Free wheel clutch mechanism for bicycle drive train

An exercise bicycle including a frame having a seat and handlebars, a high-inertia flywheel having a hub at a center of rotation, the flywheel being rotatably supported on the frame at the hub, and a drive train including a drive sprocket, a crank arm attached to and extending from the drive sprocket, and a pedal attached to the crank arm, the drive train being rotatably supported by the frame. The drive train also includes a slave sprocket fixed to the flywheel at the hub, with the drive and slave sprockets connected in a direct-drive relationship, the drive train driveable in a forward and rearward directions to cause the flywheel to rotate. A clutch mechanism is positioned in engagement with the slave sprocket and the hub to create a frictional engagement between the sprocket and the hub, and to establish a break-free force threshold. When the drive train is actuated in the forward direction, the slave sprocket and the hub move together, and when the drive train is actuated in the rearward direction under the influence of a force greater than the break-free force threshold, the clutch mechanism slips between the slave sprocket and the hub, allowing the slave sprocket and the flywheel to move independently of one another.

FIELD OF THE INVENTION 
This invention relates generally to free wheeling devices, and more 
particularly to a free wheel clutch mechanism useful with crank operated 
exercise bicycles employing an inertia flywheel. 
BACKGROUND 
The benefit of exercising on a direct drive exercise bicycle is well known. 
Direct drive exercise bicycles typically utilize a high-inertia flywheel 
driven by a fixed-gear drive train. The flywheel is driven by the rider up 
to relatively high revolutions per minute (rpm). Because of the direct 
drive feature, the drive train must rotate at a fixed ratio of rpm as 
compared to the flywheel based on the gear ratio. One benefit of the 
direct drive exercise bicycle is that the direct drive gear train provides 
"pedal-through assistance" for the rider. The "pedal-through" feature 
assists the rider by pushing the pedal through the top and bottom dead 
center pedal positions to help make the transition smooth and efficient. 
Other benefits are derived from the direct drive interaction between the 
inertia flywheel and the crank arms to which the rider's feet are 
attached. The inertia flywheel provides a smooth, non-jerky pedaling 
rhythm which provides an efficient and rigorous exercise for the rider, 
especially at relatively high rpms, such as 60 to 100 rpm. 
In the application of this invention to an inertia flywheel exercise 
bicycle, positive drive is required to rotate the inertia wheel in order 
to overcome regulated retardation torque applied by brake means used to 
provide resistance against which the rider/operator works. The inertia 
wheel provides means for continued drive train (wheel to crank to leg) 
movements during those periods when the crank is in top dead center or 
bottom dead center positions, where the rider's legs are somewhat weaker 
in providing rotary motion to the activating crank arms. The flywheel 
affords smooth and steady operation for the rider. 
The direct drive relationship between the flywheel and the drive train is 
also a drawback of exercising on this type of bicycle. The direct drive 
relationship is inconvenient when the rider wishes to quickly stop the 
pedals, or loses the pedaling rhythm required to keep up with the rotating 
flywheel. In the usual flywheel exerciser employing such a direct drive 
relationship, it is necessary for the rider/operator to gradually decrease 
his cranking rate in order to slow down the inertia wheel. The rider 
cannot suddenly stop pedaling inasmuch as the inertia flywheel continues 
to drive the crank arms. 
Of similar importance is the desirability of providing pedal assist to the 
rider/operator's legs when cranking at a speed slower than that necessary 
to positively drive the flywheel, and providing for a gradual reengagement 
and lockup between the pedal actuated drive shaft and the free wheeling 
flywheel in order to avoid abrupt impact when reengaging the moving 
flywheel. 
It is with these issues in mind that the present invention was developed. 
SUMMARY OF THE INVENTION 
The present invention in general terms concerns a clutch mechanism for use 
on an exercise bicycle, and consequently, the present invention recognizes 
that it is desirable to have a free wheeling mechanism for an exerciser of 
the inertia flywheel type which provides means for selectively disengaging 
the flywheel from the drive means. The clutch mechanism allows for the 
beneficial direct-drive connection between the drive train and the 
flywheel, and also allows the drive train and flywheel to move 
independently from one another, or "break free", when a sufficient force 
is applied to the drive train or the flywheel. 
In general, the invention is an exercise bicycle including a frame having a 
seat and handlebars, a high-inertia flywheel having a hub at a center of 
rotation, the flywheel being rotatably supported on the frame at the hub, 
and a drive train including a drive sprocket, a crank arm attached to and 
extending from the drive sprocket, and a pedal attached to the crank arm, 
the drive train being rotatably supported by the frame. The drive train 
also includes a slave sprocket fixed to the flywheel at the hub, with the 
drive and slave sprockets connected in a direct-drive relationship, the 
drive train driveable in a forward and rearward directions to cause the 
flywheel to rotate. A clutch mechanism is positioned in engagement with 
the slave sprocket and the hub to create a frictional engagement between 
the sprocket and the hub, and to establish a break-free force. When the 
drive train is actuated in the forward direction, the slave sprocket and 
the hub move together under a mechanical engagement, and when the drive 
train is actuated in the rearward direction under the influence of a force 
greater than the break-free force, the clutch mechanism slips between the 
slave sprocket and the hub, allowing the slave sprocket and the flywheel 
to move independently of one another. There is no mechanical engagement 
between the sprocket and the hub in the rearward direction as there is in 
the forward direction, established by the one-way bearing. 
More specifically, the slave sprocket defines a sprocket collar mounted on 
the hub and also includes an engagement collar. A one-way bearing is 
mounted between the sprocket collar and the hub to allow the sprocket 
collar to drive the hub when the sprocket collar is driven in a forward 
direction, and to allow the sprocket collar to spin independently of the 
hub when the sprocket collar is driven in the rearward direction. An 
engagement flange fixedly mounted on the hub corresponds to the engagement 
collar, and compression means are mounted on the flywheel to bias the 
flange and the collar towards one another. A clutch material member is 
positioned between the engagement flange and the collar, and is clamped 
therebetween by the compression means to cause the engagement flange to 
move in conjunction with the sprocket collar. The engagement creates a 
break-free force required to cause the sprocket collar to move 
independently of the engagement flange. When the drive train is actuated 
in the forward direction, the sprocket collar and the engagement flange 
move together, and when the drive train is actuated in the rearward 
direction and overcomes the break-free force, the engagement flange slips 
with respect to the collar, allowing the sprocket collar and the flywheel 
to move independently of one another. 
