1. a. Fixed Displacement hydraulic bidirectional motor-It produces the flow necessary for the development of pressure which is a function of resistance to fluid flow in the system. Brake valve that is a modified sequence valve. It supplies braking force as well as control of a negative work load. Under normal conditions, system pressure holds the brake valve open for free discharge from the motor. A negative load reduces pressure at the motor inlet, and the brake valve closes to throttle motor discharge and create a backpressure.
b. Pressure Relief Valve (safety valve) - controls it in forward direction. Line pressure is limited to the setting of the valve, secondary part is directed to tank. A shuttle valve feeds the pilot port from either motor port to open the pressure control valve. The external drain line allows internal leakage to return to tank.
c. Pressure Relief Valve (safety valve) - line pressure is limited to the setting of the valve, secondary part is directed to tank. Controls it flow in backward direction. A shuttle valve feeds the pilot port from either motor port to open the pressure control valve. The external drain line allows internal leakage to return to tank. To control the motor in both directions of rotation, install two brake valves.
d. Fixed Displacement hydraulic bidirectional pump
It generates flow with enough power to overcome pressure induced by the load at the pump outlet. When a hydraulic pump operates, it creates a vacuum at the pump inlet, which forces liquid from the reservoir into the inlet line to the pump and by mechanical action delivers this liquid to the pump outlet and forces it into the hydraulic system.
e. DC motor powers the fixed displacement pump
f. Variable throttle valve with check -free flow one direction, blocked flow in other direction. The purpose of the check valve is to permit flow in one direction and block it in the opposite direction. Also it allows continuous control of the rate at which some fluid moves from a region of relatively high pressure into a region of relatively low pressure
2. The goal of a hydraulic motor is to produce a constant rotational speed at a sufficient torque to move the load. A variable delivery pump will vary flow to produce a constant pump outlet pressure. When pressure reaches the setting of the cross-port relief valve, the valve opens and allows flow to the opposite motor port. Backpressure equal to or greater than what it took to start the motor now holds back against the load. The energy of the over-running load dissipates over a short period of time to eliminate shock. Variable throttle valve regulates flow rate to a constant value. The Pressure Relief Valve (safety valve) controls the flow in either clockwise or anticlockwise direction. Fixed Displacement hydraulic bidirectional pump will then generate flow with enough power to overcome pressure induced by the load.
3. With this circuit it is hard to maintain a constant back pressure during rod extension and preventing lunging if the load drops quickly or reverses. Provision for compensation of pump slip is not given.
