US 3850339 A
A two or three piece metal container is adapted to hold a pressurized product for dispensing through a valve mounted on the container. The container has a safety venting system therein, whereby the product may be vented from a filled pressurized container through the system when an increase in internal pressure threatens to blow the top or bottom off the container. The venting system comprises a plurality of triple scores formed in the seam where the container body is joined to the top closure of the container. When the internal pressure of a filled container increases sufficiently, the periphery of the top closure buckles outwardly causing the residual of the main score in the triple score to fracture and thus produce a plurality of vents to permit the highly pressurized contents of the sealed container to safely escape and prevent end blow-off.
Description (OCR text may contain errors)
United States Patent [191 Kinkel [451 Nov. 26, 1974 TRIPLE SCORE PRESSURE RELIEF SYSTEM FOR AN AEROSOL CONTAINER Primary E.raminer.l0hn Petrakes Attorney, Agent, or FirmRobert P. Auber; George P,
 Inventor: Christian Frederick Kinkel, Ziehmer Prospect Heights, Ill.
 Assignee: American Can Company,
Greenwich, Conn.  ABSTRACT  Filed: May 7, 1973 A two or three piece metal container is adapted to hold a pressurized product for dispensing through a pp N05 357,606 valve mounted on the container. The container has a safety venting system therein, whereby the product 52 us. CI. 220/89 A, 220/44 R 222/397 may he vented hem e filled Pressurized Container 51 lm. Cl 865d 83/14, 1305b 7/32 through the System Wheh eh htereeee ht ihtethel P 58 Field of Search 220/44 R, 89 A 67" Sure threatens to blew the top or bottom Off the 222/397 tainer. The venting system comprises a plurality of triple scores formed in the seam where the container  References Cited body is joined to the top closure of the container.
When the internal pressure of a filled container in- UNITED STATES PATENTS creases sufficiently, the periphery of the top closure 53369190 12/1943 LO Y iZO/gg A buckles outwardly causing the residual of the main score in the triple score to fracture and thus produce H1965 gfig g 222/397 a plurality of vents to permit the highly pressurized g 12/1966 y contents of the sealed container to safely escape and 3:450:3Q5 19 9 prevent end blOW-Off.
3.680.743 8/1972 Reinnagel 222/397 3,786,967 1/1973 Giocomo et al. 222/397 2] 11 Clam, 9 Drawlhg Flgures l I l l L a a -1 TRIPLE SCORE PRESSURE RELIEF SYSTEM FOR AN AEROSOL CONTAINER BACKGROUND OF THE INVENTION The present invention relates generally to a metal aerosol container having a pressure relief system whereby the internal contents of the container may be vented therefrom when the internal pressure rises sufficiently to a level threatening blowing the top or bottom end off the container. More particularly this invention relates to a two or three piece metal aerosol container having a simple venting system to eliminate explosion of a filled aerosol container when the internal pressure rises considerably, which may be encountered during excessive heating of the container.
For many years pressurized aerosol containers have been marketed to the general public. These containers usually comprise a three piece metal container having therein a product to be dispensed, together with a propellant that provides the internal pressure necessary to dispense the product through a valve mounted on the container. Products such as foods, cosmetics, insecticides, etc. have been packaged in these types of containers with considerable success.
However, due to the fact that the container is pressurized, problems have been encountered when the internal pressure of the container rises rapidly above that pressure to which the container construction has the capacity to hold. In some instances this rapid increase in internal pressure, resulting from rapid heating, has
caused the container to explode. This has sometimes occurred in warehouse fires where large quantities of these aerosol containers are stored. In some cases, firemen have been injured during such explosions and in some instances firemen are unable to control the flames since they cannot approach them. Over the years many attempts have been made to design containers having pressure relief systems in order to eliminate the possible explosive danger from pressurized aerosol containers. Many of these constructions include specialized valves which rupture upon heating or when exposed to extremely high internal container pressures. However, in general, such constructions have greatly increased the cost of these containers to such a degree that they are not economically practical.
Other safety features have included weak areas in the container body such that under excessive internal pressure the weakened portion would rupture and permit venting of the container contents. One such construction is shown in US. Pat. No. 3,074,602. In this patent a pressure sensitive area is formed in the valve cup such that when the dome of the container everts or buckles due to high internal pressure, venting will occur through a rupture produced in the pressure sensitive area. However positioned, this weakened portion would not necessarily rupture when the dome of the container buckles and venting through the single area of failure would not necessarily be rapid enough to prevent explosion of the container.
