US2531340A - Hydraulic mechanism - Google Patents

Description

L 195% M. A. MATHYS 2,5313% 7 HYDRAULIC MECHANISM Filed Jan. 8, 1944 6 Sheets-Sheet 1 Filed Jan. 8, 1944 i 6 Sheets-Sheet 2 NW, 21, 1950 M. A. MATHYS HYDRAULIC MECHANISM 21, 1950 M MATHYS HYDRAULIC MECHANISM Filed Jan. 8, 1944 6 Sheets-Sheet 3 A 59 SD 52 59 A 5\ V I? J A s3 JDINVE-NTO 1 M. A. MATHYS HYDRAULIC MECHANISM Filed Jan. 8, 1944 6 Sheets-Sheet 4 max,

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Patented Nov. 21, 1950 HYDRAULIC MECHANISM Max A. Mathys, Detroit, Mich., assignor to Ex- Cell-O Corporation, Detroit, Mich., a corporation of Michigan Application January 8, 1944, Serial No. 517,541

18 Claims. 1

' The present invention pertains to a novel hydraulic mechanism, and more particularly to one which is especially suited for efiecting, in the course of its cycle of operation, an accurately controlled step-by-step motion of a driven member, such as may be employed, for example, in accomplishing the infeed of the wheel slide of a traverse grinder.

The general aim of the present invention is to provide a hydraulic mechanism or actuating system of the general type indicated which is fully automatic and which is characterized not only by its precision of operation but also by its versatility of adjustment to accommodate different operating requirements.

More particularly, one object is to provide such a system in which a novel arrangement is provided for adjustably and precisely determining the limits of the last step in a step-by-step advance, thereby especially accommodating the same for use in a machine where such last step is used in making a finish pass or cut in bringing a work piece exactly to size.

Another object is to provide in a system employing withdrawal of metered increments of fiuid from a piston and cylinder type actuator in effecting step-by-step advance, a novel arrangement for eiiecting an automatic reversal of the actuator after completion of the step-by-step advance.

. Another object is to provide in a system employing withdrawalfrom an actuator of metered increments of fluid to effect the advance of such actuator, a novel arrangement'for safeguarding the 'metering-out circuit against leakage.

,Another object is to provide in a hydraulic system, a novel arrangement for insuring the precision stoppage of an actuator in a final preselectable position therefor and which arrangement operates with the same fidelity in duplicating the final position of the actuator at the terable starting point, such arrangement being adapted for employment either with or without step-by-step advance of the member in at least a portion of a cycle of reciprocation therefor.

Further objects and advantages of the invention will become apparent as the following description proceeds, taken in connection with the accompanying drawings in which:

Figure 1 is a generally schematic perspective view of the major elements of a traverse grinding machine having applied to its wheel slide a, hydraulic actuating system embodying the present invention.

Figs. 2 to 5 are simplified hydraulic diagrams of the actuating system, Fig. 2 indicating the flow of fluid during rapid approach of the slide, Figs. 3 and 4 indicating the flow of fluid during two successive steps in the step-by-step forward feed movement of the slide, and Fig. 5 indicating the fiow of fluid during the rapid return motion of the slide.

Figs. 6, 7 and 8 are successive stop motion views of the stop mechanism in the end of the actuating cylinder which serves to determine adjustably the length of the last step of advance of the actuator, the parts being shown partially in ion-- gitudinal section.

Figs. 9 to 12 are simplified hydraulic diagrams of the control portion of the hydraulic circuit, illustrating the successive conditions of fluid flow in the same incident, respectively, to rapid approach, completion of the next to the last step and last step of the step-by-step advance of the actuator, and to rapid return movement of the same.

Fig. 13 is a complete hydraulic diagram of the system, illustrating in section the preferred form of the various valves.

While the invention is susceptible of various modifications and alternative constructions, I

have shown in the drawings and will herein describe in detail the preferred embodiment, but it is to be understood that I do not thereby intend to limit the invention to the specific form disclosed, but intend to cover all modifications and alternative constructions falling within the spirit and scope of the invention as expressed in the appended claims.

Referring more particularly to the drawings, in Fig. 1 has been shown generally schematically the major elements of a traverse grinding machine, such a machine being simply representative of the type of installation in which hydraulic systems embodying the present invention are especially suited for use. Such major therefrom.

elements include a table I adapted to carry and reciprocate axially a revolving Work piece 8 which is to be ground. On a wheel slide I is a revoluble grinding wheel 9 engageable with the Work 8. The herein disclosed hydraulic system is adapted to effect the so-called infeed of the wheel slide, in a direction transaxially of the work.

In brief, the preferred controls-for'the wheel slide I6 are such that upon starting, an automatic cycle is executed which consists of a rapid approach of the slide in to working position, thereafter successive steps of advance for the slide alternated with passes of thework by the reciprocating table 7, and a rapid return.of.the.1slide to starting position after it has completed its step-by-step advance to a predetermined depth of cut.

In the illustrated embodiment, movement of the slide II] is effected by the coaction of a first fluid typeactuator, consisting of a cylinder lla anddiiierential'piston I2, witha second fluid actuator, or moreijspecifically, a. fluid. plunger devicenthe latter consistin of a cylinder Ila and plung' er III. Boththe cylinders TI Ia and Ho. are sftationarilymounted, as, for example, in the base of. t h'efr'na'chinef .Theslide. IE! is in efiectfforced constantly againstthepiston I2 by theplunger .II. .To .advancethe slide; IE3, fiuidis withdrawn from-the cylinder l 2a at-h the forward face .of the ,pisto'nsokthatthe pistonI-Z actsas a, retreating n -abutment for-limiting the advance of the slide under'the constant urge of the plungerII. To cause the slide-toreturmrthe application of pres- .surelfluidtothe cylinder IZais reversed, the plunger II being overpowered. The length of travel fcrtheslide Iaisthus determined bythe fixed-stroke of the-actuator piston. I2, but the .startingpoint can be adjustably varied by ad- .-iusting the length -of=the coupling between the actuator I2, Ma and slide, the plunger I Iserving ,thr-Q l hQut-such range of =-adjustment to retain .theyslide and actuator engaged,

