METHOD FOR EXTENDING OR RETRACTING THE WHEELS OF A LIFTING WORK PLATFORM ON SWIVEL ARMS

Description

[0001] The present invention relates to the field of mobile elevating work platforms (also known by the acronym MEWP, or in English as mobile elevating work platforms and its abbreviation MEWP ), also commonly called aerial work platforms (or in English aerial work platforms and its abbreviation AWP ).

[0002] Aerial work platforms (AWPs) are machines designed to allow one or more people to work at height. They consist of a work platform designed to accommodate one or more people. This platform is supported by a lifting mechanism that raises it from a lowered position on the platform's chassis to the desired working position at height. AWPs can be moved on the ground, in which case they are equipped with wheels or tracks for this purpose. They are often self-propelled, meaning they are motorized to allow for independent movement on the ground. The work platform is equipped with a control panel containing controls that allow an operator to activate the lifting mechanism and, if necessary, move the AWP on the ground.

[0003] The invention relates more particularly to four-wheeled lifting platforms, namely two front wheels and two rear wheels, which allow the lifting platform to be moved on the ground and whose lateral spacing - commonly called the track - is modifiable so as to be wider in working position and narrower for transport or movement on the road.

[0004] A wide lateral wheel spacing provides increased stability to the aerial work platform when it is in the working position, i.e., when the work platform is raised by the lifting mechanism to a desired working height. However, a wide lateral wheel spacing can be incompatible with transporting the aerial work platform on a truck or traveling on public roads, as it generally exceeds the maximum limits for truck transport or road travel. The fact that the lateral wheel spacing can be adjusted to be wider in the working position and narrower for transport or road travel reconciles these two considerations. In the prior art, several technologies have been proposed to allow for adjustment of the lateral wheel spacing.

[0005] According to an initial technology, each wheel is mounted at one end of a respective telescopic arm, the opposite end of which is fixed to the chassis of the aerial work platform. Under the action of hydraulic cylinders, the telescopic arms allow the respective wheels to be translated laterally relative to the chassis of the aerial work platform, and thus their lateral spacing to be varied.

[0006] This initial technology has limitations because the distance between the front and rear wheels—commonly known as the wheelbase—remains restricted by the chassis size. Furthermore, adjusting the wheel spacing is cumbersome, as the aerial work platform must be lifted off the ground using dedicated jacks to free the wheels before their spacing can be changed. In addition, the ground support feet at the ends of the jacks can sink into the ground under the weight of the aerial work platform if the ground is soft or has a weak surface.

[0007] According to a second technology, known in the industry as "X-axles," each wheel is mounted at one end of a respective arm. The opposite end of this arm pivots on the chassis around a vertical axis, allowing for adjustment of the lateral wheel spacing. One or more hydraulic cylinders allow the arms to pivot between the extended working position and the retracted transport position. This technology is exemplified by models such as US 7,198,278 B2, US 8,888,122 B2, and CN106080833A. Compared to the previous technology, this second technology allows for a greater wheelbase because the wheel support arms position the front and rear wheels further from the aerial work platform chassis, facing forward and backward respectively.This second technology therefore makes it possible to further increase the stability of the lifting platform, and thus to achieve even greater lifting heights of the work platform.

[0008] One difficulty with this second technology also lies in how to practically pivot the wheel support arms to change the wheel spacing. Several methods have been proposed.

[0009] One method is similar to that described for the first technology: it involves lifting the wheels off the ground using dedicated jacks, prior to pivoting the wheel support arms using the arm actuating jack(s). This first method therefore has the same drawbacks as those already mentioned for the first technology.

[0010] One variation, in the absence of a linear ground movement for the aerial work platform as before, involves pivoting the wheel support arms without first lifting the wheels off the ground. In other words, the aerial work platform remains stationary in the same spot on the ground while the wheel support arms pivot. In this case, the wheels, which are oriented approximately parallel to each other, rub against the ground as the support arms pivot. This has the disadvantage of putting significant stress on the tire rubber, leading to faster wear, and also risks damaging the ground surface or creating a groove in it if the ground is soft. Furthermore, the hydraulic cylinder(s) actuating the wheel support arms must be more powerful.

[0011] Another way to pivot the wheel support arms is to do so while the aerial work platform is moving horizontally along the ground. This method reduces stress on the tires and the ground compared to the previous method, but does not eliminate it entirely. It has also been proposed to orient the front and rear wheels at an angle, making them convergent or divergent as appropriate, in order to create forces on the wheels that facilitate pivoting the wheel support arms in the desired direction. Consequently, the cylinder(s) actuating the wheel support arms can be less powerful, or even omitted according to US 7,198,278 B2; however, stress on the tires and the ground is increased.In any case, this method assumes sufficient space is available to move the aerial work platform on the ground the distance required to pivot the wheel support arms, which may not always be the case. It also requires the aerial work platform operator to be extremely vigilant regarding any people who may be in the platform's path on the ground, for obvious safety reasons.

[0012] In light of these drawbacks, it is desirable to improve the method of pivoting the wheel support arms. An older document, FR 1 113 811, which has been largely ignored in the field of aerial work platforms, contains instructions on how to pivot the wheel support arms. This document concerns a variable-gauge running chassis for vehicles of all types, for use on roads, land, and rails. It specifically describes a running chassis similar to the second technology mentioned above, that is, with four wheels—or similar—mounted at one end of a respective arm, the opposite end of which is pivotally mounted to the chassis to allow for variation of the lateral wheel spacing.

[0013] Regarding the method for pivoting the wheel support arms, he suggests, among other possibilities, doing so while the chassis is stationary by positioning the wheels tangentially to the pivot circle of the wheel support arms, and then simultaneously pivoting all four wheel support arms while the wheels are running or, failing that, by manually or mechanically operating the wheel support arms. Once the new wheel spacing is achieved, the wheel orientation is adjusted again to restore parallelism and allow the chassis to move along the ground under normal conditions.

[0014] This method avoids having to translate the chassis on the ground when pivoting the wheel support arms, and therefore the associated disadvantages, and it also avoids putting significant stress on the tire rubber and the ground due to the tangential orientation of the wheels when pivoting the wheel support arms.

[0015] However, the deployment procedure described requires operator intervention during the various phases of wheel deployment. Furthermore, this method has the drawback that during wheel deployment or retraction, the chassis may move along the ground under the effect of gravity if it is resting on an incline, which is undesirable. Indeed, there may be certain phases of wheel deployment or retraction during which the wheels are all free-wheeling with an orientation compatible with the movement of the aerial work platform along the ground.

[0016] Document US2015 / 259185A1 discloses a method according to the preamble of claim 1.

[0017] In one aspect, the aim of the present invention is to provide, for the so-called X-axle technology, a method designed to be implemented by the onboard electronics of the aerial work platform and at least partially mitigating the aforementioned drawbacks. In particular, one aim of the method of the invention is to prevent any risk of accidental movement of the aerial work platform along the ground under the effect of gravity during its operation.

