Wheel chair abstract
As a rule, wheel-chairs have large(-diameter) drive wheels (3)
and small(-diameter) steerable wheels (5), and wheel-chairs for
indoor operation have their drive wheels as their rear wheels, while
wheel-chairs for outdoor operation have their drive wheels (3) as
front wheels. In the wheel-chair according to the invention, the
seat assembly (6) is mounted for rotation about a vertical axis
by means of a supporting column (14) above the chassis (1), such
that, depending on the purpose of use of the wheel-chair, the large
drive wheels are selectively disposed in the front or rear position
with respect to the seat(ing) direction. In this way, the wheel-chair
may be used both inddors and outdoors in an optimum manner. Additional
positioning alernatives of the seat assembly, e.g. at .+-.90.degree.
relative to the chassis, open to the user new possibilities of utilization.
By an automatic switchover of the control (or steering) lever in
accordance with the position of the seat assembly, optimum operation
of the wheel-chair is obtained.
Wheel chair claims
We claim:
1. An electric wheel-chair comprising:
a chassis;
at least one first axle having drive wheels, which is connected
to the chassis;
a pair of second axles which are connected to the chassis, each
having a swivel wheel;
a seat assembly rotatively mounted on the chassis between the first
and second axles, having an axis of rotation, the seat assembly
having at least two lockable seating positions, including first
and second end positions oriented 180.degree. from each other and
normal to rotational axes of the axles;
a drive unit coupled to each drive wheel for driving that wheel
in response to control signals that are routed to assigned signal
receipt locations in the drive unit, which control signals are indicative
of desired wheel-chair maneuvers to be executed by the drive unit
with respect to one of the seating positions;
an operating unit coupled to the drive units for generating the
control signals; and
means coupled to the operating unit and the drive units for rerouting
the control signals from the operating unit to the drive unit signal
receipt locations, so that the drive units execute the same desired
wheel-chair maneuvers when the seat is positioned in at least said
first and second end positions.
2. The wheel-chair of claim 1, wherein the means for rerouting
control signals is at least one switch that is actuated by seat
rotation to another seating position.
3. The wheel-chair of claim 1, wherein the means for rerouting
control signals has at least one sensor which generates a sensor
signal indicative of the seat position and the means for rerouting
control signals performs the rerouting in response to the sensor
signal.
4. The wheel-chair of any one of claims 1-3, wherein the seat assembly
is lockable in at least one position intermediate the end positions.
5. The wheel-chair of claim 4, wherein the seat assembly is lockable
in an angular position of 90.degree. relative to the two end positions.
6. The wheel-chair of any one of claims 1-3, wherein the seat assembly
has means for vertical adjustment relative to the chassis.
7. The wheel-chair of any one claims 1-3, wherein the chassis has
a vertical supporting column positioned between the drive and swivel
wheels; the seat assembly has a rod-shaped trunnion for insertion
into the vertical supporting column and the trunnion is rotatable
within the vertical supporting column.
8. The wheel-chair of any one of claims 1-3, wherein the seat assembly
has a locking pin for locking a chosen seat position and the chassis
has means for receiving the locking pin at each seat locking position.
9. The wheel-chair of any one of claims 1-3, wherein the seat assembly
and chassis have supports for preventing horizontal movement of
the seat assembly relative to the seat rotational axis.
10. The wheel-chair of claim 9, further comprising sliding guides
coupling the seat to the chassis for slidable movement of the seat
relative to the chassis and a slide lock for locking the seat in
a desired slide position.
11. The wheel-chair of any one of claims 1-3, wherein the operating
unit has a circuit for electrically reversing control signal routing
to the drive unit signal receipt locations.
12. The wheel-chair of any one of claims 1-3, wherein the swivel
wheels are connected to the chassis through a shock-absorbing balance
beam suspension system.
13. The wheel-chair of any one of claims 1-3, further comprising
steering dampers coupling the swivel wheels to the chassis for directionally
stabilizing the wheel-chair.
14. The wheel-chair of claim 13, wherein at least one of the swivel
wheel steering dampers has means for fixing or adjusting the amount
of damping.
15. The wheel-chair of claim 3, wherein the operating unit generates
forward and reverse drive directional signals relative to one of
the end seating positions and the means for rerouting the control
signals inverts routing of the directional signals to the drive
unit signal receipt locations when the seat assembly is rotated
to the second end seating position.
