US937763A - Lens-grinding implement. - Google Patents

Description

r BUOHHOP. LENS GRINDING IMPLEMENT.

APPLIGATION' FILED D110. 16, 1908.

- Patented 00132611909.

l mu mi i I l T UNITED T OFFICE.

FERDINAND BUGHHOP, OF NEW YORK, N.Y., ASSIGNOR TQ THE MEYROWITZ MANU- FACTUBING COMPANY, A CORPORATION OF NEW JERSEY.

To all whom it may concern:

Be it knownthat I, FERDINAND BUCHHOP, a citizen of the United States, residing at the city of New York, in the borough of Brooklyn and State of New York,. have invented certain new and useful Improvements in Lens-Grinding Implements, of which the following is a full, clear, and exact description.

This invention relates to tools or apparatus employed in grinding the lens blanks for Kry tokbifocal lenses. In the manufacture 0 these lenses a depression or concavity is formed eccentrically in the surface of a major lens blank at a point which must be accurately predetermined. Afterward a minor lens of glass of higher refractive power is fused into said depression or cavity, and the entire lens blank then ground away and trimmed to form a lens for eyeglasses or spectacles inwhich a different focal length is obtained for distant vision from that obtained in reading, the line of vision being downward in the latter case and correspond ing to the location of the minor lens blank. The nature of these processes and the subsequent character of use of the glasses necessitate a somewhatprecise location and formation of the said cavity or-depression.

It is the main object of my invention to provide a combination of tool and workholding device which is adapted to do this work easily and expeditiously for a plurality of lens blanks at a single operation.

The nature of the process and the characteristics of the tools, etc., employed, embody several theoretical principles, as later pointed out. y

The structural characteristics of the ,invention will be first considered, having reference to the accompanying drawin 's which illustrate preferred embodiments of the invention.

In the drawings: Figure 1 is a sectional view showing a lens blank or work-holder and grinding head, as employed in forming the depressions or cavities of Kryptok lenses in accordance with this invention; F ig, shows a similar couple adapted for a different radius of curvature of the depression; Fig. 3 is a bottom plan .view of the holder; Figs. 4: and 5 are sectional views showing slightly modified constructions; Fig. 6 is a sectional view showing a further gnodifiv Specification of Letters Patent' VII-VII of Fig LENS-GRINDING IMPLEMENT. i

Patented Oct. 26, 1909. Application filed December 16, 1908. Serial No. 467,810.

cation, and Fig. 7 is a section on the line 6. i 1 designates a rarne having a central body 2 with a plurality of arms 3. These arms I have inner faces adapted to support lens blanks in planes 4:, the essential characteristics of which are that they all radiate at exactly equal angles from a-common axis and vertex; 7 and 9 to supportthe lens blank and which are-separated by an intermediate recess (3, and also a stop or shoulder 5 which fixes the radial location of the blank. The construction of these various features is based on theoretical or mathematical considerations as follows:

The depressions or cavities C of the blanks A, being spherical in curvature, are necesapplicability when the entire surface of the blank is ground away to the prescribed curvature, it being merely necessary to continue the grinding until a surface of more than adequate dimensions has been ground away on each blank. In grlndmg Kryptok lenses, the conditions are different, however,

.calling for a depression which is not only of certain curvature, but which is located in a predetermined position on a blank of prescribed form, and which must have a definite diameter determined by the depth to which the grinding is carried. These conditions make it necessary to provide for the various factors in some other way than merely cementing the blanks more or less carelessly in any form of concave holder in the usual manner employed for ordinary lens work. To illustrate by a practical example, it may be assumed that depressions having aradius of curvature of one and thirteen sixteenths inches and a diameter across of three-quarters of an inch, are to be formed in lens blanks ofthe ordinary sort out from plate glass to a square out-line measuring about one and three-quarters inches on each side, the depressions being centered symmetrically For this purpose each arm has seats This priublanks might, of course, be independeiitly embedded in cement by independent measuring and obtain the foregoing results,but the time and care which would be necessary would be almost prohibitive for commercial purposes. I make use of the following principles to expedite the location of the blanks, making the operation as simple or even simpler than is the case in ordinary lens gr1nd- 111g processes.

A sphere coincident with the surface of the tool B may be circumscribed by an equilateral pyramid in which case the planes of each of the faces will be tangent to the sphere. The points of tangency will furthermore be located at equal and fixed distances from the apex of the pyramid. These distances are equal, but Vary with theradius of the tool or sphere and the vertical angle of the pyramid. In order to grind lens blanks with depressions in the manner described, they may be faced in the planes of such a pyramid to determine their position in a work holder. There are other geometrical relations by which the lenses might be located and centered, for example, by seating them inside a spherical surface of different curvature from the curvature of the tool, but I have found that the pyramid relation gives a very useful and practical solution fortperfectly mounting the lens blanks, as it enables every factor to be taken into account in a very easy way. The lens blanks being square and of plate glassof substantially uniform thickness, permits their being assembled on rigid seats which fix the planes planes of'such a pyramid, and inthis relation they may be easily located bylateral stops or shoulders on center lines of the pyramid faces and at exactly located distances'from the pyramid apex. Not-only, therefore, are the lens blanks easily located in all respects, but the grinding action is insured to proceed in a way which is easily mathematically predetermined for a particular holder and tool.

