US2047055A - Grinding machine and method - Google Patents

Description

July 7i, 1936. H, BLQOD ,@47@

GRINDING MACHINE AND METHOD Filed June 1,1934 sheets-sheet 2 harold Lwmi July 7 1936 H. I .BLooD ,7,@55

l l GRINDING MACHINE AND METHOD Filed June l, 1954 4 Sheets-Sheet 3 .uly '7, 1%@ H. L. BLOOD GRINDING MACHINE AND METHOD Filed June l, 1934 4 Sheets-Sheet 4 womm,

OVEIRBIZE WORM UNDERS\ZE WORK Patented July 7, 1936 UNITED sTATEs PATENT .oFFiice The Heald Machine Company,

Worcester,

Mass., a corporation of Massachusetts Application June 1, 1934, Serial No. A228,566

32 Claims.

The present invention relates to grinding ma#I chines, and its particular utility is in connection with internal grinding machines for grinding the cylindrical or conical inner surfaces of sleeves, gears, bushings or like articles. This application is a continuation in part of applicants prior copending application for Grinding machine, Serial No. 684,970, filed August 14, 1933.

In the Einstein Patent No. 1,772,932, dated August 12, 1930, the workpiece is supported on its cylindrical outer surface by a centerless type of -work-supporting. structure which normally comprises a positively rotated wheel which engages the outer surface of the workpiece and procures a corresponding rotation thereof, a work support spaced from the wheel, and a pressure member which also engages with the outer surface of the workpiece and urges the latter against the positively rotated wheel and the work support. The copending application of Highberg, Serial No. 266,287, led March 31, 1928 now U. S.

Patent No. 2,003,713 dated June 4, 1935, and the Guild Patent No. 1,887,154, dated November 8, 1932, the latter being an improvement on the application above referred to, also show a type of centerless work-supporting structure correspondingin general to that of Einstein patent.,

In each of these constructions, the relative cross `feed betweengrinding wheel and workpiece, forthe progressive enlargement of the latters-bore, takes place in a plane substantially radial to the axis of thepositively rotated wheel.

When work-supporting structures such as above referred to are used in connection with size control mechanisms of the type disclosed in the Guild Patent No. 1,682,672, and the Taylor Patent No. 1,682,673, both dated August 28, 1928, each successive grinding operation is automatically terminated when the cutting surface of the grinding wheel reaches a predetermined vertical plane, which plane is spaced a xed distance away from the surface of the positively rotated work-supporting wheel. This machine arrangement is fairly satisfactory when the accuracy required in the ground bore is nogreater than the accuracy within which the outside diameters are formed. It is apparent, however, that variations in the outside diameters of successive workpieces ',or anl irregularity in the outer surface oi` any workpiece will result, whenvworkpieces are ground singly, in, corresponding variations in the internal diameters of the workpieces or in corresponding irregularities in the inner surface, since, by the arrangement shown, each ,workpiece is reduced to a predetermined uniform wall thickness independently of the variations in outside diameters of the several workpieces. The ground bore of each workpiece can accordingly be no more accurate than the accuracy of the outer surface. One of the objects of the pres- `entinvention lis to provide :for the grinding of successive workpieces all to substantially the same internal diameter, independently of variations in the outside diameters when the workpieces are ground in machines which incorporate a size control mechanism of the type above re ferred to.

' Variations ininternal diameters due to nonuniiorm outside diameters have been partly overcome by the mechanical arrangement disclosed in the Nenninger Patent No. 1,881,870, dated October 11, 1932, in which a gage member, actuated by the grinding wheel, is shifted relative to the work-supporting structure to compensate for the varying outside diameters of successive work- 2o pieces. Although this machine compensates for variations in outside diameter when the workpieces are ground singly, the bore of each workpiece is no more accurately cylindrical than the outer surface since each workpiece is reduced to la uniform wall thickness independently of irregularities in the outer surface. A further lobject of the invention is to avoid this objection by providing ior grinding of the inner bores of workpieces in centerless machines to produce workpieces whose inner surfaces are more accurately cylindrical than the preformed outer surfaces.

The compensatory mechanism disclosed in the Nenninger patent above cited is effective for compensating for over-size .or under-size workpieces only when the workpieces are ground singly. Where several workpieces are positioned in axialalinement in the work-supporting structure for grinding of said workpieces in multiple, the l 4 0 compensatory mechanism is effective only in' connection with the workpiece having the largest diameter and the remaining workpiecs, whose outer diameter is smaller, will not be reduced tol the proper internal diameter.

A similar objection arises in the use for multiple grinding of Athe size-controlling mechanism disclosed in the Guild and Taylor patents, above referred to. The several workpieces positioned at one time in the work-supporting structure 5o will, all be reduced to a uniform wallthickness and, accordingly, if theoutside diameters of the several workpieces vary, there will be a corresponding and equal 4variation in the internal diametenvthus preventing the grinding of the inrternal bores oi' workpieces in multiple within closer limits than the limits, of thepreviously formed outer surfaces.

In the use of plug gages oi.' the type disclosed in the Kempton and Gallimore Patent No. 1,731,719, dated October 15, 1929, for controlling the size o! workpieces in centerless work-supporting structures of the type above referred to. each ground workpiece is accurately sized only when the individual workpieces are ground separately or when all of the workpieces are precisely the same outside diameter. In the grinding of workpieces in multiple with the sizing of said workpieces by plug gages, all of the workpieces, during a single grinding operation, are reduced to the same wall thickness. Since the gage is effective only on the workpiece adjacent thereto, and since the outside diameter of the workpiece adjacent to the gage maybe oversize (but within the limits required); or may be precisely to the desired size, each successively ground group of workpieces will vary in wall thickness, depending on the outside diameter of the workpiece adjacent to the gage. Accordingly, the workpieces ground during each successive grinding operation will not have a uniform internal diameter; in fact, Ias will be apparent, the variation in the internal diameters will be twice as great as the variation in the outside diameters of the workpieces. One of the principal objects of the present invention is to provide for the grinding of workplaces in multiple to produce finished workpieces Whose internal diameters are all the same size, within predetermined limits, independently of the variations in the outside diameters of said workpieces, the invention providing for the grinding of the inner surfaces within closer limits than the outside diameter of the workpieces.

