Abstract:
A rotor system for a bicycle ( 1 ), for the purpose of bearing a fork ( 8 ) and transmitting the actuations of Bowden cables ( 31, 32 ), which each having a core ( 31   a;    32   a ) includes first and second transmission elements ( 36, 37 ), that rotate relative to one another and are arranged in the area of the bearing ( 21, 23, 25 ) of the fork ( 8 ). The transmission elements include an annular region, mounted on a fork steerer ( 12 ) and surrounded by a head tube ( 21 ), and connection areas ( 36   b;    37   b ) for the direct or indirect attachment of the rotor-side ends of the cores ( 31   a    32   a ). At least one of the transmission elements ( 37 ) includes a connection area ( 37   b ) with a connecting element, which ( 32   b ) can be form-fittingly attached, interacting with, or being integrally connected to, the rotor side end of the core ( 32   a ) that is assigned with said at least one transmission elements ( 37 ).

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a United States National Phase Application of International Application PCT/EP2013/052900 filed Feb. 13, 2013 and claims the benefit of priority under 35 U.S.C. §119 of German Patent Applications DE 10 2012 103 465.6 filed Apr. 20, 2012 and DE 10 2012 111 204.5 filed Nov. 21, 2012, the entire contents of which are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to a rotor system for a bicycle for the bearing of a fork and for the transmission of actuations of Bowden cables each having a core, with at least a first and a second transmission element which are rotatable relative to one another and which are arranged in the area of the bearing of the fork. 
       BACKGROUND OF THE INVENTION 
       [0003]    From the DE 199 29 093 C2 a rotor system for a bicycle for bearing, rotatably by 360°, a fork and for the transmission of actuations of brake cables is known, with a rotor unit, arranged in the area of the bearing of the fork, which is movable on the whole relatively to the fork in axial direction and which comprises at least two transmission elements that are rotatable relative to one another, wherein the transmission elements at least in radial direction are surrounded by a housing. 
         [0004]    Another rotor system, which also makes possible a 360° turn of the fork, is known from WO 2012/005610 A2. A first Bowden control cable is guided from the handlebar into the fork steerer. At the end of its core a bar is fixed, which protrudes out of the fork steerer through fork steerer openings, where it is taken up by the first transmission element. The arrangement of the core of the second Bowden cable leading to the back wheel at the upper ring-shaped second transmission element is done by means of a fixture bent at a right angle screwed onto the transmission element, in whose radially outwards extending area, which is provided with a slotted receiving opening for introducing the core, the thickened end of the core is suspended. At the housing a comparable overturned brake arm is screwed, which with its area extending outwards in radial direction, that is formed according to the above mentioned fixture, adheres to the first fixture from the bottom and supports it. This kind of arrangement also corresponds to the technical realization of DE 199 29 093 C2, in which the arrangement of the cores of the Bowden mechanisms serving as brake cables is only illustrated schematically. 
         [0005]    In FR 571 408 a transmission mechanism is known, which uses bars and levers. In the stem a crank is mounted, at which a bar introduced into the fork steerer is articulated, which in the area of the lower end carries a bar that protrudes out of the fork steerer through fork steerer openings. A first transmission element sits on the bar. The second transmission element is formed bifurcated, with the shaft articulated at the transition from the head tube to the lower tube and resting with the fork peaks on the first transmission element. At the shaft of the second transmission element a Bowden control cable is fixed, which is guided further through the lower tube. The transmission elements do not form a unit, but perform different movements when a braking is executed. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention is based on an object of improving a rotor system of the abovementioned type. In particular, the Bowden cable arrangement is to be simplified and the total rotor system is to be more economical to produce. 
         [0007]    A bicycle, which is particularly designed as a BMX freestyle bicycle, comprises a rotor system according to the invention in order to avoid a twisting of the Bowden mechanisms serving as brake cables and in order to be able to actuate the rear wheel brake at any time. The bicycle, in particular when it is designed as a mountain bike, also can have a rotor system according to the invention for those Bowden cables, which serve as gear cables, in order to be able to operate the gear change at any time. 
         [0008]    The two transmission elements form the essential components of a rotor unit of the rotor system according to the invention. A first Bowden cable of the provided Bowden cables is guided from the handlebar to the rotor unit and is in operative connection with the first transmission element. With the second transmission element, another Bowden cable of the provided Bowden cables is in operative connection, which is guided from the rotor unit to the rear wheel of the bicycle, in particular to a rear wheel brake or to a gear change. The two transmission elements cooperate in axial direction in order to transmit the actuation of the Bowden cables (more precisely that of the first Bowden cable on the second Bowden cable). The fork steerer defines the axial direction. For the direct or indirect arrangement of the cores of the Bowden cables at the transmission elements, the latter each comprise connection areas. The term “indirect” is to indicate the use of a separately formed and detachably mounted intermediate element, the term “direct” the absence of such an intermediate element. The term “detachable” is to indicate a separation possibility without destruction. 
