Lens surfacing pads and method of making the same
United States Patent 3921344
Lens surfacing pads of foraminous material having a continuous puncture resistant thermoplastic film on one side only. The film is applied to the pads by lamination under heat and pressure and supports a layer of adhesive for attaching the foraminous pads to lens surfacing tools.
US Patent References:
Grinding disk and method of making the same
Budds - June 1937 - 2085211
Granular coated article and its manufacture
Kirchner - June 1942 - 2286208
Overlay for and method of grinding lens blanks
Seifert - July 1956 - 2752738
Aluminum foil lens grinding pad
Faas - August 1964 - 3144737
Method and apparatus for forming a lens surface
Brandt - December 1965 - 3225497
Grinding disk and method of making the same
Budds - June 1937 - 2085211
Granular coated article and its manufacture
Kirchner - June 1942 - 2286208
Overlay for and method of grinding lens blanks
Seifert - July 1956 - 2752738
Aluminum foil lens grinding pad
Faas - August 1964 - 3144737
Method and apparatus for forming a lens surface
Brandt - December 1965 - 3225497
Application Number:
05/359825
Publication Date:
11/25/1975
Filing Date:
05/14/1973
View Patent Images:
Export Citation:
Assignee:
American Optical Corporation (Southbridge, MA)
Primary Class:
Other Classes:
451/548, 451/539, 51/298, 451/42, 51/297
International Classes:
B24B13/01; B24B13/00; B24D17/00; B24D11/02; B24D9/00
Field of Search:
51/358,395-398,400-402,404-407,284,131,29DL,DIG.34,298,297
US Patent References:
Primary Examiner:
Kelly, Donald G.
Attorney, Agent or Firm:
Berkenstock Jr., Nealon William H. R. C.
Claims:
I claim
1. A disposable lens surfacing pad comprising the laminate of:
2. A disposable lens surfacing pad according to claim 1 wherein said film is a thermoplastic resin.
3. A disposable lens surfacing pad according to claim 2 wherein said sheet of foraminous material is a screen of woven wire.
4. A disposable lens surfacing pad according to claim 2 wherein said foraminous material is a sheet of woven fibers.
5. A disposable lens surfacing pad according to claim 2 wherein said foraminous material is a perforated sheet of metal.
6. A disposable lens surfacing pad according to claim 2 wherein said foraminous material is a perforated sheet of plastic.
7. A disposable lens surfacing pad according to claim 2 wherein said foraminous material is perforated foil.
8. A disposable lens surfacing pad according to claim 1 wherein said layer of adhesive comprises a sheet of double-faced pressure-sensitive tape.
9. A lens surfacing tool comprising:
10. A lens surfacing tool according to claim 9 wherein said foraminous material is a screen and said thin film of highly abrasion and puncture resistant material is a thermoplastic resin.
11. A lens surfacing tool according to claim 9 wherein said foraminous material is a perforate sheeting and said film of said highly abrasion and puncture resistant material is a thermoplastic resin.
12. The method of making a disposable lens surfacing pad comprising the steps of:
13. The method according to claim 12 wherein said film is a thermoplastic resin and said temperature and pressure suitable for effecting said bonds are approximately 275°F and approximately 4,000 pounds per square inch respectively.
14. The method according to claim 12 further including the step of applying a readily removable protective cover over said adhesive material.
1. A disposable lens surfacing pad comprising the laminate of:
2. A disposable lens surfacing pad according to claim 1 wherein said film is a thermoplastic resin.
3. A disposable lens surfacing pad according to claim 2 wherein said sheet of foraminous material is a screen of woven wire.
4. A disposable lens surfacing pad according to claim 2 wherein said foraminous material is a sheet of woven fibers.
5. A disposable lens surfacing pad according to claim 2 wherein said foraminous material is a perforated sheet of metal.
6. A disposable lens surfacing pad according to claim 2 wherein said foraminous material is a perforated sheet of plastic.
7. A disposable lens surfacing pad according to claim 2 wherein said foraminous material is perforated foil.
8. A disposable lens surfacing pad according to claim 1 wherein said layer of adhesive comprises a sheet of double-faced pressure-sensitive tape.
