A SCREENED ELECTRICAL CABLE

Abstract: A screened electrical cable has a central core (2) of aromatic polyamide filaments embedded in a semi-­ conductor layer (3) around which is wound a helix (4) of conductive wire which in turn in surrounded by an insulating layer (5) encased within an outer cladding layer (6) resistant to high temperatures and chemical agents. At least one end of the screened cable (1) is provided with an electrical connector in the form of a substantially cylindrical longitudinally split body (11), (13) clinched around the end of the cable (1) in electrical contact with one arm (20b) of a U-shape clip (20) the other arm (20a) of which is inserted into the end of the cable between the insulator layer (5) and the helical coil (4) and in electrical contact with the latter.

Description: The present invention relates to a screened electrical cable, that is one which is provided with means for preventing electrical signals on the electrical conductor from causing interference with nearby electrical equipment such as television receivers, radio receivers, computers, word-processors and the like, and which likewise is screened against picking up unwanted external signals. Considerable difficulties are currently encountered in the production of screened electrical cables in that it is very difficult to obtain an adequate mechanical strength together with a good screening against interference. One application of such screened cables is as the high tension leads of a spark-ignition internal combustion engine, in which application the cable must be able to resist high temperatures and aggressive chemical agents. Known screened cables are not always able to resist these relatively high temperatures and external chemical agents, however, and thus prove unsatisfactory and have a short service life. The document US-A-4 435 692, on which the pre-characterizing part of the claim has been based, discloses a screened electrical cable which comprises a core of filaments of aromatic polyamide fibre within a semi-conductor layer around which is is wound a helix of electrically conductive wire, said helix being disposed within an insulating layer in turn encased by an outer cladding layer. The document JP-O-56 159 081 discloses a U clip which present a pointed arm provided for driving in an insulating layer of a cable. The document "NHK LABORATORIES NOTE" No. 120, June 1968, pages 13-16, Tokyo, JP; "Designs of Resistive Wire Wound Type Cable" discloses the use in a screened electrical cable of a ferrite compound with polyvinylchloride for the semiconductor layer of the screened electrical cable. Finally, the document US-O-3 423 718 discloses a terminal for a screened electrical cable, which terminal has a contact body having a longitudinally split substantially cylindrical conformation, which is joined to a clinching collar which can be clinched around the outer cladding layer of the electrical screened cable. The object of the present invention is that of eliminating the above mentioned disadvantages by providing a screened electrical cable which is structured in such a way as to present both a notable mechanical resistance against breakage, so as to be usable even in the most severe conditions, and a good resistance to aggressive chemicals. According to the present invention, this object is achieved by a screened electrical cable having the features of the characterizing part of the claim. One advantage of the invention is that it provides a screened electrical cable the screening of which is truly effective, and which does not cause external interference even in the most difficult conditions of use. Another advantage of the screened electrical cable of the present invention is that it allows connection to be made to electrical terminals with rapidity and security. A further avantage of the present invention is that it provides a screened electrical cable which is able to offer the widest guarantees of reliability and security in use. One embodiment of the present invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic perspective view of the screened electrical cable of the invention, shown partly cut-away with its component elements exposed; Figure 2 is a cross-section on an enlarged scale of the screened electrical cable of Figure 1; Figure 3 is an exploded perspective view of a connector terminal which can be fitted to the end of the cable of Figure 1; and Figure 4 is an axial section showing the terminal of Figure 3 connected to the end of the cable of Figure 1. Referring now to the drawings, the screened electrical cable according to the invention, which is generally indicated with the reference numeral 1, comprises an inner core having a mechanical support function, which is composed of a plurality of filaments 2 of aramide fibre, for example, KEVLAR® . The core 2 is encased in a semi-conductor layer 3 which, advantageously, is composed of a semi-conductor compound formed of a ferrite and polyvinyl chloride. Around the semiconductor layer 3 is formed a helix 4 of electrically conductive wire, which advantageously is made of ferro-nickel wire, which gives the desired external interference screening. Around the helix 4 is provided an insulating layer 5 made of medium to high density E.P.D.M. rubber, which is formed preferably by extrusion. The insulating layer 5 is externally clad in an outer cladding layer 6 made of HYPALON® which is resistant to high temperature and external chemical agents. At the ends of the cable 1 there are provided terminals, generally indicated with the reference numeral 10, comprising a contact body 11 having a longitudinally split substantially cylindrical shape, which is joined, by means of a bridging portion 12 of reduced cross-section, to a clinching collar 13 which likewise has a longitudinal split substantially cylindrical shape to enable it to be clinched to the end of the cable 1. electrical contact between the terminal 10 and the conductive helix 4 is obtained by means of a substantially U-shape clip 20 having two parallel arms 20a and 20b one arm 20a of which can be inserted axially into the end of the cable between the insulating layer 5 and the conductive helix 4, whilst the other arm 20b is disposed outside the cable 1 in contact with a portion of the clinching collar 13 which is clinched onto the end of the cable 1 thus effectively pressing the component parts forming the various layers of the cable together and in particular pressing the arm 20a of the clip 20 into electrical contact with the conductive helix 4 and the arm 20b into electrical contact with the clinching collar 13. The arms 20a and 20b are joined together by a bight portion 20c which, when the terminal is mounted on the cable, extends generally radially of the cable from its periphery to the conductive helix 4. With the described arrangement there is provided an electrical cable able to allow a very high performance, both mechanically and electrically, in which electrical connection to terminals is obtained in an extremely simple manner by means of the clip 20.

Claims: A screened electrical cable (1) comprising a core of filaments (2) of aromatic polyamide fibre within a semi-condutor layer (3) around which is wound a helix (4) of electrically conductive wire, said helix (4) being disposed within an insulating layer in turn encased by an outer cladding layer (6), there being further provided at least one contact terminal (10) clinched to said outer cladding layer (6), characterized in that said contact terminal (10) is provided with a U-shaped contact clip (20) for making electrical contact between said helix (4) and said terminal (10), in that said terminal (10) includes a contact body (11) having a longitudinally split substantially cylindrical conformation, comprising a clinching collar (13) which can be clinched around said outer cladding layer (6) and positioned in contact with one of the arms (20b) of said U-shaped clip (20), the other arm (20a) of said clip (20) being inserted axially into the end of said electrical cable in electrical contact with said conductive helix (4), in that said contact body further comprises a recessed bridging portion (12) of reduced cross-section coupling said contact body (11) to said clinching collar (13), and in that said clinching collar (13) is provided with substantially circumferential parallel slots.

Inventors: CODRINO, GIUSEPPE
Applicants: CAVIS CAVETTI ISOLATI S.P.A.
Application year: 1987
Main classification: H01B7
IPC codes: H01R4, H01B7