JP3229055B2 - Core of wire rope, method of manufacturing the same, and wire rope - Google Patents

Abstract

A tubular outer member 1 of plastics material is extruded onto an extruded solid cylindrical central member 3 of plastics material. The outer member 1 has symmetrically spaced helical grooves 2 for receiving respective wire strands 4. Plastics materials are specified, and may incorporate fibres. Member 3 may be lubricated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a core for a wire rope, in particular a steel wire rope.

[0002]

BACKGROUND OF THE INVENTION British Patent No. 2,219,014 discloses a core for a wire rope with a grooved member of a polymeric or elastomeric material having helical grooves spaced symmetrically around an outer surface. Each groove has an elliptical arc shape in cross section (in a plane perpendicular to the longitudinal axis of the core). The manufacturing characteristics and control (adjustment) of the core can be substantially improved during extrusion by incorporating a reinforcement member or cord constituted by a fiber core or a separate wire rope core.

[0003] However, British Patent No. 2,219,014
The use of conventional types of stiffeners, such as those illustrated in U.S. Pat. Both the fiber core and the independent wire rope core, due to the nature of their inherent twisted structure, entrain air that detrimentally affects the support stiffness that the core can supply to the rope. This is particularly important in wire ropes where the core is generally subject to very high radial pressures. That is, the compressibility of the core reduces the diameter of the rope under tension and, therefore, often increases the stretching properties of the rope that are not desirable in practice. In addition, the significant reduction in rope diameter causes the outer strands (strands) of the rope to contact each other at the crown of the wire rope, thus creating a very high stress on the contacts. On a rope that moves back and forth on a sheave or flexes repeatedly,
These stresses can cause fretting on the outer wires due to the resulting loss of fatigue performance.
Cause damage.

[0004]

[Problems to be Solved] British Patent No. 2,21
Experiments with the conventional type of stiffener disclosed in 9,014 indicate that the stiffener may prematurely fail before any significant damage (easy to inspect) of the outer strands of the rope occurs. Also shown. This mode of weakness is not only undesirable from a test standpoint,
There is also a loss of load carrying capacity and structural integrity of the wire rope.

[0005] There is a need for a core that can reduce or avoid these disadvantages.

In order to solve the above-mentioned problems, a core for a wire rope according to the present invention comprises a tubular outer member made of an extruded plastic material and a high rigidity made of an extruded plastic material. A cylindrical inner surface of the outer member is in close contact with an outer surface of the center member, and an outer surface of the outer member is a corresponding wire of a wire rope. A plurality of helical continuous grooves symmetrically arranged at predetermined intervals to receive the strands, wherein the outer diameter of the central member is at least 70% of the valley diameter of the outer surface grooves of the outer member. Wherein the cross-sectional area of the central member is at least 40% of the cross-sectional area of the core.

[0006]

The illustrated core comprises a tubular outer member 1 made of a plastic material and a solid cylindrical central member 3 made of a plastic material. The outer member 1 has a cylindrical inner surface, and the inner surface is in close contact with the outer surface of the central member 3. The outer member 1 is slidable in the longitudinal direction with respect to the center member 3. At the boundary between the outer member 1 and the center member 3, a thin film of a lubricant or a release agent can be optionally provided. The outer surface of the outer member 1 is formed with symmetrically spaced spiral grooves 2 for receiving a corresponding wire strand 4 made of steel.

In the illustrated example of the wire rope shown in FIG. 2, there are six strands 4. However, it is clear that different numbers of strands (eg, 5, 7, and 8) may be used. Each strand 4 is a round strand in which the circumscribed envelope E forms a circle having a diameter d ₁ in a cross section perpendicular to the strand axis. Since each strand extends helically, the envelope E appears slightly elliptical in cross section in the plane of the drawing, but this plane is also perpendicular to the axis of the core. Each groove 2 has a cross section perpendicular to the groove,
An arc of diameter d _1.

In order to maximize the contact area between the wires of the strand 4 and the core, the strand has a diameter d _{1 in} a cross section perpendicular to its axis.
Is a strand of Dyform (registered trademark-Bridon) having a small structure including the outer edge 6a which is an arc of the circle.
However, instead, conventional strands made from round wires may be used. Further, non-round strands having grooves of suitable cross-section may be used.

A core having a solid cross section provides the strand 4 with good support. Having a groove 2 of sufficient depth,
By providing a sufficiently large cross section to the core, the effective clearance between adjacent strands 4 (working cl
earance) guarantees even the breaking load of the rope. The use of two independent (external and central) members 1, 3 selects the properties of the members 1, 3 to meet various requirements for the physical (and chemical) properties of the overall core. To make things possible.

