Patent ID: 6122848
Filing Date: 2000-09-26
Classification: E02F

Abstract:
A hydraulic drive working vehicle comprising:a working machine;a travel hydraulic circuit for traveling the vehicle;a working machine hydraulic circuit for driving the working machine and for receiving, into said working machine hydraulic circuit, pressurized oil of said travel hydraulic circuit having a pressure which exceeds a pressure of oil of said working machine hydraulic circuit;a pilot pressure source;a pouring changeover valve, having a first pilot pressure receiving portion for receiving a pilot pressure from said pilot pressure source; said pouring changeover valve being switchable between (a) a pouring position, wherein pressurized oil of said travel hydraulic circuit is poured into said working machine hydraulic circuit, and (b) a shutoff position, wherein said travel hydraulic circuit and said working machine hydraulic circuit are isolated from each other;a first changeover valve, disposed between said pilot pressure source and said first pilot pressure receiving portion, said first changeover valve having a second pilot pressure receiving portion for receiving pressurized oil of said travel hydraulic circuit and being switchable from its shutoff position to its communicating position when oil pressure of said travel hydraulic circuit exceeds a predetermined oil pressure;a pouring command switch; anda second changeover valve, connected with said first changeover valve in series between said pilot pressure source and said first pilot pressure receiving portion, said second changeover valve having a solenoid portion, said second changeover valve being switchable from its shutoff position to its communicating position upon receipt, at said solenoid portion, of a pouring command from said pouring command switch; andwherein said pouring changeover valve is switchable to its pouring position when the oil pressure of said travel hydraulic circuit exceeds the predetermined oil pressure and the pouring command is outputted.