Patent ID: 7270194

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, the supply valve comprising a shaped slide movable within a cylinder and a shut off piston connected to the slide; 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; and wherein the drive mechanism includes a coupling shaft for changing the mode of driving the driving mechanism, the coupling shaft being axially biased by a coupling spring into a coupling chamber, the coupling chamber being positioned in the pneumatic circuit, and wherein the pneumatic circuit includes a connector for receiving compressed air, the control valve being configured in relation to the pneumatic circuit so that, when the control valve is in the first position the coupling chamber is not open to the connector, but is open to the supply valve, via the pneumatic circuit.