Lifting mechanism for a building board lifting apparatus, lifting apparatus comprising such a mechanism, lifting method using such an apparatus

Abstract

The invention proposes a safe, easy-to-handle, quiet, and fast plate-lifting mechanism that ensures smooth raising and lowering without risk of jamming. The device comprises a telescopic mast with three segments (12), a chain (20) arranged inside the fixed segment (12) around two sprockets (121-122), one of which is driven by a motor, and a lower end of the terminal moving segment being fixed to the chain (20). The segments have respective drive stops so that the mast extends and retracts according to the rotation of the chain.

Description

[0001] The invention relates to a mechanism for a construction plate lifting device, a plate lifting device comprising such a mechanism, and a method for lifting construction plates using such a device.

[0002] In particular, the invention relates to lifting and handling devices used during work, for the handling and positioning of heavy objects, such as sheets of materials (plasterboard, wood panels, etc.) to make false ceilings or fittings under sloping roofs or on partitions.

[0003] This type of device, called a panel lifter, has the following general structure: a telescopic mast, controlled by a lifting mechanism, is mounted on a rolling base. A panel support is mounted to pivot at the end of the mast via a pivoting mechanism, between a nearly vertical position for placing the panel, and a nearly horizontal or angular position for fixing the panel against a ceiling or roof slope.

[0004] The telescopic mast comprises a first fixed element and at least one telescopic movable element relative to the fixed element. Generally, the mast comprises two telescopic movable elements.

[0005] There are several types of lifting mechanisms.

[0006] The most common one, illustrated in document FR2758150, is a pulley system comprising a winch, several turning pulleys and a cable connected to the winch, passing through the pulleys and through the telescopic elements of the mast.

[0007] To improve safety in the event of cable breakage, the lifting mechanism includes a double ratchet winch connected to a lifting cable and a safety cable (in case of breakage of the lifting cable) that is slightly less taut than the lifting cable. Such a device is also described in document FR3073215.

[0008] However, this winch mechanism is very noisy: 87 dB (measured using a smartphone known as an "iPhone"®< with the application known as "Decibel Ultra"®<, 30 cm from the winch, with an ambient noise level of 31 dB). Furthermore, the metal cables used wear out very quickly and can either break or fray, potentially injuring the user.

[0009] Furthermore, because the mechanism is accessible, there is a significant risk of a user's fingers getting caught.

[0010] A second type of lifting mechanism is a hybrid mechanism comprising a rack driven by a flywheel via a reduction gear system, as well as a cable pulley system to erect the telescopic moving elements.

[0011] Such a device is described in document WO2016071589.

[0012] This mechanism is much quieter and safer than a winch mechanism because the rack and pinion does not wear out. Furthermore, it includes an emergency brake that prevents the mast from falling back down if the user releases the brake.

[0013] Finally, the described gear system allows for motorized operation using a screwdriver. The screwdriver must be coupled to the rotating shaft when the user requires motorized operation. In this case, the user no longer uses the handwheel to lift the mast, but the screwdriver. However, they must still operate the emergency brake with their other hand. This system therefore requires some practice to operate and use the plate lift.

[0014] Another motor-operated lifting mechanism was also disclosed in document EP0969165. This mechanism is also hybrid and includes a worm gear engaging with one of the telescopic elements of the mast and a motor whose shaft is coupled to the worm gear via a set of return pulleys.

[0015] The worm gear is arranged inside the mast, coaxially and guided inside the telescopic mast.

[0016] The worm gear is engaged with a nut bearing attached to the first moving section of the telescopic mast. The second moving section is erected by a cable pulley system that tightens as the first moving section rises.

[0017] Such a plate lifter has a very significant weight and size due to the size of its motor, which is fixed and offset from the mast, and its drive system to be able to drive the worm screw.

[0018] In practice, however, a drywall lift is constantly being moved from one room to another, and also along walls or ceilings each time a drywall panel has been screwed in and the next area needs to be prepared. Weight and size are therefore very important factors.

[0019] Furthermore, the contact area between the worm gear and the bearing-nut attached to the first moving element of the telescopic mast is critical: it cannot be too thin, as it risks twisting under the weight, nor too thick, as it risks making the tool excessively heavy. The contact surface between the worm gear and the bearing-nut must therefore be optimal.

[0020] This also determines the thread pitch. If a large contact surface is desired, the thread pitch must be very small. The drawback is that the raising and lowering time will be very long.

