US2417714A

US2417714A - Thread grinding machine

Info

Publication number: US2417714A
Application number: US495162A
Authority: US
Inventors: Stewart Gilbert; Brinkmann Guenther; Harold N Seyferth
Original assignee: Ex-Cell-O Corp
Current assignee: Ex-Cell-O Corp
Priority date: 1943-07-17
Filing date: 1943-07-17
Publication date: 1947-03-18
Anticipated expiration: 1964-03-18

Description

March 18, 1947. s. STEWART ET Al. 2,417,714-

THREAD GRINDING MACHINE Filed July 17, 1943 11 Shuats-$hut i [anemic/as h 8 Qlzberfi Sieuxari Guenfker Brzkkmann Harald 4V2 figferdh m-rras uga-as Q March 18, 1947. e. STEWART ETAL 2,417,714

THREAD GRINDING MACHINE li werdors Gilerf Sfewar Guenlzer Brinbnazm Harold M Sfzyferih ,ax 02 44 49.? MAJ-.

jlwbma-m March18, 1947. @STEWART ETAL 2,417,714

THREAD GRINDING MACHINE Filed July 17, 1943 11 Shats-Sheet 3 Q Q W L 3 n N n I at a Q 0 g is r Q? 3 i N T I 9 rm 'm 1% Q a a m a I Q n l w I s a T I E =0 w 5 5'3 53 .5: 3 i S I EN g 'o i ,3, 3: 2 Q a jizaezzfora P3 9 Gilbert Steam/e15 3 uenfberfi'inkmann March 18, 1947. STEW RT ET AL 2,417,714

THREAD GRINDING MACHINE Filed July 17, 1943 11 Sheets-Sheet 4 Gilberi Siewarf Guexzilzer Brz'rzkmarm HaroZZ fl LS yferh- March 18, 1947. 'G. STEWARTETAL "minim x mmnme momma Filed July 17, 1943 r 11 Sheets-Sheet 5 March 18, 1947 STEWART g- 2,417,714

"rams/m GRINDING VIACH'INE Filed Jul 17. 1943 11 Sheets-Shoot 'r [raven fans Gilbert Stewart Gus/tiller Brinkmaan Harold Ms yferflz I wronqgpas Man-ch18,- 1947. G. STEWART ETAL 2,417,714

' THREAD amunme momma FilQ-July 17. 1945 11 Shasta-Sheet a In uniors Gizber Stewari GuenJ/zer Pinkman/z Harold M-Sgferih PW OTTO QLE-m s," STEWART. ET AL 2,417,714

THREAD GRINDING MACHINE Filed July 17, 1943 11 Sheets-Sheet 9 March 18, 1947. e. STEWART ETAL 1 4 7 THREAD GRINDING MACHINE Filad July 17. 1943 11 Sheets-Sheet 1o [rzzneazzzlora Gilber 66ewar Glue/like! Brzhkmann CATTOWJ v mean M n a. 1947 a UNIT STATES, PAT

p \GilbertTStewart.and"Guentherlirinkmann.

i troit, and liaroldjN. Seyferth,1 East Detroit,

I Mich assignors to Ex Cell-0 Corporation, De-

. troit, Micla, a cerporation ofM ichigan Application-July 17, 1943, Serial No. 495,162

recla ms. (01. 515-95 The present invention relates toima chine tools; and has particularyreference to thread grinding machines. q

One of the objects of the inventionisi toprovide a novel thread grinding machine which may be operated with an automatic cycle, andg which embodies. a simp1ifled and comparatively inexpensive. structure for effecting wheel feed, dresser feed, wheel retraction and advance, andtaper adjustment. f5;

A more specific o bject is toprovide a new and improved thread grinding machine inwhich an .valve panel forming part of a hydrau1icidrive stant-ially alongline, e-sor Fig. 4.

Fig. 515a fragmentary plan viewtaken sub .Figgs is a detail verticalsectionalview taken. substantially-alongline 8-- 6of Fig. 4. view of the cross feed anddresser teed mecha Fig. 7 afragm ntary horizontal sectional nisms.

Fig. 8is' aliragmentary longitudinal vertical sectional, view of the dresser ieed mechanism.

Fig. 9is afragmentary plan view of a control transmission for thework table and spindle.

movements of the grinding" wheel are effected? through. a single wheel. slide, and in which wheel retractionand' advance and taper adjustment are imparted through an actuating linkage to "the wheel slide without ment. 1

Anothen object is to provide a novel thread grinding machine having a 'cOmbined hydraulic and mechanical drive for rotating and translat-' ing the work spindle in timed relation and in which the drive is subject toselectivefspeed variation at different points in the rnachine cycle." for example, to vary the speed selectively tor a series ofrough grinding passes; over the thread altering the infeed adjustproper, one finish grinding pass over the thread Other cbjectsand advantages willbecome'ap- 40 parent as. thedescription proceeds.

In the, accompanyingldrawings,

Figure l. is a front perspective view of grinding machine invention:

[with a Fig. 2 is a rearperspectiireview of themachinei Fig. 3 is a fragmentary transverse vertical sectional view of thecross feed mechanism of the machine.

Fig. 4 is a fragmentar ammothint V of the crossfeedmechanism.

view of. the work spindle head.

tend ,tolimitthe inventiontothe specific form mbodying the features of our" Fig, 10 is a side elevational view of the control valve panel shown in Fig a. h

Fig. 11 is a transverse vertical sectional view of; the valve panel. taken along line lI-ii of Fig.110.x

is a vertical sectional view through the valvepanel taken along line i2--i2 of Fig. 11." J 1 Fig. 13 is a diagrammatic representation of the hydraulic transmission and control circuits for thework table and spindle drives. l

- Fig. 14 is a diagrammatic.representation oi th hydraulic transmission and control circuits for the entiremachine.

Fig. 15 is a diagrammaticrepresentation oi the mechanicaiand hydraulic drives of themachine.

