U.S. patent application number 16/132994 was filed with the patent office on 2019-06-06 for grinding disc device for a grinding apparatus.
This patent application is currently assigned to JOBRA Metall GmbH. The applicant listed for this patent is JOBRA Metall GmbH. Invention is credited to Josef Brandstetter.
Application Number | 20190168361 16/132994 |
Document ID | / |
Family ID | 60889739 |
Filed Date | 2019-06-06 |
United States Patent
Application |
20190168361 |
Kind Code |
A1 |
Brandstetter; Josef |
June 6, 2019 |
Grinding Disc Device for a Grinding Apparatus
Abstract
A grinding disc device for a grinding apparatus is described,
having at least one grinding layer and a carrier disc fixedly
connected to the grinding layer. The grinding layer has at least
one connection surface (F.sub.V) connected to the carrier disc and
forms an abrasive grinding surface (F.sub.S) lying opposite the
connection surface (F.sub.V) and facing away from the carrier disc.
The carrier disc made of a plastic material is produced by
injection molding and is connected immediately and directly to the
connection surface (F.sub.V) of the grinding layer, wherein the
plastic material of the carrier disc is sprayed by injection
molding immediately and directly onto the connection surface
(F.sub.V) of the grinding layer, such that the carrier disc and the
grinding layer are connected to one another in a material-locking
manner.
Inventors: |
Brandstetter; Josef;
(Rottenberg a.d. Laaber, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
JOBRA Metall GmbH |
Rottenberg a.d. Laaber |
|
DE |
|
|
Assignee: |
JOBRA Metall GmbH
Rottenberg a.d. Laaber
DE
|
Family ID: |
60889739 |
Appl. No.: |
16/132994 |
Filed: |
September 17, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B24D 13/20 20130101;
B24D 13/14 20130101; B24D 18/00 20130101; B24D 13/18 20130101; B24D
9/08 20130101; B24D 7/16 20130101 |
International
Class: |
B24D 9/08 20060101
B24D009/08; B24D 7/16 20060101 B24D007/16 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 6, 2017 |
DE |
DE202017107425.0 |
Jul 4, 2018 |
DE |
DE102018116242.1 |
Claims
1. A grinding disc device for a grinding apparatus comprising: at
least one grinding layer and a carrier disc fixedly connected to
the grinding layer, wherein the grinding layer comprises a
connection surface (F.sub.V) connected to the carrier disc and
forms an abrasive grinding surface (F.sub.S) lying opposite the
connection surface (F.sub.V) and facing away from the carrier disc,
wherein the carrier disc is made of a plastic material produced by
injection molding and is connected immediately and directly to the
connection surface (F.sub.V) of the grinding layer, wherein the
plastic material of the carrier disc is sprayed by means of
injection molding immediately and directly onto the connection
surface (F.sub.V) of the grinding layer, such that the carrier disc
and the grinding layer are connected to one another in a
materially-bonded manner.
2. The grinding disc device according to claim 1, wherein the
grinding layer consists essentially of a flat, circular grinding
disc or a sanding disc.
3. The grinding disc device according to claim 1, wherein the
grinding layer is formed by a fiber disc or a vulcanised fiber
disc.
4. The grinding disc device according to claim 1, wherein the
grinding layer is composed of grinding lamellas.
5. The grinding disc device according to claim 1, wherein the
connection surface (F.sub.V) and the grinding surface (F.sub.S)
lying opposite the connection surface (F.sub.V) are each
constituted as essentially continuous, annular surfaces.
6. The grinding disc device according to claim 1, wherein the
grinding surface (F.sub.S) is formed by a ceramic grain abrasive
medium scattered on a carrier material.
7. The grinding disc device according to any claim 1, wherein the
grinding surface (F.sub.S) of the grinding layer connected to the
carrier disc is constituted dish-shaped.
8. The grinding disc device according to claim 1, wherein cooling
air slots are formed in the carrier disc distributed over a
periphery of the carrier disc for passage of cooling air.
