Abstract:
The invention relates to a bicycle twist-grip shifter, which is connectable to a fixed handgrip and is mountable as a structural unit on a handlebar. In this way the fixed handgrip is securely fixed on the handlebar. Moreover, the individual components have an advantageous size for production in an injection molding process. The twist-grip shifter gives the operator a precise operation by avoiding disruptive frictional effects of the rotatable handgrip part on the mounting tube, for which purpose ball bearings are used for bearing the take-up spool, and a metallic positioning ring is used in the positioning mechanism.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a rotatable grip actuator, or as more commonly known, a twist-grip shifter for shifting of bicycle gear units, such as multi-speed hubs or derailleurs. 
     EP 0 700 827 discloses a twist-grip shifter for controlling bicycle gear units. This twist-grip shifter includes a shifter housing with a shift mechanism, a clamping device for fixing the shifter on the handlebar, a rotatable take-up spool, a mounting tube on which a twist-grip part is rotatably mounted, and a grip end piece seated non-rotatably on the handlebar. The separate grip end piece is generally an elastomeric tube which is frictionally mounted on the handlebar and primarily transmits the manual supporting forces to the handlebar and, unlike twist-grip shifters without an additional fixed handgrip part, prevents unintentional shifting operations. In order to reduce friction, a plastic intermediate ring can be disposed between the twist-grip part and the fixed elastomeric tube. 
     In a further development of the twist-grip shifter, EP 1 157 919 discloses a fixed handgrip part or grip end piece of a twist-grip shifter which is formed integrally with the mounting tube. When the mounting tube and shift housing are fixed on the handlebar by means of a screw in a clamping clip, the grip end piece is fixed relative to the handlebar. In this way, unwanted shifting of the grip end piece or even possible slipping off the handlebar is avoided and safety during use is increased. The fixed handgrip part integrally connected to the shifter housing has a corresponding length in the axial direction. This places corresponding demands on the size of injection moulding machines used for the production of the shifter, which is a disadvantage. 
     BRIEF SUMMARY OF THE INVENTION 
     An object of the present invention, therefore, is to design a mounting tube and fixed handgrip assembly of a twist-grip shifter capable of being fitted and removed so that on the one hand they are connected to one another securely when fitted on the handlebar but also are nevertheless produced and handled individually. In one solution according to the invention, it is proposed to dispose resilient elastic tongues on the mounting tube, the tongues being equipped at the end with a catch profile or catch in order to form a positively engaged connection, which is fixed against torsion or displacement, to a matching profile on the shift housing. A screw on the clamping clip is tightened to ensure a reliable seating of the twist-grip shifter including the fixed handgrip on the handlebar. In this case, unlike previous twist-grip shift actuators, the additional working step of pushing on the separate fixed handgrip is omitted when fitting the twist-grip shift actuator. This design includes the possibility of providing and using a twist-grip shifter both in a variant with and a variant without a separate fixed handgrip part. 
     The twist-grip should freely rotate about the mounting tube. This is assisted by a closed mounting base on a ring which is disposed on the end of the mounting tube and which can be produced simply and with sufficient precision as a rotationally symmetrical part. There are no edges on the body over which the twist-grip would have to slide when the twist-grip shifter is actuated. 
     Moreover, the arrangement of ball bearings between the mounting tube and the twist-grip in the axial region, where the spool for winding of the cable to be actuated is located, is a measure for minimising friction. 
     A further object is that the parts belonging to the device according to the invention can be produced simply and cost-effectively. 
     One aspect of the invention provides a twist-grip shifter for actuation of bicycle gear units by pulling and releasing a cable, including a shifter housing configured to be received on a handlebar. A central mounting tube is disposed inwardly of the shifter housing. The central mounting tube includes a proximal end and a distal end, wherein the proximal end of the central mounting tube is fixedly connected to the shifter housing. A rotatable handgrip is rotatably disposed about the central mounting tube and adjacent the shifter housing. A take-up spool is rotatable with the rotatable handgrip for pulling and releasing the cable. A fixed handgrip includes a fixed grip tube configured to be non-rotatably received on the handlebar, and a connector releasably connecting the distal end of the central mounting tube to the fixed grip tube. 
     Other aspects of the invention provide a twist-grip shifter wherein the connector may include a first catch on the distal end of the central mounting tube, a second catch on the fixed grip tube, and a catch ring releasably connecting the first and second catch. The catch ring may be formed one-piece with one of the central mounting tube and the fixed grip tube. The central mounting tube and fixed grip tube may be disposed about and directly adjoining the handlebar. The catch ring may include on an inner periphery thereof a circumferential catch protrusion which projects radially inwardly, the catch protrusion releasably connecting the first and second catches. The central mounting tube and the fixed grip tube may be connected when the first and second catches are bent radially inwardly and pushed axially over the catch protrusion. The connector may include a first catch on the distal end of the central mounting tube and a second catch recess on the fixed grip tube, the second catch recess receiving the first catch. The connector may include a second catch on the fixed grip tube and a first catch recess on the distal end of the central mounting tube, the first catch recess receiving the second catch. The twist-grip shifter may further include a bearing disposed between the central mounting tube and the take-up spool. The shifter housing may include a metallic positioning ring and a positioning spring resiliently engaging the positioning ring. 
