Method and device for determining the load of an aerial work platform

Abstract

The invention relates to a device (40) for determining the load of an aerial work platform, the device comprising at least one upper part (61) and at least one lower part (62), each part being pivotably connected to a part (50) on the boom side and to a part (11) on the platform side so as to pivot about axes (71-73) in such a way as to allow the part (11) on the platform side to move vertically with respect to the part (50) on the boom side. The load supported by the part (11) on the platform side is transferred to the part (50) on the boom side by, preferably, a connecting rod (81) which couples them via at least one ball joint (82) for eliminating interfering forces from the connecting rod (81). The load can be determined by means of a sensor such as an instrumented shaft (90) which measures the force transmitted by the connecting rod (81), optionally also if the load is negative.

Description

[0001] Method and device for determining load for lifting platform work platform

[0002] The present invention relates to the field of mobile elevating work platforms (also referred to by the acronym MEWP, or in English by mobile elevating work platforms and its abbreviation MEWP) also commonly called aerial work platforms (or in English aerial work platforms or its abbreviation A WP). The invention relates to a method and a load determination device for determining a load placed on a work platform of an elevating work platform which work platform is mounted at the upper end of a mast used to move the work platform in height, the load determination device being intended to be mounted interposed between the upper end of the mast and the work platform.The method and device for determining load according to the invention are applicable to lifting platforms of any type provided that the lifting mechanism of the work platform comprises a mast at the upper end of which the work platform is mounted. They apply in particular to self-propelled lifting platforms, but also to towed or truck-mounted lifting platforms. The invention also relates to a lifting platform comprising a load determining device according to the invention.

[0003] Aerial work platforms are machines designed to allow one or more people to work at height. To this end, they include a work platform designed to accommodate people as well as equipment or tools. The work platform is supported by a lifting structure that allows it to be raised from a lowered position on the aerial work platform chassis to the desired working position at height.

[0004] Different types of lifting structures are used, but the invention relates more particularly to lifting platforms whose lifting structure comprises a telescopic mast which supports the working platform at its upper end.

[0005] The telescopic mast is often arranged on a turret pivotally mounted on the chassis, which allows the orientation of the telescopic mast - and therefore of the work platform - to be changed relative to the chassis.

[0006] Finally, the chassis is generally equipped with wheels or tracks to move the aerial work platform on the ground. It is most often motorized to allow autonomous movement of the aerial work platform on the ground. The work platform is usually equipped with a control station allowing an operator on board the work platform to cause its movement to reach the desired working position at height. Each model of aerial work platform is designed to support a maximum load that must not be exceeded in order to avoid the risk of accidents, for example to prevent the aerial work platform from tipping over. Therefore, it is desirable to equip the aerial work platform with a device to determine the load on board the work platform in order to restrict or prevent the lifting of the work platform or the movement of the aerial work platform on the ground depending on the size of the load.Contemporary regulatory developments also make the presence of such a load determination device mandatory for certain lifting platforms and require a certain degree of precision in the measurement taken.

[0007] To this end, it is known to interpose a load determining device between the upper end of the lifting mast and the working platform, the working platform being entirely supported by means of the load determining device. EP 1 382 562 A1 thus proposes a load determining device comprising a test body mounted on one side to the mast and on a side opposite the working platform, the test body being provided with one or more strain gauges used to determine the weight of the working platform. The test body is designed in such a way that the strain gauge(s) only "see" the weight of the working platform and not the forces due to the moment resulting from the cantilevered mounting of the working platform relative to the upper end of the mast, as well as those due to the torsional moment resulting from an off-center placement of the load on board the working platform.

[0008] A disadvantage of this device lies in the complexity of producing the test body, which makes it expensive, and in its significant weight, which increases the overall load supported by the mast.

[0009] According to another approach, at least one upper part and at least one lower part are each pivotally mounted by one end to a mast-side part and by an opposite end to a work platform-side part so as to form an articulated parallelogram allowing vertical movement of the work platform relative to the mast. This first subassembly serves to transfer to the mast the forces due to the moment resulting from the cantilever mounting of the work platform at the upper end of the mast. A second subassembly also connecting the work platform-side part to the mast-side part is provided specifically to transfer the weight of the work platform to the mast and serves to determine a load on the work platform.

[0010] The second subassembly is implemented in various ways. In implementations proposed in NL 1023556 C2, US 6,585,079 Bl, US 2006 / 0045713 Al, CN 202661141U, CN 107161922 A, it comprises an elastic element by means of which the weight of the working platform is transferred to the mast and a position switch is provided to detect overloading of the working platform due to excessive downward displacement of the working platform relative to the mast. A disadvantage of these implementations is that they do not allow the load on the working platform to be measured, although this may be desirable. For example, it is not possible in this case to vary a limiting extension envelope in the space in which the work platform is allowed to move relative to the chassis of the aerial work platform depending on the load on the work platform.Another disadvantage is that it is not possible to detect the case where excessive force is urging the work platform upwards, for example when it comes to rest on some obstacle, which is desirable if only to be able to automatically stop a movement during the lowering of the work platform. In WO 2017 / 177219 A1, the second subassembly comprises a force sensor in the form of a bar provided with strain gauges. The weight of the work platform is transferred to the mast via the force sensor, which makes it possible to measure the load on the work platform. More precisely, the force sensor is attached to a part on the mast side while a load element is attached to the work platform. The load element rests with a spherical head directly on the force sensor or on the head of a screw which is screwed into a thread of the force sensor.A disadvantage of this solution is that it does not allow the measurement of vertical forces exerted on the work platform upwards, for example when it comes to rest on an obstacle, if they are such that the load element moves away from the load measuring cell. In addition, unloading the load measuring cell in this way risks causing a loss of calibration of the latter, or even its deterioration due to impacts of the load element on the load measuring cell, despite the presence of a stop intended to limit the upward movement of the work platform relative to the mast.

[0011] In CN 107601383 A, the second subassembly is produced in the form of a connecting rod pivotally mounted on two of the pivot axes of the articulated parallelogram formed by the first subassembly, the connecting rod extending along a diagonal of the articulated parallelogram between the work platform and the mast. A unidirectional pressure sensor is arranged on the connecting rod to determine the load of the work platform. A disadvantage of this solution is that the pressure sensor is unidirectional, which does not make it possible to determine the intensity of the upwardly oriented vertical forces which are applied to the work platform if it comes to rest on an obstacle external to the lifting platform.Another disadvantage is that the first subassembly in the form of an articulated parallelogram is liable to deform despite its rigidity, in particular under the effect of the torsional moment resulting from a load placed towards a lateral side of the working platform relative to the upper end of the mast. Parasitic forces are then applied to the second subassembly, which degrades the accuracy of the determination of the load of the working platform by the pressure sensor.

