Machines with Eccentric Drive

This shedding principle is characterized by a direct, rigid connection of the shafts and the primary drive shaft. The motion sequence is repeated with every revolution of the drive shaft. Eccentric drives allow very high weft insertion frequencies. Their disadvantages are a small pick repeat and the large effort necessary when changing products. Machines with eccentric drives are mostly used in mass production. 

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The most common type of jaw crusher is the Blake crusher, illustrated in Fig. 29.2. In this machine an eccentric drives a pitman connected to two toggle plates, one of which is pinned to the frame and the other to the swinging jaw. The pivot point is at the top of the movable jaw or above the top of the jaws on the centerline of the jaw opening. Thp greatest amount of motion is at the bottom of the V, which means that there is little tendency for a crusher of this kind to choke. Some machines with a 1.8- by 2.4-m (72- by 96-in.) feed opening can accept rocks 1.8 m (6 ft) in diameter and crush 1200 ton/h to a maximum product size of 250 mm (10 in.). Smaller secondary crushers reduce the particle size of precrushed feed to 6 to 50 mm ( to 2 in.) at much lower rates of throughput. 

Figure 13.9 Drive technologies for reciprocating positive displacement machines (a) crankshaft with stroke adjustment with the eccentric radius s(r) (b) spring-cam drive with stroke adjustment (A) (c) linear drive s(A) ...

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