9. A lens surfacing tool comprising:
10. A lens surfacing tool according to claim 9 wherein said foraminous material is a screen and said thin film of highly abrasion and puncture resistant material is a thermoplastic resin.
11. A lens surfacing tool according to claim 9 wherein said foraminous material is a perforate sheeting and said film of said highly abrasion and puncture resistant material is a thermoplastic resin.
12. The method of making a disposable lens surfacing pad comprising the steps of:
13. The method according to claim 12 wherein said film is a thermoplastic resin and said temperature and pressure suitable for effecting said bonds are approximately 275°F and approximately 4,000 pounds per square inch respectively.
14. The method according to claim 12 further including the step of applying a readily removable protective cover over said adhesive material.
Description:
BACKGROUND OF THE INVENTION
1. Field of the Invention
Lens surfacing pads with particular reference to disposable pads of foraminous material which are readily conformable and releasably attachable to lens surfacing tools.
2. Description of the Prior Art
Disposable foraminous lens surfacing pads of wire mesh, woven fibrous material or perforated sheet metal and other perforate materials which are generally readily conformable to curved working surfaces of conventional lens surfacing tools have, heretofore, been detachably applied to such tools with mechanical clamps or adhesives, the latter usually being in the form of a layer of pressure sensitive adhesive attached to one side of the foraminous pad. U.S. Pat. Nos. 2,886,923 and 3,225,497 are exemplary.
While the ungainliness and complication of mechanical clamps may be avoided by the use of adhesive attachment means, there remains the problem of material of the adhesive passing through interstices in the pad and lodging at the interface between a lens being surfaced and the pad. This causes "graying" (faulty or incomplete grinding) of the lens surface due to incomplete contact between the lens and pad and induces pad slippage which is also detrimental to lens surface quality.
With the foregoing problem in mind, prior art foraminous pads have been dipped in solvent base polymeric coating solutions to bridge and seal their porosities against penetration by the pad adhesives. The resulting coatings, however, cover both sides of the foraminous pads and restrict the grinding quality, i.e., sharpness, of the abrading side of the pad. Additionally, solvent base polymeric solutions currently being used to coat the pads are hazardous in being highly flammable and the coating process requires time consuming and costly operations of removing excess coating material with doctor blades after dipping and long periods of storage for conditioning of the pads for the application of adhesives thereto. Also, coating by dipping has been found to leave weak spots and/or skipping of some interstices through which the pad adhesives may pass uninterruptedly or by rupture of the weakened coating material as a result of pressure applied to the pad during its use.
With a view to overcoming the aforementioned and related drawbacks of prior art lens surfacing pads and methods of making the same, the present invention contemplates the use of a tough, puncture resistant continuous or imperforate film on one side only of the foraminous pads for receiving the adhesive. The film is applied with a non-hazardous laminating operation requiring no post curing or aging. The opposite working sides of the pads are left bare for direct surface engagement with lenses to be abraded. Thus, when suitable conventional abrasive slurries are applied thereto in lens surfacing operations such as are shown and described in U.S. Pat. Nos. 2,886,923 and 3,225,497, the present invention offers the advantages of a fully exposed uncoated bare foraminous abrading surface, adhesive attachment means and protection against interference of the adhesive with lens surfacing operations. Still further, the present invention avoids prior art hazards, tedious and expensive operations in the manufacture of the pads and the prior art necessity for large inventories resulting from curing and aging cycles having to last several weeks before readiness for sale and use of the pads.
SUMMARY OF THE INVENTION
Foraminous surfacing pads are produced according to the present invention from a sheet of woven wire, woven synthetic fibers or perforate sheet metal, plastic or other material by laminating to one side of the selected foraminous sheet material a thin film of a thermoplastic resin, e.g., of a type derived from polyethylene, which has a high resistance to abrasion and puncture. The film is applied with a simple time-temperature-pressure cycle eliminating prior art hazardous manufacturing operations and lengthy curing cycles. An adhesive, preferably a double-faced pressure sensitive tape, is applied to the laminate for attaching pads cut therefrom to lens surfacing tools.