[0018] To this end, the present invention proposes a method implemented by on-board electronics of an aerial work platform to move a pair of front wheels and a pair of rear wheels of the aerial work platform between an initial position and a final position, one of which corresponds to a retracted position and the other to a deployed position, the aerial work platform resting on the ground by means of the wheels with a spacing of the front pair of wheels and a spacing of the rear pair of wheels which are greater in the deployed position compared to the retracted position, the aerial work platform comprising a chassis and four arms each supporting one of the respective wheels, each wheel being mounted at a first end of the corresponding arm, the second distal end of which is pivotally mounted to the chassis to move the wheel between the retracted position and the deployed position along a pivoting path of the arm,each of the wheels having a rolling direction on the ground that can be modified by a controlled change in the orientation of the wheel relative to the corresponding arm, the method comprising for each wheel the following successive steps: , a. changing the orientation of the wheel relative to the corresponding arm to have an orientation tangential to the pivoting trajectory of the corresponding arm, b. moving the wheel from the initial position to the final position by pivoting the corresponding arm, any wheel braking system being inactive during the movement and the wheel being maintained oriented tangentially to the pivoting trajectory of the arm during the movement, and optionally c. controlling a change in the orientation of the wheel relative to the corresponding arm so that, after execution of step c) for all wheels, the wheels all have a rolling direction that corresponds to a common direction of movement of the lifting platform on the ground, in which the execution of steps a), b) and where applicable c) for all wheels is desynchronized so that, at any time from the start of step a) until the end of step b) or where applicable step c) for all wheels, at least one of the following conditions is met: the braking system of at least one wheel is active, at least one wheel is subject to motorized rotation, the relative orientation of the wheels with respect to each other prevents any translation of the lifting platform on the ground under the effect of gravity, it being understood that this last condition is assessed of course for an inclination of the ground on which the lifting platform rests which is less than or equal to a maximum inclination authorized to carry out the operation of deploying or retracting the wheels.

[0019] Thanks to the desynchronization as defined, any risk of accidental movement of the lifting platform 1 along the ground under the effect of gravity during the execution of the procedure is eliminated when the lifting platform 1 rests on an inclined surface, at least when the inclination of the ground does not exceed the maximum inclination permitted for using the lifting platform. For the sake of simplicity, the arms supporting the wheels are preferably each made as a rigid, single-piece unit.

[0020] According to the invention step b) is launched synchronously for a first pair of wheels; step b) is launched synchronously for a second pair of wheels, the second pair of wheels being formed by the wheels other than the two wheels forming the first pair of wheels; and step b) is launched for the second pair of wheels with a time offset relative to the first pair of wheels.

[0021] In preferred embodiments, the invention comprises one or more of the following features: the execution of steps a), b) and where applicable c) for all wheels (2, 3) is desynchronized so that, at any time from the start of step a) until the end of step b) or where applicable c), at least one of the following conditions is met: the braking system of at least two wheels is active, at least two wheels are subject to motorized rotation, the relative orientation of the wheels with respect to each other prevents any translation of the lifting platform on the ground under the effect of gravity; step a) is started for each of the wheels before the execution of step b) is completed for any of the other wheels; the execution of step b) for each of the wheels overlaps at least partially in time with the execution of step b) for the other wheels;Step b) is executed synchronously for the first pair of wheels, and step b) is executed synchronously for the second pair of wheels. The pivoting actuation of the arm during step b) is achieved: by means of an actuator dedicated to the actuation of one or more arms, and / or by motorized rotation of the wheel corresponding to the arm; the pivoting actuation of the arm during step b) for at least one of the wheels includes or consists of motorized rotation of the wheel. For one wheel, a change in the direction of rolling on the ground relative to the corresponding arm is achieved by pivoting the wheel about a pivot axis that is offset from a median plane of the wheel perpendicular to the axis of rotation of that wheel, and the change in the orientation of the wheel relative to the corresponding arm of step a) and / or step b) is achieved or assisted by motorized rotation of the wheel;the process is implemented by the on-board electronics upon actuation of at least one control by an operator, in which the execution of the process is continued by the on-board electronics until a final position of the wheels corresponding to an extreme retracted or deployed position as long as the actuation of the control is maintained by the operator and is interrupted by the on-board electronics in the event of release of the control by the operator before the extreme retracted or deployed position of the wheels has been reached; in this latter case, the on-board electronics may also prevent the lifting of a work platform of the elevating platform in the event that the wheels are not all in the extreme deployed position;preferably, in the latter case, if the execution of the process is interrupted by the on-board electronics due to the release of the control by the operator and the wheels are not all in the extreme deployed position, then the on-board electronics triggers a signal informing the operator that the lifting of the work platform is prevented;the process is implemented by the on-board electronics upon actuation of at least one control by an operator, wherein the execution of the process is continued by the on-board electronics until a final position of the wheels corresponding to an extreme retracted or deployed position as long as the actuation of the control is maintained by the operator and in the event of release of the control by the operator during the execution of step b) for each of the wheels before the extreme retracted or deployed position of the wheels has been reached, the on-board electronics continues the execution of the process until a modified final position of the wheels which is intermediate between the extreme retracted position and the extreme deployed position;Preferably, if the on-board electronics continue the execution of the process until a modified final position of the wheels that is intermediate between the extreme retracted position and the extreme deployed position, then the on-board electronics further prevent the lifting of a work platform from the aerial work platform or limits a maximum height to which the operator can lift the work platform compared to the case where the wheels are all in the extreme deployed position.

[0022] The invention also proposes a lifting platform, comprising: a chassis, a work platform, a lifting structure mounted on the chassis and supporting the work platform for raising it to a height, a pair of front wheels and a pair of rear wheels movable between a retracted and a deployed position, the lifting platform resting on the ground by means of the wheels with a spacing of the front pair of wheels and a spacing of the rear pair of wheels which are greater in the deployed position compared to the retracted position, on-board electronics, four arms each supporting one of the respective wheels, each wheel being mounted to a first end of the corresponding arm, the second distal end of which is pivotally mounted to the chassis to move the wheel between the retracted and deployed positions along a pivoting path of the arm,each of the wheels having a rolling direction on the ground that can be changed by a change in the orientation of the wheel relative to the corresponding arm, the on-board electronics being designed to control a change in the orientation of the wheel relative to the corresponding arm, a braking system for at least two of the wheels and which is designed to be controlled by the on-board electronics, in which, for each of the wheels, it is provided that the wheel is driven, the motorized rotation of the wheel being controllable by the on-board electronics, and / or that the corresponding arm is pivotable by an actuation device of the lifting platform, and in which the on-board electronics is configured to implement the method according to the invention.

[0023] According to a preferred embodiment, the lifting platform further comprises one or more manual control devices preferably arranged on a control panel mounted on the work platform, the on-board electronics being provided to implement any of the preferred features of the process relating to the actuation of a control by the operator as opposed to the actuation of the manual control device or at least one of the manual control devices.

