Note: Descriptions are shown in the official language in which they were submitted.
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~~ BICYCLE INCORPORATING BIF~RCATED FRAME
Back~round of the Invention.
1. Field of the Invention.
The present invention generally relates to a
suspension system for a two-wheeled vehicle and, more partic-
ularly, to a vehicle employing bifurcated frame sections incor-
porating a resilient coupling therebetween.
2. Prior Art.
The prior art discloses many designs for bicycles,
light motorcycles and the like, all of which attempt to provide
adjustable suspensions. Although it is understood the present
invention is applicable to any type of two wheeled vehicle, for
exemplary purposes the present invention shall be described with
respect to a pedal driven bicycle.
lS The problems inherent in bicycle construction
relate to the suspension or shock absorption capabilities as well
as performance characteristics. A motor driven cycle taught by
the prior art provides for a bifurcated frame having a fixed
coupling intermediate the front and rear frames. To stabilize
the suspension, a shock absorber is mounted intermediate the
front and rear frames beneath the seat and a diagonal support of
the rear frame. The problems inherent in this design relate to
its inapplicability to a pedal driven bicycle. Since the front
and rear frames are coupled at a fixed location, it fails to
provide any means to deactivate the suspension.
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~ A pedal driven bicycle must include means for
deactivation of the suspension while pedaling yet permit activa-
tion on rough terrain when the user is not rotating the pedals.
The present invention has solved this problem by providing for a
s selectively, adjustable coupling between the front and rear
frames. By permitting adjustment of the structural coupling
between the front and rear frames, the orientation of a shock
absorbing member relative to the axis of the crank and pedals may
be changed. Furthermore, by changing the axis of movement of the
shock absorbing member, the force necessary to activate the
suspension may be altered.
Another device taught by the prior art provides
for front and rear frames which are pivotally connected directly
adjacent the axis of rotation of the crank and pedal assembly. A
horizontally disposed shock absorbing member is coupled between
the front and rear frames forwardly of the seat support. As the
front and rear frames pivotally change position relative to one
another in response to the underlying terrain, the shock is
absorbed by the resilient coupling of the shock absorber. This
design exemplifies one of the problems inherent in bicycle
construction. Where bicycles employ bifurcated frames as part of
a system for absorbing shock, it is necessary to prevent the
pedals from coming in contact the ground. This is generally
referred to as "pedal droop." This problem may occur when the
rotating crank and pedal assemblies are vertically deflected
independent of the rear wheel.
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~ In the device described by the prior art, the
front frame and rear frame pivot about a point rearwardly of the
crank assembly thereby allowing the crank and rotatable pedal
assembly to vertically change position relative to the axis of
the rear wheel. Pedal droop will occur if the vertical change of
position of the crank and pedal assembly is excessive relative to
the rear wheel. The present invention resolves the problem of
pedal droop by utilizing a rear frame which stabilizes the
position of the crank and pedal assembly relative to the rear
lo wheel. Since the present invention utilizes a pivotal coupling
intermediate the front and rear frames which is forwardly of the
shock absorbing member, the problem of pedal droop is fully
alleviated.
The present invention solves those problems left
unresolved by the prior art by altering the manner in which the
front and rear bicycle frames are coupled to one another. The
bicycle is comprised of a bifurcated frame assembly. The front
frame includes the front fork and wheel, handlebar and steering
assembly and the seat. The seat is coupled to the steering
assembly by a top tube, a diagonal support tube being extended
forwardly and downwardly therefrom. A supporting plate secures
the diagonal support tube to the steering assembly. The support
plate provides a plurality of alternative pivot points to which
the rear frame may be coupled. The rear frame is generally
triangular and includes the crank and pedal assemblies, extending
rear arms, coaxial rear and center stays and the rear wheel. The
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crank assembly is joined to the forward terminus of the center
stay by a diagonal down tube. At the forward intersection
between the center stay and diagonal down tube the rear frame is
pivotally coupled to the support plates of the front frame. A
shock absorbing member is mounted between the intersection of the
center and rear stays of the rear frame and the diagonal support
tube of the front frame. By adjusting the position at which the
upper end of the shock absorber is secured to the diagonal
support tube, the suspension may be adjusted to compensate for
the force imposed on the bicycle seat (i.e., weight of the
rider). By changing the position of the pivotal coupling inter-
mediate the front and rear frames, the force necessary to acti-
vate the shock absorbing suspension may be changed thereby
improving performance characteristics.
~ummary of the Invention
The basic idea of the present invention is a bicycle
which is bifurcated into a front frame and a rear frame. The
front frame generally comprises the front wheel, front fork,
handlebar and steering assembly and the seat. The rear frame
generally comprises the crank and pedal assemblies, rear stays
and rear wheel. The present invention is achieved by the struc-
ture of the front and rear frames and the manner in which the
front and rear frames are coupled to one another.
