Abstract:
A multi-speed sprocket assembly is suggested, including at least two sprockets, with both sprockets having at least one common upshift transitional region in which, when the chain is displaced from the smaller sprocket to the larger sprocket for the purpose of shifting gears, the chain leaves the smaller sprocket, with a trailing tooth of the smaller sprocket being the last to engage between a trailing link plate pair of the chain, and moves onto the larger sprocket, with a leading tooth of the larger sprocket either being the first to engage between a first outer link plate pair or being located adjacent to a first inner link plate pair, and with at least the larger sprocket having in its upshift transitional region a double spacewidth created by omitting a tooth, which is immediately followed by the leading tooth. Only one chain link crossing from the smaller sprocket to the larger sprocket is located between the trailing chain link and the leading chain link. The chain roller of the link connection between the crossing chain link and the trailing chain link is located directly across from a rear tooth flank of the trailing tooth of the smaller sprocket. The leading tooth cooperates with a circumferential surface of a link plate of the crossing chain link using its front tooth flank, with the leading tooth being in contact with either the inner surface of an outer link plate or with the outer surface of an inner link plate of the leading chain link. In the region of the double spacewidth, the larger sprocket is embodied in such a way that the crossing chain link comes into contact with the larger sprocket only in the region of the leading tooth.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The invention relates to bicycle shifting systems, and more particularly, to a multi-speed sprocket assembly for a bicycle shifting system that ensures proper shifting from a smaller sprocket to a larger sprocket. 
         [0002]    Derailleurs, in particular for bicycles, have existed for a long time. In spite of their open and therefore unprotected construction as compared, for example, to hub shifters, derailleurs are very popular due to their high level of efficiency, light weight, and cost-effective structure. In recent times, attempts have been made to improve shifting function, in particular for shifting under load as well as to reduce the gear step by correspondingly increasing the number of sprockets. For example, a ten-gear shifting system has been attempted with ten respective sprockets, with consecutive sprockets differing from one another by only one tooth. 
         [0003]    In derailleurs, the most critical issue is shifting up from a smaller sprocket to a larger sprocket, under load if possible. In such cases, the provision of a special upshift transitional region in which favorable conditions exist for shifting has been known. No shifting occurs in the regions between the transitional regions because, in these regions, the chain is deflected from the larger gear wheel and remains on the smaller gear wheel. 
         [0004]    In order to ensure an even and jolt-free shifting process in the transitional regions, the same gear wheels are offset from one another at an angle such that, taking into account the chain pitch, the chain assumes a desired course. However, it must be kept in mind here that the chain does not include identical chain links; rather, it includes alternating chain links with interior link plate pairs, the inner links, and chain links with outer link plate pairs, the outer links. Therefore, when a leading tooth of the larger sprocket cooperates for the first time with a chain link while the chain is being thrown, it often occurs that, if this leading chain link is an outer link, then the leading tooth engages between the outer link plates, but when the leading chain link is an inner chain link, then the leading tooth is located next to the inner pair of link plates. This situation must be taken into account when designing the derailleur. Here, it is important in both shifter configurations, among other things, to ensure that the teeth following the leading tooth opposite the running direction be securely engaged in the chain. Thus, the chain must be prevented from “riding” on the larger sprocket, in that a chain link lands on a tooth tip. 
         [0005]    To ensure proper shifting, sufficient room must be provided for the oblique chain, which is normally achieved by providing corresponding recesses on the side of the larger sprocket facing smaller sprocket. Here, the base of the recess forms a contact surface for a chain link or a chain pin of the chain that is crossing from the smaller sprocket to the larger sprocket for the axial alignment of the chain (EP 0 313 345 B1). 