[0024] In the latter case, the manual control device(s) include or consist of at least one switch pre-pressurized to a rest position, and more preferably include or consist of: at least one reversing switch which is pre-stressed towards a central rest position, the on-board electronics being designed to cause the wheels (2, 3) to move to the deployed position only if the switch is actuated in a given direction and to cause the wheels (2, 3) to move to the retracted position only if the switch is actuated in an opposite direction; and / or at least two switches each pre-stressed towards a rest position, the on-board electronics being designed to cause the wheels (2, 3) to move to the deployed position only if one of the switches is actuated and to cause the wheels (2, 3) to move to the retracted position only if the other switch is actuated.

[0025] Other aspects, features and advantages of the invention will become apparent from the following description of a preferred embodiment of the invention, given by way of example and with reference to the attached drawing of a four-wheeled lifting platform that can be moved from a retracted position to an extended position and vice versa. [ Fig.1 [ ] represents a perspective view of the aerial work platform with its four wheels in the retracted position. Fig.2 [ ] represents a top view of the aerial work platform with its four wheels in the retracted position. Fig.3 [ ] represents a perspective view of the aerial work platform with its four wheels in the deployed position. Fig.4 [ ] represents a top view of the aerial work platform with its four wheels in the deployed position. Fig.5 [ ] represents a perspective view of the aerial work platform chassis observed from a point above the chassis, with the wheels in the deployed position. Fig.6 [ ] represents a perspective view of the aerial work platform chassis observed from a point below the chassis, with the wheels in the deployed position. Fig.7 [ ] represents a perspective view of the aerial work platform chassis, with the wheels in the retracted position, corresponding to an initial position from which the wheels will be moved to the deployed position. Fig.8 ] represents a top view of the chassis, with the wheels in the [ Fig.7 ]. Fig.9 [ ] represents a top view of the chassis, with the wheels and their support arms in a specific position at a given moment during the wheel deployment process. Fig.10 ] represents a top view of the chassis, the wheels and their support arms being in a position at a moment in the wheel deployment process that is subsequent to that of the [ Fig.9 ]. Fig.11 ] represents a top view of the chassis, the wheels and their support arms being in a position at a moment in the wheel deployment process that is subsequent to that of the [ Fig.10 ]. Fig.12 ] represents a top view of the chassis, the wheels and their support arms being in a position at a moment in the wheel deployment process that is subsequent to that of the [ Fig.11 ]. Fig.13 ] represents a top view of the chassis, the wheels and their support arms being in a position at a moment in the wheel deployment process that is subsequent to that of the [ Fig.12 ]. Fig.14 ] represents a top view of the chassis, the wheels and their support arms being in a position at a moment in the wheel deployment process that is subsequent to that of the [ Fig.13 ]. Fig.15 ] represents a top view of the chassis, the wheels and their support arms being in a position at a moment in the wheel deployment process that is subsequent to that of the [ Fig.14 ]. Fig.16 [ ] represents a flowchart of a preferred embodiment of the process of the invention. ] Fig.17 ] represents the control console mounted on board the work platform of the aerial work platform.

[0026] An example of implementing the method according to the invention will now be detailed with reference to a lifting platform 1, an overview of which is illustrated by the figures 1 And 2 on the one hand and the figures 3 And 4 on the other hand. In the following description, any reference to a vertical or horizontal orientation is defined with respect to the case where the lifting platform 1 rests on a ground forming a horizontal reference plane.

[0027] The aerial work platform 1 comprises a chassis 10 and an elevating structure 20 supporting a work platform 30 designed to carry personnel and equipment for work at height. The platform 10 typically includes a floor 32 and a guardrail 34. A control panel 40 is mounted on the work platform 30. This panel allows an operator on board the work platform 30 to control the elevating structure 20 to move the work platform 30 upwards to the desired position, as well as to move the chassis 10 on the ground.

[0028] The lifting structure 20 comprises a turret 22 mounted on the chassis 10 and a telescopic boom 24 pivotally mounted on the turret 22 about a horizontal axis. The turret 22 is pivotally mounted about a vertical axis on the chassis 10, which allows the orientation of the lifting structure 20, and therefore the orientation of the work platform 30 relative to the chassis 10, to be changed. To allow the work platform 30 to be moved locally without acting on the boom 24, the lifting structure 20 also includes a pendulum arm 26 articulated at one end to the upper end of the telescopic boom 24, while the other end of the pendulum arm 26 articulates the work platform 30. It will be understood that the lifting structure 20 may differ from the one described.For example, it may additionally include a pantographic articulated arm mounted at one end on the turret 22 around a horizontal axis and supporting at its other end the telescopic boom 24, also around a horizontal axis, the articulated arm being designed to extend vertically. Alternatively, the pendulum arm 26 may be omitted. The lifting structure 20 typically includes a set of actuators to produce the various movements of the lifting structure 20, for example, a hydraulic motor to rotate the turret 22 and a set of hydraulic cylinders for extending the telescopic boom 24, for local movement of the pendulum arm 26, and for the movement of the work platform 30.

[0029] The chassis 10 is equipped with two front wheels 2 and two rear wheels 3 designed to make contact with the ground: the front and rear sides of the lifting platform 1 are indicated by the arrow labeled AV and AR, respectively. In use, the lifting platform 1 rests on the ground via the wheels 2 and 3, which allow the platform to move along the ground.

[0030] Wheels 2 and 3 are each supported by a respective arm, referenced 4 for each of the front wheels 2 and 5 for each of the rear wheels 3. More specifically, each of the wheels 2 and 3 is mounted to one end of the corresponding arm 4 or 5, while a second distal end of the arm is pivotally mounted to the chassis 10. As is most clearly visible on the figures 5 And 6, arms 4 and 5 preferably have the same length and are arranged symmetrically with respect to the longitudinal vertical median plane L of the lifting platform 1. The normal translation direction of the lifting platform 1 forwards and backwards coincides, in top view, with plane L. Alternatively, arms 5 may have a different length than arms 4.

[0031] The pivoting of each arm 4, 5 relative to the chassis 10 allows the corresponding wheel 2 or 3 to be moved between a retracted position illustrated by the figures 1 And 2 and a deployed position illustrated by the figures 3 And 4 . For this purpose, the pivot axis 14, respectively 15 of each arm 4, respectively 5, relative to the chassis 10 is vertical - or at least has an inclination with a vertical component - so as to move the corresponding wheel between the retracted position and the deployed position.

[0032] As can be seen on the figures 2 And 4 The horizontal distance 'D' between the rear wheels 3 in the deployed position is greater than their horizontal distance 'd' in the deployed position. The same applies to the horizontal distance – not referenced in the figures – between the front wheels 2. In both the retracted and deployed positions, the horizontal distance of the front wheels 2 is preferably identical to the horizontal distance 'd', or 'D', of the rear wheels 3. Alternatively, however, their distance could be different.

