Патент USA US2121729код для вставки
June 21, 1938. R, A, COLE ' 2,121,729 SIZING APPARATUS FOR INTERNAL GRINDING MACHINES \ Filed Jan. 9, 1937 65 67 j “Q?” =9/v 7? ' J v64 . 22/ 6,2 VA Y ‘X 2 ’ 92 //5 /0/ (Y6 Y2 C73 63 w , 3 Sheets-Sheet 2 7/, ‘7 <25 0:7 74 75 I O i ‘57 6%9 60’ I45 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 ,121,729 Patented June 21, 1938 UNITED STATES2,121,729 SIZING APPARATUS FOR INTERNAL GRINDING MACHINES Raymond A. Cole, Worcester, Mass, assignor to Norton Company, Worcester, Mass, 2:. corpo ration oi’~ Massachusetts Application January 9, 1937, Serial No. 119,772 4 Claims. ((71. 51-165) internal grinding machine, for example that dis The invention relates to internal grinding ma closed in McDonough Reissue Patent No. 16,141, chines, and particularly to automatically actuat using one of the gauges thereof to initiate a dress ing size controlling apparatus therefor. One object of the invention is to provide a sen sitive photoelectric sizing apparatus and method iii for an internal grinding machine. Another ob ject of the invention is to provide van 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 instru mentalities including size determining’ apparatus of sensitive characteristics. Other, objects will be in part obvious or in part pointed out herein after. ' The invention accordingly consists in the fea tures of construction, combinations of elements and arrangements of parts, as will be exempli?ed .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 25 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 35 mirror instrumentalities which includes two re ilecting surfaces; 40 ‘ Figure 7 is a further optical diagram in which the rays are projected into a single plane for pur poses of illustration; and‘ Figure 8 is a fragmentary sectional view, on an enlarged scale, showing a portion of the optical apparatus. Referring ?rst to Figure 1, I provide an inter nal grinding machine which may be of the gen--' 45 eral type identi?ed 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 ad vance beyond the dressing plane to control ?n 50 ished size of work pieces, I substitute the photo electric apparatus herein particularly to be de scribed. It should be understood, however, that I may embody the sizing apparatus more partic-, 55 ularly described herein with any other type of ing 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 Ill 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 suit able drive for the spindle i5 is provided. The Ways supporting the carriage i3 guide the car riage I3 in the direction of the axis of the spindle 20 I5 whereby the grinding wheel l6 may be ad vanced 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 25 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 ?uid pressure actua- 30 tion as, for example, by the use of hydraulic mechanism described in Heald and Guild Pat ent No. 1,582,468, which includes a cylinder-pis ton unit, not shown, actuating a piston rod 23 which is connected by a bracket 24 to the carriage 35 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 to- a bar 26, one end of ‘which is secured to the bridge 12 and the other end of 40 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 pat- 45 ent referred to. ' ‘ The control of the rectilinear movement of the carriage l3 may be achieved by fluid pressure con trolling and reversing mechanism described in aforesaid Patent No. 1,582,468 to Heald and Guild, 50 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-?re devices 55 ' 2 2,121,729 are provided and the lever 38 controls a. revers ing valve to reverse the direction of motion of the manner fully described in Taylor Patent No. table I3, as will be found described in the afore said patent to Heald andGuild, it being now well known to control the motion of a' grinding car riage by the actuation of carriage dogs on an in line of the grinding wheel on the work piece at ?nished size will bear substantially the same re—' 1,682,673 whereby the vertical plane of the cutting lation to the vertical plane of the dressing line throughout the grinding of a whole series of terposed reversing lever, such as the lever 3|. The - work pieces ground to the same size. Accord carriage dogs which control the reversing lever ingly the speci?c compensation mechanism of the 3|, as shown in Figure 1, include a ?xed dog 32 Taylor patent need not be in detail'described I 10 adjustably mounted as by means of worm 33 and herein. 