US2121729A - Sizing apparatus for internal grinding machines - Google Patents

Description

June 21, 1938. R, A, COLE 2,121,729

SIZING APPARATUS FOR INTERNAL GRINDING MACHINES Filed Jan. 9, 1937 3 Sheets-Sheet 2 65 63 64 6,2 67 j J VA Y Q 2 =9/ 7? 92 5 /0/ (Y6 Y2 w 2 gwuc/wkw FFH/MUND Fl. CULE June 21, 1938. R. A. COLE 2,121,729

SIZING APPARATUS FOR INTERNAL GRINDING MACHINES Filed Jan. 9, 1957 s Sheets-Sheet 3 Fig 8 Swan/wk RHYME/v17 Fl. EIJLE SXIMMM 1 iii Patented June 21, 1938 UNITED STATES SIZING APPARATUS FOR INTERNAL GRINDING MACHINES Application January 9, 1937, Serial No. 119,772

4 Claims.

The invention relates to internal grinding machines, and particularly to automatically actuating size controlling apparatus therefor.

One object of the invention is to provide a sensitive photoelectric sizing apparatus and method for an internal grinding machine. Another object of the invention is to provide an internal grinding machine achieving precision results in the grinding of work pieces. Another object of the invention is to provide a completely automatic internal grinding machine with precision instrumentalities including size determining apparatus of sensitive characteristics. Other, objects will be in part obvious or in part pointed out hereinafter.

The invention accordingly consists in the features of construction, combinations of elements and arrangements of parts, as will be exemplified .in the structure to be hereinafter described, and the scope of the application of which will be pointed out in the following claims.

In the accompanying drawings illustrating one of many possible embodiments of the mechanical features of this invention,

Figure 1 is a front elevation of an internal grinding machine incorporating the invention;

- Figure 2 is an electrical diagram;

Figure 3 is a horizontal axial sectional view of the optical apparatus for directing the rays against the work piece;

Figure 4 is a sectional view, taken on the line 4-4 of Figure 3; I

Figure 5 is an optical diagram;

Figure 6 is a perspective view of one of the mirror instrumentalities which includes two reilecting surfaces;

Figure 7 is a further optical diagram in which the rays are projected into a single plane for purposes of illustration; and

Figure 8 is a fragmentary sectional view, on an enlarged scale, showing a portion of the optical apparatus.

Referring first to Figure 1, I provide an internal grinding machine which may be of the gen--' eral type identified by the trade-mark Size- Matic and which, so far as some of its features are concerned, will be found-described in United States Letters Patent No. 1,682,612 and No. 1,682,- 673 but, instead of relying on a predetermined advance beyond the dressing plane to control finished size of work pieces, I substitute the photoelectric apparatus herein particularly to be described. It should be understood, however, that I may embody the sizing apparatus more partic-,

ularly described herein with any other type of internal grinding machine, for example that disclosed in McDonough Reissue Patent No. 16,141, using one of the gauges thereof to initiate a dressing operation.

Considering now the illustrative embodiment of 5 the present invention, the machine includes a base ID, a work head Ii mounted on a bridge I2, and a carriage l3 mounted for reciprocatory movement on the base In under the bridge l2. The machine further includes a wheel head 14 10 mounted on a cross slide, not shown, which is mounted on the carriage 13 so that the wheel head I l may be moved transversely ,of the direction of reciprocation of the carriage 13, that is tosay substantially at right angles thereto. The wheel 15 head I4 journals a spindle 15 upon which is mounted a small grinding wheel i6, and any suitable drive for the spindle i5 is provided. The Ways supporting the carriage i3 guide the carriage I3 in the direction of the axis of the spindle I5 whereby the grinding wheel l6 may be advanced into a work piece 20, grind the work piece and thereafter withdraw to the position shown in Figure 1. The cross feed of the wheel head M on the carriage i3 is procured by rotation of a screw shaft 2| controlled by a hand wheel 22 and other 7 mechanism more fully described in the patent to Taylor No. 1,682,673 referred to. The rectilinear movement of the carriage l3 may be procured by mechanical actuation or by fluid pressure actuation as, for example, by the use of hydraulic mechanism described in Heald and Guild Patent No. 1,582,468, which includes a cylinder-piston unit, not shown, actuating a piston rod 23 which is connected by a bracket 24 to the carriage 5 i3. Automatic cross feed of the wheel head I4 is, as described in the Taylor patent referred to, achieved by a relative engagement of a cam 25 (adjustably fastened toa bar 26, one end of which is secured to the bridge 12 and the other end of which is secured by means of a bracket 21 to the base ill) with a roller, not shown, connected to a pawl 21. Pawl 2i actuates a ratchet wheel connected by reduction gearing to the screw shaft 2 I, all as is in detail illustrated in the Taylor patent referred to.

