Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02697301 2014-10-07
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Profile shape for a crane boom
5 The
present invention concerns a crane boom for a crane having a longitudinal
axis and a notional contour line which extends in a transverse plane relative
to an axis
of symmetry in at least approximately mirror-symmetrical relationship and is
of a
straight configuration at least portion-wise, wherein the contour line
intersects the axis
of symmetry at a first and a second intersection point and narrows in the
direction of
10 the
second intersection point at least before the last third of the spacing
between the
first and second intersection points.
Such a crane boom is shown for example in Figure 13 of EP 583 552 Bl.
That crane boom suffers from the disadvantage that, particularly upon being
= installed in a jib system, it involves a disadvantageous application of
force in the upper
15
region of the crane boom. Furthermore manufacture of such a crane boom is
relatively
complicated and expensive.
The object of the invention is to overcome the discussed problems of the state
of the art.
20 It
will be appreciated that a real crane arm has both an outside contour and an
inside contour by virtue of the material thickness of the components forming
it. The
'notional contour line' refers to the outside contour of the crane boom.
= The term centroid is used in the context of this disclosure to denote the
center of
= gravity of the overall region enclosed by the notional contour line
(Figure 2). The term
25
'centroid' is therefore not to be interpreted in relation to the area enclosed
between the
= outside and inside contours.
The measures according to the invention provide that the crane boom can be
made from a single metal sheet. The upper part of the crane boom can be used
as a
whole for the application of force, in particular between the jib extensions,
when fitted
30 into
a jib system. The narrowing of the contour line upwardly affords a favora. ble
relationship between the limb length and the sheet metal thickness. The
invention
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CA 02697301 2014-10-07
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makes it possible to use thinner metal sheets than was the case in the state
of the art.
In accordance with this invention there is provided a crane boom for a crane
having a longitudinal axis and a notional contour line which extends in a
transverse plane
relative to an axis of symmetry (s) in at least approximately mirror-
symmetrical relationship
and is of a straight configuration at least proportion-wise, wherein the
contour line intersects
the axis of symmetry (s) at a first and a second intersection point (S1, S2)
and narrows in the
direction of the second intersection point (S2) at least before the last third
of the spacing
between the first and second intersection points (Si, S2), wherein the
narrowing of the contour
line continues to the second intersection point (S2) and ends in a rounded
configuration at the
line of symmetry (s), wherein the contour line between the first intersection
point (Si) and a
center point (M) arranged equidistantly relative to the first and second
intersection points (Si,
S2) has at least partially an at least approximately arcuate portion (ki) that
the center point of
curvature (K) of the arcuate portion (ki) is on or in the proximity of the
axis of symmetry (s)
and wherein the contour line has a straight portion (gi) whose notional
extension (gi) in the
direction of the second intersection point (S2) intersects the axis of
symmetry (S) at an angle
(0), wherein a second straight portion (g2) which ends in the rounded
configuration adjoins the
first straight portion (g1).
The invention further concerns a jib system for a crane, wherein at least one
jib
and/or jib extension is in the form of a crane boom. Preferably there are
provided between one
and twenty, preferably between five or ten, jib extensions. It is particularly
preferable for
more than five jib extensions to be provided.
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The invention further concerns a crane, in particular a loading crane, having
a
= crane boom according to one of the aforementioned embodiments or a jib
system of the
aforementioned kind as well as a utility vehicle equipped with such a crane.
Figure 1 a shows a first embodiment of the notional contour line of a crane
=
boom according to the invention,
Figures lb and lc show the construction of a contour line (Figure lb) and the
corresponding sheet metal structure (Figure 1c) of an embodiment in which the
arcuate
= portion k1 is approximated by a polygonal line,
Figure ld shows a jib system having three jib extensions as shown in Figure
lb,
Figure le shows the crane boom of Figures la through lc, showing the position
of the centroid,
Figure 1 f shows a jib system having a jib extension, showing the arrangement
of mounting elements, =
= Figure 1 g shows a jib system with a jib extension, wherein the arcuate
portion
in the jib and the jib extension was approximated by different polygons,
Figure 2 shows the crane boom of Figures la through lc and le, wherein that
area to which the centroid relates has been shown in dash-dotted lines
representatively
for all embodiments,
Figure 3 shows a second embodiment of the contour line of a crane boom =
= according to the invention,
Figure 4 shows a perspective view of a jib system as shown in Figure ld, and
Figure 5 shows a utility vehicle with a crane according to the invention.
