Wheel chair abstract
The present wheel chair lift apparatus has a rotatable post at
the front of a doorway in the side of a van. A pivotally mounted
electric motor rotates this post through a pinion and gear drive
at the lower end of the post. A carriage for the wheel chair lift
platform is slidable up and down along this post. A vertical lead
screw is coupled to the carriage through a ball nut and a lost-motion
coupling. The lead screw is driven from an electric motor through
gear wheels. The lead screw motor has an electric brake which prevents
the screw from turning when the motor is stopped. The lift platform
has a pivoted retainer lip at its outer edge which is pulled up
before the lift platform can move up or down. Provisions are made
for manually moving the platform in case of power failure.
Wheel chair claims
We claim:
1. In a wheel chair lift platform comprising:
a horizontal lift platform;
a rotatable vertical support post;
a carriage slidable along said support post and operatively coupled
to said support post to turn in usison with it;
means rigidly connecting said lift platform to said carriage for
movement in unison with it;
a rotatable, vertical power driven lead screw for raising and lowering
said carriage along said support post;
retractable retainer means operatively pivotally associated along
the rear edge of said lift platform for movement between a retracted
position in which it permits the wheel chair to move onto or off
the platform and a raised position in which it retains the wheel
chair on the lift platform;
motors for raising and lowering the aforesaid carriage along said
rotatable post and for turning said post between its inner and outer
positions; and
control means for connecting said disconnecting electrical power
to said motors;
the improvement which comprises:
on-center retainer actuating train means operatively connected
with said carriage such that said retainer actuating train means
is operated from a retracted to a raised position when said carriage
is supporting the weight of said lift platform;
reinforcing means associated with said retainer actuating train
means such that said retainer actuating train means is capable of
retaining a wheel chair positioned on the lift platform;
a lost motion coupling consisting of a ball nut threadedly engaging
said lead screw;
said ball nut attached to a ball nut housing consisting of upper
and lower horizontal elongated plates;
said plates attached to a cylindrical vertical guide post;
said post slidably coaxially disposed inside a vertical tubular
cylindrical sleeve rigidly attached to said slidable carriage, where
said guide post is longer than said sleeve by a short amount, such
that said ball nut housing is vertically movable between an upper
and lower position relative to said carriage by a distance equal
to said short amount;
a first actuating generally vertical rod with its upper end in
a loosely jointed connection attached to aforesaid ball nut housing
and with its lower end pivotally attached to a lever at a point
on said lever that is generally midway between the two ends of the
lever;
said lever extending generally horizontally and radially from the
axis of the aforesaid pivotable vertical post attached pivotally
in a vertical plane to said carriage at the end of the lever nearest
to said axis, and such that the end of the lever farthest away from
said axis desribes a vertical arch between an upper and lower position
in unison with the upper and lower positions of the aforesaid ball
nut housing;
a second actuating rod attached to the end of said lever farthest
away from said axis in a loosely jointed connection and sloping
generally downward to a point of rigid attachment to a stirrup positioned
as an inverted U with its two prongs pointing downward in extension
of said second actuating rod with the lower ends of said prongs
pivotally attached to the apex closest to the rear edge of said
platform of two actuators shaped as two obtuse triangles disposed
in two parallel vertical planes where said actuators are attached
pivotally in a vertical plane about a pivot pin disposed horizontally
and parallel with the rear edge of said platform; and
through that apex of said triangular actuators that is nearest
to the upper surface of said platform; and
through a hole in a vertical first projection, said first projection
disposed in a vertical plane parallel with and between the vertical
planes defining said actuators;
said projection, rigidly attached to the upper surface of said
platform and such that the third apex of said triangular actuators
can describe an arch of generally 90 degrees in the vertical plane
as said actuators are pivoted from a generally horizontal position
oriented toward the front edge of said platform to a generally vertical
position, as said second actuation rod is operated between its upper
and lower position by aforesaid lever;
an actuating bar, at one end generally horizontally oriented, disposed
in a vertical plane perpendicular to the rear edge of said platform
between said actuators attached at one end pivotally to the third
apex of said triangular actuators and at the other end attached
pivotally to a second projection attached to the upper surface of
aforesaid retaining lip attached pivotably to the rear edge of said
platform such that as the aforesaid two triangular actuators are
pivoted between their horizontal and vertical positions,
said actuating bar will operate said retaining lip to pivot between
its raised position and its retracted position in which it is generally
co-planar with said platform and such that in its raised position
the three points namely the point of attachment between said second
projection and said actuating bar, the point of attachment between
said triangular actuators and said first projection and the point
of attachment between said actuating bar and said triangular actuators
are disposed on a straight line thereby placing said two last-mentioned
points on center with the first-mentioned point of attachment.
2. Apparatus as recited in claim 1 further comprising:
direct drive speed reduction gears between said motors and said
rotatable post and said lead screw.
3. Apparatus as recited in claim 2 further comprising:
means for braking the rotation of said motors when power to the
motors is disconnected;
said braking means consisting of an electrically actuated brake
connected to the drive shaft of said motors.
4. Apparatus as recited in claim 3 further comprising:
toggle switches with said control means responsive to said toggle
switches;
first relay means responsive to said toggle switches such that
electrical contacts associated with said relay means are capable
of connecting power to said motors to operate them in their forward
rotational direction or in their reverse direction.
