Patented Sept. 5, 1933 l@9259897 UNITED STATES PATENT OFFICE 1,925,897 SERVO CLUTCH Thomas L. Fawick, Akron, Ohio, dssignor to Fawick Manufacturing Company, Waukesha,. Wis., a corporation of Wisconsin Application November 23, 1931 Serial No. 576,724 11 Claims. This invention relates to friction clutches and siini'.ar apparatus such as brakes, but especially to the former. My principal object is to provide for greater i-) ease of control and operation of such - apparatus, this being particularly important in the larger, or heavy-duty clutches which in most cases heretofore have required the exertion of considerable,(, physical force to effect their engagement 'or to release the clutch-engaging spring, although my ii,ivention also applies to smaller clutches such as used on automobiles. To that end I provide a novel servo m@chanism including a pilot or secondary friction clutch for utilizing the power of the rotary driving member to produce the engagement of the clutch, in combination with a centrifugally balanced main clutch which permits easy operation of the pilot clutch, especially during release. A further object is to provide an improved form of enclosed clutch whose interior workiilg parts are protected from the entrance of dust etc. for use on road rollers and in other situations where ,@,uch qualities are desired. 2 A still further object is to, provide improved i,neans for clutch control throu@h a fluid-pressure medium such as the vacuum furnished by the suctioii of an internal-combustion engine. Of the accompanying drawings, Fig. I is an 311 axial section through a mechanic ally-controlled servo clutch illustrating one form of my invention, the section being taken on the line 1-1 of Fig. 2. Fig. 2 is a transverse section, partly broken 35 away, taken on the line 2-2 of Fig. 1. Fig. 3 is an axial section showing a modificatioii in which the clutch-engaging movement of the i2ontrol iiiember is effected by means of a spring and its releasing movement by a pedal 40 lever or the like. Fig. 4 is an end elevation showing a modified ,@hap e of servo 'cam Fig. 5 is an axial section illustrating a modification adapted for the use of engine vacuum as a 45 coiitrolli-ng medium. Referring at flrst to Figs. 1 and 2, 10 is a c UPshaped rotary wheel, drum, pulley or the like, such as the hywheel of an engine or a wheel driven by the engine, said wheel having a rim or flange 11 whose cylindrical inner surface forms the driving surface of the clutch. 12 is a driven shaft centrally journaled in the web of the wheel 10 and having a reduced inner-end portion 13 within said wheel. 14 is a @pider having a longitudinally-split hub (Cl. 192-35) keyed and clamped on the reduced end portion 13 of the driven shaft and having three arms which pivotally support an equal number of outwardlyactiiig shoes 15 each provided with a suitable friction facing o@ttached to a shoe body having side plates which straddle the respective spider arms. The shoes 15, together with their counterbalanced operating levers and the mode of mounting and coordinating said shoes and levers, which C,5 will briefly be described, are prefer4bly of the gener al character disclosed in my Patent No. 1,847, 389, dated March 1, 1932, but the present inventio n is not confined to that type of clutch and any suitable equivalent for these shoes and Op- 70 eratin g levers might be employed. Pivo t pins 16 for one end of each of the shoes 16 are -mounted to turn in bearings at the ends of the spider arms and detachably held in nonturnin g relation to the shoes by means of forked 75 retaini ng plates' 17 which also hold . the pins 'again st axial displacement in their bearings. For each of the shoes 15 there is provided an operat ing lever 18 ceiinected with said shoe by means of a link 19 and mounted to turn coaxially 80 with the pivot pin 16 of the next adjacent shoe on a fixed journal formed by the outer side of the spider -arm bearing for said shoe, these. operating levers being located between the side plates of the shoes 15 at the rear or right-hand side of 8,5 the spider arms as viewed in Fig. 1. Each of the lever @ 18 is provided with a 6ounterbalancing weigh t 20 attached to its arm opposiie to the arm connected with the link 19 for counteracting th6 effect of centrifugal force on th@ linked end 90 of the shoe 15, and each weight 20 in this case has a hook 21 connected by a spring 22 with a pin 23 on the adjacent shoe for releasing said shoe. The linked arm of each shoe is extended to carry a cam roller 24. 05 The front and rear sides of the shoes 15 and their,l evers 18 are made symmetrical and said shoes and levers may be reversed on their pins 16 when it is desired to assemble the clutch for operatio n in an opposite direction of rotation. The 10( directi on of rotation, as viewed in Fig.'2, is preferably counter-clockwise in order that the driving wheel 10 may have a servo action on the shoes tendin g to increase their frictional pressure agains t the rim of said wheel when once engaged 105 there with. For actuating the friction shoes 15 to produce clutch engagement through their operating levers 18, I provide a cam 25 having a limited rotation about the driven shaft 12 in the plane of the 110

