US1797857A - Grinding machine - Google Patents

Description

` MalCl'lZL 1931. H FORD 1,797,857

GRINDING MACHINE Filed May 28, 1929 3 Smets-sheet 1 ATTORNEY.

I@ Ng@ March 24, 1931. H, FORD 1,797,857

GRINDING MACHINE Filed May 28, 1929 5 Sheets-Sheet 2 March 24, 1931. l H FORD 1,797,857

GRINDING MACHINE Filed May 28, 1929 3 Sheets-Sheet 5 BYMUM1-` center 5W volv Patented Mar. 24, 1931 HENRY Form,- OFY DEARBORN, MICHIGAN',

AssIGNon To FORD MOTOR ooMPANYy-or DEARBORN, amenacen; ecoronnrion orA DELAWARE GRINDENG. MACHNE Application vfiled May 28,

The objectl of my invention' is to provide a'grinding machine of simple, durable'and inexpensiveconstruction; y kStilla furtherobject of'my invention is to provide a grinding machine Which Will :autoinatically grind the bore in a split type valve bushing. These valve bushings consi'stlofa pair of semi-circular halves -so formedl that When' placed together (a bushing very similar to the solid valve bushing 'ordinarily usedfin motor car engines in produced.A f

Many'advantages are' gainedjv'hen these bushings :\1"e;'i1se"cl'y in an' engnathe. principal advantage bei ng' that each half# of: the bushingv may be die' castjseparately andallovved to' chill'intlie `moldth'ereby `forming an eX- trennelyv hardA`V valve stem bearing. surface for theb'us'hing.- Then'ieeting Hat-faces are then ground on an' ordinary surface grinder! after which the outer` diameter ot a pair oflbu'shings? is ground' round.' rIfhe semi-circular bearing surfaces in which the"valve stemrecip'rocatcs are thengrou'nd Withr` a' large Jforni Wheeh the cutting .edge olitvhich li'a's previousbeen dressed to the'radius of thevalve stem.

, It may be readilysee'n that these busliings were made solid 'instead of in'halves, the

bore inthe bushing Would have to-be drilled n or ground with a Wheelo'f smaller dia-meter than the'valve' stem.: Drilling chilledbushingsis, of' course,` impossible; Whilegrinding'lthe' bore with" a'n extremelyjsniallivvheel is not `rcomme'rc'ially` successful.l With thi-s so called i, split bushing,` the' applicant uses: a l'arge'f'orm Wheel to grind the valve stem bearing surface, and thegrindingv machine which is the subject of this application" performs thisfgrinding operation.

Each of these half bushings must be an exa/.ct duplicate of'each other,` the bearing'surfaces must be aneXact-semicircle havinga hired radius andA the outer" circumference must be concentricrvith the borejso thatr any tivo'ha'llivbushings which maybe picked at random Will'produce a perfect bushing.

Still a further Obj ect of myinventilon' is t-oV provide a grinding' machine in which" the Work to be ground is rotated arou'ndax'ed toposition adjacent to aser'ies'of're- 1929. serial No. aeeeec.

radial position o't/heworl-: as it'rot'ates so that th'eline 'diconta'ct ofthe 'Work with the revolving' grinding Wheels isY tangent to the Wheels. f

In most progressivemachine operationsthe piece to be machined is passed"y from one machinel to the neXton' al conveyor or some siinilar device,y the piece; being clamped tothe conveyorv or reclamped infied dies on each machine. Due to thefeitreme'-'accuracy required in tliisfparticular partg it has. been found inipractical'to usean'y type of conveyor or the 'like'sfbr' advancing the *Work yfrom one grindingwvheel tofthe next as the location* of the Work in reference* to eachl succeeding grinding Wheel cannot be held accurately enough'. If'th'e yWorlifis successively clamped in af series of' diesf held -Vin fixedj position in relation vto the grinding:ivheelsthe variation obtained when clamping the4 Work in the various diesprbduces variations in the 1 tinished dimensionsiofithe piece:

In the majority of grincliiigopei'ations in which great vaccuracy is obtainedhtlie Work isv 'rotated around a" center andthe grindingv Wheel moved againstthe Work thereby grinding a very' accurate'- circumference, Qnly arcuate surfaces may begroundLby'this method-because regardless ofhoW' large the-radius of' gri'ndingis made" an' arc'l Will be' formed and not anat surface. i 1

ln' the applicantsmachine the Werl;- i`s rotated arounda' iXed'center and the distance of the ivor'k from the fixed cent-er is varied the Work revolves. so that the successif'e points of'contactofthe Workwith the grinding Wheel results-inY a straightline. The accuracy obtaincdwith the circular grinding processr isv t-hus1obtained together Withf the advantage? thfatflativork" may be' ground thereon.

With a very:l minor changeV in the" applicants mac-hine',y.surfaces= may bef ground to a desiredfirre'gularcontour. These irregular surfaces are-very difiicult to grind'to accurate di'in'en'sionsby any* other method known to the'applicant. A-lth ugh the grinding ot" a piece having a" dat surface ist Kn'iforeA` fully cleseibefd' inl the specificati" a'nyfirregular or arcuate surface may be just as readily ground in the machine.

Still a further object of my invention is to provide a novel means for rotating the Work holder very slowly while the work is being f ground and rapidly between the grinding operations. Various designs of elliptical gears have been used to vary the velocity of two shafts, but the limit of variation obtainable with these gears together with theV fact that smooth grinding work cannot be accomplished where this type of gearing is used has made it imperative that a variable motion device having a wide range and smoother operating characteristics be devised. The applicants structure is very simple and produces a very steady acceleration and deceleration of the work holder.

Still a further object of my invention is to provide a grinding machine in which the work is resiliently held in a. work holder and to provide means so that when the work holder is rotated through one revolution the work will be automatically discharged from the machine. It is only necessary in the applicants machine to place the bushing into theV work holder, they being automatically conveyed to each of the three grinding wheels and then automatically discharged from the machine.

With these and other objects in view my invention consists in the arrangement, construction and combination of the various parts of my improved device, as described in the specification, claimed in the claims, and illustrated in the accompanying drawings, in which:

Figure 1 shows a vertical central sectional view through the main spindle of the machine. i

Figure 2 shows a sectional view taken on the line 2-2 of Figure 1. v

Figure 3 shows a diagrammatic view of the work holders, grinding wheels, and stationary cam, to illustrate the sequence of the grinding operations and the method used to develop a fiat grinding surface.

Figure 4 shows a plan view of one oi the work holder assemblies.

Figure 5 shows a sectional view taken on the line 5-5 of Figure 4. y

Figure 6 shows an enlarged sectional view taken on the line 6 6 of Figure 5, aud

YFigure 7 shows a sectional view of the inner side of the work holder onv the line 7 7 of VFigure 1. Y

Referring to the accompanying drawmgs.

I have used the reference numeral 10 to indicate generally the base of the machine. This base 10 consists of a rectangular box shaped structurehaving aflat machined upper surface 11 to which the various parts of the machine are secured. A'rim 12 is secured to the late 1'1 and extends around its outer edge to orm a pan or trough for collecting the meist? cooling Huid used with the machine. The base member 10 is internally braced to give great rigidity to the parts mounted thereon to thereby secure very accurate work with the machine.

A bracket 13 is secured on one end of the base plate 10 and extends vertically therefrom. The center portion oi this bracket is provided with a bearing 14 for the main spindle of the machine. In this machine three grinding wheels. are rotated by means of electric motors and the work to be ground is passed successively underneath each of these wheels. Each of the electric motors 15 are secured to a slide 16 which is mounted for radial movement in the bracket 13. The slides themselves have not been shown in detail as they are of ordinary structure and )form no` part of the invent-ion except as a means for adjustably mounting the grinding wheels. y

The motors 15 extend forwardly from the slides 16 and guard members 17 are secured tothe opposite side of the 'slides and partially enclose the grinding wheels used kon the machine. The grinding wheels, motors and slides are of the conventional direct'connected type used for ordinary grinding.

