US1186616A - Lens grinding and polishing machine. - Google Patents

Description

J. E. STRECKER.

LENS GRINDING AND POLISHING MACHI APPLICATION FILED NOV-18.1912.

Patented June 13,- 1916:

2 SHEETS-SHEET I.

rlllllll m v INVENTOR G0/ M a A;

WITNESSES A TTORNE Y 2 SHETSSHEET 2.

J. E. STRECKER.

LENS GRiNDING AND POLISHING MACHINE.

APPLICATION FILED NOV-18 1912- Patented June 13 INVENTOR ATTORNEY rim; 6

WITNESSES ED STATES PATE a Enron.

LENS GRINDING AND POLISHING CHINE.

Specification of Letters fatent.

Patented June 13, 1916.

Application filed November 18, 1912. Serial No. 731,925.

To all whom it may concern:

Be it known that I, JOHN E. STREoKEB, a citizen of the United States of America, residing in the city and county of Philadelphia, in the State of Pennsylvania, have invented a certain new and useful Improve- :nent in Lens Grinding and Polishing Ma- :hines, of which the following is a true and exact description, reference being had to.

the accompanying drawings, which form a part thereof.

My present invention is an improved lens grinding machine especially adapted for grinding multifocal lenses, such as the b1- focal and trifocal spectacle lenses in common use.

The primary object of thepresentinvention is to provide a simple and efl'ective lens grinding mechanism which can be qulckly and easily adjusted to grind lens surfaces of different curvatures, and in which the shape of the grinding-wheel used need not conform to, nor depend upon, at least within close limits, the shape of the surface ground.

In carrying out my invention, I provide means for rotating the lens about one axis, and for rotating the grinding-wheel about another axis which is transverse, though not necessarily perpendicular, to the axis of rotation of the lens, and I provide means for moving the lens and grinding-wheel with respect to one another. to carry the point of contact between the grinding-wheel and lens across the surface of the latter being ground.

In the practical application of my 1nvention I prefer to maintain either the grinding-wheel element or the lens or other work holding element in a fixed position except as to its movement about its axis of rotation during any one stage of the grlnding operation, while moving the other of these two elements through the proper path. The shape of this path depends upon the character of the lens being ground and may be in whole or in part a straight line but in general, the path through which the movable element is to be carried is a curve, or combination of different curves, and usually either a circular are or a compound curve made up of two or more circular arcs of differing radii of curvature. The means which employ to define this path enable me to give any shape desired to the path and consequently to the surface ground, and it is an important and highly advantageous characteristic of m improvedlens grinding machine that it is readily adaptable to grind plane surfaces, or concavely or convexly spherical surfaces, or concave or convex surfaces other than spherical surfaces, or surfaces having portions of different character, that is, partly plane and artly curved, or having curved portions of difiering curvatures. My improved machine is thus adapted for grinding spectacle lenses, and also practically all other lenses and refractive surfaces required for general optical pur poses.

To cause the movable element to follow the proper path, I give it a primary move- ,ment in a direction generally transverse to the axis of rotation of the work holding element, and at the same time cause the movable element to move or hold it against I movement in a direction transverse to, though not necessarily perpendicular to the direction of said primary movement by causing it to bear against a former cam or templet of the proper shape. Practically I prefer in grinding multifocal lenses to employ two or more templets each of the proper shape for, and employed in grinding a corresponding one of the different fields of the bifocal, trlfocal or other multifocal lens be ing ground.

The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, however, and of the advantages possessed by it, reference should be had to the accompanying drawings and descriptive matter in which I have illustrated and described various forms of apparatus embodying my invention.

