CA1128341A - Power tool with torque sensing control means - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A pneumatic power tool having a torque sensing control system is disclosed which is capable of consistently applying a precise torque to a fastener so that uniform tightening of any number of fasteners can be obtained. A torsional strain responsive transducer is mounted internally in the tool body and includes a strain gauge network mounted on a torsionally resilient portion of one of the gear cases of the drive train of the tool, the gear case being subject to a reaction component of the torque being transmitted through the drive train. The strain gauge network provides a control signal which effects energization of a solenoid-actuated air shut-off valve in the handle of the tool to automatically terminate the operation of the tool when a predetermined torque is obtained at the output spindle. The control system permits adjustment of the torque output of the tool and provides a visual readout of such output.
Because of its fast action, the solenoid-actuated shut-off valve substantially eliminates reaction torque at the handle of the tool and the components thereof are compactly arranged. The sound level of the exhaust air from the pneumatic motor is attenuated by a tortuous flow path through the interior of the tool, and the electrical conductors for the strain gauge network are also routed through the interior of the tool. Consequently, the exterior of the tool is clean. The portion of the housing of the tool that surrounds the transducer is in two parts so that certain of the components of the tool may be assembled without relative rotational movement. The two-piece housing also facilitates access to the transducer and other parts of the tool without disassembling the same.

Description

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Th.is invention relates to po~er too1.s, ancl more particular~y r~la-tcs to a power tool hav:ing a torque senSincJ
control sys~em Eor precisely controll.inc3 the torque output of the tool.
Of the many requirements to be satisfiecl by power tools utilized to apply torque to threaded fasteners in mass procluction operations, such as automobile assembl.y plants and the like, preciseness and consistency oE the torc~ue output are most important. Consequently, various types of con-trol devices and systems have been developed in an effort to obtain uniform tensioning of the fasteners in production line items.
While many of the torc~ue control devices and systems heretoEore advanced have proven generally satisfactory for their intcnded purpose, others have not, for various reasons.
Some of such reasons are inconsistent control o~ tlle peak dynamic torque output of the tool, difficulty and/or com-plexity of adjustment of the torque output setting of the tool~ slow response to peak torque values resulting in the application o~ undesirably high reaction torque forces on the operator, large size resulting in excessive tool bulk, and high cost.
Accordingly, it is a general object of the present invention to provide a novel power tool and torclue sensing control system which is not subject to the foregoinc3 dis-advantages.
Another object is to provide a novel power tool haviny a consistent ana precise torque output.
A more particular object is to provi.clc a noveL
power tool having a control system for control.lincJ the .~

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; torque output of the tool, where:in a reaction~type ~rans-ducer is utili~ed to provide a control signal to the con-trol system ~or eEfecting a shut-oEf of the t.ool at a pre-determined torque value.
Still ano-ther objec-t is to provide a novel. power tool and torque control system of the foregoing character, wherein the transducer is mounted in the tool so as to be subject to the reaction torque in the drive train of the tool.
~ further object is to provide a novel transducer construction for use in a torque control system for a power tool, wherein a plurality of s-train gauges are utilized as torque responsive elements and wherein the strain gauges can be easily and accurately mounted on the transducer.
Still another object is to provide a novel trans- .
ducer.construction of the foregoing character, wherein the sensitivi-ty of the transducer can be varied to suit the requirements of different tools.
A further object is to provide a noveL arranyement or routing the electrical conductors of the torque responsive control system of a power tool through the interior of the tool so that the exterior of the tool is "clean".
Still another object i5 to provide a novel arrange-ment for temporarily locking the drive t.rain of a power tool having an internally mounted reaction-t~pe transducer so that the associated electronic torque control system of the tool can be adjusted and/or calibrated without dis-assembling the tool.
~ further object is to provide a novel solenoid controlled shut-off valve for automatically shu-tting off ~ - 2 -:

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the supply of air to the pneumatic motor of a power tool in response to a peak dynamic torque signal from an electronic torque responsive transducer in the tool.
A still further object is to provide a novel shut-off valve for a pneumatic power tool which is capable of rapidly shutting off the supply of air to the air motor of the tool throughout a wide range of line pressures so that reaction free operation of the tool is maintainedO
Another object is to provide a novel mounting arrangement for the electrical reset switch of a torque control system for a pneumatic power tool, wherein the swltch is actuated in res-ponse to movement of the throttle lever of the tool.
Still another object is to provide a novel two-piece housing construc~ion for a power tool, which facilitates the assembly and disassembly of the tool, provides access to the interior of the tool for inspection and testing of internal com-ponents, and interchanging of modular components of the tool.
A further object is to provide 2 novel exhaust system for a pneumatic power tool, which effectively attenuates the sound level of the exhaust air flow of the tool without supplemental muffling or increasing the bulk of the tool.
~ t least .he broad aspects are attained by the inven-tion which contemplates a transducer construction adapted for use with a power tool having a housing, a motor~ a torque output member, and drive means mounted in the housing connecting the motor with the torque output member. The transducer construction comprises an annular member adapted to encircle at least a portion of and be connected to the drive means so as to be sub-jected to at least a portion of the torque being transmitted thereby. The annular member has an annular sensing section having an outer diameter less than the diameter of the remaining portions of the annular member. A plurality of torsional strain -~ responsive means is carried by the annular member on the ~L~Z~33~L

