GB2214728A

GB2214728A - Mounting cable gland without twisting cable

Info

Publication number: GB2214728A
Application number: GB8801218A
Authority: GB
Inventors: Alan Charles Durward Wales
Original assignee: C M P
Current assignee: C M P
Priority date: 1988-01-20
Filing date: 1988-01-20
Publication date: 1989-09-06
Anticipated expiration: 2008-01-20
Also published as: GB8801218D0; GB2214728B

Abstract

A cable gland assembly for an aperture (12) in a wall (14) of an enclosure comprises an intermediate sleeve (46) which is formed with an external right-hand thread (46) on one end and an internal left-hand thread (44) on the other. By rotating the intermediate sleeve the external thread (48) enters the aperture (12) and a gland sleeve (24) engages the intermediate sleeve (46) simultaneously. To ensure that the intermediate sleeve (46) mates with the wall (14) at the same time as the gland sleeve (24) mates with the intermediate sleeve (46), the external thread (48) is formed with a marking line (53) which corresponds to the degree of insertion required of the intermediate sleeve (46) in the aperture (12) before the mating of the three items will be achieved simultaneously by the turns of the intermediate sleeve (46). Thus, no additional rotation of the main body sleeve, sealingly attached to a cable (10), is required. Thus, the attitude of the main body sleeve (24) remains fixed with respect to the wall during assembly fund disassembly, A variety of glands mounted in this way are disclosed. <IMAGE>

Description

IMPROVEMENTS IN CABLE GLAND ASSEMBLIES This invention relates to cable gland assemblies for the junction between a wall of, for example, a housing and a cable which passes through an aperture in the wall.

The junction between a cable and an aperture in a wall is required in many applications to effectively maintain an isolation between the atmospheres on either side of the wall. This may be, for example, in some circumstances to prevent moisture or corrosive material from passing the boundary provided by the wall and/or to prevent combustible gases from migrating across the boundary.

In other circumstances a cable gland is required to provide an earthing clamp for the wire armour of the cable.

In a harsh industrial environment using continuous processes, such as the chemical and oil industries, electric apparatus, for example, electric motors, are found to suffer relatively rapid deterioration. This means that the electrical apparatus has to be replaced or removed for repair at frequent intervals. Each time repair is carried out the cable supplying the apparatus will have to be disconnected.

When a resilient gland seal is initially compressed onto the plastics outer sheath of a cable the initial seal is affected by the reaction between the sealing force exerted by the seal and the elasticity of the cable sheath and internal core insulation. This reaction squeezes the core insulation sheath axially away from the circular area on which the seal pressure is exerted until there is an equalisation of forces and the true sealing condition is achieved.

If such a seal is released, in order to permit removal of a piece of electrical apparatus, neither the gland sealing ring nor the sheaths of the cable and core will resume their original shape. It is, therefore, not possible to assume that the same sealing ring in the same position on the cable will create as effective a seal a second time.

Consequently, disconnection of the cable wall will require that extensive impedance and earth continuity tests of the reclamped protective electrical armouring braid are carried out when the cable is reinstalled.

Thus, it is necessary to provide new sealing components to be confident that an adequate seal is effected.

It has been proposed to connect the cable having a gland seal mounted on it to the wall, so that the cable core passes through the aperture therein, by means of an intermediate sleeve having threads of opposite hands on each end. The threads engage with complementary threads associated with the aperture and the adjacent end of the gland sealing sleeve respectively. By rotating the intermediate sleeve in one sense, the threads at each end engage their respective threads associated with the aperture and the gland sealing sleeve respectively. In this way the components are drawn together.

However, it is not possible with this proposal to judge with any degree of certainty whether the two seals between the wall and intermediate sleeve, and intermediate sleeve and intermediate sleeve and gland sealing sleeve, will achieve mutually sealing engagement after the same number of turns of the intermediate sleeve.

Without this, it is necessary to take up the remaining slack on one or the other of the connections by rotating at least the cable gland sealing sleeve relative to the wall. Twisting of the sheath is to be avoided as it will cause relative movement of the components of the cable gland and the cable which may affect the quality of the cable seal.

Furthermore, movement of the gland relative to the wall during removal of the cable is not addressed by the prior proposal.

According to the present invention there is provided a cable gland assembly for a cable passing through, for example, an aperture in a wall, the assembly comprising: an intermediate sleeve having a first thread of one hand and first sealing face adjacent one end, and a second thread of the other hand and a second sealing face adjacent the other end; and a cable gland, for engaging the cable, the gland having a third thread which is complementary to the first thread, and a third sealing face; the first and third threads being engageable to create a seal between the first and third sealing faces and/or the second thread being engageable with a fourth thread associated with the aperture to create a seal between the second sealing face and a fourth sealing face also associated with the aperture; wherein the assembly is provided with a mark or visual indication which, during construction of the assembly, is positionable with respect to a predetermined point associated with the assembly or aperture to indicate a predetermined axial relationship between the intermediate sleeve and either the wall or cable gland sleeve.

