# US 4,395,160 A · Tensioning system for marine risers and guidelines > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 4,395,160 A - Document ID: US4395160A - Status: Granted - Kind: A - Application number: 06/216,800 - Filed: 1980-12-16 - Granted: 1983-07-26 - Earliest claimed: 1980-12-16 - Assignees: Lockheed Corporation - Inventors: Sijtze deJong - Web page: https://patentgrep.com/patent/US4395160A ## CPC - E21B 19/006: {including heave compensators} - B63B 21/502: {by means of tension legs} - E21B 7/128: from floating support with independent underwater anchored guide base - E21B 19/09: specially adapted for drilling underwater formations from a floating support using heave compensators supporting the drill string - Y10T 74/18992: Reciprocating to reciprocating - E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS - B63B: SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING (arrangements of vessel ventilation, heating, cooling, or air-conditioning B63J2/00; floating substructures as supports of dredgers or soil-shifting machines E02F9/06) - Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION ## 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). ## Claims ### Claim 1 A method of maintaining substantially constant tension on an elongate structure, said elongate structure being secured to a stationary underwater object and extending upward to a buoyant object, said method comprising the steps of: (a) positioning a weighted structure in proximity to said elongate structure; (b) positioning first rack means to interact with said elongate structure so that said elongate structure restrains upward motion of said first rack means; (c) securing second rack means to said weighted structure, said second rack means facing said first rack means; (d) securing pinion means to said buoyant object, said pinion means extending between said first and second rack means and having teeth that mesh with corresponding teeth on said first and second rack means, gravity acting downward on said weighted structure thereby causing said second rack means to exert a torque on said pinion means that causes said pinion means to impart an upward force to said first rack means, said pinion means undergoing rotational motion as said buoyant object changes position relative to said underwater object, said rotational motion of said pinion means causing said pinion means to travel vertically along said first rack means and to produce concomitant vertical motion of said weighted structure relative to said elongate structure, said upward force imparted to said first rack means remaining substantially constant as said pinion means travels along said first rack means, thereby causing a substantially constant upward tension to be transmitted to said elongate structure. ### Claim 2 (depends on 1) The method of claim 1 wherein the step of positioning said weighted structure in proximity to said elongate structure comprises positioning a weighted structure around said first rack means. ### Claim 3 (depends on 2) The method of claim 2 wherein the step of positioning said first rack means to interact with said elongate structure comprises attaching a first plurality of racks to external surface portions of a sleeve, said sleeve being positioned around said elongate structure, upward motion of said sleeve being restrained by a collar attached to said elongate structure. ### Claim 4 (depends on 3) The method of claim 3 wherein the step of securing said second rack means to said weighted structure comprises attaching a second plurality of racks to an inner wall portion of said weighted structure, each rack of said second plurality of racks on said weighted structure facing a corresponding rack of said first plurality of racks on said sleeve. ### Claim 5 (depends on 4) The method of claim 4 wherein the step of securing said pinion means to said buoyant object comprises attaching a plurality of pinions to support members affixed to said buoyant object, said support members extending into spacing between said first and second rack means so that each pinion is positioned between one of the racks on said sleeve and one of the racks on said weighted structure. ### Claim 6 (depends on 5) The method of claim 5 wherein corresponding racks of said first and second rack means are aligned with each other by means of rollers, said rollers being secured to structure supporting racks of one of said rack means so as to bear against structure supporting racks of the other of said rack means. ### Claim 7 (depends on 6) The method of claim 6 wherein said rollers are secured to said weighted structure so as to bear against portions of said sleeve. ### Claim 8 (depends on 6) The method of claim 6 wherein said rollers are secured to said sleeve so as to bear against portions of said weighted structure. ### Claim 9 (depends on 5) The method of claim 5 wherein corresponding racks of said first and second rack means are aligned with each other by means of rollers, said rollers being secured to said pinion support members so as to bear against portions of said sleeve and said