WO1996008856A1

WO1996008856A1 - Interference-protected cable connector housing

Info

Publication number: WO1996008856A1
Application number: PCT/FI1995/000500
Authority: WO
Inventors: Reijo Nurmi
Original assignee: Nokia Telecommunications Oy
Priority date: 1994-09-16
Filing date: 1995-09-14
Publication date: 1996-03-21
Also published as: AU3389095A; FI96458B; FI96458C; FI944324A0

Abstract

The invention relates to an interference-protected cable connector housing, which comprises a metal shield structure (1) and a surrounding outer casing (2), and during the use of which the sheath (14) of the cable (12) is grounded to a frame structure (8) of a device (3), a circuit board (9) or the like to protect especially against electromagnetic interference. The shield structure consists of a uniform flexible shield (1), which encircles the connector (10), to the inner surface (13) of which the sheath (14) of the cable (12) is grounded with a direct contact, the edges of the shield, placed against the device (3), being formed into tongues (7) that are in close contact with the frame structure of the device, the circuit board or the like, when the connector (10) is fixed in place, and when the shield is detachably attached both to the connector (10) and to the interior of the outer casing (2).

Description

Interference-protected cable connector housing

The invention relates to an interference- protected cable connector housing, which comprises a metal shield structure and a surrounding outer casing, and during the use of which the sheath of the cable is grounded to a frame structure of a device, a circuit board or the like to protect especially against electromagnetic interference (EMI). The problem with cable connector housings is how to ground the sheath of the cable to the frame structure of the apparatus so well that it provides sufficient interference protection. This problem is common in connectors manufactured from electrically non- conductive materials (for example a EURO connector).

There have been previous efforts to solve this problem for example in connection with so-called D connectors by utilizing structures prepared in such a way that inside a plastic housing there is a two-part sheet metal, which firmly connects the cable sheath to the metal frame of the connector, from which the grounding is performed via the attachment points (usually two) of the connector. However, the space between the attachment points is usually too long to provide good protection.

The connector housing can also be manufactured entirely from metal, for example aluminium cast. Such housings can be found from manufacturers' lists for D connectors. In such connectors the aluminium housing comes into contact with the connector frame from where it is carried off to the earth from the attachment points of the connector of the circuit board. This manner is not applicable for electrically non-conducting connectors. Furthermore, also here the space between the attachment points can be too long to provide sufficient protection.

Plastic connector housings are also known, the surface of these housings being nickel plated so that an electrically conductive coating can be provided on the surface of the housing. The connector frame is then connected to the earth from one point. The capacity of this housing to inhibit interference is poor.

Such plastic connector housings have also been used where an earth conductor encircling the sheath of the cable is directed from the sheath to an available pin of the connector, from where the conductor is supplied further to the circuit board or to the frame structure of the device. This does not provide adequate protection, since one conductor cannot equalize the potential differences of the sheath or prevent the interference radiation of the other conductors to the environment.

One manner has been to strip the cable before the connector and the housing, and to ground it to the frame of the device or the device carrier for example by means of an attachment clamp. The problem has been that the interference can propagate further from between the point of grounding and the connector. The problems of interference protection occur especially in connection with plastic EURO connectors or the like, as it was stated already in the beginning. These connectors themselves contain no protection against electromagnetic interference, but they must be shielded with separate housings and groundings. The need for protection results from the fact both RF signals and normal data cables may criss-cross in the same device. Therefore the interference can be connected to the data cables from the open spaces. Open connectors are also a source of interference when for example clock signals have to be transmitted from them.

None of the known arrangements can eliminate the above-described problems especially when connectors made of a non-conducting material are used.

The object of the present invention is to eliminate the problem using as a starting point the cable connector housing described in the beginning. This aim is achieved with the cable connector housing according to the invention, characterized in that the shield structure consists of a solid flexible shield,

- which encircles the connector,

- to the inner surface of which the sheath of the cable is grounded with a direct contact, - the edges of which, placed against the device, are formed into tongues that are in close contact with the frame structure of the device, the circuit board or the like, when the connector is fixed in place, and - which is detachably attached both to the connector and to the interior of the outer casing.

The invention is based on a two-part housing wherein the outer casing (for example plastic) of the housing acts as a supporting structure and the inner part (thin sheet metal) as the actual EMI shield. The essential idea of the structure is that it provides a good and, in view of the RF signals, close contact between the cable sheath and the frame of the device. The tongues of the shield have spring-like properties ensuring the contact to the frame of the device within a wide area.

When the cable connector housing according to the invention is used, the shield of the cable is connected via the shortest path to the frame of the device and it ensures reliable protection around the entire connector. The protection-attenuation ability of the cable can thus be utilized to the maximum, since it is at least as effective as that of the cable sheath. The possibilities of designing the flexible tongues of the shield are unlimited, and there may be several optional materials and thicknesses for the shield. The structure of the housing is simple (only two parts and it is inexpensive to manufacture. Furthermore, it is possible to take the shield out of use, if desired, if the connector is used in places where no EMI protection is needed.