16. The wheel-chair of claim 3, wherein:
the seat assembly has a seating position oriented 90.degree. relative
to the first and second end seating positions;
the operating unit generates left/right steering signals and forward/reverse
sped signals which are routed to the drive unit control signal receipt
locations for effecting desired wheel-chair motion relative to one
of the end seating positions; and
when the seat is rotated to the 90.degree. seating position, the
means for rerouting the control signals reroutes the left/right
steering signals generated by the control unit to the first seating
position forward/reverse speed signal receipt locations in the drive
unit and reroutes the forward/reverse control signals generated
by the control unit to the left/right steering signal receipt locations
in the drive unit.
17. The wheel-chair of claim 16, wherein the means for rerouting
the control signals reduces the amplitude of the forward/reverse
control signal before rerouting that signal to the drive unit left/right
steering signal receipt locations.
Wheel chair description
The invention relates to an electric wheel-chair, comprising a
chassis having larger drive wheels on a first axle or a first pair
of axles and smaller (castor) swivel wheels on second axles; a seat
assembly mounted on the chassis; one drive unit each for the drive
wheels; and an operating unit for controlling the drive units.
Generally, electric wheel-chairs are classified in two categories
in accordance with their primary purpose of use, and the chassis
is constructed differently depending on the respective purpose of
use. In wheel-chairs intended primarily for indoor use (first category),
large (or large-diameter) drive wheels are mounted in the rear section
and small swivel wheels are provided in the front section of the
wheel-chair, while wheel-chairs intended predominantly for outdoor
use (second category) have the large drive wheels in the front section
and the small swivel wheels in the rear section. Normally, in these
two categories the location of the center of gravity of the seat
assembly or of the unit comprising seat assembly and chassis is
selected differently, too.
In view of the fact, however, that disabled persons who need a
wheel-chair are normally living both indoors and outdoors, there
are generally needed two wheel-chairs to provide for optimum conditions
in each respective application. This is not only very costly, but
often also troublesome because of, for example, the frequently necessary
changing of wheel-chairs or the storing and transport of two wheel-chairs.
It is the object of the invention to provide an electric wheel-chair
of the type as outlined at the beginning, which can be used in an
optimum manner for both modes of operation, namely indoors and outdoors,
with the conversion from the one mode of operation to the other
being possible to be performed easily and in a short time.
According to the invention, this object is solved in that the seat
assembly is mounted on the chassis for rotation about a vertical
axis of rotation disposed in the central region between the wheel
axles, and adapted to be locked in at least two end positions displaced
from each other by 180.degree. C., with the seat(ing) direction
in each end position extending perpendicular (or normal) to the
wheel axles, and the drive wheels serving selectively as front wheels
or rear wheels; and that the handling characteristics of the drive
units are likewise adapted to be reversed in accordance with the
rotation of the seat assembly.
Accordingly, in the electric wheel-chair according to the invention,
one single chassis including one single seat assembly is required
for either of the indicated modes of operation, while there are
nevertheless available the optimum wheel size of the drive and swivel
wheels as well as optimum mode of driving for the respective mode
of operation. This is made possible in that by means of a relative
rotation of seat assembly and chassis the respective front and rear
wheels are exchanged with each other, and the handling characteristics
are also switched over correspondingly.
The rotatable mounting of the seat assembly on the chassis provides
further advantages. For example, in addition to the two above-mentioned
end positions for opposite directions of travel, it is also possible
to set further intermediate positions of the seat assembly, such
as in an angular position of 90.degree. to the longitudinal direction
of the chassis. In this manner, a disabled person may be positioned,
for specific purposes, in a more favorable or comfortable position
transversely of the direction of travel, such as for getting in
or out from the wheel-chair of for certain treatments, for example.
Naturally, other intermediate positions at any desired angles may
be set too, if necessary. In addition, the design may be made so
that the seat assembly is adapted to be adjusted vertically relative
to the chassis.
In order to render possible rotation of the seat assembly relative
to the chassis, the chassis may include, for example, a vertical
supporting column for the seat assembly, which column is centrally
positioned between the wheels and in which a rod-shaped trunnion
for the seat assembly is mounted (for rotation). In this structure,
there may be provided a locking device which locks the chassis and
the seat assembly to each other in the respective angular positions
desired. To this end, there may be provided, for example, receiving
holes, formed on the chassis on a circle around the axis of rotation,
for a locking pin adjustably or movably arranged on the seat assembly.
