GB2407073A

GB2407073A - Tubular frame member

Info

Publication number: GB2407073A
Application number: GB0321328A
Authority: GB
Inventors: Daniel Brendan Farrell
Original assignee: Pashley Holdings Ltd
Current assignee: Pashley Holdings Ltd
Priority date: 2003-09-11
Filing date: 2003-09-11
Publication date: 2005-04-20
Anticipated expiration: 2023-09-11
Also published as: GB0321328D0; GB2407073B

Abstract

A bottom tube member 26 for a vehicle such as a bicycle or tricycle 10 has a rectangular cross-section and is arranged with opposite corners in a vertical plane. The member extends forwardly from a bottom bracket 27 via a steering column 22 to a front axle 13. Opposite corners of the member are also aligned horizontally. Semi-circular cutouts 32 and 33 at the rear of the tube member locate with a seat tube 21 and bottom bracket 27 respectively. A foot 34 of shallow V form may be used to affix the front axle by welding or brazing.

Description

Tubular Frame Member The present invention relates to a tubular member of

a frame of a vehicle, particularly the frame of a bicycle, tricycle or the like.

Tubular frames of vehicles are well known, and form a light but strong structure to which may be attached other elements such as seat, drive mechanism and steering mechanism.

Generally speaking round tubes are preferred, but other sections may be used for example to increase bending strength in a particular plane, or for economic reasons relating to ready availability of certain sizes and shapes.

The method of joining tubes must also be considered having regard to strength of the joint, the manufacturing method and cost of assembly. In for example a bicycle frame, the traditional method of using lugs and a brazed joint has generally been replaced by electric deposit welding using MIG or TIG techniques.

However whereas the use of lugs provides a means of locating the tubes extending therefrom, electric welding relies solely on a jig to hold adjacent tubes in abutment prior to joining; self location is not generally possible.

The present invention provides a novel and attractive frame member, suitable for electric welding and having both economic and structural advantages.

According to the invention there is provided a tubular frame member for the frame of a vehicle, the member being of metal, having a substantially rectangular cross-section and being adapted for use in an orientation in which two opposite corners are substantially in a common vertical plane. i

Such a frame member can be said to have a cross-section in the form of a diamond, with respect to the ground. The frame member is preferably adapted for substantially orthogonal attachment of other parts of a frame, in planes defined by opposite corners of the frame member.

In a preferred embodiment the frame member is adapted to be substantially horizontal in the frame. This orientation gives greater resistance to bending in the vertical plane because the corners are further apart than the sides. The frame member is adapted for attachment of other frame parts in substantially horizontal and vertical planes.

In one preferred embodiment, the frame member is for the frame of a pedal vehicle, and is adapted to extend forwardly from a bottom bracket. The opposite corners in the horizontal impart increased stiffness to the bottom bracket so as to resist twisting thereof under pedalling forces.

The frame member may include an opening adapted to receive another tube on a corner axis thereof. The opening may be a through hole.

This tube is preferably a close fit in the opening, and is adapted for permanent attachment, for example by welding or brazing. Attachment on a corner axis allows a longer line of contact and thus a greater fixing length, represented by e.g. weld bead.

Preferably this tube is of circular cross-section, permitting the opening to be formed by drilling. Furthermore the 'diamond' orientation of the frame member permits attachment of another tube having a 'v' cut in one end for location, with the consequent advantage of greater line of contact than would be possible with a planar butted joint.

In both cases the line of fixing extends in two planes substantially at 90 . This arrangement avoids welding onto a flat surface and the consequent risk of buckling due to the heat of welding. Furthermore attachment in two planes gives greater resistance to fatigue fracture.

In another embodiment one end of the frame member may be cut away perpendicular to the long axis thereof to remove three corners. The single remaining corner length provides a protruding foot adapted for connection to a flat side of another frame member at right angles. Such a foot has a 'v' section and is relatively strong compared with a planar foot.

In the case of a common size of square section tubing, the foot provides support for a cross tube, wherein the tube corner opposite the foot can be flush with a flat side of the cross tube. This arrangement is particularly neat and strong, the flush upper face permitting straightforward attachment of e.g. an insulated container for ices.

In one preferred embodiment the frame member is for a tricycle having two wheels at the front and a single pedal driven wheel at the rear. The frame member has at one end a 'v' foot for attachment of a cross tube constituting a front axle, and at the other end semicircular recesses to receive a cylindrical bottom bracket and substantially upright seat tube. Intermediate the ends is provided a circular through hole to receive an upright tubular steering column.

Other features of the invention will be apparent from the following description of a preferred embodiment shown by way of example only in the accompanying drawings in which: Fig. 1 is a side elevation of tricycle incorporating a frame member according to the present invention; Fig. 2 shows the frame member in side elevation; Fig. 3 shows the frame member in end elevation; and Fig. 4 shows the frame member in plan.

With reference to Fig. 1 a deliver tricycle 10 has the rear part of a bicycle with a single drive wheel 11 and a forwardly extending frame supporting twin wheels 12 (one shown) on a common axis 13. The usual pedals, chain wheel and chain are omitted for reasons of clarity, as is the steering arrangement of handlebars 14. The tricycle has the usual seat 15 and carries a box 16 for e.g. ices.

