GB2549291A

GB2549291A - Outer coaxial isolator device

Info

Publication number: GB2549291A
Application number: GB1606158.2A
Authority: GB
Inventors: Martin David; Chapman Paul; Shelley Gareth
Original assignee: Technetix BV
Current assignee: Technetix BV
Priority date: 2016-04-12
Filing date: 2016-04-12
Publication date: 2017-10-18
Anticipated expiration: 2036-04-12
Also published as: ES2637564R1; PL421295A1; PL229710B1; NL2018666A; ES2637564A2; NL2018666B1; ES2637564B2; GB2549291B

Abstract

An isolator device for the outer coaxial shielding of a cable TV network comprises ring capacitors 22 and ferrite blocks 20 in the form of discs with apertures, an electrically conductive hollow tube 30 extending through the apertures and being in electrical contact with the capacitors 22 and ferrite blocks 20. A set of electrically conductive tabs 32, 50 contact opposite sides of the ring capacitors 22, the tabs 32 and 50 being formed by deforming parts of the hollow tube 30 and the housing 18. Electrical boundary interfaces are reduced, which improves reliability and efficiency. Conductive washers (26, figure 7, 60, figure 12) may be used instead of either the tabs 50 or 32. The device may be used within double galvanic isolator assemblies that provide voltage protection for the outer coaxial shielding in a cable TV network.

Description

Title: Outer Coaxial Isolator Device Field of the invention

This invention relates to an outer coaxial isolator device, in particular a device used within double galvanic isolator assemblies to provide voltage protection to outer coaxial shielding.

Background to the invention

Coaxial shielded cable is used to supply power for devices within a cable television network. Double galvanic isolator circuits are used to improve shielding characteristics of the coaxial cable, either protecting the outer coaxial shielding or protecting the inner conductor of the coaxial cable. The double galvanic isolator circuits are housed within or form part of an RF shielded housing. Problems arise with electrical boundary interfaces between different components within the double galvanic isolator circuits.

Summary of the invention

In accordance with the present invention, there is provided an isolator device for outer coaxial shielding, the isolator device comprising at least one capacitive element and at least one inductive element, each element in the form of an apertured disc, and an elongate electrically conductive element, or tube, extending through and in electrical contact with the apertured discs, wherein at least one electrically conductive tab is provided to contact with at least part of the capacitive element, thereby to provide an additional region of electrical contact with the capacitive element apart from just the elongate conductive element. The electrically conductive tab is thus in physical contact with the capacitive element, and by being electrically conductive improves the electrical contact between the capacitive element and any elements in electrical communication with the tab.

Typically the apertured discs forming the capacitive element and the inductive element have a first face, a second face and a central channel extending between the first and second faces, the elongate conductive element being disposed within the channel of each apertured disc.

The at least one tab may extend at substantially 90° to the elongate conductive element so as to contact an outer face of the capacitive element.

The elongate conductive element may be in the form of a hollow tube and more preferably a hollow flexible tube deformable to produce at least one tab extending across at least part of the capacitive element, and preferably extending across at least two thirds of a contact face of the capacitive element.

Where the tube is deformable, preferably a plurality of radial slits is provided at at least one position along the elongate conductive element, the slits extending through the wall so that the wall is aperture in the region of the slit.

Preferably each slit extends in the direction of elongation of the elongate conductive element. By having slits extending part way along the length of the tube, the tube can be deformed to produce tabs extending across at least part of the capacitive element, and in particular across one face of the capacitive element. A set of slits formed from a plurality of radial slits may be repeated at spaced apart intervals along the tube, with the spacing between each set of slits corresponding to the distance between which tabs are required. Thus a first set of radial slits will provide a first set of tabs for contacting with a face of a first capacitive element with the next set of slits providing a second set of tabs for contacting a second capacitive element spaced along the tube, and repeated sets of slits being provided dependent on the number of capacitive elements located on the conductive element.

Preferably the slits are circumferentially equally spaced, and 2, 3, 4, 5 or even more slits may be provided, with in particular four slits preferred.

The capacitive elements may preferably be ring capacitors, with the inductive elements preferably formed from ferrite material and typically each in the form of an apertured ferrite block.

The isolator device may further comprise a housing, typically metal or other electrically conductive material, within which the at least one capacitive element, at least one inductive element and the elongate conductive element are located, wherein tabs are formed from regions of the housing.

The housing may be formed with predefined tab regions, with the predefined tab regions readily deformable away from the remainder of the housing so as to engage with the capacitive elements.

Where tabs are formed from the housing, the tabs may contact both a capacitive element and an insulating element, acting to hold the insulating element in place.

In a particularly preferred embodiment, both the conductive element and the housing may both be provided with tabs, such that tabs associated with the tube contact one face of each capacitive element and tabs associated with the housing contact the other face of each capacitive element.