         [0009]    The connection area according to the invention in case of at least one of the transmission elements (preferably of the second transmission element) is arranged completely or almost completely inside the head tube (I. e. radially inside the head tube), thus does not protrude radially outwards, which facilitates the assembly. The fork steerer defines the radial direction. At this connection area a connecting element is form-fittingly attachable, the connecting element at least in axial direction directly interacting with the connection area. On the other hand, the connecting element cooperates with the rotor side end of the respective core (preferably of the second Bowden cable) detachably (and is formed separate from said end) or is connected in one piece with said end. This arrangement provides a simple, fast possibility of attaching the core at the transmission element. A tool, which hitherto was necessary for screwing the support of the end of the core, is no more necessary. Moreover, by the elimination of the screw, the number of parts can be reduced. Preferably, the connecting element at least partially embeds the rotor side end of the respective core. The end of the core can then be stretched (instead of forming a loop). In particular preferably the connecting element is molded directly at the core end, or cast onto it, or pressed onto it, or connected in one piece in another way, so that the number of parts can be further reduced. 
         [0010]    For the attachment at the connection area, the connecting element may have a jut (guiding), which interacts with a guide groove of the second transmission element extending parallelly to the axis of the fork steerer (i.e. in axial direction). This jut of the connecting element can be for example cuboid or dovetailed. Alternatively, the connecting element comprises two juts, which under elastic deformation engage like a clip in undercut areas of the transmission element in the connection area, in which for the engagement an elastic deformation of the connecting element is provided. By the clipping a simple assembly is possible. One of the two juts preferably extends parallelly to the fork steerer axis and, from a front part of the transmission element, engages into a corresponding opening. The second of the juts is preferably, but not necessarily, perpendicular to it and engages in radial direction into a corresponding opening or deepening of the transmission element. 
         [0011]    The two transmission elements have as basic form a cylinder ring, i.e. a sleeve, which allows a simple mounting. The two transmission elements can be arranged in alignment with each other (in axial direction in alignment with each other, i.e. axially one after the other) on the fork steerer, which requires the smallest radial installation space. However, they can also be concentric to one another (in radial direction concentric to one another, i.e. radially one inside another), i.e. the second transmission element—at least sectionally with respect to its axial extension—embeds the first transmission element (or vice versa), which allows a simple and defined mounting of the two transmission elements in relation to each other. The preferred mounting is a combination thereof, i.e. partially flush and partially concentric. For this purpose, the two transmission elements preferably comprise steps, by means of which they lie on top of each other. For all the mountings, there is a direct contact between the two transmission elements, preferably a sliding contact, for which purpose both transmission elements are preferably plastic injection molded parts. An intermediate ring, as it is used in the state of the art, can be omitted, so that the number of parts can be further reduced. With the same purpose preferably the connection area is formed one-piece on the second transmission element. 
         [0012]    Preferably, the core of the first Bowden cable is introduced from the handlebar into the fork steerer, which exploits the already present installation space and saves installation space between fork steerer and head tube, thus allowing a particularly slim embodiment of the head tube. For the attachment of the core of the first Bowden cable at the first transmission element, preferably a bar is provided, which is mounted on the core, in the mounted state for example lies on a nipple or similar at the end of the core, and for the assembly is preferably tiltable relatively to the core. The bar protrudes through oblong-hole-formed fork steerer openings in radial direction out of the fork steerer (beyond the outside extension of the fork steerer), so that the first transmission element, which is mounted outside on the fork steerer, can be connected with the bar, for example set or pressed on it. Accordingly, the bar is introduced with its ends in seats, in particular openings or grooves, in order to cooperate form-fittingly and if necessary in force-locking manner with the first transmission element. For a connection with a (small) force-locking contribution the bar may engage into the first transmission element, for which purpose the bar (or the transmission element) comprises suitable catch noses, for example frontally. 
         [0013]    The first Bowden cable with bar according to the invention and the second Bowden cable with connecting element according to the invention are preassembled components and can be sold separated from the bicycle or from the rotor unit as spare-parts or together with the rotor unit as kit of the rotor system. 
         [0014]    In order to guide the core of the second Bowden cable, which by means of the connecting element is applied at the connection area of the second transmission element, to the rear wheel, the head tube, which bears the fork by means of headsets, has a—preferably oblong-hole-formed—head tube opening, by which the connecting element from the outside can engage into the head tube for the connection area at the second transmission element. 
         [0015]    Preferably a third Bowden cable is provided, which is guided from the handlebar to the front wheel to a front brake. In order to guide, apart from the first Bowden cable, also this third Bowden cable through the fork steerer, the fixing device, which is provided for fastening the stem at the fork steerer, is modified accordingly. In the respective cap and the star grip nut placed in the fork steerer, or alternatively in the fixing screw to be screwed into the fork steerer, two openings or passages are provided, I. e. apart from the central passage known per se also an eccentric passage. Compared to an enlarged central passage, this conformation has the advantage that the seat of the star grip nut in the fork steerer is not weakened. The first Bowden cable, more precisely its core, is then introduced through the central passage, in order to catch if possible centrally at the bar. The third Bowden cable guided to the front brake is guided through the eccentric passage offset as to the known central passage. 
