CA2713307A1 - Wheelchair lift - Google Patents

Abstract

The wheelchair lift has fixed structure fixable in position relative to a lower landing and an upper landing; a mobile structure slidably connected to the fixed structure;
and an elevator mechanism controlling the sliding movement of the mobile structure relative to the fixed structure. In one embodiment, the fixed structure has an upper landing gate integrated thereto. In another embodiment, the mobile structure has a gate which is hinged about a horizontal axis and is openable by pivoting downwardly against the lower landing to act as a ramp. In another embodiment, the upper landing gate and/or the lower landing gate has a locking system which is caused mechanically engage the closed gate by action of the movement of the mobile structure.

Description

WHEELCHAIR LIFT
BACKGROUND

Wheelchair lifts, sometimes referred to as vertical lifts or personal elevators, are typically purchased by residential or commercial owners and installed to allow staircase-free elevation between a lower landing and an upper landing, and can be designed for outdoor and/or indoor use. They can be used or adapted for other applications than wheelchairs, but the use for wheelchairs (or scooters) is the most common.

Former wheelchair lifts typically include a mobile platform slidingly connected to a mast which includes a drive system which controls the vertical movement of the platform relative to the mast. To be safe, these former wheelchair lifts include a number of security features.
For instance, a lower landing gate and an upper landing gate are typically used to prevent falls. The lower landing gate is provided on the platform and is locked closed when the platform is raised to prevent falling off the platform onto the lower landing.
The upper landing gate is provided as a separate assembly and is locked closed when the platform is lowered to prevent falling off from the upper landing onto the platform. The locking has been known to be provided via sensing of the movement of the platform by limit switches.
The former wheelchair lifts had several drawbacks. For instance the system which locks upper landing gate depends on the sensing of the position of the platform. The sensing of the position of the platform can be influenced by relative movement between the elevator assembly and the upper landing gate assembly. This has been known to cause inconveniences when the lift is used outdoors, especially in cold climates, where freezing and thawing of the ground led to displacements of the elevator assembly relative to the upper landing gate assembly. Inconvenient maintenance issues thus occurred.

Further, the mast, which was quite tall and somewhat cumbersome, was placed on a side of the platform other than the side of the upper and lower landings, not to interfere with mobility through the gates, between the platform and the landings. Room had to be allocated DOCSQUE: 885267\1 for the mast during planning. Also, significant costs were associated to design considerations of the mast to render its appearance less disturbing.

There were other inconveniences as well, including the area which had to be allocated for the opening of the upper gate over the upper landing, planning requirements to ensure that the upper gate, once opened, would not block access to or from the upper landing, and the ramp component which allowed passage between the platform and the lower landing.
Also, the costs of sensors, and the safety systems globally, in former lifts, were a concern.

Henceforth, although former wheelchair lifts were satisfactory to a certain degree, there remained significant room for improvement.

SUMMARY

Among other innovative features, the instant specification teaches : an upper landing gate which can be made part of the mast structure and therefore solve former issues stemming from relative movement which occurred between the former lift unit and the former separate upper landing gate assembly; a lower landing gate which is hingedly mounted about a horizontal axis to the platform and which can serve both as a locked lower landing gate with a distal end thereof raised when the platform is raised and a lower landing ramp to access the platform from the lower landing once the distal end is lowered; and a locking system which uses a slidingly mounted rod with vertical freedom of movement which is downwardly biased toward a locking position where the first engaging member associated with one of the gates is engaged with a second engaging member which is associated with the rod, thereby locking the gate, and a sensor which detects if the rod is in the downward position, a combination which allows using a single sensor as both a limit switch or height sensor to signal the position to halt the movement of the platform as it reaches the landing and as a locking system sensor to trigger a safety alarm and halt the movement of the platform if the locking engagement is not detected within a predetermined distance of movement.

DOCSQUE: 885267\1 In accordance with one aspect, there is provided a wheelchair lift comprising a unitary fixed structure fixable in position relative to a lower landing and an upper landing; a mobile structure slidably connected to the fixed structure and thereby movable in height between the lower landing and upper landing, the mobile structure having a platform; and an elevator mechanism controlling the sliding movement of the mobile structure relative to the fixed structure; the fixed structure further having an upper landing gate integrated thereto, which selectively provides or closes access between the upper landing and the platform.

