Note: Descriptions are shown in the official language in which they were submitted.
CA 02233696 2006-03-27
DUAL SEAT TWO WHEEL DRIVE BICYCLE
The present invention relates to bicycles, and more particularly to
bicycles for two riders.
Various muitipie-rider bicycles have been proposed. The most well-
known is the "tandem bicycle, which is a stretched version of t conventional
bicycle
with an extra set of handlebars, pedals and seat at the centre of the bicycle.
A
number of different variations on this type of bicycle are known, inciuding
those
described in Stanfietd United States patent 3,414,288 issued 3 December 1968;
Kennedy United States patent 3,717,360, issued 20 February 1973; and Hartmann
United States patent 4,666,172, issued 19 May 1987. The Stanfield patent
discioses
a dual propulsion trlcycie with a chain drive for the rear wheel and a dinect
pedal and
crank drive for the front wheel. Kennedy discloses a dual propuision, three-
rider
velocipede with outrigger wheels. Hartmann is an articulated frame bicycle
with two
riders riding the respective frame components. The patent is concerned with
planetary transmissions in the front and rear wheel hubs to provide a dual
direct
drive.
All of these earlier bicycles require speciaity constnicted frames. They
are not, in prectice, useful as singie-rkler bicycles.
The present invention is concemed with a system that is useful for
modifying a standard bicycle to include an auxiliary seat for carrying a
child.
According to a first aspect of the invention there Is provided an
auxiliary seat system for a bicycle, the bicycle having a frame with a head
tube, a
rear wheel mounted on the frame to rotate about a transverse rear wheel axis,
a
steerabie front fork with a stem rotatably mounted in the head tube, a front
wheel
mounted on a the front fork to rotate about a front wheel axis in front of the
head
tube and a main seat mounted on the frame between the rear wheei axis and the
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head tube, the auxiliary seat system comprising:
an auxiliary seat; and
means for mounting the auxiliary seat on the stem of the front fork, at a
position above the head tube, for rotation with the stem.
With the seat mounted on the stem of the front fork, the child using the
seat will rotate as the bicyde is steered. This does not allow the child to
take part in
or interfere with steering of the bicycle. With the front of the seat located
above the
stem, the child's legs are so positioned with respect to the head tube and the
front
fork that there is no interference with the steering range of the bicyde.
The handlebar is preferably mounted in front of the head tube so that
the child may comfortably grip the handlebar. Standard bar ends may be mounted
on the handlebar as auxiliary hand grips for the child.
The child's feet may rest on foot pedals carried by the front fork. In
preferred embodiments, the pedals are mounted on a crank and dtfire the front
wheel thrnugh a chain drive with a deraiileur.
Both the front and rear seats may be equipped w{th mounts that allow
the forward and rearward adjustment of the seats for the comfort of both
riders.
According to a second aspect of the invention there is provided an
auxiliary seat system in combination with a bicycle, the bicycie having a
frame with a
head tube, a rear wheel mounted on the frame to rotate about a transverse rear
wheel axis, a steerable front fork with a stem rotatably mounted in the head
tube, a
front wheel mounted on a the front fork to rotate about a front wheel axis in
front of
the head tube and a main seat mounted on the frame between the rear wheel axis
and the head tube, the auxiiiary seat system comprising:
an auxiliary seat and
means mounting the auxiliary seat on the stem of the front fork, at a
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position above the head tube, for rotation wfth the stem.
According to a third aspect of the invention, there is provided in a
bicycle having a frame with a head tube, a rear wheel mounted on the frame to
rotate about a transverse rear wheel axis, a steerable front fork with a stem
rotatably
mounted In the head tube, a front wheel mounted on a the front fork to rotate
about a
front wheel axis in front of the head tube and a main seat mounted on the
frame
between the rear wheel axis and the head tube, an auxiliary seat system
comprising:
an auxiliary seat; and
means mounting the auxiliary seat on the stem of the front fork, at a
position above the head tube, for rotation with the stem.
