Hydraulic and earth engineering – Marine structure or fabrication thereof
Patent
1980-12-16
1983-07-26
Corbin, David H.
Hydraulic and earth engineering
Marine structure or fabrication thereof
74110, 114264, 166367, 405198, E02B 1700
Patent
active
043951600
ABSTRACT:
A double rack and pinion device (17) is used to maintain substantially constant upward tension on a marine riser (16) that extends from stationary equipment (11) on the ocean floor to a floating structure (10) on the ocean surface. A preferred embodiment of the double rack and pinion device (17) comprises a sleeve (21) fitted over an upper segment of the riser (16), with a generally cylindrical weighted structure (40) surrounding the sleeve (21). Racks (33, 34, 35) are secured to or formed integrally on the exterior surface of the sleeve (21), and corresponding racks (53, 54, 55) are secured to the interior surface of the weighted structure (40). Pinions (63, 64, 65) are supported by the floating structure (10), and extend into the spacing between corresponding pairs of racks on the sleeve (21) and on the weighted structure (40). Thus, teeth on the pinion (63) engage teeth on the racks (33 and 53), teeth on the pinion ( 64) engage teeth on the racks (34 and 54), and teeth on the pinion (65) engage teeth on the racks (35 and 65). The gravitational force downward on the weighted structure (40) causes a torque to be applied by the racks (53, 54, 55) to the pinions (63, 64, 65), thereby tending to rotate the pinions (63, 64, 65). Concomitantly, the pinions (63, 64, 65) exert an upward force on the racks (33, 34, 35) tending to urge the sleeve (21) upward. Upward movement of the sleeve (21) is restrained, however, by a collar (22) affixed to or formed integrally on the upper segment of the riser (16). As the floating structure (10) changes position on the ocean surface due to environmental forces, vertical motion is imparted to the pinions (63, 64, 65). The pinions (63, 64, 65) travel up and down along the racks (33, 34, 35), producing concomitant vertical motion of the weighted structure (40) relative to the riser (16). In this way, a substantially constant upward tensioning force is exerted on the riser (16) regardless of the position of the floating structure (10) relative to the stationary equipment (11).
REFERENCES:
patent: 3311063 (1967-03-01), Grable
patent: 3525102 (1970-08-01), Braun
patent: 3540396 (1970-11-01), Horton
patent: 3760875 (1973-09-01), Busking
patent: 4135841 (1979-01-01), Watkins
Corbin David H.
Lockheed Corporation
Morrissey John J.
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