telescopic boom for aerial work platform and aerial work platform including

Abstract

The telescopic boom 26 for a lifting platform comprises an inner boom section 26b inserted telescopically into an outer boom section 26a, and an electric actuator 50. The latter includes a screw-nut system 70, housed at least partially within the boom sections 26a and 26b, which serves to retract and extend the inner boom section 26b relative to the outer boom section 26a. It also includes a rotary drive unit with an electric motor and reversible direction of rotation for actuating the screw-nut system 70. At least a portion of the screw 71 is contained and exposed within a chamber 80 delimited radially by at least one of the boom sections 26a and 26b. This design of the electric actuator 50 makes it compact and lightweight, as the boom sections 26a and 26b protect all or part of the screw against impacts.

Description

Title of the invention: Telescopic boom for aerial work platform and aerial work platform comprising

[0001] The present invention relates to a telescopic boom for a lifting platform, the telescopic boom of which is designed to support and move a working platform of the lifting platform upwards. The invention also relates to a lifting platform comprising such a telescopic boom.

[0002] 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 them and possibly also loads such as equipment and tools, or materials such as paint, cement, etc. The work platform comprises a platform surrounded by a guardrail. It is supported by a lifting mechanism that allows it to be raised from a lowered position on the platform's chassis to a desired working position at height. The work platform is equipped with a control panel allowing an operator on board to move the work platform to reach the desired working position.

[0003] There is a wide variety of aerial work platforms to meet different desired uses. In particular, different technologies are used for the lifting mechanism of the work platform.

[0004] The present invention relates specifically to aerial work platforms whose work platform lifting mechanism includes a telescopic boom, sometimes also called a telescopic mast. The telescopic boom comprises at least two boom sections inserted one into the other in a telescopic manner.

[0005] Traditionally, aerial work platforms are equipped with a hydraulic circuit including at least one hydraulic pump to power, among other things, hydraulic cylinders used to control the tilt of the telescopic boom as well as to extend and retract it. The hydraulic pump is usually driven by an internal combustion engine or an electric motor depending on whether the aerial work platform is intended for outdoor or indoor use.

[0006] A recent trend, however, is to develop electrically powered aerial work platforms even when intended for outdoor use, in order to limit environmental and noise pollution and to allow both indoor and outdoor use: see for example WO 2020 / 157094 A2.

[0007] The present invention aims to further the electrification of telescopic boom lifts by contributing to the replacement of the hydraulic circuit with electrical solutions. Indeed, the hydraulic circuit and its components present drawbacks, particularly in terms of efficiency and pollution due to potential hydraulic fluid leaks.

[0008] The present invention aims more specifically to replace the hydraulic cylinder usually housed in the telescopic boom for retracting and extending it with a simple, reliable and economical electrical solution.

[0009] To this end, the present invention proposes a telescopic boom for a lifting platform, the telescopic boom being designed to support and move a work platform of a lifting platform upwards. The telescopic boom comprises two hollow boom sections, one forming an inner boom section and the other an outer boom section into which the inner boom section is inserted telescopically. The telescopic boom also includes an electric actuator. This electric actuator comprises a screw-nut system including a screw and a nut mounted on the screw. The screw-nut system is housed inside the boom sections to selectively retract the inner boom section into the outer boom section and extend the inner boom section out of the outer boom section.This electric actuator also includes a rotary drive unit with an electric motor and reversible direction of rotation to actuate the screw-nut system. At least a portion of the screw is contained and exposed within a chamber delimited radially by at least one of the arrow sections.

[0010] When the telescopic boom according to the invention is integrated into a lifting platform, the rotary drive unit, in particular its electric motor, is connected to the lifting platform's onboard electronics for control. More specifically, the onboard electronics control the rotary drive unit to retract or extend the telescopic boom according to commands entered by an operator at a control panel on the lifting platform.

[0011] According to the invention, at least a portion of the screw of the screw-nut system is contained and exposed within a chamber delimited radially by at least one of the boom sections, it being specified that the radial direction is defined relative to the screw of the screw-nut system. This chamber is thus delimited in the radial direction of the screw by at least one of the boom sections for the entire length of this portion of the screw. This or these boom sections therefore provide protection for this portion of the screw against radial impacts with objects or obstacles external to the telescopic boom.

[0012] The fact that this part of the screw is exposed in this chamber implies that this part of the screw is not surrounded by a part or subassembly forming around It features a rigid, radially closed housing interposed between this part of the screw and the boom sections. This characteristic simplifies the electric actuator and reduces its size, weight, and cost compared to using an electric cylinder, while providing the same level of reliability. It is common practice to replace the hydraulic cylinders of any machine with electric cylinders when the hydraulic circuit needs to be replaced with purely electrical solutions. A simplified kinematic diagram of an electric cylinder is shown in [Fig. 3]. An electric cylinder generally comprises a screw-nut system 170, in which the screw 171 is driven in rotation by a rotary drive block 160 with an electric motor and reversible direction of rotation.The screw 171 is housed in a cylinder body 100, at one end of which the rotary drive block 160 is fixed, unless it is also housed in the cylinder body 100. The cylinder rod 110 is usually formed by a tube fixedly attached to the nut 172 of the screw-nut system 170 and closed at its free end. The tube forming the cylinder rod 110 is mounted to slide within the cylinder body 100. The cylinder rod 110 is shaped like a tube to allow the screw 171 to extend inside it. When the screw 171 is rotated by the rotary drive block 160, the nut 172 translates along the screw 171 and carries the cylinder rod 110 with it. The cylinder rod 110 then retracts into the cylinder body 100 or protrudes out of the cylinder body 100 depending on the direction of rotation of the screw 171.The cylinder body 100 and the tube forming the cylinder rod 110 protect the screw 171 of the screw-nut system 170 against radial impacts with external elements and against external dirt.

