This instant specification relates to height-adjustable seat posts, commonly called “dropper seatposts” or “dropper posts”.
Modern dropper posts can be heavy and may require frequent service. This may contribute to why dropper posts have not been broadly adopted by all cycling sectors (cross-country mountain biking, cyclecross, road, recreational, etc.).
In general, this document describes height-adjustable (“dropper”) seat posts. Namely, a dropper seatpost that is lightweight yet reliable, reducing intervals between service. When the dropper seatpost needs service, service should be user friendly.
The systems and techniques described here may provide one or more of the following advantages:
1. Headless stanchion and one-piece lower
2. Trimmable Stanchion
3. Full insertion lower tube w/ integrated clamp and frame integration
The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from the description and drawings.
In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific examples in which the disclosure may be practiced. It is to be understood that other examples may be utilized and structural or logical changes may be made without departing from the scope of the present disclosure.
Dropper Post Description
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At the top of the upper tube A is a saddle clamp E. The saddle clamp E attaches the bicycle saddle F to the upper tube A. When the upper tube A slides within the lower tube B, the saddle F slides with it, adjusting the saddle F height with respect to the bicycle frame. Sliding in this matter is the fundamental role of a dropper post. Traditionally, the saddle clamp E is in fixed position with respect to the upper tube A and only allows for offset and tilt adjustments of the saddle F. This is called a “fixed head” saddle clamp E. In
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At the top of the upper tube 1 is a saddle clamp 9. The saddle clamp 9 attaches the bicycle saddle 7 to the upper tube 1. When the upper tube 1 slides within the lower tube 2, the saddle 7 slides with it, adjusting the saddle 7 height with respect to the bicycle frame. Sliding in this matter is the fundamental role of a dropper post. In examples, the saddle clamp 9 is adjustable with respect to the upper tube 1 and allows for height, rotation, tilt, and offset adjustments of the saddle 7. The saddle clamp 9 is a “floating head height” or “floating height” saddle clamp 9, an example of which is disclosed in U.S. Provisional Patent Application Ser. No. 62/651,379, to which this application claims priority under 35 U.S.C. § 119(e).
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Traditionally, the lower tube 2 is clamped by the post clamp 10 in the frame seat tube 13 within certain limits. The dropper post should not be installed any shallower than the minimum insertion depth. In the opposite extreme, since the post collar 22 of the lower tube 2 is a larger diameter than the frame tube, the lower tube 2 can only be inserted up to the post collar 22. This is called the maximum insertion depth 17 of the post. The minimum insertion depth is determined by the minimum length of lower tube 2 that should be supported in the frame seat tube 13 in order to support the maximum bending moments applied to the dropper post (pure axial loads require less insertion depth and therefore the bending moments are the leading factor to the minimum insertion depth).
Maximizing the room inside the dropper post allows for the locking mechanism (or cartridge assembly) of the dropper post (typically a pneumo-hydraulic or mechanical system). However, some of this room is taken up by the thickness of the telescopic tubing. The thicker the lower tube 2, the smaller the ID (inner diameter) of the lower tube 2. Therefore, the upper tube 1 may also be smaller. For the upper tube 1 to also withstand bending moments, it may also have a thick wall. Therefore, the thicker the upper tube 1, the smaller the ID of the upper tube 1. Traditionally, there has not been much room remaining for the locking mechanism, restricting the architecture and layout of components to what we have as modern seatposts—heavy, unreliable, and difficult to service.
Most dropper post users seek to achieve as much dropper travel as possible for their frame-to-saddle height 20. Traditionally, when choosing a dropper post for their bike, the user attempts to find one with a collar-to-saddle height 21 that does not exceed their frame-to-saddle height 20.
Users also consider the maximum insertion depth 17. Some bicycle frame designs have depth limiting frame features 23 in the way (tube bends, suspension pivot points, welds, etc.) that will not allow the dropper post to be inserted all the way to the maximum insertion depth 17. Therefore, the difference between the maximum insertion depth 17 and the available depth in the frame (maximum insertion depth of the frame 18), is added to the collar-to-saddle height 21. If the adjusted collar-to-saddle height 21 exceeds the frame-to-saddle height 20, the dropper post may be too long for the user. This information may not be readily available to the user, often leading to confusion and mis-purchased dropper posts. Sometimes this information may not be publically available to the consumer for the consumer to make an educated purchase.
Stack height 19 is another dimension that users evaluate when deciding which dropper post to install on their bike. Stack height 19, as a minimum stack height, is the collar-to-saddle height 21 when the dropper post is fully compressed (technically, the collar-to-saddle rail height). A lower stack height 19 enables the saddle 7 to be as low as possible when the dropper seatpost is fully compressed.
