Note: Descriptions are shown in the official language in which they were submitted.
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ABRADING MACHINE WITH ABRADING DISCS, WHICH ARE MOVED IN A RECIPROCATORY
MOVEMENT TRANSVERSE TO THE ITEM
The invention relates to an abrading machine for abrasion of substantially
plane
items using rotating abrading discs, which simultaneously reciprocate, i.e.
move
forwards and backwards, transverse to the item and preferably has downwardly
extending abrasive lamellae.
It is preferred that the machine also comprises one, typically two, counter
rotating
abrading cylinders equipped with elongated abrasive elements, which are
radially
mounted on the abrading cylinder with the abrasive lamellae extending radially
from
the cylinder.
BACKGROUND OF THE INVENTION
For abrasion of items with a plane surface an abrasive belt often used, which
is
mounted on a belt sander. However, this abrading method is only suitable for
abrasion of completely plane surfaces, as carvings in or other shapings of the
surface
will be "smoothed out" and the lowered surface will not be abraded by the
abrasive
belt. At the same time, the exactness of the abrasion is thereby not
satisfactory in
relation to many abrading tasks. This means that this abrading method is
unsuitable
for many abrading tasks within, e.g., the furniture industry where a gentle
but at the
same time complete abrasion is required. Similar problems with performing a
complete deburring and abrasive or polishing surface treatment in connection
with
cut-out, milled out and laser-cut items are known from the metal industry as
well as
in production and surface processing of so-called "solid surface" items.
Within, among others, the production of furniture many different abrasion
tasks
depend on the size and shape of the item. Within the last decades, a
considerable
automation of the production of wood products has taken place within, among
others,
the furniture industry, which also makes new demands on the abrading tools.
In,
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among others, WO 01/76824 and US-A-6,267,660 a rotating abrading tool is
described in the form of a roll with abrasive elements, a so-called abrading
cylinder,
which is suitable for abrasion of profiled or plane items. Here, the plane
item is
conveyed through the abrading device on a conveyor belt, a trolley or the like
in a
continuous movement. The roll is brought to rotate about its longitudinal axis
and the
rotating abrading tool is brought into contact with the surface, whereby a
gentle
abrasion may take place. This abrasive method is gentle due to a low abrasive
pressure but it may be a slow abrasive process in relation to abrasive tasks
on a
general plane face having shapings, e.g., a door. In this case, it is
necessary to move
the abrading tool in a complicated movement around along the shapings to
ensure a
complete abrasion of these. In this connection it is also of great importance
which
rotational direction the abrading tool has in relation to the profile curves.
The result
is that the conduction of the abrasive task becomes slow and at the same time
may be
difficult to fully automate which also makes the tool inefficient seen from a
production cost view.
Thus, to achieve an efficient working procedure at abrasion of items with
shapings or
other carvings in a substantially plane surface, it may be necessary to apply
belt
abrasion for the plane faces and a rotating abrading tool for the shaping
areas, where
the abrading tool is moved about along the shapings.
Thus, it is a purpose of the present invention to achieve an abrading device
which
complies with the disadvantages of the known techniques as described above by
enabling an efficient, simultaneous and uniform abrasion or processing of an
item's
surface.
By the present invention an abrading device for abrasion of substantially
plane items
is provided, said device comprising means for conveyance of the items in a
direction
of feed, suspension means for suspension of a plurality of abrading discs for
abrasion
of a side of the items, means for driving rotation of the abrading discs
around axes
being substantially perpendicular on the side of the items, and means for
driving the
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abrading discs in a reciprocatory movement transverse to the direction of feed
of the
items. By moving the abrading discs in an oscillatory or reciprocatory
movement
transverse to the direction of feed of the items it is achieved that traces
etc. from the
different abrasive properties of the abrading discs across the diameter of the
disc are
eliminated as well as all parts of milled out areas etc. are abraded evenly,
especially
if the preferred abrading device is arranged to apply abrading discs with
abrasive
means which comprise abrasive lamellae of an abrasive sheet, such as abrasive
cloth
where the surface of which has abrasive properties and which extends from the
face
of the abrading disc. Such abrading discs are, e.g., described in US-A-
4,493,170, in
DE-A-24 11 749 and in EP-A-0 922 535.
