GB2491553A

GB2491553A - Stairlift control method

Info

Publication number: GB2491553A
Application number: GB201103713A
Authority: GB
Inventors: Nigel Titchener
Original assignee: Stannah Stairlifts Ltd
Current assignee: Stannah Stairlifts Ltd
Priority date: 2011-03-04
Filing date: 2011-03-04
Publication date: 2012-12-12
Anticipated expiration: 2031-03-04
Also published as: GB2491553B; GB201103713D0

Abstract

The invention provides a method of controlling a stairlift, and a suitable stairlift, along a track that may be curved (Fig 8) or may have two or more sections with differing angles or directions of slope (Fig 7). The stairlift 10 comprises a rail 12, a carriage 11 and safety edges 16 and 17 for detecting obstructions. There may also be a safety edge 18 under the footrest 15. The safety edges are under the control of a control system 22 and are selectively activated independent of the requested or actual direction of travel. When an obstruction is contacted by the safety edges, the control system only permits movement away from any obstruction and has means for controlling the speed of such movement. The stairlift may have position and direction sensing facilities and a memory recording the direction of slope at each point on the rail.

Description

IMPROVEMENTS IN OR RELATING TO STAIRLIFTS

Field of the Invention

This invention relates to stairlifts and, in particular, to stairlifts in which there is a variation in the angle between the stairlift rail and a horizontal plane.

Background to the Invention

Generally a stairlift is mounted to a staircase so that the carriage moves along a rail extending between a lower landing and an upper landing.

Usually the slope of the rail is in one direction only although the rail may include sections of differing gradient, including horizontal sections where the stairlift passes over an intermediate landing. Occasionally, when viewed from the lower landing, a staircase may include both upwardly and downwardly sloping sections when the moving in one direction. Such an arrangement is shown in Figure 5 and, due to limitations in stairlifi leveling arrangements, may require the installation of two stairlifts to enable the entire staircase to be traversed.

With the advent of electronic stairlift leveling, such as is described in European Patent No. 0 738 232, a stairlift can be provided which is able to accommodate both upwardly and downwardly sloping sections as shown in Figure 5. However, existing arrangements are not sufficient to guarantee compliance with safety standards in the event the carriage encounters an obstruction during its journey along the rail.

More particularly, a stairlift includes directional safety edges or surfaces that will stop the stairlift if the same comes into contact with an obstacle during its journey along the rail. These safety edges are conveniently located on the footrest but may also be located elsewhere on the stairlift carriage. These safety edges are provided in sets. A first set is provided on the up' side of the carriage and are enabled or become active when a command is given to power the stairlift up the rail. A second set is provided on the down' side of the carriage and are enabled or become active when a command is given to power the carriage down the rail. When an active safety edge encounters an obstruction, the edge is displaced and a switch is opened to cut power to the main drive motor. However the stairlift control system will then allow the carriage to be reversed away from the obstruction. Without this latter provision, the stairlift could be become stranded thus tempting a passenger to alight other than in the normal park positions. This could be dangerous.

It is important to note that, when one set of safety edges is active, the other set is inactive and only becomes active when the directional command is reversed. In this event the set previously active, become inactive.

As described in our British Patent No. 2 435 463 we provide further safety edges on the underside of the footrest to protect against crushing hazards directly underneath the footrest when the stairlift is moving in a downwards direction. Vertically operating safety edges give rise to a potential problem in the event the rail is configured in the manner shown in Figure 5. In this arrangement the control system will not know where the carriage is situated on the rail and will therefore be unable to ascertain the direction in which the carriage is to be driven in order to reverse the carriage away from the obstruction. Further there may also be instances, particularly in tight horizontal bends, where an object might be contacted by the reverse sweep of the trailing edge of the carriage. In this event the safety edges would not assist as, being on the trailing edge, they would not be active.

It is an object of the present invention to provide a method of andlor apparatus for controlling a stairlift which 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 controlling a stairlift, said stairlift including: a stairlift rail; a carriage mounted on said rail; a motor responsive to a directional command to drive said carriage along said rail; at least one directional safety device aligned with a first direction of movement of said carriage and at least one directional safety device aligned with a direction of movement of said carriage opposite to said first direction; and a control system operable to cut power to said motor upon contact between one of said directional safety devices and an object in the path of said carriage during movement thereof; said method being characterized in that it comprises configuring said directional safety devices and said control system so that a safety device may be selectively enabled by said control system irrespective of said directional command.

Preferably said method comprises configuring said control system to respond to an actuation of a said safety device and to control subsequent direction of movement of said carriage having regard to the position of said carriage on said rail andlor the operating direction of said motor.

Preferably said method includes establishing the position of said carriage along said rail using a position sensing facility.

Preferably said method includes establishing the position of said carriage along said rail by counting the revolutions of said motor from a datum position on said rail.

