Internals of an E61 Brew Head [video]

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HB
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Postby HB » Mar 13, 2013, 7:51 pm

Bill Crossland explains how the E61 operates using a cutaway model:



For those who prefer diagrams, below is an excerpt from Is there a purpose for the E61 middle brew lever position? that covers many of the same points:

HB wrote:For the benefit of those who are wondering what these valves look like, a few diagrams from Lino. Please do not copy these images.

The first image shows the E61 lever at the rest position. The two lower valves are open to allow the brew chamber and expansion chamber to drain. The uppermost valve is closed. Water from the HX circulates through the upper port on the left, passes alongside the "mushroom" to heat the grouphead; as the water cools it descends through the lower port on the left. The temperature difference creates a thermosyphon that circulates water between the boiler and grouphead.

Image

The next image shows the E61 lever at the mid position. The two lower valves are closed and the upper valve is barely open. If this pump has line pressure, water will flow through the upper port, grouphead cap and screen, gicleur (yellow), descend towards the brew chamber (orange cam), and finally through the L-shaped channel to the brewhead. It's easy to see the purpose of the Allen screw (gray); it caps the hole drilled during manufacturing for the first leg of the channel.

Image

The final image shows the E61 lever in the brew position. The upper valve is held open by the orange cam. The valve at the bottom of the expansion chamber is held tightly closed by a spring. The spring above it holding the second valve closed is weaker; it will open at about 4 bars of pressure. It only takes a second or two for the brew chamber containing the orange cam to pressurize. As the pressure builds, water eeks pass the valve below the orange cam, allowing the pressure to drop. This action is the novelty claim of the E61 patent since the pressure is automatically lower as the expansion chamber fills. Once the lower chamber fills, the pressure equalizes in all chambers and the valve below the cam closes.

Image

The familiar "whoosh" that follows the lever being lowered is water evacuating the brew chamber and expansion chamber. Again at rest, the expansion chamber and brew chamber are empty. Water continues to circulate along the jacket of the uppermost chamber as the thermosyphon re-establishes itself.

I respectfully offer another explanation to Bill's answer to the purpose of the second exhaust valve (5:59). It's key to the E61 patent as explained in the paragraph above starting with "The final image shows the E61 lever in the brew position."

On a related note, Randy's article Simple Lubrication of the E-61 Group provides instructions and accompanying video for fixing squeaky E61 lever arms:



If your E61 goes drip drip drip, Randy's follow-up article Overhauling and Lubricating the E-61 Group and EspressoCare's Rebuild Kit are all you need. See Constant dripping from E61 grouphead for discussion and more photos.
Dan Kehn

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TomC
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Postby TomC » Mar 13, 2013, 8:24 pm

Bill's the boss! Thanks!

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erics
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Postby erics » Mar 13, 2013, 9:10 pm

If you have any form of preinfusion when an E61 lever is in the "middle" position, sumptin is wrong.

There is a reason why the lever has a little free-play here and that is because you are on the base circle of the cam where both the brew valve and the pre-infusion valve are closed. If you do happen to experience some preinfusion, you have a worn brew valve seal or a tolerance stackup that would not "pass muster".

See this for a good explanation of how the E-61 works: http://www.espressocare.com/PDF-Files/Vibiemme/VibiemmeCompleteManual.pdf - top of page 8.
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Postby HB » Mar 13, 2013, 10:10 pm

erics wrote:If you do happen to experience some preinfusion, you have a worn brew valve seal or a tolerance stackup that would not "pass muster".

I can't say whether it's a bug or feature. Some E61's I've tested raised the brew valve in the mid-position, some didn't (they were all new when tested). For those who are interested, I wrote a little about "prewetting" in The Secret Life of Ristrettos.
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Postby erics » Mar 13, 2013, 10:39 pm

Well, if you have a "worn" brew valve (the sealing mechanism, not the pin), the assembly will sit lower and thus will/may be lifted by the cam as it rotates into the middle position. I have measured two different "E-61's" with essentially new parts and there was no movement of the brew valve when the lever was lifted into the middle position.

But, this really doesn't matter . . . my point is that it is NOT a design feature. But, it is obviously another interesting variable :) in this espresso world.
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Postby Randy G. » Mar 14, 2013, 12:44 am

The VBMs I have had both worked the same- the true, "at rest" mid position did nothing. All three valves are closed in that position. You can test it; in that position the lever has a bit of freeplay and you can wiggle it. Lifting just a tad further opens the brew valve but does not close the contacts of the switch to start the pump.
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Postby JmanEspresso » Mar 17, 2013, 4:45 pm

Depending on how your particular machine is set up, most notably, how far out the microswitch for the pump sticks from the wall of the machine, will dictate if you can pre-infuse in the middle position.

Eric is correct. A properly sealing, properly working E61 group, should be sealed closed on both ends(intake and exhaust), when the lever is naturally in the middle position, or "at rest" as Randy said. But there is a good deal(relative)of travel from the middle position, to fully open/brew position, and you can very slowly move the lever upwards and open the brew path, allowing water into the group/portafilter, before you hit the microswitch and engage the pump.

Anybody can test this, whether or not your microswitch is positioned to let you, is unknown. My Quickmill Anita, and my current Alex Duetto II, can both "pre-infuse" at the "middle" position. BUT, my Quickmill Andreja, couldn't. Purely because the microswitch was positioned ever so slightly further out from the front wall, so it engaged almost right after hitting the middle "notch" on the cam.


whether this is of any use, is a totally different issue/ Im inclined to believe those who have plumbed in machines, and therefore, line pressure, might be able to play around and see some, at least repeatable, results. reservoir machine users, probably will have a much hard time repeating anything

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Postby LaDan » Mar 18, 2013, 12:56 am

Brandon asked good questions. I especially appreciated the question about the back flushing. I was always a bit foggy about what exactly is going on in there with the back flush.

But to clean the passageway from the left over coffee between shots, a regular purge/flush of 2 seconds will clean it, so it seems.

It is misleading to say that some can preinfuse in the middle/rest position. You can't say both that in the middle position the two valves are closed, and also that you can preinfuse if your microswitch is positioned a little deeper. You can't. It's either the valves are closed or they are not. They cannot be both open and closed at the same time. And people have been saying this countless of times, confusing the heck out of many users. :roll:

You can preinfuse at a position a little up from, or a little after the middle/rest position. Not at the middle position. And if your switch turns on right away, then you can easily readjust it a little deeper and have a preinfusion angle between the middle and the switch engagement point.

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Postby radudanutco » Mar 18, 2013, 9:21 pm

LaDan wrote: And people have been saying this countless of times, confusing the heck out of many users. :roll:

yes, and this is rolling on further with the video clip: while quite instructive on the video part, the explanations are confusing when it comes (min. 6) to the role of those two lower valves, and the passive preinfusion is ignored ;(

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Postby skydragondave » Mar 18, 2013, 9:39 pm

Great videos, thanks so much for putting them together! Really cleared up a lot of things for me.
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