The present invention relates to a tail lift for loading and unloading a vehicle. In particular, it

concerns a lift in which the load bearing platform is made up of two leaves which can be folded away from each other, towards the sides of the lift, so that the lift can be installed in the interior of a vehicle and results in an unobstructed view for the vehicle driver.

This type of lift with two folding platform leaves is known, but existing devices use complex mechanisms involving actuators and rotating knuckle joints. These mechanisms result in jerky motion and are difficult to maintain. The joints are subject to high loads and thus inherently

unreliable. The present invention addresses these problems and limitations of the prior art.

The present invention provides a lift for attachment to a vehicle, comprising a base assembly for attachment to a vehicle, a platform assembly for receiving and

raising/lowering a load, and a linkage assembly connecting the base assembly to the platform assembly for moving the platform assembly between a stowed position and a deployed position, wherein the platform assembly comprises at least one platform leaf and a cradle for attaching the leaf to the linkage assembly, the cradle is rotatable relative to the linkage assembly about a first non-rotatable shaft defining a first axis and the platform leaf comprises a second shaft defining a second axis perpendicular to the first axis, and the leaf is rotatable relative to the cradle about the second axis, the lift further comprising first gear means secured to the first shaft and in engagement with second gear means secured to the second shaft, whereby rotation of the cradle about the first axis causes rotation of the platform leaf about the second axis .

In this way an improved mechanism for operating a split-platform lift is provided which is compact, robust, easy to maintain, more reliable and provides smooth

operation.

Preferably, the first gear means comprises a bevel gear non-rotatably secured to the first shaft and the second gear means comprises a second bevel gear non-rotatably secured to the second shaft.

Preferably, the platform assembly comprises first and second platform leaves, each including a second shaft, and wherein the first shaft comprises first and second shaft sections each having gear means mating with the gear means of a respective second shaft of a platform leaf.

The linkage assembly may comprise a pair of linkage assemblies supporting the cradle therebetween, wherein the first shaft section is secured to one linkage assembly and supports one side of the cradle and the second shaft section is secured to the other linkage assembly and supports the other side of the cradle.

Preferably, a first end of each shaft section is secured non-rotatably to a respective linkage assembly, a second end of the shaft section is received in a bearing in the cradle, and the first gear means is secured to the first shaft section between the first and second ends.

Preferably, the or each linkage assembly comprises a first parallelogram linkage and a linear actuator movable between a contracted configuration and an extended

configuration, wherein in the stowed position the actuator is in the extended configuration and in the deployed

position the actuator is in the contracted configuration.

In addition, the or each linkage assembly may comprise a push arm having first and second ends, for rotating the cradle about the first axis, wherein part of the

parallelogram linkage defines a cam surface and the first end of the push arm comprises a cam follower which travels along the cam surface as the lift moves between the deployed position and the stowed position, and the second end of the push arm is pivotably secured to the cradle at a location spaced from the first axis such that movement of the cam follower along the cam surface exerts a rotational force on the cradle about the first axis.

In a preferred embodiment, the or each platform leaf further comprises a wall along one edge thereof parallel to the second axis, wherein the leaf is rotatable relative to the wall such that in the stowed position the wall and the leaf are substantially parallel to one another and in the deployed position the wall and the leaf are substantially perpendicular to one another.

To assist with deployment of the platform assembly, the or each linkage assembly further comprises spring means which is lockable in a compressed state in the stowed position and upon release is operable to expand and act upon the linkage mechanism to initiate movement from the stowed position to the deployed position.

For safety purposes, the lift may further comprise reaction means on the cradle and on the or each linkage assembly which come into contact one another to limit rotation of the platform assembly about the first axis .

