SAFETY BRAKE FOR STAIRLIFTS

Abstract: The present invention relates to an overspeed governor for a stairlift and is characterised in that it can operate in two opposite directions. This means that the same device can be fitted to stairlifts regardless of whether the stairlift installation is left or right handed.

Description: SAFETY BRAKE FOR STAIRLIFTS Field of the Invention This invention relates to stair mounted elevators or lifts, commonly known as stairlifts. In particular, the invention relates to a governor or speed-limiting device to control or brake movement of a stairlift carriage in the event that some failure or malfunction in the drive mechanism, driving the carriage along a stairlift rail, allows the carriage to exceed a predetermined maximum speed. Background Stairlifts, in the form of a carriage mounted for movement along a rail, are well known for moving aged or handicapped persons up and down staircases. Typically stairlifts incorporate a drive motor in the carriage, the output of which engages a rack, extending along the rail, via a gearbox. However, if there is a failure of or in the motor, gearbox or rack, the carriage may be left to travel down the sloping rail in an uncontrolled manner. There is a requirement, at least in the United Kingdom, that stairlifts incorporate an overspeed governor to automatically apply a braking force in the event that component failure or malfunction allows the carriage to exceed a predetermined speed whilst moving down the rail. In the past these devices have tended to be quite complex in form and have only been able to apply a braking force when the carriage is moving in one direction. Thus, depending on which side of the stairway the stairlift apparatus is mounted, a different governor must be used. It is an object of this invention to provide a governor for a stairlift which addresses the aforementioned problems or which at least provides a useful choice. Summary of the Invention Accordingly, in one aspect, the invention provides a governor for a stairlift carriage, said carriage being moveable along a stairlift rail in two directions, said governor including: a braking member displaceable into contact with said stairlift rail; and operating means operable, when the speed of said carriage along said rail exceeds a predetermined maximum, to cause said braking member to engage said rail, said governor being characterised in that said operating means is operable in the event of excessive speed in both of said two directions. Said operating means is preferably constructed and arranged to trigger under the influence of a force induced centrifugally. To this end, said operating means preferably includes guide means rotatable with the movement of said carriage along said rail, and a roller in sliding contact with said guide means, said roller being connected to said braking member. Said roller is preferably mounted for rotation on a first end of an operating lever, the other end of said operating lever being pivotally mounted to said braking member. Preferably said braking member is mounted for rotation about the same axis of rotation as said guide means, said braking member having cam surfaces which are non-concentric with respect to said axis of rotation. Preferably said guide means includes an inner guide surface and an outer guide surface, said roller contacting said inner guide surface when the speed of said carriage is below said predetermined maximum, and contacting said outer guide surface when said speed exceeds said predetermined maximum, said outer guide surface being constructed and arranged to allow the position of said roller to be locked with respect to said guide means. Preferably said outer guide surface includes at least one locking notch sized to receive said roller. Preferably said braking member has a central, inoperative position in which said braking member is symmetrical about an axis passing through the axis of rotation thereof. Preferably said governor further includes a catch to retain said braking member, against rotation, in said central position when not under the influence of said operating means. In a second aspect the invention provides a stairlift carriage including the governor as set forth above. Many variations in the way the present invention may be performed will present themselves to those skilled in the art. The description which follows is intended as an illustration only and the absence of description of particular alternatives or variants should in no way be applied to limit the scope of the invention. Such description of specific elements which follows should also be interpreted as including equivalents whether existing now or in the future. The scope of the invention should be defined solely by the appended claims. Brief Description of the Drawings One form of governor incorporating the various aspects of the invention will now be described with reference to the accompanying drawings in which: Figure 1 : Shows an elevational view of a governor according to the invention; Figure 2: Shows a similar view to that shown in Figure 1 but with certain detail omitted ; Figure 3: Shows a sectional view through the governor shown in Figure 1 ; and Figure 4: Shows a view along the line IV-IV in Figure 3. Description of Working Embodiment Referring to the drawings, the present invention provides a governor 5 for a stairlift carriage (not shown), the carriage being moveable, in the conventional manner, along a rail, a surface of which is indicated by reference numeral 6 in the drawings. As will be apparent from Figure 3 the rail surface 6, in this embodiment, is aligned at 45 ° to the horizontal. In the form shown, the governor 5 includes a mounting bracket 7 which forms the basis of the governor. The bracket 7 comprises an angled upper mounting section 8 so configured that when section 8 is mounted on a vertical side plate 9 of the carriage, the locking members of the governor (described in detail below) are arranged to engage rail surface 6 aligned at 45 ° to the horizontal. The mounting section 8 extends down into a lower section 10. Mounted on, and extending through, the lower section 10 is a bearing journal 11 in which shaft 12 is rotatably mounted. Mounted at one end of the shaft 12 is a drive gear 13. The drive gear 13 is configured and mounted so as to engage a drive rack 13a extending along the rail surface 6, the drive rack fo-rming part of the main drive system serving to power the stairlift carriage along the rail. Mounted at the opposite end of shaft 12, so as to rotate with drive gear 13, is a flywheel 14 forming part of an operating means which will be described in greater detail below. The governor further includes a braking member 15 which is rotatable on the outer surface of the journal 11 , is thus independent of the drive gear 13, and is displaced about journal 11 by a link arm 16. Link arm 16 is pivotally mounted, at one end thereof, on the braking member 15 and includes, at its other end, a roller 17. The roller 17 engages in guide track 18 (Figure 4) provided on the inner surface of flywheel 14, thereby connecting the flywheel 14 to the braking member 15. As will be described in greater detail below, the connection is a sliding connection for so long as the speed of the carriage is below the predetermined maximum speed, but becomes a fixed connection in the event the speed of the carriage exceeds the predetermined maximum. It will be appreciated that arrangement of the arm 16 and roller 17 is such that the roller normally rests, under gravity, on the inner guide surface defined by the inner central part 19 of the flywheel. The system is so configured that, at acceptable operating speeds, gravity is sufficient to maintain the roller in contact with inner central part 19. However, should the speed of the carriage (and thus the rotational speed of shaft 12 ) exceed an acceptable level , the roller moves outwards under centrifugal action to engage outer guide surface 20. As can be seen from Figure 4, outer guide surface 20 is adapted to lock the position of roller 17 and, to that end, preferably includes at least one, and more preferably two, braking notches 21. It will be appreciated that, when the roller 17 enters one of the notches 21 further rolling action over the outer guide surface is prevented and the position of the roller is effectively locked with respect to the guide. In this event, the rotation of the flywheel 14 is transferred to the braking member 15 through link arm 16. As can be seen most clearly in Figure 2, the braking member 15 has a central in-operative position in which the member 15 is substantially symmetrical about a vertical line 22 passing through the pivot axis on which the braking member is mounted. To either side of line 22 the braking member includes cam surfaces 23 arranged to engage the rail surface as the braking member is pivoted about its mounting axis. The cam surfaces may be provided with teeth 24 or the like to enhance frictional engagement with the rail as the braking member is pivoted into engagement with the rail 6. To prevent the braking member inadvertently moving into engagement with the rail 6, catch means is preferably provided to maintain the braking member in the central position as shown in Figures 1 and 2, when not under the influence of the flywheel 14. However, the catch means is such that the same is overridden by flywheel effect when the roller 17 engages in one of locking notches 21. In the form shown the catch means comprises a simple leaf spring 26 mounted on bracket 7 and having a central indent (not shown) to receive one end of locking pin 27 extending from the rear face of braking member 15. When roller 17 engages in one of notches 21, the pin 27 is forced out of the indent in the leaf spring 26. Finally, in the form of governor depicted and described herein, electrical switch 30 is provided, the switch 30 being mounted so as to be activated by upper lobes 31 on the braking member 15, when the barking member 15 is pivoted into an operative position, to cut power to the carriage drive motor (not shown). Since the braking member and the inner guide surface are symmetrical, the governor as described herein, will work equally effectively in both directions. This means that the same governor can be used regardless of whether the carriage is to be left or right-handed. This in turn reduces expense and the likelihood of installation-related problems. It will thus be appreciated that the present invention, at least in relation to the working embodiment described herein, provides a relatively simple form of over-speed governor for a stairlift capable of effective operation regardless of the orientation of the stairlift installation.