In accordance with another aspect, there is provided a wheelchair lift comprising a fixed structure fixable in position relative to a lower landing and an upper landing; a mobile structure slidably connected to the fixed structure and thereby movable in height between the lower landing and upper landing, the mobile structure having a platform having a lower landing edge adjacent the lower landing when moved to the lower landing height, and at least one other edge contiguous to the lower landing edge and having a receiving structure upwardly extending therefrom, and a lower landing gate having a proximal end horizontally hinged to the lower landing edge of the platform, and being pivotable thereabout between an upright closed position where a distal end thereof, opposite the proximal end, is placed against the receiving structure, and an open position where the distal end is pivoted downwardly against the lower landing and the lower landing gate acts as a ramp between the platform and the lower landing, and an actuator mechanism controlling the pivoting movement of the lower landing gate to selectively provide or close access between the lower landing and the platform; and an elevator mechanism controlling the sliding movement of the mobile structure relative to the fixed structure.

In accordance with another aspect, there is provided a wheelchair lift comprising a fixed structure fixable in position relative to a lower landing and an upper landing and having an upper landing gate; a mobile structure slidably connected to the fixed structure and thereby movable in height between the lower landing and upper landing, the mobile structure having a platform and a lower landing gate; an elevator mechanism controlling the sliding movement of the mobile structure relative to the fixed structure; whereat at least one of the DOCSQUE: 885267\1 upper landing gate and the lower landing gate has a locking system which is caused mechanically engage and lock the corresponding landing gate into a closed position by movement of the mobile structure away from the height of the corresponding landing, while the elevator mechanism is activated.

In the instant specification, the expression wheelchair lift is used for the sake of clarity due to its widespread use in the art, and is not intended to be interpreted limitatively as restricting the field of use of the innovations. In the context of this specification, it is to be understood that an elevator referred to as a wheelchair lift can be used of other uses than for wheelchairs.

DESCRIPTION OF THE FIGURES
In the appended figures, Figs. 1 to 4 are sequential perspective views showing an example of a wheelchair lift during different steps of operation;

Fig. 5 is a block diagram of the wheelchair lift;

Fig. 6 is a flow chart of a locking system of the wheelchair lift;

Figs 7 and 8 are sequential perspective views showing components of a security system of the lower landing gate assembly of the wheelchair lift;

Fig. 9 includes Figs. 9A to 9C, which are perspective views showing components of a security system of the upper landing gate assembly of the wheelchair lift; and Fig. 10 is a perspective view showing components of an elevation system of the wheelchair lift.

DOCSQUE: 885267\1 DETAILED DESCRIPTION

In Fig. 1, an example of a wheelchair lift 10 is shown. The wheelchair lift 10 can be seen to generally include a mobile structure 12 with a platform 14, which is slidingly connected to a fixed structure 16 which has a mast 17. The wheelchair lift 10 is mounted in a manner to provide elevation, such as to wheelchair users for instance, between a first-height area referred to as the lower landing 18, and a second-, higher-height area referred to as the upper landing 20. Typically, the wheelchair lift 10 is intended to allow bypassing a staircase or other obstacle (not shown).

To prevent falling down from the upper landing 20 onto the platform 14, an upper landing gate 22 is provided. The upper landing gate 22 is provided in an upper portion 24 of the mast 17, to allow passage between two posts 26, 28 of the mast 17 which are interspaced from each other by a given width 30. In this example, the width between the posts 26, 28 in the lower portion 25 is permanently closed. As will be detailed further below, the upper landing gate 22 has a locking system which maintains it shut when the platform 14 has moved downwardly from the height of the upper landing 20.

The mobile structure also has a lower landing gate 32 which in this embodiment has a proximal end 34 which is horizontally hingedly connected to a lower landing edge 36 of the platform 14, and an actuator 38 which can pivot a distal end 40 of the lower landing gate 32 about the hinge 34 between a raised position (Fig. 2) where the lower landing gate 32 can be locked as will be detailed further below, and a lowered position (Fig. 1) where the lower landing gate 40 can advantageously be used as a ramp 32a between the lower landing 18 and the platform 14.

