Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02627128 2010-07-06
GRINDING OR POUSHING DISC HAVING A THREADED INSERT
Field of the Invention
The invention relates to a grinding or polishing disc comprising a
rotationally symmetrical
carrier disc, with a hollow cylindrical through-opening for receiving a drive
shaft of a drive motor,
the axis of the hollow cylinder coinciding with the axis of rotation; and a
threaded insert for a
grinding or polishing disc, with a continuous inner thread, the axis of
symmetry of which coincides
with the axis of rotation, for receiving a drive shaft of a drive motor.
Background of the Invention
_ Machine-operated grinding or polishing discs of this type are conventionally
screwed tight
to a drive shaft of an electrically operated machine. As grinding or polishing
discs are consumables
and it is also necessary to switch between various grain sizes relatively
frequently, simple
mounting must be possible. Different mounting systems are thus provided and
used for the
various grinding or polishing discs. in the most common variation, the
grinding or polishing disc is
attached to the drive shaft and subsequently fastened thereto with the aid of
a damping nut. In
another embodiment, the disc itself comprises an inner thread in the through-
opening. This allows
the grinding or polishing disc to be screwed directly onto the drive shaft
which has an outer
thread corresponding thereto. The latter variation thus allows particularly
rapid mounting and
dismantling of the grinding or polishing disc. The direction of rotation of
the thread of the drive
shaft is in this case configured in such a way that the grinding or polishing
disc is continuously
tightened in the grinding process and thus cannot come loose.
In addition to the mechanical properties, compatibility with the requirements
of the
environment and of health and safety play a significant part in the selection
of the materials to be used
for grinding or polishing discs. Under these conditions, it is advisable to
use various plastics materials.
Reinforcement with natural fibers has in this regard also proven a successful
way of achieving the
properties which are important for the grinding process.
The manufacture of grinding or polishing discs having an inner thread in the
through-
opening necessitates more extensive production activities compared to grinding
or polishing discs
having merely a through-opening, and this leads to higher production costs. In
the other case, in
the use of clamping nut for fastening grinding or polishing discs to the drive
shaft, a separate
CA 02627128 2011-03-17
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clamping nut is nevertheless, required. As the separate clamping nut is
handled separately from the
grinding or polishing disc, the grinding or polishing disc cannot be fastened
if the separate clamping
nut is lost. Grinding or polishing is then not possible.
The object of the invention is therefore to disclose a grinding or polishing
disc of the above-
mentioned type that is suitable in a simpler and improved manner for direct
mounting on a drive shaft
of a drive motor.
Summary of the Invention
As an aspect of the present invention there is provided a rotationally
symmetrical grinding or
polishing disc comprising a carrier disc which is equipped on its front with
grinding plates and which
has at its center a hollow cylindrical through-opening, and having a threaded
insert in the
through-opening for receiving a drive shaft of a drive motor, wherein the
length of a cylindrical part
of the threaded insert that is located in the through-opening is shorter than
the length of the
through-opening and is designed in such a way as to form on the back of the
grinding or polishing disc
a circular depression which is used to receive a disc-shaped shoulder on the
drive shaft, wherein at
least one welding protrusion is arranged in the area of a joint patch for
establishing a joint between
the carrier disc and the threaded insert via vibration welding, wherein the
welding protrusions are built
in such a way that they melt during vibration welding due to the friction
between the jointing
components, providing a conveniently and securely welded joint.
The length of the receptacle for the disc-shaped shoulder of the drive shaft
should in this case
be somewhat greater than the height of the shoulder on the drive shaft itself,
thus allowing the lower
free end of the cylindrical part to be screwed in during the grinding process
while tightening is still
being carried out in the direction of the drive shaft, thus allowing the
threaded insert to continue to
be tightened with the grinding or polishing disc. This produces a safe
operating state during polishing
or grinding. A press fit thus also allows the threaded insert to be joined
into the carrier disc in a simple
manner. The grinding or polishing disc is attached to the spindle of the drive
of the drive motor and
rotated on by hand, wherein the operator has merely to tighten the disc gently
using his fingers along
the circumferential edge of the carrier disc in order to obtain secure holding
of the grinding or
polishing disc on the spindle. During the grinding or polishing process
itself, the carrier disc having the
threaded insert is then drawn tight onto the spindle of the drive motor.
