Power Tool With Torque Control

Abstract

The drawings illustrate a power tool whose torque output may be continuously measured and controlled by the torque reaction on a rotatably mounted planetary ring gear, with transducer means associated therewith for converting the torque reaction to a fluid pressure signal to cut off the fluid flow to the motor rotor at a predetermined torque.

Description

This invention relates generally to power tools and, more particularly, to torque-controlled tools.

At the present time torque-controlled power tools are known to include valving actuated in response to torque output which serves to block the exhaust and stall the motor. Other arrangements include back pressure-sensing devices which upset a delicately balanced poppet, in response to torque output, to cut off incoming air. Still other present day arrangements include mechanical linkage for controlling an incoming air-poppet valve in response to torque output. Additional designs include spring-loaded clutches which become disengaged at a predetermined spring tension in response to output torque.

It should also be noted that the prior art torque-controlled tools which include planetary gearing for reducing a fast motor speed to a practical output speed for most applications, generally include a planetary ring gear which is secured to the outer shell of the tool.

An object of the invention is to provide an improved rotary power tool whose output torque may be continuously controlled and/or measured by resistance to the reactive torque of a ring gear of a planetary drive unit thereof which ring gear is arranged to rotate through a predetermined arc in response to output torque.

Another object of the invention is to provide an improved torque-controlled power tool, wherein the ring gear of one of the planetary drive units thereof is rotatably mounted, with transducer means associated therewith for responding to the rotary reaction of the planetary ring gear to output torque to provide a fluid pressure signal, upon attainment of a predetermined torque, to cut off the air supply to the motor.

A further object of the invention is to provide a torque-controlled power tool including a rotatably mounted planetary ring responsive to output torque, and transducer means responsive to such rotary movement of the ring gear to cut off the air supply to the motor section rotor, with the transducer being encased within the power tool housing.

Still another object of the invention is to provide a torque-controlled power tool including a rotatably mounted planetary ring gear responsive to output torque and which is formed integrally on a cam follower member having rollers associated therewith and riding on camming ramps formed on a cam spline member which is moved axially when the rollers move along the ramps, with the axial movement thereof compressing a plurality of adjacent bellows, for providing a fluid pressure signal indicative of output torque to cut off the air supply to the motor section of the power tool upon the attainment of a predetermined output torque.

A still further object of the invention is to provide a torque-controlled power tool including a rotatably mounted planetary ring gear responsive to output torque and having a shoe and linkage member rotatable with the ring gear to tangentially compresa a bellows or a pressure-sensing load cell, for example, providing a fluid pressure signal to cut off the air supply to the motor upon the attainment of a predetermined output torque.

These and other objects and advantages of the invention will be apparent when reference is made to the following description and accompanying drawings, wherein:

FIG. 1 is a perspective view of a rotary power tool embodying the invention;

FIGS. 2a and 2b are cross-sectional views of the FIG. 1 structure;

FIG. 2c is a schematic view of a fluidal circuit which may be used with the FIGS. 2a and 2b structures;

FIG. 3 is a fragmentary cross-sectional view of a portion of the FIG. 2a structure illustrating an operational position thereof;

FIG. 4 is a schematic view of selected operational conditions;

FIG. 5 is a fragmentary perspective view of an alternate embodiment of the FIG. 1 structure;

FIG. 6 is a fragmentary cross-sectional view of a portion of the FIG. 5 structure;

FIG. 7 is a cross-sectional view taken along the plane of line 7--7 of FIG. 5, and looking in the direction of the arrows;

FIG. 8 is an end view taken along the plane of line 8--8 of FIG. 7, and looking in the direction of the arrows;

FIG. 9 is a cross-sectional view similar to FIG. 7, illustrating an operational position thereof;

FIG. 10 is a fragmentary cross-sectional view illustrating an alternate embodiment of the FIG. 7 arrangement; and

FIG. 11 is a fragmentary cross-sectional view illustrating an alternate embodiment of a portion of the FIG. 2b structure.

FIGURES 1-4 EMBODIMENT

Referring now to the drawings in greater detail, FIG. 1 illustrates a power tool assembly 10, including generally a handle section 12, a motor section 14, a transducer section 16, a planetary section 18, and a head section 20.

