GB1592884A

GB1592884A - Arrangement in a chain stopper

Info

Publication number: GB1592884A
Application number: GB46087/77A
Authority: GB
Original assignee: Kockums AB
Current assignee: Saab Kockums AB
Priority date: 1976-11-15
Filing date: 1977-11-04
Publication date: 1981-07-08
Also published as: NO144333C; NO773885L; FR2370628A1; DE2750397A1; NO144333B; FI773321A; DK492077A; SE7612715L

Description

(54) AN ARRANGEMENT IN A CHAIN STOPPER (71) We, KOCKUMS AKTIEBOLAG, formerly known as Kockums Varv (Shipyard) AB, a company duly organized and existing under the laws of Sweden, of P.O. Box 832, S-201 80 Malmö, Sweden, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to chain stoppers for locking the chain used when mooring or anchoring a vessel, such as chain stoppers for relieving the anchor windlass when the vessel is at anchor, or chain stoppers to be used when mooring the vessel to a mooring buoy.

In the chain stoppers for anchor chains com- monly used so far the chain is locked by means of a sturdy bar which can be lowered transversely of the anchor chain and, engaging a vertical chain link, locks the chain against a pulley wheel or a stationary chain-way.

Since the bar in that case abuts against the chain in section thereof, the locking connection takes up the force in the anchor chain substantially by single-cutting shear of the link. This means that the expected effective brake load of the chain is reduced to about 50%, although the bar has been proportioned for the entire brake load of the chain. Attention has been paid to this fact recently by the classifying associations, and at least one of these associations does not accept at this time chain stoppers of the type described above.

Therefore, a chain stopper construction has been developed recently which comprises an arrangement of two co-operating lock bars which can be moved towards each other in a plane perpendicular to the chain. In locking position the bars abut against a vertical chain link at each side of a horizontal link. In this embodiment there is obtained a double-cutting load on the vertical chain link which means that the chain stopper is able to transfer the entire brake load of the chain to the support sructure supporting the chain stopper. However, since the lock bars in that case abut against the curved portion of the vertical chain link, the two bars are effected by component tensile forces in the chain which tend to separate the two bars. The lock bars and the associated lock arrangement therefore must be proportioned to take up said component ten sile forces.Since large forces have to be taken up particularly in large vessels, e.g. forces of the order of 1,000 tons in a tanker of 350,000 tons d.w., it is realized that the component tensile forces in the chain tending to separate the lock bars can be of a considerable size.

It follows therefore that lock bars and the associated lock arrangement must be generously proportioned and consequently will be heavy and cumbersome to handle.

The chain stopper of the invention is of the type comprising an upwardly open slide-way wherein the chain can be laid down from above and supporting the horizontal chain links of the chain in parallel with said slide-way and including a guide groove for vertical chain links of the chain, which extend in a perpen dicular symmetry plane of the slide-way, and two lock bodies which can be moved to and from locking engagement with a horizontal chain link on the slide-way, said lock bodies, when in locking engagement with a horizontal chain link on the slide-way abutting against a curved end portion of said horizontal chain link at each side of the symmetry plane of the slide-way.

The object of the invention is to provide a chain stopper which, when locking the chain, loads the chain link locked by the lock bodies in a double-cutting manner and thus makes it possible to transfer the total brake load of the chain to the support structure supporting the chain stopper, the chain force being pre vented in a simple and effective manner from producing in the lock bodies component forces which tend to open the locking connection.

A further object of the invention is to provide a chain stopper which is simple to produce and the operation of which is reliable.

According to the invention, there is provided in a chain stopper of the type referred to above an arrangement which is characterized in that the lock bodies, when in locking engagement with said horizontal chain link, each form an extension of a sturdy stationary support body up to said horizontal chain link, the side of the lock body remote from said horizontal chain link abutting against the support body, the contact surfaces between the support body and the lock body and between the lock body and the chain link, respectively, being arranged such that the component tensile force in the chain acting through the tangential point of said horizontal chain link is directed along the lock body, intercepting said contact surfaces The invention will be described below with reference to the accompanying drawings.

In the drawings: Fig. 1 is a plan view of the lock arrangement in a preferred embodiment of the chain stopper according to the invention; Fig. 2 is a sectional view taken along line A-A in Fig. 1; Fig. 3 is a sectional view taken along line B--B in Fig. 1; Fig. 4 is a sectional view taken along line in in Fig. 1; Fig. 5 is a plan view of an alternative embodiment of the invention; Fig. 6 is a sectional view taken along line D-D in Fig. 5, with the lock body in a blocking position; and Fig. 7 is a sectional view as that in Fig.

