GB2418906A

GB2418906A - Stairlift with flexible drive

Info

Publication number: GB2418906A
Application number: GB0422455A
Authority: GB
Inventors: Raymond John Drayton; Stephen Ashley Hobden
Original assignee: Stannah Stairlifts Ltd
Current assignee: Stannah Stairlifts Ltd
Priority date: 2004-10-09
Filing date: 2004-10-09
Publication date: 2006-04-12
Anticipated expiration: 2024-10-09
Also published as: GB2418906B; GB0422455D0

Abstract

A stairlift 10 includes a rail 11, a carriage 12 mounted for movement along said rail and a drive mechanism including a flexible transmission 14 means windable onto a driven drum 16. The drum is preferably mounted on the carriage and the flexible transmission means is at least one web or belt. The flexible transmission means may comprise two webs 14a, 14b side-by-side located adjacent the upper edge of the rail. Means may be provided to sense a reduction in tension of the flexible transmission means which may be used to cause an over-speed governor to be triggered and bring the carriage to an immediate halt or lower the carriage to the bottom of the rail. The over-speed governor may brake the drum to a halt should the speed of rotation of the drum exceed a pre-determined maximum.

Description

24 18906 IMPROVEMENTS IN OR RELATING TO STAIRLlFTS

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; a carriage mounted on said rail for movement along said rail; and a drive mechanism to drive said carriage along said rail, said stairlift being characterized in that said drive mechanism includes a driven drum and a flexible transmission means windable onto, and from, said drum.

Preferably said rail has an upper end and a lower end, said drum is mounted within said carriage, and said flexible transmission means extends between said drum and said upper end of said rail.

Preferably said flexible transmission means comprises at least one length of web material. More preferably said flexible transmission means comprises two lengths of web material arranged side-by-side.

Said web material is preferably belt-like in form having a width substantially greater than the thickness thereof.

Preferably said stairlift further includes monitoring means to sense a reduction in tension in said flexible transmission means.

Preferably said rail has an upper edge and a lower edge, said flexible transmission means being located adjacent said upper edge.

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

The invention, and modifications thereof, will now be described with reference to the accompanying drawings in which: Figure 1: shows an isometric view of a certain stair lift components to illustrate the invention; and Figure 2: shows a side elevation of that which is shown in Figure 1.

Detailed Description of Working Embodiment

Referring firstly to Figure I, according to the invention a stairlift 10 is provided, the assembly 10 including a stairlift rail 11 and a carriage, the bulk of which is shown at 12, the carriage 12 being mounted on, for movement along, the rail 11. The stair lift includes a novel drive mechanism, including flexible transmission means 14 windablc on to, and off, drum assembly 16, to displace the carriage 12 along the rail 11. This drive mechanism is described in greater detail below.

The rail 11 has an upper end 20 and a lower end 21 and, in the form shown, the carriage is displaced over the upper edge 22 of the rail. The precise form of the rail is not an essential feature of the invention but it may, as shown, be substantially of the form described and illustrated in our European Patent 1 124 749.

Bus-bars 23 may be provided along the rail to relay a charging current to batteries (not shown) provided within the carriage 12.

The carriage 12 is supported for rolling movement along the rail 11 on a plurality of rollers 25. In the known manner, these rollers 25 are positioned and arranged to ensure the carriage is firmly supported on the rail, yet can roll freely along the rail.

Again the precise roller arrangement does not form part of this invention.

In the form shown herein, the drive mechanism is mounted within the carriage 12. It could, however, be mounted externally to the carriage.

In this particular embodiment, drum assembly 16 is mounted in bracket 30 fixed to the upper side of gearbox 32. The gearbox 32 is driven by an electric motor 33 and includes output drives 35 on either side thereof. The motor 33 and gearbox 32 are mounted directly to the chassis 37 of the carriage 12. It will be appreciated that this s arrangement allows the width of the carriage to be kept to a minimum whilst still allowing the flexible transmission means 14 to be arranged centrally along the upper edge 22 of the rail.

In order to apply the output of gearbox 32 to the drum assembly 16, the drum assembly 16 is provided with a pair of outer driven wheels 38. These driven wheels 38 are positioned above the output drives 35 of the gearbox 32 and are linked to the output drives by cranks 40. Cranks 40 are mounted eccentrically to the centres of rotation both of the output drives 35, and the driven wheels 38. This ensures that rotation of the output drives 35 is translated into rotation of the drum assembly l 6.

It will be appreciated that other drive arrangements could be provided without departing in any way from the scope of this invention. By way of example only, the wheel and crank arrangement could be replaced by a inter-engaging gears or by spaced pulleys linked together by toothed belts or chains. Further, a suitable drum assembly could be mounted directly on the output of the gearbox. In such a case the drum would be positioned so that the flexible transmission means 14 was correctly located with respect to the rail 11 or, alternatively, the transmission means 14 could be led to the rail via one or more diverters so that, at the rail surface, the transmission means 14 was located in the desired position.

