Chapter 3 Functional descriptions
SMSO-2-02.03- 15.07.03 69
3.4.2 Brewing system (coffee) ......... 01.04.2002
......... Serial no. 505123
Product serving:
Requirements:
A large cup of coffee
Coffee machine in operation, heated, with flush valve, programmed to produce a large cup of coffee. No
“pre-brewing” and no “chamber opening” during the process.
Notes
Some processes are shown in simplified form in the following description. See the section entitled
“Components” in this chapter for detailed functional descriptions of individual components (e.g.
pump with bypass, flowmeter etc).
Depending on the equipment and programming of machines with simple apparatus, some parts of
this process may occur at the same time. The important processes in the individual components
are the same. In the main, the functional contexts are the same.
See “Instant heater, temperature control system for brewing system” for information on the instant
heater temperature control system.
Process
step
Control system (electronic/electrical) Hydraulic system Mechanical processes
Product selection
1 The “large coffee” button has been
pressed.
The signal from the button panel reaches
the unit control system; the program
analyses the command and starts the
product preparation cycle.
Grind coffee
2 Grinder motor switches on: The power
transistor connects through; the grinder
motor goes into operation for the set
number of units (approx. 4.5 seconds).
3 Grinder operates, freshly ground coffee falls
through the powder chute into the brewing
cylinder of the brewing unit.
Close brewing unit, brewing process
4 Piston motor switches on: Power transis-
tor connects through
The brewing cylinder moves upwards and
compresses the ground coffee.
As soon as the compression pressure has
been reached, the rise in current in the
piston motor during a specified period
sends a “piston closed” signal and the
piston motor switches off.
5 Rotary vane pump switches on; relay
connects.
Pump produces the pressure in the water
system and holds it constant.
6 Brewing valve opens, power transistor
connects through.
Brewing valve opens, hot water flows from
the instant heater first through the open flush
valve into the drip tray, thus warming the
pipe as far as the connection to the brewing
unit. Any residual water from the previous
brewing cycle is rinsed out of the brewing
pipe through the nozzle in the T-piece.
7 After 3 seconds of rinsing time, the flush
valve closes; power transistor connects
through
Flush valve closes. Water now flows into the
brewing cylinder. The programmed amount
of water now flows into the brewing cylinder.
Water metering
8 The water metering process is activated
The flowmeter supplies the amount of water
in accordance with the pulses for the quan-
tity dosing. It is counted from the time the
flush valve closes.
The coffee flows from the brewing cylinder
via the coffee outlet into the cup.
9 The brewing process ends once the
programmed water quantity has been
dispensed Brewing valve closes, flush
valve opens and the rotary-vane type
pump switches off .
Brewing valve closes, hot water inlet to
brewing unit stops. Flush valve opens and
the pump stops. The pressure in the system
falls to “local pressure”.
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