         [0016]    In the following, the invention is explained more in detail on the basis of several embodiments represented in the drawing. The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    In the drawings: 
           [0018]      FIG. 1  is a partially cut side view in the area of the bearing of the fork with a rotor unit according to a first embodiment; 
           [0019]      FIG. 2A  is a section view of transmission elements, connecting element and bar according to the first embodiment; 
           [0020]      FIG. 2B  is a perspective view of the construction group of  FIG. 2A  from the top; 
           [0021]      FIG. 2C  is a perspective view of the construction group of  FIG. 2A  from the bottom; 
           [0022]      FIG. 2D  is a first Bowden cable; 
           [0023]      FIG. 3A  is a perspective view of a bar; 
           [0024]      FIG. 3B  is a section view of the bar of  FIG. 3A ; 
           [0025]      FIG. 3C  is a perspective view of a modified bar; 
           [0026]      FIG. 3D  is a section view of the modified bar of  FIG. 3C ; 
           [0027]      FIG. 3E  is a side view of a bicycle according to the invention; 
           [0028]      FIG. 4A  is a schematic sectional view of the connecting element according to the first embodiment; 
           [0029]      FIG. 4B  is a schematic sectional view of the connecting element according to the second embodiment; 
           [0030]      FIG. 4C  is a schematic sectional view of a modified connecting element; 
           [0031]      FIG. 4D  is a perspective representation of the second transmission element with a connecting element according to  FIG. 4C ; 
           [0032]      FIG. 4E  is an exploded view corresponding to  FIG. 4D ; 
           [0033]      FIG. 4F  is a sectional view of  FIG. 4D ; 
           [0034]      FIG. 5A  is a perspective view in the area of the bearing of the fork with a rotor unit; 
           [0035]      FIG. 5B  is a section view of a fixing device of  FIG. 5A ; 
           [0036]      FIG. 5C  is a perspective view of a bearing cup; 
           [0037]      FIG. 6A  is a section view of an adjustment screw of the fixing device; 
           [0038]      FIG. 6B  is a perspective view of the adjustment screw of  FIG. 6A ; 
           [0039]      FIG. 6C  is a section view of a fixing screw of the fixing device; 
           [0040]      FIG. 6D  is a perspective view of the fixing screw of  FIG. 6C ; 
           [0041]      FIG. 6E  is a side view of a cap of the fixing device; 
           [0042]      FIG. 6F  is a top view of the cap of  FIG. 6E ; 
           [0043]      FIG. 6G  is a section view of a star grip nut of the fixing device along the line VI-VI in  FIG. 6H ; 
           [0044]      FIG. 6H  is a top view on the star grip nut of  FIG. 6G ; 
           [0045]      FIG. 7A  is a top view of a modified fixing device; 
           [0046]      FIG. 7B  is a perspective view of the fixing device of  FIG. 7A ; 
           [0047]      FIG. 7C  is a section view in the area of the bearing of the fork with a rotor unit according to a second embodiment; 
           [0048]      FIG. 8  is a section view in the area of the bearing of the fork with a rotor unit according to a third embodiment; and 
           [0049]      FIG. 9  is a section view in the area of the bearing of the fork with a rotor unit according to a modification of the third embodiment. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0050]    Referring to the drawings in particular, a bicycle  1  indicated as a whole with  1 , which is designed as a BMX freestyle bicycle, comprises a frame  3  that at its rear end bears the rear wheel  5  of the bicycle  1 . At the front end of the frame  3 , a fork  8  is rotatably beared. At its lower end, the fork  8  bears the front wheel  10  of the bicycle  1 . On a fork steerer  12  forming the upper end of the fork  8  a stem  14  is fixed. The stem  14  comprises a horizontally extending handlebar seat  16 , which embeds the handlebar  18  of the bicycle  1 . The fork steerer  12  with its circular cylindrical symmetry defines the directions used in the following. 
         [0051]    For bearing the fork  8 , the frame  3  has a generally circular cylindrical head tube  21  open on both faces, which is generally vertically oriented. The fork steerer  12  extending in axial direction is arranged, over a part of its length, inside the head tube  21  concentric with it. A lower headset  23  and a upper headset  25  consist of several components and can be twisted in themselves, each being mounted outside at the lower or upper end of the head tube  21  and inside on the fork  8  or its fork steerer  12 . 
         [0052]    A rotor unit  30  described more in detail in the following is arranged inside the head tube  21  between the upper headset  23  and the lower headset  21 . The rotor unit  30  is displaceable by sliding in axial direction on the fork steerer  12 . An upper, first Bowden cable  31  is guided from a brake lever, merely suggested in the drawing, at the handlebar  18  to the rotor unit  30 , from which a lower, second Bowden cable  32  is guided along the frame  3  to a rear wheel brake at the rear wheel  5  not represented in the drawing. Accordingly, the first Bowden cable  31  (i. e. its core  31   a ) comprises a handlebar side end and a rotor side end and the second Bowden cable  32  (i. e. its core  32   a ) a rotor side end and a brake side end. A third Bowden cable  33  is guided from a further brake lever at the handlebar  18  through the fork steerer  12  to a front brake at the front wheel  10  not represented in the drawing. The rotor unit  30  and further components for bearing or for power transmission, preferably the first Bowden cable  31  and/or the second Bowden cable  32 , and the headsets  23  and  25  if appropriate, define a rotor system. 
         [0053]    The rotor unit  30  comprises a first transmission element  36 , which is mounted rotatably and displaceably on the fork steerer  12 , and a second transmission element  37 . The first transmission element  36  comprises for its mounting on the fork steerer  12  an—at least approximately—ring-shaped area. Preferably, both transmission elements  36  and  37  are manufactured as injection molded parts in a resilient plastic material, in metal or in an appropriate compound material. The two transmission elements  36  and  37  are mounted rotatably relative to one another and arranged concentrically with the fork steerer  12 . With respect to a movement along the fork steerer  12 , the two transmission elements  36 ,  37  are coupled for entrainment: when the first transmission element  36  moves upwards along the fork steerer  12 , it entrains the second transmission element  37 , and when the second transmission element  37  moves upwards along the fork steerer  12 , it entrains the first transmission element  36 . 
