Field of the Invention

This invention relates to a stairlifts and, in particular though not necessarily solely, to a stairlift suitable for use on narrow stairways and/or for use by persons whose leg flexure is compromised.

Background to the Invention

The design of stairlifts necessarily involves a number of compromises. One compromise arises from the need to minimize the intrusion of the stairlift into the stairway. This rises in significance when the stairway is narrow and there is a risk that a user, particularly the user's knees or feet, will come into contact with the stairway during movement of the stairlift up and down the stairway.

A further compromise arises from the need to accommodate users whose knee and/or ankle flexure is impaired. In some cases, assuming a fully seated position may cause a user pain or other discomfort.

Conventionally, a stairlift proceeds up and down a rail mounted on a stairway with the user seated facing in a direction perpendicular to the direction of motion, and the user's knee joints substantially defining right angles. Not only does this configuration maximize the intrusion of the user into the stairway but it also requires considerable knee flexure which can be painful.

Published International Patent Application No. WO2005/087644 seeks to address the intrusion problem by providing a mechanism that pivots the stairlift chair about a vertical axis during movement of the stairlift along the rail, the pivot angle being dependent on the position of the stairlift along the rail. European Patent Application No. 2 119 660 describes an arrangement in which the chair can not only be pivoted to face in a downward direction, but can also be lowered and slanted backwards to provide increased clearance between a passenger and a ceiling overlying the stairway.

Whilst the two patent applications mentioned above address the issue of narrow stairways, each presents a problem in that it is generally considered undesirable for a stairlift to be facing in a downwards or downhill direction whilst in motion. This is because, in the event of a malfunction in the stairlift, the stairlift could come to a halt at some point in its journey. In this event a passenger would be exposed to additional danger if he/she attempted to dismount from the stairlift, because the distance from the chair to the adjacent (downhill) part of the stairway is that much greater than when the stairlift is in the more conventional configuration. A further problem with both proposals is that they do nothing to limit the flexure of a user's knees.

The issue of knee flexure is addressed by stairlifts in which the user stands, supporting his/her own weight, during the journey. This leads to safety concerns, it being generally accepted that users should be positively supported during a stairlift journey. A variation of the standing stairlift, and one which offers a degree of support, is the perch stairlift where the user's bottom is partly supported. This form of stairlift requires the user to push back on the perch and, in the event the user looses his/her footing, gravity will cause the user to be displaced from the perch and, potentially, ejected from the stairlift.

It is an object of the present invention to provide a method of supporting a stairlift user, and/or a stairlift, that will go at least some way to addressing the aforementioned drawbacks; or which will at least provide a novel and useful choice. Summary of the invention

Accordingly, in one aspect, the invention provides a method of supporting a user having a bottom, feet and knee joints on a stairlift having a seat to

vertically support said user, said seat including a front edge and a rear edge;

and a footrest, said method being characterised in that it comprises

configuring said seat to resist movement of said user in a direction from said rear edge towards said front edge, and establishing a vertical distance between said footrest and said seat so that when said user is seated on said seat with

said feet in contact with said footrest, an included angle defined by said knees is greater than 90°.

Preferably said method includes configuring said seat so that, with a user seated, at least part of said front edge is higher than said rear edge.

Preferably said method includes configuring said seat so that at least part of said front edge is capable of accommodation between the legs of said user. Preferably said method includes dispacing said seat, in the absence of a user, to lower said front edge relative to said rear edge.

Preferably said method further includes biasing the movement of said seat to lower said front edge relative to said rear edge.

Preferably the vertical spacing between said seat and said footrest is set so that said included angle lies in the range of 95° - 165°.

Preferably said method includes configuring said seat with one or more indentations between said front edge and said rear edge and positioned to receive the ischial tuberosities of a user. Preferably said method includes forming said seat of materials of at least two different densities.

Preferably said method comprises providing a strip of material across said seat between said one or more indentations and said front edge, or in part defining those parts of said one or more indentations closest to said front edge, said strip of material being of a density greater than the density of the material in which said one or more indentations are formed.

