GB2561012A - Bicycle frame for an electric-motor-powered bicycle - Google Patents

Abstract

A bicycle frame 10 for an electric-motor-powered bicycle comprises a seat tube 12 for carrying a seat at one of two opposite ends and a down tube 13 connected with the seat tube at the other one of the opposite ends. The down tube 13 defines in its interior an elongate circumferentially enclosed battery-receiving compartment 18 extending longitudinally of the tube 13 and the frame 10 has an access opening 19 in the region of the junction of the down tube 13 and the seat tube 12 for insertion of an elongate electric-motor power supply battery into and removal of the battery from the compartment 18 in the longitudinal direction of the down tube 13. The access opening 19 may comprise electrical connections to the battery and a charging port 24 may be supplied on the down tube.

Description

(54) Title of the Invention: Bicycle frame for an electric-motor-powered bicycle

Abstract Title: Battery mounted in down tube of electric motor powered bicycle (57) A bicycle frame 10 for an electric-motor-powered bicycle comprises a seat tube 12 for carrying a seat at one of two opposite ends and a down tube 13 connected with the seat tube at the other one of the opposite ends. The down tube 13 defines in its interior an elongate circumferentially enclosed battery-receiving compartment 18 extending longitudinally of the tube 13 and the frame 10 has an access opening 19 in the region of the junction of the down tube 13 and the seat tube 12 for insertion of an elongate electric-motor power supply battery into and removal of the battery from the compartment 18 in the longitudinal direction of the down tube 13. The access opening 19 may comprise electrical connections to the battery and a charging port 24 may be supplied on the down tube.

'1'

BICYCLE FRAME FOR AN ELECTRIC-MOTOR-POWERED BICYCLE

The present invention relates to a bicycle frame for an electric-motor-powered bicycle.

Bicycles with a motor drive, essentially to supplement rather than replace normal pedal drive, have long been known and in a comparatively recent development the motor drive has taken the form of a battery-powered electric motor integrated in the bicycle frame. More particularly, the motor is positioned at the junction of a seat tube and a down tube of the bicycle frame and transmits drive to the foot pedal shaft with a usual chain-andsprocket drive coupling to the hub of the rear wheel. The motor typically has a relatively low output of about 250 to 750 watts, which is governed by considerations relating to battery size and also power limitation to preclude classification of the bicycle as a motor vehicle. However, in order to provide power supply to the motor sufficient under variable load conditions for an acceptable range, for example up to about 50 miles, the battery is a relatively bulky and heavy component and a challenge to fit in the bicycle without adding excess volume and detracting from aesthetics. In many applications the battery is simply an attachment pack mounted on the seat tube or down tube or more remotely below a carrier above the rear wheel of the bicycle, which elevates the centre of gravity of the bicycle.

In a more integrated approach, the battery - which can be a relatively long component of some 325 millimetres length - is housed in a recess cut into the frame down tube. This not only places the battery near the motor, but also confines much of its profile to the limits of that of the down tube so that the battery is visually less intrusive. However, any detraction from the structural strength of the down tube, which is an evitable consequence of providing a recess or any other reduction in the ideal cross-section of a down tube, is a significant disadvantage particularly in the context of bicycles intended at least in part for cross-country use. In that case, substantial loads are imposed on the bicycle frame and the load-bearing capacity of, in particular, the down tube should not be compromised.

It should be noted that in the context of the present specification the terms seat tube, down tube and also top tube are to be understood as conventional or historical nomenclature for the constituent members of a bicycle frame and do not imply cylindricality, circular sections or even continuous internal cavities.

It is therefore the principal object of the invention to enable integration of a battery in a frame for an electric-motor-powered bicycle in such a way that the aesthetics of the frame may be preserved without compromise to the structural integrity of the frame.

A supplementary object of the invention is to house a battery in a bicycle frame in such a way that the battery is easy to fit and remove and is protected from impact or other external force and from weather.

Other objects and advantages of the invention will be apparent from the following description.