[0012] In CN 111792591 A, the second subassembly comprises a connecting rod pivotally mounted at one end to the upper part of the first subassembly about a dedicated axis and by its other end to the lower part of the first subassembly about another dedicated axis. One of the dedicated axes is an instrumented axis making it possible to determine the forces applied to it by the connecting rod. Here too, a disadvantage is that parasitic forces can degrade the accuracy of the load determination due to a deformation of the first subassembly in the form of an articulated parallelogram under the effect of the torsional moment resulting from a load placed towards a lateral side of the work platform relative to the upper end of the mast. In addition, a lack of parallelism of the pivot axes can also generate parasitic forces on the instrumented axis and therefore degrade the accuracy of the load determination of the work platform.

[0013] In CN 215402946 U, the second subassembly is reduced to an instrumented axis for determining the load. It connects the working platform to the mast by being mounted in a fixed bearing on the mast side and in another fixed bearing on the working platform side. This approach is not realistic because it is hyperstatic and almost impossible to mount in practice. In addition, the accuracy of load measurement would be degraded by parasitic forces applied to the instrumented axis due to a possible deformation of the first subassembly in the form of an articulated parallelogram that can be generated by a torsional moment resulting from a load shifted towards a lateral side of the working platform relative to the upper end of the mast.

[0014] In another approach proposed by US 2018 / 0072550 A1, the first subassembly in the form of an articulated parallelogram is replaced by a structure with two horizontal flexible plates spaced vertically apart and capable of bending downwards under the effect of a load placed on the work platform. This structure further comprises a set of plates welded together and to the two flexible plates. It is designed to be very rigid in the horizontal plane and with respect to torsional moments. A force sensor in the form of a bar equipped with strain gauges is rigidly supported on the mast side by an end region. When a load is placed on the work platform, its weight is transferred to the mast via the two flexible plates.If the load on the working platform increases, the upper plate flexes and presses on the opposite end region of the force sensor via a load transfer element coupled to the force sensor, which makes it possible to determine the load present on the working platform. The force sensor supports almost the entire vertical load because it is much stiffer than the flexible plate structure. This approach also has several disadvantages. First, the structure with two flexible plates is a particularly complex and expensive welded part. In addition, if it were to be damaged due to an impact, it must be completely replaced. Second, this solution also does not allow the vertical forces exerted on the working platform in an upward direction to be measured.Furthermore, the load measurement accuracy may be degraded by parasitic forces applied to the force sensor due to deformation of the flexible plate structure despite its rigidity, this deformation possibly being due to the torsional moment resulting from a load shifted towards a lateral side of the work platform relative to the upper end of the mast.

[0015] US 6,585,079 B1 discloses load determination devices using flexible bars, some of which are combined with joints, and which have similar drawbacks to those already mentioned. US 4,655,306 discloses other load determination devices which use a deformable structure, the production of which is complex and expensive, and which have the same type of drawbacks as those already mentioned.

[0016] The aim of the present invention is to provide a method and a device for determining load which at least partially overcomes the aforementioned drawbacks.

[0017] More particularly, the invention aims to provide a load determination device which is simple, economical and precise.

[0018] To this end, the present invention provides a load determining device for determining a load on a working platform of a lifting platform, which working platform is mounted at an upper end of a mast of the lifting platform for moving the working platform in height, and the load determining device is mounted or intended to be mounted interposed between the upper end of the mast and the working platform. The load determining device comprises: a mast-side part forming part or intended to form part of the upper end of the mast or intended to mount the load determining device at the upper end of the mast, a working platform-side part forming part or intended to form part of the working platform or intended to support the working platform, at least one upper connecting part and at least one lower connecting part,the upper connecting piece being pivotally mounted, on the one hand, to the mast-side piece about a first axis and, on the other hand, to the work platform-side piece about a second axis, the lower connecting piece being pivotally mounted, on the one hand, to the mast-side piece about a third axis and, on the other hand, to the work platform-side piece about a fourth axis, the first, second, third and fourth axes being separate parallel axes allowing vertical movement of the work platform-side piece relative to the mast-side piece by pivoting the upper connecting piece and the lower connecting piece, a load transfer element coupling the work platform-side piece to the mast-side piece to transfer the load borne by the work platform-side piece to the mast-side piece,and a force sensor for measuring the force transmitted by the load transfer element from the work platform-side workpiece to the mast-side workpiece, wherein the load transfer element couples the work platform-side workpiece to the mast-side workpiece via at least one ball joint.,

[0019] Due to the interposition of the load determining device between the upper end of the mast and the working platform, the mast fully supports the working platform by means of the load determining device. The upper connecting piece(s) and the lower connecting piece(s) transfer to the mast via the mast-side part the forces due to the moment resulting from the cantilevered mounting of the working platform relative to the upper end of the mast. These forces are therefore not supported by the load transfer element. Under normal conditions of use, the latter only serves to transfer the vertical load supported by the work platform-side part, in other words the weight of the work platform and the load placed on it.The force transmitted by the load transfer element from the work platform side part to the mast side part is therefore representative of the weight of the loaded work platform. The load present on the work platform can thus be determined from the measurement of this force made by the force sensor. This determination of the load can be carried out for example by on-board electronics of the lifting platform to which the force sensor is connected to provide it with the measurement signals.

[0020] The fact that the load transfer element couples the work platform side part to the mast side part makes it unnecessary to provide a stop to limit the upward movement of the work platform relative to the mast and avoids the risk of loss of calibration of the force sensor, or even its deterioration, in the case where an upward vertical force is applied to the work platform, for example if it comes to rest on an element external to the lifting platform while a lowering movement of the work platform is in progress. In addition, this makes it possible to measure the intensity of such an upward vertical force, including if it is sufficient to cause a reversal of the direction of the force transmitted by the mast side part to the work platform side part.For this, it is sufficient that the force sensor is designed to also carry out the force measurements transmitted by the load transfer element in the opposite direction to the normal case where it transmits the weight of the work platform and of the heavy load placed on it, if applicable.

[0021] It will be understood that the load transfer element may be mounted directly to the work platform side part and the mast side part to couple them together, but it may also be mounted indirectly through other parts such as, for example, the upper connecting part and / or the lower connecting part. It will also be understood that the force sensor may be a separate component from the load transfer element or the load transfer element may serve as a test body for the force sensor which may be implemented, for example, in the form of one or more strain gauges arranged on the load transfer element.

[0022] The ball joint(s) make it possible to greatly limit, or even completely eliminate, the application of any parasitic forces on the load transfer element due to the torsional moment resulting from a laterally offset placement of a load on the work platform relative to the upper end of the mast. In other words, the ball joint(s) limit or eliminate the parasitic forces on the load transfer element due to the torsional moment having a horizontal vector direction perpendicular to the first, second, third and fourth axes, the horizontal referring to the case where the lifting platform is placed on horizontal ground. The determination of the load on board the work platform from the force measurement carried out by the force sensor is therefore particularly precise.