According to the present invention, the workpieces to be ground are supported'so that variations in the outside diameters of the workpieces Jivill result in an oisetting of the axes oi.' the workpieces relative to each other in a direction substantially perpendicular to the direction of movement of the grinding wheel relative to the workpiece' during the radial feeding movement of said v wheel against the workpiece, whereby to minimize the variations in internal diameters as a result of the variations in the outside diameters. Other and 'further objects and advantages of the invention will appear from theA 'following detailed description taken in connection with the accompanying drawings, in Which:-

' Fig. 1 is afragmentary front elevation of a machine embodying the invention.'

Fig. 2 is a. large scale vertical section of the workhead. 1

Fig. 3 is a. diagrammatic view of the work-supporting parts shown in Figs. 1 and 2, indicating the relative positions of two workpieces when one is the proper'outside diameter and the other is somewhat oversize, the variations in diame being greatly exaggerated;

Fig. 4 is a horizontal sectional view substantially along the line 4--4 of Fig. 3, indicating diagrammatically the grinding of workpieces in multiple under the control of gages.

Fig. 5 is a view corresponding to Fig. 4 indicating diagrammatically the sizing of workpieces by mechanism responsive to the crossfeed movement.

Fig. 6 is a diagrammatic view showing the error introduced in the grinding 'of workpieces under the control of gages when the workpieces are supported in the usual centerless workheads.

ters v Fig. 7 is a view corresponding to Fig. G with the gage entering the normal-sized workpiece.

Figs. 8 and il are diagrammatic views indicating the errors introduced in the multiple grinding oi' workpieces supported in the usual centerless workheads when the workpiece size is controlled by mechanism responsive to the crossfeed movement.

Fig. 10 is va diagrammatic view showing the location of workpieces in the usual centerless worksupporting structure.

f Fig. 11 is a greatly exaggerated diagrammatic view indicating, in connection with the present invention, the small change in internal diameter of a workpiece resulting from a relatively large change in the outside diameter.

Fig. 12 is a vertical sectional view through the workhead when the machine' is controlled by gages.

Fig. 13 is a diagrammatic View corresponding to Fig. 3, showing a workpiece having an irregular outer surface positioned in the crosshead.

Fig. 14 is a view corresponding to Fig. 13, with the workpiece in another relative position.

Like reference characters refer to like parts in the diierent gures.

Referring first to Fig. 1, the machine has a base I on which the usual reciprocatory table or car-' riage 2 is slidably mounted. In such a machine,

either the grinding wheel or the work to be ground may be carried on the table, the reciprocations of the latter being utilized in either case to produce a relative traversing movement between the grinding wheel and the workpiece. As

here shown, the table supports and carries a Workhead f 3 supporting the workpiece to be ground, and the spindle 4 for the grinding wheel 5 is journaled in a wheelhead 6 mounted on a bridge I which spans the slideways provided by the base of the machine for the movement of the table. 'I'he grinding wheel 5 is rotated at a high speed by anysuitable well-known mechanism and the workpiece is rotated at 'a slower speed by a structure which will be disclosed hereinafter. Y y

The back and forth movement of the table 2 to cause the grinding wheel to make the required traversing movement relative to the workpieces a in the workhead is imparted by any suitable structure such as that disclosed/in the Heaid and Guild Patent No. 1,582,468, issued April 27, i926. It is suiiicient to note for the purposes of the present application that iluid under pressure is alternately directed to opposite ends of a cylinder, not shown, positioned within the base of the machine to procure movement of a piston therein, the latter being suitably connected to the table. The now of fluid to the cylinder is controlled by a reversing member 8 having upwardly projecting lugs I0 and II which, during the grinding operation, when `the grinding wheel is positioned within the bore of the workpiece. are engaged by the reversing dogs I2 and I3 respectively. Engagement between the reversing dogs and the lugs on the reversing member procure shifting movement of said member and accordingly reverse the direction of owof fluid to the cylinder, thereby mountedA on the block I5 by a pin I 6 to provide 4 for elevation of said dog out of alinement with the cooperating lug I0 of the reversing member 75 eration, for purposes which-will hereinafter appear.

The grinding wheel is given a lateral or crossfeed movement on the bridge to position'and maintain the surface of said wheel in engagement with the surface of the workpiece. The crossfeed movement is procured in response to the reciprocations of the table `by a mechanism fully disclosed in the copending application of Guild, Serial No. 658,745, filed Feb. 27, 1933, now U. S. Patent No. 1,971,138 dated August 21, 1934. It is suiiicient to note for the purposes of the present application that the wheelhead ismounted on a cross-slide, not shown, and movement thereof i is obtained by rotation of a crossfeed screw I1 which engages an internally threaded portion, not shown, of the cross-slide. During the crossfeed movement, the crossfeed screw I1 is rotated in unison with a ratchet wheel I8 actuated in response to the reciprocations of the table. A compensatory mechanism, not shown, connects the ratchet wheel I6 to the crossfeed screw il so that, during the retraction of the crossfeed movement between successive grinding operations, the reduction in size of the grinding wheel will be compensated for. Thus, when the cam 26, which is rotatable with the ratchet wheel I6, strikes an adjusting screw 2l, the cutting surface of the grinding wheel will always be in a predetermined vertical plane relative to the workhead regardless of the reduction in size of said wheel.

