US2723507A - Method of and apparatus for conjugate grinding of irregularly shaped articles - Google Patents

Description

Nov. 15, 1955 c. E. CLUTTER ET AL 2,723,507

METHOD OF AND APPARATUS FOR CONJUGATE GRINDING OF IRREGULARLY SHAPED ARTICLES Filed April 20, 1953 15 Sheets-Sheet 1 INVENTORS CARL E. CLUTTER THOMAS E. DUGLE y MICHAEL FIELD FRANK M. FOSTER ATT RNEY Nov. 15, 1955 Filed April 20, 1953 c. E. CLUTTER ET AL 2,723,507 METHOD OF AND APPARATUS FOR CONJUGATE GRINDING OF IRREGULARLY SHAPED ARTICLES l5 Sheets-Sheet 2 INVENTORS CARL E. CLUTTER THOMAS E. DUGLE BY MICHAEL FIELD FRANK M. FOSTER MM aw- Nov. 15, 1955 c, cLu -rE ET AL 2,723,507

METHOD OF AND APPARATUS FOR CONJUGATE GRINDING OF IRREGULARLY SHAPED ARTICLES Filed April 20, 1953 15 Sheets-Sheet 5 I I/ ,M W I Q who wow 8m 8m b N6 05 wow m mwm R |1l N8 mm 7 NNm 9 3 03 I. l A lllom gm A I l A com .68 I Now w m8 s m 08 w i 1 .lhl| mwm 8m fi|||i w m N: wwm 5m I i WWN &

IN VEN TORS GLUT CARL E. R THOMAS E. ou E MICHAEL FIELD FRANK M. FOSTER 4 1 TTOR 8/ Nov. 15, 1955 c. E. CLUTTER ET AL 2,

METHOD OF AND APPARATUS FOR CONJUGATE GRINDING OF IRREGULARLY SHAPED ARTICLES Filed April 20, 1953 15 Sheets-Sheet 4 INVENTORS CARL E. GLUTTER THOMAS E. DUGLE y MICHAEL FIELD FRANK M. FOSTER Nov. 15. 1955 c. E. CLUTTER ET AL METHOD OF AND APPARATUS FOR CONJUGATE GRINDING OF IRREGULARLY SHAPED ARTICLES 15 Sheets-Sheet 5 Filed April 20, 1953 s m THE R N L E ETGET V U s N m 1 E ESfl A L N mmm MTMF Filed April 20, 1953 Nov. 15, 1955 c, CLUTT ET AL 2,723,507

ND APPARATUS F CONJUGATE. GRINDING OF IRREGULARLY SHAPED ARTICLES 15 Sheets-Sheet 6 METHOD OF A 1N! T TORS CARL E. CLU ER THOMAS E. DUGLE y MICHAEL FIE FRANK M. FOST CLUTTER ET AL METHOD OF AND APPARATUS FOR CONJUGATE GRINDING 15 Sheets-Sheet 7 Filed April 20, 1953 INVENTORS E, CLUTTER FRANK M. FOSTER I /M M Wow J CARL THOMAS By MICHAEL Nov. 15, 1955 c. E. CLUTTER ET AL 2,7

METHOD OF AND APPARATUS FOR CONJUGATE GRINDING OF IRREGULARLY SHAPED ARTICLES Fi Ap l 2 1953 15 Sheets-Sheet 8 IN VEN TORS FRANK M. FOSTER Nov. 15, 1955 c. CLUTTER ET AL 2,723,507 I METHOD OF AND APPARATUS FOR CONJUGATE GRINDING OF IRREGULARLY SHAPED ARTICLES Filed April 20, 1953 15 Sheets-Sheet 9 INVENTORS CARL E. CLUTTER THOMAS E. DUGLE BY MICHAEL FIELD FRANK M. FOSTER Nov. 15, 1955 c E. CLUTTER ET AL 2,723,507

METHOD OF AND APPARATUS FOR CONJUGATE GRINDING OF IRREGULARLY SHAPED ARTICLES Filed April 20, 1953 15 Sheets-Sheet 10 I TORS #am- 955552 y MICHAEL FIELD FRANK M. FOSTER Nov. 15, 1955 c. E. CLUTTER ET AL 2,723,507

FOR CONJUGATE GRINDING HAPED ARTICLES METHOD OF APPARATUS OF EGULARLY S 15 Sheets-Sheet 11 Filed April 20, 1953 l7 7 7 NM Q? r 4? w xxx h w s W xfiw A w Ry fi l 2% 1? Np on 2., w mm mm f m 1\ III w a 9% 7 ww AM J1 1| ilk 2% min [1 w a E m9 wfl T w w o9 mm INVENTORRS L E. GLUTTE MAS E. DUGL HA CAR THO BY MIC EL FIELD FRANK M. FOSTER W 3A TOR Nov. 15, 1955 c. E. CLUTTER ET AL 2,

