CA1127729A - Helically preformed wire gripping device having different pitch angles within each convolution thereof - Google Patents

Abstract

HELICALLY PREFORMED WIRE-GRIPPING DEVICE
HAVING DIFFERENT PITCH ANGLES WITHIN
EACH CONVOLUTION THEREOF

ABSTRACT OF THE DISCLOSURE
Improved wire-engaging structure is disclosed for devices adapted to grippingly engage a wire or line. In one form of the invention a preformed wire line tie for securing elongate line conductors to a conventional support has a pair of conductor-engaging, coiled leg members particularly configured to permit substantially effortless installation while at the same time providing the zapability to grippingly engage a wide range of conductor sizes. The coiled members comprise a series of equi-lead, axially aligned convolutions each having helical segments of unequal helix angles.
Alternate steep and shallow angles presented by the helical segments cooperate to provide required positive engagement with any one of a number of various size conductors while at the same time permitting the members to be easily positioned around the conductor. Other forms of the invention show the use of the equi-lead, multiple helix angle design concept for the coiled wire-engaging members in a deadend and an armor rod.

(Dkt. 15967)

Description

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HELICALLY PREFORMED WIRE-GRIPPING DEVICE
EIAVING DIFF~ ;N'l I?l'L~;li A~ L~;~i WITHIN
EACH CONVOLUTION THEREOF

This invention relates to wire-engaging devices in general, and is particularly concerned with an improved wire-gripping coiled member for preformed line ties, deadends, armor rods or the like.
Wire-engaging devices find extensive use in electrical transmission and distribution hardware. For example, preformed line ties are widely employed by electric utilities for securing conductive distribution lines to insulative supports.
Conventional line ties have a support-engaging bight cooperative with a pair of coiled leg members adapted to be wrapped around the conductor in gripping engagement with the latter for securely holding the conductor against vement away from the insulative support. Other types of wire-engaging devices commonly used by electric utilities include: deadends, armor rods, and splices.
One problem common to all wire-engaging products iB that of properly mating with various sizes of wires.
Thus, for example, while early designs of preformed line ties required use of a different size tie for each standard size of conductor and insulator, improved universal line ties have been developed in an effort to reduçe the number of line tie sizes which must be stocked by a utility employing a full range of conductor and insulator sizes. One such universal tie is disclosed in U.S. Letters Patent 4,015,073 issued to Dickerson and entitled "Universal Line Tie And Method Of Making Same". The measure of the ability of a wire-engaged device to accept different sizes of wires is generally known as range acceptance.

(Dkt. 15967) -1-.~

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In addition to high range acceptance, a wire-gripping device desirably should exhibit necessary load holding capability to avoid release of the wire under stress.
In the past, the load requirements for line ties and other devices have proved to be a limitation on their range accep-tance such that heretofore, universal ties have been able to provide the desired gripping strength through only a very narrow acceptance range.
Gripping strength requirements also present another problem in the design of wire-gripping devices. In this regard, it is an additional important essential of such devices that they be relatively easy to install inasmuch as installation i8 usually an awkward manual operation (for example, line tie installation is often performed by a lineman in the field while perched at the top of a utility pole). However, in conventional preformed wire-gripping designs, the difficulty of application is generally inversely related to the ultimate holding strength developed by the device. That is to say, the greater the holding strength of a conventional line tie or other device, the more difficult it is to properly install.
One effort to overcome this design dilemma is embodied in the variable pitch line ties disclosed in U.S.
Letters Patent 2,172,810 and 3,899,629. In these patents, the helix angle of the helical convolution in the coiled legs, rather than being uniform throughout the length of the leg, gradually decreases as the free end of the leg is approached. By employing such a design, it is argued that improved holding power is realized without significantly increasing the difficulty of applying the legs to the con-ductors. While such designs may offer installation ease, they do not provide a wide acceptance range, and hence the ~lZ77;:9 utility companies are still presented with the problem of stocking a large number of line tie sizes in order to accom-modate the various sizes of conductors in their distribution systems.
The present invention overcomes the problems discussed hereinabove by the provision of an improved line-gripping coiled leg member for preformed line ties, deadends or the like, each leg presenting a series of equi-lead, spiral convolutions comprising helical segments of different helix angles for grippingly engaging a conductive or supportive line. This design permits the construction of a line tie or other line-gripping device that is easy to install and exhibits adequate holding strength over a wide range of conductor sizes.
In the line-gripping member of the present invention, each convolution has steep and shallow helix angle segments extending approximately 180 respectively whereby the convolu-tions develop strong gripping power associated with steep helix angle convolutions, yet may be easily positioned in coaxial engagement with wires of various diameters. In preferred forms, the steep helix angle is approximately twice as great as the shallow helix angle.
The line tie embodiment of the present invention is generally U-shaped, having a central section presenting a bight and a pair of helically formed leg members secured to the central section and extending away from the bight. When used in combination with a conventional line conductor and support therefore, the bight is placed in straddling engage-ment with the conductor on one side of the insulative support, the remaining portion of the central section is placed in retaining engagement therewith, and the preformed helical legs are wrapped around the conductor on the opposite side ~1~772~