[0023] The load transfer element is preferably a connecting rod, which facilitates a particularly simple and reliable implementation of the load determination device. But it can be other structures, for example a bar rigidly coupled at one end to the mast-side part while the other end is coupled to the work platform-side part via a ball joint.

[0024] According to other preferred embodiments, the load determining device according to the invention comprises one or more of the following features: the load transfer element is a connecting rod; two opposite ends of the connecting rod are each mounted to a respective element among the mast-side part, the work platform-side part, the upper connecting part and the lower connecting part; the force sensor comprises a test body in the form of a fifth axis on which the ball joint is mounted, the fifth axis being distinct from the first, second, third and fourth axes; the connecting rod is mounted by a first end on the ball joint; the ball joint is mounted in a sliding pivot connection on the fifth axis; the connecting rod is mounted by a second end opposite the first end by a pure pivot connection;the fifth axis and a second end of the connecting rod opposite the first end are each mounted on a respective one of the mast-side part and the work platform-side part; the second end is mounted on one of the first, second, third and fourth axes; the connecting rod is the test body of the force sensor or the force sensor is integrated into the connecting rod; the connecting rod is mounted by two opposite ends by means of a respective ball joint; the connecting rod is mounted to the third axis by a first end and to the second axis by a second end opposite the first end, or the connecting rod is mounted to the first axis by a first end and to the fourth axis by a second end opposite the first end; the connecting rod is mounted inclined relative to the vertical direction so as to extend obliquely between the mast-side part and the work platform-side part;the angle between the connecting rod and the vertical direction is preferably between 10 and 80 degrees; the force sensor is capable of measuring the force transmitted by the load transfer element from the part on the work platform side to the part on the mast side regardless of the direction of this force.;

[0025] According to another aspect, the invention provides a lifting platform, comprising a work platform, a mast having an upper end to which the work platform is mounted and used to move the work platform in height, and a load determining device according to the invention which is mounted interposed between the upper end of the mast and the work platform.

[0026] In other words, the invention also provides a lifting platform, comprising a work platform, a mast having an upper end to which the work platform is mounted and used to move the work platform in height, and a load determining device which load determining device comprises: a mast-side part forming part of the upper end of the mast or by means of which the load determining device is mounted at the upper end of the mast, a work platform-side part forming part of the work platform or supporting the work platform, at least one upper connecting part and at least one lower connecting part, the upper connecting part being pivotally mounted, on the one hand, to the mast-side part about a first axis and, on the other hand, to the work platform-side part about a second axis, the lower connecting part being pivotally mounted, on the one hand,to the mast-side part about a third axis and, on the other hand, to the work platform-side part about a fourth axis, the first, second, third and fourth axes being separate parallel axes allowing vertical movement of the work platform-side part relative to the mast-side part by pivoting the upper connecting part and the lower connecting part, a load transfer element coupling the work platform-side part to the mast-side part to transfer the load borne by the work platform-side part to the mast-side part, and a force sensor for measuring the force transmitted by the load transfer element from the work platform-side part to the mast-side part, wherein the load transfer element couples the work platform-side part to the mast-side part by means of at least one ball joint.,

[0027] According to a preferred embodiment, the lifting platform further comprises on-board electronics to which the force sensor is connected, the on-board electronics being designed to determine the load on board the work platform from the measurement signals provided by the force sensor.

[0028] According to an advantageous embodiment, the on-board electronics are provided to stop a lowering movement of the work platform in progress if it determines a negative load on board the work platform which is greater in absolute value than a predetermined non-zero threshold. This threshold is preferably set at a value greater than or equal to 10 daN and more preferably at a value greater than or equal to 25 daN. This value is preferably less than or equal to 200 daN and more preferably less than or equal to 100 daN, or even 75 daN.

[0029] According to yet another aspect, the invention provides a method for determining a load on a work platform of a lifting platform, which work platform is mounted at an upper end of a mast used to move the work platform in height, a load determining device according to the invention being mounted interposed between the upper end of the mast and the work platform, the method comprising determining the load on the work platform by on-board electronics on the basis of at least one measurement signal provided by the force sensor.

[0030] According to preferred embodiments, the method according to the invention comprises one or more of the following features: recording by the on-board electronics in a data storage device on board the lifting platform of at least one preferably time-stamped data item which is representative of the load on the work platform and / or sending at least one such data item by the on-board electronics to a remote server via a wireless communication link; the on-board electronics records or sends such data if the determined load is greater than a predetermined non-zero positive threshold, the threshold preferably corresponding to the maximum authorized load of the work platform;the on-board electronics records or sends such data if the determined load is negative and non-zero or if the determined load is negative and greater in absolute value than a predetermined non-zero threshold, this threshold preferably being set at a value greater than or equal to 10 daN and more preferably at a value greater than or equal to 25 daN. This value is preferably less than or equal to 200 daN and more preferably less than or equal to 100 daN, or even 75 daN.;

[0031] According to another aspect independent of the preceding description of the device and method for determining load according to the invention, as well as of the lifting platform according to the invention, the invention proposes a lifting platform comprising a work platform, a lifting structure on which the work platform is mounted and used to move the work platform in height, a load determining device for determining the load on the work platform and on-board electronics provided for recording in a data storage device arranged on board the lifting platform at least one preferably time-stamped data item which is representative of the load on the work platform determined by the load determining device and / or for sending at least one such data item to a remote server via a wireless communication link.

[0032] According to one embodiment, the on-board electronics are provided to record and / or send such data if the load determined by the load determination device is greater than a predetermined non-zero positive threshold. This threshold is preferably the maximum load that is authorized to be placed on the work platform. According to another embodiment, the on-board electronics are provided to record and / or send such data if the determined load is non-zero negative or more preferably if the determined load is negative and greater in absolute value than a predetermined non-zero threshold. This threshold can be set at a value greater than or equal to 10 daN and more preferably at a value greater than or equal to 25 daN. This value is preferably less than or equal to 200 daN and more preferably less than or equal to 100 daN, or even 75 daN.According to yet another embodiment, the on-board electronics are provided to stop a lowering movement of the work platform in progress if it determines a negative load on board the work platform which is greater in absolute value than a predetermined non-zero threshold, this threshold preferably being set at a value greater than or equal to 10 daN and more preferably at a value greater than or equal to 25 daN. This value is preferably less than or equal to 200 daN and more preferably less than or equal to 100 daN, or even 75 daN.