As-,to vthe:particular coupling set-up shown in IEigglgtheractuatorpiston I2. has at its outerend an abutment roller Izflil bearing against the curved face of a transverse link IOI. The ends of .the link tItIlI are yoke-shaped, the righthand end beingvpivote dasiindicated'at I02 onasleeve I03 whichris journaledupon a shaftdfldythe sleeve beingrestrained against axial movement with respect-tothe shaft. The shaft itself is threaded ewithin a nut I05, the'latter being held against 'rotation'by a-stationary spline key I06 entering a longitudinal slot in the nut. Bearing against the outer end face of the nut 1.05 is an adjustable abutment: I'filffixed to the slide II). -By revolving the shaft Hi l the same is screwed into or out of the.'nut.Iil5,-thus adjusting the position of the islidez-iillrelative to its actuator I2, I2a. In this -way.the.locati-on of the slide IE] relative to the uWOl'k 8 may-be'adjusted atwill even though its actuator I2, IZa has a stroke of fixed'length.

The plunger I I serves to urge the slide In con- :stantlyinaa: forward direction to retain the slide abutment I 0? constantly in engagement with the end of the nut Hi5. For this purposethe plunger Ii is arranged to bear against theface-of a bracket. I88 rigid with the slide IO-and depending The-usual sizewheel I69 serves to adjust the shaft Iiinvithin the nut I65. This wheel is connected through gears I Hi with a gear I I I splined 'on the shaft I04 so that turning of the wheel I09 a'diusts the slide I0 either forwardly or-rear- .the rod I I5 being pivoted to the lefthand end of the latter link. With such an arrangement, as the tableadvances the sine bar II2 shifts the member H3, thereby causing the link IUI to --"fulcrum about-the. roller I60 so that the slide I0 is advancedin timed relation with the axis of the work'to produce a tapered surface on the latter.

Power circuits of the system The preferred hydraulic circuit embodying the actuator, I 2, l2a and plunger I I isshown in full inEi'gfBfbut, its intricacies will best be understood. after. a preliminary consideration. of certainjsirnplified or partial'showings of the circuit inflordefthat the general plan of operationmay be clear. For that purpose the fluid flow for the actuator or power. circuits .proper has. been diagrammed in'Figs; 2' to dim successive cycle steps, and thefluld flow for the control circuits ofithe systemjhas'. been similarly diagrammed in Figs. 9 tol2. Reference may be first made to Fig. 2. As there, shown, fluid such as .oilis supplied under pressure. from a suitable constant pressure source such, for example, as a constant deliverypumpP equipped with a conventional spring loaded working pressure relief valve V. Thejpump draws fluid 'fiomareservoir R' and delivers'the'same under pressureflthe relief 'valve'serving to return such "excess fluid tothe reservoir as may be required toimairitain the pump delivery pressure substantially-constant-at a'valuev determined by the adjustment of'ithe relief valve. Pressure fluid from the pump- P is delivered through pressure line I8 directly and constantly-to'the outer end of the plunger I I andal's'p to a starting. and reversing valve-Fig 3. The latter is a two- -position valve having forward and reverse positions and when in its, forward position it dispatches'fiuidfrom the pressure line "I81through '1ine23 tothe cylinder fz'affdr advancing the piston [2. In FigS. 2130.5

and Q to 12 the heavy black shading indicates "fluid under pre'ssuredirectly. from the pump while a dottedlin'e" in the conduit indicates'fluid, at an xliaust pressure. 'iIn.E ,gs.f3" and 4 the broken --heavy'lines'incertain fthe conduits indicate fluid trappedin the, metering circuit and. which is reta'inedfunder pressure substantially equal to the pump discharge pressure, for a purpose which will ater app ar- ?To institute .acycleof operation, rapid advance of the .slide llljjisinitiated by shifting thevalve 'f3tojits, forwardposition (indicated in Fig. 2),

whereupon 'itdispatches pressure fluid from line {Bf-through. line 23 .to the actuator. cylinder I2a and causesllfiuid to becexhausteld from theoppos1te-end of such cylinder" through line 24 and thence through line 25 and aimed control valve '15) back to; the reservoir Rthroughexhaust line .I 9 ='If desired, a conventional spring loaded back pressure valve I9a may be interposed in the er the plunger being reduced in diameter to. pre:-

sent a cross-section one-half that of the inner end. Pressure from the pressure line [8 is applied tothe face 28 of the shoulder on the plunger between its large and small-portion and through -a line 29 to the'inner end 3|] of the plunger.

Since the area at 3B is twice as large as that of theshoulder 28, the plunger is yieldably thrust outward against a bushing 3| fixed in the valve casing 21. In such position of the valve, the lin is connected through an internal bore 34 and cross passages 33 in the punger to exhaust line IQ for the free exhaust of fluid from the line 25 to effect rapid'approach of the slide as noted above. A separate plunger 14 in the lower end of the valve casing serves to thrust the main plunger 26 outward upon application of pressure fluid in a manner hereinafter described to set the plunger 26 in its projected position. Once the plunger 26 is so projected it will remain, due to the differential pressure action on it, until mechanically thrust in a short distance, whereupon fluid resistanceto such thrust is relieved so that the. plunger can. continue its retraction without impediment.

plunger 26 of the feed valve l5 (Fig. 3). Shift- 0 .ing of this valve plunger 26 causes the valve I5 to interrupt the exhaust of fluid from the cylinder l2a through line [9 and to direct the fluid from such cylinder through an arrangement which meters the fluid out of the cylinder in predeter- .mined. small increments. Each increment of fluid so metered out permits the piston l2 to advance a corresponding fixed distance.

When the dog thrusts the valve plunger 26 inward, the exhaust line 19 is connected through the passage 29 to the rear end 30 of the plunger so that the latter can complete its inward movement without impediment. Such inward shift of the plunger 26 cuts off the connection to exhaust from the line 25 and blocks the latter (seeFig. 13). A separate sliding plunger 14 limits the inward movement of the main valve plunger 26.

