Background Stairlifts, in the form of a carriage mounted for movement along a rail, are well known for moving aged or handicapped persons up and down staircases.

In our pending International Patent Application PCT/GB99/03447 we describe and claim a form of stairlift in which the stairlift carriage is supported on a narrow tubular rail including four rolling surfaces arranged about the rail cross- section at 45° to a horizontal plane through the rail. To this end, the carriage includes roller pairs which bear on the rolling surfaces extending along the rail, and the above application describes how these rollers are provided in upper and lower pairs. The pending application further describes the use of axle pins mounted in eccentric through bores in the lower rollers which allows adjustment of the lower rollers to take up unwanted play between the carriage and the rail.

In practice, we have found that the particular rail and carriage configuration does not best lend itself to adjustment in the manner described. Further, accessing and manipulating the eccentric mounts of the lower rollers can be difficult for an

installer.

It is an object of this invention to provide a stairlift which allows adjustment in installation and/or operation which addresses the aforementioned problems, or which will at least provides a useful choice.

Summary of the Invention Accordingly, in one aspect, the invention provides a stairlift carriage for movement along a stairlift rail, said carriage including: a plurality of first rollers arranged to engage said rail from a first direction; a plurality of second rollers arranged to engage said rail from a second direction, said second direction being substantially opposed to said first direction; and adjustment means operable to adjust the spacing between at some of said first rollers and said second rollers, said carriage being characterised in that said adjustment means includes a common member on which at least two of said first rollers are mounted and displacement means operable to displace said common member towards said second rollers.

Preferably all of said first rollers are mounted on said common member.

Preferably said carriage further includes a spaced pair of side plates which, when said carriage is in its normal operating position, overlie opposite sides of said rail, wherein said rollers are mounted to project inwardly from said side plates.

Preferably said displacement means is operable to displace said common member with respect to the side plate from which said first rollers project. Said displacement means conveniently comprises one or more grub screws, each grub screw being mounted in a stud fixed to said side plate.

In a second aspect the invention provides a stairlift including the carriage as herein before set forth.

Many variations in the way the present invention may be performed will present themselves to those skilled in the art.

The description which follows is intended as an illustration only and the absence of description of particular alternatives or variants should in no way be applied to limit the scope of the invention. Such description of specific elements which follows should also be interpreted as including equivalents whether existing now or in the future. The scope of the invention should be defined solely by the appended claims.

Brief Description of the Drawings One form of stairlift carriage incorporating the invention will now be described with reference to the accompanying drawings in which:

Figure 1: Shows an end sectional view of a stairlift carriage incorporating the invention mounted on a stairlift rail; Figure 2: Shows, in a smaller scale, a view along the line II-II in Figure 1 with certain components omitted for clarity; Figure 3: Shows, in a larger scale than Figure 2, a view along the line A-A in Figure 2; and Figure 4: Shows, in a larger scale than Figure 2, a view along the line B-B in Figure 2.

Description of Working Embodiment Referring firstly to Figure 1, the present invention provides a stairlift carriage 10 mounted substantially above, for movement along, a tubular rail 11 of constant cross section. The carriage is supported on the rail by a first roller set 12 and a second roller set 13 and it will be appreciated that the roller sets 12 and 13 engage opposite sides of the rail and from substantially opposite directions.

The rail and roller configuration is such as to permit smooth movement of the carriage longitudinally of the rail yet prevent tilting, skewing and rotation of the carriage about the rail.

In the form shown, each of the roller sets 12 and 13 comprises four rollers, the first set 12 being shown in entirety in Figure 2

and comprising individual roller pairs 12a, 12b and 12c and 12d, the rollers 12c and 12d being mounted to engage the rail at a position longitudinally spaced from that engaged by the rollers 12a and 12b.

The roller set 13 is a mirror of the roller set 12.

In accordance with conventional practice, the rail 11 has a plurality of rolling surfaces 14,15,16 and 17 for rolling engagement by the roller sets 12 and 13. As can be seen, the rolling surfaces are arranged about the cross section of the tubular rail, extend longitudinally of the rail 11 and are formed by the same elements that define the structural elements of the tube. This leads to a compact and structurally efficient rail.