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In an expedient development, the grinding or polishing disc has an annular
cylindrical
reinforcement which protrudes on the front of the carrier disc along the
through-opening in order
to reinforce the through-opening along its outer opening edge in the direction
of the axis of
rotation-
This reinforcement serves, on the one hand, as a contact face for the threaded
insert and,
on the other hand, to extend the through-opening as an additional holding face
on the holding
spindle of the drive.
In a particularly preferred embodiment, the grinding or polishing disc has
ribs which
emanate radially from the annular cylindrical reinforcement and arc arranged
on the front of the
carrier disc.
This measure increases the stability of the carrier disc. However, it is
likewise possible to
arrange ribs also or only on the back of the carrier disc.
In a further embodiment, the grinding or polishing disc has, on the inner
circumferential
face of the through-opening, a molded-on locking ring which protrudes radially
into the inner
region of the through-opening. The threaded insert has in its first region a
widening toward its free
end, so the free end of the threaded insert is positioned in engagement after
the locking ring
when the assembly is pressed-in in the carrier disc.
This locking ring is attained as a function of production by removing the
injection core
which is left over when the injection core, which is arranged as a function of
symmetry in the
through-opening in the carrier disc, is punched out. This degree of break-off
can in this case be
further reworked in order to serve in this embodiment as a locking edge for
the threaded insert In
order to achieve engagement, the threaded insert thus preferably has a conical
widening In the
region which Is Inserted into the through-opening. In other embodiments,
instead of the
widening, this region of the threaded insert can also, for example, be
produced by the
introduction of protruding locking lugs, locking projections, which penetrate
slots along the axis of
rotation of the threaded insert in the first region or by radial locking rings
which are arranged
along the cylindrical circumference of the first region of the threaded
insert.
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However, joining of the threaded insert into the carrier disc does not have to
be limited
to a press fit. Further connections are possible, such as for example by
bonding, shrinking,
crimping of the threaded insert onto the carrier disc or by vibration welding.
In accordance with the invention, the threaded insert according to the
invention for a
rotationally symmetrical grinding or polishing disc is made of a plastics
material/natural fibre
mixture. In a particularly preferred embodiment, the threaded insert Is thus
in particular made of
a plastics material/hemp fiber mixture.
The carrier disc is thus preferably manufactured by injection-molding with the
addition of
hemp fibers. This allows environmentally friendly manufacture both of the
carrier disc and of the
threaded insert, as the content of the plastics material Is reduced by the
content of the hemp
fibers. The addition of natural fibers, In particular hemp fibers, thus helps
to increase the
toughness and strength of the parts.
In an expedient development, the threaded insert has a first region which Is
formed
cylindrically and a second region which is configured so as to radically hang
over the first region,
the overhanging part of the threaded insert resting on the front of the
carrier disc.
This design thus provides a stop allowing the annular end face of the second
region to rest
on the reinforcement of the carrier disc.
In an advantageous development, ribs, which are oriented parallel to the axis
of rotation
and are formed in their rib height in such a way that the threaded insert can
be joined in the first
region into the through-opening by a press fit, are arranged in the first
region of the threaded
insert on the outer circumferential face.
The ribs, the height of which allows the press fit to be defined, provide a
simple measure
for carrying out the joining between the threaded insert and carrier disc. In
terms of production,
this is a beneficial method. Differingly marked press fits can accordingly be
obtained, depending
on the height of the ribs. The press fit is thus to be configured in such a
way as to allow simple
tightening of the carrier disc with the threaded Insert joined therein on the
spindle of the drive
motor without the threaded Insert continuing to rotate in the through-opening
during lightening of
the carrier disc,
CA 02627128 2010-07-06
In an advantageous development, the ribs are configured in such a way that
they are
formed so as to decrease in height In the direction of the free end of the
first region.
This allows simple insertion of the first region of the threaded insert into
the through-
opening in the carrier disc. This wedge-type configuration of the ribs
facilitates joining which is to
be carried out with increasing force and also allows manual press-fitting if
the maximum rib height
is configured accordingly.
