GB2308342A

GB2308342A - Reversible armrest-driven wheelchair

Info

Publication number: GB2308342A
Application number: GB9525918A
Authority: GB
Inventors: Shy-Jun Mu
Original assignee: EDEN SOCIAL WELFARE FOUNDATION
Current assignee: EDEN SOCIAL WELFARE FOUNDATION
Priority date: 1995-12-19
Filing date: 1995-12-19
Publication date: 1997-06-25
Also published as: GB9525918D0

Abstract

A wheelchair (fig. 2) may be propelled forwards and backwards by movement of its armrests, through two ratchet wheel mechanisms 5. Each such mechanism includes a casing 51 having one end coupled to an armrest by a connecting bar 4, and an opposite end furnished with a ratchet wheel 511. Each ratchet wheel is mounted on one end of the wheelchair axle 21. A triangular control block 512 is turned between first and second positions to choose between forward and backward motion. Upper and lower pawls 513, 513' are supported on springs 514, 514', and disposed on opposite sides of the control block, which alternately pushes each pawl out of engagement with the ratchet wheel, so that the wheelchair is driven forwards or backwards as required by oscillation of the armrests.

Description

STRUCTURE OF ARMREST-DRIVEN WHEELCHAIR BACKGROUND OF THE INVENTION The present invention relates to wheelchairs, and relates more particularly to an armrest-driven wheelchair which is propelled by the armrests thereof and, which can be driven to move forwards as well as backwards.

Figure 1 shows a conventional armrest-driven wheelchair in which a ratchet wheel mechanism is mounted on each end of the wheel shaft (B1) adjacent to the respective wheel (B) and coupled to one armrest (C). The ratchet wheel mechanism comprises a ratchet wheel (EO) mounted one end of the wheel shaft (B1), and a plurality of pawls (E) supported on respective springs (El) and forced by the springs (El) into engagement with the ratchet wheel (B) to limit the rotary motion of the ratchet wheel (B) and the respective wheel (B) in one direction. The ratchet wheel (EO) has a projecting coupling portion (E2) coupled to the fixed end (C1) of the respective armrest (C) by a connecting rod (D). When the armrest (C) is continuously turned up and down, the wheel (B) is propelled forwards. This structure of armrest-driven wheelchair is functional, however it is still not convenient in use because the wheels can only be turned forwards.

SUMMARY OF THE INVENTION The present invention has been accomplished to provide a wheelchair which eliminates the aforesaid problem. The first object of the present invention is to provide a wheelchair which can be driven only by the armrests. The second object of the present invention is to provide an armrest-driven wheelchair which can be conveniently driven to move forwards as well as backwards by one hand. According to the preferred embodiment of the present invention, the armrest-driven wheelchair is propelled forwards and backwards by the armrests thereof through two ratchet wheel mechanisms, wherein each ratchet wheel mechanism comprises a casing which have one end coupled to one armrest by a connceting bar and an opposite end fixedly mounted with a ratchet wheel, which is fixedly mounted around one end of the wheel shaft of the wheels of the wheelchair, a triangular steering control block turned between a first position and a second position, an upper pawl member and a lower pawl member respectively supported on a respective spring and disposed at two opposite sides relative to the steering control block and alternatively forced by the steering control block into engagement with the ratchet wheel to limit the rotary motion of the ratchet wheel in the forwards or backwards direction.