In another embodiment, the slave sprocket defines a sprocket collar mounted 
on the hub and defines an inner and outer engagement collars. A one-way 
bearing is mounted between the sprocket collar and the hub to allow the 
sprocket collar to drive the hub when the sprocket collar is driven in a 
forward direction, and to allow the sprocket collar to spin freely on the 
hub when the sprocket collar is driven in the rearward direction. An inner 
engagement flange is fixedly mounted on the hub corresponding to the inner 
engagement collar, and an outer engagement flange is fixedly mounted on 
the hub corresponding to the outer engagement collar. Compression means 
are mounted on the flywheel to bias the inner flange and the inner collar 
towards one another, and to bias the outer flange and the outer collar 
towards one another. A clutch material member is positioned between the 
outer engagement flange and the outer collar, and between the inner 
engagement flange and the inner collar, and clamped therebetween by the 
compression means to cause the inner and outer engagement flanges to move 
in conjunction with the sprocket collar. The engagement creates a 
break-free force required to cause the sprocket collar to move 
independently of inner and outer engagement flanges. When the drive train 
is actuated in the forward direction, the sprocket collar and the inner 
and outer flanges move together, and when the drive train is actuated in 
the rearward direction and overcomes the break-free force, the inner and 
outer engagement flanges slip with respect to the inner and outer collars, 
allowing the sprocket collar and the flywheel to move independently of one 
another. There are other embodiments of the invention disclosed which 
perform the same function with very similar structure. 
Also, the invention includes an exercise bicycle frame for use with the 
clutch mechanism. The frame includes a front support, a rear support, and 
a brace member extending between the front and rear ground supports. In 
addition, front forks are included that have a top end and a bottom end, 
and are attached at the bottom end to the front ground support. The front 
forks rotatably support a high-inertia flywheel. A rear post is included 
that has a top member and a bottom member, the top member attaching to the 
bottom member in a rear offset overlapping manner, the rear post defining 
a top end and a bottom end. The rear post is attached at the bottom end to 
the brace member. An articulated beam is attached to and extends from the 
top end of the front forks downwardly and rearwardly to a midpoint between 
the front forks and the rear post, then extends horizontally to the rear 
post at the intersection of the top and bottom members of the rear post. A 
rear truss extends from the top member of the rear post to the rear 
support. A handlebar is attached at the top end of the front forks, and a 
seat is attached at the top end of the rear post. A front area is defined 
by the front forks, articulated beam, rear post and brace member forming a 
five-sided polygon, and a rear area is defined by the rear post, rear 
truss, and brace member forming a five-sided polygon. 
Accordingly, it is a primary object of the present invention to provide a 
free-wheeling clutch mechanism that allows an exercise bike to include the 
direct-drive relationship between the drive train and the flywheel, and at 
the same time allow the drive train and the flywheel to turn independently 
from one another under certain conditions. 
Other aspects, features and details of the present invention can be more 
completely understood by reference to the following detailed description 
in conjunction with the drawings, and from the appended claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
In light of the above items, a free wheel clutch mechanism 40 has been 
developed for use on direct-drive exercise bicycles 42 utilizing an 
inertia flywheel 44 (FIGS. 1-4). While the present invention is described 
below associated with an exercise bicycle, it is contemplated that it 
could be used on normal bicycles or other exercise equipment, including 
magnetic resistive bicycles, air-resistance bicycles and other non-bicycle 
exercisers (such as upper body exercisers), each having rotary-driven 
mechanisms (wheels, etc.), in the proper circumstances. The free wheel 
clutch mechanism works in a direct-drive manner when the rider pedals the 
bicycle in the forward direction (counter-clockwise in FIGS. 1 and 2, 
clockwise in FIG. 3), but has a release, or free wheel, characteristic 
when the rider applies a required force on the pedal (or to the drive 
train somewhere) opposite or against the forward pedaling direction. Upon 
application of the appropriate opposite force ("break free force 
threshold"), the drive train free-wheels to allow the pedals to turn in 
the opposite direction with respect to, or more slowly than, the rotation 
of the flywheel. The rider can then either simply drive the pedals at a 
relatively lower rpm than the normal gear ratio to the flywheel, stop the 
pedals, or can rotate the pedals backwards. 
The opposite force required to be applied to the pedals to cause the free 
wheeling action can be adjusted based on the design of the free wheel 
clutch mechanism, and is typically between 0.00 and 100 pounds, preferably 
55 pounds at the pedals, depending on the application. The break free 
force threshold is based on the static frictional engagement between the 
clutch material and the clutch plates which the clutch material is clamped 
between, as well as the mechanical advantage provided through the drive 
train. The clutch plates, as defined below, are on different members that 
in normal circumstances are to rotate together. The friction force between 
the clutch material and the clutch plates facilitates this relationship. 
At a certain point (the break free force threshold), the opposing clutch 
plates overcome the static frictional force and spin at different speeds 
(r.p.m.'s) in the same direction, or in the opposite direction. The 
surface area of the clutch plates and the clutch plate material, the 
material property of the clutch plates and the clutch material, and the 
force at which the clutch plates clamp the clutch material are all factors 
that can be specifically designed to affect the break free force 
threshold. The break free force (as measured at the pedal) is affected 
also by the gear ratio and the length of the crank-arms. 
The free wheel clutch mechanism 40 is integral to the drive train of the 
exercise bicycle. The drive or gear train includes the drive sprocket 46, 
the crank arms 48 and associated pedals 50 attached to the drive sprocket, 
the drive axle assembly 52, the slave sprocket 54, and the chain or belt 
56 that interconnects the drive and slave sprockets, as shown in FIG. 3. 
Typically, the drive sprocket is rigidly mounted to one of the crank arms, 
and each crank arm is removably mounted to the drive axle assembly. The 
drive axle assembly is positioned in the hub on the frame to allow 
rotating movement, in either direction of the crank arms. 
