GB2195100A - Lens surfacing pad with improved attachment to tool - Google Patents

Description

1 GB2195100A 1

method which reduces these difficulties. Further understanding of this invention will be had from the following description and accompanying drawings.

SPECIFICATION

Lens surfacing pad with improved attachment to tool BACKGROUND TO THE INVENTION

The present invention relates to grinding and polishing pads and, in particular, to grinding and polishing pads used in conjunction with lens lapping tools for grinding and polishing optical and ophthalmic lenses. More specifi cally, the present invention relates to an im provement in the means by which ophthalmic lens surfacing pads are attached to lens lapp ing tools.

Optical and ophthalmic lenses are generally made by generating a lens blank to the de sired curvature on a curve generator and then lapping the lens by means of an abrasive slurry and an oscillating lapping tool. Lapping tools are usually cast iron or aluminiurn tools having various lapping surfaces, each of a cur vature corresponding to a desired lens curva ture. Thus, an optical manufacturer requires a set of lapping tools in order to manufacture lenses of various prescriptions.

Lapping pads which conform exactly to the lapping tool curvature are generally used on the surface of each lapping tooL Lapping pads, sometimes referred to as surfacing pads, usually wear relatively quickly and are replaced after several lenses are ground. But lapping pads provide a relatively inexpensive surface which will wear instead of the rela tively expensive lapping tool.

Recently, improved lapping pads have been developed which contain lapping abrasive on the surface of the pad or impregnated into it.

One lapping procedure using such pads in voives adhesively attaching a first fining sand paper pad to a lapping tool and fine grinding a lens under running water to the proper curve.

Then, a second fining pad of smaller grit than the first pad is placed over and adhered to the first pad and the lens is subjected to a second fining step under running water. Next, both pads are removed from the lapping tool, a flocked polishing pad is adhered to the tool and the lens is polished to a clear finish under a polishing slurry.

The aforementioned lapping procedure can be used for glass and plastic lenses. However, the procedure has certain disadvantages. An operator must frequently attach and remove the pads of which are adhesively secured either to the surface of the lapping tool or to a pad on the surface of the too[ and can be difficult to peel off the tool. Furthermore, the pads can be difficult to attach to the tools without wrinkles, which adversely effect the performance of the pad. Coolant water flowing over the pads serves to further increase the difficulties encountered in attaching and re moving the pads. The present invention pro vides an improved lens surfacing pad and 130 SUMMARY OF THE INVENTION

The present invention relates to a surfacing pad adapted for use with a lapping tool, the surfacing pad having a substrate sheet and mechanical retention means for retaining the pad in position on the tool. The retention means preferably comprises a projection extending generally transversely from the surfacing pad and sized to closely interfit in an as- sociated recession in a lapping tool.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a perspective of a lens surfacing pad of the present invention shown in opera- tive association with a lens lapping tool.

Figure 2 is a bottom view of a lens surfacing pad of the present invention.

Figure 3 is a sectional view taken along line 3-3 in Fig. 1.

Figure 4 is a bottom view, broken away, of an alternative embodiment of the present invention.

Figure 5 is a side view, broken away, of the alternative embodiment of the present inventionas shown in Fig. 4.

Figure 6 is a bottom view, broken away, of another alternative embodiment of the present invention.

Figure 7 is a side view, broken away, of the alternative embodimen tion shown in Fig. 6.

Figure 8 is a bottom view, broken away, of another alternative embodiment of the present invention.

Figure 9 is a side view, broken away, of the alternative embodiment of the present invention shown in Fig. 8.

Figure 10 is a bottom view, broken away, of another alternative embodiment of the pre- sent invention.

Figure 11 is a side view, broken away, of the alternative embodiment of the present invention shown in Fig. 10.

Figure 12 is a sectional view similar to that of Fig. 3, broken away, showing another alternative embodiment of the present invention.

Figure 13 is a sectional view similar to that of Fig. 3, broken away, showing another alternative embodiment of the present invention.

Figure 14 is a sectional view similar to that of Fig. 3, broken away, showing another alternative embodiment of the present invention.

Figure 15 is an exploded view illustrating still another alternative embodiment of the present invention.

