Aerial work platform

Abstract

This lifting platform includes a basket, which is supported by a deployable lifting structure by means of a hydraulic actuator (22), so as to raise the basket. The lifting platform includes a safety device (120), which includes a safety valve (121) that is switchable between an open and a closed position and is returned to the closed position by a return member (127). The safety device includes an auxiliary line (130) that bypasses the safety valve (121) and is configured to push the safety valve (121) back into the open position against the return member (127) when a pressure inside the auxiliary line (130) exceeds a switching pressure. A restrictor device (132) is arranged on the auxiliary pipe (130) to limit the fluid flow through the auxiliary pipe (130). (See Figure 5 for abbreviations.)

Description

Title of the invention: Lifting platform

[0001] The present invention relates to a lifting platform.

[0002] A lifting platform is a mobile elevating work platform for personnel. Several types of lifting platforms are known, including articulated boom lifts, mast lifts, telescopic boom lifts, scissor lifts, etc. A lifting platform—also simply called a "boom"—comprises a chassis, which is equipped with ground-traveling means, notably wheels; a basket, which is adapted for an operator to stand on; and a lifting structure, which is interposed between the basket and the chassis so as to adjust the height of the basket relative to the chassis. The lifting device generally includes at least one actuator, for example, a hydraulic cylinder, which is arranged to extend or retract the lifting device, raising or lowering the basket.

[0003] The basket, which includes a platform surrounded by a guardrail, is designed to accommodate one or more people and possibly also loads such as tools or other equipment, materials such as paint, cement, etc.

[0004] In the case of a scissor lift, the lifting device comprises bars that are articulated at their center in a scissor-like fashion. Several of these scissor mechanisms are mounted one above the other by their ends, which are pivotally connected, so that the assembly formed by the articulated bars can fold and extend vertically. The actuator is arranged between the articulated bars to extend or fold them. To allow the basket to be lifted, the ends of the upper bars are connected to pads designed to slide in rails provided under the basket platform, while the ends of the lower bars are connected to pads designed to slide in rails provided on the chassis.The lifting device thus allows the basket to be raised from a lowered position on the chassis to the desired working height, generally by means of one or more hydraulic cylinders, with the basket then in a raised position.

[0005] We are interested here in platforms whose actuator(s) are hydraulic, generally hydraulic cylinders. The platform then includes a hydraulic pump, which is driven by an electric motor. One end of each cylinder is fixed to an element of the lifting structure, the cylinders being fluidly connected to the pump via a flexible hose, so as to accommodate the deformations of the lifting structure during the raising or lowering movements of the basket.

[0006] Safety standards, for example EN 280-1:2022 §4.10.2, require the provision of a safety device which limits the descent speed and immobilizes the basket in In the event of accidental rupture of the flexible hose while the basket is in the raised position, a calibrated orifice and a poppet valve (or a proportional poppet valve) are typically installed at an actuator outlet to limit the descent speed and immobilize the basket in case of accidental rupture of the flexible hose.

[0007] We are particularly interested in platforms comprising an electrical energy storage device, which powers the electric motor via a variable frequency drive. The hydraulic pump is advantageously reversible, so that it is possible to recover energy during the descent of the basket, thus recharging the storage device. US-2023 / 0174354-A1 describes, for example, such a lifting platform equipped with such a calibrated orifice. However, the calibrated orifice (or the proportional solenoid valve) causes pressure losses, reducing the amount of energy recoverable by the electric motor, which is undesirable.

[0008] It is these problems that the invention intends to remedy in particular, by proposing a lifting platform that ensures the safety of the basket in the high position in the event of accidental rupture of the hoses, while limiting pressure losses in energy recovery mode.

[0009] To this end, the invention relates to a lifting platform, which comprises: - a chassis, which is equipped with ground contact elements, - a basket, which is adapted so that an operator can stand on it, - a lifting structure, which is interposed between the chassis and the basket, the lifting structure supporting the basket and being deployable so as to raise the basket relative to the chassis, - a hydraulic circuit which comprises: • at least one hydraulic actuator, which acts on a part of the lifting structure in such a way as to deploy the lifting structure more or less, • a lifting circuit, through which a fluid circulates between a reservoir and the hydraulic actuator, • a pumping unit, which is configured to, in a so-called lifting phase of operation, draw fluid from the reservoir and discharge the fluid into the lifting circuit, the lifting circuit being connected to a main port of the hydraulic actuator and being configured to raise the basket when the pumping unit is in the lifting phase, • a descent circuit, which is different from the ascent circuit and through which the hydraulic fluid circulates, during a descent phase of the lifting platform, from the hydraulic actuator to the reservoir,

[0010] wherein the lifting platform also includes a descent system, which comprises: - a down valve, which includes an inlet, which is connected to the main port of the actuator, and an outlet, which is connected to the down circuit, the down valve being switchable, under the action of a user, between an open position, in which the inlet is fluidly connected to the outlet through the down valve, and a cut-off position, in which fluid circulation between the inlet and outlet through the down valve is prevented.

