Note: Descriptions are shown in the official language in which they were submitted.
TRANSMISSION
=
BACKGROUND
Technical Field
The present disclosure relates to transmissions including cycle
transmissions including bicycle transmissions.
Description of the Related Art
- The modern single speed bicycle has a crank actuated chain driven
drivetrain. A chain runs from the crank to a sprocket which is coupled to the
rear wheel.
When the crank is turned by the rider, the crank pulls the chain, the chain
pulls the
sprocket, and as the sprocket is coupled to the rear wheel, the turning of the
sprocket
rotates the rear wheel.
Modem bicycles have many different seating positions, including the
upright position, the recumbent position, and a forward racing position. The
position of
the rider affects wind resistance, comfort and ease of pedaling. The chain
drive bicycle
transmission allows for the rider to sit in a generally upright position with
their legs
generally below them such that they can operate the cranks to turn the rear
wheel,
generally located behind the rider.
Chain drive bicycle transmissions allow for only one gear unless complex
derailleurs and cogsets are employed. The derailleur system allows the rider
to choose
the gear ratio between the crank chain ring and the cogset. However, such a
chain and
derailleurs based transmission can only change the gear ratio when the chain
and rear
wheel are in motion.
US Patent No.: 6,199,884 employs a helical drive transmission actuated
by a slider. The riders legs provide force to move the slider up and down. The
slider
has a notch which engages a helically twisted bar. The linear motion of the
slider
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causes the helical bar to rotate. The helical bar has a bevel gear mounted at
one end
which engages a bevel gear coupled to the rear wheel and as such, via the
twisting
motion of the helical bar, the linear motion of the slider is converted into
rotational
motion.
The invention disclosed in US Patent No.: 6,199,884 suffers however,
from significant drawbacks. Firstly, the rider is required to move their legs
in a linear
fashion, as opposed to the circular fashion used in the more common crank-
based
chain drive transmission. Secondly, the rider is required to position their
feet radially
from the rear wheel to actuate the skier.
BRIEF SUMMARY
A transmission is disclosed comprising a crank, a drive shaft, a drive
spring, a helical drive having a helical drive groove, a yoke, a drive bevel
gear having a
follower, a wheel bevel gear and a wheel, whereby the crank is rotationally,
coupled to
the drive shaft and the drive spring is frictionally engaged between cranks
and helical
drive, and whereby the drive shaft is adapted to pass through helical drive,
such that
under rotation of the cranks, a force is imparted to the drive shaft, which
passes through
helical drive compressing drive spring and imparting a force on helical drive,
and
whereby helical drive is adapted to pass through yoke and drive bevel gear,
and
whereby drive bevel gear circumscribes helical drive such that the follower of
drive
bevel gear engages helical drive groove, such that the force imparted on
helical drive by
drive spring causes helical drive to pass through drive bevel gear and whereby
the
linear motion of helical drive groove relative to follower causes drive bevel
gear to
rotate, and whereby drive bevel gear is adapted to engage wheel bevel gear
such that a
rotation of drive bevel gear causes wheel bevel gear to rotate, and whereby
wheel bevel
gear is adapted to engage wheel such that rotation of wheel bevel gear causes
wheel to
rotate.
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In another disclosed embodiment, a transmission is disclosed comprising
a crank, a drive shaft, a helical drive having a helical drive groove, a yoke,
a drive bevel
gear having a follower, a wheel bevel gear and a wheel, whereby the crank is
coupled
the drive shaft, such that under rotation of the cranks, a force is imparted
to the drive
shaft and in turn, to the helical drive, and whereby helical drive is adapted
to pass
through yoke and drive bevel gear, and whereby drive bevel gear circumscribes
helical
drive such that the follower of drive bevel gear engages helical drive groove,
such that
the linear force imparted on helical drive by drive spring causes helical
drive to pass
through drive bevel gear and whereby the linear motion of helical drive groove
relative
to follower causes drive bevel gear to rotate, and whereby drive bevel gear is
adapted
to engage wheel bevel gear such that a rotation of drive bevel gear causes
wheel bevel
gear to rotate, and whereby wheel bevel gear is adapted to engage wheel such
that
rotation of wheel bevel gear causes wheel to rotate.
