AUTOMATIC METHOD FOR DETERMINING THE PHYSICAL LIFTING POSITION OF A MUFFLUSH OF A TOWER CRANE DURING A LIFTING OPERATION

Description

[Technical field]

[0001] The invention relates generally to the technical field of cranes, and in particular tower cranes. It relates more particularly to an automatic method for determining a physical end-of-travel position of the crane block, for the safety of the crane and its equipment.

[0002] The invention finds a preferred, and non-limiting, application for element-mounted cranes and self-assembling cranes. [State of the art]

[0003] As is known, when a crane is working and a load is lifted by its block during an upward lift, the block can move upwards until it reaches a limit height corresponding to an upper end-of-travel position, and distant from the underside of a distribution trolley, on which the block is suspended, by a predefined safety distance. The purpose of stopping the block at this upper end-of-travel position is to prevent it, during its ascent, from hitting the distribution trolley moving in translation on the boom. A collision between the trolley and the block can, on the one hand, damage them both, as well as possibly elements of the boom; and on the other hand potentially cause overtension and breakage of the lifting cable, as well as the fall of all or part of the load lifted by the block to the ground, risking damage to equipment and / or injuring a worker located under the block at the time of the load drop.

[0004] The upper end-of-travel position is a parameter that the crane's control-command system memorizes following a determination procedure designed to determine it, and which is normally carried out by the crane operator at the start of the day when the crane is put into service; and which the control-command system then applies automatically for the rest of the day when the crane is working and maneuvered during one or more lifting operations, with lifting limiters in communication with the control-command system reducing the speed of the block when it approaches the upper end-of-travel position, and stopping it when it reaches it.

[0005] Conventionally, the determination procedure is carried out manually, with the crane operator visually estimating the safety distance and returning the block, which is not carrying a load, to the upper end-of-travel position that he considers correct. Consequently, this determination procedure is imprecise, with an estimated upper end-of-travel position more or less close to the actual upper end-of-travel position, and therefore not very reproducible from one determination procedure to another. This is why additional safety margins in terms of distance are taken by the crane operator with respect to the upper end-of-travel position, resulting in the crane not being used optimally. It is also not uncommon for the crane operator to omit this operation at start-up in order to start the crane work as soon as possible.

[0006] Known solutions, such as those in documents WO21243981 and CN208964423, propose automatically stopping the block at the upper end-of-travel position by means of electronic devices which have the disadvantage of: being added to the equipment already included in the crane and communicating with its control-command system; and which are made up of several elements.

[0007] Document CN208964423 discloses the preamble of claim 1. The solution proposed for example in WO21243981 comprises in particular for its realization a connection table, a programmable controller, a frequency converter, and a Modbus R< multi-loop absolute value encoder communicating with the lifting motor of the crane; all of these elements being in interaction and the programmable controller communicating with the control-command system.

[0008] Document US2020 / 0247647A1 proposes, for telescopic boom cranes, to determine an intermediate position of a hook corresponding to a position of change of state of the lifting cable and the sling cables, which pass from a relaxed state to a taut state, in order to avoid a horizontal swing phenomenon when lifting the load. [Summary of the invention]

[0009] The invention proposes to address the above-mentioned problems by means of an automatic method for determining a physical end-of-travel position for load lifting operations. The advantages of this automatic method are as follows: a reduction in human intervention, and therefore a minimization of the risk of human error and a gain in safety; the reproducibility of the automatic process and the repeatability of the settings that can result from the determination of the physical end-of-travel position.

[0010] Another object of the invention is to determine precisely, following the determination of the physical end-of-travel position, the upper end-of-travel position when the crane is working, the upper end-of-travel position subsequently being called the maximum end-of-travel position.

[0011] The invention has two advantages on this particular point: a time saving during commissioning of the crane, the automatic process determining the physical end-of-travel position quickly while the crane operator generally estimates the maximum end-of-travel position for at least ten minutes, thus offering a significant time saving for the operation and profitability of the crane; an improvement in performance, particularly in height under the hook. Since the physical end-of-travel position and the maximum end-of-travel position are estimated accurately, it is possible to possibly reduce the safety distance separating the two positions, thus optimizing the crane's capacities.

[0012] Another object of the invention is that the automatic process is implemented without adding equipment to that already included in the crane.

