Abstract:
A fork assembly for a bicycle including a frame having a head tube. The fork assembly includes a fork having a fork crown, a steerer tube, and a transition that couples the fork crown to the steerer tube. The transition is adapted to be positioned within the head tube, and defines a transition point between the transition and the steerer tube. The transition has an outer dimension that increases from the steerer tube toward the fork crown. The fork assembly also includes a bearing located adjacent the transition point and configured to rotatably support the fork within the head tube.

Description:
RELATED APPLICATIONS 
       [0001]    This patent application is a continuation application of U.S. patent application Ser. No. 11/370,750, entitled “Bicycle Fork Assembly,” filed on Mar. 8, 2006, the entire contents of which are hereby incorporated by reference. 
     
    
     BACKGROUND 
       [0002]    The present invention relates to a fork assembly for a bicycle. More particularly, the invention relates to a fork and a lower bearing assembly configured for use in the fork assembly. 
         [0003]    Most bicycles include a front fork that is rotatable to turn a front wheel. The fork typically includes two fork blades, and the front wheel is rotatably supported between the two fork blades. The fork blades are coupled at one end to form a crown, and a steerer tube typically extends from the crown. The steerer tube is rotatably supported within a head tube by at least two bearings, an upper bearing and a lower bearing. The head tube is coupled to and comprises a portion of a frame of the bicycle, and the bearings allow the fork to rotate relative to the head tube and frame. Generally, a handle bar is attached to the steerer tube to allow a rider to rotate the fork and steer the bicycle. 
       SUMMARY 
       [0004]    The present invention provides a bicycle fork assembly that includes a fork having a fork crown, a steerer tube, and a transition that couples the fork crown to the steerer tube. A transition point is defined between the transition and the steerer tube, and the transition has an outer dimension that increases from the steerer tube toward the fork crown. A bearing is configured to rotatably support the fork within a head tube of a bicycle frame, and the bearing is located adjacent the transition point. 
         [0005]    The present invention a bicycle that includes a frame having a head tube, a fork, and a lower bearing. The fork includes a fork crown having a brake mount, a steerer tube, and a transition that couples the fork crown to the steerer tube and defines a transition point between the transition and the fork crown. The transition has an outer dimension that increases from the steerer tube toward the fork crown. The lower bearing is recessed within the head tube and is configured to rotatably support the fork within the head tube. The brake mount is a distance from the lower bearing. A ratio is defined as the distance from the brake mount to the lower bearing divided by an outer dimension of the transition at the transition point, and the ratio is at least about 0.5. 
         [0006]    Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a side view of a bicycle including a fork assembly embodying the present invention. 
           [0008]      FIG. 2  is an exploded view of the fork assembly of  FIG. 1  and a portion of the frame of the bicycle of  FIG. 1 . 
           [0009]      FIG. 3  is a cross-section of a portion of the fork assembly taken along line  3 - 3  in  FIG. 1 . 
           [0010]      FIG. 4  is a cross-section of a portion of the bicycle taken along line  4 - 4  in  FIG. 1 . 
       
    
    
       [0011]    Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings. 
       DETAILED DESCRIPTION 
       [0012]      FIG. 1  illustrates a bicycle  10  that includes a front wheel  15 , a rear wheel  20 , and a frame  25 . The frame  25  can be made from any suitable material, such as steel, aluminum, carbon/epoxy composite, KEVLAR composite, fiberglass composite, or other composites and the like. 
         [0013]    Referring to  FIGS. 2 and 4 , the frame  25  includes a head tube  30  having an outer dimension D 1  (47 mm in the illustrated embodiment). While the illustrated head tube  30  is cylindrical with a generally constant outer dimension D 1 , in other constructions the head tube  30  can have an outer dimension D 1  that varies. For example, the outer dimension D 1  of the head tube  30  may decrease from a lower portion  35  toward a center portion  40 , then increase from the center portion  40  toward an upper portion  45 . In yet other constructions, the head tube  30  can take shapes other than a cylinder. For example, the head tube  30  can have an outer surface  50  with a plurality of sides, such as three, four, or more sides, or the head tube can be aerodynamically shaped. For purposes of this patent application, the outer dimension D 1  of the head tube  30  should be measured laterally across the lower portion  35  of the head tube  30 . 