5. Apparatus as recited in claim 4 where said control means further
comprise:
limit switches responsive to actuators where said actuators which
are mechanically attached to said vertically slidable carriage and
to said rotatable post operatively engage said limit switches to
disconnect power to said motors when said carriage or said post
enter the limits of their movement.
6. Apparatus as recited in claim 5 where said control means further
comprises:
second relay means operatively responsive to the limit switch for
the upper limit of said slidable carriage such that said second
relay means may enable rotation of said rotatable post with said
carriage and lift platform slidably attached thereto only when said
carriage is at its upper limit of its movement.
7. Apparatus sa recited in claim 1 further comprising:
a helical spring disposed coaxially with the aforesaid first actuating
rod in a compressed condition such that said helical spring at its
upper end rests against the underside of said ball nut housing and
at its lower end against the upper side of the aforesaid lever and
such that when said ball nut housing is at its lower position of
its lost motion with all the elements of aforesaid actuating train
means in their lower position for retracting said retaining lip,
said helical spring will impart to all said elements a degree of
downward pressure which is further imparted to said retaining lip
in its retracted position so that it will rest firmly against the
ground or the floor of the van.
8. Apparatus as recited in claim 2 wherein said rotatable vertical
support post at its one end is further equipped with an adaptation
for engagement with a matching post implement such that in the case
of failure of the drive motor for rotation of said post said rotatable
post can be rotated manually by engaging said post implement with
said post adaptation and where said lead screw at one end is equipped
with a lead screw adaptation for engagement with a matching lead
screw implement such that in the case of failure of the motor for
turning said lead screw, said screw can be turned manually by engaging
said lead screw implement with said lead screw adaptation.
9. Apparatus as recited in claim 8 further comprising:
means for manually detaching said motor and gear reduction assembly
for rotating said post from engagement with said post;
said means consisting of a horizontally slidable retractable wedge
which in its engaged position locks said motor and gear reduction
assembly in its normal position in engagement with said rotatable
post and which in its retracted position unlocks said assembly which
is horizontally pivotable about a vertical pivot post such that
the assembly can be pivoted away from engagement with said post,
and such that the rotatable post may be manually rotated using aforesaid
post implement.
Wheel chair description
BACKGROUND OF THE INVENTION
This invention relates to a vehicle-mounted wheel chair lift apparatus
of the general type disclosed in our U.S. Pat. Nos. 3,847,292 and
4,133,437. The lift apparatus of those patents include a horizontal
lift platform which is normally stored in the van. When the occupant
of a wheel chair wants to enter the van, the lift platform is raised
slightly and then is pivoted horizontally out of the van and lowered
vertically. After the wheel chair is on this platform it is elevated
to a raised position outside the van and then is pivoted horizontally
into the van slightly above floor level and then lowered to floor
level. The reverse sequence of operations is carried out when the
wheel chair occupant wants to leave the van. Various power-operated
devices and controls are provided for affecting these operations
with a minimum of effort required of the wheel chair occupant.
SUMMARY OF THE INVENTION
The present invention is directed to a wheel chair lift apparatus
of the same general type but with several modifications to simplify
and improve the reliability and safety of its operation
In the presently-preferred embodiment of this invention the raising
and lowering of the lift platform is effected through a vertical
lead screw which drives a ball nut. Preferably, a lost motion coupling
is provided between the ball nut and a carriage which is slidable
vertically along a rotatably supported post. The carriage is coupled
rigidly to the lift platform. The lost motion coupling delays briefly
the up movement of the carriage and the lift platform when the lead
screw first begins to turn in upward direction.
In this embodiment the lead screw is driven through a speed reducing
gear wheel drive at its lower end from an adjacent electric motor.
A brake applies friction to the motor to prevent the lift platform
from coasting down when power to the motor is stopped. This brake
automatically locks the lead screw when the motor stops.
The vertical post is rotated by a second electric motor through
a gear drive. This motor is pivotally mounted at the floor of the
vehicle for selectively disconnecting this gear drive.
The lift platform has a pivoted retainer lip at its outer edge
for preventing the wheel chair from rolling off. This lip is raised
by the ball nut whenever the lead screw is supporting the weight
of the lift platform.
The lift platform also may have a slidable extension which is engageable
by the wheels of the wheel chair to enlarge the effective size of
the lift platform when the wheel chair rolls onto it.
A principal object of this invention is to provide a novel and
improved wheel chair lift apparatus on a motor vehicle, particularly
a van.
Another object of this invention is to provide such an apparatus
which is relatively simple mechanically while at the same time being
reliable and safe in operation.
Another object of this invention is to provide a novel wheel chair
lift apparatus on a vehicle which uses a motor-driven vertical lead
screw for raising and lowering a horizontal lift platform.
Another object of this invention is to provide a lift apparatus
as just mentioned in which the lead screw is driven through speed
reducing gear drive provided with a frictional restraint for preventing
the lift platform from coasting down when the lead screw drive motor
is stopped.
Another object of this invention is to provide a novel wheel chair
lift apparatus having a vertical lead screw for raising and lowering
the lift platform, a vertically reciprocable carriage rigidly connected
to the lift platform, and a novel lost motion coupling acting between
the lead screw and the carriage.
Another object of this invention is to provide a novel wheel chair
lift apparatus as just described which has a hinged wheel chair
retainer on the lift platform which is coupled to the lead screw
substantially without lost motion so as to be raised to its wheel
chair retaining position substantially as soon as the lead screw
is turned in direction for raising the lift platform through the
lost motion coupling and carriage.