10 worm rack 34 on the carriage l3 and a pivotally Referring now to Figure 1, the work piece 20 mounted dog 35 which is capable of lifting over is held by means of a suitable chuck 60 which is the reversing lever 3! when the carriage is trav ersed to the left, but will engage the lever 3| when 15 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 20 connected to a block 38 which is adjustably se cured 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 25 former being mounted in front of the latter, and mounted on the end of a work spindle 6|. Re ferring now to Figure 3, the spindle 6| is jour naled 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‘ a‘belt drive, not shown. Extend ing rearwardly from the journal member 63 in the work head H are brackets 65 and 66.- These 20 brackets 65 and 66 have slideways 61 and 68, re spectively, 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 both being mounted on the front of the machine, rock shaft 10 upon which is mounted an optical 25 as shown in Figure 1. These electromagnets con tube 1|. Extending rearwardly from the optical trol levers 42 and 43. The lever 42 is in the verti tube ‘H is an arm 12 through which extends a cal plane of the latch 31'. The lever 43 is in the rod 13 having a spring 14 thereon which engages 30 vertical plane of the dog 35. When the lever 42 the arm. The spring ‘I4, which is backed up by is lifted, the latch 31 will be raised, thus to al . a nut 15, urges the arm and also the optical tube 30 low the block 3'6 to slide, relatively, along the car ‘H ‘in a clockwise direction, Figure 3. The front riage [3, extending the reciprocatory traverse end of the rod 13 is supported by a resilient bar stroke of the grinding wheel I 6 to pass it by a 88 having a notch 8| in a position to engage a 35 dressing diamond 45 which is at that time low— detent 82 on the arm 12. The arm 12 may be , ered into the path of travel of the wheel l6. used as a handle to swing the optical tube ‘H in Raising of the lever 43 causes the dog 35 to a counterclockwise direction and the detent 82 pass over the reversing lever 3| to extend the and the notch 8| will hold it there. This facili stroke of the carriage l3 to the right, thereby to tates the introduction into and removal of work ” 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 45 41 mounted on a trunnion 48 provided by a suit able 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 ?uid 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 55 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 60 65 70 75 pieces from the chuck 60. , Still referring to Figure 3, the tube ‘H has a central partition 85. On one side of this par 40 tition 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 45 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 be tween 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 50 89 and ?rmly fastened in place is a lamp 9| hav ing a point source of illumination 92. The lamp 9| is an incandescent electric lamp, the ?laments 93 of which are dark, all light being given from 55 the point 92. The point 92 is located in the axis of the tube 81. In the tube 81 are suitably fas tened a pair of condensing lenses 96 and 91. in many machines now on the market, and there These are lenses which have substantially fore I do not describe the same in more detail. spherical surfaces to refract the light in two di In the present embodiment of this invention, the mensions to direct the rays toward a true focus. 60 grinding wheel 16 is advanced into the work In front of them and mounted in the tube 8‘! is piece 28 and grinds witha reciprocatory stroke ‘a color ?lter I00 to eliminate all rays excepting just long enough to effect the grinding action those of one color, in order that diffusion of light and, after preliminary grinding has been by refraction of the different wave lengths at achieved, the automatic dressing indicated is ef different angles will be avoided to a su?icient ex fected, whereupon the wheel l6 returns into the tent. Inthe tube B'l'is also a condensing lens work piece for the ?nal and ?nishing cuts. The “H which may be of the same general type as wheel I6 is finally removed from the work piece lenses 9‘6 and 91, but in the present illustrative by energization of magnet 4! which lifts the dog embodiment of the invention it is shown as a 35, and magnet 4| is controlled by the size con double convex lens whereas the lenses 96 and 9'! trolling apparatus now particularly to be de— are single convex lenses. Referring now to Fig. scribed. During the outward movement of the ure 5, three rays of light will be traced, these carriage I3 at the end of a grinding operation, being designated a, b, and c. The ray a is the compensation ‘of the cross slide is achieved in‘a ' central ray and the'rays b and c are marginal 75 3 2,121,729 rays. The ray a passes through all three lenses Figure 'l, which is an illustration of the light rays 96, 91 and IM and also the color ?lter I99 with /in projection‘. Since the projection plane of out being deviated from its straight line course. Figure 7 is not identical with the diagrammatic It next passes through a double concave lens I92, view of, Figure 5, 