Self releasing cable system

An embodiment of a self-releasing cable lift system may include a latch coupled to a winch and operable to lift an object, such as a gangway, into a secured position before self-releasing after the object is locked into place. Such a latch may be biased to an open position when setting free, but biased to a closed position when acted upon by an outside surface. Thus, the latch includes a first biasing surface that is operable to bias the latch to the closed position when the latch is moved into contact with a latch receptacle in a first direction. Further, the latch includes a second biasing surface that is operable to bias the latch to a closed position when it is moved into contact with a sleeve, in a second direction. In this manner, the latch may engage a gangway, when lowered, but then self-release when the gangway has been raised.

BACKGROUND

Transporting crew members of ships from the ship to a location off-ship, such as to a nearby oil platform, can be challenging in times of inclement weather. Wave heights of 30-40 feet may be common in the high seas and wind speeds of 30-40 knots can be common, thus making getting on and off ships difficult because the ship may be listing about in relation to any nearby structure.

In the past, helicopters and/or cranes were used to lift and carry baskets that held crew. The crane or helicopter would engage and lift the basket and then carry the basket, with crew in tow, to the destination, e.g., from the ship to the platform. This method, however, is time-consuming and requires many levels of coordination both on and off the ship for arranging for crew members to get on or off the ship.

More recently, gangway techniques have been used wherein a free end of a ramp attached to the deck of a platform may be maneuvered to engage the nearby ship. Such techniques are only suitable for use in relatively low sea states since inclement weather may produce substantial movement of the ramp. Of course, substantial movement of the ramp poses safety risks to any crew members that may be using the ramp at the time. Further, cables that may be attached to the ramp are typically secured via manual attachment. Thus, if the ship needs to get away from the platform fast in an emergency, the securing cables need to be released by a crew member in a manual fashion. This is time-consuming and inefficient.

DETAILED DESCRIPTION

The following discussion is presented to enable a person skilled in the art to make and use the subject matter disclosed herein. The general principles described herein may be applied to embodiments and applications other than those detailed above without departing from the spirit and scope of the present detailed description. The present disclosure is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed or suggested herein.

The subject matter disclosed herein is related to a self-releasing cable lift system. In one embodiment, the system may include a latch coupled to a winch and operable to lift an object, such as a gangway, into a secured position before self-releasing after the object is locked into place. Such a latch may be biased to an open position when setting free, but biased to a closed position when acted upon by an outside surface. Thus, the latch includes a first biasing surface that is operable to bias the latch to the closed position when the latch is moved into contact with a latch receptacle in a first direction. Further, the latch includes a second biasing surface that is operable the bias the latch to a closed position when it is moved into contact with a sleeve, in a second direction. In this manner, the latch may engage a gangway, when lowered, but then self-release when the gangway has been raised.

FIG. 1shows an embodiment of a system including a vessel100positioned next to a nearby platform120. The vessel100may be anchored near the platform120for the purposes of loading or offloading crew and cargo to and from the platform120. Thus, a gangway150may extend from the vessel100to the platform120. Such a vessel100may be a cargo ship or personnel transport and the platform120may be an oil derrick or off-shore drilling facility. A skilled artisan will understand that the embodiments discussed herein may equally be applied to any vessel and any stationary platform on the ocean or other body of water.

InFIG. 1, one can see that the top deck103of the vessel100is below the lowest deck123of the platform120. As such, the gangway150may be used to provide a coupling between the vessel100and the platform120. Such a gangway150may be permanently fixed at one end to the top deck103of the vessel100and then maneuvered or lifted into position when needed for vessel ingress and egress. When in position, the other end of the gangway150may be removably attached to the lowest deck123of the platform120. In other embodiments not depicted inFIG. 1, the top deck103of the vessel100may be above the deck of the platform120to be engaged. Thus, the gangway150may engage with different decks of the platform120. In still further embodiments, the gangway150may be permanently fixed to the platform120and removably attached to the vessel100when in use. Various aspects of such a gangway150are described in greater detail in related U.S. patent application Ser. No. 12/552,175 entitled CLOSED-LOOP CONTROL SYSTEM FOR CONTROLLING A DEVICE assigned to the same assignee of the present disclosure and is hereby incorporated by reference.

