EP0436315A2 - Tampons de rodage en matière plastique moulés par injection - Google Patents

Tampons de rodage en matière plastique moulés par injection Download PDF

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Publication number
EP0436315A2
EP0436315A2 EP90313344A EP90313344A EP0436315A2 EP 0436315 A2 EP0436315 A2 EP 0436315A2 EP 90313344 A EP90313344 A EP 90313344A EP 90313344 A EP90313344 A EP 90313344A EP 0436315 A2 EP0436315 A2 EP 0436315A2
Authority
EP
European Patent Office
Prior art keywords
lap
lap according
ribs
polymer
rim
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP90313344A
Other languages
German (de)
English (en)
Other versions
EP0436315A3 (en
Inventor
Don H. Rotenberg
Milton F. Whitmarsh
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Gerber Coburn Optical Inc
Original Assignee
Coburn Optical Industries Inc
Pilkington Visioncare Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Coburn Optical Industries Inc, Pilkington Visioncare Inc filed Critical Coburn Optical Industries Inc
Publication of EP0436315A2 publication Critical patent/EP0436315A2/fr
Publication of EP0436315A3 publication Critical patent/EP0436315A3/en
Withdrawn legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B13/00—Machines or devices designed for grinding or polishing optical surfaces on lenses or surfaces of similar shape on other work; Accessories therefor
    • B24B13/01—Specific tools, e.g. bowl-like; Production, dressing or fastening of these tools