         [0006]    A radial guide of a link pair may be provided in the transitional region, specifically with the aid of a link contact ramp on the side of the larger sprocket facing the smaller sprocket in an end region of a double spacewidth of the large sprocket (EP 0 642 972). Because an axial guide is present as well, there are good conditions per se for a flawless shifting function. However, it has been shown that, under certain conditions, the chain slides off of the ramp and is displaced in the direction of the small pinion. This leads to an extension of the crossing chain section, which is comprised of two chain links, with the result of faulty shifting function. 
         [0007]    The above solutions are sensitive to dirt because dirt between the radial or lateral guide surface and the link plate may lead to a malfunction. In general, it is also possible to use only one type of chain, which is adapted to the multi-speed sprocket assembly. Although the shifting chains produced by different manufacturers have the same basic dimensions (interval 12.7 mm, inner width 2.38 mm, and roller diameter 7.75 mm in accordance with ISO 082 for derailleurs), there are differences in the structure of the outer link plates, for example, due to an arcing of the outer link plates, as well as in the length of the link pins with a corresponding larger or smaller distance past the respective outer link plate. 
         [0008]    DE 39 36 921 A1 discloses a multi-speed sprocket assembly with a tooth number difference of 1 between consecutive sprockets. In order to facilitate the crossing of the chain and thus obtain a radial guide, a tooth of the smaller sprocket is shaped in the transitional region to correspond with the contour of the crossing link plate, in order to be able to radially support, in places, the crossing link plate that is located farther from the sprocket. 
       SUMMARY OF THE INVENTION 
       [0009]    The object of the invention is to provide a multi-speed sprocket assembly that ensures reliable shifting even in the case of small gradations between gear steps, is also suitable for shifting chains with different structures, and, moreover, is not sensitive to dirt. 
         [0010]    The radial guide, which is important for proper shifting, is attained by adapting the one crossing chain joint between the rear tooth flank of the trailing tooth of the smaller sprocket and the front tooth flank of the leading tooth of the larger sprocket. The axial guide results from the engagement of the trailing tooth between the link plates of the trailing chain link preceding the crossing chain link in the travel direction of the chain. Here, an allowance is made based on the shifting configuration with the leading tooth on the interior of an outer link plate of the first link connection (referred to in the following as an “outer link plate configuration”), the crossing chain must be displaced to the smaller sprocket by the thickness of the leading tooth in order to arrive in the alternate configuration (referred to in the following as an “inner link plate configuration”) with the leading tooth to be adjacent to the exterior of an inner link plate of the leading chain link. Because according to the invention only one chain link is provided between the leading tooth of the larger sprocket and the trailing tooth of the smaller sprocket, the trailing tooth in the outer link plate configuration is also located between two outer link plates of the trailing chain link such that, here, the chain may be displaced relatively far in the axial direction toward the large sprocket (maximally up to the stop on the inner side of the corresponding outer link plate). In the inner link plate configuration, on the other hand, the trailing tooth is located between two inner link plates with the axial play of the chain on the trailing tooth having been reduced by the thickness of one inner link plate. During the shifting process in the outer link plate configuration, the shifting chain, with engagement only on the trailing tooth, is therefore able to be displaced by the derailleur further toward the larger sprocket than in the inner link plate configuration such that, as the sprockets continue to rotate, the leading chain link arrives on the appropriate side of the leading tooth. This results in a guidance of the chain, and therefore a proper shifting operation, for both configurations. 
         [0011]    The radial guidance as well as the axial guidance on the smaller sprocket are independent of the special structure of the manufactured form of the shifting chain, in particular with regard to the shape and thickness of the outer link plate as well as the length of the link pin. This results in a compatibility with chains from various manufacturers. The guide function is generally independent of any dirt, which collects between the sprockets because the double spacewidth according to the invention is so large that no contact occurs between the larger sprocket and crossing chain link, except during cooperation with the leading tooth. 
         [0012]    It is preferable to provide for the larger sprocket to have a region that has been removed to form the double spacewidth with such a shape that the larger sprocket, viewed in the axial direction, does not overlap at all with the crossing chain link. For one, this results in a very cost-effective production because cutting out or stamping out is more cost-effective than, for example, punching processes. An advantageously low weight results as well. 
