Abstract:
A cycle derailleur incorporates an indexing mechanism (indexer) as an integral part of the derailleur. More specifically, the indexer is a physical part of the derailleur structure, and is activated by the pull or release of a cable (e.g., operated via gearshift control on a cycle handlebar). Actuation of the indexer requires exertion of a threshold force sufficient to overcome built-in resistance of a detent-style, spring-loaded mechanism. As shifts are made from one gear to another, the indexer is adapted to urge the derailleur into precision alignment with each selected gear. In each of the described embodiments, the indexed derailleur and a method for indexing (digitizing) gear changes by means of, for example, a movable bearing/detent mechanism, are characterized by a deformable parallelogram linkage actuated via the cable through a gearshift control. The result is an improved cycle shifter system that fosters accuracy and avoids derailleur mislocation between shifts.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    This invention relates to cycle derailleurs, and specifically to mechanically actuated derailleurs that are indexed to positively effect gear change accuracy. More particularly, the invention is directed to improvements in the indexing functions of cycle (e.g., bicycle) derailleurs for enhancing such accuracy.  
           [0003]    2. Discussion of the Related Art  
           [0004]    “Multi-speed” cycles are generally well known in the art, with the most familiar being a bicycle. Such cycles are usually designed to provide three, five, ten, or more distinct speeds. There are numerous ways of providing the distinct ratios, which provide the multi-speed capability. In the case of a ten-speed cycle, for example, there are two distinct “gear clusters” or sprocket wheels. (The terms “gear” and “sprocket” or “sprocket wheel” are used interchangeably, herein, as well as the terms “cluster” and “cassette”.) In a typical rear cassette of a ten-speed cycle, the number of gear selectable sprocket wheel positions is five. Thus, the rear gear cluster comprises five gears having different numbers of teeth, the gears situated fixedly about a wheel hub in a coaxial side-by-side relationship. As those skilled in the art will appreciate, selection of any one of the five sprocket gear positions of the cassette is achieved via a rear derailleur device, which effects the shifting of the cycle chain position axially (i.e., laterally) or from sprocket-to-sprocket, in a manner such that the cycle chain is disengaged from a first sprocket, and is caused to move laterally to a selected second coaxial sprocket.  
           [0005]    In the case of the ten-speed cycle, there is also typically provided a second front gear cluster comprised of two or more sprockets having different numbers of teeth, and wherein front gear sprockets are also situated in a coaxial side-by-side relationship. The front gear cluster is, as is the rear cluster, also provided with a derailleur device for shifting the cycle chain position laterally, or in a manner such that the chain disengages a first sprocket and is then caused to move to a selected second coaxial sprocket. In the case of the described ten-speed cycle, the front gear cassette comprises only two sprocket gears. With respect to both front and rear gear clusters, the chain is adapted to re-engage any desired gear in either cluster as a function of any particular selected gear ratio. Thus, in the described ten-speed cycle, the front derailleur effects shifting of the cycle chain between the two gears of the front gear cluster, while the rear derailleur effects shifting of the cycle chain between the five gears of the rear gear cluster.  
           [0006]    In most prior art multi-speed cycles, two levers provided on the frame are connected to cables passing respectively to the front and rear derailleurs for effecting gearshifts. Each of the cables is normally maintained in tension by a spring mechanism built into the respective derailleur, and shifting of gears is accomplished by moving one or both of the derailleurs via the cables. This is accomplished by manually pulling or pushing respective cable wires via the levers against the spring bias. A friction device normally retains each lever in its moved position, so that the cycle chain can be properly positioned on the selected front and rear gears. Movements of either or both levers between their extreme positions will operate the respective derailleurs to cause shifting between gear ratios as desired by an operator of the cycle.  
           [0007]    In the ten-speed configuration described, and as is typical in most multi-speed cycles, the levers are typically operated independently of one another. Since the levers are normally mounted on a so-called front down tube, head tube, or the handlebars of the bicycle, a bicycle operator is required to steer the bicycle with one hand on the handlebars, and to use the other hand to successively operate one or both of the levers. As a general rule, the smoothness in gear speed changing is a function of the rider&#39;s deftness or skill with respect to shifting to a desired sprocket. In most cases, to shift gears on conventional prior art cycles in proper sequence requires a mental analysis on the part of the bicycle rider, or a memorization of proper operating sequences of the two levers. In this respect, there is no simple means for a bicycle rider to determine a particular gear position with absolute accuracy. Indeed, efforts to effect a shift via the rear derailleur from one gear to another of a rear cassette, particularly where an intended skip of at least one intermediate gear of the cassette is involved, often results in shifting to an undesired intermediate gear setting.  
