NZ207406A - Lift platform moving vertically and extending horizontally - Google Patents

Description

Priority Date(s): #-3 Complete Specification Filed: Class: Publication Date: ... ^ 3 1985 • ■ P.O. Journal, No: J'pi-3% N.Z.No. fVM<- NEW ZEALAND Patents Act 1953 COMPLETE SPECIFICATION "LIFT/. " We, ALPHA LIFTS LIMITED, a British company of Unit 31, Pensnett Trading Estate, Kingswinford, West Midlands, DY6 7PU England do hereby declare the invention, for which we pray that a Patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement : - ^ (Followed by 1A.) lA 207406 LIFT This invention relates to a lift.

Negotiating short flights , of steps can present problems for invalid and infirm people who are confined to wheelchairs, or have difficulty in walking, and for the movement of loads or cumbersome objects. Ramps are sometimes provided which enable the steps to be by-passed 10 but even they are not always easy to negotiate, and there are situations where ramps cannot be provided.

The invention consists in a lift comprising a support structure, a load-supporting, horizontally extensible 15 platform mounted on the support structure comprising first and second parts both of which are constructed to provide support for a load on the platform and of which the first part is vertically movable relative to the support structure and the second part moves with the 20 first part and also horizontally with respect to the first part, drive means by which the first part is moved vertically relative to the support structure, and guide means on the support structure with which the second part co-operates whereby as the first part is moved vertically 25 the second part is caused to be moved horizontally relative to the first part to form a horizontal extension thereof.

Because the second part extends the platform 30 horizontally as it is moved vertically, the lift may be used in association with steps. The lift is arranged for such use so that the second part extends over the steps as the platform is moved up and down with respect to the steps and enables a user of the lift to move straight on 35 to and off the platform at the different levels connected by the steps. rv a 207406 2 Preferably the second part is arranged to lie directly underneath, within the downwardly projected plan area of, the first part when the platform is in its lowermost position.

The platform may have a ramp or ramped approach surface or edge by which a wheelchair, for example, can be run on to the platform when it is in its lowermost position. It would be possible alternatively for the 10 lift to be set into ground or floor, as the case may be, at the lower of the two levels it is to connect such that in the lowermost position of the platform its surface lies level with the ground or floor. The latter arrangement makes it desirable for the lift to be 15 installed as a fixture for use, however there is not a general necessity for the lift to be installed as a permanent fixture for use and so it may possibly be made as a portable unit.

A hand rail or rails may be provided on the platform, and/or side walls to close in a user of the lift whilst it is in operation.

The drive means for moving the first part of the 25 platform may take various forms. A mechanical drive may be provided, for example, by means of one or more screw jacks operating between the support structure and the first part, or by toggle or lazy tong linkages, or by chain or rack and pinion drives. An hydraulic or pneu-30 matic drive may be used. In a preferred embodiment the first part is moved vertically by means of an air bag underneath the platform. An air has the advantage that when deflated it can collapse to occupy minimal space and it 207406 3 thereby imposes minimal limitations on the level to which the platform can be lowered on the support structure.

Conveniently the drive means is powered by an electrically energised prime mover. Mains or battery 5 electric supply may be used. Mains electric may be used as the primary supply and a battery electric supply may be provided as a stand-by in case of failure of the mains supply. For reasons of safety it is desirable that the electric supply is limited to being of not more than 12 10 volts. Controls for the electric supply may be provided at the platform to be operated by a user riding on the lift, and may also be provided to be positioned at the levels between which the lift operates when installed for use. Limit switches are preferably installed to cause 15 the drive means to be stopped automatically at the limits of the vertical movement of the platform. Safety switch means may also be provided on the platform to cause the platform to be stopped automatically in the event that the platform meets an obstruction in the path of its 20 vertical movement.

