Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to a transmlssion unit for muscle-
operated or driven vehicles or appliances for converting forward and
backward movements into rotational movement having a constant
direction of rotation by means of two freewheeling devices which
are driven alternately in opposite directions and act on a shaft
in identical directions.
BACKGROUND OF THE INVENTION
To convert forward and backward movements into a rotational
movement having a constant direction of rotation, transmission units
are known from European Patent Publication No. O 00~ 205A1 and U.S.
Patent Specification NO. 3 301 574, such transmission unlts having
reverse motion and operating with direction-reversible adjusting rat-
chat mechanisms. However, these transmission units are disadvantage-
ous because they only utilise one of the two driving movements for
the rotational movement of the drive and they all include an
idling stroke.
The invention seeks to provide a light-weight transmission
unit of the above-described type which is as small as possible and
in which the direction of movement is to be selectively converted
into forward and backward movements without the need for idling
to be bridged.
SUMMARY OF THE INVENTION
This object is achieved with a transmission unit as described
above when at least one additional freewheeling device is driven
at the same time, though it operates in the opposite direction, a
clutch mechanism either permitting the freewheeling devices to
act in the same direction on the shaft for forward motion, or
permitting the freewheeling devices to act in opposite directions
on the shaft for reverse motion7 or permitting none of the free-
wheeling devices to act on the shaft during idling. ~$
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In addition to providing the two freewheeling devices which have
the same direction of rotation and are used for forward motion, it is
preferable to provide at least one further freewheeling dev:ice
which has an opposite direction of rotation. All of the freewheeling
devices do not act directly on the drive shaft, but the two free-
wheeling devices which have the same direction of rotation act on
an internal ring which is intended for forward motion, and the
freewheeling device which operates in the opposite direction acts
on an internal ring which is in the form of a reverse sleeve for
backward motion. Both internal rings may selectively be connected
to a hollow shaft, serving as a drive shaft, by means of shift teeth
or remain disconnected from the hollow shaft during idling.
It is also preferable for the driving lever of the transmission
unit to be connected to the freewheeling devices via an open cable
drive and a crossed cable drive so that the freewheeling devices
can always be driven in opposite directions to one another. In
addition, the driving lever may be used to actuate the brake when
it is displaced towards its pivot point and may be used for steering
purposes when it rotates about its longitudinal axle. Also, by
connecting the shift rod and the steering rod, it is ensured that
positive steering becomes effective during forward and backward
motion and automatic steering of the muscle-operated vehicle
becomes effective during idling.
Additionally preferred embodiments of the invention are
described in the claims. The scope o~ protection extends not only
to the individual features which are claimed, but also to any
combination of such features.
3o
BRIEF DESCRIPTION OF THE DRAWINGS.
_ . _
Fig. 1 is a vertical, semi-sectional view of the transmission
unit provided with wheel hub and freewheeling devices;
Fig. 2 is a side elevational view of the driving lever which
is connected to the transmission unit;
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Fig. 3 i~ a schematic, side elevational view of the shift
rod in its idling position with a released steering wheel;
Fig. L~ iS a plan view of the connection between the steering rod
and steering wheel fork; and
Fig. 5 is a schematic, side elevational view of the shift rod
shown when the steering rod is locked into the steering wheel fork.
DETAILED DESC~IPTION OF PREFERRED EMBODIMENTo
. . .
A transmission unit 10 is rotatably mounted on a half-shaft 11
of a vehicle, for example a wheelchair, by means of antifriction
bearings 13 and 14 on a hollow shaft 12. A wheel hub 15 is secured
to this hollow shaft 12 by means of screws 16 or similar securing
means, and the spokes (not shown) are secured to the wheel hub 15 in
conventional manner for a wheel rim 17 of a muscle-operated vehicle,
such as a wheelchair or the like. The wheel hub 15 constitutes the
driving member of the transmission unit 10. A first free-wheeling
device 18 is disposed within the wheel hub 15 and is driven by a wheel,
for example a cable wheel 19. A second free-wheeling device 20 is dis-
posed adjacent the first free-wheeling device and is driven by a second
cable wheel 21. The free-wheeling devices 18 and 20 are mounted so
that they operate in the same direction of rotation,whilst the two
cable wheels 19 and 21 are driven in oscillating manner in opposite
directions and are provided for the forward movement of the wheel hub 15.
The switchable idling movement is effected in that the two
free-wheeling devices 18 and 20 do not act directly on the shaft 12
but act on an internal ring 22 which is in the form of a forward
sleeve. In the position shown in Fig. 1, the forward sleeve 22 can
rotate on the hollow shaft 12 without causing said shaft to rotate
therewith. The forward sleeve 22 is therefore in its idling
position. Coupling elements, such as the internal toothing 23 of
the forward sleeve 22 which engages in an external toothing 24
of the hollow shaft 12 when the forward sleeve 22 is displaced to
the right, permit the hollow shaft 12 to be carried
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along by the forward sleeve 22. Such displacement may be effected
by rotating a connecting bush 25 on the half-shaft 11 since the
periphery of said connecting bush is provided with three or more
radially inclinedly extending slots 26 which accommodate balls 27
guided externally in the annular groove 28 formed in the forward sleeve
22 and guided internally in longitudinal slots 29 formed in the
half-shaft 11. The shift rod 30 may effect rotation of the
connecting bush 25.
