U.S. patent number 3,757,558 [Application Number 05/324,115] was granted by the patent office on 1973-09-11 for apparatus for necking-in tubular members.
This patent grant is currently assigned to American Can Company. Invention is credited to Carl William Heinle.
United States Patent |
3,757,558 |
Heinle |
September 11, 1973 |
APPARATUS FOR NECKING-IN TUBULAR MEMBERS
Abstract
Method and die assembly for necking-in tubular members wherein
the die assembly comprises an outer reducing die and an inner die
pilot comprised of a T-shaped holder on which is mounted a pilot
ring that floats radially on an also mounted spring biased axially
floating retaining ring means. The reducing die has a recessed
inwardly angled directing surface on the wall of its inner chamber,
and the pilot ring has a wide diameter circumferential step surface
and two supporting surfaces of lesser diameter. A clearance is
provided between the pilot ring supporting surfaces and the outer
reducing die. The outer reducing die is brought into telescoping
engagement with the marginal edge portion of the wall of a tubular
member. This causes the reducing die directing surface to direct
the marginal edge portion inwardly against the pilot ring step
whereby the edge portion is directed into a groove formed by the
pilot ring, the outer reducing die and a control surface which
transversely engages the edge of the wall and controls its axial
movement in relation to the die assembly. In the groove, the
marginal edge portion is formed into a rim of reduced diameter. As
the outer reducing die continues to move axially over the tubular
wall, the directing surface directs the flow of tubular wall
material into the aforementioned clearance and toward the lesser
diameter pilot ring surfaces against and along which it rests to
form a neck having a diameter less than that of the rim. The method
and die assembly accomodates can bodies having side seams and
utilizes a spring means to compensate for irregularities in and for
changes in wall length which occur during the necking-in
operation.
Inventors: |
Heinle; Carl William (Short
Hills, NJ) |
Assignee: |
American Can Company
(Greenwich, CT)
|
Family
ID: |
23262144 |
Appl.
No.: |
05/324,115 |
Filed: |
January 16, 1973 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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231207 |
Mar 2, 1972 |
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Current U.S.
Class: |
72/361;
413/69 |
Current CPC
Class: |
B21D
51/2615 (20130101); B21D 51/2638 (20130101); B21D
41/04 (20130101) |
Current International
Class: |
B21D
41/00 (20060101); B21D 41/04 (20060101); B21D
51/26 (20060101); B21d 019/06 () |
Field of
Search: |
;72/352,353,354,370
;113/1G,12AA,12R |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Herbst; Richard J.
Parent Case Text
This is a division, of application Ser. No. 231,207, filed Mar. 2,
1972.
Claims
I claim:
1. A die assembly for necking-in an end portion of a tubular member
comprising:
an outer reducing die having a recessed inwardly angled directing
surface, and a rim-forming surface adjoining and interior of said
forming surface,
a die interior of and telescoped within said reducing die, a pilot
ring mounted on said pilot and having an upper circumferential step
of greater diameter than the rest of said pilot ring,
an axially moveable retaining ring means contiguous to said pilot
ring for retaining said pilot ring in position on said pilot, said
retaining ring means including a control surface adjacent to and
protruding slightly beyond said pilot step, said control surface
being for transversely engaging the edge of and essentially
stopping the movement of a tubular member brought thereagainst,
spring means contiguous with said retaining ring means and
providing biasing pressure against said retaining ring means,
spring support means contiguous with said spring means for rigidly
supporting said spring means,
mounting means for mounting said die pilot, pilot ring, retaining
ring means, spring means and spring support means thereon and for
carrying said pilot and each of said means axially in and out of
said reducing die,
means for independently advancing and retracting said reducing die
and said pilot such that they cooperate and that
said directing surface and the marginal edge portion of said
tubular member are movingly engaged before said pilot is fully
positioned within an open end of said tubular member,
said directing surface directs said marginal edge portion inwardly
against said pilot step,
a portion of said marginal edge portion is brought into abutting
engagement with at least a portion of a groove formed by said
control surface, said retaining ring means and said pilot step to
thereby form a rim of a reduced diameter out of said marginal edge
portion, and
said directing surface is moved axially and engagingly through and
along wall portions of said tubular member to progressively direct
said wall portions inwardly against the rest of said pilot without
engaging said rim-forming surface with said inwardly-directed wall
portions, to thereby form a neck in said tubular member, said neck
having a diameter less than that of said rim.
