WO2024134182A1

WO2024134182A1 - A rear derailleur for a bicycle

Info

Publication number: WO2024134182A1
Application number: PCT/GB2023/053307
Authority: WO
Inventors: David Foster
Original assignee: North Yorkshire Project Management Ltd
Priority date: 2022-12-21
Filing date: 2023-12-19
Publication date: 2024-06-27
Also published as: GB202219431D0

Abstract

The present invention provides for a bicycle rear derailleur for shifting a chain onto a desired sprocket of a multiple sprocket assembly having a plurality of diametrically different sprockets, comprising an actuator mechanism (e.g. gear selector), positioned on a bicycle frame forward of the multiple sprocket assembly and configured to selectively move the chain onto any one of the diametrically different sprockets of the multiple sprocket assembly. A tensioner mechanism (e.g. chain tensioning unit) is positioned on a bicycle frame forward of said actuator mechanism and configured to maintain chain tension within a predetermined range. A chain transmission system is operably coupled between said actuator mechanism and said tensioner mechanism and configured to retainingly guide the chain, during use.

Description

A REAR DERAILLEUR FOR A BICYCLE

Technical Field of Invention

The present invention generally relates to bicycle derailleurs. More specifically, the present invention relates to an alternative rear derailleur that displaces a chain between a pair of bicycle sprockets in cooperation with a chain tensioner.

Background

Many bicycles are provided with a drivetrain that allows the rider to change a gear ratio to allow the transfer of power from the pedals to the rear wheel. Often the drivetrain uses one or more derailleurs to change the gear ratio. In many bicycles, a front derailleur is mounted to the bicycle frame (i.e. seat tube) adjacent to front sprockets (or chainring) to shift a chain laterally between the front sprockets, while a rear derailleur is mounted adjacent to a hub of the rear wheel to shift the chain laterally between rear sprockets.

The basic function of a derailleur (front or rear) is to simply change the gear of the rear or front sprockets. The gears are changed using a gear shifter, usually mounted to the handlebars, configured to move or actuate the derailleur either via a cable (e.g. a Bowden cable) or electronically (e.g. a wireless signal adapted to trigger an selector of the derailleur). When actuated or triggered, the derailleur moves the chain between the sprockets, i.e. the chain is moved in or out on the rear cassette to provide a different sized chain ring within the drivetrain (and change the gear ratio). Another function is to maintain a suitable tension in the chain. Due to the transcending sizes of the chain rings within the rear cassette, the derailleur needs to change its length to reflect this, and thus additional jockey wheels are required on a spring-biased chain guide (also known as cage) to maintain chain tension (a well-known mechanism).

In particular for Mountain bikers (MTBs), the rear derailleur is considered to be the “weak link” of the bicycle drivetrain (the transfer of power from the pedal to the rear wheel via the chain). Although, the currently available mechanisms of typical derailleurs have proven to work sufficiently, the general design is still plagued with quite a few disadvantages.

For example, the location of the traditional derailleur is below the centre axle of the rear wheel, for some bicycles approximately 100 mm above the ground and outside of the rear swinging arm. Also, the rear derailleur is very exposed to the environment (i.e. not protected from potential damage). Thus, rear derailleurs are at constant risk to get hit by rocks, boulders or any other loose element (e.g. bracken, heather, branches). Even a slight knock can put off the alignment of the chain leading to slipping of the chain and potential damage of any one of the componentry until the derailleur is re-aligned. Further, as the chain feeds into the lower sprocket and whilst traveling through, vegetation may get pulled into the drivetrain potentially stopping the cogs from working. This will then lead to slipping of the chain so as to potentially cause damage to the componentry until the derailleur is re-aligned. Other elements that could cause problems include snow, where the derailleur may get clogged up with snow stopping or reducing performance until the snow is cleared away. The very action of the cog being driven by the chain can actively pull in material or debris, significantly increasing wear on the components eventually leading to malfunction and/or damage.

Because current derailleurs accommodate both actions, i.e. change gears and maintain chain tension, the mechanism is complex, comprising numerous components, making the derailleur vulnerable and expensive.

Also, in recent years, single front chains and large rear cassettes have become the norm for mountain bikes, because it simplifies the drivetrain and function and improves ease of use. However, the increase in number and size of the rear chain rings has been significant, including rear cassette sprockets up to 300 mm in diameter. Therefore, the traditional derailleur had to increase in size significantly to accommodate for the change.

These issues and problems identified with current rear derailleurs are magnified when used with the increasingly popular electric mountain bikes. Here, significantly more power and torque is provided in conjunction with an electric motor, and the weakness and frailty of known rear derailleurs becomes all the more apparent.