It will be presupposed that all Figures are true to scale insofar as the
lengths of
the individual contour portions and the illustrated angles are shown in the
correct ratio
=
=
2a
=
CA 02697301 2010-03-03
to each other. All angle references relate to degrees, so that a full angle
corresponds to
360 degrees. An angle of less than 1/4 full angle is interpreted as an acute
angle. An
angle of greater than 1/4 and less than 1/2 fuii angle is interpreted as an
obtuse angle. An
angle equal to 1/4 full angle is identified as a right angle.
Figure la shows a first embodiment of the configuration of the notional
contour
line of the crane boom in a transverse plane of the crane boom. In this
respect the term
transverse plane is used to identify a plane through which the longitudinal
axis of the
crane boom passes in orthogonal relationship. All crane booms according to the
invention have an axis of symmetry s which is arranged in the transverse plane
and in
relation to which the contour line of the crane boom extends in the transverse
plane in
at least approximately mirror-image relationship. For the situation where the
crane
boom is of the same cross-sectional shape over a large part of or its entire
longitudinal
extent, that axis of symmetry s represents the straight section line of the
transverse
plane with the plane of symmetry extending along the longitudinal axis (median
plane).
In all embodiments the contour line intersects the axis of symmetry s at first
and second
intersection points SI, S2. The center point M arranged on the axis of
symmetry s
equidistantly relative to the first and second intersection points Si, S2
represents the
position of half the height of the crane boom in the transverse plane.
Starting from the
center point M in the direction of the intersection point S2, that affords a
region of the
crane boom which, in operation, is predominantly subjected to a tensile
loading. The
region of the crane boom, that is between the center point M and the first
intersection
point S1, is substantially subjected to a compression loading in operation.
The configuration of the contour line of the crane boom shown in Figure 1 has
four portions 1(1, gi, g2, g3 which can be distinguished from each other.
The portion ki which is arranged in the region of the compression loading that
is greatest in operation is of an arcuate configuration since, as is known per
se, that
cross-sectional shape has reduced compression stresses and involves a
reduction in the
risk of buckling. It is sufficient if that portion is at least approximately
arcuate in the
sense that it can be approximated by a polygon, as is shown in Figures lb and
lc.
Approximation of the arcuate portion I:1 by a polygon permits easier
manufacture by
folding of the metal sheets forming the crane boom. It will be appreciated
however that
an arcuate configuration can be implemented by means of a rolling operation.
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The arcuate portion k1 can also be only approximately arcuate in the sense
that
it can be formed for example by one or more ellipse portions of suitably
slight
eccentricity. It would also be possible to envisage a configuration for the
arcuate
portion k1 by arranging in joining relationship suitably short straight,
elliptical and/or
arcuate segments.
As shown in Figure 1 it is particularly advantageous if the arcuate portion k1
is
in the form of a quarter-circle arc, that is to say it extends over an angle
of about 90
degrees. It is possible in that way for the large part of the configuration of
the contour
line between the first intersection point Si and the point M to be produced in
the form
of an arcuate portion 1(1. The variant shown in Figure 1 is particularly
preferred, in
which the center point of curvature K of the arcuate portion ki is in the
proximity of or
on the axis of symmetry s and the center point of curvature K of the arcuate
portion k1
is between the first intersection point S1 and the center point M. Unlike the
situation
shown in Figure 1 the arcuate portion k1 can certainly extend as far as the
first
intersection point SI. In that case therefore the entire contour line in the
region of the
intersection point S1 and the center point M is in the form of an arcuate
portion k1.