According to the present invention there is provided a bicycle frame for an electric-motorpowered bicycle, comprising a seat tube for carrying a seat at one of two opposite ends and a down tube connected with the seat tube at the other one of the opposite ends, wherein the down tube defines in its interior an elongate circumferentially enclosed battery-receiving compartment extending longitudinally of the tube and the frame has an access opening in the region of the junction of the down tube and the seat tube for insertion of an elongate electric-motor power supply battery into and removal of the battery from the compartment in the longitudinal direction of the down tube.

A frame embodying the invention offers the advantage that the battery, which in a proprietary construction is of elongate form, for power supply Of an electric motor of a bicycle incorporating the frame can be concealed from view and thus also weatherprotected entirely within one of the principal structural elements, namely the down tube, of the frame. Provision of the battery compartment can be achieved simply by appropriate dimensioning of the interior of the down tube and without cutting into the tube wall or otherwise reducing the tube cross-section, since the opening to allow insertion and removal of the battery in longitudinal direction of the down tube can be located at an end face of the tube where it has no influence on the intrinsic strength of the tube. The crosssectional size of the down tube may, as a consequence of enclosing the battery compartment, be increased in relation to a tube without such a compartment, but such a size increase is not necessarily able to be readily appreciated in the overall appearance of the frame and has no effect on the dynamics of a bicycle incorporating the frame. Insertion and removal of the elongate battery via the opening can be a simple procedure of sliding into and out of the compartment.

For preference, the compartment extends from the region of the opening through the down tube over a length substantially corresponding with a given length of a battery intended for reception in the compartment. In practice, having regard to the typical length of a proprietary battery for a bicycle motor the compartment may occupy approximately half the length of the down tube. The internal dimensions of the down tube may remain the same over an even greater length of the down tube, but this is not essential and beyond the compartment the tube cross-section can change in shape and/or size if necessary or desirable for any purpose. Since the compartment extends from the region of the opening, a received battery can as a consequence be located as low as possible in the down tube, which similarly keeps the centre of gravity of the frame with the received battery low and thus contributes to the stability of a bicycle incorporating the frame.

The cross-section of the compartment transversely to the length direction thereof can be of substantially the same shape as a given shape of a corresponding cross-section of a battery intended for reception in the compartment. In that case, the cross-sectional shape of the down tube can be selected on the basis of standard dimensions of a proprietary battery designed and intended for power supply of a bicycle electric motor. As a result, the compartment does not have to be larger or significantly larger than necessary to accommodate a particular battery, so that the volume of the down tube can be kept close to that of the battery concerned. However, the transverse cross-section of the compartment is preferably greater in area by a predetermined tolerance than the area of the corresponding cross-section of the battery intended for reception in the compartment, so that the battery can be inserted into and removed from the compartment without difficulty by virtue of the tolerance, which can be suitably small. The battery is thus generally kept in place in the compartment by approximate dimensional agreement of the battery and compartment. In that connection, with advantage the transverse cross-section of the compartment is of substantially constant shape and size over at least a major part of the length of the compartment, which simplifies manufacture of the down tube and provides, in effect, a uniformly dimensioned shaft related to the battery size and shape.

The transverse cross-section of the compartment can be substantially oblong so as to be compatible with the transverse cross-sectional shape of a standard proprietary battery for bicycle motor power supply. In that case, the shorter sides of the oblong preferably lie in planes substantially parallel to a common medial plane of the tubes, so that these shorter sides, rather than the longer sides, dictate the dimension of the compartment and thus ultimately of the down tube in side view of a bicycle incorporating the frame. The down tube can therefore be more slender in the side view, as distinct from less important front view, of the bicycle.