A lift embodying the invention will now be described by way of example with reference to the accompanying drawings in which Figure 1 is a perspective view of the lift showing 25 its platform in a partially raised position, Figures 2 and 3 are side and end views respectively of the lift in the partially raised position, and Figures 4 and 5 are enlarged fragmentary views showing joints between members of a support 30 structure of the lift. n-) < n The lift comprises a support structure 1, a platform 2 and an air bag 3. An electrically driven compressor for inflating the air bag 3 is not shown, nor are controls for controlling the operation of the 5 compressor.

The support structure 1 comprises a rectangular base frame 4 having two side members 5 and front and rear end members 6, 7, a pair of upright members 8 and a pair of sloping guide members 9. All of the members are made of 10 similar, standard rolled channel-section having inwardly-turned flanges 10, see Figures 4 and 5, at the open side of the channel. The side members 5 of the base frame 4 are disposed with their open sides facing, and the end members 6, 7 are disposed with their open sides 15 uppermost. At their rearward ends the side members 5 are fixed on top of the rear end member 7. They are fixed by means of angled tie plates 11, Figure 4, which are fitted with their limbs against the adjacent open sides of the respective side member and the rear end member 20 and fixed to the members by bolts 12 passed through the tie plates, through the mouths of the open sides of the members and tightened into retaining plates 13 located inside the members by the inwardly-turned flanges 10. At their forward ends the side members 5 are fixed to the 25 rear sides of the upright members 8, the upright members being fixed on top of the front end members 6. The upright members 8 are disposed with their open sides facing. The side members are fixed to the upright members 8 by means of angled tie plates 14, Figure 1, 30 having lateral extensions to their upright limbs, the lateral extensions and upright limbs respectively extending across the open sides of the side and upright members and bolts being passed through the tie plates 14, through the mouths of the open sides of the members and 35 tightened into retaining plates located inside the 207 4 06 members by the inwardly-turned flanges 10. The upright members 8 are fixed on the front end members 6 by means of the horizontal limbs of the angled tie plates 14, which sit on the front end members, and by bolts which 5 are passed through those limbs and tightened into retaining plates located inside the front end members. The sloping guide members 9 are connected by hinges 15 at their lower ends on top of rearward ends of the side members 5. Their higher, forward, ends are fixed to the 10 upper ends of the upright members 8 by flat tie plates 16 which extend across the open sides of the members and bolts 17 which are engaged with the tie plates and tightened into retaining plates 16' located inside the members at their open sides, Figure 5. The sloping guide 15 members 9 are disposed with their open sides facing and they present facing, parallel inclined guide-ways 18. The end members 6, 7 are adapted to be secured by bolts or screws to the surface on which the support structure 1 is to stand for use to fix the structure against 20 movement.

The members of the support structure may be fixed together in other suitable ways, if desired. At least the side and end members and the upright guide members may, for example, be fixed together by welding.

Fixed to the undersides of and extending between the end members 6, 7 at intermediate parts thereof are flat, longitudinal sub-frame members 19 which are spanned at intermediate parts of their lengths by three flat, transverse, sub-frame members 20. One of the transverse 30 sub-frame members 20 is posi-tioned on- the central transverse axis of the base frame and the other two transverse sub-frame members are equally spaced in front of and behind that central member. 6 The platform 2 comprises a horizontal top part 21 and a lower, horizontal extension part 22, each being formed by a rectangular plate.

The top part 21 is of a similar length to the base 5 frame 4 and its width is slightly less than the horizontal spacing of the side members 5, and of the upright members 8. Secured to the underside of the top plate 21, along the two longer sides of the part, are two angle-section members 23 by which an under-frame 24 is 10 secured below the top part. The under-frame 24 comprises a pair of bearer members 25 extending longitudinally of the top part directly below its longer sides, a cross-member 26 fixed on top of the bearer members at the forward end of the top part, which is directly above the 15 front end member 6 of the base frame, two intermediate transverse members 27 fixed between the bearer members, and two intermediate longitudinal members 28 fixed between the intermediate transverse members 27. The intermediate transverse and longitudinal members 27, 28 20 are disposed to be centrally above the longitudinal and transverse sub-frame members 19 and 20 respectively. The cross-member 26 has up-turned end portions 29 by which it is fixed to the angle-section members 23 at the forward end of the top part, adjacent to the upright member 8 of 25 the support structure. Outrigger brackets 30 fixed to the bearer members 25 of the rearward end of the under-frame 24 have upstanding lugs 31 on them which are fixed to the angle-section members 23 at the rearward end of the top part.

