telescopic boom for lifting platform and lifting platform including it

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 comprises a screw-nut system 70, housed at least partly in the boom sections 26a, 26b, which serves to retract and protrude the inner boom section 26b relative to the outer boom section 26a. It also comprises 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 in a chamber 80 delimited in the radial direction by at least one of the boom sections 26a, 26b. This design of the electric actuator 50 gives it compactness and lightness, the boom sections 26a, 26b protecting all or part of the screw against impacts.

Description

Title of the invention: telescopic boom for lifting platform and lifting platform comprising it

[0001] The present invention relates to a telescopic boom for a lifting platform, which telescopic boom is provided for supporting and moving in height a work platform of the lifting platform. The invention also relates to a lifting platform comprising such a telescopic boom.

[0002] Lifting platforms are machines designed to allow one or more people to work at height. To this end, they comprise a working platform designed to accommodate them and possibly also loads such as equipment and tools or materials such as paint, cement, etc. The working platform comprises a tray surrounded by a guardrail. It is supported by a lifting mechanism which allows it to be raised from a lowered position on the chassis of the lifting platform to a desired working position at height. The working platform is equipped with a control panel allowing an operator on board it to cause the working platform to move to reach the desired working position.

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

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

[0005] Traditionally, lifting platforms are equipped with a hydraulic circuit including at least one hydraulic pump to power, among other things, hydraulic cylinders used to manage the inclination 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 lifting platform is intended for outdoor use or indoor use.

[0006] A recent trend, however, is to develop electrically powered lifting platforms even when they are intended for outdoor use, with the aim of limiting environmental and noise pollution and allowing both indoor and outdoor use: see for example WO 2020 / 157094 A2.

[0007] The present invention is concerned with going further in the electrification of telescopic boom lifting platforms by contributing to the replacement of the hy hydraulics by electrical solutions. Indeed, the hydraulic circuit with its components has disadvantages, particularly in terms of efficiency and pollution due to possible leaks of hydraulic fluid.

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

[0009] To this end, the present invention provides a telescopic boom for a lifting platform, which telescopic boom is intended to support and move in height a work platform of a lifting platform, the telescopic boom comprising two boom sections which are hollow, one forming an inner boom section and the other an outer boom section into which the inner boom section is telescopically inserted. The telescopic boom also comprises an electric actuator. This electric actuator comprises a screw-nut system comprising a screw and a nut mounted on the screw, the screw-nut system being housed inside the boom sections to selectively retract the inner boom section into the outer boom section and protrude the inner boom section from the outer boom section.This electric actuator also comprises a rotary drive block with an electric motor and reversible direction of rotation for actuating the screw-nut system. At least a portion of the screw is contained and exposed in a chamber delimited in the radial direction 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 on-board electronics of the lifting platform to control it. More particularly, the on-board electronics controls the rotary drive unit to retract the telescopic boom or extend it according to the commands entered by an operator at a control panel of the lifting platform.

[0011] According to the invention, at least a portion of the screw of the screw-nut system is contained and exposed in a chamber delimited in the radial direction 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 screw portion. 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 a subassembly forming around it a radially closed rigid envelope interposed between this part of the screw and the arrow sections. This characteristic brings both a simplification of the electric actuator and a limitation of its size, weight and cost compared to the use of an electric cylinder while providing the same level of reliability. It is common to replace the hydraulic cylinders of any machine with electric cylinders when it is desired to replace the hydraulic circuit with purely electric solutions. A simplified kinematic diagram of an electric cylinder is shown in [Fig.3]. An electric cylinder generally comprises a screw-nut system 170 whose 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 is fixed the rotary drive block 160 unless it is also housed in the cylinder body 100.The cylinder rod 110 is usually formed by a tube fixedly associated with the nut 172 of the screw-nut system 170 and closed at its free end, the tube forming the cylinder rod 110 being slidably mounted in the cylinder body 100. The cylinder rod 110 is made in the form of 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 drives the cylinder rod 110 with it in translation. 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, due to its design, more bulky and heavier than a hydraulic cylinder and its installation more complicated. As a result, the installation of an electric cylinder in place of a hydraulic cylinder inside the telescopic boom of a lifting platform can be tricky and make the telescopic boom heavier.

