GB2609486A - Lever propulsion system for self-propelled wheelchair - Google Patents

Abstract

The retrofit lever propulsion system for a self-propelled wheelchair having disc brakes comprises two levers 1, one for each side of the wheelchair, each lever 1 connected to a push rod 5 that is connected to a rotor arm 6 having a fixed calliper 7. Actuating the callipers 7 can be used to brake the wheelchair, but used in combination with pushing or pulling the levers 1 causes forwards or reverse motion. This allows the user’s hands to be away from the tyres of the wheels and inside the footprint of the wheelchair, while using a movement of upper limbs that incorporates larger muscle groups than required to operate conventional push rims. The axial position of the levers 1 relative to a pivot point 3 may be adjustable to affect the overall mechanical advantage of the system, which acts as gearing, to assist with progress over changing topography.

Description

Lever Pro V -ion System for Self-Propelled Wheelchair DescOption This invention relates to self-propelled wheelchairs Probiem Self-propelled wheelchairs (SPWs) typically incorporate the use of push rims fixed to the rear wheels so that the user can control movement forward, backward, turn and stop. Push rims are often simple in design, light weight, robust and relatively inexpensive.

It has been documented that the use of SPWs with push rims results in fatigue and over time, upper limb injury. The muscular skeletal form of the human body does not lend itself well to the forces, movement and repetition required for the use of push rims on SPWs.

Additionally, as push rims have such a close proximity to the tyres on the wheels and therefore the ground. The user's hands are regularly exposed to dirt with obvious hygiene issues. Water from rain and puddles will affect the level of friction available to operate push rims without suitable gloves.

The widest extremities of a SPW are the push rims. Therefore, when navigating close to objects such as door frames the user's hands are at risk of injury from collision.

Soution An alternative method of applying forward, backward and braking forces to the rear wheels of a SPW that negates the use of push rims. This new system should position the user's hands away from the tyres of the wheels, inside the footprint of the SPW and allow a more natural movement of the upper limbs that incorporates larger muscle groups than those required for conventional push rims, so that fatigue and the risk of upper limb injury are reduced in comparison. Additionally, the removal of the push rims will reduce the width of the footprint, aiding manoeuvring around obstacles.

Proposai For simplicity the following text and complementary drawing (Figure 1) describes the system on one side of the wheelchair (singular), in practice the layout is on both sides (left & right).

Drawings: Figure 1 shows a side view representation of the system.

A lever (1) fixed to the chassis of the wheelchair via a pin joint (3) and allowed to pivot so that the handle (2) is situated and moved within an ergonomic envelope as discussed above. The opposing end of the lever is connected to a push rod (5) via a pin joint (4). The opposite end of the pushrod is pin jointed to a rotor arm (6) that is allowed to rotate about the axle on which it is mounted. The rotor arm has a disc brake calliper (7) fixed to it, positioned to engage with the brake disc (8) when actuated by the brake lever (9). The brake disc is fixed to the back/inside of the wheel (10) which is allowed to rotate freely on the axle.

A large portion of the components required for this assembly are standard bicycle parts, wheelchair parts and engineering components. However, some items require design and manufacture/reworking.

ueration This system simply replaces the interface of the user's hands and push rims of a SPW with disc brakes. Providing an efficient means of gripping the discs and applying force to them through the lever/push rod assembly, creating moments to both instigate and arrest rotation of the wheel: Thus, the higher torque at the disc that is required to dive the large wheel is achieved, while affording a more ergonomic position for the user's upper limbs to operate the levers.

Forward: From a stationary position, the user depresses both (left & right) and pushes the levers forward, by releasing the brake levers toward the end of the push stroke, the wheelchair will be allowed to freewheel in that direction.

Backward: From a stationary position, the user depresses both (left & right) and pulls the levers rearward, by releasing the brake levers toward the end of the push stroke, the wheelchair will be allowed to freewheel in that direction.

Braking: To arrest movement when freewheeling, the user depresses the brake levers while holding the position of the levers against the turning force of the wheels.

Turning: Turns can be made by the user by employing a combination of forward/backward/braking inputs on the separate levers.

Mechanical advantage/gearing: By altering the position of the pin joint (3) relative to the lever (1) the mechanical advantage (effective gearing) of the system can be changed: A shortened distance between the lever's connection with the push rod (4) and the pivot point (3), the greater the mechanical advantage of the push rod system. This scenario would also increase the distance between the pivot point and the handle (2) increasing the mechanical advantage further.

Therefore, the use of predetermined, indexed positions for the lever relative to the pivot point that can be changed by the wheelchair user on-the-fly will provide effective gear selections to aid high speed cruising/hill climbing as required. Thus, the wheelchair user will be better able to maintain good progress through topographical changes.

Claims (2)

1. A retrofit lever propulsion system for a self-propelled wheelchair that uses disc brakes mounted to each of the individual rear driving wheels, where two levers (left & right) are connected to their corresponding callipers fixed to rotor arms via connecting rods so that lever movement can be translated into independent forward motion, backward motion and braking of each wheel as required by the user.

2. A retrofit lever propulsion system for a self-propelled wheelchair according to claim 1, where the lever's axial position relative to its pivot point can be altered on the fly by the user resulting a change in the mechanical advantage (effective gearing) of the system to aid in hill climbing or high-speed cruising.