The invention will now be described in detail, by way of example only and with reference to the accompanying drawings in which: Figures 1-5 show perspective views of a lift in

accordance with the present invention as it moves form the stowed position in Figure 1 to the deployed position in Figure 5, although some parts of the mechanism have been omitted for clarity;

Figure 6 is a side view of part of the lift in the stowed position, showing the linkage assembly and the cam assembly, although some parts have been omitted for clarity; Figure 7 is similar to Figure 6, but showing the lift part way between the stowed and deployed positions,-

Figure 8 is similar to Figures 6 and 7, but showing the lift in the deployed position; Figure 9 is an enlarged perspective view showing the cam assembly part way between the stowed and deployed positions; Figure 10 is a perspective view showing the lift in the stowed position;

Figure 11 is a perspective view showing the lift part way between the stowed and deployed positions;

Figure 12 is a perspective view showing the lift part way between the stowed and deployed positions, at the point when the platform assembly is level with the floor of a vehicle; and

Figure 13 is an underneath view of part of the lift showing the mechanism for rotating the cradle and one of the platform leaves. A tail lift 10 in accordance with one embodiment of the present invention includes a base assembly 12 for mounting in a vehicle, a platform assembly 14 for receiving and raising/lowering a load, and a linkage assembly 16 for supporting the platform assembly 14 and moving it relative to the base assembly 12 between a stowed position inside a vehicle and a deployed position outside the vehicle and with the platform at ground level.

In the following description, the lift 10 will be described as if it is secured to a vehicle for normal use. The parts of the lift 10 closest to the vehicle will referred as being at the front of the lift 10 and the parts farthest from the vehicle referred to as the rear or

rearward parts of the lift. Similarly, the terms upper and lower, horizontal and vertical will be used with reference to normal use of the lift 10 when installed on a vehicle standing on a flat surface.

The base assembly 12 comprises a support plate 18 securable to the interior floor of a vehicle adjacent to an opening. Typically, this might be a minibus with a door at the rear or side, and the lift 10 is intended to be used to allow a person in a wheelchair to enter and exit the

vehicle. However, the lift 10 may be used for other applications, such as for loading freight. A bracket 20 extends upwardly from each end of the support plate 18 for connection to the linkage assembly 16 as described further below.

The platform assembly 14 comprises a pair of platform leaves 22 rotatably mounted to a cradle 24. In the fully deployed position (figure 5) , the leaves 22 lie horizontal and side by side to form a load-bearing platform. In the stowed position (figure 1) , the leaves 22 are folded away from one another and stand vertically, adjacent to the two brackets 20.

The platform assembly 14 also includes a bridging plate 26, a pair of side walls 28 and a pair of ramp plates 30.

The cradle 24 is a substantially U-shaped member comprising a supporting beam 32 with a longitudinal axis A parallel to the support plate 18, and with support arms 34 extending perpendicularly from each end. The cradle 24 is rotatably mounted to the linkage assembly 16 as described further below for rotation about an axis A.

The platform leaves 22 are rotatably mounted to the cradle 24 for rotation about respective axes B which are perpendicular to axis A and run parallel to the outer side edge of each leaf 22.

The bridging plate 26 is rotatably mounted to the front of the cradle 24 and rotates about an axis C parallel to and forward of axis A. Each side wall 28 and ramp plate 30 is rotatably mounted to a side and front edge respectively of a platform leaf 22. The linkage assembly 16 comprises an identical assembly on each side of the lift 10 for connecting the base assembly 12 to the platform assembly 14. Accordingly, the linkage assembly 16 on one side of a lift 10 will be described, the linkage assembly 16 on the other side being identical.

The linkage assembly 16 comprises upper and lower links 36, 38 which are parallel to one another. At their front ends, that are closest to the vehicle in which the lift is installed in use, the links 36, 38 are pivotally secured to the bracket 20. At their rear ends, the links 36, 38 are rotatably secured to the upper end of a drop arm 40. Thus, the bracket 20, upper and lower links 36, 38 and upper part of the drop arm 40 together create a parallelogram linkage. The drop arm 40 extends generally vertically downward from the links 36, 38. At the lowermost end of the drop arm

40, a shaft 66 extends normal to the drop arm 40 and towards the other linkage assembly 16 on the opposite side of the lift 10. The cradle 24 is rotatably mounted on the shaft 66, which thus defines the axis A for rotation of the platform assembly 14. A linear actuator 42, such as a hydraulic ram, extends from a pivot point 44 where the front end of the lower link 38 joins the bracket 20, to a pivot point 46 where the rear end of the upper link 36 joins the drop arm 40. The actuator 42 is illustrated schematically in Figures 5 and 8 but omitted elsewhere for clarity.

