Bicycles have been used as a means of recreation and transportation for many years. With the advent of the fuel crisis in the 1970""s and the rise in overall health consciousness in society, bicycling recently gained even greater popularity. Finally, just recently, mountain biking has become the most popular form of bicycling with sales of mountain bikes surpassing those of ordinary road bikes.
With the increase in the popularity of mountain biking, bicycle developers have been faced with issues that were of little or no concern when most bicycle riders road on the street. Foremost of these issues is the issue of shock absorption devices for a bicycle. Mountain bikers quickly learned that a rough trail could equate to a sore body without proper suspension for the bicycle.
Hence, there have been many recent developments of shock absorbers for bicycles. These developments have tended to consist of a variety of linear shock absorbers placed at various locations on a bicycle frame to provide for front and rear shock absorption. While satisfactory results have been obtained, unfortunately there have been problems associated with traditional shock absorbers for bicycles. Specifically, linear shock absorbers tend to be expensive, high maintenance devices that tend to wear out long before most of the other bicycle parts. Owners have been forced to either buy a new bicycle or replace the shock absorbers, both of which are very costly.
Torsion springs are also well known devices. Torsion springs are very low maintenance, inexpensive, and tend to have a long life that often equals or surpasses that of the equipment on which they are being used. Torsion spring prior use has included many applications, such as: exercise equipment, military equipment, automobiles and trucks.
Dip Brazing
Dip brazing is a method of joining together metals by dipping the work into a hot, molten salt bath and using a filler metal with a melting point above 800 deg. F. but lower than that of the metals to be joined. Dip brazing is well known in the prior art. Currently, hollow tubular bicycle frames are made by extruding individual frame sections. These frame sections can then be bent to a desired shape, coped and individually welded together. Some of the major disadvantages to making bicycle frames in this manner are: 1) the manufacturer is limited by the amount and type of bending and coping that he is able to do to the extruded frame sections, and 2) the extra time it takes to align and weld each frame member and frame.
Prior Art Drop Protectors/Derailleur Hangers
The bicycle rear drop is that portion of the bicycle frame to which the rear wheel attaches. It is usually fused to the rear portion of the bicycle frame. Typically, the derailleur hanger is rigidly attached to the bicycle drop. The bicycle drop is subject to tremendous amounts of stresses and forces. Because the drop is fused to the rear portion of the bicycle, the entire rear portion of the frame would need to be replaced if the drop is damaged.
In the prior art, drop protectors and replaceable hangers are currently available. However, current drop protectors and hangers only protect the outside of the bicycle drop. Moreover, current drop protectors are screwed into the side of the drop, requiring significant time, effort and tools to replace. In addition, current drop protectors do not create a clamping action on the drop when the rear wheel axle is tightened to the rear drop.
What is needed is a shock absorption device for a bicycle that is low maintenance, inexpensive and has a long life.
The present invention provides a bicycle with a torsional shock absorber comprised of a torsion spring assembly. The elements of the torsion spring assembly include: housing, a shaft positioned within the housing, a rubbery substance positioned between the interior surface of the housing and the outer surface of the shaft. The torsional shock absorber is mounted on the bicycle such that shock forces are converted into rotational forces tending to rotate the shaft within the housing. These rotational forces are resisted by the spring force created by the rubbery substance within the torsion spring assembly; thereby absorbing the shock forces. In a preferred embodiment, the rubbery substance is bonded to the interior surface of the housing and the outer surface of the shaft. In a preferred embodiment, the front and rear portions of the bicycle frame pivot about the pedal spindle axis. Also, in a preferred embodiment, the housing of the torsion spring assembly is rigidly connected to the front portion of the bicycle frame in-between the top tube and middle brace and just in front of the seat tube. The rear portion of the bicycle frame is pivotally connected to two torsion arms rigidly connected to the shaft.