U.S. patent number 3,869,011 [Application Number 05/320,115] was granted by the patent office on 1975-03-04 for stair climbing tracked vehicle.
This patent grant is currently assigned to Ramby, Inc.. Invention is credited to Howard Jensen.
United States Patent |
3,869,011 |
Jensen |
March 4, 1975 |
STAIR CLIMBING TRACKED VEHICLE
Abstract
A wheel-chair-like stair-climbing vehicle having a pair of main
tracks and a pair of auxiliary tracks hinged in front thereof, an
automatic (partly and preferably hydraulic) pitch control mechanism
controlling the rate of relative rotation between the main and
auxiliary tracks, and a self-leveling seat.
Inventors: |
Jensen; Howard (Huntington,
NY) |
Assignee: |
Ramby, Inc. (Bronxville,
NY)
|
Family
ID: |
27186481 |
Appl.
No.: |
05/320,115 |
Filed: |
January 2, 1973 |
Current U.S.
Class: |
180/9.23;
280/5.22 |
Current CPC
Class: |
B62D
55/075 (20130101); B62B 9/02 (20130101); A61G
5/061 (20130101); A61G 5/066 (20130101); B62B
2301/256 (20130101) |
Current International
Class: |
A61G
5/06 (20060101); A61G 5/00 (20060101); B62D
55/075 (20060101); B62D 55/00 (20060101); B62B
9/02 (20060101); B62B 9/00 (20060101); B62d
055/04 (); B62b 009/02 () |
Field of
Search: |
;180/9.24 ;280/5.22 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Goodman; Philip
Attorney, Agent or Firm: Curtis, Morris & Safford
Claims
I claim:
1. A stair-climbing vehicle comprising a pair of main tracks, a
pair of auxiliary tracks each being aligned and pivotally joined to
a main track adjacent the forward end of said respective main
track, propulsion means for driving said main tracks, independently
of each other when necessary, self-leveling seat means mounted on
said vehicle, automatic pitch-control means mounted to act between
each prospective main track and its auxiliary track for limiting at
least the rate of pivoting of said auxiliary track with respect to
said main track from below said main track towards alignment
therewith, said pitch-control means comprising an elbow linkage
between each auxiliary and main track pair and having a hydraulic
cylinder forming at least part of the linkage forearm and also
having a locking means for maintaining the linkage and cylinder in
the raised angled position and for locking the linkage and
unlocking the cylinder in the lowered position.
2. A vehicle as claimed in claim 1 wherein said seat leveling means
comprises a dampened pendulum, two electrical switches respectively
activated by said pendulum swinging forward or backward relative to
said vehicle when said vehicle pitches forward or backward, the
first such switch controlling a solenoid means for closing two
additional switches to connect the seat-leveling motor means to
operate to bring the seat back up to the level position, the second
such switch controlling a second solenoid means for closing two
other additional switches to connect the seat-leveling motor means
to operate in the opposite direction, neither such first mentioned
switches being closed by the pendulum when the seat is in the level
position.
3. A vehicle as claimed in claim 1 further comprising castors
mounted near the front of said main tracks so as to move from an
inoperative position to an operative position extending slightly
below the front of the main tracks as the auxiliary tracks are
moved from their operative position to their inoperative
position.
4. A vehicle as claimed in claim 1 wherein each track comprises an
endless tread having an elongated substantially flat lower run
extending between at least two sprocket wheels, said tread having
interior teeth for non-slip engagement with said sprockets and
having exterior cleats, and an anti-friction support positioned on
the upper side of the lower run of said tread.
5. A vehicle as claimed in claim 4 where each main track has the
lower run of its tread supported in a slightly downwardly bowed
shape.
6. A vehicle as claimed in claim 5 where each track at its free end
is upwardly and outwardly inclined.
7. A vehicle as claimed in claim 4 further comprising a
friction-clutch down fail-safe means mounted in an auxiliary track
so as to engage the interior teeth of its tread when the auxiliary
track is inclined downwardly and to disengage in any other position
for preventing unpropelled downward forward motion of the
vehicle.