sensing section and is operable to provide a signal proportional to the torsional strain in the annu]ar member and consequently ~o the torque output at -the torque output member. The radially inner periphery of the sensing section is cylindrical and includes eight symmetrically arranged flat surface portions on the outer periphery of the sensing section, with each of the torsional strain responsive means comprising a strain gauge mounted on one of the flat surface portions of the sensing section.
In another embodiment, the inventlon contemplates a transducer assembly adapted for use in the housing of a power tool having a motor and a torque output member which comprises a generally annular means having a stationary portion at one end adapted to be non-rotatably fixed to the tool housing, with the annular means having an annular central section adapted to extend within the housing. The annular means has an enlarged section adjacent the central section opposite the stationary portion with an internal ring gear, and torsional strain responsive means carried by the central section are operable to provide a signal proportional to the strain in the central section and the torque delivered by the tool. That central section has an outer diameter less than the outer dlameter of the enlarged section, and has planetary gearing driven by the motor and drivingly connected to the torque output member in-cluding a first planetary gear set and a second planetary gear set. The second planetary gear set engages and reacts against the enlarged section ring gear to transmit torque to the central section. A bearing means is fixed with respect to the housing supporting the first planetary gear set, and a bearing means is fixed with respect to the housing supporting the second planetary gear set, wi~h the first and second planetary gear sets being unsupported in the teeth of the internal ring gear.

Other objects and advantages of the invention will become apparent from the following detailed description and accompanyiny sheets of drawings, wherein:

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Fig. 1 is an elevational view showing the overall construction and arrangement of the parts of the power tool and torque control system of the present invention;
Fig. 2 is a somewhat enlar~ed, hro~en, longitudinaL
sectional view with some parts in elevation, of the power tool shown in Fig. 1, portions of the tool being displaced for convenience of illustration;
Fig. 3 is a fragmen-tary, longitudinal section view, with some parts in elevation, taken along the line 3-3 of Fig 2;
Fig. 4 is a transverse sectional view taken along the line 4-4 of Fig. 2;
Fig. S is a layout showing the moun-ting arrangement of and electrical connections between the strain gauges of the torque sensing transducer of the invention;
Fig. 6 is a fragmentary longitudinal sectional view, with some parts in elevation, of one of the gear cases of the tooL and showing the rou:ing arrangement of an electrical cable of the tool from the gear case through the other parts thereof to the handle; appearing with Fig. 1 and Figs. 7-10, inclusive~ are sexies of fragmentary sectional views taken along the lines 7-7, 8-8, ~-9 and 10-10~ respectively of Fig 6; appearing with Fig. 1.
Briefly described, the present invention contemplates a novel ~ower tool capable of consisten-tly applying a precise torque to a threaded fastener s~o that a uniform degree of tightening of any number of the fasteners can be obtained. To this end, the tool incorporates a novel torque responsive control means which serves -to rapidly and precisely terminate the operation of the tool when the required torque has been applied to a Eastener. ~ reac~ion-type transducer, which utilizes a plurality o~ electro-mechanical torsional strain responsive elernents, is , 339t~

incorporated into one o~ the structural elemen-ts oE the tool so as to be subject to the torque being transmitted through the drive train of the tool. The cor~s-truc-tion of the transducer is such that the ~orsionaL resilience, and hence the sensitivity o~ the transducer, may be varied after ~anufacture to suit the sensitivity requirements oE
different tools.
A series of bores and recesses are provided in the various parts oE the tool to permit electrical conductors, which are connected to the transducer, to be conveniently routed through -the interior of the tool. The exterior of the tool is thus free o-E eLectrical conductors and connectors.
A novel clamshell-type construction is utiliæed in the portion o the housing of the tool surrounding the transducer so that the transducer is accessible from the exterior of the tool without completely disassembllng the same and so that the transducer cable is not stressed.
The power tool, to be hereinafter described in detail, also includes a novel arrangement for externally Locking the motor of the tool against rotation so that the visual readout of the torque control system can be pèriodically checked ànd adjusted.
A novel shut-off valve assembly is mounted in the handle of the tool for automatically shutting-of~ the flow of air to the pneumatic motor of the tool when a predetermined torque has been applied to a fastener. The shut-off valve assembly includes a fluid pressure actuated shut-off valve member and solenoid-actuated pilot valve member. The pilot valve member serves to vent pressure from a chamber at one end of the control valve, which is ~6--.. . . ... .

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pressure balanced, so that a rapid closure of the shut-off valve member is obtained, regardless of the line pressure at the tool.
- In the specific embodiment of the invention -to be hereinafter descri~ed, a pneumatic motor is utilized as the prime mover of the tool and a manually actuated throttle valve is utilized to control the operation of -the mo-tor.
An electrical switch is mounted in -the handle of the tool so as to be actuated by a lever which shifts the throttle valve. The electrical switch serves to reset the electrical circuitry of the control system at the completion oi a torquing operation when the throttle lever is released.

The Overall Construction of The Tool and Its Torque Control System In Fig. 1, a power tool T embodying the features of the present invention, is illustrated.. In the presen-t instance, the tool T comprises a nutsetter which employs a pneumatic motor as ltS prime mover. Thus, air under pressure is supplied to the tool T through-an air hose Ll which includes a "whip" portion 12 and an extension portion 13 connected to a remote, regulated, source of the air under pressure. A reaction type transducer, to be hereinafter described in detaiL, is moun-ted in the tool T and provides an electrical signal proportional to the torque output of the tool. A torque setting and readout device, which con-tains the electrical circuits of the control system and which will be described more fully hereinaf-ter, is indicated generalLy at A.

The control device A is connected to the tool T by a multiple conductor electrical cable, a portion 14 of which .