BRIEF DESCRIPTION OF THE INVENTION
The present invention relates to an abrading device for abrasion of
substantially
plane items, said device comprising
means for conveyance of the items in a direction of feed,
suspension means for suspension of a plurality of abrading discs having
abrasive means for
abrasion of a side of the items,
means for driving rotation of the abrading discs around axes, which are
substantially perpendicular to the side of the items, and
means for driving the abrading discs in a reciprocatory movement transverse to
the direction of feed of the items.
According to an embodiment of the present :invention, there: is provided an'
abrading device for abrasion of substantially plane items, said device
comprising:
means for conveyance of the items in a direction of feed;
suspension means for suspension of a plurality of abrading discs having
abrasive means for abrasion of a side of the items;
means for driving rotation of the abrading discs around axes, which are
substantially perpendicular to the side of the items;
means for driving the abrading discs in a reciprocatory movement
transverse to the direction of feed of the items; and
at least one abrading cylinder, which is arranged to abrade a side of the
item and which comprises abrasive means extending substantially radially from
an elongated core, wherein said at least one abrading cylinder extends
transversely to the direction of feed and is driven to rotate about a
longitudinal
axis.
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The suspension means for suspension of the abrading discs is preferably made
as one
single structure so that the reciprocatoiy movement of all the abrading discs
can be
driven by the same drive means. This or these means may typically be an
electrical
or hydraulic motor, which drives rotation of an axis with an eccentric
attachment to
the suspension means but may, e.g., instead consist of an elastic suspension
of the
suspension means and a solenoid which is turned on and off at a given
frequency by
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a relay, thus performing regularly changing forces between the suspension
means
and a stationary part of the abrading device.
This reciprocatory movement transverse to the direction of feed of the items
is
preferably a substantially strictly transverse movement but may also, e.g.,
comprise a
circular or elliptical shaped movement of the abrading discs as long as the
movement
pattern includes said reciprocatory movement. The reciprocatory movement of
the
abrading discs has in one embodiment preferably a length of stroke of 40-100%,
preferably 60-85%, of the diameter of the discs to eliminate the tendency to
groove
formation. By length of stroke is understood the distance between the two
extreme
positions in transverse direction of the centre axis of an abrading disc.
It is preferred that the suspension means are arranged for suspension of
abrading
discs with abrasive means, which extend from the face of the abrading disc in
as
much as such abrading discs, as, e.g., known from US-A-4,493,170, from DE-A-24
11 749 and from EP-A-0 922 535, are particularly suitable for abrasion of
lowerings
in the surface such as milled out areas or perforations. According to the
invention,
the device may, however, also comprise abrading discs with plane abrasive
means
such as a yielding disc mounted with an abrasive ring of abrasive paper or
abrasive
cloth, which may vary in hardness depending on the task.
The abrading device may advantageously comprise a plurality of abrading discs
with
undercut grooves for reception and fixing of profile rails which form a part
of
elongated abrasive elements comprising abrasive means, said grooves preferably
extend in a mainly radial direction on the face of the abrading disc. Thereby,
the
abrading discs can receive elongated abrasive elements which consist of
abrasive
means in the form of lamellae of abrasive cloth of which the front side has
abrasive
properties and the back side is supported by support elements being elastic in
the
tangential direction of the disc, so that the front side of the abrasive cloth
is pressed
into abutment with a relatively high abrasive pressure with the surface to be
abraded
and thus the abrasion can take place at low feed velocity of the abrasive
element, i.e.
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low rotational speed of the abrading disc, in order to prevent strokes at the
point
between faces and profiles and partly in order to keep the front side of the
abrasive
cloth in continuous contact with the surface of the item to be abraded, which
results
in a uniform and complete abrasion. The support elements are preferably
brushes,
5 e.g., natural brushes, which extend from the face of the disc in a shorter
distance than
the abrasive means so that the support elements are not normally in contact
with the
item. The abrasive means and support elements are secured in a profile rail
with a
cross section corresponding to the cross section of the grooves such that the
abrasive
elements are easily pushed into and retained by the grooves and also easily
removed
from them whereby a replacement of worn abrasive elements or a conversion of
the
device to another kind of processing with other abrasive elements is easily
performed. Suitable kinds of abrasive elements are described in, e.g., WO-A-
01/76824.
