Patent ID: 7048077

Claim:
A pneumatic drilling machine with an automatic control system, comprising: a pneumatic motor; a tool holder spindle; a drive mechanism connecting the motor to the spindle, the drive mechanism being configured to drive the spindle through a driving cycle, the driving cycle commencing and ending with the spindle being stationary, the driving cycle including a feed mode of driving the spindle and a retraction mode of driving the spindle, the drive mechanism including: a pneumatic circuit; a control valve positioned in the pneumatic circuit, the control valve being movable between a first position to select the feed mode of driving the spindle and a second position to select the retraction mode of driving the spindle; and a supply valve positioned in the pneumatic circuit for supplying compressed air to the motor, the supply valve being movable between a closed position in which compressed air to the motor is interrupted and an open position in which air to the motor is supplied; wherein the drive mechanism is configured to send, upon conclusion of the retraction mode of driving the spindle, a pneumatic signal to the supply valve via the pneumatic circuit, the supply valve being configured to move from the open position to the closed position upon receiving the pneumatic signal, the pneumatic signal deriving from a fixed quantity of air trapped at elevated pressure within a reservoir located within the drive mechanism.