Patent Description:
Articulated cranes are systems equipped with a plurality of bodies, normally a column pivoting with respect to a base and one or more arms comprising extensions that are mutually movable in translation, connected to each other in succession, such as to form an open kinematic chain with a plurality of degrees of freedom, translational and/or rotational in space. A winch-operated hook is typically provided at the end of the extensions for lifting loads.

Articulated cranes are normally operated by a remote operator using a radio control. In particular, the operator can move the crane bodies and manipulate/move loads, even very high loads, by means of the crane hook.

Therefore, articulated cranes are generally subjected to high stresses, necessitating periodic maintenance. In particular, cranes have numerous tightening devices, typically threaded connecting parts, such as screws and/or bolts, which must be periodically checked to ensure that there has been no loosening or breakage that could compromise the safe operation of the crane.

For example, in slewing ring loader cranes between the column and the base a bearing coupling (the slewing ring) is provided for their relative rotation. The column and the slewing ring are coupled together by a plurality of screws tightened with a predetermined torque, which must be able to support the moment from the column to the slewing ring even under maximum extension of the extensions and high loads lifted. Clearly, if one or more of these screws were to be poorly tightened or damaged, the safety of the crane would be severely compromised.

Although periodic maintenance work is intended, among other things, to avoid such situations, there is still the possibility of some unintended screw failure (e.g.: loosening of tightening and/or breakage, due to fatigue or overloading). <CIT> discloses a safety system according to the preamble of claim <NUM>.

It is therefore an object of the present invention to provide a safety system for the moving of an articulated crane such as to overcome at least in part the drawbacks mentioned with reference to the prior art.

This and other objects are achieved by a safety system for moving an articulated crane according to claim <NUM>.

Dependent claims define possible advantageous embodiments of the invention.

To better understand the invention and appreciate its advantages, some of its non-limiting exemplary embodiments will be described below, referring to the attached figures, in which:.

With reference to the attached <FIG>, therein is an example of an articulated crane, e.g., a hydraulic loader crane (commonly referred to as a "loader crane"), more particularly of the rack-and-pinion type, shown as a whole under reference <NUM>. It should be noted, however, that the present invention can find application in the safety of loader cranes in general, such as loader cranes with slewing ring, according to the variant shown for example in <FIG>.

Crane <NUM> comprises a column <NUM> rotatable around its own axis, and one or more, possibly extendable, arms <NUM>', <NUM>". Compared to what is shown in <FIG>, one or more additional extendable arms may optionally be provided. Extensibility of the arms, where provided, is achieved by a plurality of extensions <NUM> movable in translation relative to each other so that the axial extension of the respective arm can be changed. In the example in <FIG>, only the second arm <NUM>" is extendable by movement of the extensions <NUM>. In the following description, the first arm <NUM>', lacking the extensions, will be referred to as the "main arm," while the second arm <NUM>", provided with the extensions <NUM>, will be referred to as the "secondary arm. " The main arm <NUM>' is rotatable with respect to column <NUM>, while the secondary arm <NUM>" is rotatable with respect to the main arm <NUM>'.

The free end <NUM> of the last extension of the secondary arm <NUM>" is commonly referred to as the end-effector. A hook <NUM> that can be handled, for example, by a rope winch <NUM> may be provided at the end-effector <NUM>.

Crane <NUM> comprises a plurality of actuators to move the bodies forming the kinematic chain and support the related loads. Referring to <FIG>, a first hydraulic jack <NUM>, which moves the main arm <NUM>' relative to the column <NUM>, a second hydraulic jack <NUM>, which moves the secondary arm <NUM>' relative to the main arm <NUM>', and an actuator <NUM> for moving the column <NUM> relative to the fixed reference are visible. There are also additional actuators <NUM>, e.g., hydraulic, for moving the extensions <NUM>, as well as an actuator, also e.g., hydraulic, for moving the winch <NUM>.

Column <NUM> can be rotatably coupled to a base <NUM> by means of a rotary coupling of various types. For example, according to what is illustrated in <FIG>, the rotary coupling between column <NUM> and base <NUM> can be of the rack-and- pinion type, or, according to the variant illustrated in <FIG>, column <NUM> can, for example, be rotatably coupled to base <NUM> by means of a rotary coupling comprising a slewing ring <NUM>. The term "slewing ring" refers to an axial bearing particularly suitable for low rotational speeds and high axial loads, comprising an inner ring and an outer ring coupled by means of one or more rows of balls or rollers such as to allow relative rotation.

