GB2377829A

GB2377829A - Cable gland with captive clamping ring

Info

Publication number: GB2377829A
Application number: GB0216003A
Authority: GB
Inventors: Franz Lackinger
Original assignee: Ccg Australasia Pty Ltd; CCG AUSTRALASIA Pty Ltd
Current assignee: Ccg Australasia Pty Ltd; CCG AUSTRALASIA Pty Ltd
Priority date: 2001-07-18
Filing date: 2002-07-11
Publication date: 2003-01-22
Anticipated expiration: 2022-07-11
Also published as: GB2377829B; GB0216003D0; AU2002300105B2

Abstract

A cable gland (1) has an armour clamp assembly consisting of an armour clamping cone (4) associated with a first body part (2) and a cooperating capture armour clamping ring (5) held releasably captive relative to a second body part (3) that forms an outer cover to the clamping ring is provided. The clamping ring is held releasably captive relative to said second body part by means of a helically extending ridge (15) on an outer surface (16) of the clamping ring, the helically extending ridge being received in a generally cylindrical cavity (14) located at an inner end of an internal screw thread (6) cooperating in use with an external screw thread (6) of the first body part to interconnect the two body parts. The helically extending ridge is configured to cooperate with the internal screw thread to permit of introduction and removal of the clamping ring from the second body part by a screwing motion. The helically extending ridge is preferably constituted by a short axial length of screw thread typically of the order of at least about one or two convolutions thereof preferably extending over only a part of the axial length of the clamping ring intermediate its ends.

Description

ELECTRICAL CABLE GLAND PERMITTING OF INTERNAL INSPECTION FIELD OF THE INVENTION This invention relates to an electrical cable gland of the general type adapted to be employed for terminating armoured electrical cables where they enter an electrical connection box or other housing in which the electrical conductors of the cable are connected to terminals of one form or another.

More particularly, the invention relates to an electrical cable gland of the type having an armour clamp in the form of a cone having an outer conical surface for engaging the inside of the armouring of a cable and adapted to cooperate with a clamping ring having an inner surface of complementary conical shape so that the armouring can be clamped firmly between the two conical surfaces.

Still more particularly the invention relates to an electrical cable gland of the general type described in international patent application publication no WO 01/93395 filed under an identical title and the content of which is incorporated herein by reference.

BACKGROUND TO THE INVENTION Applicant believes that the original installation of a cable gland is substantially facilitated and rendered less susceptible to difficulties or faults associated with the loss or dropping of loose components such as a loose clamping cone and/or a loose clamping ring by simply avoiding the use of such loose components insofar as is possible. The reason for this is that with

loose components a technician installing a gland may have difficulty holding all the necessary components; may drop and possibly lose a cone or ring; and may close the gland with the dropped or lost part missing with possible serious consequences.

Applicant's preferred solution to this problem is to render both the armour clamping cone and ring captive relative to the associated part of the body of the cable gland to provide a cable gland that, at least at the time of installation, comprises but two sub-assemblies.

However, as described in more detail in said published international patent application, it is desirable that the gland can be opened to permit of inspection of the armour clamp, as well as possibly the inner seal, without releasing the grip of the armour clamp on the armouring of an electrical cable. Part of the solution to this problem is put forward in said earlier patent application, and is to render the armour clamping ring releasably captive relative to its associated part of the body of the cable gland. Various expedients are described for achieving this goal, the most preferable one being described as the provision of a resilient wire clip cooperating with grooves provided in the outer surface of the ring and the inner surface of the associated body part.

It has now been found that manufacture of a cable gland having the armour clamping ring held captive relative to its associated part of the body of the cable gland can be appreciably facilitated. At the same time, the resultant gland requires less force to be exerted on the armour clamp when the associated part of the body of the cable gland is removed as opposed to the instance in which a resilient wire clip must be caused to disengage associated grooves.