As shown in FIG. 4, the free wheel clutch mechanism 40 includes a sprocket 
collar 58 rotatably mounted on a slave axle assembly 60. The slave 
sprocket 54 is attached to the flywheel 44 adjacent to the hub 62. The 
slave axle assembly is mounted in the hub, and attaches to the frame to 
allow the flywheel to rotate with respect to the frame, under the force of 
the drive train through the movement of the slave axle assembly. The slave 
axle assembly is actually mounted in the hub, and includes an axle 
housing. Typically, the slave sprocket is mounted on the axle housing. 
The free wheel clutch mechanism can be mounted in association with the 
drive sprocket, cranks and drive axle assembly, or can be mounted in 
association with the slave sprocket, slave axle assembly and flywheel. The 
placement of the free wheel clutch mechanism is a matter of choice 
dependent on the particular implementation. The only difference between 
the two positions of the free wheel clutch mechanism is that when mounted 
in association with the slave sprocket, the actuation of the free wheel 
clutch mechanism affects the movement of the chain and drive sprocket 
(slow down, stop or reverse). When the free wheel clutch mechanism is 
mounted in association with the drive sprocket, the actuation of the free 
wheel clutch mechanism allows the pedals and cranks to be slowed down, 
stopped, or reversed while the drive sprocket, chain and slave sprocket 
and flywheel continue to rotate. As described herein, the free wheel 
clutch mechanism is mounted in association with the slave sprocket. 
More specifically as shown in FIGS. 4 and 5A, the free wheel clutch 
mechanism includes a sprocket collar 58 (in this case a "slave" sprocket 
collar) that is mounted in a one-way drive relationship with the axle 
housing 64 such that the rotation of the slave sprocket collar in one 
direction directly drives the axle housing, and the rotation of the slave 
sprocket collar in the reverse direction does not drive the axle housing 
(allows "free wheeling"). This free wheeling relationship is established 
by one-way bearings 66 or a ratchet and pawl structure used between the 
slave sprocket collar and the axle housing. 
The free wheeling motion of the slave sprocket collar 58 with respect to 
the axle housing 64 (and hence hub 62 and flywheel 44) is tempered, or 
reduced, by clutch plates 68 and clutch or braking material 70 acting upon 
the slave sprocket collar. A clutch plate collar 69 is secured to the axle 
housing 64 to fixedly position one end of the free wheel clutch mechanism 
40. The clutch plates 68 are rigidly mounted to turn with the axle housing 
(and hence the hub and flywheel), and are forced into contact with the 
sprocket collar 58 by a biasing means, such as a spring member 72. The 
braking material 70 is positioned between the sprocket collar and the 
clutch plates to provide a frictional interface between the two. The 
braking material can be mounted to either the sprocket collar, the clutch 
plates, or can be free-floating. The area of contact between the clutch 
plate and the sprocket collar (through the braking material) in 
combination with the compression force applied by the biasing means 72, 
creates the "break free" force required to be applied through the sprocket 
collar to allow the sprocket collar to "free wheel" on the axle housing. 
If the applied force is not sufficient to overcome the "break free" force, 
then the sprocket collar is not able to free wheel on the axle housing. 
The free wheeling clutch mechanism is self-adjusting under the bias force 
to accommodate for the reduction in thickness of the braking material 70 
wearing out through use. The clutch plates 68 "float" on the axle housing 
to adjust and maintain contact with the sprocket collar as the braking 
material becomes thinner. 
Particular embodiments of the free wheeling clutch mechanism are described 
in more detail below. 
An exercise bicycle 42 incorporating the present invention is shown in FIG. 
1. The bicycle includes a frame 80 supported on a support surface by 
ground engagement members 82, an adjustable seat 84, adjustable handlebars 
86, a flywheel 44 rotatably positioned between a pair of front forks 88 of 
the frame, and a gear train 54 attached to the frame adjacent to and below 
the seat. 
The frame 80, as shown in FIG. 1, includes front and rear ground supports 
90 attached by a horizontal frame brace member 92 extending there between, 
front forks 88, and a rear post 94. The front forks and rear post are 
attached by an articulated beam 96 sloping from the top of the front forks 
down to approximately midway between the front forks and the rear post, at 
which point the articulated beam extends horizontally rearwardly to engage 
the rear post. The articulated beam thus includes two members connected at 
an angle to one another, and extends between the top of the forks to the 
approximate midpoint of the rear post. 
An aperture is formed at the top of the forks to receive a handlebar post 
98, the handlebar post being vertically adjustable in the top of the forks 
by a pop-pin structure, as is known in the industry. Handlebars are 
attached to the top of the handlebar post in any known manner for use by 
the rider. An aperture is formed in the top of the rear post for receiving 
a seat post 100. The seat post is vertically adjustable in the rear post 
by a pop-pin structure, as is well known in the art. The seat can be 
forwardly and rearwardly adjusted on the seat post, such as by the 
mechanism disclosed in U.S. Pat. No. 4,772,069 to Szymski, incorporated 
herein by reference, in addition to being vertically adjustable. 
The rear post 94 includes a top member 102 and a bottom member 104. The top 
member 102 is attached to extend from the rear side of the bottom member 
104, and extends beyond the top of the bottom member 104 in a rear-offset 
overlapping manner. The articulated beam 96 is affixed to the rear post 94 
at the top of the bottom member 104 and the front side of the top member 
102. This attachment of the articulated beam to the rear post forms a 
strong structural connection. 
The crank arms 48 for each of the pedals 50 are attached to a hub 106 which 
is supported by the rear post at a location along the height of the rear 
post where the bottom and top members of the rear post coextend. The rear 
post 94 attaches to the horizontal frame member 92 about midway between 
the front and rear ground support members 90. A rear truss 106 extends at 
an angle from the rear post 94 down to the rear ground support member 90 
for added strength. The frame is constructed of rectangular or hollow 
cylindrical steel tubing, as is known in the art. Rectangular tubing is 
preferred. 
