US3264017A

US3264017A - Anchoring means for flexible tension member

Info

Publication number: US3264017A
Application number: US492973A
Authority: US
Inventors: Lagarde Roe Howe
Original assignee: EW Bliss Co Inc
Current assignee: EW Bliss Co Inc
Priority date: 1965-09-10
Filing date: 1965-09-10
Publication date: 1966-08-02
Anticipated expiration: 1983-08-02

Description

' Aug. 2, 1966 R. H. LAGARDE 3,264,017

ANCHORING MEANS FOR FLEXIBLE TENSION MEMBER Original Filed May 9. 1963 2 Sheets-Sheet 1 INVENTOR ROE HOWE LAGARDE WW ATTORNEY Aug. 2, 1966 R. H. LAGARDE ANCHORING MEANS FOR FLEXIBLE TENSION MEMBER Original Filed May 9. 1965 2 Sheets-Sheet 2 FIG.8.

INVENTOR ROE HOWE LAGARDE ATTORNEYS United States Patent 3,264,017 ANCHORING MEANS FOR FLEXIBLE TENSION MEMBER Roe Howe Lagarde, Oxford, Md, assignor, by mesne assignments, to E. W. Bliss Company, Canton, Ohio, a corporation of Deiaware Continuation of appiication Ser. No. 279,672, May 9, 1963. This application Sept. 10, 1965, Ser. No. 492,973 3 Claims. (Cl. 28782) This application is a continuation of application S.N. 279,672 filed May 9, 1963 now abandoned, which was in turn a continuation-in-part of my copending application S.N. 154,011, filed November 21, 1961, now abandoned, which was in turn a continuation-in-part of my copending application S.N. 83,442, filed January 18, 1961, now abandoned.

The present invention relates generally to fittings adapted for use with a variety of flexible tension members such as synthetic or natural fiber rope, wire rope, webbing, and the like, and more particularly to an end fitting for a flexible tension member which is characterized by a flared cavity containing the expanded end of the tension member, the elements of which are surrounded by a resilient bonding agent.

A simple, strong and durable method of attachment has not previously been devised which is suitable for a wide range of tension members. New developments such as synthetic monofilaments and the plastic-sheathed continuous filament synthetic ropes cannot be effectively secured or joined with the fitting arrangements heretofore available. Similarly, synthetic webbings which have unusually high tensile strengths cannot suitably be secured by conventional means for holding the tension member when the tension thereon approaches the maximum tensile strength of the member.

The present invention has proved superior to knots and splices for securing rope. Knots have a tendency to untie, increasingly so if improperly chosen or tied. Additionally, knots weaken rope with sharp bends, and present a poor appearance. Satisfactory splices are diificult to execute in synthetic rope, and are almost impossible to execute with braided rope, require considerable skill, and may pull out if improperly executed. Both knots and splices require the use of thimbles therewith in attaching rope to various types of metal fittings.

It is accordingly a primary object of the present invention to provide a simple, light-weight, easily secured fitting for attachment to tension member ends which may be used with a wide variety of tension members including synthetic, natural fiber or wire ropes, monofila-ment or continuous filament synthetic ropes, and Webbing.

Another object of the invention is to provide a tension member fitting as described which by actual tension tests has proven stronger than the attached tension member.

A further object is to provide a tension member fitting as described which is adaptable to combination in a unitary construction with a variety of fittings such as shackles and hooks.

Another object is to provide a tension member fitting which requires a minimum length of the tension member for attachment thereto.

A still further object is to provide a tension member fitting which requires little time and experience for attachment and which presents a neat appearance in assembled form.