6 but with the lock body in an "open" position.

In the chain stopper disclosed in Fig. 1 the chain comprising horizontal chain links 1 and vertical chain links 2 is supported by a guiding slide-way 3 for the chain. The guiding slideway 3 begins adjacent to the anchor windlass (not shown in the figure), and extends to a hawse pipe (not shown in the figure), the chain runr.ing through said hawse pipe. The feedout direction of the chain is indicated by an arrow in the figure. The slide-way 3 forms a guiding slide-way 4 for the horizontal chain links 1 as well as a channelled guide-way 5 for the vertical chain links 2 of the chain. The chain stopper comprises two lock bodies 6 and 7 which are shown in the figure in locking engagement with a horizontal chain link 1, one at each side of a vertical symmetry plane through the chain.Each of the lock bodies 6 and 7 extends in a vertical plane which is perpendicular to the tangent in the abutment point of the chain link 1 and the lock body 6 and 7, respectively. The abutment surfaces of the chain link 1 and the lock bodies 6 and 7 are formed as tangential surfaces of the chain link. The force from the chain thereby is transferred from the horizontal chain link 1 to the lock bodies 6 and 7 in a direction which extends radially outwardly towards both sides of the horizontal chain link 1 through the tangential point of the associated lock body 6 and 7, respectively.

Each lock body abuts against a stationary support 8 and 9, respectively, at the side thereof which is turned away from said tangential point of the chain link 1, the abutment surface of the lock body 6 and 7, respectively, and the support 8 and 9, respectively, being orientated in a plane perpendicular to said direction of the force. The support 8 and 9, respectively, comprises a sturdy plate which is connected by welding to the support structure supporting the chain stopper so that the forces transferred from the chain are taken up entirely by the support structure without providing detrimental spot loads.

As will be seen from Figs. 1 to 3, the lock bodies 6 and 7 are pivoted to be swung between a blocking position shown by solid lines in the figures, and an outer or "open" position shown by dot and dash lines, in order to clear the slide-way 3 so that the chain can move freely in the longitudinal direction thereof. For this purpose the lock bodies are provided with two pairs of brackets 10 and 11, respectively, for cooperation with associated bracket fittings 12 and 13, respectively, which are fixedly connected to the lower side of the slide-way 3. The brackets 10 and 11 as well as the bracket fittings 12 and 13 are pivotally connected to each other by shafts 14. Thus, the lock bodies 6 and 7, respectively, can be swung about these shafts from the blocking position to the outer position, and vice versa.

In the outer position the lock body bears against a support shoulder which is formed by a projecting portion of the bracket fitting 12.

Furthermore, the lock bodies can be secured in the blocking position as well as the outer position by means of a sturdy pin 15 which can be located in holes provided in the brackets 10 and in the associated bracket fittings 12.

Swinging of the lock bodies between the blocking position and the outer position is achieved according to the preferred embodiment shown by means of two double-acting hydraulic cylinders 16. Then, the end of the piston rod of the hydraulic cylinder is pivo tally connected to the two brackets 11, and the end of the cylinder is pivotally connected to a stationary support as is diagrammatically shown in Fig. 3. Pressure fluid is supplied to the hydraulic cylinder 16 from a hydraulic system, not shown in the figure, with associated control valves. Preferably, the hydraulic cylinders 16 are connected over control valves to a hydraulic system available for other purposes on the deck of the vessel.

As mentioned initially, the chain stopper according to the invention is intended to be used for locking the chain and thus for relieving the anchor windlass when the vessel is at anchor. When the anchor has been dropped and a sufficient length of the chain has been fed out through the hawse pipe, further feedout of the chain is stopped by means of the anchor windlass brake; it is seen to it that the chain is positioned in the slide-way such that the lock bodies can be swung to a position between two horizontal chain links.When the lock pins 15 have been removed the lock bodies are swung inwardly to the blocking position by activating the hydraulic cylinders 16 for swinging the lock bodies 6 and 7 about the pivot shafts 14 from the outer position of the lock bodies to the blocking position thereof wherein the lock bodies are secured by inserting the pins 15 in the associated holes. By disengagement of the anchor windlass brake the horizontal chain link located adjacent to the lock bodies, is brought into contact with the lock bodies which thereby relieve the anchor windlass entirely.

