Hydraulic valve and pressure differential type liquid dispenser having the same

A hydraulic valve, comprising:

• a valve housing including an inlet port for connection to an inlet pipeline, a lateral port for connection to a reservoir, an outlet port for connection to an outlet pipeline, and a chamber;
• the valve housing further defining a bypass through which the inlet port is in fluid communication with the chamber, a first passageway through which the chamber is in selective fluid communication with the lateral port, a second passageway through which the inlet port is in selective fluid communication with the first passageway, and a third passageway through which the chamber is in fluid communication with the outlet port;
• a first one-way valve member disposed in between the inlet port and the second passageway to permit fluid flow in a direction from the inlet port to the second passageway only;
• a regulation valve member disposed in the chamber of the valve housing and being movable between a close position where the first passageway is blocked from fluid communication with the chamber, and an open position where the first passageway is in fluid communication with the third passageway via the chamber, wherein the regulation valve member moves to the close position if actuated by fluid coming from the bypass, and to the open position if actuated by fluid coming from the first passageway;
• and
• a second one-way valve member disposed in between the third passageway and the outlet port to permit fluid flow in a direction from the third passageway to the outlet port only.