Figure 16 is a somewhat schematic view illustrating a method of making a lens surfacing pad of the present invention.

of the present inven- DESCRIPTION OF THE INVENTION

2 GB2195100A 2 Now referring to the drawings, Fig. 1 illus trates a lens surfacing pad 10 of the present invention shown in operative position on sur face 12 of lens lapping tool 14. As will be appreciated by those skilled in the art, in use, 70 a blocked lens will be oscillated over pad 10 mounted upon lens lapping tool 14 in a grind ing or polishing operation. Surface 12 of lens lapping tool 14 has a shape corresponding to the curvature desired for a lens. Convention ally, lens surfacing pads are adhesively se cured to the curved surface of lens lapping tools. In accordance with the present inven tion, however, lens surfacing pad 10 is pro vided with mechanical retention means -16 for securing lens surfacing pad 10 in position on surface 12 of lens lapping tool 14.

As is best illustrated in Fig. 3, lens surfac ing pad 10 comprises a polyester substrate sheet 18 which carries a plurality of diamond 85 grit particles 20 which are secured onto sheet 18 by metal matrix layer 22. To facilitate close adherence to the surface 12 of lens lapping tool 14, lens surfacing pad 10 has a plurality of generally radially extending slots 24 therein.

Substrate sheet 18 can alternatively be made of any flexible sheet material suitable for its intended uses. For example, substrate sheet 18 can be metal, such as copper, alumi num or steel, or polyester, polypropylene, polyethylene or other polymeric material. Suit able substrate sheet thicknesses can vary widely. For example, sheet thicknesses of from 1/1000 inch to 1/16 inch can be suit able. Substrate sheet 18 can comprise one or multiple layers. A preferred substrate sheet is aluminum metallized polyester.

Substrate sheet 18 carries abrasive grit par ticles 20 bonded thereto by a suitable bonding 105 layer 22 which is preferably a metal matrix when diamond abrasive particles are used.

Suitable metals or metal matrixes and methods of plating metal to bond diamond grit to substrate sheets are well known in the 110 art. Suitable metals include nickel and its alloys and plating methods include electroplating, chemical reduction and vacuum metal deposition. 50 Suitable abrasive particles will, of course, vary with the intended use of the pad. For example, aluminum oxide, silicon carbide or other grit particles can be used and conventionally bonded to a carrier substrate. How55 ever, diamond particles, suitably from 10 mi- 120 crons to 100 microns in diameter, are preferred because of their longer life in use. In accordance with the present invention, lens surfacing pad 10 has a mechanical reten60 tion means 16 for retaining the pad in position 125 on lapping tool 14. As illustrated in Figs. 2 and 3, retention means 16 is shown as a projection, generally cylindrical in shape, which extends generally transversely to the general plane of substrate 18 and extends down- 130 wardly into a correspondingly shaped recess 26 in the body of lens lapping tool 14. Thus, it will be appreciated by those skilled in the art that in use, while a lens is being surfaced, the pressure of the lens against the pad will retain retention means 16 in recess 26 and hence will retain lens surfacing pad 10 on lens lapping tool 14.

Figs. 4 through 15 show various alternative retention means for retaining lens surfacing pad 10 on a lens lapping tool 14. Thus, Figs. 4 and 5 show a lens surfacing pad 50 of contruction generally analogous to lens surfacing pad 10 but having retention means 52 generally in the shape of a cross. Thus, retention means 52 has four legs 54, 56, 58 and 60, which extend generally downwardly from substrate 62 of lens surfacing pad 50. As will be appreciated by those skilled in the art, retention means 52 is adapted to closely interfit into a corresponding recession in lens surfacing tool 14. Because of the shape of retention means 52, lens surfacing pad 50 will be retained on the surface of lens lapping tool 14 with no rotation thereof.

Figs. 6 and 7 illustrate yet another alternative embodiment of the present invention. Thus, lens surfacing pad 70 has a retention means 72 in the form of a ridge extending downwardly from substrate 74 of lens surfacing pad 70. Retention means 72 is adapted to closely fit into a corresponding recess in a lens surfacing tool, and once interfit therein, to provide means for positioning and retaining lens surfacing pad 70 on the lens lapping tool.

Now referring to Figs. 8 and 9 still another alternative embodiment of the present invention is shown. Thus, lens surfacing pad 80 has retention means 82 comprising a pair of generally cylindrically shaped projections 84 and 86 extending downwardly from substrate 88 of lens surfacing pad 80. Projection 80 can be positioned, for example, in the center of lens surfacing pad 80 and projection 86 positioned off center to facilitate placement of the pad onto a lens surfacing tool and to prevent rotation of the pad on the tool once in place thereon.

Still another alternative embodiment is illus- trated in Figs. 10 and 11 and indicated generally by the numeral 100. Lens surfacing pad 100 has a retention means 102 extending downwardly from substrate 104 of lens surfacing pad 100. Retention means 102 is generally elliptical in shape when viewed in bottom view as illustrated in Fig. 10. Thus, when retention means 102 is closely interfit into a correspondingly shaped recess in the lens lapping tool, rotation of lens surfacing pad 100 will be prevented.