[0014] Compared to the use of an electric cylinder as a replacement for a hydraulic cylinder in a telescopic boom of a lifting platform, the design of the telescopic boom according to the invention makes it possible to do without 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 fulfill the function of protecting 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 in the radial direction by at least one of the boom sections against weather and dirt coming from the side radially outside the telescopic boom. This protection is not necessarily total. In other words, the boom section(s) boom sections, as the case may be, do not necessarily provide a complete seal to the chamber containing the relevant part of the screw of the screw-nut system against dirt and bad weather from the outside. Indeed, the walls of the boom sections, in particular those of the outer boom section, may have access openings used for assembly, maintenance or servicing operations of the telescopic boom. These access openings may possibly be closed by removable covers or hoods to limit or eliminate the intrusion of dirt. In addition, the bearings or other guide elements arranged where appropriate between the boom sections to ensure their relative sliding limit to a certain extent the intrusion of dirt into the telescopic boom without providing a complete seal.Furthermore, the upper end of the telescopic boom is not necessarily sealed. For these reasons, it may be useful to provide the lower end of the telescopic boom with one or more openings allowing dirt to be evacuated by gravity from the telescopic boom.

[0016] The fact that dirt can get into the telescopic boom to a certain 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 provided to limit the risks of fouling of the screw-nut system, for example by equipping one side of the nut of the screw-nut system or both with a brush scraping the screw.

[0017] Finally, it will be understood that if the telescopic boom according to the invention is advantageously intended to equip an electric motorized lifting platform, it can nevertheless also be used to equip lifting platforms with an internal combustion engine or even hybrid lifting 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 element interposed between said part of the screw and the at least one boom section 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 subassembly arranged in interposition between said part of the screw and at least one boom section 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 portion of the chamber which first longitudinal portion of the chamber is delimited in the radial direction by at least one of the arrow sections, and a second longitudinal portion of the screw located on the second side of the nut is contained and exposed in a second longitudinal portion of the chamber which second longitudinal portion of the chamber is delimited in the radial direction by at least one of the arrow sections; 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 comprise 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 completely 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 unit is completely housed inside the boom sections; the rotation axis of the electric motor of the rotary drive unit is collinear with the longitudinal axis of the screw of the screw-nut system; the electric motor of the rotary drive unit is mounted outside one of the boom sections, the electric motor driving the screw-nut system by means of 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 rotary 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 side of the telescopic boom foot and the inner boom section is located on the side opposite the telescopic boom foot; the two boom sections and the electric actuator together form an electric cylinder having a cylinder body formed by the boom section exterior and a cylinder rod formed by the interior boom section.

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

[0020] Other aspects, characteristics and advantages of the invention will appear on reading the following description of a preferred embodiment of the invention, given by way of example and with reference to the attached drawing.

[0021] [Fig-1] represents a lifting platform of the articulated platform type which is 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 cylinder.

[0024] [Fig.4] represents a sectional view of the telescopic boom of the lifting platform of 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 tee arrow telescopic of this preferred embodiment which includes the electric actuator of [Fig.5].

[0027] [Fig.7] schematically represents a perspective view of only the sections of boom and the electric actuator of the telescopic boom of [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 as well as a lifting platform 1 which is equipped with it with reference to figures 1, 2 and 5 to 7. It is specified that the references to the horizontal and to the vertical are made in relation to the situation in which the lifting platform 1 rests on a flat horizontal ground.

