Land vehicles – Wheeled – Occupant propelled type
Reexamination Certificate
1999-02-25
2001-10-30
Hurley, Kevin (Department: 3619)
Land vehicles
Wheeled
Occupant propelled type
Reexamination Certificate
active
06308975
ABSTRACT:
This invention relates to two wheeled cycle vehicles and in particular to a suspension system for the rear wheel of a bicycle, the wheel being a small wheel having an overall diameter of 16 to 20 inches.
This invention has as its object to provide such a system which is of the trailing, swinging arm type; which is afforded resilient suspension means; and which is easily rendered demountable from the remainder of the bicycle so that the machine may be folded so as to occupy a smaller volume or a space rendered more convenient for transport or storage.
Broadly stated this invention provides a pedal bicycle having front and rear wheels wherein the rear wheel is supported on an arm structure which is pivotally connected to a main frame of the bicycle, the pivotal connection between the arm structure and the main frame being by a rubber bushed pivot bearing means so constructed and arranged that the rubber is wound elastically in torsion as the arm structure moves pivotally relative to the main frame of the bicycle.
Preferably, the rubber bushed pivot bearing means includes a cyclindrical body of rubber bonded between inner and outer cylindrical metal shells with the outer metal shell being held fixed relative to the bicycle main frame and with the inner metal shell being held fixed relative to the arm structure which carries the rear wheel.
Advantageously, said arm structure has at a leading end a housing within which is rotatable an axle bridging two pedal cranks, said axle and a spindle of the rear wheel being parallel to one another.
In one preferred embodiment the pivot bearing means including a pivot shaft passing through a housing which is fixed to the bicycle frame and said shaft being disposed parallel to the pedal crank axle, said axle and said pivot shaft being spaced a predetermined distance apart.
The trailing arm structure may comprise a skeletal framework made up of small diameter tubes welded together, having forks extending rearwardly on each side of the rear wheel; and said structure will being shaped to have a generally triangular aspect in side view, with firstly, at a front apex, a transverse tube for housing the pedal crank axle of the cycle; with secondly, a rear apex where the wheel spindle is mounted on fork ends; and with thirdly, an upper apex where there is a spring controlling swinging movement of the forks relative to the cycle frame; such swinging movement being permitted and achieved by a pivot located transversely on the cycle frame at the base of a seat tube thereof and immediately above the transverse tube housing the pedal crank axle with the said tube having upwardly projecting lugs for connection with said transverse pivot.
This framework which constitutes the swinging fork arm therefore has the housing for the pedal crank axle integral with it. As a result the distance between the pedal crank axle and the rear wheel spindle is fixed with these elements being carried by the framework so that they may be demounted, together with the pedals, the chain wheel, the chain, the rear wheel and the gear assembly, all as a single unit, from the remainder of the machine.
Such demounting will be achieved by disconnecting the lugs from the transverse pivot; by disconnecting the spring at the top apex of the framework; and if necessary, disconnecting any cables leading to rear wheel brake systems of gear changing mechanisms associated with the pedal driven rear wheel.
Also by this system now proposed whereby the distance between the pedal crank axle and the rear wheel spindle is fixed, there is avoided torsional wind up of the suspension caused directly by chain tension during pedalling.
The cycle frame will be provided with an upwardly extending saddle supporting structure which is stout and robust and which may be in the form of a stiff tube. At its lower end this structure will mount the transverse pivot which supports swinging of the trailing arm framework. In order to give adequate location to the trailing arm the seat tube will need to give structural support over a lateral span of preferably three inches. The distance between the lugs upstanding from the bottom bracket at the framework front apex will exceed this span.
Said lugs will be connected to opposite ends of a an axial pin which extends through the pivot tube within a rubber to metal bonded bearing bush carried within the pivot tube. This bearing bush includes at least one cylindrical body of rubber bonded and precompressed between inner and outer metal sleeves,the arrangement being such that the rubber is wound in torsional shear during pivotal movements of the trailing arm structure relative to a main frame of the bicycle. Such a rubber bushed bearing will provide very stiff resistance to movements of the trailing arm structure which cause the rubber to be deformed in compression; and less stiff resistance when the rubber is deformed in torsional shear.
In a preferred embodiment the rubber bushed bearing has an axial length(transversel of the bicycle) of 3 inches which is only ½ inch less than the distance between the throws of the cranks of the left and right pedals of the machine. Such a rubber bushed bearing is well adapted to hold the trailing arm structure and the rear wheel carried thereby, correctly in their intended positions while absorbing the heavy loadings imposed by the rider as he operates the pedals of the bicycle.
An upper region of the saddle supporting structure will also receive the reaction forces generated by the spring located at the swinging framework upper apex. This spring may be a rubber spring which is resiliently distorted during the working of the suspension, deforming preferably in both compression and shear. It may have associated with it hydraulic damping means and it may be provided with a gas spring whose internal pressure may be raised or lowered to alter the springing characteristic.
In one embodiment the spring device comprises a frustro conical-rubber bonded unit at the upper apex of the rear triangular forked framework but in which water based fluid is contained. The inner volume is separated by a member in which there is an adjustable orifice. Low pressure air pumped by a bicycle tyre pump can provide sufficient pressure to augment the damping in the rebound mode.
REFERENCES:
patent: 2452758 (1948-11-01), Hutchins
patent: 3151878 (1964-10-01), Uncles
patent: 3952546 (1976-04-01), Nakano et al.
patent: 4421337 (1983-12-01), Pratt
patent: 4629352 (1986-12-01), Nemoto
patent: 4957279 (1990-09-01), Thorn
patent: 5217241 (1993-06-01), Girvin
patent: 5427208 (1995-06-01), Motobu et al.
patent: 5975550 (1999-11-01), Schonfeld
Hurley Kevin
Moulton Developments Limited
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