GB2204746A

GB2204746A - Cable gland

Info

Publication number: GB2204746A
Application number: GB8711083A
Authority: GB
Inventors: John David Sowerby
Original assignee: C M P
Current assignee: C M P
Priority date: 1987-05-11
Filing date: 1987-05-11
Publication date: 1988-11-16
Anticipated expiration: 2007-05-11
Also published as: GB8711083D0; GB2204746B

Abstract

A cable gland for sealing a cable (6) against the ingress of moisture or other contaminants comprises a gland sleeve (2), a compression collar (4) axially movable with respect to the sleeve, a sealing ring (36) and a set of nested inter- engaging skid washers (30, 32 and 34). When the compression collar (4) is tightened on the sleeve (2), a flange (21) engages the outermost one (30) of the skid washers and thus a compressive force is transmitted from the compression ring (4) to the sealing ring (36) which deforms radially inwardly into sealing engagement with the cable (6). <IMAGE>

Description

"IMPROVEMENTS IN CABLE GLANDS" The present invention relates to sealing glands for use on electrical cables and similar conduit.

A known cable gland fitted to the outside of a cable comprises a gland sieve on which is threadingly engaged a compression nut. An elastomeric sealing ring is squeezed between the nut and sleeve, as the nut is turned on the sleeve, to distort it radially inwardly into sealing engagement with the outer surface of the cable sheath. The annular clearance between the inner surface of the sleeve and the outer surface of the sheath is taken up by a so-called skid washer which is interposed between a flange on the nut and an adjacent surface of the sealing ring. In this way, the gland prevents moisture from ingressing into the junction between the cable and a further piece of cable for a fixture to which the cable is attached.

However, such known cable glands suffer from disadvantages. Among these, it is necessary to drill out the skid washer on-site in accordance with the diameter of a particular cable to which the gland is to be fitted. It is seldom possible to carry out such onsite work and maintain the standards of quality of finish and cleanliness that are required if a sufficiently good seal is to be effected.

It is an object of the present invention to provide a seal that is adaptable to a range of sizes of cable without elaborate on-site preparations.

According to the present invention there is provided a cable gland comprising a gland sleeve, a compression collar axially movable with respect to the sleeve, the sleeeve and collar together defining an aperture to receive the cable to be sealed, a sealing ring for forming a seal between the sleeve and the cable and a set of two or more nested skid washers engaging the sealing ring, the skid washers being of progressively smaller internal diameter, the outermost washer being engaged axially by the compression collar, each washer being arranged to engage the adjacent inner washer axially.

Thus, axial compressive force from the collar is transferred to the outermost washer and then to the next inner wahser, and so on, with any or all of the washers compressing the sealing ring to form the seal.

With such an arrangement it is possible to select the number of skid washers to suit the annular clearance between the outer surface of the cable to be sealed and the inner surface of the radially adjacent portion of the sleeve or collar.

The present invention therefore provides a nest of skid washers of differing diameter which are interengage in the axial direction to transmit the compressive force between for example a flange on the compression collar and a flange on the sleeve. By utilizing such a set of pre-formed washers the appropriate ones may be selected on-site to accomodate the annular space between the cable and the gland sleeve without having to modify the washer to fit.

The present invention can be put into practice in several ways two embodiments of which will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a partially sectioned view of a first embodiment of a cable gland according to the present invention; and Figure 2 is a partially sectioned view of a second embodiment of a cable gland according to the present invention.

Referring to Figure 1, a first embodiment of a cable gland according to the present invention comprises a gland sleeve 2 (the end of which is shown) and a gland compression collar 4 which is received by the end of the sleeve 2. The sleeve and collar assembly is mounted on a length of cable 6 about which the seal is to be formed.

The inner surface of the sleeve 2 comprises a first straight-sided tubular inner wall portion 8 which is terminates in an annular recess 10 which accomodates a coaxial retention ring 12. The edge of the recess 10 remote from the inner wall 8 is formed into an axially projecting lip 14 thus creating a channel 15 between the lip and a radially more outward second straightsided inner wall portion 16 which extends axially from the lip 14. The outside of the sleeve radially in the region of the second wall portion 16 is formed with a thread 18.

The compression collar 4 comprises a cylindrical skirt 20 which is formed with an internal thread which engages the threaded portion 18 on the sleeve 2. The end of the collar 4 remote from the sleeve 2 is formed with a radially inwardly-extending flange 21 which projects past the inner extent of the sleeve 2.

