WO1998033236A1

WO1998033236A1 - Cable shield terminator

Info

Publication number: WO1998033236A1
Application number: PCT/GB1998/000163
Authority: WO
Inventors: Bruno Lemonnier
Original assignee: Raychem S.A.; Raychem Limited
Priority date: 1997-01-23
Filing date: 1998-01-19
Publication date: 1998-07-30
Also published as: GB9701380D0

Abstract

A termination for a plurality of shielded cables (5), said termination comprising a hollow body (1) with at least one open end, a shielding member (3) closing one end of said body and having a plurality of passages (6) through which cables can pass, a plurality of shielded cables (5) whose shielding (8) terminates at the shielding member (3), each shielding (8) being provided with a connecting member (10) adapted to engage with the shielding member (3) so as to electrically connect the shielding member (3) and the shielding (8) and to retain the cable on the shielding member, wherein the connecting member (10) comprises a first part (16) extending along and bonded to the shielding (8) and a second part (17) substantially at right angles to the first part and wherein the shielding member (3) and each connecting member (10) are adapted to be held together in individual screwed connection.

Description

CABLE SHIELD TERMINATOR

The present invention relates to cable shield terminations.

It is well-known that to use screened cables for communications. Such screened cables comprise one or more inner conductors which carry signals and are separated by insulation from an outer conductor which acts as a screen to prevent external electrical fields interfering with the signal or signals carried by the conductors within the screen. It is often necessary to connect a plurality of screened cables to electrical equipment, which is itself screened e.g. by an earthed conductive casing. It is important to provide a connector which minimises the opportunity for external electrical fields to penetrate to electrical equipment through the connector.

An example of an electrical connector for terminating a plurality of screened cables is disclosed in US 4 820 201. This discloses a connector comprising a cylindrical body. At the outer end of the body (i.e. the end through which the screened cables enter) a metal shielding plate is provided which closes the interior of the cylindrical body. The shielding plate has a plurality of apertures through which the shielded cables are passed. The shielding on the cables is connected to the shielding plate by ferrules mounted on the shielding of each cable. The ferrules are held in place on the shielding plate by flanges spaced apart on the ferrule by a distance corresponding to the thickness of the shielding plate. Each ferrule has a slot at its inner end which enables it to be temporarily deformed so that the flange at the inner end can be passed through the aperture.

Another cable shield termination is disclosed in US 5 246 376. In this device the shielding plate, which fits within a cylindrical body, has a plurality of slots around its periphery. A flanged ferrule is fitted over the screen of each cable which is to be connected. The ferrules fit within the slots and a pair of flanges on each ferrule engages with opposed sides of the shielding plate to prevent movement in the axial direction. There is, however, no restriction on radial movement during the initial assembly. All the ferrules must be in place on the shield plate before a retaining member in the form of a pair of half rings can be placed around the shield plate and a locking ring must be tightened on the body before the ferrules are held securely in place.

EP-B-0295154 discloses an arrangement for shielding an aperture in an electrical connector housing in which the aperture is closed by an electrically conductive shielding member which receives a plurality of shielded cables. Two of the embodiments disclosed have flanged ferrules and a slotted shielding plate similar to those disclosed in US 5246376. A third embodiment has a shielding plate having holes rather than slots. However, the shielding plate is used together with a locking plate provided with recesses in which the flanged ferrules are held by their flanges, before the ferrules are brought into contact with the shielding plate. There is no restriction on axial movement in this initial stage of assembly. All the ferrules must be in place on the locking plate before connection can proceed.

Individual cables can be disconnected by taking the connector apart but when this is done there is a possibility for all the cables, and not just the cable of interest, to slip out of the slots.

According to the present invention there is provided a termination for a plurality of shielded cables, said termination comprising hollow body with at least one open end,

a shielding member closing one end of said body and having a plurality of passages through which cables can pass,

a plurality of shielded cables whose shielding terminates at the shielding member, each shielding being provided with a connecting member adapted to engage with the shielding member so as to electrically connect the shielding member and the shielding and to retain the cable on the shielding member wherein the connecting member comprises a first part extending along and bonded to the shielding and a second part substantially at right angles to the first part and

wherein the shielding member, and each connecting member, are adapted to be held together in individual screwed connection.

A connector suitable for making a shielded connection with a plurality of shielded cables, said connector comprising:

(a) a hollow body with at least one open end,

(b) a shielding member closing one end of said body and having a plurality of passages through which cables can pass,

said shielding member having a plurality of lands adjacent its periphery defining between them a plurality of depressions, each aligned with a passage, a plurality of threaded means, one within each said depression, each said threaded means being located outwardly of the corresponding passage, and

(c) means for retaining the shielding means within the body.

The connector of the present invention has the advantage that individual cables can be separately secured to the shielding member before the shielding member is inserted into the body of the connector. There is no need to place all the cables in position before the cables are secured to the shielding member with the risk that some of the cables will move out of the desired position before all the cables have been placed in position. Furthermore, cables may be replaced, or added in unfilled positions, without disturbing the securement of existing cables. The body is of conductive material or has one or more conductive layers to provide electrical shielding for the interior of the body and to make electrical contact to the shielding member.