In this example, the lower landing edge 36 of the platform 14 (i.e. the edge the user runs across when moving to the lower landing 18) is opposite from the upper landing edge 42 of the platform 14, and two other parallel edges 44, 46 have side walls 48, 50 extending upwardly therefrom and preventing a user to fall to the sides. In this embodiment, the side DOCSQUE: 885267\1 walls 48, 50 also act as a receiving structure 52 for the lower landing gate 32, as will be detailed below.

The particular configuration of location of side walls 48, 50 is known in the art as a "straight' configuration, or 180 configuration. In alternate embodiments, the position of the lower landing gate 32 can be switched with the position of one of the side walls 48, 50 of the illustrated embodiments, into a 90 configuration, for instance, in which a user enters straight, and exits on one side. In some cases, wheelchair lifts are also provided with a 0 or 360 configuration. This all depends on the specific area which the lift is to be adapted to.
The operation of the wheelchair lift 10 can be visualized by sequentially referring to Figs 1, 2, 3 and 4. In Fig. 1, the lower landing gate 32 is lowered and acts as a ramp 32a allowing the user to access the platform 14 in the mobile structure 12. Once on the platform 14, the user can activate controls 54 (visible only in Fig. 7) and the lower landing gate 32 is raised and placed into abutment with the receiving structure 52 provided by the side walls 48, 50 as shown in Fig. 2. Subsequently, the mobile structure 12, with the user, can be raised along the fixed structure 16, from the lower landing height, shown in Fig. 2, to the upper landing height, shown in Fig. 3. When the mobile structure 12 is raised, the lower landing gate 32 is locked into position and thereby prevents the user from falling down to the lower landing 18.
After the mobile structure 12 has been fully raised (as shown), the upper landing gate 22 is unlocked, and opened (see Fig. 4), and the user is allowed out from the mobile structure 12, onto the upper landing 20. These steps are simply repeated in the opposite sequence when a user travels from the upper landing 20 to the lower landing 18.

Referring to Fig. 4, it is seen that the upper landing gate 20, in this embodiment, is provided in the form of two door halves 60, 62 which each have a corresponding distal end 64a, 64b which come into abutment when the upper landing gate 22 is closed and the two door halves 60, 62 are aligned (as shown in Fig. 1, for instance). This particular form of upper landing gate 62, which can be referred to as a "western style gate", combined by the positioning of the upper landing gate 22 in the mast 17 of the fixed structure 16 (which typically renders it DOCSQUE: 885267\1 at least somewhat recessed from the upper landing 20), results in providing an upper landing gate 22 (see Fig. 4) which is highly uncumbersome when open. It will typically allow one to circulate on either side of the upper landing 20 and across it when the gate 22 is open. This can be highly advantageous when compared to traditional single door gates which were provided as part of a separate gate assembly and which were thus positioned closer to the landing (directly onto the landing). Henceforth, with this design, the planning requirements for installation and the versatility of wheelchair lifts can be significantly improved. Still referring to Fig. 4, a hinged ramp 66 is provided at the bottom of the upper landing gate 22 and bridges the gap between the platform 14 and the upper landing 20. Shifting of the fixed structure 16 and its mast 17 which can occur when the lift 10 is installed outdoor in cold climates due to freezing and thawing of the ground, can be compensated simply by the use of the hinged ramp 66 in this configuration.

Referring to the block diagram shown in Fig. 5, the relative movement between the mobile structure 12 and the fixed structure 16 is controlled by an elevator mechanism 70, which can be any suitable elevator mechanism, and which, in turn, can be operated by a controller 76 which receives input from a user interface.

For security reasons, in this example, both the upper landing gate 22 and the lower landing gate 32 have a closed-state sensor 72, 74 which detect whether or not the corresponding gate 32, 22 is in the closed state. These closed-state sensors 72, 74 can be connected to the controller 76, which can be configured to arrest activation of the elevator mechanism 70 to prevent movement of the mobile structure 12 (and its platform 14) from the corresponding landing height when the gates are not detected to be closed. The controller 76 can also receive instructions from the user via a user interface 77. In this case, the controller also controls operation of the lower landing gate 32 via a gate activator 38 For even greater security, both the upper landing gate 22 and the lower landing gate 32, in this example, also have a locking mechanism 78, 80. As will be detailed below, in both cases in this example, the locking mechanism 78, 80 is mechanically engaged by action of the DOCSQUE: 885267\I

relative movement between the mobile structure 12 and the fixed structure 16.
Furthermore, a locking sensor 82, 84 (also referred to herein as locking system sensor) detects whether or not the locking mechanism 78, 80 is correctly engaged. The controller 76 can be configured in a manner that if detection of the correct engagement of the locking mechanism 78, 80 is not detected within a predetermined travel distance of the mobile structure 12 (which can be of 2" for example), the mobile structure 12 is prevented from further movement. This function is depicted in the flow chart which is provided at Fig 6.