The seat for the bicycle is coupled to the steering
assembly by a horizontal top tube which extends therebetween. A
diagonal support tube extends generally from the seat post
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MAP-PAT . 2-1801
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forwardly, the end thereof being coupled to the steering assembly
by a support plate which provide for a selectable pivot point
between the front and rear frames.
The rear frame comprises a substantially triangular
structure. The crank and pedal assemblies are coupled to the
rear wheel by a pair of extending rear arms which lie on either
side of the rear wheel. A center stay axially extends rearwardly
into a pair of rear stays which lie on either side of the rear
wheel. A vertical front stay connects the pedal and crank
assemblies to the intersection of the center stay and rear stays.
A diagonal down tube connects the pedal and crank assembly to the
forwardmost terminus of the center stay.
The rear frame is pivotally coupled to the front frame
at the support plate. At the intersection between the center
stay and diagonal down tube of the rear frame, a pivotal coupling
is formed which will determine the force needed to activate the
suspension. The angle between the frame coupling and a vertical
plane extended through the center of the front wheel must not
exceed 60 of arc. To provide shock absorption, a resilient
coupling in the form of a shock absorber is mounted between the
intersection of the center and rear stays of the rear frame and
the diagonal support tube of the front frame. The selected
position of the upper mounting between the shock absorber and the
diagonal support tube provides the ability to compensate for the
weight imposed on the bicycle seat thereby allowing one to adjust
the degree of stiffness of the suspension.
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It is an object of the present invention to provide an
improved construction for a bicycle.
It is another object of the present invention to
provide a bifurcated frame for a bicycle which improves perfor-
mance characteristics.
It is still another object of the present invention toprovide a bicycle frame which provides for adjustable suspension
while maintaining a fixed relationship between the pedal assembly
and rear wheel.
It is still yet another object of the present invention
to provide an improved bicycle frame which is simple and inexpen-
sive to fabricate.
The novel features which are believed to be character-
istic of the invention, both as to its organization and method of
operation, together with further objectives and advantages
thereof, will be better understood from the following description
considered in connection with the accompanying drawing in which a
presently preferred embodiment of the invention is illustrated by
way of example. It is to be expressly understood, however, that
the drawing is for the purpose of illustration and description
only, and is not intended as a definition of the limits of the
invention.
Brief Descri~tion of the Dra~in~.
FIGURE 1 is a side elevation view of a bicycle con-
structed in accordance with the present invention.
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FIGURE 2 is a perspective view of the front frame of
the present invention shown in FIGURE 1.
FIGURE 3 is a perspective view of the rear frame of the
present invention shown in FIGURE 1.
FIGURE 4 an enlarged view of the pivotal coupling
between the front frame and rear frame of the present invention.
FIGURE 5 is a cross-sectional view of the pivotal
coupling intermediate the front and rear frames of the present
invention taken through line 5-5 of FIGURE 4.
FIGURE 6 is an enlarged view illustrating the shock
absorbing member intermediate the front and rear frames of the
present invention.
Description of the PresentlY Preferred Embodiment
The bifurcated frame assembly used in the construction
of the present invention may be best understood by reference to
FIGURES 1, 2 and 3. The present invention bicycle incorporates a
front frame 8 and rear frame 9 which are coupled together to meet
the objectives of the present invention. The front frame 8
includes the front fork 12, front wheel 10, handlebar assembly
13, steering assembly 14 and seat 15. A top tube 17 is secured
between the steering assembly 14 and seat post 16. A diagonal
supporting tube 18 extends forwardly and downwardly relative to
top tube 17. The structural integrity of front frame 8 is
provided by a securing gusset 19 which is in planar alignment
with top tube 17, diagonal supporting tube 18 and seat post 16.
As will be described in detail hereinbelow, a plurality of
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apertures 20 are laterally disposed through gusset 19 adjacent
the bottom edge thereof for selectively mounting a resilient
coupling between front frame 8 to rear frame 9. A pivot adjust-
ment plate 21 is secured intermediate the forward end of diagonal
supporting tube 18 and steering assembly 14, pivot adjustment
plate 21 being coplanar with top tube 17 and diagonal supporting
tube 18. As will be described in detail hereinbelow, pivot
adjustment plate 21 defines a receiving channel bounded by a
plurality of alternatively selectable apertures 22a, 22b or 22c
to which rear frame 9 is pivotally coupled.