More specifically, as may be noted in FIG. 2b, the handle section 12 includes a valve assembly 21 mounted in a transverse opening 22 formed through a wall portion 24 in the handle section 12 adjacent an air inlet chamber 26 to which air is communicated via an air inlet fitting 28 (FIG. 1) mounted in the end of the handle section 12. The valve assembly 21 includes a sleeve member 30 secured in the opening 22 and having a central chamber 31. A spring 32 is mounted between the outer end face 34 of the sleeve member 30 and a manual button 36. The button 36 is secured to a valve stem 38 having an O-ring seal 40 mounted therearound and slidably mounted within the sleeve member 30. A frusto-conical valve 42 is formed on the inner end of the valve stem 38 for cooperation with a valve seat member 44 formed on the inner end 46 of the sleeve member 30. An extension shaft 48 formed on the valve 42 extends across a passage 50 adjacent the chamber 26 and is slidably mounted in an opening 52 which may be formed in a plug member 54 threadedly mounted in a threaded opening 56 formed in the handle section axially aligned with the opening 22. An O-ring seal 57 is mounted around the extension shaft 48 in the opening 52.

A plurality of ports 58 are formed in the fixed sleeve member 30 for communication with a passage 60 which, in turn, communicates with a chamber 61 which is divided into two variable chambers 62 and 63 by a poppet valve 64 slidably mounted therein. A passage 66 communicates between the chambers 62 and 63 radially outwardly of the poppet valve 64. A stem 67 is formed on the poppet valve 64, extending away from the sleeve member 30. An axial passage 68 is formed part-way through the stem 67, including a bleed plug 70 secured in the right end (FIG. 2b) of the axial passage 68. Radial ports 72 and 74 are formed in the stem 67 a predetermined distance apart, the ports 72 communicating between the axial passage 68 and the chamber 62 to the left of the poppet valve 64. An opening 75 communicates between the left chamber 62 and a chamber 76 and, thence, with a supply passage 77.

The stem 67 is slidably mounted in and extends through an axial opening 78 formed in a piston housing 80 secured in a central opening or chamber 82 formed in the handle section 12. A piston 84 is secured to the end of the stem 67 opposite the poppet valve 64 and is slidably mounted in a chamber 86 of the piston housing 80, dividing the chamber 86 into two variable chambers 87 and 88. A suitable seal 89 is mounted around the outer periphery of the piston 84 within the chamber 86. A spring 90 is mounted between the piston 84 and an end wall 92 of the chamber 86. A signal inlet port 94 is formed in the handle section 12 communicating with the chamber 86 to the right (FIG. 2b) of the piston 84, while a bleed port 96 formed in the handle section 12 communicates the chamber 86 to the left (FIG. 2b) of the piston 84 to the atmosphere.

The motor section 14 includes a motor rotor 98 mounted within a sleeve member 100 secured by pins 102 to the handle section 12. An outer vane portion 103 of the motor rotor 98 receives air under pressure in a conventional manner from the supply passage 77 via suitable conduitry (not shown). A motor shaft 104 is formed on the motor rotor 98 and rotatably mounted in bearings 106 (FIG. 2b), 108 (FIG. 2a), and 110 mounted in the handle section 12, the motor section 14 and the planetary section 18, respectively. An annular chamber 112 is formed around the sleeve member 100, with exhaust ports 114 communicating with the atmosphere. Suitable seals 116 and 118 are mounted adjacent the respective ends of the annular chamber 112.

An outlet port 120 is formed in the transducer section 16, communicating internally with an annular passage 112 which, in turn, communicates with a pair of ports 124 formed in a fixed wall 125 of the motor section 14, and leading, respectively, to a pair of bellows 126 located radially outwardly of an intermediate portion of the motor shaft 104. The bellows 126 are mounted between the fixed wall 125 and an end face 128 of a cam spline member 130, the latter being slidably mounted on splines 132 formed in a chamber 134 within the transducer section 16, and the open end of the bellows 126 being sealed by an O-ring seal 133 mounted in a groove 135 formed in the wall 125. A spring 136 is mounted around the motor shaft 104 between the end face 128 and an annular groove 137 formed in the wall 125. A line 138 communicates between the outlet port 120 (FIG. 2a) and a suitable adjustable valve means, represented by 139. A line 141 communicates a fluid pressure signal from the valve means 139 to the signal inlet port 94 and, thence, to the chamber 87 once the pressure within the bellows 126 reaches a predetermined level. As illustrated in FIG. 2c, air is supplied from any suitable high pressure source, represented at 143, through a line 145 including a pressure regulator 147 and a check valve 149, the latter providing a predetermined amount of preloading of the bellows 126. Pressure within the line 138 may be measured on a suitable gage 151 operatively connected thereto.