METHOD OF AND APPARATUS FOR CONJUGATE GRINDING OF IRREGULARLY SHAPED ARTICLES Filed April 20, 1953 15 Sheets-$heet l2 INVENTORS CARL E. CLUTTER THOMAS E. DUGLE BY MICHAEL FIELD FRANK M. FOSTER Nov. 15, 1955 c. E. CLUTTER ET L METHOD OF AND APPARATUS FOR CONJUGATE GRINDING OF IRREGULARLY SHAPED ARTICLES 15 Sheets-Sheet 13 Filed April 20, 1953 IN VEN TORS CARL E. CLUTTER THOMAS E. DUGLE MICHAEL FIELD FRANK M. FOSTER Nov. 15. 1955 c. E. CLUTTER ETAL 2,723,507

METHOD OF AND APPARATUS FOR CONJUGATE GRINDING OF IRREGULARLY SHAPED ARTICLES Filed April 20, 1953 15 Sheets-Sheet 14 INVENTORS CARL E. CLUTTER THOMAS E. DUGLE BY MICHAEL FIELD FRANK M. FOSTER Nov. 15, 1955 c. E. CLUTTER ET AL 2,723,507

METHOD OF AND APPARATUS FOR CONJUGATE GRINDING 0F IRREGULARLY SHAPED ARTICLES Filed April 20, 1953 15 Sheets-Sheet 15 INVENTORS 532 CARL E. OLUTTER THOMAS E. DUGLE y MICHAEL FIELD g2 FRANK M. FOSTER United States Patent METHOD OF AND APPARATUS FOR CONJUGATE glldillglglDlNG OF IRREGULARLY SHAPED ARTI- Carl E. Clutter, Mason, Thomas E. Dugle,

Michael Field, Indian Hill, and Frank M. Foster, Cineinnati, Ohio, assignors, by mesne assignments, to Metcllllit Research Associates, Cincinnati, Ohio, a partner- P Application April 20, 1953, Serial No. 349,778 16 Claims. (Cl. 51-143 This invention relates to a method of and apparatus for grinding irregularly shaped articles, such as, by way of example, the blades and buckets of gas turbines, by passing an endless abrasive belt between the said irregularly shaped article and a conjugate form.

An object of the invention is to teach a method of grinding both the concave and convex surfaces of an irregularly shaped article by means of an endless abrasive belt passed between the article and a conjugate form while the article or the form is being moved along a guided path for sequentially disposing the surface of the form in conjugate coincidence with portions of the surface of the article.

Another object of the invention is to provide simple yet highly effective devices for enabling our method of grinding to be mechanically performed, in lieu of by hand.

A further object of the invention is to provide a device for accurately grinding concave surfaces in an article by means of a conjugate form mounted for planetary cyclic motion relative thereto for guiding an abrasive belt over the surface of the article.

Another object of the invention is to provide a device for accurately grinding convex surfaces in an article by means of a fixedly mounted conjugate form relative to which the article is moved in a planetary cyclic motion.

Still another object of the invention is to provide grinding devices having the hereinabove described characteristics, with means for accurately controlling the rate at which the grinding is effected.

Another object of the invention is to provide simple and efiective means for automatically equalizing the tension across the face of an endless abrasive belt after leaving the conjugate form.

These and other objects are attained by the means described herein and as disclosed in the accompanying drawings, in which:

Fig. 1 is a front elevation of a device embodying the teachings of the present invention, which is particularly adapted for grinding concave surfaces on an article.

Fig. 2 is a view, partly in section, taken along line 22 of Fig. 1.

Fig; 3 is a sectional View of the conjugate form supporting means and its actuating mechanism only taken on line 3-3 of Fig. 1.

Fig. 4 is a partial elevational view of the right end of Fig. 3.

Fig. 5 is a top view of Fig. 4.

Fig. 6 is a view of the left end of the conjugate form and spindle only of Fig. 3.

Fig. 7 is a sectional view taken on line 7--7 of Fig. 6.

Fig. 8 is a sectional view taken on line 8--8 of Fig. 1.

Fig. 9 is a sectional view taken on line 9-9 of Fig. 8.

Fig. 10 is a sectional view taken on line 10-10 of Fig. 3.

Fig. 11 is a front elevation of a device embodying the teachings of the present invention, which is particularly adapted for grinding convex surfaces on an article.

Cincinnati,

- 2 Fig. 12 is a view, partly in section, taken along line 12-12 of Fig. 11.

Fig. 13 is a sectional view taken on line 13-43 of Fig. 1 1.

Fig. 14 is an elevational view of the left end of Fig. 13 with parts thereof being broken away for clarity of detail and understanding.

Fig. 15 is a top view of Fig. 14 with the top cover thereof removed, and with the control housing in cross section for clarity of detail and understanding.

Fig. 16 is a sectional view on line 16-16 of Fig. 15.