Typically, some form of sensor is used and connected to the controller 76 to indicate to the controller 76 that the mobile structure 12 has reached the height of the corresponding landing and that the activation of the elevator mechanism 70 is to be stopped. In the example described herein and illustrated in the attached figures, the locking system sensor 82, 84 can advantageously be used to effect this function, which in turn can reduce costs and improve overall simplicity of the design. This is done by configuring the controller 76 to stop the movement of the mobile structure 12 toward the height of the desired landing based on the detection by the corresponding sensor 82, 84 that the corresponding locking mechanism 78, 80 has been disengaged. This will be described in further detail below. In alternate embodiments, a separate height sensor can be used specifically for this function.

The particulars of the locking system 77 of the lower landing gate 32 are now detailed with reference to Figs. 7 and 8. The lower landing gate 32 can be seen to have hooks 86a, 86b which are flat and extend perpendicularly from the ramp 32a on opposite sides, near the distal end 40, in this embodiment. The receiving structure 52, formed by the side walls 48, 50 in this embodiment, has corresponding slots 88a, 88b allowing penetration by the hooks 86a, 86b. Because both sides are identical in this example, only one will be described in full detail. A rod 89 is slidingly mounted relative to the receiving structure 52 in a manner to have vertical freedom of movement. The rod 89 is biased downwardly, by a compression spring in this specific example, and has a pin 90 which is functionally maintained into locking engagement with the hook 86a by action of the downward bias, in a position referred to herein as the locking position (shown in Fig. 8), thereby locking the gate 32 closed. In this DOCSQUE: 885267\1 example, the hook 86a can be said to be a first locking member associated with the gate 32, whereas the pin 90 can be said to be a second locking member associated with the rod 89. In alternate embodiments, the second locking member can have a male component and the first locking member can have a female component, for example. Furthermore, the rod 89 has a foot 91 (visible in Fig. 7) which extends downwardly and protrudes from the mobile structure 12 in a manner that it comes into abutting contact from below with the ground, which pushes the rod 89 upwardly when the mobile structure 12 is lowered to the height of the lower landing 18, thereby pushing the pin 90 (Fig. 8) out from the hook 86a and disengaging the mechanical lock of the locking mechanism 78. The locking system sensor 82 can sense whether or not the rod 89 is at a relative height which corresponds to its correct engagement with the hook 86a. A closed-state sensor 72 (or gate close sensor) detects whether or not the lower landing gate 32 is in the closed state (shown in Fig.
8) by detecting the presence of the tip of the hook 86a protruding behind the rod 89. Once the mobile structure 12 is raised along a given distance, the foot 91 (Fig. 7) is eventually freed from the ground and the pin 90 is thereby brought into engagement with the hook 86a. If after raising the mobile structure 12 the predetermined distance, the rod 89 is not detected to be at the correct relative position, this indicates that the lock is not correctly engaged and the controller can prevent further raising of the mobile structure. If the rod 89 is not correctly engaged with the hook 86a, the bias will not achieve in pushing the pin 90 into the hook 86a and the incorrect resulting relative position of the rod will be detected by the locking system sensor 82. The fact that both the locking system sensor 82 and the closed-state sensor 72 are engaged is the signal to the controller 76 (Fig. 5) that ascension can commence, in this embodiment. In this embodiment, the locking system sensor 82 which detects the relative position of the rod 89 can also be used as a height sensor to indicate to the controller that the mobile structure has reached the height of the lower landing. The rod 89 can be said to be a sliding component and the foot 91 can be said to be an abutment portion of the sliding component. Alternately, in some embodiments, such a locking system can be used on only one side instead of both, such as to reduce costs for instance.