8. A vehicle as claimed in claim 7 further comprising a ratchet up
fail-safe means mounted in a main track so as to swing into locking
engagement with said outer cleats of its tread when said main track
is inclined upwardly and to swing out of engagement by gravity in
any other position for preventing backward motion of the
vehicle.
9. A stair-climbing vehicle for transporting a load comprising a
parallel pair of main tracks; a load support carried on said
vehicle; elongated stabilizing means for preventing precipitous
pitching forward of said vehicle, being pivotally joined to said
vehicle and, when operatively positioned, extending forwardly from
such pivot joinder to engage the ground beyond the combined center
of gravity of said vehicle and of its load; propulsion means for
driving said main tracks; rotation retarding means mounted to act
between said vehicle and said elongated stabilizing means pivoted
thereon for slowing automatically at least the rate of pivoting of
said elongated stabilizing means upwardly against gravity so as to
control the rate of pitching forward of said vehicle; sensing means
mounted on said vehicle for sensing the inclination of said load
support and for signaling any significant variation of said load
support from the horizontal; load support leveling means for moving
said load support relative to said main track responsive to the
signaling of said sensing means so as to keep said load support
substantially level and for moving the same at a rate of rotation
at least substantially equal to the rate of rotation of said
elongated stabilizing means.
10. A vehicle as claimed in claim 9 wherein said elongated
stabilizing means is a pair of auziliary tracks each pivoted to a
respective main track adjacent the front thereof, and said main and
auziliary tracks include non-slip endless belts being a
multiplicity of external cleats.
11. A vehicle as claimed in claim 10 wherein said rotation
retarding means comprise two hydraulic cylinders each mounted
between the vehicle and a respective auxiliary track pivoted
thereon, said cylinders being contracted to be retractable under
pressure at a controlled predetermined rate.
12. A vehicle as claimed in claim 10 wherein said rotation
retarding means comprises two elbow linkages each respectively
mounted between each auxiliary track and said vehicle and having a
hydraulic cylinder forming at least part of the linkage forearm and
also having a locking means for maintaining the linkage and
cylinder in the raised angled position and for locking the linkage
and unlocking the cylinder in the lowered position.
13. A vehicle according to claim 1 wherein said self-leveling seat
means comprises a gimbeled seat.
14. A vehicle according to claim 1 wherein said self-leveling seat
means comprises a seat; sensing means mounted on said vehicle for
sensing the inclination of said seat and for signaling any
significant variation of said seat from the horizontal; leveling
means for moving said said seat relative to said main track
responsive to the signaling of said sensing means so as to keep
said seat substantially level and for moving the same at a rate of
rotation at least substantially equal to the rate of rotation of
said pitch-control means.
Description
The present invention relates to vehicles particularly adapted for
use by a physically handicapped person in ascending and descending
stairs (in addition to normal horizontal travel), preferably being
self-propelled; although more broadly being capable of transporting
a wide variety of loads with or without the assistance of an
attendant.
For generations there has been a recognized need for an
economically feasible and commercially practical substitute for the
common wheel chair, which would at least substantially maintain the
desirable attributes of a modern day wheel chair and yet have the
added capability of permitting the occupant to traverse the stairs
and similar inclined obstructions typically encountered in everyday
living.
The search for a vehicle having the foregoing capabilities was
given added impetus over a decade ago when the National Inventors
Council (now called the Office of Invention and Innovation,
National Bureau of Standards, Department of Commerce) sponsored a
$5,000. contest for development of such a device.
U.S. Pat. No. 3,276,531, patented Oct. 4, 1966, is an example of
the best of the prior art which resulted, and also gives a good
summary of the drawbacks of previous prior art as well as a summary
of many of the objectives of the present invention (which are
hereby incorporated by reference).
