US2020312A - Apparatus for grinding and polishing cylindrical lenses - Google Patents

Description

Nov. 12, 1935. A. J. HOLMAN 2,020,312

' APPARATUS FOR GRINDINGAND POLISHING GYLINDRICAL LENSES Filed Feb 8, 1930 5 Sheets-Sheet 1 NQv. 12, 1935. A. J. HOLMAN 2,020,312

APPARATUS FOR GRINDING AND POLiSHING CYLINDRICAL LENSES Filed Feb 8, 1930 s sheets-sheet 2 Nov. 12, 1935. A. J. HOLMAN APPARATUS FOR GRINDING AND POLISHING CYLINDRICAL LENSES Filed Feb. 8, 1930 :s sheets sheet's jve7z ar I I, v a WA 1", I 722:5 207 Patented Nov. 12, 1935 UNITED STATES NT OFFICE A APPARATUS FOR GRINDING AND POLISH- ING CYLINDRICAL LENSES Claims.

My invention relates to means for grinding and: polishing concave cylindrical surfaces in lenses,. and it has been. the special object of my invention to provide a simple apparatus which 5. will function with precision. so as to produce a truly cylindrical. surface.

My device may be best understood by reference to the accompanying drawings in which.

Fig. l is a plan view of my device with bearlO ing brackets for the sliding carriage partly broken away to show the means for supporting the carriage.

Fig. 2 is a front view showing the method of shifting. the link connections for oscillating the lap when. a cylinder of short radius is to be ground.

Fig. 3; is a plan view of the lens chuck and lens centering andv positioning ring- Fig.4 is a plan view of the lens centering and positioning ring.

Fig. 5 is aside view of my device.

Fig- 6- is a cross section. on line 66 of Fig. 3 of the lens chuck and lens centering and positioning ring;

5 Referring now more. specifically to the drawings, I is the main frame which may be suitably attached to the bench. 2;. Bolted to the back wallv 3 of the mainv frame I is a bracket 4 which has integral. therewith bearing brackets 5 and 6,

3 wherein is mounted the crankshaft l, and bearing brackets 8 and 9 (Fig. 2) wherein is mounted the drive" shaft ll). The bracket 4 also carries a bearing bracket H which supports one end of. the crank shaft [2,. the other end of which 35; isjournaled in the: bearing bracket l3 which is bolted to the main frame Ir.

The crankshaft I carries a. crank block M to which is attached in an adjustable manner the crank pin I5. A gear Hi is fast mounted on crank shaft 1 and meshes with a gear ll fast mounted on: drive. shaft II]. which carries also a drive pulley l8, and. a helical gear I!) which meshes with a helical gear 20 on crank shaft [2. Thrust bearing 21 on shaft I0; and thrust bearing. 22 on shaft [:2 carry the end thrust resulting from the interaction. ofthe. helicalv gears I9 and 2D.

A. crank block 23 is mounted on crank shaft l2 and carries-the adjustably mountedv crank pin 2d.

Bolted tothe top of the main frame I are parallel. bearing brackets 25 and 26 in which are slidablymounted rods 21 and 28 to which is attached the cross member 29. A connecting rod 391 mounted on. crank pin l-5 enters a recess 55: in the cross member 2-9. andv is hingedly attached thereto by means of the pin 3| fixed in the lugs 32 and 33 which are-integral with the cross member 29.

A chuck carrier 34 is hingedly connected to bosses 35 and 36, which are integral with cross 5 member 29, by the hinge pins 3-1 and 38 fast mounted respectively in said bosses 35 and 36.

A bar 39, which is rectangular in cross section,

is fixedly mounted at one end in a boss 40 integral with the chuck carrier 34, being retained 10 in position by the pin M. The bar 39 is also secured in a slot in a. rib 42' on the chuck carrier 34 by means-of the cap-plated? which is attached by screws 44 and 45 to said rib. The bar 39' may drop into close fitting engagement with the 15 slotted top of the bracket 46 which: is attached to the main frame I by'bolts. 41' and 48.

A dependent arm 49 having a flanged top 50 is secured by bolts 51 and 52' to the bottom of the main frame I. an integral rib 53 having thereina row of tapped holes 54 inany one of which may be screwed the bolt 55 which passes through a slot in the base of the bracket 56 and retains the bracket in the desired position. of vertical. adjustment. The 25 bracket 56' has a forked end 51 wherein is. hingedly mounted on pin 58 the bracket 59 which is adjustably secured to the oscillating arm 60 by means of the bolt 6| which passes through a slot in the base of the bracket 59 and enters one 3.0 of the tapped holes 62 in rib 63 on the oscillating arm 60.

The upper end 64' (Fig; 5') of the oscillating arm til is flanged tosupport-the lap tray 65 which is secured thereto by screws 66. Within the lap 3.5 tray 65 is secured the'cylindrical lap 61. Mounted between bolts M and 48 which enter the main frame I is an arched guide bar 68 which has. a. close sliding fit within a slot in the upper end of the oscillating arm 6|]. A connecting rod 69 40 is connected at one end to the crank pin 24 and at the other end is hinged on the pin- 70 which is fixed in the upper portion of the oscillation arm 60.

