Concrete pipe handling grab - has selector bar pin alternately striking and passing lug opening and shutting arms

摘要

The grab is for handling heavy items of round or oval cross-section, and particulary laying concrete pipes. The locking device on one of the grab arms (1, 2) has a control groove working in conjunction with the other locking device, which is a selector bar (17) attached to one of the levers (10). A pin on the lower end of the bar works in the groove. The groove is so shaped that, after a first lowering, on lifting the grab arms again the pin strikes a lug and lifts them in the open position. After lowering a second time, and then lifting, is slides past the lug causing the arms to grip the load under the lifting action of the crane, acting on the levers (10, 11).