[0030] Figures 1 and 2 show the lifting platform 1 in the folded state and in the deployed state respectively. The lifting platform 1 comprises a chassis 2 equipped with wheels 4 allowing its translation on the ground. At least two of the wheels 4 are preferably steered. Alternatively or in combination with wheels, the chassis 2 is equipped with tracks for the same purposes. The chassis 2 is motorized to ensure the autonomous movement of the lifting platform 1 on the ground. This is preferably an electric motor powered by an autonomous source of rechargeable electrical energy mounted on board the lifting platform 1 such as a battery or a fuel cell. Alternatively, the lifting platform 1 is not self-propelled, but is intended to be towed by a separate vehicle.

[0031] The lifting platform 1 comprises a lifting mechanism 20 supporting a work platform 10 intended to receive on board personnel and equipment for carrying out work at height. The work platform 10 comprises a floor 12 and a guardrail 14. A control panel 16 is arranged fixedly or removably 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 in height to the desired position as well as 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 at the upper end of the pantographic articulated arm 24 and a pendulum arm 30 mounted by 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 pivotally mounted about a vertical axis on the chassis 2, which makes it possible to modify the orientation of the rest of the lifting mechanism 20 and of the platform 10 relative to the chassis 2.

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

[0035] As best seen in [Fig. 2], the pantographic articulated arm 24 comprises two parallelograms 24a and 24b arranged so as to be able to unfold and fold in the manner of 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 possibility of movement illustrated by the arrow F1 in [Fig. 2]. As a result, the pantographic articulated arm 24 allows the telescopic boom 26 to be raised and lowered without modifying the angle of the latter relative to the chassis 2.

[0036] The telescopic boom 26 is pivotally mounted at the upper end of the articulated pantographic arm 24 in order to be able to raise and lower the telescopic boom 26 by modifying its inclination relative to the articulated pantographic 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 articulated pantographic arm 24 is omitted and the telescopic boom 26 is then pivotally mounted on the turret 22 to be able to raise and lower the telescopic boom 26 by modifying its inclination relative to the turret 22. The lifting platform 1 is then of the type commonly called a telescopic platform (usually called “telescopic boom lift” in English).

[0038] The telescopic boom 26 conventionally has a hollow tubular structure. It is composed of several hollow boom sections inserted into each other in a sliding manner to provide its telescopic character. These boom sections conventionally have a box shape open at their opposite ends. They preferably have a cross section of square or rectangular shape or any other shape preventing them from pivoting relative to each other 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 by its lower side on the upper end of the pantographic articulated arm 24 and an inner boom section 26b slidably mounted in the outer boom section 26a so as to be retractable 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 arrow F4 in [Fig.2]. The pendulum arm 30, which is shorter than the telescopic boom 26, makes it possible to locally adjust the elevation height of the work platform 10 without acting on the articulated pantographic 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 about an axis extending vertically when the lifting platform 1 is in use, that is to say when the floor 12 of the work platform 10 is horizontal.

[0043] The lifting platform 1 comprises 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 as a function of 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. [Fig. 4] illustrates in isolation a longitudinal sectional view of the telescopic boom 26, but according to a design of the prior art, which is why it is referenced 26' in [Fig. 4]. Other reference numbers are 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 mounted pivotally about a horizontal axis on a connecting piece 25 forming part of the upper end of the pantographic articulated arm 24, which makes it possible to vary the inclination of the telescopic boom relative to the pantographic articulated arm 24. A hydraulic cylinder 41 is housed inside the boom sections 26a, 26b, its body being fixed on the mounting bracket 27 while the free end of its rod is fixed to the inner boom section 26b inside the latter. The hydraulic cylinder 41 thus makes it possible to selectively shorten or lengthen the telescopic boom 26 by retracting the inner boom section 26b into the outer boom section 26a or by protruding 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 makes it possible to vary the inclination of the telescopic boom 26 relative to the articulated pantographic arm 24. Two other hydraulic cylinders 43a, 43b arranged in master / slave mode in the same hydraulic circuit define a system for maintaining the level of the work platform 10, the function of which, when the lifting platform 1 is in use, is to keep the floor 12 of the work platform 10 substantially horizontal when the inclination of the telescopic boom 26' is modified by means of the hydraulic cylinder 42.

