GB2428664A

GB2428664A - Friction/gear drive for stairlift

Info

Publication number: GB2428664A
Application number: GB0515208A
Authority: GB
Inventors: Alan Neil Russell Stannah
Original assignee: Stannah Stairlifts Ltd
Current assignee: Stannah Stairlifts Ltd
Priority date: 2005-07-23
Filing date: 2005-07-23
Publication date: 2007-02-07
Anticipated expiration: 2025-07-23
Also published as: GB2428664B; GB0515208D0

Abstract

The present invention provides a drive for a stairlift which combines both a friction drive element and a positive drive element, such as a rack and pinion.

Description

IMPROVEMENTS IN OR RELA TING TO STAIRLIFTS

Field of the invention

This invention relates to stairlifts and, in particular, to a drive arrangement for a stairlift.

Background to the Invention

A variety of drive arrangements are known for displacing a stairlift carriage along a stairlift rail. Probably the most common arrangement is a rack and pinion drive where the pinion is mounted for rotation in the carriage and is positioned to drivingly engage a rack extending along the rail. Rack and pinion drives are easily established and reliable but need to kept lubricated if formed from metal components. This, in turn, provides the potential to soil clothing and objects coming into contact with the rack as well as requiring regular checking and maintenance.

In an attempt to avoid the use of lubricants, it has been proposed to form both pinion and rack from self-lubricating plastics. However there is a widespread view that single pinion and rack drive arrangements are not sufficiently robust to ensure safe and reliable stairlift operation over extended periods. Current regulations governing the design and construction of stairlifts do not favour (and in some cases positively prevent) the adoption of drive systems formed from plastics components.

One alternative to a rack and pinion drive arrangement is a friction drive in which the geared pinion is replaced by a wheel having a plain periphery, and the rack is replaced by a planar drive surface. However, our experience suggests that an effective friction drive arrangement experiences high levels of wear in use.

It is an object of the invention to provide a drive arrangement for a stairlift which will go at least some way in addressing the aforementioned problems; or which will at least provide a novel and useful choice.

Summary of the Invention

Accordingly, in a first aspect the invention provides a stairlift drive characterised in that it includes both a rotating friction drive element and a rotating positive drive element.

Preferably said friction drive element is concentric with said positive drive element.

Preferably a friction drive element is located on either side of said pinion drive element.

Preferably said positive drive element comprises a geared pinion.

Preferably said friction drive element(s) is formed integrally with said pinion.

Preferably said drive is moulded from plastics material.

In a second aspect the invention provides a stairlift including a stairlift rail; a carriage mounted on said rail for movement there-along; and a drive included at least in part in said carriage to effect displacement of said carriage along said rail, said stairlift being characterised in that said rail includes a friction drive surface and a positive engagement drive surface; and said drive includes a rotating positive drive element engageable with said positive engagement drive surface and a rotating friction wheel engageable with said friction drive surface.

Preferably said rotating positive drive and said rotating friction drive are concentric.

Preferably said rail includes two friction drive surfaces extending along said rail on either side of said positive engagement drive surface.

Preferably said positive engagement drive surface and said rotating positive drive element comprise a rack and pinion respectively.

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 limited by the appended claims alone.

Brief Description of the Drawings

One preferred form of the invention will now be described with reference to the accompanying drawings in which: Figure 1: shows an isometric view of a section of stairlift drive component for use in the invention; and Figure 2: shows an edge view of a drive wheel for use with the drive component shown in Figure 1

Detailed Description of Working Embodiment

The present invention provides a novel drive system for a stairlift in that it combines aspects of both positive drive and friction drive systems. In its broadest aspect the drive system includes both a positive drive and a friction drive but these are preferably integrated into two co-operating components.

The term positive drive as used herein is intended to mean any drive which relies on the positive engagement of interacting components. Examples include peg and hole drives and co-operating hook and ball arrangements, but the most common form of positive stairlift drive is a rack and pinion.

In the form shown in the drawings, and in the conventional manner, the drive system includes one drive component fixed to a stairlift rail, and a rotating component mounted on, and driven within, the stairlift carriage.

The rail -mounted component 5 includes a rack 6 which is purely conventional in form and is mountable on a stairlift rail. Extending along the rail component is at least one, and preferably two, friction drive surfaces 7. As can be seen, the friction drive surfaces 7 extend along both sides of the rack 6 and are preferably positioned tangential to the pitch circle diameter of the gear with which, in use, the rack 6 is meshed. In this way the friction surfaces are at substantially the same level as the rack and pinion point of contact.

The rack 6 and friction drive surfaces 7 may be fabricated separately and joined together, but are preferably integrally formed. Most preferably the component 5 is moulded from a plastics material. The surfaces 7 may be post-treated by, for example, coating to improve the frictional resistance provided thereby.

As one alternative, the components herein described may be formed from metals which may then be treated to reduce friction. Suitable treatments include surface coating with low friction, self-lubricating plastics.

Referring now to Figure 2, the rotating drive element 10 preferably comprises a conventional geared pinion section 11, the teeth of which are sized and shaped to engage with the rack 6. Mounted on either side of the pinion section 11, and concentric therewith, are friction wheels 12 which are sized to engage the friction drive surfaces 7 when the pinion 11 is in mesh with the rack 6.

It will be appreciated that the combination of the positive drive arrangement with a friction drive arrangement means that one provides a back up for the other and therefore reduces the operating load on the individual drives. This, in turn, means that lubrication free drive systems, preferably moulded from plastics materials, can be reliably incorporated into a stairlift drive arrangement. Drive loading can be further reduced by providing more than one of the units described herein, preferably mounted in series in the stairlift carriage.

It is also envisaged that, whilst the combined drive arrangement would be provided at places on the stairlift rail where the drive system is subjected to high loading, for example at steep rail angles, at places on the rail where the loading is low, the positive drive arrangement might be omitted and the friction drive alone used to displace the carriage.

It will thus be appreciated that the present invention provides a simple yet effective form of drive for a stairlift which, at least in the case of the embodiment described herein, provides the possibility of a lubrication-free drive whilst addressing safety and reliability concerns.

Claims

Claims 1. A stairlift drive characterised in that it includes both a

rotating friction drive element and a rotating positive drive element.
2. A stairlift drive as claimed in claim 1 wherein said friction drive element is concentric with said positive drive element.
3. A stairlift drive as claimed in claim 1 or claim 2 wherein a friction drive element is located on either side of said pinion drive element.
4. A stairlift drive as claimed in any one of the preceding claims wherein said positive drive element comprises a geared pinion.
5. A stairlift drive as claimed in claim 4 wherein said friction drive element(s) is formed integrally with said pinion.
6. A stairlift drive as claimed in any one of the preceding claims when moulded from plastics material.
7. A stairlift including a stairlift rail; a carriage mounted on said rail for movement there-along; and a drive included at least in part in said carriage to effect displacement of said carriage along said rail, said stairlift being characterised in that said rail includes a friction drive surface and a positive engagement drive surface; and said drive includes a rotating positive drive element engageable with said positive engagement drive surface and a rotating friction wheel engageable with said friction drive surface.
8. A stairlift as claimed in claim 7 wherein said rotating positive drive and said rotating friction drive are concentric.
9. A stairlift as claimed in claim 7 or claim 8 wherein said rail includes two friction drive surfaces extending along said rail on either side of said positive engagement drive surface.
10. A stairlift as claimed in any one of claims 7 to 9 wherein said positive engagement drive surface and said rotating positive drive element comprise a rack and pinion respectively.
11. Any novel combination of the integers disclosed herein capable of addressing a problem in the stairlift art.