[0011] According to the invention, the lifting platform also includes a safety device, which comprises: - a safety valve comprising: • an inlet port, which is fluidly connected to the outlet of the drain valve, • an output port, which is different from the input port and is configured to be connected to the downlink circuit, • The safety valve is switchable between an open position, in which the passage of fluid from the inlet port to the outlet port through the safety valve is not prevented, and a closed position, in which the passage from the inlet port to the outlet port through the safety valve is prevented. • a return mechanism, which is configured to return the safety valve to the closed position, - an auxiliary line, which fluidly connects the inlet port of the safety valve to the outlet port of the safety valve, the auxiliary line being configured to push the safety valve back into the open position against the return element, when a pressure inside the auxiliary line is greater than a switching pressure, the switching pressure having a predetermined value, and - a restrictor device, which is arranged on the auxiliary line and configured to limit the fluid flow through the auxiliary line.

[0012] Thanks to the invention, in the event of a line rupture, particularly in the event of a rupture of the flexible line, the hydraulic pressure in the auxiliary line drops below the switching pressure, and the safety valve automatically switches from the open position to the closed position, thus forcing the fluid to pass through the restrictor device. The safety of the platform in the raised position is thus ensured. In normal operation, particularly when the basket is in the raised position and descending, the pressure in the auxiliary loop remains above the switching pressure, keeping the safety valve in the open position. The fluid exiting the actuator passes through the control valve without restriction. flow rate, which does not reduce the amount of recoverable energy. Thanks to the invention, the amount of recoverable energy is greater than that of prior art gondolas. Safety is ensured by means of passive elements, that is to say, elements which do not require energy, particularly electrical energy, to operate, and automatically, without external intervention.

[0013] According to advantageous but not mandatory aspects of the invention, such a hydraulic system may incorporate one or more of the following features taken individually or in any technically permissible combination: - The restriction device includes a calibrated orifice. - The safety valve is a 2 / 2 hydraulically piloted valve, the hydraulic piloting being done by means of the auxiliary line. - The downpipe valve is a solenoid valve, which is switchable, by electrifying a solenoid of the downpipe valve, between: • a first position, in which a check valve on the downpipe prevents fluid flow from the main port to the safety device, while allowing fluid flow from the safety system to the main port, and • a second position, in which the fluid passage from the main port to the safety system through the down valve is prevented,

[0014] whereas the down valve includes a return element, configured to return the down valve to the first position when the solenoid is not electrified, the down valve passing into the second position when the solenoid is electrified. - The pumping unit is an electric pumping unit, which includes: • a pump, • an electric motor, • a dimmer, and • an electricity storage device,

[0015] whereas the pump is reversible, the pump being configured to operate: • according to a pumping mode, in which the energy stored in the storage device is used by the variable frequency drive to control the electric motor and drive the pump, circulating the fluid in the hydraulic circuit, • a regeneration mode, in which the fluid circulating in the hydraulic circuit drives the pump, which drives the electric motor, which generates electrical energy, which is used by the drive to recharge the electricity storage device. - The downhill driving section includes a flexible portion, while the hydraulic circuit also includes a regulating valve, which is located on the downpipe and is fluidly interposed between the safety device and the pumping unit, the regulating valve being located between the flexible section and the pumping unit, and that the control valve is switchable, by electrifying a solenoid of the control valve, between: • a resting position, in which fluid flow through the downpipe is prevented, • an activation position, in which fluid flow through the downpipe is not impeded,

[0016] the control valve comprising a return element, configured to return the control valve to the first position. - The hydraulic circuit also includes: • a backup connection, which is a fluid connection arranged between the safety device and the regulating valve, • a backup line, fluidly connecting the backup fitting to the tank, and • a relief valve, which is arranged on the relief line between the relief fitting and the tank, the relief valve being switchable between a closed position and an open position. - The relief valve is a manual valve, while the down valve includes a manual actuation device, which is configured to manually move the down valve into the open position. - The hydraulic circuit also includes: • a bypass fitting, which is an additional fluid connection, different from the emergency connection, and which is arranged on the downpipe between the safety device and the regulating valve, • a bypass line, which fluidly connects the bypass fitting to the tank, without passing through the pump, • a bypass valve, which is arranged on the bypass pipe between the bypass fitting and the tank, • a non-return valve positioned on the bypass pipe,

[0017] whereas the bypass valve is a solenoid valve, which is switchable between a closed position, in which the fluidic circulation from the downpipe to the tank through the bypass pipe is prevented, and an open position, in which the fluidic circulation from the downpipe to the tank through the bypass pipe is not prevented. - The lifting platform is a scissor lift.

