Note: Descriptions are shown in the official language in which they were submitted.
CA 02316815 2004-11-12
1
Cutting apparatus for a plastic closure --.
Description
The invention relates to an apparatus for
making at least one cut running in the circumferential
direction of a plastic closure, having at least one
cutter, held by a holding device, and having a securing device for the
closure, wherein the closure is mounted rotatably about its centre axis
1 0 ~ the cut can be made by a rotation of the closure about its
centre axis.
A cut made in the circumferential direction o'f
a plastic closure serves, for example, for forming a
guarantee ring which, when opening a container on which
the plastic closure is fitted, is separated at least in
certain portions from the plastic closure and/or is
irreversibly deformed in such a way that opening of the
container for the first time is indicated. Apparatuses
of the type referred to here are known. They have a
plurality of fixedly arranged cutters, which are passed
by by a plastic closure which can be displaced along a
path of movement. In general, three cutters arranged
one behind other - seen in the direction of
displacement of the closure - are used for this
purpose, the closure being pressed against the said
cutters and rolling along them as a result of its
displacement movement along the path of movement. In
this operation, a partial cut running over 120° of the
circumferential surface of the closure is respectively
made in the said circumferential surface by each
cutter, the said cuts adjoining one another and thereby
forming a continuous cut. Although a continuous cut is
made in the circumference of the closure by the known
cutting apparatus, the cut has a varying depth - seen
in the circumferential direction - on account of the
arrangement of the cutters and the cutting edge
geometry. The cut profile is such that the depth of
the cut is very small in the initial region of a
cutter, greater towards the centre of the cutter and
less again from the centre towards the end region of
the cutter. Due to this depth-of-cut profile, it
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' cannot be ensured in all cases that the forces acting
on the guarantee ring when the container is opened are
adequate to damage or deform the said ring in the
desired way, with the result that opening for the first
time cannot be detected with certainty. A further
disadvantage of the cut of varying depth is that the
guarantee ring can already be separated from the
closure in certain portions, in the regions with the
greatest depth of cut, during its production or fitting
onto the container, which in turn reduces the
reliability of the guarantee ring.
It is therefore the object of the invention to
provide an apparatus by means of which a cut running in
the circumferential direction of a closure can be made
with a constant, or least substantially constant depth.
To achieve this object, a cutting apparatus
> according to one embodiment of the invention has
a holding device that can be displaced with
respect to a path of movement of the closure by
means of a control system, the closure is
mounted rotatably about its centre axis and the
cut can be made by a rotation of the closure about its
centre axis, the distance between the closure and the
cutter being constant or substantially constant during
the rotation. In the case of a circumferential cut,
the closure is rotated through 360°. For making the
cut running in the circumferential direction of the
closure, the closure is firstly brought together with
the cutter, which is fixed by a holding device, and,
after making contact with the cutter, is rotated in a
defined manner about its centre axis. At least one cut
running in the circumferential direction of the closure
is thereby made with a constant depth. The uniform
depth of cut over the circumference of the closure is
achieved by the distance between the closure and the
cutter not being changed during the rotation of the
closure about a centre axis. That is to say, at least
the region of the cutter at the smallest distance from
the centre axis of the closure has a fixed position
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with respect to the closure during the cutting
operation. Since only a single cutter is required for
making the cut running in the circumferential direction
of the closure, the construction of the cutting
S apparatus can be simplified and consequently the costs
thereof can be reduced.
Particularly preferred is an exemplary
embodiment of the cutting apparatus which is
distinguished by the fact that the path of movement of
the closure is a circular path and that the holding
device holding the cutter can be displaced along a
closed, curve-shaped contour path, the centre point of
which lies on the centre point of the circular path.
The cutting apparatus has a carousel-like construction,
that is to say the closure and the cutter, or the
holding device holding the cutter, are displaced
together along the path respectively assigned to them,
preferably at the same circumferential speed, during
the cutting operation.
In a preferred exemplary embodiment of the
cutting apparatus, the control system is designed as a
cam control system, which here has a disc cam. The
latter is felt by a feeling element, interacting with
the holding device for the cutter. The feeling element
is preferably connected to the holding device on which
the cutter is fastened. Thus, the contour path along
which the holding device is displaced is defined by the
disc cam.
In an advantageous development of the
invention, the depth of cut can be set. This makes it
possible to adapt or set the cutting apparatus to
plastic closures with different wall thicknesses or
shapes and/or of different plastics.
Also preferred is an exemplary embodiment of
the cutting apparatus in which the position of the
cutter with respect to the closure can be set. As a
result, a defined angle of cut can be set, with the
result that the cut surface is inclined with respect to
an imaginary horizontal by an angle which is greater
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than 0° and less than 90°. In another exemplary
embodiment, it is provided that the cut surface formed
during the cutting operation is parallel to the
imaginary horizontal, in other words runs
perpendicularly with respect to the circumferential
surface of the closure.
