Chemistry: electrical current producing apparatus – product – and – With control means responsive to battery condition sensing...
Reexamination Certificate
1999-06-11
2001-04-17
Maples, John S. (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
With control means responsive to battery condition sensing...
C429S057000, C429S178000
Reexamination Certificate
active
06218040
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to controlling the flow of current from a battery and, more particularly, to controlling the flow of current from a rechargeable battery by way of an automatic circuit breaker which interrupts the flow of current from the battery upon the development of a predetermined overcurrent, with a device resistance of less than or equal to 0.2 milliohms.
2. Related Art
Batteries in the related art include circuit breakers for stopping the flow of current from the battery upon a predetermined condition. In particular, U.S. Pat. No. 4,188,460 to Kang et al. discloses an internal battery fuse in which excessive built-up heat resulting from a short circuit is concentrated in a portion which then heat fuses and interrupts the circuit. The heat fusible portion is formed as a thinned strip making up a portion of the current collector and is surrounded by a heat shield. When current exceeds a predetermined threshold, the thinned strip provides a greater electrical resistance than the rest of the current collector, and thus heats up. Because the shield retains the heat around the thinned strip, the thinned strip fuses to break the electrical connection within the current collector thus terminating current flow from the battery. Alternatively, the thinned strip may be a separate element which is welded between two portions of the current collector. However, Kang includes the disadvantage that the circuit is broken at a point within the cell itself. That is, the heat fusible portion is located adjacent the electrode stack which produces gasses that may be ignited by any arcing in the fusible portion. Further, because Kang requires a heat shield as well as either a thinned portion of an elongate strip current collector or a thinned strip welded to different portions of the current collector, his battery fuse is complex.
U.S. Pat. No. 4,690,879 to Huhndorff et al. and U.S. Pat. No. 5,057,382 to Tucholski also disclose complex mechanisms for interrupting the flow of current from a battery. In each of these batteries, the current flow is terminated upon the bulging of the cell due to excessive pressure therein. When pressure builds up within either battery, the ends bulge. In Huhndorff, the current is terminated due to a break in a weld connection between a cover terminal and a metal container upon the battery's bulging. In Tuchoski, the current is interrupted by the relative sliding movement between a secondary conductive cover and a container contact member upon the battery's bulging.
SUMMARY OF THE INVENTION
An object of the present invention is to overcome the disadvantages of the prior art.
A further object of the present invention is to provide a simple to manufacture mechanism which automatically interrupts the flow of current from a battery upon the development of a predetermined overcurrent. In the present invention, because a weld connection around the periphery of an aperture determines the current path, the diameter of the aperture determines the amount of current that will break the weld thereby opening the circuit. Thus, merely selecting a different aperture diameter allows variation in the amount of current allowed through the connection before it automatically opens.
A further object of the present invention is to provide a mechanism which automatically interrupts the flow of current from a battery with reduced risk of igniting gasses produced in an electrode stack of an electrochemical cell. The present invention includes an epoxy covering the weld connection which is broken to interrupt the flow of current such that the epoxy contains any arcing that occurs during interruption of current. Further, the weld connection which is broken to interrupt the flow of current is located on the outside of the battery enclosure so that even if any arcing does occur, it occurs away from gasses produced in the electrode stack, thereby reducing the risk of ignition.
The present invention automatically interrupts the current flow in a battery upon a predetermined overcurrent. In the battery of the present invention, a bussing structure within the battery enclosure is connected to a terminal assembly on the outside of the battery enclosure by an electric feed through. The electric feed through is connected to the terminal assembly by a weld connection formed around the periphery of an aperture formed in the terminal assembly. When a predetermined overcurrent develops, the weld connection is broken. The weld connection is circular and, thus its length is determined by the diameter of the aperture in the terminal plate around which the weld connection is made. The amount of overcurrent which breaks the connection is controlled by controlling the length of the weld which defines the length of conductor between the current bussing structure within the battery enclosure and the terminal plate on the outside of the battery enclosure. Further, the amount of overcurrent is controlled by the thickness and resistivity of the material chosen for the terminal assembly. Thus, the amount of overcurrent which breaks the connection is easily controlled by selecting an appropriate diameter for an aperture in, as well as thickness and resistivity of, a portion of the terminal assembly. Further, because the weld connection which breaks to interrupt current flow is formed between a terminal assembly and an electric feed through, on the outside of the battery enclosure, there is reduced risk of igniting battery gasses upon interruption of current.
In a lithium-ion cell, for example, the terminal assembly is made of copper and nickel, whereas the electric feed through is made of molybdenum. However, any suitable material may be used for the terminal assembly and electric feed through, depending on the type of battery in which the automatic circuit breaker is employed. In one embodiment of a lithium-ion cell, the thickness and resistivity of the terminal assembly, as well as the aperture diameter are selected so that the device has a resistance of less than or equal to 0.2 milliohms. Further, although the connection between the terminal assembly and the electric feed through is described as a weld connection, any suitable connection along the periphery of the aperture in the terminal assembly may be used. Moreover, although the present invention is particularly useful on rechargeable batteries used in electric vehicles, it may be used with any type of battery.
REFERENCES:
patent: 4188460 (1980-02-01), Kang et al.
patent: 4690879 (1987-09-01), Huhndorff et al.
patent: 5057382 (1991-10-01), Tucholski
Alcatel
Maples John S.
Sughrue Mion Zinn Macpeak & Seas, PLLC
LandOfFree
Automatic circuit breaker for a battery does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Automatic circuit breaker for a battery, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Automatic circuit breaker for a battery will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2436015