FR2511334A1 - FRONT FORK OR SADDLE FORK IN PROFILED TUBULAR ELEMENTS, FOR BICYCLE FRAMES - Google Patents

Abstract

The invention relates to a front fork or a saddle fork, composed of tubular profile elements for bicycle frames and is composed of sleeves (4) whose upper parts have an elliptical cross-section and are flattened off to form profiled claws (4') with a concave and rounded-off area which is offset in terms of angle in order to rest on the circumference of a swivel tube (3) or of a saddle tube, an adjustment device which is formed axially on the concave area cooperating, by means of insertion, with a cavity or recess which is formed on the swivel tube (3) or the saddle tube in order to ensure the symmetrical, both angular and elongate, position of the sleeves (4) arranged at a distance from one another.

Description

 The present invention relates to cycle frames and more particularly the fixed saddle forks connected to the bottom bracket, as well as the front forks mounted for free rotation in the steering pivot tube.

 In the front forks of bicycles, it is well known that the steering pivot tube is connected to the sheaths, constituting the branches of the fork by means of an attached fork head, obtained by stamping or otherwise, and established to give The symmetrical spacing of said sheath tubes, while allowing their fixing relative to the pivot tube.

 This achievement is storytelling due to its manufacture, while counteracting an increase in the weight of the frame.

 It is also known to produce fixed saddle forks, connecting the bottom bracket to the seat tube, and intended to allow the free passage of the front part of the rear wheel in order to reduce the distance between the wheel axle and the bottom axle , for better transmission efficiency.

In this type of fork, the tubes constituting the branches are directly fixed tangentially to the seat tube by non-profiled cylindrical ends.

 According to a characteristic of the invention, each sheath is established from a profiled tube of progressive section, the upper part of which is preferably elliptical in shape is flattened along a certain length to form a substantially flat stamped leg whose rounded concave inner face transversely, is offset axially and angularly with respect to the longitudinal axis of said tube so as to constitute a centering and circular positioning surface on the pivot tube or seat tube.

 According to another characteristic, the extreme upper part of the tab forms a rounded clearance, leaving an axial tongue folded down transversely to engage in an opening established in the thickness of the pivot tube or seat tube, so as to allow positioning both longitudinal than circular of the sleeves, further apart progressively and symmetrically with respect to each other by their lower parts for fixing by brazing or otherwise.

 According to another characteristic and in the case of a front fork, the upper ends of the assembled sleeves, contiguously circular, are machined concentrically at the periphery of the pivot tube to constitute a supported shoulder supported by the fixed cone fitted on said tube, and intended for receive the lower steering bearing members.

 According to another characteristic and in the case of a front fork, the lower projecting end of the pivot tube relative to the assembly area of the sleeves is curved and pierced for the engagement of the fixing screw of the whole of the brake.

 These characteristics and others will emerge from the following description.

To fix the object of the invention without however limiting it, in the accompanying drawings
Figure 1 is a small perspective view of a bicycle frame equipped with a saddle fork and a steering fork made according to lginvention.

 Figure 2 shows on a small scale, the separate elements, before machining and assembly, of a saddle fork according to the invention.

 Figure 3 is an enlarged cross-sectional profile view of the flattened upper end and profi-ted diun sheath.

 FIG. 4 is an external front view corresponding to FIG. 3.

 FIG. 5 is an exterior plan view corresponding to FIG. 4.

 Figure 6-is an external profile view of the fork after assembling the sleeves on the seat tube.

 FIG. 7 is a cross-sectional view of the fork illustrated in FIG. 6.

 FIG. 8 is a plan view, in cross section along line 8-8 of FIG. 7.

 Figure 9 is an external half-view in profile and a half-sectional view of a front steering fork according to the invention.

 FIG. 10 is an external front view corresponding to FIG. 9.

 FIG. 11 is a plan view corresponding to FIG. 9.

 In the case of application to a saddle fork of a bicycle frame, the latter is established with a saddle tube (1), of short length arranged angularly to review and fix the saddle support rod in the known manner.

 At its lower end, the seat tube (1) symmetrically receives two identical sheaths (2) arranged with a determined spacing to allow a slight passage of the rear wheel of the cycle, in order to reduce the distance between the wheel axle and the bottom bracket axle.

 According to the present invention each sleeve (2) is established with a progressive section, preferably round at its lower end and elliptical (21) at its opposite upper end.

This section (21) is flattened along its minor axis by stamping or other means so as to produce a profiled tab (22) and offset with
3 on one side a longitudinal recess or indentation (2) rounded transversely whose radius (r) corresponds to that of the seat tube (1).

 This imprint (2) is also angularly offset relative to the longitudinal axis of the sleeve (2) at an angle ot, so as to allow a slight oblique positioning of said sleeve (2) relative to the axis of the tube. saddle (1).

 It should be considered for this purpose that the imprint (2) constitutes a centering and circular positioning surface on the periphery of the seat tube (1) to ensure the precise positioning of the spacing etda symmetry of the sheaths (2) with respect to to the axis of said tube (1).

