US1812003A - Grinding machine - Google Patents

Description

June 3o, 1931.

w. J. GUILD GRINDING MACHINE 1928 4 Sheets-Sheet l Filed May 31 June 30, 1931. w. J. GUILD 1,812,003

GRINDING MACHINE Filed May 31, 1928 4 Sheets-Sheet 2 flmlllll.ll-llllllllllllllll!! l 30 '4f/m f/f/ /ZQ/ l/ 6a g S14/vento@ F7 @aldo Quim w, ya@

June 30, 1931. w. J. GUILD 1,812,003

GRINDING MACHINE gwventot I? 5 K (/Oolclo EI Guild.

g @y www i June 30, 1931. w. J. GUILD GRINDING MACHINE Filed May 31. 1928 4 Sheets-Sheet 4 Patented June 30, 1931 UNITED STATES PATENT OFFICE WALDO J. GUILDf OF WORCESTER, MASSACHUSETTS,.ASSIGNOR TO THE HEALD MA- CHINE-COMPAN'Y, OF WORCESTER, MASSACHUSETTS, A. CORPORATION OF MASSA- CHUSETTS GR-INDING MACHINE Application filed May 31, 1928.

The invention relates to grinding machines of the general type sho-wn and described in Guild Patent N. 1,682,672 and Taylor Patent No. 1,682,673, both dated August 28, 1928; in the machines of said patents, the work-pieces are automatically ground to a predetermined size, responsive to movement of a transverse feeding mechanism through a predetermined-distance, following a dressing operation by` which the grinding wheel is made tangent to a given plane. The machines of said prior patents provide a cross feeding mechanism carrying an element which maugurates a dressingoperation when it reaches one point, and which subsequently stops the grinding when it reachesa second point; suitable compensating meansv being provided to periodically retract this element in relation to the cross feed screw, in order to overcome attrition of the wheel by wear and dressing, andv to insure that substantially the same amount of material may be taken off the grinding wheel lat each dressing operation.

The present invention contemplates an improvement in machines of this class, by way of separating the transverse feed that moves the grinding Wheel, the work head, and the dressing tool in relation to each other, into two separate feeds, one being the normal pro.

gressive feed that maintains the grinding Wheel and the workpiece in cutting relation, and the other being what may be termed a compensating or dressing feed, which feeds the grinding wheel toward'the dressing plane.

In the machine herein disclosed the kdressing device is always brought to a fixed posidressing device, but otheriarrangements of" these elements and motions can be made, the invent-ion contemplating broadly the separation of the dressing or compensating feed from the normal or grinding fee-d. In the drawings Fig. 1 is a front elevation of a grinding Serial No. 281,700.

n machine constructed in accordance with the parts throughout the drawings.

i Referring particularly to Fig. "l, the machine provides the usual reciprocatory table' or carriage l, which is ordinarilyy provided in any internal grinding machine. In such a machine, either the grinding wheel or the work to be ground may be carried on the table 1, the reciprocations of the latter being utilized ineither case to produce a relative traversing movement between the grinding wheel and the work. As here shown the `table 1 supports and carries a wheel' head 2 of the usual construction,-while the work which is to be operated upon is held in a work head 3, the latter being carried by a. bridge 4 which spans the slideways provided by the machine frame for the back and ment of the table 1.