weighted structure. ### Claim 10 (depends on 5) The method of claim 5 wherein corresponding racks of said first and second rack means are aligned with each other by means of first and second sets of rollers, the rollers of said first set being secured to said sleeve and the rollers of said second set being secured to said weighted structure, the rollers of said first and second sets bearing against structure extending from said buoyant object into spacing between said sleeve and said weighted structure. ### Claim 11 (depends on 2) The method of claim 2 wherein the step of positioning said first rack means to interact with said elongate structure comprises attaching a first plurality of racks to surface portions of a bar that is fastened to the upper end of said elongate structure, said bar extending collinearly with respect to said elongate structure. ### Claim 12 (depends on 11) The method of claim 11 wherein the step of securing said second rack means to said weighted structure comprises attaching a second plurality of racks to an inner wall portion of said weighted structure, each rack of said second plurality of racks on said weighted structure facing a corresponding rack of said first plurality of racks on said bar. ### Claim 13 (depends on 12) The method of claim 12 wherein the step of securing said pinion means to said buoyant object comprises attaching a plurality of pinions to support members affixed to said buoyant object, said support members extending between said first and second rack means so that each pinion is positioned between a rack on said bar and a rack on said weighted structure. ### Claim 14 (depends on 13) The method of claim 13 wherein corresponding racks of said first and second rack means are aligned with each other by means of rollers, said rollers being secured to structure supporting racks of one of said rack means so as to bear against structure supporting racks of the other of said rack means. ### Claim 15 (depends on 14) The method of claim 14 wherein said rollers are secured to said weighted structure so as to bear against surface portions of said bar. ### Claim 16 An apparatus for maintaining substantially constant tension on an elongate structure, said elongate structure being secured to a stationary underwater object and extending upward to a buoyant object, said apparatus comprising: (a) a weighted structure positioned in proximity to said elongate structure; (b) first rack means positioned to interact with said elongate structure so that said elongate structure restrains upward motion of said first rack means; (c) second rack means secured to said weighted structure, said second rack means facing said first rack means; and (d) pinion means secured to said buoyant object, said pinion means extending between said first and second rack means and having teeth that mesh with corresponding teeth on said first and second rack means, gravity acting downward on said weighted structure thereby causing said second rach means to exert a torque on said pinion means that causes said pinion means to impart an upward force to said first rack means, said pinion means undergoing rotational motion as said buoyant object changes position relative to said underwater object, said rotational motion of said pinion means causing said pinion means to travel vertically along said first rack means and to produce concomitant vertical motion of said weighted structure relative to said elongate structure, said upward force imparted to said first rack means remaining substantially constant as said pinion means travels along said first rack means, thereby causing a substantially constant upward tension to be transmitted by said first rack means to said elongate structure. ### Claim 17 (depends on 16) The apparatus of claim 16 wherein said weighted structure surrounds said first rack means. ### Claim 18 (depends on 17) The apparatus of claim 17 wherein said weighted structure comprises a number of weighting segments, the number of said weighting segments being selected to determine the magnitude of the upward tension transmitted to said elongate structure. ### Claim 19 (depends on 17) The apparatus of claim 17 wherein said weighted structure comprises a tank for receiving a fluid, the quantity of said fluid introduced into said tank determining the magnitude of the upward tension transmitted to said elongate structure. ### Claim 20 (depends on 17) The apparatus of claim 17 wherein said first rack means comprises a first plurality of racks attached to external surface portions of a sleeve, said sleeve being positioned around said elongate structure, upward motion of said first rack means being restrained by a collar attached to said elongate structure. ### Claim 21 (depends on 20) The apparatus of claim 20 wherein the racks of said first plurality are arranged symmetrically around said sleeve. ### Claim 22 (depends on 20) The apparatus of claim 20 wherein said second rack means comprises a second plurality of racks attached to an inner wall of said weighted structure, each rack of said second plurality of racks on said