GB2369344A

GB2369344A - Wheelchair access ramp for a vehicle

Info

Publication number: GB2369344A
Application number: GB0123226A
Authority: GB
Inventors: David Moore
Original assignee: PERCY LANE PRODUCTS Ltd
Current assignee: PERCY LANE PRODUCTS Ltd
Priority date: 2000-10-03
Filing date: 2001-09-27
Publication date: 2002-05-29
Also published as: GB0024215D0; GB0123226D0

Abstract

A wheelchair access ramp for a vehicle comprises a plate 20, a drive assembly 30 for moving the plate horizontally and guide members 24 for guiding the plate into a deployed position. Each guide means is attached to the rear of the plate and comprises of a pair of guide rollers (201, 202 Fig 6) which run along a channel (420 Fig 6) in a guide rail 42. When the plate is near full extension, the front roller (202) drops slightly with respect to the rear roller (201) and thus the front edge of the plate is lowered to the ground. Springs (51,52 Fig 3) are provided to ensure that the plate lowers smoothly and also to store energy to assist in the lifting of the plate. The drive assembly 30 comprises two drive arms 31,32 which cooperate with the plate and with each other.

Description

Wheelchair Access Ramp for a Vehicle

The present invention relates in general to a wheelchair access ramp for a vehicle.

It is desired to provide an access ramp such that a wheelchair user may enter and exit a vehicle conveniently and safely. In one example, the vehicle is a public service vehicle such as a bus. Preferably, the access ramp is carried on the vehicle and deployed when access is required, ideally without any manual intervention.

Further, it is desired that a main surface of the ramp is at a moderate angle when deployed, suitably no greater than 15 or 200 to the horizontal. However, it is also desired that the overall slope length of the ramp is as short as possible, such that the ramp is relatively compact for storage on the vehicle when not deployed. A problem arises in that reducing slope angle and reducing slope length are inherently incompatible.

Another problem arises in that it is desired to provide a ramp having a smooth main surface, ideally free from perturbations. For example, the ramp should present a local step height no greater than about 15mm. In particular, it is desired to avoid a substantial change of level where the main surface of the ramp meets an entry threshold of the vehicle.

Another problem arises in that it is desired to provide a ramp which may be deployed with a smooth movement. Ideally, it is desired to avoid any sudden movements. Also, it is desired that the ramp should minimise the risk of collisions during deployment.

Further still, it is desired that the ramp has a construction which is robust and reliable in use, and preferably which is easy to install and maintain.

An aim of the present invention is to provide a wheelchair access ramp which addresses at least some of the problems discussed above. Preferred embodiments of the invention aim to provide a wheelchair access ramp which provides a reasonable compromise between slope angle and slope length, presents a smooth slope surface, deploys smoothly and safely, and/or is compact, robust and reliable.

According to the present invention there is provided a wheelchair access ramp for a vehicle, comprising a leaf, a drive assembly for moving the leaf along a generally rectilinear path from a retracted position toward a deployed position, and guide means for guiding movement of the leaf in a direction generally transverse to the generally rectilinear movement.

Preferably, the drive assembly is arranged for rectilinear movement within a generally horizontal plane, and the guide means is arranged such that a forward edge of the leaf depends downwardly of that horizontal plane as the leaf moves to the deployed position. The leaf is arranged to travel in a generally horizontal plane for a major portion of the rectilinear movement.

Preferably, the guide means comprises a first guide means co-operating with a second guide means to constrain the relative orientation of the first guide means during movement of the leaf from the retracted position toward

the deployed position, and arranged to allow alteration of the relative orientation of the first guide means as the leaf moves to the deployed position. Suitably, the first and second guide means are arranged such that gravity assists alteration of the relative orientation of the first guide means. Preferably, the guide means is arranged such that altering orientation of the first guide means causes a rearward edge of the leaf to rise as the leaf moves to the deployed position. Preferably, the second guide means comprises a guide channel, and the first guide means comprises a channel follower, such as a plurality of guide rollers. In one embodiment the guide means comprises a pair of guide rollers co-operating with a guide channel, the guide channel having a first portion arranged to maintain the pair of guide rollers in a fixed position relative to one another, and a second portion arranged to allow the guide rollers to alter relative position. Suitably, the guide rollers are carried by the leaf, and a guide rail defines the guide channel. Such a guide means is ideally provided to either side of the leaf.

