U.S. patent application number 13/759193 was filed with the patent office on 2013-08-08 for grinding wheel for longitudinal or transverse grinding.
The applicant listed for this patent is Egon EVERTZ, Ralf Evertz, Stefan Evertz. Invention is credited to Egon EVERTZ, Ralf Evertz, Stefan Evertz.
Application Number | 20130203326 13/759193 |
Document ID | / |
Family ID | 47603294 |
Filed Date | 2013-08-08 |
United States Patent
Application |
20130203326 |
Kind Code |
A1 |
EVERTZ; Egon ; et
al. |
August 8, 2013 |
GRINDING WHEEL FOR LONGITUDINAL OR TRANSVERSE GRINDING
Abstract
A grinding wheel has an inner core part and an outer annular
grinding part connected the inner core part. The outer grinding
part is made of a granular abrasive medium and plastic or glass
fibers. The fibers form between 0.15% and 1%, preferably 0.2% to
0.4%, by weight of the grinding part.
Inventors: |
EVERTZ; Egon; (Solingen,
DE) ; Evertz; Ralf; (Leichlingen, DE) ;
Evertz; Stefan; (Solingen, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
EVERTZ; Egon
Evertz; Ralf
Evertz; Stefan |
Solingen
Leichlingen
Solingen |
|
DE
DE
DE |
|
|
Family ID: |
47603294 |
Appl. No.: |
13/759193 |
Filed: |
February 5, 2013 |
Current U.S.
Class: |
451/540 |
Current CPC
Class: |
B24D 3/342 20130101;
B24D 3/001 20130101; B24D 5/08 20130101; B24D 5/04 20130101; B24D
3/344 20130101; B24D 5/14 20130101 |
Class at
Publication: |
451/540 |
International
Class: |
B24D 3/00 20060101
B24D003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 6, 2012 |
DE |
102012002105.4 |
Claims
1. A grinding wheel comprising: an inner core part; and an outer
annular grinding part connected the inner core part and comprised
of a granular abrasive medium and plastic or glass fibers, the
fibers forming between 0.15% and 1% by weight of the grinding
part.
2. The grinding wheel defined in claim 1, wherein the fibers form
between 0.2% and 0.4% by weight of the grinding part.
3. The grinding wheel defined in claim 1, wherein the fibers have a
length of between 5 mm and 15 mm and a thickness between 0.8 mm and
1.2 mm.
4. The grinding wheel defined in claim 1, wherein the core part has
a substantially cylindrical outer peripheral surface formed with
indentations and the outer grinding part has a substantially
cylindrical inner peripheral surface engaging the outer surface and
formed with projections complementary to and engaging into the
indentations of the outer surface, whereby relative shifting of the
parts at the surfaces is inhibited by inherit of the indentations
and projections.
5. The grinding wheel defined in claim 1 wherein the grinding wheel
is made of particles of Al.sub.2O.sub.3, SiC, CBN, ZrO.sub.2,
diamond or mixtures thereof.
6. The grinding wheel defined in claim 5, wherein the particles
have particle sizes of a maximum diameter of 1 mm.
7. The grinding wheel defined in claim 1 wherein the core part and
grinding part have thermal coefficients of expansion that deviate
from each other by less than 5%.
8. The grinding wheel defined in claim 1, wherein the grinding part
has a matrix of a metal or metal alloy or of a thermally curable
resin in which is embedded granules of abrasive media and the glass
fibers in a generally homogenous distribution.
9. The grinding wheel defined in claim 8, wherein the core part is
substantially made of a metal or metals and filler materials.
10. The grinding wheel defined in claim 1, wherein at least one of
the parts contains a thermally curable resin and cross-linking
agents and fillers.
11. The grinding wheel defined in claim 11, wherein the fillers are
as SiC, Al2O3, bauxite, graphite or molybdenum sulfide.
12. The grinding wheel defined in claim 1 wherein first the core
part, then the grinding part are compacted by cold shaping to form
a combined green compact that is heated to 180.degree. C. to
200.degree. C. and compacted to desired dimensions.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a grinding disk or wheel.
More particularly this invention concerns such a disk or wheel that
can grind both longitudinally and transversely.
BACKGROUND OF THE INVENTION
[0002] A typical grinding wheel for longitudinal and transverse
grinding has an inner core part and an outer annular grinding part
that are connected to each other. The grinding part is made of a
material that contains a granular abrasive compound. EP 1,129,824
discloses a grinding wheel of this kind.
