Stairlifts

Abstract

A footrest safety pad arrangement is incorporated in a stairlift carriage in which movement of a safety pad relative to the carriage is sensed by an electromagnetic sensor and a control signal applied to the stairlift drive motor.

Claims

1. A stairlift comprising: a carriage; at least one safety edge mounted on said carriage but displaceable with respect to said carriage; and a single programmable electro-magnetic facility configured to sense displacement of said safety edge relative to said carriage.

2. The stairlift according to as claimed in claim 1, wherein said at least one safety edge is incorporated in a footrest mounted on or forming part of said carriage.

3. The stairlift according to as claimed in claim 2, wherein a plurality of safety edges are provided on said footrest and wherein a single electromagnetic sensing facility is configured to sense displacement of each safety edge.

4. The stairlift according to as claimed in claim 3, wherein said plurality of safety edges are defined in or on a common member.

5. The stairlift as claimed in any one of the preceding claims according to claim 1, wherein said single programmable electro-magnetic facility is configured to determine direction of displacement of said safety edge relative to said carriage.

6. The stairlift chair footrest as claimed in any one of the preceding claims according to claim 1, wherein said single programmable electro-magnetic facility includes a Hall-effect sensor and a permanent magnet, the construction and arrangement being such that displacement of a safety edge effects relative displacement between said Hall-effect sensor and said magnet.

7. The stairlift as claimed in any one of the preceding claims according to claim 1, further including a drive motor and a control system, wherein said control system is configured to receive signals from said a single programmable electro-magnetic facility and, in response thereto, apply a control to said drive motor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

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

(2) FIG. 1: shows a schematic front elevation of a typical stairlift incorporating the invention;

(3) FIG. 2: shows a plan, sectional, view of a footrest assembly suitable for incorporating the invention;

(4) FIGS. 3A to 3F: show schematic plan views, and corresponding sectional side views, of a stairlift chair footrest according to the invention in several different states; and

(5) FIGS. 4A to 4C show a sequence of plan views of a stairlift moving through an outside bend.

DETAILED DESCRIPTION OF WORKING EMBODIMENT

(6) With reference to FIG. 1, the invention provides part of a safety system for a stairlift installation 5, the installation 5 including a rail 6, a carriage 7 mounted on the rail for movement along the rail, and a chair 8 mounted on the carriage.

(7) In the conventional manner, the chair 8 comprises a seat base 9, a backrest 10, two armrests 11 and a footrest 12.

(8) Included within the carriage is a drive motor 13 on the output of which is a pinion 14 engaging with a rack 15 extending along the underside of the rail 6. Control of the motor is effected by means of a hand control 16 mounted on one of the armrests 11, and an electronic control unit 17.

(9) It is to be emphasised that the arrangement described above is by way of example and other configurations and other drive arrangements may be provided without departing from the scope of the invention.

(10) Conventionally, as part of a system provided to ensure passenger safety, safety pads or edges are provided on the carriage, and in particular the footrest 12 so that, in the event the stairlift encounters an obstruction during travel, a safety edge will be displaced, activate a switch connected to the control unit 17, and cause the carriage to come to a halt. An example of safety edges included in a footrest is described in UK Patent No. GB 2 435 463. In this patent the safety edges are included in a single tray-like member fixed to the underside of the foot support part of the footrest but in a manner that allows the tray-like member to be displaced both laterally and vertically with respect to the footrest, and in directions which are combinations of lateral and vertical movement. While in the embodiment of the present invention described herein, an arrangement of foot support 18 and under-tray 19 is proposed, those skilled in the art will appreciate that the principles of the invention may equally be applied to arrangements in which individual safety edges, both on the footrest and elsewhere, are provided to address obstructions encountered in different directions.

(11) The under-tray 19 may be mounted to the foot support 18 in any manner that allows the under-tray to move laterally with respect to the foot support i.e. along the x axis in FIG. 1 in the direction of arrow A and arrow B. As will become apparent from the description that follows, the mounting arrangement preferably also allows the under-tray to move vertically upwards with respect to the foot support i.e. along the z axis in FIG. 1 and in the direction of arrow C; and to rotate, at least to a limited extent, with respect to the foot support i.e. about the z axis. Combinations of movements along the x, y, and z axes can also be accommodated.

(12) In the illustrated example, these ranges of movement are accommodated by configuring both the support 18 and the tray 19 with similar shapes when viewed in plan, in this case as rectangular members, and further configuring the tray so that the outer periphery 20 extends up to overlie the edges of the foot support 18 as can be seen most clearly in FIGS. 3A-3F. In this way the tray, which may be a relatively light plastics moulding, can be fixed to the support 18 by means of coil springs 21 extending, as shown in FIG. 2, between the corner apices of the support 18 and the corresponding inner corner apices of the tray 19. Given that there is no movement along the y axis shown in FIG. 2, whether the footrest is in the operating state shown in FIG. 1 or the folded states, one or more stops 22 may be inserted between the tray and the foot support in this direction.

(13) Each of the springs 21 should be under a similar degree of compression so that the tray is retained in a neutral position as shown in FIGS. 2 & 3A and the tray is restrained in all three x, y and z directions by the springs from falling vertically down.