The structure of rear frame 9 may be best understood by
reference to FIGURE 3. Rear frame 9 is generally triangular in
profile and incorporates the crank assembly 25 and pedal assembly
26. Crank assembly 25 and pedal assembly 26 are rotatable about
an axis 27 which is perpendicular to the frame of the present
invention bicycle. A pair of extending rear arms 29 and 30
extend rearwardly from pedal housing 31 of pedal assembly 26,
extending rear arms 29 and 30 being adapted to lie on either side
of rear wheel 11. A front stay 33 extends upwardly from housing
31. Center stay 34 is in axial relation to extending rear stays
35 and 36. Rear stay 35 is secured to extending rear arm 29,
rear stay 36 being secured to extending rear arm 30. The for-
wardmost end of center stay 34 is connected to the forwardmost
end of diagonal down tube 37. Center stay 34, rear stays 35 and
36, extending rear arms 29 and 30, front stay 33 and diagonal
down tube 37 generally define a common planar surface. As will
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be described in detail hereinbelow, apertures 38a, 38b and 38c
are disposed through the flap extending forwardly of the inter-
section of center stay 34 and diagonal down tube 37 and provide
means by which the rear frame 9 is pivotally coupled to adjust-
ment plate 21. A pair of parallel flanges 39 extend upwardly
from center stay 34, the flanges 39 being adapted to mount a
resilient coupling which will be described in detail hereinbelow.
The pivotal coupling between front frame 8 and rear
frame 9 can be best understood by reference to FIGURE 4 and
FIGURE 5. The pivotal coupling between front frame 8 and rear
frame 9 is made at pivot adjustment plate 21. As can be best
seen in FIGURE 5, pivot adjustment plate 21 forms a channel
between spaced, parallel panels 44 and 45, each of which has a
plurality of aligned apertures 22a, 22b and 22c disposed there-
through. As stated hereinabove, the extending flange of down
tube 37 forwardly of the intersection of center stay 34 and diag-
onal down tube 37 has a plurality of apertures 38a, 38b and 38c
disposed therethrough. Apertures 38a, 38b and 38c define the
alternative locations at which rear frame 9 will be pivotally
coupled to one of the aligned set of apertures 22a, 22b and 22c
of pivot adjustment plate 21. To change the pivotal couplings
between front frame 8 and rear frame 9, a coupling 46 will be
made either at apertures 22a and 38a, 22b and 38b or 22c and 38c.
FIGURE 5 illustrates an exemplary coupling 46 which will permit
rear frame 9 to pivot with respect to pivot adjustment plate 21.
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~ As stated hereinabove, an objective of the present
invention is to provide means whereby the bicycle user can adjust
the conditions at which the suspension will be activated.
Generally, it is not desirable to have the suspension activated
when the user is pedaling the bicycle. However, when traveling
over rough terrain, a rider will typically stand upon or impose
force on the pedals whereupon the bicycle suspension should
absorb the shock. The plurality of aligned sets of apertures 22
and 38 provide alternative positions about which rear frame 9
will pivot relative to front frame 8. By altering the selection
between aperture sets 22 and 38 by which rear frame 9 is coupled
to front frame 8, the rider will be able to adjust the conditions
under which the suspension will be activated. However, the
angular deflection 50 between a vertical plane passing through
the center of and the front wheel 10 and the pivotal coupling
between the front frame 8 and rear frame 9 must not exceed 60~ of
arc.
An objective of the present invention is to provide a
suspension system for a bifurcated bicycle frame which improves
the comfort and performance characteristics of the bicycle.
Referring to FIGURE 6, an enlarged view of the suspension system
can be best seen. As stated hereinabove, rear frame 9 is
pivotally coupled to front frame 8 at pivot adjustment plate 21.
The relative movement of rear frame 9 and front frame 8 during
operation is controlled by a resilient coupling in the form of a
shock absorber 55 coupled between gusset 19 and center stay 34.
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S~ck absorber 55 typically comprises a conventional hydraulic
damper 56 and piston 57 and a compression coil spring 58 wound
around the damper 56 and contained between limiters 59 and 60.
Shock absorber 55 is positioned between gusset 19 and center stay
34, damper 56 being secured to one of the apertures 20 disposed
through gusset 19, piston 57 being secured between the flanges 39 "
which extend upwardly from center stay 34.
When road conditions cause rear frame 9 to pivot with
respect to front frame 8 in a manner which causes a reduction in
the distance between top tube 17 and center stay 34, coil spring
58 will be compressed. When the condition causing compression has
dissipated, coil spring 58 will expand until it reaches its
quiescent state. The effect of shock absorber 55 is to produce a
resilient coupling which will dampen the shock caused by road
conditions.
one of the objectives of the present invention is to
provide the capability to adjust the suspension to compensate for
the weight of the rider. To meet this objective, gusset 19 is
provided with a plurality of apertures 20 adjacent its lower
edge, each of which provides a selectable point for coupling
shock absorber 55. Coupling shock absorbers 55 forwardly along
gusset 19 will soften the suspension. As a corollary, coupling
shock absorber 55 rearwardly along gusset 19 will stiffen the
suspension.
The present invention provides a bicycle with substan-
tially improved performance and suspension characteristics. By
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providing the ability to alter the position of shock absorber 55
relative to its coupling to front frame 8, one achieves the
capability of adjusting the stiffness of the suspension to be
commensurate with the weight of the rider. By providing the
ability to change the location about which rear frame 9 may pivot
with respect to front frame 8, the rider is able to select the
conditions under which the suspension will be activated. The
present invention is therefore a substantial improvement over the
prior art.
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