US2991615A - Rope - Google Patents

Description

2 Sheets-Sheet 1 INVENTOR.

ROBERT L. STANTON R. L. STANTON ROPE IG. I.

v //4/ H P 2 \M FIG.2.

July 11, 1961 Filed March 19, 1958 July 11, 1961 STANTON 2,991,615

ROPE

Filed March 19, 1958 2 Sheets-Sheet 2 INVENTOR.

ROBERT L. STANTON United States Patent 2,991,615 ROPE Robert L. Stanton, Maplewood, NJ., assignor to Amerij can Manufacturing Company, Incorporated, a corporation of Delaware Filed Mar. 19, 1958, Ser. No.'722,575

' 4 Claims. (Cl.'57144) This invention relates to plastic cored rope and the method for constructing the same.

In its most common and simplest construction, present day rope or cordage is composed of a cluster of cylindrical strands of intertwisted fibers or yarns, helically laid around one another or about a heart or core, which is usually composed, of hemp or other twisted yarn. Rope or cordage of this construction has been found to possess no peripheral uniformity and, in addition, is subject to certain inherent weaknesses when subject to heavy work and sudden stress.

It is well known that a lack of uniformity in rope is due to the inherent non-uniformity of natural fibers and some synthetic fibers, after spinning. It would, therefore, appear that to obtainrope uniformity, it would be necessary to bring about dimensional adjustments within the rope structure to compensate for such localized fiber non-uniformity.

This invention, therefore, has for its principal object to provide rope or cable of the characterreferred to with a centrally and axially disposed, deformable core or tube of plastic material which will under-go permanent adjustments in its periphery when subjected to compression exerted thereon by the outer strands during the laying operation, thus providing the compensation necessary to bring about the desired rope uniformity.

Itis also obvious .thatrope with fiber cores is subject to considerable internal friction and abrasivewear in that the fibers of the core rubagainust the fibers of the outer strands, thus resulting in a shorter life use of the rope. Similar considerations apply to conventional three strand ropes the strands of. which rub against and abrade each other. It is, therefore, a further object of this invention to eliminate or materially reduce the presence of this internal friction or abrasive wear by the provision of an axially disposed flexible and elastic core of plastic material. This invention also forms an arrangement which provides an effective support as between the strands themselves.

Another weakness inherent in the ordinary fiber core rope is that the fiber core is prone to break when heavy or, sudden loads are applied to the rope. Under such conditions, ordinary fiber cores elongate less than the outer strands and break prematurely, leaving the rope distributed and unbalanced and subject to early failure.

It is another object of this invention to provide a rope construction with a flexible and elastic core or tubing of such characteristics that it will not break when heavy or sudden loads are applied to the rope and wherein the outer strands remain in their proper relative positions and share tensile stresses equally under the most severe operating conditions. It is apparent that the core or tubing acts as a cushion and imparts more life to the rope itself by absorbing a large portion of the shock loads encountered during use. Ordinary fiber centers can absorb no shock loads because of their low elongation properties.

Other and further objects, benefits and advantages of this invention will become apparent from the description thereof contained in the annexed drawings, specifications and claims, or will otherwise become obvious. It will be understood that the invention herein disclosed may be used for other purposes for which the structure and arrangement are adapted.

r 2,991,615. Patented July 11, 1961 In the accompanying drawings:

FIGURE 1 is a front elevational view of a die assembly showing a section of rope in the process of passage therethrough and embodying the instant invention;

'FIGURE 2 is a view similar to FIGURE 1 showing a section of rope in the process of passage through the die under the increased application of pressure; f

FIGURE 3 is a cross section of rope embodying the instant invention in which the deformation of the core tubing is at a minimum as a result of the application of light radial pressure during the laying operation;

FIGURE 4 is a cross section of a rope embodying the instant invention in which deformation of the core tubing is considerably more pronounced than that shown in FIGURE 3, due to the application of increased radial pressure during the laying operation; and

