Improvements in or relating to stairlifts

Abstract

A means of monitoring the operation of a stairlift overspeed monitoring device (OSDD) 30 of a stairlift 10. A carriage 13 is driven along a rail 12 by a drive wheel, such as pinion 26, coupled to a motor 25 with the OSDD being in rotational contact with the rail. The rotational speed of the OSDD is compared with that of the drive wheel and if the difference is greater than a predetermined amount, which may occur during a fault condition of the OSDD, an alert is generated and possibly transmitted to a remote location wirelessly. The drive wheel may incorporate an encoder 28 and the OSDD may have embedded magnets (35 fig.3) to generate pulses in a magnetic proximity switch (36 fig.3).

Description

This invention relates to stairlifts and, in particular, to a method of and / or apparatus for monitoring the operation of a stairlift component. Background to the Invention A stairlift is a safety-critical piece of equipment. Manufacturers of stairlifts are required to comply with strict standards governing design and construction. Among the standards applicable to stairlift are those relating to the detection of an overspeed occurrence. In a particular case, applicable to a friction drive overspeed detection device (OSDD), EN8l-40:2020 provides: “If the overspeed detection device is friction driven, the control system shall include circuitry to monitor rotation of the overspeed detection device during travel. If rotation ceases, the supply to the driving motor and brake shall be interrupted within 10 s. Further travel shall be by releasing and reactivating the directional control button, until the boarding point has been reached and no further travel is permitted. Return to normal operation shall require the intervention of a competent person. ” It will be appreciated that in the event the OSDD ceases to rotate, causing the stairlift to stop functioning, delay and expense will be incurred whilst a competent person attends and effects the necessary repair or re-set so that normal operation of the stairlift can resume. It is an object of the invention to provide a method and / or apparatus which will go at least some way in addressing the aforementioned problem; or which will at least provide a novel and useful choice. Summary of the Invention Accordingly, in a first aspect, the invention provides a method of monitoring the operation of an overspeed detection device (OSDD) fitted to a stairlift, the stairlift having a rail, a carriage, a drive wheel in contact with the rail, a drive motor operable to rotate the drive wheel to, in use, displace the carriage along the rail, and an OSDD mounted to the carriage and in rotational contact with the rail independently of the drive wheel, the method comprising: comparing in the speed of rotation of said OSDD with an expected speed; and generating an alert in the event the speed of said OSDD varies from the expected speed by a predetermined amount. Preferably the method is applied to an OSDD in frictional engagement with said rail. Preferably the expected speed is greater than zero. Preferably the expected speed is derived from the speed of rotation of the drive wheel. Alternatively, or in addition, the expected speed is established according to the position of the carriage on the rail. Preferably the method further includes communicating said alert to a remote location. In a second aspect the invention provides control means for a stairlift, the stairlift having a rail, a carriage, a drive wheel in contact with the rail, a drive motor operable to rotate the drive wheel to, in use, displace the carriage along the rail, and an overspeed detection device (OSDD) mounted to the carriage and in rotational contact with the rail independently of the drive wheel, wherein the control means is configured to compare a detected speed of rotation of said OSDD with an expected speed; and a communications facility configured and operable to generate an alert in the event the detected speed differs from the expected speed by a predetermined amount. Preferably the control means is configured for inclusion in a stairlift in which the OSDD is in frictional contact with said rail. Preferably said control means is configured to derive the expected speed from the speed of rotation of said drive wheel. Alternatively, or in addition, the control means includes in memory expected speeds of the OSDD at various positions of said carriage on said rail. Preferably said control means is further configured to cause said carriage to move to a parking position in the event the detected speed of said OSDD is zero. Preferably said control means is configured to select said parking position having regard to the position of the carriage on the rail at the time the detected speed of said OSDD is zero. Preferably said control means configured to send a message to a remote location in the event the speed of said OSDD detected in real time differs from the expected speed by said predetermined amount. Preferably said control means is configured to receive rotational speed signals from both of said drive wheel and said OSDD. The rotational speed signals may be obtained from encoders which may be optical or magnetic-based or a combination of both. In a third aspect the invention provides a stairlift configured to perform the method as set forth above. In a fourth aspect the invention provides a stairlift including the control means as set forth above. The invention may comprise any novel combination of elements or components claimed or described herein that may combine to provide a method of monitoring a stairlift OSDD, control means including a stairlift OSDD, or a stairlift including a control means, and should not be confined to the particular combination or combinations of elements or components described in the following example. 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. Subject to the scope of the appended claims, 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 form of the invention will now be described with reference to the accompanying drawings in which: Figure 1: shows an isometric, schematic, view of a stairlift installation to which the various aspects of the invention may be applied; Figure 2: shows a schematic view of a stairlift rail and carriage; Figure 3: shows a schematic view of one alternative applicable to a stairlift OSDD: Figure 4: shows a schematic view of a signal processing arrangement applicable to the invention; Figure 5: shows a plot of signals received by the processing arrangement of Figure 4; and Figure 6: shows a schematic view of a stairlift according to the invention in a wider environment. Detailed Description of Working Embodiment The invention is applicable to a stairlift 10 fitted to a staircase 11, the stairlift including a rail 12 and a carriage 13 moveable up and down the rail between an upper boarding