GB2488141A

GB2488141A - Steering mechanism for an all terrain wheelchair

Info

Publication number: GB2488141A
Application number: GB1102759.6A
Authority: GB
Inventors: Tim John Morgan; John Edward Wardle
Original assignee: MOUNTAIN TRIKE Co Ltd
Current assignee: MOUNTAIN TRIKE Co Ltd
Priority date: 2011-02-17
Filing date: 2011-02-17
Publication date: 2012-08-22
Also published as: GB201102759D0

Abstract

A vehicle such as an all terrain wheelchair includes three or more ground engaging wheels 1, 16, and a steering assembly which allows a single user-actuated lever 19 to control the direction of steered wheel 16. The steering assembly includes a mounting member 13 having actuation means 49 operated by the lever, a steering member 43, and a bearing 47. The steering member 43 rotates coaxially with the bearing 47 about the steering axis of the steered wheel, and the mounting member, actuation means and steering member are detachable as a single unit. The wheelchair includes suspension means 12 allowing vertical displacement of the steered wheel. The mounting member is preferably detachably held in place by an engagement member 44, which may comprise a bush-button release mechanism 50. The actuation means are preferably cables which cause the steering member to rotate about the steering axis when the lever is pivoted. The wheelchair preferably includes front wheels 1 driven by a propulsion system 2, 4, 5 operated via reciprocal motion of levers 20. The suspension means may comprise an air spring damper 12, a coil spring (see figure 4), or a torsion spring (see figure 5).

Description

All Terrain Wheelchair This invention relates to a device that enables users to travel over rough terrain whilst seated and whereby movement of the vehicle is effected by the power of the arms.

Normally people with fully functioning limbs can travel over rough ground using bicycles or tricycles designed for the purpose and where the power is provided by the legs. There are a number of people who for various reasons do not have the ability of using their legs for driving such vehicles. These people will typically use a wheelchair and drive it by using their arms, normally by rotating wheels positioned either side of their body when seated. These wheelchairs are satisfactory when the terrain is smooth and the incline of the path is not steep. As the terrain becomes rough and the inclines varied so it becomes both difficult and hazardous to move the vehicle whilst seated.

Standard wheelchairs have good practicality on smooth surfaces, but have poor off-road performance and limit the terrain which can be tackled. People who use these wheelchairs are restricted from moving over rough ground, so they cannot freely travel around many gardens and parks or natural fields and walks which the able bodied people take for granted. It is a purpose of this invention to provide such people the facility of moving into spaces that are currently impossible for them to visit, whilst still maintaining the practicality and transportability of a standard wheelchair.

Certain four wheeled downhill racing wheelchairs have good off-road performance and allow the user to tackle a high level of rough terrain, but lack the practicality of a standard wheelchair for everyday use due to their size and weight.

Typically, in order to steer the standard wheelchair a different force is applied to one wheel relative to the other wheel. Such an operation clearly limits the force available to drive the vehicle forward which may restrict the user to less challenging terrain. In addition, since the wheels and axles must be conveniently located to enable the user to effectively apply force to the wheels to drive the vehicle forwards, then the relative position of the centre of gravity of the user to the point of contact of the wheels on the ground is not optimised to maximise stability of the vehicle. A standard wheelchair however has good practicality in terms of its ability to be folded or dismantled by the User in order to occupy less space and break down into modules of manageable weight for a wheelchair user. This enables the wheelchair to be transported in a vehicle or stored in their house or garage. This is crucial as the User will need to take their wheelchair wherever they go in their car. Therefore the additional aim of this invention is to provide this usability by allowing the User to fold and dismantle the device quickly and easily for transportation, whilst still overcoming the fundamental shortcomings of a standard wheelchair in terms of its ability to travel over rough terrain.

According to the present invention, there is provided a vehicle as defined in the attached claims.

The invention aims to overcome the shortcomings of standard wheelchairs by providing a propulsion means so that the user can deliver sufficient force to the wheels to drive over obstacles and over soft ground; that there is braking means provided to prevent the vehicle from rolling backwards down inclines and control the speed of descent forwards; that there is a steering means provided to steer the vehicle without reducing the power available to drive the vehicle forward and that there is a configuration means provided to position the user relative to the supporting wheels so as to improve stability on inclined surfaces. The main drive wheels, drive levers and steering mechanism are detachable and the rear wheel folds to enable the transportability function.