As the collar 4 is screwed onto the sleeve 2, the flange engages a first outermost skid washer 22 of a series of three annular skid washers. The first skid washer 22, in turn, slides over a second skid washer 24 and engages it by means of an annular abutment on the second washer 24 which is accomodated by a complimentary annular ledge on the innermost end of the first skid washer 22. A similar arrangement of abutment and ledge between a second and a third washer 26 thus causes all three skid washers to be urged inwardly with respect to the sleeve 2 as the collar 4 is turned on the sleeve 2.

An elastomeric displacement type annular sealing ring 28 is located between the inner ends of the skid washers 22, 24 and 26 and the axially outer end of the retention ring 12. The sealing ring 28 is normally tubular in construction, but in use its axially outer face is deformed to be inclined inwardly away from the axis of the sleeve 2 by the inner faces of the skid washers 22, 24 and 26 which are each formed with a similarly inclined end face 29 with respect to the axis of the sleeve 2.

As the collar 4 is turned on the sleeve 2, drawing in the inter-engaging skid washers, the sealing ring 28 is at once forced axially and radially inwardly to abut the retention ring 12, conforming to the profile of the lip 14 and channel 15 on the one hand, and to bearing on the surface of the cable 6 on the other. A seal is thus created by the sealing ring 28 in contact with the sleeve 2 and the cable 6.

The diameter of the cable to be sealed will determine the number of skid washers that are required to take up the clearance between the inside of the sleeve and the cable itself.

The sealing ring is selected from a family of such sealing rings of different radial thickness to limit the diametrical clearance between it and the cable in order that a seal can be achieved within the extent of axial travel of the collar 4 with respect to the sleeve 2.

Referring to Figure 2, a second embodiment of the present invention is shown applied to a compression seal. The sleeve 2 and collar 4 are similar to those in Figure 1. The flange 21 of the sleeve 2, however, bears against one end face of a first outermost one 30 of a series of three inter-engaging coaxial skid washers, the other end faces of which are perpendicular to the axis of the sleeve 2. Each of the second and third skid washes 32 and 34 have similarly axially perpendicular abutments 35 which are received on complimentary annular ledges on an outer adjacent skid washer.

A compression type elastomeric sealing ring 36 which is tubular in its normal state is deformed by the axial movement of the skid washers to bow radially inwardly to bear against the external surface of the cable 6. Again, the axially inner end of the sealing ring 36 is deformed to conform to the profile of the lip 14 and channel 15 and become seated in the channel.

As in the first embodiment, the sealing ring 36 is selected from a family of sealing rings of differing radial thickness in order to accomodate the clearance between the sleeve 2 and cable 6 sufficiently for the sealing ring to sealingly deform within the extent of axial movement of the skid washers as caused by the collar 4 with respect to the sleeve 2. The diameter of the cable to be sealed will determine the number of skid washers that are required to take up the clearance between the inside of the sleeve and the cable itself.

Claims

CLAIMS:

1. A cable gland comprising a gland sleeve, a compression, axially movable with respect with the sleeve, the sleeve and collar together defining an aperture to receive the cable to be sealed, a sealing ring for forming a seal between the sleeve and the cable, and a set of two or more nested skid washers engaging the sealing ring, the skid washers being of progressively smaller internal diameter, the outermost washer being engaged axially by a compression collar, each washer being arranged to engage the adjacent inner washer axially.

2. A cable gland as claimed in Claim 1 in which the sleeve was formed with an external thread, and a collar is formed with a corresponding internal thread, the collar also having a radially inwardly extending flange at its free end which engages the outermost washer.

3. A cable gland as claimed in Claim 1 or Claim 2 in which the outermost washer is formed with a circumferential recess in its radially inner surface at the end remote from the position of the collar flange, and the adjacent radially inner washer is formed withy an integral ring which is received in the recess.

4. A cable gland as claimed in any preceding claim in which each washer is formed with a circumferential recess in its radially inner surface at the end remote from the position of the collar flange, and the adjacent radially inner washer is formed with an integral ring which is received in the recess.

5. A cable gland as claimed in any preceding claim in which the outermost washer is formed with a ledge in its radially outer surface, the ledge being engaged by the collar flange.

6. A cable gland as claimed in any preceding claim in which the axially inner edges of the washer form the radially and axially inclined surface which engages the sealing ring.

7. A cable gland as claimed in Claim 1 to Claim 6 in which the axially inner ridges of the washers form a radial surface which engages the sealing ring.

8. A cable gland as claimed in any preceding claim in which a portion of the sealing ring which is remote from the washers engages a retention ring fixed to the sleeve.

9. A cable gland constructed and arranged substantially as herein specifically described with reference to and as shown in Figure 1 or Figure 2 of the accompanying 'drawings.