But how does the machine know the difference between a foam overlow and a liquid one? In the case of a foam overflow the machine stops and then tops off. In the case of a liquid overflow it sounds like it just stops. Unless it knows the difference between foam and liquid, I don’t see how this answers this part of the behavior. Also, when there is a foam overflow, does it stop for a specific amount of time or does it somehow determine when the foam has settled?
While I agree that this would somewhat level the playing field, I don’t think it takes into account short and fat vs. tall and skinny vessels. They might hold the same amount of liquid but exert different forces on the bar.
Unfortunatly, we don’t have access to this type of dispenser. We may have to concentrate our efforts on the type that Rigamarole seems to have access to.
I don’t blame you folks for being bewildered by this, it seems like witchcraft to me. Perhaps we can see if ducks and small rocks float in the cups?
It the case of this type of machine, the machine stops pouring when the bar gets wet. Since the foam and the liquid are “connected”, if you will, it doesn’t matter to the machine if it’s foam or liquid. Both would be causing the machine to overflow. So, once the foam subsides, it’s not touching the bar anymore, and the machine starts pouring again.
It would be pretty easy for the Soda Guy to adjust the resistance and range of the bar, to accurately stop pouring at the right ammount of pressure for the size of cups that business uses.
Are you envisioning the sensor bar inside or outside the cup?
My experiences as Ohio Pike’s Burger King Drive Thru Guru (94-96).
We had the same type setup as the OP describes.
The levers that the cups rest on were solid metal…no noticeable sensors front or back. If you were looking down the lever length-wise you would notice a dip in the middle that goes all the way down. Kinda like this:
_ _
V
Such that when there was overflow the liquid would want to run down the V part…maybe there was a way to sense the difference between the two sides of the lever when liquid hit it?
When we were really busy and serving lots of drinks the levers would get pretty sticky and gunked up. This would allow pretty normal flow, but it seemed to make it overly sensitive to cutting off when foam hit the lever.
In fact, now that I think about it it seems that it was good about letting the foam run down the side and only stopping when actual soda hit the lever. But only if clean. Once I noticed the gunk affecting a lever a simple wipe with a wet towel had it running normal again.
During heavy use the levers would be constantly splattered and wet, but would still work fine, only stopping flow once the soda from the cup hit.
They did a great job of filling the cups to the exact right level. But you could also keep tapping the cup against the lever in case it wasn’t full enough. Which my dipshit manager would do even when the cup was at the perfect level thereby filling them right up to the rim. And when you do that putting on the lid causes soda to seep out and get everywhere, and as I’d hand it to the poor customers there would be pop coming out the straw insert slats…Man I hated that manager!
Anyhoo, I’d been wondering about this myself…my best guess is that there is some sort of way to tell the difference between the sides of the lever. I don’t think it is an optical sensor deal as this was around in 94 before such stuff was as commonplace. I also don’t think there is a censor in the drainage area as that would have been too much of a delay…these things stopped the instant soda hit.
Jeff
Also, the units we had you could put all the pressure you wanted and it would still pour.
The idea in the one I described is that the cups all tip over when full. I am going to try to draw a conceptual diagram.
Sorry for the shoddy quality but I think it gets the concept accross. However, I am not sure what is calibrated to make sure it works… the cup shapes, the ramp angle, the on/off range, etc.
Now I see what you are saying.
Instead of dealing with torque and height, your idea would simply require a cup design that made it so that all sizes tip when full at the same angle of tilt. Nice. It doesn’t require fancy electronics or fidgety wighting of the bar.
Just do this:
Look all around your machine for a make and model number. Then, googe the model and I’m sure it will explain everything for your particular machine. No guessing or anecdotes necessary.
I’ve never seen a soda machine where you put the bar on the inside. Have you? I think MilTan nailed it with his capacitance theory, for that type of machine.
BTW, groman, sweet drawings! Looks like there are probably at least 3 was to get the soda to stop flowing. Your idea is by far the least complex (which, as we all know in DFM (design for manufacture), is a good thing!)