DOCSQUE: 885267\1 The particulars of the locking system 92 of the upper landing gate 22 are now detailed with reference to Figs. 9A to 9C. Because the locking system 92 of both half-doors 60, 62 (Fig. 1) are identical in this embodiment, only one is described in detail. The half door 60 can be seen to have a hinge connector plate 93 which has three holes 94, 95, 96. The first one of the three holes 94 corresponds with a hinge axis 96 of the half-door 60 and is designed to receive a hinge pin (not shown). The second one of the three holes 95 is associated with the closed-state sensor 74, which determines whether or not the half-door 60 is correctly closed by detecting the alignment of the second hole 95 with the fixed-position closed-state sensor 74.
When the half-door 60 is opened, the second hole 95 is moved out from alignment, which is detected. The controller 76 (Fig. 5) does not allow lowering of the mobile structure/platform when either one of the half-doors 60, 62 (Fig. 1) is detected to be open.
Finally, the third one of the three holes 96 is associated with the locking mechanism 80, and is sized to receive a locking pin 97 therein which is to lock the closed door 60 in the closed state. This third hole 96 can be said to be a first locking member associated with the upper landing gate 22, and the locking pin 97 can be said to be a second locking member, engageable with the first locking member. In this particular example, the locking pin 97 extends downwardly and is connected to a rod 98 in a manner that both the rod 98 and the locking pin 97 have simultaneous and collective vertical freedom of movement. The rod 98 and the locking pin 97 are downwardly biased by a compression spring in this example. The rod 98 has a foot 99 extending downwardly therefrom. The rod 98 can be said to be a sliding component and the foot 99 can be said to be an abutment portion of the sliding component. When the mobile structure 12 is raised to the height of the upper landing, it comes into abutment with the foot 99 and raises the foot 99, thereby moving the rod 89 upwardly which, in turn, moves the pin 97 upwardly and disengages the mechanical lock. The disengagement of the pin 97 is detected by a lock system sensor 84. In this particular example, the lock system sensor 84 can also be used to provide the signal to the controller that the mobile structure 12 has reached the upper landing height and that the elevator mechanism can be stopped. When the mobile structure 12 is lowered from the upper landing height, the controller can be configured to automatically stop the elevator mechanism if the engagement of the pin 97 into DOCSQUE: 885267\1 the third hole 96 is not detected within a predetermined distance, which can be of 2" or any other suitable distance for example.

In both the cases of the locking system 77 of the lower landing gate 32 and the locking system 92 of the upper landing gate 22, the locking system sensor can also serve as a height sensor, and both cases use a combination of a first locking member associated with the gate, and a slidably movable component including a rod which has a second locking member and which is downwardly biased into a locking position where the first locking member is engaged with the second locking member, and wherein the disengagement of the locking members is caused by a downward-facing abutment surface receiving abutting contact from below as the mobile structure 12 is moved toward the height of the desired landing. In both cases, a sensor which detects the relative movement of the movable component 12 can be used both as a limit switch or height sensor to halt the movement of the platform as it arrives at the desired height, and as a locking system sensor to trigger a form of safety signal if the locking engagement is not detected within a predetermined distance as the mobile structure 12 is moved away from the height of a corresponding landing gate.

It will be understood that in alternate embodiments, the upper landing gate 22 can have a single door hinged about a horizontal axis like the lower landing gate of the depicted embodiment, or hinged about a vertical axis, for instance, and/or the lower landing gate can have a vertically hinged door, for example.

Fig. 10 shows the particular elevator mechanism 70 which is used in this example in further detail. In this example, the elevator mechanism has two endless screws 102a 102b, one extending upwardly in each one of the two posts 26, 28 of the mast 17 and to which the mobile structure 12 is connected. The endless screws 102a, 102b each have a driving pulley 104a, 104b at a bottom thereof, which is driven by a single, common, motor 106 via a strap and pulley arrangement 108. It will be understood that any alternate suitable elevator mechanism (sometimes called drive mechanism) can be used to control the sliding DOCSQUE: 885267\1 movement of the platform 14 relative to the mast 17, such as cable, hydraulic, or endless screw mechanisms for instance.

In this embodiment, the actuator 38 which is used to activate the pivotal movement of the lower landing gate 32 between the lowered (open) position and the raised (closed) position has been selected to be a hydraulic cylinder, for practical considerations.
However, any other suitable type of actuator, such as a pneumatic actuator or electric motor can be used if desired. The particulars of the locking systems can also differ in alternate embodiments.