Three grinding wheels are provided, as shown in the diagrammatic view in Figure 3. The lirst and second wheels 18 are roughing wheels, while the third wheel 19 is a finishing wheel. As the grinding wheels wear down the slides 16 are moved inwardly to compensate for-the wear of the wheel so that the travel of the work to be ground can be a fixed path, irrespective of the wear on the wheels.

The opposite end of the base plate 10 is provided with a housingV 21 which is secured tothis plate by means of an integral flange 22. A bearing 23 is formed in the outer end lof housing 21 and is aligned with the bearing 14 in the bracket 13. Y

A spindle 24 is rotatably mounted on the bea-rings 14 and- 23 and a cap 25 is secured to the outer end of the bearing 14 to absorb the end thrust produced by the spindle 24. A second cap 26 is secured Vover the outer end of the bearing` 23 to enclose the spindle 24. A thrust ,screw 27 is secured in the spindle 24 adjacent to the cap 26 and a thrustplate 28 is resilieutly mounted in the cap 26 by means of the springs 29 so that the spindle 24 may be resiliently urged against the thrust plate 25 by the springs 29.

. A drum shaped member 30 is formed integral with the spindle 24 adjacent to the inner end of bearing 14 and extends radially therefrom.v A plurality of bearings 31 are provided in the'periphery of the drum 30 parallel to the spindle 24 and a work holder assembly is rotatably mounted in each of these bearings V3l. In the vform of machine here shown, eight work holders are provided equally spaced around the drum 30. When the spindle 24`rotatcs in the bearings 14y and 23th=e Y.dru1`n'30 and worlt'holders 4also rotate'.

v4Referringto FiggureV 47 a *sleeve V3Q is' rotata'# bly mounted in each bearingl 3l, the oute'r'end of. eachI sleeve having y an' arm 33 extending alngthe periphery of the drinn 30. A 'hloch 34 is formed integral with` theouter oft-he arm 33"and is of rectangular shapeY and has an outwardly opening .longitudinal slot 35 formed therein.l A pair offpl'ates36 partially enclose the slot'35 andare securedI to the block means of the screws 37. space, slightly wider than the thickness ofthe grinding-'wheels 18.*-0119 is allowed betweenthe two plates 36'vso that there is ample clearance for these wheels to operate between the two Platesf The inner end kof each=sleeve`32 is secured to a second arm 33 by means of the screws 39 and extendssubstantially parallel to the arm 33; A roller 40 is pivotally mounted between th'eears 421011 the youter end of the arn138 by nreans of a pin 41. 7 y

