US2939732A - Cable fitting - Google Patents

Description

June 7, 1960 W. L.. RRRRRRR ER, JR 2,939,732

ATTORNEYS June 7, 1960 w. 1 ROCHESTER, JR 2,939,732

CABLEFITTING Filed May 19, 1958 2 Sheets-Sheet 2 INVENTOR WILL/,4M L. ROCHESTER JR.

ATTORNEYS United `States Patent O CABLE FITTING William L. Rochester, Jr., Warrenton, Va., assgnor to Rochester Ropes, Inc.

Filed May 19, 1958, Ser. No. 736,070

4 Claims. (Cl. 287-78) This invention relates to terminal type fittings for use with strand, flexible cable, wire rope and the like.

Wherever wire cable is used, there is a necessity for attaching a tting of some kind, either at the ends of the cable or at an intermediate point on the cable. Better methods of applying ttings have been the goal of Workers in this artfor many years, but they have only developed a limited number of successful styles, for example: (l) wire rope sockets applied with molten zinc, (2) hand splices, (3) swagings, (4) pressed-on fittings, and (5) wire rope clips and clamps.

These prior art types of fittings require very expensive and bulky machinery to apply, a high degree of manual skill, or they do not develop suicient efficiency for the degree of effort required. The prior art wire rope sockets develop, when properly applied, 100 percent of the breaking strength of the cable. rect application are correct temperature of molten Zinc, purity of zinc, chemical cleanliness of the open and brushed end of the cable to which it is to be applied, and correct alignment of the socket on the wire rope prior to zinc being poured. The cost of labor `and materials for this fit-ting is quite high, labor and materials exceeding the cost of the actual fitting itself.

The hand splice on cable requires a high degree of manual skill and strength, in addition to the splicing tools which, although not expensive, are bulky and not portable. A correctly applied hand splice cannot be trusted to exceed 75 percent of the breaking strength of the cable used.

Workers in the prior art have discovered that swaging produces a fitting which often is stronger than the cable itself. Other workers have found that some fittings could be applied by hand tools whichwere quite satisfactory up to a certain strength, but were not of the neat and smooth appearance of Vthe usual machine-applied swage-type. Appearance as well as strength, of course, is of vital importance around consumer viewed fittings such as those found in yachts and airplanes. Swaged fittings involve an expensive, -very accurate machined fitting, applied usually by means of a rotary swaging machine which is both non-portable and very expensive, and a high degree of skill in the operator of the machine applying this fitting. The cost of machinery to apply fittings to rope in excess of 1/2" in diameter is extremely high because of the power needed and the size of the machinery used. This tting will develop 100 percent of the breaking strength of the rope.

Clips and clamps, although inexpensive, are unsatisfactory wherever appearance and strength are paramount.

One prior ar-t method of applying ttings has involved the use of an inner metal core tapered to conform with a `tapered inner surface of an outer sleeve. Such .prior art fittings provide Vsome degree of grip on the cable member, but they all require an unreasonable amount of power to be applied to grip suiiiciently to approach the breaking strength of the cable. This excess power which must be `applied normally distorts the designed shape of the cable which materially reduces the actual strength thereof. One object of the invention described herein is to provide fittings for cables which may be applied without The factors involved in cor-v the use of expensive machinery with the application of a minimum amount of power, without highly skilled operators, and which fittings normally will develop at least percent of the design strength of the cable to which applied.

These and other objects of the invention will be readily understood by lreference .to the following description and accompanying drawings, in which:

Fig. 1 is a longitudinal exploded view of one embodiment of the invention shown partly in section;

Fig. 2 is a sectional view of the embodiment of Fig. l, with the parts assembled;

Fig. 3 is an end view of one unit of the sleeve section shown in Fig. l;

Fig, 4 is a section taken along the line 4-4 of Fig. l;

Fig. 5 is a section taken along the line 5-5 of Fig. 2 showing the sleeve cold flowed on the cable;

Fig. 6 is a perspective view showing a further embodiment of the present invention, showing a lone-half portion of a malleable sleeve section;

Fig. 7 is a close-up View of a conventional cable;

Fig. 8 is a View similar to Fig. 4 with an elliptical figure imposed therein to facilitate further description of the invention;

Fig. 9 is a plan View showing a further embodiment of the invention.

