Douwe Egberts Cafitesse 700, Back Office Manual

Page: 161 / 265

July 2004
5A - 19
Functions - water system
Fig. 3
Opening and closing the valve
• Water pipeline pressure is applied to the top
side and to the bottom side of the dia-
phragm. Pressure compensation is achieved
through a very small opening in the dia-
phragm.
• The compensation hole (1) is pierced by a
cleaning needle (2). This means that each
time the valve is opened, i. e. during each
movement of the diaphragm, the compensa-
tion hole is cleaned.
• There is a higher pressure on the upper side
of the diaphragm (3) than on the lower side
as there is no water pressure on that part of
the lower side, which is covered by the outlet
spout. (Fig. 3)
• This way the diaphragm keeps the outlet
spout closed.
• When an electric current is applied to the
coil, the tappet (4) is pulled upward and
exposes the bore (5) in the centre of the
diaphragm. (Fig. 3)
Water can then flow downward from the top
chamber.
• As the pressure compensation hole is much
smaller than the opening in the centre of the
diaphragm, the pressure cannot be compen-
sated any longer.
• The pressure on the upper side of the dia-
phragm decreases compared to the mains
pressure on the bottom side.
• As a result, the diaphragm moves upward
and exposes the outlet spout.
• Water then flows from the water pipeline
through the valve.
• As soon as the current supply to the coil is
interrupted, the tappet closes the drilled hole
in the centre, which causes the pressure on
the upper side of the diaphragm to increase.
• The valve closes.
Additional spring
• The additional spring (6) pressing onto the
diaphragm from above, only slightly influ-
ences the valve function described above.
(Fig. 3)
• The spring, however, achieves a faster
closing of the valve enabling a more precise
level control in the boiler.
• The additional spring also prevents water
from flowing out of the boiler if the water
supply line is disconnected.
2
5 1
3
4
6
Cafitesse 700 - Functions - water system