The construction just referred to consists briefly of a sleeve havin-ga pairof arms eX- tending from' each side* nthereofgfone of` the arms being provided with a roller atfits outer end-and the other arm with alblock so that movement ofi'theroller willcau'se' a like move- A shaft 43 `is extended through the sleeve 32 and anarm 44 is formed integral with the outer' end of the shaft and extendssubstan- Y ,tially parallel to thearm 3,8. The outer end I the plates 36g ofthe arin44'extends into the slot 35 in the bloclt34- and a; shoe 46 pivotallysecured to tliisarmrwithin the slot 35 by means of a pin 47. The outer face of the shoe 46 is provil-led with a`v V-sha'ped groove so that the bushing to beA groundp shown by the dotted lines 48, may be clampedv between this V shaped groove inthe'shoe andthe plates 36. There is aconsiderable movement of the shoe 46 within theslotv 35 sothat when the arm 44 is. rotated clockwise, referringv to Figure 5, theshoe 46 will clamp the bushing 48 against y A-lever 45 is fastened to the inner end of the shaft 43 bymeans lof the'studs 49 and eX- tends' in thegeneral Ydirection of the arm 38. Aleaf spring 61` is secured to the` leverl 45 adjacent to its hub` also by means offthe studs 49 and the `outer end 'of this springbears againstan adjustable stopsecured to the lever 3 8. Then the spring 6l is installed it is flexed to such position Vthat 'the shaft-43 and a11n744will resilientlyV force the shoe 46 against the plates 36; VAn eccentric sleeve 5() is rotatably mounted on a. stud 62 extending from the arm 3S beneath thefspring61- Suitable slots 5L are provided in theper-iphery' of thev eccentric '50 'forrotatngsame" for ady justment.; .A nutl isarranged tolo'ck'the ec- 5f() in any desiredpesitioii around the Tt may 'thus be seenthat rotating "the 'eccentric 56'w`ill vary` the spring pressnreof the leaf spring 61 thereby varying,the pressure operator' of the machine is thus able to resiliently' clfampthe bushing 48 between the shoe 46 and the plates 36 withjafwide range of adjustable springpressures` lWhen it is desired to release the bushing 48 f fro'rnfbetween the plates l36and shoe 46,1 the outer e'nd ofthe leyer 45 is moved inwardly thereby rotating the shaft 43r'against the5 r'e'- f silient pressure of the spring'61 ltothereby lower lthe shoe 461from ther bushing. This ysaine operation is repeatedwhen itis desired toinsertia new bushing intheb'lock 34'.l

y It will be'noticedthat the'sle'eve32', shaft 43. arnis 33, 33,` and 445 together with'tlfe lever 45 and spring 61,Aoscillate asa. unitin the bearingl during allof the;` grinding operations. The bushing 48 isV clamped at the beginning of arevolntion of the dru1n3() and is not released untilit'hais passed beneath the three chlferentI grinding wheels ofthe machine. y y l y A cover plate '53 is secu'redto the inner end of the'ho'usingil kand an extensionj54 is formed integra'lwith this coverplate 53 and extends between. the' cover plate and the M.

such position that when the drum' 30 is ro- 4.

tated the rollers 40'will follow the contour of this com 52' to thereby oscillate the lsleeves f 32 inthe bearings '31.

` Three substantiallyllat'portions 56 aregprovided on theicani 52` so thatthe'rollers 40 will operate thesefat port-ions' when the:

bushings 48 are' being.A ground by the grin`ding wheels. Tt may bei well totinention here that due tothe "arcuate travel ofthe sleeve 32,

the cani surface 56 isnot exact-ly flat butl is .i

ofV such a contour that al straightl snrf'a'ce willl be ground bythe wheels 17 and 18in the bushings 48; ln the 'building' of the inachine,v the cani 52 is niachinedto approximate size andv thenmoun'ted on the coverj 53.

grinding wheels' 18"; and l9`a21f1d` a: finished bushing is placedinr the work holder.' A portable grinding wheel is rotatably mounted on A-, solid steel wheel isf clampedv in placeof the the clevison the endof the`a`ri'n38-in placeY 5 of the 'roller 40kandthe'shaft` 24 is then ro? tated.' The bushing' 481is' held upagainfst the flat surface o'fthe aforei'nentioned steel roller and the slight radius is? ground o'n'the the contour of the cam 56 to produce a corre- If an irregular surface is desired to be ground, a template or finished piece is inserted instead of the bushing 48 and the cam 56 is finished from this template. When the machine is normally operated the ground surface will be identical with the template used to grind -the cam56.

The normal operation of the device is just the reverse of the method used to grind the cam, that is, the roller'40 operates against sponding ground surface Von the piece to be ground. Y Y

A pin 57 extends inwardly from the arm 38 and one end of a coil spring I58 is hooked over this pin and the other end secured to the spindle 24 so that the roller -40 may be resiliently urged against the cam 52 by means of this spring. y

A trip block 59 -is mounted in the interior of the extension 54 and projects inwardly so that the outer end of the lever 45 will be forced inwardly as 'itpasses this trip blocs. The bushing 48 which .is clamped inthe work holder at this time is thereby released and drops to the bottom of the machine.

v A second trip block 60 is Secured to the plate 11 in the path of the outer ends of the levers 45, so Vthat as each lever advances over this trip block a new-bushing may be placed in the work holder by the operator of the machine. Vhen the drum 30 advances so that the outer end of a lever 45 slides over the trip block 60, the spring 61 clamps the bushing 48 between the shoe-46 and the plates 36.