The example(s) described above and illustrated is(are) provided for illustrative purposes. The scope is indicated by the appended claims.

DOCSQUE: 885267\1

Claims (26)

1. A wheelchair lift comprising a unitary fixed structure fixable in position relative to a lower landing and an upper landing; a platform slidably connected to the fixed structure and thereby movable in height between the lower landing and upper landing, the mobile structure having a platform; and an elevator mechanism controlling the sliding movement of the mobile structure relative to the fixed structure; the fixed structure further having an upper landing gate integrated thereto, which selectively provides or closes access between the upper landing and the platform.

2. A wheelchair lift comprising a unitary fixed structure fixable in position relative to a lower landing and an upper landing; an upper landing gate to selectively provide or close access to or from the upper landing; a mobile structure slidably connected to the fixed structure and thereby movable in height between the lower landing and upper landing, the mobile structure having a platform; and an elevator mechanism controlling the sliding movement of the mobile structure relative to the fixed structure; the wheelchair lift unit being CHARACTERIZED IN THAT the upper landing gate is integrated to the unitary fixed structure.

3. The wheelchair lift of claim 1 or 2 wherein the unitary fixed structure has a mast having two upright and parallel side posts with a given width therebetween, a closed lower portion between the two side posts, and an upper portion having the upper landing gate extending between the two side posts.

4. The wheelchair lift of any one of claims 1 to 3 wherein the upper landing gate has two lateral halves, each half being vertically hinged to a corresponding one of the two side posts in a manner to be openable by pivoting from an aligned closed position toward the upper landing.

5. The wheelchair lift of any one of claims 1 to 4 wherein the upper landing gate has a locking system which is mechanically engaged to lock the upper landing gate into the closed position when the platform is lowered from the upper landing gate height.

6. The wheelchair lift of claim 5 wherein the locking system comprises a first engaging member fixed to the upper landing gate, a rod being slidably connected to the fixed structure and being downwardly biased, the rod having a second locking member which is matingly engageable with the first engaging member to lock the upper landing gate, and having a foot protruding downwardly, the mobile structure being engageable against the foot when raised, to move the rod upwardly, against the bias, and thereby disengage the second locking member from the first locking member.

7. The wheelchair lift of claim 5 wherein the locking system comprises a hinge plate fixed to the upper landing gate, having a first vertical hole receiving a hinge pin, and an other vertical hole spaced from the first hole, a rod being slidably connected to the fixed structure and being downwardly biased, the rod having a vertically-oriented pin which is downwardly engageable with the other vertical hole, and having a foot protruding downwardly, the mobile structure being being engageable against the foot when raised, to move the rod upwardly, against the bias, and thereby disengage the pin from the other vertical hole.

8. The wheelchair lift of any one of claims 5 to 7 comprising a locking system sensor which detects engagement of the locking system, and a controller which stops the movement of the mobile structure if the engagement of the locking system is not detected within a predetermined distance.

9. The wheelchair lift of claim 8 wherein the locking system sensor also acts as a height sensor by sending to the controller a signal indicative that the mobile structure has reached the height of the upper landing, the controller thereafter halting the movement of the mobile structure.

10. The wheelchair lift of any one of claims 1 to 9 wherein the fixed structure further comprises an upper landing ramp bridging a gap between the fixed structure and the upper landing, the upper landing ramp being hinged to the fixed structure about a horizontal axis.

11. A wheelchair lift comprising a fixed structure fixable in position relative to a lower landing and an upper landing; a mobile structure slidably connected to the fixed structure and thereby movable in height between the lower landing and upper landing, the mobile structure having a platform having a lower landing edge adjacent the lower landing when moved to the lower landing height, and at least one other edge contiguous to the lower landing edge and having a receiving structure upwardly extending therefrom, and a lower landing gate having a proximal end horizontally hinged to the lower landing edge of the platform, and being pivotable thereabout between an upright closed position where a distal end thereof, opposite the proximal end, is placed against the receiving structure, and an open position where the distal end is pivoted downwardly against the lower landing and the lower landing gate acts as a ramp between the platform and the lower landing, and an actuator mechanism controlling the pivoting movement of the lower landing gate to selectively provide or close access between the lower landing and the platform; and an elevator mechanism controlling the sliding movement of the mobile structure relative to the fixed structure.

