GB2139163A - Cycle handlebar stems - Google Patents

Abstract

The stem comprises an arm carrying means 2, 3, 4, 5 at its leading end to which the centre of a pair of handlebars can be clamped, & also comprises an upright pillar 6 whose lower end is slotted 7 for co-operation with a truncated cone expander 9 that will spread the portions of the pillar 6 between the slots 7 outwardly into firmly gripping engagement with a surrounding steering tube of unslotted formation. The cone expander 9 is drawn upwardly to cause the spreading effect by co-operation between an axially threaded bore 10 therethrough and the threaded shank of a long bolt 11 whose head 12 is accessible from the top of the pillar 6. In order to avoid it being necessary to strike said head 12 with a heavy hammer or other tool to dislodge the jammed cone expander 9 downwardly, the bolt head 12 is sunk into a recess 13 and a circlip 15 is engaged in a groove 14 immediately above the head 12. The head 12 is rotated by a hexagon key entered through the circlip 15 and, as soon as said head 12 abuts against the circlip 15, further rotation of the bolt 11 can only be accommodated by downward displacement of the cone expander 9. <IMAGE>

Description

SPECIFICATION Cycle handlebar stems The handlebars of both pedal and motor-cycles have almost universally, and for very many years, been carried by a stem which comprises a clamp to hold the handlebars centrally, said stem being adjustable upwardly and downwardly, to suit persons of different stature, in a tubular upper portion of the front forks of the cycle frame, that upper portion being turnably journalled in the frame for conventional steering purposes.A pillar of the stem is firmly engaged in said tubular portion, after initial installation or an adjustment, by clamping a lower end of the pillar in that upper tubular portion of the front forks and this is achieved, from the upper end of the pillar, by turning the head of a long bolt that extends axially downwards through the pillar to a lower end region thereof which is formed with two or more axial slots at regular angular intervals around the longitudinal axis of the long belt.

The lower end of the long bolt is threaded and co-operates with a screw-thread through an axial bore in a truncated cone expander of small conical angle, the smaller diameter end of the expander being uppermost. As the bolt draws the cone expander upwards in the lower slotted end of the stem pillar, that end is spread by the cone into very firm frictionally gripping engagement with the interior of the surrounding turnably journalled but unslotted upper end of the cycle front forks. However, the cone expander tends to become so firmly jammed in the upper end of the forks that it cannot be shifted downwardly, even after the head of the long bolt has been rotated in a loosening direction, without using a heavy hammer or other tool on said bolt head with a consequent danger of breakage or, at least, a risk of unsightly damage being caused.

Various complicated and/or unsatisfactory constructions have been proposed to overcome this disadvantage of an otherwise strong, reliable and time-proven arrangement but an object of the present invention is merely to modify the known arrangement, so as to keep its advantages, whilst substantially overcoming the drawback discussed above.

According to the invention, there is provided a stem for carrying the handlebars of a cycle or other vehicle, the stem comprising means to clamp to it a pair of handlebars and a pillarfortelescopically adjustable entry in a surrounding steering tube of the vehicle, said pillar being tubular and having a lower end region thereof formed with a plurality of substantially axially extending spaced-apart slots for spreadable co-operation with the external surface of an upwardlytapering cone expanderformed with a screw-threaded bore which receives the threaded shank of a bolt whose head is accessible from the upper end of the pillar, wherein the upper end of the pillar is recessed to a sufficient extent to receive the head of said bolt wholly therein, the recess being arranged to carry, above the bolt head, means which will allow said bolt to be rotated but which will prevent upward axial displacement of the bolt beyond a position in which its head abuts against said means.

For a better understanding of the invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying single Figure of drawings which is a part-sectional side elevation of a cycle handlebar stem constructed in accordance with the invention.

