GB2092703A

GB2092703A - Chain assemblies

Info

Publication number: GB2092703A
Application number: GB804188A
Authority: GB
Original assignee: Bradney Chain & Engineering Co
Current assignee: Bradney Chain & Engineering Co
Priority date: 1981-02-11
Filing date: 1981-02-11
Publication date: 1982-08-18

Abstract

To provide compatible chain 10, 12 and shackle 14 components for, for example, a mooring system for boats, the shank of a shackle pin 16 has an oblong transverse cross- section with a maximum width of 50% of the maximum depth and each link of the chain has a maximum outside length within the range 5.15d to 5.40d (where 'd' is the material diameter of the chain). In this manner shackle eye width can be reduced by nearly 20% from that of a conventional round-pin shackle, and chain which closely approximates to Short Link chain can be coupled by means of a shackle which is at least as strong as the chain. <IMAGE>

Description

SPECIFICATION Chain assemblies Moorings for boats usually involve the use of chain in the connection between the vessel and an anchor, sinker or other mooring point. A mooring system may well comprise also a swivel, rope and other components, and such chain as is used may be in more than one length. It is necessary for the various components of a mooring system to be connected together, and for connecting chain it is common for Dee, or Bow, shackles to be used; such shackles may, for example, meet one of British Standard Specifications BS 825 and BS 3032 or be of Admiralty pattern.

Conventional shackles have removable pins comprising shanks of circular or elliptical crosssection. The pins may be threaded at one end, for retention in one eye of the shackle, or may be retained by means of a split cotter pin or a forelock.

It is usually considered essential that the chain used in a mooring system should approximate to Short Link chain, rather than Long Link chain; Long Link chain may be strong enough but the risk of its becoming side-jammed virtually rules out its use. The term "Short Link" chain is used herein as recognised by the International Standards Organisation to apply to chain in which the maximum outside length of each link does not exceed 5 times the material diameter and the maximum outside width of each link does not exceed 31 times the material diameter.

A practical problem exists in connecting two lengths of Short Link chain by means of conventional shackles in that the strength of the shackle will be substantially less than the strength of the smallest size of chain with which it can be used. This problem arises from the relative dimensions of the shackle and the chain. To connect two lengths of chain it is necessary to pass one eye of the shackle through the end link of one of the lengths of chain; the end link of the other length of chain can be retained simply by insertion through it of the shackle pin. The difficulty which arises with Short Link chain is that the available length within the end link, through which the shackle eye must be passed, is not greater than twice the material diameter of the chain.For a shackle of similar strength to the chain, the eye width of any conventional shackle will be substantially greater than the available length in the chain link, and accordingly a smaller shackle has to be used.

As a consequence of that problem, mooring systems commonly either comprise chain which is in itself larger (and more expensive) than is really necessary for the size of vessel involved, or, more seriously, comprise one or more shackles which are insufficiently strong for the job they are doing.

Difficulties can particularly arise where, as is very common, moorings for yachts and boats are made up somewhat informally with chains, shackles and other pieces of equipment which are chosen more because they happen to be at hand, and fit, than because they are suitable for the particular job.

It is an object of the present invention to provide improved apparatus comprising chain and shackle components, which may be such as to be suitable for use in a mooring system.

The invention provides in one of its aspects apparatus comprising chain and shackle components wherein the shank of the shackle pin has an oblong transverse cross-section with a maximum width of not more than 60% of the maximum depth, and wherein the maximum outside length of each link of the chain is not more than 5.50d, where d is the diameter of the material of the chain, the arrangement being such that an eye of the shackle can be passed through an end link of the chain to couple the shackle with the chain, and the ultimate tensile strength of the shackle being not less than the ultimate tensile strength of the chain.

In a preferred arrangement, the shackle pin shank cross-section has a maximum width of approximately 50% of the maximum depth, and each link of the chain has a maximum outside length within the range of 5.15 to 5.40d.

In another of its aspects the invention provides a shackle suitable for use in apparatus according to the last preceding paragraph but one and comprising a pin of which the shank has an oblong transverse cross-section having a maximum width of not more than 60% of the maximum depth.

We have found that by means of a pin having a shank of which the cross-section has a maximum width of approximately 50% of the maximum depth, it is possible for the shackle eye width to be reduced by up to nearly 20% from the width of the eye of a shackle (of comparable size) employing a pin of conventional circular cross-section. We have found that suitable dimensions for the pin shank cross-section can be arrived at by making the maximum depth equal to approximately 1.25D and the maximum width equal to approximately 0.62D, where D is the diameter of the shank of the appropriate round pin for that size of shackle.