Further advantageous embodiments emerge from
the remaining subclaims.
The invention is explained in more detail below
with reference to the drawing, in which:
Figure 1 shows a plan view of an exemplary
embodiment of the cutting apparatus according to the
invention and
Figure 2 shows a side view of an exemplary
embodiment of a securing device for the closure.
Figure 1 shows a plan view of a basic diagram
of an exemplary embodiment of an apparatus, referred to
in the following as cutting apparatus 1, for making at
least one cut in a closure 3, which consists of plastic
and is used for closing a container, for example a
bottle. The closure 3 is mounted rotatably about its
centre axis 5 by means of a securing device,
represented in Figure 2, and can be displaced along a
path of movement 7, represented by dashed lines. In
this exemplary embodiment, the path of movement 7 is a
circular path with the centre point 9. The closure 3
is represented in Figure 1 in several positions A to F,
which it assumes or passes through one after the other
inside the cutting apparatus 1.
The cutting apparatus 1 comprises a holding
device 11, which can be displaced about the centre
point 9 of the path of movement 7 and has a setting
element 13, on which a cutter 15 is fastened. The
setting element 13 is guided in a groove 17 and can be
fixed on the holding device 11 with the aid of at least
one fastening means 19, for example by means of two
locking screws. The longitudinal centre axis 20 of the
groove 17 intersects the centre point 9, that is to say
the cutter 15 can be displaced both in the direction of
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the centre point 9 and in the direction of the path of
movement 7 by a displacement of the setting element 13
in the groove 17. The holding device 11 further
comprises a guiding part 21 for the closure 3, which
has a semicircular depression 23, open at the edge, for
receiving the closure. The depression 23 is made in
the guiding part 21, starting from a planar side face
25 of the said part facing the path of movement 7. The
cutter 15 fastened on the setting element 13 is
positioned on the holding device 11 in such a way that,
in order to come into engagement with the closure, it
protrudes into the depression 23 of the guiding part
21, thereby fixing the depth of the cut to be made into
the circumference of the closure 3. The depth of cut
can be adjusted in a simple way by varying the position
of the setting element 13, on which the cutter 15 is
fastened, within the groove 17. At the end of the
holding device 11 facing away from the guiding part 21
there is provided a feeling element 27, which interacts
with a control system 29 of the cutting apparatus 1,
which will be discussed in more detail below.
The control system 29 is designed in this
exemplary embodiment as a cam control system, which
comprises a contour disc 31, which is also referred to
as a cam disc, is of a substantially circular design
and the centre point of which lies on the centre point
9 of the path of movement 7 of the closure 3. The
contour disc 31 has a fixed position and, when there is
a displacement of the holding device 11 and the closure
3, does not rotate at the same time but remains in the
position represented in Figure 1. The contour disc 31
has a curve-shaped outer contour 33, which is felt by
the feeling element 27 of the holding device 11,
mounted displaceably in the direction of the
longitudinal centre axis 20. As a result, when there
is a rotation about the centre point 9, the holding
device 11 is positively driven and is displaced along a
contour path, the profile of which corresponds to the
outer contour 33 of the contour disc.
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The contour disc 31 has a sub-portion 35.1,
which extends over a circumferential region of about
110° and is designed as a portion of a circular path.
The sub-portion 35.1 is adjoined - seen in the
direction of displacement of the holding device 11 and
of the closure 3 (arrow 37) - by a sub-portion 35.2,
which extends over a circumferential region of about
140° and is likewise designed as a portion of a circle,
the radius of which is less than the radius of the sub-
portion 35.1. The sub-portion 35.2 is adjoined by a
third sub-portion 35.3, which extends over a
circumferential region of about 35°. The radius of the
contour disc 31 in the region of the sub-portion 35.3
is greater than the radius both in the region of the
sub-portion 35.2 and in the region of the sub-portion
35.1. The transitional region from the sub-portion
35.3 to the sub-portion 35.1 has a profile which is
curved inwards - seen in the direction of the centre
point 9 - in other words is concave. The transition
from one sub-portion to the other extends over a
relatively large circumferential region of the contour
disc 31 and does not have any sharp edges or abrupt
changes. The shaping of the transitions can be used to
set the rate of displacement at which the holding
device 11 can be displaced with respect to the path of
movement 11.
In a displacement, that is to say rotation, of
the holding device 11 in the direction of the arrow 37
about the centre point 9 by means of a guiding device
(not shown), its distance, and consequently the
distance of the cutter 15, from the path of movement 7
of the closure 3 changes on account of the positive
driving by the feeling element 27. In the
circumferential regions of the contour disc 31 of
constant radius, in other words in the sub-portions
35.1, 35.2, 35.3, the holding device 11 has a constant
distance from the path of movement 7 of the closure 3.
