Aerial lift

Abstract

The invention relates to an aerial lift comprising a basket that is supported by a lifting structure deployable by means of a hydraulic actuator (22) so as to lift the basket. The aerial lift includes a safety device (120) that comprises a safety valve (121) which is switchable between an open position and a closed position and which is returned to the closed position by a return member (127). The safety device comprises 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) is higher than a switching pressure. A restriction member (132) is arranged on the auxiliary line (130) so as to restrict the fluid flow rate through the auxiliary line (130).

Description

[0001] TITLE: Aerial Work Platform

[0002] The present invention relates to a lifting platform.

[0003] A boom lift is a mobile elevating work platform for personnel. Several types of boom lifts are known, including articulated boom lifts, mast lifts, telescopic boom lifts, scissor lifts, etc. A boom lift—also simply called a "platform"—consists of a chassis, which is equipped with ground-mounted traction devices such as wheels; a basket, which is designed for an operator to stand on; and a lifting structure, which is positioned between the basket and the chassis to adjust the basket's height relative to the chassis. The lifting mechanism generally includes at least one actuator, such as a hydraulic cylinder, which is designed to extend or retract the lifting mechanism, raising or lowering the basket.

[0004] 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.

[0005] In the case of a scissor lift, the lifting mechanism comprises bars hinged at their center like scissors. Several of these scissor mechanisms are mounted one above the other at their ends, which are pivotally connected, allowing the assembly of hinged bars to fold and extend vertically. The actuator is positioned between the hinged bars to extend or fold them. To enable the basket to be lifted, the ends of the upper bars are connected to pads that slide in rails located beneath the basket platform, while the ends of the lower bars are connected to pads that slide in rails on the chassis.The lifting device thus makes it possible to raise the basket from a lowered position on the chassis to the desired working height, generally by means of one or more hydraulic cylinders, the basket being then in a raised position.

[0006] This section focuses on platforms with hydraulic actuators, typically hydraulic cylinders. The platform includes a hydraulic pump driven by an electric motor. One end of each cylinder is attached to a component of the lifting structure. The cylinders are fluidly connected to the pump via a flexible hose, allowing them to accommodate deformations in the lifting structure during the basket's raising and lowering movements. Safety standards, such as EN 280-1:2022 §4.10.2, require a safety device that limits the descent speed and immobilizes the basket in the event of an accidental rupture of the flexible hose while the basket is in the raised position.Generally, a calibrated orifice and a poppet valve (or a proportional poppet valve) are installed at an outlet of the actuator, in order to limit the descent speed and immobilize the basket in case of accidental rupture of the flexible pipe.

[0007] We are particularly interested in aerial work platforms incorporating an electrical energy storage device that powers the electric motor via a variable frequency drive. The hydraulic pump is advantageously reversible, allowing energy to be recovered during the platform's descent, thus recharging the storage device. US-2023 / 0174354-A1 describes, for example, such an aerial work platform equipped with a calibrated orifice. However, the calibrated orifice (or proportional solenoid valve) causes pressure losses, reducing the amount of energy recoverable by the electric motor, which is undesirable. CN-111 392 617-A, on the other hand, describes a safety valve that switches on in case of pressure loss in the hydraulic circuit, with the hydraulic fluid flow being diverted, in the event of a pressure loss, through an auxiliary line equipped with a calibrated orifice.

[0008] It is these problems that the invention intends to address in particular, by proposing a lifting platform that ensures the safety of the basket in the raised 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 connection devices, 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:

[0010] • 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,

[0011] • a lifting circuit, through which a fluid circulates between a reservoir and the hydraulic actuator,

[0012] • 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,

[0013] • 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, in which the lifting platform also includes a descent system, which includes: a descent valve, which includes an inlet, which is connected to the main port of the actuator, and an outlet, which is connected to the descent circuit, the descent valve being switchable, under the action of a user, between an open position, in which the inlet is fluidically connected to the outlet through the descent valve, and a cut-off position, in which the fluid circulation between the inlet and the outlet through the descent valve is prevented.

