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Method of operation
Charging position
Control piston(6) and cut–out piston(2)
are held in their lower or upper end
positions, respectively, by compres-
sion springs(7) and (14), so that out-
let(1) and inlet(8) are closed while
outlet(3) is open.
One half of the air supplied by the
compressor flows through port 1 and
screen(12)–where coarse impurities
such as oil carbon are retained–and
on to check valve(10) ; it opens the
latter valve and flows via port 21 into
the pipeline to the supply air reser-
voirs ; at the same time, air is fed
through passage(9) to act upon con-
trol piston(6). The other half of the air
supplied also travels to the supply air
reservoirs, though by way of the relief
valve AE13..(15).
Cut–out
As the pressure in the supply air
reservoirs rises, the same pressure
builds up below control piston(6), via
passage(9), causing this piston to
move upwards. The spring–loaded
valve plunger(5) follows this movement
until outlet(3) is closed. When the
pre–determined cut–out pressure has
been reached, control piston(6) lifts off
valve plunger(5), and inlet(8) opens ;
compressed air passes down through
the drilling in valve plunger(5) to act
upon cut–out piston(2), and it is also
communicated, via port 23, to the con-
trol device of relief valve(15).
Cut–out piston(2) is moved down-
wards, thereby opening outlet(1) so
that air continuously supplied by the
compressor exhausts to atmosphere,
through exhaust port 3, taking with it
any oil carbon particles that may have
accumulated. As a result of the con-
trol pulse fed in from port 23, the air
supplied via relief valve(15) is also dis-
charged to atmosphere.
Cut–in
When, as a result of air being with-
drawn, the pressure in the supply air
reservoirs and thus the pressure in the
chamber below control piston(6) drops
to cut–in pressure, the spring loaded
control piston(6) closes inlet(8) while
outlet(3) opens ; the pressure prevailing
above cut–out piston(2) and, via port
23, in the control pipeline to relief valve
(15) is reduced through port(4). Com-
pression spring(14) causes cut–out pis-
ton(2) to move upwards until outlet(1)
is closed. The air supplied by the com-
pressor is allowed to travel again
through ports 21 of both the unloader
valve and the relief valve(15) to the
supply air reservoirs.
Safety valve
In the event of the unloader valve not
cutting out, due to a malfunction, safety
valve(11) will limit the supply air reser-
voir pressure by allowing the air supplied
to exhaust to atmosphere when the
opening pressure has been reached.
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