GB503326A - Improvements in or relating to methods of and apparatus for laying submarine electric cables - Google Patents

Abstract

503,326. Laying submarine cables. BRITISH WESTERN UNION, Ltd. Sept. 3, 1937, No. 24130. Convention date, Feb. 30. [Class 36] [Also in Group I] In a method of laying submarine cables as described in Specification 452,141, wherein the cable is installed in a trench formed in the ocean bed by a plough towed by the cable laying ship, the plough is so formed that the depth of the trench formed by it automatically varies as the ground resistance offered to the passage of the plough, the arrangement being such that a shallower trench is formed in hard ground than in soft ground, so that excessive variations in tension of the towing cable of the plough are avoided. In the construction shown, the plough comprises frameworks D, E, the latter consisting of two plates 26 connected together by transverse stays, such as 32, and provided with four skids 22 by which -the two frameworks are supported on the ocean bed. The forward skids are connected by a bridle 24a to which the towline 24 is connected. The framework D extends longitudinally of the framework E in a channel formed between plates 29 attached to the inner edges of the plates 26, the framework D being attached to the framework E by pivoted links 11 so that the framework D may move relatively to the framework E in a direction perpendicular to the plane of the plates 26. The framework D carries a ploughshare 36 for forming the trench, 'a passage 65, Fig. 4, being provided behind the ploughshare through which the cable C is led into the trench as the latter is formed. A pulley 66 disposes the cable in the bottom of the trench. The cable is guided to the passage 56 by pulleys 60, 61, 64. A plate 38 attached to the framework D lifts the ploughshare over obstructions. Springs 14, Figs. 1 and 2, connect the two frameworks and are so arranged as to urge the framework D, and the ploughshare carried thereby, downwards relatively to the framework E, downward movement being limited by members 42, Fig. 4, of the framework D engaging transverse stays 25a, 32 of the framework E. When the plough is used in soft soil the member 42 rests on the stays 25a and 32 and the ploughshare cuts a full depth trench, but when harder ground is encountered the increased resistance to the passage of the ploughshare causes the framework D to move upwardly against the tension of the springs 14, through a distance dependent upon the actual increase in ground resistance, and the ploughshare to cut a shallower trench in consequence. The springs lower the framework D when the ground resistance decreases. The towline, which is preferably formed as a chain so as to be free from torsional stresses is handled by the paying out and braking mechanism described in Specification 452,141.