GB2540372A

GB2540372A - Bicycle structure

Info

Publication number: GB2540372A
Application number: GB1512291.4A
Authority: GB
Inventors: Smart Simon
Original assignee: Smart Aero Technology Ltd
Current assignee: Smart Aero Technology Ltd
Priority date: 2015-07-14
Filing date: 2015-07-14
Publication date: 2017-01-18
Anticipated expiration: 2035-07-14
Also published as: GB2540372B; GB201512291D0

Abstract

A bicycle structure includes a frame 102 and a seat post 116 that is attachable to the frame. The frame 102 includes a frame element 110 having a first mounting formation 126, and the seat post 116 includes a second mounting formation 124 that is complementary to the first mounting formation 126. The seat post may 116 be attached to the frame element 110 by bringing the second mounting formation 124 into engagement with the first mounting formation 126 in a mounting direction that is substantially perpendicular to a longitudinal axis of the seat post 116. There may be at least one fixing element (e.g. screw, bolt, etc.) for fixing the seat post 116 to the frame element 110. The seat post 116 and frame element 110 may have complimentary profiles so that when attached they have an aerodynamic profile. There may be a fairing that is removably attachable to the rear of the seat post 116.

Description

BICYCLE STRUCTURE

The present invention relates to a bicycle structure including a frame and to a seat post that is attachable to the frame. The invention also relates to a bicycle that includes such a bicycle structure.

Most commercially available bicycles include an adjustable seat post that allows the height of the seat to be adjusted to accommodate cyclists of different heights. Traditional steel framed bikes have for many years employed a telescopic seat post that slides longitudinally within the seat tube, allowing the height of the seat to be adjusted. A clamp is provided at the top of the seat tube for clamping the seat post in the required position.

Modem racing bicycle frames are often made from composite materials, for example carbon fibre composites, and are designed to be lightweight and aerodynamically efficient. Frames made from these materials require a different clamping mechanism. For example, it is known to use a clamping device comprising an expanding stop member that compresses the seat tube to lock it in position. However, this mechanism is difficult to manufacture and it results in redundant parts, which add to the weight of the bicycle frame. Clamping can also damage or split the frame if an excessive force is applied.

It is also known to provide a bicycle frame with an integrated fixed seat post, which can be cut to the required length. The seat can then be attached to the upper end of the seat post. However, once the seat post has been cut it cannot be restored to its original length, which can affect the re-sale value of the bicycle. Also, as the seat post is integrated with the frame and increases the overall height of the frame, this can cause problems with packaging and transportation. A further complication that affects racing bikes is that for some cycling events the bikes have to comply with specific regulations, as specified by the UCI (Union Cycliste Internationale), which specify an “envelope” into which the dimensions of the bike must fit. This precludes certain aerodynamic improvements to the frame, such as increasing the length of the seat tube from front to back. However, not all cycling events are governed by the UCI regulations and for some events, for example triathlon races, it is permissible to use frames that fall outside the UCI regulations. Therefore, athletes taking part in both UCI and non-UCI events may require two different bikes.

It is an object of the present invention to provide a bicycle frame that mitigates one or more of the aforesaid disadvantages.

According to one aspect of the present invention there is provided a bicycle structure including a frame and a seat post that is attachable to the frame, wherein the frame includes a frame element having a first mounting formation, and the seat post includes a second mounting formation that is complementary to the first mounting formation, wherein the seat post may be attached to the frame element by bringing the second mounting formation into engagement with the first mounting formation in a mounting direction that is substantially perpendicular to a longitudinal axis of the seat post.

In a conventional telescopic seat post assembly the seat post is introduced into the seat tube in an axial direction. In contrast, in the present invention the first and second mounting formations of the seat post and the frame element are brought into engagement in a direction that is substantially perpendicular to the longitudinal axis of the seat post. In other words, the seat post/frame element assembly is divided substantially longitudinally into two parts that engage one another face-to-face through the mounting formations. This provides a structure that is light and strong with no redundant or superfluous material. The structure is also suitable for parts manufactured from composite materials, and allows the assembled structure to have a smooth aerodynamic profile.