[0045] To replace the hydraulic circuit of any machine with purely electric solutions, it is usual - as already mentioned - to replace its hydraulic cylinders with electric cylinders. In the present case, this consists for the telescopic boom 26' of [Fig.4] in replacing the cylinders 41 and 42 with electric cylinders equivalent in terms of power and extension length of its rod. A simple replacement of the hydraulic cylinders 43a, 43b arranged in master / slave by electric cylinders not being possible, the system for maintaining the level of the work platform 10 can be modified by omitting the cylinder 43a and replacing the 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 lifting platform 1 as a function of a sensor determining the angle of inclination of the telescopic boom 26 relative to the articulated pantographic arm 24 or relative to the chassis 2.

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

[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 4L As already mentioned, the hydraulic cylinder 42 is preferably replaced by a cylinder electric cylinder 142 and the hydraulic cylinder 43b is preferably replaced by an electric cylinder 143 while the hydraulic cylinder 43a is deleted.

[0048] In the following, the description focuses on the electrical solution for replacing 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. As a result, the nut 72 is immobilized relative to the inner boom section 26b both in translation in the direction of 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 illustrated - fixed on two opposite faces of the inner boom section 26b and penetrating into two corresponding housings made on two opposite radial sides of the nut 72.Each half-axis may have a base or be fixed on a yoke which serves for fixing on the corresponding outer wall of the inner boom section 26a, each half-axis projecting inside the inner boom section 26a through a corresponding opening made in the wall of the inner boom section 26a. The base or the yoke 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 outer boom 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 and consequently a translation of the inner boom section 26b relative to the outer boom section 26a. The rotary drive block 60 thus makes it possible to retract the inner boom section 26b into the outer boom section 26a or to cause the inner boom section 26b to protrude 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 rotary drive block 60 is completely arranged inside the outer boom section 26a, which makes its ins simple installation and protects it against impacts with elements external to the telescopic boom 26 and also to a certain extent against weather and dirt coming from outside the telescopic boom 26.

[0053] The rotary drive block 60 is mounted so as to be immobilized relative to the outer boom section 26a 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.

[0054] In the embodiment shown, the rotary drive unit 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, which makes it possible to vary the inclination of the telescopic boom 26 relative to the pantographic articulated arm 24. According to another embodiment in which the aerial work platform 1 is a telescopic work 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 bracket 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 pivotally mounting the rotary drive block 60 on the mounting bracket 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 relative 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 in one piece, in other words they form a single piece made from one 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 rotary drive block 60 on the one hand and by the nut 72 on the other hand. Other ways of supporting the rotary drive block 60 and / or the screw 71 can be implemented. For example, the screw 71 can be supported at its free end by a bearing slidably mounted in the inner boom section 26b. It can also be supported on the side of the rotary drive block 60 by a bearing fixed in the outer boom section 26a in the case where, unlike the embodiment shown, the inner boom section 26b retracted to the maximum in the outer boom section 26a does not extend to this level of the outer boom section 26a.

[0059] The rotary drive block 60 can be produced in a manner known per se from the same way as that of an electric jack. It includes an electric motor whose direction of rotation is reversible to be able to drive the screw 71 in the two opposite directions of rotation. It can also include a speed reducer to reduce the rotation speed applied to the screw 71 by the electric motor. It can 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 for determining the amount of rotation of the screw 71 in order to determine the position of the nut 72 along the screw 71 and therefore 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 another type. The rotary drive unit 60 may also include a tachometer dynamo for controlling the rotational speed of the electric motor. The rotary drive unit 60 may further include a force limiter for stopping the electric motor in the event of an overload.

