US2998696A - Gripping surface for preformed helical rods - Google Patents

Description

Sept. 5, 1961 R. L. PAYER 2,998,696

GRIPPING SURFACE FOR PREFORMED HELICAL RODS Filed June 5, 1959 2 Sheets-Sheet l PmoR ART 1 4 5 PRxOR ART Sept. 5, 1961 R. L. PAYER GRIPPING SURFACE FOR PREFORMED HELICAL RODS 2 Sheets-Sheet 2 Filed June 5, 1959 tteol htates signor to N. Slater Company Limited, Hamilton, ntario, Canada 0 Filed June 5, 1959, Ser. No. 818,385 (Claims priority, application Canada Apr. 13, 1959 6 Claims. (Cl. 57--145) This invention relates to the manufacture of an improved helically preformed rod of the type particularly used by those private companies and public utilities concerned with the distribution of electrical energy. More particularly the invention relates to a method and means for providing an improved gripping surface on such rods.

Preformed helical rods have now proved themselves in the electrical distribution industry to be both timesaving and more economical than equipment previously employed. These rods, which are of the type described by Thomas S. Peterson in his US. Patent No. 2,587,521 and later improvement US. Patent 2,609,653, are employed in a variety of ways by line crews in both the telephone and electrical industries. For instance, should a transmission cable break, a quick and effective repair can be made by applying preformed rods of the type mentioned above to the adjoining ends of the broken cable; these preformed rods then carry the tension of the cable across the break in the line and also transmit the electrical energy around the break.

Another example occurs when these rods are used for dead ending lines or guy wires in the manner desscribed by Peterson in his US. Patent No. 2,761,273 and by the present applicant in co-pending application Ser. No. 751,- 764, filed May 21, 1958, entitled Dead Ends for Cables, now abandoned. This latter use has been particularly successful since the alternative method of forming an eye in the cable and securing it by a bolted clamp has been frequently found to lead to slippage whereas the preformed rod installation will hold indefinitely without any slip.

The preformed rods mentioned are produced with an inner coating of friction producing crystal to prevent any ippage along the cable. Slippage may occur whenever ne preformed rods are required to assume the full tensional load normally carried by the cable to which they are attached. The amount of slippage may be quite small but nevertheless for certain applications it is highly desirable that there be no slippage at all once the preformed rods have been applied to the cable. For some time therefore attempts were made to find a solution to the problem of retaining the inherent advantages of the preformed rods while at the same time overcoming the tendency of the rods to slip relative to the cable when they are subjected to a high tensional load which must L. an mitted through the rods to the cable.

solution that was adopted comprises coating the surface of the preformed rod that comes into contact with the cable, which may thus be usefully designated as the g ipping surface, with a suitable adhesive material and then dusting this adhesive with an abrasive material such as aluminum oxide preferably in a crystalline form. This procedure is certainly successful so far as obtaining an improved grip is concerned since it has been found in use that the cable to which the rods were attached would to ensure a gripping surface to prevent slippage between break before the rods would slip. However, this method stem Patented Sept. 0, 1951 2 of obtaining an improved gripping surface has disadvantages when certain specific characteristics for certain specific applications are contemplated.

The present invention overcomes inherent difficulties encountered in the use of a coating of crystal material the cable and the preformed rods when applied to the cable; two significant points being:

(a) in manufacturing it eliminates the separate and time consuming operation of applying the adhesive and crystal coating and drying or hardening time involved.

(b) The intimate contact of the preformed rods of the present invention with the body of the cable or conductor to which the preformed rods are applied overcomes a widespread objection based on the relatively poor electrical conductivity of the crystal coated method when applied under circumstances requiring the carrying of the electrical current by the preformed rods as in the making of a line splice with preformed rods.

The prime object of the present invention is to exploit the advantages of preformed rod applications as delineated in the patents above referred to and at the same time to improve the electric current carrying etiiciency of the application by the elimination of any content of poor electrical conductivity characteristics; the advantages in manufacturing are subordinate, but are of significance.