Returning now again to <FIG>, in order to enable the supply to and withdrawal from the above-mentioned hydraulic actuators of a working fluid, specifically pressurized oil, crane <NUM> generally comprises a hydraulic circuit. The working fluid parameters determine the operating parameters of the crane itself. Specifically, the flow rate of working fluid affects the kinematic quantities of the articulated arm bodies and of the winch (in particular, the column rotation speed and the translation speed of the extensions, as well as the rotation speed of the winch), while the working fluid pressure affects the maximum load that can be lifted by them. Therefore, by changing the working parameters of the working fluid, the operating parameters (kinematics and maximum load) of crane <NUM> are changed accordingly.

Of course, although in cranes the actuators are normally hydraulic, it is generally possible to provide actuators of a different nature (for example: electric or pneumatic). In these cases, too, it is of course possible to act on the actuators to change the operating parameters of the crane, particularly the kinematic magnitudes and the sustainable load. For example, in the case of electric rotary motors, limiting the maximum torque and angular speed of the motor will consequently limit the maximum sustainable load and the translation/rotation speeds of the arms. Similar considerations apply to pneumatic actuators, where limiting the pressure and flow rate of gas (e.g., air) will consequently limit the maximum sustainable load and translation/rotation speeds of the arms.

Depending on the type of actuator used (hydraulic, electric, or pneumatic), crane <NUM> may include suitable sensors for detecting the working parameters of the actuators that affect the crane's operating parameters. For example, in case of hydraulic cranes, such sensors may measure the flow rate and pressure of the working fluid.

Optionally, the crane <NUM> may comprise a plurality of sensors so that coordinates, such as Cartesian coordinates, of the end-effector <NUM> and/or its velocity can be determined. According to a possible embodiment, with reference to crane <NUM>, the plurality of sensors may include one or more of:.

For example, sensors may include linear or angular encoders, magnetostrictive sensors, or similar. From the signals from the above sensors, it is possible, by means of geometric relations, to determine the absolute coordinates of end-effector <NUM>, or even, by derivation in time, its velocity.

Alternatively or additionally, a sensor, such as a rotary sensor, can also be provided for determining the amount of cable unwrapped by the winch <NUM> and/or the rotational speed of the winch.

Crane <NUM> comprises a control unit <NUM> functionally connected to the above-described actuators, for their movement, and to the possible sensors, to receive signals representative of the above-mentioned quantities and thus be able to move various moving bodies and/or the winch according to specific commands received. For this purpose, a user interface device <NUM> connected to the crane control unit <NUM> is also provided to allow an operator to move the crane and possibly access other functions. For example, the user interface device <NUM> may comprise a radio control and the control unit <NUM> may comprise a transmission module to communicate with the latter (e.g., a radio transmission module). By means of the radio control, by acting, for example, on a joystick, the operator can visually move the end-effector <NUM> and/or the hook <NUM> moved by the winch <NUM> by sending appropriate commands to the control unit <NUM> of the crane <NUM>, in response to which the control unit <NUM> determines the operating parameters of the actuators necessary for the articulated arm and/or the winch to perform the movements desired by the operator, possibly carrying a load. According to a further variant not shown in the figures, the user interface device <NUM> may comprise a control panel located on the crane <NUM> itself, comprising, for example, levers and/or buttons operable by the operator. The control unit <NUM> then, under normal conditions, controls the actuators according to these operating parameters (hereinafter referred to as "regular operating parameters"). The above-mentioned sensors are conveniently exploited by the control unit of the crane <NUM> so that the movements commanded by the operator are carried out, in ways that are in themselves known to the skilled person.

Crane <NUM> comprises at least one sensorized clamping member <NUM>, connecting at least two of its parts, that is capable of sensing a stress acting on it. The term "stress" means a force or torque, static or dynamic, such as a clamping force or torque, or an external force acting on it, such as a shear force and/or a compressive or tensile axial force, or a torque or bending moment) and to provide a signal representative of the same.

Such sensorized clamping members are known in the state of the art. They generally comprise a clamping body, such as a threaded rod, for mechanical clamping, alone or in cooperation with other complementary clamping bodies, such as a clamping nut. The clamping body includes a measurement module capable of measuring directly or indirectly, such as by ultrasound, stresses acting on the clamping body, as well as a transmission module, configured to transmit the measured physical quantity, wirelessly and/or via a data communication cable, to the crane control unit <NUM>. Optionally, the sensorized clamping member <NUM> can detect temperature, which can have an influence on the expansion of the clamping member itself and thus on the stress measurement.

An example of sensorized clamping member <NUM> is provided by <CIT>, the contents of which are fully incorporated herein by reference.

