US2375333A - Face grinding - Google Patents

Description

May 811945- H. P. TROENDLY ETAL 2,375,333

` FACE GRINDING Filed Nov. 14, 1942' 6 sheets-sheet' 5 May 8, V1945.

6 Sheets-Sheet 6 4free EK Patented May e, 194s u 2,375,333

UNITED STATES "PATENT jon-TICE y az'xzaaal t non GBINnlNG mm' r. rroenaly, chicago, m., ana/Frank'nms; Waterbury, Conn., asslgnors to The Torrington Manufacturing Co., Torrington, Conn., a corporation of Connecticut Application November 14, 1942,l Serial'No. 465,824

19 Claims. (Ci. 51-118) This invention relates to improvements in face grinding, and more particularly to improved methods of and means for grinding planar face or end portions of coil springs, bushings, rings,

va lower linear speed than abrasive portions acting on other of the elements, thus resulting in pins, short shaft elements,` and similar units. markedly dierential removal of metal from the The method and 'equipment herein described face portions under treatment. have been particularly, although not exclusively, Another of the older types of grinding equipdesigned for grinding the opposite end faces of ment employs a rotating work carrier of a relacoil compression springs, hence in the` interest tively small diameter in conjunction with a roof brevity, the description will make reference, tatable grinding disc, but with the two rotatable without limitation, to its principles and usage in elements in such relation that dierent 'units of this connection. the same batch of work pieces receive markedly The more prevalent practices prior to commer-A different abrasive treatment. It is accordingly cial usage of the present improvements in the a general object of the present invention to overgrinding of coil springs, involved the use of one come each and all 'of the diillcultles above noted, or more grinding discs or wheels operating adand to provide for a more uniform grinding efjacent to one or both of the ends of the several feet, particularly in face grinding operations, Work units. Heretofore prevalently the units in than has heretofore been provided inmaehines process were passed but once, or at most a very of the type under discussion. limited number of times through the grinding A further and very important object of the inzone, with no established uniformity of movevention is attained inv a face grinding assembly ment of the .different work units with respect to utilizing rotatable abrasive discs or wheels in abrasive material, and under conditions such that which, for reasons to be discussed, the abrasive an excessive feeding pressure was set up between discs are self dressing when used with metals of each grinding disc and the adjacent faces of the the usual ranges of hardness, .including coil units in work. This older practice presents a Springs formed of steel wire. Y number of serious and expensive disadvantages, Yet another important object of the invention among which may be noted an irregular or unis attained in an improved correlation of operateven removal of metal from the two ends and ing and control characteristics of an automatic unevenness in each face of the springs, resulting grinding assembly. The operational result of` in failure satisfactorily to approacha true planar these improvements is reflected in a more uniaspect, where desired, of the end face or faces form and more gradual feeding rate and feeding of the work piece. A further and economically pressure maintained through the greater porvery serious disadvantage of the noted older tion of the grinding period between the abrasive practice, is found in the gouging effects of the discs and the work units in process; an improved relatively sharp ends of springs or the like, parrelation of the paths of movement of the work ticularly upon their first encounter with the holding portion of a work carrier wheel andthe abrasive face of the grinding disc, thus seriously grinding discs, and an improved relation between channeling the face of the wheel, and resulting rotative speeds and hence of linear speeds of difin need for frequent dressing of the wheel, and 4o ferent portions of the Work holding element and its early replacement. the grinding discs.

y Other disadvantages of heretofore prevailing Still another object of the invention is attained face-grinding practice have been noted in the through a relatively slow yet substantially unimarkedly differential abrasive treatment, in form infeed rate and pressure. POgCther with a semi-automatic or automatic grinders, of diiier-A fairly rapid rotative speed of work holder, reent units of work of the same batch or lot. This sulting in what may be termed a light touch disadvantage has been particularly prevalent in treatment of the springs or other work units inthose types of grinding equipment wherein the traversing the grinding zone. work units are carried into and across the grind- A further object of the invention is attained ing field by a reciprocal work carrier having a in improved facilities for a substantially continrectilinear movement, and coacting with a rotatuous, yet technically intermittent operation of ing grinder wheel. It is inevitable in equipment the grinding assembly, attained through an imof this type that some of the units of work, such proved relation of a plurality of work holdingy as springs, are subjected to a longer period of Wheels operable alternately in conjunction'with abrasive action than others in the same lot, and

the grindingdiscs constituting a grinding iield alternately functioning on the work in the plurality of work holders. This enables loading or unloading a given one of a plurality of the work holders while another thereof is in operative p osition with the work units therein in the grindlng zone. 1

An additional and practically important objective of the present assembly is attained in an improved stop shifting arrangement for quickly preselecting a desired one of several fixed lengths of infeed travel. This facility, as will later be apparent, enables alternate grinding operations on work units of diifering length, without timeconsuming changeovers in machine setting.

Yet another and important object of the invention is attained in a markedly superior infeed mechanism which is of somewhat broader application than to the present field of face grinding, and which serves to eilect an extremely low rate of approaching movement, of work and a power tool,

and similarly is adapted for maintaining an exceedingly light yet uniform feeding pressure between the work piece and tool.

Numerous additional objectives of the invention, to note only a few of the more outstanding, include noveland improved facilities for effecting a slow infeed motion to bring work and grinder elements toward each other, and as desired, to

effect a quick translatory separationof the work and tool such as a grinder disc; an improved power assembly-for tilting. a rotatable work holder feeding elements all as viewed along line l-l of Fig. l;

Fig. 5 is a side elevation of one of the Ferris wheel assemblies. this view showing some of the Ferris4 wheel structure as same would appear when viewed from line 5-5 of Fig. 1;

Fig. 6 is a sectional elevation showing certain elements of the Ferris wheel-drive and tilting mechanism, as same would appear when viewed from line 6-8 of Fig. 1

Fig. 'l is a diagrammatic, single-line showing, illustrating the relation of paths of movement of the work carrying band of the Ferris wheel, and I one of the grinding wheels or discs, and

Fig. 8 is a schematic hydraulic diagram embodying an outline of the various hydraulic units between a loading and unloading position and a y position for advance of the work holders into the processing zone; improved means for effecting a translatory movement of a work holder such as rotatable work carrier or Ferris wheel, in which the work units are iloatingly retained, each in an individual compartment or pocket, and in which the compartment is so proportioned to the Work unit that the latter is free to be shifted endwise orto rotate in either direction when in the grinding zone.

The foregoing and numerous additional objects will become more'fully apparent when considered `in connection with the accompanying description taken in conjunction with the drawings illustrating a single preferred embodiment of the `invention, and in which:

Fig. 1 is a top or plan view of a grinder assembly including a pair of normally spaced, mutually opposed grinding discs. and a pair of rotatable Ferris wheels constituting carriers for the units of work in process;

Fig. 2 is a .side elevation partly in section of the assembly shown by Fig. l, but illustrating one of the Ferris wheels in operative position to subject the springs or work units therein, to abrasive action in the grinding zone, and showing an opposite Ferris wheel in a position for loading or unloading of its work units; Y

Fig. 3 is a vertical sectionall elevation in a plane indicated by line 3-3 of Fig. l, and particularly illustrating the more important elements of thel of the assembly, the preferred circuit, and locations therein of the several hydraulic controls.

vReferring now by characters of reference to the drawing; for deilniteness of alignment, as well as certainty of leveling and sufilciency of support, the assembly is preferably mounted in part on a base structure conveniently formed of structural steel shapes, and indicated generally at 20. The longitudinal elements shown are cross-tied at substantial intervals as by spacer or distance elements 2l. Although the sill elements may be continuous from end to end, the structure may in fact consist, as shown, of similar base units on opposite sides or ends of the grinder assembly proper, and the latter supported on a separate intermediate base 23 as will appear.

' The upper portions of elements 20, indicated at 24, may be utilized as spaced, paired track elements; on the track portions 24 are a plurality of the work holder or Ferris wheel assemblies, each comprising drive mechanism, and tilting mechanism, for the related wheel, the whole of which is mounted on a deck generally indicated at 25. As will appear from a comparison of the two Ferris wheel assemblies shown by Figs. l and 2, each of the decks 25 together with the elements thereon, is adapted for a translatory movement, by means hereinafter described, to enable shifting of the Ferris wheel assembly, or each thereof into and out of the grinding zone. Details of structure of each of the Ferris wheel assemblies will be hereinafter more fully described.