.Fig. .16 is a diagrammatic representation 01 I the electric control (-ircuitsfor the machine.

Figi 1.71s a fragmentary longitudinal sectional Whilefthe invention is susceptible oi various modiflcationsfiand alternative constructions, we have shown in the drawings and will hereindescribe in detail the preferred embodiment, but it is to be understeod that we do not thereby indisclosed.ybut intend to cover all modifications and, alternative. constructions falling within the spirit and scope oithe invention as expressed in the appended claims.

Referring more particularly to thefdrawings, the machine constituting the exemplary embodi merit of the invention'is adapted for grinding screw threads on various types andtorms of workpieces, and in the present instance a work blank W. of an aircraft engine cylinder barrel is shown. I

The machine comprises an elongated horizon tally disposed main base I formed on the top".

E NT omcs reciprocatory work table 3, and having a rearward extension 4 formed with a set of transverse ways 5 for supporting a tool head 6, A rotary tool spindle 1 is mounted in the tool head 6 for rotation on an axis extending generally longitudinally of the table 3, and supports a suitable grinding wheel G.

A headstock or work head 8, and a suitable tailstock 9, are mounted in longitudinally spaced relation on thevtable 3 for reciprocation therewith. Journaled in the headstock '8 is a work spindle l having a chuck II in which one end of the work blank W is secured for rotary drive. The other end of the blank is'rotatably supported by the tailstock 9. mechanical drive transmission is provided for translating the table 3 and rotating the work spindle In in timed relation and in forward and reverse directions at different selective speeds;

Thus, the work blank W is adapted for rotation and translation axially through cutting engage-.-

ment with the rinding wheel G in timed relation to the rotation as determined by the lead of the thread orthreads to be ground.

The tool 6 is shiftable transversely of the work spindle 10 either forwardly to locate the grind-" in'g' wheel G in operative grinding position, or rearwardly to locate the wheel inidle or retracted position. A cross feed mechanism 12 is provided for automatically 'adJustingthe operative grinding position of the wheel G step-by-step in timed relation to the successive working passes of the work spindle l0 until the blank W has been ground to final size. The shifting of the tool head 6 is effected by a retract mechanism l3 which isautomatically operable to separate'the grinding wheel G laterally from the blank W for each rapid traverse return'movement of the table 3 without changing the setting 'ofthe cross feed mechanism. A taper mechanism I4 is optionally available for automatically superim posing ataper adjustment .on the infeed position of thegrindin Wheel G in timedrelation to the longitudinal traverse of the table 3 'as-determined by the form or degree of taper desired on the work.

Mounted on the tool head 6 atthe rear of the grinding wheel G is a suitable dressing mechanism l for dressing or truing the grinding surface. The dressing mechanism 15 is automatically operable at selected times in'the machine cycle, and in each operation serves to effect a dresserfeed'ofthe dressing tool or tools toward the grinding wheel, and simultaneously a compensating feed of the tool head 6 toward the axis of the work spindle i0 so as to compensate for the reduction in diameter of the grinding wheel G. v i The operation of the machine is controlled by a combined hydraulic and electridsystem in which the movements of the main'units are interlocked and timed, and which is selectively adjustable to obtain different automatic machine cycles. In one illustrative cycle, adapted for grinding the threads on aircraft'engine cylinder barrels. the work table 3 is reciprocated a predetermined number of times, each reciprocation consisting of aforward grinding pass at a relatively slow speed and a return stroke at a rapid traverse speed. For example, there may be five roughing passes at a fast grinding speed and a final or finishing pass at a slow grinding speed. At the end of each roughing and finishing pass, the grinding speed isredu'c'ed during A combined hydraulic and the final work spindle revolution or preselected portion thereof if the incomplete thread convolution on the leading end of the work blank is to be removed. The spindle I0 i always rotated in timed relation to the table traverse, and is reversed upon each reversal of the table. At the,

ment into retracted position after any desired number of grinding passes, for example after the first and third roughing passes, and again after the fifth roughing pass before the final or finishing pass. In each dressing operation, the dressing cycle is initiated at the start of the retract movement of the tool head 6, and continues during the following free return movement of the work head 8, and if necessary the table 3 will dwell at the end of the return movement topermit completion of the cycle. The dressing cycle comprises a feed of the dressing mechanism l5 toward thegr-inding wheel G, a compensating feed of thewheel G toward the work axis, and truingof the grindin surface to the depth of the dresser feed. During the dressing operation, the grinding wheel G preferably is driven at a reduced speed. I I

The work head i The workhead 8 per se forms no part of the present invention, and therefore is not-described in full detail. The mechanical drive transmission within thework head 8 for the table 3 and spindle I0 is generally. similar to that shown in a copending application for United States Letters Patent by Guenther Brinkmann, Serial No. 435,- 224,. filed March 18, 1942 (now Patent No. 2,389,- 590, issued November 27, 1945), and comprises a screw shaft 16 geared .to the spindle I0, and connected through a meshing worm l1 and worm wheel 18 to an inlet shaft l9 extending to the rear of the head 8 for connection to a suitable source of power. The wheel 18 is slidably splined to the shaft l6 so as to permit relative axial movementof the latter, and is itself constrained against axial movement by bearing lugs |8a at opposite sides rigidly supported within the head. A lead screw Men the shaft l6 engages a nut 2| fixed in relation to the machine base I to complate the drive for the table traverse. Upon rotationof the power inlet shaft IS, the work spindle I 0 and the lead screw 20 are driven in positively timed relation to rotate and translate the workpiece Win accordance with the thread lead to be ground thereonin forward and reverse directions. I A lead pick-up mechanism, operable by means of a hand wheel 22 at the front of the machine, is provided for adjusting the position of translation of the table 3 relative to the position of rotation of the work spindle I0, as required to locate the work thread in proper position for en agement by the grinding wheel G.