         [0054]    The core  31   a  of the first Bowden cable  31  is at the rotor side in operative connection with the first transmission element  36 , whereas the core  32   a  of the second Bowden cable  32  is at the rotor side in operative connection with the second transmission element  37 . The sleeve of the second Bowden cable  32  is supported—at least indirectly—by the head tube  21 , whereas the core  32   a  of the second Bowden cable  32  with its rotor side end is directly connected to a connecting element  32   b.    
         [0055]    In the present case, the connecting element  32   b  is an injection molded part of metal, however also an appropriately resilient plastic material or another compound material can be used. Moreover, the connecting element  32   b  can also be produced in another way, for example milled from a metal or forged. Preferably, the connecting element  32   b  is directly firmly connected to the core  32   a  of the second Bowden cable  32 , in particular pressed with the rotor side end of the core  32   a , or molded to it or cast or connected in one piece in another way. Alternatively, the connecting element  32   b  is a separate component (I. e. not one-piece with the core  32   a ), in which the core  32   a  for example is clipped, suspended or otherwise form-fittingly introduced or with which the core  32   a  interacts detachably in another way. For example, a barrel-formed, ball-formed or conical thickened nipple, provided at the rotor side end of the core  32   a , can be suspended in the alternative connecting element  32   b , the connecting element  32   b  incorporating it for example with a (upwards open) funnel that preferably is laterally slotted. 
         [0056]    The connecting element  32   b  is (in all embodiments) directly form-fittingly attachable at a connection area  37   b  of the second transmission element  37 , in an aid-free way. For this purpose, the connecting element  32   b  is preferably hook-like and comprises a jut  32   c , with which the connecting element  32   b  engages from above into an axial guide groove (or another undercut partition) of the connection area  37   b . As shown in the drawing, the jut  32   c  can be cuboid or alternatively dovetailed and is introduced into an appropriately formed seat of the connection area  37   b . By appropriate choice of the fit, the jut  32   c  can be kept purely form-fittingly, where applicable by appropriate excess also additionally in a force-locking manner. The connection area  37   b  preferably protrudes radially outwards, in the fashion of an oriel, so that the hook-shaped connecting element  32   b  can be suspended without needing installation space radially inside the second transmission element  37 . The connection area  37   b  can be formed alternatively as a simple groove (without oriel). In both cases, however, the connection area  37   b  is still arranged (completely) inside the head tube  21 . Due to the stable tension load of the core  32   a , which is given by a not represented spring of the rear wheel brake, a detachment of the connection during operation can be safely prevented. In case of a repair, however, a very simple, tool-free detachment of the connection is possible. 
         [0057]    The connecting element  32   b  can be formed in various variants. For example, the suspension at the connection area  37   b  can be developed into a clipping, by providing apart from the jut  32   c  a further jut  32   d , which is formed nub-like at the lower end of the connecting element  32   b  and protrudes radially inwards. This further jut  32   d  penetrates in an appropriate deepening in the connection area  37   b , i.e. after an elastic deformation of the connecting element  32   b  the latter grasps the connection area  37   b  (at least partially form-fittingly), i.e. the connecting element  32   b  is secured like a clip on the second transmission element  37 . In the drawing, both juts  32   c  and  32   d  of the connecting element  32   b  working as clip are formed nub-like, they can however have any type of suitable form which allows a safe engagement and hold in case of a tensile load of the core  32   a.    
         [0058]    By means of the rotor system, a brake actuation (I. e. an actuation of the brake lever for the rear wheel brake) is transmitted from the handlebar  18  to the rear wheel  5 . The rotor unit  30  (with its both transmission elements  36  and  37  rotatable relative to one another) serves for power transmission from the first Bowden cable  31  to the second Bowden cable  32 . 
         [0059]    If the user of the bicycle  1  wants to perform a steering movement, he turns the fork  8  by means of the handlebar  18  and thus the front wheel  10 . In this turning movement the fork steerer  12  and the first transmission element  36  are entrained. The second transmission element  37  remains together with the second Bowden cable  32  in the position that it has occupied relatively to the head tube  21  attached to the frame. A shift of the rotor unit  41  along the fork steerer  12  does not occur or only imperceptibly. 
         [0060]    If the user of the bicycle  1  wants to brake with the rear wheel brake, he pulls, by means of the brake lever, the core  31   a  of the first Bowden cable  31  and with it the first transmission element  36 . Thus the rotor unit  41  is moved upwards along the fork steerer  12  so that also the second transmission element  37  is pulled upwards. The second transmission element  37  pulls the core  32   a  of the second Bowden cable  32 , by which the rear wheel brake is actuated. A braking with the front brake is done directly by means of the third Bowden cable  33 . 
         [0061]    Insofar, the embodiments are similar. There are differences in the mounting of the transmission elements  36  and  37  and the supply of the Bowden cables  31  and  32 . Equal components and components with the same effect have the same reference signs. 