The mechanism for metering out increments of fluid from the cylinder l2a consists of a plunger l6 slidable within a cylinder l6a provided with an adjustable stop pin 38 at one end thereof for limiting the path of travel of the plunger. A micrometer head (see Fig. 13) on the stop pin 38 servesto adjust its position. Cooperating with the metering plunger l6. and connected theretoby lines 36, 3'! is a reversing valve 14 which serves to direct fluid to alternate ends of the plunger Hi from the outlet of the actuator cylinder l2a and in each case to exhaust the opposite end of cylinder lGa to line [9. The valve i4 is fluid operated in timed relation with the table I in such manner that the valve I4 is actuated upon each stroke of table movement. For this purpose a reversing pilot valve 1a (Fig. 3) is actuated by the table 1 to direct pressure fluid through alternate ones of pilot lines or conductors 2|, 22 and exhaust the other, thereby alternating the position of the plunger of valve l4.

Since the shifting of the valve l5 to institute feed blocks the line 25, as heretofore described, so that fiuidfrom the cylinder l2a' can no longer go to the exhaust line, l9, it is, instead, forced through the valve l4 into one end or the other of the metering cylinder 16c as determined by G the position of the valve l4. Under theconditions shown in Fig. 3, fluid is forced out of the-actuator cylinder lZa through the line 24 and is directed by the valve l4 into the lefthand end of the metering cylinder I611, thus forcing the metering plunger 16 to the right to -the limit position determined by the adjustable stop 38. Simultaneously, valve I4 exhausts the opposite end of the metering cylinder I6a by connecting it to exhaust line l9. An increment of fluid is thus displaced from the actuator cylinder l2a which is equal to the volume of the space vacated by the plunger [5 in its shift, and the actuator piston l2 together with the slide in is advanced a corresponding fixed distance. Upon the completion of the shift of the metering plunger IE to the right, the slide [0 comes to rest, since no further fluid can be displaced from the actuator cylinder l2a.

Upon the completion of the next stroke of the work supporting table I the pilot valve la is actuated thereby to reverse the pressure conditions in the pilot lines 2!, 22 (Fig. 4) so that pressure is applied through line 2| and fluid exhausted through line 22, thus shifting the reversing valve id. Such shift of the valve I4 directs fluid into the righthand end of the metering cylinder Mia and connects the lefthand end .to exhaust through line l9. Thereupon the metering plunger [6 is displaced to the left, a corresponding amount of fluid being received from the actuator cylinder l2a so that the slide It] can advance another step. In this same general manner the metering plunger i6 is shuttled back and forth with one stroke of the plunger upon the completion of each stroke of the work supporting table I, so that the slide it is advanced one step after each stroke of the table.

Provision is also made for instituting drive of the work spindle as an incident to shift of the valve'l5 at the completion of rapid approach. For that purpose the valve l5 connects line 29b to exhaust line l9, thereby exhausting fluid from a cylinder 290 so that a spring-urged plunger 29d moves downward to close its associated switch contacts 29c. Closure of these contacts may be used to complete the energizing circuit for the electric drive motor (not shown) which revolves the work piece 8.

- Upon completion of the step-by-step feeding advance of the slide l5, its motion is reversed through the medium of an automatic control arrangement hereinafter described, and it is automatically returned to starting position. During such rapid return movement of the slide (see Fig. 5) the valve I3 is in its reverse position, while the valve i5 is restored to the position which it occupied during the rapid approach movement illustrated in Fig. 2. The control circuits for operating the valves I3 and I5 to effect reversal are hereinafter detailed in connection with Figs. 9 to 13. Incidentally, it will be noted that the springurged dog 35 rides freely over the plunger 26 during its return movement and consequently does not actuate the latter during such return. For the rapid return movement in question, pressure fluid from the line [8 (Fig. 5) is dispatched by the valve 3 to theouter or lefthand side of the piston l2 through line 24 and fluid is exhausted from the righthand end of the actuator cylinder through line 23, valve l3, line 25, valve 15, and thence through exhaust line l9 back to the reservoir. Although the application of pressure fluid to the plunger H is continued during such return movement, the greater area of the At h 'eii f. mail-earn fiv fi j it co mesto i'e'st upon abutment cif the piston 12 against t .rig th li e d. cubetilinien'ld- D ri eth iwmpf t e li eihs spinql ent-ita sw iehw iap ar Q ened hr' ressii efluid supplied fromthepressure line l8 through the "valve I5 and line 29b.

Readily adjustable step-by-step motion of the As will be evident J is-limited to an amount proportionate to the shift ofthe'plunge r It. Such plunger shift can be readilyadjusted by changing its stroke through ithe use'ofthe stoppin 38.

Control of last feed-step Special provision is made 'for adjustably controlling" the length or the'last step in the stepby step'adiiance of the slide Ii]; Such adjustment is quite'independent Of the length of the preceding-steps which, as'heretofore explained, are determined by the setting of the adjustable stop p'in 38. Precise and a'ccurate-control'of the length of the last step of advance is especiall desirable in that the-length of such step commonly determines the amount'of' metal which is to be removed during the last or finishing'passof the work past the tool. It is requisite" not only that thelength of this step should be accurately controlled, but alsothat thefinal position of the slide be-determined with extreme certainty as Well as exactitude since that position determines the final size of the work.-

In accomplishing such control of thelast step I otadvance of the slide, a movable stop in the form of a bushing H is interposed in the path of advance of the piston l2 (see Figs. 2, and 6 to This stop it intercepts theadvance of the piston at the end of the next to the last step, and for the final step thestop I I is permitted to retreat an accurately determined distance. The stopbushing I7 is slidable axially within a bore i1 a coaxial with and openinginto the end of the cylinder lzc oppositethe large face of the piston (2.. .Qutward movement of the stop bushin'g- I] is limited by the seating of its outer end against an abutment. surface 48- on the end wall o f the bore lla; while movement of the bushing in an opposite or inward direction toward the piston I 2 is limitedby engagement of projections 5| with mating projections 49a on a 1 1. iikey di li e ndw s W t a ta n.- .irhws W A qr er a iu ne w .3 is threaded on the plug 49 and held against endf P ait? qiu t sk p fl 9 w 21 42 mm el is isa .ni i by. a e i th se q pel e ii t ab imen s tiaqe .4 and lp i qii s. 42 eiihailihe l n theimrmfliedsix kel gr the p. bu hing-J1 .i r sbandin ly a lst d. i.

