US2644280A - Sanding disk accessory - Google Patents

Description

July 7 1953 v.1. R. o'NEn., JR A 2,644,280

SANDING DISK ACCESSORY Filed Sept. 13, 1950 2 Sheets-Sheet 1 Fm. I

IN V EN TOR.

JOSEPH R. O'NEIL JR.

Wa-@7 ATTORNEY July 7, 1953 J. R. oNElL, JR 2,644,280

sANDING DlsKAccEssoRY Filed sept. 13, 195o 2 sheets-sheet 2 INf/ENTOR. JOSEPH R. ONEIL JR.

ATTORNEY Patented July 7, 195,3k

SANDING DISK ACCESSORY Joseph R. oNeil,` Jr., Niagara Falls, N.,Y., as-

signor to The Carborundum Company, Niagara Falls, N. Y.,a corporation of Delaware `Application September 13, 1950, Serial No. 184,613

Claims.

. l 1 This invention relates to a'new and improved sanding disc accessory which is useful in conjunction with all types of rotary surfacing, polishing, sanding and grinding devices and the like.

In the use-of all types of portable sanding and grinding equipment employing discs, buffs, grinding wheels and other abrasive orpolishing media, it is normally the practice to secure the abrading or surfacing means to the machine spindle with y or without a threaded sander pad by means of al threaded nut of one design or another, or to employ draw stringsv or similar means to maintain'the position of the bumg media or the like. Practices of this type have been acceptable under many operating conditions, but from a method and equipment viewpoint, these Various mount'- ing techniques heretofore used have interfered with the development of unusually good surfaces and'nishes since the threaded nut or comparable mounting has prevented the obtaining of a satisfactorily flat contact in substantially all cases. Even in those circumstances where the threaded nut'is recessed, as in the use of specially designed sanding discs, there is a substantial unsupported depressed area to permit the recessing. of the threaded nut referred to above. The use of such portable equipment employing coated abrasive discs or the like often presents the further problem ofmaintaining the abrasive medium in perfectly "at condition since the center may be drawn down excessively or the curvature ofthe sanding disc may be either convex or concave as mounted so as to produce high and low spots which interfere seriously with the finish to be obtained. A y Y It is further noted that the use of such threaded nuts and/or draw strings requires the expenditure of a substantial amount of time in the replacement of the worn-out abrasive article or material on the spindle orv shaft of thev abrading device.

lit is an object of the present invention to provide an improved sanding disc accessory which will constitute an improvement over the various mounting means lheretofc'nre .employed as described labove With a' resultant' improvement in the development of superior finishes.

It is a further object to provide a sanding disc accessory of the aforesaid improved type which will offer additional improvements in respect of (a)v The time and effort required to replace the worn-'out abrasive or surfacing means used therewith, and l Y (b) The uneven, drawn, curved or curled characteristics commonly produced with otherv types of conventional equipment and practices.

In accordance with the present invention an improved sanding disc accessory is provided comprising a resilient cushion or pad of substantial thickness which is precoated on one or both at sides with a'pressure-sensitive adhesive cementl the cement being protectedfrom-the accretion or accumulation of dust-and dirt by the attachment upon the pressure-sensitive adhesive-coated surface or surfaces of a removable layer or-layers of thin protective sheet material. For example, a resilient layer of soft foam rubber approximately 1 in thickness is coated with pressurefsensitive adhesive cement on both sides, the one sidebeing lsufficiently coatedV to hold a conventional coatedv abrasive disc or buff or felt, or any sheet materiall to which abrasive particles are bonded,

coated, included or applied inany manner whatsoever, while the other side is coated either over the entire surface, or concentricallyonly, to asuf cient degree to hold the article in a concentric position on atypical sander pad of rubber, sisalA fibre or other* conventional body material. The foam rubber or other type of porous or soft rubber body constituting at least the greater part of the overall thickness of the sanding pad as herein described is'normally of extreme softness so Vas to provide the maximum amount vof resilience or cushioning action for Athe abrasive or surfacing w device With which it is used. For example, the foam rubber or other type'of soft, resilient material used toY make up the major` part of the bodyof the present sanding pad should normally give a very loW Shore durometer reading in the neighborhood of 5 to l0 or less, although under certainA conditions Aof use such as sanding -primer surfacers, Sealers, and the like on fiat surfaces, the basic body of the deviceA can be so provided asto Yhave higher'durometer readings even as high as 50.

