SAFETY SYSTEM FOR MOVING AN ARTICULATED CRANE

Abstract

 Safety system for moving an articulated crane (101), comprising:
- said articulated crane (101), comprising a plurality of bodies (102, 103', 103", 104) consecutively connected in order to form an open kinematic chain, and/or a winch (107), and a plurality of actuators (108, 109, 111, 117) for moving said bodies and/or said winch;
- one or more sensorized clamping members (114) which connect parts of said articulated crane (101), apt to detect a stress acting on them and to provide signals representative of said stress;
- a user interface device (110) configured to command the movements of the articulated crane (101) by an operator,
wherein said articulated crane comprises a control unit (115) 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 (110), said actuators according to regular operative parameters such that the articulated crane performs movements commanded by the operator, wherein said control unit (115) is further configured to command, responsive to commands of the operator on the user interface device (110), 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.

Description

Technical field of the invention

[0001] The present invention relates to a safety system for moving an articulated crane, particularly a loader crane, i.e., a system such that the crane's response to an operator's commands is modified upon the occurrence of certain hazardous conditions.

Prior art

[0002] 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.

[0003] 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.

[0004] 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.

[0005] 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.

[0006] 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).

Summary of the invention

[0007] 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.

[0008] This and other objects are achieved by a safety system for moving an articulated crane according to claim 1.

[0009] Dependent claims define possible advantageous embodiments of the invention.

Brief description of the drawings

[0010] 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:

Figure 1 is a schematic illustration of a safety system for moving an articulated rack and pinion crane;

Figure 2 is a perspective view of an articulated crane column connected to a slewing ring.

Detailed description of the invention

[0011] With reference to the attached Figure 1, 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 101. 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 Figure 2.

[0012] Crane 101 comprises a column 102 rotatable around its own axis, and one or more, possibly extendable, arms 103', 103". Compared to what is shown in Figure 1, one or more additional extendable arms may optionally be provided. Extensibility of the arms, where provided, is achieved by a plurality of extensions 104 movable in translation relative to each other so that the axial extension of the respective arm can be changed. In the example in Figure 1, only the second arm 103" is extendable by movement of the extensions 104. In the following description, the first arm 103', lacking the extensions, will be referred to as the "main arm," while the second arm 103", provided with the extensions 104, will be referred to as the "secondary arm." The main arm 103' is rotatable with respect to column 102, while the secondary arm 103" is rotatable with respect to the main arm 103'.

[0013] The free end 105 of the last extension of the secondary arm 103" is commonly referred to as the end-effector. A hook 106 that can be handled, for example, by a rope winch 107 may be provided at the end-effector 105.

[0014] Crane 101 comprises a plurality of actuators to move the bodies forming the kinematic chain and support the related loads. Referring to Figure 1, a first hydraulic jack 108, which moves the main arm 103' relative to the column 102, a second hydraulic jack 109, which moves the secondary arm 103' relative to the main arm 103', and an actuator 111 for moving the column 102 relative to the fixed reference are visible. There are also additional actuators 117, e.g., hydraulic, for moving the extensions 104, as well as an actuator, also e.g., hydraulic, for moving the winch 107.

[0015] Column 102 can be rotatably coupled to a base 112 by means of a rotary coupling of various types. For example, according to what is illustrated in Figure 1, the rotary coupling between column 102 and base 112 can be of the rack-and- pinion type, or, according to the variant illustrated in Figure 2, column 102 can, for example, be rotatably coupled to base 112 by means of a rotary coupling comprising a slewing ring 113. 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.

[0016] Returning now again to Figure 1, in order to enable the supply to and withdrawal from the above-mentioned hydraulic actuators of a working fluid, specifically pressurized oil, crane 101 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 101 are changed accordingly.

[0017] 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.

[0018] Depending on the type of actuator used (hydraulic, electric, or pneumatic), crane 101 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.

[0019] Optionally, the crane 101 may comprise a plurality of sensors so that coordinates, such as Cartesian coordinates, of the end-effector 105 and/or its velocity can be determined. According to a possible embodiment, with reference to crane 101, the plurality of sensors may include one or more of:

1) an angular sensor for measuring the rotation of column 102 about its axis, relative to a fixed reference;

2) an angular sensor for measuring the rotation of the main arm 103'. This rotation can be absolute, that is, referred to a fixed reference such as the horizontal, or it can be relative, with respect to the column 102;

3) an angular sensor for measuring the rotation of the secondary arm 103". This rotation can be absolute, that is, referred to a fixed reference such as the horizontal, or it can be relative, with respect to the main arm 103";

4) a linear sensor for measuring the translation of the extension arm 104 relative to the secondary arm 103".

[0020] 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 105, or even, by derivation in time, its velocity.