           [0008]    There are additional problems associated with prior art arrangements. In many cases, the shift lever stroking or positioning is often determined strictly by “feel” or guesswork. In such cases, there is no positive positioning of the derailleur with respect to any given selected gear because the lever stroke is subject to non-discrete motions throughout all intermediate positions.  
           [0009]    In other cases, discrete motions are designed into the lever stroke, such as when detent mechanisms are employed. However, such detent mechanisms are heretofore located near or within the lever mechanism, i.e. on the front down tube, head tube, or handlebars of the bicycle frame. Generally, even after periods of relatively short usage, the cables stretch, resulting in inconvenient and occasionally even dangerous (e.g., if in midst of road traffic) mislocation of derailleur position relative to desired gear selection. Normally, the shifting is completed when the associated bicycle chain engages a selected gear. However, the shifting becomes incomplete when the derailleur is mis-positioned, or is otherwise not in a consistent position for selection of desired gear.  
           [0010]    The effect of a stretched cable may therefore cause a derailleur to be positioned between gear positions, because as the cable stretches, misalignment of the derailleur position and the remotely positioned indexed lever is created. When such a detent mechanism is used after shift cables have become stretched, a rider will tend to continually visually examine the particular gears in the cluster over which the bicycle chain is passing to confirm proper gear engagement. This can be annoying, and even dangerous in some situations, particularly when the driver is in substantial traffic. Many attempts have been made to reduce the randomness of shifting the derailleur. One effort to reduce such randomness has involved the provision of a single cable that operates both the front and rear derailleurs.  
         SUMMARY OF THE INVENTION  
         [0011]    A cycle derailleur incorporates an indexing mechanism as an integral part of the derailleur structure. Upon activation by the pull or release of a cable (e.g., via gearshift control on the cycle handlebar), the derailleur is forced by an integral indexing mechanism to move into a selectable index position. This causes a derailleur pulley gear to be precisely aligned with a selected sprocket gear. The invention incorporates both an indexed derailleur device and a method for indexing (digitizing) gear changes of a cycle by means of, in one embodiment, a movable ball bearing detent mechanism.  
           [0012]    In the one described embodiment, a bicycle derailleur incorporates an indexing mechanism (indexer) as an integral part of the derailleur. As a physical part of the derailleur structure the indexer is activated by the pull or release of a cable operated by a gearshift control on the handlebar of the bicycle. Actuation of the indexer requires exertion of a threshold force adequately sufficient to overcome a built-in resistance of a detent-received, spring-loaded ball bearing. As shifts are made from one gear to another, the indexer urges the derailleur into precision alignment with each selected gear. In each of the described embodiments, the indexed derailleur and method for indexing (digitizing) gear changes by means of the movable ball bearing detent mechanism are characterized by a deformable parallelogram linkage actuated by means of the cable through a gearshift control. The result is an improved cycle shifter system that encourages safety, as well as improved performance, through avoidance of derailleur-induced mislocations of the gear chain during shifts.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 is a perspective view of a bicycle that includes one described embodiment of the improved rear derailleur mechanism of the present invention.  
         [0014]    [0014]FIG. 2 is an enlarged side view of a rear wheel of the bicycle of FIG. 1, providing an enlarged view of the improved rear derailleur mechanism.  
         [0015]    [0015]FIG. 3 is a further enlarged side view of the subject improved rear derailleur mechanism.  
         [0016]    [0016]FIG. 4A is a view along lines  4 A- 4 A of FIG. 3 of one described embodiment of the improved rear derailleur mechanism.  
         [0017]    [0017]FIG. 4B is a view along lines  4 B- 4 B of FIG. 3 of a second described embodiment of the improved rear derailleur mechanism.  
         [0018]    [0018]FIG. 5 is a side view similar to that of FIG. 3, but depicting an additional embodiment of the improved rear derailleur mechanism.  
         [0019]    [0019]FIG. 6 is a perspective view of a portion of the improved derailleur mechanism of FIG. 5. 
     
    
     DETAILED DESCRIPTION OF EMBODIMENTS  
       [0020]    Referring initially to FIG. 1, a bicycle  10  is defined by a frame  12  to which are individually secured rear and front spoked wheels  14   a  and  14   b.  The rear wheel  14   a  contains spokes  14   c  attached to wheel hub  9 , while the front wheel  14   b  contains spokes  14   d,  attached to wheel hub  11 , as shown. The bicycle  10  further contains a seat  16  situated on a seat post  17  that projects upwardly from a portion of the bicycle frame  12 .  
