US 3718945 A
A cargo sling, tow-rope or the like comprises two cables embedded in a continuous elastomeric sheath of generally elliptical cross-section, these cables being disposed substantially in the longitudinal plane containing the major axis of the ellipse and in a substantially symmetrical relationship with the longitudinal centerline of the sheath; the cables extend beyond the sheath on at least one end, their projecting extremities being interconnected to form a loop or to engage an attachment such as an extension cable or a coupling member. The cables may be provided with deformations inside the sheath, such as undulations or shoulders, to prevent relative longitudinal slippage. The sheath can be produced by extrusion about the juxtaposed cables.
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Description (OCR text may contain errors)
United States Patent [191 Brindejonc de Treglode SLINGS, TOW-ROPES AND THE LIKE  Inventor: Pierre Brindejonc de Treglode, 14
rue Dailly, 92 Saint-Cloud, France 221 Filed: 0a. 8, 1970 21 Appl.No.: 79,205
 Foreign Application Priority Data Oct. 13, 1969 France ..6935549 Sept. 16, 1970 France ..7034l93  U.S. Cl ..24/73, 294/74  Int. Cl ..A44b 31/00, B66c 1/12  Field of Search...24/73 ES, 115 K, 122.3, 122.6; 294/30.5 TC, 74
 References Cited UNITED STATES PATENTS 2,304,306 12/1942 Hobbs ..294/74 X 2,569,912 10/1951 Andersen ....;....294/74 2,643,638 6/1953 Villmer ..294/74 X 3,079,192 2/1963 Otley ..294/74 3,018,128 l/l962 Nelson et al ..294/74 March 6, 1973 3,310,333 3/1967 Hutson ..294/74 3,317,233 5/1967 Black ..294/74 3,512,223 5/1970 Willinger ..294/74 Primary Examiner-Paul R. Gilliam Attorney-Karl F. Ross [5 7] ABSTRACT A cargo sling, tow-rope or the like comprises two cables embedded in a continuous elastomeric sheath of generally elliptical cross-section, these cables being disposed substantially in the longitudinal plane containing the major axis of the ellipse and in a substantially symmetrical relationship with the longitudinal centerline of the sheath; the cables extend beyond the sheath on at least one end, their projecting extremities being interconnected to form a loop or to-engage an attachment such as an extension cable or a coupling member. The cables may be provided with deformations inside the sheath, such as undulations or shoulders, to prevent relative longitudinal slippage. The
sheath can be produced by extrusion about the juxtaposed cables.
6 Claims, 29 Drawing Figures PATENTEU 6 I975 3.718.945
SHEET 10F 4 Pierre Brindejonc de Treglode INVENTOR Attorney PATENIEDMAR elm 3 71 ,945
7 SHEET 2 [1F 4 Pierre Brindojonc d9 Trcglada INVENTOR Attorney PATHQ'TED 61973 v 3,718,945
SHEET 3 BF 4 [ml/b,
Pierre Brindojonc do Traglode INVENTOR PATENTEDHAR 61m 3,718,945
SHEET 4 0F 4 Pierre Brindojonc do Tragloda INVENTOR Attorney SLINGS, TOW-ROPES AND THE LIKE My present invention relates to cargo slings, towropes and the like, hereinafter referred to for simplicity as slings.
At the present time it is known to use flat slings in the form of several metal cables embedded in rubber. However, such slings have the drawback that they operate under adverse conditions if their runs extend obliquely in relation to a load being carried, since the effort is then exerted along one edge of the sling so that the forces may have to be carried by a single cable, with the result that this particular cable fails.
Furthermore, such slings have hitherto been manufactured by passing a metal cable over pulleys or cylinders in order to form a series of parallel runs, which are then stretched and finally embedded together with the pulleys or cylinders in a rubber sheath which is subsequently vulcanized. This method is expensive, and is restricted to the production of slings of predetermined lengths, because a special mold is required for each length. The individual cables are spaced apart in the sheath so that the width of the sling becomes substantial for slings having a load rating above a given force, and the amount of rubber is much larger than that actually required to bind the cables together.