Backlash compensating means likewise is provided for automatically adjusting the position of translation of the table 3 relative to the position of rotation of the spindle ID in one direction or the other to the extent of the backlash in the drive upon each reversal of the lead screw 20, i

so as to maintain the work thread in proper relation tothe grinding wheel G in both directions of table translation. In the present instance,

the backlash compensating means comprises a. I

hydraulic actuator 23 (Fig'l) which is reversible upon each reversal of the work table 3to adjust the drive connection through a predetermined adjustable distance required to compensate for backlash. The actuator 23 comprises a piston 24 reciprocable in a cylinder 25 having fluid supply lines 2 6 and 21 opening to opposite ends and connected to a control valve 28 form- 1 ing part oi the main valve panel 28. The valve 28 is of the two-position type, and is adapted for. operation by two solenoids SVCR'Iand SVCL:

in the electric control circuits for themachine. During the forward drive tothe right, thesoleconnected in the hydraulic transmission system depending on the adjustments of the

valves

39 and 48 to receive fluid discharging from the actuator 32, and to build upa back pressure which is reflected in the inlet side or the system to control the pressure in the pump control line 46; and therethrough to vary the output of the pump" in accordance with the fluid. requirements at different times. in the machine cycle;

The

valves

39 and 48 and the restricted adjustable orifices 52 to 55 are incorporated in a unitary valve panel 51 mounted in the front of the machine base I. The panel 51 consists of a rectangular blockiFigs. l1 and 12) suitably supported on the base at the front of the machine, and formed withcored passages connected- 4 48 and 56; and other cored passages defining the w noid SVCR is energized to actuate the valve 28 into one end position in which the cylinder lines 26 and 21 are connected ,respectively to fluid pressure and

exhaust lines

38 and 3| to take up the backlash in the proper direction. During the return drive to the left, the solenoidSVCR is deenergized; and they solenoid SVCL is mer gized to actuate the valve28 into the other position, thereby reversing the connections to the cylinder lines 26 and 21 so as to take up the backlash in the opposite direction.

The work head drive The drive for the work head 8 is automatically adjustable to vary the speed of spindle translation and rotation in accordance with the nature of the work being done at different points in the machine cycle; and comprises a reversible hydraulic motor 32 ,of the rotary type having a constant displacement at any given speed. A pulley 33 on the shaft 34 of the motor 32 is connected through a belt 35 to a pulley 36 on the rear outer end of the power inlet shaft 18 of the toolhead 8 (Fig. 2).

The motor 32 has fluid supp lines 31 and 38* connected in a hydraulic transmission system (Fig. 13) to receive fluid under pressure, subject to control by a direction valve 39and an-orifice selection valve 40, from the pressure line 4| of a variable delivery pump 42 driven by an electric motor 43. The pump 42 has an inlet line 44 taking fluid from a reservoiror sump 45 in thebase of the machine, and its displacement or output is subject to variation in response to the pressure in a control line 48 adapted tobe connected to the pressure line 4| by the valve 39 when adjusted to effect traverse of the table 3.

The direction valve.39 has an intermediate or stop position, and opposite end positions to effect reversible operationof the motor 32,and in said opposite end positions serves to-direct fluid discharging from the motor 32 respectively to one or the other of two

exhaust lines

41 and 48. The exhaust line 41 leads to the inlet ofthe orifice selection valve 4|| which has three positions of adjustment to direct the exhaust fluid respec tively" to three

orifice lines

49, 58 and 5| during forwardfeed operation. A plurality of independently adjustable restricted orifices; 52, 53 and 54 for feed control are respectively interposed in the lines "49 58 and 5|, and discharge to a drain line 56 returning to the reservoir 45. An adjustable restricted oriflce'55 is connect-edto receive fluid f romthe exhaust line 48during rapid traverse return and also discharges to the drain to the respective inlet and

outlet lines

31, 38, 4|,

lines 41 to 5|. Each ofthe orifices isprovided with an indicator dial on the front of the block The direction valve 39 comprises a horizontal bore opening crosswisethrough the block 51 and having a valve sleeve 58 fixed therein. The sleeve 1 58 is formed with longitudinally spaced sets oi .

radial ports

59, 60, 5|,, B2 and 63, opening to the inner periphery, and connected respectivelyto the

coredpassages

48,31,4l, 38 and 41. Two spaced sets of'restricted ports 84 and B5 are also formed "in the valve sleeve 58,and are connected in parallel through fixed orificeplugs 68 to the cored control passagellfi'.

Avalve plunger 61 of the spool type is reciprocable in the valve sleeve 58 with a snug sliding fit, and is formed with end lands 68 and G9, and anintermediate land 10 separated by peripheral grooves 1| and 12. i i

The orifice selection valve 48 is generally similar, in construction to the direction valve 39, and

comprises a horizontal bore opening crosswise through the block 51 in parallel verticalspaced relation to the bore of the direction valve. A valve grooves83 and 84 for selectively blocking and line 56. The selective controlorifices 52j -53, 54

and 55 are, therefore, adapted-to 'bedndividually connecting the valve ports in difierent positions of adjustment of the valve.

The direction valve 39 has three positions, namely, an intermediate stop position and opposite end positions. Normally, the valve is biased by spring pressure into the intermediate stop position. A valve stem 85 projects from one end of the valvemember 51 for connection to suitable actuating means, and has a rod 86 of reduced diameter extending axially through the valve member;

A nut 81 is threaded onto the free end of the rod 86to clamp the valve member rigidly to the stem 85. The stem 85 extends through a bore 88 in a bracket 89 mounted on one end of the panel block 51, and is formed with a peripheral enlargement defining a shoulder 58 in opposed ax-- ially spaced relation to theadjacent end of the valve member 81. 'Slidably disposed on the valve stem within the bore 88 are two fiangedrings 9|1and92 urged apart by a coiled compression spring 83.

The pump 42 is substantially e that shown in an application for unitea -state -rett r Patent 1 i by Max Mathys, Serial No. 379,211, filed February 17, 1941.

