US2793903A

US2793903A - Material handling slings

Info

Publication number: US2793903A
Application number: US332899A
Authority: US
Inventors: James B Mallard
Original assignee: Individual
Current assignee: Individual
Priority date: 1953-01-23
Filing date: 1953-01-23
Publication date: 1957-05-28
Anticipated expiration: 1974-05-28

Description

y 8, 1957 J. B. MALLARD 2,793,903

MATERIAL HANDLING SLINGS Filed Jan. 23, 1953 2 Sheets-Sheet l (James B. Ma Hard INVENTOR.

BY Q g a A TTORNE Y y 8, 1957 J. B. MALLARD 2,793,903

MATERIAL LHANDLING SLINGS Filed Jan. 23, 1953 2 Sheets-Sheet 2 dam es 5. Mafia/'0 INVENTOR.

B QM 6 #w r 2,193,903 Ice Patented May 28, 1957 MATERIAL HANDLING SLINGS' James B. Mallard, Houston, Tex.

Application January 23, 1953, Serial No. 332,899

4 Claims. (Cl. 294-74) This invention relates to an improved sling for handling material, and particularly to a sling for handling covered or coated pipe.

Each year more and more material which is conveyed from one location or position to another by material'handling equipment is provided with a protective coating or covering. For example, the large pipe used in conveying petroleum products, such as natural gas, is generally covered, as with fibre glass, paper and tar, to reduce the deterioration effects of moisture and of the soil in which it will be buried. Consequently, the sling used in handling this pipe should be so designed that it will not tear this protective covering. Standard wire rope slings are not suitable for this purpose both because of the rough surface of the ropes themselves, because of the dangerous and awkward irons, or end members, used, and because of the distribution of the load on such a small supporting area. With such slings the covering often is damaged during handling and frequently tears when the sling is withdrawn, after the pipe is laid in the ground. Moreover, smooth surface belt type slings such as those made of duck and rubber, or nylon and rayon, have not, when used alone, been satisfactory for this purpose. One reason is that the belts stretch every time the load is put on them and this stretching is frequently sufficient to tear the pipe covering. Moreover, such belts, particularly after long usage, will be strained to the point of breaking without the weakness being noticeable to the eye. Consequently, they are subject to sudden complete failures, sometimes with disastrous results to men, material I A compromise sling is sometimes used which comprises a standard wire rope sling having its and equipment.

ing or tearing of the covering or coating upon withdrawal of the sling from under the pipe, after it has been laid in position. While such comprise slings are an improve ment over the standard slings just described, the entire load is still carried on the relatively small area presented by the cables themselves. This unequal load distribution often causes damage to the pipe covering at the point where the cables contact it through the sling belt. Moreover, the means of connecting the cables to their respective end pieces, and the cables themselves, except along the intermediate portions of their lengths, are not covered by the belt. Consequently, there is still some danger of tearing the pipe covering while withdrawing the sling. In addition these belts have not been satisfactorily anchored in place, relative to the wire ropes. Accordingly it is the primary object of this invention to provide a new and improved material handling sling in which the load of the material handled is properly distributed over a relatively large bearing area.

Another object of my invention is to provide a new and improved sling having a contact face smooth enough for safe handling of coated or covered material without damage thereto.

It is a further object of my invention to provide a sling so designed that it can be withdrawn from under the load without likelihood of damage to the load surface.

It is a still further object of my invention to provide an improved sling which is strongand durable, relatively inelastic, and which is not likely to fail without giving clear and early warning.

Other objects as well as advantages of myinvention will be pointed out in the following specification and appended claims. I

' In the presently preferred embodiment of my invention I provide a material handling sling having both the advantages of the standard wire rope sling and the belt type sling, along with new and improved features not present in either type. I provide a plurality of wire ropes, usually four, which are permanently joined together at their respective ends to form, in effect, an endless rope arrangement. At each end of the sling, where the ends of the ropes are joined together, the arrangement adapts itself for ready attachment of both ends to a single grappling hook or the like. This eliminates the customary irons, or end members, which are dangerous to personnel and difficult to use without damage to the protective covering of the load. The wire ropes are spaced apart throughout a major portion of their lengths by spreader bars placed near the respective ends of the sling. Along the load supporting portion of each wire rope, between the spreader bars, are attached a plurality of bearing plates, the surfaces of which may be suitably curved to conform to the contour of the material handled. The bearing surface of these plates, the load portion of the wire ropes, and, preferably, the spreader bars, are shielded from contact with the material handled by means of a protective covering. This covering is usually in the form of a belt which may vary from a friction surface conveyor belt to a soft rubber, according to the nature of the expected load. For best results this cover or belt is attached to at least some, and preferably all, of the bearing plates by means of suitable bolts. The bolt heads, while preferably on the load contacting side of the belt, are drawn into a recess in the face of the bearing plate below its contact surfaces, upon tightening of-the attaching bolts.

