CÍG .E F/'GJE 33% Patented Sept
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Sept. 27, 1932. E. D. TILLYER 1,88€),029 OPHTHALMIC LENS Filed Nov. 4, 1929 /CÍG .E f/'GJE 33% Patented Sept. 27, 1932 1,880,0Z9 UNITED STATES PATENT eres EDGAR 1). TILLYEB, or SO'UTHBRIÍDGE, MASSACHUSETTS, ASSIGNOR,TÓ AMERICAN OPTICAL COMPANY, or SOUTHBRIDGE, MASSACHUSETTS, A VOLUNTARY_ASSOGIA TION OF MASSACHUSETTS OPHTHALMIG LENS' 'Application ?led. November 4, 1929. Serial 1\To. 404,664. This invention relatos to ophthalmic lenses lens embodying a modi?ed form of the in and has particular reference to an improved vention. ” multifocal lens and blank and to a process Fig. VII is a front view of an ophthalmic V of making the same. lens emboclying a further modi?cation of the The principal object of this invention is to invention. b _ provide a simple and economical? form of _ It has long been apparent that multifocal multifocal lens which can be made without lenses having a full Circular reading field fear of 'warping during the process of have various' drawbacks and that the most manufacture. _ _ satisfactory form 'of multifocal lens has a 10 'Another object of theinvention is to pro substantially 'straight 'line forming the top 60 vide improved means and process of forming of the reacling' ?eld at the juncture with the a fused bifocal or. multifocal lens wherein a distance portion. In manufacturing this composite piece of glass formed of two pieces type of lens varions methods have been tried, of glass having optical surfaces fnsed face to the most satisfactory for some purposes being 15 face may be fused edge to edge with another to embed a full circular reading ?eld in a dis 65 piece of glass without causing the said edge tance portion and then out through both the and fused optical snrfaces to warp and be reading ?eld .and distance portion, thus come distorted and impractical for use. forming two substantially semi-circular por Another object of this invention is to pro tions, and then to uni te one of these portions 20 vide a process for making such a' multifocal with another semi-circular portion having no lens wherein the reading portion is not re reading ?eld. (This practicewas outlined in striåted as to position within the distance Reissue Patent No. 16.830, but it has been ?el . » A ' found that the process disclosed therein is not Another object of this invention is to pro« entirely satisfactory' from a mannfacturing 25 vide means whereby the lens may be made standpoint. One of the defects of this type 75 monocentric if desired. ' of lens' is that the composite portion of the r Other objects and aclvantages of the inven major blank which has the reading segment tion will become apparent from the follow fused in a countersink formed therein and ing description taken in Connection with the the separate portion of the major blank 80 accompanying drawing and it will be ap_ which is fusedv edge to edge with said com 36 parent that many changes may be made in posite piece of glass have the same fusion the details of construction, arrangements of point and when subjected to heat, both por parts and steps of the process without de tions melt and join together. This causes parting from the Spirit of the invention as the fusion edge at the top of the segment and 35 expressed 'in the accompanying claims. I, the portion of the countersink curve which 85 therefore, do not wish to be limited to the underlies the segment adjacent the fusion exact details shown and described as the pre edge to distort and become blurred and im_ ferred forms only have been shown by way practical for usef ' ' of illustration._ v ' It is theprime object of this invention to 40 Referring to the drawing: depart from the processdisclosed in the fore 90 Fig. I is a front view of an ophthalmic lens going patent and provide an improved means embodying the invention. ' of forming a. multifocal lens of the desired Fig. II is a section on line II,_II of Fig. I. type, wherein the top ofthe reading ?eld and Fig. III is a front view of the lens at a portion adjacent said top will not distort and Certain stage in the process. _ r become blurred and impractical for use. Fig. IV is a section on line IV_-IV of Referring to the drawing wherein similar Fig'. III. characters of reference denote correspond Fig. V is a front view of the lens at another ing parts throughout the several views, the stage of the process. - ' ISO numeral 1 denotes the