In order to define the preferred size of the core, the diameter d ₁ indicates the diameter of the outer strand 4 of the rope and the diameter d ₂ is the root diameter of the grooved member 1, ie in any two diametric directions. See FIG. 1, which shows the minimum distance between the bottoms of the facing grooves. Also with respect to the type and structure of any given rope, the smallest root diameter d ₂ may be expressed as a function of the diameter d ₁ of the outer strands. The exact relationship depends primarily on the number of external strands in the rope and the twist angle (or pitch) at which these strands are twisted, although the structure and practical efficiency of the strands are considered elsewhere. For example, different elements are required for a rope whose strand is substantially triangular. Regarding the structure and twist of a more general round strand rope, the following relationship can be recommended.

[0011]

The two parts 1, 3 may be made from the same type of plastic material or from different types of plastic material. For each case, the plastic material
For example, it may be selected from the following types. Polypropylene Polyethylene (medium to high density) Polyester (Dupont registered trademark Hytre
l etc.)

The physical properties of the specific grades of the materials and their properties are shown in Table 2 below.

[0014]

The above characteristics are used for illustration purposes only. With some loss of rope flexibility, additional property enhancements can be obtained by increasing the material hardness or by including reinforcing fibers (eg, glass fibers) in the polymer.

Optimum blend (combination) of core properties
Can be obtained by using two dissimilar materials to make the core. For example, the external member 1
It may have a material with good elongation properties to accommodate high bending strains, and may be locally deformed to provide close conformity to the surface shape of the outer strands of the rope However, the central member 3 is
It is preferred to be composed of a higher hardness and stiffer material, possibly including reinforcing fibers.

Whatever material is selected, the core is preferably machined in two separate extrusion operations, the first operation of which creates the solid cylindrical member 3. Solid cylindrical member 3
, A lubricant or a release agent may be added. Then
This is sent to the extruder for further operation to create the grooved member 1, the central member 3 greatly contributing to the control of the second extrusion operation.

The size of the central member 3 can vary with respect to the size of the core, such that one size of the central member is used over a range of different sizes of the core; Thereby, savings in manufacturing costs can be achieved. However, the sectional area of the central member 3 is
Preferably at least 40% (more preferably at least 45%), preferably at most 60% (more preferably at most 55%) of the cross-sectional area of the core, the preferred ratio is
Approximately 50% (allows for uniform extrusion speed)
It is. Thus, the center member 3 preferably has a circular cross-section with a diameter d ₁ of at least 70% (more preferably at least 75%) of the root diameter d ₂ . That is, the diameter d ₃ is at most 90% (85%) of the diameter d _2.
Is more preferable), and a preferable ratio is about 80%.

[0019]

The present invention provides a core that avoids and mitigates the disadvantages of conventional reinforcing members for wire ropes.

[Brief description of the drawings]

FIG. 1 is a line sectional view of a core for a wire rope.

FIG. 2 is a line cross-sectional view of a wire rope including a core.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 External member 2 Groove 3 Center member 4 Strand 6 External wire 6a External edge

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Michael Thomas Badft Dien 47 United Kingdom Doncaster West Besaker Hennings Close 16 (56) References JP 4-214488 (JP, A) JP 4-A 214486 (JP, A) UK Patent Application 2219014 (GB, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) D07B 1/00-9/00

Claims (6)

(57) [Claims] 1. A core for a wire rope, comprising: a tubular outer member formed by extrusion of a plastic material; and a highly rigid solid cylindrical center member formed by extrusion of a plastic material. The cylindrical inner surface is in close contact with the outer surface of the central member, and is symmetrically disposed on the outer surface of the outer member at predetermined intervals to receive corresponding wire strands of the wire rope. A plurality of spiral continuous grooves are formed, an outer diameter of the center member is at least 70% of a valley diameter of an outer surface groove of the outer member, and a cross-sectional area of the center member is at least a core cross-sectional area. 40
% Core. 2. The core according to claim 1, wherein the plastic material of the central member includes discontinuous reinforcing fibers. 3. The core according to claim 1, wherein a thin film of a lubricant or a release agent is interposed at a boundary between the outer member and the center member. 4. The core is formed by two separate continuous extrusion steps, the first step forming a center member and the second step forming an outer member outside the center member. A method for manufacturing a core according to claim 1. 5. A wire rope comprising: the core according to claim 1; and a wire strand received in each groove. 6. The wire rope according to claim 5, wherein the core prevents contact between the strands.