[0021] Conversely, if a rapid ascent and descent is desired, the thread pitch must be increased, but this reduces the contact area between the screw and the bearing and makes the device fragile.

[0022] Finally, these devices all have cables that can wear out, even when enclosed in the telescopic moving parts, and that can become temporarily jammed, affecting the raising and lowering of the mast, as well as user safety when the cable suddenly becomes unjammed by the weight of the parts.

[0023] The present invention therefore aims to provide a safe plate lifter, i.e. without risk to the user, but nevertheless easy to handle and operate by a single user, quiet, fast, and easy to maintain, and ensuring a smooth ascent and descent, without risk of jamming.

[0024] The idea behind the invention is to provide an internal mast lifting mechanism without cables by designing the telescopic system of the mast in a novel way, the intermediate mobile segment not being driven by the lifting mechanism, as is conventional.

[0025] Another idea is to require the user to use both hands to manipulate and operate the plate lifter, without having to use one hand to operate an emergency brake.

[0026] To this end, the invention relates to a lifting mechanism comprising a mast with three telescopic segments: a fixed segment, an intermediate segment, and a terminal segment. A chain is arranged inside the fixed segment around two sprockets, one of which is driven by a motor. The lower end of the terminal segment is attached to the chain. The segments have respective drive stops so that the mast extends and retracts according to the rotation of the chain.

[0027] More specifically, the invention relates to a lifting mechanism for a plate lifter, comprising, with reference to the operating position: a telescopic mast comprising a fixed segment, a first mobile telescopic segment called "intermediate" mounted to slide inside the fixed segment, and a second mobile telescopic segment called "terminal" mounted to slide inside the intermediate segment; characterized in that the lifting mechanism further comprises: a chain arranged inside the fixed segment and forming a loop in mesh around a first sprocket arranged at an upper end of the fixed segment and around a second sprocket arranged at a lower end of the fixed segment, one of the two sprockets being in mesh with a control shaft of a means for rotating the shaft, a lower end of the terminal moving segment being fixed to a strand of the chain; and in that: The fixed segment includes an upper internal stop for guiding the intermediate moving segment during sliding; the intermediate moving segment includes a lower external stop for guiding against the fixed segment, and an upper internal drive stop; and the terminal moving segment includes a lower external stop for parallel guiding the intermediate moving segment, and an upper external stop for lifting the intermediate moving segment.

[0028] According to other embodiments: the fixed segment may include a peripheral tubular part having a lower end and an upper end, and in which is centrally fixed a profile having an open face and projecting from the upper end of the tubular part by a determined height, the first pinion being arranged at an upper end of the profile, and the second pinion being arranged at a lower end of the profile, the terminal moving segment being arranged, seen in section, around and near the profile, and the intermediate moving segment being arranged between the terminal moving profile and the fixed segment; the means for rotating the control shaft may be an electric motor connected to an electrical supply;The lifting mechanism may further include a control station arranged outside the fixed segment, and having two handles, one for each hand of the user, each handle having at least one control of the electric motor actuable by a single finger while the rest of the user's hand remains in grip of the handle, the control station including at least one mast extension / retraction control with a first speed, and a mast extension / retraction control with a second speed lower than the first speed for fine adjustment; the electric motor may be connected to the control shaft via a speed regulator possibly combined with a reduction gear; the motor may be arranged at the lower end of the fixed segment, and connected to the control shaft of the second pinion;The power supply may include a fixed base and a removable battery, the base being electrically connected to the electric motor and the battery having a connection system to the base to allow battery replacement; the lifting mechanism may further include a limit switch arranged to detect the chain attachment element to the first telescopic moving segment in the vicinity of one or each sprocket; the lifting mechanism may further include a force sensor arranged to reversibly cut off the power supply to the motor in a direction of mast extension rotation when a compressive force exceeding a predetermined threshold is detected; the force sensor may be a torque breaker arranged on at least one of the chain sprockets, and capable of cutting off the power supply to the motor when a torque exceeding a predetermined threshold is reached.

[0029] The invention also relates to a plate lifter for lifting a construction plate, characterized in that it comprises: A previous mechanism, A rolling base fixed to the lower end of the fixed segment of said mechanism; A plate holder mounted pivoting at an upper end of the terminal moving segment of the mechanism.

