Patent Application
20230192228
This is an original U.S. patent application.
The invention relates to bicycle frame components. More specifically, the invention relates to rear-wheel dropouts that hold the rear wheel’s axle securely in severe duty situations.
Bicycles are comprised of a number of parts (wheels, handlebars, brakes, pedals, seat) secured to each other and to a frame. Many parts are secured by simple friction clamping (e.g., the seat post is often clamped into a concentric seat tube of the frame). Friction clamping is simple, inexpensive, and can permit easy fine adjustment.
Some bicycle parts experience significant stresses in use, particularly during competition and in certain styles of riding. Downhill racing and BMX trick riding in particular present challenges to bicycle components and securing mechanisms.
One joint where a conventional friction clamp is often used, but can fail under hard service, is the rear axle to frame connection. A conventional rear axle is clamped into the frame by threaded fasteners (nuts) or by a cam-operated quick-release spindle. But hard landings after jumps or tricks can knock the axle out of position, resulting in a crooked rear wheel and poor or unexpected bicycle behavior.
Sophisticated mechanisms (often modeled after motorcycle rear-wheel connections) can hold a bicycle rear wheel securely, but these mechanisms are often expensive or heavy. An alternate solution to hold a bicycle rear wheel securely that is lighter and less expensive may be of significant value in this field.
Embodiments of the invention are bicycle rear-wheel dropouts having a longitudinal slot to permit adjustment of the rear wheel axle, with a plurality of grooves oriented roughly perpendicular to the slot; and locking plates having a plurality of complementary grooves, where the locking plate is placed around the rear wheel axle and secured against the grooves of the dropouts to hold the axle securely in place.
Chain-driven bicycle 100 comprises a front wheel 110, which rotates about a front axle 115. The front axle is secured to the fork 120. The fork is coupled to the frame 125 at the head tube 130. Handlebars 135 are coupled to the fork 120.
At the rear of the bicycle, a rear wheel 140 rotates about a rear axle 145, which is secured to the frame 125 between right and left dropouts (circled at 150). A driven sprocket is coupled to the rear wheel and concentric about the rear axle, but is not clearly visible and therefore is not identified in this view.
A driving sprocket 155 carries a chain 160, which loops around the driven sprocket near the rear axle 145. The driving and driven sprockets and the chain are arranged so that adjusting the position of rear axle 145 along an adjustment direction 165 can loosen or tighten the chain.
The rear portion of frame 125 is made up of a seat tube 170 and pairs of seat stays 175 and chain stays 180. The rear dropout, chain stay and seat stay on either side of the rear wheel 140 form a triangle, with the seat tube 170 forming a common forward edge of the left and right triangles. Bicycle frames are often constructed of appropriately-sized tubing welded together at joints. Many of these joints include a fitting or bracket brazed or welded to the tubes. For example, the head tube typically includes bearing races to allow the fork to turn smoothly, and a pedal-operated bicycle conventionally includes a large “bottom” bracket to support a crankshaft extending from the left crank and pedal through to the right crank and pedal.
Embodiments of the invention form part of the frame of a bicycle near the junction of the chainstay, seat stay, and rear axle, at a part conventionally known as a “dropout.”
This figure shows two different types of mounting features: a cylindrical boss 240, suitable for inserting inside a tubular seat stay; and a notch 250, into which a tubular chainstay may be inserted. Typically, both mounting features of a single dropout are similar, rather than heterogenous as shown here. Dropouts may be cast or drop-forged, machined from billet, or stamped or cut by saw, waterjet or laser from a sheet or bar of strong material that is compatible with the process used to secure the dropout to the rest of the frame.
An embodiment further comprises a locking plate, which may be in the general shape of a washer 360, or a different shape 370. The locking plate has an opening (365 or 375) which is large enough to accept the rear axle. Further, in an embodiment of the invention, at least a portion of one face of the dropout 300 is provided with grooves, serrations or locking channels 390. Complementary grooves, serrations or locking channels are formed on at least one face of the locking plates. When the bicycle is assembled, the channeled faces of the dropout and the locking plates are placed adjacent each other and urged into contact by a threaded fastener on the rear axle, by a “quick-release” spindle through the rear axle, or by another similar mechanism. When the rear wheel is secured into the dropout, then, the mating serrations of the dropout and the locking plate prevent the rear axle from sliding forward or backward in the parallel-sided slot. This is important for a bicycle whose rear wheel is subjected to extreme stresses, such as in downhill racing or BMX trick riding.
The embodiment comprises a locking plate 460, which has a hole large enough to admit the rear axle 445 and a plurality of complementary channels across one face (the channeled face is oriented away from the viewer in this figure, but the edges of the complementary channels can be seen at 465). A threaded fastener (nut) 470 can be tightened onto the axle 445 to urge the locking plate 460 against the dropout 400. When the complementary channels are engaged, the rear axle 445 is prevented from moving back and forth in the slot 410. The channels in the dropout face 420 and the locking plate may be square or trapezoidal.
In similar fashion, the depth of the interlocking channels may be of similar dimension to the pitch of the grooves, or somewhat less than the groove pitch. Deeper grooves are more difficult to manufacture, with limited benefits. Grooves that are too shallow may not provide enough resistance to rear axle movement.
The applications of the present invention have been described largely by reference to specific examples and in terms of particular allocations of functionality to certain physical features of embodiments. However, those of skill in the art will recognize that bicycle rear axles can be held securely and adjustably by components that achieve the effects of the present invention differently than the embodiments depicted in the figures. Such variations and alternate structures are understood to be captured according to the following claims.