The gangway150may include an associated control mechanism (not shown in detail inFIG. 1) wherein an operator may maneuver the gangway150into a deployed position (i.e., attached to the nearby platform120as is shown inFIG. 1) or into a stored position on the deck103of the vessel100. The gangway150may be stored for when the vessel100is underway and not needed. As such, the stored position may include additional securing means to prevent the gangway150from moving about while the vessel100is underway. Such storage mechanisms are not shown in detail in any FIG. Aspects of the control mechanism are described below with respect toFIGS. 2 and 3.

FIG. 2shows a more detailed isometric view of an embodiment of a gangway150that may be part of the system ofFIG. 1. The gangway150may be permanently fixed to the top deck103of the vessel100(as described above) at a first end225of the gangway. Further, the other end, i.e., a second end220may be attached to a deck123of a nearby platform (FIG. 1). Thus, when the vessel requires crew and/or cargo to be loaded or off-loaded, the gangway150may be used for ingress of egress when coupled to the deck123of the platform (FIG. 1).

When a vessel100first arrives at the platform, the gangway150may be moved into position in a number of ways. In one embodiment, a winch190may lower cables (not shown inFIG. 2) to the second end220of the gangway150(hereinafter called the gangway head220) which may be resting on the deck103of the vessel100. Then, the winch190may lift the gangway head220up to the deck123of the platform and attach the gangway head220to the deck123. As shown inFIG. 2, the gangway150has been lifted and secured into place with respect to the platform deck123. A system300for interconnecting the lowered cables from the winch190and the gangway head220are detailed below inFIGS. 3A-3C.

In other embodiments, a control system250may control one or more hydraulics lifts210to maneuver the gangway150into place. Such a hydraulic control system250may include a number of hydraulic lifts210(all of which are not shown in detail) and may control the gangway150in several different directions, which are herein referred to as degrees of freedom. Such a hydraulic control system is discussed in greater detail in related U.S. patent application Ser. No. 12/552,175 entitled CLOSED-LOOP CONTROL SYSTEM FOR CONTROLLING A DEVICE assigned to the same assignee of the present disclosure and is hereby incorporated by reference. The remainder of this specification is related to a self-releasing cable lift system300as shown inFIGS. 3A-3C

FIG. 3Ashows a system300for interconnecting a device (such as the gangway head220) with a platform deck123and the like. The system300provides a means for engaging a gangway head220when stored on the deck of a nearby vessel, then lifting the gangway head220to a secured position at a platform deck123, and then self-releasing the cable attachments used to raise the gangway head220. Further, when released, the gangway head may be secured to the platform deck using a securing mechanism and a locking device that ensures that the gangway head is attached to the platform deck123before the cable attachments are released. These and other aspects are described in greater detail in the following paragraphs.

The system300includes at least one cable310that is coupled at one end (not shown) to a winch190(FIG. 2) or hoist. Other embodiments not shown may include two or more cables and related cable components. The end of the cable310that is shown inFIG. 3Ais coupled to a latch330that may be housed (when in a stored position) inside a sleeve320attached to the platform deck123. The latch330may further include an interior member331that is designed to be biased to an open or closed position depending on differing forces acting upon it.

As shown inFIG. 3A, the latch330is uncoupled from the gangway head220and despite the close proximity as illustrated inFIG. 3A, this may represent a situation when the latch330is retracted near the platform deck123and a considerable distance is between the platform deck and the gangway head220. Thus, this proximity is for illustrative purposes only.

In this initial state, the latch330is not yet engaged with the gangway head220. Further, the platform deck123includes a securing mechanism365that is able to engage with a locking device360on the gangway head220. As this is an initial state, the securing mechanism365is also not yet engaged with the locking device360. Additionally, the interior member331is in an “open” position. That is, the natural state of the interior member is to have a first protrusion332and a second protrusion336extending outside the circumference of its housing. When the interior member331encounters and exterior force (e.g., comes into contact with a surface or the like, the interior member may contract into a “closed” position such that the first and second protrusions are pulled inside the circumference of the housing. As such, maneuvering the latch in specific directions to contact specific surfaces may cause the interior member331to close or allow it to open.

Looking closer at the latch330, the interior member331is able to be biased to a closed position when moving in at least two directions. The interior member331may be biased to closed by the latch330coming into contact with one or more surfaces, namely a surface at the sleeve320or a surface at a latch receptacle354that is part of the gangway head220. Based upon these surfaces biasing the interior member331, the latch330may engage or disengage from the gangway head220. These interactions between surfaces and the interior member331are shown and described in greater detail as the method for engaging and disengaging the gangway head220is detailed.