When the anchor is to be raised the chain is withdrawn by means of the anchor windlass to such extent that the lock bodies are relieved. The pins 15 are removed and then the lock bodies are swung to their respective outer positions by means of the hydraulic cylinders 16. Then, the anchor is raised in the usual order.

According to the preferred illustrative embodiment described, the lock bodies are operated by means of hydraulic cylinders. However it should be pointed out that the hydraulic operation is not necessary for moving the lock bodies between the blocking position and the outer position. In fact, there is achieved by this invention that the dimensions of the lock bodies will be reasonable enough to make possible a pure manual control by means of a lever or the like, although the lock bodies have to transfer large forces.

In Figs. 5 to 7 there is disclosed an alternative embodiment of the invention. The essential difference in relation to the embodiment described above is that the lock bodies 17 according to the alternative embodiment are operated between the blocking position (Fig.

6) and the "open" position (Fig. 7) by displacement perpendicularly to the slide-way.

The lock bodies in the embodiment shown are circular-cylindric and project below the slideway where mechanical, pneumatic or hydraulic operating means can be provided for the displacement; such means are not shown in the figures. Thus, in the blocking position the lock bodies 17 project above the slide-way and, abutting against a horizontal chain link, transfer the chain force to support means 18 located behind the associated lock body. In the lowered position, i.e. the "open" position, the upper surfaces of the lock bodies form part of the slide-way.

As in the preferred embodiment previously described, the embodiment according to Figs.

5 to 7 can be used for locking the sturdy anchor chain when the vessel is at anchor.

The procedure at the use then will be analogous with the procedure described with reference to the preferred embodiment in Figs. 1 to 5.

However, the embodiment according to Figs. 5 to 7 is particularly well suited as a chain stopper for anchoring the vessel to a buoy, e.g. at off-shore loading and unloading of the loads of the vessel or while waiting for calling at a harbour. The chain used in that case has considerably smaller dimensions than the anchor chain, which means that the chain stopper will have dimensions which make it particularly well suited for the embodiment according to Figs. 5 to 7. This embodiment is also particularly well suited to be produced as a cast steel standard unit 20 which is con nected by welding in a suitable position on the deck of the vessel.

The invention is not limited to the illustrative embodiments shown and described but can be varied within the scope of the following

Claims

claims. WHAT WE CLAIM IS:-

1. An arrangement in a chain stopper for locking a chain used in mooring or anchoring a vessel, comprising an upwardly open slide way wherein the chain can be laid down from above and supporting the horizontal chain links of the chain in parallel with said slide-way and including a guide groove for vertical chain links of the chain, which extend in a per pendicular symmetry plane of the slide-way, and two lock bodies which can be moved to and from locking engagement with a horizontal chain link on the slide-way, said lock bodies, when in locking engagement with a horizontal chain link on the slide-way abutting against a curved end portion of said horizontal chain link at each side of the symmetry plane of the slide-way, characterised in that the lock bodies, when in locking engagement with said hori zontal chain link, each form an extension of a sturdy stationary support body up to said horizontal chain link, the side of the lock body remote from said horizontal chain link abutting against the support body, the contact surfaces between the support body and the lock body and between the lock body and the chain link, respectively, being arranged such that the component tensile force in the chain acting through the tangential point of said horizontal chain link is directed along the lock body, intercepting said contact surfaces.

2. An arrangement according to Claim 1, wherein the lock bodies can be moved to and from locking engagement with the chain link by movement of the associated lock body in a plane which is substantially parallel to a plane perpendicular to the slide-way, through the tangent of the point where the chain link and the lock body contact each other.

3. An arrangement according to Claim 2, wherein each lock body is pivoted to be swung between a position outside the slide-way and a blocking position in engagement with a horizontal chain link located on the slide-way.

4. An arrangement according to Claim 1 or 2, wherein each of the lock bodies comprises a pin displaceable from a position below the slide-way of the chain link to a position of engagement with said chain link.

5. An arrangement in a chain stopper for locking the chain used for mooring or anchoring, substantially as herein described with reference to Figs. 1 to 4.

6. An arrangement in a chain stopper for locking the chain used for mooring or anchoring, substantially as herein described with reference to Figs. 5 to

7.