The control of the rectilinear movement of thecarriage l3 may be achieved by fluid pressure controlling and reversing mechanism described in aforesaid Patent No. 1,582,468 to Heald and Guild, the reversing valve being controlled by a lever 30 which'is interlocked with a reversing lever 3| so that when the lever 30"is to the right, the lever 31 is to the left, as shown in Figure 1, and vice versa. Suitable detents or load-and-flre devices 5 are provided and the lever 38 controls a. reversing valve to reverse the direction of motion of the table I3, as will be found described in the aforesaid patent to Heald andGuild, it being now well known to control the motion of a' grinding carriage by the actuation of carriage dogs on an interposed reversing lever, such as the lever 3|. The

carriage dogs which control the reversing lever 3|, as shown in Figure 1, include a fixed dog 32 adjustably mounted as by means of worm 33 and worm rack 34 on the carriage l3 and a pivotally mounted dog 35 which is capable of lifting over the reversing lever 3! when the carriage is traversed to the left, but will engage the lever 3| when the carriage I3 is traversed to the right and when the lever 3| is between the dogs 32 and 35. The dog 35 is mounted on a sliding block 36 capable of sliding with respect to the carriage l3 and controlled by a latch 31 which in turn is pivotally connected to a block 38 which is adjustably secured to the carriage l3 by means of a worm 39 and the worm rack 34.

Referring now to Figures 1 and 2, the machine further includes electromagnets 40 and 4|, the former being mounted in front of the latter, and both being mounted on the front of the machine, as shown in Figure 1. These electromagnets control levers 42 and 43. The lever 42 is in the vertical plane of the latch 31'. The lever 43 is in the vertical plane of the dog 35. When the lever 42 is lifted, the latch 31 will be raised, thus to allow the block 3'6 to slide, relatively, along the carriage [3, extending the reciprocatory traverse stroke of the grinding wheel I 6 to pass it by a dressing diamond 45 which is at that time low ered into the path of travel of the wheel l6. Raising of the lever 43 causes the dog 35 to pass over the reversing lever 3| to extend the stroke of the carriage l3 to the right, thereby to cause the grinding action to cease, the carriage I3 being stopped in the withdrawn position by devices not shown herein. The dressing diamond 45 is mounted on an adjustable screw plug 46 which in turn is carried by a swinging member 41 mounted on a trunnion 48 provided by a suitable standard 49 rising from the stationary frame of the machine. When the lever arm 42 is moved, a downward extension 50 thereof moves a valve 5|, thus making the pressure fluid active against the piston, not shown, which is connected by means of a link 52 to the member 41, so that when the electromagnet 40 is operated, the stroke of the grinding wheel I5 is extended and as it starts outwardly, the diamond 45 moves into its path, thereby to procure a dressing operation.

The foregoing instrumentalit'res are now well known in grinding machines; are described in the patents referred to and in others and embodied in many machines now on the market, and therefore I do not describe the same in more detail. In the present embodiment of this invention, the grinding wheel 16 is advanced into the work piece 28 and grinds witha reciprocatory stroke just long enough to effect the grinding action and, after preliminary grinding has been achieved, the automatic dressing indicated is effected, whereupon the wheel l6 returns into the work piece for the final and finishing cuts. The wheel I6 is finally removed from the work piece by energization of magnet 4! which lifts the dog 35, and magnet 4| is controlled by the size controlling apparatus now particularly to be de scribed. During the outward movement of the carriage I3 at the end of a grinding operation,

compensation of the cross slide is achieved ina Taylor patent need not be in detail'described I herein.

