TECHNICAL FIELD

The present invention relates to a jointing clamp, or cable clamp, intended for joining together electrical cables or conductors and comprising an insulating, conical outer sleeve having arranged therein an electrically con¬ ductive, screw-like conical inner sleeve, preferably in the form of a worm spring.

BACKGROUND PRIOR ART Such jointing clamps are to be found in various forms. In their earliest forms, the outer sleeve of ^• such clamps was made of porcelain and was normally provided with grip- enhancing flutes. The narrow end of the sleeve was closed, and at times had the form of a hexagonal screw-cap. Cable jointing clamps are primarily used to connect together single wires or multi-wire cables in junction boxes or wall terminal boxes of different kinds, either placed in wall or ceiling cavities or surface-mounted. When joining the wires, or conductors, together, the wire-ends are first bared and then spliced or bunched together, where¬ after a jointing clamp is placed around the location of the joint and twisted axially a number of turns, where¬ upon through the combined agency of the internal screw- thread on the electrically conductive inner sleeve and also its conical configuration, firm electrical contact is established, both directly between the electrical conduc¬ tors themselves and via the inner sleeve. By shaping the narrow end of the jointing clamp in the form of an hexa¬ gon, it was possible to tighten the clamp quickly and reliably, with the aid of a socket spanner or like tool.

At a later stage of development, the outer sleeves of such

cla ps were made of plastics, which were less bulky than the porcelain sleeves and enabled the sleeves to be pro¬ vided with "wings" or lugs in the manner of a wing nut, so as to enable the clamps to be assembled and tightened by hand, without the use of a tool.

However, there were many who considered such hand-assembly of the clamps unsatisfactory and wanting, and consequently tools were developed to fit the wings of lugs on the outer sleeve. These tools, however, resulted in such powerful tightening of the clamps that the ends of some of the wires or conductors in the wire-bunch embraced by the clamp were able to pass through the narrow end of the plastics outer sleeve, such as to represent a safety haz¬ ard. This, in turn, initiated the creation of several types of inner sleeves which were of complicated manufac¬ ture and the end parts of which were drawn together or otherwise closed, in order to prevent the wires from coming into contact with and passing through the outer sleeve.

At times it is necessary to carry out control checks or to search for faults in the location of joins embraced by such jointing clamps, requiring an instrument or indicator to be connected to the cable join insulated by the jointing clamp. With present day jointing clamps of this kind, it is necessary to dismantle the clamp by unscrewing the sleeves, carry out the check required and then reassemble the clamp. When this work is carried out a number of times, one or more of the wires in the cable join are li¬ able to break-off, meaning that the join must be re-made.

SUMMARY OF THE INVENTION The object of the present invention is to provide a cable jointing clamp which when assembled about a cable join will enable an electrical contact to be established with

the join embraced by the clamp. Another object is to provide a jointing clamp with which the risk of wires in the cable join exiting through the narrow end of the outer sleeve is fully eliminated in a simple manner. A further object is to provide a jointing clamp which in addition to the advantages recited above will not require more space in the junction boxes or wall terminal boxes than conven¬ tional cable or wire jointing clamps, and which can be assembled and tightened with the aid of everyday, conven- tional tools. These objects are achieved by means of a jointing clamp constructed in accordance with the inven¬ tion and having the features set forth in the following claims.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described in more detail with reference to the accompanying drawings, in which Figure 1 is a sectional view of a jointing clamp; Figure 2 is a side view of the clamp shown in Figure 1 ; and Figure 3 is a plan view of said clamp.

DESCRIPTION OF A PREFERRED EMBODIMENT

In the Figures, the reference numeral 1 identifies a cable or wire jointing clamp that comprises an electrically in¬ sulating, conical outer sleeve 2, preferably made of a plastics material, and an electrically conductive inner sleeve 3 which is arranged within the outer sleeve and which has the form of a worm spring wound from wire 4 of square cross-section with the wire-profile placed on edge, such that the inner sleeve obtains both an outer and an inner screw-thread configuration. The spring-like inner sleeve 3 is held positioned between an internal flange 5 and a metal ball 6 which rests against a seating 7 lo¬ cated at the narrow end of the conical outer sleeve 2. The inner sleeve 3 has a greater conicity than the outer

sleeve 2 and consequently the outer sleeve has provided internally thereof guide promonatories or camming surfaces 8 which ensure that the two sleeves are centred in relation to one another, such that the ball 6 will fully close the narrow end of the inner sleeve and therewith prevent a wire or like electrical conductor, from penetrating the narrow end of the inner sleeve and out through the plastic wall of the outer sleeve when the jointing clamp is in use.

The seating 7 incorporates a through-passing hole 10 which opens into a tubular extension 9 located adjacent the narrow end of the outer sleeve 2, this tubular extension being so formed as to enable contact to be made with the ball 6 with the aid of a test probe or the like, said metallic ball 6 in this context functioning as an electri¬ cal contact which, in the assembled state of the clamp, is either in direct electric contact with the wiring joint enclosed by the clamp, or in contact with said joint via the inner sleeve 2. The tubular extension 9 prevents finger-contact with the ball 6, or contact therewith through a blunt electrically conductive object or tool thereby reducing the risk of accidents during installation work.

As illustrated in Figures 2 and 3, the outer sleeve 2 has provided thereon grips or lugs 11 by means of which the jointing clamp can be rotated axially about a joint or splice location. The tubular extension 9 of the illus¬ trated embodiment has externally the shape of a hexagon, thereby enabling a spanner to be used to effect rotation of the clamp about its longitudinal axis. The extension 9 may also be provided with a hexagonal-shaped recess for engagement with an Allen-key or like insert spanner, to the aforesaid end.

It will be understood that the illustrated and described jointing clamp can be modified within the scope -of the inventive concept, and that the combined protective/con¬ tact element 6 need not necessarily have the form of a sphere, but may have another suitable configuration. A spherical form, however, affords the best advantages in this context, since when assembling the jointing clamp the ball 6 need only be dropped into the outer sleeve 2 and will find its own position, whereas a corresponding element of different configuration would have to be placed in posi¬ tion.

In order to establish good contact between inner sleeve 3 and contact element 6, it is important that the inner sleeve 3 presses firmly against the contact element 6. When the inner sleeve 3 consists of a worm spring, as in the present case, this can readily be achieved by winding all or some of the spring turns loosely, such that the various spring turns will not come into contact with one another until the helically wound inner sleeve 3 is pressed into place in the outer sleeve 2.