In operation, when the stem 85 is not externally actuated, the spring 93 will maintain the rings 9| and 92 in spaced relation respectively against the end of the valve member 61 and the shoulder 90 and also against the end of the valve sleeve 58 and the outer wall of the bore 88. Upon actuation of the stem 85 outwardly, the ring 92 will be moved to the left by the valve member 61 to compress the spring 93. Upon actuation of the stem 85 inwardly, the ring 9| will be moved by the shoulder 90 to compress the spring 93. Upon releasing the valve stem 85 in either instance, the spring 93 will expand to return the valve member 61 to intermediate position.

The orifice selection valve 40 also has three positions, and normally the valve member I9 is biased by a compression spring 94 into the intermediate position. The means coacting with the spring 94 are the same in construction as in the case of the direction valve 39 and, hence, need not be again described. It is suflicient to state that the valve member I9 has an axial stem 95 projecting from one end through a bracket 96 for connection to suitable actuating means.

The direction valve 39 and the orifice selection valve 40 are shiftable into their opposite end positions respectively by solenoids SVFW and SVREV and, solenoids SVI and SV2 which are mounted on the rear of thetblock 51 and are connected in the electrical control circuits of i to translate the work table 3, for example at a the machine. The solenoids SVFW and SVREV forthe direction valve 39 are disposed in end alinement, and have a core 9! extending axially therethrough and provided on opposite ends with suitable heads 98 for limiting the extent of movement. One end of the core 91 is pivotally connected through a clevis99 to one end of a lever I00 in turn pivotally connected intermediate its ends at IN on the bracket 89. The other end of the lever I00 is pivotally connected through two parallel links I02 in turn pivotally connected to the flattened outer end of the valve stem 05.

When both solenoids SVFW and SVREV are deenergized, the spring 93 will locate the valve member 61 in its intermediate or stop position in which the lines 3! and 38, leading toopposite sides of the motor 32, are interconnected and con 'nected to the pressure and control lines 4| and 46, and are blocked from the

exhaust lines

41 and 48, thereby adjusting the pump 42 for minimum displacement sufficient to maintain a delivery pressure.

When the solenoid SVFW alone is energized, the valve member 61 is shifted out of intermediate position to the right so as to connect the pressure port 6| to the motor line 31 and to connect the other motor line 38 to the exhaust passage 41. Upon deenergization of the solenoid SVFW and energization of the solenoid SVREV, the valve member 61 is shifted from the intermediate position to the left into the opposite end position to connect the motor lines 38' and 31, respectively, to the pressure line 4| and the exhaust line 48.

Th solenoids SVI and SV2 for the orifice selection valve 40 are disposed in end alinement on the rear of the panel block 51, and over the solenoids for the direction valve 39, and have a core I93 operatively connected to the stem 95 in the same manner as in the case of the valve 39. Upon energization of the solenoid SVI, the valve member 19 is shifted out of intermediate position to the right so as to connect the exhaust passage 41 .to the passage 5| for rough slow feeding speed during each roughing pass, a faster feeding speed during each finishing pass, a speed slower than that-for rough grindin during the grinding of the incomplete end thread convolution, and a high rapid traverse speed during each free return stroke.

Tool head The tool head 6 comprises a wheel slide I04 which is mounted directly on the rearward base extension 4 for reciprocation along the ways 5 transversely of the work axis. The grinding wheel spindle l is suitably supported on the forward end of the slide I04 for angular adjustment in accordance with the lead angle of the thread, and is adapted to be driven through a belt 106 by an electric motor I01. I

When an incomplete end thread convolution is to be removed from the leading end of the workpiece W, a second grinding wheel G" is fixed on the spindle 'I in axially spaced relation to the grinding wheel G to take a grinding cut on the convolution at the end of each roughing pass and each finish pass. The method of removing the incomplete thread convolution is more fully disclosed in a copending application for United States Letters Patent by Gilbert Stewart, Serial No. 426,112, filed January 9, 1942, to which reference may be had for a more detailed understanding. During the end portion of each grinding pass, the solenoids SVI and SV2 are both energized to reduce the speed of the table 3.

Slidably mounted on therear end portion of the wheel slide I04 on transverse'ways I08 is a dresser slide I09 (see Fig. 8). A suitable dressing device IIO having one or more dressing tools I I I is mounted on the slide I09 and is adapted to be reversibly driven in any position of the slide by an electric motor II2 through a flexible shaft II3 to traverse the tools across the cutting contour of the wheel G.

The wheel slide I04 is adapted to be translated hydraulically either forwardly into an operative grinding position for each grinding pass, or rearwardly into an idle or dressing position for each return stroke of the table 3. The means for this purpose includes a leadscrew II4 which is rotatably anchored against relative endwise movement in the lower portion of the wheel slide I04, and which is normally non-rotatable but operated as hereinafter described to impart a compensating forward feed to the slide for each dresser feed. The forward end of the lead screw II 4 is in threaded engagement with a nut II5 fixed in the rear end of a cylindrical plunger or stop member IIB slidably disposed for independent longitudinal adjustment in a bore II! in the wheel slide I04, and constrained against rotation therein by a spline key II8. A stop bolt H9 is adjustably threaded into the forward end of the stop plunger I I 6, and is arranged for abutting engagement with the rear end of a coacting stop plunger or member I20. A coiled tension constantly in endabutment with the stop member I20.

