EP0172816A1

EP0172816A1 - Coaxial cables and couplings therefor

Info

Publication number: EP0172816A1
Application number: EP84901604A
Authority: EP
Inventors: Henry Roy Smith
Original assignee: HR Smith Technical Developments Ltd
Current assignee: HR Smith Technical Developments Ltd
Priority date: 1983-04-21
Filing date: 1984-04-16
Publication date: 1986-03-05
Also published as: IT8467419A0; GB2139805A; WO1984004428A2; AU2860584A; JPS60501136A; GB8310809D0; IT8467419A1; IT1178929B; WO1984004428A3

Abstract

Câble coaxial ayant une couche de blindage formée par dépôt d'ions métalliques sur les surfaces extérieures d'une couche d'un matériau diélectrique entourant un noyau d'un matériau électriquement conducteur. Dans un autre mode de réalisation, le noyau est formé par dépôt d'ions d'une bande métallique sur une surface équivalant à la moitié du matériau diélectrique et par fixation de l'autre moitié du matériau diélectrique sur cette surface. La couche de blindage à dépôt ionique peut être recouverte d'une autre couche protectrice, par exemple en matériau diélectrique et la surface externe du câble peut être peinte. Des accouplements pour des câbles coaxiaux sont également décrits et sont formés par moulage de matériaux thermoplastiques, les surfaces des parties formant l'accouplement en contact avec les couches de blindage exposées des câbles coaxiaux étant ensuite métallisées par dépôt d'ions. Les accouplements décrits comprennent des connecteurs et des terminaisons de câble.Coaxial cable having a shielding layer formed by depositing metal ions on the outer surfaces of a layer of dielectric material surrounding a core of electrically conductive material. In another embodiment, the core is formed by ion depositing a metal strip onto an area equivalent to half of the dielectric material and attaching the other half of the dielectric material to that area. The ion-deposited shielding layer may be covered with another protective layer, for example of dielectric material, and the outer surface of the cable may be painted. Couplings for coaxial cables are also disclosed and are formed by molding thermoplastic materials, the surfaces of the coupling forming portions in contact with the exposed shield layers of the coaxial cables then being metallized by ion deposition. The couplings described include connectors and cable terminations.

Description

TITLE: COAXIAL CABLES AND COUPLINGS THEREFOR

DESCRIPTION

The invention concerns coaxial cables and couplings therefor. The term couplings used within this

Specification, and in the Claims attached hereto, encompasses both cable connectors by which two coaxial cables may be joined and cable terminations by which a coaxial cable may be terminated e.g. as an electrical plug and/or socket. Coaxial cables are well known and generally provide a central core of an electrically conductive material surrounded by a layer of dielectric material outside which a screen of electrically conductive material is located. Generally the core material is a solid or stranded metal wire and the screening is provided by a metal web or mesh.

An outer protective layer may be provided er-lying the screening layer to provide electrical isulation and mechanical protection of that layer.

Difficulties found with such coaxial cables include the complexity and cost of their manufacture, and the fact that the screening provided by the metal mesh may leak (that is to say may allow electrical signals to pass therethrough).

In an attempt to alleviate and/or overcome these difficulties a first aspect of the present invention provides a coaxial cable comprising an electrically conductive central core surrounded by a layer of dielectric material, the outer surface of which a layer has a layer of electrically conductive material ion deposited thereon to form an electrical screen for the central core. A layer of protective material may be formed on the surface of the ion deposited layer of electrically conductive material, the protective layer preferably being of the same material as the dielectric material. With advantage the dielectric material is a thermoplastics material foamed into position, for example polyethersulphone (P.E.S.).

The electrically conductive central core desirably comprises a metallised strip ion deposited on to a surface of half of the dielectric material, the other half of the dielectric material then being fixed into position. With advantage a single cable formed in this way may include a plurality of electrically conductive cores and the layer of electrically conductive material ion deposited on to the dielectric material can be provided optionally either as a continuous screen or as a plurality of discrete layers forming a plurality of separate screens.

