Patent Application
20050242658
This invention relates generally to spoked wheels and, more specifically, to a light weight, fatigue resistant bicycle wheel with a straight spoke arrangement.
Many have attempted to design light weight, durable wheels, from wagon wheels to bicycle wheels for both road and mountain bikes. Low weight becomes especially important in wheel applications for human powered machines, such as bicycles since the rider can provide only a small amount of horsepower. Furthermore, mass at or near the periphery of a wheel requires more effort to accelerate due to the inertial forces that must be overcome to rotate the mass. However, weight reduction of a wheel must be carried out carefully to maintain durability. Low weight is of little help if the wheel breaks, especially without ease of repair.
Most bicycle wheels include a rim that accepts a tire, a hub that mounts to an axle, and spokes that support tension between the hub and rim. Rim thicknesses have been reduced in certain designs. However, some structural mass is required to maintain a strong connection to the spokes. Spokes have typically been threaded to a nipple fed through the outer portion of the rim under the tube and tire mount location. This has required radial holes in the rim through which to insert the nipples. Such holes cause weakness and stress risers in the rim due to the discontinuous structure. The rim must be strengthened in surrounding areas, adding weight. Furthermore, the holes require coverage with rim tape or rubber strips to protect the tube from expanding into the holes, abrasion, and punctures. The tape or rubber also adds weight. With the spoke-attaching nipples inserted through the rim, deflation and removal of the tire is required when replacing broken spokes. The holes are also very difficult to seal against tire pressure, preventing the use of tubeless tires.
Standard spokes are also unreliable. Such spokes include a 90 degree bend with a mushroomed head adjacent the bend. The opposite end of the spoke includes threads to engage the rim-supported nipples. Such spokes may include reduced center sections (butted spokes) to reduce weight. However, such spokes typically fail at the bend, leaving the cyclist, at best, with a wheel out of true that rubs on the brake pads. The cyclist may even be stranded with an unridable bicycle or injured in a related fall.
Attempts to solve these problems have not been satisfactorily successful. A patent to Mercat (U.S. Pat. No. 6,402,256) discloses a rim that does not include nipple insertion through the tube/tire mounting location. Instead a separate inner wall or “bridge” connecting two sidewalls is provided in the rim apart from the outer wall or bridge upon which the tube would sit. Holes extend through this inner wall into which “end pieces” may be secured for connection to the spokes. The inner wall must be strong enough to deal with the tensile spoke forces and metal fatigue caused by spoke force variation during riding. The wall must also accommodate the relatively large end-piece holes. Thus the bridge is formed with a large thickened wall section surrounding the holes that extend toward the inside of the casing. An additional process of “flow drilling” is required at the holes to create the “chimney-like” structure for securing the end pieces. Thus while Mercat provides a good seat for the tube and tire, the bridge arrangement adds weight and complexity to the rim and its production. The Mercat spoke attachment still suffers from broken spoke problems, not simply due to the 90 degree bend at the hub, but also due to the stress concentration at the rim attachment. A stress concentration is created at the first thread. Further problems discussed above are also left unsolved.
A patent to Rasmussen (U.S. Pat. No. 5,487,592) discloses attempts to solve problems relating to the stress risers in the bend of conventional spokes by providing a system that employs straight spokes, threaded at both ends. The outer ends, however, are secured with nipples inserted through the rim in a conventional manner—creating holes in the tube/tire seating location. Thus the integrity of the seat is compromised and spokes cannot be replaced without removal of the wheel from the frame and the tire from the rim. The Rasmussen arrangement also suffers from stress concentration on the spokes at the first thread, as discussed above.
The rim disclosed in a patent to Herting (U.S. Pat. No. 6,425,641) achieves a tube/tire seat without holes but requires an additional bend in the spoke at the rim attachment. Further, Herting may not be suitable for tubeless tires as the rim is of multi-part construction with a joint in the seat.
Two patents to Dietrich (U.S. Pat. Nos. 6,428,113 and 5,931,544) disclose a front hub mounting system combining a few straight spokes with bent spokes. The system requires that all spokes be inserted through the rim, with attendant holes. The straight spokes used are secured to the middle of the front hub (on the center plane of the wheel). Thus they are of limited application and the wheel still suffers from the disadvantages discussed above.
Therefore, an unmet need exists for a bicycle wheel arrangement that is lightweight and easy to manufacture, that also reduces the tendency for spokes to break and simplifies spoke replacement.
The present invention includes a bicycle wheel having a hub, a plurality of spokes, and a rim. The spokes are connected to the hub, each spoke having two ends and a major axis. The ends of each spoke are substantially aligned with the major axis of such spoke. The rim provides a plurality of fixed spoke mounts secured to the spokes. The spoke mounts decrease in section as they extend away from the main body of the rim.
