Safety vented cover for sealed container and method of manufacturing same

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מכסה מחורר ובטיחותי עבור מכולה חתומה ושיטה לייצורו

SAFETY VENTED COVER FOR SEALED CONTAINER AND METHOD OF

MANUFACTURING.SAME

EMERSON ELECTRIC CO.

C: . 04149

The present Invention relates to sealed container covers and, 1— of making safety vents in containers and a novel a safety vent membrane;

more particularly, to a method -.1 covers for hermetically sealed cover for such a container Includhg

It IS generally well known _{t0 hern1e״oal} ״־־talners with a rupturable safety vent membrane with! ^b°^{dy S}° ^{that 1£} 90s pressures develop

Ithln the container beyond a predetermined limit, the membrane ruptures to permit release of gas, avoiding “״.־.״״״ . ־.Λ, possible personal and property damages occasionally ssoclated therewith. Several such arrangements as taught by ־.״ prior art l־״l_{ude! a ptassure} «9״« device as disclosed In _U._S. _patent ״_o. _{3 7״}to Robert J. Bosben on November 2, 1971, a reduced area' o ^container wall thickness designed to rupture in circumferential stresses —t as disclosed in U.S.

on Nov. 20, a sealed container

U.S. patent Tamura, et al, oh Mar.17׳, relief safety membranes as disclosed 4 476 200, Issued to c. Markin, et al, formation of Such safety, vents, in the been accomplished by mechanical means Γ ^{M St}“^Pln9. ^{SUCh £}1™־η, means have caused a״d^em־ta^Cr°Tⁿ ׳“¹״”“־״⁰״ ^ln ־״tai thick־־־״ metal grain structure _wh1_ch, _ln .

״״״«״,f״־, pressure senslvlty and pressure r־־po״_s1_v1_ty . characterioHno ׳*«־vnsivicy sealed in the response to predetermined < ־ occuring within the container patent ₁₆₆ 175 4 .0״, _iEsusd1979,. a cruciform shaped incision in c _ of V-shaped cross-section as disclosed In No. 4 256 812, i_ssued to K. 1981; and, pressure in U.S. patent No. on oct. 9,1984. The past has generally such as stamping. ־

The present Invention recognizing _{the lmportance}such uniformity.in th!״ safety membranes in potentially ־xpioslv־ sealed containers and further e importance of carefully controlling the dimensions and pressure sensitive characteristics of such membranes so as to be uniformily responsive to predetermined pressures provides a-unique and novel method of manufac5 taring safety vent membranes in covers for hermetically sealed containers in an efficient, straightforward and economical manner to permit mass production of a novel and inventive product without sacrifice of desired critical pressure responsive uniformity.

Although the broad use of producing tearing lines in containers by etching is old, as disclosed in U.S. patent No. 3 723 269, issued to E. Hofling on March 27, 1973, the present invention, recognizing the desirability and importance of uniformity in pressure sensitivity, and responsivity of safety vent membranes for sealed containers, provides a new and novel method and a unique product which affords such pressure sensitivity and responsivity in a manner previously unknown in the art.

Various other features of the present invention will become obvious to one skilled in the art upon, reading the disclosure set forth herein.

More particularly’, the present invention provides a method of making a safety.vent in a cover for a herme/tically sealed container comprising: feeding a container 25' cover blank into a printing zone; printing the container . . cover blank while, in the printing zone, with a masking

- . resist pattern having.an uncovered channel, area to’;corres- pond to a safety vent area; feeding the masked יprinted . container cover blank to an etching: zone; subjecting . 30־ the container cover blank while in the etching zone to a controlled etching process to etch the uncovered channel area to a uniform preselected depth to leave a uniform preselected material thickness which serves as: a safety vent . membrane capable of withstanding a preselected pressure before rupturing; and, feeding the uniformly. etched cover through, a rinsing zone to . remove the resist and etching materials. In addition,

- .3 the present invention provides a cover for a hermetically sealed container, the cover having at least one channel etched therein to extend in spaced relation from the surrounding peripheral edge thereof, the channel being of a preselected uniform depth to provide a safety vent membrane of preselected uniform thickness capable of withstanding a preselected pressure before rupturing.

It is to be understood that various changes can be 10 made by one skilled in the art in the several steps of the method and in the several parts of the product disclosed herein without departing from the scope or spirit of the present invention. For example, the etching step,, the container cover material, the rupture limits and geometry 15 of the safety vent, all can be changed by one skilled in. the art to obtain desired results without departing from the inventive scope of the disclosure herein.

