Electrical resistors – Resistance value responsive to a condition – Current and/or voltage
Reexamination Certificate
1996-09-27
2001-04-10
Easthom, Karl D. (Department: 2832)
Electrical resistors
Resistance value responsive to a condition
Current and/or voltage
C338S332000, C338S254000, C338S260000, C338S322000, C338S328000, C338S319000, C338S205000
Reexamination Certificate
active
06215388
ABSTRACT:
BACKGROUND OF THE INVENTIONS
This application relates to the art of thermal protectors and, more particularly, to thermal protectors having electrical current limiting capabilities. The invention will be described with particular reference to thermal protectors that include a thin sheet of polymeric compound containing carbon particles and having a positive temperature coefficient of resistance. However, it will be appreciated that the invention has broader aspects and that it is possible to use other materials having a positive temperature coefficient of resistance.
Thermal protectors that have a positive temperature coefficient of resistance are commonly referred to as PTC devices and the materials that provide such a resistance characteristic are commonly referred to as PTC materials. A thin layer of PTC material in a PTC device conducts electricity in a direction perpendicular to its thickness. Decreasing the resistance of such a PTC device during normal operation can be achieved by increasing the area of the PTC material layer. However, PTC devices must fit in confined spaces and it is not always possible to enlarge the surface area of the PTC material layer to the extent that would be necessary to provide a desired low initial resistance while still fitting in the available space.
It would be desirable to have an arrangement for enlarging the area of a PTC material layer without greatly increasing the peripheral size of a PTC device.
SUMMARY OF THE INVENTION
A PTC device of the type described has a plurality of metal plates and a plurality of PTC material layers sandwiched together with one PTC material layer connected in series between one pair of metal plates and with all of the other PTC material layers connected in parallel with the one layer. This arrangement makes it possible to adjust the total area of the PTC material while minimizing the peripheral size of the PTC device.
In a preferred arrangement, the plurality of metal plates have connecting tabs for selectively interconnecting selected ones of the plates to connect the other PTC material layers in parallel with the one layer.
In one arrangement, selected ones of the connecting tabs have openings therein for receiving a finger on other tabs. Solder is then used for securing the finger in the openings and providing good electrical continuity.
In accordance with another aspect of the application, an outer metal plate on the PTC device includes a laterally extending support projection for supporting the PTC device on a circuit board or the like. The laterally extending support projection may have spaced-apart legs extending downwardly therefrom for reception in openings in a circuit board or the like.
It is a principal object of the present invention to provide a PTC device having a PTC material area that is much larger than the area within the periphery of the PTC device.
It is also an object of the invention to provide a compact PTC device having a plurality of PTC material layers connected in parallel.
It is another object of the invention to provide a PTC device having a plurality of metal plates separated by a plurality of PTC material layers and with the plates having tabs for selective interconnection to place the PTC material layers in electrical parallel.
REFERENCES:
patent: 996862 (1911-07-01), Kraus
patent: 2143414 (1939-01-01), West
patent: 3447118 (1969-05-01), Ferree
patent: 3878501 (1975-04-01), Moorhead et al.
patent: 3916264 (1975-10-01), Berg
patent: 4414530 (1983-11-01), Bouffard et al.
patent: 4698614 (1987-10-01), Welch et al.
patent: 4918421 (1990-04-01), Lawless et al.
patent: 5089688 (1992-02-01), Fang et al.
patent: 5233326 (1993-08-01), Motoyoshi
patent: 5262619 (1993-11-01), Karner
patent: 5270521 (1993-12-01), Shikama et al.
patent: 5382938 (1995-01-01), Hansson et al.
patent: 5488348 (1996-01-01), Asida et al.
patent: 5493266 (1996-02-01), Sasaki et al.
patent: 5663861 (1997-09-01), Reddy et al.
patent: 5682130 (1997-10-01), Styrna et al.
patent: 5688424 (1997-11-01), Asida
patent: 5691688 (1997-11-01), West et al.
patent: 5777541 (1998-07-01), Vekeman
patent: 2054487 (1978-02-01), None
patent: 944974 (1956-06-01), None
Easthom Karl D.
Harness & Dickey & Pierce P.L.C.
Therm-Q-Disc, Incorporated
LandOfFree
Parallel connected PTC elements does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Parallel connected PTC elements, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Parallel connected PTC elements will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2435511