CONTROLLABLE SERVO DISTRIBUTOR Russian patent published in 2000 - IPC

FIELD: control of position, rate and force in advance cylinders or control of position, rotational speed and torque in rotary hydraulic motors. SUBSTANCE: servo distributor has four main straight-way ports, main spool valve plunger moving in axial direction and return spring; plunger is provided with four cut-off edges; return spring is used for flexible locking the main spool valve plunger in midposition. Bush in which main spool valve plunger moves is provided with circular cavities communicated with first, second and third main straight-way ports and front hole which is communicated with fourth main straight-way port. First front end of main spool valve plunger is located opposite this hole in axial direction. Second end of main spool valve plunger is located in return spring chamber forming surface for axial balancing of plunger relative to pressure of liquid. For balancing main spool valve plunger relative to pressure created in fourth main straight-way port, this pressure is transmitted to spring chamber through relief passage available in plunger, thus acting on balancing surface of plunger. Relief passage is communicated with auxiliary connecting chamber via transversal hole; auxiliary chamber is separated from third main straight-way port by fourth cut-off edge of main spool valve plunger. EFFECT: improved dynamic characteristic. 7 cl, 2 dwg