US1965020A - Grinding machine - Google Patents

Description

My, 3, m4,.

R. w. YOUNG 1,965,020 GRINDING MACHINE v11661 Nov. l5. 1930 '7 Sheets-Sheet l @OM HMM July 3, 1934.

R'. W. YOUNG GRINDING- MACHINE Filed Nov. 15, 1930 7 Sheets-Sheet 2 R. W. YOUNG GRINDING MACHINE l Filed Nov.`15. 1930 '7 Sheets-Sheet 3 My 3 3934 R W. YQUNG 1,965,020

GRINDING MACHINE vFiled Nov. l5, 3.930 7 Sheets-Sheet 4 Juy 3, E934 R. W. YQUNG l965,020 Y GRINDING MACHINE Filed NOV. 15 1930 7 sheets-sheet 6 l Jaw/2%# @OWMUMM MQ' Judy 3 i934.

R. W. YQUNG LGSZG GRINDING MACHINE Filed Nov. l5, 1930 7 Sheets-Sheet 7 @//MJ www,

Patented July 3, 1934 UNITED STATES istanza PATEN QFFCE GRINDING MA EINE corporation cf Illinois Application November 15, 193i), Serial No. 495,825

6 Claims.

This invention relates to improvements in grinding machines and more particularly to a type of automatic multiple spindle grinder designed to meet the demand for increased production without sacrificing accuracy in the dimensions of the finished Work.

Accordingly the object of the invention is to provide a grinding machine which will operate continuously without the necessity of periodic adjustments to compensate for wear of the abrasive elements, this being accomplished by continuously feeding the grinding wheels toward the work at the rate calculated on the normal Wear on the grinding face, and simultaneously dressing the faces of the wheels so that they not only present the most efficient cutting surface to the work at all times, but are continually maintained in planes xed as the dimensional limits for the ,work passing therebetween.

A further object of the invention is to provide a grinding machine having two or more sets or pairs of grinding wheels whereby the work is advanced from one set to another, thus undergoing a succession of grinding operations, as for instance, the roughing, semi-iinishing and iinishing operations. These sets of grinding wheels are moreover independently driven and adjustable so that the amount of metal removed by each may be varied to meet different working conditions.

Before undertaking the description of the machine embodying the features hereinbefore enumerated, it may be observed as a matter of general knowledge that heretofore machines have been designed for work of this character which include a pair of spaced grinding wheels 'between which the work is advanced. Manifestly, the spacing of the Wheels determines the nal dimension of each piece, and so long as the spacing does not vary, the work will be uniform. But grinding wheels are subject to wear, and hence require periodic readjustments when the 'allowable error in dimension has been reached. Furthermore, the surface of a grinding wheel becomes dull after a period of use, due to the fact that the abrasive particles become worn to such an extent that their cutting action is impaired, from which it follows that the work offers greater resistance to the grinding wheels, thus subjecting the machine to greater strains and demanding more power to drive it. This condition also must be remedied by periodic dressing of the wheel surfaces, so that in the ordinary type of grinding machine the operation is continually being interrupted for readjustments, which not only reduces the output but the accuracy of the work, which is wholly dependent upon the care exercised by the operator in resetting the wheels. And iinally between readjustments there is a continuous change in the operating conditions as well as the character of the work being performed, G0 inasmuch as the wearing and dulling of the wheels is a gradual process.

By visualizing a pair of grinding wheels which are constantly moving bodily toward each other at a scarcely perceptable rate of speed, and each wheel provided with an accurately set diamond point dressing tool which passes across the face of the wheel, say, once in every 250 revolutions, it is possible to gain a general idea of the principle underlying the construction and operation of the improved machine.

As an example of the class of Work for which the improved machine may be used to advantage, the present disclosure shows a type designed for the grinding of valve tappets used in the manulacture of internal combustion motors, the particular operation being that of removing a given amount of metal from each end in three stages so that they are iinished to an exact length. Such a machine is illustrated in the accompanying drawings, wherein Figure 1 is a view in front elevation of the machine with parts broken away to show parts concealed within the casing.

Figure 2 is a view in end elevation of the 85 machine.

Figure 3 is a view in vertical section taken transversely through the machine on line 3-3 of Figure l.

Figure 4 is an enlarged detail View of a section 90 of the feed drum.

Figure 5 is a view in vertical section taken longitudinally through the machine on line 5-5 of Figure 2.

