Abstract:
A suspension method for stabilizing a bicycle frame is provided with an elastically deformable damping suspension in order to absorb shocks, wherein said method consists of elastically deforming a suspension device by a torsional effect perpendicularly to the bicycle frame. The suspension device extends over a frame plane and is fitted out to implement the method by providing a damping torsional device arranged about at least one axis contained in a torsional plane perpendicular to the frame plane.

Description:
FIELD OF THE INVENTION 
     The invention relates to a suspension method for a bicycle frame, a suspension device for implementing such, a bicycle frame provided with said suspension device, especially for a rear wheel fork of said frame, and a bicycle equipped with such a frame. 
     PRIOR ART 
     The bicycles of the prior art, and especially the mountain bikes, are commonly provided with front wheel and/or rear wheel suspension devices in order to absorb shocks and vibrations for damping the bike during a ride. These devices comprise generally at least one spring (two for the front fork), usually coupled with a hydraulic piston. The hydraulic piston works with the spring in such a way that the wheels can move vertically within a range of motion of about 5 to 15 centimeters when climbing on a rock or passing above a pothole. Such suspension devices are placed either on the front fork and/or between the central rigid frame and a rear fork that supports the rear wheel. 
     These suspension devices are however heavy and complex to manufacture because of the numerous pieces. Furthermore, they are not easily mountable or dismountable, e.g. to fix or replace them, because of the tight combination of the pieces. Moreover, their efficiency is not sufficient in hard or extreme conditions (e.g. very rough ground, sports competition or high jump) because of the low range of vertical motion of the bike wheels equipped with such a suspension device. 
     OBJECTS OF THE INVENTION 
     It is an object of the present invention to provide a solution to at least one of the aforementioned problems. 
     SUMMARY OF THE INVENTION 
     For that purpose, the object of the invention is to provide a bicycle frame with an elastically deformable damping suspension for stabilizing purposes, that is more practical than springs and pistons usually used. 
     The invention relates more specifically to a suspension method for stabilizing a bicycle frame in order to absorb shocks, wherein said method consists of elastically deforming said suspension by a torsional effect perpendicularly to the bicycle frame. 
     The invention also relates to a suspension device to stabilize a bicycle frame extending over a frame plane and fitted out to implement such a method, and comprising damping torsional means about at least one axis contained in a torsional plane perpendicular to the frame plane. 
     In a preferred embodiment, such axis is perpendicular to the frame plane. 
     The invention also relates to a bicycle frame comprising: 
     a tubular rigid structure which extends substantially over a frame plane, 
     at least one wheel fork made up two tubular arms symmetrically arranged in view of the frame plane and defining a medium longitudinal direction in the frame plane, 
     at least one suspension device linking the wheel fork to the tubular rigid structure to absorb shocks, 
     wherein said suspension device comprises a damping means which is torsionally deformable about an axis, said axis being at an angle substantially ranged between 30 and 90 degrees regarding said medium direction, and preferably at right angles. 
     Preferably, said bicycle frame further comprises different means for connecting said damping means to the rear fork on one hand, and to the tubular rigid structure on the other hand. 
     Advantageously, one suspension device comprises a first rigid plate fixedly secured to the fork facing a second rigid plate fixedly secured to the rigid structure, and said damping means is a damping pad fixedly secured between and to the first and second rigid plates. 
     According to a preferred embodiment of the present invention, each of the two tubular arms of the wheel fork is linked to the tubular rigid structure by a suspension device comprising: 
     an external rigid plate fixedly secured respectively to internal parts of the arms of the fork, 
     an internal rigid plate fixedly secured to opposite sides of a tube of the tubular rigid structure, 
     each internal rigid plate facing an external rigid plate and a damping pad being respectively fixedly secured and arranged between a pair of internal and external rigid plates. 
     Preferably, the two suspension devices of a wheel fork are coaxial with a common axis perpendicular to the frame plane. 
     Each damping pad is preferably made of rubber and is permanently bonded to the internal and external rigid plates by means of vulcanization. Therefore, the damping means forms an integral unity with the plates. 
     According to preferred embodiments, each internal rigid plate is provided with two anti-rotational studs for its securing to the tubular rigid structure, and each external plate is provided with two holes for its securing to a tube of the rear fork. 
     Preferably, each damping means has a circular shape. 
     The invention also relates to a bicycle provided especially with said frame, the rigid structure of which having a crank gear, and two wheel forks, a front and a rear one to fit respectively a front and a rear wheel. In preferred embodiments, the wheel fork suspended is the rear wheel fork and said suspension device is arranged just above the crank gear and coaxial with said crank gear. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic perspective view of a bicycle frame provided with a suspension device according to the present invention, 
     FIG. 2 is a detailed view of FIG. 1, 
     FIG. 3 is a partial perspective view of the suspension device of FIG. 2, 
     FIG. 4 is a front view of FIG. 3, 
     FIG. 5 is a side view of FIG. 3, 
     FIG. 6 is another side view of FIG. 3, and 
     FIG. 7 is a view similar to FIG. 1 but with two wheel forks. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIGS. 1 and 2 describe a bicycle frame  10  according to the present invention. This frame  10  comprises several hollow tubes made of metal like stainless steel or aluminum alloy, or even carbon fiber. These tubes are linked together, for example by a welding technique, so as to form a substantially triangular-shaped tubular rigid structure  11  which extends substantially over a frame plane P. 