[0018] The invention will be better understood, and other advantages thereof will become more apparent in the light of the following description of two embodiments of a lifting platform, in accordance with its principle, given solely by way of example and with reference to the accompanying drawings, in which: - [Fig.1] [Fig.1] is a perspective view of a lifting platform conforming to a first embodiment of the invention; - [Fig.2] [Fig.2] is a schematic representation of a circuit actuation of the nacelle of [Fig.1], the actuation circuit being in a first configuration; - [Fig.3] [Fig.3] represents the actuation circuit of [Fig.1] in a second configuration; - [Fig.4] [Fig.4] represents the actuation circuit of [Fig.1] in a third configuration; - [Fig.5] [Fig.5] represents the actuation circuit of [Fig.1] in a fourth configuration; - [Fig.6] [Fig.6] represents the actuation circuit of [Fig.1] in a fifth configuration; - [Fig.7] [Fig.7] is a schematic representation of a circuit actuation system belonging to a lifting platform according to a second embodiment of the invention, the actuation circuit being in a first configuration, and - [Fig.8] [Fig.8] represents the actuation circuit of [Fig.7] in a second configuration.

[0019] An example of a lifting platform 10 according to a first embodiment of the invention is shown in [Fig. 1]. The lifting platform 10 is here a scissor lift. In an alternative not shown, the lifting platform 10 is of another type, for example a telescopic lift, the principles of the invention described with reference to the scissor lift 10 being applicable to other types of lifting platforms.

[0020] The lifting platform 10, also referred to simply as "platform 10" in the rest of the description, comprises a chassis 12 capable of resting and moving on a ground 13 by means of connecting elements, here wheels 14. The wheels 14 define a forward direction, which is a preferred direction of movement of the chassis 12 and, by extension, of the scissor platform 10. According to an alternative example, the connecting elements are tracks.

[0021] The platform 10 also includes a basket 16, and a lifting structure 18 for the basket 16. In the illustrated example, the basket 16 includes a platform 17A, a guardrail 17B, and a control panel 17C for the platform 10. As part of a In normal use of the lifting platform 10, an operator stands on the platform 17A and pilots the lifting platform 10 using the control panel 17C.

[0022] The lifting structure 18, which is interposed between the chassis 12 and the basket 16, comprises a set of articulated bars 20 supporting the basket 16, such that the elevation of the basket 16 relative to the chassis 12 is variable and controlled by the set of bars 20. The platform 10 also includes an actuator 22, which acts on a portion of the lifting structure 18 so as to move said portion relative to the rest of the lifting structure or relative to the chassis, controlling the height of the basket 16 relative to the chassis 12, and by extension relative to the ground 13 on which the scissor lift 10 moves. In the first embodiment, illustrated in Figures 2 to 6, the lifting platform 10 comprises two actuators, including a first actuator 22 located closest to the chassis 12, while the second actuator is located further from the chassis 12 than the first actuator. 22, is referenced as 22'.The number of actuators 22 is not limited and generally varies depending on the size of the platform 10. Generally, the lifting platform 10 includes at least one actuator 22, in particular at least the first actuator closest to the chassis 12. The actuators 22 are here hydraulic actuators, in particular hydraulic cylinders, each comprising a body 22A and a piston 22B, the piston being received in a bore of the body 22A and being movable in translation relative to the body 22A. Each actuator 22 includes a main port 22C, through which the actuator 22 is supplied with hydraulic fluid so as to control a configuration of the actuator 22, i.e. here, to control a position of the piston 22B relative to the body 22A.

[0023] The lifting platform 10 comprises a hydraulic circuit 24, through which a fluid flows between a reservoir 26 and each actuator 22# / #22', and a pumping unit 28, which is configured to draw the fluid from the reservoir 26 and deliver the fluid through the hydraulic circuit 24 to the actuators 22. The hydraulic circuit 24, the reservoir 26, and the pumping unit 28 are shown in various configurations in Figures 2 to 6. The actuators 22 are considered to be part of the hydraulic circuit 24. The fluid is, for example, an oil, which is considered incompressible. In the figures, when a fluid flows through a portion of the hydraulic circuit 24, this portion is indicated by a solid line, while the direction of fluid flow is indicated by arrows. In the example in [Fig. 2], the hydraulic circuit 24 is shown in a standby configuration.This configuration is found in particular when the basket 16 is stationary relative to the chassis 12, i.e. that the fluid does not circulate in the hydraulic circuit 24. .

[0024] The tank 26 and the pumping unit 28 are preferably supported by the chassis 12, while a part of each actuator 22 is fixed to the lifting structure 18.