[0021] Alternatively or additionally, a sensor, such as a rotary sensor, can also be provided for determining the amount of cable unwrapped by the winch 107 and/or the rotational speed of the winch.

[0022] Crane 101 comprises a control unit 115 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 110 connected to the crane control unit 115 is also provided to allow an operator to move the crane and possibly access other functions. For example, the user interface device 110 may comprise a radio control and the control unit 115 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 105 and/or the hook 106 moved by the winch 107 by sending appropriate commands to the control unit 115 of the crane 101, in response to which the control unit 115 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 110 may comprise a control panel located on the crane 101 itself, comprising, for example, levers and/or buttons operable by the operator. The control unit 115 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 115 so that the movements commanded by the operator are carried out, in ways that are in themselves known to the skilled person.

[0023] Crane 101 comprises at least one sensorized clamping member 114, 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.

[0024] 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 115. Optionally, the sensorized clamping member 114 can detect temperature, which can have an influence on the expansion of the clamping member itself and thus on the stress measurement.

[0025] An example of sensorized clamping member 114 is provided by WO 2022/084813 A1, the contents of which are fully incorporated herein by reference.

[0026] For example, one of these sensorized clamping members 114 can connect the column 102 to the slewing ring 113, as shown in Figure 2. 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 114. According to a further variant, one or more additional sensorized clamping members 114 may be provided to connect the winch 107 to one of the arms 103', 103", as will be described in more detail below.

[0027] 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 114. For example, in the case where the crane 101 includes a truck (not shown in the figures) that supports and moves the crane, the base 112 and the truck may be connected to each other via one or more sensorized clamping members 114.

[0028] According to the invention, the control unit 115 is further configured to control, in response to commands received from the operator via the radio control 110, 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 114, 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 105 (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 105 and thus the moment applied to the column 102.

[0029] In the following some possible situations detectable by the sensorized clamping members 114 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.

Loosening or breakage of a sensorized clamping member

[0030] 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 114.

[0031] For this purpose, the control unit 115 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 114 goes below a predetermined clamping force threshold value.

[0032] 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.

[0033] 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.

[0034] These threshold values can be stored, for example, in a memory module of control unit 115.

Overloading of the crane or part of it

[0035] 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.

[0036] For this purpose, the control unit 115 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 114, exceeds a predetermined threshold force value above the nominal clamping force.

[0037] 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.

[0038] 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 115.

[0039] 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.

Winch overload

[0040] An additional hazardous condition that may require the use of modified operating parameters of the actuators is overloading of the winch 107, 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.

[0041] For this purpose, the control unit 115 can be configured to stop the actuator driving the winch 107 if the signal representative of the dynamic magnitude, e.g., the total sensed force, provided by at least one sensed clamping member 114 connecting the winch to the crane arm exceeds a predetermined threshold force value greater than the nominal clamping force of the sensed clamping member 114.

[0042] 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 101 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.

[0043] 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.

[0044] 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 115 with respect to the signals representative of the stress detected by the sensorized clamping members 114 according to specific predefined mathematical functions (e.g., linear functions).

[0045] In an embodiment, the control unit 115 comprises a transmission module capable of transmitting the measured quantities by the one or more sensorized clamping members 114 to a remote control unit 116, 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 115 or, alternatively, it can be separate from the control unit 115 and operationally connected to it.

[0046] As an example, the transmission of information between the remote operations center 116 and the control unit 115 of the crane 101 enables the following operations:

• sending alarms or maintenance requests when screws are badly tightened, broken, or when there are abnormal vibrations;
• scheduling of maintenance work, suitable for restoring clamping force and/or replacing one or more clamping members, based on the analysis of the measurement trend provided by the crane's sensorized clamping members over time, thus avoiding unnecessary operations;
• monitoring the fatigue cycles of a given crane component based on the force cycles detected by the sensorized clamping members, estimating its remaining life;
• monitoring at one or more points the stresses of the crane, thereby among other things optimizing the sizing of joints, verifying their stresses under real and not just simulated conditions.

[0047] 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 110, which can be configured for this purpose to provide the above-mentioned information/alarms and perform the above-mentioned monitoring.

[0048] As mentioned earlier, the transmission module of each sensorized clamping member can communicate with the crane control unit 115 wirelessly or via cable. For example, the wireless mode can be achieved by a direct Bluetooth^® connection between the crane control unit 115 and each of the sensorized clamping members 114, or via a gateway. The wired mode can, for example, take advantage of a CAN BUS line on the crane 101 itself.