In spite of the many solutions proposed by the prior art, there has
never resulted to this day a commercially acceptable (nor
available) vehicle of this type. Applicant, drawing on personal
experience, has discovered and focused upon two major reasons
probably responsible for the unacceptability of any of the prior
art. The device should be easily operated, i.e. not require any
"driving skill" or specialized coordination (particularly since it
is primarily intended for persons already having some degree of
physical handicap). Secondly, it must give a strong sense, as well
as the actuality, of security when in use upon the stairs. Further
objectives of this invention are therefore the satisfaction of
these two additional criteria. An added sense of control and
security is given to the occupant of the vehicle if the ascent and
descent are accomplished facing in the direction of travel and in
the normal upright sitting position. Furthermore, the transition
from the horizontal to the incline of the stairs should be
accomplished smoothly and with controlled and automatic simplicity,
the accomplishment of which yield still further and major
objectives of the present invention.
According to a preferred embodiment of the present invention, these
and other objectives (which shall become self-evident in the
following discussion) are accomplished by a vehicle having a pair
of horizontal main tracks on which is supported a self-levelling
seat and to the front of which is pivotally articulated a pair of
respective auxiliary tracks. Each main track and its corresponding
auxiliary track are pivotally restricted by a pitch-control
hydraulic cylinder. An advantage of this pitch-control means is
that it can smooth the transition of the vehicle between the
horizontal and inclined travel positions by preventing any abrupt
change in the angle between the auxiliary and the main tracks.
However, the principal and necessary feature of this pair of
pitch-control hydraulic cylinders is in at least automatically
preventing the vehicle from pitching forward at the top of the
stairs in either direction during the transition between the
horizontal and the inclined orientation, as the center of gravity
of this vehicle passes over the top tread of the stair. The
operation of this significant feature (and alternative thereof)
will be more fully discussed below. The effectiveness of this and
other features described herein have been fully proven by the
construction and use of an actual prototype.
Another major feature of the present invention is the
self-levelling seat, preferably motorized to be automatic, whereby
the occupant is at all times maintained in an upright
forward-facing seated postion. This not only gives a greater sense
of security, but also affords a proper and more normal clear view
of the forward progress.
In the preferred embodiment, the vehicle for simplicity is
propelled by crank arms through chain and sprocket drives, with one
set for independently driving each of the main tracks. Where the
strength or handicap of the occupant is such that this is
impractical or is otherwise not desired, a motorized substitute
propulsion means may be utilized.
Although the broader aspects of my original levelling seat concept
has been partially subsequently disclosed in U.S. Pat. No.
3,288,234, issued Nov. 29, 1966; my subsequent tests have also
demonstrated that the patentee's disclosed automatic self-levelling
mechanism is effectively inoperative; resulting in rapidly failing
batteries or burned-out motors. I have ultimately determined that
the probable cause of the failure of the prior art design is due to
the mercury switches which cause (a) continuously occurring rapid
start-stop opposing adjustments (very hard on the motor and
demanding of electricity), (b) inaccurate levelling adjustments due
to "sloshing" of the mercury caused by the motion of travel, and
(c) similarly caused short-circuiting or overloading when both
mercury switches would be in the "on" mode simultaneously.
Accordingly, in an improvement of this aspect of the present
invention, the self-levelling mechanism incorporates a dampened
level sensor.
A more simplistic alternative, not taught by any of the prior art
known to applicant, is to have the seat mounted on gimbals to
thereby be kept level by the weight of the occupant. The seat pivot
would preferably be dampened, to prevent undue swinging during
transition and to increase the occupant's sense of security, and
further may have a lock mechanism for the chair during the actual
horizontal or inclined travel.
A further feature of the present invention includes fail-safe
mechanisms automatically operative for both the ascending and
descending mode. The ascending automatic fail-safe is preferably a
gravity operated device working on a rachet principal to allow the
gripping cleats of the endless tread of the main track to pass by
the fail-safe as the vehicle ascends, but to jam and hold the main
track against operating in the reverse direction, unless purposely
swung into the inoperative position. Gravity also acts to swing
this latter fail-safe into the inoperative position upon horizontal
or descending travel.
The descending fail-safe is preferably a friction clutch which is
gravity actuated to swing into operative position when the vehicle
is inclined in the descending attitude. Preferably the friction
clutch is adjusted to hold the vehicle motionless in the descending
position and to require a positive, though comparatively minimal,
effort from the propulsion system to overcome the resistance of
this friction fail-safe.
