Note: Descriptions are shown in the official language in which they were submitted.
9~
WHEELCHAIR LOADING DEVICE FOR AIRCRAFT
This invention relates to devices for loading persons in
wheelchairs into and out of passenger aircraft, preferably smaller
so called "commuter aircra~t".
Certain handicapped people require aircraft boarding
as~istance at airports; usually wheelchairs are used to move such
people around airports and into aircraft. There is no difficulty
loading such people in wheel~hairs into passenger aircraft at
airports where permanent level enkry boarding ramps are available
for passenger loading since a wh~elchair and occupant can be simply
wheeled along such a boarding ramp and into the aircraft.
Difficulties arise at airports, especially smaller airports,
handling aircraft, especially commuter aircraft, which have
"airstairs" (steps built into an aircraft door) for loading
passengers or require a movable fliqht of steps to service boarding
needs. Neither of the foregoing accommodates the enplaning or
deplaning of passangers in wheelchairs and, therefore, air travel
of the handicapped is restricted or rendered difficult. Lifting and
carrying handicapped passengers by hand onto and off of commuter
aircra~t is often required.
At present the United States Federal Aviation
Administration guidelines require either the airport or the carrier,
depending on responsibility~ to provide boarding assistance for
disabled people, who request assistance. These guidelines require
the airport or the carrier, where there are no level entry boarding
ramps, to provide mechanical lifts, ramps, boarding chairs and
personnel necessary to operate them.
There is an exception to this applying to aircraft with a
passenger capacity of 19 or less, where physical limitations prevent
the use of level entry boarding ramps, mechanical lifts and other
feasible devices. Here the only presently available method is to
load the disabled person by hand. However, carrier and airport
personn01 are not required to do this for reasons o~ safety and
dignity.
Carriers and airports are required to use any feasible
devices that are developed. Refusal of service would not be
acceptable if a feasible device existed but was not available at a
particular airport.
DISCUS ION OF PRIOR ART
A prerequisite for any wheelchair loading device for
aircraft is height adjustability as the various aircraft in use
today have different designed door sill heights which also vary
according to aircraft load. Loading devices exist for handicapped
persons in wheelchairs. O'Brien, in U.S. Patent 3,~88,463, issued
June 10, 1975 teaches a hoist operable by the wheelchair occupant,
which consists of a self levelling platform mounted on paired
hydraulically operated booms. The platform can move from a position
level with the ground to an elevated position. A substantial
disadvantage with this device is that the wheelchair has to move on
and off in the same direction, i.eO, either reverse on, forward off,
or forward on, reverse off.
Koerber, in U.S. Patent 4,493,602, issued January 15, 1985,
teaches a hoist built into a vehicle comprising a column in the
vehicle mounting a hoist which can be vertically raised or lowered
z~
by a drive screw to a level just above the vehicle floor, and th~n
horizontally swung about a pivot into the vehicle for load ng or
discharge. Integration of such a device into a commuter aircraft
is undesirable for many reasons, especially cost. Also, desirably
any wheelchair loading d~vice would incorporate adjustable stair
means for use by other passengers. Adjustable stairs are fairly
well known in building construction but these are not adjustable
when installed; the adjustable feature lies in their adaptability
to fit a number of building situations and exemplary are U.S. Patent
4,593,503 issued June 10, 1986 to Koslowski, and U.S. Patent
4,615,160 issued October 7, 1986 to LeBlond. These patents disclose
stairs both extendable in length and adjustable in angle of rise,
while maintaining level (horizontal) treads. Mobile adjustable
access stairs for aircraft are less common and those known allow no
wheelchair access. See U.S. Design Patent 149,392 issued April 20,
1948 to Varrieur, U.S. Patent 2,551,345 issued May 1, 1955 to Scott,
U.S. ~esign Patent 177,858 issued May 29, 1956 to Phelps, U.S.
Patent 2,812,528 issued November 12, 1957 to Odell, and U.S. Patent
3,910,264 issued Octobar 7, 1975 to Mahieu.
Thus, there is a need for a wheelchair loading device for
aircraft, especially commuter aircraft, which conveniently, safely
and with dignity provides for loading of passengers in wh~elchairs.
It would be most suitable, as well, if such a device could
accommodate boarding of such aircraft by other, non-disabled
passengers, both for the convenience of the other passengers and to
provide for a disabled passenger a greater sense that he or she is
not so different from other passengers. Disabled persons are
striving generally for provision of support equipment and services
that can also be used by non-disabled persons to put the former more
into the mainstream of normal life.
SUMMARY OF THE INVENTION
The invention provides a lift comprising in combination a
base, platform and means for vertically moving said platform with
respect to said base between lower and upper levels, said platform
comprising an apron adapted ~or loading and unloading persons in
wheelchairs at said lower and upper levels. The apron may comprise
either a drawbridge ramp or a retractable apron. Preferably the
drawbridge ramp is attached to the platform by a piano hinge. In
one version first and second drawbridge ramps are hingeably attached
to the platform; these first and second drawbridge ramps may be
opposed, on opposing sides of the platform. In a less preferred
form the first and second drawbridge ramps are adjacent. In a most
preferred form the apron is a single apron slideably mounted beneath
said platform, adapted for loading and unloading persons in
wheelchairs at first and second opposed platform sides. The single
apron may be operated manually or, most preferably, by electric
means.