One object of the present invention is to provide an improved sling construction which overcomes these drawbacks. i
The sling according to my invention comprises two cables embedded in an elastomeric'sheath of generally elliptical cross-section, the cables being located substantially in the longitudinal plane containing the major axis of the ellipse and in a substantially symmetrical manner on either side of the longitudinal centerline of the sheath; the cables project from the sheath on at least one end, where they are connected together to form a loop or to engage an attachment.
Thanks to this arrangement, the sling can be disposed skew to the load being lifted without any ill effect, the resulting stresses being readily transmitted from one cable to the other. Furthermore, the contact between the sling and a load having a sharp corner is not limited to a linear zone but is spread over a relatively wide face owing to the compression of the enveloping material of the convex sheath, the contact area increasing with the load.
In addition, the area of contact between sling and load is not disposed opposite a cable, and this serves to prevent shear in the elastomeric material. If loading is such that one cable is located at the outside, it will be initially subjected to a higher force than the interior cable, but the two cables automatically adjust their positions on account of the loop formed by their ends, so that the part of the sling which is located beneath the load can reposition itself slightly until the forces to which the two cables are subjected balance one another. Finally, the rigidity of the sling is improved because of its convex cross-section, which makes it easier to push a cable beneath a load.
The sheath material may be rubber or polyvinylchloride. It may be transparent so that the cables can be seen and their condition inspected.
In a preferred method of manufacture, two cables are fed through an extruder in which an enveloping material is extruded around them to form a sheath 2 v tion, the assembly then being cut to provide any desired length of sling whereupon the cable ends are bared and interconnected to form a loop.
The invention will now be described with reference to the accompanying drawing in which:
FIG. 1 is an elevational view of one exemplary embodiment;
FIG. 2 is a sectional view on the line IIII of FIG. 1;
FIG. 3 is a schematic diagram illustrating a preferred method of manufacture;
FIG. 4 is a detail view of a loop formed at one of the ends of the sling shown in FIG. 1;
FIG. 5 is a detail view of a loop in one alternative exemplary embodiment;
FIG. 6 illustrates another exemplary embodiment;
FIG. 7 illustrates yet another exemplary embodiment;
FIG. 8 is a transverse section on the line VIII-VIII of FIG. 7;
FIG. 9 is a transverse section on the line IX-IX of FIG. 7;
FIG. 10 is a fragmentary view of a sling passing' of another exemplary embodiment;
FIG. 12 is a view similar to that of FIG. 11, showing yet another exemplary embodiment;
FIG. 13 is a transverse sectional view on the line XIIIXIII ofFIG. 12;
FIG. 14 is a fragmentary longitudinal sectional view showing the construction of yet another embodiment;
which is relatively flexible and elastic in the cold condi- FIG. 15 is an elevational view of an exemplary embodiment provided with hook-and-eye terminations;
FIG. 16 is a section on the line XVI-XVI of FIG. 15;
FIG. 17 illustrates an alternative method of securing a ring to one end of a sling;
FIG. 18 is a section on the line XVIII-XVIII of FIG. 17;
FIGS. 19 to 23 illustrate various alternative linking strips suitable for use in constructing slings in accordance with the invention; and
FIGS. 24 to 29 are cross-sectional views of still further embodiments.
In the exemplary embodiment shown in FIGS. 1 and 2, a sling l is constituted by two metal cables 2a and 2b embedded in a continuous sheath 3 of elastomeric material.
The sheath has an elongate cross-section, and in this embodiment the two faces 30 and 3b flanking the major axis of the generally elliptical cross-section are convex. The cables 2a and 2b are preferably made of strands twisted in opposite directions in the two cables, in order to avoid any distortion of the sling when it forms a loop or knot. The cables are located substantially in the longitudinal plane containing the major axis of the cross-section of the sheath 3, substantially symmetrically in relation to the longitudinalaxis of the envelope. Their ends are bared and connect-ed together to form loops l2.
FIG. 3 shows a preferred method of manufacture of the sling l, the cables 2a and 2b being fed from two from the extruder, which can subsequently be stored until required, and from which the requisite length for any particular sling can be cut.
In order to form the loops 12 of the sling, the bared ends of the cables can be looped and joined together, at locations close to the end of the sheath, by two sleeves 9a and 9b, as shown in FIG. 4. Alternatively, an auxiliary cable 18 can be used, which is curved back on itself, its ends being clamped by retaining sleeves 9a and 9b to respective extremities of the cables 2a and 2b, which in this case have been bared over a short length only, as shown in FIG. 5.
