Abstract:
A bottom bracket assembly for bicycle frames aligns crankshaft bearings. The assembly is press fitted into the bottom bracket shell to journal the crankshaft. An elongated, rigid, unibody sleeve comprises a terminal end and a spaced apart leading end which both receive and support a radial contact bearing that is press fitted into a machined bore. Each bore comprises an interference fit zone for bearing retention and a larger, pressure relief zone comprising a channel and an adjacent, buffering slope that compensates for stresses. Dust shields coaxially abut the bearing exteriors. An inner, tubular buttress bushing coaxially occupies the sleeve interior and extends between the spaced apart bearings to brace them. Externally the sleeve has a pair of integral, friction retention contact interfaces separated by a reduced diameter optimization zone. The sleeve terminal end has an integral stop flange that abuts the frame bottom bracket shell contacting the crank arm.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This utility patent application is based upon, and claims priority from, U.S. Provisional patent application Ser. No. 61/911,836, filed Dec. 4, 2013, entitled “Bottom Bracket for Bicycles”, by inventors Wesley Warren Wolfenbarger and Gary Edward Mailhiot Jr., the entire disclosure of which is hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     I. Field of the Invention 
     The present invention relates generally to improvements in bicycle bearing bottom brackets in which a rotatable crankshaft is journaled for rotation. More particularly, the present invention relates to single-piece, bearing modules that support bearings disposed at opposite ends of the crankshaft proximate the bicycle pedals, and to bearing fitments for said bearings. 
     Bicycling has grown in popularity for numerous reasons. Bicycling is a popular form of recreation, offering the rider vigorous outdoor exercise. Of course, bicycling is a means of transportation utilized by many. Moreover, bicycling has become a very popular competitive sport for both amateurs and professionals. Lightweight bicycle frames formed of fiber and resin composite materials have become very popular, and such composite designs exhibit numerous advantages and benefits when compared to older, heavier, mostly metallic designs. 
     Modern composite bicycles are characterized by numerous advantages relating to efficiency. For example, they offer reduced aerodynamic drag, enhanced lateral stiffness, and appreciably lower mass than metallic designs. Benefits provided by reduced weight bike parts are well known. Benefits include increased acceleration, enhanced maneuverability, and in some cases, improvements in overall reliability. To further reduce the weight, lighter, composite materials have been substituted for the more commonly used metals. 
     Composite materials are created from plastics involving high-strength fiber reinforcements and an appropriate matrix material. Layers of graphite fibers, glass fibers, aramid fibers, polyethylene fibers or other fibers are employed in composite designs. Modern composite monocoque bicycle frames are molded entirely of resin impregnated carbon fiber material. Because most of these designs lack any metallic features into which threads could be cut to mechanically retain bearing housings in the frame bottom bracket shell, the facility for an unthreaded, press fit, or friction fit bottom bracket has been adopted industry-wide. 
     Whether the bicycle is used for recreation, transportation, exercise, or competition, various bicycle components are continuously evolving. Simply stated, the basic design goal is to increase strength and durability, while reducing weight and friction. One area that has been extensively redesigned involves the bicycle frame bottom bracket shell, which is a tubular housing or passageway in which the pedal-supporting crankshaft is rotatably supported by the bottom bracket bearing assembly. The bottom bracket bearing assembly within this housing is often termed a “bottom bracket” in the art. 
     Different types of bottom bracket bearing assemblies exist. Generally speaking, a conventional bicycle bottom bracket bearing assembly supports a rigid, rotating shaft connecting to and supporting crank arms on opposite sides of the frame. Suitable bearings rotatably support the crankshaft or spindle on opposite ends. The bottom bracket bearing assembly aligns the bearings to the rotating axis of the crankshaft or spindle. The shaft may be journaled for rotation within a tubular sleeve structure coaxially fitted within the bicycle&#39;s tubular shell at the lower frame region. The crank arms dynamically support the cyclists&#39; pedals. 
     Some bottom bracket bearing assemblies hold left and right bearings internally via a separate cup that is threaded into the frame bottom bracket shell. For example, one common type of bottom bracket bearing assembly is the Shimano-style cartridge bottom bracket. The cartridge bearings are inserted into the bottom bracket shell of the bicycle frame. Cups are threaded into opposed sides of the bottom bracket shell to hold the cartridge in place. 