9. The grinding disc device according to claim 1, wherein the
carrier disc is constituted in one piece with a hub part, wherein
ventilation ribs extend radially outwards from the hub part.
10. The grinding disc device according to claim 9, wherein the hub
part comprises an inner thread for the fastening of the grinding
disc device on a drive shaft of the grinding apparatus.
11. The grinding disc device according to claim 9, wherein cooling
air passage slots are also formed into the hub part.
12. The grinding disc device according to claim 1, wherein the
carrier disc is produced from a thermoplastic polymer.
13. The grinding disc device according to claim 12, wherein the
carrier disc is made from a thermoplastic terpolymeror an
acrylnitrile-butadiene-styrene copolymer (ABS).
14. The grinding disc device according to claim 12, wherein the
carrier disc is made from a polyamide PA6 or a glass
fiber-reinforced polyamide PA6.
15. A method for producing a grinding disc device for a grinding
apparatus by injection molding, comprising the steps of:
introducing a grinding layer with a connection surface (F.sub.V)
and an opposite abrasive grinding surface (F.sub.S) into a molding
tool of an injection molding machine, in such a way that the
connection surface (F.sub.V) of the grinding layer points in a
direction of a predefined cavity of the molding tool, forming a
carrier disc connection to the grinding layer by injecting a
plastic material suitable for producing the carrier disc into a
closed molding tool at a predefined temperature and under a
predefined pressure, such that the plastic material of the carrier
disc is sprayed immediately and directly onto the connection
surface (F.sub.V) of the grinding layer thereby producing the
grinding disc device.
16. The method according to claim 15, wherein the carrier disc is
constituted in one piece with a hub part and/or that slots
distributed over the periphery of the carrier disc are formed for a
passage of cooling air.
17. The method according to claim 16, wherein an inner thread is
formed in the hub part for the fastening of the grinding disc
device on a drive shaft of the grinding apparatus and/or that the
hub part is formed with corresponding cooling air passage
slots.
18. The method according to any one of claim 15, wherein a flat,
circular vulcanised fiber disc with a scattered ceramic grain
abrasive medium is used as a grinding layer and that a glass
fiber-reinforced polyamide PA6 is the plastic material for the
carrier disc sprayed onto the grinding layer.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The invention relates to a grinding disc device for a
grinding apparatus, in particular to a grinding disc with a carrier
disc.
2. Description of the Related Art
[0002] Grinding disc devices or grinding tools are sufficiently
well known. In the case of known grinding disc tools, grinding
bristles can, for example, be molded on a plastic base essentially
constituted of plate-shaped or grinding filaments which can be
embedded in a plastic matrix. Such a grinding brush, wherein
grinding bristles with abrasive particles are molded on a plastic
base, is disclosed for example in U.S. Pat. No. 6,179,887 B1,
wherein the grinding surface with this kind of grinding brush is
formed by the ends of the bristles at the free-end side. German
Patent No. DE 196 50 393 A1 in turn describes a grinding tool,
wherein a bundle of grinding monofilaments is attached to a hub and
the grinding monofilaments attached to the hub are embedded in an
elastomer foam. With their tips facing away from the hub, the
embedded grinding monofilaments form an annular or cylindrical
grinding surface.
[0003] Furthermore, a grinding tool is known from PCT Publication
No, WO 2005/115716 A1, which is produced by means of an injection
molding process. To produce the grinding tool of PCT Publication
No, WO 2005/115716 A1, particles of an abrasive granulate, or an
abrasive agglomerate are scattered into an injection mold and
thermoplastic elastomer material is then injected into the
injection mold, so that the particles of the abrasive granulate are
embedded in the thermoplastic elastomer material.
[0004] A drawback, however, is that the aforementioned grinding
tools often do not produce the desired grinding performance,
especially for specific purposes or in specific applications.