Said back'and forth movement of the table 1, to cause a rotating grinding wheel 5 to make the required interior traverse of the workpiece held in the rotatingchuck 6 may be imparted in any well known manner, as for instance by the use of the iiuid pressure controlling andc reversing mechanism which forms the subject matter of U.'S. Letters Patent 4#1,582,468 to Heald and Guild, grant-ed April 27, 1926. Such mechanism, or its equivalent, forms no part of the present invention and a detailed description thereof is therefore unnecessary; but as an illustrative embodiment of such itis sufficient to note that forth movethe driving means employed for the reciprocation of the table 1, may produce the reversal of said table at each end of the latters normal working stroke in response to the en- 5 gagement by spaced adjustable dogs 7 and 8, arried by the'table, with an interposed mem- Although the driving means for the table 1 might be a gear drive or any other suitable l0 type, I prefer to employ a hydraulic drive, and consequentlythe reversing member 9 is connected in a manner not necessary to be de# scribed herein, to a valve member 10, which is therefore oscillated, and which controls the admission of fluid, put under pressure by a pump 11, to first one side and then the other of a cylinder 12, containing the usual double acting piston whose piston rod 13, as'clearly shown in Fig. 1, isl connected to the table 1. For further details of a particular hydraulic means for actuating a reciprocating table re-ference should be had to the aforesaid patent.y

As best shown in Fig. 4, the machine may be driven by an electric motor 14 to the drive shaft 15 of which is attached one element of a clutch 16. The other element 17 of the clutch is formed integrally with a pulley 18 around which, as best shown in Fig. 5, the

work driving belt 19 passes. The latter extends upwardly inside the hollow base 20 of the machine to a pulley 21 that is fastened to the chuck holding spindle 22, being guided and held under proper tension by a stationary idler pulley 23 and a tensioning idler pulley 24 that is mounted on a pivotal arm 25 and pressed against the belt by means of the usual spring 26. The belt 19 likewise passes around a pulley 27, the vconsequent rotation of which is utilized to effect the normal transverse feed between wheel and workpiece, ab will be hereinafter described. The work head 3, in which the chuck spindle 22 is journaled, is not fastened directly to the bridge 4 that spans the .slideways .28, 28 provided for the reciprocatory travel of the table 1, but is fastened to a cross slide 29, which rests upon ways 30, provided by said bridge in order that the work head may 'be moved transversely of the machine. The bridge 4 is pivotally attached to the machine at 31, and is adjustably held on the other side by a screw adjustment device 32K. Referring to Figs. 3 and 4, this device comprises a bracket 33, fastened to the base and extending upwardly on Vone side of the bridge, with its upper end between a pair of projecting ears 34, 34. An adjustment screw 35, which passes through the end; of the bracket and the ears 34, 34, is provided to permit angular adjustment of the bridge 4 on the machine base. In this manner the angular position of the work head can be regulated to present the axis of the workpiece in a line e5 exactly parallel to the axis of the rotating grinding wheel 5, or to generate a slight angle between these axes in order to grind workpieces having tapered holes.p The table 1 provides a long slot 36 at 'its left-hand end,

as best shown in Fig. 5, in order that it shall Y not interfere with the belt 19 when the Wheel plate 41 attached to the base 20. In order.

that this mechanism may be readily removed as a unit, the arm 27a is likewise attached to the front plate 41. To the front of the shaft 39 is fastened` a crank member 42 havj ing a radial T-slot 43. `A block 44 is located in che said Slot 43, and said bleek pmvides a projecting stud 45 to which a connector 46 may be pivotally fastened as by means of a nut 47. The block 44 can be adjusted to any position lengthwise of said slot as by means of an adjusting screw 48, thus to vary the radius of the circle described by the stud 45 and consequently to vary the oscillations imparted to the connector 46, it being noted that the block may be so positioned as to locate the stud 45 coaxially with the shaft 39 which -results in no motion of the connector 46.

The upper end of the connector 46 is pivotally attached by means of a stud 49 to an arm 50 which, as best shown in.Fig. 3, is pivotally mounted at 51 to the bridge 4. The arm 5,() carries a pivotally mounted pawl 52 which, when said arm is raised, is pressed, by devices which it is not necessary to describe herein, against a ratchet Wheel 53. Oscillation of the connector 46 and the arm 50 induced by rotation of the shaft 39 imparts oscillation to the pawl 52 and consequently rotatesthe ratchet 53 intermittently.