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e~tends between the device A and an outlet boss 15 on a junction fitting 16 in the air hose 11. A socke-t 17 is mounted in ~he boss 15 for receiving a ma~ing pluy 18 on the end of the cable 14. The cable la enters the in-terior of the air hose 11 at the fitting 16 and then proceeds through the whip portion 12 to the tool T.
A tee fitting 18 ~ay be connected to the upstream end of the ~unction fitting 16 to provide an inlet for one end of an oiler hose 22. The opposite end of the hose 22 is connected to a suitable oiling system (not shown) which supplies measured quantities of oil to the interior of the air hose 11 for lubricating the pnewmatic motor in the tool T.
A union 24 may be provided between the tee-fitting 18 and the portion 13 of the air hose 11, The Construction of The Tool T
Referring now to Fig. 2, in conjunction with Fig. 1, the tool T comprises a generally cylindrical tool body 30 having a handle 31 secured to one end thereof, and torque output means in the form of a right angle nutsetter attach-ment 32 is secured to the opposite end of the body 30.
The body 30 includes a motor~ indicated generallyat 35, which is of the pneumatic type and which includes a cylindrical cylinder bloc~ 36 that is enclosed and supported by a sleeve-like housing 37. A rotor 38 is rotatably supported in the cylinder block 36, and a plurali-ty o~ ;
radially extending, longitudinally arranged slots (nat shown) are provided in the rotor ~or receiving a plurali-ty of blades 42. The blades 42 are urged radially outwardly in the ro-tor slots and into fluid pressure sealed engagement with thè inner wall of the cylinder block 36 by bleed air .

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~rom the air supply passages in the bod~ 30. ~he blades 42 ~hus de:Eine chambers therebetween for receiving air under pressure from an air suppl~ passage in the hand].e 31. Air under pressure :Elows into the chambers in the motor 35 through a pair of circum~erentially extending, axially spaced slots (not shown) in the cylinder block 36, such air being communicated to the inlet slots by con-necting passages in the cylinder blocX 36 and a plurality of intersecting axial bores 41 (Fig. 7) in an end plate 43. The end plate 43 also serves to support a bearing assembly 44 for the rear or right end of the rotor 38, as seen in Fig. 2.
Exhaust Air Flow Arrangement Air exhausts radially outwardly from the chambers o.f the motor 35 through a series of circumferentially ex-tending, axially spaced slots (also not shown) in the side wall o~ the cylinder block 36 in spaced relation from the inlet slots. The exhaust air then enters a clearance space 45 between the cylinder block 36 and.sleeve 37 from whence it ~inds its way to an annular clearance 46 around a sleeve 47 which abuts the opposite end of the c~linder block 37. The sleeve 47 also serves as a mounting for another bearing assembly 48 -for the rotor 38. From the annular clearance 46, the exhaust air proceeds through a plurality of circum~erentially spaced, axially extending grooves 49 (Figs. 2 and 7) in a year case member 50. The exhaust air then proceeds through clearances between the gears of a second stage planetary reduction gear train, to be described presently~ and thence to an annular chamber 51 within another gear case member 52 at the left end o-f ~2~33~L

the tool body 30 as viewed in Fig. 2. Exhaus-t air in the chamber 51 discharges to ~he atmosphere throu~h at least one exhaust air discharge port in ~he gear case member 52.
In the present instance, such exhaust air discharge por-t comprises a ring o, angularly extending bores 53 in the member 52 The aforementioned tortuous path of the exhaust air flow, which terminates with the ring of bores 53 in the gear case member 52, effectively attenuates the sound level of the exhaust air flow so that no additional muffling is required. Thus, size, weight or cost of the tooL T remains unchanged as a result of the foregoing exhaust air arrange-~ment.
In order to multiply the torque available from the motor 35, reduction gearing is provided. Such reduction gearing, in the present instance, comprises a two-stage planetary system which includes splines 54 on the left end, as viewed in Fig. 2, of the rotor 38, which mesh with a plurality of idler or planet gears 55. In the present instance, four idler gears 55 are meshed with the splines 54 and are rotatably mounted on pins 56 which are carried in the carrier portion 57 of another spindle 58. A beariny assembly 59 is mounted in the sleeve 47 and serves to support the adjacent end of the carrier 57. The idler gears 55 mesh with teeth 60 formed on the interior of an axially extending portion 62 of the gear case member 50.
The gear case member 50 is fixedly mounted in -the tool body 30 by a plurality of screws 64 which extend -through openinys in a two-piece housing 65, the construction and mode of operation of which will be described more fully hereinafter.

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The second stag~ o~ the plane-tary reduction gear sys-tem comprises splines 68 on the sp:inclle 5~ hich mesh with a plurality o~ plane-t or idler gears 72 that are mounked on pins 73 secured in the carrier portion 7~ or another spindle 76. Four circumEerentially spaced idler gears 72 are carried by the carrier portion 74, the idler gears 72 meshing with teeth 71 on the interior of an axially ex-tending portion 75 of the gear case member 52 and cornprising the ring gear of the second stage planetary reduction gear system. The right end of the spindle 76, as viewed in Fig. 2, is supported by a bearing assembly 77 which is mounted in the gear case member 50. The left end oE the spindle 76 is rotatably Mounted in another bearing assembly 78, which is carried in an axially extending~ circumferentially interrupted flange portion 79 of the gear case member 52.
The remote left end, as viewed in Fig. 2, of the spindle 76 is externally splined as at 82 to mesh with the input shaft 83 o~ the right angle nutsetter attachment 32, The attachment 32 includes a housing 84 in which the input shaft 83 is rotatably journaled. A torque output membex or spindle 86 is also rotatably journaled in the housing 84 with its axis extending at a right angLe to the axis of the input shaft 83. Bevel gears 87 and 88, on the shaft 83 and spindle 86, respectively, serve to transmit torque ~rom the shaft 83 to the spindle 86. ', ' The right angle nutsetter attachment 32 is de-tachably connected to the body 30 o~ the tooL T by a collar 92 which threadably engages the ~lange portion 79 of the gear case member 52. Set screws 93 are provided to prevent unintentional unthreading o:E the collar 92 from the body 30.

