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Publication numberUS2701192 A
Publication typeGrant
Publication dateFeb 1, 1955
Filing dateFeb 2, 1949
Priority dateFeb 2, 1949
Publication numberUS 2701192 A, US 2701192A, US-A-2701192, US2701192 A, US2701192A
InventorsEdward W Maass
Original AssigneeAmerican Optical Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Polishing pads
US 2701192 A
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Description  (OCR text may contain errors)

E. W. MAASS POLISHING PADS Feb. 1, 1955 2 Sheets-Sheet 1 Filed Feb. 2, 1949 s m MA VM w a A w D e ATTORNEY E. W. MAASS POLISHING PADS Feb. 1, 1955 2 Sheets-Sheet 2 Filed Feb. 2, 1949 INVENTOR.

EDWARD W. MAASS ATTORNEY United States Patent POLISHING PADS Edward W. Maass, South Woodstock, Conm, assignor to American Optical Company, Southbridge, Mass., :1 voluntary association of Massachusetts Application February 2, 1949, Serial No. 74,180

11 Claims. (Cl. 51-298) This invention relates to improved means and methods of forming polishing pads and has particular reference to forming polishing pads of a type used in the ophthalmic art for polishing the surfaces of glass articles such as ophthalmic lenses.

One of the principal objects of the invention is to provide a relatively dense solid polishing pad that is inherently abrasive-free and composed essentially of cellulosic particles of corn cob or wood flours held in adjacent bonded relation with each other by a matrix of bonding material and formed to have an effective surface of a controlled fhape for use in polishing the surfaces of articles such as enses.

Another object is to provide a polishing pad of the above character and method of making the same which embodies particles of ligno-cellulose material such as corn cob or wood flours held in bonded relation with each other by a matrix of a vulcanizable elastomeric material and having a controlled surface shape, which matrix can be formed by conventional methods to produce a pad of a substantially uniform thickness suitable for use with conventional polishing machines.

Another object is to provide polishing means of the above character and method of making the same which embodies finely divided particles of corn cob wood flours substantially uniformly dispersed throughout a matrix or binder possessing an inherently elastomeric character which is resistant to oxidation and which is of such nature that the surface may be wetted by the slurry of polishing compounds such as rouge and water, clay and water, or any of the other commonly known polishing compounds.

Another object is to provide a polishing pad of the above character provided with recessed and raised areas on its effective surface whereby said raised areas will be free to flex and more uniformly allow the pad to conform to the shape of the surface of the article or articles being polished and said recessed areas will tend to retain therein the slurry or polishing compound thus insuring a more uniform distribution of said compound during the polishing operation.

Other objects and advantages of the invention will become apparent from the following description taken in connection with the accompanying drawings, in which:

Fig. 1 is a diagrammatic front elevational view illustrating an embodiment of the invention;

Fig. 2 is a plan view of a polishing pad embodying the invention;

Fig. 3 is a sectional view illustrating a modification in the polishing pad and method of using same;

Fig. 4 is a fragmentary plan view of the polishing surface of the modified pad;

Fig. 5 is a fragmentary sectional view of the pad diagrammatically illustrating its yielding characteristics during a polishing operation;

Fig. 6 is a fragmentary plan view of a pad having-different surface irregularities; and

Fig. 7 is a sectional view taken on line 77 of Fig. 6.

Referring more particularly to the drawings wherein like characters of reference designate like parts throughout the views, the invention is directed particularly to the provision of a polishing pad 3 embodying finely divided particles of ligno-cellulose material such as corn cob or wood flours substantially uniformly dispersed throughout a suitable matrix or binder and shaped to have a surface conforming substantially to that of the shape of the surface of an article 4 to be polished by said pad. The surice embodying the invention, is preferably shaped substantially to the final shape desired by fine grinding with emery or the like after first being formed by commonly known rough grinding methods employed in the ophthalmic art as through the use of coarse abrasives, diamond abrading tools or other suitable means.