The steering means is preferably provided by a ground engaging wheel or wheels the direction of which can be controlled by means of a manually operated lever and cable arrangement so adjusting the direction of travel of the vehicle. The steering means is detachable from the main chassis via a quick release arrangement to enable easy transportation without requiring interruption to the steering setup. The steering wheel or wheels may be mounted to the frame via a means of cushioning. The propulsion means is provided by a manually held lever and ratchet mechanism which operates a drive mechanism to turn the wheels and propel the vehicle forwards or backwards. A cushioning means may be provided such that the axis of the driving wheels may be displaced relative to the attachment means. A braking means is preferably provided by manually squeezing a lever which operates a cable and brake mechanism very like that used on conventional bicycles. The propulsion mechanism and drive wheels are detachable from the main chassis such that the means of cushioning and drive mechanism remain intact as one unit allowing easy transportation. The resultant design provides a means for the user to steer, drive and brake the vehicle using only the hands and arms without losing grip, whilst the additional ability of these systems to be detached with no interruption to their setup (i.e. disconnecting steering cables or drive chain) enables easy transport of the device.

The cushioning means suspending the steering and propulsion should preferably be damped suspension struts such as an air or coil spring shock absorber, but could also be achieved via other means such as a torsion spring or rubber blocks.

The cushioning means may be adjustable so that the degree of cushioning and damping may be modified to suit different users.

The steering means is preferably provided by operating cables which twist the steering wheel left or right due to an input from the user. It may also be provided by use of hydraulic or pneumatic mechanisms.

The propulsion means is preferably provided by a one way clutch, but could also be provided by use of a ratchet free-wheel.

The drive mechanism to translate the operation of the lever to the rotation of the drive wheels is preferably provided by a chain and sprocket. However, it could also be provided by a belt and pulley arrangement or shaft drive.

The propulsion means may be adjustable so that different speeds of travel may be achieved by varying the mechanical advantage of the system. This may be achieved by introducing a means of changing the gear ratio between the lever and the drive wheel or alternatively by varying the length of the propulsion lever.

In order to achieve satisfactory stability and a better ability to overcome obstacles the vehicle is preferably arranged so that the larger diameter drive wheels are at the front and the steering wheel or wheels at the rear. The device may also be arranged with the larger diameter wheels at the rear and the steering wheel or wheels in the front.

The braking means is preferably provided by a disc brake mounted at the hub of the ground contacting wheel and a hand operated lever mounted on the propulsion lever. However, the braking means may also be provided by a rim brake or drum brake.

It is preferred that the steering means, arrangement of larger diameter drive wheels at the front, propulsion means and suspension system are all used in conjunction as each system in isolation does not work effectively if fitted to a standard wheelchair. It may also be possible to install the steering means without the propulsion means or cushioning means, or in the less preferable arrangement with the larger diameter wheels at the rear. The installation of any of the aforementioned subsystems in isolation is possible but not preferred for optimum performance.

The propulsion means, cushioning means, steering actuation lever and front drive wheels form a drive module which is removable without disconnecting the drive means or dismantling the suspension. There is a left and right drive module, mounted to opposing sides of the vehicle. One of the modules houses the steering actuation lever which is linked to the frame mounted steering actuation unit via cables. Therefore it must also be possible to remove the steering actuation unit from the frame when the drive module is removed.

The steering means which effects directional change of the steering wheel is detachable via a push button such that the cables maintain tension, allowing the steering means to be detached along with the steering lever to which it is linked via the cables. However, the detachment means could also be provided by a quick release cam lever clamp or locating pin and groove.