The embodiment shown in Figure 1 is particularly preferred however in which a
third straight portion g3 tangentially adjoins the arcuate portion 1(1 in the
direction of the
first intersection point Si, the third portion g3 including an angle 7 of less
than 90
degrees with the axis of symmetry s (here the angle 7 is about 72 degrees).
That affords
good weldability of the crane boom, better suitability for clamping for the
welding
operation by virtue of the portions which meet each other inclinedly and the
possibility
of producing a longitudinal weld seam without additional edge preparation.
Overall that
affords a configuration which is more reliable in terms of process
implementation.
The angle is preferably less than 80 degrees. Preferably the angle y is
greater
than 70 degrees.
In the Figure 1 embodiment the center point of curvature K of the arcuate
portion ki is disposed directly on the axis of symmetry s between the center
point M
and the first intersection point S. Unlike the situation shown the center
point of
curvature K can also be arranged displaced somewhat relative to the axis of
symmetry
s. It should however always be in the region between the center point M and
the first
intersection point SI.
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The first straight portion gi adjoins the arcuate portion k1 in the direction
of the
second intersection point S2 tangentially to the auxiliary circle illustrated
in Figures 1 a
and lb, the first portion gi extending over the large part of the contour
configuration
between the center point M and the second intersection point S2. That straight
configuration which is extended in length in the upper region of the crane
boom and the
resulting narrowing in cross-section forms a zone which is better suited than
in the state
of the art to carrying the tensile forces occurring here and the bearing and
reaction
forces which occur when arranged in a jib system. The notional extension gi'
of the
straight portion gi (see Figure lb) includes with the axis of symmetry s an
acute angle p
which in the illustrated embodiment is about 18 degrees. Quite generally the
acute
angle [3 can also be in a range of greater than 10 degrees, preferably greater
than 15
degrees. In that respect an upper limit of 25 degrees is preferred in each
case in order to
exclude an excessively shallow configuration in respect of the straight
portion gi.
In the embodiment shown in Figure 1 a second straight portion g2 directly
adjoins the first straight portion gi, the second portion extending as far as
the axis of
symmetry s, ending there in an edge configuration 7 and intersecting it at the
second
intersection point S2. As can be seen in particular in Figure lc, for reasons
relating to
manufacturing technology it may be desirable if the second straight portion g2
(unlike
the situation shown in Figure la) is connected to the first straight portion
gi not directly
but by way of a preferably curved further portion.
In the Figure 1 embodiment the second straight portion g2 includes with the
axis
of symmetry s an angle a which is smaller than 90 degrees (in the Figure 1
embodiment the angle a is about 65 degrees). A range for the angle a of less
than 70
degrees is particularly preferred. The angle cc in this embodiment should
however be
larger than 60 degrees.
The second straight portion g2 which ends in a rounded configuration in the
form of an edge configuration 7 has the advantage that this arrangement, in
the region
around the tip of the crane boom, permits favorable local application of
forces, as
occurs for example when supporting slide packets between individual jib
extensions.
The short limb length affords a favorable relationship between the sheet metal
thickness and the limb length so that deformation of the crane boom is
prevented in the
upper region.
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It will be noted however that basically it would also be possible for the
contour
configuration in that region to be in the form of a second arcuate portion k2
(see Figure
3). That however only represents a special variant of the more general idea
according to
the invention, namely the idea that the contour line ends in a rounded
configuration at
the line of symmetry s. As an alternative to the illustrated configuration of
the rounded
configuration in the form of an arcuate portion k2 the rounded configuration
could for
example also be in the form of an edge configuration 7.
Quite generally it must be said in relation to all configurations of the crane
according to the invention that the centroid F of the area enclosed by the
contour line in
the transverse plane lies in a region between the center point M and the first
intersection point SI, that is to say below half the height of the crane boom.
That
provides that the cross-section concentration of the crane boom is displaced
as much as
possible downwardly into the compression zone, thereby affording a lower
compression stress component.
