COMPRESSED AIR SCREW-FASTENING MACHINE

PROBLEM TO BE SOLVED: To enlarge striking power, while preventing harmful influence on the performance and the life of an air motor.SOLUTION: In a compressed air screw-fastening machine, an open valve 46 in which lateral movement operation is carried out with a button 45 is inserted slidably into a valve chamber S7 prolonged in parallel to a pressure reducing valve 26. An O ring 46a and an O ring 46b are attached to the open valve 46 to form a space S8. The space S8 is communicated with a ventilation groove 43 via a communication hole 47 and with a pressure accumulation chamber S1 via a communication hole 48, respectively. When the open valve 46 is made to shift to the opposite side by the button 45, the communication hole 47 and the pressure accumulation chamber S1 are communicated via the space 8, and the pressure accumulation chamber S1 serves as the pressure which is supplied from an air intake 4.