Additional objects and advantages of the invention will be more readily apparent from the following detailed description of embodiments thereof when taken together with the accompanying drawings in which:

\FIGURE 1 is a perspective view of a fitting attached 3,264,017 Patented August 2, 1966 to a laid-up rope end in accordance with the present invention;

FIGURE 2 is a sectional side view of the fitting of FIGURE 1 attached to a braided Dacron rope having a braided nylon core showing the sectional shape of the fitting and the manner in which the rope filaments are distributed within the fitting;

FIGURE 3 is a view similar to FIGURE 2 showing a fitting attached to a plastic sheathed continuous filament synthetic rope;

FIGURE 4 is a greatly enlarged partial sectional view of a rope end strand after attachment to the rope fitting showing bonding material packed between the individual rope filaments;

FIGURE 5 is a perspective view showing the rope fitting disengaged from the bonded molded end of a laid-up rope;

FIGURE 6 is a view similar to FIGURE 5 showing a fitting adapted for use with natural fiber or synthetic webbing in accordance with the present invention;

FIGURE 7 is an elevational view of the embodiments of FIGURE 6 showing the webbing in the secured position;

FIGURE 8 is a sectional view taken along line $-8 of FIGURE 7; and,

FIGURE 9 is an end view of the rope webbing fitting.

Referring to the drawings, FIGURE 1 shows in illustrating a specific embodiment of the invention a fitting or lug supporting element generally designated as 10 attached to a tension member 12 by means of a lug, sometimes referred to as a plug, formed on the end of the tension member. The fitting 10 integrally includes a tension member. The fitting 10 integrally includes atension member securing portion 14 and a connector portion 16 projecting longitudinally therefrom for securing the lug supporting element, or fitting, to a supporting object. Although a variety of rope connecting fittings such as hooks, rings, swivels, or other such as bolted or encased split fittings could be combined with the rope securing means of the invention, for purposes of illustration and not of limitation on the scope of the invention, a shackle is shown and described as an integral part of the described embodiments. I

The lug securing portion 14 includes a hollow casing 17 having a rope end cavity 18, the specific shape of which is of particular importance in providing a fitting which does not give rise to shear stresses in any of the individual rope fibers or filaments when they are under high tensile stress. As can be seen in FIGURE -2 in which the fitting is shown applied to a Dacron braided rope having a braided nylon core, the fitting interior is characterized by a cylindrical throat portion 20 of a diameter substantially equal to that of the rope with which the fitting is used. The cavity 18 fiares outwardly in curved walls 22 extending in the present instance tangentially from the throat portion 20, so that the walls gradually merge into the portion 20 without sharp bends or shoulders. The fiared portion of the cavity terminates in a second cylindrical portion 24 of a diameter more than one and a half times the diameter of the rope.

To attach the fitting to a rope of appropriate size, the rope end 26 is introduced into the cavity in the fitting through the cylindrical portion 20 and pulled through the cavity 18 and out beyond the connection 16. The rope strands 28 of the rope end 26 are then unlaid and untwisted for a length corresponding to at least the length of the flared portion 22 of the fitting so as to expose and separate the individual rope filaments 30. A fine-toothed comb is useful in untwisting and preparing the filaments in a uniformly longitudinal arrangement. A bonding agent 32 is then liberally applied to the unlaid strands and untwisted filaments of the rope end.

The rope is then drawn back through the fitting until the rope end 26 is encased within the cavity 18. The cavity is so dimensioned and the bonding agent is of such a consistency and is applied in such an amount that a tight fit of the rope end in the casing results, conforming the bonded filaments to the cavity shape.

Upon hardening of the bonding agent the rope end is secured within the fitting and forms a solid plug 33 therein. The expanded diameter of the bonded portion of the rope due to the impregnation by the bonding agent of the strands and filaments protects the fragile filaments from shearing forces and precludes the passage of the plug through the cylindrical portion 20. FIGURE 5 is a partial sectional view of such a bonded strand and shows in a greatly enlarged view the manner in which the bonding agent 32 impregnates and separates the rope filaments 30. There should be a sufficient amount of bonding agent around the exterior of the rope end such that a layer separates the outer filaments from the cavity wall. This separation of the filaments results in the expanded rope crosssection necessary for secure attachment of the rope end.