Means have been provided for increasing the speed of the spindle 24 when the bushings 48 are travelling between thefgrinding wheels. If a constant rotation ofthe shaft 24 were provided, only a very small percentage of the time required for one rotation of each shaft would be utilized in grinding the bushings, and as the grindingoperation is such that an appreciable amount of time must be taken for grinding each bearing, a great saving of time is obtained ifthe spindle 24 is speeded up between the grindingoperations.

A sleeve 63 is rotatably lmounted on the spindle 24 adjacent to the bearing 23 and the worm wheel 64'is secured to thissleevc by means of a radial flange 65 formed integrally with the sleeve 63. A gear 66 is'machined in the opposite end of the sleeve 63. A worm 67 is mounted in the lower part of the housing 21 transversely-to the spindle 24 in position to' mesh with the worm wheel64. Y Suitable bearings 68 are 'provided for this worm and anY electric motor 69 is connected thereto through an extension shaft, notshown in the drawings- The Arotation of the motor 69 thereby rotates the worm 67 which operates with the worm wheel 64 to rotate the sleeve 63 and gear 66.

An arm 70 is. rotatably mounted on the spindle 24 adjacentto the` sleeve 63 and extends downwardly to a position near the base plate 10. A bearing 71 is provided in the lower end of the arm 70 parallel with the spindle 24 and a shaft 72 is rotatably mounted in this bearing. A gear wheel 73 is secured to the rear end of the shaft 72 by means of kcys 74 and a cap screw 75 and washer 90.

An eccentric 76 is secured to the shaft 72 adjacent to the forward end of the bearing 71 and a pinion 77 is formed integral with the forward end of this shaft adjacent to the eccentric 7 6. The gear 73, shaft 72, eccentric 7 6, and pinion 77 are for all purposes a unit and rotate together at all times. A bull gear 78 is secured to the spindle 24 by means of keys 79 and a nut 80 in positionto mesh with the pinion 77.

A link 81 is pivotally secured to one wall of the housing 21 by means of a pin 82 and clevis 83, the latter being formed integrally with the housing 21. A large split bearing 84 is formed on the opposite end of this link which is j ournalled on the eccentric 76. This bearing is provided with the conventional bearing cap `85 lwhich is secured thereto by kmeans of the screws 86.

When the shaft 72 is rotated, the eccentric 76 rotates with it and oscillates the link 81 around the pin 82, the link being free to osciliate in an arcuate path around the pivot pin 82. The shaft 72 being mounted inthe bearing 7l of the arm 70 which is rotatably mounted on the spindle 24, is not free to oscillate in this arcuate plane but is only free to oscillate in an arcuate plane having the spindle 24 as a center. It will thus be seen that when the shaft 72 is rotated an oscillating movement will be imparted to the link and arm 81 and 70 around the pivot pin 82 and spindle 24, respectively, the link 81 compensating for the vertical movement of the eccentric and the arm 70 compensating the lateral movement of this eccentric.

To operate the device, the motor 69 is started which rotates the worm 67, worm wheel 64,'and gear 66. The gear 73 being in mesh with the gear 66 thereby rotates the shaft 72, eccentric 76, and pinion 77 in a counterclockwise direction, referring to Figure 2. As has been previously explained, the rotation of the eccentric 76 oscillates the arm 70 and shaft 72 around the Spindle 24 and, as the pinion 77 is formed integral with the shaft 72 the bull gear 78 would also be oscillated if it were not for the rotary movement imparted thereto by the pinion 77. This gear 78 will thereby rotate in a clockwise direction, looking from the forward end of the machine, an amount equal to the pitch line of travel of the pinion 77 plus the movement of the shaft 72 around theV center of the spindle 24. This results in a fast movement n of the gear 78 and spindle 24.