weighted structure facing a corresponding rack of said first plurality of racks on said sleeve. ### Claim 23 (depends on 22) The apparatus of claim 22 wherein said pinion means comprises a plurality of pinions attached to support members affixed to said buoyant object, said support members extending into spacing between said first and second rack means so that each pinion is positioned between one of the racks on said sleeve and one of the racks on said weighted structure. ### Claim 24 (depends on 23) The apparatus of claim 23 wherein corresponding racks of said first and second rack means are aligned with each other by means of rollers, said rollers being secured to structure supporting racks of one of said rack means so as to bear against structure supporting racks of the other of said rack means. ### Claim 25 (depends on 24) The apparatus of claim 24 wherein said rollers are secured to said weighted structure so as to bear against portions of said sleeve. ### Claim 26 (depends on 24) The apparatus of claim 24 wherein said rollers are secured to said sleeve so as to bear against portions of said weighted structure. ### Claim 27 (depends on 23) The apparatus of claim 23 wherein corresponding racks of said first and second rack means are aligned with each other by means of rollers, said rollers being secured to said pinion support members so as to bear against portions of said sleeve and said weighted structure. ### Claim 28 (depends on 23) The apparatus of claim 23 wherein corresponding racks of said first and second rack means are aligned with each other by means of first and second sets of rollers, the rollers of said first set being secured to said sleeve and the rollers of said second set being secured to said weighted structure, the rollers of said first and second sets bearing against structure extending from said buoyant object into spacing between said sleeve and said weighted structure. ### Claim 29 (depends on 17) The apparatus of claim 17 wherein said first rack means comprises a first plurality of racks attached to external surface portions of a bar fastened to the upper end of said elongate structure, said bar extending collinearly with respect to said elongate structure. ### Claim 30 (depends on 29) The apparatus of claim 29 wherein the racks of said first plurality are arranged symmetrically around said bar. ### Claim 31 (depends on 29) The apparatus of claim 29 wherein said second rack means comprises a second plurality of racks attached to an inner wall of said weighted structure, each rack of said second plurality of racks on said weighted structure facing a corresponding rack on said first plurality of racks on said bar. ### Claim 32 (depends on 31) The apparatus of claim 31 wherein said pinion means comprises a plurality of pinions attached to support members affixed to said buoyant object, said support members extending into spacing between said first and second rack means so that each pinion is positioned between one of the racks on said bar and one of the racks on said weighted structure. ### Claim 33 (depends on 32) The apparatus of claim 32 wherein corresponding racks of said first and second rack means are aligned with each other by means of rollers, said rollers being secured to structure supporting racks of one of said rack means so as to bear against structure supporting racks of the other of said rack means. ### Claim 34 (depends on 33) The apparatus of claim 33 wherein said rollers are secured to said weighted structure so as to bear against portions of said bar. ### Claim 35 (depends on 33) The apparatus of claim 33 wherein said rollers are secured to said bar so as to bear against portions of said weighted structure. ### Claim 36 (depends on 32) The apparatus of claim 32 wherein corresponding racks of said first and second rack means are aligned with each other by means of rollers, said rollers being secured to said pinion support members so as to bear against portions of said bar and said weighted structure. ### Claim 37 (depends on 32) The apparatus of claim 32 wherein corresponding racks of said first and second rack means are aligned with each other by means of first and second sets of rollers, the rollers of said first set being secured to said bar and the rollers of said second set being secured to esaid weighted structure, the rollers of said first and second sets bearing against structure extending from said buoyant object into spacing between said bar and said weighted structure. ### Claim 38 An apparatus for maintaining substantially constant tension on an elongate structure, said elongate structure being secured to a stationary underwater object and extending upward to a buoyant object, said apparatus comprising: (a) a lateral member having an aperture through which said elongate structure passes; (b) means for maintaining substantially constant upward tension on said lateral member, said tensioning means including a plurality of tensioning devices connecting said lateral member to said buoyant object, each of said tensioning devices being a double rack and pinion device having: (i) a