Stairlifts

Abstract

A mechanically-based arrangement for locking a stairlift chair relative to a stairlift carriage in the event of a failure within the drive that is provided to maintain the chair level as the stairlift is in operation. The arrangement uses inter-engaging components that are engaged and dis-engaged in timed relationship to rotation of the levelling motor. At all times at least one set of inter-engaging components are engaged.

Claims

1. A stairlift having a carriage moveable along a rail, the stairlift comprising: a chair pivotally mounted on said carriage; a levelling motor operable to pivot said chair relative to said carriage; and a safety facility configured and operable to lock said chair relative to said carriage in the event of a failure between said levelling motor and said chair, said safety facility comprising a plurality of inter-engaging components constrained to engage and dis-engage between said levelling motor and said chair, at least one of said inter-engaging component engages when at least one of said inter-engaging component disengages.

2. The stairlift as claimed in claim 1 wherein said inter-engaging components comprise a plurality of pins, and a plurality of slots.

3. The stairlift as claimed in claim 2, further including a gearbox driven from a motor output shaft of said levelling motor and having a gearbox output shaft connected to said chair, said pins being displaced into said slots by one or more cam members rotating in timed relationship with said motor output shaft.

4. The stairlift as claimed in claim 3 wherein said one or more cam members are mounted on, and rotate with, said gearbox output shaft.

5. The stairlift as claimed in claim 3 wherein said slots are arranged at a constant radius about an axis of said gearbox output shaft.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) One form of the invention will now be described with reference to the accompanying drawings in which:

(2) FIG. 1: shows a schematic rear view of a stairlift which may incorporate a safety facility according to the invention;

(3) FIG. 2: shows an exploded view of a number of components that combine to provide a stairlift having a safety facility according to the invention;

(4) FIG. 3: shows a motor/gearbox assembly incorporating a safety facility according to the invention;

(5) FIG. 4: shows an isometric view of the operative parts of the assembly shown in FIG. 3; and

(6) FIGS. 5A-5G: show the components of FIG. 2 assembled and in successive relative positions.

DETAILED DESCRIPTION OF THE INVENTION

(7) Referring to FIG. 1, the invention provides a stairlift 5 which includes a carriage 6 supported on a rail 7 by rollers 8. Mounted within the carriage 6 is a main drive motor/gearbox 9 having a drive pinion 10 mounted on the output thereof. The drive pinion 10 engages a rack 11 so that as the drive motor rotates, the carriage 6 is driven along the rail 7.

(8) A chair 12 is mounted on the carriage 6 so that the chair can pivot relative to the carriage 6. As shown the chair is mounted on a chair interface 14 which is directly and pivotally connected to part 15 (FIG. 2) being part of the chassis of carriage 6.

(9) The pivotal movement of the chair 12 relative to the carriage 6 is effected by a motor and gearbox 16, having an output shaft 17, the shaft 17 passing through aperture 18 in the carriage part 15 and being fixed to the interface 14 by fixing plate 19 and fixing bolts 20. This arrangement ensures that the output shaft 17 is not subjected to vertical loads applied through the chair 12 and/or interface 14.

(10) In our European Patent (EP) 0 738 232 we describe a method of controlling the operation of the motor 15 to ensure that the chair is maintained level as the angle of the rail 7 varies relative to a horizontal plane, however other forms of levelling are also possible and the present invention is not limited in application to the levelling arrangement described in EP 0 738 232.

(11) In accordance with the invention, the motor/gearbox unit 16 and the interface 14 are provided with inter-engaging components that selectively engage and dis-engage to limit the degree of rotation of the chair 12 relative to the carriage should there be a failure within the levelling system, but which do not interfere with the levelling action during normal operation. In the form shown, the inter-engaging components comprise a plurality of pins 24a, 24b, 24c projecting from the motor/gearbox unit 16, and a plurality of slots 25a, 25b, 25c, 25d, 25e & 25f provided in the interface 14. The pins 24 and slots 25 are preferably (though not necessarily) arranged at the same distance from axis 22 and are respectively circumferentially spaced. The pins 24, which can project from the unit 16 to a variable degree pass through, and are supported by, apertures 27 in the chassis plate 15 and, depending on the position of the interface 14 relative to the carriage and the extent of projection of the pins 24, the pins 24 can engage in the slots 25.

(12) A suitable control facility is provided to control the projections of the pins 24 in timed relationship to output of the chair levelling motor. Referring now to FIGS. 3 & 4, motor/gearbox unit 16 includes a housing 30 on the exterior of which is mounted a chair levelling motor 31 and inside of which are components forming a gearbox. In the particular form shown the motor output shaft 32 drives gearbox input shaft 33 through bevel gears 34a, 34b. Mounted on the gearbox input shaft 33 is a worm gear 35 which drives for rotation therewith. So far then the motor/gearbox unit 16 is entirely conventional however, as can be seen, one or more cams 37 are mounted on the motor output shaft 32 for rotation therewith, each earn serving to displace one of the pins 24. Springs (not shown) may be provided to maintain the pins in contact with their respective cam.

(13) FIGS. 5A-5G show a sequence of chair positions relative to the carriage, advancing in about 5° increments, to illustrate the operation of the invention. In this sequence the chair interface 14 is moving in a counter-clockwise relative to the carriage 6 or the carriage 6 can be viewed as moving clockwise relative to the interface.

(14) In FIG. 5A pin 24a is projected out by the cam surface to engage through slot 25a in the interface, and pin 24b is projected out to engage slot 25b. Pin 24c is retracted. As the chair moves in a counter-clockwise direction relative to the carriage the slots are displaced relative to pins 24a & 24b as shown in FIG. 5B. In FIG. 5C the pin 24b remains engaged in slot 25b but pin 24a is retracted out of engagement with slot 25a. In FIG. 5D and in FIG. 5E pins 24b and 24e are in full engagement with slots 25b and 25c while pin 24a is retracted. In FIG. 5F the pin 24b is also retracted leaving pin 24c engaged in slot 24c while in FIG. 5G the pin 24c remains engaged in slot 25c while the pin 24a is again projected to engage slot 25d.

(15) It will be appreciated that, as at least one pin 24 is engaged in one slot 25 at all times, in the event of mechanical failure in the levelling drive, the maximum uncontrolled movement of the chair relative to the carriage is limited to the available movement of the slot over the engaged pin. By increasing the number of pins and slots, this movement can be kept to a minimum, the limiting factor being space to provide further slots and of the shear strength of the pins.

(16) Arrangements other than that described above will present themselves to those skilled in the art. For example, rotation of the gearbox could be sensed electronically and electro-mechanical arrangements used to project the pins 24.