,.,\;. .t e o ter nd 9f thestop.bushin .l a c nh .2. s. provid dut wwhic re sure. fl i is. sup,- n i din mann r, er in it rs escribed s tha the pr ss r f su ...fl d,: u m n e by aispr ne 46,..n rmall ,.urg s the. op bushi ar h -pistonl2 whose mo tion it intercepts. {Fig. jfi),

vSlidable axially within the bushing l isjthe stem 53a" of a disk-shaped valveelement ,5?! which seats on" an annular seat 58 formedvon the outer face'of the bushing. The valve element is urged into "seated position by .a' compression spring, interposed between the bottomhof a bore'iin the plug 49 and theo'uter face-of the'valvediskfl. .Whenthe valve element 53 is unseated',-pressufe fluid" passes by "the same and out a" 'passa'ige 59 from the chamber 52 to condition .the"contro1 circuits hereinafter described so that upon the next stroke of the work table I the'chambr '52 wi 11'-be=exhausted, thereby permitting the actuator piston rzj to ro ethe bushing [1 to the'left'and againstjtheabutmeht' face 48 for the last step of advance'of the actuator piston; i

Asjthe actuator piston approaches the stop "fig n the parts occupy the relative "p" ishown Fig; 6, the'biishin bing' yil'd any urgedfiowa rd the actuator piston by the t awamnes a-n imiw em'aw b 525-. n'i d u efq ili m tg j 1 5 step lof' ad nee-of the ectuator piston f2" the litter l ts .ans .I IdfiLfii' W -Idi. plunger 5 3a' ther'by unseatingjtlfefvjalve c vmmodat is i hg qtionqih ilfunsir fita'is ens on d' pi n a't i, t it an' i chlb d t e f ce D? .1 sla h n t in a h en v menace thelastistep offadvance of the actuator piston .thepartsfcoiiieito restin' the positi; hown in File 7., n thella tterpositioiijthestopbushingjf is s illtlii usfito thefright;intercepting the'p st l2" in the desired'position for institutiolrf'o laet stepior the latter. Even though th yalv'e for th 'lasti'stepiof. advanc s'tillfthe 'pressiire"has not heri' relieved in hamber 152' so: the; bi i isi" is still df f i s u e. are" it matin'g'p'rojectionflgi As her t ielcb' n etiorl or 'th ext stroke; of the work table results-in the :ekhaust' of 'fiu'id from the chamber 52; whereupon the actuator vpistc'yni.it s free dtothrust the stopbushirig" I'Lt'o the left against the abutmentfaces' 48 for the last: Step of; advance of the actuator piston. In enti y th r id-a u ent 48 .li 'ii ve r' d fi 'r' n .ti final position of thlactuatorpiston Ig ana, a simple s in t i ei c p he a vs mm knob 56a determines the length of such last step of piston advance.

A'zztoifiittic ri'ieisdl O ni 'o i th flv v 53 a' ide 'n b i in the course of the next to the last step of advance for ;the actuator piston not only conditions the circuit for retreat or -the stop bushing] 1. as indica ted, but in addition s i s ,9 the C'i cuitsfofiim interrelated control valves which takes place,

preceding and as an incident to reversal of the slide I is shown generally diagrammatically in Figs. 9 to 12. Fig. '9 exemplifies the conditions prevailing during rapid approach movement of the slide. Fig. 10 exemplifies the circuit conditions at the completion of the next to the last step of advance, thus matching Fig. 7; while Fig. 11 shows the circuit conditions prevailing after the last step of advance of the slide, but during the succeeding stroke of the work table, thus matching Fig. 8. Finally, Fig. 12 shows the fluid flow in the control circuit after the last stroke of the work table.

Included in the portion of the circuit to be considered in connection with reversal and the delayed action control thereof are, in addition to the reversing valve l3 and feed valve l5 already identified, four pilot valves 54, 55, 55 (Figs. 9 to 12) and 51 (Figs. 11 and 12). Each of the additional valves noted is fluid operated, all being of the sliding plunger type, and of them the valves 54,55 and 51 are two-position valves, while the valve 55 is of the three-position type, having a normally centered plunger.

In brief, the arrangement is such that the pilot valve 54 is shifted in response to completion of the next to the last infeed step of the actuatorpiston I2. Thereafter the pilot valves 55, 55 coact to delay withdrawal of the stop bushing until after'one further stroke of the work table i and to delay operation of the valve 51 (which controls the reversing valve |3) until after two further strokes of the work table.

the same irrespective of which of the intermittently reversed lines 2|, 22 happens to be connected to pressure at the time When'the next to the last step of infeed is completed.

Attention may now be given to the successive conditions of fluid flow diagrammed in Figs. 9

to .12. During rapid approach of the actuator piston l2 (Fig. 9) the feed valve l5 dispatchesfluid from the pressure line l8 through a branch conduit 29, to the valve 54 so that the latter is shifted to the left. With the valve 54 in the latter position, pressure fluid from the line I8 passes through an annular peripheral groove 65?;

in valve 5 1 (see Fig. 13) and thence through the branched conduits 60 to the chambers 50a at opposite ends of the valve 55, thereby centering the latter.

the line it through line 55 to the chamber 53- located at the outer face of the stop bushing l? as heretofore described. The pressure fluid thus supplied to the chamber 52 urges the stop bushing i! toward the actuator piston l2 in position to intercept the latter at the completion of'the next to the last step of the step-by-step infeed which is to follow. By connections which will later The pilot valves are coordinated so that the action shall be Pressure fluid in the conduit 6|) also shifts the valve 56 to the right, the right end of 10' appear (Fig. 13) pressure fluid in line 69 also shifts a valve 5'! to the right.