In another disclosed embodiment, the transmission may comprise a crank,
a drive shaft having a forward end and a rearward end, the drive shaft coupled
to the
crank at the forward end of the drive shaft, a drive spring coupled to drive
shaft at the
forward end of the drive shaft, the drive spring circumscribing the drive
shaft, a helical
drive adapted so as to allow the rearward end of drive shaft to pass through
the helical
drive, the helical drive further adapted to engage drive spring, the helical
drive having a
helical drive groove, and a drive bevel gear circumscribing helical drive, the
drive bevel
gear having a follower adapted to engage helical drive groove, drive bevel
gear adapted
to engage a wheel bevel gear, and a wheel coupled to wheel bevel gear, such
that
under rotation of the cranks, a force is imparted to the drive shaft and a
force is
imparted to the drive spring, such that drive shaft passes through helical
drive, and
helical drive is motivated rearwardly by drive spring, such that under the
rearward
movement of helical drive, helical drive groove imparts a rotational force on
follower,
which imparts a rotational force on helical drive gear, which imparts
rotational force on
wheel bevel gear, which imparts a rotational force on wheel such that when the
rotational force on wheel is sufficient to overcome opposing forces, wheel
will rotate.
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In another disclosed embodiment, the transmission may comprise a right
side crank arm, a right side drive shaft having a forward end and a rearward
end, the
right side drive shaft coupled to the right side crank arm at the forward end
of the right
side drive shaft, a right side drive spring coupled to right side drive shaft
at the forward
end of the right side drive shaft, the right side drive spring circumscribing
the right side
drive shaft, a right side helical drive adapted so as to allow the rearward
end of the right
side drive shaft to pass through the right side helical drive, the right side
helical drive
further adapted to engage right side drive spring, the right side helical
drive having a
right side helical drive groove, and a right side drive bevel gear
circumscribing right side
helical drive, the right side drive bevel gear having a right side follower
adapted to
engage right side helical drive groove, right side drive bevel gear adapted to
engage a
right side wheel bevel gear, and a wheel coupled to right side wheel bevel
gear, such
that under rotation of the right side crank arm, a force is imparted to the
right side drive
shaft and a force is imparted to the right side drive spring, such that right
side drive
shaft passes through right side helical drive, and right side helical drive is
motivated
rearwardly by right side drive spring, such that under the rearward movement
of right
side helical drive, right side helical drive groove imparts a rotational force
on right side
follower, which imparts a rotational force on right side helical drive gear,
which imparts
rotational force on right side wheel bevel gear, which imparts a rotational
force on wheel
such that when the rotational force on wheel is sufficient to overcome
opposing forces,
wheel will rotate, the transmission further comprising a left side crank arm,
a left side
drive shaft having a forward end and a rearward end, the left side drive shaft
coupled to
the left side crank arm at the forward end of the left side drive shaft, a
left side drive
spring coupled to left side drive shaft at the forward end of the left side
drive shaft, the
left side drive spring circumscribing the left side drive shaft, a left side
helical drive
adapted so as to allow the rearward end of the left side drive shaft to pass
through the
left side helical drive, the left side helical drive further adapted to engage
left side drive
spring, the left side helical drive having a left side helical drive groove,
and a left side
drive bevel gear circumscribing left side helical drive, the left side drive
bevel gear
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having a left side follower adapted to engage left side helical drive groove,
left side drive
bevel gear adapted to engage a left side wheel bevel gear, and a wheel coupled
to left
side wheel bevel gear, such that under rotation of the left side crank arm, a
force is
imparted to the left side drive shaft and a force is imparted to the left side
drive spring,
such that left side drive shaft passes through left side helical drive, and
left side helical
drive is motivated rearwardly by left side drive spring, such that under the
rearward
movement of left side helical drive, left side helical drive groove imparts a
rotational
force on left side follower, which imparts a rotational force on left side
helical drive gear,
which imparts rotational force on left side wheel bevel gear, which imparts a
rotational
force on wheel such that when the rotational force on wheel is sufficient to
overcome
opposing forces, wheel will rotate.