In the accompanying drawings, which illustrate an exemplary
embodiment of the present invention:
Figure 1 is a side eievation view of a bicyde equipped with the system
of the present invention;
Figure 2 is a partis plan view showing the front end of the bicycle of
Figure 1;
Figure 3 is a front view of the bicycie with the chain omitted for otarity;
and
Figure 4 is a side view of the front fork.
in the drawings, the control cables have been omitted for clarity.
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Referring to the accompanying drawings, there is illustrated a bicycle 10
with a conventional frame 12. The frame includes a head tube 14. A crossbar
16, a
down tube 18 and a seat tube 20 form a triangular main frame structure
supporting
the head tube at the front. Two seat stays 22 slope downwardly from the
junction of
the crossbar and the seat tube. Two chain stays project to the rear from the
junction
of the seat tube 20 and the down tube 18. The seat stays 22 are connected to
the
chain stays 24 by spaced gusset plates 26. At the juncture of the seat tube 20
and
the down tube 18 is a hub 27 carrying a pedal assembly 28 including two pedals
30
mounted on a crank 32. The crank carries a sprocket assembly 34. The rear
gusset
plates 26 carry a rear wheel 36 rotatable about a transverse rear axle. A
sprocket set
38 is fixed to the hub of the rear wheel. A rear derailleur 40 is mounted on
one of the
gusset plates 26 while a front derailleur 42 is mounted on the frame adjacent
the front
sprocket assembly 34. A chain engages the front sprocket assembly 34, the rear
sprocket set 38 and the two derailleurs 40 and 42. The derailleurs serve to
shift the
chain from sprocket to sprocket to vary the drive ratio between the pedal
crank 32 and
the rear wheel.
At the front of the bicycle is a front fork 44. This carries a front wheel 46
rotatable on a transverse front axis. The fork has an upright stem 48 that is
mounted
rotatably in bearings in the head tube 14.
At the top of the front fork stem is a saddle support 50. This includes a
stem tube 52 that fits into the top of the stem 48 and is anchored in place
using an
internal clamp of the type conventionally used for mounting handlebars on the
front
fork of a bicycle. A seat tube 56 projects rearwardly from the stem tube and
carries
an auxiliary bicyde seat 58. This is a conventional bicycle seat with the
clamp 60
usually used for clamping the seat to the seat post of a bicycle turned to a
horizontal
orientation to clamp onto the seat tube. The position of the auxiliary seat on
the seat
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tube may be adjusted by loosening the clamp 60, adjusting the seat and then re-
tightening the clamp.
Attached to the top of the stem 48 is a tie bar 62 that projects from the
front of the stem, in a direction opposite the seat tube 56 and is secured
using
standard bicycle hardware normally used at this location. The tie bar includes
a
clamp 65 at the front end, which clamps onto an upright handlebar tube 64. The
clamp is adjustable along the handlebar tube to accommodate different lengths
of
head tube 14. The handlebar tube 64 carries a conventional handlebar 66 with a
stem 68 that clamps into the tube 64 as it would normally clamp into the top
end of the
fork stem. The handlebar is fixed to the tube 64 but may be adjusted
vertically in the
tube as can be done with conventional handlebars mounted in the top of the
fork
stem. The bottom end of the tube 64 is connected to a transverse hub 70. The
tie
bar 62 carries a lug 69 to which the front brake cable (not shown) is
adjustably
attached.
Above the front wheel 46, the front fork carries a forwardly projecting
tube 74. This is rigidly attached to the fork below the head tube of the
bicycle frame.
The forward end of the tube is connected to the hub 70. The hub is coupled to
a
gusset plate 75 at the bottom end of the front fork 44 on opposite sides of
the front
wheel by two pedal stays 76. The hub 70 carries a sprocket 84 and a pedal
crank 80
with two pedals 82 on opposite sides of the front wheel. The hub of the front
wheel
carries a sprocket set 86 and a derailleur 88 on the same side of the front
fork as the
sprocket 84. A chain 90 engages the pedal sprocket 84 with the front sprocket
set 86
and the derailleur 88 to drive the front wheel using the pedals 82. The drive
ratio is
selected using derailleur 88.