Accordingly, it is an object of the present invention to provide an improved, as well as, a simplified bicycle rear derailleur that is adapted to provide reliable shifting and relatively constant chain tension. Further, it is an object of the present invention to provide a rear derailleur that is more cost effective and more sustainable by having an increased life span.

Summary of the Invention

Aspects of the invention are set out in the independent claim(s). Dependent claims describe optional features. According to an aspect of the invention, there is provided a bicycle rear derailleur for shifting a chain onto a desired sprocket of a multiple sprocket assembly having a plurality of diametrically different sprockets, comprising: an actuator mechanism, positioned on a bicycle frame forward of the multiple sprocket assembly, mounted to the swinging arm and configured to selectively move the chain onto any one of the diametrically different sprockets of the multiple sprocket assembly, the actuator mechanism comprising: a actuator base bracket, mountable to the bicycle frame; a shaft member, extending away from said actuator base bracket in a direction and at an angle aligned with the cone shape formed by the diametrically different sprockets of the multiple sprocket assembly; a first chain guide, operably coupled to said shaft member, configured to guidingly receive the chain and axially move along said shaft member between a high-gear position, towards said selector base bracket, and a low-gear position, away from said selector base bracket, and a shifter, operably coupled with said first chain guide, adapted to move and retain said first chain guide into a desired position along said shaft member; a tensioner mechanism, positioned on a bicycle frame forward of said actuator mechanism, mounted to the swinging arm and configured to maintain chain tension within a predetermined range, the tension mechanism comprising: a tensioner base bracket, mountable to the bicycle frame, and a second chain guide, operably coupled to said tensioner base bracket via a first biasing member, configured to guidingly receive and elastically urge the chain in a direction so as to tension the chain; a chain transmission system, operably coupled between said actuator mechanism and said tensioner mechanism, configured to retainingly guide the chain between said second chain guide and said first chain guide, during use.

The shaft member is adjustable so as to ensure that the carriage is lined up with the cassette gear wheels. Adjustable stops may be provided to at both ends of the shaft member to control the range of movement. Advantageously, said actuator mechanism comprises a second biasing member adapted to bias said first chain guide towards said high-gear position. Preferably, said second biasing member is a coil spring axially arranged between said selector base bracket and said first chain guide. Alternatively, said first biasing member is a leaf spring. In yet another alternative embodiment, said first biasing member is a series of static and/or dynamic gear wheels suspended on the swinging arm. The suspended series of static and/or dynamic gearwheels may be spring-biased.

Advantageously, said transmission member is a tube.

Advantageously, said first and second chain guide comprise any one or any combination of a sleeve member and a guide pulley.

Advantageously, said actuator mechanism and said tensioner mechanism are mounted to the swinging arm so as to operate above the bottom chain portion.

Brief Description of the Drawings

An exemplary embodiment of the invention is explained in more detail hereinbelow with reference to the figures:

Figure 1 (prior art) illustrates a side view of (a) a typical bicycle drivetrain on a Mountain bike, and (b) a known rear derailleur including a spring biased cage;

Figure 2 shows a simplified schematic illustration of the rear derailleur system (a) when in the highest gear and (b) when in the lowest gear;

Figure 3 illustrates an example embodiment of the rear derailleur system (a) in a perspective rear view and (b) in a perspective bottom view;

Figure 4 illustrates the movement of the rear derailleur of Figure 3 from (a) the highest gear (i.e. smallest sprocket on cassette) (b) through the mid gear to (c) the lowest gear (largest sprocket on the cassette);

Figure 5 illustrates a perspective side view of an example embodiment of the rear derailleur system in situ, (a) when in the lowest gear (spring biased selector fully extended) and (b) when in the highest gear (spring biased selector is fully retracted, e.g. by a Bowden cable (not shown));

Figure 6 shows simplified schematics of an example embodiment of the present invention, side and top view; Figure 7 shows simplified illustrations of component parts of an example embodiment of the derailleur of the present invention, including an selector bracket and spring biased selector and chain guides;

Figure 8 shows simplified illustrations of further component parts of an example embodiment of the derailleur of the present invention, including the spring biased selector (selector) component;

Figure 9 shows simplified illustrations of component parts of an example embodiment of the derailleur of the present invention, including a tensioner comprising a mounting bracket, spring element and chain guide;

Figure 10 shows simplified illustrations of component parts of an example embodiment of the derailleur of the present invention, including a tube member (chain guide between tensioner and selector;

Figure 11 shows a simplified schematic illustration of the rear derailleur system (a) when in the highest gear and (b) when in the lowest gear for an alternative tensioner embodiment (option 1);

Figure 12 shows another alternative tensioner mechanism (derailleur not shown) when in the lowest gear (i.e. largest rear sprocket) and with the dynamic wheel moved closer to the crank (a) in a perspective side view and (b) in a top view (option 2), and

Figure 13 shows the alternative tensioner mechanism (derailleur not shown) of Figure 12 when in the highest gear (i.e. smallest rear sprocket) and with the dynamic wheel moved furthest away from the crank (a) in a perspective side view and (b) in a top view (option 2), and.