In a second aspect, the invention provides a stairlift for supporting a user

having a bottom, feet and knees, said stairlift having a seat to vertically

support said user, said seat including a front edge and a rear edge; and a

footrest and being characterised in that said seat is configured to resist

movement of said user in a direction from said rear edge towards said front

edge, and a vertical distance between said footrest and said seat is established to ensure that, when said user is seated on said seat with said feet in contact

with said footrest, an included angle defined by said knees is greater than 90°.

Preferably, with a user in position, at least part of said front edge is higher than said rear edge.

Preferably said seat is configured so that said at least part of said front edge is capable of accommodation between the legs of said user. Preferably said forward edge is provided with a pommel.

Preferably said seat is displaceably mounted to enable said front edge to be lowered relative to said rear edge.

Preferably a biasing facility is provided to, in the absence of a user, displace said front edge into a lower position relative to said rear edge. Preferably the vertical spacing between said seat and said footrest is set so that said included angle lies in the range of 95° - 165°.

Preferably said seat includes one or more indentations between said front edge and said rear edge, said one or more indentations being positioned to receive the ischial tuberosities of a user.

Preferably said seat is formed of materials of at least two different densities.

Preferably said seat includes a strip of material extending laterally of said seat in a position between said one or more indentations and said front edge; or in part defining those parts of said one or more indentations closest to said front edge, said strip of material being of a density greater than the density of the material in which said one or more indentations are formed.

Preferably said seat is included in a chair having a backrest and at least one armrest.

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.

Brief Description of the Drawings

The various aspects of the invention will now be described with reference to the accompanying drawings in which: Figure 1 : shows an isometric schematic view of a stairlift according to the invention;

Figure 2: shows a side elevation of the stairlift shown in Figure 1 with a user seated thereon.

Figures 3a: show side views of part of the stairlift shown in Figure 1 in to 3c positions of different loading;

Figure 4: shows a view corresponding to Figure 3c of a biasing facility to displace a stairlift seat between the positions shown in Figures 3a, 3b & 3c; and

Figure 5: shows a isometric view of a seat surface suitable for use in a stairlift according to the invention.

Detailed Description of Working Embodiment

This invention provides a method of and means for supporting a user on a stairlift. The essential features of the invention are that a user is supported in a manner so that the knees have substantially less flexure yet the user's weight is still supported substantially through the bottom rather than through the legs. As a consequence, because the knees are subjected to less flexure, users having limited knee and/or ankle flexure are subjected to less discomfort and, because the knees are drawn back substantially when compared to existing stairlifts, the intrusion of the stairlift and user into the stairway is reduced. This, in turn, means that a stairlift according to the invention is particularly

As can be seen in the drawings, a stairlift 10 is provided which includes a carriage 11 mounted for movement up and down a rail 12. Mounted on the carriage 11 are a chair 13 having a seat 14, an interface 15 and a footrest 16.

In the conventional sense, the chair also includes a backrest 17 and at least one armrest 18. In the drawings only one armrest 18 is shown on which an

operating control 19 is mounted.

The carriage 11 and rail 12 may be of any conventional form and do not

comprise part of the invention. Accordingly no further description of these

components need be provided.

Figure 2 shows a user or passenger 20 seated on the seat 14 supported

vertically on his/her bottom 21, and with his/her feet 22 resting on the footrest

16. As can be seen more clearly in Figures 3a to 3c, the seat 14 has a front

edge 24 and a rear edge 25, and is configured to resist movement of the user in a direction from said rear edge towards said front edge i.e. in the direction of

arrow 26 in Figure 2. Further, the vertical distance x between the footrest 16

and the seat 14 is established to ensure that, when the user is, as shown in

Figure 2, seated on the seat with feet resting on the footrest, an included angle

0 defined by flexure of the knees 27 is greater than 90°.