Since the load on the sling during use is divided equally between the cables 2a and 2b, but is carried in full by the cable 18, the latter preferably has a higher strength than that of either of the cables 2a and 2b. However, in certain cases it may be desirable that the weakest point of the sling be located in a loop, where it is easy to maintain serveillance, rather than at a point where the cables are embedded in the solid body of the sheath. In this case, the cable 18 may have the same strength as each of the cables 2a and 2b, or may even have a lower strength than they. The reverse case is equally possible, that is to say, the cable 18 may be stronger than the two cables 2a and 2b combined, if it is desired to ensure that any failure should take place beyond the loop.
If it is desired to fit a sliding attachment to form a running knot, the loop can be engaged in a slip through type of eyelet 10 which contains an elongate opening 11 whose length is grater than the external width of the eyelet, as shown in FIG. 6. Preferably the two sleeves 9a and 9b are disposed inside the arms of the eyelet 10 in order to avoid an excessive rigid length. Alternatively, a half eyelet 10a can be used, as shown in FIG. 5, to engage the auxiliary cable 18 but to limit the length of the rigid part.
Since it is frequently desirable to protect the loops, in a simple embodiment it is possible to form the auxiliary cable 18 from a section of sheathed cables similar to or identical with that used to make up the body of the sling.
Thus, in the embodiment shown in FIGS. 7 to 9, the loop is formed by two extension cables 18a and 18b located in a sheath 19 which has two mutually opposed convex faces like the body 1 of the sling, albeit preferably of a smaller section. At each end, the cables 18a and 18b are fixed to the respective cable 2a or 2b by a respective sleeve 9a or 9b. The cables 18a and 18b can have the same strength as the cables 2a and 2b, or a lower strength in order to localize possible failures in the loop, or alternatively a higher strength if it is desired to guard against failures in the loop. In order to facilitate inspection of the loop, the sheath 19 is preferably made of a transparent material.
The sling just described does not twist, and retains its orientation, even after intensive use. This is due to the fact that when the sling is passed beneath a load, the cables 2a and 2b are not disposed vertically in relation to the point of contact but are spaced laterally to a small extent, on either side of the zone of contact. If the sling contained only one cable, this would not be the case and the cable could shear the elastomeric material of the sheath. In addition, in the sling described, the upper convex face 3a of the sling flattens under the effect of the load, and this tends to spread the two cables 20 and 2b slightly further apart whereas the tension developed in the cables tends to maintain the cables at their initial spacing, an equilibrium being thus established between these two forces.
When the sling is passed over two sharp edges of a load, the cables do not slide in relation to the sheath and the locations of the sharp edges of the load, thereby avoiding any risk of the envelope being sheared. Instead, the whole assembly slides over the sharp corners and the section of the sling which is defined between these sharp corners is urged against the bottom of the load.
In addition, if the sling is passed obliquely beneath a load, as shown in FIG. 10, in such a manner that the rearward cable 2a is initially subjected to a larger force than the cable 2b, but the two cables adjust automatically thanks to the free loops over their ends, and the part of the sling located beneath the load deforms slightly until the forces to which the cables 2a and 2b are subjected are in balance.
The tension in the cables at a point in contact with a sharp angle during a lifting operation lead to the danger of producing shear in the sheath material. If it is desired to reduce this shear effect, the cables are advantageously bonded to the sheath.
The ratio between the height and the length of the elliptical cross-section can be selected in accordance with the desired application. This ratio can be small in the case where the load to be lifted is not fragile, or may be close to unity if it is necessary to place around the cables 2a and 2b a substantial quantity of envoloping material, as is the case, for example, if the load to be lifted has sharp angles or is fragile. On the other hand, in a sling having a given height and width, cables of different sizes can be used depending upon the strength which the sling is to have.
In order to reduce the possibility of a sling cable breaking at a sharp corner of a load, the cables can be provided with deformations in the form of closely spaced beads or fittings. FIG. 11 shows an embodiment of the invention in which individual fittings 14 are provided on each cable to form transverse shoulders preventing slippage relative to the sheath. FIGS. 12 and 13 illustrate an embodiment in which fittings 15 are provided which are common to the cable pair. In these latter Figures, the fitting 15 has two elongate holes 16 through each of which passes a cable, 20 or 2b respectively. The ends of the fitting are formed with external teeth 17, in order to provide an improved bond between the fittings and the sheath material. The sling is otherwise designed in a manner hereinbefore described, the beads or fittings being slipped over the cables prior to extrusion.
