Method of manufacturing a safety vented container and product

• US 4,803,136 A
• Filed: 04/23/1987
• Issued: 02/07/1989
• Est. Priority Date: 09/30/1985
• Status: Expired due to Term

• Current Assignee: Emerson Electric Company
• Original Assignee: Emerson Electric Company
• Inventors: Bowsky, Benjamin, Burrows, Larry G., Wilson, Edward E., Honkomp, Glenn A.
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): Anderson, Andrew J.
• Application Number:
  US07/041,478
• Time in Patent Office: 656 Days
• Field of Search: 156/638, 156/639, 156/645, 156/659.1, 156/660, 156/664, 429/56, 429/175, 429/176, 220/207, 220/89 A
• US Class Current: 429/56
• CPC Class Codes: B65D 83/70 Pressure relief devices
• CPC Class Codes: C23F 1/02 Local etching
• CPC Class Codes: F16K 17/162 of the non reverse-buckling-type F16K17/1633 takes precedence
• CPC Class Codes: H01G 9/12 Vents or other means allowing expansion
• CPC Class Codes: H01M 50/3425 in the form of rupturable membranes or weakened parts, e.g. pierced with the aid of a sharp member
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A method of making a safety vent in an hermetically sealed electro-chemical container device and a novel container portion including such safety vent comprising a unique series of steps including printing a preselected area of the container portion with a masking resist pattern having an uncovered planar area of preselected geometric configuration corresponding to a safety vent area for the container portion and etching the uncovered area to a preselected uniform material thickness to provide a safety vent in the container portion capable of withstanding a preselected pressure before profound and instantaneous rupture.

Claims

1. A method of making a safety vent in a portion of an hermetically sealed container for an electrochemical device, the safety vent being capable of withstanding a preselected pressure before profoundly rupturing with the metal adjacent the rupture remaining attached to an initial portion of said container portion for effective pressure relief, comprising:

feeding said container portion having initial stress and grain characteristics into a printing zone;

printing said container portion while in said printing zone with a masking resist pattern having an uncovered preselected planar strip-like area having preselected length and breadth to correspond to a safety vent area;

feeding said masked printed container portion to an etching zone;

subjecting said container portion while in said etching zone to a controlled etching process using preselected etching materials to etch said uncovered preselected planar area to a uniform preselected depth to leave a uniform preselected remaining material thickness throughout the etched planar area having said preselected length and breadth to be in the form of a flat membrane having stress and grain characteristics substantially like said initial stress and grain characteristics, said remaining materials of said etched planar area formed as said flat membrane being of uniform thickness and preselected surface area to have a controlled and uniform pressure sensitivity of substantially unchanged residual stress to serve as a safety vent and, feeding said uniformly etched container portion through a rinsing zone to remove said etching materials.

2. The method of claim 1, said rinsing zone including a neutralizing stage, a resist stripping stage and a washing stage.

3. The method of claim 1, said printing of said container portion including masking resist patterns with uncovered channel areas in opposed mirror image relation on both faces of said container portion.

4. The method of claim 1, said printing of said container portion including a masking resist pattern having a covered area to provide a piercing point therein.

5. The method of claim 1, said container portion being one of a plurality of covers printed and etched on a continuously moving etchable strip of material fed through said printing zone, etching zone and rinsing zone from a coiled stage in a supply zone.

6. The method of claim 1, said container portion comprising a steel alloy with a rating of at least one quarter hardness in the range of 0.008 to 0.06 inches thickness with the etching of said uncovered strip-like area having said preselected length and breadth to be in the form of a flat membrane being controlled to provide a uniform remaining metal thickness in the range of 0.001 to 0.006 inches with a width of 0.040 to 0.300 inches.

7. The method of claim 1, said container portion comprising a steel alloy of preselected thickness with the etching of said uncovered planar area having said preselected length and breadth to be in the form of a flat membrane being controlled to a width-to-depth of remaining material thickness ratio of at least six (6) to leave a metal thickness capable of withstanding a preselected pressure in the range of approximately 50 to approximately 900 pounds per square inch before profound rupture due to controlled uniform pressure sensitivity within approximately 200 to 400 micro-seconds.