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

Figure 1 shows a schematic electrical diagram of an outer coaxial isolator device; Figure 2 shows a cut-away view of a first embodiment of the invention incorporating an elongate conductive element;

Figures 3(a) and (b) show the conductive elongate element in side view and end view respectively;

Figures 4 to 6 show perspective views illustrating assembly of the first embodiment; Figure 7 shows an exploded view of the components within the first embodiment; Figure 8 shows a cut-away view of a second embodiment and course of invention; Figures 9 to 11 show assembly of the second embodiment;

Figure 12 shows an exploded view of the components within the second embodiment; Figure 13 shows a cut-away view of a third embodiment of the invention; and Figure 14 shows an exploded view of the components within the third embodiment.

Description

Figure 1 shows an electrical schematic of an outer coaxial filter element of a double galvanic isolator device or module 10 comprising a plurality of ferrite blocks 12 electrically in series and associated shunt capacitors 14. The number, size, and values of the components 12, 14 vary depending on the required performance. Problems arise with electrical boundary interfaces between the components which affect efficiency and reliability.

To reduce electrical boundary interfaces and so improve reliability and efficiency, modified double galvanic isolator devices are proposed as shown with reference to Figures 2 to 14. A first embodiment is shown in relation to Figures 2 to 7. Double galvanic isolator module 16 is shown in vertical cross-section such that half the module is represented and comprises an electrically conductive module body 18 within which are located ferrite blocks 20 and ring capacitors 22 in the shape of apertured discs having outer circular faces with a central channel extending between the two faces. Ferrite insulators 24 having a central aperture or channel are disposed between adjacent ferrite blocks and ring capacitors so as to prevent electrical contact between ferrite blocks and ring capacitors. An electrically conductive disc washer 26 is disposed between each ring capacitor 22 and ferrite insulator 24 and is arranged to physically and electrically contact conductive housing 18 to ensure an electrical connection between housing 18 and ring capacitor 22.

Hollow flexible elongate tube 30 is electrically conductive and extends through apertured elements 20, 22, 24, 26 and incorporates groups of tabs 32 at longitudinally spaced apart positions corresponding to the location of ring capacitors 22, such that tabs 32 are in direct physical and electrical contact with an adjacent ring capacitor 22. The electrically conductive tabs 32 provide regions for electrical contact between tube 30 and each capacitor, so reducing electrical boundaries between inner tube 30 and ring capacitor interfaces. Whilst the housing is shown with two ferrite blocks 20 and two ring capacitors 22, pairs of a single ferrite block and a single capacitor can be repeated as needed to achieve the desired characteristics of the module and the module housing length increased as required.

Tube 30 is shown in more detail with reference to Figures 3(a) and 3(b) and has three sets 34, 34’, 34” of radial slits 36 of equal length spaced along the length of tube 30, with four radial slits 36 in each set equispaced around the tube circumference. Each slit is cut or formed so as to extend through the wall surface. The number of slits in each set and the spacing between the sets is dependent on the number and spacing of ring capacitors 26, with a set of slits being provided for each ring capacitor 22. Although Figure 3 shows three sets of four radial slits along tube 30, the number of slits per set could be two, three, four or more. Flexibility of malleable tube 30 allows the slitted regions to deform during assembly of the module to form tabs 32 as seen in Figure 2. This can be seen with reference to Figures 4 to 7 where construction of module 16 is shown.

To assemble module 16, a sub-assembly of holding ring 40, end outer insulator 42, electrically conductive disc washer 26, ring capacitor 22 and pre-slit inner tube 30 is formed. Tube 30 is fed into the channel or aperture of capacitor 22 to abut holding ring 40. Tube 30 is then urged in towards capacitor 22, see Figure 5, causing the tube walls to splay outwards in the region of slits 34 so as to create hinged tabs 32 having a double wall thickness, with tabs 32 forming direct physical and electrical contact with ring capacitor 22. Thus boundaries between the inner tube and ring capacitor interfaces are reduced by the folded tabs contacting with one face of each ring capacitor 22. The length of each slit is approximately twice the radial distance between the outer diameter of tube 30 and the outer edge of ferrite block 20, with an allowance for the bend radius at the end of the tab so as to ensure each tab 32 extends to cover two thirds of the exposed contact face of capacitor 26.

Ferrite block 20 is added to this partial assembly, such that tube 30 extends through the central aperture or channel of ferrite block 20. In order, ferrite insulator 24, electrically conductive disc washer 26, and ring capacitor 22 are then added to the assembly as shown and the tab forming process repeated for the slits associated with set 34’, see Figure 6.

This ordering of components and tab formation is repeated for as many capacitors as module 16 requires, and finally end insulator 44 is fitted followed by electrically conductive module body or housing 18. Figure 7 shows all the components within module 16 in exploded view. Whilst tube 30 is shown with protruding tabs 32 the tabs are not created until after each ring capacitor 22 is placed on tube 30. Once all components are positioned on tube 30, the components are pressed together so that all fingers of electrically conductive washers 26 tightly grip module body 18 and the overall assembly is held in compression through the fit between the module body 18 and holding ring 40, producing the finished module as shown in Figure 2. A second embodiment 48 is shown in Figure 8 where tabs 50 are formed in module housing 18 to physically and electrically connect ring capacitors 22 to the electrically conductive housing 18. Electrically conductive tube 52, formed without slits, extends through the central apertures of the disc components. By piercing and folding tabs from body 18 during assembly, module body 18 is brought into direct physical contact with one face of ring capacitor 22, so reducing electrical boundaries between module body 18 and ring capacitor interfaces.

