SRAM has revealed a patent (initially filed final summer season, on June 23, 2021) detailing a suspension fork with an automated venting system, whereby differential stress arising between the ambient surroundings and the cavity contained in the decrease legs would self-equalize whereas using. The invention, we think about, would possible change the rider-operated lower-leg stress reduction valves discovered on 2023 Rockshox ZEB, Lyrik, and Pike forks. The auto-venting system would have the very same objective as these bleed valves, however wouldn’t require any enter from the bicycle owner, apart from merely using the bike over uneven terrain. The revealed patent doc particulars a lot of separate design ideas (or embodiments) that might every be applied to realize this new automated operate, a couple of of which we are going to define right here…
SRAM Suspension Fork with Automated Venting
Keep in mind when Fox filed authorized motion towards SRAM for the usage of lower-leg bleed ports on their 2023 Rockshox Suspension Forks? The previous claimed that SRAM have been infringing upon their very own patent (#9739331) which describes the usage of valves operable by the rider to equalize stress between the ambient surroundings and the area inside their fork lowers. The valves serve to alleviate stress constructed up contained in the lowers throughout exhausting using (and thus, temperature adjustments), or certainly any stress differential between the 2 environments, as which might additionally come up from elevation adjustments, or touring from one excessive of climate to the subsequent along with your bike.
A brand new SRAM patent (US 20020411007) revealed December 29, 2022 describes an automated venting system for a telescopic suspension fork that eliminates the necessity for any rider enter, apart from using the bike as regular, that’s. A number of designs are described throughout the doc, however most appear to heart upon dual-lipped k-shaped wiper seals (crimson, in our illustrations) between the decrease legs and the stanchions which can be in a position to switch pockets of air (168) between the ambient air stress of the skin surroundings and the air in any other case trapped contained in the fork lowers.
How? By advantage of a collection of dimples, or an annular recess (148, beneath), positioned on the stanchions themselves.
In these designs, the easy telescopic motion of the stanchions relative to the decrease legs throughout compression and rebound occasions would permit an alternate of air between the 2 areas, equalizing any stress differential that will exist as the principle Ok-seal passes the dimples. Importantly, in all designs, airflow is bi-directional.
After all, if air may be exchanged between the 2 environments, then it stands to motive that moisture, dust, and oil may, too. The patent describes use of an “air permeable absorbent” materials (inexperienced, in all figures) sitting simply beneath the dual-lipped wiper seal that might forestall any lubrication oil contained in the decrease legs from escaping. This sounds very like a generic foam ring that might be discovered inside any trendy suspension fork. The doc says this element may very well be made from closed-cell foam, open-cell foam, or a sponge materials fashioned from polymer-based supplies. Beneath the air permeable absorbent ring, the patent describes the usage of a standard bushing (blue, in all figures) with a small cut up to permit the passage of air between the areas above and beneath it.
Appears to us from these diagrams that, with the intention to forestall the stanchion recess from dragging particles down into the lowers, the entire stanchion would must be protected with some form of versatile boot. With out that, the recess would merely serve to fill the dual-lipped wiper seal with any particles that ended up on the stanchion, blocking it such that there’d be little alternate of air anyway.
Nevertheless, one other model of the automated venting system lacks these dimples, or annular recesses, on the stanchions. To equalize any stress differential, an outlet port is positioned additional down the decrease leg. It provides a pathway for bi-directional airflow between the decrease leg inside and the skin world, with (Fig. 17) or with out (Fig. 18) use of an inlet valve and an exhaust valve (yellow) that may very well be configured to open at respective pre-determined stress differentials. This embodiment appears much more just like the stress reduction valves in use on the 2023 Rockshox forks, although it appears they might equalize any stress variations mechanically, with out the necessity for the rider to press a button.
One can think about a state of affairs whereby stress builds up contained in the decrease legs throughout an extended descent, and when it reaches a threshold worth, the exhaust valve is compelled open to permit that stress to “blow-off”. This might merely occur whereas using, so the rider wouldn’t should endure any further undesirable ramp-effects coming from the decrease legs. And due to this fact, they might get rather more constant efficiency from the fork, I think about.
For enduro racers at the very least, this may very well be preferable to user-operated lower-leg bleed ports/stress reduction valves. I imply, contemplate that EWS racers are often subjected to hellishly lengthy levels that may typically take greater than quarter-hour to finish, protecting a number of elevation and measurable warmth build-up of their forks. That mentioned, with out these user-operated bleed ports, it is probably not really easy to equalize pressures ensuing from vital adjustments in elevation.
There may very well be a manner round that, nonetheless, notably within the design that depends upon these dual-lipped wiper seals and dimpled stanchions. If the dimples (and thus air by-pass quantity) have been positioned across the sag zone, the rider would merely must bounce up and down on the fork a couple of instances after hopping off the chairlift with the intention to equalize any stress differential that will have arisen on the journey to the highest.
The place is SRAM going with this?
It’s exhausting to say, actually.
It appears the dual-lip wiper seal-dimpled stanchion mixture may necessitate the usage of a fork boot to forestall mud, water and dust ingress, lest all of the dust that recurrently sits on prime of our wiper seals get wiped contained in the fork. And we will’t actually see Rockshox taking place that route.
Nevertheless, the decrease leg valve with automated exhaust vent appears to be a extra believable design that might be much less more likely to lead to contaminants coming into the decrease legs. And, if executed as described by the patent, we reckon it may get rid of that end-stroke ramp impact that usually stops riders from accessing the final valuable few millimeters of journey. Going additional, it may even enhance the consistency of a suspension fork’s efficiency on an extended tough descent.
