US2616226A

US2616226A - Apparatus for abrading

Info

Publication number: US2616226A
Application number: US752115A
Authority: US
Inventors: D Avaucourt Pierre De Vitry
Original assignee: Individual
Current assignee: Individual
Priority date: 1947-06-03
Filing date: 1947-06-03
Publication date: 1952-11-04
Anticipated expiration: 1969-11-04

Description

1952 P. DE v. D'AVAUCOURT 2,616,225

APPARATUS FOR ABRADING Filed June 3, 1947 4 Sheets-Sheet 1 r I z I J\ E ,loo 6 m4 y 5 98 M3 M2 9*! 7 we 7 I 8 1--f 1 is E H 4 I09 8 84 In). T

INVENTOR. 62w, Ana 4* W Nov. 4, 1952 P. DE v. D'AVAUCOURT 2,516,226

APPARATUS FOR ABRADING Filed June 3, 1947 4 Sheets-Sheet 2 4/ I uumuununuuuuuuuwm 5e 40 INE/ENTOR.

Nov. 4, 1952 P. DE v. o'AvAucduRT 2,516,226

APPARATUS FOR ABRADING Filed June 3, 1947 4 Sheets-Sheet I5 D 72 7/ s in IN VEN TOR. Mal

1952 P. DE v. DAVAUCOURT 2,616,226

APPARATUS FOR ABRADING Filed June 5, 1947 4 Sheets-Sheet 4 IN V EN TOR.

Patented Nov. 4, 1952 UNITED STATES PATENT OFFICE APPARATUS FOR ABRADING Pierre de Vitry dAvaucourt, Bainbridge, Pa.

Application June 3, 1947, Serial No. 752,115

Claims. 1

This invention relates to an apparatus for abrading and, more particularly, to an apparatus for generating surfaces on lenses and other similar articles. It is particularly useful in rough grinding of lens blanks.

In the generation of surfaces on lens blanks, either concave or convex, the blank is rotated with respect to the grinding element, commonly referred to as a lap, the lap and blank rotating about axes of rotation inclined one with respect to the other. In grinding plane or plano surfaces, the axes are parallel. Mechanism is provided on such generating machines for adjusting the angle of inclination between the axis of rotation of the lens blank and the annular lap to vary the radius of curvature formed on the surface of the blank and mechanism is also provided for transversely moving the blank and lap relative to one another to make possible the generating of concave and convex surfaces with the same lap.

An object of my invention is to provide a machine incorporatin the two adjustments men tioned above in combination with mechanism for adjusting the position of the lens blank laterally of lap. With the machine of this invention, it is possible to quickly adjust the lap and lens blank holder in three directions to thereby bring the lap and blank into a position where the lap will engage the blank along a l ne which extends from edge to edge of the blank and passes through the axis of rotation of the blank. By provision of such an apparatus, it is possible to double the output of the machine because grinding is accomplished on both sides of the axis of rotation of the blank along a line which extends from edge to ed e of the blank rather than from the axis of rotation to one edge as is the common practice.

It has been the general practice in this art to remove the lens blanks from the lens holder by hand, the operator generally using a fingernail to lift the blank by engagement with the edge thereof. This is not only hazardous, but is extremely time consuming. It is an object of my invention, therefore, to provide an apparatus which may be incorporated in a standard grinding machine which will be effective for quickly, conveniently, and with safety removing the lens blank from the lens holder and for extracting the blank from the removing means so that the same may be discharged from the machine by the operator with a simple motion. This also permits the operator to work with both hands and speeds up the operation of the abrading process. 7

A further object of my invention is to provide a simple, quick-acting brake for the lens holder spindle. It is common practice to use magnetic brakes and the like on the spindle, but these require complicated and expensive mechanism; whereas, according to the present invention, a very simple braking arrangement is combined with the lens picker.

Another object of my invention is to provide a combined mechanism for removing the lens blank from the lens holder and for braking the mechanism which rotates the lens holder. Thus with the machine of the present invention, it is possible for the operator to stop the rotation of the lens holder, mechanically pick out the lens blank, and insert a new lens blank in a small fraction of a minute. The prior practice has been to remove the lens blank after the spindle has stopped rotation and since the spindle is rotating at a relatively high speed, the inertia will cause the rotation to continue for a substantial length of time.

Another object of my invention is to provide for automatically establishin a supply of coolant to the lens blank and lap during the grinding operation and for cutting off the s pply of such coolant automatically upon completion of the grinding cycle. A still further ob ect is to combine the coolant control with means for automatically starting and sto ping the power supply for the lens holder spindle. Thus the whole mechanism is automatic in o eration and provides the utmost safety for the operator. When the lap is in grinding position. the motor which rotates the lens holder spindle is automatically started. and the supnlv of the coolant is fed to the surface of the lens blank and to the grinding surface. The supply of coolant continues until the rindin o eration is completed; whereupon, the supply of coo ant is discontinued and the po er supply for the lens holder spindle is sto ed.