[0005] Grinding disc devices, i.e. grinding discs with carrier
discs, are also known which usually comprise a carrier disc or
support disc or a carrier plate with an abrasive grinding disc or
grinding layer fastened or connected thereto. Such a grinding disc
with a carrier disc is known for example from German Patent No. DE
10 2016 102 037 B4, wherein an abrasive grinding layer is applied
to a rigid carrier disc made of polyamide or ABS, the grinding
layer comprising grinding lamellas arranged fan-shaped.
[0006] In order to fasten the grinding layer on the carrier disc,
use is made, for example, of an adhesive, which ensures a durable
connection between the grinding layer and the carrier disc. Such an
adhesive must therefore satisfy a variety of conditions, in
particular an unlimited strength even in a continuous operation and
at high temperatures. Furthermore, the fastening of the grinding
layer by means of the adhesive on the carrier disc requires
sufficient hardening, which delays production considerably.
[0007] Despite the solutions known from the prior art, there is
therefore a need for easily and cost-effectively producible,
improved grinding disc devices, which are suitable for the most
diverse kinds of application and exhibit an adequate grinding
performance.
SUMMARY OF THE INVENTION
[0008] The present invention, therefore, provides a grinding disc
device, which can easily be produced and provides an improved
grinding performance, and with which the drawbacks of the prior art
caused by the adhesive are avoided without limitations.
[0009] The present invention provides a grinding disc device for a
grinding apparatus, which comprises at least one grinding layer and
a carrier disc fixedly connected to the grinding layer. The
grinding layer comprises on a first side at least one connection
surface connected to the carrier disc and, with a second side lying
opposite, forms an abrasive grinding surface lying opposite the
connection surface and facing away from the carrier disc. The
carrier disc is made of a plastic material and is produced by means
of injection molding. The carrier disc is connected immediately and
directly to the connection surface of the grinding layer. The
plastic material of the carrier disc is sprayed by means of
injection molding immediately and directly onto the connection
surface of the grinding layer in such a way that the carrier disc
and the grinding layer are connected to one another in a
materially-bonded manner.
[0010] A grinding disc device for a grinding apparatus is
essentially understood in the present case to mean a grinding disc
with a carrier disc or carrier plate. In the sense of the present
invention the grinding disc device is to be regarded as a grinding
body, which can also be described as a grinding tool or grinding
plate or as a carried or held or supported grinding disc. The
grinding disc is designed particularly for rotating surface
fine-machining and is configured for use in a grinding apparatus
correspondingly driven rotationally or such machine tool, for
example a grinding machine, in particular an angle grinder.
[0011] In the present case, the carrier disc can also be described
as a carrier plate and is essentially to be understood as a support
body, a support disc, or a support plate. A grinding layer, in the
sense of the invention, is to be understood as an essentially flat
or planar disc-like element or a flat or planar disc-like structure
with a first side or side face and an opposite second side or side
face. The first side face forms the connection surface, which is
immediately and directly connected to the carrier disc, and the
opposite second side face forms the outwardly orientated grinding
surface which defines an underside of the grinding disc device. The
grinding layer may consist of a single part, or also of a plurality
of assembled parts, which together form the flat or planar
disc-like structure. According to the present understanding,
therefore, the connection surface and the grinding surface can also
be constituted as non-planar surfaces and can for example comprise
steps or graduations, offset edges or protruding regions, which may
perhaps arise if a plurality of parts are arranged together in a
preferably fan-shaped arrangement to form a flat structure.
[0012] To solve the aforementioned problem, according to the
invention, the carrier disc made of plastic is sprayed by means of
an injection molding process immediately and directly onto the
grinding layer, i.e. onto the connection surface of the grinding
layer, without an intermediate layer, in particular without an
adhesive or bonding agent applied in between.
[0013] Compared to the prior art, this solution has the
considerable advantage of a straightforward and quick production,
which essentially requires only one process step, i.e. the
injection molding process or the forming by means of injection
molding and takes place without the frequently impracticable
influences of an adhesive, because the plastic material of the
carrier disc is sprayed directly onto the grinding layer. The
essentially liquid, i.e. plasticised, plastic material connects in
an integrally, materially-bonded manner with the connection surface
of the grinding layer. As a result, after only a short hardening
time of less than a minute, a firm, durable connection between the
two parts arises, which is also extremely durable at high speeds of
the grinding disc device and therefore at high temperatures.