To avoid any interference between the chain 90 and the front brake 91,
an idler assembly 92 is used to draw the chain away from the brake. The idler
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assembly includes a lug 94 projecting from the pedal stay 76 on the chain side
of the
bicycle and a clarap 96 that darrips a rod 98 onto the lug. A transverse shaft
100
projects horizontally inward from the rear end of the rod 98 and carries an
idler
sprocket 102 that engages the back side of the chain. The idler sprocket may
slide
transversely along the shaft to accommodate lateral movements of the chain.
At the top of the seat tube 20 is a stem tube 104 that extends into the
seat tube and is clamped in place in the usual way.
Attached to the stem tube 104 is a seat tube 106 that projects horizontally to
the rear
of the stem tube 104. The rear seat 111 of the bicycle is mounted on the seat
tube
106 and may be dju9ted forward4y and rearwardy on the seat tube by releasing
a
clamp 108 and re-tightening the clamp once the seat is in the desired
position.
For mounting and parking purposes, a tether 112 extends between the
rear stem tube 104 and the back of the auxiliary seat 58. The tether is a
webbing
strap with a quick-release buckle 114. The length of the tether is adjustable
using a
buckle 115. The tether will hold the front fork in place while a child is
mounting the
auxiliary seat at the front of the bicycle.
The system is completed with two auxitiary handgrips 116 mounted on
the handlebar 66. These are conventional bar ends mounted inwardly from the
handlebar end grips and project outwardly to provide a child in the auxiliary
seat with
handgrips that do not interfere with the normal use of the bicycle. Standard
toe clips
118 ensure that the child's feet are retained on the front pedals 82.
As will be understood from the foregoing, the bicycle described in the
foregoing is based on a standard bicycle with the front forks replaced with a
specialized front fork mounting a seat, pedals and a drive wheel. The
auxiliary seat is
a ceuwentkxiW sent of dual spring constniction to absorb shocks. The tube
assembly
mounting this seat is mounted into the stem of the front fork that normally
receives the
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handlebars. With the described seat mounting arrangement, the seat is mounted
above the head tube and can be adjusted forwardly and rearwardly with respect
to the
head tube. The child moves in rotation with the steering of the bicycle. This
does not
allow the child to take part in or interfere with the steering either with the
feet or
hands. The child's legs are clear of the main bicycle frame so that a full
range of
travel of the bicycle steering is available.
The child has access to a shift lever 120 which controls the front
derailleur 88 so that this derailleur can be adjusted to the child's
preference.
The present system may be provided as a retrofit kit that will fit a wide
variety of bicycles. Where desired, it may also be provided as an integrated
part of a
bicycle. Many of the parts are standard bicycle parts, so that maintenance and
repair
may be done readWy and at reasonable cost.
Although this system can be mounted on most styles of bicycles, it is
intended for an terrain bicycles (ATB) with a strong frame. Cycling should be
no more
challenging than light off road touring.
While one particular embodiment of the present invention has been
described in the foregoing, it is to be understood that other embodiments are
possible.
It is of particular importance to note that while the standard bicycle frame
described in
the foregoing has a horizontal crossbar, other styles with sloping crossbars
or stays
that extend from the head tube to the rear wheel gusset plate will also accept
the
auxiliary seat of the present invention. The embodiment described above has an
auxiliary pedal and front wheel drive system that may be omitted in other
embodiments. In such embodiments, stationary pedals may be used on the front
fork. Other em#aodiments use a disc brake on the front wheel. This eliminates
the need for the idler assembly 92 on the front wheel drive. These and other
embodiments are included within the scope of the appended claims.
