BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to wheelchair access systems employing platforms, and more particularly to a wheelchair lift platform structure having folding platform sections for use in conjunction with a vehicle having a floor from which the system is deployed and stowed to provide an unobstructed view from within the vehicle.

2. Description of the Related Art Vehicular wheelchair access systems for handicapped persons, such as lifts and ramps, can be mounted on vehicles and made deployable/stowable with respect to the vehicle. Wheelchair users typically move their wheelchair along the lift or ramp platforms in order to transfer from the ground to the vehicle and from the vehicle to the ground using a lift mechanism and platform structure, which may be operated mechanically, electrically, pneumatically or hydraulically, etc. Known wheelchair lift platform structures include solid rigid panels or floors as platform structures that must be stowed away within the vehicle itself. Accordingly, the wheelchair access system is used in conjunction with a portion of the floor space of the vehicle and further may obstruct passageways and restrict the amount of available space within the vehicle.

For handicapped persons, mobility is enhanced with the availability of wheelchair access systems that are powered to provide much or all of the movement of the motorized platform structure. This is particularly useful due to the inconvenience of physical activity by the wheelchair passenger. Such lifts typically have pivotal mechanisms for raising and lowering platform structures, see e. g. , U. S. Patent No. 5,261, 779 to Goodrich for"Dual Hydraulic, Parallelogram Arm Wheelchair Lift"issued 16 November 1993 and U. S. Patent No. 6,238, 169 to Depuy, et al. for"Dual Function Inboard Barrier/Bridge Plate Assembly for a Wheelchair Lift"issued 29 May 2001 to applicant's assignee. Each of these disclose dual hydraulic, parallelogram arm wheelchair lift assemblies for use typically in commercial vehicles. The lift assembly has a platform connected to a parallelogram linkage. In both of the above assemblies, when the platform of the lift is in a stowed position, the platform essentially blocks the doorway, making it very inconvenient to use the doorway or the windows on the vehicle door. Moreover, the wheelchair access system being fixed on the floor of the vehicle itself may provide limited space and visibility from and within the vehicle.

Other wheelchair lifts that do not completely block the door when in a stored position <BR> <BR> have been described, e. g. , U. S. Patent No. 4,664, 584 to Braun, et al. for"Rotary Wheelchair Lift"issued 12 May 1987 discloses a rotary hydraulic lift having a vertically-telescoping slide tube and a horizontal wheelchair platform support arm attached to the lower end of the slide tube allowing the platform into or out of the vehicle parallel to the slide tube. However, the platform structure and pivotal mechanism employed in rotatable wheelchair lifts require a substantial amount of space.

Devices known in the prior art have only been partially successful in providing safety, stability and ease of operation in regard to the design of the lift and platform structure.

Foldable and multiple section platform assemblies are known to decrease the platform area when not in use. Known examples of platform structures employing hinges between inner and outer platform sections such that the outer section rises and folds against the inner section on the outer side include U. S. Patent No. 6,379, 102 to Kameda for"Wheelchair Lift with Foldable Platform"issued 30 April 2002. A lack of predictability of operation while being folded or unfolded, however, is a substantial disadvantage associated with this type of platform assembly when the platform structure is deployed from its stowed position. For example, in the stowed position the outer platform section, unless properly hooked, can dangle and assume a variety of positions. Safety barriers and motion damping to prevent and protect against predictable movements of the lift structural componentry have either not been provided or are not effective.

To address the growing concern for passengers who are handicapped or otherwise have limited mobility, it would be desirable to provide compact, storable wheelchair access systems that minimize the space they occupy on the floor of the vehicle for storing the lift platform structure while providing for enhanced access to the door and particularly the door window for unobstructed views from within the vehicle.

SUMMARY OF THE INVENTION The present invention relates to a wheelchair access system facilitating deployment from the floor of a vehicle with limited space for storage within the vehicle while providing an unobstructed view for occupants from within the vehicle. In a described embodiment, the wheelchair access system utilizes a parallelogram lift with a platform structure including at least two platform sections providing an extended platform floor when deployed. The platform sections include a first platform section and a second platform section, which may be pivotally stacked for storage in a stowed orientation with a low vertical profile allowing for an unobstructed view from within the vehicle.