[0061] For safety purposes, limit switch sensors 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 be able to actuate the screw-nut system 70 taking into account the maximum load to be moved in height by means of the work platform 10 for which the lifting platform 1 is designed. The technology and the dimensioning of the screw-nut system 70 are similarly chosen to be capable of actuating the telescopic boom 26 taking into account the maximum load to be moved in height. In particular, a ball screw or 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 delimit an interior space 80 in which the screw-nut system 70 is housed. This interior space 80 is delimited in the radial direction by the boom sections 26a, 26b. Consequently, the boom sections 26a, 26b make it possible to protect the screw-nut system 70 against impacts with objects or obstacles external to the telescopic boom 26. As a result, it is unnecessary to provide parts or subassemblies dedicated to protecting the screw-nut system 70 against such impacts.

[0064] The boom sections 26a, 26b also protect - at least to a certain extent which is sufficient - the screw-nut system 70 against weather and dirt coming from the side radially outside the telescopic boom 26. From this point of view, it is generally acceptable that the walls of the boom sections, in particular those of the outer boom section 26b, have access openings serving for assembly, maintenance or servicing operations of the telescopic boom, for example to access the rotary 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, conventionally, a guide pad 41 is arranged on the outside of the inner boom section 26b at its lower side, i.e. the side towards the mounting bracket 27, i.e. in the direction of the foot of the telescopic boom 26. Another guide pad 42 is arranged on the inside of the outer boom section 26a at its upper end, i.e. on the side towards the end of the telescopic boom 26 by which the working platform 10 is supported. The guide pads 41, 42 serve for sliding guidance of the inner boom section 26b in the outer boom section 26a.The pads 41, 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 inner 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 in 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 in the first longitudinal portion 80a of the chamber 80.As a result, the first longitudinal portion 71a of the screw 71 is protected against impacts with external objects or obstacles as well as, at least to a certain extent, against weather and dirt coming from the side radially outside the telescopic boom 26 only by the boom sections 26a, 26b. On the contrary, if an electric cylinder were used instead of the electric actuator 50, the first longitudinal portion 71a of the screw 71 would have been enveloped by the cylinder body - cf. reference 100 in [Fig. 3] - in addition to the boom sections 26a, 26b. Compared to the use of an electric cylinder, the electric actuator 50 therefore makes it possible to save on 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 in a second longitudinal portion 80b of the chamber 80 which is delimited in the radial direction 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 in the second chamber 80b. As a result, the second longitudinal part 71b of the screw 71 is protected against impacts with external objects or obstacles and at least to a certain extent against weather and dirt coming from the side radially outside the telescopic boom 26 only by the inner boom section 26b possibly doubled by the outer boom section 26a when the inner boom section 26b is retracted at least partly into the outer boom section 26a. On the contrary, if an electric cylinder were used instead of the electric actuator 50, the second longitudinal part 71b of the screw 71 would have been enveloped by the cylinder rod tube - see reference 110 in [Fig. 3] - in addition to the boom sections 26a, 26b. Compared to the use of an electric cylinder, the electric actuator 50 therefore also makes it possible to save on the cylinder rod tube.

[0068] It will be noted that 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 overlapped by the nut 72 correspond at least to 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. In other words, the entire useful part of the screw 71 is protected by the boom sections 26a, 26b against impacts with external objects or obstacles and at least to a certain extent against bad weather and dirt coming from the side radially outside the telescopic boom 26.

[0069] It is advantageous for the first longitudinal part 80a of the chamber 80 to 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 likely to penetrate into the chamber 80.

[0070] It is preferable that the second longitudinal portion 80b of the chamber 80 is 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 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 portion 80b of the chamber 80 is closed because dirt entering the chamber 80 can be evacuated to the outside through the lower end of the outer boom section 26a.The outer contour of the nut 72 may be chosen so as 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 part 80b of the chamber 80 to the first longitudinal part 80a of the chamber 80.

