US2382311A - Apparatus for internal grinding - Google Patents

Description

1945. R. A. HEALD 2,382,311

APPARATUS FOR INTERNAL GRINDING Filed April 13, 1942 5 Sheets-Sheet 1 Q 945. R. A. HEALD APPARATUS FOR INTERNAL GRINDING Filed April 13, 1942 5 Sheets-Sheet 2 1 Richard AHealcl wmg Aug. 14, R. A. APPARATUS FOR INTERNAL GRINIQENG 5 Sheets-Sheet 3 \vE v \t 7/1 Q Aug; 5. I R. A. HEALD 2,382,311

APPARATUS FOR INTERNAL GRINDING Filed April 13,1942 5 Sheets-Sheet 4 3 Richard/ Heald w @aM Aug. 14, 1945. v HEALD 2,382,311

APPARATUS FOR INTERNAL GRINDING Filed April 15, 1942 5 Sheets-Sheet s 141 G: 138 ii 3 5 139 2 Znncntor Rica?" Heald talisman, i945] APPARATUS FOR INTERNAL GRINDING Richard AlgHeald, Worcester, Mass, assignor to The Heald Machine Company,

-Worcester,

Mass; a corporation of Massachusetts Application April 13, 1942, Serial No. 438,754

. 6 Claims.

The present invention relates to internal grinding by the centerless-or chuckless method. More particularly, the invention resides in certain novel procedures and arrangements which enable the centerless method or technique to be utilized in a highly advantageous fashion for the precision internal grinding of various types of workpieces which, because of irregularity of shape, suscepti- ;bility to distortion, unwieldiness, or any other reason, can only with considerable difficulty and much loss of time be handled in a chuck-equipped or center-type internal grinder.

An example of such work is furnished by cer..

tain relatively-large thin-walled cylindershaving a multiplicty of external heat-radiating fins, such as are used in airplane engines. In finishing the bores of such cylinders (or similar workpieces) on a center-type internal grinding machine, it has never been possible to avoid frequent and lengthy periods during which said machine must remain wholly idle and unproductive; these interruptions are imposed by the necessity, following each introduction of an unground cylinder to theworkholder of the machine, for laborious and time-consuming manipulations of said cylinder within said workholder, to make certain, before any grinding is undertaken, that the thin-walled bore runs. absolutely true, in the rotation of the work holder. 'Ihis'truing-up of the work, always a slow and painstaking task, is rendered even more so because the-operator, being obliged to stand at some distance from the workholder, is in an awkward and disadvantageous position for the performance of the many work-positioning and clamping operations that are required.

' My invention overcomes all these difiiculties and delays by an arrangement and procedure which enables each cylinders (or other work-- pieces) truing-up operation to be performed in a position convenient to the operator and to be completed during my improved machines grinding period on a preceding cylinder or other workpiece; notwithstanding this said truing-up is in every case secured with reference to the selfsame rotational axis that is effective for the workpieces rotation during the ensuing grinding operation on the workpiece bore. By this utilization ,of the grinding time on one workpiece for the truing-up of the next workpiece, my invention obtains a. materially greater rate of production than was heretofore obtainable in the internal grinding or work of this class.

or similar unwieldy pieces of work is greatly facilitated. Other and further objects and advantages of my invention will more fully appear from the following detailed description, taken in connection with the accompanying illustrative drawinss in which Fig. 1 is an isometric view showing the principal elements of an lntemal grinding machine embodying the principles of my invention.

Fig. 2 is a view showing portions of the machine at the left hand end of Fig. 1, in side ele- .vation, other parts being shown in section.

Fig. 3 is a large scale sectional view of parts shown at the right hand end of Fig. 2.

Fig. 4 is a sectional view of one of the workreceiving shuttles or thimbles, and showing a piece of work therein.

Figs. 4a and 4b are fragmentary sectional views, on lines la-la and 4b-'4b respectively of Fig. 4, showing certain details of said work-receiving shuttle.

Fig. 5. is a diagrammatic showing of certain electrical and hydraulic features and connections of said machine. I

Like reference characters refer to like parts in the different figures.

Fig. 4 shows one of the airplane engine cylinder mentioned above as typical of the kinds of workpieces which despite their difllcult or unwieldy nature, can be expeditiously handled for precision bore grinding by the apparatus of my 1 rotary chuck having radial work-gripping jaws.