[0013] Another aim of the invention, linked to the previous one, is that the automatic determination method is implemented by the crane control system.

[0014] Thus, the invention proposes an automatic method for determining a physical end-of-travel position of a block of a crane movable up and down by means of a lifting cable, said block being suspended by the lifting cable from a distribution trolley, said automatic method comprising a phase of raising the block during which a force on a strand of the lifting cable is measured by a monitoring device, said physical end-of-travel position, which corresponds to a position in which the block is physically in contact with the distribution trolley, being reached and determined as a function of a variation in the force on the strand of the lifting cable.

[0015] In other words, the determination of the physical end-of-travel position is implemented in an automated manner and is based on a measurement by a monitoring device of the force exerted on the lifting cable lifting the block when said block is raised in the direction of the crane boom during a lifting phase; the physical end-of-travel position being reached and determined when a variation in the force is measured by this monitoring device during this lifting phase of the block.

[0016] In fact, as long as the pulley block is below the physical end-of-travel position, the force on the strand of the lifting cable is stable, and on the other hand, once the physical end-of-travel position is reached (in other words when the pulley block makes physical contact), this force varies suddenly, and it is this variation which indicates that the physical end-of-travel position has been reached.

[0017] In the process, the variation of the force on the strand of the lifting cable is observed from the moment when the block comes into contact with the underside of the trolley mounted on the crane boom.

[0018] According to a characteristic of the invention, the physical end-of-travel position is determined from an increase in the force on the strand of the lifting cable.

[0019] In other words, the variation in the force on the cable strand observed at the moment of contact between the pulley and the trolley results in an increase in this force, and in particular a sudden increase.

[0020] According to a characteristic of the invention, the increase in the force on the strand of the lifting cable is characterized by an excess of the force beyond a given force threshold, or by a slope of variation of the force above a given slope value.

[0021] In other words, during the ascent phase, the force on the strand is representative of a weight lifted by the lifting cable. The physical end-of-travel position is determined and considered to have been reached if: the force on the strand exceeds a force threshold representative of an additional tension exerted on the cable and which would not be solely due to the weight lifted by the lifting cable. More precisely, the force threshold is representative of the weight lifted by the cable to which is added the overtension occurring, for this given weight, when the block comes into contact with the trolley; and / or the increase in force is sufficiently abrupt / rapid in time, that is to say that it presents a steep variation slope over a very short time interval, meaning that the instant t preceding this slope corresponds to the moment of contact of the block with the trolley, and that the slope corresponds to the weight lifted added to the overtension exerted in the lifting cable by the weight lifted and the force exerted by the block while being blocked under the trolley while trying to continue to rise.

[0022] According to a characteristic of the invention, the ascent phase is carried out with the vacuum muffle.

[0023] Thus, the force on the strand during the ascent phase and before the block comes into contact with the carriage is only due to the weight of the block itself.

[0024] The ascent phase is carried out with the empty block for several reasons: not to exert unnecessary overtension on the lifting cable at the moment of contact between the pulley and the trolley by attaching a load to the pulley hook; the weight of the pulley being constant, the forces on the strand observed before and at the moment of contact are both invariant from one implementation of the automatic process to another, therefore making the process precise and reproducible.

[0025] According to a characteristic of the invention, the climb phase is operated at a climb speed below a minimum speed.

[0026] The block is raised at low speed during the ascent phase and when determining the physical end-of-travel position in order to avoid it colliding too quickly with the trolley from which it is suspended and damaging it (and / or damaging itself). This speed does not exceed a predetermined minimum speed depending on the type of crane, as well as the variator, winch, and reeving system used.

[0027] According to a characteristic of the invention, the ascent phase is stopped as soon as the physical end-of-travel position is reached and determined.

[0028] In other words, when the variation in the force on the strand of the lifting cable is observed by the monitoring device, this means that the block has just reached the physical end-of-travel position. Its upward progression, and therefore the ascent phase, is immediately stopped. The physical end-of-travel position is then memorized by the crane (for example, by a memory in a control system).

[0029] According to a characteristic of the invention, the monitoring device is a load sensor mounted on the crane to be able to measure the dead weight of the pulley.

[0030] In other words, this feature proposes to use a load sensor which is conventionally present on the crane, because it is used to determine the weight of the load suspended from the block; which is advantageous because it does not require a dedicated sensor, but rather a sensor already present.