In a preferred embodiment the frame comprises locating means arranged in the compartment to locate a battery when received therein, in particular to firmly hold the battery in place so that it is not susceptible to vibration or shock in use of a bicycle incorporating the frame. Exposure of the battery to shock-induced damage can thus be avoided. The locating means is preferably arranged to fix the battery at a point spaced from the opening, so that the battery can be inserted into the compartment and held as soon as inserted. In that connection, the locating means can be arranged to grip the battery at an end thereof, in which case, for example, the battery can simply be pushed into the compartment until gripped and thus arrested by the locating means. The locating means can be a clip, sleeve or other form of securing device which automatically engages the battery when pushed into the compartment and from which the battery can be released by, for example, application of a suitable pulling force.

In addition, with advantage the frame comprises cushioning means positioned or positionable in the compartment to cushion a battery when received in the compartment. The cushioning means can be of any suitable form, for example an element or elements of resilient material, such as soft sponge rubber, lining or partly lining the compartment or even separately fitted to the battery prior to insertion into the compartment. Cushioning means of this kind provides shock absorption of the battery relative to the rigid walls of the down tube.

For preference, the frame comprises an openable cover closing the opening, whereby in use a battery received in the compartment may be able to be enclosed in sealed manner. The cover can also have the function of locating the battery firmly in the compartment, for example by being fitted in such a way as to press against the battery directly or via a resilient element against a stop, for example provided by the afore-mentioned locating means. The cover can be secured by any suitable means, such as one or more screws, over-centre fasteners, clips, clamps or the like, and can be, for example, hinged or removable in its entirety from the down tube.

Moreover, such a cover can be constructed to enable electrical connection with electrical power supply terminals of a battery when received in the compartment. In one simple form, the cover can be provided with apertures for the passage of suitable connectors connectible with the terminals. In a more developed configuration, the cover itself can be provided with electrical connecting means connectible with the terminals, for example connectible automatically when the cover is fitted to close the access opening. In that case, in use in a motorised bicycle the electrical connecting means could be permanently wired to the bicycle motor so that electrical connection with a battery received in the compartment can be produced simply by fitting the cover to close the access opening.

Since batteries of the kind provided for power supply to a bicycle electric motor are normally rechargeable, the down tube is preferably provided with a port for connection of charging means with a charging terminal of such a battery when received in the compartment. Consequently, recharging can be carried out without any need to remove a battery accommodated in the compartment.

For preference, the frame defines a mounting location for an electric motor in the region of the junction of the down tube and the seat tube. The frame is thereby specifically adapted for use in an electric-motor-powered bicycle and the wiring between a motor mounted in the mounting location and a battery received in the compartment can be kept short and possibly even enclosed in one or other frame tube.

In one preferred construction of the frame the down tube is a fabricated component formed by two parts joined together longitudinally of the tube, which represents a simple method of creating a monocoque tube with ah internal cavity which may depart from a circular cross-section. In that case, economy of manufacture is enhanced if the two parts are substantially identical in shape and size and are joined together in mirror image. The two parts can be made of, for example, aluminium alloy, which is light and will allow the parts to be readily shaped by pressing over suitable forming mandrels. A further advantage of this form of construction is that the afore-mentioned locating means can be secured to one of the parts before joining to the other part. If, for example, the locating means is itself an aluminium component it can be welded to one of the down tube parts before the parts are joined and thus render the compartment inaccessible for welding. Welding in this way enables secure fixing of the locating means in place without the need to use, for example, screws penetrating a wall of the down tube.

However, the down tube could, if desired, be made by other methods and materials, for example by laying carbon fibre.

The frame may also include a top tube connected with the seat tube and the down tube in a triangular arrangement so as to provide a conventional frame layout for a man's bicycle or a stiff-construction cross-country or off-road bicycle. However, a seat tube and down tube are sufficient frame components for a lady's bicycle of conventional format or a town or commuter bicycle.

The present invention also embraces an electric-motor-powered bicycle comprising a frame according to the invention. Such a bicycle in that case preferably includes an electric-motor power supply battery received in the compartment of the down tube of the frame and electrically connected with an electric motor of the bicycle.

A preferred embodiment of the present invention will now be more particularly described with reference to the accompanying drawing, the single figure of which is a schematic partly sectioned side view of a bicycle frame embodying the invention.