A second aspect of the invention provides a method of forming a coaxial cable as defined above which method comprises the steps of forming a central core for the cable by ion depositing a metallised strip on to one surface of the layer of dielectric material, the step of fixing another layer of dielectric material onto said one surface to form a central core of electrically conductive material surrounded by dielectric material, and the step of ion depositing onto the outer surface of said layer of dielectric material a further metallised layer to form an electrical screen for the cable. With advantage the method includes forming an outer protective coating on the ion deposited screen, the outer coating may be provided by forming a layer of thermoplastics material on the outer surface of the ion deposited screen layer.

Couplings for coaxial cables which are known generally provide an internal metal electrical connection for coupling a core of a coaxial cable to a termination (or the core of another cable) the metal connection being located, within, and spaced from, a metal casing which forms a screening layer for the coupling.

Difficulties in such a coupling include their considerable cost, the difficulty in ensuring that the coupling is electrically equivalent to the cable it is used to couple (the free air zone in the coupling as compared with the dielectric layer in the cable), the difficulties encountered in joining the screening layer of the cable to the metal casing of the coupling,- and the fact that the couplings known to date do hot generally provide effective weather resistance preventing the ingress of water .

In accordance with a third aspect of the invention there is provided a coupling for use with a coaxial cable comprising a dielectric material body part the surfaces of which for contacting the screening layers or layers of coaxial cables are metallised by ion deposition.

With advantage a coupling embodying the invention for providing electrical connection between the ends of a pair of coaxial cables includes means for holding the ends of the cables to be coupled such that the central cores of the cables are electrically interconnected and the screen layers of the cables are continuous and in contact with the ion deposited metallised surfaces of the coupling.

The coupling may include a dielectric material block mounted therein which supports an electrical connector one end of which is adapted to make electrical contact with the central core of one cable to be coupled and the other end of which is adapted to make electrical contact with the central core of another cable to coupled. In this arrangement the means interconnecting the central cores of the two cables may comprise a pin carried in the block within the body of the coupling. Alternatively the means for electrically interconnecting the central cores of the coaxial cables may comprise a metallised layer formed as a strip to run through a block of dielectric material, the ends of which layer are exposed and adapted within the the coupling to contact exposed metallised cores of coaxial cables cut complimentary to the exposed ends of the blocks in the coupling.

One embodiment of the invention provides a coupling including male and female coupling parts and in which the central core of a cable to be coupled is first exposed and soldered to a connector pin passing through both those parts, the coupling parts then being held in blocks by dielectric material housed respectively within male and female coupling shells, the female coupling shell being provided with means for its attachment to the male coupling shell to hold the two coupling she-lls together.

A coupling embodying the invention may include means enabling it to be held in an aperture in an equipment casing and to provide an electrical connection between a coaxial cable coupled to that coupling and the casing.

The coaxial cables and couplings described in this specification are preferably formed of polyethersulphone but it is to be appreciated that. anyother suitable thermoplastics material may be used for example polysulphone, polyetheretherketone and polyamides. Embodiments of the invention will now be described with reference to the accompanying drawings in which:-

Figures 1A and 1B illustrate diagrammatically two forms of coaxial cable embodying the invention.

Figure 2 illustrates diagrammatically another form of coaxial cable embodying the invention.

Figure 3 illustrates diagrammatically a coaxial cable coupling embodying the invention and showing: at 3A a sectional side view of the coupling: at 3B a sectional side view of the coupling partially disassembled, and at 3C details of parts of the coupling.

Figure 4 illustrates another form of coaxial cable for coupling embodying the invention, Figure 5 illustrates another form of coaxial cable coupling embodying the invention, and Figure 6 illustrates two further forms of coaxial cable couplings embodying the invention.

Figure 1 shows at 1A a coaxial, cable which is circular in cross-section and at 1B a coaxial cable which is generally rectangular in cross-section. The two cables are electrically identical and parts of the cable illustrated at lA corresponding to those illustrated at 1B are given the same reference numerals. The illustrated cable 10 comprises a central metallic core 11. The core may be of a conventional stranded or solid type and is of sufficient cross-section to carry the electrical current for which cable 10 is designed. The metal of core 11 may be any suitable metal e.g. copper, silver or the like.

The core 11 is surrounded by a dielectric material 12 which is a thermoplastics material in solid or foam form. The dielectric material 12 is preferably applied to the core 11 in a continuous extrusion process which produces an impervious outer surface for the dielectric material suitable for further processing in an ion deposition process. The dielectric material may be any suitable plastics material, preferably a thermoplastics material such as polyethersulphone (P.E.S.).