Referring now to Figure 1, the work piece 20 is held by means of a suitable chuck 60 which is mounted on the end of a work spindle 6|. Referring now to Figure 3, the spindle 6| is journaled in journals 62 and '63 incorporated in the work head II. Fastened to the spindle 6| is a pulley '64 by means of which the spindle 6| may be rotated by abelt drive, not shown. Extending rearwardly from the journal member 63 in the work head H are brackets 65 and 66.- These brackets 65 and 66 have slideways 61 and 68, respectively, supporting a slide 69 which is shaped in the form of the capital letter D, as shown in Figure 4. Extending between'the-top and bottom of the slide 69, as shown in Figures 3 and 4, is a rock shaft 10 upon which is mounted an optical tube 1|. Extending rearwardly from the optical tube H is an arm 12 through which extends a rod 13 having a spring 14 thereon which engages the arm. The spring I4, which is backed up by a nut 15, urges the arm and also the optical tube H in a clockwise direction, Figure 3. The front end of the rod 13 is supported by a resilient bar 88 having a notch 8| in a position to engage a detent 82 on the arm 12. used as a handle to swing the optical tube H in a counterclockwise direction and the detent 82 and the notch 8| will hold it there. This facilitates the introduction into and removal of work pieces from the chuck 60.

Still referring to Figure 3, the tube H has a central partition 85. On one side of this partition 85 is a camera chamber 86 for the passage of light. On the other side of the partition is a tube 81 forming another camera chamber for the passage of light. The tube 81 is supported by a plurality of partitions 88 which, as shown in Figure 4, surround the tube 81 and extend between it and the inside of the tube ll. At the ends of the tube H are right'angle extensions 89 and 98, respectively. In the right angle chamber 89 and firmly fastened in place is a lamp 9| having a point source of illumination 92. The lamp 9| is an incandescent electric lamp, the filaments 93 of which are dark, all light being given from the point 92. The point 92 is located in the axis of the tube 81. In the tube 81 are suitably fastened a pair of condensing lenses 96 and 91. These are lenses which have substantially spherical surfaces to refract the light in two dimensions to direct the rays toward a true focus. In front of them and mounted in the tube 8! is a color filter I00 to eliminate all rays excepting those of one color, in order that diffusion of light by refraction of the different wave lengths at different angles will be avoided to a suflicient extent. Inthe tube B'l'is also a condensing lens H which may be of the same general type as lenses 96 and 91, but in the present illustrative embodiment of the invention it is shown as a double convex lens whereas the lenses 96 and 9'! are single convex lenses. Referring now to Fig.- ure 5, three rays of light will be traced, these being designated a, b, and c. The ray a is the central ray and the'rays b and c are marginal The arm 12 may be rays. The ray a passes through all three lenses 96, 91 and IM and also the color filter I99 without being deviated from its straight line course. It next passes through a double concave lens I92, also suitably fastened in the tube 91, without being diverted from its straight line course. The rays b and c, however, were altered from their path of divergence by the lenses 96 and 91, being brought into parallelism with the ray a between the lenses 91 and IN. The lens I9I brought the rays b and toward a focus. Considering the light now as a beam, it started out as a diverging beam from the source of light 92, as every luminous body sends rays in all directions. The lamp 9| should have its glass painted black excepting in the very small circle sufficient to send forth enough light to cover the face of the lens 96. The lenses 96 and 91 produced a beam with parallel rays. The lens I9I brought this beam towards a focus. Before it came to a focus, this beam passes through the double concave lens I92- which changed it into a beam of paralleLrays again. The reason for condensing the beam that existed between the lenses 91 and MI, thereafter to cause it to reassume the form of a beam with parallel rays, is in order to intensify. the light, or stating this in another way, in order to collect as many rays as possible to form a strong beam of light. The beam in the tube 81 is a beam all the rays of which are substantially in parallelism. It will be recognized that this is a condition the complete attainment of which is not possible but by providing a point source of light, triple condensing lenses and a double concave lens, this desired condition is achieved for the practical purposes of this invention. The beam after the lens I92 may also be described as a beam the focus of which is at infinity distance from the lens I92.

Referring now to Figures 3, 5, and 8, at the front or right-hand end of the tube 81 is a double convex lens I95 of characteristics quite different from the lenses 96, 91 and IN. This lens I95 is a cylindrical lens; that is to say, its outline is that of a parallelogram when seen from above, as in Figures 3 and 5. However, when seen from in front, it looks like the lens II. This lens-I95 causes the rays to converge .in a vertical plane but not in a horizontal plane. 4

