US1702267A

US1702267A - miller

Info

Publication number: US1702267A
Authority: US
Publication date: 1929-02-19
Anticipated expiration: 1946-02-19

Description

H. G. MILLER GRINDING MACHINE Feb. 19, 1929. 1,702,267

Filed Sept. 18, 1925 5 Sheets-Sheet 1 5/17///// A "Hakim [1 kg gluon Ito's z'i a/rry Jlille Feb. 19, 1929. 1,702,267

H. G. MILLER GRINDING MACHINE Filed Sept. 18, 1925 5 Sheets-Sheet 2 HM if Feb. 19, 1929.

. 1,702,267 H. G. MILLER GRINDING MACHINE File d Sept. 18, 1925 5 Sheets-Sheet 3 Zarry J/iller a toz mug Feb. 19, 1929. 1,702,267

H. G. MILLER GRINDING MACHINE Filed Sept- 18. 1925 5 Sheets-Sheet 4 iii "IL;

a2, I Within? Feb. 19, 1929.

l,702,267 H. G. MILLER I GRINDING MACHINE Filed Sept- 18, 1925 5 Sheets-Sheet 5 I Z L-J-wnn 2 4??? Miller.

l a al ke-cum will proceed to describe the same in detail, reference being made to the accompanying drawing in which is illustrated an embodi- Inent thereof.

In this drawing:

Fig. 1 is a top plan view of my improved machine showing a valve in place and the machine adjusted for grinding purposes;

Fig. 2 is a section cutting the carriage tail stock on the line 2-2 Fig. 1, shown on a larger scale;

Fig. 3 is an elevation looking in the direction of arrow 3, Fig. 1, parts being broken away and the carriage shifted to present a straight end view;

Fig. t is a vertical section. taken through the head stock of the carriage on the line 44, Fig. 3, shown on a larger scale;

Fig. 5 is a horizontal section taken through the cruciform standard supporting the head stock end of the carriage, looking downwardly upon the adjustable segmental member. This section may be indicated by the line 5-5, Fig. 6;

Fig. 6 is an elevation looking in the direction of arrow 6, Fig. 1;

Fig. 7 is a section taken through the carriage and the stem of the valve to be ground, on the line 77, Fig. 1, the grinding wheel being diagrammatically outlined;

Fig. 8 is a view similar to Fig. 7 and showing a leaf spring engaging the valve stem in opposing relation to the open bearing;

Fig. 9 is a section similar to Figs. 7 and 8 showing a modified form of open bearing for the valve;

Fig. 10 is a top view of the head stock end of the carriage with the valve in place, illustrating the adjustment for varying the grind- 111g angle, two positions being shown. In this view the grinding wheel is illustrated for position only;

Fig, 11 is a fragmentary elevation of the head stock end of the carriage, showing its adjustable relation to the emery wheel. This is a modification of the construction shown in Figs. 3, 12 and 13;

Fig. 12 is a vertical section taken through the structure below the head stock end of the carriage, for moving the latter toward and away from the grin ding wheel, the parts being shown on a larger scale than in the previous views taken on line 1212 of Figure 6;

Fig. 13 is a section on line 1313, Fig. 12;

Fig. 14 is a horizontal section of the machine partly broken away, illustrating means for automatically imparting the oscillatory movement to the work-holding carriage during the grinding operation Figs. 15 and 16 are vertical sections taken on the lines 1515 and 1616 respectively of Fig. M;

Fig. 17 is a View similar to Fig. 15 illus trating a modified form of construction;

Fig. 18 is a fragmentary view showing means for the vertical adjustment of the grinding wheel so that the contact line between the wheel and valve face may be at, or above or below a horizontal plane passed through the center of the wheel.

In this drawing let the numeral 5 designate a base upon which is mounted and secured an electric motor 6. Also, mounted on the base is a frame member 7 which extends upwardly above the motor and in which is journaled the shaft 8 upon which is mounted and connected to rotate therewith, a grinding wheel 9 of the usual or any suitable form. Upon the motor shaft 10 and mounted to 1'0- tate therewith, are two

pulleys

11 and 12, the pulley 11 being relatively large and connected by a belt 13 with a small pulley 14 connected to rotate with the grinding wheel shaft, and whereby rapid mot-ion is transmitted to the grinding wheel when the machine is in operation. There are also mounted on the base, in a position that may be termed forward of the motor, relatively