[0033] According to yet another aspect, the invention provides a method for determining the load on board a work platform of a lifting platform in which the work platform is mounted on a lifting structure for moving the work platform in height, the lifting platform comprising a load determining device for determining the load on the work platform, the method comprising the recording by on-board electronics of the lifting platform in a data storage device arranged on board the lifting platform of at least one preferably time-stamped data item which is representative of the load on the work platform determined by the load determining device and / or the on-board electronics sends at least one such data item to a remote server via a wireless communication link.

[0034] According to one embodiment, the on-board electronics records and / or sends such data if the load determined by the load determination device is greater than a predetermined non-zero positive threshold. This threshold is preferably the maximum load that is authorized to be placed on the work platform. According to another embodiment, the on-board electronics records and / or sends such data if the determined load is non-zero negative or more preferably if the determined load is negative and greater in absolute value than a predetermined non-zero threshold. This threshold is preferably set at a value greater than or equal to 10 daN and more preferably at a value greater than or equal to 25 daN. This value is preferably less than or equal to 200 daN and more preferably less than or equal to 100 daN, or even 75 daN.According to yet another embodiment, the on-board electronics stops a lowering movement of the work platform in progress if it determines a negative load on board the work platform which is greater in absolute value than a predetermined non-zero threshold, this threshold preferably being set at a value greater than or equal to 10 daN and more preferably at a value greater than or equal to 25 daN. This value is preferably less than or equal to 200 daN and more preferably less than or equal to 100 daN, or even 75 daN.

[0035] Other aspects, characteristics and advantages of the invention will appear on reading the following description of a preferred embodiment of the invention, given by way of example and with reference to the appended drawing.

[0036] [Fig. 1] represents a lifting platform according to one embodiment of the invention.

[0037] [Fig. 2] represents a local view which shows the pendulum arm and the working platform, as well as the load determination device interposed between them.

[0038] [Fig. 3] shows an isolated perspective view of the work platform support to which the load determining device is attached.

[0039] [Fig. 4] represents a perspective view of the load determining device observed from above from the other side with respect to Fig. 3.

[0040] [Fig. 5] represents a perspective view of the load determining device observed from below from the other side with respect to Figure 3.

[0041] [Fig. 6] shows, in side view, a vertical section through the assembly consisting of the load determining device and the support of the working platform.

[0042] [Fig. 7] represents the same sectional view as Fig. 6, but limited to the region of the load determining device.

[0043] [Fig. 8] represents a perspective view of the load determining device observed from above, in which some of the parts are omitted and others are cut away in order to better show the structure of the load determining device.

[0044] [Fig. 9] shows a section through the load determining device along a plane passing through the pivot axes of the weight transfer rod of the work platform.

[0045] [Fig. 10] represents a perspective view of the instrumented axis of the load determination device.

[0046] [Fig. 11] represents a perspective view of a load determining device according to another embodiment.

[0047] With reference to figures 1 to 10, we will describe a preferred embodiment of a lifting platform 1, as well as a load determination device 40 which equips it.

[0048] By convention, any reference made in this description to the vertical or horizontal direction is assessed in relation to the case where the lifting platform 1 rests on horizontal ground.

[0049] As can be seen in Figure 1, the lifting platform 1 comprises a chassis 2 equipped with wheels 4 to allow its translation on the ground, at least two of the wheels 4 being steered. Alternatively or in combination, the chassis 2 can be equipped with tracks for the same purposes. The chassis 2 is motorized to ensure the autonomous movement of the lifting platform 1 on the ground.

[0050] The lifting platform 1 comprises a lifting structure 18 supporting a work platform 10 intended to receive on board personnel and equipment for carrying out work at height. The work platform 10 comprises a floor 12 and a guardrail 14. A control console 16 is arranged on the work platform 10. It allows an operator on board the work platform 10 to control the lifting structure 18 to move the work platform 10 in height to the desired position, as well as to move the chassis 2 on the ground.

[0051] In this embodiment, the lifting platform 1 is of the type commonly called an articulating boom lift. The lifting structure 18 comprises a turret 22 mounted on the chassis 2 and a mast 20 mounted on the turret 22, the mast 20 supporting at its upper end 28 the working platform 10 by means of the load determining device 40. More particularly, the mast 20 comprises an articulated arm 24, a telescopic arm 26 and a pendulum arm 30. The articulated arm 24 is mounted on the turret 22 and the telescopic arm 26 is mounted at the upper end of the articulated arm 24. The pendulum arm 30 (or articulating jib in English) is mounted by one end at the upper end of the telescopic arm 26. The opposite end of the pendulum arm 30 supports the working platform 10 by means of the load determining device 40.

[0052] The turret 22 is pivotally mounted about a vertical axis on the chassis 2, which makes it possible to modify the orientation of the mast 20 and the platform 10 relative to the chassis 2. The articulated arm 24 forms a pantograph so that its upper end can be raised and lowered vertically by unfolding and folding respectively relative to the turret 22.

[0053] The telescopic arm 26 is pivotally mounted about a horizontal axis at the upper end of the articulated arm 24 so that it can be raised and lowered by changing its inclination relative to the articulated arm 24.

[0054] The pendulum arm 30 is pivotally mounted about a horizontal axis at the upper end of the telescopic arm 26 so that it can be raised and lowered relative to the telescopic arm 26. The pendulum arm 30, which is shorter than the telescopic arm 26, makes it possible to locally adapt the elevation height of the work platform 10 without acting on the telescopic arm 26. The pendulum arm 30 can optionally also be pivotally mounted about a vertical axis relative to the telescopic arm 26.

[0055] The pendulum arm 30 is designed to keep the work platform 10 horizontal when the pendulum arm 30 is raised or lowered relative to the telescopic arm 26 when the aerial work platform 1 is in use, which can be conventionally achieved by the pendulum arm 30 having an articulated parallelogram structure.

[0056] The working platform 10 is preferably pivotally mounted relative to the pendulum arm 30 about an axis extending vertically when the lifting platform 1 is in use, which makes it possible to change the orientation of the working platform 10 relative to the pendulum arm 3 by means of a rotary actuator 29.

[0057] The lifting platform 1 conventionally comprises actuators assigned to the different movement possibilities of the lifting structure 18 which have just been described.

[0058] It will be understood that the load determining device 40 which will be described later can be applied to lifting platforms having a different lifting structure 18. In general, it can be applied to any lifting platform provided with a mast supporting at its upper end a working platform in order to move it in height. Thus, in another embodiment, the lifting platform 1 is of the type commonly called telescopic boom lift, that is to say which is devoid of articulated arm 24, the telescopic arm 26 being mounted directly on the turret 22. In another embodiment, the pendulum arm 30 is omitted, the working platform 30 being mounted at the upper end of the telescopic arm 26 by means of the load determining device 40, the lifting platform 1 being able to be of the articulated boom lift type or of the telescopic boom lift type.In yet another embodiment, the lifting platform 1 is of the type commonly referred to as a vertical mast lift, in particular of the vertical mast type having a pendulum arm 30, that is to say a lifting platform comprising a non-tilting vertical telescopic mast mounted either on a pivoting turret or directly on the chassis 2 and supporting at its upper end the pendulum arm 30 which in turn supports the work platform 10 by means of the load determining device 40.