[0030] According to other embodiments The base may include at least three feet, of which at least two feet are mounted to pivot between a working position in which the feet are spaced apart to ensure the stability of the plate lifter, and a transport position in which the pivoting feet are folded close together; the end of the mast may have two casters arranged so that they do not touch the ground when the feet of the base are in the working position, and that they touch the ground when the feet are in the transport position; two adjacent feet may include a pair of wheels, a first wheel being arranged near the mast and a second wheel being arranged near a free end of the foot, the wheels near the mast being arranged so as to support the weight of the apparatus for transport by rolling when the feet are in the transport position.

[0031] The invention also relates to a method for implementing a previous lifting device, comprising the following steps a) provide a previous plate lifter; b) place a plate on the plate holder; c) grasp a handle on the control station in each hand and position the device in a suitable location for the plate; d) operate a control on the electric motor with one finger while keeping the rest of the hand on the handle, until the telescopic mast has extended and the plate is in the fixing position; e) release the control; f) fix the plate; g) operate a control on the electric motor with one finger while keeping the rest of the hand on the handle, until the telescopic mast has folded back by rotating the chain, gradually and in a controlled manner.

[0032] Other features of the invention will be set forth in the detailed description below, made with reference to the attached drawings, which represent, respectively: [ Fig. 1 ], a general schematic perspective view of a plate lifter equipped with a lifting mechanism and a control station according to the invention; [ Fig. 2 ], a partial schematic plan and frontal section view along line XX of the plate lifter of the figure 1 and showing the lifting mechanism according to the invention; [ Fig. 3 ], a partial schematic view in perspective and frontal section along line XX of an enlargement of the mechanism of the figure 2 at the point of attachment between the rotating chain mounted on the fixed segment and the terminal moving segment; [ Fig. 4 ], four partial schematic views in frontal section along line XX of the mechanism of the figure 2 , respectively in rest position, intermediate deployment position, deployed position and intermediate retracted position; Fig. 5 ], a schematic cross-sectional view along line YY of the plate lifter according to the invention, viewed from above and illustrating the interlocking of the different segments of the mast; [ Fig. 6 ], a schematic perspective and front section view along line XX of the upper part of the fixed segment of a plate lifter according to the invention; [ Fig. 7 ], a schematic perspective and front section view along line XX of the lower part of the fixed segment of a plate lifter according to the invention; [ Fig. 8 ], a partial schematic perspective view, taken from one side, of an example embodiment of a control station according to the invention; and [ Fig. 9 ], a partial schematic perspective view, seen from a second side of the control station according to the invention of the figure 8 .

[0033] There figure 1 illustrates a plate lifter equipped with a lifting mechanism according to the invention in the position of use. The plate lifter 1 comprises a lifting mechanism 100, a rolling base 200 fixed to the lower end of the fixed segment of said mechanism 100 (see below), and a plate holder 300 pivotally mounted at an upper end of the terminal moving segment of the mechanism 100.

[0034] The lifting mechanism 100 according to the invention comprises a telescopic mast 10 including a fixed tubular segment 12 intended to be integral with the rolling base 200, a first mobile telescopic tubular segment 14, called "intermediate", mounted to slide inside the fixed segment 12, and a second mobile telescopic tubular segment 16, called "terminal", mounted to slide inside the intermediate segment 14.

[0035] The lifting mechanism 100 also includes a chain 20 (visible on the figures 2 à 6 ), arranged inside the fixed segment 12.

[0036] As shown by figure 2 This illustrates the normal operating position, on a floor S, of a plate lifter 1 equipped with the lifting mechanism 100. The fixed tubular segment 12 comprises, fixed on an inner face, a first pinion 121 arranged at an upper end and a second pinion 122 arranged at a lower end. One of the two pinions 121-122 meshes with a drive shaft 31 of a means for rotating said drive shaft 31 (for example, an electric motor 30).

[0037] More specifically, and preferably, it is the second pinion 122, in the lower position, that engages with the drive shaft. The latter is preferably the drive shaft 31 of an electric motor arranged near the lower end of the fixed segment 12 (and therefore of the mast), which allows the center of gravity of the assembly to be lowered.

[0038] The chain 20 forms a loop around the first sprocket 121 and the second sprocket 122. The two portions of chain arranged between the sprockets are subsequently called chain strands.

