clairn: 145 1. in a ppwei@ traiismittifig eltitch a rotatable driving e emenl, comprigiiig @,@ coiled spring, a rc)tatable driven elernelit w!tL a hollow wall witliln v-jhich "lie spring ;s disposed, mcaii,3 for i'adially expanding the spring l@;0 hand of an opera@uoi- at taidn or 1 achi e I

4 1,954,620 to cause it to frictionally drivingly engage the wall comprising a cam surface portion of the driven element receiving tangential thrust from a spring convolution and resiliently yieldable axially. 2. In a power transrnitting clutch mechanism, a rotatable driving element comprising a coiled spring, a rotatable driven element provided with a hollow waR within which the spring is axially 10 disposed, means for radially expanding the spring to cause it to frictionally drivingly engage the waU comprising a, cam surface portion of the driven element receiving tangential thrust from q, spring convolution and resuie,-itly yieldable 15 axially, to disengage the spring upon the occurrence of tangential thrust beyoA@Ld a predetermined value. 3. In a power trensl-ifting clutch mech,@,nism, rotatable driving element comprising a coiled 20 spring, a rotatable dri-ve-ii element provi(ied with a horow wall tithin which the sp@-ing i,,@, axially disposed, means f or rodia'ily exppnding the spring to cause it to frictionally &ivingly engage the wall comprising an inclined cam surface portion 25 of the driven eleme-,it enFoZed by an end of the spring and resiliently yieldable axially of the spring to dlqengagc,, the spriiig upon the occur., rence of engagement force above P. predetermined value. 30 4. In a power trensrnitting automaticary releasable cluteli meelianisa-n, a rotatoble dri-vb.-)ig element comprising a lielice?l .priy)ty, formed to have gn extemf?,l LencraL!y cyliiid,,@ica.1 surfpce, a rotatable driven l@i@-vLng p,@ KLGUGW cylin@@ 35 &ical wall coayii.1 @@:' the vrall and c@ubst,antially fitting the saiio, P,.Li resilientl@@ yiel.dable zlaemtsc,,x; Gf tb-e drivc@xi ele@ment having an inclined f w.,e engavlne nn end convolution of the spririg, resistance to rotatio7.i of 40 the driiyen vfill cause tlie tangentially engw6ing force bafv4een tl-ie spring end apd face to thL, npx,ing radiall:y, to cpuse it to drivfilctionally engace the cylinder wall ond -tolier,@3by upon risz@ oi' driven load of a predeter45 Lt)ji@x@,hd value ttie spring end will move the yieldal@l.e me-mber and ride over the cam face to effect cc&,3atioii of transmissioii. or. Iri, P. po,@ver trarisiyiitting autoniatically recliit,.h niechaiiisrn, a rotatable driving EO cjc;aic-nt a helicpl spring formed to zlii ext,@rrial geiierally cylindrical surface, votite@ole driv6n c-it-@:nent having a hollow cylinwall coaxial of the spring wall and sub,,tp-ntially --.'itting the same, an axially resiliently ,@'ioldable iaei-aber of the driveii element having iiielined cpm face enming aii end convolution of tb-e spring, wherebyresistance to rotation of the &iven element will cause a relatively small tankential eiigagixlg fc)rce between the spring end GO and the ba.%-- to expaiid the spring radially to cause it to drivir@gly frictiorally engage the cylinder wall with a relatil),ely grest driving torque, and vil-.kereby upon i-ise of the driven load to a predeterni-ine, vqliie, the spri,.,iE., e.)nd will move C3 the yieldable itieyriber ax@,slli, ard, ride over the cam face to eff cot 6. In a pnAkTeR- F-@i@toriiatically releasable @.,otptable e,,r@,ving element he!;La'@. to hav(, en eritert?,U y a rotatatDIe holl@@;w c@yl"ndiical waR we7tl P staiitially fitting@ tli@" Yieldable me--@'oc-r of th,(@ 75 of the spring, whereby resistaaice to rotation of the driven element will cause the tangentially engaging force between the spring end and face to expand the spring radially to cause it to drivingly frictionally engage the cylinder wall and 80 whereby upon rise of driven load to a predetermined vaiue the spring end will move the yieldable member and ride over the cam face to effect cessation of transniission and @t spring for opposing axial movement of the yieldable member 85 and a means for adjil-st-Ang the tension of the sdring to vary the predetc-rmined value. 7, In a Dower transtrutting clutch mechanism-, a rotatable driving element comprising a coiled spring, a rotatable driven element provided wiih a hollow wall wilhin which the spring is a)cially disposed, mealis for radially expanding the spring to cause it to frictionally &ivingly engage the wall comprising a cam surface portion of the driven element receiving tangential thrust from 95 a spring convolution and resiliently yieldable axially, driving means for said driving element and mutually engageable and disengageable operable clutch devices associated with the dilving raeans and the driving element. 