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It will be understood that other -types of attah-ments, such as a screw ~river~ or the like, couLd he con-nected to the body 30 of the tool T and drlven by the spindle 76, ins-tead o~ the nutsetter 32.
The handle portion 31 of the tool 10 comprises an elongated housing 102, which is detachably connected to the right end o~ the body 30, as viewed in Figs. 1 and 2, by a threaded collar 103. Specifically, -the collar 103 is threaded onto the right end o~ the motor cylinder housing 37. Indexing means (not shown) serves to maintain the housing 102 of the handle 31 properly oriented with respect to the mo-tor housing 37. The dis-tal or right end, as viewed in Figs. 1 and 2, of the handle 31 is threaded to receive a hose fitting 104 carried on the whip portion 12 of the air hose 11. Thus, air under pressure enters the handle 31 through the fitting 104 and then passes through passages in the handle to a throttle valve assembly, indicated generally at 105. The throttle valve assembly 105 includes a spool-type throttle valve 106, which is shiftably mounted ln a bushing 107 and which is normally biased to a closed position by a spring 108. The valve 106 is manually shi~ted to an open position by a lever 109, which is pivotally secured to the housing 102 by a pin 112.
Thus~ when the handle 108 is depressed by the operator to initiate a torquing operation, the valve 106 is shifted downwardly in its bushing 107 thereby permitting air under pressure from the air hose 11 to ~low through the passages in the handle -to a chamber 113 at the lower end o~-the valve 106, around the valve, and thence through ports (not shown) in the bushing 107 to a chamber 114 which communicates .: ,, . ~ .

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~ith a shut-o~f valve assernbly, indicated yeneral~ly at 120 in Fig. 2.
The construction of The Shut-Off Va'lve ~ssembL~ 1.20 . The shut-o~f valve assembly 120 inclucles a pilot valve portion 121 and a shut-off valve portion 122. The pilot valve portion 121 compris*~ a spool-type valve 123, which is shiftably mounted in a bore 124 in an elonga-ted bushing 125. The bushing 125 is in turn mounted in a bore 126 in the handle housing 102, whic'n extends transversely to the a~is of the housing 102. A pair of ports 127 and 128 intersect the bore 123 and are axially offset wi-th respect to the axis of the bore. Communication between the ports 127 and 128 is controlled by the upper, fuLl diame-ter portion 131, of ~he spool valve 123, as viewed in Fig. 2.
The pilot valve 123 is normall~ biased to its closed position in Fig. 2, by a coil spring 132, the inner end of which engages the adjacent end of the valve and the outer end of which bears against the inner surface of a cap 133 threaded onto the projecting end of the bushing 125. Aligned cross bores 13~ and 136 in the bushing 125 and cap 133, respectively, assure free movement of the valve 123 in its bore 124.
Upward movement of the valve 123 in its bore 124 to a posi-tion establishing communication between the por-ts 127 and 128 is effected by a solenoid 1~0 mounted in a counterbore 142 in the end, indicated at 143, of the bushing 125, opposite from the end 137. The inner end, indicated at 144, of the solenoid 140 is threaded into a reduced diameter portion o~ the counterbore 1~2, and a cap 146 is ~13-3~

threaded onto -the end 143 of the bushing 124 ~o close -the bore 142 and to provi~e a dir~ seal.
The pluncJer, indicated at 1~7, oE -the solenoid 140 engages ~he lower end face, as viewed in Fig. 2, of the pilot valve 123 and serves to shift -the pilot valve upwardly to establish communication be-tween the ports 127 and 128 when the solenoid 140 is energi~ed. The electrical con-ductors for the solenoid 140 are indica-ted at 152 and 153, respectively, in Fig. 2.
The shut-o~f valve portion 122 of the shut-off valve assembly 120 includes a shut-off valve member 155, which is also of the spool-type and which serves to control com-munication between the chamber 114 and a generally axially extending passage 156 in the handle housing 102. ~he passage 156 communicates with the intersecting axial bores 41 (Fig. 7) in the plate 43 and hence with the inlet ports in the cylinder block 36 of the motor 35, as previously described.
As will be apparent from Fig. 2~ the shut-off valve 155 is mounted in a bushing 157 positioned closel~v adjacent to the pilot valve bushing 125 and having its a~is parallel with the axis of the bushing 125. The shut-off valve 155 includes a pair of spaced lands 162 and 163 of substan~ially the same outside diameter, and a reduced diameter, connec-tin~
portion 164 defining an annular space therebetween. The lower land 163, as viewed in Fig. 2, is cup-shaped so as to permit a projection or stop 167 on a plug ]68 tha-t is threaded into the housing 102, to extend into the interior of the land 163 and engage the inner end ace 166 of the cavityO The stop 167 thus limits downward movement of the valve 155.