The stop member I20 issiidably disposed in a sleeve bearing I22 on the base extension 4, and is held therein against rotation byrneans of a spline key I23. Fixed inthe forward end of the stop member I20 is a feed nut I24 in threaded enaurfm.

gagement with the cross feed screw I25. Thev forward end of the" feedscrew I25 has a shaft I26 which is connected to the cross feed mechanism I2, and which constitutes an anchor ad-- justable individually or conjointly by the retract mechanism I3 and the taper mechanism I4 to control theposition of the wheel slide I04 independently of the cross feed. 1

I The retract mechanism I3 and the tapermechanism I4 jointly control the axial position of the cross feed screw I25 through the medium of a lever I21. with a yoke I28 engagingtrunnlons I23 on an end thrust bearing I30 rotatably secured on the feed screw I25. The other'end-of the lever I21 is similarlyfformed with a yoke I3I engaging trunnions I32 on an end thrust bearing I33 rotatably secured to one end of a slidable plunger I34 forming part of the taper 'mechanism I4. The .trunnions I32 constitute a fulcrum about which the lever I 21 isoscillated by the retract mechanism. I3 to shift the cross feed screw I25 axially in forward and reverse directions. Inits preferred form, the retract mechanism I3 in? cludes a'hydraulic actuator I35 comprising a cylinder I36 fixed in the base I, and a piston I31 reciprocable inthe cylinder and having a rod One end ofthelever I21 is formed andis formed in itsinner end witha longitudinal .diametrical slotl54receiving the segment III which engages the outer end of the slot to complete the operative connection between the plunger I34 and the pin I41. 5 I

Upon movement of the pin I41 along the sine bar I43, the operation .of the plunger I34 will be determined by the angle of the bar. If the bar is horizontaLnotaper movement will result; If the baris inclined, the plunger I34 will be shifted infthe course of the table movement as determined by the angle of adjustment to oscillate the lever I21 about the fulcrum I39, andthereb'y adjust the grinding wheel G transversely ofthe work axis in accordance with the desired work I taper. I

Means is provided for disabling the taper r mechanism I4, and in thepresent instance this means comprises a slide I55 mounted in the housing I49 for adjustment longitudinally of the plunger I34, and having a stop lug I56 projecting into the lower opening of theslot I54. An ad justing screw I51 extends rotatably through the front wall of the housing I49 into threaded engagement with the slide I55, and upon adjustment serves'to change the position of thelug 1 I56 and I the permissibierange of movement of the plunger I34. If the slide I55 is adjusted into its outer-- most position (Fig. 6) it serves to hold theplunger I34 inidle position out of functional association with the sine bar I43 and hence disables the taper mechanism. In this event, the trun- .I38 pivotally-connectedat I39 tothe lever I21 intermediate its ends. The cylinder has two fluid lines I40and I4I adapted tobe connected by a direction ,valve I42 reversibly to the pressure line 30 and exhaust line 3|. The valve I42 is of the two-position type, and is normally biasedinto oneend position to-direct fluidinto the line I so as to effect movement of the wheel slide I04 forwardly into its operative grinding position.) A s nions I32 constitute a fixed instead ofshiftable fulcrum about which the lever I21 is adapted for oscillation by the retractmechanism I3. I

f Grinding wheel dressing 1 Prior to each dressing operation, an incrmental dresser feed. is imparted to the dresser slide; I09 to shift the dressing tools III toward the periphery of the grinding wheel G, and sub-' stantially at the end of each feed increment, a

limit switch LS5 is actuated to institute operationof the dressing device 0. Thereupon, the dressing device IIO is-operated through'a cycle 1 of forward and return dressing strokes under the solenoid SVR is operable upon being energized to shift the valve I42 into its other end position to direct fluid into the line I40 so as to retract the wheel slide I04 intoits idle or dressing position. The solenoid SVR is connected in the 'electric'circuits for the machine, and is energiied, as an incident to each reversal of the work table 3, during each return strokeand deenergized during each grinding pass. Preferably, a throttle orifice I40 is inserted in the line I40. to control thespeed of the actuator I35.

The taper mechanism I4 comprisesia sine bar control of two limit switches LSDF and LSDR.

The dresser feed mechanism includes a feed screw I58 rotatably anchored against endwise movement in the'wheel slide I04 andextending' is flxed for rotation with thepinion Iii, and

' I43 which isinounted for angularadiustment about a pivot I44 at one end on the front of the work table 3. The other end ofthebar I43 is guided by a pin and slot connection I45; and is adapted to be secured in different positions of adjustmentby means of a locating clamp block I46. A vertical follower pin I41 is reciprocable in a boss I46 on'a housing I49 'securedto the meshes with a spiral gear I63 fixed on a cross.

shaft I64 extendingthrough a sleeve I to one side of the base extension 4. The shaft I64 is journaled at opposite ends in the sleeve I65, and extends therefrom through a housing I66. A

suitablehand wheel I61 is secured to the outer front ofa mounting plate I50bolted to the front .wall of the base I. The-upper end of the pin I41. is arranged for'wiping engagement with; the

lower edge of the sine bar I43 in the course. of the table translation. The lower endoi the pin I41 engages one side of a bell crank or segment I5I pivotally mounted on a shaft I52 within the housing I49. The plunger I34 extends slidably through a bushing I53 into the housing I49.

end of the shaft I64 and affords means for effecting manual operation of the dresser feed.

, The housing I66 encloses suitable drive means for automatically operating the "dresser feed shaft I I64. In the present instance-the drive means comprises a ratchet- I66 keyed to the shaft I64,

and a gravity pawl I63 adaptedforengagement with theratchet and mounted on the end of a pawl carrier or arm I10 oscillatory about the shaft. The free 'end of the pawl carrier I10 is formed with a gear segment Ill operable by a hydraulic actuator I12 on the housing. I66. In the present instance; the actuator comprlses a 11 plunger I13 reciprocable in a cylinder I14 and formed in one side intermediate its ends with a longitudinal gear rack I1I' meshing with the segment I'II. Thus, movement of the plunger I13 in one direction will advance the pawl I69 in a feed stroke to impart rotation to the ratchet I68, and movement of the plunger in the reverse direction will oscillate the pawl in an idle return stroke.

