GB2296908A - Stairlift - Google Patents

Abstract

A stairlift comprising an elongate track (10, Fig 1) upon which a driven chair or platform is mounted, and a section (10a) of the track being movable selectively between aligned and misaligned positions thus to avoid obstructing, for example, a doorway (14). The movable track section (10a) is raised by a gas strut (28) and lowered by a linear actuator (35). Locking bars (24) act upon compression springs (50) to absorb the driving force of actuator (35) in the event of an obstruction. Movement of the bars (24) against the springs (50) is arrested when a micro switch (46) is actuated to stop a driving motor (38). Thus drive to the track section (10a) is arrested safely in the event of an obstruction.

Description

A SIAIRLIFT THIS INVENTION concerns stairlifts being devices principally for transporting personnel or goods up and down a staircase.

Such devices consist of a fixed elongate track extending usually along one side of a staircase, and a driven chair or platform mounted for travel along the track.

Stairlifts are often used by persons who are aged or infirm and for whom the utmost safety and comfort must be ensured.

In some instances an end section of the track at the upper or lower end would obstruct a doorway or adjacent wall located close to the bottom or top of the stairs and in such cases it is necessary for that section to be movable, usually pivotally, with respect to the remainder of the track such that when the chair or platform does not occupy that section the section may be raised so as not to obstruct the doorway or the space immediately adjacent a wall.

Commonly, such pivotally connected track sections are movable either manually, sometimes with the assistance of a so-called gas strut, or automatically using a motor driven mechanism.

To ensure complete safety when manoeuvring the movable track section with respect to the remainder of the track, in the case of the powered device, it is necessary to ensure that should any object, such as the user's fingers, become trapped between the relatively moving parts, the powered movement must be arrested to prevent injury or damage.

Conventionally, this is effected by the use of a slipping clutch between the drive motor and the movable part, or alternatively by a current sensitive overload device which, by means of electronic control, stops the motor as soon as the current load increases.

Such measures are often expensive and cumbersome, and may not take effect instantaneously.

According to the present invention there is provided a stairlift comprising an elongate track, a driven chair or platform mounted for travel along the track, a section of the track being movable selectively to become aligned or misaligned with respect to the remainder thereof, and powered means for moving said track section between aligned and misaligned positions; characterised by resilient means associated with said powered means to permit movement of said track section to be arrested safely in the event of an obstruction.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a schematic side view of a stairlift track having a bottom section pivotable with respect to the remainder thereof; Fig. 2 is a cross-section of the track taken on line II-II of Fig. 1; and Fig. 3 is a schematic isometric view of a mechanism to permit safe pivoting movement of the movable track section.

Referring now to the drawings, in a typical application a length of track 10 is fixed to one side of a staircase 11 by means of upright brackets 12 at spaced positions along the track and Includes, for example, a fixed rack 13 (see Fig. 2) such that a driven chair or platform (not shown) may travel along the track from end to end.

In this example, the bottom section 10a of the track would, as shown in dotted lines lOb, obstruct a doorway 14 If permanently located at the bottom of the staircase 11. To avoid this the section 10a may be pivoted upwardly as indicated by arrow 15 to the position illustrated in solid lines. Thus, the bottom section 10a is pivotally attached to the remainder by a pivoting arm 16.

A typical section of the track 10 is illustrated in Fig. 2, the driven chair or platform riding on rollers 18 disposed within a pair of rails 17 at the upper edges of the track. Further rollers 19 afford linear stability to the driven chair by riding along vertical surfaces of the track.

Referring now to Fig. 3, the bracket 16 is pivotally attached at 20 to a baseplate 21 bolted or otherwise attached to an internal horizontal bottom surface of the track 10 close to the joint with the track section 10a. Upstanding from the baseplate 21 at its outer end with respect to the main track section are a pair of upstanding lugs 22 each having an aperture 23 through which may pass one of a pair of elongate locking bars 24. When track section 10a is aligned with the remainder of the track the locking bars, as will be described, extend through the apertures 23 and through complementary apertures in opposed upstanding lugs within the track section 10a thus to lock the latter in alignment with the main track section.

Upstanding from baseplate 21 are a pair of parallel spaced support plates 25 between which extend a pin 26 disposed on pivotal axis 20 and a pin 27 disposed adjacent the pivotal axis 20.

Pivotal arm 16 is mounted on pin 26 whilst similarly mounted on pin 27 is a gas strut 28 having its opposite end pivotally mounted at 29 on a right-angled extension 30 of pivotal arm 16. The gas strut 28 is provided to counterbalance the weight of track section l0a and is in fact biassed towards linear extension such that the track section, if freely pivoted, would rise to the position illustrated in Fig. 1.

Alignment of the track section 10a is effected by opposing the extending bias of the gas strut 28.

A pair of supporting rails 31 form horizontal extensions of the supporting plates 25 whereby the rails 31 are fixed with respect to the baseplate 21. Mounted between the rails 31 to be movable linearly with respect thereto is a member 32 attached by means of a chain 33 and fixed sprocket 34 to the pivoting arm 16.