The guide means defines a pivoting movement of the leaf about a pivot axis. Suitably, the pivot axis is moved along a generally rectilinear path, in response to movement of the leaf by the drive assembly. Preferably, the pivot axis moves along a travel path that extends forward of a front edge of the leaf, when in the retracted position. In use, the pivot axis is moved to lie outside a vehicle carrying the access ramp.

Preferably, the leaf comprises a rearward edge region, and the drive assembly is arranged to lie at least

partially forward of the rear edge region of the leaf, when the leaf is in the retracted position, more preferably to lie mostly forward of the rear edge region of the leaf, and most preferably substantially completely forward of the rear edge region of the leaf, when the leaf is in the retracted position.

Preferably, the drive assembly comprises at least one actuator arranged underneath and/or to one side of the leaf, when in the retracted position, and coupling means for coupling between the leaf and the actuator. The coupling means is arranged for operation in a plane parallel to and vertically offset from the path of generally rectilinear movement of the leaf, and preferably the coupling means is arranged to lie underneath the leaf, when in the retracted position.

Preferably, the drive assembly is arranged to drive two spaced apart mounting points of the leaf, the mounting points moving with respect to each other during movement of the leaf from the retracted position toward the deployed position. Co-ordinating means is provided for coordinating movement of the two mounting points with respect to each other. The co-ordinating means comprises a pair of actuators, and/or a co-ordinating mechanical linkage. The co-ordinating means constrains the drive assembly such that the mounting points move together in co-ordination.

Preferably, the drive assembly comprises at least one drive arm coupled to the leaf and arranged for pivoting movement in a plane generally parallel to the direction of rectilinear movement. In one embodiment the drive assembly

comprises a pair of drive arms, and preferably co-ordinating means including a pair of actuate gears for co-ordinating movement of the drive arms.

Preferably, the access ramp comprises energy transfer means for storing energy released as the leaf moves from the retracted position to the deployed position, and releasing the stored energy to assist return of the leaf from the deployed position toward the retracted position.

Preferably, the leaf comprises first and second portions coupled by a breakout arrangement for maintaining the first and second portions in rigid relation during normal use and allowing relative motion between the first and second portions when the leaf is subject to unexpected loading.

Preferably, the access ramp comprises a cassette holder suitable for permanent installation on a vehicle, and a cassette comprising the leaf and/or the drive assembly and/or the guide means, the cassette being readily releasably coupled to the cassette holder.

For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings in which: Figure 1 is a perspective view of a vehicle carrying a wheelchair access ramp according to preferred embodiments of the present invention; Figure 2 is a perspective view of a leaf;

Figure 3, 4 and 5 are a sequence of perspective views showing operation of a drive arrangement and a guide arrangement; Figure 6 is a detailed perspective view showing part of a preferred guide arrangement; Figure 7 is a detailed perspective view showing part of a preferred leaf; Figure 8 is a detailed perspective view showing a retaining arrangement of the drive and guide assembly; and Figure 9 is a perspective view of a cassette holder assembly.

The preferred embodiment of the present invention will be described with reference to the example of a public service vehicle such as a bus. However, the wheelchair access ramp described is equally applicable to a wide range of vehicles. The access ramp is applicable to a variety of road vehicles including, for example, buses, coaches, and light vehicles, as well as towed trailers.

The access ramp is also applicable to a wide variety of rail vehicles including trams, light rail vehicles, and trains. Further, the access ramp will find application in water borne and airborne vehicles.

The preferred embodiment of the present invention relates to an access ramp, intended to allow easy and convenient access of a wheelchair user into a passenger

vehicle. However, the invention is also applicable to, for example, the loading of goods onto a goods vehicle.

Referring to Figure 1, part of a road vehicle 1 is shown including a lower and outward part of a vehicle body 2, and a road wheel 3. The body 2 is supported on a chassis including a substantial chassis member 4.

Conveniently, the vehicle 1 has a pneumatic suspension system allowing the ride height of the vehicle above a ground surface G to be reduced when the vehicle is stationary, thereby to reduce the height differential between an entry threshold 5 and a pavement or kerb K. A wheelchair access ramp 10 is carried on the vehicle 1 and deployed to provide a continuous access surface between the vehicle threshold 5 and a rest surface such as the kerb K or the ground surface G.