Ramps or cam surfaces 140 (FIG. 3) are formed on the opposite face 142 of the cam spline member 130, and are contacted by cam rollers 144 rotatably mounted in suitable bearings 146 mounted in a cam follower or roller carrier 148 within the planetary section 18. While two rollers and ramps are illustrated, one or more than two roller-ramp combinations could be utilized.

The roller carrier 148 is mounted inwardly on the bearing 110 and outwardly on a bearing 150 mounted around an internally toothed ring gear 152 of a first planetary unit 154, the ring gear 152 being integrally formed on the roller carrier 148 for rotation therewith. The bearing 150 is mounted within a stepped sleeve member 156 mounted within the planetary section 18 and restrained from movement therein by a fixed radial pin 158.

A plurality of pinion gears 160 are rotatably mounted on a shaft or pin 162 by needle bearings 164. The shaft 164 is secured to a pinion gear carrier 166 mounted at one end thereof within the cam follower 148 on bearings 168. The pinion gears 160 mesh with the ring gear 152 and with a sun gear 170 mounted on the end portion 172 of the motor shaft 104 by splines 174. A cylindrical spacer 176 is mounted around the motor shaft 104 between oppositely disposed end faces of the sun gear 170 and the bearing 110, with the sun gear 170 being retained against the spacer 176 by a retainer ring 178 secured to the shaft end portion 172.

A second planetary unit 180 includes an internally toothed ring gear 182 formed integrally on the forward end portion of the stepped sleeve member 156, a plurality of pinion gears 184 rotatably mounted on shafts or pins 186 by needle bearings 187 and by a carrier 188 having a reduced forward end portion 189 rotatably mounted on bearings 190 retained axially by a retainer ring 191 within the outer shell 193 of the head section 20. The pinion gears 184 mesh with the ring gear 182 and with a splined sun gear 192 formed on an end 194 of the carrier 166 of the first planetary unit 154.

A plurality of splines 196 are formed on the inner surface of the carrier 188, radially inwardly of the bearings 190. The splines 196 mesh with splines 198 formed on an end 200 of a shaft 202 extending into the head section 20, being rotatably supported therein on a plurality of needle bearings 204.

A first bevel gear 206 is formed on the forward end of the shaft 202 for meshing with a second bevel gear 208 formed on a transverse shaft 210 rotatably mounted on bearings 212 and 214 in the head section 20. A square drive tool connector 216 is formed on the shaft 202, extending through an opening 218 formed in the head section 20, at right angles to the axis of the aligned planetary, transducer, motor, and handle sections 18, 16, 14, and 12, respectively. Any suitable tool fastener device (not shown) may be connected to the square drive tool connector 216.

OPERATION

High pressure air enters the air inlet chamber 26 and the adjacent passage 50 via the fitting 28 from any suitable source (not shown). Once the valve button 36 is manually depressed, the high pressure air is communicated from the passage 50 past the valve seat member 44 into the chamber 31, through the ports 58 into the passage 60 and the chamber 62, and, thence, through the passage 66, the chamber 63, the opening 75, and the chamber 76, to the adjacent supply passage 77 which communicates with the outer vane portion 103 of the motor rotor 98 to rotate the motor rotor 98 and its shaft 104. The air is exhausted to the atmosphere via the annular chamber 112 and the exhaust ports 114.

Rotation of the motor shaft 104 rotates the sun gear 170 of the first planetary unit 154 therewith, for example, in a clockwise direction as viewed from the right in FIG. 2a. Such rotation of the sun gear 170 causes the pinion gears 160 to each rotate in a counterclockwise direction about its respective shaft 162, while meshing with the ring gear 152, with the carrier 166 being caused to rotate in a counterclockwise direction about the axis of the motor shaft 104. The ring gear 152 is initially restrained from rotating by virtue of the rollers 144 on the cam follower 148 being positioned at the low point or "start" position (FIG. 4) of the fixed ramps 140.

