Electrical terminal with integral PTC element

Details Electrical terminal with integral PTC element Electrical terminal with integral PTC element

1998-05-12

2001-01-09

Kincaid, Kristine (Department: 2831)

Electricity: conductors and insulators

Conduits, cables or conductors

C174S07000A, C174S09400S, C338S221000

Reexamination Certificate

active

06172303

ABSTRACT:

FIELD OF THE INVENTION
This invention relates in general to electrical terminals such as those used in multi-pin electrical connectors, and more specifically to such a terminal having an integral positive temperature coefficient device to protect associated circuitry against over-current conditions.
BACKGROUND OF THE INVENTION
Positive temperature coefficient (PTC) materials exhibit an electrical resistivity (resistance per unit thickness) which is relatively low at a design operating temperature and increases abruptly as the temperature of the material rises above a critical temperature. This property can be used to create devices which protect electrical circuits against over-current conditions.
A PTC circuit over-current protection device generally comprises a layer of PTC material sandwiched between two plates of electrically conductive metal. Electrical leads are attached to each of the plates and are connected to the electrical circuit. At a given operating temperature, there is a maximum steady level of electrical current which can pass from one plate to the other through the PTC material without causing significant resistance heating of the device. This level of current is known as the “pass” or “hold” current. If the current level rises above the hold current, resistance heating causes the temperature of the PTC element to rise above the critical temperature and the resistance of the device increases sharply so that only a very low level of current can pass through the device, effectively opening the circuit.
PTC devices are typically used in place of conventional fuses and/or circuit breakers in various electrical and electronic devices, and are usually mounted on a printed circuit board or otherwise hard-wired into the circuit to be protected. PTC materials include compositions such as conductive polymers and ceramics.
SUMMARY OF THE INVENTION
It is an object of this invention to eliminate the additional wiring and interconnections typically required when connecting an over-current protection device to a circuit.
A further object of the invention is to incorporate a positive temperature coefficient (PTC) material into terminals providing electrical connection within the circuit to be protected.
In a first illustrative embodiment of the invention, a surface of a male electrical terminal is covered by a layer of PTC material. When the male terminal is inserted into mating engagement with a female terminal, the PTC material is interposed between the surfaces of the mated terminals to create a PTC device through which electrical current must pass in order to flow through the circuit in which the terminals are connected. As a result, over-current protection is provided to the associated circuitry without the need for soldering or otherwise connecting a separate PTC device into the circuit. In an alternative construction of such a terminal, an inner surface of a female terminal is covered by the PTC material. When placed in mating engagement with a conventional male terminal, the PTC material is interposed between the surfaces of the two terminals to create a PTC device.
In a second illustrative embodiment of the invention, a terminal comprises a contact portion for making electrical connection with a mating terminal, a wire connection portion for connection to a wire, and a layer of PTC material interposed between adjacent surfaces of the contact portion and wire connection portion. The layer of PTC material is the only electrically conductive connection between the two portions of the terminal so that current must flow through the layer in order to pass through the circuit.


REFERENCES:
patent: 3835434 (1974-09-01), Kahn
patent: 4327481 (1982-05-01), Woods
patent: 4635026 (1987-01-01), Takeuchi
patent: 5451921 (1995-09-01), Crawford et al.
patent: 5590011 (1996-12-01), Hein
patent: 5606483 (1997-02-01), Sawai et al.
patent: 5682130 (1997-10-01), Styrna et al.
patent: 5801612 (1998-09-01), Chandler et al.
patent: 5835004 (1998-11-01), Gemperle et al.
patent: 5909168 (1999-06-01), Miyasaka et al.

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