Chapter 3 Functional descriptions
SMSO-2-02.03- 15.07.03 73
3.4.3 Brewing system (coffee) with booster 02.04.2002 .........
Serial no. 505124 .........
Product serving:
Requirements:
A cup of espresso coffee
Coffee machine in operation, heated, programmed to produce an espresso with prebrewing.
Notes
Some processes are shown in simplified form in the following description. See the section entitled
“components” in the chapter entitled “Functional descriptions, components) for detailed functional de-
scriptions of individual components (e.g. pump with bypass, flowmeter etc).
Process
step
Control system (electronic/electrical) Hydraulic system Mechanical processes
Product selection
1 The “espresso” button is 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).
Grinder operates, freshly ground coffee falls
through the powder chute into the brewing
cylinder of the brewing unit.
Close brewing unit, pressure increases
3 Piston motor switches on: Power transis-
tor connects through
The brewing cylinder moves upwards and
compresses the ground coffee.
As soon as the compaction pressure has
been reached, the piston motor is
switched off due to the current measured.
4 Rotary vane pump switches on; relay
connects.
Pump produces the pressure in the water
system and holds it constant.
5 Brewing valve opens, power transistor
connects through.
The brewing valve opens, hot water flows
from the instant heater into the booster, is
further heated there, and then moves into
the brewing cylinder.
Prebrewing / water metering
After the number of pulses set for the
prebrewing process, the brewing valve is
closed for the programmed prebrewing
period and then reopened.
The water flow into the brewing cylinder is
interrupted briefly.
After the prebrewing process, coffee flows
into the cup.
Brewing process
6 The water metering process is activated
The flowmeter supplies the amount of water
in accordance with the pulses for the quan-
tity dosing.
7 The brewing process ends once the pro-
grammed water quantity has been dis-
pensed. Brewing valve closes and at the
same time opens the discharge way. The
rotary vane type pump is switched off.
Brewing valve closes, hot water inlet to
brewing unit stops. Discharge way opens
and the pump stops. The pressure in the
system falls to “local pressure”.
Heating the instant heater
8 The instant heater heating is switched on
and off according to the programmed
control conditions (transistor switches
power relay 11)
The water in the instant heater is heated.
Repress
9 Switch on piston motor to repress the
coffee grounds. The piston motor stays on
for approximately 0.2 seconds.
The brewing cylinder travels upwards a little
higher and presses the remaining water out
of the coffee grounds
The remaining water in the coffee grounds
flows through the brewing pipe and the
discharge way into the drain funnel.
Ejection of coffee grounds, brewing unit moves back to the start position
10 End re-press process, reverse the direc-
tion of the piston motor to open the brew-
ing cylinder. Right at the bottom, the
direction of rotation is reversed based on
the measured current.
Brewing cylinder now travels down. The
wiper ejects the coffee grounds from the
brewing cylinder into the drawer for coffee
grounds. The brewing cylinder moves back
to the start position
Start position of brewing unit
11 The microswitch sends a “start position
reached” signal; the piston motor switches
off
The brewing unit is in the start position.
Additional water
To made a weak coffee (for example so that a spirit can be added) there is a bypass system that is used for a programmed
period, while the product is discharged (step 6) to mix hot water from the instant heater through the bypass valve into the coffee
outlet pipe.
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