major portion of my Fig. VI is a front view of an ophthalmic improved lens, into which I grind a counterâ 100 2 1,88o,029 sink 2, which for purposes of this descrip crown basehaving a high fusion point, and tion may be in the geometrical center of the fuse to this my upper portion of soft crown major portion 1. ' having a low fusion point. It will be obvious In order to avoid the troubles of the prior that in this way I can support the segment in art, I preferably form my major portion 1 the hard crown base until the soft crown por 70 of the kind of glass known in the industry tion, which has a. lower fusion point7 melts as hard crown, which is distinguished _from to 'the shape of the hard crown edge and soft crown by its higher fusion point. Hav fuses thereto without causing said hard crown ing formed my countersink 2, I next embed, edge and segment portion to melt and distort. 10 preferably by fusing, a button '3 therein. This Vavoids the drawbacks associated with 75 The button 3 may be of the; usual ?int glass fusing the blank in two operations and' great having a different index of refraction to ly facilitates the process of 'manufacturing the hard crown glass used for the major -this improved type of :multifocal lens. It portion 1. will also be obvious that in the process previ 16 The foregoing steps of?the" process are' ously described I have formed a monocentric 80 shown in F igs. III, and IV of the drawing. lens inasmuch as the line of joinder 6 passes After the button 3 has been inserted in the through the optical aXis of the segment 3. major blank 1, I separate the said major This is an advantageous type of lens .to form blank 1 along the line ¿Ja-_4: which preferably as 'there is no ump in the line of vision when 20. passes through the geometrical center of the passing' from-one ?eld into the other but I 86 blank 1, although as will be presently shown do not necessarily have ,to con?ne my process this is not necessary; I next fuse aportion to this type of lens. 5 to the separated part of the-blank 1 and In Fig. VI, I have illustrated a modi?ca again depart from the prior art by using a tion of the foregoing process. This type of 25 different kind of crown glass to that used for lens is made with a* straight line 6 at the top the portion 1 of the original blank. The of thesegmentportion and another straight portion 5 is made of similar shape to the part line 9 at the lower portion of the segment. I of the separated blank l used for the lower preferably form' this lens by embedding my portion, but is made of a soft crown glass segment 3 below the geometrical ,center of 30 having a lower fusion point than the hard the major lens blank l. > I' next separate the ,95 crown glass previously described; Both of blank along the dotted lines 10 lying on either the crown glasses used may' have the same side of the optical center of the segment and index of refraction, from which it follows thus have a strip of hard crown glass having that the line 4-4 will disappear fromthe a segm-ental portion 3 in its center. To the a fused'blank except at theportion designated upper and lower portions of this strip I next with numeral 6 in Fig. I where the reading fuse, two pieces of soft crown glass to give a segment joins the major ?eld. The portion circular lens shape, and it will be obvious surrounding the segmental ?eld 3 will pre that as in the previously described process the sent an unbroken surface pleasing to the eye. dotted lines 10 will' disappear leaving the I can now place any desired base curve 7 straight lines 6 a-nd 9 at the poínts of j oinder on the concave surface and a desired prescrip of the segment to the maj or ?eld. tive curve 8 on the other side, thus complet In a further modi?cation shown in Fig. ing my improvedmultifocal lens, as shown VII, I also embed my segment portion 3 in Fig. II. r lower in the major ?eld l than in the process 45 The foregoing process may be carried illustrated in Fig. III. I next separate the 110 through without hindrance from the draw blank into two portions along the dotted line backs associated with the prior art. Previ 11, which is preferably substantially midway ously it has been attempted to fuse together between 'the _optical center of the segment the upper and lower portions of this type portion 3 and its upper edge. I can now fuse of lens when using a single kind of crown a soft crown portion 5 to the upper straight 11.5 glass for both portions.