Note: Descriptions are shown in the official language in which they were submitted.
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STRAPPING-BAND CUTTER
The invention relates to a band cutter for
strapping, comprising a movable pusher element, a foot with a
pushing edge for the strapping that can be fixed between the
foot and the pusher element, and a cutting blade for severing
the fixed strapping band.
Band cutters for strapping are used in a variety of
ways to make strapped goods accessible. In the simplest case,
such cutters can be a pair of scissors with a movable and a
fixed blade. In addition, a clamp is usually provided to hold
the severed strip. This is necessary inasmuch as such severed
strips often involve considerable spring "jump back" and
thereby damage or in the worst case, they can even cause
injuries to operating personnel. Typical examples of such
devices for severing a strip of strapping band are described
in EP 1 495 978 [US 7,913,599].
In the generic prior art according to EP 3 013 538
[US 9,630,265], a battery-operated band cutter is seen. This
has a pressure device that can be moved into contact with the
strapping. In this way, the band can be stabilized against a
foot. While the pressure device holds down the band, an
additionally provided cutting blade cuts the band on a pushing
edge. That has basically been preserved.
In addition, the prior art according to US 8,160,748
describes the possibility of moving such a cutter with the aid
of a three-dimensional robot arm. In order to position the
cutter, a band detector is also provided. In that case, this
is a camera.
However, the known band cutters for strapping are
associated with the disadvantage that, in particular, steel
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strapping bands that are quite thick, such as those used for
wrapping and holding together strip-metal coils, can
practically not be cut or with such a strapping cutter since
it cannot be ensured that when it is severed end it does not
pop open in an uncontrolled manner despite any provided
clamping devices.
This is because the known clamping devices
ultimately ensure that the steel strips in question are
gripped, for example with the aid of friction surfaces, as are
used by way of example in the further prior art according to
WO 2008/052175. However, such friction surfaces fail in the
field of application described, because, for example, steel
strips for strapping metal strip coils can have pretension of
40 to 50 kN or even more. Such pretensioned bands can
practically not be controlled with conventional gripping
devices, so that the previously known cutters fail in the
described field of application. The invention aims to provide
a remedy here overall.
The object of the invention is to provide such a
band cutter for strapping that securely and reliably prevents
the severed strapping from escaping and securely holds the
severed end of the strapping.
In order to attain this object, a generic cutter for
strapping is within the scope of the invention characterized
in that the pusher element is formed as a punch that at least
partially penetrates the strapping.
In the context of the invention, in contrast to the
prior art according to EP 3 013 538, the pusher element not
only ensures that the strapping is held between the foot and
the pusher element. Rather, the pusher element penetrates
more or less into the strapping as a punch and thereby ensures
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a pronounced punching in the strapping. As a result of this
punching and a punch-out produced by the punch in the
strapping band, the severed end of the strapping band is in
effect not held by frictional forces. Rather, the punch-out
extending wholly or partially from the strapping ensures that
the severed end of the strapping is held in place like a claw
with the aid of the punch. In this way, the previously
mentioned pretensioning can be controlled in such strapping
bands in the strapped state, at levels of 50 kN and even more.
This is not possible with the cutters made available so far.
In fact, the band cutter for strapping bands
according to the invention opens up the option of being able
to cut thick and high-strength strapping bands (made of steel)
for the first time. Such so-called high-performance bands
have tensile strengths of 1200 N and more, for example. In
addition, breaking loads of more than 50,000 N or 50 kN and
even up to 57 kN are observed for such high-performance bands
that are consequently equipped with a material thickness
greater than that of the steel bands of, for example, 1.4 mm
and more. As a result of the use of high-strength steel,
special requirements are placed on cutters that are not met by
the cutters known in the prior art but that can, on the other
hand, be cut through properly and safely for the first time
using the solution according to the invention.
According to an advantageous embodiment, the design
is made such that the foot has a recess for the punch. As a
result, when it passes through the strapping band, the punch
creates the previously mentioned punch-out that, either alone
or together with the punch, extends into the recess in the
foot when it is formed. At the same time, the recess together
with the punch and the punch-out in the recess provide
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additional support for the severed end of the strapping band.
This reliably prevents the severed strapping band, in
particular steel band, from escaping, and any damage or even
health hazards for operating personnel can be reliably
prevented.