Figure 6 is a vertical section through one end 95 of the machine as taken on line 6-6 of Figure 5.

Figure 7 is an enlarged detail view or" the driving gear for the oscillating wheel dressing mechanism as taken on line '7-7 of Figure 5.

Figure 8 is an enlarged detail in elevation of 100 one of the diamond point setting devices.

Figure 9 is an enlarged detail View in vertical section through the driving end of the machine, as taken on line 9-9 of Figure 2 and showing the drive for advancing the grinding wheel units.

Figure 10 is an enlarged detail View of one of the release locks for the feed shaft of one of the grinder units, taken on line 10-10 of Figure 9.

Figure 11 is a sectional View of the feed drum as taken on line ll-ll of Figure 4, showing the 11,0

Loeaoeo wheel 12 and which meshes with another gear wheel 21 immediately below it. On the same shaft with the gear wheel 21 and turning with it is a worm 22 (Figure 2), which in turn meshes with two worm wheels 23 and 24, the former being mounted on a vertical counter-shaft 25 midway of its ends, and the latter mounted on one end of a horizontal counter-shaft 26 extending toward the rear of the machine housing. Now, the vertical shaft 25 is offset from the ends of the lead screws 19, 19 of the upper and lower grinding units, and the ends thereof are journalled in bearing brackets 27, 27 (Figure 9) which also serve as bearings for extremities of the lead screws exterior the end of the machine housing.

Mounted at the lower and upper ends of the counter-shaft 25 are worms 28, 29 which mesh with worm wheels 30, 31 on the lower and upper lead screws 19, 19, respectively. Similarly the horizontal shaft 26 carries at its rear end a worm 32 which meshes with a worm wheel 33 on the end of the screw shaft 19 of the rearmost or intermediate grinder unit (Figure 2).

Now, both shafts 25 and 25 are driven at the same speed from the shaft 5 of the feed drum, but a slightly variable speed is imparted to the lead screws by using worms and worm wheels of different pitch, that is, the lead screw for the roughing grinder unit is driven from the countershaft 25 with a single pitch worm and worm wheel, the semi-finishing unit with a double pitch worm and worm wheel, and the finishing unit with a triple pitch worm and wheel, so that there is a corresponding reduction in the speeds of the three lead screws.

Thus, the lead screws to the roughing grinding wheel units may turn at the rate of, say, 1 revolution in 100 minutes; the semi-finishing unit lead screws at 1 revolution in 30() minutes, and the finishing unit shafts at 1 revolution in 400 minutes. These speeds, however, are not definite but `merely indicative of the slow speed at which the screw shafts turn and the relative speeds between them. Manifestly these speeds are further reduced in the conversion of the rotative movement of the lead screws to linear motion of the grinder units through the intermediate 'threaded connection, so that the actual movenient of wheels is, say, from to 1/8 of an inch in 3 hours of continuous operation, or equal to the rate at which the wheels wear during the same period plus the amount removed by the dressing operation.

Referring further to one of the grinding units,

^ it is to be observed that when the grinding wheel has been worn to such a degree as to require renewing, or in initially setting the wheel at the commencement of a grinding operation, it is necessary to provide for the shifting of the unit by hand. Hence provision is made for disconnecting the lead screw from its driving countershaft and turning the same by a crank. Thus in Figure 10, the lead screw 19 may be one of any of the six grinding units', say, the lower unit shown in Figure 9, and is driven from the vertical counter-shaft 25 by the worm 28 and worm wheel 30. It will be noted that the end of the lead screw 19 extends beyond the wheel 30 in a square end 19a and just inwardly therefrom is a threaded portion 19h on which is a nut 34, which bears against a clutch collar 35 slidably keyed to the screw shaft and coacting with a complementary clutch member a in the form of clutch teeth formed at the end of the hub portion of the worm wheel 30, which mesh with teeth a on the adjacent face of the clutch collar 35. Between the clutch collar 35 and the worm wheel 30 is a clutch spring 36 so that by backing off the nut 34 the clutch teeth are disengaged, thus permitting the worm wheel to turn loosely on the screw shaft and permitting the latter to be turned by applying a crank 37 to the square end.

As heretofore explained, the dressing of the grinding wheels is performed by pointed diamonds which travel across the cutting face of each wheel at prescribed intervals. Each wheel has its separate dressing appliance, and the same general arrangement is used throughout.