For example, one of these sensorized clamping members <NUM> can connect the column <NUM> to the slewing ring <NUM>, as shown in <FIG>. According to one embodiment, only one of the clamping members between the column and the slewing ring is of the sensorized type, while the other clamping members are ordinary threaded connecting organs. Alternatively, one or more of the ordinary connecting organs, possibly all of them, can be replaced by as many sensorized clamping members <NUM>. According to a further variant, one or more additional sensorized clamping members <NUM> may be provided to connect the winch <NUM> to one of the arms <NUM>', <NUM>", as will be described in more detail below.

Of course, although not explicitly described, there can be numerous other variants in which different parts of the crane are connected via one or more sensorized clamping members <NUM>. For example, in the case where the crane <NUM> includes a truck (not shown in the figures) that supports and moves the crane, the base <NUM> and the truck may be connected to each other via one or more sensorized clamping members <NUM>.

According to the invention, the control unit <NUM> is further configured to control, in response to commands received from the operator via the radio control <NUM>, at least some of the actuators according to operating parameters different from the regular operating parameters (hereinafter referred to as "modified operating parameters") depending on the stress-representative signal provided by the sensorized clamping members <NUM>, in particular when one or more stresses indicative of a risk or failure condition are measured, for example low clamping force, overload or breakage. Hazard or failure conditions that require actuators to be controlled according to modified operating parameters generally define possible situations in which the articulated crane must work with different, generally reduced, performance than under regular conditions. For example, under such conditions it is required that the speed of the end-effector <NUM> (and consequently of each of the articulated arm bodies) and/or the maximum load that can be lifted by the articulated arm is reduced. Alternatively, it may be required that the crane be stopped altogether. Alternatively, the maximum extension of the extensions may be limited, so as to limit the overall overhang of the end-effector <NUM> and thus the moment applied to the column <NUM>.

In the following some possible situations detectable by the sensorized clamping members <NUM> that require actuators to be controlled according to the modified operating parameters will be described. In the system according to the invention all or only some of the following conditions may be taken into account, possibly in combination with each other.

A first condition that may require the use of modified actuator operating parameters is the breakage or loosening of the tightening of one or more of the sensorized clamping members <NUM>.

For this purpose, the control unit <NUM> can be configured to control the actuators according to modified operating parameters if the stress-representative signal, e.g., clamping force, provided by at least one of the sensorized clamping members <NUM> goes below a predetermined clamping force threshold value.

For example, if the clamping force measured in the sensorized clamping member is less than a threshold value less than or equal to the nominal clamping force established at the design stage, this may indicate a loosening of the screw and thus the need for the crane to be operated at reduced performance until the nominal clamping condition is restored.

Note that multiple threshold values may be provided, to which different crane performances correspond. For example, decreasing threshold values may be provided, corresponding to progressive loosening of the clamping member compared to the nominal clamping force, to which gradually decreasing performance of the crane corresponds, until it possibly stops. For example, in the case of zero force detection, this may mean that the clamping member has broken and therefore it may be necessary to stop the crane altogether.

These threshold values can be stored, for example, in a memory module of control unit <NUM>.

An additional hazardous condition that may require the use of modified operating parameters of the actuators is overloading of the crane or any part of it, which results in overloading of the clamping members. Such a condition may occur, for example, in the case of excessive moment applied to the column, which results in overloading of the column's clamping members e.g., at the slewing ring, which may occur, for example, in the case of excessive overhang of the end-effector under a high load, or a load that is generically excessive in relation to the crane's capacity.

For this purpose, the control unit <NUM> can be configured to control the actuators according to modified operating parameters if the stress representative signal, for example, the force acting on at least one of the sensorized clamping members <NUM>, exceeds a predetermined threshold force value above the nominal clamping force.

For example, if the force measured in the sensed clamping member is greater than a threshold force value greater than the nominal clamping force, this may indicate an overload of the screw and thus the need for the crane to be operated at reduced performance until the sensed force returns below the threshold force value. Reduced performance may include a limitation of the overhang of the end-effector (thus a limitation of its Cartesian coordinates, which can be measured by the above-mentioned sensors, at least along the horizontal) and/or also a limitation of accelerations/decelerations that could result in additional overloads due to the forces/moments of inertia on the column.

Note that here, too, multiple threshold values may be provided, to which different crane performance corresponds. For example, increasing threshold values can be provided, corresponding to increasing load conditions, to which gradually decreasing crane performance or a gradually reduced overhang of the end-effector, up to possibly complete crane shutdown and/or total retraction of the extensions (i.e., minimum coordinates of the end-effector) correspond. Such additional threshold values can also be stored, for example, in the memory module of control unit <NUM>.

Note that the above-described safety criterion can be exploited in conjunction with other per se known overload safety criteria that limit crane performance if pressure in the hydraulic jacks above a threshold value is detected.