Thus, the cable can be disconnected from the apparatus and removed from the aperture without disturbing the gland. The gland itself can be constituted by a flameproof seal, a moisture seal, an explosion seal, an armour cable earthing clamp or any combination thereof.

When more than one kind of gland is incorporated in the gland sleeve, it is possible to mount a series of suitable seals in an axial line on the cable. It is thus not necessary to increase the overall diameter of the assembly.

Preferably, the mark is located on the intermediate sleeve and is positionable with respect to the wall by engagement of the-second and fourth threads to indicate the axial relationship. Preferably, the mark is constituted by a ring on the second thread, one axial edge of which is alignable with the face of the wall adjacent the intermediate sleeve. Preferably, the positioned mark indicates a predetermined relationship between the unengaged turns of the first and second threads before sealing engagement of the first and third, and second and fourth, sealing faces.

Preferably, the positioned mark indicates an equal number of unengaged turns on both the first and second threads before sealing engagement between the first and third and second and fourth sealing faces.

Alternatively, the mark may be located on the cable gland sleeve and is positionable with respect to a predetermined point, associated with the assembly or aperture, to indicate a predetermined axial relationship between the intermediate sleeve and either the wall or the cable gland sleeve.

According to a second aspect of the invention there is provided a method of assembling a cable gland assembly as described in the first aspect of the invention the method comprising: positioning the indicating mark with respect to the predetermined point to adopt the axial relationship between the sleeve and the cable gland sleeve or the wall; maintaining the angular position of the cable gland sleeve with respect to the wall; rotating the intermediate sleeve to sealingly engage the first and third and second and fourth sealing faces substantially simultaneously.

Preferably, the mark is aligned with the predetermined point and then the other of the gland sleeve and wall is brought into engagement with the corresponding complementary thread on the intermediate sleeve.

Preferably, when the mark is an axial ring on the second thread of the intermediate sleeve, the edge of the ring is aligned with the surface of the wall adjacent the second sealing face and then the cable gland sleeve is offered up for engagement between the first and third threads.

Alternatively, when the mark is located on the cable gland sleeve it is aligned with the predetermined point and then the second thread on the intermediate sleeve is brought into engagement with the complementary thread associated with the aperture.

According to a third aspect of the invention there is provided a method of dismantling a cable gland assembly as described in the first aspect of the invention the method comprising: maintaining the angular position of the cable gland sleeve with respect to the wall; and rotating the intermediate sleeve to disengage the cable gland sleeve or the intermediate sleeve from the intermediate sleeve or the wall respectively.

The present invention can be put into practice in several ways, some of which will now be described by way of example with reference to the accompanying drawings in which: FIGURE 1 is a longitudinal section through a first embodiment of a cable gland assembly according to the present invention; FIGURE 2 is a longitudinal section through the gland of Figure 1 partly assembled; FIGURE 3 is a longitudinal section through a second embodiment of a cable gland assembly according to the present invention; FIGURE 4 is a longitudinal section through a third embodiment of a cable gland assembly according to a third embodiment of the invention; and FIGURE 5 is a longitudinal section through a fourth embodiment of a cable gland according to the present invention.

Figures 1 and 2 show a cable gland assembly for mounting a cable 10 with respect to an aperture 12, in a wall 14 of a housing for electrical equipment. The assembly includes an intermediate sleeve 46, a main body sleeve 24, a locking sleeve 34 and a clamping ring 38.

The cable 10 has an outer cable sheath 16 and an inner cable sheath 18 between which there is a braided armour wire layer 20. The inner sheath 18 surrounds conductors 22 which extend through the aperture 12.

The main body sleeve 24 has a hexagonal nut flange 26 for engagement by a spanner. To one side of the flange 26 is a length of external right-hand thread 28 and to the other side of the flange 26 is a left-hand external thread 30. On the opposite side of the right-hand thread 28, the main body sleeve 24 is formed with an outer tapered surface 32. The outer surface 32 may be knurled to provide a keyed surface against which the armour wire 20 is secured in a conventional manner by means of the armour locking sleeve 34 which has a complementary internally tapered surface to engage the armour wire 20 and thus clamp it against the surface 32.