Referring particularly to Figures 5 to 8, and to one of the dressing devices, the pointed diamond 38 is set into a metal holder 39 which in turn is mounted at the end of a rocking lever 40 carried at the end of a rock shaft il and journalled in a bearing 42 supported in one of the two vertical walls la, la which enclose the space in which the grinding wheels are located as shown in Figure 5. Manifestly there are six dressing devices, one to each wheel, and each is independent of the others, although each group of three on opposite sides of the feed drum are driven from a single source of power as will presently be described.

Now, the axis of each rock shaft is offset out- '-1 wardly beyond the periphery of its associated grinding wheel, as well as the path of the work, so that the rocker arm holding the diamond swings back and forth in a plane parallel with the face of the wheel with the diamond point projecting toward the same.

As shown in the drawings, Figure 6, the grinding Wheels are of the ring type and not solid discs so that the diamond point need only travel through a relatively small arc in order to traverse the face of the wheel.

Now, the point of the diamond, or better7 the plane transversed thereby determines the plane of the cutting surface of the wheel, and hence provision must be made for setting the diamond point. Beyond the arc of travel of each diamond pointed dressing tool, but in prolongation thereof, is a gauge plug 43 mounted in the vertical walls la of the housing on the adjacent side of the feed drum. These plugs are pins of hardened steel which are mounted in suitable bearings in said walls la, with end portions having flat faces projecting into the spaces on opposite sides of the feed drum. Each plug is adjustable endwise, have a knurled inner end portion 43a,

and a lock-nut 43h for securing the plug in position. There is a pair of gauge plugs for each pair of grinding wheels which are located exactly opposite each other so that the distance between them can be measured accurately, this 1e distance being the dimension to which the pieces are to be reduced by the particular pair of grindlng wheels with which the gauge plugs are associated. Thus if the points of the diamond dressers are set so they just touch the ends of the gauge plugs, it follows that the faces of the wheels will be dressed to coincide with the planes initially established by the setting of the gauge plugs.

The setting of the diamond points manifestly is completed before the grinding operation is commenced, and in so doing it is necessary to temporarily disconnect the rock levers holding the diamond points from the rock shaft so that they can be swung beyond their normal arc of travel, as well as to be shifted endwise in order to bring the points into contact with the ends of the plugs.

As a preferable arrangement, each rock shaft 41 is split near the bearing 42 at its forward end, and its adjacent ends inserted into a sleeve 44 (Figure 8), having a radial arm 44a. The main section of the rock shaft 4l is keyed to the sleeve as at 41a, while the other short section 41a. carrying the rock lever 40 fits loosely in the opposite endy of the sleeve, and has a collar 45 fixed thereto which is provided with a shouldered abutment face 45a normally intertting with a complementary abutment face at the end of the sleeve 44. And finally a lock ring 46 surrounds the collar 45 on the shaft and has threaded engagement with the end of the sleeve 44, so that when the lock ring is tightened the collar is drawn up against the sleeve and the sections of the shaft are united. Now, projecting from the inner end wall la of the housing is a rod 47 located below and offset to one side of the rock shaft but in line with the end of the radial arm 44a of the sleeve 44. At the end of this rod is attached a coil spring 48 which is secured to the end of the radial arm 44a and extends at right angles thereto. Thus the rocking movement of the shaft 41 and lever 4i) is resisted bythe tension of the spring, it being manifest that the sleeve 44 rocks with the shaft, since it normally joins the split ends together. However, on loosening the connections between the sections of the shaft, by backing off the lock ring 46 from the threaded end of the sleeve 44, the section 41a of the shaft 4l beyond the collar and the arm 40 holding the diamond are disconnected from the main section of the shaft 4l and are thus free to be swung through the extended arc necessary to bring the diamond point opposite the end of the gauge plug 43 for its initial setting.

Assuming then that the diamond points are set from the gauge plugs and the rocker arms 40 are lockedy to their rock shafts, the movement of the points across the face of the grinding wheels will remove a minute layer of abrasive over and above the normal wear in contact with the work. This is because the wheels are being constantly fed or advanced toward the work, and simultaneously dressed, so that their surfaces are always true, and maintained at a high degree of cutting efficiency, and of more importance their surfaces are always coincident with the xed planes established by the gauge plugs.