[0014] According to the invention, the lifting platform also includes a safety device, which comprises: a safety valve including:

[0015] • an inlet port, which is fluidly connected to the outlet of the drain valve,

[0016] • an output port, which is different from the input port and is configured to be connected to the downlink circuit,

[0017] • 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.

[0018] • a return device, 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 device, when a pressure inside the auxiliary line is greater than a switching pressure, the switching pressure having a predetermined value, and a restricting device, which is arranged on the auxiliary line and which is configured to limit the fluid flow through the auxiliary line.Thanks to the invention, in the event of a pipe rupture, particularly a rupture of the flexible hose, the hydraulic pressure in the auxiliary line drops below the switching pressure, and the safety valve automatically switches from the open to the closed position, forcing the fluid through the restrictor. This ensures the safety of the platform in the raised position. During normal operation, especially 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 open. The fluid exiting the actuator passes through the regulating valve without flow restriction, thus not reducing the amount of recoverable energy. Thanks to the invention, the amount of recoverable energy is greater than that of prior art platforms.Safety is ensured by means of passive elements, that is to say, which do not require energy, particularly electrical, to function, and automatically, without external intervention.

[0019] 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:

[0020] The restrictor device includes a calibrated orifice.

[0021] The safety valve is a 2 / 2 hydraulically piloted valve, with the hydraulic piloting being done by means of the auxiliary line.

[0022] The downpipe valve is a solenoid valve, which is switchable, by electrifying a solenoid of the downpipe valve, between:

[0023] • 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

[0024] • a second position, in which the fluid passage from the main port to the safety system through the downpipe valve is prevented, while the downpipe valve includes a return device, configured to return the downpipe valve to the first position when the solenoid is not electrified, the downpipe valve passing into the second position when the solenoid is electrified.

[0025] The pumping unit is an electric pumping unit, which includes: a pump, an electric motor, a variable frequency drive, and an electricity storage device. The pump is reversible, configured to operate:

[0026] • 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,

[0027] • 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.

[0028] The downpipe includes a flexible section, while the hydraulic circuit also includes a control valve, which is located on the downpipe and is fluidly interposed between the safety device and the pumping unit, the control valve being located between the flexible section and the pumping unit, and the control valve is switchable, by electrification of a solenoid of the control valve, between:

[0029] • a resting position, in which fluid flow through the downpipe is prevented,

[0030] • an activation position, in which fluid circulation through the downpipe is not impeded, the control valve including a return element, configured to return the control valve to the first position.

[0031] The hydraulic circuit also includes:

[0032] • a backup connection, which is a fluid connection arranged between the safety device and the regulating valve,

[0033] • a backup line, fluidly connecting the backup fitting to the tank, and

[0034] • 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.

[0035] The relief valve is a manual valve, whereas the down valve includes a manual actuation device, which is configured to manually move the down valve into the open position.

[0036] The hydraulic circuit also includes:

[0037] • 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,

[0038] • a bypass line, which fluidly connects the bypass fitting to the tank, without passing through the pump,

[0039] • a bypass valve, which is arranged on the bypass pipe between the bypass fitting and the tank,

[0040] • a check valve positioned on the bypass pipe, while the bypass valve is a solenoid valve, which is switchable between a closed position, in which the fluid circulation from the downpipe to the tank through the bypass pipe is prevented, and an open position, in which the fluid circulation from the downpipe to the tank through the bypass pipe is not prevented.

[0041] The lifting platform is a scissor lift.