[0013] However, the use of an electric cylinder has the disadvantage of being, by design, bulkier and heavier than a hydraulic cylinder, and its installation is more complicated. Therefore, installing an electric cylinder in place of a hydraulic cylinder inside the telescopic boom of a lifting platform can be tricky and add weight to the telescopic boom.

[0014] Compared to using an electric actuator to replace a hydraulic actuator in a telescopic boom of a lifting platform, the design of the telescopic boom according to the invention eliminates the need for parts corresponding to the cylinder body and / or the tube forming the cylinder rod. This is acceptable because the electric actuator is housed inside the boom sections, which can also serve to protect the screw of the screw-nut system against radial impacts with external elements.

[0015] In the design of the telescopic boom according to the invention, the boom section(s) also protect to a certain extent the part of the screw contained and exposed in the chamber delimited radially by at least one of the boom sections. against weathering and dirt coming from the radially external side of the telescopic boom. This protection is not necessarily total. In other words, the boom section(s), as applicable, do not necessarily provide a complete seal to the chamber containing the relevant part of the screw-nut system against dirt and weathering from the outside. Indeed, the walls of the boom sections, particularly those of the external boom section, may have access openings used for assembly, servicing, or maintenance of the telescopic boom. These access openings may be closed by removable covers or caps to limit or eliminate the intrusion of dirt.Furthermore, the bearings or other guiding elements, if any, placed between the boom sections to ensure their relative sliding, limit to some extent the intrusion of dirt into the telescopic boom, without, however, providing a complete seal. Moreover, the upper end of the telescopic boom is not necessarily sealed airtight. For these reasons, it may be useful to provide the lower end of the telescopic boom with one or more openings allowing dirt to drain away by gravity.

[0016] The fact that dirt may enter the telescopic boom to some extent and thus reach the screw of the screw-nut system is generally not problematic for the proper functioning of the screw-nut system. If necessary, measures can be taken to limit the risk of fouling of the screw-nut system, for example by equipping one or both sides of the screw-nut system nut with a brush that scrapes the screw.

[0017] Finally, it will be understood that although the telescopic boom according to the invention is advantageously intended to equip an electrically powered aerial work platform, it can nevertheless also be used to equip aerial work platforms with an internal combustion engine or hybrid aerial work platforms equipped with both an electric motor and an internal combustion engine.

[0018] According to preferred embodiments, the invention comprises one or more of the following features: - the telescopic boom is devoid of any interposed element between said part of the screw and at least one section of the boom to protect said part of the screw against impacts with external elements foreign to the telescopic boom; - the telescopic boom is devoid of any part or sub-assembly arranged in interposition between said part of the screw and at least one section of the boom and forming a rigid envelope around said part of the screw; the nut has a first side and a second side which are two opposite sides of the nut in the longitudinal direction of the screw, a first longitudinal part of the screw located on the first side of the nut is contained and exposed in a first longitudinal part of the chamber which first longitudinal part of the chamber is delimited in the radial direction by at least one of the arrow segments, and a second longitudinal part of the screw located on the second side of the nut is contained and exposed in a second longitudinal part of the chamber which second longitudinal part of the chamber is delimited in the radial direction by at least one of the arrow segments; the first longitudinal part of the screw and the second longitudinal part of the screw together with the part of the screw overlapped by the nut include at least the threaded part of the screw which is traversed by the nut for a maximum sliding stroke of the inner boom section relative to the outer boom section; the screw is totally contained and exposed in the chamber which chamber is delimited in the radial direction by the arrow sections for the entire length of the screw; the rotating drive block is completely housed inside the boom sections; the rotation axis of the electric motor of the rotary drive block is collinear with the longitudinal axis of the screw of the screw-nut system; the electric motor of the rotary drive block is mounted outside one of the boom sections, the electric motor driving the screw-nut system via a motion transmission device; the nut of the screw-nut system is connected to the inner boom section so as to be immobilized relative to the inner boom section both in translation in the direction of the longitudinal axis of the screw and in rotation about the longitudinal axis of the screw, and the screw of the screw-nut system is arranged inside the outer boom section so as to be immobilized in translation relative to the outer boom section in the direction of the longitudinal axis of the screw, the rotating drive block being arranged to drive the screw of the screw-nut system in rotation; the nut of the screw-nut system is connected to the inner boom section in an end region of the inner boom section through which the inner boom section is inserted into the outer boom section; - the outer boom section is located on the foot side of the telescopic boom and the inner boom section is located on the opposite side of the foot of the telescopic boom; - the two boom sections and the electric actuator together form an electric cylinder having a cylinder body formed by the outer boom section and a cylinder rod formed by the inner boom section.

[0019] The invention also proposes an elevating platform, comprising a telescopic boom according to the invention and a work platform supported by the telescopic boom.

[0020] 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.