Definitions

  • the present invention relates to a lapping article used for the grinding, fining, and polishing of glass and plastic ophthalmic lenses and, in particular, to laps made of plastic.
  • the lapping of glass ophthalmic lenses was originally performed by cast iron laps which were rotated and/or oscillated against a glass lens blank with loose abrasives disposed therebetween to perform grinding, fining and polishing operations on the blank.
  • grinding machines were developed to perform the grinding step, but the fining and polishing operations continued to be performed by cast-iron laps.
  • laps tended to wear rapidly, necessitating that they be frequently recut and retrued.
  • the considerable weight of the cast iron laps induced a rapid wearing of the bearings and imposed limitations on both the maximum oscillatory speed which could be attained and the energy efficiency of the lap-driving mechanism.
  • the practice of using loose abrasives was phased out in favor of mounting replaceable abrasive pads on the face of the lap. Because the lap itself would then be subjected to less wear, the laps could be formed of materials exhibiting less toughness and weight than cast iron, such as aluminum and plastic for example.
  • German OS 36 40 678 and OS-37 12 148 which describe plastic laps used in conjunction with replaceable pads.
  • the laps described therein are of solid construction and the bottom faces thereof are provided with customary side notches and central rectangular aperture for proper mating with a face of a receiver to which the laps are to be mounted.
  • the techniques presently available for manufacturing plastic laps are limited, due to the need for achieving and maintaining a precision curvature of the pad-receiving front face of the lap.
  • the primary function performed by such a lap is to provide a proper shape to the abrasive pads; the pads are flexible and will assume the shape of the front face of the lap. That face must thus exhibit the true optical curvature being imparted to the lens. It is, therefore, necessary that the techniques for making the plastic laps ensure that the proper curvature of the front face will be maintained.
  • the laps cannot be made by faster and less expensive techniques, such as high-speed injection molding, because such a large piece of solid plastic would cool much too slowly in the mold and would tend, as it cools, to shrink excessively, as well as to shrink at different rates in different directions, whereby the resulting lap would be warped and the molding cycle excessively long.
  • Such a semi-finished plastic lap would also desirably be easily machinable to exact front-surface curvature on standard lap-cutting machines as has hereinbefore been done with solid plastic and aluminum laps to match the exact curvature desired on the lens surface.
  • the present invention relates to a lapping article used for the grinding, fining and polishing of glass and plastic ophthalmic lenses and, in particular, to laps made of plastic.
  • the lap comprises a one-piece injection-molded polymer body with a curved front surface adapted to receive an abrasive pad for grinding, fining, or polishing a glass or plastic ophthalmic lens. Projecting from the rear side of the lap is a skeletal rib structure comprising a plurality of interconnected ribs.
  • the polymer has fiber and/or mineral reinforcement.
  • the rear side of the lap comprises an annular outer peripheral rim extending along at least a portion of the outer circumference of the rear side, and a recessed surface disposed radially inwardly of the rim and recessed relative to the rim in a direction toward the front surface, said skeletal rib structure projecting rearwardly from said recessed surface.
  • Preferred polymers suitable for forming the lap include the various homo- and copolymers of polyesters, polyacetals, polyamides, polysulfides and polyimides.
  • a lap 10 according to the present invention comprises a one-piece injection-molded body 12 having a curved front surface 14 adapted to receive an abrasive pad for grinding, fining, or polishing a glass or plastic ophthalmic lens. Accordingly, the curvature of the front surface corresponds to the shape of the lens surface being made. While the molded front curvature of the semi-finished plastic lap is close to the desired lens surface curvature, the final exact curvature is cut on a standard lap cutting machine as is done for solid aluminium and plastic laps.
  • a rear side of the body 12 comprises an annular outer peripheral rim 15 extending along at least a portion of the outer peiphery of the body 12.
  • the rim 15 includes annular ridges 16 which have rearwardly facing annular surfaces 17.
  • Disposed radially within the confines of the rim 15 is a recessed surface 18 which is recessed relative to the rim in a direction toward the front surface 14.
  • the recessed surface 18 is preferably curved generally complementary to the front surface 14.
  • the rib structure 19 includes a pair of parallel main ribs 20 recessed radially inwardly of portions of the rim 15 to form side notches 21 (see FIG. 3). Interconnecting the main ribs 20 are a plurality of parallel, shorter secondary ribs 22. Two of the secondary ribs 22 are spaced apart to define a central rectangular aperture 23. A plurality of intermediate ribs 24 interconnect the secondary ribs 22 and are disposed parallel to the main ribs 20. A pair of end ribs 26 extend parallel to the secondary ribs 22 and interconnect respective main ribs 18 with a ridge 16. Ends of the main ribs 20 are interconnected by curved walls 28 which define tall extensions of the ridges 16.
  • the cross-sectional thickness t of the ribs and the cross-sectional thickness t' between the surfaces 14, 18 does not exceed 1.27cm (0.5 in.). Most preferably, those thicknesses are in the range of 0.25 to 0.89 cm (0.1 to 0.35 in.). As a result, the lap will cool rapidly enough to be produced by high speed injection molding.
  • the lap can be economically formed by high speed injection molding operations. That is, since the maximum cross-sectional thickness of the ribs and front portion is 1.27 cm (0.5 in.), the injection molded lap will cool at a sufficiently rapid rate to adapt to high speed injection molding. Furthermore, the rib structure imparts sufficient strength and rigidity to the front portion to ensue that the front surface will hold its shape during contact with a lens being made. Hence, the lens will be shaped with a proper curvature.
  • the polymers used in construction of the lap must, in addition to being moldable, have adequate rigidity, strength, thermal resistance, and stability to chemical attack e.g. chemical resistance to organic solvents for repeated use as a lapping tool.
  • Suitable materials include crystalline engineering plastics.
  • the crystallinity provides the requisite chemical resistance, and crystallinity, together with the particular molecular structure of the polymer, provides engineering characteristics such as strength and rigidity.
  • Chemical resistance is important because typical prescription laboratories use chemicals such as acetone or other ketones, and esters which will readily dissolve most non-crystalline polymers.
  • the specific strength and rigidity characteristics and/or other characteristics of the polymer are dictated by the particular use intended, for example, expected life of the lap, lap size and lap curvature.
  • One skilled in the art can readily select a specific polymer having the requisite characteristics based on the polymer's known physical properties, e.g. strength and modulus values.
  • polymers useful in the invention include homo- and co-polymers of polyesters and polyacetals, polyamides, polysulfides, and polyimides.
  • polyamides various nylons have good properties, but some absorb significant amounts of water and result in variation in dimensions in actual use. Other polyamides absorb less water but are more expensive. polysulfides and polyimides, while both have good properties, are significantly more expensive.
  • suitable polymers include polybutylene terethalate, polyethylene terephthalate, polyoxymethylene, the various nylons, polyphenylene sulfide, and polyimide.
  • the polymer is preferably filled. While the unfilled polymer is both strong and chemically resistant, it oftentimes cannot be processed easily by injection molding because as it cools, it shrinks excessively and differently in the flow and transverse directions. In addition, unfilled polymer can warp as it cools and thus cannot be made to hold simple tolerances. Incorporation of mineral fillers, and possibly glass or carbon fibers, or combinations thereof, allows for much less and more uniform shrinkage. Warpage will be generally eliminated, and the molded part will hold the required tolerances.
  • Typical short fiber glass useful as a filler consists of fine particles having a length of from about 0.015 cm to about 0.036 cm (about 0.006 to about 0.014 in. ), while suitable longer fiber glass has a length of from about 0.25 cm to about 0.76 cm (about 0.1 to about 0.3 in.), with about 0.51 cm (about 0.200 in.) being typical.
  • the typical mineral filler is finely divided and blended calcium carbonate or mica. Filler content can range from about 10 to about 50 weight percent of the polymer composition, while the polymer itself constitutes from about 90 to about 50 weight percent. Preferred levels of filler are from about 20 to about 45 weight percent with the remainder being the polymer.
  • the ratio of mineral to glass filler can range from 100% mineral to 25% mineral and 75% glass. Similar ratios apply to the use of carbon fiber fillers.
  • the lap had no chemical resistance as it can be attacked by acetone and other common laboratory chemicals such as Pad Cement Solvent, a solution of ketone and aromatic solvents defined as Coburn Optical Part Number 9839-70.
  • a hollow, cored lap (maximum cross-section thickness 0.838 cm (0.330 in.); height 3.51 cm (1.38 in.)
  • injection molded from unfilled polyoxymethylene designated Delrin 500 from E. I. Dupont deNemours Company resulted in a short molding cycle (less than one minute), but showed unacceptable and non-uniform shrinkage and poor dimensional reproducibility.
  • the lap was not usable because of the warpage.
  • a hollow, cored lap (maximum cross-section thickness 0.838 cm (0.330 in.); height 3.51 cm (1.38 in.)), injection molded from polybutylene terephthalate filled with 20% mineral and 20% glass designated Valox 735 from General Electric Company resulted in a short molding cycle (less than one minute).
  • the lap had minimum and uniform shrinkage and good dimensional reproducibility. The lap was usable and the optical surface could be machined over a full range of curves.
  • a hollow, cored lap (maximum cross-section thickness 0.838 cm (0.330 in.); height 3.51 cm (1.38 in.)), injection molded from polybutylene terephthalate filled with 25% mineral designated Valox 745 from General Electric Company resulted in a short molding cycle (less than one minute), minimum and uniform shrinkage and good dimensional reproducibility.
  • the lap was usable and the optical surface could be machined over a full range of curves.
  • a hollow cored lap (maximum cross-section thickness 0.838 cm (0.330 in.); height 3.51 cm (1.38 in.)), injection molded from a polyamide filled with 33% glass designated Zytel Nylon 70G-33L from E. I. DuPont deNemours Company resulted in a short molding cycle (less than one minute).
  • the lap had minimum and uniform shrinkage and good dimensional reproducibility. The lap was usable over a full range of curves.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Polishing Bodies And Polishing Tools (AREA)
  • Grinding And Polishing Of Tertiary Curved Surfaces And Surfaces With Complex Shapes (AREA)
  • Finish Polishing, Edge Sharpening, And Grinding By Specific Grinding Devices (AREA)
EP19900313344 1990-01-03 1990-12-07 Injection moldable plastic laps Withdrawn EP0436315A3 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US46037890A 1990-01-03 1990-01-03
US460378 1990-01-03

