轮胎式和履带式起重机的起重臂一般分为伸臂式和吊臂式两种类型;塔式起重机的起重臂一般分为小车变幅式和俯仰变幅式两种类型。其中吊臂俯仰变幅式起重臂均因其外伸端由绳索支承,使臂架轴向受压,故又统称压杆式起重臂架。现在起重臂长度大都在30米,有的甚至达到60米以上。它的主要优点是自重 The booms of the tire type and crawler type cranes are generally divided into two types: the arm extension type and the boom type; the booms of the tower type cranes are generally divided into two types: the trolley luffing type and the pitching luffing type. Among them, the jib pitcher luffing type boom is supported by the rope due to its outstretched end, so that the jib is axially compressed, so it is collectively referred to as the pressure lever type jib. Now the booms are mostly 30 meters long, and some even reach 60 meters or more. Its main advantage is its weight