The surface of the dielectric material 12 is metallised by having formed on it a screen 13 of metal, e.g. copper, in an ion deposition process. The ion deposited screen 12 is then itself covered by an outer coating 14 applied by spray or dip coating with a solution of P.E.S. in any suitable solvent (e.g. acetone). After drying the outer coating 14 a flexible and light coaxial cable is achieved having low losses. Another protective layer 15 of paint may be applied, if desired.

The cable 10 shown at 1B is electrically the same as that at 1A. In the arrangement shown at 1B, however, the inner core 11 comprises a metallic strip, e.g. copper, which is formed by an ion deposition process onto a layer 12' of P.E.S. in solid or foam form. A second layer 12'' of P.E.S. is then bonded to the first layer 12', using any suitable adhesive or a solution of P.E.S. in acetone, to form a composite layer of dielectric 12 having a central metal core 11. The dielectric 12 is then provided with a screen 13 again making use of ion deposition processes, and an outer protective layer 14 applied to the cable.

The protective layer 14 may be applied by spraying or dipping as appropriate or alternatively by using thin-film stacking techniques including bonding or pressure heat rolling. Once again a layer of paint 15 may be provided, as shown.

The "stripline" coaxial cable shown at Fig. 1B may be produced as a single core cable, as shown, or, as illustrated in Figure 2, as a cable having a plurality of cores and discrete, or coupled, screens as required.

The parts of the cable 10 shown in Figure 2 corresponding to those shown in Figure 1 are given the same reference numerals. It will be seen from Figure 2 that a multiplicity of cores 11 are provided located within a dielectric material 12 formed from two layers 12' and 12'' upon the first of which the cores have been ion deposited. Screens 13 are provided on the outer surface of dielectric 12 and they may be separated as shown at 13', 13'' and 13''' to the top of the cable as seen in Figure 2, or provided as a continuous screen 13 across the surface of the dielectric material, as shown at the bottom of Figure 2. Once again a protective layer 14 is provided, and, optionally, a layer of paint 15.

Coaxial cable couplings usable with the above, and other coaxial cables will now be described.

Figure 3 illustrates a first coupling in the form of a cable termination for use at an equipment casing. To prepare the cable for coupling its end is first cut to expose the core 11 which is then soldered to one end of a male contact piece 31 through which is passed a connector pin 30 suitably comprising a length of drawn wire. The male contact piece 31 (Fig. 3C) comprises a short length of conductive metal tube cut as shown. As core 11 of cable 10 is soldered to piece 31 the end of that piece is held in abutment with the dielectric material 12 of cable 10 and it is after soldering encased in a cylindrical dielectric sleeve 32. The sleeve 32 is externally sized to give in conjunction with the contact piece 31 the same ohmic value as the cable dielectric 12 in conjunction with its core 11. The inner diameter of sleeve 32 is such that the contact piece 31 is an interference fit within it. The outer layer 14 of cable 10 is also stripped for a length as shown to expose the ion deposited layer 13. which When the coupling is assembled is held in contact with metallised surfaces 331 of the part 33. The outer surface 14 (or 15) of cable 10 then has a suitable adhesive applied to it and a male coupling shell 33 is then slid along cable 10 to bring it to the position shown. The male coupling shell 33 has part of its surfaces metallised by ion deposition as illustrated at 33I. When in position, as shown, cable 10 is bonded to the male coupling shell 33

and a moisture-free, moisture proof joint is formed between the two. The metallised screen 13 forms a good and continuous electrical contact with the metallised inner surfaces 331 of the coupling shell 33. A sliding locking sleeve 34 is provided on the male coupling shell 33 and may adopt either of two positions. In a first position (Fig. 3B) the end 35 of a locking sleeve 34 lies in an annular peripheral groove 36 formed on the surface of shell 33. In the other position (Fig 3A) the lugs 35 lie in an annular peripheral groove 37 spaced from groove 36, and the end 38 of the locking sleeve 34 spaced from the end 35 overlies the cooperating end of a female coupling shell 39. The female coupling shell is attachable to, for example an equipment casing 40, by means of a locking nut 41 mounted on a threaded part 42 as shown. The female coupling shell 39 has all of its surfaces metallised as shown at 391 by an ion deposition process. A female contact piece 43 is cut to match the shape of the male contact piece 31 as shown and is enclosed within a dielectric cylinder 44 housed in the female coupling shell 39. The connector pin 30 passes into and is a interference fit in the female coupling part 43 as the coupling is effected making a good electrical connection between the core 11 of cable 10 and the part 43. The end of a split locking ring forming an extension of the female coupling shell 39 engages in annular groove 46 provided as shown in the male coupling shell 33. Once the end of ring 45 is engaged in the groove

46 the locking sleeve 34 is moved to the position shown in Figure 3A and the coupling is complete.