[0033] In the retracted position of wheels 2 and 3, their spacing 'd' is preferably less than or equal to 2.5 m, making the aerial work platform 1 suitable for travel on standard-width roads or for loading onto a trailer for transport on such roads. The retracted position of wheels 2 and 3 therefore corresponds to a road transport or travel configuration for the aerial work platform 1.

[0034] The extended position of wheels 2 and 3, on the other hand, is a working configuration of the aerial work platform 1 designed to lift the elevating structure 20 in order to position the work platform 30 at a desired working height. In this position, the distance 'D' between wheels 2 and between wheels 3 is preferably greater than 3 m, or even greater than or equal to 4 m, and can even reach 5 m. In the extended position, the wheelbase, i.e., the distance between the front wheels 2 and the rear wheels 3, is preferably approximately equal to the distance 'D'. The relative positioning of wheels 2 and 3 in the extended position provides significantly increased stability to the aerial work platform 1 compared to the retracted position. It is therefore possible for the lifting platform 1 to lift the work platform 30 to very high heights, for example more than 40 m, which would not be possible in the retracted transport position.

[0035] The retracted and extended positions of arms 4 and 5 preferably correspond to the extreme pivoting positions in which wheels 2 and 3 are closest together and furthest apart. However, the lifting platform 1 can also be designed for use with wheels 2 and 3 only partially extended; in other words, arms 4 and 5 are then placed in an intermediate pivoting position between the two extreme pivoting positions.

[0036] Arm actuators are provided to rotate each of the arms 4 and 5 between the retracted and deployed positions. In this case, as is most clearly visible on the figures 5 And 6Each arm 4, 5 is actuated by a corresponding cylinder 18, respectively 19, arranged between the frame 10 and the corresponding arm. Alternatively, a common actuator for both arms can be used, for example, one cylinder for the front arms 4 and another for the rear arms 5. In this latter case, the cylinder can be mounted between the two corresponding arms at one end. Alternatively, the cylinder can be mounted at one end to the frame 10 and at its opposite end to a hinged mechanism connecting the two corresponding arms so that the cylinder pivotally actuates the two arms via the hinged mechanism. In another variant, the pivoting of the arms 4, 5 can also be achieved by rotating the corresponding wheels when the wheels are driven, as will be seen later.In this case, the dedicated actuator—that is, in this example, the corresponding cylinder 18 or 19—can act in coordination with the wheel rotation drive or be omitted. These different variants can be combined: for example, the actuation technology can be different for a first pair of arms compared to a second pair of arms.

[0037] It is preferable to protect the cylinders 18 and 19 from potential impacts against obstacles external to the lifting platform 1 during its movement on the ground. As illustrated by the figures 5 And 6, this protection can be obtained by a front extension 10a and a rear extension 10b of the chassis 10 relative to which the cylinders 18, respectively 19, are placed in the rear direction, respectively rear, regardless of the angular position of the corresponding arm 4 or 5 between the retracted position and the deployed position. Thus, it is the chassis 10 that will absorb the impact with any obstacle without the latter coming into contact with the cylinder(s) 18 or 19. It is preferable that the front extension 10a and the rear extension 10b be located at a level below the cylinders 18 and 19, respectively, in order to effectively protect the cylinders 18 and 19 against an obstacle on the ground extending at approximately the same height as the cylinders 18 and 19. The extensions 10a and 10b can be made of a material with a base plate of the chassis 10, in particular with a lower base plate of the chassis 10 as illustrated by the figures 5 And 6 .

[0038] A locking system is provided for each arm 4 and 5 to selectively lock their pivoting relative to the frame 10 in the extreme pivoting positions, i.e., in the retracted and extended positions, and even in intermediate pivoting positions. One way to achieve locking is to block the pivoting of an arm 4 or 5 by hydraulically blocking the corresponding cylinder 18 or 19, for example, by providing two controlled valves associated with the cylinder to selectively block the hydraulic fluid in the two chambers of the corresponding cylinder 18 or 19, implemented as a double-acting hydraulic cylinder. This method is simple to implement and allows the arms 4 and 5 to be locked in any intermediate pivoting position.

[0039] Other locking systems are possible. For example, the locking system may consist of continuously actuating the corresponding cylinder 18 or 19 in both the retracted and deployed positions in order to constantly push the arm 4 or 5 against a dedicated stop on the frame 10. According to another example, a dedicated electromechanical or hydraulic device may be provided to selectively mechanically lock the arm 4 or 5 to the frame 10 in the desired pivoting positions, for example a device provided directly at the pivot axes 14, 15 so as to prevent the rotation of the arms or a spindle mechanism linked to one to selectively engage dedicated openings which are associated with the other.

[0040] The lifting platform 1 is motorized to allow for autonomous movement on the ground. In this case, each of the wheels 2 and 3 is driven. Although this may vary, it is preferable for an electric or hydraulic motor – not shown – to be integrated into each drive wheel 2 and / or 3. This avoids the need for a complex drive system from the chassis 10, which would be necessary if the motor(s) were installed on the chassis 10 or on the corresponding arm 4 or 5. Alternatively, only the front wheels 2 may be driven, or conversely, only the rear wheels 3 may be driven.

[0041] Each of the wheels 2 and 3 is equipped with a braking system – not shown – which can be of any suitable type known per se, for example, a hydraulic or solenoid valve braking system. Alternatively, only some of the wheels are equipped with such a system, for example, only the front pair of wheels 2 or the rear pair of wheels 3. In this case, references to the active or inactive state of the braking system will be ignored for the wheel(s) concerned in the subsequent description of the deployment method for wheels 2 and 3. The active state of the braking system can, if necessary, be replaced by placing at least two of the wheels in a mutually different orientation, providing the same effect of holding the lifting platform 1 in place on the ground.

[0042] Each of the wheels 2 and 3 is directional. To achieve this, the front wheels 2 are each pivotally mounted on their corresponding arm 4 around a vertical axis 16, or at least an axis inclined with a vertical component. The same applies to the rear wheels 3 relative to their corresponding arm 5: see the pivot axis referenced 17. Changing the direction of rolling on the ground of each wheel 2 and 3, in other words, changing their orientation relative to the corresponding arm 4 or 5, is ensured by a respective steering actuator, in this case a cylinder mounted between the arm and the wheel in question. This can be a hydraulic or electric cylinder. Other actuation technologies are possible.

[0043] The lifting platform 1 includes on-board electronics which allows control of the drive wheels 2 and / or 3, the actuators of the arms 4 and / or 5, the locking systems for the pivoting of arms 4, 5, the steering actuators of wheels 2, 3 and the braking systems of wheels 2 and / or 3.

