GB1563898A

GB1563898A - Pulling eye for optical cables

Info

Publication number: GB1563898A
Application number: GB43323/76A
Authority: GB
Original assignee: Standard Telephone and Cables PLC
Current assignee: STC PLC
Priority date: 1976-10-19
Filing date: 1976-10-19
Publication date: 1980-04-02
Also published as: CH624246A5

Abstract

In order to stress the cable (12) as uniformly as possible when an optical-fibre cable is pulled into a cable duct, the pulling-head arrangement has both clamping means (40, 41) for the reinforcing element and clamping means (32, 38, 39) for the cable sheath. Clamping takes place by screwing a pulling head (33) in at one end of a sleeve (31) and a cap nut (32) at the other end of the sleeve. <IMAGE>

Description

(54) PULLING EYE FOR OPTICAL CABLES (71) We, STANDARD TELEPHONES AND CABLES LIMITED, a British Company, of 190 Strand, London W. C. 2, England, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement :- This invention relates to pulling eye assemblies for attachment to a strain member and to the outer sheath of a fibre optic cable.

A major problem with fibre optic cables is the difficulty of pulling such a cable into a cable duct without applying an excessive stress to the optical fibres.

The practice of forming a toop with the end of the cable for use as a pulling eye almost inevitably results in damage to the optical fibres, and may be employed only when it is acceptable to discard the last few metres of the cable. This is not possible with cables in which the fibres have been factory terminated for fitting to connectors, and even where field termination is to be employed it is desirable to avoid having to cut back the cable ends. Applying tension either to the strain member only or to the sheath only can also set up shear stresses within the cable again causing damage to the individual fibres.

The object of the invention is to minimise or to overcome this disadvantage.

According to the invention there is provided a pulling eye assembly for attachment to a fibre optic cable of the type having an outer protective sheath and an axial longitudinal strain member, the assembly in cluding a flexible sleeve so dimensioned as to receive the cable sheath, a pulling eye having a substantially cylindrical surface portion for receiving the sleeve, and means for securing the sleeve to the cable sheath and to the surface portion, and wherein said pulling eye is provided with an inwardly deformable frusto-conical collet for securing the eye to the strain member.

Embodiments of the invention will now be described with reference to the accompanying drawings in which :- Fig. 1 is longitudinal section of a pulling eye assembly for attachment to a cable, the fibres in which have been terminated in ferrules; Fig. 2 shows the construction of the pulling eye of the assembly of Fig. I ; and Fig. 3 shows an alternative pulling eye for use with the assembly of Fig. 1.

Referring to Fig. l, the pulling eye assembly inclues an outer elongated flexible sleeve 11 which is fitted over the outer sheath of the cable 12, an inner sleeve member 13 for receiving the strain member 14 of the factory terminated cable 12, and a pulling eye 15 whereby the arrangement may be drawn through a cable duct. Clamp members 16 are provided on the sleeve 11 for securing the sleeve to the cable sheath and to the pulling eye.

As shown in Fig. 2 the pulling eye comprises the sleeve member 13 which has an enlarged bore portion 21 at one end provided with a screw thread for receiving the eye 22. A series of circumferential grooves 23 is provided on the sleeve member 13 to facilitate gripping of the outer sleeve 11.

The eye 22 has a conical bore 24 containing a frusto-conical collet 25 having an axial bore 26. The collet bore is profile (not shown in Fig. 2) and of such a size that, when the strain member 14 is inserted in the bore 26 and the inner sleeve 13 and the eye 22 are screwed together, the collet 25 is compressed so as to grip the strain member. When in use the pulling eye assembly is secured both to the strain member 14 and to the sheath of the cable 12 such that tension is applied to both portions of the cable. In this way the shear stress on the cable fibres is minimised.

The pulling eye of Fig. 3 is similar to that of Figs. I and 2 with the exception that the frusto-conical collet arrangement is reversed with respect to the cable. In this arrangement the tube member is provided with a conical bore 45 for receiving the collet 41. Screwing the eye into the tube member deforms the collet 41 inwardly so as to grip the cable strain member.

Claims

WHAT WE CLAIM IS :- 1. A pulling eye assembly for attachment to a fibre optic cable of the type having an outer protective sheath and an axial longitudinal strain member, the assembly including a flexible sleeve so dimensioned as to receive the cable sheath, a pulling eye having a substantially cylindrical surface portion for receiving the sleeve, and means for securing the sleeve to the cable sheath and to the surface portion, and wherein said pulling eye is provided with an inwardly deformable frusto-conical collet for securing the eye to the strain member.
2. A pulling eye assembly for attachment to a fibre optic cable of the type having an outer protective sheath and an axial longitudinal strain member, the arrangement including a pulling eye provided with an inwardly deformable frusto-conical collet for attachment to the strain member and having a tubular portion which when the assembly is in use, receives the strain member, a tubular flexible sleeve member so dimensioned as to fit over the tubular portion and the cable sheath, and means for camping the flexible sleeve to the tubular portion and the sheath.
3. An optical fibre cable pulling eye assembly substantially as described herein with reference to Figs. I and 2, or to Figs.

I and 3 of the accompanying drawings.
4. A method of securing a pulling eye to an optical fibre cable, which method is substantially as described with reference to Figs. 1, and and of the accompanying accompanying ings.
5. An optical fibre cable when fitted with a pulling eye assembly as claimed in anv one of claims I to 3.