Wheel chair abstract
A wheel chair having two rear wheels, two front wheels, a supporting
frame, a seal and a backrest, where the seat can be moved from a
sitting position to a driving position, and vice versa, and wherein
the center of gravity of a user's body is moved rearwardly and downwardly
when adjusting from the sitting position to the driving position.
Wheel chair claims
What is claimed is:
1. A wheel chair (1) comprising at least two rear wheels (2a, 2b),
at least two front wheels (3a, 3b), a supporting frame (4), a seat
assembly (5) and a backrest assembly (6), wherein the seat (5) can
be moved from a passive sitting position to an active driving position,
and vice versa, wherein the seat (5) is tilted relative to a pivoting
point (9) located some distance under the seat (5) upon being adjusted,
in such a manner that the center of gravity of a user's body is
moved rearwardly in a direction toward the rear wheels (2a, 2b)
upon adjustment to the driving position, and that the center of
gravity of a user's body is moved forwardly in a direction away
from the rear wheels (2a, 2b) upon adjustment to the sitting position,
and wherein an angle .beta. included between the seat (5) and the
backrest (6) is made smaller upon adjustment to the driving position,
and it is made larger upon adjustment to the sitting position, characterized
in that the wheel chair (1) comprises a leg support (7), wherein
an angle .gamma. included between the seat (5) and the leg support
(7) is made smaller upon adjustment to the driving position and
larger upon adjustment to the sitting position, and wherein the
leg support (7) is moved upwards in a direction towards the rear
wheels (2a, 2b) upon adjustment to the driving position, and downwards
in a direction away from the rear wheels (2a, 2b) upon adjustment
to the sitting position, said leg support (7) being positioned between
the two front wheels (3a, 3b).
2. The wheel chair (1) according to claim 1, wherein the angle
.beta. included between the seat (5) and the backrest (6) in the
sitting position is adjustable.
3. The wheel chair (1) according to claim 2, wherein the angle
.beta. included between the seat (5) and the backrest (6) in the
driving position is adjustable.
4. The wheel chair (1) according to claim 1, wherein said wheel
chair (1) is collapsible.
5. The wheel chair (1) according to claim 2, wherein the backrest
(6) is connected to the supporting frame (4) by means of the seat
(5) and by means of an arm (13) which is adjustable for length,
which arm (13) is pivotally connected to a point of attachment (14)
on the supporting frame (4) and to a point of attachment (15) on
the backrest (6), wherein several points of attachment for the arm
(13) are provided in, respectively, the supporting frame (4) or
the backrest (6), which points of attachment (14, 15) substantially
lie on a circular arc, which circular arc has as its center the
point of attachment (15, 14) on, respectively, the backrest (6)
or the supporting frame (4) in the sitting position or in the driving
position.
6. The wheel chair (1) according to claim 5, wherein the points
of attachment (14, 15) that lie on said circular arc are spaced
5-18 degrees, preferably 7-15 degrees, apart on said circular arc.
Wheel chair description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a wheel chair comprising at least two
rear wheels, at least one front wheel, a supporting frame, a seat
assembly, simply called "seat" hereinafter and in the
claims, and a backrest assembly, simply called "backrest"
hereinafter and in the claims.
2. Description of the Related Art
A wheel chair of this kind is known from Dutch patent No. 1001164
(Revab BV). The supporting frame of the prior art wheel chair consists
of tubular sections, whilst the seat is built up of a seat cushion
which is positioned on a seat edge, a flap and a supporting strap.
When the supporting strap is fully tightened, the flap is positioned
approximately level with the seat edge, and in effect a user does
not experience a seat angle. When the supporting strap is adjusted
less tight, the seat cushion sinks slightly along with the flap,
as a result of which a relatively larger angle of inclination of
the seat is obtained. The prior art backrest consists of a backrest
cushion, deformation of which can be adjusted individually for each
user through adjustment of the straps present therebehind.
One objection of the wheel chair as known from the aforesaid Dutch
patent publication is that it does offer an disabled person a possibility
to slightly adjust the seat, as regards the angle of inclination
thereof, to his or her individual requirements, to be sure, but
that it has become apparent in practice that this enables an acceptable
seating position only in passive condition, that is, at rest, when
the user is for example eating, writing or reading. In active condition,
when the user is driving, the prior art wheel chair does not enable
an acceptable seating position from an ergonomic point of view.