The invention will be described in greater detail below with reference to the accompanying drawings, in which

Figure 1 is a perspective view of the cable connector housing according to the invention and of a counter connector provided in the frame of the device, in partial profile, Figure 2 shows the parts of the cable connector housing shown in Figure 1 before the assembly,

Figure 3 is a cross-section of the cable connector housing according to the previous figures, and the counter connector of the device, and Figures 4A, 4B and 4C show a preferred manner of locking the outer casing of the cable connector housing according to the invention to the counter connector of the device.

The cable connector housing according to the invention shown in the drawings consists of two parts, i.e. an electrically conductive metal shield 1 and a preferably plastic outer casing 2 encircling the shield 1.

The shield 1 is formed of a solid thin sheet metal having spring-like properties and a thickness of for example 0.1 mm. According to Figure 2, the sheet metal is bent and compressed into the position of application shown in Figures 1 and 3, into an elongated object having a substantially U-shaped cross-section. Actually, the shield 1 is substantially U-shaped only when it is inserted into the outer casing 2 having a corresponding shape, since when the shield 1 is detached from the outer casing 2, its branches 4 and 5 are further away from each other than when the shield is positioned in place.

The edges of the branches 4 and 5 of the shield 1 that are positioned against the device 3 are bent into several tongues 7 that protrude to the side (inwards or outwards) from the branches 4 and 5, that are separated from one another by means of cuts 6, and that come into close contact with the frame structure 8 of the device 3, the earth foil of the circuit board 9, or with some other corresponding surface providing grounding, when the connector 10 placed in the shield 1 is attached to the counter connector 11 provided in the device 3.

When the cable 12 is connected inside the housing, the bottom area 13 inside the U formed by the shield 1 comes into close contact with the stripped sheath 14 of the cable 12, and correspondingly the connector 10 to which the wires 15 of the cable 12 are connected will be substantially encircled by the shield 1 so that the connection will be grounded and protected as well as possible against electromagnetic interference. The cable 12 is attached to the housing in such a way that both the shield 1 and the outer casing comprise within this area openings 16 and 17 via which the cable 12 can be clamped against the bottom area 13 of the U for example by means of cable ties 18.

In the embodiment according to Figures 1 to 3, the connector 10 leans in the shield 1 on the end walls formed of the end projections 19 of the branches 4 and 5 of the shield 1, the end walls preventing the connector 10 from moving towards the bottom of the U, acting as additional interference shield. By means of the outer casing 2, the connector 10 is again locked in place so that it cannot come off the housing. However, since all parts have to be easily detachable from one another when necessary, for example when the cable connector housing is used in places where interference protection is not needed and when the shield 1 is to be removed, it is preferable that the connector 10 and the outer casing 2 are locked for example by means of a snap connection or other corresponding form locking.

Figures 4A to 4C show a preferred manner of implementing the aforementioned interlocking of the outer casing 2 and the connector 10. It comprises a one- part elongated outer casing having a substantially U- shaped cross-section and containing two branches 20 and 21, which can be stretched away from each other and the ends of which are provided with gripping jaws 22 for gripping the ends of the connector. The structure is such that it keeps the connector 10 in place even if it were not supported against the aforementioned end walls of the shield 1. This also enables the use of the outer casing 2 without the shield 1, if desired.

The above is only intended to illustrate the invention, since a person skilled in the art can realize the details in several alternative ways within the scope of the appended claims.

Claims

1. An interference-protected cable connector housing, which comprises a metal shield structure (1) and a surrounding outer casing (2), and during the use of which the sheath (14) of the cable (12) is grounded to a frame structure (8) of a device (3), a circuit board (9) or the like to protect especially against electromagnetic interference, c h a r a c-t e r i z e d in that the shield structure consists of a solid flexible shield (1),

- which encircles the connector (10),

- to the inner surface (13) of which the sheath (14) of the cable (12) is grounded with a direct contact,

- the edges of which, placed against the device (3), are formed into tongues (7) that are in close contact with the frame structure (8) of the device, the circuit board (9) or the like, when the connector (10) is fixed in place, and

- which is detachably attached both to the connector (10) and to the interior of the outer casing (2).

2. A cable connector housing according to claim

1, c h a r a c t e r i z e d in that the shield (1) is an elongated object which has a mainly U-shaped cross- section when mounted in place and which is formed of sheet metal by bending.

3. A cable connector housing according to claim

2, c h a r a c t e r i z e d in that the bottom (13) of the U forms a contact surface for the sheath (14) of the cable (12), and that the walls of the shield (1) and the outer casing (2) comprise in this area openings (16, 17) via which said sheath (14) can be locked from the outside of the housing by means of binding means, for example cable ties (18), to have close contact with the bottom (13) of the U.

4. A cable connector housing according to claim

1, c h a r a c t e r i z e d in that the tongues (7) are formed by bending the ends of the branches (4, 5) of the U, and that several tongues (7) are formed in each branch (4, 5) by means of cuts (6) provided in the branches.

5. A cable connector housing according to one of the preceding claims, c h a r a c t e r i z e d in that also the outer casing (2) is a uniform elongated preferably plastic object the cross-section of which is mainly U-shaped, and that the walls of the outer casing are provided with gripping means (22) for gripping the connector (10) and for locking it in place.

6. A cable connector housing according to claim 5, c h a r a c t e r i z e d in that the outer casing (2) comprises two branches (20, 21) which can be stretched away from one another, and that said gripping means are formed of gripping jaws (22) provided at the ends of the branches.