[0025] Preferably, the pumping unit 28 is an electric pumping unit, which includes: - a pump 30, which is a hydraulic pump, configured to transform a rotational movement into a suction force and a discharge force of a hydraulic fluid, - an electric motor 32, configured to drive the pump 30 in rotation, - a device for storing electrical energy, for example batteries, - a variator 36, configured to transform a direct current voltage from the batteries into a variable alternating current voltage suitable for controlling the electric motor 32.

[0026] The pump 30 is connected to the reservoir 26 via an inlet line 40, and is connected to the rest of the circuit

[0027] The pump 30 is preferably reversible, that is to say that the pump 30 is configured to operate selectively: - according to a pumping mode, in which the energy stored in the electricity storage device 34 is used by the variable speed drive 36 to control the electric motor 32 and drive the pump 30, circulating the fluid in the hydraulic circuit 24, and - according to a regeneration mode, in which the fluid circulating in the hydraulic circuit 24 drives the pump 30, which drives the electric motor 32, which then functions as an electrical energy generator, the generated electrical energy being used via the variator 36 to recharge the storage device 34.

[0028] The hydraulic circuit 24 is described with reference to the operating modes of the nacelle 10. In [Fig.3], the hydraulic circuit 24 and the nacelle 10 are in an ascending configuration, i.e. the pumping unit 28 is configured to pump the fluid from the reservoir 26 in order to deploy the actuators 22 / 22'.

[0029] The circuit 24 includes a lift circuit 50, which connects the pump 30 to the main port 22C of the actuator 22. In the example of [Fig. 3], considering the direction of fluid flow, the lift circuit 50 includes, successively after the pump 30, a filter 52, a lift valve 54, and at least one check valve 56. The filter 52 and the lift valve 54 are optional. The lift valve 54 is preferably a solenoid valve, that is, a valve comprising a solenoid and controllable by a user between an open position, in which the lift valve 54 allows the passage of fluid, and a closed position, in which The riser valve 54 prevents the passage of fluid. In the standby configuration, the riser valve 54 is in the closed position, as in [Fig.2], while in the rise configuration, the riser valve 54 is in the open position, as in [Fig.3].

[0030] In the illustrated example, the lifting platform 10 includes two actuators 22 / 22', so the lifting circuit 50 includes two check valves 56, the lifting circuit 50 includes an extension loop 51 which supplies hydraulic fluid to the second actuator 22', the extension loop 51 being connected to the lifting circuit between the two check valves 56.

[0031] Thus, during the raising of the basket 16, the lifting valve 54 is in the open position, allowing the passage of the fluid pumped by the pumping unit 28, the check valves 56 also being configured to allow the fluid to pass to the main port 22C of the actuator 22. Once the basket 16 has reached the desired height, the user returns the platform 10 to the standby configuration.

[0032] To lower the basket 16, the lifting platform 10 also includes a lowering circuit 60, which is separate from the ascent circuit 50 and connects the main port 22C to the reservoir 26, and a lowering system 100. Since the pumping unit 28 is reversible, the lowering circuit 60 is connected to the reservoir 26 via the pump 30. Thus, the lowering circuit 60 and the ascent circuit 50 have a common section 70, through which the lowering circuit 60 and the ascent circuit 50 are connected to the pump 30. A control valve 71 is provided on the lowering circuit 60 to prevent hydraulic fluid from circulating in the lowering circuit 60 when the lifting platform 10 is in the ascent phase.The control valve 71 is preferably a solenoid valve, which is switchable, on command, between a closed position, in which fluid circulation in the downpipe 60 is prevented, and an open position, in which fluid circulation in the downpipe 60 is not prevented. The control valve 71 includes a return element, not referenced, which is configured to return the control valve 71 to the closed position.

[0033] It is understood that during the descent of the basket 16, the piston 22B retracts into the body 22A and expels the hydraulic fluid through the main port 22C. The descent system 100 includes a descent valve 110, which comprises an inlet 112, connected to the main port 22C of the actuator 22, and an outlet 114. The descent valve 110 is switchable, by user action, between an open position, in which the inlet 112 is fluidically connected to the outlet 112 through the descent valve 110, and a closed position, in which the fluid circulation between the inlet 112 and the outlet 114 through the valve is closed. Descent is prevented. The descent valve 110 is therefore in the shut-off position when the platform 10 is in standby or ascending configuration.

[0034] Advantageously, the downpipe valve 110 is a poppet valve, which is switchable, by electrification of a solenoid 115 of the downpipe valve 110, between: - a first position, in which the fluid passage from the inlet 112 to the outlet 114 through the downpipe valve 110 is prevented, as illustrated in [Fig. 3], and - a second position, in which the fluid passage from the inlet 112 to the outlet 114 through the downpipe valve 110 is permitted without restriction, as illustrated in [Fig.4].

