GB2561547A

GB2561547A - Bicycle dropout arrangement

Info

Publication number: GB2561547A
Application number: GB1705015.4A
Authority: GB
Inventors: Farrell Daniel
Original assignee: Moulton Bicycle Co Ltd
Current assignee: Moulton Bicycle Co Ltd
Priority date: 2017-03-29
Filing date: 2017-03-29
Publication date: 2018-10-24
Anticipated expiration: 2037-03-29
Also published as: GB201705015D0; GB2561547B

Abstract

A bicycle dropout arrangement permits adjustment of the transmission chain or belt tension by allowing the wheel axle 8 to be moved fore-and-aft whilst maintaining a constant or near-constant distance between wheel axle 8 and the centre of the disc brake pad 11 to ensure efficient braking. A dropout plate 12 joined to chain stay 10 and seat stay 2 features a dropout slot 1 that describes an arc about the centre of the disc brake pad 11. Mounts 4,5 for a disc brake caliper may be included. This arrangement means that there is no need for the added complexity and added weight inherent with commonly-used auxiliary adjustable dropout plates.

Description

(71) Applicant(s):

The Moulton Bicycle Company Limited Holt Road, BRADFORD ON AVON, Wiltshire, BA15 1AH, United Kingdom (72) Inventor(s):

Daniel Farrell (74) Agent and/or Address for Service:

The Moulton Bicycle Company Limited Holt Road, BRADFORD ON AVON, Wiltshire, BA15 1AH, United Kingdom (51) INT CL:

B62K 25/02 (2006.01) B62K 19/38 (2006.01) (56) Documents Cited:

US 6386328 B1 US 20140054873 A1

US 20070278055 A1 US 20030183463 A1 (58) Field of Search:

INT CL B62K, B62L

Other: EPODOC, WPI, Full text (54) Title of the Invention: Bicycle dropout arrangement

Abstract Title: Bicycle adjustable dropout arrangement with constant disc caliper position (57) A bicycle dropout arrangement permits adjustment of the transmission chain or belt tension by allowing the wheel axle 8 to be moved fore-and-aft whilst maintaining a constant or near-constant distance between wheel axle 8 and the centre of the disc brake pad 11 to ensure efficient braking. A dropout plate 12 joined to chain stay 10 and seat stay 2 features a dropout slot 1 that describes an arc about the centre of the disc brake pad 11. Mounts 4,5 for a disc brake caliper may be included. This arrangement means that there is no need for the added complexity and added weight inherent with commonly-used auxiliary adjustable dropout plates.

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Bicycle Dropout Arrangement

The present invention describes a bicycle dropout arrangement that allows for the tensioning of a bicycle chain or belt (to compensate for wear and allow for correct fitting) and allows for the simple fitting of a disc brake calliper.

Background

A bicycle with a single gear, or an internal hub gear system, requires a method of tensioning the chain (or belt) that is used for the transmission of power from the chainwheel (driven by a pedal and crank arrangement) to the rear sprocket mounted on the rear wheel hub. A bicycle chain wears with usage, and if no method of tensioning is provided, the chain will 'jump' under pedal pressure and prevent transmission of power to the rear wheel.

One conventional method of tensioning the chain is by altering the position of the rear wheel. It will be appreciated that increasing the distance between the centres of the chainwheel and the rear sprocket will increase the tension of the chain or belt. This method requires a substantially horizontal dropout. Typically a bicycle designed for road use will have a dropout with a slot around 30 degrees to the horizontal (Fig. 1 shows general layout, Fig. 3 shows detail). The reason for this is to reduce or eliminate the need for adjustment of brake blocks bearing on the wheel rim when the wheel is moved forwards or rearwards. The dropout slot (1) is substantially perpendicular to the bicycle frame seat stays (2), and hence is substantially parallel to the brake blocks (represented by line (3)), so the effect of wheel movement is minimised. Bicycles designed for racing on a closed track (velodrome) will have a fully horizontal dropout as a rim brake is not fitted.

On a small-wheeled bicycle (typical example Fig. 1), or a bicycle with lowered seat stays (Fig. 4) it is not conventionally possible to achieve the geometry described above, as if the dropout slot (1) is perpendicular to the seat stay (2), the dropout slot will not be substantially horizontal and hence chain tension function would be poor (little adjustment would be possible) and any adjustment would be achieved by undesirable change in height of the bicycle as the wheel is moved up or down. It can be see that the line of the brake blocks (represented by line 3) is no longer parallel to, or near parallel with, the dropout slot (1). As a result, any significant movement of the wheel axle in the dropout slot (1) will require adjustment of the brake blocks and may reduce tyre clearance.

Another method of tensioning the chain is to mount the chainwheel/crank assembly in an eccentric housing, but this introduces other problems including variation of the saddle to pedal distance.

The introduction of disc brakes to bicycles complicates the chain tensioning problem further. The brake disc is fitted concentrically to the rear wheel hub and hence moves when the wheel is moved to tension the chain. The disc brake calliper is rigidly attached to the bicycle frame with bolts through holes (4, 5) and has no conventional means of adjustment. Typically this problem is overcome by the fitment of auxiliary dropout plates (6) (that feature both a dropout slot and a disc brake calliper mount) as seen in Fig. 6. These plates are bolted to the bicycle frame in a way that allows for adjustment - i.e. increase the distance between centres of the crank/chainwheel assembly and rear sprocket/rear wheel either by substantially horizontal slots or by a single pivot and a curved slot, and secured by appropriate fasteners (7). This method adds complication and weight to the bicycle, both of which are undesirable.

There is no such complication required on a bicycle fitted with derailleur gears, as the rear wheel axle centre (8) and the disc brake calliper can be located in a fixed position (Fig 5).