Common practice in the rior art had been to provide the lens chuck with a conical s indle engaging surface and to provide se arate c ucks for receiving blanks of different sizes and also for receiving blanks having a concave surface to be ground and others for blanks havin a convex surface to be ground. This ne essitates a large number of chucks and also reo ires that the chuck be carefully adjusted into its conical holder. Another object of my inv ntion, therefore, is to provi e a universal chucking arran ement which will receive and hold lens blanks having either concave or convex surfaces to be ground, the chuck bein rotatable through to permit the reception of blanks of different sizes on one side or the other thereof.

Machines now on the market for lens grinding are provided with ball bearing thrust arrangeents. It has been found in the operation of such machines that the spindle will not run absolutely true due, it is believed, to the fact that the race which receives the balls will wear unevenly, and, as a consequence, rotation of the spindle about the bearing will cause a slight defection along a line parallel to the axis of the spinde as the spindle moves on the balls which are received within irregularly shaped openings in the race due to wear. This will cause a slight movement of the lens blank during the grinding operation and this is mirrored in the finished surface. Accordingly, it is an object of my invention to provide a thrust arrangement consisting of a single point suspension, preferably operating submerged in oil so as to avoid wear.

Another object if my invention is to provide a novel method of grinding whereby the lens blank will be first grooved and then the upstanding portions between the grooves will be chipped away, thus providing for extremely rapid rough grinding, far in excess of that attainable by methods currently employed.

Further objects of my invention will become adjustable stop 9 is threaded on the member l and is secured in position by a locking nut I 9. A projection I I is provided on the machine frame against which the stop 9 comes into engagement to limit downward travel of the spindle 3. This adjustment controls the lens thickness as will be more fully hereinafter described.

Attached to the spindle 3 is a lap I2 (Figure 2) which, in the embodiment illustrated, has an annular grinding surface I3 which may be formed of diamond particles embedded in a matrix. The lap I2 is secured to the spindle 3 by a conventional Morse taper chuck arrangement as shown.

Mounted upon an upright column i 6 which constitutes the main connection of the machine to its base is a bracket I5 which supports the lens holder and its associated mechanism, including the mechanism for rotating the lens holder and the mechanism for adjusting the position'of the lens holder with respect to the lap. A crank mechanism (not shown) with associated rack and pinion members is provided for raising and lowering the bracket I5 and the mechanism which is carried by it.

to as shown in Figures 1 and 3. A plate I9 is apparent from the following specific description 5 of a preferred embodiment thereof.

In the drawings:

Figure 1 is a side elevation of a lens grinder illustrating the present invention;

Figure 2 is a view partially in elevation and partially in section taken from the front of the machine and with the guard removed in order to make the rotating and other equipment visible, the figure being partially broken away to show the traversing mechanism;

Figure 3 is a partial side elevation of the machine with th guard removed and is taken from the side of the machine opposite to the side shown in Figure 1;

Figure 4 is a detailed elevational view showing control mechanism associated with the lap spindle;

Figure 5 is a sectional view showing the improved chuck or lens holder of the present invention;

Figure 6 is a schematic view illustrating the operation of the lens picker; Figures 7-11 are diagrammatic views illustrating the method of my invention; and

Figure 12 is a diagrammatic view showing an arrangement for raising and lowering the abrading element spindle.-

Referring first to Figure 1, the machine comprises a standard spindle rotating mechanism generally indicated by the numeral 2 which may be purchased from a manufacturer of machine tools. A standard drill press unit may be used for this purpose' The spindle is indicated at 3 and the motor which drives the spindle is indicated at 4. Mechanism is provided for raising and lowering the spindle 3 and'in the embodiment illustrated, this includes a rack and pinion arrangement shown diagrammatically in Figure 12 which is actuated through a hand lever 5 which may be adjustably counterweighted as shown in Figure 1. This is part of the standard drill press equipment. Encircling the spindle 3 and movable vertically therewith is a stop arrangement generally indicated at 6 which includes a threaded member I which is attached to a bracket 8, movable with the spindle 3 in a vertical direction. An

positioned for transverse movement along the ways I! and I8, being guided by dovetailed elements 2!) and 2I which are secured to the plate I 9 and interfit between the ways.

The plate I9 may be moved transversely with respect to the lap spindle 3 by mechanism which will be now described with particular reference to Figures 2 and 3. A bearing 22 is attached to the plate I9, being secured thereto by bolts which are not shown in the drawing. An adjusting screw 23 is received within the bearing 22 and is provided with collars 24 and 25 which are fixed to the shaft 23. A threaded block 26 is bolted to the plate I6 and this block receives the threaded end of screw 23. A knurled hand wheel 21 is pro- Vided for rotation of the screw 23.

As will be seen from examination of the Figure 2, the axis of rotation of the spindle 3 which carries the lap I2 is disposed in a vertical plane and the plate I9 which is disposed in a vertical plane parallel to the axis of rotation of the spindle 3 may be moved with respect thereto by rotation of the hand wheel 21 which effects a movement of the plate I9 through the block 26 and the threaded end of the screw 23. The lens holder and its associated mechanism are carried by plate I9 and by adjustment of plate I9 transversely with respect to the axis of rotation of the lap, it is possible to bring the lens blank and lap into proper transverse relationship for either concave or convex grinding with the line of contact between the lap and lens passing through the axis of rotation of the blank.

