Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1. 2V2121~
"OVERTURNING-PREVENTING DEVICE FOR CRANE TRUCKS AND
SIMILAR MACHINES"
The present invention relates to an overturn;ng-
preventing device for crane trucks and s;miLar machines,
such as lift trucks, graders, and still other machines
formed by a self-propelLed truck supporting operating
means, with said truck compris;ng a rear axle, the wheels
of which are linked to each other by means of an axle
constrained to the truck by means of vertical elements.
The overturning risk is constantly present during
the operating steps of working machines, and, in
particular, of the crane trucks.
It ;s known that an overturning occurs when the
overturning torque, which causes it, exceeds determined
threshold values which are a function of the structure,
and of the we;ght of the crane truck.
Mechanical overturning-preventing devices are known,
which substantially provide for the crane truck-driving
operator to verify, moment by moment, the load condition,
on the basis of a suitable table which reports the
maximum allowed values of lifted load as a function of
the range reached by the crane.
Unfortunately, such devices are affected by the
shortcoming that they are only indicative of the
approaching of the danger condition, in that not always
the value of the lifted load can be exactly evaluated.
In such cases, in order that a reasonable safety can
be achieved, ;t ;s essential that the operator has
matured a meaningful experience both in estimating the
weight of the loads to be lifted, and in the use of the
specific machine he is controlling and that he, on the
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basis of said experience is also capable of perceiv;ng
the danger premonitory signaLs, which are typical for
that particular crane truck type.
Other devices, develsped at a later t;me, are those
of electronic type.
Such devices, which are part;cularly complex,
expensive and delicate, are based on the pr;nciple
consisting in monitoring, by means of sensors installed
at one or more suitably selected points on the crane
truck structure, the value of the mechanical stresses
generated by the lifted load, so as to be able to
determine, at any time, the value of the overturning
torque generated by the same load.
The s;gnals detected by the one or more sensors are
processed by an on-board computer, which compares the
value of the overturning torque generated by the lifted
load, to the max;mum allowed torque value for that crane
truck.
In case the value of the overturning torque becomes
too similar to the value of the maximum allowed torque,
the electronic device signals the danger condition, and
stops the operation of the crane truck.
The electron;c dev;ces, bes;des being ~as already
said) complex, delicate, and consequently expensive, are
affected by the serious drawback that they give the
operators a safety feeling, which is not always
justified. In fact, the operators, aware of the fact that
the devices automatically interrupts, with rapidity and
precision, any dangerous operations, do not take very
much care in evaluating the dynamics of the lifting~
The lifting operation is carried out leaving to the
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3 20212~5
electronic dev;ce only the task of superv;s;ng ;t, and of
interrupt;ng ;t in the event it becomes dangerous.
~ut in case the device, owing to a large number of
reasons, does not operate, or is affected by operat;ng
anomalies, the accident is practically ;mmed;ate,
unavoidable, and, most t;mes, also with fatal
consequences.
Furthermore, often, both the presently used
mechanical and eLectronic devices do not suitably exploit
the lifting potential of the machine on which ~hey are
installed, due to a series of reasons, which we'll
illustrate very briefly, in that they are already well-
known by those sk;lled in the art.
As regards the mechan;cal devices, such a situation
is clearly purposeLy wished, in order to secure a safety
margin which is large enough for compensating for any
poss;ble ;naccurac;es ;n load s;tuat;on evaluat;on.
In case of electron;c devices, the missed full
exploitation of the power of the machine derives most
2û times by the fact that ow;ng to cost reasons onLy one
type of electron;c devices ;s manufactured, with the
ind;v;dual devices be;ng then adapted, with marginal
modif;cat;ons, to heavy-axle crane trucks, as well as to
l;ght-axle crane trucks.
~ut, as well-known, ;nasmuch as the rear axle of the
crane truck is in the opposite position relat;vely to the
position of the lifted Load, it has a major influence on
the usefuL load the same crane truck can lift; not tak;ng
th;s fact ;nto due account, ;s obviously to the
detriment, according to cases, either of the machine (in
case of a heavy-axLe mach;ne) or of the safety ~in case
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of a light-axle mach;ne).