[0031] According to one embodiment of the invention, the load sensor is a gauge shaft mounted on a lifting cable return system.

[0032] In other words, the gauge shaft is mounted on a return system on which the lifting cable is wound or unwound, the gauge shaft measuring a torsional force from which the force exerted on the strand of the cable is deducted.

[0033] Advantageously, the gauge axis is an integral part of the equipment installed on the crane in order to measure the force exerted on the lifting cable and ensure the proper progress of lifting operations when the crane is working. It is not an additional monitoring device added to the crane solely to enable the determination of the physical end-of-travel position.

[0034] According to a characteristic of the invention, the automatic method comprises a step of calculating a maximum end-of-travel position of the pulley, located below the physical end-of-travel position at a predefined safety distance.

[0035] More precisely, the physical end-of-travel position, once determined, is used as a reference to calculate the maximum end-of-travel position of the block. The calculation involves the safety distance separating the two positions, which is different depending on the type of crane considered. Thanks to the invention, this safety distance can be reduced compared to what is currently implemented when the maximum end-of-travel position is established manually and visually.

[0036] According to a characteristic of the invention, the safety distance is between 40 and 100 cm.

[0037] Advantageously, the safety distance is defined so that the automatic process can be implemented in element-mounted cranes (for a suitable safety distance between 80 and 100 cm) and self-erecting cranes (for a suitable safety distance between 40 and 80 cm).

[0038] According to a characteristic of the invention, once the physical end-of-travel position is reached and determined, the pulley block is lowered until it reaches the maximum end-of-travel position.

[0039] In other words, once the block has reached the physical end-of-travel position, it is lowered by a height corresponding to the safety distance to reach the maximum end-of-travel position, which is then memorized by the crane (more precisely by the memory of the crane's control system).

[0040] According to a characteristic of the invention, the maximum end-of-travel position is a maximum position not to be exceeded for the block when the crane is working.

[0041] As previously stated, the maximum end of travel position corresponds to the upper end of travel position corresponding to the height at which the block is stopped when carrying a load and moves upwards in the direction of the boom when the crane is working.

[0042] According to a characteristic of the invention, the automatic process is carried out when the crane is started, before any work involving moving a load.

[0043] Thanks to the invention, this process can be implemented in a forced manner each time the crane is started, without the crane operator being able to override it.

[0044] According to a characteristic of the invention, the automatic process can be repeated between two periods of crane activity.

[0045] Advantageously, the crane operator has the possibility of restarting the automatic process during the day so that the physical and maximum end-of-travel positions can be determined and adjusted again, for example if he notices, following any action of the crane (a lifting or distribution maneuver for example), a notable modification or an inconsistency in the height at which the block stops when it must return to its maximum end-of-travel position.

[0046] In order for the physical and maximum end-of-travel positions to be determined accurately again, the automatic process must be restarted between two periods of crane activity, after taking care that no load is suspended on the block.

[0047] According to a characteristic of the invention, the automatic method is implemented in a control / command system included in the crane, said control / command system being connected at least to a lifting winch coupled to the lifting cable, and to the monitoring device.

[0048] Advantageously, the automatic process is implemented in the crane's control system and implemented by it.

[0049] In the case where a load sensor (such as a gauge pin) is used as a monitoring device, this means that no additional external equipment, either for the implementation or operation of the automatic process, or for monitoring and measuring the force exerted on the strand, is necessary in determining the physical end-of-travel position. [Brief description of the figures]

[0050] Other characteristics and advantages of the present invention will appear on reading the detailed description below, of a non-limiting example of implementation, made with reference to the appended figures in which: [ Fig 1 ] is a schematic view of a crane illustrating the control / command system connected in particular to the lifting winch which is coupled to the lifting cable used to raise and lower the block, as well as to the monitoring device used to measure / monitor the force of one of the strands of the lifting cable, in an application context for which the raising phase of the automatic process is implemented by the control / command system, with the block being raised in the direction of the crane boom; [ Fig 2 ] is a schematic view equivalent to the Figure 1, for which the ascent phase of the automatic process is stopped, with the pulley having come into contact with the underside of the distribution carriage and having reached the physical end-of-travel position; [ Fig 3 ] is a curve showing the evolution of the force measured by the monitoring device on the strand of the lifting cable considered, during the ascent phase and after the block has come into contact with the underside of the distribution trolley; [ Fig 4 ] is a schematic view equivalent to the Figures 1 and 2 , for which the control / command system implements a descent phase during which the pulley block is lowered from the physical end-of-travel position to the maximum end-of-travel position; [ Fig 5] is a curve showing the evolution of the speed at which the block is raised in the direction of the boom when the crane is working, the speed gradually undergoes decelerations when it reaches different positions determined once the physical end-of-travel position is known. [Detailed description of one or more embodiments of the invention]