Referring again to Figure 2, the lens holder or chuck is indicated at 28. The chuck is shown in section in Figure 5. It comprises a body 28I which has a central bore 282. It will be noted that the opening 283 in one end of the chuck is larger than the opening 284 in the opposite end. This provides for the reception of lenses of two different sizes, such as 50 mm. in

opening

283 and 54 mm. in the opening 284. Soft

compressible gaskets

285 and 286 of rubber or other material are provided in the

openings

283 and 284 respectively. This provides suflicient frictional engagement between the lens blank and holder to permit grinding Without the use of adhesives or mechanical holding mechanism fol-the lens blank, the lens blank being preferably wetted with water prior to insertion into the chuck to enhance the engagement. Set screws 28'! are provided for holding the chuck on the chuck spindle 29. The spindle 29 is received within ball bearings 39 and 3f, the housings of which are fixed .to a plate 32 by means of mounting

brackets

33 and 34. The plate 32 is pivoted to a plate 35 which is welded to a plate 36 disposed parallel to and in surface engagement with the plate 19. (See Figure 3.)

The plate 36 is attached to the plate I 9 and moves with it and is also arranged for pivotal movement with respect to plate l9 so that the plate 36 which carries the lens blank chuck and its associated mechanism may be rotated about a pivot 31 which joins

plates

19 and 36. The axis of pivot 31 extends substantially at 90 to the plane of plates [9 and 36 and substantially intersects the axis of rotation of the chuck or work holder spindle 29 substantially at the upper surface of the chuck 28 .as shown in Figure 2. By having the pivot point so positioned, it is'possible to adjust the angle of curvature to be formed on the lens blank without changing the transverse adjustment of the plate H! by use of hand wheel 21. This makes the machine versatile in operation with a minimum of adjustment.

In order to effect a movement of the plate 36 and its associated mechanism about the pivot 31, an adjusting mechanism is provided which is shown in Figure 2. It is similar to the mechanism shown in the same figure for imparting a transverse motion to the plate 19 in the ways I! and I8. It consists of a. bearing 38 which is pivoted to the plate 19. A threaded block 39 is pivoted to the plate 36, and a threaded adjusting screw 40 passes through the block 39 and is received within the bearing 38, collars being provided affixed to the screw 40 to engage opposite ends of the bearing 38. A knurled hand wheel 4! is fixed to the end of the screw 40. By rotation of the hand wheel 4!, it is possible to rotate about the pivot point 31 plate 35 which carries plate 32 to which the lens chuck 28 and its spindle 29 are fixed. Thus the angle of attack between the lens to be ground and the lap may be adjusted to produce the desired curvature on the lens. The axis of the lap spindl 3 is substantially vertical and is not adjustable. When the axis of the lens chuck spindle 29 is parallel to the axis of the lap spindle 3, a plano surface will be generated on the blank, and as the axis of the lens chuck spindle is inclined with respect to the axis of the lap spindle the curvature of the surface generated upon the lens blank will vary. This is true either in the formation of concave or convex surfaces. The motion of rotation of the lens chuck spindle 29 about the pivot point 31, the axis of which is disposed to intersect the axis of rotation of the spindle 29 substantially at the surface to be generated on the lens is possible regardless of the adjusted position of the plate [9. This is essential, for the cutting line of the lap 12 must be adjusted so that it passes through the axis of rotation of lens blank regardless of curvature being generated upon the lens and regardless of whether a concave, convex, or plane surface is being formed.

As previously mentioned, the plate 35 is connected to the plate 33 and is disposed normal to the plane of plate 36. The plate 32 is secured to the plate 35 by means of a pivot connection 42. Thus it is possible. to effect a limited rotation of the plate 32 which carries the lens chuck 6 spindle '29 with respect to the plate 3'5 about-tn pivot 42. This limited rotation is effective, of course. for adjusting the axis of rotation of the lens chuck spindle laterally with respect to the axis of rotation of the lap spindle 3 to bring the cutting surface of the lap into engagement with the lens blank on both sides of the axis of rotation of the lens, accomplished by bringing the plane :of rotation of the lens chuck spindle substantially into the plane of rotation of the lap spindle. The adjustment is effected through mechanism which is best shown in Figure 3. It consists of a bearing 43 which is pivoted to the plate :32. A pivoted threaded block 44 is affixed to the plate 35. An adjusting screw 45 passes through'the bearing 43 and is received within the screw threaded block 44, collars being provided on the screw 45 on opposite sides of the bearing 43 to prevent axial movement of the screw. A knurled hand wheel 46 is provided for rotation of the screw 45. Upon rotation of the hand wheel 46, the screw 45 moves through the block 44 pivoting the plate 32 with respect to the plate about the pivot point 42. Therpitch of the thread on the spindle is relatively fine in order to eflect minute movement of the spindle 29 to bring the lens blank carried in the chuck 28 into proper relationship with respect to the cutting surface of the lap .I 2.

