US2292875A

US2292875A - Internal thread grinding machine

Info

Publication number: US2292875A
Application number: US378033A
Authority: US
Inventors: Ralph E Flanders
Original assignee: Jones and Lamson Machine Co
Current assignee: Jones and Lamson Machine Co
Priority date: 1941-02-08
Filing date: 1941-02-08
Publication date: 1942-08-11
Anticipated expiration: 1959-08-11

Description

R. E. FLANDERS INTERNAL THREAD GRINDING MACHINE 7 Sheets-Sheet l Filed Feb. 8, 1941 Q Q E E Aug. 11, 1942.

E. FLA NDERS INTERNAL THREAD GRINDING= MACHINE Filed Feb. 8, l94l 7 Sheets-Sheet 2 APR Aug. 11, 1942. t E. FLANDERS INTERNAL THREAD GRINDING MACHINE Filed Feb. 8, 1941 VSheets-Sheet ks Q 11, 1942- v R. E. FLANPERS ,29

' INTERNAL THREAD GRINDING MACHINE Aug. 11, 1942. FLANDERS V INTERNAL THREAD GRINDING MACHINE 7 Sheets-Sheet 5 Filed Feb. 8, l94l 22%)22? mid? W 1942- R. E. FLANDERS 2, 75

INTERNAL THREAD GRINDING MACHINE Filed- Feb. 8, 1941 7'SheetS-Sh6ei-6 11, 1942- R. E. FLANDERS 2,292,875

INTERNAL THREAD GRINDING MACHINE Filed Feb. 8, 1941 7 Sheets-Sheet 7 g Q a ZZZ/22707 Patented Ar ig.

' rrinaan GRINDING MACHINE Ralph ii. Flanders, Springfleld,l.Vt., assiznor to Jones the ,Lamlon Machine Company, Springfield, Vt., a corporation of Vermont 4 Application Febrnary- 8,1941, No. 3178.033

This invention relates tb internal'grinding and, more particularly to machines for grindi temal threads.

One object of the invention is to obtainautoe; matic and accurate truing of the grinding wheel.

A further object is of the work.

Still another object is to obtain these results to obtain automatic sizing ls-connected through a splined shaft 6 to driving 'mechanism in a; casing I which may be the same that in thecasing 22I in my patent hereinflbefore mentioned.

-- Movable "transversely to the direction of traverse ot thework carriage is a wheel carriage I 9 which may. be mounted on antifriction rolls H by the use oian attachment applicable to an external grinder of well known type. g For a more complete understanding of. this .invention, reference may be had to the accompanying drawingsin which l Figureil is a fragmentary front elevation of a grinding machine embodying .the invention.

Figure 2 is a detail section online 2-2 of Flxure'l.- Y Figure 3 is a horizontal section on line 3-4 of Figure 1.

Figure 4 is a right hand elevation of the same to a larger scale, the wheel being in grinding position. I i Y I 1 Figure 5 is a view similar to a portion of Figure 4, but with the grinding wheel in truing position;

Figure 6 is a view similar to a portion ofFigure 1, but to a larger scale and with parts'broken as shown best in Figures substantially as shown in Figure 13'otPatentNo.2,187,227. This wheel carriage or slide isi'provided with an arcuate cradle l2 for rockably supporting a wheel sup port 13 which may *beangularly adjusted as by turning a shaft l4 having a worm l5 thereon meshing with teeth in a worm segment is secured as by screws I! to the support l3. Cooperating indices i8 and I! on the wheel support and carriage, as shown in Figure 9, may be employed to show the angular adjustment at any time. This angular adjustment is toadjust the wheel to the helix angle of the threads to be ground. The casing shown in my prior patent which carries the external wheel shaft is removed for the pres 1 ,m invention and a casing 20 is substituted therefor. This casing 20 has a forwardly and upwardly extending arm 2! which has pivoted thereto nearits outer upper end a casing 22.

away and in section and with parts shown in dash lines.

Figures 7 and 8 are sectional views taken on lines 'l-l and 8-8, respectively, of Figure 4, i the arm d tending parts being omittedm Figure 8; through thigsleevefl and joumaled in bearings figure 9 is a fragmentary transverse vertical and 2 9a topposite,ends Of the sleeve 23 is a, section through the wheel slide showing an inu h t 'l i 1 4 end 0f this countershaft m t 1 I is secured fla beltpulley 3| for connection by a Figure 10 is a diagrammatic w of a fl id 35 belt 32 (seFigiiles 2 and 4) with the drive pulpressure system and an electrical controlcircuit therefor. t

Figure 11 is a wiring diagram of an automatic control-for the machine.

fTliei.invention is shown herein as embodied in a grinding machine of the general type shown in my Patent No. 2,187,227 granted January 16, 1940, for Grinding machine, the machine here,

however,. being provided with a special holder, for an internal grinding wheel and means for moving said wheel between either of two positions, in the outer of which it is in grinding'position and in the inner of which it is in truing position. As shown,-therefore, the machine comprises a bed I having longitudinal ways 2 (Figure 2) for the reception of a traversing carriage I to which may be clamped a headstock 4 provided with a rotary spindle to which the work 5 may be secured as by some suitable chuck mechanism (not shown). This headstock spindle having a I thereon -(Figure 6) within hub portions 26 and- Thepivotal connection comprises a sleeve 23 i'roif spaced bushings 24 and 25 ley 33 of a driving motor 34 corresponding to the wheel motor I09 shown in my prior patent.

' The other end of'the shaft has fixed thereto a pulley 40 over which passes a belt 4| extending downwardly within-a cover member 42 over a pulley 43 on a wheel shaft 44. An idler 45 bears against the back stretch of the belt 4!,

- being journaled in one arm of a be l crank lever tened face of the pivot 48 and a collar 5! thread- 46, the other arm of which is connected to a rod 41 slideable transversely of a pivot 48 held on a pivot bolt 49 of the casing 22, A coil spring 50 surrounding the rod 41 bears between a fiated' on a portion of the rod 41. The tension of the spring 80 provides the pressure applied to the belt tightener roll 45.

The wheel shaft extends beyond a concaved face of the casing 22 and has secured at its outer end an internal thread grinding wheel 56. The central plane of this wheel 56 is sub- 1939, and may be actuated at suitable times by the turning of a shaft 8| corresponding to the shaft I88I shown in said patent.