8. The method of claim 1, and feeding said etched container portion from said rinsing zone to a stamping zone to form said etched container portion having said flat membrane into a preselected shape.

9. The method of claim 1, including feeding said etched container portion into a second forming zone to pressure form an indentation area within said planar safety vent area forming said flat membrane, said indentation area being of uniform preselected remaining material thickness capable of withstanding a second preselected mean pressure below the means pressure limitation of said etched planar safety vent area forming said flat membrane.

10. The method of claim 9, wherein said indentation area is press formed into said planar safety vent area forming said flat membrane by a coining step.

11. the method of claim 9, wherein said planar safety vent area forming said flat membrane and said indentation area therein are formed in said container portion to be on the outer side of said container.

12. The method of claim 9, the forming of said planar safety vent area forming said flat membrane including providing mirror image safety vent areas on both faces of said container portion to form said flat membrane.

13. The method of claim 9, wherein said planar safety vent area forming said flat membrane and said indentation area therein are formed in said container portion to be on the inner side of said container.

14. The method of claim 9, said container portion comprising a steel alloy in the range of approximately 0.008 to 0.06 inches thickness with the formation of said planar safety vent area forming said flat membrane being controlled to provide a uniform remaining material thickness in the range of approximately 0.0025 to 0.0035 inches and the formation of said indentation area being controlled to provide a uniform remaining material thickness in said planar safety vent area forming said flat membrane in the range of approximately 0.0005 to 0.002 inches.

15. A method of making safety vents in metallic covers for hermetically sealed battery containers for electro-chemical devices, the safety vents in each cover being capable of withstanding a preselected pressure before profoundly rupturing with the metal adjacent the rupture remaining attached to the cover for effective pressure relief, comprising:

feeding a metallic sheet of steel alloy material having initial stress and grain characteristics and preselected thickness from a supply zone through a printing zone;

printing said sheet while in said printing zone on the opposite surfaces thereof with a chemical masking resist pattern to provide a masked printed strip which includes spaced uncovered planar areas in the form of horseshoe-shaped circular arcs having preselected length and breadth, each to extend parallel the periphery of a cover for approximately 270°

;

feeding said masked printed strip to an etching zone;

subjecting said strip while in said etching zone to a chemical etching process of constant specific gravity and vigorous flow to etch said uncovered planar areas to uniform preselected depths leaving said areas with a uniform remaining metal thickness and preselected surface area throughout the etched area having said preselected length and breadth to be in the form of flat membranes having stress and grain characteristics similar to the initial stress and grain characteristics which serve as safety vents formed as said flat membranes to have a controlled and uniform pressure sensitivity of substantially unchanged residual stress, each flat membrane being capable of withstanding a preselected pressure in the range of approximately 50 to approximately 900 pounds per square inch before profound rupture for effective pressure relief, feeding said etched strip through a rinsing zone which includes a chemical neutralizing stage, a resist stripping stage and a washing stage; and

then feeding said rinsed strip to a stamping zone to stamp said etched strip into a plurality of battery covers and to stamp indentations into said etched planar areas forming said flat membranes, each cover including a planar, arc-like flat membrane safety relief vent.

16. The method of claim 15, said chemical masking resist patterns on at least one surface of said strip including spaced uncovered planar areas formed as flat membranes to each include a piercing point therein geometrically opposed to the masked covered portion of said circular arc to facilitate tearing when preselected pressure is exceeded.

17. The method of claim 15, said metallic sheet of steel alloy material comprising a steel alloyin the range of approximately 0.008 to 0.06 inches thickness with the formation of said etched flat membrane areas being controlled to provide a uniform remaining material thickness in the range of approximately 0.0025 to 0.0035 inches and the stamping of said indentations in said etched planar areas forming said flat membranes being in the form of V-shaped grooves of approximately 90°

controlled to provide a uniform remaining material thickness in said indented areas of said flat membranes in the range of approximately 0.0005 to 0.002 inches.