     However, deficiencies exist with such bottom bracket assemblies. First, the threads of the bottom bracket shell increases the cost of manufacturing the bicycle frame. Second, the threaded portions are cut into the frame post facto, leading to bearing alignment issues which increase dag and can shorten bearing service life. Furthermore, the pre-load, or axial end play setting of the coaxial bearings that determines how tight or lose the bearings will run in their races must be carefully adjusted by an experienced professional, or else bearing performance can be compromised, usually through bearing misalignment in response to crankshaft load. 
     The latest bicycle frame designs are entirely constructed of carbon fiber and feature unthreaded, press fit, or friction fit bottom bracket shells. These frame bottom bracket shells require press fit, or friction fit bottom bracket bearing assemblies. Said assemblies are generally comprised of two, identical composite bearing housings containing press fitted bearings. The composite housings are pressed into the bicycle frame bottom bracket shell, one into each side, and are unitized only by the frame and the journaled crankshaft or spindle. Shortcomings of this design include uneven radial compression of bearings due to lack of molded frame shell concentricity, shortened bearing service life due to side-loading, and increased bearing friction or “drag” caused by a lack of, or inconsistency of coaxial bearing alignment. Our design is an improvement of this two piece, press fit format. 
     U.S. Pat. No. 3,578,829 issued May 18, 1971 discloses a bicycle bottom bracket having a pair of ball bearings for supporting a crankshaft, at least one of the bearings having an inner race slidable with respect to the crankshaft, and a coil spring pressuring the bearings to mitigate the need for the aforementioned pre-load adjustment by a professional. The construction facilitates smooth rotation of the crankshaft. 
     U.S. Pat. No. 3,903,754 issued Sep. 9, 1975 discloses a crank shaft assembly for a bottom bracket which permits accurate adjustments of the crank shaft. A housing receives a shaft, bearings for rotatably supporting the shaft, and adjustable retaining members for retaining the shaft in the housing in axial alignment. 
     U.S. Pat. No. 4,252,384 issued Feb. 24, 1981 discloses a bicycle crank gear assembly including a replaceable cartridge. The weather sealed, preadjusted cartridge is replaceably installed in a crank gear box in a cycle frame. A clamping device secures the cartridge in the crank gear box. 
     U.S. Pat. No. 5,076,601 issued Dec. 31, 1991 discloses a high strength, composite bicycle frame in which the instant invention may be advantageously employed. The frame comprises fiber reinforced, resin impregnated composite material. 
     U.S. Pat. No. 5,209,581 issued May 11, 1993 discloses means for rotatably mounting bicycle crank arms in a bottom bracket. The crank shaft unit includes a crank shaft having connecting projections formed at opposite ends thereof for engaging inside walls of bosses of the crank arms, a cylindrical member surrounding the crank shaft, and bearings for rotatably supporting the crank shaft inside the cylindrical member. The adapters are mounted between an inside wall of the bottom bracket and the crank shaft unit. 
     U.S. Pat. No. 5,924,336 issued Jul. 20, 1999 discloses a hollow bicycle crankshaft including a shaft assembly having a first shaft member fastened to a second shaft member, a hollow left crank arm, a hollow right crank arm, a tubular housing member, a first shaft bearing, a second shaft bearing, and a sprocket bracket. The shaft assembly is housed within the tubular housing. The first and second shaft bearings, disposed at each end of the housing member, secure the tubular housing member about the shaft assembly in coaxial and concentric alignment. 
     U.S. Pat. No. 6,435,726 issued Aug. 20, 2002 discloses a bicycle bottom bracket assembly including an outer tube connected to a bicycle frame with first and second inner threaded sections respectively defined in opposite, inner ends of the tube. A roller bearing is engaged with an inner periphery of the first end of the inner tube. A positioning ring is engaged with the second inner threaded section of the outer tube. An axle extends through the roller bearing and the bearing. 