The wheel casing 22 is provided with two difi'erent angular positions. When the wheel shaft 44 is in its outer position shown in Figures 2 and 4, the grinding wheel is in grinding position rela-' tive to the work and out of truing relation to the truing mechanism. However, the casing 22 may be rocked to the position shown in Figure 5 with the grinding wheel in the dotted line position shown in Figure 2, whereupon this wheel is in position to be trued by the truing mechanism.

Means are provided for swinging this wheel casing from one to the other of its positions. As shown best in Figure 4, at I8 is shown a fluid pressure cylinder mounted by suitable trunnions II on a bracket 12 carried by the wheel slide I2. This cylinder I8 is provided with a piston therein shown in dotted lines at" on a piston rod I4 which extends through a slot 18 in the rear wall of the cover member 42, the forward end of this piston rod I4 engaging over a pivot pin 11 secured to the outer wall member 18 of the casing 22. This cylinder 18 has fluid pressure connections through the pipes 88 and 8I with a control valve 82, these connections being shown diagrammatically in Figure 10. Fluid under pressure. such as air, is supplied from any suitable source through the pressure pipe 88 to. the valve casing 82. A valve 88 within this casing controls communication through a pressure passage 81 leading from the pipe 88 to the opposite ends of the piston 88 to either selected of the pipes 88 and 8|, discharge taking place to the pipe 88 or 8| through the discharge passage 88 and discharge pipe 89. In the position shown in Figure fluid pressure is admitted through the pipe 8I to the right hand end of the cylinder I8, while the pipe 88 is open to the passage 88 through the discharge pipe 89, the piston rod 14 then being in its outer position with the grinding wheel in grinding Position.

In Figure 10 there is illustrated a manually operated electrically actuated control for this valve. At each end of the cylinder 82 is shown a discharge pipe 88 normally closed by a valve 8|, which, however, can be opened by energization of a solenoid 92. These solenoids are arranged in series with their respective push button switches 98 through the leads 94 and 98 and the source of electric power 98. By closing either of these push buttons 93, the right hand push button being shown as closed, the corresponding end of the cylinder 82 is open to discharge so that the pressure acting on the opposite end of the valve 88 forces this valve to one or the other end of the cylinder 82, thus to move the piston rod I4 in the corresponding direction and to swing the wheel casing 22 to either truing or grinding position. As soon as the push button 88, which is shown depressed, is allowed to rise, the pressure at each end of the valve 88 equalizes and the discharge from either end of the cylinder 82 ceases. i

It is desirable that the wheel be held in either its grinding position or its truing position and provision is therefore made by whichshould the pressure fail, the wheel will be retained in either position in which it may happen to be when the pressure fails. To this end there is connected to the pressure pipe 85 through the flexible connection I88 a latch cylinder I8I (see Figure 7) having a piston I82 therein provided with a piston rod I88. The outer end of this piston rod I88 is formed as a latch bolt which, when no pressure is in the connection I88, is forced by a coil spring I84 bearing between the cylinder IN and check nuts I88 threaded on the piston rod, into latching engagement with either one of a pair of stop dogs I 88, I81. Should the pressure fail when the wheel is in its dressing position, as shown in Figures, this piston rod I83 will engage the stop I88 and retain the wheel in dressing position, or should pressure fail while the wheel is in grinding position asshown in Figure 4, it will engage with the stop I81 as shown in Figure 4 and prevent the wheel from leaving this positon.

Cycle control mechanism in the operative cycle of the machine.

The cycle of operations is at least partly determined by a rotatable control cam drum I88 having switch actuating cams arranged thereon and a second cam drum 424 mounted on the same shaft with the I88 and rotatable as a unit therewith and having mechanical controls in accordance with the cycle desired. At each free actuation these drums rotate either continuously or in two steps one half a revolution and then stop and their rotation is started at each end of the work traverse. They provide for motion of the wheel between grinding and truing positions and for an actuating impulse of the truing mechanism when the work is at that end of the traverse where the wheel is retracted from the work. Actual truing, however, takes place only at one or more predetermined times in the sizing cycle, actuating impulses at other times being ineffective for that purpose.

The ca'm drums I88 and 424 are rotated by a three phase'motor I8I controlled by a normally open magnetically closed switch I82. The wheel driving motor 84 is also a three phase motor controlled by the normally open magnetically closed switch I88. The work is rotated and its traverse is produced by the three phase motor I84 controlled by the normally open magnetically closed switch I88. The truing mechanism is actuated by a separate direct current motor I88 and takes power from the direct current lines I81 and I88 controlled by a normally open electrically closed switch I89. The alternating current lines I88, I8I and I82 supply three phase current to the alternating current system.

Work rotating and traversing mechanism Referring to Figure I, the work rotating and I traversing motor I84 is connected through a suitable train of gearing indicated generally by 488 to a shaft 48I. This-shaft 48I is Journaled for rotation in the work supporting carriage 3 and is axially movable therewith. It is therefore splined so as to be rotatable by but movable axially relative to a driving gear 482 carried thereon and one end portion is formed as a lead screw at 488 for engagement with a nut 484 fixed in the machine bed I'. The train of gearing 488 includes a reverse drive mechanism having the reversing clutch 466 which is actuated by shifting rod 466 pivoted to the upper end of a lever 401 fulcrumed at 406 in the machine bed. The shaft 461 is connected through a chain of gearing 416 to a drive shaft 411 connected through suitable gearing 2 to rotate the work spindle to which is fixed the chuck 4|3 of any suitable description to which may be secured for rotation the work 416. The train of gearing 416 includes change gearing indicated generally at 416 by which the ratio of angular rotation of the work to its axial displacement may be adjusted in accordance with the lead of the threads to be ground.

From the foregoing description it will be seen that by reversing the position of the reversing clutch 466 the direction of rotation of the work and also its direction of traverse will be changed simultaneously, and this reversal is effected by rocking the lever 4II1,'for which purpose. its lower end is connected as through a rod 426 to an arm 421 fulcrumed at 422 and having a cam follower at 423 actuated by suitable cams (not shown) on the cam drum 424. As shown in Figure 1, this. cam drum 424 is carried on the.

same shaft as the cam drum 160. As shown'thedrive for both of these cam drums comprises a worm 430 on the shaft of the motor 161. which meshes with a worm gear 46l on the cam drum shaft 462.