The first embodiment of this invention described below accomplishes all of the objects and advantages of a machine swaged tting through the use of a structure generally comprising a malleable sleeve pre-shaped internally to be fitted onto a portion of the cable and pre-shaped externally to generally repeat the internal configuration, a compression member to surround the malleable sleeve, and a terminal piece connected to the compression member through the use of a thread arrangement by which tightening of the terminal connector to the compression member will result in the malleable sleeve being cold flowed into the interstices of the wire cable.

Referring now to Fig. 1 of the drawings, 10 indicates a complete tting adapted to be placed on the end of cable 20. A malleable sleeve, generally designated as 30 in the embodiment shown, is made of a series of rings 31. Referring -to Fig. 3, it can be seen that the interior surface 39 and the exterior surface 33 of each of said rings generally approximates the lay of the cable; i.e., the configuration of .the cable Z0, which generally comprises, as shown in Figs. 4 and 5, six outer strands 21 and an axial strand 22. Each strand, as shown in Fig. 7, is composed of a series of wires 23. In the form shown in Fig. 7, the wires 23 are set with a reverse twist relative to that of the strands 21. The strands 21 form lands 24 along their outer surfaces and form grooves 25 along their adjoining surfaces.

The malleable sleeve sections 31, as shown particularly in Figs. l, 3 and 4, are provided internally with lands 34 and grooves 35 generally mating with the lands 24 and grooves 2S of the cable 20. The sleeve sections 31 are provided externally with lands 36 and grooves 37 which generally repeat the interior lands and grooves 34 and 35. The sections 31, in one form, taper or decrease progressively in diameter, away from the end of the cable, as in Fig. l.

While the exterior surfaces of the malleable sleeve 30 in preferred form is shown in tapered form having a taper slightly greater than the taper of the internal surface 41 of the outer compression member 40, it will be apparent that the present invention is not limited to the provision of a taper on the exterior surface of the sleeve 30. In the event a taper is employed, it is preferable to construct the taper sufficiently low pitched to prevent action thereof as a shoulder through friction, particularly in such construction, as s hoWn in Fig. l, where the internal surface area 42A is first contacted by the most reu mote portion 32 comprising the largest tapered portionv 32 of the malleable sleeve 39.

After the rings 31 have been properly arranged according to taper on the cable. Z6, the compression member 4t2# is1 slipped over the sleeve. The member 4d has an interior portion-V threaded at 45; and another interior portion` tapered; at 41. This taper if can be the same as the taper 36 of sleeve 30, or it can be less than the taper ofthe sleeve 30, as represented by the line 36; The rings 3'1 progressively decrease in outside diameter, so that their resultant taper, represented by line 36, is the same as or less than the taper 4f of the member di);

To complete. the fitting, a ten'ninall connector 50 is provided, consisting of an abutment portion 51, a threaded portion 52 and an anchorage hook or eye portion 53'.

The interior cross sectional' diameter atA point 42 of the member 40 is slightly less than the maximum outside diameter of the most` remote and maximum diameter portion 3:2V of the malleable sleeve30. As the member 40 ismoved toward the sleeve 30 in Fig. l, the ring' will act asJ an abutment. The terminal connector Sii i's then threaded into member 4t) at 43. The connector is rotated to force taper 41 into. progressive abutment with portion 31. By. virtue ofthe. present'construction, the malleable sleeve 30 is finally collapsed and cold flowed in and about the cable As the threading continues, preceding portions of the core come into progressive abuttingY contact with taper 41 of the member 4b until the entire sleeve is collapsed and the metal cold flowed into the interstices of the cable.

