Abstract:
A baggage lift system connected between an elevated inclined jet bridge and the ground utilizes actuators which have the ability to change their effective length in order to level the load when lowered to the ground and align the load with the angle of the jet bridge when raised which facilitates safe and effective loading and unloading of baggage and other loads to and from the jet bridge.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a regular US Patent application claiming priority of pending U.S. Provisional Patent application Ser. No. 60/596,051 filed Aug. 26, 2005, the entirety of which is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     Embodiments of the invention relate to lifts, lifts cantilevered from other support structures and levelling systems for loading to structures which vary in inclination. More particularly, embodiments of the invention relate to baggage lifts supported from a structure such as a jet bridge which provide a level position for loading carts or other devices at ground level and which align the load at an inclination corresponding to the structure when lifted.  
       BACKGROUND OF THE INVENTION  
       [0003]     Lifting aids or devices are known for raising loads from a ground surface to an elevated structure, such as lifting baggage carts and the like from the ground for loading to and from an aircraft.  
         [0004]     Jet bridges are typically used for accessing elevated access doors of aircraft. Adjacent to the aircraft, the jet bridge has an exit door to a landing and stairs leading down to the tarmac which enables access outside the jet bridge and to the baggage hold of the aircraft. In the last few years, a problem has developed in the air travel industry with carry-on baggage. Increasingly, passengers are arriving at the door of regional aircraft, typically smaller commuter aircraft, with baggage that cannot be taken into the aircraft passenger area because it is too large or there is no room onboard.  
         [0005]     Currently, this baggage is being handled by airline staff who must take the bags out the exit door of the jet bridge and down the stairs on the outside of the jet bridge to the baggage hold of the aircraft or the reverse for an inbound flight. This is time consuming, staff intensive, and has a high injury rate because of the weight of the baggage and the slope of the stairs.  
         [0006]     An additional complication in the technology is that the design of jet bridges varies widely with no consistency in other equipment which is hung underneath. Several manufactures have proposed or built lifts that attach to the jet bridge by welding and bolting and which have a capacity of about 500 lbs and uncertainty as to the strength of the upper structure. These lifts typically consist of a small platform on which the bags are loaded and which travel to ground level for manual unloading to a cart which is then taken to the aircraft baggage hold. Applicant is not aware of any of these known lifts which is capable of supporting or raising and lowering a baggage cart which may weigh up to about 1000 lbs when loaded.  
         [0007]     Further, jet bridge modifications are expensive and are generally discouraged. Welding in the vicinity of aircraft and the airport tarmac is similarly discouraged due to the prevalence of aircraft fuel and other combustibles.  
         [0008]     A further challenge is encountered in providing a lift to the jet bridge as the jet bridge is typically inclined and the cross slope can change from 0 to up to a 1 in 7 slope. Conventional lift apparatus supported from the jet bridge and which are aligned to the slope of the jet bridge are in a different plane than the ground when lowered, hindering loading of a baggage cart and requiring manual loading of each individual piece of baggage. Similarly, lifts which are aligned to the ground are not aligned with the jet bridge and therefore one cannot transport a baggage cart to and from the jet bridge. Further use of a ground-aligned lift may present safety issues for personnel loading baggage from the elevated jet bridge to the lift.  
         [0009]     There is a demonstrated need for a lift apparatus which adapts to an existing elevated structure, such as a jet bridge, without significant modification and is adaptable to variations in angular alignment between the elevated structure and the ground over which the structure is positioned.  
       SUMMARY OF THE INVENTION  
       [0010]     Embodiments of the invention provide automatic lift ground levelling and jet bridge angle adjustment. Substantially horizontal alignment of the lift structure at ground level permits a load supporting structure such as a loaded baggage cart to be rolled onto the lift. When raised to the elevated position, the inclined, aligned position of the lift permits safe loading for transport of the load to the ground below.  
         [0011]     In a broad aspect of the invention a lifting apparatus for conveying a load between a lower surface and an elevated inclined surface comprises: a first actuator connected to a high point of the inclined surface and having an actuator axis extending towards the lower surface and a second actuator connected between a low point of the inclined surface and being spaced from and parallel to the axis of the first actuator; and a load supporting structure for supporting the load and having a first end supported by the first actuator and a second end supported by the second actuator, wherein the load supporting structure is movable axially along the first and second actuators between a first lowered position and a second elevated position; wherein when the load supporting structure is in the first lowered position, the second actuator has a first effective length shorter than that of the first actuator, the load supporting structure is substantially parallel to the lower surface; and when the load supporting structure is in the second elevated position, the second actuator has a second effective length of about that of the first actuator and load support structure is substantially parallel to the elevated inclined surface.  