The body may be of tubular form, open at each end. The end opposite that by which the cables enter the body may be provided with means e.g. screw threads for connecting it to other components, usually a metal housing or backshell. Thus the body may be connected to a shell which surrounds the individual unshielded cables and the shell may be provided with means, e.g. a screw thread, to allow the shell to be attached to a screened enclosure.

The body may comprise portions defining a tubular bore having different cross-sectional areas along its axis. The body may have an internal step separating the portions of different cross-sectional area, the size of the step being such that the shielding member can be passed into the body through the portion of the bore of greatest cross-sectional area until it makes contact with the step, against which it may subsequently be secured, by a lock nut for example. Alternatively, the body may have a bore of continuously decreasing cross-sectional area. In such a case the shielding member may have an outer portion corresponding form for engaging with the interior of the body when it has been inserted a sufficient distance into the body.

The body may be in one piece. In such a case the shielding member may be inserted into the body from only one direction when there is a change in the cross-sectional area of the bore defined by the body.

However it is preferred for the body to comprise a first part defining an internal bore which is sufficient to allow the shielding member to pass completely through the bore, and a detachable second (locating) part for engaging with the first part of the body and with the shielding member to locate the shielding member within the bore. Such an arrangement can facilitate connecting cables as it allows the shielding member to be passed through the body in the absence of the second part. Thus the shielding member may be passed into a housing where connections are made to it. The shielding member may then be withdrawn. The second (locating) body part may then be mounted either within the body or on the shielding member. The shielding member is then passed back into the body

until its further movement is prevented by the interaction of the shielding member with the second body part and of the second body part with the first body part.

The second body part may be a pair of half-rings. When the shielding member is in position within the body these may be held in a step in the shielding member and a step in the bore defined by the first body part.

The shielding member may be retained within the body by means of a nut with an external screw thread which engages with an internal screw thread on the body. The nut may hold the shielding member against a step or other portion of reduced cross-sectional area within the bore defined by the body.

The shielding member is also of conductive material or has one or more layers of conductive material to provide the required shielding. The shielding member is preferably removably located within the body. It may be held within the body by a locking nut which fits within the body and holds the shielding member against an internal step in the body.

The shielding member is preferably made in one piece.

Preferably the passages in the shielding member are a plurality of holes spaced from the periphery of the shielding member. The shielding member is preferably adapted to hold the connecting members by having a plurality of internally threaded holes located between the periphery and the passages for the cables. The passages in the shielding member may alternatively be located at the periphery of the shielding member in the form of a plurality of slots extending inward from the periphery. In this arrangement, the screwed connections to the shielding means are made to a plurality of locations located inwardly of the passages.

Preferably the passages, whether peripheral slots, or more centrally-located holes, are elongated with the longest direction towards the periphery of the shielding member. The elongation of the passages allows easier passage therethrough of the cables, which, at this stage of assembly of the connector, usually have a contact member, for example a crimp connector, already fitted to the exposed ends of their conductors. Also, the elongation allows for some small adjustment of the positioning of the cables during assembly.

The shielding member preferably has a plurality of lands (raised portions) spaced apart round the periphery so as to leave depressions between the lands containing the means for making the screwed connection to the shielding member. The shape of the depressions preferably corresponds to the shape of the second part of the connecting member. This helps to locate the connecting member correctly on the shielding member, and to prevent its rotation, and thus rotation of the associated cable.

The connecting member is preferably connected to the shielding member of the cable using a heat shrinkable sleeve containing solder. The part of the connecting member to be connected to the shielding is introduced into the sleeve which has previously been fitted over the shielding. The sleeve is then heated to melt the solder and shrink the sleeve on to the cable.

The portion of the connecting member in contact with the shielding of the cable is conveniently in the form of a straight bar.

The second part of the connecting member may be adapted to be held in screw threaded engagement with the shielding means by being in the form of a flat lug with straight sides and a slot at its outer end. The lug may be introduced into the space between the lands in the shielding member so as to be mechanically located and to be aligned with a hole with an internal screw thread. The connecting member may be then held in place on the shielding member by a bolt. The bolt may be provided with a outer edge, e.g. hexagonal, to which a driving means e.g. spanner, may be applied. Alternatively the bolt may have an upper surface with a depression shaped to engage with a suitable driving means, e.g. screw driver or Allen key.

In the preferred arrangement the connecting member is permanently connected to the cable and is releasably connected (by the screwed connection) to the shielding member.

