1.21.5. Screed Vibration System

TM 5-3895-373-20 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 motors. 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 valve solenoid. 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 kPa). 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. 1-50