This locking pin may be biased by spring force towards the receiving
hole so as to engage (a hole) when reaching a respective locking
position. Naturally, the movable part, in the form of a locking
pin or in any desired other form, may be provided also on the chassis,
while the receiving means therefore may be provided in the rotatable
seat assembly. In general, however, it is more favorable to connect
the movable locking member with the seat assembly, so that this
member is always in the same position for operation by a person
occupying the seat assembly, regardless of the respective angular
position.
Preferably, the seat assembly rotatably mounted on the chassis
is adapted to be readily removed from the chassis, so as to be replaceable.
In this way, different special constructions of seat assemblies
may be readily exchanged with each other as desired. In view of
the fact that, further, it is beneficial in some instances that
the center of gravity of the seat assembly is not located exactly
in the center position between the wheel axes, since different centers
of gravity with respect to the wheel axes may be desirable depending
on the mode of operation indoors or outdoors, it is provided according
to an expedient further embodiment that the seat assembly is also
adjustable in the horizontal direction relative to the axis of rotation.
To this end, there may be provided sliding guide means on which
the seat assembly is movable and adapted to be locked in the respective
position desired.
Normally, rotation and even the above-mentioned horizontal adjustment
or movement of the seat assembly are performed manually. However,
it is also conceivable to provide a respective servo motor for these
rotating or sliding movements. Also, switchover of the drive unit
may be performed manually by means of a switch, which switch is
expediently located in the region of the operating instrument.
Particularly easy, however, is an automatic switchover operation
by means of sensors disposed in the junction region between the
chassis and the seat assembly, which sensors act to automatically
detect the relative position between chassis and seat assembly.
Further beneficial embodiments and further developments are disclosed
in the subclaims.
Below, the invention is explained in exemplary embodiments with
reference to the drawing, wherein:
FIG. 1 is a side elevational view of an electric wheel-chair embodied
in accordance with the invention;
FIG. 2 is a plan view showing the four wheels of the wheel-chair
and diagrammatically illustrating four different positions of the
seat assembly;
FIG. 3 is a schematic front elevational view of the steerable wheel
assembly;
FIG. 4 is a schematic plan view of the steerable wheel assembly;
and
FIG. 5 is a diagram illustrating the interlinking of the speed
and steering signals for the various positions shown in FIG. 2.
The electric wheel-chair shown in FIG. 1 comprises a chassis 1
having four wheel axles. The first two wheel axles 2 mount relatively
large (large-diameter) drive wheels 3, while a pair of swivel wheels
5 of a small diameter compared to the drive wheels, are mounted
on a third and fourth axle 4 each.
The large wheels are used for driving purposes, while the small
wheels are used for steering. The suspension of the small wheels,
i.e. the steerable or swivel wheels, will be explained below.
A seat assembly 6 is mounted on the chassis 1 substantially centrally
between the wheel axles. This seat assembly comprises, in a manner
known per se, a seat member 7, a back rest 8 and a foot rest 9 which
may be adjustable, for example, and which, in the example shown,
includes a pair of separate rests for each foot (see FIG. 2). Further,
the seat assembly has mounted on the sides thereof respective arm
rests 11, with the right-hand arm rest being provided with an operating
unit 12 including a control (or steering) lever 13. In these regards,
the structure of the seat assembly corresponds to conventional constructions.
In the position of the seat assembly 6 above the chassis 1 as shown
in FIG. 1, a wheel-chair for indoor use is illustrated, because
the large drive wheels are mounted on the rear end of the chassis
in correspondence with the seat(ing) position, and the swivel wheels
are mounted on the front end. For outdoor use of the wheel-chair,
however, it is more favorable to position the drive wheels on the
front side and the movable swivel wheels on the rear side, because
it is easier in this manner to travel across irregularities and
small obstacles. Now, in order that the wheel-chair shown in FIG.
1 can be used also outdoors (outside the house), the seat assembly
6 is rotatably or pivotally mounted on the chassis 1. To this end,
the chassis includes a supporting column 14 on which the seat assembly
6 is mounted by means of a single rod-shaped trunnion 15 having
a vertical axis of rotation. Accordingly, the seat assembly may
be rotated from the position shown in FIG. 1 by 180.degree. relative
to the chassis, such that the seat then is directed to the right-hand
side in FIG. 1, and thus the drive wheels 3 are located on the front
side with respect to the seat direction, while the swivel wheels
5 are on the rear side of the chassis. The operating unit 12 is
fixedly coupled to the seat assembly so that it can be reached and
operated in always the same way by the disabled person seating in
the wheel-chair. In the respective travel position, the seat assembly
6 is locked relative to the chassis 1 by means of a locking device
16.