The invention will now be described by way of example with reference to the accompanying drawings in which

Figure 1 is a side view, partly in cross-section, of a cable termination in accordance with the invention,

Figure 2 is an end view of the cable termination shown in Figure 1, looking in the direction II-H,

Figure 3 is a view of a sleeve containing solder, a connecting member, and a screened cable before assembly,

Figure 4 is a view of the components of Figure 3 assembled together,

Figures 5a, 5b and 5c are views of the connecting member shown in Figures 3 and 4,

Figure 6 is a cross section through the shielding member which is a component of the cable termination shown in Figure 1 ,

Figures 7 and 8 are further views of the shielding member, and Figure 9 is a side view, partly in cross-section of an alternative cable termination.

Referring to Figure 1 the cable termination comprises a hollow body 1, within which there is a step 2 against which rests a shielding member 3. The shielding member 3 is held against the step 2 by a backnut 4, which has an externally threaded portion which engages with an internally threaded portion of the body 1.

A plurality of shielded cables 5 extend through apertures 6 in the shielding member 3. Each cable comprises a plurality of insulated conductors 7 surrounded by a layer of braided conductor 8 acting as a screen. The braid is itself surrounded by insulation 9. The screen is bonded by a solder connection to a connecting member 10 which is held against the shielding member 3 by a threaded bolt 1 1 which engages with a threaded aperture 12 in the shielding member.

The bonding of the connecting member 10 to the screened cable is best understood from Figure 3, 4 and 5a, b, c. A heat shrinkable sleeve 13 of polymeric material contains a ring 14 of hot melt adhesive and a ring 15 of solder. The connecting member 10 is an L-shaped metal stamping comprises a braid connection part 16 and a shield engaging lug 17 which has a recess 18.

The sleeve 13 is fitted over the braid and the braid insulation and the braid connection part 16 of the connecting member 10 is inserted into the sleeve 13 over the braid 8.

Heat is then applied to shrink the sleeve 13 on to the cable and to melt the ring 14 of hot melt adhesive to provide a seal between the sleeve 13 and the braid insulation 9. The solder ring 15 is melted to bond the connecting member 10 to the braid.

Once the connecting member has been bonded to the braid, the connecting member is fixed to the shielding member using the bolt 11. This bolt (see Figure 2) has a hexagonal depression 18 in its head by which it can be rotated to engage with threaded aperture 12 (see Figures 6, 7, 8).

The shielding member has a plurality of raised lands 19. Between these lands are depressions into which fit the lugs 17 of the connecting members 10. The sides of the lands help to hold the connecting member in place while it is being screwed to the shielding member.

Figure 9 shows a modified form of cable termination.

The hollow body 1 comprises a first part la having a step 2. A part of half rings constitute the second body part lb The half rings are held between the shielding member 3 and step 2 in body part la. The outer diameter of shielding member 3 is less than the minimum diameter of the bore within body part la.

The body 1 is shown connected to a back-shell 19 which is shaped so as to fit on a connector 20.

When making an electrical connection the cables 5 can be inserted into the apertures in the shielding member 3 and the screens of the cables can then be connected to the shielding member. The shielding member can then be passed through the body to facilitate making connections to connector 20. It can then be withdrawn and the two half rings lb placed in bodypart la. The shielding member is then inserted into the body until it engages with the half rings lb, and the backnut 4 is then screwed into place to hold the shielding member against the half-rings.

Claims

1. A termination for a plurality of shielded cables, said termination comprising

a hollow body with at least one open end,

a plurality of shielded cables whose shielding terminates at the shielding member, each shielding being provided with a connecting member adapted to engage with the shielding member so as to electrically connect the shielding member and the shielding and to retain the cable on the shielding member

wherein the shielding member and each connecting member are adapted to be held together in individual screwed connection.

2. A termination according to claim 1 wherein the passages for the cables are a plurality of holes spaced from the periphery of the shielding member.

3. A termination according to one of claims 1 or 2 wherein the shielding member is adapted to hold the connecting members by providing a plurality of internally threaded holes located between the periphery and the passages for the cables.

4. A termination according to any one of the preceding claims wherein the shielding member has a plurality of lands spaced apart round the periphery so as to leave depressions between the lands containing means for making screwed connection to the shielding member.

5. A termination according to Claim 4 wherein the shape of the depressions corresponds to the shape of the second part of the connecting member.

6. A termination according to any one of the preceding claims wherein the second part of the connecting member is an apertured lug and is held to the shielding member by a threaded bolt.

7. A termination according to any one of the preceding claims wherein the body defines a bore having portions of different cross-sectional area and comprises (a) a first part defining a bore whose minimum of cross-sectional area is such that the shielding member can be passed through it, and (b) a detachable second part which engages with the first part of the body and with the shielding member to locate the shielding member within the bore.

8. A termination according to Claim 7 wherein the second body part is a pair of halfrings.

9. A connector suitable for making a shielded connection with a plurality of shielded cables, said connector comprising.

(a) a hollow body with at least one open end,

(b) a shielding member closing one end of said body and having a plurality of said shielding member having a plurality of lands adjacent its periphery defining between them a plurality of depressions, each aligned with a passage a plurality of threaded means, one within each said depression, each said threaded means being located outwardly of the corresponding passage, and

(c) means for retaining the shielding means within the body.