Coated abrasive endless abrasive belts have been joined together by a variety of splices. One type of splice which has proved highly effective is the lap splice which requires that one end of the abrasive sheet material be overlapped on the other end of the abrasive sheet material, and usually adhesively joined to the other end. In order to avoid a disruptive lump in the coated abrasive belt, some special steps must be taken in order to reduce the thickness of the coated abrasive belt at this junction. Usually the method employed has been to grind away a portion of the coated abrasive belt on one end, producing a feather edge which can be adhesively joined to the other end. This joint is relatively complicated to produce.
Another form of splice is the patch splice, wherein two ends of coated abrasive sheet material are abuttingly juxtaposed, and covered with a patch which is adhesively joined to the back (nonabrasive) side of the backing sheet. Fabric splices for this purpose have been proposed in the past, however, they pose certain problems. For example, it is found that when the splice is made directly perpendicular to the running direction of the belt, particularly with a patch splice, the disruptive effect of a thicker portion of the belt in the location where the ends are joined together is objectionable to operators of machinery utilizing coated abrasive belts. Accordingly, coated abrasive belts are usually manufactured with the joint set at an angle other than perpendicular (usually between 30.degree. and 70.degree.) the running direction of the belt, so that the entire splice will not pass over the material being ground with the abrasive belt at the same time. For wider belts (for example, those over 14 inches in width), this angle can be nearly perpendicular to the running direction of the belt, conventionally 70.degree. from the running direction of the belt. Narrower belts are joined at sharper angles. In either case, but particularly in the case where the angle of the splice is relatively sharp with respect to the running direction of the belt, the use of fabric splices presents a dilemma. On the one hand, it is much more convenient to use "straight slit" fabrics, i.e., to cut the fabric patch material in directions which are parallel to the running direction of the yarns which make up the fabric. If this is done, however, the fill yarns of the patch material which is used for the splice are stretched parallel to the running direction of the belt, during operation of the belt. This results in distortion of the joint (called "yawing" of the joint) which is found objectionable, if not totally unallowable, by users of coated abrasive belts.
In order to prevent this yawing problem, it has been proposed to use "bias slit" fabrics for patch splices for coated abrasive belts. In the bias slit patch, the fabric which is to be used as the patch material is cut along the bias of the fabric, at the same angle as the splice is to bear to the running direction of the belt. Thus, some of the yarns in the patch are parallel to the running direction of the belt, and others are perpendicular to the running direction of the belt. This bias slitting operation consumes time, as well as wasting a portion of the material which is to be used for the coated abrasive splice. Furthermore, because the material is cut on the bias, only limited lengths of fabric can be produced, since the fabric is cut from a roll of material of limited width, and being cut at an angle, the edge of the fabric is soon reached. Since it is undesirable to produce a patch for a coated abrasive belt which itself contains a splice between two portions of splice material, this results in additional loss of fabric and requires additional time in the fabrication of the splice, due to the fact that the splice operator must rethread his machine with a new piece of bias slit fabric, every few splices.
It is, therefore, a object of the present invention to produce an improved splice for abrasive belts, and an improved endless belt containing such a splice.