The innovation of the inventor, in fact, preserves all the advantages of the preformed rod devices as now produced with a crystal coating as a contact surface and adds the advantage of metal to metal contact between the preformed rods and the cable to which the preformed rods are applied for better electrical contact and conductivity.

According to the present invention the method of improving the grip to be obtained from the surface of a helically preformed resilient element to be wrapped in tightly gripping engagement about an elongated body comprises forming the surface of the element, which is in contact with the body when so wrapped, irregularly transverse to the length of the element.

The invention will now be described in conjunction with the accompanying drawings which illustrate a preferred embodiment of the invention and are included for purposes of illustration and not of limitation.

In the drawings:

FIGURE 1 illustrates in side elevation the basic helically preformed rod employed in the present invention and FIGURE 2 shows the rod of FIGURE 1 in end elevation.

FIGURE 3 shows the helical rod of FIGURE 1 applied to a stranded cable.

FIGURE 4 shows the rod and cable of FIGURE 3 in end elevation.

FIGURE 5 illustrates how a number of preformed helical rods may be grouped together to provide a means for enclosing the cable to which they are attached.

FIGURE 6 shows a preformed helical rod of the type shown in FIGURE 1 which embodies the present invention.

FIGURES 7, 8 and 9 show in side, plan and end views respectively a section of the preformed helical rod embodying the present invention which is illustrated generally in FlGURE 6.

FIGURES 1 to 5 inclusive do not actually relate to the present invention but depict various embodiments of the prior art and have accordingly been labelled as such. However, it is felt that an understanding of the basic heli- '3 cal rod and its mode of use is essential to any proper appreciation of the present invention and so these figures have been included to give this understanding.

FIGURE 1 shows the basic preformed helical rod described by Peterson in his US. Patent 2,587,521. The rod is formed into a regular helix and its chief physical characteristics are its pitch length, that is the longitudinal distance occupied by one complete revolution of the helix; its internal diameter d, that is the internal diameter of the hollow body formed when the rod is viewed in end elevation; and the nature and composition of the material used to form the rod.

It will be appreciated that one basic requirement is that the rod be resilient, so that it is capable of being wrapped around a cable or other such elongated body from the side without exceeding the elastic limit of the materials used in its construction. Within this broad limitation it is possible to use a wide variety of materials and the one chosen is selected on the basis of the use to which the rod is to be put and also the type of cable around which it is to be Wrapped, as care must be taken to assure that electrolytic deterioration does not take place between the rod metal and the metal of the cable. Typical materials used are aluminum, galvanized steel, bronze, stainless steel, copper and non-ferrous covered steel. It is also possible to use materials having electrical insulating properties, such as synthetic or treated wood.

Referring to FlGURE 1 therefore, the preformed rod 1 is shown of pitch length l and, as shown in FIGURE 2, defines a hollow body of internal diameter d. This rod is wrapped around a stranded cable 2 in the manner shown in FIGURE 3.

The individual rods 1 may be grouped in the manner shown in FIGURE to form a composite body 4 which may be wrapped around the cable. It will be appreciated that if enough rods are so grouped they will completely enclose the cable to which they are applied thus forming what is known as a whole-lay. The usual manner of forming a whole-lay is to take two groups of rods each of which constitutes a half-lay and such a half-lay is depicted in FIGURE 5. This configuration is called a' half-lay since the rods together extend over approximately half the pitch length l of the individual rods of which it is formed.

A rod formed as a preferred embodiment of the present invention is shown generally in FIGURE 6. Here it will be seen that the surface of the rod which comes into contact with the cable when wrapped thereabout-which may be conveniently defined as the gripping surface 5 of the rod-has been formed into a series of corrugations or indentations 6 which extend across the gripping surface 111 a direction generally transverse to the axis of the rod itself. This is shown in greater detail in FIGURES 7, 8 and 9. The corrugations or indentations may be of any configuration or design that will implement resistance to slipping.