Publications (2)

Publication Number Publication Date
EP0436315A2 true EP0436315A2 (fr) 1991-07-10
EP0436315A3 EP0436315A3 (en) 1991-12-11

Family

ID=23828473

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19900313344 Withdrawn EP0436315A3 (en) 1990-01-03 1990-12-07 Injection moldable plastic laps

Country Status (6)

Country Link
EP (1) EP0436315A3 (fr)
JP (1) JPH04135153A (fr)
AU (1) AU641962B2 (fr)
BR (1) BR9006670A (fr)
CA (1) CA2033360C (fr)
ZA (1) ZA918B (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1992007688A1 (fr) * 1990-10-29 1992-05-14 Honore Mecteau Outil et procede servant a fabriquer une lentille
US5779529A (en) * 1996-11-25 1998-07-14 Bizer Industries Thermoplastic optical lap with reinforced webbing

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112207877B (zh) * 2020-09-07 2022-04-26 中国工程物理研究院激光聚变研究中心 一种环形抛光中沥青抛光盘表面螺旋槽的生成方法

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2811446A1 (de) * 1977-04-21 1978-10-26 American Optical Corp Adapter fuer ein werkzeug zur oberflaechenbehandlung von linsen
US4148160A (en) * 1977-12-05 1979-04-10 American Optical Corporation Lens surfacing tool and tool holder
US4377057A (en) * 1978-06-14 1983-03-22 Lortone, Inc. Hand cabbing apparatus
US4382803A (en) * 1980-07-31 1983-05-10 Rowland, Incorporated Tools for optical lenses
DE3712148A1 (de) * 1986-11-28 1988-06-09 Klaus Kassner Auflagerkoerper
EP0286469A1 (fr) * 1987-03-27 1988-10-12 ESSILOR INTERNATIONAL Compagnie Générale d'Optique Outil autoconformable à la surface d'une lentille ophtalmique

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2811446A1 (de) * 1977-04-21 1978-10-26 American Optical Corp Adapter fuer ein werkzeug zur oberflaechenbehandlung von linsen
US4148160A (en) * 1977-12-05 1979-04-10 American Optical Corporation Lens surfacing tool and tool holder
US4377057A (en) * 1978-06-14 1983-03-22 Lortone, Inc. Hand cabbing apparatus
US4382803A (en) * 1980-07-31 1983-05-10 Rowland, Incorporated Tools for optical lenses
DE3712148A1 (de) * 1986-11-28 1988-06-09 Klaus Kassner Auflagerkoerper
EP0286469A1 (fr) * 1987-03-27 1988-10-12 ESSILOR INTERNATIONAL Compagnie Générale d'Optique Outil autoconformable à la surface d'une lentille ophtalmique

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1992007688A1 (fr) * 1990-10-29 1992-05-14 Honore Mecteau Outil et procede servant a fabriquer une lentille
US5779529A (en) * 1996-11-25 1998-07-14 Bizer Industries Thermoplastic optical lap with reinforced webbing

Also Published As

Publication number Publication date
AU6801490A (en) 1991-07-04
EP0436315A3 (en) 1991-12-11
JPH04135153A (ja) 1992-05-08
BR9006670A (pt) 1991-10-01
AU641962B2 (en) 1993-10-07
CA2033360A1 (fr) 1991-07-04
ZA918B (en) 1992-08-26
CA2033360C (fr) 2001-10-30

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