Coaster brake

A drive for a wheeled vehicle including a hub adapted to receive the driving wheel of such vehicle. The hub receives and rotatably supports an axle having a worm screw thereon and positioned within such hub. The worm in turn supports an eccentrically weighted driver of drum-like configuration so that rotational force transmitted to the axle in either direction traverses the weighted driver back and forth within the hub in a generally upright position. The driver resists rotation with the axle by reason of its eccentrically weighted configuration. Driving contact is made between the outer face of the driver and the inner face of the hub ends at opposite sides thereof so that rotation of the axle will cause driving force to be imparted to the hub in either direction dependent on which end of the hub the driver is contacting. When the axle is stationary, the driver is normally positioned out of contact with both of the hub driving faces and accordingly permits the hub to freely rotate about the axle with neither braking nor driving force imparted thereto.

BACKGROUND OF THE INVENTION 
This invention relates to a drive mechanism for a wheeled vehicle wherein 
the driving wheel of such vehicle may be driven in either rotational 
direction and wherein force applied in the opposite direction to which the 
wheel is traveling will effect a braking action thereto. Such driving 
mechanisms have particular utility for transmitting a driving force from a 
pedal operated vehicle such as a bicycle or tricycle to its driven wheel 
so that the vehicle can be moved in either direction. With such vehicles 
it is also desirable that they be able to coast, that is, move without the 
application of force to the drive wheel, and to further enable the driving 
wheel to be braked as by the application of force to the driving wheel in 
a direction opposite to that in which it is traveling. 
Devices of this general type are known and include those devices disclosed 
in U.S. Pat. No. 2,246,191 to Schmitz issued June 17, 1941 and U.S. Pat. 
No. 3,650,363 to Cristie issued Mar. 21, 1972. The device disclosed in the 
Schmitz patent includes a driving wheel hub having an axle rotatably 
supported therethrough. The axle is in turn provided with a threaded 
portion adapted to receive a driving member 15 comprising a pair of 
interfitting collars 17, 19 so that rotation of the axle will drive the 
collars as a unit side to side within the hub. The hub further includes a 
shoulder portion 27 on one side and a chamfered portion 31 on the other 
side of the hub with which portions of the collar are adapted to engage in 
frictional driving relationship so that rotational force imparted to the 
axle in either direction will impart such force to the driving hub. The 
driving element made up of the cooperating collar members is prevented 
from rotating as a unit with the threaded portion of the axle by means of 
spring clip finger portions 20 which extend in slidable engagement with 
the surface of the driver member 15. 
A similar device in the form of a clutch mechanism is disclosed in the 
above-identified Cristie patent in which a clutch cone 62 moves axially 
within a sleeve 56 upon an axle 46 between an engaged driving position and 
a disengaged position. In the disengaged clutch position, it is possible 
to simultaneously provide a braking action to the forward movement of the 
wheel supported by the sleeve or hub 56. This action is accomplished by a 
screw upon which the clutch cone is mounted for axial movement within the 
sleeve upon rotation of the axle. 
The above citations and discussion of those patents believed pertinent 
constitute applicant's Prior Art Statement and in that regard copies of 
the above-indicated patents are enclosed with the subject application. 
Although the prior art devices are useful for the purposes indicated, it 
would be desirable if a more simple and economic means could be devised to 
permit traversing motion of the driver of such a driving mechanism while 
preventing it from rotating around the axle without resorting to 
arrangements such as the spring fingers of Schmitz which are subject to 
wear and breakage and the complex and accordingly expensive mechanisms of 
Cristie. It is accordingly a primary object of the present invention to 
provide a drive mechanism in which an axially movable threadedly mounted 
driver member is restrained from concurrent rotation with the axle by 
means of its configuration rather than by means of outside or added 
elements and which accordingly is less complex and less expensive than 
known prior art devices. 
A further object of the present invention is the provision of a device of 
the immediately aforementioned type in which the axially movable driver 
element is eccentrically weighted in such a manner that it resists 
concurrent rotation with the axle upon which it is threadedly mounted. 
Another object is the provision of means which cause the driver to more 
readily break away from driving engagement when the rotational direction 
of the axle is reversed. 
These and other objects of the present invention are accomplished by the 
provision of a drive mechanism comprising a hub, said hub having contact 
faces at opposite inner ends thereof, an axle extending through said hub 
and supported thereby for rotation in opposite directions, said axle 
having a threaded screw portion disposed within said hub and an 
eccentrically weighted driver threadably mounted within said hub upon said 
screw portion for non-rotational longitudinal movement therewith whereby 
rotation of said axle in opposite directions traverses said driver from 
side to side into driving contact with said opposite faces of said hub 
wherby driving force in opposite directions is imparted to said hub. 
Other objects, features and advantages of the invention shall become 
apparent as the description thereof proceeds when considered in connection 
with the accompanying illustrative drawing.