The punch can have very different shapes and cross-
sectional designs. As a rule, the punch is of polygonal cross
section. Trapezoidal, square, hexagonal, octagonal or other
polygonal shapes can be implemented and realized here. It is
also conceivable for the punch to be oval or round in cross
section. In principle, such combinations are conceivable.
A design of the punch that has a triangular cross-
section has proven particularly advantageous. Because this
allows any expansion forces of the strapping to be cut to be
absorbed particularly well. In fact, such expansion forces
generally act along the axis of symmetry of the relevant
triangle and are thereby over the respective legs of the
triangle is introduced evenly into the punch, which in turn is
not overloaded in this way.
The punch also has a point projecting in the
direction of pressure and an adjoining stop shoulder. Because
the point of the punch projects, it ensures that the point
penetrates the strapping band can go through it. As a rule,
the point is located at the apex of the strapping band
[punch], which is triangular in cross-section, so that the
apex point can penetrate the strapping band particularly
easily and effectively and cut it in the area of this apex
point. At the same time, the angled stop shoulder that
adjoins the projecting point ensures that the punch-out that
is formed in this way is bent into the strapping from a
surface of the band.
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Thus, the punch-out is still connected to the
strapping at its base opposite the apex of the triangle. As a
result, the base of the triangular punch-out can be bent over
against the surface of the band, with the help of the stop
shoulder. The punch-out formed in this way is thus of
triangular shape following the shape of the punch and is
connected to the strapping band with the base of the triangle.
At the same time, the punch-out is bent toward the surface of
the band and as a result, more or less pronouncedly dips into
the recess in the foot. In any case, the punch, the punch and
the recess in the foot ensure that the severed end of the
strapping is properly held and is only released by the
severing device when the punch is returned to its original
position.
The punch is generally arranged approximately in the
middle of the foot. The cutting blade is usually an upper
cutting edge that works together with a foot edge as a lower
cutting edge. Thus, one edge of the foot functions as a lower
cutting edge while the cutting blade takes on the function of
the upper cutting edge in the scissors or metal shear realized
in this way. In this way, cutting angles can be introduced
into the strapping to be severed, which are fundamentally
variable and, for example, are or can be values in the range
from 1 to 50 , based for example on the transverse direction
of the band.
The punch and the cutting blade are each for the
most part moved vertically relative to the foot or are
correspondingly designed to be vertically movable compared to
the foot. For this reason, a ram can be provided to act on
both the punch and the cutting knife. In this connection, the
design is usually made such that the punch is equipped with a
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projection opposite the cutting knife and, taking this
projection into account, is connected to the ram together with
the cutting knife. The projection ensures that the punch
first penetrates completely or partially into the strapping
band and in this way holds the end of the strapping band to be
severed subsequently. Only when the punch has fully or
partially penetrated the strapping does the cutting knife, as
an upper cutting edge, in conjunction with the foot edge as a
lower cutting edge, ensure the desired cutting process and the
severing of the strapping.
The punch and/or the cutting knife are generally
mounted on a common support flange. The support flange also
guides the ram. For this purpose, the punch and the cutting
knife are oriented opposite in comparison to the support
flange in the middle. In addition, the punch or the cutting
knife can be mounted floating above the support flange. In
principle, the support flange as a whole can have a floating
bearing opposite a machine frame. As a result, when the punch
penetrates the strapping and due to its tensile stress,
overall reduced shear forces act on the punch. The same may
apply to the cutting knife. As a rule, however, it is mainly
the punch that is gloatingly mounted opposite the support
flange. For this purpose, one or more springs are generally
provided which on the one hand provide unaltered linear
guidance of the punch with the aid of the support flange, but
on the other hand allow the punch to move sideways.
In addition, a band detector is provided for
position detection in relation to the strapping to be cut.
Thus, with the help of the band detector, the above-described
band cutter according to the invention is aligned with respect
to the strapping to be cut. Such a position detection and
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band detector is particularly recommended for the case that
the band cutter works in a stationary manner and is connected,
for example, to a robot arm or generally to a three-
dimensionally displaceable adjusting device. For mobile use
of the band cutter, which is also possible, such a band
detector is of course not absolutely necessary because the
positioning of the band cutter is carried out by an operator.