     U.S. Pat. No. 7,762,571 issued Jul. 27, 2010 discloses a split bottom bracket assembly with an upper portion is formed integrally with the bicycle frame and a lower portion is detachably connectable to the upper portion, the lower portion. The bottom bracket assembly journals a crankshaft with associated bearings. 
     U.S. Pub. No. 20070137424 published Jun. 21, 2007 discloses a bicycle bottom bracket assembly has a crank axle, a pair of bearing units and a pair of retaining clips. The bearing units are configured to be mounted in a tubular hanger part or bottom bracket tube of a bicycle frame. 
     U.S. Pub. No. 20070204722 published Sep. 6, 2007 discloses another bottom bracket assembly. 
     U.S. Pub. No. 20080056635 published Mar. 6, 2008 discloses a bottom bracket assembly for bicycles with two open ends with tapered, inner peripheries that seat specialized taper-roller bearings with tapered outer bearing races. A spindle featuring distal splines extends between the two bearings to rotatably attach crank arms via said splines. 
     U.S. Pub. No. 20080164673 published Jul. 10, 2008 discloses another bottom bracket assembly with beveled bearing races fitted to a shell with beveled inner peripheries. The bottom bracket shell may be threadless. 
     Other publications of interest include U.S. Pub. No. 20090145262 published Jun. 11, 2009; U.S. Pub. No. 20100220947 published Sep. 2, 2010; U.S. Pub. No. 20110126666 published Jun. 2, 2011, and U.S. Pub. No. 20130064488 published Mar. 14, 2013. 
     SUMMARY OF THE INVENTION 
     This invention provides an improved bottom bracket bearing assembly for use in composite, lightweight bicycles that require an unthreaded, press fit, or friction fit, assembly. 
     Our modular, bicycle bottom bracket assembly is designed for use with modern, composite bicycle frames for maintaining the critical pedal crankshaft bearings in proper alignment during strenuous use. Forces experienced by the crankshaft bearings might otherwise dislodge, disorient, or deform bearings, resulting in excessive friction on the crankshaft, which disadvantages the bicycle rider. The assembly is press fitted to the generally tubular, hollow bicycle bottom bracket shell to journal a crankshaft that supports conventional pedals engaged by a rider for propulsion. 
     The bottom bracket assembly comprises an elongated, rigid sleeve coaxially fitted within the bottom bracket shell. The bicycle crankshaft penetrates the sleeve. Preferably the rigid sleeve comprises a unibody piece machined from aluminum. A leading sleeve end, directed through the frame pass-through during installation, internally receives a radial contact bearing that is press fitted into a machined bore. A similar machined bore at the spaced apart sleeve terminal end receives another bearing. Each bearing bore comprises an interference fit zone for bearing retention and a larger diameter pressure relief zone. Preferably the relief zone has a channel facing an adjacent, progressive buffering slope that compensates for excessive pressures placed on the bearings by the crank. The bearings are protected by dust shields that coaxially abut the bearing exteriors. Preferably the assembly comprises an inner, tubular buttress bushing that coaxially occupies the tubular sleeve. It extends between the inner race of the spaced apart bearings to brace them for maintaining alignment. 
     The sleeve has a pair of integral, friction retention contact interfaces separated by a reduced diameter optimization zone. The contact interfaces have an external diameter that insures a tight press fit. The contact interfaces have a diameter greater than that of optimization zone. The sleeve terminal end has an integral stop flange that abuts the frame bottom bracket shell. The stop flange comprises an outer, ring-shaped portion with an integral bezel having a clearance face externally facing the inner face of a rotating crank arm. 
     Thus a very general object of our invention is to provide a bottom bracket bearing assembly for bicycles that reduces friction and increases reliability and efficiency. 
     A related object of our invention is to provide a bicycle bottom bracket bearing assembly in which potentially damaging stresses imparted to the bearings by inconsistent tolerances of the bicycle&#39;s molded composite frame are mitigated or eliminated. 
     Another object is to provide a lightweight bottom bracket bearing assembly that provides increased versatility with respect to the crank shaft assembly without compromising the strength of the bottom bracket bearing assembly. 
     A further object of our invention is to provide improved fitments for bearings installed in bicycle bearing module bores. 