The lift of the invention may be placed against an aircraft
side with the platform in a lowered position. In such position, a
wheelchair and occupant are pushed up the apron onto the platform,
the apron is raised or retracted, the platform is raised to a level
suitable for the aircraft, the apron is lowered or extended to the
aircraft door-sill, or airstair sill in a lowered aircraft door, and
the wheelchair and occupant are pushed over the apron, all without
rotating the wheelchair. Under certain circumstances it may be
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desirable to have one drawbridge ramp at right angles to another.
As there is considerable variation in door-sill level due to
aircraft type and loading, it is desirable to provide an equal
variety of possible upper levels. In practice the desirable maximum
upper level of the lifk above a substrate i5 65 inches (1.65m),
while the minimum upper level is 40 inches (1.02m), to load/unload
current commuter aircraft. To ensure matching possible door levels
the platform can be held at any height within this range. In
practice the apron as a drawbridge may be 19 inches ~0.4Bm) wide and
48 inches (1.22m) long. As the platform must be lowered onto the
base which can hardly be less than 4 inches (O.lm) high, the
drawbridge provides a reasonable ramp angle of 1:12 (4.78 degrees),
within official guidelines. An extendible, slidiny inner ramp
within a hinged outer ramp (drawbridge) may be provided if a longer
drawbridge, or drawbridge with variable extension part is desired.
When the apron is a single, retractable apron mounted beneath the
said platform, preferably it is about 6 feet long, 18 inches wide
and operable to extend about 5 feet beyond either opposed end of the
said platform.
Advantageously the base is mounted on a chassis having
wheels, wherein the base conveniently forms the lowest part of the
chassis. As the wheels are xetracted, the base is lowered into
ground contact. The retractable wheels therefore allow the lift
device to be towed or pushed to the aircraft, and the base to be
lowered into ground contact.
In another form, the invention is a lift comprising in
combination a base, platform and means ~or vertically moving tha
platform with respect to the base means, the platform comprising
39;~
an apron adapted for loading and unloading persons in wheelchairs
at the lower and elevated levels, the means for vertically moving
the platform with respect to the base means comprising support means
attached to the platform, moveable means attached to each support
means to move vertically the support means, the moveable means being
mounted on the base, and an actuator to actuate each moveable means,
drive mechanism to drive each actuator, the drive mechanism being
synchronized, and mounted on the base.
The platform preferably has bracket means each comprising
a bushing engaging a substantially vertical ball screw, which is
rotatably journalled in upper and lower brackets attached to a
substantially vertical upright means attached to the base, an
actuator being attached to the base of the ball screw. The actuator
is conveniently selected from the group consisting of a pulley
adapted for V belt drive, a sprocket wheel adapted for sprocket
chain drive, a timing wheel adapted for timing belt drive, and a
miter gear adapted for miter gear drive. The bushing is preferably
a ball nut.
The platform most preferably has brackets comprising an
acme screw rather than the said ball screw, and a bushing that is
a nut. Further preferably the brackets include a rocker means on
such nut ~or transferring weight of the platform vertically onto the
nut notwithstanding non-vQrtical movements of the platform. Also
preferably, the acme screw is mounted to receive loads in tension
rather than compression, for instance by attachment at a top portion
thereof to an upright support.
Preferably stairs are extendible between a first upper
level o~ said platform and a second upper level of said platform,
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whereby persons on foot may use such lift as stair access. The
stairs may be aligned at right-angles to the direction of extension
of the said single apron. Also, when upright members are attached
to the base, the said stairs may be attached between the upright
members. The apron may comprise first, second and third drawbridge
ramps, pr~ferably attached by piano hinges to the platform, and may
be extendible. Most preferably the apron is a single apron
slideably mounted beneath said platform.
In another aspect the invention is an improvement in a
wheelchair lift having a platform, suitable for loading and
unloading aircraft, the improvement comprising an apron adapted to
load and unload persons in wheelchairs from said platform to
aircraft, and an apron, preferably the same as the immediately
a~oresaid apron, adapted to load and unload persons in wheelchairs
from platform to ground. The wheelchair lift may comprise a base
mounted on a chassis having wheels. The base may form the lowest
part of the chassis, and the wheels may be retractable, so the base
may be lowered into ground contact.
The platform deck is preferably 32 inches (0.9m) by 60
inches (1.2m) to provide room for an occupied wheelchair and
attendant.
The base preferably includes channels about 4 inches ~O.lm)
high with internal flanges to accommodate the drive system.