In addition to the disengagement of the rocker arm holding the diamond points permitting their free swinging movement to the gauge plugs 43, provision must also be made for shifting the rocker arm laterally or axially of their rock shafts in order to bring the points of the diamonds into contact with the faces of the plugs. This is accomplished by a separate adjustment between the short section of the shaft 41a and the hub-portion 40a of each diamond point holding rocker arm 40 (Fig. 8). Without going into detail as to exact arrangement, which may be varied to obtain the same results, the adjustment is in the nature of a threaded connection between the end of the short shaft section 41a and a collar 49 mounted on the inner end of the hub-portion 40a of the rocker arm 4f) and beyond the bearing 42, and having a micrometer scale 49a about its periphery with a pointer 49h mounted on the bearing 42a. Suitable looking means (not shown) are employed so that by rotating the collar 49 the rocker arm is shifted just enough in either direction to afford the necessary adjustment. The divisions on the micrometer are in thousandths of an inch and calculated to the pitch of the threads connecting the end of the shaft 41a andthe hub 40a of the rocker arm, so that by turning the adjusting collar 49 so many divisions on the scale will shift the point of the diamond a corresponding distance in an axial direction.

It is to be observed, moreover, that while the diamond points are very hard, they nevertheless undergo an appreciable wear, which must be taken into account if accuracy is to be insured. It can be pretty well established by test the rate at which a diamond point will wear down in use, and compensation duly made therefor by the same micrometer adjustment. Thus, having determined the setting of the diamond point by the pointer on the scale 49a at the beginning of the grinding operation, and knowing the rate at which the points wear down, the necessary adjustment for wear can be made by the operator from time to time without interrupting the operation of the machine or resetting the points from the gauge plugs.

Referring now to the driving mechanism for the wheel dressing devices, each of the rock shafts 4l extends lengthwise of the housing on either side of the grinding wheels and are journalled` at their outer ends in bearings provided in the outer end walls lb (Figure 5).

The mechanism for imparting a rocking motion to these rock shafts will now be described. Near the outer ends of the machine housing and supported upon the base casting 2 is an electric motor 50, it being observed that the same mechanism is duplicated at the opposite end of the machine. This motor is directly connected with a variable speed reducer 51 of a standard design. The speed reducer in turn is directly connected to a train of gearing including a miter gear 52 mounted on the driven shaft 51a of the speed reducer 51 (Figure '7) which in turn meshes with a larger miter gear 53 mounted on a shaft 54 carrying a worm 55, the latter meshing with a worm wheel 56.

The gearing just described is enclosed within a gear case 57, provided with bearings for the several elements therein. On the shaft 56a supporting the worm wheel 56 is a crank plate 58 to which is journalled a short connecting rod 59 connected with a rocker arm 60 keyed to the lowermost rock shaft 4l, and extending upwardly in a vertical direction. Also mounted on the lower rock shaft 4l is another rocker arm 60a extending approximately at right angles to the rocker arm 60 and in a rearwardly direction (Figure 6). A long link 61 connects the rocker arm 60a with a parallel rocker arm 62 on the rock shaft 4l directly above and near the top of the machine housing. Also connected with the rocker arm 60 is a shorter link 63 extending horizontally and rearwardly and is connected with a rocker arm 64 on the intermediate rock shaft 41. Thus all of the rock shafts 4l which operate the three diamond point dressers for the corresponding groups of grinding wheels are fe driven from a single power unit, there being a similar unit at the opposite end of the machine for the other group of dressers as heretofore explained. Thus during the operation of the machine these diamond point dressers are continually oscillating across the faces of the grinding wheels, say, once in every five or six revolutions of the wheels, although the speed of oscillation can be varied, depending on the class of work being performed.

lwise therein alternately pets after y 1t remains' now to discuss the work feeding device, and in this connection it may be stated that a detailed description is unnecessary inasmuch as this part of the machine is an adaptation of an already well known construction.

Thus in Figure 1 are shown two hoppers 65, 65 into which the work to be ground is piaced, which in this case are valve tappets T shown in Figures 11 and 12. These hoppers are located on 0pposite sides of the feed drum 4 and at the iront of the machine, and are kept filled by the operator. Leading from` the hoppers are guideways a, 66 (Figure 3) extending to the periphery of the feed drum. It may be explained that the tap-- pets are fed to the chute alternately from each hopper, and in so doing are presented to the feed drum with their head ends alternately reversed as shown in Figure 12.

