GB2193174A

GB2193174A - Self powered vehicle

Info

Publication number: GB2193174A
Application number: GB08618529A
Authority: GB
Inventors: Alan J Weller
Original assignee: S & P Parkwood Ltd
Current assignee: S & P Parkwood Ltd
Priority date: 1986-07-30
Filing date: 1986-07-30
Publication date: 1988-02-03
Also published as: GB2193174B; GB8618529D0

Abstract

A vehicle is driven by a wheel 50 which is lowerable into a driving position for driving the vehicle at a slow speed but which can be raised to allow the vehicle to be towed at a much higher speed on non driven support wheels. The transmission for the drive is preferably hydraulic, generated by a battery driven electric motor driving an hydraulic motor. <IMAGE>

Description

SPECIFICATION Self powered vehicle The present invention relates to a self powered vehicle and more particularly to a vehicle which is required to be moved occasionally a relatively short distance and is also capable of being towed when required over longer distances.

The particular invention will be described with reference to aircraft steps but it is applicable to other vehicles which perform in a similar manner, being moved only occasionally.

The problem with vehicles that are moved only occasionally is that it is normally too expensive to provide them with a petrol engine which allows them to be self propelled and therefore they are normally towed by a vehicle such as a small tractor unit. In the case of aircraft steps which weigh possibly 2 or 3 tons then the tractor unit is required for even the smallest manoeuvre and often the tractor unit has to be fetched from a long distance location causing delay and expensive in time and fuel.

It is an object of the present invention to provide a self powered vehicle which can propel itself over short distances and can be readily towed over longer distances if required.

Accordingly the present invention provides a self propelled vehicle including a plurality of non-driven support wheels and including a further driven wheel which is movable in a vertical direction to engage the ground to drive the vehicle and which when not required can be lifted clear of the ground.

Preferably the driven wheel is powered by a hydraulic ram to move in a vertical direction and is powered by a hydraulic motor to move the vehicle in a forward or reverse direction.

Preferably the hydraulic motor is provided with hydraulic fluid under pressure from a hydraulic pump powered by an electric drive provided by one or mqre batteries mounted on the vehicle. The vehicle is also preferably provided with a battery charger and an electric lead for connection of the battery charger to a mains power supply point for recharging the batteries when required.

Preferably the driven wheel is normally held clear of the ground by spring means. In a preferred embodiment the pressure exerted by the driven wheel on the ground is controlled by pressure relief valve means oeprating in combination with the hydraulic ram to maintain the ram at a predetermined maximum pressure.

There is preferably provided a hydraulic valve to maintain pressure in the hydraulic system even when the electric motor is turned off. This provides a braking effect on the drive wheel which thereby brakes the vehicle.

A further braking force may be obtained by using the hydraulic pressure to power a brake on one or more of the non-driven vehicle support wheels as required.

A release lever is preferably provided on the side of the vehicle to release the hydraulic pressure allowing the vehicle to be towed using a tow bar attachment.

Preferably the hydraulic system is controlled with a control box mounted preferably on a flying lead such that a single operator can manoeuvre the vehicle.

In a preferred embodiment the vehicle is a set of aircraft steps which are adjustable in height by a further hydraulic ram which may be powered from the hydraulic motor. The steps may be provided with side supports in the form of retractable struts and these may be provided with hydraulically operated legs also powered by the hydraulic motor.

Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 illustrates the principle of the invention and shows a self powered vehicle in outline detail only; Figure 2 shows diagrammatically the chassis for a self powered vehicle according to the present invention; Figure 3 shows in greater detail the driven wheel assembly shown in Figures 1 and 2; and Figure 4 shows a set of aircraft steps mounted integrally with a self powered vehicle according to the present invention.

With reference now to Figure 1 the vehicle 10 is represented for simplicity by a chassis 20 with four wheels 22, 24, 26, 28 at each corner. The chassis could carry any suitable body such as in Figure 4.

The chassis 20 is provided with a turntable bogey arrangement 30 at the front of which the front wheels 24, 26 are attached. A tow bar 32 is hingedly attached to the bogey 30, the tow bar being counterbalanced by a weight 34 so that it can be readily held by an operator and when the vehicle is in motion turned to steer the vehicle.

A control box 36 may be positioned on the tow bar and is preferably detachably mounted (by, for example, a magnetic base) so that using a flying (or wander) lead 36 the operator can manoeuvre the vehicle whilst standing slightly remotely therefrom, for example, to obtain a better view.

The power unit for the vehicle comprises a hydraulic control and power unit 40 which powers a driven wheel 50 as will be explained with reference now to Figures 2 and 3. In Figure 1 the wheel 50 is shown in both its upper and lower position.

The power unit 40 comprises a tank 41 for storage of hydraulic fluid, a hydraulic pump 42 and electric motor the pump 43. The electric motor is powered, by a battery pack 44 of preferably four six volt power batteries. A battery charger 45 is provided for charging the battery from a normal mains (230 volt) supply. The hydraulic fluid pressurised by pump 43 is controlled by a fluid valve arrangement 46. Hydraulic lines 51, 52, 53, 54 provide output hydraulic fluid from valves 46 to various hydraulic transducers as follows.

