U.S. patent application number 12/730872 was filed with the patent office on 2011-01-20 for steel one-piece necked-in aerosol can.
Invention is credited to George B. Diamond, Ralph Helmrich.
Application Number | 20110011896 12/730872 |
Document ID | / |
Family ID | 43464578 |
Filed Date | 2011-01-20 |
United States Patent
Application |
20110011896 |
Kind Code |
A1 |
Diamond; George B. ; et
al. |
January 20, 2011 |
STEEL ONE-PIECE NECKED-IN AEROSOL CAN
Abstract
A one-piece, steel, aerosol can formed by a draw and iron
process with varying wall thicknesses, including a main body of a
first wall thickness, a cone area above of a greater second wall
thickness and a curl area above of a third thickness smaller than
the second thickness and adapted to fit a standard aerosol valve. A
process for shaping the can with the respective wall thickness
sections. The process includes necking the can near the top end.
The bottom of the can may be supported to maintain a shape during
necking. The can interior may be pressurized during necking to
resist permanent deformation of the can during necking.
Inventors: |
Diamond; George B.; (Glen
Gardner, NJ) ; Helmrich; Ralph; (Rolla, MO) |
Correspondence
Address: |
OSTROLENK FABER GERB & SOFFEN
1180 AVENUE OF THE AMERICAS
NEW YORK
NY
100368403
US
|
Family ID: |
43464578 |
Appl. No.: |
12/730872 |
Filed: |
March 24, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61226963 |
Jul 20, 2009 |
|
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|
Current U.S.
Class: |
222/394 ; 493/1;
493/76; 72/379.4 |
Current CPC
Class: |
B21D 51/2638 20130101;
B21D 51/2615 20130101; B65D 83/38 20130101 |
Class at
Publication: |
222/394 ; 493/1;
493/76; 72/379.4 |
International
Class: |
B65D 83/38 20060101
B65D083/38; B21D 51/26 20060101 B21D051/26 |
Claims
1. A steel can adapted for necking and adapted for use as an
aerosol can, the can comprising: a can body comprised of a can
wall; a lower region of the can wall having a first thickness and
being of a first diameter; a cone area of the can wall above the
lower region, and the cone area having a second wall thickness; a
curl area of the can wall above the cone area, the curl area having
a thinner third thickness than the second thickness of the cone
area, wherein the second and third thicknesses are selected for
enabling necking of the can wall at the cone area and the curl area
and for enabling forming a curl of the can wall at the curl area
after the necking.
2. The can of claim 1, wherein the third thickness of the can wall
at the curl area is different than the first thickness of the lower
region of the can body.
3. The can of claim 2, wherein the second thickness is different
than the first thickness.
4. The can of claim 1, wherein the can body has a closed bottom and
an open top having the curl area at the top, and the can wall is
necked to a smaller second diameter opening at the curl area.
5. The can of claim 4, wherein the can body and bottom are
integral.
6. The can of claim 4, wherein the can body and bottom are of one
piece.
7. The can of claim 1, wherein the can body is of one piece.
8. The can of claim 7, wherein the can body is formed by a draw and
iron process.
9. The can of claim 1, wherein the can is an aerosol can.
10. The can of claim 1, wherein the can has an opening and the can
further comprising an aerosol dispensing valve secured into the
opening of the can at a base of the curl area.
11. A process for forming a one-piece steel can with a narrow
opening, the method comprising forming a can body having a can wall
with a lower region of a first wall thickness, a cone area of the
can wall above the lower region with a second wall thickness and a
curl area of the can wall above the cone area with a third
thickness smaller than the second thickness, the curl area
surrounding and defining an opening into the can body; necking the
can by applying force to the can for reducing the diameter of the
can at the curl area to a smaller diameter than the diameter of the
lower region and forming the can body in the cone area to define
the smaller diameter for the curl area for shaping the opening for
receiving an aerosol valve after necking and curling.
12. The method of claim 11, wherein the can body is formed in a
draw and iron process.
13. The method of claim 11, further comprising forming the second
thickness to be different than the first thickness.
14. The method of claim 13, further comprising forming the third
thickness to be different than the first thickness.
15. The method of claim 11, further comprising forming the third
thickness to be different than the first thickness.
16. The method of claim 11, further comprising installing an
aerosol valve in the opening at the curl area.
17. The method of claim 11, wherein the can body has a can bottom
below the lower region of the can wall; the method further
comprising supporting the can bottom on a shaped die or mandrel
which resists deformation of the can bottom during can necking.