Fig. 17 is a sectional 'view of the article supporting cradle and its actuating mechanism only taken on line 1717 of Fig. 11.

Fig. 18 is an elevational view of the right end of Fig. 17.

Fig. 19 is a sectional view taken on line 19--19 of Fig. 17.

Figs. 20 and 21 are schematic views illustrating the sequential steps followed in grinding the convex surface of the airfoil shape of the blade or bucket for a turbine type engine, Fig. 20 illustrating a compressor blade, Fig. 21 illustrating a turbine bucket.

Fig. 22 is a diagrammatic view of the fluid control system comprising a detail of the present invention.

At the outset it should be noted that the present invention embodies simple, yet highly efliective means for quickly and accurately grinding to any desired finish concave or convex surfaces on irregularly shaped articles by guiding an endless abrasive belt over a conjugate form,

and of moving either the article or conjugate form, but

not both, for disposing the surface of the form in conjugate coincidence with the surface of the article throughout the grinding operation. We are well aware that the surfaces of irregular articles such as turbine blades and buckets have heretofore been ground to size, by means of an endless abrasive belt which is caused to pass between a conjugate form and that surface of the article to be ground, wherein' both the article and the conjugate form are simultaneously moved in timed relationship.

In sharp contrast thereto we effect conjugate grinding of the surface of irregularly shaped articles by passing an endless belt between the article to be ground and a conjugate form wherein the article is held immovable and stationary in two planes for movement in a third plane toward and away from the conjugate form and wherein the conjugate form is caused to move in a predetermined path relative to the article so that the surface of the form is coincident with the surface of the article at all points of contact throughout the movement of the form about or relative to the article, in those instances when a concave surface is being ground. Conversely, when convex surfaces are to be ground, the conjugate form is held immovable and stationary in two planes for movement in a third plane relative to the article which is mounted for movement along a predetermined path relative to the with the surface of the article as it is moved about or relative to the form.

For clarity of detail and understanding, we shall first describe one type of means which has given uniformly excellent results in grinding the convex surface of irregularly shaped articles.

With particular reference now to Fig. 11, the numeral 30 denotes, generally, a housing which includes a rear wall 32 to which an oscillatable blade cradle is mounted.

With particular reference now to Fig. 17, the numeral 34 denotes an inner cradle and the numeral 36 an outer cradle. The upper end of forward wall 38 of the outer cradle is pivotally journaled to front wall or bearing column 40 as at 42. The upper end of the rear wall 44 of the outer cradle is secured to and carried by spindle other.

46, by meansv of bolts or other suitable retaining means 48.

Spindle 46 is journaled within housing 50 by means of suitable anti-friction elements 52 and 54. A gear 56 is keyed to portion 47 of the spindle, said gear engaging rack 58, the reciprocation of said rack being utilized to rotate the spindle in opposite directions for imparting an oscillatory motion to outer cradle 36.

The upper end of the forward wallv 60 of the inner cradle is suitably journaled as at 62 to the forward wall 38 of the outer cradle at a location below the pivotal mounting of the front wall of the outer cradle to bearing column 40. The rear wall 64 of the inner cradle is keyed to the forward end of shaft 66, said shaft being journaled in bearings 68'and 70 to the rear wall 44 of the outer cradle.

A planet gear 72 is keyed to that end of shaft 66 remote from the inner cradle, said gear being in normal driven relationship with sun gear 74 secured to and carried by the forward end of a. stationary shaft 76. Shaft 76 is rigidly and non-rotatably mounted with respect to housing 50 by means of clamp plate 78 which, as best illustrated in Fig. 18, may be secured to housing 50 by means of bolts 80. In the preferred embodiment of. the invention clamp plate 78 is provided with means, such as a slit 82 and a slot 84 in radial alignment with the clamp plate in order that said plate may be securely though releasably fastened to the free outer end of shaft 76.by means of a bolt 86 which when tightened: will draw the opposite portions of slot 84 together for clamping; the shaft.

Still referring to Fig. 18, it will be noted that rack 58, hereinafter referred to as the power rack, is adapted to be reciprocated by means of a pair of opposed pistons 90 and 92 of cylinders 94 and 96, respectively, which are suitably secured in axial alignment to opposite ends of a block 98 such as, by way of example, tie rods 95, note Figs. 4 and 5, which extend through and interconnect end plates 97 and 99, respectively. The rack is mounted to reciprocate within the blockwhich, note Fig. 17, is suitably fastened to wall 100 of housing50.

Fluid media under pressure is alternately introduced into cylinders 94 and 96 for driving the rack 58 toward one end or the other of its stroke, it being noted that the opposite ends of the rack, note Fig. 18, are provided with reduced contact areas 102 against which the outer faces of pistons 90 and 92 abuttingly engage.