This aforementioned movement occurs during one half of the revolution of the ,shaft R15-.the movement of thel arm 7() in the opposite direction. rlhis results in a slow movementl offthe spindle 24.

h vrlhe ratio of Vhe pinion rWto the bullgear '18 islas one isto eight, so that there willibe eight variable speed cycles of the bull gear 77 litor veach revolution thereof.

As there -are cightwork holders on the drum 30, each cycle advances the drum the distance between each workholder. 'The partsfoit the-device are so timed that during'the slow movement ofAv the vdrum ,30 the bushings 48 in the worklliolders 34 will be passing beneath the grinding wheels 18 and 19. 'Y

Any desired grinding speed canfbe obiained .for the bushings V48 vby varying Athe ythrow of the cccentric relative tothe pitch circle Iof the `pinion ZTQ this device one half vorthe operating cycle ot lthe machine is used to move the bushingsl between the grindn ing wheels ,while therest yof the cyclevis used for the actual grinding operation on the hushing. A much greater production is woby tained by the use of this structure over a machinein which .a constant velocity isgiven tothe drum r80. y

The lubrication of the device is accomplished by providing a pocket 87 in thebase plate 10' adjacent to the gear 73 which vmay be filled with oil so that when the gear 73 rotates through this pocket the gear teeth will be lubricated. A second pocket 88 is also provided in the base plate 10 adjacent to the eccentric 76 and is also filled with oil so that this eccentric may be likewise lubricated. A third pocket 89 is provided in the housing 21 adjacent to the Worm 67 and is also filled with lubricant to lubricate the worm GT and worm wlieel64. Suitable oil cups andiittings are provided for the other bearings ot the machine but are not shown in the drawings because of their conventional nature. L'

Many advantages arise through the use ot my improved grinding machine and it may he Well to point out that with this machine a fiat straight trough may be ground in a piece of Work which is attached to a rotating work holder thereby insuring .great accuracy in the ground surface. rlfhe work is not reclamped between any of the grinding operations which. adds materially to t-lie accuracy obtained. Y

Further, a novel means is provided for varying the speed of rotation of the work holders, and one which produces a .very steady acceleration and deceleration ot this work holder.

Some changes may he made in the construction, arrangement, and combination ci' the various parts of my improved device A the cam,

.without departing from the spirit of my ii1- Vvention fand l it; is my intention to cover by myclaimssuchV changes .as may reasonably 'Ibeincluded within the scopeftliereof.

il claim as. Iny invention l. In a grinding machine, a drum -loiatmachine, an aruiextendingffrom one end, of

each of said shafts' having aroller rotatably mounted thereon in position toco-act with the cam.,`. a second `arm"extending front the oppo- 'site enld `1 oteach of said .shafts in position adj acentto sai-d. grinding wheels, and a work ofthe path of the .work holders.- will; be tangent to each of saidv grinding wheels.

2. .Inagrindingxmachinehaving .a drum rotatablyr mounted, a sleeve` mounted in. said ndrum parallel to its axis, a ldriven grinding wheel, a stationary.y cam;1nember,an armextending from Voneend. oisaid sleeve; to position ad) acent to: the grinding-wheel andfhavying a work holder. formed, .on its .outer end,

a second arm extending from the opposite end of said sleeve to-a position adjacent to extend-ing to .position tocofact. with said Work holder, and a. spring secui'edto the kopposite end otsai-d shaftv` and (3o-,acting with said second mentioned arml toresilieiitly vurge the j third mentioned arm into engagementfwith sai d work holder.r

3.` vIn a grinding machine, a drumrotatably mounted, a plural-ity ,of driven Y grinding Awheels mounted laround said-drum, a plu- `formed on its outer end, .a second arm extending .trom 4the opupositeend `of. said sleeve adjacent to the cani and having a roller pivotally mounted therein, a :shaft extending through said ,n sleeve, anr arm secured to. the said. shaftand extending into the work holder and ,adapted to. clamp thework to be ground insa'id work holder, a leaf springsecured tothe. opposite end orf-said shaft, andan eccentric'bushing rotatably mounted on the said second mentioned arm in position to co-'act with saidleat spring `for varying the clamping .I pressure between the third mentioned arm and the'work holder.

