This invention relates to a female F-connector with improved screening in relation to electromagnetic signals.

Background to the invention

F-connectors are connectors used with coaxial cables typically in television, cable television and broadband cable networks. The F-connectors are used in male/female pairs, with the male connector using a solid conductive inner wire of a coaxial cable as its pin. The pin is inserted into the female F-connector to establish a connection between the coaxial cable and processing circuitry relating to a device or equipment connected to the female F-connector.

The coaxial cables distribute radio frequency signals around a network and are configured to provide very good electrical screening to the inner conductive wire. A high level of screening is needed to ensure no signal leakage from the inner conductor through the coaxial cable casing and to ensure that unwanted signals cannot enter the coaxial cable casing and introduce noise to the wanted signal carried by the inner conductor. Whilst the cable itself is well screened, connectors must be attached to ends of the coaxial cable to allow it to be connected to complementary connectors on other items of equipment.

To prevent ingress and other unwanted signals entering the network, the coaxial cable and connectors are constructed in such a way to try and keep unwanted signals from out of the signal transmission line. However, problems still arise with unwanted signal ingress where respective male and female connectors are joined together.

Summary of the invention

In accordance with the present invention, there is provided a female F-connector comprising an outer electrically conductive threaded portion, typically made of metal, wherein an annular groove is formed in the threaded portion and a resilient electrically conductive ring member is located in the annular groove. The resilience of the ring member ensures that it does not interfere with interconnection of a male and female F- connector, compressing as the male connector is tightened around it and then expanding outwardly to close any gap between the male and female connector. Even if the connected male and female connectors loosen with respect to each other, the ring member will maintain an electrically conductive seal between the male and female connectors and ensure there are no air gaps permitting leakage or ingress of RF (radio frequency) signals.

Preferably the ring member is a ring spring made from metal.

The annular groove is preferably proximal to an open end of the female connector which is capable of receiving a pin from a male connector. By having the annular groove proximal to the open end of the female connector, the seal will be maintained even where the female connector has become greatly loosened from the male connector.

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

Figure 1 shows a cross-section through prior art male and female connectors before they are connected together;

Figure 2 shows connected prior art male and female connectors;

Figure 3 shows a cross-section through loosened prior art male and female connectors;

Figure 4 shows a cross-section of a female F-connector in accordance with the present invention;

Figure 5 shows a side view of the connector of Figure 4; and

Figure 6 shows the inventive female F-connector when in use.

Description

Figure 1 shows a cross-section through an end portion of a prior art male F-connector 10 and female F-connector 12. Male connector 10 comprises a metal collar 14 with integral post plate attached to an internally threaded connector ring 16 and has an electrically conductive centre pin 18 formed from an inner conductor of a coaxial cable attached to the male connector. An electrical screening sheath of the coaxial cable, not shown, is connected to the metal collar. Female connector 12 comprises an externally threaded cylindrical metal outer portion 20 within which is nested cylindrical plastics insert 22 defining a cavity within which is secured conductive spring 24 electrically connectable to electrical circuitry or equipment associated with the female connector.

When the two connectors 10, 12 are screwed together as shown in Figure 2, inner conductive spring 24 receives pin 18 to establish an electrical connection between the coaxial cable attached to the male connector 10 and any electrical circuitry to which female connector 12 is connected. To ensure good electrical screening, male and female connectors 10, 12 are tightened with respect to each other so that metal collar 14 adjoins metal portion 20 so forming a closed connection and ensuring there is no electromagnetic signal leakage from or ingress into inner pin 18. However, if male connector 10 is not fully tightened on female connector 12, perhaps because it was not properly secured originally or it has become loose due to vibration or thermal effects, metal portion 20 of female connector 12 no longer adjoins metal collar 14 leaving an open gap 26. Electromagnetic signals can now leak to the outside through gap 26 and small gaps between the cooperating threaded portions and also unwanted signals can enter the inner conductor 18 by the same route.

To avoid this signal leakage, a female F-connector 30 in accordance with the invention is shown in Figure 4. In the connector according to the invention, an annular groove 33 is formed in the external threaded portion, proximal to an open connector end 34 which receives male pin 18. Electrically conductive ring spring 36 sits within this groove, see Figures 4 and 5, and provides a resilient electrically conductive annular member that can compress when force is exerted on it and restore to its original shape after the force is removed. The resilience of the ring member ensures that it does not interfere with interconnection of a male and female F- connector as it will be compressed and urged inwardly towards a central axis of the female connector as the male connector is tightened around it. The resilience ensures that the ring member expands outwardly to close any gap between the male and female connector. Even if the respective connectors loosen with respect to each other, the ring member will maintain an electrically conductive seal between the male and female connectors preventing leakage or ingress of RF (radio frequency) signals via the co-operating threads. Typically ring spring 36 will be made from metal but other electrically conductive materials can be used.

When the connector of the present invention is secured to a prior art male connector, resilient ring spring 36 will deform to allow the two connectors to be screwed together but will expand to ensure there is a complete seal between the internal face of male connector 10 and the external face of female connector 30. This sealed area prevents electromagnetic signals entering or leaving the conjoined connectors and gaining access to inner conductor 18. Where there is a failing connection due to loosening of a male and female connector, the female connector can be substantially loosened until the point where the ring spring no longer adjoins any of the external male thread before any leakage of signal occurs.