GB2421018A

GB2421018A - Stairlift with longitudinal drive element

Info

Publication number: GB2421018A
Application number: GB0422457A
Authority: GB
Inventors: Andreas Csaba Szentistvany
Original assignee: Stannah Stairlifts Ltd
Current assignee: Stannah Stairlifts Ltd
Priority date: 2004-10-09
Filing date: 2004-10-09
Publication date: 2006-06-14
Anticipated expiration: 2024-10-09
Also published as: GB0422457D0; GB2421018B

Abstract

Stairlift drive element in which the drive includes a displaceable longitudinal transmission section or driving element which is maintained in contact with a length of the stairlift rail. The transmission section is preferably included in a looped belt or chain. This form of drive avoids the high point loading of conventional stairlift drive systems.

Description

IMPROVEMENTS IN OR RELATING TO STAIRLIFTS

Field of the invention

This invention relates to stairlifts

Background to the Invention

Stairlifts, including those travelling in a single direction at a single angle of inclination (straight-line stairlifts), typically comprise a carriage mounted on a stairlift rail for movement along the rail. The carriage includes a drive motor and gearbox and includes some form of drive mechanism, such as a rack and pinion or friction drive, which contacts the rail to effect movement of the carriage along the rail. Whilst this arrangement is well proven, an increasing demand has been identified for a low cost, straight-line stairlift which can be installed by the purchaser. Obviously, when a stairlift is sold through a trade outlet for installation and subsequent service by an unknown purchaser, control over the stairlift is lost, and there is a concern that product reliability may suffer, and passenger safety may be compromised.

Existing stairlift designs do not lend themselves to safe and reliable amateur installation, and servicing, for a number of reasons.

Firstly, existing rack and pinion drive systems require the rack to be fitted to the rail.

Where a stair lift is supplied as a kit to be fitted to a variety of possible stairways, the rack will invariably be fitted, on site, by the installer. This is not only an additional step which has to be undertaken, but is also a safety critical step.

Existing rack and pinion drives also need to be greased. If grease is not liberally applied to the rack, wear in the drive system increases significantly. In opposition to the wear issue, greasing the rack is undesirable as the grease is typically exposed and can soil clothing and other material which comes into contact with the rail.

It is an object of this invention to provide a straight-line stairlift which goes at least some way in addressing the problems set out above; or which will at least provide a novel and useful choice.

Summary of the Invention

Accordingly, in one aspect, the invention provides a stairlift including a stairlift rail having drive surfaces thereon; a carriage mounted on said rail for movement along said rail; a drive mechanism within said carriage engageable with said drive surfaces on the rail to displace said carriage along said rail, said stairlift being characterised in that said drive mechanism includes a flexible transmission member having drive transmitting surfaces thereon engageable with the drive surfaces on said rail.

Preferably a plurality of said drive transmitting surfaces are engaged with a plurality of said drive surfaces.

Preferably said flexible transmission member is embodied in an endless belt.

Preferably said flexible transmission member has drive transmitting surfaces on both faces thereof.

Preferably said flexible transmission member is supported on a pair of spaced wheels.

Preferably each of said spaced wheels is driven.

Preferably each of said wheels includes at least one side plate, said at least one side plate including projections shaped and positioned to engage with said drive surfaces on said rail in the event of failure of said flexible transmission member.

Preferably said drive mechanism further includes a follower operable to maintain said drive transmitting surfaces in engagement with the drive surfaces on said rail.

Preferably the drive transmitting surfaces on said rail are defined by apertures formed in said rail.

Many variations in the way the present invention can be performed will present themselves to those skilled in the art. The description which follows is intended as an illustration only of one means of performing the invention and the lack of description of variants or equivalents should not be regarded as limiting. Wherever possible, a description of a specific element should be deemed to include any and all equivalents thereof whether in existence now or in the future. The scope of the invention should be determined by reference to the appended claims alone.

Brief Description of the Drawings

One form of stairlift incorporating the various aspects of the invention will now be described with reference to the accompanying drawings in which: Figure 1: shows an isometric view, from the front, of a stairlift carriage and rail according to the invention; Figure 2: shows in an isometric view, from the rear, of that which is shown in Figure 1; Figure 3: shows an end elevation of the stairlift components shown in Figures 1 & 2; and Figure 4: shows an rear elevation of the carriage forming part of the stairlift shown in Figures 1 to 3, removed from the stairlift rail.

Detailed Description of Working Embodiment

Referring firstly to Figure 1, according to the invention a stairlift assembly 10 is provided, the assembly 10 including a stairlift rail 11 and a carriage 12 mounted for movement along the rail. Included within the carriage 12 is a novel drive system which will be described in greater detail below.