In this specification and the accompanying drawings I have shown
and described a preferred embodiment of my invention and have
suggested various alternatives and modifications thereof; but it is
to be understood that these are not intended to be exhaustive and
that many other changes and modifications can be made within the
scope of the invention. These suggestions herein are selected and
included for purposes of illustration in order that others skilled
in the art will more fully understand the invention and the
principles thereof and will thus be enabled to modify it and embody
it in a variety of forms, each as may be best suited to the
conditions of a particular use.
In the accompanying drawings:
FIG. 1 shows parallel perspective view of a preferred embodiment
according to the present invention, adjusted for normal horizontal
travel;
FIG. 2 is a partially schematic side elevation of the vehicle shown
in FIG. 1, adjusted for normal horizontal travel;
FIG. 3 is a view similar to FIG. 2 illustrating the vehicle in the
operative position for inclined travel just prior to descending a
flight of stairs;
FIG. 4 is a view similar to FIG. 2 illustrating the vehicle in the
initial stages of effecting the transition from the horizontal to
inclined travel;
FIG. 5 is a view similar to FIG. 2 illustrating the vehicle at the
stage of descent where the center of gravity of the vehicle has
passed beyond the top riser of the staircase and the vehicle is in
automatically controlled transition to having its tracks assume the
angle of inclination of the stairs;
FIG. 6 is a view similar to FIG. 2 illustrating inclined travel
down a staircase;
FIG. 7 is a view similar to FIG. 2 illustrating a typical arrival
at the base of the stairs;
FIG. 8 is a view similar to FIG. 2 illustrating the vehicle in the
initial stages of climbing a staircase;
FIG. 9 is a view similar to FIG. 2 illustrating the vehicle
climbing at the top of a staircase and the initial stage of
transition between inclined and horizontal travel;
FIG. 10 is a view similar to FIG. 2 illustrating the vehicle
climbing towards the horizontal at the top of a staircase just
prior to the center of gravity thereof passing over the top
riser;
FIG. 11 is a view similar to FIG. 2 illustrating the vehicle having
ascended a staircase and being in the final stage of transition to
the horizontal;
FIG. 12a is an enlarged schematic detail of the down fail-safe in
inoperative position;
FIG. 12b is an enlarged schematic detail of the down fail-safe in
operative position;
FIG. 13a is an enlarged detail schematic of the up fail-safe
inoperative position;
FIG. 13b is an enlarged schematic detail of the down fail-safe in
the operative position;
FIG. 14a is a side elevation detail of the elbow linkage locking
the auxiliary track in the raised inoperative position;
FIG. 14b is a view similar to FIG. 14a but with the elbow linkage
locked in the lowered operative position for the auxiliary
track;
FIG. 14c is a view similar to FIG. 14a but with the elbow linkage
locked in the lowered position and with the pitch-control hydraulic
cylinder extended;
FIG. 15 is a schematic parallel perspective view of the dampened
seat levelling mechanism;
FIG. 16 is schematic wiring diagram of a modified embodiment of the
device illustrated in FIG. 15; and
FIG. 17 is view similar to FIG. 2 of an embodiment with modified
tracks.
In the foregoing drawings, shading has been indicated by spaced
lines parallel to the principal axes of the element being
illustrated, with sectioning being indicated by lines diagonal
thereto.
Referring to FIG. 1 there is illustrated as a preferred embodiment
a vehicle 20 with two main tracks 22, each having sprockets 24 and
26 with endless traction belts 28 extending therebetween. These
traction belts are preferably made from commercially available,
high quality timing belts having steel cable tension members giving
them extremely high strength and having a castellated interior
tread, the square teeth 108 of which securely fit into
corresponding grooves in the sprockets 24 and 26 to positively
assure against slippage. The exterior tread of the traction belts
are deeply and transversely grooved in order effectively to grip
the stair or other inclined surface. The individual projections 30
(see FIG. 12a) of the belt 28 may advantageously be formed of an
approximately one-half inch thickness of a firm density rubber (or
the like), preferably molded into the face of the belt 28 in order
to provide a non-marring, high friction surface to give positive
traction and gripping. Each of the pair of parallel main tracks 22
have pivotally attached to the forward end elongated stabilizing
means in the form of a respective auxiliary track 32 of similar
construction, but preferably shorter in length. In the preferred
embodiment, the auxiliary track sprocket 34 is mounted on the same
shaft 36 as the main track sprocket 26. The shaft 36 drives both
the main traction belt 28 and the auxiliary traction belt 38 via
their respective sprockets 26 and 34. This drive shaft 36 is in
turn driven by crank arm 40 through a gear box 42 and a sprocket
chain 44 which passes over a sprocket 46 mounted on its inner
end.