Preferably upright guides, which may be square or circular in cross-
section and contain the moving means, are 3 inches (0.075m) wide on
each side if square, or in diameter if round, and 65 inches ~1.65m)
high from ground to top. A commercially available ball screw or
acme screw can be used in the operation of the invention.
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As will be appreciated by those skilled in the art, the
dimensions given aboYe are for guidance only; they can be varied
within acceptable limits without changing the structure or ~unction
of the lift.
SUMMARY OF THE DRAW NGS
Preferred embodiments of the invention are illustrated in
the drawings in which: -
Figure 1 shows a perspective view of one embodiment of the
lift device of the invention;
Figure 2 shows a perspective view of the lift platform of
the lift device of Figure l;
Figure 3 shows a cross-sectional view of another embodiment
of the lift platform of the lift device of Figure 1, an apron
mounted under the platform and a mechanism to drive the apron;
Figure 4 shows a perspective, part transparent view of one
corner of the platform shown in Figure 3;
Figure 5a shows a side view through a cut-away section of
an upright guide where there are connections to the platform of the
lift device of Figure 1;
Figure 5b shows a side, cross-sectional view through the
upright guide of Figure 5a;
Figure 6a shows a side, cross-sectional view of a top area
of the upright guide of Figure 5a, where an uppar end o~ an acme
screw is mounted;
Figure 6b shows a side, cross-sectional view of a bottom
area of the upright guide OI Figure 5a, where a lower end of an acme
screw is mounted;
2~
Figure 7 shows a perspective view of the chassis and
selected support members of the lift device of Figure 1;
Figure 8 shows an overhsad plan view of a preferred drive
mechanism for the lift platform of the lift de~ire of Figure 1;
Figure 9 shows a perspective view of a preferred lift
plat~orm for a lift devic~ according to the invention;
Figure 10 shows another perspectiYe view of the preferred
plat~orm of Figure g;
Figure 11 shows a perspective view of a stairs arrangement
that may be used with the lift device o~ Figure 1;
Figure 12 shows a perspective view of a retractable side
wheel mount that may be used with the lift device of Figure l;
Figure 13 shows an overhead plan view of two lift devices
according to the invention positioned for use adjacent aircraft
doorways.
DETAILED DESCRIPTION OF THE DRAWINGS
Figure 1 shows one preferred version of the lift device of
the invention. The lift device comprises generally a platform lift
section 1 preferably having four corner upright guides 2, 3, 4 and
5 for a vertically moveabl~ platform 6 extending over a base 7 (or
chassis) o~ the lift device. The platform 6 is shown in Figure 1
in an elevated position. The lift devi also preferably comprises
a flight of stairs 8 with hand rails 9, 10. The ~ase 7 preferably
has attached two side wheels 11 (one not visible in Figure 1) and
one pivotable nose wheel assembly 12, preferably including tWQ
wheels 98, and all of the wheels may be fully retractable. When the
wheels are in a fully retracted position, the base 7 rests on the
2~101~
ground providing stability for the lift device when in use. A tow
bar 13 is provided for attachment to a tow vehicle ~not shown) for
moving the device to and from aircraft. Optionally the nose wheel
may be driveable to assist manoeuvring of the vehicle when close to
an aircraft. Otherwise it may be so manoeuvred by hand. Housing
14 accommodates batteries and motor for driving the platform 6
vertically and optionally battery charger, electric powered
hydraulic pump and hydraulic cylinder for raising and lowering side
wheèls. ~he batteries also may provide power for other operable
parts of the lift device, such as a retractable apron for assisting
movement on or off the platform 6, or driveable nose wheels 98. The
platform 6 preferably has a single retractable apron 15 for
supporting the movement of persons in wheelchairs or non-disabled
persons onto or off of the platform 6 either at ground or aircraft
door-sill level. The apron 15 is extendable from the platform 6
from either of ends 16 and 17 of the platform 6. This facilitates
loading a wheelchair onto the platform 6 at one end (16 or 17), for
example in a forward direction and, when the platform has moved to
a different level, unloading the wheelchair off of the platform 6
at the other end, also in a forward direction. This is a feature
of convenience ta those moving wheelchairs in that tric~y, backing-
up manoeuvres can be avoided.
Figure 13 shows how the lift device of the invention
preferably is positioned adjacent a commuter aircraft for enplaning
and deplaning passengers. It can be seen that the stairs 8 and
apron 15 are at right angles, which arrangement allows for
convenient sharing of the apron 15 and platform 6 by passengers in
wheelchairs and non-disabled passengers. Such arrangement also
1 0
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allows for safe enplaning and deplaning in either front-door or
rear-door use, in that all passengers are kept away from the wing
and propeller. In Figure 13 the aprons 15 are shown extended both
to th~ aircraft doorways and the ground, although in use only one
such extension at a time can be accommodated in the preferred
embodiment of the invention.