The hardened properties of the bonding agent are of critical importance in producing a tension member end fitting to realize the extremely high strength potential of the present concept. The bonding agent when hardened must be of a non-rigid type having suflicient resilience and compressibility to permit a gradual transfer of the stress from the tension member to the walls of the cavity. The bonding agent must not adhere to the walls of the cavity and to prevent such adherence the cavity walls should be machined and polished accordingly.

Careful observations of test loadings have revealed the fact that the bonded expanded tension member end is resiliently extruded to a graduated degree along the flared arcuate walls of the cavity. Movement at the widest point of the cavity is very slight, while movement in the narrow throat is most pronounced. Due to the progressively larger volume of resilient bonding agent and filaments encompassed by the cavity walls as the cavity arcs to its widest diameter it can be understood that the resilient extrusion or necking down of the bonded end gradually decreases as the cavity opening increases. It is this resilient graduated movement which permits the tension stress on the individual filaments to produce a gradually diminishing elongation of the filaments along the extended portion of the filaments encompassed within the arcuate flaring walls of the cavity. This permits the stress on the filaments to be gradually transferred to the fitting along the length of the arcuate wall.

Prior art fittings of the filled type have generally been characterized by use of an inflexible filler such as Babbitt metal or similar substance, the theory being that a better gripping effect could be provided by the use of such a filler. With such fittings, using a non-resilient filler, the filaments abruptly passed from a condition under which elongation under stress was possible, e.g. external to the fitting, to a condition under which elongation was prevented by the rigid filler, e.g. internal of the fitting. The abrupt change in condition gave rise to stress concentrations in the filaments at that point and a consequent weakening of the fitting.

The shape of the cavity 18 and the disposition of the tension member filaments within the cavity are of importance in providing a distribution of tension stresses longitudinally along the filaments without developing shear forces or stress concentrations. Although a curved cavity shape which tangentially merges with the throat portion is preferred and produces the strongest fitting attachment, any smoothly curved outwardly flared cavity shape which is free of sharp bends or shoulders will produce an attachment of unexpected strength within the concept of the invention. Pins and wedges have been tried but have proved useless and in fact have been found to weaken the assembled fitting since shearing occurs in the filaments distorted by the pins or wedges.

Although the filaments of the tension member are preferably disposed in substantially parallel arrangement within the cavity, in practice this may be difficult to achieve and it is sufficient that the filaments be so arranged as to run in substantially the same direction.

The flared curve of the cavity must be of a sufficiently large radius to prevent breakage of the filaments upon tension loading thereof. In experimental use it has been found that a radius of approximately 3% times the difference between the rope and the plug diameters provides excellent results. The curved radius must be at least as large as the diameter of the rope to provide a satisfactory fitting.

A material suitable for use as the bonding agent comprises a hundred percent polymerizable resinous material comprising a mixture of monomers and polymers cured by ethylenic polymerization or condensation polymerization having a high degree of memory and a minimum amount of cold flow. Although it is desirable that the bonding agent be of the readily prepared, fast drying type, the important characteristic is the resilience and compressibility of the agent in its hardened state. As described above, there must be sufficient compressibility and resilience in the hardened plug to permit a necking down or extrusion of the bonded tension member end in the fitting. While the degree to which such an effect takes place will vary depending upon the tension member used, the shape of the fitting cavity, and the load applied, it can be understood that the bonding agent must be selected considering these conditions such that a certain degree of extrusion of the plug will result without danger of the lug being pulled through the fitting. In general, it can be said that a more resilient bonding agent is desirable with a relatively resilient tension member such as nylon rope. On the other hand, with wire rope, better results may be obtained using a less resilient bonding agent.