[0044] Furthermore, the lifting platform 1 includes sensors known per se to indicate to the on-board electronics the angular orientation of the wheels 2, 3 relative to the corresponding arm 4, 5, as well as the pivoting position of the arms 4, 5 relative to the chassis 10. By way of non-limiting examples, these may be any of the following sensor technologies: linear measurement of the output of the cylinder rods by a Hall effect sensor or magnetostrictive sensor placed in the cylinder concerned, measurement of the angle on the pivot of the arm or the steering pivot by a Hall effect sensor positioned on the pivot concerned, on / off measurement in the extreme pivoting positions of arms 4, 5 by a mechanical sensor or a reed switch for example.

[0045] We will now describe the process of moving wheels 2, 3 from their retracted position to their deployed position with reference to the flowchart of the [ Fig.16 It will be understood that this flowchart only indicates the beginning of the steps of the process in relation to each other, but not the end of the steps in relation to each other.

[0046] The retracted and deployed positions of wheels 2 and 3 correspond to the extreme pivoting positions of arms 4 and 5, but they could also be intermediate pivoting positions. figures 8 à 15 The diagrams illustrate the chassis 10 and the configuration of the arms 4, 5 and the wheels 2, 3 at different stages of the process. It is implemented automatically by the on-board electronics of the aerial work platform 1 after a corresponding command is activated by an operator. It will be understood that every action of the process described below is controlled by the on-board electronics, even in the absence of explicit mention to that effect.

[0047] The process is implemented starting from an initial configuration of the lifting platform 1 shown in the figures 7 And 8 It is identified by box 100 of the flowchart of the [ Fig.16 and corresponds to a time t0 on the time axis. In this configuration, the lifting platform 1 is stationary and in transport configuration. In other words, the braking systems for wheels 2 and / or 3 are activated, and wheels 2 and 3 are retracted. The arm pivot locking systems are activated. Wheels 2 and 3 are parallel to each other along the longitudinal axis L of the lifting platform 1. In other words, wheels 2 and 3 have a common rolling direction, allowing the lifting platform 1 to move in a straight line along the ground in the forward (AV) or backward (AR) direction.

[0048] If wheels 2 and 3 have a different initial orientation, the process may include a preliminary step in which the on-board electronics control the steering actuators of the relevant wheels 2 and / or 3 to orient them as described above. Alternatively, the subsequent step can also be performed directly from any orientation of wheels 2 and / or 3.

[0049] We will first describe the steps relating to the deployment of the rear wheels 3.

[0050] In a first step 110 which starts at time t 1, the on-board electronics control the steering actuators of the rear wheels 3 so that they adopt an orientation tangential to the pivoting trajectory T 5 , T 5 ' of the corresponding arm 5 around its pivoting axis 15. In other words, the rolling direction of each of the wheels 3 is made tangential to the pivoting trajectory T 5 , T 5 ' of the corresponding arm 5. This situation is illustrated by the [ Fig.9 ], the direction of pivoting of the rear wheels 3 around the pivot axes 17 being symbolized on the [ Fig.8 ] by the dashed, curved arrows.

[0051] If, as in the illustrated example, the pivot axes 17 of the wheels 3 are offset by a non-zero distance 'e' from the median plane P of the rear wheels 3, which is perpendicular to their axis of rotation R - cf. [ Fig.8 It is preferable that the rear wheel braking system 3 be deactivated for the duration of this first step. This prevents the tire treads of wheels 3 from rubbing against the ground, and also avoids creating a rut in the ground if it is soft.

[0052] In addition, the motorized drive in rotation of the wheels 3 is activated during this first stage to assist the change of direction of the wheels operated by the steering actuators of the wheels 3. This allows for a smaller dimensioning of the latter.

[0053] Alternatively, the steering actuators of the wheels 3 can be configured to handle the change of direction of the rear wheels 3 on their own. In this case, the wheels 3 are left free-wheeling to roll freely on the ground during the direction change operation. This eliminates the need for synchronizing the motorized rotation drive of the wheels 3 with the action of the steering actuators of the wheels 3.

[0054] Alternatively, it can be provided that the tangential orientation of the rear wheels 3 to the pivot trajectory T5, T5' of the corresponding arm 5 is obtained exclusively by the motorized rotation drive of the rear wheels 3, i.e. without active participation of the steering actuators of the wheels 3. This also avoids having to synchronize the rotation drive of the wheels 3 with the action of the steering actuators of the wheels 3.

[0055] If, contrary to the illustrated example, the pivot axes 15 were contained in the median plane P and crossed the axis of rotation R of the wheels 15, the first step is executed by means of the steering actuators of the wheels 3 alone, i.e. without motorized drive in rotation of the wheels 3. Therefore, it is not necessary in this case to deactivate the braking system of the wheels 3.

[0056] Once the first step 110 is finished, in other words when the wheels 3 are placed in an orientation tangential to the pivoting trajectory T 5, T 5' of the corresponding arm 5 as illustrated in the [ Fig.9 ], the on-board electronics launch - - cf. instant t 2 - a second step 120 which consists of rotating the arms 5 to bring the wheels 3 into the deployed position.

[0057] To achieve this, the on-board electronics deactivate the pivot locking system of the arms 5 and cause the arms 5 to pivot to their pivot position corresponding to the deployed position of the wheels 3. This position is illustrated by the [ Fig.12 ]. The wheel braking system 3 is deactivated during this second step 120 and the tangential orientation of the wheels 3 to the pivoting trajectory T5, T5' of the corresponding arm 5 is maintained throughout the duration of this second step 120.

[0058] The pivoting of the arms 5 can be caused only by means of the actuators of the arms 5, i.e. in this case the cylinders 19. In this case, the wheels 3 are left in free wheeling during the second step 120, which allows them to roll on the ground during the pivoting of the arms 5.

[0059] Conversely, the pivoting of the arms 5 can be achieved solely by motorized rotation of the wheels 3, causing them to roll on the ground. This motorized rotation of the wheels 3 causes the arms 5 to pivot due to their tangential orientation relative to the pivoting path T5, T5' of the corresponding arm 5. In this variant, the dedicated actuators for the arms 5 – in this case, the cylinders 19 – can be omitted.

[0060] Preferably, the pivoting of the arms 5 is caused by the combined action of the actuators of the arms 5 - i.e. in this case the cylinders 19 - and the motorized drive in rotation of the wheels 3. This has the advantage of limiting the power required by both the actuators of the arms 5 and the motorization of the drive of the wheels 3.

[0061] In these three ways of causing the pivoting of the arms 5, there is almost no friction of the tread of the tires of the wheels 3 on the ground and the risk of digging a furrow in soft soil is almost zero.

[0062] The arm pivot locking system 5 is activated at the end of the second step 120, i.e. when the arms 5 have reached their pivot position corresponding to the deployed position of the wheels 3.