With reference now to Figs. 17 and 18, it will be noted that spur gear 104 is rigidly secured to portion 47 of spindle 46, said gear engaging the teeth of control rack 1.06. A pair of dogs 108 and 110 are secured to and carried by control rack 106 for selectively engaging levers 112 and 114, respectively, of reversing valve denoted generally by the numeral 116, it being understood that this valve controls the flow of fluid under pressure, from a suitable source, not illustrated, alternately to either of cylinders 94 or 96. If desired, valve 116 may be a pilot valve for actuating a-main, master, or control valve for the actuating fluid delivered to cylinders 94 and 96. In Fig; 22 the valve 116is shown as a pilot valve for actuating the master reversing valve 120 which controls the flow of fluid from pressure line 200 to either one or the other of cylinders 96 and 94 for thereby shifting the power rack from one end of its stroke to the The structural details and operating cycle of valves 116 and 120 will hereinafter be .more fully discussed.

With reference now to Fig. 18, it will be noted that control rack 106 will be translated to the left by rotation of gear 104 until such time as dog 108 contacts lever 112 which will be shifted for changing the flow of fluid from cylinder 94 to cylinder 96, thereby reversing the direction or travel of power rack 58 to the right, and thereby reversing the direction of rotation of spindle 46, gear 104 and rack 106.

It. will, be noted that rotation of. spindle 47 will. cause the outer cradle 36 to oscillate or rock about an axis extending through stationary shaft 76 and pivot 42. This oscillation will cause the planet gear 72 of the inner cradle 34 to be driven by sun gear 74which is secured to and carried by stationary shaft 76, for thereby imparting a planetary motion to the inner. cradle.v It will be noted that the motion thus imparted to inner cradle 34 will be relative to the outer cradle 36, said motion being likewise relative to the framework ofthe machine,

Suitable means, such as a mounting, pad 122, are provided on the inner cradle for securely though releasably clamping an article, such as, by way of example, a blade having an irregular convex. surface which is to be ground. The present invention is neither directed to nor concerned with the particular means utilized for thus securely though releasably fastening a blade relative to the pad of the inner cradle.

With particular reference now to Fig. 11, the numeral denotes an endless abrasive belt which passes over idler. pulleys 132, 134, a tensioning pulley 136, drive pulley 138 and over the outer. face 140 of a conjugate form. 141 fixedly mounted relative to and carried by feed arm 142. Drive pulley 138 may be keyed to shaft 144 of an electric motor denoted generally by the numeral 146, said motor being utilized to drive the endless belt at a substantially constant lineal speed.

As best illustrated in Figs. 11 and 12, feed arm 142 is securely fastened to shaft 148, said shaft being rotatably journaled in bearings and 152 in walls 154 and 156, respectively, of housing 30. Shaft 148 is retated by means of lever 158, the upper end of which is suitably clamped onto a free end of the shaft, see Fig. 12. The opposite end of the lever is pivoted at to a clevis 162 secured to and carried by piston rod 164 of a cylinder 166 pivotally mounted as at 168 to a mounting bracket 170.

The weight of feed arm 142 is simply and effectively counter-balanced by means of spring 172 which surrounds rod 174 pivotally securedto the lower end of lever 158 at 176, and which freely passes through vertical leg 178 of a bracket 180 carried by wall 1180. The free outer end of the rod is provided with a stop element 182, spring 1'72 being disposed between adjacent faces of leg 178 and element 182, whereby axial movement of rod 174 to the left will be resiliently resisted by the counterforce of spring 172.

It will be understood that the application of fluid pressure to cylinder 166 will move lever 158 and arm 142 in a clockwise direction about shaft 148 for thereby lowering that end of the feed arm remote therefrom.

In the preferred embodiment of the invention the downward motion of the feed arm 142 is controlled by the operating characteristics of a post 210, the upper free end of which isadapted to be contacted by the free lower end of a rest button 212 fixedly secured to and depending from feed arm 142. The travel of post 210 is accomplished in two stages, a rapid and a slow feed, said rates of feed being controlled by means of the post actuating mechanism illustrated in Figs. 13-1 6, inclusive. Post 210 is mounted for free axial movement within bushing 214 mounted in vertical leg of a housing 216. The lower end of post 210 terminates in an inclined surface 218, and if desired this inclined surface may be incorporated in a shoe suitably secured to' and carried by the post. Axial movement of post 210 is controlled and determined by the relative position-of .wedge 220 movable axially in a direction at right angles with the longitudinal axis of post 210. Axial movement of wedge 220 is accomplished by means of yoke 224 which is shiftable axially of and in a horizontal direction along and between laterally spaced walls 226 and 228 of a top cover denoted generallyby thenumeral 230,.see. Fig. 14. An axially disposed elongated grow e232. having opposed parallel.v side walls .234- and 236. and 1a b'ottom wall 238 is provided in lower case 240 and between front and rear walls 242 and 244. i

As best illustrated in Fig. 13, a feed wedge 220, a sizing wedge 246 and an intermediate wedge 248 are mounted within elongated groove 232, wherein the feed and sizing wedges are mounted for endwise movement in a horizontal plane, the intermediate wedge 248 being mounted for transverse movement in a vertical plane.