As indicated in Fig. 1, an arm 22 is pivotally mounted on the shaft I1 and has secured in its outer end a pin 23 on which a lever 24 is mounted. One arm of said lever carries a pawl 25 engageable with the ratchet wheel Iii, and a second arm of the lever is engageable with an adjustable stop 26 positioned in the casing 21 mounted on the front of the bridge 1. An abutment, not shown, is provided on the arm 22 and engages with the second arm, above referred to, of the lever 24 to prevent counterclockwise turning movement of said lever beyond the position shown. A third arm of the lever 24 is in a position for engagement with a roller 28 on a bell crank lever 3B journaled on a pin, not shown,

in the casing 21. The other arm of the lever 36 is connected by a link 3I to one arm of a bell crank lever 32 journaled on a pin 33 in the casing 21. The opposite arm of the lever 32 carries a roller 34 which, during the grinding operation, when the grinding wheel is positioned within the bore of the workpiece, engages and Ais elevated by a cam 35 adjustably positioned on the front of the table. Each reciprocation of the table procures an elevation of the roller 34 and a corresponding elevation of the roller 28, moving the latter into engagement with the lever 24, and rocking said lever about the pin 23 until the pawl 25 engages the ratchet wheel. Thereafter, in response to further elevation of the roller 28, the lever 22 is rocked about the shaft I1, and procures a slight clockwise turning movement of the ratchet wheel.

During the grinding operation, the cam 2 0, above referred to, is advanced clockwise and engages and elvates the adjusting screw 2|, the latter being positioned as shown in Fig. 1 in an arm 36 journaled on the pin 33. Movement of the arm 36, when the screw 2| is struck by the cam 20,4 shifts a contact member 31 on said arm linto engagement with a stationary contact 38 to complete a circuit that (as illustrated by Patent No. 1,682,672) procures cessation of the grinding operation. The arm 36 is normally retained in the position shown by a spring 40 which resiliently connects an arm 4I integral with the above identified, or by mechanism disclosed in the Guild application above referred to. It is sufficient to note, for the purposes of the present application, that when the contacts 31 and 38 are brought together, an electrical circuit is es tablished for elevating the dog i3 out of alinement with` the lug II, as by raising the cam surface 42 on an arm 43 into alinement with the lower end of said dog. Elevation of the dog I3 prevents said dog from engaging the lug Il so that the reversing member is not shifted and iiuid under pressure urges the table to the left beyond its operative position into the position of Fig. l where it is brought to rest by any suitable mechanism such as that shown in the Heald and Guild Patent No. 1,582,468, above reierred to.

The above described mechanism is not, in itself,

mechanism at a relatively slow speed to procure,

by its engagement with the periphery of the workpieces,la slow rotation of said workpieces. Opposite to the bracket 3', the workhead supports a `movable bracket 46 in which is journaled a spindle 41 on which a roll 48 is mounted. The spindle 41 is preferably in horizontal alinernent with the shaft 44 and said-spindle and shaft are preferably parallel to each other. The rolls 45 and 48 are also substantially equal in diameter and as the roll 48 also engages the periphery of the workpieces a, the latter are supported above and betweenthe rolls with the axis of said workpieces in a vertical plane midway between the axes of said rolls. The bracket 46 is adjustable transversely of the machine by a screw 56 held against axial movement in a lug 5I on the table and engaging a threaded bore in the bracket 46. Turning of the screw 50 by a knurled knob 52 in the end thereof procures a transverse movement of the roll 48 toward or away fromthe roll 45, for adjusting the machine to accommodate various sizes of workpieces. In the normal operation of the machine, the roll 48 is adjusted so that the axes 'of the workpieces a coincide with the horizontal plane of movement of the grinding wheel during the crossfeed movement.

The bracket 3 supports a bracket 53 thereon and the latter has a pin 54 which provides a pivotal support for a plurality of arms 55. Said arms project forwardly from the bracket and each is downwardly to hold the rolls 56 resiliently against the workpieces. 'Ihe arms 55 project forwardly from the spindle 61 and have handles 62 on the forward ends thereof by which said arms may be manually elevated for the release oi! iinished workpieces from within the workholder and the insertion of unground workpieces therein.

The spindles 51 are preferably positioned at a slight angle to the axis ofthe spindle 41 and shaft 4,4, thereby urging the workpieces, as the latter are rotated, into ergagement with a rotary backing plate 63 corresponding in structure to the backing plate disclosed in the Guild Patent No. 1,887,154 above referred to. As shown, the rotating backing plate has a projecting stud 64 journaled in a bracket 65 extending upwardly from the table. The backingiplate supports the workpieces against axial movement in the work-supporting structure and has a recess 66. as indicated, to prevent contact between said plate and the grinding wheel while the latter is operating on vthe workpieces.

Referring now to Figs. 3 and 11, the normalsized workpiece a has its center oi.' rotation at the point b, and the grinding. wheel 5, whose center of rotation is in the same horizontal plane as said point b, engages the workpiece in said plane and is fed relative to the workpiece in said plane. The grinding operation, which is under the control of the mechanism above described, is automatically terminated when the cutting surfaceof the wheel reaches the point d in a. vertical plane e, which is in predetermined relation to a vertical plane f passing through the axis of rotation of the workpiece. When the grinding wheel is in this position, the center of rotation being then at the point c', the wheel is withdrawn from the workpiece as above pointed out. The distance b, d between the planes e and f represents the radius of the finished bore of the workpiece.