     Another object is to prevent fretting/chattering of the crankshaft. 
     Another object is to enable smooth, low resistance pedaling. 
     Another object is to provide a bottom bracket bearing assembly that maintains alignment of the bearings&#39; integral, constituent parts, such as inner and outer races and individual ball bearing, and reduces radial compression, or preload of said parts. 
     An object of the present invention is to provide a bicycle bottom bracket assembly that is relatively easy to service and/or replace due to its modular design. 
     A further object of the present invention is to provide a modular bicycle bottom bracket assembly of the character described in which the bearings will be aligned stably and retained against axial movements. 
     These and other objects and advantages of the present invention, along with features of novelty appurtenant thereto, will appear or become apparent in the course of the following descriptive sections. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the following drawings, which form a part of the specification and which are to be construed in conjunction therewith, and in which like reference numerals have been employed throughout wherever possible to indicate like parts in the various views: 
         FIG. 1  is a fragmentary, exploded isometric view of a typical bicycle frame showing our modular bottom bracket bearing assembly in the installation position along with a typical crank-set assembly; 
         FIG. 2  is a fragmentary, exploded isometric view of our modular bottom bracket bearing assembly showing the unthreaded, press fit, or friction fit composite bicycle bottom bracket shell in which it is deployed; 
         FIG. 3  is an enlarged, exploded isometric view of our modular bottom bracket assembly; 
         FIG. 4  is an enlarged, isometric view of the assembled modular bottom bracket assembly; 
         FIG. 5  is a side elevational view of the assembled modular bottom bracket assembly; 
         FIG. 6  is a longitudinal sectional view of the modular bottom bracket assembly taken generally along line  6 - 6  of  FIG. 5 ; 
         FIG. 7  is an enlarged, sectional view taken generally along line  7 - 7  of  FIG. 2 ; 
         FIG. 8  is an enlarged, fragmentary sectional view derived from circled region “ 8 ” in  FIG. 7 ; 
         FIG. 9  is an enlarged, fragmentary sectional view that is similar to  FIG. 7 ; 
         FIG. 10  is an enlarged, fragmentary sectional view derived from circled region “ 10 ” in  FIG. 9 ; 
         FIG. 11  is an enlarged, partially exploded fragmentary sectional view that is similar to  FIGS. 7 and 9 ; 
         FIGS. 12 and 13  are diagrammatic views sequentially illustrating the removal process; 
         FIG. 14  is an enlarged, fragmentary sectional view of the modular bottom bracket assembly during the initial phase of the removal process taken generally along line  10 - 10  of  FIG. 12 ; 
         FIG. 15  is a partially fragmentary, exploded isometric view of the composite bicycle bottom bracket shell with a modular bottom bracket assembly aligned for installation with installation apparatuses, and; 
         FIG. 16  is an enlarged, sectional assembly derived generally along line  16 - 16  of  FIG. 15  with installation assembly substantially completed. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Turning now to  FIGS. 1 and 2 , our modular bottom bracket bearing assembly  10  and a conventional, typical crank set  9  are disposed proximate a typical, unthreaded, press fit, or friction fit composite bicycle frame that is generally indicated by the reference numeral  8 .  FIG. 2  shows our modular bottom bracket assembly disposed proximate the lower section  9  of the typical, unthreaded, press fit or friction fit composite bicycle frame  8 . Composite bicycle frame  8  comprises a frame reinforcement element  12  and a pair of diverging, tubular frame elements  14  and  15  that rearwardly project from the frame bottom bracket shell  17 . As will be recognized by those skilled in the art, the bicycle rear wheel and suitable drive sprockets will be disposed between the ends of the elements  14 ,  15 . A generally tubular, forwardly projecting frame downtube  18 , extends from frame bottom bracket shell  17  at an angle with respect to the tubular frame elements  14  and  15 , and supports steering tube  19  ( FIG. 1 ) for the handle bar assembly (not shown). Frame bottom bracket shell  17  defines a generally tubular, hollow passageway or frame pass-through  20  into which a bottom bracket assembly is pressed to journal a spindle or crankshaft that supports conventional crank sets such as crank set  9  and conventional pedals (not shown). Our new modular bottom bracket assembly  10  is press fitted, or friction fitted into shell  20  to rotatably mount a spindle or crankshaft for low friction, highly efficient rotation. 