Rotation of the carrier 166 at its end portion 194 causes the sun gear 192 of the second planetary unit 180 to also rotate in the counterclockwise direction, thereby rotating the pinion gears 184, which are meshing with the fixed ring gear 182, in a clockwise direction about their respective shafts 186, and the carrier 188 in a clockwise direction about the axis of the carrier end portion 194. Such clockwise rotation of the carrier 188 directly rotates the shaft 202 via the splines 196 and 198, thereby rotating the bevel gears 206 and 208 and the tool drive connector 216.

As indicated above, the ring gear 152 of the first planetary unit 154 is initially restrained by virtue of being formed on the cam follower 148 whose rollers 144 are initially seated against the low portions of the respective ramps 140 of the fixed cam spline member 132, the latter being urged leftwardly in FIGS. 2a and 3 by the spring 136. However, as torque at the output end of the tool drive connector 216 increases under load conditions, the reaction sensed by the ring gear 152 overcomes the force of the spring 136, causing the ring gear 152 to move in the clockwise direction, as urged by the pinion gears 160, thus rotating the cam follower 148 and the rollers 144. Such rotation of the rollers 144 moves the latter along the ramps 104 toward the "maximum pressure" position (FIG. 4), forcing the cam spline member 130 to slide axially along the splines 132, compressing the pair of bellows 126 to build up the pressure therein to a predetermined point.

As illustrated in FIG. 4, the maximum pressure or stop position of each roller 144 is at some predetermined point adjacent the elevated end of the respective ramps 140, say, for example, 135 degrees away from the low end or start position. Any point between the start position and the maximum pressure position may be selected as the release point for the transmission of the fluid pressure signal and is determined by the adjustment of the valve means 139. At this point, the pressure within the bellows 126, transmitted via the line 138 to the valve means 139, will be relayed as a fluid pressure signal through the line 141 to the signal inlet port 94. This fluid pressure signal is communicated from the inlet port 94 to the chamber 87, moving the piston 84 to the left in FIG. 2b, against the force of the spring 90, and pulling the poppet valve 64 to the left, seating the valve 64 adjacent the opening 75, thereby closing off the passage 66 and its communication via the chamber 63 with the chamber 76 and the supply passage 77. Hence, the air supply to the motor rotor 98 is cut off and the rotation of the tool drive connector 216 is stopped. The valve 64 is held in seated position by high pressure in the chamber 61, and the high pressure in the chamber 87 is reduced by air escaping through the motor 98 and the exhaust outlet 114, which allows the valve means 139 to close and the bellows 126 to return to starting preload position. After the motor rotor 98 is stopped by the seating of the valve 64, the valve button 36 is released. High pressure air in the chamber 61 is released through the bleed plug 70 and the radial ports 72 into the chamber 77, then through the motor rotor 98 and the exhaust outlet 114, allowing the spring 88 to return the valve 64 to its original position. It should be noted that preloading, although not essential to the operation of the control and monitoring circuit, provides a conveniently variable means of regulating the rotational movement of the roller carrier 148 and the ring gear 152 (FIGS. 2a and 3) by limiting the displacement of the bellows 126. The mechanical force exerted against the bellows 126 is balanced by the air pressure within the bellows 126 at the time the maximum torque output, as preset by the adjustable valve means 139, is reached. A pressure-monitoring means, such as the gage 151, may be provided to allow observation and/or recording of both the preload pressure and the output torque pressure developed within the control circuit. This output torque pressure will be an accurate measure of the torque produced at the square drive tool connector 216.

FIGURES 5-9 EMBODIMENT

The alternate embodiment of a power tool assembly 220 shown in FIGS. 5-9 includes a transducer section 222 in lieu of the bellows 126, the cam spline member 130, the ramps 140, the rollers 144, and the cam follower 148. In this arrangement, the ring gear 224 (FIG. 6) of the first planetary unit 226 is secured to a wall of the planetary section 18 by a fixed pin member 228. The ring gear 230 of a second planetary unit 232 is rotatably mounted within a cylindrical bearing member 233 secured in the transducer section 222, meshing with pinion gears 234 on bearings 236 around pinion shafts 238 supported by a carrier 240. The pinion gears 234 also mesh with a sun gear splines 242 formed on an extended end 244 of the carrier 246 of the first planetary unit 226. Splines 248 are formed on an inner surface of the carrier 240 to drivingly connect with splines 250 formed on the output shaft 252. The carrier 240 is supported in bearings 253 retained in the outer shell 254 of the head section 20 by a retainer ring 255.

