GB2258956A

GB2258956A - Clamp for cable lead-in

Info

Publication number: GB2258956A
Application number: GB9216705A
Authority: GB
Inventors: Heinz Niemann
Original assignee: Atlas Elektronik GmbH
Current assignee: Atlas Elektronik GmbH
Priority date: 1991-08-07
Filing date: 1992-08-06
Publication date: 1993-02-24
Anticipated expiration: 2012-08-06
Also published as: GB9216705D0; GB2258956B; DE4126135C1

Description

2 2 739 -5 j CABLE LEAD-IN The invention relates to a cable lead-in for

securing an electric cable introduced through a hole in a part of a wall, more particularly in the casing wall of an electronics cabinet.

Cable lead-ins or lead-throughs are known and defined in DIN 89280 for ship's cables having a plastic jacket. DIN stands for Deutsche Industrie Norm, equivalent to German Industrial Standard for technical products, and DIN 89280 relates to the standardisation of cable entry fittings for devices. As a rule they are used even where the cable lead-ins do not need to be water-tight. Normally the prior art cable leadins consist two coaxial members, an outer and an inner member, which each enclose the cable and are assembled in the zone of the hole, for example, by screwing. Such cable lead-ins take up a relatively large amount of assembly clearance in the casing for the assembly of the cable and the lead-in. Moreover, various sizes of cable lead-ins must be kept in stock for particular cable diameters. In the case of a screened cable the screening braiding must be relatively accurately cut to length. After assembly the cable lead-in can no longer be checked for accurate contact making or the position of the screening.

It is an object of the invention to provide a cable lead-in of the kind specified which can be cheaply manufactured and simply g assembled and which requires very little assembly space and ensures high strain relief. Water-tightness is not required.

This problem is solved according to the invention in a cable lead-in of the kind defined in the preamble to claim 1 by the features of the characterizing part thereof.

The cable lead-in according to the invention is very simple from the aspect of manufacturing technique and therefore extremely cheap, more particularly since only the strap must be made separately, as against which the cable clamp used can be a commercially available mass product. In the range of use, for example, for cables up to 23 mm in diameter.. the cable lead-in is independent of cable diameter, so that only one single size must be produced and kept in stock. During assembly the cable lead-in according to the invention only takes up half as much space as the prior art cable lead-ins described hereinbefore.

Advantageous embadiments of the cable lead-in according to the invention, with convenient further developments of and additions to the invention can be gathered from the other claims.

When the cable lead-in is used for screened electric cables, according to a preferred embodiment of the invention the retaining strap and the cable clamp are made from an electrically conductive material. Before the cable clamp is fastened, a portion of the screening bared by skinning is drawn over that zone of the jacket of the electric cable which extends through the hole. It is not necessary to cut the screening precisely to - 3 length. After assembly the result can be checked without problems for satisfactory contact making and for the position of the screening.

In special cases in which the cable screening must be applied to a screening connection, according to another embodiment of the invention a copper wire is wound several times round the portion of the screening drawn over the zone of the jacket, the end of the copper wire extending to the screening connection of the electronics cabinet. When the cable lead-in is assembled, the cable clamp engages over the copper wire winding, which is clamped together with the cable firmly and nonpositively on the retaining strap.

In a preferred embodiment of the invention a separate retaining strap is attached on each side of the part of the wall in the zone of the hole and the electric cable is attached to each of the two retaining straps by means of a cable clamp. The result is not only very considerable strain relief on the cable connections, but the electric cable is also prevented from bending or twisting in the lead-in.

According to a preferred embodiment of the invention the retaining strap is formed by one arm of an angle whose other arm bears against the part of the wall and is attached thereto, preferably by screws. To ensure the reliable seating of the cable clamp on the retaining strap, provided at the free end of the arm forming the retaining strap are two retaining lugs which are unitary therewith and which project laterally beyond the J 1 retaining strap, thereby preventing the cable clamp from slipping off the retaining strap.

For two through-holes disposed one beside the other in the portion of the wall, a single angle can be used on each side of the portion of the wall and correspondingly bear two retaining straps spaced out at the distance of the holes.