In Figure 2 the platform 6 is shown to have a flat deck 18,
openable end gates 19, 20 and a side barrier 21. As shown in
Figures 9 and 10, preferably the openable end gates lg, 20 are each
configured as telescoping door 70. Each door 70 preferably
comprises a pivot shaft 71, panel 73 and positive positioning tab
72. The positive positioning tab 72 can hold the door 70 in a
closed position across the end (16 or 17) of the platform 6. The
door 70 is opened from a closed position as shown in Figure 10 by
first li~ting the door 70 up with its pivot shaft 71, thereby
disengaging the pivot shaft 71 from a notch of the positive
positioning tab 72 so that the door 70 can then be rotated about its
pivot shaft 71, about 90 degrees, to an open position (as shown in
Figure 9), whereupon the door 70 can then be lowered with its pivot
shaft 71 to engage another notch of the positive positioning tab 72
and thereby be kept in the open position. These steps can be
reversed in order to close each door.
The door 70 preferably has a telescoping feature for added
safety and convenience~ When the door 70 is open, panel 73 can be
extended along guides 75 in a direction in parallsl with the
direction of extension of apron 15 to provide a barrier and handrail
for the safety of passengers moving along the apron 15 to or from
an aircraft.
~0~9~
In the embodiment of the invention shown in Figures 1 and
2, the end gates 19 and 20 may be non-telescoping doors hinged to
adjacent support panels 76 or 77 and 78 or 79 respectively. In such
case, and in particular where such gates are not suitable for
functioning as a barrier and handrail when open as in telescoping
door 70~ it may be advantageous to provide panels 23, 24 slideably
mounted on supports 76 and/or guide rails (not shown). Panels 23,
24 are slideable in either direction of extension of apron 15 so
that when apron 15 is in use at an elevated position adjacent an
aircraft doorway, such panels may act as barriers and provide
handrails for the safety of persons moving along the apron 15.
Optionally only one of panels 23, 24 may be provided. The panels
23, 24 are secured to the platform 6 such that they move with the
platform 6 during vertical motion.
In Figures 2, 9 and 10, space 22 is shown which allows
walking passengers to move between the platform 6 and stairs 8
enroute to or from the aircraft. The space 22 would be spanned by
the panel 23, if used, during vertical movement of the platform 6
or during towing and storage of the lift device. End gates 19, 20,
barrier 21, supports 77, 78, 79, 80 and panel 23 when used,
substantially enclose the platform 6 at its perimeter during
vertical motion of the platform 6. The top edges 25 of such gates,
barrier, supports and panel may act as handrails. The flat deck
18 of the platform 6, the deck of apron 15 and the steps of stairs
8 may be provided with an anti-skid surface.
Below each gate 19, 20 there is preferably provided a
transition flap 67. Such flap is hinged to the edge of the platform
6 at each end 16, 17 thereof. In Figures 1, 2 and 10 tha transition
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flap 67 is shown in a vertical position for when, Eor example, the
platform 6 is in motion. When the platform 6 is in a position for
loading or unloading passengers, the transition flap is in a lower~d
position as in Figure 9, in contact with the deck of apron 15 so as
to provide a smooth, gradient transition, suitable for wheelchair
movement thereover, between the level of the flat deck 18 of the
platform 6 and the lower level of the deck of apron 15. The
transition flaps 67 may be spring-loaded to hold the same in either
a vertical or lowered position, as desired.
The single retractable apron 15 is slideably mounted under
the flat deck 18 of the platform in channel side openings 41, 42.
Wedge-shaped rubber ends 26 are provided on each e~tremity of the
apron 15, so that when either of such ends 26 is in contact with an
aircraft, damage to the aircraft from rubbing, scraping or bumping
is prevented, for instance during movement of the aircraft while
passengers enplane or deplane. The apron 15 preferably also has
raised side panels 27 which prevent wheelchair wheels from rolling
off the apron 15 at sides thereof when wheelchairs are moved along
the apron 15.
Figures 3 and 4 show a preferred arrangement for
control].ing movement of the apron 15. The apron 15 is slideably
mounted to the underside of platform 6 preferably on nylon slides
36 adjacent each side of the apron 15 ~only one of the nylon slides
36 is ~hown in Figure 3). Attached along most of the lPngth of the
underside of the apron 15 is a rack 29 engaged with a pinion 30 in
turn connected through a bearing block 31 and mounting supports, for
attachment to a flange 32 of the underside of the platform 6 near
one end 16 or 17 thereof, to a torque limiter 33. The torque
9~
limiter 33 is driveably connected to the gearmotor 34 by a roller
chain 35. A second roller chain 37 is arranged to driveably connect
with a second pinion (not shown) mounted near the other end of the
underside of the platform 6, which second pinion also engages the
rack 29. Wires 38, shown in Figure 4 curving around an upright
guide 5, connect electrical control panel 39 to a power source, e.g.
batteries in housing 14. Other wires (not shown) connect the
control panel 39 to the electric gearmotor 34O The control panel
39 can be mounted at the top of support 40 ~xtending from the deck
18 up to a height convenient for operation by a standing operator.
Preferably, the control panel 39 and support 40 are located near an
end 16 or 17 of the platform 6, and a duplicate of control panel 39
and support 40 are provided near the other end of platform 6.