         [0062]    In the first embodiment, the basic form of both transmission elements  36  and  37  is a cylinder ring (sleeve). The first transmission element  36  is mounted directly on the fork steerer  12  in a sliding way, preferably with small backlash. Due to the preferred formation in plastic material, a slidable coating can be dispensed with. The second transmission element  37  is mounted on the first transmission element  36 . For this purpose, the first transmission element  36  has a radial first step protruding inwards  36   a , on which the second transmission element  37  is placed by means of a suitable second step  37   a . The two transmission elements  36 ,  37  thus are arranged, on the one hand, in axial alignment with each other (due to the areas of the steps extending radially) and at the same time, on the other hand, radially one inside another, i.e. concentrically with each other (due to the axially extending areas of the steps). From the fork steerer  12 , the second transmission element  37  is radially distanced, i.e. the internal diameter of the second transmission element  37  is greater than the internal diameter of the first transmission element  36 . In axial direction, the two transmission elements  36  and  37  are held together by the prestressing in the Bowden cables, in particular of the rear wheel brake. 
         [0063]    The dimensions of the rotor unit  30  are selected in such a way that its axial length is greater than its diameter. The two headsets  23  and  25  each have a bearing cup  41  as the part (of normally three parts) that is to be connected to the head tube  21 . The funnel-shaped bearing cup  41  takes up a ball bearing with a large end, whereas with the other tapered end is pressed into the head tube  21  (or otherwise firmly attached to it). The internal diameter L41 of the tapered end of the bearing cup  41 , thus the internal diameter at the narrowest point of the bearing cup  41 , amounts to L41=36.0±0.2 mm, which is slightly larger than in known bearing cups. In this way, the rotor unit  30  can be introduced into the head tube  21  (or if necessary removed from it), even if the bearing cups  41  of the headsets  23  and  25  are already in the head tube  21 . The external diameter of the large end of the bearing cup  41 , thus the external diameter at the largest point, amounts to 45.0 mm, which corresponds to that of known bearing cups. The wall thickness of the bearing cup  41  is generally 1.5 mm. Head tube  21  with integrated bearing cups  41  can also be used. The inner diameter of such a head tube  21  is preferably 36.5±0.2 mm. 
         [0064]    For the connection of the first transmission element  36  with the first Bowden cable  31 , a bar  42  is provided having an oblong form similar to a bolt and a cross-section that is definite as possible (i.e. not circular). In the present case, the cross-section corresponds to a rectangle with strongly rounded corners. On the first transmission element  36  on the radially inwardly facing side, two grooves are formed  36   b , which face each other radially, extend over a part of the axial length of the second transmission element  36 , and are accessible from the bottom. By means of these grooves  36   b , the second transmission element  36  can receive the bar  42 , which then extends in radial direction. Instead of the grooves  36   b , other openings/seats may be provided, for example holes. Preferably, the bar  42  at each of its ends comprises a catch  42   a , which, when introducing the bar  42  into the first transmission element  36 , dig (engage) into the ground of the grooves  36   b , so that the first transmission element  36  and the engaged bar  42  are connected to each other. Preferably, each groove  36   b  comprises a small cavity, which receives the assigned catch  42   a  for improving the engaging. On its upper side at both ends, the bar  42  can have a step so that it abuts at the end of the grooves  36   b  and slightly protrudes into the groove-free area of the first transmission element  31 . 
         [0065]    The bar  42  penetrates the fork steerer  12  at two fork steerer openings  12   a  radially opposite to each other, i.e. its length is greater than the external diameter of the fork steerer  12 , and it protrudes in radial direction beyond the outer circumference of the fork steerer  12 . The fork steerer openings  12   a  are designed as oblong holes, so that the bar  42  with the first transmission element  36 , on the one hand, occupies a defined position in circumferential direction and follows a steering movement of the fork  8 , and, on the other hand, does not obstruct a movement of the rotor unit  30  along the fork steerer  12  during a braking. 
         [0066]    The bar  42  is mounted on the core  31   a  of the first Bowden cable  31  between the end of the core and the sleeve of the first Bowden cable  31 . For this purpose, the bar  42  centrally has a channel for the passage of the core  31   a  of the first Bowden cable  31  and on the bottom a deepening for—preferably form-fitting—insertion of a nipple  31   b  at the end of the core  31   a  (or of an otherwise thickened end of the core  31   a ) of the first Bowden cable  31 . On this nipple  31   b  the bar  42  is seated in the mounted state. Although the bar  42  and the core  31   a  of the first Bowden cable  31  are oriented orthogonally towards each other in the mounted state, the bar  42  is preferably tiltable relatively to the core  31   a —for facilitating the assembly. For this purpose, the bar  42  comprises tilts that are oriented towards the channel, and during installation allow a tilting of the bar  42  relatively to the core  31   a  of the first Bowden cable  31 . These tilts can be formed symmetric or unilateral and on the upper side and/or on the bottom of the bar  42 . The drawing shows such alternatives. 
         [0067]    The internal diameter of the head tube  21  is slightly greater than the external diameter of the transmission elements  36  and  37 , so that in the head tube  21 , a head tube opening  21   a  is provided, through which the connecting element  32   b  protrudes. More precisely, the second Bowden cable  32  is guided on the outer side of the head tube  21  up to the head tube opening  21   a , through which the connecting element  32   b  protrudes and is connected with the second transmission element  37  inside the head tube  21 . 
         [0068]    The head tube opening  21   a  is designed as an oblong hole, so that the connecting element  32   b  with the second transmission element  37 , on the one hand, occupies a defined position in circumferential direction and remains fixed during a steering movement of the fork  8 , and, on the other hand, does not obstruct a movement of the rotor unit  30  along of the fork steerer  12  during a braking. 