Upon the dog operation of the feed valve l5 to change from rapid approach to step-by-step infeed movement in the manner heretofore described, such shift of the valve l5 connect the line 29 to the exhaust line l9 and disconnects it from the pressure line I8. At-that point in' the cycle both ends of the valve 54 are thus connected to exhaust so that it remains in the positicn to which it was shifted by the previous application of pressure shown in Fig. 9. At the end of the next to the last step of infeed for the actuator piston l2, the valve 53 is, as heretofore explained, opened by contact of the piston l2 with the end of the valve stem 53a.

Such opening of the valve 53 directs pressure fluid from the line and chamber 52 into a" line 59 leading to one end of the pilot valve 54. The opposite end of such valve 54 having been previously connected through line 29] to exhaust, the valve 54 is shifted to the right. The

shift invalve 54 results in connecting line to pressure, to one of the ends of the centralportion of the valve through the corresponding one of lines 6|, 62 and connection of another part of such central portion of the valve 55 to exhaust through the other one of lines BI, 52 and the other of the pair of lines 2|, 22."

, The central portion of the valve 55 is constructed in a manner such that application of pressure through the line 2| and exhaust through line 22 causes it to shift to the right and, con

versely, application of pressure through line 22 and exhaust through line 2| shifts the valve 55 to the left. But in either case, whether the valve 55 is shifted right or'left, it connects to the exhausted one of the pair of lines 2|, 22, a

line 55'leading from the right end of the final collars or lands 53 and is disposed within a central chamber 54 in the valve housing. The lines 5|, 52 open into the central chamber 6 at points spaced apart slightly more than the spacing of the collars 63, whereas the line to the right end of the valve 55 opens into the centerof the chamber of valve 55 and lines 68, 69

lead from spaced points in such chamber.

The cooperatin pilot valve 54'has an axial bore 54b in its plunger 54a, such borebeing'; always connected to exhaust line l9 by transverse passage 540 in the valve plunger. Such transverse passage 540 also registers with'line' 52, as does a second transverse passage 54d with line 5!, so that both lines 6|, 62 are exhausted."

5|, 62, and chambers 6511 at the ends of valve 55 are connected to exhaust line l9: through line' 69.- a transverse bore Ste in-theplunger of valve Pressure fluid is dispatched from f 54, and the axial bore 54b. in the latter. Accordingly, should pressure be available in line 2| the plunger of valve. 55 is shifted to the right, while if pressure is available in line 22 such plunger is shifted to the left. Ineither case the one of the lines having pressure in it is connected to the correspondin one of lines 68, 69 while the other or exhausted one of lines 2|, 22 is connected to line 65.

The net efiectof shifting the pilot valves 54 and 55 as just described (see Fig. is, as-

noted, to connect the right end of the third pilot valve 56, through line 65, to the one of the lines 2|, 22 which is at the moment exhausted. That does not result in any shift of the valve 56, for its right end was previously connected to exhaust through conduit 61 and an annular pee ripheral groove (see also Fig. 13) in the plunger 14b. The latter connection is, incidentally, interrupted by the shift of thevalve 55. But the newly established connection to the valve 56 does insure'its actuationupon the next succeeding reversal of pressure in the lines 2|, 22. Accordingly, when the table I completes .its next stroke (i. e., for the last roughing cut in the cycle of operation ofrthe grinding machine) the consequent reversal in pressure in the lines 2|, 22 causes the valve 56' to be shifted to the left (Fig. 11)

Buildingup of undue pressure in the line 24 from the actuator cylinder is prevented after contact of the piston I2 with valve stem 530. by arrangingthe. pilot valve 54, when shifted to the right, to connect line 24 to exhaust (Fig. 13). Thus a cross passage 90 in theplunger. of valve 54connects line 24 to exhaustline I9 through the central bore 54b.

The first result of shifting the pilot valve 56 to the left is to establish a connectionthrough it from the chamber 52- to exhaust so that thestop I'I is-withdrawn to permit the final infeed step of the actuator piston I2 (Fig. 11). For thatpurpose the line 45.1eadingfrom the chamber 52 is connected to the exhaust line I9 through an an nular peripheral groove 56b in the plunger 56a of the-valve 56 (see Fig. 13).

A secondary result of shifting the pilot valve 56 is to establish a connection for actuation of. the reversing valve 5'! upon completion of the next or final stroke of the work table I (Fig. 12'). At the completion of such final table stroke (i. e., for the final finishing cut on the. work in the cycle of the grinding machine) pressure conditions in the lines 2 I, 22 are again reversed (compare Figs. 11 and 12). Accordingly, if line 2| istheone of the pair put under pressure at that time, as is. the condition indicated in Fig. 12, pressure fluid is supplied from line 2 I, through valve 54, line 6|, valve 55 and line 68 and valve 56 to a-line III leading through a valve 66 and line 8| to therighthand end of the valve 51, lines 68 and I0 being interconnected through an annular peripheral groove 560 in the plunger of the valve 56 (see Fig. 13). Thisshiftsthe plunger 51a of the valve 5T to the left, its left end being connectedtoexhaust through line 60 and valve 54. Similarly, if pressure happens tobe applied to line 22fat such time. pressure fluidwill also be supplied to line 16 with like result, but this time through valve 54, 1ine.62, valve 55, and thence through line 69 and the annular groove-56c'in valve 56 (Fig. 13).

Shiftingof thev valve 5'! to the left asdescribedl causesthevalvefl to be Shifted/5011135 [reversin position and the feed valve I5 to berestored toits initial or rapidposition (Fig. 12).. Thuszvalve 51 applies pressure from the pressure line I8 through the line 13 and a choke I2 to achamber at the upper end of the plunger of the valve I3 to force the same downward. Pressure fluid is also supplied to a chamber at thelower end of the actuatingpiston 14 of the valve I5 to thrust the plunger 26 of this valve outward, such pressure fluid being applied through line 13 and a choke I2 as Well as from the. pressure passage 19.

and a. choke 9| after the'valve I3 has shifted. The purpose of the chokes 12.and 9| is to make it possibl to supply line.'|3 via either the valve 51 or I3. The valves I3 and I5 are thus conditioned for rapid return movement of the slide in the manner heretofore described in connection with Fig. 5,

It will thus be seen that the stop I! is Withdrawn an the slide actuator I2, I2a reversed in proper sequence, and all in carefully coordinated timed relation with the intermittent reversals of pressure and exhaust in lines 2 I, 22 occasioned by reciprocations of the Work table 1.