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The upper por-tion, indicated at 172, of the bore of the bushin~ 157, as viewed in E~ig. 2, is o:E somewnat grea-ter diamete.r than the portions o~ the bore :in w'hich the lands 162 and 163 are mounted, and a cup-shap~d cap 173 is slidably mounted in the bore portion 172 so as to engage an upwardly or outwardly projecting stem portion 174 of the valve land 162. The arrangement is such tha-t when the cap 173 and valve 155 are shiEted upward'Ly, as viewed in Fig. 2, to their fullest extent, the land 163 will prevent air under pressure in the chamber 114 ~rom flowing through a ring of ports 176 in the lower end of the sleeve 157, as viewed in Fig. 2, and tllus to the passa~e 156.
The shut-off valve 155 is held in its open position illustrated in Fig. 2 by the force resulting from pressure in a chamber 177 defined in part by the outer or upper end face, indica-ted at 175, of the valve cap 173. Air at sub-stantially the same pxessure as in the chamber 114 is com-municated to the chamber 177 by a transverse bo:re 178 in the handle housing 102, and a connecting bore 179 which is of sufficiently small diameter to prevent rapid flow of air through the bore 178 into the chamber 177.
~ short transverse bore 182 in a housing portion 180 ~-E -the shut-off valve assembly 120 intersects a longi-tudinal bore 183 therein, one end of the bore 183 registering wi-th the port 127 in the pilot valve portion 121 and the opposite end of the bore 183 being closed by a threaded plug 184. Thus, the chamber 177 will be vented to the abmosphere through the bores 182 and 183 and ports 127 and 128 in the pilot valve portion 121 when the pilot valve 123 ~L5- ~.

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is shiEted to its open posi-tion by the solenoid l~rO . When this occurs, ~he rapid venting o~ pressure i~ the chamber 177 to -the a~mosphere w;1-L occur and the shut-ofE valve 155 will be rapidly shifted to its closed position as a result of the pressure in the chamber 11~ acting on -the end face surfaces of the land 163. Consequently, the flow oE air under pressure to -the motor 35 is cut-off in a matter oE a ~ew milliseconds and the torque output of the mo-tor is thereby reduced to zero in substantially the sam2 time interval.
Energization of -the solenoid 140 o~ the shut-off valve assembly 120 by supplying current to the conductors 152 and 153 thereof is controlled by electricaL circuitry in the torque control and readout device A (Fig. 1). How-ever, before the solenoid 140 is energized, a control signal of predetermined magnitude must be received by the device A.
Such control signal, which is a function of the torque being delivered by the output spindle 86 o-E the tool T, is derived from transducer means in the -tool T, now to be described.

Construction of the Torque Responsive Transducer Re~erring now to Figs. ~-6, inclusive, in conjunction ~ith Fig. 2, the tool T includes transducer msans, indicated generally at 200, for generating a signal proportional to the -torque output at the spindle ~6. Such signal actuates circuitry in the control device A to energize the solenoid ~0 of the shut-off valve assembly 120 to terminate a torquiny operation ~hen the torque output at the spindle 86 reaches a predetermined pea~ dynamic value. The transducer means 200 thus comprises a torsionally resilient portion 201~ and 3~
at least one and preferably a plurality of torsional strain res-ponsive signal generating elements, indicated generally at 202, and mounted on the torsionally resilient portion 201.
The torsionally resilient portion 201, in the present instance, comprises an annular, thin-wallea portion of the gear case member 52 between the ring gear 75 and main body portion of the member. Since the ring gear 75 and thin-walled portivn 201 are integral with the gear case memher 52, the thin-walled portion 201 is subjected to the reaction torque ~rom the ring gear 75 when the tool T is in operation. Consequently, the portion 201 will deflect torsionally in direct proportion to the reaction torque imposed on the ring gear 75, and the torsional strain in the por-tion 201 at any instant will be a direct function of the torque output at the spindle 86 and hence of the torque being applied to a nut or other fastener to which the spindle 86 is connected.
The outer diameter and thickness of the torsionally re-silient portion 201 of the transducer 200 are selected for a given sensitivity, i.e., torsional deflection under a given load, to minimize the radial distortions of the sensing portion imposed by the planet gears 72 acting radially outwardly against the ring gear 75. In this way the strain gauges 202 respond substantially only to torsional loads and not to radial loads.
The torsional strain responsive signal generating ele-ments 202 comprise at least one and, in the present instance, eight strain gauges, respectively indicated at 211-218, inclusive, in Figs. 4 and 5. Each of the strain gauges 211-218, in the pre-sent instance, is preferably of the foil type and has a nominal resistance of 350 ohms plus or minus .2% and a gauge fac~or of

2.095 plus or minus .5%.
In one exemplary mounting arrangement of the strain gauges 211-218, the outer periphery of the toxsionally resilient portion 201, may be provided with eight flat surface portions 221-228, inclusive, for receiving the strain gauges 211-218, respectively. In other words, the - 17 ~

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outer periphe~y o:E -the .resilien-t portion 201 i.s octayonal in cross section, as will be apparent from F:ig. 4. The aforementioned clifference in cJeometrical shape be-tween the outer and inner peripheries of the portion 201 (octagonal and circular, respectively) provi.des an important advantage in that the wall thic~iness of the material o~ the portion 201 at the center o~ each of the flat surface portions 221-228, inclusive, is thinner than ak the corners of -the surface portions. Consequently, the greatest torsional flexure of the material of the portion 20L will occur at the center of the flat surface portions 221-228. This is desirable since the strain gauges 211-218, inclusive, are mounted centrally on -the surface portions 221-228.
It should also be noted that the strain gauges 211-218 are mounted on the surface portions 221-228 so tha-t their lines of maximum response are generally disposed parallel to the lines of maximum torsional strain of -the material of the torsionally resilient portion 201. In other words, the strain gauges 211~218g inclusive, are oriented at 45 with respect to the axis of the torsionally resilient por-tion 201 and the màximum response axes of the gauges are respec~ively disposed at alternate angles of 45 with respect to the axis of the resilient portion 201.
The strain gauges are electrically connected in a ~heatstone bridge network, the various branches of the net-work terminating in a terminal strip having four contacts indicated at 231, 232, 233 and 234~ respectively. Two pairs o~ trimming resistors 236 and 237 are provided in -the strain gauge circuit to facilitate calibration of the t~ansducer 200 prior to installation of -the same into the tooL T, as 834~

