Automatically folding boom for cranes

Claim 1

A CRANE OF THE TYPE COMPRISING A VEHICLE, A BOOM PIVOTALLY MOUNTED ON SAID VEHICLE FOR SWINGING MOVEMENT IN A VERTICAL PLANE, SAID BOOM BEING DIVIDED INTO UPPER AND LOWER PARTS, A PIVOTAL CONNECTION JOINING SAID UPPER AND LOWER PARTS, MEANS FOR SUPPORTING SAID LOWER BOOM PART IN A PREDETERMINED ANGULAR POSITION, A WINCH MOUNTED ON SAID VEHICLE, A CABLE CONNECTED BETWEEN SAID WINCH AND THE UPPER TIP OF SAID UPPER BOOM PART, WITH GUIDE MEANS FOR SAID CABLE BEING POSITIONED BETWEEN SAID WINCH AND BOOM TIP AND VERTICALLY SPACED ABOVE SAID PIVOTAL CONNECTION, TO INCREASE THE EFFECTIVE LIFTING COMPONENT EXERTED ON SAID BOOM TIP WHEN TENSION IS APPLIED TO SAID CABLE BY SAID WINCH, SAID UPPER BOOM PART BEING PROVIDED WITH PULLEY MEANS NEAR ITS UPPER TIP, AND BOTH SAID UPPER AND LOWER BOOM PARTS CARRYING UPWARDLY PROJECTING LEVER ARMS NEAR THEIR ADJACENT ENDS, BOTH OF SAID ARMS CARRYING PULLEY MEANS, SAID CABLE COMPRISING A MAIN LINE FIXED TO SAID BOOM TIP AND AN AUXILIARY LINE CONNECTED TO SAID MAIN LINE INTERMEDIATE SAID WINCH AND BOOM TIP, SAID AUXILIARY LINE THEN PASSING SUCCESSIVELY OVER THE PULLEY MEANS ON SAID BOOM TIP, THE PULLEY MEANS ON THE ARM PROJECTING UPWARDLY FROM SAID LOWER BOOM PART, AND THE PULLEY MEANS ON THE ARM PROJECTING UPWARD FROM SAID UPPER BOOM PART, AND BEING ATTACHED AT ITS END TO THE ARM ON SAID LOWER BOOM PART.