The front area defined by the forks 88, articulated beam 96, rear post 94, 
and horizontal frame member 92 is a five-sided polygon. The rear area 
defined by the rear post 94, rear truss 106 and horizontal frame member 92 
is also a five-sided polygon. A friction break 108 is mounted adjacent to 
the top of the front forks to selectively engage the opposing outer rims 
of the flywheel 44 to provide an additional friction load against which 
the rider must work in exercising on the exercise bicycle. This frame 
design, to the geometry of the frame structure, is very strong and 
durable, and is capable of withstanding the rigors of frequent use. The 
portion of the frame that supports the crank arms and chain ring is 
especially strong and durable in this design as a result of the overlapped 
construction of the rear post 94. 
As shown in FIGS. 1, 2 and 3, the drive or gear train (as described above) 
includes a drive sprocket 46 rotatably mounted on the frame, crank arms 48 
and associated pedals 50 attached to the drive sprocket for driving the 
drive sprocket, a free wheel clutch assembly 40, a slave sprocket 54 
attached on the flywheel 44, and a chain 56 connecting the drive sprocket 
to the slave sprocket, and to the free wheel clutch assembly. The chain 
could be replaced by a belt with accommodating modifications made to the 
drive and slave sprockets, with no adverse affect on the operation of the 
free-wheeling clutch mechanism of the present invention. 
As with a standard direct drive exercise bicycle, the rider pedals the 
exercise bicycle using the crank arms and pedals, to drive the drive 
sprocket 46. The chain 56, engaged between the drive sprocket and slave 
sprocket 54, causes the flywheel 44 to rotate at the given rpms based on 
the gear ratio between the drive sprocket and the slave sprocket. 
The free wheel clutch mechanism 40 engages the flywheel, as is described 
below, to allow the transfer of rotational movement from the slave 
sprocket 54 to the flywheel 44 in a direct-drive relationship when driven 
in the forward direction. Normal pedaling circumstances include the use of 
the exercise bicycle during an organized exercise class or individually, 
and include starting at 0.00 rpms and increasing and decreasing the rpms 
as is required or desired for certain exercise programs, whether the rider 
is standing, sitting or alternating during use. The free wheel clutch 
mechanism 40 of the present invention maintains the "pedal-through" 
benefit of standard direct drive exercise bicycles. The pedal-through 
benefit helps the rider pedal continuously and smoothly through the top 
and bottom pedal positions where riders typically are weakest. 
The free wheel clutch mechanism 40 converts the direct drive relationship 
between the pedal revolutions and the flywheel revolutions to a "free 
wheel" relationship to allow the pedals 50 to be stopped, reversed in 
direction, or rotated more slowly than the flywheel 44, when a sufficient 
force is applied in the reverse direction to either of the pedals or 
anywhere on the drive train (where the clutch mechanism is positioned on 
the inertia wheel). Examples of the application of an opposite force 
include, but are not limited to, the intentional application of the 
reverse force by the rider while pedaling, for instance due to fatigue, or 
the contact of the pedal on the rider's lower leg when a foot is 
accidentally released from the pedal. 
As shown in FIGS. 4, 5A, 5B, 6 and 7, the free wheel clutch mechanism 40 
mounts on the slave axle assembly 60 adjacent to the hub 62 of the 
flywheel 44. A cylindrical slave axle housing 64 is press-fit into a 
cylindrical axial bore formed through the hub 62 of the flywheel. The end 
of the axle housing extending from the hub is externally threaded to 
receive the clutch plate collar 69. 
In the description below, the terms "inside" and "inner" refer to the end 
closest to the flywheel 44, and the terms "outside" and "outer" refer to 
the end farthest from the flywheel. The clutch plate collar 69 includes a 
hollow cylindrical main body 118 with internal threads at one end for 
engagement with the external threads on the outer end of the axle housing 
64. The clutch plate collar 69 has an outer radially extending engagement 
flange 120 attached to the outside end of the cylindrical main body 118, 
and an inner radially extending engagement flange 122 moveably attached to 
the inside end of the cylindrical main body. 
Referring to FIGS. 5A and 5B, the inner flange 122 is able to move axially 
(longitudinally) along the all or a portion of the length of the 
cylindrical main body 118 of the clutch plate collar 69. Referring to 
FIGS. 7, 8 and 9, the inner flange 122 has a central bore 124, defining a 
plurality of radially inwardly extending keys 126. Corresponding 
longitudinally extending slots 128 are formed on the surface of the 
cylindrical main body of the clutch plate collar 69 at its inner end, and 
extend at least partially along the length of the main body, to receive 
the keys 126 and allow the inner flange 122 to move (float) axially along 
the length of the cylindrical main body, to the extent of the length of 
the slots. The benefit of the axial movement of the inner flange of the 
clutch plate collar 69 is described in more detail below. When the 
cylindrical main body 118 is threadedly connected to the axle housing 64, 
the inner flange is positioned so the keys are slidably received in the 
slots, and the inner flange is retained on the end of the cylindrical main 
body by the hub 62 or the axle housing (by end of axle housing as shown in 
FIG. 5A). The intersection of the keys 126 in the slots 128 make the inner 
flange turn with the cylindrical main body 118. 
A one-way bearing 66, such as an INA shell-type roller clutch as found in 
the INA Bearing Company, Inc. of Fort Mill, S.C., catalog #305, 1988 at 
page 164, is mounted on the cylindrical main body 118 of the clutch plate 
collar 69 between the end of the slots 128 and the outer flange 120. The 
rollers of the bearing 66 engage the outer surface of the cylindrical main 
body member 118, and can slide (float) along the length of the main body, 
as described in more detail below. The one-way bearing permits 
direct-drive in one direction, and free-wheeling in the other rotational 
direction, also described in more detail below. 
Referring to FIGS. 5A, 7, and 10-13, a sprocket collar 58 defines a central 
bore and is positioned concentrically over the cylindrical main body 
member 118 of the clutch plate collar 69, and is attached to the outer 
race of the one-way bearing. The sprocket collar 58 defines an outer 
radially extending engagement collar 130 spaced away but substantially 
coextensive with the outer flange 120 of the clutch plate collar 69, an 
inner radially extending engagement collar 132 spaced away from but 
substantially coextensive with the inner flange 122 of the clutch plate 
collar 69, and the slave sprocket 54 formed about the outer surface of the 
sprocket collar 58 and between the inner and outer extending collars 130 
and 132. The chain 56 engages the slave sprocket 54. The engagement 
collars 130 and 132 are extensions of the sidewalls of the sprocket 
collar, and provide more surface area if needed for the clutch-finction 
they perform, as defined below. 