Preferably the dielectric material cylinder 44 is fixed in position in the coupling shell 39 by means of a suitable adhesive, or perhaps solder, as shown at 47 and the female coupling part 43 is fixed to the cylinder 44 in a similar manner, as shown at 48. The The free end 49 of the female coupling part 43 is formed as a solder bucket as shown but other forms of termination may be provided.

A resilient sealing ring 50 may be provided, as shown, to lie between the free, inner, end of the cylinder 44 and the extension of the female coupling part 39.

The surface of part 51 of the coupling shell 39 incorporates an array of projections 52 designed to force their way through any sealant to be applied to the joint between it and the equipment casing 40 in a mannner similar to that described in U.K. Patent Specification 1 351 597. The metallised projections 52 form a good R.F. contact coupling the screen 13 of cable 10 to the equipment casing 40.

Figure 4 shows another, coupling formed as a cable connector 60 the inner surface of which is metallised as shown at 60I in an ion deposition process for an equipment casing. The coupling shown in Figure 4 is of particular use with coaxial cables having a central core 11 formed of stranded metal wires. Figure 4 shows that one end of a cable 10 to be coupled is cut and has part of its outer protective layer 14 stripped away to expose the metallised screen surface 13 beneath it. The cable 10 is then passed into an end 61 of the connector 60 and the stranded central core 11 of cable 10 is brought into contact with the end of a pin 62 rigidly held in position in the connector 60 within a block of dielectric material 63. The cable connection to the other side of connector 60 is made in exactly the same way as has been described. The outer surfaces 14 (or 15 ) of the cables 10 are coated with an adhesive before they are passed into the ends 61, 64 of the connector 60. A flange 65 is provided which cooperates with a nut 66 mounted on a threaded portion 67 of the body of the connector 60 to clamp the connector 60 in position in an aperture in an equipment casing (not shown).

It will be appreciated that the particular connector shown in Figure 4 - a right angled bulk head joint - may be varied, e.g. the angle of the joint could be any that it is desired to use - and the connector could be formed as an "in-line" connector. The lugs 65 nut 66 and threaded portions may be omitted if the connector 60 is not to be used at an equipment casing. Figure 5 illustrates a device for terminating a stripline coaxial cable such as is illustrated in Figure 1B or 2.

The coaxial cable 10 is prepared by cutting away its outer cover 14, the screening material 13 and half of the dielectric layer 12 (e.g. 12''). Assembly is effected, as shown in Figure 5, by bonding an outer cable connector part 70, the inner surface of which is metallised by an ion deposition process as shown at 701, onto the outer cover 14 of the cable 10 and making an electrical contact between the metallised surfaces 13 and 71I. Core terminations 72 are moulded into a terminal block 73 having exposed metal surfaces 74 formed by metal ion deposition. When the cable end is brought into the termination as shown electrical contact is established between cable screen 13 and the surface 70I and also between the core 11 and the inner, metallised, surface 74 of the part 73 housing the cable termination 72. The block 73 is fixed in a part 74 as shown the surfaces 75I and 761 of which are metallised. The parts 70 and 74 are held together by moulded clips 77 and the part 74 can be fixed to an equipment casing (not shown) by means of screws or nuts 78 passing through apertures 79 formed therein. The projections 80 on the end face of part 74 again provide for good termination of the screening 13 by forcing through any sealant at the joint between the coupling and an equipment casing. Figures 6B and 6C illustrate respectively an. "in-line" and a "right-angle" bulkhead connector for use with stripline coaxial cables such as are shown in Figures 1B and 2. In the arrangement of Figure 6A. the connector 90 is in two parts 91 and 92 held together by an annular clipping ring 93. A first cable 10' to be jointed has its end stripped as described above with reference to Figure 5, and is passed into the coupling 91 as shown. The other cable 10'' to be coupled is then cut complimentary to cut end of cable 10' as shown and is passed into the part 92. The inner surfaces of the parts 91 and 92 at 91I and 92I are pre-metallised in an ion deposition process. In the arrangement of Figure 6A the two core parts 11' and 11'' of cables 10' and 10'' are in mechanical and electrical contact and the screens 13' and 13'' of those two cables are coupled by the inner metallised surfaces 91I and 92I of the parts of the connector 90.