In the drawing there is diagrammatically illustrated one method of polishing an ophthalmic lens 4 or other similar article. Referring to Fig. l, the pad 3 is shown secured to a support 5 by a layer or coating of adhesive 6 such as rubber cement, pitch, or other conventional and Well known adhesives. The support 5 is carried by a spindle 7 rotatably mounted within a bearing 8 and driven by any suitable source of power through means such as pulley 9 and belt 10. The lens blank or other article 4 to be polished is secured to a block 11 by means such as a layer of pitch 12 or other suitable adhesive commonly used in the art. The block 11 is provided with a socket 113 in which is extended a pin member 14 carried by a supporting member 15, which member is carried by a shaft 16 rotatably mounted in a suitable bearing 17. The shaft 16 may be rotated by any suitable means such as a pulley 18 and belt 19, which means may be operated by any suitable source of power.

The polishing operation is performed by applying to the exposed surface of the pad 3 a suitable polishing compound such as rouge and water, clay and water, or any other of the well known glass polishing compounds, and by causing the pad 3 to be rotated through rotation of the shaft 7, and finally causing the article 4 to be moved over the surface of the pad 3 in a path controlled by the eccentric relationship of the pin 14 and shaft 16 which is in turn rotated.

It has been found that in the past some polishing compounds, although extremely efiective as glass polishing agents, have caused considerable wear of polishing pads particularly when such pads were made of felt as now commonly used in the art. The pad 3 as described above has been found to be much more resistant to wear during the polishing operation and has a life which greatly exceeds that of the above mentioned commonly used pad materials.

The pad 3 which embodies a plurality of finely divided particles 2'0 of ligno-cellulosic material substantially uniformly dispersed throughout a binder or matrix 21 can be fabricated in sheet form or to a controlled shape. One matrix or binder which has proven to be very effective is compounded from rubber, either natural or synthetic; others from plastics.

As an example, the following formula produces a desirable pad using approximately 205 parts by weight of natural rubber as "the major ingredient in the matrix:

To this formula is added approximately 200 parts by weight of particles of ligno-cellulosic material such as corn cob or an amount ranging from approximately to 600 parts by weight, and preferably between 35 and 60 mesh. It is essential that all of the ingredients be free from particles of metal such as iron, or bits of sand or grit, that is, any material which would be hard enough to cause scratching of the surface of the article being polished. V

A ligno-cellulose material of the fibrous-woody type, imparts improved polishing characteristics to the resultant pad and others such as walnut shell flour, mahogany and pine and wood fiours like might be used, with corn cob particles, however, being preferable. Fillers such as clay, rouge, carbon black or other similar ingredients may be added to the ligno-cellulose ingredient if desired, it being necessary, however, for satisfactory results, to include the ligno-cellulose ingredient as at least 50% of the filler.

The bonding material of said formula may comprise synthetic rubber such as butadiene-acrylonitrile copolymer rubber, organic polysulfide rubber, polyisobutylene rubber, or reclaimed rubber, or colloidal blends of butadiene-acrylonitrile copolymer rubber and polyvinyl chlorides, these ingredients to be substituted for the natural rubber in Table A either in whole or in part or in combination and so embody about 200 to 205 parts by weight of the mix. Reduction or increase in the above quantities of vulcanizing agents may be necessary to secure comparable physical properties when mixtures are made by substituting synthetic or reclaimed rubber in the above mentioned formula. The sulphur is however preferably kept within the range of 4 to 12 parts by weight.

Plasticizers other than coumarone-indene resin may be used if desired such as stearic acid, chlorinated diphenyls, dioctyl phthalate, and diglycol sebacate and the like. They may be varied between and parts by weight.

Three other formulas producing satisfactory pads in accordance with the present invention are:

Table B Parts by Weight Butadieneacrylonitrile copoly'mer rubber Blend of Butadienaacrylonitrile copolymer rubber and polyvinyl chloride Sulphur Zinc Oxide Benzothiazyl Disulphide Zine Salt of Coconut Oil Fatty A (is Chlorinated Diphenyl gliglycol Sebacate Corn Cob Polysulfide type Synthetic Rubber Polymer" Ooumarone-indene resin Tetrametbyl thiuram monosulphide between the dies, pressing it to the shape desired, and

then subsequently applying heat while held under pressure.