Furthermore, holding elements may be arranged between the abrasive elements in
order to limit the deflection of the abrasive means. The effect of the holding
elements
is that the abrasive means at a certain deflection thereof become engaged with
the
holding element at the back, which results in an increased stiffness of the
abrasive
means and thereby requires greater force for further deflection. The holding
elements
preferably comprise a holding brush having a shorter length than the abrasive
elements and which is mounted in a profile rail, which is received in a
corresponding
undercut groove on the face of the abrading disc.
The means for driving the rotation of the abrading discs is normally arranged
in such
a way that all abrading discs are rotated the same way. However, it is also an
option
according to the present invention that adjacent abrading discs are rotated in
the
opposite direction which in combination with the reciprocatory movement of the
abrading discs results in a more uniform abrasion of all parts of the item
surface.
The plurality of abrading discs may preferably be arranged so that they are
aligned
transversely to the direction of feed of the items. In a further preferred
embodiment,
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the plurality of abrading discs are arranged in two consecutive rows
transversely to
the direction of feed of the items, wherein the discs in one row are staggered
with
respect to the discs in the other row. In the latter arrangement, the length
of stroke
may be reduced and is preferably a magnitude of 20-50%, preferably 30-43%, of
the
diameter of the discs.
The abrading device, according to the invention, may further comprise at least
one
abrading cylinder, preferably two opposite rotating abrading cylinder, which
are
arranged to abrade a side of the item, and which preferably comprises abrasive
means extending substantially radially from an elongated core, said abrading
cylinder(s) extending transversely to the direction of feed and is/are driven
to rotate
about their longitudinal axes. Preferably, the at least one abrading cylinder
is
arranged after said side has been abraded by the abrading discs but may
alternatively
be arranged before, so that the items meet the cylinder prior to the abrading
discs. An
abrasion with rotating abrading discs can be relatively aggressive as there
will be
some transversal abrasion of the items and the device is typically designed
for a
relatively high abrasion pressure and low rotational speeds of the abrading
disc in
order not to deform possible shapings in the work piece. Thus, some "wild"
abrasive
scratches will occur due to the rotation but these will be removed by the one,
two or
more abrading cylinder, which will, typically, be equipped with a rougher grit
size
than the abrading discs. Alternatively, the machine may be constructed with an
extra
similar module with a plurality of abrading discs in order to leave out the
abrading
cylinders.
SHORT DESCRIPTION OF THE DRAWING
Preferred embodiments of an abrading device according to the invention is
described
in the following with reference to the enclosed drawing in which
Fig. 1 illustrates the abrading device seen from above with some parts left
out so that
the abrasive parts are visible,
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Fig. 2 illustrates a part of the abrasive device seen from the feed end in a
perpendicular section through the abrading discs; in which the abrading discs,
their
slide and the drive are illustrated,
Fig. 3 illustrates the abrading device seen from the side in a perpendicular
section,
Fig. 4 illustrates an abrading disc, the slide of the abrading discs and their
suspension
and drive seen from the side in a partly section, and
Fig. 5 illustrates a second embodiment of the present invention.
DETAILED DESCRIPTION OF AN ABRADING DEVICE ACCORDING TO THE INVENTION
In the following, a preferred embodiment of an abrading device according to
the
invention is described as an example and illustration of the invention. The
example
does not serve to limit the invention and from the description and the claims,
the
skilled person will be able to embody a number of alternative devices, which
will all
be within the scope of the invention.
The abrading device 1 comprises a conveyor belt 2 driven continuously or
stepwise
by a motor 3 and is used to convey substantially plane items through the
abrading
device 1 from a feed end 4 in a direction of feed indicated by the arrow A on
Fig. 1.