In the form shown, rollers 12a and 12d engage rolling surface 14, rollers 12b and 12c engage rolling surface 15, rollers 13b and 13c engage rolling surface 16 and rollers 13a and 13d engage rolling surface 17.

As shown, the carriage 10 further includes a main chassis 20 which, when the carriage is mounted in position on the rail 11, spans over the rail. Mounted at spaced points on the chassis 20, preferably along opposite edges of the chassis, are side plates 21 and 22 which extend down to overlie at least part of both sides of the rail 11. As will be described in greater detail below, the side plates also serve as mountings for the roller sets 12 and 13.

Included on the chassis 20 is a mounting base 23 which is angled to the remainder of the chassis and serves as a

mounting surface for main drive motor 24 and gearbox 25. The chassis 20 further includes a central aperture 26. This gives clearance to enable drive pinion 28, mounted on output shaft 27 of gearbox 25, to engage with drive rack 29 located below the chassis 20 on rail 11. Rotation of the pinion 28 causes the carriage 10 to be displaced along the rail 11.

The lower part of side plate 22 is preferably provided with an internal triangulated bracing member 30, the bracing member extending along the carriage and adding considerable stiffness to that section of the carriage which provides the mount to the rail 11. As can be seen, the bracing member also provides convenient mounting points for the second rollers 13. Indeed, the configuration of bracing which provides significant natural strength-a triangle-also perfectly positions the rollers 13a, 13b, 13c and 13d to engage the perpendicular rolling surfaces 16 and 17 of the rail 11.

In order to provide adjustment between the rollers 12,13 and the rail 11, the first rollers 12 are mounted for movement toward and away from the rollers 13. To this end, at least some, and preferably all, of the rollers 12 are mounted on a common member or bogie 31 which, in turn, is mounted on the inner surface of side plate 21 for movement toward and away from the side plate 21 and away from and toward the roller set 13.

Referring now to Figures 2 to 4, the bogie 31 has a solid centre section 32 of rectangular cross-section and two end sections 33a and 33b of triangular section, the rollers 12 being mounted on the end sections 33a, 33b so as to mirror the configuration

of the rollers 13. As can be seen from Figure 4, each of the rollers 12 (and indeed each of the rollers 13) is mounted on an axle pin 34 via a roller bearing 35. Each axle pin 34 is screwed into threaded bores 36 provided in end sections 33 of bogie 31.

Referring now to Figure 3, the centre section 32 of bogie 31 includes a pair of spaced bores 37 which slidingly receive a pair of studs 38 fixed to, and projecting inwardly from, the side plate 21. Screw fitted into a central bore 39 in each stud 38 is a grub screw 40 and it will be appreciated that as the grub screws 40 are screwed into bores 39, the bogie 31 is displaced away from the inner surface of side plate 21. Simultaneously, the rollers 12 are displaced toward the rollers 13 to more firmly clamp the carriage 10 onto rail 11.

Once the desired roller adjustment has been achieved, the bogie 31 may be locked in place by locking bolts 41 (Figure 2) which pass through end tabs 42 of a fixing plate 43 fixed to side plate 21, and engage in bores drilled in the end faces of the end sections 33a and 33b.

Although the bogie 31 has been described as a single component, it could be provided in two parts with one pair of rollers on each part.

In use, the installer sets the carriage 10 on the rail 11 which he has previously mounted on the stair. The carriage is preferably mounted so that the side plate 22 is adjacent one wall defining the stairway and the side plate 21 is on the outside of the installation. The installer can then tighten the carriage 10 on the rail 11 by inserting an Allen key into each bore 39 in turn

and causing bogie 31 to be displaced away from side plate 21 until the rollers pairs 12 and 13 are firmly yet rotatably engaged with opposite sides of the rail 11. Once the bogie 31 has been positioned correctly, the installer tightens bolts 41 to lock the bogie with respect to the side plate 21.

It will thus be appreciated that the present invention, at least in the case of the embodiment thereof described above, provides a simple yet effective means of providing for roller adjustment to be effected on a stairlift installation from a position easily accessed by an installer.