The purpose of the present invention is to provide
an overturning-preventing device which is capable of
obviating all those shortcomings which der;ve from the
use of the above mentioned overturning-preventing
dev;ces, without thereby giving up the relevant
advantages.
Such purposes are achieved by the overturning-
prevent;ng device for crane trucks and similar mach;nes,
formed by a self~propelled truck supporting operating
means, with said truck compr;s;ng a rear axle, the wheels
of which are linked to each other by means of an axle
constrained to the truck by means of vertical elements,
characterized in that it is interposed between said
vertical elements of the rear axle and the truck, and
comprises: first plate means integral with the vertical
elements, second piate means integral with the truck, a
hinge constraining, relatively to its own axis, said
first plate means and said second plate means, with said
first plate means and said second plate means enabling,
as the above mentioned rotation occurs, means for
discontinuing the operation of the crane.
The advantages deriving from the device accord;ng to
the present invention are the following:
- safety in operation, insensitivenss to the faiLures,
simpleness and low cost of manufactur;ng and
operat;ons, typical for the mechanical devices;
- precision comparable to the precision of the electronic
devices;
- possibility of suitably exploiting, with full safety,
the maximum lifting potential offered by a whatever
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5 20212~
type of operating machine, whether ;t ;s a crane truck,
or another type of machine, whether of the heavy-rear-
axle or of the light-rear-axle type;
- possibility of adjusting the sens;tiv;ty of
;ntervention of the device;
- possib;lity of predetermining, according to
requ;rements, and by means of the same adjustment of
the sensitivity of intervention, the minimum load to be
transmitted ~y the axle to the ground before the device
stops the operations of the crane;
- possib;lity of applying the device to the single-wheel
axles also, whether of heavy or of light type~
The invent;on ;s illustrated for merely
illustrative, non-limitative purposes, ;n the f;gures of
the hereto attached drawing tables, where;n:
Figure 1 shows a schematic side v;ew of a crane
truck equ;pped with a device according to the invention;
Figure 2 shows a schematic rear view of the rear
axle of a heavy-rear-axle crane truck, with said rear
axle being equipped with an overturning-preventing device
according to the present invention;
Figure 3 shows a schematic view of the rear axle of
Figure 2, wherein the overturn;ng-preventing device is in
the cond;t;on of interruption of the lifting operation;
Figure 4 shows a schematic rear view of the rear
axle of a light-rear-axle crane truck, with said rear
axle being equipped with an overturning-preventing device
according to the invention;
Figure 5 shows a schematic view of the rear axle of
Figure 4, wherein the overturning-preventing device is in
the condition of interruption of the lif~ing operation;
6. 202121~
F;gure 6 shows a schematic rear view of the rear
axle of a heavy-rear-axle crane truck with single-wheel
rear axle, with said rear axle being equipped with an
overturning-preventing device according to the ;nvent;on;
F;gure 7 shows a schemat;c v;ew of the rear axle of
Figure 6, where;n the overturning~preventing device is in
the condit;on of ;nterruption of the lift;ng operat;on;
Figure 8 shows a schematic side view of the rear
axle of Figures 6 and 7.
Figure 9 shows a schematic rear view of the rear
axle of a light-rear-axle crane truck with single-wheel
rear axle, w;th said rear axle being equipped with an
overturning-preventing device accord;ng to the invent;on;
F;gure 10 shows a schematic v;ew of the rear axle of
Figure 9, wherein the overturning-preventing device is in
the cond;tion of interruption of the lifting operation;
Figure 11 shows a schematic side view of the rear
axle of Figures 9 and 10.
Referring to the above c;ted figures, and in
particular to Figures 1 through 5, the overturning-
preventing device, generally indicated by the reference
numeral 1, is integral part of a steering, driving rear
axle 2 of a crane truck 3. The crane truck 3 comprises a
crane 4, with a telescopic arm 5, const;tuting operating
means borne by a self-propelled truck 6.