point 14 and a lower boarding point 15. In the conventional manner a chair 16, or platform, is mounted on the carriage 13 to accommodate the needs of a passenger wishing to move between the floors coincident with the boarding points 14 and 15. In the example shown in Figure 1, the rail comprises straight sections 17 and 18 linked together by positive transition bend 19, outside bend 20, and negative bend 21. Those skilled in the art will appreciate that the single rail arrangement shown in Figure 1 is for illustrative purposes only and should not be confused with the twin rail arrangements shown in Figures 2, 3 &6. The invention is applicable to both single rail and twin rail embodiments of stairlift. The carriage 13 is driven along the rail 12 by a drive motor 25 under the control of directional hand control 24 positioned on the chair 16 for ready engagement by a user. In this example the motor 25 rotates a drive wheel in the form of pinion 26, the pinion 26 being in engagement with rack 27 extending along the rail; although the scope of this invention is not to be confined to such a drive arrangement. An encoder 28 or the like is preferably provided to allow the rotation of the pinion 26 to be monitored. An overspeed detection device (OSDD) 30 is also held in contact with the rail 12. While the OSDD may be driven by a further geared pinion in contact with rack 27, the invention has been developed in particular, although not necessarily solely, for application to stairlift installations in which the OSDD is driven by frictional contact with a surface of the rail 12. The OSDD 30 comprises a wheel 31 fitted with a rotational monitor unit 32 which passes signals to the stairlift electronic control unit or ECU 33. In its broadest sense the invention consists in the ECU monitoring the speed signals from the OSDD 30 to determine if the OSDD is functioning correctly. In the event the ECU determines that the OSDD is not functioning for a short period of time, according to regulation up to 10 seconds, the power to the motor is cut. The invention supplements this facility by monitoring the operation of the OSDD over time so that remedial action can be taken before the OSDD ceases to function. In the form shown, the rotational monitor unit 30 comprises a plurality of magnets 35 embedded in wheel 31, and a magnetic proximity switch 36 which, in the known manner, generates a pulse as each magnet 35 passes whilst the wheel 31 rotates. The resulting stream of pulses is passed to the ECU 33 and provides an indication of the speed of rotation of the OSDD at any given time. The speed of the stairlift carriage and thus the rotational speed of the OSDD varies as the carriage moves along the rail. For example, the control system causes the carriage to slow as it negotiates bends in the rail, and as it nears a boarding point. This variation in speed should be taken into account, as should any variation in the frictional characteristics of the rail, when assessing the health of the OSDD. In its simplest form, an embodiment of the invention could comprise comparing the relative rotational speeds of the drive pinion 26 and the OSDD 30. In the event the rotational speed of the OSDD declined relative to the expected speed, in this case the rotational speed of the drive pinion, by a preset amount, an alert would be generated. However, a more sophisticated arrangement is envisaged in which the expected speed of the OSDD is established at various positions of the carriage on the rail so forming an expected speed profile. The actual speed of the OSDD is then monitored in real time and compared with the expected speed as the carriage moves along the rail. In this way the location of the carriage in the event of failure of the OSDD can be readily determined. Further, as the ECU 33 collects data from the OSDD over time, it can generate an alert in the event the rotational speed of the OSDD relative to expected speed, falls below a set threshold. In this particular embodiment the encoder 28 serves as a position monitoring unit and, as can be seen in Figure 4 inputs from both the rotational monitoring unit 32 and the position monitoring unit 28 are inputted to the ECU to allow the speed of the OSDD to be assessed relative to carriage position. The OSDD speed profile could be established by recording the speed of the OSDD as it is driven along the rail, and when the OSDD is known to be in a healthy working condition. This could, for example, be undertaken at the time of installation and / or at a planned service call. Figure 5 illustrates pulse trains from both the OSDD and the pinion encoder 28 as inputted to the ECU 33. As the carriage moves continuously along the rail a continuous pulse train 38 is emitted from the encoder 28. In the case of a healthy functioning OSDD a further continuous pulse train 39 is emitted from the rotational monitoring unit 32. Should the OSDD fail, the pulse train 39 ceases as shown at x. If the pulse train re-establishes while x is less than 10 seconds, then the stairlift can continue as normal. If, however x is 10 seconds or more, then the carriage should be moved to a boarding point and further use of the stairlift prevented until intervention and re-sent or repair by a competent person. Whether the OSDD fails, or a decline in performance below a threshold is detected, the ECU 33 generates an alert. In its simplest form this could comprise an onboard diagnostic feedback but preferably the ECU is configured to pass the resulting alert to a remote location, preferably via a wireless communication system, one example of which being the system known as Stannah Connect™. As indicated in Figure 6 an alert generated by the ECU 33 in carriage 13 may be passed to remote site 40 via the internet 41. Precise details of appropriate communication protocols will be known to those skilled in the art and are not deemed to be part of the invention. The ECU 33 may be further configured to select the boarding point in the event the OSDD fails. For example, an installer could obtain the user’s preference for the boarding point to which the carriage should move in the event of failure of the OSDD, and set the ECU accordingly. The appropriate boarding point could also be set to avoid a situation where the carriage, at one boarding point, could obstruct a doorway. As yet a further alternative, the ECU could be programmed to determine the nearest boarding point at the onset of OSDD failure, and drive the carriage to that boarding point. Variations may be made to the embodiment above, and to any working embodiment incorporating the invention. The term ‘encoder’ may, in addition to the optical and magnetic forms described above, may include any device that can detect angular or linear motion to indicate position or speed. Such devices may derive speed or position relative to the rail by both contact and non-contact methods.