Manual control If desired, the machine ma be operated by manual control of the advance of the slide I0 rather than with an automatic cycle of successive steps as described. Such operation is especially required for obtaining the initial setting on the size wheel I69, while setting the machine to a new work piece. In such manually controlled infeed'of the slide the size control wheel I69 (Fig. 1) is turned a desired distance for each successive step. To'condition the machine for such manually controlled operation, two valves ar utilized in addition to certain of those heretofore noted; namely, an automatic" feed disconnect valve 66 and a size pick-up valve '81 (Fig. 13).

The'disconnect valve66isa simple manually operable twoposition rotary valve. When'inits automatic feed position shown in Fig. 13, itconnects line Ill to line 8| for supply of pressure fluid for shifting the valve 51 at the appropriate point in the cycle, as heretofore described. Turngrooves 92c, 92d and 92e in the plunger are interconnected by an axial bore 92f in the plunger,

grooves 920 and 92dhaving the same spacing as portsfrom the lines 25 and I9.

Assuming the slide I0 is withdrawn its full distance, the machine is conditioned for manual operation by turning-thevalve 66 to connect line 8| to exhaust. The valve I3 is then shifted man ually to its forward position, whereupon the slide advances rapidly, just as in the automatic cycle, until the valve Ifi'is-tripped. Then the operator pushesinvalve 8], connecting line 25 to exhaust so that the-advance of the piston I2 continues without interruption until it comes up against the stop bushing IT. The direction of travel for the table "I is reversed manually. This will exhaust chamber 52 causing piston I2 to be shifted to the maximum forward stop position. Either desired subsequent advanceof the wheel slide It! forgrinding or location of the wheel slide at a desired finalstopped position maybe obtained byturning theslzewheel I69. If it is desired togrind automatically, after the size setting is thus established, valves 66 and I3 are shifted, dog 35, knob 50a and pin 38 are adjusted, and the machine is ready for the automatic cycle.

The valve 81 may also be used in effecting rapid restoration of the wheel slide III to a previous operating position after interruption of the automatic cycle. Should it be necessary to withdraw the grinding wheel at any time during the automatic infeed, the operator need only shift the valve I3 to its reverse position by means of the rotary operating device I3a (Fig. 13) having thereon an eccentric pin l3b received in a slot in the side of the plunger I3c. Then to restore the wheel to its previous position, the slide need not be advanced step-by-step in alternation with strokes of the table. Instead, the valve I3 is shifted manually to its advance position, and when the rapid advance of the slide has been terminated by tripping of the valve I5, the operator pushes in the valve 81. As previously noted, this connects line 25 to exhaust so that the slide piston I2 advances rapidly. When the operator observes that the grinding wheel is approached close to its previous position, he releases the valve 81. The latter is thrust back out by the biasing pressure from line I8, thereby interrupting the connection of the line 25 to exhaust, and the system resumes its normal automatic stepby-step advance of the wheel slide.

Leakage prevention in metering circuit Step-by-step advance of the slide I is, as heretofore described in connection with Figs. 3 and 4, accomplished by metering out successive increments of fluid from the actuator cylinder In via the lines 24, 25 and metering plunger I5. In the event that each step of advance is but a few thousandths of an inch, as is the case in a grinding machine, even a small volume of fluid leaked from the metering line or circuit would result in a large percentage error in the length of the step. Even in instances where longer steps are used, precision results depend upon the prevention of loss of fluid from the metering line.

Examination of the detail of the path of fluid through the metering circuit (see Fig. 13) reveals sliding surfaces, along which leakage might take place, at a number of points, viz.: along the piston I2, the stop bushing II, the plunger I30 of the valve I3, the plunger 26 of the valve I5, plunger I 411 of the valve I4, the plunger 54a of the pilot valve 54, and along the metering plunger I6 itself. Even with precision fitting which should be used for these sliding parts, some leakage would tend to occur.

The general plan followed in preventing leakage from the metering circuit along the various sliding parts noted is to maintain the metering circuit pressure substantially equal to that in some available source of pressure fluid, here the pressure line I8, and apply pressure'from the latter at the sliding parts in question in a manner to counteractany tendency of fluid to flow out of the metering circuit between the sliding surfaces and thus to prevent leakage therealong.

To maintain the pressure in the metering circuit equal to that in the pressure line I8, the active faces of the piston I2 and active face of the plunger II are suitably dimensioned. This is relatively simple in a grinding machine, diamond boring machine, or the like since the load or resistance to the tool oifered by the work is very uniform as well as being substantially ne li iblein comparison with the positioning pressure 14 from the plunger I I. Accordingly, the area of the plunger II is but slightly less than the differential in area between the two faces of the piston I2, the plunger having been shown as exaggeratedly small in the drawings for the sake of clarity. In machines having heavy work resistance, the same can be compensated by dimen= sioning piston I2 and plunger II or by making some exterior provision for fluid pressure control. It will be understood, of course, that the reference herein to maintenance of pressure in line z iedual to that in line I8 has to do only with the feed portion of the cycle (Figs. 2 and 3), for in rapid approach the line 24 is exhausted (Fig.

With the pressure in lines I8 and 24 equalized as described, the fluid pressures, that is, the

forces per unit area, on opposite faces of the piston I2 are balanced so there is no tendency for fluid to leak past it from either and to the other (see Fig. 13). Pressure from line I8,"via line 23, is also applied to annular interconnected grooves Ila and ill) in the stop bushing I! so that leakage along it is likewise prevented. In this way leakage of fluid trapped in the cylinder Iila on the advancing side of the piston I2 is prevented and all of it forced to emerge from the cylinder into the line 24.