Preferably the pin shank has a flat-sided roundedged form.

In another of its aspects the invention provides a mooring system comprising apparatus as set out in the last preceding paragraph but three.

There now foilows a description, to be read with reference to the accompanying drawing, of mooring apparatus comprising chain and shackle components which illustrates the invention by way of example.

In the accompanying drawings: Figure 1 is a perspective view showing two lengths of chain connected by a shackle; and Figure 2 is an end view of one eye of the shackle, with the shank of the shackle pin shown in cross-section in position within the eye.

The apparatus shown in Figure 1 forms part of a mooring system for a boat. The system comprises two lengths 10 and 12 of chain (of indefinite length, only two links of each length being shown) end links of the lengths being connected by a shackle 14. The chain 10 and 12 and the shackle 14 are each of mild steel.

The chain 10 and 1 2 is slightly larger than Short Link chain as recognised by the International Standards Organisation, the maximum outside length L1 of each link being 5% greater than the maximum dimension permitted for Short Link chain. That is to say, L1 = 5.25Ld, where Ld is the diameter of the material of the chain. In other embodiments, in accordance with the invention, the dimension L1 could be up to 10% greater than the standard maximum dimension, which is to say that L1 might be as great as 5.50Ld. The maximum outside width Lw of each link may be somewhat below the maximum of 3.5d permitted by the standard.

The shackle 14 comprises a pin comprising a shank 1 6 and a head 1 8, the pin shank being of a flat-sided round-edged form which is oblong in transverse cross-section (as shown in Figure 2).

The shank has a cross-section having a maximum width Pw which is equal to 50% of the maximum depth Pd; in other embodiments according to the invention the dimension Pw could be as much as 60% of the dimension Pd.

In a conventional manner, the shackle 14 comprises two eyes 20 connected by a U-shaped portion 22 of circular cross-section. However, the eye width Ew is substantially less than it would be if, instead of the pin shown in the drawings, a conventional round pin were employed (as determined by, for example, BS 825 or BS 3032).

If D be taken to be the diameter of a round pin suitable for use with the shackle (of which the material diameter is Sd) then Pd = 1.25D and Pw = 0.62D, and Ew is nearly 20% less than it would be to accommodate the round pin of diameter D.

The eye width Ew of the shackle 14 is such that it can be passed through either of the end links of the chain 10 and 12, to couple the shackle with the chain, Ew being less than 2.25Ld (which is the available length within the links). The other end link can be retained by the shackle pin, which is secured by means of a split cotter pin 24.

The ultimate tensile strength of the shackle is approximately equal to, but not less than, the ultimate tensile strength of the chain 10 and 12.

A mooring system may comprise other components such as a swivel and rope. Although in the apparatus described above the shackle secures together two lengths of chain, it will be appreciated that in other mooring systems the shackle might be used to secure chain to other components than chain.

Furthermore, similar apparatus could find application in mechanically assembled chain slings, a shackle for that application probably being fitted with a cylindrical sleeve, over the pin shank, between the shackle eyes.

Claims

1 Apparatus comprising chain and shackle components wherein the shank of the shackle pin has an oblong transverse cross-section with a maximum width of not more than 60% of the maximum depth, and wherein the maximum outside length of each link of the chain is not more than 5.50d, where d is the diameter of the material of the chain, the arrangement being such that an eye of the shackle can be passed through an end link of the chain to couple the shackle with the chain, and the ultimate tensile strength of the shackle being not less than the ultimate tensile strength of the chain.

2. Apparatus according to claim 1 in which the shackle pin shank cross-section has a maximum width of substantially 50% of the maximum depth.

3. Apparatus according to either of claims 1 and 2 in which each link of the chain has a maximum outside length within the range of 5.15d to 5.40d.

4. Apparatus according to claim 3 in which each link of the chain has a maximum outside length of substantially 5.25d.

5. Apparatus comprising chain and shackle components substantially as hereinbefore described with reference to the accompanying drawings.

6. A shackle suitable for use in apparatus according to claim 1 in which the shank of the shackle pin has an oblong transverse cross-section having a maximum width of not more than 60% of the maximum depth.

7. A shackle according to claim 6 in which the shank cross-section has a maximum width of substantially 50% of the maximum depth.

8. A shackle according to either of claims 6 and 7 in which the pin shank has a flat-sided roundedged form.

9. A shackle substantially as hereinbefore described with reference to the accompanying drawings.

10. A mooring system comprising apparatus according to any one of claims 1 to 5.