In US. Pat. No. 2,795,350 (Lapin), a nick is formed in the periphery of the body closure of the container where it forms a double seam with thecontainer body. In this two piece aerosol container extremely high pressure supposedly causes the concave bottom wall to buckle and rupture the nick to form a vent through the bottom of the container. However. in the usual case the bottom would not buckle uniformly and-should the buckling begin to occur opposite the nick, no relief vent would be formed until the full bottom of the container would blow off. Moreover, a single nick would not provide an adequate venting rate.
The prior art more recently has witnessed an improvement over Lapin wherein a multiplicity of single scores are employed in the upper double seam where the tubular container body is joined to the domed top closure. This latest safety feature protects against can failures in the packing and marketing of aerosol cans. If excessive internal pressure develops in a filled can due to an unusual situation, the safety feature activates rapidly and provides adequate venting to completely vent the container contents before the container fails explosively.
Full cans will vent if excessive pressure develops in the can due to misuse. This might involve placing the can on a hot stove or radiator, near a hot iron, or in the glove box, trunk, or window of a car sitting out in the sun.
Generally, partially filled cans will also vent under the conditions mentioned above; however, near-empty cans may fail at the side seam in typical three piece metal cans before the pressure required to activate the safety feature is generated under prolonged exposure to intense heat.
Aerosol cans which are considered empty or nearly empty usually contains a small amount of residual product and propellant. These small amounts are sometimes not sufficient to generate the pressure needed to activate the safety feature when the can is incinerated. Under the intenseheat of incineration, some of these cans will vent or rupture at the side seam of a three piece can. This is due to the fact that the side seam is adhered with a solder or relatively low temperature material. This side seam rupture will occur at pressures below the pressure required to buckle the top closure and thus form the safety venting feature. This failure, although dangerous, is less violent than blow-off of the top or bottom end.
Certain products in cans which are thrown away as empty or nearly empty will generate sufficient pressure to activate the safety feature when incinerated. This is entirely dependent upon the amount and type of product and propellant remaining in the can. Full or partially full cans will also vent safely if they are incinerated.
As is well-known, there is some controversy in the usage of aerosol containers due to the fact that they are under high internal pressures and subject to abusive use. To date, the various concepts for pressure relieving an aerosol container have proved uneconomical. Any relief concept must function under both normal use conditions and under uncontrollable use conditions which violate general precautionary labeling. Such abusive conditions include storage in direct sunlight, storage in enclosed automobiles during summer months and warehouse fires.
Also, the relief concept must allow function of the container under controllable use conditions in violation of precautionary labeling so long as the temperature does not exceed 250 F for approximately one hour. At temperatures below 250 F, the time of exposure can be significantly increased.
The greatest danger, when three-piece aerosol containers are subject to temperature abuse, is that the bottom of the container may evert or buckle under extreme internal pressure and blow off. Due to the fact that the bottom is constructed to withstand extreme internal pressures, when these pressures are reached, the bottom end may buckle and separate from the remainder of the container, possibly resulting in propelling parts of the container about the immediate area.
A secondary type of failure encountered when internal pressure increases over the maximum allowable by the three-piece container construction is a side seam rupture, described above, which generally results from exposure to high temperatures. The side seam failure is dependent upon exposure temperature, the position of the container with respect to the heat source, the type of product and propellant packed in the container, the quantity of product and propellant remaining in the container, and the container size. For a container of average size, such as those of 3 inches in diameter and approximately 7 9/16 inches in height, it has been found that the relief mechanism must be capable of releasing l4 cubic feet per minute of internal gas at 200 psig. Less release capacity is required for smaller containers as vent capacity is strictly dependent upon volumetric capacity.
Although a plurality of single scores, as described above, function well as a venting mechanism, their consistency of performance is not deemed high enough for commercial standards. High score residuals are required to prevent premature fracturing, especially during manufacture (subsequent forming and double seaming operations), while low score residuals are required for adequate venting. However, if the score residual is too low, the score is likely to fracture prematurely, and if the score residual is too high, the score is likely to either not open at all, or open insufficiently to provide an adequate venting rate to prevent explosive failure of the container. The difference between the maximum possible score residual and the minimum possible score residual is called the working range. As large a working range as possible is preferred to allow for numerous variations in manufacture.