         [0013]    Especially for small sprockets, such a large removed area may cause a considerable mechanical weakening of the sprocket. In the context of the invention, therefore, when the larger sprocket has a removed area forming the double spacewidth with such a shape, then the larger sprocket, viewed in the axial direction, has an overlap with the crossing chain link, albeit with a clearance between the crossing chain link and the larger sprocket in the region of the overlap. 
         [0014]    In further embodiments of the invention, the larger sprocket has a recess, preferably a stamped recess, in an overlap region with the link plates of the trailing link plate pair to provide a clearance between the recess and the trailing link plate pair. In particular in the case of small sprockets, there may be space problems for the link plates of the trailing chain link that were cleared by the recess. Here as well, a clearance is provided between the recess and the trailing link plate pair in order to attain the advantages of the invention, namely compatibility with various models of shifting chains and insensitivity to dirt. According to the invention, an axial guide through the base of the recess is not necessary, because the axial guidance is ensured by the trailing tooth of the smaller sprocket engaging in the trailing plate pair. 
         [0015]    In particular in the case of sprocket combinations with a difference of 1 between the nominal tooth numbers, it has been shown to be advantageous for the leading tooth in the region of a corner of a tooth tip formed on the radially outer end of the front tooth flank to cooperate with the link plate of the crossing chain link. However, the front link connection of the crossing chain link, i.e., its chain roller, is located directly across from the rear tooth flank of the trailing tooth such that, depending on the actual shifting situation and cable load as well as the current elongation of the shifting chain, a more or less pronounced contact may occur between the chain roller and the rear tooth flank. Contact may also occur if, at the end of the shifting process, the teeth of the larger sprocket following the leading tooth engage in the chain. However, after long use with a given chain length, it is also possible that no direct contact occurs between the chain roller and the rear tooth flank. However, this does not hinder the function of the sprocket assembly because the respective link plate (outer link plate or inner link plate) of the crossing chain link then comes into contact with the corner of the tooth tip of the leading tooth in a slightly higher position. 
         [0016]    To further ensure proper shifting, the leading tooth may be offset from the course of the crossing chain link. Moreover, the thickness of the leading tooth may correspond to the thickness of an inner link plate of the shifting chain. As has been stated above, the thickness of the tooth corresponds to the lateral displacement path of the shifting chain on the leading tooth when both shifting configurations are compared to one another. The lateral displacement path of the shifting chain, which has been bent by the derailleur, across from the trailing tooth when changing from one configuration to the other configuration also corresponds to the thickness of the inner link plate, such that both displacement paths are substantially the same size. 
         [0017]    In order to make even more certain that, during shifting, the leading chain link will arrive on the side of the leading tooth that is appropriate in the current shifting configuration without “riding” on it, it is possible to provide the leading tooth in the region of a corner of a tooth tip formed on the radially exterior end of the front tooth flank of the leading tooth with a positioning slope for an outer link plate of the leading chain link. 
         [0018]    The use of the invention in a multi-speed sprocket assembly in which the nominal numbers of teeth on the larger and the smaller sprockets differ by 1 is particularly preferred. In this context, the term “nominal number of teeth” is understood to mean the number of teeth that the sprocket would have if none of the teeth had been removed to form a double spacewidth. 
         [0019]    The invention also relates to a bicycle shifting system including a driving sprocket assembly and a driven sprocket assembly as well as a shifting chain connecting these two sprocket assemblies, with at least one of the sprocket assemblies being embodied as a multi-speed sprocket assembly as described above and with a derailleur being provided between the two sprocket assemblies in an intake area for displacing the chain, which transfers the chain for shifting gears from one of the two sprockets to the other sprocket. 