2. The die assembly of claim 1 wherein there is also included
retaining ring control means engaging said retaining ring means,
for preventing inward axial movement thereof beyond a certain
preset distance.
3. The die assembly of claim 1 wherein said pilot ring floats
radially in relation to said retaining ring means to compensate for
an extra thickness in the marginal edge portion of said tubular
member.
4. The die assembly of claim 2 wherein said pilot ring floats
radially in relation to said retaining ring means to compensate for
an extra thickness in the marginal edge portion of said tubular
member.
5. The die assembly of claim 4 wherein said retaining ring means
includes a control ring having said control surface thereon and
being in abutting engagement with said retaining ring means and
said pilot ring, and means tied to said retaining ring means for
adjustably holding said control ring in place and for maintaining a
gap between said control ring and said pilot ring which will allow
said pilot ring to float radially.
6. The die assembly of claim 3 wherein said retaining ring means
includes a control ring having said control surface thereon and
being in abutting engagement with said retaining ring means and
said pilot ring, and means tied to said retaining ring means for
adjustingly holding said control ring in place and for maintaining
a gap between said control ring and said pilot ring which will
allow said pilot ring to float radially.
7. The die assembly of claim 6 wherein said reducing die has a
slightly inwardly tapered initial guiding surface adjoining and
exterior of said directing surface.
8. The die assembly of claim 5 wherein said reducing die has a
slightly inwardly tapered initial guiding surface adjoining and
exterior of said directing surface.
9. The die assembly of claim 1 wherein said reducing die has a
slightly inwardly tapered initial guiding surface adjoining and
exterior of said directing surface.
10. The die assembly of claim 1 wherein said reducing die has a
slightly inwardly tapered initial guiding surface adjoining and
exterior of said directing surface, and wherein said retaining ring
means includes a control ring having said control surface thereon
and being in abutting engagement with said retaining ring means and
said pilot ring, and means tied to said retaining ring means for
adjustably holding said control ring in place and for maintaining a
gap between said control ring and said pilot ring which allow said
pilot ring to float radially.
Description
BACKGROUND OF THE INVENTION
This invention relates to the necking-in of tubular members. More
particularly, the invention relates to necking-in, i.e., reducing
the diameter of or forming a neck in, one or both ends of metal can
bodies often having side seams of double metal thickness, and
coatings of enamels, inks and other materials on their respective
internal and external surfaces. Still more particularly, the
invention relates to an improved method and die assembly apparatus
for necking-in can bodies which can accomodate side seams and
minimize scratches in the aforementioned surfaces, and coatings, as
well as folds cracks and other irregularities in the overall
necked-in areas of can bodies.
Currently, when can bodies are necked-in by use of die assemblies
which consist of an outer reducing die and an inner die pilot,
relative movement is effected between the die assembly and can body
to bring the substantially straight wall of the can body into the
die assembly necking-in area between the reducing die and the inner
pilot. The marginal edge portion of the can body is movingly
frictionally compressed between the respective die surfaces and has
its diameter reduced by an inwardly angled shoulder-forming surface
on the interior of the outer die.
This type of necking-in operation is problematical for several
reasons. When the edge portion of the can is subjected to the
friction and compressive forces exerted by outer and/or inner die
surfaces, scratches and scores are obtained in interior enamel and
in exterior enamel and decorative coatings. Inner scratches can
result in metal pickup by and consequent deterioration of container
contents. Another problem is that when the diameter of a can body
is reduced, metal in the reduced area is pressed into folds,
puckers and other irregularities which often form cracks during
subsequent flanging and double seaming operations.