18. A container portion for a hermetically sealed container for an electro-chemical device, having at least one planar area chemically etched therein to provide a safety vent of preselected uniform thickness with stress and grain characteristics substantially like the stress and grain characteristics of the remaining material of said container portion in the form of a flat membrane to have a controlled and uniform pressure sensitivity of substantially unchanged residual stress capable of uniformly responding to and withstanding a preselected pressure before profoundly rupturing under preselected pressure with the metal adjacent the ruptured flat membrane safety vent remaining attached to said container portion.

19. The container portion of claim 18, said container portion including opposed mirror image channels etched therein on opposite surfaces of said cover to provide said flat membrane safety vent of uniform thickness.

20. The container portion of claim 18, said container portion being a steel alloy in the range of 0.008 to 0.06 inches thickness with a safety vent uniform thickness in the range of 0.001 to 0.006 inches.

21. The container portion of claim 18, said etching depth being sufficient to provide a safety vent of uniform thickness capable of withstanding a preselected pressure in the range of approximately 50 to approximately 900 pounds per square inch before rupturing.

22. The container portion of claim 18, said container portion being in the form of a container cover with said etched area forming said flat membrane extending in spaced relation from the peripheral edge of said cover less than the entirety of said surrounding edge to leave a retention portion of full cover thickness capable of retaining the remaining material portion of said flat membrane adjacent said etched area when the preselected pressure is exceeded.

23. The container portion of claim 18, said etched planar area forming said flat membrane having a triangular unetched remaining initial material portion extending into said etched planar flat membrane area opposed thereto to provide a piercing point when the preselected pressure is exceeded.

24. The container portion of claim 18, said planar area forming said flat membrane having a width-to-depth of remaining material thickness ratio of at least six (6).

25. The contain portion of claim 18, said planar area forming said flat membrane being chemically etched in said container portion in mirror image relation on both surfaces thereof.

26. The container portion of claim 18, and an indentation formed in said etched planar area forming said flat membrane, said indentation having a preselected remaining material thickness to provide a safety vent capable of uniformly responding to and withstanding a preselected mean pressure lower than the preselected mean pressure of said planar area before rupturing.

27. The container portion of claim 26, said indentation within said planar area forming said flat membrane being press formed therein.

28. The container portion of claim 26, said planar area forming said flat membrane including said indentation having a width-to-depth of remaining material thickness ratio of at least six (6).

29. The container portion of claim 26, said container portion being a steel alloy in the range of approximately 0.008 to 0.06 inches thickness with said etched planar safety vent having a uniform remaining material thickness in the range of approximately 0.0025 to 0.0035 inches and said indentation having a uniform remaining material thickness in the range of approximately 0.0005 to 0.002 inches, capable of rupturing instantaneously within approximately 200 to 400 micro-seconds.

30. A circular steel alloy battery cover for a hermetically sealed container for a lithium electrochemical battery device, said cover having a thickness in the range of 0.008 to 0.06 inches and having opposed chemically etched planar areas therein in the form of horseshoe-shaped arcs of 270°

extending parallel to and spaced from the peripheral edge of said cover to provide a safety vent of uniform preselected thickness in the range of 0.001 to 0.006 inches with stress and grain characteristics similar to the stress and grain characteristics of the remaining material in the form of a flat membrane having preselected length and breadth to have a controlled and uniform pressure sensitivity of substantially unchanged residual stress capable of uniformly responding to and withstanding a preselected pressure in the range of approximately 50 to 900 pounds per square inch before profound rupture under preselected pressure with the metal adjacent the safety vent remaining attached to said cover, said arcs surrounding an aperture therein sized to receive an assembly part to be fused therein; and

,

coin punched indentations of V-shape of approximately 90°

in said etched horseshoe-shaped planar arcs forming said flat membrane of said cover of the container to provide a second safety vent within said first safety vent forming said flat membrane having a uniform remaining material thickness of approximately 0.0005 to 0.002 inches capable of uniformly responding to and withstanding a preselect means pressure in a range approximately up to 850 pounds per square inch before rupture