GB2543940A

GB2543940A - Bicycle stem

Info

Publication number: GB2543940A
Application number: GB1616463.4A
Authority: GB
Inventors: Lionel David Sparrow Roger
Original assignee: Individual
Current assignee: Individual
Priority date: 2015-09-29
Filing date: 2016-09-28
Publication date: 2017-05-03
Also published as: GB201616463D0; GB201517192D0

Abstract

A bicycle stem with a stem body and two complementary clamp members 21, 22 mounted substantially within the stem body, wherein the clamp members 21, 22 engage both the steerer tube S and handlebar H. At one end the tapered clamp members 21, 22 together form a concave wedge (fig 3: 27) which engages a V member (fig 3: 29) such that when the clamp members 21, 22 are pushed together by screw 25 the V-member is forced against either the handlebar or steerer to lock the stem in place. At the other end the clamp members have a concave semi-circle cross section 26 to directly contact the tube, or may instead grip the tube via an abutment member. The stem body is formed from four generally parallel limbs 3, 4, 5, 6 arranged in square formation, connected at a first end with a pair of horizontal U-shaped bridge members 7, 8 at the steerer end and a pair of vertical bridge members 9, 10 at the handlebar end.

Description

BICYCLE STEM

The present invention relates to a bicycle stem, that is to say a bracket that interconnects the handlebars and the steering shaft or steerer, attached to the front forks.

It is known to offset the handlebars from the steerer and to connect them by a stem. Known stems are generally clamped to the handlebar and steerer by either a clamp including a slit in an encircling member, with bolts closing the slit, or a clamp including a separate saddle piece closed by bolts at both ends. It is also known to use a split wedge drawn together by a bolt and carried by the stem to clamp the handlebar or steerer to the stem at a bore in the stem.

The object of the present invention is to provide an improved stem.

As used herein a “compound U-strap” means a strap having four generally parallel limbs arranged to intersect planes transverse to them at the four comers of a rectangle in the plane, the limbs being interconnected in pairs at one end by two fiends and interconnected in the other pairs at the other ends by two other U-ends, the arrangement being such that when viewed in one elevation the strap appears to be U-shaped with the U-end at one end and when viewed in another orthogonal elevation to be U-shaped with the U-end at other end. This definition expressly includes the limbs diverging / converging in either elevation whilst remaining generally parallel, i.e. geometrically parallel or slightly angled to each other.

According to the invention there is provided a bicycle stem for connecting a handlebar to a steerer, the stem comprising: • a compound U-strap, whose U-ends are shaped complementarily to the handlebar and the steerer, • a pair of spaced clamp members arranged at least substantially within the limbs of the compound U-strap, o the one ends of the clamp members being U-shaped to abut the handlebar or steerer directly or engaging with separate, so-shaped abutment members to abut the handlebar or steerer indirectly and o the other ends of the clamp members being complementarity shaped to form opposing wedge surfaces to abut directly the other of the handlebar and steerer or to abut indirectly via a V-member shaped complementarity to the wedge surfaces on one side and the other of the handlebar and steerer on the other side and • means for urging the clamp members towards each other to cause the wedge surfaces to urge the handlebar and steerer against the respective U-ends, whereby the stem structurally unites the handlebar and steerer.

Whilst it is possible, though unlikely that the U-ends would not be closely complementarity shaped to the handlebar and steerer cross-sectional, in practice semi-circularly curved, it is envisaged though not preferred due to irregular stress imposition that the ends of the clamp members or the abutment members or the V-member could be shaped for limited contact with the handlebar or steered, in particular by being V-shaped, or semi-V-shaped in the case of wedge surfaces.

Again, whilst the compound U-strap provides simplicity in fitting to the handlebar in particular, where sliding on from the end can be obstructed by brake controls and/or the shape of the handlebar, in that the U-strap can be fitted by passing the handlebar into the respective U mouth, either or both pairs of the U-ends can be provided with bridges between their limbs at the U-ends.

It is envisaged that the stem could be of aluminium alloy or composite material.

To help understanding of the invention, a specific embodiment thereof will now be described by way of example and with reference to the accompanying drawings, in which:

Figure 1 is a central cross-sectional plan view of a bicycle stem in accordance with the invention;

Figure 2 is a perspective view of the stem of Figure 1; and

Figure 3 is a perspective cross-sectional view of the stem.

Referring to the drawings a bicycle stem 1 for connecting a handlebar H to a steerer S has a compound U-strap 2. This has a four generally parallel limbs, that is an upper pair 3,4 and a lower pair 5,6.