As shown in Figure 2, the spindle 29 rotates in

bearings

30 and 31. The lower end 41 of the spindle 29 is provided with a thrust arrangement which consists of a single ball 48 which is received within an opening within the lower end 41 of the spindle 29. 49 and the cup is held in adjusted position by means of an adjusting screw 50 which is threaded into an angle bracket 5| which is bolted to the plate 32. A lock nut 52 is provided for holding the adjusting screw 50 in proper adjusted position. The cup 49 is preferably filled with oil to a point above the lower end of the spindle 41 in order to lubricate the ball thrust. With this arrangemerit all of the thrust is taken by the ball 48 and ther is, therefore, absolutely no vibration of the lens holder 28 in an axial direction and concomitantly there is no vibration of the machine. As heretofore mentioned, any vibration of the lens holding and rotating mechanism results in the generation of an irregular surface on the lens, for axial movement of the spindle 29 will result in a variable depth of grinding irregularly over the-surface.

A motor 53 is mounted upon the plate 36 and serves to drive the spindle 29 through a belt 54. the spindle 29 being provided with a pulley 55 and the shaft of the motor 53 being provided with a pulley 56 about which the belt 54 is trained.

The lens picker and braking arrangement is shown in Figures 2 and 3. The lens picking mechanism is mounted within a fluid tight receptacle 51. A standard 58 is attached to the bottom of the receptacle 51 and to this standard 58 is attached an arm 59 which is free for rotation about a projecting stud 60 and is also freefor limited rocking movement with respect thereto. the opening in the arm 59 through which the stud 60 passes being enlarged to permit such movement. An operating handle 6| is provided and this is attached to one end of the arm 59 by means of a nut 62, with the end of the handle 6| being shouldered and threaded to receive the nut. The opposite. end of the arm 59 carries a suction cup 93 which is secured to the arm by means of The ball 48 is received within a cup v 7 astud 64 and a'nut 65, the stud-being attached to the suctioncup 63.

A bracket 66 is attached to the receptacle 51 and serves as a table to receive the lens L (see Figure 6) when the same is discharged from the suction cup 63. This discharge is effected by means of an extraction plate 61 which lies in the path of movement of the lens held by the suction cup. When the handle 6| is rotated from a position above the lens chuck to a position over the table 66, the lens will come into engagement with the extraction plate 61 and as further rotation is imparted to the handle 6|, the suction cup will slide over the lens, leaving the same on the table 66. The table 66 is generally of a width less than the diameter of the blank, as seen in Figure 6, .to permit the blank to overlie the tabl and provide for convenient grasp by the operator. The table may be made larger, however, and a slot provided to permit the operator to get his index finger below the blank for removal of'the blank from the table. 7

Since rotation of the spindle 29 must be stopped prior to removal of the lens blank from the holder 28, mechanism is provided for braking the rotation of the spindle 29 after the motor 53 has been de-energized. This mechanism is preferably directly combined with the lens picking mechanism so that the operator can, with a simple motion, first effect a braking of the spindle 29, and then perform the lens picking operation. 4

The brake arrangement is shown in Figures 2 and 3 and consists of a brake drum 68 which may be in the form of a V-pulley which is aifixed to the lens chuck spindle 29. A brake band 69 par tially encircles the brake drum 68 and is attached to an arm 10, which is pivoted at II to a pivot plate 12, pivoted at 13 to a bracket I4. attached to plate 35. An operating link I is pivoted to the plate I2 at the point I6. TI is pivoted to the receptacle 5! by a bolt I8. The link I5 is pivoted to the actuating plate I? by a bolt I9. An elevating surface 80 is provided on the actuating plate I? and the plate 1'! is recessed to receive th handle H. The end of the receptacle 5? is cut away at 8| to permit the handle 6| to move into the recess in the actuating plate so that the cover for the receptacle may be moved into closed position.

The lens blank and lap are supplied with a coolant during the abrading operation and this supply should be out 01f when the grinding is complete to permit the picking of the lens. Also the motor which rotates the lens chuck spindle should be de-energized upon completion of the abrading operation on each blank. The following mechanism is effective for performing the combined functions of automatically establishing and discontinuing the supply of coolant for the lens and lap and power for the lens chuck spindle motor, coincident with the movement of the lap spindle into and out of operating position.

The mechanism is shown best in Figures 1 and i. The coolant which may be an oil and water emulsion is fed by a pump from a source of supply, which is not shown but which may be in the form of a small tank, through a flexible line 62. A manual control valve 83 is provided in the line 82 to regulate the pressure of the coolant supplied to line 84. A mechanical Valve 85, normally spring closed, is provided which is actuated by a controller 86 (Figure 4) which is pivoted at 81 to an extension line 88 leading from the valve 85. The controller 86 engages a pin 89 which is attached to a spring urged An actuating plate closing plunger 90, which controls the opening and closing the valve 85. A cam 9I is attached to the lever 5, the cam 9| being provided with a lobe 92 effective for depressing the controller 86, thereby rotating it about the pivot point 81 and pulling the plunger 90 forward, opening the valve 85 and permitting coolant to pass from the line 34 through the valve 85 and into a line 93 which enters the receptacle '5! and terminates in a nozzle 94 (Figure 2) which directs the coolant to the surface where the grinding element en-- gages the lens blank under treatment. A return line R connects with the supply tank.

Also associated with the lever 5 is a cam which is effective for controlling the energization of the lens chuck spindle motor 53. The cam 95 actuates a normally open microswitch 96. When the lever 5 is moved to bring the spindle 3 into operating position, the cam 95 will force the microswitch plunger 91 inwardly and this will make electrical contact for a magnetic switch 98 which effects energization of the motor 53. Thus when the lever 5 is moved downwardly, the motor 53 is started and, when the lever 5 is returned to its normal position, the motor 53 is de-energized.