         [0014]    A fork assembly  55  is received and supported by the head tube  30 . The fork assembly  55  includes a fork  60  having a steerer tube  65 , a transition  70 , a fork crown  75 , two fork blades  80 , and two fork dropouts  82 . The illustrated steerer tube  65 , transition  70 , fork crown  75  and fork blades  80  are integrally formed as a single piece made from a carbon/epoxy composite. Of course other materials such as plastics, fiberglass composite, KEVLAR composite, or other composites, and the like can be used to integrally form the steerer tube  65 , transition  70 , fork crown  75  and fork blades  80 . In other constructions, the steerer tube  65 , transition  70 , fork crown  75  and fork blades  80  may not be integrally formed as a single piece. For example, in one construction the fork blades  80  can be made separate from the fork crown  75 , and then the fork blades  80  can be bonded to the crown using epoxy or any suitable adhesive. In yet another construction, the steerer tube  65  can be formed separate from the transition  70  and then coupled to the transition using an adhesive, such as epoxy. Furthermore, the steerer tube  65 , transition  70 , fork crown  75 , and fork blades  80  may not all be formed from composite material. In one such construction the transition  70  can be made from aluminum and the steerer tube  65  and fork crown  75  can be made from a composite material. Other various combinations of materials can also be utilized. 
         [0015]    Referring to  FIG. 3 , the steerer tube  65  is generally cylindrical and defines a central axis  85 . While the illustrated steerer tube  65  is cylindrical in shape, in other constructions the steerer tube  65  can be frustoconical, such that an outer dimension D 2  (29 mm in the illustrated embodiment) of the steerer tube  65  either increase or decreases from a lower portion  90  toward an upper portion  95 . Furthermore, while the illustrated steerer tube  65  is hollow with a uniform wall thickness, in other constructions the wall thickness may not be uniform. For example, in other constructions the wall thickness can decrease from the lower portion  90  toward the upper portion  95 . 
         [0016]    Referring to  FIGS. 2 and 3 , the transition  70  extends from the fork crown  75  to couple the fork crown  75  to the steerer tube  65 . An upper transition point  100  is defined by the location where the transition  70  couples to the steerer tube  65 , and lower transition point  101  is defined by the location where the transition  70  couples to the fork crown  75 . The transition  70  has a first outer dimension D 3  (29 mm in the illustrated embodiment) at the upper transition point  100  and a second outer dimension D 4  (40 mm in the illustrated embodiment) where the transition  70  couples to the fork crown  75  at the lower transition point  101 . While the illustrated fork  60  includes a radius portion  102  located between lower transition point  101  and the fork crown  75 , in other constructions the fork  60  may omit the radius portion  102 . Therefore, for purposes of this patent application, the lower transition point  101  will be defined as the point where the transition  70  couples to the radius portion  102 , or in embodiments that omit the radius portion  102 , the lower transition point  101  will defined as the point where the transition  70  couples to the crown  75 . 
         [0017]    In the illustrated embodiment, the first outer dimension D 3  of the transition  70  is equal the outer dimension D 2  of the steerer tube  65  at the upper transition point  100 , and the first outer dimension D 3  of the transition  70  increases from the upper transition point  100  toward the fork crown  75 . A ratio is defined by the second outer dimension D 4  of the transition  70  divided by the first outer dimension D 3  of the transition  70 . In the illustrated construction, the ratio is about 1.4, and in other constructions the ratio is greater than about 1.2. 
         [0018]    The frustoconical outer surface of the transition  70  defines an angle α between the outer surface of the transition  70  and the central axis  85  of the steerer tube  65 . The illustrated angle α is about 20 degrees, and in other constructions, the angle α is greater than about 10 degrees. While the illustrated transition  70  is frustoconical in shape, in other constructions, the transition can have a plurality of sides. For example, in other constructions, the transition can have three, four, or more sides. 
         [0019]    Referring to  FIGS. 2 and 4 , the fork assembly  55  also includes an upper bearing assembly  105  and a lower bearing assembly  110 . The upper bearing assembly  105  includes an upper bearing  115 , a compression ring  120 , and an upper cup  125 . The upper cup  125  is rotationally fixed with respect to the head tube  30  and supports the upper bearing  115  within the head tube  30 . The compression ring  120  is located between the steerer tube  65  and the upper bearing  115  and is generally fixed with respect to the steerer tube  65 . The upper bearing  115  is located between the upper cup  125  and compression ring  120  and provides for relative rotation between steerer tube  65  and the head tube  30 . The upper bearing  115  can be any suitable bearing, such as a loose ball bearing, a retainer ball bearing, a cartridge type bearing, and the like. 
         [0020]    Referring to  FIG. 3 , the fork crown  75  includes a brake mount in the form of an opening  103  extending through the fork crown  75  and defining a brake-mounting axis  104 . The function and operation of the opening  103  is well known to one of ordinary skill in the art. It should be understood that other types of brake mounts could be used with the present invention. 
         [0021]    The lower bearing assembly  110  includes a lower bearing  130 , a crown race  135 , and a lower cup  140 . The crown race  135  can be made from any suitable material, such as aluminum, steel, plastic, composite, etc. The crown race  135  is coupled to the fork  60  circumferentially around the upper transition point  100  such that the crown race  135  is fixed with respect to the fork  60 . In the illustrated construction, the crown race  135  is co-molded to the fork  60 , while in other constructions the crown race  135  can be bonded to the fork  60 . 