of the support to provide a positive securement for the line. The line ties are preferably used in cooperative pairs to provide maximum holding power on the conductor line.
Other embodiments of the invention involve the use of the above-described improved wire-gripping member in deadends and armor rods.
In the drawings:
Figure 1 is an elevational view of a line tie installation showing one embodiment of the present invention;
Fig. 2 is an enlarged elevational view of the line tie shown in Fig. l;
Fig. 3 is a plan view of the line tie;
Fig. 4 is an enlarged, elevational view of the coiled leg of the line tie in Fig. 2, showing an imaginary central cylindrical core in broken lines;
Fig. 5 is an enlarged cross-sectional view taken along 5-5 of Fig. 4;
Fig. 6 is an enlarged elevational view of the coiled leg of a prior art line tie having a constant helix angle;
Fig. 7 is a plan view of a deadend showing a second embodiment of the present invention;
Fig. 8 is a side elevational view of the deadend in Fig. 7 shown attaching a wire to support hardware; and Fig. 9 is a side elevational view of an armor rod installation illustrating a third embodiment of the instant invention.
In Figs. 1-6 there is depicted a line support assembly 10 comprising an elongate conductor or line 12, an insulative support 14 and a pair of universal preformed wire line ties 16 securing the line 12 to the support 14. The 112~7~9 assembly 10 shown in Fig. 1 illustrates the line 12 "top tied" to the insulative support 14 but it is to be understood that the present invention is also intended for use in "side tie" applications as well as any number of other tying techniques.
Each of the line ties 16 is constructed of a single unitary strand of substantially shaped-retaining, bendable metal wire formed in a general U configuration to present a bight-defining central section 18, and a pair of coiled leg members 20 extending from opposite sides of the central section 18. A symmetrical bight 22 is disposed in a plane extending substantially perpendicularly to a common plane containing the longitudinal axes of leg members 20 as shown for example in Fig. 2. In practice, ties 16 have been formed from aluminum-coated steel wire and resistance heat treated after forming. The central section 18, including bight 22, is covered by a sleeve 24 of abrasion-resistant material for the purpose of reducing wear on the line tie, insulator and conductor.
~- 20 As best illustrated in Fig. 4, each leg member 20 is formed in a manner to present a series of identical spiral convolutions 26 arranged end-to-end in axial align-ment and having equal undeformed leads or pitch lengths L.
A8 shown further in Fig. 4, each convolution 26 comprises a irst helical segment 28 having a relatively steep helix angle and a second helical segment 30 having a relatively shallow helix angle (as measured from the longitudinal axis of the member 20). The segment 28 extends approximately 180 and has an axial length B; the segment 30 likewise extends 180 but has an axial length A somewhat greater than length B. By way of compari60n, the prior art coiled leg illustrated in Fig. 6 also has a number of identical spiral ~ 112~7zg i convolutions each having a pitch length L. However the heiix angle of the convolutions in the prior art coiled leg remains constant through each convolution such that the axial length X of the first 180 in any given convolution is equal to the axial length Y of the second 180 in the same convolution.
Of course, it is to be noted that the leg 20 in Fig.
4 is shown in its undeformed state prior to being applied to line 12. As shown in Figs 4 and 5, in the undeformed state the convolutions 26 of each leg 20 are formed around an im-aginary cylinder having a diameter D. It is to be under-- stood that the diameter D will be of a value somewhat less than the diameter of line 12 in order that each convolution 26 will be slightly deformed upon installation. Thus, there is developed a gripping force on the line 12 for holding the latter in the desired manner. Though not illustrated, it is noted that the lengths L, A, and B as described hereinabove would change somewhat upon deflection of the leg members 20 to receive a line 12 of a diameter greater than D. Thus for example, first and second helical segments 28 and 30 res-pectively would extend for a shorter axial distance after installation.
The relative terms steep and shallow have been used to describe the helix angles of segments 28 and 30. The term "helical angle" in this context is an imaginary angle a or ~
a~ marked in Fig. 4. It can also be referred to, for the sake of simplicity, as "an angle with the longitudinal axis of the wire" even though the "angle" is only apparent as the convo-lutions do not actually intersect the axis. In preferred forms the steep helix angle a of the first segment 28 is less than 90 and is at least twice as great as the shallow helix angle ~ of the second segment 30.

