Note: Descriptions are shown in the official language in which they were submitted.
CA 02612503 2007-11-27
GRINDING WHEEL AND WHEEL HUB THEREFORE
Background of the Invention:
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.
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.
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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. Patent
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. Patent
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
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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.
Summary of the Invention:
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.
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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.
Description of the Drawings:
Referring now to the drawings, wherein like elements are numbered alike in the
several FIGURES:
FIGURE 1 is a top plan view of the grinding wheel hub in accordance with the
present invention;
FIGURE 2 is a bottom plan view of the hub of FIGURE 1;
FIGURE 3 is a cross-sectional elevation view along the line 3-3 of FIGURE 2;
FIGURE 4 is a cross-sectional elevation view along the line 4-4 of FIGURE 2;
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FIGURE 5 is a cross-sectional elevation view along the line 5-5 of FIGURE 2;
and
FIGURE 6 is a cross-sectional elevation view showing the hub of FIGURE 3
incorporated with a grinding wheel.
Description of the Preferred Embodiment:
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 FIGURES 4 and 6, aperture bushing
14 is substantially cylindrical, extending from grinding face end 16 to
backing face end
18 (FIGURE 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 (FIGURE 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 FIGURES 2, 3, and 6, the
lower surface
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 FIGURE 6) for receiving an appropriate
bonding
material. In the particular embodiment disclosed herein, recess 32 has a
generally
25 annular shape defined by an inner diameter wa1136 and an outer diameter
wa1138. 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
30 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
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disclosed in the '205 patent such that the keys 46 mate with a complimentary
keyway 47
(see FIGURE 6) in the grinding wheel to form a mechanical interlock to prevent
rotation
between the hub and the grinding wheel.
Referring now to FIGURES 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 FIGURE 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 (FIGURES 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 FIGURE 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 FIGURE 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 FIGURE 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
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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 FIGURE 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.
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