It is a further object of the invention to provide a wheel chair
lift apparatus with simplified operation by means of limit switches
which control the outer limits of the vertical and pivoting motion
of the lift platform.
It is a still further object of the invention to provide wheel
chair lift apparatus with means for operating the wheel chair lift
in case of power failure.
Further objects and advantages of this invention will be apparent
from the following detailed description of a presently-preferred
embodiment thereof, which is shown in the accompanying drawings
in which:
FIG. 1 is an elevational view of a van with its sliding side door
open and with the present wheel chair lift lowered outside the van;
FIG. 2 is an elevational, part cross-sectional view of the present
lift apparatus in its lowered position outside the van seen along
the line 2--2 of FIG. 1;
FIG. 3 is a horizontal cross-section taken along the line 3--3
in FIG. 2;
FIG. 4 is a fragmentary horizontal view showing part of the gear
drive and motor operating the pivoting carriage and the lift platform
seen along the line 4--4 of FIG. 2;
FIG. 5 is a part cross-sectional view of the horizontal cross-section
of FIG. 3 along the line 5--5 showing the latch and wedge operating
to selectively disengage the pivoting motor and gear assembly;
FIG. 6 is a vertical elevational view of the lift apparatus showing
the carriage and lift platform outside the van in partially lowered
position with the retaining lip in its raised position with part
broken away to show the fixed rear retaining lip;
FIG. 6a is a vertical elevational, part cross-sectional view of
the actuating train for retracting the retaining lip showing the
actuating elements in their raised position in solid lines and in
their lowered position in phantom lines, with the platform in a
partially lowered position outside the van seen from the rear of
the van;
FIG. 6b is a vertical elevational part cross-sectional view of
the actuatng train for raising the retaining lip with the actuating
elements in their raised position seen along the line 6b--6b in
FIG. 6a;
FIG. 6c is a vertical elevational, part cross-sectional view of
the lower actuating elements of the actuating train showing the
elements in their lowered position with the retaining lip in the
horizontal retracted position seen along the line 6b--6b in FIG.
6a;
FIG. 7 is a vertical elevational view of the rotatable post with
the carriage in its lowest position with the lift platform outside
the van operating the outer limit switch, looking out from inside
the van;
FIG. 8 is a horizontal fragmentary view of the lift platform in
its position inside the van and showing part of the retainer lip
in its lowered position and details of the rotatable post with pivoting
drive motor and lead screw drive motor, seen along the line 8--8
in FIG. 7, and the inner limit switch for the pivoting motor;
FIG. 9 is a part fragmentary perspective view of the upper part
of the rotatable post and of the lead screw showing details of means
provided for operation in case of power failure;
FIG. 10 is a vertical cross-sectional view of carriage and lead
screw with upper and lower pivot pins in bushings;
FIG. 11 is a horizontal cross-section of pivot post and lead screw
seen along the line 11--11 in FIG. 6;
FIG. 12 is a vertical view showing part of the lead screw and ball
nut end assembly in the lift apparatus; and
FIG. 13 is a circuit schematic diagram of the electrical control
circuit showing the manual switches and limit switches power source
and relays.
Before explaining the present invention in detail, it is to be
understood that the invention is not limited in its application
to the details of construction and arrangement of parts illustrated
in the accompanying drawings, since the invention is capable of
other embodiments and of being practiced or carried out in various
ways. Also, it is to be understood that the phraseology or terminology
employed herein is for the purpose of description and not of limitation.
DETAILED DESCRIPTION
The invention is illustrated herein as applied to an automotive
van 20 (FIG. 1) having a sliding door 22. A particular embodiment
of the invention has been installed on a Chevrolet sliding door
van 10 series. However, it will be understood that the invention
may be applied to other vehicles.
In the van 20 the driver's seat is removed so that a wheel chair
24 can be positioned under the steering wheel. The van is especially
equipped to enable the occupant of the wheel chair to drive the
vehicle seated in the wheel chair 24 even though the driver may
be partially disabled. Preferably, the van 20 has power brakes,
power steering and automatic transmission, and suitable controls
are provided in known manner (not shown) to enable the occupant
of the wheel chair to drive the van. The invention is not specifically
directed to these driving controls, so they are not illustrated
herein.
A support 26 in the form of a squared tubular post is mounted inside
the vehicle at the front edge of a door opening 52 in its right
side. The door opening is normally closed by a sliding door 22.
In FIGS. 6 and 10 support post 26 is rotatably mounted on a base
120. The lower end of post 26 is attached to a reduced cylindrical
pivot pin 30 (FIG. 10) which is rotatably received in the bushing
28 attached to base 120. At the upper end of post 26 a similar pivot
pin 34 is rotatably received in bushing 33 carried by an upper bracket
32 near the top of the door opening 52. As shown in FIGS. 6, 7 and
10, the base 120 is mounted on the floor 35 of the van, and the
bracket 32 is attached to a door post 38 so that the post 26 is
located inside the vehicle.
A carriage 40 of tubular square cross-section is slidably mounted
on the outside of the post 26 for up and down movement. A lift platform
44 is rigidly attached to the vertically slidable carriage 40 by
means of rigid, interconnected brace members 41, 42 43 and 47, as
best seen in FIG. 2. These brace members form a rigid frame suspending
the lift platform 44 from the carriage 40 such that the carriage,
frame and platform can move together up and down along the support
post 26. The frame and platform are also movable horizontally in
and out of the doorway 52 when the door 22 is open since the support
post 26 is rotatable relative to the base 120 and the bracket 32.