         [0069]    The sleeve of the second Bowden cable  32  is supported on the head tube  21  preferably in the area of the head tube opening  21   a . For the support at the outside of the head tube  21  an appropriate stopper  21   c  can be applied, for example by means of screwing, as for example disclosed in  FIG. 4A  the WO 2012/005610 A2, or by welding. This stopper  21   c  can be positioned in such a way that, at the same time, it also forms a stopper for the connecting element  32   b  in the lowest position of the connecting element  32   b . Alternatively, the core  32   a  of the second Bowden cable  32  can also be deflected, so that the stopper for example may also be provided inside a tube (of the frame  3 ), within which the second Bowden cable  32  runs. If appropriate, the tube inlet, through which the core  32   a  is introduced into the tube guiding to the rotor unit  30 , can form the stopper itself, i.e. the core  32   a  runs over a long distance freely inside the corresponding (frame) tube. With an appropriate prestressing in all working conditions, the stopper can also be mounted at the housing like the connecting element, e. g. at the head tube  21 , or frame  3  of the bicycle  1 , i.e. in particular applied form-fittingly on it rather than screwed. 
         [0070]    For fastening the stem  14  at the fork steerer  12 , a fixing device  50  is provided. The stem  14  is pushed on the fork steerer  12  until it—if necessary interposing a ring—is seated on the upper headset  23 . The multi-component fixing device  50  comprises, as a part, a star grip nut  52 , which is arranged at the upper end of the fork steerer  12  inside it. The star grip nut  52  comprises a hollow-cylindrical base body with an internal thread  52   a  and (in the present case each time six) radially distanced star grip nut arms  52   b  at both ends (on top and at the bottom). he star grip nut  52  is hammered into the fork steerer  12  so that it is firmly connected to it. The star grip nut internal thread  52   a , being concentric with the fork steerer  12 , defines a central star grip nut passage  52   c . Unlike known star grip nuts, the present star grip nut  52  comprises an eccentric star grip nut passage  52   d  on top and at the bottom between two adjacent arms  52 . 
         [0071]    As further part of the fixing device  50 , a cap  54  is provided, which has the form of a plate and is put at the top of the stem  14 . A centrally arranged centric cap opening  54   c  of the cap  54  aligns with the central star grip nut passage  52   c , whereas an eccentric cap opening  52   d  aligns with the eccentric star grip nut passage  52   d.    
         [0072]    A fixing screw  56  as third part of the fixing device  50  has a fixing screw external thread  56   a , a fixing screw internal thread  56   b , a fixing screw longitudinal groove  56   c  and, at the upper end, a fixing screw head  56   d , in the present case designed as a polygon. The hollow fixing screw  56  is screwed through the cap  54  at the cap opening  54   c  into the star grip nut  52 , i.e. with the fixing screws external thread  56   a  into the star grip nut internal thread  52   a . In this way the fixing screw  56  tenses the stem  14  against the upper headset  23 . 
         [0073]    As fourth part of the fixing device  50  an adjustment screw  58  is provided. The hollow adjustment screw  58  has an adjustment screw external thread  58   b , an adjustment screw longitudinal groove  58   c , and an—in the present case corrugated—adjustment screw head  58   d . The adjustment screw  58  is screwed into the fixing screw  56 , i.e. with the adjustment screw external thread  58   b  into the fixing screw internal thread  56   b . Adjustment screw  58 , fixing screw  56  and star grip nut  52  are thus concentric with each other and arranged towards the fork steerer  12 . 
         [0074]    The first Bowden cable  31  is guided from the handlebar  18  to the fixing device  50 , where its sleeve is supported by the adjustment screw  58 , whereas its core  31  is guided through the hollow adjustment screw  58 —and thus also through the hollow fixing screw  56 , the centric cap opening  54   c  and the central star grip nut passage  52   c -into the fork steerer  12  up to the bar  42 . The relative position of adjustment screw  58  and fixing screw  56  generates a tension in the first Bowden cable  31 . In order to introduce the core  31   a  also with nipples at both ends into the hollow screws  56  and  58 , the adjustment screw longitudinal slot  58   c  and the fixing screw slot  56   c  are provided, through which the core  31   a  of the first Bowden cable  31  can be introduced laterally into the screws  58  and  56 . Useful care is taken to ensure that, in case of mounted fixing device  50 , the longitudinal slots  56   c  and  58   c  are not congruent, in order to prevent an excessive lateral buckling of the core  31   a.    
         [0075]    The third Bowden cable  33 , which is centrally guided instead of the first Bowden cable  31  in known fixing devices, is eccentrically guided in the present fixing device. I.e., the third Bowden cable  33  is guided through the eccentric cap opening  54   d  and the eccentric star grip nut passage  52   d  into the fork steerer  12  up to the front brake. 
         [0076]    A modified fixing device  50  consists of the adjustment screw  58  and of a modified fixing screw  56 ′. The modified fixing screw  56 ′ comprises a larger diameter and is screwed by means of its external thread directly into the fork steerer, in which for this purpose an internal thread was cut. The modified fixing screw  56 ′ comprises a fixing screw internal thread  56   b , in which the hollow adjustment screw  58  is screwed. The guiding of the core  31   a  of the first Bowden cable  31  is done as described before. The third Bowden cable  33  is guided through an eccentric passage (in the present case with a kidney-shaped cross-section) into the fork steerer  12 . 