The platform structure of the wheelchair access system deploys the first platform section alongside the second platform section with an actuator powerable for pivotally moving the platform sections between stowed and deployed orientations. Accordingly, the stowed orientation stores the platform sections for a low vertical profile. To this end, the vertical height of the stacked platform structure may be approximately half the horizontal length of the unfolded platform structure with the wheelchair lift in the deployed orientation.

Briefly summarized, the present invention relates to a wheelchair access system with a folding platform for use in conjunction with a vehicle having a floor. This access system includes right-side and left-side vertical arms and an actuator powerable for moving between positions both inboard and outboard the vehicle. A first platform section is coupled to a vertical arm for movement by means of the actuator. A second platform section is moveable between folded and unfolded positions with respect to the first platform section as the actuator moves the right-side and left-side vertical arms between positions inboard and outboard the vehicle, respectively. The second platform section is coupled for movement with the actuator. The access system employs a gear assembly for coupling the first platform section to the second. The gear assembly pivotably moves the second platform section in a controlled operation with respect to the first platform section.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view of a vehicular wheelchair access system having a platform in a vertically stowed, folded position.

Fig. 2 is a perspective view of the wheelchair access system of Fig. 1 with the platform partially deployed.

Fig. 3 is a perspective view of the wheelchair access system of Fig. 1 with the platform unfolded and extending from the vehicle in a transfer level position.

Fig. 4 is a perspective view looking in the outboard direction of another embodiment folding mechanism with the platform in a horizontal transfer level position.

Fig. 5 is a perspective view looking in the inboard direction of the folding mechanism of Fig. 4 with the platform in a vertically stowed, folded position.

Fig. 6 is a perspective view looking in the outboard direction of the folding mechanism of Fig. 4 with the platform in a vertically stowed, folded position.

Fig. 7 is a perspective of the wheelchair access system of Fig. 1 showing one configuration of an attachment arrangement between the cable mechanism, the lifting structure and the platform.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Any such alterations and further modifications in the illustrated embodiments, and such further applications of the principles of the invention as illustrated herein are contemplated as would normally occur to one skilled in the art to which the invention relates.

Referring now to Fig. 1 there is illustrated a vehicular access system 10. Although access system 10 is illustrated as a wheelchair lift type system, it is also contemplated that the present invention has application in wheelchair ramp type systems. Access system 10 is mounted in the door of a vehicle (not shown) to provide wheelchair passenger access to and from the vehicle. Access system 10 has a platform movable in the inboard and outboard directions relative to the vehicle, as indicated by arrow I (inboard direction) and arrow O <BR> <BR> (outboard direction. ) Examples of wheelchair access systems are provided in U. S. Patent No.

6,238, 169; U. S. Patent No. 5,806, 632; U. S. Patent No. 5,261, 779; and U. S. Patent No.

6,065, 924; each of which is incorporated herein by reference in its entirety. Another example of a wheelchair access system is The Braun Corporation's EV BRAUN ENTERVAN wheelchair access ramp.

In the illustrated embodiment, access system 10 includes a motive source 12 operatively coupled to paired parallelogram type lifting mechanisms 14. Parallelogram lifting mechanisms 14 include vertical arms 20 to which an inboard end of platform 22 is pivotally coupled. When not in use, it is desirable to stow platform 22 in the vehicle in a vertical orientation adjacent the door of the vehicle to minimize its intrusion into the vehicle.

Due to vertical clearance and sightline requirements, it can also be desirable that the platform fold 22 into a reduced height configuration when it is vertically stowed. It is contemplated that platform 22 include an outer section 24 foldable relative to an inner section 26 such that platform 22 has a reduced height in the vehicle doorway when in the vertically stowed position of Fig. 1. However, it should be understood that aspects of the invention described herein do not require that platform 22 include foldable sections.

Access system 10 also includes articulated lever assemblies 16 pivotally connected to the inboard end of platform 22 at one end and to a corresponding one of the vertical arms 20 at their other end. Articulated lever assemblies 16 can include a longer arm 80 pivotally connected to a shorter arm at a common center along with a saddle block 130 for contacting the bottom arm of parallelogram lifting mechanisms 14, such as shown and described in the wheelchair lift apparatus previously disclosed by applicant's assignee in U. S. Patent no.