Hereafter, the upper side of the item contacts with six abrading discs 5
arranged in a
row which is transversal in relation to the direction of feed of the item and
where the
abrading discs 5 are rotated clockwise and counter-clockwise alternately such
that
two adjacent abrading discs 5 are rotated in separate directions as indicated
by the
arrows B-G on Fig. 1. Alternatively, the drive of the abrading discs 5 may
also be
arranged such that all the abrading discs 5 rotate in the same direction. The
abrading
discs 5 are mounted on a slide 10 which during operation is moved in a
reciprocatory
movement as indicated by the arrow H on Fig. 1, where the movement has a
length
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of stroke so that the extreme positions of each of the abrading discs 5 centre
positions
in the reciprocatory movement are situated with a mutual distance of 75% of
the
diameter of the abrading discs 5. Each abrading disc 5 consists of a disc 6
which, on
the bottom side facing down towards the item, has a plurality of undercut,
radially
running grooves (not shown) in which abrasive elements (not shown) are
received
comprising a profile rail which retains a number of abrasive lamellae of which
the
front side has abrasive properties and of which the back side is supported by
a
number of support brushes. The abrasive lamellae extend downwards from the
disc
towards the item substantially perpendicular to the rotation plane of the
disc. A
suitable type of such abrasive lamellae consisting of profile rail, abrasive
lamellae
and brushes is, e.g., described in WO-A-01/76824. The abrasive elements are
orientated in such a way that the front side of the abrasive elements with the
abrasive
properties are at the front in the rotational direction. The abrasive elements
are
secured on the disc by the interaction between the profile rail and the
undercut
grooves having a dovetailed cross section of the opening, and by a ring, which
extends around the periphery of the disc and closes the open end of the rails
at the
periphery of the disc. This ring is removable after which the abrasive
elements can be
pushed out of the grooves and new abrasive elements can be pushed in. After
having
passed the abrading discs 5 the items are transported further on the conveyor
belt 2
under two opposite rotating abrading cylinders 7, 7' which remove possible
scratches
in the surface of the items and give the surface the final finish. The
abrading
cylinders 7, 7' are driven by associated motors 8, 8'. Suitable abrading
cylinders are,
e.g., described in WO-A-01/76824. Thereafter, the conveyor belt 2 conveys the
items
out of the abrading device at its exit end 9.
As shown in Figs. 2-4 the abrading discs 5 are mounted on a common slide 10
which
is movable in transverse direction in relation to the direction of feed of the
items in
as much as the slide 10 comprises two rails 11 that run in three sets of
wheels 12
which are securely mounted on a transverse beam 13 which is secured to the
frame
14 of the abrading device 1. Each abrading disc 5 is mounted on a vertical
axle 15,
which is embedded in the slide 10 with bearings 16 such that it turns freely
about its
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vertical axis with minimal friction. The axle 15 extends through the slide 10
and has
at its upper end a pulley 16 to cooperate with a v-belt 17 for driving the
rotation of
the abrading discs 5. All abrading discs 5 are driven by a motor 18 mounted on
the
slide 10, which has a pulley 20 mounted on its driving axle 19. On Fig. 3 and
4 the
extension 21 of the abrasive lamellae in vertical direction is indicated.
The reciprocatory movement of the slide 10 transverse to the direction of feed
of the
items is driven by a separate motor 22 via an eccentric mechanism 23.
The embodiment shown in Fig. 5, the abrading discs 5, 5' are arranged in two
successive rows transversely to the direction of feed A of the items, and the
discs 5 in
the first row are staggered with respect to the discs 5' in the second row.
All the discs
5, 5' are arranged on a common slide 10 which, due to the staggered
arrangement,
during operation is moved in a reciprocatory movement as indicated by the
arrow H
on Fig. 1, with a length of stroke of about half of the magnitude of the
embodiment
shown in Fig. 1, i.e. the extreme positions of each of the abrading discs 5,
5' centre
positions in the reciprocatory movement are situated with a mutual distance of
about
35-40% of the diameter of the abrading discs 5, 5'.