short frame members

15 and 16. In the upper extremity of the frame member 15 is threaded a relatively large adjusting screw, the upper part of the frame member being split as shown at 18 and adjustable by means of a screw D. The forward end of the screw 17 is provided with a hand wheel 19 for operating purposes. The screw 17 (Figure 12) is hollow to receive a head stock supporting rock shaft 20 which is mounted for both rotary and longitudinal movement therein. The extremity of the screw 17 remo e from the hand wheel abuts against a shoulder 21 formed on the rock shaft 20. From the shoulder toward the right (see Fig. 12) the rock shaft 20 is enlarged and provided with a hollow portion 22 in which is located a coil spring 23, one end of which engages the rock shaft 20 at the closed end of the hollow portion, while the other end engages the frame member 16 at 24 which member is cored out as shown at 25 to receive the spring and the hollow portion of the rock shaft 20.

Secured to the enlarged portion of the rock shaft 20 by screws 26 is a. collar 27 which, as shown in the drawing, is formed integral with an upwardly projecting head stock member 28 having a horizontally extending cylindrical bearing portion 29 in which is journaled a shaft 30 to whose opposite extremities are secured

pulleys

31 and 32 respectively, the axis of this shaft extending at right angles to that of the rock shaft 20. The pulleys 12 and 81 are connected by a belt 1 whereby motion is transmitted from the motor shaft to the shaft 30. The upper portion of the head stock member 28 provided with a part 33 having a flat face 34. upon which is rotatably mounted a segmental part 35, whose curved edge is graduated as shown at 36 and coincides with asimilar peripheral edge 37 screw 47.

of the part 33, having a zero mark 38. The contacting faces of the

parts

33 and 35 are held in cooperative relation by a small block 39 which is secured to the part 33 by a screw A and recessed to receive both parts, theportion of the block overhanging the part 35 having an opening threaded to receive a set screw 40 for holding the two

parts

33 and 35 in any desiredposition of adjustment, and for a purpose hereinafter explained. The two parts 33and 35 are connected as shown at 41 (see Fig. 5) to permit the part 35 to move in the performance of its function when the set screw 40 is released. The part 33 is provided with a number of holes 42, either of which, by the movement of the part 35, may

be made to register with the hole 43 formed in'the part 33 whereby the two cooperating segmental members may be positively locked in certain predetermined positions, by a pin E. Y

' Extending upwardly fromthe part 35 and as shown in the drawing formed integral therewith is an upper head stock member 44 whose upper portion 45 is cored to'receive a centering spindle 46 (Figures 1, 4 and 10) which is held relatively stationary by a set The extremities of the spindle arecone-shaped and one of them engages the center of the valve 48 to be ground, when the machine is in operation. As hereinafter explained it fixes the center of the valve in line with the axis of the spindle and stem regardless of the original eccentricity of the valve before it is ground.

Journaled on the spindle 46 is a pulley 49 carrying two spring actuated pins 50 which engage the valve 48 at equal distances from the center and whereby the valve may be rotated for grinding purposes. The pulley 49 is connected with the pulley 32 by a belt 3 whereby rotary movement is transmitted to the pulley 49 for rotating the valve during the grinding operation.

The upper extremity. of the upper head stock member 44 is also provided with a part 51 cored to receive one end of a rod 52 which is secured therein. Near this end of the rod is mounted a'bracket 53 having an arm 54 (Figures 6 to 9) whose extremity remote from the rod has an open curved recess 55 adapted to receive bushings or bearings 56 which are provided with pins 57 adapted to engage an opening in the arm communicating with the recess, whereby any bushing is readily removedas circumstances may require. The arm is adapted to hold bushings of sizes varying to correspond with the size of the stems of the valves to be ground.

The rod 52 is also provided with a tail stock bracket 58 cored at one extremity to receive the rod as shown at 59, the bracket being longitudinally slidable on the rod and held in the desired position of adjustment by a set screw 60. The opposite extremity 61 of the bracket is cored to receive a plug 62 (see Fig. 2) which is surrounded within the part 61 by a coil spring 63 which acts upon a shoulder ofthe plug to move the latter against the head 64 of a spindle 65 which is located in a central longitudinal opening formed inthe plug, the extremity of the spindle bearing against a ball 66 at the inner extremity of the opening.

The plug 62 passes entirely through the cored part 61 of the bracket, its extremity remote from the head 64 being slotted as shown at 66 to receive a cam 67 which is pivotally connected with the plug as shown at 68 and provided with a handle 69 whereby it may be turned on its pivot and brought into engagement with the relative stationary bracket, for the purpose of moving the plug against the spring and away from the head of the spindle which is recessed to receive the tappet end of the stem 70 of the valve to be ground.

