Chair on Wheels

Background

The present invention relates to a chair on wheels.

Pushchairs for carrying infants and other chairs on wheels generally comprise three or four independent wheels supporting a carriage and/or frame. Pushchairs provide a convenient method of transporting infants as the infant can be constrained within the carriage and the user of the pushchair is able to transport the infant relatively unencumbered.

Prior Art

There exists a problem with pushchairs of this type, as they are not easily used on a terrain not presenting a flat and solid surface.

One example of such terrain is a flight of stairs. A conventional pushchair cannot be moved in the usual manner down stairs. Depending upon the exact location of wheels, steps engage the wheels of the carriage so as to vary the incline, and change the angle of incline during movement of the pushchair. This tends to be impractical and potentially dangerous to an infant being carried within the pushchair.

Alternatively in order to ascend or descend stairs with a conventional pushchair, a user is often required to carry the pushchair. This presents an inconvenience, particularly where there are a number of items being carried by the pushchair, such as for example, shopping.

Another example of terrain not suitable for conventional pushchairs is soft terrain such as mud or sand. The wheels of a conventional pushchair are not likely to frictionally engage sand and are prone to sink and become stuck in sand. The problem is exacerbated when moving the pushchair across grass or soft land as mud tends to stick to the wheels.

Similar problems are encountered with wheelchairs. However, as the mass of a wheelchair and occupant tend to be greater than that of a pushchair and occupant, the problems encountered are more pronounced. An object of the present invention is to overcome the aforementioned problems by providing an improved wheeled vehicle, particularly a pushchair or wheelchair.

Summary of the Invention

According to a first aspect of the present invention there is provided a chair on wheels wherein the wheels are within an endless track which passes around them and engages with them so as to move along its length with their rotation.

In use, a lower run of the endless track, which is in contact with the ground, may react against a row of juxtaposed rollers which can be mounted on a structure of the chair between front and rear wheels of the chair, each roller being mounted for rotation on the structure of the chair between front and rear wheels of the chair.

Ideally each roller is mounted for rotation about an axis which is substantially parallel to the axes of rotation of the front and rear wheels of the chair.

It is preferred that the wheelbase of the chair is sufficient to span across more than two stairs of a stairway. The length of the wheelbase spanned by the articulated band is preferably greater that the span of three steps.

Ideally the endless track is an endless belt or an articulated band. Alternatively the endless track comprises a plurality of stiff or rigid plates that are interconnected so as to permit relative movement between adjacent plates.

It is preferable that the length of each link of the articulated band is greater than the distance between the axes of rotation of adjacent pairs of rollers so that each link reacts against a respective pair of the rollers.

The seat in which the child sits is ideally suspended or supported on damped springs. This provides for additional comfort, and in the event of a steep incline enables the occupant to move to tilt to a comfortable angle of orientation.

Preferably a braking mechanism is incorporated which may be a dynamic brake: that is one which applies more braking force in dependence upon the velocity of the pushchair.

A further safety feature is a safety brake which is configured to deploy in the event of the pushchair accelerating down a slope. For example a ratchet, acting as a safety brake, is operable to engage a tread of a stair in the unlikely event of the pushchair descending uncontrollably down a slope.

The pushchair ideally also has at least one failsafe stair brake which, for example, operates by deploying a lever from below. The lever is dimensioned and arranged to engage a tread of a stair. This may be configured to deploy automatically when the pushchair is being pushed up a flight of stairs.

The chassis is ideally made from titanium, carbon fibre, aluminium tube or extrusion. The whole chair is most preferably adapted to be folded to allow for easy storage or transport.

The chassis may also include a luggage drawer which is located between the tracks. This is attached to the main chair chassis so remains level when the chair is on stairs or a slope.

The drawer slides out to the rear of the chair to provide easy access to its contents.

The pushchair handles are ideally adjustable for different height people.

A larger version of the chair could be used for the transport of disabled children which could be also be motorised.

Brief Description of the Figures

Preferred embodiments of the present invention, will now be described, by way of example only, and with reference to the drawings in which:

Figure 1 is a perspective view of a pushchair, which embodies the present invention;

Figure 2 is a side view of the pushchair of Figure 1 ;

Figure 3 is another side view of the pushchair of Figure 1 , wherein the pushchair is in a second configuration for traversing stairs;

Figure 4 is a diagrammatical representation of a pushchair with a braking control system; and

Figure 5 is a diagrammatic view of a safety ratchet.