[0021] [Fig-1] represents an articulated boom lift in the folded state.

[0022] [Fig.2] represents the same lifting platform in a deployed state.

[0023] [Fig.3] represents a simplified kinematic diagram of an electric actuator.

[0024] [Fig.4] shows a cross-sectional view of the telescopic boom of the lifting platform figures 1 and 2 in which the telescopic boom is according to a prior art design.

[0025] [Fig.5] schematically represents an isolated view of an electric actuator for implement a telescopic boom according to a preferred embodiment of the invention for the lifting platform of figures 1 and 2.

[0026] [Fig.6] schematically represents a longitudinal section of the arrow telescopic of this preferred embodiment which includes the electric actuator of the [Fig.5].

[0027] [Fig.7] schematically represents a perspective view of only the sections of boom and electric actuator of the telescopic boom of the [Fig.6].

[0028] [Fig.8] schematically represents a longitudinal section of the telescopic boom of another embodiment of the invention.

[0029] We will now describe a preferred embodiment of a telescopic boom according to the invention and an elevating platform 1 which is equipped with it with reference to figures 1, 2 and 5 to 7. It is specified that the horizontal and vertical references are made with respect to the situation in which the elevating platform 1 rests on a flat horizontal ground.

[0030] Figures 1 and 2 show the lifting platform 1 in its folded and extended states, respectively. The lifting platform 1 comprises a chassis 2 equipped with wheels 4 for its movement on the ground. At least two of the wheels 4 are preferably steerable. Alternatively, or in combination with wheels, the chassis 2 is equipped with tracks for the same purpose. The chassis 2 is motorized to ensure the Autonomous movement of the aerial work platform 1 on the ground. This preferably involves an electric drive powered by a self-contained, rechargeable electrical power source mounted on board the aerial work platform 1, such as a battery or fuel cell. Alternatively, the aerial work platform 1 is not self-propelled but is designed to be towed by a separate vehicle.

[0031] The elevating work platform 1 includes a lifting mechanism 20 supporting a work platform 10 designed to carry personnel and equipment for working at height. The work platform 10 includes a floor 12 and a guardrail 14. A control panel 16 is fixedly or removably mounted on the work platform 10. It allows an operator on board the work platform 10 to control the lifting mechanism 20 to move the work platform 10 upwards to the desired position and to move the chassis 2 on the ground.

[0032] The lifting mechanism 20 comprises a turret 22 mounted on the chassis 2, a pantographic articulated arm 24 mounted on the turret 22, a telescopic boom 26 mounted on the upper end of the pantographic articulated arm 24 and a pendulum arm 30 mounted at one end at the upper end of the telescopic boom 26 while the working platform 10 is mounted on the other end of the pendulum arm 30.

[0033] The turret 22 is mounted pivoting around a vertical axis on the chassis 2, which allows the orientation of the rest of the lifting mechanism 20 and the platform 10 to be changed relative to the chassis 2.

[0034] Because it includes the pantographic articulated arm 24 in addition to the telescopic boom 26, the lifting platform 1 is of the type commonly referred to as an articulated boom lift (usually called an "articulating boom lift" in English).

[0035] As can be most clearly seen in [Fig. 2], the pantographic articulated arm 24 comprises two parallelograms 24a and 24b arranged so as to be able to extend and retract like a pantograph. Thus, the pantographic articulated arm 24 allows its upper end to be raised and lowered vertically relative to the turret 22: see this movement capability illustrated by arrow Fl in [Fig. 2]. Consequently, the pantographic articulated arm 24 allows the telescopic boom 26 to be raised and lowered without changing the angle of the latter relative to the chassis 2.

[0036] The telescopic boom 26 is pivotally mounted at the upper end of the pantographic articulated arm 24 so that the telescopic boom 26 can be raised and lowered by changing its inclination relative to the pantographic articulated arm 24: see arrow F2 illustrating this pivoting movement in [Fig. 2]. Furthermore, as its name indicates, the telescopic boom 26 is telescopic, which allows it to be lengthened or shortened: see arrow F3 in [Fig. 2].

[0037] According to another embodiment, the pantographic articulated arm 24 is omitted and the telescopic boom 26 is then pivotally mounted on the turret 22 so as to be able to raise and lower the telescopic boom 26 by changing its inclination relative to the turret 22. The lifting platform 1 is then of the type commonly referred to as a telescopic platform (usually referred to as "telescopic boom lift" in English).

[0038] The telescopic boom 26 typically has a hollow tubular structure. It is composed of several hollow boom sections inserted into one another in a sliding manner to provide its telescopic characteristic. These boom sections typically have the shape of open boxes at their opposite ends. They preferably have a square or rectangular cross-section, or any other shape that prevents them from pivoting relative to one another around the longitudinal axis of the telescopic boom 26.

[0039] For convenience, in the described embodiment, the telescopic boom 26 has only two boom sections, namely an outer boom section 26a mounted on its lower side on the upper end of the pantographic articulated arm 24 and an inner boom section 26b mounted sliding in the outer boom section 26a so as to be able to be retracted into the outer boom section 26a and to be able to protrude out of the outer section 26a.

[0040] The pendulum arm 30 is pivotally mounted at the upper end of the telescopic boom 26 so that it can be raised and lowered relative to the telescopic boom 26: see boom F4 in [Fig. 2]. The pendulum arm 30, being shorter than the telescopic boom 26, allows the elevation height of the work platform 10 to be adjusted locally without affecting the pantographic articulated arm 24 or the telescopic boom 26.