Another embodiment includes a bicycle comprising a front wheel, a rear
wheel, and a frame, the front wheel rotationally coupled to the frame, the
rear wheel
rotationally coupled to the frame, the bicycle further comprising a
transmission, the
transmission comprising a right side crank arm, a right side drive shaft
having a forward
end and a rearward end, the right side drive shaft coupled to the right side
crank arm at
the forward end of the right side drive shaft, a right side drive spring
coupled to right
side drive shaft at the forward end of the right side drive shaft, the right
side drive spring
circumscribing the right side drive shaft, a right side helical drive adapted
so as to allow
the rearward end of the right side drive shaft to pass through the right side
helical drive,
the right side helical drive further adapted to engage right side drive
spring, the right
side helical drive having a right side helical drive groove, and a right side
drive bevel
gear circumscribing right side helical drive, the right side drive bevel gear
having a right
side follower adapted to engage right side helical drive groove, right side
drive bevel
gear adapted to engage a right side wheel bevel gear, the rear wheel coupled
to right
side wheel bevel gear, such that under rotation of the right side crank arm, a
force is
imparted to the right side drive shaft and a force is imparted to the right
side drive
spring, such that right side drive shaft passes through right side helical
drive, and right
side helical drive is motivated rearwardly by right side drive spring, such
that under the
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rearward movement of right side helical drive, right side helical drive groove
imparts a
rotational force on right side follower, which imparts a rotational force on
right side
helical drive gear, which imparts rotational force on right side wheel bevel
gear, which
imparts a rotational force on rear wheel such that when the rotational farce
on rear
wheel is sufficient to overcome opposing forces, rear wheel will rotate, the
transmission
further comprising a left side crank arm, a left side drive shaft having a
forward end and
a rearward end, the left side drive shaft coupled to the left side crank arm
at the forward
end of the left side drive shaft, a left side drive spring coupled to left
side drive shaft at
the forward end of the left side drive shaft, the left side drive spring
circumscribing the
left side drive shaft, a left side helical drive adapted so as to allow the
rearward end of
the left side drive shaft to pass through the left side helical drive, the
left side helical
drive further adapted to engage left side drive spring, the left side helical
drive having a
left side helical drive groove, and a left side drive bevel gear
circumscribing left side
helical drive, the left side drive bevel gear having a left side follower
adapted to engage
left side helical drive groove, left side drive bevel gear adapted to engage a
left side
wheel bevel gear, and the rear wheel coupled to left side wheel bevel gear,
such that
under rotation of the left side crank arm, a force is imparted to the left
side drive shaft
and a force is imparted to the left side drive spring, such that left side
drive shaft passes
through left side helical drive, and left side helical drive is motivated
rearwardly by left
side drive spring, such that under the rearward movement of left side helical
drive, left
side helical drive groove imparts a rotational force on left side follower,
which imparts a
rotational force on left side helical drive gear, which imparts rotational
force on left side
wheel bevel gear, which imparts a rotational force on the rear wheel such that
when the
rotational force on the rear wheel is sufficient to overcome opposing forces,
rear wheel
will rotate_
In another disclosed embodiment, the transmission many comprise a
crank, a drive shaft having a forward end and a rearward end, the drive shaft
coupled to
the crank at the forward end of the drive shaft, a drive spring coupled to
drive shaft at
the forward end of the drive shaft, the drive spring circumscribing the drive
shaft, a
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helical drive adapted so as to allow the rearward end of drive shaft to pass
through the
helical drive, the helical drive further adapted to engage drive spring, the
helical drive
having a helical drive groove, and a drive bevel gear circumscribing helical
drive, the
drive bevel gear having a follower adapted to engage helical drive groove,
drive bevel
gear adapted to engage a wheel bevel gear, and a wheel coupled to wheel bevel
gear,
such that under rotation of the cranks, a force is imparted to the drive shaft
and a force
is imparted to the drive spring, such that drive shaft passes through helical
drive, and
helical drive is motivated forwardly by drive spring, such that under the
forward
movement of helical drive, helical drive groove imparts a rotational force on
follower,
which imparts a rotational force on helical drive gear, which imparts
rotational force on
wheel bevel gear, which imparts a rotational force on wheel such that when the
rotational force on wheel is sufficient to overcome opposing forces, wheel
will rotate.
