Metal working – Method of mechanical manufacture – Electrical device making
Patent
1999-02-05
2000-03-14
Valentine, Donald R.
Metal working
Method of mechanical manufacture
Electrical device making
296232, 29731, 29743, 427296, 118500, 204260, H01M 600, B23P 1900, B05D 300, B05C 1300, C25B 1100
Patent
active
060355182
DESCRIPTION:
BRIEF SUMMARY
The invention relates to cylindrical cells of the type that comprises a cylindrical cathode with a hollow interior, an anode arranged coaxially in the interior, and a separator winding that separates the anode from the cathode. More particularly, in a first aspect the invention relates to a method for preparing a cylindrical separator from sheet material and for inserting the separator in the cylindrical anode space of a semi-finished cell. In a second aspect the invention relates to a tool for preparing a cylindrical separator from a sheet material and for inserting the separator in the cylindrical anode space of a semi-finished cell. In a third aspect the invention relates to a cylindrical cell with a cylindrical separator between the anode and the cathode. The cell is preferably an alkaline primary or secondary cell.
In cylindrical cells, in which the electrodes are arranged coaxially around each other, the separator takes the form of a thin upright cylinder often closed at the bottom. The closure of the bottom end requires folding of the separator material which is connected with wrinkling of the materials, and special measures have to be taken to overcome such difficulties.
In Swiss patent No. 669.479 issued to Ruetschi a multi layer separator cylinder was used, which was inserted in the cell as a distinct product. The required insulation between the cell can and the anode space was provided by the application of a sealant. In one of the embodiments the separator took the form of an upright cylinder open at both ends, and the open bottom portion was closed by a polymer washer and a sealant material.
In the Hungarian patent application 4046/91 published under publication number T/67990 the separator was again an upright cylinder open at both ends, and the required insulation at the cell bottom was solved by the specific application of a sealant.
The Hungarian patent application 4044/91 published under publication number T/67993 describes a separator structure which is a thin cylinder open at both ends wound from a fibrous layer and a non-fibrous microporous layer, in which the microporous layer overlaps the first layer to close the passage of dendrite growth at the edge region of the wrap.
In these prior publications the distinct separator cylinder must be inserted in the hollow interior of the cathode. The insertion of a vulnerable thin structure of minimum rigidity is a difficult step to perform, the separator cylinder must be guided and perfectly aligned with the central axis of the cell during the insertion step. The easy insertion requires that the diameter of the separator cylinder be smaller than the diameter of the central opening of the cathode, and the required gap provides a loss of volume in the cell. One of the most significant problems connected with the incorrect insertion of the separator cylinder is the hazard of contamination of the interior of the separator with the cathode material. Such contamination can be critical in mercury free alkaline cells regarding the increased danger of gas evolution.
The primary object of the invention is to provide a cylindrical separator that can be easily made and inserted in the cell, which can fully utilize available space and get pressed to the interior of the cathode.
A further object of the invention is to provide a tool which is capable of carrying out the method.
A still further object is to provide a cell, in which the separator fits more snugly in the available space.
According to the invention it has be recognized that the separator can be wound from a sheet material around a mandrel to have a diameter smaller than the diameter of the cathode so that the sheet is temporarily affixed to the outer surface of the mandrel by providing vacuum through the mandrel wall, and the so obtained winding can be inserted axially in the cathode cylinder. When the insertion is ready, the vacuum can be disrupted, and the wound structure will expand and fill the available space.
In a preferable embodiment a rotating cylindrical spindle can be used to feed the
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Battery Technologies Inc.
Chari Santosh K.
Valentine Donald R.
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