1.5 As can be seen from the Figures the contour line of all embodiments
has,
between the first intersection point S1 and the second intersection point S2,
an extreme
point E at maximum distance e from the axis of symmetry S. The spacing D
between
the first intersection point and the second intersection point S1, S2 can in
that case be at
least twice as great as the distance e. Preferably the spacing D is at least
two and a half
times as great, particularly preferably 2.75 times as great, as the distance
e. The spacing
D can be in each case less than three times the distance e.
It can be provided that the spacing d of the contour line from the axis of
symmetry s, at approximately a quarter of the spacing D between the first and
second
intersection points SI, S2, starting from the second intersection point S2, is
less than or
equal to 0.8 times the maximum distance e.
In the Figure 1 embodiment the extreme point E is between the center point M
and the first intersection point Si approximately at the height of the center
point of
curvature K. In the Figure la configuration the contour line has only one
single extreme
point E, that is to say the width of the crane boom decreases both in the
direction of the
first intersection point S1 and also in the direction of the second
intersection point S2,
starting from the extreme point E. When the arcuate portion k1 is approximated
by a
polygonal line, as shown in Figure lc, it will be appreciated that all points
on the
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polygonal portion, by which the arcuate portion k1 is approximated in the
region of the
extreme point E, involve that maximum distance e.
Starting from the auxiliary circle shown in Figure 1 a, of the radius r, the
embodiment of Figure 1 involves a profile width b in accordance with b 2r, a
profile
height D in accordance with D 3r and a profile width upward b1 in accordance
with b1
r. Those particularly advantageous dimensions can be provided quite generally
in
crane booms according to the invention.
Figure 1 e shows for the embodiment of Figure 1 the position of the centroid F
between the center point M and the first intersection point S1 on the axis of
symmetry s.
In this case the centroid F refers to the area shown in dash-dotted lines in
Figure 2, that
is to say the entire area enclosed by the notional contour line (corresponds
to the
outside contour).
Figure 1 f shows a jib system 5 with a jib extension, showing in addition the
mounting of the jib system 5 by way of a mounting element 1 and mounting of
the jib
extension in the jib by way of mounting elements 2. It will be appreciated
that the
illustrated embodiment is intended purely by way of example in relation to the
number
of illustrated jib extensions. The same mounting elements can be used in jib
systems
having any number of jib extensions.
The embodiment of Figure 1 g shows two crane booms which involve for
example a jib extension arranged in a jib. It is of significance that the
arcuate portion k1
is approximated by different polygons. The inwardly disposed cross-sectional
profile
has fewer edges in the region of the arcuate portion, which can be of
advantage in
particular when dealing with small profiles, in terms of manufacturing
technology.
Production of a crane boom according to the invention can be effected for
example in such a way that the crane boom is formed from two shells which are
shaped
in mirror image relationship with each other, wherein one of the shells
respectively
corresponds to one of the embodiments. The two shells can be joined together,
for
example welded, in the region of the first intersection point S1 and the
second
intersection point S2.
It will be noted however that it is particularly preferably provided that the
crane
boom is produced from a single metal sheet at least along a portion of its
longitudinal
extent, the metal sheet being suitably shaped and then closed along a single
line (for
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example by welding). That line can extend for example in the region of the
first
intersection point S1 or the second intersection point S2.
Shaping of the metal sheets can be effected in known manner or by folding or
bending and/or rolling, and for example welding.
If different gauges are required, the outside contour should preferably remain
the same and the sheet metal thickness should be applied inwardly.
Figure 4 shows by way of example a jib system 5 having a jib extension
arranged in a jib.
Figure 5 shows by way of example a utility vehicle 3 on which a crane 4
according to the invention is arranged. The crane 4 has a jib system 5
according to the
invention, in which case the individual jib extensions can be telescopically
displaced
relative to each other by way of thrust cylinders 6. It will be appreciated
that telescopic
displaceability can also be ensured by other drive means. A loading structure
(not
shown) could be arranged for example in the rearward region of the utility
vehicle 3.
8