DESCRIPTION OF THE INVENTION 
Turning now to the drawing and in particular FIGS. 1-4, the device 10 of 
the present invention includes a hub or housing 12 of generally hollow 
cylindrical configuration. Such hub includes an open end 14 which is 
normally closed by an end plate 16 having an inwardly extending boss 18 
which in turn includes a first hub driving surface or face 20. The other 
end of the hub is also generally closed as by an inwardly downwardly 
extending shoulder 22 to which another boss or disc 24 is secured in any 
known manner and which in turn comprises a second hub driving face 26. 
Both of the bosses 18, 24 include bearings 28 supported therein and upon 
which an axle 30 is adapted to rotate. The axle is in turn provided with a 
double lead worm screw 32 attached thereto or integrally formed therewith 
in any suitable manner and which is disposed within the hub 12. A driver 
element in the form of a weighted metal drum 34 is supported by the screw 
32 and is adapted to ride thereon. The drum 34 is in turn provided with an 
internal threaded bore 35 which receives the threads of the screw portion 
32 with driver faces 36 on either side thereof. The top portion of the 
drum 34 is provided with a rather large chordal cutout portion 38 which 
serves to concentrate the greater proportion of the drum's weight on the 
bottom thereof. The drum is accordingly eccentrically weighted and acts in 
the manner of a pendulum. Thus as the axle is rotated in either direction 
the drum will remain more or less stable in the upright position depicted 
in FIGS. 4-6 rather than rotating as a unit with the axle and screw member 
30, 32 respectively. 
Turning now to FIG. 5, it will be seen that counterclockwise rotation of 
the axle 30, assuming the normal right-hand thread of screw 32, axially 
forces the drum 34 to the left as shown until the hub driving face 26 and 
the left-hand side driver face 36 frictionally contact each other. Further 
rotational force of the axle 30 will cause the drum 34 to rotate the boss 
24 and accordingly the entire hub 12 as a unit about the axle and 
accordingly impart a counterclockwise motion to the hub 12. It should also 
be brought out that a driving wheel (not shown) is normally attached to 
the outside of the hub 12 as by spokes and the like and that accordingly 
such counterclockwise motion to the hub 12 as shown in FIG. 5 would be 
translated into a rearward motion of the vehicle in which the driving 
mechanism of the present invention is mounted. Similarly, if the vehicle 
is moving in a forward direction when the counterclockwise or rearward 
force is imparted to the hub 12, such force will act as a brake and serve 
to stop the vehicle. 
Turning now to FIG. 6, the same effect as above described in regard to FIG. 
5 but in an opposite direction is illustrated. Therein a clockwise force 
imparted to the axle 30 serves to traverse the drum 34 to the right 
wherein its right-hand driving face 36 contacts the hub driving face 20 
and accordingly imparts a clockwise or forward motion to the driven wheel 
which will either serve to drive the vehicle in a forward direction or act 
as a brake should the vehicle have previously been moving in a rearward 
direction. 
When the drum 34 is in an intermediate position, that is, when the driving 
faces 36 thereof are not in contact with either end of the hub 12, then 
the hub is free to rotate about the axle 30 and neither driving or braking 
force is imparted to the driving wheel of the vehicle, whereby the vehicle 
is in a coast or free wheeling attitude. In any case, it will be seen that 
it is not necessary to utilize other mechanisms to restrain the drum 34 
from rotating with the axle 30, but rather such result is inherently 
obtained by the eccentrically mounted and weighted configuration of the 
drum itself. Such construction enables the producton of an extremely low 
cost yet effective combination driving and brake mechanism. 
It is desirable that immediately upon the cessation of rotational force in 
either direction to the axle 30 that the driving force be terminated. To 
this end each of the bosses 18, 24 is provided with an annular recess 40 
in which a coil spring 42 is positioned and adapted to project outwardly 
of the front faces 20 and 26 respectively. Accordingly, it is necessary 
when the drum 34 is traversed from side to side that such spring 42 be 
initially compressed prior to permitting either of the driving faces 36 of 
the drum 34 to contact either of the hub driving faces 20, 36 
respectively. Similarly, when rotational force is terminated at the axle, 
the spring serves to immediately force the drum 34 away from contact with 
the hub driving surface into which it is incorporated. This causes the 
drum to break free more readily and quickly. Also it is preferable that 
the screw portion 32 be, as previously indicated, of a double lead worm 
which because of its increased pitch over a single lead will enable the 
drum to traverse from side to side more quickly. 
While there is shown and described herein certain specific structure 
embodying the invention, it will be manifest to those skilled in the art 
that various modifications and rearrangements of the parts may be made 
without departing from the spirit and scope of the underlying inventive 
concept and that the same is not limited to the particular forms herein 
shown and described except insofar as indicated by the scope of the 
appended claims.