ill be describ~d more fully hereinafter.
I~he strain gauges 211-21~ are secured -to the flat outer sur~aces oE ~he torsionally resilient portion 201 by conventional bonding techniques, i.e. by applying a suitable adhesive to the flat surface to ~hich the strain gauges are to be attached and, after the strain ~auges have adl~ered to the surface, covering the same with successive layers of suitable protective coatings.
Calibration of The Transducer 200 After the strain gauges 211-218 have been en-capsulated, the gear case member 52 is then mounted in a dead-weight checker and the voltage change versus torsional load for the transducer 200 is then plotted. Any variation of the curve from a standard curve are then made by adjust-ments to the trimming resistors 236 and 237. The dead-; weight checker is also used to check the torque readout on the screen, indicated at 235, of -the device A. The sensitivity o~ -the transducer 200 may be increased by milLing or otherwise removing material from the inner surface of the resilient portion 201.
After the transducer 200 has been calibrated, ~he gear case member 52 is installed in the body 30 of the tool T in the manner illustrated in Fig. 2 and secured therein by the screws 64. The conductors of the cable 14 are then connected to the contacts 231-234 oE the -trans-ducer 200, as by soldering.
~outing o~ The Electrical Cable 14 The electrical cable l~ is routed -through the interior of the tool T, in the manner illustratea in Fig~ 6 in order to improve the safe operating characteristics of ~19-.

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the tool and to prevent damage to the cable. To this end, the cable 14 extends rearwardLy or toward the right, as vie~ed in Fiys. 2 an~ 6~ from the gear case member 52 be-tween the exterior of the por-tions 201 and 75 and the inner surface oE the housing 65. The cable 14 then extsnds through one of the axially extending, semicylindrical recesses 49 (Figs. 6 and 10) in the periphery o~ the gear case member 50.
From ~he gear case member 50, the cable 14 extends into the clearance space 46 between the outer periphery of the bearing support sleeve 47 and the housing 65 and then passes through a bore 238 (Fig. 9) in the sleeve 47, which e~tends inwardly from the right end face thereof, as viewed in Figs. 2 and 6. The bore 238 is in alignment with another axially extending bore 239 (Figs. 8 and 9), in the cylinder block 36 of the motor 35.
The cable 14 then e~tends through a drilled hole 242 in the motor end plate 43 from which the cable 14 passes through another axial hole 243 in the recessed end wall 244 oE the handle housing 102. A cable seal bushing 246 prevents fluid pressure loss between the cable 14 and hole 243.
The outer or right end of the hole 243 communicates with the chamber 114 so that the cable 14 passes through this chamber and around the bushings 157 and 125 of th~
shut-off valve assembly 120 in the manner illustrated in ~ig. 2. The cable then proceeds through another seal bushing 247 in the handle housing 102 before entering the hose fitting 104 and air hose 11.
The TWo-Piece Construction oE ~he Housin~ 65 The aforementioned two-piece construction of the 9~2~34~

housin~ 65 facili ta t~s assembly of ~he tool T and holds the components thereof in assembled relation. rrhe housing G5 also facili-tates connection of the conductors o~ the cable 14 to the contacts 231-234 of the -transducer 200 during assembly and disassembly of the tool and prevents any stress from being imposed on the cable 14 due to relative rotatiOn between the various parts of the tool. The housing 65 thus includes a pair of semi-cylindrical portions 2~7 and 248 (Figs. 1~ 2 and 4) having radially inturned flange portions 249 and 250 at the opposite ends thereof. The flange portions 249 and 250 e~tend into annular grooves 251 and 252 in the gear case member 52 and motor housing 37, respectively, when the housing portions 247 and 248 are assembled. SUCh assembly is accomplished by radially shifting the housing portions 247 and 248 into engagemant ~ith the other parts of -the tool body 30, wi-th a "clamshell"-type movement~ and securing the parts toge-ther with the screws 64. A similar movement is employed w~nen the housing portions 247 and 248 are disassembled.
Operation of The Tool T and Control Device A
After the transducer 200 has been calibrated and the gear case member 52 mounted in the tool T, as previously described, the latter is ready for operation. It is assumed that the pressure of the source of air to which the air hose 11 is connected is regulated and has been set to provide the required line pressure at the tool T so as to obtain a desired dynamic peak torque output at the output spindle 86 during a torquing operation. It is further assumed that the control device A is energized and is set in the torque readout mode. The torquing operation is initiated when the -21~

~%~3~

operator of the tool depresses the lever 108 to open the valve 106 o~ the throttle valve assembly 105 and thereby permit live air to flow through the passages in ~e handle 31 to the motor 35 in the tooL body 30. Such flow passes through passages in the handle housing 102, through the throttle valve assembly 105 and into the chamber 114 (Figs.
2 and 3), which extends around the pilot valve bushing 125 and communicates with the ring of inlet ports 176 in the shut-off valve bushing 157. Air under pressure in the chamber 114 then flows through the inlet ports 176 around the reduced diameter portion 164 of the shut-off valve 155 and thence through the passage 156 to the inlet bores 41 (Fig. 7) in the motor end plate ~3. The live air then enters the chambers in the motor 35 to drive the same and ef~ect rotation of the rotor 38 thereof. The torque output from the spindle 38 is multiplied by the two-stage planetary reduction gear system 54, 55, 62 and 68, 72, 75. The torque output from the second stage planetary gear train is trans-mitted by the spindle 76 to a torque applying attachment connected to the tool body 30, in the present instance the right angle nutsetter 32. The drive from the spindle 76 is through splines 82 on the outer or left end thereof, as viewed in Fig. 2, through an input shaft 83 in the attach-ment 32, bevel gearing 87 and 88, and thence to the output spindle 86 thereof.
As the fastener to ~hich the tool T is connected becomes progressively tig~tened, the reaction force in the drive train, including the ring gear 75 of the gear case member 52, lncreases. Such reaction torque causes a degree o~ torsional de~lection in the torsionally resilient portion 83~