Considering further Figures 3 and 4, to the inside of the tube H I fasten a mirror fixture I96 comprising a base portion I91 which may be screwed to the tube H and a glass wedge I98 secured thereto which has integrally connected thereto a non-rectangular parallelepiped I99 of glass. The wedge I98 and the parallelopiped I99 have reflecting surfaces H9 and III which form dihedral angles with the flat surface II2 of the base I91 of 135. Surfaces I19 and III may be silvered surfaces. Light from the lens I95 is directed onto the surface III and thereby is turned at right angles into the plane of revolution of the work piece. This light is reflected and some of it is reflected by the surfaces II9 into a pair of beams, all the rays of which are parallel, passing through the camera chamber 96. In the camera chamber 86 and at 135 to the axis thereof is a mirror I I5 in line with holes I I6 in the wall 85, tube 81 and tube II. From the mirror H5, the light passes to various other mirrors and finally to a photoelectric cell I29.

I But beams with parallel rays, i. e. with focal length at infinity, leave the mirror I I9 only when the work piece 29 is at predetermined finished size, as will now be explained in connection with Figure 'l, which is an illustration of the light rays /in projection. Since the projection plane of Figure 7 is not identical with the diagrammatic view of Figure 5, 'the rays a, b and 0 cannot be identifieds' However, rays 0:, y, z, x, y and z are identified in Figure 7, and these rays represent rays actually approaching the work piece 29 toward the finished surface 29 thereof between said surface and the mirror .I I I; beyond the mirror III they are shown in their image positions, that is to say with their incident paths projected backwards. Construction circles xa, ya. and 2a are drawn in Figure '1 tangent to rays 2:, y, z, m, y and 2.. It will be seen that upon reflection from the surface 29', rays :22, y, z, :n', y and z are tangent to the other sides of the circles :ca, ya and 2a. The reflected paths of these rays are parallel to each other. However, with the work piece surface at 29", the rays 1:, y, z, 2:, y

and 2', upon reflection, assume the positions indicated by'the dotted line rays. These rays are not in parallelism and the refiectedbeam comes to a focus I. The beam has a focal length which has a small finite value, in inches. After passing the focal point I, the rays'are absorbed in the walls of the various tubes'through which they pass. In order to produce a-reflected beam whose rays are in parallelism from a am the rays of which are in parallelism, lens I95 and the mirror III [are placed in the relative positions shown to produce converging rays :1:, y, 2,37, y

and .2 having focal point ,f in the mirror III relative to the circle of the work piece, as shown in Figure '1, and it is sufficient that the lens I95 be of a convexity and index of refraction to bring the rays to this focal point. As the focal point I has a definite geometrical relation, shown in Figure '1, to the circle 29' of thefinished work piece, this relation is destroyed for any other size of work piece such as is represented by the circle 29", and therefore only when the work piece is at a given finished size will the rays be reflected from the surface thereof as a parallel beam with focal length infinity. The mirror III intercepts a part of this parallel beam but the two side portions thereof are picked up by the mirrors H9, H9 and set along the tube H in the camera chamber 86. As is shown inl 'igure '1, a large cross sectional area of the original beam is directed toward the mirrors H9, H9.

The walls of the camera chamber 86 as well as the interior wall of the tube 91 are paintedwith a dull black paint, such as any paint having a carbon pigment without a glossy surface, so that all rays which strike these walls will be, as much as possible, absorbed. After leaving the mirror I I5 the rays of the beam of light or parallel beams of light are reflected by a mirror I25 whose position is indicated in Figure l and which is placed at an angle of 45 to the horizontal so that the light will be reflected downwardly in a vertical direction. The mirror I25 is at the top of a tube I26 which is held by the machine base I9, as shown in Figure 1. The interior wall of the tube I26 is likewise painted with a dull black pigment paint. At the bottom of the tube I26 is a mirror I21 at the junction of this tube I26 with a tube I29. Tube I28 extends along the entire length of the machine base and at the right-hand end thereof is a mirror I29 which is also at the botare at 45 angles, as shown in Figure 1, so that light is directed from the tube I28 into the tube I30 and then axially into the tube I32. Tubes I28, I30 and I32 are likewise painted black inside. Only a beam or beams of light of very great focal length can pass along these tubes,

as otherwise the light is absorbed by the wallsof the tubes.