`In a grinding machine, a spindlerotat` ably mounted, a v.work 'holder supported 1 by .said spindle, aigrinding wheel in -positionjso lthatiwhen said. spindleis rotatedthe `work holder will travel.adjacentftheretm an arm rotatably mounted on said spi-ndle, a shaftL al shaft extending through `said "sleeve, a third arm secured-to saidshaftand hold/cr. secured .-toithe. out-er end of ,eachl second mentioned arm,1the `partsbeing so ari-anged. that as the-drumrevolves a portion rotatably mounted in said arm parallel to said spindle, means for driving said spindle through said shaft, and means for oscillating said arm to vary the rotating speed of said 5. In a grinding machine, a spindle rotatably mounted and having a drum secured to one end thereof, a `plurality of grinding Wheels mounted on said machine, a plural- `end of said shaft and in mesh with the driven gear, an eccentric secured to said shaft, and

an eccentric arm rotatably mounted on said eccentric and pivotally mounted in said machine, the parts being so arranged that a uniform motion of said driving gear will produce a non-uniform motion of said driven gear.

6. In a grinding machine, a plurality of grinding Wheels mounted in said machine, a spindle rotatably mounted in said machine, a plurality of Work holders carried by said spindle, means for moving the Work holders tangent to said grinding wheels :over a por tion of a revolution of the spindle, and means for varying the speed of rotation of said spindle so that the said Work holders Will travel substantially slower over the tangential path than over other portions of their travel.

7. In a grinding machine, a plurality of driven grinding Wheels, a spindle rotatably v mounted in said machine and having a drum securedV thereto, a plurality of Work holders mounted on said drum and arranged for tan- 'gential movement relative to said grinding wheels, a driving gear rotatably mounted on said spindle, a driven gear secured to said spindle, an arm rotatably mounted on said spindle between said mentioned gears, a'shaft rotatably mounted in said arm, and gears on each end of said shaft in mesh with said first mentioned -gearsrespectivay, an eccentric secured to'said shaft having an eccentric arm pivotally mounted in said machine, and means for driving said driving gear.

8. In a machine ofthe character described, a frame, a tool rotatably mounted on said frame, a drum rotatably mounted on said fra-me, a Work holder pivotally mounted on a fixed aXis in said drum, means for clamping Yan article in said Work holder, the surface of said article to be machined being spaced from said aXis, and means for oscillating said work holder as the drum revolves so that a nonincase? circular path is described by the surface to bc machined.

9. In a machine ofthe character described, a frame, a tool rotatably mounted on said frame, a drum rotatably mounted on said frame, a Work holder pivotally mounted on a fixed axis in said drum, means for clamping an article in said Work holder, the surface of said article to be machined being spaced from said axis, and a stationary cam around which said Work holder revolves adapted to oscillate said Work holders so that a non-circular path is described by the surface to be machined.

10. In a machine of the character described, a frameV having Va tool rotatably mounted therein, a drum rotatably mounted in said frame, a Work holder rotatably mounted on a fixed axis in said drum and means for oscillating said Werl; holder as the drum revolves so that the resultant path of the Work holder will be tangent to the rotatingtool.

11. In a machine of the character described, a frame having a grinning Wheel rotatably mounted therein, a drum rotatably mounted in said frame, a plurality of Work holders mounted to rotate on fixed axes in said drum, and means for oscillating said Work holders as the drum revolves so that the resultant paths of the Work holders Will be rtangent to the grinding Wheel.

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