WVhen the cam is loose, as shown in Figures 1 and 2, the spring acts on the plug to hold the latter against the head 64 of the spindle whereby the valve is properly positioned be tween the two

spindles

46 and 65 during the valve grinding operation, the open bearing engaging the stem intermediate its extremities, and cooperating with the end spindles and the grinding wheel to secure perfect concentrlcv action of the valve during the grinding operation.

The bracket 53 is provided with an arm 71 (Figures 6, 7 and 8) extending downwardly at right angles to the arm 54 and terminating in a cylindrical member 72 which is connected with a similar coredframe member 73 by a pin 74 which is fast in the connected parts. As the member 7 3 is formed integral with the frame part 44 and connected with the rod supporting member 51 by a web B, the bracket 53 is securely held against independent movement on the carriage, this term being applied to the rod 52 and its connections and attachments for holding and carrying the work. When the machine is in operation, the carriage and the

head stock members

44 and 28 and their attachments are adapted to oscillate about the axis of. the rock shaft 20 in the

upright frame members

15 and 16 which are preferably integral with the base 5. During this oscillating movement, the face of the valve to be ground is carried back and forth upon the peripheral face of the grinding wheel as heretoforeexplained.

The aforesaid oscillating movement of the structure composed of the various parts mentioned may be limited by a tail piece 7 5 which preferably and as shown in the drawing is integral with the collar 27. The lower extremity of this tail piece extends into an openiug 7 6 formed in the base of the frame and is provided with a pin 77 threaded in an opening in said piece and adapted to engage the walls 7 8 and 7 9 of the opening according to the direction of oscillation. Or, the carriage may be mounted on a horizontally disposed pivot pin 80 (see Fig. 11) mounted on a member 81 extending upwardly from the base as shown in Figure 11 where a modified form of construction is diagrammatically illustrated. In this case the upright carriage supporting frame part-s are designated 82 and 83, respectively, carrying the cooperating

segmental plates

33 and 35 for varying the angle of the carriage depending on the re uirements of the valve to be ground.

n Fig. 9 the open bearing for the valve stem is shown V-shaped and is designated 56 In this case the end of the arm 54 remote from the carrying rod 52 is formed flat to engage the adjacent face of the bearing and is bored to receive a pin 57 which is held in place by a set screw 84:-

111 Fig. 8 the open bearing 56 is cut away as shown at 85, the pin is dispensed with, and a leaf spring 86 secured to the lower end of the bracket arm 71 engages the valve stem and holds the latter, as well as the open bearing 56, firmly in place. The spring 86 is secured to the bracket arm by a screw 87.

The frame which supports the grinding wheel is provided with two V-shaped rests or supports 88 adapted to receive the valve stem when it is desired to true its tappet end by bringing it in contact with the flat side of the grinding wheel. In this event the stem occupies a position parallel. with the shaft of the wheel (Figure 3). This frame is also provided with two other Vshaped members 89 in which the valve stem is held when it is desired to finish its tappet end by bevelling its edge.

From the foregoing description the use and operation of my improved machine will be readily understood.

In order to grind a valve the latter is mounted on the carriage between the head and tail stock members or so that the tappet end of the valve stem engages the recess in the head 64 of the spindle 65, while the valve is centered on the spindle 46 and engaged on opposite sides thereof by the yielding pins 50 of the pulley 4-9, the stem at a suitable location between its extremities, engaging the open bearing carried by the bracket arm 54. Then as the motor is started rotary movement is transmitted to the grinding wheel through the medium of the

pulleys

11 and 14 and the belt 13, and to the head stock pulley 419 through the medium of the

pulleys

12 and 31, the belt t and the pulley 32 which is connected with the pulley 49 by the belt 3.

Home, as soon as the motor is started, rotary movement is transmitted to the grinding wheel and the valve, both of which as shown in the drawing, rotate in the same direction.

The entire frame work upon which the head stock end of the carriage is supported, is fed toward the grinding wheel by manipulating the hand wheel 19 mounted on the feed screw 17. The plate 35 is also adjusted on the plate 33 to properly position the valve so that its face may be ground at the desired angle; This may be accurately determined by means of the graduated periphery of the segmental plate 35 and by the zero mark on the cooperating plate 33. As shown in the drawing, reference being made more particularly to Fig. 1, it is assumed that the carriage is so adjusted as to grind the face of the valve at an angle of degrees to the axis of its stem, as this is the usual valve face angle.