 The upper end of the profiled tab (22) is further cut during stamping to form a rounded clearance (24) leaving in the longitudinal axis of the sleeve (2), a tongue (25) folded transversely and perpendicularly relative to the imprint (2).

 A hole (11) drilled diametrically in the seat tube (1) according to a longitudinal dimensioning (L) determined with respect to its lower end, allows when pressing the impressions (23) of the opposite sleeves (2), the engagement of the tongues (25) for the precise positioning, both circular and longitudinal, of the said sleeves (2), while their symmetrical spacing is ensured, as indicated previously by the anglecX of the imprints (23) relative to the longitudinal axes of the said scabbards.

 This positioning being ensured, the fixing of the sleeves (2) is obtained in the known manner by peripheral brazing of the external sides of the profiled tab (22) relative to the external part of the seat tube (1), and penetration of the weld over the entire contact surface.

 Note that the end face of the seat tube (i) disposed between the sleeves (2) is preferably rounded at (12), concentrically with the tire or hose of the rear wheel, in view of an aesthetic presentation.

 It is important to note that these provisions also apply in the case of a front fork of a bicycle, as illustrated in FIGS. 9, 10 and 11.

In this embodiment, the steering pivot tube (3) of appropriate length taking into account the dimensioning of the frame, authorizes the support and the positioning, both circular and longitudinal, of the symmetrical sleeves (4) previously bent and shaped. Note, however, that in this case, the profiled tabs (4) provided with strips (4) have longitudinal impressions (43) which are more enveloping so as to obtain circularly joined ends on the pivot tube (3). ex-
end of the sleeves (4) is machined by turning or other machining means so as to obtain a shouldered seat (44) allowing the support of the fixed cone
(5) steering fitted on the pivot tube (3) to cooperate in known manner with the lower rolling means housed in the steering tube of the frame.

 It must be considered that in this embodiment the pivot tube (3) is drilled at (31) between the close ends of the sleeves (4) 'to allow the engagement of the front brake fixing bolt.

 In the case of the saddle fork, provision is made to fix tilt shims (2), not shown, which also allow the rear brake to be radially fixed.

 It is also noted that the lower ends of round section of the sleeves (2) are engaged and centered in indentations or holes for positioning the bottom bracket, before their fixing by brazing or otherwise.

 The advantages are clear from the description and it is emphasized in particular: - the absence of a fork head, significantly reducing the weight of the frame, and its cost price - the ease of production - the aesthetics and the new presentation.

 The invention is in no way limited to that of its modes of application any more than to those of the embodiments of its various parts which have been more particularly indicated; on the contrary, it embraces all its variants.

Claims (6)

DREAM ND I CAT I O NS - 1 - Bicycle forks in tubular profiled elements comprising sheaths fixed to a pivot tube in the case of the front fork, or sheaths fixed to the seat tube in the case of a fixed saddle fork connected to the bottom bracket, characterized by the fact that each straight or curved sheath (2 - 4) is established from a profiled tube, the upper part of which, preferably of elliptical section, is flattened to form profiled legs (2 - 4) with a span concave and rounded (2 - 4) angularly offset to apply to the periphery of the pivot tube (3) or the seat tube (1), a positioning means formed axially on the concave seat, cooperating by embedding with a recess or cavity formed on the pivot tube (3) or seat tube (1) in order to ensure symmetrical positioning both circular and longitudinal of the sheaths (2 - 4) apart. - 2 - Forks according to claim 1, characterized in that the profiled lug (22 - 41) established at the end of each sheath (2 ~ 4 forms on one side a concave seat (2 - 4) rounded transversely and whose radius (r ) corresponds to that of the seat tube (1) or of the pivot tube (3), while being offset angularly at an angleOtW to ensure the oblique positioning of said sheath (2 - 4). - 3 - Forks according to claims 1 and 2 taken together, characterized in that the means for positioning each sleeve (2 - 4) relative to the tube (1 or 3) is obtained by a tongue (25 - 4) formed axially at the end of the legs (22 - 41) of said sleeves and folded transversely to engage in the ends of a diametral hole drilled in the tube 3 (1 or 3), on. which take support and center the spans (23 - 4). - 4 - Forks according to claims 1, 2 and 3 taken together, characterized in that the legs (2 - 4) of the sleeves (2 - 4) allow - by their periphery the fixing by brazing on the tubes (l - 3). - 5 - Forks according to claims 1, 2, 3 and 4 taken together, characterized in that in the case of a front fork, the concave surfaces (43) of the legs (41) are more enveloping to surround the periphery of the pivot tube (3), so as to be machined circularly after welding to obtain a shouldered bearing surface (44) authorizing the support of the fixed c8ne (5) of direction fitted by its bore on said tube (3). - 6 - Forks according to claim 5, characterized in that the pivot tube (3) is pierced axially at (31) between the close ends of the sleeves (4) for the engagement of the front brake fixing means.