Lever espresso machine designs

#1: Post by **Zlobny_leshiy** » May 1st, 2021, 7:23 am

Hey everyone. I studied different styles of lever espresso machines and I just can't understand one thing. All of them have the water inlets in the cylinder exposed at the very top of the piston travel and I can understand why. The pressure won't build up as there are holes on the bottom of the pressure chamber.

But here's the thing. As we lift the piston air comes through the puck of coffee into the chamber and as the water comes in it wets the puck making it some kind of airtight and all the air is locked in. Then, as we push the piston down the air is compressed and when it gets to the filter basket and all the water is out it should be released with this specific noise. Why doesn't this happen?

I am trying now to design a lever machine that has a valve in the piston which opens when we pull the piston upwards thus letting the water above it in the cylinder. I don't know if anyone had attempted such design. Maybe it doesn't worth all this work and the existing designs just work perfectly as they are?

#2: Post by **Phaedrus** » May 1st, 2021, 7:57 am

This is how the La San Marco group works.

May 1st, 2021, 8:33 am

Thank you for your reply.

#4: Post by **pizzaman383** » May 1st, 2021, 10:03 am

If wyou filled from the bottom with a manual lever the water would probably push the lever up to tell you when the cylinder was full.

#5: Post by **kalo925** » May 1st, 2021, 1:05 pm

"as the water comes in it wets the puck making it some kind of airtight and all the air is locked in. Then, as we push the piston down the air is compressed and when it gets to the filter basket and all the water is out it should be released with this specific noise."

"all the air is locked in" - I don't think that is the case at all.

I would think, in general, as one lifts the lever the air which is coming in to the cylinder is displaced by pressurized boiler water as the piston nears the top of the range and the boiler inlet hole is exposed. The air leaves the cylinder through the puck just as came in. It didn't make noise coming in, why would it make noise going out? The cylinder is mostly filled with water (not locked in air) as we push the lever/piston down. I say mostly, because people get different volume outputs at times. It seems like the only possible reason would be that a small volume of air got trapped above the puck somehow. That's the way I see it anyway.

#6: Post by **kalo925** » May 1st, 2021, 1:35 pm

https://www.google.com/search?q=lever+e ... e&ie=UTF-8

There are several posts on HB discussing this topic. GL

Dalton's law (And problems from it)

#7: Post by **armindillo** » May 1st, 2021, 1:59 pm

The Arrarex Caravel has that kind of valve in the piston.
It is basically a hole in the piston face such that the hole is blocked when the lever pushes down on the piston and unblocked when the piston is pulled up.
I believe the Strietman is a modern machine that uses the same idea.

#8: Post by **marcism** » May 2nd, 2021, 1:35 am

armindillo wrote:The Arrarex Caravel has that kind of valve in the piston.

Really? Man I need to get one of those. Seems like it's ahead of the curve in a lot of ways.

#9: Post by **domo** » May 2nd, 2021, 2:28 am

armindillo wrote:The Arrarex Caravel has that kind of valve in the piston.

Also the Faema Faemina and - as far as i know - the Strietman as an actual machine.

#10: Post by **Bluecold** » May 2nd, 2021, 2:41 am

La Peppina also has valves to ensure no air is drawn through the puck.

Zlobny_leshiy wrote: Then, as we push the piston down the air is compressed and when it gets to the filter basket and all the water is out it should be released with this specific noise. Why doesn't this happen?

It does with my Lambro! However it takes a while after te brewing is done. First the air pushes out the remaining water. This is why the coffee keeps coming even after the piston has stopped moving. After the water is displaced, and the puck is dry, there is not much pressure left, and it takes a while, but eventually you get a bit of foaming at the surface of the basket. This is the air leaving the cylinder.