[0063] After the second step 120, the on-board electronics initiate a third step 130 – see time t 3 – which consists of again changing the orientation of the rear wheels 3 so that they adopt a rolling direction on the ground corresponding to a translational direction of the lifting platform 1 on the ground. Preferably, the rear wheels 3 are placed in a parallel orientation with each other along the longitudinal axis L of the lifting platform 1, as was the case in the initial step 100. In other words, the rear wheels 3 again have a common rolling direction, allowing rectilinear translation of the lifting platform 1 on the ground in the forward (AV) or backward (AR) direction. This situation is illustrated by the [ Fig.13 ] which corresponds to the moment when the rear wheels 3 have reached this new orientation.

[0064] The actuation operating the change of orientation of the rear wheels 3 during this third step 130 is carried out in any of the ways described for the change of orientation of the rear wheels 3 operated during the first step 100.

[0065] At the end of the third stage 130, the rear wheel 3 braking system is activated again.

[0066] Steps 110, 120, and 130 are specific to the deployment of the rear wheels 3. The deployment of the front wheels 2 is done in the same way as for the rear wheels 3. In other words, the same steps 110, 120, and 130 are applied. mutatis mutandis to the front wheels 2, the stages having been referenced correspondingly 110', 120' and 130' in the flowchart of the [ Fig.16 The only difference is that steps 110', 120', and 130' are executed with a time delay relative to steps 110, 120, and 130. As can be seen in the flowchart, the first step 110' for the front wheels 2 is launched at a time t1' later than the time t1 at which the first step 110 for the rear wheels 3 is launched. Consequently, the second and third steps 120' and 130' relating to the front wheels are also launched at times t2' and t3' later than the times t2 and t3 at which steps 120 and 130 are launched for the rear wheels 3, respectively, given that the execution speed of the different steps is preferably approximately the same for the front wheels 2 and the rear wheels 3. The execution speed could, however, be different.

[0067] There [ Fig.10 ] represents the position of the arms 5 and the rear wheels 3 during the second step 120 at time t 1' where the first step 110' begins, that is, at the beginning of the change in orientation of the front wheels 2 to orient them tangentially to the pivoting trajectory of the corresponding arms 4. In this case, time t 1' is located between times t 2 and t 3, but this could be different, for example between times t 1 and t 2.

[0068] There [ Fig.11 ] represents the position of the arms 5 and the rear wheels 3 during the second stage 120 at the instant when the front wheels 2 reach at the end of stage 110' an orientation tangential to the pivoting trajectory of the corresponding arms 4.

[0069] There [ Fig.12 ] represents the position of the arms 4 and the front wheels 2 during the second stage 120' at time t 3 where the stage 130 of reorientation of the rear wheels 3 starts.

[0070] There [ Fig.13 ] represents the position of the arms 4 and the front wheels 2 during the second stage 120' at the moment when the rear wheels 3 have finished being reoriented during stage 130.

[0071] There [ Fig.14 ] represents the position of the arms 4 and the front wheels 2 at time t3' when the reorientation of the front wheels 2 of the third step 130' begins while the rear wheels 3 have already been reoriented in step 130.

[0072] There [ Fig.15 ] represents arms 4; 5 and wheels 2, 3 in their final configuration after the execution of steps 130 and 130', i.e. where wheels 2, 3 are in the deployed and reoriented position, which corresponds to box 140 of the flowchart of the [ Fig.16 ].

[0073] The advantage of desynchronizing the deployment of the front wheels 2 from that of the rear wheels 3 is to eliminate the risk of the aerial work platform 1 moving in translation under the effect of gravity if it is resting on an inclined surface. Indeed, if the deployment of all four wheels 3, 4 were synchronized, there would be moments during the deployment operations when the front wheels 2 and the rear wheels 3 are simultaneously free-wheeling with a substantially identical or sufficiently close orientation, such that there would be a risk of the aerial work platform 1 moving in translation.

[0074] This risk exists despite the use of motorized drive for the rotation of wheels 3 and 4 during all stages 110, 120, and 130 and 110', 120', and 130' if they were executed synchronously. Indeed, the transition between stage 110 and stage 120 requires a reversal of the direction of rotation of the rear wheels 3, and the same applies to the corresponding stages for the front wheels 2. This reversal of rotation implies a period of a few seconds during which wheels 2 and 3 are freewheeling before being effectively driven in the opposite direction. However, as can be seen on the figures 9 And 11This situation occurs when arms 5 and 4 are still folded down while the rear wheels 3 and front wheels 2 are oriented tangentially to the pivoting path of the corresponding arm 4 or 5. Consequently, wheels 2 and 3 have an orientation close to perpendicular to the longitudinal axis L – or even corresponding to it depending on the design of the lifting platform 1 – which can allow the lifting platform 1 to translate under the effect of gravity if it rests on a surface inclined in that direction.

[0075] The duration of this risky situation is usually longer when motorized rotation of wheels 3 and 4 is not used during steps 110, 120 and 130 and 110', 120' and 130'. It is therefore preferable to use motorized rotation of wheels 3 and 4 during all steps 110, 120 and 130 and 110', 120' and 130' to immediately limit the risk of movement of the lifting platform 1 under the effect of gravity.

[0076] In all cases, the desynchronization of the deployment of the front wheels 2 relative to that of the rear wheels 3 can be implemented in such a way as to eliminate the risk of the lifting platform 1 moving under the effect of gravity, as explained above. Indeed, the desynchronization can be implemented so that, at any time during the deployment operations, at least one of the following conditions is met: the braking system of at least one wheel 2 or 3, more preferably of two wheels, is active, at least one wheel 2, 3, more preferably two wheels, is subject to motorized rotational drive, the relative orientation of the wheels 2, 3 with respect to each other, in other words their rolling direction, is sufficiently different to prevent a translation of the lifting platform 1 on the ground under the effect of gravity on inclined ground.

[0077] Each of its modalities is sufficient in itself to exclude a risk of translation of the lifting platform 1 on the ground under the effect of gravity in the case where the lifting platform 1 rests on an inclined ground.

[0078] According to the structural design of the chassis 10 and the arms 4, 5, there may also be a risk of the lifting platform 1 pivoting on itself under the effect of gravity if it rests on an inclined surface while the wheels 2, 3 are all oriented tangentially to the pivoting path of the corresponding arm 4, 5: in our example, this corresponds to the part of steps 120 and 120' which is executed in temporal overlap. Despite the pivoting paths of the arms 4, 5 not being exactly superimposed, this risk can exist when their pivot axes 14, 15 are relatively close to each other compared to the length of the arms 4, 5. This risk can then be eliminated by subjecting at least one of the wheels 2, 3 to a motorized rotation drive at least during the moments when all the wheels 2, 3 are simultaneously oriented tangentially to the pivoting path of the corresponding arm 4, 5.Another way to exclude this risk is to ensure that the set of wheels 2, 3 are never simultaneously oriented tangentially to the pivoting trajectory of the corresponding arm 4, 5, which however lengthens the duration of the deployment operations of wheels 2, 3.