FIGURE 5 is a fragmentary view of a four strand rope in accordance with the present invention, partly broken away to illustrate the deformation of the core during the laying operation. I

In its more general aspect, the instant invention comprises a rope construction wherein the outer or peripheral surface of the rope is maintained at a uniform diameter and wherein the irregularities or non-uniformities of the fiber plies or strands comprising the rope are displaced to the rope center. Furthermore, the axial space or rope center formed in multi-strand ropes is occupied by a tubular elastomeric plastic material which has been deformed so as to compensate for the aforementioned irregularities and to fill in the interstices between the rope strands. In laying the rope conventional methods and apparatus, not shown, are employed. The condition of the rope at this stage is illustrated in cross-section in FIGURE 1. It will be noted that at this stage, the tubular core element 13 presents a cylindrical surface which has not been deformed in any manner. It is further to be noted that the voids 1-4 are formed surrounding said tubular member, due to the variations in the dimensions of the yarns and strands which comprise the rope structure. These voids also result from the helical twist which is imparted to the yarns and strands as well as from variations in tension etc., which occur during the preceding stages of manufacture. Similarly, such non-uniformities also occur along the outer peripheral surface of the rope structure itself as heretofore pointed out. In order to eliminate such dimensional differences occurring along the peripheral surface of the rope, in accordance with the present invention, radial pressure is applied to the rope surface whereby these non-uniformities are displaced in the direction of the rope center. FIGURE 1 illustrates a rope in the process of formation in accordance with the present invention. The rope structure is designated generally by the numeral 10 and comprises a number of assembled strands 11. Each of the strands is formed of a number of plies 12 of suitable filamentary material. A four strand rope is .illustrated, it will however be understood that this invention is not limited to any specific number of plies or strands. In the assembly process of such rope, the strands are first for-med by assembling and twisting a number of yarn plies. The strands thus formed are then helically twisted about the common axis of the rope. In the usual form of rope construction, a void or space results at the center of the rope and this space may be occupied by a core of suitable material. I

In accordance with the present invention a tubular core element 13, having a substantially cylindrical crosssection is introduced into the rope center or axis, during the process of laying the rope strands. As the rope is withdrawn from the laying device, itis passed through a die arrangement designated generally by the numeral 15, which imparts a uniform diameter and peripheral surface thereto by displacing the non-uniformities-therfifl from the periphery of the rope to the rope center. The die arrangement 15, through which the rope is drawn for this procedure, which is herein referred to as a sizing operation, is illustrated more particularly in FIGURES l and 2 Said arrangement comprises adie frame 16 within which there is disposed a split die comprising the stationary die member 17 and a movable die member 18, The die members are each provided with semi-circular openings as indicated at 19 and 20 which are disposed in confronting relation. In their assembled form the die members thus provide a circular opening which is-rnade'to correspond to the-desired circumferential configuration and diameter ofthe finished rope. The die frame 16 is provided'with an arm 21 which is pivotally supported upon the die frame as shown at 22 and carries a depending projection 23 which bears upon the upper surface of the movable die member 18 thus exerting pressure in the direction of-the mating stationary die member 17. The free end ofpivoted arm 18 is weighted as shown at 24' to exert desired pressure upon the movable die member 18. As the rope is'drawn through the die arrangement, radical pressure-is applied to the rope body causing it to be compressed and displacing any enlarged areas in the rope structure in the direction of the. central axis of the rope. The die arrangement herein described is advantageously employed to produce the desired result since it provides for the ready interchangeability of dies and for the regulation and control of the pressure applied thereby. Furthermore, the die arrangement. permits ready, access in the event thatit becomesjammed or clogged or if the rope breaks for any reason during the course of the sizing operation. It will be understood however, that other forms of'die arrangementmay be employed in the practice of this invention. Thus for example, a single die unit may be employed such as a tubular member having a progressively tapered bore to provide for the gradual sizing of the rope structure as it passes therethrough.

