Land vehicles – Wheeled – Occupant propelled type
Patent
1996-07-19
1998-12-01
Johnson, Brian L.
Land vehicles
Wheeled
Occupant propelled type
2802883, B62K 302
Patent
active
058427112
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an adjustable bicycle frame, to the method for manufacturing and assembling same, as well as to such a frame having an interchangeable triangular rear assembly.
2. Description of Related Art
Currently, manufactured frames are primarily obtained by means of welded, soldered or glued metallic profile sections. Some are obtained by adhesion of elements made of carbon or carbon-KEVLAR (trademark) composite materials. Others are obtained by molding of materials such as dural or magnesium light alloys, or by pressure casting of glass or carbon fiber-reinforced thermoplastic materials.
The manufacture of bicycle frames according to these methods has some disadvantages.
With respect to frames made of steel or light alloys, assembled by mechanical welding, the deformations caused by overheated portions require passage of a surface plate in order to straighten them, the conformance to geometrical tolerances being thereby rendered very uncertain. Additionally, production periods are very long and therefore expensive.
Furthermore, the lack of elasticity in these materials subjects the frames to permanent deformations in the case of shocks.
Furthermore, an excessive rigidity associated with a very good propagation of vibration waves renders the bicycle frames very uncomfortable.
Some of the above materials are sensitive to corrosion and therefore require varnish or paint protection, preceded by a pretreatment rendering the application of a decorative finish delicate and expensive.
The above materials with a natural dark color limit the decoration processes such as sublimation.
Frames obtained by molding of aluminum- or magnesium-based light alloys require lengthy post-manufacturing deburring and machining operations.
Glass or carbon reinforced thermoplastic materials considered until now offer flexural moduli not exceeding 15,000 Mpa. In order to obtain a good flexural and torsional stiffness in these conditions, the thickness of the sections constituting the frames must then be oversized, at the expense of increased weight and cost.
With respect to frames formed of carbon or carbon-KEVLAR composite materials, in addition to the high cost of the materials, the processing periods are very long, resulting in prohibitive costs.
The proximity of the metallic elements in the environment of these materials has a tendency to produce a catalytic effect detrimental to these assemblies that require good contacts.
SUMMARY OF THE INVENTION
The bicycle frame according to the invention should make it possible to considerably simplify the manufacturing and assembling process and, therefore, to reduce the costs in a significant manner. The use of thermoplastic materials with a partially aromatic resin matrix makes it possible to have flexural moduli greater than 20,000 Mpa and, mixed with certain additives, these materials achieve a good compromise of rigidity, comfort, resistance to corrosion, and are easily decorated.
Moreover, the rear portion is interchangeable and thus can enable the user to adapt to all terrains.
Indeed, the frame according to the invention is composed of a body constituted of three pultruded profile sections capable of being coextruded in a thermoplastic coating with a partially aromatic resin matrix, assembled to one another by a steering housing, a saddle rod housing and a crank-gear housing, all three being molded of a thermoplastic material with a partially aromatic resin matrix.
The molecular structure of such material is comparable to the structure of a certain polyamide, "66", the difference being that polyamide 66 comprises a molecular interchain matrix of adipic acid, whereas an aromatic polyamide comprises a molecular interchain matrix of isophthalic acid, these matrices being grafted on hexamethylenediamine-type molecular chains.
Such materials with a partially aromatic resin matrix have flexural moduli greater than 20,000 Mpa and ultimate tensile strengths greater than 250 kg/mm.sup.2. These properties, associ
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Bird S.A.
Johnson Brian L.
Savitt Gary
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