FIG. 14 illustrates an embodiment in which the cables 2a and 2b are not straight but deformed to follow a serpentine path within the sheath, the undulations of one cable being symmetrical with respect to those of the other in relation to the longitudinal center-line of the sling. The sling can thus extend elastically at the same time that the enveloping sheath material located between the cables is compressed or stretched, thereby guarding against failure of the sling when it is subjected to a heavy shock load. The undulations or corrugations can extend over the whole of the length of the sling or over a part only. The pitch of the undulations in the two cables could also differ from one another, the amplitude of the undulations of larger pitch being smaller than that of the undulations of the other, so that the lengths of the serpentine portions of the two cables are substantially the same. The cables are preferably given the serpentine form prior to extrusion.
FIGS. and 16 illustrate an exemplary embodiment of the invention in which one end of the sling 1 has been attached to a ring through the medium of a stirrup link having two legs 21a and 21b which are attached to the cables 2a and 2b by a common sleeve 22. The other end of the sling 1 has been connected in a similar manner to a hook 23. The legs 21a and 21b of the stirrup link are preferably roughened in order to improve the connection between the link and the sleeve 22.
FIGS. 17 and 18 illustrate an exemplary embodiment in which one of the ends of the sling 1 has been secured to a ring 20 by means of a flat anchor plate 24 and a composite link formed by two elements a and 25b interconnected by a pin 26. The plate 24 has a hole 26a (FIG. 19) receiving the element 250 of the composite link, the plate being secured to the cables 2a and 2b by a sleeve 9 which keeps it clamped between these two cables.
The major faces of the plate 24 can be keyed and/or given an undulation in the plane of the plate, as also shown in FIG. 19, and/or currugated perpendicularly thereto, as shown in FIG. 20.
Instead of being perforated at 26a, the anchor plate 24 may be formed integrally with a threaded portion 24a as shown in FIG. 21, or a yoke 24!) (FIG. 22), or a chain link 24c (FIG. 23). In this latter case, the attachment of the sling to a ring 20 is effected in a manner similar to that shown in FIG. 17, by slipping a mating element 25b into the ring and attaching that element to the anchor plate by the pin 26.
Alternative sheath cross-sections are shown in FIGS. 24 to 29.
The sling can have one flat face la (FIG. 24),'or even or be of concave one (not shown), a flattened convex section (FIG. 25). External striations or fluting 27 may be provided to improved its adhesion, as shown in FIG. 26, or a central bead 28 as shown in FIG. 27. Finally, one or more internal cavities 29 or 30 may be provided, as shown in FIGS. 28 and 29 respectively.
The cables 20 and 2b can be made of a natural or synthetic textile material instead of metal. As will be noted particularly from FIGS. 2 and 24-29, the axes of cables 2a, 2b substantially coincide with the centers of curvature of the generally elliptical cross-section of the sheath 3 at opposite ends of its major axis.
The individual features described can be combined in various ways, and modified to form further embodiments of the invention.
What we claim as our invention and desire to secure by Letters Patent of the United States is:
l. A sling comprising two spaeedly juxtaposed cables embedded in a continuous elastomeric sheath and provided with interconnected extremities projecting from said sheath and forming a pair of loops at opposite ends thereof, said sheath having a generally elliptical crosssection with the major axis of the ellipse substantially passin through the axes of said cables on opposite sides 0 the longitudinal centerline of the sheath and at substantially equal distances from said centerline, the axes of said cables substantially coinciding with the centers of curvature of said cross-section at opposite ends of said major axis.
2. A sling as defined in claim 11 wherein said cables are provided with deformations within said sheath for preventing relative longitudinal slippage between said sheath and said cables.
3. A sling as defined in claim 2 wherein said deformations are undulations of said cables. i
4. A sling as defined in claim 3 wherein said undulations are mutually symmetrical.
5. A sling as defined in claim 2 wherein said deformations are longitudinally spaced fittings on said cables.
6. A. sling as defined in claim 5 wherein said fittings are part of a set of transverse links interconnecting said cables within said sheath.