Winding – tensioning – or guiding – Unidirectional winding and unwinding – Partial wrap around plural rotatable supports
Reexamination Certificate
1999-04-21
2001-02-06
Walsh, Donald P. (Department: 3653)
Winding, tensioning, or guiding
Unidirectional winding and unwinding
Partial wrap around plural rotatable supports
C254S265000, C254S290000, C254S1343FT
Reexamination Certificate
active
06182915
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a detention unit for a winch retrieving an elongated body, e.g., a cable, such as a seismic cable, to avoid damage to the elongated body by local high tension and too hard spooling of the cable at reels or winch drums.
2. Description of the Related Art
In the retrieval of elongated bodies such as cables and the like from the sea onboard a boat, the cables are normally retrieved by a winch and stored on storage reels or are reeled in on a winch drum for storage. Such devices are used for rope and wire of high strength. For more sensitive equipment, such as a seismic cable, however, the high tension and the pressure on the cable on the winch drum or reel while reeling up the cable, may result in a damaged cable. To solve this problem different detention units has been developed.
A known detention unit used e.g. for rope, comprises two discs facing each other to defined a wedge between them. This device gets a good grip on the rope if the tension is great so that the line to be retrieved is wedged between the discs. However, the pressure will lead to deformation and possible destruction of a seismic cable if it were pulled through the device.
Another solution comprises a frustoconical drum on which the elongated body is wound one or more turns. The rope, fishing net or longline to be retrieved enters the drum at the largest diameter and leaves the drum at a lesser diameter, to keep the elongated body in place. This device is not applicable for a sensitive cable, as the cable has to move relative to the drum and may be turned and thus damage the cable.
Another known approach is to use interconnected winches, where the cable to be retrieved is sequentially placed around the winches. To get adequate friction between the cable and the winches, the cable must either be turned several times around each winch or more than two winches have to be used. None of these solutions is acceptable for practical or economical reasons. A solution using several winches is both heavy and expensive, whereas several turns around each winch results in the above-mentioned problem relating to the movement of the cable against the winches.
Another solution used today for cables that can withstand rough handling, is a linear system where the cable is pulled by opposing wheels or conveyor belts. Using this type of device may result in a situation where the cable is starting to run out, because more tension is built up in the starting portion of the system than in the end of the system. This results in undesirable tension and strain on the cable and may result in jerky displacement of the cable. Thus, this solution is not applicable for sensitive cables.
JP 01.176.797, DE 2.631.723, GB 2.294.442 and U.S. Pat. No. 5.152.506 teach pulling in a cable by squeezing it between two endless belts. This solution may result in unacceptable pressure at sensitive parts of a seismic cable in addition to unacceptable local tension on the cable.
SE 364.930 teaches a device for retrieval of a cable, having an endless belt to retrieve the cable and pull the cable towards a reel or winch drum. The device does not provide sufficient detention for the cable and if the tension becomes great the cable might slip against the conveyor and may be damaged.
U.S. Pat. No. 5.082.248 teaches a device having an endless belt pulling, guiding, and pressing the cable towards a drum. This device is not sufficiently gentle for a sensitive seismic cable.
GB 1.566.904 teaches a device using an endless track helically wound around a plurality of drive shafts and where the elongated body is pulled in by means of the endless track. The endless track provides a large contact surface between the track and the elongated body. If the tension becomes too great the elongated body might slip against the track, producing high local tension that may damage the cable.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a detention unit that treats an elongated body, such as a sensitive cable, gently during retrieval, and overcomes the shortcomings of the units described above.
According to the present invention there is provided a detention unit for retrieval of an elongated body, such as a cable, comprising two or more movable friction surfaces adapted to pull in the elongated body, wherein the moveable friction surfaces are arranged relative to each other so that the elongated body may bear or rest against a part of at least two friction surfaces in a sequential manner, the part of the friction surfaces adapted to pull the elongated body defining an arc section, and each friction surface being provided with a separate propulsion unit.
As each moveable friction surface has its own population unit the tractive power for each friction surface may be adjusted so that the local tractive power is kept low enough not to damage the cable. The number of friction surfaces is selected so that the total tractive power from all the friction surfaces are sufficient to pull in the elongated body.
Preferably the part of the friction surface that is adapted to pull in the elongated body defines an approximate half circle.
According to a first preferred embodiment, the moveable friction surfaces are two or more wheels or drums. The wheels or drums are preferably angled so that the elongated body in the area between two consecutive wheels or drums chiefly follows mutual tangents to the wheels or drums.
According to the second preferred embodiment, the device is made up of modules, wherein each module comprises an endless belt, a support for the endless belt and a propulsion unit for the endless belt.
Preferably this second preferred embodiment is constructed of two groups of modules, each group consisting of two or more parallel modules wherein the module groups are placed relative to each other such that the parts of the tracks defining arc sections are facing away from each other.
It is also preferred for this second embodiment that the module groups be offset and displaced relative to each other so that the elongated body in the area between to consecutive modules chiefly follows the mutual tangent of the two modules so that the elongated body is not exposed for sideways forces.
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Dragsund Inge
Kvalsund Bård
Nixon & Vanderhye
Odim Holding ASA
Walsh Donald P.
Webb Collin A.
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