The bearer members 25 are made of standard rolled channel-section, similar to the sections used in the support structure. They are aligned with their open sides directed outwards away from one another. The intermediate transverse and longitudinal members 27, 28 207 A 7 are also made of standard rolled channel-section and they co-extensively on top of each bearer member 25 is a channel-section to the bearer member but shorter than the bearer member. The guide members 32 are disposed with their open sides facing inwards towards one another.

The top part 21 of the platform 2 is connected at opposite sides of its under-frame 24 to the side 10 members 5 of the base frame 4 by two pairs of scissor links 33, 34, that is links which are pivoted together in scissors fashion. The scissor links 33, 34 of each pair are of equal lengths and are pivoted together about a horizontal pivot 35 which is slightly offset from the 15 mid-points of the lengths of the links towards lower ends of the links. A first link 33 of each pair-, which is innermost, is pivoted at a lower, rearward end about a fixed pivot 36 to an angle bracket, not shown, secured to the respective side member, at the inner side of that 20 member, towards the rearward end of the member. An upper, forward end of that first link is pivotally and slidably connected to the respective bearer member 25 of the under-frame 24 by means of a roller 38 engaged in the open-side of the bearer member. The second link 34 of 25 each pair is pivoted at an upper, rearward end about a fixed pivot 39 to one of the outrigger brackets 30 (that is above the fixed pivot 36 of the rearward end of the first link 33) , and at a lower, forward end is pivotally and slidably connected to the respective side member by a 30 roller 40 engaged in the open-side of the side member. The rearward ends of the first links 33 of the two pairs of scissor links are joined by a cross rod 41. The rearward ends of the second links 34 are also joined by a cross rod 42, the bearer . members 25 being suitably 35 cut-away to allow the cross rod 42 to extend through them are disposed with their open sides uppermost. Fixed horizontal guide member 32 of similar rolled />' ""V 8 between the outrigger brackets 30. The scissor links can be pivoted to a position in which they are almost horizontal, the angle brackets 37 and the positions at which the links are pivoted together allowing the cross 5 rod 42 joining the second links 34 to move down rearwardly beyond the cross rod 41 joining the first links 33.

Hand rails 43 are mounted on the opposite sides of the top part 21 of the platform. They are each formed 10 from a length of round-section metal tube bent to an inverted U-shape, the transverse portion of the U forming the hand rail proper, and the parallel limbs of the U forming supporting legs 44.

Extension part 22 of the platform 2 is shorter than 15 the top part 21 and it is sufficiently narrow to fit between the two angle-section members 23 at the sides of the top part. Angle-section side members 45 are secured to the underside of the extension part along its opposite sides. Mounted on the underside of the extension part 22 20 towards its rearward end, by angle-brackets 46, Figure 3, are co-axial guide rollers 47 which run in the open sides of the horizontal guide members 32. At a position intermediate those guide rollers 47 and the rearward end of the extension part two further co-axial rollers 48 are 25 provided which are mounted one on the outside of each of the angle-section side members 45. These rollers 48 run in the inclined guide-ways 18 of the sloping guide members 9. Adjacent to the forward end of the top part 21, the extension part 22 is supported on a pair of 30 co-axial support rollers 49, Figure 3, mounted on upstanding angle brackets 50 secured on the cross-member 26 of the under-frame 24. 9 It will be understood that the extension part 22 is immediately below the top part 21 on the under-frame 24. The extension part 22 can slide from a withdrawn position in which it is completely contained underneath the top 5 part to projected positions in which it extends horizontally forwards from the top part and forms an extension of the top part. The sliding movement is guided by the guide rollers 47 of the extension part running along the horizontal guide members 32, the 10 extension part moving over and being supported by the support rollers 49 during the movement. When the extension part is fully withdrawn its forward end is set back from the forward end of the top part.