In thevembodiment selected for present disclosure, the grinding assembly consists of a pair of axially displaceable grinding head assemblies, generally designated at 26 in Fig. l, the two heads being mounted in relatively opposed relation as will appear from Figs. l and 3. Since the two assemblies 26 are or may be identical in structure, it is sufficient to note that each is comprised of major elements including a grinder wheel 3|), drive motor 3|and suitable power transmission means generally indicated at 32, for driving the grinder wheel shaft 33 from the motor 3l. The rotatable elements of the grinder head are supported by and form parts of an upper base structure 34, which is movable for alignment purposes upon an intermediate slide base or carriage generally indicated at 35 the latter in turn being slidably-supported on a main slide base structure or carriage 36. A suitable infeed mechanism later to be described in detail, serves to advance both of the grinding heads generally indicated at 26, in an axial direction, toward or away from each other whereby to establish the infeeding motion and pressure set up for grinding purposes between the abrasive discs 30 and the work units in the grinding zone or eld indicated at 39.

It will now have appeared by way of general plurality of Ferris wheels will now have become obvious in that one of the wheels' may be brought to a substantially horizontal position as appears at the left hand side of Fig. 2, in which position the wheel is best adapted to be loaded with or Y relieved of the work units in process.

be done obviously while the Ferris wheel at the right hand side (Fig. 2) of the grinder assembly` is being rotated to bring the work units carried thereby in successively traversing relation to the grinding zone, wherein the units are acted upon by the opposed spaced abrasive wheels or discs 36. In this manner the grinder heads may be kept substantially continuously in operation, although it will be noted that the abrasive discs thus operate on successive batches of the units in work alternately presented by the opposite Ferris wheels.

It is perhaps in order iirst to describe the details of structure of the grinding heads and infeeding mechanism. For conformance with machines now in production usage. reference will. be made to an assembly. employing the described pair of opposed grinder heads. although it will be understood that, provided only a suitable abutment is afforded for one end of the springs or like units in process, a single grinder head and appurtenances may of itself embody the princi-` ples of the present invention. Similarly. instead of employing a. pair or more of the' Ferris wheel assemblies such as supported by decks 25, only a single such rotatable work holder may be utilized in full practice of the more essential steps of the method and features of structure.

Grinding assembly and infeed mechanism The grinding assembly proper includes as a primary supporting structure. the hollow base 23. heretofore generally mentioned. This may consist of a heavy walled structure of a generally rectangular shaping in plan, and suitably reinforced by internally projecting, integral ribs o1' the like 31. The upper longitudinal margins of base 23 are machined to provide smooth track elements which serve slidably to receive similarly machined surfaces on the lower margins of each This mayA of the pair of hollow, generally rectangularly shaped, main slide bases or carriages 36. Supported on and slidably movable relative to each of the main slide bases 36, is an intermediate slide base or carriage 35, heretofore noted. the structures 35 and 36 meeting along horizontal planar surfaces 4|, those on base 36 constituting trackage for the companion surfaces on the slide base 35. From this it will now appear that the structures 35 and 36 may be and normally are movable together as a unit axially of the grinder and of the fixed base 23. However for purposes of certain adjustments, and sometimes for quick translatory movements at the end of the grinding period, and for occasional access to the grinder discs 3l, the intermediate slide bases 35 may each Y be moved along and upon the associated bases 36.

Rotation of each of the grinder discs 30 is effected through a. driving motor 3|, provided with a multiple V-belt drive pulley 42 and a multiple groove, variable speed driven pulley 43. pulleys 42 and 43 being connected by any desirable plurality of V-belts 44. Obviously, any suitable methoh eter of the wheel.

form of power transmission may be employed between the motor 3| or other suitable prime mover, and shaft 33 for the grinding disc 30. The abrai sive discs 30 each consists ,of a hollow center, or

5 annular type abrasive wheel, the center opening of each of which is normally closed as by a circular closure plate, (shown diagrammatically in Fig. '7), and for which a suitable adjustment (not shown) may be provided for retraction of the l0\closure plate to keep it in or slightly to the rear f the plane of the grinding face of the wheel. Many expedients for this purpose are well known in t e art, and need not'here be detailed. It is a distinct preference in connection with the present of grinding that the center portion of the wheel 30 be entirely devoid of any abrasive action on the springs or other units of work in process, and that this hollow center area and its closure, be a substantial portion of a total diam- For example, in an abrasive disc of 48" diameter, a relieved or hollow central area, and hence therclosure therefor, should be at least of the order of 16 diameter.

With further reference to the abrasive. disc assembly it is preferred, for obvious reasons, laterally and peripherally to enclose the abrasive discs 3|), as by partly cylindrical, side open shielding elements 45, each of which may be connected to an exhaust duct system to assure removal of flying particles of abrasive material Afrom the wheels and fine particles resulting from grinding the work in process. For purposes of augmenting circulation in and beyond the enclosures 45, and with some incidental cooling effect, the wheel plate 46, constituting the backing element of the a). grinding head assemblies, there may be provided `between the slide bases 35 and 36, separate ad# justable track elements 50 and 5|, best appearing in Fig. 4, and provided with takeup provisions to compensate for occasional wear, as indicated by studs or screws 52 and 53. It is a preference in providing for the slidable association of main slide base 36 on base 23, to include trackage elements 55 on base 23 and a coacting and slidably engaging element 56, making contact with the undercut face portion of each of elements 55. Take-upfor wear is conveniently provided for by set screws `5`| and 58 (Fig. 4).

A further advantageous feature of the grinderv assembly is found in the provision for effecting, when desired, a relatively quick axial shifting movement of the intermediate slide base. This is desirable as will appear, when changing certain of the variable length of work stops, and possibly at other times for affording quick access to the grinding wheels 3|). of a pair of hydraulic cylinders on each side of the slide base assembly, and indicated generally at 60. These are supplied with fluid, preferably oil, kept under pressure as through feed and return pipes 6|62 constituting part of a hydraulic system hereinafter described. When it is desired to effect a quick translatory movement of the intermediate carriage, a control valve is actuated causing relative displacement of the cylinder and piston, (outlined in the .diagram of Fig. 8), lWithin each of the cylinders 60. The cylinders of these assemblies may be connected to wing brackets 63 (Fig. 4) the latter being xedly carried by the base 23, whereby a relative longitudi- "15 nal movement of the intermediate slide base is This arrangementA consists effected as desired and for the purposes'noted, by

admitting oil under pressure to corresponding ends of the cylinders, and proportionately re; lieving the opposite ends of the several cylinders.

Proceeding now to a description of the infeeding mechanism, the immediate source of infeed motion comprises an elongate hydraulic cylinder 84 preferably several feet in length, the disclosed example illustrating a cylinder containing a piston (outlinedin Fig. 8), adapted for a. 48" stroke. 'I'he cylinder 64 is supplied from the hydraulic system through a special feed valve hereinafter referred to in connection with the hydraulic supply system. The cylinder 64 is further of a nature to be supplied from either of its ends, and with an outlet; at the other end, so that the two ports 55 and 66 may each alternately serve as an inlet and as a discharge port, as will hereinafter better appear in later reference to the hydraulic system. The piston in the cylinder 64 is of so-called double-faceltype and is direct-connected to a piston rod 10, extending through a suitable stuiling box or gland. The rod 10 is secured as by a threaded end and double nut arrangement 1|-12 to an apertured upstanding arm 13 on an elongate cam bar generally indicated at 14. This camming element is carefully machined to provide a gradually sloping wedge profile, resulting in a camming surface 15, and the cam bar is guidedly constrained to a rectilinear path of movement through provision of guiding or track elements 18.

sists of a double-arm link 69 between the spaced arms of which is pivotally carried a follower roller 80, the follower assembly including link 89, being constrained to follow a` vertical path of v movement, (normally downwardly for infeeding motion of the grinder heads) as by spaced, opposed guide members 8| serving as a type of crosshead. The follower structure is provided at the end opposite roller- 80, with a pivot pin 82. As thus far described, the elements of the infeeding mechanism are or may be common to the opposed, oppositely movable, grinder heads for infeeding thereof. It will be significantly noted that the follower structure 69 and pivot; 82 operate in a plane produced downwardly of that which extends medially of the grinding field 39.

