US1143895A - Mold for lens-mounting blocks. - Google Patents

Description

W. W. ESSICK.

NoLD FOR LENS MOUNTING BLOCKS.

APPLICATION FILED IAN. I9. 1914. I

Patented June 22, 1915.

NNNNNNNN MYX/fam W 55mm,

'WILLIAM W. JESSICK, 0F REING, PENNSYLVANIA.

MOLD FOR LENS-MOUNTING BLOCKS.

Application led January 19, 1914i.

T0 all whom it may concern Be it known that ll, WILLIAM W. lEssIon, a citizen of the United States, residing at Beading, in the county of Berks and State of Pennsylvania, have invented' certain new and useful `improvements in Molds for Lens-Mounting Blocks, of which the following is a specification.

My invention relates particularly to lens grinding, and my object broadly is to provide for producing with great economy of laborand a minimum of special skill and judgment, lenses which will conform with extreme accuracy and uniformity to determined requirements.

lln the method of grinding commonly employed, a series of the roughly shaped blanks are mounted upon the surface of a holder or block, and are subjected to abrasive action by a corresponding grinder; the-holding surface of the block being commonly of a pitch composition to Which the lenses adhere as placed by the operator. ln

order to insure some degree of accuracy in thus mounting the blanks, facets have been formed on the holding surface to facilitate the proper placing of them; these facets being formed by correspondingly shaped molds for the surfacing pitch composition. rllhe accuracy of themounting then depends primarily upon the correctness and uniformity of the facet-forming recesses in the mold, and also upon the accurate placing of the lenses upon the facets. lit Will be readily understood that a very slight variation in the facet-forming recesses, such for instance as is apt to occur through Wear of a cutting tool; or a very slight misplacing of the lens or blank relative to the focal axis; will result in a more or less seriously defective lens.

. My invention provides for avoiding these defects by insuring the accuracy of the lensmounting 4facets upon the holder and the accurate placing of the blanks.

Figure l illustrates a lens holder or block in cross-section, with the pitch surfacing thereon; the facets to the right of the latter being represented as adapted for mounting the flat blanks for the first grinding, and those to the left for remounting to grind the other surface. Fig. 2 indicates a grinder employed therewith. Fig. 3 is a plan view of my improved lens-block mold, a portion only of the facet-forming segmenta being shown in position. '.Fi. t is a Specification of Letters Patent.

Patented J une 22, JlQJl. serial No. 312,925.

cross-section thereof on the line 4 4. Figs. 5 and 6 show one of the facet-forming segments; Fig. 7 is a plan view of the mold therefor with the coping portion removed; Fig. 8 is a cross-sectional view of the complete segment mold; and Fig. 9 shows separately the facet-forming portion thereof, modified in shape as required for producing a vsecond-grind lens holder for convex spherical grinding. Figs. 10, 11, and 12 indicate modified forms adapted for cylindrical grinding.

'lhe holder or block 2 shown in Fig. l, is of convex vform adapted for convexly grinding lenses; a similar concaved form being employed for concave grinding as is Well understood. The pitch-surfacing 3 of the holder 2 is shaped on the completed correspondingly concaved mold Figs. 3 and 4f, the novel construction of which is specifically described.

his improved mold as shown in Figs. 3 and 4, comprises a rigid shell or backing l0, the spherically concaved surface 1l of which is accurately finished to a curvature of greater radius than that of the holder 2 3, as determined by the thickness of the facetforming segmental lining with which it is provided. This lining is' made up of segments l5, l5, 15b, preferably arranged in circular series forming successive zones as indicated; the segments in each zone being exactly alike, but varying in outline from those which form the other zones. rlhese zones are bounded by circles of increasing diameter, a I) c UZ as shown, to which the parallel ends 15, 15d of each segment conform, While its sides 15e, l5e converge to- Wardthe center 16 of the mold, as indicated in Figs. 3 and 5. Fach of these segments is provided with a facet-forming recess l? as shown; and practically absolute accuracy of arrangement of these relative to the focal center, which is an essential requirement, is secured by the use of segment forming molds such as is illustrated in Figs. 7, 8, and 9: the showing being specifically adapted for producing a series of the segments 15a illustrated in Figs. 5 and 6.

rlhis facet-forming segment mold comprises a base portion 20, a 4coping portion 21, and an interposed segment-Wall portion 22; Which portions are formed as illustrated, with parallel spherically curved opposing surfaces, 2].a of Which conforms accurately Withthe surface ll of the mold'shell illustrated in l 10 so as to properly seat upon the latter. The base portion 20, as shown, is formed with a counterbored central opening extending throughthe boss to which is adjustably fitted a separate facet-forming mold portion 26, having a head 27 fitted to said counterbore, and an oval facet 28- on said head.

As shown in Fig. 8 this projecting oval facet 28 has aflat `face; While in Fig. 9 it is shown with a spherically concaved face; one or the other of these being used according as the lens holder to be produced is intended for mounting unground blanks, or

such as have been already ground on one face to suchspherical curvature. In either case the shape and size of the facet is made to correspond with the lens intended to be yseated thereon; and its face is accurately centered and squared to the radial line of the spherical curvature of the opposing surl faces of the mold portions 20, 21, and accurately spaced from said surfaces.V It will be readily understood that practically absolute accuracy-may be readily secured by such construction, so when a series of like segments are .produced in the mold and assembled in the mold shell 10 as indicated 1n Fig. 3, each facet will bey accurately located relative to the focal axis of grinding. ln arranging the mold preliminary to forming these segments, the facet-forming portion 26 may be-accurately adjusted in its opening so as to properly set the axial line 30 of the facet, as indicatedin Fig. 7, the operation otherwise being obvious from the drawing. It will be readily understoodalso that when two or more series of segments are employed, arranged in different zones as indicated in Figs. 3 and'4, the wall portion 22 of the segment mold Will be correspondingly varied for each series of segments Without varying the determined .uniform relation of the facets to the focal axes when the segments are properly assembled in the lens-holder molding shell 10 as indicated; and that the pitch-surfacing 3 of the lens-holder 2, as formed theifein, will provide similarly ac-- curate lens-attaching facets. Y

