The present invention relates to a height adjustable seat post typically, but not exclusively, for bicycles.

When riding a bicycle it is sometimes necessary to adjust the height of the bicycle seat. This may be to account for different riders, or a change in riding conditions. For example, a lower centre of gravity is desirable when going downhill. Conversely, a higher/normal position may be desirable when going uphill.

Presently, it is known to have a height adjustable seat post. This may be mechanical, or electrically powered. Often, the control mechanism is disposed under the seat, making it difficult for the cyclist to operate safely whilst in motion. It is known that some cyclists contort themselves to avoid altering the seat height whilst in motion.

The abstract of US 2011/0,049,945 reads as follows:

"A motorized bicycle seatpost assembly is basically provided with a first tube, a second tube, a motor and a movement mechanism. The first tube has a first end and a second end. The second tube has a first end and a second end. The first end of the second tube is open such that the second end of the first tube is telescopically disposed in the first end of the second tube. The motor is arranged in at least one of the first tube and the second tube. The movement mechanism is connected to the motor to change a relative axial position between the first and second tubes."

The object of the present invention is to provide an improved height adjustable seat post. Particularly, one that is conducive to operation whilst in motion.

According to the invention there is provided a height adjustable seat or handle bar post, for a bicycle, comprising:

• an inner telescopic member adapted to support a seat or handlebars, and

• an outer telescopic member, • a spindle within the members for determining the extension of the inner member relative to the outer member,

• the spindle having a fast lead thread such as to turn upon application of longitudinal force, the spindle being threadedly engaged with one member and thrustingly joumaled with the other member.

• resilient means for urging the inner telescopic member outwards for extension of the post and lifting of the seat, and

• a releasable lock for locking the spindle against rotation and extension of the post,

the arrangement allowing, when the lock is released, for a rider to depress the seat with his/her weight, or to permit the resilient means to lift the seat, the seat being retained in position when the lock is reapplied.

Normally, the inner and outer telescopic members are restricted from relative rotation by using a key and keyway. One or more key and key way may be used. The key may be on either the inner or outer telescopic member, with the key way on the other telescopic member. Alternatively,

Normally, the inner member is adapted to receive the spindle by introducing a fixed nut, wherein the fixed nut is appropriately threaded. The fixed nut may be fixed by threading it such that it engages with the inner member, by splining it, using adhesive or other mechanical means. Alternatively, the internal diameter of the telescopic member could be threaded. Any suitable alternative known in the art may be used.

In the preferred embodiment, the spindle has a fast lead thread. A fast lead thread allows for a good amount of travel of the spindle for each turn. This enables fast control of the height of the seat or handlebar post.

Threads per inch is a means of measuring how many threads there are per inch of a threaded member. The threading of the spindle is preferred to be in the range of 4-12 threads per inch (TPI). More preferable is for the threading to be in the range of 6-10 TPI. Most preferable is having 8 TPI. In order to achieve the desired mechanical advantage, it is preferred that the spindle has multi-start threading. Normally this is in the range of 4 to 12 starting threads, preferably it is in the range of 6 to 10 starting threads. In the preferred embodiment, there are 8 starting threads.

The lead of each thread upon the spindle, wherein the lead is the linear travel the nut makes per one screw revolution, is normally 15mm to 35mm. More preferably it is between 20mm and 30mm. In the most preferred embodiment, it is 27mm.

The pitch of the threading on the spindle, this being the distance between the threads, is normally in the range of 1mm and 3mm. Preferably, the pitch is 2mm.

The helix angle of the threading upon the spindle is preferably above 30°. Normally, it is in the range of 36 ⁰ to 48 °, preferably still is a helix angle in the range of 40 ° to 44 °. Most preferably, the helix angle is 42°. This allows for fast travel of the spindle, the locking means prevent the spindle from travelling when undesired.

Normally, the diameter of the spindle, measured from peak to peak of the threads, is in the range of 6mm to 12mm. preferably, the diameter is in the range of 8mm to 10mm. In the preferred embodiment, the diameter of the spindle is substantially 9mm.

The ratio of lead to diameter should be substantially, if not exactly, equal when scaling any measurement up or down. This ensures that the helix angle is sufficient to provide the required rate of travel for the spindle, when it is released.

The spindle is axially restricted by a locking means. The locking means must be capable of preventing rotation of the spindle. The locking means may be a clutch, such as a dog clutch. However, it is envisaged that sprung pins, or collets may be used. Any suitable alternatives may also be used.

