E61 Group Espresso Machine: Is its reputation justified?

[HB]

Espresso machines based on the E61 brew group are unquestionably popular and HB has reviewed several to-date, namely the Isomac Amica, Andreja Premium by Quick Mill, La Valentina* by Ala di Vittoria, Grimac Mia*, Fiorenzato Bricoletta, and Expobar Brewtus. The non-E61s reviewed to-date include the Rancilio Silvia, La Spaziale S1, Cimbali Junior DT1, and Elektra A3.


In the thread La Spaziale Vivaldi S1 or Expobar Brewtus, I said:

The E61 has an expansion chamber to aid preinfusion and that helps its espresso performance score.

To which Chris replied:

I know it's a sacred cow... but I cannot honestly say that there is concensus on that statement.

While I don't attribute "sacred cow" status to E61s, there are many who reserve the highest praise for it. For example, the article "The E61 Brew Group. Demystifying the Mystique" on WholeLatteLove says "It's been hailed as the industry standard, revered in coffee circles worldwide, and reverently passed over the lips of every espresso connoisseur in search of the perfect espresso machine - from the newbie to the well-seasoned barista."

What do you think? Is the E61's reputation justified?



(*) La Valentina and Mia have a solenoid in place of the expansion chamber, so aren't E61s as defined by the patent.

[HB]

For reference, below is the E61 patent text corresponding to the drawing in the previous post. The sections up until the claims are fairly comprehensible; I am considering a reference article to translate this into more practical layman's terms.

_________________

United States Patent Office 3,230,974
Patented January 25, 1966

ALTERNATELY SEATING VALVES

Earnest Valente, Via G. Ventura 5, Milan, Italy
Filed September 25, 1961, Serial Number 140,609
Claims priority, application Italy, September 24, 1960
2 Claims

Introduction

There are already know coffee making machines where the water infusion is available at a temperature ideal for obtaining "creamy coffee" and with a pressure sufficient for forcing said water across the dose of coffee powder contained and compressed in the filter.

In this manner the distributing device acts as a simple cock with 3 outlets, fitted for connecting the infusion chamber with the container of the water infusion and alternatively with the outlet.

But such machines present the inconvenience that the water infusion rapidly permeates and crosses the dose of coffee powder, and does not allow sufficient time for the preparation of infusion, while, on the contrary, this is possible particularly with devices with a piston which can be operated by hand.

The present invention removes the above mentioned inconvenience, allowing the desired interval of infusion between the opening of the cock and the distributing of the drink.

An embodiment of the device of the present invention will be described, by way of example, in the accompanying drawing, in which:

Figure 1 is a vertical sectional view, taken along the line I-1 of Figure 2. Figure 2 is a view from the top of the device, assumed to be mounted on the machine.

With reference to the drawing, the hollow body 11 of the distributing head illustrated, the cavity 3 of which represents an integral part of the container of pressure hot water infusion, is provided with the usual prolongation, shaped as a bell, serving as a support 12, intended to receive the filter carrier having herein a filter (not shown in the drawing) and is also provided with a substantially tubular downwardly-extending prolongation 13. In the body 11 is formed a chamber 14, which is connected with the infusion chamber, below the bell (not shown in drawing), by means of the conduits 4, and in said chamber there is rotatably supported a cam 6, which can be operated from outside by means of the handle 15.

Said cam 6 is intended to alternatively cooperate with the stem guide 16 and 17, respectively, of the sealing device 5, which is kept against its own seat by the spring 18, and of the sealing device 10, which, in its turn, is kept against its own set by the spring 19.

The sealing device 5, its corresponding seat and the spring 18 are located in a chamber 20, formed in the body 21 which is disposed, watertight, in the cavity 3 of the body 11.

Said chamber 20 communicates with the cavity 3 only by means of an opening 2, in which is engaged a cleaning pin 1, which may be operated by pressure from the outside.