The lens blanks which are attached to a holder having flat facets as shown'to the right of Fig. 1, may vary from the normal indicated at m, so as to require excessive' or unequal grinding,-as for instance the prismatic form of blank indicated vat y. This` like thickness with one face convexly ground to the required curvature ,-as indicated at ato the left of Fig. 1, where the lenses are shown mounted upon the'corresponding concaved facets so as to properly expose the otherl faceto the' second grinding process which results in the finished lens indicated at fw. Heretofore the rough-edged blanks have been mounted upon the lens-holders, and both faces ground before bevcling the edges; but I am enabled to double-bevel the edges first, making this beveling true to one face of the lens regardless of the other as indicated at y, thus providing blanks of uniform shape and size so far as the flat mounting face y1 and the beveled edge is concerned, which greatly facilitates the accurate setting of the blanks upon the correspondingly formed facets; any excess grinding required upon the exposed face, as on lens y, merely equalizing the edge beveling, and the final face grinding producing a finished product which is not liable to be scratched or otherwise damaged as when the belveling of the edges is effected by a subsequent operation.

To further facilitate the proper placing of the lenses upon the facets, I preferably provide setting means consisting as indicated in Fig. 5 of an oval guide'ridge 35 parallel with the rim of the facet. This 'to accurately and quickly place the latter.

The ridge 35 is readily formed on the segment by means of a corresponding groove 35a provided in the segment mold (Fig. 7).

As indicated in Figs. 10, l1, and 12 my segmental lining may also be advantageously j applied to forming other than spherical lens holders, though the need thereof in the latter case is considered to be practically greater. As shown in these figures the base portiony 10 of the mold is cylindrically curved, and segments of corresponding form, as made in a corres ondingly modified segment mold such as s own in Fig. 8, are fixed either to the cylindrically convexed or concaved surfaces as required; or such surface may obviously be made plane, with correspondingly formed lining .segments if fiat lenses are to be produced,

or adapted for prismatic lenses if desired. After my improved segmental mold has been thus built up in any required form, solid duplicates thereof may be cast therefrom ofsuitable material and be similarly used in molding like lens holders.

What I claim is 1. A lens-block mold comprising va spherially-surfaced base portion, and a sectional facing for said spherical surface made up J of separately formed facet-forming spherical segments the marginal portions of each of'whch abut adjacent segments.

2. A lens-block mold comprising a spherically-surfaced base portion, and a sectional facing for said spherical surface made up of separately formed facet-forming spherical segments arranged in a spherical zone, thc side Walls of each segment abutting adjacent segments.

i ci) zof 3. A lens-block mold comprising a spherically-surfaced base portion, and a sectional facing for said spherical surface made up of separately formed facet-forming spherical segments arranged in zone series, the segments of each series being different in contour from those of each other sries substantially as set forth.

facet forming sphericalsegment mold comprising base and coping portions. providing parallel spherically-curved surfaces and one of whichis provided with a facet-forming portion squared to a radial line of said surfaces, and segment walls between said surfaces inclosing said facetvforming portion.

, 5. A lfacet forming Yspherical segment mold comprising base and coping portions providing parallel spherically-curved suraces, a facet-forming fitting to one of said portions squared to a radial line of said sur; faces, and segment walls between said surfaces inclosing said facet-forming portion.

facet forming spherical segment moldcomprising base and coping portions providing parallel spherically-curved surfaces, an adjustable facet-forming ttin'g to one ofsaid portions squared to a radial line of said surfaces, and segment walls between said@ surfaces inclosing said facet-forming portion. l,

7. A facet forming providing parallel spherically-curved surfaces, and one of which is provided with a facet-forming portion squared to a radial line of said surfaces, and a segment-wall portlon fitted between1 ysaid spherically curved surfaces.

spherical fsegment `mold cmprislng base and coping portions 8. A facet forming sphericalsegment mold comprising base and coping portions providing parallel spherically-curved surfaces, one of which is provided with a facetforming portion squared to a radial line of said surfaces, and a segment-wall portion fitted between said spherically curved surfaces; said segment-wall portion having opposite parallel walls and converging intersecting walls substantially as set forth.

9. A` lens-block mold having lens facets which are ridged to form lens-setting grooves.

10. A facet-forming segment mold comprising base and copingfportions providing opposing` surfaces, and segment-walls between said surfaces; one of said portions being provided with a lens facet which is formed with a lens-setting groove.

11. A facet-forming segment mold comprising base and coping portions providing opposing surfaces, and segment-walls between said surfaces; one of said portions being provided witha lens facet.

12. A lens-block mold comprising a spherically-surfaced base portion, and a. sectional facing for said spherical surface made up of separately formed facet-forming spherical segments arranged in zone series, the segments of each series being different in contour from those of each other series, and the marginal portions of each segment abutting adjacent segments.

In testimony whereof I affix my signature in presence of two witnesses.

WILLIAM W. ESSICK.

Witnesses:

D. M. STEWART, ADAM L. OTTERBEIN.

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