         [0012]     The effective length of the second actuator can be achieved in a variety of ways such as a telescoping portion which collapses to cause the second actuator to be shorter than the first or in the case where the load is engaged through fasteners connected between the actuators and the load can be achieved by permitting the second actuator to disengage the load and to travel past the co-operating fastener permitting engagement of the first actuator in advance of the second actuator.  
         [0013]     In one embodiment, a mono beam multi-adjustable clamping system enables adaptation of the lift system for support from virtually any jet bridge of other elevated structure. The lift controls are interlocked with the jet bridge to sympathetically adjust the ground engaging portions should the jet bridge elevation be changed. Further, the lift controls are designed to disengage when the lift reaches extremes in position including ground-engagement and jet bridge alignment. Further the lift is interlocked to avoid actuation when the jet bridge safety gate is open. The gate is also mechanically locked to prevent it from opening if the lift is not at the jet bridge elevation.  
         [0014]     Accordingly in the present proposal, a multi-adjustable clamping system was developed to allow the lift to be attached almost anywhere under the jet bridge and adjusted in both horizontal directions and vertically (3 axis adjusting system). This is done by using a single large (approx. 7″×7″) hollow structural steel member which can be moved horizontally in two directions on the main jet bridge beams. This single member has on the outer end of it a similarly large cross member extending to the vertical tracks for the lift. This arrangement allows for almost complete adjustability of the structure in the field and transfer of a lift to other locations.  
         [0015]     In one embodiment of the invention, the load supporting structure is a platform wherein a baggage cart is movable and can be rolled onto the platform when it is at ground level which eliminates the need for double handling of the bags. In another embodiment using fasteners to engage the laod supporting structure, the baggage cart, wheel chair or the like is the load supporting structure.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]      FIG. 1  is a side view of a highly inclined jet bridge with an embodiment of the lift platform at the ground and level thereto and having received a baggage cart thereon, the first and second elevating members being behind the frame members;  
         [0017]      FIG. 2  is a side view of the lift according to  FIG. 1  wherein the lift is partially elevated and the platform conforms with the angle of the jet bridge, the first and second elevating members being behind the frame members;  
         [0018]      FIG. 3  is a side view of the lift according to  FIG. 1  wherein the lift is elevated to the jet bridge platform and the platform conforms with the angle of the jet bridge, the first and second elevating members being behind the frame members;  
         [0019]      FIG. 4  is an end view of the lift according to  FIG. 1  wherein the lift platform is level with the ground and illustrating the mono-beam;  
         [0020]      FIG. 5  is a partial perspective view of the mono-beam having a mounting portion and one vertical flange with a lift rail secured therealong;  
         [0021]      FIG. 6  is a view of the lift with the platform on the ground in the level loading position;  
         [0022]      FIG. 7  is a upward view of the low side rail and closed jet bridge safety gate;  
         [0023]      FIG. 8  is a view of the lift with the platform on the ground in the level loading position;  
         [0024]      FIG. 9  is a view of the lift with the raised to the jet bridge platform and wherein the platform is parallel with the jet bridge angle;  
         [0025]      FIG. 10  is a close-up view of the telescoping members lift with the platform on the ground in the level loading position;  
         [0026]      FIG. 11  is an underside view from under the jet bridge towards the lift illustrating the mono-beam clamped to the I-beam underside of the jet bridge and with a view of the lift with the platform on the ground in the level loading position;  
         [0027]      FIG. 12  is a view of the mounting portion of the mono-beam with the high side vertical mounting flanges supporting the lift rails for the lift frame;  
         [0028]      FIG. 13  is an underside view from the baggage side of the jet bridge looking under the jet bridge illustrating the mono-beam clamped to the I-beam underside of the jet bridge;  
         [0029]      FIG. 14  is a view of the lift drive, motor, cable drums, cables, four-bar mount and attachment to the vertical flange with the drive in the top-lift position as the platform is elevated off of the ground and tension are in the lift cables;  
         [0030]      FIG. 15  upward view of the jet bridge showing the safety gate and upper structure of the lift rails and drive;  