While not essential to the operation and successful use of my sling, I prefer to extend the covering belt not only to cover the spreader means at each end of the sling, but at one end to cover a substantial portion of the wire ropes extending beyond the spreader bar. This gives added protection to the surface of the material handled, particularly in the case of a coated or covered pipe. When the sling is withdrawn after the pipe is in position in the ground, the belt cuts a channel in the soft earth below the pipe through which the uncovered end portions of the Wire ropes can be withdrawn without cutting or tearing the pipe coating- Moreover, when the belt extends substantially to the end of the wire ropes at one end of the sling, as in my preferred embodiment, it gives added assurance that the pipe covering or coating will not be damaged by contact with the wire ropes. In handling pipe for burial in the ground the sling is withdrawn by unhooking the end having the additional belt covering and exerting a pulling force on its other end.

My invention will be more fully understood from the following detailed description taken in connection with the accompanying drawings and its scope will be pointed out in the appended claims.

In the drawings Fig. 1 is a top plan view, fragmentary in its center portion, of the sling, showing the contact surface of the belt; Fig. 2 is a bottom plan-view, fragmentary in its center portion, illustrating the positioning of the spreader bars and bearing plates; Fig. 3 is a sectional view of a spreader bar, taken along the lines 3-3 of Fig. 2; Fig. 4 is a sectional view of a bearing plate, taken along the lines 44 of Fig. 2; Fig. is a sectional view of the bearing plate of Fig. 4 taken along the lines 5- 5; and Fig. 6 is a sectional view similar to Fig. 5 but showing a modified clamping cleat for use with the bearing plate.

Referring now to Figs. 1 and '2 of the drawings, a sling 1 is provided with a plurality of substantially inelastic strength members 2 which are preferably wire ropes. The ropes -2 are permanently joined together at "their respective ends to provide

end members

3 and 4 by which the sling can be attached to a single lift member, not shown, such as a grappling hook. The Wire ropes or cables 2 are preferably so joined as to provide a smooth end which can be withdrawn from underneath the material handled without likelihood of damaging it.

In order to space the wire ropes, which in the form shown may be considered portions of a continuous wire rope, I provide spreading means in the form of bars 5 'and 6 attached to the respective cables by cleats 7 and "suitable bolts '8. Between the spreader bars, which are fixed to the cables near their respective ends, the wire ropes form a flexible supporting frame of sufficient length to cradle the particular material or pipe size to 'be handled. The relative inelasticity of the wire ropes forming the sling cradle limits the stretching of the sling contact surface, and the fact that a plurality of ropes are used, which are readily visible from below the sling provides insurance against sudden failure of the sling while under load conditions. Moreover, any desired strength can be obtained merely by changing the size of the wire rope used.

The spaced wire ropes distribute the load in a manner suitable for many material handling operations. In the case of the handling of material in which special care is required, however, such as covered or coated pipes (which are considered as equivalent in the description of this invention, and in the appended claims) an even better load distribution is desirable. Accordingly I attach a plurality of bearing plates 9 to each of the wire ropes 2 at spaced intervals extending over a greater part of the distance between the spreader bars 5. These bearing plates 9 are preferably curved in the manner shown in Fig. 4, to conform to the contour of the material to be handled, such as the circumference of a pipe. As best shown in Figs. 2 and 5, each bearing plate 9 is securely attached to its wire rope by means of a cleat or strap 10 and a pair of bolts 11, one on each side of the wire rope and each extending through the bearing plate. Suitable nuts 12 are used for tightening the strap 10 against the rope and plate. The bearing plates may be of any suitable material such as cast aluminum, and in like manner the clamping cleats or straps 19 may be of a similar material, it being preferable that they be of a relatively soft material compared to that of the wire ropes, so that, upon tightening the nuts 12, the straps It) may bend slightly to accommodate the cable. I have also found it preferable to form the bearing plates with a longitudinally extending notch or recess 13 to accom- -modate the cable. By making this recess in the general form of a V, I find that upon applying pressure by means of the clamping cleat 10, the cable 2 is wedged securely, thereby preventing relative movement between it and the bearing plate. In :the embodiment shown in the drawings the bearing plate is made thicker in the center portion from end to end in both a longitudinal and lateral direction. This is both to accommodate the longitudinal recess 13 and to provide additional strength to the bearing plate.

Referring again to Fig. 1, I provide a protective con- 'tact surface for my sling by means of a beltor other 'covering-14,' =which belt may be made of any suitable material such as 'duck'and' rub-her, soft rubber, or other material, depending on the nature of the load which is expected to be handled. In the case of handling coated pipe I prefer to use duck and rubber belting with a friction surface. This belt covers the contact portion of the sling completely, extending from the spreader bar 5 to the spreader bar 6, and, in the preferred form shown, extending beyond the spreader bar 5 substantially to the end of the sling to protect the pipe upon withdrawal of the sling by pulling on the other end. The extended portion of the belt 14 preferably tapers toward the end of the sling, and may be secured to the wire ropes beyond the spreader bar by means of a strap 15 positioned beneath the ropes, into which extend screws or bolts 16. The heads of the bolts 16 are on the contact side of the belt but are withdrawn below the contact surface upon being tightened, thereby preventing contact with the pipe upon withdrawal of the sling.