To achieve bac~ard motion, a further free-wheeling device 31
in addition to the freewheeling device 20 is provided in the cable
wheel 21 and is mounted in the cable wheel 21 so that its direction
of rotation is opposite that of the freewheeling device 20. This
freewheeling device 31 acts on the reverse sleeve 32 which is in the
idling position shown in Fig. 1 and may rotate freely on the hollow
shaft 12. During axial displacement of the reverse sleeve 32
to the left, however, its internal toothing 33 engages in an
external toothing 3L~ of the hollow shaft 12, and in consequence
the freewheeling device 31 can rotate the hollow shaft 12, such
rotation being in the reverse direction of rotation. In co-operation
with a flanged ring 36 which is pressed securely into the forward
sleeve 22 (internal ring), the retaining ring 35 which is pressed
securely into the reverse sleeve 32 ensures that the reverse sleeve
32 is able to participate in the axial displacement of the forward
sleeve 22, though it can rotate independently of said
forward sleeve. During axial displacement to the right (forward
gear), the reverse sleeve 32 may slip into the "wrong" freewheeling
device 20. This situation is remedied by means of a bevelled
portion 37 of the reverse sleeve 32. The same applies to a bevelled
portion 38 of the forward sleeve 22.
The reverse gear, which is provided by the freewheeling
device 31, is only a single-acting mechanism which is only active
in the push or pull stroke of a driving lever 39 (see Fig. 2).
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This is sufficient because the reverse gear is not used very often.
If a double-acting reverse gear were desired, an additional
fourth ~reewheeling device would have to be inserted in the cable
wheel 19. As shown in Fig. l, the double-acting forward gear,
the single-acting reverse gear and the idling device, including the
shift mechanism, have very small dimensions and are therefore
accommodated in a weight-saving manner in the wheel hub 15.
The width of the transmission 10, which substantially results from
the width o~ the three freewheeling devices 18, 20 and 31, produces a
flanged spacing from the wheel hub 15, which spacing corresponds
to that of conventonal wheel rims 17 of muscle-operated vehicles.
According to the above-described transmission principle, the
cable wheels 19 and 21 always have to be driven so that they oscillate
in opposite directions. If they were to end in toothed wheels, they
could be driven with a double toothed rod. If they were to end in
levers, they could each be driven by a push-rod. Toothed wheel
drives, chain drives or belt drives are also possible. As shown in
Fig. 2, cable drives are even simpler, more space-saving and
more economical. While one cable wheel 19 is connected as
a looped drive to a larger semi-circular wheel 40~ the cable wheel
21 which is disposed upstream thereof and has a crossed looped drive
acts on a larger semi-circular wheel 40. This causes the
cable wheels 19 and 21 always to rotate in opposite directions to
one another with every forward and backward movement of the larger
semi-circular wheel 40. The basic gear ratio, which is appropriate
for the particular purpose, e.g. wheelchair drive, is produced
by the diameter ratio of the small cable wheels 19 and 21
relative to the larger semi-circular wheel 40. It is possible to
achieve other gear ratios easily by providing the semi-circular
wheel 40 with other diameters, without meshing with the transmission 10
shown in Fig. l. Since all of the cable wheels 19, 21 and 40
only execute oscillatory movements, the ends of the cables 41, 41a,
42 and 42a are secured to the semi circular wheel 40 and the
cable wheels 19, 21 in a form-locking manner.
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A tubular driving sleeve 43 iS secured to the larger semi-
circular wheel 40, and a driving lever 39 is detachably mounted
in said driving sleeve and has a handle 44~ A pre-determined
lever length can be ensured by spring-mounted balls 45 in the driving
lever 39, in association with openings 46 in the driving sleeve 43,
and such balls mark, so to speak, the first, second and third gears.
Provided that the arc length and operating frequency at the drivi.ng
lever 39 are constant, this alteration of the lever length
constitutes a genuine gear shift, that is to say, a longer lever
produces a greater torque at lower speed.
Because of the above-mentioned diameter ratio between the
cable wheels 19, 21 and 40 and because of the minimum radius
of the curvature of the cables 41 and 42, the fulcrum or pivot point 47
Of the larger wheel 40 is situated in the vicinity of the wheel rim
17, said rim being connected to the wheel hub 15 by means of spokes
and, in consequence, rotating about the half-shaft 11. In the
additional embodiment of the transmission, thi.s arrangement is used
to operate, by means of the handle 44, a brake which is independent
of the angular position of the semi-circular wheel 40 and its
driving lever 39. This is achieved when the top of the brake
lever 48 is situated in the vicinity of the pivot point 47 of the semi-
circular wheel 40 and, by displacing the driving lever 39 with
- its end face 49, the brake lever 48 can be rotated about the
axle 50 so that the brake lining can be pressed against the wheel
rim 17 when the handle or hand grip 44 is depressed with a greater
or smaller force. This produces a radial pressure on the wheel rim
17. With greater exertion, an axial pressure on the wheel rim 17 may
also be realised instead.