It will also have appeared that as the piston rod 10 is actuated say to -the right (Fig. 3) the effect of the gradually sloping camming face'15, operating on roller 80, hence on the linkA 69, will be to move the latter downwardly very slowly and in va vertical plane. This motion is carried on to the grinder heads in the example shown through the provision of a pair of bellcrank levers. Since each of these levers is individual to one of the grinder heads, it is regarded as sufficient to describe only one thereof. The noted bellcrank lever for the left hand assembly' (Fig. 3) consists of a long arm 83 provided with a` shear pin or bolt 19, and arranged for normal pivotal movement about a short shaft 84, the latter being iixedly supported in suitable bearing arms (not shown) in base 23. The shorter arm of the bellcrank lever is indicated at 85 and there are, by preference, a pair of these spaced apart in parallel relation, the companion short lever arms engaging laterally extending trunnionsA 86 carried by a two-part, substantial collar structure 90. The latter is axially fixed in `position `between a pair of projections on a sleeve structure 9i from which it will appear that incident to normal infeeding motion derived from piston rod 10, the

, slow, yet highly uniform infeeding movement, I

arm elements 85 and both of the carriage or slide` base structures 35 and 36 will have an extremely such as slowly and regularly-to advance the grinding head at the left of the assemblyV (Fig. 3) toward and into the grinding zone 33. To complete -the connection between lever arms 85 and A follower coacting with the attenuated,y gradually sloping surface 15 of ycam bar 14, conthe slide base structures, it will be noted that main slide base 38 is provided with a depending projection 92 horizontally apertured at 93 for the reception of an operating bar. 94. The latter is llxedly held against axial movement and in its horizontal position by a pair of lock nuts 95 and 96, the latter serving as a stop element to determine the infeed movement, as will later appear. The operating bar 94 is provided at its outer end with a head element 91 and is provided 'with a bushing |00'within the sleeve 9|, this sleeve and the bar 94 being normally kept in operative assembly through a feed-disengaging nut I 0| which is internally threaded to engage external threads on the outer margin of sleeve 3|. It now becomes apparent that by removing -the feed disengaging nut |0|, the carriage or slide base 38 may be operatively disengaged from the operating bar and hence from the infeeding mechanism associated with the bellcrank lever structure 83-85. 'Ihis is desirable at times, for example, in backing away the slide bases and grinder thereon for the purpose of renewing worn grinding wheels or for other service attention. It is preferred that the bushing |00 be of bronze or the like, to avoid any tendency for the adjacent steel elements 3| and 84 to seize, and resist their operative disengagement.

'I'he function of the shear bolt 13, above referred to, will now be obvious from its location and the earlier reference thereto. In the event of abnormal resistance to infeeding movement of 40 the grinder assembly and slide base, occurring from any cause, this element serves to prevent breakage by yielding or shearing, thus permitting continued downward movement of arm 83 about a separate pivot |02, thus obviating any continuing movement, perhaps disastrously, `of

Athe short arm 85 of the bellcrank lever, and hence of the slide base assembly and grinding elements.r

For limiting the infeeding movement of each slide base 3B and parts thereon, there isprovided a hollow operating 4bar 94, through which extends the rotatable shaft |03, common to both grinder heads where more 'than one is employed.

' At each outer end of shaft |03 is a hand wheel |04, and disposed approximately below Athe respective wheels 30 is an assembly including a pair of headed stop elements |05 and |08. One or more stationary brackets |01 conveniently being extended portions of base 23, serve to receive a sleeve element |08, mounted therein for a limited longitudinal sldable movement, and being slidably keyed to the bracket |01. In each end of the sleeve |08 is a tapped bore portion, one such portion being provided with right hand threads and the other with left hand threads, respectively engaged byexternal threads on the stop elements |05 and |06. It will be noted that the latter are bored and key slotted so as slidably to receive the direction of threading is reversed on either with respect to the other,- because of which the end faces or heads of stop elements |05 and |06 may -be adj-usted to any Ipredetermined distance apart in which adjustment they willremain until subsequent rotation of adjusting shaft |03.

As heretofore mentioned, during the grinding operation with infeeding movement, the stop elements 96 heretofore mentioned move toward the heads of elements 05 and |06, and when abutting contact is made, the movement rof each element 96 ceases and hence the heads or face portions thereof, of elements |05 and |06 are always at a predetermined spacing, and the amount of infeed movement of stops 96 and hence the grinding heads, is assured to be uniform for each grinding operation. Thus, neglecting abrasive wear for which separate adjustment is made, successive batches of units in work will, when desired, be finished to exactly the same length.

It should be noted as a preference that sleeve |08 is made slidable to compensate for usual tolerances in manufacture of elements 69, 83, 85, etc., and for the purpose of attaining a positive clamping of both grinding heads at the end oi their infeed movement. For example, it is sometimes ypossible, because of tolerance differences in the parts of the two infeeding assemblies of the respective grinding heads, that, but for the floating stop assembly, infeed movement of one head might be determined by abutment of associated parts 96 and |05, slightly before determination of infeed by corresponding parts of the opposite assembly. Such a result would cause uneven strains in the levers and other infeed elements of the respective grinding head and carriage assemblies, and furthermore, might at times leave the paired grinding assemblies without assurance that they would stop infeeding in the same place in succeeding grinding operations.

The difficulty stated is overcome by making the sleeve |08 slidable, within moderate limits, in the bracket |01. In this manner whichever pair of coacting abutments are rst engaged, such initial .engagement is enabled to'cause a slight axial movement of the entire stop assembly 05, |08 and |06, toward the other movable stop 96. It will now be apparent that both grinding heads will have their infeeding movement determined at the same time, and that in succeeding operacuracy in finished length of the ground units in work, all slack, play or looseness is desirably removed from the infeeding mechanism at the end of infeed movement of the heads and slide bases. The stops |05 and |06 are so adjusted that at the time their abutment faces are contacted by the elements 96, the cam 14 is still permitted to move an inch or so to the right (Fig. 3). This slight period of end movement serves to relieve the infeed mechanism of all play, and effectively clamps the grinding heads in their now fixed inner positions, through the stop mechanism described. 'I'his result is possible largely because of the floating characteristic of the sleeve |08, because of which the floating stop assembly (hereinafter referred to by reference to floating stops |05 and |06), is enabled to serve as a distance piece tightly bridging and spacing the two heads a fixed axial distance apart.

One of the advantages afforded by the present assembly is that of facilitating alternate grinding operations on batches of work pieces of differing lengths. In order to enable a quick changeover from work pieces of a given length in one of the Ferris wheels, to those of a greater or lesser length in the other Ferris wheel, means are provided for quickly changing the length-of-work stops incident to the requirement for different initial axial placements of the grinder wheels due to longer or shorter work pieces. To this end the main slide base 36 is provided in its outer wall portion with a large rotatable nut H0. The element I l is carried by and rotatable (but not axially movable) in a hand wheel screw III. The nut IID acts essentially as a turret member, and serves threadedly to receive a pair or more of adjustable stop screws shown at |I2 and |I3. It will be noted that each of these stop elements is individually adjustable endwise, upon predetermined rotation, in the element IIO, the latter being in non-threaded but rotatable relation to the hand wheel screw I I while the latter is externally threaded and engages internal threads in a bore II4 in the end wall of, or a fitting in, main slide base 36. The intermediate slide base 35 is provided with a depending abutment or projection I I5 of such length that it can be engaged by only one at a time, of the stop screws |I2-|| 3. A suitable handled element (not shown) is provided for effecting a quick rotary shift of the turret nut IIO for changing from one of the stops to the other, according to the length of work to be initiallydisposed in the grinding zone 39. Locking means (not shown) are provided for fixing the adjusted position of nut I|0, and locking provisions are also preferably employed (but omitted for clarity of illustration), to prevent casual or unintended displacement of member III.

For the purpose of enabling freedom of movement of the nut IIIJ between different stop positions, it is desirable, during such adjustment, to shift the slide base 35 axially out of a. position of abutment by either of the stop screws last noted. This is accomplished through the agency of the paired, hydraulic cylinders 60 heretofore referred to. In order to assure that the translatory movement of slide base 35 is never such as to bring the grinding wheels into mutual engagement, there is provided an upstanding internal projection I6 on the base 36, this projection serving to receive a safety stop screw which is initially adjusted to such position that it is engaged by projection I I5 of base 35 at one extreme of movement of the base relative to base 36, thus preventing any possibility of impact of the two wheels or of impact of either wheel with the work carrier in case the latter happens to be in place in the grinding zone.