The ratchet wheel 53 and a hand wheel 54 are both fastened to a screw shaft 55 which, as shown in Fig. 3, is suitably journaled in bearings 56 provided by the bridge 4 and the screw threaded part of which passes through a nut 57 suitably attached to and depending from the cross slide 29. rl.`he nut 57 may, as shown in Fig. 5, simply comprise a depending portion of thecross slide which is screw threaded.

It will be apparent that clockwise -rotai tion of the ratchet wheel 53 will result in drawing the cross slide 21 to the front of the machine thus producing a relative feed between the workpiece and the grinding wheel. In order to eliminate lost motion betwen the vnut 57 and the screw 55," as best shown in Figs. 3 and 5, I provide a set of vsprings 58, fitting in holes 59 provided by a depending projection 60 attached to the cross slide, and kpressing agaist a stationary portion 61 of the bridge 4.

Adjustably fastened in any desired angular position on the hand wheel or the casting 54a is a ring 62. This ring may carry the scale markings which are provided by cross feeding instrumentalities for machine tools for convenience in setting the machine, and at` all events it carries a cam projection 6'3. In the clockwise rotation of the dial ring 62, the cam 63 is adapted to successively engage adjustable screws 64 and 65 located inthe path of said cam projection, as best shown in Fig. 1. These adjustment screws 64 and 65 are carried by lever arms 66h and 67, the exact construction of which it is unnecessary to set forth here, as it forms no part of the present invention. s

Referring now to the wiring diagram vof Fig. 7, the lever 66 which is first rocked by engagement of the cam projection 6'3 with the screw 64, carries a movable contact point 66a which, when the lever is rocked, closes an electric circuit by contact with a station-J ary contact point 665. The closing of this electric circuit as hereinafter described,

, causes wheel dressing instrumentalities of ,the machine to be broughtinto operation. The lever 67 carries a contact terminal 67 a which in similar fashion is caused to engage a contact terminal 67 b and this closes another electric circuit, procuring longitudinal separation of the grinding wheel 5 from the workpiece, thus terminating the grinding operation.

The exact manner in which the dressing operation occurs comprises briefly the temporary withdrawal of the grinding wheel/5 from the workpiece, that is to say an amplification of its normal working stroke, and the disposal simultaneously of a wheel dressing member or diamond in the said ampliiied path thereby to dress and true the periphery of the wheel 5. As shown by the wiring diagram of Fig. 7, electric current may be supplied by a direct current generator 69 driven continuously by any suitable means, not shown, from the same source of power that is used for the rotation of the grinding wheel or the' workpiece or from any other source. One terminal 'of this generator 69 is grounded, as'shown at 70, and the other is connected by a supply lead 7l to a bar 72 of a switch,-the latter being designated as a whole by the-numeral 73 andI being disposed, as shown in Fig. 1, on the front of the machine. Said switch 73 provides an additional Contact plate or bar 74 which is adapted to be alternately connected and disconnected from the bar 72 by a connector 75, which is mounted on an oscillatory member 76 comprising part of'said fswitch; The latter is pivoted at 77 and in its normal position, as shown in Fig. 7, disposes the connector 75 in contact with and across the two plates 72 and 74; in the other position of movable member 76 said bars are wholly disconnected.

When the contact plates 72 and 74 are electrically connected, the supply lead 71 from the generator 69 is connected to a lead 78 running from the contact plate or bar 74 to the Energization of electromagnet 79 causes attraction of an armature member 82 and the consequent elevation of its attached lever arm 83, these parts lbeing pivoted at' 84 on the front of the machine. Integrally attached t0 -the armature '82 and the lever arm 83 is a depending arm 85, which consequently must .move when the first two named parts move.