8. In a power transn-iitting clutch -tnecha-riism, a rotatable driving element comprising a coiled spring, a rotatable cfriven element provided viith a hollow wall within which the spring is a-xially disposed, n-teans for radislly expat-iding the spring 100 to cause il, to frictionally drivingly eiigage the wall comdrising a carri. suiface portior). of the driven elenient receivirig tangential thrust from a spring convolution P,.nd resiliently yieldable axially, to disen,@age the spiing upon the occur- 110 1'exice cf tangential tilrust upon a, predetermined value, dri@ving means for said &iving element and I-Du'ually engageable and disengageable operable clutch devices associated with the driving means and the driving elernent. 115 9. In a power transmitting clutch mechanism, a rotatable &iving element comprising a, coiled spring, a rotatable driven element provided with a hollow wall witltn which the spring is axially disposed, means for radially expanding the spring 12(b to cause 'it to frictionally drivingly engage the wall comprising an inclined cam surface portion of the driven element engaged by an end of the spring an d resiliently yieldable axially of the spring to disengage the spring upon the occur- 125 rence of engagement force above a predetermined value, driving means for said driving element and mutually engageable and disengageable operable clutch devices associated with the driving means 130 and the driving element. 10. In a power transriaitting automatically releasable clutch mechaiiism, a rotatable drivilig element comprising a helical spring formed to have an external generally cylindrical surface, a rotatable driven element having a hollow cylin- Iss drical wall coaxial of the spring wall and substanlially fitting the same, an axially resiliently yieldable member of the driven element having an inclined cam face engaging q--Yi end convolution of the E@DrL-1g, whereby resi.@taii-ce to rotation oil 14C the - driven element wiL' cause the tangentially engagiiig force between the sp@@iiig end and face to expand sprint@ )."adially to cause it to drivi-r.Lly ergage tlie c@ylinder wall and cf cletire?-i load, to a predeter14E eiid -v7ill move the yieldcam face to effect 6-riv!rg nieans for said iz -, ui-utnp-hy engageable and r).u@@ch devices assa@--iated '50

1,954,620 5 with the driving means and the driving element. 11. In a power transmitting automatica.Uy releasable clutch mechanism, a rotatable driving element compi-ising a helical spring formed to 5 have an external generallycylindrical surface, a rotatable driven element having a hollow cylindrical wall coaxial of the spring wall and substantially fltting the same, an axially resiliently yieldable member of the driven element having 10 an inclined cam face engaging an end convolution of the spring, whereby resistance to rotation of the driven element wfll cause a relatively small tangential engaging force between the spring end and the face to expand the spring radially to 15 cause it to drivingly frictionally engage the cylinder Wall with a relatively great driving torque, and whereby upon rise of the driven load to a predeterniined value, the spring end will move the yieldable member axially and ride over the cam 2o face to effect cessation of transmission, driving means for said driving element and mutually engageable and disengageable operable clutch devices associated with the driving means and the driving element. 25 12. In a, power transrrjitting automatically releasable clatch mechanism, a rotatable driving element comprising a helical spring formed to have an external generally cylindrical surface, a rotatable driven element having a hollow c n30 drical wall coaxial of the spring wall and substantially fitting the same, an axially resiliently yieldable member of the driven element having an inclined cam face engaging an end convolution of the spring, whereby resistance to rotation 35 of the driven element will cause the tangentially engaging force between the spring end and face to expand the spring radially to cause it to drivingly frictionally eng whereby upon rise of 40 mined value the spring end will move the yieldable member and ride over the cam face to effect cessation of transrflission and a spring for opposing axial movement of the yieldable member and a means for adjusting the tension of the spring to 4,5 vary the predetermined value, driving means for said driving element and mutually engageable and diserigageable operable clutch devices associated with the driving means and the driving element. 50 13. In a power transmitting clutch mechanisin, a rotatable driving element coinprising a coiled spring having an abutment on a convolution thereof, a hollow rotatable load torque applying driven element haviiag an inner wall witliin which 55 the spring is axia-Ily disposed, means for radially expanding the spring to cause it to frictionary drivingly engage the wall when rotation of the driven element is resisted by load, comprising an auxiliary element rotatable with the &iven ele60 ment and having a connection therewith preventing rotational movement reiative thereto but perniitting axial movement relative thereto and having an inclined cam surface disposed to receive tangential thrust from the convolution 65 abutinent, and means yieldingly holding the auxiliary element against axial movement to maintain yielding engagement of the abutment and cam suxface. 