A third sealing device 7, on the same axis as the sealing device 10, is kept against its seat by a spring 8, and in this manner intercepts the communication between the chamber 14 and a chamber 9 of a predetermined volume.

The communication between chamber 9 and the outlet is intercepted by the sealing device 10, cooperating with its own seat.

The stem guide 17 does not directly cooperate with the cam 6, but only by means of the stem guide 22 of the sealing device 7, which extends, like the stem 16, towards the chamber 14, in which is found the cam 6. While the two sealing devices are in operative position (as shown in the drawing) there is continuity between the two stems, with the lower end of the stem 22 pressing against the upper end of the stem 17. But, while the two sealing devices are in the off position, there is no such continuity.

On the other hand, the spring 8 is regulated in such a manner that, in practice, the sealing device 7 opens under a pressure of 1.5 atmospheres, while the sealing device 10 opens under a pressure near to 7 atmospheres. The cam 6 kinematically opens both the sealing devices.

The system of operation is as follows:

In the drawing the device is represented with the cam in the position of open outlet. In such a position the cam presses against the stem 22, overcoming the power of the spring 8. The sealing device 7 is raised over its seat. For reasons of continuity, it also presses the stem 17, so that the sealing device 10 is in the operative position. Now, we suppose that the cavity 3 is connected with the container of pressure hot water.

For obtaining coffee, it is necessary to apply to the bell 12 the filter carrier, containing a filter, containing the dose of coffee powder.

By during the handle 15, the cam receives a rotation of 90 degrees. Thus, said cam no longer presses the stems (17, 22) and therefore the sealing devices 7 and 10 close. But said cam, now, presses against the stem 16, so that the hot water crosses the opening 2, falls into the chamber 20, floods the chamber 14 and then, by means of the conduits 4, steeps the coffee powder contained in the filter.

In practice, during some moments, there is no pressure. Then, the pressure begins to be formed. When the pressure in the chamber 14 reaches (in the case in question) 1.5 atmospheres, this pressure overcomes the power of spring 8 and the sealing device 7 becomes detached from the seat. But in the supposition in question, the sealing device 10 remains in the off position. As the hot water still arrives in 14, this water, little by little, fills the cavity 9. After this filling, the pressure in 14 and above the coffee powder contain in the filter, rapidly increases under the action of the pressure in 3, and then the infusion is distributed. After this distribution, by operating the handle 14 in the opposite manner, the starting conditions are reestablished.

It is evident that, by regulating the opening 2, the spring 8, and the volume of chamber 9, it is possible to obtain the desired period of the phase of infusion with the desired pressure of infusion.

I claim:

1. A distributing head for a coffee-making machine comprising a body having a first chamber adapted to be connected to a source of hot water under pressure for infusion, a projection on said body for connection to a bell defining an infusion chamber containing a body of ground coffee in operation, said body comprising a second chamber having a cam disposed therein, said cam bring connected to a manually-operable handle and being movable between a first position and a second position, means defining a first conduit for connecting said first chamber with said second chamber, said first conduit having a first inlet orifice communicating with said second chamber, first valve means for controlling flow through said outlet orifice and said valve means being positioned to be actuated by said cam to displace it from said outlet orifice when said cam is in said first position, means defining a third chamber in said body having a second inlet orifice communicating with said second chamber, second valve means for closing said second inlet orifice, said second valve means positioned to be unseated to open said second inlet orifice when said cam is in said second position, and outlet conduit on said project for application of hot water under pressure to the infusion chamber in operation, and an adjustable needle valve for varying the size of said first inlet orifice.
2. A distributing head for a coffee-making machine comprising a body having a first chamber adapted to be connected to a source of hot water under pressure for infusion, projection on said body for connection to a bell defining an infusion chamber containing a body of ground coffee and having an outlet to communicate with said body of ground coffee in operation, said body comprising a second chamber having a cam disposed herein, said cam being connected to a manually-operable handle and being movable between a first position and a second position, means defining a first conduit for connecting said first chamber with said second chamber, said first conduit having a first inlet orifice communicating with second chamber, first valve means for controlling flow through said outlet orifice and said valve means being position to be actuated by said came to displace it from said outlet orifice when said cam is in said first position, means defining a third chamber having a second inlet orifice communicating with said second chamber and having a second outlet orifice, second valve means for closing said inlet orifice and third valve means for closing said second outlet orifice, said second valve means being position to be unseated to open said inlet orifice when said cam is in said second position, said third valve means being positioned to be actuated to open said second outlet conduit when said second valve is unseated, and a third outlet conduit leading from said second chamber to the first-named outlet on said projection for application of hot water under pressure to the infusion chamber in operation, spring means for each of said valve means loading each of the said valve means in the direction of closing, said third valve means being under a higher spring load than said second valve means, and an adjustable needle valve for varying the size of said first inlet orifice.