2 i,925,897 clutch, said cam having three lobes as shown, with curved operating edges acting semi-radially on the lever rollers 24, each lobe in this instance being non-symmetrical or having an abrupt end face which allows the acting edge of said lobe to have a gradual rise of maximum angular extent. The cam 25 is detachably connected by screws 26 to the forward side of a cam-supporting plate 27 in order that said cam may be reversed con10 formably with the shoes and levers for an opposite direction of clutch rotation. Plate 27 is carried by a ball bearing 28, preferably closed at both ends to make it dust proof, on the rear end of the driven shaft 12, through the medium of a pair 15 of shouldered plates 29, 30 secured to the shaft by a central screw 31 and holding the inner baU race of the bearing 28 between them. The cam-supporting plate 27 is a servo member formed with a radial friction :ffange 32 adapted 20 to be engaged by a complemental friction facing ring 33 which is riveted to the radial flange of an axially-movable controlling and servo actuating member 34, centrally provided with a hardened ball 35 which is fixed in its hub por25 tion, and adapted to be moved and held in a forward position for producing clutch engagement by a suitable abutment 36, under the control of an operator. The controlling member 34 is attached by a 30 ring 37 and screws 38, of which one is shown in Fig. 1, to the inner margin of a thin, annular, flexible metal plate 39 whose outer margin is secured by screws 40 to the rim 11 of the driving wheel 10, said outer margin beinghorizontally 35 flanged over at 41 upon said wheel rim iind packed by a soft gasket 42 to make the joint dust proof. The intermediate portion of plate 39 is formed with concentric corrugations 43, 44 to increase its flexibility. Thus it will be seen 40 that the working parts of the clutch are completely enclosed and protected against dust, nioisture, etc. within the interior space of the hollow wheel 10, which is closed on its forward side by the web of said wheel and on its rear side by 45 the:ftexible plate 39, the servo cam actuating and controlling member 34 and its central contact ball 35. The controlling abutment 36 therefore acts mechanically, by a substantially sealed connection, formed in this instance in part by the 50 flexible end waU including plate 39 of the driving drum, through said end waU, upon the intemal adjustable friction member 33 of the servo secondary or paot clutch, to engage said secondary clutch and thereby actuate the cam 25; 35 but it will be understood that other modes of mechanically communicating the motion of an external controuing member through a sealed end wall to the internal secondary clutch could be adopted without departing from my inven60 tion. In the operation of this form of my invention, the driving wheel 10 being in rotation and the friction shoes 15 retracted, the engagement of the main clutch formed by the driving riin 11, 6-5 the shoes 15 and their immediate supporting and operating devices, is brought about by the operator applying axial force to the abutment 36 contadting with the hardened baU 35. This moves the controlling member 34 which, together with the facing 33 and the driven member 32. constitutes the secondary clutch, until its friction facing engages the complemental friction face on member 32 of the cam plate 27, thereby rotating the cam 25 about the driven shaft 12, causing the lever rollers 24 to ride up on the lobes of said cam, thus turning the levers 18 against the force of springs 22 and through the links 19, forcing the friction shoes 15 radially outward into clutching engagement with the rim of the wheel 10. At the conclusion of this en- 80 gaging movement the cam is brought to the same speed of rotation as the driving wheel and there is thereafter no relative movement or friction between the two as long as the clutch shoes remain tightly engaged. Should ine.reasing torque 85 resistance cause the shoes to slip slightly on the driving