US3468569A

US3468569A - Terminal fitting for wire ropes

Info

Publication number: US3468569A
Application number: US521389A
Authority: US
Inventors: Donald S Ballard; Charles R Wilson; Harlan G Burns
Original assignee: Armco Inc
Current assignee: Armco Inc
Priority date: 1966-01-18
Filing date: 1966-01-18
Publication date: 1969-09-23
Anticipated expiration: 1986-09-23

Description

Sept. 23, 1969 I 5, BALLARD ET AL 3,468,569

TERMINAL FITTING FOR WIRE ROIES Filed Jan. 18, 1966 INVENTOR DONALD J BALLAED AND CHARLES E. W/LSON AND HA/ZLAN G. Bum/s,

United States Patent 3,468,569 TERMINAL FITTING FOR WIRE ROPES Donald S. Ballard and Charles R. Wilson, Kansas City, and Harlan G. Burns, Independence, Mo., asslgnors to Armco Steel Corporation, Middletown, Ohio, a corporation of Ohio Filed Jan. 18, 1966, Ser. No. 521,389

Int. Cl. F16b 7/00 US. Cl. 287-82 2 Claims ABSTRACT OF THE DISCLOSURE A wire rope end and a terminal fitting secured there-. to, the terminal fitting comprising a conical portion hav ng a tubular cylindrical extension, the cylindrical extension and the valleys between adjacent strands in the wire rope end being filled with an epoxy resin which is bonded to the individual strands and to the inner surface of the cylindrical extension.

This invention relates to a terminal fitting for wire ropes and more particularly to the combination of such a terminal fitting with a wire rope end.

Where a. wire rope end is to be secured to a piece of machinery which, during its operation, would subject the rope to vibration or fatigue type stresses, it is necessary to provide a terminal fitting for the wire rope. Such terminal fittings are conventionally used and they may be provided with forks through which a pin may pass or they may be provided with loops or rings in a conventional manner. In the past, the terminal fitting has comprised a tubular member of conical shape. The end of the wire rope was secured to such a fitting by seizing the wire rope a short distance from the end and unlaying the strands or brooming them. The broomed ends were then temporarily tied and the end of the rope was passed through the small end of the conical tubular member and the temporary tie then removed so that the broomed portion of the wire rope fanned out into the conical interior of the fitting. The fitting and the rope in such position were then held in a vise and molten zinc was poured into the conical tubular member to fill the interstices between the strands of wire rope to seal the broomed wire rope into the fitting.

In the prior art, it has been the practice to etch the broomed wires with acid to clean them thoroughly and to insure a good bond with the zinc.

In order to get the zinc to flow through the interstices into the broomed end of the wire rope, the zinc of course had to be molten and thus the broomed strands of the wife rope were subjected to quite a high temperature. This is known to have a deleterious effect on the fatigue resistance of the wires.

Furthermore, the etching of the broomed strands for cleaning results in minute stress-raisers and imperfections on the wire surface. These imperfections cause early failure of the connection when bending and vibration stresses occur. Corrosion can occur in the completed fitting if the acid used in etching has not been completely removed or neutralized prior to the application of the molten zinc. This is true also as to the fluxes which would normally be used to promote bonding, and which are corrosive in nature. Furthermore, it often happens that the strands just beyond the broomed portion and where they emerge from the conical tubular fitting will be slightly out of their original position in the wire rope and they are, therefore, more susceptible to fatigue. Additionally, when the wire rope and fitting are loaded under tension, there is a natural tendency for the rope to unlay or unwind. This tendency results in a small rotational movement of the rope up to the face of the fitting at which point the rope is least able to resist this motion because of the heat effects and the etching effects outlined above.

With the foregoing considerations in mind, a principal object of the present invention is to provide a modified fitting wherein the advantages of the prior art fitting with regard to the acceptance of zinc poured sockets are retained while at the same time providing for a substantial length of the wire rope beyond the broomed portion to be held in a fixed concentric and natural position to accept the bending and vibrational stresses and resist fatigue failure of the fitting.

These and other objects of the invention which will be described in more detail hereinafter or which will suggest themselves to those skilled in the art upon reading these specifications, are accomplished by that certain construction and arrangement of parts of which the following describes certain exemplary embodiments.

Reference is made to the drawing forming a part hereof and in which:

FIG. 1 is an elevational view of a typical prior art structure comprising a wire rope end and terminal fitting.

FIG. 2 is a cross sectional view of the terminal fitting of the present invention showing a wire rope end secured thereto; and

FIG. 3 is an enlarged cross sectional view taken on the line 33 of FIG. 2 showing a modification.

Briefly, in the practice of the invention the terminal fitting differs from the prior art fitting in that a tubular cylindrical extension is provided beyond the conical portion. This extension is of substantial length and is adapted to contain and hold in position a substantial portion of the wire rope in its natural condition. In general, an extension length of from 1 to 4 times the rope diameter is sufficient to achieve the results desired. It is preferably sealed with a hardenable substance which, in the process of hardening, will not damage the wire by either thermal or chemical effects but Will hold the rope securely and concentrically in said cylindrical extension.