The fact that the seat post is replaceable means that it can easily be exchanged for another seat post when the need arises. For example, a longer or a shorter seat post can be attached to fit the bike to a taller or shorter cyclist. Seat posts with alternative profiles can also be used. For example, a seat post with a short front-rear length can be fitted when the bike must comply with UCI regulations, and this can be replaced with a seat post having a greater front-rear length, or an aerodynamic fairing can be fitted, when UCI regulations do not apply. The problems associated with the use of fixed integral seat posts as described above are also avoided.

Advantageously, the first mounting formation is provided on a rear face of the frame element and the second mounting formation is provided on a front face of the seat post, so that in use the seat post is positioned behind the frame element with respect to the direction of forward travel. This arrangement avoids any interference with the joint between the frame element (for example, the seat tube) and the top tube.

The bicycle structure preferably includes at least one fixing element for fixing the seat post to the frame element. Said at least one fixing element preferably comprises a fastener, for example a bolt, that extends in the mounting direction through the seat post and the frame element. This provides a strong fixture between the seat post and the frame element without interfering with the aerodynamic profile of the assembled components.

Advantageously, the seat post and the frame element have complementary external profiles, so that when the seat post is attached to the frame element the assembled components have an aerodynamic profile. For example, the assembled components may have an oval or aerofoil profile to minimise aerodynamic drag.

Advantageously, the bicycle structure includes a fairing that is removably attachable to the rear of the seat post to increase the aerodynamic efficiency of the seat post/frame structure. The fairing may for example increase the length:width ratio of the seat post/frame element/fairing assembly. This allows the aerodynamic profile of the assembled components to be optimised for events when UCI regulations do not apply, thus minimising aerodynamic drag. For events governed by UCI regulations the fairing may be removed or replaced so as to comply with the regulations. The use of alternative replaceable fairings also allows for the use of a larger fairing having a storage compartment, for example for tools and a spare tyre, or fairings adapted to different wind conditions.

Advantageously, the first and second mounting formations are configured to prevent relative movement of the seat post and the frame element when the seat tube is attached to the frame element.

Advantageously, the seat post includes a mounting for a seat at the upper end of the seat post.

Advantageously, the bicycle structure includes a seat attached to the upper end of the seat post.

Advantageously, the frame is a diamond-type frame comprising a top tube, a head tube, a down tube, a seat tube, a pair of seat stays and a pair of chain stays.

Advantageously, the seat tube comprises the frame element having the first mounting formation.

Advantageously, the frame and/or the seat tube are made from a composite material, for example a carbon fibre composite material.

In one embodiment the bicycle structure includes a plurality of seat posts of different lengths, which are attachable alternatively to the frame element.

In another embodiment the seat post can be cut to a desired length and includes a seat mount assembly for mounting a seat to an upper end of the seat post.

According to another aspect of the present invention there is provided a bicycle including a bicycle structure according to any one of the preceding statements of invention, the bicycle further comprising a pair of wheels, a set of pedals and a transmission system for transferring drive from the pedals to at least one of the wheels.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings wherein:

Figure 1 is a side view of a prior art bicycle frame with an adjustable seat post;

Figure 2 is an exploded view of the bicycle frame shown in Figure 1;

Figure 3 is a side view of a prior art bicycle frame with an integrated seat post;

Figure 4 is an exploded view of the bicycle frame shown in Figure 3;

Figure 5 is a side view of a bicycle frame according to an embodiment of the invention;

Figure 6 is an exploded view of the bicycle frame shown in Figure 5;

Figure 7 is a side of the bicycle frame shown in Figure 5, with the addition of optional aerodynamic fairings; and

Figure 8 is an exploded cross-section view of a seat post, frame element and fairing assembly of the bicycle frame shown in Figure 7.

Figures 1 and 2 illustrate an example of a modem carbon fibre composite bicycle frame 2. The frame 2 is based on a traditional diamond design and includes a top tube 4, a head tube 6, a down tube 8, a seat tube 10, a pair of seat stays 12 and a pair of chain stays 14. The seat tube 10 includes an upper portion 10a into which a seat post 16 can be inserted and a lower portion 10b that extends between the forward ends of the seat and chain stays 12, 14. A seat 18 is attached to the upper end of the seat post 16.

