AU731085B3 - A drive attachment for a wheelchair - Google Patents

Description

I

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A PETTY PATENT Name of Applicant: Actual Inventor: Address for Service: Invention Title: SUZANNE CHRISTINE ROBERTS IAN WARREN ROBERTS CULLEN CO., Patent Trade Mark Attorneys, 239 George Street, Brisbane, QId. 4000, Australia.

A DRIVE ATTACHMENT FOR A

WHEELCHAIR

The following statement is a full description of this invention including the best method of performing it known to me: A DRIVE ATTACHMENT FOR A WHEELCHAIR The present invention is directed towards a drive attachment for a manual drive wheelchair such that the wheel chair may be power driven.

Wheelchairs which can be manually propelled by an occupant are well known. Such wheelchairs have a pair of large rear wheels, each wheel having a hand rail, and a pair of front castor wheels. An occupant is able to propel and steer the wheelchair chair by grasping hand rails and rotating the rear wheels. The wheelchairs also have a pair of rear handle bars which are used by a carer to push and steer the chair from behind.

Manual wheelchairs are light weight and are able to be folded which allows them to transported easily in a conventional motor vehicle. Some wheelchair users do not have sufficient arm strength to enable them to self propel a wheelchair for a long periods of time and/or may have difficulties in propelling the wheelchair up ramps or the like. In this case, the mobility of a person may be limited. In order to overcome this limitation they must rely on the assistance of a carer to push the wheelchair.

Electric wheelchairs having an electric motor for propulsion are also known. Electric wheelchairs are designed for use by persons who are unable to operate a manual wheelchair. A major disadvantage with electric wheelchairs is that they are heavy and also very expensive. Also, because of their size and weight it is not possible to transport them in conventional motor vehicles. Typically, they must be transported in specially modified vans having lifts or ramps for loading the wheelchair. For these reasons, electric wheelchairs are not suitable for use in all circumstances.

It is also known to convert a manual wheelchair to an electrically driven or power assisted wheelchair by mounting an electric motor, battery and drive mechanism to the wheelchair. This can provide a wheelchair user with a greater mobility without having to rely on a carer to push the wheelchair.

Such known devices typically have a drive wheel which is mountable to the front of the wheelchair and between or in font of the castor wheels. Attached to the drive wheel is a steering column and handle bars by which an occupant is able to steer the drive wheel. A disadvantage of the front wheel drive in a wheelchair is the uneven weight distribution between the front and the rear wheels. The combined weight of a wheelchair and occupant is typically up to about 100kg. Most of this weight is distributed over the rear wheels. This results in very little weight being transferred to the drive wheel. This adversely affects traction between the drive wheel and the ground surface.

This lack of traction can cause slippage of the drive wheel. In some cases, such as when being driven up an incline such as a ramp, this may lead to a potentially dangerous situation.

It is also known to fit a drive mechanism to a manual wheelchair such that the drive wheel is located at the rear of the wheelchair. Whilst this may partially overcome the problems associated with lack of traction to a front drive wheel, an additional problem is introduced is that it is not possible for an occupant to steer the wheelchair when it is being motor driven. The wheelchair can only be steered by a carer who guides the direction of the wheelchair by using the rear handles.

It is therefore an object of the present invention to provide a drive attachment for a manual wheelchair which may at least partially overcome the above disadvantages or provide the public with a useful choice.

According to a first broad form of the invention there is provided a drive attachment for a manual wheelchair, the attachment having a frame mountable to a wheelchair, the frame supporting a motor and a drive wheel and when the frame is mounted to the wheelchair, the drive wheel is located at the rear of the wheelchair, a steerable wheel which in use is located at the front of the wheelchair; and steering means which can be actuated by a person seated in the wheelchair so as to control the steerable wheel.

The motor as used in the present invention may be any suitable type of motor and is typically a battery operated electric motor. In this case the frame typically also supports a battery or power pack. Typically, the motor and, if present, the battery are mounted on the frame such that in use they are located at the rear of the wheelchair and close to the drive wheel. In this way, the weight from the battery and motor may assist in imparting weight to the drive wheel so as to assist in creating traction between the drive wheel and a ground surface.

The drive attachment also includes a drive wheel. Typically the drive attachment includes a single drive wheel, although an additional drive wheel may be included in some circumstances. Typically the drive wheel is pneumatic and has a tread to optimize traction and grip on a ground surface.

The drive wheel is located at the rear of the wheelchair and preferably at the point midway between the rear wheels of the wheelchair. In this position, most of the combined weight of the wheelchair and occupant is transferred to the drive wheel. In this way traction between the drive wheel and a ground surface may be optimized.