When the workpiece a', however, which is slightly oversize is positioned in the work-supporting structure, either simultaneously with the workpiece a, as indicated in Figs. 1 and 2 or subsequently thereto, the larger outer diameterof the workpiece causes a vertical displacement of the axis of rotation of said workpiece to a point b in the same vertical plane f as the axis of rotation b/ -oi the normal-sized work-piece a. This vertical4 displacement of the axis of rotation of the oversize workpiece will cause the grinding wheel 5 to engage the bore of said oversize workpiece at a point d which is in the same plane as the axis of rotation vc of the grinding wheel and the axis b' of the oversize workpiece, the grinding wheel and the inner surface of the workpiece being tangent at this point. The grinding operation is brought to a close when the grinding wheel becomes tan- -g'ent to the plane e, but, sincethe actual distance between the points b and b' is afrelatively small amount, the distance between the points d and d' is also relativelyl small and the point d on the grinding wheel is substantially in the plane Ve so that the oversize workpiece is reduced to the same diameter as the workpiece a, within very close As an example of the above, it the pressure rolls 45 Aand 4I are' each twelve inches in diameter and the workpiece a is exactly rour inches in outside diameter, the rolls 46 and 4I are preferably spaced apart such' a distance that a line connecting the center of rotation b of the workpiece vmand either ot the centers of rotation n oi' the supporting rolismakes an angle -oi' 30 with the horizontal plane passing through the centers of rotation a. It the normal-sized workpiece is to be reduced to an inside diameter of two inches, the plane e to which the wheel becomes tangent, must be spaced from the plane l a distance of, exactly one inch which corresponds to the inner radius of the work piece. When the diameter of the grinding wheel 5 is .'75 inch, the center c of the wheel 1s spaced from the center of rotation b of the workpiece exactly .25 inch.

In computing the variation in internal diameter of. the oversize workpiece a' to determine the error introduced; the following calculations are made. The distance bg which represents the radius of the normal workpiece and the radius of one of the supporting rolls is eight inches and accordingly the distance yh, since the angle bah is will be exactly 6.9 28 inches. Assuming that the outside diameter of the oversize workpiece a is 4.004 inches, this being a muchl greater variation in size than would normally occur in the grinding 'of workpieces, the 'distance lbg will be 8.002 inches. With the distance hg and the distance gb both known, the distance hb is readily determined to be 4.004. The 'distance bh being exactly four inches, it is apparent that the center of theoversize workpiece is spaced a distance above the axis of rotation of the normal-sized workpiece a distance of .004 inch, this distance also being the height ofthe center of .the oversize workpiece a above the plane bf the crossfeed movement of the grinding wheel.

In order to determine the distance bd', which will bethe radius of the inner surface of the oversize workpiece, it is necessary to determine the distance cb',which distance added to the distance cd (which is known to be .75 inch) will givethe actual radius. Since the distance bc is known to be .25 inch and the distance bb". to be .004 inch the distance bc is readily computed to be .25003 inch and the distance b'd vis accordingly 1.00003 inches. From this it will be apparent that the oversize workpiece is so nearly equal in internal diameter to the normal-sized workpiecevthat the variation in size is not measurable by any of the usual instruments. It will' be apparent that when the outside diameters of the workpieces are held within closer limits, which normally are as low as .0004 inch oversize,

- the variation in internal diameter will be .0000006 inch, much less than that computed above for a larger variation in outside diameter. Thus, the error in internal diameter is substantially one percent of the variation in size of the outside diameter.

The centerless workhead above described is applicable not only to the sizing of workpieces by the mechanism disclosed in the Guild Patent No. 1,682,672 above, but also to the sizing of workpieces by the well-known gage mechanism of the Kempton and Gallimore Patent No.' 1,731,719. Referring now to Fig. 12, the workhead corresponds in all respects to the workhand above described with reference to Fig. 2., In'

addition, che stud sa which supports the rotating backing plate has an axial bore therethrough for the reception of a gage rod 61 on the end of which are positioned one or more gages 68 corresponding in general to the gages disclosed in said 70 Kempton and Gallimore patent. l'Ihe gages operate through a control mechanism o1' the typeiully disclosed in said patent orithrough a I -control mechanism, of the type disclosed in the and Burns cope\nding application Serial Blood No. 681,334, filed July 20, 1933 now U. S. Patent No. 2,011,705 dated Aug. 20, 1935; in either mechanism, entry of one of the gages within the bore of the workpiece, which occurs when said bore is reduced to the proper internal diameter, is arranged to procure cessation of the grinding operation and runout of the table 2 to rest position.

In this workhead, the gage, as is customary, is allowed to have a slight radial movement and the vertical shifting of the axes of successive workpieces as a result of variations in the outside diameters thereof is not sufficient to prevent the gage from entering the bore thereof. When workpieces are ground singly in the above described workhead, the internal bore is ground more accurately cylindrical than the outer surface of the workpiece since, as will be apparent', variations in the external surface do not result in corresponding variations in the inner surface, and the gage sizing is thus more accurate.

The structure and operation of the gage mechanism is well known and need not be further deyso scribed. It may be noted, however, that the gage rod is connectedto and movable with a parallel rod 68', one end of which engages the bridge during the reciprocations of the table for withdrawing the gage from the workpiece to prevent contact between the grindingwheel and said gage.

