 76 towards a nail (99) Figs. 5 and 6 (not shown) which is retained in a muzzle part (73) of the barrel by a ball catch (96) and guide washer (101). The muzzle (73) Figs. 7, 8 and 9 (not shown) is surrounded by a collar (102) which serves firstly to limit the rearward travel of the barrel when the muzzle is pressed rearwards ready for firing and secondly to enable the muzzle to be unscrewed from the barrel. After a nail has been driven in, the tool is prepared by depressing a thumb lever (139) Figs. 16 to 21 (not shown) to retract a cylindrical portion (130) of a lug (79) sufficiently from within a recess in a slot 78 in the barrel to allow the barrel to be pulled or moved forwardly either under its own weight or by centrifugal force until stopped by the lug engaging an end surface 80 of the slot 78; in this position the piston is trapped between the lug and the rear end of the cylinder of the barrel. The cartridge is then inserted into the cartridge chamber 69 and the barrel pushed in until stopped by the lug 79 engaging the opposite end surface of the slot 78. With a nail (99) inserted in the muzzle, the barrel is pushed back against the action of helical springs 29, 34 by pressing the muzzle against a working surface until the cylindrical portion (130) re-engages under the action of a compression spring (144). In this loaded position the bolt 18 of the firing mechanism is aligned ready for firing by operation of a trigger 52. Elastomeric rings 35, 36, 37 help to absorb recoil forces and an elastomeric ring 82 with a tubular rigid sleeve 84 serve to brake the forward movement of the striker piston 76 and protect the lug 79. Trigger mechanism.-When the trigger 52 is squeezed, Fig. 15, against the action of a spring 55 the upper lever 41 is caused to pivot about a pin 43 and lift the slide 18 of the breech block 16 against the action of a compression spring 19 within a cylindrical unit 16, such movement retracting a catch and releasing the firing pin 22 within a transverse hole 20 in the slide. When the trigger 52 is returned under spring pressure a chamfer 129 on the trigger pivots the lever 41 to lower the slide 18. The slide 18 carries a lug 25 on its lower side for sliding in a groove 26 in the liner 9 when the barrel is moved; when the barrel is pulled out, the lug 25 moves out of register with the end 42 of the trigger mechanism lever 41 so that firing is prevented. Cartridge chamber.-For a cartridge case 63, Fig. 12, the cartridge chamber has a main cylindrical bore 119, a counterbore 115 for receiving the cartridge flange 62, and an inner portion 120 of decreasing diameter for receiving the crimped forward end 118 of the cartridge and leading from the main cylindrical bore to one of smaller diameter 121. When the cartridge is initiated, the edge 122 of the conical portion of the chamber acts as a breaking edge to cause the crimped part of the cartridge to open and lie against the conical portion and against the bore 121. Exhaust gas escape.-Under the slot 78 in the barrel 68 is an axial groove 86 in the part 3 which opens into a pocket 87, Fig. 10. Gases from the cartridge chamber pass into the pocket and move in a loop before passing through channels formed between ribs 91 on the liner 9 and out through the annular gap between the flange 10 of the liner and end of the jacket 4. Due to their passage through the channels, the gas streams are phase-shifted and silencing is thereby effected. Powder residues left in the pocket may be removed through a removable cover. Cartridge case extraction.-When the barrel 68 is pulled out, the cartridge 63, Fig. 3 is held back ready to fall away from the tool by means of a spring-urged arm 60 which is mounted in the cylindrical unit 16 and engages behind the cartridge flange 62 when the barrel is pushed in.