As already explained, the feed drum 4 has the general form oi a disc and about its periphery is a ring 67 made up of segments or blocks of channel section bolted to the disc. The ring thus formed has an annular groove between radial flanges 67a, 67a extending entirely around the disc, and through the flanges are drilled sets of registering holes or bores 67h sized to receive the shank portions of the tappets T. Each block or segment oi this ring 67 is provided with two of the holes 6719 located near opposite ends, andl between the anges midway between each pair ci holes is a toggle operated work retaining device consisting of pivotaliy connected pressure fingers 68, 68 extending endwise toward the holes 67h (Figure 4), a spring pressed plunger 69 below the toggle joint, and a toggle lever 70 pivoted at a point oiset from and bearing on the pressure :lingers at the toggle joint. Each toggle lever 'l0 extends somewhat tangentially to the periphery of the disc and in a direction opposite the direction of rotation of the disc which is counterclockwise.

Thus as shown in Figure 3, the periphery of the disc carries a plurality of the toggle levers To, each operating a set of work-retaining pressure nngers ior two pieces of work T. Surrounding the periphery of the disc is an endless sprocket chain 7l which is led away from the disc adjacent the point at which the work is fed thereto, and travels about a small idler sprocket 'l2 mounted at the upper end of a vertically arranged lever 73 pivoted intermediate its ends and provided with a tension adjusting spring .'74 at its lower end for varying the tension of the sprocket chain. The chain travels in the plane oi the toggle levers 70, and as each comes into contact with the lower lead of the chain, it is pressed down, thus actuating the pressure fingers to hold the tappets T in place within their bores, said tappets having been previously inserted endfrom opposite sides of the reed drum. Mechanism is provided for feeding the tappets into the feed drum from the chute 66, and likewise for discharging the finished tapthey have been carried around almost a complete revolution on the disc and between the three sets of grinding wheels. This part of the feeding mechanism, however, has been omitted for reasons already stated, and particularly since it is somewhat complicated although typical of automatic feeding devices.

1t will suffice to say, therefore, that each tappet is fed to the feed drinn and locked in place before reaching the first set of grinding wheels 13, 13, and are released and discharged from 65d which connect with an inclined chuteA the drum after passing between the last or finishing grinders 15, 15.

As an example of the manner in which the grinding operations are performed, it may be assunied that the tappets are 2.260 inches in length in the rough, and are to be finished to 2.245 inches,

in other words, .015,inch of metal is to be removed. Now, this metal is to be removed from each endl and in three grinding operations, so that the three .Y sets of grinding wheels must be initially set to rey Thus the move their predetermined portion. gauge plugs for rough grinding wheels 13, 13

would be set 2.250 inches apart, so that .010 inch would be removed during the rst or roughing cut. Similarly the semi-finishing grinders would,

be set to 2.245 inches to remove .004 inch, and finally the finishing grinders are set at 2.245 indica-the specified length,so that they would remove only the remaining .001 inch of metal.

However, it is to be observed that the path of the work between the sets of grinding wheels is nearly diametrical, and since the grinding wheels are ring shaped, each tappet transverses two cut-..

ting surfaces, that is, as it enters the space between two wheels and as it leaves. Now, it is deemed to be productive of greater eihciency to divide the work accomplished by each set of wheels in two operations or cuts, rather than remove the entire amount in a single cut, as for example, as the tappet enters the grinding Zone. This division of the work can be readily accom-` plished by offsetting the axes of each set ofl wheels just enough so that the surfaces will be slightly nearer together at the rear or leaving side ci the grinding zone, than at the forward or entering side. This arrangement is shown greatly exaggerated in Figure 12 in which the planes of l the wheels are shown as converging slightly in the direction traversed by the work and a tappet entering and leaving the grinding zone.

Thus if these wheels are assumed to be the rough grinders and the total amount of metal to be removed is .010 inch, the axes of the wheels would be offset so that at the entering edges they are spaced apart 2.255 inches and 2.250 inches at the leaving edges. Thus .005 inch of metal or one-half the full amount would be removed during the entering cut and the remaining .005 inch would be removed on the second or leaving cut.l

'125. ed `more uniiormly and the power required to drive them can be reduced accordingly, inasmuch as no- In this way the wear on the wheels is distributone cutting surface takes the full depth of cut. Similarly the other wheels would be set to divide the work between the entering and leaving cuts. And finally the tappets are alternately reversed end to end in order to evenly distribute the wear between the grinding wheels of each pair, inasmuch as a greater amount is removed from the head end.