The sliding movement is brought about through the 15 engagement of the further rollers 48 of the extension part 22 with the inclined guide ways 18 of the sloping guide members 9. As the platform is moved vertically, the rollers 48 run along the inclined guide ways 18 and thereby cause the extension part to move horizontally 20 relative to the top part. The arrangement is such that as the platform is raised the extension part projects forwards progressively from the top part, and as the platform is lowered the extension part is progressively withdrawn until at the lowermost position of the platform 25 the extension part is fully withdrawn underneath the top part. At the lowermost position of the platform the scissor links 33, 34 are almost horizontal so that the platform is close to the surface on which the support structure stands for use of the lift. Typically the 30 upper surface of the top part is about 3.5 inches (8.89 cms) above the surface. At the top of the vertical movement the top part is close to the level of the top of the upright members 8 of the support structure, as indicated in Figure 2. 20740 As the forward end of the extension part is set back from the forward end of the top part when it is fully withdrawn, which is the position the extension part occupies when the platform is at its lowermost position, 5 the extension part does not project from the top part in the initial stages of upward movement of the platform.

Vertical movement of the platform is effected by means of the air bag 3. The air bag is of cylindrical concertina form and extends centrally between. the base 10 frame 4 and the under-frame 24 of the top part 21 of the platform. Its ends are anchored respectively to the sub-frame members 19 and 20 at the base frame and to the intermediate transverse and longitudinal members 27, 28 of the under-frame. The air bag is of a diameter such 15 that is occupies a substantial part of the width of the under-frame. When collapsed the air bag is contained within the height of the side members. 5 of the base frame.

The scissor links maintain the platform in a 20 horizontal attitude as it is moved vertically by the air bag. As the rearward ends of the links are pivoted at the fixed pivots 36, 3 9 the forward ends of the links move towards and away from those fixed pivots during the relative angular movement of the links as the platform is 25 respectively raised and lowered, the rollers 38 at the forward ends of the first links 33 running along the bearer members 25 of the under-frame 24 and the rollers 40 at the forward ends of the second links 34 running along the side members 5.

Air is supplied to the bottom of the air bag 3 by a supply line, not shown, from the compressor which, depending upon the situation in which the lift is to be used, may be located underneath the support structure or 2074 06 n at some suitable position remote from the support structure. As the air bag is effective on a large area of the platform it can operate under relatively low pressure to raise the platform. The compressor is 5 powered by a mains electric supply. The electrical system of the lift is limited to 12 volts. An electrically operated vacuum exhaust, not shown, extracts air from the air bag to control deflation of the air bag, and thereby lowering of the platform. A relief valve and 10 the weight of the platform may be relied upon as an alternative for lowering the platform but the vacuum exhaust is preferred for the better control it affords over the lowering of the platform. A low pressure valve, not shown, is provided at the air bag which senses 15 the change in pressure during lowering of the platform resulting from, for example, jamming of the platform for any reason or puncturing of the air bag, and causes the vacuum exhaust to be stopped, or to operate at a slower rate to reduce the deflation of the air bag.

Limit switches, not shown, are positioned on one of the upright members to be operated by the top part of the platform to cause the compressor or vacuum exhaust, as the case may be, to be stopped automatically when the platform reaches the limits of its vertical movement. 25 Control switches are located on one of the hand rails 43 for manually controlling operation of the air bag through the compressor and vacuum exhaust, and there are further control switches which when the lift is installed for use will be located at suitable positions for manual 30 actuation at the levels between which the lift is to operate.