Using the multiplicity of single scores, it was found that inconsistent and poor venting of the aerosol containers was due to variations in the lots of material to be used for end closures, as well as other factors. It was learned that the working ranges for various materials varied, and that the working range for single scores in any given material was very narrow. When a variety of materials were to be processed on one line of production, the effective working range for manufacturing purposes was further reduced because the effective minimum possible score residual that could be used on the production line would correspond to the highest of the various minimum score residuals of the various materials and the effective maximum possible score residual that could be used would correspond to the lowest of the various maximum score residuals of the various materials. Since a manufacturing line handles various materials, it is constrained according to the effective working range, which for single scores turns out to be very narrow, thus leaving little room for variation or error in manufacture. It is this narrow working range that causes the plurality of single scores to bend less consistently than is required commercially.
Accordingly, it was determined that a means of expanding the working range of score residuals was necessary to provide scores that would not fracture prematurely and yet would provide adequate venting consistently. It was unexpectedly discovered that the use of anti-fracture scores oneither side of the main single score expanded the working range by lowering the minimum possible score residual and raising the maximum possible score residual, thereby preventing premature fracture to a greater extent, improving venting and permitting the use of a wide range of plate tempers.
SUMMARY OF THE INVENTION Accordingly, the instant invention provides an improvement for safely venting excessive internal pressure in a pressurized aerosol dispenser container having a tubular body closed at one end and a metal end wall closing the other end, the end wall being secured to the tubular body by an annular convoluted seam, comprising: a plurality of venting scores, and an anti-fracture score flanking each side of each of said venting scores, said venting and anti-fracture scores penetrating partially through the metal of the end wall and extending from at least a portion of the most interior layer of the seam to the top portion of the seam, whereby when the internal pressure within the container increases and threatens to cause rupture of said container, the end wall will buckle outwardly causing the residual of said venting scores to fracture to thereby produce a plurality of vents to permit the pressurized contents to escape safely therethrough.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view of a three-piece metal container utilized to dispense pressurized products.
FIG. 2 is a top plan view of the container of FIG. 1.
FIG. 3 is an enlarged, partial, sectional view showing the periphery of the dome and the container body prior to their being seamed together in forming of the container.
FIG. 4 is an enlarged, sectional view taken substantially along the line 4-4 in FIG. 3.
FIG. 5 is an enlarged, fragmentary, sectional view of the double seam formed by the periphery of the dome and the top of the container body.
FIG. 6 is an enlarged, fragmentary, side elevational view of the seam shown in FIG. 5 more fully illustrating the triple score.
FIG. 7 is an enlarged, partial, section view similar to FIG. 5 but illustrating the vent score on the interior of the periphery of the dome.
FIG. 8 is an enlarged, fragmentary, sectional view illustrating the periphery of the dome after high internal pressure has buckled the head and fractured the vent score to form a safety pressure relief vent.
FIG. 9 is an enlarged, fragmentary, side elevational view illustrating the ruptured score after buckling of the dome.
DESCRIPTION OF THE PREFERRED EMBODIMENT As a preferred or exemplary embodiment of the instant invention FIGS. 1 and 2.show a container, generally designated 12, comprising a tubular metal body 14 having a side seam 15. The side seam 15 is generally sealed with solder, as is well known in the art, although it may also be welded. Closing the bottom of the container is an end 16 hermetically seamed to the bottom of the body 14 by a seam 18.
As the container 12 will ultimately be utilized as an aerosol container, a dome 20 is seamed to the top of the body 12 by an annular, convoluted, double seam (five layers of interfolded material) 22. The upper end of the dome 20 has an orifice 23 defined by a top curl 24. After filling with product and a suitable propellant, a valve cup, not shown, is placed into the orifice 23 and a suitable dispensing valve, also not shown, is positioned within the valve cup to seal the container 12 and to permit dispensing of the product and propellant from the container 12.
A plurality of radial venting scores 26 are formed, preferably with a scoring punch when the dome 20 is flat, in the periphery of the dome 20 in the area that is to be the top of the double seam 22. As may be seen better in FIGS. 3-6, the scores 26 are narrow grooves formed in the periphery of the dome 20 and penetrate only partially through the metal of the dome 20. For example, a score 26 has a depth of approximately 0.009 inch for a total metal thickness of 0.014 inch, leaving a solid-metal residual 30 of 0.005 inch. The developed length of the score is approximately 0.125 inch. As shown in FIG. 4 the included angle of the venting score 26 is approximately 60 and it is desirable that this angle not be below 40. As will be noted the bottom 28 of the venting score 26 is essentially flat in cross sectional appearance. This provides greater integrity and prevents premature cracking through the residual 30 of the material which would result in leakage of product and propellant from the container 12.