Hence the previous practice in the bore grinding of such cylinders or like workpieces, has been to equip the internal grinding machine with a rotary My invention also provides novel means by which loading and handling of such cylinders pot-type chuck large enough to receive the entire cylinder; and fitted with special devices for holding the cylinder by engagement preferably with non-'distortable portions thereof, such as its an-' nular barrel flange 11 and/or any unfinned portions c' of the cylinder head.

To properly chuck such a workpiece under these conditions is always a long. and tedious pperation. With such a thin-walled cylinder (see Fig. 4) only a very limited removal of stock by bore grinding is permitted, and this stock removal in the nature of things must be distributed absolutely uniformly. Hence it is incumbent with the feeler of a suitably mounted dial indi-' cator or equivalent device, and repeated clampings and unclampings of the workpiece for the needed positional readjustments within the chuck, before the required exactly trued-up position, by such cut-and-try methods, can be achieved. During all these prolonged periods of manipulation on each workpiece, the internal grinding machine that provides this special chuck must remain idle and wholly unproductive.

These lon and frequent periods of enforced idleness for a machine used to grind a succession of such bores, are practically eliminated, according to my invention, by employing an internal grinding machine of the centerless or chuckless type having special equipment as hereinafter described which enables this truing-up of each workpiece bore in preparation for grinding to be completed during the bore-grinding period of said machine on the preceding workpiece; thus said machine is rendered almost continuously productive.

Referring first to Figs. 1 and 2, th internal grinding machine of my invention has a suitable base that comprises an elongated portion which supports the work-rotating and grinding instrumentalities, and also a shorter portion la, substantially at right angles to the portion I, for a purpose to be hereinafter described. Th base portion has the usual ways 2, 2 (Fig. 2) for the travel of a reciprocatory table 3, the latter providing transverse ways 4, 4 for the movement of a cross slide 5 which carries the wheelhead 6 of the machine. Suitably journaled in said wheelhead is the spindle of rotating grinding wheel 8, the latter as here shown being driven by a belt 9, connecting a pulley I0 on said spindle with a driving motor suitably mounted on cross slide 5. 1

The base portion I supports a transverse bridge l2 which spans the longitudinal ways 2, 2 substantially in line with the shorter base portion Ia. On thi bridge I 2 are mounted the machines centerless or chuckless work-supporting and work-rotating instrumentalities, consisting as shown of a backing or regulating roll l3, a support roll l4, and a pressure roll IS. The backing roll I3 is supported for rotation .by suitable bearings carried by bridge |2 at the opposite ends of said roll, the latter being driven in any suitable manner, as by a belt connection It, Fig, 2, to a shaft journaled at the rear of base I, said shaft in turn being driven by a belt connection l8 to a driving motor l9. The effective contact surfaces of said backing roll |3 are the spaced-apart accurately-finished cylindrical surfaces 20, 20 of limited width at the two ends of said roll, immediately adjacent the latters bearings. Between said surfaces 29, 20, said backing roll I3 is appreciably reduced in diameter, as shown at 2|, for a purpose to be later described.

For centerless reception between the. rolls l3, l4, IS, the machine's equipment includes at least two hollow work-receiving shuttles or thimbles, as indicated at 22 and 22a, Fig. 2, each shuttle presenting accurately-finished externally-cylindric surfaces having the same spacing as the backing roll surfaces 20, 20. Each shuttle, for the particular type of workpiece here selected for illustration may be substantially of the construction shown by Figs. 4, 4a and 4b. The shuttle there shown includes a shell or body 23 having at one end an inturned fiange 24, the latter presenting an external circular surface 25 to which is fitted a hardened end ring 26. At its other end the shell or body 23 has an inturned flange 21, to whose circular surface 28 is fitted a hardened end ring 29, the two rings 26 and 29 being secured to the shell 23 by any suitable means, such as the bolts 23. The outer peripheries of the two end rings 26 and 29 are accurately finished to provide the aforesaid spaced cylindricalsurfaces 30, 30 adapted to have rolling contact with said backing r011 surfaces 20, 20 and with the support and pressure rolls l4 and I5. Said end rings 26 and 29 beyond their surfaces 30, 30 have flanges 3|, 3| adapted, when the shuttle or thimble is operatively positioned in the machine, to overlap the ends of said rolls 3, l4 I5; these flanges have accurately finished peripheral surfaces 3|a, 3|a, for a purpose to be later described.

