Electrical connectors – With circuit component or comprising connector which fully... – Termination circuit
Reexamination Certificate
1998-11-23
2001-02-06
Bradley, Paula (Department: 2833)
Electrical connectors
With circuit component or comprising connector which fully...
Termination circuit
C439S696000, C333S181000
Reexamination Certificate
active
06183304
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to electrical devices such as multi-part plug and socket assemblies, switches, feed throughs, test leads, signal wires, and relays, and more specifically relates to electrical devices that incorporate an antenna-effect inhibiting feature to protect signals carried by the device from electromagnetic and/or electrostatic discharge type interference.
The invention relates further to protecting electrical circuits from receiving electromagnetic or electrostatic discharge interference which might be induced in conductors leading to the electrical circuit. More specifically the invention relates to electrical connectors which provide for suppression of electromagnetic or electrostatic discharge interference by means which form part of the connector itself or as an accessory thereto.
This invention applies to the fields of use wherein there is necessity for including an electrical device in a low level signal circuit, e.g. a thermocouple sensor, and provides a new apparatus for eliminating undesired electromagnetically-induced or electrostatic discharge type stray signals.
2. Description of the Prior Art
In the prior art of connectors there are disclosures of the use of ferrite material in the following:
(I) U.S. Patents assigned to AMP Inc: U.S. Pat. Nos. 4,699,590, 4,359,620, 3,789,263, U.S. Pat. No. Re 29,258, U.S. Pat. Nos. 3,735,705, 3,987,380, 4,936,800.
(II) U.S. Patent assigned to The Whitaker Corp: U.S. Pat. No. 5,219,305.
(III) U.S. Patent William Baird Fritz U.S. Pat. No. 3,743,978
(IV) U.S. Patent assigned to Stanford Research Institute and Amplex Corporation: U.S. Pat. No. 3,533,948.
(V) Un-examined Japanese Patent Application, AMP Inc., 90-032246/05 JO 1279-584-A discloses an electrical connector which has a noise filter with a ferrite head fitted to a terminal lead formed by a central conductor of a feed-through capacitor.
(VI) German Patent assigned to AMP Inc., Auslegeschrift No. 2,058,419 discloses a method for the manufacture of a high frequency filter from a ferrite tube, which is in the form of a highly compressed tube and which is bonded on its outer surface with a covering of dielectric material, the layer of dielectric material carrying an electrode in the form of a metallic outer sleeve, and a further electrode is provided in similar manner on the inside of the ferrite tube, characterised in that the covering (
6
) of dielectric material is laid down directly onto the outer surface of the ferrite tube (
5
) by electrophoresis.
SUMMARY OF THE INVENTION
It is known that electrical signals carried by connectors, or adjacent apparatus, may be subject to electromagnetic interference as the result of induced signals picked up from the radiation of adjacent electrical equipment. Such interference results from leads acting as an antenna that senses stray electromagnetic radiation; accordingly, the sensing of stray signals in this manner is known as the “Antenna-effect”. Various efforts have been made to avoid or suppress the result of the antenna-effect, but such efforts have been found to be inconvenient and/or expensive to implement, or both.
For example, it has been found in the past that antenna-effect stray signals can be avoided by encapsulating leads in sheaths of magnetic-shielding sheet material, or by determining the strength of nearby stray signal fields and then moving all such nearby sources to a physical distance from the leads that has been calculated to prevent the possibility of undesired signals being picked up by electromagnetic induction. It can be seen, readily, that such preventive methods and techniques are indeed costly and inconvenient. Other attempts to reduce or avoid antenna-effect stray signals have involved the use of ferrite cores. However, until now such uses have required additional circuit elements, such as insertion of a jumper cable, having a permanently included ferrite core, in series with the main conductors in the circuit; or, awkwardly and inconveniently surrounding one or more of the circuit conductors with separately applied ferrite cores.
It is established practice, in industries that make use of thermocouple sensors, to couple the sensor into a related electrical circuit by means of an electrical connector. When for example thermocouples are connected to instruments such as panel meters, controllers and transmitters, the input signal from the sensor or transducer usually travels substantial distances along fine gauge electrically conductive wire leads. The length and nature of such leads and the environment in which they must function often create conditions that favour occurrence of the antenna-effect. In many cases, the leads or signal wires from a sensor or thermocouple are first attached, for convenience, to an electrical connector, for coupling to an instrument or the like. As soon as the conductors of the connector are electrically coupled to the circuit, a potential antenna is created. Of particular importance are thermocouple connectors which are particularly susceptible to the antenna-effect because of the long lead conductive path of the conductors themselves and the high input impedance of the instrumentation.
The term “ferrite”, as commonly understood in the electronics field, denotes a particulate material having one or more oxides of iron in particulate form in a carrier such as a plastics material. This usage of the term “ferrite” is to be distinguished from the usual dictionary definition which is a generic name for a number of oxides of iron. In this specification, the term “ferrite” is to be understood as including within its scope any suitable material having an absorption and/or shielding effect as concerns electromagnetic waves which may be emitted at or adjacent to a zone of completion of an electrical circuit. Known ferrite elements consist of ferrite material sintered into a convenient shape. Other known “ferrite” materials for the suppression of electromagnetic interference are nickel-zinc compositions and manganese-zinc materials, of different compositions to permit selection of an optimum type for a given application; pressed parts, components, and powders are known.
OBJECTS OF THE INVENTION
Accordingly, it is an object of this invention to provide means associated with an electrical device that is capable of avoiding stray signals that may be induced in the leads of the device.
It is another object of this invention to provide an apparatus for eliminating the effects of undesired stray signals in circuits, that is uncomplicated in design, and that is simple and relatively inexpensive to produce.
It is still another object of this invention to provide means associated with an electrical device for eliminating the effects of undesired stray signals in its circuits, that is easily adaptable to single-wire or multi-wire connections.
Another and further object of this invention is to provide means associated with an electrical device for eliminating the effects of undesired stray signals in its circuits, that can be manufactured easily in various configurations to accommodate differing circuit requirements.
And yet another and further object of this invention is to provide means associated with an electrical device for elimination of the effects of undesired stray signals in its circuits in which operative elements of the device may be configured to facilitate insertion and removal of wire conductors.
A further object is to provide a method for the formation of a twin, or other multiple, wire arrangement, such as a thermocouple, assembly with a housing composed wholly or mainly of ferrite material, for example by molding or machining.
A further object is to provide a single wire arrangement, e.g. for a “banana” type plug and a method of incorporating the single wire in a housing composed wholly or mainly of ferrite material, for example by molding or machining.
Other objects are to provide:
(A) In an electrical device e.g. a plug and socket, a switch or a relay, which includes at least two contact members with res
Hollander Milton Bernard
McKinley William Earl
Stewart Russell
Bradley Paula
Drucker William A.
Omega Engineering Inc.
Ta Tho D.
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