[malachi]

I would say that its reputation is justified historically. But I think that its current value (to the barista) is more in doubt.

[HB]

Reading the patent carefully, I notice that its claim of novelty is based exclusively on automated preinfusion ("But such machines present the inconvenience that the water infusion rapidly permeates and crosses the dose of coffee powder, and does not allow sufficient time for the preparation of infusion, while, on the contrary, this is possible particularly with devices with a piston which can be operated by hand."). If you have a lever machine, no claimed benefit. Steve and the LMWDP should like that.

Today many home baristas will focus on the E61's temperature stability and only mention its preinfusion in passing. Since so many online readers think of E61 as synonymous with temperature stability, it's worth understanding the mechanism behind it, specifically the role of the thermosyphon. I explained this in How I Stopped Worrying and Learned to Love HXs, excerpted below:

How to get the group to the desired brew temperature

The means by which the brew group arrives at the desired brew temperature depends on the machine's design. Many commercial machines rely on direct thermal conduction by attaching the group directly onto the boiler. Other machines, like those we're considering in this article, use a thermosyphon to circulate water from the boiler through the group, as shown in the schematic to the right. As the water in the heat exchanger portion of the loop warms (double lines), it rises and flows towards the group (red arrow). The water then cools and descends towards the bottom of the group (blue arrow), returning to the boiler where it reheats and repeats the circuit.


Thermosyphon circuit and heat exchanger

Note that the large bell-shaped grouphead has changed over the years. In the patent drawing it shows a cavernous chamber 3 in which the boiler water circulates. In the modern group designs I've seen, the back of the E61 grouphead is flat and accepts two copper tubes. The top one comes from the boiler's heat exchanger, the second returns to it along the bottom. Lino drilled out these fittings as part of his custom-built espresso machine, revealing how small this chamber is.

[HB]

But I think that its current value (to the barista) is more in doubt.

Would you elaborate? The patent claims in essence that E61 = automatic preinfusion. Are you saying that claim is false, preinfusion doesn't matter, or something else?

[espressobsessed]

Lever up or down, that is the question....

I've never seen anything written about this online, so this is a good place to begin. After pulling a shot, one normally would depress the lever, to dispense any pressurized water into the trip tray...

but what about when you flush the machine - should you depress the lever into the machine, until you're ready to pull your shot, or should you leave it midway...

I believe one method closes off the group; the other... not so much.

thanks in advance,
j.o.

[HB]

Lever down.

In the patent diagram, the lever is in the downward position (see cam 6). At the midway position, sealing device 5 is (just barely) open. If left in that position, the thermosyphon circuit is open and the heat exchanger will eventually boil dry.

[espressobsessed]

excellent. I'll bet you this is little known information among e61'ers!

[lino]

Per Dan's comment,
here's some pictures of a modified E61... Gives an idea of the volume inside.
Note: clear brass (no chrome) shows where I modified it.

