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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;
FIG. 3 is a cross-sectional elevation view along the line 3-3 of FIG. 2;
FIG. 4 is a cross-sectional elevation view along the line 4-4 of FIG. 2;
FIG. 5 is a cross-sectional elevation view along the line 5-5 of FIG. 2; and
FIG. 6 is a cross-sectional elevation view showing the hub of FIG. 3 incorporated with a grinding wheel.
For definitional purposes, throughout this disclosure, the terms “axial” and “co-axial” shall refer to a direction substantially parallel to the axis rotation of wheel hub 10 and/or grinding wheel 12. The terms “transverse” and “radial” shall refer to directions substantially orthogonal to the axial or co-axial direction.
Referring now to the drawings, as shown in FIGS. 4 and 6, aperture bushing 14 is substantially cylindrical, extending from grinding face end 16 to backing face end 18 (FIG. 3). Backing face end 18 is provided with a hex head 20. A central bore 22 extends axially along the length of the bushing. The bushing has a predetermined outer diameter sufficient to enable grinding face end 16 of bushing 14 to be slidably received within central aperture 24 of grinding wheel 12 (FIG. 6). Central bore 22 and hex head 20 facilitate fastening wheel hub 10 to a conventional grinding apparatus (not shown) in a manner familiar to one skilled in the art.
Disc shaped flange 26 extends radially from a medial portion of bushing 14 and terminates at peripheral lip 28. Referring now to FIGS. 2, 3, and 6, the lower surface 30 of the disc shaped flange 26 includes a recess 32. This recess 32 may have any appropriate shape and/or volume such that when the flange 26 is mated with the grinding wheel 12, a cavity 34 is formed (see FIG. 6) for receiving an appropriate bonding material. In the particular embodiment disclosed herein, recess 32 has a generally annular shape defined by an inner diameter wall 36 and an outer diameter wall 38. The outer diameter wall 38 has a series of spaced arcuate sections 40. Recess 32 additionally includes two “T” shaped raised regions 42 with a pair of smaller raised regions 44 between each raised region 42.
Each raised region 42 includes an optioned rectangularly shaped further extension 46. Extensions 46 cooperate to define a key and are substantially identical to the keys 46 disclosed in the aforementioned '205 patent. The keys 46 function in the same manner as disclosed in the '205 patent such that the keys 46 mate with a complimentary keyway 47 (see FIG. 6) in the grinding wheel to form a mechanical interlock to prevent rotation between the hub and the grinding wheel.
Referring now to FIGS. 2 and 5, the bottom surface 30 of flange 26 is provided with a series of discontinuities or grooves 48 which serve to increase the surface area of contact with the bonding material. In a preferred embodiment, as shown, discontinuities 48 comprise a series of radially extending groves of substantially V-shaped or saw-tooth cross-section as in FIG. 5. The grooves are preferably radially spaced about the flange.
Hub 10 may be fabricated from any number of materials capable of providing the requisite structural characteristics, such as, for example, a metallic material or alloy. In a preferred embodiment, hub 10 is fabricated from a zinc alloy.
The hub may be formed by any convenient method, including, for example, casting, forging or powder metal forming. In a preferred embodiment, hub 10 is formed by die casting.
Hub 10 is installed onto wheel 12 by filling cavity 34 with a suitable bonding agent such as an epoxy resin. Grinding face end 16 (FIGS. 3 and 6) of bushing 14 is then inserted into central aperture 24 of wheel 12 until bottom flange surface 30, 42 and 44 engages backing face 50 of the wheel as shown in FIG. 6. Once so disposed, grinding face end 16, which extends a predetermined distance beyond grinding face 54, is then swaged or flanged in a conventional manner to splay the walls thereof radially outward and form a flange or annular bead 56 as show in FIG. 6. Bead 56 serves to engage grinding face 54 about the perimeter of central aperture 24 to capture wheel 12 between the bead and flange 26 and thus complete assembly of hub 10 onto wheel 12. Once sufficient time has elapsed to permit the epoxy resin to cure, the hub and wheel assembly may be utilized in a conventional manner in combination with a grinding apparatus.
As best shown in FIG. 6, the diameter of flange 26 is configured so as to extend beyond the outermost diameter of the depressed center 60 of wheel 12 and terminate along the sloped region 62 of wheel 12. Termination of flange 26 along the sloped region 62 provides improved support and protection relative to the hub of the '317 patent (where the flange terminates at the periphery of the depressed center). Specifically, the termination of the flange 26 along the sloped region 62 provides far greater protection to the concavo-convex portion of the grinding or cutting wheel as compared to the '317 patent. This is a significant improvement as the concavo-convex portion of the wheel in the '317 patent is exposed and therefore susceptible to damage, i.e., it can be cut by the material as the wheel works its way through the material. Moreover, by terminating at the sloped region 62, the hub avoids any interference with the grinding face of wheel 12 as was common with, for example, the hub of the '205 patent.
Still referring to FIG. 6, peripheral lip 28 is configured so as to form a gap 64 relative to sloped region 62. This gap allows for looser tolerances than is required by the annular engagement surface of the '317 patent.
It will be appreciated that there are many physical points of contact between the hub 10 and wheel 12. During the application of the hub, the rollover process preferably used to secure the hub places great pressure on the center of the wheel. The presence of the many physical points of contact helps to alleviate or eliminate stress on the center portion of the depressed center and minimizes the possibility of distortion or damage to the wheel during this rollover process.
Although the grinding wheel hub of the subject invention has been shown and described in combination with depressed center grinding wheels, one skilled in the art should recognize that the hub may be utilized in combination with grinding wheels of substantially any configuration, including, but not limited to, dish wheels, recessed wheels, Type 27 and 28 wheels, or any other grinding wheel having a depressed center and a central mounting aperture, without departing from the spirit and scope of the subject invention.
While preferred embodiments have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustration and not limitation.