The right angled bulkhead connector shown in Figure 6B in essence provides a connector similar to that shown in Figure 6A, with an interposed central part 100 provided to link two outer parts 101 and

102. In a manner similar to that already described the ends of cables 10', 10'' to be joined are cut complementary to ends of a central block 103 having a centrally located conductor 104. The ends of the cables are then passed into respective ones of parts 101 and 102 and these parts are then linked to the central part 100 by moulded lock rings 105. All the inner surfaces of the parts 100, 101 and

102 are metallised (as is the outer surface of the central block 103) as shown at 100I, 101I, 102I and 103I. When assembled good electrical, connections are established between the cores 11' and 11'' via the conductor 104 and between the screens 13' and 13'' via the metallised surfaces of the parts 100, 101, 102 and 103. The central part 100 may be provided with a flange 106 apertured as at 107 to receive, screws, or bolts (not shown) by means of which the connector can be rigidly fixed to equipment casing.

In each of the above described embodiments the body parts of the different cables and couplings preferably of foamed or moulded polyethersulphone, but other forms of thermoplastics materials such as pόlysulphone, polyetheretherketone or polyamides may be used. Metallisation of the various surfaces as required is provided by standard metal ion deposition techniques.

Particular advantages of the described arrangements are that it provides a simple method of producing cables, and couplings, matched electrically, to one another, and that cables and couplings produced in the way now proposed have a core which is surrounded by a homogenous material preventing moisture ingress and (particularly in view of the homogenity of the material) provides an excellent base for the screening layers ion deposited on the surfaces thereof.

International Bureau

INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PC

(51) International Patent Classification ³ : (11) International Publication Number : WO 84/ 0 H01R 17/12; H01B 11/18, 13/00 A3 (43) International Publication Date: 8 November 1984 (08.

(21) International Application Number: PCT/GB84/00129 (81) Designated States: AT (European patent), AU, B ropean patent), CH (European patent), DE (

(22) International Filing Date: 16 April 1984 (16.04.84) pean patent), FR (European patent), GB (Eur patent), JP, LU (European patent), NL (Europe tent), SE (European patent), SU, US.

(31) Priority Application Number: 8310809

(32) Priority Date: 21 April 1983 (21.04.83) Published

With in temational search report.

(33) Priority Country: GB Before the expiration of the time limit for amendi claims and to be republished in the event of the

(71) Applicant (for all designated States except US): H.R. of amendments.

SMITH (TECHNICAL DEVELOPMENTS) LIMITED [GB/GB]; New Mill, Crawley Road, Witney, Ox(88) Date of publication of the international search r fordshire OX8 5TF (GB). 20 December 1984 (20.1

(72) Inventor; and

(75) Inventor/Applicant (for US only) : SMITH, Henry, Roy [GB/GB]; Thorney, Darbys-Green, Knightwick, Worcester WR6 5PU (GB).

(74) Agent: FITZPATRICKS; Kern House, 61/62 Lincoln's Inn Fields, London WC2B 6EX (GB).

(54) Title: COAXIAL CABLES

(57) Abstract

Coaxial cable in which a screening layer for the cable is formed by metal ion deposited onto the outer surfaces layer of dielectric material surrounding a core of electrically conductive material. In another embodiment the co formed by ion depositing a metal strip onto a surface of half of the dielectric material and then fixing the other half o dielectric material onto that surface. The ion deposited screening layer may be covered with a further protective laye of dielectric material and the outer surface of the cable may be painted. Couplings for coaxial cables are also describ which the body parts of the couplings are formed by moulding thermoplastics materials, the surfaces of those body for contacting exposed screen layers of coaxial cables then being metallised by ion deposition. The couplings describe clude both cable connectors and terminations. FOR THE PURPOSES OF INFORMAπON ONLY

Codes used to identify States party to the PCT on the front pages of pamphlets publishing international applications under the PCT.