18. The method of claim 11, further comprising applying pressure
inside the can body during the step of necking to assist the can
body in resisting permanent deformation during the can necking.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention concerns a steel, one-piece,
necked-in, aerosol can, which does not require a separate cone
intermediate the wider top of the can body and the narrower outlet
from the can or from a dispensing valve that is disposed in the
outlet. It also concerns a method of manufacture of such a one
piece can.
[0003] 2. State of the Art
[0004] A typical two or three piece steel aerosol dispensing can
has a selected diameter, which may be typically from 11/2 inches
(38 mm) to three inches (76 mm). Dispensing from an aerosol can is
through a valve supported at the top of the can. The valve includes
an attachment base, called a valve cup, by which it is attached to
the can by crimping. The valve cup is narrower than the can body,
e.g., a standard aerosol valve has about a one inch (25.4 mm)
diameter. In order to support the valve at the top of the wider can
body, a second can piece or dome (cone) is attached between the
wide top of the can and the narrower valve cup. The dome has a
wider bottom, having the diameter of the top end of the can body,
and a narrower diameter top opening in which the valve cup is
disposed. The bottom edge of the dome is shaped to mate with and be
sealed to the top edge of the can in any of numerous conventional
ways, but usually by seaming. However, the primary areas of
possible leak or separation of the dome from a domed can is at the
seam between the dome and the can body and a separate (in the case
of a three piece can) seam between the bottom of the can and the
can body. The top opening of the dome is sized to receive the valve
cup and that opening also is defined by a small radius, inward or
outward curl of the upper end of the dome. That curl provides a
properly dimensioned seat for the valve cup and a gasket to seal
against and strengthens the area where a connection is made to the
valve cup, again conventionally, e.g. by crimping.
[0005] Alternately, the can body with an integral top with the
opening to receive the valve may be made with an open bottom and a
bottom closure may then be seamed on to complete the two piece
can.
[0006] In the case of the separate seamed-on dome (or cone) or the
integral body and top with an open bottom, the curl is formed with
the aid of an internal mandrel or male die part to support the
shoulder area of the dome or the integral top during the curl
forming operation and thus prevents shoulder collapse. This mandrel
cannot be used to support the shoulder during the necking and curl
forming of a one-piece can since the bottom of the one-piece can is
closed and will not allow insertion of the internal mandrel or male
die part.
[0007] To avoid having to separately produce a dome (or bottom) and
body (in the case of two piece cans) and a dome, cylindrical body
and bottom (in the case of three piece cans), to save metal and
energy, to simplify can assembly by avoiding the dome (and bottom)
application step(s), to increase the pressure resistance of the
crimped can, and to achieve a safer, more reliably sealed can, it
would be desirable to form the can main body with an integral
bottom and a selected diameter, yet have the body necked down in
diameter to receive a valve or other closure at its reduced
diameter opening at its upper end. This is commonly done by the
method of impact extrusion followed by die or spin necking using
pure aluminum or the more malleable alloys of aluminum although the
resulting can is uneconomically thick with a high life-cycle energy
cost. This may also be accomplished with certain aluminum alloys by
forming a cylindrical body by the draw and iron, deep draw, or
draw-thin-redraw method and subsequent die necking steps. To date,
none of these methods has been successfully used to make a
one-piece steel aerosol can, particularly in the diameter range of
38 mm to 76 mm.
[0008] When a cylindrical body of metal having a first thickness is
necked down by the die necking process, the metal in the necked
down region becomes progressively thicker as the diameter
decreases. With many metals used for cans, such as steel, the
necked down region also becomes work hardened during the necking
step, and therefore more difficult to work and likely to crack when
subsequently manipulated, as by being curled or attached, e.g. by
crimping, to another part.
[0009] The undesired excess thickening effect is experienced with
all metals and the work hardening effect is experienced with steel
and some other metals, but excessive work hardening is typically
not experienced with a softer metal, such as pure aluminum or its
more malleable alloys. In these malleable, easy to work alloys, the
thickening effect does not negatively impact the necking, curling
and crimping operations. The upper end of a can of essentially pure
aluminum or other soft, malleable metal can be necked down in
diameter to reduce the size of an outlet opening to a selected
smaller diameter without damage to the can or significant work
hardening of the metal. Although steel 2-piece drawn and ironed
food or beverage cans can be necked down to accept a conventional
reduced diameter end (either plain or pop-top) of about 2 inch
diameter, they have not been necked down to a diameter approaching
the 1 inch diameter opening needed to fit a standard aerosol valve.