[0039] According to the invention, and as illustrated in the enlarged view at the figure 3 , a lower end 16a of the terminal mobile tubular segment 16 is fixed to only one 21 of the two strands of the chain 20. This fixing is done, in the illustrated example, by means of a rider 161 engaged with a link of the chain 20 and screwed by screws 162 to the terminal mobile tubular segment 16.

[0040] There figure 2 also illustrates the different stops which equip segments 12-14-16 of mast 10, and which participate in its deployment without cable, by means of chain 20 alone.

[0041] Thus, the fixed segment 12 has an internal upper stop 123 (because it faces inwards towards the segment on an inner face) that guides the intermediate moving segment 14 during sliding. This internal stop 123 slides along the outer faces of the intermediate moving segment 14 and ensures a substantially constant distance between the fixed segment 12 and the intermediate moving segment 14 during deployment.

[0042] Similarly, the intermediate mobile segment 14 includes an external lower stop 141 (because it is turned outwards from the segment on an external face) for guidance against the fixed segment 12 and which slides along the internal faces of the fixed segment 12. The intermediate mobile segment 14 also includes an internal upper drive stop 142 which slides along the external faces of the second terminal segment 16 during the deployment of the mast 10.

[0043] Finally, the terminal moving segment 16 includes a lower external stop 163 for parallel guidance of the intermediate moving segment 14, and an upper external stop 164 for lifting the intermediate moving segment 14 when it comes into contact with the upper internal stop 142 for driving the intermediate moving segment 14.

[0044] These various stops 123, 141, 142, 163, 164 can be peripheral, or in several parts (for example, in the form of plastic washers) on two, three, or four sides of the segment on which they are mounted. This ensures the centering of segments 12-14-16 in pairs.

[0045] There figure 4 illustrates the operation of the mechanism according to the invention, and in particular the role of the chain 20 (illustrated in dotted lines) and the stops 123, 141, 142, 163, 164 in the kinematics of the deployment and folding of the mast.

[0046] Four deployment stages are illustrated: in 4A, the mechanism is in the rest position, i.e., not unfolded, in 4B, the mechanism is being deployed, in 4C, the mechanism is fully unfolded, and in 4D, the mechanism is being refolded.

[0047] At rest, in position 4A, the two moving segments of the mechanism are in the lowered position. The fixing means 161 of the terminal moving segment on the chain 20 is also in the lowered position, close to, or even against, the second lower sprocket 122. The latter can therefore advantageously serve as a mechanical stop for the resting position of the terminal moving segment 16.

[0048] The lower external stops 163 and upper external stops 164 of the terminal mobile segment 16 ensure parallelism between the terminal mobile segment 16 and the intermediate mobile segment 14.

[0049] Similarly, the lower external stop 141 of the intermediate moving segment 14 and the upper internal stop 123 of the fixed segment 12 ensure parallelism between the fixed segment 12 and the intermediate moving segment 14.

[0050] During movement, the stops 123, 141, 163 and 164 ensure the parallel guidance of the segments towards each other.

[0051] When the lifting mechanism is activated, in 4B, the second sprocket 122 is driven by the motor in the direction of arrow F1. The fastening means 161 being fixed to one 21 of the strands 21-22 of the chain 20, it rises and drives the terminal moving segment 16 upwards, sliding relative to the intermediate moving segment 14.

[0052] During the upward movement of the terminal moving segment 16, its upper external stop 164 comes into contact with the upper internal stop 142 of the intermediate moving segment 14, which forces the lifting of the intermediate moving segment 14 which rises at the same time as the terminal moving segment 16.

[0053] The lifting mechanism according to the invention is fully deployed, in 4C, when, for example, the fixing means 161 of the terminal mobile segment 16 on the chain 20 comes into contact with the first upper sprocket 122, which stops the rotation of the chain and the rise of the terminal mobile segment 16 and the intermediate mobile segment 14.

[0054] To avoid dangerous contact between the fastening means 161 and the sprockets 121-122 during raising or lowering, the lifting mechanism according to the invention may advantageously include a limit switch sensor arranged to detect the chain fastening element to the first telescopic moving segment in the vicinity of one or each sprocket.

[0055] Alternatively, or in combination, to prevent damage to the plasterboard lift when the plasterboard fixing height is less than the maximum extension height of the mechanism, the lifting mechanism according to the invention may advantageously include a force sensor arranged to reversibly cut off the motor's power supply in a direction of rotation F1 of mast extension when a compressive force exceeding a predetermined threshold is detected. Thus, the motor's power supply is cut off if the head attached to the terminal moving segment 16 is in contact with the ceiling.