The drive bevel gear may be adapted to ratchet so as to not impart a
rearwardly
rotational force to the wheel under forward motion of the helical drive.
In an embodiment, the wheel bevel gear may be adapted to ratchet so as
to not impart a rearwardly rotational force to the wheel under forward motion
of the
helical drive.
In an embodiment, the crank may be comprised of a crank arm and a
crank axel and wherein the drive shaft extends forwardly beyond the crank arm.
In an embodiment, the drive bevel may engage the wheel bevel gear at
the rearward side of wheel bevel gear.
In an embodiment, the drive bevel may engage the wheel bevel gear at
the forward side of wheel bevel gear.
In an embodiment, the transmission may further comprise a pre-load
adjuster to adjust preload on drive spring.
BRIEF DESCRIPTION OF DRAWINGS
In the drawings, identical reference numbers identify similar elements or
acts. The sizes and relative positions of elements in the drawings are not
necessarily
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drawn to scale. For example, the shapes of various elements and angles are not
drawn
to scale, and some of these elements are arbitrarily enlarged and positioned
to improve
drawing legibility. Further, the particular shapes of the elements as drawn,
are not
intended to convey any information regarding the actual shape of the
particular
elements, and have been solely selected for ease of recognition in the
drawings.
Figure 1 is a perspective view of a transmission according to one
embodiment.
Figure 'IA is a perspective exploded of a transmission according to one
embodiment.
Figure 2 is a plan view of a transmission according to one embodiment.
Figure 3 is a top view of a transmission according to one embodiment.
Figure 4 is a perspective view of an embodiment of a drive bevel gear.
Figure 5 is a plan view of an embodiment of a drive bevel gear.
DESCRIPTION OF SPECIFIC EMBODIMENTS
In the following description, certain specific details are set forth in order
to
provide a thorough understanding of various disclosed embodiments. However,
one
skilled in the relevant art will recognize that embodiments may be practiced
without one
or more of these specific details, or with other methods, components,
materials, etc. In
other instances, well-known materials, structures and methods associated with
transmissions have not been shown or described in detail, to avoid
unnecessarily
obscuring descriptions of the embodiments.
Unless the context requires otherwise, throughout the specification and
claims which follow, the word "comprise" and variations thereof, such as,
"comprises"
and "comprising" are to be construed in an open, inclusive sense, that is as
"including,
but not limited to."
Reference throughout this specification to "one embodiment" or "an
embodiment" means that a particular feature, structure or characteristic
described in
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connection with the embodiment is included in at least one embodiment. Thus,
the
appearances of the phrases "in one embodiment" or "in an embodiment" in
various
places throughout this specification are not necessarily all referring to the
same
embodiment. Furthermore, the particular features, structures, or
characteristics may be
combined in any suitable manner in one or more embodiments.
As used in this specification and the appended claims, the singular forms
"a", "an", and "the" include plural referents unless the content clearly
dictates otherwise.
It should also be noted that the term "or" is generally employed in its sense
including
"and/or" unless the content clearly dictates otherwise.
The headings and Abstract provided herein are for convenience only and
do not interpret the scope or meaning of the embodiments.
The present disclosure discusses cycle transmissions. Figure 1 is a
perspective view of a transmission 100 according to one embodiment. Figure 2
is a
plan view of a transmission according to one embodiment. Figure 3 is a top
view of a
transmission according to one embodiment. In Figures 1, 2, and 3, cranks 10
have a left
crank arm assembly 12 and a right crank arm assembly (not called out in Figure
1 for
clarity), connected by a crank axel 13. Throughout Figures 1, 2, and 3, the
elements for
both side of the depicted two-sided transmission are not specifically called
out for
clarity. Crank axle 13 resides within the bicycle frame (not shown). Crank arm
12 is
comprised of sub-crank-arms 12A and 12B. Sub crank arms 12A and 12B are
coupled
by a coupling shaft 14. Coupled to the outward sub-crank arm 12B, on each
side, is a
pedal 15. Coupled to coupling shaft 14 is a drive shaft 18. Drive shaft 18 is
coupled to
the coupling shaft 14 at the forward end of the drive shaft 18 in such a way
as to allow it
to rotate about coupling shaft 14. Drive shaft 18 is coupled, at its rearward
end, to a
helical drive 20. Drive shaft 18 has a primary axis running from the coupling
shaft 14 at
the forward end to the helical drive 20 at its rearward end. Drive shaft 18
has an
associated drive spring 22. Drive spring 22 is not fixed to drive shaft 18
along the
length of drive spring 22. Drive spring 22 is free to move coaxially with
drive shaft 18
except that it is stopped at the forward end by pre-load adjuster 34 and at
the rearward
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end by helical drive 20. When cranks 10 are not under motive force by a rider,
drive
spring 22 may be under some compression between pre-load adjuster 34 and
helical
drive 20. In another embodiment, pre-load adjuster 34 may be located at
helical drive
20, or may be eliminated.