5,261, 779 to Goodrich for"Dual Hydraulic Parallelogram Wheelchair Lift"issued 16 November 1993, U. S. Patent No. 6,238, 169 to Depuy, et al. for"Dual Function In Board Barrier/Bridgeplate Assembly for a Wheelchair Lift"issued 29 May 2001, and U. S. Patent No. 5,806, 632 to Budd, et al. for"Spring Assist System for Gravity Deployment of Stowed Platform Wheelchair Lifter"issued 15 September 1998, which are hereby incorporated by reference in their entirety. A safety shield 18 extends from a corresponding one of the vertical arms 20 along each side of articulated lever assemblies 16 to prevent a part of a person or object from being placed therebetween before and/or during lift operation.

Motive source 12 is operable to swing lifting mechanisms 14 along path R to move platform 22 from the folded vertically stowed position of Fig. 1, to the unfolded transfer level position or horizontal entry level position of Fig. 3, to the ground level position of Fig. 7, and back as discussed further below. Motive source 12 can be electrically coupled to the vehicle power source and include hydraulic and/or electrical motors, pumps, and other components to accomplish the desired movement for lifting mechanisms 14.

Mounting members 93 are secured to base plate 56 of the access system 10, and the base plate 56 is bolted to the floor of the vehicle. Lifting mechanisms 14 are pivotally mounted to a corresponding one of mounting members 93. Each lifting mechanism 14 includes an upper arm 88 and a lower arm 90. Upper arms 88 are each pivotally coupled at their inboard end to a corresponding one of the mounting members 93. Lower arms 90 are also each pivotally coupled at their inboard end to a corresponding one of the mounting members 93 below upper arm 88. A cylinder 92 is pivotally coupled at its outboard end 92a to lower arm 90 and also to vertical arm 20. The inboard end of cylinder 92 is pivotally coupled to the inboard end of upper arm 88 at mounting member 93. The cylinder 92 is a hydraulic cylinder that includes a tube housing in which a piston is movably positioned and is attached to one end of a rod. Hydraulic pressure acts on the piston and rod for movement between an extended position in which arms 88,90 are deployed horizontally and spaced apart from one another, as shown in Fig. 7, and a retracted position in which arms 88,90 are vertical or near vertical and adjacent one another, as shown in Fig. 1. A deploy assist mechanism 86 is provided to assist in initiating movement of lifting mechanism 14 from the vertical position of Fig. 1 toward the deployed position of Figs. 7 below.

Under normal operation to stow platform 22, hydraulic pressure is supplied to the piston of the cylinder to retract moving lifting mechanisms 14 from the transfer level position of Fig. 3 to the vertically stowed position of Fig. 1. To deploy platform 22, hydraulic pressure is vented from the outboard side of cylinder 92 to extend moving lifting mechanisms 14 from the vertically stowed position of Fig. 1 toward the transfer level position of Fig. 3. It is contemplated that the weight of platform 22 and lifting mechanism 14 cause extension and venting of hydraulic pressure until the transfer level position of Fig. 3 is attained.

In its stowed position, the center of gravity of access system 10 can be at or closely aligned with cylinders 92. The extension of cylinder 92 caused by venting of hydraulic pressure to allow movement of piston of the cylinder 92 may not occur as quickly as desired to initiate deployment of each of the lifting mechanisms 14 from the vertically stowed position. In embodiments employing deploy assist mechanism 86, deployment assist mechanism 86 initiates or assists in extending cylinder 92. This places the center of gravity of access system 10 in the outboard direction a sufficient amount so that the weight of access system 10 extends cylinder 92 to continue deployment of lifting mechanisms 14 and platform 22 in a smooth, uninterrupted manner.

Using deploy assist mechanisms 86, it is contemplated that lifting mechanisms 14 and even platform 22 can be stowed in an over-vertical orientation such that, when stowed, each extends at an angle in a slightly inboard direction relative to a vertical axis. This can reduce the inboard-outboard profile of the stowed access system 10 in the vehicle. In such an over- vertical stowed orientation, deploy assist mechanisms 86 provide an initial push on cylinder 92 sufficient to push lifting mechanisms 14 and platform 22 through the vertical axis in the outboard direction until gravity deployment takes over with the weight of access system 10.