The function of the cutting apparatus 1 is
explained in more detail below on the basis of a
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cutting operation: in the position A, the closure 3 is
transferred from a processing station (not shown) for
the closure 3 to the cutting apparatus 1. As shown in
Figure 1, the closure 3 is thereby introduced into the
semicircular depression 23 of the guiding part 21 of
the holding device 11 and is centred. In this
position, the side face 25 of the guiding part 21 lies
on the path of movement 7. Then, the closure 3 and the
holding device 11 are displaced together in the
direction of the arrow 37, the closure 3 along the path
of movement 7 and the holding device 11 along the
contour path predetermined by the outer contour 33 of
the control disc 31. On account of the smaller radius
of the contour disc 31 in the region of the sub-portion
35.2 in comparison with the sub-portion 35.1, the
holding device 11 is displaced with respect to the path
of movement 7 of the closure in the direction of the
centre point 9. The distance between the holding
device 11 and the path of movement 7 is increased in
such away that the guiding part 21 releases the closure
3, that is to say the closure 3 fixed by the securing
device, not shown in Figure 1, is guided outside the
range of effect of the depression 23. In the region
between the position B and the position D, the closure
3 and the holding device 11 are at a constant distance
from each other. In the transfer region between the
position B and the position D, the closure 3 can be
processed, preferably at least one perpendicular
incision is made into the region of the closure
circumference, in which subsequently the guarantee ring
is formed by a circumferential cut.
The cut running in the circumferential
direction of the closure 3 is made in the region of the
sub-portion 35.3. In this sub-portion, the holding
device 11 is displaced outwards in the direction of the
path of movement 7, with the result that the closure 3
is guided in the depression 23 of the guiding part 21,
the distance between the closure 3 and the cutter 15
protruding into the depression 23 being so small that
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the cut can be made into the circumference of the
closure 3. For this purpose, the closure 3 is rotated
in the region of the sub-portion 35.3 at least by 360°
about its centre axis 5, whereby a cut running in the
circumferential direction of the closure 3 is made.
The fact that the contour disc 31 has a constant radius
in the region of the sub-portion 35.3 has the effect
that the distance between the closure 3 and the cutter
is constant during the 360° rotation, in other words
10 so too is the depth of the cut. In the position F, the
closure 3 is subsequently guided out of the cutting
apparatus 1.
Figure 2 shows an exemplary embodiment of a
securing device 39 for the closure 3, which has a pin
15 shaped holding element 41 and a gearwheel 43 connected
to the latter in a rotationally fixed manner. The
gearwheel 43 interacts with a drive device (not shown),
by means of which the rotational speed of the closure 3
about its centre axis 5 can be set. The rotational
speed of the closure 3 in the region of the sub-portion
35.3 is at least so high that it carries out a 360°
rotation, whereby the cut running in the
circumferential direction is made.
In a further exemplary embodiment - not shown
the cutting apparatus 1, described on the basis of
Figure 1, has a plurality of holding devices 11, with
in each case at least one cutter. As a result, its
throughput, that is to say the number of closures
processed by the cutting apparatus, can be increased.
It is also advantageous that, by the use of a plurality
of cutters, their service life is increased and
consequently so too are the maintenance intervals of
the cutting apparatus at which the cutters which are
subject to wear are exchanged. In each case, one
closure and one holding device, having a cutter, are
guided together from the run-in (position A) of the
cutting apparatus to its run-out (position F), that is
to say they have the same circumferential speeds.
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The cutter 15 fastened on the setting element
13 is preferably designed as an exchangeable insert,
with the result that when the cutter is worn it can be
exchanged simply and quickly. In the exemplary
embodiment represented in Figure 1, the cutter 15 has a
straight cutting edge, which is aligned, purely by way
of example, tangentially with respect to the
circumference of the closure. In order to make a cut
of constant depth in the circumference, the cutter can
also be inclined with respect to the closure at an
acute or obtuse angle.
To sum up, it can be stated that, with the
cutting apparatus 1, an exact cut running in the
circumferential direction of a closure can be made in
the said closure, whereby preferably a guarantee ring,
also referred to as a guarantee band, is formed. The
depth of cut is fixed by the contour disc 31, which
controls the relative movement of the holding device 11
with respect to the path of movement 7 of the closure
3. With the aid of the setting element 13, on which
the cutter 15 is fastened, a fine setting of the depth
of cut can be performed, in order for example to
compensate for tolerances of the individual parts of
the apparatus. During the cutting operation, the
distance between the cutter and the closure is
constant, with the result that the cut has a constant
depth over the entire circumference of the closure,
whereby the originality-indicating function of the
guarantee ring can be ensured with great certainty. It
is also found, moreover, that cuts running in the
circumferential direction which do not run all the way
around, that is to say are not uninterrupted, can also
be made into the closures. To accomplish this, it is
merely necessary to limit the rotating movement of the
closure which is in the sub-region 35.3, for example to
120°, 240° or the like.