When it is desired that the apron 15 be extended to meet
an aircraft doorway, an operator activates a power switch on the
control panel 39, preferably a spring-return toggle switch in the
direction in which the apron 15 is desired to be moved. Power is
then supplied to the electric gearmotor 34 which turns the roller
chain 35 to drive the torque limiter 33, the roller chain 37 and
pinions 30. Turning of the pinions 30 moves the rack 29 and
attached apron 15 until the operator deactivates the power switch
or the apron 15 reaches a positive stop mounted on each end of the
underside of platform 6. The use of positive stops prevents
overtravel of the apron 15. When a positive stop is encountered,
further extension of the apron 15 is halted, the torque limiter 33
begins slipping and thereby prevents damage to the gearmotor 34.
Also, if the apron 15 accidentally rams into an aircraft during
extension to reach the doorway of the aircraft, the torque limiter
~0~
will slip as it would if the apron 15 had encountered a positive
stop, thereby stopping further extension of the apron 15 and
consequently preventing damage to the aircraft.
The apron 15 preferably maintains a generally level (i.e.
horizontal) to modestly inclined plane, that is inclined downwardly
~rom the level of the platform 6, at various extension positions
of the apron 15 preferably by means of mounting in the pair of
parallel, nylon slides 36, which are U-shaped in cross-section and
firmly attached along flanges 81 of the underside of the platform
6. Into each of the nylon slides 36 slideably fits a nylon runner
68 secured respectively along each side of the apron 15.
Preferably, some vertical clearance is provided for the nylon
runners 68 within the slides 36, more so towards the ends of the
slides 36, so that as the apron 15 is extended it acquires an
incline which is at its greatest when the apron 15 is fully
extended; increased vertical clearance towards ends of the slides
36 may he provided by using slides 36 having vertically wider U-
shaped cross-sections towards their ends, or more preferably by
using runners 68 which are tapered towards their ends.
The preferred embodiment of the lift device of the
invention allows the platform 6 to be lowered to a level close to
the ground. At its lowest position, the deck 18 is about 7 inches
o~f the ground. Such a low level i5 attained by means of the
retractable wheels 11 and wheel assembly 12, which allow the base
7 to be lowered to rest on the ground, and location supports for the
platform 6, in the preferred embodiment namely acme screws 41 within
upright guides 2, 3, 4 and 5, at or outside the perimeter of the
platform 6 rather than underneath the platform 6. Nevertheless, in
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2~ 8
the preferred embodiment, the apron 15 is required as a ramp to
provide a smooth transition for the mov~ment of wheelchairs from the
platform 6 to the ground and vice versa. When the apron 15 is
nearly fully extended in either of its directions of extension only
one of the pinions 30 is in contact with the rack 29, namely the one
closest to the end of the platform 6 from which the apron 15 is
extending. As well, the apron 15 is su~ficiently extended as to be,
with respect to its mounting in the nylon slides 36, tilted
downwardly. Notwithstanding tilting of the apro~ 15 in this manner,
contact between the said one o~ the pinions 30 and the rack is
maintained. Thus, the apron 15 can be retracted from a tilted
position extending downwardly to the ground (or aircraft door-sill)
by operation of a switch on the control panel and consequential
driving of the said one of the pinions 30.
Preferably, when preparing to extend the apron 15 to an
aircraft doorway, the platform 6 is first positioned at a level
hîgher than the aircraft door-sill level. The apron 15 is then
extended until at least rubber end 26 reaches over the door-sill.
The platform 6 is then lowered until rubber end 26 rests on the
door-sill; a downward incline of the apron 15 from platform 6 to the
door-sill may be maintained.
Although the arrangement for electrical operation of the
apron 15 as shown in Figures 3 and 4 is pre~erred, manual mechanisms
(not shown) for such control may also be used, for instance using
a wheel, belt (or chain) and pulley systsm wherein the operator
selectively turns a control wheel 28 (see Figure 1) provided
ad~acent a handrail on the platfo~m 6, which conseguently, through
pulley and belt connectors, turns pinions corresponding to pinions
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30 acting on a rack, corresponding to rack 29, beneath the apron 15
so as to move the same.
Although the single, retractable apron 15 and the control
mechanisms for such apron described above are preferred means for
providing access to and from the platform 6, alternative means, such
as a drawbridge at each end 16 and 17 of the platform may be used.
Such a drawbridge, which is hinged where it meets an end of the
platform 6, may be moved from a vertical position to an
approximately horizontal to modestly inclined position to facilitate
movement of passengers over it from platform 6 to and from an
aircraft or to and from the ground.