Details of the invention will become apparent from the following description taken in conjunction with the accompanying drawings.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a plan view of a lens surfacing pad exemplifying a preferred embodiment of the present invention, portions of the pad being broken away to more clearly illustrate its structure;
FIG. 2 is a side elevational view of a lens surfacing tool having a surfacing pad of the type shown in FIG. 1 applied thereto as a facing for its working surface;
FIG. 3 is an enlarged fragmentary cross-sectional view of the lens surfacing tool of FIG. 2 showing a portion of a lens in abrading relationship therewith;
FIG. 4 is a diagrammatic illustration, partially in cross-section, of an apparatus and method used in the manufacture of lens surfacing pads acccording to the invention; and
FIG. 5 is an enlarged fragmentary cross-sectional view of lens surfacing pad material of the type formed according to the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Pad 10 which is intended for use as a facing for lens surfacing tools, e.g., tool 12 (FIGS. 2 and 3), comprises a laminate of a foraminous sheet 14 of woven wire, woven fibers or perforate sheet material having a thin film 16 of a thermoplastic resin affixed to its inner side and an adhesive 18, e.g., double-faced pressure sensitive tape, applied to film 16 for use in detachably securing pad 10 to tool 12. During storage, adhesive 18 is protected by a strip-off covering 20. A preferred construction would comprise a foraminous sheet 14 of galvanized soft steel wire screening having approximately 30 × 30 strands per inch and a wire size of approximately 0.007 inch; a 0.002 to 0.004 inch thick film 16 of a thermoplastic resin derived from polyethylene such as, for example, the highly abrasion and puncture resistant commercially available film material currently known as Surlyn, a proprietary name applied by E. I. DuPont De Nemours and Co. (Inc.) to the film material; an adhesive 18 of double-faced pressure sensitive tape; and a strip-off protective cover 20 of paper or a thin plastic material preferably having a glazed or release coated surface for ease of removal from adhesive 18. It is to be understood, however, that foraminous sheet 14 may be formed of woven hard plastic or natural fibers, perforated aluminum foil or other metallic and plastic sheet materials of various thicknesses.
With protective covering 20 stripped away from pad 14, it is applied as a facing for tool 12 simply by pressing adhesive 18 against the working surface 22 of tool 12 (FIG. 3). In so doing, and with additional pressure applied to the pad 14 by a lens L being surfaced by tool 12 (FIG. 3), pad 14 will assume the curved shape of surface 22 whether convex (as illustrated) or concave (not illustrated). Grinding the surface 26 of lens L to a shape complimentary to that of working surface 22 of tool 12 is accomplished by producing relative motion between lens L and tool 12, e.g., oscillatory or circular or combinations thereof, while introducing a slurry 24 of emery particles or other abrasive materials into the space between lens surface 26 and tool 12, over pad 14 and through its interstices. Those interested in greater details of this technique of surfacing or grinding lenses and lens blanks may refer to U.S. Pat. Nos. 2,886,923 and 3,225,497.
Pad 14 is fabricated as follows:
A sheet 14' (FIG. 4) of a particular preselected type of foraminous material is placed flatly upon a platen 28 and covered by a film 16' of the aforementioned 0.002 to 0.004 inch thickness of thermoplastic resin. A pressure plate 30 is then brought into place flatly against film 16' and pressure is applied to plate 30 uniformly over the extent of its coverage of film 16' while the film is heated by plate 30, e.g., with electrical heating coils 32 therewithin, for a period of time sufficient to attach film 16' to sheet 14' as a laminate. An exemplary time-temperature-pressure cycle is approximately 1 minute at approximately 275°F with a pressure of approximately 4,000 pounds per square inch. In order to prevent heated platen 30 from adhering to film 16' during application of heat and pressure a protective barrier, such as a silicone coated release paper 17 should be placed between a platen 30 and film 16'.
Following lamination of film 16' to foraminous sheet 14', plate 30 and the release paper are removed and a layer 18' of adhesive material, e.g., a double-faced pressure sensitive tape having one side protected with a cover sheet 20' (FIG. 5) is applied to film 16'. Pads 14 of the circular shape illustrated in FIG. 1 or of other desired shapes and sizes are then punched or otherwise cut from the completed laminate 10' and are immediately ready for use.