To insure a secure assembly it is necessary that the cross-sectional width of the bonding lug at its most ex panded point be more than 1 /2 times the cross-sectional width of the cavity at its throat or most constricted point. The fitting should be designed for a specific size rope or Webbing such that the cavity snugly engages the rope or webbing at the constricted end opening of the fitting. In the drawings, the constricted end includes a cylindrical portion 20. This is not essential to the invention. -The cavity may terminate at the point at which the flared portion is constricted to the mini-mum diameter.

Depending upon the shape of the fitting cavity and the type of tension member and bonding agent employed, the cylindrical portion 24 may not be essential, or, if included, may alternatively be of another shape. It has been found, for example, with resilient tension members such as nylon rope, that such an added cylindrical portion is unnecessary. However, with wire rope, it has been found necessary to include this portion to avoid a central depression of the plug due to the necking down of the bonded plug. Thus, although unusual strength characteristics result using a fitting, the cavity of which terminates at the end of the flared portion, it should be understood that for the maximum strength of attachment when using non-resilient tension members such as wire rope that an additional portion such as the cylindrical portion 24 should be included.

Regardless of the shape of this added portion, the unusual strength properties of the invention will result only if the maximum cavity cross-sectional width is greater than one and a half times the cross-sectional width of the constricted end opening.

In using the present fitting with the plastic-sheathed continuous filament rope, it is necessary to cut away the sheathing 34 and the thin plastic coating 36 from the rope end to permit a necessary radial expansion of the rope end filaments as shown in FIGURE 3. The filaments of this type of rope are larger in number than those of a corresponding size laid-up or braided rope, resulting in a substantially increased load capacity. The increased number of filaments counter-balances the fact that the plastic sheathing extends part way into the fitting, occupying space otherwise available for rope filaments.

Although a variety of materials may be used to produce the fitting, a strong non-corrosive material such as stainless steel is preferable since the above-described tension members are used mainly in outdoor installations and may be subjected to moist corrosive conditions. The fitting need not necessarily be of metal, but could be made, for example, of a high impact plastic such as Delrin.

The present invention not only provides an attachment of improved strength, but also minimizes the length of tension member necessary for attachment of a fitting. Little experience or time is required to execute attachment in the manner described, and a neat appearance of the attached tension member end fitting results with each use of the device. The fact that the bonded plug may be withdrawn from the cavity provides a distinct advantage, permitting inspection of the plug during use and also permitting reuse of the fitting.

A modified embodiment of the invention as shown in FIGURES 6-9 is a fitting similar to that previously described, adapted for use with natural fiber or synthetic webbing. The fitting includes a Webbing securing portion 38 and a connector portion 40. Webbing 42 is inserted into the fitting through a throat 44 which is in the form of a slot, and the webbing, following extension through the fitting as shown in FIGURE 6, is unlaid and untwisted so that the individual filaments may be treated by a bonding agent in the manner described above with respect to various types of rope. The fitting cavity 46 into which the webbing end is encased is of a sectional shape similar to that of the rope fittings, both in the elevation and plan views as shown in FIGURES 7 and 8. FIGURE 9 shows the cavity 46 in a view looking into the connector end of the fitting. A connecting pin 48 is shown in FIGURES 7 and 8, illustrating a suitable type of connector for use with the illustrated shackle fitting. The webbing fitting is adapted for use in practically all situations in which webbing is presently used, and by effectively utilizing the full strength potential of the webbing, is particularly useful in such applications as catapults, arresting gear, safety belts, and the like.

It is apparent that the embodiment of FIGURES 69 utilizes the same concept and basically the same structure as the embodiment of FIGURES 1-5. The webbing is snugly engaged by the throat 44 and is then expanded within a cavity having smoothly flared walls to a size providing in each width dimension a cross-sectional width more than one and a half times the slot cross-sectional width, the slot width being equivalent to the cross-sectional width of the unexpanded webbing.

