In this article, I’ll be showing you a Bicycle Fork by Tan, US design patent D902,086. The publication date is Nov. 17th, 2020 and the filing date is Sept. 18th, 2018.
The USPTO defines a design patent as:
A design consists of the visual ornamental characteristics embodied in, or applied to, an article of manufacture. Since a design is manifested in appearance, the subject matter of a design patent application may relate to the configuration or shape of an article, to the surface ornamentation applied to an article, or to the combination of configuration and surface ornamentation.
This is another design patent, so the document has no context whatsoever. The inventor is only claiming ornamental novelty, not any functional novelty. But, I got a dude smarter than me to provide some input on the actual suspension layout.
Huge thanks to Ryan Rasmussen for this thorough analysis on the design:
Tan’s design is of the “girder fork” style, which has been in use on two-wheeled vehicles for over one hundred years. Mountain bikers may be most familiar with the Girvin and Noleen models (left) of the ’90s or the Fournales-Look models (right).
The typical layout of a girder fork resembles a parallelogram, when viewed from the side, formed by the steerer tube and fork legs, connected by a set of upper and lower links. The shock typically sits inside this parallelogram. Tan’s design certainly fits this description.
A large number of variants are possible and nearly every one of them can be found in the history of girder forks. For example, the upper and lower links may or may not have bracing between the left and right sides of the links, and these braces could be near the steerer or the fork legs – or both ends could have braces. The links could pivot on either side of the axes of the steerer and fork legs, or be exactly aligned with these axes. The shock could be mounted to the links, the legs, the crowns, the stem, or nearly any combination thereof. And so on and so forth.
Many of these differences are subtle and may have minimal impact from a functional perspective. For example, the performance would be similar if the lower mounting point of the shock were on the legs or the lower link, as long as the mounting points are extremely close to the pivot. From an intellectual property perspective, however, such differences may represent the novelty necessary to secure a patent.
Dissecting the design shown in this patent produces the following observations:
- Upper link:
- Fore pivot ahead of the legs
- Aft pivot in front of the steering axis
- Two cross-braces: one located near the aft pivot that is integrated with the upper link and one concentric with the fore pivot that appears to be separate from the link and the legs
- Lower link:
- Fore pivot ahead of the legs
- Aft pivot behind the steering axis
- One cross-brace, located near the aft pivot and behind the shock
- Shock mounts:
- Upper mount is on the upper link
- Lower mount is on the legs
- Shock is nearly aligned with the legs when the shock is fully extended
My brief search of current and historical designs did not turn up anything that matched all of the above criteria, though I’m sure I missed many designs from a century of girder forks.
Let me know what you think about this design. I think this is pretty cool. Would you put this on your bike?
I love a linkage fork! 3 of my 5 bikes have them and one I built myself. The bike is a Proflex but it came with a telescopic fork, not a Girvin Vector so I made my own modified Girvin. It uses a modern air shock and the geometry is intended to prevent bobbing when pedalling. It works! I believe that the advantages of girder/linkage forks have not been fully realised so any new developments are good news . Small bump sensitivity is better than telescopic. What’s not to like?
In 1999 when the 29″ wheel size came to light in looking for a sus fork it was determined that a linkage fork would be among the easiest to adapt/make longer for the 35mm necessary. The Fournales, as seen at Interbike that year, was targeted and lengthened by a few builders but soon new lowers were made for tele shocks and production bikes went that route.
In this day and age of long travel they will never make that grade. They would make fine forks for commuter type bikes but their looks will probably never allow this to happen. That said I still use a converted one on my hardtail mtb that has been on there for over 10yrs. Also after converting a Girvin years ago the plastic bushings gave up very quickly whereas the annular bearing design of the Fournales has more than stood the test of time.
Don’t forget Amp Research, from the same era as Girvin. I’m still running one on a single speed – definitely a conversation starter!