Preferably said method comprises combining information as to the position of said carriage on said rail with information in memory representing the direction of slope of said rail at the said position.

Preferably said method further comprises controlling the speed of said carriage following operation of a said electrical safety device.

In a further aspect the invention provides a stairlift including: a stairlift rail; a carriage mounted on said rail; a motor responsive to a directional command to drive said carriage along said rail; at least one directional safety device aligned with a first direction of movement of said carriage and at least one directional safety device aligned with a direction of movement of said carriage opposite to said first direction; and a control system operable to cut power to said motor upon contact between one of said directional safety devices and an object in the path of said carriage during movement thereof; said stairlift being characterized in that said directional safety devices and said control system are configured so that a safety device may be selectively enabled by said control system irrespective of said directional command.

Preferably said control facility includes a direction sensing facility.

Preferably said direction sensing facility is configured to make use of said directional command.

Preferably said control facility includes an encoder to determine the position of said carriage relative to a datum.

Preferably said control system includes information as to the position of said carriage on said rail together with information indicating the allowable direction of movement of said carriage should a directional safety device operate.

Preferably said control system is further operable to monitor the state of each said safety device.

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

One embodiment of the invention, as applied to a stairlift, will now be described with reference to the accompanying drawings in which: Figure 1: shows a schematic view of a stairlift carriage and control system suitable for incorporation in the invention; Figure 2: shows a schematic view, in smaller scale than Figure 1, of a conventional stairlift installation having rail sections arranged at different angles to a horizontal plane but all aligned in a single direction; Figure 3: shows a schematic view of a simple conventional stairlift installation in which a straight rail has a horizontal parking' facility at its upper end; Figure 4: shows a schematic view of a possible stairlift configuration to which the present invention might be applied; Figure 5: shows a conventional arrangement for providing stairlift mobility in situations where a staircase has sections sloping in two directions; Figure 6: shows a schematic view of a further stairlift configuration to which the present invention might be applied; Figure 7: shows in greater detail that which is shown in Figure 6; and Figure 8: shows a plan view of a stairlift carriage moving through a horizontal bend and illustrating a further crushing scenario able to be addressed by the invention.

Detailed Description of Working Embodiment

Referring firstly to Figure 1, a stairlift installation 10 is shown comprising a carriage 11 mounted on rail 12. As can be seen in Figures 2 & 3, the rail 12 is, in turn, mounted on a stairway 13. In the manner of a typical stairlift a chair 14 is mounted on the carriage 11, the chair including a footrest 15.

For the purposes of this description, unless otherwise the differentiation is specifically expressed, reference to the carriage should be interpreted as including reference to the carriage/chair combination. In particular, safety edges (referred to below) which are described as being mounted on the carriage could also be mounted on the chair, chair interface and/or footrest.

The carriage further includes one or more directional safety devices, the function of which is to bring the stairlift to a halt in the event the carriage encounters an obstruction whilst moving up or down the rail. These directional safety devices may be configured and positioned in a number of ways however, in order to illustrate the invention, the safety devices are shown as displaceable edges or flaps mounted on the footrest 15. Thus a first safety edge 16 is provided on the upward facing side of the stairlift and is aligned with the direction of travel of the carriage as the carriage 11 moves up the rail 12. In a similar manner a second safety edge 17 is provided on the side of the footrest opposite to that on which first safety edge 16 is mounted and is aligned with the direction of travel as the carriage 11 moves down the rail 12.

In our published International Patent Application No W020051085 115 we describe a stairlifi rail in which a section at the lower end of the rail is essentially vertical. It will be appreciated that, when the carriage is traversing this section or another section of rail arranged at a steep angle to the vertical, any obstruction encountered by the carriage will be positioned substantially below the footrest and thus not be in the path of either of the safety edges 16 or 17. To this end we also provide a safety edge 18 on the underside of the footrest which will cause the carriage to be halted in the event the carriage crushes down substantially vertically on an obstruction.

Conventionally the safety pads 16, 17 and 18 are enabled by a directional command typically given by way of user hand control 20 mounted on armrest 21 of the chair 14. Thus, if an up' command is given, the safety edge 16 is enabled and, in the event the safety edge 16 encounters an obstruction as the carriage moves up the rail, the safety edge 16 will be displaced, open a switch (not shown) and bring the carriage to a halt. In a similar manner, if a down' command is given, the safety edge 17 will be enabled and, in the event the safety edge 17 encounters an obstruction as the carriage moves down the rail, the safety edge will be displaced, open a switch, and bring the carriage to a halt.

All the safety edges are wired into the control system 22 of the stairlift and this control system is configured to allow the carriage to be reversed away from the obstruction. Without this facility the stairlift could become stranded at that point on the rail at which the obstruction was present and, as a consequence, the user could attempt to alight from the stairlift when it was not at a designated parking position. This could cause a potential tripping hazard to the user.