Successful experiements have been conducted using the present type of fitting modified so that the cavity walls are expanded only in one radial plane. One cross-section of such a fitting for webbing would be the same as FIG- URE 7, while the other taken normal to the first would show the webbing extending into the fitting with its width unchanged. Such a modified form would be considerably cheaper to manufacture in the webbing type fitting. It could also be employed with the rope type fitting for use in confined areas.

The principle of the invention may be used in a further manner by employing a split fitting similar in all other respects with those described above. The split fitting could be bolted or adapted to telescope within an additional fitting having a smaller end opening larger than the plug portion of the rope. This would permit removal and substitution of fittings on a rope and would also facilitate attachment in relatively inaccessible situations.

Manifestly minor changes in details of construction can be effected by those skilled in the art without departing from the spirit and scope of the invention as defined in and limited solely by the appended claims.

I claim:

1. A combination fastening means formed with the end of a multiple synthetic organic fiber strand flexible tension member wherein the strands at the end of the tension member are separated into individual strands extending outwardly from the unseparated portion of the tension member comprising:

(a) a substantially rigid lug formed about the separated individual strands;

(b) said lug formed of a hardened resin plastic having a high degree of memory and a minimum amount of cold flow, wherein the resin in a liquid state is placed about the strands and cure-hardened;

(c) the cured hardened resin being compounded to harden to a point to give the lug a slight amount of compressibility and elasticity without stress cracking when the tension member is approaching its substantially maximum tension;

(d) the outer end of the lug being substantially larger than the inner end thereof and having a concave tapered face, said face being tapered inwardly from a point substantially adjacent the outer larger end to a thickness of the tension member;

(e) the separated individual strands of the tension member being extended outwardly from the unseparated portion and through the area of the tapered section of the lug;

(f) a rigid lug supporting element having means for receiving the lug;

(g) the lug receiving means being in the form of a cavity being larger at one end than at the opposite end and of such dimensions and configuration as to closely receive the lug and having an opening at the smaller end substantially the size of the tension member, the compressibility and elasticity of the lug being such that the lug cannot be drawn through the small opening in the cavity when tension on the tension member has approachced substantially its tensile strength;

(h) means carried by the lug supporting element for securing the same to a supporting object.

2. A combination fastening means formed with the end of a multiple syntheti organic fiber strand flexible tension member wherein the strands at the end of the tension member are separated into individual strands extending outwardly from the unseparated portion of the tension member comprising:

(a) a substantially rigid lug formed about the separated individual strands;

(b) said lug formed of a hardened resin plastic having a high degree of memory and a minimum amount of cold flow, wherein the resin in a liquid state is placed about the strands and cure-hardened, said resin being a one hundred percent polymerizable resinous material comprising a mixture of monomers and polymers cured by ethylenic polymerization or condensation polymerization;

(c) the cure hardened resin being compounded to harden to a point to give the lug a slight amount of compressibility and elasticity without stress cracking when the tension member is approaching its substantially maximum tension;

(d) the outer end of the lug being substantially larger than the inner end thereof and having .a concave tapered face, said face being tapered inwardly from a point substantially adjacent the outer larger end to a thickness of the tension member;

(f) a rigid lug supporting element having means for receiving the lug;

(g) the lug receiving means being in the form of a cavity being larger at one end than at the opposite end and of such dimensions and configuration as to closely receive the lug and having an opening at the smaller end substantially the size of the tension member, the compressibility and elasticity of the lug being such that the lug cannot be drawn through the small opening in the cavity when tension on the tension member has approached substantially its tensional strength;

-(h) means carried by the lug supporting element for securing the same to a supporting object.