[0051] The automatic method for determining a physical end-of-travel position zphys which is the subject of the invention is implemented and executed by the control / command system 6 of the crane 1, which control / command system 6 can be installed for example in the control cabin of the crane 1.

[0052] With reference to the simplified diagram of the Figure 1, the crane 1 is a tower crane which comprises a mast 10 mounted on a platform which can be fixed to the ground or be mobile (for example by being placed on rails); and a rotating assembly formed at least by a boom 11 and a counter-jib, not shown, substantially aligned, said rotating assembly being rotated around a vertical extension orientation axis, by means of an orientation ring coupled to at least one orientation motor, causing the boom F to sweep a circular zone around the orientation axis.

[0053] The loads are lifted by the crane 1 by means of a hook located at the end of a block 2 which is moved vertically by means of several strands of a lifting cable 3. The block 2 is raised in the direction of the boom 10 and lowered towards the ground by winding and unwinding the lifting cable 3 around the cylinder of a lifting winch 7 coupled to a lifting motor, with several pulleys used to transmit the movement of the lifting cable 3. The lifting motor is physically connected and / or in communication with the control / command system 6 which controls the winding and unwinding of the lifting cable 3.

[0054] The strands of the lifting cable 3 are attached to a distribution trolley 5 movable in horizontal translation on a rolling path provided along the boom 11, from a rear end-of-travel position X1 located closest to the mast 10 to a front end-of-travel position corresponding to the tip of the boom 11. The rolling path is also constituted by a distribution cable 50 winding and unwinding around the cylinder of a distribution winch 8 coupled to a distribution motor which is controlled by the control / command system 6 to implement the winding or unwinding. Pulleys are also used for transmitting the movement of the distribution cable 50 so that the distribution trolley 5 moves between the two front and rear end-of-travel positions X1.

[0055] The automatic process can be implemented in the case of GMA self-erecting and GME element-erecting cranes equipped with a simple pulley system (two strands, as illustrated Figure 1 as well as Figure 2 And Figure 4 ) or a double pulley (four strands).

[0056] The determination of the physical end-of-travel position zphys by the automatic method is based on a measurement by a monitoring device 4 of the force F exerted on the strand 30 of the lifting cable 3 when the block 2 is raised in the direction of the arrow 10; the physical end-of-travel position zphys being reached when the block 2 comes to a stop under / against the distribution carriage 5, the monitoring device 4 then measuring a variation in the force F.

[0057] The monitoring device 4 is physically connected and / or in communication with the control / command system 6 in order to transmit the measured forces F to it. Depending on the measured force F values, the control / command system 6 implements or not the different phases that comprise the automatic method and which are described later. The force F on the strand 30 of the lifting cable 3 is measured by the monitoring device 4 and transmitted to the control / command system 6 continuously / in real time.

[0058] In the embodiment described, the monitoring device 4 is a load sensor, more precisely a gauge axis mounted on a return system associated with one of the pulleys used to transmit the winding and unwinding movement of the lifting cable 3; the gauge axis being used to determine the weight of the load suspended from the block 2 when the crane 1 is working, and measuring a torsional force transmitted to the control system 6 and from which the automatic method deduces the force F exerted on the strand of the lifting cable 3.

[0059] As previously explained, the advantage of this embodiment is to implement the automatic method of determining the end-of-travel position zphys by the control / command system 6 of the crane 1 on the basis of the measurements carried out by a load sensor with which it is equipped as standard, meaning that the automatic method does not require the installation and / or integration of additional external systems for its execution.