The following explains the relative movement and drive characteristics of 
the clutch plate collar 69, sprocket collar 58, and flywheel 44 with the 
structure described at this point. When the slave sprocket 54 is driven in 
the forward direction (clockwise with respect to FIG. 3, counter-clockwise 
with respect to FIGS. 1 and 2) by the chain 56, the one-way bearing 66 
engages and causes the the slave sprocket 54 to rotate the sprocket collar 
58, in turn rotating the clutch plate collar 69, which in turn rotates the 
axle housing 64, which causes the flywheel to turn. If the slave sprocket 
54 is caused to move in the opposite direction (counter-clockwise in FIG. 
3, clockwise in FIGS. 1 and 2), the one-way bearing would allow the 
sprocket collar 58 to free-wheel on the clutch plate collar 69. 
Ideally a friction clutch or braking material 70 in the form of a flat 
washer (a disk with a central aperture formed therein) is positioned 
between the outer flange 120 of the clutch plate collar 69 and the outer 
collar 130 of the sprocket collar 58, and between the inner flange 122 of 
the clutch plate collar 69 and the inner collar 132 of the sprocket 
collar, as best shown in FIGS. 5A, 5B, and 7. The friction clutch material 
70 can be attached to either the outer flange 120 or the outer collar 130, 
and the friction clutch material 70 can be attached to either the inner 
flange 122 or the inner collar 132, to anchor the clutch material. The 
clutch material 70 can be felt, cork, standard brake material, or any 
material that provides a sufficient frictional relationship between the 
coextensive flanges and collars. Preferably, clutch facing, as shown in 
McMaster-Carr Company catalog number 101, 1995, at page 2530, is used at a 
thickness of approximately 2.0 mm. Insert description for collar for 
inside diameter for free-floating and not connected to either side. In 
some instances, such as when the clutch material is not attached to either 
the clutch plate collar or the sprocket collar, but instead just floats 
between the two, a bearing washer is attached to the perimeter of the 
central aperture to help support the clutch material on the axle housing. 
Compression means, such as a compression spring 72, is positioned around 
the hub 62 of the flywheel 44 to engage the inner flange 122 of the clutch 
plate collar 69 to bias the inner flange toward the outer flange 120 of 
the clutch plate collar. The spring 72, such as a jumbo compression spring 
in the McMaster-Carr catalog number 101, biases the inner flange 122 
outwardly to clamp the clutch material 70 between it and the inner collar 
132, and also clamps the clutch material 70 between the outer collar 130 
and the outer flange 120. The designed axial movement of the inner race 
(such as by sliding) on the cylindrical main bearing 66 (keys 126 sliding 
in the slots 128) allows the sprocket collar 58 to float and transmit the 
force of the spring 72 to the outer flange 120. The combination of the 
bias force created by the spring 72, and the engagement of the clutch 
plate collar 69 and the sprocket collar 58 with the clutch material 70 
inbetween creates a friction force having an upper limit ("break free") 
force required to cause the sprocket collar 58 to move independently of 
the clutch plate collar in the reverse direction. 
For instance, where the spring force is approximately 225 pounds when fully 
compressed, and the clutch material has an inner diameter of 1.65 inches 
and an outer diameter of 2.52 inches, where two clutch material disks were 
used (FIG. 5B), the break free force has been tested to be approximately 
55 pounds at the pedal. It has been found that as the spring extends due 
to wear of the clutch material, the spring force reduces to approximately 
200 pounds, and the break free force actually increases. This is believed 
to be due to the fact that the engaging surfaces clamping the clutch 
material become polished and increase the surface area, thus increasing 
the static friction force to be overcome. 
The following explains the relative movement of the clutch plate collar 69, 
sprocket collar 58 and flywheel 44 given the structure described to this 
point. When the slave sprocket 54 is driven in the forward direction, as 
defined above, the one-way bearing creates the direct-drive relationship 
with the flywheel 44 desired for this type of exercise bicycle. When the 
slave sprocket 54 is driven in the backward direction, or there is a 
reverse force applied to the slave sprocket to attempt to rotate it in a 
direction opposite the direction of rotation of the flywheel, the one-way 
bearing does not drive the flywheel 44, but instead allows the pedals to 
free wheel. However, the friction force generated between the clutch plate 
collar 69 and the sprocket collar 58 due to the engagement of the outer 
flange 120 and the outer collar 130 with the inter-positioned clutch 
material 70, and the inner flange 122 and inner collar 132 with the 
inter-positioned clutch material 70, acts to create a threshold friction 
force that must be overcome to allow the rider to drive the sprocket 
collar 58 independent of the flywheel 44. If the force applied by the 
rider to the pedals is large enough to overcome the friction ("break 
free") force, then the pedals cause the sprocket collar 58 to turn 
independently of the clutch plate collar 69, with the clutch material 70 
being rubbed and worn down in the process. 
As the clutch material 70 wears down and becomes thinner, the spring 72 
extends to push the inner flange 122 (floating) along the slots to 
maintain the appropriate force on the clutch material 70. The sprocket 
collar 58 is also pushed outwardly to maintain the desired force, and 
resulting "break free" characteristics. The spring 72 thus allows for 
automatic adjustment to compensate for the wear of the clutch material 70. 
The spring 72 must be selected to have a relatively predictable and stable 
spring constant along its length of extension to insure the development of 
the proper friction forces. The spring can be replaced with an elastomeric 
tube 73 having sufficient spring properties in the axial direction, such 
as is shown in FIG. 5C. Some elastomeric materials have very stable spring 
constants. One such suitable elastomeric material is a polyurethane made 
by Kryptonics Inc. of Louisville, Colo. Preferably, the tube 73 is 
approximately 1 inch long, 0.887 inches when initially compressed, and has 
a wall thickness of approximately 0.225 inches. In addition, an adjustable 
compression spring could also be used that would allow the spring force to 
be adjusted to modify the break free force when desired. 
The inner or outer clutch material 70 can be replaced by a bearing if it is 
desired to use only one clutch material 70. The break-free force threshold 
may be modified accordingly as a result. 