A cylindrical spacer member 256 supports bearings 257 for the first planetary carrier 246 and is mounted within the outer shell 254 of the head section 20 between oppositely disposed end faces of the bearing member 233 and the first ring member 224.

An arcuate pocket 258 (FIG. 7) is formed in part on the outer periphery of the second ring gear 230, and in part in the adjacent cylindrical ring gear bearing member 233 secured within the transducer section 222. A shoe 260, having an arcuate seating surface 262 formed thereon, is slidably mounted in the arcuate pocket 258. A flat side or end face 264 is formed on the shoe 260 for at times abutting against both respective edges 266 and 268 (FIG. 7) of the ring gear 230 and the fixed bearing member 233. A transverse groove or slot 270 is formed on the side of the shoe 260 opposite the flat side 264, suitable for the seating thereagainst of an end of a torque link member 272. The torque link member 272 extends through a tangentially extending opening 274 formed in the transducer section 222, abutting against a disc 276 slidably mounted in a chamber 278. A bellows 280 is mounted in the chamber 278 intermediate the disc 276 and an end cover 282, the latter being secured to the transducer section 222 by bolts 284, and the open end of the bellows 280 being sealed by an O-ring seal 285 mounted in a groove 287 formed in the end cover 282. A port 286 formed in the end cover 282 communicates between the interior of the bellows 280 and an outlet passage 288 formed in the end cover 282.

In operation, as torque builds up under load at the tool drive connector 216, the second ring gear 230 is caused to rotate against the force of the bellows 280, moving the shoe 260, the torque link member 272 and disc 276 to the right as illustrated in FIG. 9, compressing the bellows 280 and providng a pressure change in the outlet passage 288 which may be transmitted to any suitable pressure-actuated means, such as the valve means 139 of FIG. 2a, to cut off the supply of air to the motor rotor 98 as explained above.

The inherent springiness of the bellows 280 will return the disc 276, the torque link member 272 and the shoe 260 to the respective positions illustrated in FIG. 7 once the rotation of the tool drive connector 216 is stopped.

FIGURE 10 EMBODIMENT

FIG. 10 illustrates an alternate embodiment of the transducer section 222 including a pressure-sensing load cell 290 adjacent the disc 276, in lieu of the bellows of the FIG. 7 structure. It should be noted that an arcuate pocket 292 is included which is substantially shorter than the arcuate pocket 258 of FIG. 7. An end cover 294, secured to the transducer section 222 by bolts 296, has an outlet opening 298 formed therein suitable for the extension therethrough of a plurality of electrical conductors 300. This arrangement provides a signal-generating means involving a minimum of movement of the ring gear 230, the shoe 260, the torque link member 272, and the disc 276.

FIGURE 11 EMBODIMENT

FIG. 11 illustrates an alternate embodiment of the valving portion of the handle section 12 which may be used in conjunction with the load cell arrangement of FIG. 10. In this structure, a solenoid 302 is mounted in the chamber 86 and has an axial passage 303 formed therein for the slidable mounting therein of the poppet valve stem 67 in lieu of the piston 84 illustrated in FIG. 2b, and the signal is communicated thereto via leads 304 rather than by the fluid pressure inlet 94 and the chamber 87 associated with the piston 84. A spring 306 is mounted intermediate a fixed wall 308 and the adjacent face 310 of the poppet valve 64. Once the torque build-up signal is transmitted via the leads 304 through suitable amplification and electrical interface means to the solenoid 302, the latter is energized and pulls the valve stem 67 farther into the axial passage 303, against the force of the spring 306, thereby pulling the poppet valve 64 past the passage 66 to thus cut off the air supply to the motor supply passage 77.

It should be apparent that the invention provides an improved torque-controlled rotary power tool wherein a rotatable planetary ring gear and an adjacent transducer section combine to efficiently control and/or provide a means of continuously measuring output torque in proportion to the pressure developed on the transducer by rotation of the ring gear as it reacts to operational output torque.

While several embodiments of the invention have been shown and described, other modifications thereof are possible.

