Douwe Egberts Cafitesse 50, Service Manual

Page: 62 / 106

Functions (dosing) - 6
Version 1.36
02/2004
1 2 3
Tappet lifted
by bellows Bellows
compressed;
pressure opens
valve Tappet ring
pulled down
by coil Upper valve opens
due to pressure
difference (low
pressure bellows)
: bellows refills
atmospheric
pressure
Bellows
is filled with coffee
concentrate
System at rest Dosing coffee
concentrate Refilling
Dosing sequence
1. The system is at rest. There is coffee concentrate present in the bellows.
2. When a magnetic field is generated, the tappet (consisting of the tappet ring, ring carrier and
inlet valve) is pulled downwards.
The bellows filled with concentrate is squeezed and delivers the coffee concentrate via the outlet
valve to the trough.
The dosing pump will deliver approx. 0,105 cc during 1 pulse of 6.8 ms
(effective pulse duration: 6.5 ~7.2 ms).
3. Directly after the pulse, the tappet moves upwards the bellows assumes its normal shape and
the next bit of coffee concentrate flows into the bellows via the inlet valve that has been opened
by the pressure difference. (atmospheric pressure - low pressure inside the bellows as its shape
is restored)
Coffee empty detection
The dosing coil assembly features an optical infra-red sensor (consisting of a transmitter and a re-
ceiver). An IR beam is continuously directed through a transparent part of the dosing tube and as long
there is coffee inside the pack a black floater blocks the beam.
When the coffee inside the pack has been consumed, a black floater inside the tube drops and does
not any longer block the beam of the transmitter. The receiver will thereupon send a signal to the main
PCB.