Referring to the drawings which disclose one advantageous embodiment of the present invention and 20 several modifications thereof:

Figure 1 is a flow diagram setting forth schematically the several steps involved in carrying out the inventive process;

Figure 2 is an enlarged plan view of a portion . 25 of a strip of material which has been subjected to. the inventive process of Figure 1; .

. Λ . Figure. 3 is a further, enlarged cross-sectional view . of the material of Figure'2 taken in .a plane passing through line 3-3 of Figure 2; ־ ’ .

Figure 4 is a perspective, view of an inventive .cover for a hermetically sealed container, further ׳ disclosing a central aperture therein; . ־ . Figure 5 is a plan view of. a sheet of material ' disclosing two possible positions in which a plurality 35 . of modified, safety vent members can be formed on a single sheet of material in accordance.with the present .invention;

. Figure 6 is an enlarged plan view of a portion of the sheet of material of Figure 5;

Figure 7 is a cross-sectional view taken in a plane through line 7-7 of Figure 6-, disclosing a safety vent membrane formed by treating the . sheet in mirror image fashion on opposed surfaces thereof;

Figure .8 is a perspective view of one face of a cover for a hermetically sealed container in accordance with Figures 5-7;

Figure 9.is an enlarged plan view of a further modified safety vent membrane, disclosing a piercing point on one face thereof;

Figure 10 is a cross-sectional view of the membrane of Figure 9 taken in a plane through line 10-10 of Figure 9;

Figure 11 is a perspective view of one face of a cover for a hermetically sealed container, in accordance with Figures 9 and 10; and

Figure 12 is a perspective view of the other face of a cover for a hermetically sealed container, in accordance with Figures 9 and 10.

. Referringto Figure 1 of the drawings, a strip. 2 of material is fed from .a supply.zone 3 where it can be stored in the form of a coil to a .printing zone 4. . The strip 2 of coiled material can'be any one of a .: number of known materials used in .the manufacture of^; covers for hermetically sealed׳ containers, which is responsive to the hereinafter described controlled etching processes and, in the manufacture of battery covers such .as.those utilized for hermetically sealed batteries of the button type, a suitable metallic alloy such as cold rolled alloyed carbon steel (for example C1010) having a thickness in the range of 0.20 to 35 1.52 mm (0.008 to 0.06 inches), and, advantageously , approximately 0.50 mm (0.020 inches) plus or minus

0.05 nun (0.0,02 inches) can be used. It is to be .

-.

understood that prior to carrying out the etching process, an appropriate cleaning and degreasing of the metallic alloy can be accomplished in a satisfactory cleansing and degreasing bath (not shown).

In the event a metallic steel alloy strip is used, as in the example hereinafter described, a suitable bath using a caustic cleansing agent would suffice.

In printing zone 4, opposed printing rolls 6 , frequently or continuously treated with a suitable masking resist agent or etching ground which can be ־ selected from appropriate chemical materials in accordance with the material to be etched and the subsequent chemicals to be used in the etching process, mask all surfaces of the strip of material not to be etched with an appropriate etching resist coating, for example, a synthetic resin capable of resisting the particular etching step to be employed.

The unmasked portion of the strip of material to which no resist coating.has been applied in printing zone 4 by rolls 6 can be in any one of several geometric pattern forms in accordance.with the present invention.

. . In the embodiment of Figures 2 and 3, the geometric . pattern includes spaced uncovered channel areas in.the 25 form.of circular.arcs 7 of less than 360 degrees, with a portion of each otherwise complete circle being . . masked, to. provide aretention portion; In .the embodiment ־- of Figures 4 -12, each of the circular arcs 7 surrounds . an uncovered hole defining central area 8 on at -least one .30 surface thereof and in the embodimentsof Figure 5-8, the arcs 7 are on opposite surfaces of material strips 2 ; in.opposed mirror image relationship. In Figures 9-12, the geometric pattern of unmasked mirror image circular arcs 7 on opposite surfaces of the strip of 35 material' 2, each,include an enlarged unmasked chord section 9 located at the base of the arc. It is to be noted that one surface of the strip of material 2 in the Fagures j _{8 ״ a},_sOn01udee. _{a trlangular reslst ma־k}area that extends Into chord section 9 of each channel 7 0־ that upon etching each channel 7 on one ־!de l״c_orp_orat־־ a sharp piercing point 11 therein. Piercing point 11 1־ geometrically disposed opposite to the masked covered retention portion of the otherwise circle defining circular arc 7 0־ as to facilitate tearing and retention port ⁶ r⁰״״^rtl0n יי״“ ^preSele0t*^d ^־״ - the etched portion of the cover is exceeded.