The invention will now be described solely by way of example with reference to the accompanying drawings in which: Figure 1 shows the overall preferred layout of the device with larger diameter drive wheels at the front and steering wheel at the rear Figure 2 shows the overall layout of the device in isometric view with the front wheels hidden for clarity Figure 3 shows a Detachable Direct Steering mechanism with cushioning means Figure 4 shows a Detachable Direct Steering mechanism with alternative cushioning means Figure 5 shows a Detachable Direct Steering mechanism with another alternative cushioning means Figure 6 shows a Detachable Direct Steering system Figure 7 shows a Detachable Direct Steering mechanism in cross section Figure 8 shows a Detachable Direct Steering mechanism Figure 9 shows a Quick Release button for a Detachable Direct Steering mechanism in its engaged position Figure 10 shows a Quick Release button for a detachable direct steering mechanism in its disengaged position Figure 11 shows a detachable direct steering mechanism with alternative actuation means Figure 12 shows a detachable lever operated propulsion system linked to a detachable steering module Figure 13 shows the device with its lever operated propulsion systems detached for transport Figure 14 shows an alternative attachment arrangement for the Detachable Direct Steering system Figure 15 shows an alternative attachment arrangement for the detachable direct steering system in its engaged position Figure 16 shows an alternative attachment arrangement for the detachable direct steering system in its disengaged position In Figure 1, the wheelchair features front wheels number 1 which are of larger diameter than the rear steering wheel number 16. The front wheels number I are driven via a propulsion mechanism consisting of a chain 4, input sprocket and output sprocket 2 and a propulsion lever 20 including a freewheel element allowing the device to travel without causing the propulsion lever to rotate. The propulsion system is supported by a swing arm member 18 which is freely hinged at its upper end and carries the ground contacting wheel and axis at its lower end. The swing arm 18 and propulsion lever 20 both pivot about the same point such that the propulsion system is unaffected by vertical displacement of the ground contacting wheel. A sprung suspension strut 7 and the swing arm 18 is connected to main frame thus allowing vertical displacement of the ground contacting wheel and also allowing full detachment of the propulsion system whilst maintaining assembly of suspension and propulsion mechanisms. A member 14 is free to rotate at its upper end and supports the rear steering wheel at its lower end. A sprung suspension strut 12 is connected between 14 and 6 allowing vertical displacement of the rear wheel in order to cushion impacts from an uneven road surface. The rear steering wheel 16 is connected to member 14 by a steering fork 15 which is constrained horizontally by member 14, but is free to rotate about a vertical axis and detachable steering module 13 locates axially with steering fork 15 thus allowing the wheel 16 to steer the device left or right according to the input of the user. The user operates the steering from the steering lever 19 which is located at the upper end of the propulsion lever 20.

The arrangement described in Figures 1 and 2 allows the device to be propelled over uneven ground, up and down steep slopes and allows the user to control the direction in which the device travels effectively. The systems of propulsion and steering should be used in conjunction in order to facilitate effective operation of the device as the user activates the steering and propulsion from the same point; hand grip 8. It is possible to implement these two subsystems in isolation; however this would result in poor usability and performance. For example, the direct steering is necessary with the wheel arrangement described in order to avoid dynamic instability when cornering.

Figure 2 shows the right and left Propulsion levers 20 and 25 which allow drive to be applied independently to the right and left wheels. The steering lever 19 may be fitted to either the right or left propulsion lever depending on the preference of the user. The left and right brakes may also be operated independently of each other to allow effective manoeuvrability.

Figure 3 shows the packaging of the Detachable Direct Steering with a means of cushioning provided by an air sprung damper unit which benefits effective steering by keeping the steering wheel 16 in contact with the ground over uneven terrain by allowing vertical displacement of the wheel without effecting steering actuation in order to cushion impacts from an uneven ground surface.

Preferably the air shock absorber should be adjustable for different users by varying the air pressure in the piston and adjusting the damping rate using conventional valves and adjuster dials.

Figure 4 shows an alternative embodiment where a coil spring damper unit is used. Preferably the shock absorber unit should be adjustable for different users by conventional adjustment means such as a screw thread end stop and damping rate adjustment dial.

Figure 5 shows another alternative method of cushioning where a torsion spring element is mounted between the main frame 8 and the swing arm 9 at the hinge point of the two members thus allowing vertical displacement of the ground contacting steering wheel.