A fluid actuated cylinder 250 is provided with its piston in driven relationship with yoke 224 via piston rod 252 suitably secured to the end wall of the yoke whereby movement of the piston rod will be imparted to the yoke.

With reference now to Figs. 11 and 13, it should be noted that arm 142 will be elevated after each grinding cycle and before the initiation of a subsequent grinding cycle and that when said arm is in its elevated nonoperative position, rest button 212 will be spaced above and out of contact with the uper end of post 210. Post 210 will likewise be elevated to the fully advanced position illustrated in broken outline in Fig. 13, it being understood that the feed wedge 220 will be disposed in a fully advanced position to the left for thereby shifting post 210 to a fully elevated position.

With reference to Fig. 15, the numeral 254 denotes a control rod one end of which is secured to and carried by yoke 224; the other end of the rod is provided with a camming surface 256 and a free outer end 258. A suitable limit switch denoted generally by the numeral 260 having a contact arm 262 is mounted adjacent the axial travel of rod 254 whereby contact element 262 of the switch will be actuated incident to movement of rod 254 to the right.

When contact arm 262 is elevated or engaged by camming face 256 of rod 254, switch 260 is utilized to interrupt an electrical circuit to solenoid 480 of a fluid valve r 476, see Fig. 22, for decreasing the rate of flow of actuating fluid from cylinder 250, thereby slowing the linear movement of feed wedge 220 to the right, resulting in lowering of post 210 at a lesser rate.

The lowering cycle of the feed arm142 is as follows:

Initially it will be rapidly lowered from a fully raised or elevated position until stop' button 212 engages the free upper end of fully elevated post 210. As will hereinafter be more fully explained, fluid pressure is applied to cylinder 250 after contact button 212 of the feed ram 142 has engaged the upper end of the fully elevated post 210 for materially decreasing the rate at which the post and feed arm 142 is lowered. It should be understood that fluid pressure will be continuously applied to cylinder 166 during the entire grinding cycle for exerting a constant lowering force to the feed arm, said force being opposed by post 210.

With reference again to Fig. 13, it will be noted that the lower surface 270 of feed wedge 220 rests upon and slidably engages the upper horizontal surface 272 of the intermediate wedge 248. The lower surface 274 of the wall 238 of the elongate groove 232, and inclined surface 276 of the intermediate wedge 248 rests on and slidably engages inclined surface 278 of the sizing wedge.

Suitable means are provided for imparting axial movement to the sizing wedge for shifting its lower surface .60 sizing wedge 246 rests upon and slidably engages lower It will be ed by means of a lead screw 284 which threadably extgages nut 286 securely though releasably fastened to the wedge by means of retaining plate 288 fastened to the end of the wedge by means of bolts 290. The lead screw is rotatably journaled in plate 292 by bearings 294, said lead screw being thus retained against endwise axial movement. Preferably the free outer end of the lead screw is provided with a socket 296 for the reception of a suitable key, or the like, by which rotary motion may be imparted to the screw.

In the preferred embodiment of the invention suitable means such as, by way of example, a commercially available counter denoted generally by the numeral 298, is connected by gears 300, 302 and 304 to gear 306 formed integral with lead screw 284, whereby rotation of lead screw 284 will actuate the counter mechanism, thereby enabling an operator to locate the relative position of the s1zmg wedge by noting the indicia appearing on the counter, it being further noted that the relative horizontal position of the sizing wedge determines the vertical position of post 210.

With reference now to Figs. 14, 15 and 16, the numeral 310 denotes a second lead screw which threadably engages an internally threaded non-symmetrical sleeve 312, the inner end of which terminates in an abutment 314, said sleeve and abutment being mounted for endwise movement in a complementary channelway 316. A stop 318 secured to and carried by yoke 224 is adapted to engage abutment 314 for determining and limiting the maximum forward endwise travel of the yoke and its associated feed wedge 220 incident to shifting of the yoke to the left, to its fully advanced position under the influence of a moving force applied through cylinder 250. In other words, the relative position of abutment 314 determines the maximum height of post 210 for any given setting of the sizing wedge 246.

As in the case of lead screw 284, suitable means are provided in association with lead screw 310 for enabling an operator to ascertain and/or pre-set abutment 314 for effecting a desired maximum elevation of post 210.

As illustrated in Fig. 15, a third lead screw 320 threadably engages a non-symmetrical sleeve 322 mounted for endwise movement in a non-symmetrical channelway 324. A rod 326 is secured to and carried by sleeve 322, the end of said rod projecting through a suitable opening in end wall 244. Switch 260 is secured to and carried by rod 326, it being noted that the relative location of switch 260 and its arm 262 may be shifted to the right or to the left for thereby determining the end of the initial or rapid feed of the feed wedge 220.

