Abstract:
A device for guiding and supporting the cable for actuating a front derailleur for bicycles. The device provides the cable guide parts with alternative cable routing paths, wherein the cable guide parts are securely connected to the connecting arm. The cable clamping screw for clamping the control cable is housed in a space saving manner in an opening in the cable guide part, wherein a direct transfer of the actuating forces to the connecting arm is possible with small frictional losses.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a device for guiding and supporting the cable for actuating a front derailleur for bicycles. 
     Front derailleurs on bicycles serve the purpose of moving the drive chain between various chain wheels mounted on the pedal crank. These front derailleurs have a stationary part, a parallelogram mechanism, and a moveable part. The stationary part is connected to the bicycle frame, and a chain guide for interacting with the chain is mounted on the moveable part. In order to mount on the bicycle frame, the stationary part has a fastening clamp, of which the size also varies as a function of the diameter of the seat tube. To some extent the seat tube exhibits an oval cross section. In this case the stationary part is screwed to a soldered-on part that is attached to the seat tube; or a flexible clamp is used. The chain guide is adapted to the ratio of the number of teeth and/or the ratio of the diameters of the chain wheels. Racing bikes have typically two chain wheels, whereas mountain bikes have three chain wheels. The chain guide has suitably designed guide parts in the regions, in which contact with the chain occurs when changing gears. The seat tube on the bicycle has various angular positions in relation to the chain stay, a feature that has an additional impact on the design of the chain guide. 
     There exist a plethora of other embodiments of derailleurs as a function of whether the actuating cable is run either towards the bottom around the pedal bearing housing or towards the top following the seat tube. Finally, the derailleurs may be alternatively actuated from the retracted position into the extended position either by actuating the cable control device or by the force of the return spring. 
     The available design space, in which a derailleur can be housed, consists of the free space inside the chain wheels, outside the seat tube and above the pedal bearing housing as well as to a limited degree between the rear wheel tire and/or the mud guard and the seat tube. In this case a mountain bike has significantly more free space between the seat tube and the tire than a racing bike, where there is the tendency to push the rear wheel as far as possible in the direction of the pedal bearing, as a result of which the rear wheel tire comes very close to the seat tube. 
     EP 0 653 347 shows a derailleur that has a pronounced cable guide region on the inner tensioning arm. Hence, the tensioning arm is significantly enlarged and more expensive to manufacture. As a result of the one-piece connection between the originally rod shaped arm and the cable guide, there is no longer any disturbing resilience that could result in a loss in the actuating path of the cable control device. 
     EP 1 040 992 shows a removable cable guide adapter that, in addition to the advantages of a cable guide, also makes it possible to adapt the derailleur to various conditions with respect to actuating the cable. The drawback with this design is that all of the deformations at the adapter have a direct impact on the cable actuation system. In any case it has to be guaranteed that after the adapter is mounted on the actuating arm, said adapter is securely connected to this actuating arm; and it must be achieved without incurring a high cost in terms of construction. 
     SUMMARY OF THE INVENTION 
     In accordance with an embodiment of the invention, an aspect of the invention is to provide a cable guide that is connected to the tensioning arm and that does not exhibit any of the aforementioned drawbacks. This is achieved by the fact that the tensioning arm and the cable guide are connected together in a secure manner. The cable guide is constructed in conformity with the requirements. It has guide means that guarantee a reliable guide and support of the actuating cable, both for running the cable to the top and also towards the bottom. In addition, the cable guide is space saving and the losses in actuating force as a result of friction are low. In addition, a clamping projection on the connecting arm is passed through an opening on the cable guide, as a result of which the forces generated during the actuation operation engage close to the plane in which the cable guide extends. Furthermore, the cable clamping screw is screwed in by means of the cable guide, as a result of which the elements for clamping the cable are positioned on one side of the cable guide, whereas the screw head of the clamping screw is situated on the opposite side of the cable guide. The cable clamping screw is oriented to provide easy access to the screw head with the tool. This feature is in the interest of the bike rider who can install and align the derailleur in a simple way. The situation is similar when a bike manufacture does the installation. 
     In this approach to a solution the connecting arm does not have to exist in a larger number of design variants. The adaptation to different installation conditions is performed by combining a connecting arm with various cable guides and then using this combination to install the complete derailleur. 
     These as well as other aspects and advantages of the invention will become further apparent to those of ordinary skill in the art by reading the following detailed description, with reference where appropriate to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG. 1  shows a front derailleur that is intended for a bicycle and that uses the cable control actuating device according to an embodiment of the invention, wherein the control cable is run toward the bottom; 
         FIG. 2  shows a front derailleur that is intended for a bicycle and that uses the cable control actuating device according to an embodiment of the invention, wherein the control cable is run toward the top; 
         FIG. 3  shows the connecting arm and the cable guide part, which is connected in a secure manner to the connecting arm, wherein the viewing direction makes it possible to see the cable clamping screw that extends obliquely through the cable guide part; 
         FIG. 4  shows the connecting arm and the cable guide part, which is connected in a secure manner to the connecting arm, wherein the viewing direction makes it possible to see the cable clamping device positioned on the opposite side in relation to the screw head on the cable guide part; and 
         FIG. 5  shows the connecting arm and the cable guide part in the state prior to the installation. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1 and 2  show the inventive cable guide on a front derailleur. In  FIG. 1  the actuating cable is routed downwards; and in  FIG. 2  upwards. The derailleur includes the stationary part  1 , the moveable part  2  and the parallelogram mechanism  7 , which connects the stationary part  1  to the moveable part  2 . The main components of the parallelogram mechanism  7  are the connecting arm  4  and the guide arm  13 . The connecting arm  4  is pivotably connected to the hinge pin  21  on the stationary part  1  and to the hinge pin  22  on the moveable part  2 . The guide arm  13  is pivotably connected to the hinge pin  23  on the stationary part  1  and to the hinge pin  24  on the moveable part  2 . The hinge pin  21  is arranged at a lower position than the hinge pin  23 . 