14. In a power transmitting clutch mechanisriii 10 a rotatable driving element comprising a coiled spring having an abutment on a convolution thereof, a hollow rotatable load torque applying driven element having an inner wall within which the spring is axially disposed, mearis for radi75 ally.expanding the spring to cause it to frlctionc er wa an to a predeterally drivingly engage the,war when rotation of the driven element is resisted by load, comprising an auxiliary element rotatable with the driven element and having a connection therewith preventing rotational movement relative thereto but 80 permitting axial movement relative thereto and having an inclined cam surface disposed to receive tangential thrust from the convolution abutment, and means yieldingly holding the auxfliary eIement against axial movement to maintain yield- 85 ing engagement of the abutment and cam surface at all torque loads below a predeterniined load only. 15. In a power transmitting automatically releasable clutch mechanism, a rotatable driving go element comprising a helical spring formed to have an external generally cylindrical surface, a torque applying rotatable driven element having an intemal cylindrical wall coaxial of the spring surface and substantially fitting the same, the 95 driven member comprising an auxiliary element connected thereto by connecting megns preventing, relative rotation but permitting axial movement relative thereto, and provided with an inclined cam face engaging an end convolution of 100 the spring, resilient means yieldingly opposing axial movement of the said au:Kiliary element yieldingly maintaining engagement of the spring and cam face to cause the tangential engaging force between the spring end and face effected by 105 load resistance to rotation of the driven element, to expand the spring racbally into driving friction engagement with the cylindrical wall and to cause the spring end to move the auxiliary element axially and to ride over the cain face to 110 effect cessation of transmission upon attainment of driven load to a predetermined maximum value, 16. In a power transmitting autoniatically releasable clutch mechanism, a rotatable driving 115 element comprising a helical spring formed to have an external generally cylindrical surface, a torque applying rotatable driven element having an internal cylindrical wall coaxial of the spring surface and substantially fltting the same, the driven member comprising an auxiliary element connected thereto by connecting means preventing relative rotation but permitting axial movement relative thereto, and provided with an inclined cam face engaging an end convolution of 125 the spring, a spring yieldingly opposing axial movement of the said auxiliary element yieldingly maintaining engagement of the spring and cam face to cause the tangential engaging force bet ween the spring end and face effected by load 1 50 r esistance to rotation of the driven element, to e xpand t-he spring radiauy into driving friction e ngagement with the cylindrical wall and to cause th e spring end to move the auxiliary element a xially and to ride over the cam face to effect 1 35 c essation of transmission upon attairanent of d riven load to a predetemilned maximum value, a nd means for adjusting the tension of the second m entioned spring to adjustably vary the said pred eterinined maxiinum load. 1 40 17. In a power transmitting automatically rele asable clutch mechanism, a main frame, a s ource of power and a rotary power driven ciutch d evice supported on the frame, a drivable memb er rotatably and axially movably supported on 1 45 th e frame and having clutch means engageable w ith and disengageable from the clutch device by r elative axial movement of the clutch device and th e clutch means, a helical spring formed to have a n external generally cylindrical surface, the drlv1 50

6 1,954,620 able member having an inner cylin&ical wall coaxial of the spring cylin&ical surface and substantially fltting a portion of the same, and one end convolution of the helical spring engaged with the drivable member whereby upon rotation of the drivable member it may rotate the helical spring about its axis, a second member having an inner cylindrical wall substantially fitting another portion of the spring cylindrical surface the second 10 member being rotatably supported upon the first member in substantially fixed axial relation thereto whereby when the clutch device and the clutch means are engaged, the drivable member may be rotated and through the helical spring may rotate '15 the second member, an auxiliary element having a connection with the second member preventing relative rotation but permitting axial movement relative thereto and having an inclined cam face engaging the other end convolution of 2o the helical spring, a second spring resiliently yieldably constraining the auxiliary element against axial movement in the direction to diserigage the face and spring end, the face and second spring tension being proportioned 'so that 25 load resistance to rotation of the second member may cause the engaging force of the said helical spring other end and said face to expand the helical spring radially to cause it to &ivingly f rictionally eiigage the cylindrical walls of the said 30 members and so that upon rise of &iven load resistance to a predeternlined maximum value the spring end will move the said auxiliary elernent axially and ride over the cam face to effect cessation of power transmission, and means for 35 adi azting, the tension of the second spring to vary the said predetermined value. 