In this article, we’ll be discussing a Bicycle Front Derailleur by Shimano, US patent 11,161,569. The publication date is Nov. 2nd, 2021 and the filing date is Feb. 15th, 2018. This patent is granted.
Short article, today.
Brief Summary (tl;dr)
Shimano are developing a new front derailleur system that simply attaches a bracket to some ISCG tabs around the bottom bracket, so the front derailer can be clocked and mounted fairly easily. There’s really not much more to it than that.
Traditionally, a front derailleur is attached to the seat post, shown below. Some manufacturers just clamp them to the post, and some have dedicated tabs that allow for bolting the derailleur to the seat post. Either way, this has been normal and seems to work just fine.
ISCG tabs are the little threaded holes around the bottom bracket. They allow for chain guides, back guides, and idlers to be mounted in that area. I use the hell out of my ISCG tabs with, at least, a bash guard at all times. They’re cheap and give me some great peace of mind that I have less of a chance of breaking a chain or worse. There’s more than one bolt pattern for the ISCG tabs, but that’s not important here.
So, Shimano are looking to develop a new front derailleur that mounts the ISCG tabs around the bottom bracket. Blackspire actually makes something very similar in the E Type Stinger, which is an ISCG mounted derailleur bracket. Funny enough, it’s made to accept Shimano derailleurs.
As far as a legal difference between these, I’m not sure and I can’t comment on it.
If you’ve been reading this website long enough, you’ll know my impartialness to Shimano patents, mostly due to trying to fill this section out. But, they’ve offered some reasoning behind this, which is totally expected and not news:
One object of the present invention is to provide a bicycle front derailleur that can be easily coupled to a frame of a bicycle.
That’s it, just to make it easier to install. I think we all saw that coming. It should provide some more advantages, though, like being more robust and possibly easier to adjust.
FIGs. 1 and 3 show this new derailer is all its glory. The bracket mounts to the ISCG tabs, and you’re good to go. The cable casing holder 78 is integrated into the bracket, not the derailleur. In this example, the chain guide moves via pivots 48A and 48B, which should provide a linear movement, I think. I’m going to go ahead and assume this is a side swing, but Shimano put it all in the document.
The bicycle front derailleur 40 is configured to perform a swing action. The swing type of the bicycle front derailleur 40 is, for example, a side swing, a top swing, or a down swing.
FIGs. 5 and 7 show another example, which is pretty similar to the previous example, but the big addition is slot 94 at the top of the derailleur, and the bracket includes a joggle (bend). The derailleur is bolted to the top of the bracket, and you get a little more north/south adjustability. The slot isn’t in the bracket, in case you were wondering.
You may have noticed the bolt 22 in all of these figures. That’s a ‘support member’. In short, that’s bolted through the bracket and provides a secondary support by butting against the seat tube. Shimano say that’s not required, but it can be used.
First, I’d like to say that writing about a derailleur is the worst. I can’t spell it no matter how many times I write it. Derralier, derallieur, deralleiur, deraliiers.
There’s not much to this one. It’s pretty simple, but it also seems pretty dated being that front derailleurs are pretty much extinct on any mountain bike in the last 5 years. I say that because I’m not aware of any road bikes that include the ISCG tabs, which still use front derailleurs. I could be wrong (gravel?). Technology is cyclical, right? Beepers are coming back, maybe front derailers will, too.
Anyone know the overlapping period of ISCG tabs and front derailleurs? That might be why this is so late.
Have a great weekend!