1. Field of the Invention
This invention relates generally to electrical connectors, and more particularly to coaxial cable connectors capable of being connected to a terminal.
2. Description of the Related Art
Coaxial cable connectors, such as type F connectors, are used to attach coaxial cable to another object or appliance, e.g., a television set or VCR having a terminal adapted to engage the connector. The terminal of the appliance includes an inner conductor and a surrounding outer conductor.
Coaxial cable includes a center conductor for transmitting a signal. The center conductor is surrounded by a dielectric material, and the dielectric material is surrounded by an outer conductor; this outer conductor may be in the form of a conductive foil and/or braided sheath. The outer conductor is typically maintained at ground potential to shield the signal transmitted by the center conductor from stray noise, and to maintain a continuous desired impedance over the signal path. The outer conductor is usually surrounded by a plastic cable jacket that electrically insulates, and mechanically protects, the outer conductor. Prior to installing a coaxial connector onto an end of the coaxial cable, the end of the coaxial cable is typically prepared by stripping off the end portion of the jacket to bare the end portion of the outer conductor. Similarly, it is common to strip off a portion of the dielectric to expose the end portion of the center conductor.
Coaxial cable connectors of the type known in the trade as “F connectors” often include a tubular post designed to slide over the dielectric material, and under the outer conductor of the coaxial cable, at the prepared end of the coaxial cable. If the outer conductor of the cable includes a braided sheath, then the exposed braided sheath is usually folded back over the cable jacket. The cable jacket and folded-back outer conductor extend generally around the outside of the tubular post and are typically received in an outer body of the connector; this outer body of the connector is usually fixedly secured to the tubular post. A coupler is rotatably secured around the tubular post and includes an internally-threaded region for engaging external threads formed on the outer conductor of the appliance terminal.
When connecting the end of a coaxial cable to a terminal of a television set, equipment box, or other appliance, it is important to achieve a reliable electrical connection between the outer conductor of the coaxial cable and the outer conductor of the appliance terminal. This goal is usually achieved by ensuring that the coupler of the connector is fully tightened over the connection port of the appliance. When fully tightened, the head of the tubular post of the connector directly engages the edge of the outer conductor of the appliance port, thereby making a direct electrical ground connection between the outer conductor of the appliance port and the tubular post; in turn, the tubular post is engaged with the outer conductor of the coaxial cable.
However, in many cases, it is difficult for an installer to reach the connection ports of the appliance with a wrench, and in some instances, it is even difficult for the installer to reach such connection ports with his or her fingers. As a result, it can often happen that type F connectors are not fully tightened to the appliance port. In such a loose connection system, wherein the coupler of the coaxial connector is not drawn tightly to the appliance port connector, a gap exists between the outer conductor of the appliance port and the tubular post of the connector. Unless an alternate ground path exists, poor signal quality, and RFI leakage, will result.
As mentioned above, the coupler is rotatably secured about the head of the tubular post. The head of the tubular post usually includes an enlarged shoulder, and the coupler typically includes an inwardly-directed flange for extending over and around the shoulder of the tubular post. In order not to interfere with free rotation of the coupler, manufacturers of such F-style connectors routinely make the outer diameter of the shoulder (at the head of the tubular post) of smaller dimension than the inner diameter of the central bore of the coupler. Likewise, manufacturers routinely make the inner diameter of the inwardly-directed flange of the coupler of larger dimension than the outer diameter of the non-shoulder portion of the tubular post, again to avoid interference with rotation of the coupler relative to the tubular post. In a loose connection system, wherein the coupler of the coaxial connector is not drawn tightly to the appliance port connector, an alternate ground path may fortuitously result from contact between the coupler and the tubular post, particularly if the coupler is not centered over, and axially aligned with, the tubular post. However, this alternate ground path is not stable, and can be disrupted as a result of vibrations, movement of the appliance, movement of the cable, or the like.
Alternatively, there are some cases in which such an alternate ground path is provided by fortuitous contact between the coupler and the outer body of the coaxial connector, provided that the outer body is formed from conductive material. This alternate ground path is similarly unstable, and may be interrupted by relative movement between the appliance and the cable, or by vibrations. Moreover, this alternate ground path does not exist at all if the outer body of the coaxial connector is constructed of non-conductive material. Such unstable ground paths can give rise to intermittent failures that are costly and time-consuming to diagnose.