     Two tubular arms  12  and  13  are connected to a substantially vertical tube  15  of the rigid structure  11 , just above a crank gear  16 , to form a suspended rear fork  14 . The tubes  12  and  13  are symmetrically arranged in view of the frame plane and define a medium longitudinal direction D in said frame plane. The tubes  12  and  13  are articulated according to the rigid structure  11  and pivot about an axis xx′ perpendicular to the frame plane P. 
     A rear suspension device  20  links each arm  12  and  13  of the rear wheel fork  14  to the vertical tube  15  of the frame  10  so as to absorb shocks and vibrations in order to damp the bike when riding. 
     As it can be seen on FIG. 2, the suspension device  20  comprises two parts  22  and  24  symmetrically arranged on two opposite sides of the vertical tube  15 . 
     Each part  22  or  24  of the suspension device  20  comprises a damping pad  25 , arranged between an external rigid plate  26  and an internal rigid plate  27 . The plates, which are made of an aluminum alloy, are arranged parallel to each other and to the frame plane, as shown in FIGS. 3 to  6 . 
     Each damping pad  25  is a rubber disc thicker than the rigid plates and fixedly secured to said plates by permanent bonding, for example during a vulcanization molding process not described here. 
     The two external rigid plates  26  are respectively fixedly secured to the tubes  12  and  13  of the rear fork  14 . 
     For this purpose, each external rigid plate  26  has substantially the shape of a drop and is provided with a first central hole  26   a  coaxial with the axis xx′ and a second hole  26   b  arranged near the narrow part of the drop (see FIGS.  3  and  4 ). These holes are adapted to receive a screw or a bolt (not shown) for fixing the external rigid plate  26  to the corresponding arm  12  or  13  of the rear wheel fork so as to avoid any rotation of the external rigid plate  26 . 
     Each internal rigid plate  27  has the shape of a thin disc and is provided with two prominent studs  27   a  and  27   b  arranged symmetrically in view of the axis xx′ (see FIGS.  3  and  6 ). The anti-rotational studs  27   a  and  27   b  penetrate inside two holes (not shown) of the vertical tube  15  so that, when the rear fork  14  swivels about the axis xx′, the rigid plate  27  can not turn. The internal plate  27  is also provided with a central hole  27   c,  for example for a fixing bolt. 
     When a bicycle equipped with the suspension device  20  is ridden by a rider, for example in woods or on uneven ground, said suspension device  20  absorbs the shocks and vibrations that the rear wheel and the rider (his legs, bottom and arms) would absorb without said suspension device. Thus, the device helps the rider to stabilize the bike so that he can ride it more efficiently. 
     In operation, the two damping pads  25  are deformed by torsional forces exerted between the external plates  26  and the internal plates  27 , as well as between the static rigid structure  11 , especially the vertical tube  15 , and the rear fork  14 . The rubber of the disc pad  15  is strongly fixed to the plates  26  and  27  and is tough enough to bear the high torsion forces. 
     Such torsional suspension device can provide a range of motion as much as 30 centimeters of vertical travel of the rear wheel, which is very interesting for example for a professional mountain bike racer. This arrangement also produces a system which is relatively soft in the vertical direction and provides high stiffness in the lateral direction to counteract side loading during turning. 
     In the foregoing description, a specific example has been used to describe the invention. It is understood by those skilled in the art that modifications or adaptations can be made to this example without departing from the spirit and scope of the invention. 
     For instance, the sizes (shape, thickness) of the plates or/and damping pads may vary. 
     In other respects, the material used for the plates may vary, i.e. they may be made of carbon fiber or titanium for a better strength and lightness. 
     Furthermore, the device may be place closer or further to the crank gear according to the shape of the rear fork and the main tubular rigid structure. It may even be placed just under the bicycle seat. 
     Moreover, the plates may be irreversibly fixed to the vertical tube and/or rear fork, for example by welding or riveting, and the damping means may also takes place in a front fork, see reference numeral  40  in FIG. 7, or a handlebar. One failsafe stop can also be provided to arrest excessive vertical travel of the wheel in each direction. 
     The ends of the arms of the wheel fork, which bear the damping means, may be inclined in view of the medium longitudinal direction. Thus, each damping means is torsionaly deformable about an axis that is not perpendicular to the frame plane but for example in a range of substantially 30 to 90 degrees regarding the medium direction. 
     As such, an invention has been disclosed in terms of preferred embodiments thereof which fulfills each and every one of the objects of the present invention as set forth above and provides a new and improved suspension method for a bicycle frame, a suspension device for implementing such, a bicycle frame provided with said suspension device, especially for a rear wheel fork of said frame, and a bicycle equipped with such a frame. 
     Of course, various changes, modifications and alterations from the teachings of the present invention may be contemplated by those skilled in the art without departing from the intended spirit and scope thereof. It is intended that the present invention only be limited by the terms of the appended claims.