' Of the drawings: .Figure 1 is a plan view of one form of grinding-machine embodying my invention. Fig. 1 is a partial sec tion on the line 1*-1 of Fig. 1. Fig. 2 is a side elevation of the machine shown in Fig. 1. Fig. 3 is a rear side elevation of a portion of the machine shown in Fig. 1. Fig. 4: is a partial section on the line 44 of illustrating the lens grinding operation with the lens shown in section on the line 77 of Fig. 6. Fig. 8 is a plan of one former cam which I may employ.. Fig. 9 is a plan of another former cam which I employ. Fig. 10 is a section on the line 10-10 of Fig. 9; and Fig. 11 is a plan view of a modified form of grinding-machine.

In'the particular embodiment of invention shown in Figs. 1 to 4, A representsthe bed or base of themachine. Adjacent one end of the" machine the base A is provided with transverse guides A on which is mounted a sliding carriage B. The carriage B is formed with a guideway B receiving a table 0 which is movable therein in a direction transverse to the movement of the carriage B on the guides A. Adjustably secured to the table C is the support D for the lens holder shaft E. 'As shown, the support D is formed with a base having slots D through which pass the bolts D which secure the member I) to the table C. At opposite sides the member D is provided with bracket arms, or posts, D carrying at their upper ends bearings for the shaft E. The latter has secured to it between its two bearings a gear wheel E, and the lens in the bracketears A projecting from one side of the base A. The shaft G has mounted on it adjacent one end a driving pulley G whichmay be connected to the shaft G to rotate the latter, or be disconnected therefrom to permit the pulley to turn free on the shaft, by a clutch mechanism conventionally illustrated at G". vAt its other end the shaft G is provided with a crank -pin-H, which, as shown, is adjustably. re-

ceived in a radial slot G formed in the crank disk G directly secured to the end of the shaft G. A connecting rod I is journaled at one end to the crank pin H, and at the other end is journaled between bracket ears J of a'member J. The latter is slidingly movable in a direction parallel to the length of the guides A, in a guideway B formed on the underside of the carriage B. 7

To adjust the member J relative to the carriage B an adjusting screw K is provided. The screw K has an operating head or handwheel K at its outer end and is held against movement in the'direction of its length with respect to the carriage B by means of a collar K on the screw K, and a keeper B secured to the carriage B. The threads of ment of the crank pin H, the limits of the to and fro movement of carriage B will be determined by the adjustment effected by the rotation of the threaded adjusting member K, of the member J relative to the carriage B. When the crank pin H is set coaxial with the shaft G, the carriage B is locked against movement along the guide A, although such movement may still be brought about by rotating the screw K. As the carriage B is moved back and forth along the guides A, the table C is moved in its guideway B in the carriage B, by means of a former cam or guide secured to the bed A, and a guide engaging part secured to the table C, and caused to engage the guide. In the particular form of apparatus shown in Figs. 1 to 4:, inclusive, the part carried by the table C and directly engaging the former cam, is a shoe 0 which is pivotally mounted in and carried by a yoke N. The latter in turn is formed with a socket receiving the reduced inner end of an adjusting screw M which passes through a threaded aperture in a member L. The member L is formed with a threaded bolt like extension L which passes through a slot C formed in table C. A nut on the extension L forms a means for detachably securing the member L to the table C in any desired adjustment of the extension L along the length of the slot C Springs C at the opposite sides of the table 0, and each secured at one end to the table O and at the other end to the carriage B means support N for the shoe O is extended to engage the upper and lower surfaces of the former P, and thus prevent a rotation of the member'N tending to disarrange the apparatus.

In the particular form of machine shown in Fi s. l to 4, the support R for the grinding-w eel S is secured to a table 0 mounted in a carriage 6 working on a second pair of uides A formed on the base member A. ad- Jacent the right end of the machine as shown in Figs 1 and 2. The carriage b and table 0 are similar to the carriage B and table C respectively, and are given similar movements by similar means and, in the drawings, some of the parts duplicated at the opposite ends of the machine are indicated by capital letters with their exponents at the left end of the machine, and by correspond ing lower case letters and exponents at the right end of the machine.