3. A combination fastening means formed with the end of a multiple synthetic organic fiber strand flexible tension member wherein the strands at the end of the tension member are separated into individual strands extending outwardly from the unseparated portion of the tension member comprising:

(a) a substantially rigid lug formed about the separated individual strands;

((1) the outer end of the lug being substantially larger than the inner end thereof and having a tapered face, said face being tapered smoothly and uniformly inwardly from a point substantially adjacent the outer larger end to a thickness of the tension member;

(f) a rigid lug supporting element having means for receiving the lug;

(g) the lug receiving means being in the form of a cavity being larger at one end than at the opposite end and of such dimensions and configuration as to closely receive the lug and having an opening at the smaller end substantially the size of the tension member, the compressibility and elasticity of the lug being such that the lug cannot be drawn through the small opening in the cavity when tension on the tension member has approached substantially its tensile strength;

References Cited by the Examiner UNITED STATES PATENTS 808,199 12/1905 Double 24-122.3 997,488 7/1911 Campbell 24123.1 1,214,709 2/1917 Orr 24126 FOREIGN PATENTS 804,154 7/ 1936 France. 1,204,191 8/1959 France.

489,874 8/ 1938 Great Britain. 874,324 8/ 1961 Great Britain.

CARL W. TOMLIN, Primary Examiner.

T. A. LISLE, Assistant Examiner.

Claims

1. A COMBINATION FASTENING MEANS FORMED WITH THE END OF A MULTIPLE SYNTHETIC ORGANIC FIBER STRAND FLEXIBLE TENSION MEMBER WHEREIN THE STRANDS AT THE END OF THE TENSION MEMBER ARE SEPARATED INTO INDIVIDUAL STRANDS EXTENDING OUTWARDLY FROM THE UNSEPARATED PORTION OF THE TENSION MEMBER COMPRISING: (A) A SUBSTANTIALLY RIGID LUG FORMED ABOUT THE SEPARATED INDIVIDUAL STRANDS; (B) SAID LUG FORMED OF A HARDENED RESIN PLASTIC HAVING A HIGH DEGREE OF MEMORY AND A MINIMUM AMOUNT OF COLD FLOW, WHEREIN THE RESIN IN A LIQUID STATE IS PLACED ABOUT THE STRANDS AND CURE-HARDENED; (C) THE CURED HARDENED RESIN BEING COMPOUND TO HARDEN TO A POINT TO GIVE THE LUG A SLIGHT AMOUNT OF COMPRESSIBILITY AND ELASTICITY WITHOUT STRESS CRACKING WHEN THE TENSION MEMBER IS APPROACHING ITS SUBSTANTIALLY MAXIMUM TENSION; (D) THE OUTER END OF THE LUG BEING SUBSTANTIALLY LARGER THAN THE INNER END THEREOF AND HAVING A CONCAVE TAPERED FACE, SAID FACE BEING TAPERED INWARDLY FROM A POINT SUBSTANTIALLY ADJACENT THE OUTER LARGER END TO A THICKNESS OF THE TENSION MEMBER; (E) THE SEPARATED INDIVIDUAL STRANDS OF THE TENSION MEMBER BEING EXTENDED OUTWARDLY FROM THE UNSEPARATED PORTION AND THROUGH THE AREA OF THE TAPERED SECTION OF THE LUG; (F) A RIGID LUG SUPPORTING ELEMENT HAVING MEANS FOR RECEIVING THE LUG; (G) THE LUG RECEIVING MEANS BEING IN THE FORM OF A CAVITY BEING LARGER AT ONE END THAN AT THE OPPOSITE END AND OF SUCH DIMENSIONS AND CONFIGURATION AS TO CLOSELY RECEIVE THE LUG AND HAVING AN OPENING AT THE SMALLER END SUBSTANTIALLY THE SIZE OF THE TENSION MEMBER, THE COMPRESSIBILITY AND ELASTICITY OF THE LUG BEING SUCH THAT THE LUG CANNOT BE DRAWN THROUGH THE SMALL OPENING IN THE CAVITY WHEN TENSION ON THE TENSION MEMBER HAS APPROACHED SUBSTANTIALLY ITS TENSILE STRENGTH; (H) MEANS CARRIED BY THE LUG SUPPORTING ELEMENT FOR SECURING THE SAME TO A SUPPORTING OBJECT.