GB2338846A

GB2338846A - Coaxial line surge protector assembly

Info

Publication number: GB2338846A
Application number: GB9914599A
Authority: GB
Inventors: David Dominic Hall
Original assignee: Whitaker LLC
Current assignee: Whitaker LLC
Priority date: 1998-06-23
Filing date: 1999-06-22
Publication date: 1999-12-29
Anticipated expiration: 2019-06-22
Also published as: GB9813534D0; GB2338846B; GB9914599D0

Abstract

A surge protection assembly 2, for mounting on an electrical coaxial line 3 for protecting against surges (eg. due to lightning) between inner and outer conductors 6, 4 of the line 3, comprises a conductive cap 8 and a magnet 12 mounted on the cap 8 for holding a surge protector capsule 14 against a contact face of the cap 8. Contact pads 18, 20 of the capsule 14 are typically made of ferro-magnetic material, such as steel, facilitating retention of the capsule 14 against the cap 8 by means of the magnet 12. The magnet 12 may be retained in a recess 32 in the cap 8 due to magnetic attraction between the magnet 12 and a magnetic cap 8, or if the cap 8 is made of non-magnetic material (such as brass) magnet 12 may be retained in recess 32 by a rolled-over retention lip 42. The cap 8 is screwed into the outer conductor 4 with a thick rubber gasket 10 therebetween to provide a seal and to assist in providing good electrical connection between the conductors 4, 6 and the contact pads 18, 20. The assembly 2 enables easy removal and replacement of the surge protection capsule 14, for example in a coaxial connector of a coaxial line, and enables protector capsules of various sizes and shapes to be mounted on cap 8.

Description

2338846 COAXIAL LINE SURGE PROTECTOR ASSEMBLY This invention relates to an

electrical surge protector assembly installable on an electrical coaxial line, for exampleYon a coaxial connector thereof.

Electrical coaxial interconnections used in the telecommunications industry (for example, for interconnecting electrical and electronic equipment of transmitters and receivers of a wireless communications base station) are often provided with surge protectors, particularly. for protection against voltage and current surges generated by lightning. The surge protector is typically a small, substantially cylindrical component with metal contacts at opposed ends of the cylindrical body. A surge protector capsule is inserted between a coaxial inner conductor and outer conductor, whereby the opposed contact pads of the surge protector capsule make electrical connection with the inner conductor and outer conductor. respectively. The surge protector capsule becomes conductive when the potential difference between the inner and outer conductors is large enough. The absorption of electrical energy causes deterioration of the surge protector which. therefore. has a limited life. Surge protector capsules in coaxial interconnections thus need to be replaced. at certain intervals or possibly after the occurrence of lightning strikes on telecommunications equipment.

Surge protector capsules may, for example,be mounted in connectors or taps of the electrical coaxial line. It is typical to mount the surge protector capsule on a metal cap that is screwed to the outer conductor, whereby the capsule is inserted into the coaxial line and abuts the inner conductor at the other end thereof.

40836 GB(1) 2 Conventional caps are machined from solid metal and provided with separate conductive spring inserts that clasp the surge protectors at one end thereof. The separate insert provides resilience and good electrical contact between the surge protector contact pad and metal cap whilst enabling the removal and replacement of surge protectors. It is advantageous to clasp the surge protector with a cap, as access to certain telecommunications equipment is difficult. The separate insert is, however, fairly expensive to produce and different surge protector shapes and sizes require different inserts. Furthermore, the resilient arms of the inserts are prone to damage.

It is an object of the present invention to provide a more economical and versatile surge protection-assembly for coaxial lines, in particular, to enable easy removal and replacement of surge protectors in coaxial lines.

To this end, the invention consists in a surge protection assembly for mounting on an electrical coaxial line for protecting against voltage and current surges between an inner conductor and outer conductor of the coaxial line, the assembly comprising a conductive cap and a magnet mounted on the cap for holding a surge protector capsule to the cap against a contact face thereof.

Surge protector capsules which are usually provided with steel end caps forming the contact pads thereof, can thus be held in a particularly simple manner to the cap by the force of the magnetic field. This enables surge protector capsules having various shapes and sizes to be mounted on a cap without modifying the design thereof. The magnet may be in the form of a small cylindrical puck received in a complementary recess extending into a surge protector capsule contact face of the cap. The cap

3 may be of a magnetic material, such as steel, such that the magnet may be held to the cap without additional mechanical fixing means. If the cap is made of a non-magnetic material, such as brass, a simple and advantageous means of fixing the magnet in the recess of the cap is by providing a lip around the recess that can be rolled inwards after insertion of the magnet in the recess to form a mechanical clasp that retains the magnet to the cap. The contact surface of the cap may be slightly recessed with respect to an outer or peripheral lip that positions the surge protector capsule approximately centrally against the contact surface of the inner cap. A thick elastomeric gasket may be provided against a flange of the cap for compression against the outer conductor thereby providing a seal. The cap may be threaded to the outer conductor as in conventional designs.