In a further embodiment, the threaded insert has, on the inner annular end
face of the
second region, radially protruding securing projections which are used for
securing on the carrier
disc, in particular on the annular end face of the projection on the carrier
disc.
Tightening of the carrier disc with the threaded insert allows the securing
projections to
engage with the surface of the reinforcement of the carrier disc, and this
both reinforces the
fastening of the threaded Insert to the carrier disc and reinforces the
fastening of the carrier disc to
the spindle of the drive motor. This further increases operational safety.
In an expedient development, the cylindrical part of the threaded insert thus
also has
securing projections which extend along its circumferential face In the
circumferential direction
and are likewise used for securing in the carrier disc. The securing
projections can be formed in
addition to the securing projections in the second region or as an alternative
thereto.
This embodiment further increases operational safety, thus all but ruling out
automatic
detachment of the grinding or polishing disc.
in an expedient development, the lateral end face of the second region of the
threaded
insert is configured spherically or In a rounded-off manner.
This ensures that the head of the threaded insert does not become damaged or
wom
during grinding or polishing as a result of the inclination of the grinding or
polishing disc_ During
operations in which the grinding or polishing disc Is held at an oblique angle
to the surface to be
machined, the machining is facilitated or not impeded only as a result of the
spherical or
rounded-off shaping, as this region of the threaded insert does not cause an
obstruction.
CA 02627128 2010-07-06
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In an expedient development, the threaded insert has In Its lateral end face
of the second
region at least two, preferably four blind holes which are arranged point-
symmetrically and at
uniform angles to one another and are used for screwing the grinding or
polishing disc to and
releasing it from the spindle. These blind holes are corresponding receptacles
for hand-held tools
like face pin spanner wrenches. Instead of a circular face cross section of
the blind holes, other
defined cross-sectional profiles can also be arranged, such as for example
square profiles,
triangular profiles or simply grooves. This allows the threaded insert to be
screwed or released,
when using depressions having defined cross-sectional profiles, only using
specific hand-held tools
which are provided only by a specific supplier. On the other hand,
standardized face pin spanner
wrenches are used to allow simple and secure handling of the threaded insert
for fastening and
removing the grinding or polishing disc which is fastened via the threaded
insert.
In an expedient development, at least one welding protrusion is arranged in
the area of the
join patch between the threaded insert and the carrier disc. Welding
protrusions turned out to be
extremely advantageous while jointing of jointing components via vibration
welding. The welding
protrusions melt during vibration welding due to the friction between the
jointing components
and provide a conveniently and securely welded joint. Less pressure, thus less
power is needed
for the joint by using welding protrusions so that the costs and also the
stress on the jointing
component are reduced. Welding protrusions are located either on the inner
annular end face of
the threaded insert or on the reinforcement of the carrier disc. The welding
protrusions are point-
or rib-shaped whereas they are distributed on the contact surface. Preferably,
multiple welding
protrusions are arranged rotation-symmetrically around the axis of rotation of
the threaded insert.
Preferably, curved and rib shaped welding protrusions are used whereas the
curvatures of the rib-
shaped welding protrusions are preferably adapted to the curvature of the
circumferential edge of
the inner annular end face so that the welding protrusions and the
circumferential edge preferably
have a constant distance from each other. Thereby, the welding protrusions are
preferably spaced
apart evenly of each other in the circumferential direction so that there are
free sections without
welding protrusions between the curved welding protrusions. Preferably, the
welding protrusions
have a tapering cross-sectional profile, for example triangular profile.
Through this, it is achieved
that the contact surface of the joint components, for example the contact
surface of the welding
protrusion and the reinforcement of the carrier disc, is small at the
beginning of the vibration
welding process and then increases continuously so that the stress on the
components due to
CA 02627128 2010-07-06
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pressure and friction is reduced. The height of the welding protrusions Is
only a few tenth of
millimeter, in particular 0.3 mm.
