Patent Application
20100274409
This invention relates to stairlifts and, in particular, to the control of the movement of a stairlift carriage along a stairlift rail.
The movement of a stairlift carriage along a stairlift rail must be carefully controlled. This is particularly so in the case of curved stairlifts. Not only must the speed of the carriage along the rail be controlled within pre-determined limits, but also care must be taken to ensure that, as the stairlift carriage traverses transition bends in the stairlift rail, the chairlift chair does not depart from the horizontal to a noticeable extent. In this context, a transition bend is a bend which links sections of rail at different angles to a horizontal plane.
By regulation, stairlifts must have some form of device which prevents the stairlift carriage going “over-speed”. This is typically provided in the form of a over-speed governor mounted within the carriage which, in the event the stairlift carriage exceeds a pre-determined speed, displaces under centrifugal force, and releases or activates a safety gear. The safety gear, in turn, engages the rail, and brakes the carriage from further movement.
Whilst these forms of over-speed governor have been in use for many years, they are not without their problems. Because of manufacturing tolerances, they can be unreliable, and trigger the operation of the safety gear at speeds below the intended trip speed. The consequences can be particularly inconvenient as some installations require a serviceman to be called out in order to release the safety gear and re-set the over-speed governor.
An alternative form of over-speed governor to the centrifugal type, is described in UK Patent Application 2,339,419. The governor described in this patent does not operate under the influence of centrifugal force but, rather, senses the carriage speed electronically. When an over-speed situation is sensed, a solenoid is de-energised. This, in turn, releases the safety gear which brings the carriage to a halt.
Whilst the electronic speed sensing feature described in UK Patent Application 2,339,419 addresses the triggering unreliability of conventional governors operating under centrifugal force, the particular form of device described in this patent presents other problems. Firstly, the operation of the device described in UK Patent Application 2,339,419 relies upon the safety gear release solenoid being kept in a static, energized, configuration at all times. When any mechanical or electromechanical component is kept in a set is position for long periods of time, it is susceptible to seizure. This is of particular concern in the case of a component forming part of a safety system, such as a stairlift over-speed governor. Further, if an occupier vacates the premises in which the stairlift is fitted, say by going on vacation, then a supply of power must be left on to ensure the over-speed governor does not trigger in the occupier's absence. As a matter of convenience, this is important because, in the event the governor is triggered, and for whatever reason, the governor described in UK Patent Application 2,339,419 will require the attendance of a serviceman to in order to be re-set.
As stated above, curved stairlifts require the provision of a levelling function to maintain the chair level, whatever the angle of the rail with respect to the horizontal. Traditionally this function has been provided by various forms of mechanical arrangement, which have been regarded as ‘fail-safe’. Now, however, there is an increasing trend amongst stairlift manufacturers to effect levelling using a separate, electronically controlled, chair levelling motor. The advent of electronically controlled chair levelling motors has brought with it, concerns about safety. Rightly or wrongly, there is a concern amongst some in the stairlift industry, that electrical or electronics-based systems are, inherently, not as safe as mechanical systems. In the particular case of motorized chair levelling, there is a concern about the possibility of the chair going off-level to a dangerous extent, in the event of main drive failure occurring, particularly main drive failure occurring whilst the carriage is traversing a transition bend in the rail.
Typically the stairlift carriage is slowed when passing over a transition bend. Thus, should a failure occur in the drive system whilst the carriage is traversing a transition bend, it will take a greater length of time for the carriage to build up to a speed sufficient to generate the centrifugal forces necessary to trigger the over-speed governor, than would be the case if the carriage were traversing a straight section of rail. The worst case would arise in the event of failure as the carriage is moving in an uphill direction, and through a transition bend.
When the carriage is traversing a transition bend, the chair levelling motor is operating, under careful electronic control. The programming of the levelling motor control is established, on the basis of an expected carriage speed, so as to maintain the chair level within carefully defined parameters. Should the carriage drive suddenly fail in this instance, and the carriage speed suddenly increase, it is unlikely that the levelling function could react sufficiently quickly, before the carriage was halted by the over-speed governor, to ensure the chair level remained within acceptable limits. Furthermore, the chair levelling mechanism will have its own ‘over-angle’ sensor which, when the chair moves off level by more than say 5°, will cause power to the drive systems of the installation, including the chair levelling motor to be cut. If, at this time, the carriage is still in motion through a transition bend, the chair will be taken beyond this 5° limit as the carriage reverses out of the transition bend.