[0049] Alternatively or in addition to the above, the crane control unit 115 and the sensorized clamping members 114 can be indirectly connected to each other via the remote control unit 116. This allows simultaneous transmission of sensed quantities to both the crane control unit 115 and the remote control unit 116 achieving the following advantages:

• sending real-time information about any dangerous situations to the remote control unit 116 (for example: to a maintainer or crane dealer);
• integrating the data received in real-time from the crane 101 with other data stored by the remote control unit 116 (e.g.: historical data from other similar cranes, previously determined trends for a specific crane model, geographical location of the crane, which may have an effect on the need for maintenance e.g. due to particular weather conditions or temperature). Note that all or some of the previously mentioned predetermined threshold values can also be stored in the remote control unit 116 and possibly updated and/or modified and transmitted to the crane control unit 115;
• possible greater computational power than that provided by the crane control unit 115;
• storing individual crane data remotely, without overloading the memory of the crane control unit 115.

[0050] 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.

[0051] To the described embodiments of the safety system for the moving of an articulated crane, the skilled person, in order to meet specific contingent needs, may make numerous additions, modifications, or substitutions of elements with functionally equivalent ones, without, however, departing from the scope of the attached claims.

Claims

1. Safety system for moving an articulated crane (101), comprising:

- said articulated crane (101), comprising a plurality of bodies (102, 103', 103", 104) consecutively connected in order to form an open kinematic chain, and/or a winch (107), and a plurality of actuators (108, 109, 111, 117) for moving said bodies and/or said winch;

- one or more sensorized clamping members (114) which connect parts of said articulated crane (101), apt to detect a stress acting on them and to provide signals representative of said stress;

- a user interface device (110) configured to command the movements of the articulated crane (101) by an operator,

wherein said articulated crane comprises a control unit (115) 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 (110), said actuators according to regular operative parameters such that the articulated crane performs movements commanded by the operator, wherein said control unit (115) is further configured to command, responsive to commands of the operator on the user interface device (110), 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.

2. System according to claim 1, wherein said regular and modified operative parameters of the actuators are related to the speed of the bodies of the articulated crane (101) and/or of the winch (107), and/or to the coordinates of the end-effector (105) and/or the maximum load hoistable by the winch.

3. System according to claim 2, wherein the modified operative parameters are correlated to the speeds of the bodies of the articulated crane (101) and/or of the winch (107) and/or to the coordinates of the end-effector (105) and/or to the maximum load hoistable by the winch, reduced with respect to the ones correlated to the regular operative parameters.

4. System according to anyone of the preceding claims, wherein said actuators (108, 109, 111, 117) comprise hydraulic actuators operating by a pressurized working fluid, and said regular and modified operative parameters comprise flow rate and pressure of said working fluid.

5. System according to anyone of the preceding claims, wherein said one or more sensorized clamping members (114) are apt to detect a tightening force applied to the same, wherein said control unit (115) is configured to command the articulated crane (101) according to said modified operative parameters if the signal representative of the tightening force is less than a predetermined tightening force threshold value less than or equal to a nominal tightening force.

6. System according to anyone of the preceding claims, wherein said one or more sensorized clamping members (114) are apt to measure a total force, or a component thereof, applied to the same, wherein said control unit (115) is configured to command the articulated crane (101) according to said modified operative parameters if the signal representative of the total force is greater than a predetermined force threshold value greater than a nominal tightening force.

7. System according to anyone of the preceding claims, wherein said plurality of bodies of the articulated crane (101) comprises a pillar (102) rotatively coupled to a base (112) by a rotative coupling comprising a slewing ring (113), wherein at least one of said one or more sensorized clamping members (114) connect said pillar (102) and said slewing ring (113).

8. System according to anyone of the preceding claims, wherein at least one of said one or more sensorized clamping members (114) connect said winch (107) to a body of said plurality of bodies of the articulated crane (101).

9. System according to anyone of the preceding claims, wherein said one or more sensorized clamping members (114) comprise a measuring module apt to detect the stress and a transmission module apt to transmit the signals representative of said stress.

10. System according to the preceding claim, wherein said transmission module of the sensorized clamping members (114) is wirelessly or by wire, directly or indirectly, connected to a transmission module of the control unit (115) of the articulated crane (101).

11. System according to the preceding claim, comprising a remote control unit (116) wirelessly connected to the transmission modules of the sensorized clamping members (114) and/or to the transmission module of the control unit (115) of the articulated crane (101).

12. System according to the preceding claim, wherein said transmission modules of the sensorized clamping members (114) and of the control unit (115) of the articulated crane are in communication with each other by the remote control unit (116).

13. System according to anyone of the preceding claims, wherein said control unit (115) of the articulated crane (101) and/or said remote control unit (116) are configured to provide, based on received signals representative of the stresses, alerts and/or alarms and/or information regarding the state of the articulated crane (101) and/or regarding required maintenance services.

14. System according to anyone of claims from 11 to 13, wherein said remote control unit (116) is configured to update and transmit to the control unit (115) of the articulated crane (101) said modified operative parameters.

Drawing