The invention will now be described in greater detail with reference to embodiments thereof illustrated in the drawings, wherein:

Fig. 1 is a section through a portion of a wall of an electronics cabinet, with cable lead-in and screened electric cables, before and after assembly, and Fig. 2 is similar to Fig. 1, but with coaxial cables.

An electronics cabinet 10, a portion of which is diagrammatically shown in perspective in Fig. 1, has in one part of its wall 102 through-holes 11, 12 for the introduction of electric cables 13, 14 and bears on its part of the wall 102 oriented at right angles thereto a terminal board 15 with flat plugs 16 on to which cable terminals 17 of conductors 18 of the multi-core electric cables 13, 14, provided with said cable terminals 17 at the ends, are fitted. In each electric cable 13, 14 all the insulated conductors 18 are enclosed by a screening braiding 19 itself enclosed by a plastics jacket 20.

a 1 To relieve the strain on the cable terminals 17 fitted on to the flat plugs 16 and for their uncoupling from cable movements, provided at the holes 11, 12 are cable lead-ins 21, 22 by means of which the electric cables 13, 14 are so fixed at part 101 of the wall that neither tensile forces acting on the electric cables 13, 14 nor other forces can have any effect at the connection between the flat plug 16 and the cable terminals 17. Fig. 1 shows the cable lead-in 21 for the left-hand hole 11 prior to cable assembly and for the right-hand hole 12 following cable assembly.

The two cable lead-ins 21, 22 are identically constructed and each consist of two metal retaining straps 23, 24 and two conventional cable clamps 25, 26. Again, the two retaining straps 23, 24 and the two cable clamps 25, 26 are identically constructed. The retaining straps 23, 24 are attached to part 101 of the wall in the zone of the hole, the retaining strap 23 extending from the inside wall of the part 101 of the wall and the retaining strap 24 extending out from the outside wall of the part 101 at right angles in the longitudinal direction of the cable. The retaining straps 23 of the two cable lead-ins 21, 22 are formed by an arm, recessed in the central portion, of an angle 27 whose other arm bears against the part 101 of the wall and is attached, in this case screwed thereto. In the same manner the retaining strap 24 of the two cable lead-ins 21, 22 is formed by an arm, recessed in the centre, of an angle 28 whose other arm bears against the outside of the part 101 of the wall and is attached at that place in the same manner. The two angles 27, 28 are identically constructed, fitted laterally inverted on 1 1 - 6 to the part 101 of the wall and screwed to one another via bores 29, 30 in the bearing arms and matching bores in the part 101 of the wall. At the free end of each retaining strap 23, 24 two retaining lugs 31, 32 unitary therewith project laterally. The distance between the retaining lugs 31, 32 and the bearing arm of the angle 27; 28 for the fastening thereof is larger than the axial width of the cable clamps 25, 26. The width of the angles 27, 28 is substantially identical to the distance, enlarged by the diameter of the hole, between the two holes 11, 12 disposed one beside the other, the two retaining straps 23 on one angle 27 and the retaining straps 24 on the other angle 28 having a width substantially corresponding to the diameter of the holes 11, 12 and lying directly thereon.

For the assembly of the cables 13, 14 the cables are skinned at the front end as far as the screening braiding 19. The exposed portion of the braiding 19 is drawn over the front zone of the plastics jacket 20 of the cables 13, 14. As shown on the left in Fig. 1, the electric cable 13 thus prepared is guided through the hole 11 and fitted via the cable terminals 17 on the flat plugs 16. Then the cable clamp 25 is placed around the portion of the screening braiding and around the retaining strap 23 and tightened. As a result, on the one hand the electric cable 13 is located non-positively on the retaining strap 23, while on the other hand the screening braiding 19 is connected electrically conductively to ground. Then the cable clamp 26 is placed around the jacket 20 of the electric cable 13 and around the retaining strap 24 and also tensioned. The completely mounted electric cable 13 is then retained in the same manner at 1 6 the cable lead-in 21 as the electric cable 14 is retained at the cable lead-in 22. The construction of the cable clamps 25, 26 is known. They are conventionally made of metal and are also known ashose clamps. The clamp diameter can be increased or reduced as desired to a certain extent by turning a tightening screw 23 on the cable clamps 25, 26, thereby securing the electric cables 13, 14 non positively on the retaining straps 23, 24.