Still other problems involved in current necking-in operations are
that the die assemblies do not accomodate changes in length of can
body walls when their diameters are reduced. Extra length
accentuates the aforementioned scratching and cracking problems.
Further, current die assemblies are not adaptable for working can
bodies made of various metals of various strengths, or those of
various types, e.g., those having or not having side seams of
various types. For example, the assemblies cannot control or vary
in the amount of pressure or force exerted lengthwise on can body
walls as would be required to work say both steel and thin light
gauge aluminum bodies with the same die assembly. Further, some die
assemblies require orientation of can body side seams in order to
compensate for the double metal thickness of the can side seam.
Still further, because inner pilots usually are inserted quite
deeply and are held quite tightly by the can bodies during the
necking-in operation, considerable pressure is required to strip
the can bodies from the pilots.
SUMMARY OF THE INVENTION
In view of the aforementioned problems encountered in current die
necking-in operations, it is an object of this invention to provide
a method and a die assembly for necking-in tubular members which
provides and utilizes a clearance between the outer die and inner
die of the die assembly to greatly reduce the friction and
compressive forces exerted by the die surfaces on tubular walls
being worked and thereby greatly minimize the amount of scratches,
scores and other defects which usually appear in the necked-in wall
surfaces.
It is another object of this invention to provide a method and a
die assembly for necking-in tubular members which greatly reduces
the amount of folds, cracks and other irregularities which usually
appear adjacent the necked-in areas and reduced diameter areas of
the walls of tubular members.
It is another object of the invention to provide a die assembly
that is suitable for necking-in tubular members made of different
materials of different strength, and can bodies of varying type
diameter, length and thickness.
It is another object of this invention to provide a die assembly
for necking-in tubular members wherein compressive forces exerted
by the die assembly on the walls of the tubular members can be
controlled and adjusted to compensate for the aforementioned
differences and variations.
It is still another object of this invention to provide a die
assembly for necking-in tubular members having side seams, which
does not require orientation of the side seam therewith.
It is yet another object of this invention to provide a die
assembly for necking-in tubular members whose pilot is not tightly
held by the tubular member and which requires little pressure to
remove the tubular members therefrom.
The manner in which these and other objects and advantages are
achieved will become more apparent and more fully understood from
the following description which when read in conjunction with the
accompanying drawings, discloses a preferred embodiment of the
invention.
IN THE DRAWINGS
FIG. 1 is an enlarged fragmentary vertical section taken through an
outer reducing die and an inner die pilot of a die assembly, and
through the top of a straight-walled tubular can body aligned for
entry into the forming area of the die assembly.
FIG. 2 is an enlarged fragmentary side view of the top of the can
body of FIG. 1 after it has been necked-in with the die assembly of
FIG. 1.
FIG. 3 is a sectional plan view taken through line 3--3 of FIG. 1
showing the pilot ring after floating radially to compensate for
the side seam of a can body, were the can body of FIG. 1 located in
the forming area of the die assembly of that Figure.
FIGS. 4-9 are enlarged fragmentary sectional views showing
successive stages wherein one wall of the can body of FIG. 1 is
being necked-in by a corresponding sectioned side of the die
assembly of that Figure. FIG. 4 shows the can body after entering
the mouth of the outer reducing die.
FIG. 5 shows the marginal edge portion of the can body directed
inwardly by the outer reducing die and engaging the step of the
inner pilot ring.
FIG. 6 shows a portion of the marginal edge of the can body in
groove G and transversely engaging the control surface of the
retaining ring means.
FIG. 7 shows a rim of reduced diameter formed between the outer
reducing die, control surface and pilot ring step.
FIG. 8 shows the can body wall being directed to lay against the
smaller diameter portions of the inner die pilot ring.
FIG. 9 shows the can body wall after it has been necked-in.
DETAILED DESCRIPTION OF THE DRAWINGS
Referring to the drawings in detail, FIG. 1 shows a die assembly
generally designated 10 and, aligned therewith, a tubular can body
generally designated C. Die assembly 10 is comprised of an outer
reducing die 12, often called a punch, and to the interior thereof,
an inner die pilot generally designated 14. Outer reducing die 12
has a chamber 6 having at its mouth an inwardly angled orienting
surface 18, a guiding surface 20 which can be substantially
vertical and/or slightly inwardly angled, a recessed, more inwardly
angled directing surface 22 and a rim-forming surface 24.