Since there is produced a substantially uniform dispersion of cob in any of the above matrix material the thickness of the polishing pad used is immaterial provided that the surface in contact with the glass is shaped substantially to the surface shape of the article being polished.

Such a pad as disclosed herein can be easily adapted to simultaneously polish a plurality of articles such as ophthalmic lenses rather than a single article. Such a polishing operation is diagrammatically illustrated in Fig. 3 wherein a plurality of lenses 22 are attached, as by a layer of pitch or other suitable adhesive 23, to a block 24 or similar lens holding device with the surfaces of the lenses to be polished directed toward the polishing pad 25. The pad 25 is shaped substantially to the shapes of the surfaces of the lenses and is secured to a support 26 by a layer or coating of suitable adhesive 27, such as rubber cement, pitch or the like, the support 26 being mounted for oscillating or rotating movement so as to move the pad 25 over the surfaces of the lenses 22.

The surfaces of the lenses 22, which are to be polished by the pad 25 embodying the invention, will preferably be shaped substantially to the final shape desired by fine grinding with emery or the like after first being formed by commonly known rough grinding methods.

The polishing operation is performed similarly to the method described in connection with Fig. l by applying to the exposed surface of the pad 25 a suitable polishing compound such as rouge and water, clay and water, or any other of the well known glass polishing compounds, and by causing the pad 25 to be moved over the surfaces of the lenses 22 through conventional means, and finally causing the block 24 carrying the lenses 22 to be rotated so that the cooperating movements of the support 26 and the block 24 will cause the pad 25' to polish the surfaces of all the lenses 22.

It has been found that when blocks 24 are provided with lenses 22 which have'been previously surfaced and rough polished, the radii of curvatures of the partially finished lens surfaces may vary slightly from one another and from the radius of curvature of the polishing pad due to various conditions such as wear or misalignment of machine parts used in any of the preceding lens surfacing operations or in attaching the lenses to the block 24, so that it has been found that the radii of all of the lens surfaces in some instances do not conform to the radius of the pad, thus causing certain portions of the surfaces to be incompletely polished when rigid pads are used. In such instances the polishing pads may polish only portions of the lenses while leaving untouched the remaining portions of the lenses.

Although the pad possesses some inherent yielding characteristics due to its composition, it has been found desirable in instances where there is a variation in surface characteristics of the lenses to provide additional means to insure complete conformation of the polishing surface of the pad to the lens surfaces. This is done by providing the pad with an irregular polishing surface as illustrated in Figs. 3-7. The preferred method is to form alternate spaced concentric grooves and ridges 20 and 29 respectively.

Thus, in cases where there is a variation in radii between a lens surface and the surface of the pad, the application of the necessary polishing pressure to the pad will cause displacement of the ridges 29 so that these ridges will maintain substantial engagement with the surface of the glass to be polished. This is illustrated in Fig. 5 wherein a lens 22 which has the desired surface curvature conforming to the radius of the pad surface is located on the block 24, and held thereon by the adhesive 23. This lens 22 will be engaged by the ridges 29 formed on the pad 25 substantially as shown by solid lines. However, when a lens 22 is poorly attached to the block or provided with a surface curvature having a radius different than the abrading surface of the pad, such as shown by dotted outline, the ridges 29 will be inclined to substantially the positions indicated by dotted lines. This feature assures that all surfaces of the lenses 22, regardless of variations therein, will be efiiciently polished.

It has also been found in the past that after considerable use polishing pads which are formed with a continuous substantially smooth or even surface are apt to glaze, the glazed surfaces resulting in very ineficient polishing. By providing the pad 25 with the grooves 28 the polishing surfaces of the ridges 29 are less apt to become glazed due to the deformable characteristics thereof.