Wheel feed and truing feed mechanism As in my Patent No. 2,187,227, to which reference has heretofore been made, means are provided for moving the grinding wheel toward and from the work and for moving a truing device toward and from the wheel at suitable times. There is also provided means for-retracting the wheel from the work, as for relieving the work, or for permitting an idle traverse of the wheel in one direction, and there is also provided means by which after a definite extent of wheel feed, the truing mechanism is fed against,the wheel and the feed of the wheel is continued by the same amount so that this final wheel feed has no effect to determine the finished size of the work, but the wheel at that time is in accurate contour so that the work when completed is accurately ground to the size and'contour desired. Since the mechanism for the foregoing purposes is somewhat different from that shown in my prior patent, it has been illustrated ,in Figures 1, 2 and 3 hereof. The wheel carriage II has journaled therein but held against axial motion relative thereto a sleeve 440. Its rear end portion slidably engages the splined forward end 441 of a shaft 442 which is iournaled at its rear end in a casing member 446 secured to the bed I, so that as the shaft 442 is turned, the sleeve 446 is rotated with it. The rotation of the shaft 442 also actuates the feed of the truing mechanism. The shaft 442 carries a gear 666 engaging a long gear 66l (Figure 2) carried by a shaft 662 Journaled on the wheel carriage. With this gear 661 there meshes a gear 562 secured to a shaft 663 having threaded engagement with the wheel carriage and against the rear end of which engages a part 664 of the truing device casing 566 which is held thereagainst as by a suitable spring (not shown) as in my Patent No. 2,184,011 to which reference has been made. These parts are so proportioned that rotation of the shaft 442 feeds portion 446 of a shaft 446 and this shaft 446 is held against rotation as by being pinned to an arm 441 slidably engaging a post 441a. The forward extremity of the shaft 446 as at 448 is threaded into the rear end of a sleeve 446. This sleeve 446 is housed within and secured to a hub 466 of a gear wheel 461. Back of the hub 466 is a sleeve 462 within which the sleeve 446 may rotate and this sleeve 462 has pivoted thereto on and the truing mechanism. The wheel carriage I6 is normally held retracted as far as is permitted by the engagement of opposite ends of the lever 46!, its upper end on the plate 451 and its lower end on an abutment 466, by means such as the spring 461 which is connected from a fixed point 462 at the bed of the machine to a sprocket chain 466 engaging over a sprocket wheel 464 on the shaft 466, which shaft has a second sprocket. wheel 466 thereon rigid with the sprocket wheel 464 and over which engages a length of chain 461, the forward end of which is attached to the carriage 16, as at the point 468.

It will be seen from this arrangement the retraction of the abutment 466 will permit the lower end of the lever 466 to swing backwardly and permit the spring 461 to retract the wheel carriage and the wheel from the work,--while rotation of the gear wheel 461 will, through its threaded connection with the shaft 446, move the shaft 446 axially and thus move the wheel carrlage. The rotationof the gear 46l is employed to produce the normal feed and retraction of the wheel with respect to the work, while rotation. of the sleeve 444 in which the rear end of the shaft 446 is threaded is employed to produce a feed motion of the wheel carriage and a feed of the truing mechanism in order that after the truing mechanism becomes effective to true the wheel, the wheel is fed forwardly an amount equal to the truing so that the final sizing of the work 'is completed with the wheel trued to proper contour.

. Truing of the wheel after the normal wheel feed is ineffective to bring the grinding faces of the wheel closer to the axis of the work since these faces are trued OK to .the same extent as the wheel carriage is fed Motion of the lever 455 to effect the with-. drawal of the wheel carriage and parts carried thereby necessary for relief, or clearance during an inoperative direction of traverse, is produced by the following mechanism. The plunger 466 has secured to its inner end a cam follower element 416 suitably held against rotation, and cooperating with this cam follower is a rocking cam 4" carried by a rock shaft 412. This cam 411 is a face cam and has high and low portions against which the follower 411i rides. This cam 411 is also provided with a segmental gear portion 413 with which engages rack teeth on" a bar 414,.one end of which is pivoted as at 4140 (see Figure 1) to a lever 416 fulcrumed at 411 and having a follower 416 actuated"b suitable.

the wheel toward the work and the truing device cams (not shown) on the cam rum 424. The inner end of the rack bar 414 may be supportedin engagement with the segment portion 416 as by means of a bar 416 (see Figure 2) having a neck portion 416 to receive the rack bar, and this bar 416 may also engage in a slot in the lower end of the cam follower member 410 to hold this follower member against rocking with the cam 41I.

As before noted the normal feed of the grindlng wheel for work sizing is produced by rotation of the gear wheel 45L For this purpose there meshes therewith a gear wheel 480 (see Figure 3) to the hubof which is secured a hand wheel I by which it may be turned whendesired. This hub also has secured thereto a ratchet wheel 482 and rockably mounted on the stub shaft 483 on which the gear wheel 480 is journaled is a collar 484 carrying a pair of angularly related arms 485 and 488. The arm 485, as shown in Figure 1, carries a pawl 481 so that by rocking of the collar 484 the ratchet wheel 482 is rotated inone direction step by step, thus to rotate the gear 451 of the main feed shaft.-

The rocking of the collar 484 in feedingdirec-r. tion is produced by means of a linke490, the upper end of which is secured to the arm 486 and the lower end of which rests upon an arm 49I of a rocker member 492 Journaled on a shaft 493 carried by brackets 494 and 495 on the forward face of the machine bed. This link 49 however, has a yieldable element 495 there which permits the arm 49I to lift the lower end of the link without the upper end being corremined regardless of the amount of truing. Whenever a dog 524 is in position to hold the latch lifted, trulng is effected when the arm 5I5 is next lifted. The extent of truing at each ratchet movement may be regulated'by the angular adiustment of a shield 580 and likewise the extent of wheel feed without truing may be determined at each actuation by angular adjustment of a similar shield 53I for the feed ratchet wheel 482 in the well understood manner.

Rocking of the rocker member 5I5 is produced from cams (not shown) on the cam drum 424 which actuate a lever 540 connected by a link 54I with a rocker arm 542. This rocker arm 542 is provided with a segment fl-provided witha slot 544 across its face in which may be secured as desired a lug 545 in position to engage against H the lower face of the rocker 5| 6, so that as the segment 543 is rocked in one direction from a central position, the lug 545 is lifted to rock the member 5I5. As shown this segment may have a pair :of dogs 545 both of which may be used for external grinding but only one is employed v p when the machine is conditioned for internal spondingly moved, the relative motion of the parts being taken up in' compression of the spring 495. After an upward motion of the arm.