Referring to Fig. 2, via the aforedescribed cable lead-ins two coaxial cables 131, 141 extend through the part 101 of the wall of the electronics cabinet 10. The left-hand coaxial cable 131 is again shown prior to assembly on the cable lead-in 21, the right-hand coaxial cable 141 being shown following assembly on the cable lead-in 22. In the case of high frequency cables, such as the coaxial cables 13f, 141 are, the cable screening must extend to a screening connection 34 in the electronics cabinet 10. TO this end a copper wire 35 is wound several times round that portion of the screening braiding 19 which is drawn over the jacket 20 of the coaxial cable 131; 14f, one end of the copper wire 35 extending forwardly to the start of the cable. In the assembly of the coaxial cable 131; 141 the end of the copper wire is inserted in the screening connection 34, and the cable clamp 25 is placed over the copper wire winding 351 and then secured on the retaining strap 23. The other cable clamp 26 is placed in the same manner as shown in Fig. 1 over the jacket 20 of the coaxial cable 131; 141 and clamped to the outer retaining strap 24.

The invention is not limited to the embodiments thereof disclosed hereinbefore. In the case of electric cable lead-ins without screening, the retaining straps and cable clamps can also be made of plastics.

1 1

Claims

1. A cable lead-in for securing an electric cable introduced through a through-hole in a part of a wall, more particularly in the casing wall of an electronics cabinet, characterized by at least one retaining strap (23, 24) which is attached in the zone of the hole in the part of the wall (101) and which extends therefrom at right angles in the longitudinal direction of the cable, and a cable clamp (25, 26) which engages around the retaining strap (23, 24) and the electric cable (13, 14; 13f, 141) extending past said strap.

2. A cable lead-in according to claim 1 for a screened electric cable having a screening disposed below the cable jacket, characterized in that the retaining strap (23) and the cable clamp (25) are made of electrically conductive material, and prior to the attachment of the cable clamp (25) a portion of the screening (19) bared by skinning is drawn over that zone of the jacket of the electric cable (13, 14; 131, 14f) which extends through the through-hole (11, 12).

3. A cable lead-in according to claim 2, characterized in that a copper wire (35) is wound several times round the portion (19) of the screening drawn over the zone of the jacket, the cable clamp (25) engages over the copper wire winding (351), and one end of the copper wire (35) extends to a screening connection (34).

1 '..

- 10 4. A cable leadin according to one of claims 1 to 3, characterized in that a retaining strap (23, 24) is attached on each side of the part of the wall (101) in the zone of the hole, and the electric cable (13, 14; 13', 14f) is attached to each retaining strap (23, 24) by means of a cable clamp (25, 26).

5. A cable lead-in according to one of claims 1 to 4, characterized in that the width of the retaining strap (25, 26) is of the order of magnitude of the diameter (11, 12) of the hole.

6. A cable lead-in according to one of claims 1 to 5, characterized in that two retaining lugs (31, 32) unitary with the retaining strap (23, 24) project laterally at the free end thereof.

7. A cable lead-in according to claim 6, characterized in that the length of the retaining strap (23, 24) is larger as far as the retaining lugs (31, 32) than the axial width of the cable clamp (25, 26).

8. A cable lead-in according to one of claims 1 to 7, characterized in that at least one retaining strap (25, 26) is formed by one arm of an angle (27, 28) whose other arm bears against the part of the wall (101) and is attached thereto.

9. A cable lead-in according to claim 8, characterized in that two spacedout retaining straps (23 and 24) are formed by a central recess of the retaining strap arm.

11 - 10. A cable lead-in according to claim 9, characterized in that the width of the angle (27,28) is substantially equal to the distance, increased by the diameter of the hole, between two holes (11,12) disposed one beside the other in the part (101) of the wall.

11. A cable lead-in according to claim 1 substantially as herein described and shown in the accompanying drawings.