lit ^{Referring t0} figure 5, it can be seen that a pluraty of unmasked channels 7 can be positioned on strip 2 ך ^on°1 ־ a number of different geometric orientations, spending upon material grains and the results desired, in the embodiment of Figure 5, each of the horse-shoe shaped channel7 ־ in the right half of strip 2 .is ־how״ as oriented In a position which is at 90 degrees to the lorse-shoe shaped channels 7 In the left half of the ־trip 2 for purposes of Illustration. It Is to be understood that other positions can also be utilised and that, generally, all channels on a strip are oriented a similarly selected position, As also will be noted

n. gure 5, strip 2 can be In the form of individual sheets rather than a continuous coll as Figure 1.

In accordance with the inventive disclosed in process and. again referring to Figure 1, after strip 2 has been suitably masked .with a resist coating m the manner above scusse , strip 2 Is fed along Spaced idle rollers 10 through an etching sone 12, a rinsing sone 13, a lubrlcat114 ־״־־ 9״ and finally a stamping or forming sone 16 wiere Individual container covers 17, such as disclosed in Figures 4, 8, 11 and 12, are formed, it Is to be understood that strip 2, after passing through rinsing ־one 13, could be again coiled for subsequent treatment elsewhere. It, also, is to be noted that various types :.

7.

- ר - י of rims 20 can be formed on covers 17 or rims canbe eliminated, if so desired.

In passing through zones 12, 13 and 14 strip 2 is fed along suitable idle rollers 10, as above noted.

In etching zone 12, strip 2 can be fed through a suitable acid etching bath, such as ferric chloride if the material to be etched is a steel alloy. The density and temperature of the etching bath and even the number of 10 baths can be controlled to avoid gas bubbling. Also, such parameters as the rate of' feed or residence time of the strip within the bath or baths, the acidity concentrations of the bath and bath temperatures are all carefully controlled so that the etching depth and thus the 15 thickness of the material is carefully predetermined and maintained uniform along the unmasked surfaces. For example, when a steel alloy of 0.50 mm (0.020 inches) is used, the etching is controlled to provide a uniform membrane thickness in the range of 0.02 to 0.101 mm 20 (0.001 to 0.004 inches) plus or minus 0.005 mm (0.0002 ' inches) throughout the uncovered area. It is to be understood that advantageously, when battery covers for hermetically sealed containers are being processed, the ; depth'of etching is so controlled as to leave safety 25' membranes of metal thickness capable of withstanding .

a preselected pressure within the sealed containers of , which such covers־form a part .in the range of approximately 0.34 to approximately 3.10 MPa (approximately 50. to approximately 450 pounds per square inch) before the 30 safety membranes rupture.

. Once strip 2 has been.properly etched in etching zone 12, it is then fed through rinsing zone 13. In the inventive embodiment of Figure 1; rinsing zone 13 can include three stages, namely, a neutralizing stage •18, 35 a resist stripping stage 19 and a washing stage 21.

The neutralizing stage 18.can include a bath of suitable caustic or alkaline solution such as sodium hydroxide.

I be fed to a is fed into 17 from strip 2.

times and bath stages ’~ ־

-.

^{1 1e stri}PPing stage can include an « bath depending upon the chemistry of the“״ coatlng applied to printing _r0U* ‘”θ ”^{a־k resi}־t ^{5 and t״e wa}shlng stage 21 can be a plain ta! the last stage _{of rlnslng} ».th.

suitable oil lubricatin forming or stamping zone 16 to י׳ ־־. As in etching _zone !2, the concentrations in the

Stages 18 19 rinsing with th ²¹ θ³^{be control}led with the results desired.

changes _can be made^UnderSt°°^{d that} various and product disclosed wi thou t depart in״ ζ

Invention. _For example, £»£־» the hermetically sealed containers and other container material used In the Inventive process and tn ־־ ־־ ־־ a״a channel ,,ometrlcs^nL Χ to membranes which will iron will accommodate other pressures for containers.

zone 13, strip 2 can 1g zone 14 before it form covers residence zone 13, in accordance s those for can be so manufactured ’ besides steel alloys can be .:s ¹ provide safety predetermined