GB2231028A - Stairlift - Google Patents

Abstract

A stairlift comprises a rail 1, Fig 3 fixed along a flight of stairs so as not to overhang an upper landing 41. A carriage 44 carries a footrest 49 and is movable between an upper position, Figure 3, in which the top surface 50 is level with the upper landing 41, and a lower position (Figure 4), in which the bottom 51 of the footrest 49 rests on the lower landing (52). The carriage may also comprise a stop 18, Fig 1, operative to engage the track 2 over a predetermined maximum speed. <IMAGE>

Description

STAIRLIFT The present invention relates to a stairlift.

Stairlifts are known for allowing disabled or elderly people to negotiate stairs. Such stairlifts are usually installed in the home and comprise a rail which is installed along a flight of stairs and a carriage driven by a motor along the rail. The rail extends from the bottom to the top of the flight of stairs and is securely fixed in place to an adjacent wall and/or some of the stairs and/or to landing floors at the top and bottom of the flight of stairs. The rail comprises a channel or other section of metal, such as extruded aluminium or welded steel, and generally includes a toothed metal rack fixed to or machined on a channel or section.

The carriage comprises a chassis supporting a plurality of idler rollers which support and guide the chassis on the rail. A propulsion motor is mounted on the chassis and drives, via a reduction gearbox, a pinion which meshes with the rack on the rail. A solenoid-operated brake for stopping the carriage and holding it in position, for instance at the top of the rail, is provided on the motor shaft.

The chassis carries a seat and footrest for a user and a set of switches for controlling operation of the stairlift. These switches include, for instance, useroperable "up" and "down" switches, top and bottom "limit" switches cooperating with the rail for preventing the carriage from over-running its uppermost and lowermost positions, and safety switches for permitting operation of the stairlift only when the footrest and seat are properly deployed.

With such stairlifts, braking of the carriage relies on the solenoid operated brake which brakes the motor output shaft. Because of the reduction gearing provided by the gearbox, the braking force applied to the carriage is magnified. However, in the event of a failure between the part of the motor shaft to which the brake is connected and the engagement between the pinion and rack, the brake ceases to operate, thus leading to a potentially very dangerous situation. It is possible for a breakage to occur in a key securing the pinion to an output shaft of the gearbox, a shaft or tooth of the pinion or a gear within the gearbox, the connection between the motor shaft and the gearbox input shaft, or the motor shaft itself, and any of the breakages would disable the brake.If such a fault occurred with the carriage in any position other than at the bottom of the rail, the carriage would run uncontrollably to the bottom of the carriage would subject the user to a severe jolt or even throw the user off the stairlift. The risk of serious injury would thus be very great.

According to a first aspect of the present invention, there is provided a carriage for a stairlift, comprising a chassis, a motor-driven pinion for cooperating with a rack on the rail for propelling the chassis along the rail, a stop for engaging the rack so as to prevent movement of the chassis along the rail, speed determining means for determining when the speed of the carriage along the rail exceeds a predetermined maximum speed, and engaging means for engaging the stop with the rack.

Preferably the engaging means comprises a spring urging the stop towards engagement with the rack and means, such as a solenoid, for moving the stop out of engagement against the action of the spring. Thus, failure of the moving means does not disable the brake. The solenoid may be connected to the stop by a lever providing a mechanical advantage, thus allowing a smaller less powerful solenoid to be used.

Preferably the speed determining means includes a sensor for cooperating with teeth of the rack to provide a signal representing the speed of the carriage along the rail. The sensor may be a proximity switch or detector, for instance of the capacitive, inductive, or variable reluctance type. This provides a relatively simple and compact arrangement which does not require any modification of or addition to the rail and is reliable since it does not depend on any mechanical connection between the carriage and the rail. Preferably the speed determining means includes means for counting the number of teeth per unit time detected by the sensor or for measuring the time interval between teeth, preferably consecutive teeth, detected by the sensor.

Preferably the stop comprises a pin or tooth which is slidable into meshing engagement with the rack. The stop may comprise a plurality of teeth, for instance in the form of a short rack which is slidable for moving the teeth into meshing engagement with the rack.