     An embodiment of a rotatable grip actuator according to the invention will be described in the following with the use of figures. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a perspective view of one embodiment of the invention, wherein the mounting tube and the fixed handgrip are removed; 
         FIG. 2  is a cutaway view of the snap connection between the mounting tube and the fixed handgrip in the twist-grip shifter of  FIG. 1 ; 
         FIG. 3  is a perspective view of the catches in the snap connection of  FIG. 2 , without the components of the twist-grip shifter located radially outside these catches; 
         FIG. 4  is an exploded view of the shifter housing with the rotatable handgrip part and the positioning mechanism of the twist-grip shifter of  FIG. 1 ; and 
         FIG. 5  is a perspective view of the components of the twist-grip shifter with the shifter housing removed from the side of the positioning mechanism. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  is a twist-grip shifter  1  according to an embodiment of the invention for actuation of a cable  5  (see  FIG. 5 ) for shifting between individual gears in a gear shift device on a bicycle. The twist-grip shifter  1  is provided with a connector  10  between a shifter component with a shifter housing  2  and a rotatable handgrip  6  on the one hand and a fixed handgrip  13  on the other hand. The rotatable handgrip part  6  is disposed so as to be rotatable relative to a central or shifter mounting tube  7  (see  FIG. 2 ). The twist-grip shifter  1  is usually fitted on a handlebar, as is well known, which handlebar exteriorly receives the central mounting tube  7 . 
     A twist-grip shifter  1  according to the invention can be seen in  FIGS. 1 and 4 . The shifter housing  2  accommodates the mechanism for pulling and releasing a cable  5 , which is wound or unwound from a take-up spool  4 . In order that after completion of pulling or releasing operations the cable  5  remains positioned in one of the positions which correspond to the individual gears, a corresponding positioning device is provided, which will be described in detail below. The cable  5  is located on the take-up spool  4  primarily in a plane perpendicular a central axis  3  of the shifter  1 , an axis shared by the handlebar when the shifter is mounted thereon. The outgoing cable  5  is guided in a cable guide  19  in the direction corresponding to its further path on the bicycle frame as far as the gear shift component to be shifted. The central mounting tube  7  and the shifter housing  2  form the mounting base for the movable elements of the cable actuation mechanism and for the rotatable handgrip part  6  on which the shifter is actuated by the cyclist. In the illustrated embodiment, the shifter housing  2  and the central mounting tube  7  are connected to one another in one piece and formed integrally on the proximal end  8  of the mounting tube, so that connecting elements between them are not necessary. A clamping clip (not shown) which is disposed around the proximal end  8  of the central mounting tube  7  ensures the fixing of the twist-grip shifter  1  on the handlebar. The clamping clip may also be disposed at other positions of the shifter, for example directly in the shifter housing  2  or on a fixed grip tube  17  of the fixed handgrip  13 . 
     The fixed handgrip  13  includes a radially internally disposed fixed grip tube  17  with a catch  16 , which will be referred to as the second catch, and a radially externally located fixed rubber handgrip  18 , as can be seen in  FIG. 2 . According to the invention, the connector  10  is located between the central mounting tube  7  and the fixed handgrip  13 , as shown in  FIG. 1 . 
     The connector  10  comprises a first catch  11  on the distal end  9  of the central mounting tube  7 , a catch ring  15 , and the second catch  16  on the fixed handgrip  13 , as shown in  FIG. 1 . The first catch  11  may have multiple portions in engagement with matching profiles on the catch ring  15 , in order to fix this in the axial direction relative to the central mounting tube  7 . In order that the first catches  11  can engage in the matching profiles on the catch ring  15  or disengage from the matching profiles, they are bent radially inwardly. If in the state where the twist-grip shifter is fitted onto the handlebar, the handlebar is located radially within the central mounting tube  7 , and the first catch  11  cannot move radially inwards. Consequently, in the mounted state, the first catch  11  cannot disengage from the matching profile on the catch ring  15 . 
     In the catch ring  15 , the first catches  11  on the distal end  9  of the central mounting tube  7  and the second catches  16  on the fixed grip tube  17  bear against one another and are disposed to interleave in the circumferential direction, as shown in  FIGS. 2 and 3 . The catches  11 ,  16  extend through the central opening in the catch ring  15 , wherein they engage with their ends in circumferential catch recesses  12  on the catch ring  15 . For reasons of simple production and uncomplicated fitting, the catch recesses  12  are uninterrupted circumferentially. A catch ring  15  may be produced as a simple turned part made of metal, or formed from a molded plastic or a composite material, for example. 
