US 6,393,837 B1Granted

Air tool with safety device

AssigneeFuji Air Tools Co., Inc.

InventorIsao Tomioka

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Abstract

A rotary air tool includes an axially moving automatic speed control valve which responds to changes in rotary speed by varying the amount of air fed to its air motor. When the speed tends to increase under light load, less air is fed to the air motor to maintain a generally constant rotary speed. A safety device is triggered when the speed exceeds a predetermined maximum due, for example, to a malfunction in the speed control valve. The safety device includes a weight which is radially movable at the predetermined maximum speed to release a latch. The latch permits resilient actuation of the speed control valve toward its closed position. In one embodiment, a second latch maintains the safety device in the actuated condition so that the air tool remains substantially shut off until the reason for the overspeed condition is investigated. In a further embodiment, the speed control valve is not fully closed by actuation of the safety device so that at least a small amount of air is admitted to the air motor.

Claims7

Dependent claims

An air tool with a safety device comprising:

a main body casing;
an air passage in said main body casing;
an air motor rotated by air supplied through said air passage;
a valve seat in said air passage;
a safety valve body movable toward and away from said valve seat to change an effective opening of said air passage;
first urging means for urging said safety valve body in a direction to ward said valve seat;
a rotary member rotating with an output shaft of said air motor;
a safety valve stopper connected to said rotary member;
said safety valve stopper being displaceable outward in a diametrical direction by a centrifugal force generated by a rotation of said rotary member;
second urging means for urging said safety valve stopper in a direction opposite to a direction in which said centrifugal force is applied;
a lock mechanism for locking a motion of said safety valve body during steady operation;
said first urging means urging said safety valve body away from said valve seat thereby moving said safety valve body away from said valve seat against an urging force of said first urging means thereby increasing an effective opening of said passage, disengaging said lock so as to move said safety valve body in a direction closer to said valve seat by said first urging means, thereby reducing said effective opening of said passage when a rotation rate of said output shaft of said air motor exceeds a predetermined value and said safety valve stopper moves against said urging force of said second urging means due to centrifugal force, and again locking motion of said safety valve body in this state between said safety valve body and said safety valve stopper.

9 more elements

Dependencies are inferred from the claim text.