         [0020]    These and other features and advantages of the present invention will be more fully understood from the following description of one or more embodiments of the invention, taken together with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    In the drawings: 
           [0022]      FIG. 1  is a side view of a multi-speed sprocket assembly according to one embodiment of the present invention engaged by a section of a chain; 
           [0023]      FIG. 2  is a side view of the multi-speed sprocket assembly of  FIG. 1 , but in an outer link plate configuration; 
           [0024]      FIG. 3  is a view in the radial direction (Arrow III) of the arrangement shown in  FIG. 1 , but with a shortened chain segment; 
           [0025]      FIG. 4  is a view corresponding to  FIG. 3 , but with a configuration of  FIG. 2  (arrow IV); 
           [0026]      FIG. 5  is a perspective view of an arrangement of four relatively small sprockets, which are in turn part of a multi-speed sprocket assembly, which is otherwise not shown; 
           [0027]      FIG. 6  is a partially sectioned perspective view at an oblique angle from the top of a sprocket of the arrangement of  FIG. 5  with a nominal number of teeth of  13 ; 
           [0028]      FIG. 7  is a side view with a slight inclination of the sprocket of  FIG. 6 , also partially sectioned; 
           [0029]      FIG. 8  is a side view of the sprockets with a nominal number of teeth of  12  and a nominal number of teeth of  13  of  FIGS. 5 to 7  with a chain section in the upshift transitional area in an inner link plate configuration similar to  FIG. 1 ; 
           [0030]      FIG. 9  is a view of the sprockets of  FIG. 8 , but in an outer link plate configuration similar to  FIG. 2 ; and 
           [0031]      FIG. 10  is a side view of a bicycle shifting system. 
       
    
    
     DETAILED DESCRIPTION 
       [0032]      FIGS. 1-4  illustrate a multi-speed sprocket assembly  18  for a bicycle shifting system according to one embodiment of the present invention. Looking to  FIG. 10 , the bicycle shifting system  10  generally include a front sprocket assembly  12  driven by pedals  14 , a rear sprocket assembly  18  connected to a wheel hub (not shown) and a bicycle chain  16  connecting the front and rear sprocket assemblies  12 ,  18 . 
         [0033]    In the example shown, the front sprocket assembly  12  includes two sprockets; it is also generally possible to provide three sprockets. A front derailleur  20  is used to displace the chain from one sprocket to the other. Correspondingly, a rear derailleur  22  is also arranged behind the rear sprocket assembly  18 . Each of the two derailleurs  20  and  22  is provided in the intake area of the chain  16  such that it is possible to shift the chain between the sprockets in the desired manner. 
         [0034]    As described below with reference to  FIGS. 1 to 9 , the invention has to do with an improved embodiment of multi-speed sprockets and, in principle, is therefore applicable to the driving sprocket assembly  12  as well as to the driven sprocket assembly  18 , although it is preferred for the latter. 
         [0035]    The principle structure of multi-speed sprocket assemblies (also referred to as cassettes) and their installation on corresponding axes is known. Therefore, the drawings are limited to the depiction of the sprockets (gear rims) and their cooperation with the shifting chain. For the purpose of explaining the shifting principle, the drawings are also limited to the depiction of two sprockets each, with the exception of  FIG. 5  with four sprockets, which are, in turn, only part of a cassette that includes, for example, ten sprockets. 
         [0036]    In  FIGS. 1 to 4 , two large sprockets are shown, a sprocket  24  with a nominal number of teeth of  16  as well as a sprocket  26  with a nominal number of teeth of  17 . Because each of the two sprockets has an upshift trailing transitional region  24   a  and  26   a , in which one tooth has been omitted in order for a double spacewidth to result, the sprocket  24  actually has only 15 teeth  28  and the sprocket  26  has only 26 teeth  30 . Single spacewidths  32  are formed between consecutive teeth  28  and single spacewidths  34  are formed between consecutive teeth  30 . 