486, it is pulled down-to-return the ratchet 481 to starting position as by means of a spring 401.

As previously noted, the feed for the truing is effected by rotation of the 8188??!40 relative to the threaded portion 445 of the non-rotatable shaft 445, and this is effected by rotation of the shaft 442. The rear end of thisshaft is connected through the train of gears 500, 50I, and

502 with a shaft 503. The forwardend of this shaft 508 has secured thereto a ratchet wheel 504 and a hub portion-505 outwardly of which the shaft may be squared as at 508 for the reception of a handle for manual turning. Back of the ratchet wheel 504 there is rockably mount-v ed on a sleeve 501 within which the shaft 503 is -journaled a collar 508 having the ratchet dog arm 509, an actuating arm -5I0, anda Iatch arm 5 extending therefrom. The arm 509 carries the pawl 5I2 engaging the teeth of the ratchet wheel 504 and the arm 5! carries the upper end of a link m similar to the link can and theilower end of which rests upon an arm 5I5 on a P rocker 5I5 also journaled on the shaft 493. A spring 5 tends to hold the pawl carrying arm 509 in retracted position and, as in the case of the link 490, the arm 5I5 may'be lifted without rocking the ratchet arm if this ratchet arm is prevented from such motion. It may beprevented from such motion by a latch arm 520 having a notch'52l engaging over a pin 522 car ried by the arm 5. The opposite end of the arm 520 is provided with a dog 523 which may be struck by one or more suitable dogs 524 ad- Justably secured in any angular positiondesired in an annular face groove 525 in the gear h.

Thus after a predetermined extent of rotation of,this gear 45I in feeding direction, the latch 520 will be lifted by one of these dogs 524 so a that any action while the latch is lifted tending to lift the link 5 will be effective to step around the ratchet wheel 504 so that feed of the truing mechanism as well as the wheel is produced, so that the finished'size of the work is predeter- .with the rocker 5I0 lowered, as by means of a slide 548 mounted on a rod-541 and having a tail portion 548 guided along a rod 549 on which a are positioned centering springs 550 engaging "9mm m- 4 ""i iim' l d? 19 Referring particularly ii, there is opposite sides of the tail 548.

The wheel feed ratchet mechanism is actuated by the rocking of an .arm 555; carrying a plate 558 having a slot. 5 51f or the'adjustable securement-of a lugl55l; for engagement with the rocker 492. AspringJSS ttendsgitohold me III in downw rd @oeition so that arm' I is" down 1 with thej feed 'ratcheVdog inTi-etracted position. ,The; a n i giifiiis carried 'bya-"shaft 558 provided I {camsinot shown) onthe controls I 4 had operatioe cycle:

shown 'awiring f diagram of f various electrical controls'of this machine. In this'flgure the cam (ilfu'mf I50 is shown; developed and 7 various parts ar shown injcondition' r013 thei'start-of'the machine, but with'fall the} drivingmechanisms stopped. The first'a'ctlonis to idepres'sthe normally open start switch button I88." This establishes an electric circuit from line I50 through lead I10, the start button switch I, the normally closed stop switch I12, lead I14, solenoid I18 of the wheel motor switch I53, leads I18 and I19 to line I52. This closes the switch I55 which starts the wheel motor, and at the same time closes a switch arm I82, which completes a holding circuit from line I80, through leads I88 and I84, the switch arm I82, lead I88, closed stop switch I12, lead I14, coil I15, leads I18 and I18 to the line I52, so that on opening of the starter button the wheel motor continues to rotate, but

it can be stopped at any time by pressing the stop switch button I12.

At the start of the sizing cycle the work is in position in the work holder and the work holder is retracted in its left hand position as viewed in Figure 1, so that the wheel is out of the work and the wheel itself is in retracted position where it may have been trued in the previous cycle.

gopen. To button I88- i switch 315.

2,292,825 I fl Also the feed. wheel 451 has as; turnedback I the cam drumISO'actuatesthe switch is mot-- wardly to its starting angular position rfrom switch I88 is open and the stop switch. 3'18 is,

start the cycle, the start, switch push is depressed, this closing the stop This closes a circuit from the main I "line I60 through leads I68 and I90,1start push button I88-through lead I92, a switch 2L8 hav-.-

ing a-contact arm I94 closed to lead I98, closing coil I98 of a switch I to themain line I62." As the solenoid I98 of switch I3CR is energized, it closes the contacts of a normally open two-pole switch, the arm 202 v V which it will rotate in counterclockwise direction 1 untilthe end of the grinding cycle, the start cycle tween the lead 240 and I ing theswitch arm-242110 break connection be-j the cam drum stops.- The';.cam, drum is-nowat direction, and rotation oi. the work holder in the proper direction is also; started by the same ac- ISCR and leads 200 and 2o] I I tion. The parts are thus conditioned 'for grindof which then closes a circuit from the main line 7 E50 through lead I69, stopswitch 315,1eads I69 and 204, switch arm 202, lead 206, solenoid 208 of a normally open two-pole switch-40R,leads 250 and 28!, to the main line I62. As the solenoid 208 is energized, it closes the normally open contacts of the double pole switch 4GB, closinga circuit from the line 560 through lead I68, the, closed stop switch 375, leads I69 and 2, switch arm 2I2, lead 2i6, coil 2I8 of the work motor closing switch I55, leads 220 and E to the line I82. This closes the switch I55 and starts the work motor I55 rotating.

The closing of the switch iiiCRalso closes the switch arm 2 66, which establishes a circuit from the main line 566 through leads I68, closed stop switch 3E5, leads I69 and 204, switch am 268, lead 210,. closed switch am 2.12, lead 214, left one or ies t-wo stopping positions, momma. m, ingjthis rotation, memechamcar connections 1 from the cam drum- 424 actuate ,thewheel-feed through the lever540,yas previously described, and the work. slide is; started to move to i the rightby the throwing otthe clutchg408 inproper ing in one direction and the traverse continues I while the cam drums I80 and I54 are stationary.