The preferred lifting mechanism for the platform 6 is shown
in detail in Figures 5, 6. The platform 6 is mounted at each of
its four corners onto an acme scr~w encased by an upright guide 2,
3, 4 or 5. A vertical slot runs the length of each upright guide,
facing the platform 6 through which connections from the acme screw
to the platform 6 extend. Referring to Figure 5, the acme screw 41
is rotatable through nut 42 such that nut 42 may be raised or
lowered along the length of the acme screw 41 as the screw 41 is
turned. Locked onto the nut 41 is a stem 43 which projscts into a
slot 44 in a nylon block 45, bolted onto a side of platform 6 at 106
(see Figure 9), which slot 44 provides clearance around and at the
end of the stem 43 to accommodate small, e.g. preferably up to 1/2~
inch, movements of the stem as the nut 41 is moved by selective
turning of the screw 41. Resting on top of the nut 41 is nylon
rocker 46 having a stem 47 firmly attached to it and extending
laterally through the vertical slot of the upright guide into and
preferably through nylon block 45 above the slot 44. Further
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preferably the stem 47 projects through nylon block 45 and through
a hole or slot 107 (Figure 9) in the side of platform 6 to which the
nylon block 45 is bolted or otherwise attached at 106 (Figure 9),
which hole or slot is larger in diameter or width respectively than
the diameter of the stem 47. The stem 47 is firmly in contact with
the nylon block 45 especially since, in this preferred embodiment,
the weight of the platform 6 is acting through th~ nylon blocX 45
onto the stem 47. If the stem 47 projects through a hole or slot
107 in the side of platform 6 as aforesaid, such side does not
contact stem 47 in view of the aforementioned larger diameter of the
hole, only the nylon block 45 is in contact with stem 47, thereby
allowing for the platform 6 to slide on stem 47.
All of the weight of the platform 6 is thus distributed
through its four corners proportionately to each acme screw via the
nylon block 45, stem 47, nylon rocker 46 and nut 42. The nylon
rocker 46 surrounds the acme screw 41 but is normally not in contact
with the acme screw 41 by reason of the provision of a hole of
larger diameter than the diameter of the acme screw through the
center of the nylon rocker 46. This ensures that all of the weight
of the platform that is transferred to the nylon rocker from the
stem 47 is transferred vertically to the nut 42 and not directly
from the nylon rocker 46 to the acme screw 41, e.g. even if the
platform 6 tilts the stem 47 and the nylon rocker 46. The stem 47
may tilt (see arrows 48) by reason of one or more of several motions
of the platform 6. Although it is ideal to achieve in the
construction of the lift device vertical, parallel alignment of all
four acme screws in the upright guides 2, 3, 4, 5, so that the
distances separating such acme screws from each other are identical
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898
from the bases to the tops of the acme screws, in practical terms
there is some variation of such distances. Thus, as the platform
6 is raised or lowered, -the slight variation in such distances
causes the platform 6 to move slightly towards or away from a given
acme screw, in a roughly horizontal plane. Passenger movement may
also cause the plat~orm 6 to move slightly up or down, or jiggle.
These motions, as well as motions from the changing forces during
starting and stopping vertical movement of the platform 6, can cause
tilting of the stem 47.
The nylon rocker 46 is smaller in diameter than the inside
diameter of the upright guide 2 so as to allow for rocking motion
of the nylon rocker 46 in response to the aforementioned motions of
the platform 6 without binding on the inside wall of upright guide
2. Nylon material is by its nature also less likely to bind; it is
self-lubricating to some extent. In view of the aforementioned
larger diameter hole in the nylon rocker 46, binding with the acme
screw 46 is also prevented.
The platform 6, when mounted as described above, is "free-
floating" in that only vertical loads are transmitted to the acme
screws 41 via the nuts 42. The platform 6 is free to move in a
horizontal plane within the constraints of the upright guides 2, 3,
4, 5.
The stem 43 is prevented, by contact with one or other side
walls of the slot 44, from pivoting with attached nut 42 about the
acme screw 41. This prevents the nut 42 from rotating as the acme
screw 41 is selectiYely turned and results in the nut 42 either
being raised or lowered on the acme screw 41. Vertical motion of
the nut 42, occasioned by selective turning of the acme screw 41,
-- 19 --
2~ 9~3
in turn carries with it the nylon rocker 46 resting on its upper
surface and r through the rigid connections of the nylon rocker to
the stem 47, nylon block 45 and platform 6, the platform 6 as well.
The aforementioned clearancs in the slot 44 allows for tolerance of
the above-described motions of the platform 5, without any resulting
forc~ being applied to the stem 43 or, consequentially, the nut 42,
and thereby preserves smooth, non-binding motion of the acme screw
through the nut 42 when the acme screw is selectively turned. Also,
if downward motion of the platform 6 is obstructed and does not
follow downward motion of the nut 42 when the acme screw 41 is
selectively turned 50 as to effect a desired lowering of the
platform 6, perhaps because the one of the nylon rockers 46 is stuck
against a side wall of an upright guide 2, 3, 4 or 5 ice or dirt,
the stem 43 will, preferably after only about 1/2-inch of downward
movement of the nut 42, contact the bottom of the slot 44 and itself
push downwards on the nylon block, in most cases so as to free the
nylon rocker 46, or other obstructed attachment to the platform 6,
from the obstruction. This self-unsticking capability would return
downward movement to the platform at the previously o~structed area
as the nut 42 continues to descend.