Detailed Description

The described example embodiment relates to a rear derailleur mechanism or system for mountain bikes, and in particular for electric mountain bikes. However, the invention is not limited to mountain bikes or electric mountain bikes but may be used for any suitable drivetrain using chain and sprockets.

Certain terminology may be used in the following description for convenience only and is not limiting. The words Tight’, ‘left’, ‘lower’, ‘upper’, ‘front’, Tear’, ‘upward’, ‘down’, ‘downward’, ‘above’ and ‘below’ designate directions in the drawings to which reference is made and are with respect to the described component when assembled and mounted (e.g. in situ). The words ‘inner’, ‘inwardly¹ and ‘outer’, ‘outwardly’ refer to directions toward and away from, respectively, a designated centreline or a geometric centre of an element being described (e.g. central axis), the particular meaning being readily apparent from the context of the description.

Further, as used herein, the terms ‘connected', ‘attached’, ‘coupled’, ‘mounted’ are intended to include direct connections between two members without any other members interposed therebetween, as well as, indirect connections between members in which one or more other members are interposed therebetween. The terminology includes the words specifically mentioned above, derivatives thereof, and words of similar import.

Further, unless otherwise specified, the use of ordinal adjectives, such as, ‘first’, ‘second’, ‘third’ etc. merely indicate that different instances of like objects are being referred to and are not intended to imply that the objects so described must be in a given sequence, either temporally, spatially, in ranking or in any other manner.

Through the description and claims of this specification, the terms ‘comprise’ and ‘contain’, and variations thereof, are interpreted to mean ‘including but not limited to’, and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality, as well as, singularity, unless the context requires otherwise.

Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract or drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Referring now particularly to Figures 2 to 5, the derailleur of the present invention aims to break down the complexity and simplify the typical derailleur/cage design. As the common derailleur has developed over the years, it has simply increased in size, using different materials, but also increase in cost of manufacture.

The derailleur system of the present invention comprises three parts, a chain tensioning unit (CTU) or tensioner mechanism, a chain transmission system (CTS) and a gear selector mechanism (GSM), i.e. the actuator. The complete system is mounted to the chain stay or swinging arm (MTB suspension). The complete derailleur system may be retrofitted, or may be manufactured (or incorporated) into the swinging arm during manufacture of the bikes.

(i) The Chain Tensioning Unit (CTU)

As shown in Figure 2, the chain tensioning unit (CTU) is located forward on the chain stay, i.e. close or adjacent to the crank, wherein the selector or actuator is located towards the rear of the chain stay or swinging arm close to the rear cassette. The CTU comprises a tensioner mount or bracket, configured to fixedly attach to the chain stay, that is coupled to a first chain guide member via a spring element.

Currently there are three options reflecting the variety of the rear cassettes. For a small rear cassette it is envisaged that a sprung loaded guide will be sufficient to take up the slack chain. However for larger rear cassettes a set of gear wheels will be required.

• CTU for small cassettes

As particularly shown in Figure 5, the spring element (e.g. a leaf spring) is configured to bias the first chain guide member towards the tensioner mount, thus, maintaining a predetermined tension (range) in the chain during use. It is understood by the person skilled in the art, that any suitable spring element may be used to provide a bias between the tensioner mount or bracket and the first chain guide member so as to control the tension of the chain during use. However, this type of tensioning system is most preferable with a smaller rear cassette (i.e. a relatively small difference between the largest and the smallest gearwheel or sprocket), particularly in entry level bicycles.

• CTU for larger cassettes (option 1)

Referring particularly to Figure 11 , the chain will exit off the crank and move onto the first static gear wheel. It will then feed onto the dynamic gear wheel which will move in a longitudinal direction under tension, then feed onto the second static gearwheel. This will in turn feed into the chain transmission system. The chain will then exit the transmission tube at the gear selector mechanism and is directed onto the rear cassette. The static gear wheels will direct the chain, whereas the dynamic gear wheel will take up the slack in the chain or add tension when required due to a change in gear. This unit in turn will be hinged to accept the lateral loading on the chain.