Referring now to Figs. 1-3 and 7, the foldable platform sections 24,26 will be further described. Platform 22 has outer section 24 and inner section 26 foldable relative to one another, as shown in FIG. 1, to assume a reduced height Configuration when platform 22 is vertically stowed in the vehicle. In one form, platform 22 is coupled to vertical arms 20 with a pair of pivot pins, each of which are located at a corresponding one of the vertical arms 20 to couple to the inboard end of platform 22 thereto. In another form, platform 22 is coupled to vertical arms 20 with an axle that extends between each of the vertical arms 20 along the inboard end of platform 22.

Outer platform section 24 has side barriers 28 and inner platform section 26 has side barriers 30. Platform sections 24,26 can each be provided with meshed grid-like transfer surface between their respective side barriers. In the preferred embodiment, a standard, expanded wire mesh is used, alternating a solid plate-like surface that may be provided between the respective side barriers. Solid transfer surfaces can be provided since the platform sections are folded relative to one another to a reduced height configuration, avoiding obstruction of all or part of a window of the vehicle adjacent the lift. In addition to improved aesthetics, a solid transfer surface provides a uniform and smooth rolling surface for a wheelchair. In one particular form, the transfer surface of each of the platform sections 24,26 is an aluminum plate with a non-slip powder coating adhered thereto.

A pair of coupling members 32 (only one illustrated, the other being blocked by side barriers 28,30) are provided to couple outer section 24 to inner section 26. In the illustrated embodiment, coupling members 32 are in the form a plate having a first end pivotally connected to side barrier 28 and another end pivotally coupled to side barrier 30. Platform section 24 pivots relative to the end of coupling member 32 to which it is coupled and platform section 26 pivots relative to the opposite end of coupling member 32. Thus platform sections 24,26 are foldable relative to one another about coupling members 32 between folded and unfolded positions with respect to the first platform section as the actuator moves the right-side and left-side vertical arms between positions inboard and outboard the vehicle, respectively. The second platform section is coupled for movement with the actuator. The access system employs a gear assembly for coupling the first platform section to the second.

The gear assembly pivotably moves the second platform section in a controlled operation with respect to the first platform section. Bumpers 34 are engaged to the outer surface of each plate 32 and contact the inner surface of vertical arms 20 to center the folded platform 22 therebetween when in the position of Fig. 1.

Side barriers 28 each include a first engaging member 36 coupled at an inboard endwall of side barrier 28, and side barriers 30 each include a second engaging member 38 coupled at an outboard endwall of sidebarrier 30 to provide a gear assembly with a pair of spur gears mounted in parallel shaft mounts with engaging teeth for controlled movement as the second platform section is pivotably folded and unfolded with respect to the first platform section. First engaging member 36 of the gear assembly includes a number of teeth that interdigitate or mesh with teeth on second engaging member 38 of the gear assembly. First engaging member 36 and second engaging member 38 key outer platform section 24 to inner platform section 26 so that the platform sections move in concert with one another in a smooth, repeatable manner and are maintained in this smooth concerted movement between the folded and unfolded configurations. First engaging member 36 and second engaging member 38 are keyed with one another to ensure that both of the platform sections 24,26 are, for example, horizontally oriented when unfolded as shown in Fig. 3. Engaging members 36, 38 also provide bearing support when platform 22 is loaded to prevent outer section 24 from moving relative to inner section 26.

Access system 10 includes a pair of flexible coupling mechanisms in the form of cable mechanisms 40 that are each coupled at a first end 40a to a corresponding one of the side barriers 28 of outer section 24 and at an opposite second end 40b to vertical arm 20. In the illustrated embodiment, second end 40b is engaged to a projecting member extending in the inboard direction from vertical arm 20. Cable mechanism 40 control the folding and unfolding of outer section 24 relative to inner section 26. For example, as platform 22 moves from its Fig. 1 position toward its Fig. 2 position, cable mechanisms 40 pull on or bias outer section 24 to swing the outboard end of outer section 24 in the direction of arrow S until the Fig. 3 configuration is obtained. Cable mechanisms 40 also assist in maintaining outer section 24 and inner section 26 in their Fig. 3 and Fig. 7 horizontally deployed positions.