During polishing operations, it has also been found that at times the slurry or polishing compound which is initially applied to the effective surface of the pad may be thrown off to such an extent that an additional amount must necessarily be added or the polishing done with little or no compound resulting in inefficient polishing. However, with a pad formed according to the present disclosure, the polishing compound or slurry will gather in the grooves 28 and so will continuously lubricate the surfaces of the lenses 22 being polished during the polishing operation.

Although the preferable surface structure of a pad 25 is illustrated in Figs. 3, 4 and 5, it is to be understood that the polishing surface of the pad may be, if desired, formed with straight, parallel grooves 30 (Figs. 6 and 7), thus leaving raised squares or flats 31 which will be in abutment with the articles being polished, or with grooves cut radially or tangentially and in parallel or staggered relation.

From the foregoing description it will be understood that by incorporating a controlled amount of corn cob or Wood flour particles in a natural or synthetic rubber matrix, a polishing pad can be fabricated therefrom on plasticizing and vulcanizing, which pad will have improved efficiency and wear resistance characteristics, and by providing the polishing pad with an irregular abradmg surface as described the pad will have still greater efiiciency and wear resistance characteristics as well as ability to conform to the shapes of the surfaces being polished, and will accomplish all the objects of this mventlon.

Reference may be also had to the copending patent application of Albert J. Laliberte, Serial No. 74,066, filed of even date with this patent and owned by the same assignee wherein there are disclosed and claimed other polishing pads embodying mixtures of natural or synthetic rubbers with controlled amounts of thermoplastic resins and cellulosic fillers.

While the novel features of the invention have been shown and described and are pointed out in the annexed claims, it will be understood that various omissions, substitutions, and changes in and widely difierent embodiments of the invention can be made without departing from the scope thereof and it is intended that all matters contained in the above description and shown in the accompanying drawings be interpreted as illustrative and not in a limiting sense.

I claim:

1. An inherently substantially abrasive-free pad for use in polishing glass articles, said pad comprising the vulcanized relatively dense solid product of approximate ly 205 parts by weight of rubber, approximately from 8-12 parts by weight of sulphur, approximately from 5-7 parts by weight of zinc oxide, approximately from 3-5 parts by weight of zinc stearate, approximately from O.30.6 part by weight of thiuram monosulfide, approximately from 4-6 parts by weight of benzothiazyl disulfide, approximately from 5-20 parts by weight of coumarone-indene resin, and approximately from 100-600 parts by weight of corn cob particles.

2. An inherently substantially abrasive-free pad for use in polishing glass articles, said pad comprising the vulcanized relatively dense, solid product of approximately 205 parts by weight of rubber, approximately parts by weight of sulphur, approximately 6 parts by weight of zinc oxide, approximately 4 parts by weight of zinc stearate, approximately 0.4 part by weight of thiuram monosulfide, approximately 5 parts by weight of benzo thiazyl disulfide, approximately 10 parts by weight of coumarone-indene resin, and approximately 200 parts by weight of corn cob particles.

3. The method of making a pad for use in polishing glass articles having controlled surface shapes comprising the steps of making a mixture containing approximately 205 parts by weight of rubber, approximately from 812 parts by weight of sulphur, approximately from 5-7 parts by weight of zinc oxide, approximately from 35 parts by weight of zinc stearate, approximately from 0.30.6 part by weight of thiuram monosulfide, approximately from 4-6 parts by weight of benzothiazyl disulfide, approximately from 5-20 parts by weight of plasticizer, bonding together the particles of approximately from 100600 parts by weight of corn cob of sizes ranging approximately from 35 to 60 mesh with said mixture, and under heat and pressure vulcanizing said mixture to form a relatively dense solid having a surface shaped substantially to the shape of the surface to be polished.