Referring now in greater detail to the drawings, a typical prior art fitting is generally indicated at 10 in FIG. 1. The particular fitting shown has the

fork elements

11 and 11a, both of which have axially aligned apertures through which a pin 12 may pass. The pin may be held in place by a cotter pin 13. The fitting 10- has the conical portion 14 and the wire rope 15 enters the small end of the conical portion and the end of the wire rope beyond the face 16 of the fitting is broomed out to fill the conical space within the fitting 10. The wire rope is secured within the fitting by holding the assembly in a vertical position with the broomed end of the wire rope up and filling the fitting 10 with molten zinc after having plugged the lower end of the fitting 10 at the face 16 with clay or other suitable material to prevent the zinc from leaking through. The broomed end of the wire rope of course has been acid etched for cleaning and generally a flux is used in connection with the molten zinc. When the zinc has solidified, it will be seen that a conical plug is provided within the fitting 10 which is well adapted to resist pure tensile stresses. However, as pointed out above, the wire rope at and just outside the face 16 of the fitting is highly susceptible to fatigue failure as a result of bending or vibrational stresses for the reasons pointed out heretofore.

In FIG. 2, which represents an embodiment of the present invention, the numbering system responds to that of FIG. 1 insofar as it is applicable. It will be observed that the only difference in the fitting itself is that beyond the face 16 there is provided a cylindrical extension 17 of substantial length. The extension 17 may have a cylindrical inside surface or it may be provided with splines 18 as shown in FIG. 3.

In assembling the device of FIG. 2, the wire rope is seized in a conventional manner at and beyond the seizing it is broomed as at 20. Again the broomed end 20 is temporarily tied and passed into the fitting through the tubular extension 17 from the end 21 of the fitting so that the broomed portion of the wire rope 20 extends into the conical portion 14 of the fitting. The broomed portion may be etched as in the priorart and the cavity in the conical portion may be filled with molten zinc with the addition of a flux. If the seizing at 19 is not suflicient to prevent the molten zinc from flowing down into the area 22, a damming material will be used as is well known in the art. Thereafter the fitting is inverted so that that end 21 is uppermost and the tubular extension 17 is filled with a hardenable substance which will not damage the wire either by thermal or chemical effects but it will hold the wire rope 15 securely and concentrically within the extension 17. Various resins are suitable for this purpose and particularly the epoxy resins. The epoxy resin with a hardener added is simply poured into the extension 17 so that it fills the extension and the valleys between the strands of rope while the rope is carefully maintained in a concentric position with respect to the extension 17 The resin hardens in a relatively short time and thus holds the wire rope securely in its concentric position and in its natural state. If splines 18 are. provided as shown in FIG; 3, the epoxy resin also fills the splines so as to prevent rotation of the rope when subjected to tensile loads but to permit longitudinal stretching. The epoxy resin is indicated in FIGS. 2 and 3 at 22.

It will be understood that if desired the epoxy resin or other suitable material may be used to secure the broomed portion 20 of the wire rope instead of the zinc and this operates as well or better than zinc.

Prior art fittings have been tested in severe impact fatigue tests and have shown a life of 25,000 to 35,000 cycles before failure. Fittings according to the present invention exhibit a life in the vicinity of 1,000,000 cycles before failure. It is believed that the reason for this greatly increased life resides in the fact that a substantial portion of the rope in its natural position now accepts the bending and vibrational stresses and the wire rope in its natural position is better able to resist these strains and thereby give a longer operating life. The broomed portion accepts the tensile loads, but the Present invention forces all the strains to which the rope and fitting are subjected, excepting only tensile loads, to take place in a region removed from that where the wires have been deleteriously affected either by heat from the molten zinc or the etching procedure and in a region where the normal position of the strands in the rope have not been disturbed.

It has been found that a clearance between the wire rope and the interior of the extension 17 from about inch to about /2 inch on the diameter, is sufficient to obtain complete penetration of the epoxy resin into the entire length of the extension. The particular clearance in any case will of course depend upon the surface tension and fluidity of the particular bonding agent used.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In the combination of a wire rope end and a terminal fitting secured thereto which are to be used in connection with machines which will subject them to vibration and fatigue stresses, said wire rope end being seized near the end thereof and broomed beyond said seizing, said terminal fitting comprising a conical tubular member, the broomed portion of said wire rope end being seated in said conical tubular member, said conical tubular member and the interstices between the broomed strands therein being filled with a hardened substance to accept tensile stresses on said combination, the improvement wherein said hardened substance in said conical member is zinc, said conical tubular member is provided with a cylindrical internally splined extension of substantial length, the length of said extension being from about 1 to about 4 times the diameter of said wire rope, and wherein the cylindrical extension and the valleys between adjacent strands therein are filled with an epoxy resin which is bonded to the individual strands and to the inner surface of said cylindrical extension, filling said splines, and

holds the rope securely and concentrically of said cylindrical extension, whereby rotation of the portion of said wire rope in said cylindrical extension is prevented but longitudinal stretching thereof is permitted, and whereby a substantial portion of said wire rope is securely held and retained in its natural condition, to accept and withstand bending, vibration, and fatigue stresses, and to provide longer life for said combination.

2. The structure of claim 1, wherein the inside diameter of said extension is from about to about /2 inch larger than the diameter of said wire rope.

References Cited OTHER REFERENCES Beck, German printed application No. 1,174,871, published July 30, 1964.

The Condensed Chemical DictionarySixth edition, published by Reinhold Publishing Co., New York, 1961, p. 445 relied on.

LARAMIE E. ASKIN, Primary Examiner US. Cl. X.R.