Helical drive 20 is, in one embodiment, a cylindrical tube with a helical
drive groove 24. Circumscribing helical drive is drive bevel gear 26. Drive
bevel gear
26 has a follower 50 (not shown in Figure 1) on the inside of the drive bevel
gear 26
which is adapted to engage helical drive groove 24 of helical drive 20.
Helical drive is
housed within a yoke 32 which is rotationally coupled to a wheel axle (not
shown) to
rotate in the plane of the rotation of wheel 20 under motion of the helical
drive 20
imparted by drive spring 22 imparted by cranks 10. That is, cranks impart a
locomotive-
style reciprocating motion on helical drive 20 which is driven through yoke 32
and yoke
32 is coupled to a wheel axle (not shown in Figure 1) to allow for such
movement.
Wheel axle (not shown) runs within the wheel hub 38 and affixes the rear wheel
to the
bicycle frame (not shown). Drive bevel gear 26 is adapted to engage a wheel
bevel
gear 28. Wheel bevel gear 28 is coupled to the wheel 30.
As the rider imparts a force to cranks 10, cranks 10 turn in a rotating
fashion. As cranks 10 rotate, a reciprocating motion is imparted on drive
shaft 18.
Drive shaft 18 is adapted to push through cylindrical tube 23 of helical dive
20. In the
embodiment shown in the Figures, a pre-load adjuster 34 is configured about
drive shaft
18. Pre-load adjuster 34 serves two functions. Firstly, pre-load adjuster
serves as a
stop affixed to drive shaft 18 so as to prevent drive spring 20 from sliding
off drive shaft
18. Pre-load adjuster 34 also serves to adjust the pre-load on drive spring
22. Thus,
as drive shaft 18 is driven rearwardly under the motion of the cranks 10, and
as drive
shaft 18 slides through helical drive 10, pre-load adjuster 34 (or a simple
stop employed
instead of pre-load adjuster), imparts a force on drive spring 22 which in
turn imparts a
force on helical drive 20.
This force imposed on helical drive 20 by drive spring 22, urges helical
drive 20 through yoke 32. Helical drive 20 does not rotate or twist. Rather,
as helical
CA 2801148 2018-08-21
drive 20 pushes through the yoke 32, the follower 50 (as shown in Figure 4) on
drive
bevel gear 26 (follower not shown in Figure 1) runs within helical drive
groove 24. As
helical drive 20 is advanced through follower on drive bevel gear 26 helical
drive groove
24 twists, relative to drive bevel gear 26, the linear motion of helical drive
20 causes
drive bevel gear 26 to rotate.
Drive bevel gear 26 is adapted to engage wheel bevel gear 28, and under
rotation of the drive bevel gear 26, drive bevel gear 261mparts a rotational
force to the
wheel bevel gear 28. Wheel bevel gear 28is coupled to the wheel 20, the
rotational
motion of wheel bevel gear 28 imparts a rotational force to the wheel 30.