OBJECT OF THE INVENTION It is thus an object of this invention to provide a cable gland of the general type described in said earlier international patent application but wherein the manufacture of the gland may be expedited and release of the armour clamping ring may be facilitated.

SUMMARY OF THE INVENTION In accordance with this invention there is provided a cable gland comprising a body and an armour clamp assembly wherein the latter has an armour clamping cone associated with a first body part and a cooperating armour clamping ring held releasably captive relative to a second body part that forms an outer cover to the clamping ring, the cable gland being characterized in that the clamping ring is held releasably captive relative to said second body part by means of a helically extending ridge on an outer surface of the clamping ring, the helically extending ridge being received in a generally cylindrical cavity located at an inner end of an internal screw thread cooperating in use with an external screw thread of the first body part to interconnect the two body parts, the helically extending ridge further being configured to cooperate with the internal screw thread to permit of introduction and removal of the clamping ring from the second body part by a screwing motion.

Further features of the invention provide for the helically extending ridge to be constituted by a short axial length of screw thread, of the order of at least about one or two convolutions thereof; for the helically extending ridge to extend over only a part of the axial length of the clamping ring, preferably over a part of the axial length intermediate the ends of the clamping ring; for the cable gland to have a two-part construction with the armour clamping cone being held captive relative to the first body part; and for the cable gland

to embody both inner and outer seals, typically compression seals, for sealing onto the inner and outer sheaths of a cable passing through the gland.

Preferably, the armour clamping cone is, as indicated above, also held captive relative to its associated body part, namely the first body part of the cable gland. Whilst this can be achieved in many different ways it is preferably done by way of an interference fit as described in said international patent application.

Also preferably, the conical clamping surfaces have at least one substantially circumferentially extending ridge standing proud of the conical surface and shaped, in cross-section, to present a contact edge sufficiently sharp to bite slightly into the outer surface of armour wires engaged thereby during assembly of the gland. This feature too is preferably as described in said international patent application.

In order that the invention may be more fully understood one preferred embodiment thereof will now be described with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings :- Figure 1 is an elevation of a cable gland according to the invention with the upper half thereof shown in section; Figure 2 is an enlarged view of the clamping cone and clamping ring illustrated in Figure 1;

Figure 3 is an elevation similar to Figure 1 but showing the two body parts of the gland separated from each other to illustrate the two sub-assemblies for secure installation purposes; and, Figure 4 is an elevation similar to Figure 1 but showing the body parts of the gland separated from the armour clamp in an installed condition to permit inspection thereof.

DETAILED DESCRIPTION WITH REFERENCE TO THE DRAWINGS In the embodiment of the invention illustrated in the drawings a cable gland, generally indicated by numeral (1) in Figure 1, is composed of two body parts (2) and (3), the first body part (2) of which has an armour clamping cone (4) held captive relative to it and the second body part (3) of which has a clamping ring (5) held releasably captive relative to it. The two body parts have cooperating screw threads (6) whereby they may be urged axially towards each other to move the cone (4) into the ring (5).

The cone has a rearwardly directed tubular extension (7) that simultaneously compresses an elastomeric inner compression seal (8) in well established manner. The entry end of the gland has an elastomeric outer compression seal (9) that is Independently brought into service by means of a union nut (10) screwed onto the entry end of the body.

The cone (4) and clamping ring (5) have cooperating conical clamping surfaces indicated by numerals (11) and (12) respectively. The cone angle of these surfaces is substantially conventional (for example a cone angle of 20 degrees or, in other words, 10 degrees to the axis of the gland) and of self locking type. These surfaces are adapted to clamp the armour wires (13) of a cable between them, in use (see Figure 4).

Reverting now to the releasable attachment of the clamping ring to the second body part, this, in this particular embodiment of the invention, is achieved by forming a cylindrical cavity (14) at the inner end of the thread (6) of the second body part (3) so that the internal diameter of the cavity is slightly larger than the diameter of the valleys of the screw thread.