Note that for convenient distinction, like structures found on the
other side of the vehicle 20 are indicated by like numerals bearing
a prime (').
Extending between the sprockets 24 and 24' is an axle 48.
Similarly, extending between sprockets 26 and 26' is a hollow axle
housing 50 which carries therein bushings for the drive shafts 36
and 36'. Said hollow axle housing 50 incorporates a bridging
casting (not shown) in which the drive sprockets 46' rotate and
upon which the pedestal 52 is affixed. The pedestal 52 in addition
to supporting the gear box 42 and the drive cranks 40, 40', also
carries the load support 54 (here illustrated as a seat). The rear
of the seat 54 is supported by struts 56, 56', the other end of
each being pivoted about the axis of the axle housing 50.
The seat 54 may advantageously be constructed to swivel in order to
facilitate the seating of the occupant on the vehicle.
Additionally, the structure of the seat may be modified to be
vertically adjustable. Alternatively, the pedestal 52 may be hinged
at the level of the seat 54 to simplify the seating procedure.
The crank handles 40, 40' are geared to approximately a one to two
gear ratio for horizontal travel. By shifting the gear shift 58,
the gear ratio is reduced by a factor of four. This latter ratio is
used for ascending or descending a stairway where greater power and
control are required.
The remaining structure of the vehicle 20 will be discussed in
connection with a description of the operation of the vehicle. In
traveling on the horizontal, the occupant seated astride the
pedestal 52 proceeds forward by rotating the cranks 40 and 40' at
the same rate thereby driving the traction belts 28 and 28' which
engage the floor 60 in the vicinity of the rear sprockets 24, 24'.
By varying the relative speed and/or direction in which the
respective crank arms 40 and 40' are rotated, the vehicle is thus
turned to the left or to the right. This turning is made possible
by having the front end of the vehicle ride on casters 62. These
casters 62, 62' are mounted so as to rotate with the auxiliary
tracks 32; so that when the tracks 32 are lowered, the casters are
raised off the floor 60 into an inoperative position (see FIGS. 3
through 11). With the auxiliary track 32 lowered, the main track 22
is flat on the floor or level ground 60 making it impossible as a
practical matter to turn the vehicle, particularly when traveling
over a deep pile rug or the like. Some maneuverability of the track
22 on a flat surface may be imparted (but at some expense to its
traction) by slightly bowing the underside of the main track (see
the modified main track 22a illustrated in FIG. 17); this assumes
that the auxiliary track is not also in contact with the floor 60
when a turn is attempted.*
The traction belt 28 is supported as it traverses the underside of
the track 22 by a guide member 64. As shown in FIGS. 13a and 17,
the member 64 may be advantageously supplemented along the middle
of the track 22 by support wheels 65; similarly, wheels 65 could
completely replace the guide members 64. The guide member 64 is
preferably made from a solid bar of Teflon or a steel structural
member faced with a strip of Teflon (such as is typically used on a
snowmobile runner).
Descending a staircase (or other similarly abruptly-inclined ground
configuration) 66 is accomplished by the occupant pushing on the
spring-loaded lock buttons 68, 68' of handles 69, 69' (see FIGS.
14a to 14c) to unlock the elbow linkages 70, 70' thereby permitting
the lowering of the auxiliary tracks from the position in FIGS. 1
and 14a onto the level ground 60, see FIGS. 3 and 14b.