wheel, the resulting relative movemen o cam 25 on the driving shaft will cause the lever rollers 24 to ride further up on the cam lobes and thus automatically tighten the clutch engage- 90 mont wliile the secondary clutch remains tight because of its mechanical advantage over the main clutch obtained through the power-multiplying cam and levers. Whatever may be the form of the main clutch, it is important that its friction element or elements, exemplified in this instance. by the shoes 15, shall be substantially balanced against the action of centrifugal force, as is here done by the counterweighted levers 18 and might be otherwise accomplished in other If", clutch structures, in order to obtain easy clutch release under all conditions by the avoidance of binding or uneven action upon the cam or equivalent member controlled by the secondary clutch, as well as easy clutching action of said secondary l@.) clutch under all conditions. Upon retraction of the abutment 36 to refease the secondary and main clutches, the cam 25 is reversed through reaction upon its lobes by the lever rollers 24, produced by the pull of the springs 22 ' I t@) This clutch requires no adjustment for wear, since it automatically furnishes its own adjustment until the friction facings are worn out. The engagement is effected with a very sniall exertion of physical f6rce by the operator, because the engaging force is furnished most,ly by the &iving wheel through the described servo action. The release may also be easily effected by removing the pressure of the abutment 36, whereupon the frictional -engagement between the members 34 and 27 is relieved and the cam 25 is turned back and the shoes 15 released by the force of the springs 22. Should there be a suddenly-applied negative torque imposed through the driving end, as by suddenly closin.- the engine throttle and thereby causing the driven mechanism (such as a vehicle) to drive the engine, the main clutch will automatically release and produce a "free-wheelin.-" action by the forward slip of the fly-wheel 10 upon the clutch shoes 15, the pressure of the springs 22 thereupon causing the rollers 24 to ride down the cam lobes 25, whereas, if the throttle is gradually closed, this will not occur, but the main clutch will remain tight so that the engine acts as a brake. - M,9. 3 illustrates a modification adapted for a clutdh of the automobile type in which the driving wheel or engine flywheel, the clutch shoes, their operating levers and the shoe support or spider' 14, the shoe actuating cam 25, its rotary servo suppoiting. plate 27, the coacting servo camactuating and controlling meinber 34 and the flexible wall plate 39 are or may be the same as in the embodimpnt previously described except for the hub shape of said controlling member 34. In this case member 34 is provided witli a tubular hub portion 45 siii,t-oundiiig a Lleeve 46 v,,Iijch is slidable axially on the diiven ,,,Iiaft 12a, atid a spring 47 contained withiii said sleeve is iiiterposed betwee.-i the forward end fiange 48 of the

1,925,897 3 sleeve and a shoulder .49 on the shaft. Rearwardly abutting agairist the rear end flange 50 of said sleeve is a ball thrust bearing 51 adapted to be engaged by the inwardly-projecting studs '5 of a clutch-releasing lever 52, such as a pedal lever. - Between the forward bearing race and the rear face of the controlling meinber hub 45 is interposed a soft washer 53 for dust exclusion. It will be evident that in this form of the invention 10 the clutch parts are normally held in engagement by the action of the spring 47 in holding the friction face of the controlling member 34 against that of the servo cam plate 27, and,release is effected through the action of the pedal lever 52 1.5 in withdrawing the sleeve 46 against the pressure of said spring. In Fig. 4 is shown a modified cam which doe@ not require reversal when the clutch is assembled ,for an opposite direction of rotation, since the 20 lobes are of syrnmetrical shape on both sides of their central axes. The range of angular movement, however, in this case is less than for the shape shown in Fig. 2. In Fig. 5 I have represented a further embodi25 ment which includes a rotary device carried by the driving wheel and operated, by a fluid-pressure medium, such as atmospheric pressure opposed to a vacuum which may be furnished by the suction of an internal-combustion erigine, 30 for effecting tiie operation of the servo actuating and controlling member from a remote point by means of a suitable valve. The constrtiction and mode of operation of the clutch mechanism are the same