Pneumatic tool with pressure intensifier

Claim 1

A pneumatic tool used with an air supply source which supplies compressed air and having a manually operated trigger mechanism and a housing; and further comprising within the housing: a drive rod for striking the fastening element to be driven into a receiving material; a drive piston formed as a unitary structure with the drive rod; a drive cylinder for housing the drive piston in a manner to be slidable therein; a pressure chamber communicating with the drive cylinder; a main valve mechanism disposed between the drive cylinder and the pressure chamber interrupting communication therebetween under the control of the trigger mechanism; a pressure intensifier means provided between the pressure chamber and the air supply source for intensifying the pressure of the compressed air from the air supply source and for supplying the highly compressed air to the pressure chamber for storage from which the highly compressed air stored in the pressure chamber may be introduced into the drive cylinder to actuate the drive piston, the pressure intensifier means including a boost-up piston having a drive piston head of a large effective area and a compressing piston head of a small effective area interconnected by a boost-up piston rod, the drive piston head is reciprocably mounted within a large inside diameter cylinder and the compressing head is reciprocably mounted within a small diameter cylinder; a timing valve positioned and shaped to be switched by the boost-up piston rod near the top and bottom dead centers of its stroke; and a change-over valve positioned and shaped to be actuated by a control air pressure based on the switching operation of the timing valve whereby air for driving the drive piston head will be repeatedly charged into and discharged from the large inside diameter cylinder by the operation of the change-over valve to automatically drive the boost-up piston reciprocatingly also driving the pressure intensifier means.