BRIEF SUMMARY OF THE INVENTION
The object of the invention is to provide a wheel chair which creates
an optimum seating position for a user, both at rest and while driving.
In order to accomplish that objective, a wheel chair of the kind
referred to in the introduction is characterized in that the seat
can be moved from a sitting position to a driving position, and
vice versa, wherein the center of gravity of a user's body is moved
parallel to the direction of movement of the wheel chair.
The invention will now be explained in more detail with reference
to illustrations of a preferred variant of the invention which are
shown in a drawings, wherein:
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
FIG. 1 is a schematic, perspective view of a wheel chair according
to the invention;
FIGS. 2 and 3 are schematic side views of the wheel chair of FIG.
1, showing the sitting position and the driving position, respectively;
FIG. 4 is a detailed view of the backrest cushion of the wheel
chair of FIGS. 1, 2 and 3; and
FIG. 5 is a schematic, perspective view of a variant of a wheel
chair according to the invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
The wheel chair disclosed here is characterized in that the seat
can be moved wherein the center of gravity of a user's body is also
moved. In particular it is possible for a user to move the seat
himself with the aid of spring means, for example a gas spring,
between the sitting position and the driving position while sitting.
The invention is in particular based on the insight that the location
of the body's center of gravity while sitting and driving is a decisive
factor in the realisation of the ideal seating position of a wheel
chair user. According to the invention, in active condition this
center of gravity of the body must be located downwardly and rearwardly,
seen in the direction of movement, of the position of the center
of gravity of the body in passive condition. According to the invention,
when the seat is being moved the body's center of gravity is moved
so that an optimum seating position of the disabled user is ensured
at all times both in the active condition, that is, in the driving
position of the seat, and in the passive condition, that is, the
sitting position of the seat.
In one preferred embodiment of a wheel chair according to the invention,
the seat is tilted relative to a pivoting point located some distance
under the seat upon being adjusted, in such a manner that the center
of gravity of a user's body is moved to rearwards in a direction
towards the rear wheels upon adjustment to the driving position,
and that the center of gravity of a user's body is moved forwards
in a direction away from the rear wheels upon adjustment to the
sitting position. The aforesaid distance is measured from the underside
of the seat and it ranges in particular between approximately 4
and 12 cm. Preferably, said distance is approximately 8 cm. As a
result, the wheel chair will exhibit better driving characteristics,
that is, it will drive more lightly, be easier to manoeuver, etc.
When the seat is tilted back, the body's center of gravity is moved
to the front again, so that a stable sitting, working and/or eating
position is realized. The user can move his body more easily in
that case, whilst the risk of tilting backward is minimized.
In another preferred embodiment of a wheel chair according to the
invention the angle included between the seat and the backrest is
made smaller upon adjustment to the driving position, and it is
made larger upon adjustment to the sitting position. In particular
the backrest is moved rearwards in a direction towards the rear
wheels upon adjustment to the driving position, and it is moved
forwards in a direction away from the rear wheels upon adjustment
to the sitting position. Accordingly, the backrest is likewise movable
from a sitting position to a driving position, and vice versa. Preferably,
the present wheel chair comprises a leg support, wherein the acute
angle included between the seat and the leg support is made smaller
upon adjustment to the driving position and larger upon adjustment
to the sitting position.
In another preferred embodiment of a wheel chair according to the
invention the leg support is moved upwards in a direction towards
the rear wheels upon adjustment to the driving position, and downwards
in a direction away from the rear wheels upon adjustment to the
sitting position. Accordingly, the leg support is also movable from
a sitting position to a driving position, and vice versa. As a result,
additional clearance is available between a footrest which is present
at the bottom of the leg support and the ground while driving, which
adds to the manoeuvrability of the wheel chair, in particular when
negotiating curbs and the like. The aforesaid clearance is minimal
in the sitting position of the leg support, so that an ideal and
stable sitting, working and/or eating position is obtained, whilst
the present wheel chair can readily be driven under a tabletop.
More in particular, the leg support is thereby positioned between
the two front wheels.