The locking sleeve 34 extends from the tapered surface in the form of a cylinder 36 having an external thread which is engaged by the clamping ring 38 which has a complementary internal thread. The end of the clamping ring 38 is formed with a radially inwardly turned collar 39 which engages a ferrule 40. When the clamping ring 38 is drawn onto the external thread of the cylinder 36 it draws the ferrule axially along the cable 10. A chamfered face at the end of the ferrule 40 remote from the collar 39 is forced against a Neoprene seal 42 which abuts the end of the cylinder 36 and forces it radially inwardly into sealing contact with the outer sheath 16 of the cable 10.

Engaging the left-hand external thread 30 on the sleeve 24 is a complementary internal thread 44 on the intermediate sleeve 46. The internal thread 44 is terminated within the sleeve by an inner annular sealing face 47 lying normal to the axis of the sleeve.

There are a maximum of five complete turns between disengagement of the main body sleeve 24 and sealing contact between the sealing face 47 and a conplementary end face 51 on the main body sleeve 24.

The outer surface 49 of the intermediate sleeve 46 axially opposite the sealing face 47 is formed as an external sealing face which is parallel to the adjacent surface of the wall 14. The end of the intermediate sleeve 46 remote from the internal thread 44 is formed with an external right-hand thread 48 up to the sealing surface 49, which thread engages a complementary internal thread 50 formed on the surface wall defining the aperture 12. The intermediate sleeve 46 is also formed with a hexagonal nut flange 51 for engagement by a spanner.

The end of the external thread 48 on the intermediate sleeve 46 remote from the face 49 is indelibly marked with a black ring 53. The axially inner edge of the ring 53, nearest the sealing face 49, coincides with the end of the fifth complete turn of the external thread 48. Thus, when the inner edge of the ring 53 is aligned with the plane of the wall, there is a maximum of five complete turns between disengagement of the intermediate sleeve 46 from the aperture 12 and a sealing contact between the surface of the wall 14 and the outer sealing face 49.

A black arrow 54 is marked on the outer surface of the intermediate sleeve 46 to indicate the sense of rotation of the intermediate sleeve 46 to assemble the gland.

The quality of the sealing engagement between the outer surface 49 and the wall 14, and the inner surface 47 and the end of the main body sleeve 26 will depend on the use to which the assembly is put. The abutting face-to-face contacts shown provide a heavy duty seal for particularly harsh environments. In some circumstances the sealing contact might more appropriately be achieved by use of a Neopreme sealing ring interposed between one or other of the pairs of opposing seal faces. In such a case the relative numbers of the relevant threads and the position of the ring 53 would be adjusted appropriately.

The method of assembly will now be described, again with reference to Figures 1 and 2.

Firstly, the sub-assembly of the main body sleeve 24, the locking sleeve 34 and the clamping ring 38 are fixedly located on the cable. Then the intermediate sleeve 46 is threadedly inserted into the aperture 12 in the wall 14 until the axially inner edge of the black circular marking ring 53 is aligned with the face of the wall 14 adjacent the intermediate sleeve 46.

The left hand external thread 30 on the main body sleeve 24 is then offered up to the left-hand internal thread 44 of the intermediate sleeve 46. The intermediate sleeve 46 is then further rotated in the direction of the black arrow 54 to draw the main body sleeve 24 and intermediate sleeve 46 towards the wall 15.

By taking account of the indicating ring 53 marked on the right-hand external thread 48 of the intermediate sleeve 46 the number of turns required to effect sealing engagement of the outer surface 49 on the intermediate sleeve 46 and the adjacent surface of the wall 14, and the number of turns required to effect sealing engagement of the inner surface 47 and the abutting end face 51 of the main body sleeve 24 is substantially the same. Thus, the two seals will be made substantially simultaneously as the intermediate sleeve 16 is rotated. In this way the gland seal does not have to be unduly disturbed by rotating the gland/cable assembly to take up any unengaged threads in either of the connections.

When the assembled gland seal is to be be disconnected from the wall in order to repair or replace the equipment associated therewith, the main body sleeve 24 is held in its radial position with respect to the wall 14. The intermediate sleeve 46 is then rotated to disengage its right- and left handed threads 44 and 48 simultaneously from both the aperture 12 and the main body sleeve 24. Again, the gland seal is undisturbed by the rotation of the intermediate sleeve 46. The gland seal can remain on the cable 10 and re-engaged with the wall 14, through the intermediate sleeve 46, when connection is to take place.

Figure 3 illustrates a second embodiment of the invention in which the cable gland incorporates only a sealing device constituted by a Neoprene ring 142 and a ferrule 140 arrangement substantially the same as in Figure 1. The ring 142 is urged radially inwardly by a threaded bush 138 which engages threads on a cylindrical extension of a sleeve 134. Again, an intermediate sleeve 146 engages the aperture with a right-hand external thread 148 and a main body sleeve 124 with an internal left-hand thread 144.