         [0037]    In particular, a trailing shifting tooth  281  of the smaller sprocket  24  is significant for the shifting process from the smaller sprocket  24  to the larger sprocket  26 , and it is followed immediately in the direction opposite the chain travel direction L by the trailing transitional region  24   a  with the double spacewidth. Moreover, a leading tooth  30   e  of the larger sprocket  26  is also significant and it is followed immediately in the direction opposite the chain travel direction L by the leading transitional region  26   a  with the double spacewidth of the larger sprocket  26 . The leading and trailing transitional regions  26   a ,  24   a  are aligned with each other. 
         [0038]    A section  16   a  of a shifting chain is resting on both sprockets  24  and  26 ; in order to simplify the illustration, the link connections  36  have been indicated only as circles and, in addition, are sectioned. However, the link connections  36  include a chain roller and a link pin, with an optional chain sheath between the chain roller and the link pin. The link connections  36  are connected to one another in an alternating fashion by outer link plates  38  and inner link plates  40 . In  FIGS. 3 and 4 , chain rollers  42  as well as link connection axes  44  can be seen. 
         [0039]    The shifting chain  16  is a conventional shifting chain for derailleurs whose basic dimensions are in compliance with norms (ISO No. 082). The chain pitch b is predetermined, i.e., the distance of 12.7 mm between consecutive link connection axes  44 , the roller diameter dl of a maximum of 7.55 mm, and the inner width b 1  (clearance between the inner link plates  40 ) with a minimum of 2.38 mm. 
         [0040]    Otherwise, chain manufacturers have essentially free rein in structuring their shifting chains. Therefore, there are shifting chains in which the outer link plates are markedly arced outwards in a middle region. There are also derailleurs in which the link pins visibly protrude, in contrast to other chains in which the link pins essentially end flush with the outer link plates. As will be explained in greater detail below, the specific form of the chain is inconsequential to the orderly shifting function according to the invention, as long as the shifting chain complies with norms. 
         [0041]    These chains may generally be divided into chain links  48 , more precisely into inner links  50  composed of a pair of inner link plates  40  and sheaths as part of the corresponding chain joint as well as further into outer links  52  composed of a pair of outer link plates  38  and, connecting them, link pins protruding through the sheaths of the inner link plates  50 . These link pins pass through the sheaths of the inner link plates and, along with the chain rollers  42 , form the link connections  36 . 
         [0042]    At the transition from the sprocket  24  to the sprocket  26 , there are specific chain links  48 , which will play a role in the following, namely a trailing chain link  481  that, as the trailing chain link, still cooperates with a tooth, namely the trailing tooth  281  of the sprocket  24 , which is followed in the direction opposite the chain travel direction L by a chain link  28   q  crossing to the larger sprocket  26 . The next chain link is the leading chain link  48   e , which is the first to cooperate with a tooth, namely the leading tooth  30   e  of the larger sprocket  26 . Because the chain links  48  are not identical, but rather alternate between inner links  50  and outer links  52 , there are also two possible configurations for shifting gears. In the inner link plate configurations shown in  FIGS. 1 and 3 , an inner link  50  cooperates with the leading tooth  30   e  of the larger sprocket  26  and an inner link  50  also cooperates with the trailing tooth  281  of the smaller sprocket  24 . Conversely, in the outer link plate configuration according to  FIGS. 2 and 4 , an outer link  52  cooperates with the leading tooth  30   e  and an outer link  52  also cooperates with the trailing tooth  28   l.    
         [0043]    Looking to  FIGS. 1 and 2 , the leading transitional region  26   a  or leading transitional region forms a double spacewidth because the tooth of the larger sprocket  26  that would normally follow the leading tooth  30   e  at a distance p according to the chain pitch in the direction of rotation L is not present. The leading transitional region  26   a  is cut out so markedly inwards in the radial direction that there is not only no overlap between the outer contour of the crossing chain link  48   q  and the larger sprocket  26 ; in addition, as can be clearly seen from  FIGS. 1 and 2 , the outer contours of the crossing chain link  48   q  and the sprocket  26 , viewed in the axial direction, are located at a considerable distance from one another, except in the region of contact with the leading tooth  30   e . In detail, the leading transitional region  26   a  is formed by a contour line  54  of the sprocket  26  that originates from a rear tooth flank  30   lh  of the tooth  30   l  relative to the travel direction L of the chain and passes into a front chain tooth flank  30   ev  of the leading tooth  30   e.    
