GB1461890A - Fastener driving tool - Google Patents

Abstract

1461890 Impelling tools DUO-FAST CORP 9 April 1974 [11 May 1973] 15708/74 Heading B4C A power actuated fastener driving tool comprises a head portion 22 and a handle 40, the head portion containing a driving piston 28 and a combustion chamber for igniting a compressed fuel/air mixture the chamber containing a valve 38 which contains the mixture during ignition until the pressure in volume 24 exceeds the pressure in a volume 72 above the valve whereupon the valve moves upwardly to allow the combustion gases to act on a piston 28 the rod 30 of which impels a nail 36 into a workpiece. Air is conducted by a pipe 107 and fuel, such as propane through a conduit 116, both passing through a pressure regulator 50 into the handle 40 of the tool. In the handle a manually operable valve 20 is provided which has three positions which permit introduction of fuel and air to various parts of the tool at different stages. In the first position of the valve fuel is fed to a space 104 at a relatively low pressure and compressed air is passed through a regulator valve 90 through the chamber, to the cylinder 26 as the valve 38 is in its upper position and out through vent holes 154, 158. In the next position of the valve 20 air is passed above the valve 38 to move it downwardly to tis seating position and is no longer fed to chamber 24 which is then connected through the valves 20, 90 to space 104 containing the fuel so that fuel under a relatively low pressure is fed to chamber 24. At this point the piston 28 is raised manually by inserting a rod through an outlet passage 32 and a nail 36 is inserted in said passage. The valve 20 is then moved to its third position and the supply of fuel is cut off from the space 24, air under a higher pressure enters the space 24 to mix with the fuel and when the pressures in chambers 88 and 24 are equal valve 90 closes to isolate the explosive mixture in chamber 24. Valve 90 closes since its other end is connected to the relatively low fuel pressure in space 104. When trigger 144 is actuated a glow plug 48 ignites the mixture, valve 38 moves upwards since pressure in space 24 is greater than in space 72, the ignition gases pass below the valve 38 to cylinder 26 and the nail is driven out.