It willlbe noted that due to the difference in tapers of 41 and 36.there is a point by point circumferential contact made along the entire malleable sleeve. This point by point application of pressure taken. in conjunction with the high mechanical advantages gained through the use` of the threads or the like, cold ows the sleeve into. the interstices of the cab-le. Fig. 2 shows the sleeve completely'cold; flowed, and Fig. 5 is an enlarged cross sectional viewl thereof showing the sleeve metal cold flowedr into. the interstices of' the cable.

Despitethe tremendous pressures concentrated through the point by point application'` of power, and developed by. the mechanical' advantage of screw threads, the present construction provides further assurance of obtaining maximum strength. This further assurance becomes increasingly important as the diameter of the cable becomes greater.

One l'aw ofv mechanicswhichV is to be. accounted for in applying this type fitting can best be expressed by the visualization of`a walled cylinder whose cross sectional shape isa perfect circle. When an equal force is applied to all points along the exterior circumference of this cylinderY directly toward the center, this force is transferred from a force toward the center to a compressive force Within the Wall of the cylinder. Metal being relatively incompressible, a cylinder of this type builds up a very high resistance'to being compressed, collapsed or swaged.

One reason the prior art has never reached the degree of streng th sought apparently is because the shape of the malleable portion either is, or becomes, a cylindrical tube prior to the filling of the cable portion between the strands. This may be expressed by the mathematical phenomenon described symbolically in A. E. H. Loves formula (Marks Handbook-McGraw-Hill Book Company, Third Edition, page 433):

P=collap'sing pressure, p.s.i.

t=thickness of tube, in inches:

D'=outside diameter of tuhe,.in inches E==mod'ulus of elasticityV m=P-oissons ratioY (seepage 412 of1Marlss Handbook) On page 433 of the Handbook there is also given a correction factor for ellipticity andY variations. in. thickness. The correction factor demonstrates the dramatic reduction in force necessary'to collapse a tube which deparents from true circular shape. This correction factor (C) can be expressed as: C:(Dmm/DmaXWUmm/tmx. v

When considering this correction factor, Loves formula become P=[2CE/ l*m2] (t/D)3 for thin tubes, where t=average thickness, and Dis diameter in inches.

A simple applicationl of` these formulaeV indicates the mode of operation, of the present invention. Assume for the purposes, of the problem that it is intendedto compress a brass core of 1/1'6 thickness and having an' outside diameter of For. brass` tubes E=14,000,000 and ml=1.357, therefore collapsing pressure 204,000,000) @ies 0)- uerena X es 1*:1/16"l Dmax=largest outer diameter=%" Dmm=srnallest outer diameter=.292

Correction factor :(Dmin/DMQSX (Tiniu/ Tum)s haar grani thereforel the collapsing pressure necessary to collapse the fitting as designed will be P= .102, .32,090 :3,270 psi.

It will be noted that' each non-circular element will have a tendency to compress, or collapse at almost/o the pressure necessary to compress or collapse a true tubular element. It is desired to point out that the invention is not to be restricted to any particular theory, such as that propounded above, the advantages being obtained by the novel structureof the present invention.

The phenomenon expressed in the above formulae appear to be related to the fitting combination herein described. In'breaking up the tubular sleeve into a series of non-circular sleeves, the entire sleeve will have a greater tendency to collapse. The shape ofthe sleeve must be such that a circular tube will not be created prior to the cold owing of sufcient metal into the interstices of the cable.

Another advantage of the configuration can be seen in Fig. 8. When a pressure P is applied at a point on the land 33 of the sleeve 36, forces P and P" are applied in a non-concentric direction which provides for improved multi-directional cold flowing of the malleable sleeve metal. Y

Having the inner and 'outer surfaces of the sleeve generally conform to the surface of the cable, has'the additional. advantage of requiring the metal to be cold flowed. only a `short distance before yreaching the interstices of thecable; i.e., the sleeve metal is already preformed into the grooves 25.

