working principle of rope grab

     Close cycle
   If the grab is open, hoisting rope did not stop the action, hoisting rope closure, the closure through the rope pulley driven by through girder grab to make up close.

   Start cycle
   If the grab is closed, hoisting rope did not stop the action, close abseiling, rope through the pulley blocks closed so that the relaxation so that the decline in the through girder, grab quick to open.