In the form shown the rail 11 is formed from a combination of folded sheet metal sections and comprises a first section 14 and a second section 16, the two sections being fixed together by, for example, rivets 17. The first section 14 includes an upright centre web 18, an upper flange 20, and a lower flange 22. The flanges 20 and 22 are substantially parallel and the upper flange 20 has strengthening rib 21 extending along the outer edge thereof whilst the lower flange 22 has an angled strengthening rib 23 extending along the outer edge thereof.

As can be seen in Figures 1 & 2, the upper flange 20 has included therein, a plurality of drive surfaces, preferably formed in the wall of the material comprising the flange 20. As shown, these drive surfaces comprise a series of evenly-spaced, parallel slots 24 formed along the flange 20. These slots may be laser-cut into the flange 20 although other methods of forming the slots will be known to those skilled in the art.

After formation of the slots, the edges thereof may be smoothed off and/or tailored more closely to the profile of the driving transmission member by, for example, applying a punch to each slot.

The second section 16 of the rail includes a centre web 26, and a bottom flange 28 having a angled strengthening rib 29 extending along the outer edge thereof. When the sections 14 and 16 are fixed together in the intended manner, the flanges 22 and 28 are aligned and form mirror images about the centre-line of the rail 11.

The rail 11 as described above, can be readily formed using conventional sheet-metal forming techniques which do not require expensive tooling investment.

It should be appreciated, however, that the rail need not be formed as two components, or formed from sheet metal, as described above. The rail could, for example, be extruded and the slots 24 post-fonned by punching or other suitable technique.

The carriage 12 has a central chassis member 30 which may be cast, or machined from a solid block of metal. The chassis member might also be formed from other materials including injection moulded plastics.

A number of rollers are provided to support the chassis on the rail 11 and, in the form shown, include two spaced, vertical, support rollers 32a and 32b which are in rolling contact with the flange 22 of the rail; and a plurality of horizontal rollers arranged to resist rotation of the carriage about the rail. As shown the horizontal rollers include a spaced pair 34a and 34b which bear against rib 21, and a spaced pair 36a and 36b which bear against the upper margin of centre web 18. The rollers 34 are mounted at opposite edges of the main chassis 30 whilst the rollers 36 are mounted on brackets 38 extending from, but fixed to, the rear surface of the chassis 30.

The horizontal roller set is completed by central bottom roller 40 which is positioned to bear against the rib 23 of first rail section 14.

A characteristic feature of the stairlift according to the invention is the drive mechanism included within the carriage 12 to displace the carriage 12 along the rail 11. This drive mechanism includes a flexible transmission member having drive transmitting surfaces thereon which are engageable with the slots 24 on the rail in such a way that displacement of the flexible transmission member leads to displacement of the carriage along the rail.

As is best seen in Figure 4, the flexible transmission member is advantageously provided in the form of an endless belt 44 having drive transmitting surfaces in the form of teeth 46 and 48 extending from the inner and outer faces, respectively, thereof. The teeth 48 extending from the outer surface of the belt 44 are selected to engage with, or determine, the profile of slots 24 in the rail. The teeth 46 are selected to engage with, or determine, the toothed peripheries (not shown) of spaced drive wheels 50a and 50b on which the belt 44 is mounted and supported.

The belt 44 is preferably a readily available, off-the-shelf, timing belt. These are typically rubber/plastics/synthetic/fabric composite items manufactured by Gates amongst others. A particular feature of these belts is that they operate without the need for any lubrication.

It will be appreciated that the upper span 52 of the mounted belt engages the under- surface of the flange 20, and thus the teeth 48 engage with slots 24 from below. In this way, the moving belt is kept out of contact with the exterior of the stairlift assembly. The span 52 of the belt is vertically supported by, and maintained in contact with flange 20, by a static rubbing block or follower 54 which is positioned within the loop defined by the mounted belt. The follower ensures that the section of belt which, at any time defines the upper span 52, cannot sag and allow the teeth 48 thereon to become disengaged from the slots 24.

A feature of the drive mechanism herein described is that a plurality of the teeth 48 are engaged in slots 24 at any particular time. The number of teeth 46 engaged in slots 24 is determined by the length of the upper span 52 of the belt. By way of example, with a span of 230mm, 23 teeth are fully engaged in slots 24, each tooth 48 having a width of about 5mm. The fact that more than one tooth 48 is engaged with the rail, reduces the loading on the individual teeth and thus reduces the likelihood of tooth failure. The relatively low loading on each tooth also enables the use of non- metallic materials.