Claims

I claim:

1. A rotary power tool for use with a source of fluid under pressure, said rotary power tool comprising a housing including a fluid-actuated motor rotor, passage means communicating between said source of fluid and said motor rotor, valve means operatively mounted in said passage means for controlling the flow of said fluid therethrough, a motor shaft extending from said motor rotor, at least one planetary unit including a ring gear rotatably mounted in said housing, a sun gear operatively connected to and driven by said motor shaft, a carrier member, a plurality of pinion gears rotatably mounted on said carrier member and meshing with said sun and ring gears, rotary output means operatively connected to said carrier member, a bellows unit operatively connected between said ring gear and a fixed wall of said housing and having a predetermined initial internal pressure, said ring gear rotatably reacting to increasing output torque on said rotary output means to increase said internal pressure of said bellows unit, and signal means responsive to said increased pressure to cause said valve means to cut off said fluid flow through said passage means upon the attainment of a predetermined output torque.

2. The rotary power tool described in claim 1, and an indicating means operatively connected to said bellows unit, said internal pressure of said bellows unit being continuously monitored by said indicating means.

3. A rotary power tool for use with a source of fluid under pressure, said rotary power tool comprising a housing including a fluid-actuated motor rotor, passage means communicating between said source of fluid and said motor rotor, valve means operatively mounted in said passage means for controlling the flow of said fluid therethrough, a motor shaft extending from said motor rotor, at least one planetary unit including a ring gear rotatably mounted in said housing, a sun gear formed on said motor shaft, a carrier member, a plurality of pinion gears rotatably mounted on said carrier member and meshing with said sun and ring gears, rotary output means operatively connected to said carrier member, ramp means splined to said housing, roller means mounted on said ramp means and operatively connected to said ring gear so as to be caused to roll along said ramp means in response to rotary motion of said ring gear, pressure-reacting means mounted intermediate said ramp means and a fixed wall of said housing, said ring gear rotatably reacting to increasing output torque on said rotary output means to axially actuate said ramp means through said roller means to increase the pressure of said pressure-reacting means, and signal means responsive to said increased pressure to cause said valve means to cut off said fluid flow through said passage means upon the attainment of a predetermined output torque.

4. A rotary power tool for use with a source of fluid under pressure, said rotary power tool comprising a housing including a fluid-actuated motor rotor, passage means communicating between said source of fluid and said motor rotor, valve means operatively mounted in said passage means for controlling the flow of said fluid therethrough, a motor shaft extending from said motor rotor, at least one planetary unit including a ring gear rotatably mounted in said housing, a sun gear formed on said motor shaft, a carrier member, a plurality of pinion gears rotatably mounted on said carrier member and meshing with said sun and ring gears, rotary output means operatively connected to said carrier member, an arcuate pocket formed in said ring gear, a shoe having a seat formed in a face thereof, a torque-link member abutted against said seat and extending therefrom for converting the rotary motion of said ring gear to tangential motion, pressure-reacting means mounted intermediate said torque-link member and a fixed wall of said housing, said ring gear rotatably reacting to increasing output torque on said rotary output means to actuate said torque-link member via said pocket and shoe to increase the pressure of said pressure-reacting means, and signal means responsive to said increased pressure to cause said valve means to cut off said fluid flow through said passage means upon the attainment of a predetermined output torque.

5. A rotary power tool for use with a source of fluid under pressure, said rotary power tool comprising a housing including a fluid-actuated motor rotor, passage means communicating between said source of fluid and said motor rotor, valve means operatively mounted in said passage means for controlling the flow of fluid therethrough, a motor shaft extending from said motor rotor, cam means operatively mounted in said housing, a plurality of bellows mounted intermediate said cam means and a fixed wall of said housing, at least one planetary unit including a ring gear formed on said cam means, a sun gear formed on said motor shaft, a carrier member, a plurality of pinion gears rotatably mounted on said carrier member and meshing with said sun and ring gears, rotary output means operatively connected to said carrier member, said ring gear rotatably reacting to the output torque on said rotary output means to cause said cam means to compress said bellows and increase said pressure thereof, and signal means responsive to said pressure to cause said valve means to cut off said fluid flow through said passage means upon the attainment of a predetermined output torque.

