Synthetic rope

Abstract

A synthetic rope (20) comprises a core (22) and at least a first layer surrounding the core (22). The first layer has first layer strands (26). The core has a fluted outer surface with spaced apart helical concave grooves. Each of these grooves contacts one of the first layer strands (26). The grooves have a radius of curvature (24) that is greater than the radius of curvature (14) of a circle having a same diameter as the contacting first layer strand before twisting.

Claims

1. A synthetic rope comprising a core comprising a load bearing member and a core cover, and at least a first layer surrounding said core, said first layer having first layer strands, said core having a fluted outer surface with spaced apart helical concave grooves, each of said grooves contacting one of said first layer strands, said grooves having an actual radius of curvature that is greater than a hypothetical radius of curvature of a circle having the same cross-section as the cross-section of a first layer strand, said actual radius of curvature being the same throughout an entirety of said grooves, wherein the load bearing member of the core and the core cover of the core are made from different materials.

2. The synthetic rope of claim 1, wherein said core comprises convex curves between said concave grooves.

3. The synthetic rope of claim 1, said core cover being an extruded layer.

4. The synthetic rope of claim 1, said core load bearing member being a synthetic strand or synthetic rope.

5. The synthetic rope of claim 4, said synthetic strand being a braided construction.

6. The synthetic rope of claim 4, said synthetic strand being a wire laid strand.

7. The synthetic rope of claim 1, said core load bearing member being a solid cylindrical member.

8. The synthetic rope according to claim 1, said rope comprising a second layer surrounding said first layer.

9. The synthetic rope according to claim 8, said rope comprising a third layer surrounding said second layer.

10. The synthetic rope according to claim 9, wherein said second layer strands and said third layer comprises third layer strands, some of said first layer strands, second layer strands and third layer strands each have a braided or extruded cover.

11. The synthetic rope according to claim 10, wherein said first layer, said second layer and said third layer may have a braided or extruded cover.

12. The synthetic rope according to claim 9, wherein said first layer, said second layer and said third layer may have a braided or extruded cover.

13. The synthetic rope according to claim 1, said rope comprising high strength polymer fibres.

Description

BRIEF DESCRIPTION OF FIGURES IN THE DRAWINGS

(1) FIG. 1 is a conceptual drawing explaining the difference between a fluted core member of a steel wire rope and a fluted core member of a synthetic rope according to the invention.

(2) FIG. 2 is a cross-section of a first embodiment according to the invention.

(3) FIG. 3 is a cross-section of a second embodiment according to the invention.

(4) FIG. 4 is a cross-section of a third embodiment according to the invention.

(5) FIG. 5 is a cross-section of a fourth embodiment according to the invention.

MODE(S) FOR CARRYING OUT THE INVENTION

(6) Referring to FIG. 1, the difference between a fluted core member of a steel wire rope and a fluted core member of a synthetic rope according to the invention is explained.

(7) Take as starting point a hypothetical steel wire rope 10 having a fluted core member 12 with helical concave grooves, shown in dotted lines. The grooves follow the contours of the round steel wire strands. Each groove has a radius of curvature 14 that is about equal to the radius of the circumscribing circle of the steel strands 15, which is half the so-called tube diameter or equivalent diameter.

(8) On the one hand, for a synthetic rope, this small radius of curvature 14 is not needed, even not desired.

(9) On the other hand, for a synthetic rope a core with only convex parts may need to be avoided to prevent strands from shifting and abrading against one another. The wedge packing of the first layer strands leads to very small radii in the corners of those strands. An objective of the concave curves is to increase these radii.

(10) In contrast with steel ropes, the radius of curvature 16 for the grooves of a fluted core member for synthetic ropes is greater than the radius of curvature 14, e.g. 10% greater, preferably 20% or more preferably 30% or 40% greater than the radius of curvature 14.

(11) A fluted member that is adapted for synthetic ropes is shown in full lines on FIG. 1. Between the equally spaced concave grooves 17, convex parts 18 may be present.

(12) FIG. 2 shows a first embodiment of a synthetic rope 20 according to the invention.

(13) The synthetic rope 20 has a fluted solid core member 22 with spaced apart concave helical grooves with a radius of curvature 24 that is greater than in the case of a steel wire rope. One single layer of first layer strands 26 surrounds the core 22, each first layer strand 26 fits in one concave groove.

(14) FIG. 3 shows a second embodiment of a synthetic rope 30 according to the invention.