4. The method of making a pad for polishing glass articles having controlled surface shapes comprising the steps of making a mixture containing approximately 205 parts by weight of rubber, approximately 10 parts by weight of sulphur, approximately 6 parts by weight of zinc oxide, approximately 4 parts by weight of zinc stearate, approximately 0.4 part by weight of thiuram monosulfide, approximately 5 parts by weight of benzothiazyl disulfide, approximately 10 parts by weight of plasticizer, adding to this mixture approximately 200 parts by weight ,of corn cob particles of sizes ranging approximately from 35 to 60 mesh, and then under heat and pressure vulcanizing the whole to a relatively dense solid having a surface shaped substantially to the shape of the surface to be polished.

5. An inherently substantially abrasive-free pad for use in polishing glass articles consisting of the vulcanized product of approximately 100 parts by weight of butadiene-acrylonitrile copolymer rubber, approximately 100 parts by weight of a blend of butadiene-acrylonitrile copolymer and polyvinyl chloride, approximately 4 parts by weight of sulphur, approximately 6 parts by weight of zinc oxide, approximately 5 parts by weight of benzothiazyl disulphide, approximately 4 parts by weight of zinc salt of coconut oil fatty acids, approximately 20 parts by weight of chlorinated diphenyl, approximately 20 parts by weight of diglycol sebacate, approximately 50 parts by weight of clay, and approximately 250 parts .6 by weight of corn cob particles, said vulcanized product being a relatively dense "solid mass shaped to be useful for polishing said glass articles.

6. An inherently substantially abrasive-free pad for use in polishing glass articles consisting of the vulcanized product of approximately 75 parts by weight of butadiene-acrylonitrile copolymer rubber, approximately 70 parts by weight of a blend of butadiene-acrylonitrile copolymer and polyvinyl chloride, approximately 10 parts by weight of sulphur, approximately 6 parts by weight of zinc oxide, approximately 5 parts by weight of benzothiazyl disulphide, approximately 4 parts by weight of zinc salt of coconut oil fatty acids, approximately 200 parts by weight of corn cob particles, approximately 60 parts by weight of polysulfide type synthetic rubber polymer, approximately 10 parts by weight of coumarone-indene resin, and approximately 0.4 part by weight of tetramethyl thiurammonosulphide, said vulcanized product being a relatively dense solid mass shaped to be useful for polishing said glass articles.

7. An inherently substantially abrasive-free pad for use in polishing glass articles consisting of the vulcanized product of approximately parts by weight of butadiene-acrylonitrile copolymer rubber, approximately 50 parts by .weight of a blend of butadiene-acrylonitrile copolymer and polyvinyl chloride, approximately 10 parts by weight of sulphur,-approximately 6 parts by weight of zinc oxide, approximately 6 parts by weight of benzothiazyl disulphide, approximately 4 parts by weight of zinc salt of coconut oil fatty acids, approximately 250 parts by weight of 'corn cob particles, approximately 50 parts by weight of polysulfide type synthetic rubber polymer, approximately 15 parts by weight of coumarone-indene resin, and approximately 0.4 part by weight of tetramethyl thiuram monosulphide, said vulcanized product being a relatively dense solid of controlled shape.

8. An inherently substantially abrasive-free pad for use in polishing glass articles, said pad comprising the vulcanized relatively dense solid product of Approximate Ingredient Parts By Weight bonding material from the group consisting of natural 200 to 205.

rubber, butadiene-aerylonitrile copolymer rubber, or- 1 game polysulphlde rubber, blend of butadiene-aeryloptlltrilefcopolymer and polyvinyl chloride, and mixtures ereo sulphur 4 to 12. Zinc oxide 5 to 7. zinc salt of fatty acid 3 to 5. thiuram monosulphide 0.3 to 0.6 benzothiazyl disulphid 4 to 6. plasticizer l 5 to 20. cellulosic particles from the group consisting of corn cob 100 to 600.

and wood flours.