., 1127!729 In testing line ties 16 constructed in accordance with the principles of the present invention, it has been found that the leg members 20 have an acceptance range which is at least three times that of standard uniform pitch universsl ties. The reasons for this unexpected increase in ~.

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range acceptance experienced in the present invention are not fully known. It is believed that, as the tie 16 is applied to line 12, the steep helix angle segments 28 gripping engage the line 12 in a manner to form fulcrums for deforming the shallow helix angle segments 30 as required to conform to the diameter of the line 12.
Though the present invention is illustrated and described in a line tie application, it is contemplated that the equal lead, variable helix angle, convolution construction may be advantageously utilized in the line-engaging structure of any number of devices adapted for line or guy-wire secure-ment. For example, the same concept could be used to similar advantage in deadends, splices or armor rods.
Considering then Figures 7 and 8, there is shown a second embodiment of the present invention comprising a deadend 50 constructed of a bundle of strands of substantially shape-retaining, bendable wire formed in a manner to present a generally U-shaped central section 52, and a pair of coiled leg members 54 supported in parallel laterally offset reLation by the section 52.
The multiple-strand leg members 54 are substantially identical in construction to the single strand members 20 of line tie 16. Each leg member 54 presents a series of equi-lead spiral convolutions 26 arranged in axial alignment, each convolution 26 having a pair of helical segments 28 and 30. Thus, it is noted that the discussion concerning the prior art in comparison with the convolutions 26 of the legs 20 as illustrated in Figs 4 and 6, is equally applicable to the convolution~ 26 of the leg member 54.
As shown in Fig. 8, the section 52 presents a bight for engaging support hardware such as that designated by the numeral 56. Note that when the deadend 50 is attached to the wire 58, the convolutions 26 of members 54 are coaxially positioned around the wire 58 in a manner similar to the engagement of legs 20 with line 12 in the first-described embodiment. Since the strands of section 52 are normally disposed in parallel planes as shown in the drawings, deadend 50 is of the straight bight variety as opposed to the twisted loop type.
Yet a third embodiment of the present invention is disclosed in Fig. 9 wherein there is shown an armor rod 60 in engagement with line 12. Armor rod 60 comprises a formed bundle of strands of yieldable material similar to the bendable metal used in construction of line tie 16 and deadend 50.
The formed bundle of strands defines a coiled member 52 presenting a series of generally helical convolu-tions 26. As in the previously described embodiments, the convolutions 26 of armor rod 60 have equal leads and each presents a steep helix angle segment 28 and a shallow helix angle segment 30.
Preferably, the number of strands in the formed bundle of strands defining the mem~er 52 is sufficient to present a substantially continuous protective shell when the armor rod 60 is secured to line 12 as shown in Fig. 9. It i8 desired that the armor rod 60 grippingly engage line 12 to avoid wear from rubbing therebetween.
Though the embodiments disclosed are preferred, it i8 contemplated that the convolutions 26 might alternatively be comprised of helical segments having continuously variable helix angles, a~ opposed to the constant helix angle segments 28 and 30. In such a construction, the helix angle in any convolution would not remain constant, but rather would vary gradually between maximum and minimum values at diametrically ~ 72~