Referring now to the drawing there is shown a bicycle frame 10 for a bicycle (not shown) powered by an integrated electric motor 11 in conjunction with conventional drive by pedal cranks and foot pedals, the motor acting as an alternative to drive by pedalling when required. The motor, which is not part of the frame as such, is schematically depicted by dashed lines. In the described embodiment, the frame 10 is intended for a cross-country or off-road bicycle, but can be used with or without adaptations in a bicycle for any purpose.

The frame 10 comprises a seat tube 12 intended to carry a seat (not shown) at one of two opposite ends, in particular an upper end in use orientation of a bicycle incorporating the frame, a down tube 13 connected at one of two opposite ends with the other (lower) end of the seat tube 12 and a top tube 14 connected at its two ends with the seat tube 12 and down tube 13 to complete a torsionally stiff triangular arrangement. The connection of the top tube 14 with the seat tube 12 is stiffened by a triangulation brace 15. A head tube 16 for reception of a front wheel and handlebar shaft is provided at the junction of the top tube 14 and down tube 13. A mounting location 17 for the motor 11 is provided in the vicinity of the junction of the seat tube 12 and down tube 13. In a completed bicycle which incorporates the frame 10 and has a motor 11 fitted in the mounting location 17, the motor transmits drive to a shaft carrying the pedal cranks.

The motor 11 is powered by a suitable on-board battery (not shown), typically a rechargeable polymer-cased 36 volt lithium-ion battery of elongate box-shaped configuration having a length of, for example, approximately 325 millimetres and an oblong cross-section of, for example, approximately 70 x 75 millimetres transversely to the length direction. Battery supply terminals are located at one end of the battery and a terminal port for recharging is provided on a side adjacent to the end with the terminals. Batteries of this kind are proprietary items produced specifically for electric-motor-powered bicycles, also called electric bicycles.

As mentioned in the introduction, current methods of mounting batteries in electricmotorised bicycles are generally to the disadvantage of one or more of aesthetics, structural strength of the frame and bicycle centre of gravity. These issues are addressed in the frame 10 embodying the invention by enclosure of the battery entirely within the down tube 13, which accordingly is specifically designed to define in its interior an elongate circumferentially enclosed battery-receiving compartment 18 of such a shape and size as to be able to accommodate a proprietary battery with the stated dimensions. The battery in that case is slidably insertable into and removable from the compartment in the longitudinal direction of the down tube by way of an access opening 19 provided at the end of the down tube 13 in the vicinity of the junction with the seat tube 12 and thus near the mounting location 17 for the motor 11. The compartment 18 accordingly extends from the region of the opening 19 through the down tube 13 over a length predetermined to be sufficient to receive the intended battery, thus, for example, a length of or slightly greater than 325 millimetres in the case of the battery size mentioned in the preceding paragraph. However, it is entirely possible for the compartment 18 to be of greater length and reduced to a desired length by location in the interior of the down tube 13 of a suitable lengthreducing insert. Similarly, the cross-sectional shape and size of the compartment 18 transversely to the length direction of the down tube 13 is selected to approximately correspond with that of the intended battery, in particular an oblong of 70 x 75 millimetres, but greater by a tolerance to facilitate sliding insertion and removal of the battery. The oblong cross-section, which is substantially constant over the length of the compartment 18, is oriented with the shorter sides of the oblong lying in planes parallel to the drawing so that in side profile of the frame 10, as shown in the drawing, the down tube 13 is not thicker than necessary.

It is emphasised that the shape and size of the compartment 18 indicated in the preceding paragraph are merely by way of example. The dimensioning of the compartment is designed with reference to the given or known dimensioning of the particular battery intended to be accommodated, but, as indicated, can be constructed to be oversize in one or other respect and reduced to appropriate dimensions by suitable inserts or adapters.