     With joint reference now directed to  FIGS. 1-11 , the preferred modular bottom bracket assembly  10  comprises an elongated, rigid, tubular, unibody sleeve  24  that is coaxially fitted within the frame pass-through  20 . Sleeve  24  preferably comprises a single, unitary part that is machined from metal, such as aluminum, or steel. Alternatively sleeve  24  may be molded from plastic. The leading sleeve end  26  is directed into frame pass-through  20  when press fitting the assembly  10  into the bicycle frame shell  20  during installation. Sleeve end  26  coaxially, internally receives a radial contact bearing  28  ( FIG. 3 ), that is press fitted into machined bearing bore  60 , as seen in  FIG. 10 . A bearing bore  60  is disposed at each end of the sleeve  24 . Each bearing bore  60  comprises an interference fit zone  62  and an adjacent, bearing pressure relief zone  61  ( FIG. 10 ) whose diameter is greater than the diameter of fit zone  62 . The interference fit zone  62  provides the press fit or friction fit surface required for bearing retention. Bearing pressure relief zone  61  is comprised of a channel  65  and an adjacent, progressive slope  67  that provides a buffer in case of excessive external pressure placed on bearings within housing  24  by the bicycle frame passage  20  in the event that frame passage  20  is not concentric or its diameter is otherwise out of specification. Radial contact bearing  28  is protected from debris during use by bearing dust shield  30  ( FIG. 3 ). As best seen in  FIG. 6 , bearing dust shield  30  comprises an offset, internal coaxial lip  31  that provides clearance for the inner race of radial contact bearing  28  to rotate independently of said bearing&#39;s outer race, which is press fitted into sleeve end  26 , and therefore stationary. 
     The terminal end of the tubular sleeve  24  has been generally designated by the reference numeral  38 . Component parts described hereinafter are fitted through sleeve end  38 , best seen in  FIG. 3 . These components include an inner, sleeve-like buttress bushing  44  that coaxially occupies tubular sleeve chamber  40  and extends between the inner race of radial contact bearing  28  and the inner race of identical, radial contact bearing  49  that is similarly press fitted into terminal sleeve end  38 . Radial contact bearing  49  is contacted by a bearing dust shield  52  at terminal end  38  that is similar to dust cover  30  described above. As best seen in  FIG. 8 , bearing dust shield  52  has an integral offset, coaxial lip  53  that abuts the inner race of radial contact bearing  49  in sleeve end  38 . Bearing dust shield  52  is depicted with a pair of optional 0.5 mm. shims  56  that are coaxially fitted against the dust cover  52  as needed to set proper compression of wave washer  58  during final fitment with a spindle or crankshaft. Radial contact bearings  28  and  49  both press fit within tubular sleeve  24 , being precisely internally located a set distance apart during the final stage of press fitting by abutting suitable integral shoulders  59  (i.e.,  FIG. 2 ) at opposite interior ends of the sleeve. 
     With emphasis now directed to  FIGS. 4-6 and 11 , tubular sleeve  24  has a preferred external configuration. End  26  has a press fit centering chamfer  70  that aids assembly. Centering chamfer  70  borders an integral, friction retention contact interface  72  that presents a raised external diameter of tubular sleeve  24 . Said diameter is preferably 1.814″ for Specialized branded Oversized Bottom Bracket, or OSBB-equipped bicycle frames, such as that depicted in  FIG. 11 . Dimensions vary from manufacturer to manufacturer. A transition region  76  separates contact interface  72  from central, tubular mass optimization zone  78  ( FIG. 4 ). A transition region  82  separates contact interface  72  from another friction retention contact interface  84  that extends toward tubular end  38  of the tubular sleeve  24 . Contact interfaces  72  and  84  are constructed substantially identically, possessing a diameter greater than that of mass optimization zone  78 . Turning now to  FIG. 11 , contact surfaces  72  and  84  in this example are slightly larger than the contact surfaces  63  and  64 , which are substantially identical. This difference provides the interference fit necessary to retain our modular bottom bracket bearing assembly  10 . 