- ing on the camelement closing the connection :between theswitch arm 242 and the lead 296, a circuit is established from the line I60 through leads I68, 238, 240, switch arm 242 of switch IILS, lead 296, contacts 285, through the switch arm 28I, lead 289gthrough the coil 29I of the switch ICR through-the armature of this switch, leads 250 and 20ILto the lin I62. This energizes the coi1"*29.I and swings the armature 293 r of the switch ICE to the left, closing contact behand solenoid 92, leads 216, 211;: 20I to the main 7 line I62. The energization of the left hand solenoid 92- opens to discharge fluid pressure from the spacefto the left of the 7 ing the grinding wheel to its grinding position, breaking contact at 254 and making contact at. 218 in the switch22LS. The closing of the start button I88also closes the connection, from line I60 through leads I68 and I90, push button I88,

' leads III, through the arm 224 of limit switch 3LS to lead 226 through magnet coil 228 of the switch 3CR, and in case the armature 230 or this switch is in engagement with the armature of the electromagnet 302 through the armature. 230, leads-I19 and 20I to the line I62. This insures the positioning 0! the switch 3GB as shown in Figure 1 where it would not have been should the stop switch 315 have been opened prior to the hand setting of the limit switchBLS. 7

It will be noted thatin the position of the cam drum I50, shownin Figure 11, with the switch arm 242 of the switch IILSVin normal position,

a circuitis completed from the line I60 through leads I68, 238, 240, switch arm 242 of switch IILS, lead 244, through the'coil 246 of the threepole switch IICR, leads 248, 250 and 20! to line I62, so that the switch I ICE is closed. The energization of the coil 2.46 of the switch IICR closes the

switch arms

295 and 252, this completing the circuit from line I60 through lead 288 to closed contacts 218 of switch 221.8 (the grinding wheel now being in grinding position), through the lead 280 to closed switch arm 236 of switch 3CR, lead 30I, lead 284, closed switch arm 252 of switch IICR, lead 286, switcharrn 288 of switch 6CR, lead 290, coil 292 of the cam operating motor switch I52, lead 294, closed switch arm 295 of piston 73-, thus move tween this armature and the lead 295, thus reestablishing the circuit through the cam motor control switch solenoid 292 from line I60, through leads I68 and 238, switch 22LS at the wheel carrying arm, contacts 218, leads 260 and 280, switch arm 236 of switch 30R, leads 30] and .284, closed switch arm 252, lead 288, through closed switch arm 288 of switch 603, lead 290, solenoid 292 of the cam motor controlled switch,

leads 294 and 295, armature 293 of switch ICE,

leads250 and 20I, to line I62.

The camdrums then rotate through 180' and are stopped when the right hand cam element (1 actuates the switch IILS. During this 180 rotation of the cam drum 424, first the wheel may be fed mechanically if a feed at both ends of the traverse is desired, or it may be fed only at the outer end, there being no feed at this time. Thereafter the, clutch 405 is actuated by cams on the same drum 424 to reverse the direction of rotation and traverse of the work, after which switch IICR, leads 248, 250 and 2M back to line I82. Thus the cam control motor starts as soon as the grinding wheel reaches grinding position. As thecams I50 and 424 rotate, their motion continues until the left hand cam element d on 7 thedrums reach their other revolution points and the switch-:IILS is actuated to disconnect the connection between the leads 240 and 244, whereupon the cam control motor again stops.

The reversetraverse then continues until the opposite end of the traverse is approached, whereupon the switch ILS is again placed in the position shown in Figure 11 by the other stop dog 219. The cam drum now starts again for another 180?} revolution'which stops the traverse, efiectsa feeder the work, and starts the traverse in the flrstdireotiomiust after which the cam drum stops through actuation of switch L8 to break contact with lead 296. This. cycle of operations continues until such time as it is desired to dress the wheel. 3 p

When automatic dressing of the wheel is desired, it is first necessary to close the hand operated switch 320 which establishes a circuit from line I60 through lead I68, switch 320, lead 322, coil 324 of switch IBCR, leads 326 and 20I back to line I62. Energization of the coil 324 closes the fwhereupon; q

both switch arms 328 and 360 which conditions the circuits for the automatic truing control, as will now appear. Dressing occurs only when the work is at its inner traverse limit, when the wheel and its shaft are out of work, and when one of the cam blocks 52 on the feed wheel 45I has lifted the latch bar 520, at which time during the rotation of the cam drum 424, a lifting impulse has been exerted on the arm I5. This lifting impulse is then effective to step around the truing feed ratchet wheel 504. The lifting of the latch bar 520 actuates the switch 2L5 to move it from the position shown in Figure 11,

where it connects the leads I92 and I96 to-- gether, to the position where it connects the leads I92 and 330 together. While the switch 2LS is in this position and the drum I63 is still rotating, the switch 4L8 is moved by its actuating cam 11 into the position shown in Figure 11, breaking contact between the

leads

280 and 284 and making contact between the

leads

280 and 304.

These actuations of the switches 2L3 and 4L3 closes a circuit from line I60 through leads I68 and I90, button I88, line I92, switch 2L8, lead 330, coil 334 of switch 60R, leads 336, 326 and 20I to line I 62. Energization of the 0011 334 of switch 6CR actuates the switch arm 288 to open the circuit through the solenoid 292, allowing the cam switch I52 to open, thus stopping the operation of this cam. Energization of the coil 334 also closes the switch arm 338, energizing the truing motor switch closin coil 342. The circuit for this is from the line I60, through lead I84, switch arm I82, leads I86 and 33I, the closed switch arm 328, lead 329, switch arm 338, lead 340, solenoid 342, lead 20I to the line I62. This starts the truing motor, since energization of the coil 342 closes the switch arm I59 in the direct current truing motor circuit between the direct current lines I51 and I58. and the switch 5L8 is closed, a cam depression of cam 346 riding out from beneath it. Next the wheel is moved to truing position by energization of the right hand fluid valve solenoid 92. This is done by the closing oi the switch arm 356 of switch 60R which closes a circuit from line I60 through lead 238, closed switch 218 (the wheel then being in grinding position), leads 280 and 353, closed switch arm 356 of switch 6CR, leads 351 and 306, closed switch arm 264, lead 308, solenoid 3I0 of switch I4CR, lead 20I to line 262. Energization of .the solenoid 3| 0 of switch I4CR closes switch arm 3 I 2 and energizes the right hand solenoid 92 from the line I60 through leads I68, stop switch 315, leads I69 and 3I4, closed switch arm 3I2, lead 3I6, right hand solenoid 92, leads 3I8, 211 and MI to line I62. The motion of the truing motor continues until it rotates its cam drum 346 sufficiently to close the switch 6L8 by its cam element b which completes a circuit from the line I60, lead I84, switch arm I82 of. the wheel motor holding circuit, leads I86 and 33I and closed switch arm 360 of I6CR, lead 36I, switch 6LS, lead 362. solenoid I98 of switch I3CR, leads 200 and 20I to the line I62 Energization of the solenoid I98 of switch I3CR re-starts the cam drum I50 to complete its 180 and returns the wheel arm 22 to its grinding position for the next inward traversing cycle as previously explained. Continued rotation of the truing motor drum after closing the switch 6LS allows this switch to open after which the switch 5L5 opens, the depression in its cam drum riding beneath it, breaking the holding circuit for the solenoid i'ective.