         [0031]      FIG. 16  is a view of one proximity sensor, model Siemens 3RG4014-0KB00 for the drive interlock;  
         [0032]      FIG. 17  is another view of the lift drive, motor, cable drums, cables, four-bar mount and attachment to the vertical flange, with the drive in the mid-position as the platform is in contact with the ground in the normal loading position;  
         [0033]      FIG. 18  is an underside view of the platform in the elevated position and illustrating the ground engaging castors;  
         [0034]      FIG. 19  is a view of the gat, gate rails and jet bridge platform;  
         [0035]      FIG. 20  is a perspective view of the lift frame with the platform on the ground and a baggage cart poised for loading onto the platform ramp;  
         [0036]      FIG. 21  is a plan view of a portion of a rail engaged with an elevating member for axial movement of the lift therealong, a pulley at a top of the elevating member having been removed for clarity;  
         [0037]      FIG. 22  is a side view of a highly inclined jet bridge with an embodiment of the lift at the ground and level thereto having a baggage cart as the load supporting structure and cooperating fasteners for engaging the lift with the baggage cart; and  
         [0038]      FIG. 23  is a side view of the lift according to  FIG. 22  wherein the lift is partially elevated and the baggage cart conforms with the angle of the jet bridge; and  
         [0039]      FIG. 24  is a detailed view of the co-operating fasteners comprising hooks on the elevating members and loops on the baggage cart in the lowered position and in an embodiment of a lift according to  FIG. 22 , the rails being removed for clarity.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0040]     Embodiments of the invention are discussed herein in the context of a lift connectable to a jet bridge for use with loading and unloading carry-on baggage from the jet bridge to the ground below to permitting stowing said carry-on baggage in the hold of an aircraft. Description in this context is in no way intended to limit the scope of the invention to lifts for use with jet bridges and aircraft only or to the loading of carry-on baggage. Embodiments of the invention are applicable to lifts connectable between any elevated variable angle surface and a lower surface which may be angled or which is generally a substantially horizontal surface for any type of load.  
         [0041]     Having reference to  FIGS. 1-4  and  22 - 24 , a jet bridge  1  is shown in an extreme angle of repose, pivotable about a hinge point off-drawing to the left, for variable angle connection between an elevated gate at an airport and the door of an aircraft, typically lower than the gate elevation. In one embodiment, a lift structure  10  is supported from an underside  2  of the variable angle jet bridge  1 . The lift structure  10  comprises first and second spaced apart, substantially parallel actuators  11 , 12  connected between the jet bridge  1  and a load supporting structure  13 . The first and second actuators  11 , 12  extend toward a lower surface, typically horizontal surface  3 , such as the ground and have an actuator axis A substantially perpendicular to a jet bridge axis B. Each of the first and second actuators  11 , 12  comprises a bracketing upstanding pylon, fixed portion or rail  14  oriented substantially perpendicular to the angle of the jet bridge  1  and an elevating member  15  axially moveable thereon. As shown also in  FIGS. 4 and 5 , the rails  14 , 14  are supported on a mono beam clamping system  40  connected to the underside  2  of the jet bridge  1  without modification of the jet bridge  1 , to bear the reactive lifting loads and to permit positioning of the rails  14 , 14  in three dimensions. The multi-adjustable clamping structure  40  is discussed later in greater detail.  
         [0042]     The lift structure  10  is capable of accepting and supporting a load C, such as a baggage cart or a wheelchair or the like. First and second elevating members  15   a , 15   b  engage the load supporting structure  13  which extends between the first and second elevating members  15   a , 15   b  for forming a substantially rigid structure  16 . The first and second elevating members  15   a , 15   b  are actuated for axial movement of the substantially rigid structure  16  along the rails  14 , 14  between a ground engaging, lowered position wherein the load supporting structure  13  is aligned substantially parallel with the ground  3  and a raised position at the jet bridge  1  wherein the load supporting structure  13  is aligned substantially parallel to the angle of the inclined surface of the jet bridge  1 . This capability would be trivial were it not for the fact that the jet bridge cross slope may vary from zero to up to a 1 in 7 slope, meaning that were it not for this ability, the load supporting structure  13  would be at a 1 and 7 slope at ground level which would make it impossible to push a 1000 lbs. loaded baggage cart onto it.  