Figures 9 to 12 illustrate assembly of the second embodiment. Firstly end insulator 42 and electrically conductive inner tube 52 are inserted into empty module body 18, see Figure 9. Multiple circumferentially equispaced tabs 50 are then created by piercing or stamping into the side of module body 18 and bent down to secure end insulator 42 in position against end return 54, see Figure 10, and so provide an electrical and physical contact point for the next component, ring capacitor 22. Ring capacitor 22 is then fed along tube 52 and located on end insulator 42, an apertured electrically conductive inner cup washer 60 is fed along tube 52 until both inner cup washer 60 and tabs 50 of module body 18 are in good electrical contact with ring capacitor 22. Ferrite block 20, ferrite insulator 24 are each fed in turn along tube 52, and another set of tabs 50’ pierced into module body 18 and bent inwards to secure the components in position , see Figure 11. The creation of contact tabs 50 in module body 18 reduces electrical boundaries between module body 18 and ring capacitor interfaces.

Figure 12 shows components for the assembly of module 48, with each group of components between successive sets of longitudinally spaced tabs repeated as necessary to obtain the required electrical characteristics for module 48. Thus whilst shown with two ferrite blocks 20, 20’, any number of ferrite blocks and associated components can be contained within module 18.

To complete the assembly of module 48 for the components shown in Figure 12, another set of tabs are pierced into module body 18 above first ferrite insulator 24 and bent down. The process of adding capacitor 22’, inner cup washer 60’, ferrite block 20’, ferrite insulator 24’ followed by piercing and bending of tabs 50 in module body 18 is repeated until the required number of capacitors 22 have been fitted. The last insulator 24’ is secured with the last set of tabs and finally end capacitor 22”, end washer 60” and end insulator 44 added and holding ring 62 pressed into module body 18 to complete the assembly.

The third embodiment 70 shown in Figures 13 and 14 combines the use of external tabs depressed inwardly from housing 18, as in embodiment two, with tabs formed from the slitted flexible electrically conductive tube of the first embodiment so as to provide a minimum electrical boundary configuration. Inner cup washers 60, 60’, 60” are not required in this embodiment as tube 30 provides tabs 32 for physically and electrically contacting one face of ring capacitors 22 and tabs 50 contact the other face of ring capacitors 22.

The present invention reduces electrical boundary interfaces within an outer coaxial isolator device through reduction of the number of internal components, for example with washers replaced by tabs integrally formed as parts of required components. Thus modules are provided containing the elements required for an outer coaxial filter within a sub-assembly which compared with the prior art, reduces the electrical boundary interfaces between components for improved unit efficiency and reliability.

Claims

1. An isolator device for outer coaxial shielding, the isolator device comprising at least one capacitive element and at least one inductive element, each element in the form of an apertured disc, and an elongate electrically conductive element extending through and in electrical contact with the apertured discs, wherein at least one electrically conductive tab is provided to contact with at least part of the capacitive element.

2. An isolator device according to claim 1, wherein the at least one tab extends at substantially 90° to the elongate conductive element.

3. An isolator device according to claim 1 or claim 2, wherein the apertured discs forming the capacitive element and the inductive element have a first face, a second face and a central channel extending between the first and second faces, the elongate conductive element being disposed within the channel of each apertured disc.

4. An isolator device according to any of the preceding claims, wherein the elongate conductive element is a hollow tube.

5. An isolator device according to any of the preceding claims, wherein the elongate conductive element is a flexible hollow tube.

6. An isolator device according to claim 5, wherein the tube is deformable to produce at least one tab extending across at least part of the capacitive element.

7. An isolator device according to claim 6, wherein a plurality of radial slits is provided at at least one position along the elongate conductive element.

8. An isolator device according to claim 7, wherein each slit extends in the direction of elongation of the elongate conductive element.

9. An isolator device according to claim 7 or claim 8, wherein the slits are circumferentially equally spaced.

10. An isolator device according to any of claims 7 to 9, wherein a set formed from a plurality of radial slits is repeated at spaced apart intervals along the tube.

11. An isolator device according to any of the preceding claims further comprising a housing within which the at least one capacitive element, at least one inductive element and the elongate conductive element are located, wherein tabs are formed from regions of the housing.

12. An isolator device according to claim 11, wherein the tabs contact both a capacitive element and an insulating element, acting to hold the insulating element in place.

13. An isolator device according to claim 11 or claim 12, wherein the housing is formed with predefined tab regions.

14. An isolator device according to any of the preceding claims, wherein the capacitive elements are ring capacitors.

15. An isolator device according to any of the preceding claims, wherein the inductive elements are formed from ferrite material.

16. An isolator device substantially as herein described with reference to and as illustrated in Figures 2 to 14.