Referring to the accompanying drawing, the stem that is illustrated has a forwardly projecting arm 1 which, when the stem is in use, will be approximately, if not exactly, horizontally disposed. Its leading end is formed as a clamp assembly which comprises a horizontally extending bore 2 that can be tightened around the centre of a pair of handlebars (not shown) by using a clamping bolt 3 a sleeved nut 4 and a washer 5. The bore 2 has a diameter of substantially 25.62 mm when fully opened but, when the nut 4 is fully tightened onto the bolt 3 to clamp a pair of handlebars firmly and reliably in position, that diameter may be reduced to substantially 25.49 mm.

The stem also comprises a pillar 6 which pillar will, when in use, generally be upright but not strictly vertically disposed, usually being at a relatively small angle to the vertical in accordance with the design of the front of the pedal cycle, motorcycle or other steerable vehicle of which it is to form a part.

The pillar 6 may conveniently have a length of 142 mm and its lowermost end is formed, at regular intervals around its longitudinal axis, with a plurality (preferably three or more) of axially extending slots 7 each of which terminates at its upper end in a substantially circular hole 8 that is provided to prevent the lower end of the pillar 6 from splitting. A truncated cone expander 9 that tapers upwardly and that has a small angle of conicity is entered in the lower tubular end of the pillar 6, said expander 9 having a screw-threaded axial bore 10 through which is entered the correspondingly screwthreaded shank of a relatively long bolt 11.

The bolt 11 extends axially through the pillar 6 and its head 12 is accessible from the upper end of the pillar. Upon rotating the bolt 11 in one direction, the cone expander 9 will be drawn upwardly into the slotted lowermost end of the pillar 6 to expand the portions of that lowermost end that lie between the slots 7 outwardly, the maximum diameter of the cone expander 9 being greater than the internal diameter of the lowermost end of the pillar 6. In use, at least the lower end of the pillar 6, and usually the majority thereof, will be closely telescopically slidably surrounded by a turnably mounted steering tube affording the upper end of the front forks of, for example, a pedal cycle or motorcycle.It will be apparent that spreading the lowermost end of the pillar 6 outwardly will cause the outer surface of the portions of that pillar which lie between the slots 7 very firmly to grip the interior of said tube which may be considered, for the purposes of this document, as being a "steering" tube.

What has been described up to the present point is substantially conventional except that the head 12 of the long bolt 11 usually stands proud of a substantially horizontal surface at the upper end of the pillar which surface surrounds the mouth of the axial bore through which the shank of the bolt 11 is entered downwardly. The known arrangement has proved to be very strong and reliable and substantially the only disadvantage thereof appears when the pillar 6 is to be loosened prior to an upward or downward telescopic sliding movement to suit the stature of a different rider or the changed stature of, for example, a growing child rider.Particularly if an adjustment has not been made for some considerable time, it is usually found that the cone expander 9 is so tightly jammed in the lowermost slotted end of the pillar 6 that, after loosening the long bolt 11 to a considerable extent, it is necessary to hit its head 12 quite forcibly with a heavy hammer or other tool before the cone expander 9 can be persuaded to move downwardly and release the pillar 6 priorto making the required upward or downward adjustment of that pillar followed by re-tightening of the bolt 11 to draw the expander 9 upwardly once again into the slotted end of the pillar 6.Even when only a short period of time has elapsed between adjustments and the cone expander 9 has been maintained in a well-greased or otherwise lubricated condition, striking the head 12 of the bolt 11 is usually necessary to effect release but, after a long period of time, many an unwary amateur mechanic has either caused breakage by the too enthusiastic application of heavy hammer blows or, more often, has accidently struck some other part of the cycle or other vehicle causing unsightly damage.

The present invention seeks to overcome this disadvantage in a simple manner and, accordingly, the bolt head 12 does not stand proud of the upper end of the pillar 6 but is received in a recess 13 that may conveniently have a diameter of 13 mm and a depth of 14.5 mm. The bolt head 12 has a circular cylindrical external surface and is of the kind known as a "cap head bolt" formed with an axially extending recess having flats to co-operate with a hexagon key or "Allen" (Registered Trade Mark) key. The bolt head 12 has an axial length of substantially 10.5 mm so that, when fully engaged atthe bottom ofthe recess 13, its upper end will be sunk below the top of the pillar 6.Immediately above the upper end of the bolt head 12, a groove 14 is formed in the cylindrical wall of the recess 13, said groove 14 conveniently having a diameter of 13.6 mm and an axial depth in a direction parallel to the bolt 11 of 1.1 mm, the upper surface of the groove 14 being spaced downwardly from the flat upper end of the pillar 6 itself by substantially 1.6 mm.