Su1table indicating means such as a counter-mechanism 298 is associated with lead screw 320, as with lead screw 310 and 284, for enabling an operator to accurately pre-set the relative position of switch 260 for controlhng initiation of the slow feed cycle of the feed wedge.

From the foregoing, it will be noted that an operator may, by merely observing the indicia appearing at windowspn the various counter-mechanism 298 associated with each of the various lead screws 284, 310 and 320, accurately determine the limits and relative cycle phases of and through which the post 210 is moved incident to actuation of feed arm 142. A conjugate form 141 having a cam surface 140, which is coincident with the finished surface to be imparted to the article mounted on the inner cradle 34 is secured to and fixedly mounted relative to feed arm 142 by means of a suitable bracket 330 fastened to said arm by means of bolts 332. It will be noted that the outer surface of conjugate form 141 is so related to the surface of the art cle as to provide substantial line contact with the article as it is moved by the inner cradle 34 relative to the form 141.

For a more complete understanding of the relationship which occurs between the conjugate cam surface and the blade, reference is made to Figs. 20 and 21, wherein the numeral 74 denotes the" sun gear and the numeral 72 the planet gear of Fig. 17. It will be noted that belt 130 contactsouter surface 140 of the conjugate form 141 between points A and B, the direction of belt travel over the conjugate form being indicated by the headed arrow 334, it being understood that the abrasive surface of the belt is positioned away from the outer surface of the conjugate form.

The letters C, C1, C2, C3, C4 and C5 illustrate the manner in which an article, in this case a blade, secured to and carried by inner cradle 34 is presented to the outer surface of the conjugate form incident to the relative motion and oscillation of the inner and outer cradles relative to the fixed form, it being understood that these relationships are constant throughout the grinding cycle of a particular blade. It should likewise be understood that the path tirough which the conjugate form 141 is moved incident to lowering of the feed arm 142 is along asubstantially vertical axis during the grinding operation and that deviation from straight linear movement of the conjugate form is so minute as to be disregarded for all practical purposes.

With reference now to Fig. 17, it will be noted that the interior of stationary shaft 76 is hollow as at 340 for providing a passageway through which a quantity of coolant may be introduced via nipple 342 threadably engaging the free outer end of shaft 76. A fluid conduit 344 is provided in the rear wall 44 of outer cradle 36, said conduit being in open communication, as at 346, with the interior of shaft 76. A pair of laterally spaced distribution channels 348 (note Fig. 19) are provided along and interiorly of outer cradle 36, said distribution channels being in open communication with a plurality of discharge openings 350, whereby coolant introduced via hollow shaft 76 will be discharged upwardly for thoroughly drenching the blade and both sides of the endless belt during the grinding process.

Automatic controls In Fig. 22 we have diagrammatically illustrated the various fluid controls which are utilized for enabling an operator to manually initiate a grinding cycle after having mounted an article on the pad 122 of the inner cradle whereby the convex surface of the article will be automatically ground and the machine automatically stopped at the completion of the grinding cycle for enabling the operator to remove the finished article and insert another article preparatory to the next grinding cycle.

In Fig. 22 the numeral 400 denotes generally a pump for circulating a fluid from a sump or reservoir 402 through a pressure line 260, the numeral 404 denoting a drain line under atmospheric pressure and the numeral 406 an exhaust line in which the pressure is somewhat above atmospheric pressure.

Fluid will be introduced at a predetermined pressure into high pressure line 2110, and through line 410 to a spring actuated relief valve 412, the fluid being discharged from the valve through lines 414 and 416, wherein line 416 is in open communication with exhaust line 406, and wherein line 414 is in communication with intake 418 of a double-acting, two-way valve 420 which is normally maintained in the position illustrated in the drawing by means of spring 422 whereby fluid entering port 418 will be discharged via line 424- into exhaust line 416. In this manner the net pressure of fluid in line 200 will be considerably reduced, thereby lessening the energy required to operate pump 406i and precluding undue heating of the pressure media.

A double-acting, four-way reversing valve 426 is normally conditioned by means of spring 428 to connect line 430 in open communication with line 432 to end 434 of the cylinder 166 which, through piston rod 164, actuates feed arm 142 about shaft 148 for normally disposing the said feed arm in a fully elevated position.

A solenoid indicated generally by the numeral 436 is adapted to reverse valve 426 whereby fluid under pressure from line 430 will be introduced into line 438 which is in open communication with end 440 of cylinder 166. Line 442 is in open communication with line 438 for transmitting the pressure within line 438 and end 440 of cylinder 166 to a pressure switch 444.