An additional hazardous condition that may require the use of modified operating parameters of the actuators is overloading of the winch <NUM>, which results in overloading of the clamping members that connect the winch itself to the respective crane jib. In such a case, the actuator that will be controlled according to modified operating parameters is the actuator that drives the winch. Such a condition may occur, for example, in case of excessive load applied to the winch hook, which results in overloading of members clamping the winch to the crane jib.

For this purpose, the control unit <NUM> can be configured to stop the actuator driving the winch <NUM> if the signal representative of the dynamic magnitude, e.g., the total sensed force, provided by at least one sensed clamping member <NUM> connecting the winch to the crane arm exceeds a predetermined threshold force value greater than the nominal clamping force of the sensed clamping member <NUM>.

For example, if the force measured in the sensorized clamping member is greater than a threshold value greater than the nominal clamping force, this may indicate an overload of the winch and thus the need to stop its movement. Optionally, one or more of the other actuators that move the articulated crane <NUM> bodies can also be controlled according to modified operating parameters in case of winch overload determined according to the above. This will prevent, for example, the load from being lifted not only by the winch, but also by moving the crane arms.

It should be noted that the above safety criterion can be exploited as an alternative to the commonly used winch stop system, which involves connecting the winch to the crane arm with ordinary clamping members and attaching a load cell in such a position that it is able to derive, from its own compression due to the applied load, the force applied to the winch hook. According to the invention, it is thus possible to eliminate the load cell, with a reduction in the crane's overall dimensions and weight.

It should also be noted that, as an alternative to a change in the modified operating parameters when successive predefined threshold values are exceeded, as described above, a continuous change in the modified operating parameters can be provided by the control unit <NUM> with respect to the signals representative of the stress detected by the sensorized clamping members <NUM> according to specific predefined mathematical functions (e.g., linear functions).

In an embodiment, the control unit <NUM> comprises a transmission module capable of transmitting the measured quantities by the one or more sensorized clamping members <NUM> to a remote control unit <NUM>, such as a remote operations center, and receiving information from it. For example, transmission can be via the Internet by taking advantage of a cellular data connection or a Wi-Fi network. This allows information on the status of the crane to be provided to such a remote operations center and, if necessary, interventions to be planned. The transmission module can be an integral part of the control unit <NUM> or, alternatively, it can be separate from the control unit <NUM> and operationally connected to it.

As an example, the transmission of information between the remote operations center <NUM> and the control unit <NUM> of the crane <NUM> enables the following operations:.

It should be noted that, alternatively or in addition, the above-mentioned operations can be carried out directly on site, such as through the user interface device <NUM>, which can be configured for this purpose to provide the above-mentioned information/alarms and perform the above-mentioned monitoring.

As mentioned earlier, the transmission module of each sensorized clamping member can communicate with the crane control unit <NUM> wirelessly or via cable. For example, the wireless mode can be achieved by a direct Bluetooth® connection between the crane control unit <NUM> and each of the sensorized clamping members <NUM>, or via a gateway. The wired mode can, for example, take advantage of a CAN BUS line on the crane <NUM> itself.

Alternatively or in addition to the above, the crane control unit <NUM> and the sensorized clamping members <NUM> can be indirectly connected to each other via the remote control unit <NUM>. This allows simultaneous transmission of sensed quantities to both the crane control unit <NUM> and the remote control unit <NUM> achieving the following advantages:.

Note that in this description and the attached claims, control units, as well as the elements referred to as "module," may be implemented by hardware devices (e.g., control units), by software, or by a combination of hardware and software.

Claim 1:
Safety system for moving an articulated crane (<NUM>), comprising:
- said articulated crane (<NUM>), comprising a plurality of bodies (<NUM>, <NUM>', <NUM>", <NUM>) consecutively connected in order to form an open kinematic chain, and/or a winch (<NUM>), and a plurality of actuators (<NUM>, <NUM>, <NUM>, <NUM>) for moving said bodies and/or said winch;
- one or more sensorized clamping members (<NUM>) which connect parts of said articulated crane (<NUM>), apt to detect a stress acting on them and to provide signals representative of said stress;
- a user interface device (<NUM>) configured to command the movements of the articulated crane (<NUM>) by an operator,
wherein said articulated crane comprises a control unit (<NUM>) operatively connected to said actuators, to said user interface device and to said one or more sensorized clamping members, configured to command, responsive to commands of the operator on the user interface device (<NUM>), said actuators according to regular operative parameters such that the articulated crane performs movements commanded by the operator, characterised in that
said control unit (<NUM>) is further configured to command, responsive to commands of the operator on the user interface device (<NUM>), at least some of said actuators according to operative parameters modified as a function of said signals representative of the stress, different from the regular operative parameters.