[0035] The downpipe valve 110 includes a return element 116, which is configured to return the downpipe valve 110 to the first position when the solenoid is not energized, and the downpipe valve 110 to the second position when the solenoid is energized. In other words, the first position is a rest position.

[0036] Advantageously, the lowering valve 110 includes a manual actuating element 118, which is configured to manually move the first solenoid valve into the second position. The manual actuating element 118 is, for example, a pull handle or equivalent. It is thus possible to manually lower the basket 16, for example, in the event of a malfunction of the electrical systems of the platform 10 while the basket 16 is in a raised position. This aspect is described later.

[0037] The lifting platform 10 also includes a safety device 120, which includes a safety valve 121. The safety valve 121 includes: - an inlet port 122, which is fluidly connected to the outlet 114 of the downpipe valve 110, and - an output port 124, which is different from the input port 122 and which is configured to be connected to the down circuit 60.

[0038] The safety valve 121 is switchable between an open position, in which the fluid passage from the inlet port 122 to the outlet port 124 through the safety valve 121 is not prevented, and a closed position, in which the passage from the inlet 122 to the outlet 124 through the safety valve 121 is prevented.

[0039] The safety valve 121 also includes a return element 127, which is configured to return the safety valve 121 to the closed position. In other words, the closed position is a rest position for the safety valve 122.

[0040] The safety device 120 also includes: - an auxiliary conduit 130, which fluidly connects the inlet port 122 of the safety valve 121 to the outlet port 124 of the safety valve, here in bypassing the safety valve. The auxiliary line 130 is configured to push the safety valve 121 into the open position against the return member 127, when a pressure inside the auxiliary line 130 is greater than a switching pressure, the switching pressure having a predetermined value. - a restrictor 132, which is arranged on the auxiliary line 130 and configured to limit the fluid flow through the auxiliary line. Preferably, the restrictor includes a calibrated orifice. This calibrated orifice is sized to slow the descent in the event of a hose rupture or in manual descent mode.

[0041] By way of non-limitation, the switching pressure is typically between approximately 5 and 25 bar, with lower or higher switching pressure values ​​being possible depending on the configurations.

[0042] Thus, it is understood that as long as the pressure in the auxiliary line 130 is greater than the switching pressure, the safety valve 130 remains in the open position, and fluid flow through the safety valve 121 is not impeded. In other words, fluid flow from the inlet port 122 to the outlet port 124 is possible both through the safety valve 121 and through the auxiliary line 130. If the pressure in the auxiliary line 130 falls below the switching pressure, the safety valve 130 moves to the closed position. The fluid passage from the inlet port 122 to the outlet port 124 is then only possible via the auxiliary line 130, the flow being limited by the restriction device 132. According to a preferred example, the safety valve 121 is a 2 / 2 hydraulically piloted valve, the hydraulic piloting being done by means of the auxiliary line 130.The safety device 120 includes a pilot member, which is mounted on the auxiliary line 130 and is configured to actuate the safety valve according to the fluid pressure in the auxiliary line 130, the restriction member 132 being arranged between the pilot member and the lowering valve 110. In other words, the restriction member 132 is located upstream of the pilot member, considering the normal direction of fluid flow during the descent of the basket 130. The pilot member is not shown.

[0043] Starting from the standby configuration, the lowering valve 110 is placed in the first position, for example by electrifying the solenoid 115. Under the effect of gravity, the basket 16, in a raised position, exerts a force on the actuator 22 via the lifting structure 18, which generates a fluidic pressure in the lowering circuit 60. Schematically, the fluidic pressure in the lowering circuit 60 is considered to be equal to the fluidic pressure in the auxiliary line 130.

[0044] Thus the safety valve 121 is pushed back into the open position, allowing fluid to pass through the safety valve 121. The lifting platform 10 is then in the configuration of [Fig.4].

[0045] The control valve 71 is then switched and put in the open position to allow the oil supply to the pump 30.

[0046] Typically, during descent, the fluid pressure in the descent circuit 60 is greater than the switching pressure of the safety valve 121.

[0047] The fluid circulating in the downpipe 60 flows advantageously through the pump 30, the pumping unit 28 acting here as an electricity generator, to recharge the batteries 34. It is understood that, unlike the known prior art nacelles, the fluid here encounters no particular restriction, in particular does not pass through any flow limiting device between the cylinder 22 and the pump 30 which would generate undesired pressure losses and antagonistic to the objective of energy recovery.

[0048] In this “recovery” energy configuration, the descent speed is adjustable via the speed control of the pump 30 by the variator 36.