Having made these adj ustments, the valve holding :arriage oscillated to cause the face of the valve to move back and forth past the grinding face of the grinding wheel, the proper contact being maintained by the adjustment of the feed screw 17. During this movement the axis of oscillation is that of the rock shaft 20 as the carriage and its entire supporting structure move together. It will be obvious in Figure 1 that when the alve is at the center of its arc of oscillation across the face of the grinding wheel, the center of its seating surface registers with the central plane of the grinding wheel surface, this plane being also a vertical plane through the axis of the rock shaft 20. The rock shaft 20 is located near the base 5 of the machine. It is as distant from the valve as is conveniently practical and only a slight rocking i'novement (limited by the stop pin or screw 77) is suflicient to allow the valve to move across the face of the grinding wheel, owing to the long radius. The short are in which the valve moves has slight curvature, also due to the long radius, and when the adjustment is such that its contact with the grinding wheel is substantially in a horizontal plane through the axis of that wheel the oscillatory movement of the valve may, for practical purposes, be regarded as substantially a reciprocating movement in a straight line. It will also be understood that inasmuch as the valve is centered on the axis of the stem regardless of its own eccentricity and merely engaged for driving purposes by the head stock chuck pins without reference to its own center, the valve will be ground true to the axis of the stem. The stem being free from torque the valve engaging head stock chuck holds the valve against vibration and compels it to revolve with perfect accuracy on said axis. The contact of the face of the valve with the grinding wheel during the os cillatory movement, for ordinary purposes or for the purpose of refacing a valve having an area of peripheral contact with its seat of substantial width, or what may be termed a flat face, is in a line that intersects the adjacent extremity of a horizontal diameter of the grinding wheel at the center of the grinding face of the latter. With an adjustment of the grinding wheel for this purpose, the

valve will be reciprocated in an arc of slight curvature the central portion of which is a little above the horizontal diametrical plane of the wheel and the ends a little below that plane and the seating surface of the valve will be substantially flat in the sense that its transverse lines in planes radial to its axis will be straight lines. In other words, if the'val-ve has a beveled seating surface it will be ground to a substantially true cone, its movement being in a plane substantially tangential to the cylindrical periphery of the wheel.

But if the wheel is raised so that the valve reciprocates in a substantially parallel plane nearer to the wheel axis, i. e., ina chord of its periphery the valve axis, (stem axis) will be tilted in opposite directions at the respective ends of the reciprocating stroke and the wheel will then grind only at one margin of the seating surface when at one end of the stroke and at the other margin when at the other end of the stroke, the wheel receding from the seating face of the valve at all other points. Therefore the seating surface will be ground to a distinctly convex form. The converse will be true when the grinding wheel is lowered to a point where all portions of the arcof reciprocation are below said horizontal plane. The seating face of the valve: will then reciprocate in a chord of the wheel periphery but grinding will take place principally at the center of the arc, the marginal portions of the wheel and of the seating face of the valve, receding from the central point of grinding contact. If it is desired that the valve face should have a concave form, it is made to engage the grind ing wheel above the horizontal diameter; while if it is desired to give the valve face a convex form, the contact is made below such diameter or below a horizontal plane intersecting the center of the wheel.

Provision is made as illustrated in Figure 18 for the Vertical adjustment of the grinding wheel for the aforesaid purpose. By giving the valve face a convex form, a single peripheral line of contact between the valve and its seat may be maintained. This construction will give better results than where there is a substantial area of face contact between the valve and its seat for obvious reasons.

In Figure 18 the grinding wheel is shown mounted on a separate frame piece 90 slotted as shown at 91 to receive screws 92 which are threaded into the stationary part 93 of the whereas if the wheel is adjusted to bring its center above that of the valve, the face of the latter will be given a convex form.

This provision of my improved machine, whereby the valve face may be made substantially flat, or concave, or convex with the same machine, and by a simple variation in the vertical adjustment of the grinding wheel whereby the grinding contact line may be in a horizontal plane at or above or below the center of the grinding wheel, is a very important feature.

It is obvious that the vertical adjustment of the valve holding carriage, while the grind: ing wheel remains stationary will produce the same result, as the only desideratum is the vertical variation of the position of the line of grinding contact between the faces of the valve and grinding wheel.