Referring to just one linkage 70, note that the handle 69 is
affixed to the upper arm 73 by stop-fitting 81 (see the latter
particularly in FIG. 14a, mainly in dotted outline). Similarly,
note that the free end of the piston rod 86 of the hydraulic
cylinder 84 is pinned to the circular elbow plate 71 and to the
catch support 83 (see the latter particularly in FIG. 14c, mainly
in dotted outline). Thus the handle 69, stop 81, and arm 73 rotate
as a unit relative to the unit comprised of the plate 71 (its
integral lock ring 78), support 83 and rod 86. These two units of
the elbow linkage 70 are fixed relative to one another by the wedge
72 of the handle 69 nesting into one of the grooves 76 in the lock
ring 78. The lock ring 78 is preferably integral with the elbow
plate 71 (being milled therefrom). The lock shaft 74 is axially
journalled within the handle 69 with the wedge 72 connected to one
end and with the button 68 connected at the other end. Note that in
FIGS. 6, 8, 9, 14a, 14b, 14c the handle 69 is affixed at right
angles to the arm 73. This proved difficult to operate in the
prototype and therefore an alternative positive at an obtuse angle
is shown in the other figures. In all figures (except FIG. 1) the
handle 69 and the stop 81 are at the same angle and affixed
directly to one another.
In an alternative preferred embodiment, the grooves 76 of the lock
ring 78 may be formed to function cooperatively with the wedge 72
as a ratchet, in all except the full-up position (e.g., of FIG.
14a) and with a stop in the aligned-down position (e.g., of FIG.
14b). With the linkage 70 in ratchet form the auxiliary track 32
can rotate down by gravity (particularly useful in ascending the
stairs as described below), but can be raised only by pushing on
button 68 to release wedge 72.
With the vehicle positioned as shown in FIGS. 3 and 14b, the stop
81 engages the rear of the catch 80 forcing it counterclockwise
about the pivot 82 (mounted on support 83-FIG. 14c) against a
spring or other biasing means (not shown), thus releasing the
hydraulic cylinder 84 from the catch 80.
The vehicle is advanced from the position in FIG. 3 to the position
in FIG. 4 by rotating the cranks 40, 40' clockwise in the low gear
ratio. Preferably the auxiliary track 32 is keyed into the drive
shaft 36 to be driven simultaneously with the main track 22 (at
least when the auxiliary track is in its lowered position).
The hydraulic cylinder 84 is preferably constructed to have a
restricted internal flow past its piston such that it extends on
its piston rod 86 in a controlled manner preventing the auxiliary
track 32 from dropping precipitously onto the staircase 66 (thereby
preventing a jouncing or even lurching of the vehicle).
As the vehicle proceeds from the top of the stairs illustrated in
FIG. 4 to traveling along the stairs as illustrated in FIG. 6, this
transition is accomplished smoothly and automatically, without any
necessity for halting the forward progress of the vehicle nor any
skilled manipulation, by rotation retarding means illustrated in
this preferred embodiment as principally including the hydraulic
cylinder 84 retracting slowly along its rod 86 thereby preventing a
precipitous pitching forward of the vehicle. See the intermediate
position illustrated in FIG. 5. Although a controlled relatively
slow extension of the hydraulic piston 84 is preferable, the
controlled retraction thereof is a necessity (in both the ascending
and descending mode).
During the foregoing maneuver, a sensing means in the form of a
level sensing mechanism 88, illustrated as being positioned under
the seat 54, has actuated the load support leveling means which
includes a jack screw 92 driven by a motor 90 thereby drawing the
pedestal 52 towards the main track 22 so as to keep the pedestal 52
and the attached seat 54 in an upright level position at all times.
The motor 90 drives the jack screw 92 through a gear reducer 94 and
is supplied by electricity from a battery 96 (carried under the
seat 54).
Note that by reference to FIG. 2, one can most clearly see in
dotted outline the pivot joint 98 of the jack screw 92 to the
pedestal 52.
See FIG. 7 for the position of the vehicle 20 in transition to the
horizontal at the bottom of the descent. Experience has shown that
there is no need to jacknife the auxiliary track 32 relative to the
main track 22 at this point, since the drop off the bottom step is
typically relatively negligible. If this is considered a problem,
the modification shown in FIG. 17 may be used, employing two end
sprockets 24a and 24b which angle the belt 28 to reduce this
drop.