All of the safety edges aligned in a particular direction of travel are wired in series with the directional control. Thus in the event that any edge in either the up' set or the down' set is displaced, the carriage will be halted.

However the safety edges are under the command of, or enabled by, the direction chosen by a user and imposed through hand control 20. Thus when the user operates the hand control 20 to move in an upward direction, the set of safety devices that includes edge 16 is enabled but the set of safety devices that includes edge 17 is not enabled and the safety edges in this set (the down' set) do not function. As will be described in greater detail below, this leaves certain possible operating scenarios open to a degree of risk.

The present invention addresses the problem by taking away the primary enablement of the directional safety devices from the directional command or hand control, and placing the enablement or operation of these devices under the control of the stairlift control system 22. As a result, scenarios which cannot be accommodated by present safety edge operations can be identified, and the control system configured to operate selected safety edges, whether on the up or down side of the carriage, to address these scenarios.

To understand the existing scenarios, reference is first made to Figure 2 which shows a common prior art scenario. As can be seen, the rail 12 includes a first rising section 25, a second horizontal section 26, a third rising section 27 and a short, horizontal parking' section 28. The rail configuration is such that it rises and falls in one direction only. Upward movement is always to the right and downwards movement is always to the left. Thus, during operation of the stairlift, safety edge 16 is enabled during movement of the carriage in the up' direction and safety edges 17 and 18 are enabled during downward movement of the carriage. If safety edge 18 comes into contact with an obstruction 30 on the stairway, whilst the carriage 11 is moving to the left down the rail, the carriage 11 will not only be halted but the control facility 22 within the carriage is configured to allow the carriage 11 to be reversed, upwardly to the right, away from the obstruction.

Figure 3 shows an even more simple scenario in which carriage 11 moves on a straight length of rail 31 topped by a horizontal parking section 32. As with the previous example, the stairlift will be halted in the event the safety device or edge 18 bears down on obstruction 30 whilst the carriage 11 is moving down the rail. Also in common with the previous example, the control system is configured to allow the carriage to be reversed upwards, away from the obstruction.

Figure 3 illustrates that, in some stairlift installations, the distance between the footrest 15 and the floor or landing 33 may be greater than desired. To address this, a configuration such as is shown in Figure 4 could be adopted. In this scenario, the rail has an upwardly sloping section 35 and a downwardly sloping section 36. The downwardly sloping section allows the footrest-to-landing spacing to be optimized but, in doing so, gives rise to a further problem. Using conventional logic, if the carriage is travelling down section of rail 30, encounters an obstruction on the stair, and triggers the safety edge 18, then the control system will only allow the carriage to be reversed up the rail. If, however, the safety edge 18 is displaced by an obstruction while the carriage is travelling down section 36, conventional logic would have the carriage moving to the right to clear the obstruction. This, of course, is not possible.

In one embodiment of the invention, this scenario is addressed by understanding where, on the rail, the carriage is positioned at any time and, in addition, understanding the profile of the rail i.e. understanding whether the rail is sloping down to the left or to the right. This allows the control system to be configured to direct the carriage drive motor to operate in whatever direction is necessary to reverse the carriage in an upward direction and away from the obstruction. In another embodiment of the invention, the control system is programmed to know the direction of operation of the stairlift at the time a safety edge is displaced, and to only allow movement in the reverse direction until the obstruction is cleared.

Referring now to Figures 5 to 7, a scenario is shown in which a stairway has a section 37 which slopes upwardly when moving to the right, and a section 38 which slopes upwardly when moving to the left. In the case of traditional forms of stairlift having mechanical levelling mechanisms, this would have required the provision of two separate installations 39a and 39b, as shown in Figure 5. Now, with the advent of electronic-based levelling systems such as shown, for example, in European Patent No. 0 738 232, a single rail can be provided which spans both stairway sections 37 and 38, and a single carriage then provided for travel along the entire length of the rail. However, as with the arrangement shown in Figure 4, the control system must be programmed to understand whether the carriage is on section 37 or section 39, and to control the operation of the carriage drive motor to ensure that, when safety edge 18 is displaced, the control system 20 commands the carriage to be driven in the correct direction to reverse the carriage away from the obstruction.

Referring back to Figure 1, the carriage 11 includes a rotational drive motor 40. Mounted on the output shaft of the motor is a pinion 41 which engages a rack 42 fixed to the rail. As shown, the motor may also be provided with a rotary encoder 43 which works from a datum (generally one end of the rail) and can thus calculate where, along the rail, the carriage is situated at any particular time. The output from the encoder 43 is passed to the control system 22. Stored within a memory within the controller 22 is data representing the profile, and particularly the slope of the rail 12, at any particular position along the rail. Thus, in the event of the directional safety edge 18 being displaced, the control system 22 is able to determine the direction in which the motor needs to be driven in order to move the carriage upwards and away from the obstruction. Further, the direction of rotation of the drive motor can be deduced according to whether the encoder count is increasing or decreasing or by some alternative means such as a system which is able to record in memory the direction of travel imposed via the stairlift direction control 20. Thus, in an alternative embodiment, the control system can be configured to simply reverse the drive motor in the event a safety edge 18 is tripped.