` I-t is preferred to provide the sanding pads of the present invention with greater durability against breakdown which might be caused by frequent removal and replacement of the abrasive materials usedtherewithv byY constructing the sanding pad body of a composite oflayers Wherein themain body or thickness of the pad is composed of a foam or other porous or soft rubber of extremely low durometer reading, or inother Words, a foam or other porous or soft rubber of maximum softness and compressibility', faced on one or both sides with a relatively thin layer of -porous rubber of higher durometer reading, i. e., having greater stiifness and less compressibility, or a thin layer fllm'or skin of soft rubber suchas can be obtained by spraying the surfacerof the foamporous or soft rubber making up the main body of the article with a thin layer of natural Vor synthetic rubber latex or by the adhesive attachment of a thin layer of soft vulcanized, tough rubber such as a layer of soft polychloroprene.

Resilient sanding pads as above described can be made by preparing or obtaining foam rubber or otherwise porous rubber of suitable Vdurorneter reading in sheet form and dyeing or otherwise cutting disc shapes of the desired diameter from the selected sheet material, A surface layer of the desired thickness of stronger porous rubber or a lm of soft rubber can be adhesively applied, when desired, to either or both surfaces before or after cutting the disc shaped pieces from the sheet material. Y ,Y

As an alternative to making the herein ,described sander pad from porous rubber sheetstock the desired pad body structure can be formed by a molding operation wherein the pad is molded directly to the desired shape in a suitable mold vfrom natural or synthetic rubber of suitable composition to yield a porous rubber body structure of the desired softness and resilience. l

A Afurther modification of the presentV invention is rthe construction of aresilient, cushioningsander Ypad accessory in which the mainporous or soft Vrubber body structure `of the device is replaced by a substantially fiat, circular, hollow, soft rubber bag o f the desired diameter and thickness,.the soft rubber bag being either inflated with air or.other.gas or filled with fragments of porous or soft rubber. The outer iiat surface or surfaces of the hollow bag is, asin the case of `the foam rubber body structures described above, coated ...with pressure-sensitive adhesive which is in turnprotected by a removable layer of thin protective sheet material.

The pressure-sensitive adhesive which is applied to one or both of the fiat sides of themain body structure of the pad can be selected from the manyA conventional pressure-sensitive adhesive cements now available on the market or it can be one of the specific compositions described later herein, in either case, however, being an adhesive which will providek the necessary strength to hold the coated abrasive sander disc or other surfacing material to the front face of the pad during use, and, where theV pressuresensitive adhesive is also applied to the back side of the pad or cushion it will berof sufficient strength to hold the pad to the supporting sander head.v Obviously, the pressure-sensitive adhe sive used for one side'of the pad may be the same (ir-different from that employed on the opposing side. The pressure-sensitive 'adhesive can be applied by knife coatingLbrush coating, roll coating, spray coating or other means of coating'common to the art..Y After the material is coated" it is either air-dried or oven-dried, after which a thin layer of protective sheet material is attached to the pressure-sensitive adhesive-coated surface to protect it from ther accumulation of dust and dirt and to permit convenient and satisfactory handling of the article. r y

In using the herein described pads the pro,-4 tective coating on the rear flat side of the pad is removed and the pad positioned as near center as possible on a conventional flexible sander head supporting pad of rubber, sisal fibre orA other type, the pad being held in place by means of the exposed layer of pressure-,sensitive adhesive. The protective coating of sheet material o n the other side of the pad is thenfremoved andthe coated abrasive sheet material, orV other surfacing me-..

