Description of Invention

This invention relates to an assembly comprising a track and a carriage which runs along the track. The invention has been devised primarily in connection with a carriage suitable for transporting one person along the track. Typically, the track is installed in a stairwell and the assembly is used to transport a person between different levels in a building.

Stairlifts having rectilinear tracks are well-known. It is also known for stairlifts to have two parallel tracks which are not rectilinear but where at least a portion of each track is inclined to the horizontal. One such assembly is described in European patent application No. 81710002.7 published under No. 0 033 294. The assembly comprises an upper track comprising either teeth or holes on its upper or lower surface. A running element, which also serves as a locating element, is attached to the carriage and comprises corresponding formations enabling it to mesh with the upper track. The carriage also comprises roller which rest against the lower track. The carriage further comprises a motor which drives the running and locating element to move the carriage up or down the tracks. This assembly however suffers from a number of disadvantages, the most important of which is an unacceptable level of safety. The running and locating element supports the carriage, drives the carriage and must provide any braking available to the carriage, and if this element or its supporting elements suffer a failure the carriage could fall off the tracks or run away down the tracks.

Another form of assembly is described in European patent application No. 90830123.7 published under No. 0 394 201. In this assembly a running element runs on the top of each track and couples with it by means of a cogged fit, the running element on the upper track being driven. Each running element is. associated with a bogey which rotates about the same axle and which runs along the bottom edge of the respective track to ensure stability of the carriage. Auxiliary tracks are mounted along some portions of the upper track and engage with rollers for added stability on these portions. This assembly also suffers from

the disadvantage that the driven running element also serves to support most of the weight of the carriage and act as the primary locating element. Any failure of this element could cause the carriage to run away down the tracks.

A further known form of assembly is described in International application No. PCT/EP92/00236 published under No. WO 92/14673. In this assembly a carriage is located on the upper and lower tracks by respective pairs of rollers, one of each pair being located above the respective track and the other below. At least one of each pair of rollers is driven and, since there are no inter- engageable formations on the tracks or the rollers, drive is achieved by friction. The rollers are pressed against the contact surface of the track by spring force so that motive force exerted is transmitted substantially without slipping. However, in order to exert sufficient clamping loads to achieve drive the tracks are distorted.

This assembly also suffers from a number of problems, one of which is that the running elements providing drive are also locating the carriage. In addition if the tracks are clean steel, thus providing a high coefficient of friction, there" is significant risk of pick-up or cold welding between the drive rollers and the track. Use of oil, grease or household polish on the track will reduce the risk of pick-up but will lower the coefficient of friction by as much as 80%, thus seriously affecting the drive capability. The assembly is described as incorporating polyurethane coated drive rollers, and a roughened track, to increase friction. However, the clamping loads described are sufficient to exceed the compressive strength of the polyurethane resulting in plastic flow and failure of the coating.

It is an object of the invention to provide an improved form of assembly comprising a track and a carriage which runs along the track.

According to the present invention, there is provided an assembly comprising an upper rail and a lower rail, the rails not being rectilinear, at least a portion of each rail being inclined to the horizontal and the rails being a substantially constant vertical distance apart, the assembly characterised in that it further comprises upper and lower racks and a carriage having supporting

means for supporting a person, locating elements adapted to locate the carriage on the rails and to maintain the carriage at a constant attitude, two running elements each adapted to drivingly engage with a respective elongate element and driving means adapted to drive each running element along the respective elongate element.

Examples of assemblies embodying the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 shows a diagrammatic representation of an assembly embodying the invention;

Figure 2 shows a diagrammatic representation of an alternative embodiment of the invention;

Figure 3 shows a diagrammatic representation of the driving means of the Figure 2 embodiment; and

Figures 4 and 5 show a diagrammatic representation of the locating means of the Figure 2 embodiment.

Referring to Figure 1, an assembly 9 is mounted in a stairwell which comprises a flight of steps 10. An upper track 11 and a lower track 12 are mounted on a wall of the stairwell above the steps 10. The tracks 11, 12 are not rectilinear. Each includes a portion 13 which is inclined uniformly to the horizontal and a portion 14 which is inclined at a different angle to the horizontal or in this example, is horizontal. The lower track 12 lies below the track 11 and is at least along straight portions parallel to the track 11. The vertical distance between corresponding parts of the upper and lower tracks is uniform and in this example the tracks 11, 12 are in the same vertical plane. Each of the tracks 11 and 12 incorporates a rail and an elongate element in the form of a rack extending along the entire length of the track.

The assembly further comprises a carriage 15 having running elements in the form of pinions 16, 17 which run on the upper and lower tracks respectively. Each of the pinions 16, 17 incorporates pinion teeth which are

enmeshed with the rack of the corresponding track. It will be understood that the pinions are spaced apart vertically by the same distance as the tracks 11 and 12 are vertically spaced. The tracks may be identical with each other. Rollers mounted on the carriage, but not shown in the drawing, run on the tracks and act as locating elements to maintain the required positional relation between the carriage and the tracks.