Interiorly of the shell 23 of each shuttle are Provided suitable devices which enable a cylinder or other similar workpiece to be clamped and held by endwise, rather than radial, pressure, thus avoiding any distortion. To this end as shown by Fig. 4, the flange 24 of the shuttle carries a series of equally-spaced hardened buttons 32, 32, usually three in number, against which is seated flange d of cylinder barrel b, when the latter as shown in Fig. 4 is entered in the shuttle from the latters other or left hand end. Suitable clamping members, usually three in number, adapted to bear against the opposite side of flange d are indicated at 33, 33, each of these members being tumable on a suitable post 34 extending lengthwise of the shell 23, and being accessible through a window or opening 35 of said shell, for turning out of the way of said flange, (Fig. 4a) and then for turning into clamping position, (Fig. 4) after said flange is seated against the buttons 32, 32. Preferably, each clamping member 33, is adapted to be held frictionally in any position to which it is turned by the drag imposed by a suitable coil spring 36 surrounding the post 34.

Each clamping member 33, when in operative position preferably bears at its ends only (by lugs 40, 40) against flange d and a suitable surface of the shuttle (a wall of window 35). Adequate clamping pressure, between said bearing points, is applied by the screwing down of a sleeve 31,,in threaded engagement with post 34, and having a head of hexagonal or square section, as indicated at 38, which is accessible through a Window or opening 39 of the shell 23 for the application of a wrench or other suitable tool by which to turn said sleeve for the tightening or loosening of its associated clamping member 33.

Additional devices for supporting the inserted workpiece are preferably provided at the other "end of the shuttle, these being a series of fingers 4|, 4|, usually three in number (only one appearing in Fig. 4) for peripheral engagement with the flange e. Each of said fingers projects from a bolt 42, rockably mounted in the end ring 29 and adjacent flange 21, for turning movements that permit said fingers, before insertion of the workpiece, to be swung out of the way of the barrel flange d; afterwards, said fingers 4|, 4| are turned, so as to bear against the periphery of flange e, to support and steady the workpiece at this end of the shuttle, being locked in such operative positions by means of suitable nuts 43,

43 on each of the carrying bolts 42, 42. Said nuts are accessible for the application thereto of wrenches or the like through other openings or windows 44, 44 of the shell 23'.

Such a shuttle 22 or 220. carrying a cylinder or other workpiece to be internally ground, provides the means by which said. workpiece is subiected to rotation during the grinding operation on its bore, this rotation, upon introduction of such loaded shuttle to the machines rolls |3, l4 and I5 being on an axis determined by the shuttle's pre-formed external surfaces 38, 38 that are contacted bysaid rolls. According to my invention these selfsame pro-formed surfaces 38, 38 which govern a workpieces rotation during grinding, are utilized prior to such grinding, to govern the rotation by which the truing-up of said workpieces thin-walled bore within a shuttle is secured. To this end, my machine, on its base portion la, provides means of the same character as the aforesaid center-less roll l3, l4, l5, for shuttle support and rotation by rolling contact with the shuttle surfaces 38, 30, in association with suitable truing-up devices arranged for contact with the bore of the workpiece contained in each so-rotated shuttle.

Asshown in Figs. 1 and 2, base portion Ia carries a suitably journaled roller 45, in line with and of substantially the same length as the rolls |3, I4, |5. The upper portion of this roller 45 projects appreciably above the level ofa pair of spaced guides 68, 68 hereinafter described, which are secured to the top surface of base portion la. The roller 45 is adapted to be driven in any suitable manner, as by belt connection 46 with a shaft 41 which is driven through suitable reduction gearing, not shown, by a driving motor 48, the latter being controlled for starting and stopping by a conveniently located push button switch 49, shown in Fig. 2, at the end of substantially in line with a member 53 which is.

