Background to the Invention The carriage of a curved stairlift must be able to traverse a variety of bends in a stairlift rail. These bends may include inside/outside bends in which the carriage turns in a substantially horizontal plane; transition bends in which the stairlift carriage changes direction in a substantially vertical plane; and helical bends in which the carriage changes direction both in a horizontal and in a vertical direction.

A stairlift carriage is typically supported on the stairlift rail by means of a plurality of rollers. Whatever the particular roller configuration, the rollers must not only prevent rotation of the carriage about the rail axis, but also allow smooth passage of the carriage along the rail, and about any type of curve included within the rail.

In our published international Patent Application No. WO 02/064481 we describe forms of roller configuration designed to accommodate the various type of bend described above.

The particular embodiment depicted in figures 12 to 18 of WO 02/064481 has proven to be effective in normal testing but demonstrates some drawbacks when subjected to prolonged use on rails which are mounted at steep angles to the horizontal. In such situations, the top roller in the upper most roller set can lift off the rail.

In an attempt to overcome this, heavier springs 90 have been fitted but this, in turn, increases the resistance to passage of the carriage over transition bends.

Increasing the spring force also leads to higher loading of the rollers on the rail which leads to increased wear on both the rollers and to any surface coating applied to the rail.

A further characteristic of the carriage roller arrangement described in WO 02/064481 is that, when the carriage is traversing an inclined section of rail, the contoured rollers which engage the side edges of the rail are subjected to considerable side loading and thus, considerable wear.

It is an object of this invention to provide a stairlift carriage and/or components for use in a stairlift carriage, which will go at least some way in addressing the aforementioned considerations; or which will at least provide a novel and useful choice.

Summary of the Invention Accordingly, in one aspect, the invention provides a stairlift carriage for mounting on a stairlift rail, said carriage including: a central roller set including a top roller positioned to, in use, engage an upper surface part of said rail and a bottom roller positioned to, in use, engage an opposed lower surface part of said rail, a line through the geometric centre of said central roller set, perpendicular to the alignment of said rail contacted thereby, defining a reference axis; a first outer roller set on one side of said central roller set; a second outer roller set on an opposite side of said central roller set,

said first and second roller sets being simultaneously displaceable with respect to said central roller set along first and second axes respectively, said first and second axes being substantially parallel to said reference axis, said first and second roller sets being pivotable about said first and second axes, respectively in a manner such that pivotable movement of said first outer roller set about said first axis is mirrored by pivotable movement of said second roller set about said second axis, said carriage being characterised in that each outer roller set is mounted to swivel about an axis substantially perpendicular to a vertical plane passing through a longitudinal centre line of said rail, and includes a top roller positioned to, in use, engage said upper surface part of said rail and a bottom roller positioned to, in use, engage said lower surface part of said rail.

Preferably each outer roller set further includes a plurality of rollers positioned to engage opposed side surface parts of said rail.

Preferably the lower roller of each outer roller set is displaceable with respect to the upper roller of each outer roller set about an axis which is substantially parallel to the longitudinal centreline of said rail.

Preferably said central roller set further includes rollers positioned to engage opposed side surfaces of said rail, said rollers being configured to resist rotational movement of said carriage about the axis of said rail.

Preferably said carriage further includes a drive pinion, said drive pinion being mounted concentrically with said bottom roller of said central roller set.

Preferably said carriage is configured for use with a rail as described in International Patent Application WO 2004/043845, each outer roller set being configured and mounted to swivel about an axis passing through the upper half of said rail.

Preferably each said outer roller set is configured and mounted to swivel about an axis passing through the point of maximum width of the upper half of said rail.

Preferably the bottom roller of at least one of said outer roller sets is displaceable, in a plane perpendicular to the longitudinal centre-line of said rail, to the top roller of said at least one of said outer roller sets.

Preferably the bottom roller of each of said outer roller sets is displaceable with respect to the upper roller in the same set.