[0042] The invention will be better understood, and other advantages thereof will become more apparent, in light of the following description of two embodiments of a lifting platform, conforming to its principle, given solely by way of example and with reference to the accompanying drawings, in which:

[0043] [Fig 1] Figure 1 is a perspective view of a lifting platform according to a first embodiment of the invention;

[0044] [Fig 2] Figure 2 is a schematic representation of an actuation circuit for the nacelle in Figure 1, the actuation circuit being in a first configuration;

[0045] [Fig 3] Figure 3 represents the actuation circuit of Figure 1 in a second configuration;

[0046] [Fig 4] Figure 4 represents the actuation circuit of Figure 1 in a third configuration;

[0047] [Fig 5] Figure 5 represents the actuation circuit of Figure 1 in a fourth configuration;

[0048] [Fig 6] Figure 6 represents the actuation circuit of Figure 1 in a fifth configuration;

[0049] [Fig 7] Figure 7 is a schematic representation of an actuation circuit belonging to a lifting platform according to a second embodiment of the invention, the actuation circuit being in a first configuration, and [Fig 8] Figure 8 represents the actuation circuit of Figure 7 in a second configuration.

[0050] An example of a lifting platform 10 conforming to a first embodiment of the invention is shown in Figure 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.

[0051] 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.

[0052] The platform 10 also includes a basket 16, and an elevating structure 18 of 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. In normal use of the elevating platform 10, an operator stands on the platform 17A and pilots the elevating platform 10 using the control panel 17C.

[0053] The lifting structure 18, which is interposed between the chassis 12 and the basket 16, includes 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 includes two actuators, including a first actuator 22 located closest to the chassis 12, while the second actuator, further from the chassis 12 than the first actuator 22, is referenced 22'.The number of actuators 22 is not limited and generally varies depending on the size of the platform 10. Typically, the lifting platform 10 includes at least one actuator 22, specifically at least the first actuator closest to the chassis 12. The actuators 22 are hydraulic actuators, specifically hydraulic cylinders, each comprising a body 22A and a piston 22B. The piston is received in a bore of the body 22A and is free to move translationally relative to the body 22A. Each actuator 22 includes a main port 22C, through which the actuator 22 is supplied with hydraulic fluid to control a configuration of the actuator 22, in this case, to control the position of the piston 22B relative to the body 22A.

[0054] The lifting platform 10 includes 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 it 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, oil, which is considered incompressible. In the figures, when a fluid flows through a portion of the hydraulic circuit 24, that portion is indicated by a solid line, while the direction of fluid flow is indicated by arrows. In the example in Figure 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.

[0055] The tank 26 and the pumping unit 28 are preferentially supported by the chassis 12, while a part of each actuator 22 is fixed to the lifting structure 18.

[0056] 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 rotation of the pump 30, an electrical energy storage device 34, for example batteries, a variable speed drive 36, configured to transform a direct current voltage from the batteries into a variable alternating current voltage suitable for driving the electric motor 32.

[0057] The pump 30 is connected to the reservoir 26 via an inlet line 40, and is connected to the rest of the circuit

[0058] The pump 30 is preferably reversible, that is to say, the pump 30 is configured to operate selectively: in a pumping mode, in which the energy stored in the electricity storage device 34 is used by the drive 36 to control the electric motor 32 and drive the pump 30, circulating the fluid in the hydraulic circuit 24, and in 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 operates as an electrical energy generator, the generated electrical energy being used via the drive 36 to recharge the storage device 34. The hydraulic circuit 24 is described with reference to the operating modes of the nacelle 10.In Figure 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'.

[0059] 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 in Figure 3, considering the direction of fluid flow, the lift circuit 50 comprises, 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 lift valve 54 prevents the passage of fluid. In the standby configuration, the riser valve 54 is in the shut-off position, as in Figure 2, while in the rise configuration, the riser valve 54 is in the open position, as in Figure 3.

[0060] 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.

[0061] 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.

[0062] 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 share a common section 70, through which both 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.

[0063] 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 has 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 fluidly connected to the outlet 112 through the descent valve 110, and a closed position, in which fluid circulation between the inlet 112 and the outlet 114 through the descent valve is prevented. The descent valve 110 is thus in the closed position when the basket 10 is in the standby or ascending configuration.

[0064] Advantageously, the down valve 110 is a poppet valve, which is switchable, by electrification of a solenoid 115 of the down valve 110, between: a first position, in which the fluid passage from the inlet 112 to the outlet 114 through the down valve 110 is prevented, as illustrated in Figure 3, and a second position, in which the fluid passage from the inlet 112 to the outlet 114 through the down valve 110 is allowed without restriction, as illustrated in Figure 4.