vertically slidable in the base. At its lower end the member 53 carries a cam roller or follower 54, the latter resting upon a cam surface 55 provided by a member 56 which is secured to a rockshaft 51, suitably journaled in a projecting boss I '58 provided by the front wall of base la. To the outer end of the rockshaft 51 is secured an operating lever 59, for raising or lowering the roller 58, by rocking of its supporting yoke 5| about the pivot 52; that is, when the lever 59 is swung clockwise by the operator to carry the higher part of cam surface 55 beneath the member 53, the

roller 58 will be raised substantially to the level of the roller 45, the extent of this movement being determined by engagement of a lug 6| on yoke 5| with a stop screw 62 on the base. Rocking of lever 59 in the opposite direction carries ed to be rolled, in one direction toward the grinding station provided by the rolls I3, I4, l5 and in the other direction toward the truing-ui station provided by the rollers 45 and 58. For this purpose said guides are preferably of the angular cross-section shown at 65, Fig. 1; their spacing apart, in opposed relation, is such as to receive upon their inner fiat surfaces 66 the peripheral surfaces 3|a, 3|a of the shuttle flanges 3|, 3|, the latter being inside of and confined by the upright guide surfaces 61. A newly-loaded shuttle on said track is permitted, by depression of roller 58, to be rolled to the left, Figs. 1 and 2, into engagement ,with the roller 45; thereupon, by the clockwise rocking of lever 58 the roller 58 will be raised into operative position, with a resultant slight lift of the shuttle, to transfer its support from the flat track surfaces 66, 56 to the accurately finished peripheral surfaces 68, 68

at the ends of these two rollers, which surfaces 68 have the same spacing as the shuttle surfaces 88, 38. Thus, upon starting up of the driving motor 48 for the roller 45 the shuttle will be rotated on an axis determined by its pre-formed externally- cylindric surfaces 38, 38,

for the truing-up, by aid of associated devices now to be described, of the bore of the workpiece carried by said shuttle.

In association with the rollers 45 and 68 is provided a sensitive indicating mechanism of any type well known in the art, to aid in the truingup of the bore of a workpiece contained in a shuttle which has been moved as above described onto said rollers, for rotation thereby. Said indicating mechanism as here shown is carried by a bracket 69 secured to and extending upwardly from the base portion la, and said mechanism may consist of an arm 18 pivoted at 1| to said bracket, and carrying adjustably at its free end the lower part of cam 55 beneath member 53, to

an elongated member 12 which extends at right angles to said arm. Said elongated member 12 is thus adapted by adjustment of its position on the arm 18, to be projected to a greater or less extent into'thebore of a workpiece whose position within a shuttle on said rollers 45 and 58 is being trued-up. At itsinner end, for contact with said bore, said member 12 carries the usual delicately-mounted feeler 13, whose varying displacements resulting from such contact are communicated, by suitable movement-multiplying connections ordinarily employed in mechanisms of this character, to the pointer of a dial indicator 14 carried by the outer end of member 12.

The use of such or similar indicating devices, in. truing-up by cut-and-try methods the position of rotating workpieces to the axis of such rotation is well known in the art, and needs no entirely overcome in my machine, which per-' mits the operator to stand directly in front of the work during the trulng-up operation, and to have free and full access thereto from the back and from all sides.

in height to provide a supporting surface 15 at a";

relatively low level. On this portion of the base is mounted a turntable 16, the same consisting essentially as shown in Figs. 1 and 2 of a horizontal circular plate 11 mounted on the end of a vertical shaft, not shown, the latter being suitably journaled in bearings provided in a shell or casing 88 which is supported on and secured to the base surface 15 by a flange 8|.

Above and to the rear of turntable 18, the base portion Ia supports a rockshaft 82, the latter extendinghorizontally lengthwise of said base portion, andbeing mounted in suitable bearings not shown. Secured to said rockshaft 82 is a shuttle-elevating member 84 which provides two portions at right angles to each other, namely a ortion 85 that is adapted to be engaged by the shuttle peripherally and a portion 86 adapted to be engaged by the end of the shuttle. In the particular angular position of rockshaft 82 which is shown by Figs. 1 and 2, the portion 85 stands vertically and the portion 88 projecting laterally from the lower end of portion 85 stands horizontally; in such position, said portion 88 has its upper surface 81 substantially at or slightly below the level of turntable 16, the middle part of member 86 for this purpose being cut away at 88 to receive said turntable between the end portions 89, 89 that are adjacent to and substantially flush with the turntable surface.

In this shuttle-receiving position of member 84, a shuttle 22 or 22a resting by its end ring 28 on the turntable l6, overlaps the end parts 89, 88 of member 86, and has its flanges 3|,3l seated against two spaced track or guide members 68a, 88a corresponding in section, spacing and arrangement to the guide members 68, 68, and carried as shown in Figs. 1 and 2 by the vertical portion 85 of member 84. As shown in Figs. 1 and 2, the track surface 68 of each of these guides 88a, 88a has midway of its ends a shallow depression 98 which permits the adjacent \shuttle flange 3| in each case to roject slightly beyond or below the flat track surface 88.