Referring now to Figs. 6 and 7, which show the grinding of workpieces in multiple in the usual centerless machine in which the workpiece-size is controlled by gages, and in which the axis of the regulating wheel 69 is in the plane of the crossfeed movement, the normal sized workpiece a is positioned in substantial alinement with the oversized workpiece a with both of said workpieces being held against the regulating wheel 69' (see also Fig. 10) by a pressure roll 10, the workpieces beingV further supported by a supporting rollll. In this type of structure, the regulating wheel, which is a fixed member, has its axis in the plane of the crossfeed movement of the grinding wheel and also. substantially in the plane of the axis of rotation of the workpiece or workpieces being ground. 'lIhe regulating wheel forms a positive backing for the workpieces, so that as best indicated in Fig. 10, if one of the workpieces be oversize, the axis of this workpiece will be offset from the cutting surface of the grinding wheel and in a plane substantiallyparallel to the plane of the crossfeed movement of said grinding wheel. With the arrangement `shown in Fig. 6, the grinding 'operation is brought to a close when the oversize workpiece a' is reduced to the proper diameter as indicated by the gage member 12. ing the outside diameter of the workpiece a. to be .0004'inch oversize, the normal-sized workpiece a. will have its innersurface .0004 inch undersize, the arrangement of the machine being such that`each of the workpieces a and a is necessarily reduced to the saine wall thickness since a single grinding wheel operates on both of the workpieces simultaneously and is spaced a predetermined distance away from the regulating wheel when the grinding operationv is brought to a close. Thus in the grinding of workpieces in' multiple, there is no certainty that the inner bores of th several workpieces ground will be` the same siz In the use of a gage mechanism in connection ASSum- Referring now to Fig. '7, in which the normalsized workpiece a is located adjacent to the gages and the oversize workpiece a is spaced therefrom in precisely the opposite arrangement to that of Fig. 6, the grinding operation is brought to a close when the workpiece a, reaches the proper size as determined by the gage and the workpiece a being .0004 inch oversize will have its internal diameter oversize by the same amount since both the workpieces a and a," are reduced to the same wall thickness.

Since it is impossible to tell whether the normal-sized workpiece or the oversize workpiece is located adjacent to the gage so that the vcondition of either Fig. or Fig. '7 may prevail, the resulting errors in ,the `internal diameters will be the lsum of the errors indicated in both of these gures. In Fig. 6, the workpiece a was undersize by the amount that the oversize workpiece was oversize; in Fig. '7, the inner diameter of the oversized workpiece was oversize an 'amount corresponding to the oversize in the y will be reduced to the proper size at the end of the grinding operation. Since the workhead is arranged, however, to procurean offset of the axes of the several workpieces relative to each other in a plane perpendicular to the"plane of the crossfeed movement of the grinding wheel, the axes of the workpieces a and a will be in vertical alinement and the variation in internal diameter of the two workpieces will 'be immeasurable. The

computed error, above given for the resultant error in oversize workpieces is applicable to this figure; it will -be clear that even though the workpiece a' be oversize by as much as .004 inch, the variation in size of the workpiece a will be .00003 inch approximately. The several workpieces simultaneously ground are accordingly reduced to the same size independently of variations in the outside diameters thereof.

Referring now to Figs. 8 and 9, which show a. machine arrangement for the grinding of workpieces in multiple in the usual centerless worksupporting structures, with the size controlled by mechanism of the type shown inthe Guild Patent No. 1,682,672, the normal-sized workpiece a is reduced to a predetermined wall thickness, the thickness being determined by the spacing of the cutting surface of the grinding wheel from th'e f regulating wheel 69, at the close of the grinding operation. During each successivey grinding operation, thewall thickness remains uniform, since the wall thickness is determined by th position of the dressing tool 69'.. This dressing tool which dresses the wheel during each grinding operation, is adjusted for the proper sizing of normal-sized workpieces and produces a uniform wall thickness regardless of the variation in the outside diameter of the workpieces since the grinding wheel is operating on the several workpieces at one time in predetermined relation to the regulating wheel. In the arrangement of Fig. 8, the workpiece a which is oversizewill have an internal diameter which is oversize to the same amount as the outside diameter of said workpiece; in the arrangement of Fig. 9, in vwhich the normal-sized andy oversize workpieces are reversed, the same result obtains since each grinding operation ends when the workpieces are reduced to a predetermined wall thickness. The variations in size in the internal diameters of workpieces ground by mechanism of this type will accordingly be equal to the variations in the outside diameters of the workpieces and, accordingly. by this arrangement, the inner diameters can be no more accurate than the outer diameters.

This diiculty has been overcome by the workhead disclosed in Figs. 2, 3 and 5. Referring to Fig. 5, which shows diagrammatically the grinding of workpieces in this type of workhead, the several workpieces being simultaneously ground are all reduced to the same internal diameter regardless of the variations in outside diameter. vAlthough, in this arrangement, the axes of the normal-sized workpiece a and the oversized workpiece a' do not coincide, said axes are displaced' in a plane at right angles to the advance of the grinding wheel and the error introduced by this displacement of the axes is so small as to be negligible. As 'pointed out above, even an error as great as .004, inch will not produce a measurable variation in the inner diameter.

Where the outer surface of the workpiece is somewhat out-of-round, the workhead above described minimizes the out-of-roundness in the inside surface. Referring particularly to Figs. 13 and 14, the workpiece a" is supported by a regulating wheel 13 and a supporting wheel 1 4, the axes of both of these wheels being below the plane of the crossfeed movement of the grinding wheel 5', and the workpiece is held against the wheels 13 and 14 by a pressure roll 1i suitably mounted as disclosed in Figs. 1 and 2. The normal irregularities in the outer surface of the workpiece would be relatively small, being normally less than .0004 inch; accordingly the hump 16, diagrammatically represented in Figs. 13 and 14, is greatly exaggerated in order to show the eect of cut-ofroundness in the workhead; It will be noted that the wheels 1I and 14 are not. equal in diameter; the position of said wheels, however, provides for a shifting of the axis ofthe workpiece as a result of a variation in outside diameter, along a line making 'a relatively large angle with the plane of the crossfeed movement.

In the showing of Fig. 13. the hump 16 in the full line position of the workpiece, is in engagement with the supporting roll 1'4, and thewworkpiece is accordingly urged upwardly from its n ormal center of rotation b" to a center of rotation b'". At thistime, since the axis of rotation of the wheel I' is at the point c', the surface of said wheel engages the workpiece at a point d" in the same plane as the centers of rotation of the workpiece and the grinding wheel. 'I'he wheel at the finish of the grinding operation is tangent to the plarfe e' as above pointed out, and accordingly the grinding wheel, when the workpiece is in the full line position of this ligure, does not grind quite to the desired inner cylindrical surface of the workpiece, but rather produces a small hump 16' on the inner surface, said hump being spaced from the hump 1i on the outer surface, as indicated. This hump 16' is much smaller 'than the hump 18 on the outer surface, thus materially reducing the out-of-roundness.

