GB2413996A

GB2413996A - Steering bearing assembly

Info

Publication number: GB2413996A
Application number: GB0410924A
Authority: GB
Inventors: Lloyd Townsend; Lee Musselwhite
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-05-15
Filing date: 2004-05-15
Publication date: 2005-11-16
Also published as: GB0410924D0

Abstract

Bearing support cups (1) utilised on a bicycle steering assembly are fitted directly to the bicycle frame headtube (2) by means of a thread-in fitting (1A). A lower bearing race is also fitted directly to the bicycle forks by means of a thread-on fitting.

Description

STEERING BEARING ASSEMBLY

FIELD OF THE INVENTION

This invention relates to the bearing assembly used for steering a single front wheel and particularly to the bearing support journals fitted on bicycle frames for allowing the rotation of the bicycle forks for steering.

BACKGROUND OF THE INVENTION

Bicycle steering assemblies comprise a pair of fork legs carrying the front wheel with a stem portion forming a steering shaft inserted into a hollow tubular frame generally above the wheel. A steerer, usually itself tubular, is also located within the frame and rotates the fork about the longitudinal axis of the shaft. The steering so shaft and the steerer are supported by a ball or roller bearing assembly known as the "headset". The journals carrying the bearings are typically a cup and cone combination but other configurations, such as a cartridge bearing, are often used. The headset carries an upper and a lower bearing set. At least the upper bearing set, furthest from the wheel, is secured to the frame. The lower bearing set is known as the fork crown race.

Bicycle steering assemblies have evolved into various types e.g. different tube diameters used, threaded and so threadless forks systems, frame cups that sit outside the headbube, cups that sit inside the tubes (hidden) etc. However, fundamentally, one thing remains constant; in that the bearing support cups or other journals fittedinto the bicycle frames (top and bottom) have remained a press fit.

A press fit system is relatively cheap to manufacture' and fast and simple to fit in bicycle production factories.

However, aftermarket users and ill-equipped workshops often encounter problems with removing and fitting press fit cups.

SUMMARY OF THE INVENTION s

Bicycle frames are tubular. In order to reduce weight, the tubes are generally thin-walled. We have now discovered that steering bearing assemblies can be attached by threaded direct fittings without weakening the tubes.

According to one aspect of the present invention there is provided a bearing assembly for supporting a steering shaft rotating within a tubular frame, the bearing assembly including at least one journal which is threaded for attachment to the frame. Preferably the bearing assembly comprises two cup and cone bearings or equivalent, both of which are threaded for attachment to the frame.

As indicated above, the journals carrying the bearing sets are typically a cup and cone combination but other configurations are possible. As used herein, the terms so "cup" and "cone" include any element having an equivalent function. Conveniently, cup elements are attached to the frame and cone elements are attached to the steerer or shaft, as the case may be. This convention is adopted throughout this Specification. However, it will be readily apparent that the respective cup and cone functions may be reversed and the invention is not limited to either configuration.

Thread-in cups can be utilised in virtually every instance that the standard press fit cups are used, and are so therefore potentially suitable for all bicycle styles and types.

Apart from the installer/service agent not requiring special press fit tools, additionally, Thread-In cups offer the following advantages over press fit cups; 1) A better precision alignment between the bearing cups and therefore the complete steering assembly. (No risk of a cup not being pressed fully home in all points.) 2) A stronger integrated assembly, where the cups effectively become a strengthening structural member of bicycle frame.

3) Reduced risk of the bearing race twisting longitudinally under excessive load in a way that may damage the frame or steering shaft tubes. This is a common problem on existing press fit types, where the bottom race in particular may twist longitudinally and force the tube from round to oval shape, under a leverage effect onto the lo headset bearing area from a combination of the steering head angle not being 90 degrees and a leading axle designed forks, both of which are required for stable bicycle steering and handling.

4) Reduced risk of frame and cup damage from misalignment during cup installation.

5) Ability to fit, remove and re-fit with minimal wear or risk of tolerance change, unlike press fits, where each time a press fit is applied material is by its very design nature stretched to fit together and does not return to its so original dimensions when disassembled.

6) Reduced risk of installer fit tolerance error by trying to fit an incorrect size (if close) cup into a frame.

7) Simple screw-in installation.

The previous section relates to attachment of the headset to the frame. It is also necessary to attach the headset to the forks.

The lower bearing 'cone' on a bicycle headset is attached to the forks (that turn upon bearings installed so into the frame). The headset bearing cups are fixed into the frame and hold one bearing set each. The upper (and adjustable) part of the headset is fitted to the forks in various manners (including threaded and threadless systems).

The lower cone part of the headset bearing assembly is referred to as the crown race. Conventionally the crown race has always been a press fit onto the bicycle forks and particularly onto the steering shaft (stem) portion.