[0071] The electric actuator 50 is therefore more compact than an electric cylinder since it does not have neither body dedicated to the image of the cylinder body 100 of [Fig.3], nor tube dedicated to the image of the tube forming cylinder rod 110 of [Fig.3] to house the screw-nut system 50. In fact, we note 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, it may be provided that either the first longitudinal part 71a of the screw 71, or the second longitudinal part 71b of the screw 71 is contained in a dedicated part forming a dedicated protective envelope in the manner of a cylinder body or a tube forming a cylinder rod. Such an embodiment then makes it possible to save on one or other of the dedicated envelope parts depending on the case. The embodiment shown in the figures is nevertheless preferable since it saves on such parts for the two longitudinal parts 71a, 71b of the screw 71.

[0073] As mentioned, the rotary drive block 60 is housed inside the telescopic boom 26. For reasons of compactness, it is preferable that the axis of rotation of the electric motor of the rotary drive block 60 is 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 balancing of the thrust of the screw 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 is offset. This can in particular make it easier to house the rotary drive unit 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 relative to the latter.

[0075] According to yet another embodiment, the electric motor of the rotary drive unit 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 by means of a transmission, for example a belt transmission or a gear or gear train which 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 by [Fig.8] in which the electric motor and the transmission are symbolized and are designated respectively by the letters M and T.

[0076] The rotary drive unit 60 is connected to on-board electronics of the nacelle lifting device 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 provided.

[0077] Of course, the present invention is not limited to the examples and embodiments described and shown, but it is susceptible of numerous variants accessible to those skilled in the art included within the scope of the claims. Thus, the invention is applicable to a telescopic boom comprising more than two boom sections inserted into each other in a telescopic manner. In this case, as is known when a hydraulic cylinder is used, a hauling system may 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 method 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 method consists in that the screw 71 is 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 method 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 rotary drive block 60 fixedly associated with the outer boom section on the side towards the upper end of the telescopic boom.

Claims

Claims

1. Telescopic boom (26) for a lifting platform (1) which telescopic boom is provided for supporting and moving in height a work platform (10) of a lifting platform (1), 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 telescopically inserted, 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) for selectively retracting the inner boom section (26b) into the outer boom section (26a) and protruding the inner boom section (26b) out of the outer arrow section (26a),and • a rotary drive unit (60) with an electric motor and reversible direction of rotation for actuating the screw-nut system (70), in which at least a part (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 element interposed between said part (71a; 71b) of the screw (71) and the 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 the at least one boom section (26a; 26b) and forming a rigid envelope around said part (71a; 71b) of the screw (71).

4. A 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 sections (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 portion (71a) 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) comprise at least the threaded portion 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. A telescopic boom according to any one of claims 1 to 5, wherein the screw (71) is completely contained and exposed in the chamber (80) which chamber (71) is radially delimited by the boom sections (26a, 26b) for the entire length of the screw (71).

7. A telescopic boom according to any one of claims 1 to 6, wherein the rotary drive unit (60) is completely housed within 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 rotary drive unit (60) is collinear with the longitudinal axis (A) of the screw (71) of the screw-nut system (70).

9. A telescopic boom according to any one of claims 1 to 6, wherein the electric motor (M) of the rotary 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 rotary drive block (60) being arranged to drive the screw (71) of the screw-nut system (70) in rotation.

11. A telescopic boom according to claim 10, 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).

12. A telescopic boom according to any one of claims 1 to 11, wherein the outer boom section (26a) is located on the side of the foot of the telescopic boom (26) and the inner boom section (26b) is located on the side opposite the foot of the telescopic boom (26).

13. A telescopic boom according to any one of claims 1 to 12, 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).

14. A lifting platform (1), comprising a telescopic boom (26) according to any one of claims 1 to 13 and a working platform (10) supported by the telescopic boom (26).

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