| 摘要 |
A power control device for a pneumatic motor includes a pressure air supply flow limiting means in the form of a flow restriction having a diverging, pressure recovering outlet. The device also comprises a load responsive pressure relief means which is located downstream of the flow restriction and which is arranged to gradually release pressure air from the motor into the atmosphere in response to decreasing load applied on the motor. The device is effective in reducing the motor power in response to decreasing load upon the motor. The disclosed motor is a hammer piston impact tool, and the motor load responsive pressure release means comprises the forward end of the motor cylinder and passages on a thrust sleeve which receives the shank of a chisel and which is slidingly received in the cylinder. A motor load balancing spring is arranged to bias the motor load responsive pressure relief valve toward its open position, such that, upon increasing motor load, the spring yields and permits the motor load responsive pressure relief valve to move toward its closed position. |