While the process has been described as involving the use of a fixed platen 28 and movable pressure plate 30, these components may be constructed and arranged for simultaneous movement toward and away from each other. It is also contemplated that long lengths of the combination of foraminous sheet 14' and film 16' may be fed through one or more sets of heated rollers preferably covered with a silicone rubber and having a squeezing pressure applied thereto for producing the laminated product of film 16' and sheet 14'.
1. Field of the Invention
Lens surfacing pads with particular reference to disposable pads of foraminous material which are readily conformable and releasably attachable to lens surfacing tools.
2. Description of the Prior Art
Disposable foraminous lens surfacing pads of wire mesh, woven fibrous material or perforated sheet metal and other perforate materials which are generally readily conformable to curved working surfaces of conventional lens surfacing tools have, heretofore, been detachably applied to such tools with mechanical clamps or adhesives, the latter usually being in the form of a layer of pressure sensitive adhesive attached to one side of the foraminous pad. U.S. Pat. Nos. 2,886,923 and 3,225,497 are exemplary.
While the ungainliness and complication of mechanical clamps may be avoided by the use of adhesive attachment means, there remains the problem of material of the adhesive passing through interstices in the pad and lodging at the interface between a lens being surfaced and the pad. This causes "graying" (faulty or incomplete grinding) of the lens surface due to incomplete contact between the lens and pad and induces pad slippage which is also detrimental to lens surface quality.
With the foregoing problem in mind, prior art foraminous pads have been dipped in solvent base polymeric coating solutions to bridge and seal their porosities against penetration by the pad adhesives. The resulting coatings, however, cover both sides of the foraminous pads and restrict the grinding quality, i.e., sharpness, of the abrading side of the pad. Additionally, solvent base polymeric solutions currently being used to coat the pads are hazardous in being highly flammable and the coating process requires time consuming and costly operations of removing excess coating material with doctor blades after dipping and long periods of storage for conditioning of the pads for the application of adhesives thereto. Also, coating by dipping has been found to leave weak spots and/or skipping of some interstices through which the pad adhesives may pass uninterruptedly or by rupture of the weakened coating material as a result of pressure applied to the pad during its use.
With a view to overcoming the aforementioned and related drawbacks of prior art lens surfacing pads and methods of making the same, the present invention contemplates the use of a tough, puncture resistant continuous or imperforate film on one side only of the foraminous pads for receiving the adhesive. The film is applied with a non-hazardous laminating operation requiring no post curing or aging. The opposite working sides of the pads are left bare for direct surface engagement with lenses to be abraded. Thus, when suitable conventional abrasive slurries are applied thereto in lens surfacing operations such as are shown and described in U.S. Pat. Nos. 2,886,923 and 3,225,497, the present invention offers the advantages of a fully exposed uncoated bare foraminous abrading surface, adhesive attachment means and protection against interference of the adhesive with lens surfacing operations. Still further, the present invention avoids prior art hazards, tedious and expensive operations in the manufacture of the pads and the prior art necessity for large inventories resulting from curing and aging cycles having to last several weeks before readiness for sale and use of the pads.
SUMMARY OF THE INVENTION
Foraminous surfacing pads are produced according to the present invention from a sheet of woven wire, woven synthetic fibers or perforate sheet metal, plastic or other material by laminating to one side of the selected foraminous sheet material a thin film of a thermoplastic resin, e.g., of a type derived from polyethylene, which has a high resistance to abrasion and puncture. The film is applied with a simple time-temperature-pressure cycle eliminating prior art hazardous manufacturing operations and lengthy curing cycles. An adhesive, preferably a double-faced pressure sensitive tape, is applied to the laminate for attaching pads cut therefrom to lens surfacing tools.