As a further safety precaution, a slackness monitor 56 is preferably provided which acts against the bottom span 58 of the belt and determines if the span 58 becomes slack due to, for example, breakage of the belt 44. In the event the monitor 56 senses slackness of the belt 44, an internal switch is broken cutting power to the carriage drive.

Whilst a toothed flexible belt as described above is the preferred form of flexible transmission member, other drives are possible without departing from the scope of the invention. For example, a chain based drive system could be provided having teeth or the like, projecting from the individual chain links, to engage in slots 24 in the rail.

Toothed wheels 50a and SOb are preferably both driven. To this end, the wheels are mounted on the output shafts of motor/gearbox units 60a and 60b. The units 60a and 60b are mounted on the front face of the chassis 30 but so that the output shafts thereof pass through the chassis. The units 60a and 60b are preferably selected so as to be self-sustaining. That is to say, the units will not free-wheel whilst not energised and subjected to a displacing force. The self-sustaining feature overcomes the necessity to provide separate braking for the carriage.

Batteries 62a and 62b are clamped to the rear of the chassis 30 to provide power for the motor/gearbox units and for the other electrical based functions of the stairlift, the latter being under the control of an ecu-based control system 64 provided on the upper edge of the chassis 30.

To further enhance safety, each of the wheels may be provided with side plates 51 which not only serve to maintain the belt 44 from slipping sideways off the wheels 50, but may also be provided with peripheral projections or teeth 61, some of which are shown on wheel 50a. The teeth 61 are shaped and spaced to protrude within slots 24 but not, normally, to engage the slot edges and provide a drive function. However, in the event of the belt 44 loosing tension or breaking, power is cut to the motor/gearbox units 60 and the teeth 61 may then engage the edges of the slots 24 and lock the carriage in position.

Finally, a boss 66 is mounted to project from the front surface of the chassis 30 to provide a mounting point for a chair interface.

It will thus be appreciated that the present invention provides a simple yet effective form of stairlift assembly which, at least in the case of the embodiment above described, is believed to have the following advantages: a) The assembly has a particularly simple form of carriage which is compact, provides low seat height, and creates greater scope for chair and interface design.

b) The chassis, being extremely simple and robust in form, lends itself to simplified manufacturing techniques including plastics injection moulding.

c) The use of two drive systems reduces the required power and torque rating of each individual motor. This in turn means that there is a greater range of available units from which to choose.

d) The combination of two self-sustaining motor/gearbox units in combination with the follower 54 and slackness monitor 56 provides all the required safety systems and is believed to obviate the need for an over-speed governor.

e) The flexible toothed-belt drive system is highly efficient and the fact that so many teeth are in contact with the slots in the rails means than individual tooth loading is low. The rubber/plastics based belt also obviates the need for additional lubrication to be added to the drive system.

1) The rail, being unhanded and having the rack formed integrally therewith, is ready to be mounted for every installation. The step of positioning and fixing the rack has been eliminated.

g) The rail configuration and drive system opens the possibility of the stairlift being installed by non-expert technicians.

Claims

Claims 1) A stairlifi including a stairlifi rail having drive surfaces

thereon; a carriage mounted on said rail for movement along said rail; a drive mechanism within said carriage engageable with said drive surfaces on the rail to displace said carriage along said rail, said stairlifi being characterised in that said drive mechanism includes a flexible transmission member having drive transmitting surfaces thereon engageable with the drive surfaces on said rail.
2) A stairlift as claimed in claim 1 wherein a plurality of said drive transmitting surfaces are engaged with a plurality of said drive surfaces.
3) A stairljfi as claimed in claim I or claim 2 wherein said flexible transmission member is embodied in an endless belt.
4) A stairlift as claimed in any one of claims 1 to 3 wherein said flexible transmission member has drive transmitting surfaces on both faces thereof.
5) A stairlift as claimed in any one of the preceding claims wherein said drive transmitting surfaces are defined by teeth on said flexible transmission member.
6) A stairlifi as claimed in any one of the preceding claims wherein said flexible transmission member is supported on a pair of spaced wheels.
7) A stairlift as claimed in claim 6 wherein each of said spaced wheels is driven.
8) A stair lift as claimed in claim 6 or claim 7 wherein each of said wheels includes at least one side plate, said at least one side plate including projections shaped and positioned to engage with said drive surfaces on said rail in the event of failure of said flexible transmission member.
9) A stairlift as claimed in any one of the preceding claims wherein said drive mechanism further includes a follower operable to maintain said drive transmitting surfaces in engagement with the drive surfaces on said rail.
10) A stairlift as claimed in any one of the preceding claims wherein the drive surfaces on said rail are defined by apertures formed in said rail.
11) A stairlift when constructed arranged and operable substantially as herein described with reference to, and as illustrated in, the accompanying drawings.