Those steel cans that require an opening smaller than about 2 inch
diameter are fitted with a separate end, cone or dome with the
appropriate opening.
[0010] Heretofore, if an attempt was made to make a one piece steel
aerosol can with a necked down region and a reduced sized opening,
necking down the steel during the can forming process usually
causes the steel to crack or buckle. When the curl area around the
outlet from the necked down region is curled over or receives the
valve cup and is crimped, it is likely to crack. Further, the metal
in the necked down region becomes thickened, work hardened and thus
less malleable.
[0011] Furthermore, eliminating a separate dome eliminates the
steps of producing and of attaching the dome and also eliminates
the additional material required for producing the dome and the
scrap generated in the production of that dome. Thus, a one-piece
can is inherently more environmentally friendly by virtue of its
reduced use of source materials and the reduction in scrap.
SUMMARY OF THE INVENTION
[0012] According to the invention, a steel one-piece aerosol can
body has varying wall thicknesses at different height regions along
the can for serving respective purposes. Such a can can be made by
a draw and iron process and can then be formed through necking and
curling dies to form a one piece necked-in can with a larger
diameter can body and a smaller diameter top opening. The region at
and below the opening is called the neck. The top of the can body
defines an area called the shoulder, at which the can body begins
necking in. Between the narrow neck and the wide shoulder there is
a narrowing frustoconical shape region called the cone.
[0013] The region of the neck at the opening into the can can then
be curled to accept a standard aerosol valve cup. The can has a
sloping "cone" shape joining the shoulder of the body and the neck.
This "cone" may be of any one of a number of appropriate shapes
including spherical, oval, conical, tapered, stepped, etc. The body
of the can may be formed into any one of a number of
non-cylindrical shapes for aesthetic or ergonomic purposes.
[0014] The invention particularly concerns selection of can wall
thicknesses of a preferably one piece, preferably steel can
according to the purpose each region of the can body, namely, the
bottom, side wall, shoulder, cone, neck and curl area performs, how
the can is formed and particularly necked to receive a valve cup at
its opening and the characteristics of the metal, preferably steel,
of the can body. In particular, in a one-piece steel can, the curl
area above the shoulder and the cone is made appropriately thin
prior to necking so that when it is thickened by being necked in,
the curl area is then capable of being worked into a curl without
damage to the can body or shoulder. Further, the cone area must be
thick enough to not collapse when it is necked in, typically by a
die element applying force to the shoulder in the axial direction
or by a spinning device with a roller assist. Also, the valve,
which is supported by its valve cup on the curl area, has a base
piece which is shaped and sized to be crimped against and form a
seal with the inside of the shoulder. The cone area above the
shoulder must be thick and strong enough to resist buckling under
the axial loads generated during necking, curling and crimping and
also to maintain the seal formed during the crimping.
[0015] In a typical can according to the invention, before the can
is necked, the can wall at the curl area is thinner than the can
wall at the cone area below the curl area. Even after necking in,
which thickens the curl area proportionally more than the cone
area, the curl area remains thinner than the cone area.
[0016] In addition, the cone area of the necked-in can, between the
narrowed neck and the can body, should be sufficiently strong to
resist collapse of the neck of the can due to axial loads applied
to the can during its forming. This is accomplished by providing a
sufficient thickness of metal in the cone area between the main can
body and the narrowed neck or curl area. In the case of the softer
metals, such as aluminum, the axial load required to form the cone
and neck is much lower than that required for forming the cone and
neck of a steel can. The present invention permits a valve cup to
be attached to steel cans of various diameters.
[0017] As the can diameter increases, the thickness of the cone
area is preferably adjusted due to the force required to neck in
from the wider diameter shoulder, to avoid collapse of the
cone.
[0018] To make the curling operation easier, to reduce the axial
loads generated during curling, and to eliminate cracking and cone
area collapse, the portion of the upper can wall above the cone
area and that will become the curl area can be thinned to a
thickness other than the thickness of the cone area beneath the
curl area so that after necking the curl area, is of a thickness
that is optimal for curling.
