US 3785094 A
A flexible grinding tool made up a synthetic resin impregnated fiberglass mat with a layer of abrasive grains attached to both surfaces of the mat by a synthetic resin binder containing short fibers of glass, asbestos, ceramic material or graphite therein.
Description (OCR text may contain errors)
1Jn1ted States Patent 1191 Hohhauer 1 Jan. 15, 1974 1 ABRASIVE MEDIUM  Inventor: Rudolf Holzhauer,  References Cied Marienheide/Rh1d., Germany UNITED STATES PATENTS 73 Assigneez Firma August Ruggeberg, RMeIL n an m... Rhmeland Germany 2,768,483 10/1956 Hurst 51 293  Filed: Aug. 25, 1971 3,529,945 9/1970 Charvat 1 51 295 2,2 4,716 6 1942 B 51 297 211 Appl. NO.Z 174,655 8 Related US. Application Data Primary ExaminerDona1d G. Kelly  Continuation-impart of S61. No. 115,164,, Feb. 16, Browdy et D  ABSTRACT 1 Foreign Apphcatmn Pnomy Data A flexible grinding tool made up a synthetic resin im- May 11, 1971 Germany 1. P 21 23 126.5 pregnated fi gl mat i a ay of abrasive grains attached to both surfaces of the mat by a syn-  U.S. CI. 51/401, 51/206 NF thetic resin binder Containing Short fibers of glass,  [Illbestos ceramicmateria] O1. g p therein  Field of Search 51/206 NF, 400, 401,
- 7 Claims, 2 Drawing Figures ABRASIVE MEDIUM This application is a continuation-in-part of U. S. application Ser. No. 1 15,164 filed Feb. 16, 1971, entitled Abrasive Medium.
In the parent application, Ser. No. 1 15,164, an abrasive medium is disclosed consisting of a synthetic resin impregnated fiberglass mat backing to which a layer of abrasive grains is attached by a synthetic resin binder. Short fibers of glass, asbestos, ceramic material, graphite, or the like are contained in the impregnating resin and/or in the abrasive grain binder. The fiberglass mat consists of individual fiber elements in the form of fiber segments stretched out straight and oriented in all directions.
In making abrasive media which are attached to a base, heretofore use has been made of paper, cotton cloth, vulcanized fiber and the like as backing materials for the layer of abrasive grains, i.e., materials made preferably from plant fibers. The fiberglass mat proposed as the backing material in Ser. No. 1 15,164 filed Feb. 16, 1971, has significant advantages over the backing materials listed above as far as the state of the art is concerned, because it has extremely high heat resistance as well as particularly high flexibility, in addition to being insensitive to climate and moisture. Hence, such an abrasive material may be used readily in wet grinding. Distortion of the abrasive material due to differential absorption or loss of moisture is excluded. In addition, there is no-change in mechanical strength under the influence of heat and humidity, in contrast to the ordinary backing materials used heretofore.
Further, the addition of short fibers of glass, asbestos, ceramic material, graphite or the like, having a length of 0.1 to about 3 mm, is of considerable significance when added to the impregnating resin and/or the abrasive grain binder, because the addition of these fillers produces an especially good anchoring of the abrasive grains and binder to the very flexible fiberglass mat. This admixture of short fibers can amount to about 2 to percent by weight based on the resin or binder. The short fibers have reinforcement or bridge formation, that has a definitely beneficial effect on the adhesion of the abrasive grains to the binder and the surface of the fiberglass mat. This effect is particularly evident in the'desired higher flexibility of the abrasive. This effect not only gives satisfactory values for resistance to wear, satisfactory abrasion and ability to withstand thermal stress, but also provides a particularly high resistance to wear, shifting, and bending.
The present invention which is an improvement over the abrasive medium described in application Ser. No. 1 l5,l64 filed Feb. 16, 1971 consists in the following: the fiberglass mat is covered on both sides with a layer of abrasive grains to form a flexible grinding disk suitable for surface grinding as well as for cutting.
In this manner, a multipurpose tool is obtained,
which has the further advantage when used for surface grinding that both sides of the disk can be used, thus doubling the lifetime of the tool. This possibility for a combination, i.e., surface grinding on both sides and/or optional cutting surfaces with exactly the same type of abrasive material, makes this tool of special interest for the home workshop.
the effect of a micro- An extraordinary wide range of applications is possible with the abrasive material according to the invention, depending on the type of grain used (corundum or silicon carbide). All metals can be ground or cut, as well as tile, roofing tile, asbestos-cement and slate, and other stones or synthetics can be handled flexibly. This tool allows easy and safe removal of rust and all kinds of paint from metal and wood. It has been shown that this tool has a blast resistance of more than 175 m/s, so that particularly high safety is assured. The feature by which a fiberglass mat is produced, in which the individual fiber elements are stretched out straight and consist of fiber segments oriented in all directions is also of critical importance for the circular abrasive disk according to the present invention. In the first place, strength which is equal in all directions is attained under rotational stress. It has been found, however, that a uniformly high resistance to wear is attained along the entire circumference when the disk is used as a cutter, because glass fiber ends are available as a reinforcement practically everywhere along the circumference of this abrasive medium.