[0079] The transition of wheels 2 and 3 from their deployed to their retracted position is achieved by reversing the process. Desynchronizing the movement of the front wheels 2 from that of the rear wheels 3 provides the same advantages as those mentioned for deployment.

[0080] The described procedure can be adapted in many ways. For example, the steps can be reversed so that the deployment of the front wheels 2 is initiated before that of the rear wheels 3. The third step, 130 or 130', can also be omitted if it is not planned to move the aerial work platform 1 once the wheels 2 and 3 are deployed into the working position. In this case, the braking system for wheels 2 and / or 3 is activated at the end of steps 120 and 120'.

[0081] It can also be arranged that the movement of wheels 2 and 3 between the retracted and deployed positions is achieved by synchronizing a first pair of wheels with each other and a second pair of wheels with each other, other than the front wheels 2 and the rear wheels 3 respectively. For example, the first pair of wheels could consist of wheels 2 and 3 on the left side, and the second pair of wheels could consist of wheels 2 and 3 on the right side. Or, the first pair of wheels could consist of the front left wheel and the rear right wheel, and the second pair of wheels could consist of the front right wheel and the rear left wheel. Naturally, the movement of the first pair of wheels relative to the second pair of wheels is desynchronized to achieve the advantages mentioned above.

[0082] It is advantageous to synchronize the movement of a first pair of wheels with each other and the movement of a second pair of wheels with each other because it has been found that this limits the movements induced at the level of the work platform 30 by the implementation of the deployment or retraction process of wheels 2, 3, and consequently this limits the discomfort of the operator on board the work platform 30.

[0083] For the same reasons of limiting induced movement at the work platform 30, it has been found that it is preferable to initiate the deployment or retraction of the second pair of wheels while the deployment or retraction of the first pair of wheels is underway. This also has the advantage of reducing the time required to deploy wheels 2 and 3 compared to initiating the deployment or retraction steps of the second pair of wheels after the deployment steps of the first pair of wheels are complete. It is also preferable that the front wheel pairs 2 and the rear wheel pairs 3 be synchronized with each other.

[0084] There [ Fig.17 ] illustrates the control panel 200 of the elevating platform 1 which is mounted on board the work platform 30. It conventionally includes control devices allowing an operator to cause the work platform 30 to be raised to a height, as well as the movement of the elevating platform 1 on the ground.

[0085] It also includes a control unit 210 that allows the operator to trigger the deployment or retraction of wheels 2 and 3. Specifically, the control unit 210 is a push-button switch with a neutral center position. Pushing it upwards causes the on-board electronics to deploy wheels 2 and 3 as long as the operator holds it in the upward position. If the operator releases the lever, it returns to the neutral center position, at which point the on-board electronics stop the wheel deployment operations and resume them when the operator pushes the lever upwards again. The operation is the same when the operator pushes the lever downwards to retract wheels 2 and 3. This mechanism provides a safety feature compared to the automatic nature of the wheel deployment or retraction operations.Indeed, the operator simply needs to release control device 210 to stop the deployment or retraction of wheels 2 and 3 if they perceive any risk of collision between wheels 2 and 3 or arms 4 and 5 with an obstacle or a person. Furthermore, the operator is protected from the risk of collision by wheels 2 and 3 or arms 4 and 5 because they must remain at the control panel 200 at all times during these operations. In addition, the onboard electronics are preferably designed to prevent the lifting of the aerial work platform if wheels 2 and 3 are not all in their fully extended position.If the execution of the wheel deployment or retraction operations is interrupted by the on-board electronics due to the release of the control by the operator and the wheels are not all in the extreme deployed position, then the on-board electronics triggers a signal informing the operator that the lifting of the work platform is prevented, for example on the screen 220 mentioned later.

[0086] A marking 211, respectively 213, placed above, respectively below, the switch symbolizes the deployed, respectively retracted position of wheels 2, 3 and arms 4, 5. The upper marking 211, respectively lower marking 213, is supplemented by arrows pointing in the direction of deployment, respectively retraction, of wheels 2, 3 and arms 4, 5.

[0087] An indicator light 212, or 214 respectively, is positioned at the upper marking 211, or lower marking 213 respectively. When wheels 2 and 3 are in the extended or folded position respectively, the indicator light 212, or 214 respectively, remains continuously illuminated. This informs the operator of the current position of wheels 2 and 3.

[0088] When the operator activates the control unit 210 to cause the deployment, respectively the retraction, of wheels 2, 3, the on-board electronics flashes the indicator 212, respectively 214.

[0089] The control panel 200 also includes a display screen 220. When the operator activates the control unit 210, the on-board electronics display a message indicating that the deployment or retraction operations of the wheels 2, 3 are in progress, as well as a graphic animation of the chassis 221 showing the progress of the deployment or retraction operations of the wheels 2, 3 and the arms 4, 5. It also displays a progress bar 222 which increases or decreases in length as the deployment or retraction operations of the wheels 2, 3 progress. When the deployment or retraction operations of the wheels 2, 3 are complete, the on-board electronics display a corresponding message on the screen 220.

[0090] When wheels 2, 3 are in the folded position without the control unit 210 being activated, the on-board electronics display on screen 220 an information indicating that lifting the work platform 30 is not possible.

[0091] It will be understood that the control unit 210 can be of a different type. For example, it can have two separate switches, one to deploy wheels 2 and 3 and the other to retract them. In another example, the deployment or retraction of wheels 2 and 3 can be initiated by touching a dedicated display on the display screen 220.

[0092] It is also possible to remotely launch the wheel deployment or retraction operations, for example by means of a smartphone via wireless communication with the onboard electronics of the aerial work platform 1. Displays similar to those on screen 220 can be provided on the screen of the smartphone.

[0093] In one variant, the on-board electronics can be configured to, if the operator releases control device 210 during the execution of steps 120 and before the wheels 2, 3 reach their maximum retracted or extended position, continue the deployment or retraction operations until the wheels 2, 3 reach a modified final position that is intermediate between the maximum retracted and extended positions. If the on-board electronics continue the process until the wheels reach a modified final position that is intermediate between the maximum retracted and extended positions, then the on-board electronics preferably prevent the lifting of the work platform 30 or limit the maximum height to which the operator can lift the work platform 30 compared to the case where all wheels 2, 3 are in their maximum extended position.

[0094] Of course, the present invention is not limited to the examples and embodiment described and represented, but is susceptible to many variations accessible to those skilled in the art.