The frame 10 as a whole and the down tube 13 in particular can be constructed from any suitable materials and by any appropriate method. In a preferred example particularly suitable for realising the internal battery-receiving compartment 18, the down tube 13 is a fabricated monocoque constructed from two identical elongate half shells of pressed aluminium alloy of, for example, 16 or 18 gauge and welded, especially robot-welded, together in mirror image along the centre lines of faces which are at right angles to the plane of the drawing. The resulting structure has the torsional rigidity associated with monocoque construction and the relatively substantial box-section cavity produced by this form of construction is adaptable, by appropriate dimensioning as discussed above, for use as a battery compartment 18, the walls of the compartment being provided by the walls of the monocoque.

Although the battery compartment 18 can be dimensioned to provide a relatively snug fit for the battery, for preference it is dimensioned, as already mentioned, to be slightly oversize in relation to the intended battery so as to ease insertion and removal. In that case it is desirable to provide locating means for locating the battery in a fixed position so that it is not susceptible to bouncing or other potentially damaging movement. Such locating means can be realised in a variety of ways, for example and as shown in the drawing, by a stop member 20 arranged in the compartment 18 to fix the battery at a point spaced from the access opening 19, in particular at an end of the compartment remote from the end near the opening. The member 20 can optionally be constructed or arranged to grip or otherwise hold an inserted battery at its upper end. In the case of the described fabricated construction of the down tube 13, such a member 20 can be conveniently fixed, for example welded, to an interior face of one of the half shells prior to joining to the other half shell to complete the down tube 13. However, the member 20 can also be fixed in place - even after construction of the down tube 13 - by, for example, a screw or other fastener inserted through a hole in the tube. Various other forms of locating means and methods of fixing are conceivable, including pushing into the tube 13 an insert of resilient material held in place by compression of the material and/or adhesive.

Undesired movement of an inserted battery in the compartment 18 can be prevented and shock absorption at the same time provided by appropriate cushioning means, here shown in the drawing - merely by way of example - as a full of partial compartment lining 21 of soft resilient material such as sponge rubber or plastic foam material. Material of this kind is available in the form of thin self-adhesive strips and can be applied to inside surfaces of the down tube 13 to extend along at least part of the compartment 18.

The access opening 19 is closed by an openable, here entirely removable, cover 22 which can be provided in a suitable form and secured by any appropriate method. As shown in the drawing, again merely by way of example, the cover 22 can have the form of a plate 22a which can extend over the opening 19 and which has an oblong-section spigot 22b engageable in the down tube interior to locate the cover. The cover 22 can be secured by way of, for example, one or more screws inserted through a hole 23 or holes in the down tube 13 and screwed into the spigot 22b. In the secured state of the cover 22 the spigot 22b can bear against the adjacent end of an inserted battery to urge the battery towards the locating stop member 20 and thus assist in locating the battery in a fixed position. In that case, a resilient element (not shown) can be associated with the spigot 22b and/or the stop member 20 to provide resilient fixing and damage protection of the battery casing. Ingress of water or moisture into the interior of the down tube 13 via the access opening 19 can be prevented by provision of a sealing gasket between the plate 22a and the end face of the down tube 13 around the access opening 19.

The cover 22 is also constructed to enable electrical connection with the electrical supply terminals of an inserted battery. In the simplest form, the cover 22 can have apertures (not shown) to allow attachment of electrical leads to the terminals, but in a preferred construction the cover 22 is provided with electrical connectors (also not shown) connectible with the terminals. This connection can be arranged to be automatically realised when the cover 22 is secured to the down tube 13 to close the access opening 19 and the connectors themselves can be attachable or attached to wires connected or for connection with terminals of the motor.

Finally, the down tube 13 is provided with a port 24 for connection of a charging plug with a charging terminal of the battery while it is housed in the compartment, the port 24 being provided in a side wall of the down tube 13 and preferably closed by a removable rubber or plastics material plug (not shown).

