Patent ID: 7793811

Claim:
A fastener driving apparatus for driving a fastener into a workpiece, the fastener driving apparatus comprising: a power source; a control circuit electrically coupled to the power source; a motor electrically coupled to the power source and responsive to the control circuit; a first cylinder; a first piston reciprocally movable within the first cylinder to execute a compression stroke and a return stroke in an operation cycle of driving the fastener into the workpiece, the first piston defining a gas chamber within the first cylinder, the gas chamber capable of accommodating gas therein; a linear motion converter driven by the motor and operationally coupled to the first piston for reciprocally moving the first piston within the first cylinder; a second cylinder pneumatically connected to the first cylinder; a second piston reciprocally movable within the second cylinder; an anvil coupled to the second piston, the anvil capable of striking the fastener to drive the fastener into the workpiece; a valve arrangement operationally disposed between the first cylinder and the second cylinder for pneumatically connecting the first cylinder and the second cylinder, the valve arrangement configured to define a gas passageway between the first cylinder and the second cylinder in an open position and blocking the gas passageway in a closed position; and at least one sensor electrically coupled to the control circuit, the at least one sensor configured to detect at least one position of the operation cycle and communicate the detected position of the operation cycle to the control circuit, wherein during the compression stroke, the first piston is configured to move towards a top dead center of the first cylinder for compressing the gas in the gas chamber, the valve arrangement assuming the open position for communicating the compressed gas to the second cylinder causing the second piston to move linearly and enabling the anvil to drive the fastener into the workpiece; and wherein during the return stroke the valve arrangement assumes the closed position and the first piston is configured to move towards a bottom dead center of the first cylinder thereby creating a vacuum in the first cylinder between the top dead center of the first cylinder and the first piston; and wherein at a predetermined position of the first piston during the return stroke the valve arrangement assumes the open position, thereby communicating the vacuum created in the first cylinder to the second cylinder and causing the second piston and the anvil to retract to initial positions of the second piston and the anvil; and wherein during the return stroke, based on the at least one detected position by the at least one sensor, the control circuit is configured to disconnect the power source from the motor to stop the operation cycle.