Note: Descriptions are shown in the official language in which they were submitted.
CA 02715530 2010-08-17
ROUGH GRINDING TOOL
FIELD OF THE INVENTION
The invention relates to a rough grinding tool
- with a support plate, which
-- is concentrically configured with respect to a centre
longitudinal axis and
-- has a centre opening for receiving a drive shaft of a drive
machine,
and
- with a fiber grinding disc, which
-- consists of a fiber disc, with a resin-bound grinding means
covering,
-- has an outer annular grinding region arranged radially with
respect to the centre longitudinal axis,
-- is supported on the support plate and
-- has a grinding side.
BACKGROUND OF THE INVENTION
Rough grinding tools of this type are known in large numbers in practice.
Fiber grinding discs of this type are configured flexibly and are detachably
attached to the support plate. The fastening on the support plate takes place
by means of a flange that can be screwed on in the bend region of the fiber
grinding disc. During work, in which uniform surface structures have to be
achieved by means of the rough grinding tool on the workpiece to be
machined, the service life of the fiber grinding disc is short, for example
only about 1 minute. After this time, the grinding grain of the fiber
O5.Ot 1lOR/R.PIOONWA-2OIOO3T1f9.A.
1
CA 02715530 2010-08-17
-2-
grinding disc shows the first signs of wear, so the surface of the workpiece
to be machined no longer becomes completely uniform. The fiber grinding
disc is therefore already exchanged after this time.
In order to allow a rapid exchange of fiber grinding discs of this type, a
rapid change system was developed, as shown and described in US 2007-
0010184-Al. Fine-grain grinding grain is used for the application
mentioned. These fine grains, during grinding, lead to a large thermal load
of the workpiece. If, the material to be ground is, for example, high-grade
steel, or has low heat conductivity, blooming occurs. For this reason, in the
rapid change system mentioned according to US 2007-0010184-A1,
cooling channels were provided in the support plate in order to achieve
good cooling of the grinding disc.
If - as conventional in practice - grinding discs with coarse-grain grinding
means are used for rough grinding, there is a risk of the base carrying the
grinding means tearing. This applies, in particular, if discs being used for
the grinding means made of not very strong material are used as the base.
Grinding means on a base, such as are generally conventional, are known
from EP 0 750 539 B 1 and EP 0 617 652 B 1, which thus consist of a
resiliently flexible disc being used as a carrier or base, on which a grinding
grain is fastened by means of a synthetic resin.
So-called fan grinding discs are known from DE 10 2006 010 366 B3 and
DE 90 17 256 Ul in which the grinding plates are glued onto a carrier in
the conventional manner.
CA 02715530 2010-08-17
-3-
SUMMARY OF THE INVENTION
The invention is based on the object of configuring a rough grinding tool of
the generic type in such a way that it has high service lives with a simple
and economical structure.
This object is achieved according to the invention in a rough grinding tool
of the generic type in that the fiber grinding disc is glued to a support
plate.
It has been surprisingly shown by the gluing of the fiber grinding disc to
the support plate that the fiber grinding disc does not tear despite the high
loads during the rough grinding. This can be explained by the fact that the
torque occurring during the rough grinding does not have to be completely
absorbed by the fibers of the fiber disc. To a considerable extent there is a
transfer to the support plate. Even with a torque overload and if the outer
edge of the fiber grinding disc strikes against a workpiece, a break of the
fiber grinding discs does not occur. In other words, no relatively small or
large segments detach from the fiber grinding disc, so that injuries to the
user are substantially ruled out.
The fiber disc consists of vulcanized fiber, a material, which has been
known for one and a half centuries and is produced on the basis of cotton
fibers. Surprisingly, it has also been found that the rough grinding tool is
far superior to conventional rough grinding discs both with regard to the
machined mass per time unit and also with regard to the total mass that can
be machined. This applies, in particular, if ceramic grain is used as the
grinding means.
It has proven to be particularly advantageous if the grinding disc with the
grinding means covering is slightly convexly curved toward the grinding
CA 02715530 2010-08-17
-4-
side. As rough grinding discs of this type, in other words rough grinding
tools, are used on hand-held grinding machines, an exact angle position of
the grinding tool compared to the area to be ground is generally not
adhered to during use. The slight curvature leads to the fact that no high
local surface pressures between the grinding disc and the workpiece to be
machined, resulting in a corresponding tearing of the grinding grain, occur.
This leads to a substantial increase in the service time or the machining
output. If, furthermore, the grinding region is divided into a main grinding
region and a radially outer smaller outer grinding region, the outer grinding
region being even more strongly curved toward the rear of the grinding
tool, the risk of the detachment of the grinding disc from the support plate
is further reduced. Furthermore, the grinding tool may also be used
herewith briefly for face grinding.