In the procuring of the dressing operation 'as hereinbefore briefly outlined, the lever arm 83 acts to cause amplification ofthe path of travel of the grinding wheel 5, and the depending arm 85 causes the dressing point or diamond 68 to be lowered into the path of the wheel. y

The dressing device or diamond 68 is-desirably mounted in a screw plug 86, carried by an oscillatory member 87 which is mounted in bearings provided by a standard located at the rear of the machine, and it may be accurately adjusted as regards its operative position by means of a knob with scale markings 88, all `set forth. in a patent to Guild and Grimshaw, No. 1,655,903, granted January 10, 1928. Such mounting of the dressing point to swing. it into the path of the grinding wheel 5 and to acurately adjust its position of engagement with said wheel, and to hold it firmly against any pressure which may be exerted upon it, forms no part of the present invention-and will be found fully disclosed in the patent referred to. Suffice it to say that counterclockwise swinging of a lever 89, Fig. 5, which draws rearwardly a link 90 attached tothe oscillatory member-87, serves to lower said dressing diamond 68. The iuid pressure generated by the pump 11 is used to move this bell crank lever 89, a branch lead 91 from said pump'leading the fiuid to a valve gen-A erally designated by the-numeral 92; The

slidable valve member 93 of said valve isconnected, as shown in Fig. 1 at 94, to the depending arm 85, and when the said depending arm is moved in a counterclockwise direction by the magnet 79, the valve 93 is moved from the position shown in full lines in Fig. 6 to the\dotted line position of saidfgure.

,This admits fluid under pressure through said cylinder 98, and a pin 100@ provided by it is in engagement with the bell crank lever 89, and consequently rearward movement of said piston, in'response to iuid pressure actuation as described, swings said bell crank rlever in a counterclockwise direction to lower y the diamond 68 into the path of travel of thei wheel 5. i

Turning now to the manner in which upward movement of the leverarm 83 causes the normal path of travel of the wheel 5 to be amplified, and referring to Fig. 1, the left-hand table dog 8 which limits the righthand movement lofsaid table is carried by a block 101, which instead of being secured directly to the table 1, as'in the case of the block 102 of dog is mounted so as to be capable of sliding freely longitudinally of said table. Under normal conditions, when the table 1 is making its usual working reciprocations to traverse the grinding wheel 5 back and forth within the workpiece, the block 101 of dog 8 is held in definite spaced relation to block 103,1 which latter, the same as the block 102 of right-hand dog 7 is a stationary block adapted to maintain its predetermined setting or adjustment longitudinally of the table 1, as given it by any suitable adjustment or holding devlce, such as thefhand screw nut 104, shown in Fig. 1, applied to block 103, there being a similar device pro vided by the block 102 which is not shown. Said hand screw 'nuts engage with a screw rack 105 provided by the table 1.

The device employed to hold the slidable block 101 inspaced relation to the fixed block 103 is here shown as a latch lever 106, pivoted at'107 on the bloc-k 103, and having its free end disposed by gravity in abutting relation to a shoulder 108 on theblock 101, thereby holding the block 101 at apredetermined distance to the right of the block 103. When the latch member 106 is lifted to free its end from theshoulderi`108, the normal connection between theslidhble block 101 and the fixed block 103 is broken, and when this occurs on the -right-hand movement of `block 101, the dog,8 willbear without effect against the member 9. Thus the right-hand movement ofthe table 1 on this particular stroke will be 'extended beyond the usual reciprocatory working path, and the grinding wheel ,5 will be carried out of the hole in the workpiece to a point just beyond that occupied by the dressing device 68, which is moved into operative position the path of said wheel 5 as'the amplified right-hand travel of the table 1 begins. This amplified right-hand travel of table 1 involves relative sliding movement betwen said table and the block 101, owing to the obstruction which the reversing member 9 imposes against the dog' 8 to preventrblock 101 from moving with the table; finally, the block 101 brings up against 55 .the block 103, whereupon the solid backing thus afforded for the block 101 enables the dog 8 to shift the member 9. This procures reversal of the direction of travel of the table 1 and the left-hand movementof said table thus inaugurated is caused to restore the parts automatically to normal position in the following manner. 4 c