[0059] Figure 2 shows more particularly the pendulum arm 30 of the mast 20 and the working platform 10 of the lifting platform 1, as well as the load determining device 40 which is interposed between them. The mast 20 fully supports the working platform 10 exclusively by means of the load determining device 40. As a result, the load determining device 40 fully transfers the weight of the working platform 10 to the mast 20 and more generally all the forces that the working platform 10 exerts on the mast 20, in particular those due to the moments linked to the cantilevered mounting of the working platform 10 at the upper end 28 of the mast 20, as well as to the possible lateral offset of the load placed on the working platform 10 relative to the upper end of the mast 20. The load determining device 40 will now be described in more detail with reference to FIGS. 3 to 9.The load determining device 40 comprises a mast side part 50 and a work platform side part 11.

[0060] In this embodiment, the mast-side part 50 is designed as a mounting bracket and serves to mount the load determining device 40 to the upper end 28 of the mast 20 of the lifting platform 1. Therefore, the mast-side part 50 is intended to be fixed to the upper end 28 of the mast 20 preferably in a detachable manner. In an alternative embodiment not shown, the mast-side part 50 is a part forming part of the upper end 28 of the mast 20.

[0061] In this embodiment, the work platform-side part 11 is designed as a support for fully supporting the work platform 10. In an alternative embodiment not shown, the work platform-side part 11 is part of the work platform 10: it may, for example, be a frame of the floor 12 of the work platform 10.

[0062] In the illustrated example, the work platform side part 11 is a mechanically welded structure that supports the work platform 12. The work platform 12 can be fixed thereto by screwing or welding or any other suitable means. The work platform side part 11 supports the entire weight of the work platform 10 and the load determining device 40 transfers this to the mast 20 via the mast side part 50.

[0063] In the example illustrated, the mast-side part 50 is a mechanically welded part comprising two parallel plates 51, 52 separated from each other by a spacer 53 arranged towards one of their ends. At their opposite ends, the plates 51, 52 are provided to receive between them, at the level of openings 54, the rotary actuator 29 which is mounted elsewhere at the upper end 28 of the mast 20 and which serves to pivot the work platform 10 relative to the pendulum arm 30. Of course, the structure of the mast-side part 50 may be different from that which has just been described.

[0064] The mast 20 therefore supports the load determining device 40 via the mast side part 50.

[0065] The load determining device 40 also comprises two sub-assemblies 60 and 80 which are best seen in Figures 6 to 8. The two sub-assemblies 60 and 80 are each connected, on the one hand, to the mast-side part 50 and, on the other hand, to the work platform-side part 11. The two sub-assemblies 60 and 80 together transfer to the mast 20 all of the forces exerted by the work platform 10 on the mast 20.

[0066] The first subassembly 60 comprises an upper connecting rod 61 and a lower connecting rod 62 also visible in FIGS. 4 and 5 respectively. The upper connecting rod 61 is pivotally mounted by one end to the mast-side part 50 about an axis 71 and by an opposite end to the work platform-side part 11 about an axis 72. Similarly, the lower connecting rod 62 is pivotally mounted by one end to the mast-side part 50 about an axis 73 and by an opposite end to the work platform-side part 11 about an axis 74.

[0067] The axes 71, 72, 73 and 74 extend horizontally and parallel to each other, occupying the vertices of a fictitious parallelogram. As a result, this parallelogram is deformable by pivoting the connecting rods 61 and 62 around their respective axes. In other words, the connecting rods 61 and 62 form a mechanism commonly referred to as a four-bar mechanism or four-bar link. The first subassembly 60 allows the work platform 10 to move freely in a vertical direction relative to the upper end 28 of the mast 20. Of course, the movement is not purely vertical, given the pivoting links of the connecting rods 61 and 62.

[0068] The second subassembly 80 comprises a connecting rod 81 pivotally mounted by one end 81a to the work platform side part 11. More precisely, the end 81a is pivotally mounted on the axis 72 in this embodiment. The connecting rod 81 is mounted by its opposite end 81b on an instrumented axis 90 by means of a ball joint 82. The instrumented axis 90 is secured to the mast-side part 50. More precisely, in this embodiment, the instrumented axis 90 is housed in holes made in two separate and parallel plates 56 and 57 which are part of the mechanically welded part forming the mast-side part 50. To transfer the weight of the work platform 10 to the mast-side part 50 by means of the connecting rod 81, the imaginary plane passing through the axis 72 and the instrumented axis 90 is not a parallel plane but intersecting the imaginary planes passing respectively through the axes 71 and 72 and through the axes 73 and 74.

[0069] The instrumented axis 90 is equipped with strain gauges for determining the radial forces applied to it, in this case by the connecting rod 81. It is of a type known per se. An example is illustrated in Figure 10. The ball joint 82 is mounted on a section 92 of the instrumented axis 90. The section 92 is delimited by two circumferential grooves 93 and 94 in which the strain gauges are placed. The instrumented axis 90 is equipped with a connector 91 for outputting the force measurement signals determined by the strain gauges, the connector 91 being connected to on-board electronics 5 of the lifting platform 1. The on-board electronics 5 are housed in the turret 22 as shown in Figure 1, but they can be housed in the chassis 22 or elsewhere.As can be seen in Figures 4 and 5, a part 95 fixed to the mast-side part 50, in this case to the plate 56 thereof, engages a groove 95 of the instrumented shaft 90 in order to stop the instrumented shaft 90 in the axial direction and to lock it in rotation relative to the mast-side part 50. From a functional point of view, when the lifting platform 1 is in normal operating conditions, that is to say in the absence of any element external to the lifting platform 1 stressing the work platform 10, the subassembly 60 transfers to the mast 20 - by means of the mast-side part 50 - all of the forces exerted by the work platform 10 on the mast 20, with the exception of the weight of the work platform 10. More precisely, the two connecting rods 61 and 62 transfer to the mast 20 the forces due to the moment resulting from the cantilevered mounting of the work platform 10 relative to the upper end 28 of the mast 20.The vector direction of this moment is parallel to the Z axis of the instrumented axis 90 - visible in figure 7 - to which all axes 71, 72, 73 and 74 are parallel.

[0070] The two connecting rods 61 and 62 also transfer to the mast 20 the forces due to the torsional moment resulting from a possible lateral shift of the center of inertia of the loaded work platform 10 relative to the upper end 28 of the mast 20, in other words a shift in the direction of the Z axis relative to the upper end 28 of the mast 20. The vector direction of this torsional moment is parallel to the X axis visible in FIG. 7. This lateral shift of the center of inertia of the loaded work platform 10 can conventionally result from the fact that a load is placed on the work platform 10 towards a lateral side, it being specified that in a conventional manner the load determining device 40 preferentially supports the work platform 10 by the middle of one side thereof.