When the hump 16 reaehesthe position of Fig.

14, said hump then engaging with the regulating wheel 13, the workpiece is urged upwardly until its center of rotation is iat a -point 12", this point being spaced above the normal center of rotation of the workpiece and away from the regulating wheel. The grinding wheel, however, being in the position shown, tangent to the plane e', produces a small indentation 16 in the inner surface of the work. This indentation, as-

will be apparent from either Fig. 13 or Fig. 14, is substantially in alinement with the hump 16 on the outer surface, but is materially less in be much smaller, generally so small as to be inimeasurable. Obviously, .the relative positions of the regulating wheel and\the supporting wheel control the amount' of variation in internal diameter resulting from irregularities in the outer surface. In the usual centerless machine outlined diagrammatically in Fig. 10, a hump 16 would procure a corresponding hump of equal size in the internal surface. since, when the workpiece was backed up directly by a regulating wheel in the plane of the cross-feed movement, the finished workpiece is reduced to a uniform wall thickness. The present invention minimizes the variations in the internal surface vof a workpiece resulting from variations in outer-of-roundness in the outer surface, such as chatter-marks yand the like, thus providing an inner surface as nearly truly cylindrical as possible.

From the foregoing, it will be vapparent that the present invention provides for the grinding/of workpieces in multiple in a centerless y grinding machine to produce nished workpieces At the'same time,

ing machine in the same manner to produce accurately-sized internal bores. In addition,`the present invention provides for the grinding of the internal surfaces of workpieces to a more accurately cylindrical form than. that of the outer -surfaces of the workpieces.

inside diameter are minimized, and advancing the grinding wheel in the plane of the crossfeed movement for a cutting action on th'e workpieces. f

2. In the grinding of workpieces in multiple, the method of reducing all the workpieces to substantially the same internal diameter which involves supporting the workpieces in substantiallly axial alinement on their outer surfaces in such a manner that the axes of the workpieces. as a result of variations inthe outside diameters thereof, are offset relative to each other substantially in a predetermined plane, and -advancing the grinding wheel relative to the workpieces for the crossfeed movement in aplane substantially perpendicular to said predetermined plane, whereby the resultant variations in inside diameter are minimized. y

3. In the grinding of workpieces in multiple, the' method of reducing all'the workpiecesto substantially the same internal diameter which involves supporting the workpiecesinsubstantially axial alinernent ontheirvouter surfaces on fixed supports to procure an offset of the axes of the workpieces relative to each other substantially in a predetermined plane when there is a variation in the outside diameters of the workpieces, and advancing the grinding wheel relative to the workpieces for the crossfeed movement in a plane substantially perpendicular to said predetermined plane, whereby the resultant variations in inside diameter are minimized. y

4. In a method of reducing the bores of successive cylindrical workpieces all to a predetermined size, in which the cutting surface of the grinding wheel is advanced to a predetermined point relative to the work-supporting structure for a crossfeed movement in a predetermined plane during the grinding of each workpiece, the step which comprises supporting and rotating each workpiece successively on its preformed outter surface during the cutting operation on the y bore thereof in such a manner that, as a result grinding wheel is in a predetermined relation of a variation in outside diameter of a workpiece, its axis will be oifset from the position of the axis of a normal-sized workpiece and in' a plane substantially perpendicularly to the plare of crossfeed movement of the grinding wheel.

5. In a method of reducing the bores of successive cylindrical workpieces all to a predetermined size, in winch the cutting surface of the to the work-supporting structure at the end of each grinding operation, the step which coml prises so supporting and rotating each workpiece on itsl preformed outer surface in the worksupporting structure that variations in said outter surface will result in shifting the axis ofthe workpiece substantially in a plane parallel to the normal plane of tangency of' the cutting surface of the grinding wheel and the inner surface of a workpiece whose outer surface is the proper size.

6. In the grinding of workpieces in multiple, the method of reducing all thev workpieces to sub' stantially the same internal diameter which involves supporting the workpieces in substantially axial alinement on their outer surfaces in such a manner that the Vaxes of the workpieces, as a resultl of variations in the outside diameters thereof, are offset relativeto each other subtantially in a predetermined plane, advancing the grinding Wheel relative to the workpieces for the crossfeed movement in a plane substantially perpendicular to said predetermined plane, and controlling the size of the workpieces by a gage member which Vcontacts with only one of said workpieces.

7. In a grinding machine', the combination with a grinding Wheel, means for procuring a crossfeed movement of said wheel relative to a workpiece, and means governed by the extentof the crossfeed movement for controlling the progress of the grinding operation, of a work-supporting member for supporting and rotating a workpiece on its preformed outer surface sol that 'a `variation in sizeof the outer surface will shift the axis of the workpiece substantially in a plane perpendicular to the planeof the crossfeed movement of the grindingwheel. n

8. In agrinding machine, the combination with' a grinding wheel, means for procuring a crossfeed movement ofY said wheel relative to a workpiece,

of a work-supporting member for supporting and f i feed movement of said wheel relative to a workpiece, and means governed by the extent of the crossfeed movement for controlling the progress of thergrinding operation, of a work-supporting member for supporting and rotating consecutive f workpieces successively on their preformed outer surfaces, said member having means positioned to procure anofiset of the axes of successive Workpieces from the position of the axis of a normal-sized workpiece substantially in a plane perpendicular to the plane of crossfeed movement in response to variations in outside diameter of said workpieces.