As illustrated in FIGS. 2, 4, 6 and 9, each of the venting scores 26 is flanked by a pair of shallower antifracture scores 27 having a depth of approximately 0.005 inch for the total metal thickness of 0.014 inch, leaving a solid metal residual 31 of 0.009 inch. The most effective differential in score depths irrespective of the score depths is on the order of about 3 mils. The developed length of the antifracture scores 27 is about the same as the developed length of the venting score 26, approximately 0.125 inch. As shown in FIG. 4, the included angle of the anti-fracture scores 27 is approximately 70 and it is desirable that this angle not be less than 40. As can be seen in FIG. 4, the bottom 33 of the anti-fracture scores 27 is essentially flat. The center-tocenter spacing between the vent score 26 and each of the anti-fracture scores is approximately 60 mils, with a preferred range being between 50 and 70 mils.
As can be seen in FIG. 3, the dome 20, prior to double seaming, has a corrugation 34 adjacent the seam area connecting the top of the body 14 with the dome 20. The location of the venting score 26 is critical to the consistency of venting. The venting score 26 must extend from at least a portion of the most interior layer which fits within a curl 38 which forms the peripheral edge of the dome 20. In forming the annular, convoluted double seam 22, the flange 36 is interfolded with the curl 38 to hermetically seal and close the container 12 as the double seam 22 is formed. In addition, a small amount of sealing compound 40 is positioned along the interior wall of the curl 38 to provide a hermetic seal in forming the double seam 22. A similar type of double seam may be used to form the seam 18 at the bottom of the container 12.
The fully formed double seam 22, shown in FIG. 5, thus hermetically seals the dome to the body 14. Spaced about the top of the double seam 22 are a plurality of venting scores 26 flanked by a pair of antifracture scores 27, all of which extend radially within the top of the double seam 22.
32 of the seam 22 to the top portion of the seam 22. It
In a modified construction, shown in FIG. 7, a plurality of radial venting scores 42 and anti-fracture scores (not shown) are formed on the interior of the periphery of the dome 20. Thus, when the double seam 22 is formed by the flange 36 and curl 38, the scores are hidden by being entirely within the double seam 22. In certain instances this has aesthetic advantages in that the multiplicity of scores are not seen by the user as are the exterior scores. However, either type of scoring will function in the manner described hereinafter to provide a pressure relief system for a filled container 12.
It can be seen in FIGS. 8 and 9 that when the internal container pressure increases sufficiently the dome 20 buckles and the corrugation 34 also deforms as the double seam 22 partially unfolds, raising the radial venting score 26 (and anti-fracture score 27) away from the seam and rupturing it to form a vent 44. This vent 44 permits pressurized product and propellant from within the container 12 to escape and safely vent the container. The anti-fracture scores 27 do not open to form any vents.
As may be seen from the drawings, a plurality of radial venting scores 26 have been formed in the double seam 22. This is to insure that no matter where the dome 20 begins buckling due to increased internal pressure, a vent 44 will be formed almost immediately and as the buckling continues about the periphery of the dome 20 additional vents 44 will form about the periphery of the dome 20 as additional radial venting scores 26 are deformed and fractured.
It has been found that at 200 psig inside a 300 X 709 (3 inch diam, 7 9/16 inch height) can, 12 radial venting scores will vent from 14 to 21.5 cubic feet per minute of gas. Eight radial venting scores per end will vent from 1 1.5 to 14 cubic feet per minute of gas, and six radial venting scores per end will vent from 10 to 12.5 cubic feet per minute of gas. In these tests air temperature was about 78 F. Thus, it can be seen for a container of such size a minimum of eight venting scores will permit reasonably safe evacuation of the internal gases within an overpressurized filled container, al-
though at least 12 score vents are preferred for greater reliability.
It must be noted that these tests were all conducted with filled containers containing sufficient amounts of GRAPH 1 STEEL TYPE w to melt the conventional solder side seam so that failure could occur at the side seam rather than by buckling the dome 20 to form the vents 44. But failure of the side seam is far less serious than explosive failure at the bottom or top where blow off could cause serious damage if container parts are propelled about the area.
Experiments were conducted to evaluate the contribution of the anti-fracture scores. A multiplicity of single venting scores were compared with a multiplicity of triple scores (venting score plus two anti-fracture scores) on two different diameter cans, 202 (2 2/16 "ENTING RATE (CFM) inch) and 207.5 (2 /32 inch) using two different steel plates for the end wall that isdesigned to buckle under excessive pressure. One steel, designated W, had not been successful with single scores because of poor venting rates. The other steel, designated G, had a problem with the scores leaking. For successful commercial runs, it is necessary to use both types of steel plate, which represent different tempers, T3 and T4. It became apparent that different score residuals were required for different steels if only single scores were employed. It is strongly desirable that a single score resid ual be used for different steels so that scoring equipment does not have to be changed every time a different steel is run.