[0041] The pendulum arm 30 has a deformable parallelogram structure, which makes it possible to keep the angle of inclination of the work platform 10 constant relative to the horizontal - and more particularly to keep it horizontal when the lifting platform 1 is in use - when the pendulum arm 30 is raised or lowered relative to the telescopic boom 26.

[0042] The work platform 10 is pivotally mounted on the pendulum arm 30 around an axis extending vertically when the lifting platform 1 is in use, i.e. when the floor 12 of the work platform 10 is horizontal.

[0043] The lifting platform 1 includes actuators assigned to each of the aforementioned movements of the lifting mechanism 20 which are controlled by on-board electronics of the lifting platform 1 according to commands entered at the control panel 16 by an operator.

[0044] In the prior art, these actuators are usually hydraulic cylinders, except for the rotation of the turret 22. Figure 4 illustrates, in isolation, a longitudinal cross-sectional view of the telescopic boom 26, but according to a prior art design, which is why it is referenced as 26' in Figure 4. The other reference numbers remain unchanged for identical or corresponding parts. The lower end of the outer boom section 26a is fixedly mounted on a mounting bracket 27. The mounting bracket 27 is pivotally mounted about a horizontal axis on a connecting piece 25 forming part of the upper end of the pantographic articulated arm 24, thus allowing the inclination of the telescopic boom relative to the pantographic articulated arm 24 to be varied.A hydraulic cylinder 41 is housed inside the boom sections 26a and 26b, its body being fixed to the mounting bracket 27, while the free end of its rod is fixed to the inner boom section 26b. The hydraulic cylinder 41 thus allows the telescopic boom 26 to be selectively shortened or lengthened by retracting the inner boom section 26b into the outer boom section 26a or by extending the inner boom section 26b out of the outer boom section 26a. Another hydraulic cylinder 42, mounted between the mounting bracket 25 and the outer boom section 26a, allows the inclination of the telescopic boom 26 to be varied relative to the pantograph arm 24.Two other hydraulic cylinders 43a, 43b arranged in master / slave in the same hydraulic circuit define a leveling system for the work platform 10 which has the function, when the lifting platform 1 is in use, of keeping the floor 12 of the work platform 10 substantially horizontal when the inclination of the telescopic boom 26' is changed by means of the hydraulic cylinder 42. .

[0045] To replace the hydraulic circuit of any machine with purely electrical solutions, it is common practice – as already mentioned – to replace its hydraulic cylinders with electric cylinders. In the present case, this involves replacing the cylinders 41 and 42 of the telescopic boom 26' in [Fig. 4] with equivalent electric cylinders in terms of power and rod extension length. Since a simple replacement of the master / slave hydraulic cylinders 43a and 43b with electric cylinders is not possible, the leveling system for the work platform 10 can be modified by omitting cylinder 43a and replacing hydraulic cylinder 43b with an equivalent electric cylinder.The extension length of the rod of the electric cylinder replacing the hydraulic cylinder 43b can be controlled by on-board electronics of the aerial work platform 1 as a function of a sensor determining the angle of inclination of the telescopic boom 26 relative to the pantographic articulated arm 24 or relative to the chassis 2. .

[0046] As the use of an electric cylinder has the disadvantage of being by design more bulky and heavier compared to a hydraulic cylinder and its installation more complicated, the replacement of the hydraulic cylinder 41 housed inside the telescopic boom 26' by an electric cylinder can prove to be delicate.

[0047] Figures 5 to 7 illustrate a preferred embodiment of the telescopic boom 26 according to the invention which implements a reliable electrical solution which is simpler and more compact than an electric cylinder to replace the hydraulic cylinder 41. As already mentioned, the hydraulic cylinder 42 is preferably replaced by an electric cylinder 142 and the hydraulic cylinder 43b is preferably replaced by an electric cylinder 143 while the hydraulic cylinder 43a is eliminated.

[0048] In the following, the description focuses on the electrical replacement solution for the hydraulic cylinder 41, namely an electric actuator referenced 50. The electric actuator 50 comprises a screw-nut system 70 and a rotary drive block 60. The screw-nut system comprises a screw 71 and a nut 72 mounted in a helical connection on the screw 71.

[0049] The screw-nut system 70 is completely housed inside the boom sections 26a, 26b. The longitudinal axis A of the screw 71 extends substantially along the longitudinal axis of the telescopic boom 26. The nut 72 is pivotally mounted on the inner wall of the inner boom section 26b along an axis perpendicular to the longitudinal axis A of the screw 71. Consequently, the nut 72 is immobilized relative to the inner boom section 26b both in translation along the longitudinal axis A of the screw 72 and in rotation about the longitudinal axis A of the screw 71. This pivotal mounting of the nut 72 in the inner boom section 26b can be achieved by any suitable means, such as two half-axes – not shown – fixed to two opposite faces of the inner boom section 26b and entering two corresponding recesses formed on two opposite radial sides of the nut 72.Each half-axis may have a base or be fixed to a clevis which serves to fix it to the corresponding outer wall of the inner boom section 26a, each half-axis protruding inside the inner boom section 26a through a corresponding opening provided in the wall of the inner boom section 26a. The base or clevis has a limited thickness so that it can be placed in the interstitial space between the inner wall of the outer boom section 26a and the outer wall of the inner boom section 26b without interfering with the outer boom section 26a.