Preferably the carriage includes a motor and reduction gearbox for driving the pinion and a control circuit for stopping the motor when the stop engages the rack.

Preferably the control circuit prevents the motor from starting until after the stop has been disengaged from the rack. This prevents the motor from being subjected to excess loads when the stop is engaged with the rack.

The motor may be provided with a thermal cut-out and motor shaft brake, and the stop may be arranged to engage the rack after the motor has stopped. Thus, apart from providing braking in the event of failure, engagement of the stop with the rack holds the carriage in place on the rail, for instance when the carriage reaches the top of the rail, during normal operation.

Preferably means are provided for engaging the stop with the rack if the speed of the carriage along the rack is less than a predetermined minimum speed at a predetermined time interval after movement of the carriage has been demanded. This allows correct operation, for instance of the speed determining means, to be monitored and prevents or limits potentially unsafe operation of the carriage.

According to a second aspect of the invention, there is provided a stairlift including a carriage in accordance with the first aspect of the invention and a rail provided with a rack.

According to a third aspect of the invention, there is provided a stairlift for deployment along a flight of stairs between an upper landing and a lower landing, comprising a rail arranged to be fixed along the flight of stairs without overhanging the upper landing, a carriage, and a footrest mounted on the carriage, the carriage being arranged to move along the rail between an upper position, in which the footrest is at or adjacent the level of the upper landing, and a lower position, in which the footrest is at or adjacent the level of the lower landing.

By avoiding any rail overhang at the upper landing, it is possible to deploy the stairlift in situations where the upper landing must be free from obstructions, for instance where a door is located at the top of the uppermost stair of the flight. By arranging for the footrest to be substantially flush with the upper and lower landings, a user can mount and dismount without having to negotiate any substantial step. Thus, problems associated with previously known stairlifts are overcome.

Preferably the carriage is supported on the rail by a plurality of support rollers, an uppermost of which remains in contact with the rail when an upper surface of the footrest is substantially level with the upper landing.

Preferably the carriage comprises a chassis whose lowermost point is at or above a lower surface of the footrest.

The invention will be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a cross-sectional view of a stairlift constituting a preferred embodiment of the invention; Figure 2 is a block schematic diagram of the stairlift of figure 1; Figure 3 is a diagrammatic side view of an upper part of the stairlift of Figure 1 showing a carriage at its uppermost position; and Figure 4 is a diagrammatic side view of a lower part of the stairlift of Figure 1 showing the carriage at its lowermost position.

The stairlift comprises a rail 1 formed by a box-section of aluminium, for instance by extrusion. The rail 1 has an integrally formed rack 2, for instance formed by machining teeth into an upwardly extending flange of the rail.

The stairlift further comprises a carriage having a chassis formed by two parallel plates 3, only one of which is shown in figure 1 and which straddle the rail 1.

A gearbox 4 is mounted in the chassis and provides reduction gearing between its input shaft (not shown) and its output shaft 5. A pinion 6 is keyed to the gearbox output shaft 5 and meshes with teeth of the rack 2. The input shaft of the gearbox 4 is connected to a shaft 7 of a motor 8 which drives the pinion 6 through the gearbox 4 so as to propel the carriage along the rail 1. The carriage is provided with a plurality of idler rollers (not shown) which run on various vertical and horizontal surfaces and flanges of the rail 1 so as to provide vertical guidance and support and lateral guidance. The upper end of the motor shaft 7 is provided with an electrically operated brake 9, for instance comprising a drum brake operated by a solenoid 10.

A solenoid 11 is mounted on a spacer 12 which spaces apart the plates 3. The solenoid 11 has a plunger 13 which is pivotally connected at its upper end to one end of a lever 14. The lever 14 has a fulcrum 15 and is pivoted at its other end to a slide 16. The slide 16 is slidably mounted in another spacer 17 and, at its lower end, is provided with a stop or lock 18. The lock 18 comprises a short rack having teeth which are arranged to mesh with the teeth of the rack 2. A helical compression spring 19 act between the spacer 17 and the lock 18 so as to urge the lock into mesh with the rack 2.