Accordingly, the experimental objective was to de- SCORE RESIDUAL (MILS) fine, with the use of graphs, the maximum possible score residual at which score fracture would occur after seaming the end to the can body to give commercially consistent venting, and the minimum possible TRIPLE SCORE MIN. RESIDUAL score residual which would not fracture prematurely, for both single and triple scores for the two different steel plates.
SINGLE SCORE MIN. RESIDUAL- VENTING RATE (CFM) ture of the various types of metals.
The two graphs below of vent rate versus score residual for a given venting score illustrate a set of vent rate curves for 202 diameter ends. The table following sum- 3 RE$IDUAP marizes pertinent data for 202 and 207.5 diameter TABLE 207.5 DIAMETER Steel Type W Steel Type G Maximum Score Residual for 0.l25 CFM Vent Rate Single Score .0045" .0053" Triple Score .0054 .0055" Minimum Score Residual Single Score .0033" .0042" Triple Score .0027" .0032" Working-Range Single Score .00l2" .0011" Triple Score .0027" .0023" Steel Type G T 202 DIAMETER Single Score 036" Triple Score 0046" Minimum Score Residual Single Score Triple Score less than .0034" Working Range Single Score .0001" Triple Score greater than .0012" Maximum Score Residual for 0.125 CFM Vent Rate .0040 less than .0036" .0005" greater than .0016" The graphs and table show that the score residual which will permit a venting score to open sufficiently to give a vent rate of 0.125 c.f.m., a commercially feasible venting rate, is always higher for triple scores than for single scores. It appears that the anti-fracture scores permit the venting scores to open to a greater extent. In other words, using triple scores enables the use of higher score residuals.
Furthermore, it can be seen that lower score residuals can be used with triple scores without premature fracture. This would seem due to certain strain reliefs provided by the anti-fracture scores. The net result is that with triple scores the working range is significantly increased, the table indicating increases from 100 to greater than 1000 per cent.
It can be seen from the above data that the antifracture scores make a substantial contribution to the success of manufacturing an end having venting scores in at least the following five areas:
1. Enables the use of higher residuals, significantly increasing the safety factor with respect to premature fracturing. 2. Permits a wider working range. 3. Is less sensitive to normal plate property variations, and permits the use of plate which could not be used with single scores.
4. Allows the commercial production of scored ends within normal manufacturing tolerances (i.e. plate and residual variations) which would be very difficult to produce with single scores only.
5. Permits ends made from different materials to be scored with the same tooling setup on one production line.
It is thought that the invention and many of its attendant advantages will be understood from the foregoing description and it will be apparent that various changes may be madein the form, construction and arrangement of the parts without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the form hereinbefore described being merely a preferred embodiment thereof.
What is claimed is:
1. In a pressurized aerosol dispenser container having a tubular body closed at one end and a metal end wall closing the other end, the end wall being secured to the tubular body by an annular convoluted seam, the improvement for safely venting excessive internal pressure, comprising: a plurality of venting scores, and an anti-fracture score flanking each side of each of said venting scores, said venting and anti-fracture scores penetrating partially through the metal of the end wall and extending from at least a portion of the most interior layer of the seam to the top portion of the seam, whereby when the internal pressure within the container increases and threatens to cause rupture of said container, the end wall will buckle outwardly causing the residual of said venting scores to fracture to thereby produce a plurality of vents to permit the pressurized contents to escape safely therethrough.
2. The improvement of claim 1 wherein the tubular body is metal and the anti-fracture scores are shallower than the venting score.
3. The improvement of claim 2 wherein the closed end is formed by a separate end double seamed to the tubular body.
4. The improvement of claim 3 wherein the scores extend radially across the end wall.
5. The improvement of claim 4 wherein the closed end is concave.
6. The improvement of claim 5 wherein the scores are located on the interior of the metal end wall.
7. The improvement of claim 5 wherein the end wall is domed.
8. The improvement of claim 1 wherein the centerto-center spacing between the venting score and the anti-fracture scores is between 50 and mils.
9. The improvement of claim 8 wherein the spacing is 60 mils.
10. The improvement of claim 9 wherein the difference in depth between the venting and anti-fracture scores is on the order of about 3 mils.
11. The improvement of claim 8 wherein the residual of the venting score is between 4 to 6 mils, and the residual of the anti-fracture scores is between 6 to 9 mils.