Chemistry: electrical current producing apparatus – product – and – Means externally releasing internal gas pressure from closed... – Blowout type
Reexamination Certificate
1999-02-08
2001-08-07
Kalafut, Stephen (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Means externally releasing internal gas pressure from closed...
Blowout type
C429S171000
Reexamination Certificate
active
06270918
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to electrochemical cells and, more particularly, to a low profile seal assembly for sealing the open end of a cell container such that the seal vents when exposed to excessive pressure.
Conventional alkaline electrochemical cells generally include a steel cylindrical can having a positive electrode, referred to as the cathode, which comprises manganese dioxide as the active material. The electrochemical cell also includes a negative electrode, referred to as the anode, which comprises zinc powder as the active material. The cathode is generally formed against the interior surface of the steel can, while the anode is generally centrally disposed in the can. Alternately, in jelly-roll cells, the anode and cathode are spirally wound. A separator is located between the anode and the cathode, and an alkaline electrolyte solution simultaneously contacts the anode, the cathode, and the separator. A conductive current collector is commonly inserted into the anode active material, and a seal assembly, which includes a seal member, provides closure to the open end of the cell's steel can to seal the active electrochemical materials in the sealed volume of the can.
Cylindrical alkaline cells are commonly sealed closed by placing an annular nylon seal above a bead formed near the open end of the cell can and then crimping the upper end of the can inwardly and over the outer periphery of the seal to compress the seal against the bead. However, electrochemical cells employ electrochemically active materials such as zinc which generate hydrogen gas during storage, under abusive conditions and sometimes during or following service use. When the container can is sealed, the build-up of high pressure gases within the sealed container may cause damage to the cell and/or the device in which the cell is employed.
One approach to avoiding a potentially excessive build-up of pressure in the cell container has been to employ a resealable valve system that periodically releases excessive gas pressure from within the active cell volume. However, the periodic and continuous release of gas pressure may, in some situations, permit electrolyte leakage containing salt and other particulate which may foul the resealable valve, and generally requires additional costly components. Another approach to avoiding excessive build-up of pressure involves employing a sealed membrane that is intended to blowout when exposed to excessive pressure either by puncture or rupture of the membrane itself. Puncture mechanisms such as a spiked member may be employed to punch a hole in the thin membrane once the pressure reaches a predetermined amount. Alternately, a rupture mechanism may be employed in the form of a thin membrane which ruptures when the internal pressure of the cell becomes too great. One example of a thermoformed film membrane employed as a vent mechanism is disclosed in U.S. Pat. No. 4,581,304, entitled “THERMOFORMED FILM MEMBER VENT FOR GALVANIC CELLS,” the disclosure of which is incorporated herein by reference. The aforementioned patent discloses the use of a thermoformed film member retained across a vent aperture located in the inner cover of the electrochemical cell such that the thermoformed film member is intended to rupture at high pressure to provide a vent passage from the sealed internal volume to the surrounding atmosphere.
Other approaches to venting excessive cell pressure have included the use of a vent formed in the seal of the battery which is intended to rupture upon experiencing an excessive pressure build-up in the cell. For example, U.S. Pat. No. 5,080,985 discloses a groove formed in both the top and bottom surfaces of a plastic grommet seal such that the groove is designed to shear open at very high pressure. While the prior approaches for venting high pressure gas from the cell have resulted in the ability to vent excessive pressure, many of the prior approaches having not optimized the volume consumed by the seal member, while other approaches lack an accurate rupture pressure mechanism.
Accordingly, it is therefore an object of the present invention to provide for an electrochemical cell having a pressure release mechanism which occupies a minimum amount of cell volume. It is also an object of the present invention to provide for such a pressure release mechanism that effectively vents gas when exposed to an expected rupture pressure.
SUMMARY OF THE INVENTION
The present invention improves the protective safeguards of an electrochemical cell with an enhanced low profile seal assembly for sealing the open end of the electrochemical cell's container to provide controlled pressure venting. To achieve this and other advantages, and in accordance with the purpose of the invention as embodied and described herein, the present invention provides for a seal assembly for sealing the open end of an electrochemical cell container, an electrochemical cell having a low profile seal assembly, and a method of assembling an electrochemical cell having a low profile seal assembly. The seal assembly comprises a seal member disposed in the open end of the cell's container to provide a sealed closure to the open end of the container. The seal member has a stress concentrator including a groove formed in a surface of the seal member. In addition, the seal assembly has a support member disposed in the open end of the container and against the seal member. The support member has a surface area that covers substantially the open end of a cell container and has at least one opening formed therein. The groove formed in the seal member is located against the support member so that the groove is located adjacent to at least one opening in the support member and is located against the support member at other locations. The low profile seal assembly occupies a minimal amount of cell volume and serves as an accurate pressure relief mechanism.
These and other features, advantages and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims and appended drawings.
REFERENCES:
patent: 3218197 (1965-11-01), Carmichael et al.
patent: 4191806 (1980-03-01), Levy
patent: 4581304 (1986-04-01), Beatty et al.
patent: 5080985 (1992-01-01), Wiacek et al.
patent: 5173379 (1992-12-01), Ichinose et al.
patent: 5532081 (1996-07-01), DePalma et al.
patent: 5853912 (1998-12-01), Naing et al.
patent: 5925478 (1999-07-01), Tucholski
patent: 5932371 (1999-08-01), Tucholski
patent: 6022635 (2000-02-01), O'Hara, III et al.
patent: 6042967 (2000-03-01), Sargeant et al.
Eveready Battery Company Inc.
Fraser Stewart A.
Kalafut Stephen
Tsang Susy
LandOfFree
Low profile ventable seal for an electrochemical cell does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Low profile ventable seal for an electrochemical cell, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Low profile ventable seal for an electrochemical cell will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2482342