Further features, advantages and details of the invention emerge from the
following description of embodiments with the aid of the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 shows a first embodiment of a rough grinding tool according
to the invention in a rear view according to the viewing arrow
I in Fig. 3,
Fig. 2 shows a plan view of the grinding side of the rough grinding
tool according to the viewing arrow II in Fig. 3,
Fig. 3 shows a cross section through the rough grinding tool along
the section line III-III in Fig. 1,
CA 02715530 2010-08-17
-5-
Fig. 4 shows a cross section through a second embodiment of a
rough grinding tool according to the invention,
Fig. 5 shows a cross section through a third embodiment of a rough
grinding tool according to the invention and
Fig. 6 shows a hand grinding machine with a rough grinding tool
according to the invention during grinding use.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The rough grinding tool shown in Figs. I to 3 has a support plate 1, which
consists in the conventional manner of glass fibers which are compressed
and impregnated with phenol resin and which, in the conventional manner,
has a flat, annular clamping region 2, in which an also circular opening 3 is
configured to receive a drive shaft of a drive machine. The annular
clamping region 2 surrounding the opening 3 is provided with a metal ring
5 on the rear of the support plate 1 remote from a grinding side 4. A bend
region 6 adjoins the clamping region 2 and is also annular and rises radially
with respect to the axis 7 of the support plate 1 toward the grinding side 4.
An annular grinding region 8 adjoins the bend region 6 and is inclined
radially with respect to the axis 7 counter to the bend region 6, and
specifically radially with respect to the axis 7 outwardly away from the
grinding side 4. This configuration of a support plate 1 is generally known
and conventional.
A fiber grinding disc 9 is fastened to the grinding side 4. This is a so-
called
grinding means on a base, which consists of a fiber disc 10 as the carrier or
CA 02715530 2010-08-17
-6-
base and a resin-bound grinding means covering 11. The fiber disc 10
consists of vulcanized fiber, being a bound, compressed material based on
cotton fibers. The grinding means covering 11 is formed by ceramic grain
11.1, which is produced from a microgranulate by sintering. Micro
granulates break out of the respective grain individually, so the service life
of the ceramic grain 11.1 in comparison to conventional grinding means is
thereby considerably increased. The resin-bound grinding means covering
11 is connected in the conventional manner to the fiber disc 10. The fiber
disc 10 of the fiber grinding disc 9 is connected to the grinding side 4 of
the support plate 1 by means of an adhesive layer 12.
The radius R1 of the support plate 1 - as can be inferred from Fig. 1 - is
slightly smaller than the radius R9 of the fiber grinding disc 9, without the
fiber grinding disc 9 projecting radially with respect to the axis 7 over the
outer edge 13 of the support plate 1. The bend region 6, at the transition to
the main grinding region 8, has a radius R6 from the axis 7. The main
grinding region 8 has a radius R8 from the axis 7 which is equal to the
radius R9 of the fiber grinding disc 9. The following applies with respect to
the radii R6 and R8 in relation to the radius R9:
0.45 R9<R6<0.7R9
R9 = R8
The use of the grinding tool takes place in the conventional manner at an
angle to the axis 7.
If in the second embodiment according to Fig. 4, the same or similar parts
or regions are present as in the embodiment according to Figs. 1 to 3, the
same reference numerals are used with a superscripted dash. The support
CA 02715530 2010-08-17
-7-
plate 1' consists of a glass fabric impregnated with epoxy resin. It has - as
in the embodiment according to Fig. 1 to 3 - a constant thickness h. The
also annular clamping region 2' is also configured with a circular opening
3' to receive a drive shaft of a drive machine. The flat clamping region 2'
surrounding the opening 3', in this embodiment, is not reinforced with a
metal ring. The bend region 6' adjoining the clamping region 2' is also
annular and rises radially with respect to the axis 7' of the support plate 1'
toward the grinding side 4'. The flat clamping region 2' passes with a radius
of curvature r2' into the bend region 6'. The bend region 6' is in turn
adjoined by an annular main grinding region 8', which is inclined radially
with respect to the axis 7' counter to the bend region 6', specifically
radially
with respect to the axis 7' outwardly away from the grinding side 4'.
Viewed outwardly, from the axis 7', the grinding region 8' is thus inclined
away from the grinding side 4'. In the configuration according to Fig. 4, a
fiber grinding disc 9' is also fastened to the grinding side 4' of the support
plate 1'. This is a so-called grinding means on a base, which consists of a
fiber disc 10' as a support or base and a resin-bound grinding means
covering 11'. The fiber grinding disc 9' is thus a grinding disc, which is
independent per se, which could be used, as was described above with
regard to the prior art according to US 2007-0010184-A 1. It is flexible, in
other words bendable. The structure of the fiber grinding disc 9'
corresponds to that already described above with respect to Figs. 1 to 3.
