1.21.5. Screed Vibration System. The screed vibration
system consists of electrical and hydraulic components.
Electrical components include the screed vibrator switch,
travel switch, control handles, solenoid valve and two
relays. Hydraulic components include right auxiliary
hydraulic pump, auxiliary hydraulic vibration pump, flow
dividers, pressure regulators, and screed vibration
The screed vibration switch on the operator switch panel
energizes the vibration valve solenoid in the manual or
automatic mode. Positioning the switch down, "MAN"
position, allows 12 VDC from CB6 to energize the
vibration valve solenoid.
Positioning the switch up, "AUTO" position, requires two
conditions to energize the vibration valve solenoid: both
control handles must be out of the center detent position,
and the travel switch must be in the "F/R" position.
Power for the control handles comes from CB1. When
the right control handle is out of the center detent
position, a 12 VDC signal from the control handle
energizes relay RI. When the left control handle is out of
the center detent position, a 12 VDC signal is applied to
the contacts of relay RI. When relay RI is energized, the
signal will pass through the relay and energize relay R2.
When in AUTO mode, power from CB6 is applied to the
contacts of relay R2. Energizing relay R2 applies the
power from the screed vibration switch to the vibration
Both the right auxiliary hydraulic pump and the auxiliary
hydraulic vibration pump supply hydraulic oil for the
screed vibration system.
The right auxiliary hydraulic pump contains two pumps,
0.7 and 0.58 cu in. (11,5 and 9,5 cc) outputs, mounted
on a common shaft. The 0.58 cu in. (9,5 cc) output
pump supplies oil to a 50/50 flow divider. The 50/50 flow
divider splits the hydraulic flow, sending half of the flow
to the tow point movement system. The oil returned
from the tow point movement system merges with the
output of the auxiliary hydraulic vibration pump. A
pressure regulator limits the output pressure of the
auxiliary hydraulic vibration pump to 2000 psi (13 790
The vibration valve directs the combined hydraulic flow to
the return manifold or the screed vibration motors. The
normally open vibration valve allows hydraulic oil to flow
directly to the return manifold. Hydraulic power thus
bypasses the vibration motors. When the vibration valve
solenoid closes the vibration valve, the combined flow of
hydraulic oil powers the main screed vibration motor.
The output of the main screed vibration motor is split by
a 50/50 flow divider. Half of the flow operates each
extension screed vibration motor. Output from the
extension screed vibration motors returns to the
hydraulic reservoir through the return manifold.
The screed vibration control valve under the operator
platform allows some of the hydraulic oil to bypass the
screed vibration motors. As the screed vibration control
valve is opened, more of the fluid power flows to the
return manifold. The reduced flow to the screed vibration
motors reduces the screed vibration rate.