4 dium to be used therewith, is applied to the exposed pressure-sensitive adhesively-coated surface. As far as the herein described sander pad accessory is concerned it can be used under either wet or dry surfacing conditions depending entirely upon the nature of the polishing or surfacingmedia used in `conjunction with the pad. f

In order that the invention may be more clearly understood, reference is made to the drawing, in which:

Figure 1 is a perspective view of a foam rubber sander disc accessory made in accordance with the present invention;

.Figure 2 is a vertical sectional view through the line 2*-2 of Figure 1;

Figure 3 is a view similar to Figure 2 showinga modified form of sanding disc accessory;

Figure 4 is a view similar to Figure 2, showing a still further modification of the present invention;

Figure 5 is a view similar to Figure 2 showing still another modification of the present inven.-` tion;

Figure 6 is a back plan viewof a molded sanding disc accessory rmade in accordance with the present invention; Y Y

Figure 7 is a vertical sectional view through the line I-- of Figure 6; and

Figure 8 is a view similar to Figure 2, but

vshowing a sandingv disc accessory in which the main body structure is constructedkof a hollow inflated soft rubber pad in place of the porous rubber body structures ofthe previously shown modifications. v

Referring furtherk to Figures. 1 and 2 of the drawing, the simplest and most inexpensive type of sander disc pad which can be made following the practices and principles of the present invention is as shown and is composed of a circular resilient layer ill ofrnatural latex foam rubber of very low Shore durometer reading and approximately FA" to 1" thickness. Although latex foam rubbers are preferred because of their greater softness-resilience and yieldability, the foam rubber can be replaced by a layer of soft vulcanized natural rubber or synthetic rubber suchas polychloroprene when the pad V,is to be used where `maximum softness andvresilience are not required. The foam or soft rubber body structure lil is coated on both flat sides with a layer of pressure-sensitive adhesive H, which is shielded byk a removable thin protective sheet material I2 such as disc shaped sheets of tough creped paper. However, any other relatively inexpensive protective sheet material can be used although it is preferred to use a material which will be creped or otherwise provided with a rugose surface so as to facilitate the removal of the protective sheet material when desired and at the same time permit a satisfactory and thorough protection to the pressure-sensitive adhesive. If desired, Vthe protective sheet material on the one side of the body structure can be a layer of the abrasive-coated sheet 'material which is ultimately to be used in conjunction with the sander disc accessory pad. v

By pressure-sensitive adhesive is meant any adhesive which under ordinary atmospheric conditions Vis tacky and non-dryingV and in a condition such that adhesion is secured by the application of Slight pressure and. without the necessityof activating the adhesiveby: ASolvents or otherwise treating it for` firm adherence to,.or

removal from surfaces. Examples of such permanently tacky adhesive are as follows-z Paraplexis an alkyd resin manufactured` and Vsold by the Resinous Products Company of Philadelphia,V Pa.

Example II Per cent Rubber 80 Rosin 16 Zinc oxide 4 Example III' y Per cent Pale crepe rubber 45 Zinc oxide 35 Hydrogenated rosin 20 `In these compositions, the rubber and the cellulosederivative provide strength to the adhesives while the resins and the zinc oxide make the adhesives tacky.

The adhesives are dissolved in a suitablev solventY and applied in solution, the solvent being removed by evaporation.

A commercially available pressure-sensitive adhesive cement which has been found satisfactory in carrying out the present invention is that known and sold by the Flintkote Company under they trade-mark designation as Syntex 11563EJ, and which is understood to be a pressure-sensitive adhesive based upon a mixture of an aqueous reclaimed rubber dispersion and a suitable rubber tackifying resin dispersion. 1

Other pressure-sensitive adhesive compositions which can be used in carrying out the present invention are those described in U. S. Reissue Patent No. 19,128 wherein the preparation and compositions of a number of suitable pressure-sensitive adhesives are fully described.

