TWELVE-STRAND ROPE EMPLOYING JACKETED SUB-ROPES
A rope structure is formed by forming a sub-rope structure comprising a core and a jacket, twisting the sub-rope structure to form a twisted sub-rope structure, and forming the rope structure by braiding together a plurality of lengths of the twisted sub-rope structure.
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The present invention relates to rope structures, systems, and methods and, in particular, to such structures, systems, and methods in which a twelve-strand rope is formed by jacketed sub-ropes.
BACKGROUNDRope structures are commonly used when a tension load is to be applied between two structures. One common use of a rope structure is as a mooring tether or line adapted to extend between a first structure (e.g., oil drilling or production platform or vessel) and a second structure (an anchor on the sea floor).
Mooring tethers or lines are commonly formed with a core for tensile strength and a jacket to cover and protect the core. The core in turn is formed by strands. The protective jacket prevents visual inspection of the load bearing core and/or the strands forming the load bearing, so it is difficult to determine whether the load bearing core of a jacketed mooring tether or line may be subject to failure.
The need thus exists for improved mooring lines that facilitate visual inspection of individual strands of a jacketed core.
SUMMARYThe present invention may be embodied as a method of forming a rope structure comprising the following steps. A sub-rope structure comprising a core and a jacket is formed. The sub-rope structure is twisted to form a twisted sub-rope structure. The rope structure is formed by braiding together a plurality of lengths of the twisted sub-rope structure.
The present invention may also be embodied as a rope structure comprising a plurality of lengths of a sub-rope structure comprising a core and a jacket. A reference line substantially parallel to a longitudinal axis of the sub-rope structure when the rope sub-structure is initially formed is substantially parallel to the longitudinal axis of the rope sub-structure when the plurality of lengths of the sub-rope structure are braided together to form the rope structure.
The present invention may be embodied as a method of forming a rope structure comprising the steps following steps. A rope sub-structure comprising a core and a jacket is provided. An amount of braid twist obtained when braiding the rope sub-structure to form the rope structure is determined. A twisted sub-rope structure is formed by pre-twisting the sub-rope structure to compensate for the braid twist. Lengths of the twisted sub-rope structure are braided together to form the rope structure.
Referring to
Referring initially to
Schematically depicted in
As perhaps best shown in
12-strand braiders such as the example 12-braider system 82 inherently form a twist in the sub-rope structures braided thereby. For many sub-rope structures, the twist is inconsequential. For jacketed sub-rope structures, the twist formed by the 12-strand braider deforms the jacketed sub-rope structure and thus the twelve-strand braided rope formed thereby. Accordingly, jacketed sub-rope structures are not effectively used to form a rope structure using 12-strand braiders.
The Applicants have discovered that the performance of the pre-twist step to twist sub-rope structure ultimately taken up by a conventional 12-strand braider can compensate for the twist applied by a 12-strand braider. In particular, the pre-twist step performed by the second twister system 70 is configured to yield a twisted sub-rope structure 74 having an amount of pre-twist in a first direction to compensate for an amount of braid twist applied in a direction opposite the first direction by the 12-strand braider system 82.
Accordingly, as shown in
Because the assembled sub-rope structures 84 are not twisted, these sub-rope structures 84 do not deform and/or result in deformation of the final rope structure 20. Further, the final rope structure 20 need not be jacketed to cover the assembled sub-rope structures 84 because the assembled sub-rope structures 84 are themselves jacketed. If the final rope structure 20 is used, as an example, as a mooring tether or line, the assembled sub-rope structures 84 are easily inspectable.
As shown in
The filaments 42 may be made of one or more fibers made of the following materials: Polyester, Polyethylene, Polypropylene, Nylon, Aramid, Liquid Crystal Polymer, copolymers, High Modulus Polyethylene, Glass, Carbon, and Basalt.
Claims
1. A method of forming a rope structure comprising the steps of:
- forming a sub-rope structure comprising a core and a jacket;
- twisting the sub-rope structure to form a twisted sub-rope structure;
- forming the rope structure by braiding together a plurality of lengths of the twisted sub-rope structure.
2. A method as recited in claim 1, further comprising the steps of:
- forming strands from filaments; and
- combining lengths of the strands to form the core and the jacket of the sub-rope structure.
3. A method as recited in claim 2, in which:
- the step of combining the strands to form the core comprises the step of braiding together twelve lengths of the strands; and
- the step of combining the strands to form the jacket comprises the step of braiding together twelve lengths of the strands around the core.
4. A method as recited in claim 1, in which the step of twisting the sub-rope structure to form the twisted sub-rope structure further comprises the steps of:
- determining an amount of braid twist applied when the lengths of twisted sub-rope structures are braided together to form the rope structure; and
- applying sufficient pre-twist when forming the twisted sub-rope structure to compensate for the braid twist.
5. A method as recited in claim 1, further comprising the step of arranging a filter member between the core and the jacket.
6. A method as recited in claim 1, in which the step of forming the rope structure comprises the step of braiding together twelve of lengths of the twisted sub-rope structure.
7. A rope structure comprising a plurality of lengths of a sub-rope structure comprising a core and a jacket, where a reference line substantially parallel to a longitudinal axis of the sub-rope structure when the rope sub-structure is initially formed is substantially parallel to the longitudinal axis of the rope sub-structure when the plurality of lengths of the sub-rope structure are braided together to form the rope structure.
8. A rope structure as recited in claim 7, in which:
- lengths of strands are braided together to form the core and the jacket of the sub-rope structure; and
- the strands comprise filaments.
9. A rope structure as recited in claim 8, in which:
- the core of the rope sub-structure comprises twelve lengths of the strands; and
- the jacket of the rope sub-structure comprises twelve lengths of the strands.
10. A rope structure as recited in claim 8, further comprising a filter member between the core and the jacket.
11. A rope structure as recited in claim 8, in which the rope structure comprises twelve of lengths of the sub-rope structure.
12. A method of forming a rope structure comprising the steps of:
- providing a rope sub-structure comprising a core and a jacket;
- determining an amount of braid twist obtained when braiding the rope sub-structure to form the rope structure; and
- forming a twisted sub-rope structure by pre-twisting the sub-rope structure to compensate for the braid twist;
- braiding lengths of the twisted sub-rope structure together to form the rope structure.
13. A method as recited in claim 12, further comprising the steps of:
- forming strands from filaments; and
- combining lengths of the strands to form the core and the jacket of the sub-rope structure.
14. A method as recited in claim 13, in which:
- the step of combining the strands to form the core comprises the step of braiding together twelve lengths of the strands; and
- the step of combining the strands to form the jacket comprises the step of braiding together twelve lengths of the strands around the core.
15. A method as recited in claim 13, further comprising the step of arranging a filter member between the core and the jacket.
16. A method as recited in claim 13, in which the step of forming the rope structure comprises the step of braiding together twelve of lengths of the twisted sub-rope structure.
Type: Application
Filed: Mar 14, 2013
Publication Date: Sep 18, 2014
Applicant: SAMSON ROPE TECHNOLOGIES (Ferndale, WA)
Inventor: Samson Rope Technologies
Application Number: 13/831,142