A shuttle 22 or 22a thus resting, on the tumtable, is in convenient position for the lowering endwise into same of a cylinder or like workpiece, and the turntable supporting said shuttle provides a convenient means by which to swing the same into different angular positions, for access to the several clamping devices 33 and steadying fingers 4| by which is obtained preliminarily the secure attachment of the workpiece to the shuttle, so that the two parts can thereafter be handled together. In such handling of a so-loaded shuttle, the first operation involves an upward counterclockwise swinging of member 84 through approximately 90 degrees to carry its portion 85 to a horizontal position; to this end, therockshaft 82 is arranged to be rocked back and forth by power, through an angular distance of approximately 90 by any suitable means, said rockshaft for this purpose having a drive connection, through speed-reduction gearing of any suitable character, with the shaft of a reversible motor 91, also supported at the rear of base portion la; Said motor 91 is controlled by suitable pushbutton switches. 98, 98preferably mounted, as

shown in Figs. 1 and 2, arhacent the switch 49 101- the driving motor of roller 48; associated with tions through degrees, in either direction- That is, upon depressing one of the switch buttons 98, the motor 91 will obtain an upward swinging of member 84 through 98 degrees, thereby transferring the loaded shuttles support from arms 89, 89 to the track sections 88a, 88a, and at the completion of this movement the shuttle will be restrained from any accidental rolling in either direction,by the reception of its flanges'Si, 3| in the shallow depressions 98, 98. The member 84 will be stopped and heidin this upper. position by the automaticv stopping of motor '91. Afterwards, the so-raised member 84 can be used to lower a shuttle that has been rolled onto it, by depression of the other motor switch 98, for driving the motor 81 in the opposite direction, this motor actuation being stoppedafter shaft 82 has turned through 90 degrees, to dispose the member 84 in the position shown by Figs. 1 and 2, with the shuttle resting by its end ring 28 on the turntable l8 and arms 89, 89 of portion 88.

The elevation of member 84 as above described aligns the track sections 68a, 68a at one end with the two track sections 88, 68 that lead to the truing-up station, and at the other end with two similar track sections 88b, 881) which are carried by bridge l2 and which lead to the grinding station of the machine. These other track sections 68b, 68b are at the same level as sections 68, 68; this track level, as shown in Figs. land 2 is slightly above the upper surface of the support roll l4, and the track sections 88b, 88b are extended to partly overhang said roll, so that a loaded shuttle as it rolls off the ends of said track sections will deposit itself in the grinding throat which is formed by the backing roll l3 and support roll I4.

The gap is the shuttle track which is bridged by the above described track sections 88a, 88a of member 84 is also adapted at other times to be bridged by other similar track sections 880, 880, the latter being carried by a generally flat member 99, whose central portion as shown in Fig. 1 has a lateral ofiset I88 by which to obtain pivotal mounting of said member on the shaft 82. Said member 99 remains for most of the time in its vertical inoperative position shown by 'Fig. 2; at certain intervals, it is seized by the operator and swung downwardly to horizontal position, being stopped'attrack level by the abutment of its track's overhanging cleats IN, IN against the upper surfaces of track sections 68, 88.

In this horizontal position of member 99, its track sections 880, 88c align with the track sections 88, 60 and 88b, 88b, to complete the track along which a shuttle, after final positioning and clamping of its contained workpiece at the truing-up station, is rolled into grinding position, it being understood, of course, that previously the way will have been cleared for such movement by the discharge from grinding position of the other shuttle, and the lowering of said other shuttle by member 84' onto table 18 for removal of the workpiece whose bore-grinding has been completed. A prerequisite to this discharge from grinding Position of a work-containtion of the pressure roll II, which duringeach grinding operation bears downwardly on the shuttle then inthe "grinding throa and has rolling contact with the shuttle surfaces 30, 30.