A ball nut 48 (FIGS. 11 and 12) is carried by a three-sided rectangular
bracket or housing 48a which, as shown in FIG. 10, extends vertically
between upper and lower horizontal plates 49 and 50 and is welded
to both of them. A vertical guide post 51 extends between the upper
and lower plates 49 and 50 near the vertically slidable carriage
40. A vertical sleeve 55 (FIG. 11) is welded at 53 to the carriage
40 and slidably receives the guide post 51. The sleeve 55 is shorter
than the guide post 51 and therefore the unitary assembly of the
ball nut carrier 48a, upper and lower plates 49 and 50, and the
guide post 51 can move up and down a limited amount with respect
to the sleeve 55 (FIG. 11) and the carriage 40 which supports the
sleeve.
The ball nut 48 engages a vertically elongated lead screw 54. FIG.
10 shows the lower end of this lead screw fitting in bushing 154
keyed with key 155.
A horizontally disposed gear sector 59 (FIGS. 2, 3, 4, 6 and 7)
is welded to the post 26. This gear sector is engaged by a pinion
60 drives through a gear reduction unit 61 from an electrical motor
62. This post drive motor and gear reduction unit is mounted as
a sub-assembly generally at 121 on FIGS. 2 and 3 on a generally
horizontal panel 63 which is attached pivotally to a short vertical
post 64 which is rigidly attached to the base plate 120. The base
plate 120 is bolted to the floor 35 of the van. The pinion 60 which
is normally in engagement with the gear sector 59 may selectively
be disengaged therefrom by pivoting the entire sub-assembly 121
about the vertical post 64.
During normal operation the sub-assembly 121 is maintained in its
engaged position by means of a group of elements generally at 130
in FIG. 4 comprising wedge 122 normally positioned between an extension
128 of the gear reduction unit 61 and a horizontally disposed elongated
vertical plate 124 which is rigidly attached to the base plate 120.
The wedge is rigidly attached to a horizontally disposed, elongated,
horizontally movable plate 123 which is best seen in FIG. 3 and
in a vertical elevation in FIG. 5, which shows a view of the aforesaid
elements 130 of the mechanism serving to control the engagement
or disengagement of the sub-assembly 121, seen along the line 5--5
of FIG. 3. The elongated horizontally movable plate 123 is at the
end opposite the end attached to the wedge, pivotably connected
to two links 125, which are in turn pivotably connected to the end
of a threaded rod 131, (FIG. 5) which is screwed into a tubular,
internally threaded member 129, which is, in turn pivotally connected
to a vertical projection 127, rigidly attached to the base plate
120. The tubular member 129 has on its upper surface, welded thereto,
a generally horizontal handle 126. The elements generally shown
at 130 are shown in their normal position where the pivotable sub-assembly
generally shown at 121 is engaged with the gear sector 59.
The upper end of the lead screw 54 (FIG. 10) is reduced in diameter
to form pivot pin 76, pivotally positioned inside bearing 77 which
in turn is tightly fitted in an aperture 71 in upper horizontal
bracket 74. The pivot pin 76 extends a distance beyond the bearing
77 such as to provide a cylindrical extension generally at 78.
The extension at 78 serves to support a cylindrical collar part
80, which has at its lower end a concentric cylindrical bore, matching
extension 78 in a tightly fitting connection. To further secure
the connection, set screws 70 are positioned in threaded holes in
the perimeter of collar part 80. The collar part 80 has in its upper
end a square hole 79, which serves to receive a matching squared
tap on a hand crank (FIG. 9) which serves to rotate the lead screw
in case of power failure.
Aforesaid horizontal bracket 74 is also seen in perspective view
in FIG. 9 and in an elevational end view in FIG. 2. As described
above, one end of bracket 74 supports the upper end of the lead
screw 54, while the other end of the bracket is rigidly attached
to the upper end of the pivotable tubular post 26, such that as
post 26 pivots about its vertical axis, bracket 74 being attached
thereto, pivots therewith.
A drive motor 142 (FIGS. 2 and 6) is positioned vertically on top
of the gear box 140 and attached thereto. The motor 142 and the
gear box 140 which are readily available construction parts are
obtainable from various sources and are therefore not described
in detail here. A power cord 152 connects the motor 142 with the
electrical control system.
The motor 142 has at its upper surface rigidly attached thereto
an electrically controlled brake 143. The brake is internally, mechanically
connected with the drive shaft of the motor such that, when the
motor and the brake are not energized, the brake will produce a
frictional drag which will restrain the motor shaft from turning.
It is an important safety aspect of the present invention that
the lead screw 54 is frictionally restrained from rotating when
the drive motor 142 is not energized. The weight of the lift platform
and the very low friction between the lead screw would tend to produce
slow rotation of the lead screw that would cause the lift platform
to coast down when the motor 142 is not energized.
