Hydraulic control circuit for selfloading scrapers

Claim 1

IN A HYDRAULIC CONTROL SYSTEM INCLUDING A HYDRAULICALLY DRIVEN MOTOR AND AT LEAST ONE OTHER HYDRAULICALLY DRIVEN MECHANISM, THE COMBINATION COMPRISING: A FIRST SOURCE OF HYDRAULIC PRESSURE; A SECOND SOURCE OF HYDRAULIC FLUID PRESSURE; A FIRST VALVE MEANS COMMUNICATING WITH SAID FIRST SOURCE; A SECOND VALVE MEANS COMMUNICATING WITH SAID FIRST VALVE MEANS; SAID FIRST VALVE MEANS COMMUNICATING WITH THE HYDRAULICALLY DRIVEN MECHANISM AND OPERABLE IN ONE OF ITS POSITIONS TO COMMUNICATE SAID FIRST SOURCE WITH THE MECHANISM; SAID FIRST VALVE MEANS HAVING A SECOND POSITION IN WHICH COMMUNICATION IS ESTABLISHED BETWEEN SAID FIRST SOURCE AND SAID SECOND VALVE MEANS THROUGH SAID FIRST VALVE MEANS; MEANS COMMUNICATING SAID SECOND SOURCE TO SAID SECOND VALVE MEANS, SAID MOTOR TO BOTH SAID SECOND SOURCE AND SAID SECOND VALVE MEANS; AND MEANS COMMUNICATING SAID SECOND VALVE MEANS WITH A LOW PRESSURE SUMP; SAID SECOND VALVE MEANS HAVING A FIRST POSITION IN WHICH FLUID FROM SAID SECOND SOURCE AND SAID FIRST VALVE MEANS ARE DIRECTED TO SAID SUMP WITHOUT PASSING THROUGH THE MOTOR, A SECOND POSITION IN WHICH FLUID FROM SAID SECOND SOURCE IS DIRECTED THROUGH THE MOTOR WHILE FLUID FROM SAID FIRST VALVE MEANS IS DIRECTED TO SAID SUMP WITHOUT PASSING THROUGH THE MOTOR; A THIRD POSITION IN WHICH BOTH THE FLUID FROM SAID SECOND SOURCE AND FIRST VALVE MEANS IS DIRECTED THROUGH THE MOTOR, AND A FORTH POSITION IN WHICH THE FLUID FROM SAID FIRST VALVE MEANS IS DIRECTED THROUGH THE MOTOR AND THE FLUID FROM SAID SECOND SOURCE IS BYPASSING TO SAID SUMP.