9. An inherently substantially abrasive-free pad for use in polishing glass articles, said pad comprising the vulcanized relatively dense solid product of hp roximate Ingredient P rts By Weight bonding material from the group consisting of natural 200 to 205.

rubber, butadiene-acrylonitrile copolymer rubber, or-

game polysulphide rubber, blend of butadiene-acrylortitiltrilefcopolymer and polyvinyl chloride, and mixtures ereo and wood flours.

the polishing surface of said pad being formed with a plurality of grooves.

10. An inherently substantially abrasive-free pad for use in polishing glass articles, said pad comprising the vulcanized relatively dense solid product .of

the p lishing su f o ai p d b ng orme with a plurality of grooves.

Ingredient bonding material {mm the group consisting of natural rubber, .butadiene-acrylonitrile .copolymer rubber, organic poly sulphide rubber, blend olibutadiene acry- :lztlilnitrilecopolymer and-polywinylchlonde, andmlxtures ezeof.

plasticizer corucob particles,

'11. An inherently substantially abrasive-free pad for use in polishing glass articles, said 113d comprising the vulcanized relatively dense 'solid product of EA Q QQ References Cited in the file .of this patent fgg g UNITED STATES PATENTS 494,472 Gardner Mar. 28, 1893 200101205. 1,953,983 Benner s Apr. 10, 1934 2,318,578 .Bal zlet al. May 11, 1943 2,378,630 Hill June 19, 1945 2,384,684 Kistler Sept. 11, 1945 Ag -l 2,388,568 Penning Nov. 6, 1945 2,8, 2,434,314 Felker Jan. 13, 1948 0.3150 0.6. 2,450,433 Leeman .Oct. 5, 1948 3:83 2,582,741 Ayers Jan. 15, 1952 IOU/$0600. FOREIGN PATENTS 117,723 Australia Nov. 3, 1943 OTHER REFERENCES Ingredient bondingrnaterial from the group consisting of natural "rubber, butadiene-acrylonitrile lcopolymer rubber, organic ,polysulphide rubber, .blend.ofbutadiene-agrylon'itrile copolymer and polyvinyl chloride, .andmixtures thereof.

sulphur zinc oxide zinc salt of fatty acid thiurammonosulphide benzothiazyl disulphide 'plaszicizen 1 corn cob particles Article dealing with Characteristics, Properties and Approximate Applications of .Geon ,Polyblend .by J. E. ,Pi'ttenger and lwi f G. F. Cohan, page 5631 5111 Rubber Age, August, 1947. mg Modern Plastics ,No. 32, vol. 25 October 1947, pages 91 and 96. -200to 205.

41:0 12. 5-110 7. 3-t0 5. 0;3-t00.6. .4to 6.

Patent Citations
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Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US2733138 *Jun 14, 1950Jan 31, 1956 Agricultural residue abrasives
US3149442 *Mar 15, 1961Sep 22, 1964Jr Joseph H MackayFinishing articles and support members therefor, finishing materials and method of making same
US4019289 *Feb 23, 1976Apr 26, 1977Clayton Paul KorverReplaceable lens surfacing pad with integral wear indicating pattern
US4096131 *Mar 15, 1976Jun 20, 1978Albright & Wilson LimitedSilanized polysulfide, moisture curable
US5489233 *Apr 8, 1994Feb 6, 1996Rodel, Inc.Polishing pads and methods for their use
US7140088Feb 23, 2006Nov 28, 2006Toho Engineering Kabushiki KaishaTurning tool for grooving polishing pad, apparatus and method of producing polishing pad using the tool, and polishing pad produced by using the tool
US7516536Dec 12, 2005Apr 14, 2009Toho Engineering Kabushiki KaishaMethod of producing polishing pad
Classifications
U.S. Classification51/298, 51/303, 51/299, 524/13, 106/164.3, 524/14, 451/118, 451/921, 524/15, 524/925
International ClassificationB24D13/00
Cooperative ClassificationB24D13/00, B24B37/02, B24B37/26, Y10S524/925, B24B13/01, Y10S451/921
European ClassificationB24B37/02, B24B13/01, B24B37/26, B24D13/00