A member 109 pivotally mounted at 110 on the frame of the machine has a pair of inclined surfaces 111 and 112 for co-operation with inclined surfaces 113 and 114 at the lower corners of the block 101. A spring 115 presses said'member 109 upwardly. In the norma-l grinding operation of the machine, whon the blocks 101 and 103 arev connected by latch 106, the surfaces 111 and 112,

`although in the path of the block 101, offer no effective obstruction to the back and forth travel of said vblock in unison with the table 1, it being obvious that when either lower corner of the block under these conditions strikes either of the beveled surfaces 111 or 112, such contact will wedge the spring 1 15 downwardly, said spring yielding sufliciently to allow the block 101 to pass over the member 109. However, when the block 101 has been freed from the block 103 as above described, to amplify a single right-hand stroke of the table 1, the ensuing reversal of said table, with the block 101 still free, inds the surface 111 in osition to contact with the corner 113 of said lock, and under these conditions, the obstruction offered is suflicient to overcome whatever` friction there is to cause the block 101 to move to theleft with the table. The block 101 being thus held sta.

tionary while the table 1 and block 103 continue to move to the left, the latch member 106 finally resumes its normal position relative to the block'101, the end of said latch member dropping behind the shoulder 108 and the parts being thus automatically restored to normal position at the conclusion of each single amplied reciprocation of the table 1.

At the end of the amplified stroke of the table 1 to cause the dressing of the wheel 5 as just described, the valve member 93 is automaticallyreplaced in its initial position, as shownin full lines in Fig. 6, this operation ion being brought about by the movement of the table 1. As shown in Fig. 1, the block 101 provides a shoulder 116 which is adapted to contact with a vertical shoulder 117 of the leverarm 83. When the block'101 is in engagement with the block 103 and the dog 8 proceeds to swing over the reversing mem- .82, 83 and 85 in a clockwise direction to their normal position, where they are, held by the friction of the valve member 93 in the valve 92, the magnet 79 being deenergized at this time, as will be described. Such return of `subsequent return of the table 1 to normal grinding position procures theelevation of said dressing point 68 by the engagement of a cam member 119 provided by said table 1 with a roller 120 on the end of the bell crank lever 89, as will be apparent from the views of Figs. 4 and 5. 1

On the right-hand amplied dressing stroke of the table 1, as just described, an arm 121 pivoted at 107 and hanging by gravity, as shown in Fig. 1, strikes an arm 122 of the movable switch member 76, thereby rocking the connecting bar of'said switch member away from the lcontact bar 74 and thus preventing a repetition of the dressing stroke. Y

The machine is so set and adj usted that the dressing of the wheel 5, as just described, occurs after preliminary grinding of the workpiece. By said dressing operation the grinding wheel 5 is made tangent to a known vertical plane,.as determined by the position of the dressing device 68 when it is moved into operative osition. At the time of the inauguration oi) this dressing stroke the axis of the workpiece Yis located at a definite known positiony relative to the machine frame, depending only on the adjustment of.

the cam 63 andthe screw 64, and therefore if a predetermined and `known amount of cross feed movement of said workpiece is given thereto subsequent to the dressing operation, and the grinding then terminated, it

will be apparent that the workpiece will be brought to a definite known size. The wheel 5 having been subsequently returned into the workpiece to finish the grinding operation, the cross feed brought about by rotation of the screw shaft 55, as hereinbefore set forth,

proceeds for an exact predetermined amunt as measured by the angular turning of the ratchet 53, the dial ring 62 and the cam mem- -ber 63, until such time as said cam 63 engages The movement of' the adjustment screw 65. said screw 65, with consequent rocking of the lever 67 to bring the contacts 67 a and 67 b together, procures the termination of the grinding operation. As the Workpiecevhas been fed an exact predetermined amount since the location of the cutting edge of the grinding wheel 5 in adenite relation to the axis of the workpiece, the said grinding operationv is terminated with the workpiece at the exact desired size.

