Joints and connections – Rod side to plate or side – Laterally spaced rods
Reexamination Certificate
1998-10-23
2002-02-05
Browne, Lynne H. (Department: 3629)
Joints and connections
Rod side to plate or side
Laterally spaced rods
C403S385000, C074S551100
Reexamination Certificate
active
06343891
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention pertains to an improved bicycle stem clamping structure for providing a cantilevered support for a handlebar, especially for mountain bikes or the like.
2. Discussion of the Prior Art
Bicycles include handlebars to apply directional control to a front fork and wheel, for steering the bicycle. A front fork includes a substantially vertical steering or steerer tube inserted coaxially within the head tube of the bicycle frame. A bicycle handlebar stem is usually supported within a fork steerer tube and retained therein by an offset expander wedge providing pressure applied by an expander bolt. The stem also normally includes a roughly horizontal, cantilevered support portion terminating in a transverse stem clip which, along with a binder bolt, can be used to clamp a substantially horizontal handlebar in place. The handlebar, as is well known in the art, is used to steer the bicycle; the stem, combining the horizontal cantilevered portion and the vertical portion within the steerer tube, provides one method for supporting the handlebar and applying pressure from the handlebar to the front fork for steering the bicycle. A number of attempts have been made to provide greater support for mountain bike handlebars which frequently endure greater stress in technical riding, competition or the like. In particular, the ball type handlebar, popular in the late eighties, incorporated the handlebar and stem into a one piece unit including an expander bolt and an expander wedge for clamping the handlebar and integral stem into the steerer tube. A number of problems were observed with the ball type handlebar, including a lack of adjustability.
Others trying to solve the problems inherent in mountain bike handlebar mounting and adjustment created the “Aheadset™” bicycle stem including a steerer tube attachment, a substantially horizontal stem member, and a removable handlebar clamping member, thereby providing added flexibility in bike fit but incorporating a complicated and inherently weaker structure into a mechanism for mounting a handlebar to a mountain bike.
There is a need, therefore, to provide a strong, mechanically robust and yet simple structure for mounting a mountain bike handlebar onto steerer tube which permits easy adjustability.
OBJECTS AND SUMMARY OF THE INVENTION
Accordingly, it is a primary object of the present invention to overcome the above mentioned difficulties by providing a strong, mechanically robust and yet elegantly simple structure for mounting a mountain bike handlebar onto steerer tube while permitting convenient adjustment.
Another object of the present invention is to mount a handlebar onto a bicycle with an economically manufactured clamping structure.
Yet another object of the present invention is adjustably clamping a handlebar onto a bicycle in an aesthetically pleasing, rigid clamping structure made from a selected material, thereby allowing the user to select the structure and material best suited to their riding style and budget.
The aforesaid objects are achieved individually and in combination, and it is not intended that the present invention be construed as requiring two or more of the objects to be combined unless expressly required by the claims attached hereto.
In accordance with the present invention, a bicycle stem clamping structure is readily manufactured in two matching parts. A twisted bicycle stem includes first and second helically twisted clamping members fastened together using four threaded fasteners received in four corresponding threaded apertures. The assembled twisted stem defines, at one end, a vertical cylindrical receiving aperture opposite, at the other end, a transverse, substantially horizontal cylindrical receiving aperture having a central axis offset by 90°, or in perpendicular relation, with the central axis of vertical receiving aperture. The first and second helically twisted clamping members each comprise one-half of the finished stem structure for receiving the substantially horizontal handlebar and the substantially vertical steerer tube.
The first and second helically twisted clamping members are preferably manufactured of steel, aluminum, titanium, magnesium or thermoplastic or plastic engineering resin such as Grivory GV-5H™ brand reinforced thermoplastic, preferably reinforced with a 50% glass fiber fill or carbon fiber fill using high tensile strength filaments.
Each of the helically twisted clamping members includes a twisted longitudinal external scoop or groove and functions as a twisted I-beam, thereby saving material and weight and providing a shape which permits the helically twisted clamping members to be cast or molded and removed from the mold with both mold and cast or molded clamping member intact. A plurality of identical helically twisted clamping members are preferably fabricated in a single mold and two members are used to fabricate a twisted bicycle stem. The transverse extent of the scoop is bounded by first and second opposing ribs, also helically twisted in a 90° turn or quarter twist.
In an alternative embodiment, the helically twisted clamping member vertical receiving aperture and horizontal receiving aperture are defined by first and second sleeves fabricated from aluminum, titanium, thermoplastic or thermoset plastic. The first and second helically twisted clamping members have helically twisted inwardly facing surfaces which, in the assembled twisted bicycle stem, are in intimate contact with one another. In an alternative embodiment, an aluminum, titanium or steel sheet is incorporated into each helically twisted clamping member on the inwardly facing surface, thereby imparting additional strength to the finished twisted bicycle stem. In another alternative embodiment, each helically twisted clamping member has a pin or tab and corresponding symmetrically disposed hole or slot on an inwardly facing surface, where the hole is adapted to receive the pin on the mating helically twisted clamping member or the slot is adapted to receive the tab on the mating helically twisted clamping member, thereby assisting in aligning and indexing the first and second helically twisted clamping members and providing additional mechanical support to the resulting twisted bicycle stem structure.
The helically twisted clamping members may alternatively be machined from titanium, aluminum, steel or the like. Machined helically twisted members can be substantially hollow inside, thereby defining a cavity, once assembled into a finished twisted bicycle stem. For those embodiments having removable sleeves, the user has additional flexibility since the sleeves can be sized to receive different vertical stem tube and handlebar diameters. The length of each sleeve can be varied to provide greater adjustment in rise or stack height. The length between the vertical cylindrical receiving aperture and horizontal cylindrical receiving aperture (i.e., the distance between the central axes of the receiving apertures) can be varied to give a twisted bicycle stem of any desired stem extension (from steerer tube to handlebar). A steerer tube of any desired length and diameter can then be received in the vertical cylindrical receiving aperture and a handlebar of any desired diameter can be received in the horizontal cylindrical receiving aperture. Thus, helically twisted clamping members each comprise one-half of the finished stem structure for receiving the handlebar and the steerer tube. In the preferred embodiment, the helically twisted clamping members are substantially identical and are therefore more economical to manufacture than differing parts. Removal of threaded fasteners permits simultaneous removal of the stem and handlebar, thereby allowing rapid changes in equipment or ease of access to individual parts for ease of maintenance.
A machined, twisted bicycle stem is assembled using threaded fasteners received in threaded apertures and clamping a substantially horizontal handlebar that is separated by a stem extension distance from a subs
Browne Lynne H.
McKinney, Jr. J. Andrew
Walsh John B.
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