201 of the -transducer 200, which deflection is in direct propor-~ion to the torque output at the spindle 86. The torsional deflection of the por-tion 201 causes the resistance in the strain gauges 211-218 of the transducer 200 to change. Such resistance change is sensed by strain gauge circuitry in the device A and comprises a control signal which serves to energize another circuit in the device A
to cause current -to be supplied to the solenoid 140 of -the shut-off valve assembly 120 when -the torque output at the spindle 86 reaches a prede-termined peak dynamic value.
Energization of the solenoid 140 causes the pilot valve 123 to be rapidly shifted upwardly in its bore 124, as viewed in Fig. 2. Consequently, the ports 127 and 128 are brought into communication so that air under pressure in the cham~er 177 of the shut-off valve portion 122 is vented to the atmosphere through the bores 182 and 183 in the shut-off valve housing portion 180. Venting of the chamber 177 permits air at line pressure in the chamber 114 to act only upon the end face portions of the land 163 of the shut-off valve 155 so that the latter is rapidly shifted upwardly in the bushing 157 to a position preventing further flow of air under pressure to the outlet passage 156 in the handle 31~ Consequen-tly, the mo-tor 35 o~ the tool T rapidly stops. Such rapid shut-off of the ~low of air to the mokor ~, 35 prevents any substantial reaction tor~ue from being applied through the handle 31 o:E the tool to the operator.
Assuming that the pea]~ dynamic torque applied to tlle fastener is within production tolerances~ the operator ~' need only remove the tool from the fastener and then release the throttle ~ever 109 so that the lat-ter moves to -the !~ ~
_23~

position thereo:E illustrated in F:igs. 1 and 3. ~s the lever 109 moves to such position, -the plunger 254 (Figs.
1 and 3) o~ a control device reset switch 255 moves to its closea position. The switch 255 is connected by a pair of wires 256 and 257, which may be par-t o~ the cable 14~ to circuitry in the control device A. Such circuitry deenergizes the circuit which supplies current to the solenoid 140 of the shut-off valve assembly 120. Con- ¦
sequently, the pilot valve 123 shi-Ets to the position -thereof illustrated in Fig. 2 so that -the chamber 177 is no longer vented to the atmosphere. Pressure then again builds up in the chamber 177 as a result of the bleed air flow thereto through the passages 178 and 179, and the shut-off valve 155 is then moved to its open position, as illustrated in Fig. 2~ Conse~uently, the tool T is then ready ~or another torquing operation.
In order to permit periodic checking o~ the accuracy of the torque readout on the screen 235 while the tooL is in operation and a~ter assembly, a locklng arrangement is provided ~or temporarily locking the rotor 3~ of the motor 35 against rota-tion so that the tool may be placed ` in a dead-weight analyzer and a known load applied to the spindle 86 to chec~k the torque readout o~ such load on the screen 235. The a~orementioned loc]cing arrangement, in the present instance, comprises a radial bore 262 (Fig. 2) in ths side wall o~ the motor housing 37, and a coaxial bore in the side wall o~ the motor cylinder block 36. Such bores 262 and 263 permit a suitable locking device, such 1, as a pin or rod (not sho~m) to be inser-ted therethrough and in-to one o~ the chambers between a pair o~ the hlades ' 33~

42 oi -the motor 35. The rotor 38 is thus locked against rotatiOn by the pin or rocl and a known load may -then be applied by the dead-weight device to the .spindle ~6. :[f ~he readout on the screen 235 does not coincide wi-th the torque applied from the dead-weight device, ~he readout may be corrected by adjusting a trimming potentiometer (not shown) in the device A~ j After -the readout on the screen 235 has been adjusted to correspond with the known applied load on the spindle 86, the tool T is then ready for further operation. The aligned holes 262 and 263 may be closed by a set screw 264 when not in use.
l~hen the tool T is to be utilized in a production line application where a central computer ;s utilized to control the operation of other tools on the line, the control device A could be simplified to eliminate the torque readout screen 235 and other circuitry other than that required to provide an analcg signal.
It should be understood that while the invention herein disclosed has been described in connection with the tool T, which utili~es a pneumatic mo-tor as its prime mover, the torque sensing and control structure of the invention is also usable with electric motor driven power tools. Such an application is therefore within the 5cope of the present invention.

25_ ~.

Claims (16)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A transducer assembly adapted for use in the housing of a power tool having a motor and a torque output member, comprising; a generally annular means having a stationary portion at one end adapted to be non-rotatably fixed to the tool housing, said annular means having an annular central section adapted to extend within the housing, said annular means having an enlarged section adjacent the central section opposite the stationary portion with an internal ring gear, torsional strain responsive means carried by the central section and operable to provide a signal proportional to the strain in the central section and the torque delivered by the tool, said central section having an outer diameter less than the outer diameter of the enlarged section, planetary gearing driven by the motor and drivingly connected to the torque output member, including a first planetary gear set and a second planetary gear set, said second planetary gear set engaging and reacting against the enlarged section ring gear to transmit torque to the central section, bearing means fixed with respect to the housing supporting the first planetary gear set, and bearing means fixed with respect to the housing supporting the second planetary gear set, said first and second planetary gear sets being unsupported in the teeth of the internal ring gear.

2. A transducer assembly adapted for use in the housing of a power tool having a motor and a torque output member, as defined in Claim 1, wherein only the second gear set engages and reacts against the enlarged section ring gear.