In the preferred construction, and referring to Fig, 8, a. circle 61 struck about the dualaxis, O, of the cable andf sleeve, which circle is tangent to the points 35a 011V the inner surfaces 35 farthest from center O, will also pass through the bottoms 37a of the outer grooves 37. Sucht geometrical accuracy, while preferred, isillus;

trative rather than restrictive of the invention; so that circle 61 passes only approximately through points 37a and 35a. This avoids the difficulty of compressing or deforming a cylinder.

A further embodiment of the malleable sleeve 30 is `shown in Fig. 6 where the sleeve 70 is cast into two longitudinally separated pieces each of which is of the shape shown in Fig. 6. The interior surface 71 has the general shape of the cable 20 and the exterior surface 72 likewise has a general configuration like the cable 20, and in addition, preferably has a taper 73 similar to taper 36 in the embodiment of Fig. 1.

Fig. 9 shows a further embodiment, the fitting being in the form f a sleeve having a cable-shaped exterior 81 and a cable-shaped interior 82. The tting has an integral terminal connector anchorage portion 83. This embodiment has the further advantage that it may be cold flowed onto Ia cable by means of a conventional press or swaging machine of very low power rate. The fitting 80 in effect serves the same purpose as the malleable sleeve in the embodiment of Fig. 1 with a connector portion already attached.

Referring now to Fig. 7, disclosing a conventional wire y cable 20, vthe primary strands 21 `are shown twisted in one direction, while the wires 23, making up each primary strand, are twisted in an opposite direction. Thus, it will be apparent that when fittings of the present construction are cold owed into the interstices of the cable, a resistance to rotation in either direction is created. Also, it will be apparent that the resistance the fitting has to slipping oft the cable is, in effect, equal to the total cross-sectional shear resistance of the metal cold flowed into the interstices. The holding principle involved in this invention is not primarily one of friction but rather one of shear resistance.

In a general manner, While there has been disclosed in the above description, What are deemed to be the most practical and efficient embodiments of the invention, it will be understood that the invention is not limited to such embodiments as changes may be made in the arrangement, disposition and form of the parts without departing from the principle of the present invention as comprehended within the spirit and scope of the accompanying claims.

I claim as my invention:

1. A fitting for a cable comprising in combination, a malleable sleeve and a compression member, said sleeve adapted to iit between a portion of said compression mem ber and said cable, the exterior surface of the sleeve and the interior surface of said compression member being in contact at one point and being progressively further out of contact along their length toward the end oppo site said point Iof contact, said compression member having an interior threaded section, a threaded terminal anchorage member adapted to mate with said threaded section whereby said malleable sleeve will be compressed progressively as said anchorage member is tightened into said compression member.

2. A malleable sleeve adapted to be cold iiowed onto a wire cable of the type having lands and grooves on the surface thereof along its length and throughout its cross-Section, said sleeve having on its interior and exterior surfaces lands and grooves generally conforming to the configuration of the lands and grooves of said wire cable, wherein a circle about the axis of the sleeve as a center, and having a radius passing substantially through the bottoms of the several exterior grooves is also substantially tangent to the interior grooves at points farthest removed from said center.

3. The sleeve `as defined in claim 2 wherein said exterior surface has a taper throughout the longitudinal length of said sleeve.

4. 'Ihe fitting as described in claim 1 wherein said malleable sleeve has on its interior and exterior surfaces lands and grooves generally conforming to the configuration of the lands and grooves 'of said cable.

References Cited in the file of this patent UNITED STATES PATENTS 570,631 Hannum Nov. 3, 1896 1,258,580 Lassiter Mar. 5, 1918 1,867,043 Wirschitz July 12, 1932 2,060,864 Hedler Nov. 17, 1936 FOREIGN PATENTS 340,081 Great Britain Dec. 24, 1930

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