The drive attachment also includes a steerable wheel which in use is located at the front of the wheelchair. Typically, the steerable wheel is mounted to the frame. In this case the drive attachment may be in two separate parts, a drive portion and a steerable portion, each being independently mountable to a wheelchair. Typically, the steerable wheel is removably mounted to the wheelchair such that if desired, the wheelchair may be driven by the drive wheel, the steering being controlled by a carer at the rear of the wheelchair.

The drive attachment includes means for allowing an occupant of the wheel chair to actuate the steerable wheel. Typically, the drive attachment includes a steering column extending upwardly from the steerable wheel and which terminates in a pair of handle bars, tiller or the like. Typically the steering column is detachable from the steerable wheel. Removal of the steering column can allow a user easier access when getting into and out of the chair.

Typically a control cable extends from the motor to the handle bars to enable an occupant to control the drive speed and also the direction, i.e.

forward and reverse. Alternatively, the steerable wheel may be steered by a foot operated mechanism. The drive attachment may include left and right peddles mounted to the frame and which are operatively connected to the steerable wheel. In this arrangement, in order to turn left, the left peddle is depressed: Alternatively, the drive attachment may include a single footplate connected to the steerable wheel. The steering may.be regulated by a side thrust by the feet to the required direction. In this form of the invention, controls for the motor may be located at a suitable location on the wheelchair.

Foot manipulated steering may be suitable for sufferers of conditions such as cerebral palsy and the like.

Typically the drive attachment includes means for allowing the front castor wheels of the wheel chair to be elevated from the ground to a height such that the castors do not interfere with the steering of the steerable wheel.

The steerable wheel is also typically pneumatic. The steerable wheel may also be castored to allow a carer to control the wheelchair direction from behind by exerting pressure on the right or left rear handle bars as desired.

Typically, the drive attachment further includes a speed control mountable to the rear of the wheelchair to allow a carer to control the speed of the drive wheel.

The drive attachment may also include a free wheeling wheel located to the rear of the drive wheel. Generally, the free wheeling wheel is mounted to the frame so that in normal use, the free wheel does not contact a ground surface. This free wheel offers a safety function in that should the wheelchair be tipped backwards, the free wheel engages the ground and the drive wheel is lifted from the ground and is effectively disengaged.

According to a further broad from of the invention there is provided a drive attachment for a wheelchair, the attachment having a drive wheel and motor for driving the drive wheel which are mountable to the wheelchair, the attachment further including a free wheel located behind the drive wheel when the drive wheel is driving in a forward direction, and the free wheel is raised such that it does not contact the ground when the wheelchair is at a normal attitude.

The drive attachment of the second form of the invention may also include a steerable wheel, steering control means and speed control means as described for the first broad form.

Typically the free wheel is adjustable such that the height from the ground may be varied. Thus the position of the wheel may be adjusted to suit the surface and conditions. The free wheel may also be able to be adjusted so as to lift the drive wheel from the ground. This allows the wheelchair to be driven manually or pushed by a carer if required.

By way of Examp!e only, the present invention will now be described with reference to the following drawings in which: Figure 1 is a schematic side view of a preferred drive attachment of the present invention; Figure 2 illustrates an alternative steering arrangement for use with the drive attachment of Figure 1; Figure 3 illustrates a further alternative steering arrangement for use with the drive attachment of Figure 1; Figure 4 shows a detail of a hitching arm for use in mounting the drive attachment of figure 1 to a wheelchair; Figure 5 is a detail of a hitch pin for use in mounting the drive attachment of figure 1 to a wheelchair and Figure 6 is a detail of a bar locator for use in mounting the drive attachment of Figure 1 to a wheelchair.

Figure 1 illustrates a preferred drive attachment 11 of the present invention. The drive attachment is mountable to a conventional manual wheelchair of the type having a pair of large rear wheels and a pair of front castor wheels. The drive attachment has a frame 12 made from heavy gauge sheet metal. The frame 12 includes a longitudinal "spine" 12a which imparts a degree of strength to the frame. The frame also includes a pair of hitching ears 64. The ears are used to mount the drive attachment to a wheelchair as will be described in more detail below.

A gear motor 13, a mount 14 for a battery or power pack and an axle assembly 15 including a drive wheel 16, are mounted to the frame. The drive wheel is pneumatic. The gear motor 13 and battery mount 14 are mounted beneath the frame. This avoids the gear motor 13 and battery mount 14 interfering with the folding of the wheelchair. The battery mount 14 is located immediately in front of the drive wheel 16. This assists in imparting weight to the drive wheel which can assist in traction.

The rear section of the drive attachment has a narrow profile when viewed in plan. This narrow profile reduces the likelihood of interfering with the feet of a carer who may be pushing the wheelchair or controlling the motor drive.