Due to the open structure of the fiberglass mat, e.g., with a weight of 200 to 1000 g/m it is extremely valuable to have the layers of abrasive grains which are applied to both sides in making the disk to penetrate into the fiberglass backing. This is especially beneficial when this disk is used asa cutter.
The drawing shows an example of an embodiment of the object of the invention, wherein:
FIG. 1 is a top plan view of a circular abrasive element, partly in cross section; and
FIG. 2 is an enlarged cross sectional view taken along the line 11-" in FIG. 1.
The backing for the circular abrasive element forming an abrasive disk consists of a fiberglass mat 1 with a glass weight of 200 to about 1000 g/m A fiberglass mat with a loose structure of fiber elements 2 and 3 is used, these elements being oriented in all directions as shown in FIG. 1 and made in the form of fiber segments stretched out straight. The individual fiber elements consist of fiber segments 50 to mm long. These fiber segments can be in the form of clustered or individual fiber segments.
The abrasive grains 4,4a are made of corundum, silicon carbide or the like. They are anchored to the fiberglass mat 1 by an ordinary synthetic resin binder. As also shown in FIG. 2, these abrasive grains 4,4a penetrate the loose structure of the fiberglass mat l, which is saturated in turn by a synthetic resin. The abrasive grains 4,4a are soaked with a resin coating before being placed on the base, thus insuring a positive anchoring on the base and an inner bond with the impregnating resin in the fiberglass mat.
Short fibers 5, preferably of glass, are added to the synthetic resin for impregnating the fiberglass mat 1 and/or the synthetic resin binder for the abrasive grains 4,4a which is applied to both sides of fiberglass mat 1; these short fibers are shown as dots in FIG. 2, while the synthetic resin or layer of synthetic resin binder is labeled 6. The short fibers 5 have a length of about 0.1 to 3 mm; a diameter of about 0.003 0.0012 mm and their amount by weight is 2 to 20 percent based on the weight of the solid synthetic resin or synthetic resin binder used. The binders used may be based on epoxy, polyester, melamine, or preferably on phenolic resin and specially elasticized.
The addition of short glass fibers may also be combined with powdered fillers such as marble dust (CaCO cryolite (Na (AlF pyrite (FeS iron oxide (FeO, Fe2O and the like. The mechanical agd thermal properties of the abrasive medium can be influenced within broad limits by these fillers.
Combination tools are known which are also recommended for simultaneous usability in surface grinding and cutting. These known tools also have a woven fabric fiberglass disc as a backing. The geometric structure of every woven fabric fiberglass disc, however, shows a directional orientation of its strength, with the highest tensile strength values found for a stress in the direction of the warp or woof and definitely reduced values, e.g., at an angle of 45 to the direction of the warp or woof. This is a disadvantage in rotating tools. Moreover, the edge strength in cutting using a fiberglass disk as a backing is definitely limited. Uniform wear of the outer edge of the disk can be achieved only with difficulty under these conditions.
Vulcanized fiber grinding disks are also known, which are coated on both sides with abrasive grains. These abrasives can admittedly be used on both sides for surface grinding, but not for cutting. The sheetform vulcanized fiber material does not allow any penetration of abrasive grains, however, so that the circumferential grinding required for cutting is impossible.
The short fibers are preferably glass fibers, and good results are obtained when the short glass fibers as well as the fiberglass elementary fibers of the mat, as well as the abrasive grains were treated with adhesive agents which consist mainly of monomer silicon compounds generally known in the trade as Silans. This Silan treatment also considerably increases the resistance of the abrasive medium to the effect of moisture, which is especially important in wet grinding.
It should be understood that the term ceramic material as used in the present claims is intended to be generic to glass.
It will be obvious to those skilled in the art that various changes may be made without departing from the spirit of the invention and therefore the invention is not limited to what is shown in the drawings and described in the specification, but only as indicated in the appended claims.
What is claimed is:
l. A flexible grinding tool, comprising:
a synthetic resin impregnated fiberglass mat, the individual fiber segments of which are stretched out straight and oriented in all directions; and
a layer of abrasive grains on each side of said mat,
each said layer being attached to said mat by a synthetic resin binder;
wherein said synthetic resin binder contains fibers of asbestos, ceramic material or graphite therein, said fibers being of a length of about 0.1 to approximately 3 mm.
2. A tool according to claim 1 wherein said synthetic resin impregnating said fiberglass mat contains short fibers of asbestos, ceramic material or graphite therein, said short fibers having a length of about 0.1 to approximately 3 mm.
3. A tool according to claim 2 wherein said short fibers are added in an amount of between 2 20 percent by weight based on the solid resin material.
4. A tool according to claim 1 wherein said abrasive grains are corundum or silicon carbide.
5. A tool according to claim 1 wherein said abrasive grains penetrate into said fiberglass mat.
6. A tool according to claim 1 wherein said ceramic material is glass.
7. A tool according to claim 2 wherein said ceramic material is glass.
Disclaimer 3,785,094.Rud0lf H olzlzau-w, Marie-nheide/Rhineland, Germany. ABRA- SIVE MEDIUM. Patent dated Jan. 15, 1974. Disclaimer filed Feb. 6, 1974: by the assignee, F 51mm August Ruggebea 'g. Hereby disclaims the term of the patent subsequent to Oct. 2, 1990.
[Oyficz'al Gazette July 8, 1.975.]