Bicycle steering assembly

A bearing assembly for a bicycle comprises a bearing with a first race rigidly connected to the head tube and a second race provided with a neck portion which can be elastically clamped around the steering tube of the bicycle fork.

BACKGROUND OF THE INVENTION 
The present invention relates to bicycle steering assemblies of the known 
type comprising: 
a head tube forming part of a bicycle frame, 
a steering tube which is for connecting the front fork of the bicycle to 
the bicycle handlebar, 
a bearing assembly for rotatably supporting said steering tube within said 
head tube, 
wherein said steering tube has a smooth, i.e. non threaded, outer surface, 
and in which said bearing assembly includes: 
a first race rigidly connected to said head tube, 
a second race mounted on said steering tube, and 
a locking ring for pushing axially said second race towards the first race 
and for rigidly connecting said second race to the steering tube. 
A steering assembly of the above indicated type is for example disclosed in 
European Patent EP-B-0 479 138. In this known solution, said second race 
of the bearing assembly is mounted with clearance above the steering tube 
to enable said locking ring to be interposed between the steering tube and 
the second race for rigidly connecting the latter to the steering tube. To 
this end, the locking ring has an outer conical surface able to engage a 
corresponding conical inner surface of the second race, so that the 
locking ring is forced between the steering tube and the second race 
causing the latter to be locked on the steering tube. 
SUMMARY OF THE INVENTION 
The object of the present invention is that of providing a steering 
assembly of the above indicated type which keeps the advantages of the 
above described known solution, i.e. the elimination of the outer 
threading on the steering tube which is instead present in the most 
conventional solutions, while improving simplicity and locking safety of 
the device. 
In order to achieve this object, the invention provides a steering assemble 
having all the features which have been indicated at the beginning and 
further characterized in that said second race is provided with a neck 
portion surrounding the steering tube which can be elastically clamped on 
the latter and in the said locking ring has an inner conical surface able 
to be pressed axially above a corresponding outer conical surface of said 
neck portion to complete clamping of the neck portion on the steering tube 
with the resulting rigid connection of the second race to the steering 
tube. 
Although theoretically said neck portion can be made in one piece with said 
second race, in a preferred embodiment of the invention the neck portion 
is constituted by an end portion having an outer conical surface of a bush 
which is separated from the second race and rigidly connected thereto, 
said end portion having a plurality of longitudinal slots which define 
longitudinal tabs which are elastically deflectable, in order to be 
clamped on the steering tube as a result of the engagement of the locking 
ring on said neck portion. Preferably said bush is constituted by a 
one-piece body of plastic material. 
Also in said preferred embodiment, said first race is rigidly fixed within 
a cup-shaped housing body having a tubular tail fixed within the head tube 
and the locking ring is provided with a protective circumferential skirt 
which covers the upper portion of said cup-shaped body, in order to 
protect the various parts of the bearing from dust and foreign bodies. 
The means for locking axially said locking ring includes, in a way known 
per se, a spacer tube slidably mounted around the steering tube (which 
forms part of a structure for connection to the handlebar) and is 
interposed axially between the locking ring and the head of a stop element 
fixed to the top of the steering tube. According to the invention, said 
stop element is constituted by an expandable device which can be locked 
within the steering tube by means of a screw. 
The steering assembly according to the invention is characterized by a 
relative simplicity while it ensures a perfect locking of the assembly in 
the mounted condition.

DETAILED DESCRIPTION OF THE INVENTION 
With reference to FIG. 1, by 1 there is designated a head tube, forming 
part of the frame of a bicycle, within which there is rotatably mounted a 
steering tube 2 connected at its lower end to a front fork 3 of a bicycle, 
and at its upper end to a tubular portion 4 forming part of a support 
structure for the bicycle handlebar. 
The steering tube 2 is rotatably mounted within the head tube 1 by means of 
an upper axial-radial bearing 5 and a lower bearing 6 which is also of the 
axial-radial type. The steering tube 2 has a smooth outer surface without 
threadings. 
The lower bearing 6 includes balls 7 interposed between a first race 8 
forced over the steering tube 2 and axially abutting against surface 9, 
and a second race 10 forced within a housing body 11, for example of light 
alloy, with an overturned cup-like shape, and a tubular tail 12 which is 
forced within the head tube 1. 
The upper bearing 5, similarly, has a first race 13 forced within a housing 
body 14 of light alloy, with cup-like shape, having a tubular tail 15 
forced within the head tube 1. The bearing 5 comprises balls 16 interposed 
between the first race 13 and a second race 17. 
In the preferred embodiment which is shown in the annexed drawings (see 
FIG. 2), within second race 17 there is forced a portion of a bush of 
plastic material 18 (see also FIG. 3) having an end portion 19 
constituting a neck portion surrounding the steering tube 2. The end 
portion 19 has a plurality of longitudinal slots 20 extending from the end 
edge of bush 18, so as to define a plurality of longitudinal tabs 21 which 
are elastically deflectable so as to be able to be clamped over steering 
tube 2 in order to rigidly connect the second race 17 to the steering tube 
2. In order to provide complete locking, there is provided a locking ring 
22 having an inner conical surface 23 able to engage a corresponding outer 
conical surface 24 formed on the end portion defining the longitudinal 
tabs 21 of bush 18. The locking ring 22 is further provided with a 
peripheral skirt 25 which covers the upper portion of the cup-shaped body 
14 in order to protect the parts of the bearing from the outer 
environment. 
The locking ring 22 can be axially clamped by means of tube 4 which is 
axially slidably mounted around steering tube 2 and is axially interposed 
between a ring 26 resting above locking ring 22 and the head 27 of an 
expandable device 28 which can be locked by means of a screw 29 within the 
steering tube 2. 
Purely by way of example, an expandable device 28 is illustrated herein 
which is of the type comprising two end elements 30, 31 which can be moved 
axially towards each other by means of said screw 29 which has its head 
resting above element 30 and its threaded portion screwed within a 
threaded hole 32 of element 31. Elements 30, 31 have facing conical 
surfaces between which there are interposed three sectors 33 of plastic 
material (two of which are visible in FIG. 1) held together by a split 
elastic ring 34, which on their turn have conical surfaces engaging the 
conical surfaces of elements 30, 31. The axial movement of elements 30, 31 
towards each other causes a radial outward displacement of the three 
sectors 33 which are compressed against the inner wall of steering tube 2 
so as to be locked within said steering tube. Naturally, however, any 
other stop element can be used as an alternative to that described above 
purely by way of example. For instance, the upper end portion of the 
steering tube 2 can be internally threaded, and head 27 can be connected 
to a threaded bush screwed within the steering tube. 
As clearly apparent from the foregoing description, the device according to 
the invention is relatively simple and constituted by a reduced number of 
parts. At the same time, the arrangement of a neck portion 19 rigidly 
connected to the second race 17 which can be clamped around the steering 
tube 2 enables a safe connection of the assembly to the steering tube to 
be obtained. Naturally, although the described example has a bush 18 of 
plastic material which is separated with respect to the second race 17 and 
rigidly connected thereto, nothing prevents, theoretically, from providing 
a neck portion 19 in one piece with the second race 17. 
Naturally, moreover, while the principle of the invention remains the same, 
the details of construction and the embodiments may widely vary with 
respect to what has been described and illustrated purely by way of 
example, without departing from the scope of the present invention.