Thus It can be seen that movement of the member 32 away from upright members 25, and between rails 31, causes the pivotal arm 16 to pivot downwardly thus bringing the section 10a into alignment with the remainder of the track 10.

To effect this movement a linear actuator 35 having a ram 36 attached to member 32, and a body 37, is disposed between the rails 31. The actuator is linearly driven in opposite directions selectively by a motor 38. A pin 39 extends transversely from ram 36 outwardly through a pair of slots 40 in the two side rails 31.

Tension springs 42 are connected to and extend between pin 39 and fixed anchor points 43 at a position along the rails 31 remote from the slots 40. Thus, the ram 36 is biassed by the tension of the springs 42 towards a position of retraction within body 37.

At the rear end of body 37 a further pin 45 extends transversely through the body and through short slots 44 in the remote end regions of rails 31. Anchored to pin 45 on each side of the actuator 35 is a sleeve the free end of each of which is welded to one end of each locking bar 24.

A micro-switch 46 is attached to the outer face of one of the rails 31, to be actuated by the sleeve on pin 45 coming into contact with the switch as a result of movement along slot 44.

A pair of compression springs 50 are captively mounted on locking bars 24 for a purpose to be described.

In use, assuming the track section 10a to be aligned with the remainder of the track, when the chair or platform has ascended towards the top of the track a switch (preferably mounted on the track for actuation automatically by the chair or platform) is actuated to energise motor 38 to cause ram 36 to extend from body 37. This in turn advances chain 33 and permits pivotal arm 16 to rise under the action of gas strut 28 which in turn causes the track section 10a to be elevated to its misaligned position. Reverse operation of the motor 38 (preferably automatically by further action of the switch as the chair or platform approaches the bottom of the track) retracts ram 36 which retracts chain 33 and consequently lowers the track section 10a. This action is assisted by the tension springs 42 acting through pins 39 attached to the ram 36. When the track section 10a reaches its aligned position the residual closing movement of the actuator 35 causes pins 45 to move forwardly with body 37 along slots 44 until the sleeve contacts and actuates switch 46 whereupon the motor is stopped. Forward movement of the pins 45 causes locking bars 24 to extend outwardly through apertures 23 to become interlocked with the corresponding apertures in the track section 10a. The compression springs 50 captively mounted on locking bars 24 serve to control this action.

If during downward movement of the track section 10a it encounters an obstruction preventing further movement and thus arresting further retraction of ram 36 into body 37, consequent advancing movement of the latter causes locking bars 24 to move against the compression springs 50 which therefore serve as a safety device to retard the driving force gradually and reduce the risk of injury. When the springs 50 are almost completely compressed, micro-switch 46 is actuated by pin 45 to stop the motor. Thus pressure on the obstruction is absorbed initially by the compression springs 50 and subsequently relieved by discontinued drive.

Similarly, if an obstruction occurs when the track section 10a is rising, since the driving effect of gas strut 28 is only sufficient to overcome the weight of the section and to elevate it slowly, only a minor force would be applied against the obstruction, and this is minimised further by the resistance imposed by tension springs 42.

By this arrangement the track section 10a Is afforded a smooth driven motion both in alignment and misalignment with the remainder of the track section and with perfect safety in the event of an obstruction.

It will be appreciated that the invention is not limited to the example described above. For example, the compression springs 50 may be replaced by any other resilient means which will initially take-up and then discontinue the motion of the track section if an obstruction should occur. Such resilient means avoids the need for complex slipping clutches or electronic overload devices.

Claims (8)

1. A stairlift comprising an elongate track, a driven chair or platform mounted for travel along the track, a section of the track being movable selectively to become aligned or misaligned with respect to the remainder thereof, and powered means for moving said track section between the aligned and misaligned positions; characterised by resilient means associated with said powered means to permit movement of said track section to be arrested safely in the event of an obstruction.

2. A stairlift according to Claim 1, wherein said powered means is a linear actuator comprising a pair of members linearly driven in opposite directions one of said parts being drivingly connected to the movable track section, and the other to a further movable part.

3. A stairlift according to Claim 2, wherein said further movable part is capable of limit movement against said resilient means, switch means being provided and actuated by movement of said further movable part to discontinue operation of the linear actuator.

4. A stairlift according to any one of Claims 1 to 3, including at least one locking bar driven by said powered means and arranged to lock the track section in said aligned position.

5. A stairlift according to any one of Claims 1 to 4, including a gas strut connected to the movable track section and biased to move the track section towards its misaligned position, thus to counterbalance the weight of the movable track section.

6. A stairlift according to Claim 3, wherein the linear actuator is motor driven and connected to said resilient means such that if the movable track section should encounter an obstruction during its movement in one direction thus preventing further movement, initial continued drive of the actuator is effective against the resilient means for a limited period before the switch means is actuated to disconnect power to the motor.

7. A stairlift according to Claim 6, wherein said resilient means comprises at least one compression spring adapted and arranged to absorb at least a part of the driving force of the powered means in the event of an obstruction, the switch means being arranged to disconnect power from the motor after the compression spring has absorbed the driving force.

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