In accordance with one aspect of the invention, the spoke mounts are integrally formed with the rim. The rim also includes a tire mounting structure on the exterior side of the rim opposite the spoke mounts. The tire mounting structure includes sidewalls and a bottom wall. The bottom wall is preferably free from spoke assembly openings.
In accordance with a further aspect of the invention, one end of each of the straight spokes is in direct threaded engagement with a respective spoke mount.
In accordance with a further aspect of the invention, one end of each of the straight spokes is in direct engagement with a respective spoke mount. The engagement interface is preferably threaded, as is the spoke mount for receiving the spoke threads. In an alternate embodiment, one of the ends of each of the spokes is conically shaped. In this embodiment, the spoke decreases in section as it extends inward through at least a portion of the spoke mount. In another aspect, the spoke mounts include holes into which the spokes are mounted. Each of the outer ends of the spokes includes a portion of increased section larger than the holes.
In accordance with another aspect of the invention, each of said spoke mounts includes an attachment portion configured to disperse the tensile load from the spoke mounted thereto beyond the initial engagement at the inward end of the mount. Each spoke mount includes a threaded end within which internal threads are disposed. In one embodiment, stress grading (i.e., load dispersion) is accomplished with at least one external side of the mount being sloped inward toward the threaded end. In a preferred embodiment of the invention all sides slope inwardly toward the threaded end. In accordance with a further aspect of the invention, a ferrule abuts the threaded end of the spoke mount. The ferrule has a substantially frustoconical shape and a bore for receiving a spoke.
In accordance with yet further aspects of the invention, the spoke mount external side slopes non-linearly along a substantially circular path. In alternative embodiments, the path of curvature is parabolic, oval, or hyperbolic.
Another aspect of the invention includes a spoke mount having two sets of internal threads. Such threaded holes are side-by-side for receiving the outer ends of two spokes, such as paired spoke designs.
Still another aspect of the invention includes a spoke mount having a threaded end within which the internal threads are recessed from the inward leading end of the mount.
Preferably the spoke mounts extend inwardly from the interior of the rim, each spoke mount having an internal threaded hole for securing a respective spoke. Such holes are situated with at an angle from the rim within seven degrees laterally and 20 degrees longitudinally from a radial line extending from the rim to the hub.
In accordance with other aspects of the invention, spoke adjustment mechanisms secure the spokes to the spoke mounts. Such mechanisms allow spoke tension adjustment. In one embodiment the spoke adjustment mechanisms comprise turnbuckles secured between the spoke mounts and the spokes. Alternate arrangements for the turnbuckle are provided herein. In one arrangement, the turnbuckles comprise barrels and links coupling the barrels to the spoke mounts. Each of the barrels include right-hand threads within one end for engaging the spokes and left-hand threads within the opposite ends to engage the links. In another arrangement, the barrels include relatively course threads within one end receiving a respective one of the spokes. Relatively fine threads are disposed in the opposite ends, receiving a respective one of the links. In still another embodiment of an adjustment mechanism, an adjustment nipple is rotatably coupled to a spoke mount. The nipple has an internally threaded end coupled to a spoke.
The adjustment mechanism turnbuckles may each alternatively include a body having a threaded recess in one end and a stud projecting from the opposite end. The threaded recess receives a spoke. The stud engaged at least one of the spoke mounts. The stud may be integrally formed with the outer body or may be a separately inserted part. The body includes flats on the exterior thereof for facilitation of turning the body for spoke tensioning adjustment. The stud is preferably left-hand threaded, such that rotation of the body selectively loosens or tightens the spoke.
In accordance with yet another aspect of the invention, spoke adjustment mechanisms are secured between the hub and the spokes. Such mechanisms provide tension adjustment for the spokes. The spoke adjustment mechanisms include threaded adjustment nipples. Each nipple is rotatably secured to the hub and has a threaded end for engagement with one of the spokes.
The present invention also includes a method of securing a wheel rim to a hub. The steps of the method include providing a plurality of straight spokes, threaded on both ends. One end of each spoke is threaded into a fixed mount on the rim. The opposite end of each spoke is threaded into a rotatable nipple secured to the hub. Preferably a ferrule is placed on one end of a spoke before threading that end into the fixed mount on the rim. The invention further includes a bicycle rim constructed with an extrusion and machining process. The process begins with extruding a metal into a shape including a tire engaging portion, an intermediate wall, and a center flange opposite the tire engaging portion. Portions of the center flange are machined away to leave spoke mount projections. The projections decrease in section as they extend away from the intermediate wall. Preferably, the height of each spoke mount projections is at least ten percent of the width. More preferably, the height is at least one-fourth of the width. Threaded holes are created in the ends of the spoke mount projections for receiving spokes. The metal is formed into a substantially circular shape with the angle of each of the threaded holes being within seven degrees laterally and 20 degrees longitudinally from a radial line extending from the rim.
The invention also includes a spoke for engaging a hub and a rim. The rim has spoke apertures. The spoke includes first and second ends and a shaft. The first end engages one of the apertures with a portion having a section larger than the aperture. The second end is engageable with the hub. The second end and shaft have sections no larger than the aperture such that they may be inserted therethrough.
