I'm discontent with all of the travel mugs I've run across. The problem of a good travel mug design has been somewhere in the back of my mind for a while, so I've been looking at mugs (their lids, specifically) when I find them. And they all annoy me.
My ideal travel mug is simple (most of them basically have this) but moreover simple to really clean. Ideally this means my hand fits in it comfortably (since I mostly end up doing my dishes by hand), though this sacrifices the ability to fit in car cup holders. More importantly, 'cleanable' means, for starters, no screw on lid - I never feel like the threading gets really clean. In fact, no interior corners at all - mugs (dishes in general) should be smooth. The worst part about all travel mugs I've seen is the lid though. They all involve some sort of moving bit with an inside (or underneath or between) that liquids can get to, but you can't (short of disassembly). That's terrible.
So, what does my lid look like then? How does it work? Well, I'm honestly not sure how to create my ideal lid, reasonably, but I'm sure it is possible. Here's what I'm envisioning: near the top of the (circular) mug, there will be an interior rim (remembering no corners) on which a circular lid will sit. I've kinda got a man-hole cover in mind here. The lid should be a solid disk. What makes the lid useful is a single button (maybe two? or one of them is a slider?) on the top. After setting the lid down on the rim of the mug, you can press the button and the diameter of the lid increases (this is the part I'm not sure how to engineer - see below). Now the lid fits tightly against the mug (in an ideal setup, this forms a perfect container, you could turn the mug upside down and not have any issues). So how do you drink out of it? Well, press the other button on top, and some part of the disk shrinks back, making a place for liquid to come out (looking at the lid from the top, it'd look like a circle except for a point on the edge where somebody pushed in with their finger, I recon). Of course, travel mugs have that extra little hole opposite the bit you drink from, so that air can get into the mug and you don't have to worry about vacuums. No problem. Just, when you press that second button, have a little indentation show up opposite the drinking indentation (all one mechanism, doing the same functionality on both sides, just much smaller on one side).
I have some vague thoughts on how to implement such a lid. Part of me wonders about having the interior of the lid have an air bladder. Then pushing on the button on top forces the disk to increase diameter. I'm not sure how you then have a separate button to open/close the drinking hole - perhaps the interior has two air bladders, or the lid is made out of two materials or so? I also worry about the air bladder popping, or leaking, so it's not my first choice. Another idea that comes to mind is along the lines of the steamer tray I have. Its a little tray that you stick in whatever pot you are using, and its got a bunch of metal wedges that fit together, and can lie flat to fit in larger pots, or stand up straighter for smaller pots. Now, for my lid, flip that tray over, and wrap it in some sort of rubber. Pushing down expands the diameter. Using a spring mechanism like in clicky pens, pushing down again unclicks it and decreases the diameter. I figure this has potential, because you could pick one of the wedges and (somehow) make it so that you could decrease just the size of that wedge, without affecting anybody else. That gives you your hole to drink from.
Anyway, if anybody ever reads this and knows how to make this dream a reality (or knows that somebody else already has, and can point me in the right direction), I'd be delighted to hear about it. I'm also happy to try to clarify any of my descriptions above. Maybe I'll get truly ambitious and post some picture(s) here. If this thing doesn't already exist, I want somebody to use some sort of open source manufacturing or whatever to get it in production. That is, the design and plans are online, and people can view them to make their own or change the design to make improvements and fit their needs. If it doesn't exist, and this is my idea, I'm allowed to ask for such a thing (the open manufacturing bit), right?