In Figure 6, a Detachable Direct Steering system consists of a pivoting lever 19 which is mounted on the end of propulsion lever 20 where it is hinged freely. This allows the User to pivot the lever 19 left or right to steer whilst still being able to apply force to the propulsion lever. Lever 19 pulls cables A and B which are threaded through hollow flexible tubes such as cable outer housings and attached at their lower end to the steering pivot 43. Member 43 applies axial rotation to the steering fork 15 50 that axial rotation of the steering lever 19 is translated to axial rotation of the fork 15 and in turn the ground contacting steering wheel 16 which is fixed to the fork 15. In order to steer left for instance, the User pivots the steering lever left with their hand which pulls cable B that in turn causes steering pivot 43 to rotate, thus causing the steering wheel 16 to rotate axially. In order to steer right, the User pivots the steering lever right with their hand which pulls cable A that in turn causes steering pivot 43 to rotate, thus causing the steering wheel 16 to rotate axially. Steering Pivot 43 houses Cables A and B in a groove or grooves such that the cables pull tangentially to pivot 43 throughout steering movement. This system facilitates effective control of the direction in which the device may travel.

Figure 7 shows a cross section view of a Detachable Direct Steering system consisting of steering pivot 43 and steering terminal 42 which form one detachable unit. Steering pivot 43 locates axially with steering terminal 42 via bearing 47 such that the location of steering pivot 43 relative to terminal 42 is maintained even when terminal 42 is detached from swing arm 14 during transport. Steering Terminal 42 houses steering actuation cables A and B such that tension is maintained between the cables and steering pivot 43 even when terminal 42 is detached from swing arm 14 during transport.

Steering terminal 42 locates in swing arm member 14 such that it cannot rotate about the axis of fork 15, therefore providing a stationary mount for cables A and B. Steering pivot 43 locates coaxially with fork 15 in order to transmit axial rotation of steering wheel 16 via steering engagement member 44. Steering fork 15 is held in place by fork clamp 45 and is free to rotate axially in bearing 46.

Figure 8 the position of the Detachable Direct Steering mechanism where steering engagement member 44 acts as a push button allowing the steering pivot 43 and steering terminal 42 to be detached when the propulsion system is also detached due to the two systems being linked by the actuation cables A and B. Figure 9 shows the Detachable Direct Steering system in plan view where engagement member 44 acts as a means of transmitting axial rotation of the steering pivot 43 whilst also locking it in position on fork 15 by fitting into a key hole slot in fork 15. In its engaged position, spring 50 pushes engagement member 44 so that its larger diameter sections fit into the key hole slot in fork 15.

Figure 10 shows The Detachable Direct Steering system in its disengaged position where engagement member 44 is pressed in by the User, allowing its smaller diameter section to align with the key hole slot in the fork 15 thus allowing the steering pivot 43 and steering terminal 42 to be slid up off the top of fork 15 enabling detachment of the Direct Steering System with no need to disassemble the actuation cables. The function of engagement member 44 may also be achieved alternatively by use of a quick release cam lever such as item 10, though this arrangement is not preferred.

Figure 11 shows an alternative Detachable Direct Steering embodiment where hydraulic or pneumatic pistons 51 are activated by the steering pivot 43, which via displacement of hydraulic fluid or air, activate identical pistons 51 that apply force to the steering pivot 43 thus causing axial rotation of the ground contacting steering wheel to facilitate steering.

In Figure 12 the detachable lever operated Propulsion system is linked to the detachable direct steering system 13 via actuation means 27 such that propulsion system and steering system can be removed in their fully assembled state without the need for detaching actuation means or drive chain, allowing easy dismantling for transport in a vehicle or storage. The detachable direct steering system us detached by the user pressing engagement member 44 and the detachable propulsion system is detached by the User unlocking quick release cam lever 10 and removing the system from the slots in the main frame assembly 29.

Figure 13 shows the device in its component modules with Left hand propulsion system 28 detached from main frame assembly 29. Right hand propulsion system 26 is linked to steering system 13 via the actuation means in such a way that the actuation means can remain fully assembled to both steering and propulsion systems when detached from the device. The steering system 13 may be linked to either left or right hand propulsion systems, depending on the preference of the User.

Figure 14 shows an alternative attachment arrangement for the Detachable Direct Steering system in plan view where cam lever 52 acts as a means of clamping the steering pivot 43 in position on fork 15 by compressing the slot in the steering pivot by pushing the cam lever in, thus securing the steering pivot to the fork axially and in rotation. The steering pivot is removed by pulling the cam lever 52 to release pressure on the slot, thus allowing the steering pivot to be slid up off the fork 15 enabling detachment of the Direct Steering System with no need to disassemble the actuation cables..