'the rays a, b and 0 cannot be identi?eds' However, rays 0:, y, z, x’, y’ and z’ also suitably fastened in the tube 91, without be are identi?ed in Figure 7, and these rays repre ing diverted from its straight line course. The sent rays actually approaching the work piece 29 rays b and c, however, were altered from their toward the ?nished surface 29’ thereof between path of divergence by the lenses 96 and 91, being brought into parallelism with the ray a between 10 the lenses 91 and IN. The lens I9I brought the rays b and 0 toward a focus. Considering the light 'now as a beam, it started out as a diverg ing beam from the source of light 92, as every luminous body sends rays in all directions. The 15 lamp 9| should have its glass painted black ex-_ cepting 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 20 towards a focus. Before it came to a focus, this beam passes through the double concave lens I92 said surface and the mirror .I I I; beyond the mirror III they are shown in their image posi 10 tions, 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 re?ection from the surface 29', rays :22, y, z, :n', y’ 15 and z’ are tangent to the other sides of the circles :ca, ya and 2a. The re?ected 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 re?ection, assume the positions in- 20 _ dicated by'the dotted line rays. These rays are _ “which changed it into a beam of paralleLrays not_ in parallelism and the re?ectedbeam comes again. The reason for condensing the beam that to a focus I’. . The beam has a focal length which a small ?nite value, in inches. After passing existed between the lenses 91 and MI, thereafter has the focal point I’, the rays'are absorbed in the 25 25 to cause it to reassume the form of a beam with - walls of the various tubes'through which they parallel rays, is in order to intensify. the light, pass. In order to produce a-re?ected beam whose or stating this in another way, in order to col am the rays lect as many rays as possible to form a strong rays are in parallelism from a beam ‘of light. The beam in the tube 81 is a of which are in parallelism, lens I95 and the 30 mirror III [are placed in the relative positions 80 beam all the rays of which are substantially in parallelism. It will be recognized that this is a shown to produce converging rays :1:, y, 2,37, y’ ' condition the complete attainment of which is and .2’ having focal pointv ,f in the mirror IIIv not possible but by providing a point source of relative to the circle of the work piece, as shown . in Figure '1, and it is sufficient that the lens I95 light, triple condensing lenses and a double con be of a convexity and indexv of refraction to bring 35 35 cave lens, ‘this desired condition is achieved for the rays to this focal point. As the focal point the practical purposes of this invention. The beam after the lens I92 may also be described I has a de?nite geometrical relation, shown in as a beam the focus of which is at in?nity dis ‘Figure '1, to the circle 29' of the‘?nished work piece, this relation is destroyed for any other tance from the lens I92. size of work piece such as is represented by the Referring now to Figures 3, 5, and 8, at the 40 front or right-hand end of the tube 81 is a double circle 29", and therefore only when the work convex lens I95 ‘of characteristics quite different piece is at a given ?nished size ‘will the rays be from the lenses 96, 91 and IN. This lens I95 is re?ected from the surface thereof as a parallel a cylindrical lens; that is to say, its outline is beam with focal length in?nity. The mirror III 45 that of a parallelogram when seen from above, intercepts a part of this parallel beam but the 45 as in Figures 3 and 5. However, when seen from two side portions thereof are picked up by the in front, it looks like the lens II“. This lens-I95 mirrors H9, H9 and set along the tube H in causes the rays to converge .in a vertical plane but not in a horizontal plane. 50 4 Considering further Figures 3 and 4, to the inside of the tube H I fasten a mirror ?xture 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 55 thereto a non-rectangular parallelepiped I99 of glass. The wedge I98 and the parallelopiped I99 have re?ecting 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 60 silvered surfaces. Light from the lens ‘I95 is directed onto the surface III and thereby is turned at right angles into the plane of revolu tion of the work piece. This light is re?ected 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 ?nally to a photoelectric cell I29. the camera chamber 86. As is shown inli'igure '1, a large cross sectional area of the original beam is directed toward the mirrors H9, H9. 