Combustion gas powered fastener driving tool.

摘要

An efficient, portable, easy to operate fastener applying tool (10) is disclosed that is powered by the gases produced from the internal combustion of a fuel and air mixture. A supply of liquified gas stored under pressure in a cylinder (12) provides the source of power. A piston (28) connected to a fastener driver (30) is slidably mounted within a cylinder (12) to move reciprocally downwardly and upwardly through a driving and a return stroke. A combustion chamber (21) is formed at the upper end of the cylinder (12). A compression chamber is formed at the lower end of the cylinder (12). A spark plug (63) powered by a piezo-electric firing device (77) is located within the combustion chamber (21). The combustion chamber (21) features a set of fan blades (51) driven by an electric motor (61) which is continuously in operation when the tool (10) is in use. A main valve mechanism (37) actuated by a set of lifting rods (42a, 42c) which are moved upwardly and downwardly when the tool (10) is moved toward and away from the workpiece, is used to control the flow of fresh air through the combustion chamber (21). When the combustion chamber (21) is isolated from the atmosphere and the fuel and air are thoroughly mixed, the spark plug (63) is fired to explode the fuel and air mixture and force the piston (28) through its driving stroke. Air compressed by the lower end of the piston (28) at the lower end of the cylinder (12) is used to form an air bumper to keep the piston (28) from striking the bottom of the cylinder (12). An exhaust valve (68) is mounted at the side of the cylinder (12) to discharge combustion gases at the end of the driving stroke. The rapid discharge of combustion gases at the end of the driving stroke produces a thermal vacuum within the combustion chamber (21). Additional air supplied to the lower face (35) of the piston (28) from the atmosphere forces the piston (28) through its return stroke. A simple but reliable interlock mechanism (75) is used to insure the safe operation and sequencing of the various components of the tool (10). The unique use of the electric fan (22) improves the overall operation of the tool (10) and the utilization of the liquified combustible gas. It also insures that the piston (28) is forced through its return stroke by atmospheric pressure alone.