[0014] Due to the immediate and direct connection of the grinding
layer to the carrier disc according to the invention, the present
grinding disc device particularly advantageously has an improved
grinding performance, since the bonding of the grinding layer to
the carrier disc is thereby improved and is thus much more stable.
This leads to an overall harder grinding disc device, in particular
to a stabilised grinding surface with a greater degree of hardness.
The grinding disc device according to the invention can thus
advantageously be operated in a rotating manner in a grinding
apparatus with the avoidance of disruptive vibrations, i.e.
particularly advantageously vibration-free. This proves to be
particularly advantageous, since such grinding apparatuses are
operated at high speeds, for example in a range from 10,000 to
15,000 revolutions per minute, and the avoidance of vibrations at
such high speeds leads to a particularly reliable and efficient
operation.
[0015] In order to further improve the stability, in particular the
dimensional stability and/or the rigidity of the grinding disc
device, reinforcing structures can optionally be provided in the
carrier disc, and more precisely at an upper side of the grinding
disc device, which reinforcing structures can be constituted for
example in the form of annular ribs. In addition, or alternatively,
structures for improving the elasticity of the grinding disc
device, in particular for improving the elasticity during
application when grinding, can also be provided, which structures
can for example be constituted in the form of annular grooves.
[0016] According to a preferred embodiment, the grinding layer of
the grinding disc device may consist of a flat, circular grinding
disc, in particular a sanding disc. The grinding layer can then
preferably be formed by a conventional, commercially available
grinding disc, which usually comprises a carrier or carrier
material and an abrasive medium applied thereon. In accordance with
such a construction, paper carriers, fabric carriers, or vulcanised
fiber carriers are used as carriers and the abrasive medium can for
example be a ceramic grain. The side of the carrier which is loaded
with the abrasive medium represents the grinding surface and the
opposite, unloaded side of the carrier represents the connection
surface. In this embodiment, the connection surface is thus
essentially formed from the material of the carrier of the grinding
disc.
[0017] Preferably, the grinding layer is formed by a fiber disc, in
particular a vulcanised fiber disc, and the grinding surface is
formed preferably by a scattered ceramic grain abrasive medium.
Such grinding discs are produced and marketed for example by the
firm "VSM Vereinigte Schmirgel- and Maschinen-Fabriken AG" and are
available in the market under the trade name "VSM CERAMICS
Fiberscheiben".
[0018] In these particularly preferred embodiments, the carrier
material of the vulcanised fiber carrier of the grinding disc forms
the connection surface of the grinding layer for direct connection
to the plastic material of the carrier disc.
[0019] The grinding layer can also be composed of grinding
lamellas, which are arranged for example in a fan-shaped manner to
form the flat structure of the grinding layer. In all cases, the
plastic material for the carrier disc can be injected in the
desired manner into the molding tool of the injection molding
machine and sprayed directly onto the connection surface of the
grinding layer.
[0020] The connection surface and the grinding surface lying
opposite the connection surface are each preferably constituted at
least as annular, essentially continuous surfaces. In the present
case, this is understood in particular to mean that the two
aforementioned surfaces, in at least one annular section, form a
continuous, closed surface without interruptions. The annular,
essentially continuous surface or the annular, continuous surface
section preferably occupies more than half, particularly preferably
more than 60% and with particular preference more than 70% of the
total area of the underside of the grinding disc device. More
preferably, the annular, continuous surface section has a surface
segment area of more than 80% or more than 90% of the total area of
the underside of the grinding disc device. On the one hand, the
connection surface, onto which the plastic material of the carrier
disc is sprayed, is thus constituted at least in an annular section
as a continuous surface, which ensures a uniform and reliable
connection between the grinding layer and the carrier disc. On the
other hand, the grinding surface is sufficiently large to permit a
good grinding performance and efficient use.