FIG. 2 shows schematically above the two pairs of wheels 3 and
5 according to FIG. 1, illustrated in plan view, various seat positions
that can be obtained. Illustrated in FIG. 2 are only the foot rests
9 which indicate the seat(ing) direction by their position relative
to the wheels. Shown as position 1 is the orientation according
to FIG. 1 in which the foot rests 9 are located on the left-hand
side of the drawing in front of the small swivel wheels 5; the foot
rests are denoted 9-1 to identify position 1. Illustrated in the
center between the four wheels is an example for a possible design
of the locking device 16. This locking device 16 is mounted to the
seat assembly and includes a locking pin 17 which is movable in
the direction perpendicular (or normal) to the axis of the supporting
column 14, and which is biased in this direction towards the supporting
column 14. Connected with the supporting column 14 is a locking
disc or plate 18 which includes for each selectible seat position
a receiving member 19 for the tip end of the locking pin 17. When
the seat assembly is to be rotated from the position shown in FIG.
1, the locking pin 17, illustrated in FIG. 2, is retracted (position
20') by means of a handle 20, whereby the seat assembly 6 is unlocked
from the supporting column. For reversing the direction of travel,
the seat assembly is then rotated by 180.degree. to position 2,
whereby the foot rests assume the orientation (position) 9-2 according
to FIG. 2. The locking pin is (slidably) mounted on the seat group,
and after the above-described rotation the locking pin likewise
assumes a position rotated by 180.degree., which position is not
shown in FIG. 2. Then, the locking pin 17 engages (snaps into) the
receiving member 19 under its bias (from above in the drawing).
As the seat assembly 6 is mounted (for rotation) through a trunnion
15 on a supporting column 14 of the chassis 1, it is also possible
to easily replace or exchange the seat assembly such that, depending
on the kind and degree of handicap of a person, different chassises
may be combined in an easy manner with seat assemblies of different
designs. In this manner, different handling characteristics can
be provided by the different chassises. However, the rotatable mounting
of the seat assembly also permits to set, without extra expenditure,
not only two seat positions to the front and rear of the travel
direction; rather, additional intermediate positions may be set,
too. For example, it is possible to lock the seat assembly in an
angular position of about 90.degree. relative to the travel direction,
whereby the disabled person seating in the wheel-chair can assume,
for certain purposes, a more favorable or comfortable position transversely
of the rolling direction of the wheels. Such positions are shown
in FIG. 2 as positions 3 and 4, respectively, as indicated by the
schematically illustrated foot rests 9-3 and 9-4, respectively.
Locking in these additional positions is effected in the same manner
as described above for the two primary seat positions. Naturally,
it would be conceivable to define in case of need further additional
angular positions, and to correspondingly form the locking device.
With a rotation of the seat assembly by 180.degree., it is also
necessary to correspondingly modify the control or driving of the
drive wheels since the changed directions of rotation for forward
and reverse travel and the changed driving (handling) conditions
in the steering system must be considered with respect to the drive
wheels which are now in the front position. A further modification
is necessary when the seat direction is rotated by 90.degree. relative
to the travel direction of the drive wheels. The electrical switchover
of the drive units, which is required in this instance, can be effected
by, for example, actuating a switch 21 in the operating unit. Alternatively,
it is possible to effect automatic switchover, with the signal for
each required setting of the drive units being produced by sensor
means 22 which is positioned in the junction region between the
chassis and the seat assembly, and which responds to relative movement
between the seat assembly on the one hand, and the chassis on the
other hand. Two sensor elements are required for the binary scanning
of four potential positions of the seat assembly. For eight positions,
three sensors would be required, i.e. 2.sup.n sensors each, with
n being the number of possible positions. As sensor elements, there
may be considered a variety of conventional components, such as
microswitches, Hall elements, optoelectronic elements, inductive
or capacitive proximity switches, etc. In the case of a greater
number of positions that can be chosen, it is also possible to use
incremental angle transmitters (or sensors) of a conventional design,
the output values of which may be evaluated electronically in order
to provide for smooth transitions between the various seat positions.