The carriage also carries a sensor 20 which cooperates with the teeth of the rack 2 so as to sense the proximity of the teeth. The sensor 20 is a proximity switch or transducer, for instance of the capacitive, inductive, or variable reluctance type.

As shown in figure 2, the sensor 20 is connected to a tooth detector circuit 21 which detects the presence or absence of a tooth adjacent the sensor 20. The circuit 21 is connected to a speed determining circuit 22 which provides an output signal representing the speed of the carriage along the rail 1. The speed determining circuit 22 may, for instance, comprise a counter arrange to count the number of teeth sensed by the sensor 20 per unit time, or a timer arranged to time the interval between teeth passing the sensor 20. For instance, the time interval between consecutive pairs of teeth passing the sensor 20 may be timed.

The output of the speed determining circuit 22 is connected to first inputs of first and second comparators 23 and 24. The first comparator 23 has a second input which receives a reference signal Vo representing the maximum permissable speed of the carriage along the rail 1. In the case where the normal carriage linear speed is 7.5 cm per second, the reference Vo may, for instance, correspond to 15 cm per second. The second comparator 24 has a second input which receives a reference signal Vu representing a minimum predetermined speed or under speed, which is generally less than about 80% of the normal speed. In the above case, the reference signal Vu may, for instance, represent 3 cm per second.

The outputs of the comparators 23 and 24 are connected to a control and drive circuit 25 which controls the operation of the stairlift and provides drive signals for the motor 8, the solenoid 10, and the solenoid 11. The control and drive circuit 25 has inputs connected to a plurality of switches 26 to 37 whose operation will now be described.

The switch 26 is a normally closed micro-switch which is opened is a footrest of the stairlift strikes an obstacle when the carriage is moving upwardly. The switch 26 is connected in series with a normally closed micro-switch 27 which is arranged to open by abutting against a stop when the carriage is at the uppermost end or top of the rail 1. The switches 26 and 27 are connected to a continuous currently loop which detects opening of either switch and stops movement of the carriage in the upward direction. Thus, the carriage cannot move upwardly unless the footrest remains clear of obstacles, and stops automatically when the carriage reaches the top of the rail.

The switch 28 is a normally closed micro-switch which is opened if the footrest strikes an obstacle when the carriage is moving downwardly. The switches 29 and 30 are normally closed micro-switches which cooperate with stops for detecting when the carriage is at its lowermost position or bottom of the rail 1. The switches 28 to 30 are connected in series to a continuous current loop arrangement as described for the switches 26 and 27.

Thus, the carriage cannot move downwardly unless all of the switches 28, 29, and 30 are closed. The carriage cannot therefore move unless the footrest remains clear of obstacles, and downward movement is stopped when either of the switches 29 and 30 is opened by coming into contact with the bottom stop.

The switches 31 to 33 are like-wise connected to a continuous current loop and movement of the carriage is prevented unless all three switches are closed. The switch 31 is a final limit switch for preventing the carriage from running off the rail at the top and/or bottom, the switch 32 is a seat interlock, and the switch 33 is a key switch which is operated by a key for enabling and disabling operation of the stairlift so as to control access to operation of the stairlift.

The switches 34 and 35 are normally open "up" and "down" switches mounted on the carriage in a position convenient for a user. The user actuates the switch 34 to start the carriage in an upward direction and actuates the switch 35 to start the carriage in a downward direction. The switches 36 and 37 are remote "call and send" switches and are located adjacent respective ends of the rail 1.

The switches are connected in parallel and by suitable contact means to the control and drive circuit 25 in the carriage. When the carriage is at the end of the rail 1 adjacent the switch 36, actuation of the switch 36 causes the carriage to travel to the other end of the rail 1.

When the carriage is at the other end, actuation of the switch causes the carriage to return. Operation of the switch 37 is, of course, identical.