[0021] Particular advantages arise from the fact that the grinding
surface of the grinding disc device, i.e. the grinding surface of
the grinding layer connected to the carrier disc, is constituted
dish-shaped. This is understood to mean that the grinding surface
does not run even or flat in a plane, but rather has an arch or
curvature. For example, the grinding surface is arched in a radial
direction, starting from an edge of the grinding disc device in the
direction towards the center, and more precisely for example with a
gradient angle in a range from approximately 3.degree. to
10.degree., preferably in a range from approximately 4.degree. to
7.degree., and more preferably of around 5.degree..
[0022] According to a preferred embodiment of the present
invention, slots distributed over its periphery for the passage of
cooling air are designed or formed in the carrier disc. Such slots
are known for example from the aforementioned German Patent No. DE
10 2016 102 037 B4. These slots provide, especially at high speeds,
for an effective cooling air flow in the direction of the grinding
layer and the machined workpiece, without the durability and
service life thereby being adversely affected. In a continuous
operation, temperatures over 100.degree. C. can be tolerated over a
long period.
[0023] In a development of the invention, the carrier disc is
constituted in one piece with a hub part, from which ventilation
ribs extend radially outwards. By means of the latter, a cooling
air flow is additionally generated, which markedly reduces the
working temperature.
[0024] Preferably, the hub part comprises an inner thread for the
fastening of the grinding disc device on a drive shaft of the
grinding apparatus. Cooling air passage slots can also be fashioned
into the hub part, which again assist efficient and effective
cooling.
[0025] The carrier disc is preferably produced from a thermoplastic
plastic, in particular from a thermoplastic polymer. For example,
the carrier disc can be made from a thermoplastic terpolymer,
preferably from an acrylnitrile-butadiene-styrene copolymer (ABS).
According to an alternative variant of embodiment, the carrier disc
can be made from a polyamide, preferably from polyamide PA6, in
particular from a glass fiber-reinforced PA6. Polyamide PA6 is a
thermoplastic, partially crystalline construction plastic, which
can be processed as a tough, hard industrial material. The main
properties are a high impact resistance, rigidity, and a good
damping capacity, as well as a relatively high dimensional
stability. As a result of a possible glass fiber reinforcement, for
example with a glass fiber content of 30%, the plastic is
ultimately even firmer and more rigid. As a result of the use of
PA6 or PA6-GF30, the production of the grinding disc device can
take place in the optimum manner by means of injection molding,
wherein the stability, strength, and hardness of the grinding disc
device are at the same time also matched in the optimum manner to
the technical requirements.
[0026] The present invention also includes a method for producing a
grinding disc device for a grinding apparatus by injection molding.
In the method, a grinding layer with a connection surface and an
opposite abrasive grinding surface is first provided and introduced
into a suitable molding tool of an injection molding machine. The
grinding layer is introduced into the suitable molding tool of the
injection molding machine in such a way that the connection surface
of the grinding layer points in the direction of a predefined
cavity of the molding tool. A carrier disc directly connected to
the grinding layer is then formed, wherein a plastic material
suitable for producing the carrier disc is injected into the closed
molding tool at a predefined temperature and under pressure. More
precisely, the plastic material of the carrier disc is sprayed
immediately and directly onto the connection surface of the
grinding layer and the grinding disc device is thus produced.
[0027] In injection molding, which numbers among the primary
shaping processes, a suitable material, in particular a plastic
material is liquefied, i.e. plasticised, and injected under
pressure with an injection molding machine into a cavity of a
corresponding mold, i.e. into the molding tool or injection molding
tool. The cavity represents the shaping hollow space. In the
molding tool, the plastic material transforms back into the solid
state by cooling or a cross-linking reaction and can be removed as
a finished part after the opening of the molding tool.