         [0077]    For the assembly of the fork  8 , in a first step, the star grip nut  52  is hammered into the fork steerer  12 . In a second step, the first Bowden cable  31  (with bar  42 ) is pushed upwards from the bottom through the fork steerer  12  and through the star grip nut  42 , while the bar  42  is tilted relatively to the core  31   a  of the first Bowden cable  31  when it arrives in the fork steerer  12 . In a third step, the bar  42  (simultaneously tilting back relatively to the core  31   a ) is put with its ends through the fork steerer openings  12   a  so that the bar  42  is in the correct position. In a fourth step, the rotor unit  30  is pushed from above onto the fork steerer  12 , until the bar  42  is engaged in the first transmission element  36 . The preassembled unit obtained in this way is then, during installation of the whole bicycle  1 , in a fifth step, pushed into the head tube  21 . In a sixth step, the stem  14  is set up and the fixing device  50  completed, i.e. by tightening the fixing screw  56 , the fork  8  is fixed (clamped). In a seventh step, the second Bowden cable  32  with the connecting element  32   b  is fixed at the connection area of the second transmission element  37 , for which purpose the connecting element  32   b  is introduced through the head tube opening  21 , and suspended (and/or clipped) in the way described above. 
         [0078]    The fixing device  50  according to the invention is particularly conceived for forks  8  whose fork steerer  12  finishes with a diameter of 1⅛″ (28.6 mm). However, forks are also known whose fork steerer finishes with a diameter of 1″ (25.4 mm) and can have a thread outside. The fixing device known for this purpose, which also could be used in the present case alternatively to the fixing device  50 , consists of a steerer stem which is thickened at its upper end so that the stem  14  can be pressed or clamped onto the steerer stem (I. e. on its top). At its lower end, the steerer stem is slanted (as a cylinder cut). The steerer stem is penetrated along its length by an adjustment screw, which extends centrally in axial direction and is accessible from the top. By means of this adjustment screw, the two sections of the steerer stem are displaceable in relation to each other, i.e. along the tilted cut surface. Introduced into the fork steerer  12 , the two sections of the steerer stem can be supported by the inner wall of the fork steerer  12  and be clamped mutually. In this way, the stem  14  is fixed at the fork steerer  12 . The optionally present thread outside on the fork steerer  12  serves to bias, by means of a union nut, the upper headset  25  in axial direction and to keep together its components. In order to be able to introduce also the third Bowden cable  33  into the fork steerer  12 , the steerer stem preferably comprises an additional opening, for example besides the head of the adjustment screw. 
         [0079]    The second embodiment ( FIG. 7C ) coincides with the first embodiment, unless otherwise described in the following. Here too, the core  31   a  of the first Bowden cable  31  extends inside the fork steerer  12 ; the introduction into the fork steerer  12  can occur at any location, in principle, for example through the stem or directly from the brake levers at the handlebar, preferably with the above described fixing device  50  (or the alternative, known fixing device). At the end of the core  31   a , in the present case, a bar  42  in plastic material is molded in one piece. In the present case, the production of the corresponding Bowden cable is done by introducing the core into the sleeve, afterwards at one end the bar  42  and at the other end (not shown) a nipple are molded for the brake lever, so that the core  31   a  can no longer be removed from the sleeve without destruction of the bar  42  or of the nipple, which has great advantages with regard to production. However, bar  42  and core  31   a  can also be separately formed—as in the first embodiment —, i.e. the core  31   a  can be introduced, for example, into an opening provided in the bar  42  and be clamped with it. 
         [0080]    The sleeve-shaped first transmission element  36  is displaceable in axial direction on the fork steerer  12 . The ends of the bar  42  protrude through oblong-hole-shaped fork steerer openings  12   a  in radial direction something beyond the outer circumference of the fork steerer  12  and are incorporated in downwards open slots of the first transmission element  36 . Two downwards open slots facilitate the assembly. In principle, however, a slot or oblong hole is also possible in connection with an opening adapted to the form of the bar  42  on the opposite side or two openings adapted to the form of the bar  42 . When the bar  42  is at the lower end of the fork steerer opening  12   a , the free area above the upper side of the bar  42  and the upper end of the fork steerer opening  12   a  has a length L36. 
         [0081]    With the first transmission element  36 , the second transmission element  37  cooperates, which in the present case is formed by a displaceable ring placed directly on the fork steerer  12  above the first transmission element  36  with the connection area  37   b . The connection area  37   b  and the connecting element  32   b  are formed as described above. 
         [0082]    In the present case, the connecting element  32   b  protrudes through a head tube opening  21   a  towards outside the head tube  21 , i.e. the core  32   a  of the second Bowden cable  32   a  in the present case also extends outside the head tube  21 . The head tube opening  21   a  is, in the present case, oblong-hole-shaped, and in the non-operated state of the Bowden cables  31 ,  32  the distance between the upper side of the connecting element  32   b  inside the head tube opening  21   a  and the upper end of the head tube opening  21   a , thus the free area in the head tube opening  21   a , is designated with L37. As to the aforementioned length L36, in the present case L37 is maximally equal ample (preferably slightly greater than L36), i.e. the fork steerer opening  12   a  serves as safety limit for the maximum shift of the transmission elements  36 ,  37 , so that the connecting element  32   a  is not damaged by forces from the top. On the other hand, in case of a definition of L44 equal L55, it can be ensured additionally that in the case of a design of the connecting element  32   b  with a jut  32   c  to be introduced into a seat of the connection area  37   b , the connecting element  32   b  is completely introduced. The different or same lengths L44 and L55 can be realized also in the first embodiment similarly and with equal function. The support of the sleeve of the second Bowden cable  32  is done as in the first embodiment. 