To more easily actuate ,the oscillating arm 60 45 when the device is adjusted for cylinders of short radius by an extreme elevation of the brackets 56 and 59, the connecting rod 69 may be disconnected from pin l0- and connected to' the pin H which is mounted on a rocking. bracket 12 50 pivoted on a pin 13 fixed on the arm 49. A link 1A, is then employed to connect the oscillating arm 50 and the rocking bracket 12, being attached by pin l5 fixed in the arm 6!] and by pin 16 fixed in the swinging bracket 12. 55

This arm 49- is provided with 20 The lens 11 to be ground is mounted and positioned in the chuck I8 in the following manner: The lens is placed upon a warming plate, the face to be ground being placed against the warming plate and the ring I9 is then placed about the lens TI. This ring I9 is of a thickness substantially equal to that of the part of the lens which is to project from thechuck I8 when mounted therein, and the internal diameter of the ring I9 is such as to permit it to fit closely about the lens II. Four rectangular bosses 80 project from the upper surface of the ring I9, their inner faces being located symmetrically with respect to the center of said ring. The chuck I8 has four projecting bosses8l, the outer faces of which are located symmetrically with respect to the center of the chuck I8 and are spaced so as to fit within the bosses 80 on the ring I9 (Figs. 3 and 6) Hence when the cavity of the chuck I8 is coated with pitch 82 and the chuck is pressed down upon the ring I9 which contains the lens 11, the lens will be centered and squared in said chuck. A slow application of heat will cause the pitch to adhere to the lens and after cooling, the ring I9 may be removed, and the chuck I8 bearing the lens TI is now ready for mounting in the grinder.

To maintain the chuck I8 in proper position in the grinding machine, I have provided a pair of diametrically opposite pins 83 thereon and on a diameter at right angles thereto, I have provided a pair of rectangular slotted bosses 84. The chuck carrier 34 is provided with a pair of oppositely placed dependent slotted lugs 85 which will closely embrace the pins 83 on the chuck I8. As the hingedly mounted chuck carrier 34 is dropped into position over the chuck I8, the bar 39 enters the slots in the bosses 84 and so aligns the chuck that the slotted lugs 85 will embrace the pins 33 when the chuck is moved longitudinally into the proper position.

Before proceeding to grind a lens thus mounted in the machine a lap of the desired curvature has been, of course, selected and mounted in the machine in the manner heretofore described. The brackets 56 and 59 are so positioned with respect to the lap that the axis of the pin 58 coincides with the axis of the cylindrical surface of the lap. Hence when the oscillating arm is rocked the lap surface will oscillate about its own axis of ourvature and retain its true contour and impart a like contour to the surface of the lens being ground.

An examination of Figs. 1, 2, and 5, will show that the slidably mounted cross member 29, the chuck carrier 34, which is hinged thereto by the hinge pins 3! and 38, the rectangular bar 39 rigidly attached to the chuck carrier 34 and fitting into the slotted top of the bracket 46, and the "slotted lugs 85 (integral with the chuck carrier 34) which embrace the pins 83 on the chuck I8, are all designed and arrange-d to prevent any and all movement of the lens 11 in a direction tangential to the cylindrical surface of the lap 61. Thus the lens IT has no freedom of motion except that of translation along a straight path parallel to the axis of the abrading surface of the lap. However, as the glass is ground away by the abrading action, the lens Il is free to feed radially downward toward the axis of the cylindrical surface, due to the hinge action at the pins 83, which permits the top of the lens chuck 8 to remain always parallel to its initial position.

It will also be observed that the pin 58 centered on the axis of the cylindrical surface of the lap 67, and the arched guide bar 68 which fits closely within a slot in the upper end of the oscillating arm 60, are designed and arranged to constrain the cylindrical surface of the lap to travel only over an extended cylindrical surface which is coincident with its own cylindrical contour.

ously essential in any device wherein the lens blank is to be restrained from rocking and tilting, and constitutes the feature which is characteristic of my device and which distinguishes it from all 10 cylindrical grinding mechanisms wherein pivot mounting of the lens blank must be provided. This movement of the lap causes the abrading surface to remain truly cylindrical throughout the grinding operation, and, moreover, it eliminates 15 all tendency for the lens, due to contact with the moving lap, to move in any direction except tangentially to the lap surface, and, as has already been pointed out, the lens carriage structures are designed to prevent such tangential motion of 20 the lens. Thus the structures provide constant and exact alignment of the axis of the lens with respect to the axis of the lap, combined with ideally smooth and uniform abrading action, both on the lens blank and on the lap. 25

Thus, my device combines two simple movements; namely, linear reciprocation of the lens and pure oscillation of the lap supporting member, each of which movements takes place in a plane at right angles to the other, and the struc- 30 tures are so arranged that neither moving element can change or in any way affect the motion of the other. The abrading action between lens and lap which results from the combination of these two simple movements, takes place, as pre- 35 viously indicate-d, without periodic rocking, tilting or rotating of the lens, therefore the cylindrical surfaces generated by my device are far more accurate than the surfaces produced by former cylinder grinding machines. especially useful in producing large surfaces such as are required in certain reflector arc condenser lenses, wherein a cylindrical surface having a radius of curvature of 32 inches is required to be formed in one face of a condenser lens 8 inches 45 in diameter. Such large cylindrical surfaces must be made very accurately to meet the requirements of non-intermittent motion picture projection, and no apparatus heretofore constructed is suitable for producing such large and precise 60 work.