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A further improvement of the transmiss on is achieved when
the shift rod 30 actuates the connecting bush 25. Since the
arrangement shown in Fig. l does not have synchronising means
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for the toothings 23, 21l and 33, 3LI, the ends of said toothings may
protrude above one another during shifting, so that no meshing
occurs. If the toothings movecl 510wly relative to one another,
the shifting operation would have to be effected by touch so
that the teeth could enter the gaps for the teeth.
It is more advantageous if the gears can be pre-selected
by means of a rocker switch which is shown in Figs. 3 and 5. In
Fig. 3, the connecting bush 25 is in its idling position. For
comfortable operation, the shift rod 30 is provided with a ball
handle 52. A toggle lever 54 and a compression sprin~ 55 are mounted
in a pivot joint 53 on the shift rod 30, and said compression spring
is supported, in turn, at the fixed pivot point 56. Since the
points of application of the toggle lever 54 and the compression
spring 55 are in alignment in Fig. 3, the system is in metastable
equilibrium. After slight pulling on the ball handle 52
to the left (see Fig. 5), the compression spring 55 presses further
to the left and pulls with it the koggle lever 54, the shift rod 30
and the connecting bush 25. If the toothings 23 and 24 protrude
one another in such a case, the position which is sketched in
Fig. 5 is not reached immediately, but, after slight relative move-
ment of the toothings 23 and 24, said toothings automatically
mesh with the influence of the compression spring 55 without the
need for the ball handle 52 to be additionally operated. Pre-
selection of the reverse gear is also effected in a similarmanner: By pressing the ball handle 52 over the position shown
in Fig. 3 to the right, the compression spring 55 snaps further
to the right, so that the connecting bush 25 is pressed into the
reverse position via the shift rod 30. In this case also, the
3o toothings 33 and 34 automatically mesh with one another. A leaf
spring 57, for example, may be provided as an additional means
of ensuring the metastable equilibrium for the idling position
shown in Fig. 3.
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When the transrnission 10 which is described here is used
for a conventional wheelchair, the i~ling position sketched in
Fig. 3 is adopted so that this wheelchair can be driven in
conventional manner by means of` its grip tyres because the
transmission 10 is disconnected when there is no meshing of
teeth. In such a case, the driving lever 39 may be pivoted into a
position which does not interfere with actuation of the grip tyres.
Grip tyre driving is particularly suitable for driving in a room
and in a tight space. In such a case, the steerling wheels of the
wheelchair can automatically rotate through 360C. When driving
in open spaces, however, it is considerably more appropriate for
the wheelchair to be driven by hand levers. However, steering may
prove difficult on roads which have to be travelled and which slope
transversely to the direction of travel.The steering wheels, which
are then set downhill, are advantageously forcibly steered via the
driving sleeve 43 which is mounted on the larger semi-circular
wheel 40 and is rotatable about the longitudinal axle 58 (see Figs.2).
Because the arm 59 is secured to the driving sleeve 43 on a level
with the pivot point 47 (see Fig.4), the steering wheel fork 63
is rotated about its axis of rotation 64 via a ball joint 60 and
a steering rod 61 by means of its pin 62, this being effected
by rotation of the hand grip 44. This type of steering, however,
is only desirable for a set forward or reverse gear. For this
reason, the steering rod 61 may be separated from the steering wheel
fork 63 (see Fig. 3), this being effected by a mechanical connection,
for example a cable-like mechanical connection 65, between the
steering rod 61 and the shift rod 30 while, for the idling
position, the toggle lever 54 brings the shift rod 30 into a higher
position, thereby also raising the steering rod 61, so that its
pin 62 separates from the opening 66 in the steering wheel fork 63.
By pressing the ball handle 52 into the forward or reverse gear,
the shift rod 30 is lowered, as is the steering rod 61, so that its
pin 62 can be inserted into the opening 66 in the steering wheel fork
63. However, the steering wheel fork 63 may have been rotated about
its rotational axle 64, so that the pin 62 plunges into an empty space.
For this reason, the pin end of the steering wheel rod 61 is
secured by the double ring 67 so that it is rotatable about the
rotational axles 64, and the steering wheel fork 63 is provided with
- inclinations 68 which, together with the tip of the pin 62, cause
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the pin 62 to be automatically threacled into the opening 66
in the wheel fork 63 during rotation of the wheel fork 63. Because
of this connection between the shift rod 30 and the steering rod 61,
a changeover from automatic steering to compulsory steering is
effected without further assistance by pre-selecting the transmission
lO into forward or reverse gear. The changeover from compulsory
steering to automatic steering is effected by switching the
transmission unit 10 into its idling position.
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