As the inner section 26 is pivoted relative to vertical arms 20 from its horizontal orientation toward its vertical orientation, each of the cable mechanisms 40 contacts the upper edge of a corresponding one of the side barrier 28. Side barriers 28 each include a cantilevered portion 28a that provides an extended upper edge surface profile for side barrier 28 of sufficient length and height to maintain cable mechanism 40 in a taut condition during folding/unfolding of platform 22 and also after platform 22 is folded. A guiding portion having sidewalls and a groove or track therebetween sized to receive cable mechanism 40 can be provided along the upper edge of each of the side barriers 28 to maintain cable mechanism 40 in contact with the upper edge of side barrier 28 and cantilevered portion 28a. A guiding portion having sidewalls and a groove or track therebetween sized to receive cable mechanism 40 can also be provided along a portion of the upper edge of each of the side barriers 30 to maintain cable mechanism 40 in contact therewith as platform 22 moves between its folded and unfolded configurations.

Side barriers 30 each have an outboard notch 30a configured to receive the corresponding cantilevered portion 28a when inner and outer sections 24,26 are deployed, as shown in Figs. 3 and 7. Side barriers 30 also each include a cutout 30b located so that side barrier 30 does not contact or interfere with the corresponding cable mechanism 40 and its connection with vertical arm 20 at second end 40b when platform 22 is folded and vertically stowed.

Access system 10 further includes handrails 42 extending horizontally from vertical arms 20 when platform 22 is deployed in a horizontal position as shown in Figs. 3 and 7.

Handrails 42 fold vertically relative to vertical arms 20 so as to extend along vertical arms 20 when platform 22 is in its vertically stowed position of Fig. 1. Access system 10 also includes a spring-loaded rollstop 46 pivotally connected to the outboard end of platform 22 that is normally spring-biased to a raised safety barrier position as shown in Fig. 3. Rollstop 46 includes feet 46a, 46b that contact the ground (Fig. 7) to move rollstop 46 to an extended transfer level position.

When platform 22 is in its folded, vertically stowed position, bumpers 44 contact respective ones of handrails 42 and push handrails 42 against the adjacent vertical arm 20.

This pivots outer section 24 about its connection with coupling member 32 to exert a biasing force on outer section 24, pushing it against the underside of inner section 26. The inboard/outboard profile of folded platform 22 is minimized by pushing feet 46a, 46b against the underside of inner section 26 to deploy spring-loaded rollstop 46 downwardly to its extended transfer level position. This minimizes the profile of the folded platform 22 in the inboard/outboard directions, and also prevents outer section 24 from moving relative to inner section 26 when folded thereagainst and rattling of the folded platform 22 when the vehicle is in operation.

When platform 22 is in its folded, vertically stowed configuration of Fig. 1, feet 46a, 46b (see Fig. 2, only one illustrated) can contact corresponding ones of bumpers 60 positioned on the bottom side of inner platform section 26 adjacent the inboard end of platform 22. As feet 46a, 46b push against bumpers 60, spring-loaded rollstop 46 is deployed to an extended position. In this extended position, the width of the folded wheelchair lift 10 along the vehicle floor in the inboard/outboard direction is minimized. It is contemplated that bumpers 60 can be made from an elastomer material or other shock absorbent material so as to minimize noise that might be created by the folded lift 10 during vehicle operation.

Bumpers 60 can also extend from the underside of inner section 26 a sufficient distance for deployment of rollstop 46 to be initiated before platform 22 is fully folded, and to ensure that biasing members 44 can exert sufficient force to deploy rollstop 46 when platform 22 is fully folded.

Access system 10 further includes a bridge plate 50 pivotally coupled to the inboard end of platform 22. A pair of actuator assemblies 52 are provided to couple bridge plate 50 to each of the articulated lever assemblies 16. Actuator assemblies 52 and articulated lever assemblies 16 operate in concert such that contact between articulated lever assemblies 16 and bottom arms 90 of lifting mechanisms 14 variously raise and lower bridge plate 50 between a raised safety barrier position (Fig. 7) and a generally horizontal transfer level position (Fig. 3.) Referring to Figs. 1-4, access system 10 includes a floor plate 56 having guide members 54 extending therealong. Guide members 54 form a slot along floor plate 56 sized to receive bridge plate 50 therein. As platform 22 is moved from the transfer level position of Fig. 3 to its folded vertically stowed position of Fig. 1, bridge plate 50 moves in the inboard direction and is received in the slots between guide members 54 and floor plate 56. Guide members 54 maintain bridge plate 50 against the floor plate 56, preventing bridge plate 50 from being raised off the floor where it could be a tripping hazard when platform 22 is vertically stowed. Bridge plate 50 is held down by guide members 54 to maintain smooth operation of platform 22 as it unfolds. Also, the telescoping arms of articulated lever assembly 16 tend to alternately extend and retract relative to one another as platform 22 is folded and/or unfolded. Guide members 54 maintain continuous movement between the telescoping arms in a corresponding one of the extend and retract directions as platform 22 is folded or unfolded. A locking function preventing bridge plate 50 from being raised while access system 10 is being stowed may be provided with a hook on saddle block 130 of the articulated lever assembly as set forth in the aforementioned U. S. Patent No. 6,238, 169, hereby incorporated by reference.