Serviceability: Assembly/Disassembly
With the traditional dropper post, in order to remove the upper tube A from the lower tube B, the upper tube A is slid out through the top of the lower tube B. This is because the saddle clamp E is permanently mounted to the top of the upper tube A and will not fit through the ID of the lower tube B. However, with the upper tube A and the lower tube B including bushings, similar to lower bushing 4 and upper bushing 3, respectively, and the upper tube A including anti-rotation pins, similar to anti-rotation pins 5, in attempting to remove the upper tube A through the top of the lower tube B, the bushings will collide with each other, stopping removal. In addition, the anti-rotation pins will collide against the upper bushing. If the anti-rotation pins can be removed, but not the lower bushing, the lower bushing will collide with the upper bushing, preventing the upper tube A from being removed.
Removal of the upper tube A through the top of the lower tube B can be accommodated by a couple of methods: 1) The lower tube B and post collar G can be a multi-piece design in which the post collar G can be removed and the upper bushing can be extracted, allowing room for the lower bushing and anti-rotation pins to slide out of the lower tube B. 2) The lower bushing and anti-rotation pins can be removed from the upper tube A first, before the upper tube A is pulled through the top of the lower tube B. This can be accommodated by a removable cap on the bottom of the upper tube A. When the cap is installed, the lower bushing and anti-rotation pins are secure, when the cap is removed, the bushing and anti-rotation pins are free to be stripped off the end of the upper tube A.
Multi-piece lower tube B and upper tube A designs may add manufacturing complexity, more parts, and weight. But the biggest drawback to these configurations is that they limit the internal configuration of the locking mechanism (in the case of a removable cap on the upper tube A) or increase the stack height 19 (in the case of a two-piece post collar G).
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Further to the overall architecture of the dropper post 100, the “floating head” saddle clamp 9 provides the dropper post 100 with additional height adjustment. With reference, for example, to
Often, the user wants the most travel that can be fit in their frame. If the user tries to fit a conventional post and the collar-to-saddle height 21 is too much, then they are forced to go to the next shorter travel size. This has two drawbacks: 1) the user will not get as much travel, and 2) the lower tube 2 is extended out of the frame to achieve the frame-to-saddle height 20. With the “floating head” saddle clamp 9, a second degree of height adjustment at the interface of the saddle clamp 9 to upper tube 1 is provided, such that a change in height can be made to an otherwise too long of a dropper post. This also allows a user to keep the post collar 22 of the lower tube 2 as close to the frame as possible (the dropper post is inserted into the frame as far as possible).
If the amount of adjustment available at the top of the upper tube 1 is great enough, the lower tube 2 can be fully inserted in the frame seat tube 13 and does not have to extend out of the frame. This provides an advantage in that, with the lower tube 2 fully inserted into the frame, the walls of the lower tube 2 are reinforced by the frame seat tube 13. No longer does the lower tube 2 have to be designed for a variety of extension heights and bending moments. This means that the lower tube 2 wall thickness may decrease. A decrease in lower tube 2 wall thickness means an increase in lower tube 21D. An increase in lower tube 21D means more room for the upper tube 1 to slide and a larger upper tube 10D. A larger upper tube 10D means more resistance to bending and thus a thinner wall. A thinner upper tube 1 wall means a larger upper tube 11D. A larger upper tube 11D provides more room for internal locking mechanisms.
A thinner lower tube 2 also means a lighter lower tube 2. Since the upper tube 1 may grow in length, it will need to be able to handle the increased bending moment. But because the upper tube 1 increases in diameter, typically the upper tube 1 wall thickness can decrease (the biggest effect on resistance to bending moment is the outside diameter) and still handle the bending moment. This provides even more internal room for locking mechanisms.
With the dropper post 100, manufacturing of parts and assembly/disassembly are made easier, fit range per seatpost size increases, weight decreases, and internal architecture for locking mechanisms opens.
Further Use of this Technology
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One step further would be full frame integration where the splined lower tube 2 is the frame seat tube 13. In place of the post clamp 10 would then be the post collar 22 to support the upper bushing 3 and wiper seal 6. The lower end cap that holds the bottom of the locking mechanism can be attached to the bicycle frame by a multitude of methods.
Although specific examples have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific examples shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific examples discussed herein.
This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application Ser. No. 62/651,379 filed on Apr. 2, 2018, and incorporated herein by reference.
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