The limbs within the upper pair and the lower pair diverge slightly from their stem end U-ends 7,8 towards their handlebar U-ends 9,10. The stem U-ends are bridged by bridge pieces 11,12, with plain bores 14,15 inside the U-ends and the bridges, which are an ordinary clearance for a standard 28.5mm /1 1/8 inch steerer. The degree of divergence is from an outside dimension of the steerer U-ends of 42mm to an outside dimension at the handlebar of 55mm, the overall length of the stem being 101 mm. The limbs within the upper and lower limbs at either side of the stem 3,5; 4,6 are parallel, leaving a gap between them of 32mm. These limbs are connected by the plain handle bar abutting semi-circular U-ends 9,10.

Two clamp member 21,22 with parallel upper and lower faces 23,24 are accommodated between the parallel upper and lower limbs 3,5; 4,6. They are identical, save that one is threaded receive a clamp screw 25, whilst the other has a clearance bore for the screw. At their handle bar abutting ends 26, the clamp members are semi-circularly scalloped.

At their other ends, the clamp members are formed with divergent wedge surfaces 27, which abut against similarly angle surfaces 28 of a V-member 29. This has a stem-abutting, semi-circular-scallop surface 30. A detail is that the wedge surfaces have grooves 31 and the V-member has ribs 32 engaging in the grooves. These keep the clamp members aligned at the steered end of the stem, which in the interest of lightness and easy of fitting to the handlebar has no top to bottom connection at the steerer end.

Tightening of the screw 25 has no direct effect at the handlebar, with the scalloped end 26 moving inwards. At the steerer, the moving inwards of the wedge surfaces 28 urges the V-member against the steerer. With the separation of the handlebar and steerer being constrained by the compound U-strap, tightening of the screw unifies the handlebar and the steerer.

It should be noted that normally, though not necessarily, the clamp members are be sized such that their surfaces shaped complementarity with the slightly divergent limbs will be flush with them when the screw is tightened. However, it will be appreciated that the stack of tolerances may result in them protruding or being inset when the screw is tightened.

We have tested the stem and found it to provide torsional stiffness against one pedal then the other rider applied load. Equally it is simple and light and can be tightened with the one screw only.

The invention is not intended to be restricted to the details of the above described embodiment. For instance, a V-member similar to member 29 could be provided at the handle bar. However this would not provide additional clamping with the clamp members being slidable along the V in this orientation and the clamping action coming from the V member acting on the steerer. The arrangement can be reversed with the clamping Vee acting on the steerer. In this arrangement, the clamp members are arranged one above the other and the clamping screw arranged vertically or at least parallel to the steerer.

The V member 29 can be omitted completely if the wedge surfaces are complementary to be steerer. Flat wedge surfaces are possible for this.

Dowels 41 can be provided to maintain angular alignment of the clamp members.

To provide quick release, the screw can be replaced by an over-centre clamp.

Claims

CLAIMS:

1. A bicycle stem for connecting a handlebar to a steerer, the stem comprising: • a compound U-strap, whose U-ends are shaped complementarity to the handlebar and the steerer, • a pair of spaced clamp members arranged at least substantially within the limbs of the compound U-strap, • the one ends of the clamp members being U-shaped to abut the handlebar or steerer directly or engaging with separate, so-shaped abutment members to abut the handlebar or steerer indirectly and • the other ends of the clamp members being complementarity shaped to form opposing wedge surfaces to abut directly the other of the handlebar and steerer or to abut indirectly via a V-member shaped complementarily to the wedge surfaces on one side and the other of the handlebar and steerer on the other side and • means for urging the clamp members towards each other to cause the wedge surfaces to urge the handlebar and steerer against the respective U-ends, whereby the stem structurally unites the handlebar and steerer.

2. A bicycle stem as claimed in claim 1, wherein the ends of the clamp members are shaped for limited contact with the handlebar or steerer by being V-shaped, or semi V-shaped in the case of wedge surfaces.

3. A bicycle stem as claimed in claim 1 or claim 2, wherein the abutment members are shaped for limited contact with the handlebar or steerer by being V-shaped, or semi V-shaped in the case of wedge surfaces.

4. A bicycle stem as claimed in claim 1 or claim 2 or claim 3, wherein the V-members are shaped for limited contact with the handlebar or steerer by being V-shaped, or semi V-shaped in the case of wedge surfaces.

5. A bicycle stem as claimed in claim 1, wherein the U-strap is adapted to be fitted by passing the handlebar into the respective U mouth, wherein either or both pairs of the U-ends have a bridge between the limbs at the U-ends.

6. A bicycle stem as claimed in claim 1, wherein the material of construction is an aluminium alloy or a composite material.