The access ramp assembly 10 includes a leaf 20 providing a major generally planar access surface between the vehicle 1 and the kerb K, and a flap 50 arranged to assist transition between the leaf 20 and the threshold 5 of the vehicle 1. The leaf 20 and the flap 50 move between a deployed outboard position shown in solid lines in Figure 1 and a retracted inboard position shown in dashed lines.

Firstly, the leaf 20 will be described in more detail referring to Figure 2. Then, portions of the ramp assembly which provide movement of the leaf 20 between the inboard and outboard positions will be described in more detail with reference to Figures 3 to 9.

Referring to Figure 2, the leaf 20 presents a generally rectangular platform with a planar access surface 21 over a major portion thereof leading to a tapered section 22 that aids transition to or from a leading edge 23 of the ramp, such as onto a kerb K as shown in Figure 1. An edge strip 27 is provided to protect the leading edge 23. The edge strip 27 preferably comprises collision sensing means. In one preferred embodiment a pneumatic sensing arrangement is employed.

The leaf 20 is preferably integrally formed, to avoid any substantial dislocations in the main access surface 21,22 and to give a stronger, simpler structure. However, whilst a single leaf is preferred, the invention is equally applicable to a leaf comprising multiple sections, such as a telescopic leaf assembly or a folding leaf assembly. The guide portion 24 carries a pair of guide rollers 201,202 at either side thereof. Also, the guide portion 24 provides mounting means 211,221 such as a slide bar for coupling to a leaf drive arrangement described below.

Figure 3 is a perspective view of a leaf drive assembly, with the leaf removed for clarity. The leaf drive assembly 30 comprises a pair of drive arms 31,32.

The first drive arm 31 is coupled at one end thereof to the rearward (innermost) edge of the leaf 20. Preferably, a slider 311 is coupled to the mounting means 211 (shown in Figure 2). The drive arm 31 rotates about a pivot point 312 with a second end 313 of the drive arm 31 being coupled to an actuator, in this case a pneumatic cylinder 33. The drive arm 31 is formed as a lever about the pivot point 312, such that the slider end 311 moves in a broad

arc about the pivot point 312 for a relatively short travel of the second end 313. The second drive arm 32 likewise runs from a slider 321 over a pivot point 322 to a second end 323 coupled to a second actuator 34.

Figure 3 shows the drive assembly in a retracted position, such that the leaf 20 is drawn inboard of the vehicle. Figure 4 shows the drive assembly midway through a drive operation to extend the leaf, and Figure 5 shows the leaf drive assembly in a fully extended position. To extend the leaf 20, the actuators 33,34 pull on the second end 313,323 of each drive arm 31,32 thereby moving the sliders 311,321 about the respective pivot points 312,322 and thereby imparting a generally linear outboard motion to the leaf 20. To retract the leaf 20, the drive assembly is operated in reverse.

It will be noted that the path of each drive arm 31, 32 crosses the other. To avoid interference between the drive arms 31,32, each is cranked in a horizontal plane 314,324 and in a vertical plane 315,325, such that each drive arm has a swan-necked configuration (best shown in Figure 5).

Referring briefly to Figure 1, a problem arises in that the vehicle 1 will typically have a substantial chassis member 4 inboard of the threshold 5, which limits the space available for mounting the ramp assembly 10 on the vehicle 1. Referring again to Figures 3,4 and 5, it will be appreciated that the drive assembly 30 is provided underneath the leaf 20 and to either side thereof, but with minimal components at the rear (inboard) edge 26 of the leaf. Therefore, the leaf 20 may be sized to

substantially fill the available inboard depth between the threshold 5 and the chassis member 4 of the vehicle. This depth is, for example, of the order of some 720mm.

Advantageously, the drive assembly 30 allows the leaf 20 to be formed as a single leaf, presenting a smooth and continuous access surface, whilst maximising slope length and therefore minimising slope angle when deployed.

It is desired that the leaf 20 be driven smoothly and reliably. In particular, it is desired to avoid a twisting movement of the leaf, i. e. rotation in the major plane of the leaf, because twisting causes the leaf to judder or even jam completely. The drive assembly 30 may comprise a single drive arm 31 or 32 mounted, for example, approximately centrally across the width of the leaf 20.

However, the use of two drive arms 31,32 minimises twisting movement. The drive arms act in opposition to substantially cancel sideways movement, resulting in a smooth rectilinear movement of the leaf.