18. A power transniitting mechanism as described in claim 17 and in which the auxihary eleinent is provided with means extending there40 from into the helical spring provided with a spring connectible portion disposed relatively remotely from the auxiliary element and the said second spring engages the spring connectible portion by one end and at its other end engages a portion of 4,5 the second member. 19. In a power transmitting automatically releasable clutch mechanism, a Totatable driving element comprising a helical spring formed to have an external generally cylindrical surface, a 50 rotatable driven element having an internal cylindrical wall coaxially of the spring surface and substantially fitting the same, the driven element comprising an auxiliary element having a spline connection with the driven element and provided 5r, with an inclined cam face engaging a convolutioii of t)-ie spring, a second spring yieldingly opposin@@ axial iiiovement of the auxiliary element, the sprii-ia tension and cam face being proport i oned so That resistance to rotation of the driven elenieiit will. cause the 6iigaging force between the helical spring convolution ard cam face to exI)and tlit- hcli,-al spring radially to cause it to frictionally engage the cylindrical wall 7@o that ijpon i,ise of driven load to a predetei'miiied valilie. the helical spring will move the mov,,ible element and ride over the cam face to effect ceqs,,ttion of transmission. 20. In a power transmitting autorraticahy releasable eltitch mechanism, a rotatable driving 10 eleiiient coiipr;sqng a helical spring formed to ha,.,e aii external @enerally cylindrical surface, a rot.i.table clriven elemeiit having an internal cylindi,ical wall coaxial of the spring,surface and substantially fitting the sarne, the driven element 7. comprising an auxiliary element having a connection with the driven element permitting relative axial movement but preventing relative rotational movement therewith, and provided with an inclined cam face engaging a convolution of the spriiig, a second spring yieldingly opposing 80 axial movement of the auxuiary element, the spring tension and cam face being proportioned so that resistance to rotation of the driven element will cause the engaging force between the helical spring convolution and cam face to ex- 85 pand the helical spring radially to cause it to drivingly frictionally engage the eyliiidrical wall and so that upon rise of driven load to a predetermined value, the helical spring will move the movable element and ride over the cam face to 90 effect cessation of transmission. 21. In a power transmitting automatically releasable clutch mechanism, a rotatable driving element comprising a helical spring formed to have an external generally cylindrical surfac:e, a 91. rotatable driven element having an internal cylindrical wall coaxial of the spring surface and substantially fitting the same, the driven element comprising an auxiliary element having connection with the driven element permitting relative 100 axial movement but preventing relative - rotational movement therewith, and provided with an inclined cam face engaging a convolution of the spring, an extension on the auxiliary movable element projecting into the helical spring and 105 provided with a spring engageable portion relatively remotely disposed from the auxiliary element, a second spring yieldingly opposing axial movement of the auxiliary element and engaging the spring engageable portion of the exteni sion at one of its ends and at its other end engaging portion of the driven element, the spring tension and cam face being proportioned so that resistance to rotation of the driven element will cause the engaging force between the helical spring convolution aiid cam face to expand the helical spring radially to cause it to drivingly frictionauy engage the cylindrical wall so that upon rise of driven load to a predetermined value, the helical spring will move the movable element and ridd over the cam face to effect cessation of transmission. 22, In a power transmitting autiomatically releasable clutch mechanism, a rotatable driving element comprising a helical spring formed to 2 r, have an external generally cylindrical surface, a rotatable driven elementhaving an internal cylindrical wall cdaxial of the spring surface and substantially :fttting the same, the driven element comprising an auxiliary element having a connection with the driven elem'ent permitting relative axialmovementbutpreventing relative rotational movement therewith, and provided with an inclinedfaceengaginga convolution of the spring, a secondspringyieldingly opposing axial movement 1 &c; of the auxiliary element, the spring tension and cam face being proportioned so that resistance to rotation of the driven element will cause the engaging force between the helical spring convolution and cam face to expand the helical spring radially to cause it to drivingly frictionally engage a cylindrical wall so that upon rise of driven load to a predetermined value, the helical spring will move the movable element and ride over the cam face to effect cessation of transmission, and i45 means for adjusting the tension of the second spring to vary the said predetermined value. 23. In a power transmitting automatically releasable clutch mechaliism, a rotatable driving element comprisin@ a helical spring formed to 150