         [0021]    Gearshift levers  15  and  16  situated on a handlebar  18  are adapted to swivel relative to the frame  12 . The levers  15  and  16  are relatively movable on the handlebar  18  to effect shifting of gears as will be described herein below. The handlebar  18  is rigidly attached to a steering fork  20  that is also attached to, but movable with respect to, the frame  12  so as to swivel and to thus facilitate steering of the front wheel  14   b,  as will be appreciated by those skilled in the art.  
         [0022]    A rear portion  22  of the frame  12  defines a portion of the frame to which the rear wheel  14   a  is attached. A pair of pedals  24  is adapted to operate a continuous chain  25  that extends between front and rear sprocket cassettes  26  and  28 , respectively. In the described embodiment, the front sprocket cassette  26  comprises two axially aligned sprocket gears, and is situated in a lower mid-portion of the frame  12 , as shown. The rear sprocket cassette  28  comprises five individual sprocket gears. As will be appreciated by those skilled in the art, the particular combination of gears between the front and rear cassettes defines a 10-speed bicycle.  
         [0023]    Referring now also to FIG. 2, a rear derailleur  30  is attached to the rear portion  22  of the frame  12  via a connection bolt  31 . The derailleur  30  is adapted to shift the chain  25  from one sprocket gear to another on the rear sprocket cassette  28 . The movement of the derailleur  30  to effectuate such gear changes is achieved via movements of the gearshift lever  16  on the handlebar  18 ; the latter controls only the shifting of the rear derailleur. Conversely, a front derailleur (not shown) is normally situated adjacent the front sprocket cassette  26 , and controlled by the gearshift lever  15 . As the front derailleur is not a part of the present invention, its structure and operation are not particularly described herein.  
         [0024]    Referring to FIG. 2, the rear derailleur  30  is formed of an upper deformable parallelogram structure  32 , and a lower pulley cage portion  34  secured to and supported by one deformable leg of the parallelogram structure  32 , as will be described in reference to FIG. 3. The pulley cage  34  supports an idler pulley gear  36  as well as a chain guide pulley gear  38 , as shown. Those skilled in the art will appreciate that the guide pulley gear  38  is adapted to precisely align the chain  25  with a sprocket gear of the rear sprocket cluster  28  in accordance with a desired gearshift selection performed by a cycle rider. Those skilled in the art will appreciate that the guide pulley gear  38  is cammed, so as to move laterally between limits of movement corresponding to the distance between first and fifth sprocket gear positions of the rear sprocket cassette  28 . Such movement is in response to deformation of the parallelogram structure  32 , which causes the pulley cage portion  34  to pivot outwardly from the wheel hub  9  to effectuate desired gear changes.  
         [0025]    Referring now to FIG. 3, the derailleur  30  is shown in greater detail. Specifically, the upper deformable parallelogram  32  is comprised of a right side vertical leg  40  to which the lower pulley cage portion  34  is rigidly secured. In addition, the parallelogram  32  contains a left side vertical leg  42  that includes a detent bearing arm  50  as will be described herein. The parallelogram  32  also includes a top or upper horizontal leg  44  that contains a detent plate portion  54  containing a plurality of detents  56 , each being positioned to represent a position of the parallelogram  32  that is associated with selection of one sprocket gear of the rear sprocket cassette  28 . The leg  44  also contains an integral extension that receives the connection bolt  31  through an aperture therein not shown. Finally, the parallelogram  32  includes a lower or bottom horizontal leg  46 ; it will be appreciated that all of the respective legs are hinged together by means of connection grommets  48   a, b, c,  and  d,  as shown in FIG. 2.  
         [0026]    As previously noted, the left side vertical leg  42  includes a detent bearing arm  50  that is hinged at a connection grommet  48   a  to the upper horizontal leg  44 . It will be appreciated that the bottom of the left side vertical leg  42  overlies a pivot connection grommet  48   d  (hidden), by which the leg  42  is movably attached to the lower or bottom horizontal leg  46 . Referring now also to FIG. 4A, a first described embodiment of the derailleur  30  incorporates a protuberance  52  that extends axially from the arm  50 . The protuberance  52  is positioned and adapted to cooperate with detents  56  situated in the detent plate portion  54  of the top horizontal leg  44 . In this embodiment, the detent bearing arm is formed of spring steel, and is adapted to have a threshold force that must be overcome via countering forces of a cable wire  68  to permit the protuberance  52  to become dislodged from, and to move from one detent  56  to a next adjacent detent  56 . Movement of the cable wire  68  is effected via the lever  16 , which as earlier noted is employed to effect gear shifts by a cycle operator. Even though this invention has been described with reference to cable actuation, the invention is broad enough to reach devices involving non-cable devices, such as those including hydraulic actuation or electric actuation, for example.  