As heretofore stated, a tubular core element 13 is introduced into the rope center during the laying operation and forms part of the rope structure during the herein above described sizing operation. The core element 13 comprises a relatively thick walled tube of plastic material. In laying the rope strands, the core-is merely subjected to contact pressure of the rope strands and is sufliciently dimensionally stable to retain its initial cylindrical' configuration. However, upon passage through the die arrangement, the yield value of the plastic material is exceeded by reason of the applied pressure and the core materialis caused to flow into the interstices or voids which are distributed along the center surfaces of the rope. During the sizing operation therefore, the core material is deformed and dimensionally adjusted tocompensate for random or localized fiber or strand nonuniformity. The degree of deformation of the plastic core may be adjusted by regulation of the amount of external pressure applied to the rope structure as for example by increasing the weights 24 as shown at 25. Thus the applied pressure may be relatively light, so that the plastic flow of the core materiaLis limited to suchlocalized areas of non-uniformity. The plastic material is therefore displaced to adjacent voids to a relatively small degree.v This condition is shown moreparticularly in FIGURE 3. On the otherhand where the particular application makes. it desirable, considerably more pressure may be applied so that the plastic. material comprisingthe core is caused to be extruded into, and enter, all voids, interstices and other spaces in the rope center. In this event the dimensional adjustment of the core material causes it to occupythe helical grooves normally formed at the rope center, effectively supporting and anchoring the rope strands against displacementandpreventing the entrance of dirt orgrease in this region. This condition ismore particularly illustrated in FIGURES 2 and 4.

4. FIGURE 5 further. illustrates the configuration. of. the core after deformation in the sizing operation. It will be noted that ahelically grooved surface is formed on the core which conforms exactly to the complementary configuration of the interior of'the rope center. The depth and configuration of thisgroove, and deformation of the wall is controlled by the degree of die pressure applied and by the localized variationswhich exist or are displaced, to the rope center. The. core material i's'thus translated to a second dimensionally stable configuration.

The tubular.core:-13 isadvantageously formed of plastic material as by the: extrusion. process, and is dimensionally stable when introduced into the rope body. It has been found advantageous to employ a'tube formed of plasticized polyvinyl chlorideresin for-this purpose, The resin to plasticizer ratio is adjusted so'that'thecore material has a durometer hardness of between -90: Suitable formulations for the core material comprise between 64 to 66 parts of polyvinylchlorideresin to from 34- to3'6 parts ofiplasticizer. The plasticizer employed may be of conventional type such as dioctylphthalate, tricresylphosphate and similar plasticizing materials well known in the art. Fillers may also be incorporatedin the formulation. The core, as heretofore stated, is advantageously formed by the continuous extrusion process.

The diameter and wall thickness of the tubular core may be varied in accordance with the requirements of the particular application. Thus, as is well=knownin the art, antincrease in the number ofstrands in the rope structure results in an increase in the diameter of the space formedin the rope center. Such ropes would; of coursev require an increase inthe diameter of the core material. Although variation in' the wall thickness ofthe corein ay, be tolerated within limits, it has been found advantageous to employ a: ,wall't hickness which is at least as large asthe diameter of the core lumen. The tubular configurationofthe core material significantly contributes to the overall advantages of therarrangement. The deformation of the core 'materialis considerably facilitated .by the absence of material at the centerv thereof. The applied pressure does not only cause adeform'a tion of the core material by initiating plastic flow but also significantly. distorts the. configuration of the core wall so asto allow the core to more readily accommodate itself topthe requisitefdirnensional changes. The tubular configuration of the core thus allows the wallthereof to be placed under elastic stress and contributes to they desireddegree of elasticity and resilience of the material. The presence of an air pocket at the core, center, is a further-factor contributing to the desired resilience. The core material itself is dimensionally stabilized after plastic. deformation so that it fills the interstices of, the rope center and compensates for irregularities or localizeddimensional differences displaced to, the rope center. The core is thusintegrated inthe rope structure, and the-elasticity thereof permitsit to follow dimensional changes of they rope strands during use. By thismeansthe core provides additional support for the rope strands, maintaining them in 1 relatively fixed, relation and. distributing the stresses and strains applied to the rope body more, evenly. The air pocket formed in the core also contributes 001 the, requisitemesilience without the sacrifice of Wall thickness, hardness. or'strength of the core-materialitself. A distinct cushioning is introduced into the-structure .by reasonof the aforesaid tubular. configuration-of an; elastic core material,