[0071] In contrast, the second subassembly 80 exclusively transfers the entire weight of the working platform 10 to the mast 20 via the mast-side part 50. Of course, the weight of the working platform 10 refers to the loaded working platform 10 if applicable and therefore also includes the weight of the load placed thereon. Thus, the instrumented axis 90 is subjected exclusively to the forces resulting from the weight of the loaded working platform 10 which are transmitted to it by the connecting rod 81, and not to the forces due to the aforementioned moments which are taken over by the first subassembly 60. The forces measured by the instrumented axis 90 therefore allow the on-board electronics 5 of the lifting platform 1 to reliably determine the load on board the working platform 10.According to a preferred embodiment, a calibration procedure is provided to establish the relationship between the measurements provided by the force sensor of the load determining device 40, in this case the instrumented axis 90, and the load on board the work platform 10. This then allows the on-board electronics 5 of the lifting platform 1 to directly determine the load on board the work platform 10 from the measurement provided by the force sensor on the basis of this relationship when the lifting platform 1 is in use. The on-board electronics 5 can conventionally be provided to restrict or prohibit the movements of the work platform 10 as a function of the load on board the work platform 10 determined using the load determining device 40.In order to obtain an accurate determination of the load on board the working platform 10, the connecting rods 61 and 62 are preferably mounted on the respective axes 71, 72 and 73, 74 by means of plain bearings or plain bushings. This is also the case for the pivoting mounting of the connecting rod 81 on the axis 72. This measure makes it possible to avoid as much as possible that parasitic forces are applied to the connecting rod 81 - and therefore to the instrumented axis 90 - due to friction at these axes.

[0072] On the other hand, it is advantageous for the connecting rod 81 to be inclined relative to the vertical as can be seen in the figures. Indeed, the force applied by the connecting rod 81 to the instrumented axis 90 is all the greater relative to the weight of the working platform 10 as the angle of the connecting rod 81 with the vertical increases. This therefore allows a more precise determination of the weight of the working platform 10 by means of the instrumented axis 90. From this point of view, the angle of the connecting rod 81 with the vertical is preferably greater than or equal to 10 degrees. It is also preferably less than or equal to 80°, which prevents the force transmitted by the connecting rod 81 from becoming too great.

[0073] Furthermore, the ball joint 82 also improves the accuracy of the determination of the load on board the work platform 10 by means of the instrumented axis 90. In fact, the ball joint 82 avoids or drastically limits the instrumented axis 90 being subjected to parasitic forces due to the torsional moment parallel to the X axis which results from a possible lateral offset of the center of inertia of the loaded work platform 10 relative to the upper end 28 of the mast 20, in other words an offset in the direction of the Z axis relative to the upper end 28 of the mast 20.

[0074] As mentioned above, the forces due to this torsional moment are in principle supported by the first subassembly 60 so that the second subassembly 80, in particular the connecting rod 81 and the instrumented axis 90, should not be subjected to them. In reality, although the first subassembly 60 and the work platform side part 11 are by design very rigid, they can nevertheless undergo deformations caused by the forces resulting from this torsional moment. Therefore, if the connecting rod 81 of the second subassembly 80 were only pivotally mounted to the instrumented axis 90, the second subassembly 80 would be subjected to parasitic forces due to the torsional moment. Eliminating these deformations by the sole dimensioning of the parts is generally not possible due to their weight and volume which would become too great to be compatible with an optimal design of the lifting platform.

[0075] The difficulty is overcome by connecting the connecting rod 81 to the instrumented shaft 90 by means of the ball joint 82. The ball joint 82 in fact makes it possible to prevent the instrumented shaft 90 from being subjected to parasitic forces due to the torsional moment or at least to limit them drastically.

[0076] The ball joint 82 is best seen in Figure 9. It typically comprises an inner ring 83 and an outer ring 84. The outer ring 84 is mounted on the inner ring 83 by a respective spherical surface. Thus, the outer ring 84 is joined to the inner ring 83 by a spherical connection. In other words, the outer ring 84 is free to pivot about the three axes x, y and z - visible in Figure 9 - relative to the inner ring 83. The ball joint 82 is held by means of the outer ring 84 in a through bore of the connecting rod 81 while the inner ring 83 of the ball joint 82 is mounted on the instrumented axis 90, namely on its section 92 designated in Figure 10.Thus, if the connecting rod 81 were to leave a purely radial positioning relative to the instrumented axis 90 due to deformations of the first subassembly 60, the ball joint 82 prevents corresponding parasitic forces from being applied to the instrumented axis 90 which would have the effect of distorting the determination of the weight of the work platform 10.

[0077] Still with the aim of maximizing the accuracy of the load determination on board the work platform 10 thanks to the instrumented axle 90, it is preferable for the inner ring 83 of the ball joint 82 to be mounted as a sliding pivot on the instrumented axle 90. In this way, the ring 83 can slide axially relative to the instrumented axle 90, which also makes it possible to avoid applying any parasitic forces to the latter. On the other hand, the end 81a can be mounted in a pure pivot connection on the axle 72, with the mounting clearance close. Alternatively, the end 81a can be mounted by a ball joint on the axle 72, but mounting by a simple pivot connection is more economical. The design of the second subassembly 80 also has the advantage of coupling the work platform side part 11 to the mounting part 50, that is to say of uniting them in all circumstances regardless of whether the connecting rod 11 is subjected to compressive forces or to tensile forces.Thus, if the work platform 10 were to rest on an obstacle external to the lifting platform 1 so that an upward force is exerted on it to the point that the load on board the work platform appears to be negative, this is perceived by the instrumented load 90. The load determination device 40 therefore makes it possible not only to detect this situation, but also to determine the magnitude of the negative load, including if the direction of the forces transmitted by the connecting rod 11 were to be reversed, that is to say when the vertical upward force applied to the work platform 10 exceeds the weight of the work platform 10 supplemented with that of the heavy load possibly placed on it. The on-board electronics 5 of the lifting platform 1 can then automatically implement appropriate procedures depending on the magnitude of the negative load, in particular for reasons of safety and integrity of the lifting platform 1.For example, the on-board electronics may be provided to automatically stop the movements of the work platform 10, in particular the lowering movement, as soon as the negative load exceeds a predetermined threshold. This threshold may be set at zero daN, but it is preferable to set it at a non-zero value to avoid untimely triggering of the safety procedure due to transient phenomena. From this point of view, this threshold is preferably set at a value greater than or equal to 10 daN, or even 25 daN. On the other hand, this value is preferably less than or equal to 200 daN and more preferably less than or equal to 100 daN, or even 75 daN, which limits the risk of damage caused to the lifting platform 1.