Similar relative movement is found when the exercise bicycle incorporating 
the present invention is in use, and more clearly depicts the advantages 
of the free wheel clutch mechanism of the present invention. When a rider 
is exercising on the exercise bicycle, the forward drive of the drive 
train causes the slave sprocket 54 to drive the sprocket collar 58 in the 
direction of engagement of the one-way bearing, in the end to drive the 
flywheel 44 in a direct drive manner. If the rider desires, by applying a 
force of approximately 50 pounds in the opposite direction, the threshold 
friction force between the clutch plate collar 69, the sprocket collar 58 
and the clutch material 70 is overcome (the "break free" force), and the 
sprocket collar 58 can free wheel with respect to the clutch plate collar 
69 and the flywheel 44. The sprocket collar 58 thus moves in the opposite 
direction with respect to the direction of rotation of the flywheel 44. 
The rider can thus pedal irrespective of the movement of the flywheel 44 
until the friction between the clutch plate collar and the sprocket collar 
(caused by the clutch material) reduces the rpms of the flywheel to a 
point where, based on the gear ratio, the rpms match to cause "lock-up". 
In a more extreme situation, if the foot of the rider slips off the pedal 
and the pedal strikes the rider's leg, a sufficient force is generated to 
overcome the "break free" force and the pedals can stop to reduce the 
chance of serious injury, letting the flywheel continue to rotate until 
the friction force stops the rotation of the flywheel. 
An axle 134 (FIG. 5A and 5B) is positioned associatede bore in the hub, 
with associated bearings to support the flywheel 44 and allow it to rotate 
as driven by the gear train. 
The one-way bearing is not necessary for the application to work on an 
exercise bicycle. However, without the one-way bearing the sprocket collar 
would "free wheel" in the forward direction too when the drive force was 
greater than the "break free" force, thus limiting the amount of force the 
rider could apply while pedaling the bicycle in the forward direction. 
The one-way bearing 66 can be replaced by a spring-loaded ratchet and pawl 
drive mechanism found in normal bicycle applications, or other one way 
drive mechanisms that can functionally replace the one-way bearing 
described above. One such suitable commonly available ratchet and pawl 
mechanism is the LMA-8 from the LIDA Machinery Company, Ltd. of Taoyuan, 
Taiwan, as shown in the Taiwan Bicycle Source 1997-98 catalog at p. 370. 
FIGS. 8 through 16 show details of some of the components described above. 
An alternative embodiment of the free wheel clutch mechanism is shown in 
FIGS. 17-20. This alternative embodiment works on the same principle as 
the first embodiment described above, except basically replaces the single 
large spring surrounding the hub 150 with the plurality of smaller springs 
152 positioned between the flywheel 154 and the inner clutch plate 156. 
These plurality of springs 152 act to push the inner clutch plate 156 
outwardly as the clutch material 158 wears down from use. As can best be 
seen in FIGS. 19 and 20, each of the plurality of springs surrounds a 
guide rod 160 mounted to the flywheel 154 which is received in a guide 
bore 162 mounted to and extending from the inside side of the inner clutch 
plate 156. The sliding interaction between the guide rod 160 and the guide 
bore 162 helps ensure that the inner clutch plate 156 is squarely moved 
outwardly under the bias of the springs as the clutch material wears as a 
result of use. The interaction of the guide rod with the guide bore also 
causes the inner clutch plate 156 to turn with the flywheel 154 because 
the guide rods are laterally fixed in position inside the guide bores, and 
as the guide rods turn with the movement of the flywheel, they cause the 
inner clutch plate to turn also. 
The axle housing 164 is press-fit into the hub 150 and extends from the 
flywheel 154, and has an outer end 166 with external threads. After the 
inner clutch plate 156 and associated compression springs 152 are mounted 
over the axle housing and positioned adjacent the hub, the slave gear 
collar 170 is positioned to engage the outer surface of the axle housing 
164 as in the previous embodiment, including having the same bearing 
structure 172. The slave gear collar has an inner surface 174 adjacent the 
outer surface 176 of the inner clutch plate, between which is positioned 
an inner clutch material washer 178. The inner clutch material washer 178 
is preferably fixed to either the outer surface of the inner clutch plate 
156 or the inner surface of the slave gear collar 170. A set of gear teeth 
180 are formed about the outer circumference of the slave gear collar 170 
for receiving the chain used to drive the flywheel. 
The outer clutch plate 182 (or anchor plate) is then threaded on to the 
externally threaded outer end 184 of the axle housing. An outer clutch 
material washer 186 is positioned between the outer surface of the slave 
gear collar 170 and the inner surface of the outer clutch plate 182. 
Preferably, the outer clutch material washer 186 is fixed to either the 
outer surface of the slave gear collar 170 or the inner surface of the 
outer clutch plate 182. The outer clutch plate is fixed to the axle 
housing by a lock-nut 188 to keep the outer clutch plate from turning 
loose under the force of the free wheel mechanism. 
This alternative embodiment of the present invention operates in 
fundamentally the same manner as the previously described embodiment. When 
a reverse force is applied to the drive train, normally through a reverse 
force being applied to the pedals, and this reverse force overcomes the 
"break free" force, the slave gear overcomes the friction force between 
the slave gear collar 170 and the outer clutch plate 182 and inner clutch 
plate 156 which rotate with the flywheel 154. This allows the flywheel to 
continue spinning while the drive train is either stopped, pedaled 
backwards, or pedaled more slowly than the flywheel is spinning. The 
bearings 172 connecting the slave gear collar 170 to the axle housing 164 
are one-way bearings as described above, and when the drive train is 
actuated in the normal or forward direction, the bearings lock and act as 
a direct drive connection between the drive train and the flywheel. 