SUMMARY OF THE INVENTION Fig. 1 is a schematic drawing showing the armrest-driven transmission mechanism of an armrestdriven wheelchair according to the prior art; Fig. 2 is an elevational view of an armrestdriven wheelchair according to the present invention; Fig. 3 is a plain view of a ratchet wheel mechanism according to the present invention; and Fig. 4 is a schematic drawing showing the ratchet wheel mechanism propelled by the respective armrest according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to Figure 2, an armrest-driven wheelchair in accordance with the present invention is generally comprised of a chair frame (1), two main wheels (2) and (2"), two auxiliary front wheels (20) and (20') two armrests (3) and (3'), two connecting bars (4), and two ratchet wheel mechanisms (5). The chair frame (1) holds a seat (10) for sitting, and a wheel shaft (21) below the seat (10). The main wheels (2) and (2') are mounted on the wheel shaft (21) at two opposite ends to support the armrest-driven wheelchair on the ground. A front wheel fork (13) is pivotably connected to the chair frame (1) by two folding frames (21) to hold the auxiliary front wheels (20) and (20') and two footplates (12) and (12'). The armrests (3) and (3') are respectively turned about a respective pivot (30) on the chair frame (1). Each of the armrests (3) and (3') has a rear end (31), and a longitudinal series of pivot holes (310) at the rear end (31). The ratchet wheel mechanism (5) are respectively mounted on main wheels (2) at two opposite ends of the wheel shaft (21) The connecting bars (4) are respectively coupled between the ratchet wheel mechanism (5) and the pivot holes (310) of the rear ends (31) of the armrests (3) and (3').

Referring to Figures 3 and 4, the ratchet wheel mechanism (5) comprises a casing (51) which have one end pivoted to one connecting bar (4) and an opposite end fixedly mounted with a ratchet wheel (511), which is fixedly mounted around the wheel shaft (21) at one end, a steering control block (512) of substantially triangular shape turned manually between the forward position and the backward position within 1200 angle, two pawl members (513) and (513') respectively supported on respective springs (514) and (514') and disposed at two opposite sides relative to the steering control block (512) and having a respective front end (5131) facing the ratchet wheel (511). When the steering control block (512) is turned to the backward position, the upper pawl member (513) is forced away from the ratchet wheel (51) by the steering control block (512), and the lower pawl member (513') is forced into engagement with the ratchet wheel (511) by the steering control block (512), and therefore the ratchet wheel (511) can be driven to turn the respective main wheel (2) backwards. When the steering control block (512) is turned through 120D angle from the backward position to the forward position, the lowr pawl member (513') is forced away from the ratchet wheel (51) by the steering control block (512), and the upper pawl member (513) is forced into engagement with the ratchet wheel (511) by the steering control block (512), and therefore the ratchet wheel (511) can be driven to turn the respective main wheel (2) forwards.

It is to be understood that the drawings are designed for purposes of illustration only, and are not intended as a definition of the limits and scope of the invention disclosed.

Claims

CLAIMS:

1. An armrest-driven wheelchair, comprising a chair frame having a transverse wheel shaft and a folding front wheel fork, two main wheels mounted on said transverse wheel shaft at two opposite ends, two auxiliary front wheels mounted on said folding front wheel fork, two ratchet wheel mechanisms respectively mounted on said main wheels, two armrests turned about a respective pivot on said chair frame, and two connecting bars pivotably connected between said armrests and said ratchet wheel mechanism and driven by said armrests to propel said main wheels forwards and backwards, wherein each ratchet wheel mechanism comprises a casing which have one end pivoted to one connecting bar and an opposite end fixedly mounted with a ratchet wheel, which is fixedly mounted around said wheel shaft at one end, a steering control block turned between a first position and a second position, an upper pawl member and a lower pawl member respectively supported on a respective spring and disposed at two opposite sides relative to said steering control block and having a respective front end facing said ratchet wheel, said upper pawl member being forced away from said ratchet wheel and said lower pawl member being forced into engagement with said ratchet wheel when said steering control block is turned to said first position, for permitting said ratchet wheel to be driven to turn the respective master wheel backwards by the respective armrest, said upper pawl member being forced into engagement with said ratchet wheel and said lower pawl member being forced away from said ratchet wheel when said steering control block is turned from said first position to said second position, for permitting said ratchet wheel to be driven to turn the respective main wheel forwards by the respective armrest.

2. The armrest-driven wheel chair of claim 1 wherein said steering control block is made of substantially triangular shape having three angles respective chamfered.

3. The armrest-driven wheel chair of claim 1 wherein said steering control block is manually turned between said first position and said second position within 120C angle.