Patent attributes
A travel control device enables a crawler type hydraulic excavator to start slowly regardless of the preset speed ratio whenever the manipulation amount of a manual travel control device is small. The travel control device includes left and right travel motors respectively provided with speed changing mechanisms, a high speed shifting valve provided on a high speed signal line for cutting off or transmitting a high speed signal pressure to the speed changing mechanisms, a travel signal detection means for detecting a travel control signal pressure outputted from manual travel control devices. A shutoff valve is provided on the high speed signal line for closing or opening the high speed signal line to keep the speed changing mechanisms in a low speed condition or a high speed condition depending on the magnitude of the travel control signal pressure supplied from the travel signal detection means.