• CTU for larger cassettes (option 2)

Referring particularly to Figures 12 and 13, for this design there is two gearwheels on the crank with a dynamic wheel sliding along the swinging arm. The chain is presented onto the first gearwheel from the top of the rear cassette. Following a rotation the chain moves onto the dynamic cog where tension is applied I released. Following this cog the chain moves onto the second gearwheel and then into the chain transmission system feeding the selector mechanism.

(ii) The Chain Transmission System (CTS)

The transmission is how the chain is relayed from the CTU to the selector for which there could be two methods:

• Gear wheels (commonly known mechanism)

A gearwheel will support the chain coming out of the CTU. A gearwheel could also be on the spindle or shaft of the gear selector to present the chain to the rear cassette.

• Tube member

In a preferred embodiment, a transmission tube is used to connect the CTU to the selector or actuator. Here, the chain guide member comprises a tube member to carry and support the chain. The tube member may be made from a material adapted to provide a smooth (almost) frictionless bore or passage through which the chain passes. The tube guide would act directly onto the chain to increase I decrease tension within the chain.

Further, in this particular example, the tube is provided with a metal cap at either end. At its proximal end, the metal cap is fixed to the CTU, whereas, at its distal (rear) end, it is fixed to the carriage upon the spindle or shaft of the selector. This will provide for protection and delivery of the chain out of the CTU onto the rear cassette. Onto which gear of the rear cassette the chain is moved is controlled by the selector or actuator mechanism. The transmission tube may be made from a suitable polymer material, or may be a composite material. Inter alia, comprising materials such as ceramic, metal, polymer, rubber, silicone etc.

(iii) The Gear Selector Mechanism (GSM)

Referring now to Figure 3, the mechanism comprises a selector mount or bracket, configured to fixedly attach to the chain stay, an selector guide arm coupled to the bracket at a predetermined angle with respect to the operating plane of the sprockets (rear cassette) and rear wheel, and a second chain guide member operably coupled to the selector guide arm so as to allow axial movement along a longitudinal axis of the selector guide arm between a first, high gear position and a second, low gear position. The second chain guide member is biased towards the second, low gear position. During operation, the selector or selector moves the chain up and down selector guide arm (e.g. a spindle) thus moving the chain onto different sprockets of the rear cassette.

It is further envisaged that the spindle must be in line with the width (the width of the different sized sprockets forming a cone) and angle (i.e. the cone angle formed by the different sized sprockets of the cassette) of the rear cassette so there will be different variants reflecting the rear cassette makeup. The carriage or chain guide member (tube or jockey wheel(s)) is sprung loaded or biased, and configured to slide up and down the spindle I selector arm, in line with the sprockets of the rear cassette. The spring forces the carriage or chain guide member down the spindle towards the wheel (i.e. biased towards the low gear position). The carriage or chain guide member is operably coupled to a gear shifter (handle bar) via a cable (e.g. Bowden cable) so that the biased chain guide member can be pulled back up the spindle or selector arm towards the swinging arm (i.e. towards the high gear position).

In different embodiments of the present invention, the tensioner (CTU) and selector may be part of a single unit which will be attached to the swinging arm. This may be retrofitted, but it is preferable to design the mechanism into the bicycle swinging arm during manufacture.

A guard may be mounted over the length of the swinging arm for additional protection, thus, protecting the underside of the CTU, GSM and the CTS. This guard is mounted in a position in line with the bottom of the crank and largest gear wheel of the rear cassette and is configured to take any potential impact in order to protect the mechanicals. Specific advantages provided by the derailleur system of the present invention include the following:

• An existing derailer design is broken into its the key constituent parts, i.e. a selector and a chain tensioning unit. The selector is positioned under the rear swinging arm so as to reduce or minimise possible collisions, but above the bottom chain line within the largest sprocket of the rear cassette and crank to further reduce or minimise possible collisions. The tensioner is mounted either under or alongside the swinging arm and above the bottom line of the chain. This arrangement provides maximum protection of the gear changing mechanism during use.

• Value is added through the chain transmission system which further protects the chain and its transmission.

• Once the system is installed on a bike, maintenance is minimised because of minimal external interaction required. Regular cleaning and oiling of gear wheels is the only requirement common to all bikes, as damage from external impacts will be significantly reduced, if not prevented completely.

• The system provides for a significantly reduced number of components therefore reducing its complexity and cost of manufacture and/or repair and increased sustainability.

• The system is adapted to be retrofitted to bikes but can also be fully incorporated into the manufacture of a new bike design. The advantage of this is to reduce cost and develop a more efficient and economical design.