Claims

1. A method implemented by on-board electronics of an aerial work platform (1) for moving a pair of front wheels (2) and a pair of rear wheels (3) of the aerial work platform (1) between an initial position and an end position, one of which corresponds to a retracted position and the other to an extended position, the aerial work platform resting on the ground via the wheels (2, 3) with a spacing between the pair of front wheels (2) and a spacing (d; D) between the pair of rear wheels (3) that is greater in the extended position than in the retracted position, the aerial work platform comprising a chassis (10) and four arms (4, 5) each supporting a respective one of the wheels (2, 3), each of the wheels being mounted at a first end of the corresponding arm, a second distal end of which is pivotally mounted to the chassis (10) to move the wheel between the retracted position and the extended position along a pivoting path (T4, T4', T5, T5') of the arm, each of the wheels (2, 3) having a ground rolling direction modifiable by a controlled change of orientation of the wheel with respect to the corresponding arm (4; 5), the method comprising for each wheel (2, 3) the following successive steps: a) changing the orientation of the wheel with respect to the corresponding arm to have an orientation tangential to the pivoting path of the corresponding arm, b) moving the wheel from the initial position to the end position by actuating the corresponding arm to pivot, a possible braking system of the wheel being inactive during the movement and the wheel being kept oriented tangentially to the pivoting path of the arm during the movement, and optionally c) controlling a change in orientation of the wheel with respect to the corresponding arm so that, after execution of step c) for all the wheels, the wheels all have a rolling direction that corresponds to a common direction of travel of the aerial work platform on the ground, wherein the execution of steps a), b) and if applicable c) for all the wheels (2, 3) is desynchronized so that at any time from the beginning of step a) until the end of step b) or if applicable step c) for all the wheels, at least one of the following conditions is satisfied: - the brake system of at least one wheel (2, 3) is active, - at least one wheel (2, 3) is subject to a motorized rotation drive, - the relative orientation of the wheels (2, 3) with respect to each other prevents any translation of the aerial work platform (1) on the ground under the effect of gravity, characterized in that: - step b) is initiated synchronously for a first pair of wheels; - step b) is initiated synchronously for a second pair of wheels, the second pair of wheels being formed by the wheels other than the two wheels forming the first pair of wheels; and - step b) is initiated for the second pair of wheels with a time shift with respect to the first pair of wheels.

2. The method according to claim 1, wherein the execution of steps a), b) and if applicable c) for all the wheels (2, 3) is desynchronized so that at any time from the beginning of step a) until the end of step b) or if applicable c), at least one of the following conditions is satisfied: - the brake system of at least two wheels (2, 3) is active, - at least two wheels (2, 3) are subject to a motorized rotation drive, - the relative orientation of the wheels (2, 3) with respect to each other prevents any translation of the aerial work platform (1) on the ground under the effect of gravity.

3. The method according to claim 1 or 2, wherein step a) is initiated for each of the wheels before the execution of step b) is completed for any of the other wheels.

4. The method according to claim 3, wherein the execution of step b) for each of the wheels at least partially overlaps in time with the execution of step b) for the other wheels.

5. The method according to any one of claims 1 to 4, wherein the initial position and the end position correspond one to an extreme retracted position and the other to an extreme extended position.

6. The method according to any one of claims 1 to 5, wherein: - step b) is executed synchronously for the first pair of wheels; and - step b) is executed synchronously for the second pair of wheels.

7. The method according to any one of claims 1 to 6, wherein the pivotal actuation of the arm (4, 5) in step b) is executed: - by means of an actuator dedicated to the actuation of one or more arms (4, 5), and / or - by motorized rotation drive of the wheel (2, 3) corresponding to the arm.

8. The method according to claim 7, wherein the actuation for pivoting the arm (4, 5) in step b) for at least one of the wheels (2, 3) comprises or consists of a motorized rotation drive of the wheel (2, 3) corresponding to the arm.

9. The method according to any one of claims 1 to 8, wherein for a wheel: - a change in ground rolling direction with respect to the corresponding arm is effected by pivoting the wheel with respect to a pivot axis which is offset with respect to a median plane of the wheel perpendicular to the axis of rotation of this wheel, and - the change of orientation of the wheel with respect to the corresponding arm of step a) and / or of step c) is achieved or assisted by a motorized rotation drive of the wheel.

10. The method according to any one of claims 1 to 9, which is executed by the on-board electronics upon actuation of at least one control by an operator, wherein the execution of the method is continued by the on-board electronics up to an end position of the wheels (2, 3) corresponding to an extreme retracted or extended position as long as the actuation of the control is maintained by the operator and is interrupted by the on-board electronics if the control is released by the operator before the extreme retracted or extended position of the wheels (2, 3) has been reached.

11. The method according to claim 10, wherein the on-board electronics prevents the lifting of a working platform of the aerial work platform if the wheels (2, 3) are not all in the extreme extended position.

12. The method according to claim 11, wherein, if the execution of the method is interrupted by the on-board electronics due to the operator releasing the control and the wheels (2, 3) are not all in the extreme extended position, then the on-board electronics switches on a signaling informing the operator that the lifting of the working platform is prevented.

13. The method according to any one of claims 1 to 9, which is executed by the on-board electronics upon actuation of at least one control by an operator, wherein the execution of the method is continued by the on-board electronics up to an end position of the wheels (2, 3) corresponding to an extreme retracted or extended position as long as the actuation of the control is maintained by the operator, and if the control is released by the operator during the execution of step b) for each of the wheels before the extreme retracted or extended position of the wheels (2, 3) has been reached, the on-board electronics continue the execution of the method up to a modified end position of the wheels (2, 3) which is intermediate between the extreme retracted position and the extreme extended position.

14. The method according to claim 13, wherein if the on-board electronics continues the execution of the method up to a modified end position of the wheels (2, 3) that is intermediate between the extreme retracted position and the extreme extended position, then the on-board electronics further prevents the lifting of a working platform of the aerial work platform or limit a maximum height to which the operator can lift the working platform with respect to the case when the wheels are all in the extreme extended position.

15. An aerial work platform (1), comprising: - a chassis, - a working platform, - a lifting structure mounted on the chassis and supporting the working platform for lifting it to height, - a pair of front wheels (2) and a pair of rear wheels (3) movable between a retracted position and an extended position, the aerial work platform resting on the ground via the wheels (2, 3) with a spacing between the pair of front wheels (2) and a spacing (d; D) between the pair of rear wheels (3) that are greater in the extended position than in the retracted position, - on-board electronics, - four arms (4, 5) each supporting a respective one of the wheels (2, 3), each of the wheels being mounted at a first end of the corresponding arm, a second distal end of which is pivotally mounted to the chassis (10) to move the wheel between the retracted position and the extended position along a pivoting path (T4, T4', T5, T5') of the arm, each of the wheels (2, 3) having a ground rolling direction modifiable by a change of orientation of the wheel with respect to the corresponding arm (4; 5), the on-board electronics being provided to control a change of orientation of the wheel with respect to the corresponding arm (4; 5), and - a braking system for at least two of the wheels (2, 3) which is provided to be controlled by the on-board electronics, wherein for each of the wheels (2, 3) it is provided that the wheel is driven, the motorized rotation drive of the wheel being controllable by the on-board electronics, and / or that the associated arm can be actuated to pivot by an actuating device of the aerial work platform, and wherein the on-board electronics is configured to carry out the method according to any one of claims 1 to 14.