In accordance with another important aspect of this invention,
and as shown in FIG. 6, 6b, 6c and 8 the horizontal lift platform
44 is provided with a pivotable retaining lip 85 at its rear outer
edge. Normally, when the platform is resting on the ground or the
van floor as shown in FIG. 8, this lip extends horizontally substantially
co-planar with the floor of the lift platform 44. After the wheel
chair is on the lift platform, the lip 85 may be pivoted up to the
upwardly projecting position (shown in FIGS. 1, 6 and 6b) behind
the adjacent wheel 25 of the wheel chair, so that the wheel chair
cannot accidentally roll off the lift platform.
The lip 85 is pivotally actuated through an actuating train of
elements shown in detail in FIGS. 6a, 6b and 6c.
The actuating train consists of a first actuating rod 81 attached
at its upper end by means of two lock nuts 82 to the lower horizontal
plate 50 of the ball nut housing 48a and at its lower end vertically
pivotally attached at 84 to the lever 83. A helical spring 81a,
disposed concentrically with first actuating rod 81 rests at its
upper end against the lower surface of plate 50 and at its lower
end against the upper surface of lever 83, thereby exerting a moderate
downward pressure against lever 83. Lever 83 is attached vertically
pivotally to the horizontal brace member 46 at its innermost end
at 86. The lever 83 is at its outermost end, at 87, in a loosely
jointed connection attached to the upper end of second actuating
rod 89, which, at its lower end is rigidly attached to stirrup member
90, shaped like an inverted letter U with two downward facing prongs
90a.
Each of the two prongs 90a is at its lower end pivotally connected
with the upper apex of two identical pivotable actuators 93, shaped
as two obtuse triangles disposed in two vertical parallel planes.
Said actuators are pivotally at 92, by means of pivot pin 92a, attached
to a projection 94 which is, in turn, rigidly attached to the upper
surface of platform 44. The third apex of said actuators is at 99
pivotally connected with one end of the generally horizontally oriented
actuating bar consisting of two sections 95 and 96, where 96 is
constructed as two parallel bars welded to each vertical side of
section 95. Section 96 is at its other end pivotally connected with
projection 98 which is in turn rigidly attached to the upper surface
of aforesaid retaining lip 85.
In the above description, the train of actuating elements are all
shown in FIGS. 6a and 6b in full lines in the position that will
exist at the time when the platform 44, attached to slidable carriage
40, is being supported by the lead screw 54, in other words at the
time when the platform is not resting on the ground or on the floor
of the van. In this condition all the elements are in the position
shown in full lines on FIGS. 6a and 6b. In this position the ball
nut assembly 48a is in its upper position relative to the sleeve
55 and carriage 40, as is the lever 83, second actuating rod 89,
stirrup 90 with its point of attachment 91 to the triangular actuators
93. With attachment point 91 being raised and pivot point 92 of
the actuator being in a fixed position in relation to the floor
of the platform, it follows that the triangular actuators will be
in their position shown in full lines in FIGS. 6a and 6b with the
pivot point 99 in its outermost position pulling actuator bar 95
in a direction away from retainer lip 85 holding it in its pivoted
upper position, such that a wheel chair situated on the platform
is prevented from rolling off.
Conversely, when the platform is lowered to the point that it makes
contact with the van floor or the ground beside the van, the lost
motion of the ball nut assembly 48a comes into play. In this condition
the platform 44 with carriage 40 and sleeve 55 stops in its downward
movement, but the lead screw 54 continues to move the ball nut housing
another short distance downward until the motor driving the lead
screw is stopped as the lower limit switch is actuated as described
later under the description of the control apparatus.
As the ball nut housing 48a is lowered to its lowest position as
indicated by phantom lines in FIG. 6a, relative to the sleeve 55
and carriage 40, all the elements of the actuating train will be
in their lower positions, as shown in phantom lines. In this position,
as shown on FIG. 6c, the triangular actuators 93 wil be rotated
counterclockwise about pivot point 92 approximately 90 degrees,
and the point 99 of attachment of the outer end of actuating bar
95 and 96 will describe an arch of also approximately 90 degrees
thereby pushing the actuating bar 96 toward its outermost position
shown in FIG. 6c, where the outermost end of the actuating bar attached
to the pivotable retainer lip at point 97 will operate to pivot
said retainer lip to its lower position where it is generally co-planar
with the surface of aforesaid platform 44. In that position the
wheel chair can freely be rolled onto or off the platform.
When the actuating train elements are in their uppermost positions
as shown in solid lines on FIGS. 6a and 6b, the actuating bar 95
and 96, as described above will be in its innermost position with
the retaining lip 85 in the upper position. In this position the
three points, pivot point 97 of the connection between the actuating
bar and the retaining lip 85, pivot point 92 of the connection between
triangular actuators 93 and projection 94 and pivot point 99 of
the connection between the actuating bar 95 and the triangular actuators
93 will all be positioned on a straight line, so that the pivot
point 99 will be on-center with pivot points 92 and 97. As a result,
no amount of pressure exerted against the retaining lip in the direction
from the platform toward its rear edge will cause the triangular
actuators to be pivoted counterclockwise thus allowing the retaining
lip to yield to the pressure. This arrangement affords an important
safety feature in protecting the wheel chair's position on the platform.