     In another embodiment, the catch recesses  12  could also be interrupted, when the fixed handgrip  13  has a preferred angular position about the central axis  3 . An equally circumferential catch protrusion  21 , over which the first and second catches  11 ,  16  must move as they extend through the catch ring  15 , is located on the inner periphery of the catch ring on the ends of the catch ring in the axial direction between the two catch recesses  12 . 
     Alternatively, two catch protrusions could be disposed on the axial ends of the catch ring  15  between which a single catch recess is located. However, when manufacture takes place in a plastic injection moulding process this embodiment is more difficult to de-mold. 
     The catches  11 ,  16  have a general V shape in the axial direction, so that on the one hand a simple installation is possible, and on the other hand an almost play-free connection in relation to a reciprocal rotation in the circumferential direction is possible in the connector  10 . The V shape is shown from the interior in  FIG. 2  and from the exterior in  FIG. 3 . A plurality of slots, which extend in a direction parallel to the central axis  3 , are provided in the circumferential direction between the first catches  11  and between the second catches  16 . In this way, favourable spring characteristics are obtained. The elasticity of the catches  11 ,  16  is adjustable by means of the length of the slots. 
     Instead of the fixed handgrip  13  illustrated in  FIG. 1 , a closing ring, which constitutes a limit for the displacement movement of the rotatable handgrip part  6  in a direction parallel to the central axis  3  of the handlebar, can be disposed at the distal end  9  of the central mounting tube  7 . Such a closing ring may offer a closed outer cylindrical surface on its external circumference as a mounting base for the rotatable handgrip part  6 , on which the rotatable handgrip part  6  slides with an inner circumferential surface on an axial end. 
     In further alternative embodiments, the catch ring  15  between the central mounting tube  7  and the fixed grip tube  17  may be omitted. Then there is only one set of catches for the engagement in matching profiles on the counterpart tube. The catches can either be disposed on the central mounting tube  7  or on the fixed grip tube  17 . 
       FIG. 4  shows the components of the positioning mechanism which are accommodated between the radially inner central mounting tube  7  and the radially outer shifter housing  2 . The positioning mechanism has a positioning spring  22  which is disposed on the take-up spool  4  and also locks the take-up spool in the exact position when tensile forces act on the cable  5 . 
       FIG. 5  shows the components of the positioning mechanism with the shifter housing  2  removed. The end nipple of a cable  5  is inserted in the take-up spool  4 , so that the cable together with the take-up spool is moved in a clockwise direction of rotation for pulling or is moved in a counter-clockwise direction of rotation for releasing of the cable  5 . In the counter-clockwise direction, the cable  5  is acted on by a return spring (not shown) on the component to be shifted with a force, for example from a derailleur. In the same direction of rotation, a positioning spring  22 , which engages a positioning tooth  25  of a positioning ring  24  and is mounted on the take-up spool  4 , prevents a rotary movement of the take-up spool  4 . There is a torsional backlash between the rotatable handgrip part  6  and the take-up spool  4 . When the rotatable handgrip part  6  moves rotationally in the counter-clockwise direction, the disengaging finger  23  mounted on the rotatable handgrip part  6  moves towards the positioning spring  22  and disengages it from the positioning tooth  25 . A spring (not shown), which acts in the circumferential direction between the rotatable handgrip part  6  and the take-up spool  4 , gives the operator using the torsional backlash a resistance when shifting in the release direction until the intended disengagement of the positioning spring  22  from the positioning tooth  25  on the positioning ring  24  and the progressive release of the cable  5  are achieved. 
     The engagement of the positioning mechanism which is perceptible for the cyclist is reinforced by the fact that disruptive frictional forces are reduced to a minimum by the arrangement of ball bearings  26  between the take-up spool  4  and the central mounting tube  7 . Bearing shells  27 , for which sheet metal pressed parts which are cost-effective to produce can be used, are pressed in from both axial sides into the take-up spool  4 . The balls of the ball bearings may roll directly on the central mounting tube  7 . Since the tensile force on the cable  5  constitutes a transverse force on the take-up spool  4 , the arrangement of the ball bearings  26  within the take-up spool has a particularly positive effect with regard to low friction. 
     The precise operation for positioning the take-up spool  4  is ensured by the use of a positioning ring  24 , which may be made of a metallic material. Moreover, the metallic sound when the positioning spring  22  engages the positioning ring  24  reinforces the impression of precise operation. 
     The cable guide  19  is advantageously not disposed in a plane through the central axis  3  in order to avoid a collision with lever components by the brake lever mounted in the vicinity of the twist-grip shifter on the handlebar. The brake lever components extend generally in a region around a plane through the central axis  3 . 
     While this invention has been described by reference to a particular embodiment, it should be understood that numerous changes could be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the disclosed embodiment, but that it have the full scope permitted by the language of the following claims. Any modifications and variations of the device described and claimed herein are considered the invention; for example, those variations that combine separate parts are contemplated to fall within the scope of the invention. Thus, a wide variety of combinations and sub-combinations of parts, for example connecting parts, are contemplated to be alternative embodiments of the invention.