In operation, a force will be required to rotate wheel 30. Cranks 10 will be
rotated by rider, or by some other means. Due to the generally circular
rotation of
cranks 10, at any point, the force imparted will have two orthogonal force
components,
or an x and y component. As cranks 10 rotate from the maximum forward position
towards the maximum rearward position, the x component of the force will be
imparted
on drive shaft 18, such that drive shaft 18 will be pushed towards and through
helical
drive 20, but drive spring 22 will be stopped by helical drive 20, and will
compress under
the force imparted by cranks 10 reducing the distance between cranks 10 and
helical
drive 20. The x component of the force of cranks 10 will contribute to the
force
imparted on drive shaft 18. The y component of force will cause the drive
shaft to pivot
upwardly and downwardly with the rotation of the cranks 10, which is permitted
by the
pivoting nature of yoke 32.
The potential energy stored by the compression of drive spring 22 will be
equal to the spring constant (a property of the spring) multiplied by the
compression
distance. As cranks 10 rotate, drive spring will continue to be compressed
until the
force imparted on the helical drive 20 by drive spring 22 overcomes the force
required to
push helical drive 20 through yoke 32. The force required to push helical
drive 20
through yoke 32 is related to the force required to rotate the wheel 30. The
force is
directed from helical drive 20 to drive bevel gear 26, to wheel bevel gear 28,
to wheel
30.
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Helical drive groove 24 is not linear in degree of twist. Rather, the forward
end of helical drive groove 24 has a slacker helical angle than the helical
angle at the
rearward end of helical drive groove 24. That is, the helical angle of helical
drive
groove 24 increases from the forward end to the rearward end. The greater the
helical
angle, the greater the rotation of drive bevel gear 26 will be for any given
distance the
helical drive 20, travels through the yoke 32, and in kind, the drive bevel
gear 26. The
particular helical angle at any one point along helical drive groove 24 yields
a gear ratio
as between the distance travelled by helical drive 20 through yoke 32 and the
rotation of
the drive bevel gear 26 and in turn the wheel bevel gear 28 and wheel 30.
Drive spring 22 will continue to be compressed under rotation of cranks 10
until the potential energy stored by drive spring 22 yields a force equal to
the force to
turn wheel 30. Drive spring 22 will then continue to be pushed at the forward
end of
drive spring 22 under continued rotation of cranks 10 but will also exert
force on helical
drive 20, pushing helical drive 20 through yoke 32. As helical drive 20 is
pushed
through yoke 32, the follower in drive bevel gear 26 will be engaged by
helical drive
groove 24, such that the linear motion of helical drive 20, will impart a
rotation of drive
bevel gear 26, as follower engages helical drive groove 24. Drive bevel gear
26 in turn
engages wheel bevel gear 28, turning wheel 30.
As cranks 10 continue to be turned by rider, drive spring 24 will continue
to exert force on helical drive 20 urging it through yoke 32. As helical drive
20 is pushed
through yoke 32, the particular gear ratio Will adjust as the degree of twist
of helical
drive groove 20 changes over its length. For each stroke, drive spring 22 will
push
helical drive 20 through yoke 32, and in turn rotate wheel 30, an amount
corresponding
to the force exerted by rider. Where a rider exerts greater force, helical
drive 20 will be
pushed further through yoke 32 and will rotate wheel 30 a greater degree,
provided the
degree of force is sufficient to turn wheel 30.
As such, drive spring 22 will self select the appropriate gear ratio by
pushing helical drive 20 through yoke 32 until the force exerted no longer
exceeds the
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force required to rotate wheel 30 at that particular gear ratio, as determined
by the
degree of twist in helical drive groove 24.
Helical drive groove 24 may initially have a low degree of twist, increasing
the degree of twist from the forward end of helical drive 20 to the rearward
end of helical
drive 20. The twist profile of helical drive groove 24 along its length may
increase at a
rate that may be selected for a particular rider's pedal stroke force profile,
or
preference. The twist profile of helical drive groove 24 along its length may
increase at
variable rate, decrease, or may be flat for some portion of the profile.
Drive spring 24 may be selected with a particular spring constant for a
particular rider's force ability or preference, which may be affected by the
rider's
strength and weight. Further, drive shaft 18 may include a means to adjust pre-
load or
adjust spring constant, dependant on the type of spring used in a particular
embodiment, as is described elsewhere herein.
The force of each side of the cranks 10 will only impart a forward motion to
wheel 30 for 180 degrees of a 360 degree rotation. For the remainder of the
360
degree stroke, each side of cranks 10 will result in a 180 degree of return
stroke.