The cylinder I14 of the hydraulic actuator I12 has twofluid supply lines I15 and I16 opening thereto at opposite ends of the plunger I13, and adapted to be connected by a direction valve I11 reversibly to ,the pressure line 30 and exhaust line ill, The, valve I11 is of the two-position type, and is normally biased into one end posit-ion to direct fluid into the line I15 so as to effect oscillation of the pawl I69 in its free return stroke. A solenoid SVD is operable upon being energized to'shift the valve I11 into its other end position to direct fluid into the line I16 so as to oscillate the pawl I69 through its feeding stroke. The solenoid SVD is connected in the electric circuits forthe machine, and is adapted to be energized at predetermined points in the machine cycle, for example after every two grinding passes under the control of an electric counter having an operating coil or relay B and aclutch coil or relay, A.

The extent of the dresser feed movement is adjustably controlled by a cam I18 arranged to lift the pawl I69 out of engagement with the ratchet I68 to terminate the feed. Substantially at the end of the dresser feed, the carrier I10 actuates a limit switch LS to initiate the cyclic operation of the dressing mechanism I5.

Upon each dresser feed, a cross feed increment of the same extent is imparted simultaneously to the wheel slide I04 so as to compensate for the reduction in the diameter of the grinding wheel G resulting from the removal ofstock in the dressing operation. The compensatory cross feed drive comprises a' gear I19 on the dresser feed screw I58, an idler gear I80 meshing with the gear I19. and a gear I 8i on the compensatory feed screw I I4 and meshing with the gear I80. It will ,be seen that upon rotation of the dresser feed screw I58, rotation will be imparted to the compensation cross feed screw I I4 so as to retract the rear stop member H6, and thereby cause the spring I2I.to advance the grinding wheel G through a like distance towards the work axis.

Cross feed mechanism The cross feed mechanism I2 for the grinding wheel G is operable to adiust, the position of the forward stop member I20 by rotating. the cross feed screw I25, and thereby to control the size setting of the grinding wheel G in relation to the workpiece W. The mechanism is manually operable to adjust the grinding wheel G into initial setting as required by the-diameter of a particular workpiece 'W to be ground, and during the machine cycle is automatically operable to impart a cross feed increment of predetermined depth once for each grinding pass, after the initial grinding pass, of the work head 8 until the thread is ground to final size or depth.

In its preferred form, the cross feed mechanism I2 comprises a body bracket I82 integral with,the mounting plate I50, and formed with a bore I83 coaxialwith thefeed screw I25. A fixed bushing I84 is securedin the bore I83, and projects forwardly therefrom. Rotatably disposed in the bushing I84 is a tubular sleeve I85 which 12 constitutes the terminal or outlet shaft of the cross feed mechanism I2, and in which the screw shaft I26 is axially splined for joint rotary drive and independent axial movement.

The forward projecting end of the tubular shaft I is formed with axially spaced peripheral flanges I86rotatably supporting a hub member I81. Preferably. a bearing sleeve I88 is fixed in the. hub member I81, and engages the flanges I86 with a snug rotary fit. The forward end of the hub member I81 is formed integral with a circular plate I89 having a forwardly projecting annular flange I90. Rigidly secured in coaxial relation to the flange I90 is a hand wheel I9I provided with a suitable hand grip I92 for effecting a manual cross feed. I

Adis'engageable speed-reduction gear drive is provided between the hand wheel I9I and 'the shaft I85. In its preferred form, this gear drive includes a large gear I93 bolted to the forward end of the shaft I85 in coaxial relation therewith. The gear I93 meshes with one end of an elongated axially shiftable pinion I94. The other end of the pinion I94 is slidable in and meshes with an internal gear I95 which is journaled in the inner face of the hand wheel I9I, and is integral with an external gear I96. An idler gear I91 rotatably mounted on the inner face of the hand wheel I 9i meshes with the gear I96. Meshing with the gear I91 is a gear I98 on a shaft (99 extending axially through the hand wheel I9I, and provided on the outer end with a hand lever 200. A spring actuated detent 20I is carried by the free end of the hand lever 200, and is adapted when released to engage selectively in any one of an annular series of holes 202 provided at the front of the hand wheel I9I concentrically about the shaft I99.

.The gear I94 is provided on one end with an axial pin 203 adapted for engagement in a recess 204 within the plate I89, and is provided on the other end with a hand knob 205 whereby it may be retracted axially out of meshing engagement with the large gear I93. A spring actuated detent 206 serves to hold the gear I94 releasably in either position of adjustment. When the gear I 94 is disengaged from the gear I93, the hand wheel I9I can be rotated independently of the shaft I85 as required for coarse adjustment relative to a fixed reference point or pointer 240. Assuming the gear I94 to be in mesh with the gear I93, when the detent 20I is disengaged from the holes 202, the lever 200 may be manually revolved to effect a fine adjustment of the hand wheel I9I relative to the shaft I85, the gears I98, I91, I86 and I95 acting to roll the gear I94 about the gear I93. If the hand wheel I9I is held against rotation, operation of the lever 200 will rotate the gear I93 to adjust the-screw I25. By these operations, the screw I25 may be adjusted into correct size position, with the wheel I9I registering with a zero point. When the detent 20I is engaged in any one of the holes 202, the hand wheel I Si is locked through the gear train to the shaft I85 for direct rotation therewith.

A pawl and ratchet mechanism is provided for imparting an incremental automatic feed adjustment to the shaft I85, and preferably comprises a ratchet 201 rigidly secured to the rear end of the hub member I81. A pawl carrier 208 is mounted for oscillation on the outer end of the bushing I84, and is confined in axial position between the plate I50 and the end of the hub member I81. Pivotally mounted by a pin 209 in the end of the pawl carrier 208 is a pawl 2| 0 adapted for en- 13 I gagement with the periphery of the ratchet 201. A spring detent 2II coacts with the pin 2ll3-to maintain the pawl 2l0 either in operative position to engage the ratchet 201 or in a lifted position out of engagement with the ratchet.