The grinding-wheel supporting frame R is adjustably secured on the table 0 by bolts R passing through slots B formed in the base of the supporting frame R. The latter is formed with two posts or brackets R and R. The bracket R is formed with a split bearing R for a purpose hereinafter described and carries a fixed conical ended pivot It. The other bracket R is formed with a threaded socket receiving a bolt R having a conical inner end serving in cooperation with the pivot lt as the pivot pins on which the grinding wheel-S is journaled.

R represents a clamping screw for securing the screw R in any desired adjustment, and the latter may be readily backed ed to permit of the removal of the grinding-wheel S which has secured to it at one side a driving pulley S, and is formed with bearings for the pivots R and R.

The lens blank X shown in Figs. 6 and 7 is of the type from which spectacle lenses are commonly out after the lens blank is ground. As shown, the blank X is in the form of a concave-convex body of circular outline which is ultimately ground to have an outer spherical zone X and an inner spherical zone X The radius of curvature of the zone X is different from, and in general, greater than the radius of curvature of zone X Two or more spectacle lenses may ultimately be cut from the blank as indicated by the dotted lines X in Fig. 6 which intersect the inner zone X of a single lens including all or the major portion of the zone X may be cut from the blank as indicated by the dotted line X. In the latter case the zone X would ordinarily be smaller than in the first case and one of the practical advantages of my invention is the ease with which blanks of the general character shown by Fig. 6 may be formed with zones X of different sizes and curvatures. The blank X after being secured in the holder F in any usual or proper manner as by cementingit 1n lace, may have the zone X ground by 100 ing the carriage b, and thereby the table c in fixed position, and then, with the grind ing-wheel and the lens holder F each rotating about its own axis, moving the carriage B back and forth on the guides A, to carry the point of contact of the grinding wheel with the lens blank back and forth between the inner and outer margins of the zone X, while at the same time giving the table G the proper to and fro movement in its guideway B. The proper movement will obviously be given to the table C as the table B is moved back and forth on the guide A. if

the former cam P has the proper contour.

If, as in the machine shown, the axes of rotation of the lens carrier and the grindingwheel and the point of contact between the grinding-wheel and lens blank all lie in the same plane, the contour of the working edge or face of the former P should correspond exactly to the line in the surfaceof the zone X of the blank cut by a plane passing through the axis of rotation of the lensholder; and in any disposition of the apparatus there will be an easily ascertained relation between the contour to be ground and the shape of the former cam needed for its grinding. After the zone X is ground in this manner, the zone 'X may be ground by clamping the carriage B to the base A, and reciprocating the carriage 5 along its guides with the shoe 0 bearing against a suitable former p. It will be understood that the shape of the working face, or edge of the formerp is governed by the same considerations which control the shape of the former PI While the mode of operation heretofore described is that which i prefer to employ for certain practised reasons in grindinglenses with the particular mechanism shown in Figs. 1 to 4, it will be apparent that both zones 1 and 2 of the lens blank can be ground with either of the two carriages B and I) held stationary and the other movable throughout the grinding operation. This may be accomplished when the table 0 is held stationary by the simple expedient of replacing the former P by the former p after the zone X is ground and shifting the member J so that the subsequent to and fro movement of the movable carriage B will carry the point of contact of the grindingwheel and the lens blank from the outer margin of the zone X into orbeyond the center of the zone, or, preferably entirely across the zone. In lieu of employingtwo separate formers and grinding the zones X and X in separate and successive stages, I may employ a simple compound former as shown in Fig. 8 and in Figs. 9 and 10. In such caseIimpart sufficient movement to the movable cal riage B to carry the oint of contact of the lens blank and grin ing-wheel clear across the face of the blank, or atleast from the outer side of the zone X to or beyond the center of the blank. When such a compound cam is employed it may be in a single iece PA as indicated in Fig. 8, or it may we 1 be built up', as by superimposing the formers P and p on one another, as shown in Figs. 10 and 11. In this case the simple former engaging parts hereinbefore described may well be replaced by the arrangement shown in Fig. 10 wherein two shoes OA and 0A one coiiperating with each of the two former parts p. and P are mounted in a single holder NA which has guiding surfaces engaging the under, side of the under-former, and the upper side of the upper former. The