The acme screws in each of the upright guides 2, 3, 4, 5
are synchronized for simultaneous turnîng so that the corners of the
platform 6 will be raised or lowered simultaneously; this pre~erves
the horizontal, level plane of the platform 6 during raising and
lowering of the platform 6.
Figures 6a and 6b show the preferred mounting arrangement
of each acme screw 41 in upright guides 2, 3, 4 and 5. A top
portion of the acme screw 41 is secured for bearing vertical loads
- 20 ~
2(~ 9~3
while remaining rotatable via bearing 50, bearing mounts 51 to the
inside wall 49 of the upright guide 2, castle nut 52 and flat washer
52a The bearing 50 should be able to bear at least 1/4 of the
gross platform weight in thrust, i.e. axial, not radial, loading.
The acme screw 41 can turn in the bearing 50 when the acme screw 41
is selectively turned. Vertical loading on the acme screw 41 causes
ten.sion from where it is mounted above bearing 50 down the acme
screw 41 to the point of loading.
At a bottom section of the acme screw 41, there is shown
in Figure 6b a preferred support of the acme screw 41 in relation
to the inside wall of upright guide 2 incorporating self-aligning
bearing 53. The acme screw preferably is slideably fitted through
the bearing 53 and is not also mounted so as to bear compression
loading. The usually slender acme screw 41 may buckle undar
compression loading, causing platform support failure. It i~
preferred that the acme screw 41 be hung from the said top portion
accordingly. The acme screw 41 is connected to a gear pulley 54 in
an area 55 beneath the bottom of the upright guide 2, such that when
the gear pulley 54 is selectively turned by a belt (not shown in
Figure 6b but see the toothed belt 61 in Figure 8) the acme screw
41 is also turned. The gear pulley 54 may be provided with ribs for
engaging a toothed belt, or with sprockets for engaging a chain,
rather than a belt.
It is noteworthy that there is sufficient friction between
the acme screw 41 and the nut 42 that when the acme screw 41 is not
selectively turning at the instance of an operator, the nut 42 will
not, despite the force of the weight of even a fully loaded platform
acting upon it from above, itself force the acme screw to turn and
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-- ~0~ 398
cause descent of the nut 42 and the platform 6 with it. Thus, when
the platform 6 is not being vertically moved to raise or lower
passengexs, for instance when it is stationary at a level allowing
passengers in wheelchairs to be whealed onto or off of an aircraft,
the platform 6 will not, even slowly, descend; no safety stop
preventing unwanted descent is required.
In an alternative embodiment, a ball bearing screw, such
as the kind supplied by the Warner Electric Brake and Clutch Company
of Troy, Michigan, U.S.A., may be used in place of each acme screw
41. The nut mounted on a ball bearing screw which corresponds to
the nut 42 of the acme ~crew 41 rides smoothly and with ~ar less
friction than the latter over the ball bearing screw. However,
friction is sufficiently low that the force of the weight of the
platform 6 acting on the nut on a ball bearing screw may cause the
ball bearing screw to turn and, consequently, the nut on such screw
and platform 6 to descend. Thus, when the platform 6 is at a
desired level, a stop must be provided to prevent unwanted possible
descent of the platform 6. Use of the acme screw 41 eliminates the
need for such a stop and, in view of its lower cost, is presently
preferred over the ball bearing screw.
Each upright guide 2, 3, 4 and 5 is mounted on bas~ 7,
preferably at locations shown in Figure 1. In Figure 7, braces 56
and 57, for supporting vertical alignment of a pair of adjacent
upright guides are clearly shown. Each upright guide 2, 3, 4 and
5 may be mounted on the base 7 as shown in Figure 6b. Conventional
nuts and bolts 58 secure part 59 of the base of the upright guide
to plate 60 over part of the base 7. The gear pulley 54 is thus
under plate 60 of the base 7.
- ~2 -
39~
Engaged around part of each gear pulley 54 is a belt,
toothed (or timing) belt or chain (61 in Figure 8), which runs
within a space, best shown in Figure 7, bordered by base members 62
and beneath plates 60 (overlying further base members perpendicular
to base members 62). The belt or chain 61 also engages a main drive
pulley 63 (see Figure 8), and may also engage adjustable tensioner
pulleys 64 and fixed tensioner pulleys 65. The belt or chain 61
projects through a hole (not shown) in the base member 62 closest
to the stairs 8 in order to engage the main drive pulley or sprscket
63. The main drive pulley or sprocket 63 is attached to a motor and
gearbox 66 which is covered by housing 14. When an operator
actuates the motor, the main drive pulley or sprocket turns, thereby
moving the engaged belt or chain 61 and, conseguentially, each gear
pulley or sprocket 54 and the acme screw 41 to which it is attached,
in a synchronous manner. The main drive pulley or sprocket can be
turned selectively clockwise or counter-clockwise, thereby moving
the engaged belt or chain 61 and acme screws 41 clockwise or
counter-clockwise respectively to move the platform 6 upwards or
downwards respectively if the acme screws 41 have right-hand
threads.