In a second aspect the invention a stairlift carriage for mounting on a stairlift rail, said carriage including: a central roller set including a top roller positioned to, in use, engage an upper surface part of said rail and a bottom roller positioned to, in use, engage an opposed lower surface part of said rail, a line through the geometric centre of said central roller set, perpendicular to the alignment of said rail contacted thereby, defining a reference axis; a first outer roller set on one side of said central roller set; a second outer roller set on an opposite side of said central roller set,

said first and second roller sets being simultaneously displaceable with respect to said central roller set along first and second axes respectively, said first and second axes being substantially parallel to said reference axis, said first and second roller sets being pivotable about said first and second axes, respectively in a manner such that pivotable movement of said first outer roller set about said first axis is mirrored by pivotable movement of said second roller set about said second axis, said carriage being characterised in that the bottom roller of at least one of said outer roller sets is displaceable, in a plane perpendicular to the longitudinal centre-line of said rail, to the top roller of said at least one of said outer roller sets.

Preferably the bottom roller of each of said outer roller sets is displaceable with respect to the top roller in its outer set.

In a third aspect the invention provides a stairlift installation including a carriage as hereinbefore set forth.

In a fourth aspect the invention comprises any novel combination of any of the elements disclosed herein capable of addressing a problem in the stairlift art.

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 The various aspects of the invention will now be described with reference to the accompanying drawings in which: Figure 1: shows an isometric view of a typical curved stairlift installation; Figure 2: shows a rear isometric view, from below, of a carriage roller arrangement according to the invention; Figure 3: shows a front isometric view, from above, of the carriage roller arrangement shown in Figure 2; Figure 4: shows an end elevational view of the carriage roller arrangement shown in Figures 2 and 3, in position on a stairlift rail; Figure 5: shows a vertical cross-sectional view through a central roller set of a carriage roller arrangement according to the invention; Figure 6: shows a vertical cross-sectional view through an outer roller set of the carriage roller arrangement shown in Figures 2 to 4; Figure 7: shows a view similar to Figure 6, but of an alternative roller configuration; Figure 8 : shows an isometric view of the roller arrangement of Figures 2 to 4 negotiating a helical bend;

Figure 9: shows a plan view of the roller arrangement shown in Figures 2 to 4 negotiating a helical bend; Figure 10: shows a view, from the rear, of that which is shown in Figures 8 and 9 ;- Figure 11: shows an end on isometric view of the roller arrangement in a helical bend; and Figure 12: shows a view similar to Figure 11 but of an alternative form of end roller set arrangement.

Detailed Description of Working Embodiment Referring firstly to Figure 1, the invention provides a roller arrangement for mounting a stairlift chair/carriage 12 on a stairlift rail 13, the rail extending along staircase 14. Whilst the roller arrangement described herein can readily accommodate carriage travel through inside/outside bends (not shown) in which the rail is curved in a substantially horizontal plane, and transition bends (not shown) in which the rail is curved in a substantially vertical plane, the particular roller arrangement disclosed herein has been devised, in particular, to allow passage of the carriage over helical bends whilst addressing wear issues inherent in the roller arrangement shown in our pending International Patent Application WO 02/064481. A further objective is to keep the carriage firmly in contact with the rail-even at steep rail angles.

In this context a helical bend is one in which the rail turns and rises at the same time. Such a bend is shown at 15 in Figure 1.

Referring now to Figures 2 to 4, a roller arrangement for a skate 20 is shown, the skate 20 being included within the chair and carriage assembly 12. In the form shown, this skate 20 comprises a central roller set 22, a first outer roller set 24 and a second outer roller set 26. As can best be seen from Figures 8 and 9, the outer roller sets 24 and 26 are located on opposite sides of the central roller set 22 and, when the carriage is traversing a straight section of rail, the roller sets 22, 24 and 26 are arranged in line.

At this point it should be emphasised that the particular roller configuration described below has been established to operate in conjunction with a rail cross section as described in our published International Patent Application WO 02/064481 or as described in our published International Patent Application WO 2004/043845, the latter cross section being shown in Figures 4, and 8 to 12. The important feature of both of these forms of rail is that they comprise, when viewed in cross-section, one round section located vertically above another. It will be appreciated, however, that the invention could be adapted for use with rails of alternative cross-sections.