If the air bag is left inflated for a long period some air may be lost and consequently the platform may sink to some extent from a raised position in which it 35 has been left. To deal with this eventuality a 12 compensating switch, not shown, is positioned on one of the upright members to be operated if the platform sinks a pre-determined distance from the raised position and cause the compressor to be energised to top up the air bag again with air and move the platform back to the raised position. Typically the compensating switch is arranged to be operated if the platform sinks % inch (1.27 cm) from the raised position.

A ramp 51, having an associated barrier 52, is hinged to the rearward end of the top part 21 of the platform. The ramp 51 comprises a plate of similar width to the top part with angle-section side members 53 secured along opposite sides of the underside of the plate. Blocks, not shown, with co-axial horizontal bores in them are fixed beneath the forward end of the plate and align with eye brackets 54 fixed to a transverse angle-section member, not shown, secured to the underside of the top part along its rearward end. A rod 55 passed through the blocks and eye brackets hingedly connects the ramp to the top part 21. The barrier 52 comprises a parallel pair of rigid plate strips 56 fixed flat against the top of the plate of the ramp adjacent to and projecting forwards from the forward end of the plate, and a cross plate strip 57 fixed across the forward ends of the parallel plate strips 56. When the platform is in its lowermost position the ramp slopes down at a relatively shallow angle from the top part to provide easy access on to the top part for, for example, a wheelchair. The barrier 52 is disposed in an inoperative position close to the upper surface of the top part in this position of the platform and so does not hinder access on to, or movement off, the top part. As the platform is raised from the lowermost position the ramp pivots, under gravity, about its hinged connection to the top part, its rearward end moving forwardly towards the support 207406 13 structure. The movement of the ramp raises the barrier away from the top part. In the raised position it is able to prevent a wheelchair, for example, from being moved off the rear end of the top part whilst the 5 platform is raised. The forward swinging movement of the ramp is limited by a stop, not shown, such that when the ramp is lifted out of contact with the surface on which the support structure stands it depends at an angle which will allow it to be moved rearwards about the hinged 10 connection upon re-engagement of its rearward end with the surface when the platform is lowered again.

It will be understood that the lift may be made in a range of sizes to suit flights of steps of different lengths and heights. By adjustment of the position of 15 the upper limit switches the extent of the vertical movement of the platform may be adjusted to suit . the height of a flight of steps with which the lift is intended to be used.

For use the lift is positioned at the bottom of the 20 flight of steps with which it is to be used, the forward end of the platform towards the riser of the bottom step. The support structure is anchored to the surface on which it stands. As the platform is raised the extension part 22 moves forwards horizontally over the steps. When 25 the platform reaches its fully raised position the extension part extends to the top of the flight of steps and so forms a bridge from there to the top part of the platform. The delay before the extension part projects from the top part in the initial stages of the upward 30 movement of the platform is sufficient to allow the platform to move past the bottom step without the extension part fouling the riser. 2074 06 14 The lift user may operate the lift himself from the control switches at the one hand rail, or someone else may operate the lift for him at either of the levels served by the lift by means of the control switch at the 5 respective level.

As illustrated the inclination of the sloping guide members 9 is such that there is a substantially 1:1 relationship between the vertical movement of the platform and the horizontal movement of the extension 10 part. However the inclination may be altered to give a different relationship, if desired. The hinge connection of the sloping guide members to the side members 5 of the base frame facilitates this, and enables fine adjustment of the inclination to be made on site. The upper ends of 15 the sloping guide members are cut as necessary for proper engagement with the upright members for them to be secured together by the tie plates.

Lost motion to delay the start of forward movement of the extension part during the initial stage of the 20 upward movement of the platform may be provided by forming a dog leg in the lower ends of the sloping guide members 9. Thus the horizontal movement may be delayed until the platform is above the level of the bottom step of a flight of steps.