12. The wheelchair lift of claim 11 wherein the lower landing gate has a locking system which is mechanically engaged to lock the lower landing gate into the closed position when the platform is raised from the lower landing gate height.

13. The wheelchair lift of claim 12 wherein the locking system includes a hook provided at the distal end of the lower landing gate, a rod being slidably connected to the receiving structure and being downwardly biased, the rod having a pin which is downwardly engageable with the hook to lock the lower landing gate in the closed position, and having a foot protruding downwardly from the platform, the foot being engageable against the ground when the mobile structure is moved downwardly to the lower landing height to move the rod upwardly, against the bias, and thereby disengage the pin from the hook.

14. The wheelchair lift of any one of claims 12 or 13 comprising a sensor which detects engagement of the locking system, and a controller which stops the movement of the mobile structure if the engagement of the locking system is not detected within a predetermined distance.

15. The wheelchair lift of claim 14 wherein the controller stops the movement of the mobile structure towards the lower landing height based upon detection of disengagement of the locking system by the sensor.

16. A wheelchair lift comprising a fixed structure fixable in position relative to a lower landing and an upper landing and having an upper landing gate; a mobile structure slidably connected to the fixed structure and thereby movable in height between the lower landing and upper landing, the mobile structure having a platform and a lower landing gate; an elevator mechanism controlling the sliding movement of the mobile structure relative to the fixed structure; whereat at least one of the upper landing gate and the lower landing gate has a locking system which is caused mechanically engage and lock the corresponding landing gate into a closed position by movement of the mobile structure away from the height of the corresponding landing, while the elevator mechanism is activated.

17. The wheelchair lift of claim 16 wherein the locking system includes a vertically slidable component biased toward a locking position relative to the at least one of the upper landing gate and the lower landing gate, the vertically slidable component having an abutment surface which comes into abutment and is thereby displaced against the bias, thus disengaging the lock, when the mobile structure is moved to the corresponding one of the lower landing gate height and the upper landing gate height.

18. The wheelchair lift of claim 16 wherein the locking system comprises a first engaging member fixed to the corresponding one of the landing gates, a sliding component being slidably mounted with vertical freedom of movement, and being downwardly biased toward a locking position, the sliding component having a second locking member which is matingly engageable with the first engaging member to lock the corresponding landing gate when in the locking position, and having an abutment surface facing downwardly and receiving an abutting contact from below during movement of the mobile structure, as the mobile structure reaches the height of the corresponding landing, thereby moving the sliding component upwardly, against the bias, and disengaging the second locking member from the first locking member.

19. The wheelchair lift of claim 17 or 18 wherein the locking system is provided for the lower landing gate, the sliding component is slidingly connected to the mobile structure, and the abutment surface protrudes downwardly from the wheelchair platform for abutment against the ground as the mobile structure is lowered to the lower landing gate height.

20. The wheelchair lift of claim 17 or 18 wherein the locking system is provided for the upper landing gate, the sliding component is slidingly connected to the fixed structure, and the abutment surface receives the mobile structure as the latter is raised to the upper landing gate height.

21. The wheelchair lift of any one of claims 17 to 20 wherein the sliding component has a rod.

22. The wheelchair lift of any one of claims 17 to 20 wherein the abutment surface is part of a foot which protrudes downwardly.

23. The wheelchair lift of any one of claims 16 to 22 comprising a sensor which detects engagement of the locking system, and a controller which stops the movement of the mobile structure away from the corresponding landing gate height if the engagement of the locking system is not detected within a predetermined distance.

24. The wheelchair lift of claim 21 wherein the controller stops the movement of the mobile structure toward the corresponding landing gate height based on the detection by the sensor that the locking system has been disengaged.

25. The wheelchair lift of claim 23 or 24 wherein the sensor detects engagement of the locking system by sensing the relative position of the sliding component.

26. The wheelchair lift of any one of claims 16 to 25 further comprising a gate close sensor detecting a closed-state of the gate when the gate is closed and connected to the controller, the controller allowing movement of the mobile portion only when the gate is detected to be in the closed state.