as in Figs. 1 and @95 2 and the parts are designated by the same reference numerals, as far as the fiietion facing of the controfling member, here designated as 34a. Said member is attached by a hollow stem or bolt '54 and nut 55 to the axially-movable center of 40 the vacuum-operated device, which includes innET-, and outer metal plates 56, 57 connected at their outer margins with the rim 11 of the driving wheel 10 by means of screws 58 and suitable joint packings and separated by a space 59 constituting a vacuum chamber. The inner plate 56 is substantially rigid and is formed with broad conec,ntric corrugations 60, 61 to increase its stiff ness. The outer plate 57 is flexible and provided with a larger number of narrow concentric corrugations 62, 63, 64, 65, 66, to increase its flexibility. A central flat, metal reinforcing plate, or disk 67, formed with radial slots 68 to provide air pa'ssages, lies against the inner face of the flat central portion of the outer plate 57, and a second flat metal plate or disk 69, of srnaller diameter, lies against said plate 67 to cover the imier portions of said air passages and provide a spacer. Between the plate 69 and the rear flat portion of the pressed metal body of the.controlling member 341, is clamped the inner margin of a flexible diaphragm 70 made of a suitqble non-metallic material, such as rubber reinforced with fabric. This diaphragm has its outer margin fastened, to' the inner margin of the rigid inner plate 56 and thus serves to complete the inner wall of the vacuum chamber 59 and permit the axial movements of the outer plate 57 and the controllirig member 34a. In this latter as in the previously described embodiment of my invelition, the working parts of the clutch are thoroughly protected against the entrance of dust and moistiir6. The inner ends of the air passages 68 cominunicate through ports in the wall of the stem-bolt 54 with the central aperture 71 of said bolt, and a non-rotary chambered block or fitting 72 having a screwed end cap 73 surrounds the body of the bolt 54. A flexible pipe 74 provided with a suitabl e control valve (not shown) is attached to the cap 73 and connects with the interior of said cap and thence through the passages 71 80 and 68 with the chamber 59 foi- transmitting the engine vacuum to said dhamber or shutting it off and restoririg atmospheric pressure therein. A ball bearing 75 is provided between the fitting 72 and the outer end portion of the bolt 54 to permit 85 free rotati6n of the latter within said fitting, a space r sleeve 76 is interposed between the inner. ball race of said bearing and the rear face of the plate 57, and the running or swivel joint is packed or sealed by means of a lip packing 77 embraced 90 by a constricting spring 78. A soft, felt dust washe r 79 is also interposed as a packing retainer betwe en the fitting. 72 and the plate 57. When the ce ' nter of plate 57 is moved axially inward in 95 respo nse to a vacuum in the chamber 59, it carries with it, as a unit, the rotary parts 34a, 54, 55, 67, .69 and 76, as well as the swiveled, non-rotary - parts 72, 73. I n the operation of this embodiment it will be eviden t that the axial inward movement of the 100 servo. actuating and controlling member 3411, to. bring its friction facing into. contact with the cornpl emental friction surface on the flange 32 of the cam-supporting plate 27 and thereby to rotate the serv6 cam 25 about the driven shaft 12 105 until said cam, is brought up to the same speed as the controlling member, whereby the clutch shoe @ 15 through their operating levers 18 are outwa rdly set against the rim of the driving wheel, is . ieadily accomplished from a remote point by 110 openin g the v@lve in pipe 74, thus creating i vacuui n in chamber 59 which permits the external atmos pheric pressure to produce said axial movement of the flexible plate and controlling member. 115 Si nce a brake is a special form of friction cliitch in which the shoes or equivalent friction members are held against revolving and the rotary brake drum corresponds to the driviiig member, it will 120 be obvious that features of any of the described embo diments may be applied to a brake with such modifi cations bf structure as may be required to adapt the invention to that use except that the de@c ribed centrifugal balancing expedients ar6 125 peculi arly applicable to a clufch. It will als6 be understbod that the form of embodim ent may be furthek.varied within the scope of the claims and the invention is not intended to be restricted except as required by the claims 130 and the prior state of the art. I