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Grinding wheel and wheel hub therefore

1. Field of the Invention

This invention relates to abrasive grinding and cutting wheels, and more particularly to an improved wheel hub for mounting a grinding or cutting wheel to a grinding or cutting apparatus.

2. Background of the Invention

Grinding machines that utilize abrasive grinding wheels mounted thereon may be employed to perform many distinct grinding operations. The varied operations have led to the development of a wide variety of grinding wheel shapes and sizes. One type of grinding wheel in particular is the depressed center wheel, characterized by the central portion of the wheel being offset in the axial direction from the wheel periphery. The wheel thus has a concavo-convex stub portion in which a grinding face has a depressed or concave central portion. This design allows a user to perform face grinding operations using the grinding face having the depressed center portion. Often, such operations are performed on metal, masonry or concrete surfaces and the like, using portable grinding machines. Depressed center wheels are classified by the American National Standards Institute (ANSI) as Type 27 and 28 grinding wheels.

The means by which a grinding wheel is secured to the grinding machine spindle is particularly important with a depressed center wheel. In general, the mounting means must be capable of holding the wheel perpendicular to the spindle during grinding operations, and must provide support to the wheel to distribute stresses away from the central mounting aperture, where stresses tend to concentrate. The mounting means also must be firmly secured to the abrasive wheel, to prevent any slippage therebetween. In addition, the mounting means for Types 27 and 28 wheels have generally been provided with extra support to the wheel periphery, as well as to the central portion of the backing (non-grinding) face of the wheel to resist the additional stresses imposed by face grinding operations.

To satisfy these requirements, it is common to provide Type 27 and 28 wheels with a hub having a flange that extends over the central raised portion, the concavo-convex stub portion, and onto and in contact with the peripheral portion of the wheel, to resist side pressure or otherwise uneven force applied to the grinding face of the wheel. The opposite face of the wheel is provided with a flange contained completely within the depressed area thereof. An example of such a hub construction is disclosed in U.S. Pat. No. 4,541,205 ('205), which is assigned to the assignee hereof and incorporated herein by reference thereto.

Although such hub constructions may produce satisfactory results in many instances, it is not without drawbacks. In particular, extension of the flange beyond the raised stub portion of the backing face tends to limit the useful life of the wheel. In this regard, the wheel must be replaced before it is ground down to the diameter of the backing flange to avoid potentially damaging contact between the backing flange and the work piece. Accordingly, grinding wheels that utilize this hub construction tend to be discarded with a substantial portion of valuable and otherwise usable abrasive remaining thereon. Such relative under-utilization of the wheel tends to add undesirable expense to grinding operations in terms of both wheel cost and labor costs associated with the frequency of wheel removal and installation.

An attempt at solving the foregoing problem is disclosed in U.S. Pat. No. 5,895,317 ('317). The '317 patent discloses a grinding wheel hub for mounting an abrasive grinding wheel on a grinding apparatus. The hub is adapted for use with an abrasive grinding wheel of the type that has a mounting aperture disposed centrally therein, and a grinding face and a backing face disposed on opposite sides of the abrasive grinding wheel. The grinding wheel hub includes an aperture bushing of substantially cylindrical configuration, adapted for extension through and engagement with the surface of the mounting aperture. A grinding face fastener is disposed on the aperture bushing and adapted to extend radially outward from the mounting aperture to engage the grinding face of the wheel. A backing flange of substantially discoid shape, extends radially outward from the aperture bushing member and is adapted for being superposed with the backing face. An annular engagement surface is located along a periphery of the backing flange and is adapted to engage the backing face of the wheel. The backing flange has a bond surface adapted to face the backing face, and is sized and shaped to provide a cavity between the backing flange and the backing face of the grinding wheel when the annular engagement surface is engaged with the backing face. The cavity is adapted to receive a bonding agent therein to bond the grinding wheel.

However, the grinding wheel hub of the '317 patent also has certain drawbacks and deficiencies. For example, the hub of the '317 patent requires an annular engagement surface which must mate with the grinding wheel to form the bonding cavity. However, any gaps in this engagement due to problems with manufacturing tolerances can cause leakage of the bonding material from the cavity. In addition, the hub of the '317 patent cannot extend beyond the outermost circumference of the backing face of the wheel thus leading to a less optimal degree of support relative to a hub which does extend beyond the outermost circumference. Thus, there continues to be a need for improved grinding wheel hubs and grinding wheels incorporating such hubs for use with depressed center and other grinding wheels.

The above-discussed and other drawbacks and deficiencies of the prior art are overcome or alleviated by the improved grinding wheel hub and grinding wheel incorporating such hub of the present invention.

In accordance with the present invention, a grinding wheel hub is provided for mounting an abrasive grinding wheel on a grinding apparatus. The hub is adapted for use with an abrasive grinding wheel of the type that has a mounting aperture disposed centrally therein, and a grinding face and a backing face disposed on opposite sides of the abrasive grinding wheel. The grinding wheel hub includes an aperture bushing of substantially cylindrical configuration, adapted for extension through and engagement with the surface of the mounting aperture. A grinding face fastener is disposed on the aperture bushing and adapted to extend radially outward from the mounting aperture to engage the grinding face of the wheel. A backing flange of substantially discoid shape, extends radially outward from the aperture bushing member and is adapted for being superposed with the backing face. The backing flange has a bond surface adapted to face the backing face. The bond surface includes at least one recess formed therein. Preferably, the recess has a radial and/or concentric orientation with respect to the center of the aperture bushing. This recess is sized and shaped to provide a cavity between the backing flange and the backing face of the grinding wheel when the backing flange is engaged with the backing face. This cavity is adapted to receive a bonding agent therein to bond the grinding wheel hub to the abrasive grinding wheel.

Significantly, the at least one recess and resultant cavities formed therefrom avoids the necessity of an annular engagement surface as was required in the prior art hub of the aforementioned '317 patent. The lack of any annular engagement surface (and the need for strict tolerances associated therewith) represents an improvement over the hub of the '317 patent.

The backing flange of the present invention has a diameter which allows it to terminate in the sloped region of the grinding wheel between the outermost circumference of the substantially flat depressed center and the substantially flat grinding wheel portion. This feature provides for maximum support of the grinding wheel while still avoiding any limitation to the useful life of the wheel. Additionally, this feature protects the concavo-convex portion of the wheel from possible damage by the material being cut. Hence, this feature provides yet another improvement relative to the grinding wheel hub of the aforementioned '317 patent.

The above-discussed and other features and advantages of the present invention will be appreciated by and understood by those skilled in the art from the following detailed description and drawings.

Referring now to the drawings, wherein like elements are numbered alike in the several FIGURES:

FIG. 1 is a top plan view of the grinding wheel hub in accordance with the present invention;

FIG. 2 is a bottom plan view of the hub of FIG. 1;