The problems outlined above are addressed in a substantial way by the form of over-speed governor and stairlift operating methodology described in our published International (PCT) Patent Application No. WO 2004/014773. However, proposed new regulations limiting the distance a stairlift can travel following a failure of the main drive, mean that the response times of all safety to features need to be enhanced still further.
It is an object of this invention to go at least some way in addressing the requirements and concerns expressed above; or which will at least provide a novel and useful choice.
Accordingly, in one aspect, the invention provides a stairlift including a stairlift rail;
a carriage mounted for movement along said rail;
a chair mounted on said carriage,
speed sensing means operable to sense the speed of said carriage along said rail; and
braking means operable to brake said carriage with respect to said rail in response to said speed sensing means determining a tripping speed,
said stairlift being characterised in that:
direction determining means are provided to determine the direction of movement of said carriage, said direction determining means being capable of causing actuation of said braking means.
Preferably said stairlift further includes drive means to drive said carriage along said rail, said speed sensing means being independent of said drive means.
Preferably said speed sensing means is operable to sense, electronically, the speed of said carriage along said rail.
Preferably said speed sensing means includes a roller in rolling contact with said rail; and means to determine the speed of rotation of said roller.
Preferably said speed sensing means includes a plurality of magnets which rotate with said roller; and a sensor responsive to the passage of said magnets thereby, said sensor providing an output signal representative of the speed of rotation of said roller.
Alternatively said roller includes a plurality of radially extending fingers or vanes, said speed sensing means including a detection facility responsive to the passage of said fingers or vanes thereby and operable to generate an output signal representative of the speed of rotation of said roller.
Preferably said detection facility includes one or more Hall-Effect sensors.
Preferably said direction determining means is provided at least in part by said speed sensing means.
Preferably said speed sensing means includes a further sensor, said further sensor providing a further signal output representative of the speed of rotation of said roller, said further signal output being out of phase with said signal output, said direction determining means including a facility to compare the phase difference between said further signal output and said signal output.
Preferably said sensor and said further sensor comprise Hall-Effect sensors.
As a further alternative said roller may include, rotating therewith, a disc configured to allow a single detector to detect both speed and direction of rotation of said roller.
As an alternative said speed sensing means and said direction sensing means is provided by an electrical generator wherein the voltage output is representative of speed and the polarity is representative of direction; said stairlift further including means to monitor the polarity of said generator, and to cause actuation of said braking means in the event of unexpected changes in polarity.
Preferably said generator includes output terminals and wherein, in the event a tripping speed is detected or a change in polarity is detected, said terminals are short-circuited to lock said generator.
Alternatively, in the event a tripping speed is detected or a change in polarity is detected, said generator is positively driven to engage said braking means with said rail.
Preferably said chair is capable of pivotal movement as said carriage moves along said rail, said stairlift further including angle determining means operable to determine out of level positions of said chair, wherein said angle determining means being capable of causing actuation of said braking means.
In a second aspect the invention provides control means for a stairlift, said stairlift including:
a stairlift rail;
a carriage mounted on said rail for movement there-along;
a chair mounted on said carriage;
speed sensing means operable to sense the speed of said carriage along said rail;
braking means operable to brake said carriage with respect to said rail;
direction sensing means operable to sense the direction of movement of said carriage along said rail,
said control means including a microprocessor operable to receive signals from said speed sensing means and from said direction sensing means, and to generate a command to operate said braking means in response to said speed sensing means sensing a carriage speed at or in excess of a tripping speed, or said direction sensing means sensing an unexpected change in direction of movement of said carriage.
Preferably said control means is applied to a stairlift having a rail including rail sections at different angles to a horizontal plane; said chair being capable of pivotal movement as said carriage moves along said rail, to allow said chair to be maintained substantially level, wherein said control means further includes angle sensing means operable to sense positions of said chair at which the angle thereof with respect to said horizontal plane is at or in excess of a limit, said microprocessor being further operable to receive signals from said angle sensing means and to generate a command to operate said braking means in response to said angle sensing means sensing a chair angle in excess of a predetermined maximum.
Preferably said microprocessor is programmed to compare the sensed speed at various positions of said carriage along said rail with an expected speed for said carriage at corresponding positions of said carriage along said rail, the expected speeds being stored in memory; and wherein said microprocessor is programmed to generate a tripping command to said braking means should the sensed speed exceed the corresponding expected speed by a defined amount.