(15) This synthetic rope 30 has a fluted core member with concave spaced apart helical grooves. The core member has a load bearing member in the form of a synthetic strand with a core 31 and a surrounding layer 32 of six synthetic elements. The core 31 and the layer 32 are covered with an extruded layer 33 of a polymer material that gives the grooved shape to the core. The helical shape can be provided either by a rotating extrusion die or by having the fluted core rotating when twisting the surrounding strands. The concave grooves of the core have a radius of curvature 34 that is greater than in case of a steel wire rope; as explained in FIG. 1. A layer of synthetic first layer strands 35 surrounds the core member. Each such strand 35 is accommodated in a groove of the core thereby avoiding shifting of the first layer strands 35 and thus mitigating fretting. A layer of synthetic second layer strands 36 surrounds the first layer.

(16) FIG. 4 shows a cross-section of a third embodiment of a synthetic rope 40 according to the invention.

(17) The core of this synthetic rope 40 has a cylindrical member 41 and an extruded layer 42 provided with helical grooves. A layer of synthetic first layer strands 43 surrounds the core. Each first layer strand 43 is enveloped with a braided cover 44. As an alternative to the braided cover 44, an extruded layer may be provided around each first layer strand 43. A layer of synthetic second layer strands 45 surrounds the first layer. Although not shown on FIG. 4, a braided cover or an extruded layer may be provided also around some or all of the synthetic second layer strands 45.

(18) FIG. 5 shows a cross-section of a fourth embodiment of a synthetic rope 50 according to the invention.

(19) This synthetic rope 50 has a fluted core member with concave spaced apart helical grooves. The core member has a load bearing member in the form of a synthetic strand with a core 51 and a surrounding layer 52 of six synthetic elements. The core 51 and the layer 52 are coated with an extruded layer 53 of a polymer material that gives the grooved shape to the core. The grooves have a radius of curvature 54 that is greater than in the case of steel wire strands, as explained in FIG. 1. A layer of first layer strands 55 surrounds the core. Each first layer strand 55 fits in a groove of the core. A layer of second layer strands 56 surrounds the first layer and a layer of third layer strands 57 surrounds the second layer. A braided cover 58 envelops the first layer thereby mitigating contact and abrasion between the first layer and the second layer and at the same time keeping torsions of the first layer limited. Instead of a braided cover 58, an extruded layer may be provided around the first layer.

(20) Although not shown on FIG. 5, a braided cover or an extruded layer may also be provided around the second layer.

(21) FIG. 2, FIG. 3, FIG. 4 and FIG. 5 show embodiments of synthetic ropes 20, 30, 40, 50 with one, two or three layers. Each of these layers is shown with a particular number of strands. The invention, however, is not limited to the number of strands shown.

(22) A synthetic rope according to the present invention may be used, for example, on winches and cranes and other pulling and hoisting devices e.g. abandonment and recovery (A&R), knuckle boom crane, riser pull in, riser tensioners, drag shovel hoist, anchor lines and deep shaft hoisting drum and friction winding applications. In these applications, particular demands are placed on a rope as it passes over sheaves and pulleys, is wound under tension onto a drum containing multiple layers or is progressively loaded by friction through a traction drive. The design of the synthetic rope of the present invention enables it to be integrated onto such systems designed for steel wire rope with minimal system modification and reduces internal wear and fretting mechanisms, where duty cycles or tensions are high.

REFERENCE NUMBERS

(23) 10 hypothetical rope with cylindrical strands 12 rope core 13 round steel wire strands 14 radius of curvature of circle circumscribing the steel strands 15 circle circumscribing round steel wire strands 16 radius of curvature of invention grooves in core member 17 invention groove 18 convex part between grooves 20 synthetic rope of first embodiment 22 solid core 24 radius of curvature of grooves of solid core 26 first layer strand 30 synthetic rope of second embodiment 31 core of reinforcing core member 32 layer of reinforcing core member 33 extruded layer 34 radius of curvature of groove in extrusion layer 35 1.sup.st layer strand 36 2.sup.nd layer strand 40 synthetic rope of third embodiment 41 tubular core member 42 extruded layer 43 1.sup.st layer strand 44 braided cover surrounding 1.sup.st layer strand 45 2.sup.nd layer strand 50 synthetic rope of fourth embodiment 51 core of reinforcing core member 52 layer of reinforcing core member 53 extruded layer 54 radius of curvature of groove in extrusion layer 55 1.sup.st layer strand 56 2.sup.nd layer strand 57 3.sup.rd layer strand 58 braided cover enveloping the layer of first strands