[0028] With the method according to the invention, the grinding
layer, and more precisely for example in the form of a grinding
disc, in particular a vulcanised fiber disc, is first introduced or
placed into the cavity of the molding tool of the injection molding
machine prior to the injection of the plastic material. The
grinding layer is placed into the cavity of the molding tool in
such a way that the connection surface of the grinding layer is
facing the hollow space, i.e. the cavity or the lumen of the hollow
space. That is to say that the side of the grinding surface lies
against an inner wall or hollow-space wall of the molding tool. As
a result, the grinding surface is facing outwards in the finished
molded part of the grinding disc device.
[0029] During the injection of the plastic material into the
shaping hollow space, which injection takes place for example under
a pressure in a range from 500 bar to 2000 bar and at a temperature
in a range from 200.degree. C. to 330.degree. C., the plastic
material is sprayed directly onto the connection surface of the
grinding layer, which is formed for example by the vulcanised fiber
material of the vulcanised fiber carrier of the grinding disc. No
prior treatment of the connection surface whatsoever is required,
i.e. any kind of use of additional binder or adhesive agents or
adhesives, bonding agents or such can be completely avoided.
[0030] As a result of the hardening in the injection molding
machine, the plastic material of the carrier disc hardens and is
directly bonded or fixed to the connection surface of the grinding
layer. In particular, it is connected in a materially-bonded manner
to the latter.
[0031] The carrier disc is preferably constituted in one piece with
a hub part by the injection molding. In addition or alternatively,
slots distributed over the periphery of the carrier disc for the
passage of cooling air can also be formed by the injection
molding.
[0032] Preferably, an inner thread is formed in the hub part for
the fastening of the grinding disc device on a drive shaft of the
grinding apparatus.
[0033] In addition, or alternatively, the hub part can also be
formed with corresponding cooling air passage slots.
[0034] With the method, a flat, circular vulcanised fiber disc with
a scattered ceramic grain abrasive medium can, for example, be used
as a grinding layer. At the same time, a glass fiber-reinforced
polyamide PA6 as a plastic material for the carrier disc is sprayed
onto the grinding layer. The preferred glass fiber-reinforced
polyamide PA6 has for example a glass fiber content of 30%.
BRIEF DESCRIPTION OF THE DRAWINGS
[0035] The invention will be explained below in greater detail with
the aid of examples of embodiment in connection with the
drawings.
[0036] FIG. 1 shows a diagrammatic plan view of a first example of
an embodiment of the grinding disc device according to the
invention;
[0037] FIG. 2 shows a cross-section through the grinding disc
device of FIG. 1;
[0038] FIG. 3 shows a perspective view of the grinding disc device
of FIG. 1;
[0039] FIGS. 4-6 show an alternative embodiment of the grinding
disc device according to the invention in plan view, in a
cross-sectional representation, and in a perspective view;
[0040] FIGS. 7-9 show a further alternative embodiment of the
grinding disc device according to the invention, wherein the
grinding layer comprises grinding lamellas, in plan view, in a
cross-sectional representation, and in a perspective view;
[0041] FIGS. 10-12 show a further alternative embodiment of the
grinding disc device according to the invention, wherein the
grinding layer comprises grinding lamellas, in a view from beneath,
in a cross-sectional representation, and in a perspective view from
beneath;
[0042] FIGS. 13-15 show a further alternative embodiment of the
grinding disc device according to the invention, wherein the
grinding layer comprises grinding lamellas, in a view from beneath,
in a cross-sectional representation, and in a perspective view from
beneath;
[0043] FIGS. 16-18 show yet another embodiment of the grinding disc
device according to the invention, in plan view, in a
cross-sectional representation, and in a perspective view and
[0044] FIGS. 19-21 show yet another embodiment of the grinding disc
device according to the invention, in plan view, in a
cross-sectional representation, and in a perspective view.
DETAILED DESCRIPTION OF THE INVENTION
[0045] All the examples of embodiment described below have in
common that grinding disc device 10, according to the invention,
comprises an essentially circular carrier disc 12 provided with an
abrasive grinding layer 14, such that grinding layer 14 and carrier
disc 12 are immediately and directly connected to one another
without an intermediate layer. The side of grinding disc device 10
on which abrasive grinding layer 14 is arranged represents an
underside U of grinding disc device 10. Opposite underside U of
grinding disc device 10 lies an upper side O defined by carrier
disc 12.