Figure 4 illustrates a third embodiment of the invention in which the cable gland incorporates only an armour wire clamping device comprising a tapered surface 232 on a main body sleeve 224 which co-operates with a complementarily shaped surface on a clamping ring 238 to clamp the wire there between. An intermediate sleeve 246, similar to the intermediate sleeve 46 in Figure 1, is disposed between the main body sleeve 226 and an aperture 212 in a wall 214.

A fourth embodiment of a cable gland assembly according to the invention is illustrated in Figure 5 and comprises a moisture and explosion-proof inner seal 360, an armour clamping device 363 and a weatherproof seal 364.

The armour clamping device 363 and weather-proof seal 364 are similar to those described in relation to Figure 1. The explosion proof seal comprises an annular sealing ring 366 located inside a supplementary sleeve 368. The right-hand end of the sleeve 368 is internally threaded and receives the external thread of a main body sleeve 326. The sealing ring 366 sits on a chamfered face in the sleeve 368 and is urged radially inwardly thereby as' the end of the main body sleeve 366 forces it axially towards an intermediate sleeve 346.

The ring 366 thus engages the inner sheath 318 of the cable 310.

In all other respects the assembly is substantially the same except that the left-hand internal thread 344 on the intermediate sleeve 346 is engaged by a complementary thread on the supplementary sleeve 368.

Claims

1. A cable gland assembly for a cable passing through, for example, an aperture in a wall, the assembly comprising: an intermediate sleeve having a first thread of one hand and first sealing face adjacent one end, and a second thread of the other hand and a second sealing face adjacent the other end; and a cable gland for engaging the cable, the gland having a third thread which is complementary to the first thread and a third sealing face; the first and third threads being engageable to create a seal between the first and third sealing faces and/or the second thread being engageable with a fourth thread associated with the aperture to create a seal between the second sealing face and a fourth sealing face also associated with the aperture; wherein the assembly is provided with a mark or visual indication which, during construction of the assembly, is positionable with respect to a predetermined point associated with the assembly or aperture to indicate a predetermined axial relationship between the intermediate sleeve and either the wall or cable gland sleeve.

2. An assembly as claimed in claim 1, wherein the mark is located on the intermediate sleeve and is positionable with respect to the wall by engagement of the second and fourth threads to indicate the axial relationship.

3. An assembly as claimed in claim 2, wherein the mark is constituted by a ring on the second thread, one axial edge of which is alignable with the face of the wall adjacent the intermediate sleeve.

4. An assembly as claimed in claim 1, 2 or 3, wherein the position mark indicates a predetermined relationship between the unengaged turns on the first and second threads before sealing engagement of the first and third, and second and fourth, sealing faces.

5. An assembly as claimed in claim 4, wherein the position mark indicates an equal number of unengaged turns on both the first and second threads before sealing engagement between the first and second and second and fourth sealing faces.

6. An assembly as claimed in claim 1, wherein the mark is located on the cable gland sleeve and is positionable with respect to a predetermined point, associated with the assembly or aperture, to indicate a predetermined axial relationship between the intermediate sleeve and either the wall or the cable gland sleeve.

7. A method of assembling a cable gland assembly as claimed in any preceding claim, the method comprising: positioning the indicating mark with respect to the predetermined point to adopt the axial relationship between the sleeve and the cable gland sleeve or the wall; maintaining the angular position of the cable gland sleeve with respect to the wall; and rotating the intermediate sleeve to sealingly engage the first and third and second and fourth sealing faces substantially simultaneously.

8. A method as claimed in claim 7, in which the mark is aligned with the predetermined point and then the other of the gland sleeve and wall is brought into engagement with the corresponding complementary thread on the intermediate sleeve.

9. A method as claimed in claim 7 or 8, in which when the mark is an axial ring on the second thread of the intermediate sleeve, the edge of the ring is aligned with the surface of the wall adjacent the second sealing face and then the cable gland sleeve is offered up for engagement between the first and third threads.

10. A method as claimed in claim 7 or 8, in which when the mark is located on the cable gland sleeve it is aligned with the predetermined point and then the second thread on the intermediate sleeve is brought into engagement with the complementary thread associated with the aperture.

11. A method of dismantling a cable gland assembly as claimed in any of claims 1 to 6, the method comprising: maintaining the angular position of the cable gland sleeve with respect to the wall; and rotating the intermediate sleeve to disengage the cable gland sleeve or the intermediate sleeve from the intermediate sleeve or the wall, respectively.

12. A cable gland assembly for a cable passing through an aperture in a wall substantially as specifically described herein, with reference to the accompanying drawings.

13. A method of assembling a cable gland assembly substantially as specifically described herein.

14. A method of dismantling a cable gland assembly substantially as specifically described herein.