PULSE TOOL

The invention is an impulse wrench (1) that employs a fluid coupling between its anvil (53) and hammer members. The tool (1) includes a pulse cylinder (45) that forms the tool's hammer and has a shaped inner surface (82) that defines a side wall of fluid-filled chamber (81). An end portion of the anvil (53) is received within the chamber (81) and includes two retractable vanes (70) that sweep the pulse cylinder's inner surface (82) when the pulse cylinder (45) is rotating about the anvil (53). To achieve only a single impact per revolution of the pulse cylinder (45), fluid bypass channels (94, 97) are employed to intermittently allow fluid to pass around the vanes (70). In addition, the tool (1) including a unique torque-sensing shut-off mechanism (110) that is engaged to the tool's motor (30) and makes use of inertia force to actuate a power shut-off device (120).