US3214253A

US3214253A - Abrasive article backed with stretchable-compressible material

Info

Publication number: US3214253A
Application number: US295265A
Authority: US
Inventors: Jr Wilfred M Mccord
Original assignee: Vermont American Corp
Current assignee: Robert Bosch Tool Corp
Priority date: 1963-06-26
Filing date: 1963-06-26
Publication date: 1965-10-26
Anticipated expiration: 1982-10-26

Description

Oct. 26, 1965 w. M. M coRD, JR 3,214,253

ABRASIVE ARTICLE BACKED WITH STRETCHABLE'COMPRESSIBLE MATERAL Original Filed April 18. 1960 IN V EN TOR.

ZZ/dg 7120517. fc Cora/ 5M 2M5 6W United States Patent O ABRASHVE ARTICLE BACKED WITH STRETCH- ABLE-COMPRESSIBLE MATERIAL Wilfred M. McCord, Jr., Louisville, Ky., assiguor to Vermont American Corporation, a corporation of Kentucky Continuation of application Ser. No. 22,860, Apr. 18, 1960. This application June 26, 1963, Ser. No. 295,265 3 Claims. (Cl. 51-297) This application is a continuation of my copending application, Serial No. 22,860, filed April 18, 1960, now abandoned, and relates to a new and improved abrasive article and a new and improved method of making the same. While the article is well adapted for manual use, it is particularly suited for machine use for removal of stock and for surface finishing of a wide variety of materials such, for example, as woods, plastics, cements and even metals.

'Heretofore it has been common to employ sheets of paper, or sometimes cloth, to which has been glued grit material in the form of grains or particles of sand, aluminum oxide, metal carbides, diamonds and the like. The grit material comes in various sizes and is distributed in various densities upon the sheets. However, such sheet material, particularly when formed of paper, has had a short life because of its lack of strength and tendency to tear or crack. Also the grit material has a tendency to become loosened after a short working period.

While the foregoing disadvantages of prior abrasive articles may have been mainly an inconvenience for hobbyists and home workshop use, they have been an expensive addition to the cost of production in industrial operations, not merely because of the short life of the abrasive article but even more so because of the down time of the machines employing them, and the cost of labor in frequently replacing the articles.

To overcome the disadvantages of the prior articles mentioned above, a more permanent type of abrasive article has been provided in which tungsten carbide grit is copper brazed to a thin sheet steel backing. Such an abrasive sheet is much more durable than the ordinary sandpaper and similar products, but it also has certain disadvantages. For example, if the edge of the thin sheet becomes dented, the sheet at that area becomes work hardened and it is very difiicult to eliminate the dent and return the sheet to a truly flat surface. Usually a point or a ridge remains and it will undesirably scratch or scour the surface being worked on. Denting, sharp bending, or similar deformations may occur whether the sheet is being employed manually or in a machine.

In certain machine-uses the abrasive sheet is subjected to repeated flexing at a limited location, more or less along a line, and results in fatigue of the metal, cracking or other failure. For example, in a vibrator sander at the end of each stroke there is a flexing of the metal sheet around a radius near or at the location where the metal sheet is fastened or at a location where the sheet bends around a platen.

Accordingly, it is an object of my invention to provide an abrasive article having a thin sheet metal base which will be protected against the effects of denting, bending, flexing and the like and thereby have its useful life increased and avoid the danger of undesirably scratching or scouring the surface of the material which is being finished. To that end I provide the abrasive sheet with a flexible backing secured to the sheet on the opposite side from the abrasive grit. That backing by reason of its inherent stretchability and compressibility and its greater thickness than the metal sheet serves to spread the stresses, resulting from abrupt contact or bending or flexing, over a greater area of metal rather than letting 3,214,253 Patented Oct. 26, 1965 them be applied along a line or other limited area. To put it another way, the backing resists sharp bends.

The backing also provides a cushioning effect. The cushioning effect is useful when heavy grinding loads are applied, quite apart from bending stresses, since grit fracture and loss of grit is minimized. The backing may be made of fabrics, plastic materials or rubber and of a thickness substantially greater than the sheet steel base. I have found that a tightly woven cotton or other fabric will provide substantial body to the overall article and will stretch or compress as the article is bent or deflected. Any suitable adhesive which is bendable will be satisfactory for joining the backing to the sheet metal base. A rubber backing may be vulcanized to the base.