The chain tensioning function is handled by the rear gear change mechanism.

Drawings

Figure 1. Typical small-wheeled bicycle

Figure 2. Typical conventional diamond frame bicycle

Figure 3. Rear dropout / seatstay and chainstay arrangement, diamond frame bicycle - showing how the seat stay bridge / brake blocks (3) are substantially parallel to the dropout slot (1)

Figure 4. Rear dropout / seatstay and chainstay arrangement, small-wheeled bicycle - showing how the seat stay bridge / brake blocks (3) are not parallel to the dropout slot (1)

Figure 5. A rear dropout with disc brake mount for derailleur geared bicycle - no adjustment required as chain tension is handled by rear derailleur gear.

Figure 6. A rear dropout for hub gear/single speed with adjustable sliding plate (6) affixed to bicycle frame (shaded grey)

Figure 7. Preferred embodiment of the present invention

Figure 8. Alternative embodiment of the present invention

Summary of the Invention

The primary objective of the present invention is to provide a simple means of adjusting the tension of the bicycle chain, whilst allowing for the use of disc brake calliper. This method is suitable for both small-wheeled and large-wheeled bicycles, and does not require adjustment of the brake position or any supplementary hardware.

To achieve this objective, the present invention provides a rear dropout for a bicycle frame of substantially flat shape. The dropout is permanently fixed to the bicycle frame chainstays and seat stays by a suitable method (brazing, welding, bonding). The dropout is provided with a slot to accept the rear wheel axle.

This dropout slot, whilst being substantially horizontal, is formed in an arc about the centre of the disc brake calliper pad (11). Thus it can be seen that as the wheel is moved rearwards to tension the chain or belt, the distance from the wheel axle to the centre of the disc brake pad does not change.

Detailed Description of the Invention

A preferred embodiment of the present invention is described below with reference to fig.

7.

In the preferred embodiment there consists a dropout plate (12) that is permanently fixed to the seatstays (2) and the chainstays (10) of the cycle by means of welding, brazing or any other means of permanent fixing.

The dropout plate (12) is of substantially flat shape and typically of thickness 4 to 12mm and is formed from a suitable material such as steel, stainless steel, titanium, aluminium or carbon fibre.

The dropout plate (12) is provided with suitable locations for the mounting of a disc brake calliper. In the preferred embodiment, this is depicted by two holes (4) and (5) but any suitable mount type may be used including flat mount and post mount. The disc brake rotor (13) is mounted concentrically on the wheel axle.

The dropout plate (12) is provided with a dropout slot to locate the rear wheel axle, typically of a width between 9 and 20mm to accommodate an axle of diameter 9mm to 20mm. In conventional usage, the axle is of conventional size (10-llmm in diameter) and is provided with flats on the axle and anti-rotation washers to locate on these flats and into the dropout slots (3).

In the preferred embodiment, in order to allow removal of the wheel from the bicycle frame, the dropout slot features a change in angle (14) to provide an exit route for the wheel axle from the dropout slot. The dropout slot (1) is 'forward facing'. A conventional chain tensioning device may be used to aid tensioning the transmission chain or transmission belt, and the outer shape of the dropout plate may be contoured advantageously for this reason.

The dropout slot (1) is formed in an arc substantially about the centre of the disc brake pad (11). This ensures that the wheel axle centre (8) stays a constant distance from the centre of the disc brake pad (11). As the disc brake rotor (13) is mounted concentrically with the wheel axle centre (8), the disc brake pad (11) remains centred on the sweep of the rotor. The arc is typically of a length to allow at least 12mm of adjustment of position of the wheel axle centre (8).

The preferred embodiment is suitable for any seat stay (2) angle and hence is suitable for large- or small-wheeled bicycles and most frame designs.

An alternative embodiment is described in Fig. 8. In this alternative embodiment, the dropout slot (1) is open to the rear of the bicycle. This makes wheel removal more difficult but potentially allows for greater adjustment of wheel position. As in the preferred embodiment, the arc of the dropout slot (1) is substantially formed about the centre of the disc brake pad (11). A conventional chain tensioning device may be used and the outer shape at the rear of the dropout plate may be profiled advantageously to support this.

In an alternative embodiment, the brake calliper mounts (4) and (5) are positioned further to the rear than in the preferred embodiment. This allows for a steeper seat stay (2) angle (as on a conventional diamond frame bicycle depicted in Fig. 2) whilst keeping the seat stay substantially coincident with the wheel axle centre (8).

Claims

Claims 29 03 18

1 A bicycle dropout arrangement that permits adjustment of the transmission chain or belt tension by allowing the wheel axle to be moved in a substantially fore-and-aft plane, whilst maintaining a constant or near-constant distance between wheel axle and the centre of the disc brake pad to ensure efficient braking, without the need for auxiliary adjustable dropout plates.

2 A bicycle dropout arrangement according to claim 1, where the dropout slot describes an arc centred on or near the centre of the disc brake pad.

3 A bicycle dropout arrangement according to preceding claims 1 or 2, where the dropout slot features a distinct change in angle / path to facilitate the easy removal of the wheel from the bicycle.

4 A bicycle dropout arrangement according to preceding claims 1, 2 or 3, where the dropout slot is open towards the front of the bicycle.

5 A bicycle dropout arrangement according to preceding claims 1 and 2, where the dropout slot is open to the rear of the bicycle.

6 A bicycle dropout arrangement according to any of the preceding claims, where the dropout is provided with an integral mount for a disc brake calliper.

7 A bicycle dropout arrangement according to any of the preceding claims, where the outer profile of the dropout is contoured to facilitate the fitment of a chain- or belttensioning device.

Intellectual

Property

Office

Application No: GB1705015.4 Examiner: Mr Philip Osman