[0003] When processing plate slabs in the manufacture of steel, the
surfaces undergo abrasive machining to remove any faulty areas such
as voids that may be present. A grinding wheel is used to this end
containing particles in the abrasive compound thereof in the
grinding part. The selection of the abrasive particles depends on
the workpiece being machined. In most cases, abrasive particles
should be very hard, with sufficient particle toughness and
resistance to heat, as well as suitable particle sizes and shapes.
Frequently used abrasive particles are made from carborundum
(aluminum oxide), silicon carbide, cubic boron nitride or diamond,
which grinding materials have been named in the order of ascending
hardness. The shape of the abrasive particles as well as the
particle sizes thereof depend on the type of machining, namely,
whether so-called rough-grinding, pregrinding, finish-grinding or
precision-grinding.
[0004] During the grinding process, the grinding wheel is rotated
at relatively high speeds of 80 m/s or more. Considerable
centrifugal forces are generated at such grinding speeds requiring
high-level security measures. The relatively high susceptibility of
the grinding wheels to breakage poses a risk for operators, as it
can cause single large pieces of the grinding disk or even entire
segments of grinding parts to detach. Despite necessary safety
steps, namely by balancing the grinding wheel, sound testing before
the start-up of operation, careful mounting of the grinding wheel
and enclosing the grinding wheel inside a protective hood, the
durability of the grinding wheel is of the utmost importance. In
particular, any detachment of individual segments of the grinding
part must be effectively avoided.
OBJECTS OF THE INVENTION
[0005] It is therefore an object of the present invention to
provide an improved grinding wheel.
[0006] Another object is the provision of such an improved grinding
wheel that overcomes the above-given disadvantages, in particular
that is very rugged and unlikely to come apart even if rotated at
very high speeds.
SUMMARY OF THE INVENTION
[0007] A grinding wheel has according to the invention an inner
core part and an outer annular grinding part connected the inner
core part. The outer grinding part is made of a granular abrasive
medium and plastic or glass fibers. The fibers form between 0.15%
and 1%, preferably 0.2% to 0.4%, by weight of the grinding
part.
[0008] Although the use of filler materials, including glass
fibers, has been proposed previously for cutting wheels of smaller
diameters or even for larger grinding wheels, in these instances,
the goal was to minimize cost of the grinding wheel. The
centrifugal force of a grinding wheel is calculated from the
product of mass, square of the angular velocity and distance from
the axis of rotation; this means that especially grinding wheels
that have a large mass and a large diameter are subject to enormous
centrifugal forces. Correspondingly, the formation of hair-line
fractures that triggers the detachment of parts from grinding parts
at a later time must be avoided. For this reason, strict adherence
to the percentage parts of mass for plastic or glass fibers is
required. The risk of breakage increases dramatically above 1.0
mass % of the grinding part. Below 0.3%, any addition of plastic or
glass fibers is for the most part without effect at all. Only the
restricted quantity of 0.15% to 1.0% in fact results in good
adhesive power of the grinding wheel portions without compromising
toughness.
[0009] Preferably, glass fibers of a length of 5 mm to 15 mm and a
thickness of 0.8 mm to 1.2 mm are used.
[0010] The grinding wheels according to the invention have, for
example, a standardized diameter of 615 mm with a thickness of 79
mm and an inner bore hole in the core part with a diameter of 203
mm. The outer diameter of the core part is 340 mm. The weight of
such a grinding wheel, including any embedded iron reinforcement
rings, is about 63 kg. To avoid any relative movement of the core
and grinding parts in the direction of rotation, the substantially
cylindrical outer surface of the core part is formed with
individual grooves or singular recesses, and the cylindrical inner
surface of the grinding part includes complementary individual
ridges or singular bumps. The ridges or singular bumps engage in
the grooves or singular recesses of the core part, respectively, to
produce an effective "keying" between the core part and the
grinding part. The corresponding grooves, recesses or bumps can be
easily incorporated during cold shaping.
[0011] The present invention provides, in principle, for the use of
all common grinding materials, preferably Al.sub.2O.sub.3, SiC,
CBN, ZrO.sub.2, diamond or mixtures of these material, the maximum
particle diameter being no more than 1 mm.
[0012] As known, in principle, from above-cited EP 1,129,824 T2,
the core part and the grinding part have the same thermal
coefficients of expansion. If necessary, the coefficients of
expansion can deviate by a maximum of 5% from each other. This
measure ensures that, when the grinding wheel becomes hot during
operation, differential stresses between the core region and the
grinding part are for the most part avoided.