The rear axle 2 comprises a wheel axle 8 with
relevant wheels 7, a differential 9, a pa;r of vertical
elements 10, the same overturning-preventing dev;ce 1, a
hinge 11, with a relevant rotation-limiting device 14, a
steering un;t 12, and a bearing-carrier sleeve 13
directly linked to the self-propelled truck 6.
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In the depicted case the vertical elements 10 are
rig;d, but they could be constituted as ~ell by
traditional leaf springs or sp;ral springs associated
with shock absorbers in case the h;nge 11 ;s replaced by
5a r;gid l;nk.
The rotation-limiting device 14, which limits the
rotation of the hinge 11, compr;ses a pa;r of horizontal
arms 15 bear;ng adjust;ng screw means 16.
The steering un;t 12 ;s composed by at least one
10hydraul;c cylinder 18 interposed between the self-
propelled truck 6 and the rear axle 2, and acting on sa;d
rear axle through at least one lever element 17 ;ntegral
w;th a shaft 19 protrud;ng from the sleeve 13, and the
axis of wh;ch co;nc;des with the steering ax;s 25. The
15shaft 19 is linked through the h;nge 11 to the
overturning-prevent;ng dev;ce 1.
The overturning-preventing device 1 compr;ses f;rst
plate means 20 and second plate means 21, linked along
one of the;r edges by means of a h;nge 22, the rotat;on
20ax;s 26 of wh;ch is perpend;cular to the revolution ax;s
27 of the wheels 7.
The edges of the plates oppos;te to the edges
engaged by the h;nge Z2 are connected w;th means for
interrupt;ng the operat;on of the crane 4, wh;ch are
25const;tuted by a sw;tch 23 and a relevant electr;cal
c;rcuit not shown in the figures, w;th these latter means
be;ng enabled by the rotat;on of the f;rst plate means 20
and of the second plate means 21 relatively to the h;nge
22.
30The rotat;on of the plate means 2û and 21 around the
h;nge 22 ;s l;m;ted by a br;dge element 24 wh;ch, in case
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8 2~212~
of need, is capable of supporting the weight of the wheel
axle 8, of the wheels 7, of the vert;cal elements 10,
and, obviously~ of the second plate means 21.
The overturning-preventing device 1 operates
associated w;th means 28A, 28~ for adjusting the minimum
load transmitted by the axle to the ground.
The adjustment means 28A and 28~ are of two types,
according to whether the axle is of light type, or of
heavy type. By "light axle", an axle type ;s meant, the
weight of which, relatively to the structure of the crane
truck, does not contribu~e to a considerable extent to
generate the couple which opposes the overturning couple.
The light-axle crane trucks are generally the long-wheel-
base crane trucks, which therefore counteract the
overturning couple by mainly exploiting the geometric
characteristics of their self-propelled truck, rather
than exploiting the axle mass characteristics.
On the contrary, by "heavy axle" a type of axle is
meant, the weight of which, relatively to the structure
of the crane truck, contributes to a major extent to
generate the torque opposing the overturning torque.
The heavy-axle crane trucks are generally
characterized by their short wheel base, wh;ch gives them
a h;gh manageability, but lim;ts the;r l;ft;ng
potent;aL;t;es.
The rotation-limiting device 28A ~F;gures 2 and 3)
;s part;cularly suitable for applicat;on to heavy axles,
where;n the weight of the axle should be exploited as
extensively as possible, of course within the safety
limits, in order to generate the torque opposing the
overturning torque, whilst the rotation-limiting device
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9. 2~2~2~
28B (F;gures 4 and 5) is, on the contrary, better suited
for be;ng applied to light axles, on the we1ght of wh;ch
one should not rely in order to ;ncrease the torque
oppos;ng the overturning torque.
The device 28A comprises a fulcrum 29, integral with
either one of the vert;cal elements 10, poss;bly through
a connecting rod 30, a lever 31, an adjustable-pre-load
spr;ng 32 and a flange 33 interposed between the lever 31
and the f;rst plate elements 20.