When a particular side of cranks 10 transition from a drive stroke to a return
stroke, the
respective side of drive spring 22 and drive shaft 18 will transition from
being pushed
rearward to being pulled forward. As drive spring 24 and drive shaft 18 are
pulled
forward, drive spring 24 will be decompressed and drive shaft 18 will pull
back through
helical drive 20. Drive shaft 18 has a stop 36 at the end of drive shaft 12
such that it will
engage the helical drive 20 on the return stroke as drive shaft 18 is pulled
forward by
cranks 10, as shown in Figure 1A. This force will pull drive shaft 18 back
through yoke
32. As helical drive 20 is pulled forward, helical drive groove 24 engages
follower in
drive bevel gear 26. Without a ratchet or freewheel mechanism, this forward
motion of
helical drive 20 would tend to impart a backwards rotational force to wheel
30. Thus,
one or both of drive bevel gear 26, or wheel bevel gear 28 are adapted to
ratchet or
freewheel so that the forward motion of helical drive 20 does not impart a
forward
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=
rotating force on wheel 30. Freewheel assemblies for rear wheels of bicycles
are well
known in the art
With each 360 degree rotation of cranks, first the right drive spring 22 is
pushing its respective helical drive 20 through its respective yoke 32, such
that drive
bevel gear 26, via follower (not shown in Figure 1), engages helical drive
groove 24 to
impart a force on wheel bevel gear 28 to rotate wheel 30 forward. As one crank
arm 12
is engaged in the drive stroke, the opposite crank will be engaged in the
return stroke,
described above, such that at least one side of crank 10 is imparting force to
its
respective drive spring 22 to result in forward motion of wheel 30 throughout
both of the
sequential 180 degree semi-rotations of cranks 10.
Cranks 10 are turned in a circular motion On the drive stroke, the circular
motion of cranks 10 pulls the forward end of drive shaft 18 downwardly,
relative to the
axis running from the crank axle 13 to the axis of the wheel bevel gear 28. On
the
return stroke, the circular motion of cranks 10 pulls the forward end of drive
shaft 18
upwardly, relative to the axis running from the crank axle 13 to the wheel
bevel gear 28.
Yoke 32 is coupled concentrically with wheel bevel gear 28 such that it can
rotate about
the axis of wheel bevel gear 28 and swivel to accommodate the upwardly and
downwardly motion imparted by cranks 10 on the forward end of drive shaft 18.
In the embodiment shown in the Figures, cranks 10 have crank arms 12.
Each crank arm has two sub-crank arms 12A and 12B coupled by coupling shaft
14.
Drive shaft 18 is coupled to the cranks at the coupling shaft 14_ A person of
ordinary
skill in the art could replace the cranks in the depicted embodiment with
traditional =
cranks where crank arms do not have sub-crank arms and where drive shaft would
be
coupled to crank arm at the pedal axel.
In the embodiment shown in the Figures, coupling shaft extends forwardly
from crank arm 12 to increase the length of drive shaft 18 beyond the distance
between
crank arm 12 and yoke 32. A longer drive shaft 18 allows for a longer drive
spring 22
which may allow for a drive spring 22 of preferred spring characteristics. A
person of
ordinary skill in the art could replace coupling shaft 14 such that it does
not extend
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forwardly from crank arm 12. Dive shaft 18 may be located such that it extends
forwardly below coupling shaft 14 but could be coupled to coupling shaft 14 at
coupling
shaft 14, or above coupling shaft 14. In the Figures, drive shaft 18 is shown
such that it
extends forwardly and above coupling shaft 14.