From'the foregoing it will beseen that a more uniform rope product has been effectively achieved.- Actualcomparative measurements have shown that, in practicing the foregoinginvention, a rope structureisachievedwhich is: 30% more uniformthan comparable products made by prior art methods and using'prior-art core materials. Theflexible tubing introduced. into the rope center is elastic and. will not break when heavy-or sudden; loads e applied. The outer strands of, the ropeare-maintained in their proper relative positions, and share tensile stresses equally under the most severe operating conditions. This continuous, equal load distribution assures longer rope life. As distinguished from a fiber core, for example, the instant core due to its elasticity will elongate uniformly with the outer strands, thereby avoiding premature breakage of the rope or the introduction of any distortion or unbalance therein. The elastomeric characteristic of the core material and the structure thereof introduces an elastic cushioning effect which imparts some life to the rope and absorbs a large proportion of the shock encountered during use. Furthermore the invention herein disclosed results in a reduction of internal abrasive wear in the rope since during fabrication, the elastic tubing is caused to flow into the interstices between the fiber strands in such a manner that dirt and other abrasive material frequently found present in rope cores, are sealed out. The tubing itself is far less abrasive than other core material with the result that fiber strand life is increased considerably.

I have here shown and described a preferred embodiment of my invention. It will be apparent, however, that this invention is not limited to this embodiment and that many changes, additions and modifications can be made in connection therewith without departing from the spirit and scope of the invention as herein disclosed and hereinafter claimed.

I claim:

1. The process of forming a rope comprising intertwisting non-metallic filamentary material and laying the strands thereof over a core of plastic material, passing said intertwisted filamentary material and core through a die opening of smaller diameter than said rope as initially formed thereby, subjecting the peripheral surface of said rope to pressure sufficient to exceed the yield value of said plastic core to thereby cause said plastic material to flow in plastic condition and dimensionally conform itself to portions of the configuration of said strands along the rope center whereby said plastic core remains dimensionally stable in conformed condition after its emergence from said die opening.

2. A rope comprising strands of intertwisted filamentary material helically laid over a tubular core of elastomeric material, said rope being of uniform outer diameter throughout its length, the localized dimensional irregularities of said intertwisted filamentary material comprising said rope being displaced to the rope center, said core material being correspondingly dimensionally deformed to conform to the irregularities of the configuration of said intertwisted strands along said rope center.

3. A rope comprising strands of intertwisted filamentary material helically laid over a tubular core of elastomeric material, said core defining an axially extending air pocket, said intertwisted filamentary material having localized dimensional irregularities disposed along the rope center only, said rope being of uniform external diameter throughout its length, said core material being dimensionally stable and conformed to the configuration of the irregularities of said strands along said rope center.

4. The process of forming a rope comprising intertwisting filamentary material and laying it over a tubular core of elastomeric plastic material, drawing said rope through a die opening and thereby subjecting the peripheral surface of said rope to pressure sufficient to displace localized dimensional non-uniformities initially formed along the peripheral surface thereof during the intertwisting operation toward the rope center, said pressure being sutficient to cause plastic flow of said core material to thereby conform said core material to the configuration of said rope center to which said non-uni-formities have been so displaced, whereby said rope retains its uniform external diameter after passage through said die opening and said core material remains stable in deformed condition.

References Cited in the file of this patent UNITED STATES PATENTS 1,769,945 Erkert July 8, 1930 1,868,681 Wyatt July 26, 1932 2,074,956 Carstarphen Mar. 23, 1937 2,348,234 Warren May 9, 1944 2,480,005 Ewell Aug. 23, 1949

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