have an external generally cylindrical surface, a rotatable driven element having an internal cylindrical wall coaxial of the spring surface and substantially fitting the same, the driven element comprising an auxiliary element having a connection with the driven element permitting relative axial movement but preventing relative rotational movement therewith and provided with an inclined cam face engaging a convolution Df the 10 spring, a second spring yieldingly opposing axial movement of the auxiliary element, an extension on the auxiliary element projecting into the helical spring and screw-threadedly adjustable relative to the auxiliary element provided with a 15 spring-engageable portion, the spring tension and cam face being proportioned so that resistance to 20 25 so 35 40 1,954,620 7 rota tion of the driven element will cause the engagi ng force between the helical spring convolution and cam face to expand the helical spring radi ally to cause it to drivingly frictionally engag e the cylindrical wall so that upon rise of the 80 driv en load to a predeternlined value, the helical spri ng will move the movable element and ride ove r the cam face to effect cessation of transmission, the said second spring being connected at one end to the spring-engageable portion of the 85 exte nsion and at its other end to a portion of the driv en element, and the tension of the second spri ng being adjustably variable to vary the predete rmined value. by adjusting the screw.thread con nections. 90 EDWIN L. CONNELL. 95 100 105 110 115 45 50 1 1 3 0 55 60 135 65 140 70 145 75

Patented Apr. 10, 1934 1999,620 UNITED STATES PATENT OFFICE 1,954,620 CLUTCH Edwin L. Connell, East Cleveland, Ohio Application April 25, 1932, Serial No. 607,355 23 Claims. This invention relates to clutches and particularly to self-releasing clutches adapted to release upon the occurrence of excessive transniitted load. It is an object of my invention to provide an improved clutch for transmitting power from a driving to a driven machine element. Another object is to provide a clutch having improved releasing mechanism whereby when the load transmitted by the clutch from a driving. 10 to a driven machine element exceeds a predetermined value the clutch will automatically be released, to break the driving connection from the driven element. Another object is to provide such a clutch 15 having improved adjusting means for adjusting the predetermined value at which the clutch automatically releases. Another object is to provide in a device such as clutch having mutually'engageable clutching 20 elements, improved structural means for effecting a clutching engagement between the elements. A.,iother object is to provide in a clutch comprising mutually engaged clutch elements adapted to transmit relatively great load, means where@5 by a resiliently yieldable element exerting relatively small force may maintain the clutch elements in engagement. Another object is to provide a self-releasing clutch mechanism in which a relatively smau .10 force exerted by a yieldable clutch actuating element may maintain the clutch elements in relp.tive engagements to transmit relatively great loads. Another object is to provide a power transmit33 ting clutch in which the engaged clutch elements comprise an expanding helical spring engaging the inner wall of a tubular element. Another object is to provide a cliatch having the characteristics set forth hereinbefore where4.) by rotary power may be transmitted from a rotary driving to a rotary driven element. Another object is to provide a self-releasing rotary clutch having improved releasing means whereby upon release, at the attainment of a, 43 load above a predetermined value, the clutch ieleasing elements are protected aga!Tsst undue wear. Another object is to pi-o@vide a self-releasing clutch of the ro'Llary power transnziittlng type 60 adapted automatically to be m6vc-d Jxito clutfh engaged condition by an a@,,,ial thrus'G- upor. the mechanism. Another object is to provide a clutch mechanism of the charai3teristics set forth hereixibefore 55 which will have greater durability aild longer life (Cl. 192-56) in service than self-releasing clutches heretofore pro posed. A nother object is to provide a clutch of the clas s referred to which will be positive in action both upon the engagement of the clutch elements 60 and upon disengagement thereof. A nother