A lower limit switch 133 (FIG. 10) is carried by a bracket 134
welded to the vertically slidable carriage 40. The movable actuator
135 for this switch is positioned to be engaged by the lower plate
50 which is part of the lost motion coupling between the ball nut
48 and the carriage 40. When the weight of this carriage with the
rigid framework 41, 42, 43, 45 and 47 and the lift platform 44 is
not being carried by the lead screw 54, such as when the lift platform
is resting on a sidewalk or on the van floor, the switch actuator
135 will be engaged by plate 50 as shown in FIG. 10 and the contacts
of switch 133 will be open. When the lead screw 54 is supporting
the weight of the lift platform, carriage and framework, the lower
plate 50 will be displaced up away from engagement with the switch
actuator 135 and the contacts of switch 133 will be closed. Thus,
the switch 133 senses whether or not the lead screw is carrying
this weight.
Limit switch 133 is operatively electrically connected to the motor
142 for stopping the latter when the lift platform can be lowered
no farther. A manual switch is provided for raising and lowering
the lift platform. With the manual switch held in its "lower"
position, the platform will come down until limit switch 133 is
operated (opened), de-energizing the motor 142.
A normally open upper limit switch 136 (FIG. 10) with a pivoted
actuator 96 is mounted on the vertically slidable carriage 40. The
movable actuator 96 is positioned such as to engage with the lower
end of slidable upper stop post 97 when said carriage enters the
limit of its upper vertical travel. Said slidable upper stop post
97 is slidably vertically contained in bushing 137 such that said
stop post is restrained to slide vertically axially inside said
bushing. The upper end of said stop post 97 is positioned such that
when said carriage enters the upper limit of its travel, a vertically
fixed stop post 99 positioned coaxially with and above said lower
stop post 97 and attached at its upper screw-threaded end to aforesaid
support plate 74 by means of two threaded nuts 100-101 with one
nut on each side of aforesaid support plate and with the upper post
end positioned through a clearance hole in said plate.
As seen in circuit schematic diagram FIG. 13, and as described
in greater detail below, switch 136 controls the lead screw drive
motor 142, such that a continuous electrical power connection is
maintained from the van's power bus 150 through that side of the
toggle switch 110 that, when manually operated to the "up"
position serves to energize the side 151 of the drive motor 142
that, in turn, drives the lead screw in such rotational direction
that the lift platform 44 is raised. As the platform reaches its
upper limit, aforesaid stop posts 97 and 99 mutually engage. Ihe
lower post 97 is driven downward against switch actuator 96 which
normally maintains post 97 in its upper position aided by the helical
spring 91, thereby causing switch actuator 96 to operate the switch
136 such that its contacts are opened, thereby causing removal of
power to the motor 142 and stopping the upward motion of the lift
platform. As power is first applied to the motor, the friction brake
143 is simultaneously powered, thereby disengaging the brake, allowing
the motor to rotate. As power to the motor and the brake is again
disconnected, as the platform reaches its upper limit, the brake
is again engaged, holding the motor in its stopped position.
Conversely to the upward movement of the lift platform, the downward
movement is performed by manually operating the toggle switch 110
to its DN position. In this case the lead screw drive motor 142
is energized at its reverse rotation side 152, causing the motor
to lower the platform. Power to drive the motor in its reverse rotation
passes through the lower limit switch 133, which at this time has
its contacts closed, because the weight of the platform holds the
ball nut housing 48a in its upper lost motion position, which, as
explained above, maintains the limit switch 133 with its contacts
closed. At the end of its vertical downward travel, when the lift
platform reaches either the ground or the floor of the van, the
weight of the platform will no longer be borne by the lead screw,
the ball nut housing will move to its lower lost motion position
where the limit switch 133 will be actuated and its contacts opened,
thereby removing power to the motor 142 with the brake 143 and the
motor will stop.
In a manner similar to the up and down motion of the lift platform,
the motor 62 with brake 62a which drives the platform to its "in"
or "out" position, is controlled by a toggle switch 111
which, like toggle switch 110, has two nonlocking positions namely
"in" and "out" and a neutral center position.
Assuming the platform is inside the van and it is desired to operate
the drive motor to rotate the platform to its "out" position,
the toggle switch 111 is manually operated to its "out"
position, thereby causing the energizing of the drive motor 62 to
the side 154 that causes the motor to rotate in the direction that
causes the platform to rotate out of the van. Conversely, when it
is desired to rotate the platform in the direction of "in",
toggle switch 111 is manually operated to its nonlocking position
"in" which energizes the motor 62 to rotate in the "in"
direction.
As is the case with the up and down movement of the lift platform,
the rotate "in" and "out" movements are controlled
by two limit switches 112 which serves to stop the out movement
and 115 which serves to stop the in movement. Limit switch 112 in
FIG. 3 is mounted on bracket 114 which is rigidly attached to the
base plate 120, and is stationary in relation to the platform. An
actuator 113, best seen on FIG. 2, is attached to vertical base
plate 116 which is again attached to gear wheel sector 59.
Actuator 113, being attached to gear wheel sector 59, rotates in
a horizontal plane about the vertical axis of rotatable post 26
when the lift platform rotates between its extreme "in"
and "out" positions, such that, as the platform rotatably
reaches the limit of its "in" movement, actuator 113 engages
limit switch 115 to operatively de-energize the inward driving side
153 of motor 62. Conversely, as the lift platform rotates in the
"out" direction, as it reaches its extreme "out"
position, actuator 102 engages limit switch 112 attached to bracket
114 such that the outward driving side of motor 62 is de-energized
and the motor is stopped.
Circuit schematic diagram FIG. 13 with additional components of
the control system for the motors driving the lift platform in its
vertical and rotational movements is described in more detail below.