CF Centxal African Republic MG Madagascar

CG Congo MR Mauritania

CH Switzerlind MW Malawi-

CM Cameroon NL Netherlands

DE Germany, Federal Republic of NO Norway

DK Denmark 10 Romania

FT Finland SD Sudan

FR France SE Sweden

GA Gabon SN Senegal

GB United Kingdom sir Soviet Union

Hϋ Hungary TD Chad

JP Japan TG Togo

KP Democratic People's Republic ofKorea υs United States of America

Claims

1. A coaxial cable comprising an electrically conductive central core surrounded by a layer of dielectric material, the outer surface of which layer has a layer of electrically conductive material ion deposited thereon to form an electrical screen for the central core.

2. A cable as claimed in Claim 1, further including a layer of protective material formed on the surface of said ion deposited layer of electrically conductive material.

3. A cable as claimed in Claim 2, in.which the protective layer is the same material as the dielectric material.

4. A cable as claimed in any one of Claims 1 to

3, in which the dielectric material is a thermoplastics material which has been foamed into position.

5. A cable as claimed in any one of Claims 1 to

4, in which the electrically conductive central core comprises a metallised strip ion deposited onto a surface of half of the dielectric material, the other half of the dielectric material being then fixed into position.

6. A cable as. claimed in Claim 5, and including a plurality of electrically conductive cores.

7. A cable as claimed in Claim 6, in which the layer of electrically conductive material ion deposited on the dielectric material is provided as a plurality of discrete layers to form a plurality of separate screens thereon.

8. A method of forming a coaxial cable as claimed in any one of Claims 1 to 7, comprising the steps of forming a central core for the cable by ion depositing a metallised strip onto one surface of a layer of dielectric material, and then fixing another layer of dielectric material on said surface to form a central core of electrically conductive material surrounded by a layer of dielectric material, and then ion depositing on the outer surface of said layer of dielectric material a further metallised layer to form an electrical screen for the cable.

9. A method as claimed in Claim 8, further comprising the step of providing an outer protective coating on the ion deposited screen layer.

10. A method as claimed in Claim 9, in which the outer protective coating is provided by forming a layer of thermoplastics material on the outer surface of the ion deposited screen layer.

11. A coupling device for use with a coaxial cable, comprising a dielectric material body part the surfaces of which for contacting the screening layer of a coaxial f-able are metallised by ion deposition.

12. A coupling as claimed in Claim 11, adapted to provide electrical connection between the ends of a pair of coaxial cables, in which the coupling includes means for holding the ends of the cables to be coupled such that the central cores of thecables are electrically connected and the screen layers of the cables are continuous and in contact with the ion deposited metallised surface of the coupling.

13. A coupling as claimed in Claim 12, and including a dielectric material block mounted therein which supports an electrical connector one end of which is adapted to make electrical contact with the central core of one cable to be coupled and the other end of which is adapted to make electrical contact with the central core of the other cable to be coupled.

14. A coupling as claimed in Claim 13, in which said. means for interconnecting the central cores of the two cables to be coupled comprises a pin located in a block fixed within the coupling.

15. A coupling as claimed in Claim 13, in which the means for electrically interconnecting the central cores of the coaxial cables comprises a metallised layer formed to run through a block of dielectric material the ends of which layer are exposed and adapted to contact exposed metallised cores of coaxial, cables cut complimentary to the exposed ends of the central core of the coupling.

16. A coupling as claimed in Claim 13, including male and female coupling parts, in which the central core of a cable to be coupled is exposed and soldered to a connector pin passing through both the male and female coupling parts, in which the coupling parts are held in blocks of dielectric material housed respectively in male and female coupling shells, and in which the female coupling shell is provided with means for its attachment to the male coupling shell to hold the female and male coupling shells together.

17. A coupling as claimed in any one of Claims

11 to 16, further including means enabling the coupling to be held in an aperture in an equipment casing.

18. A coaxial cable as claimed in Claim 1, and as herein described with reference to the accompanying drawings.

19. A method of making a coaxial cable as claimed in Claim 18, and substantially as herein described.

20. A coupling for coaxial cables substantially as herein described with reference to the accompanying drawings.