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9
Unit function
Pressure and flow control
with the Servopress handgun
1
Threaded plug
2
Pressure holding valve
3
Spring
4
Ball
5
Valve seat
6
Connecting channel to suction chamber
7
Piston Rod
8
Threaded fitting
9
Spring
10
Pressure switch
11
Locking nut
12
Adjusting nut for pressure switch
13
Locking nut
14
Adjusting nut for operating pressure
15
High-pressure outlet
16
Control pressure injector
17
Connecting channel between injector
and overflow valve
18
Pressure chamber
19
Pressure gauge connection
1.
When the Servopress handgun is
opened
When the Servopress handgun is fully opened,
water flows out of the pressure chamber (18),
through the pressure holding valve (2) and injec-
tor (16) then on to the high-pressure outlet (15).
The ball (4) in the overflow valve is pressed
against the valve seat (5) by the pump pressure
and closes off the connecting channel (6) to the
suction chamber. The pressure gauge shows
the operating pressure within the pressure cham-
ber (18). The action of the injector (16) results in
a pressure level in the connecting channel (17)
that is approx. 30 bar lower.
2.
The Servopress handgun is partially
closed
When the handgun is partially closed, the pres-
sure in the pressure chamber (18) does not
increase. Due to the decreased water flow rate,
the effect of the injector action (16) is reduced, so
that the pressure in the connecting channel (17)
rises. The pistonrod (7) is pushed to the left
slightly against the spring pressure (9). The tape-
red tip of the rod pushes the ball (4) away from its
seat (5) slightly, so that a part of the pump flow rate
flows into the suction chamber (6).
Note:
Opening or closing the Servopress handgun
while the cleaner is operating in high-
pressure mode does not result in a change
to the motor current consumption. The
current consumption is only reduced when
the cleaner is being operated in cleaning
agents mode.
3.
The Servopress handgun is
completely closed
As the handgun closes, the pressure in the
pressure chamber (18) rises abruptly. This peak
of pressure acts upon the pistonrod (7) via the
connecting channel (17) and forces the piston-
rod (7) all the way to the left (approx. 4 mm). The
tapered tip of the pistonrod (7) pushes the ball (4)
completely off its seat, so that the entire pump
flow rate flows through the connecting channel
(6) into the suction chamber.
As soon as the handgun is closed, the pressure
holding valve (2) closes. This trapped pressure
holds the valve in the by-pass mode.
When this position is reached, the pressure
switch (10) is actuated, the electrical supply
interrupted and the motor switched off.
4.
The Servopress handgun is opened
If the handgun is opened again, the pressure in
the system drops off abruptly.
The overflow valve is pushed back towards the
right into its original position by the spring. The
pressure switch (10) reconnects the electrical
supply and the motor is switched on again.
Summary of Contents for HD 1090
Page 1: ...HD 1090 Service Handbook 0 I 5 905 212 03 02...
Page 4: ...2 Unit function Equipment 10 15 12 9 10 13 11 14 16 1 8 2 3 4 5 6 7 0 I...
Page 6: ...4 Unit function Functional diagram 5 3 7 8 9 10 11 12 13 14 2 1 15 16 17 4 6...
Page 8: ...6 Unit function Pump 15 17 18 10 12 13 11 14 16 20 9 12 11 1 8 2 3 4 5 6 7 11 19 21...
Page 10: ...8 Unit function Pressure and flow control with the Servopress handgun 1 2 4 3...
Page 14: ...12 Unit function Handgun with pressure and flow control Servopress with low effort version...