The grinding means covering 11' in other words has ceramic grain 11.1'. In
the embodiment according to Fig. 4, the fiber disc 10' of the fiber grinding
disc 9' is also connected to the support plate 1' by means of an adhesive
layer 12'
As can be inferred from Fig. 4, the bend region 6' passes into the grinding
region 8' with a radius of curvature r6'. The main grinding region 8' itself
is
CA 02715530 2010-08-17
-8-
also curved, specifically slightly convexly to the grinding side 4' with a
radius of curvature r8'.
The outer grinding region 15' adjoining the main grinding region 8' is
inclined away, viewed radially outwardly, from the grinding side 4' and
convexly curved with respect to the grinding side 4' with a radius of
curvature r 15'.
The curvatures with the radii of curvature r6', r8' and r15' are configured
convexly to the grinding side 4'; the reason for this is that the use of the
rough grinding tool in the conventional manner takes place at an angle to
the axis 7'. The fiber disc 10' ends - as can be inferred from Fig. 4 - flush
with the outer edge 13' of the support plate 1'. The following relationships
apply to the radii of curvature r2', r6', r8' and r15':
15 mm :5 r2'< 30 mm and preferably 20 mm < r2'< 25 mm
15 mm < r6'< 40 mm and preferably 15 mm < r6'< 20 mm
190 mm < r8'< 300 mm and preferably 200 mm < r8'< 250 mm
17 mm < r15' < 40 mm and preferably 15 mm < r15' < 20 mm
The fiber grinding disc 9' has a radius R9' from the axis 7'. The bend region
6' at the transition to the main grinding region 8' has a radius R6' from the
axis 7'. The main grinding region 8' has a radius R8' from the axis 7', which
is only equal to the radius R9' of the fiber grinding disc 9' if no separate
more strongly curved outer grinding region 15' is present. With respect to
the radii R6' and R8', the following applies in relation to the radius R9':
0.45R9'<R6'<0.7R9'
0.75 R9' <R8' <R9'
CA 02715530 2010-08-17
-9-
The embodiment according to Fig. 5 differs from that according to Fig. 4 in
that the support plate 1" has a radially outwardly increasing resilience, in
other words a lower rigidity or greater flexibility. All the parts or regions
coinciding with Fig. 4 are therefore designated by the same reference
numerals and all the similar parts or regions are in each case designated by
the same reference numerals as were used in Fig. 4, supplemented by a
superscripted double dash, without another description being necessary.
The increasing resilience of the support plate 1" in the direction of the
outer
edge 13" is achieved in that the support plate 1" has a plurality of
respective annular portions 16, 17 or 18, which have a different, radially
outwardly decreasing thickness. In the embodiment according to Fig. 5, the
portion 16 extends approximately to the transition from the bend region 6'
into the main grinding region 8"; it has the thickness h here. The annular
portion 17 adjoining this radially outwardly extends radially up to in front
of the outer grinding region 15". The portion 17 has a thickness h'; the
outer portion 18 has a thickness h", wherein h > h' > h". Basically, in a
stepped configuration according to Fig. 5, it is to be assumed that at least
two portions of this type and at most five portions of this type are provided.
The above relationships apply to the radii R6', R8" and R9'.
The use of the rough grinding tool according to the invention on hand
grinding machines 19 emerges from Fig. 6. The rough grinding tool is
placed on an output shaft 20 of the hand grinding machine 19, which is
placed through the opening 3 of the grinding tool, so the axis 7 coincides
with the centre axis of the output shaft 20. The fastening of the grinding
tool on the output shaft 20 takes place by means of a clamping nut 21.
CA 02715530 2010-08-17
-10-
The convex curvature of the main grinding region 8" toward the grinding
side 4' means that during surface grinding of workpieces 22, in other
words, in the main use region of grinding tools of this type, even with
unavoidable oscillating movements of the grinding tool, a uniform load of
the grinding means covering 11' occurs, in other words, no extreme surface
pressures occur. In these rough grinding tools always used on hand
grinding machines, this leads to lower wear and therefore a higher service
time and a higher removal output of the grinding disc. This advantageous
effect is further reinforced by the outwardly increasing resilience of the
grinding tool according to Fig. 5.
The greater curvature in the outer grinding region 15' or 15" means that
when the outer edge 13' or 13" of the grinding disc strikes against an
object, no detachment of the fiber grinding disc 9' together with the
grinding means covering 11 from the support plate ' or 1" takes place.