On the back, the upper port (threaded hole) is the original inlet water hole (I plug it). The "remains" of the lower one can be seen at the bottom of the oval cut that I made. You can see a little sliver of chrome, that's where the other port was. It is the outlet of the thermosyphon, where the cooler water "fell" back to the bottom of the HX.

The "chamber" runs vertically about the length of the flat back of the casting. It's a little less than 1.125 in diameter. The chrome cylinder you see inside is another tube in the center of the chamber. It's not part of the thermosyphon. It's item 21 in the patent pic above in Dan's post.

Water flow "thermosyphons" around in the large chamber, then when you open the valve (lift lever), it travels up into the nuts on the top (gicleur's in there) turns around and goes back down the center tube, into the valve chamber (14, and middle pic), then out the screen...


Backside with modified water inlet


Chamber 14 which contains cam 6


Better view into chamber 3 and 21; part 21 is sometimes called "the mushroom" because of its shape

ciao,
lino

[malachi]

But I think that its current value (to the barista) is more in doubt.

Would you elaborate? The patent claims in essence that E61 = automatic preinfusion. Are you saying that claim is false, preinfusion doesn't matter, or something else?

1) Preinfusion is a good thing
2) But I prefer the preinfusion style of a 1 group Synesso or a LM GS (for example) and also the preinfusion style of a Mistral
3) I consider a saturated group to be better for thermal stability than a thermosyphon (personally)

Basically, what I'm saying is that things have progressed since 1961. Not that the E61 is not great, or that it is not important or that it was not revolutionary. But there are better options and solutions to the same problems. The use of the E61 has become a crutch that is holding machines back.

[Teme]

In my humble opinion as a consumer - yes, the E61 has earned its rep.

It may not be the be all end all design but it certainly has helped a lot of consumers enjoy their coffee more than they may have done in the past. This may be partly due to the E61's looks (as in getting people to buy a more expensive and potentially superior machine than they initially intended to) and partly due to its technical merits.

Like I said, just my humble opinion and even as an owner of an E61 machine I actually wanted to say no but could not come up with reasoning to overrule the yes vote...

Br,
Teme

[lennoncs]

1) Preinfusion is a good thing
2) But I prefer the preinfusion style of a 1 group Synesso or a LM GS (for example) and also the preinfusion style of a Mistral
3) I consider a saturated group to be better for thermal stability than a thermosyphon (personally)

Basically, what I'm saying is that things have progressed since 1961. Not that the E61 is not great, or that it is not important or that it was not revolutionary. But there are better options and solutions to the same problems. The use of the E61 has become a crutch that is holding machines back.

Hi Malachi,

I agree with your position on the E61 but I would also add that the LM machines suffer from fundamental problems in thermal performance also, as would machines based on LM components or concepts. The problem is systemic to the industry not just a particular design. I would like to see some real development in the design of new machines, not just dressing up last years hardware with new controls.

Sean

[lino]

...but I would also add that the LM machines suffer from fundamental problems in thermal performance also, as would machines based on LM components or concepts.
... I would like to see some real development in the design of new machines...

Sean

Hello,

Could I persuade you to elaborate on the problems? I'm interested in other's views of what's needed.

ciao

lino

[HB]

But I prefer the preinfusion style of a 1 group Synesso or a LM GS (for example) and also the preinfusion style of a Mistral

That reminds me, I would like to plumb an E61 / rotary to allow manual preinfusion under line pressure when the lever is in the midway position.

I consider a saturated group to be better for thermal stability than a thermosyphon (personally)

A few meta-comments:

First, for those who are reading along, a "saturated group" is one where the boiler water fills the group extending all the way to the grouphead. For example, the La Marzocco's group extends out like ET's neck from the boiler and boiler water fills ("saturates") the entire assembly. The benefit is that the grouphead and the boiler are effectively one (and in some models they're welded together), reducing the boiler / group temperature differential. In contrast, a thermosyphon is transferring a percentage of the steam boiler's heat to the group. While its shortcomings with regard to HX flushing are well documented, I've been impressed how well they are tuned on the machines I've tested. The measured in-basket temperature of an idle HX / thermosyphon is in the 195F range and the grouphead zeros in fairly quickly after a few shots, again assuming the flushes are correct.

