,.
10
1. outline oi electric slide valve acwator
2. balt screw seal holder
3. pilot valve disc
4. pilot valve pin (sPQOI valve)
5. ball screw
6.
sllde vatve rod
7. hydrautic cylmder
8. channel between lnboard chamber ai,d
suction ohamber
9. stator
1 O. sucóon housing
1 l. shde vaNe piston
12. baJI nut
13. retaining shöulder bolt
14. regulaMg shaft
FIG. 2.6 HVDRAULIC CVLINDER WITH PISTON AND PILOT VALVE
the piston-rod-slide valve assembly in the unloaded posi
tion.
As the pîlot valve is moved backward (to the left}, the
drain port B (another radial piston channel) is opened
which allows the oîl to drain trom behind the piston into
the inboard chamber
(7)
of the hydraulic cylinder and the
gas force to push the piston-rod sllde valve assembly to
the loaded position. The oîl drain mentioned is possible,
because the inboard chamber is not filled with oil but com
mu.nicates via a channel (14) with the compressor suction
èhamber (16)_
• Since the piston-rod-slide valve assembly follows the pilot
valve exactly, the refrigerating capacity can be regulated
by just positioning the pilot valve. AdjUsting of the pilot
valve trom the outside of the compressor takes place via
a very simple and reliable mechanism, consisting of a ball
nut ( 12, connected to the disc 11) and bal! screw (13) as
sembly, which is rotated by a small electric motor in a so
called slide valve actuator mounted on the outside of the
hydraulic cylinder and coupled to the regulating shaft (1)_
For a detailed description of this so-callecf "Electrïc slide
Valve Actuator" (EVA), refer to paragraph 3.4.
IMPORTANT!
When start.ing the compressor, the sfide valve and thus the
EVA-indicator should always be in "minimum capacity" posi
tion.
- For the actual design of this so-called internal by-pass
control system, refer to fig. 2.3, pos. 23 to 32, and to fig
.
2.6, which shows a longitudinal drawing of only the hy
d raulic cylinder.
- To prevent the slide valve from touching the rotors by ro
tating around its axial axis or by being lifted out of its bore
(by oil pressure), a guiding device (30 in fig. 2.3) is pro
vided on the discharge end of the valve, rnounted just out
side the stator on its end face. Refer to fig. 2.7 tor design
details of this device, which basically consists of a horse
shoe shaped guide support and two adjustable guide
shoes resting on each upper
side
of the slide valve.
1 . !erna.Ie 101or
2.
guide
shoe
3. adjusong bolt
4. guide support
5.capscrew
6_ slîde valve
7
.
sta
l
or
FIG. 2.7 SLIDE VALVE GUIDING DEVICE
Page 2.6
Compressor Package GSLP
92.01