Embodiments of this invention will now be described by way of example with reference to the accompanying drawings in which:

Figure 1 is a cross sectional view through an electrical surge protection assembly for coaxial lines, according to this invention; Figure 2 is a similar view to Figure 1 of a different embodiment where an end cap of the assembly is made of a magnetic material; Figure 3 is a cross sectional view of a surge protector assembly according to this invention, mounted on a coaxial line partly shown; Referring to the accompanying drawings, a surge protection assembly 2 for mounting on a coaxial line 3 having an outer conductor 4 and inner conductor 6, comprises a cap 8, an elastomeric gasket 10, a magnet 12 and a surge protector capsule 14. The surge protector capsule 14 may be one of a number of different surge protector capsules that are commercially available and. for example. comprises a cylindrical ceramic body 16 and a pair of contact pads 18, 20 mounted on opposed ends 22, 24, respectively,of the cylindrical body. The contact pads 18, 20 are typically made of a ferro-magnetic materia4 such as steel. The surge protector capsule 14 is adapted to absorb the electrical energy generated by a large difference in electrical charge between the inner and outer conductors 4, 6. for example. due to lightning strikes close to telecommunications equipment interconnected by the coaxial line 3. The voltage surge protector capsule 14 can withstand only a limited number of electrical surges and.thus.needs to be installed in a replaceable manner.

The cap 8 has roughly the form of a bolt with a bolt head 26 and a threaded portion 28 that is received in a complementary thread 30 extending through the outer conductor 4 of the coaxial line 3. The portion of coaxial line 3 shown in figure 3 mayfor example,be part of a coaxial connector assembly having an outer body machined from metal and a solid metal inner conductor. The cap 8 can,thus, be unscrewed from the outer conductor 4 for removing the used surge protector capsule and replacing with a new surge protector capsule.

40836 GB(I) The magnet 12, which in this embodiment is in the form of a small cylindrical puck. is received in a complementary recess 32 that extends into the cap from a contact face 34 thereof that abuts against the surge protector capsule contact pad 18. In the embodiment of figures 2 and 3, the cap 8 is made of a ferro-magnetic material,such as steel,whereby the magnet 12 is held in the recess 32 by magnetic force, and a supplementary mechanical retention of the magnet 12 in the recess 32 is thus not required. It may be noted that the direction of the magnetic field through the magnet 12 is generally in the direction (A) of the axis 36 of the assembly. In other words, the north and south poles of the magnet 12 are respectively on opposed sides 38, 40 of the puck.

The magnetic force thus holds the surge protector capsule 14, by way of the ferro-magnetic contact pad 18 thereof,against the cap contact face 34. The cap contact face 34 may be slightly recessed with respect to the peripheral lip 42 which helps in positioning the surge protector 14 roughly centrally with respect to the axis 36 of the cap.

As the coaxial line 3 may be in places that are difficult to access, it is important, in many circumstances. to hold the surge protector capsule 14 to the cap 8 when it is unscrewed and removed f rom the coaxial line, the surge protector capsule is replaced, and the end cap is screwed back to the line.

The thick rubber gasket 10 not only seals the connection between the cap and outer conductor 4, but also provides frictional forces which serve to stop the cap from unscrewing and becoming loose. By this feature it helps to ensure that good electrical contact between 40836 GB(1) the surge protector contact pads 18, 20 and the cap and inner conductor 4, 6. respectively, is maintained.

Referring to figure 1, the cap may be provided with a mechanical retention means for the magnet which, in this embodiment, is in the form of a small lip extending around the periphery of the recess 32 and which is rolled over the edge of the recess 32 to form a clasp 42 that mechanically retains the magnet 12. The clasp 42 may be provided where the cap is made of an non-magnetic material such as brass. The magnetic field isy nevertheless, still present and attracts the ferromagnetic contact pad 18 of the surge protector capsule theretowards. The retention lip 42 may be screw machined and the rolled over the edge of the recess 32 after the magnet is inserted therein.

is 1 40836 GB(1) 7

Claims

1 A surge protection assembly for mounting on an electrical coaxial line for protecting against voltage and current surges between an inner conductor and outer conductor of the coaxial line, the assembly comprising a conductive cap and a magnet mounted on the cap for holding a surge protector capsule to the cap against a contact face thereof.

2. The assembly of claim 1, wherein the magnet is dispensed within a complementary recess in the contact face of the cap.

3. The assembly of claim 2, wherein the magnet has opposed faces which are substantially orthogonal to the axis of a cylindrical surge protector capsule held to the cap, said magnet being substantially fully received within the recess in the contact face.

4. The assembly of claim 2 or 3, wherein the cap is formed with a retention lip bent over an edge of the recess in the contact face of the cap such that the magnet is mechanically retained within the recess.

5. The assembly of claim 4, wherein the retention lip is produced by screw machining and is rolled over the edge of the recess after the magnet is inserted therein.

6. The assembly of any one of the preceding claims, wherein the cap is made of a magnetic material and the magnet is retained in the cap by magnetic force.

7. The assembly of any one of the preceding claims, wherein the magnet is in the form of a cylindrical puck.

8. The assembly of any one of the preceding claims, wherein the contact face of the cap is recessed to form a peripheral lip which serves to position the surge protector capsule approximately centrally with respect to a central axis of the assembly.

9. A surge protection assembly substantially as hereinbefore described with reference to the accompanying drawings.