The clamping ring is provided with a short length, say two convolutions, of screw thread (15) on its outer surface (16), the screw thread being of complementary configuration to the internal screw thread (6) of the second body part (3). This screw thread forms the helically extending ridge and could extend over any part, or even all, of the length of the clamping ring. In this embodiment of the invention it is shown as being located roughly in the center of the length of the ring.

It will be understood that, with this construction, the clamping ring is free to move axially within the cavity to a limited extent but is generally captive as it cannot be moved axially past the internal screw thread of the second body part. It can, however, be introduced into, or removed from the cavity by engaging the screw thread (15) on its outer surface with the internal screw thread (6) of the second body part and screwing the clamping ring along the latter appropriately by relative rotation of the ring and body part.

This construction is highly advantageous from a manufacturing point of view as the additional cavity in the second body part and the screw thread on the clamping ring can be formed during machining of the parts at minimal additional cost. Also, an additional component, the resilient ring described in the said published international patent application, and its installation, are obviated.

Apart from this the cable gland is very much as described in said international patent application with the tubular extension (7) of the cone (4) having an outwardly directed flange (17) that is an interference fit with

respect to an inwardly directed circumferentially extending ridge (18) at the open end of the first body part (2) (see Figure 2). Also, the clamping surfaces preferably have a series of circumferentially extending sharp edged ridges (19) as described in said international patent application.

Installation of a cable gland as described above can be effected expeditiously and securely as a result of the fact that it can be handled as two sub-assemblies as illustrated in Figure 3.

After installation, in the event that it is required to remove the second body part to permit inspection of the armour clamp, the second body part is simply unscrewed from the first body part and then unscrewed off the clamping ring to a position illustrated in Figure 4. The clamp is clearly visible and capable of proper inspection. During this movement the armour clamp will generally be subjected to less stress than in the case in which a resilient ring has to be disengaged.

It will be understood that numerous variations may be made to the embodiment of the invention described above without departing from the scope hereof. In particular, the helically extending ridge could assume different forms provided it cooperates with the internal screw thread of the second body part in the general manner indicated above.

The invention therefore provides a cable gland in which the gland can be supplied in the form of two sub-assemblies for easy and reliable installation whilst it allows for periodic inspection of the armour clamp, and if required, also the inner seal of an electrical cable gland of this general type.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification

(including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment (s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

CLAIMS : 1. A cable gland comprising a body and an armour clamp assembly wherein the latter has an armour clamping cone associated with a first body part and a cooperating armour clamping ring held releasably captive relative to a second body part that forms an outer cover to the clamping ring, the cable gland being characterized in that the clamping ring is held releasably captive relative to said second body part by means of a helically extending ridge on an outer surface of the clamping ring, the helically extending ridge being received in a generally cylindrical cavity located at an inner end of an internal screw thread cooperating in use with an external screw thread of the first body part to interconnect the two body parts, the helically extending ridge further being configured to cooperate with the internal screw thread to permit of introduction and removal of the clamping ring from the second body part by a screwing motion.
2. A cable gland as claimed in claim 1 in which the helically extending ridge is constituted by a short axial length of screw thread.
3. A cable gland as claimed in claim 2 in which the short axial length of screw thread is of the order of at least about one or two convolutions thereof.
4. A cable gland as claimed in any one of the preceding claims in which the helically extending ridge extends over only a part of the axial length of the clamping ring intermediate its ends.
5. A cable gland as claimed in any one of the preceding claims in which the cable gland has a two-part construction with the armour clamping cone being held captive relative to the first body part.

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6. A cable gland as claimed in any one of the preceding claims in which the cable gland embodies both inner and outer seals.
7. A cable gland as claimed in claim 6 in which the seals are compression seals.
8. A cable gland as claimed in any one of the preceding claims in which the armour clamping cone is also held captive relative to its associated body part, namely the first body part of the cable gland.
9. A cable gland substantially as herein described and exemplified with reference to the accompanying drawings.