[0049] The hydraulic circuit 24 comprises rigid sections, made in particular of metal tubes, and flexible sections, made in particular of polymer pipes, which are designed to accommodate the deformations of the lifting structure 18 when the height of the basket 16 changes. In the figures, the rigid sections are represented by straight lines, while the flexible sections are represented by curves. In particular, the downpipe 60, which connects the hydraulic system 100 to the pumping unit 28, includes a flexible section 61, while the hydraulic downpipe 100 is supported by the lifting structure 18 and is connected to the actuator 22 by a rigid pipe. In the schematic example shown, only one flexible section 61 is represented, although this may be the case in reality. Preferably, the flexible section 61 is located between the control valve 71 and the safety device 100.

[0050] The rigid pipe, and by extension any portion of the hydraulic circuit considered rigid, is generally made of metal tubing and is considered unbreakable. At least, under normal operating conditions, the risk of accidental rupture is very low. In comparison, the flexible portion 61, and by extension any so-called "flexible" portion of the hydraulic circuit, is generally made of elastomer, possibly reinforced by a braid of fibers, particularly metallic ones. Despite all the care taken in the manufacture of the flexible portion 61, the risk of rupture is not zero and must be anticipated.

[0051] In the example of [Fig. 5], it is assumed that the gondola 10, initially in the descent configuration, suffers a rupture of the flexible portion 61 of the circuit of descent, creating a leak. The rupture of the flexible section 61 is represented by a pair of scissors severing the flexible section 61. The pressure in the descent circuit 60 decreases, including in the auxiliary loop 130, below the switching pressure. The safety valve 121, initially in the open position, as in [Fig. 4], then moves to the closed position, as in [Fig. 5]. The fluid expelled by the actuator 22 then passes exclusively through the auxiliary line 130, the flow rate being limited by the restrictor 132. It is understood that the descent speed of the basket 16 is limited by the fluid flow rate through the auxiliary line 130. The restrictor 132 is configured to sufficiently reduce the flow rate through the auxiliary line 130 so that the descent speed does not pose a danger to any users who may be present in the basket 16.Thus, thanks to the safety device 120, it is possible to ensure the safety of persons in the event of accidental rupture of the flexible portion 61, without generating additional pressure losses in the event of normal operation of the platform 10.

[0052] Advantageously, the hydraulic circuit 24 also includes an emergency line 80, which connects the descent circuit 60 to the reservoir 26, without passing through the pump 30.

[0053] In the illustrated example, the hydraulic circuit 24 includes a relief fitting 82, which is a fluid connection arranged on the downpipe 60 between the safety device 100 and the control valve 71, preferably between the flexible section 61 and the control valve 71. The hydraulic circuit 24 also includes a safety valve 84, which is arranged on the safety line 80 between the fluid connection 82 and the reservoir 26. The safety valve 84 is switchable between a closed position, in which fluid circulation through the relief line 80 is prevented, and an open position, in which fluid circulation through the relief line 80 is not prevented. Preferably, the safety valve 84 is a manual valve.

[0054] During normal operation of the lifting platform 10, the emergency valve 84 is left in the closed position. In the event that all electrical systems of the platform 10 become unavailable while the basket 16 is in a raised position, it is possible to lower the basket 16 in a controlled manner: - by manually moving the downpipe valve 110 into the second position using the manual actuating member 118, and - by moving the safety valve 84 into the open position.

[0055] In this emergency descent configuration, lines 130 and 61 are connected to the reservoir, and the pressure is lower than the switching pressure of the safety valve 121, which remains in the closed position. In other words, the safety device 120 limits the flow of fluid, just as it does in the event of a rupture of hose 61, and the descent speed of the basket 16 is regulated by the restrictor 132.

[0056] Alternatively, emergency drainage can be achieved by equipping the control valve 71 with a manual control allowing the valve to be switched to the open position. In this configuration, the flow returns directly to the reservoir via the pump 30. The safety valve 84 and the return line to the reservoir 80 are then no longer required.

[0057] A hydraulic circuit 24', belonging to a lifting platform according to a second embodiment of the invention, is shown in Figures 7 and 8. In the second embodiment, the elements analogous to those of the first embodiment bear the same reference numerals and function in the same way. The following mainly describes the differences between the first and second embodiments. If a reference numeral is mentioned in the description but not shown in a figure, or shown in a figure but not mentioned in the description, it designates the same element as the one bearing the same reference numeral in the first embodiment.

[0058] In the second embodiment, the downpipe valve 110 is a proportional-type poppet valve. The downpipe valve 110 is switchable between: - the first position, in which the fluid passage from inlet 112 to outlet 114 through drain valve 110 is prevented, - the second position, in which the fluid passage from inlet 112 to outlet 114 through drain valve 110 is permitted without restriction, and - a third position, intermediate between the first and second positions, in which the fluid passage from the inlet 112 to the outlet 114 through the downpipe valve 110 is permitted with restriction / braking, as illustrated in [Fig.8].