To further improve smooth movement of the leaf 20, the drive assembly 30 comprises means for co-ordinating movement of the drive arms 31,32. In the preferred embodiment the co-ordinating means comprises interlocking arcuate gears 35,36. Suitably, the arcuate gears 35,36 are carried on the drive arms 31,32 respectively and follow an arcuate path about the same pivot point 321, 322. The co-ordinating means 35,36 regulate relative movement of the drive means 31,32. Other co-ordinating arrangements are readily envisaged including, for example, a toothed belt arrangement, or a system of twin links. In an alternate embodiment of the invention (not shown) the co-ordinating arrangement 35,36 allows one of the

actuators 33, 34 to be removed by transferring drive power from, for example, the first drive arm 31 to the second drive arm 32.

Referring again to Figure 1, it will be appreciated that deploying the ramp 10 involves a generally horizontal movement of the leaf 20 between inboard and outboard positions, together with a pivoting movement such that the leaf 20 achieves the desired slope angle depending from the vehicle threshold 5. A problem arises in that the height differential to the kerb K is not constant, and it is desired that the ramp 10 is able to cope with a variety of height differentials between the threshold 5 and the top of the kerb K. Further, in some circumstances the vehicle 1 is not able to pull along side a raised kerb K, and the ramp 10 is deployed to rest on the ground surface G. In each case, it is desired that the ramp 10 provides a smooth travelling surface to meet the interior floor level of the vehicle 1 at the threshold 5. Further, it is desired to retract the leaf 20 to a substantially horizontal position, i. e. parallel with the nearest portions of the vehicle 1, to minimise storage space.

Therefore, in addition to driving the leaf horizontally, some form of guide is desired to control pivoting movements of the leaf. In some embodiments the guide is provided integral with the drive arrangement.

Alternatively, the guide arrangement is separate from the drive arrangement.

Referring to Figures 3,4 and 5, the preferred guide arrangement 40 comprises a pair of guide rails 41,42 arranged either side of the leaf 20. Figure 6 shows in more detail a forward portion of the right-hand guide rail

42. The guide rail 42 comprises a channel 420 for receiving the pair of guide rollers 201, 202 at the respective side of the guide portion 24 of the leaf 20. A first channel portion 421 is sized closely corresponding to the diameter of both guide rollers 201,202, such that the leaf 20 is maintained in a generally horizontal plane.

The first portion 421 runs for a majority of the rail 42, corresponding to a majority of the desired travel of the leaf 20. At a forward (outermost) portion of the rail 42, a second channel portion 422 is provided. The second channel portion 422 is broader than the guide rollers 201, 202, such that the guide rollers 201,202 may rotate about each other to a limited degree, in a generally vertical plane.

During deployment of the ramp 10, the leaf 20 is moved by the drive means 30 and guided along the first channel portion 421 of the guide rails 42, such that the leaf moves generally horizontally outwardly of the vehicle.

When the guide rollers 201,202 reach the second portion 422 of the guide rails 42, i. e. suitably when the leaf 20 is almost fully outward of the vehicle, the guide means 40 allows the leaf 20 to pivot downwardly and rest upon a suitable surface such as the kerb K. Advantageously, unwanted collisions, for example with a upward surface of the kerb K or debris on the road surface G, are avoided.

In the preferred embodiment of the present invention the guide rollers 201,202 are arranged at or adjacent the rearward edge 26 of the leaf 20. When the leaf 20 is nearly fully deployed, the weight of the leaf 20 provides a turning moment to pivot the first guide roller 201 about the second guide roller 202 (or vice versa). Preferably,

the second channel portion 422 is shaped such that the first guide roller 201 rises with respect to the level of the second guide roller 202, which results in a slight upward movement of the rear edge of the leaf 20.

Advantageously, such upward movement minimises a step difference between the rearward edge of the leaf 20 and the threshold 5 of the vehicle 1. Further, the ramp assembly maintains a minimal threshold step difference for all angles of leaf deployment.

To take advantage of this slight upward movement, and to maximise the available slope length, it is desired that the leaf is deployed completely clear of the vehicle 1.

Suitably, the guide arrangement 40 extends in co-ordination with the leaf 20. In the preferred embodiment, at least a portion of the guide arrangement is moveable, the moving portion suitably comprising at least the second channel portion 422. Conveniently, at least one and preferably both guide rails 41,42 are arranged to slide relative to the drive assembly 30, such that the second channel portion 422 projects outwardly when the leaf 20 is deployed. Suitably, movement of the guide arrangement 40 is performed in co-ordination with driving of the leaf 20. In the preferred embodiment, a linkage 43,44 is provided between each rail 41,42 and one of the drive arms 31,32, respectively (see Figure 5).