Heretofore in this description, it has been assumed that the oscillatory movement of the carriage to cause the valve face to move past or across the grinding face of the wheel, has been directly accomplished by the hands of the operator. This operation may, however, be accomplished automatically by mechanism illustrated in Figures 14, 15 and 16 of the drawing. As shown in these views, the motor shaft is extended beyond the large pulley 11, and a pulley 94 is mounted thereon, and connected by a belt 95 with a larger pulley 96 mounted on a worm shaft 97 whose worm 98 engages a worm wheel 99 fast on a shaft 100 j ournaled in frame members 101 and 102 (see Fig. 16). On the shaft 100 is loosely mounted an eccentric cam 103 which when locked on the shaft acts on an anti-frictional roller 104 carried by an arm 105 formed integral with and projecting laterally from the collar 27 and the tail piece 75. Formed on the tail piece and projecting therefrom in a direction opposite the arm 105, is'a tubular part 106 arranged to telescope loosely in an opening formed in a frame piece 107 fixed on the bed plate. A coil spring 108 is located in the parts 106 and 107 and so arranged as to be placed under tension as the tail piece is actuated by the cam and serves to impart movement to the tail piece in the opposite direction as the cam recedes. In order to control the movement of the cam, the latter is normally loose on the shaft which, however, extends into a sleeve 116 which has a limited sliding movement on the shaft, but is connected to rotate therewith by means of a pin 117 fast on the shaft and extending into a slot 118 in the sleeve. This sleeve has a hand wheel 119 at its outer extremity, while its inner end is provided with a clutch face 120 adapted to interlock with a corresponding face 121 formed on the cam.

Referring to Figures 14, 15 and 17 of the drawing it should perhaps be explained that the opening in the part 107 is large enough to compensate for the slight are described by the tubular member 106 during its telescoping movement in the frame part 107, due to the oscillation of the part 7 5.

It is evident that this construction will automatically impart the necessary oscillating movement to the carriage to move the valve face back and forth across the grinding face of the emery Wheel in the same manner as when the operation is manually accomplished. Instead 01 using the worm-gear-operated earn, a single hand operated feed screw 110 (see Fig. 17) may be threaded in a lug 108 fast on the frame, the end of the screw engaging a projection 109 formed on the lower end of the tail piece and in opposing relation to the spring 108 and its associated parts.

It is evident that by turning this feed screw by the use of the hand .wheel 111 and in a direction to place the spring under tension, and then reversing the action at the feed screw, the oscillatory movement of the carriage may be accomplished for the purpose stated.

In feeding the carriage toward the grinding wheel by mechanism best shown in Fig. 12, a space 112 is left between the collar 27 and the adjacent end 113 of the "frame when the parts are in the position shown. In order to keep this space free from foreign matter, which might interfere with the proper operation of the machine, a dust cap or plate 114 is clamped to the collar 27 by a screw 115, and overlaps the adjacent cored out frame part. This cap of sufficient size to accomplish the aforesaid function. i

The outer flat side C of the large driving pulley 11, may be made a grinding surface (see Fig. 3) and utilized for grinding articles as piston rings, requiring a relatively large grinding area. In. grinding these rings the sides of the rings are held against the fiat grinding face of the pulley.

It should perhaps be explained that the reason the spindle 46 is cone-shaped at both ends, is in order to make it reversible and so that either of these ends may be used.

Having thus described my invention, what I claim as new is:

1. In a machine for grinding stemmed valves true to the axes of? their stems, the combination with a grinding wheel, of: a work support having stem centering means operative upon the stem independently of the valve supporting end thereof and at widely separated points, one of which is in proximity to the valve, said supporting means being adapted to permit instant removal and re placement by longitudinal and lateral manipulation, and a driving head adapted to engage and rotate a valve about the axis of its stem without lateral displacement prc sure.

2. In a machine for grinding stem-med valves true to the axes of their stems, the combination with a grinding wheel, of a opposite sides of their stem axes and yield able independently of each other along lines parallel with said axes, whereby a valve may be engaged and rotated without developing resultant lateral pressures.

3. In a valve grinding machine, the com bination with a grinding wheel, of a carriage for the valve and its stem provided with head and tail stock members, a centering device on the tail stock member, a co-operating intermediate open bearing for the stem, and driving means carried by the head stock and adapted to engage the valve to rotate the latter about the axis of the stem as it is supported in the tail stock and intermediate bearings.