During normal operation of the stairlift, movement of the carriage along the rail 1 is controlled by the switches 34 to 37. When one of the switches 34 to 37 is actuated, the circuit 25 actuates the solenoid 10 to release the brake 9 and supplies power to the motor 8 for rotation in the appropriate direction. The solenoid 11 is energised after a delay of about half a second, and withdraws the lock 18 from meshing engagement with the rack 2. Any incorrect state of any of the switches 26 to 33 prevents such operation, of course. After a time interval of, for instance, 10 seconds, the circuit 25 checks the output of the comparator 24 to ascertain whether the speed of movement of the carriage along the rail 1 is greater than the minimum speed, thus checking for correct operation of the sensor 20, the tooth detector circuit 21 and the speed discriminating circuit 22. If the output of the comparator 24 indicates that the minimum speed has not been exceeded, the circuit 25 deactuates the solenoid 11, deactuates the solenoid 10 and cuts off power to the motor 8. The brake 9 is therefore applied and the lock 18 is urged into locking engagement with the rack 2 by the spring 19.

The circuit 25 continuously monitors the output of the comparator 23 and, if, at any time, the speed of the carriage along the rail 1 exceeds the maximum or overspeed, the circuit 25 deactuates the solenoids 10 and 11 and cuts off power to the motor 8, thus positively locking the carriage to the rail 1. This locking occurs even if there is a failure or breakage of the motor shaft 7, the gearbox 4, or the pinion 6.

The circuit 25 is arranged such that, whenever an underspeed or overspeed condition is detected, the stairlift is prevented from further operation until the power supply is removed and reconnected.

During normal operation, in the absence of a fault condition, the solenoid 11 is deactuated after a time interval of about half a second following deactuation of the solenoid 10 and cutting off of power to the motor 8.

During normal operation, whenever the actuated switch 34 or 35 is released or when the limit switch 27, 29, or 30 is actuated, the lock 18 engages with the rack 2 of the rail 1, after the short delay, following a normal stopping sequence in which the power to the motor 8 is cut off and the brake 9 is applied by deactuating the solenoid 10. However, when an overspeed condition is detected, and possibly also when an underspeed condition is detected, the solenoid 11 is immediately deactuated so that the lock 18 engages the rack 2.

When the stairlift is disconnected from a power source, such as the normal domestic AC MAINS SUPPLY, then the lock 18 will mesh with the rack 2, thus locking the carriage to the rail 1. This prevents any movement of the carriage during a supply failure or supply fault.

It is therefore possible to provide a simple but reliable stairlift having two independent braking systems, one of which operates irrespective of any failure in the drive system for propelling the carriage along the rack 1. The danger of injury to a disabled person using the stairlift because of any malfunction or failure is therefore greatly reduced compared with previously known stairlifts.

In order for a stairlift to be convenient for a disabled person to use, the carriage should be capable of moving between an uppermost position, in which the upper surface of a footrest is substantially level with a floor or landing, and a lowermost position, in which the footrest effectively sits on a floor or landing (the term "landing" as used herein is intended to include both a landing as such and an area or part of a floor adjacent a flight of stairs). This permits mounting and dismounting with a minimum of inconvenience by eliminating or reducing as much as possible the height of any step between the footrest and the landing.

It is desirable and, in some situations, essential for the rail of the stairlift not to overhang the upper landing i.e. for the rail not to extend past a vertical plane including the vertical riser of the uppermost stair of the flight. For instance, in those situations where a door is located at the top of the flight of stairs, the upper end of the rail must not foul the door. In situations where no constraint is imposed by the proximity of a door, any overhang may nevertheless be inconvenient or dangerous. For instance, passers-by are liable to scratch their legs and ankles on the ends of the rail, especially in the case of landings and stairways which are relatively narrow.

Figure 3 shows the upper end of the rail 1 in relation to an uppermost stair 40 of a flight of stairs and a landing 41 at the top of the flight. The top end of the rail 1 does not overhang the landing 41 but, instead, ends in a vertical plane 42 which represents an extension of the riser 43 of the uppermost stair 40.