Furthermore, it will be noted that the central part of the beam has been cut out by a second reflection from the mirror surface I III. Therefore, the central axial ray does not pass along the tubes at any time, 'andconsequently excepting only atthe moment when the focal length of the light beam is. substantially infinity will any light at all reach the photo I4I which are preferably of rubber.- The steel L walls I40 bear against the work piece and determine the position of the tube H which is urged in a clockwise direction, Figure 3, by the spring 14. These walls I40 together with the walls I4I keep grinding coolant water out of the extension 90, at'least to a very considerable extent. walls I M, however, will readily deform slightly to conform to the different curvatures of the work piece during grinding. It will be appreciated that the relative change in size of the work piece, as indicated in Figure 7, is grossly exaggerated, to the end that the principles of the invention may be made readily apparent.

In order to prevent the tube H from vibrating as the work piece 20 is revolved, I provide a support I which, as shown'in Figure 1, may be hinged at I46 to a bracket I41 that is bolted to the work head II. This support I45 is in the form of a bent arm which may be swung into and out of position, being held in operative position by means of spring clamps I49. This support I45 rests under a cylindrical boss I50 integral with a screw cover I 5| which closes the right-hand end of the tube 1I.

The lenses 96, 91, IM and I02 in place in the tube 81 because once the light beam in the tube 81 has been brought to a condition of focal length infinity, there is no further occasion for adjustment. However, in order that this condition may be achieved in each new piece of apparatus despite unavoidable variations in manufacturing operations, the lamp 9| is preferably made adjustable in a direction parallel may be cemented with the axis of the tube 81. This adjustment may be achieved in any suitable manner, not herein indicated, as by the use of holding screws extending into slots.

It is, however, desirable that the apparatus be adjustable so that'it may be used to grind work pieces to diiferent internal diameters, Accordingly the lens I05 is adjustable in the tube 81 by means of the construction shown in Figure 8.

*The lens I05 is cemented to a metal annulus I through which pass a pair of adjusting screws I56 withsknurled heads, these screws I56 extending also into threadedbores in integral lugs I51 located in the inside of the tube 81. Screws I56 are rotatable in the annulus I55 but are axially immovable relative thereto, as by the provision of collars I60 press fitted onto the screws I56. The

annulus I55 is secured to the inside of the telescoping tube I6I By turning the screws I56 substantially together, the tube I 6| maybe moved The axially in the tube 81. Howeventhe relative angular position of the tubes 81 and I6! is unchanged and, therefore, the relative angular position of the lens I05 is not disturbed by the adjustment. The adjustment moves the center of the lens I05 towards and away from the surface III and, therefore, adjusts the focal line of the crossing beam relative to the surface of the work piece towards which the beam is directed.

Considering now one electric circuit which may respond to light impinging upon'the cathode I64 of the photoelectric cell I20, and referring to Figure 2,.a 110 volt A. C. line I65 has connected to it conductors I66 and I61 leading to terminals I68 and I69 of a transformer primary I10. Three secondary coils I1I, I12 and I13 are energized by the primary cell I10. A non-inductive potentiometer resistance I14 is connected across conductors I 15 and I16 of the coil I1I. Conductor I15 leads to the anode I 11 of the photoelectric cell I20. Conductor I16 leads to a condenser I18 which is connected by conductor I19 to conductor I which connects to cathode I64 of the photoelectric cell I20.

Secondary coil I12 energizes filament I83 of an amplifying or triode' tube I84. A grid I85 of the tube I84 is connected by a conductor I86 to a non-inductive resistor I81, the other end of which is connected to the conductor I80. A plate I90 in the tube I84 is connected to a conductor I9I which is connected to a terminal I92. The secondary I 13 has one end thereof connected to a terminal I93. Connected in parallel by the terminals I92 and I93 are a condenser I94 and a sensitive relay coil I95. The other end of the secondary coil I13 is connected to a conductor I96 which connects to the movable element I91 of potentiometer I14. Conductor I96 is also con: nected by a lead I 98 to the mid point of coil I12; It will now be seen that a certain degree of illumination of the photoelectric cell cathode I64 causes energization of relay coil. I and the apparatus is adjustable by means of the potentiometer I14-I91. In so much as the energization of the relay I95 may be momentary, I have further provided a relay to close and keep closedthe final circuits upon any energizationwhatsoever of the sensitive relays. As shown in Figure 2, a conductor I66 also connects to a terminal 200. Conductor I61 connects to a relay coil 20I. The other end of the relay coil MI is connected to a terminal 202. Apendulum contactor 203 is adapted to connect terminals 200 and 202 and this contactor is arranged to be operated by a long arm 204 of an armature 205 actuated by the coil I 95. Therefore,