Although the sanding disc accessory pad shown in Figures 1 and 2 is highly satisfactory and renders commendable performance under many conditions of use and is often favored because of its relatively inexpensive structure, a preferred form of sanding disc accessory or pad made according to the present invention is that shown in Figure 3, which is more durable and therefore suitable for use under more exacting conditions. The pad shown in Figure 3 is of substantially the same overall thickness as that shown in Figures 1 and 2 and the main body structure of the pad is likewise composed of a layer I of natural latex foam rubber of very low Shore durometer reading. In other words, the layer of foam rubber I0 is very soft, highly compressible and resilient, and provides the article with a maximum cushioning ability. However, the foam rubber body structure is faced on both flat sides with relatively thin layers, usually from 11e t0 1/4 of an inch each in thick- AnessV permanently bonded to the main body structure I0. These surface'layers `III have. a higher Shore durometer hardness and are therefore less compressible, stronger and more resistant to breakdown than the main body layer IIJ and as facings protect the main body structure from destruction during the course of the removal of the protective sheet material or operating sheet material from the upper surface as Well as protecting the pad Vduring its removal from thepermanent sander headA supporting lar pad differing from -that shown ldisc which latter maybe attached totherback ofthe pad by means `cfa suitable adhesive cement vof either the permanent or pressure-sensi:-` tive type. 'Onematerial which hasr been found highlyv satisfactory' for facing ypurposes is -a sheet of polychloroprene closed cell porous rubber. 1/8 of an inchinjthckness'. Figure 4 shows va simiin Figure. v3 only; in thatithe protective facing .of polychlorof prene or. other relatively .toughporous rubber facingV is'provided. on the top side only of the accessory pad. Again', the sisal bre. o-r other permanent. supporting disck can be attached-to the back side of the accessory pad `by a per,- manent adhesive or by means of a pressuresensitive adhesive, either as the accessory .pad is supplied or later by the user. 1

Sanding disc accessory pads of the type-shown in A'Figures 3 and 4 have been found capable of use under rotating speeds as high as 2500 revolutions per minutev although the recommended operating speeds for sanding operations involving the use of'such pads or cushions are between 900 and 1300 revolutions per minute. yFurthermore, discs of the described construction-are of suiiicient strength due to the` facing layers I4 to permit repeated removal of worn out abrasive sheet material from the surface and replace: ment by new abrasivel coated material without breakdown of the pad structure.

1 A vmodified form of sanding disc accessory `pad such as that shown in Figure 5 can be made in which the main resilientbody portion I0 of foam rubber is provided withxsurface facingsY I5 of soft rubber'in place of the facings I4 ofporous rubber embodied in the article of Figure 3.2 Thethin soft rubber facings I5y of the article shown in Figure 5 can be applied to the foam rubber body on both sides as shownin Figure 5 or, ifdesired, the Vsoft rubber facing may be applied to one side only of the foam rubber body. One mannerof providing a soft rubber skin or facing layer is to apply a thin latex over the surface of the foam rubber and air-dry the thusly coated foam rubber disc in air followed by a suitable oven cure at 200 F. for 2 or more hours to set the adhesive latex film to a non-tacky condition. The resulting soft rubber coated pad is then coated with a layerrof pressure-sensitive adhesive II which is. allowed to air-dry an hour in air and then dried in an oven for 2 hours at approximately 200VF. in the manner described in connection with the method of making the previously described pads. -The pressure-sensitive adhesive-coated surface is then protected by attaching the sheet or sheets of thin protective sheet material I2 which can be any of the protective sheet materials pre-v viously set forth and is preferably a creped paper or .other crinkled fibrous materialrtol facilitate its removal. l

The foam rubber or other porous or soft rubber. main body structures of the pads described above and shown in Figures 1-5, inclusive, have been obtained by dyeing or otherwise cuttingthe' foam, porous or soft porous or soft rubber sheet stock in the form of circular discs of the desired diameter size. However, similar disc shapes can be alternatively obtained by a molding procedure wherein the disc shaped body structure of the pad is obtaineddirectly by molding to the desired size and thick-v ness. One specific modificationy of a molded foam or porous rubber pad made in laccordance with the present invention and` embodying cer-l film of natural or synthetic rubber rubber from suitable foam,

, syntheticrubber latices.