In another preferred embodiment of a wheel chair according to the
invention, the angle included between the seat and the backrest
in the sitting position is adjustable. Moreover, it is to be preferred
to make the angle which the backrest includes between the sitting
position and the driving position adjustable. All this takes place
as follows. The backrest is connected to the supporting frame by
means of the seat and by means of an arm which is adjustable for
length, which arm is pivotally connected to a point of attachment
on the supporting frame and to a point of attachment on the backrest,
wherein several points of attachment for the arm are provided in,
respectively, the supporting frame or the backrest, which points
of attachment substantially lie on a circular arc, which circular
arc has as its center the point of attachment on, respectively,
the backrest or the supporting frame in the sitting position or
in the driving position. All this implies that the angle included
between the seat and the backrest in the sitting position can be
adjusted individually for each user, independently of the "stroke"
which the backrest makes upon being adjusted, which is likewise
individually adjustable as desired. The point of attachment of the
arm on the backrest preferably coincides with a user's sitting bumps.
Important is that the lumbar-pelvic rhythm is followed upon adjustment
of at least substantially all parts of the wheel chair. The term
lumbar-pelvic rhythm is understood to mean the motion rhythm of
a wheel chair user, in particular as regards the low back and pelvis
regions, upon changes in the seating position.
In another preferred embodiment of a wheel chair according to the
invention the backrest comprises a hard material in the user's pelvis
region, which functions to support the pelvis, whilst the backrest
comprises a soft material at the location of the central and/or
upper part of a user's back, which functions to support the central
and/or upper back regions. In particular, the pelvis is supported
on a hard foam material. The backrest is made of a soft foam material
near the lumbar and low thorax regions, so that said material does
support the back but does not need to absorb any large forces whilst
nevertheless being capable of meeting the aforesaid lumbar-pelvic
rhythm requirement. In one preferred variant, recesses are formed
in the backrest to enable a user to freely move his arms/elbows
in rearward direction.
In another preferred embodiment of a wheel chair according to the
invention, the wheel chair is collapsible, which makes the whole
easily transportable. In one preferred variant the pivot axis of
a front wheel slopes upwards towards the rear with respect to the
vertical, seen in the forward direction of movement of the wheel
chair, in particular at an angle of about 1.5' with respect to the
vertical, in order to prevent the so-called "shimmying"
effect, that is, the phenomenon whereby the front wheels in the
form of castor wheels position themselves transversely to the direction
of movement, frequently at high speeds, in the case of low perpendicular
loads. In practice it has become apparent that the aforesaid effect
is efficiently suppressed due to the fact that one component of
the force of gravity urges the castor wheels back to the correct
position every time this phenomenon occurs.
FIG. 1 shows a wheel chair 1 according to the invention, which
comprises two spoked rear wheels 2a, 2b, which are interconnected
by means of a rigid rear axle, two smaller castor wheels 3a, 3b,
which function as front wheels, a supporting frame 4, as well as
a seat assembly 5 and a backrest assembly 6. For easy reference,
lest the figure becomes too complicated, the two assemblies are
shown without a seat cushion and a backrest cushion, respectively.
A leg support 7 is furthermore provided, on the lower end of which
a footrest 8 is mounted.
The seat assembly 5, hereinafter also called "seat",
is capable of tilting movement with respect to supporting frame
4, about a pivoting point 9 that is located some 8 cm below the
seat, and that from a sitting position, as shown in FIG. 1, to a
driving position yet to be explained in more detail with respect
to FIG. 3, and vice versa. The center of gravity of a user's body
is moved to the rear, seen in the direction of movement of the wheel
chair 1, in a direction towards the rear wheels 2a, 2b upon adjustment
to the driving position. Whilst subsequently, upon adjustment to
the sitting position which is shown in the present figure, said
center of gravity is moved to the front, in a direction away from
the rear wheels 2a, 2b. Adjustment of the seat to the above positions
can be effected by hand by the user himself from a seated position
with the aid of a gas spring 11, which can be activated by means
of an actuating element 10. The gas spring 11 is connected to supporting
frame 4 at its lower end and to seat 5 at its upper end, in such
a manner that seat 5 is tilted to the sitting position in the extended
position of a piston rod 12 of gas spring 11 and that seat 5 is
pivoted to the driving position in the retracted position of piston
rod 12.
The backrest assembly 6, hereinafter also referred to as "backrest",
can likewise be tilted from a sitting position to a driving position,
and vice versa. Of major importance is thereby the fact that the
tilting angle, that is, the angle through which the backrest moves
between the sitting position and the driving position, as well as
the angle included between seat 5 and backrest 6, is individually
adjustable for each user. This is done in the following manner.