[0050] The screw 71 is supported so as to be immobilized in translation relative to the external arrow section 26 in the longitudinal direction A of the screw 71.

[0051] The rotary drive block 60 is used to rotate the screw 71 of the screw-nut system 70 about its longitudinal axis A. When the rotary drive block 60 rotates the screw 71, the rotation of the screw 71 causes a translation of The nut 72 along the screw 71 results in a translation of the inner boom section 26b relative to the outer boom section 26a. The rotary drive block 60 thus allows the inner boom section 26b to be retracted into the outer boom section 26a or extended outwards from the outer boom section 26a, depending on the direction of rotation applied by the rotary drive block 60 to the screw 71.

[0052] In the embodiment shown, the rotating drive block 60 is completely arranged inside the outer boom section 26a, which makes its installation simple and protects it against impacts with elements external to the telescopic boom 26 and also to some extent against weathering and dirt from outside the telescopic boom 26.

[0053] The rotary drive block 60 is mounted so as to be immobilized with respect to the outer boom section 26a both in translation in the direction of the longitudinal axis A of the screw 71 and in rotation around the longitudinal axis A of the screw 71.

[0054] In the embodiment shown, the rotating drive block 60 is mounted on the mounting bracket 27, on which the lower end of the outer boom section 26a is fixedly mounted. As mentioned with reference to [Fig. 4], the mounting bracket 27 is pivotally mounted about a horizontal axis on a connecting piece 25 forming part of the upper end of the pantographic articulated arm 24, thus allowing the inclination of the telescopic boom 26 relative to the pantographic articulated arm 24 to be varied. According to another embodiment in which the lifting platform 1 is a telescopic platform, the pantographic articulated arm 24 is omitted and the mounting bracket 27 is pivotally mounted about a horizontal axis directly on the turret 22.

[0055] In another embodiment, the rotary drive block 60 is mounted not on the mounting support 27, but directly to the outer boom section 26a.

[0056] In more detail, the rotary drive block 60 has a body provided with a mounting bearing 61 for mounting the rotary drive block 60 pivotally on the mounting support 27 - or on the outer boom section 26a - around a mounting axis extending transversely to the longitudinal axis A of the screw 71. This mounting axis extends parallel to the pivot axis of the nut 72 with respect to the inner boom section 26b.

[0057] According to one embodiment, the output shaft of the rotary drive block 60 and the screw 71 are made as a single unit; in other words, they form a single piece from a single material. According to another embodiment, the rotary drive block 60 comprises an output shaft coupled to the screw 71.

[0058] In the embodiment shown, the screw 71 is supported only by the rotating drive block 60 on the one hand and by the nut 72 on the other. Other Various methods can be used to support the rotating drive block 60 and / or the screw 71. For example, the screw 71 can be supported at its free end by a sliding bearing mounted in the inner boom section 26b. It can also be supported on the side of the rotating drive block 60 by a bearing fixed in the outer boom section 26a in cases where, contrary to the embodiment shown, the inner boom section 26b, when fully retracted into the outer boom section 26a, does not extend to this point in the outer boom section 26a.

[0059] The rotary drive block 60 can be made in a manner known per se, similar to that of an electric actuator. It comprises an electric motor whose direction of rotation is reversible so as to drive the screw 71 in two opposite directions of rotation. It may also include a speed reducer to reduce the rotational speed applied to the screw 71 by the electric motor. It may also include an electromagnetic brake to selectively block the rotation of the screw 71.

[0060] The rotary drive unit 60 may include other components useful for controlling the electric motor. In particular, it may include a rotary shaft encoder to determine the amount of rotation of the screw 71 in order to determine the position of the nut 72 along the screw 71 and thus the degree of extension of the inner boom section 26b out of the outer boom section 26a. This may conventionally be an optical or electromagnetic encoder, or of another type. The rotary drive unit 60 may also include a tachogenerator to control the rotational speed of the electric motor. The rotary drive unit 60 may also include a load limiter to stop the electric motor in case of overload.

[0061] For safety purposes, limit switches may also be provided to detect the extreme positions of the nut 72 on the screw 71.

[0062] The power of the electric motor is chosen to be sufficient to operate the screw-nut system 70, taking into account the maximum load to be moved vertically using the work platform 10 for which the aerial work platform 1 is designed. The technology and dimensions of the screw-nut system 70 are similarly chosen to be suitable for operating the telescopic boom 26, taking into account the maximum load to be moved vertically. In particular, a ball screw, a screw with one or more trapezoidal threads, or any other suitable type of screw may be used.

[0063] As can be seen in [Fig. 6], the boom sections 26a, 26b together define an internal space 80 in which the screw-nut system 70 is housed. This internal space 80 is delimited radially by the boom sections 26a, 26b. Consequently, the boom sections 26a, 26b protect the screw-nut system 70 against impacts with objects or obstacles external to the boom. telescopic 26. Therefore, it is unnecessary to provide parts or sub-assemblies dedicated to protecting the screw-nut system 70 against such shocks.