If desired, a light or other signal may be provided to indicate to the operator the fact that a lens blank has been completely ground. This arrangement is shown in Figure l where the stop 9 is associated with an operating arm 99 to actuate a microswitch Illil which controls a lamp I9! in the line of vision of the machine operator. The arm 99 is pivoted as indicated at I 92 and has a portion I93 which projects into the path of the stop 9, there being provided a radial extension I94 on the stop 9 which is adapted to engage the portion I03 and rock the arm 99 about the pivot I02, elevating the plunger I95 of the microswitch I90. Thus, as the lever 5 is rotated, bringing the spindle 3 into operating position, the stop 9 moves therewith since it is attached to the bracket 8. The stop I04 will engage the arm 99 when the grinding operation has been completed, closing microswitch I66 and completing the circuit for light I OI An adjusting screw I95 is provided on the arm 99 so that the switch I96 will be actuated only upon the completion of the grinding operation with the spindle limiting stop 9 in engagement with the projection I I or closely adjacent thereto, as the operator may prefer.

As shown in Figure 1, the lid I97 of the receptacle 57 is hinged and is arranged to be opened automatically by rotation of the operating lever 5. A collar I08 is attached to the lever 5 and a cable I09 is connected to the collar H38 and the lid I 97. Thus when the lever 5 is rotated to bring the spindle 3 into operating position, the lid is closed and when the lever 5 is returned to the position shown in Figure 1 upon completion of the grinding cycle, the lid I 9'! is automatically raised. When the lid is lowered, it will not be possible to elevate the actuating plate ll of the brake mechanism, thus insuring that the brake will not be applied until the grinding operation has been completed and the spindle 3 elevated, raising the lid I91.

In the operation of my device, a rough blank to be ground is inserted in the lens chuck 29 and the operating lever 5 is brought down, rotating the cam 95 and actuating the microswitch 96, starting the motor 53 for the lens chuck spindle 29. As rotation of the operating lever 5 continues, the cam 92 engages the controller 89 which opens the valve 85 and lubricant is fed 'from the line 82 into the-vicinity of the rou'gh blank under. treatment 'as shown in Figure' -Z.

The lap spindle 'motor l is continuously opcrating. As the'operating lever-5' is rotated further, the annular lap-12 is brought down into engagement with the rough blank. In my preferred embodiment as *shown -in the drawings, the chuck zfi is rotated b'etWeen 2500 and 3,000 R. RMJ in one direction and -the' lap' is rotated at about 4,090? Rf M.,--preferably inthe opposite direction to the direction of rotation'of the chuck 28.

'The lens chuckspindle 29 is adjusted' byrotatien of the hand- =w-heel 21-'-so-that thecutting line of the lap 52 intersects the rough blank along a line Which-passes through the 'axis of rotation of "the lens blank. This---adj'u'stment -once ma de generally 1 need" not-be remade sd long as blanks or the same diameterare being operated upon. When-the sizes 'of' the" blank "or the la-p are changed, then this adiustment mustbe remade. 'Alsawhen changing f-roma" concave -to -a"convex surface "in -the grinding,adjustment "must 'be made so as to bring the proper portion of the'lap into engagement with the-rough blank. In" convexjgrinding as shown in -Figurefl, the axisofrotation ofthe lens'blank isto'the "right'ofthe axis of rotation of'the 'lap and'i-n' concave grinding a lens of similar curvaturefa*corres-ponding position to'-the left or the axis or rotation of'the lap-would be assumed by adjustment or the hand wheel 21.

The second adjustment which "is "efiected through the hand "Wheel- M whichrotates the spindleie-about the pivot'point 3'L'changes the curvature or radius formed on the "rough blank in the grinding operation, byrotating the'lens chuck spindle aboutthe pivot 31. This adjustment, of course, is the same for both concave or convex grinding and would also be use'din adjusting the machine "to form a plane surface where the vertical axis of the lap"'-w0uld be parallel' to the axis of the lens chuckspindle.

In the eventthe lap l2 not cutting throughout the entire curvature of the blank, i. eJ-alo aline extending from edge to edge of theblank and intersecting the axis of rotation of the blank, then the hand *whe'el -dtw'ill' be *rotated to pivot the spindle -"Z9=about=the pivot 42. to 'br-ing 'the lens chuck spindle and the lap spindle into posi tions where theiraaxesfall in a common'plane. By making this adjustment, it ispossible-to cut on the entire surface of the-blank uponapproxiniately each one-half revolution ofthe 'blank and thus materially'spee'dup the cutting operation over the prior practice where the lap merely-cuts along a line extending' 'from the center of l the blank to the periphery. With this-adjustment also, it ie-possible to obtain.a true -spherical curvature on the surface of thelens-blank'and avoid the'defect "-which' commonly occurs-with the prior art machines k-nownnasa double-curve or nonspherical surface which extends from the center of the A blank "-out towa'r d the periphery thereef.