In the embodiment described above, four possible or potential seat
assembly positions were assumed, such that, thus, the seat assembly
takes a position of 0.degree..+-.90.degree. or 180.degree. relative
to the travel direction of the drive wheels. A scheme for automatic
correlation of the speed and steering signals from the operating
unit to the drive units is shown in FIG. 5. This Figure indicates
for each of the positions of the foot rests as shown in FIG. 2 (corresponding
to the direction of the seat assembly) the respective conversion
of the signals provided by the operating unit.
For position 9-1 (0.degree. position), the speed signal (GS) from
the operating unit is supplied to the drive units without any variation,
same as the steering signal indicating a desired change of direction.
In position 9-4 corresponding to a rotation of the seat assembly
by 90.degree. to the right, the speed signal (GS) is converted into
a steering signal (LS) for the drive units (AE), whereby the amplitude
is reduced through a level adjusting unit (PE). This means that,
for example, forward movement of the control (or steering) lever
in the operating unit for the drive wheels, is converted into a
steering signal to the right (forward or reverse, depending on the
additionally fed speed signal). Simultaneously, the steering signal
(LS) generated by the operating unit from pivoting of the control
lever to the left or right is converted into a speed signal (GS)
for forward or reverse drive of the drive wheels. Furthermore, this
signal is inverted through an inverter (IN), such that a right-hand
steering signal results in reverse rotation, and a left-hand steering
signal results in forward rotation of the drive wheels 3.
In position 9-2 of the foot rests, the seat position is rotated
by 180.degree.. In this instance, if suffices to invert only the
speed signal (GS) by an inverter (IN), whereas the steering signal
is transmitted as such to the drive units.
In position 9-3 of the foot rests, corresponding to rotation of
the seat assembly by 90.degree. to the left from the original position,
the steering signal (LS) for the drive units, again, is converted
into a speed signal, but without being inverted. On the other hand,
the speed signal (GS) is converted by an inverter (IN), and additionally
by a level adjusting unit (PE), into a steering signal (LS) for
the drive units (AE). In this instance, the handling characteristics
are adjusted or conformed in a corresponding manner.
If further intermediate positions for the seat assembly are provided,
the automatic quadrant matching (or control) of the operating unit
also must be refined correspondingly.
If in special instances the center of gravity of the seat assembly
and of the person occupying the seat assembly must be shifted from
the central region, namely with e.g. an extreme adjustment of the
seat depth or an extreme inclination of the back rest, a corresponding
adjustment of center of gravity can be effected even in the rotatable
seat assembly for either direction of travel. To this end, in the
example of FIG. 1 there is provided sliding guide means in the seat
assembly, which allows for horizontal movement of the entire seat
assembly relative to the trunnion 15. Some portions of the seat
assembly are indicated in FIG. 1 in their shifted position, such
as an arm rest 11', a foot rest 9' and the shifted operating unit
12'. The sliding guide means as such is not shown in detail, as
guide members of this type are familiar to the expert.
In order to ensure optimum handling characteristics for every application
of the electric wheel-chair both indoors and outdoors, the swivel
wheels 5 are suspended in a special manner. The two swivel wheels
5 are each mounted for free swivelling through wheel forks 23 on
vertical axes 24, and suspended from a balance beam system for conforming
themselves to different ground conditions. The balance beam 25 is
pivotally mounted on a horizontal pivot shaft 26 and damped relative
to the chassis through spring members 27. In this way, irregularities
of ground can be properly absorbed, particularly in outdoor operation.
In order to further keep stable the given direction of travel in
either application (indoors and outdoors), there are additionally
provided pneumatic-hydraulic damper members 28 which can selectively
be set to be fixed or adjusted by means of a setting screw 29. This
measure improves the directional stability of the freely pivotable
swivel wheels particularly at a high speed of travel. FIG. 4 illustrates
in schematical plan view such steering dampers 28. It can be seen
from this schematical view that the steering dampers (or shock absorbers)
are disposed at an angle to the axis of the balance beam 25.
Incidentally, it may be noted that in the embodiment shown the
swivel wheels are mounted for free pivoting or rotating movement;
this means that change of direction of the wheel-chair is brought
about by different speeds of rotation of the two drive wheels. In
this case, the swivel wheels turn automatically to the desired direction.
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