Other suitable arrangements may be provided instead of the scissor links for retaining the platform in the horizontal state as it is raised and lowered, and for moving the extension part of the platform horizontally relative to the top part. For example, the support 30 structure may have upright guide members with which the top part engages, or elements associated therewith engage, to guide the platform in its vertical movement. The extension part may co-operate with links which as the 2074 0 * platform is moved vertically causes the extension part to move horizontally relative to the top part. For example, the extension part, guided for horizontal movement by guide members on the top part, may have connecting elements, such as pins or rods, which slidingly engage in slots extending along links pivoted about a horizontal axis to the base frame of the support structure. In such an arrangement the pivotal axis of the links is towards the forward end of the base frame and the links extend rearwards from the pivots. In the lowermost position of the platform the links may be almost horizontal. As the platform is raised the resultant forward pivoting of the links causes the extension part, by the engagement of the connecting elements with the slots, to be projected fowards from the top part. The action is reversed as the platform is lowered. Some lost motion may be afforded between the connecting elements and the links to permit some initial upward movement of the platform before the extension part commences its horizontal projecting movement.

The lift may be used indoors and out of doors. 16 2074O6

Claims (19)

WHAT WE CLAIM IS:

1. A lift comprising a support structure, a 5 mounted on the support structure comprising first and second parts both of which are constructed to provide support for a load on the platform and of which the first part is vertically movable relative to the support structure and the second part moves with the 10 first part and also horizontally with respect to the first part, drive means by which the first part is moved vertically relative to the support structure, and guide means on the support structure with which the second part co-operates whereby as the first part is 15 moved vertically the second part is caused to be moved horizontally relative to the first part to form a horizontal extension thereof.

2. A lift according to claim 1 wherein the second 20 part lies directly underneath, within the downwardly projected plan area of, the first part when the platform is in its lowermost position.

3. A lift according to claim 2 wherein fixed to and 25 underneath the first part is an under-frame which supports the second part.

4. A lift according to claim 3 wherein the under-frame includes guide members extending 30 horizontally in the direction of horizontal movement of the second part, the second part has runner elements which engage with and are supported by the guide members, and the under-frame also has supporting elements which are spaced from the runner elements in 35 the direction of horizontal extending movement of the second part and over which supporting load-supporting, horizontally extensible platform 207406 17 second part passes, the arrangement being such that the second part is supported at horizontally spaced positions by the engagement of the runner elements of the second part with the guide members and by the 5 supporting elements on the under-frame.

5. A lift according to claim 4 wherein the runner elements of the second part and the supporting elements are rollers.

6. A lift according to any preceding claim wherein the platform is retained in a horizontal attitude within the range of its vertical movement by pairs of links pivoted in scissors fashion at opposite sides of 15 the platform, being pivotally connected about spaced horizontal axes to the support structure and to the first part with the respective pivotal connections at the support structure and the first part being relatively movable horizontally to allow the relative 20 angular movement between the links as the first part is moved vertically.

7. A lift according to claim 6 as dependent from any one of claims 3 to 5 wherein one link of each pair is 25 pivoted at a lower end about a fixed horizontal axis to the support structure and is connected at an upper end by a horizontally slidable pivot to the under-frame, and the other link of each pair is pivoted at an upper end about a fixed horizontal axis to the under-frame 30 and is connected at a lower end by a horizontally slidable pivot to the support structure.

8. A lift according to claim 7 wherein the slidable pivots of the links are provided by rollers, and the 35 under-frame and the support structure have 10 18 207406 10 channel-section members in the open sides of which the rollers are engaged.

9. A lift according to any one of claims 1 to 5 wherein the first part is guided in its vertical movement by upright guide members incorporated in the support structure having vertically extending guide-ways with which elements of the first part co-operate.