.tain additional structural features is that shown inr Figures 6 and 7. As there shown the foam latex body portion I6 of the pad is molded directly to shape by filling a mold of the required shapeV with a natural or synthetic rubber` latex composition which has been mechanically frothed or. contains chemical foamingV agents and which' when cured or set in the mold will form a porousl body structure conforming to the desired shapev'and in the course of its molding operation will '.be provided with an impervious tough rubbesurface film or' skin I1 entirely surrounding thecentral porous rubber body of the molded pad. VSuch moldedpads can be made of 4the same simple disc shapes shown for the. pads rpresented'in Figures 1-5, inclusive, and (can be likewise provided, if desired, `with a sisal or other supporting padof the same or lesser diameter permanently cemented tothe backside of the pad by permanent or pressure-sensitive adhesive cement. The molded pads can also be provided,

if desired, with a tapered side which tapers inwardly toward the back side of the disc so as to provide an added degree of yieldability to a narrow-peripheral portion of the pad. However, the specific pad shown is featured by having the back face of the pad recessed to provide a central circular cavity I3 of sulhcient depth to accommodate a latex impregnated sisal fibre reinforcing pad I9 to which is mounted a .rigid threaded mounting flange 20.. The sisal fibre pad I9 is also threaded to provide additional mounting security. The frontal face of the molded pad I6 is coated with a layer II of pressure-sensitive adhesive of the type and by the process Vdescribed in connection with the pads made according to Figures 1-5, and similarly provided with an attached thin protective sheet material I 2. The

pad I9 is cemented or bonded in place by means of a layer 2| of rubber cement of any conventional type as well known in the art.

VA still further modication of the present invention is the sanding disc accessory shown in Figure 8 in which the resilience or cushioning effect of the pad is obtained by means of a molded lfiat circular inflated soft rubber bag 22 and in which the fiat faces of the inflated bag are coated with the same pressure-sensitive adhesive films used in the previous modifications, the pressuresensitive adhesive being protected by attached layers I2 of protective sheet material.A Instead of using a hollow inflated soft rubber bag as the main body of the pad the hollow bag may be filled with fragments of porous or sof-t rubber of suiTcie-nt softness and in sufcient quantity to provide the desired degree of softness and cushioningelect to the pad.

' In making the various specific types of sander disc accessory pads hereinabovedescribed where-- in the main body portion of the pad is composed of a thick layer of porous or soft rubber most satisfactory results have been obtained with the use 'of `a foam rubber made from natural and/or Such porous foam rubbers, which are made directly from the aqueous rubber latex possess the unusually high degree of softness and resilience, and maximum Vcompressibility desired to provide the greatest amount of cushioning and yieldability in lthelinal product.

' This high degree of resilience and compressibility are desirable so that the surfacing material will follow the contours lof the work'being surfaced with a minimum of scratching accompanied by a maximum efficiency in removing 'surface irregularities and imparting a high degree-of satisfactory and uniform surface tothe finished article. Although for the above reasons it is preferred to use foam rubber for the main body portion of the herein described pads, chemically blown sponge rubbers or expanded rubbers, either natural or synthetic, can be used providing the material is of suiiicient softness and compressibility. However, the various chemically blown or expanded sponge rubbers commonly available Ycommercially are usually too stiff and lack the required resilience of maximum efliciencywhen incorporated in products made according to the present invention except for those instances where the conditions of use may be more severe or rugged or a lesser amount of cushioning effect is soughtl A detailed description and explanation of-'the Various foam `rubbers which it is preferred to use in carrying out the present invention, together with an explanation of the diferences between those foam rubbers and other types of chemically blown Vor expanded porous rubber products, is set forth'in the India Rubber World, volume 121, No.4, on pages 419-423.