Following down the line 24 (Fig. 13) it will be seen that in the valve I3 the valve ports are formed in a stationary sleeve l3d fixed in the casing I3e and receiving the sliding plunger I30. When the plunger iSc is in its upper or advance position shown, a peripheral groove I3 therein 1 connects lines 2!: and 25. In the plunger I3c on opposite sidesof the annular passage I3) are transverse. passages, interconnected by a longitudinal bore 'ifia and to which pressure fluid is supplied from the line I8 through the peripheral annular groove I 3y which also supplies fluid to the line 23. The length of the groove I39 insures registry of the same with the port of line I8 in either position of the valve plunger so that pressure is always applied in as, '59 from the line 18.

' Such provision of fluid at 18, I9 equalized in pressure with that in lines 23, 25 efiectually prevents leakage from the latter along the valve plunger I30.

Similar precautions against leakage are taken in the valves I l, I and 54 (see Fig. 13); Thus in the valve I4 the valve plunger Ida is provided with two peripheral annular grooves Mb and I40 which serve to connect the lines 36, 3'5 leading from opposite ends of the metering plunger cylinder a, respectively, to lines and I9 in alternate positions of the valve plunger; To guard against the leakage of fluid from the line 25 along the valve plunger Ida from either of the passages Mb or I lc pressure fluid from the line I8 is supplied to transverse passages 88 in the valve plunger through a longitudinal bore BI and an annular peripheral passage 82 in the plunger. ihe latter passage 82 is long enough to register with the port from the line I8 in either of the alternate positions of the plunger Ma;.

and the transverse passages 88, leading to annular peripheral grooves, are located on respective opposite sides of each of the annular passages I-ib and Me.

In the valve I5 pressure fluid from the line I8 is supplied to opposite sides of the port from line 25 to annular grooves 85 and a surrounding the valve plunger, on opposite sides of the port from line 25. In the pilot valve 5!! pressure fluidzrl from the line as is directed into ports which,

when the valve plunger is in its left position:

shown, register with annular grooves-'86 located in the valve plunger onopposite sides of the portv leading from the line 2-4;

In the case of the metering; plunger l6 and its associated adjustable stop pin 38, pressure is applied from the line l8 to annular grooves 83 and 84 surrounding respective ones of the same to prevent leakage along them.

I'claim as my invention:

1. In a hydraulic system: for effecting a stepby-step relative movement of apair of members, the combination of a piston and-cylinder type fluid actuator, means for withdrawing metered increments of fluid from the cylinder to efiect successive steps of advance of the piston within the cylinder, means including a movable stop for intercepting the-advance of the piston, means for'adjustably limiting movement of said stop both toward and away from the piston in the directionof piston travel, means for urging said stop to'its limit of movement toward the piston, and means responsive to completionv of the advance ofthe piston forward into juxtaposition with s'aid'stop for freeing'the stop for movement to its opposite limit position under the thrust of the piston in asubsequent and final step of advance of the latter, whereby the setting of the limit positions of the stop by said adjustable limit means determines the length of said final step of advance for the piston.

2 The combinationwith a piston and cylinder type actuator, and means for withdrawin determinate metered increments of, fluidv from the cylinder to effect successive steps of relative advance for the piston: within the cylindenof stop means positionable in response .to fluidpressure for adjustably predetermining the length or only the last step inthe series,

3. The vcombination with a piston and cylinder type actuator, and means for withdrawingmetered increments. of fluid from the cylinder to effect successive steps of relative advance for the piston within the cylinder, of adjustable stop means positionable in response to fluid pressure for predetermining the length of the last step in the series and positively arresting further advance of the piston upon the completion of said last step.

4. The combination of a piston and cylinder type actuator, means for supplying pressure fluid to one side of said piston and for intermittently withdrawing determinate meteredincrements of fluid from the cylinder at the opposite side of said piston to effectsuccessive steps of advance for the piston relative to the. cylinder, adjustable stop means positionablein response to fluid pressure. for predetermining the length of the last step in the series and for positively arresting further advance of the piston upon completion of. said last step. and means rendered operable upon completion of such last step of advance for automatically initiating a change in the pressure fluidconnections to effect an uninterrupted supply of pressure fluid to said'other side of the piston and an uninterrupted exhaust of'fluid from said cylinder at said one side of the piston to thereby effect a substantially continuous relative movement of said piston and cylinder in a direction opposite to said stepped advance.

5. In a delayed action hydraulic control, the combination with a fluid operable valve, a pair of fluid'conductors, and means for intermittently connecting alternate ones of said conductors to a source of pressure fluid and the remaining one to exhaust,. of means including; a second. fluid operable valve shiftable alternatively inopposite: directions from-an initial mid-position upon ap-- plication thereto of pressure fluidfromzcorre sponding ones of said conductors for connecting the other or exhausted one of said conductors-in each case tosaid first valve.

6. In a delayed action'hydraulic control, the combination with a fluid operable valve, apair: of fluid conductors, and means for intermittently; connecting alternate ones of said conductors toa source of pressure fluid-and theremaining-mneto exhaust, of means operable upon actuation: thereof for establishing a connection-to said .valve;

- fromtheone of said conductors whichlislat the moment of such actuation exhausted and: for: maintaining such connection throughout atl'east. the next succeeding alternation in' pressure and: exhaust conditionsinsaid conductors.

'7. In a delayed' action hydraulic"controhthe combination of a pair of fluidtcon'ductors;means? for intermittently connecting alternate: ones: of; said conductors to a source of pressurev fluid and the remainingone'to exhaust, a; first fluid oper-= able valve, means includinga second fluid op'er able valveshiftable'alternately in opposite'dire'ctions from an initial mid-position upon app1ication thereto of pressure fluid from corresponding ones of said' conductors for: connec't'ing'the other or exhausted one of said'conductorsin each case to said first valve, means for shifting said first valve from a first position thereof to a second position upon application thereto of pressure fluid at the next succeeding alternationiof pres-- sure and exhaust in said conductors following a shift of said second valve, and means operable in response to shiftof said first valve from said first to saidsecond position thereof for establishing a connection to said third valvefrom the one: ofsaid conductors which isexhausted in said next succeeding alternation of pressure and exhaust conditions, whereby pressure fluid will be supplied through the last-mentioned connectionto said third valve upon the second succeeding alternation in pressure and exhaust condifions following the shift of said second valve.

