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How does a lever coffee machine work?

How does a lever coffee machine work?

How a lever espresso machine works

Take a look at the range of lever espresso machines and some espresso machines, although very similar in appearance, have different price ranges. This is due to improved features and quality of material. Now let's remove everything that helps to make better espresso and leave only the bare minimum.

For all coffee machines of any price range, we are left with this: the water pump + the heating element + the extraction chamber, where hot water is forced through the ground coffee under a pressure of about 9 bar.

This is the basis of any coffee machine. It is here that the specific choice of these three components of the coffee machine makes a difference to the quality of the coffee and thus the final price of the coffee machine.

A greatdemonstration of this lever coffee maker principle is demonstrated by the preparation on a manual Flair Espressomachine.

Moving away from automatic components and targeting the basic requirements of true espresso preparation makes the travel coffee maker Flair Espresso an inexpensive yet perfectly functional coffee maker.

The metal heart of the espresso machine - the pump

Because water needs sufficient force to pass through the entire coffee machine all the way to the tamped coffee bud, it needs the pump to help.

Previously, the absence of a pump was solved by pistons attached to large levers. Baristas had to pull these levers by hand to force water through the coffee. Coffee makers with this design can now be found on the market among coffee makers from Victoria Arduino. However, it takes an experienced barista to operate them.

Vibrating pump

It consists of a piston, a magnet and a metal coil. The electromagnet moves the plunger, which pushes the pump to draw water into the machine.

✔ indoes not significantly increase the overall price of the machine or its dimensions

❌ the pressure caused by the vibration is not stable and the machine cannot be connected directly to the water line

❌noisier with limited lifetime

Vibrating pumps for Ascaso coffee machines.

Rotary pump

This type of pump works on a vane wheel system that rotates to push water in the pump chamber into the coffee machine system at a constant pressure.

✔ It maintains a constant water pressure and the coffee machine can also be run on a direct water supply

✔ quieter with a long service life

❌ is larger and more expensive, thus affecting the price of the coffee machine

The rotary pump in the Nuova Simonelli coffee machine.

Indicates the performance of the coffee machine - the heating element

Thewater pumped into the coffee machine system must be heated to a temperature of approx. 92 °C in order for the expected coffee extraction to take place. For this purpose,heating elements such as boilers or thermoblocks are used in the coffee machine. Their specific type, volume and number then influence the performance of the coffee machine. The price and size of the machine are also related to this.

Single thermoblock

The use of a thermoblock in coffee machines has its advantages in its smaller size and lower production costs. It works on the principle of a metal block that conducts heat and heats the spiral (or otherwise) water distribution system in the coffee machine.

The thermoblock heated water is ready on demand for making coffee. Generally, however, thermoblocks are not very good at maintaining a constant temperature of water, which is quite problematic for espresso preparation. Scaling is also more risky with a thermoblock. But the plus side is their quick heating of the water.

Thermoblock in Ascaso coffee machines.

Single boiler

Single boiler coffee makers work in much the same way as kettles. Water is introduced into the metal container and heated inside. The size of the boiler mainly affects the time it takes to heat the water to the temperature needed to make coffee.

Boiler coffee makers work in much the same way as kettles. Water is introduced into the metal container and heated inside. Its volume mainly affects the heating time. The big advantage of a boiler is themuch better temperature stability of the water for making espresso.

The boiler in the Nuova Simonelli coffee machine.

Boiler + thermoblock

In both of the previous options - coffee machines with a single heating element - it is typical to wait for a higher temperature to be reached to use steam to whip the milk.

A better solution is if the coffee maker has a dual heat source system. In theirs, the boiler willtarget the ideal temperature for the coffee. And at the same time,the thermoblock will prepare hot steam for whipping the milk. A system with two thermoblocks and a double boiler coffee maker can have a similar task layout.

Boiler + HX

The larger number of heating elements has space requirements increasing the size of the coffee machine.Boilers with HX (heat exchange) or heat exchangerssolve this volume aspect of double boiler coffee machines in a great way.

In this case, one boiler isfed through the other. In addition to saving space, it also solves more pleasant energy consumption because there is internal heating between the boilers, and better temperature holding.

Extraction area - coffee machine head

The place where water and ground roasted coffee beans become espresso. This space is the so-called head of thecoffee machine. Also known as group head, brew group or simply referred to as 1 gr (single group coffee machine).

All types of coffee maker heads have two basic tasks. They are the part of the coffee maker where hot water is pushed out through the coffee maker's shower. They are where the lever, or portafilter, isinserted with a basket full of inflated ground coffee. The second job of the coffee maker head is to stay warm so as not to affect the temperature of the coffee extraction water.

What type of coffee maker head design is used determines the water heating system chosen. Each version of the coffee maker head has its own way of dealing with the task of thermal stability. Within this, then, the following are the most common types:

Circular

In this type of coffee machine head, the heating takes place by the very conductivity of the metal materials that transfer the heat. This is the easiest and most common solution for basic coffee makers. However, instability and heat loss can occur.

Saturated (saturated)

The design of the saturated head is directly connected to the boiler, they are a unified part of the coffee maker. Heating thus takes place simultaneously. In the internal space of the coffee head, hot water is circulated. This is a very efficient solution for temperature stability.