10. In a grinding machine for the reduction of the internal bores of successive workpieces all to the ysaine predetermined size,the combination with a grinding Wheel, and means for procuring a crossfeed movement relative to a workpiece, of a, worksupporting member for supporting .and rotating each workpiece successively in proper position relative to the grinding wheel, said work-supporting member comprising supporting members engageable with the periphery of the workpiece at spaced points and positioned to procure, in response to variations in the outside diameter of successive workpieces, `an offset of the 'axes of said workpieces from the position' of the axis of a normal-sized workpiece substantially in a plane perpendicular to the plane of the crossfeed movement, and a pressure member engageable resiliently with the workpiece for retaining the latter in engagement with the supporting members.

11. In a grinding machine for the reduction of the internal bores of successive workpieces all to the same predetermined size, the combination with a. grinding wheel, means -for procuring a crossfeed movement relative to a workpiece, and means governed by the extent of the crossfeed movement for controlling the progress of the grinding operation, of a work-supporting'member for supporting and rotating each workpiece successively in proper position relative to. the

grinding wheel, said Work-supporting member comprising supporting members engageable with the periphery of the workpiece at spaced points and positioned to procure, in response to variations in theoutside diameter of successive workpieces, an offset vof the axes of said workpieces from the position of the axis of a normal-sized workpiece substantially in a plane perpendicula -to the plane of the crossfeed movement. r

12. In a grinding machine, the combination with a grinding wheel, means forprocuring-fbi crossfeed movement of said wheel relativeto a workpiece, and means governed by the extent of the crossfeed movement for controlling the progress of the grinding operation, of a work-supporting member for supporting and rotating the workpiece in proper position relative to the grinding wheel, said work-supporting member comprising supporting rolls engageablewith the periphery of the workpiece and rotatable about ixed axes in a plane substantially parallel to the direction o1' the crossfeed movement, and a pressure member holding the workpiece in engagement with said rolls.- n

13. In a grinding machine, the combination with a grinding wheel, means for procuring a crossfeed movement of said wheel relative to a workpiece, and means governed by the extent of the crossfeed movement for controlling the progress of thegrindin'g operation, of a work-supporting member for supporting and rotating the workpiece in proper position relative to the grinding-wheel, vsaid work-supporting member comprising supporting members engageable with the periphery of the workpiece at spaced points in a plane substantially parallel to the direction of the crossfeed movements and a pressure member for holding the workpiece in engagement with said supporting members. Y

14. In a grinding machine, the combination with a grinding wheel, means for procuring a crossfeed movement of said wheel relative to a workpiece, and means governed by the extent of the crossfeed movement for controlling the progress of the grinding operation, of a work-supporting member for supporting and rotating thev workpiece in proper position relative to the grinding wheel, said work-supporting member compris-y ing supporting rolls engageable with the periphery of the workpiece at points in a plane substantially parallel to the direction of thelcrossfeed movement, and a pressure member for holding the workpiece in engagement with said rolls.

15. In a grinding machine, the combinationl with a. grinding wheel, means for procuring a crossfeed movement of said wheel relative to a workpiece, and means governed by the extent of the crossfeed movement for controlling the progressl of the grinding operation, of a work-supporting member for supporting and rotating the workpiece in proper position relative to the grinding wheel, said work-supporting member comprising supporting rolls egageable with the periphery of the workpiece and rotatable about iixed axes in a plane substantially parallel to the direction of the crossfeed movement, and areslientlyfsupported pressure member for holding said workpieces in engagement with said rolls.

16. A work-supporting device for grinding machines and. the like, said machine having a cutting tool movable relative to the work-supporting device for a crossfeed movement, said device comprising spaced supporting members engageable with the periphery of the workpiece at spaced points in a plane substantially parallel toy the plane of the crossfeed `movement, and a pressure member holding the workpiece in engagement with said supporting members, one of said members procuring rotation of the workpiece in the device.

17. lIn a grinding machine, the combination with a grinding wheel, of a work-supporting structure for supporting and rotating a workpiece on its preformed outer surface, said structure comprising supporti g means positioned tov procure, in response tc v iations in the outside diameter of the said workpiece, a shifting movement of the axis of the workpiece substantially in a plane parallel to the normal plane of -tangency'of the cutting surface oi the wheel to the workpiece, and a pressure member engageable resiliently with theworkpiece for retaining theA latter in engagement with 'the supporting members. 18. In a grinding machine for the reduction of internal bores of successive workpieces all to the same predetermined size, the combination with a 5 grinding wheel, and means operative when the cutting surface ot the grinding wheel reaches a predetermined position for procuring a change in y the grinding operation, of a work-supporting member for supporting and rotating each workpiece successively in proper position relative to the grinding wheel, said work-supporting member comprising supporting members engageable with the periphery oi' the workpiece at spaced points and positioned to procure, in. response to variations in the outside diameter of the workpieces, an offset of the axes of said workpieces from the position of thel axis of a normal sized workpiece substantially in a plane parallel to the normal plane of tangency of the cutting surface of the wheel to the workpiece, and a pressure member engageable resiliently with the workpeceforretaining the latter in engagementl with the supporting members.

19. In a centerless grinding machine for the reduction of alplurality of workpieces all to subment, whereby to minimize th variations in size of the internal diameters.

20. In a centerless grinding machine for the reductionof a plurality of workpieces all to sub-f stantially the same size, a work-supporting structure, a grinding wheel, means for procuring a crossfeed movement between said wheel and said structure, size controlling means, 'and means responsive to said size controlling means for terminating the grinding operation, said work-supv porting structure comprising a. plurality of ilxed supports arranged to procure an onset of the axes of the workpieces from the position of the axis of a normal-sized workpiece, as a result oi variations in outer diameters thereof, substantially inf a plane making a sufllciently large angle with the plane of the crossfeed movement so that workpieces having varying outside diameters will all be reduced to the lsame internal diameter.