Preferably, the lock is at a journaled end of the spindle, this can be either the top end, or bottom end. Normally, the lower end of the spindle will be adapted to engage with the locking means, such as a clutch plate, or equivalent component. The locking means is housed in a housing which normally contains the locking means and a triggering means. The housing is normally located at the lower end of the outer telescopic member, and adapted such that it seals the outer telescopic member. The triggering means extends through the housing to enable the user to actuate the triggering means whilst the bicycle is in use.

It is envisaged that the inner and/or outer sliding member will comprise bearings to aid the sliding of the telescopic members relative to each other. They will usually be plastic, such as Polytetrafluoroethylene, but any alternative materials with the suitable low friction properties may be used.

The housing is envisaged to have a shaped lower portion, wherein the nut has a substantially tight fit. The shape may be square, pentagonal, hexagonal, heptagonal etc. In fact, it may be any shape that would inhibit rotation of the nut, or equivalent component, such as a star or cross.

A triggering means for the locking means renders the spindle realisably rotatable. The triggering means will normally be a Bowden cable. However, it is envisaged that the tensioning means could be any mechanical linkage, such as a rod or cable. Alternatively, any suitable known means may be used to trigger the locking mechanism.

The spindle normally has an adaptation at its lower end to correspond with the locking means. This could be a corresponding clutch plate, for example, or an alternative discussed above such as sprung pins.

Normally the housing will have a shaped lower section that is at least partially deeper than the clutch plate or equivalent feature. Disposed beneath the clutch is a spring or other resilient member, so that when the triggering means is released, the locking means re-engage, normally the clutch plate with the spindle clutch plate. It is envisaged that the resilient means for moving the inner telescopic member outwards will be a spring. However, an alternative known to an individual of ordinary skill may be used, such as an elastic. Alternatively, a simple seal or piston could be used to create an air chamber, the varying pressure resultant from the varying volume of the void should be sufficient to urge the required movement. The resilient means are intended to be of suitable strength to urge the inner telescopic member outwards when there is no, or little load on the top of the inner telescopic member.

The resilient means are situated around the spindle, or alternatively within the inner telescopic member. In fact, the resilient means may be situated anywhere in the assembly wherein it can urge the inner telescopic member outwards.

The means to which a bicycle seat may be attached are well known in the art. As such, no description of such a feature is thought necessary.

Preferably, the material of construction will be a metal, or an alloy thereof. It is envisaged that a plastic, or composite material such as carbon fibre may also be used. As mass is important with bicycles, especially higher end bicycles, any material with the correct properties, such. Strength, durability etc. may be used for any component.

Different components are generally constructed of different materials.

Normally, the inner and outer telescopic members are of metal/alloy construction. Alternatively, they could be a composite material such as carbon fibre, they may also be plastic.

The fixed nut will generally be made of plastic, but may also be made of metal or a composite material. The same may be said for the keys which are employed to restrict rotation of the telescopic members relative to each other. Alternatively, PTFE or other low friction materials may be used for the keys.

The spindle will normally be metal. Alternatively, any durable material may be used. The lower end of the spindle and the locking nut, or equivalent component, may or, may not be of the same material. It is envisaged that a durable plastic, or metal may be used.

The invention and its constituent components are not intended to be limited to the above identified materials. Any suitable alternative may be employed.

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

Figure 1 shows an external view of the invention.

Figure 2 shows a cross section of a height adjustable seat or handle bar post in accordance with the invention

Figure 3 shows the spindle with clutch plate at its lower end.

Figure 4 is a cross sectional view of the housing for the locking means and triggering mechanisms.

Figure 5 a plan view of part of the locking means.

Figure 6 shows a cross section of a height adjustable seat or handle bar post in accordance with another embodiment of the present invention.

Referring to Figure 1, the adjustable seat post 1 can be seen. The seat post 1 comprises of an inner telescopic member 2, which fits into an outer telescopic member 3. A threaded coupling 4 is provided, this keeps the inner and outer telescopic members in contact, whilst allowing extension of the inner telescopic member relative to the outer telescopic member. Extending from the bottom of the outer telescopic member 3 is a triggering mechanism 5. The Bowden cable 6, part of the triggering mechanism, can also be seen.