In the particular example shown in the drawings at least part of the front edge 24 of the seat is formed into an upwardly extending protrusion or pommel 30. This pommel 30 is preferably configured to be accommodated between the legs of the user or, expressed in an alternative manner, the user straddles the pommel 30. Clearly, when the user is seated, the pommel 30 firmly locates the user and inhibits movement in the direction of arrow 26. The user's legs may then assume such flexure as may be required to enable the feet to contact the footrest 16 yet, as with conventional stairlift chairs, little or no vertical loading is placed on the legs. The pommel 30 is preferably flared down into the seat 14 in both the longitudinal and lateral directions to enhance passenger comfort and to ensure that both the ischia and the under-thighs are adequately and comfortably supported yet with the thighs not being subjected to concentrated loads.

The interface 15 is preferably adjustable in length, or a selection of fixed length interfaces provided, so that distance x may be tailored to specific passengers. Distance x is preferably established so that angle 0 for a particular passenger lies in the range of 95° - 165°.

Referring specifically to Figures 3a to 3c, and Figure 4, the seat 14 is preferably pivotally mounted to assist a user mounting, and dismounting from, from the stairlift; and to reduce the lateral intrusion of the stairlift when not in use. In the particular embodiment shown, the seat 14 is mounted by a four-bar pivoting arrangement provided by sets of two bars 31 and 32 on opposite sides of the seat, each bar being pivotally mounted at opposite ends to the underside of the seat 14 and to the chair base 33 respectively.

Three alternative positions for the seat 14 are shown in Figures 3a to 3c. In Figure 3a the seat is shown in the position that is assumed when a user is seated on the seat. As a user leaves the seat, the seat assumes the position shown in Figure 3b under the influence of a biasing facility, one form of which is described below. With no user in place on the seat, the seat may be further displaced into a stowage position as shown in Figure 3c. When a user is again about to occupy the seat, the seat is first manually displaced to the position shown in Figure 3b.

It will be appreciated that when the seat is in the position shown in Figure 3b the rear edge 25 of the seat is positioned at a level above that of the front edge 24 and the pommel 30 is effectively lowered making it easier for a passenger to mount the seat. Positioning the seat as shown in Figure 3b has the added benefit of ensuring that, when mounting the seat, the user's bottom engages an upper part of the seat 14 and the user is thus displaced back in the chair 13 as the seat rotates to the position shown in Figure 3 a. This, in turn, assists the objective of reducing the passenger intrusion into the stairway. The seat is preferably held in the positions shown in Figures 3b & 3c by a biasing facility which may, as shown schematically in Figure 4, comprise a compression spring 35. The compression spring is preferably provided in the fonn of a small gas compression strut mounted between one of the arms 31 and the chair base 33.

Turning now to Figure 5, the seat 14 may be configured to provide an

enhanced anatomical engagement with a user and/or formed or clad in

materials of different densities with the objective of enhancing the user's

feelings of security.

As can be seen, the seat surface is provided with one or more (in this case two) indentations 36 which are sized and positioned to receive the user's ischial

tuberosities. These indentations 36 are likely to be located closer to the rear

edge 25 of the chair so as to position the user as close as possible to the

backrest 17, and obviously provide a further means of resisting movement of

the user in the direction of arrow 26. As a further contribution to the user's

feeling of security a strip 37, of material of greater density to the material

defining the surrounding seat, may be provided across the seat in a position

between the indentations 36 and the front edge 24 or, as shown, in part

defining those edge parts of the indentations 36 closest to the front edge 24.

It will thus be appreciated that the invention, at least in the case of the

embodiment described, not only positively supports and retains a user on the

stairlift chair, but also enables the passenger's legs to be held in a

configuration which subjects the knee and ankle joints to less flexure than

conventional stairlift chairs. A further benefit is that the stairlift intrudes into

the stairway to a significantly lesser extent that conventional stairlifts whilst

not requiring the chair to be aligned with the direction of travel and thus,

potentially, compromising user safety.