Exhaust line 406 is connected to the discharge port 446 of valve 426 via line 443. Drain line 404 is suitably connected through line 450 to that side of valve 426 with which spring 428 is associated for returning any leakage which might occur in the valve back to sump or container 402.

End 452 of cylinder 250 is normally connected in open communication with pressure line 200 through line 454 to intake 456 of a double acting valve 458, line 460, rate valve 462, check valve 464 and lines 466 and 468. A second rate valve 470 is connected between lines 460 and 468 by lines 472 and 474, it being noted that a double acting valve 476 controls the flow of fluid through rate valve 470. A spring 478- normally maintains valve 476 in closed condition, said valve being opened incident to energization of solenoid 480 for establishing a flow of fluid through the last mentioned rate valve.

Spring 459 normally maintains valve 458 whereby line 460 is in open communication with line 454. A solenoid 461 is provided for actuating this valve for selectively connecting line 482 in open communication with line 454.

The spring loaded ends or other portions of the housing of each of valves 45% and 476 are connected to drain line 404 by lines 484 and 486, respectively. Each of the rate valves 462 and 470 are likewise connected via lines 488 and 490 to the drain line 404.

From the foregoing it will be noted that end 452 of cylinder 250 will be normally subjected to fluid pressure for disposing feed wedge 220 in a fully advanced position for elevating post 210.

Fluid from line 200' is likewise supplied to doubleacting valve 120 via line 492 for distribution through lines 494 and 496 to one or the other of cylinders 94 and 96, the pistons and 92' of which, note Fig. 18, engage opposite ends of power rack 58.

The intake 498 of pilot valve 116' is connected by line 500 to pressure line 200, and when this valve is in the position illustrated in Fig. 22, the fluid of line 500 will be introduced into cylinder 502 through line 503 for shifting valve 120 for introducing fluid into cylinder 96, it being understood that the pilot valve is actuated by dogs 108 and 110 contacting levers 112 and 114, see Fig. 18. When lever 114 has been shifted to the left, fluid from line 500 will be introduced through line 504 to cylinder 506 for introducing fluid from line 492 into cylinder 94 via line 494.

Line 507 connects outlet port 568 of valve in open communication with double-acting valve 510 which is normally closed by spring 512 for thereby precluding a flow of fluid through line 492 whereby pistons 90- and 92 will remain stationary. A solenoid 514 is provided for actuating valve 510 to an open position connecting line 507 with line 516, through an adjustable rate valve 513 to exhaust line 406 via line 520. The rate valve is connected to drain line 404 by line 522.

A solenoid 524 is provided to actuate valve 428 for blocking the flow of fluid therethrough to line 416, thereby increasing the pressure of fluid in line 294).

A suitable filter 530 is provided in exhaust line 4% and a safety valve 532 is placed in parallelism with the filter for precluding damage thereto incident to clogging thereof.

After the pump 400 has been operated for providing fluid under pressure in line 260, and after an article has been mounted on the upper cradle, the operator may then initiate a cycle by which a flow of coolant is established, motor 146 started for driving belt and solenoids 436, 480 and 524 energized. Energization of solenoid 436 will actuate valve 426 for applying fluid under high pressure to end 440 of cylinder 166 for rapidly lowering feed arm 142 until button 212 engages the free upper end of post 210.

Energization of solenoid 480 will place rate valve 470 in open communication between lines 472 and 468.

Energization of solenoid 524 actuates valve. 420 to block the flow of fluid therethrough for placing line 200 under high pressure.

A pressure build up will occur in end 440 of cylinder 166 after the initial rapid lowering motion of feed arm 142 has been checked by post 210. This build up in pressure actuates the pressure switch 444 for closing an electrical circuit to solenoids 461 and 514 for actuating valves 458 and 510, respectively, to introduce fluid from line 454 to line 482 and connect line 460 with exhaust 406 via line 411, for retracting the feed wedge 220, thereby lowering post 210; and for simultaneously placing exhaust line 507 in open communication with line 516 for permitting fluid to flow from one or the other of cylinders 94 and 96 forreciprocating the power rack 58.

When limit switch 260, see Fig. 15, has been actuated, solenoid 480 is de-energized for actuating valve 476 to interrupt a flow of fluid, through 472 sojthat the exhaust of fluid from end 452 of cylinder 250 is restricted to line 466, thereby providing a slow feed of the feed wedge 220 and a very slow lowering of post 210.

As best illustrated in Fig. 15, a limit switch 351 is mounted whereby it will be actuated by the free outer end 258 of rod 254 as feed wedge 220 reaches the end of its stroke. Switch 351 opens an electric circuit to a so-called tarry timer, not illustrated, which initiates a short dwell after the post 210 has been fully lowered for thereby permitting the grinding operation to continue for a moment or two with the conjugate form, endless belt and article being ground'in fixed relationship for thereby enabling so-called spark-out to occur, and to allow any deflections induced incident to the grinding operation to be relieved.

