US2140410A - Lens and method of manufacturing the same - Google Patents

Description

Dec. 13, 1938. E' H, ||TMU55` LENS AND METHOD 0F MAN'UFACTURING THE SAME Filed Nov.' e, 193e f. I l /f//ff/ A.

,pdlllllllllll/flglm Patented Dec. 13, 1938 Ther present invention relates lto lenses ,and methods of manufacturing the same. .f s

. A primary object of the invention is to Qro; vide a compound lens blankwhichwill permit the measurement of the thickness of thelens section being ground Without removing the blank from the grinding holder. 1 1,

Another object of the invention is to provide a compound lens blank which will permit the measurement of each of the lens sections thereof during the grinding of said sections, without re-l moving the blank from the grinding holder. -Y A further object of the invention is to provide a method of manufacturing a lens blank having ihe above advantages, and a method of finishing such a blank into a lens. v Various other objects of the methods and article disclosed herein will be apparent as the specification progresses. f In the drawing, which discloses a form of the article of the present invention, and illustrative methods whereby the blank may be formed and finished, which drawing is in no sense restrictive Figure 1 is a top plan view of a lens blank of the present invention, showing one of the lens sections broken away to illustrate the construction of the blank. Figure 2 is a vertical sectional view through a lens grinding device, showing the compound lens in position for concave grinding.

Figure 3 is a vertical sectional view-0f :another grinding device, With the compound lens positioned for convex grinding. .l Figure 4 is a vertical sectional view takenidiametrically through the lens blank,"after the same has been ground. I .Figure 5 is a similar vertical sectional -view through the nished lens. g Y The ophthalmic lens disclosed in the drawing is one of the compound type, comprising what I will term for convenience a rst lens lsection i0 and a second lens section l2, secured '1together by any appropriate adhesive materiall I4. This adhesive-material isvoi`the type ving a sufcient toughness and adequate gripping qualities when applied to glass surfaces for .immovably securing lensfs'ections together, .andwhich Will aid in reinforcing the sections against shattering or breaking. 4.The adhesive material will be of such transparency that it will not impede the passage of rays of light through the lens'. While -I have shown in the drawing a compound lens of the type in which the lens sections i0 `and 'l2 are alike in size, it will be obvious from the :J:5 Quoting descirtonfhat-ihe.inventive .may .be

LENS AND- ivre'rnon oF MANUFACTURING SAlVlE "f 3:5; i ,i Edward H. VTitmus, Petersburg, Va., assigner to Titmus Optical Company, V"Petersburg, Va., a corporation of Virginia 'ff' j Application Novem'ifs, 193s, se

s Cahiisf`- w1 Sis-154)? practicedfdin the mvanuhfac'tureoft other types of z compound .lenses, such 4as, bifocal lenses or other types,.in which one lens section is not entirely coextensive Vwith lthe otherl lens section.

; The lens sections I0 and .l2 are shown having engaging surfaces of `complementary curvature, .and itwill be understood that the term complementary curvature may mean that the engaging faces of said lens sections are at planes in a special,case. A

, In the manufacture of lenses, it is common to takealens blank of approximate form, and secure the same to a holder, which holder is rotated relatively to a grinding tool while a face of the lens is being ground. During the grinding operation, the edges of the blank may extend outwardly beyond the periphery of the grinding tool, so that the thickness of the lens may be measured. It has also been the custom to proyide s lots in the edge of the lensholder to receive calipers Afor measuring the thickness of the lens during the grinding operation. In grinding lens blanksl having only a single section, holes have been drilled into the blank `to a depth indicating the amount of glass to be removed, and when grinding has been performed to this depth, the disappearanceof the hole indicatesthat the lens is groundto proper thickness.

vN one of thes e methods 4are practical in the manufacture l of compound lenses of the type disclosed in the present application, in which it is desirable to control the thickness and contour of a section of aicompound lens being ground, or each of the sections 'of 4.a compound lens when both are being ground, without removing the blankfromits holder during the grinding operation-ifi ..1

Fig 1,.the .first lens section HJ is shown .provided with apair; of diametrically opposed notches; or apertures I6 extending entirely through fthe vthickness thereof, Awhile the second lenssection-lZ-is likewise provided diametrically opposed aperturesi8 also i extending entirely through the thickness of said section.

,55, The lens sections .are assembled and adhesively secured to one .another withvthe apertures staggered -9Qf from the yapertures I8, so that a portion of ,each lens blank will Voverlie the aperture in..the.edge .of the opposed lens blank. It .will be noted that the edgeof each lens section adjacent wheregit overlies the opening in the engaging lens .se'ction -does not extend beyond the edgeof-saidengaging lens section, so that .the measurement .of the particular lens section is takenin the openingin itscngaging lens section, the adjacent portions of the edge of the overlying lens section not being free to be engaged by calipers or the like. I term this condition of the edge of the lens section adjacent its overlying portion as underlying the edge of the engaging section which has the opening therein, in the sense that the edge of the adjacent portion is covered so that lthe measurement must be made in the opening'. It will be apparent from Figure l, that the thickness of each lens blank K, may be measured at diametrically opposed'" points, by applying calipersKorother .measuring .if devices at the openings in the opposed lens sec-il tions.

While 1 have disclosed theaprtures mariej la' in the edge of the respective lens sections, it will f.,-

be evident that the present invention is not 'I'he holder 30 and grinding tool 34 may be mounted on spindles for rotation, and are capable of adjustment with respect to one another to control the grinding operation in a manner well known in the art.

During the convex grinding of the rst lens section I0, measurements of the thickness and contour of said section may be made without removing the blank from the holder by applying .calipers to the blank in the apertures I8 in the Asecond lens section- I2. As discussed before, the measurements taken; at apertures I8 may be compared in order to determine the adjustment of the holder and grinding tool necessary to corectthe grinding operation.