According to my invention the movements of pressure roll it between operative and inoperative positions are utilized most advantageously for shuttle discharge (at completion of grinding) and shuttle deposit (at commencement of grinding), the pressure roll movements for this purpose being actuated hydraulically, preferably by the same fluid pressure medium which usually serves in grinding machines of, this and other types, to produce the table movements by, which are obtained the relative reciprocatory traverse between grinding wheel and work and the approach and separation of these parts, at the beginning and end respectively of each grinding operation. The table '3 of my machine is preferably connected to and actuated by such a system; the latter, however, forms no part of the present invention, and a description thereof is unnecessary. It is sufficient to note that in my machine a supply of fluid under pressure, whether it be from the actuating system of Table 3 or from any other source, is available for the operation of a piston and cylinder unit which, as will now be described, secures the deposit of each shuttle, without impact or shock, at the bottom of the grinding throat, and subsequently its discharge from said throat, this mechanical handling of each shuttle being accompanied by raising and lowering movements of pressure roll I5.

As shown in Fig. 3, there is carried by the bridge I2, above the bearings of backing roll I3, a suitable bracket I02, which at its opposite ends provides aligned trunnions I03, I03 for the pivotal support of a member I04, the latter being of inverted-box form, and providing near its outer end suitable bearings I05, wherein the pressure roll I5 is journaled, in position for rolling contact with shuttle surfaces 30, 30 when the member I04 is swung downwardly about its pivotal mounting I03. The swinging movements of member I04 are controlled by a hydraulically actuated piston I06, which is contained in a cylinder I0'I, secured as here shown to the back side of bracket I02. A rod I08 extending forwardly from piston I06 is suitably connected as shown in Fig. 3 with the pivoted member I04 to obtain,-by the admission of pressure fluid to the left hand end of cylinder I01, the upward swinging of said member, and by the discharge of such pressure fluid from said cylinder the downward swinging of said member. To this end, as shown in Fig. 3, member l04provides a. pivotal mounting I09 for a block III), the latter being offset from trunnion I03 so as to be in line substantially with the piston rod I08. Said rod I08 has at its free end an enlargement III wherein is formed a slot II2 which slidably receives the pivoted block IIO, this slidable and ing roll axis, and having at each end a forwardly extending lug II. The opposed inner surfaces of lugs Iii, I II are spaced apart by a distance slightly greater than the overall length of a shuttle; in other words, said inner surfaces of lugs II5 are in substantially the same vertical planes as the upright track surfaces 51, 01, so as to perform the same functions as said track surfaces in guiding a shuttle and preventing its endwise displacement in either direction. Below these movable lugs Hi, the bridge I2 supports similarly-arranged stationarylugs H6, H6; these lugs I I6, I I6 are at such a level that after a shuttle has been lowered into the grinding throat, they slightly overlap the ends of said shuttle and thus serve to prevent its endwise displacement in either direction while the grinding operation on the contained workpiece is being performed.

Upon completion of such a grinding operation the operator by depression of a conveniently-lo- -.cated switch button I I? (see Fig. 5), causes pressure fluid to be admitted to the left hand end of cylinder I01, driving piston I08 to the right, and thereby rocking member I04 upwardly, as shown by broken lines in Fig. 2; this movement elevates the pressure roll I5 into inoperative position and simultaneously subjects a shuttle then in the grinding throat to an upward and outward push by bar II4; this causes the thus-freed shuttle to be lifted as shown by broken lines in Fig. 2 over the top of support roll I4 and discharged onto the tracks 60b, 60b; during this discharge any endwise shifting of the shuttle is prevented by the inner surfaces of lugs I I5, H5. Subsequently, and while the pressure fluid admitted to cylinder I0! is still effective to hold the roll I5 and the arm H3 in the raised broken line position of Fig. 2, a

newly-loaded shuttle is rolled along tracks 60b,

elevated bar II4 whose lugs H5, II! are in position at this time to overlap theends of the shuttle and prevent its endwise displacement. There-.

pivoted connection between the piston rod I08 and the member I04 permitting the latter to respond by angular movement to the straight line movement of the former,

parts in the 'zone of their tangency; below said zone of tangency the arm II3 terminates in a bar I I4, extending substantially parallel to the backupon the operator depresses a second conveniently located switch button H0 (see Fig. 5) to initiate the discharge of pressure fluid from cylinder I01, for return of the parts to the positions shown by Fig. 3; according to my invention, a shuttle so positioned at the entrance to the grinding throat, is adapted to be lowered slowly and gradually into said throat, without shock, and without possibility of damage to the accurately finished surfaces 20, 20 and 30, 30, this being accomplished by regulating and restricting the rate at which the fluid under pressure is permitted to discharge from the cylinder I01, so as to materially slow down the return of arm H3 to the position shown in Fig. 3.