The band detector is usually designed as a laser-
type detector. With the aid of the laser-type detector, for
example, the surface of a metal strip coil strapped with a
steel band is scanned. The strapping appears on this surface
as a rectangular elevation, which can be determined via the
laser-type detector and at this point by distance
measurements. This allows the position of the strapping to be
determined and the band cutter to be precisely aligned. In
addition, after the position of the strapping has been
determined, the cutter is usually pushed down with the foot
under the tensioned strapping with the help of the three-
dimensional adjusting device so that the pushing edge formed
on the foot ensures that the strapping can be lifted from the
strapped material and the foot can be pushed under it. Only
then does the separation process described above in detail
take place.
For the drive of the punch and the cutting knife,
all drive forms that are basically possible in this context
can be used. In fact, a hydraulic and/or pneumatic and/or
electric drive is conceivable at this point. If an electric
drive is used, it can work with AC voltage from the mains.
However, it is also possible to use battery operation for
portable use. Consequently, the cutter can be designed to be
mobile or stationary overall.
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As a result, a band cutter for strapping is provided
that works particularly safely and reliably. This also
applies, and in particular, to strapping with steel bands
subject to particularly high tension during the cutting
process, as is observed, for example with steel strapping
bands used for strapping strip-metal coils can be used. In
the case of strapping bands of this type, the band cutter
implemented according to the invention ensures that the
severed end of the strapping band in question cannot spring
open in an uncontrolled manner and cause damage or injury to
operating personnel. This is not possible with previously
known cutters used in practice. This is where the main
advantages can be seen.
In the following, the invention is described in more
detail with reference to a drawing showing only one
embodiment. Therein:
FIG. 1 is an overview of a strapping cutter,
FIGS 2A to 2D show details of the cutter according
to FIG. 1 from different angles, and
FIG. 3 shows the severed end of the strapping band
with the punch-out.
The drawing shows a band cutter that can cut a
strapping band indicated at 1 in FIG. 1. The strapping bands
1 are mostly steel strapping bands. The invention is of
course not restricted to this. According to the embodiment,
the steel band or strapping band 1 in question is looped
around strip-metal coils, which are not shown in detail, and
have to be cut for further processing of the strip-metal
coils. For this purpose as shown in FIG. 1 a foot 2 of the
cutter with a pushing edge is pushed under the tensioned
strapping band 1 in the direction shown by a double arrow in
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FIG. 1. To this end, the cutter shown in the overview in FIG.
1 is carried on a three-dimensional actuating device 5 shown
schematically in FIG. 1. The actuating device 5 is
advantageously a robot arm. Of course, this is only an
example. In addition, the actuating device 5 can in principle
be dispensed with in the event that the cutter is designed to
be mobile and is manipulated by an operator.
In any case, the actuating device 5 shown in FIG. 1
ensures that the cutter, which is to be described in detail
below, is pushed under the tensioned strapping 1 with its foot
2. The wedge shape of the pushing edge 3 ensures that this
process can be carried out and the tensioned strapping 1 is
increasingly lifted off the strapped material. For this
purpose, the sliding edge 3 may have an angled upper face
indicated in FIG. 1 and forming with respect to a horizontal
line an angle a of approximately 100. Typically, angles of
inclination a between 5 and 20 are observed. Of course,
this is not restrictive. The angle a also corresponds to a
cutting angle when the strapping band 1 is severed, which is
still to be described.
In particular, the detailed views of FIGS 2A to 2D
now show the foot 2 with the pushing edge 3 and additionally a
pusher element 4 and a cutting blade 5. Using the pusher
element 4, the strapping 1 can be gripped between the foot 2
and the pusher element 4. This fixation ensures that, during
a cutting process with the aid of the cutting blade 5, the
tensioned strapping 1 does not spring open after cutting and
that the end of the strapping 1 that has been cut through by
the cutting blade 5 is held in place.
The cutting blade 5 for severing the fixed strapping
1 an upper cutting edge during this process. An edge 6 on the
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foot 2 takes on the function of a lower cutting edge 6. In
this way, the movable cutting blade 5 and the foot edge 6
define a pair of metal scissors 5, 6 or shears 5, 6, provided
that the strapping 1 is a steel band. Both the cutting blade
5 and the pusher element 4 are for the most part designed to
be movable vertically compared to the foot 2, as indicated by
a double arrow in FIG. 2B. According to this embodiment, a
common and schematically indicated ram 7 moves the pusher
element 4 and the cutting blade 5. The punch 7 can also be a
cylinder. In any case, the ram 7 executes the traversing
movements shown in FIG. 2B vertically in comparison to the
foot 2. A hydraulic drive may provide for the drive of the
ram 7 or a cylinder at this point.