When the bolt 11 has been installed and its head 12 occupies substantially the position in the recess 13 that is shown in the drawing, a circlip 15, which is easily installed and removed by the use of conventional circlip pliers, has its external edge sprung into the groove 14, the internal diameter of the installed circlip 15 being, as will immediately be evident from the drawing, significantly less than that of the bolt head 12 but still being large enough to enable a hexagon key or other tool to be entered therethrough.

The internal circlip 15 affords means which allows the bolt head 12 to be rotated but which prevents upward axial displacement of the bolt 11 beyond a position in which its head 12 abuts thereagainst and it will immediately be evident that, upon rotating the head 12 of the bolt 11 using a hexagon key pr other tool, the head 12 will first move upwardly until it abuts against the lower surface of the circlip 15.

Subsequent rotation of the bolt 11 can only be accommodated by forcing the cone expander 9 at the lowermost end of the pillar 6 downwards and out of co-operation with that slotted lowermost end. It will be found in almost all casesthatthe cone expander 9 is quite quickly released from the pillar 6 without the use of a heavy hammer or other hazardous tool although, as with the known arrangement, it is recommended to keep the conical surface of the expander 9 in a well greased or otherwise lubricated condition. In the example which is being described, the bolt 11 has a diameter of substantially 7.9 mm but it will be apparentthatall of the dimensions are given purely by way of example and that parts of alternative dimensions could equally well be employed having regard to the particular vehicle with which the handlebar stem assembly is to be employed. The example that has been described is intended particularly for use with a pedal cycle but it will be realised that, as well as motorcycles, the invention could be employed in substantially any vehicle having handlebar steering where upward and downward adjustment of the handlebars is desirable to suit persons of different stature or changed stature.

Claims (10)

1. A stem for carrying handlebars of a cycle or other vehicle, the stem comprising means to clamp to it a pair of handlebars and a pillar for telescopically adjustable entry in a surrounding steering tube of the vehicle, said pillar being tubular and having a lower end region thereof formed with a plurality of substantially axially extending spaced-apart slots for spreadable co-operation with the external surface of an upwardly tapering cone expander formed with a screw-threaded bore which receives the threaded shank of a bolt whose head is accessible from the upper end of the pillar, wherein the upper end of the pillar is recessed to a sufficient extent to receive the head of said bolt wholly therein, the recess being arranged to carry, above the bolt head, means which will allow said bolt to be rotated but which will prevent upward axial displacement of the bolt beyond a position in which its head abuts against said means.

2. A stem as claimed in claim 1, wherein said means is afforded by a circlip whose outer edge is received in a groove formed in the wall of said recess at a level above that of the top of the head of said bolt.

3. A stem as claimed in claim 2, wherein said groove has a depth of substantially 1.1 mm.

4. A stem as claimed in claim 2 or claim 3, wherein said groove has a diameter of substantially 13.6 mm.

5. A stem as claimed in any one of claims 2 to 4, wherein the upper surface of said groove is spaced beneath the top of the pillar by a distance of substantially 1.6 mm.

6. A stem as claimed in any preceding claim, wherein the recess is of circular cylindrical configuration having a diameter of substantially 13 mm and an axial depth of substantially 14.5 mm.

7. A stem as claimed in claim 6, wherein said bolt is a cap head bolt having a head of circular cylindrical configuration formed with an axial recess that is shaped for co-operation with a matching key or other tool.

8. A stem as claimed in claim 7, wherein the recess in the bolt head is of hexagonal configuration.

9. A stem for carrying the handlebars of a cycle or other vehicle, the stem being substantially as hereinbefore described with reference to the accompanying drawing.

10. A pedal cycle, motorcycle or other steerable vehicle when comprising a handlebar stem as claimed in any preceding claim.