In the embodiment shown in the Figures, yoke 32 and drive bevel gear 26
are positioned such that drive bevel gear 26 engages wheel bevel gear 28 at
the
rearward side of drive bevel gear 28. A person of ordinary skill in the art
could replace
yoke 32 such that drive bevel gear 26 engages wheel bevel gear 28 at the
forward side
of wheel bevel gear 28. Where drive bevel gear 26 engages wheel bevel gear 28
at the
forward side of wheel bevel gear 28, the helical drive groove 24 in helical
drive 20 would
have to be reversed so that drive bevel gear 26 imparted a forward rotational
motion on
wheel bevel gear 28. Further, the embodiments show a configuration where the
helical
drive 20 is urged through the drive bevel gear 26 such that the force is
imparted on the
wheel 30 as helical drive 20 is urged rearwardly. A person of ordinary skill
in the art
would appreciate that the helical drive groove 24 could be reversed, and the
ratchet
mechanism could be reversed such that a forward turning force is imparted on
wheel 30
as helical drive 20 is pulled forwardly through drive bevel gear.
In the embodiment shown in the Figures, drive spring 22 is a helical spring
circumscribing drive shaft 18. A person of ordinary skill in the art may
replace drive
spring 22 with an inline helical spring, or drive shaft may be telescoping
with an
associated slave spring. Springs may be helical, or gas, elastomeric, or other
spring
types known in the art. A drive shaft 18 may also provide direct force to
helical drive 20
and not provide spring actuated force to helical drive 20.
In the embodiment shown in the Figures, a pre-load adjuster 34 is
configured about drive shaft 18, to adjust the pre-load on drive spring 22,
altering the
force imparted by the drive spring 22 on helical drive 20 throughout the
stroke of cranks
10. A person of ordinary skill in the art may elect to include a pre-load
adjuster, of a
form known in the art, or may elect to exclude preload adjuster 34.
CA 2801148 2018-08-21
In the embodiment shown in the Figures, a stop 36 (specifically shown in
Figure 1A) is located at the rearward end of drive shaft 18 to prevent drive
shaft 18 from
forwardly pulling out of helical drive 20. The form of stop 36 may be selected
by a
person of ordinary skill in the art. Stop 36 may be configured to also act as
a preload-
adjuster for drive spring 22. For example, stop 36 may be a nut threaded onto
drive
shaft 18 such that the greater distance stop 36 is forwardly threaded on drive
shaft 18,
the greater the pre-load imparted on drive spring 22.
In the embodiment shown in the Figures, a tubular helical drive 20 is
shown with a helical groove 24 therein. A helical drive 20 may have a single
helical
groove 24 therein, or may have a plurality of helical grooves. Drive bevel
gear 26 may
have the same number of followers 50 as helical drive grooves, one follower
corresponding to each helical drive groove. Drive bevel gear 26 may have less
than
the number of helical drive grooves, if desired. A person of ordinary skill in
the art may
substitute a heical drive of the form disclosed in US Patent 6,199,884, in
Figures
9,10,11 for example, in place of the tubular helical drive groove disclosed
herein. In
such cases, drive bevel gear could include a slot shaped follower, adapted to
received
the helically twisted bar drive.
Figure 4 is a perspective view of an embodiment of a drive bevel gear 26
showing followers 50 of a tooth embodiment.
Figure 6 is a plan view of another embodiment of a drive bevel gear 26
with followers 50 of a ball bearing embodiment, ball bearing follower 50 being
disposed
within the space defined by the helical groove 24 and drive bevel gear 26.
A person of ordinary skill in the art will, recognize that the disclosed
embodiments could be implemented in a bicycle, tricycle, or other human
powered
wheeled conveyances. Further, the disclosed embodiments could be implemented
in
motorized machines as well.
The above description of illustrated embodiments, including what is
described in the Abstract, is not intended to be exhaustive or to limit the
embodiments
to the precise forms disclosed. Although specific embodiments of and examples
are
16
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described herein for illustrative purposes, various equivalent modifications
can be made
without departing from the spirit and scope of the disclosure, as will be
recognized by
those skilled in the relevant art. The teachings provided herein of the
various
embodiments can be applied to other fiber reinforced materials, not
necessarily the
exemplary methods and apparatus generally described above. For example, the
various embodiments described above can be combined to provide further
embodiments.
These and other changes can be made to the embodiments in light of the
above-detailed description. In general, in the following claims, the terms
used should
not be construed to limit the claims to the specific embodiments disclosed in
the
specification and the claims, but should be construed to include all possible
embodiments along with the full scope of equivalents to which such claims are
entitled.
Accordingly, the claims are not limited by the disclosure
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