Application :

The Grab differential Limit Switch is driven by holding and closing winches is used in auxiliary circuits for single lever grab control.

It is used for stopping the closing motor after closing or opening, regardless of the height of the grab and starting the holding motor after closing, for transition to the hoisting action as well as for stopping the holding & closing motors at the hoisting & lowest grab position.

Construction :
The switch contains six cam operated switch elements which are used as auxiliary circuit limit switches (See switching sequence diagram). The dimension drawing shows that the switch has two shafts which must be driven by the holding and closing winches. The contracts of limit switches are 40 Amps rated at 500 V. A. C.

Mode of operation :
The switches N5, N6 are limit switches for the highest and lowest grab positions. The 'Grab closed' and 'Grab open' limit positions are monitored by the switches N1 & N4, whereas N2 & N3 initiate the switching operations for single lever grab control.

Installation :
The switch is best arranged to one side of the winch space between the drums where it should be easily accessible. It can be mounted either in a horizontal or a vertical position. However, the former is preferred since the switching equipment and gearing can be reached more easily when the cover has been removed. Auxiliary shafts connected to the winch of the grab hoisting gear are best used for
driving the switch. The closing winch is connected to shaft 1 at the differential gear end and the holding which is joined to shaft 2 at the same or opposite end of the switch.

Accessories :
A special wrench is needed to release the locking nut when adjusting the cam discs. This wrench is included with the switch.