[0059] In other words, the downpipe valve 110 is adjustable, so as to restrict the passage of fluid in a variable manner.

[0060] The hydraulic circuit 24' includes a bypass line 90, which connects the downpipe 60 to the reservoir 26, without passing through the pump 30. In the illustrated example, the hydraulic circuit 24 includes a bypass fitting 92, which is an additional fluidic fitting, different from the emergency fitting 82, and which is arranged on the downpipe 60 between the safety device 100 and the control valve 71, preferably between the flexible section 61 and the control valve 71. The bypass line 90 is here arranged in parallel, fluidically speaking, with the safety line 80.

[0061] The hydraulic circuit 24 also includes a bypass valve 94, which is arranged on the bypass line 90 between the fluid connection 92 and the reservoir 26. The bypass valve 94 is a solenoid valve, which is switchable between a position A closed position, in which fluid flow from the downpipe 60 to the reservoir 26 through the bypass pipe 90 is prevented, and an open position, in which fluid flow from the downpipe 60 to the reservoir 26 through the bypass pipe 90 is not prevented. A check valve 96 is advantageously located between the bypass valve 94 and the reservoir 26, the check valve 96 being configured to maintain, in a portion of the hydraulic circuit 24' located between the safety system 100 and the bypass valve 94, a pressure higher than the switching pressure when fluid flows through the bypass valve 94 in the open position.

[0062] Preferably, the safety valve 94 is a solenoid valve, the closed position being a rest position of the solenoid valve, while the open position is an excited position of the solenoid valve.

[0063] In [Fig. 7], the hydraulic circuit 24' is shown in its standby configuration. In [Fig. 8], during a basket descent phase, the proportional lowering valve 110 is in the open position, and the bypass valve 94 is also in the open position. Since the pressure in the auxiliary line 130 is maintained above the switching pressure, the safety valve 121 remains in the open position. The hydraulic fluid flows to the reservoir without passing through the pump 30, in other words, without generating electricity. This situation occurs particularly when the batteries are already sufficiently charged.

[0064] In this configuration, the descent speed is defined by the degree of opening of the descent valve, here a proportional solenoid valve.

[0065] In the illustrated embodiments, the safety system according to the invention ensures a controlled descent of the basket in the event of a rupture of the flexible hoses, without, however, restricting the hydraulic fluid flow during normal operation. This avoids pressure losses and limits energy losses when the platform is designed to regenerate electrical energy during the basket's descent. Of course, the safety system according to the invention can be used with platforms not designed to recover energy; in such cases, only the safety function is performed.

[0066] The embodiments and variants mentioned above can be combined with each other to generate new embodiments of the invention.

Claims

Demands

1. Lifting platform (10), wherein the lifting platform (10) comprises: • a chassis (12), which is equipped with ground connection devices (14), • a basket (16), which is adapted so that an operator can stand in it, • a lifting structure (18), which is interposed between the chassis (12) and the basket (16), the lifting structure (18) supporting the basket (16) and being deployable so as to raise the basket (16) relative to the chassis (12), • a hydraulic circuit (24; 24') which includes: • at least one hydraulic actuator (22; 22'), which acts on a part of the lifting structure (18) so as to deploy the lifting structure (18) more or less, • a lifting circuit (50), through which a fluid circulates between a reservoir (26) and the hydraulic actuator (22; 22'), • a pumping unit (28), which is configured to, in a so-called lifting phase of operation, draw fluid from the reservoir (26) and discharge the fluid into the lifting circuit (50), the lifting circuit (50) being connected to a main port (22C) of the hydraulic actuator (22; 22') and being configured to raise the basket (16) when the pumping unit (28) is in the lifting phase, • a descent circuit (60), which is different from the ascent circuit (50) and through which the hydraulic fluid circulates, during a descent phase of the lifting platform (10), from the hydraulic actuator (22; 22') to the reservoir (26), in which the lifting platform (10) also includes a descent system (100), which includes: • a downpipe valve (110), which includes an inlet (112), which is connected to the main port (22C) of the actuator, and an outlet (114), which is connected to the downpipe circuit (60), the downpipe valve (110) being switchable, under the action of a user, between an open position, in which the inlet (112) is fluidically connected to the outlet (114) through the downpipe valve (110), and a closed position, in which fluid circulation between the inlet (112) and the outlet (114) through the downpipe valve (110) is prevented, characterized in that the lifting platform (10) also includes a safety device (120), which comprises: • a safety valve (121) comprising: • an inlet port (122), which is fluidly connected to the outlet (114) of the downpipe valve (110), • an output port (124), which is different from the input port (122) and which is configured to be connected to the downlink circuit (60), • The safety valve (121) is switchable between an open position, in which the fluid passage from the inlet port (122) to the outlet port (124) through the safety valve (121) is not prevented, and a closed position, in which the passage from the inlet port to the outlet port through the safety valve (121) is prevented, • a return device (127), which is configured to return the safety valve (121) to the closed position, • an auxiliary line (130), which fluidly connects the inlet port (122) of the safety valve (121) to the outlet port (124) of the safety valve (121), the auxiliary line (130) being configured to push the safety valve (121) back into the open position against the return member (127), when a pressure inside the auxiliary line (130) is greater than a pressure switching, the switching pressure having a predetermined value, • a restriction device (132), which is arranged on the auxiliary line (130) and which is configured to limit the fluid flow through the auxiliary line (130).