The present invention can also provide protection in the scenario shown in Figure 8. In this example, when viewed from eye position 45, let us assume that the stairlift 10 is moving to the right, in the direction of arrow 46 across a horizontal or helical bend in the rail 12. In this instance there is a potential area 47 for crushing as the carriage moves further to the right. This is protected by safety edge 48 on the footrest 49. However, as the leading edge of the carriage swings through the radius of the bend, the trailing edge of the carriage pivots in the opposite direction, indicated by arrow 50, thus creating a further potential crushing zone 51. Crushing could arise in the zone 49 if, for example, the leg of a passenger slipped from the footrest and became trapped between the trailing edge of the footrest 48, and the rail 12. This would cause safety edge 52 to be displaced. With existing installations there would be no protection offered in zone.51 because as the carriage moves to the right or up, safety edges on the opposite side will not stop the stairlift, if displaced. In the case of the present invention, however, the carriage constantly monitors the operation of all the safety edges, irrespective of the direction of movement of the stairlift, and understands where the stairlift is positioned on the rail, and the direction being travelled. Accordingly each safety edge or associated circuit can be identified by the control system and those that can be activated at any point can be prescribed. Thus, in the scenario illustrated in Figure 8, the control system would be configured to stop the carriage in the event of safety edge 52 being displaced. The control system would be further configured to then allow the carriage to move to the left in order to free the obstruction in zone 51. Once the safety edge 52 was clear of the obstruction, the control system would restore the carriage to its normal operating direction and speed.

It will thus be appreciated that the invention provides a stairlift control method and apparatus which can be implemented in the stairlift without the need for further physical hardware yet permits a more intelligent analysis and handing of obstacles which might bring the stairlift to a halt in the course of a journey and allows the control system to be configured to ensure that, when an electrical safety device is triggered, the carriage can always be moved away from the obstruction to a safe position for the user to alight.

Claims

Claims A method of controlling a stairlift, said stairlift including: a stairlift rail; a carriage mounted on said rail; a motor responsive to a directional command to drive said carriage along said rail; at least one directional safety device aligned with a first direction of movement of said carriage and at least one directional safety device aligned with a direction of movement of said carriage opposite to said first direction; and a control system operable to cut power to said motor upon contact between one of said directional safety devices and an object in the path of said carriage during movement thereof said method being characterized in that it comprises configuring said directional safety devices and said control system so that a safety device may be selectively enabled by said control system irrespective of said directional command.
2. A method as claimed in claim 1 comprising configuring said control system to respond to an actuation of a said safety device and to control subsequent direction of movement of said carriage having regard to the position of said carriage on said rail and/or the operating direction of said motor.
3. A method as claimed in claim 2 including establishing the position of said carriage along said rail using a position sensing facility.
4. A method as claimed in claim 2 or claim 3 including establishing the position of said carriage along said rail by counting the revolutions of said motor from a datum position on said rail.
5. A method as claimed in any one of claims 2 to 4 comprising combining information as to the position of said carriage on said rail with information in memory representing the direction of slope of said rail at the said position.
6. A method as claimed in any one of claims 1 to 5 further comprising controlling the speed of said carriage following operation of a said directional safety device.
7. A stairlift including: a stairlift rail; a carriage mounted on said rail; a motor responsive to a directional command to drive said carriage along said rail; at least one directional safety device aligned with a first direction of movement of said carriage and at least one directional safety device aligned with a direction of movement of said carriage opposite to said first direction; and a control system operable to cut power to said motor upon contact between one of said directional safety devices and an object in the path of said carriage during movement thereof; said stairlift being characterized in that said directional safety devices and said control system are configured so that a safety device may be selectively enabled by said control system irrespective of said directional command.
8. A stairlift as claimed in claim 7 wherein said control facility includes a direction sensing facility.
9. A stairlift as claimed in claim 8 wherein said direction sensing facility is configured to make use of said directional command.
10. A stairlift as claimed in any one of claims 7 to 9 wherein said control facility includes an encoder to determine the position of said carriage relative to a datum.
11. A stairlift as claimed in any one of claims 7 to 10 wherein said control system includes information as to the position of said carriage on said rail together with information indicating the allowable direction of movement of said carriage should a directional safety device operate.
12. A stairlift as claimed in any one of claims 7 to 11 wherein said control system is further operable to monitor the state of each said safety device.