3. A transducer assembly adapted for use in the housing of a power tool having a motor and a torque output member, as defined in Claim 1, wherein the wall thickness of the central section is substantially less than the stationary portion and the enlarged section.

4. A transducer assembly adapted for use in the housing of a power tool having a motor and a torque output member, as defined in Claim 3, wherein the radially outer periphery of said thin-walled central section has at least one flat surface portion, and said torsional strain responsive means being mounted on said flat surface portion.

5. A transducer assembly adapted for use in the housing of a power tool having a motor and a torque output member, as defined in Claim 4, including a plurality of said flat surface portions on the outer periphery of said central section, and said torsional strain responsive means including a plurality of strain responsive elements each mounted on one of said flat surface portions.

6. A transducer assembly adapted for use in the housing of a power tool having a motor and a torque output member, as defined in Claim 5, wherein each of said torsional strain responsive elements includes a strain gauge mounted on one of said flat surface portions.

7. A transducer assembly adapted for use in the housing of a power tool having a motor and a torque output member, as defined in Claim 6, wherein the axes of the strain responsive elements of said strain gauges are substantially parallel to the lines of maximum strain in said central section when said annular means is subjected to a torsional force.

8. A transducer assembly adapted for use in the housing of a power tool having a motor and a torque output member, as defined in Claim 7, wherein the axes of the strain responsive elements of said strain gauges are disposed at an angle of substantially 45 degrees with respect to the axis of said annular means.

9. A transducer assembly adapted for use in the housing of a power tool having a motor and a torque output member, as defined in Claim 8, wherein the axes of said strain gauges are disposed at alternate angles of substantially 45 degrees with respect to the axis of said annular means.

10. A reaction transducer adapted to be mounted within a tool housing having a drive train therein to provide an output signal representing torque delivered by the tool, comprising; generally annular means having a stationary portion at one end adapted to be non-rotatably fixed to the tool housing, said annular means having an annular central section adapted to extend within the housing, said annular means having an enlarged section adjacent the central section opposite the stationary portion having gear means to engage and react against the drive train, and torsional strain response means carried by the central section and operable to provide a signal pro-portional to the strain in the central section, said central section having an outer diameter less than the outer diameter of the enlarged section, said central section having an outer diameter and thickness selected for a given sensitivity to reduce the radial distortion produced by the drive train acting against the gear means.

11. A reaction transducer adapted to be mounted within a tool housing to provide an output signal representing torque delivered by the tool, as defined in Claim 10, wherein the strain responsive means includes a plurality of strain gauges mounted on the outer surface of the central section.

12. A reaction transducer adapted to be mounted within a tool housing to provide an output signal representing torque delivered by the tool, as defined in Claim 11, in which the central section has a plurality of flat surfaces on the outer periphery thereof extending in chordal directions, and each of said strain gauges being mounted on one of the central section chordal surfaces.

13. A transducer assembly adapted for use in the housing of a power tool having a motor and a torque output member, comprising a generally annular means having a stationary portion at one end adapted to be non-rotatably fixed to the tool housing, said annular means having an annular central section adapted to extend within the housing, said annular means having an enlarged section adjacent the central section opposite the stationary portion with an internal ring gear, torsional strain responsive means carried by the central section and operable to provide a signal pro-portional to the strain in the central section and the torque delivered by the tool, said central section having an outer diameter less than the outer diameter of the enlarged section, and planetary gearing driven by the motor drivingly connected to the torque output member, said planetary gearing engaging and reacting against the enlarged section ring gear to transmit torque to the central section, said planetary gearing including a first stage planetary gear set and a second stage planetary gear set and with only said second stage planetary gear set engaging and reacting against the enlarged section ring gear, said annular central section having an outer diameter and thickness selected for a given sensitivity to reduce the radial distortion produced by the second stage planetary gear set acting against the enlarged section ring gear.

14. A transducer assembly adapted for use in the housing of a power tool having a motor and a torque output member, as defined in Claim 13, wherein said first and second planetary gear sets are unsupported in the annular means.

15. A transducer assembly adapted for use in the housing of a power tool having a motor and a torque output member, comprising; a generally annular transducer means having a stationary portion at one end adapted to be non-rotatably fixed to the tool housing, said annular means having an annular central section adapted to extend within the housing, said annular means having an enlarged section adjacent the central section opposite the stationary portion with an internal ring gear, torsional strain responsive means carried by the central section and operable to provide a signal proportional to the strain in the central section and the torque delivered by the tool, and planetary gearing driven by the motor and drivingly connected to the torque output member, said planetary gearing including a planet carrier having a plurality of planet gears engaging and reacting against the ring gear of the annular transducer means, said central section having an outer diameter less than the outer diameter of the enlarged section to permit an increase in the thickness of the central section, said central section having an outer diameter and thickness selected for a given sensitivity to reduce the radial distortion produced by the planet gears acting against the transducer ring gear.

16. A transducer assembly adapted for use in -the housing of a power tool having a motor and a torque output member, comprising; a generally annular transducer means having a stationary portion at one end adapted to be non-rotatably fixed to the tool housing, said annular means having an annular central section adapted to extend within the housing, said annular means having an enlarged section adjacent the central section opposite the stationary portion with an internal ring gear, torsional strain responsive means carried by the central section and operable to provide a signal proportional to the strain in the central section and the torque delivered by the tool, and planetary gearing driven by the motor and drivingly connected to the torque output member, said planetary gearing including a planet carrier having a plurality of planet gears engaging and reacting against the ring gear of the annular transducer means, said central section having an outer diameter less than the outer diameter of the enlarged section, said central section having an outer diameter and thickness selected for a given sensitivity to reduce the radial distortion pro-duced by the planet gears acting against the transducer ring gear.