342, allowing the switch I59 to open, thus stopping the truing motor I56. The closing of the switch 6LS acts to start the cam motor I5I to complete the 180 rotation thereof before the traverse is resumed as it closes the circuit from the line I60 through lead I84, the closed switch arm I82, lead I86, lead 33I, closed switch arm 360, lead 36I, switch arm 61S, leads 362 and I86 through coil I98 of switch I 30R, leads 200 and 20I back to the line 262. This closes switch I 30R and thereby energizes the left hand solenoid 92 so as to return the grinding wheel to grinding position, since switch I3CR then closes a connection from the line I60, through lead I68, stop cycle switch 315, leads I69, 204, switch arm 268, lead 210, switch arm 212, lead 214, left'hand valve solenoid 92, leads 216, 211 and MI to the main line I62. As before noted, switch 6L3 opens again before the truing cam 346 stops. The swinging forward of the wheel arm 22 to grinding .position closes the contacts at 218, which, as previously described. closes the cam motor controlling switch, so that the cam drums I 68 and 424 continue their rotation until they com plete their 180 travel, whereupon they' are stopped by the action of switch III-S actuated by .the cam drum as previously described.

The machine then resumes its grinding traverse as previously described, and if at the end of the next outward traverse, the latch 520 is raised, another truing action takes place as previously described, but if it is not raised, the action proceeds without truing. The cycle of the machine is then repeated until the feed wheel 451 has been turned to an extent suflicient for the limit switch 318 to be engaged by the lug 31! secured to the feed wheel 45I. This stops the rotation of this feed wheel so that further feeding impulses imparted'to the link 493 are inef- Impact of this lug 311 on the limit switch 3LS'm0ves this switch from the position shown in Figure 11 to break connection between the leads Ill and 226 and to make connection between the lead Ill and the lead 300. The breaking of the connection with the lead 226 acts to disconnect the solenoid 228 of the switch 3GB and the making of contact with the lead 300 acts to energize the opposite solenoid 302 of this same switch 3CR, the circuit then being from th line I60 leads I68 and I starting switch I88, lead I", arm 224 of switch 3L8, lead 300, solenoid 302 of the switch 3CR through the armar ture 230, leads I19 and 20I to the line I62. This throws the armature 230 to its reverse position, breaking the connection between the armature and the coil 302 and opening the arm 236 of switch 3CR to break connection with the lead MI and to make connection between the switch arm 234 and the lead 306. The breaking of the circuit at the arm 236 is, however, ineffective to break the circuit through the cam motor drive switch.292 at this time for the reason that bypass connection is made through the switch 282 of switch 418 which is then making contact between the lead 260 and the lead 284. The lead at 280 connects to the switch arm 236 and the lead 284 connects through the lead 30I to the opposite side of this switch arm. When the switch 4LS is thereafter actuated by its cam dog a to break the connection at 284, the connection through the cam motor actuating coil 292 is interrupted and this cam motor stops. The switch arm 282 being then closed to the lead 304, it closes a circuit from the line I60, through leads I69 and 238, the contacts 218 at the wheel arm (which is now'in grinding position), through the lead 286, through the switch am 282 of switch 4LS, through lead 304, closed switch arm 234 of switch SCR, through lead 306, through switch arm 2% of switch IOCR, which is now closed, lead 308, coil 310 of switch I4CR, lead 2!" to line [62. The energization of the coil 3H! closes the switch arm N2 of switch l lCR which closes a circuit from line Hi0, through ead 168, stop switch 315, leads I69 and 314, switch arm N2 of switch CR, lead 3H3, right hand valve coil 92, lead M8 and 211 to lead 20! and the line I52. By this action the fluid pressure is exhausted from the right hand end of the cylinder I0, whereupon pressure on the other side returns the wheel to truing position, breaking the circuit at 218 and making the circuit at 254.

The sizing cycle is now complete, the work being stationary in retracted position and the grinding wheel retracted in truing position but with the truing motor stopped. The wheel motor and the work motor are still rotating, but the work motor is disconnected from the work.

The work motor may be stopped by depressing the stop button 325 which also opens the start button I88, or both the wheel motor and-work motors may be stopped by pressing the stop button switch H2. The depression of the stop button ll2 stops the work motor since it allows switch dCR to open the switch arm M2 in the circuit of the work motor closing coil 2".

For the start of a new cycle with the cycle start button I88 closed; the clutch being inneutral, the feed wheel is turned backwardly manually to starting position and the limit switch 3L8 is then returned manually to the condition shown in Figure 11. This return of the switch 3L5 breaks the connection between leads 222 and 3&8 and makes a connection between the lead 222 necessary.

The cam lug a whichactuates the switch 4LS may be adjusted to either of two positions, in one of which, shown in dotted lines in Figure 11,

it is in advance of the truing feed as determined by the cams on the cam drum 424. When it is so positioned, the cam drums are stopped at the end of the sizing cycle before there is any opporing a traversing work carriage, a wheel carriage mounted for motion transverse to the direction of motion of said work carriage, a wheel support mounted for motion on said wheel carriage in the general direction of motion of sold wheel carriage between limits at one of which limits a wheel carried by said support is in operative position and at the other of such limits said wheel is in truing position, truing mechanism for truing said wheel when said wheelis in truing position, power means for moving said wheel support from one to the other of said positions, means for traversing said work carriage,. means for moving said wheel carriageto feed and retract said wheel relative to the work, and means re sponsive to failure of power-"iorsald power means for retaining said wheel support in that position whether operative or truing where it happens.

to be when such. power failure occurs.