After cranking onto the level ground 60 at the bottom of the
stairs, the occupant lifts on the handles 69 of the elbow linkage
70 by depressing the lock button 68 thereby permitting engagement
of the catch 80 with the hydraulic cylinder 84 and also permitting
rotation of the elbow linkage 70 into its raised angled position
illustrated in FIG. 14a. This not only raises the auxiliary track
32 from their previous ground-engaging position, but also lowers
the casters 62 into their operative position, all as illustrated in
FIG 2.
The ascent up the staircase is quite similar. The vehicle 20 is
driven to the staircase, again facing forwardly, but this time
arriving at the bottom. The elbow linkage 70 (pivoted from shoulder
stanchion 75) is released dropping the auxiliary tracks 32, 32'
down onto the first stair riser. In the illustrated embodiment, the
auxiliary tracks are locked in this position. The vehicle is then
driven forward in this attitude until the main tracks 22, 22'
assume the inclined position. The auxiliary tracks 32, 32' are then
dropped manually (or have dropped by gravity, if ratchets are used
in linkage 70) the rest of the way and locked in the aligned
position illustrated in FIG. 14b. Upon arriving at the top of the
stairs, the hydraulic cylinders 84, 84' extend forward on the
piston rods 86, 86', preferably in a controlled manner as before,
dropping the auxiliary tracks 32, 32' onto the level ground 60 (see
FIG. 9). The vehicle continues to ascend the staircase 66 (as shown
in FIG. 10) and pitches slowly forward on the main tracks 22, 22'
in a controlled manner as the center of gravity of the vehicle 20
passes over the top riser of the staircase, all in a smooth
transition made possible by the pre-set slow retraction of the
piston rods 86, 86' into the hydraulic cylinders 84, 84'. The
vehicle soon settles from the slightly jackknifed position of its
respective main and auxiliary tracks (as shown in FIG. 11) into
full floor contact (similar to the illustration in FIG. 3, but this
time facing away from the staircase 66).
The descent of the vehicle along an inclined surface (such as the
staircase 66) is materially assisted by a friction clutch mechanism
100 which also serves as the down fail-safe. This mechanism 100 is
carried within the auxiliary track 32 housing 102 and rotatably
fixed therein about pivot 104. When the auxiliary track 32 is
level, the fail-safe 100 is retained in the inoperative position
against a stop 106 fixed to the housing 102 (see FIG. 12a). When in
the descending position illustrated in FIG. 6 and 12b, the sprocket
wheel 107 of fail-safe 100 engages the castellated teeth 108 of the
traction belt 28 and presses the belt 28 against the pressure plate
110. With the traction belt 28 thus engaged by the fail-safe 100,
the belt 28 is held immobile, unless the crank arms 40 are
positively driven against the frictional resistance of the friction
clutch (not specifically shown) incorporated in the down fail-safe
100.
The up fail-safe is illustrated in FIGS. 13a and 13b, which are
substantially self-explanatory. The ratchet lever 112 is swung out
of engagement of the cleats 30 of the traction belt 28 when in the
horizontal position by action of gravity upon the counterweight
114. When the main track 22 of the vehicle 20 is in the ascending
position, the counterweight 114 swings the ratchet lever 112 into
engagement with the cleats 30 to catch positively thereon should
the traction belt 28 attempt to move back against the ratchet lever
112 (which captures the belt 28 pressing it against backup plate
116).
The level sensing mechanism 88 as disclosed in the preferred
embodiment illustrated in FIG. 15, consists of a pendulum 118
suspended in a container 120 which is filled with a viscous
dampening medium. On either side of the pendulum 118 are
respectively positioned, fore and aft, two sets of reed contacts
122 and 124. Each contact is wired to a respective solenoid 126 and
128 which in turn activates a respective pair of dual switches 130
and 132 to close a circuit for ultimately operating the reversible
motor 90 in one direction or the other, dependent upon which
solenoid is activated. Thus when the seat 54 and its attached
sensing mechanism 88 is substantially level, even though subject to
the normal vibrations of travel, the motor 90 is unaffected,
because the dampening fluid in the container 120 prevents the
pendulum from swinging to engage either of the contacts 122 or 124.