compound formers shown in Figs. 8, 9 and 10 are adapted to grind a surface having an inner convex portion of one radius of curvature and an outer concave portion having a longer radius of curvature. After the lens blank is ground in the manner described, 1t may be polished by means of a cast iron or other suitable polishing head T of usual form which has its supporting shaft T mounted in the split bearing R of the grinding wheel support It, as shown in Fig. 5. It will be understood that a suitable polishing powder is employed in the polishing operation.

In Fig. 11 I have illustrated in a somewhat diagrammatic manner a modification of the machine shown in Figs. 1 to 4, which difi'ers from that machine in that the grinding-wheel support R is directly clamped to the base AA of the machine, while in lieu of employing automatic means for giving the carriage B its to and fro movement on the guides A, this movement is imparted manually by means of a shaft U which is provided with a handle U by which it may be rotated and carries a spur gear U? meshing with a rack B carried by the underside of the carriage B.

It is apparent that with the mechanism described the contours of the lens surfaces ground do not, in general, depend upon the form of the grinding-wheel. Where the latter is in the form of a disk-like wheel, as shown in the drawings, the grinding-wheel may be set with its plane parallel to the line of movement of the tables C and c, or oblique thereto, as shown in dotted lines in Fig. 7

without changing the contour of the surfaces ground, though it is to be noted that such a change in position of the grindingwheel necessitates an adjustment of the members J or 9', or the former cams to bring the former or formers used into their proper relation with the lens blank.

Heretofore it has been standard practice to grind bifocal lenses by the use of a cast iron grinding disk engaging the lens as does the polishing disk T in the construction shown in Fig. 5. Grinding bifocal lenses in this manner, it has been found practically impossibleto keep a clear line of demarcathis arises.

While in accordance with the provisions of the statutes I have illustrated and described the best forms of my invention now known to me, it will be apparent to those skilled in the art that chan es may be made in the forms of apparatus isclosed without departing from the spirit of my invention, and that under some conditions certain features of my invention may be used without a corresponding use of other features' Having now described my invention, what I claim as new and desire to secure by Letters Patent, is: I

1. In a grinding-machine of the character described, the combination of a rotatable work holder element, a grinding-wheel element rotatable about an axis transverse to the axis of rotation of the first mentioned element, means for giving one of said elements a primary movement relative to the other in a direction-transverse to the axis of rotation of said work holder element, said one element being movable in a direction transverse to the direction of said primary movement, and a templet acting upon said one element during its primary movement to control the movement of said one element in a direction transverse to the direction of said primary movement.

2. In a grinding-machine of the character described, the combination of a base, guides carried thereby, a carriage movably mounted thereon and provided with a guideway extending transversely to said guides, a table mounted in said guide-way, a templet secured to said base and engaged by said table and adapted to move the latter in said guideway as said carriage is moved along said guides, a rotatable work holder ele ment having its axis of rotation transverse to said guides, a rotatable grinding wheel element having its axis of rotation transverse to the first mentioned axis, one of said elements being mounted on said table and means for holding the other element against movement relative to said base in a direction parallel to said guides.

Kid

masters I 3. In a grinding machine of the character described, the combination of a rotatable work holder e ement, a grinding-wheel element rotatable about an axis transverse to the axis of rotation of the first mentioned element, means for giving one of said elements a primary movement relative to the other in a direction transverse to the direction of rotation of said work holder element, and a compound templet acting upon said one element during its primary movement, said templet comprising a pair of superimposed plates each having a guiding edge which is diderent in shape from the guiding edge of the other plate.