2. A machine of the class described, comprising a traversing workcarriage, a wheel carriage mounted for motion transverse to the direction of motion of said work carriage, a wheel support pivotally mounted on said wheel carriage and movable in the general'direction of motion of said wheel carriage between limits at one of which a wheel carriedbysaid support is in operative position and at the other of which said tunity for truing to be efiected, so that the machine stops with a final out without truing. If, on the other hand, the cam lug a is set to actuate the switch 4LS after the time of truing, as in the full line position, truing may be effected if one of the release-lugs 524 is in proper position, the truing then taking place after the last out, after which the cam drums are started again by the action of the truing mechanism until the switch 4L8 is actuated by its cam a, whereupon the cam drums are again stopped at the end of the sizing cycle. a point where it will release the latch lever 52!! intermediate the sizing cycle, truing will be eifected at this intermediate point.

From the foregoing description of certain embodiments of this invention, it should be evident If a dog 524 is positioned at wheel is in truing position, truing mechanismfor truing said wheel when said wheel is in said truing position, means for flxing said wheel support in angularly adjusted position about itspivot, power means for moving said wheel support from one to the other of said positions, means (or traversing said work carriage, means for moving said wheel carriage to feed and retract said wheel relative to the work, and means responsive to failure of power for said power means for retaining said wheel support in that position whether operative or truing where it happens to be when such power failure occurs. 7

3. A machine of the class described, comprisprising a traversing work carriage, a wheel carriage mounted for motion transverse to the direction of motion of said work carriage, a wheel support mounted for motion on said wheel carriage in the general direction of motion of said wheel carriage between limits at one of which limits a wheel carried by said support is' in operative position and at the other of such limits said wheel is in truing position, truingmechanism for truing said wheel when said wheel is in truing position, fluid pressure means for moving said wheel 'support from one to the other of said positions,

, means for traversing said work carriage, means for moving said wheel carriage to feed and retract said wheel relative to the work, and means responsive to loss of pressure in said fluid pressure means to retain said wheel support in the position it may be in when such loss occurs.

4. A machine of the class described including a carrier, a grinding wheel movably supported on said carrier for motion between an operative and an inoperative position, fluid pressure means for moving said wheel fromone to the other of said positions, and means responsive to the loss of fluid pressure acting to retain said wheel in that one of its positions in which it happens to be when such loss of pressure occurs.

5. A machine of the class described including -a carrier, a grinding wheel movably supported on said carrier for motion between an operative and an inoperative position, fluid pressure means for moving said wheel from one to the other of said positions, a latch having a bolt biased to I ingposition, means acting when said wheel is project into holding relation to said wheel in either of its positions, and fluid pressure means for retracting and so retaining said bolt.

6.Agrinding machine including a grinding wheel support, aerinding wheel movable on said support betweena pair.- of predetermined. posi-,-

tions, in one of which positions it may grind work and in the other of whichpositions it may be trued, truing mechanism, movable with said support, means for moving'said supportto feed retracted from the work in its traverse for effecting an impulse to'actuate said lateral wheel moving-means to position said wheel for truingand to return it to grinding position preparatory I to another grinding traverse, means for feeding the wheel toward the work, means for preventing the wheel relative to work, means for advancing 1 said truing mechanism relative to said wheel in grinding position to grind the'work to apredetermined size regardless of wheel wear and truing 7. A machine of theclass described, comprising 'a work carriage, a. grinding wheel, means for rotating said wheel, means for producing relative traverse between said carriage and wheel, means for moving said wheel laterally of the line of traverse between a grinding position and a truing position, wheel truing mechanism for truing the wheel at said truing position, another means for retracting said wheel from grinding position to idle return traverse position after said wheel has traversed the work in grinding position, and means acting whensaid wheel is retract ed from the work in its traverse for actuatingsaid lateral wheel-moving means to position said wheel for truing and said lateral wheel moving means and said other means to return it to grinding position preparatory to another grinding traverse. I

- 8. A-machine of the class described, comprising a work carriage, an internal grinding wheel, meansior rotating said wheel, means for producing relative traverse between said carriage and wheel to cause the wheel to enter and be retracted from one end or work on said work carriage, means for moving said wheel laterally of the line of traverse between a grinding position anda truing position, wheel truing mechanism for truing the wheel at saidtruing position, another means for retracting said wheel from grinding position to idle return traverse position after said wheel has traversed the work in grinding position, means acting when said wheel is retracted from the work in its traverse for enacting an impulse to actuate said lateral wheelv moving means to position said wheel for truing and to return it to grinding position preparatory to another grinding traverse, means for feeding the wheel toward the work, and means for preventing actual wheel motion to truing position as theresult of such impulse until said wheel has been fed to a predetermined position.

9. A machine of the class described, comprising a work carriage, an internal grinding wheel, means for rotating said wheel, means for producing relative traverse between said carriage and wheel to cause the wheel to enter and be retracted from one end of work on said work carriage, means for moving said wheel laterally of the line of traverse between a grinding position and a truing position, wheel truing mechanism tor truing the wheel at said truing position, another means for retracting said wheel from grinding position to idle return traverse position after said wheel has traversed the work in grindactual wheel 'motion to truing position as the result of such impulse until said wheel has been fed to a predetermined position, and means effective when said impulse is allowed to move said wheel to truing position to feed said truing mechanism by the amount of said wheel feed.

10. A machine of the class described, comprising a work carriage, a wheel carriage, means for eiiecting traverse betweensaid work and wheel carriage, means for moving said wheel carriage transverse to the line of traverse, a wheel support pivotally mounted on said wheel carriage and movable in the general direction of motion of said. wheel carriage laterally between limits at one of which awheel carried by said support is in operative position and at the other of which said wheel is in truing position, truing mechanism for truing said wheel when said wheel is in truing position, means for fixing said wheel support in angularly adjusted position about its pivot, means for moving said wheel support from one to the other of said positions, means for moving said wheel carriage to feed said wheel relative to the work, and means for retracting said wheel carriage to remove the wheel from grinding relation for an idle wheel-retracted traverse.