[0056] In one embodiment, the force sensor can be a torque breaker arranged on at least one of the chain sprockets, and capable of cutting off the power supply to the motor when a torque greater than a predetermined threshold is reached.

[0057] When the lifting mechanism according to the invention is fully deployed, the intermediate moving segment 14 acts as a mechanical relay between the fixed segment 12 and the terminal moving segment 16; that is to say, it ensures mechanical continuity between these two segments, which alone play a driving role in the lifting. It thus ensures the rigidity of the mast.

[0058] During the descent, in 4D, the lower pinion 122 is driven in the direction of arrow F2, opposite to the direction of arrow F1.

[0059] The fixing means 161 then descends, causing the terminal mobile segment 16 to descend.

[0060] The intermediate mobile segment 14 also descends by gravity, under the effect of its own weight, to the rest position identical to the situation in 4A.

[0061] Thus, according to the invention, only the fixed segment 12 and the terminal moving segment 16 are connected by the drive chain 20. The intermediate segment 14 is mounted freely in sliding between these segments, and is driven upwards or downwards only when its upper internal stop 142 is in contact with the upper external stop 164 of the terminal moving segment 16.

[0062] The lifting mechanism according to the invention therefore allows for a limited footprint since the sprockets 121-122 and the chain 20 are housed inside the fixed segment 12 of the mast 10. In addition, the lifting mechanism is cable-free and therefore has increased reliability compared to the prior art.

[0063] Since only the terminal moving segment 16 and the fixed segment 12 are driven relative to each other, they determine the lifting height.

[0064] In the case of a plate lifter, it is nevertheless necessary to ensure a loading height (i.e., in the resting position) of the plate on the head 300 that is compatible with the height of an average person. The length of the terminal moving segment 16 and the length of the fixed segment 12 are therefore limited.

[0065] According to an advantageous embodiment of the invention, illustrated in more detail in figures 5 à 7 , the fixed segment 12 comprises a peripheral tubular part 12a having a lower end and an upper end, and in which is centrally fixed a profile 12b protruding from the upper end of the tubular part 12a by a determined height h.

[0066] The first pinion 121 is arranged at an upper end of the profile 12b, and the second pinion 122 is arranged at a lower end of the profile 12b.

[0067] The latter also has an open face to allow the mounting and lowering of the fixing means 161 of the terminal mobile segment 16 on the chain 20.

[0068] The advantage of the profile 12 is multiple. First, it allows a first gable 121 to be arranged at an upper end of the profile 12b, at a height greater than the height of the peripheral tubular part 12a.

[0069] In addition, it helps to protect the chain 20 inside the fixed segment 12 by preventing any shock of the mobile segments 14-16 against the chain 20.

[0070] Finally, it serves as a guide for the moving segments during the assembly of the plate lifter.

[0071] Thus, as the figure 5 In cross-section along line YY, the terminal movable segment 16 is arranged around and near the profile 12b (which has a U-shaped cross-section whose open face allows for the movement of the fastening means 161). The intermediate movable segment 14 is arranged around and near the terminal movable segment 16, and the tubular part 12a of the fixed segment 12 is arranged around and near the intermediate movable segment 14.

[0072] In other words, the intermediate mobile segment 14 is arranged between the terminal mobile profile 16 and the tubular part 12a of the fixed segment 12.

[0073] The term "near" refers to the fact that the segments are spaced apart from each other by the thickness of the stops described previously.

[0074] This arrangement is particularly advantageous because the segments are not in direct contact with each other, which would result in a very large contact area and consequently a very powerful motor. The only contact area is that of the thrust bearings, which significantly reduces friction and requires only a small force to drive the mechanism.

[0075] Thanks to this, the means for rotating the drive shaft 31 can be an electric motor 30 connected to a modest power supply 32. For example, this power supply can include a fixed base 32a on the mast and a removable battery 32b of the type of interchangeable power tool battery, such as a screwdriver (see figures 8 And 9 ).

[0076] In this case, the base 32a is electrically connected to the electric motor 30, and the battery 32b has a connection system to the base to allow for battery replacement. This type of structure is known to those skilled in the art in the field of portable power tools and can easily be adapted to the lifting mechanism according to the invention.

