GB2260660A

GB2260660A - Cable feed-through and earthing unit

Info

Publication number: GB2260660A
Application number: GB9221673A
Authority: GB
Inventors: Jouni Knuuttila
Original assignee: Nokia Telecommunications Oy
Current assignee: Nokia Oyj
Priority date: 1991-10-16
Filing date: 1992-10-15
Publication date: 1993-04-21
Anticipated expiration: 2012-10-15
Also published as: FI914882A0; DE4233785A1; FI89426C; FI914882L; GB9221673D0; GB2260660B; FI89426B; SE503616C2; HK1006610A1; SE9203032L; SE9203032D0; DE4233785C2

Abstract

A cable feed-through and earthing unit comprises: a conductive case (1) with opposite side walls (3) for locating or feeding through cables (7); and spring contacts (6) for earthing the cables. The spring contacts may be formed as helical springs parallel to the side walls. Stripped cables (7) extending between the sidewalls are contacted by virtue of tension in the springs (6). <IMAGE>

Description

Cable feed-through and earthing unit The invention relates to a cable feed-through and earthing unit consisting of a metal case comprising at least a bottom and at least two side walls, recesses in two opposite side walls for feeding through cables, and means for earthing the cables.

An earthing unit is previously known which comprises two case halves which are to be pressed against each other and which comprise, in addition to a bottom and two side walls, partition walls in the direction of and similar to said side walls. The partition walls of each case half and the side walls in the direction of these have sharp-edged V-shaped notches, the partition walls of the second case half being laterally offset from the side walls of the first case half. When the case halves are pressed against each other, stripped cables positioned in the notches meander in the vertical direction of said walls as a result of said offset, whereby the cables tend to press against the edges of the notches for earthing.

Such earthing units are also known as comprise metal plates with notches into which the cables are pressed through a narrow opening, so that they remain in the notches after they are pushed there. The metal plates are screwed ddwn to a separate frame, and the mounted conductors are encased within the frame by means of a separate lid element which has recesses for the cables and which presses the cables against the edges of said notches.

In current feed-through and earthing units, which were exemplified above, earthing is uncertain, in particular if cables of different thickness are used. In addition, the structures are expensive and difficult to mount.

The object of the present invention is to obviate the above problems. This is achieved with the cable feed-through and earthing unit as described at the beginning, which according to the invention is characterised in that the earthing means consist of helical springs which are positioned inside the case parallel with the feed-through side walls comprising the recesses and between which the stripped cables are to be positioned, whereby the tension of the springs brings the springs into contact with the cables.

The invention is based on the use of conventional helical springs as the element in contact with the cable. The cables are passed between the helices of the springs, and the springs, being tensioned, thus press tightly against the cables.

In the unit of the invention, earthing is considerably more certain than before, the feed-through nevertheless being easy and inexpensive to realise. In addition, cables of different thickness may be passed between the same springs without contact problems. In one preferred structure of the invention the same springs may be used for inter-earthing several feedthrough units, whereby the bottom of the preceding case will be earthed to the springs of the following unit.

In the following the invention is described in more detail by means of two preferred embodiments with reference to the accompanying drawings, wherein Figure 1 is a perspective view of the first preferred embodiment of the invention, and Figure 2 is a perspective view of the second preferred embodiment of the invention.

The cable feed-through and earthing unit of Figure 1 consists of a metal case 1 having a bottom 2, two feed-through side walls 3, an additional side wall 4, a lid element 5 and helical earthing springs 6.

The feed-through side walls 3 are located on opposite sides of said bottom 2 and preferably have Ushaped recesses 3a for feeding through cables 7. Said additional side wall 4 is located at one edge of the bottom 2, between the walls 3. The lid element 5 has side walls 3' and 4' similar to those of the bottom 2, and the walls 3' which are in the direction of the walls 3 engaging the bottom 2 also preferably have recesses 3a' for the cables 7. The lid element 5 is hinged to the feed-through side walls 3 on the opposite side of the additional side wall 4.

First ends of said helical earthing springs 6 are attached to the hinging end of the lid element 5 and second ends to the additional side wall 4. Said springs 6 are therefore positioned parallel with the feed-through side walls 3. The stripped cables 7 are positioned between the helices of the springs 6, whereby the tension of the springs 6 brings them into contact with the cables 7. In addition, the springs 6 are attached here so as to be in pre-tensioned state when the lid element 5 is in the upward position. As a result, the springs 6 press the cables 7 tightly when the lid element 5 is pressed into the closed position.

In addition, the lid element 5 presses the cables 7 into the recesses 3a and 3a' and encases them within the case.

The feed-through and earthing unit of Figure 2 differs from the unit of Figure 1 in that a case 10 of Figure 2 comprises no lid element and that it comprises additional side walls 40 at both ends of the case between feed-through side walls 30, whereby helical earthing springs 6 are attached between the additional side walls 40. This structure is preferred when a large number of feed-throughs are carried out. In such a case, the case 10 is secured at its upper surface to the bottom of an identical case 10, whereby the springs 6 of the case to be secured are earthed to the bottom of the preceding case 10. Attachment may be realised e.g.

by means of grooves in the bottom of said case 10 and counterparts in the walls 40 of said case 10, which counterparts fit into the grooves (not shown in the drawing).

In the foregoing the invention was described by means of only two preferred exemplifying embodiments.

A person skilled in the art may however realise details of the unit according to the invention in numerous alternative ways within the scope of the accompanying claims.

Claims

1. A cable feed-through and earthing unit having a metal case comprising at least a bottom and at least two side walls, recesses in two opposite side walls for feeding through cables and means for earthing the cables, wherein the earthing means comprise helical springs which are positioned inside the case parallel to the feed-through side walls comprising the recesses and between which the stripped cables are to be positioned, whereby the tension of the springs brings the springs into contact with the cables.

2. A unit according to claim 1, wherein the unit comprises one additional side wall between the feedthrough side walls, and a lid element which is hinged to the feed-through side walls on the opposite side to the additional side wall and which presses the cables to be fed through into the recesses and encases them within the case, and that first ends of the helical earthing springs are attached to the lid element and second ends to the additional side wall.

3. A unit according to claim 1, wherein said helical earthing springs are attached to additional side walls between the feed-through side walls and the upper part of the case is open.

4. A unit according to claim 3, wherein the case comprises means at its upper surface for securing the case to the bottom of a further identical case, whereby the springs of the case to be secured are earthed to the bottom of the further case.

5. A cable feed-through and earthing unit having a conductive case and earthing means in contact with the case, wherein the case has a base and two opposite side walls, the opposite side walls having cable locating recesses and wherein the earthing means comprises at least one elongate resilient conducting member, the member(s) being configured to grip a cable located in the recesses and fed through the unit upon sideways engagement with the member, thereby providing electrical connection between the cable and the case.

6. A cable feed-through and earthing unit according to claim 5, wherein the conducting member is a spring.

7. A cable feed-through and earthing unit substantially as hereinbefore described with reference to Figure 1.

8. A cable feed-through and earthing unit substantially as hereinbefore described with reference to Figure 2.