Fig. 5 illustrates schematically an arrangement of hydraulic devices for this purpose, in conjunction with the electrical circuits, containing the As shown its left hand end with two fluid pressure ports I I9 and I20, the former being nearer said end, and

both being connected to acondult In which communicates through choke coil I22 with a fluid pressure line I23 to which fluid under pressure is supplied by a suitable pump I24. The supply line I23 has a branch I25 leading to a recess I26in a valve bore I21 wherein is disposed a slidable valve 420; from a second recess I20 of said bore there leads a conduit I30 which has two branches I3I and I32 communicating with the conduit I2I. In branch I3I is a downwardly-opening check valve I33 and in branch I32 is a pressure regulating valve I34 of well-known type. A third recess I35 in valve bore I21 is connected by an exhaust conduit I38 with a tank I31 containing the fluid, usually oil, that is put under pressure by the pump I24.

The valve I28 as shown, comprises two piston portions I38 and I39, connected by a portion I40 of reduced diameter. Said valve is arranged to be operated by a pair of solenoids HI and I42, these adapted to be energized by the depression, respectively of the push button switches I I1 and II 8. To this end, said solenoids are connected as'shown by Fig. 5 in electrical circuits containing said switches I I1 and H8, in such mannerthat the depression of button II1 will complete a circuit (shown by dotted arrows) through solenoid I, to draw valve I28 to the left, where its reduced portion I40 connects the bore recesses I26 and I29, leaving the third recess I35 covered and shut off by the piston portion I39. In this left hand position of valve I28, fluid under pressure from branch I25 is admitted by the valve to conduit I30 and flows unrestrictedly through check valve I33 to the cylinder I01, where itdrives the piston I06 t the right, for the elevation of pressure roll I and the simultaneous discharge of a shuttle from the grinding throat, by action of bar'I I4 as above described.

Subsequently, after positioning of another shuttle at the entrance to the grinding throat, the push button H8 is depressed; this completes a circuit (shown by heavy line arrows) through the solenoid I42, which draws the valve I28 into its right hand position shown by Fig. 5, cutting off by piston portion I38 the supply recess I and connecting by reduced portion I40 the recesses I29 and I35. This, of course, deprives the fluid in cylinder I01 of the pump pressure, whereupon the piston I06, then at the right hand end of said cylinder, begins a movement to the left, under the influence of gravity acting upon the elevated member I04. The fluid at the left of said piston is driven out through ports I I9 and I20, this expulsion being permitted by the fact that the valve I28 in this full. line position connects the recess I29 with the recess I35, the latter exhausting to the tank I31. However, such expulsion of the fluid from cylinder I01 is not free and unrestricted, because in this direction of flow, the check valve I33 is closed, compelling the expelled fluid to pass at a reduced rate/of flow through either the pressure regulating valve I34 or the choke coil I22. This retardation of flow imposed upon the fluid discharging from the cylinder I01 results in a relatively slow' downward movement of member I04 and arm I I3, so

4 that the shuttle resting against the bar H4, in-

stead of being allowed to drop into the grinding throat, is gradually and slowly lowered into said throat, thus avoiding all impact of the shuttle surfaces 30, against the rolls I3 and I4.

Before the so-lowered shuttle comes'to rest against the roll I3, at the bottom of the grinding throat, there is effected a further slowingdown of the lowering movement, this occurring when the port I20 is covered by the leftwardlymoving piston I06, which leaves the port II9 as the only exit for the fluid from cylinder I01. For a close control of this final extremely slow shuttie-depositing movement, said port H9 is preferably provided as shown with an adjustable needle valve I43, which can be positioned to give the desired rate of flow for this final shuttle-depositing movement. The electrical circuits shown by Fig. 5 are so arranged that depression of the push buttons H1 and II8 will be ineffective to raise and lower the member'l04 unless the grinding wheel 8 on table 3 has previously been moved out of the bore of a piece of work occupying the grinding throat of the machine. To this end;

allows member I41 to rise, thus keeping said secondary circuit open, with coil I45 un-energized, so that contactor I44 remains in its full-line position, to maintain at this point the circuits containing the push buttons H1 and H8. However, with the table 3 moved to a position that carries the grinding wheel 8 into the grinding throat, the high part I49 of cam bar I48 depresses switch member I41 to close said secondary circuit, thereby energizing the coil I45 and drawing the contactor I44 into its open broken-line position; this breaks both the circuits controlled by the push buttons H1 and H8. Thus, when the grinding wheel 8 is in the grinding throat, no raising or lowering of pressure roll carrier I04 can be made to take place, by operation of push buttons H1 and H8. In this way, all chance of damage to the work or to the machine, by inadvertent actuation of the shuttle-discharging and handling devices, is eil'ectually averted.