Inner die pilot 14, telescoped within outer reducing die 12, is
comprised of suitable mounting means, which can include means such
as T-shaped holder 26, shaft 28 and means such as an Allen head cap
screw 30 for fastening holder 26 to shaft 28.
Mounted on T-shaped holder 26 for axial movement thereon is pilot
ring 32, axially floating retaining ring means 42, spring means 46
and spring support means 48. Pilot ring 32 is in turn mounted for
radial floatation upon and within retaining ring means 42 biased
from the interior of inner die pilot 14 by spring means 46. Spring
means 46 preferably is comprised of conical washers but can also be
other suitable spring means such as coil springs. Spring support
means 48 preferably is adjustingly secured to holder 26 as by
threads 50, but can also be a solid extension of T-shaped holder
26.
Pilot ring 32 has an orienting surface 34, a substantially vertical
supporting surface 36, an inwardly angled step-joining supporting
surface 38 and a wide diameter step 40. Pilot ring 32 is
constructed of a dimension that leaves a gap between it and
retaining ring means 42, and a gap between pilot step 40 and outer
reducing die rim-forming surface 24, the area of the two gaps being
sufficient to allow the marginal edge portion of can body C to fit
fairly snugly and restrainingly between pilot step 40 and reducing
die rim-forming surface 24. The total width of the gap allows pilot
ring 32 to float radially and thereby compensate for and accomodate
the double metal thickness of can side seam SS.
The gap between pilot ring supporting surfaces 38 and 36 and outer
reducing die 12 provides enough clearance for a can body wall which
has been directed inwardly off of inwardly angled reducing die
directing surface 22, to flow inwardly and rest or lay against
pilot ring surfaces 38 and 36 in a manner to be more fully
explained later.
Retaining ring means 42 can be one piece but preferably is
comprised of several pieces tied together and axially moveable as a
unit as shown in FIG. 1. Shown therein is retaining ring means 42
which can be moderately L-shaped so that its lower leg extends to
the vertical plane of and has a configuration similar to that of
pilot ring support surface 36 and orienting surface 34. Retaining
ring means 42 can include control ring 43 having a control surface
44 positioned adjacent to and protruding slightly beyond pilot ring
step 40, and means such as nut 45 for adjustably holding control
ring 43 in place and for maintaining a suitable uniform radial gap
between control ring 43 and pilot ring 32 which will allow the
pilot ring to float radially.
The distance that control surface 44 protrudes beyond step 40 is a
distance that will enable surface 44 to transversely engage the
edge of a can body wall brought into groove G formed by pilot ring
step 40, control surface 44 and reducing die rim-forming surface
24. As will be more fully explained later, control surface 44 is
utilized to essentially prevent relative movement between the can
body and the surfaces of pilot ring 32 by transversely engaging the
can body edge and causing pilot ring 32 and retaining ring means 42
to move as a unit as the can body moves and to float axially
against or with the bias of spring means 46.
The distance that retaining ring means 42 and pilot ring 32 float
axially and the amount of compressive force exerted on the can body
all can be controlled by controlling the amount of tension or
pressure exerted by spring means 42. Less axial movement and
greater pressure can be obtained by lowering spring support means
48 toward retaining ring means 42.
Another means by which the aforementioned axial floatation and
compressive force can be controlled is by use of suitable retaining
ring control means such as shoulder screws 52 (only one shown)
which can, for one thing, prevent inward axial movement beyond a
certain preset distance. Shoulder screws 51 have threaded ends
which engage retaining ring means 42 on an interior side of a
portion of a T-shaped holder leg, and screw heads 53 which have
undersurfaces parallel to but removed or gapped from opposing
stopping surfaces on the exterior side of the aforementioned
portion of holder 26. When the total distance of axial floatation
desired to be set is less than the gap between the aforementioned
surfaces, a shim 54 of a thickness which establishes the desired
distance can be employed.