"The machine being adjusted to *-ifect the proper grinding, the operating lever- 5 isbrought downand theblankisground. The motion of the lever 5 is-arrested' by the stop dwhich comes into engagement with the projection l l I un -the machine frame. At the'sametime, the extension IM- on thestop 9 engages' the arm l03=of the light control mechanism, depressing the microswitch 105 'and-energizirig thedight I'Ol. This :tionnhas :been completed. :Thereupon,1theiopieratorz'reverses: the; rotation :of .the lever 5, the

i116. Hill is raised,zzand.the V811VT35 is closed, being t'normally i moved .t 1 that position by a spring. 5 'i'I'hecamr95t comes: to a-zposition'wherethe switch 2'96 :has its..=.operating .arm in outwardgposition sand:v the I motoradEszis: no clonger energized.

:L'Ifhe :perator mow t grasps the handle "'6 l I and. elevates it while mengagementwwith the actuatsingr plate: I I ,:.applying the brake. 69- to the spindle 2&3 throughlthe linki15,pivot..plate "l2 and arm :70. sTheiapplica'tiomofiforceL-iscontinued by the operator :until JheQ observes that the spindle has 'stoppe'dz'rotating. .flhisi is substantially instanzta-neous. .aI-Ie' thentdisengages the handled; i from the Zbraking mechanism: and :rotates the handle ito;the.zright asi=shownin Figure.2. until the suction cupiiitl iszinlaiposition wherei it overlies the ground blank whichl is Ireceive'd. in" the chuck 28. -Airocking-imovementais. theniiinparte'd anrup- -wardi'direction to the handleitlP-about the stud 16H: bringing 2' the suction cup 63 into engagement :withi thezirground I-b'lank. v-flhereai'terathethandle -6 Isis lowered,:- pivotingt thesisameeabout the stud 60 and lifting the lrlensa blank: out of .the' chuck :28, t the same being L held onto ithe. suction cup 63. "Thel'han'dle fil is then rotated to the letters shown in Figure' z frand thei lens b'iank is brought intoia position overlying -theatable 66. Further motioniiof the ohan'd'le :to -the:- left with the L'lens :blan'k resting on the table :66 brings the lens .blank into engagement with" the 'e'Xtractorplate 61 andas f-urthen motion to the left is eiiected, the lens and s'uction cup areseparated and the lens blank is removed by the -operator.

This-brings' the operating: handle into position aldiacenttheopening- 8 l in-the receptacle fil and the handle -is 'sli'pped within the opening Wi'in the actuator plate lL 'ready for the application of the brake upon comp'letion of' the next cycle of operation of the machine.

' Themethod ofmy -invention isYillustrated diagrammatically in Figures '7 to ll inclusive. When generatinga surface on a lens 'blankor the like, the lens --blank- 'has a sur-face: speed :which 'varies from a minimum at the center to a-maximum at the periphery of the-blank. iReferrin'g to iFig- .ure-"7; for example; the surface 'speed at the point m9 willlbe= Sl1bSliantla11yi zero. .1 Along 1 the: line I I 0, the I blank will :have aniincreased surface speed 'andiat 'the outer Speriphery: l l I itzlwiil assume: its maximum: surface :speed.

1 have foundfrom :carei'ul study oi the' grinding :operationvperiiormedioniglass lens blanks that ifutheisurface .is. firstiscored immuch' thea same manner thati a 'stonecutter: scores. 'his' Work and is :then engaged by: :abrasive Lparticles attacking the workiiat vaneanglexto the direction Softhe :grOOVBS FWhiCh arer formed, .;thertglassaisichipped away tnsmall ixbits ni-in -muc'h 'the i same 1 fashion iasastonecuttenperformshisswork;rand-.thespeed 0f grinding. is'smaterial'lyzincreased. i This chipping action is best accomplished by.so;.adjusting the1surface speed of the r. blank with respect to the linear speed of thezlap 'as' tochave'the individual L, grit. particles .of zthe lap I describe curved paths which arez spaced at tthe: periphery of the blank and .zsimultaneously bringing rabrading particles into:engagementcwith the glass between the grooves and at an angle 1 to the grooves n to chip vaWayLthe glass, simultaneously forming new spaced 'grooves,'l the glass between which issimirlarly engagedbyvabrasive partitz'les 1 and chippe'd away. :This iactio'n iiis r'diagrammatica'lly .'i1i'ustratedin Figures 8;9, .10;:arfd 1 1.

11 In Figure 8, there is shown a lap H2 having an abrading surface H3 attached thereto. I have diagrammatically illustrated in Figure 8 two abrasive points H4 and H5 on the abrading surface H3. The surface will be composed of many thousands of abrasive particles, such as diamonds; only two have been shown in Figure 8 for purposes of illustrating the action which occurs in my process of grinding.