The chassis 44 is supported and guided on the rail 1 by a plurality of support and guide rollers. Only two of the support rollers 45 and 46 are shown in Figure 3. The uppermost support roller 45 rolls along an upper internal surface 47 of the rail 1 and is held in contact therewith by a tilting moment of the weight of the carriage about a horizontal axis. With the chassis 44 at its uppermost position as illustrated in Figure 3, the point of contact of the roller 45 on the surface 47 shown at 48 is spaced by an amount a from the plane 42 on the side thereof opposite the landing 41. A footrest 49 is attached to the chassis 44 and, in the uppermost position as illustrated, an upper surface 50 of the footrest is substantially level with the landing 41 so as to allow a user to mount and dismount the carriage without the obstacle of a step up or step down.

The chassis 44 and the footrest 49 are arranged such that the chassis, including rollers, bearings, and the like, does not extend below a lower surface 51 of the footrest 49. Thus, as shown in Figure 4, when the chassis 44 is at its lowermost position, the footrest 49 rests on the lower landing 52. The step-up and step-down for a user is thus reduced to a minimum.

Claims (18)

CLAIMS.

1. A stairlift for deployment along a flight of stairs between an upper landing and a lower landing, comprising a rail arranged to be fixed along the flight of stairs without overhanging the upper landing, a carriage, and a footrest mounted on the carriage, the carriage being arranged to move along the rail between an upper position, in which the footrest is at or adjacent the level of the upper landing, and a lower position, in which the footrest is at or adjacent the level of the lower landing.

2. A stairlift as claimed in Claim 1, in which the carriage is supported on the rail by a plurality of support rollers, an uppermost of which remains in contact with the rail when an upper surface of the footrest is substantially level with the upper landing.

3. A stairlift as claimed in Claim 1 or 2, in which the carriage comprises a chassis whose lowermost point is at or above a lower surface of the footrest.

4. A carriage for a stairlift, comprising a chassis, a motor-driven pinion for cooperating with a rack on a rail of the stairlift for propelling the chassis along the rail, a stop for engaging the rack so as to prevent movement of the chassis along the rail, speed determining means for determining when the speed of the carriage along the rail exceeds a predetermined maximum speed, and engaging means for engaging the stop with the rack.

5. A carriage as claimed in Claim 4, in which the engaging means is arranged to engage the stop with the rack when the speed of the carriage along the rack exceeds the predetermined maximum speed.

6. A carriage as claimed in Claim 4 or 5, in which the engaging means comprises a spring urging the stop towards engagement with the rack and means for moving the stop out of engagement against the action of the spring.

7. A carriage as claimed in Claim 6, in which the moving means comprises a solenoid.

8. A carriage as claimed in any one of Claims 4 to 7, in which the speed determining means includes a sensor for cooperating with teeth of the rack to provide a signal representing the speed of the carriage along the rail.

9. A carriage as claimed in Claim 8, in which the speed determining means includes means for counting the number of teeth per unit time detected by the sensor or for measuring the time interval between teeth detected by the sensor.

10. A carriage as claimed in any one of Claims 4 to 9, in which the stop comprises a pin or tooth which is slidable into meshing engagement with the rack.

11. A carriage as claimed in any one of Claims 4 to 9, in which the stop comprises a plurality of teeth in the form of a short rack which is slidable for moving the teeth into meshing engagement with the rack.

12. A carriage as claimed in any one of Claims 4 to 11, including a motor and reduction gearbox for driving the pinion and a control circuit for stopping the motor when the stop engages the rack.

13. A carriage as claimed in Claim 12, in which the control circuit is arranged to prevent the motor from starting until after the stop has been disengaged from the rack.

14. A carriage as claimed in Claim 12 or 13, in which the motor is provided with a thermal cut-out and motor shaft brake, and the stop is arranged to engage the rack after the motor has stopped.

15. A carriage as claimed in any one of Claims 4 to 14, including means for engaging the stop with the rack if the speed of the carriage along the rack is less than a predetermined minimum speed at a predetermined time interval after movement of the carriage has been demanded.

16. A stairlift including a carriage as claimed in any one of Claims 4 to 15 and a rail provided with a rack.

17. A stairlift as claimed in any one of Claims 1 to 3, in which the carriage comprises a carriage as claimed in any one of Claims 4 to 15.

18. A stairlift substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.