When an operator begins an engagement method, the cable310with the latch330attached thereto may be lowered toward the gangway head220. When properly aligned, the latch330will begin to engage a latch receptacle354. The first protrusion of the interior member331has a lower surface340that will make contact with a corner341of the latch receptacle354. Because the lower surface340is angled, lowering the latch330(e.g., due to gravity or from an operator physically moving the latch330) further will cause the interior member331to move toward a closed position. Once the interior member331close far enough, i.e., the first protrusion332is moved to within the circumference of the housing of the latch330, then the entire latch330may slip through the latch receptacle354. The latch330may then continue downward to further engage the gangway head220until fully engaged as shown inFIG. 3B.

FIG. 3Bshows the latch330fully engaged with the gangway head220. As the latch330is pushed through the latch receptacle354, the first protrusion332of the interior member331eventually clears the bottom edge of the latch receptacle354. When this happens, the interior member331expands back to an open position and the latch protrusion332prevents the latch330from being pulled back through the latch receptacle354. As a result, the latch330and the gangway head220are now secured to each other and if the cable310is pulled up (e.g., the winch190(FIG. 2) begins to retract), then the entire gangway head220will be lifted toward the platform deck123because the latch protrusion332cannot retract as the interior member331is biased to its open position. That is, the interior member331will not close until it comes into contact with some other surface.

As the gangway head220approaches the platform deck123, a locking device360on the gangway head220may be aligned with a securing mechanism365that is part of the platform deck123. When the locking device360comes into contact with the securing mechanism, a secure engagement between the gangway head220and the platform123may be realized. Such an engagement is known in the industry and, as such, the securing mechanism365and the locking device360are not described in greater detail herein.

Once the gangway head is secured, the latch330may be released from the latch receptacle354. The latch330is a self-releasing latch in that another protrusion336provides a means for closing the interior member331again when being moved in a second direction. The second direction in this embodiment is substantially opposite that of gravity as the winch190(FIG. 2) is lifting the gangway head220straight up. Thus, once can see that a top surface337of the second protrusion will eventually come into contact with a corner322of the sleeve320. Again, because this top surface is angled, the interior member will be forced to a closed position again. Once closed far enough, the first protrusion332will clear the latch receptacle354, thereby releasing the latch from the gangway head220. Then, the method may move to a final secured position as shown inFIG. 3C.

FIG. 3Cshows the latch330disengaged from the gangway head220after the locking device360has engaged with the securing mechanism365of the platform deck123. The system300may be designed such that the spacing between the securing mechanism365and the sleeve are suited to not allow the sleeve320to force the interior member331closed until the locking device360is fully engaged with the securing mechanism365. Further, a sensor388may be in place to sense that the gangway head is locked into place. In one embodiment, the hoisting is interrupted if the sensor388does not indicate that the gangway head220is locked in place. This prevents the latch330from disengaging before the securing mechanism365locks the gangway head220into place.

Once secured, the securing mechanism365then controls when the gangway head may be released as opposed to having latch with cable still attached. Such a release method may be a manual release initiated by deck personnel or may be automatic in response to an emergency button actuation. Without having to unlatch any lifting cables, the gangway head220may be immediately released if an emergency arises.

In one embodiment, the overall system (e.g., the platform123, the winch190and the gangway150) includes more than one self-releasing cable system300. In the case of a gangway150, a latch330and latch receptacle354may be present on a left and right side of the gangway head220. In other embodiments, there may be only one system and the latch may secure to a latch receptacle that in evenly centered on the gangway head220. In various embodiments, the winch or hoist may be electric, pneumatic, mechanical or hydraulic.

FIG. 4shows another embodiment of the self-releasing cable system ofFIG. 3A-3Cwherein the system300is used on a ladder-truck400or man-lift. Such a self-releasing cable system300may be used to protect against power loss or hydraulic loss failures when a person may be in a basket410or at the top of a ladder. If hydraulics fail when a person is in place in the basket, the self-releasing cable system300may prevent problems that may arise from transferring the securing of the basket from the cable lift to any securing mechanism that may be present.

While the subject matter discussed herein is susceptible to various modifications and alternative constructions, certain illustrated embodiments thereof are shown in the drawings and have been described above in detail. It should be understood, however, that there is no intention to limit the claims to the specific forms disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the claims.