There is another advantage to the backing particularly when the abrasive article is used in the form of a belt on a belt sander. Most belt sanders have the belt moving over a steel platen and excessive wear can occur on the platen and belt if a steel belt is used directly in contact with the platen. Fire hazard is also a factor when steel belts are used directly at high speed over a steel platen. The backing material therefore will not only provide resilience in passing over the platen but will eliminate steehto-steel contact. The same advantages also inhere when using the abrasive article of my invention in reciprocating platen type of panel sanders.

Other uses and advantages of my invention will become apparent or be obvious from the following drawings when taken in connection with the written description. In the drawings:

FIGURE 1 is a perspective view of an abrasive article in the form of a sheet, the relative thicknesses of the parts of the article not being in true proportion because of the difficulty of depicting the relative thinness of the sheet metal base;

FIGURE 2 is an enlarged fragmentary cross sectional view of the article of FIGURE 1 showing the thickness of the parts in truer proportion; and

FIGURE 3 is a diagrammatic showing of a method of forming the article.

Referring now to FIGURES 1 and 2 an abrasive article in the form of a sanding sheet is indicated generally by the reference numeral 10 and it consists of a thin sheet metal base 11 to which is secured by an adhesive material 12 a flexible backing 13. On the side of the sheet metal base opposite from the backing 13 is secured grit material such as tungsten carbide particles. The grit is preferably copper brazed as at 15 to the base 11. The amount of copper needed for brazing the particles to the base is very little as is known in the brazing art and the particles are secured very strongly to the base 11. The sheet metal base 11 is preferably made of steel and may vary in thickness from about .001 inch to about .008 inch while the flexible backing, in the form of a fabric such as a rather tightly woven cotton may be of a thickness range of about .006.060 inch. Preferably the fabric should be in the ratio of at least approximately 5-1 relative to the sheet metal base. While plastics or rubber vulcanized to the sheet metal base woulld also give a resilience and serve as a suitable backing to prevent sharp bending or other deformation of the sheet metal, I have found that fabric is very satisfactory. It has a stretchability and compressibility as well as a cushioning effect which very satisfactorily distribute any bending forces over a suificiently large area of the sheet metal base as to avoid sharp bends which would tend to fatigue or crack the metal, particularly if the bending forces are repeated as may be the case when the abrasive article is used in sanding machines of various types. Also the fabric backing has a lower coeflicient of friction relative to a steel platen than would be the case with a rubber backing for example.

The adhesive 12 may be a commercial form such as the product identified as EC-1390 and manufactured under U.S. Patents 2,610,910 and 2,918,442. EC-1390 is a solvent type adhesive cement composition comprising a blend of polychloroprene and a normally solid phenoaldehyde resin, such as a condensation product of formaldehy'de and para-tertiary butyl phenol preferably within the proportions indicated in the aforesaid two patents. The adhesive of that type may be sprayed on, but it will be appreciated that the adhesive may be applied by a brush or silk screen. Various adhesives may be employed and some may be thermo-setting and, to a degree, pressure sensitive after being applied such for example as a modified phenolic resin adhesive.

When producing the abrasive article by a continuous method such as illustrated in FIGURE 3, it is preferred to spray on the adhesive. Therefore, while some adhesives would be suitable for painting or silk screening onto the backing member and onto the sheet metal base, they would not be as suited for a continuous process in forming the abrasive article as a long strip or belt.

Turning now to FIGURE 3, the sheet metal base consisting of a long thin steel strip 11, which may be drawn from a roll (not shown), is first spray coated on the side having the grit in order to give a pleasing copper-lacquered finish. That finish however, is for appearance and is not in any way a bonding means for the grit. I prefer to spray that onto the grit side of the sheet metal base by a spraying mechanism 16 which is positioned at a location ahead of the mechanism for spraying the adhesive on the opposite side of the sheet metal base which latter spraying mechanism is diagrammatically indicated at 17. A Web or strip of woven, or other fabric backing material 13' from a roll (not shown) may have the adhesive sprayed on it by a spraying mechanism 18 With the latter mechanism either being spaced from spraying mechanism 17, as shown, or disposed substantially adjacent mechanism 17. I have found that the two spraying mechanisms 17 and 18 need not be juxtapositioned in order for the bonding to be satisfactory.