bar on which first rack means is formed; (ii) a generally cylindrical weighted structure surrounding said bar, second rack means being secured to said weighted structure, said second rack means facing said first rack means; and (iii) pinion means secured to said buoyant object, said pinion means extending between said first and second rack means and having teeth that mesh with corresponding teeth on said first and second rack means, gravity acting downward on said weighted structure thereby causing said second rack means to exert a torque on said pinion means that causes said pinion means to permit an upward force to said first rack means, said pinion means undergoing rotational motion as said buoyant object changes position relative to said underwater object, said rotational motion of said pinion means causing said pinion means to travel vertically along said first rack means and to produce concomitant vertical motion of said weighted structure relative to said bar, said upward force imparted to said first rack means remaining substantially constant as said pinion means travels along said first rack means, thereby causing a substantially constant upward tension to be transmitted by said first rack means to said bar; and (c) means for transmitting upward tension from said lateral member to said elongate structure. ### Claim 39 (depends on 38) The apparatus of claim 38 wherein said means for transmitting upward tension from said lateral member to said elongate structure comprises a ring-like thrust bearing surrounding said elongate structure, said thrust bearing being disposed between said lateral member and a collar projecting from said elongate structure, said thrust bearing exerting an upward force on said collar when upward tension is applied to said lateral member. ### Claim 40 (depends on 38) The apparatus of claim 38 wherein said first rack means includes a plurality of first racks and said second rack means includes a plurality of second racks, each first rack facing a corresponding second rack. ### Claim 41 (depends on 40) The apparatus of claim 40 wherein corresponding racks of said first and second rack means are aligned with each other by means of rollers. ### Claim 42 A system for recovering energy resources from a deposit located beneath the floor of a body of water, said system comprising: (a) a floating structure to be positioned on the surface of the body of water generally over the deposit; (b) stationary equipment to be positioned on the floor of the body of water generally over the deposit; (c) an elongate riser extending between said floating structure and said stationary equipment; and (d) double rack and pinion means for maintaining substantially constant upward tension on said riser, said double rack and pinion means including: (i) a weighted structure surrounding said riser; (ii) first rack means positioned to interact with said riser so that said riser restrains upward motion of said first rack means; (iii) second rack means secured to said weighted structure, said second rack means facing said first rack means; and (iv) pinion means secured to said floating structure, said pinion means extending between said first and second rack means and having teeth that mesh with corresponding teeth on said first and second rack means, gravity acting downward on said weighted structure causing said second rack means to exert a torque on said pinion means that causes said pinion means to impart an upward force to said first rack means, said pinion means undergoing rotational motion as said floating structure changes position relative to said stationary equipment, said rotational motion of said pinion means causing said pinion means to travel vertically along said first rack means and to produce concomitant vertical motion of said weighted structure relative to said riser, said upward force imparted to said first rack means remaining substantially constant as said pinion means travels along said first rack means, thereby causing a substantially constant upward tension to be transmitted to said riser. ### Claim 43 (depends on 42) The system of claim 42 wherein said first rack means comprises a first plurality of racks attached to external surface portions of a sleeve, said sleeve being positioned around said riser, upward motion of said sleeve being restrained by a collar attached to said riser. ### Claim 44 (depends on 43) The system of claim 43 wherein said second rack means comprises a second plurality of racks attached to an inner wall of said weighted structure, each rack of said second plurality of racks on said weighted structure facing a corresponding rack on said first plurality of racks on said sleeve. ### Claim 45 (depends on 42) The system of claim 42 wherein said first rack means comprises a first plurality of racks attached to said riser. ### Claim 46 (depends on 45) The system of claim 45 wherein said second rack means comprises a second plurality of racks attached to an inner wall of said weighted structure, each rack of said second plurality of racks facing a corresponding rack on said first plurality.