Chapter 3 Functional descriptions
SMSO-2-02.03- 15.07.03 35
3.2.6 Brewing unit
The brewing unit is the core of the coffee machine. The quality
of the coffee depends very much on the condition of the brew-
ing unit, and whether it is functioning perfectly, and whether it
is clean. The
brewing unit is also the component that is subject to most
stress by mechanical, heat and chemical effects. For this
reason it is very important to keep it clean and maintained.
Functional description
The brewing unit consists of a very compact cylinder (cham-
ber) and piston system in which the ground coffee is com-
pacted for brewing. The entire brewing process is split into
individual steps. Filling with ground coffee, compacting to the
programmed compaction pressure,
pre-brewing, brewing,
pressing out and ejecting the coffee grounds. The brewing
cylinder/ brewing piston system is built onto a sliding carriage,
which moves between two fixed pistons. The sliding carriage
is moved by means of a spindle. Together with the moving
lower piston and the brewing cylinder, the outlet piston forms
the brewing chamber. The lower piston engages into the fric-
tion piston 2000 and pushes the grounds upwards through the
brewing cylinder, where the stripper ). then moves it into the
grounds container. The spindle is driven by an electric motor
(piston motor). This piston motor is controlled by the program,
and to some degree is dependent upon time, and to some
degree on current, depending on the brewing process. The
start position (filling) is defined by approaching a limit switch.
Brewing unit
1 Piston motor
2 Spindle
3 Friction piston 2000
4 Lower piston (brewing water inlet into the cylinder)
5 Position switch (not fitted to brewing unit)
6 Brewing cylinder
7 Outlet piston with baffle (0.6 mm opening)
8 Inlet
9 Funnel
10 Stripper
11 Brewing tube
12 Protection for friction plunger
13 Baffle
14 Non-return valve with Teflon ball
15 Elbow union
16 Left-hand and right-hand side panels
Technical data
Nominal voltage: 24 V DC
Operating voltage: 30-36 V DC
Idle current: ≥ 1.3 A
Blocking current: ≥ 8.5 A
Adjustable values: see section entitled “Technical
data, standard settings”.
Drawing symbol
Illustration
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