         [0022]    The lower cup  140  is coupled to the head tube  30 , such that the lower cup  140  is rotationally fixed with respect to the head tube  30 . The lower cup  140  can be made from any suitable material, such as aluminum, steel, plastic, composite, etc. 
         [0023]    The lower bearing  130  is located between the crown race  135  and the lower cup  140 , such that the lower bearing  130  is circumferentially around the upper transition point  100 . The lower bearing  130  can be any suitable bearing, such as a loose ball bearing, a retainer ball bearing, a cartridge type bearing, and the like. The illustrated lower bearing  130  has a diameter D 5  of approximately 36 mm. In other constructions, the lower bearing  130  can have any suitable diameter D 5 . 
         [0024]    The illustrated lower bearing  130  is located at a distance D 6  from an end of the head tube  30 . In the illustrated construction, the distance D 6  is approximately 15 mm and in other constructions is at least about 8.5 mm. In yet other constructions, the lower bearing  130  can be located either above or below the upper transition point  100 . 
         [0025]    The upper transition point  100  and the lower bearing  130  are located at a distance D 7  from the brake-mounting axis  104 . In the illustrated embodiment, this distance D 7  is 33 mm for the upper transition point  100  and 35 mm for the lower bearing  130 . In addition, the upper transition point  100  and the lower bearing  130  are located at a distance D 8  from the lower transition point  101  (essentially, the length of the transition  70 ). In the illustrated embodiment, this distance D 8  is 16 mm for the upper transition point  100  and 18 mm for the lower bearing  130 . 
         [0026]    A ratio is defined by the distance D 6  from the end of the head tube  30  to the lower bearing  130  divided by the outer dimension D 1  of the head tube  30 . In the illustrated embodiment, the ratio is about 0.33. In other embodiments, the ratio is at least about 0.28 and in yet other embodiments the ratio is at least about 0.23. 
         [0027]    A second ratio is defined by the distance D 6  from the end of the head  30  to the lower bearing  130  divided by the diameter D 5  of the lower bearing  130 . In the illustrated embodiment, the ratio is about 0.42. In other embodiments, the ratio is at least about 0.30 and it yet other embodiments the ratio is at least about 0.25. 
         [0028]    A third ratio is defined by the distance D 7  from the brake-mounting axis  104  to the lower bearing  130  divided by the diameter D 5  of the lower bearing  130 . In the illustrated embodiment, the third ratio is about 0.97. In other embodiments, the third ratio is at least about 0.8 and preferably at least about 0.7. 
         [0029]    A fourth ratio is defined by the distance D 7  from the brake-mounting axis  104  to the lower bearing  130  or the upper transition point  100  divided by the dimension D 4  of the transition  70  at the lower transition point  101 . In the illustrated embodiment, the fourth ratio is about 0.81. In other embodiments, the fourth ratio is at least about 0.63 and preferably at least about 0.5. 
         [0030]    A fifth ratio is defined by the distance D 7  from the brake-mounting axis  104  to the lower bearing  130  or the upper transition point  100  divided by the outer dimension D 1  of the head tube  30 . In the illustrated embodiment, the fifth ratio is about 0.70. In other embodiments, the fifth ratio is at least about 0.60 and preferably at least about 0.50. 
         [0031]    The upper and lower bearing assemblies  105 ,  110  allow the steerer tube  65  to rotate with respect to the head tube  30  while maintaining the steerer tube  65  in a generally fixed location with respect to the head tube  30  in both axial and radial directions. The upper and lower bearing assemblies  105 ,  110  also position the fork  60  within the head tube  30  such that a gap  145  is formed between the lower cup  140  and the crown  75 . 
         [0032]    Referring to  FIG. 1  the steerer tube  65  extends through and above the head tube  30  to provide an attachment point for a steering assembly  150 . The steering assembly  150  includes a handlebar  155 , a stem  160 , and a sleeve  165 . The stem  160  is coupled to the steerer tube  65  and retains the sleeve  165  that surrounds the steerer tube  65 , between the stem  160  and the head tube  30 . The sleeve  165  includes a cap (not shown) that covers the upper bearing assembly  105  to substantially prevent dirt, debris, liquid and the like from contacting the upper bearing  115 . While the illustrated upper bearing assembly  105 , stem  160 , and sleeve  165  are in a configuration similar to a conventional threadless headset, it should be understood that in other constructions a threaded headset can be utilized. In such a construction, an additional threaded nut is provided and the threaded nut is coupled to the steerer tube  65 , which is also threaded, thereby coupling the stem  160  and sleeve  165  to the steerer tube  65 . 
         [0033]    Thus, the invention provides, among other things, a bicycle fork assembly  55  that includes an upper bearing assembly  105 , a lower bearing assembly  110 , and a fork  60 . The fork  60  has two fork blades  80  that connect to form a fork crown  75 . A transition  70  extends from the fork crown  75  to couple the fork crown  75  to a steerer tube  65 . Various features and advantages of the invention are set forth in the following claims.