[0078] Furthermore, one or more data representative of the load on board the work platform 10 may be recorded, for example, for the purpose of analyzing events affecting the use of the lifting platform 1. In particular, such a recording may advantageously be carried out when the load determined by the on-board electronics 5 exceeds a predetermined non-zero positive threshold, for example a threshold representative of an overload of the work platform 10. Conversely, such a recording may be carried out when a non-zero negative load is determined by the on-board electronics 5, in other words when an upward vertical force is applied to the work platform 10.Or more particularly, the recording can be carried out when the on-board electronics 5 determines a negative load exceeding in absolute value a non-zero predetermined threshold, for example a threshold set at a value greater than or equal to 10 daN and more preferably at a value greater than or equal to 25 daN. In particular, this threshold can advantageously be set at a limit not to be exceeded so as not to expose the lifting platform 1 to damage. From this point of view, the threshold is set at a value which is preferably less than or equal to 200 daN and more preferably less than or equal to 100 daN, or even 75 daN.

[0079] The data thus recorded may be the load on board the work platform 10 as determined by the on-board electronics 5 or the measurement(s) provided by the instrumented axis 90 used to determine the load or any other data representative of the load. These data may be recorded with time stamping by the on-board electronics 5 itself in a storage device 5a on board the lifting platform 1. The data storage device 5a may be of any suitable type such as RAM memory, a hard disk, an SSD disk, etc. Alternatively or additionally, these data may be sent for storage to a remote server 6 by the on-board electronics 5 via a wireless communication link symbolized by the arrow 7 in FIG. 1. This may in particular be a server hosted in a cloud on the Internet.It will be understood that the recording of the data representative of the load on board the work platform 10 in a storage device 5a on board the lifting platform 1 and / or their sending to a remote server 6 can be more generally implemented for any type of lifting platform, as well as with a load determination device which is not according to the present invention.

[0080] The embodiment described with reference to figures 1 to 10 combines a particularly simple and economical design while allowing precise determination of the weight of the work platform 10 and therefore of the load on board the latter.

[0081] Many variants are however possible. According to another equally advantageous embodiment, the connecting rod 81 is mounted by its end 81a on the axis 74 instead of being mounted on the axis 72. In this case, the connecting rod 81 is subjected to a tensile force under the effect of the weight of the working platform 10 instead of being subjected to a compressive force as is the case in the embodiment illustrated by the figures.

[0082] According to another embodiment, the connecting rod 81 is pivotally mounted by its end 81a on a dedicated axis separate from the axes 72 and 74 and which is also secured to the part on the work platform side 11.

[0083] According to another embodiment, the instrumented axis 90 is mounted on the part on the work platform side 11. In this case, the connecting rod 81 is pivotally mounted by its end 81a either on the axis 71, or on the axis 73, or on a separate dedicated axis which is secured to the part on the mast side 50.

[0084] The embodiments in which the connecting rod 81 is mounted on one of the axes 71, 72, 73 or 74 are preferable because they save on a dedicated axis.

[0085] According to yet another embodiment, the connecting rod 81 is pivotally mounted by its end 81a on a dedicated axis which itself is mounted on the upper connecting rod 61 or on the lower connecting rod 62 while the instrumented axis 90 is mounted on the mounting support 50 or on the work platform side part 11.

[0086] According to another embodiment, the instrumented axis 90 is mounted on the upper connecting rod 61 or on the lower connecting rod 62. In this case, the connecting rod 81 is pivotally mounted by its end 81a to the mast-side part 50 or to the work platform-side part 11, whether on one of the axes 71, 72, 73 or 74 or on a dedicated axis separate from the latter.

[0087] According to yet another embodiment, the connecting rod 81 is pivotally mounted by its end 81a on a dedicated axis which itself is mounted either on the upper connecting rod 61 or on the lower connecting rod 62, and the instrumented axis 90 is mounted on the other of the two connecting rods 61, 62.

[0088] Whatever the embodiment, the connecting rod 81 is arranged so as to support the weight of the work platform 10 and to transfer it directly or indirectly from the work platform side part 11 to the mast side part 50 by means of the instrumented axis 90.

[0089] In the case where the end 81a of the connecting rod 81 and / or the instrumented axis 90 are mounted on one or other of the connecting rods 61, 62, the shape of the connecting rods 61 and 62 concerned can be adapted so as to define a mutual arrangement of the three axes mounted on the same connecting rod, for example according to a triangular arrangement, so that the connecting rod 81 extends in a direction chosen so that the forces applied to the connecting rod 81 due to the weight of the work platform 1 reach the desired level.

[0090] It will be noted that the connecting rods 61, 62 are pivotally mounted to the mounting part 50 and to the work platform side part 11 by means of axes distinct from the instrumented axis 90, namely the axes 71, 72, 73 and 74, in order to prevent the forces transmitted by the connecting rods 61, 62 from passing through the instrumented axis 90.

[0091] According to still other embodiments, the determination of the load on the work platform 10 is carried out without using an instrumented axis. Such an embodiment is illustrated by FIG. 11. The load determining device of FIG. 11 is referenced 140. Similar to the first embodiment illustrated by FIGS. 1 to 10, the load determining device 140 is mounted, on the one hand, to the mast-side part 50 (which in this example is made a little differently) and, on the other hand, to the work platform-side part 11.

[0092] The first subassembly 60 of the load determination device 140 is identical to that of the first embodiment. On the other hand, the second subassembly 180 is different from the first subassembly 80 of the first embodiment. More particularly, the connecting rod 81 and the instrumented axis 90 of the first embodiment are replaced by a connecting rod 181 composed of several sections rigidly connected to each other including a force sensor 190 capable of determining the tensile and / or compressive forces applied to it. This type of sensor is known per se and is commercially available. In another embodiment, the connecting rod 181 is made in one piece from one material and one or more strain gauges are added to determine the tensile and / or compressive forces applied to it.

[0093] The connecting rod 181 is mounted by its end 181a on the axis 72 by means of a first ball joint 82 and by its opposite end 181b on the axis 73 by means of a second ball joint 82. The two ball joints 82 prevent parasitic forces due to a possible deformation of the part on the work platform side 11 and of the first subassembly 60 from being applied to the connecting rod 181 and therefore to the force sensor 190. Alternatively, only one of the two ends 181a, 181b is mounted by means of a ball joint 82 while its other end is mounted by a sliding pivot connection or a pure pivot connection. However, the use of two ball joints 82 is nevertheless preferable because they eliminate or limit more effectively the parasitic forces on the connecting rod 181 which are linked to the torsional moment. The embodiment of FIG. 11 can also be the subject of numerous variants. In particular, the connecting rod 181 can be mounted on the pins 71 and 74 instead of the pins 72 and 73.It is also possible to mount the connecting rod 181 by its end 181a to a first dedicated axis and / or by its end 181b to a second dedicated axis, which dedicated axes are mounted one to the mast-side part 50 and the other to the work platform-side part 11. Alternatively, one and / or the other of these two dedicated axes can be mounted on the upper connecting rod 61 and on the lower connecting rod 62. The embodiments described with reference to FIGS. 1 to 10 are however more advantageous than that of FIG. 11 and its variants in that they only comprise a single ball joint 82 and that the connecting rod 81 is structurally simple.