According to the invention, the pusher element 4 is
formed as a punch that at least partially penetrates the
strapping 1. According to the embodiment, the punch 4 is one
of triangular cross-section. Consequently, the foot 2 has a
complementary recess 8 that is also triangular and is adapted
to the shape of the triangular punch 4. As a result, the
punch 4 as a whole can penetrate the strapping band 1 or at
least partially penetrate it and dip into the recess 8 in the
foot 2.
The punch 4 is equipped on the foot side with a
point 9 projecting in the pressing direction or the direction
of travel of the punch 4 according to the double arrow in FIG.
2B. In addition to the projecting point 9 to a rearwardly
angled stop shoulder 10. The projecting point 9 is provided
in the region of an apex of the triangle of the triangular
cross-sectional shape of the punch 4. In contrast, the stop
shoulder 10 extends in the direction of a base side of the
triangle in question opposite the apex.
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In this way, the punch 4 penetrating into the
strapping 1 forms a punch-out 11 in the strapping 1 as shown
in FIG. 3. This punch-out 11 in the strapping 1 is created in
that the punch 4 with its projecting point 9 cuts through the
strapping 1. Since the stop shoulder 10 angled back from the
projecting point 9, opposite the point 9, the punch-out 11 is
connected to the strapping 1 at the base of its triangle. In
this way, the stop shoulder 10, which adjoins the projecting
point 9, bends the punch-out 11 with respect to a band surface
of the strapping band 1.
The bent punch-out 11 can more or less dip into the
recess 8 in the foot 2 during this process. In this way, the
punch 4, the bent punch-out 11 and the recess 8 in the foot 2
taken together ensure that the subsequently severed end of the
strapping 1 is securely held by the severing device. This is
because the punch 4 penetrating into the strapping band 1
functions like a claw dipping into the strapping band 1 and
ensures a secure hold.
The punch 4 is arranged approximately centrally in
the foot 2. The same applies to the recess 8 in the foot 2
that interacts with the punch 4. It can also be seen from the
detailed views of in FIGS. 2A to 2D that the punch 4 of the
ram 7 extends by a distance U past the knife 5. This
dimension U is such that when the ram 7 acts, the punch 4
first penetrates the strapping 1 and forms the bent punch-out
11 as shown in FIG. 3. As a result, the end of the strapping
1 that is to be severed subsequently is securely held. Only
after this fixing of the end of the strapping 1 to be severed
does the cutting blade 5 sever the strapping 1. For this
purpose, the cutting blade 5 and the foot edge 6 define the
cutting shear 5, 6 described above. A support flange 14 for
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the common mounting of the punch 4 and the cutting knife 5
ensures their proper linear guidance.
In order to detect the position and align the
described cutter with respect to the strapping band 1 holding
the material to be strapped, a band detector 12 can be
provided as indicated schematically in FIG. 1. The band
detector 12 works in the present case as a laser-type
detector, as has already been described above. To control the
three-dimensional positioner S, a common controller 13 is
provided that processes corresponding measured values from the
band detector 12 and controls the positioner S accordingly, so
that it can move the foot 2 to cut the strapping 1 and thus
the band cutter as a whole.
A pneumatic motor or an electric drive can be used
to drive the ram 7. If an electric drive is used, it can be
operated with mains voltage or alternating voltage, for
example. Mobile use is also possible with a battery-operated
electric drive possible and is covered by the invention.
Consequently, the cutter can be designed to be mobile as a
hand-held device or as a stationary device in conjunction with
the actuating device S described and operating in three
dimensions. Both are expressly possible.
A comparison of FIGS. 2A to 2D shows that the punch
4 and the cutting knife 5 are mounted on the common support
flange 14. The support flange 14 provides the desired linear
guidance of both the punch 4 and the cutting knife 5. In
addition, a floating mounting can be implemented in this
connection. In fact, according to the embodiment, the
procedure is such that the support flange 14 allows a lateral
movement of the punch 4 by means of, for example, springs
attached on both sides and not shown in detail, that is in the
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longitudinal direction of the strapping 1. This cushions the
wall force exerted by the strapping 1 on the punch 4. As a
result of this, any shearing forces acting on the punch 4 are
reduced.
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