A feature of the rail described both in WO 02/064481 and WO 2004/043845 is that, when a helical is formed therein, the upper rail tubular section comprises the'control'section and the lower rail tubular section is offset from the vertical axis of the top section to create the helical. The circular cross section of the upper part of the rail allows the rollers of the outer roller sets to assume positions which are rotated about the axis of the upper part of the rail from those which are assumed when the carriage is traversing a straight section of rail.

Whatever the cross-section, the central roller set 22 provides the anchor for the carriage on the rail in the sense that the central roller set cannot move vertically with respect to the rail, or rotate about the axis of the rail. To this

end, the central roller set includes a top roller 30 (Figure 5), a bottom roller 31, an inner lower lateral roller 32 and an upper outer lateral roller 33. It will be appreciated that the vertically oriented rollers 30 and 31 locate the carriage vertically with respect to the rail, whilst the lateral rollers 32 and 33 prevent rotation of the carriage about the axis of the rail 13.

The rollers 30,32 and 33 are mounted on a central chassis 35, the chassis 35 being the main fixing point to the remainder of the carriage assembly. The bottom roller 31 is mounted over drive shaft 36. Drive shaft 36 is rotated by a motor/gearbox unit (not shown). Drive pinion 38 is keyed to the outer end of the drive shaft 36 and engages rack 40 extending along a lower edge of the rail 13. Thus, rotation of the pinion 38 causes the carriage to move longitudinally of the rail 13.

The bottom roller 31 is freely rotatable on the drive shaft 36 and can also move along the axis of the drive shaft 36.

As can best be seen in Figure 10, the central roller set has a geometric vertical centre line 39 which, for present purposes, will be referred to as a reference axis 39.

The two outer roller sets 24 and 26 are substantially identical. Each includes a top roller 42, a bottom roller 43 and two lateral steering rollers 44 and 45.

The outer roller sets are mounted on sub-frames 46, each of which is mounted on a pillar 48 extending upwardly and parallel to the reference axis 39. The sub-frames 46 are keyed together by keying member 50 to ensure that the roller sets 24 and 26 move together vertically with respect to the central set 22, and that the rotation of one of the outer roller sets about its pillar 48 is mirrored by rotation of the other set about its pillar 48. By way of example,

rotation of the set 24 in a clockwise direction about pillar 48 will cause equal rotation of the set 26, in an anti-clockwise direction, about its pillar 48.

In substantially the same manner as is described in International Patent Application WO 02/064481, the vertical movement of the outer roller sets on pillars 48 allows the carriage to traverse transition bends. The mirrored rotation of the outer roller sets about the pillars 48 allows the carriage to traverse inside/outside bends.

Referring now to Figures 2,3 and 6, the rollers 42,43, 44 and 45 of each outer roller set are mounted in a cradle 52, the cradle 52, in turn, being mounted to sub-frame 46 via a swivel bearing 54. It will be noted that there is a single swivel bearing for each outer roller set which is located to one side of the rail 13. This arrangement leaves more than sufficient space on the opposite side of the rail to accommodate the mounting brackets (not shown) for the rail 13.

Each outer roller set can rotate about axis 56 (Figures 3 & 6) although limit stops (not shown) may be included to limit inward swivel movement of the lower ends of the outer roller sets. Such limit stops would prevent interference of the bottom parts of the outer roller sets with the drive pinion 38, and would also maintain spacing between the outer roller sets, and the centre, which is advantageous in generating leverage to help drive the carriage through transition bends.

As can be seen from Figure 4, when the carriage 12 is mounted on the rail 13, the axis 56 passes through the upper half of the rail and, more particularly, through the widest point of the upper half of the rail. This position is not essential, however, and the invention could be adapted so that axis 56 was at alternative vertical locations.

When a transition bend is encountered in the rail, the outer roller sets are displaced on pillars 48 whilst the cradles 52 rotate about axes 56.