The basic requirement of the invention is that the smooth surface of the rod in contact with the cable be formed into irregularities which extend across that part of the surface of the preformed rod that comes into contact with the cable or object to which the preformed rods are applied.

The preferred form of surface irregularity is corrugation so that the gripping surface is formed into folds extending transversely to the linear axis of the rod, and the best grip is obtained when the corrugations extend substantially normally to the axis. Indentation may be carried out in two ways; either by depressing the surface or alternatively by cutting a portion of it away.

In a typical example, the corrugations were made in the gripping surface by a depression or knurling process and approximately ridges were made per linear inch of the rod and extended across the rod for approximately /2 the diameter of the rod. With such rods formed as a 4; dead end fitting for a No. 6 aluminum cable, the following results were obtained:

(1) Preformed rods, untreated gripping surface slipped at 900 lbs. tension.

(ii) Preformed rods, treated with aluminum oxide crystals held by an adhesive broke the cable (1070 lbs. tension).

(iii) Preformed rods in which the surface has been corrugated according to this invention as part of an automatic machine operationbroke the cable (1070- lbs. tension).

Thus it will be seen that knurling or otherwise forming indentations in the gripping surface of the rod in accord ance with the present invention increases its gripping capability to the point where the cable breaks before the rods slip. While this result is admittedly also achieved by the aluminum oxide crystal coating, the present inven tion does it with equivalent mechanical results and with an effective and actual electrical bond for improved conductivity.

In summary therefore, the gripping surface of the rods has been improved to a point where the cable to which they are applied will break before the rods will slip, and this improved gripping surface eliminates the problem of conductivity between the preformed rods and the cable or body to which the preformed rods are applied.

I claim:

1. In a helically preformed resilient, electrically conducting element adapted to be wrapped in tightly gripping engagement coaxially about an elongated cable, the improvement comprising: means providing an improved gripping surface including spaced apart irregularities formed in at least a portion of the surface of said element in contact with said cable when wrapped thereabout, said irregularities extending transverse to the linear axis of same element, and extending at least partially across said surface to carry substantially equal and opposite cable tensile stress, whereby said gripping surface means cooperates to relieve the tensile stress on said cable and to improve the electrical conductivity between said element and said cable.

2. In a helically preformed elongated electrically conducting resilient element for wrapping coaxially about a cable, the element having an internal diameter less than the external diameter of the cable and a pitch length less than, and in a direction of lay corresponding to, or in opposite lay to that of the strands of the cable, the improvement comprising: means providing an improved gripping surface for said element including indentations on the surface thereof along its length and extending at least partially across said surface in a direction transverse to the linear axis of said element to carry substantially equal and opposite cable tensile stress whereby said gripping surface means cooperates to relieve t..e tensile stress on said cable and to improve the electrical conductivity between said element and said cable.

'3. The improvement defined in claim 2 wherein said indentations extend across said contacting surface substantially normal to the linear axis of said element.

4. The improvement defined in claim 2 wherein said indentations define opposed surfaces substantially normal to the longitudinal axis of said cable.

5. The improvement defined in claim 4 wherein said opposed surfaces are symmetrical with respect to a plane passing therebetween normal to the longitudinal axis of the cable.

6. In a helically preformed resilient electrically conducting element adapted to be wrapped in tightly gripping engagement coaxially about an elongated cable, the improvement comprising: means providing an improved gripping surface in at least a portion of the surface of said element in contact with said cable when wrapped thereby, said gripping surface means including a corrugated surface, said corrugations providing symmetrically opposed 1,945,000 Shara! Jan. 30, 1934 6 Peterson Mar. 3, 1942 Peterson Sept. 9, 1952 Peterson Sept. 4, 1956 Floyd July 16, 1957 Smith June 2, 1959 Bertling June 28, 1960 FOREIGN PATENTS Great Britain Aug. 22, 1956

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