A cam assembly 48 is pivotably connected between the drop arm 40 and the cradle 24. This is described in further detail below.

In the stowed position (figure 1) , the linear actuator 42 is extended to its longest length. Due to the geometry of the parallelogram linkage created by the bracket 20, the upper and lower links 36, 38 and the drop arm 40, this lifts the drop arm 40 and pulls it towards the vehicle due to the fixed length of the upper link 36, to stand adjacent to the bracket 20 with the upper and lower links 36, 38 in a close- to-vertical position between the bracket 20 and the drop arm 40.

To extend the tail lift 10 to the deployed position, a lock (such as a hydraulic lock, not shown) is released to allow the actuator 42 to move freely. This allows the platform assembly 14 to pivot under gravity from the

vertical to the horizontal position. To help with initiating the pivoting of the platform assembly 14, the spring device may be incorporated in the lift 10. In this example, the spring device 74 is provided on the drop arm 40, extending forward towards the lower link 38 (see Figure 7 and 8) . In the stowed position, the spring device 74 is compressed between the drop arm 40 and the lower link 38 and locked, in any convenient manner.

Upon release of the lock, the spring device 74 expands, forcing the drop arm 40 away from the lower link 38. Once this movement has begun, the weight of the platform assembly 14 comes into play and it continues to rotate towards the horizontal position under gravity.

As the platform assembly 14 pivots, the upper and lower links 36, 38 also pivot towards a horizontal position. The drop arm 40 remains vertical but translates away from and downwardly relative to the bracket 20.

To move from the deployed position back to the stowed position, the actuator 42 is extended. Once again, due to the geometry of the parallelogram linkage, the upper and lower links 36, 38 pivot back from a horizontal to a close- to-vertical position, raising the drop arm 40 and

withdrawing it towards the bracket 20.

Furthermore, as the linkage assembly 16 moves between the stowed and the deployed positions, there is also

movement of the platform assembly 14. In the stowed position, each platform leaf 22 is vertical and adjacent to a respective bracket 20. The cradle 24 is also vertical, while the bridging plate 26 is substantially horizontal and overlies the support plate 18. As the linkage assembly 16 is extended, the cradle 24 pivots about the axis A defined by the shaft 66, from a vertical to a horizontal position. Simultaneously, each platform leaf 22 pivots about its respective axis B so that the two leaves fold towards each other and come to lie adjacent and in the same plane. The platform assembly 14 reaches the horizontal position when the platform leaves 22 lie adjacent to each other and at the same height as the floor of the vehicle so that loads can be transferred into and out of the vehicle across a surface. At this point the bridging plate 26 thus bridges the gap between the platform assembly 14 and the vehicle (Figure 12) . The platform leaves 22 further comprise a locking mechanism (not shown) to prevent the leaves 22 from rotating further in the same direction about their respective axes B, which would cause the leaves 22 to separate and to slope downwardly towards the centre of the lift 10. This locking mechanism may comprise any convenient means such as

interlocking teeth on the two leaves 22 which come into engagement with one another as the leaves 22 reach the horizontal position and lie in the same plane adjacent to one another. In addition, to prevent from the whole platform assembly 14 rotating further about axis A so as to slope downwardly from the front towards the rear of the lift 10, reaction members (not shown) may be provided on the drop arm 40 and the cradle 24 which engage against one another and block further rotation once the platform assembly 14 reaches the horizontal position. Upon further movement of the linkage assembly 16, the drop arm 40 is moved downwardly to lower the now horizontal platform assembly 14 to ground level. As this happens the bridging plate 26 pivots about axis C from a substantially horizontal to a substantially vertical position. This creates a barrier wall at the front end of the platform to prevent a wheelchair etc. from rolling off.