10. A lift according to claim 4 or claim 5, or any one of claims 6 to 9, as dependent from claim 4 or claim 5, wherein the support structure has sloping guide members adjacent to opposite sides of the platform which slope 15 upwards in the direction in which the second part is caused to be projected horizontally from the first part, the sloping guide members having guide-ways extending therealong, and the second part has runner means which co-operate with the guide-ways such that as 20 the platform is moved vertically the runner means travel along the guide-ways and cause the second part to move horizontally relative to the first part.

11. A lift according to claim 10 wherein when the 25 platform is in its lowermost position the second part has its forward end set back from the adjacent end of the first part such that in the initial stages of upward movement of the platform the second part does not project from the first part as it moves 30 horizontally.

12. A lift according to claim 10 wherein each sloping guide member has a dog leg at its lower end whereby in the initial stages of upward movement of the platform 35 the second part is held against moving horizontally relative to the first part. > ^ f'Y oft v t 19 £07406

13. A lift according to claim 4 or claim 5, or any one of claims 6 to 9 as dependent from claim 4 or claim 5, wherein links are pivoted to the support structure about a horizontal axis which is disposed towards that 5 end of the first part from which the second part is caused to be projected, the links extending upwardly from the horizontal axis and away from said end of the first part and having slots extending therealong, and the second part has connecting elements which 10 co-operate with the slots such that as the platform is moved vertically the connecting elements travel along the slots and the interengagement of the connecting elements with the slots causes the links to turn about the horizontal axis and thereby move the second part 15 horizontally relative to the first part.

14. A lift according to claim 13 wherein there is lost motion between the connecting elements and the slots in the initial stages of upward movement of the platform 20 such that the second part is held against moving horizontally in these stages.

15. A lift according to any preceding claim wherein the drive means comprises an air bag underneath the 25 platform which is inflated to raise the first part.

16. A lift according to claim 15 wherein the air bag is of cylindrical concertina form extending centrally between and anchored to the first part and a base part 30 of the support structure.

17. A lift according to claim 15 or claim 16 wherein air is supplied to the air bag by an electrically powered compressor. 35 20 207406

18. A lift according to claim 17 wherein an electrically operated vacuum exhaust extracts air from the air bag to control deflation of the air bag. 5

19. A lift according to claim ]7 or claim 18 wherein manually operated controls for controlling the electrical supply to the compressor, or to the compressor and the vacuum exhaust, are provided on the platform. claims 17 and 18 wherein manually operated controls are provided for the electrical supplies to the compressor and vacuum exhaust which controls, when the lift is 15 installed for use, are located at positions for manual actuation at the levels between which the platform is to move.

21. A lift according to claims 17 and 18, claim 19 as 20 dependent from claim 18, or claim 20, wherein limit switches are provided on the support structure which are arranged to be operated by the platform, or means associated therewith, when the platform reaches the limits of its vertical movement thereby to cause the 25 compressor or the vacuum exhaust, as the case may be, to be stopped at the ends of the movement controlled by those parts.

22. A lift according to any one of claims 17 to 21 30 wherein a compensating switch is positioned on the support structure to be operated if the platform sinks a pre-determined distance from a raised position in which it has been left, operation of the compensating switch causing the compressor to be energised to supply 35 further air to the air bag to return the platform to the raised position. 10

20. A lift according to claim 19 as dependent from 207*06 21

23. A lift according to any preceding claim wherein the platform is provided with a hand rail or rails.

24. A lift according to any preceding claim wherein 5 the platform has a ramp hingedly connected to it about a horizontal axis for access on to the platform in the lowermost position of the platform.

25. A lift according to claim 24 wherein a barrier is 10 carried by the ramp which when the platform is in the lowermost position lies in a lowered inoperative position relative to the platform in which it allows access on to and movement off the platform of, for example, a wheelchair, and which is caused to be raised 15 to an operative position by angular movement of the ramp about its hinged connection to the platform as the platform is raised.

26. A lift according to any preceding claim which is a 20 portable unit.

27. A lift substantially as described herein with reference to and as illustrated by the accompanying drawings. 25 ALPHA LIFTS LIMITED By their attorneys 30 35