GB2570443A

GB2570443A - Wheelchair lifts

Info

Publication number: GB2570443A
Application number: GB1800788.0A
Authority: GB
Inventors: Beck Adam
Original assignee: Mobility Networks Holdings Ltd
Current assignee: Mobility Networks Holdings Ltd
Priority date: 2018-01-18
Filing date: 2018-01-18
Publication date: 2019-07-31
Also published as: GB201800788D0

Abstract

The wheelchair lift system for a vehicle comprises a lift platform 10 raised by a hydraulic actuator 20, a pump 24 supplying hydraulic fluid under pressure to the actuator 20, a drive 26 for the pump 24 that draws power from a battery 28. Power generated by the flow of hydraulic fluid from the actuator 20 as the platform 10 is lowered recharges the battery 28. The drive 26 may be an electric motor such as a brushless DC motor that generates electric power when the pump 24 is driven. The drive 26 may include an electric generator powered by the flow of fluid from the actuator 20 to supply the battery 28. The electric generator may be a dynamo 54 located in a pump bypass or return line 50 that accommodates fluid flow. The bypass line 50 may include an impeller 56 to drive the electric generator.

Description

WHEELCHAIR LIFTS

Field of the Invention

The present invention relates to wheelchair lifts, and in particular to electrically powered wheelchair lifts for mounting on vehicles.

Background to the Invention

Wheelchair lifts for allowing access for wheelchairs to vehicles, such as coaches and minibuses, are well known. Such lifts are often hydraulically powered, with the hydraulic pump being powered from an electric battery. The battery is generally arranged to be recharged when the vehicle engine is running which therefore encourages running of the engine to ensure that the battery is fully charged.

It is increasingly desirable to reduce power consumption on vehicles to reduce the carbon footprint of the vehicle.

Summary of the Invention

The invention provides a wheelchair lift system for a vehicle, the system comprising a lift platform arranged to support a wheelchair, a hydraulic actuator arranged to raise the lift platform, a pump arranged to supply hydraulic fluid under pressure to the actuator, a battery, and drive means arranged to drive the pump using electric power from the battery, and to recharge the battery using power generated by the flow of hydraulic fluid from the actuator as the lift platform is lowered.

The drive means may comprise an electric motor, which may be a brushed motor or a brushless motor, for example a brushless DC induction motor. The motor may be connected to the pump, either directly or through a gear system with a variable gear ratio, and arranged to generate electric power when the pump is driven by the flow of fluid from the actuator.

The drive means may further comprise an electric generator arranged to be powered by the flow of fluid from the actuator and to supply electric current to the battery.

The wheelchair lift system may claim further comprise a pump bypass line through which fluid can flow from the actuator to bypass the pump. The electric generator may be arranged to be powered by the flow of fluid in the bypass line.

The drive means may be controllable so as to vary the relationship between the rate of descent of the lift platform and the electric current generated to recharge the battery. This may be achieved by a variable ratio gear system, or by controlling the electric motor/generator to vary the relationship between the speed or rotation of the motor and the output current of the motor/generator.

The system may further comprise control means arranged to control the drive means to vary the relationship between the rate of descent of the lift platform and the electric current generated to recharge the battery, thereby to control the rate of descent of the lift platform.

The system may further comprise, in any workable combination, any one or more features of the preferred embodiments of the invention as will will now be described by way of example only with reference to the accompanying drawings.

Brief Description of the Drawings

Figure 1 is a schematic diagram of a wheel chair lift system according to an embodiment of the invention as its lift platform is being raised; and

Figure 2 is a schematic diagram of the wheel chair lift system of Figure 1 as its lift platform is being lowered.

Description of the Preferred Embodiments

Referring to Figure 1, a wheelchair lift comprises a platform 10 arranged to support a wheelchair 12, and a pair of lifting arm assemblies 14 each of which comprises a pair of lifting arms 16, 18 and a hydraulic actuator 20. Each of the lifting arm assemblies 14 has one end connected to the platform 10 and the other end connected to the chassis 22 or body of a vehicle, and is arranged in a parallelogram arrangement so that the actuators 20 can raise the lift platform 10 relative to the vehicle chassis 22.

The hydraulic circuit that powers the actuators 20 comprises a hydraulic pump 24 driven by an electric motor 26, and connected to a hydraulic reservoir 27. The electric motor 26 is connected to, and powered by, a battery 28. The hydraulic circuit also comprises a pressure line 30 connecting the hydraulic outlet 30 of the pump 24 to the hydraulic actuators 20. For example the pressure line may be connected to a manifold which in turn is connected to each of the two actuators via respective actuator lines 34. The manifold may further be connected to other hydraulically actuated components of the system, such as a roll-off ramp actuator 36 which is arranged to raise a roll-off ramp 38 when the lift platform 10 is raised above ground level.