Back to Chris' point, I assume that a saturated group implies a dedicated brew boiler, i.e., HXs need not apply. Admittedly, if I worked in a cafe, I would prefer a dual boiler because they're easier to operate. But in the low-volume Cafe HB, either design works for me.

PS: This is a CAD picture of Lino's pseudo-saturated E61 group. I never got to see the real thing though...


(click to read article)

[HB]

Lino spent hours measuring his E61 group to input it into his CAD program. Below is one example:

He and I are collaborating on an article to explain in layman's terms how this works. He's working on an animation too. Very cool Lino, thanks! For more pictures, see E61 Group Espresso Machine: Detailed Interior Schematics.

[default]

that's one awesome drawing, for an untechnical e61 owner like me to understand.

many thanks.

[okaychatt]

He and I are collaborating on an article to explain in layman's terms how this works. He's working on an animation too. Very cool Lino, thanks!

Dan - When will the layman's terms article be ready? I'm lost, and I want to understand.

Let me be sure I've grasped things so far.

The HX thermosyphon runs through the boiler, which heats the water inside. That water is delivered to the grouphead. Because the water is overheated from the boiler temp, cooling flushes are required.

The saturated grouphead is connected directly to the boiler, making its temp higher than the water delivered from the thermosyphon.

Why is that considered an advantage? Wouldn't it take more cooling flushes than the HX? Is it a matter of stability somehow?

[HB]

Dan - When will the layman's terms article be ready? I'm lost, and I want to understand.

The proposed article mentioned above would be about the mechanisms of the E61 design, not how it addresses temperature stability, which is already discussed in Espresso 201: Heat Exchangers. In the case of a HX thermosyphon it describes, the grouphead is heated to a percentage of the (steam) boiler temperature by circulating water. Ideally that percentage of heat transfer is tuned such that the grouphead is very near the desired brew temperature. For the machines I've tested, it works surprisingly well with the grouphead idling in the 195-197F range.

As you said, the flush evacuates the overheated water from the heat exchanger, but it also warms the grouphead to brew temperature. Through continual use and attention to correct flushing, the grouphead will zero in on the brew temperature. A very neat, efficient design, however it does depend on the barista managing temperature properly.

The grouphead of a saturated group acts as a direct extension of the boiler:


See Cutaway of La Marzocco saturated grouphead for more details

In this case, the boiler is at brew temperature, not steam temperature. There's not much for the barista to do temperature-wise, since the boiler temperature directly dictates the brew temperature. In contrast, the barista must "surf" an HX machine to the desired brew temperature. This video using the thermofilter demonstrates that managing HX temperature really isn't that difficult, but there's no arguing it's more involved than machines having a dedicated brew boiler.

Why is that considered an advantage? Wouldn't it take more cooling flushes than the HX? Is it a matter of stability somehow?

My above comments cover the operational advantages of a saturated group (i.e., one less thing to worry about) and imply the advantages with regard to exceptional espresso (consistent, flat temperature profile). That's where disagreement begins concerning the merits of a slant-L (flat) temperature profile versus a "humped" temperature profile, the latter being unique to HX machines (*).

I'm firmly in the "it depends" camp.

(*) ...and many lever machines.

[barry]

The proposed article mentioned above would be about the mechanisms of the E61 design, not how it addresses temperature stability, which is already discussed in Espresso 201: Heat Exchangers.

fwiw, there seems to be a common misconception that a "heat exchanger" machine is a "thermosyphon" machine. there are several heat exchanger designs in use on commercial machines which do not use a thermosyphon.

[malachi]

And I believe that the Amica is a thermosyphon machine that is not a HX machine - right?