[0094] Of course, the present invention is not limited to the examples and embodiments described and shown, but it is still susceptible to other variants accessible to those skilled in the art.

Claims

CLAIMS 1. Load determining device (40; 140) for determining a load on a work platform (10) of a lifting platform (1), the work platform (10) being mounted at an upper end (28) of a mast (20) used to move the work platform in height, the load determining device being mounted or intended to be mounted in interposition between the upper end of the mast and the work platform, the load determining device comprising: - a mast-side part (50) forming part of the upper end of the mast or intended to mount the load determining device at the upper end of the mast, a work platform-side part (11) forming part of the work platform or intended to support the work platform, at least one upper connecting part (61) and at least one lower connecting part (62), the upper connecting part (61) being pivotally mounted, on the one hand, to the mast-side part (50) about a first axis (71) and, on the other hand, to the work platform-side part (11) about a second axis (72), the lower connecting part (62) being pivotally mounted, on the one hand, to the mast-side part (50) about a third axis (73) and, on the other hand, to the work platform-side part (11) about a fourth axis (74), the first, second,third and fourth axes (71-74) being separate parallel axes allowing vertical movement of the work platform side part (11) relative to the mast side part (50) by pivoting the upper connecting part (61) and the lower connecting part (62), a load transfer element (81; 181) coupling the work platform side part (11) to the mast side part (50) to transfer the load carried by the work platform side part to the mast side part, and a force sensor (90; 190) for measuring the force transmitted by the load transfer element from the work platform side part to the mast side part, wherein the load transfer element (81; 181) couples the work platform side part (11) to the mast side part (50) by means of at least one ball joint (82)., 2. Load determining device according to claim 1, wherein the load transfer element is a connecting rod (81; 181).

3. A load determining device according to claim 2, wherein two opposite ends (81a, 81b; 181a, 181b) of the connecting rod (81; 181) are each mounted to a respective one of the mast side part (50), the work platform side part (11), the upper connecting part (61) and the lower connecting part (62).

4. Load determining device according to any one of claims 1 to 3, in which the force sensor (90) comprises a test body in the form of a fifth axis on which the ball joint is mounted, the fifth axis being distinct from the first, second, third and fourth axes (71-74).

5. Load determining device according to claim 4 in that it depends on claim 2 or 3, in which the connecting rod (81) is mounted by a first end (81b) on the ball joint (82).

6. Load determining device according to claim 4 or 5, in which the ball joint (82) is mounted in a sliding pivot connection on the fifth axis (90).

7. Load determining device according to claim 6 in that it depends on claim 5, in which the connecting rod (81) is mounted by a second end (81a) opposite the first end by a pure pivot connection.

8. A load determining device according to any one of claims 5 to 7, wherein the fifth axis (90) and a second end (81a) of the connecting rod (81) opposite the first end are each mounted on a respective one of the mast-side part (50) and the work platform-side part (11).

9. A load determining device according to claim 8, wherein the second end (81a) is mounted on one of the first, second, third and fourth axes (71-74).

10. Load determining device according to claim 2 or 3, in which the connecting rod (181) is the test body of the force sensor or the force sensor (190) is integrated into the connecting rod (181).

11. Load determining device according to claim 10, wherein the connecting rod (181) is mounted by two opposite ends by means of a respective ball joint (82).

12. Load determining device according to claim 10 or 11, wherein: the connecting rod (181) is mounted to the third axis (73) by a first end (181b) and to the second axis (72) by a second end (181a) opposite the first end, or the connecting rod is mounted to the first axis (71) by a first end and to the fourth axis (74) by a second end opposite the first end.

13. Load determining device according to any one of claims 2 to 12, in which the connecting rod (81; 181) is mounted inclined relative to the vertical direction so as to extend obliquely between the mast-side part and the work platform-side part, the angle between the connecting rod and the vertical direction preferably being between 10 and 80 degrees.

14. Device according to any one of claims 1 to 13, in which the force sensor (90; 190) is capable of measuring the force transmitted by the load transfer element from the work platform side part (11) to the mast side part (50) regardless of the direction of this force.

15. Lifting platform (1), comprising: a work platform (10), a mast (20) having an upper end (28) to which the work platform is mounted and used to move the work platform in height, and - a load determining device (40; 140) according to any one of claims 1 to 14 which is mounted interposed between the upper end of the mast (28) and the working platform (10).

16. Lifting platform according to claim 15, further comprising on-board electronics (5) to which the force sensor (90; 190) is connected, the on-board electronics being provided for determining the load on board the work platform (10) from the measurement signals provided by the force sensor (90; 190).

17. Lifting platform according to claim 16, in which the on-board electronics (5) are provided to stop a lowering movement of the working platform (10) in progress if they determine a negative charge on board the working platform. work which is greater in absolute value than a predetermined non-zero threshold, this threshold preferably being set at a value greater than or equal to 10 daN and more preferably at a value greater than or equal to 25 daN.

18. Method for determining a load on a working platform (10) of a lifting platform (1) which working platform is mounted at an upper end (28) of a mast (20) used to move the working platform (10) in height, a load determining device (40) according to any one of claims 1 to 14 being mounted interposed between the upper end (28) of the mast (20) and the working platform (10), the method comprising determining the load on the working platform (10) by on-board electronics (5) on the basis of at least one measurement signal provided by the force sensor (90; 190).

19. Method according to claim 18, comprising the recording by the on-board electronics (5) in a data storage device (5a) on board the lifting platform (1) of at least one preferably time-stamped data item which is representative of the load on the work platform (10) and / or the sending of at least one such data item by the on-board electronics (5) to a remote server (6) via a wireless communication link (7).

20. Method according to claim 19, in which: the on-board electronics (5) records or sends such data if the determined load is greater than a predetermined non-zero positive threshold, the threshold preferably corresponding to the maximum authorized load of the work platform (10); and / or the on-board electronics (5) records or sends such data if the determined load is negative non-zero or if the determined load is negative and greater in absolute value than a predetermined non-zero threshold, this threshold preferably being set at a value greater than or equal to 10 daN and more preferably at a value greater than or equal to 25 daN.

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