Group Head E61

The year 1961 will always be a famous year in the history of coffee making, when Ernesto Valente received a patent for the design of the E61 head. The ingenious invention is still in use today (and probably won't stop). The basis is a 9 kg heavy brass part with a water chamber, a pressure and a sophisticated three-way valve.

The advantages are perfect thermal stability and the possibility to regulate the pressure during extraction to achieve a certain coffee flavour profile or for espresso preparation with pre-infusion. A slight disadvantage is the longer heating time of the robustly constructed coffee machine head (around 15 min). But here, it is definitely worth waiting a while.

Showers, strainers, seals and counter filters of the coffee machine

Most of the components of the coffee machine are hidden from view inside behind the casing. The most visible of the various processes that take place in the coffee machine when making coffee is the discharge of the resulting coffee extract - the espresso. The coffeeflows out of the portafilter, or lever, of the coffee machine.

Each portafilter is embedded in the head of the coffee machine. Inside theportafilter is a basket (if you want a bowl, a filter). The portafilter basket is filled with the required amount of ground coffee during preparation. In the area of the thread for inserting the portafilter, there is a seal of the coffee machine head (the portafilter is placed on its edge). The seal surrounds the shower strainer(filter), bolted to the shower head of the coffee maker.

Functions for controlling and adjusting the water temperature in the coffee machine

To maintain the required water temperature, the coffee machines use the following technologies: thermostat, pressostat, PID.

A thermostat is a system for detecting water temperature similar to that found in electric kettles. A temperature sensor measures the current temperature of the water and if it falls below a certain level, the coffee maker's electronics instruct it to reheat.

The water temperature indicator in the coffee machine in the form of a pressure switch works in response to a change in pressure in the coffee machine's boiler. When cooling or heating, thepressure inside the boiler changes, it pushes or releases the pressure on the pressure switch valve, thus switching the heating function on or off.

The third and most efficient way is to equip the coffee maker with a PIDsystem. The temperature in the coffee maker is electronically controlled and adjusted (even predicting the circumstances leading to a change in boiler water temperature). Coffee makers with a PID system have the most convenient, and most importantly accurate temperature control.

Are you familiar with Cool Touch technology?

Originally only on professional coffee machines, it is now making its way into home models. A special steam nozzle with an internal seal that isolates the temperature of the steam from the nozzle surface material so it won't burn you to the touch.

Coffee machine pressure control and adjustment functions

Other functions or common components of a lever coffee maker are those that display or affect the water pressure for espresso extraction. Manometer is a common part of coffee makers. In simple terms, it displays the current pressure in the boiler - the optimum is around 1.5 bar. Alternatively, as a double gauge, it also shows the extraction pressure - ideally around 9 bar.

If the manometer is used for control, what can you do to directly influence the pressure for coffee extraction? The tricky question has an easy answer. By grinding the coffee. Yes, it is in the hands of you and your grinder what pressure you use for extraction. In the case of coarse grind coffee, not enough of a barrier will form in the portafilter to impede the water for proper extraction at a certain pressure. Thus, there may be no need to move the needle on the pressure gauge at all.

On the contrary, the upper limit of the extraction pressure can already be determined by the coffee machine thanks to the OPV - pressure relief valve. The OPV is a small component located in the coffee machine system behind the pump. It limits thewater flow from the pump so that the maximum pressure is 9-10 bar. Then you do not have to worry about over-extraction of the coffee due to too much pressure.

Similarly, the strength of the water pressure can be regulated on a coffee machine with an E61 head. Its design is predestined for this. By how much you open the valve in the e61 head to allow water to flow into the shower of the coffee maker, you adjust the strength of the water, i.e. its pressure. You can thus adjust the strength of the preinfusion and get the pressure profile for a specific espresso recipe.

UX espresso? User-friendly coffee machine features

I have shown you the most important parts of coffee machines and their functions. Developments in coffee technology are constantly moving forward. In fact, it's a bit like cars. There are new coffee machine capabilities, remote control options and automation. A number of electrical circuits, chips and control boards occupy a certain part inside the coffee machine.

A stand-alone coffee machine like this can make the preparation of any espresso very easy and enjoyable. You can choose the degree of automation that is most suitable for you. From fully manual preparation on a manual coffee machine Flair Espresso, to semi-automatic (semi-automatic) coffee machines where you switch and stop the extraction time yourself.

You can opt for a coffee machine with volumetrics - these remember the set dose of water for the espresso and then repeat this consistently for the next preparation. Up to a gravimetrics system that weighs the complete brew, and repeats the extraction recipe automatically from then on.

As a much appreciated skill of the coffee maker is the separate cleaning program. Personally, I absolutely loved the automatic flushing of the coffee maker shower after removing the portafilter. It makes coffee preparation smoother, faster, plus the water consumption during rinsing is lower and controllable. Nuova Simonelli's new Eagle One series coffee machines have this feature, which includes the E1 Prima home model.

Speaking of cleaning. There is one quite simple component in coffee makers that allows for the typical cleaning process known as back flush. The component is called a solenoid three way valve. It works as a kind of three-way junction of the water line in the coffee maker. It either lets water from the boiler into the head of the coffee maker, or it closes off the path to the boiler and allows water from the head of the coffee maker to drain into the waste bowl.

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