.`-"A.fter the proper curvature has been imposed upon the convex face of the lens section I0, the

limited to such a disposition.` For instance, said -flblank will be in the condition shown in Figure apertures might be in the form of holes spacedj., inwardly from the edge of the blank, preferably close enough to the edge Jso-tha.t"\vhen the blank is cut to final size,-as hereinafter described, lthe portion thereof includingltheapertures will be removed. It will also be evident that the -apertures I6 and I8 need not necessarily be spaced a quadrants distance from each other, although this arrangement is preferable to more accurately control the grinding operation discussed below. Furthermore, as many apertures as necessary may be provided in the lens sections, and said apertures may be as closely spaced as desired, depending on the degree of accuracy necessary in the grinding operation.

The lens blanks described above are to be manufactured in quantities `for sale to artisans in the industry who grind the blanks to nal form on order. The blanks may be of any size and shape, and the artisans will obviously grind the blanks to various forms.-

When the blank is to be ground, it is secured to a conventional lens grindingholder 20 shown in Figure 2, said blank usually being cemented to said holder by a quantity of material 22.` The lens holder may be maintained in xed position, or may be rotated with a supporting spindle 24. In Figure 2, the blank vis shown disposed upon the holder in position for concave grinding, in which position the first lens section is cemented to the holder'so that the second lens section I2 is faced outwardly toward the grinding tool.

The grinding tool`2$l may be of any=conven tional form, said tool-usuallyY being rotatably cil mounted with a supportingspindle 28 driven in any appropriate manner.A

During the grinding operation calipers or other measuring devices -rnay be applied at anyA time within the apertures I6 of the rst lens section III to measure the thickness or contour ofthe second lens section` I 2. Ifthe lens is not being aclcurately ground, as indicated'by the measurement at one of the apertures I6, lor as indicated by a comparison 4of the measurements taken Vlat each of the opposedfoifspaced apertures- I6, the relative positions of 'the lens holder and grinding tool may be adjusted "to correct the grinding in a manner well known in the art. A

After the inner face of the lens has been ground as discussed above,-the blank'is -removed from the holder 20 and is mounted `upon the grinding holder 30 for convex grinding, being secured thereto in any appropriate manner as by cement 32. When the blank Iis thus mounted for convex grinding, thesecond lens section I2is secured to the holder f3D, thus presenting ,the iirst lens section to the grinding tool 34.--

4,.whe n a lens of the type used for illustration is beingmanufactured.

fI'o form the finished lens; the peripheral portion of the lens blank including the openings I6 and. I 8 is cut away, resulting in a'lens of the type shown in VFigure l5, which is in condition to be mounted. l Y i Itfwill be understood that the present methods and article are not limited to use in the manufacture Aof ophthalmic lenses, but may be of equal utility in making other types of lenses.

Various modications of the article `and methods Adisclosed herein may be made without departing from the scope of the invention.

. I claim: l

. 1. A lens blank comprising a plurality of engaging lens sections having openings adjacent the edges thereof, each opening extending completely through its respective'section, said sections being superposed one upon another and immovably secured together, said openings being of` substantial size to receive a measuring device and being oiTset from one another so that a portion of each lens section overlies an opening in its lengaging lens section, the edge of each lens section adjacent its overlying portion underlying the edge of its engaging lens section, whereby the thicknessof each lens section may be measured at an opening in its engaging lens section.

2. A lens blank comprising a pair of engaging lens sections having substantially diametrically 'opposed openings adjacent their edges, each opening extending completely through its respective section, said sections being superposed one upon another and immovably secured together, said lopenings lbeing of substantial size to receive a measuring device, the engaging faces of said sections being of complementary curvature, a portionof one lens section'overlying an opening in its engaging lens section, said lens sections being coextensive adjacent said openings, wherebythe :thickness of each lens section may be 'measured at anopening in its engaging lens section. -I" I 3. A lens blank -comprising a pair of engaging lens sections lhaving openings adjacent the edges thereof, "each opening` extending `completely through its respective section, said-sections being superposed lone upon another, and immovably secured together with a thin intermediate transparent 4webofadhesive material therebetween, said openings being of substantial size to receive 'a measuring device, the engaging faces of said sections being of complementary curvature, and said sections being superposed in such fashion Athat'an'opening in one lens section is substan- `tially'a quadrants distance 'from' an opening in aus.. N

its engaging lens section, a portion of one lens section overlying an opening in its engaging lens section, said lens sections being coextensive adjacent said openings, whereby the thickness of each lens section may be measured at an opening in its engaging lens section.

4. The method of making lenses which comprises forming a plurality of lens sections with openings of substantial size adjacent the edges thereof to receive a measuring device and extending completely through each of said sections, superposing said sections to form a lens blank and immovably securing said sections together with a portion of each lens section overlying an opening in its engaging lens section, and with the edge of each lens section adjacent its overlying portion underlying the edge of its engaging lens section, and grinding the outer faces of each of said sections and controlling the grinding operation in accordance with measurements of the Y tliickness` of said sections taken at said openings.

5. The method of making lenses which comprises forrning a plurality of lens sections with openings of substantial size adjacent the edges thereof to receive a measuring device and extending completely through each of said sections, superposing said sections to form a lens blank and immovably securing said sections together with a portion of each lens section overlying an opening in its engaging lens section, and with the edge of each lens section adjacent its overlying portion underlying the edge of its engaging lens section, grinding the outer faces of each of said sections and controlling the grinding operation in accordance with measurements of the thickness of said sections taken at said openings, and finishing the blank into a lens by removing a peripheral portion therefrom which includes said openings.

EDWARD H. I'ITMUS.

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