Figure 2 shows a cross section of a product in accordance with the present invention. In order to prevent the seat from rotating whilst being adjusted, the key and corresponding key ways 7A, 7B are included. There are one or more bearings 16 provided to aid in the sliding motion of the telescopic members relative to each other. At the inserting end of the inner telescopic member 2, there is a fixed nut 8. The fixed nut 8 has been adapted by introducing threading so that the threaded spindle 9 may travel in or out of the inner telescopic member as urged by the spring 10, and whether the rider is applying force to the seat.

The lower end of the spindle has a clutch plate 12a forming part of the locking mechanism 12. The clutch at lower end of the spindle 12a mates to the other clutch plate 12b. This may be seen in figures 3 and 4. The clutch plate 12b fits into a housing 13. The housing is shaped at its bottom portion, with the clutch plate 12b housed in the housing 13 being corresponding housed such that is has a substantially tight fit and is restricted from relative rotation. In this instance, the profile of said shaping is hexagonal.

A second spring 14, or other suitable tension means is disposed between the housing 13 and the locking nut 12b. The triggering mechanism 5 is usually enacted by a Bowden cable 6. When actuated, the Bowden cable pulls the clutch plate 12b away from the spindle adaptation 12a. This causes the spring between the housing 13 and clutch plate 12b to be depressed. When the locking mechanism 12 is separated, the spindle is able to move either into or out of the inner member 2 via the fixed nut 8. If the rider is on the seat, or punching handle bars, the post will fall, alternatively, the spring 10 will urge the inner member outwards relative to the outer post. When the triggering means is released, the clutch will reengage, inhibiting movement of the spindle, thereby determining the height of the post. Figure 3 shows the spindle 9 with the clutch plate 12a at is lower end. It can be seen that the spindle is threaded, and at the lower end of the spindle is the adaptation 12a. In the preferred embodiment, the adaptation 12a is a clutch corresponding to the locking nut 12b. It is envisaged that alternatives could be used to provide a mating interface, such as sprung pins, for example, as discussed above.

Figure 4 shows a cross sectional view of the housing for the locking nut and triggering mechanisms of the preferred embodiment. Inside the housing 13, the locking nut 12b can be seen. Passing through the locking nut 12b is the Bowden cable 6. When pulled, the Bowden cable 6 pulls the locking nut 12b down thereby depressing the spring 14. This series of events disengages the locking mechanisms constituent components 12a and 12b thereby enabling the spindle to move as described above. Figure 5 shows a plan view of the clutch 12b. the clutch 12b is complementary in shape to the housing 13 . The clutch plate having a substantially tight fit in the housing means it is restricted from rotating - thereby preventing the spindle from travelling due to the interface between the locking mechanism 12a and 12b. Only when the Bowden cable 6 has been actuated may the spindle move, as the locking means would otherwise be engaged.

The protrusions shown in figure 5 are merely an example, any interface may be used between the spindle adaptation 12a and the locking nut 12b. Figure 6 depicts a cross section of an alternative embodiment of the present invention. It is largely similar to the first aspect of the invention but differs in the location of certain components.

This aspect of the invention differs from the first in that the spindle travels downwards through the outer telescopic member 103 as opposed to travelling into the inner member 102. The locking means are shown as being at the top end of the inner telescopic member. It is envisaged that the locking means 112 could also be at the bottom end of the inner telescopic member 102.

The seat post 101 can be seen, along with the inner telescopic member 102, the outer telescopic member 103 and coupling 104. In this embodiment, the triggering means 105 and the locking means 112 are situated at the top end of the inner telescopic member 102.

Triggering the release of the locking means 112 enables the spindle 109 to rotate freely through the fixed nut 108.

The resilient means 110 are shown as a spring, however alternatives such as an air chamber may be used. The spring 109 is of sufficient strength to urge the inner member outwards when the spindle is disengaged from the locking means after compressing the resilient means 110.

Both aspects of the invention are not intended to be restricted to the details of the above described embodiments. Many alternatives to the preferred embodiment have been disclosed. For instance, the clutch of the locking mechanism may be replaced by sprung pins, or other similar features.

Additionally, the resilient means may be a spring, or an air chamber. The air chamber may be achieved by the introduction of a seal or piston. Compression of the trapped air results in a pressure build which is sufficient to urge the movement of the telescopic member, thereby adjusting the seat. This, and other weight saving alternatives may be used. Any component of the invention may be replaced by features known to an individual of ordinary skill.