[0064] The boom sections 26a, 26b also protect – at least to a sufficient extent – ​​the screw-nut system 70 against weathering and dirt coming from the radially external side of the telescopic boom 26. From this point of view, it is generally acceptable for the walls of the boom sections, in particular those of the external boom section 26b, to have access openings for assembly, servicing or maintenance of the telescopic boom, for example to access the rotating drive block 60 or the screw-nut system 70. These access openings may optionally be closed by removable hoods or covers to limit or eliminate the intrusion of dirt.Furthermore, in a conventional manner, a guide bearing 41 is arranged on the outside of the inner boom section 26b on its lower side, i.e., the side facing the mounting bracket 27, in other words, towards the foot of the telescopic boom 26. Another guide bearing 42 is arranged on the inside of the outer boom section 26a at its upper end, i.e., the side facing the end of the telescopic boom 26, which supports the work platform 10. The guide bearings 41 and 42 serve to guide the sliding movement of the inner boom section 26b within the outer boom section 26a. The bearings 41 and 42 provide, to a certain extent, a seal between the outer boom section 26a and the inner boom section 26b, limiting the penetration of dirt into the internal space 80.

[0065] Where appropriate, measures may also be provided to limit the risks of fouling of the screw-nut system 70, for example by equipping one side of the nut 72 or both with a brush scraping the screw 71.

[0066] A first longitudinal portion 71a of the screw 71, located on the side 72a of the nut 72 towards the foot of the telescopic boom 26, is contained within a first longitudinal portion 80a of the chamber 80, which is delimited in the radial direction of the screw 71 by the boom sections 26a, 26b. The length of this first longitudinal portion of the screw 71 and of the first longitudinal portion 80a of the chamber 80 vary with the position of the nut 72 on the screw 71 and therefore with the degree of extension of the inner boom section 26b out of the inner boom section 26a. As can be seen, the first longitudinal portion 71a of the screw 71 is exposed within the first longitudinal portion 80a of the chamber 80.As a result, the first longitudinal part 71a of the screw 71 is protected against impacts with external objects or obstacles and, at least to some extent, against weathering and dirt coming from the radially external side of the telescopic boom 26 only by the boom sections 26a, 26b. In contrast, if an electric cylinder were used instead of the electric actuator 50, the first longitudinal part 71a of the screw 71 would have been enclosed. by the cylinder body - see reference 100 on [Fig.3] - in addition to the boom sections 26a, 26b. Compared to using an electric cylinder, the electric actuator 50 therefore eliminates the need for the cylinder body.

[0067] A second longitudinal portion 71b of the screw 71, located on the side 72b of the nut 72 towards the upper end of the telescopic boom 26, is contained within a second longitudinal portion 80b of the chamber 80, which is delimited radially by the inner boom section 26a. The length of this second longitudinal portion of the screw 71 also varies with the position of the nut 72 on the screw 71, but the length of the second chamber 80b is fixed. The second longitudinal portion 71b of the screw 71 is exposed within the second chamber 80b.Consequently, the second longitudinal section 71b of the screw 71 is protected against impacts with external objects or obstacles, and at least to some extent against weathering and dirt coming from the radially external side of the telescopic boom 26, solely by the inner boom section 26b, possibly reinforced by the outer boom section 26a when the inner boom section 26b is retracted, at least partially, into the outer boom section 26a. Conversely, if an electric cylinder were used instead of the electric actuator 50, the second longitudinal section 71b of the screw 71 would have been enclosed by the cylinder rod tube – see reference 110 in [Fig. 3] – in addition to the boom sections 26a and 26b. Compared to using an electric cylinder, the electric actuator 50 therefore also eliminates the need for the cylinder rod tube.

[0068] It will be noted that the first longitudinal portion 7la of the screw 71 and the second longitudinal portion 71b of the screw 71, together with the portion of the screw 71 overlapped by the nut 72, correspond at least to the threaded portion of the screw 71 through which the nut 72 passes for a maximum sliding stroke of the inner boom section 26b relative to the outer boom section 26a. In other words, the entire working portion of the screw 71 is protected by the boom sections 26a, 26b against impacts with external objects or obstacles and at least to some extent against weathering and dirt coming from the radially external side of the telescopic boom 26.

[0069] It is advantageous that the first longitudinal part 80a of the chamber 80 be partially or completely open on the side of the foot of the telescopic boom 26, in order to allow the evacuation by gravity of dirt that may enter the chamber 80.

[0070] It is preferable that the second longitudinal section 80b of the chamber 80 be closed at its end towards the upper side of the telescopic boom 26 in order to limit the penetration of dirt into the chamber 80. This can be achieved by means of the mounting bracket 29 fixed to the upper end of the inner boom section 26b on which the pendulum arm 30 is pivotally mounted. However, it is not essential that the upper end of the second longitudinal section 80b of the chamber 80 be closed, as dirt entering the chamber 80 can be expelled to the outside through the lower end of the outer boom section 26a. The outer contour of the nut 72 can be chosen to provide a sufficiently large space between the nut 72 and the inner walls of the inner boom section 26b to facilitate the passage of dirt from the second longitudinal section 80b of the chamber 80 to the first longitudinal section 80a of the chamber 80.

[0071] The electric actuator 50 is therefore more compact than an electric cylinder since it has neither a body dedicated to the image of the cylinder body 100 of [Fig.3], nor a tube dedicated to the image of the tube forming the cylinder rod 110 of [Fig.3] to house the screw-nut system 50. In fact, it is noted that the boom sections 26a, 26b and the electric actuator 50 together form an electric cylinder having a cylinder body formed by the outer boom section 26a and a cylinder rod formed by the inner boom section 26b.