[0019] The wall of the main body of the can below the shoulder may
be made of a thickness suitable for the type of service, e.g., the
diameter of the can and the pressure in the can, required of the
can. The thickness of the body wall is typically not dependent upon
the thickness of the bottom, the cone area or the curl area of the
can. The thickness of the cone area can be made sufficiently thick
to resist buckling under the axial loads generated during the
necking and curling operations. The thickness of the curl area can
be chosen to optimize the forming of the curl, and so that it has
strength to retain its shape and hold the valve cup. In fact, in
some prior cans, the flange area above the cone, which is seamed or
crimped to a dome, is thicker walled than the cone area. The
foregoing thicknesses are achieved by choosing the appropriate
thickness of sheet or coil stock from which the can is made and
providing an ironing punch of the appropriate configuration to
produce the required wall thickness distribution along the length
of the can as discussed above.
[0020] The thickness of the can bottom is chosen to provide the
strength or pressure resistance required to maintain the shape of
the can bottom of a filled, fully pressurized can. For enhanced
strength resistance to deformation when a can is pressurized, the
can bottom may be domed upward, into the can. That strengthened
shape is preferably produced, or, if present, maintained when the
can is being necked. It is desirable that the can bottom also be of
a thickness substantially of the can wall. However, such a can
bottom may be too weak to maintain the original shape it had prior
to necking the can, because necking involves applying downward
force on the can and the can bottom. To maintain the desired shape
of the can bottom during necking, it may be supported on a die or
mandrel with a selected shape, so that the can bottom should not
collapse or be deformed from its desired shape. Of course, the same
die may be used to provide a preferred shape to the can bottom so
that the bottom is given its selected shape when the can is being
necked.
[0021] When a can is of a sufficiently large size, and its can wall
material is strong enough and the wall is thick enough to support a
filled can shape during normal product storage and use, the can
wall and possibly the can bottom may not be sufficiently strong to
resist being deformed by the axially or vertically directed force
applied to the can body during the necking process. Rather than
changing one of the above parameters of the can to increase its
strength, an elevated pressure condition may be temporarily
produced inside the can being necked, either by application of air
pressure or by hydraulic pressure supplied by a source of hydraulic
pressure. Residue of hydraulic pressurizing fluid can be removed in
the customary can washing step. The pressure level is selected so
as to not significantly or permanently deform the can, but to be
sufficient to aid in preventing can deformation or collapse under
the axial force applied during necking.
[0022] The present invention deals with steel one-piece aerosol
cans with reductions at the necked-in (curl) region, for example,
of about 33% for 38 mm diameter cans, about 44% for 45 mm cans,
about 52% for 53 mm cans, about 56% for 58 mm cans, and about 61%
for 65 mm cans (if economics and/or technical considerations
justify the one piece 65 mm cans).
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is a cross section of a fragment of a can showing a
formed but un-necked can wall,
[0024] FIG. 2 is a cross-section of a fragment of a can showing a
necked can wall.
[0025] FIG. 3 shows the can of FIG. 2 completed with a valve.
[0026] FIG. 4 shows a supported can bottom to maintain shape and
schematically illustrates application of pressure in the can body
during necking.
DESCRIPTION OF A PREFERRED EMBODIMENT
[0027] An aerosol can 10 is formed from a steel blank or a steel
cup using a drawn and ironing process.
[0028] As shown in drawing FIG. 1, the side wall 12 of the lower
region of the can 10, below the shoulder 17, is cylindrical and of
a substantially uniform first thickness 13, thick enough to contain
a fluid material and propellant under pressure in the can and for
the diameter of the can, yet the wall is economically thin enough.
The closed bottom 15 of the can is usually thicker than the first
thickness, and may be domed inward to strengthen it against
deformation, e.g., from pressure in the can. The thickness of the
can bottom is preferably low to keep the can of light weight and to
reduce the amount of metal used. During below described necking of
the can, the illustrated dome shape may be supported by a die or
mandrel.
[0029] As shown in FIG. 2, the can is necked narrower upward in a
"cone" shape from the condition shown in FIG. 1 at its upper region
starting upward from the shoulder 17. That cone area 14 should be
strong enough to resist cone area collapse when axial loads are
applied to the can during the necking, curling, and crimping
processes. Therefore, the cone area 14 of the side wall of the can
is made with a greater second wall thickness 16 than the first
thickness 13. The top of the lower region 12 meets the bottom of
the cone area at the shoulder 17, where the cone area 14 starts its
slope inward.