Upon termination of the cycle of thetarry timer, the electrical circuit to solenoid 436 is interrupted and spring 428 will actuate valve 426 whereby fluid will be applied to end 434 of cylinder 166 for thereby shifting arm 142 to its fully elevated position in the case of the convex machine illustrated in Fig. 11.

At the same time switch 363 is energized so that actuation of overriding lever 1363 by dog 361 secured to and carried by control rack 106 will result in de-energization of each of solenoids 461, 514 and 524, it being noted that .the cradle will thus be stopped in the same relative position at the termination of each grinding cycle.

The grinding belt and flow of coolant are likewise stopped concurrently with the de-energization of solenoids 461, 514 and 524.

Suitable means are preferably provided for enabling the cradle and its associated driving rack to be actuated by hand during those periods of time when the device is being manipulated incident to set-up. Such means may comprise a needle valve 550 disposed between lines 494 and 496, thereby permitting the fluid in each of cylinders 94 and 96 to freely pass from one cylinder to another incident to axial movement of the rack.

Concave grinding In those instances wherein it is desirable to grind the concave surface of an article, we prefer to utilize the device illustrated in Figs. 1 through 10. At the outset it may be noted that the primary distinction between convex grinding and concave grinding, by our method, amounts to a mere reversal of parts, in the sense that in convex grinding we propose to mount the conjugate form in a stationary position and of then moving the article to be ground about the fixedly mounted form in such a manner that the surface of the form will be disposed in conjugate coincidence with the surface of the article being moved thereabout. When grinding concave surfaces we fixedly mount the article to be ground relative to the conjugate form which is moved relative to the fixedly mounted article for disposing the surface of the form in conjugate coincidence with the surface of the article incident to movement of the form relative thereto. In both grinding operations an endless belt is caused to pass over and is guided by the conjugate form, the grinding operation being accomplished by reason of eflecting contacting relationship of the article with the abrasive surface of the belt as guided by the conjugate form.

With particular reference now to Fig. l, the numeral 166 denotes a cylinder one end of which is pivotally secured as at 168 to a bracket 169 secured to and projecting downwardly from the housing 31. Piston rod 164 is pivotally secured as at 161 to the lower end of lever 159 the upper end of which lever is keyed to shaft 149 for rotation therewith. One end of the feed arm 143 is provided with a clamp 141 which is securely though releasably anchored to shaft 149 by means of bolts, or the like, 145. A bearing bracket 151 is suitably secured to a side wall of the housing as by a weld, said bracket rotatably receiving the outer end of shaft 149, note Fig. 2. The numeral 123 denotes a pad to which an article to be ground is securely though releasably attached.

The introduction of fluid under pressure into the left end of the cylinder 166 will shift the piston rod 164 to the right for thereby elevating feed arm 143 upwardly about shaft 149.

With particular reference now to Figs. 2 and 8, it will be 'noted that free, unrestrained upward movement of feed arm 143 will be resisted by the upper end of abutment 213 with the free lower end of pin 215.

The numeral 211 denotes a post which is identical with and a substantial duplicate of post 210 as more fully detailed in Fig. 13, it being further understood that axial movement of post 211 is accomplished by the same or a similar mechanism illustrated in Fig. 13 for controlling the axial movement of post 210.

Upward axial movement of pin 215 is translated to a parallel, downward axial movement of rack or counter shaft 217- the lower end of which may terminate in a rodlike portion 229 the free end of which may abuttingly engage the free upper end of post 211.

As clearly illustrated in Fig. 8, pin 215 is integral with a rack 221, the teeth of which engage the teeth of a pinion gear 223 rotatably mounted for movement about shaft 225 the opposite ends of which shaft are supported by and spanningly engage a pair of duplicate side plates 227 of housing 233. The teeth of gear 223 are likewise in engagement with the teeth of rack 217 wherein the axis of racks 221 and 217 are in spaced parallelism whereby movement of one rack in one direction will produce an equal and opposite movement of the other rack.

- With reference now to Fig. 9, it will be noted that the free lower end of rod 229 is adapted to abuttingly engage the upper surface of an offset plate 231 secured to and carried by the free upper end of post 211. It should, of course, be understood that the free lower end of pin 229 could be in axial alignment with post 211, however we have ascertained that by using offset plate 231, as illustrated, an alignment problem is effectively solved without in any way impairing the efliciency of the device.

Referring again to Fig. 8, it will be noted that the racks 221, 217,- gear 223 and shaft 225 may be secured to and housed within a bracket 233 secured by means of bolts 235 to wall 237 of the frame.

It will be understood that upward movement of feed arm 143 will thus be resisted by the counter-force of post 211 by means of actuation of wedge 220 of Fig. 13.

As earlier indicated in concave grinding we propose to move the conjugate form along a predetermined path during the grinding operation. The particular means utilized to accomplish the, desired motion of the conjugate

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