         [0043]     In one embodiment, the lift structure  10  comprises the first actuator  11  oriented at a high point H of the inclined jet bridge  1 , typically the side adjacent the hinge point (not shown) and the second actuator  12  at a low point L of the inclined jet bridge  1 , typically the side adjacent the aircraft. The first and second actuators  11 , 12  have independent characteristics permitting variable inclination of the load supporting structure  13 . The load supporting structure  13  is pivotally connected at a first end  17  to the first actuator  11  and at a second opposing end  18  to the second actuator  12 . The load C is supported by the load supporting structure  13  and, when lifted, is positioned at substantially the angle of the jet bridge  1  as a result of the substantially perpendicular positioning of the fixed rails  14 , 14  relative to the jet bridge  1 , the second actuator  12  having achieved a second effective length of about that of the first actuator  11 . When the load C is lowered and the second, second low end  18  of the load supporting structure  13  touches the ground  3  and the second actuator  12  assumes a first effective length shorter than that of the first actuator  11  which permits the first actuator  11  to continue to lower and position the first high end  17  of the load supporting structure  13  on the ground  3 , the load supporting structure  13  now being aligned substantially parallel to the ground  3 .  
         [0044]     In one embodiment as shown in  FIGS. 4, 6  and  20 , the load supporting structure  13  is a platform which is pivotally connected at the first and second opposing ends  17 , 18  to each of the first and second actuators  11 , 12 , forming the substantially rigid structure  16 . For better supporting the platform  13 , the lift structure  10  further comprises first and second upstanding frame members  19   a , 19   b  connected at lower ends  20   a , 20   b  to the first and second opposing ends  17 , 18  of an opposite side  21  of the platform  13  and at upper ends  22 , 22  through crossbars  23  to the first and second elevating members  15   a , 15   b  for forming the rectangular rigid structure  16 . The second elevating member  15   b  and the second frame member  19   b  each comprise an upper portion U and a lower telescoping portion T to which the platform  13  is attached. The first elevating member  15   a  and the first frame member  19   a  are of a fixed length. The platform  13  is capable of pivoting about the connection to the first elevating member  15   a  and the first frame member  19   a  as the telescoping portions T collapse and extend.  
         [0045]     As shown in  FIGS. 1 and 8  in the lowered position, the telescoping portions T of the second elevating member  15   b  and the second frame member  19   b  collapse when the second end  18  of the platform  13  engages the ground  3  to a first effective length E′, which is shorter than the first elevating member  15   a  and the first frame member  19   a,  sufficient to permit the first end  17  of the platform  13  (high side) to continue to lower and conform to the elevation of the ground  3  and thereby the platform  13  assumes a substantially level orientation at the ground  3 . Thus, a load C, such as a baggage cart, can be rolled onto the platform  13  with ease. Typically, the baggage cart C is then secured to the platform by a raised lip or guard rail at the first end  17  of the platform  13  (high side) and by a pivoting platform access ramp  24  (best seen in  FIG. 20 ) at the second end  18  which can be raised to block the second end  18  once the baggage cart C is in place on the platform  13 .  
         [0046]     Turning to  FIGS. 2 and 9 , once the lift structure  10  is actuated and the substantially rigid structure  16  begins to rise to the second raised position, the first actuator  11  immediately lifts the first end  17  of the platform  13  from the ground  3 . The telescoping portions T of the second elevating member  15   b  and the second frame member  19   b  telescopically extend until such time as the second actuator  12  and frame member  19   b  assume a second effective length E″ of about that of the first actuator  11  which positions the platform  13  at an angle substantially aligned with the angle of the jet bridge  1 . A stop  25 , such as a through-bolt, is positioned in each of the second elevating member  15   b  and the second frame member  19   b  to arrest further extension of the telescoping portions T when the substantially rigid rectangular structure  16  is raised above the ground  3  and is aligned substantially parallel to the jet bridge  1 .  FIG. 10  illustrates the telescoping members T and the through-bolts  25  in closer detail.  
         [0047]     With reference to  FIG. 18 , castors  60  on an underside  61  of platform  13  ensure that movement of the jet bridge  1  is accommodated without dragging of the platform  13 .  