Referring again to the wiring diagram of Fig. 7 a branch71arl from the lead 71 connects to an electromagnet 123, which is located on the front of the machine directly behind the electromagnet 71 and which since it is desirably of the same form and shape as the other electromagnet, is completely hidden by it in Fig. 1. Said electromagnet 123 is, however, shown in the Wiring diagram of Fig. 7. The other terminal of the coil of this el-ectromagnet is connected by a conductor 124 to the contactterminal 67 b; From the wiring diagram, without more description, it will be apparent that the electromagnet 123 is energized upon the making of the circuit at the contacts 67a and 675.

' Pivotally mounted on the same pivot shaft 84 that carries the armature member 82, the

lever arm 83, and the depending arm 85, is

`pivotally attached to its carrying block 101.

When the lever arm 126, the end of which is shown in Fig. 1, is raised by the energiza'- tion of the magnet 123 and consequent attraction of the armature member 125, the reversing dog 8, by reason of its pivotal mounting, is free to rid-e on 4the upper surface of said lever arm; thus the striking end of said dog 8 is rcarried clear of the reversing member 9, and. the table 1 continues its movement to the right carrying the grinding wheel 5 out of the workpiece and well past the then inoperative dressing device 68, said table ultimately carrying the grinding wheel 5 into the position illustrated in Fig. 1, and there being brought to a full stop by any suitable means, such as that shown in the aforesaid patent to Heald and Guild.

Referring to Fig. 6, such stoppage of the table 1 is herein illustrated as being brought about by the striking of a pin, not shown, carried by the table 1 against a lever 127. Said lever 127 is pivotally mounted at 128 and one end of said lever engages a cap 129 which is spring pressed upwardly, and which is lmounted on the top of a rod 130. The rod 130 terminates in a head 131. below a poppet valve 132, the latter being pressed upwardly by a heavy coil spring"13r3. The spring 133 holds the poppet valve 132 away from its seat 134, and consequently normally allows the fluid to iiow through a port 135 to the left-hand of the cylinder 12, but when, by striking of the pin against the lever 127, the rod 130 is depressed, thus compressing the spring 133, the valve 132 is closed by the pressure of the fluid, and this brings the table 1 to a stop.-

If the mechanism already described were provided and no more, the grinding wheel 5 would be dressed and trued but once, since the wearing away of the grinding wheel eef which always results in use would reduce it below its original size, and on subsequent movements through the dressing position it. -would not make Contact with the dressing feed, which is in said applications disclosedas an absolute movement of the grinding wheel. The resent invention distinguishes from the subject matter of the aforesaid applications in the separation of the normal or cutting feed from the compensating feed. The first of these two, involving absolute movement of the work head, hasalready been described, and the automatic instrumentalities for periodically moving the grinding wheel in order to insure contact between it and-the dressing device will now be set forth. 1

As best shown in Fig. 1, the Wheel head 2 is not carried directly by the table 1 but is carried by an interposed" cross-slide 2a, which is mounted on cross-slide ways 136 which may be similar to the Ways provided for the movement of thecross-slide 29.- A screw shaft 137, to which is attached a hand wheel 138, is provided to m'ove saidl crossslide transversely of the table 1, there being a nut, not shown, depending from the cross-slide 2a which may be in all respects similar to the nut 57. Suitably fastened-to the screw shaft 137 or the hand wheel 138 is a ratchet wheel 139, which is shown in Fig. 2;-movement of the table 1 to the position shown in Fig. 1 causes a pawl 140 to movesaid ratchet wheel 139 through a limited distance, thus causing movement of the cross-slide 2a on the Ways 136 by a predetermined amount.

As shown in Fig. 2, the pawl 140 is pivotally mounted at 141 on an arm 142 which is in turn pivotally mounted onthe shaft 137.