50 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 55 as possible, absorbed. After leaving the mirror I I5 the rays of the beam of light or parallel beams of light are re?ected by a mirror I25 whose posi tion is indicated in Figure l and which is placed at an angle of 45° to the horizontal so that ‘the 60 light will be re?ected 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 bot-} tom of a tube I39. At the top of the tube I39 is a mirror,I3I which is also at the right-hand end I But beams with parallel rays, i. e. with focal length at in?nity, leave the mirror I I9 only when of a tube I32. At the left-hand end of the tube the work piece 29 is at predetermined ?nished I32 is located the casing I33 that holds the 75 »' size, as will now be explained in connection with photoelectric cell I29. The mirrors I29 and I3I 2,121,729 are 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 in - side. axially in the tube 81. Howeventhe relative angular position of the tubes 81 and I6! is un changed and, therefore, the relative angular posi tion of the lens I05 is not disturbed by the ad justment. The adjustment moves the center of or the lens I05 towards and away from the surface 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 walls~ III and, therefore, adjusts the focal linev of the _of the tubes. Furthermore, it will be noted that crossing beam relative to the surface of the work the central part of the beam has been cut out piece towards which the beam is directed. 10 by a second re?ection from the mirror surface I III. Therefore, the central axial ray does not pass along the tubes at any time, 'andconse quently excepting only at- the moment when the focal length of the light beam is. substantially 15 in?nity will any light at all reach the photo? electric cell I20. Referring now to Figures 4 and 8, the extension 90 is formed by horizontal upper and lower walls I40 which are .of a hard material such as 20 hardened steel and bear against the inside of the work piece 20. .Extension 90 also has side walls I4I which are preferably of rubber.- The steel walls I40 bear against the work piece and deter mine the position of the tube H which is urged 25 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. The 30 walls I M, however, will readily deform slightly to conform to the different curvatures of the Considering now one electric circuit which may ‘ ~ respond to light impinging upon'the cathode I64 of the photoelectric cell I20, and referring to Fig ure 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 15 secondary coils I1I, I12 and I13 are energized by the primary cell I10. A non-inductive potentiom eter 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. 20 Conductor I16 leads to a condenser I18 which is L connected by conductor I19 to conductor I80 which connects to cathode I64 of the photoelec-y tric cell I20. Secondary coil I12 energizes ?lament I83 of an 25 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 30 work piece during grinding. It will be appre which is connected to a terminal I92. The sec ciated that the relative change in size of the ondary I 13 has one end thereof connected to a work piece, as indicated in Figure 7, is grossly terminal I93. Connected ‘in parallel by the ter exaggerated, to the end that the principles of minals I92 and I93 are a condenser I94 and a sen 35 ‘the invention may be made readily apparent. sitive relay coil I95. The other end of the sec 35 In order to prevent the tube ‘H from vibrating ‘ondary coil I13 is connected to a conductor I96 as the work piece 20 is revolved, I provide a sup ‘which connects to the movable element I91 of port I45 which, as shown'in Figure 1, may‘ be potentiometer I14. Conductor I96 is also con: hinged at I46 to a bracket I41 that is bolted to nected by a lead I 98 to the mid point of coil I12; This support I45 is in the It will now be seen that a certain degree of form of a bent arm which may be swung into the work head II. illumination of the photoelectric cell cathode I64 causes energization of relay coil. I95 and the ap paratus is adjustable by means of the potentiom and out of position, being held in operative posi tion by means of spring clamps I49. This sup port I45 rests under a cylindrical boss I50 in 45 tegral with a screw cover I 5| which closes the right-hand end of the tube 1I. - The lenses 96, 91, IM and I02 may be cemented in place in the tube 81 because once the light beam in the tube 81 has been brought to a con 50 dition of focal length in?nity, there is no further occasion for adjustment. However, in order that this condition may be achieved in each new piece of apparatus Ldespite unavoidable variations in manufacturing operations, the lamp 9| is pref 55 erably made adjustable in a direction parallel . 