Referring now to Figure 9 and assuming that the abrading surface H3 has a diameter of 3" and the lens blank H6 has a diameter of about 2" and that the lap is rotated at approximately 4.000 R. P. M. and the lens blank at about 2,500 R. P. M., the direction of rotation of the lens blank H5 being opposite to the direction of rotation of the lap H2 as shown by the arrows in Figure 9, a point H4 on the abrading surface H3 will describe a curved path as shown by the solid line I I! in its movement from the center of rotation H8 of the blank HB to the periphery H9 thereof. In Figure 9, seven paths have been indicated by solid lines. The spacing between the paths will depend upon the speed of translation between the lens blank and the lap. It will be noted that the paths H1 each emanate from the axis of rotation H8 of the blank and move arcuately therefrom to the periphery H9 of the blank. The amount of movement is less at the center of the blank than at the periphery because, as previously stated, the surface speed increases from zero at the axis of rotation of the blank to its maximum at the periphery of the blank and the translatory motion depends upon the relative speed between any point on the surface of the lap moving over the lens blank and the speed of movement of the surface traversed by such point in its travel from the axis of rotation to the periphery of the blank. The paths are shown widely spaced in Figure 9. In actual practice, they will be very closely positioned and they will form grooves as indicated at I in Figure 11. As a matter of fact, the spacing will generally be only slightly greater than in the average particle size of the grit in the abrading element H3.

Since the abrading surface H3 engages the blank from edge to edge as shown in Figure 9, the abrasive particles I I4 and I [5 will form paths l2! shown in dotted lines in Figure 9. It will be noted that these lines are curved the same as the lines H! and intersect the lines H1 at an angle which varies from the periphery toward the center of the blank. The intersection of the lines is illustrated in Figure 10. The abrasive particles when travelling along the paths l2l will chip out the glass between the lines I I! (remembering that the lines are closely spaced) and new grooves will be formed along the lines I2]. As the blank is rotated, the lines [M will be crossed by abrasive particles moving along lines I I! and the glass therebetween will be chipped out.

Reference is now made to Figures 10 and 11 where the grooves out along the lines I I! by the particles H4 and H5 are shown as being intersected by grooves out along lines I2 I. It will be noted that the lines l2! cross the lines I H at an angle. The abrasive particles H4 and I I5 which engage the surface of the lens blank chip out the glass between the grooves formed by the abrasive particles and, at the same time, they form new grooves which are chipped out when the blank is rotated to a position Where the abrasive particles are describing opposite paths of travel. Thus, there is simultaneously eifected a formation of grooves and a chipping away of the glass disposed between the grooves. In Figure 11 there is diagrammatically illustrated the grooving effect obtained where the lens blank has made less than one complete revolution. Here the grooves I29 have not been intersected 0n the portion disposed to the left of the axis of rotation H8 of the lens blank but have been on the portion disposed to the right of the axis.

I have obtained unusually high grinding speeds by use of my method of grinding in which the lap engages the blank from edge to edge thereof and passes through the center or axis of rotation of the blank, rotating the blank at a substantially higher surface speed than heretofore practiced in the art. For example, using a surface speed of 2,500 revolutions per minute with a 2" blank and 4,000 revolutions per minute with a 3" lap, I am able to abrade away a full millimeter of glass in approximately 3 to 5 seconds; whereas, with the prior grinding machines practicing the conventional process of grinding, removal of one millimeter of glass would require from 40 seconds to 60 seconds, using the same type of glass, the same lap speed and the same grit size but rotating the blank at a substantially lower speed, in the order of 400 revolutions per minute.

While I do not wish to be limited to the foregoing theory which I believe to be responsible for the improved results, it is a plausible explanation and has been found capable of being repeatedly reproduced in actual practice.

While I have illustrated and described a preferred embodiment of my invention, it is understood the same may be otherwise embodied and practiced Within the scope of the following claims.

I claim: 7

1. In an abrading machine, a rotatable work holder, a rotatable abrading element holder, means for relatively moving the work holder and abrading element holder transversely, means for relatively inclining the axes of rotation of said holders in a substantially common plane, and means for relatively inclining said axes of rotation in a second plane disposed at an angle of substantially with respect to said first plane.

2. In an abrading machine, a rotatable work holder, a rotatable abrading element holder, means for moving the work holder transversely with respect to the abrading element holder, means for pivoting said work holder with respect to said abrading element holder in one plane, means for pivoting said work holder with respect to said abrading element holder in a second plane at substantially 90 with respect to the first mentioned plane, and means for moving said holders relative to one another to bring said abrading element into abrading relationship with respect to a work piece received in said work holder.

3. In an abrading machine a rotatable abrading element holder rotatable about a substantially vertical axis included in a vertical plane, a work holder rotatable about an axis substantially included in said plane, means for pivoting said work holder with respect to said abrading element holder about a pivot axis which extends substantially at 90 to said plane and substantially intersects the axis of rotation of said work holder substantially at the surface to be abraded, means for pivoting said work holder for adjustment in a second plane disposed at substantially 13 90 with respect 150 thefirst mentioned plane, and --means for moving saidabrading element h'oldr' toward said wo'rk h'older in a direction "al'o'ng the -axis of rotation 'of said abrading eleine'nt holde'r.