The motors 62 and 142 are reversible DC motors constructed to operate
from the 12 volt DC power system of the van. Only the van storage
battery 119 is shown, but not the means for charging the battery
which usually consist of a generator driven by the van's engine.
Each of the motors 142 and 62 has two power connections, one for
each direction of rotation of the motor. Motor 142, when energized
at its connection 151 will drive the lead screw in a direction such
as to raise the platform, while connection 152 will energize the
motor to lower the platform. Similarly, the rotate motor 62 has
power connections 153 and 154 which will energize the motor to rotate
the platform in the "in" and "out" direction
respectively.
The toggle switches 110 controlling the up and down movement of
the platform and 111 controlling the in and out movement each have
three positions, namely an upper nonlocking, a neutral center and
a lower nonlocking position. These toggle switches have contacts
with relatively low power ratings, typically a few amperes at 12
volts DC current which is inadequate to operate the motors. Therefore,
four relays 103, 104, 105 and 106 labelled Ep, Er, Rr and Rp respectively
are controlled by the toggle switches such that the relay contacts
with much higher power ratings, typically in the range of tens of
amperes at 12 volt DC current, are used to energize the motors.
A fifth relay 107, labelled Re, serves to disable the rotational
movement of the chair lift apparatus at all times when the chair
lift is not in its uppermost position. This disabling feature serves
as a safety feature since an attempt to operate the rotational apparatus
could cause structural damage and possibly personal injury unless
the platform is in its upper position where it can rotate freely.
The circuit operates as follows:
In order to initiate movement of the platform in the "up"
direction, toggle switch 110 is operated to its "up" position,
thereby connecting power through a pair of break contacts 132 of
relay Re (107) to the operating coil of relay Ep (103) which operates
such that its transfer contacts 116 remove ground and connect power
through the break side of Er contacts 117 to the side 151 of motor
142.
At the same time ground potential is maintained to the other side
152 of the motor and the brake 143 is energized, removing the braking
hold on the motor. As a result the motor starts turning in the direction
to raise the platform. As the platform reaches the upper limit of
its travel, the normally open limit switch 136 is operated and closes
its contacts causing relay Re (107) to operate and open its contacts
132, which removes power from relay Ep which in turn removes power
from the motor 142 and restores ground potential. The brake 143
is again activated and prevents the motor from turning. The platform
can now be rotated out of or into the van as the case may require
by operating toggle switch 111 to the "in" or "out"
position. Assuming the platform has to be rotated to the "In"
position, toggle switch 111 by being operated to "In"
applies power to relay coil Rp (106) from the contacts of the now
closed upper limit switch 136. Relay Rp through transfer contacts
108 removes ground potential and instead connects power to the side
153 of the rotate motor 62 through the break side of contacts 109
of relay Rr (105), and through the break contacts of limit switch
115 which causes the motor to rotate in the "In" direction
rotating the platform into the van until the limit switch "In"
is operated, thereby removing power from the rotate motor. Conversely,
if platform is to be rotated out of the van, toggle switch 111 is
operated to the "out" position, energizing relay Rr (105).
A rectifier diode 156 is connected from the "out" terminal
of switch 111 to relay Rp(106) which is also energized since the
diode allows a positive potential to be conducted in the direction
from the "Out" terminal to relay Rp (106). Since both
relays Rp and Rr now operate, transfer contacts 108 of Rp will connect
power to the make side of transfer contacts 139 of Rr which in turn
connects power through limit switch 112 to the side 154 of the rotate
motor 62 which causes the motor to rotate in the direction to rotate
the platform out of the van. The outward rotation continues until
limit switch "Out" (112) is operated thereby stopping
the rotation of the motor and the platform.
At the completion of the "In" or "Out" rotation,
the platform must again be lowered, either to the floor of the van
or to the ground outside the van, as the case may require. Lowering
the platform is performed by operating the toggle switch 110 to
the "DN" position whereby power is connected from the
toggle switch through the break contacts of lower limit switch 133
to relay Er which operates. At the same time relay Ep is operated
by power conducted through rectifier diode 155 to the coil of Ep.
With both Ep and Er operated power is connected to the side 152
of the raise motor 142 from the make side of Ep contacts 116 through
the make side of Er contacts 118, while ground potential is connected
to side 151 through the make contacts of Er contacts 117. At the
same time the brake 143 is again energized. In this condition the
raise motor 142 is energized to rotate in the "Down" direction.
The motor will continue to turn until the lower limit switch 133
is operated to open its contacts. As described above, the lower
limit switch is operated at the end of the "lost motion"
travel of the ball unit housing 48a which takes place a short distance
after the platform has touched either the floor of the van or the
ground outside the van. Limit switch 133 operating removes power
from both relays Er and Ep, such that ground potential is again
connected to both sides of the motor 142 and the brake 143, and
the motor stops with the retainer lip 85 on the platform in its
lower position, such that the wheel chair can be rolled onto or
off the platform as required. Two transient absorbers 119 and 138
are connected across the terminals of each motor. These absorbers
are normally non-conducting at potentials of approximately 15 volts
but enter a conducting state above this potential and serve to protect
the relay contacts against the high voltage inductive transient
impulses that are generated when the motors are turned on and off.
As described above both motors 142 and 62 in their non-operating
condition have ground potential connected to both sides of the motor,
so that the motors are externally short-circuited. Due to the construction
of the motors used, an external short circuit of the motor terminals
will cause the motors to resist rotation. In this manner, the inertial
energy of the vertical and rotational motion of the lift apparatus
is absorbed when the motors are stopped.