         [0044]    The leading transitional region  26   a  has been cut out or stamped out in a cost-effective manner. In this embodiment (in contrast to the embodiment according to  FIGS. 8 and 9 ), the lateral surface of the larger sprocket  26  facing the smaller sprocket  24  is not structured, for example, by stamping or machining out a recess for accommodating and pitching the shifting chain. As a result, it may be produced in a particularly cost-effective manner. The considerable weight reduction of the sprocket is also advantageous. The normal path of the chain on the larger sprocket  26  (for example, after the completion of the upshift process described above) is also ensured in the trailing transitional region  24   a  in that, here, the chain link in question is able to be supported with its front and rear chain roller on the rear tooth flank  30   lh  of the trailing tooth  30   l  or on the front tooth flank  30   ev  of the leading tooth  30   e . The angular distance between the two teeth  301  and  30   e  should be correspondingly reduced in comparison to the angular distance between the remaining teeth in the pitch p. 
         [0045]    As can be seen particularly from  FIGS. 3 and 4 , the structure of the shifting chain as alternating inner links  50  and outer links  52  results in a different spatial shifting configuration. In the inner link plate configuration according to  FIG. 3  (and  FIG. 1 ), the leading chain link  48   e  in the chain travel direction L that follows the crossing chain link  48  is an inner chain link. The inner link plate  40  located nearer to the sprocket  26  rests with its outer surface  56  against a lateral surface  58  of the leading tooth  30   e  facing the smaller sprocket  24 . The leading tooth  30   e  is placed at an incline that corresponds to the course of the shifting chain  16  such that an approximately two-dimensional disposition occurs on the opposite side. 
         [0046]    A second tooth  30   z  that follows the leading tooth  30   e  in the direction opposite the chain travel direction L, on the other hand, engages between the outer link plates  38  of the second chain link  48   z , with this tooth being advanced up to the inner surface  60  of the outer link plate  38  and resting with its front tooth flank, relative to the chain travel direction L, on the outer circumference of the inner link plate  40  of the leading chain link  48  that is above the sprocket  26  in  FIG. 3 . 
         [0047]      FIGS. 3 and 4  show the path of the chain in an imprecise manner because the chain section  16   a  is shown in an elongated fashion. The chain actually has an arced path. At the beginning of the shifting process, the chain is axially displaced by the derailleur  22  ( FIG. 10 ) in the direction of the larger sprocket  26  such that a simple, arced chain line results. Here, the trailing chain link  48   l  opposite the trailing tooth  28   l  is trying to move as far as possible toward the outer sprocket  26 , optionally until it is in contact, as shown respectively in  FIGS. 3 and 4 , with the inner surface  60  or  64  of the lower outer link plates  38  or inner link plates  40  of the trailing chain link  48   l  (implied by a dashed contour line in  FIGS. 3 and 4 ). In contrast to the drawn illustration in  FIGS. 3 and 4 , the chain path would need to be corrected accordingly (curved in the direction of the arrow A). 
         [0048]    Correspondingly, after the chain  16  has been placed on the larger sprocket  26 , a curve results in the opposite direction (arrow B) around the first and second teeth  30   e  and  30   z . Then an elongated S-shaped curve of the chain results, approximately corresponding to a chain curve line  64  indicated in the drawings with a dot-dash line. 