     With joint reference directed now to  FIGS. 2, 4, 5, and 8 , sleeve end  38  comprises an external, integral installation stop flange  90  that has a flange backstop  91  ( FIG. 5 ) that abuts the frame bottom bracket shell  17  during the last stage of press fitment into frame pass-through  20 . Stop flange  90  integrally borders contact interface  84 . Stop flange  90  comprises an outer ring shaped portion  93  that adjoins an integral bezel  95  ( FIG. 4 ). Clearance face  97  externally faces outward to provide proper clearance with the inner face of a rotating crank arm during use. 
       FIGS. 12, 13, and 14  depict components, apparatuses, and procedures associated with the de-installation process for a modular bottom bracket assembly  10  from a frame pass-through  20  of a frame bottom bracket shell  17 . De-installation die  102  threads onto die shank  104 , both of our invention. Die shank  108  fits into a receptacle in an industry standard 1⅝″ air hammer, generally referred to by  109 , wherein it is retained by tool spring  100 , which is threaded onto hammer body  108 . 
     With emphasis on  FIGS. 12, 13, and 14 , depicted is the initial setup phase of a de-installation. De-installation die  102  interfaces with bearing  28  to drive modular bottom bracket assembly  10  from composite bicycle frame  8 . 
       FIGS. 15 and 16  depict components, apparatuses, and procedures associated with the installation process for a modular bottom bracket assembly. Industry standard press  115  is fitted with module driver  119  and installation standoff, both of our invention. Module driver  119  contacts bearing  49  during press fit installation. 
     With joint reference to  FIGS. 5 and 16 , installation standoff  120  gives clearance as centering chamfer  70  and a portion of sleeve end  26  ( FIG. 4 ) pushes through frame as flange backstop  91  abuts frame during the last stage of press fit procedure. 
     Installation Procedure 
     With joint reference directed now to  FIGS. 3, 4, 7, 8, 11, 15, and 16 , the installation procedure for our invention requires an industry standard press  115  (Brand: Park Tool, Model: HPP-2, depicted) to be used in concert with module driver  119  and installation standoff  120 . Module driver  119  and installation standoff  120  are of our invention and are designed to interface with a modular bottom bracket assembly assembled to the point of that depicted in  FIG. 4 .  FIG. 4  depicts a modular bottom bracket assembly ready for installation. 
     Installation components should be assembled as depicted in  FIG. 15  to begin press fit installation. As industry standard press  115  is actuated, module driver  119  urges against radial contact bearing  28 , thereby overcoming the friction of contact surfaces  72  and  84  against the inner surface of frame pass-through  20 , contact surfaces  63  and  64 . Pressing continues in like manner until flange backstop  91  abuts frame bottom bracket shell  17 , seen best in  FIG. 8 . Installation is now complete. 
     De-Installation Procedure 
     With reference to  FIGS. 6, 12, 13, and 14 , De-installation die  102  threads onto die shank  104 , both of our invention. Die shank  108  fits into a receptacle in an industry standard 1 ⅝″ air hammer, generally referred to by  109 , wherein it is retained for actuation by tool spring  100 , which is threaded onto hammer body  108 . So configured, upon actuation, air hammer  109  generates high frequency impacts which are translated as locomotive force by die shank  104  into de-installation die  102 . 
     With emphasis on  FIGS. 12 and 13 , depicting the initial setup phase of a de-installation procedure, de-installation die  102  interfaces with bearing  28 . Upon activation of air hammer  109 , de-installation die  102  forcefully urges against bearing  28 , thereby overcoming the friction fit between modular bottom bracket assembly  10 , contact surfaces  72  and  84 , and contact surfaces  63  and  64  of frame pass-through  20 , driving modular bottom bracket assembly  10  free of frame bottom bracket shell  17 . De-installation is now complete. 
     From the foregoing, it will be seen that this invention is one well adapted to obtain all the ends and objects herein set forth, together with other advantages which are inherent to the structure. 
     It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. 
     As many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.