21. In a centerless grinding machine for `the reduction oa plurality of workpieces all to substantially the same size, a work-supporting struc- `ture, a grinding wheel, means for procuring a crossfeed movement between said wheel and said structure, size controlling means, and means responsive to said size controlling means forv terminating the grinding operation, saldi. work-supy 2,047,055 involves supporting the workpieces in substantially axial alinement on their outer surfaces in such a manner that the offset of theaxes of the workpieces from the position oi the axis of a normal-sized workpiece, as a result of variations in the outside diameters thereof, is substantially in a predetermined plane, and advancing the grinding wheel relative-to the workpiece's for a crossfeed movement substantiallyin a plane making a sufficiently large angle with said predetermined plane so that the resulting variations in inside diameter are minimized.

23. In a method of reducing the bores of successive cylindrical workpieces all to a predeter- -mined size, in which the cutting surface of the grinding wheel is advanced to the same predetermined point relative to the work supporting structure fora crossfecd movement in a predetermined plane during the grinding of each successive workpiece, the step which comprises supporting and rotating each workpiece on its preformed outer surface during the cutting operation on the bore thereof in such a manner that a variation in its outside diameter from the diameter of a normal-sized workpiecel will result in offsetting its axis from the position of the axis of a normal-sized workpiece in a direction making a sufficiently large angle with the plane 0f the cross-feed movement to minimize the resultant variations in the internal diameters of successively ground workpieces.

24. In the grinding of workpieces in multiple, the method of reducing all the workpieces to the same internal diameter, which involves supportameters thereof, is substantially in a predetermined plane, advancing the grinding wheel relative to the workpieces fo-r a crossfeed movement in a direction making a `suiiiciently large angle with said predetermined plane so that resultant variations in internal diameters are minimized, and bringing the grinding ,operation to a close when the grinding wheel reaches a predetermined point relative .to the work supporting structure.

25. In the grinding of workpieces in multiple, the method of reducing all of the workpieces to substantially the same internal diameter, which involves supporting the workpieces in substantially axial alinement on their outer surfaces in such a manner that the offset of the axes of the workpieces from the position of the axis of a normal-sized workpiece, as a result of Variations in the outside diameters thereof, is substantially in a predetermined plane, said plane being substantially parallel to the plane of tangency of the grinding wheel and a normal-sized workpiece.

26.111 a grinding machine, the combination with a grinding wheel, means for procuring a crossfeed movement of said Wheel relative to a workpiece, and means governed by the extent or the crossfeed movement for controlling the progress of the grinding operation, of a work-supporting member for supporting and rotating a. workpiece on its preformed outer surface so that a variation in size of the outer surface will shift the axis of the workpiece substantially in a plane approximately parallel to the plane of tangency of the'grinding wheel and a normal-sized workwith a grinding wheel, means for `procuring Aa crossfeed movement of said wheel relative to a workpiece, of a work-supporting member for supporting and rotating a workpiece on its preformed outer surface, said member having means positioned to procure a shifting movement of the axis of the workpiece substantially in a plane approximately parallel to the plane of tangency of the grinding wheel and a normal-sized workpiece, in response to variations inthe outside diameter of said workpiece, and means governed by the extent of the crossfeed movement for controlling the progress of the grinding operation.

28. In a grinding machine, the combination with a grinding wheel, means for procuring a crossfeed movement of said Wheel ,relative to a workpiece, and means governed by the extent of the crossfeed movement for controlling the progress of the grinding operation of a Worksupporting member for supporting and rotating consecutive workpieces successively on their preformed outer surfaces, said member having means positioned to procure an offset of the axes of successively ground workpieces which vary slightly in outside diameter from the position of the axis of a normal-sized workpiece substantially in a plane approximately parallel to the normal plane of tangency of the grinding wheel withV a normal-sized workpiece, this offsetting of the axes of successively ground workpieces being responsive to variations in outside diameters of said workpieces.

29. In a grinding machine for the reduction of the internal bores of successive workpieces all to the -same predetermined size, the combination with a grinding wheel, and means for procuring a crossfeed movement relative to a workpiece, of a work-supporting member for supporting and rotating each workpiece successively in proper,

position relative to the grinding Wheel, said worksupporting member comprising supporting members engageable with the periphery of the workpiece at spaced points and positioned to procure, in response to variations in the outside diameter of successive workpieces, an offset of the axes of said workpieces from the position of the axis of a normal-sized workpiece substantially in a plane approximately parallel to the plane of tangency of the grinding wheel and a normal-sized workpiece.

30. In a grinding machine, the combination with a grinding wheel, of a work-supporting structure for supporting and rotating a Workpiece on its preformed outer surface, said structure comprising supporting means positioned to procure, in response to variations in the outside of the cutting surface'of the grinding wheel and the workpiece, and a pressure member engageable resiliently with the workpiece for retaining the latter in engagement with the supportin members.

3l. In a grinding machine, a grinding wheel, a work-supporting structure, and means for procuring a crossfeed movement therebetween, said work-supporting structure having a plurality of spaced xed work-supporting members engageable with the periphery of the workpiece and so positioned as to procure a relative offsetting of the axes of workpieces of slightly varying diameters, said offsetting being substantially in a plane making a suiiiciently large angle with the plane of the crossfeed movement to minimize resultant variations in the insidediameters of the workpieces.

32. In a centerless grinding machine for the reduction of a plurality of workpieces all to substantiaily the same internal diameter, a. worksupportng. structure, a grinding wheel, means for procuring a crossfeed movement between said wheel and said structure, size-controlling means 10 and means responsive to said size-controlling means for terminating the grinding operation,

said' Work-supporting structure comprising a. plurality of fixed supports, ail of which are out of the plane dened by the axis of rotation of the grinding wheel and. parallel`y to the plane of the crossfeed movement and all being on the same side of said :rst plane, whereby variations in size of the internal diameters of the workpieces are minimized.

HAROLD L. BLOOD.

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