energization of the relay coil I95, even momentarily, closes a knife switch 201 electromagnetically operated by the coil 20I. Knife switch 201 connects a conductor 208 to ground. The conductor 208 is connected to one terminal of the electromagnet M, the other terminal of which is connected by a conductor 209 to one bar 2I0 of a switch 2 which will be found described in the Taylor patent referred to and which is provided for the purpose of preventing continuous dressing of the grinding wheel. When the grinding wheel has takenthe final and finishing strokes on the work piece, a contact plate 2I2 of, the movable element 2I3 of the switch 2 connects a bar 2I4 with the bar. 2I0, thus -to connect the conductor 209 to a conductor 2I5 connecting to a generator 2I6, the other terminal of which is ground, as shown in Figure 2. This generator. 2I6 is a direct current generator but in certain cases the alternating current lines I65 may be substituted for the generator 2I6.

Briefly recapitulating the action of the machine, the operator, after having placed an unground work piece 20 in the chuck 60, moves the lever 12 to swing the right-hand end of the tube 85 toward the work piece until the upper and lower walls I40 of the extension 90 contact the work piece. Having secured the cover I5I in place, the operator swings the support I45 into the position shown in Figure 3 where the tube II and all other parts are duly supported against vibration. The operator then causes the work piece 20 to be revolved in the usual manner and, moving the main control lever 30 to the left, causes the grinding wheel I6 to enter the work piece to start the grinding operation. Thereafter, automatically, as described in the Taylor patent referred to, a dressing operation takes place whenever a cam 220 operated by the cross feed engages a lever 22I connecting a conductor 222 which is grounded to a conductor 223 which is connected by way of conductor 224 to the electromagnet 40. As the carriage I3 moves to carry the wheel I6 to be dressed by the diamond 45, an arm 225 carried by the block 38 engages the movable element2 I3 of the switch 2| I and. deenergizes the magnet 40 which prevents further dressing until a new work piece is placed in the machine. Thereafter the final and finishing cuts are taken until such time as the rays of light from the point source 92 are, upon reflection from the work piece, of such great focal length that they ultimately 'reach the cathode I64 of the photoelectric cell I20 whereupon, as already described, circuits are closed which cause energization of the magnet M which trips the reversing dog 35, causing the carriage I3 to move to the right to the position shown in Figure 1, removing the grinding wheel l6 from the work piece.

By the provision of the various tubes described, the light is caused to travel a long distance .to the photoelectric cell I20 which makes the apparatus extremely sensitive. The gauging device is springpressed against a surface of the work piece and,

in the embodiment above set forth, it is to be understood that all matter hereinbefore set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. In an internal grinding machine, a grinding wheel, a work head having means to support and rotate a work piece, a table or carriage carrying one of the grinding wheels and the work head whereby the wheel may be advanced into the work piece bore and withdrawn therefrom, a source of light, lenses in front of the source of light so positioned that a beam will strike the work piece bore wall and be reflected thereby after coming to a focus, a photoelectric cell located in the path of the reflected beam, and electrical means operated by the photoelectric cell to cause a movement of the carriage carrying the grinding wheel out of the work piece.

2. In an internal grinding machine, a work head, a wheel head, a grinding wheel rotatably mounted on said wheel head, instrumentallties relatively to move the work head and the wheel head to move the wheel away from the internal bore of a work piece whereby to cause a particular grinding operation to cease, a photoelectric cell and electric circuits to actuate said instrumentalities, and optical apparatus to energize said photoelectric cell including a source of light, optical instrumentalities to condense the beam of light so positioned with regard to the internal bore of the work piece that rays cross before reaching the internal bore wall and are reflected thereby and directed toward the photoelectric cell, whereby the. photoelectric cell will respond only with'the work piece at a given range of sizes as to diameters of its internal bore.

3. In a grinding machine as claimed in claim 2, the combination with the parts and features therein specified of mirrors for directing the reflected beam in a relatively long path whereby the instrumentalities may be highly sensitive to achieve accuracy in controlling sizes of ground work pieces,

4. In apparatus as claimed in claim 2, the combination with the parts and features therein specified of a lens having a cylindrical surface included as part of the optical instrumentalities, whereby the beam of light is focused in one plane difierently from what it is in a plane normal thereto whereby the reflected beam, upon reflection from a concave cylindrical surface of the work piece, is relatively symmetrical in cross section.

' RAYMOND A. COLE.

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