Dynatest FWD - 11.3 FWD;HWD Hydraulics

2017.06.19 FwdMan2.8.17.docx 11-87
11.3 FWD/HWD Hydraulics
11.3.1 General Description
The hydraulic system incorporates the following main items (refer to drawings on the
following pages):
 A hydraulic cylinder (“Main Cylinder”) for raising/lowering of the weight catch
 Two (parallel connected) cylinders (“Side Cylinders”) for raising/lowering of the falling
weight subassembly
 A hydraulic pump including an adjustable excess pressure valve, and operated by:
 A 12V DC motor
 A “DC” (Directional Control) valve with two 12V DC coils (denoted “A” and “B”).
This valve is also called the A/B valve.
 A normally open solenoid valve (w. a 12V DC coil, denoted “C”).
 A normally closed solenoid valve (w. a 12V DC coil, denoted “D”)
 A hyd. oil reservoir (tank) which is an integral part of the falling weight subassembly
frame
 Two pressure sensitive switches (one normally closed contact and one normally open
contact) used in the electronic control circuits (please refer to descriptions in subsequent
sub-sections).
 An optional DC valve (with AL and BL coils), also called the “locks A/B” valve. (This
valve is only present in case the optional automated transport locks feature has been
acquired).
The modes of operation are best explained by a “truth table”:
Mode
A
B
C
D
M
AL
BL
Raise Weight (Lower Plate)
OFF
ON
OFF
OFF
ON
(Notes 1, 2, 3)
OFF
ON
Drop (Lower Plate)
OFF
ON
ON
OFF
ON
(Notes 1, 3)
OFF
ON
Lower Catch
ON
OFF
ON
OFF
ON
Note 5)
OFF
ON
Raise Plate
ON
OFF
ON
ON
ON
ON
OFF
M is the coil of the motor starting relay.
Note 1: “Plate” means falling weight subassembly.
Note 2: If the weight has dropped, then this will be a “Raise Catch”-mode.
Note 3: This mode will also cause lowering of the plate and will not be fully active, until
both shafts of the two “raise plate” cylinders (side cylinders) have been pressed out
completely (to their bottom position).
Note 5: This mode also lowers the catch.