After the fabric backing 13 and the sheet metal strip 11' have had the spray coating of adhesive they become slightly tacky prior to being passed together in overlying relationship through a pair of rollers 19 which press the two strips together so that the adhesive may bond them. Any suitable aligning means may be provided for guiding the strips 11' and 13', and the rollers 19 may serve as the means for drawing strips 11' and 13 from their rolls. With some adhesives it may be desirable to have the rollers heated, but with the Minnesota Mining and Manufacturing Company adhesive EC1390, that is not necessary. The abrasive strip with the backing bonded to the sheet metal base may then be coiled up on a suitable support 20 by guide means (not shown). I prefer to coil the strip with the fabric backing outside since it has 4 greater stretchability and there is less likelihood of slip between the base 11 and backing 13.

While I prefer to carry on the lacquer spraying and the adhesive spraying continuously and simultaneously at separated points along the travel path of the sheet metal base strip, it will be appreciated that the lacquer coating might be entirely done first or it might be done after the backing is secured to the sheet metal base. Also, While I prefer to spray adhesive to both the backing 13 and the base 11', bonding could be performed by spraying one or the other of the adjoining surfaces of the sheet metal base or fabric backing.

It will be appreciated that variations in the article and method of making the same are possible, in the light of my disclosure, and I do not intend to be limited to the specific article or method illustrated or described except insofar as the claims appended hereto are so limited.

I claim:

1. An abrasive article of manufacture comprising a relatively thin sheet of steel providing a generally planar working surface on one side and being of generally uniform thickness and being normally non-stretchable in use but being subject upon sufiicient impact or bending to become permanently deformed out of the plane of the working surface, and said thin sheet having a flat marginal portion exposed during usage to such possible de formation of the working surface, abrasive grit particles copper brazed to said one side of said thin sheet, and flexible deformation-resisting backing means of stretchable and compressible non-metallic material adhering to and overlying the other side of said thin sheet but not extending beyond its marginal portion, said backing means being coextensive with the thin steel sheet and having sufficient bulk as to distribute bending forces exerted on the steel sheet over a large area, the thickness range of the thin steel sheet being approximately 001-008 inch and that of the backing being approximately .006.060 inch and at least five times the thickness of the thin sheet sheet.

2. The article of claim 1 wherein the backing means adhering to the thin steel sheet is of woven fabric.

3. The article of claim 1 wherein the backing means adhering to the thin steel sheet is rubber.

References Cited by the Examiner UNITED STATES PATENTS 2,128,906 9/38 Benner et al. 51-298.1 2,187,743 1/40 Kirchner et al. 5-1-2981 2,252,587 8/41 Tone et al. 51298.1 2,906,612 9/59 Anthony et al 51-309 3,014,795 12/61 Schmidlin 51297 ALEXANDER H. BRODMERKEL, Primary Examiner.

MORRIS LIEBMAN, Examiner.

Claims

1. AN ABRASIVE ARTICLE OF MANUFACTURE COMPRISING A RELATIVELY THIN SHEET OF STEEL PROVIDING A GENERALLY PLANAR WORKING SURFACE ON ONE SIDE AND BEING OF GENERALLY UNIFORM THICKNESS AND BEING NORMALLY NON-STRETCHABLE IN USE BUT BEING SUBJECT UPON SUFFICIENT IMPACT OR BENDING TO BECOME PARMANENTLY DEFORMED OUT OF THE PLANE OF THE WORKING SURFACE, AND SAID THIN SHEET HAVING A FLAT MARGINAL PORTION EXPOSED DURING USAGE TO SUCH POSSIBLE DEFORMATION OF THE WORKING SURFACE, ABRASIVE GRIT PARTICLES COPPER BRAZED TO SAID ONE SIDE OF SAID THIN SHEET, AND FLEXIBLE DEFORMATION-RESISTING BACKING MEANS OF STRETCHABLE AND COMPRESSIBLE NON-METALLIC MATERIAL ADHERING TO AND OVERLYING THE OTHER SIDE OF SAID THIN SHEET BUT NOT EXTENDING BEYOND ITS MARGINAL PORTION, SAID BACKING MEANS BEING COEXTENSIVE WITH THE THIN SHEET AND HAVING SUFFICIENT BULK AS TO DISTRIBUTE BENDING FORCES EXERTED ON THE STEEL SHEET OVER A LARGE AREA, THE THICKNESS RANGE OF THE THIN STEEL SHEET BEING APPROXIMATELY .001-.008 INCH AND THAT OF THE BACKING BEING APPROXIMATELY .006-.060 INCH AND AT LEAST FIVE TIMES THE THICKNESS OF THE THIN SHEET SHEET.