However, when the vehicle 20 pitches forward (usually at a rate
controlled by the hydraulic cylinder 84), gravity swings the
pendulum through the viscous fluid to engage and close one of the
contacts 124 or 122 (dependent upon whether the vehicle is pitching
forwards or backwards, typically upon ascent or descent). The
circuit will remain closed so long as the seat is at an angle to
the horizontal thereby causing the motor 90 to turn the jack screw
92 in a direction to bring the seat back to the horizontal.
The alternative control device depicted in wiring diagram of FIG.
16 is substantially identical to that shown in FIG. 15; except that
the function of the dual switch 130 and its activating solenoid 126
have been respectively replaced by single switches 130a and 130b
and associated individual solenoids 126a and 126b; (similarly
switches 132a and 132b replacing dual switches 132 and solenoids
128a and 128b replacing solenoid 128).
From FIG. 16 it can be seen that when reed contact 124 is closed,
solenoids 126a and b are activated closing switches 130a and b thus
connecting the motor 90 to the battery 96 to adjust the position of
the seat 54. When the pendulum 188 then selectively closes reed
contact 122, solenoids 128a and b are activated closing switches
132a and b, thus connecting the motor 90 to the battery 96 in the
reverse direction.
For convenience and economy the solenoids 126a and b, 128a and b
may be equavalent to automobile starter relays. However, the
current required to operate such relays could be too much for the
reed contacts 122 and 124. Therefore, to improve the later's
reliability two units, each comprising a low current relay (not
shown) with an associated higher capacity switch controlled
thereby, are introduced. The switch of each unit replaces the
function of a corresponding reed contact, and the solenoid is in
turn controlled by such respective reed contact.
For the added comfort of the occupant and to *
Referring now to an alternative embodiment of the vehicle 20, not
illustrated, note that the leveling mechanism 88 can be eliminated
and replaced by a self-leveling seat mounted on gimbels. The chair
54 thereby can always maintain a level position. For the comfort of
the occupant, the gimbel pivots can be frictionally or otherwise
dampened. Also, a lock may be provided to fix the chair relative to
the main track when the angle of incline (or horizontal) is not
changing. In this embodiment, the pedestal 52 is divided into two
separate gear housing standards with respective crank arms.**
Additionally an alternative pitch-control means may replace
hydraulic mechanism 70 by a gear mechanism for controlling and
accomplishing the raising and lowering of the auxiliary tracks.
The auxiliary tracks have two manually controlled positions (up and
down-in-line), and one drop position which is automatic. A crank
and a pinion gear mounted on the vehicle 20 moves a gear rack
(which has one end mounted on the auxiliary track). As the
auxiliary tracks reach the position in-line with the main tracks,
the end of the gear rack will have just passed a lock which
automatically drops into position and the auxiliary tracks cannot
again move in an upward direction until manually released.
The auxiliary tracks assume the dropped position by their own
weight descending. The auxiliary tracks are free to drop since the
end of the rack has passed the crank pinion and a ratchet escape in
the gear box permits the rack to pass through unhindered. The
tracks return to the in-line with the main track position under the
weight of the wheelchair and operator at a pre-set speed. The
purpose of the gear box is to produce the relatively slow return of
the auxiliary tracks from the drop position. The gradual movement
is accomplished as follows: The upward rotation of the tracks
causes the return of the gear rack through the gear box. In this
direction the ratchet-escape locks and causes a large gear to
rotate. The large gear in turn is engaged with small gear resulting
in a high gear ratio. Fixed on the same shaft with the small gear
is a friction wheel. An adjustable friction device working against
the smooth perimeter of the friction wheel will determine the speed
at which the auxiliary tracks return to the inline with the main
track position.
A still further embodiment of the pitch control means may take the
form of a rotary hydraulic mechanism operative at the axles 36
(replacing the elbow linkage 70 and in particular the hydraulic
cylinder 34).
* * * * *