Details of the invention will become apparent from the following description taken in conjunction with the accompanying drawings.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a plan view of a lens surfacing pad exemplifying a preferred embodiment of the present invention, portions of the pad being broken away to more clearly illustrate its structure;
FIG. 2 is a side elevational view of a lens surfacing tool having a surfacing pad of the type shown in FIG. 1 applied thereto as a facing for its working surface;
FIG. 3 is an enlarged fragmentary cross-sectional view of the lens surfacing tool of FIG. 2 showing a portion of a lens in abrading relationship therewith;
FIG. 4 is a diagrammatic illustration, partially in cross-section, of an apparatus and method used in the manufacture of lens surfacing pads acccording to the invention; and
FIG. 5 is an enlarged fragmentary cross-sectional view of lens surfacing pad material of the type formed according to the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Pad 10 which is intended for use as a facing for lens surfacing tools, e.g., tool 12 (FIGS. 2 and 3), comprises a laminate of a foraminous sheet 14 of woven wire, woven fibers or perforate sheet material having a thin film 16 of a thermoplastic resin affixed to its inner side and an adhesive 18, e.g., double-faced pressure sensitive tape, applied to film 16 for use in detachably securing pad 10 to tool 12. During storage, adhesive 18 is protected by a strip-off covering 20. A preferred construction would comprise a foraminous sheet 14 of galvanized soft steel wire screening having approximately 30 × 30 strands per inch and a wire size of approximately 0.007 inch; a 0.002 to 0.004 inch thick film 16 of a thermoplastic resin derived from polyethylene such as, for example, the highly abrasion and puncture resistant commercially available film material currently known as Surlyn, a proprietary name applied by E. I. DuPont De Nemours and Co. (Inc.) to the film material; an adhesive 18 of double-faced pressure sensitive tape; and a strip-off protective cover 20 of paper or a thin plastic material preferably having a glazed or release coated surface for ease of removal from adhesive 18. It is to be understood, however, that foraminous sheet 14 may be formed of woven hard plastic or natural fibers, perforated aluminum foil or other metallic and plastic sheet materials of various thicknesses.
With protective covering 20 stripped away from pad 14, it is applied as a facing for tool 12 simply by pressing adhesive 18 against the working surface 22 of tool 12 (FIG. 3). In so doing, and with additional pressure applied to the pad 14 by a lens L being surfaced by tool 12 (FIG. 3), pad 14 will assume the curved shape of surface 22 whether convex (as illustrated) or concave (not illustrated). Grinding the surface 26 of lens L to a shape complimentary to that of working surface 22 of tool 12 is accomplished by producing relative motion between lens L and tool 12, e.g., oscillatory or circular or combinations thereof, while introducing a slurry 24 of emery particles or other abrasive materials into the space between lens surface 26 and tool 12, over pad 14 and through its interstices. Those interested in greater details of this technique of surfacing or grinding lenses and lens blanks may refer to U.S. Pat. Nos. 2,886,923 and 3,225,497.
Pad 14 is fabricated as follows:
A sheet 14' (FIG. 4) of a particular preselected type of foraminous material is placed flatly upon a platen 28 and covered by a film 16' of the aforementioned 0.002 to 0.004 inch thickness of thermoplastic resin. A pressure plate 30 is then brought into place flatly against film 16' and pressure is applied to plate 30 uniformly over the extent of its coverage of film 16' while the film is heated by plate 30, e.g., with electrical heating coils 32 therewithin, for a period of time sufficient to attach film 16' to sheet 14' as a laminate. An exemplary time-temperature-pressure cycle is approximately 1 minute at approximately 275°F with a pressure of approximately 4,000 pounds per square inch. In order to prevent heated platen 30 from adhering to film 16' during application of heat and pressure a protective barrier, such as a silicone coated release paper 17 should be placed between a platen 30 and film 16'.
Following lamination of film 16' to foraminous sheet 14', plate 30 and the release paper are removed and a layer 18' of adhesive material, e.g., a double-faced pressure sensitive tape having one side protected with a cover sheet 20' (FIG. 5) is applied to film 16'. Pads 14 of the circular shape illustrated in FIG. 1 or of other desired shapes and sizes are then punched or otherwise cut from the completed laminate 10' and are immediately ready for use.
While the process has been described as involving the use of a fixed platen 28 and movable pressure plate 30, these components may be constructed and arranged for simultaneous movement toward and away from each other. It is also contemplated that long lengths of the combination of foraminous sheet 14' and film 16' may be fed through one or more sets of heated rollers preferably covered with a silicone rubber and having a squeezing pressure applied thereto for producing the laminated product of film 16' and sheet 14'.