A press fit system is relatively cheap to manufacture and fast and simple to fit in bicycle production factories.

However, as discussed above, aftermarket users and ill- equipped workshops often encounter problems with removing and fitting press fit crown races.

According to another aspect of the present invention there is provided a bearing assembly including upper and lower journals for supporting a steering shaft rotating within a tubular frame, wherein the lower journal is lo threaded for attachment to the steering shaft. Preferably at least the lower journal is a cup and cone race.

Thread-on races can be utilised in virtually every instance that the standard press fit races are used, and are therefore potentially suitable for all bicycle styles and types.

Additional to the advantages discussed above, Thread-on races offer the following advantages over press fit races; 1) A better precision alignment between the fork and the crown race and therefore the complete steering assembly.

so 2) Reduced risk of installer fit tolerance error by trying to fit an incorrect size (if close) race onto a fork, often causing irreparable damage to both parts.

Preferably, the headset is also secured to the frame by threaded fittings, as described above, but this aspect of the present invention is equally applicable to headsets attached to the frame by conventional pressfittings.

For both aspects of the present invention, the type of bearing assembly is conventional. For example, the bearing assembly can utilise loose or caged ball or roller bearings directly or support a cartridge bearing.

The invention has been described in relation to bicycles, but is equally applicable to any steered single (unpaired) wheel, for example on a tricycle, motor-assisted cycle (moped) or motor cycle. Depending on the forces acting on the bearing assembly, other applications include unsteered (castor) wheels carried by a tubular frame, as - 5 - used on baby's push chairs, wheel chairs or scaffolding platforms, for example.

BRIEF DESCRIPTION OF THE DRAWINGS s

Embodiments of the invention are now described, though by way of illustration only, with reference to the accompanying Drawings in which: Figure 1 is a perspective diagram, partially disassembled, of the frame, fork and upper bearing of a cycle headset incorporating the threaded fittings of our invention; and Figure 2 is a partial diagram of cycle fork crown races showing the threaded attachment to the forks.

DESCRIPTION OF THE INVENTION

so Fig. 1 shows a bearing support cup (1) fitted by means of a thread-in fixing to the frame headtube (2). The tubular fork steering shaft (5) passes through the assembly and is supported in this example by the cartridge bearing (4) and the top cap (3). Bearing support cup (1) has a threaded portion (1A) which matches a corresponding thread on the internal surface of frame headtube (2).

Bearing support cup (1) is screwed into frame headLube (2) by hand or by using conventional tools.

so With reference to Fig.2; The headset lower bearing - crown race (C) has a thread on its internal surface and is fitted by means of a threadon fixing (B) to the bicycle fork (A).

Ci indicates a typical cone shape bearing support.

Cii shows an 8 notch system, for which a compatible tool would be used to screw-down the race (C) onto the fork (A). The 8 notch system is for example only. Any other - 6 applicable form of effectively turning the race (C) could also be employed.

The tubular fork steering shaft (A) is then fitted to the additional headset components and bicycle frame in conventional manner.

Ai and Ail indicate a typical top section of the bicycle fork legs.

Claims

1. A bearing assembly for supporting a steering shaft rotating within a tubular frame, the bearing assembly including at least one journal which is threaded for attachment to the frame.

2. A bearing assembly including upper and lower lo journals for supporting a steering shaft rotating within a tubular frame, wherein the lower journal is threaded for attachment to the steering shaft.

3. A bearing assembly as claimed in Claim 1 or Claim 2 wherein the journal comprises a cup and cone bearing.

4. A bearing assembly as claimed in Claim 3 wherein at least one cup is threaded for attachment to the frame.

5. A bearing assembly as claimed in any one of the preceding claims including upper and lower cup and cone bearings, wherein the cone of the lower bearing is threaded for attachment to the steering shaft.

6. A bearing assembly as claimed in any one of the preceding claims wherein the journal is associated with a cartridge bearing.

7. A bearing assembly as claimed in any one of the preceding claims comprising a cycle headset.

8. A bearing assembly as claimed in Claim 7 including upper and lower journals, wherein the lower bearing comprises a fork crown race. - 8

9. A bearing assembly as claimed in Claim 7 or Claim 8 associated with a bicycle, a motor-assisted bicycle, a motor cycle or a tricycle.

10. A cycle frame incorporating a threaded portion for attachment of a bearing assembly as claimed in any one of the preceding claims.

11. A cycle steering fork incorporating a threaded lo portion for attachment of a bearing assembly as claimed in any one of Claims 2 to 9.

12. A cycle incorporating a bearing assembly as claimed in any one of Claims 1 to 9.

13. A bearing assembly substantially as described and with reference to the accompanying drawings.