Electricity: conductors and insulators – Conduits – cables or conductors – Combined
Reexamination Certificate
1998-03-09
2002-01-15
Nguyen, Chau N. (Department: 2831)
Electricity: conductors and insulators
Conduits, cables or conductors
Combined
C439S616000
Reexamination Certificate
active
06339193
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to electrical grounding of shielded cables and wires to a connector housing, and more particularly to an improved backshell adapter with an easily removable interface yoke suitable for attaching cable shields and grounding leads through a low resistance path directly to the connector housing.
BACKGROUND OF THE INVENTION
Electrical connectors coupled to a cable by way of a backshell adapter provide reliable means for attaching a cable to an electrical component. The backshell adapter secures the cable to the connector while the connector provides a releasable means for transmitting the cable signals across a junction. This arrangement is of particular value for sophisticated electronics equipment requiring multiple wires transmitting signals and power to external components. Such equipment is often found in aircraft, satellites, military vehicles, electronically controlled machinery, and similar equipment.
Wires in the cables of sensitive electronic equipment are susceptible to interference from electrical and magnetic sources both internal and external to a cable. As a means of shielding wires from such interference a braided metal sleeve or shield is often placed over individual wire, pairs of wires, and/or, and entire bundle of wires comprising a cable. The shield protects wires of the cable from electromagnetic interference (EMI) as long as they are suitably grounded and shielded at the ends of the cable. For cables attached to connectors, the metal housing of the connector provides the path to ground; the means for electrically grounding the wire shields to the housing being the subject of this disclosure.
Where used, a backshell adapter serves a variety of functions to mechanically and electrically transition the cable and wires to the connector. In the region just behind the connector, wires must be stripped and prepared for insertion into the connector. Sufficient wire must be stored to allow future repair access to connector pins, and grounding of external wire shields must be accommodated. The wires must be mechanically secured to the connector. Backshells provide an enclosed housing and mechanisms to support these functions.
The backshells are typically coupled to the connector by way of a mating interface with a threaded coupling that can be removed as needed for repair. The interface configuration and dimensions are supported by military and industrial standards to insure interchangability between components from different manufacturers. The interfaces are designed to insure reliable mechanical, environmental and electrical coupling. Electrically the interface must insure solid grounding and electrical and magnetic shielding with no windows for EMI leakage. Environmentally the backshell-to-connector interface must be sealed from external hazards such as corrosion inducing moisture. Mechanically the interface must maintain the electrical and environmental functions under tensile, bending and torsion loading, in addition to shock and vibration.
Connector and cable designs are available with a wide range of performance capabilities. Increasing performance comes with increased cost. Backshell adapters are typically chosen as a means of transitioning cables to connectors when the system cost favors repair over replacement for damaged assemblies. Backshell adapters are advantageous because they are designed to optimally transition a wide variety of cable configurations to a relatively few number of standard connector designs. This maintains connector cost lower by enabling a few designs to be produced in higher quantity. The backshell separates the transitional requirements from the electrical connection requirements, allowing each to be separately optimized for cost and performance.
DESCRIPTION OF THE PRIOR ART
There are several common methods used to terminate a wire shield to a connector. These methods including utilizing pigtails, jumpers, or grounding leads to create a ground path to a point on the backshell, or to a pin within the connector. These methods are time consuming to install or repair and are generally hampered by the lack of access to the wires within the backshell. In many instances, there is no adequate means within the structure to attach the ground leads to the backshell so as to be close to the mating connector interface. Leads are often secured at the rear of the backshell hardware, increasing the resistance of the ground path. Further, these methods rely on the conductivity of the backshell and are unsuitable for applications requiring a low conductivity, or non-conductive backshell material; examples include lightweight plastics or corrosion resistance stainless steel, not good conductors or shields. If the attachment of leads takes place outside of the protective backshell housing, then the termination is vulnerable to corrosion damage.
Methods using pigtails or ground leads often attach the leads at the point of mechanical coupling of the backshell to the cable. These methods require the ground leads to be disconnected every time the backshell is loosened to give access to the connector.
One method, for terminating shielded wires to a connector is presented by Van Brunt et al, U.S. Pat. No. 4,820,201. This method extensively modifies a standard connector to include a metal disk suitable for attaching wire shields by means of a transition clip secured over the shielded braid. The metal disk includes multiple openings arranged to coincide with the wire entry points commonly used on connectors. While providing a very short ground path for shields, this method requires an expensive connector modification, precluding the use of standard off the shelf connector configurations. Further each type of connector can have many insert arrangements, each with a different hole pattern. This arrangement requires a specific grounding disk be used for each insert arrangement, making the system prohibitively expensive for most applications.
Traditional ground leads methods have proven to be inadequate for simple effective grounding of shields. Further, methods that require extensive modification of connectors designs have been found to be prohibitively expensive. There exists a need for a cost effective method of grounding shields that insures a low resistance path to ground, and a reliable well protected termination that is both easy to install and repair.
BRIEF DESCRIPTION OF THE PRESENT INVENTION
The present invention provides for an improved backshell adapter and yoke configuration that readily accommodates the termination of ground leads secured to the braids of shielded wires and cables. In particular, it provides for a conductive removable connector interface with an attached means for terminating ground leads, said removable interface being referred to here as a yoke. The yoke is removably insertable into the front of a backshell designed to accept it. When the backshell is mated to a connector, the yoke mates directly to the connector interface providing a low resistance ground path to the connector housing for any lead, particularly ground braids, secured directly to the yoke.
The removable yoke provides many benefits to the user. First, it is a secured grounding platform for shield leads residing in close proximity to the connector housing. Multiple wire leads can be attached to the yoke, by any number of methods that are common in the industry, such methods including banding, soldering, or clipping to name a few. Second, the yoke provides ample access to the lead terminations during installation and repair. The ease of access to shield leads reduces the cost of terminating a cable to a connector. Third, the yoke allows the backshell to be removed from the connector to gain repair access to the wires without having to disconnect the grounding shield. This arrangement results in substantial time saving during repair or inspection, and eliminates one of the leading causes of cable problems; namely, failure to properly reground shield leads after decoupling a backshell.
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Goett Edward P.
Spratt Robert F.
Woehl Roger
Engineered Transition Company, Inc.
Johnson Larry D.
Johnson & Stainbrook LLP
Stainbrook Craig M.
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