4. In an abrading machine having a rotatable annular abrading'eliri'nt ah'd"a'rotatable work "holder, 1 the" combinatidn bf' inwnsgre reiauvei -mov-i r'1'g the "--i-brading element d thehol'der transversely of the axisoi 'rotation ofithe' abrading element to bring the abrading element into engagement with a work piece in the work holder along a line extending through the axis of rotation of the work piece, means for pivoting the work holder about a pivot whose axis extends substantially perpendicular to the axis of rotation of the work holder and substantially intersects the axis of rotation of the work holder substantially at the surface of the work piece to be abraded to adjust the angle of attack between the abrading element and the work piece to vary the radius of curvature formed on the work piece, means for pivoting the work holder about a second point to adjust the axis of rotation of the work holder laterally with respect to the axis of rotation of the grinding element to bring said axes into a substantially common plane, and means for relatively moving the grinding element and work holder along the axis of rotation of one of said elements to bring the abrading element into working position with respect to the work piece.

5. In a lens grinding machine, the combination of a rotatable spindle carrying a lens blank chuck, a brake for said spindle, brake actuating means, a lens picker for removing a lens blank from said chuck upon discontinuance of rotation of said spindle, an operating handle, and means connecting said handle to said brake and to said lens picker, said handle being alternately operable to apply said brake and to efiect picking of said lens upon completion of the braking of the spindle.

6. In a lens grinding machine, the combination of a rotatable spindle carrying a lens blank chuck, a brake for said spindle, and actuating means for said brake comprising an arm for applying tension to said brake, a pivot plate to which said arm is pivoted, a link pivoted to said pivot plate, a pivoted actuating plate to which the link is pivoted and an actuating handle engageable and disengageable with said actuating plate to rock said actuating plate about its pivot to apply tension to said brake through said link, pivot plate and arm.

7. In a lens grinder, a receptacle in which the grinding is efiected, a hinged closure for said receptacle, a rotatable work holder disposed within said receptacle, means for braking the rotation of the work holder including an operating handle, said receptacle having a handle receiving recess therein, said recess being closed when said closure is in applied position, a grinding element disposed within the receptacle, means for moving the grinding element into and out of grinding position with respect to the work holder, and means associated with said moving means for applying said closure when said grinding element is in grinding position and for removing said closure when the element is out of grinding position, whereby said brake operating handle cannot be actuated during grinding.

8. In a lens grinder, a receptacle in which the grinding is effected, a hinged closure for said receptacle, a rotatable work holder disposed within said'recptacla means "fofi bi ak'ing the rotation of the work holder-including an operating handle, said receptacle having-a handlereceiving recess therein, said recessbeing closedi-when said closure-{is in applied position; a grinding element disposed within the receptacle, means 'for moving the grinding element -into and out of egrinding-position with res-pectto the work holder, means -associated with said 'moving meansfor 1 a-pplying said closure when said grinding element is inlgri-nding position and-for removing sald closure when the element isput of grinding-:po-

'sitionFwhereby said brake operatin ha dl a not be actuated during grindingfland a" motor for rotating the lens blank chuck, means for ener gizing the motor when the closure is applied and for de-energizing the motor when the closure is removed, whereby braking can be effected only after the motor has been de-energized.

9. In an abrading machine having a rotatable abrading element holder, means for rotating the abrading element holder, a rotatable work holder, an electric motor for rotating the work holder, means for moving the work holder and the abrading element holder relative to one another to bring the abrading element into abrading relationship with the work to be ground, and means for supplying coolant to the abrading element and the work, a normally closed valve for con- 30 trolling the coolant supply, a normally open switch for controlling the electric motor, and a combined cam carried by the means for moving the work holder and the abrading element holder relative to one another for actuating said valve and said switch to supply coolant and rotate said work holder upon movement of said moving means to bring the work holder and abrading element holder into operative abrading position. 10. In an abrading machine, a rotatable work holder a rotatable abrading element holder, a plate disposed substantially parallel to the axis of rotation of said abrading element holder, a second plate disposed at an angle with respect to said first plate, said first and second plates being pivotally connected to aflord pivotal adjustment of the second plate in a plane at an angle to the plane of the first plate, and said rotatable work holder being mounted on said sec-- ond plate for movement with both said first and second plates collectively and with said second plate independently, means for pivoting said first plate about a pivot whose axis extends substantially at 90 from said first plate and substantially intersects the axis of rotation of said work holder substantially at the surface of the work to be abraded to adjust the angle of attack between the abrading element and the work piece and thus vary the radius of curvature formed on the work piece by the abrading element, said pivotal connection between the first and second plates affording adjustment of the work holder to bring the abrading element into engagement with the work piece along a line extending from edge to edge thereof. 65 PIERRE DE VITRY nAVAUCOURT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS- Name Date Larrabee Aug. 1'7, 1909 Perkins Apr. 15, 1913 Number 76 (Other references on following page) Number '15 UNITED STATES PATENTS Name Date Simpson June 14, 1921 Taylor Dec. 27, 1921 Hill Nov. 18, 1924 Kimmel Jan. 6, 1925 Belden et al. May 26, 1931 Conradson Aug. 27, 1940 Schmidt July 1, 1941 Houchin Mar. 31, 1942 Goddu June 16, 1942 Holman Jan. 8, 1946 Walker Feb. 26, 1946 Ellis et a1. Apr. 29, 1947 Number .1 FOREIGN PATENTS Country Date Great Britain Feb. 18, 1915 Germany Sept. 4, 1924 Germany Oct. 13, 1927 OTHER REFERENCES 10 pages 43 to 45.

(Copy in Div. 58.)