In a third aspect the invention provides a method of controlling a stairlift, said stairlift including:
is a stairlift rail;
a carriage mounted on said rail for movement there along;
a chair mounted on said carriage;
speed sensing means operable to sense the speed of said carriage along said rail;
braking means operable to brake said carriage with respect to said rail; and
direction sensing means operable to sense the direction of movement of said carriage along said rail,
said method including monitoring the speed of said carriage along said rail and monitoring the direction of travel of said carriage and, in the event either said speed exceeds a tripping speed or there is an unexpected change in the direction of movement of said carriage, causing said braking means to operate.
Preferably said method is applied to a stairlift having rail sections at different angles to a horizontal plane; a chair capable of pivotal movement as said carriage passes along said rail to allow said chair to be maintained substantially level; and angle sensing means operable to sense positions of said chair at which the angle thereof relative to said horizontal plane is at or in excess of a limit, said method further including monitoring said angle sensing means and, in the event said angle departs from said predetermined limit, causing said braking means to operate.
In a fourth aspect the invention provides a method of setting the trip speed of a over-speed braking device included in a stairlift, said stairlift having:
a rail;
a carriage mounted for movement along said rail;
an over-speed braking device operable, when tripped, to brake said carriage with respect to said rail,
said method being characterized in that it comprises varying the speed at which said over-speed braking device is tripped.
Preferably the tripping speed is established according to the position of said carriage along said rail.
Preferably expected speeds of said carriage at various positions of said carriage along said rail are stored in a memory, said method comprising comparing the speed measured at various positions of the carriage on said rail, with the corresponding expected speed, said tripping speed being established when the measured speed exceeds the expected speed by a predetermined amount.
Alternatively said method comprises measuring the speed of said carriage and establishing a tripping speed in the event of a defined increase in said speed in a defined time period.
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 various aspects of the invention will now be described with reference to the accompanying drawings in which:
Referring firstly to
The carriage 12 is displaced up and down the rail 13 by suitable drive means. In the form shown, the drive means comprises a rack 14 mounted on the rail, the rack being engaged by a drive pinion 15 mounted on the output of carriage drive motor and gearbox 16, mounted in the carriage.
Aspects of the invention are applicable to both straight and curved stairlifts but the totality of benefits will be experienced in curved stairlifts and the description which follows relates to a curved stairlift.
Although not shown in the drawings the rail 13 includes a number of sections which are arranged at differing angles to a horizontal plane. For this reason the angle of the chair 11 must be capable of adjustment to ensure that, whatever the angle of the rail section with respect to the horizontal, the seat surface of the chair 11 can always be maintained substantially level. To this end, chair 11 is supported on an interface 17, which interface is pivotally mounted at 18 on the carriage 12. Level adjustment of the chair is conveniently effected substantially as described in our Patent 0 738 232. Thus, a chair levelling motor 20 is provided which, under electronic control, can pivot the interface 17 with respect to the carriage 12 as the stairlift moves through transition bends in the rail 13.
It will be appreciated that the inventive concepts described herein could also be applied to those embodiments in which the chair is fixed to the carriage and the combined chair and carriage assembly is pivoted, when the carriage moves through a transition bend in the rail, to maintain the chair substantially horizontal.
It thus follows that the precise method upon which chair levelling is effected does not form part of the present invention, although the invention is particularly suited to electronic based stairlift levelling systems, whether mapped electronic systems or sensor-based leveling systems.
As stated in the preamble above, stairlifts are required, by regulation, to have an over-speed braking facility or governor to brake the carriage to a halt on the rail in the event of a failure which causes the carriage speed to exceed a predetermined maximum limit This over-speed governor is indicated schematically by reference numeral 21 in
Additionally, and particularly in the case of stairlift installations having a separate chair levelling motor 20, means must be provided to ensure the chair 11 does not go off-level by more than a small margin, say 5°. To this end, angle determining means such as, for example, angle sensor 22 is provided on the underside of chair 11. The sensor 22 generates electronic output signals proportional to the tilt angle to either side of a vertical axis, and thus the outputs can be processed and used as triggers to cut power to the drive systems of the installation 10 when the chair angle limits are reached. As described in our European Patent 0 738 232, when the angular limit of the chair 11 is reached, a mechanical interlock such as pin 23 acting in slot 24 may also be triggered to prevent the chair 11 going further off-level.
It cannot, of course, be predicted when a drive system failure might occur leading in turn, to operation of the over-speed governor 21. There is a particular concern that the consequences will be more serious in the event failure occurs whilst the carriage 12 is negotiating a transition bend in the rail and, still more particularly, when the carriage is negotiating a transition bend while moving in an uphill direction.