OPERATION
In the operation of this apparatus, with the van door 22 open (FIG.
1), the lift platform is lowered onto the sidewalk or street surface
on which the wheel chair rests. With the retainer lip 85 on the
lift platform in its lowered, horizontally extended position, the
wheel chair is rolled onto the lift platform.
When the user operates the manual switch 110 for raising the lift
platform, the first thing that happens is that the retainer lip
85 on the outer edge of the lift platform is pivoted up to the raised
position shown in FIG. 1, so as to engage the back of the wheels
and prevent the wheel chair from accidentally rolling off the lift
platform. The initial action takes place as follows:
The manual "raise" switch (110) turns on the motor 142
which drives the lead screw 54 in a direction for raising the ball
nut 48. The upward movement of the ball nut is imparted first to
the unitary assembly of the three-sided ball nut carrier 48a, the
upper and lower plates 49 and 50, and the guide post 51, so that
this unitary assembly first moves up about an inch from the phantom
line position in FIG. 6a to the full line position. The carriage
40 remains stationary during this initial movement and the unitary
ball nut assembly moves up with respect to the guide sleeve 55 fixed
to the carriage. This initial upward movement of the ball nut is
imparted through the actuating train shown on FIGS. 6a and 6b to
the retainer lip 85 to pivot the latter up to its wheel-retaining
position, shown in FIG. 6.
Continued rotation of the lead screw 54, after the bottom plate
50 in the lost motion coupling engages the lower end of the guide
sleeve 55, now causes the carriage 40 to move up in unison with
the ball nut assembly. The carriage 40 slides up along the vertical
post 26 carrying the lift platform with it. This lost motion upward
movement of the bottom plate 50 also releases the actuator 135 for
the lower limit switch 133, so that the release of this switch occurs
when the lead screw 54 begins to carry the weight of the carriage,
framework and lift platform.
When the upper limit switch actuator 96 is operated, the lead screwmotor
142 is turned off. This happens when the lift platform has reached
its upper vertical position.
The next step is to rotate the post 26 to bring the lift platform
from its raised position outside the vehicle to a raised position
inside the vehicle. This may happen automatically following the
actuation of the upper limit switch 136 or it may be effected through
operation of the toggle switch 111. In either case the motor 62
now is turned on and through the pinion 60 and gear sector 59 it
rotates the post 26 in a direction to swing the lift platform inside
the van slightly above the floor of the van.
At the completion of this operation, the post drive motor 62 is
turned off, either automatically or manually and motor 142 is energized,
either automatically or through a manual switch, to drive the lead
screw 54 in the reverse direction for lowering the ball nut assembly.
The lift platform is lowered onto the floor of the van and then
as the lead screw 54 continues to run in reverse it causes the ball
nut assembly to move down with respect to the now-stationary guide
sleeve 55 and the carriage 40. This causes the actuating train to
lower the retaining lip 85 on the lift platform, so that the wheel
chair can be rolled off the lift platform onto the floor of the
van.
When the wheel chair is to be moved out of the van onto the sidewalk,
for example, the foreoing operating sequence is reversed.
It will be evident from the foregoing that the lost motion coupling
which acts between the ball nut 48 and the carriage insures that
the retaining lip 85 on the lift platform will be in its raised
position whenever the lead screw 54 is carrying the weight of the
lift platform. The retaining lip 85 will be down only when the lift
platform has its weight resting on some support surface, such as
the van floor or the sidewalk outside.
With the lead screw drive motor 142 stopped, the weight of the
wheel chair and its occupant on the lift platform, acting through
the low friction coupling between the ball nut 48 and the lead screw
54, is prevented from slowly rotating the lead screw in a direction
for lowering the lift platform because of the frictional restraint
exerted by the electric brake 143. Accordingly, under these circumstances
the lift platform cannot coast down along the lead screw.
In case electric power should fail so that the control components
including the motors cannot be operated by power, provisions have
been made to insure that they can be moved both vertically or horizontally
by manual means. In case the platform has to be moved vertically,
a hand crank 161 as shown in FIG. 9 is provided as one of the implements
of the present apparatus. The hand crank has a square tap 162 which
mates with the square hole 79 in the top of the collar 80 on top
of lead screw 54, shown in FIG. 9. Since the motor 62 for rotating
the platform is connected to the rotatable post 26 through a set
of gear wheels having a high turns ratio, provisions are made for
disengaging the pinion 60 from the gear sector 59. Disengagement
is performed by first lifting the handle 126 of the wedge assembly
generally at 130 in FIG. 3. By lifting the handle 126 the wedge
122 is retracted from its normal position between the vertical lip
124 and the extension 128 of gear unit 61. Removed from its normal
position the pivotable gear and motor assembly generally at 121
in FIG. 3 and mounted on the plate 63 which is pivotable about the
vertical post 64, (FIG. 3) can be rotated clockwise a small angle
so as to disengage pinion 60 (FIG. 2) from gear wheel sector 59.
After disengagement, the rotatable post 26 can be rotated manually
using a rod lever as a past implement handle. that can be inserted
into a matching post adaptation 88 (FIG. 9), which shows the post
implement as a rod 88a and the post adaptation as a hole 88, drilled
diagonally through the upper cylindrical part of the post 26. |