LUMBER TRACTOR Russian patent published in 1997 - IPC

FIELD: timber industry. SUBSTANCE: lumber tractor has self-propelled chassis with longitudinal guides installed on chassis frame for carriage travelling along guides. Platform and bunk are installed on carriage. Carriage travel motion hydraulic cylinders are secured by some ends on chassis frame, and by other ends, on platform. Hydraulic cylinder control system has travel motion pickup and four-line three-position electro- or electrohydraulically controlled distributor. With distributor in neutral position first line is connected with pump, second line, with return to tank, third line, with piston spaces of hydraulic cylinders and fourth line, with rod spaces of hydraulic cylinders connected to distributor in parallel to each other closing by third and fourth lines corresponding spaces of hydraulic cylinders. With distributor in first position, first and fourth lines are in communication with each other placing rod spaces of hydraulic cylinders in communication with pump and third and second lines are in communication with each other and place piston spaces of hydraulic cylinders in communication with return to tank. With distributor in second position, all lines are intercommunicated. Travel motion pickup is coupled with chassis transmission control slider. It has normally open electric contacts connected through electric circuits with limit change-over switches installed in control circuit of each electromagnet of distributor. Change-over switch which supplies control signal to electromagnet switching on the first position of distributor has normally closed electric contacts, breaking the circuit of electromagnet in extreme forward position of carriage. Change-over switch is electrically coupled with electromagnet switching on the second position of distributor. Switch is four-contact device electrically coupled by second group of contacts in series with additional electromagnet releasing the output element of change-over switch at beginning of moving off of tractor. EFFECT: enlarged operating capabilities. 3 dwg