Regardless of the specic type of rubber sanding disc accessory pad constructed in accordance with the various examples hereinabove set forth the pad offers the advantage of providing a smooth, uniformly even mounting surface'for th polishing or sanding medium, which notfonlyobvia'tes the vuse, of recessed threaded mounting nuts, circumferential draw strings and other previously known mounting devices and all vtheir inherent disadvantages butY the pads madeaccord'in'g to the teachings herein moreover pro# vide a most expeditious vmeans of removing la worn-out polishing or sanding material when'it has served its useful life and replacing it with a new surface sheet material with a minimum of effort and expenditure of time. Whenever necessary to do so the layer of pressure-sensitive adhesive used to provide such effective attachment can be'restored to substantially its original effectiveness by an application of an additional thin layer of pressure-sensitive adhesive cement which is preferably one of an emulsion type, many of which are available on the market. One such pressure-sensitive adhesive which has been found satisfactory for such use and which can beapplied by spraying technique is that known and sold by the Pierce and Stevens Company as Pierce and Stevens No. B9189 Cement.

The sanding disc be ined the crushing of auto-momie' bodies, furniture, radio and television cabinets, tile, tile board, wall board and elsewhere. As already pointed .out'the herein disclosed accessory pads the claims, it is intended to include by that term not only natural rubber derived from natural rubber latex, but to also include those various synthetic rubbers available commercially, such as the various butadiene-styrene copolymers, butadiene-acrylic nitrile copolymers, polychloroprene and the like either separately or combined or blended invarious proportions with naturalrubber.

Having described the invention in detail, it is desired to claim:

1. A sanding disc accessory comprising a circular `compositepad comprising a main body portion of foam rubber faced on at least one side with a relatively thin layer of porous rubber of substantially higher Shore durometer reading, and having a layer of pressure-sensitive adhesive on at least that side of the pad having the porous rubber facing, said pressure-sensitive adhesive coated surface being protected from the accretion of dust and dirt by the attachment thereon of a removable layer of thin protective sheet material.

2. A sanding disc accessory according to claim 1, and having a resilient supporting pad adhesively secured to the rear face of said foam rubber body portion. Y

3. A sanding disc accessory comprising a circular composite pad comprising a main body portion of natural latex foam rubber faced on at least one side with a relatively thin layer of porous polychloroprene rubber of substantially higher Shore durometer reading, and having a layer of pressure-sensitive adhesive on at least that side of the pad having the polychloroprene facing, said pressure-sensitive adhesive coated surface being protected from the accretion of dust and dirt by theattachment thereon of a removable layer of thin protective sheet material.

4. A sanding ldisc accessory comprising a -cirgular composite pad comprising a main body portion of foam rubber faced on at least one side with a relatively thin, tough layer of material having a Shore durometer reading substantially higher than that for the main body portion of the pad and a toughness substantially in excess of that of the skinA of a molded foam rubber body, and having a, layer of pressure-sensitive adhesive on at least that side of the pad having the tough'facing layer, said pressure-sensitive adhesive coated surface being protected from the accretion of dust and dirt by the attachment thereon of a removable layer of thin protective sheet material.

5. A sanding disc accessory comprising a circular composite pad comprising a main body portion of foam rubber faced on at least one side with a relatively thin layer ofsoft rubber of substantially higher Shore durometer reading than that of the main body portion of the pad and having a toughness substantially in excess of the toughness of the normal skin of a foam rubber molded article, and having a layer of pressure-sensitive adhesive on at least that side of the pad having the soft rubber facing, said pressure-sensitive adhesive coated surface being protected from the accretion of dust and dirt by the attachment thereon of a removable layer of thin protectivev sheet material.

JOSEPH R. oNEIL, JR.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 871,942 Leavitt Nov. 26, 1907 1,212,628 Gowlland Jan. 16, 1917 2,059,583 Jackson et al. Nov. 3, 1936 2,189,472 Peterson Feb. 6, 1940 2,227,588 'Kemp Jan. 7, 1941 2,286,208 Kirchner June 161942 2,376,783 Kingman May 22, 1945 Y2,447,102 Strand Aug. 17, 1948 2,480,217 Burnham Aug. 30, 1949 2,485,295 Larson Oct. 18, 1949 FOREIGN PATENTS Number Country Date 501,744 Great Britain Mar. 1, 1939 730,509 France May 10, 1932

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