A rock grappler is a claw shaped device used for picking up boulders. The grasping mechanism of a grappler is generally activated by a pneumatic or hydraulic cylinder, as shown in Figure 17. The cylinder is connected to each half of the claw and when activated forces the claw shut. Grapplers are used to remove or reposition boulders; they can only break rock by lifting and dropping.

There are two types of lifting mechanisms that can be used with the grappler claw. One requires that the claw be mounted on the end of a large hydraulic boom. This gives the grappler good mobility and good response to controls.

The problem with this mechanism is that an extremely strong and large boom is needed. The other lifting mechanism is an overhead crane system which uses cables and pulleys. This mechanism is strong, but is slow and difficult to maneuver into the desired position.

A grappler is most commonly used with a gyratory crusher because of the greater difficulty of access to a jaw, impact, or roll crusher (refer to figures 5 through 8). A grappler is a capital intensive piece of equipment but is a safe method of boulder removal from a crusher, although breakage must be done by other means. Those seen in field visits have required frequent overhauls and a high degree of maintenance. Another complaint with pulley and cable arrangement is that if a boulder is lifted and dropped on the gyratory cap for further breakage, the grappler sometimes twists around on the cables and requires some time to regain stability.

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