• Dimensions of the system of the present invention can be adapted or optimised for all bikes, e.g. for road bikes the system dimensions may be made slimmer and lighter than for MTBs or standard bikes. The reduced footprint of the system of the present invention can reduce drag and is beneficial to road cycling.

• As the componentry will be kept above the bottom chain line, the chances of an impact via rocks, sticks and vegetation are kept to an absolute minimum. Therefore, the life span of the componentry is maximised and maintenance is reduced. This reduces costs and increases sustainability.

• The mounting position of the system significantly improves the bike’s ground clearance.

As shown in Figures 4 (a) to (c), during normal operation of the derailleur system of the present invention, the user simply operates the gear shifter to a desired position which will either loosen or tighten a Bowden cable connected to the chain guide member of the selector so as to move the chain guide member along the spindle arm subsequently moving the chain onto a desired sprocket. In particular, as shown in Figure 4(a), a taut cable retains the selector chain guide member in its high gear position (against the force of the spring member), when shifting, the lengthening cable allows the spring member to push the guide member towards the lower gear position, so by shortening or lengthening the shifter cable (Bowden cable) the chain guide member is moved into a desired position. It is understood by the person skilled in the art that the guide member may be moved by any other suitable means, such as, for example a motorised lead-screw mechanism (e.g. driving a threaded selector arm so as to axially move a threaded chain guide member). Other stages of the chain and selector are shown in Figure 4(b) and (c).

At the same time (see Figure 5(a) and (b)), the CTU is providing a desired tension (via the spring member) to the chain when the chain is moved between different sized sprockets of the cassette.

Figures 6 to 10 show concept illustrations of the individual component parts of an embodiment of the present invention, including examples of suitable dimensions. It is understood by the person skilled in the art that the dimension given are only exemplary and limiting within the scope of the invention.

It will be appreciated by persons skilled in the art that the above embodiment(s) have been described by way of example only and not in any limitative sense, and that various alterations and modifications are possible without departing from the scope of the invention as defined by the appended claims. Various modifications to the detailed designs as described above are possible, for example, variations may exist in shape, size, arrangement (i.e. a single unitary components or two separate components), assembly or the like.

Claims

CLAIM(S)

1. A bicycle rear derailleur for shifting a chain onto a desired sprocket of a multiple sprocket assembly having a plurality of diametrically different sprockets, comprising: an actuator mechanism, positioned on a bicycle frame forward of the multiple sprocket assembly, mounted to the swinging arm and configured to selectively move the chain onto any one of the diametrically different sprockets of the multiple sprocket assembly, the actuator mechanism comprising: a actuator base bracket, mountable to the bicycle frame; a shaft member, extending away from said actuator base bracket in a direction and at an angle aligned with the cone shape formed by the diametrically different sprockets of the multiple sprocket assembly; a first chain guide, operably coupled to said shaft member, configured to guidingly receive the chain and axially move along said shaft member between a high-gear position, towards said selector base bracket, and a low-gear position, away from said selector base bracket, and a shifter, operably coupled with said first chain guide, adapted to move and retain said first chain guide into a desired position along said shaft member; a tensioner mechanism, positioned on a bicycle frame forward of said actuator mechanism, mounted to the swinging arm and configured to maintain chain tension within a predetermined range, the tension mechanism comprising: a tensioner base bracket, mountable to the bicycle frame, and a second chain guide, operably coupled to said tensioner base bracket via a first biasing member, configured to guidingly receive and elastically urge the chain in a direction so as to tension the chain; a chain transmission system, operably coupled between said actuator mechanism and said tensioner mechanism, configured to retaini ngly guide the chain between said second chain guide and said first chain guide, during use.

2. A bicycle rear derailleur according to claim 1 , wherein said actuator mechanism comprises a second biasing member adapted to bias said first chain guide towards said high-gear position.

3. A bicycle rear derailleur according to claim 2, wherein said second biasing member is a coil spring axially arranged between said selector base bracket and said first chain guide.

4. A bicycle rear derailleur according to any one of the preceding claims, wherein said first biasing member is a leaf spring.

5. A bicycle rear derailleur according to any one of the preceding claims, wherein said first biasing member is a series of static and dynamic gear wheels suspended on the swinging arm.

6. A bicycle rear derailleur according to any one of the preceding claims, wherein said transmission member is a tube.

7. A bicycle rear derailleur according to any one of the preceding claims, wherein said first and second chain guide comprise any one or any combination of a sleeve member and a guide pulley.

8. A bicycle rear derailleur according to any one of the preceding claims, wherein said actuator mechanism and said tensioner mechanism are mounted to the swinging arm so as to operate above the bottom chain portion.