[0046] Carrier disc 12 is produced by means of injection molding
and is directly sprayed onto grinding layer 14 thereby constituting
grinding disc device 10 according to the invention. Carrier disc 12
is made of plastic, for example ABS, since the material is
food-safe, has a sufficient elasticity, and has a long life. Other
injectable plastics can also be used for carrier disc 12. More
preferably, carrier disc 12 is made of a polyamide, in particular
of polyamide PA6, and even more preferably of glass
fiber-reinforced polyamide with for example a 30% glass fiber
content, such as for example PA6-GF30.
[0047] In injection molding, which numbers among the primary
shaping processes, the plastic for carrier disc 12, for example ABS
or PA6, is plasticised and injected under pressure with an
injection molding machine into a shaping hollow space, i.e. the
cavity of the molding tool. The plastic material transforms back
into the solid state by cooling. For the production of grinding
disc device 10 according to the invention, grinding layer 14 is
first placed into the cavity of the molding tool prior to the
injection of the plastic material, in such a way that the side of
grinding layer 14 forming a grinding surface F.sub.S lies against
an inner wall of the cavity and a connection surface F.sub.V of
grinding layer 14 is thus facing the hollow space. The subsequent
injection of the plastic material into the shaping hollow space
takes place under pressure in a range from 500 bar to 2000 bar and
at a temperature in a range from 200.degree. C. to 330.degree. C.
The plastic material is thus sprayed directly onto connection
surface F.sub.V of grinding layer 14. As a result of the hardening
in the injection molding machine, the plastic material of grinding
disc 12 solidifies and is directly bonded to connection surface VF
of grinding layer 14 or is connected in a material-locking manner
to the latter.
[0048] In the example of the embodiment of FIGS. 1 to 3, grinding
layer 14, comprising a connection surface F.sub.V and a grinding
surface F.sub.S, consists of a flat, circular sanding disc 16,
wherein carrier disc 12 is sprayed directly by injection molding
onto connection surface F.sub.V of grinding layer 14 or sanding
disc 16 without plastic being applied between the two latter. This
takes place by means of injection molding in a suitable injection
molding machine as described above.
[0049] Grinding layer 14 is first introduced or placed into the
hollow space of the molding tool. More precisely, grinding layer 14
is placed into the hollow space of the molding tool such that
connection surface F.sub.V of grinding layer 14 is facing the
hollow space, i.e. grinding surface F.sub.S is facing an inner wall
or hollow-space wall of the molding tool and in particular lies
against the latter. The plasticised plastic material of carrier
disc 12 is then injected into the cavity under pressure and at
raised temperature. Following a short hardening time of less than
one minute, the plastic of carrier disc 12 is hard and firmly
connected in a durable manner to sanding disc 16 or grinding layer
14.
[0050] In the example of the embodiment of FIG. 1 to FIG. 3, a hub
part 18 is formed in one piece with carrier disc 12 at upper side O
of grinding disc device 10, from which hub part ventilation ribs 20
extend radially outwards. The ventilation ribs 20 provide for a
sufficient cooling air flow over the surface of carrier plate 12 at
the speeds generated during operation.
[0051] As FIGS. 2 and 3 show, hub part 18 comprises an inner thread
22, which is also formed in the injection molding, so that carrier
disc 12 can be fastened on a drive shaft of a grinding apparatus,
in particular a grinding machine, such as for example an angle
grinder.
[0052] Essentially annular grinding layer 14, which comprises a
central perforation in the region of hub part 18, comprises an
annular, continuous connection surface F.sub.V and an annular,
continuous grinding surface F.sub.S, wherein the circular surfaces
extend over more than 90% of the total area of underside U of
grinding disc device 10.
