Bicycle frame

Details Bicycle frame Bicycle frame

1999-02-17

2001-09-25

Chilcot, Richard (Department: 2167)

Land vehicles

Wheeled

Occupant propelled type

C280S275000

Reexamination Certificate

active

06293574

ABSTRACT:

The present invention is directed to a bicycle frame, and in particular a bicycle frame in which at least the rear wheel is sprung counter to the frame.
It has been especially the development of mountain bikes which has led to an increasing demand for cushioned, resilient bicycle frames. The first step necessary in the application of resilient sprung bicycle frames was the development of front wheel suspension forks; these enable a relative movement between the front axle pivot point at the fork and the forking tube which is leading into the bicycle frame's head pipe. After the introduction of suspension forks had already yielded considerable gains in riding safety and comfort, attention increasingly turned to the development of rear wheel suspension frames.
In developing rear wheel suspension for bicycles, several design goals must be reconciled with one another. On the one hand, the entire arrangement must be very lightweight, since a heavy bicycle is unwieldy and completely useless for athletic uses. Furthermore, it must be ensured that sufficient spring deflection to prevent a bouncing or jumping of the rear wheel will be provide, even over vastly uneven terrain, as said jumping considerably impairs riding stability. In addition, the rear wheel suspension must be disposed in such a manner that it reliably guides the rear wheel, so that the stability gained through the suspension is not then lost again due to inept rear wheel guidance.
Finally, a rear wheel suspension should also be adjustably configured, in order to enable simplified adjustments in consideration of users of different weights or for different types of terrain.
It is the task of the present invention is to devise a rear wheel suspension of a type known in the state of the art, in which an especially high measure of comfort and riding safety is gained, without any detriment to the directional stability of the rear wheel.
This task is solved in accordance with the objects of the invention as claimed in claim
1
.
Preferred embodiments of the invention comprise the subjects of the dependent claims.
In the bicycle frame according to the present invention, a seat tube is disposed which is open at its upper end so that a saddle stay can be inserted. A pedal bearing housing is arranged at the lower end and is preferably soldered, welded, or glued to the seat tube.
Above said pedal bearing housing and preferably as close to it as possible, a pivot point is disposed for two chain stays which are arranged and mounted to the left and right sides of the bicycle rear wheel and which are joined to a contour for receiving the rear wheel axle, preferably by means of a customary clamping arrangement.
The fulcrum of the first seat tube pivot point is preferably arranged exactly at the center line of the seat tube.
The rotational connection between the chain stays and the seat tube is preferably provided by means of roller bearings, specifically by means of needle bearings for receiving the radial force and two axial bearings for receiving the axial force.
The use of the axial bearings, preferably axial roller bearings, enables a high initial tension between the elements which are movable relative to one another, so that a narrow chain stay guidance, largely without clearance play, results at the seat tube.
The contour is preferably a independently finished component, which in each case is soldered, welded, or glued to the essentially tube-shaped chain stays.
At the contour, and in fact preferably above the receiving of the rear wheel axle, a second pivot point is disposed, whereby a pivot point is provided at each chain stay, so that an overall essentially symmetrical construction with respect to the rear wheel results.
At the contour, the pivot point is defined by a drill hole which receives the actual bearing unit. Also at this pivot point, a combination of needle bearings for receiving the radial force and axial bearings (here too, axial roller bearings in particular) for receiving the axial force are employed. Here as well, the utilization of axial roller bearings has the advantage of high initial tensioning, thereby enabling good guidance without clearance play here as well.
The second pivot point at the contour rear is the junction point between the two chain stays and the seat stay. The seat stay is rotatably joined to the contour at this second pivot point, and indirectly joined to the seat tube at a third pivot point. Indirectly not because there are no immediate connections disposed between said seat stay and said seat tube, but rather because a still to be described rocker plate is disposed for connection with the seat tube.
The connection between the seat stay and the rocker plate is made with ball joints, so that tensioning within the rear wheel structure can be prevented.
According to the present invention, the rocker plate provides three rocker plate pivot points, namely the first rocker plate pivot point as described above at which the seat stay is flexibly affixed, and a second rocker plate pivot point, at which rocker plate and seat tube are joined together. This pivot point is disposed on the seat tube, and is in fact disposed at its rear, the rear wheel side above the first pivot point.
The rocker plate has a third rocker plate pivot point at which a spring damping element is flexibly affixed to the rocker plate. Ball joints are also preferably employed here. The spring damping element is preferably parallel to and in front of the seat tube, meaning arranged counter to the rear wheel side. The spring damping element is mounting on the frame by means of a connective fitting arrangement.
The frame is preferably of conventional construction, meaning it comprises a seat tube which, as seen from the pedal bearing, slopes diagonally down to the rear wheel, a top tube, a down tube connected to the pedal bearing housing, and a head pipe, which receives the fork tube of the front wheel fork.
The fitting arrangement in this case comprises two plates connected to the seat tube and the down tube, as well as to the pedal bearing housing if necessary, and effecting an additional reinforcement.
Ball joints are preferably employed at the latter described connective points of the spring damping element with the frame as well.
The solution according to the present invention has a succession of fundamental advantages.
For the most part, the design follows the construction of known diamond frames, so that known dimensions, for example of seat tubes, remain unchanged. The continuous seat tube has the advantage that the torque transmitted through the saddle stay to the seat tube can be dispersed over a large length of the seat tube.
The arrangement has the further advantage that frame leveling adjustments during cushioning do not generally influence chain tension. The force at work in the chain, which causes tensioning between pedal bearing and rear wheel axis, has consequently only very little influence on the spring damping properties of the rear construction.
On the basis of the geometry applied and also the preferable bearing elements employed, a very rigid lateral guidance results for the rear wheel, which in turn fundamentally improves ride stability.
Last but not least, the utilization of the rocker plate allows for the mounting of the spring damping element parallel to the seat tube, which is of particular advantage for its adjustability.
The dimensions of the rear construction are independent of the frame size, provided that customary rims and tire diameters are applied. If one draws a connective line (figuratively) from the fulcrum of the pedal bearing to the fulcrum of the rear wheel and identifies this connective line as the x-axis, and then establishes a y-axis vertical to this x-axis, a Cartesian coordinate system emerges for specifying the individual pivot points, whereby the pedal bearing forms the protruding boss and the wheel pivot point according to the definition receives the y-value 0.
An especially favorable pivot point configuration, which enables an optimal damping/spring relationship for the rear

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