[0077] Advantageously, the electric motor is connected to the control shaft 31 via a speed regulator possibly combined with a reducer.

[0078] According to another aspect of the invention, the lifting mechanism according to the invention comprises a control station 40 arranged outside the fixed segment 12, and having two handles 41-42, one for each hand of the user.

[0079] Each handle 41-42 has at least one control 43-44 of the electric motor 30 which can be operated by a single finger while the rest of the user's hand remains in grip on the handle.

[0080] In the illustrated embodiment, two types of control are shown.

[0081] Control 43 is, for example, a three-position push button Up-OFF-Down, and control 44 is a trigger, equipped with a return means, and capable of controlling the motor over a continuous range.

[0082] The control station therefore preferably includes at least one mast extension / retraction control with a first speed (here control 43), and a mast extension / retraction control with a second speed, lower than the first speed, for fine adjustment (here trigger 44).

[0083] The implementation of a plate lifter equipped with a lifting mechanism according to the invention comprises the following steps: a1) Provide a plate lifter equipped with a lifting mechanism and a control station 40 (see previous diagram), and ensure that it is in the rest position (see situation 4A of the diagram). figure 4 ) ; b1)place a plate, for example of type BA13, on the plate holder 300 c1)grasp in each hand a handle 41-42 of the control station 40 and position the device in a suitable location for the plate by rolling it on the ground S; d1)operate with one finger at least one control 43-44 of the electric motor 30 while keeping the rest of the hand on the handle, until the telescopic mast has extended and the plate is in the fixing position; e1)release the control 43-44; f1)fix the plate; g1)operate with one finger a control 43-44 of the electric motor 30 while keeping the rest of the hand on the handle, until the telescopic mast has folded back by rotation of the chain, gradually and in a controlled manner.

[0084] We can then start again to attach another plate.

[0085] This allows the user to manipulate the panel lifter to position it as desired and, potentially simultaneously, control its operation with both hands without letting go. This prevents injury and enables very precise panel positioning by raising and moving the lifter.

[0086] Such a mechanism allows the telescopic mast to be erected quickly and effortlessly, in particular thanks to the use of a motor and a very ergonomic control station which simultaneously performs the movement and deployment functions.

[0087] Finally, this lifting mechanism is extremely quiet compared to ratchet winch systems.

[0088] The lifting mechanism according to the invention is therefore very quiet, safe, reliable, and compact. According to other aspects of the invention:

[0089] The 200 base can be classic. Advantageously, as illustrated in the figures 1 And 2 , the base 200 can include at least three feet 201 of which at least two feet are mounted pivoting between a use position in which the feet are spaced apart to ensure the stability of the plate lifter, and a transport position in which the pivoting feet are folded close together, here against the mast.

[0090] The mast end preferably has two casters arranged so that they do not touch the ground when the legs of the base are in the operating position, and that they touch the ground when the legs are in the transport position. These casters allow the plate lifter to be rolled in a cantilevered position in the transport position with the legs 201 folded. In a preferred embodiment, two adjacent legs 201 each have a pair of wheels: a first wheel 202 arranged near the mast and a second wheel 203 arranged near a free end of the leg. The wheels 202 near the mast are arranged to support the weight of the device for transport by rolling when the legs are in the transport position.

Claims

1. Lifting mechanism (100) for a plate lifter, comprising, with reference to the position of use: - a telescopic mast (10) comprising a fixed segment (12), a first telescopic mobile segment called "intermediate" (14) mounted to slide inside the fixed segment (12), and a second telescopic mobile segment called "terminal" (16) mounted to slide inside the intermediate segment (14); characterized in that The lifting mechanism (100) further comprises: - a chain (20) arranged inside the fixed segment (12) and forming a loop engaged around a first sprocket (121) arranged at an upper end of the fixed segment (12) and around a second sprocket (122) arranged at a lower end of the fixed segment (12), one of the two sprockets being engaged with a drive shaft (31) of a means for rotating the shaft (30), a lower end (16a) of the terminal movable segment (16) being fixed to a strand (21) of the chain (20); and in that- the fixed segment (12) has an upper internal stop (123) for guiding the intermediate moving segment (14) during sliding; - the intermediate moving segment (14) includes a lower external stop (141) for guiding against the fixed segment, and an upper internal stop (142) for driving; and - the terminal moving segment (16) includes a lower external stop (163) for parallel guiding the intermediate moving segment (14), and an upper external stop (164) for lifting the intermediate moving segment.