     Since the distance between the hinge pins  21  and  22  in the connecting arm and, thus, the length of the connecting arm  4  is equal to the length of the guide arm  13 , the inclination angle of the chain guide  3 , connected to the moveable part  2 , does not change when pivoting from a retracted position to an extended position. The chain guide has a passage for the chain and shifts the chain between the chain wheels at the pedal bearing. 
     The movement of the chain guide from the retracted to the extended position is performed by a pull movement at the actuating cable  6 . The opposite movement is performed through the effect of a return spring that is disposed around the hinge pin  21 . 
     The stationary part  1  of the derailleur is securely connected to a component of the bicycle frame. To this end, the illustrated embodiment provides a flexible clamp  20 , which is wrapped around the seat tube and which is compressed with a tightening screw and presses the seat tube support  25  on the stationary part  1  against the seat tube. An alternative possibility of fastening consists of the use of a rigid clamp with a hinge on the stationary part  1  and a direct mounting, in which the stationary part  1  is securely screwed to a soldered-on part on the seat tube by means of a screw, for example. 
     In the assembled state the cable guide part  5  is non-rotatably connected to the connecting arm  4 , as apparent from  FIGS. 3 and 4 . The hinge pin  21  is mounted on the connecting arm  4  inside the pin bosses  27 . The center region of said hinge pin runs through the stationary part  1 , and one end of said hinge pin runs through the first opening  10  on the cable guide part  5 . A rivet head  29  of the hinge pin  21  (shown on the right in  FIG. 3 , on the left in  FIG. 4 ) and a spring lock washer  28  (shown on the right in  FIG. 4 , and on the left side in  FIG. 3 , but covered) secure the hinge pin in the axial direction in relation to the cable guide part  5  and the connecting arm  4 . The rivet head  29  and the spring lock washer  28  represent axially effective stops, of which their function could also be achieved with other means, such as a circumferential flange or an obliquely inserted pin. 
     In addition to the first connection between the connecting arm  4  and the cable guide part  5  by means of the hinge pin  21 , there is a second connection due to the bolt  17  extending through cable guide part  5  and connecting arm  4 , as shown in  FIG. 5  in the disassembled state and shown in  FIG. 3  in the assembled state. The result is a secure connection between the connecting arm  4  and the cable guide part  5 . Owing to the hinge pin  21 , the cable guide part  5  and the connecting arm  4  are securely attached to each other in the axial direction. The bolt  17  prevents the cable guide part  5  and the connecting arm  4  from rotating in any way in relation to each other about the hinge pin  21 . 
     The cable clamping screw  9  in connection with the cable clamping plate  19  and the clamping projection  8 , which fits into the second opening  11  of the cable guide part  5 , form the cable clamping device  12 . The actuating cable  6  is clamped in a groove  26  on the cable clamping plate  19  and is guided to one of the openings  16  as a function of the cable guide on the derailleur. These openings  16  serve to hold the actuating cable  6  and to prevent its release from the cable guide part  5 . The cable-clamping device  12  is located on the cable guide part  5  on the side opposite the connecting arm  4 . The result is a good accessibility, and an actuating cable  6  can be easily mounted and, if desired, replaced. On the other hand, there is only a short distance between the cable clamping and the passage of the hinge pin  21  through the stationary part  1 . This distance to the bearing point on the pin boss  27  in a direction parallel to the hinge pin  21  is a function of the size of the frictional forces. Consequently the conditions are optimal for supporting the forces that are generated by the tensile force of the actuating cable  6 . The frictional forces are kept low. 
     The longitudinal axis  15  of the cable clamping screw  9  extends obliquely to the plane in which the cable guide part  5  extends. Therefore, the screw head  18  comes to rest on the other side of the cable guide part  5  in relation to the cable-clamping device  12  and is readily accessible at this position for actuation with a tool. 
     Thus, the arrangement according to the invention offers a good solution for the requirement arising from the need for a larger number of design variants for the cable control actuating device. The connecting arm  4  that is relatively expensive to manufacture is adapted to the various conditions by the addition of cable guide parts  5  that can be designed in different ways. The connecting arm  4  and the cable guide part  5  are stable and rigidly connected to each other; and the actuating cable  6  does not suffer any losses with respect to the actuating path. In addition, the design solution offers good accessibility for the installation and replacement of the actuating cable control device, because the screw head  18  of the cable clamping screw  9  is placed at a place and orientation that is optimal for the user. 
     It should be understood that the illustrated embodiments are examples only and should not be taken as limiting the scope of the present invention. The claims should not be read as limited to the described order or elements unless stated to that effect. Therefore, all embodiments that come within the scope and spirit of the following claims and equivalents thereto are claimed as the invention.