BACKGROUND

1. Field

This disclosure relates generally to bicycles and more particularly to a bicycle having a collapsible frame.

2. Description of Related Art

Conventional bicycles provide an efficient means of transport in both urban and rural areas. Folding bicycles have application where there is limited space, or there are restrictive rules for transporting a bicycle, such as on public transport, car, airplane, ferry, or train, in urban condominiums or workplaces. Folding bicycles also have application where there is limited access to secure storage for the bicycle, such as in urban condominiums, workplaces, small dwellings, and places with difficult or tight access.

The predominant frame geometry for conventional bicycles is commonly referred to as a “diamond frame”, which has fixed front and rear triangles, or a front diamond and rear triangle and is generally accepted to provide superior riding characteristics and have good rigidity to weight ratio. Many examples of folding bicycles have non-conventional frame geometry, often have smaller wheels, and offer less than satisfactory riding performance and comfort. Existing folding or collapsible bicycles often deviate significantly from the “diamond frame” form and may also incorporate joints such as laterally pivoting hinges that add to the weight of the bicycle while reducing the rigidity of the frame. Some examples of folding bicycles are designed to locate the rear wheel under the down tube when folded, which necessitates significant departure from the “diamond frame” configuration.

Bicycles having a conventional frame geometry and sizing are generally more comfortable to ride, have improved handling, and improved road performance.

SUMMARY

In accordance with one disclosed aspect there is provided a bicycle frame. The bicycle frame includes a rear frame structure including a seat tube having a lower end and an upper end, the upper end being operably configured to receive a seat post for mounting a seat. The rear frame structure also includes a bottom bracket shell for receiving a bottom bracket operably configured to rotatably mount a crankset, and at least one chainstay extending rearwardly and terminating in a rear wheel mount for receiving a rear wheel. A forward end of the chainstay, the lower end of the seat tube, and the bottom bracket shell are rigidly connected proximate the bottom bracket shell. The bicycle frame also includes a front frame structure including a down tube rigidly connected to a forwardly disposed head tube, the head tube configured to receive a steerable front wheel mount for receiving a front wheel. The down tube is connected to the rear frame structure at a pivot proximate the bottom bracket shell, the pivot facilitating pivoting of the front frame structure with respect to the rear frame structure in a common vertical plane, about the pivot. The bicycle frame also includes a frame lock, which when engaged substantially immobilizes the pivot to place the frame in a riding condition, the frame lock, when disengaged, facilitating relative movement of the down tube and the seat tube towards each other about the pivot in the common vertical plane, to place the frame in a collapsed condition wherein the down tube lies alongside the seat tube.

The rear frame structure may further include at least one seat stay extending between the seat tube and the at least one chainstay.

The frame lock may include a crossbar spanning between the front frame structure and the rear frame structure and having an end operably configured to disconnect from one of the front frame structure and the rear frame structure to permit the front frame structure to move in the common vertical plane about the pivot.

The crossbar may have a forward end rigidly fixed to one of the down tube and the head tube and the rearward end may be operably configured to disconnect from the rear frame structure.

At least a portion of the rearward end of the crossbar may include at least one arm laterally displaced with respect to the common vertical plane to provide clearance between the crossbar and the seat tube when the frame lock is disengaged and the front frame structure is pivoted toward the rear frame structure when placing the frame in the collapsed condition.

The at least one arm may include a pair of arms laterally displaced toward either side of the common vertical plane.

The at least one arm may be operably configured to permit the rear wheel to remain mounted in the rear wheel mount when placing the frame in the collapsed condition.

The at least one arm may be operably configured to provide clearance between the at least one arm and drivetrain components of the bicycle to permit the drivetrain to remain configured for the riding condition and to further facilitate rotation of the rear wheel when the frame is in the collapsed condition.

The at least one arm may be configured to provide clearance between the crossbar and at least one of the upper end of the seat tube and the seat post when placing the frame in the collapsed condition.

The frame lock may include a fastener for connecting corresponding features on the crossbar and the front frame structure or rear frame structure to lock the frame in the riding condition.

The rearward end of the crossbar may terminate at a location partway between the bottom bracket shell and the upper end of the seat tube to provide a step through frame geometry.

The bicycle frame may include a frame retainer operably configured to releasably secure the front frame structure to the rear frame structure when the frame is in the collapsed condition.

The frame lock may be disposed proximate the upper end of the seat tube.

The frame lock may include a length of tube disposed at the rearward end of the crossbar and oriented to align with the upper end of the seat tube when the frame is in the riding condition, the length of tube being operable to act as the frame lock by receiving a seat post inserted through the length of tube and secured within the upper end of the seat tube.

The frame lock may include a brace releasably secured between a location proximate the lower end of the down tube and a location proximate the lower end of the seat tube, the brace being operable to immobilize the pivot when the frame is in the riding condition.

The brace may be disposed laterally with respect to the common vertical plane and above a chainring of the crankset and may have an arcuate shape for providing clearance for rotation of the chainring.

The pivot may be disposed adjacent to and forward of the bottom bracket such that when the frame is in the collapsed condition the down tube is generally disposed alongside the seat tube.

The pivot may be sized and configured to prevent lateral flexing of the frame about the pivot.

The pivot may be concentric with the bottom bracket shell.

The bottom bracket shell may include a pair of cylindrical bores that are laterally spaced apart, a central cylindrical bore disposed between and aligned with the pair cylindrical bores, and either the pair of cylindrical bores or the central cylindrical bore may be connected to the down tube, and a cylindrical sleeve having an outer surface sized to fit through the pair of cylindrical bores and the central cylindrical bore for forming the pivot, the sleeve having an inner bore sized to receive a bottom bracket for mounting the crankset.

The cylindrical sleeve may be fixed to at least one of the pair of cylindrical bores or the central cylindrical bore by any of a press fit, a bonding process, a threaded connection, and a welded or braised connection.

The frame lock, when engaged, may be operably configured to inhibit operation of the pivot between the pair of cylindrical bores and the central cylindrical bore when the frame is in the riding condition.

The bicycle frame may include at least one of a wheel retainer disposed on the frame for attaching the front wheel to the collapsed frame such that the front wheel lies alongside the collapsed frame, and a wheel retainer disposed on the frame for attaching the rear wheel to the collapsed frame such that the rear wheel lies alongside the collapsed frame.

The bicycle frame, when in the collapsed condition and having the front wheel and the rear wheel attached to the respective wheel retainers may have an extent that falls within commonly applicable airline travel restrictions associated with checked baggage.

The frame may be configured to generally correspond to a frame geometry and a wheel size associated with one of a conventional bicycle, an electric bicycle having an integrated electric motor for propulsion, a road bicycle, an urban commuter bicycle, a touring bicycle, a hybrid bicycle, a cyclocross bicycle, a single speed cross country mountain bicycle with rear suspension, an internally geared rear hub cross country mountain bicycle with rear suspension, and a fat bicycle.

The wheel size may include a full size wheel conventionally associated with the frame configuration.

A bicycle in accordance with another disclosed aspect may include the bicycle frame as defined above and further including a rear wheel mounted in the rear wheel mount, a steerable front wheel mount mounted in the head tube, a front wheel mounted in the front wheel mount, and a saddle mounted via a seat post in the upper end of the seat tube.

Other aspects and features will become apparent to those ordinarily skilled in the art upon review of the following description of specific disclosed embodiments in conjunction with the accompanying figures.