Claims

1. A method of monitoring the operation of an overspeed detection device (OSDD) fitted to a stairlift, the stairlift having a rail, a carriage, a drive wheel in contact with the rail, a drive motor operable to rotate the drive wheel to, in use, displace the carriage along the rail, and an OSDD mounted to the carriage and in rotational contact with the rail independently of the drive wheel, the method comprising: comparing in the speed of rotation of said OSDD with an expected speed; and generating an alert in the event the speed of said OSDD varies from the expected speed by a predetermined amount.

2. A method as claimed in claim 1 when applied to an OSDD in frictional engagement with said rail.

3. A method as claimed in claim 1 or claim 2 wherein the expected speed is greater than zero.

4. A method as claimed in any one of claims 1 to 3 wherein the expected speed is derived from the speed of rotation of the drive motor or the drive wheel.

5. A method as claimed in any one of claims I to 3 wherein the expected speed is established according to the position of the carriage on the rail.

6. A method as claimed in any one of claims 1 to 5 further including communicating said alert to a remote location.

7. Control means for a stairlift, the stairlift having a rail, a carriage, adrive wheel in contact with the rail, a drive motor operable to rotate the drive wheel to, in use, displace the carriage along the rail, and an overspeed detection device (OSDD) mounted to the carriage and in rotational contact with the rail independently of the drive wheel, wherein the control means is configured to compare a detected speed of rotation of said OSDD with an expected speed; and a communications facility configured and operable to generate an alert in the event the speed detected differs from the expected speed by a predetermined amount.

8. Control means as claimed in claim 7 when configured for inclusion in a stairlift in which the OSDD is in frictional contact with said rail.

9. Control means as claimed in claim7 or claim 8 wherein said control means is configured to derive the expected speed from the speed of rotation of said drive motor or said drive wheel.

10. Control means as claimed in claim 7 or claim 8 including in memory expected speeds of said OSDD at various positions of said carriage on the rail.

11. Control means as claimed in any one of claims 7 to 10 further configured to cause said carriage to move to a parking position in the event the detected speed of said OSDD is zero.

12. Control means as claimed in claim 11 when configured to select said parking position having regard to the position of the carriage on the rail at the time the detected speed of said OSDD is zero.

13. Control means as claimed in any one of claims 7 to 12 when configured to send a message to a remote location in the event the speed of said OSDD detected in real time differs from the expected speed by said predetermined amount.

14. Control means as claimed in any one of claims 7 to 13 when configured to receive rotational speed and / or position signals from both of said drive wheel and said OSDD.

15. Control means as claimed in claim 14 wherein said rotational speed and / or position signals are obtained from encoders.

16. A stairlift configured to perform the method as claimed in any one of claims 1 to 6.

17. A stairlift including the control means as claimed in any one of claims 7 to 15.

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