         [0049]    In the outer link plate configuration according to  FIG. 4  (and  FIG. 1 ), an outer link plate  38  of the leading chain link  48   e  is located with its inner surface  60  on an outer surface  66  of the leading tooth  30   a  facing away from the smaller sprocket  24 . This outer surface in turn is placed in an oblique fashion corresponding to the path of the chain and, in addition, inclined radially outwards in the direction of the smaller sprocket  24 . In order to prevent the corresponding outer link plate  38  from “riding” during the shifting process, the front corner of the tip of the leading tooth  30   e  facing away from the smaller sprocket  24  is provided with a bevel  68 . 
         [0050]    Because the outer surface  56  of the inner link plates  40  is generally flush with the inner surface  60  of the outer link plates  38  in the elongated path, the chain section  16   a  is displaced in the outer link plate configuration according to  FIG. 4  by the tooth thickness z of the tooth  30   e  in contrast to the inner link plate configuration according to  FIG. 3  where it is displaced in the direction of the axes  44  towards the larger sprocket  26 . 
         [0051]    A similar situation results in the region of the trailing tooth  28   l . If one assumes here that, in the inner link plate configuration according to  FIG. 3 , the trailing tooth  28   l  rests against or is located at a very short distance from the inner surface  64  of the inner link plate  40  removed from the larger sprocket  26 , then it is possible in the outer link plate configuration according to  FIG. 4  for the outer link plate  38  removed from the sprocket  26  along with its inner surface  60  to advance to the trailing tooth  28   l . This results in a transverse displacement by the inner link plate thickness e 1 . 
         [0052]    When shifting the chain  16  onto the larger sprocket  26 , it is therefore possible for chain  16  to be displaced across from the trailing tooth  28   l  by the link plate thickness e 1  farther in the direction of the larger sprocket  26  in the case of an outer link plate configuration as compared to an inner link plate configuration. Thus, as the sprockets continue to turn, the leading chain link  48   e  arrives in the desired position across from the tooth  30   e , having been displaced upwards by the thickness z of the tooth  30   e  in  FIGS. 3 and 4 . Reliable shifting is thus ensured. 
         [0053]    This axial, i.e., lateral, guidance of the shifting chain  16  during the shifting process by the trailing tooth  28   l  is independent of the structure of the shifting chain  16  as long as the chain adheres to ISO dimensions as discussed at the outset. Compatibility with shifting chains from different manufacturers is thus ensured. The engagement of the trailing tooth  28   l  in the trailing chain link plate is largely independent of dirt in the cassette as long as such dirt primarily settles between the sprockets. 
         [0054]    During shifting, the radial support of the chain section  16   a  occurs on the side of the smaller sprocket  24  at least at the beginning of the shifting movement by way of the chain roller  42   lv  on the front chain joint of the trailing chain link  48   l  with contact with the rear tooth flank of the tooth  48   l - 1  preceding the trailing tooth  48   l . At the end of the shifting motion, depending on the tension load of the chain and the elongation of the chain, a more or less pronounced contact occurs between the rear chain roller  42   ah  of the trailing chain link (=front chain roller of the crossing chain link  48   q ) and the rear tooth flank  28   lh  of the trailing tooth  28   l.    
         [0055]    The axial guidance on the larger sprocket  26  occurs due to the contact by the respective link plate  38  or  40  of the crossing chain link  48   q  with a front flank  30   ev  of the leading tooth  30   e  in the region of the tooth tip. In the inner link plate configuration according to  FIG. 3 , it affects the outer circumferential surface  72  of an outer link plate  28  and, in the outer link plate configuration according to  FIG. 4 , it affects an outer circumferential surface  74  of an inner link plate  40 . 
         [0056]    The crossing chain link  48   q  is captured in this manner between the trailing tooth  28   a  of the smaller sprocket  24  and the leading tooth  30   e  of the larger sprocket  26 . The chain link  48   q  is therefore axially and radially supported on the leading tooth  30   e , specifically in a defined spatial position appropriate for each of the two shifting configurations. The shifting chain  16  is therefore laid in a predetermined fashion on the larger sprocket  26  in the course of the continued rotation of the chain. The chain links are reliably engaged by the other teeth  30  of the sprocket  26 ; “riding” is prevented. This is the case for both shifting configurations. 