         [0027]    Referring now to FIG. 4B, an alternate embodiment of a detent mechanism is one of a spring-loaded ball  76  that is urged by a spring  74  into the plurality of selectable detents  56 ′, as will be appreciated by those skilled in the art.  
         [0028]    Referring back to FIG. 3, a cable fastening boss  62  is formed integrally with the upper horizontal leg  44  of the deformable parallelogram  32 . The boss  62  accommodates a cable fastening nut  64  to which an end of the cable wire  68  is secured. It will be appreciated that both the fastening boss and the cable fastening nut are situated mid-span of the horizontal leg  44 . The cable wire  68  is contained within a cable housing  66  that is defined by a protective sheath adapted to permit sliding movement of the cable wire within the housing  66 . A cable wire tension control  70  is threaded through an aperture  71  of a bulbous lower portion  72  of the left side vertical leg  42 . The tension control  70  provides an adjustment mechanism for limiting and controlling movements of the derailleur  30  to thereby effectuate appropriate positioning of the derailleur guide pulley gear  38  relative to the selectable five sprocket gears of the rear sprocket cassette  28 .  
         [0029]    Thus, in accordance with one aspect of the present invention, a “detent” principle is employed to index the derailleur  30  to any one of the selectable sprocket gears of the rear sprocket cluster  28 . The detents  56  are designed to be positively engaged by either a protuberance  52  or spring-loaded ball  76 , such that a positive “digitally” changed gear position results. When the cable wire  68  is moved with sufficient force, the protuberance  52  or ball  76  will disengage from a particular detent  56  at a desired threshold force value, causing the protuberance or ball to ride on a surface of the detent plate portion  54  between detents until engagement of the next proximally positioned detent. The force limits for producing disengagement depend on the spring forces designed into the mechanism, as those skilled in the art will appreciate. Finally, the derailleur is adapted to move in either direction depending upon the direction of movement of the cable wire  68  for actuating the indexing mechanism.  
         [0030]    Another embodiment of the derailleur mechanism is displayed in FIGS. 5 and 6, wherein the bulbous portion  72  (FIG. 3) of the left side vertical leg  42  has been replaced by an arrangement  80  of a cooperating elongated piston sleeve  82  and cylinder  84 . In FIG. 5, the top of the cylinder  84  has been cut away to reveal the piston sleeve  82 . The sleeve  82  is adapted to move axially within and relative to the cylinder  84 , and the surface of the piston sleeve  82  is scalloped in a manner to contain a series of adjoining ring grooves  86 , wherein one groove position corresponds to one selectable sprocket gear of the rear cluster  28 . The piston sleeve  82  is rigidly secured to the cable wire  68 ′ via a compression fitting  92 , while the cylinder  84  is secured over the piston sleeve  82 . The cylinder  84  is fixed directly to the left side vertical leg  42 . Referring to FIG. 6, a U-shaped tension clip  88  (shown in an exploded view) is adapted to engage a slot  90  in the body of the cylinder  84 , so as to fix the clip axially relative to any movement of the piston sleeve  82 . The clip  88  thus interacts with the grooves  86  of the sleeve  82 , wherein the described mechanism of FIGS. 5 and 6 provides another style of detent mechanism, as will be appreciated by those skilled in the art.  
         [0031]    Indeed, as the cable wire  68 ′ is moved axially, operation of the lever  16  will be associated with a “feel” of the piston sleeve ring grooves overcoming a force threshold to slip past the tension clip  88  as necessary to shift from one gear to the next. Obviously, it will be appreciated that each of the ring grooves  86  is associated with a selectable sprocket gear of the rear sprocket cassette  28 . Therefore, a distinct indexed sprocket gear selection may be achieved via manipulation of the cable wire  68 ′; such manipulation assures that a desired ring groove is selected that corresponds to desired gear ratio.  
         [0032]    It is to be understood that the above description is intended to be illustrative and not limiting. Many embodiments will be apparent to those skilled in the art upon reading the above description. The scope of the invention should be determined, however, not with reference to the above description, but with reference to the appended claims with full scope of equivalents to which such claims are entitled.