Returning now to the embodiment depicted, the flexible driving means 14 is preferably provided in the form of a web of flexible material and, more preferably, in the form of two webs 14a and 14b arranged side-by- side. When two webs are provided, each is selected so as to have the ability to support the operating load of the stair lift and thus, in the event of failure of one of the webs, the other web remains to support the carriage. The webs are preferably considerably broader in width than in thickness, and an equalizer (not shown) may be provided to ensure the load of the carriage is, in normal use, equally shared between the two webs.

The material from which the webs are formed does not constitute part of the invention and any flexible web material having sufficient strength and durability will suffice. By way of example only, the web may be a woven textile/synthetic based material of the type from which automotive seat belts are made. Other materials, even including those having metallic components, will present themselves to those skilled in the art.

Given the two web arrangement, the drum assembly 16 includes a pair of adjacent reels 42a and 42b mounted between the outer driven wheels 38 of the drum assembly 16, and rotatable therewith. Web 14a is engaged with drum 42a whilst web 14b is engaged with drum 42b.

Whilst, in the form shown, both drums 42a and 42b are driven from a common motor 33 and gearbox 32, each could, if desired, be driven by its own separate motor and gearbox unit.

Both webs 14a and 14b are directed from the drums 42a and 42b, down and about idler rollers 44 mounted in the lower bottom edge of the chassis 37, before extending upwardly, over the upper edge 22 of the rail, to their attachment points at the top end of the rail. Obviously the length of the webs is set so as to allow the carriage to traverse the entire working length of the rail.

It will be appreciated that, as the motor is powered to rotate the drum assembly 16 in a clockwise direction as shown in the drawings, the webs 14a and 14b are wound onto drums 42a and 42b respectively, and the carriage 12 is drawn up the rail 11. When the motor is rotated in the opposite direction, the carriage 12 is allowed to move down the rail under gravity as the webs 14a, 14b unwind from their respective drums.

It will further be appreciated that, as the webs 14a and 14b wind on to, and off, their respective drums, the carriage will be subjected to a variation in speed assuming, of course, that the motor 33 operates at a constant speed. If this carriage speed variation is deemed undesirable, suitable motor control may be introduced to vary the speed of the motor. This control may include a device to monitor the effective diameter of the web on the drum or may include an electronic-based system which computes an effective diameter of the web on the drum based on identifying the position of the carriage on the rail.

An over-speed governor (not shown) may be provided in the drum assembly 16 to brake the drum to a halt in the event the speed of rotation of the drum exceeds a pre- determined maximum speed. The precise form of the over-speed governor does not from part of the invention. Further, as shown schematically in Figure 2, each of the webs 14a, 14b may be led over monitoring means in the form of tension sensors 46 mounted within the carriage. The tension sensors, which may be electrical or mechanical in form, are configured and arranged to sense loss of tension in either web, such as would occur in the event of fracture or detachment of the web, or failure in the drive system. In the event of loss of tension in one web, the main electrical control within the stair lift would be triggered to cause the carriage to move slowly to the bottom of the rail, and thereafter prevent further use of the stairlift until the web was repaired. In the event of loss of tension in both webs the sensors 46 would cause the over-speed governor to be triggered, and the carriage 12 brought to an immediate halt.

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 the means by which the chair is mounted to the carriage.

b) The web-based drive system is highly efficient and requires minimal maintenance. Further, the inherent nature of the drive system obviates the need for lubrication, such as grease, to be added to the drive system.

c) The absence of inter-engaging rack and pinion ensures an extremely smooth ride.

d) The rail, being unhanded, is ready to be mounted for every installation. There is no additional step of attaching a rack to the rail.

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

Claims

Claims 1) A stairlift including a stairlift rail; a carriage mounted on

said rail for movement along said rail; and a drive mechanism to drive said carriage along said rail, said stairlift being characterized in that said drive mechanism includes a driven drum and a flexible transmission means windable onto, and from, said drum.
2) A stairlift as claimed in claim I or claim 2 wherein said rail has an upper end and a lower end, said drum is mounted within said carriage, and said flexible transmission means extends between said drum and said upper end of said rail.
3) A stairlift as claimed in claim I or claim 2 wherein said flexible transmission means comprises at least one length of web material.
4) A stairlift as claimed in any one of claims I to 3 wherein said flexible transmission means comprises two lengths of web material arranged side-by side.
5) A stairlift as claimed in claim 3 or claim 5 wherein said web material is preferably belt-like in form having a width substantially greater then the thickness thereof.
6) A stairlift as claimed in any one of the preceding claims further including monitoring means to sense a reduction in tension in said flexible transmission means.
7) A stair lift as claimed in any one of the preceding claims wherein said rail has an upper edge and a lower edge, said flexible transmission means being located adjacent said upper edge.
8) A stairlift when constructed arranged and operable substantially as herein described with reference to, and as illustrated in, the accompanying drawings.