object is to provide an improved clutch of the rotary power transmitting type which will be fully automatic in Its action to engage clutch ele ments upon an axial thrust thereon and to U dise ngage the same upon the attainment of P, load abo ve a predetermined value.. O ther objects will be apparent to those skilled in the art to which my invention appertains. My invention is fully disclosed in the follow7 0 ing description taken in connection with the accom panying drawing in which Fig. I is a view illust rating the applicatioli of an embcidiment6f my inventiofi to a motor driven hand operated nut driving tool; 75 Fi g. 2 is a view simflar to part of Fig. 1 drawn to larger scale and with ad(iitional pafts in cross sect ion; Fi g. 3 is a view illustrating a modified embodimen t of my invention. 50 R eferring to the drawing, I have chown generall y at 1, the external housing of a motor, the hou sing terminating in a pistol grip handle 2, to whi ch an electric current siipplying cord 3 is seettred and adjacent to which a trigger type switch 85 4 Is eisposed whereby upon gripping the haiidle 2, a-i operator may with his flnger actuate the trigger 4 to -close a circuit from the wires 3 to start a motor in the housing 1. A motor shaft 5 generally vertically disposed 9 0 as viewed in the drawing ha-s thereon a pinion 6 mes hed with a gear 7. The pinion 6 is supported on the shaft in the housing 1. The gear 7 meshed ther ewith and the parts now to be described are sup ported by a housing 208 secured to the lower 95 end of the rnotor housing as by bolts 209. T he gear 7 is keyed as at 8 to a tubular shaft 9 rotatable in a bushing 10 press-fltted into a bor e in the housing 208 9,nd the tubular shaft 9 has on the lower end thereof, a primp@,ry clutch 100 hea d 3,1 pi,ovided with one or riiore @,lutch teeth 12 and tiae liesd has end thrust bearing upon the hoilsing @Tqrough an end thrust ba'Ll bearing sho wri generady at 13. T he housing 208 has 9, tubidar e,,Ttension 14 pro1 05 vide d with an interie anrililar shoulder 15 and 9, et,@-mfial bore le which bore is pressfltted a bearing L-u,@bing 17. A lower priinary clutch head 18 has a clutch tooth 19 engageable with the tooth 12 by up- 110

2 1,954,620 ward a%,ial movement thereof in a manner to be describecl, but as illustrated -in Fig. I being axiauy spaced from the tooth 12 and therefore not engageable therewith. The clutch head 18 normally rests upon the upper end of the bushing 17 and has keyed thereto as at 20 an upper sleeve 21 rotatable in the biishing 1.7. The clutch head 18 has a cylindrical extension 22 fitted in the sleeve 21 and extendin., dowziwardly thereinto 10 a suitable distance whereby it may engage the key 20. The lower face of the extension 22 is shaped to conform to the upper convolution 23 of a helical spring preferably forined from metal of square 15 cross seftion and is accordingly provided with a surface 24 fitting the iipper termination of the helix. and a notch 25 engaging the end of the upper convolution. The helical spring shown generally at 26 siib20 stantially fits the inner wall of the sleeve 21 and preferably the outer surface thereof is finished by grinding to the surface of a cylinder, the surface being indicated at 27, whereby it may fit the inner wall of the sleeve 21, wwch is cor2.5 respondingly accurately finished, as intimately as cylindrical bearing elernents. The upper sleeve 21 terniinates as at 28 approximately miclway axially of the spring 26 . Below the upper sleeve 21 is a lower sleeve 29 30 which is also finished to fit the cylindrical outer surface 27 of the spring 26. The lower end of the sleeve 29 has a reduced diameter portion 30 in which is coaxially provided a bore 31 in which is fttted, and keyed 35 as at 32, a head 33. Upwardly axially above the bore 31, the head 33 is reduced in dianieter as at 34 to provide a shaft 34 extending axially upwardly tbrough the spring 26, through a bore 35 in the primary 40 clutch head 18 aiid into a bore 36 in the upper primary clutch head 11. The shaft 34 interiorly of the clutch head 18 is provided with a groove 37 outwardly radially from which e:cteiids a bore 38 in the clutch head 45 18, in a threaded outer portion of which is screwed a screw 39, the ii-iner end of which projects into the bore 38 and abuts iipon a ball 40 disposed in the groove 37, By the ])all and groove construction described, 50 the shaft 31- and Llirotigh its head 33, the lower sleeve 29, is supported iii 'Llie position i'Uustrated, the weight being trai-isferred to the I)aU 40 from the groove 37 and thence to the wall of the bore 38 in the clutch liead 18, the latter being sup55 poi7ued upon the bushiiif 17 as described hereinbefore, Siirrounding the shaft 34 @i,nd abiitting at one end upon the head 33 is a helical coinpression spring 41, the oppo@,it-@ end of which is disposed 60 upwardly within the helical spring 26 and abuts ari upon a washer 1.2 clisposed in the bottom of on axiallyelonffated eiip 42 through a perforati 44 in the bottom of which, the shaft 34 extends, the skirt 45 of the cup 43 exteiiding coaxially of the shaft 34 in radially spacedtelescopic relatioll therewith and the convolutions of the spring 41 being disposed within the cup skirt 45 arotind the shaft 34, 70 Ii-i the preferred constriietion, the shoft 34 has a keyvvay 46 cut thereiji aiid a tongue 47 on the washer 42 exteriding ii-iwardly radially therefrom is disposed iti the keyway 46; and the washer is I)rovided with oiie or mo.