Clamped Chainring Assembly by Specialized

In this article, we’ll be discussing a Clamped Chainring Assembly by Specialized, US publication 20200398934. The publication date is Dec. 24th, 2020 and the filing date is Jun 21st 2019.

The USPTO released a bunch of Specialized patents recently, so I figured I’d do another one. The patent is pretty simple, so the article will be pretty short. This one is a good example of an idea that isn’t earth-shattering, like suspension patents, but it can probably be considered more evolution than revolution.

1/6/21 Update: It appears as though this may have been very quietly implemented in the 2020 Levo. I couldn’t find it until a reader commented on it. This article still stands as available background. Can’t win them all.

Brief Summary (tl;dr)

Specialized are patenting an E-bike specific chainring that is splined and can be clamped onto the motor output shaft. Therefore, the chainring is significantly more secure, as both the axial and radially directions are firmly supported to the bike.

Background

A chainring is a front gear used on bikes to drive a rear wheel through a cassette with a chain. The image below shows a traditional chainring available today. The chainring is typically mounted directly to the cranks and comes in a plethora of sizes. I’m currently using a 30 tooth chainring on an Eagle cassette because I’m a bitch and my trail bike weighs like 36lbs. They also come in different shapes, such as an oval. Apparently, the oval chainrings maximize power output during the part of a pedal stroke where power is produced and minimizes power output during the part of the pedals stroke where very little power is produced. But I digress.

In the last 5-7 years, the advancement in derailleurs and cassettes have provided huge rear gear ranges, leading to the disappearance of front derailleurs and multiple front gears. SRAM offers a 52 tooth granny gear, which all but renders multiple front gears absolutely useless. Shimano also offer something similar. This has lead to additional advancements in chainring technology, such as narrow-wide teeth, or even that oval I mentioned earlier.

Intended novelty

The intended novelty of this patent is very simple. The chainring is splined and then can be clamped to the motor output shaft of an e-bike. Therefore, this system secures the chainring much more effectively for higher power applications such as an E-bike.

Why

I don’t own an E-bike, nor have I ridden one, so I’m going to assume that the current offering of E-bike cranks and chainrings are slightly modified systems that were originally designed for regular bikes and just aren’t cutting the mustard.

Specialized give a few reasons for this change:

…the use of the fastener 78 and the slotted circumferential ring 50 enables the chainring assembly 42 to be both axially and radially secured to the motor output shaft 30.

And

…clamping the chainring assembly 42 to the motor output shaft 30 can prevent the chainring assembly 42 from wobbling during operation, thereby preventing or reducing damage to or wear on the motor output shaft 30.

So, Specialized have developed a chainring that they believe will be more secure in two directions and it should reduce the likelihood of the chainring loosening and damaging other components.

Additionally, Specialized give a more pragmatic reason for this development.

Loosening fastener 78 can facilitate [the] removal of the chainring assembly 42 from motor output shaft 30… in order to perform maintenance on the e-bike 10, and can obviate a use of tools that may damage motor output shaft 30 in connection with removing chainring assembly 42.

In short, Specialized think this will make chainring maintenance easier and less likely to cause damage when doing maintenance.

What

Figure 2 shows the E-bike motor assembly in question. The important parts here are motor output shaft 30, splined region 34, and splines 38. The splined region is attached to the motor output shaft and the cranks are attached to the ends of the motor output shaft. As the rider pedals, the motor output shaft spins and away you go. Simple.

Figure 3 and 4 show the chainring that is being patented. This example is a two-piece chainring, where there is a spider 62 and the actual chainring 70. The splines 58 of the spider slide onto the splines 38 of the motor output shaft.

Then, once the chainring is in place, the user can tighten fastener 78 to secure the chainring in place. The spider has a slot 54 that allows for clamping movement when the fastener 78 is tightened down. This provides a system to prevent the chainring from moving in both the radial (slipping splines) and axial (falling outward) directions.

This patent has a lot of BS about spline spacing, but it looks like they’ll just use the DIN spline standard from the German Institute of Standardization.

Lastly, Specialized also say that this can be a one-piece system, so the spider and chainring would be a single piece like any direct mount chainring available today.

…the chainring 70 can be integrally formed as a single piece with the spider portion 62.

Conclusion

It’s strange to me that this is explicitly protected for an E-bike. The entire spec and the claims only reference an E-bike. Can something similar not be designed for a regular bike? I’d love one of these, but it’s probably much heavier than a normal chainring and will probably only be used in the E-bike market. That being said, what’s another few grams on a 36lb bike.

Thanks for reading this quick one. Let me know what you think about it. Evolution or Revolution?

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