GB971152A - Improvements in or relating to grapnels for submarine cables - Google Patents

Abstract

971,152. Grapnels. POSTMASTER GENERAL. Jan. 30, 1961 [Feb. 3, 1960], No. 3917/60. Heading B7S. A submarine cable grapnel comprises a framework 15 with at least two prongs 1 and 2, 3 or 4, cable engaging surfaces 9 which are movable longitudinally of the grapnel, sea bed engaging flukes 30 which are normally held in the inoperative position (full lines, Fig. 4) and a linkage between the flukes 30 and surfaces 9 such that, in use, on the application of a predetermined pressure on the surfaces 9, the flukes 30 are released to the operative position (shown in dotted lines, Fig. 4). The linkage comprises a rod 8 having an eye-bolt 33 at one end and a collar 27 at the other which causes the flukes 30 to rotate about pivots 31 when the rod is moved axially. The rod is prevented from making this movement by a collar 20, secured to it by a shear-pin 21, which abuts extensions 10 of the surfaces 9. When the cable is located by the prongs 1 or 2 and engaged by the surfaces 9, which are knife-edges, it exerts a gradually increasing pressure until the shear pin 21 fails thereby allowing movement of the collar 20 with respect to the rod 8. The bell-crank levers 23 are then moved out of engagement with the collar 25 and the rod 8 is allowed to move to a position which allows the flukes 30 to move to the sea bed engaging position. This resistance to movement of the grapnel results in an increase in tension of the towing cable which can be detected by the towing ship whereupon it steams to a position above the grapnel and lifts it vertically until the tension in the submarine cable causes it to be severed against the knife-edge 9. The grapnel may be provided with clamps to hold a severed end of the cable. The surfaces 9 may be non-cutting surfaces which will lift the cable without damage. The surfaces 9 may be replaced by pulleys. A second grapnel may be secured to the rear end 16. A planing board may be provided to ensure the prongs 1 or 2 pick up the cable. The sea-bed engaging part may be separate from the cable engaging part, the two being joined by a coupling which allows the former to move to operating position when the cable is located. Specification 703,782 is referred to.