         [0083]    In the third embodiment ( FIG. 8 ) the rotor unit  30  and the first Bowden cable  31  are arranged completely outside of the fork steerer  12 , in a similar manner to how it is already disclosed in DE 199 29 093 C2. 
         [0084]    The first transmission element  36  generally consists of a sleeve that, with small backlash, embeds the fork steerer  12 , and whose top is one-piece with a ring-shaped flange extending outwards. By means of a sliding bearing, the first transmission element  36  embedding the fork steerer  12  is mounted smoothly on the fork steerer  12  which, in the present case, consists of polished steel. The first transmission element  36  is, in the present case, injection molded in plastic material. At the lower end of the sleeve, a groove is formed, in which a holding element  84  is incorporated in the form of an elastic ring. Above the holding element  84 , a washer  86  is placed. 
         [0085]    Between the flange of the first transmission element  36  and the washer  86 , the second transmission element  37  is arranged on the sleeve. The second transmission element  37  generally consists of a ring, which also is injection molded in plastic material. The sleeve in this area has a continuous cylinder-shaped smooth outside so that the ring is easily rotatable relatively to the sleeve. The second transmission element  37  at its upper edge in the present case on one side comprises the connection area  37   b . In axial direction, the second transmission element  55  together with the other parts of the rotor unit  30  is arranged in a displaceable way on the fork steerer  12 , however immovably as to the first transmission element  36  due to prestressing of the Bowden cables  31 ,  32 . For the two transmission elements  36 ,  37 , the head tube  21  forms a housing, which offers protection in radial direction (with respect to the turn of the transmission elements  36 ,  37 ). As shown in the drawing, the head tube  21  forms a part of the frame  3 . 
         [0086]    The sleeve of the first Bowden cable  31  is fixed by means of a threaded joint at the stem  14  on its upper side, whereas the core  31   a  of the first Bowden cable  31  is guided through a vertical hole of the stem  14  on its bottom. Through an opening in the upper headset  25 , the core  31   a  is guided into the interior of the head tube  21  and connected with the flange of the first transmission element  36 , in the present case directly suspended in a slot in the flange. The flange corresponds in its transfer function to the above described bar  42 . The connecting area is accessible from the outside preferably through a, for example, oval head tube opening  21   a  in the head tube  21 . The head tube opening  21   a  is covered preferably by a (not represented) cap. The head tube opening  21   a  also can be formed differently, moreover it does not have to be arranged necessarily in the front, at the control ear  21 , but for example also laterally. 
         [0087]    The second Bowden cable  32  is supported with its sleeve by the head tube  21  or in the present case by an adapter piece between lower headset  23  and head tube  21 , whereas the core  32   a  of the second Bowden cable  32  is guided through an opening in the lower headset  23  or in said adapter piece into the interior of the head tube  21 . As described above, the core  32   a  of the second Bowden cable is connected by means of a connecting element  32   b  with a connection area  37   b  of the second transmission element  37 . For a simple assembly of the connection element  32   b  and the core  32   a  of the second Bowden cable  32 , the head tube opening  21   a  can be far greater and extend on one side laterally over the head tube  21 . However also a second opening at a suitable location can be provided. 
         [0088]    The third Bowden cable  33  for the front brake is pulled through a channel not represented in the drawing in the hollow fork steerer  12 . If with only one brake lever the rear wheel brake and the front brake are to be actuated at the same time, at the rotor unit  30  in an appropriate way (i. e. by means of a further connecting element and of a connection area) the core of the third Bowden cable  33  can be fixed, which can be guided through the lower headset  23  to the front brake. The fastenings of the two second cores take place in the present case preferably displaced by 180° to each other. Obviously it is also possible to provide brake levers on either side of the handlebar, the function of the brakes being identical. In the present case, two cores are applied at the flange of the first transmission element  36 . 
         [0089]    According to a modification ( FIG. 9 ) of the third embodiment, the core  31   a  of the first Bowden cable  31  is also connected with the first transmission element  36  by means of a connecting element, which is formed for example like the connecting element  32   b  or its variants, and a connection area, which is suitably formed and with which the connecting element is connected. The first transmission element  36  comprises said connection area at its upper edge. Due to the prestressing of the core  31   a  of the first Bowden cable  31 , both the core end in the connecting element (in case of a separate formation) and the connecting element in the connection area are engaged against gravity. 
         [0090]    For reasons of precaution, it is pointed out that—for example when using two different Bowden cables for rear wheel brake and gear change—also a combination of two of the abovementioned rotor units (or a combination with a rotor unit arranged outside of the head tube  21 ) is possible, which are arranged axially one upon another. The combination of the rotor unit  30  of the third embodiment or its modification, which is arranged in the head tube  21  on top, with a rotor unit  30  of the first or second embodiment, which is arranged in the head tube  21  at the bottom, is preferred. Since the first Bowden cable  31  is guided to the lower rotor unit  30  inside the fork steerer  12  and that to the upper rotor unit  30  outside of the fork steerer  12 , and since the two second Bowden cables  32  can be arranged at different places of the head tube  21 , the two rotor units  30  do not obstruct each other in case of a rotation movement of the fork  8 . 
         [0091]    While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.