A further point to note is that each cradle 52 is formed in two parts. The first part or central section 60 provides a mount for the top roller 42 and lateral steering rollers 44 and 45. The second part 62, in the form of side arms which slide with respect to the central section 60, provides a mount for the bottom roller 42.

In the embodiment shown in Figures 2 to 11, the second part 62 is secured to the central section 60 through studs 64 fixed to the central section 60. The side arms 62 include slots 66 through which the studs pass. The combination of the studs 64 and slots 66 ensures that the bottom roller 43 can displace with respect to the top roller 42 through an arc whose centre is the centre 70 of the top rail section. Geometrically this is the preferred option but the method of mounting side arms 62 to central cradle section 60 may experience high levels of friction and be susceptible to jamming. For this reason, an approximate but nevertheless acceptable solution, as shown in Figure 12, may be adopted. In this embodiment the side arms 62 are fixed to central cradle section 60 at a single pivot point 72 positioned just above the top centre of the rail 13. Thus, the bottom roller 43 will move in an arc about the pivot 72 however, since the amount of arcuate movement required of roller 43 is relatively small when compared with the radius of the arc, the solution shown in Figure 12 works quite satisfactorily.

Biasing means are preferably provided to assist the skate arrangement to negotiate helical bends. In the embodiment shown in Figures 2 to 10, this biasing means takes the form of a coil spring 74 which provides a bias on the bottom roller 43 as the carriage enters a helical, and thus keeps the bottom roller tracking with the rail. As the bend straightens out, the curved or diablo

shape of bottom roller 43 causes the outer roller sets to be drawn back into line. In the case of the embodiment shown in Figure 12, the biasing means comprises a hair spring 76.

Turning now to Figure 7, an alternative form of bottom roller 78 is shown.

The bottom roller 78 does not have the built up outer edge of roller 43, which outer edge can sometimes'pick-up'on the rail, under cornering, and cause jamming. To compensate for the removal of the outer edge from the roller, a slider 80 is further provided to maintain the roller 78 in tracking engagement with the rail.

As outlined above, the roller arrangement described above was devised with the particular intention that any carriage fitted with such a roller arrangement should be able to traverse helical bends in the stairlift rail. The roller arrangement is shown negotiating a helical bend in Figures 8 to 12 inclusive.

Assuming the carriage is moving to the left as shown in Figures 8 to 12, the outer roller set 24 first enters the bend. This causes the lower roller 43 (or 78) of the set 24, under the influence of spring 74 or 76, to displace with respect to top roller 42. This can be seen most clearly in Figures 11 and 12.

As the inside/outside element of the bend becomes apparent, the leading roller set 24 will also pivot about the pillar 48 on which it is mounted, such pivotal movement also causing the trailing roller set 26 to be pivoted in an opposite, mirror, fashion. Thus, as can be seen in Figure 9, the lower roller of roller set 24 is displaced to one side of a vertical centre-line whist the lower roller of the trailing set 26 is displaced to the opposite side.

When a straight section of rail is again encountered, the rollers 43,78 track against the straightening rail 13 back into their central positions as shown in

Figure 4.

In the description above, reference has been made to the use of'rollers'.

However, it will be appreciate by those skilled in the art that one or more of the rollers described herein could be replaced by sliding bearings. Thus, the term'roller'should be interpreted herein as including sliding bearing elements.

It will thus be appreciated that the present invention provides a novel and inventive roller configuration which, at least in the preferred embodiment described herein, and in combination with the rail configuration shown in Figure 4, has the following advantages: 1. The positive vertical location effected by the rollers 42 and 43 of the outer roller sets, in combination with top roller 30, obviates the need for compression springs, shown in WO 02/064481, to maintain the outer roller sets in full contact with the rail at all times. This results in less wear on the roller and rail surfaces.

2. The arrangement of rollers 42 and 43 also eliminates side loading on the lateral rollers experienced in the arrangement shown in WO 02/064481.

3. By swivelling the outer roller sets on one side only of the rail, and by positioning the swivel axes 56 of the outer roller sets about the upper rail section centre-line, there is a considerable space around the lower half of the rail to accommodate rail mounting hardware.