US3824777A - Lubricated plastic impregnated wire rope - Google Patents

Abstract

A wire rope, and method of making same, is provided wherein the wire rope strands are coated with a heavy viscous lubricant prior to winding the strands into rope, and the lubricated rope is impregnated with a thermoplastic material to entrap the lubricant in the strands and core. The outer strands are held in spaced relationship during the plastic impregnating step, and the plastic material does not extend beyond the outer periphery of the wire rope.

Description

United States Patent [1 1 Riggs [111 3,824,777 July 23, 1974 LUBRICATED PLASTIC IMPREGNATED WIRE ROPE Peter Philip Riggs, Essex, England Amsted Industries Incorporated, Chicago, 111.

Oct. 5, 1973 Inventor:

Assignee:

Filed:

Appl. No.:

US. Cl. 57/149, 57/162 Int. Cl D07b 1/16, D07b 7/12, D07b 7/14 Field of Search 57/139, 144, 145, 149,

References Cited UNITED STATES PATENTS 1/1936 Hodson 57/149 X l/1936 Hodsoni.

Whyte....

Dietz 57/149 Lang 57/149 X Dietz 57/149 Riggs 57 149 Smallinger 57/153 x Primary Examiner-Donald E. Watkins [5 7 ABSTRACT A wire rope, and method of making same, is provided wherein the wire rope strands are coated with a heavy viscous lubricant prior to winding the strands into rope, and the lubricated rope is impregnated with a thermoplastic material to entrap the lubricant in the strands and core. The outer strands are held in spaced relationship during the plastic impregnating step, and the plastic material does not extend beyond the outer periphery of the wire rope.

7 Claims, 3 Drawing Figures LUBRICATED PLASTIC IMPREGNATED WIRE ROPE This invention relates to wire rope and particularly to the plastic impregnation of a lubricated wire rope.

There are many known methods of impregnating wire rope with various types of thermoplastic material for the purpose of improving fatigue life, reducing wire contact stresses, and inhibiting corrosion. It has been found, however, that prior art impregnated wire ropes have not always been entirely satisfactory. For example, it has been considered virtually impossible to plastic-impregnate a lubricated wire rope because of the gas created by the lubricant at the elevated temperatures required for plastic impregnation. For this reason, it has been standard procedure to clean and degrease all wire rope which was to be plastic impregnated. Furthermore, during the course of fabrication some of the rope strands are in contact while others have excess separation, thereby making uniform impregnation difficult to accomplish.

Two known methods exist for overcoming the latter difficulty. Controlled strand separation in plastic impregnated wire ropes has been achieved by the inclusion of oversized control wires in the strands, or by the use of the conventional parallel lay construction wherein the rope strands and core strands are integrated and closed simultaneously to the same lay length. Even the parallel lay construction, however, is limited to a steel wire rope core and only approximates even strand separation. Both of the foregoing methods have their limitations in that the first method requires special fabrication while the second method obviously limits the choice of constructions available for plastic impregnation.

It is a primary object of the present invention to produce a standard stock, heavily lubricated wire rope process to be described hereinafter may be applied to The lubricated wire rope is then preheated to a temwhich is impregnated with a load bearing thermoplastic such that the viscous lubricant is entrapped in the strands and core, the rope having a consistent wall thickness of plastic between the external wire rope strands.

Another object is to provide a lubricated plastic impregnated wire rope having a smooth, continuous outer periphery with increased bearing area but without increased rope diameter.

These and other objects and advantages will be apparent from the following description and accompanying drawings wherein:

FIG. 1 is a cross-sectional view of a typical wire rope formed in accordance with the teaching of the present invention;

FIG. 2 is a longitudinal sectional view through the strand gap controller and extruder head utilized in carrying out the method and forming the wire rope of the invention; and

FIG. 3 is an end elevational view of the strand gap controller.

The present invention utilizes a conventional wire rope 10 wherein individual wires 12 are wound into strands l4, and a plurality of strands are formed about a core 16 which is also preferably formed of a plurality of strands 18. It should be understood that the strands of the core 16 may be formed of a fiber material such as hemp instead of metallic wires as indicated in the drawings. The particular rope shown in FIG. 1 is given by way of example because the plastic impregnating perature in the range of to 275F., although best results are attained if the preheat temperature is in the range of to F. This preheating step is one of the two critical steps in the method of fabrication of this invention because at the temperatures involved, the lubricant does not form a gas during the later step of plastic impregnation. The other critical step in the novel process is the balanced separation of the outer strands of the wire rope at the time of plastic impregnation. This balanced separation of the strands is achieved by means of a strand gap controller mounted on the rope input side of a plastic extruder as shown in FIGS. 2 and 3. The strand gap controller serves to balance and equalize the strand lay at the exact moment of plastic impregnation so that the internal and external interstices between the strands are filled with equal amounts of thermoplastic, this being accomplished at lower temperatures than heretofore thought possible.

Referring to FIGS. 2 and 3, it is seen that the strand gap controller, indicated generally at 20 comprises a stationary outer casing 22 in which is rotatably mounted, by means of suitable bearings 24, a cylindrical head 26. Secured internally of and rotatable with head 26 is a strand profile insert 28. Passing through the center of insert 28 is an opening 30 formed to the contour of the outer strands of the particular rope being processed. As anon-rotating wire rope is fed axially through opening 30 with the outer rope strands fitting into individual strand slots 32, the strand profile insert rotates, as the rope advances, so as always to positively hold the strands equally spaced from each other.