[0072] According to another embodiment, either the first longitudinal portion 71a of the screw 71 or the second longitudinal portion 71b of the screw 71 may be contained within a dedicated part forming a protective housing, similar to a cylinder body or a cylinder rod tube. Such an embodiment eliminates the need for one or the other of the dedicated housing parts, as appropriate. The embodiment shown in the figures is nevertheless preferable, since it eliminates the need for such parts for both longitudinal portions 71a and 71b of the screw 71.

[0073] As mentioned, the rotary drive block 60 is housed inside the telescopic boom 26. For compactness reasons, it is preferable that the axis of rotation of the electric motor of the rotary drive block 60 be collinear with the longitudinal axis A of the screw 71 of the screw-nut system 70. The longitudinal axis A of the screw 71 of the screw-nut system 70 is preferably coincident with the longitudinal axis of the boom sections 26a, 26b, which ensures a balancing of the screw thrust on the inner boom section 26b.

[0074] According to another embodiment not shown, the longitudinal axis A of the screw 71 of the screw-nut system 70 extends parallel to the longitudinal axis of the boom sections 26a, 26b, but offset. This can, in particular, make it easier to accommodate the rotary drive block 60 if its electric motor is radially offset relative to the screw-nut system 70; in other words, if the output axis of the electric motor is parallel to the longitudinal axis A of the screw 71 while being radially offset from it.

[0075] According to yet another embodiment, the electric motor of the rotary drive block 60 is arranged outside the outer boom section 26a. In this case, the output shaft of the electric motor is connected to the screw 71 of the screw-nut system 70 via a transmission, for example, a belt drive or a gear or gear train that may include the speed reducer of the rotary drive unit. In this case, the mounting bracket 27 is adapted and / or an additional block is provided for the proper mounting of the electric motor and the transmission. This embodiment is illustrated in [Fig. 8], in which the electric motor and the transmission are symbolized by the letters M and T, respectively.

[0076] The rotary drive unit 60 is connected to an on-board electronics system of the lifting platform 1 to control its electric motor according to the commands entered by the operator at the control panel 16 and taking into account in particular the signals from the sensors with which the rotary drive unit 60 is equipped.

[0077] Of course, the present invention is not limited to the examples and embodiments described and illustrated, but is susceptible to numerous variations accessible to those skilled in the art, which fall within the scope of the claims. Thus, the invention is applicable to a telescopic boom comprising more than two boom sections inserted one into the other in a telescopic manner. In this case, as is known when a hydraulic cylinder is used, a pulley system can be used to extend or retract an additional boom section and / or by using several electric actuators 50, each associated with a respective pair of boom sections.

[0078] According to other embodiments, the arrangement of the electric actuator 50 in the boom sections 26a, 26b of the embodiment shown in Figures 5 to 7 is modified, although this is preferred due to its simplicity of implementation. In the embodiment shown in Figures 5 to 7, this arrangement consists in the screw 71 being driven in rotation while being fixed in translation relative to the outer boom section 26a in the direction of the longitudinal axis A of the screw 71, while the nut 72 is fixed relative to the inner boom section 26b both in translation in the direction of the longitudinal axis A of the screw 71 and in rotation about the longitudinal axis A of the screw 71.According to another embodiment, the arrangement consists of fixedly mounting the screw 71 of the screw-nut system 70 in the outer boom section 26a, while the rotary drive block 60 is provided to rotate the nut 72, the rotary drive block 60 being fixedly arranged inside the inner boom section 26b. According to yet another embodiment, the telescopic boom 26 is mounted inverted with respect to the embodiment shown in [Fig. 6] so that the foot of the telescopic boom becomes the upper end of the telescopic boom and vice versa. In other words, the nut 72 is fixedly arranged in . the lower boom section - that is to say on the foot side of the telescopic boom - which is this time the inner boom section while the screw 72 is mounted in the upper boom section which is this time the outer boom section, the rotating drive block 60 fixedly associated with the outer boom section on the side towards the upper end of the telescopic boom.

Claims

Demands

1. Telescopic boom (26) for a lifting platform (1) wherein the telescopic boom is intended to support and move a working platform (10) of a lifting platform (1) upwards, the telescopic boom (26) comprising: - two boom sections (26a, 26b) which are hollow, one forming an inner boom section (26b) and the other an outer boom section (26a) into which the inner boom section (26b) is inserted telescopically, and - an electric actuator (50) comprising: • a screw-nut system (70) comprising a screw (71) and a nut (72) mounted on the screw, the screw-nut system being housed inside the boom sections (26a, 26b) to selectively retract the inner boom section (26b) into the outer boom section (26a) and extend the inner boom section (26b) out of the outer boom section (26a). external arrow (26a),and • a rotary drive block (60) with an electric motor and reversible direction of rotation for actuating the screw-nut system (70), in which at least a portion (71a; 71b) of the screw (71) is contained and exposed in a chamber (80) delimited in the radial direction by at least one of the arrow sections (26a, 26b).

2. Telescopic boom according to claim 1, which is devoid of an interposed element between said part (71a; 71b) of the screw (71) and at least one boom section (26a; 26b) to protect said part of the screw against impacts with external elements foreign to the telescopic boom.

