Patent Publication Number: US-6216553-B1

Title: Selector for a bicycle gear mechanism

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to selectors for actuating bicycle gear mechanisms including hub gears or derailleur gears. 
     2. Description of the Related Art 
     EP-0 686 552 A2 discloses a rotatable grip for actuating bicycle gear shifts, in which the conversion of the rotational movement of the grip into a longitudinal movement of a control means is carried out in such a way that the control means is fastened to the grip, deflected in a helical manner about the bicycle handlebar or a sleeve encasing the handlebar, and guided in a longitudinal guide that is stationary in relation to the bicycle handlebar, at a sufficiently great distance, in the rotational direction of the grip, from the fastening of the control means to the grip. This means that the travel of the fastening point of the control means that is covered when the grip is rotated along a circular path is considerably greater than the travel of the control means in its longitudinal guide. The result is thus favorable conversion of wide angles of rotation at the grip into small longitudinal movements of the control means. The grip is fixed in the positions for the respective gear stages of the bicycle gear shift by a detent so that it is possible to vary the holding force and the necessary actuating force of the detent. 
     The above-mentioned rotary shift grip has a detent which must be oriented to the predefinitions in the respective gear mechanism of the bicycle. This condition leads to the situation in which different shift travels may result in the various gears, and individual gears may lie closer together and other gears may lie further apart from one another. Where the gears lie closely adjacent one another, shift stages may be skipped inadvertently if the rider does not pay close attention to shifting. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide an ergonomic selector which is easy to use and simple to manufacture. 
     Another object of the present invention is to provide a selector having approximately equally large shift travels, whose angles of rotation have a specific magnitude. 
     Still another object of the invention is to provide a selector having a mechanism which, on the one hand, permits correction of the total shift travel and/or the individual shift travels for the gear stages, while on the other hand, permits overshift travels of any magnitude for the individual gear stages. 
     In a presently preferred embodiment of the present invention, the selector not only produces approximately identical shifting steps, but it is also possible for the total shift travel to be varied if the pulling-in of the cable which is produced by winding the control cable onto the drum does not correspond to ergonomic requirements. It is therefore possible to achieve a step-up or step-down between the pull-in of the cable, on the one hand, and the movement of the actuating elements, on the other. 
     That is not the whole story, however: the design of the selector proposed in the present invention also permits an overshift travel to be produced for each gear stage or for all gear stages, which is particularly desired when shifting the chain from a respectively smaller to a larger sprocket. This means that, during shifting, the derailleur is briefly shifted somewhat further than necessary, in order to make it easier for the chain to “climb” upward. The proposed selector permits an individual overshift travel for each gear stage, if this is necessary, and permits operation which fixes the respective position of the gear stages without a reverse rotational movement of the actuating elements. 
     Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings, wherein like reference characters denote similar elements throughout the several views: 
     FIG. 1 is an exploded view of an embodiment of a selector constructed in accordance with the present invention; 
     FIG. 2 illustrates a correction cam in cooperation with a pivoting lever of the embodiment of FIG. 1; 
     FIG. 3 schematically depicts another embodiment of the selector having a stationary cam and a correction cam; 
     FIG. 4 shows another embodiment of the selector having a rotatable drum and a correction cam engageable in the axial direction; 
     FIG. 5 shows another embodiment of the selector having a pivoting lever for varying the position of a cable inlet with respect to the rotatable drum; 
     FIG. 6 graphically illustrates the profile of the resulting cable travel versus the angle of rotation; and 
     FIG. 7 shows the design of a correction cam with protrusions in order to achieve an overshift travel for each shift stage. 
    