1t will be understood that while the machine herein disclosed is especially designed for the grinding of tappets, other shapes of work may be operated upon in the same manner, as for instance, valves or other metal parts which are to be reduced to a given length or thickness by grinding opposite end or parallel surfaces.

The advantage of such a machine for grinding operations is the greatly increased production that is obtainable and the accuracy of the work performed, due in part to the fact that the inachine can operate continuously and for long periods of time without interruptions for adjustments or dressing of the wheels, and aga-in because the grinding surfaces are always in a deiiics,

nite plane and maintained at the highest degree of cutting efliciency.

Having' set forth a preferred embodiment of my invention, I claim:

1. In a grinding machine, the combination of a rotative feed drum, in which the Work to be ground is advanced through a circular path, a pair 'of rotative grinding Wheels mounted on opposite sides of said drum and in the path of the work, a pair of adjustable gauge plugs adjacent said Wheels adapted to be set to determine the cutting planes of said wheels, a pair of rocker arms journalld adjacent said Wheels and said gauge plugs and carryirm diamond point dressers extending toward the faces of said wheels, rock shafts `connected with said rocker arms, driving means for said rock shafts including separate motor driven speed=reducing units operative to rock the same through a predetermined arc, and means for temporarily disconnecting said rocker arms from their shafts to permit the initial setting of said diamond point dressers in contact with said gauge plugs. i Y

Y2-. In a grinding machine, the combination of a rotative feed drum, in which the work to be ground is advanced through a circularpath, a pair of rotative grinding wheels mounted on opposite sides of said drum and in the path of the Work, a pair of adjustable gauge plugs adjacent said Wheels adapted to be set to determine the cutting planes of said Wheels, a pair of rocker arms journalled intermediate said Wheels and said gauge plugs and carrying diamond point dressers extending toward the face of said wheels, driving means for said rocker arms including motor driven speed-'reducing units, means for temporarily disconnecting saidgrocker arms from said driven means to permit the initial setting of said diamond point dressers in contact with said gauge plugs, and means for feeding said grinding Wheels bodily toward the planes defined by the oscillating points of said dressers.

3.` In a grinding machine, the combination of W'ork feeding means, a pair of grinding Wheels mounted on opposite 'sides of said Work feeding means, a pair of adjustable gauge members adjacent said grinding wheels, and adapted to determine the plane of grinding of each Wheel, a dressing tool mounted adjacent each of said wheels and 'adjustable for setting from said gauge members, and mechanism for operating said dressers to periodically dress the surfaces of said' wheels during the grinding operation.

4. In a grinding machine, the combination of continuous Work feeding mechanism, a pair of grinding wheels mounted on opposite sides of the path of the Work in said feeding mechanism, a gauge plug mounted adjacent each of said Wheels and adjustable endwise to determine the plane of grinding of each Wheel, a dressing tool associated with each wheel and comprising an oscillating arm, driving mechanism for said dressing tool including mechanism for imparting oscillatory movement to said arm, and means permitting the said arm to be disconnected fromA its driving mechanism for its initial setting in contact with its gauge plug.

5. In a grinding machine, the combination of continuous Work feeding mechanism, a pair of grinding Wheels mounted on opposite sides of the path of the Work in said feeding mechanism, a gauge plug mounted adjacent each of said Wheels and adjustable endvvise to determine the plane of grinding of each wheel, and a dressing tool asso ciated with each grinding Wheel comprising a rocker arm, a motor, and mechanism intermediate said motor and said rocker arm for imparting an intermittent oscillating movement to the latter.

6. In a grinding machine, the combination of a pair of opposed motor driven grinding Wheels slidably supported for axial movement, means for continuously feeding the Work to be ground between said grinding Wheels, mechanism driven from said Work-feeding means for advancing said grinding vwheels at a constant and relatively slow speed toward the work during the grinding operation, dressing tools mounted adjacent said grinding wheels and each comprising a rocker arm adapted to swing in an arc including cutting face of its respective grinding Wheel, said arms being adjustable axially of said grinding wheels, gauge plugs coacting with said rocker arms for initially setting the points of said dressing tools to a predetermined distance between the cutting faces of said Wheels, and independent driving mechanism for each of said dressing tools including a motor and speed-reducing gearing for imparting an intermittent oscillating movement to said tool-holding arms.

RALPH WALDO YOUNG.

Images