[0030] Directly above the sloping cone area 14 is the neck or curl
area 18, which is curled outward on a small radius to define a
support area for a conventional aerosol valve 20 to be crimped into
the can thus sealing the valve to the can. See FIG. 3. The valve
includes a valve cup 34 shown crimped at the base 32 of the valve
cup allowing a seal for the can contents to be formed at 36. The
peripheral edge region 38 of the valve cup is curled over to
receive the curl area 18.
[0031] The third wall thickness 19 of the curl area 18 before
necking is thinner than the second wall thickness 16 of the cone
area 14. The curl area may be either thicker or thinner than the
first wall thickness 13 of the side wall of the lower region of the
can, because these sections have different purposes, as was
described above. The curl area 18 is necked down to the maximum
extent in defining the outlet opening 21 which receives the valve
cup 34 or some other closure for the can opening. The necking
thickens the curl area from the thickness 19 in FIG. 1 to the
greater thickness 23 in FIG. 2, but not so much as to make the curl
area unbendable and uncurlable. The curl area 18 above the cone
area is still thin enough and malleable enough as to be curlable to
define the curled peripheral region 18 around the top opening
21.
[0032] The cone area 14 of the can wall is thickened as at 16 so
that it will not buckle or collapse under the axially downwardly
directed necking force applied during can forming and also during
later application of the valve to the finished can. Since the upper
section of the cone area at 22 and the curl area 18 thicken at 26
and 23 respectively during the necking process, the curl area
starts thinner at 19 in FIG. 1 so that the thickness 23 of the
necked down and thickened curl area in FIG. 2 is sufficiently thin
to reduce the chance of the metal cracking there when it is bent to
form the curl. The can wall at the cone area has a maximum second
thickness just below the curl area and just below where at 24 the
curl area 18 is joined to the top of the cone area 14. This maximum
wall thickness is selected to resist shoulder collapse due to axial
loads encountered during forming.
[0033] As described above, the bottom 15 of the can may be
supported by a die or mandrel 31 that maintains a selected shape,
e.g., a dome shape, under axial force applied by a conventional
necking device 27 in the plane of the can wall. For a can of a
relatively larger cross-section or diameter, elevated pressure is
temporarily supplied in the can during necking, e.g., by air
pressure or hydraulic pressure at 29, which helps the entire can
body resist permanent deformation under the force of necking the
can.
[0034] When the curl area 18 is necked in, the cone area 14
deflects above the shoulder to slope inwardly as well. The cone
area is thick enough at thickness 26, so that it does not buckle,
but instead the can wall slopes inward generally in the region
between the top of the can body and the cone area below where the
shoulder thickens.
[0035] In an example for illustrating the invention, in a steel
aerosol can having a diameter of 13/4'' (45 mm), before necking of
the can, the first thickness 13 of the body wall is 0.0044'' (0.112
mm), the second thickness 16 of the cone area is 0.0065'' (0.165
mm) and the third thickness 19 of the curl area is 0.005'' (0.127
mm). After the can is necked, the thickness of the material of the
cone area increase in the direction toward the narrowed neck, and
the thickness of the curl or neck area increases, possibly to
greater than 0.0062'' (0.127 mm), but remains thinner than the
thickness in the adjacent cone area. Note that the first thickness
of the body wall is independent of the second and third thicknesses
of the cone and curl areas as is the thickness of the bottom.
[0036] To neck the top of the can, the punch of a draw and iron die
(not shown) is shaped to provide the thicker wall at the cone area
14 and the thinner wall at the curl area 18. It is already known to
provide a punch in a draw and iron die to have a shape to change
the thickness of the top of a two-piece can to provide a thicker,
stronger area for the formation of a flange for seaming on an end,
dome or cone. But a punch shaped for providing a thicker wall at
the shoulder area and a thinner wall at the curl area is not known.
The punch in the draw and iron die is a direct complement to the
shape of the can wall being initially formed before the can is
necked. As described above during necking, the can bottom may be
supported to maintain its shape and the interior of the can may be
pressurized to resist and prevent permanent deformation of the can
body during the necking.
[0037] Alternatively, a conventional technique may be used for
necking the can, including using conventional shaping dies, or a
spinning device with a roller assist, coupled with ultrasonic
vibration which warms the can material and helps reorient it
without applying too much force.
[0038] Although the present invention has been described in
relation to particular embodiments thereof, many other variations
and modifications and other uses will become apparent to those
skilled in the art. It is preferred, therefore, that the present
invention be limited not by the specific disclosure herein, but
only by the appended claims.
* * * * *