In one preferred embodiment, the invention includes a bicycle rim constructed by a process including forming a rim with a threaded mount and inserting a spoke into the rim. The mount is a fixed spoke mount projecting inwardly from the interior of the rim. The mount has internal threads for securing a spoke and has a decreasing section as the mount extends inwardly. The spoke includes a shaft portion and a threaded portion. The spoke is inserted into the threaded portion of the mount such that at least a portion of the shaft portion of the spoke is forced into an interference fit with the threads in the inward end of the mount. Preferably, the spoke threads include an outer diameter greater than the spoke shaft diameter. Alternatively the spoke threads include an outer diameter no larger than the spoke shaft diameter.
As may be appreciated from the foregoing summary, the invention provides a bicycle wheel with a lightweight rim and fatigue resistant spoke arrangement. The spokes are also easy to replace without tire or wheel removal or even tire depressurization. Further, the integrity of the tire/tube portion of the rim simplifies the rim and minimizes flats. Tubeless tires may more easily be employed with the present arrangement.
The preferred and alternative embodiments of the present invention are described in detail below with reference to the following drawings.
a is a magnified sectional view of one embodiment of the spoke mount of the present invention with a circular fore and aft profile;
b is a magnified sectional view of one embodiment of the spoke mount of the present invention with a parabolic fore and aft profile;
c is a magnified sectional view of one embodiment of the spoke mount of the present invention with an oval fore and aft profile;
d is a magnified sectional view of one embodiment of the spoke mount of the present invention with a hyperbolic fore and aft profile;
a is a magnified side elevational view of a rim section with a dual spoke mount;
b is a magnified side elevational view of a rim section with paired separate spoke mounts;
Hub 12 includes a drive side 18 and non-drive side 20. Drive side 18, typically the right side of hub 12, allows for securement of rear sprockets to which a chain is entrained for driving the wheel forward. Alternatively, the wheel construction can also be made for a front wheel, which does not include a drive side. In such an instance the construction is preferably more similar to non-drive side 20 on both sides of such wheel.
In the embodiment shown in
Referring now to
Spoke mount 24 is also shown in more detail in
Rim 16 is preferably constructed by extruding a material into the A shape with an extended ridge 30. After the extrusion process, ridge 30 is then machined down to its final height to form spoke mounts 24 extending integrally inward therefrom. Rim 16 is preferably curved into a circular shape with the ends welded together to form a circular rim 16. This curving into a circular rim may be performed before or after the machining process to form spoke mounts 24. In the preferred embodiment, the steps of machining to form spoke mounts 24 and drilling bores 46 are carried out before the extruded material is curved to form rim 16 into a circular shape.
As illustrated in
Preferably the angle of bore 46 or spoke 14 from the rim is within plus or minus seven degrees laterally and plus or minus 20 degrees longitudinally from a radial line, to facilitate straight spoke pull without bending. The angle of the spoke will depend upon the width of the hub, as well as whether the spoke is being secured to a drive side of the hub or a non-drive side of the hub or front hub. Alternate embodiments of spoke mounts that may also accommodate various angles are illustrated in
The embodiments illustrated and described above with regard to spoke attachment and mounting disclose primarily hub-side adjustment, preferably with nipples that secure the hub to the inward ends of the spokes. Alternate rim-side or mid-spoke adjustable mountings are also possible with the present invention.
An alternative embodiment of a turnbuckle is illustrated in
A further embodiment of a turnbuckle 268 is illustrated in
In an alternate embodiment, stud 482 and mount 24 are both right-hand threaded with stud 482 having finer threads or coarser threads to allow tensioning adjustment by turning body 478.
The embodiment of
In all of the various embodiments described above, stress concentrations are reduced either by providing straight spokes, or by providing stress grading where spokes are secured. Such constructions will lengthen the life of the spokes. Where spoke replacement is required many embodiments of the present invention also allows such spokes to be replaced without removal of the tire from rim 16 and possibly without the removal of wheel 10 from the bicycle. In many embodiments, both ends of the spokes may be accessed without obstruction by the tire tube or hub. Thus, the present invention provides a spoke-mounting arrangement that is easier to use and maintain while also requiring less maintenance overall due to increased fatigue resistance.
The assemblies described also provide a light-weight system as the spoke mounts are small in size and use very little material, while the stress-grading features of the mounts disperse the load properly into the rim. The fortification around holes in rims that are conventionally used with nipples extending through the rims is not necessary. Furthermore, the elimination of holes through the wall 32 that seats the tube minimizes punctures.
While preferred embodiments of the invention have been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. For example, the turnbuckle may be positioned nearer the hub than the rim. Accordingly, the scope of the invention is not limited by the disclosure of the preferred embodiments. Instead, the invention should be determined entirely by reference to the claims that follow.