         [0048]     In an embodiment of the invention as shown in  FIGS. 22-24 , the load supporting structure  13  is the baggage cart C, wheelchair or the like. The structure of the cart C forms the rigid structure  16  extending between the first and second actuators  11 , 12 . Cooperating first and second fasteners  26   a,    26   b , 27   a , 27   b  act to pivotally engage the load supporting structure  13  to the first and second actuators  11 , 12 . In one embodiment second fasteners  27   a , 27   b,  such as loops, are attached to the load supporting structure  13 , typically adjacent an upper edge  30  of the load supporting structure  13 . First fasteners  26   a,    26   b,  typically protrusions such as hooks, latches or outwardly and upwardly facing pins or the like, are affixed adjacent a lower end  31   a,    31   b  of each of the first and second actuator&#39;s elevating members  15   a,    15   b  for pivotally engaging the loops  27   a , 27   b  on the load supporting structure  13 .  
         [0049]     The first and second elevating members  15   a,    15   b  are oriented substantially perpendicular to the angle of the inclined jet bridge  1  through substantially parallel connection to the rails  14 , 14  thus positioning the elevating member  15   a  of the first actuator  11  higher than that of the elevating member  15   b  of the second actuator  12 .  
         [0050]     As seen in  FIG. 22  with the rigid structure  16  aligned substantially parallel to the ground  3 , the first fastener  26   b  on the second elevating member  15   b  is lower than the loop  27   b  on the second end  18  of the load supporting structure  13  and thus disengages the load supporting structure  13  and shortens the effective length of the second actuator  12  to the first effective length E′ which permits the first actuator  11  to continue to lower and position the first end  17  on the ground  3 .  
         [0051]     With reference to  FIG. 23 , as the elevating members  15   a,    15   b  are actuated to raise the load supporting structure  13 , the first fastener  26   a  on the first elevating member  15   a,  being higher than the first fastener  26   b  on the second elevating member  15   b  engages the loop  27   a  at the first end  17  of the load supporting structure  13  and lifts the first end  17  of the load supporting structure  13  at an angle relative to the second end  18  of the load supporting structure  13 , the load supporting structure  13  pivoting thereabout. As the first fastener  26   b  on the second elevating member  15   b  reaches the first fastener  26   b  on the second end  18  of the load supporting structure  13 , the second elevating member  15   b,  extended to the second effective length E″, engages the loop  27   b  at the second end  18  of the load supporting structure  13  for lifting the second end  18 , the load supporting structure  13  being lifted at the angle of the elevated inclined jet bridge  1 .  
         [0052]     Such a latch-in configuration could accept latch-in carts or wheelchair transporter lifts for taking wheelchairs over to aircraft and lifting them to the hold or to a bag loading belt.  
         [0053]     Best seen in  FIG. 7  and  FIG. 21 , in one embodiment the elevating members  15   a,    15   b  are connected to the rails  14 , 14 , which are C-shaped, for axial movement therealong. Wheels  32  are connected adjacent a top end  33  of each of the first and second elevating members  15   a , 15   b  by pins  34  which permit the wheel  32  to ride within a channel  35  in the C-shaped rail  14  as the elevating members  15   a , 15   b  are actuated to raise and lower.  
         [0054]     Actuation of the lift structure  10  may be through a variety of actuators having the appropriate interlocks. Jet bridges  1  typically utilize both electrical and hydraulic actuators. As shown in  FIGS. 14 and 15  and in one embodiment, a combination electrical and cable lift drive  50  is implemented. An electrical winch motor  51  drives a pair of drums  52  and cables  53  for lifting the substantially rigid rectangular structure  16  up the rails  14 , 14  The electrical lift controls include interlocks to power down when the substantially rigid rectangular structure  16  engages the ground  3 . More particularly, as the substantially rigid rectangular structure  16  contacts the ground  3 , the borne weight on the drive  50  diminishes and the drive  50  can relax on its mount  54 . The drive  50  is mounted on a four-bar linkage  54  permitting a range of motion. As shown in  FIG. 17 , when the substantially rigid rectangular structure  16  is lowered to the ground  3 , the cables  53  slacken and simply without the reactive load, the drive  50  lowers, breaking a first proximity sensor  55  contact and signalling to stop the drive  50  and discontinue lowering of the substantially rigid rectangular structure  16 .  