The configuration taken by the device Z8A is the
configuration of a third class lever, wherein the power
derives from the flange 33, the res;stance is constituted
by the adjustable-pre-load spring 32, and the fulcrum is
in 29.
On the contrary, the device 28B comprises a housing
34, positioned ;n correspondence of those edges of the
plate means 20, 21 which are opposite to the edges
assoc;ated with the hinge 22, ;ntegral w;th the first
plate means 20, ;nside which a spr;ng 35 ;s housed, which
applies a pressure on the second p!ate means 21. The
spr;ng 35 operates by compression, and is pre-loaded by
means of screw means 36.
Ouring the lifting operations carried out by the crane 4, the
overturing torque generates on the rear axle 2 a force F, verti-
cally directed from bottom to the top, which causes the first plate
means 20 to separate from the second plate means 21, due to the
effect of the rotation of the same plate means around the
ax;s 26 of the hinge 22. Such a separat;on enables the
means wh;ch command the ;nterrupt;on sf the operat;on of
the crane 4, const;tuted by the switch 23 and the
relevant c;rcu;t.
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In case the force F acts on a rear axle 2 equipped
w;th a wheel axle 8 of heavy type (Figures 2, 3), the
load-adjustment means 28A acts, by using the weight of
the wheel axle 8, ;n the sense of preventing the plate
S means 20 and 21 from separating from each other, for
values of the force F, which are smaller than a certain
threshold limit, which is a function of the pre-load
g;ven to the spr;ng 32, which anyway can never be such as
to allow the axle 8 to rise relativeLy to the ground,
1û with the practical exclusion of the device 1.
When the intensity of the force F exceeds the
threshold l;m;t - which is a function of the pre-Load
given to the spring 32 -, the elasticity of the same
spring makes it possible the lever 31 to rotate
relatively to the fulcrum 29, and the pLate means 20 and
21 to consequently rotate relatively to the axis 26 of
the hinge 22, with the consequent tripping of the switch
23.
In case the force F acts, on the contrary, on a rear
axle 2 equipped with a wheel axle 8 of Light type, the
means28B for the adjustment of the load acts in the sense
of favouring the plate means 20 and 21 to separate from
each other, with such a separat;on occurr;ng as a
function of the pre-load of the spring 35 and of the same
force F; however, the pre-load given to the spring 35 can
never be such as to cause the plate means 20, 21 to
spontaneously separate from each other.
It is important to observe that, ;n order that the
overturn;ng-preventing device 1 may operate correctly, it
;s necessary that the rotat;on axis 26 of the h;nge 22 ;s
always perpendicular to the revolution ax;s 27 of the
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2121~
wheels 7, ;n case to such wheels a dr;v;ng torque ;s
appl;ed.
Should ;t be not so, the react;on torque, deriving
from the driv;ng torque transmitted to the ground by the
same wheels, would tend to disturb the correct operation
of the overturning-prevent;ng device, by turning into an
additional one of those torques which act on the same
device, by increas;ng or decreasing the level of
intervention of said dev;ce, according to the direction
of revolution of the same driv;ng torque.
The overturn;ng-preventing device 1 can be also used
on s;ngle-wheel-axle crane trucks, whether of l;ght, or
of heavy type, as shown in Figures 6 through 11.
For the sake of simpl;c;ty, ;n sa;d F;gures 6
through 11, the elements equal to such elements as
;llustrated ;n the preceding Figures 1 through 5 are
marked by the same reference numerals.
The single-wheel axle 37, whether of l;ght or of
heavy type, ;s conventionally associated with a drive
unit comprising a motor means 38 and a transmission 39
act;ng on the s;mgle rear wheel 7. The overturning-
preventing dev;ce (1~ can be f;nally also appl;ed to l;ft
trucks, ;n th;s case too the r;sk being avo;ded that sa;d
l;ft trucks may overturn ow;ng to wrong lifting
operations.