It is desired to control descent of the leaf 20, preferably to provide a smooth, safe and even descent. To this end, the ramp 10 includes energy transfer means 50, preferably comprising at least one and ideally a pair of biasing means 51,52 such as tension springs. Preferably, the energy transfer means 50 is engaged when the leaf 20

is deployed, ideally close to the position where the leaf 20 is ready for descent. Suitably, the energy transfer means 50 is engaged as the leaf 20 reaches a position where the guide rollers 201,202 transition between the first channel portion 421 and the second channel portion 422 of each guide rail 41,42. In the preferred embodiment the second end of each drive arm 313,323 engages a receiving catch 511,521 (see Figure 3). The energy transfer springs 51,52 then bias against the drive means 30, such that the leaf 20 descends smoothly and evenly. Further, when it is desired to retract the ramp 10, the energy transfer springs 51,52 release stored energy to assist raising of the leaf 20.

A problem has been identified in that during deployment or retraction of the ramp, the leaf 20 is vulnerable to unexpected loading. For example, an impatient passenger may attempt to stand on the leaf 20 before it is fully deployed (i. e. when the leading edge 23 is not supported on the kerb K). Such unexpected loading will tend to strain the drive assembly 30 and/or the guide arrangement 40. Therefore, in the preferred embodiment of the present invention the leaf 20 is provided with a failsafe breakout. Referring to Figure 7, the rearward guiding portion 24 is coupled to the main leaf portion 25 through a breakout arrangement 60. In normal use the main and rear portions 24,25 are rigidly coupled and can be treated as an integral element. The leaf breakout 60 comprises a torsion bar 61 and pivoting couplings 62.

When substantial unexpected load is applied to the main leaf portion 25, the torsion bar is overcome allowing the main leaf portion 25 to pivot relative to the guide portion 24. When the unexpected load is removed, the

torsion bar 62 returns the main leaf portion 25 to the normal position.

Although under normal circumstances it is desired that the ramp 10 is deployed and retracted automatically, without any manual intervention, circumstances may arise where automatic operation is not possible. For example, air supply to the pneumatic actuators 33,34 might fail.

In this situation, it is desired that the ramp is operable manually. Advantageously, the drive assembly 30 of the preferred embodiment is readily reversible and can be overcome manually with minimal effort. In particular, the drive arms 31,32 provide a significant mechanical advantage to overcome resistance in the actuators 31,34.

Further, the energy transfer springs 51,52 assist manual movement of the leaf 20, particularly as the front edge 23 of the leaf 20 is raised at the beginning of retraction.

Referring to Figure 8, it is desired that the leaf 20 be securely retained in the retracted position, particularly whilst the vehicle is in motion. A retaining means 70 includes a retaining pin 71 arranged on the drive assembly 30 or the guide assembly 40 and controlled, for example, by a pneumatic actuator 74. Preferably the pin 71 engages a receiving recess 72 of the leaf 20 (see Figure 2-although the recess 72 here assumes the pin is mounted on the left of the leaf 20). The pin 71 retracts to release the leaf 20 and allow the ramp 10 to be deployed. In normal use the retaining means 70 is operated automatically in co-ordination with the drive means. However, preferably the retaining means 70 comprises a manual override such as a push button 73 to selectively engage or disengage the retaining pin 71.

Advantageously, the ramp 10 may continue in service under manual operation should automatic control fail.

Another problem arises in that it is desired to install the ramp assembly 10 on the vehicle 1 with a minimum of adaptation to the vehicle. Further, it is desired that the ramp assembly is readily accessible for maintenance and repair.

In the preferred embodiment, the majority of the ramp assembly 10 is readily removable from the vehicle 1. In particular, the leaf 20, the leaf drive assembly 30 and the guide arrangement 40 together form a removable cassette 90. The cassette is readily releasably coupled to a cassette holder permanently mounted on the vehicle 1.

The readily releasable mounting may comprise, for example, slide rails and/or mounting bolts.

Referring to Figure 9, the ramp assembly 10 preferably comprises a cassette holder 80 arranged for permanent installation on the vehicle 1, including a reasonably substantial threshold member 81 arranged to lie across the width of an entrance to the vehicle, forming the threshold thereof and supporting the interior floor of the vehicle, such as plywood 6 at the threshold 5. The threshold member 81 pivotably supports the flap 50. When the ramp is retracted, the flap 50 depends from the threshold member 81 to visually hide the ramp assembly, and to protect from ingress of water and road dirt. As mentioned above, when the ramp is deployed the flap 50 assists a smooth transition from the leaf 20 into the vehicle.