Pressure line 51 is operated to power a hydraulic motor which can propel the vehicle in a forward or reverse direction. Line 52 provides power to a hydraulic ram to lower wheel 50 into contact with the ground surface. Line 53 is operable to provide hydraulic pressure to a brake cylinder 55 which can be used to operate the brakes on the non-driven wheel 28 (shown dotted) to provide a further positive braking force on the vehicle as will be explained hereafter.

Line 54 is used to provide hydraulic power to the outriders of which only one is shown.

Outrider 60 which is used to stabilise the aircraft steps or similar structures comprises a horizontal arm 62 with a hydraulically operated foot 64 which arm 62 can be moved outwardly from the chassis 20 and provide stabilisation, when the hydraulic foot is pressed down on the ground surface, for the vehicle.

With reference to Figure 3 the driven wheel 50 is mounted on an arm 80 which is pivoted on a pivot pin 82 connected on a bracket 84 to cross member 86 of the chassis 20. Arm 80 is normally held in a horizontal (non-operative) condition by springs 88 but on operation of the drive button on control box 36 the arm 80 is lowered by hydraulic ram 90 at a defined hydraulic pressure determined by pressure bypass valves (in known manner) until wheel 50 touches the ground. At this time the valve control box 46 causes wheel 50 to be rotated in a forward or reverse direction by application of hydraulic pressure on line 51.

The pressure relief valves are operative to maintain pressure when the motor 43 is turned off. Thus on release of the forward or reverse buttons the wheel 50 is braked by hydraulic motor 92. The braking effect may lapse over a defined period, or with uneven ground may not be adequate and therefore it can be arranged that on release of the forward or reverse buttons on control 36 hydraulic pressure is applied to line 53 to brake the non-driven wheel 28.

The control box 36 contains buttons as follows.

Forward Reverse Fast-normal walking speed Slow or inching speed-selectable for final positioning.

In addition individual controls may be used for the stabilising feet 64 etc.

In Figure 4 the vehicle carries steps 100 which can be raised by a hydraulic ram 102 which can be driven from the motor 43/44 if required.

If the steps are required to be moved short distances then the battery/hydraulic power unit is used. For longer distances a tow vehicle is normally used. For this purpose to relieve the pressure in the hydraulic system a lever 200 is provided, preferably separate to control box 36, on the chassis (Figure 2). The lever releases the hydraulic pressure in the system and allows spring 88 to lift wheel 50 allowing the vehicle to be towed by tow bar 32 without damage to the hydraulic motors and without the additional friction imposed by wheel 50.

Claims

1. A self propelled vehicle including a plurality of non-driven support wheels and including a further driven wheel which is movable in a vertical direction to engage the ground to drive the vehicle and which when not required can be lifted clear of the ground.

2. A self propelled vehicle as claimed in Claim 1 in which the driven wheel is powered by a hydraulic ram to move in a vertical direction and is powered by a hydraulic motor to move the vehicle in a forward or reverse direction.

3. A self propelled vehicle as claimed in Claim 2 in which the hydraulic motor is provided with hydraulic fluid under pressure from a hydraulic pump powered by an electric drive provided by one or more batteries mounted on the vehicle.

4. A self propelled vehicle as claimed in Claim 3 including a battery charger and an electric lead for connection of the battery charger to a mains power supply point for recharging the batteries when required.

5. A self propelled vehicle as claimed in any one of Claims 1 to 4 in which the driven wheel is normally held clear of the ground by spring means.

6. A self propelled vehicle as claimed in any one of Claims 2 to 5 in which the pressure exerted by the driven wheel on the ground is controlled by pressure relief valve means over ating in combination with the hydraulic ram to maintain the ram at a predetermined maximum pressure.

7. A self propelled vehicle as claimed in any one of Claims 3 to 6 including a hydraulic valve to maintain pressure in the hydraulic system even when the electric motor is turned off providing a braking effect on the drive wheel which thereby brakes the vehicle.

8. A self propelled vehicle as claimed in Claim 7 in which a further braking force is obtained by using the hydraulic pressure to power a brake on one or more of the nondriven vehicle support wheels as required.

9. A self propelled vehicle as claimed in Claim 8 in which a release lever is provided on the side of the vehicle to release the hydraulic pressure allowing the vehicle to be towed using a tow bar attachment.

10. A self propelled vehicle as claimed in any one of Claims 2 to 9 in which the hydraulic system is controlled with a control box mounted on a flying lead such that a single operator can manoeuvre the vehicle.

11. A self propelled vehicle as claimed in any one of Claims 2 to 10 in which the vehicle is a set of aircraft steps which are adjustable in height by a further hydraulic ram which may be powered from the hydraulic motor.

12. A self propelled vehicle as claimed in Claim 11 in which the steps are provided with side supports in the form of retractable struts and these may be provided with hydraulically operated legs also powered by the hydraulic motor.

13. A self propelled vehicle substantially as described with reference to the accompanying drawings.