[0060] The automatic process is launched by the crane operator when starting the crane 1 at the beginning of the day, preferably with the block 2 empty to guarantee the accuracy of measurement of the force F on the strand 30 of the lifting cable 3 by the monitoring device 4, the force F then being due only to the self-weight of the block 2 which is constant, and in order not to exert, by hanging a load on the hook 20 of the block 2, unnecessary overtension on the lifting cable 3 at the moment of contact between the block 2 and the distribution trolley and which could lead in the worst case to a breakage of the cable. Also, the automatic process is started with the distribution trolley 5 in its rear end position X1.

[0061] In an alternative embodiment, it is possible for the automatic process to be launched automatically when the crane 1 is started without intervention from the crane operator, meaning that it cannot deviate from the physical end-of-travel calibration procedure of the block 2. Before launching the automatic process, the control / command system 6 checks whether the distribution trolley 5 is in its rear end-of-travel position X1. If not, it controls the distribution winch 8 to return the distribution trolley 5 to the rear end-of-travel position X1 before launch.

[0062] In reference to the Figure 1 And Figure 3 , the automatic process begins with a P1 rise phase, the start of the P1 rise phase being indicated on the effort evolution curve Figure 3at time t = 0. During the ascent phase P1, the block 2 is raised in the direction of the boom 11 at a low speed which is lower than a minimum speed vmin, this in order to avoid damaging the block 2 and / or the distribution trolley 5, or even elements of the boom 11, when the block 2 must come into contact with the distribution trolley 5. The minimum speed vmin is a predetermined parameter which depends on the type of crane 1 used, the speed variator installed, the lifting winch 7, and the reeving.

[0063] As previously indicated, since the ascent is carried out with the block 2 empty, the force F on the strand 30 depends only on the self-weight of the block 2. This is why the force F, as observable on the Figure 3 , is constant during the rise phase P1.

[0064] In reference to the Figure 2 And Figure 3, when the block 2 comes into contact with the underside of the distribution trolley 5, corresponding to the instant t = t1 on the evolution curve, the monitoring device 4 detects a sudden increase in the force F on the 30. This sudden increase, which corresponds to the overtension exerted in the lifting cable 3 by the block 2 which, even blocked under the distribution trolley 5, tries to continue to rise, can be characterized by an excess of the force F beyond a given force threshold, or by a variation slope a of the force above a given slope value as illustrated in this embodiment. Following this detection, the ascent phase P1 is stopped. The block 2 is then in the physical end-of-travel position zphys, which is memorized by the crane 1, more precisely in this embodiment a memory of the control-command system 6.

[0065] In reference to the Figures 4 And 5, following the determination of the physical end-of-travel position zphys, the automatic process continues with a calculation step during which it uses the physical end-of-travel position zphys as a reference in order to calculate the maximum end-of-travel position zmax, which corresponds to the limit height that the block 2 must not exceed when it is raised in the direction of the jib 11 when the crane 1 is working. The maximum end-of-travel position of the block zmax is determined from a safety distance dsec separating it from the physical end-of-travel position zphys. The value of the safety distance dsec is a predefined parameter which depends on the type of crane 1 considered. It is between 80 and 100 cm for cranes with element assembly, and between 40 and 80 cm for cranes with automatic assembly. Advantageously, as explained previously, the safety distance dsec, thanks to the automatic process, can possibly be reduced.The maximum end position zmax is also stored in this embodiment by the control / command system 6.

[0066] Following the calculation step, the automatic method implements a descent phase P2 during which the pulley block 2 is lowered, at a descent speed less than or equal to the minimum speed vmin, towards the ground from the physical end-of-travel position zphys to the maximum end-of-travel position zmax.

[0067] In a first variant embodiment of the invention, the automatic method ends at the end of the descent phase P2.

[0068] In other embodiments, the automatic method can also calculate, while continuing to use the physical end-of-travel position zphys as a reference, other positions used to establish different speed regulation zones of the block 2 when it is raised in the direction of the boom 11 and when the crane 11 is working.

[0069] So, with reference to the Figure 5 , the automatic process can calculate: a stop position zstp located below the maximum end-of-travel position zmax at a stop distance dstp, and / or a slowdown position zslw which is located below the stop position zstp at a slowdown distance dslw, and / or a deceleration position zdec which is located below the slowdown position zslw at a deceleration distance ddec.

[0070] Since these three positions are relatively far from the maximum end-of-travel position zmax, the pulley block 2 can be lowered to reach them, during the implementation of the automatic method, at a lowering speed greater than the minimum speed vmin.