Operation of the motor driving the ascent or descent of
platform 6 preferably is controlled by a switch on control module
39 and on the aforementioned duplicate of control module 39. A
- manually operable ~rank attached to a shaft, in turn connected to
the gearbox, may be provided in the lift device to allow for manual
over-ride of the electrically driven system in the event of, for
example, a failure of the power supply.
The preferred embodiment of the lift device of the
20~
invention includes adjustable flight of stairs 8 comprising
(referring to Figure 11) parallelogram stringers 90 running on
wheels 91 in guide channels 92, thus providing level steps 93 at
different positions of extension and contraction of the flight of
stairs 8~ The bottom step thus mainly moves along the direction
mark~d "a" (in Figure 11) and the top step mainly moves up and down
in the direction marked "b", as the stairs 8 are moved in relation
to vertical movement of the platform 6. The hand rails 9, 10
(Figure 1) may be supported by braces 83 and may include panels 84.
When the plat~orm 6 is at its lowest level, the flight of
stairs 8 rests in its most contracted position, in which the
underside of the top-most step may be in contact with brace 56
between upright guides 2, 5 (see Figure 7). As the platform 6
ascends and reaches the level of the top-most step, hooks 94
attached to the side of the platform 6 contact the underside of the
top-most step. As the platform 6 ascends further, the hooks lift
the top-most step with it, preferably always maintaining the level
of the top-most step flush with the level of the deck 18. As the
top-most step is lifted, of course the flight of steps 8
simultaneously moves, drawing the wheels 91 along guide channels 92
towards the base member 62.
The flight of stairs 8 preferably includes paired opposed
sleeves 95 secured to the lateral edges of the top-most step, which
slideably enclose upright rods 96 attached at their upper ends to
cross pieces 97 in turn secured to upright guides 2, 5, and at their
lower ends to brace 56. The upright rods 96 secure the top-most
step from lateral, forwards and backwards motions during ascent and
descent when moved by the platform 60
- 24 -
2~)0(~39~
The nose wheel assembly 12 preferably includes a hydraulic
cylinder 100 for hydraulically lowering and raising the base 7 where
the nose wheel assembly contacts forward support structure 99 of the
base 7. The forward-most and lower-most part of the base 7 contacts
the ground when the hydraulic cylinder is appropriately activated.
Side wheels 11 preferably also include a hydraulic cylinder(s) for
lowering or raising the sides of the base 7 to which the side wheels
11 are respectively attached. Thus, when the base 7 is suficiently
lowered hydraulically at its side wheels 11 and nose wheel assembly
12, it can completely rest on the ground, providing stability for
use in enplaning and deplaning passengers. Optionally casters may
be provided on the underside of base 7 to facilitate further
positioning of the lift device once all wheels have been retracted.
The side wheels 11 can alternatively include a cranking mechanism
for manual control of lowering and raising the base 7 onto and above
the ground in conjunction with the hydraulically controlled motion
at the nose wheel assembly. Figure 12 shows a side wheel crank stub
axle 101 including crank arm 102, lever 103 and actuator 104,
mounted onto a top of side member 105 of base 7 (which also provides
a stair wheel guide channel 92). On actuation, leYer 103 rot~tes
as indicated by the arrow to raise crank arm 102, stub axle 101 and
the attached side wheel (not shown). The "raising" of the side
wheel effects a lowering of the base 7.
The preferred mechanism disclosed herein for the raising
and lowering of the platform 6, namely that incorporating driveable
acme screws or ball screws adjacent the perimeter of the platform,
can be substituted by other mechanisms such as driveable (e.g. by
chain, belt or shaft~ or hydraulic scissors, or telescoping
- 25 -
~o~9~
hydraulic cylinder lifts, preferably connected and located to sne
or more sides of the platform 6. Under-the-platform scissors or
telescoping hydraulic cylinder lift mechanisms can be expected to
be too bulky and prevent sufficient lowering of the platform 6 to
the ground accordingly. Xowever, if such are disposed to a side of
the platform, this disadvantage would be eliminated. The preferred
mechanism of the invention presently offers significant cost
advantages over scissors or telescoping hydraulic cylinder forms of
lift mechanisms.
The preferred feature of raising and lowering the base 7
from and to the ground for stability of the lift device during use
by means of retractable wheels may be substituted by a plurality of
hydraulically driven retractable stabilizer arms which are mounted
on the base and able to extend onto the ground to take up at least
some of the weight of the lift device from the wheels, in the event
lowering of the base 7 to the ground should offer no or little
advantage in particular uses of the lift device or in larger sized
versions of the lift device.
Although this invention is described in terms of specific
embodiments, it is not limited thereto, as would be understood by
those skilled in the art, and numerous variations are possible
within the scope of the invention without departing from tha scope
and nature thereof.
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