Additionally, when stowed, each side wall 28 lies approximately parallel to the surface of the respective platform leaf 22 and the ramp plate 30 is substantially perpendicular to the leaf 22. As the leaf 22 moves into the deployed position, it rotates relative to the side wall 28 so that when the leaf 22 is horizontal, the side wall 28 stands upright as a safety barrier at the edge of the platform. When the platform assembly 14 reaches ground level, the ramp plate 30 rotates relative to the leaf 22 to form an entry ramp onto the platform for ease of access by wheelchairs etc (Figure 5) .

This movement of the leaf 22, side wall 28, ramp plate 30 and bridging plate 26 are controlled by the cam assembly 48 best seen in Figures 6-12. The cam assembly 48

comprises a first push arm 50 for rotating the cradle 24 and a second push arm 52 for rotating the bridging plate 26.

These push arms 50, 52 are generally parallel to each other and located between the drop arm 40 and the lower link 38.

The first push arm 50 has upper and lower ends. The upper end is pivotably secured to a first roller 54 and to one end of a tie arm 56. The other end of the tie arm is pivotably secured to the drop arm 40. The lower end of the first push arm 50 is pivotally secured to the cradle 24 for rotation about axis D which is parallel to axis A but located rearward of it. The second push arm 52 is located forward of the first push arm 50 and pivotally connected thereto by a pair of upper and lower connectors 58, 60, thus forming another parallelogram linkage. The upper end of the second push arm 52 is pivotally connected to the upper connector 58 and a second roller 62.

A finger 64 extends inwardly from the lower cross piece 60, with a longitudinal axis parallel to axes A and C. The bridging plate 26 locates against the finger 64.

In the stowed position, the first and second rollers 54, 62 contact the underside of the lower link 38. As the platform assembly 14 rotates under gravity from the vertical to the horizontal deployed position, the rollers 54, 62 come out of contact with the lower link 38. The second push arm 52 moves upwardly relative to the first push arm 50. This raises the finger 64, tilting the bridge plate 26 from the horizontal to the vertical position. To return from the deployed to the stowed position, the actuator 42 is extended to raise the upper and lower links 36, 38 and the drop arm 40. As this happens, the second roller 62 comes into contact with the lower link 38 which acts as a cam surface along which the second roller travels. This forces the second push arm 52 downwardly, lowering finger 64 and allowing the bridge plate 26 to return from the vertical to the horizontal position. A cam surface 78 may also be provided at the edge of the bridging plate 26 along which the finger 64 travels as the second push arm 52 moves up and down. This cam surface 78 may have recesses for retaining the finger 64 at certain points to more securely hold the bridging plate 26 at certain specific positions.

Upon further extension of the actuator 24, the first roller 54 also makes contact with the lower link 38 and travels along it, forcing the first push arm 50 downwardly. This exerts a rotational force on the cradle 24, which pivots about axis A, bringing the platform assembly 14 from the horizontal back to the vertical position.

As noted above, the axis A about which the cradle 42 rotates is defined by the fixed shaft 66 which at one end is secured non-rotatably to the drop arm 40 (Figure 13) . The other end of the shaft 66 is received in a bearing 76 in the cradle 24 so that the shaft 66 is supported at both ends. A first bevel gear 68 is non-rotatably secured to a shaft 66 between the ends. A second shaft 70 is secured to the underside of each platform leaf 22, beneath its outer edge. A second bevel gear 72 is non-rotatably secured to the second shaft 70 and engages with the first bevel gear 68.

As the cradle 24 rotates about the first shaft 66, since this shaft 66 is fixed and cannot itself rotate, it forces the second shaft 70 to rotate by virtue of the engaging bevel gear 68, 72. Thus, as the cradle 24 rotates about axis A, the platform leaf 22 simultaneously rotates about axis B, folding the leaf 22 out towards the side of the lift 10 in one direction of rotation and in towards the other leaf 22 in the opposite direction of rotation.

Thus, the present invention provides an improved mechanism for a foldable tail lift in which the platform consists of two leaves which fold away from one another and towards the sides of the device as the platform assembly rotates between the horizontal and vertical positions. It is more robust and thus more reliable than prior mechanisms and provides smoother motion as the platform assembly is raised and lowered.