It is thought that, following the description of the various stop provisions made both for purposes of determining the range of infeed movement and providing facilities for shifting between work units of different lengths, the purposes of the cylinders will have become apparent. Each of these assemblies 60 is of double end type, and each is provided with the described pair of fluid connections to its opposite ends, such as 6| and 62. The pistons (shown in outline in Fig. 8) in the assemblies 60, are of double face type and may be directly connected to piston rods |22 and |323 (Fig, 1) these latter are or may be rigidly connected each to a somewhat L-shaped bracket |24 or |25, these brackets being directly connected to the intermediate slide base or carriage of the associated grinder head assembly. It may be noted that the hydraulic cylinder assemblies 60,

l connected into the hydraulic system as suggested by Fig.- 8, serve a number of purposes. Among these they act under certain conditions to return l or back feed the grinder heads after or as the l infeed operating cylinder assembly 64 has moved the cam follower assembly 8069 to a relatively retracted or initial position as shown, for exam-l serve also the function of cushioning the infeed movement, and of providing a relatively elastic infeed drive for the grinder, the hydraulic sys-- tem and particularly the control valve (hereinple,y by Fig. 3. The paired cylinder assemblies lill` after described)l for the cylinders 60, being such l as tol permit a very slight piston displacement in each cylinder 60 to attain this result. As heretofore implied, the cylinders 60, when energized to cilitating initial adjustment as well as service Vmove their pistons in one direction, serve to move 1 the slide base away from the length-of-work Several minor refinements may be noted as faattention to the assembly. Among these may be i mentioned the provision of avertical centering dowel |30, the lower end of which is centrally or medially socketed in slide base or carriage 35 and the upper vent-1 of which vis similarly socketed in the base of the housing structure 3| in which are lugs |32, each grinder wheel 30 may be adjusted l i so as to bring its planar grinding face in truly l .parallel relation to the median plane through the 3 grinding field, or somewhat differently stated, to 1 maintain the face of each grinder wheel parallelV to the face of the companion wheel and with each face in a plane truly normal to the line of infeed movement.

It will lfurther have appeared that the dowel |30 constitutes a positive driving 1 connection Ibetween housing |3| and the intermel g diate slide base 35.

As an expedient for maintaining an optimum I tension of belts 44, each motor 3| is provided with I a separate base |34. 'I'his is hingedly secured as i at |29,` to the housing structure |3|. The opposite side, being that visible in Fig. 3, is provided with l a turnbuckle adjustment |35, the upper element of which is'pivotally connected to base |34 and the lower end of which is pivotally connected to a hinge structure formed in part on a lower flange of the housing |3I.

j buckle |35 serves slightly to rock the motor and l base |34 about the hinge pivots, whereby selec,- g tively to tension the several V-belts 44.

A further refinement is to be noted in the Dro- 3 vision of an adjustable stop. consisting of an upstanding apertured lug |36 on cam bar 14. The lug |36 is provided with an adjusting screw |31. This stop may at times be desirable in case a full stroke of the cam Ibar is not needed or not desired for a predetermined infeed movement. It is entirely possible and contemplated that the adjustable stop |36|31 maybe pivotally mounted to be swung out of stop position in case its function is not necessary, and yet may be returned to operative position when wanted, and adjusted as desired.

'Ihe operation of the grinding assembly and infeeding provisions therefor has been referred to Thus extension of the turn-l 1 in part by earlier references to functions of the several elements of this assembly. To summarize this phase of operation, it may be noted that the -as from connection 66. Y pear, for infeed movement, is a so-called trickle grinder discs 30 are first placed in a retracted axial position so as to provide a width of grinding field 39 appropriate to receive therebetween, the loaded Ferris wheel containing work units such as springs, which are of known approximate initial lengths.l In keeping with the described stop-screw provisions for quick change to accommodate different work-piece lengths, the turret nut ||0 is rotated to bring into operative position the selected one of the stop screws ||2 vor H3, the one selected cooperating with the depending arm or lug ||5 on the intermediate slide base.

Thus is determined one axial limit of movement of the slidable supporting structure for the grinding head. In case any adjustment is necessary by reasonuof normal wear of the abrasive disc 30, this wear may be compensated for icy rotation of the threaded element provided with a hand wheel as shown. Assuming the finished or ground vlength of springs tor have fbeen determined, rotation of hand wheel |04 serves to bring the floating stops |05 and |06 either closer together or farther apart, in the former case to provide for shorter finished length of work pieces, and the latter to provide for relatively longer finished lengths, as of the springs to ibe ground.

For rotation of the grinder disc 30 as by motor 3|, the latter in a production construction is ofV 30 H. P., 1200 R. P. M. rating, and with a normal (although moderately variable) drive vratio between motor 3| and shaft 33 such that the grinder discs'rotate at a speed of the order of 440-530 R. P. M. The paired opposed grinder heads are or may be identical hence the foregoing description of setting and operation of each, will suffice for both.

Assuming now that one of the Ferris wheels is in placeland rotating to bring the Work pieces into, through and beyond thel grinding eld, the fluid in the hydraulic system, such as oil under pressure, is admitted to the connection 65 at the left hand end (Fig. 3) of cylinder 64, and permitted to be dischargedfrom the right hand end This, as will later al)- feed, so that there results a very slow movement of the piston in cylinder 64. This results in a barely perceptible infeed-producing movement of piston rod 10, and therewith, the cam 14, and results from the action of the cam face 15 on roller and follower 69. The result is an extremely slow, uniform, downward motion of the follower and hence of the outer ends o f the paired bellcrank lever arms 83. There results a still slower but nonetheless even infeed movement of the short arms of the b'ellcrank levers, producing through elements described, the equally slow yet regular motion, impelling the paired abrasive discs 30 toward each other and against the faces of the work pieces being ground.

By reason of the improved infeed mechanism there results also a substantially uniform infeeding pressure between the discs or' each thereof and the faces of the work units, as will now appear obvious. The infeed motion described continues until abutment of the floating stops |05 or |06 respectively by the abutment nut 96 on each of the grinding head structures, being then mechanically determined. However, in case the work units are compression springs, the end faces of which are in `process of being ground, the loading of vthe springs will result in some continuation of pressure between their end faces and the discs 30, .which pressure persists through a so-called sparking-out period. yThis `|43 (Figs. 5 and6).

remanent loading of the springs and the extent of their compression depend upon the characteristlcs and specification of the springs, and are taken into account in reference to finished ground length at the time of setting the stops |-|06 as by one of the hand wheels |04.

It is important, incident to the method hereinafter to be more fully described, to maintain no more than a light touch grinding contact between the springs and abrasive discs. As a convenient means of determining the nature and extent of grinding contact between the work and the discs, each of the motors 3| is provided, in its supply line, with an ammeter or other means providing an instant indication of motor loading. The operator is thus enabled to tell instantly whether the rate of infeeding motion is excessive or insufficient, and through control of the rate of admission of fluid under pressure to cylinder 64, may maintain his ammeter readings at optimum values. It may be noted that upon completion of the grinding cycle, return of the grinder heads including the wheels 30 to a separated position ready to receive the next work batch is accomplished by the reverse motion of the inclined plane of assembly identified with bushings |45 are necessarily somewhat shorter l than the finished length of Work units, so that the opposite end of each such unit may project appreciably beyond the bushing, even when `ground to finished length. Each of the Ferris cam 14, follower 80, hydraulic cylinder 64, etc.,

Rotatable' work holders and associated driving, tilting and shifting mechanism therefor Reference has heretofore been made, solely by way of general structure, to the provision of rotatable work holders sometimes referred to as Ferris wheels, as the agencies for carrying a great number of the units in work, into the grinding field 39, thence through and out of such field. The improved method of grinding effected by the present structure contemplates the 'use of a Ferris wheel of a much larger diameter than that of either of the abrasive discs 30. The grinding method resulting from the particular relation of Ferris wheel work band, and disc area and relative position of the grinding wheels thereto, will be hereinafter discussed more fully in detail, but it may be noted that, for example, in case the abrasive discs are of the order of 48" diameter, the work-carrying band portion of the Ferris wheel should be of the order of 84 as its maximum diameter.

The general structural arrangement of each of the Ferris wheels as such, is best seen in Figs. l and 2, wherein the wheel proper is indicated generally at |40. This Wheel is conveniently of spoke and hub construction, in which the spokes are shown at 4| integral with or secured to a hub structure |42, and the wheel properrotatively supported through its hub portion on a shaft The work carrying band of wheel |40 is in the nature of an annular compartmented structure, confined say to the outer rim portion, and being in an 84" wheel, say of 12" to 14" width, this band portion being pointed out generally by numeral |44. This work band is built up of a substantial number, say several hundred metal bushings in the nature of short cylindrical elements |45. These are suitably secured in place as by Welding together, with or wheels |40, supported through its shaft |43, is mounted together with a driving unit for rotation of `the wheel, in a frame structure identified with major elements |46, |41, |48.