[0065] 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.

[0066] Advantageously, the lowering valve 110 includes a manual actuation device 118, which is configured to manually move the first solenoid valve into the second position. The manual actuation device 118 is, for example, a pull handle or equivalent. This makes it possible to manually lower the basket 16, for example, in the event of a malfunction in the electrical systems of the platform 10 while the basket 16 is in a raised position. This aspect is described later.

[0067] 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 fluidically connected to the outlet 114 of the lowering valve 110, and an outlet port 124, which is different from the inlet port 122 and which is configured to be connected to the lowering 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 122 to the outlet 124 through the safety valve 121 is prevented.

[0068] 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 the rest position for the safety valve 122.

[0069] The safety device 120 also includes: 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, bypassing the safety valve. The auxiliary line 130 is configured to push the safety valve 121 into the open position against the return element 127 when the pressure inside the auxiliary line 130 exceeds a switching pressure, the switching pressure having a predetermined value. A restrictor 132 is also included, 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 impede the descent in the event of a hose rupture or in manual descent mode.

[0070] Without 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.

[0071] 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 closes. Fluid flow from the inlet port 122 to the outlet port 124 is then only possible through the auxiliary line 130, the flow rate being limited by the restrictor 132. In a preferred example, the safety valve 121 is a 2 / 2 hydraulically piloted valve, with hydraulic piloting achieved via 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.

[0072] 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.

[0073] 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 figure 4.

[0074] The regulating valve 71 is then switched and put in the open position to allow the oil supply to the pump 30.

[0075] Typically, during descent, the fluid pressure in the descent circuit 60 is greater than the switching pressure of the safety valve 121.

[0076] 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 nacelles of the prior art, 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 unwanted pressure losses and antagonistic to the objective of energy recovery.

[0077] In this "recovery" energy configuration, the descent speed is adjustable via the speed control of the pump 30 by the variator 36.

[0078] The hydraulic circuit 24 comprises rigid sections, made primarily of metal tubing, and flexible sections, made primarily of polymer tubing, 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 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.

[0079] Rigid pipes, and by extension any portion of the hydraulic circuit considered rigid, are generally made of metal tubing and are considered unbreakable. At least, under normal operating conditions, the risk of accidental rupture is very low. In comparison, flexible pipes, and by extension any so-called "flexible" portion of the hydraulic circuit, are generally made of elastomer, possibly reinforced by a braid of fibers, particularly metallic ones. Despite all the care taken in the manufacture of flexible pipes, the risk of rupture is not zero and must be anticipated.

[0080] In the example shown in Figure 5, the gondola 10, initially in the descending position, experiences a rupture in the flexible section 61 of the descent circuit, creating a leak. The rupture of the flexible section 61 is represented by a pair of scissors cutting the flexible section. 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 shown in Figure 4, then moves to the closed position, as shown in Figure 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 restriction device 132 is configured to sufficiently reduce the flow through the auxiliary pipe 130 so that the descent speed does not present a danger to any users possibly 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 gondola 10.

[0081] Advantageously, the hydraulic circuit 24 also includes an emergency line 80, which connects the descent circuit 60 to the reservoir 26, without going through the pump 30.

[0082] 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.

[0083] During normal operation of the lifting platform 10, the emergency valve 84 is left in the closed position. In the event that all the 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 lowering valve 110 to the second position using the manual actuation device 118, and by moving the safety valve 84 to the open position.

[0084] In this emergency lowering configuration, lines 130 and 61 are connected to the reservoir, and the pressure is lower than the switching pressure of safety valve 121, which remains in the closed position. In other words, safety device 120 limits the flow of fluid, just as it would in the event of a rupture of hose 61, and the descent speed of basket 16 is regulated by restrictor 132.

[0085] Alternatively, emergency drainage can be achieved by equipping the control valve 71 with a manual control that allows 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.

[0086] 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 primarily 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.