opposed locations on the convolution. Indeed, this construc-tion may be required for practical commercialization of the invention in view of available manufacturing techniques.
The foregoing description of the preferred embodi-ments clearly describes intended uses of the present invention.
The principles disclosed herein may have application in virtually any type of wire-gripping device, but particular adaptation of the invention is anticipated in the field of electric distribution and transmission hardware. Specifically as described, the invention is well suited for use in line ties, armor rods, deadends, splices and the like for grippingly engaging transmission lines, distribution lines, support guy wires and other wire structures.
In view of the above, it is clear that the present invention offers a wire-gripping device which is clearly superior to any similar structure heretofore available. The provision of a series of substantially identical, variable heIix angle convolutions in each gripping member significantly increases the acceptance range of the device without adversely 20 affecting the ease of application or the developed gripping strength. Thus, inventories of line ties, deadends, splices, armor rods and the like may be appreciably reduced, thereby ofering significant savings to utility companies in terms of initial cost, storage expense, and stocking costs.

Claims (16)

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

1. In a device adapted for attachment to a line, guy-wire or the like, improved wire-engaging structure comprising: at least one elongate, preformed wire-gripping member of substantially shape-retaining, yieldable material, said member having a coil section defining a longitudinally extending series of axially aligned, generally helical convolutions adapted to be coaxially disposed on said wire, said convolutions in said series having equal leads and each presenting multiple helix angles whereby said member exhibits ease of application and relatively high gripping strength over a wide range of wire diameters.

2. The structure of Claim 1, said convolutions in said series being contiguous.

3. The structure of Claim 2, said convolutions being identical in size and configuration.

4. The structure of Claim 1, each convolution having a pair of helical segments, one of said segments presenting a relatively steep helix angle, the other of said segments presenting a relatively shallow helix angle.

5. The structure of Claim 4, said helical segments each extending approximately 180° of their respective convolu-tions.

6. The structure of Claim 1, said device comprising a line tie, said structure comprising a pair of said wire-gripping members arranged in generally parallel, laterally offset, juxtaposed relation to one another, said members being defined by a single formed strand of said yieldable material, said strand presenting a U-shaped central section interconnecting said members.

7. The structure of Claim 1, said device comprising a deadend, said structure comprising a pair of said wire-gripping members arranged in generally parallel, laterally offset, juxtaposed relation to one another, said members being defined by a formed bundle of strands of said yieldable material, said bundle presenting a U-shaped central section interconnecting said members.

8. The structure of Claim 7, said strands being disposed in substantially parallel planes in said central section.

9. The structure of Claim 1, said device being an armor rod and including only said structure, said member being defined by a formed bundle of strands of said yieldable material.

10. In a device adapted for attachment to a wire, improved wire-engaging structure including: an elongate, preformed wire-gripping member of substantially shape-retaining, yieldable material, said member having a coil section presenting a longitudinally extending series of axially aligned, generally helical convolutions adapted to be wrapped around said wire in coaxial relation thereto, each of said convolutions having one segment forming a first angle with the longitudinal axis of said wire, sufficiently steep to provide strong gripping power on said wire when the member is in engagement therewith, each of said convolutions additionally having a second segment forming a second angle with the longitudinal axis of said wire, sufficiently shallow to permit a relatively high degree of deflection of said second segment when the convolutions are wrapped around said wire, whereby the member may accommodate a wide range of wire sizes.

11. The structure of Claim 10, each of said segments extending 180°.

12. The structure of Claim 10, said first angle being at least twice as great as said second angle.

13. The structure of Claim 12, said first angle being less than 90°.

14. The structure of Claim 10, said device comprising a line tie, said structure comprising a pair of said wire-gripping members arranged in generally parallel, laterally offset, juxtaposed relation to one another, said members being defined by a single formed strand of said yieldable material, said strand presenting a U-shaped central section interconnecting said members.

15. The structure of Claim 10, said device comprising a deadend, said structure comprising a pair of said wire-gripping members arranged in generally parallel, laterally offset, juxtaposed relation to one another, said members being defined by a formed bundle of strands of said yieldable material, said bundle presenting a U-shaped central section interconnecting said members.

16. The structure of Claim 10, said device being an armor rod, and including only said structure, said member being defined by a formed bundle of strands of said yieldable material.