Normal rotation of the Ferris wheel is most desirable with usual classes of work in process, such as springs, at a rate of the order of 2 to 3 R. P. M. This rotation is accomplished by a small motor indicated generally at |50 (Figs. 5 and 6) which is or may be direct-connected to a reduction gear unit |5I, provided with a power takeoff pinion shown at |52, and the latter meshing with a. gear |53 directly secured to shaft |43. It now becomes obvious that operation of motor |50, through the reduction unit |5| and gears |52|53 will effect the desired rotation of Ferris wheel |40. To facilitate manual loading and unloading of the work units to be ground, into and from the band |44 of bushing-receptacles |45, it is highlyvdesirable to provide for tilting actuation of the Ferris wheel, preferably between a horizontal position as shown at the left hand side of Fig. 2, and a vertical position as shown at the right hand side o f the same figure. When located horizontally, the wheel is at a convenient height for easy access by the operator to the open-end, pocket-forming bushings |45. Since the springs or other work pieces are introduced vertically and downwardly into the pockets therefor, it is desirable to provide temporary closures for at least one side face of the work band of the` wheel This is cared for by the requisite number of arcuate-shaped closures |54 associated with a frame structure of the wheel by means (not shown) which enables the closures |54 to be brought under the wheel portions loaded with the work units. Some of the closures are desirably fixed in position, while others are made detachable. It will appear as obvious that when the Ferris wheel is moved to bring a portion of its periphery into the grinding field, such portion is left uncovered for free access to both faces of the work units by the abrasive areas of the wheels 30.

It may here be noted in passing as desirable that the motor |50 be of reversible type, so as to facilitate reversal of rotation of the associated wheel 40, particularly when grinding soft metal units. Occasional reversal of rotation of the Ferris wheel has been found to deter, minimize and in some cases prevent entirely the tendency otherwise existing for the abrasive discs 30 to become filled and their grinding action impaired by gradual surface accumulation of metal particles.

Provision for the tilting actuation of wheels |40 and associated elements through a range of atleast as between horizontal and vertical 1n each direction, is provided for according to one successful design, by securing the Ferris wheel frame rigidly to a rock shaft |60. This shaftis carried by'v spacedjournal arms or brackl trol of rate of abrasion, is the relation between the 'paths of movement respectively of the work gears |62, which mesh withvcoacting pinion's |63j secured to a lay shaft |64. To theend of thel lattershaft is xed a pinion. |65, and. the latterl.

off element of a reduction unit |10, to which is direct-connected a motor |1I.

vIn practice, ai

l meshes with and is rotated by pinion |66. This', gear A|66 consists, as shown, of the power take-'1- moderate speed motor, say of 3 H. P. rating, has* been found suitable for tilting Ferris wheel assembly. i

The tilting operation of the goingdescription of its elements, but may be summarized in the notation that motor |1| andi reduction gear |10 actuate pinion |66, thence pinion |65 and, through `shaft |64, the lpinions |63. The latter through their engagement with actuation of the holding portion of the-Ferris Wheels or their 'Y equivalents, and the grinding discs. This factor and a discussion of underlying reasons therefor remain to bepresented hereinafter more in detail.

.A third important factor in the complete control andbest attainment of uniform grinding lto close tolerances and in; attainment of the self- 'dressing wheel effect heretofore generally referred to, is a carefully controlled speed of rotation of work holder or Ferris wheel. In the exampleA described this speed vis of the order ofA two to three R. P. M. To .be sure, the speed of the work through the grinding field 39 vis not entirely independent of the speed of rotation of the sector gears |62 will obviously serve to effect at a reduced rate, the notedtilting action of the the grinding wheels, but the noted speed range of the work isrpredicated upon rotation f the abrasive discs within usual speed ranges; for e'xsooo feetl per minute. considering the Ferris it is to be noted that in the latter showing, the

wheel has been given an advancing translatoryy movement tobrin it into the rindin field, b 1

g g g y1 3o tio will stillprovide excellent results, and a submeans now to be described.

The translatory or shifting movement of each;

Ferris wheel assembly is cared for bythe provision of the slidable base structure 25, ,operable through a short range of vlinear movement', on the base elements 20. The latter motion is efwheell work band as having a speed Aof seventy feet per minute, there thus results an optimum ratio of linear velocities of the work units and abrasive elementsv approximating 1 to 80. Ob-

Vviously some considerable variation from this rastantially self-dressing wheel, under proper control of the remaining major factors heretofore referred to. It is considered that a usually useful range of ratios -between linear speed of work and thatofthe abrasive particles lies between one fected by al hydraulic cylinder |12 (Figs. 1 and 8). C

The cylinder |12 contains a double face vpistoni and a fluid connection at each of its ends, which may serve alternately for inlet and discharge of` oil, Afor example. The connection of the piston in cylinder |12 may be'imade directly to a projec` tion (not shown)` below the associated base 2li.v As will later more fully appear in discussing the hydraulic system, admission of fluid lto one vendg and its discharge from the othery end of cylinder |12 under valve control will, as now appears ob-f grindingzone to enable further tilting movement of the wheel, pursuantto translatory movement of thev wheel in the'opposite direction. It will` now have appearedas necessarythat'the' wheell |40 be disposed in vertical position incident, to

the described advancing movement in either direction, and that tilting actuation to horizontal is safely beyond the Descrz'pfirm of I grinding control rindin' mth. n s i i g 9 e "d and fmm 0f of wheas so and |40 rented and patterned as position' be effected andpossibleonly-when the f Ferris wheel assembly grinder assembly.

There hasn-been heretofore described indetail" a preferred mechanism for attaining a gradual infeed approach of abrasive material and workl units.V In the example currently described this consists of a very gradual and yet uniform infeed movement of the paired, opposed abrasive" discs, where the two thereof are employed. This gradual infeed lmotion may be regarded as one of the important factors of the present practice and method of grinding.

The second importantA factor (not necessarily to fifty and one to two hundred fifty.

.Referring now further to the major factor of -control secondly above mentioned, the relation of paths of movement of the Work and grinding discs is graphically shown by Fig. 7, being a line drawing, diagrammatic in nature, showing the band ofthe Ferris wheel in which the work-car- `rying bushings are located, overlying the circular disc area of a grinder wheel 30. In Fig. '1 the vFerris wheel is again indicated generally at |40 and the work-carrying band at |44 as in preceding gures, with the work holding bushings designated at I 45.

` It is a distinct preference that each of the discs 30, as noted, be of hollow-center type, and so present an annular grinding face. The circular central area of the disc 30 is closed over with a steel disc `indicated diagrannnatically at |80, which is kept adjusted so that it lies in or slightly to the -rear of the plane of the grinding face of the disc 30. It is felt to be important that the diameter of the hollow center portion of disc 30 and hence of the closure disc therefor, at least equal and preferably slightly exceed the radial width of the work band |44 of the Ferris wheel. By 'this'arrangemenh and with the areas shown by Fig. 7, it will appear that each of the units of work, in traversing the grinding eld 39, is compelled to passA over, without abrasive treatment therein, the area identified with plate |80. Itis desirable that the circular median line through work band |44 pass through or extremely close to the projected axis of disc 30.

From the described pattern of work and abrasive paths it will now become apparent that the faces of the work units are first attacked by the more rapidly moving peripheral portions of the disc 30, thence by gradually slower moving abrasive areas so that the grinding rate gradually decreases. the speeds of rotation of the wheels 30 and HB each being assumed as uniform. Followe more rapidly moving peripheral portions of the disc 3l. Experience in commercial usage indicates that the described pattern and relation between paths of work and abrasive material, results in a closely miiform removal of metal from each of the batch of several hundred springs or like units in process. A period of commercial experience further teaches that the principles and factors herein described are all of importance in attaining what is an economically important result, namely, the self-dressing feature of protracted wheel operation. Numerous wheels have been successfully operated beyond the stage in which more than one-half their original face material has been worn away, leaving remaining a diminished, yet almost truly planar abrasive surface. Since the costs of wheel replacement and of repeated dressing of wheels are probably the highest components of total grinding costs, the importance of this combination of steps and controls cannot be overestimated.