[0087] In the second embodiment, the downpipe valve 110 is a proportional-type solenoid valve. The downpipe valve 110 is switchable between: the first position, in which the fluid flows from the inlet 112 to the outlet

[0088] 114 through the downpipe valve 110 is prevented, the second position, in which the fluid passage from the inlet 112 to the outlet

[0089] 114 through downpipe valve 110 is permitted without restriction, and a third position, intermediate between the first and second positions, in which the fluid passage from inlet 112 to outlet 114 through downpipe valve 110 is permitted with restriction / braking, as illustrated in Figure 8.

[0090] In other words, the 110 downpipe valve is adjustable, so as to restrict the flow of fluid in a variable manner.

[0091] 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.

[0092] The hydraulic circuit 24 also includes a bypass valve 94, which is arranged on the bypass line 90 between the fluidic fitting 92 and the reservoir 26. The bypass valve 94 is a solenoid valve, which is switchable between a closed position, in which the fluidic circulation from the downpipe 60 to the reservoir 26 through the bypass line 90 is prevented, and an open position, in which the fluidic circulation from the downpipe 60 to the reservoir 26 through the bypass line 90 is not prevented. A check valve 96 is advantageously placed 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 greater than the switching pressure when a fluid flows through the bypass valve 94 in the open position.

[0093] 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.

[0094] In Figure 7, the hydraulic circuit 24' is shown in its standby configuration. In Figure 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, meaning no electricity is generated. This situation occurs particularly when the batteries are already sufficiently charged.

[0095] In this configuration, the descent speed is defined by the degree of opening of the descent valve, here a proportional solenoid valve. In the illustrated embodiments, the safety system according to the invention ensures a controlled descent speed of the basket in the event of a rupture of the flexible hoses, without 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 for energy recovery; in such cases, only the safety function is performed.

[0096] The embodiments and variants mentioned above can be combined to generate new embodiments of the invention.

Claims

DEMANDS 1. Lifting platform (10), in which the lifting platform (10) comprises: a chassis (12), which is provided with ground connection devices (14), a basket (16), which is adapted for an operator to stand on, 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 comprises: • 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 flows, during a descent phase of the lifting platform (10), from the hydraulic actuator (22; 22') to the reservoir (26), wherein the lifting platform (10) also includes a descent system (100), which includes: a descent 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 descent circuit (60), the descent valve (110) being switchable, by the action of a user, between an open position, in which the inlet (112) is fluidly connected to the outlet (114) through the descent valve (110), and a closed position, in which the fluid flow between the inlet (112) and the outlet (114) through the drain valve (110) is blocked, in which the lifting platform (10) also includes a safety device (120), which includes: 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 member (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 switching pressure, the switching pressure having a predetermined value, a restricting member (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 electrification of a solenoid of the lowering valve (110), between: 19 • a first position, in which a check valve of the downpipe 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 the fluid passage from the main port (22C) to the safety system (120) through the downpipe valve (110) is prevented, the downpipe valve (110) includes a return member (116), configured to return the downpipe valve (110) to the first position when the solenoid is not electrified, the downpipe 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 lowering pipe (60) comprises a flexible portion (61), the hydraulic circuit (24; 24') also comprises a control valve (71), which is located on the lowering circuit (60) and which is fluidly interposed between the safety device (100) and the pumping unit (28), the valve 20. The control valve (71) being located between the flexible section (61) and the pumping unit (28), the control valve (71) is switchable, by electrification of 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 circulation through the downpipe (60) is not prevented, 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, wherein: the hydraulic circuit (24; 24') also comprises: • a backup 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 fitting (82) to the reservoir (26), • a relief valve (84), which is arranged on the relief pipe (80) between the relief fitting (82) and the tank (26), the relief 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 fluid fitting, different from the emergency fitting (82), and which is arranged on the downpipe (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), 21 • a bypass valve (94), which is arranged on the bypass pipe (90) between the bypass fitting (92) and the tank (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 of the downpipe (60) to the reservoir (26) through the bypass pipe (90) is prevented, and an open position, in which the fluid flow from the downpipe (60) to the reservoir (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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