-e axially extending 75 lugs 48 extendin.@ axially throiigh a suitable perforation or perforations 49 in the bottom of the cup element 43. The ptirpose of the washer constriiction just described is to ensure that the clip 43 will rotate in unison with the shaft 34 for a purpose to be 80 described. Upon the lower end of the cup skirt 45, is threaded a nut 50 externally knurled as at 51 whereby it may adjustably be tllr,,Ied on the thread 52 of the cup. The upper axial end of 85 the nut 51 is preferably spherical as at 53 and engages a correspol-idirig spherical surface 54 of a clutch trip device 55 comprisiiig an annular body 56 surrounding the thread 52 of the 'cup and carrying the spherical @uiface 54 and, on 90 its upward axial surface Provided with a cam projection 57 having a cam surflee 58 adapted to be engaged by a corresponding incline@l surface 59 on the end of the lowermost convolution 60 of the helical spring 26. 95 The clutch device 55 also has a pair of outwardly radially extending lugs 60 projecting iiito axially extending slots 61-61 in the wall of the lower sleeve 29. The extreme upper end of the shaft 34 in the 160 tubular shaft 9 has a pocket 62 formed therein in which is disposed one end of a compression spring 63, the opposite end provided with a button 64 abutting, in the nature of an end thrust bearing upon a washer 65 retained in the end 105 of the bore 36 by an expanding ring-form annular spring 66 set in an inte@-nal groove in the bore 36. The lower end of the shaft 34 or particularly the lower end of the head 33 thereof, may have 110 formed in the lower end as at 67 a tool receptacle such, for example, as a hexagonal socket into which a hexagonal shank 68 of a nut-&iven wrench 69 rnay be telescoped. To retain the shank 68 removably in the socket 67, the shank 115 may have turned thereon a groove 70; and in a wall of the socket 67 a perforation 71 may be provided and a ball 72 disposed therein, projecting into the groove 70. Thus the shank 68 may be rotatively driven by the bead 33 and 120 may be prevented from axial dtspla(,,emeiit in the socket 67 by the ball 72. To retain the bpll in place, a sleeve 73 is provided dispo,,;ed coaxially with the sh,@iiik 68 and head 33 and having an inwardly radially projectin@ bead 74. 125 The sleeve 73 is constrained axially resiliently by a spring 75 so that the upper end of the sleeve abuts ,As at 76 upon the lower end of the sleeve 29, the spring 75 abutting at its upper end upon the bead 74 and at its lower end upon a 1,13 shoulder 78 formed on the head 33. In this construction, the lower end of the head 33 has a reduced, generally cylindrical, portion 79 upon which the bead 74 may move axially telescopica,lly. 11)5 Upon moving the sleeve 73 downwardly against the compression tension of the spring 75, the bead 74 will be displaced axially from the ball 72 and the ball may roll outwardly through the perforation 71, ,whereupon the shank 68 may 11) be removed. The ball 72 may be prevented from dropp-ing cjut of the bore 71 ii-iwardly by suitably inwardly constrictingly pressin- or otherwise reducing the diameter of the bore 71 at the inward termina- 14,5 tion thereof as at 80. The operation of the embod-iment cif my ini,ention of Figs. 1 and 2 thus far described is as follows. N'ormally, the spring 63, exerting a downward !-,--)O

1,954,620 end thrust on the shaft 34 communicates this thrust to the clutch head 18 through the ball 40 and thus normally mainta@ns the clutch teeth 12 and 19 out of engagement. 5 Tlie operatoi@, by means of the switch tra'gger 4 may start the motor in the housing 1 whereby its rotary moveiiient will be transniitted throiigh the pinion 6 to the gear 7 and rotate the clutch head 11, having thereon the clutch tooth 12; 10 Assumiiig that the motor is to drive a nut or bolt'-screwing wrench such as 69, the operato@- presents the wrench 69 to the work, and as shoun iii Fig, I may telescope the wrench over a nut or over a bolt head 85. 1.,-) Upon pushing axially upon the wrench 69 by means of the handle 2, the shaft 34 will be moved upwardly as viewed in the drawing carrying the clutch head 18 upwardly to engage the tooth or teeth 19 thereof with the tooth or teeth 20 12 of the cluteli head lt and the torque of the motor will be tra-,ismitted to the head 18. The sleeves'21 and 29 rnove upwardly with the shaft in substantially th,,, same relative positions as illustrated and rotary movement of the head 25 18 is communicated to the spring 26 through the notch 25 and rotational movement of the spring around its blxis is transmitted from the lower end of the spring 59 to the cam surface 58 and thence into the cam projection 57 and into 30 the clutch device 55 and thence by means of the lugs 60.