It may be noted that in further reference to the patterns of work movement and abrasive par--v ticle movement, the median of the work path bisects, roughly speaking, the disc area of the wheel. This is more nearly true, the larger -the v diameter of the Ferris wheel work-carrying band l in proportion to the diameter of abrasive disc. In the present example the ratio of these diameters as illustrated is slightly less than two to one; equipment now in process of production closely approximates a two to one ratio of diameter of Ferris wheel band to grinder disc. It is considered that the diameter of work band I 44 should be at least one and one-half times that of the abrasive disc, in order usefully to approach the results above expressed in uniformity of grinding of work pieces and in attainment of the self-dressing wheel feature. It may be noted as entirely possible to move the work units unidirectionally and rectangularly or nearly so, in a closed path extending through the work zone. 'I'his is in full contemplation as being in keeping with the present method, and as included in the practice of rotating the work units through the grinding zone. However, for practical reasons the ultimate in results is closely approximated by rotation of a large-diameter work band through the grinding zone, which work band is within the range of noted ratios to grinder disc face diameters.

Hydraulic control system Since the major operative units of the assembly have now been described in detail it will appear that the control and control actuation of infeeding mechanism, Ferris wheel transfer, as

well as the return actuation of the grinder headsl eratively associated adjuncts. The choice of a fluid pressure nfeed motor unit results, it is felt, in greater uniformity of nfeed motion and one which lends itself to closer regulation of speed and resulting nfeed movement of and infeeding pressure upon the grinder heads, than is possible with any other type of mover. Similarly. the selection of hydraulic units for the cylinder BIJ provides a number of advantages heretofore noted, not only in a smoother more dependable actuation of the slide base elements but also in a definite cushioning effect above mentioned in the nfeed operation. Largely for these reasons, as well as simplicity of structure and relative freedom from excessive service attention, the system selected for description and preferred in usage. is of hydraulic type, preferably an oil filled, uniform-pressure system.

The specific system illustrated includes a number of cylinder and piston actuating assemblies, each of which is or may be of itself of a form old and recognized in the art. The system further includes a number of manual control valves of types especially suited for the present combination, but none of which is, per se, of the design of present applicants, being included herein'for completeness of description and complete functionof assembly. Each of the several latter units. specifically the control valves andl the flow control units, is a product of Vickers,

Inc., of Detroit, Michigan, and since the specific .turer hereinafter referred to for brevity as Vickers It will be noted, however, that nothing above stated in reference to specific design of flow control or valve units is to be construed as negativing invention in the general combinations within the assembly, including such units.

The hydraulic system considered as a closed circuit flow organization 'is believed to be readily apparent from the schematic diagram of Fig. 8. in which the single lines connecting the various valves. flow units, pump, and cylinders may consist of conventional seamless metal' tubing, say of "/8" outside diameter with connections and fittings of standard type. In Fig. 8 the general arrangement and relative location of the cylinders 60, |12 and 64 approximate the physical arrangement of these parts in the assembly heretofore described.

In the showing of Fig. 8 it will be noted that certain of the iluid Aleads or connections are indicated in dotted lines. Aside from those thus conventionally shown to indicate portions not normally visible, the remaining dotted lines indicate alternate paths of fluid flow, as eilected at times due to the different positions of the valves or flow control units.

By Way of general reference to the elements shown by Fig. 8, the hydraulic cylinders 60 are shown in relatively opposed relation and in their preferred paired arrangement, since they -are thus located one on each side of the base structure of each of the grinding heads 26. 'I'he piston rods of these several cylinders are shown related to the associated intermediate slide base 35. Since, in a double grinder head assembly, the four cylinders 60 are desirably actuated at the same timeand through the same range of movement, they are conveniently and as shown, arranged for facultative control through the valve |90, this valve structure |90 being desig- I nated as Vickers Catalog Number C-432-CNS. It

is essentially a three-position valve, so arranged as to supply the cylinders 60 to cause, selectively,

an approaching movement of the sliding base structures 35. a receding or separating movement of structures 35, and a neutral position in which the pistons of cylinders 60 maintain an intermediate or neutral position. The valve 110 Y| 90 and the remaining portions of the system are kept supplied with a fluid, such as oil under a moderate pressure, through a pumping, storl age and accumulator unit, a reservoir or con.`

tainer portion of which is indicated at |9| and may be designated as Vickers Catalog T-6-FC6.

Surmounted on the unit |9| is an electric motor |92, preferably direct-connected to an oil pump of centrifugal or rotary type |93, designated as Vickers VC-138-Y208.

Connected into the supply and return leads yof the system and pressure-supplied by the unit described, are the two separate control valves. onefor each of the transfer cylinders |12. The one of these to the left (Fig. 8) is indicated at piston, rod and connected Ferris wheel toward one extreme of its path of movement, while manual movement of the handle in an opposite direction, serves to cause a complete shift or translatory movement of` the associated Ferris wheel assembly to the opposite extreme of move-` ment. Each of the units |94 and |95 may be supplied as Vickers Catalog Number C-432-CNS.

An infeed cylinder 64 is,fsimi1arly to the others described, of double end type in which the fluid under pressure may controllably be supplied to either end of the cylinder, and concurrently dis-` charged'from the opposite end Furthermore, in-` cident to the normal infeeding actuation of piston rod 10 acting upon cam bar 14 and associated elements, the rod 10 will be moved to the right (Figs. 3 and 8) and at a very gradual. yet uni- `form rate, as heretofore described. This is accomplished by an extremely slow or trickle rate a quick return movement of piston rod 10, cam 14 and associated parts.

of flowl into and from'cylinder 64 there is providedl a live-position valve assembly designated as Vickers Catalog Number C-485-C, this valve` assembly being indicated by reference numeral |96. Two of the five positions of valve |96 areI such as, respectively, to cause the piston and cyl-` inder 64 to move rapidly in either direction without specific speed control; two additional control positions of valve |96 cause a flow of fluid to cause movement of rod 10 vat a denite, usually low rate of speed in either direction, the speed del pending upon the setting of the speed control h circuit, while a fifth position of valve |96 causes the piston in cylinder 64 and rod 10, to remain` fixed at a predetermined point within their range;

of travel.

Adjunctive to the infeed control through valve |96, is a flow control unit |91 arranged in the This is accomplished by` a reverse direction of flow, but at a considerably; faster rate. Accordingly, as the principal control;

circuit as shown, and which is referred to as Vickers Catalog Number RC-106-A-1. Also arranged in this portion of the circuit, are a pair of check valve . units 200 and 20|, eachunit of the pair being similar, so that each may be designated as Vickers No. C800. Each 0f the units `2||0`20| is in direct communication with one of a pair of y dial valve units 202 and 203. Since these units are or may be identical, they are thought suiliciently'designated as Vickers No. F190C, the dial valves 202-203 being both in circuit with a control unit 204 whichv is adequately identified as Vickers No. C-432-EA. y

Disposed between the valve |90, and the pump and reservoir unit |9|-|92,|93, is a further flow control .unit 205 designated as Vickers No. F-106-D-2. Tubing connections from the latter unit are directed respectively into a pair of similar flow control assemblies 2 06 and 201 each identifiedl as Vickers No, X-106-D. It may be noted that the several flow control units and valves last referred to by manufacturers designation, serve, as the dial` valve assemblies 202-203, to control rate of flow in the associated branches of the circuits, while others thereof control as will be apparent, direction and in some cases, rate and extent of flow, being included herein principally for completeness of disclosure of an operative assembly.

Summary of operation Assuming the machine to have been completely set up with the several stop screws, floating stops and similar elements suitably adjusted to the length and type of work in process, the grinding operation may follow the following suggested course:

One of the fixtures or Ferris wheels |40, with the Work units in place therein, is advanced to a position in the grinding eld 39. This is accomplished by manually actuating the appropriate hydraulic valve |94 or |95, thus causing the associated transverse cylinder |12 to translate the Ferris wheel to grinding position. The operator then observes the position of hydraulic valve which controls the several cylinders 60 at the sides of each of the grinding heads, so as to ascertain that the position of the pistons is such as to permit pressure to be kept in one end of each thereof, whereby to maintain the intermediate slide base 35 against the selected one of the length-of-work stop screws, This valve position may be referred to as the neutral position, inr

which the valve |90 is normally maintained at all times except when actuated otherwise for the purpose of changing from one to another length of stop screws, ||2 or H3, or for the purpose of displacement to permit attention to, removal of, or servicing of the grinder wheels 30.