The carrier 208 is formed with'a gear segment 2I2 which meshes with a pinion 2I3 on the forward end of the shaft 2H rotatablydisposed within a bore 2I5 in the body bracket I82. A pin ion 2IE on the rear end of the shaft 2 meshes with a gearrack 2 I! on one-side of a longitudinal rack bar2l8 reciprocable in andprojecting from a transverse bore H9 in the body bracket I82.

The outer end of the rack bar 2I8 is pivotally connected at22ll throughaaconnected rod 22I to a crank 222 operable by a hydraulic aetuator 223. In the present instance, the hydraulic actua tor 223 is mounted on the front of themachine base I, and comprises a

piston

22,4 reciprocable within a cylinder 225 and connected through a cross feed of the wheel slide I041 I ,Hy dfou lic circuits 1 y r V The various operating elementsof the hydraulic circuits have sheen describedinwthe foregoing It is to be noted that one portionof the circuit provides a hydraulicldrive for the work table 3 and spindle III.; This portion receives fluid under full pressurefrom the pump-42 through the line II. *A relief. valve. 250 is "connected to the line II to discharge excess fluid at a given pressure through a bypass linel and the exhaust line 1 53 to the sump .45. The other portion of the circuit serves various hydraulic actuators of the machine proper, viz., the retractyactuator "I35,

rack 228 andpinio'n 221 to the crank 222, The

cylinder 225 has two fluid lines 228 and 229 adapted to be connected by a direction valve 230 reversibly to the pressure line and exhaustJine 3|. The direction valve 230 is of the two-posithe dresser feed actuator I12 and the cross feed aetuator223, and receives fluid at a constant low pressure from the pumpiline 4i through apl'essure reducing valve 252 to the line 30.

tion type, and is normally biased into one end I position to direct fluid into the line 228 so as to effect movement of the pawl 2H! in a return stroke. A solenoid SVD is operable upon being energized to shift the valve 230 into. its other end position to direct fluid into the line 229 so as to move the pawl 2I0 in a feedin stroke. At the end of the feeding stroke, a cam 23I on the crank 222 acts to open a l mit switch LSF. to interrupt the circuit for the solenoid SVD.

The amount of each cross feed increment is adjustable by varying the effective strok of the pawl 2| II. .Themeans for this purpose includes a rotary shield 232, overlying the periphery of the ratchet 201, and adapted to lift the pawl 2 III outof engagement withthe ratchet teeth after i a predeterm ned extentof pawl movement. The shield 232 is rotatable about a ring 233fwhich v nzircles the hub member I81, and which is rigidly bolted to thebody housing I82 to secure the cross feed mechanism I2in mounted position. 'A feather 234 on the hous ng I82 extends through a slot 235 in the shield .232 into a groove 236 in the ring 233. andserves as an additional means for securing the parts in assembled relation. 'A

hand knob 23'! is secured to the shield 232 by means of a bolt238 extending through a periph era! slot 239 m the ring 233..and affords means for adjusting the shield relative to the pawl 2H1.

Enoircling the ring233 and rigidly secured there to outwardly from the shield 2321s an annular Electrical control circuits and operation Current is supplied for all or the various moxtors, excepting the grinding wheel motor I01,

from three main supply lines Li, L2,*La, which are adaptedto be connectedto asuitable source of three-phasealternating current by a main dis connect switch S1. Suitable lower voltage current forthe control circuits proper is derived from a step-down transformer 253 having a primary winding connected across the supply lines Li, L3

and a secondary winding, with a line Liconnected' to one terminal and a lineLs connected to the other terminal. A line L6 is adaptedto be connected to the leadLs upon closing a normally open start switch S2 for the hydraulicfmotor 43. Accordingly, the various electrical control devices of the system may be energized by connecting them acrosseither the lines L4 and L5 or L4 and La The hydraulic pump motor 43 and a lubrication pump motor-254 are adaptedto be 'connected. in parallel to'the lines L1, L2 and La through. a set of normally open switch contacts H? controlled by a relay. H. To start the pump. motors I43 and 25-I t he start switch S2 is closed,

thereby completing a circuit forthe relay H across the lines L4 and L5, the circuit being from L4 through the relay H, a series of overload and pro- 'tective relays, a normally closed-master stop disk 239 which interflts rotatably withthe outer edge of the plate I89 and supports the po nter 240 for indicating the adjustment of the hand wheel I9I. r The hand wheel I9I controls a limit switch LS SI for initiating the end or the machine cycle .when the cross feed reaches final size. The switch LSSI has an arm 2 connected through a link 242 to an ans-243; on 9. shaft 244 journaled in the base I. Secured to the forward end of the shaft 244 is an arm 2.45 in which a. finger246 is adustablypivoted for swinging movement into or out of operative position. A fixed dog 24 1 is secured to the hand wheel IS, and is arranged to engage one side of the finger-248 to actuate the switch LSSI at the end of the cross feed. A second dog 248 is adjustably secured in a peripheral T-slot 249 inthe wheel I9I, and is adapted to be'brought into engagement with the other switch Saand the switch S2 to the line L5. Energization of the relay H closes the contacts H to set the pump motors and 254 in operation, and also closes sealing contacts H to establish a holdingcircuit around the starting switch S2;

When contacts H are closed, lines L5 and Le are connected to condition the circuits forconnecting the cycle control devices across the lines Li and Le.

Closing of the switch S2 also establishes a circuit across the lines L4 and L5 for the solenoid SVI through normallylclosed contacts CRSI' and a normally closed limit switch LSI3. Aparallel circuit for the solenoid SV2 is interrupted at this time by normally open contacts CRBI Thesolenoid SVI upon being energized serves to actuate the valve 40 to direct the discharge of the hy-' drauiic motor 42 through the adjustably restricted orifice 54 set to control the table speed for rough grinding. In the event that the end thread convolution isnot. to be removed, the solenoidSVI and the limit switch ILSI3 may be removed from the circuit.

including a closed limit switch LSSI.