^ A stop pin 143 is provided to normally lo'- cate the arm 132 in the position shown in Fig. 2a spring 144 holding it inthis position, said spring extending between a stationary pin 145 and the pin 146 projecting from the hub ofthe lever arm 142. Pivotally mounted at 147 on the arm 142 is an arm 148 which normally hangs downwardly in the position shown in Fig. 1, said arm 148 being entirely free on the arm 142'except when,.as shown in Fig. 2, said arm 148 engages a stop lug 149 projecting from the hub of the arm 142. Such engagement is brought about by travel of the table 1 to the position shown in Fig. 1, and on its said outward movement, the arm 148 is rocked to the position shown in Fig. 2 by means of an inclined cam 150. When the parts have reached the position shown in Fig. 2 no further movement of the arm 148 can take place without swinging the arm 142 on its pivot 137 ;-such movement does take place and moves the pawl 140 through a limited distance, said pawl being caused to engage the teeth of the ratchet wheel 139 by cam devices which are very familiar to those skilled in this art and need not be described. This action procures limited turning of the screw shaft 137, but it should be noted that the subsequent return of the table 1 to'its operative position has no effect on the said screw shaft, since the depending arm 148 can swing to any extent to the right on its pivot 147.

Of course the hand wheel 138 can be manually moved at any time to adjust the axis of the spindle 5a, carrying the grinding wheel 5, relative to the machine base. Insomuch as the hand wheel 138 may provide a suitable scale, the adjustment of the machine for different sizes of workpieces is facilitated. Moreover, in the machine of the present invention, the relationship of the three elements which determine the proper grinding to size of workpieces, such elements being the axis of rotation of the workpiece, the axis of rotation of the grinding wheel, and the operative position of the diamond, may at all times be known by providingproper scale markings. Although it should be understood that such will not' entirely eliminate the method of trial and error in setting the machine to grind a given size of workpiece,

since no matter how carefully a machine is made, the spring in the various parts, slight play in bearings, and expansion or contraction of the metal due to'varying temperatures, as well as the actual wear of the-diamond point 68 itself make such method of trial and error necessary, nevertheless what may be termed a prima. facie setting of the machine maybe effected by the several scales provided by the hand wheels 54 and 138 and the knob 88. Furthermore the scale markings whichmay be provided in conncction with the hand wheel 138 register quickly, not only the amount of compensation given to the grinding wheel 5 between' successive grindlng operations, but serve to register the sum total of compensations, and thus serve to remind the operator of the gradual diminution of the/sizeof his grinding wheel in'volving the ltimate replacement` of the same. Other4 a vantages of the present arrangement'will readily occur tothose` skilled in the v art.

Although not herein described, because forming no part of the present invention it should be understood that separation of the grinding wheel head 2 and the work head at the termination of the grinding operation causes the clutch elements 16 and 17 to be separated, thus stopping the rotation of the spindle 22 and furthermore stopping the automatic actuation of the cross-feed shaft 5v5. This allows the operator to reposition the cross-slide 29 by manual rotation of the hand wheel 54.

I claim:

l. The combination with a grinding machine comprising means for supporting the work, means for supporting a grinding wheel, means for producing a reciprocating motion of one of said before mentioned means with relation to the other, means to so control said motion as to cause a relative traversing motion between the wheel and the work, one past the other in contact, or to cause the withdrawal ofone from contact with the other and subsequent restorationto Contact, a tool for dressing the grinding wheel so mounted that it is engaged by said wheel when the contact between the work and grinding wheel has been so interrupted, feeding mechanism to `feed the workpiece transversegto the said traversing motion to maintain grinding contact, and separate feeding mechanism to feed the grinding wheel transverse to said traversing motion and toward said dressing tool; of devices operated directly by said first named feeding mechanism and operable on said motion controlling means to cause the withdrawal motion and then to restore the contacting traversing relation of work and grinding wheel, and means for periodically moving the feeding mecha-I nism that feeds the grinding wheel, whereby the grinding may proceed by a succession of uninterrupted traversing motions confined to the surface to be ground and at a stage determined directly by the movement of the feeding mechanism the contact of grinding wheel and work is automatically interrupted, the grinding wheel being dressed despite wear because of its periodic advance toward the dressing tool, the traversing contact with the work being then resumed.