In this example embodiment, the cassette holder 80 comprises hangers 82 depending from suitable portions of the vehicle to carry the ramp cassette. A control arrangement (not shown) is provided with an umbilical including readily releasable connections to electrical power and/or compressed air and/or hydraulic systems of the vehicle.

When the ramp cassette is removed, only minimal mechanical components remain on the vehicle. The flap 50 covers the area normally occupied by the ramp cassette, avoiding any potential hazard and maintaining a pleasing visual aspect. Advantageously, the ramp cassette is readily removable for maintenance and repair, and can be moved remote from the vehicle to a more convenient position such as a work bench. Further, the vehicle can immediately return to service, either fitted with a spare ramp cassette or running without a ramp cassette. The ramp cassette can be moved to any vehicle of a fleet having a corresponding cassette holder 80 installed, allowing greater operational flexibility. Also, the cassette holder 80 can be installed at a relatively early stage during manufacture of the vehicle. The ramp cassette can be installed later, for example just as the vehicle is ready to leave a production area. Cost and convenience for the manufacturer are both improved. Further, the cassette holder 80 requires relatively minimal adaptation to an existing vehicle when retro-fitting.

In addition to the many advantages outlined above, the ramp assembly 10 is simple, robust and reliable. Only one or preferably two, actuators are required. The assembly is compact in length and makes maximum use of the limited

mounting space available on most vehicles. Also, the ramp assembly is compact in depth, thereby minimising underhang below the vehicle which reduces the risk of collision and improves longevity in the field. The ramp may be deployed and retracted whilst the vehicle doors remain closed, improving passenger safety and comfort.

The skilled person will appreciate that many changes and modifications can be made to the preferred embodiment described above. For example, a multiple-part leaf can be used, and the leaf drive assembly and guide arrangement can be achieved in many alternate arrangements. Further, whilst the preferred embodiment has been described in the context of a road vehicle such as a bus or coach, the invention is readily adapted to other forms of vehicles.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving

the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment (s). The invention extend to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1. A wheelchair access ramp for a vehicle, comprising : a leaf; a drive assembly for moving the leaf outwardly from a retracted position towards a deployed position; and guide means for guiding movement of the leaf in a direction generally transverse to the generally outwards movement.

2. The access ramp of claim 1, wherein the leaf is arranged to move outwardly along a generally rectilinear path.

3. The access ramp of claim 1 or 2, wherein the drive assembly is arranged for outwards movement within a generally horizontal plane, and the guide means is arranged such that a forward edge of the leaf depends downwardly of that horizontal plane as the leaf moves to the deployed position.

4. The access ramp of claim 1,2 or 3, wherein the leaf is arranged to travel in a generally horizontal plane for a major portion of the outwards movement.

5. The access ramp of any preceding claim, wherein the guide means comprises a first guide means co-operating with a second guide means to constrain the relative orientation of the first guide means during movement of

the leaf from the retracted position towards the deployed position, and arranged to allow alteration of the relative orientation of the first guide means as the leaf moves to the deployed position.

6. The access ramp of claim 5, wherein the first and second guide means are arranged such that gravity assists alteration of the relative orientation of the first guide means.

7. The access ramp of claim 5 or 6, wherein the second guide means comprises a guide channel, and the first guide means comprises a channel follower.

8. The access ramp of claim 7, wherein the channel follower comprises a plurality of guide rollers.

9. The access ramp of any preceding claim, wherein the guide means comprises a pair of guide rollers co-operating with a guide channel, the guide channel having a first portion arranged to maintain the pair of guide rollers in a fixed position relative to one another, and a second portion arranged to allow the guide rollers to alter their relative position.

10. The access ramp of claim 9, wherein the guide rollers are carried by the leaf, and wherein the guide means comprises a guide rail defining the guide channel.

11. The access ramp of any preceding claim wherein the guide means is arranged to guide the leaf such that its outermost edge moves downwardly relative to the innermost edge as the leaf approaches the deployed position.

12. The access ramp of any preceding claim, wherein the guide means defines a pivoting movement of the leaf about a pivot axis.

