Excavator SANY 235 Revo 170/220/240 hydraulic pump proportional solenoid valve HLPPRV06A/24V

What is the role of the directional valve and the pilot valve in series of the directional valve of the hydraulic proportional valve
The oil inlet and outlet control of the traditional reversing valve is carried out through a spool, and the corresponding relationship between the two oil port listening openings has been determined as early as the design and processing of the spool, and it is impossible to modify during use, so that the flow or pressure through the two oil ports can not be independently controlled and do not affect each other.
With the decrease of the cost of microprocessing controller and sensor components and the continuous improvement of control technology, the dual-spool control technology has been applied in the field of construction machinery. The British Utronics company uses its own technology and patent advantages to develop a double-core multi-way reversing valve, which has been widely used in JCB, Deere, DAWOO, CASE and other companies of excavators, trucks, loaders and excavating loaders and other products. In order to meet the functional requirements of hydraulic system for Chinese construction machinery products. With the continuous improvement of stability and automation control, Utronics products have entered the Chinese market in a timely manner, and have initially completed the commissioning of Xiagong (5t) loaders and Janyang (8t) excavators and entered the test stage.