Fig. 12 illustrates another alternative embodiment indicated generally by the numeral 110. Lens surfacing pad 110 is shown positioned on lens lapping tool 112. Lens lapping tool 112 has a pair of projecting portions 114 If, ii 3 GB2195100A 3 and 116 which extend partially into corresponding recesses in substrate 118 of lens surfacing pad 110. Lens surfacing pad 110 also includes a metallic layer 120 having abra- sive particles 122 attached thereon in a conventional manner.

Now referring to Fig. 13, a lens surfacing pad 140 is shown in retained position on lens lapping tool 142. Lens surfacing pad 140 has a substrate sheet 144 with metal layer 146 securing abrasive grit 148 thereon. Lens surfacing pad 140 has discrete retention means 150; that is, retention means 150 is separate from and removable from lens surfacing pad 140. Retention means 150 comprises a cylin- drical portion 152 with rounded end 153 and annular flange 154. Cylindrical portion 152 of retention means 150 extends through aperture 156 in substrate 144 while annular flange 154 has a diameter greater than aperture 156 and abuts against the outwardly facing surface 158 of substrate 144. Outwardly facing surface 160 of retention means 150 lies on the lapping surface of surfacing pad 140 as shown in the figure, or alternatively lies below the surface inwardly at the general outward plane of grit 148 so as not to interfere with the abrasive action thereof. Thus, retention means 150 when fit into correspondingly shaped hole 162 in lapping tool 142 serves to 95 retain lens surfacing pad 140 in position on lens lapping too[ 142.

In accordance with the embodiment of the present invention shown in Fig. 13, it will be appreciated that retention means 150 is a plug-like structure which can be manually inserted through aperture 156 in substrate 144 and into hole 162 in lapping tool 142 to retain pad 140 thereon. Thus, retention means 150 can be manufactured separately from pads 140 and combined therewith in this novel manner of the present invention by the end user.

Furthermore, where discrete retention means 150 are employed, a still further alternative embodiment of the present invention can be obtained. Thus, as shown in Fig. 14, a lens surfacing pad 170 is shown on lens lapping tool 172. Lens surfacing 170 has a substrate layer 174 with abrasive surfaces on both sides thereof. Thus, one side of substrate layer 174 has a first metal layer 176 securing relatively fine abrasive grit 178 thereon and the ther side of substrate layer 174 has a second metal layer 180 securing very fine abrasive grit 182 thereon.

Retention means 184 is of a construction analogous to retention means 150. Thus, surfacing pad 170 can be used either with fine abrasive grit 178 facing outwardly or with very fine abrasive grit 182 facing outwardly. Retention means 150 can be used to secure surfacing pad 170 in either position. Furthermore, in either position, the abrasive grit adja- cent the surface of lapping tool 172 will pro- vide a surface with a high coefficient of friction which will resist rotational movement of pad 170 with respect to tool 172. It will, of course, be appreciated that, if desired, an abrasive layer, or other layer with a high coefficient of friction, on the side of the surfacing pad facing the lapping tool surface can be incorporated into each of the aforementioned embodiments of the present invention. Such a layer would provide additional retention of pads on the lapping tool surfaces.

Referring to Fig. 15, still another alternative embodiment of the present invention is illustrated and indicated generally by the numeral 190. Subfacing pad 190 is shown in retained position on lens lapping tool 192. Surfacing pad 190 is illustrated as a one layer sheet without abrasive, however, it will be appreciated that surfacing pad 190 can alternatively comprise a laminate construction with or without abrasive depending upon its intended use. Lens lapping tool 192 has a channel-like keyway 194. Surfacing pad 190 includes retention means 196 which includes an elongated key 198 which is sized for interference fit with pad 190 in corresponding elongated keyway 194 to retain pad 190 in position on lens lapping tool 192.

Now referring to Fig. 16, a method for making lens surfacing pads of the present invention is illustrated in schematic form.

Substrate sheet 200 is unwound from roller 202 in direction indicated by arrow 204 and passes over thermoforming roller 206 which provides projections 208 in substrate sheet 200. Projections 208 provide means for retaining the final lens surfacing pad product on a lens lapping tool as hereinabove described. Metal sheet 210 carrying abrasive 212 is un- wound from roller 214 in the direction indicated by arrow 216. Substrate sheet 200 and metal sheet 210 are compressed between heated rollers 218 and 220 which serve to bond the respective sheets together. The bonded laminate 222 is then passed between a rotary die cutter 224 which cuts individual lens surfacing pads from laminate 222.