[0053] For further, improved cooling, slots 24 are designed or
formed distributed over the outer periphery or over upper side O of
carrier disc 12. The slots 24 provide for the passage of cooling
air both against connection surface F.sub.V of grinding layer 14,
which can also be seen as the inner surface, as well as against the
machined workpiece. Cooling air slots 24 are fashioned according to
the teaching known from German Patent No. DE 10 2016 102 037 B4,
which is incorporated herein by reference.
[0054] FIGS. 4 to 6 show a variant of the embodiment of FIG. 1 to
FIG. 3, wherein carrier disc 12 is also sprayed directly and
without adhesive onto grinding layer 14. Diverging from the example
of FIG. 1 to FIG. 3, central hub part 18 is constituted with a flat
dish-shaped and has ventilation ribs. In this example of the
embodiment of FIGS. 4 to 6, the central perforation of grinding
layer 14 in the region of hub part 18 is larger than in the example
of FIGS. 1 to 3, so that the surface segment area of annular,
continuous connection surface F.sub.V and grinding surface F.sub.S
in the total area of underside U of grinding disc device 10 is
smaller than in the example of FIGS. 1 to 3.
[0055] In the alternative, also preferred variant of FIGS. 7 to 9,
grinding layer 14 comprises grinding lamellas 26 arranged
fan-shaped. The plastic of carrier disc 12 is also sprayed without
an intermediate adhesive onto grinding lamellas 26 arranged
fan-shaped. Grinding lamellas 26 arranged fan-shaped again form a
flat grinding layer 14 with connection surface F.sub.V and grinding
surface F.sub.S, which are also constituted in this embodiment as
respective annular, continuous surfaces on account of the overlaps
of grinding lamellas 26 arranged fan-shaped.
[0056] In the embodiment of FIGS. 10 to 12, hub part 18, in the
same way as in the example of the embodiment of FIGS. 4 to 6, does
not have any ventilation ribs. The air slots at the outer periphery
of carrier disc 12 are also absent in this example of the
embodiment.
[0057] FIGS. 13 to 15 show a modified embodiment with a carrier
disc 12 constituted similar to the example of FIGS. 4 to 6, wherein
here, as also in the example of FIGS. 10 to 12, grinding layer 14
comprises grinding lamellas 26 arranged fan-shaped, onto which
carrier disc 12 is directly sprayed.
[0058] Finally, FIGS. 16 to 18 show an embodiment with a carrier
disc 12, which has cooling air slots 24 at the outer periphery for
the passage of cooling air. The flat, roughly dish-shaped hub 18 of
carrier disc 12 also comprises, in addition to ventilation ribs 20,
cooling air passage slots 28 for the passage of cooling air.
Grinding layer 14 comprises grinding lamellas 26 arranged
fan-shaped.
[0059] In FIGS. 19 to 21, an example of the embodiment of grinding
disc device 10 is shown, wherein grinding layer 14 is formed by a
grinding disc or a sanding disc 16. The grinding disc is a
vulcanised fiber disc, wherein grinding surface F.sub.S is formed
by a scattered ceramic grain abrasive medium.
[0060] In the case of grinding disc device 10 of the example of
FIGS. 19 to 21, hub part 18 is constituted with ventilation ribs 20
and with an inner thread 22. No cooling air slots are provided,
however, in carrier disc 12.
[0061] For the additional improvement of the stability, rigidity,
and bending strength, reinforcing structures are constituted on
carrier disc 12 at upper side O of grinding disc device 10, and
more precisely in the represented example in the form of an annular
rib 30. Furthermore, an annular groove 32 is provided, which serves
to improve the elasticity during grinding.
LIST OF REFERENCE NUMBERS
[0062] 10 grinding disc device [0063] 12 carrier disc [0064] 14
grinding layer [0065] 16 grinding disc or sanding disc [0066] 18
hub part [0067] 20 ventilation rib [0068] 22 inner thread [0069] 24
cooling air slots [0070] 26 grinding lamellas [0071] 28 cooling air
passage slots [0072] 30 annular rib [0073] 32 annular groove [0074]
F.sub.S grinding surface [0075] F.sub.V connection surface [0076] O
upper side [0077] U underside
* * * * *