Pneumatically operated power tool having mechanism for changing compressed air pressure

A pressure changing mechanism for use in a pneumatically operated power tool including an outer frame having a compressed air intake portion and defining therein a compressed air chamber, and a driving components disposed in the outer frame and driven by a compressed air in the compressed air chamber, the pressure changing mechanism comprising:

• a pressure reduction valve allowing a compressed air to flow from the air intake portion to the compressed air chamber and to reduce a compressed air pressure when the compressed air is flowed through the pressure reduction valve;
• and
• a change-over mechanism which is separate from the pressure reduction valve and the air chamber and which is in communication with the pressure-reduction valve, the change-over mechanism providing a first position to connect the pressure reduction valve to an atmosphere for supplying a compressed air from the intake portion to the compressed air chamber through an operation of the pressure reduction valve and a second position to connect the pressure reduction valve to the compressed air chamber for making the pressure reduction valve inoperative.