(14) The heart of the present invention lies in the use of an electromagnetic sensing facility to sense movements of the tray 19 relative to the foot support 18 and to relay signals representative of those movements to the control unit 17. As will be described in greater detail below, the control unit 17 is programmed to interpret the signals and apply the appropriate control over the drive motor 13 in light of the particular signal. In this way the complex linkages and switches of prior art footrest assemblies can be eliminated.

(15) While the benefits of the invention could be achieved by a plurality of electromagnetic sensors, the combination of foot support 18 and tray 19 as described above lends itself to the use of a single electromagnetic sensing facility. This facility preferably comprises a Hall-effect sensor on one of the components 18 or 19, and a permanent magnet on the other. In the embodiment depicted, Hall-effect sensor 23 is shown mounted substantially centrally on the underside of foot support 18 while the magnet 24 is shown mounted on the inner surface of tray 19. The Hall-effect sensor may, by way of example only, be a 3D Hall-effect sensor such as a Melexis MLX90393 TRIAXIS® magnetic field sensor manufactured by Melexis NV, Ypres, Belgium. This sensor may be used in combination with a single magnetic disc, for example a 6 mm×3 mm Neodymium magnetic disc.

(16) The system needs to be calibrated for a specific gap between the sensor 23 and the magnet 24 but the actual gap dimension is essentially arbitrary, a limitation being that the sensor needs to be able to measure a non-zero magnetic field intensity at any point. Thus, the gap could be increased if the sensitivity of the sensor were to increase or if the strength of the magnet were to increase.

(17) Referring now to FIGS. 3A to 3F, FIG. 3A shows the tray 19 in a central or un-deflected position with respect to the foot support 18. In this position, and in the absence of any other control limits, the motor 13 will respond to all inputs from the hand control 16. In FIG. 3B the carriage has encountered an obstacle while travelling in an uphill direction in FIG. 1 and the tray is displaced in the direction of arrow B. When the resultant signal generated by the Hall-effect sensor exceeds a threshold, the control unit 17 causes power to be cut to the motor 13 and the carriage to stop. In this situation, the control unit 17 may be programmed to allow the carriage to be driven in the downhill direction. In FIG. 3C an obstacle has been encountered while the stairlift is moving in a downhill direction, the obstacle being so sited as to cause the tray to be displaced both in the direction of arrow A and out of the plane of FIG. 1 i.e. along the (negative) y axis. In FIG. 3D the tray has encountered an obstacle causing it to rotate about its geometric centre.

(18) In FIG. 3E the tray is shown displaced vertically upward, in the direction of arrow C in FIG. 1, while in FIG. 3F that tray is displaced in the directions of both arrow C and arrow B.

(19) In the case of all scenarios illustrated in FIGS. 3A to #3F, the movement of magnet 24 relative to Hall-effect sensor 23 causes the generation of a signal that is fed directly to the control unit 17 without the need for any switches and, if the signal exceeds a programmed threshold, a control signal is applied to the motor 7. The signal from the sensor 23 can also provide information as to the direction of displacement.

(20) Those skilled in the art will appreciate that the any number of combinations of sensor and magnet could be used to detect safety pad movement, the invention not being confined to the detection of movement of a safety pad mounted on a footrest.

(21) Turning now to FIGS. 4A to 4C, in another aspect the invention also provides the means of addressing a potential problem if the carriage encounters an obstruction when moving through an outside bend 30 in the direction of arrow 31 in FIG. 4A. In this particular example reference numeral 32a indicates a leading safety edge and reference numeral 32b indicates a trailing safety edge. The safety edges are shown located on opposite sides of the footrest 12 and, as stated above, could be separate components or could be defined by spaced edges on a common mount.

(22) As the carriage begins moving through the bend 30 it is swivelled in the direction indicated by arrow 33 in FIG. 4B. During this movement the safety edge 32b effectively becomes the leading safety edge yet, because the overall direction of movement is that of arrow 31 in FIG. 4A, the control system will have de-activated safety edge 32b and thus displacement of the edge 32 will have no effect. The use of a electro-magnetic sensing system as described above provides a solution to this problem in that both displacement and direction of displacement are sensed so that if, while the carriage is moving through an outside bend as shown, an obstruction not encountered by edge 32a as the carriage enters the bend, is encountered by edge 32b, the carriage can be brought to a halt and subsequently ‘backed off’ the obstruction. In FIG. 4C, the carriage is exiting the bend 30 and safety edge 32a again assumes its status as the leading safety edge.

(23) The above aspect of the invention requires a knowledge of the stairlift control system knowing when the carriage is entering an outside bend. This could be achieved using suitable switching devices mounted on the rail but could also be achieved by ‘mapping’ the rail substantially as described in our European Patent 0 738 232. Thus, when the control system determines that the carriage is entering an outside bend, the control system activates the trailing safety edge.

(24) It will thus be appreciated that the invention, at least in the case of the working embodiment herein described, provides a novel and effective means of maintaining stairlift safety in case of all types of obstruction which could be encountered as a stairlift carriage moves up and down a stairlift rail.