In the example above noted a pyramid would first be theoretically determined upon of such an angle as would permit an assembling of the square blanks with their side edges at a distance of about one and onequarter inches from the pyramid apex, which is substantially uniform distance for all cases, being as compact a disposition of theblanks as possible, limited by the proximity of their adjacent corners. This compact disposition is desirable as it makes the pressure of the grinding operation more nearly normal to the surface to be ground for each blank. These conditions being determined upon, an easy mathematical computation fixes the vertical angle of the pyramid at exactly fore adopted which will fix the planes of the 92. A lens holder is thereblanks-to be ground in the faces of the fore- I going pyramid at a distance of one and onequarter inches from its apex, the planes being determined by rigid metallic seats of the holder which are adapted to be easily fitted to suit the particular vertical angle of the pyramid.

Referring now again to the practical construction, Figs. 1 and 2 show the adaptation of the lens holder to two different grinding heads B and B, respectively. Grinding head B has a radius of curvature of one and thirteensixteenths inches and grinding head B has a radius of curvature of one and eleven-sixteenths inches. The ledges 5 being located at a substantially constant point in accordance with the foregoing principles for all cases, it follows that the planes t in Figs. 1 and2 (which are parallel with the front faces of the blanks owing to the latter being. of plate should make angles of tank simple bevel angle-gage so that the plane de- Q termined by this ledge and the support 7 is exactly -16 in Fig. 1 and 14 in Fig. 2. The

machinii'ig being accomplished in this simple of their faces to be ground, accurately 1n the 1 way, it is merely necessary to mark the holder to accord to the particular grlnding head for which it was designed, and thereafter any comparatively unskilled operator can easily and expeditiously assemble the lens blanks against the seats 5, 7 and 9 and pour the usual cement into the recess 6 and insert the apparatus in a grinding machine without further attention, whereupon the lens blanks will be pro erly ground with depressions exact in matters of form, curvature, diameter and location, these factors all being determined by the action of the machine on account of the foregoing theoretical principles with respect to the pyramid which is virtually formed in, -.con-

mined radius.

In Figs. 4 and 5 and varied in a dlfferent way. In Fig. 4

- the holder has pivoted arms 10, the position of which is fixed by adjustment screws 12 and which have flat faces '11 to receive the lens blanks. In Fig. 5 pivoted arms 13 are provided with stems 1 engaged by a central plug 15', the position of which is varied by a threaded stem 16 and lock nut 17. 18 deunction with the spherical tool of deterthe planes are determined In Fig. 6 the lens the flat faces of the holder by clamps 2O having bent-over ends 21 to: engage the lens blanks and tightened thereon by set screws 22.

. Having described my invention, I claim 1. A lens grinding implement comprising a work holder having a plurality of seats therein for lens blanks in combination with a spherical grinding head ofrsuch curvature that it will be tangent to eccentric points on all of the lens blanks.

2. A lens grinding implement comprising a holder having seats for a plurality of'lens blanks, of a spherical curvature tangent to the surfaces "of the lens blanks at point's'ofiset from the centers of said blanks by -a predetermined distance.

3.v A lens 7 a' holder having seats for; a plurality of lens blanks, in combination with a grinding head' of a spherical curvature tangent to the surfaces of the lens blanks at, points offset from the centers of said blanks by a predetermined distance toward a common'point or vertex.

' i. A lens blank holder forgrinding processes, comprisin a frame having arms projecting symmetrically at equal angles from a common central axis and vertex and having interior'faces on which the lens blanks are accurately seated in ithe planes of said angl 5. esses, comprising-a fraine havmg arms projecting symmetrically at equal angles from blanks m held against in combination with a grindinghead inding. implement comprising es v.

A lens blank holder for grinding proe a common central axis and vertex, said arms having. interior faces on which the lens blanks are accurately seated in the planes of said anglesand having lugs or shoulders to 1 r locate said blankson said faces.

6. A lens blank holder for grinding processes, comprising a frame having arms pro-v jecting symmetrically at equal angles from a common central axis, said arms having interior faces with a recess Y or cavity and "adapted to seat lens blanks accurately in the planes of said angles.

7-. A lens blank holder for grinding processes, comprising-a frame having arms pro- Jectmg symmetrlcallyat equal angles from a common central ax s, said arms having 111-.

terior faces to seat the blanks accurately in the planes of said angles, and having lugs to position said blanks accurately at equal distances from said axis.

8. A lens blank holder for grinding processes,1comprising a frame having arms projecting symmetrically at equal angles from a common central axis, each arm having a ledge and a rounded extremity adapted to position the blanks accurately in the planes of said angles; said arms having a recess between said ledges and said extremities whereby the ledges may be cut away and, effect a change in the angles of the lens blanks.

In witness whereof, I subscribe my signa ture, in the presence of two witnesses.

: FE DINAND/BU HH P,

wanes s's WM. Scroomsnmen, WALDO CHAPIN.

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