[0071] All of these positions can also be memorized, for example, by a memory of the control / command system 6 of the crane 1, in order to be used during periods of activity (or work) of the crane, so as to control the ascents of the block 2 in a safe manner.

[0072] The deceleration distance ddec corresponds to a deceleration zone DEC.

[0073] The slowdown distance dslw corresponds to a slowdown zone SLW.

[0074] The stopping distance dstp corresponds to an STP stopping zone.

[0075] The lifting speed v of the block 2 towards the boom 11 is thus regulated, more precisely gradually reduced, by the lifting limiter of the crane 1 as the block 2 successively enters the deceleration zone DEC, the slowdown zone SLW, and finally the stopping zone STP. When the block 2 is located below the deceleration position, it can be raised at the maximum speed vmax.

[0076] The safety distance dsec between the maximum end position zmax and the physical end position zphys corresponds to a safe stop zone STPsec. As previously indicated, when crane 1 is working, this safe stop zone STPsec is a prohibited zone into which block 2 must not enter.

[0077] Note that the block 2 can be lowered towards the ground at the maximum speed vmax regardless of the zone in which it is located, with the exception of the safe stop zone STPsec, once the stop position zstp, the slowdown position zslw, and the deceleration position zdec have been determined.

Claims

1. An automatic method for determining a physical end-of-travel position (zphys) of a reeve-block (2) of a crane (1) which may be moved in ascent and in descent by means of a lifting cable (3), said reeve-block (2) being suspended by the lifting cable (4) from a distribution trolley (5), said automatic method being characterized in that it comprises an ascent phase (P1) of the reeve-block (2) during which a force (F) on a strand (30) of the lifting cable (3) is measured by a monitoring device (4), said physical end-of-travel position (zphys), which corresponds to a position in which the reeve-block (2) is physically in contact with the distribution trolley (5), being reached and determined depending on a variation of the force (F) on the strand (30) of the lifting cable (3).

2. The automatic method according to claim 1, wherein the physical end-of-travel position (zphys) is determined from an increase of the force (F) on the strand (30) of the lifting cable (3).

3. The automatic method according to claim 2, wherein the increase of the force (F) on the strand (30) of the lifting cable (3) is characterized by an exceeding of the force (F) beyond a given force threshold, or by a slope of variation (a) of the force (F) above a given slope value.

4. The automatic method according to any one of claims 1 to 3, wherein the ascent phase (P1) is carried out with the reeve-block (2) empty.

5. The automatic method according to any one of claims 1 to 4, wherein the ascent phase (P1) is carried out at an ascent speed (v) below a minimum speed (vmin).

6. The automatic method according to any one of claims 1 to 5, wherein the ascent phase (P1) is stopped as soon as the physical end-of-travel position (zphys) is reached and determined.

7. The automatic method according to any one of claims 1 to 6, wherein the monitoring device (4) is a load sensor mounted on the crane (1) in order to be able to measure a self-weight of the reeve-block (2).

8. The automatic method according to claim 7, wherein the load sensor is a gauge pin mounted on a system for retuning the lifting cable (3).

9. The automatic method according to any one of claims 1 to 8, comprising a step of calculating a maximum end-of-travel position (zmax) of the reeve-block (2), located below the physical end-of-travel position at a predefined safety distance (dsec).

10. The automatic method according to claim 9, wherein the safety distance (dsec) is comprised between 40 and 100 cm.

11. The automatic method according to claim 9 or 10, wherein, once the physical end-of-travel position (zphys) has been reached and determined, the reeve-block (2) descended until it reaches the maximum end-of-travel position (zmax).

12. The automatic method according to any one of claims 9 to 11, wherein the maximum end-of-travel position (zmax) is a maximum position not to be exceeded by the reeve-block (2) when the crane (1) is working.

13. The automatic method according to any one of the preceding claims, wherein said automatic method is carried out when starting the crane (1), before any work of moving a load.

14. The automatic method according to any one of the preceding claims, wherein said automatic method may be repeated between two periods of activity of the crane (1).

15. The automatic method according to any one of the preceding claims, wherein said automatic method is implemented in a control / command system (6) included in the crane, said control / command system (6) being linked at least to a lifting winch (7) coupled to the lifting cable (3), and to the monitoring device (4).