When turned in the reverse direction, the bearings 172 allow the slave gear 
collar 170 to free-wheel, the free wheeling of which is restricted by the 
frictional engagement of the slave gear collar 170 with the surrounding 
clutch material 178, 186. The compression springs 152 apply the force to 
the inner clutch plate 156 which presses the inner clutch material 178 
against the slave gear collar. The slave gear collar 170 can move 
longitudinally on the axle housing 164 (the bearing allows small amounts 
of movement in this direction) and thus transmits a force to the outer 
clutch material 186, and finally to the outer clutch plate 182. As the 
inner or outer clutch material wears down, the springs 152 extend and push 
the inner clutch plate 156 outwardly and thus maintain the contact 
necessary for the frictional engagement between the inner clutch plate 
156, the inner clutch material 178, the slave gear collar 170, the outer 
clutch material 186, and the outer clutch/anchor plate 182. 
FIG. 20 shows the adjusted relationship of the structure of this 
alternative embodiment when the inner and outer clutch material washers 
178, 186 have worn down. Contrasting FIGS. 19 and 20, note the gap between 
the inner clutch plate 156 and the outer end of the hub 150. The bearings 
172 allow the slave gear collar 170 to move longitudinally on the axle 
housing 164. Either one of the inner or outer clutch materials 178, 186 
can be replaced with a bearing if it is determined that they are 
unnecessary. 
Another alternative embodiment is shown in FIGS. 21-23. In this alternative 
embodiment a Belleville washer 200 is mounted on the end of the axle 
housing 202 to bias the outer clutch plate 204 inwardly to create the 
desired friction force between the slave gear collar 206 and the outer and 
inner clutch plates 204, 208 through the inner and outer clutch material 
washers 210, 212. In the second alternative embodiment a retainer 214 
having an outwardly flanged inner end 215 is threaded on to the end of the 
axle housing 202 extending from the hub 216, which has external threads. 
The outwardly extending flange 215 of the retainer butts up against the 
hub 216. The inner clutch plate 208 is then positioned next to the 
outwardly extending flange 215 and is retained in rotational position 
therewith by keys in slots or by any other suitable attachment method, 
such as welding (as shown in FIG. 22). Alternatively, the outwardly 
extending flange can act as the inner clutch plate. 
An inner clutch material washer 210 is positioned adjacent to and in 
contact with the inner clutch plate 208, and the slave gear collar 206 is 
mounted over the cylindrical body of the retainer 214. The slave gear 
collar 206 is similar to the slave gear collars described in the previous 
two embodiments and includes a bearing 218 positioned between the slave 
gear collar 206 and the outer circumference of the retainer 214, the 
bearing 218 being a one-way bearing allowing the slave gear collar 206 to 
free-wheel when turned in a reverse direction, and locking to provide a 
direct drive when turned in the forward direction. Gear teeth 220 are 
formed on the outer circumference of the slave gear collar 206 for 
engagement with the chain of the drive train. An outer clutch plate 204 is 
positioned over the outer circumference of the retainer 214. As shown in 
FIG. 23, the outer clutch plate 204 defines a central bore 222 having at 
least one key 224 formed for mating insertion into a corresponding slot 
formed in the retainer 214. The mating key and slot relationship between 
the outer clutch plate 204 and the retainer 214 makes the outer clutch 
plate turn with the flywheel because the retainer turns with the flywheel 
226 and the rotational interference between the key and the slot causes 
the outer clutch plate 204 to turn also, in addition to allowing the outer 
clutch plate to float or move inwardly and outwardly with respect to the 
inner clutch plate 208 along the body of the retainer as the friction 
clutch material 210, 212 wears down. 
The Belleville washer 200 is positioned about the end of the axle housing 
to engage the outer clutch plate 204 with the bias force. The bias force 
is created by an outer retainer 228 which defmes a cylindrical main body 
230 having external threads and an outwardly extending flange 232 at one 
end. The outer end of the axle housing 202 defines internal threading 234 
such that the cylindrical main body 230 of the outer retainer 228 threads 
into the outer end of the axle housing 202 to the point where the 
outwardly extending flange 232 abuts the outer end of the axle housing and 
also engages the inner rim of the Belleville washer 200 to compress the 
Belleville washer against the outer clutch plate 204. The compression of 
the Belleville washer 200 against the outer clutch plate 204 causes the 
outer clutch plate to be biased inwardly against the outer friction clutch 
material 212, which is pushed against the slave gear collar 206, which in 
turn is allowed to relatively float on the outer surface of the inner 
retainer 214 to push against the inner clutch material 210 and in turn 
frictionally engage the inner clutch plate 208. 
As the slave gear collar 206 is driven in the forward direction by the 
drive train, the one-way bearings 218 lock and create a direct drive 
relationship. When a sufficient reverse force is applied to the slave gear 
collar through the drive train, the one-way bearings release and allow the 
drive train collar to free-wheel under the influence of the frictional 
relationship with the inner and outer clutch plates, similar to the 
interaction as described with respect to the embodiments above. 
As the clutch material 210, 212 wears down and becomes thinner, the 
Belleville washer 200 extends to continue to create a friction force in 
the clutch system by pushing the outer clutch plate 204 towards the inner 
clutch plate 208, thereby clamping the inner and outer clutch material and 
the slave gear collar 206 therebetween. 
Another alternative embodiment is disclosed in FIG. 24 which shows two 
Belleville washers 240, 242 positioned back to back to allow for a longer 
adjustment stroke due to the wear of the inner and outer clutch material 
washers 244, 246. In this third embodiment the outwardly extending flange 
248 of the second retainer 250 is enlarged to engage the outer rim of the 
second Belleville washer 240. Belleville washers are very stiff and 
provide a great deal of force through the length of their extension. 
Another alternative embodiment is disclosed in FIGS. 25-26. This fourth 
alternative embodiment utilizes a band-brake to create the frictional 
break-free force. The band-brake 260 includes a retainer 262 fixed to the 
flywheel 264 through which is positioned a spring loaded adjustment screw 
266 which attaches to a housing 268. The housing includes two guide slots 
270 for slidably receiving tabs 272 formed on the flywheel. The housing is 
also fixed to the opposite ends of a belt 274. The slidable engagement of 
the guide slots 270 on the tabs 272 help ensure a properly oriented 
adjustment of the band-brake by the spring loaded screw. The slots are 
formed in the housing of the band-brake, the housing being attached to a 
belt, with the band-brake material 276 attached to the inside surface a 
reinforcement sheathing 278 of the belt (as best seen in FIG. 26). The 
tabs, spring loaded threaded screw, housing and belt are all fixed to 
rotate with the flywheel. The spring surrounding screw 266 makes the 
system self-adjusting for wear of the band material by applying a 
preferably constant tension load on the belt through the housing. The 
selection of the spring constant properties of the spring determines the 
amount of tension on the belt, and the amount of adjustment (displacement) 
the band-brake can accommodate. 