11. A machine of the class described, comprising a work carriage, a wheel carriage, means for relatively traversing said carriages, means for rotating work on said work carriage, a grinding wheel mounted for motion on said wheel carriage transverse to the line of traverse motion between grinding and truing positions, a truing mechanism carried by said wheel carriage for truing said wheel when said wheel is in truing position, means for moving said wheel carriage transverse to the line'oi traverse for feeding the wheel to the work and for retracting said wheel from the work, a rotary cam means, means for rotating said cam means, means effective adjacent to a limit of traverse for starting said rotating means to rotate said rotary cammea'ns through a definite angular extent, and means on mounted for motion on said wheel carriage 'trans-.

verse to the line 01' traverselbetween grinding and'truing positions, motor means for so moving said wheel, a truing mechanism includingan actuating motor carried by said wheel carriage for truing said wheel when said wheel is in truing position, means for moving said wheel carriage transverse to the line of traverse for feeding the wheel to the work and for retracting the wheel from the work, a rotary cam drum mechanism, means for rotating said cam drum mechanism, means eifective adjacent to a limit of traverse for starting said drum mechanism rotating means to rotate said mechanism for a definite angular extent, and means actuated by said drum mechanism for controlling said motors in predetermined sequence.

holder on said carriage, means for simultaneously rotating and traversing said carriage including a direction reversing mechanism, a wheel carriage mounted for motion toward and from work carried by said work holder, 9. wheel mounted on said wheel carriage for motion between grinding and truing positions, wheel truing mechanism carried by said wheel carriage in position to true said wheel when said wheel is in truing position, a rotary cam means, means for rotating said cam meansto'a definite; angular extent adjacent to one limitof said traverse, and means controlled by said cam means for retracting said wheel carriage for movingfsaid'wheel to truing and then to grinding positions relative ,to said wheel carriage and to actuate said truing'mechanism to true the wheel when said wheel is in truing position.

14. A machine of theclass described, compris ing a rotary work holder, means for rotating.- said holder, a grinding wheel,'means for driving said grinding wheel, means for effecting holder and'said traverse between work on said wheel, a grinding wheelcarriage movable transverse to the line of traverse, means for moving said wheel laterally of said traverse and with respect to said carriage between a grinding position and a truing position, wheel truing mecha-- nism for truing the wheel while said wheel is in truing position, and means acting at the end of a traverse to actuate said moving means to move said wheel relative to saidcarriage to truing position, to actuate saidrmechanism to true the wheel, and to actuate said'moving means to return the wheel to grinding position and to holder.

15. A machine of the class described, comprising a rotary work holder, means for rotating said holder, a grinding wheel, means for driving said grinding wheel, means for effecting traverse between work on said holder and said wheel, a grinding wheel carriage movable trans- I verse to the line of traverse, means for moving said wheel laterally of said traverse and with respect to said carriage between a grinding position and a truing position, wheel truing mechanism for truing the wheel while said wheel is in truing position, means for moving said carriage to efiect wheel feed and retractionthe ends of traverses, and means acting'fa ter a predetermined. number of grindin'ggtraverses and at the termination of a traverset'o actuate said moving means to move the wheel relative to said carriage to truing position and then to'stop the grinding cycle of the machine.

16. A machine of the class described, comprising a rotary work holder, means for rotating said holder, a grinding wheel, means for driving said grinding wheel, means for efiecting traverse between work on said holder andsaid wheel, means for moving said wheel laterally of said traverse between a grinding position and a truing position, wheel truing mechanism for truing the wheel while said wheel is in truing position, means acting at the end of each traverse for move said carriage toward work on said work producing truing feed impulse and for then starting the traverse in the-reverse direction, means for preventing such impulses from being effective, meansacting after a predeter move the wheel to truing position, to render said truing mechanism effective to true the wheel, to cause said truing mechanism after a.

truing action to condition said wheel moving means to return said wheel to grinding position, and the return of said wheel to-grinding position to cause resumption of traverse.

17. A machine of the class described, comprising a rotary work holder, means for rotating said holder, a grinding wheel, means for driving said grinding wheel, means for effecting traverse between work on said holder and said wheel, means for moving said wheel laterally of said traverse between a grinding Position and a. truing-position, wheel truing mechanism for truing the wheel while said wheel is in truing position, means for feeding said wheel relative to the work, means/acting after a predetermined extent of the ;wheel feed to condition the machine for stopping, a rotary'drum, means for :rotating said drum for a predetermined angular'extent at the end of each traverse, means controlled by the rotation of said drum for controlling said wheel moving and truing means after a predetermined extent of wheel feed to move said wheel to truing position and true the wheel and to stop its own rotation intermediate to said. predetermined angular extent, means actuated by said truing mechanism after a predetermined truing action to restart said drum toward completion of its rotation to said predetermined angular extent, and means acting selectively to stop the rotation of said drum either before or after reaching said truing mechanism actuating position, to stop the grinding action of the machine either without or with a final wheel truing but with the wheel in truing position.

18. A machine of the class described, comprising a rotary work holder, means for rotating said holder, a grinding wheel, means for driving said grinding wheel, means for effecting traverse between work on said holder and said wheel, means for moving said wheel laterally of said traverse between a grinding position and a truing position, wheel truing mechanism for truing the wheel while said wheel is in truing position, means for feeding said wheel relative to the work, a limit switch actuated by said feed-,

ing means after a predetermined extent of feed,

tating said drum through a predetermined angular extent at the end 'of each wheel traverse, electric switches'actuated by :the rotation of said drum timing-the-actuation of said, wheelmoving. meansand truing device actuating means at predetermined feed positionsof said wheel, and a stop switch inparallel with said limit switch selectively operative by the rotation of said drum. for stopping the rotation of said drum and the grinding action of the machine either before or after thetime of a truing actuation, whereby the grinding action stops after the actuation of said limit switch either without or with a final wheel truing.

19. A machine of the class described, comprising a rotary work holder, means for rotating said holder, a grinding wheel, means for effecting traverse between said wheel and work on said holder, means for moving said wheel laterally of the traverse between grinding and retracted positions, a rotary drum, means acting at the end of each traverse for rotating said drum for a predetermined angular extent, means for feedinz said wheel relative to the work, a limit device actuated by said wheel feed after a predetermined extent of feed, means actuated on the succeeding rotation of said drum after the actuation of said limit device to actuate 5 said wheel moving means to move said wheel to retracted position, and thereatter to stop its own rotation intermediate said predetermined angular extents and to stop further grinding action 01 the machine.

20. A machine 01' the class described including a carrier, a grinding wheel movably supported on said carrier for motion between an operative and an inoperative position, fluid pressure means for moving said wheel from one to the other of said positions, a latch having a bolt biased to project into holding relation to said wheel in either of its positions, and fluid pressure means connected to the supply 01 fluid pressure for said fluid pressure wheel moving means for retracting and so retaining said bolt .10 only during maintenance of the fluid pressure.

RALPH E. FLANDERB.