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 eter In so I14-I91. much as the energization of the relay I95 may be momentary, I have further provided a 4.5 relay to close and keep closedthe ?nal 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. A‘pendulum contactor 203 is adapted to connect terminals 200 and 202 and this contactor is ar ranged 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 momen tarily, closes a knife switch 201 electromagnet ically operated by the coil 20I. Knife switch 201 adjustable so that'it may be used to grind work connects a conductor 208 to ground. The con 60 ductor 208 is connected to one terminal of the pieces _to diiferent internal diameters, Accord ingly the lens I05 is adjustable in the tube 81 by electromagnet M, the other terminal of which is means of the‘ construction shown in Figure 8. *The lens I05 is cemented to a metal annulus I55 through which pass a pair of adjusting screws I56 withsknurled heads, these screws I56 extend _ing 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 ?tted onto the screws I56. The annulus I55 is secured to the inside of the tele scoping tube I6I ., By turning the screws I56 sub stantially together, the tube I 6| maybe moved 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 65 for the purpose of preventing continuous dressing of the grinding wheel. When the grinding wheel has takenthe ?nal and ?nishing strokes on the work piece, a contact plate 2I2 of, the movable element 2I3 of the switch 2“ connects a bar 2I4 70 with the bar. 2I0, thus -to_ connect the conductor 209 to a conductor 2I5 connecting to a genera tor 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 75 5 2,121,729 alternating current lines I65 may be substituted for the generator 2I6. Brie?y recapitulating the action of the ma chine, the operator, after having placed an un ground 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 10 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, 15 moving the main control lever 30 to the left, causes the grinding wheel I6 to enter the work piece to start the grinding operation. There after, 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 elec tromagnet 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 mov able 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 ?nal and ?nishing cuts are taken until such time as the rays of light from the point source 92 are, upon re?ection 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 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 10 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 re?ected thereby 15 after coming to a focus, a photoelectric cell lo cated in the path of the re?ected beam, and‘ elec trical means operated by the photoelectric cell to cause a movement of the carriage carrying the grinding wheel out of the work piece. 20 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 25' bore ofv a work piece whereby to cause a particu lar grinding operation to cease, a photoelectric cell and electric circuits to actuate said instru mentalities, and optical apparatus to energize 30 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 35 cell, whereby the. photoelectric cell will respond which trips the reversing dog 35, causing the car . only with'the work piece at a given range of sizes riage I3 to move to the right to‘ the position as to diameters of its internal bore. 3. In a grinding machine as claimed in claim shown ‘in Figure 1, removing the grinding wheel 2, the combination with the parts and features 40 ' l6 from the work piece. By the provision of the various tubes described, therein speci?ed of mirrors for directing the re the light is caused to travel a long distance .to the ?ected beam in a relatively long, path whereby photoelectric cell I20 which makes the apparatus the instrumentalities may be highly sensitive to achieve accuracy in controlling sizes of ground extremely sensitive. The gauging device is spring 45 ‘. pressed against a surface of the work piece and, work pieces, furthermore, is located in ?xed position in a ver tical plane by the supporting member I45. The entire apparatus can be adjusted by moving the D shaped slide 69 in the ways 65, 66', as by means of adjusting screw 230. It will thus be seen.that there has been pro-' vided by this invention apparatus and a method in which the various objects hereinabove set forth together with many thoroughly practical advantages are successfully achieved. As many possible embodiments may be made of the above invention and as many changes might be made 4. In apparatus as claimed in claim 2, the com bination with the parts and ‘features therein speci?ed of a lens having a cylindrical surface included as part of the optical instrumentalities, whereby the beam of light is focused in one plane 50 di?erently from what it is in a plane normal thereto whereby the re?ected beam, upon re?ec tion from a concave cylindrical surface of the work piece, is relatively symmetrical in cross ' I section. ' ' RAYMOND A. COLE.