When the drive attachment is mounted to a wheelchair, the drive wheel 16 is located between the rear wheels. In this position, an optimum amount of weight can be imparted to the drive wheel. This weight can assist in traction.

(This should be compared to a drive wheel located at the front of a wheelchair upon which there is little downward force provided by the weight of the wheelchair and occupant.) Behind the drive wheel 16 is a free wheel 17 and a foot pedal 19. This pedal 19 may be used by a carer to impart an additional downward force to the drive wheel 16. This may be desirable to increase traction and/or assist in braking. In order to further assist the traction, the drive attachment may also include one or more lightly loaded springs (not illustrated) connected at one end to the rear of the drive attachment and the other end to the frame of the wheelchair.

The free wheel 17 as illustrated in Figure 1 is raised such that its rim is above the ground level. The main purpose of the free wheel 17 is to provide an added safety feature. The height of the free wheel above the ground is calculated such that when the wheelchair is tilted back to an angle in which the free wheel contacts the ground, the wheelchair is at a "safe" angle. In use, should the wheelchair be tilted backwards to this "safe" angle, the free wheel 17 can engage the ground surface and the drive wheel 16 can be lifted off the ground. This effectively disengages the drive force of the drive wheel and prevents the wheelchair from being driven into a dangerous inclination.

The height of the free wheel above the ground can be varied to suit different ground surfaces and/or circumstances. The free wheel 17 may also be lowered such that it engages the ground and the drive wheel is lifted from the ground surface. In this position, the wheelchair is able to be manually pushed by a carer or propelled by an occupant. This modification may be desirable when a wheelchair user does not require motorized propulsion at all times.

At the front 19 of the drive attachment is a steerable wheel assembly 20. The assembly includes a steerable wheel 20 is pneumatic and slightly castored. That is, the swivel axis of the wheel is slightly offset from the rotational axis of the wheel). The slight castoring enables a carer who may be operating the motor drive from behind the wheelchair to exert some directional control.

The steering wheel assembly 20 includes a steering column 21. The steering column 21 is engaged at its lower end by a spigot 22. The steering column 21 can be disconnected from the spigot 22. This may be desirable to enable a person to get into or out of a wheelchair to which the drive attachment is mounted. The drive attachment includes an adjustment member 9 having a series of vertically spaced apertures. The steering assembly 20 has a sleeve (not illustrated) which is bolted to the adjustment member. The height of the front portion 19 of the frame relative to the ground surface can be adjusted by using different holes on the adjustment bar to bolt the steering wheel assembly to the frame.

When the drive attachment 11 is mounted to a wheelchair, the castor wheels of the wheelchair are raised above the ground. The height adjustment of the front portion of the frame 19 can be used to optimize this height and to allow for wheelchairs having different castor sizes and different sizes of wheelchair frames. Raising the castor wheels above the ground avoids the castor wheels interfering with the steering of the wheelchair.

The steerable wheel 20a is also removable from the steering wheel assembly 20 by being unbolted from adjustment member 9. This may be desirable if the chair is to be operated solely by a carer from behind the wheelchair. In this case, the wheelchair is steered in a conventional manner by the carer.

The upper end of the steering column 21 has a pair of handle bars 23 extending therefrom. The handlebars can be manipulated by an occupant of the chair to steer the wheelchair when it is being driven by the gear motor 13.

The handle bars 23 are suitably of a large diameter and are of a length to allow easy control of turning movements by an occupant of a wheelchair. In front of the handle bars are right and left proportional control handles (not illustrated) which control the gear motor. The control handles are pivoted at the center of the handle bars and are sprung to center zero. A control box (also not illustrated) for the proportional controls is mounted at the center of the handle bars. The control box has an on/off switch for operation of the gear motor. The gear motor is fitted with a brake that automatically engages when the proportional control is in the zero position and when the motor is switched to the "Off" position. The off mode is automatically activated when the steering column 21 is disconnected from spigot 22. The motor has both forward and reverse directions.

The motor and drive wheel are designed such that maximum torque is applied to the wheel in forward drive mode. When reversing, less torque is applied to the drive wheel. The torque in reverse is sufficient under normal conditions to drive the wheelchair, however, should the wheelchair inadvertently back into an obstruction such as a wall, the drive wheel will lose traction and not force the chair into a tilted or dangerous position.

The motor may also be actuated by a carer from the rear of the wheelchair. In this case, a speed control can be mounted to the rear handles of the wheelchair. The control device includes a handle fitted to a proportional speed control, which is also biased towards a center zero position. The handle typically faces forwards to avoid accidental actuation. The control is connected to the gear motor by a conventional cable and plug which fits into a socket at the rear of the gear motor. There may be a second socket on the gear motor for receiving a plug and cable leading to the front handlebars. In this case, the motor will be programmed not to drive when both sockets are connected. This is a further safety feature.