Figs. 4-6 illustrate another embodiment cable mechanism 40'. Cable mechanism 40' includes a first guide member 140'coupled to the outer side of side barrier 28 of outer section 24, and a second guide member 142'coupled to the outer side of side barrier 30 of inner section 26. Outboard end 40a'of cable mechanism 40'is coupled to the outer side of side barrier 28, and the inboard end 40b'of cable mechanism 40'is coupled to vertical arm 20. In the illustrated embodiment, first and second guide members 140', 142'are rollers having a guide path extending therearound sized to receive a portion of cable mechanism 40' therein and maintain the positioning of cable mechanism 40'outside side barriers 28,30. It is contemplated that one or both of the rollers can be rotatably engaged to the respective side barrier or non-rotatably engage to the respective side barrier.

When platform 22 is in its unfolded orientation of Fig. 4, a portion of cable mechanism 40'is positioned in the guide path of first guide member 140'. As platform 22 is folded, cable mechanism 40'bends around biasing member 44 and is received in the guide path of first guide member 140', as shown in Fig. 5, and also in the guide path of second guide member 142', as shown in Fig. 6. First and second guide members 140', 142'maintain cable mechanism 40'in the appropriate position relative to folded platform 22 to ensure that it is smoothly unfolded and the cable 22 does not get hung up or tangled with other parts of access system 10.

When platform 22 is folded, it is desirable that feet 46a, 46b of rollstop 46 are pushed against the underside of platform 22 with sufficient force so that rollstop 46 is fully deployed to minimize the inboard/outboard profile of the folded platform 22.

Referring now to Fig. 7, an attachment arrangement between platform 22, lifting mechanism 14 and cable mechanism 40 will be discussed. Each cable mechanism 40 includes a cable extending between vertical arm 20 and platform 22 that flexes when compressed. Thus, if a load were applied to platform 22 such that the cables of cable mechanisms 40 were no longer in tension or the cables were caused to bend, then platform 22 would tend to fold. For example, a load applied at the outboard end of platform 22 would tend to cause outer section 24 to fold relative to inner section 26. To counteract the tendency of outer section 23 to fold relative to inner section 26 when deployed, cable mechanism 40 can be arranged so that it remains in tension and in a taut condition when a load is applied to the outboard end of platform 22.

In the illustrated embodiment, cable mechanism 40 extends along an axis Al.

Platform 22, when in its horizontally deployed position, extends along an axis A2. Axis A2 extends through pivotal connection of inner section 26 with vertical arms 20 and also through the connection of inner section 26 with coupling member 32 and through the connection of outer section 24 with coupling member 32. It is contemplated that the extensions of axes Al and A2 in the outboard direction intersect at a location X. It is contemplated that location X is positioned at or spaced a distance from the outboard end of platform 22. It is further contemplated that axes Al and A2 could be arranged so that location X is positioned at the outboard end of deployed rollstop 46.

Location X is positioned so that cable mechanisms 40 remain in tension and/or in a taut condition if a load is applied at or near the outboard end platform 22, thus resisting rotation of outer section 24 about its connections with each of the coupling members 32. It is desirable that axis A2 remain in a generally horizontal orientation when platform 22 is deployed. The orientation of axis Al relative to axis A2 can be established by varying for each cable mechanism 40 the location of second end 40b along vertical arm 20. The orientation of axis Al relative to axis A2 can also be established by varying for each cable mechanism 40 the height H1 of first end 40a above axis A2. The orientation of axis Al relative to axis A2 can be established by varying for each cable mechanism 40 both the location of second end 40b along vertical arm 20 and the height H1 of first end 40a above axis A2.

While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only preferred embodiments have been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.