8. The combination of a pair of fluid conduc'-= tors, means for intermittently connecting alternate ones of said conductors to a source of pressure fluid and the remaining one to exhaust, a fluid operable valve, and control means operable upon actuation thereof for establishing a con-' nection to said valve for the supply of pressure fluid thereto for actuating the same from one of said conductors only after two alternations in pressure and exhaust conditions in said conductors have followed such actuation;

9. In a delayed action hydraulic control, the combination of a member shiftable between alternate limit positions, means defining a fluid pressure chamber for moving said member from one of said limit positions to the other upon application of fluid pressure to suchchamber, means defining, a relief passage for relieving the pressure in said chamber, means including a first fluid operable valve shiftable between alternate positions for opening and closing said relief passage, a pair of fluid conductors, means for intermittently connecting alternate ones of said conductors to a source of pressure of fluid and the other to exhaust, means for shifting said first valve to its relief-closing positiomand means including a second fluid operable valve shiftable in respective opposite directions upon application.

thereto of pressure fluid from corresponding ones of said conductors for connecting the other of said'conductors to said first valve to apply pressure fluid to the latter in a direction to shift the same to its relief-opening position upon the next succeeding reversal in exhaust and pressure conditions in said conductors.

10. In a delayed action hydraulic control, the combination of a member shiftable between alternate limit positions, means defining a fluid pressure chamber for moving said member from one limit position to the other upon application of fluid pressure to such chamber, a pair of fluid conductors, means for intermittently connecting alternate ones of said conductors to a source of pressure fluid and the other to exhaust, and means operable upon actuation thereof for relieving the pressure within said chamber in response to the next succeeding alternation in pressure and exhaust conditions in said conductors following such actuation.

11. In a delayed action hydraulic control, the combination of a fluid operable valve, a pair of fluid conductors, means for intermittently connecting alternate ones of said conductors to a source of pressure fluid and the remaining one to exhaust, means including a second fluid operable valve shiftable alternately in opposite directions from an initial mid-position upon application thereto of pressure fluid from corresponding ones of said conductors for connecting the other or exhausted one of said conductors in each case to said first valve, and a third valve shiftable between alternate positions in which it respectively connects and disconnects both of said conductors to said second valve.

12. The combination of a movable member, means including a reversible hydraulic actuator for traversing said member reversely to and fro along a predetermined path, a movable mechanical stop positionable in response to fluid pressure and interposed in said path to yieldably intercept the motion of said member in one direct'on along the same, means for automaticaily initiating a reversal of said actuator in response to interception of said member by said stop, and means manually operable at will to disable said reversing means, whereby said actuator continuously urges said member against the stop after interception of the member by the stop, and manually operable means for adjustably varying the stroke of said yieldable stop along said path.

13. In a hydraulic system, the combination of a piston and cylinder type actuator, a stop member located at one end of said cylinder in position to intercept the relative advance of the piston toward said one end of the cyiinder, means including a pair of rigid abutments for defining respective limit positions of movement of said stop member axially of the cylinder, means for applying pressure fluid to the outer side of said stop member to urge the same into its limit position toward said piston, means including a valve for initiating relief of such pressure on said stop member, and means positioned for contact by said piston upon approach thereof to said stop member for actuating said valve.

lei. In a hydraulic system, the combination of a piston and cylinder type actuator, a stop member located at one end of said cylinder in posilieving said fluid pressure on the stop member in response to the next succeeding alternation in pressure and exhaust conditions in said conductors following the opening of said valve by said piston.

15. In combination, an actuator cylinder having a piston slidable therein with a piston rod projecting from but one face of the piston, a stop bushing slidably mounted in the end of said cylinder adjacent the other face of said piston, means including 9. pair of rigid abutments engageable with said bushing for limiting its sliding motion axially of the cylinder, means for applying pressure fluid to the outer end of said bushing to urge the same toward said piston, a valve element having a stem slidable in said bushing and projecting from the inner end thereof in position to be contacted by said piston as the latter approaches the stop bushing, and means for initiating the relief of said fluid pressure on the stop bushing in response to actuation of said valve element by contact of the piston with said stem.

16. In a hydraulic system, the combination of a piston and cylinder actuator, means for withdrawing metered increments of fluid from the cylinder to effect a step-by-step relative advance of the piston within the cylinder, and means for maintaining during a portion of said stepby-step advance a substantial equalization of pressure on opposite sides of said piston to prevent the leakage of fluid past the same.

17. In a hydraulic system, the combination of an actuator including a piston and cylinder, a metering device including a plunger and cylinder, means defining an outlet passage from said actuator cylinder to said metering cylinder for withdrawal from the actuator cylinder of a metered increment of fluid corresponding to the displacement shift of said metering plunger upon each stroke of the latter, and means for maintaining during withdrawal of said metered increment of fluid a substantial equalization of pressures on opposite sides of said piston as well as for applying fluid to the periphery of the plunger intermediate its ends at a pressure substantially equal to that of the fluid entering said metering cylinder from said actuator cylinder.

18. In a hydraulic system, the combination of minate successive increments of fluid, a movable valve element. interposed in said passage, and

means for applying to said valve element fluid under a pressure substantially equal to that in said passage and such application being at plural REFERENCES CITED The following referencesareof record in the; file' of this' patent:

UNITED STATES PATENTS Number Name Date 448,277 Ta-ylor Mar. 17, 1891, 526,930 Maxon Oct. 2, 1894 637,461 Hartness Nov. 21,v 1-899 Number 639 651,502 882,889

20 Name Date; Leavitt ;Dec,. :26, 18992 Fitzgeraildau \June'1'2,.190.0' Hoxie Mar. 4, le9fi8 Heald Apr; "257', 1926- La ussucq; 3:926: Ernst Aug. 25",-.1'93if Speck Sept. 15932 Ernst Apr; 156,1 9.35- Maglottkfluuuu- Aug. 23 .1933 Keel May -9, H1939. Daugherty Oct. :31, .1949 :DBJViS' 53711.. 5?;13945 Waldie Feb. 5;, 19k?!

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