It will be appreciated that lens surfacing pads of the present invention can be made by other methods. For example, retention means can be individually manually adhered to suitable pads with adhesive. The embodiments of Figs. 13-15 employ discrete retention means which are not permanently attached to surfac- ing pads and, hence, would be made separate therefrom. While the foregoing disclosure sets forth several preferred embodiments of the present invention, it will be readily apparent to those skilled in the art that the present inven- tion may be subject to modification and variation from the specific embodiments disclosed. Accordingly, it is intended that the scope of the present invention be limited only by the following claims.

4 GB2195100A 4

Claims (29)

1. A surfacing pad adapted for use with a lapping too[, comprising a sheet or substrate sheet and projection means for retaining said pad on said-lapping tool.

2. A surfacing pad as in claim 1 wherein said retention means comprises a projection extending generally transversely from said sub strate sheet, said projection sized to closely fit into a corresponding recess in said lapping tool.

3. A surfacing pad as in claim 2 wherein said projection is generally cylindrical or square in shape.

4. A surfacing pad as in claim 1 wherein said retention means comprises a plurality of projections, each extending generally transversely from said substrate sheet and each sized to closely fit into a corresponding recess in said lapping tool.

5. A surfacing pad as in claim 1 wherein said substrate sheet has an abrasive layer on at least one side thereof.

6. A surfacing pad as in claim 5 wherein said substrate sheet has an abrasive layer on 90 both sides thereof.

7. A surfacing pad as in claim 5 wherein said substrate sheet has a usable abrasive layer on both sides thereof.

8. A surfacing pad as in claim 5 wherein said abrasive layer comprises diamond grit.

9. A surfacing pad as in claim 2 wherein said projection has a cross-sectional shape of a cross.

10. A surfacing pad as in claim 2 wherein 100 said projection has a cross-sectional shape of a rectangle.

11. A surfacing pad as in claim 1 wherein said projection comprises a pair of cylindrical projections.

12. A surfacing pad as in claim 1 wherein said projection has a cross-sectional shape of an ellipse.

13. A surfacing pad as in claim 1 wherein said projection means is a discrete plug having a headed portion and a projecting portion.

14. A surfacing pad as in claim 12 wherein said pad has abrasive grit on both sides thereof.

15. A surfacing pad as in claim 1 wherein said lapping tool has an elonated keyway and said projection means is an elonated key fitt ing into said keyway retaining a portion of said pad therein in an interference fit.

16. A method for retaining a lens surfacing pad on a lens surfacing tool comprising the steps of:

(A) providing a lens surfacing pad having a substrate sheet and a projection extending generally transversely from said sheet; (13) providing a lens surfacing tool having a surface with a recess therein, said recess being adapted to closely receive said projection; and (C) placing said lens surfacing pad on said surface of said lens surfacing tool with said projection interfitting into said recess.

17. A method as in claim 16 wherein said projection is generally cylindrical in shape.

18. A method as in claim 16 wherein said lens surfacing pad has a plurality of projections extending generally transversely therefrom and said lens surfacing tool has corresponding recesses therein for receiving said plurality of projections.

19. A method as in claim 16 wherein said substrate sheet has an abrasive layer on at least one side thereof.

20. A method as in claim 19 wherein said substrate sheet has an abrasive layer on both sides thereof.

2 1. A method as in claim 16 wherein said abrasive layer comprises diamond grit.

22. A method as in claim 16 wherein said projection has a cross-sectional shape of a cross.

23. A method as in claim 16 wherein said projection has a cross-sectional shape of a rectangle.

24. A method as in claim 16 wherein said projection comprises a pair of cylindrical projections.

25. A method as in claim 16 wherein said projection has a cross-sectional shape of an ellipse.

26. A method as in claim 16 wherein said projection means is a discrete plug having a headed portion and a projecting portion.

27. A method as in claim 16 wherein said pad has abrasive grit on both sides thereof.

28. A surfacing pad constructed and ar- ranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

29. A method of retaining a lens surfacing pad on a lens surfacing tool substantially as hereinbefore described with reference to the accompanying drawings.

Published 1988 at The Patent Office, State House, 66/71 High Holborn, London WC 1 R 4TP. Further copies may be obtained from The Patent Office, Sales Branch, St Mary Cray, Orpington, Kent BR5 3RD. Printed by Burgess & Son (Abingdon) Ltd. Con. 1/87.

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