Figure 1 shows a pushchair 10 which has two front wheels 12 and two rear wheels 12. The front and rear wheels on either side of the pushchair form a respective pair. Each front wheel 12 and rear wheel 12 pair are within a respective endless track 14 which passes around them. The wheels 12 are arranged so that as they rotate, the track 14 moves along its length.

The track 14 comprises a plurality of articulated elements 15 connected by way of flexible connectors 17. Wheels 12 are provided with a plurality of cogs 19 spaced so as to engage elements on the track 14. The four wheels 12 are mounted for rotation on a lower frame 16 of the pushchair 10.

The lower frame 16 is connected to an upper frame 20 which supports a carrier means 22 in which an infant may be carried. The upper frame 20 includes a pair of handles 24 to facilitate the movement of the pushchair 10 by the user.

The pushchair 10 is also provided with two rows of juxtaposed rollers 18, one row on either side of the lower frame 16 between the respective front and rear wheels 12 of the pushchair 10. The rollers 18 are also mounted for rotation on the lower frame 16 of the pushchair 10. Rollers 18 are smaller than wheels 12 and are disposed with their axes of rotation closer to the lower run of the respective endless track 14. The lower run of each of the endless tracks 14 is able to react against the respective rollers 18 and is therefore supported when the pushchair 10 is pushed over uneven terrain as shown in Figure 2. An advantage with this arrangement is that the weight of the puschair is spread over a much larger surface are than that presented just by the wheels 12 with the result that the pressure (per unit area) is greatly reduced. The practical advantage is that a pushchair does not sink into soft surfaces, such as sand or mud.

The wheels are preferably formed from metal or a synthetic plastics material. They may be offset one from another (staggered) or parallel; they may be of the same or different size diameters; they may have the same or different widths. In one preferred embodiment the pushchair has a larger wheel at the front and rear of a train of wheels and smaller wheels in between. Alternatively a plurality of smaller raised wheels are arranged in groups to assist transit over rough or uneven terrain.

The wheels in a train may have a rubber tyre which runs on the inner surface of the track.

The wheels are ideally designed to prevent the tracks from coming off and may also have debris deflectors to prevent fouling. Alternatively a scoop or shute is located at the front of the puschair which acts in a manner similar to a snowplough to remove/deflect debris from the path of the pushchair.

The wheels 12 may be connected to a suspension system to provide a smoother ride. This could be either a spring or torsion bar system (not shown) operating on individual wheels or pairs of wheels or as a sprung assembly to which one or more wheels are connected.

An advantage with the tracked pushchair is that because the portion of the pushchair that is in contact with a surface is relatively large (when compared with that of only the forward and

rearward pairs of wheels) and that the portion of the pushchair that is in contact with a surface is continuous, a puschair according to the invention may climb or descend stairs much easier than was previously possible.

An optional motor drive may be included to assist in ascending slopes. A suitable speed/torque controller may be incorporated with the motor drive. Ideally the energy supply for such a motor drive system is a battery (such as a rechargeable battery) or a fuel cell.

Figure 3 shows the pushchair 10 of Figure 1 traversing a set of stairs. The pushchair 10 is in a configuration wherein the upper 20 and lower 16 frames are connected only by a hinge means 26. The lower frame 16 is able to lie at an angle against the incline of the stairs whilst the upper frame 20 remains in an upright position. The pushchair can therefore travel up and down the stairs smoothly.

The tracks may be either individual link type or an endless belt with a tread pattern to provide purchase on stairs or slippery surfaces. Ideally tracks require little maintenance and are pre-stretched or stretch proof so that once fitted to the chair they do not have to be adjusted.

Advantageously tracks are mounted on a pivot located approximately two-thirds from the front most portion of the pushchair. This is to enable the tracks to adopt an angle of any slope or stairs the chair may negotiate, whilst allowing the infant to remain level during the ascent/decent. Ideally the pivot is variable, lockable and operated by a lever on the handlebar(s). The pivoting mechanism may also be damped to prevent it jolting during its operation.