-60 the clutch device 55 rotates the lower sleeve 29 and head 33 and the wrench 69. When the bolt or nut 85 being turned resists turning movement, the end 59 of the spring will 35 be forced against the cam surface 58 with a substantial amount of force which will cause the spring 26 to tend to unwind, causing it to expand diametrically and to grip the inner wall of the sleeve 29 as well as the inner wall of 40 the sle6ve 21. A relatively small force on the end of the spring 26 will be sufficient to cause the spring to grip the sleeve with a very great torque transmitting frictional engagement. The full power 45 of the motor may now be transmitted through the spring 26 and thence by its frictional engagement with the sleeve 29, through the latter and to the tool 69. Although the force between the end 59 of the riO spring and the cam surface 58, is a relatively small force compared with the force transmitted to the sleeve 29, nevertheless it will vary in proportion to the total torclue transmitted. Thus if the load transmitted to the wrench 69 rises to a predetennined value such as for exaniple the torque load desired to effectii@ely seat a nut or a bolt head, the force transmitted by the end 59 of the spring will likewise reach a predeterinined value at that point, When such force CO value is reached, the end of the spring 59 actin.on the surface 58 as upon a cam, will ride over the cam surface 58 shovi@ng the clutch device 55 P,s a whole downwardly against the opposing tension of the spr,.iig 41. The transniission of torque C:'; therefore will im@-nediately cease and at each revolution of the spring 26, the end 59 thereof will trip over the clutch surface 58. The value at @,vhich the clutch thus releases may be adjusted or varied by tuming the ilut 49 50 orie Nvay or the ottler to change the tension of the spring 41 in a manner that ivill noni, be understood. Upon turning the nut 50, the cup-sliaped element 43 is prevented from turn,'@li@r by its en7,@) gageireiit with the Itif,,s 48 on the Nvasher 49 and the engagement of the v@asher 49 with the keyway 46 in the shaft 34. Upon relea-sing axial pressure upon the tool 69, the spring 63 will expancl to disengage the clutch head teeth 12 and 19 and even if the 8( motor continues to run, the tool wili stop rotating. Wkien the de-,rice relea@;es as a.bc-ve described, the clutch device 55 will vibrate up and dowii axially as the sprin.@ end 59 tr;ips ovet- the clutfii 8,5 projection 57, and the slots 61 perffiit @he lu.-s 60--60 to reciprocate therein during this moveriient. Referring to ]Fig. 3, I have shown a modifteatioii of my invention in whi,-h it is applied to cio transmit, from a driving shaft 100 to a driven shaft 101. The driving shaft 100 rotatabliy clrives a clutch head 102 by means of a fe@ither key IO.'. By means of a lever 104, an operatoi, miy sl,.ift the head 102 axially say toward the right, a pin t)5 or pins 105 on a suitable fork on the lever 104, entering a eircillar groove 106 in the head 102 according to well known coistruction. Upon so shiftiiig the head 102, A tooth 107 thereon will engage a tooth 108 and rotale the 10f) clutch head 109 causing a notch 110 thei-eof to rotatably drive the hel-eal spring 111. The spring 111 ml.y engage at the end 112 thereof, a clutch tootli 113 ori a ciutch device 114 resilietlt,- ly constrained axially. A relatively sig@@t pres- 10,5 sure applied through the end 112 of the spring will cause the cylindrical body of'the spring to expand and frictionally engage the innelVall 116 of the sleeve 117 with N,ery great driving friction. 110 Rotation of the sleeve 117 is transmitted to the head 118 wwch is rigidly conne--ted thereto by bolts 119, and the head being rigidly connected as by bolts 120 to the shaft 101. drives the shaft 101, It will be observed that the ger@eral construc- 115 tion and the operation of the device of Mg. 3 is sirnilar to or the same as that of Figs. I and 2 with the exception that the teetli 108 and 1(,17 are initially enga?,'ed by manual power through a lever which may be disposed convenient to @,he 1 2 i":, -n n 4 which power is del@vei@ed j@r(%ni the s@iaft 101., III such an instaiiee, the shaft 101 rriay be idipfe@'t to apply power to a machine tool vvith V,7hich Lhe lever 104 is associat,:@d. 125 The device of Fir,,,. 3 may be iiistalled wherevc-r such a macwne tool is employed to do work in which an excess lo,,@d oii the mael-@ine may suddenly occur either in the norr@ip@l operation of the machine or accidentally. 'n-ie deviec will 130 operat e the machine uadcr normal conditions @nd upon the occurrence., of the overload releise azid the releasing load may be predetermined by adjusting the spi,ing 115. 'Me foregoing brief description of Mg. 3 is be- 135 lieved sufficient in vieaz of its similarity to Figs. 1 and 2 and the more coinplete description of the latter hereinbef ore. My invention is not Iiinited to the exact details of ronstruction shown and described. Many 140 chang es and modificatioiis may be made other than those illustrated and described and without depart ing from the spirit of my invention oi, sacrifl eing its advantages. I