2. Lifting platform (10) according to claim 1, wherein: • the restriction member (132) includes a calibrated orifice.

3. Lifting platform (10) according to any one of claims 1 or 2, wherein: • the safety valve (121) is a 2 / 2 hydraulically piloted valve, the hydraulic piloting being done by means of the auxiliary line (130).

4. Lifting platform (10) according to claim 3, wherein: • the lowering valve (110) is a solenoid valve, which is switchable, by energizing a solenoid of the lowering valve (110), between: • a first position, in which a check valve of the lowering valve (110) prevents fluid passage from the main port (22C) to the safety device (120), while allowing fluid passage from the safety system (120) to the main port (22C), • a second position, in which fluid passage from the main port (22C) to the safety system (120) through the lowering valve (110) is prevented, • the lowering valve (110) includes a return element (116), configured to return the lowering valve (110) to the first position when the solenoid is not energized, the lowering valve (110) passing into the second position when the solenoid is electrified.

5. Lifting platform (10) according to any one of claims 1 to 4, wherein: • the pumping unit (28) is an electric pumping unit, which includes: • a pump (30), • an electric motor (32), • a variable speed drive (36), and • an electricity storage device (34), • The pump (30) is reversible, the pump being configured to operate: • according to a pumping mode, in which the energy stored in the storage device (34) is used by the variator (36) to drive the electric motor (32) and drive the pump (30), circulating the fluid in the hydraulic circuit (24; 24'), • a regeneration mode, in which the fluid circulating in the hydraulic circuit (24; 24') drives the pump (30), which drives the electric motor (32), which generates electrical energy, which is used by the variator (36) to recharge the electricity storage device (34).

6. Lifting platform (10) according to any one of claims 1 to 5, wherein: • the downpipe (60) includes a flexible portion (61), • the hydraulic circuit (24; 24') also includes a regulating valve (71), which is located on the downpipe (60) and which is fluidly interposed between the safety device (100) and the pumping unit (28), the regulating valve (71) being located between the flexible portion (61) and the pumping unit (28), • The control valve (71) is switchable, by electrifying a solenoid of the control valve (71), between: • a resting position, in which fluid circulation through the downpipe (60) is prevented, • an activation position, in which fluid flow through the downpipe (60) is not impeded, • the control valve (71) includes a return element, configured to return the control valve to the first position.

7. Lifting platform (10) according to claim 6, in which: • the hydraulic circuit (24; 24') also comprises: • an emergency connection (82), which is a fluid connection arranged between the safety device (100) and the control valve (71), • an emergency line (80), fluidly connects the emergency connection (82) to the reservoir (26), • an emergency valve (84), which is arranged on the emergency line (80) between the emergency connection (82) and the reservoir (26), the emergency valve (84) being switchable between a closed position and an open position.

8. Lifting platform (10) according to claim 7, wherein: • the emergency valve (84) is a manual valve, and • the lowering valve (110) includes a manual actuation member (118), which is configured to manually move the lowering valve (110) into the open position.

9. Lifting platform (10) according to any one of claims 6 to 8, wherein • the hydraulic circuit (24') also comprises: • a bypass fitting (92), which is an additional fluidic fitting, different from the emergency fitting (82), and which is arranged on the lowering circuit (60) between the safety device (100) and the regulating valve (71), • a bypass line (90), which fluidly connects the bypass fitting (92) to the reservoir (26), without passing through the pump (30), • a bypass valve (94), which is arranged on the bypass line (90) between the bypass fitting (92) and the reservoir (26), • a non-return valve (96) positioned on the bypass pipe (90), • the bypass valve (94) is a solenoid valve, which is switchable between a closed position, in which the fluid circulation from the downpipe (60) to the tank (26) through the bypass pipe (90) is prevented, and an open position, in which the fluid circulation from the downpipe (60) to the tank (26) through the bypass pipe (90) is not prevented.

10. Lifting platform (10) according to any one of claims 1 to 9, wherein: • the lifting platform (10) is a scissor lift.

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