Hinge means 26 is provided at about a position a quarter of the length of the upper frame from the rear wheels 12 to the handles. The pushchair may also be provided with a locking mechanism wherein the user may be able to lock the upper frame 20 to the lower frame 16 to prevent the frames hinging around the hinge means 26. This locking mechanism also has a release mechanism allowing the configuration shown in Figure 3 to be achieved when the release mechanism is actioned by the user.

The wheelbase, that is the distance between the front and rear wheel axis is greater than the span of three steps. This length would typically be greater than about 0.7 metre - 0.9 metre. Since the pushchair is to be used on surfaces such as sand there is envisaged to be a problem in that the matter over which the pushchair is being moved is likely to stick to the track and this matter may be deflected upwards following the motion of the track when it is no longer in contact with the ground.

This matter may be thrown up towards the user of the pushchair thus providing an inconvenience. A solution to this problem is to provide a deflecting means which mantles the portion of the endless track so that the said matter which is deflected upwards is stopped by the deflecting means.

The rollers provide a reactive force against the track when the pushchair moves over a surface.

The sizing of the articulated elements and the positioning of the juxtaposed rollers 18 are such that, during operation, at least one roller 18 reacts against at least one abutting articulated element at any given time.

In an alternative embodiment, shown diagrammatically in Figure 4, the pushchair has a braking system 100. The braking system 100 includes forward and rear brakes 102a and 102b. Brakes 102 may be a drum brake, a disc brake or cycle type cantilever or centre pull brake, including a Bowden (Trade Mark) cable. The cycle type brake may be cantilever or centre-pull brake cable or they may be hydraulic.

A yet further type of braking system may be an electromotive brake which operates in accordance with a dynamo 104 arranged to produce an electric current as it moves through a magnetic field 106. The electric current may be used to generate an electromagnetic field 106, upon depression of a switch 112, so as to produce a dynamic brake which applies a force in proportion to the acceleration of the pushchair. Switch 112 is ideally located on a handlebar of the pushchair. Additional information about the slope up which (or down which) the pushchair is climbing (or descending) is provided by a tip switch 120. Therefore at any instant data as to the slope and velocity

of the puschair is obtained at micro-processor 122 and this is used to apply the correct front brake 102a or rear brake 102b so as to prevent toppling of the pushchair.

Use of the braking system, on a slope, ensures that, is in the event that a pushchair is moving down a slope, under an accelerating force, on application of the dynamic brake, the amount of braking force is directly proportional to the acceleration of the pushchair and on the correct set of front or rear wheels, thereby ensuring a safe a rapid arrest of the pushchair.

The brakes 102 may be adapted to operate on either the rear wheels, front wheels or all wheels. Brakes 102 are ideally adapted to be operated under control of a lever on the grip or handlebar(s). In the event where there are brakes on front and rear axels, the braking control system is ideally arranged to operate brakes so as to avoid tipping and the associated risk of toppling.

In a further embodiment a ratchet mechanism 210, shown in diagrammatical forming Figure 5, is provided whereby brakes 102 can be locked incrementally to slow the descent of the pushchair on a flight of stairs. Alternatively the ratchet mechanism 210 may be used independent of the aforementioned braking system to provide an additional failsafe mechanism. The ratchet 210 is pivoted at a pivot 212 below an axle on which a wheel 12 is mounted. The ratchet 210 has angled ends 214 and 216 on which a rubber friction pad 217, 218 is disposed. The ratchet 210 operates in a 'seesaw' fashion so that, upon depression of a handle or catch (not shown), either friction block 217 or 218 engages an inner edge of wheel 1, thereby allowing controlled descent of the puschair down stairs or steep slopes. The inner surface of wheel 12 may be keyed for additional friction resistance with the ratchet.

Ideally a footbrake (not shown) is provided for engaging mechanically with the wheels, for example via a linkage such as pin in a hole system or similar mechanism which engages in teeth/sprockets of one or more wheels.

Use of the invention therefore permits parents to take babies and young children to places where before this may have proven difficult or impossible.

Although the invention has been described by way of preferred embodiments, it will be appreciated that variation may be made to the embodiments, without departing from the scope of the invention. In this sense , although reference has been made throughout to a pushchair, the invention may be incorporated in a wheel chair for disabled or persons with restricted mobility.