Figure 15 shows an alternative attachment arrangement for the detachable direct steering system in its engaged position where the fork 15 is an angled form which mates with a matching form in the steering pivot 43 to transmit rotation to the fork. The sprung pin 53 is positioned such that it locates in a groove in fork 15, thus preventing the steering pivot 43 from moving axially.

Figure 16 shows an alternative attachment arrangement for the detachable direct steering system in its disengaged position, where sprung pin 53 is pressed inwards by the User such that the section of pin with reduced diameter aligns with the groove in fork 15, thus allowing the steering pivot 43 to be slid up off the fork 15 enabling detachment of the Direct Steering System with no need to disassemble the actuation cables.

Claims

Claims 1. A vehicle for conveying one person, comprising three or more ground contacting wheels, wherein the steering system comprises of actuation means linked to a single pivoting steering lever such that the User may effect steering input directly by pivoting said steering lever left or right using their hand, to a detachable steering member linked to the steering wheel, resulting in corresponding left or right motion of the steering wheel such that the steering member pivots coaxiafly with a bearing in a mounting member and the pivot axis of the steering wheel wherein the mounting member houses the steering actuation means allowing detachment of the steering member, steering actuation means and mounting member as one unit without interrupting steering actuation means setup and wherein the steering wheel is supported by a means of cushioning such that vertical displacement of the ground contacting wheel o is allowed without interrupting the steering action of said wheel arrangement.
2. A vehicle according to claim 1, wherein a mounting member locates on a rear swingarm to prevent axia rotation of said mounting member relative to the steering wheel.
3. A vehide according to claim 1, where steering actuation means is attached to the steering fork by a stepped pin acting on a spring in the steering member and locating in keyhole slot in the steering fork such that rotational motion is translated from the steering member to the steering fork and the user may press the stepped pin to align a thinner diameter section of the pin with the slot of the fork allowing detachment of the steering member and actuation means as one unit whilst maintaining setup of the actuation means.
4. A vehide according to daim 1, where steering actuation means is attached to the steering fork by a cam lever which clamps the steering member to the steering fork such that rotational motion is translated from the steering member to the steering fork and the user may unclamp the cam lever aflowing detachment of the steering member and actuation means as one unit whilst maintaining setup of the actuation means.
5. A vehide according to claim 1, where steering actuation means is attached to the steering fork by a stepped pin acting on a spring in the steering member and locating in groove in the steering fork such that the user may press the stepped pin to align a thinner diameter section of the pin with the groove of the fork allowing detachment of the steering member and actuation means as one unit whilst maintaining setup of the actuation means. (SI

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6. A vehicle according to claim 5 wherein a steerer fork has a hexagonal, U') square or otherwise angular form section which matches an identical form in the steering member such that rotation of the steering member about its axis translates rotational motion to the steering fork.
7. A vehicle according to claim 1, wherein actuation means is provided by cables mounted to each end of a steering member such that pulling either cable affects axial rotation of the steering member, which consequently affects axial rotation of the steering fork and steering wheel thus resulting in a steering effect.
8. A vehicle as claimed in Claim I wherein cables are threaded through hollow flexible tubes, which run from the steering member to the pivoting steering lever on the propulsion lever.
9. A vehicle as claimed in any one of the preceding Claims wherein cable tension may be adjusted via standard screw thread barrel adjusters acting on the cable housing.
10. A vehicle as claimed in claim I wherein steering actuation is provided by hydraulic hoses and pistons mounted at the pivoting steering lever and steering member to effect steering motion.
11. A vehicle according to claim 1, wherein a means of cushioning is provided by an air spring damper unit.
12. A vehicle according to claim 1, wherein a means of cushioning is provided by a coil spring damper unit. (SI

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13. A vehicle according to claim 1, wherein a means of cushioning is provided U') by a torsion spring unit.
14. A vehicle according to claim 1, wherein a clamp fits around the fork steerer tube thus holding the fork in place in the steering bearings in the rear swingarm even when the steering member is removed