The reason I asked about the bar being inside or outside the cup is because of this:
Once the liquid stops overflowing, it too is no longer in contact with the bar. Why doesn’t the machine start pouring again?
In groman’s diagrams it looks like it is the position of the bar that ultimately turns off the machine. It is just that the tipping cup causes the bar to be further depressed. Or, he could simply mean that tipping the cup causes some liquid to pour out and that stops the pouring. But then I’m still wondering how the machine knows to start again if it is foam that is coming out and not liquid.
Once the liquid stops overflowing, a meniscus is formed above the rim. The surface tension of the liquid allows it to touch the bar, the rim of the cup, and the liquid, all at the same time. Think about pouring a glass of milk, you can actually pour it higher than the brim of the glass without it spilling out. Cohesion is a wonderful thing.
groman’s drawings are for a different concept. (S)he meant that the tipping cup causes the bar to be further depressed, into its “secondary” off position.
Well first of all, let’s realize that we are talking about two different systems here. The lever-pressure system (LPS) and the rigamarole system (RS).
I haven’t heard anyone claim that the LPS is capable of topping its self off. In fact, I think groman’s diagrams are very good, and I think that minor7flat5’s interpretation is brilliant. I fully believe, now, that the combination of the angle of the ramp and the shape of the cup combine so that the cup will tip onto the lever when it is full by liquid weight thereby nullifying the effects of foam on the lever. (ie. the foam runs out until there is sufficient weight in the cup via liquid to tip it over onto the lever.) This system is possible in a fast food/movie theater environment where there are certain sizes and shapes of cups mandated by the corporation.
I believe that the problem we now need to answer is the RS mechanism. rigamarole claims that the system s/he (I think you’re a dude?) uses can fill both glasses such as pint glasses, which are angled, and pitchers, which are straight. Capacitance sounds plausible at first, but I can’t get over my initial reaction that I expressed before…
rigamarole, we need your help. Bear_Nenno has a good idea. Can you get the manufacturer name and/or model number? I haven’t been able to Google any info about this subject. I also think it would be fun if we could get you to do all sorts of crazy experiments with the machine and report back. You said earlier that you were going to mess with the machine to the point of being fired… you can’t renege now! 
What part of Rigmarole’s post #17 needs further clarification?
The part where he says liquid on the lever stops flow, but a wet sensor can fill up more glasses without hesitation*.
*I am only assuming that you can fill another glass without waiting for the sensor to dry. His test doesn’t explain this and I can’t think of a good expanation.
Yes, you can fill another glass immediately after you take one off, but I think that may be a result of the fact that when you take one glass off the lever it “resets” and begins again when the lever is depressed - for example, with the sudsy drinks described above if we want to top it off faster manually we will pull it off the lever and push it back quickly instead of waiting for all the suds to subside.
Next time I work, which is tomorrow night, I will see if there is any manufacturer information on it. Is there anything else anyone would like me to try or needs clarified?
Stinky Burrito, the sensor being wet or dry is irrelevant. What is relevant is how much electrical energy can be stored by it. If the lever is touching the liquid in the cup (because it has overflowed), it creates a bigger “tank” for the capacitance. It would be pretty easy to measure this change in capacitance. For all intents and purposes, we can pretty much assume the leve is always wet (except for the first cup poured that day). What is important is weather or not there is an electrical circuit that can be completed, that flows through the liquid in the cup.
The next time you fill a cup, loudly announce the following. “I am so baffled by this machine! How does it know when the cup is full?” Then quickly press your ear to the side of the machine. If you hear snickering, you’ve got your answer.
All this talk of overflowing drinks, makes me wonder. Doesn’t that make for a messy drink for the customer? Most of the time, my drinks are clean on the outside. Sometimes, the waitperson is sloppy, but usually the glass or cup is dry, not sticky, etc.
Next time my drink takes a long time to arrive, I will imagine Rigamarole experimenting with the machine. Then, I will know that my tardy drink was in the interest of science. 