6. A rotary power tool for use with a source of fluid under pressure, said rotary power tool comprising a housing including a fluid-actuated motor rotor, an inlet port for receiving fluid from said source of fluid under pressure, passage means communicating between said inlet port and said motor rotor, valve means operatively mounted in said passage means for controlling the flow of said fluid therethrough, a motor shaft extending from said motor rotor, a cam follower rotatably mounted in said housing around said motor shaft, a cam spline member slidably mounted in said housing around said motor shaft, a plurality of bellows mounted intermediate said cam spline member and a fixed wall of said housing and having a predetermined initial internal pressure, at least one arcuate ramp formed on said cam spline member, at least one roller rotatably mounted on said cam follower and positioned on said at least one arcuate ramp, a first planetary ring gear formed on said cam follower, a first sun gear formed on said motor shaft, a first carrier member, a first plurality of pinion gears rotatably mounted on said first carrier member and meshing with said first sun and ring gears, a second sun gear formed on said first carrier member, a second ring gear secured to said housing, a second carrier member, a second plurality of pinion gears rotatably mounted on said second carrier member and meshing with said second sun and ring gears, rotary output means operatively connected to said second carrier member, said first ring gear rotatably reacting to increasing output torque on said rotary output means to rotate said cam follower and said at least one roller to roll said roller toward the high point of said at least one ramp and thereby force said cam spline member to move axially to compress said bellows and increase said internal pressure thereof, and signal means responsive to said internal pressure to cause said valve means to cut off said fluid flow through said passage means upon the attainment of a predetermined output torque.

7. The rotary power tool described in claim 6, wherein said signal means includes second valve means for providing a fluid signal to close said first-mentioned valve means.

8. A rotary power tool for use with a source of fluid under pressure, said rotary power tool comprising a housing including a fluid-actuated motor rotor, an inlet port for receiving fluid from said source of fluid under pressure, passage means communicating between said inlet port and said motor rotor, valve means operatively mounted in said passage means for controlling the flow of said fluid therethrough, a motor shaft extending from said motor rotor, a first planetary unit including a first ring gear secured to said housing, a first sun gear formed on said motor shaft, a first carrier member, and a first plurality of pinion gears rotatably mounted on said first carrier member and meshing with said first sun and ring gears, a second planetary unit including a second sun gear formed on said first carrier member, a second ring gear rotatably mounted in said housing, a second carrier member, and a second plurality of pinion gears rotatably mounted on said second carrier member and meshing with said second sun and ring gears, rotary output means operatively connected to said second carrier member, linkage means operatively connected for tangential movement with said second ring gear, and a bellows unit mounted intermediate said linkage means and a fixed wall of said housing and having a predetermined initial internal pressure, said first ring gear rotatably reacting to increasing output torque on said rotary output means to tangentially move said linkage means to compress said bellows and increase said internal pressure thereof, and signal means responsive to said internal pressure to cause said valve means to cut off said fluid flow through said passage means upon the attainment of a predetermined output torque.

9. The rotary power tool described in claim 8, wherein said signal means includes second valve means for providing a fluid signal to close said first-mentioned valve means.

10. A rotary power tool for use with a source of fluid under pressure, said rotary power tool comprising a housing including a fluid-actuated motor rotor, an inlet port for receiving fluid from said source of fluid under pressure, passage means communicating between said inlet port and said motor rotor, valve means operatively mounted in said passage means for controlling the flow of said fluid therethrough, a motor shaft extending from said motor rotor, a first planetary unit including a first ring gear secured to said housing, a first sun gear formed on said motor shaft, a first carrier member, and a first plurality of pinion gears rotatably mounted on said first carrier member and meshing with said first sun and ring gears, a second planetary unit including a second sun gear formed on said first carrier member, a second ring gear rotatably mounted in said housing, a second carrier member, and a second plurality of pinion gears rotatably mounted on said second carrier member and meshing with said second sun and ring gears, rotary output means operatively connected for tangential movement with said second ring gear, and a pressure-sensing load cell mounted intermediate said linkage means and a fixed wall of said housing, said first ring gear rotatably reacting to increasing output torque on said rotary output means to tangentially move said linkage means to apply pressure to said pressure-sensing load cell, and signal means responsive to said pressure to cause said valve means to cut off said fluid flow through said passage means upon the attainment of a predetermined output torque.

11. The rotary power tool described in claim 10, wherein said signal means includes a solenoid and means for providing an electrical signal to cause said solenoid to close said valve means.