As shown in Figure 2 the seat post 16 has a sliding fit in the upper part 10a of the seat tube, allowing the height of the seat 18 to be adjusted. A clamping mechanism is provided, comprising a wedge 20 that fits into a slot between the seat post 16 and the upper seat tube 10a, and a pair of bolts 22 that pass through the back of upper seat post 10a and engage threaded holes in the wedge 20. The wedge 20 is jacked between the upper seat tube 10a and the seat post 16 to secure the telescopic seat post 16 in the required position.

As discussed above, unless the seat post 16 is in its fully extended position, it will include some redundant material, which increases the overall weight of the bicycle frame 2. The joint between the seat tube and the seat post can lack aerodynamic efficiency. Also, the profile of the seat post 16 cannot be adjusted to comply with different regulations, since it must fit into the upper part 10a of the seat tube.

Figures 3 and 4 illustrate another modern carbon fibre composite bicycle frame 2'. This frame 2' is also based on a traditional diamond design and includes a top tube 4', a head tube 6', a down tube 8', a seat tube 10', a pair of seat stays 12' and a pair of chain stays 14'. The seat tube 10' includes an upper portion 10a' and a lower portion 10b' that extends between the forward ends of the seat and chain stays 12', 14'. The frame includes an integrated seat post 16', which comprises a continuation of the upper seat tube 10a. A seat 18' is attached to the upper end of the seat post 16'. The seat post 16' is supplied over-length and it is designed to be cut to the correct length, so that the height of the seat 18' can be adjusted to suit the height of the cyclist. Once the seat post 16' has been cut to the correct length the seat 18' is attached to the upper end of the seat post 16'. Although the seat post 16' can subsequently be cut to a shorter length, it cannot be extended to suit a taller cyclist.

Figures 5, 6, 7 and 8 illustrate a bicycle frame according to an embodiment of the invention. The bicycle frame 102 may be made of a composite material, for example a carbon fibre composite, or any other suitable material. This frame is also based on a traditional diamond design and includes a top tube 104, a head tube 106, a down tube 108, a seat tube 110, a pair of seat stays 112 and a pair of chain stays 114. The frame also includes a detachable seat post 116 and a seat 118 (or saddle) that is attached to the upper end of the seat post 116.

As shown most clearly in Figures 6 and 8, the seat tube 110 has a cut out portion 120, which is provided at the upper part 110a of the seat tube 110 and located on the rear face thereof with regard to the forward direction of travel A. The seat post 116 has at its lower end a mounting portion 122, which has on its front face a mounting formation 124. In this embodiment the mounting formation 124 is approximately V-shaped in cross-section and is shaped to match a complementary mounting formation 126 on the rear face of the seat tube recess 120, so that the mounting portion 122 of the seat post 116 can be attached securely to the rear face of the seat tube 110. A pair of bolts 128 are provided for securing the seat post 116 to the seat tube 110. These bolts 128 pass through unthreaded holes 129 in the mounting portion 122 of the seat post 116 and engage blind threaded holes 129’ in the upper part 110a of the seat tube 110. A fairing 130 is optionally attached to the rear of the mounting portion 122 to cover the heads of the bolts 128 and provide a smooth, aerodynamic trailing edge to the seat post/frame element assembly. The fairing 130 may for example have a snap-fit connection with the mounting portion 122. Alternative fairings having different profiles may be provided. For example, a fairing with a short length to width ratio may be provided for use in UCI events where the overall length of the seat tube is regulated. For non-UCI events a fairing with a larger length to width ratio may be provided for improved aerodynamic efficiency. Alternative replaceable fairings may be provided including, for example, larger fairings that include storage compartments, for example for tools and a spare tyre, or fairings adapted to different wind conditions. The seat post 116 may also be designed so that the trailing edge of the mounting portion 122 has an aerodynamic profile, so that it can be used without a fairing.

The seat post 116 may be supplied in a number of different lengths, to allow the height of the seat 118 to be adapted to suit cyclists of different heights. If the bicycle is to be used by another cyclist it is a simple matter to replace the seat post 116 with another of a different length. Alternatively, the seat post 116 can be supplied in a single oversize length and then cut to suit the requirements of the individual cyclist. If the bicycle is subsequently sold or transferred to another cyclist, another seat post can be obtained and cut to length as required.