FIG. 2 is a side view of tubular can body C of FIG. 1, here
designated C', after it has be necked-in with the die assembly of
FIG. 1. Neck-in can body C' is shown having a rim R, an
intermediary surface r, a neck N and a shoulder Sh respectively
having the configuration of pilot ring step 40, step-joining
supporting surface 38 and supporting surface 36.
FIG. 3 is a top sectional view as would be taken along line 3--3 of
FIG. 1 were straight-walled can body C of FIG. 1 to have entered
groove G of die assembly 10. FIG. 3 shows that when can body C,
having double seam SS, enters groove G, pilot ring 32 floats
radially (to the right in FIG. 3) to compensate for the double
metal thickness of the side seam. It can be seen that whereas on
the left side of die assembly 10 reducing die rim-forming surface
24 engages side seam SS but not the adjacent single wall portions,
and whereas on the left the adjoining surfaces of retaining ring
means 42 and pilot ring 32 abut one another, on the right side of
die assembly 10 rim-forming surface 24 and step 40 engage the
single wall, and the adjoining surfaces of retaining ring means 42
and pilot ring 32 do not abut one another.
FIGS. 4 through 9 show the manner in which straight-walled can body
C is necked-in with die assembly 10. The Figures show what is
occurring at various stages during the necking-in operation and
does not necessarily show that the operation stops at each stage.
Preferably the operation is continuous. It is to be noted that
according to this invention, the can body, the outer reducing die,
the inner die pilot or any combination or combinations thereof may
be moved to effect the relative movement between die assembly 10
and can body C that is required to neck-in the can body. However,
FIGS. 4-9 show the preferred method of effecting the necking-in
operation, that is, wherein relative movement is effected by
holding can body C stationary and moving die assembly 10
telescopingly into engagement with can body C.
Any conventional means can be used for holding the can body steady.
When only one end of the can is being necked-in, the die assembly
is brought into telescoping relationship with that end while for
example a cup-shaped base applies an axially and radially
restraining force on the opposite end of the can body. When both
ends are being necked-in, the die assembly is brought into
telescoping relationship with each end while the can is held for
example by magnets lining the arcuate surface of can body-shaped
cutouts or pockets in for example the flanges of a starwheel or
turret.
Any suitable conventional means for insertingly and retractingly
moving the die assembly outer reducing die 12 and inner die pilot
14 in independent cooperating relationship can be used, such means
being well known in the industry.
FIG. 4 shows outer reducing die 12 and inner die pilot ring 32 in
telescoped relationship and together moved into telescoping
relationship with stationary can body C whereby outer reducing die
12 has moved over the mouth of body C and has thereby caused the
marginal edge portion thereof to be movingly engaged with the lower
substantially vertical portion of rim-forming surface 20. FIG. 4
also shows the previously mentioned groove G.
In FIG. 5, reducing die 12 and inner die pilot ring 32, in the same
telescoped relationship as in FIG. 4, have together moved further
downwardly over stationary can body C thereby causing its can body
wall to progressively engagingly travel along and flowingly adopt
the contour first of the lower substantially vertical and then the
upper slightly inwardly angled portion of guiding surface 20, and
then that of the more inwardly angled directing surface 22, the
latter of which reduces the diameter of the can body and directs
the flow of can body metal toward and against the large diameter of
pilot ring step 40. As the inner edge of the can body wall strikes
step 40, pilot ring 40 floats from the phantom line radially to the
right where it is shown in FIG. 5, to compensate for the double
thickness of side seam SS. Although the can body edge can be
directed to initially strike any portion of step 40, it is
desirable that it strike an upper portion thereof. Preferably, the
upper portion is sufficiently removed from control surface 44 to
allow for elongation of the can body when its diameter is reduced
by inwardly directing surface 22.
At this point, it should be noted that before and during the stage
represented by FIG. 5, the wall of can body C engages inwardly
angled reducing die directing surface 22 before pilot ring 32 is
fully inserted into can body C.