[0013] Aside from the abrasive particles, the core and grinding
parts can principally be made of the same or different materials.
According to a further embodiment of the invention, the grinding
part can contain a matrix of metal or a metal alloy or a thermally
curable resin in which the granular abrasive medium and the plastic
or glass fibers are embedded in a homogenous distribution, at least
for the most part homogeneously. The core part can substantially be
made of metal and/or metal alloys that have filler materials added
thereto, if necessary. In particular, it is possible to use the
core part multiple times. Thus after the grinding part is worn out,
what is left of the grinding part can be separated from the core
part, and a new grinding part can be formed on the core part.
[0014] In particular with regard to at least approximately equal
thermal coefficients of expansion, however, the core part
(preferably the grinding part as well) can contain a thermally
curable resin and a cross-linking agent as well as filler
materials. Fillers can be, for example, powdery SiC,
Al.sub.2O.sub.3, bauxite, graphite or molybdenum sulfide.
[0015] To be able to ensure optimum solidity of the grinding wheel,
it is preferable to produce the core section first, followed by the
cutting portion, by cold shaping. The green compact formed in this
manner, which is made of the core and grinding parts, is already
provided with grooves and ridges that engage with each other in the
manner following a tongue-and-groove principle (or, in the
alternative, singular recesses and singular pegs).
[0016] The combined compacted green compact is then heated to
180.degree. C. to 200.degree. C. and compacted to the desired final
dimensions. The compression pressures are, for example, 7.times.107
Pa (700 bar).
BRIEF DESCRIPTION OF THE DRAWING
[0017] The above and other objects, features, and advantages will
become more readily apparent from the following description,
reference being made to the accompanying drawing in which:
[0018] FIG. 1 is a top view of a grinding wheel according to the
invention;
[0019] FIG. 2 is a side view of the grinding wheel; and
[0020] FIG. 3 is a section taken along line III-III of FIG. 1.
DETAILED DESCRIPTION OF THE INVENTION
[0021] As seen in FIGS. 1 and 2 a grinding wheel according to the
invention has an inner core part 10 and an outer grinding part 11,
both centered on an axis A. The outer diameter of the grinding part
measured diametrally is 615 mm and the axial thickness of the
grinding wheel, as seen in FIG. 2, is 79 mm. Both parts 10 and 11
are, in fact annular, with the grinding part 11 outside the core
part 10 so that the cylindrical inner surface of the outer part 11
is in surface contact with and bonded to the cylindrical outer
surface of the inner part 10.
[0022] As shown in FIG. 3, a keyed connection can be created
between the core part 10 and the grinding part 11 in that the core
part 10 is provided with radially outwardly extending
circumferential ridges 12 that engage in complementary radially
inwardly open annular grooves 13 of the grinding part 11.
Alternatively as shown in the left half of FIG. 3, there are
individual bumps 14 and complementary recesses 15. Such projections
or depressions are formed already at the time of production of the
green compact by precompacting, such that the combined body, which
is made of the precompacted core part and precompacted grinding
part, is placed into a mold and subsequently heated to 180.degree.
C. to 200.degree. C., then finally compacted to the above-given
final dimensions.
[0023] According to the invention, aside from the matrix material
in which are imbedded the abrasive particles made of, for example,
aluminum oxide, the grinding part has a mass fraction of 0.15% to
1.0% of plastic or glass fibers 17. A concrete embodiment provides
for the use of about 100 g glass fibers 17 of a mean length of 10
mm and a thickness of 1 mm for the core part 10 and the grinding
part 11. The glass fibers 17 were homogeneously blended. The core
part had a total weight of 12 kg, while the grinding part, on the
other hand, had a powder weigh-in of 49.5 kg. Two additional iron
rings 16 are also embedded in the structure and have a weight of
1.0 kg, resulting in a total weight of 62.5 kg for the grinding
wheel. In the illustrated embodiment, the glass fiber fraction of
the weight of the grinding part and the core part was approximately
0.17%, respectively.
[0024] The grinding wheel was inspected during a test run at
rotational speeds of 140 m/sec; chipped spots on larger parts of
the grinding part or hair-line fractures that can result in
detachments later on were not found. Contrary to grinding wheels
without glass fiber content, by the targeted addition of glass
fibers 17 it is possible to achieve a considerable improvement in
terms of the solidity of the grinding wheel.
* * * * *