It will be understood, of course, that the belt 14 does not in itself support the weight of the load, and therefore is not subjected to the usual stresses which tend to stretch and strain similar belts in conventional slings. Instead the strength members 2 carry the weight, which is distributed over a relatively large area by means of the bearing plates 9 fixed thereto.

To secure the belt 14 in proper position I attach it to the cables 2 by securing it to the bearing plates 9.

One suitable means of attaching the belt to the bearing plates is to insert the bolts 11, used to tighten the clamping cleats 14 through the belt so that the bolt heads 17 are located on the contact side of the belt. This guards against relative movement between the cables, the hearing plates, and the belt in a simple, economical and reliable fashion. As best seen in Figs. 4 and 5, the heads 17 of the bolts 11, which are preferably elevator type bolts, are drawn below the contact sunface of the belt into a recess 18 in the central portion of the contact face of each bearing plate 9. The tightening of the nuts 12, therefore, not only brings the clamping cleat '10 securely into position to wedge the wire rope 2 into the groove 13, but draws the bolt heads 17 tightly into the recess 18 to prevent their contact with the material handled by the sling.

While it is not essential that the bearing plates 9 have their bearing surfaces curved to the exact contour of the material handled, it is desirable, particularly when the sling is designed for use in handling pipe, that such plates be curved to correspond in a general way with the curvature of the outer surface of the pipe. Plates of a fixed curvature can be used for handling pipes of varying sizes within a general range, however, and it will be understood that even plates with fiat surfaces can be used in handling some material.

In Fig. 6 l have shown a modification of the clamping cleat which is sometimes useful when the diameter of the wire ropes on which the bearing plates will be attached is not determined before-hand. The clamping cleat 10a I shown in Fig. 6 has a projection 19 depending therefrom which will bite into the cable 2 to insure against relative movement between the cable and the bearing plate 9 even in the event the cable is of such small diameter that, when laid into the bearing plate groove, it does not protrude above the back of the plate. Such cleats can be used even when larger cable is employed, as the material used in the cleat is soft reiative to that used in the wire rope; consequently, the projection, while increasing the contact pressure between the cloat and the rope, will not damage the rope to any substantial degree.

While the present invention has been described by reference to the particular preferred embodiment shown in the drawings, it Will be understood that this is by Way of illustration of the principles involved and that those skilled in the art may make many modifications. Therefore, I contemplate by the'appended claims to cover any such modifications as fall within the true spirit and scope of this invention.

What I claim is new and desire to secure by Letters Patent of the United States is:

1. A load supporting sling comprising a plurality of substantially parallel lengths of wire rope, each of said lengths having attached thereto a plurality of bearing plates, each of said bearing plates having a load-supporting surface of substantial area and being attached to a single one of said lengths, and a flexible sheet attached to the load-supporting surface of each of several bearing plates to cover said bearing plates and said lengths to shield the load to be carried from contact therewith.

2. A wire rope sling for handling covered pipe comprising a plurality of substantially parallel lengths of flexible wire rope serving as strength members, said lengths being joined together at their adjacent ends to form loops at opposite ends of said sling adapted for simultaneous engagement by a single lift member, a spreader bar adjacent each of said loops extending transversely across and secured to each of said lengths to separate and to space said lengths, a plurality of bearing plates secured along each said lengths, each of said bearing plates having a loadsupporting surface curved substantially to the contour of the pipe to be handle, and a flexible sheet attached to and covering the load-supporting surfaces of said bearing plates, said sheet extending over both of said spreader bars and over the length of wire rope therebetween.

3. A sling for handling coated or covered pipe comprising a plurality of flexible wire ropes serving as substantially inelastic strength members, said ropes being joined together at their adjacent ends to form loops at said ends adapted for attachment to a single lift member, spreader means near each of said loops for spacing said ropes apart along the major portion of their lengths, and a sheet member attached to the load carrying sides of said ropes to cover both of said spreader means and all of the ropes itherebetween, said sheet member extending substantially to at least one extremity of said sling.

4. A material handling device comprising a plurality of elongate flexible and substantially inelastic strength members, said strength members being joined together at their adjacent ends to form loops, a spacer bar near each of said loops for spacing apart said strength members throughout the load carrying portion of their respective lengths, a plurality of separate bearing plates attached to each of said strength members, and a flexible sheet 31ttached jointly to at least some of said bearing plates to cover both of said spacer bars, the strength members therebetween and all of said bearing plates.

References Cited in the file of this patent UNITED STATES PATENTS 1,168,802 Harrison Jan. 18, 1916 1,207,795 Riekenberg Dec. 12, 1916 2,598,921 Knudsen June 3, 1952