In order to recharge the battery 28 during lowering of the lift, the motor 26 may be arranged to operate as an electric generator if hydraulic fluid flows from the actuators 20, through the pressure line 30 driving the pump 24 in a reverse direction so that it acts as an impeller, and back to the reservoir 27. For example the motor 26 may be a brushless DC motor. The motor may include a drive circuit which may be controlled, for example, by a system controller 40. The system controller may be connected to a control unit 42 which may include inputs such as control buttons 44, 46 which can be operated by a user to raise and lower the lift. It will be appreciated that the drive circuit will typically be arranged to switch each of a number of windings of the motor into the electrical circuit of the motor in turn so as to drive the motor, or, if the motor is operating as a generator, so as to generate electrical current in the electrical circuit.

Alternatively, or in addition, the hydraulic circuit may comprise a pump bypass or return line 50 connected between the pressure line 30 (or the manifold 32) and reservoir, through which fluid can flow from the actuators 20 back to the reservoir as the lift is lowered. The return line 50 may have a two-way valve 52 in it which can be opened to allow fluid to flow through the return line in the direction from the actuators 20 to the reservoir 27 or closed to prevent such flow. The two way valve 52 may be connected to and controlled by the system controller 40. An electric generator or dynamo 54 may be provided, and may be connected to a hydraulic impeller 56 in the return line 50. The generator 54 may therefore be arranged to generate electric current as fluid flows through the return line 50 from the actuators 20 to the reservoir 27. The generator 54 may be connected to the battery 28, for example via a voltage regulator 58, so that power generated by the generator 54 can re-charge the battery 28. A hydraulic flow regulator 60 may also be provided in the return line 50 to regulate the flow of fluid through the return line 50 from the actuators 20 to the reservoir 27, thereby to regulate the speed of lowering of the lift.

In operation of the system, referring to Figure 1, during raising of the lift platform, a user presses the ‘up’ button 44 on the control unit 42 which provides an input to the system controller 40 indicating that the lift is to be raised. The controller 40 is arranged, if the return line 50 is present in the system, to close the two way valve 52, and to control the pump motor drive circuit to power the motor 26. This drives the pump 27 which pumps fluid from the reservoir 27 to the pressure line 30. This in turn powers the actuators 20 to raise the lift platform 10, and if appropriate, the roll-off ramp 38.

Referring to Figure 2, if the lift is to be lowered, the user presses the ‘down’ button 46 on the control unit which sends a signal to the controller 40 to lower the lift. If the return line 50 is present in the system, the controller 40 may be arranged to open the two-way valve 52 to allow flow of fluid away from the actuators 20. Reverse flow of fluid through the pump 24 will generally be prevented either by the design of the pump itself or a non-return valve. The weight of the platform 20 and the wheelchair and wheelchair user urge the platform 10 downwards, which tends to urge fluid from the actuators to the reservoir via the return line 50 and past the impeller 56 which drives the generator 54 thereby generating electrical current which flows to, and recharges, the battery 28. The speed of descent of the platform may be controlled by the regulator 60. Depending on the design of the generator, the resistance provided by the impeller and generator may be controlled by the control unit 40. This may be achieved, for example, by controlling a variable gear ratio between the impeller 56 and the generator 54. Alternatively PWM control of the generator by the control unit 40 may be used to vary the ratio between the speed of rotation of the impeller and the power output of the generator.

If the return line 50 is not present, and the motor 26 is operable as an electrical generator, then as the lift lowers fluid from the actuators 20 flows through the pump 24 to the reservoir 27, and the pump 24 drives the motor 26 causing it to generate electrical power which is input to the battery 28 to recharge it. Again, the speed of descent of the lift may be controlled by a hydraulic flow regulator, or by control of the motor 26 to control the rate of electrical power generation.

Claims

1. A wheelchair lift system for a vehicle, the system comprising a lift platform arranged to support a wheelchair, a hydraulic actuator arranged to raise the lift platform, a pump arranged to supply hydraulic fluid under pressure to the actuator, a battery, and drive means arranged to drive the pump using electric power from the battery, and to recharge the battery using power generated by the flow of hydraulic fluid from the actuator as the lift platform is lowered.

2. A wheelchair lift system according to claim 1 wherein drive means comprises an electric motor connected to the pump.

3. A wheelchair lift system according to claim 2 wherein the motor is arranged to generate electric power when the pump is driven by the flow of fluid from the actuator.

4. A wheelchair lift system according to claim 3 wherein the motor is a brushless DC motor.

5. A wheelchair lift system according to claim 1 or claim 2 wherein the drive means further comprises an electric generator arranged to be powered by the flow of fluid from the actuator and to supply electric current to the battery.

6. A wheelchair lift system according to claim 5 further comprising a pump bypass line through which fluid can flow from the actuator to bypass the pump, wherein the electric generator is arranged to be powered by the flow of fluid in the bypass line.

7. A wheelchair lift system according to claim 6 further comprising an impeller in the bypass line arranged to drive the electric generator.

8. A wheelchair lift system according to any preceding claim wherein the drive means is controllable so as to vary the relationship between the rate of descent of the lift platform and the electric current generated to recharge the battery.

9. A wheelchair lift system according to claim 8 further comprising control means arranged to control the drive means to vary the relationship between the rate of descent of the lift platform and the electric current generated to recharge the battery, thereby to control the rate of descent of the lift platform.