4. In a grinding-machine of the character described, the combination of a base, guides carried thereby, a carriage movably mounted thereon and provided with a guideway extending transversely to said guides, a table mounted in said guideway, a templet secured to said base, a templet engaging device, means securing said device to said table with provisions for adjusting said device with respect to said table in two directions transverse'to one another. a rotatable work holder element having its axis of rotation transverse to said guides, a rotatable grinding-wheel element having its axis of rotation transverse to the first mentioned axis, one of said elements being mounted on said table, and means for holding the other element against movement p'arallei to said guides,

5. in. a grinding-machine of the character described, the combination of a base. guides carried thereby, a carriage movably mounted thereon and provided with a guideway extending transversely to said guides, a table mounted in said guideway, a templet comprising a pair of superimposed plates secured to said base, templet engaging means secured to said table and adapted to engage the edge of first one and then the other or" said plates and move the table in said guide way as said carriage is moved along said guides, a rotatable work holder element having its axis of rotation transverse to the first mentioned axis, one of said elements being mounted on said table, and means for connecting the other element to said base in such manner as to prevent its movement parallel to said guides.

6. In a grinding-machine of the character described, the combination of a base, two sets of parallel guide surfaces carried thereby, two carriages mounted on said base each movable along one set of said guide surfaces.

and each formed with a guideway extending transversely to said guide surfaces, two tables one mounted in each of said guideways, two templets secured to said base, a templet en agin device secured to each table and adapte to engage a corresponding templet, means for moving each carriage along said guide surfaces, means for detachably securing each carriage against such movement, a rotatable work holder element &

mounted on one of said tables and having axis of rotation transverse to said guides,

and a rotatable grindingwheel element mounted on the other table and having its axis of rotation transverse to the first mentioned axis.

7. In a grinding-machine of the character described,.the combination of a base, two sets of parallel guide surfaces carried thereby, two carriages mounted on said base each movable along one setof said guide surfaces and each formed with a guideway extending transversely to said guide surfaces, two tables one mounted in each of said guideways, two templets secured to said base, a templet engaging device secured to each table and adapted to engage a corresponding templet, means for moving each carriage along said guide surfaces, means for detachably securing each carriage against such movement, a rotatable work holder element mounted on one of said tables and having its axis of rotation transverse to said guides, a rotatable grinding-wheel element, mounted on the other table and having its axis of rotation transverse to the first mentioned axis, and yielding means tending to hold each of said templet engaging devices against the corresponding templet.

8. In a grinding-machine of the character described, the combination of a base, guides carried thereby, a carriage movably mounted thereon and provided with a guideway extending transversely to said guides, a table mounted in said guideway, a templet secured to said base, a templet engaging device carried by said table for giving determined reciprocatory movements to said carriage along said guides, said means being adjust able to vary either or both limits of said reciprocatory movement as desired, a rotatable work holder element having its axis of rotation transverse to said guides, a rotatable grinding-wheel element having its axis of rotation transverse to the first mentioned axis, one of said elements being mounted on said table, and means for holding the other element against movement parallel to said guides.

9. Ina grinding-machine of the character described, the combination of a base, guides carried thereby, a carriage movably mounted thereon and provided with a guideway extending transversely to said guides, a table mounted in said guideway, a templet secured to said base, templet engaging means carried by said table and adapted to engage the templet and move the table in said guideway as said carriage is moved along said guide, a shaft jourualed in, said base, a crank pin adjustabl secured thereto, a connecting rod connecting the other element to said bese'in ourna ed at one end to said crank pin and a such manner as to prevent its movement par- 1 J piilllt hadljlustalily seclregl tod said 1liable to allel to said guides. H w'cteoterenosai cran pinis 5 'ournaled, a rotatable work holder element JOHN -E aving its axis of rotation transverse to the Witnesses:

first mentionedaxis one of said elements be- J OHN E. HUBBELL, ing mounted on sald table, and means for ARNOLD KATZ.

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