It is common to slow the stairlift carriage as it negotiates bends in the rail. This is particularly so in those installations employing a separate, electronically controlled chair levelling motor 20. In such cases, the motion of motor 20 must be related, with precision, to the speed of carriage 12, not only to ensure that the chair remains within narrow limits around the horizontal at all times, but also to ensure that the rate of carriage speed and/or chair levelling does not cause alarm to the stairlift user.
Bearing in mind that the carriage is moving slower when negotiating a transition bend, it will therefore physically move further (compared with the case where the carriage is moving along a straight section of rail) before the speed becomes sufficient to generate the centrifugal forces necessary to trip the over-speed governor. Further, it is whilst the carriage 12 is negotiating transition bends, that the chair levelling motor 20 is in operation. If there were to be a sudden increase in carriage speed due to drive failure, the control system operating motor 20 simply could not react fast enough to prevent chair 11 going off-level by more than 5°, and possibly not rapidly enough to avoid a user being ejected from the chair. The problem is exacerbated by the fact that the safety systems built into the chair levelling system will, by then, have locked the chair to the carriage as the chair has gone off level by more than 5°.
In our published International Patent Application WO 2004/014773 we describe an over-speed braking facility in which the over-speed governor trips not just in response to the speed of carriage 12, but also in response to over limit positions of the chair 11. Whilst this represents a marked improvement over the prior art, we have established that safety can be enhanced still further, and response time improved, by adapting the over-speed braking facility to trip in response to unexpected changes of direction of movement of the carriage 12. This adaptation is preferably provided in addition to the chair angle response facility.
Referring to
Turning now to
In the form shown, the safety gear comprises a cam member 33 which is mounted about the centre of bottom roller 34 in such a manner that bottom is roller 34 may rotate freely with respect to the cam 33. The cam 33 includes teeth 33a on the upper surfaces thereof which, when the speed sensor triggers the safety gear, engage the surface of rail 13. The arrangement is such that the cam 33 is equally effective no matter in which direction the carriage 12 is traveling.
Referring now to
Referring to
It will thus be appreciated that rings 43a and 43b, which support the cradle 42, allow the entire over-speed governor assembly to swivel, at least to some extent, about the drive shaft 32.
In the form shown the roller 34 is configured to be rotated by frictional engagement with the rail 13. It will be appreciated, however, that embodiments could be produced, falling within the various aspects of this invention, in which the roller 34, or a roller having equivalent functionality, was provided with a toothed outer surface, and positively driven.
Referring now to
The sensor 52 may, for example, be a reed switch. The magnets may be mounted so that the poles facing the sensor alternate north and south and thus ensure the sensor is positively switch each time a magnet passes thereby.
As one alternative, the sensor 52 may be a Hall-Effect sensor.
The output signal from the sensor 52 is advantageously monitored by microprocessor 25 and processed into an indication of carriage speed.
It will be appreciated that the number of magnets 50 and the type of sensor 52 establish the ability of the microprocessor to determine speed and, perhaps more importantly, to determine speed variation. By way of example only, we have found that using a roller having between 12 and 24 magnets thereon, in combination with a reed switch sensor 52, provides an adequate degree of sensitivity.
As an alternative to using magnets shown on the roller 34, a non-magnetic metal plate having radial fingers could be mounted on the rear surface 46 of the roller. A back biased Hall-effect sensor (one positioned between the plate and a fixed magnetic field) could then be used to create the pulse wave and achieve the same result.
We have also found that, by establishing a tripping speed for the over-speed governor 30 by electronic means as described, we give rise to an additional benefit in that we can vary that speed. More importantly, we can vary the tripping speed for different positions of the carriage on the rail. Thus, when the carriage is moving more slowly through a transition bend, we can set the tripping speed lower. This allows the safety mechanisms of the stairlift to respond far more quickly in the event of failure, and enhances user safety.
One way in which a variable tripping speed can be established is by reference to speed data stored in an electronic memory. In substantially the same manner as is described in our European Patent 0 738 232, expected speeds at various positions of the carriage on the rail, are stored in an electronic memory included within, or in communication with, microprocessor 25. In real time, as the carriage moves along the rail, speed readings are calculated as above described, and compared with the corresponding expected speeds stored in memory. If the measured speed exceeds the expected speed by a pre-determined factor (say, for example, 15% to 20%), an over-speed or tripping speed is deemed to exist and a command is generated to trigger the over-speed governor 30.