The frame of the tricycle comprises the usual seat tube 21, steering column 22, seat stays 23 and chain stays 24. The cross tube 25 has a counterpart extending back to the rear axle for additional strength. A bottom tube 26 extends forwardly from the bottom bracket 27 via the steering column 22 to the front axle 13, as illustrated.

The bottom tube 26 is of rectangular section, whereas the remaining tubes are of circular section.

With reference to Figs. 2-4, it will be observed that the bottom tube is of square cross-section, and disposed with opposite corners vertically and horizontally aligned.

In the illustrated example the tube is externally 51 mm square, and has a wall thickness of 1.6 mm.

A through aperture 31 is adapted to receive and locate the steering column 22, and it will be understood that a continuous weld both above and below the bottom tube 26 will extend around the steering column and on all four faces of the bottom tube. Such welds will be longer than the equivalent weld through a square section tube disposed with opposite sides horizontal and vertical, and thus provide a stronger connection for a given weld bead, whilst avoiding the risk of distortion inherent in welding a tube to a perpendicular flat surface.

Furthermore the weld can extend away from the upper and lower extremities of the bottom tube so that the weld beads above and below approach each other, and contribute to stiffness of the joint by adding material over a region of greater width.

At the rear end of the bottom tube 26 the seat tube 21 is located in a semicircular cut-out 32, and can thus be precisely positioned prior to welding. A second cut-out 33 with a horizontal axis locates and supports the bottom bracket 27. In both cases the diamond formation permits a longer weld bead extending over a greater width of tube, with the consequent increase in stiffness and strength. This is especially useful in resisting twisting loads exerted on the pedals.

At the front end, the top portion of tube is cut-away to provide a foot 34 of shallow 'v' form to which the front axle may be affixed by any suitable method, such as electric welding. This shallow 'v' provides a structurally stiff support adapted to take at right angle, for example, another square section tube 35 for supporting individual wheels on kingpins with ackerman steering. Again a longer weld bead is facilitated, and the top of the axle tube is flush with the apex of the bottom tube.

It will be appreciated that the arrangement of bottom tube provides neat and strong connections to other tubes whilst eliminating the use of lugs or other strengthening members. Machining of the bottom tube is relatively easy, requiring only conventional drilling and sawing techniques.

Furthermore the frame is neat and simple in appearance, yet avoids dirt traps and masked areas which could be difficult to paint.

The upper faces of the bottom tube are adapted to shed water and dirt, and provide a convenient location for writing in the eye line of a bystander.

It will be understood that the bottom tube provides additional resistance to bending in the vertical and horizontal planes by virtue of the corners being further apart than the sides. These attributes are useful in avoiding distortion of the frame due to cycling forces and carried loads, and generally in providing a stiff frame that is easier to pedal.

It will be understood that the frame member of the invention is useful in other pedal powered vehicles, for example between the fore and aft bottom brackets of a tandem.

Claims

Claims 1. A tubular frame member for the frame of a vehicle, the member

being of metal, having a substantially rectangular cross-section and being adapted for use in an orientation in which two opposite corners are substantially in a common vertical plane.
2. A frame member according to claim 1 and adapted for substantially orthogonal attachment of other parts of a frame, in planes defined by opposite corners of the frame member.
3. A frame member according to claim 1 or claim 2 and adapted to be substantially horizontal in a frame.
4. A frame member according to any preceding claim and for the frame of a pedal vehicle, the frame member being adapted to extend forwardly from a bottom bracket.
5. A frame member according to claim 4 and including an opening adapted to receive another tube on a corner axis thereof.
6. A frame member according to claim 5 wherein said opening is a through hole.
7. A frame member according to claim 6 and further including a close fitting tube in said opening, the tube and frame member being attached by one of welding and brazing.
8. A frame member according to claim 6 or claim 7 wherein said tube is of circular cross-section.
9. A frame member according to any preceding claim and further including a tubular member having a 'v' notch in one end thereof, the tubular member being attached to an apex of said frame member by one of welding or brazing.
10. A frame member according to any preceding claim, one end of the frame member being cut away perpendicular to the long axis thereof to remove three corners, the single remaining corner length providing a 'v' section protruding foot adapted for connection at right angles to a flat side of another frame member.
11. A frame member according to claim 10 and including a cross tube attached to said foot, the frame member and cross tube being the same size of square section tubing, wherein the corner of the frame member opposite the foot is flush with a flat side of the cross tube.
12. A frame member according to claim 4 and for a tricycle having two wheels at the front and a single pedal driven wheel at the rear, the frame member having at one end a 'v' foot for attachment of a cross tube constituting a front axle, at the other end a semicircular recess to receive a cylindrical bottom bracket and substantially upright seat tube, and intermediate the ends is provided a circular through hole to receive an upright tubular steering column.
13. A frame member substantially as described herein with reference to the accompanying drawings.
14. A tricycle frame substantially as described herein with reference to Fig. 1 of the accompanying drawings.
15. A tricycle substantially as described herein with reference to Fig.1 of the accompanying drawings.