4:. In a machine for grinding stemmed valves, the combination with a grinding wheel, of a valve holder provided With a yielding socketed centering piece to receive the end of the stem, an intermediate open bearing adapted to hold the stem in true alignment with the axis of said socket, and a driving head adapted to engage and rotate the valve about said axis, said driving head having a spindle provided with a pointed end for engagement with the valve in the line of the stem axis, said driving head having a set of fingers adapted to engage the valve on opposite sides of the spindle point, each finger being mounted for independent yielding movement along a line substantially parallel to the axis 01 the valve stem, whereby the valve may be rotated without laterally defleeting pressure.

5. In a machine for grinding stemmed valves true to the axes of their stems, the combination with a grinding wheel, of a Work holder having aligned centering pins between which the stem may be engaged, an intermediate stem engaging and aligning bearing, said work holder being pivotally supported below the grinding wheel and adapted to hold a valve for reciprocation in an arc of slight curvature across the face of the grinding wheel adjacent to a plane which includes the grinding wheel axis and the cen tral portion of the valve,means for relatively adjusting the grinding wheel and work holder support at rightangles to said plane whereby said are of valve reciprocation may lie wholly above or below said plane or inany intermediate position, said Work holder being also adapted to yieldin gly move toward or away from the grinding wheel axis to hold the valve in continuous contact with the wheel during such reciprocation.

6. In a grinding machine, the combination with a grinding wheel of a movable head stock provided with a work holder and work rotating connections, of a mounting for the head stock comprising an axially movable rockable shaft to which the head stock is secured, a fixed support provided with a socket for one end of the shaft, a coiled spring seated in said socket against said shaft end, and a feed screw arranged to actuate the other end of the shaft in opposition to said spring.

7. In a grinding machine, the combination with a grinding wheel, of a movable head stock provided with a work holder and work rotating connections, of a mounting for the head stock comprising an axially movable rockable shaft to which the head stock is secured, a fixed support provided with a socket for one end of the shaft, a coiled spring seated in said socket against said shaft end, and a feed screw arranged to actuate the other end of the shaft in opposition to said spring, said feed screw having threaded engagement with a fixed support and socketed to receive the associated end of the shaft.

8. In a valve grinding machine, the combination with a grindingwheel, of a threaded feed screw support, a tubular feed screw in threaded engagement therewith, a rock shaft having a reduced end socketed in the feed screw, a co-opcrating support in which the other end of the shaft is socketed, a spring arranged to press the shaft in the direction of the feed screw, and a work supporting head stock secured to the shaft.

9. In a valve grinding machine, the combination with a grinding wheel, of a threaded feed screw support, a tubular feed screw in threaded engagement therewith, a rock shaft having a reduced end socketed in the feed screw, a co-operating support in which the other end of the shaft is socketed, a spring arranged to press the shaft in the direction of the feed screw, and a work supporting head stock secured to the shaft, and provided with a depending arm, said supports having a recessed base portion in which said arm is loosely engaged for movement along the axis of the shaft and for limited swinging movement in correspondence with rocking movements of the shaft and head stock.

10. In a Valve grinding machine, the combination with a grinding wheel, a head stock having its lower end pivotally supported for oscillation on an aXis at right angles to that of the grinding wheel, and located substantially in the central plane of grinding wheel rotation, a work holder on the upper end of said head stock adapted in one position of grinding wheel adjustment to hold a valve in position for contact with the grinding wheel substantially in a plane which includes the axis thereof and a chord of the central portion of the arc of oscillation, and means for raising and lowering the grinding wheel.

11. In a valve grinding machine the combination with a grinding wheel, of a valve holder, means for positively rotating the grinding wheel and holder, and means for oscillating the valve during a grinding operation in an arc across the face of the grinding wheel and interchangeably at difierent levels at and adjacent to the horizontal plane of its axis.

12. In a valve grinding machine the combination with the grinding wheel, of a carriage for the valve, said carriage being provided with head and tail-stock members for positioning and supporting the valve in the posi tion to be ground, the tail-stock member having a resilient plug adapted to act on the end of the valve stem, and the head stock member having a stationary spindle adapted to engage the center of the valve and a rotary'device carrying resilient pins adapted to engage the valve on opposite sides of its center.

13. In a valve grinding machine the combination with the grinding wheel, of a carriage forthe valve, said carriage being provided with head and tail-stock members for positioning and supporting the valve in the position to be ground, the tail-stock member having a resilient plug adapted to act on the end of the valve stem, and the head stock member having a stationary spindle adapted to engage the center of the valve and a rotary device carrying resilient pins adapted' to engage the valve on opposite sides of its center, the stationary spindle passing through a central opening formed in the rotary device.

In testimony whereof I aflix my signature.

HARRY G. MILLER.