2. The combination with a grinding machine comprising-means for supporting the work, means for supporting a grinding wheel, means for producing a reciprocating motion of oneof said before mentioned means with relation to the other, means to so control said motion as to cause a relative traversing 'motion between the wheel and the work, one

past the other in contactfor to cause the withdrawal of one from contact with the other and subsequent restoration to contact, a tool for dressing the grinding wheel so mounted that it is engaged by saidwheel when the contact between the work and grinding wheel has been so interrupted, feeding mechanism to feed the`work'pieoe transverse to the said traversing motion to maintain grinding 5 erating the work feeding mechanism during the traversing contact of the work and grind- .ing wheel -before and after the withdrawal vmotion, and means for periodically moving the feeding mechanism that feeds the grinding-wheel, whereby the grinding may proceed by a succession of uninterrupted traversing motions confined to the surface to be ground and at a stage determined directly by the movement of the feeding mechanism the contact of grinding wheel and work is automatically interrupted, the grinding wheel being dressed despite wear because of its periodic advance toward the dressing tool, the traversing contact with the work being then resumed.

3. In a grinding machine, a grinding wheel, mechanism for procuring a cross-feed between said wheel and a workpiece, a dressing tool, means directly actuated and controlled by said `cross-feed mechanism in the grinding of each workpiece and set in operation only after said cross-feed mechanism has caused preliminary grinding of a given workpiece to procure ,a dressing operation on said grinding wheel, means for automatically procuring cessation of the lgrinding operation on each workpiece upon the feeding movement of said cross-feed mechanismthrough `a predetermined distance beyond the point' where said dressing occurred, and an entirelyl parallel to a geometrical element of the sur- .face of said wheel while maintaining the dressing device a fixed distance from the line of contact of said workpiece as hereinafter defined, thus to remove material from said grinding wheel, automatic means to move said first named 'feeding element, measuring means associated with saidau'tomatic feeding means to measure increments of said feed, the means for moving said iec measuring means and dress-ing device relatively beingset in operation by said'measurmg means, means to periodically move said second named feeding element, whereby the means for moving the grinding wheel and vdressing device relatively may be caused to operate after preliminary grinding at a given point in the mvement of said rst named feeding element, contact between the wheel dressing device being insured by periodic movement of said second feeding element, means to cause the automatic feeding means to cease moving the irst element, said means being also actuated by said measuring means, said measuring means and the means to cause the automatic feeding means to cease operation being thus adapted to stantially at right angles to the movement of said carriage, a grinding wheel carried by one of said cross slides, workholding and rotating means carried by the other of said cross slides, and a dressing device, movement of either of said cross slides being thus adapted to change the relative positions of the,l axes of `the 'wheel 'and workholding means, and movement of one of said cross.

A slides being adapted to change the relation between: the axis of the wheel and the dressing device, and automaticmeans to periodically move the last named cross slide.

6. In agrinding machine, a longitudinally movable carriage, a pair of transversely movable cross slides, one of said slides being mounted onsaid carriage `for movement substantially at right angles to the movement of said carriage, a grinding wheel carried by one of said cross slides, workholding and rotating means carried by the other of said lcross slides, and a dressing device, movement of either of said cross slides being thus adapted -to change the relative positions of the axes of the Wheel andworkholding means, and movement of one of said cross slides being adapted `to change the relation between the axis of the wheel and the dressing device, means to .cause said carriage to move to separate the grinding wheel and workholding means and to bring them together.. again to permit the changing of workpieces, an means operated during said extended movement to operate the cross slide that procures a relative change between the grinding wheel and the dressing device.

7. In a grinding machine, the combina# tion with awork head, a grinding Wheel,

-means for periodically giving said wheel a feed towards the dressing device to compensate for gradual diminution in size of said wheel, saidmeans being absolutely independent of themeanrs producing the cutting feed.

' WALDO J. GUILD.

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