An alternative to storing expected speed data in memory is to calculate excessive speed ‘on the fly’. For example, if the set speed for the carriage increases by a predetermined mount within a predetermined period, an over-speed or tripping speed is deemed to exist and a command is generated to trigger the over-speed governor 30.
Whatever the methodology and means for determining an over-speed state, once that state is determined, the safety gear or brake must be moved into contact with the rail in the least possible time. To this end, included in the rear surface 46 of roller 34 are a number of lock slots 54. These slots 54 are positioned at such a radius from the centre of rotation of the roller 34 that they may, in use, receive the pin 55 of solenoid 44. Thus, when solenoid 44 is de-activated upon a tripping command being generated by microprocessor 25, pin 55 is mechanically displaced by a guided compression spring (not shown) included within solenoid 44, and engages in one of the slots 54. Should the roller 34 be rotating when the pin 55 extends, the entire over-speed and safety gear assembly 30 will be rotated in its cradle 42, about drive shaft 32, thus bringing cam surfaces 33a into engagement with the outer surface of rail 13.
As shown in
Again the configuration of the slots 54 will have a bearing on the response of the safety mechanisms herein described, the greater the number of slots the quicker a locking position will be established. Examples we have tested include up to 18 slots but the precise number does not form part of the invention and more slots or less could be used, if appropriate.
Also illustrated in
As can be seen, the ultimate switch 60 is positioned on the carriage chassis such that its actuating pin 61 normally engages a flat surface part 62 formed on ring 43a of the cradle 42. If, however, the cradle 42 is rotated in either a clockwise or anti-clockwise direction about drive shaft 32, such as will happen when solenoid pin 55 locks into one of locking slots 54, the switch 60 will be actuated causing the power to be cut-off to the drive motor 16 and seat levelling motor 20.
The particular embodiment described herein combines features of the limit switches with the over-speed governor assembly. To this end, pivotally mounted at 66 on the outer end of drive shaft 32, is a trigger plate 65. The trigger plate 65 is tapered at its upper end 67 and is engaged at its lower end 68 with the switch actuation plate 40. The upper end 67 of the trigger plate is configured and positioned so as to engage charging/stop ramps 70 provided at each end of the stairlift rail 13. Each of the stop ramps 70 includes an ultimate limit 71 which, in the event of failure of the normal stopping facilities provided at each end of the rail, ensures the ultimate switch is triggered to bring the carriage to a halt. To this end, should the need arise, ultimate limit 71 engages end 67 of the trigger plate causing trigger plate to rotate about pivot 66. This, in turn, causes the switch actuation plate 40 to be displaced, so rotating the cradle 42 about drive shaft 32. When this occurs, the flat 62 on cradle 42 is moved out of its ‘neutral’ state so tripping switch 60 and causing power to be cut to the stairlift drive motor.
As described above, in one aspect the invention involves monitoring the direction of travel of the carriage 12, and responding in the event of an unexpected reversal of direction. The facility included in the stairlift to achieve this end is, in the embodiment shown in
Referring now to
In
As a variation of this alternative, instead of short-circuiting the output terminals of the generator in the event of an over-speed or reversal of direction, the microprocessor could configure the generator 78 as a motor to positively drive the cam surfaces 33a into contact with the rail.
Finally, it will be noted from
It will be appreciated by those skilled in the art that numerous other variations or modifications could be made to the apparatus described above, without departing from the scope of this invention. By way of example only, sensing direction change using a sensor based system as shown in
The operation of the apparatus above described is as follows: In the normal operating condition, the over-speed governor assembly 30 and trigger plate 65 are in the normal central position as illustrated in
Simultaneously with the speed of bottom roller 32 being monitored, the angle of the chair is also being monitored by microprocessor 25, receiving input from the level sensors 22, and movement of the carriage is monitored for unexpected reversal. Should the sensors 22 determine an “over-angle” state, or an unexpected reversal be detected, then once again the microprocessor 25 sends a signal to trigger the safety gear or brake, and isolation switch 60.
Independently of the over-speed function, or the chair angle monitoring function, or the carriage direction sensing function, isolation switch 60 can also be activated at each end of the stairlift's travel by engagement of trigger plate 65 with the end stops 70.
It will thus be appreciated that the present invention, at least in the case of the working embodiment described herein, provides for level control to be maintained and the carriage rapidly brought to a halt in the event of drive failure, particularly failure on transition and helical bends.