Brief Description of the Drawings
The invention will be described hereinafter with reference to preferred
exemplary
embodiments illustrated in the drawings, in which:
Figure 1 is a schematic cross section of a grinding disc;
Figure 2 is a schematic cross section of a threaded insert;
Figures 3a and 3b are a schematic perspective plan view and bottom view
respectively of the
threaded insert having ribs and securing projections;
Figure 4 is a schematic cross section of a carrier disc having an Injection
core;
Figure 5 is a schematic cross section of a carrier disc after removal of the
Injection core;
Figure 6 is a schematic cross section of a carrier disc having an inserted
threaded insert;
Figure 7 is a schematic plan view onto a grinding or polishing disc without
grinding plates and
having an inserted threaded insert;
Figure 8 is a schematic cross section of a threaded insert having blind holes;
and
Figure 9 is a schematic side view of a threaded insert having ribs and a blind
hole;
Figure 10 is a schematic bottom view of the threaded insert with the welding
protrusions; and
Figure 11 is a sectional view of the threaded insert with the welding
protrusions corresponding to
line A-A from figure 10.
Detailed Description of the Invention
Figure 1 is a cross section of a grinding or polishing disc 1 comprising a
carrier disc 2 on
which the grinding plates 3 are arranged on the front V of the grinding or
polishing disc 1.
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Furthermore, the grinding or polishing disc 1 has a central, hollow
cylindrical through-opening 4,
the cylinder axis of which coincides with the axis of rotation of the grinding
or polishing disc 1. In
the through-opening 4, the threaded insert 5 is arranged joined by a press
fit. The through-
opening 4 has in this case a length which is denoted by L2, When the threaded
insert 5 Is inserted
into the through-opening 4 from the direction of the front V, there remains a
circular depression 6
on the back R of the carrier disc 2, which depression provides space for
receiving a disc-shaped
shoulder of the drive shaft. The threaded insert 5 has in this case a
cylindrical part 51.
Figure 2 is a cross section of the threaded insert 5 comprising two regions B1
and B2. The
first region 61 has the cylindrical part 51. The second region 82 has the
overhanging part 52
which hangs over the cylindrical part 51. The length of the cylindrical part
51 is denoted by L1. In
this case, the length L1 is less than the length L2 of the through-opening 4
(see Figure 1). This
allows the threaded insert 5 to be tightened into the through-opening 4, as
the length L1 is
designed in such a way that it does not reach the disc-shaped shoulder of the
drive shaft. The
screwing-tight can thus cause the cylindrical part 51 to be drawn in the
direction of the drive shaft
during grinding or polishing. The second region B2 of the threaded insert 5
has an inner annular
end face 56. The lateral end face of the cylindrical part 51 forms the free
end 55. The lateral end
face of the overhanging part 52 forms the upper end 58 of the threaded insert
5. The threaded
insert is formed at least partly of a plastics material. The material used is,
in particular, a plastics
material/hemp fiber mixture.
Figures 3a and 3b are a perspective plan view and bottom view respectively of
a threaded
insert 5. In this embodiment, the threaded insert 5 has on Its lateral end
face 58 blind holes 10
which are used to receive face pin spanner wrenches. Ribs 54, which are used
for press-fitting the
cylindrical part 51 into the through-opening 4 in the carrier disc 2, are
arranged on the
circumferential face 53 of the cylindrical part 51. Depending on the design of
the height of the
ribs 54, a correspondingly strong or weak press fit Is produced. In a further
embodiment, the
lateral circumferential face 59 of the overhanging part 52 is formed at an
angle of inclination in
relation to the lateral end face 58, this angle being selected in the range of
from 1Q to 20=,
particularly preferably in the range of from 12 to 10 and in particular at 29
to the lateral end face.
The bottom view of the right-hand diagram of Figure 3 shows how the securing
projections 57 are
formed on the inner annular end face 56 of the overhanging part 52. The
securing projections are
used for additionally fastening the threaded insert 5 to the carrier disc 2
during the tightening
which is carried out during the grinding or polishing process. The securing
projections 57 can in
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this case be formed so as to be saw tooth-shaped, triangular or the like in
cross section. The ribs
54 are oriented parallel to the axis of rotation of the threaded insert and at
a uniform angle over
the circumference of the first region, in this. case the cylindrical part 51.
The ribs 54 are in this
case configured as radial projections having a height so as to allow press-
fitting of the region 81 or
cylindrical part 51 into the through-opening 4.
Figure 4 is a cross section of a carrier disc 2. This diagram shows the
production step in
which the injection core 11 is still arranged in the region of the through-
opening 4. Owing to the
injection core 11 which is present, the through-opening 4 is not yet
continuous In its formation.