    
     DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS 
     Referring now to the drawings, FIGS. 1 and 2 illustrate an embodiment of a selector constructed in accordance with the present invention. In this embodiment, the selector is configured as a rotary grip selector. The selector comprises a housing  1  and a guide tube  2  for mounting a rotary bushing  10 . The selector can be fastened to one end of the handlebar of the bicycle with a clamp  3 . In order to guide a control cable  16  from a control cable jacket  46  into the housing  1 , a cable inlet  4  for passing a cable into the selector is arranged at that part of the housing which is most remote from the handlebar. As illustrated, a bearing member  5  is dimensioned to connect substantially coaxially with the cable inlet  4  at one end and a bearing end  19  of a pivoting lever  15  at another end so as to pivotally support the pivoting lever  15 . A spring  6  has a hook portion  7  configured to engage and cooperate, at a joint location  9  in the housing  1 , with shift detents  12  in a rotary element  11 , while a dome portion  8  of the spring  6  is maintained under prestress. The rotary element  11  is connected to the rotary bushing  10  which, for its part, has a correction cam  13  which cooperates with a pivoting cam  17  arranged on the pivoting lever  15 . The pivoting lever  15  has a first cable deflection radius  18 , which at the end of the pivoting lever  15  curves toward a rotatable drum  14  so that the control cable  16 , which is guided along a depression or groove defined in the pivoting lever  15 , is led tangentially toward the circumferential wall of the drum  14 . The pivoting lever  15  also has a second cable deflection radius  20  deflects the depression in the pivoting lever  15  toward the bearing member  5  or toward the cable inlet  4  so that the control cable  16 , after exiting the control cable jacket  46 , receives practically complete guidance toward the drum  14  within the housing  1 . 
     The operation of the selector will be described with reference to a rotary grip selector. When a bicycle rider rotates the rotary bushing  10  to shift gear, the rotary element  11  together with the shift detents  12  rotates with the rotary bushing  10  past the dome portion  8  of the spring  6 , so that the drum  14  connected to the rotary element  10  can wind or unwind the control cable  16 . In this manner, the bicycle rider can clearly feel the shift detents  12  sliding past the dome portion  8  of the spring  6 . The control cable  16  runs along the depression in the pivoting lever  15 , concentrically through the bearing end  19  and the cable inlet  4 , and into the control cable jacket  46 . The control cable  16  is connected by way of the other end to the gear mechanism of the bicycle, where a tension spring provides appropriate tension to the control cable  16 . 
     In order to achieve substantially identical angles of rotation  51  for each gear stage, it is proposed to superimpose on the travel of the control cable  16  for shifting from one gear stage to another a correction travel, by means of operative cooperation between the correction cam  13  and the pivoting cam  17  of the pivoting lever  15 . In particular, the pivoting lever  15  is pivoted about the bearing point  5 , which in turn changes the distance of the first cable deflection radius  18  relative to the drum  14 . The shape of the correction cam  13  is selected so as to ensure that the travel of the control cable  16  for each gear stage has a correction or overshift travel (either an increase or a decrease from the travel required for gear shifting) while providing substantially identical or equal angles of rotation  51  for each gear stage. Also advantageous is the possibility of achieving larger angles of rotation  51  than is normally possible with the diameter of the drum  14 . This means that, over the entire or a portion of the gear-shifting range, a step-up or a step-down can be achieved. 
     The design of a selector with the superimposition of a correction travel by means of a correction cam  13  is not restricted to the embodiment of FIG.  1 . Indeed, there are other embodiments which comprises a correction cam for adding or superimposing correction travel to the travel of the control cable  16 . 
     For example, FIG. 3 depicts another embodiment of a selector comprising a drum  23  rotatably connected to a rotary bushing  22 , and a correction cam  27  rotationally fixedly connected to the drum  23 . The correction cam  27  cooperates with a cam  28  attached to the housing  21 . The drum  23  can be carried along by a lever  25  and a driver  26  which engages a slot guide  24  in the drum  23 . When the rotary bushing  22  is rotated, in addition to the travel of the control cable  16 , a correction travel is produced by the drum  23  as the central axis of the drum is displaced relative to a cable inlet  38  at the housing  21  and the rotary bushing  22 , in a direction opposite to the pulling direction of the control cable  16 . 
     FIG. 4 illustrates another embodiment of the inventive selector. As shown, the selector has a drum  30  and a pivoting lever  31  whose bearing point  33  has a pivot axis  34  extending substantially perpendicular to the central axis of the drum  30 . The pivoting lever  31  has a pivoting cam  35  configured to engage a correction cam  36  and acts in the axial direction of the drum  30 . The correction cam  36 , like the drum  30 , is connected to a rotary bushing (not illustrated here) and, when actuated, has the effect that that end of the pivoting lever  31  which is located opposite the pivoting cam  35 , together with its deflection curve  32 , is pivoted. In this manner, a correction travel with respect to a cable inlet  39  is superimposed on the travel of the control cable  16 . 
     FIG. 5 illustrates still another embodiment of the inventive selector. As depicted, the selector has a rotary bushing  40  and a drum  41  connected to the rotary bushing  40 . A correction cam  42  is arranged on either the drum  41  or the rotary bushing  40  and oriented for engagement in the radial direction of the drum  41  or rotary bushing  40  and cooperates with a cam  44  attached to or forming an integral portion of a pivoting lever  43 . One end of the pivoting lever  43  is pivotably mounted at a pivot point  47  connected to a housing (not illustrated here). The other end of the pivoting lever  43  opposite the pivot point  47  rests against a cable inlet  45 . The correction travel for the control cable  16  is thus brought about by movement of the cable inlet  45  as imparted by the pivoting lever  43 . 
     FIG. 6 graphically illustrates the total or resultant travel  50  of the control cable  16  versus the angle of rotation α. Preferably, as illustrated, the result of the above-mentioned superimposition of the correction travel is a curve which approximately approaches a straight line. This curve has a toothed profile at each gear stage. The overshift travel is noted as  52 . It is thus possible for each of the angles of rotation  51  to be approximately equal to each other for each gear stage. 
     It is contemplated that the profile need not be linear between individual gear stages. It is also contemplated that the magnitude of the overshift travel  52  may depend on the torque requirements on the selector and can, as already described above, also be of different magnitude from one gear stage to another gear stage. 
     FIG. 7 is a partially sectioned view of another embodiment of a correction cam  13  having a plurality of radially outwardly extending projections or protrusions  29  in order to achieve the aforementional overshift travel automatically for individual shift stages. Each projection  29  preferably corresponds to a transition point between a first shift stage and a second shift stage. The projection  29  is shaped such that as a cooperating cam travels over the projection, an additional portion of the control cable is pulled directly into the housing  1  so as to produce the correction travel and is then released. The projection  29  may have a different shape, depending on the requirements of the bicycle gear mechanism for the correction travel. 
     Thus, while there have shown and described and pointed out fundamental novel features of the invention as applied to preferred embodiments thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.