The wire rope passes from the strand gap controller directly into extruder head 34, suitably mounted coaxially with the strand gap controller. The extruder may be of any conventional design and is shown as comprising a crosshead 36 having an opening 38 arranged to receive a mandrel holder 40 which carries a mandrel 42. Encircling the mandrel end of holder 40 and forming therewith a passage 44 is a die ring 46 held in position by a die retainer 48 and a face plate 50.

Secured to the output end of the die retainer 48 is a die holder 52 into which is threaded a die 54.

As the preheated wire rope emerges from the strand gap controller and passes through the extruder head, a flexible thermoplastic 55 (FIG. 1) is extruded, under a pressure in the range of about 2,000 to 4,000 PSI into the interstices of the rope, completely filling them down to the outer strands of the core. The thermoplastic can be any of those capable of being extruded such as polypropylene, polyurethane, polyethylene, nylon or tetrafluor oethylene. The opening 56 in the die 54 controls the coating thickness and in the present embodiment is just large enough to permit the wire rope to pass through, thereby limiting the diameter of the plastic to the nominal diameter of the wire. rope, as seen in FIG. 1.

impregnation of a lubricated wire rope with plastic as described above prevents entrance of foreign abrasive particles into the rope while sealing lubricant inside the rope, thereby increasing the rope service life. Another advantage is a reduction in wire notching effect and internal friction because the loads placed on the rope are shared substantially equally by the spaced internal wires. Furthermore, a lubricated wire rope, impregnated with plastic while holding the outer strands spaced from each other, will have extremely good resistance to fatigue and an increased ultimate breaking strength because of a reduction in internal wire contact, all while maintaining flexibility.

What is claimed is:

1. A method of making a wire rope comprising the steps of: winding individual wires into strands; forming a plurality of strands about a lubricated core into a multi-strand rope while simultaneously coating the strands with a heavy viscous lubricant; preheating the rope to a temperature in the range of about 100 to 275F.;

holding the outer strands of the wire rope spaced from each other and, while said strands are spaced, impregnating the rope with a plastic composition so as to entrap the lubricant in the core and the strands, the outer diameter of the plastic conforming substantially to the outer diameter of the rope.

2. A method according to claim 1, wherein the spacing step includes feeding the wire rope through a strand gap controller having an opening with its peripheral configuration conforming to the outer periphery of a wire rope with equally spaced outer strands.

. 3. A method of making a lubricated plastic'impregnated wire rope, comprising the steps ofzwinding iridividual lubricated wires into strands; forming a plurality of strands about a core into a multi-strand rope while simultaneously coating the core and the strands with a heavy viscous lubricant; heating the rope to a temperature in the range of about F. to F.; feeding the heated, lubricated rope through a strand gap controller to hold the outer rope strands equally spaced from each other and, while the outer rope strands are so spaced, extruding a thermoplastic composition under pressure into the rope to surround the rope strands to a predetermined depth and entrap the lubricant in the rope, the outer diameter of the plastic conforming substantially to the outer diameter of the rope.

4. A method according to claim 3 wherein the extrusion pressure is in the range of about 2,000 to 5,000 pounds per square inch.

5. A wire rope comprising: a lubricated core, a plurality of lubricated wire strands laid around said core, and a thermoplastic material filling the spaces between said strands to retain the lubricant in the core and in the strands, said thermoplastic material extending outwardly only to the outer periphery of the wire rope.

6. A wire rope according to claim 5 wherein said plurality of wire strands are equally spaced apart in circumferential direction.

7. A wire rope according to claim 6 wherein the thermoplastic material extends inwardly to the wire rope core.

Claims (7)

1. A method of making a wire rope comprising the steps of: winding individual wires into strands; forming a plurality of strands about a lubricated core into a multi-strand rope while simultaneously coating the strands with a heavy viscous lubricant; preheating the rope to a temperature in the range of about 100* to 275*F.; holding the outer strands of the wire rope spaced from each other and, while said strands are spaced, impregnating the rope with a plastic composition so as to entrap the lubricant in the core and the strands, the outer diameter of the plastic conforming substantially to the outer diameter of the rope.

2. A method according to claim 1, wherein the spacing step includes feeding the wire rope through a strand gap controller having an opening with its peripheral configuration conforming to the outer periphery of a wire rope with equally spaced outer strands.

3. A method of making a lubricated plastic impregnated wire rope, comprising the steps of: winding individual lubricated wires into strands; forming a plurality of strands about a core into a multi-strand rope while simultaneously coating the core and the strands with a heavy viscous lubricant; heating the rope to a temperature in the range of about 120*F. to 160*F.; feeding the heated, lubricated rope through a strand gap controller to hold the outer rope strands equally spaced from each other and, while the outer rope strands are so spaced, extruding a thermoplastic composition under pressure into the rope to surround the rope strands to a predetermined depth and entrap the lubricant in the rope, the outer diameter of the plastic conforming substantially to the outer diameter of the rope.

4. A method according to claim 3 wherein the extrusion pressure is in the range of about 2,000 to 5,000 pounds per square inch.

5. A wire rope comprising: a lubricated core, a plurality of lubricated wire strands laid around said core, and a thermoplastic material filling the spaces between said strands to retain the lubricant in the core and in the strands, said thermoplastic material extending outwardly only to the outer periphery of the wire rope.

6. A wire rope according to claim 5 wherein said plurality of wire strands are equally spaced apart in circumferential direction.

7. A wire rope according to claim 6 wherein the thermoplastic material extends inwardly to the wire rope core.

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