The core 11 is broken or punched out of the region of the through-opening 4 by
the exertion of
an axial force.
Figure 5 shows the next stop in the production of the carrier disc having an
Inner locking
ring 9. The view is a cross section of the carrier disc 2 in which the core 11
has already been
removed. There remains a break-off web which is used as the locking ring 9.
This locking ring 9
can thus be further reworked in order to rework the degrees of break-off or in
order to further
define the dimension or the 'locking ring. The locking ring 9 is thus arranged
in the inner
circumferential face of the through-opening 4 and preferably oriented
orthogonally to the axis of
rotation.
. Figure 6 Is a cross section of the carrier disc 2 having an inserted
threaded insert 5 and a
locking ring 9 in the through-opening 4. In the embodiment including the
locking ring 9, the
threaded insert is expediently formed so as to widen in the region B1 toward
the open end. The
widening is in this case designed in such a way that, when the threaded insert
5 Is inserted into
the through-opening 4, the widened end of the region B1 comes to lie below the
locking ring 9,
thus producing engagement between the open end 55 and the locking ring 9. This
embodiment
provides a different possibility for press-fitting.
Figure 7 is a plan view onto a grinding or polishing disc 1. The grinding
plates 3 are not
shown in this diagram. The front of the grinding or polishing disc may be
seen. The threaded
insert 5 is arranged in the center of the carrier disc 2. In this case, the
Inner annular end face rests
on the reinforcement 7 which may not be seen in this plan view. Ribs 8, which
additionally
reinforce the carrier disc 2, are formed extending radially outward from the
reinforcement 7.
CA 02627128 2010-07-06
' I I
Preferably, the ribs 8 are arranged at uniform angles between the projection 7
and the region on
which the grinding plates 3 are arranged.
Figure 6 is a cross section of the threaded insert 5. In this embodiment,
blind holes 10 are
arranged on the lateral end face 58 of the region B2_ However, the cross-
sectional face of the
blind hole 10 can also be determined so as to be defined individually in order
thus to oblige a
supplier to provide only specific hand-held tools. Obviously, standardized
hand-held tools, such
as for example face pin spanner wrenches or the like, can also be used.
Figure 9 is a side view of the threaded insert 5. An opening of a blind hole
10 may be seen
in the lateral end face in this drawing. It may in addition be seen that the
lateral circumferential
face 59 of the second region B2 Is formed at a slight inclination toward the
lateral end face 58.
Particularly preferably, the inclination is selected so as to be approximately
24. The ribs 54 are
arranged in the region 81 which is the cylindrical part 51. In this
embodiment, the ribs produce
the press fit into the through-opening 4 in the carrier disc 2.
Highly effective securing of the threaded insert 5 in the carrier disc 2 is
also achieved as a
result of the fact that the threaded insert has ribs 54 (Fig. 3a, 3b) and that
the through-opening 4
in the carrier disc 2 contains complementary recesses (not shown) which
receive the ribs 54.
Figure 10 illustrates a bottom view of the threaded insert 5 with welding
protrusions 60.
According to this embodiment, four curved and rib-shaped welding protrusions
60 are arranged
on the inner annular end face 56 whereas the curvatures of the welding
protrusions are adapted
to the curvature of the circumferential edge of the inner annular end face 56
so that the welding
protrusions 60 and the circumferential edge of the Inner annular end face 56
are distanced
constantly to each other in the circumferential direction. Thereby, the
welding protrusions 60 are
spaced apart evenly from each other Intermitted by free sections so that the
melting film can be
distributed evenly in the jointing area in the direction of the friction, thus
is the circumferential
direction.
Figure 11 illustrates a cross-sectional view of the threaded insert 5
corresponding to line A-
A from figure 10. According to this embodiment the welding protrusion 60 has a
triangular cross-
sectional profile having a height of 0.3 mm. By this tapering profile it is
achieved that the contact
surface of the components to be jointed, for example the contact surface of
the welding
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protrusion 60 the reinforcement 7 of the carrier disc 2 is small at the
beginning of the vibration
welding process and then increases continuously so that' the stress on the
components due to
pressure and friction is reduced and that the welded joint is equal and
secure.
