Automatic throttle shut-off power tool

Claim 2

A fluid-operated rotary power tool comprising a casing; a fluid motor driving a spindle; a passage extending from a motive fluid pressure source to said motor; a valve plug movable along said passage between a first position where it is closed to a second position, said plug being shaped whereby fluid flowing in said passage is free to flow past said valve plug to said motor when said plug is located intermediate said positions; a movable annular valve seat located in said passage between said valve plug and the motive fluid pressure source and slidable along said passage between travel limits where it can be engaged with said valve plug in both said first and second positions and being normally located where it will be engaged by said valve plug in said second position, said movable valve seat being operative to close said passage when engaged with said valve plug to prevent the flow of fluid therethrough; spring means resiliently urging said movable valve seat away from said valve plug; and said movable annular valve seat having a surface that is acted on by the fluid pressure of said motive fluid when engaged with said valve plug and is operative to hold the movable valve seat against said valve plug during the movement of said valve plug from said second position to said first position.

Claim 3

The power tool of claim 1, including: a second annular valve seat located in said passage between said valve plug and motor and located to engage said valve plug in said first position to close said passage.

Claim 4

The power tool of claim 2, including: torque sensing means connected to said motor to measure the torque on said motor and being operative, in response to a predetermined torque load on said motor, to effect the movement of said valve plug to its engagement position with said movable valve seat.

Claim 5

The power tool of claim 3, including: a rod interconnecting said torque sensing means with said valve plug.

Claim 6

The power tool of claim 4, wherein said torque sensing means is a torque-responsive clutch connected to a rod extending towards said valve plug and operative to move said plug toward said movable valve seat when said clutch reaches said predetermined torque.

Claim 7

A fluid-operated rotary power tool comprising: a housing including a fluid-operated rotary motor; a valve in a passage controlling the flow of motive fluid from a fluid pressure source to said motor and movable in a single direction in said housing over a distance including first and second successive increments of travel, said valve being movable over said first increment of travel from a normally closed position to an open position and movable over said second increment of travel from said open position; means for moving said valve over said first increment of travel thereby to open said valve to operate said motor; torque sensing means connected to said motor to measure the torque on said motor and being operative, in response to the rise of the torque load to a predetermined torQue load, to move said valve over said second increment of its travel; a movable valve seat located in said passage between said valve and the fluid pressure source where it can be engaged with said valve at the end of the second increment of its travel, said valve seat being operative to close said passage when engaged with said valve to prevent the flow of motive fluid therethrough; spring means resiliently urging said valve seat away from said valve; said movable valve seat being slidable in said passage and having a surface that is acted on by said high fluid pressure when engaged with said valve that is operative to hold the valve seat against said valve during the return movement of said valve to its normally closed position.

Claim 8

A fluid-operated rotary power tool comprising: a housing including a fluid-operated rotary motor; a valve in a passage controlling the flow of motive fluid from a fluid pressure source to said motor and movable in a single direction in said housing over a distance including first and second successive increments of travel, said valve being movable over said first increment of travel from a normally closed position to an open position and movable over said second increment of travel from said open position; means for moving said valve over said first increment of travel thereby to open said valve to operate said motor; torque sensing means connected to said motor to measure the torque on said motor and being operative, in response to the rise of the torque load to a predetermined torQue load, to move said valve over said second increment of its travel; a movable valve seat located in said passage between said valve and the fluid pressure source where it can be engaged with said valve at the end of the second increment of its travel, said valve seat being operative to close said passage when engaged with said valve to prevent the flow of motive fluid therethrough; spring means resiliently urging said valve seat away from said valve; said movable valve seat being slidable in said passage and having a surface that is acted on by said high fluid pressure when engaged with said valve that is operative to hold the valve seat against said valve during the return movement of said valve to its normally closed position.

Claim 9

The power tool of claim 6, including: a second valve seat located in said passage between said valve and motor and located to engage said valve in said normally closed position.

Claim 10

The power tool of claim 7, wherein: said movable valve seat is an annular sleeve having a bore therethrough and slidable axially along said passage toward and away from said valve; and said valve plugs the end of the bore of said sleeve when engaged thereto.

Claim 11

The power tool of claim 8, wherein: said spring means is a spring located between and abutting both the valve and the movable valve seat.

Claim 12

The power tool of claim 9: including additional resilient means urging said sleeve toward said valve for allowing said sleeve to move a limited distance along said passage toward said fluid pressure source when engaged with said valve.