Fig. 2 shows in full lines a shuttle 22 in the grinding throat, for the usual bore grinding operation by grinding wheel 8 on the contained workpiece. It will be understood that for each grinding operation, the approach of the grinding wheel to grinding position, its reciprocation lengthwise of the workpiece in said grinding position and its withdrawal movements, for dressing, and at the conclusion of the grinding operation, are effected in any well-known manner, preferably by hydraulic actuation of table 3 by its connection to a piston-and-cylinder unit shown in Fig. 2 at I50. The latter is controlled and operated in a manner well known in machines of this class, by reversing member I5I which is engaged by suitable table dogs I52 and I53, the control devices also including a starting lever I54 and a speed control lever I55.

In my improved machine, the workpieces derive rotation during grinding from members which have no overhang beyond their supporting bearings, in consequence of which the axis of workpiece rotation is not subject to any deflection by grinding or other pressures. Such pressures are transmitted by the spaced end surfaces 30, 30 of the shuttle, to the backing roll surfaces 20, 20, which being immediately adjacent to and between the bearings of said roll, provide the maximum resistance to deflection.

I claim:

1. In a centerless internal grinding machine to which each workpiece is presented for bore grinding while held in a hollow shuttle having a preformed external surface adapted for rolling conwhich each workpiece is presented for bore tact with the rotary elements forming the grinding throat of said machine, a track on which each such shuttle is rolledto the entrance of said throat, said trackhaving a higherv level of shuttie-support than said throat and means for retarding the gravity descent of each shuttle from said track into said throat, said means being movable against a shuttle in said throat to discharge same onto said track.

2. In a centerless internal grinding machine to which each workpiece is presented for bore grinding while held in a hollow shuttle having a pre-formed external surface adapted for rolling contact with the rotary elements forming the grinding throat of said machine, a track on which each shuttle is rolled to the entrance of said throat, said track having a higher level of shuttle-support than said throat, a member movable hydraulically to discharge a shuttle from said throat, and means for controlling the reverse movement'of said member to lower a shuttle from said track into said throat without appreciable impact of its said surface against said rotary elements.

3. In a certerless internal grinding machine to which each workpiece is presented for bore grinding while held in a hollow shuttle having a preformed external surface adapted for rolling contact with the rotary elements forming the grinding throat of said machine, a member movable in one direction to discharge a shuttle from said throat and in the other direction to lower a shuttle into said throat without appreciable'impact of its said surface against said rotary elements, actuators for said member, selectively controlled by the operator, for procuring the shuttle-discharging and shuttle-lowering movements of said member, and means for preventing operation of grinding while held-in a hollow shuttle having a pre-formed external surface adapted for rolling contact with the rotary elements forming the grinding throat of said machine, a member movable in one direction to discharge a shuttle from said throat, and in the other direction to lower either ofsaid actuators by the operator until the grinding wheel of said machine has beenwlthdrawn from said grinding throat.

4. In a centerless internal grinding machine to a shuttle into said throat, devices selectively operable to obtain the shuttle-discharging .and shuttle-lowering movements of said member, and means for rendering both of said devices inoperable by the operator when the grinding wheel of said machine is in said grinding throat.

5. In a centerless internal grinding machine, a plurality of rotary elements forming a grinding throat and with which elements the work is adapted to have rolling contact for its support and rotation during grinding, a track arranged for the rolling movement of the work to the entrance of said throat, said track having a higher level of work support than said throat, a member movable hydraulically to discharge work from said throat, and means for controlling the reverse movement of said member to lower the work from said track into said throat without appreciable impact of said work against said rotary elements.

6. In a centerless internal grinding machine, a plurality of rotary elements forming a. grinding throat and with which elements the work is adapted to have rolling contact for its support and rotation during grinding, a member movable in one direction to discharge work from said throat and in the other direction to lower the work into said throat, devices selectivelyoperable to obtain the work-discharging and worklowering movement of said member, and means for rendering both of said devices inoperable by the operator when the grinding wheel of said machine is in said grinding throat.

RICHARD A. HEALD.

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