         [0057]      FIGS. 5 to 9  show another embodiment of the invention in which components that correspond to those in the first embodiment according to  FIGS. 1 to 4  are given the same reference numbers increased by 100.  FIG. 5  shows a perspective view of the four smallest sprockets of a ten-speed simple sprocket assembly, in order: a sprocket  101  with a nominal and actual tooth number of  11 , a sprocket  103  with a nominal tooth number of  12 , a sprocket  105  with a nominal tooth number of  13 , and a sprocket  107  with a nominal tooth number of  14 . A transitional region  103   a ,  105   a , and  107   a  has been created for each of the sprockets  103 ,  105 , and  107  by the omission of one tooth. 
         [0058]    The transitional region  107   a  of the sprocket  107  is formed simply by cutting out or stamping out a corresponding region of the sprocket  107  and thus corresponds to the transitional regions  24   a  and  26   a  of the sprockets  24  and  26  in the embodiment according to  FIGS. 1 to 4 . 
         [0059]    A region of the sprocket was also cut out or stamped out for the transitional regions  103   a  and  105   a , specifically to the extent that there is at the most a very slight overlap between the crossing chain link  148   q  and the respective larger sprocket while shifting gears to the larger sprocket. If an overlap occurs, namely during the transition from the sprocket  101  to the sprocket  103 , a recess  103   b  has been pressed out or created by removing material on the side of the larger sprocket  103  facing the smaller sprocket  101 ; this recess is configured such that, in all shifting situations, there is a clearance between the sprocket  103  and the crossing chain link  148   q . The contour line of the recess  103   b  of the sprocket  103  has been assigned the number  111 . 
         [0060]    The sprocket  105  is also provided with a recess  105   b ; however, this recess is not located across from the crossing chain link  148   q  but rather across from the trailing chain link  148   l  when the gear is shifted from the smaller sprocket  103  to the larger sprocket  105 . Here as well, the recess  105   b  is configured such that, in all shifting situations, there is a clearance between the sprocket  105  and the link plates of the trailing chain link  148   l . The essentially L-shaped contour of the recess  105   b  is indicated in  FIGS. 8 and 9  with a dot-dash line  109 . 
         [0061]    The shape of the recess  105   b  can be seen from  FIGS. 6 and 7 , as can the shape of the leading tooth  130   e . Also discernible are the front tooth flank  130   ev , the obliquely placed lateral surface  158 , the obliquely placed and inclined lateral surface  166 , as well as the bevel  168  on the front corner of the tooth tip of the tooth  130   e , where this front corner faces away from the smaller sprocket. The effective tooth thickness z has been drawn in as well. This corresponds to the transverse displacement of the chain  16  in the transition from the outer link plate configuration to the inner link plate configuration and vice versa and, due to the incline of the lateral surface  166 , depends on and the insertion depth of the tooth  130   e  between the outer link plates of the leading chain link  148   e . The tooth thickness z is of the same order as the thickness of the chain link plates, i.e., it corresponds to the transverse displacement of the chain relative to the trailing tooth during the (virtual) transition between the outer link plate configuration and the inner link plate configuration and vice versa. 
         [0062]    The shifting process corresponds to that of the first exemplary embodiment according to  FIGS. 1 to 4  with the same advantages of unlimited compatibility with shifting chains from different manufacturers and greater insensitivity to dirt. This is due to the fact that the recess  105   b , which has now been additionally provided, remains out of contact with the link plates of the trailing chain link  148   l . The same applies to the recess  113   b  on the sprocket  103   b  for the transition from the sprocket  101  to the sprocket  103 . 
         [0063]    While this invention has been described by reference to one or more preferred embodiments, it should be understood the 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 embodiments, but that it have the full scope permitted by the language of the following claims.