A circuit is also established across .the lines L4 and L5 for a relay CR1 and the solenoid SVCR through a limit switch LSTA upon movementof the table 3 to the right. The solenoid SVCR actuates the valve28 to effect operation of the actuator 23 in a direction to provide a backlash compensation to the right. Upon reversal of the switch LSTA at the end of the table travel to the right, the circuit for the relay CR1 and the solenoid SVCR is interrupted, and a parallel circuit is established for a relay CR9-and the solenoid SVCL. As a result, the valve 28 is reversed to effect a backlash compensation to the left.

The grinding wheel motor I01 is adapted to be connected across lines L1 and La connected to a source of direct current, and comprises a series field 255, a shunt field 256, and'a starter 251 having an operating coil with a timer (not shown). The field 256 is connected in series with two

adjustable resistances

258 and 259 across the lines L7 and La. 1 J

To start the wheel motor I01, and also a coolant pump motor 260 and refrigeration unit motor 26I, a hand switch S4 is closed to complete a circuit for relays C and REFR through a stop switch S5. The relay C closes sealing contacts C across the switch S4, contacts C to complete a circuit through the operating coil OP, and contacts C to connect the motor 260 to the lines L1, L2 and L3. Upon energizing the coil OP, contacts 0P OP and OP of the starter 251 are closed successively to start the grinding wheel motor I0I. At this time, the resistance 259 is shunted out through the contacts CR3I so that the motor I01 is operating at a relatively low speed adapted for rough grinding. The coil REFR closes contacts REFR to connect the motor 254 to the lines L1, L2, La. Consequently, closing of the switch S4 ifects operation of all three motors I01, 254 and 260.

Various selector switches are provided for conditioning the circuit to obtain a particular Inachine cycle. Switch Se is adjustable to control the cycle for either hand operation, single cut operation or automatic operation, and in the position shown closes all of its contacts to provide for automatic operation. Switch S1 is adjustable to condition the counter for counting table strokes or workpieces, and as shown, provides for the counting of strokes, for example, four strokes including two grinding passes. Switches Se and S9, in parallel and located at the front and rear of the machine, are adjustable to efiect continuous wheel dressing or intermittent dressing, or to disable the dressing mechanism, and as shown, provide for intermittent dressing.

At the start of the cycle, relays TRI, CRIO, CR3 and'CRI5, and solenoid SVR are energized, and the lamp RED is illuminated. The solenoid SVR maintains the wheel slide I04 in'retracted position.

The machine cycle is started by actuating a start cycle switch S10 to close a circuit across the lines L4 and L through a relay'CRI, this circuit Excitation of the relay CRI closes sealing contacts CRI across switch S10, and contacts CRI' to complete a circuit for a coolant valve solenoid-262 across lines LI and L3. The circuit for the relay CRI will remain closed unless a stop cycle switch $11 or the-masterstop switch S3 is opened, or until the limit switch LSSI is opened at the end of the wheel cross feed.

The relay CRI also opens contacts CRI to noid SVR causes the valve 42 to shift so as to effect advance of the grinding wheel G into operative grinding position.

Upon release of the start cycle switch S10, and after a time delay, the relay TRI causes closing of contacts TRI to complete a circuit for relays CR4 and CR8 and solenoid SVFW. Relay CR4 closes sealing contacts CR4 to establish a holding circuit. Solenoid SVFW shifts the valve 39 to effect movement of the work table 3 in a forward rough grinding pass.

The relay B of the counter and the clutch relay A are connected across the lines L4 and La, and hence are in a state of energization. When the relay CR4 is energized, it opens contacts CR4 to interrupt the circuit and register a pass on the counter. Since three passes of the preceding cycle were already registered thereon, the counter closes contacts 263 to complete a circuit for relay CRB which closes sealing contacts CR6. The relay CR6 also closes contacts CR6 in the circuit for the dresser feed solenoid SVD, but this circuit is not completed since contacts CR4 are open.

Near the end of the first roughing pass, the

table 3 opens the limit switch LSI3 to deenergize the solenoid SVI, and thereby reduces the feeding speed for grinding the incomplete end thread convolution by the grinding wheel G.

At the end of the first roughing pass, the table 3 actuates the switch LSTA to break the circuit for the relay CR1 and solenoid SVCR and to make the circuit for the relay CR9 and solenoid SVCL.

Relay CR9 closes contacts CR9 to close again the circuit for the relay CRIO and solenoid SVR. The relay CRIO closes contacts CRI0 to complete the circuit for the solenoid SVD for effecting the dresser feed, and the solenoid SVR effects retraction of the grinding wheel G. The relay CRIO also closes contacts CRIII to complete the circuit through contacts CR9 and CR9 for the solenoid SVREV and relay CR5 to effect free return movement of the table 3 to the left.

Operation of the dressing mechanism I5 continues during the wheel retract movement and the table return movement. At the conclusion 'of the dresser feed, the limit switch LS5 is closed momentarily to complete the circuit for dresser relay DF, which closes sealing contacts DF and opens interlock contacts DF'. Relay DF also closes contacts DF to complete a circuit for relay CR32 through contacts CR6 Relay CR32 closes contacts CR32 to shunt out the

resistances

258 and 259 so as to rotate the grinding wheel motor I01 at a slow dressing speed.

The dresser IIO now operates forwardly, and closes the limit switch LSDR to prepare the circuit for relay DR. At the end of the forward dresser movement, the limit switch LSDE is opened, and upon resultant closing of contacts DF', the dresser relay DR'is energized, opening interlock contacts DR and closing conacts DR The dresser now operates in the reverse'direction during which the switch LSDF is closed, and at the end of which the limit switch LSDR is again opened to terminate the dresser operation.

When the contacts DR are opened at the end of the forward dressing stroke, the relay CR6 is deenergized, but the circuit for the relay CR32 is maintained by the contacts DR At the end of the dresser operation, the contacts DR open to break the circuit for the relay CR32. As a re-