The upper portion 110a of the seat tube 110, the mounting portion 122 of the seat post 116, and optionally the fairing 130 are preferably designed to have complementary exterior profiles, so that the seat tube/seat post/fairing assembly has a smooth aerodynamic profile, for example an oval or aerofoil section. The assembled bicycle frame as shown in Figures 5 and 6 is designed to meet the prevailing UCI regulations. However, if the bicycle is to be used for recreational purposes or for racing in a non-UCI event the profile may be modified as required.

Figure 7 illustrates one possible modified form of the bike frame, in which the removable rear fairing 130 has an increased length so that it extends to the rear of the seat tube/seat post assembly 110, 116 for improved aerodynamic efficiency. The bike frame 102 also includes a removable brake fairing 132, which improves the aerodynamic profile of the rear brake mechanism. It will be appreciated that other modifications of the bike frame are also possible.

Various modifications of the bicycle frame described above are of course possible. For example, although the invention is described above in relation to a traditional diamond frame it is also applicable to other types of frame including for example monocoque frames and frames without a conventional seat tube. Other arrangements for fixing the seat post to the seat tube are also possible and the seat may if required form an integral part of the seat post. It may also be possible to insert one or more shims between the top of the seat post and the seat in order to make small adjustments (e.g. ±10mm) to the height of the seat, allowing the rider to make adjustments for different crank lengths, pedal designs, and to make changes that are course or position dependent.

Claims

CLAIMS:

1. A bicycle structure including a frame and a seat post that is attachable to the frame, wherein the frame includes a frame element having a first mounting formation, and the seat post includes a second mounting formation that is complementary to the first mounting formation, wherein the seat post may be attached to the frame element by bringing the second mounting formation into engagement with the first mounting formation in a mounting direction that is substantially perpendicular to a longitudinal axis of the seat post.

2. A bicycle structure according to claim 1, wherein the first mounting formation is provided on a rear face of the frame element and the second mounting formation is provided on a front face of the seat post, so that in use the seat post is positioned behind the frame element with respect to the direction of forward travel.

3. A bicycle structure according to claim 1 or claim 2, including at least one fixing element for fixing the seat post to the frame element.

4. A bicycle structure according to claim 3, wherein said at least one fixing element comprises a fastener that extends in the mounting direction through the seat post and the frame element.

5. A bicycle structure according to any one of the preceding claims, wherein the seat post and the frame element have complementary external profiles, so that when the seat post is attached to the frame element the assembled components have an aerodynamic profile.

6. A bicycle structure according to any one of the preceding claims, including a fairing that is removably attachable to the rear of the seat post.

7. A bicycle structure according to any one of the preceding claims, wherein the first and second mounting formations are configured to prevent relative movement of the seat post and the frame element when the seat tube is attached to the frame element.

8. A bicycle structure according to any one of the preceding claims, wherein the seat post includes a mounting for a seat at the upper end of the seat post.

9. A bicycle structure according to any one of the preceding claims, including a seat attached to the upper end of the seat post.

10. A bicycle structure according to any one of the preceding claims, wherein the frame is a diamond-type frame comprising a top tube, a head tube, a down tube, a seat tube, a pair of seat stays and a pair of chain stays.

11. A bicycle structure according to claim 10, wherein the seat tube comprises the frame element having the first mounting formation.

12. A bicycle structure according to any one of the preceding claims, wherein the frame and/or the seat tube are made from a composite material.

13. A bicycle structure according to any one of the preceding claims, including a plurality of seat posts of different lengths, which are attachable alternatively to the frame element.

14. A bicycle structure according to any one of the preceding claims, wherein the seat post can be cut to a desired length, the bicycle structure further including a seat mount assembly for mounting a seat to an upper end of the seat post.

15. A bicycle including a bicycle structure according to any one of the preceding claims, the bicycle further comprising a pair of wheels, a set of pedals and a transmission system for transferring drive from the pedals to at least one of the wheels.