3. Telescopic boom according to claim 1 or 2, which is devoid of any part or subassembly arranged in interposition between said part (71a; 71b) of the screw (71) and at least one boom section (26a; 26b) and forming a rigid envelope around said part (71a; 71b) of the screw (71).

4. Telescopic boom according to any one of claims 1 to 3, wherein: - the nut (72) has a first side (72a) and a second side (72b), which are two opposite sides of the nut (72) in the longitudinal direction of the screw (71), - a first longitudinal portion (71a) of the screw (71) located on the first side (72a) of the nut (72) is contained and exposed in a first longitudinal portion (80a) of the chamber (80), which first longitudinal portion (80a) of the chamber (80) is delimited in the radial direction by at least one of the arrow segments (26a, 26b), and - a second longitudinal portion (71b) of the screw (71) located on the second side (72b) of the nut (72) is contained and exposed in a second longitudinal portion (80b) of the chamber (80), which second longitudinal portion (80b) of the chamber (80) is delimited in the radial direction by at least one of the arrow sections (26a, 26b).

5. Telescopic boom according to claim 4, wherein the first longitudinal part (71a) of the screw (71) and the second longitudinal part (71b) of the screw (71) together with the part of the screw (71) crossed by the nut (72) comprise at least the threaded part of the screw (71) which is traversed by the nut (72) for a maximum sliding stroke of the inner boom section (26b) relative to the outer boom section (26a).

6. Telescopic boom according to any one of claims 1 to 5, in which the screw (71) is totally contained and exposed in the chamber (80) which chamber is delimited in the radial direction by the boom sections (26a, 26b) for the entire length of the screw (71).

7. Telescopic boom according to any one of claims 1 to 6, wherein the rotating drive block (60) is completely housed inside the boom sections (26a, 26b).

8. Telescopic boom according to any one of claims 1 to 7, wherein the axis of rotation of the electric motor of the rotating drive block (60) is collinear with the longitudinal axis (A) of the screw (71) of the screw-nut system (70).

9. Telescopic boom according to any one of claims 1 to 6, wherein the electric motor (M) of the rotating drive unit (60) is mounted outside one of the boom sections (26a), the electric motor (M) driving the screw-nut system (70) by means of a motion transmission device (T).

10. Telescopic boom according to any one of claims 1 to 9, wherein: - the nut (72) of the screw-nut system (70) is connected to the inner boom section (26b) so as to be immobilized relative to the inner boom section (26b) both in translation in the direction of the longitudinal axis (A) of the screw (71) and in rotation about the longitudinal axis (A) of the screw (71), and - the screw (71) of the screw-nut system (70) is arranged inside the outer boom section (26a) so as to be immobilized in translation relative to the outer boom section (26a) in the direction of the longitudinal axis (A) of the screw (71), the rotating drive block (60) being arranged to drive the screw (71) of the screw-nut system (70) in rotation.

11. Telescopic boom according to claim 10, wherein: - the nut (72) is pivotally mounted on the inner wall of the inner boom section (26b) along an axis perpendicular to the longitudinal axis (A) of the screw (71), - the screw 71 is supported only by the rotating drive block (60) on one side and by the nut (72) on the other, and - the rotating drive block (60) has a body provided with a mounting bearing (61) for pivotally mounting the rotating drive block (60) to the outer boom section (26a) about a mounting axis extending transversely to the longitudinal axis (A) of the screw (71), said mounting axis extending parallel to the pivot axis of the nut (72) with respect to the inner boom section (26b), the mounting support (27).

12. Telescopic boom according to claim 10, wherein: - the lower end of the outer boom section (26a) is fixedly mounted on a mounting bracket (27) designed to be pivotally mounted about a horizontal axis directly on a turret (22) or on a connecting piece (25) forming part of the upper end of a pantographic articulated arm (24), - the nut (72) is pivotally mounted on the inner wall of the inner boom section (26b) along an axis perpendicular to the longitudinal axis (A) of the screw (71), - the screw 71 is supported only by the rotary drive block (60) on one side and by the nut (72) on the other, and - the rotary drive block (60) has a body provided with a mounting bearing (61) for pivotally mounting the rotary drive block (60) on the mounting bracket (27) about a mounting axis extending transversely to the longitudinal axis (A) of the screw (71),said mounting axis extending parallel to the pivot axis of the nut (72) relative to the inner arrow section (26b), the mounting support (27).

13. Telescopic boom according to claim 10, 11 or 12 wherein the nut (72) of the screw-nut system (70) is connected to the inner boom section (26b) in an end region of the inner boom section (26b) through which the inner boom section (26b) is inserted into the outer boom section (26a).

14. Telescopic boom according to any one of claims 1 to 13, wherein the outer boom section (26a) is located on the foot side of the telescopic boom (26) and the inner boom section (26b) is located on the opposite side of the foot of the telescopic boom (26).

15. Telescopic boom according to any one of claims 1 to 14, wherein the two boom sections (26a, 26b) and the electric actuator (50) together form an electric cylinder having a cylinder body formed by the outer boom section (26a) and a cylinder rod formed by the inner boom section (26b).

16. Lifting platform (1), comprising a telescopic boom (26) according to any one of claims 1 to 15 and a work platform (10) supported by the telescopic boom (26).

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