Claims: Claims 1) A governor for a stairlift carriage, said carriage being moveable along a stairlift rail in two dire ctions, said governor including: a braking member displaceable into contact with said stairlift rail; and operating means operable, when the speed of said carriage along said rail exceeds a predetermined maximum, to cause said braking member to engage said rail, said governor being characterised in that said operating means is operable in the event of excessive speed in both of said two directions. 2) A governor as claimed in cl-aim 1 wherein said operating means is constructed and arranged to trigger under the influence of a force induced centrifugally. 3) A governor as claimed in claim 2 wherein said operating means includes guide means rotatable with the movement of said carriage along said rail, and a roller in sliding contact with said guide means, said roller being connected to said braking member. 4) A governor as claimed in claim 3 wherein said roller is mounted for rotation on a first end of an operating lever, the other end of said operating lever being pivotally mounted to said braking member. 5) A governor as claimed in claim 3 or claim 4 wherein said braking member is mounted for rotation about the same axis of rotation as said guide means, said braking member having cam surfaces which are non-concentric with respect to said axis of rotation. 6) A governor as claimed in any one of claims 3 to 5 wherein said guide means includes an inner guide surface and an outer guide surface, said roller contacting said inner guide surface when the speed of said carriage is below said predetermined maximum, and contacting said outer guide surface when said speed exceeds said predetermined maximum, said outer guide surface being constructed and arranged to allow the position of said roller to be locked with respect to said guide means. 7) A governor as claimed in claim 6 wherein said outer guide surface includes at least one locking notch sized to receive said roller. 8) A governor as claimed in any one of the preceding claims wherein said braking member has a central, inoperative position in which said braking member is symmetrical about an axis passing through the a xis of rotation thereof. 9) A governor as claimed in claim 8 further including a catch to retain said braking member, against rotation, in said central position when not under the influence of said operating means. 10) A governor for a stairlift when constructed arranged and operable substantially as described and as illustrated in the accompanying drawings. 11) A stairlift carriage including the governor as claimed in any one of claims 1 to 10 .

Inventors: JENKINS MARTYN HARRY, JENKINS, MARTYN, HARRY
Applicants: JENKINS MARTYN HARRY, STANNAH STAIRLIFTS LTD, JENKINS, MARTYN, HARRY, STANNAH STAIRLIFTS LIMITED
Application year: 2000
Main classification: B66B5
IPC codes: B66B5, B66B9