2. Lifting mechanism (100) according to claim 1, in which the fixed segment (12) comprises a peripheral tubular part (12a) having a lower end and an upper end, and in which is centrally fixed a profile (12b) having an open face and extending from the upper end of the tubular part (12a) by a determined height (h), the first pinion (121) being arranged at an upper end of the profile (12b), and the second pinion (122) being arranged at a lower end of the profile (12b), the terminal mobile segment (16) being arranged, seen in section, around and near the profile (12b), and the intermediate mobile segment (14) being arranged between the terminal mobile profile (16) and the fixed segment (12).

3. Lifting mechanism (100) according to claim 1 or 2, wherein the means for rotating the control shaft is an electric motor (30) connected to an electrical supply.

4. Lifting mechanism (100) according to claim 3, further comprising a control station (40) arranged outside the fixed segment (12), and having two handles (41-42), one for each hand of the user, each handle having at least one control (43-44) of the electric motor (30) operable by a single finger while the rest of the user's hand remains in grip of the handle, the control station (40) having at least one mast extension / retraction control with a first speed, and a mast extension / retraction control with a second speed lower than the first speed for fine adjustment.

5. Lifting mechanism (100) according to any one of claims 1 to 4, wherein the electric motor (30) is connected to the control shaft (31) via a speed regulator optionally combined with a reducer.

6. Lifting mechanism (100) according to claim 4 or 5, in which the motor (30) is arranged at the lower end of the fixed segment (12), and connected to the drive shaft (31) of the second pinion (122); 7. Lifting mechanism (100) according to any one of claims 4 to 6, wherein the power supply comprises a fixed base and a removable battery, the base being electrically connected to the electric motor and the battery having a connection system to the base to permit battery change.

8. Lifting mechanism (100) according to any one of claims 4 to 7, further comprising a limit switch arranged to detect the chain fixing element to the first telescopic moving segment in the vicinity of one or each sprocket.

9. Mechanism according to any one of claims 4 to 8, further comprising a force sensor arranged to reversibly cut off the power supply to the motor in a direction of mast extension rotation when a compression force greater than a determined threshold is detected.

10. Lifting mechanism (100) according to claim 9, wherein the force sensor is a torque breaker arranged on at least one of the chain sprockets, and capable of cutting off the power supply to the motor when a torque greater than a predetermined threshold is reached.

11. Plate lifter (1) for lifting a construction plate, characterized in that It comprises: - A mechanism (100) according to any one of claims 1 to 5, - A rolling base (200) fixed to the lower end of the fixed segment (12) of said mechanism (100); - A plate holder (300) pivotally mounted at an upper end of the terminal moving segment (16) of the mechanism (100).

12. Plate lifter according to the preceding claim, in which the base (2000) comprises at least three feet (201) of which at least two feet are mounted pivotally between a use position in which the feet are spaced apart to ensure the stability of the plate lifter, and a transport position in which the pivoting feet are folded close together.

13. Plate lifter according to the preceding claim, in which the end of the mast has two rollers arranged so that they do not touch the ground when the feet (201) of the base (200) are in the position of use, and that they touch the ground when the feet are in the transport position.

14. Plate lifter according to claim 12, wherein two adjacent feet comprise a pair of wheels, a first wheel (202) being arranged near the mast and a second wheel (203) being arranged near a free end of the foot (201), the wheels (202) near the mast being arranged so as to support the weight of the device for transport by rolling when the feet (201) are in the transport position.

15. Method for implementing a plate lifter according to any one of claims 11 to 14 when it comprises a lifting mechanism according to claim 4, characterized in thatIt comprises the following steps: a1) providing a plate lifter (1) according to any one of claims 11 to 14 when it includes a lifting mechanism according to claim 4; b1) placing a plate on the plate holder; c1) grasping in each hand a handle (41-42) of the control station (40) and positioning the device in a suitable location for the plate; d1) actuating with one finger a control (43-44) of the electric motor (30) while keeping the rest of the hand on the handle, until the telescopic mast has extended and the plate is in the fixing position; e1) releasing the control; f1) fixing the plate; g1) actuating with one finger a control (43-44) of the electric motor (30) while keeping the rest of the hand on the handle, until the telescopic mast has folded back by rotation of the chain (20), gradually and in a controlled manner.

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