Power applied to the drive pulley I8 will, through gears 11 and I6 impart rotation to the crank shaft I and through its attached crank mechanism reciprocate the slidably mounted cross 5% member 29 and the chuck carrier 34 which constitute the lens carriage thereby imparting reciprocating motion to the lens.

The drive shaft I through gears I9 and 20 also rotates crank shaft I2 which through the crank 60 mechanism attached thereto, imparts the oscillating movement above described to the lap.

The gear ratios between the power shaft I 0 and the crank shafts I and I2 are such as to impart to the lens carriage and to the lap motions of different frequencies so that any given point on the lap surface will travel through devious paths on the lens surface, thus producing a varied pattern to the wiping action and a thorough and uniform distribution of the grinding mixture. Pressure may be applied to the arm 39 as desired to secure the necessary grinding action.

To polish the lens surface after grinding a suitable polishing element is substituted for the lap above described. This polishing element may be This 5 particular movement of the lap surface is obvi- Hence my device is 40* made of either pitch or felt or a combination of pitch and felt or other fabric. I recommend as a satisfactory polisher one made up by cementing a felt covering over the surface of the lap and applying thereto a coating of beeswax. When the polisher is so constituted, it is obvious that the radius of oscillation of the surface of the polisher has been increased by an amount equal to the thickness of the material applied to the lap, and therefore it becomes necessary correspondingly to lower the oscillating arm 60.

The accuracy of grinding which is obtained by the use of my device is such that the surface is true to the curvature of the lap and consequently the polishing is accomplished rapidly and evenly, thus proving the precision with which the grinding and polishing operations areperformed.

While I have described and illustrated one preferred form of my apparatus for grinding and polishing cylindrical lens surfaces, it will be obvious to those skilled in the art that other mechanical structures may be used to provide the same action; i. e., the oscillating of a cylindrical lap about its axis and the reciprocation of a chuck along a path parallel to the axis of said lap, the oscillating and reciprocating movements being entirely independent of each other, and the combined movements providing an abrading action wherein the lens blank is not required to perform periodic rocking, tilting or rotating movements. The appended claims are drawn with a View to covering any and all apparatus suitable for and/or capable of performing successfully in the manner above described.

Having thus fully described my invention, what I claim is:

1. In a device of the character specified, the combination of a slidably mounted lens carriage provided with a hingedly mounted chuck carrier adapted and arranged to hingedly support a chuck, means for imparting reciprocating movement to said lens carriage, a lap oscillatably supported on an axis parallel to the direction of reciprocation of said lens carriage, and means for oscillating said lap.

2. In a device of the character specified the combination of a slidably mounted lens carriage provided with a hingedly mounted chuck carrier adapted and arranged to hingedly support a chuck, means for imparting reciprocating'movement to said lens carriage, said chuck carrier being provided with an outwardly extending guide bar, a slotted guide member by which the outer end of said guide bar is aligned, a lap oscillatively supported on an axis parallel to the direction of reciprocation of said lens carriage, and means for oscillating said lap.

3. In a device of the character specified the combination of a slidably mounted lens carriage provided with a hingedly mounted chuck carrier, a lens chuck, means on said chuck carrier arranged to engage and retain said chuck in proper alignment when said hingedly mounted chuck carrier is swung into operative position, means for imparting reciprocating movement to said lens carriage, a lap oscillatably supported on an axis parallel to the direction of reciprocation of said lens carriage, and means for oscillating said lap.

4. In a device of the character specified the combination of a slidably mounted lens carriage provided with a hingedly mounted chuck carrier, a guide bar mounted on said chuck carrier, said chuck carrier being provided with dependent slotted lugs, a lens chuck provided with a pair of diametrically opposite slotted bosses adapted to embrace said guide bar and a pair of diametri cally opposite pins adapted to fit within said dependent slotted lugs thereby hingedly connecting said lens chuck with said chuck carrier, means for imparting reciprocating movement to said lens carriage, a lap oscillatably supported on an axis parallel to the direction of reciprocation of said lens carriage, and means for oscillating said lap.

5. A lens chuck comprising a disc shaped body hollowed out on one side to receive a lens blank, four bosses projecting radially from said disc shaped body and lying on two diameters intersecting at right angles, the outer faces of said bosses being equidistant from the center of said chuck, a pair of diametrically opposite pins projecting from two of said bosses, and a pair of rectangular slotted bosses projecting normally from the fiat face of said disc shaped body, said rectangular slotted bosses being located adjacent the periphery of said chuck and on a diameter at right angles to the axis of said pins.

ARTHUR J. HOLMAN.

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