As best shown in FIG. 26, the slave gear collar 280 defines an annular 
axial extension 282 which fits over a portion of the hub 284 without 
contacting the hub. This annular extension 282 defines an inner rim 286 
and an outer rim 288, between which is an engagement surface 290. The band 
contacts the engagement surface 290 between the inner rim and the outer 
rim. The slave gear collar 280 includes the same bearing system as 
previously described for one-way engagement with the outer surface of the 
axle housing 292. The proper positioning of the slave gear collar 280 is 
maintained on the axle housing by a large washer 294 which is tightly 
pressed against the outer surface of the slave gear collar by a nut 296 to 
keep the slave gear collar from becoming imbalanced. A second set of 
one-way bearings could be positioned between the annular extension 282 
from the slave gear collar and the outer surface of the hub over which the 
slave gear collar annular extension is positioned. 
As the drive train is actuated in the forward direction by the rider, the 
one-way bearing 298 between the slave gear collar 280 and the axle housing 
292 engages to cause a direct drive relationship between the drive train 
and the flywheel, as in the previously described embodiments. In the event 
a sufficient reverse force is applied to the slave gear collar through the 
drive train, the one-way bearing 298 releases and allows the slave gear 
collar to free-wheel subject to the frictional engagement of the slave 
gear collar and the belt 274. The engagement surface 290 is in frictional 
engagement with the belt to create the "break free" force. The "break 
free" force is determined by the tightness of the belt around the 
engagement surface on the annular extension 282 of the slave gear collar. 
This "break free" force resists the free wheeling of the slave gear collar 
on the axle housing 292 and provides the beneficial pedal-through feature 
of traditional direct drive exercise bicycles. It also allows the drive 
train to free-wheel when a sufficient reverse force is applied to the 
drive train, likely through the pedals and cranks, to allow the drive 
train to be driven at a relatively lower RPM than the flywheel, depending 
on the gear ratio. 
As the frictional brake material 276 wears down, the housing 268 is 
adjusted by tightening the screw 266 to move the housing, and thus tighten 
the belt 274 around the annular extension 282 of the slave gear collar 280 
to maintain the desired frictional engagement, resulting in the desired 
"break free" force. 
Another alternative embodiment is shown in FIGS. 27-29. In this embodiment, 
the slave gear collar 300 has the same structure as the previous 
embodiment described, and is held in engagement with the axle housing 302 
in the same manner. A compression brake housing 304 is mounted in 
engagement with the flywheel 306 and includes means 308 for causing 
engagement of arcuate compression members 310 with the engagement surface 
312 on the slave gear (sprocket) collar annular extension 314, between the 
inner and outer rims 316, 318. The arcuate compression members 310 have a 
hard backing 320 and a frictional clutch material 32(2 mated to their 
inner concave surface for engagement with the slave gear collar annular 
extension 314. The brake housing 304 includes means 308 for radially 
adjusting the compression of the compression members against the annular 
extension 314, such as set screws which are threadedly adjustable through 
the brake housing to engage the hard back surface 320 of the arcuate 
compression members 310 to press the frictional material 322 of the 
compression members against the engagement surface 312 of the annular 
extension. These means can be self-adjusting to accommodate wear of the 
friction material, such as by being spring-loaded set-screws. As the 
frictional clutch material wears down, the set screws 324 can be used to 
maintain the proper compression of the compression members 310 against the 
engagement surface 312, which creates the desired "break free" force. 
This embodiment operates in the same manner to allow a break free clutch 
mechanism on the flywheel as the previously described embodiments. The 
brake housing 304 is held in rotational fixed orientation with the 
flywheel by a pin 326 positioned through a slot 328 in the brake housing. 
The movement of the pin in the slot allows for uneven wear of the 
compression members 310. 
Another alternative embodiment is shown in FIG. 30. Only one side, the 
inner side 329 as shown, of the sprocket collar 330 is used to create a 
frictional engagement with an engagement flange 332 attached to the axle 
housing 334 at the hub 336 of the flywheel 338. The sprocket collar is 
positioned on a sheath 333 threadably engaging the axle housing 334 at the 
hub 336, with a one-way bearing 337 (or ratchet and pawl mechanism) 
positioned between the sprocket collar and the sheath 333 for the same 
purpose as disclosed above with many of the other embodiments. Clutch 
material 340 is positioned between the side 329 of the sprocket collar 330 
and the engagement flange 332, and can be attached to either one, to 
create the frictional engagement therebetween. The engagement flange is 
moveable along the axle housing of the hub to allow the friction force to 
be kept at a relatively constant level as the clutch material wears out. 
This self-adjustment, as described above, occurs when the spring 342, or 
other means, presses the engagement flange outwardly from the hub to clamp 
the clutch material against the inner side 329 of the sprocket collar 330. 
The sprocket collar 330 is supported on the inner and outer sides by an 
inner 344 and outer 346 bearing, respectively. The inside edge 335 of the 
sheath forms the outer race for the inner bearing 344, while the sprocket 
collar forms the inner race for both the inner 344 and outer 346 bearings. 
The outer race 348, or cone, threadedly engages the outer end of the 
sheath 333 to hold the sprocket collar 330 in place and provide a thrust 
bearing against which the spring 342 pushes. 
It is contemplated that these free wheel clutch mechanism structures 
described herein could be mounted on the drive sprocket of the drive 
train, in addition to the slave sprocket of the drive train. It is also 
contemplated that a one-way bearing need not be used in all circumstances, 
in which case the clutch mechanism would be caused to slip if the 
break-free force threshold was reached in either the forward or rearward 
drive-train direction. 
Presently preferred embodiments of the present invention and many of its 
improvements have been described with a degree of particularity. The 
previous description is of preferred examples for implementing the 
invention, and the scope of the invention should not necessarily be 
limited by this description. The scope of the present invention is defined 
by the scope of the following claims.