The assembly is now conditioned for initiating the grinding operation, and an electric switch in the circuit of motor |50 is now closed, causing the Ferris wheel to rotate, and exposing the work to the abrasive discs 30. It may be advisable, incident to grinding a first batch of work of given nish dimensions, to expose the Work to the wheels in successive steps, and intervening such steps, to examine and gauge a. few of the work units, until completion ofthe grinding operation.

At the time of beginning the grinding operation or shortly thereafter, the hydraulic valve |96 is manually shifted to the position causing an infeeding actuation of the piston in infeed cylinder 64. As will now have become apparent, this causes the piston to move the cam bar 14 from lei't to right (Fig. 3) very slowly but with regular and uniform motion. In the manner described, the resulting downward vertical motion of cam roller Il operating through the bellcrank levers, operating bar, and related elements causes the main slide base 38 and all parts thereon, to move in an infeeding direction, i. e. toward the center of the grinding eld 39. It will now have become obvious that lthissalne motion is identically although oppositely imparted to the companion grinder head, so as to cause the wheels 30 to approach each other and to approach the center of the grinding field at exactly the same rate.

It will have appeared that stock removal was initiated at the time the rst loaded Ferris wheel began its rotation and the valve |96 was rst shifted. About this time valve |96 is again manually actuated to a position which first causes the grinder wheels 30 to approach each other and to approach the work at a relatively rapid rate thus causing the load on the motors 3| to build up relatively rapidly. This condition may be accurately ascertained and noted with the aid of the ammeters (not shown) in the motor circuits. As soon as the motors are about fully loaded. the valve |96 is again manually actuated to vanother of its positions such as to cause the relatively rapid infeed motion to. cease, and allowing the speed-controlled hydraulic circuit to function. This circuit, ii; may be noted, is adjusted by means of one of the dial valves 202 or 203 to such a value that the grinding wheels continue to approach the work without an overload condition on the motors 3|. This operating condition is then maintained until such time as the stop elements 96 reach the floating stops |05 and |06, fixing the inner limit of infeed movement of the grinder heads. The loaded Ferris wheel. the work band of which is in the grinding field, continues to rotate for a period during which the Wheels 30 are in xed axial positions at the infeed limit. and until the grinder wheel load (as shown by the ammeters) has dropped down to a predetermined level incident to and following the sparking out period above described.

At this stage of grinding, the Ferris wheel is now temporarily stopped from rotating, a few of the work units removed, gauged for length, and assuming they have attained nish dimensions, the grinding operation has been completed. y y

If upon measurement of the work units they were found to be ofexcessive length or incompletely ground, the amount of such excessive length is divided by two and the hand wheel screw |04 is rotated to an extent apportioned to one-half the value of the excessive length. The appropriate extent of hand ,wheel rotation is noted on a suitable gauge (not. shown) in the vicinity of the hand wheel |04. When the work units have been reduced to the predetermined nish size. they are removed from the Ferris' wheel as heretofore described.

The valve |96 will now be manually actuated to another position which causes the piston in cylinder 6l to move in a direction opposite that just described. At this stage the hydraulic cylinders 60 act as resilient agencies due to the fluid pressure on their several pistons, and as the low portion of the cam bar 14 reaches the roller 80 the cylinders il serve to move the grinding wheels 30 away from each other and away from the units of work in the Ferris wheel, serving at the same time to maintain the cam follower roller 30 in engagement with the camming face 15 of bar 14.

Upon opening the circuit to the Ferris wheel drive vmotor |50. the Ferris wheel ceases lits rotation, following which the associated valve I9! or |95 is operated to cause a retracting transfer movement of the associated cylinder |12. After the Ferris wheel now containing the ground work units is thus brought entirely clear of the grinding eld, it is tilted from vertical to horizontal position by closing the circuit to the associated motor 'I'he Ferris wheel is now ready for unloading. and when desired, reloading with a further batch of springs or the like, to be ground.

'I'he foregoing description has related to the grinding of work units in only one of th work fixtures. Assuming work units of some diifering length to be contained in the second Ferris wheel work fixture, the grinding of such different units may be accomplished by first actuating the valve to an extreme position such as to cause the arm ||5 on intermediate slide base 35 to move toward the stop screw 1. This effect will be obtained, upon control of the valve |90 as indicated. in each of the opposed grinder units simultaneously. Adjustment for the different length of work pieces in the second Ferris wheel is now made by rotating say through the turret nut element ||0 at each end of the machine so that the positions of the two length-of-work stop screws ||2| I3 are relatively reversed. 'I'he valve |90 is now shifted back to its initial positicn, causing the intermediate slide base 35 of each grinder head unit, to move back against the newly selected length-of-work stop screw, assuming of course that the latter has been accurately adjusted by threading to a'predetermined position suitable for the new batch of work umts. The machine is now completely set up to grind the work in the second Ferris wheel, and the latter. after loading, is first brought to vertical position through its motor |1| then translated to a position in the grinding ileld 39, by manual operation of the associated hydraulic valve such as |95, thus causing the associated transfer cylinder |12 to place the second Ferris wheel in grinding position. The operations heretofore described in reference to the first of the Ferris wheels are now similarly repeated for the second Ferris wheel, except that the opposite dial valve such as 203 is now utilized in establishing the rate of infeed movement of the piston of the cylinder assembly identied with cylinder il.

I t will have been obvious that after some substantial period of grinding, it will be necessary to retract disc |80 somewhat, according to the face wear of the wheel 30. This may be done by any suitable means (not shown) such as clamping elements accessible through small openings' in the closure plates |80. Obviously also. occasional minor adjustments must be made incident to wear of the faces of the abrasive discs, since such wear will influence the effective width' of the grinding zone 39. Such occasional adjustments may be sufliciently cared for by rotative movement of the elements I, one of which is provided for each of the grinder assemblies.

It will have appeared. as has been determined by commercial usage for several months, that the grinding, work holding and infeedng mechanisms described will serve to attain unusual precision in automatic or semi-automatic grinding equipment, particularly of the types adapted for face-grinding operations, and that the design throughout is such as to attain a novel, useful and economical 3 control of infeed movement,'relation of paths of movement of the work and grinding discs, to-

gether with a uniform and desirable speed of p movement of the workV through the grinding field,

all in full attainment of the described method or process of grinding and in full realization Aof the several objects expresslystated as well as those implied.

Although the invention has been described by making specific and detailed reference to a single commercial embodiment of its features, the detail of description is to be understood in a broad rather than in a limiting sense, inasmuch as many changes may be made within the full spiritV and intended scope f the claims hereunto appended.

We claim as our invention:

able spaced grinder wheels arranged in face to Wheel, holders on a peripheral portion of the Ferris wheel for supporting units of work and rol tating said units into and through the grinding field between said grinding wheels along a path; such as to subject all abrading portions of the` grinding wheels `to substantially equal wear, mounting meansjfor the grinding wheels permitting axial movement thereof for infeeding purposes, and infeeding mechanism of a hydro-mechanical type characterized by a slow-rate uni-` form infeeding motion, the infeeding mechanism including provisions for a trickle feed of pressure fluid during normal infeeding, and the infeeding mechanism being in part common to both of the grinder wheels, whereby to produce an identical 2. In a double face grinder assembly for reduci low rate movement of the wheels toward the work in the grinding zone therebetween.

`ing opposite faces of a plurality of work units torbe ground, a pair of annular or hollow center grinding wheels arranged face to face but spaced from eachother, a rotary workcarrier wheel provided with a peripheral annular band of open end compartments adapted to receive the units in work,

the carrier wheel being mounted for rotation tol bring its work holding portion into and through the grinding field between the two grinding wheels along an arc, the radius of which substantially exceeds the radius of either of the grinder Wheels,` and with a median of said work holding portion. traversing the grinding eld close to the axis of the grinding wheels, individual drive motors for each of the grinder wheels and the carrier` wheel,

together 'with operativel connections between thev motors and the respective wheels, the grinder wheel motors and connections being adapted for reverse operation at desired intervals, and infeed power means including a fluid-pressure pstong devices for supplying a trickle feed of fluid .under pressure to said piston, motion-reducing means connected to the said infeed power ymeans as parts thereof, and operatively common/at least in part. to both grinder wheels whereby to efl'ect an identical axial, infeed movement thereof at a rate of the order to maintain not more than a` light-touch grinding pressure between the wheels and the units in work through the greater part of the grinding period.