On the carriage 15, there is provided driving means for driving the pinions 16, 17 at the same speed and in the same direction. The driving means represented by way of example comprises an electric motor 18 connected via a gear train with a shaft 31 on which the pinion 17 is carried. The driving means further comprises a chain and sprocket drive 19 connecting the pinion 16 with the pinion 17 for rotation therewith. A mains power supply may be provided for the motor 18. Alternatively or additionally, the driving means may incorporate a battery of cells for energising the driving means, for example in the event of failure of a mains electrical supply.

When the pinions 16, 17 are driven along their respective tracks, the attitude of the carriage 15 relative to a horizontal plane remains constant. There are provided on the carriage a seat 20, a footrest 21 and an arm rest 22 for supporting a person on the carriage. Controls for controlling operation of the motor 18 may also be provided on the carriage to be accessible to a person seated on the seat 20.

The tracks 11 and 12 may be mounted on the treads of the stairs by means of brackets, in place of or in addition to being mounted on the wall.

Referring now to Figures 2 to 5, an assembly 29 being an alternative embodiment of an assembly according to the invention is illustrated, parts common to the assembly 9 are like referenced with the addition of a prime.

The upper and lower tracks 11', 12' each comprise a rail 11a, 12a and a rack lib, 12b below the rail. The tracks 11', 12' are supported by means of track spacers to which the rails 11a, 12a are attached, such as spacer 36 shown in Figure 4 for upper track 11'. The pinions 16', 17' run on the racks lib, 12b and

are driven along their respective racks, by driving means. The electric motor 18 is connected via a gear train (not shown) and a shaft 30 to the upper pinion 16' and via a chain and sprocket drive 19' and a shaft 31 to the lower pinion 17'. The chain and sprocket drive 19' comprises two upper sprockets 32, two lower sprockets 33 and two chains 34. A braking means in the form of an overspeed mechanism 35 is attached to the shaft 31 of the lower pinion 17'. The overspeed mechanism operates substantially as described in UK Patent Application No. 9203781.1 published as No. 2664283 and will not be described here.

The pinions 16', 17' play no part in locating the carriage 15' with respect to the tracks 11', 12'. The carriage 15' is located on and maintained in position with respect to the upper tracks 11' by rollers 37 to 40, as best illustrated in Figure 4. The rollers 37 to 40 rotate relative to their various supporting spindles, which are located within a housing 41. Rollers acting as locating elements in relation to the lower track 12' may be identical to those in relation to the upper track 11' or alternatively of a different form. A similar housing 42 is provided for the locating elements of the lower track 12'.

Primary roller 37 rotates about a spindle 43 and runs on top of the rail 11a thus supporting the majority of the weight of the carriage 15'. Further rollers 38, 39 rotate about spindles 45, 46 respectively and run on the sides of the rack 1 lb, thereby preventing oscillation of the carriage 15' laterally with respect to the track 11'. Finally, roller 40 is located about the upper end of spindle 46, rotates relative to the spindle 46, and engages with a portion of the rail 11a to provide additional lateral support particularly around corners present in the tracks 11'. An additional roller (not shown) may be provided on top of the spindle 45. Preferably each of the rollers 37 to 40 is duplicated within the housing 41, as shown in Figure 5.

Preferably the centre of gravity of the carriage 15' and its occupant is vertically above pinions 16' and 17', thus allowing each pinion/rack 16'/H', 17'/ 12' to transmit 50% of the required driving force. However, in many practical applications this is not possible and the centre of gravity is displaced to one side

or the other of the vertical line through the pinions 16', 17'. Any such shift in the line of action of the centre of gravity of the carriage 15' and its occupant can cause all the required driving force to be transmitted through one pinion/rack 16'/i or 17'/12' the other then acting solely to maintain the constant attitude of the carriage 15'. For this reason, each drive path is designed to be capable of transmitting full driving force.

The assembly 29 provides a number of advantages. Firstly, drive is transmitted by form locking rack and pinion drive which transmits only driving torque. The teeth have no locating function, so stress levels are low, minimizing risks of failures such as broken teeth. Secondly, duplication of driving force paths, in conjunction with the multiplicity and disposition of locating rollers, ensures that the drive system can tolerate any single component failure without risk of the carriage 15' falling off the tracks 11', 12' or otherwise becoming unstable.

The embodiments described above incorporate driving means comprising a single electric motor which drives one pinion directly and the other pinion indirectly by means of a chain and sprocket drive. Many alternatives are possible, for example, a single electric motor could be arranged to drive both pinions indirectly by means of chain and sprocket drives or otherwise. Alternatively, the driving means may comprise two electric motors, each of which drives one pinion directly.

The assemblies 9, 29 described above incorporate racks and pinions having teeth of involute form. However, many forms of drive paths having elongate elements and running elements are known and may be incorporated in assemblies according to the invention. In addition where racks and pinions are used the upper and lower rack and pinion drives need not be identical but should be adapted in combination with the driving means to provide identical linear speed.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process

for attaining the disclosed result, as appropriate may, separately or in any combination of such features, be utilised for realising the invention in diverse forms thereof.