A bicycle frame embodying the present invention provides a means of integrating a battery for the motor of an electric-motor-powered bicycle in such a way that the battery is out of sight and thus does not detract from the aesthetics of the bicycle. At the same time and subject to relatively straightforward dimensional adaptation, use is made of the cavity already present in a frame down tube and compromise of the structural strength of the down tube is avoided. The battery compartment is positioned so that the battery will be located close to the bicycle motor and low in the frame so as to maintain a low centre of gravity of the bicycle, which is desirable in all bicycles, but particularly in the case of offroad bicycles. The invention also extends to an electric-motor-powered bicycle incorporating such a frame, optionally with a battery received in the compartment of the down tube.

Claims (24)

1. A bicycle frame for an electric-motor-powered bicycle, comprising a seat tube for carrying a seat at one of two opposite ends and a down tube connected with the seat tube at the other one of the opposite ends, wherein the down tube defines in its interior an elongate circumferentially enclosed battery-receiving compartment extending longitudinally of the tube and the frame has an access opening in the region of the junction of the down tube and the seat tube for insertion of an elongate electric-motor power supply battery into and removal of the battery from the compartment in the longitudinal direction of the down tube.

2. A frame according to claim 1, wherein the compartment extends from the region of the opening through the down tube over a length substantially corresponding with a given length of a battery intended for reception in the compartment.

3. A frame according to claim 1 or claim 2, wherein the cross-section of the compartment transversely to the length direction thereof is of substantially the same shape as a given shape of a corresponding cross-section of a battery intended for reception in the compartment.

4. A frame according to claim 3, wherein the transverse cross-section of the compartment is greater in area by a predetermined tolerance than the area of the corresponding cross-section of the battery intended for reception in the compartment.

5. A frame according to claim 3 or claim 4, wherein the transverse cross-section of the compartment is of substantially constant shape and size over at least a major part of the length of the compartment.

6. A frame according to any one of claims 3 to 5, wherein the transverse crosssection of the compartment is substantially oblong.

7. A frame according to claim 6, wherein the shorter sides of the oblong lie in planes substantially parallel to a common medial plane of the tubes.

8.

A frame according to any one of the preceding claims, comprising locating means arranged in the compartment to locate a battery when received therein.

9. A frame according to claim 8, the locating means being arranged to fix the battery at a point spaced from the opening.

10. A frame according to claim 9, the locating means being arranged to grip the battery at an end thereof.

11. A frame according to any one of the preceding claims, comprising cushioning means positioned or positionable in the compartment to cushion a battery when received in the compartment.

12. A frame according to any one of the preceding claims, comprising an openable cover closing the opening.

13. A frame according to claim 11, wherein the cover is constructed to enable electrical connection with electrical power supply terminals of a battery when received in the compartment.

14. A frame according to claim 13, wherein the cover is provided with electrical connecting means connectible with the terminals.

15. A frame according to any one of the preceding claims, wherein the down tube is provided with a port for connection of charging means with a charging terminal of a rechargeable battery when received in the compartment.

16. A frame according to any one of the preceding claims, wherein the frame defines a mounting location for an electric motor in the region of the junction of the down tube and the seat tube.

17. A frame according to any one of the preceding claims, wherein the down tube is a fabricated component formed by two parts joined together longitudinally of the tube.

18. A frame according to claim 17, wherein the two parts are substantially identical in shape and size and joined together in mirror image.

19. A frame according to claim 18, wherein the parts are of aluminium alloy.

20. A frame according claim 18 or claim 19 when appended to any one of claims 8 to

10, the locating means being secured to one of the parts before joining to the other part.

21. A frame according to any one of claims 1 to 16, wherein the down tube is made of carbon fibre.

22. A frame according to any one of the preceding claims, wherein the frame further comprises a top tube connected with the seat tube and the down tube in a triangular arrangement.

23. An electric-motor-powered bicycle comprising a frame according to any one the preceding claims.

24. A bicycle according to claim 23, comprising an electric-motor power supply battery received in the compartment of the down tube of the frame and electrically connected with an electric motor of the bicycle.

Intellectual

Property

Office

Application No: GB1705297.8 Examiner: Mr Philip Osman