3. In a rotary power tool for processing units of metal or the like in work, a base, a work holding member, a tool supporting member, infeeding. mechanism for moving one of said members to-l ward the other along said base, and including a fluid-pressure-operated cylinder and piston assembly. a source of fluid pressure connected thereto, a cam element actuated by the piston of said uid pressure assembly, and characterized by a gradually sloping camming face of a substantial effective length, a follower arranged to be acted upon by said camming face incident to movement of the cam element, and a motion-reducing connection between the follower and said movable member.

4. The combination and arrangement of elements substantially as recited by claim 3, further characterized in that themotion-reducing connection between said follower and said movable member, includes a lever having a long arm and a short arm, said follower being operatively connected to the long arm of the lever, and the short arm thereof being operatively connected to said movable member.

5. In a power grinder forrunits of metal or the like, a work holding member, a grinder supporting member, a lbase on which one of said members is linearly movable toward the other, means for effecting an infeed movement of said one member` toward the other, and including a power driven, linearly movable cam bar, power means for imparting an extremely slow linear movement to said cam bar, said means acting continuously and uniformly on the cam bar during the period of grinding and normal infeed movement, said cam bar being formed to present a Awedge profile of extremely gradually tapering depth, a cam follower having a, rolling connection with the cam bar, and a lever serving operatively to connect said follower to said one movable member in motion-reducing relation for effecting infeeding movement thereof toward the other member.

6. In a power grinder for facing units of metal n gradually tapering depth, a cam follower having a rolling connection with the cam bar, and a lever serving operatively to connect said follower to said one movable member for infeeding movement thereof, said lever having arms of substantially differing length whereby to constitute a motionreducing connection between the cam bar and said linearly movable member inweffecting the infeeding motionv thereof.

7. A feeding mechanism for effecting an extremely low rate, uniform feeding movement of a power tool towardwork in process therewith, vthe power tool being 'operatively mounted for movement along a base, a plunger element and means for linearly moving said plunger element at a uniform low rate, a cam bar of elongate form and characterizedby a very slightly tapered wedge profile, presenting an elongate camming face. means constraining the cam bar to a rectilinear path of movement, a connection from said plunger terized by an extremely long arm pivotally connected to the Ifollower, and a short arm operatively connected to the tool supporting member.

8. In a power grinder for face grinding operation on metal units, a grinder head including an abrasive wheel, a base on which the grinder head is axially shlftable for producing an infeed movement of the wheel toward the work units, an infeed-motion-producing mechanism including an elongate plunger and means for actuating the plunger at a substantially low rate along a rectilinear path, an elongate cam bar characterized by a wedge profile and gradually tapering depth from one end of its effective camming portion to the other, a follower yoke through which the cam bar passes, and a lever having a long arm operatively connected to the yoke, and a short arm operatively connected to the grinder head.

9. In a grinder assembly of automatic type, a grinding head including a carriage, a base track upon which the'carriage is linearly movable for infeed purposes, a bellcrank lever having a short arm connected to the carriage, and a longer arm, a piston and cylinder assembly, and a source of iluid under pressure connected thereto, an elongate cam operatively connected for slow linear movement by said fluid pressure assembly, a follower connected for a substantially linear movement by said cam, and an operative connection between the follower and the longer arm of said bellcrank lever.

10. In a face grinding assembly, a pair of grinding heads provided with abrasive discs disposed in face to face relation, a base along which the grinder heads are moved toward and from each other for infeed and retracting purposes, infeeding mechanism for the grinding heads, including a piston and cylinder assembly of long stroke proportions, a source of fluid under pressure connected to the cylinder of said assembly, a controllable trickle feed valve adapted to regulate the rate of uid flow into the piston and cylinder assembly, an elongate cam bar of wedge profile characterized by an extremely gradually sloping camming face, the cam bar being operatively connected to the piston of said assembly, a cam follower, a bellcrank lever for each offsaid grinding heads, the levers being characterized by relatively short arms connected to the respective grinding heads, and being arranged in relatively opposite or reversed relation, and relatively longer arms of said levers connected to said cam follower in I a zone substantially coincident with a median plane of the grinding iield between said grinding heads.

11. In a grinding assembly, a base structure, a pair of grinder assemblies oppositely movable on thel base, means for simultaneously feeding the grinder assemblies toward and from each other and a unit of Work therebetween, paired stops for limiting the relative movement of the grinder assemblies in one direction, means for electing an identical yet opposite adjusting movement of said stops, including a. shaft, means preventingA with the grinding zone, and power means forA eiecting separate translatory movements of each work holder into and out of position in which the units of work may traverse the grinding zone, whereby either of the work holders may be moved into the grinding zone while the other holder is in loading-unloading position.

13. In a face grinding assembly, a pair of normally spaced grinding heads serving to establish therebetween a grinding zone, a pair of Ferris wheels, each constituting a, rotary holder for the units of work to be ground, one Ferris wheel being normally disposed at each side of the grinding zone, means for individually rotating each of the wheels, individual power means for tilting each Ferris wheel between a substantially horizontal work-loading and -unloading position, and a substantially vertical position close to alignment with the grinding zone, a tluid-pressure-actuated piston and cylinder assembly connected to each wheel assembly and adapted for effecting a. translatory movement thereof with the wheel in substantially vertical position, to bring it into and out of the work zone between the grinder heads, whereby either of the Ferris wheels may be moved into the grinding zone, while the other Ferris wheel is in a position to receive or discharge units 0f work.

14. In combination with a power tool assembly for processing metal units, a rotatable work carrying wheel structure, a plurality of receptacles for the individual work units, arranged on a peripheral part of the wheel structure, and proportioned so that the individual units of work project therefrom, power means for rotating the wheel structure to cause the units to traverse a. processing zone, power means for shifting the Wheel structure by translatory movement into and out of the processing zone, and power means for tilting the wheel structure about an axis substantially normal to its axis of rotation, and operable so to tilt the wheel structure between a work-receiving and -discharging position, and a position suistantially in register with the processing zone. v

15. A Ferris wheel structure for use with power grinding mechanism, including a Ferris wheel constituting a. holder for units of work to be ground, means supporting the wheel for rotation about an axis for bringing the work units into a grinding zone, means for rocking the wheel about an axis normal to that of its rotation, whereby t0 tilt the wheel between a work-receiving position and a position for advancing the units into the grinding zone, said rocking or tilting means including a motor, a reduction gear and tilting connections from the gear to Wheel supporting elements.

16. In a Ferris wheel structure for use with a power grinder, a Ferris wheel constituting a carrier for units in work to be ground, a frame for the wheel, a power drive for the wheel mounted as a unit on the frame, and power means for tilting the frame and wheel between positions respectively adapted for loading and unloading the wheel, and for enabling the wheel to be advanced to bring the units of work into a. grinding zone.

17. In a Ferris wheel structure for use with a power grinder, a Ferris wheel constituting a carrier for units in work to be ground, a frame for the wheel, a power drive for the wheel mounted as a unit on the frame, power means for tilting the frameand wheel between positions respectively adapted for loading and unloading the wheel, and for enabling the Wheel to be advanced to bring the units of work into a grinding zone, power means for eilecting a, translatory movement of the Ferris wheel assembly toward and source of uid under pressure, a pressure-actu- ;ated piston element and associated cylinder element, and a connection between one of said elementsand the wheel assembly. y

18. In a. Ferris wheel assembly for use with a power grinder or the like, a rotatable wheel constituting a carrier for articles in work, means for tilting the wheel between a substantially horizontal position for loading and unloading, and a substantially vertical position wherein the work is adapted to be moved toward, into and from the grinding zone, the wheel being characterized by a narrow peripheral compartmented band, `a frame about the wheel, and a plurality of c10- sures, shiftable in a plane substantially parallel to the plane of the Wheel, and adapted to aid in retaining the work in the compartmented band when the wheel is in loading position.

19. In a double face grinder assembly, spaced face grinding wheels, a Ferris wheel for carrying units of work into and out of a grinding zone between the grinding wheels, partition means forming pockets in a peripheral portion of the Ferris Wheel for containing the units of Work, means for rotating the Ferris Wheel at a predetermined rate to bring the work through the grinding zone, and means for translating the Ferris wheel into and out of working position with `respect; to the grinding zone, and means for tilting the Ferris wheel between substantially horizontal and substantially vertical positions at times when the Ferris wheel is displaced fromthe grinding zone.

` HARRY P'. TROENDLY.

FRANK BARES.

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