First, the angle included between seat 5 and backrest 6 in the sitting
position is adjusted through adjustment of the length of 3S the
adjustable pull rod in that position, which is done through adjustment
of the pull rod 13, which is in the form of a threaded rod. Then
seat 5 and backrest 6 are tilted to the driving position. In that
position the point of attachment of pull rod 13 to supporting frame
is adjusted by selecting as the point of attachment one of the points
of attachment 14 that all lie on a circular arc, which has the point
of attachment 15 of pull rod 13 to backrest 6 as its center. This
makes it possible to adjust the angle included between seat 5 and
backrest 6 in the sitting position and the aforesaid tilting angle
in an optimum manner, independently of each other, according to
the user's individual requirements.
Also leg support 7 can be moved from a sitting position to a driving
position, and vice versa, by the user. Leg support 7 pivots upwards
about its point of attachment 16 to seat 4, in a direction away
from castor wheels 3a, 3b, upon adjustment from the sitting position
as shown in FIG. 1 to the driving position as will be explained
in more detail yet with respect to FIG. 2. Leg support 7 can pivot
back from the thus obtained position to the sitting position by
moving forwards towards castor wheels 3a, 3b. Leg support 7 and
footrest 8 are positioned between castor wheels 3a, 3b, so that
the wheel chair can readily be driven under a table, desk or the
like to an ideal eating or working position for the user. Leg support
7 is connected to supporting frame 4 by means of a rod 17. Since
the leg support 7 is moved upwards upon adjustment to the driving
position, the wheel chair is prevented from striking against obstacles
lying in the path of the wheel chair, such as curbs and the like,
too easily.
As FIG. 1 shows, the pivot axis of castor wheels 3a, 3b slopes
upwards to the rear with respect to the vertical in order to prevent
the aforesaid shimmying effect. The acute angle thus included in
particular ranges between 0.5-10, preferably it is about 1.5'. The
angle alpha which is shown in FIG. 1 will be about 88.50 in that
case.
FIGS. 2 and 3 are side views of the wheel chair 1 of FIG. 1, showing
the seat 5, the backrest 6 and the leg support 7 in the sitting
position (FIG. 2) and in the driving position (FIG. 3), wherein
parts that correspond to parts which are shown in FIG. 1 are indicated
by the same numerals as in FIG. 1. The backrest cushion and the
seat cushion are indicated at 18 and 19, respectively, whilst FIG.
3 furthermore shows a brake mechanism 20. Upon adjustment from the
sitting position (FIG. 2) to the driving position (FIG. 3), the
angle beta included between seat 5 and backrest 6 is made smaller,
and the angle gamma included between seat 5 and leg support 7 is
likewise made smaller. Upon adjustment back to the sitting position,
said angles beta and gamma are made larger. Leg support 7 is positioned
between front wheels 3a, 3b, whereby leg support 7 can be moved
upwards in a direction towards rear wheels 2a, 2b upon adjustment
to the driving position, whilst it can be moved downwards in a direction
away from the rear wheels 2a, 2b upon adjustment to the sitting
position.
FIG. 4 is a schematic, perspective view of the backrest cushion
18, in which recesses have been formed on either side, seen in the
direction of movement, so as to enable a user to freely move his
arms/elbows in rearward direction. Cushion 18 comprises a hard foam
material 22 in the lumbar and low thorax regions to support a user's
pelvis, as well as a soft foam material 23 to support said user's
central and upper back regions.
FIG. 5 shows a variant of the wheel chair, wherein parts that correspond
to parts which are shown in FIGS. 1, 2 and 3 are indicated by the
same numerals as in said figures. In this variant the backrest 6
can be swung down, so that the wheel chair can be transported in
a compact form. Backrest 6 is pivotable about pin 24 for that purpose,
and it can be pivoted in the direction of seat 5.
Furthermore the height of the assembly consisting of seat 5, backrest
6 and leg support 7 is adjustable as a whole by means of connecting
members 25, which are provided with several unround holes 26. The
connecting members 25 consist of two parts which can be screwed
together, wherein supporting rod 27 of supporting frame 4 can be
enclosed in one of the holes 26 for the purpose of adjusting the
desired height. Since holes 26 are not round, rotation of the connecting
members 25 is not possible.
Another special feature of this variant is the fact that the leg
support 7 is not connected to supporting frame 4 by means of a rod
17, as in the preceding figures, but by means of a pin 28 mounted
on supporting rod 27, which pin is capable of sliding movement,
substantially in one direction, in a block 29 which is mounted on
leg support 7, and which is to that end provided with a slot 30.
Furthermore this variant shows two wheel guards 31, which protect
the user from coming into contact with the rotating rear wheels
2a, 2b. |