13. The access ramp of claim 12, wherein the pivot axis is moved along a generally rectilinear path, in response to movement of the leaf by the drive assembly.

14. The access ramp of claim 5 or any claim dependent thereon, wherein altering orientation of the first guide means causes a rearward edge of the leaf to rise as the leaf moves to the deployed position.

15. The access ramp of any preceding claim, wherein the leaf comprises a rearward edge region, and the drive assembly is arranged to lie at least partially forward of the rear edge region of the leaf, when the leaf is in the retracted position.

16. The access ramp of claim 15, wherein a majority of the drive assembly is arranged to lie mostly forward of the rear edge region of the leaf, when the leaf is in the retracted position.

17. The access ramp of claim 15 or 16, wherein the drive assembly is arranged to lie substantially completely forward of the rear edge region of the leaf, when the leaf is in the retracted position.

18. The access ramp of any of claims 1 to 17, wherein the drive assembly comprises at least one actuator arranged underneath and/or to one side of the leaf, when

in the retracted position, and coupling means for coupling between the leaf and the actuator.

19. The access ramp of claim 18, wherein the coupling means is arranged for operation at a location vertically offset from the path of generally rectilinear movement of the leaf.

20. The access ramp as claimed in claim 19 wherein the coupling means is arranged in a plane generally parallel to the plane of the leaf when in the retracted position.

21. The access ramp of claim 18,19 or 20, wherein the coupling means is arranged to lie underneath the leaf, when in the retracted position.

22. The access ramp of any preceding claim, wherein the drive assembly is arranged to drive two spaced apart positions for the leaf, the portions moving with respect to each other during movement of the leaf from the retracted position toward the deployed position.

23. The access ramp of claim 22, comprising co-ordinating means for co-ordinating movement of the two portions with respect to each other.

24. The access ramp of claims 22 or 23 wherein the portions are arranged to move towards each other during movement of the leaf from the retracted position towards the deployed position.

25. The access ramp of claim 23 or 24 when dependent on claim 23, wherein the co-ordinating means comprises a mechanical linkage.

26. The access ramp of claim 25, wherein the co-ordinating means constrains the drive assembly such that the mounting points move together in co-ordination.

27. The access ramp of any of claims 18 to 26, wherein the drive assembly comprises at least one drive arm coupled to the leaf and arranged for pivoting movement in a plane generally parallel to the direction of rectilinear movement.

28. The access ramp of any of claims 1 to 27, wherein the drive assembly comprises a pair of drive members.

29. The access ramp of claim 28, wherein the drive assembly comprises co-ordinating means including a pair of actuate gears for co-ordinating movement of the drive arms.

30. The access ramp of claim 29 wherein the drive members are arranged to act in a scissor like manner.

31. The access ramp as claimed in claim 30 wherein the drive arms cross each other.

32. The access ramp as claimed in claim 30 or 31 wherein one end region of each drive arm is arranged to be generally equidistant from each other during movement of the drive arms.

33. The access ramp as claimed in claim 31 or 32 in which the drive arms include cooperating gear portions that mesh with each other.

34. The access ramp as claimed in claim 33 in which the gear portions extend in an arcuate direction.

35. The access ramp as claimed in claim 33 or 34 in which the gear portions are attached to arms to form the drive arms.

36. The access ramp as claimed in claim 32 or any of claims 33 to 35 when dependent on claim 32 in which at least one actuator is arranged to drive at least one end region of at least one arm that is equidistant to another end region of another arm during movement of the drive arms in at least one direction of movement of the leaf.

37. The access ramp of any preceding claim, comprising energy transfer means for storing energy released as the leaf moves from the retracted position to the deployed position, and releasing the stored energy to assist return of the leaf from the deployed position toward the retracted position.

38. The access ramp of any preceding claim, wherein the leaf comprises first and second portions coupled by a breakout arrangement for maintaining the first and second portions in rigid relation during normal use and allowing relative motion between the first and second portions when the leaf is subject to unexpected loading.

39. The access ramp of any preceding claim, comprising retaining means for retaining the leaf in the retracted position.

40. The access ramp of claim 39, wherein the retaining means is manually releasable.

41. The access ramp of any preceding claim, comprising a cassette holder suitable for permanent installation on a vehicle, and a cassette comprising the leaf and/or the drive assembly and/or the guide means, the cassette being readily releasably coupled to the cassette holder.

42. An access ramp substantially as hereinbefore described with reference to and as shown in the accompanying drawings.