Implements or apparatus for applying pushing or pulling force – Multiple lifters
Patent
1980-08-05
1983-06-07
Watson, Robert C.
Implements or apparatus for applying pushing or pulling force
Multiple lifters
254 95, B66F 712
Patent
active
043867570
DESCRIPTION:
BRIEF SUMMARY
The present invention refers to a lifting device which produces vertical relative movements between the bridge and the bearer feet of a movable marine platform.
The device in accordance with the invention is fitted to a marine platform intended for work at sea, such as the drilling of oilwells.
A marine platform is composed of a horizontal bridge and at least three vertical feet. They bear against the bottom of the sea so as to support the bridge. The platform may be brought by floating over a predetermined site, with the feet in raised position. The feet are then lowered into the water until their soles bear against the sea bottom. The bridge of the platform is then lifted above the level of the water by bearing against the feet. The bridge and the feet of the platform are guided relative to one another by means of guide shoes. This guidance helps to assure the stability of the platform on its feet, and is the more effective the greater the distance between the lower and upper guide shoes. A relatively large clearance is provided between each foot and the associated guide shoes in order to allow normal operation and economical production.
The lifting devices which are fitted to marine platforms for assuring the relative movements between the bridge and the feet are of various kinds. Certain lifting devices are of the rack-and-pinion type. For example, the U.S. Pat. Nos. 3,183,676 and 2,924,077 describe devices of this kind. Each of these devices comprises racks which are integral with the feet and mesh with driving pinions. These driving pinions are mounted on frames which are integral with the bridge. Hence the guidance of each foot must be achieved accurately by employing guide members mounted above the pinions upon a superstructure integral with the bridge. These guide members must be separated from the guide members located at the level of the bridge by a relatively large distance. The feet and the racks may also undergo large deformations between the guide assemblies. Under these conditions the teeth of the pinions and the racks no longer mesh correctly.
The object of the present invention is a lifting device of the rack-and-pinion type in which the teeth mesh correctly even if the racks undergo deformations. The device presents the advantage of being isostatic. It enables the omission, above the driving pinions, of guide shoes connected to the bridge of the platform. It allows oscillation of the feet while avoiding overloads upon the pinions at the time of the retention of the platform in working position.
The device in accordance with the invention is fitted to a platform comprising a bridge supported by feet, and it includes, on the one hand, racks cut in uprights fixed to the feet, and, on the other hand, locomotor units each comprising a frame equipped with pinions driven in rotation by motors and meshing with the said racks, the bridge being suspended at each locomotor unit by a suspension system comprising an articulation for connection to the locomotor unit, and it is essentially characterized by the fact that the articulation to the locomotor unit is located substantially in the vertical plane of symmetry of the upright containing the longitudinal axis of the foot, and that each frame of the locomotor unit is connected to at least one other locomotor unit frame by at least three horizontal tie rods located on opposite sides of the said plane of symmetry.
The invention will now be described in greater detail by referring to several embodiments described by way of example and illustrated by the attached drawings.
FIG. 1 is a front view of one embodiment of the lifting device comprising two locomotor units associated with one foot of the platform.
FIG. 2 is a view from the left of FIG. 1.
FIG. 3 is a plan view in section along the line A--A in FIG. 1.
FIG. 4 is a plan view of a second embodiment of the lifting device comprising three locomotor units associated with one foot of the platform.
FIG. 5 is a front view of an embodiment improving upon that of FIG. 1.
FIG. 6 is a section along B--B in
REFERENCES:
patent: Re29539 (1978-02-01), Willke
patent: 2944403 (1960-07-01), Smith
patent: 3565400 (1971-02-01), Yamura
patent: 3743247 (1973-07-01), Willke et al.
patent: 3936032 (1976-02-01), Waschulzik et al.
patent: 4203576 (1980-05-01), Sutton
Societe des Engrenages Durand
Watson Robert C.
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