         [0055]     As shown in  FIG. 14  under full lifting load such as at the second elevated position at the jet bridge  1 , the drive  50  is pulled upward slightly by the cables  53  to bear against an upper stop and actuates a second proximity sensor  56  to stop the drive  50 .  
         [0056]     In other instances, the jet bridge  1  may be adjusted to fit a higher or a lower aircraft. In the case of a higher aircraft, the jet bridge  1  will be elevated, lifting the substantially rigid structure  16  from the ground  3  in the same action. The first proximity sensor  55  ( FIGS. 14, 16  and  17 ), can be activated again and should the programming permit, the substantially rigid structure  16  is automatically lowered with respect to the ground  3 .  
         [0057]     In the opposite instance, if the jet bridge  1  is lowered to accommodate a lower aircraft, a third proximity sensor  57  or alternate program for the first sensor  55  ( FIG. 17 ) causes the substantially rigid structure  16  to rise automatically to avoid driving the substantially rigid structure  16  into the tarmac  3 . As the jet bridge  1  lowers, the cable drive  50  slackens further and the four-bar linkage  54  allows the motor  51  to drop further until the third proximity sensor  57  or first sensor  55  signals to raise the substantially rigid structure  16 .  
         [0058]     Optionally, each of the actuators  11 , 12  may be independently driven and further, the effective length E′, E″ of the second actuator  12  relative to the first actuator  11  may be achieved by varying the distance the second actuator  12  is driven along the rail  14  relative to that of the first actuator  11  regardless whether the actuators  11 , 12  engage the load C through a platform  13  or through other means such as the co-operating fasteners  26 , 27 .  
         [0059]     As previously stated and with reference to  FIGS. 5, 9 ,  11  and  13 , the lift structure  10  is connected by the actuators  11 , 12  to the underside  2  of the jet bridge  1  using a large, hollow, structural steel mono-beam  41  which is clamped to the underside  2  of the jet bridge  1 . Clamps  42  engage exposed lower flanges  43  of “I”-beams  44  on the underside 2  of the jet bridge 1  and extend around the mono-beam  41 . The clamps  42  permit the mono beam  41  to be adjusted to extend laterally more or less from the side of the jet bridge  1 , transverse to the “I” beams  44 . Further, the clamps  42  can move along the “I”-beams  44  to adjust the position of the lift structure  10  along the jet bridge  1 . The elevation of the actuators  11 , 12  is adjustably positionable to the mono beam  41 . Thus, the lift structure  10  is adjustable in three dimensions relative to the jet bridge  1 .  
         [0060]     In one embodiment best seen in  FIG. 5 , the mono-beam  41  is “T”-shaped construction in plan view having a first beam  45  and second beam  46 . The first beam  45  is connected at an intermediate point  47  to the second beam  46  to from a unitary mono bean  41  and is adjustable horizontally therealong. The second beam  46  is clamped to the jet bridge  1  as described above. The first beam  45  extends along the jet bridge  1  and parallel thereto. The rails  14 , 14  of the first and second actuators  15   a,    15   b  are secured to the first beam  45 . As shown in  FIG. 12  (high side) and  FIG. 13  (low side), flanges  48   a  are spaced apart and extend up and down from extreme ends of the first beam  45  for connection to corresponding flanges  48   b  on the rails  14 , 14 . The flanges  48   a,    48   b  contain a plurality of mounting holes  49  to permit initial height adjustment of the rails  14 , 14  and the lift structure  10  to fit each particular jet bridge  1 .  
         [0061]     As shown in  FIGS. 6 , and  19  and in one embodiment, a safety gate  70  is installed between the rails  14 , 14  of the actuators  11 , 12 . The gate  70  is movable on spaced pairs of wheels or slides guided on a tubular rail. The gate  70  is counterweighted to ease hand-lifting. A proximity sensor signals when the gate  70  is closed to enable operation of the lift structure  10 . A mechanical interlock locks the gate  70  closed when the lift structure  10  is not at the jet bridge elevation. For example, a cam on the platform  13  will disengage the mechanical lock when the lift structure  10  is positioned at the jet bridge  1 .  
         [0062]     Preferably, actuation of the lift structure  10  is controlled by a fixed or handheld switch located close to the high side of the jet bridge so an operator can visualize people and hazards during operation of the lift structure.