Alternative steering mechanisms are illustrated in Figures 2 and 3.

Figure 2 illustrates a steering mechanism 30 having a single foot plate 31.

The foot plate 31 is supported by forks 32. The steerable wheel 20a can be turned in the desired direction by applying a side thrust n the desired direction by a user's feet.

Figure 3 illustrates a further alternative steering mechanism 35, which may also be controlled by a user's feet. In this case, right and left footrests 36 are provided. These footrests 36 are pivotally mounted to the frame 12 about pivot points 37. Arms 38 depends from the pivot joints 37. The lower end of each arm is connected via a ball joint 39 and linkage 40 to the forks 41 of the steerable wheel through a second ball joint 42. In order to turn left, the left footrest is depressed. A corresponding rise in the right rest will occur.

For the foot operated steering controls, the steering column is not be necessary. In this case, the motor controls may be located at any suitable location on the wheelchair body.

The drive attachment 11 can be mounted to a conventional manual wheelchair of the type having two large rear wheels having hand rails and two front castor wheels. The drive attachment is mounted by means of ears and a hitch bar and clamp as illustrated in figures 4 and 5 respectively. A conventional manual wheelchair has a pair of struts, each extending between a front and rear leg member of the wheelchair. A clamp 45, as illustrated in Figure 5, is typically mounted to. each strut at a location immediately behind the junction between the strut and front leg member. The clamp 45 is in two sections 46, 47 which can be bolted together. A bore 48 extends through the clamp 43 and is sized to snugly receive the strut. (This bore is illustrated as having a circular cross section and is suitable for mounting to a strut, also of a circular cross section. Some wheelchairs have struts having a square cross section. In this case, bore 48 will have a corresponding cross section).

Clamp 45 has three pin sockets 49, 50, 51. The clamp 45 may be mounted to the wheelchair struts in any orientation such that the pins may mounted such that they are at the upper, lower or side portions of the clamp 45 relative to the wheelchair.

The hitch bar 55, as illustrated in Figure 4 has a pin 56, 57 extending from each end thereof. In use, one of the sockets 49, 50, 51 on clamp receives one of these pins. The presence of three pins allows for the location of the bar, relative to the wheelchair struts, to be adjusted. The hitch bar has a thread 58 at one end upon which is mounted a nut 59. This allows for in/out adjustment of the hitch bar In order to mount the drive attachment to a wheelchair, the hitch bar is inserted through holes 61, 62, 63 located in the in ears 64 on the frame 12.

Three holes are provided to allow the position of the hitch bar 55 relative to the ears 64 to be adjusted. On the hitch bar 55 and between the ears 64 is a bar locator 66 as illustrated in figure 6. The bar locator 66 has a bore 67 through which bar 55 passes. The locator 66 has a screw 68 for locking the locator in place relative to the hitch bar 55. When locked in place, the locator 66 assists in keeping the ears 64 at a fixed location relative to the hitch bar It can be seen that the drive attachment of the present invention allows a manual wheelchair to be easily and quickly converted to a motor driven wheelchair. The converted wheelchair may be used in a fully manual mode in which it may be pushed by an operator, a motorized mode in which a carer has full control of the wheelchair and a motorized mode in which an occupant has speed and steering control. The drive wheel is located between the rear wheels of the wheelchair. This location optimizes the weight distribution on the wheel and thus traction can be optimized. The drive attachment has a number of safety features including a rear free wheel.

It will be appreciated that various changes and modifications may be made to the invention as described and claimed herein without departing from the spirit and scope thereof.

Claims (3)

1. A drive attachment for a manual wheelchair, the attachment having a frame, a motor and a rear drive wheel supported by the frame and when the frame is mounted to the wheelchair, the drive wheel is located at the rear of the wheelchair; a steerable wheel which in use is located at the front of the wheelchair; steering means which can be actuated by a person seated in the wheelchair so as to control the steerable wheel and mounting means for mounting the frame to the wheelchair, the mounting means including a round mounting bar removably attachable to a forward section of the wheelchair and when in use the bar extends through an aperture in a forward section of the frame.

2. The drive attachment of claim 1, which includes first and second drive control means, the first control means being mountable to the rear of the wheelchair.

3. The drive attachment of claim 1, substantially as hereinbefore described with reference. to the Figures. Dated this 3 rd day of January 2001 SUZANNE CHRISTINE ROBERTS By her Patent Attorneys CULLEN CO.