As shown in FIG. 6, as reducing die 12 and inner die pilot ring 32
continue moving in telescoped relationship downwardly over can body
C, the can body wall is directed into groove G (see FIG. 4) made up
of a portion of reducing die rim-forming surface 24, retaining ring
means control surface 44 and pilot ring step 40. When the edge of
the can body wall engages control surface 44, inner die pilot 14
essentially stops its movement into can body C. At this point
reducing die 12 can dwell, but preferably it continues moving
downward over the can body. As will be explained later, it is
believed that as the edge of can body strikes pilot step 40,
travels into groove G and transversely engages control surface 44,
pilot ring 32 and retaining ring means 42 move axially upwardly as
a unit to load, i.e., compress, conical washer spring means 46
(shown in FIG. 1).
As shown in FIG. 7, as outer reducing die 12 continues to move
telescopingly downwardly over both can body C and over pilot ring
32, groove G elongates and more of the marginal edge portion of the
can body is brought into and is abuttingly engaged with rim-forming
surface 24, control surface 44 and wide diameter step 40. As this
occurs and as FIG. 7 shows, the marginal edge portion has been
formed into a rim R having a reduced diameter, the rim being
contained or restrained in and by the surfaces making up groove
G.
As seen in FIG. 8, reducing die 12 continues to move downwardly
over stationary can body C. As it does, inwardly angled directing
surface 22 continues to direct the flow of can body wall metal
progressively inwardly and downwardly against and along the
perimeter of pilot ring 32 below the wide diameter of step 40,
namely, along the reduced diameters of inwardly angled step-joining
supporting surface 38. This action further reduces the diameter of
and thereby gradually necks in the can body. It is to be noted that
reducing the diameter of the lower portions of pilot ring 32
provides a clearance for and allows the inwardly directed metal to
continue flowing on its path away from reducing die rim-forming
surface 24 so that surface 24 does not rub against or in any way
having the outside can body wall portions that form the neck in the
can body. It is also to be Figure, that the inwardly flowing metal
is not compressed against but is merely gradually directed to
gently rest of lay against the lower reduced diameter portions of
pilot ring 32.
As shown in FIG. 9, the continued downward movement of reducing die
12 in relation to the stationary can body C of previous Figures has
caused directing surface 22 to continue to progressively direct the
inwardly flowing metal away from reducing die 12 and to lay it
against the length of stationary pilot ring supporting surfaces 38
and 36. FIG. 9 shows the finished necked-in can body C' having neck
N, no part of its outer surface having come into contact with or
being in contact with the length of reducing die rim-forming
surface 24. In this FIG., reducing die 12 has approximately
completed its downward stroke and has formed a shoulder Sh in can
body C'.
After completion of its downward stroke, inner die pilot 14
preferably remains stationary while reducing die 12 is retracted
from telescoping engagement with can body C' leaving its rim R
fitting fairly snugly around wide diameter pilot ring step 40, and
its intermediary portion r and neck N resting fairly loosely around
the lower portions of pilot ring 32. Because the narrow rim R is
the only portion that has been frictionally compressed into fairly
snug engagement, very little pressure is required to strip a
necked-in can form inner die pilot 14. Usually, pressure from one
finger of the hand is sufficient when only one end has been
necked-in. When both ends are necked-in about 4 lbs maximum per end
is required. This is to be compared with conventional die
assemblies which often require up to 40 lbs per end when both ends
are necked-in.
To remove inner die pilot 14 from can body C', it has been found
that it is only necessary to merely retract die pilot 14 enough to
retract step 40 from within the can body rim R. Commercially, it is
preferable to utilize some conventional means for holding the can
in say its turret pocket location as the finished can is passed out
of the necking-in working stations to other stations or machines
for flanging and later for double seaming of container end closures
to one or both ends of the can body.
It is important to note the manner in which spring means 46
functions throughout the necking-in operation. Although its full
function is perhaps not clearly understood, it is believed to be as
stated herein. Before can body C strikes some portion of pilot ring
32 and thereafter transversely engages control ring surface 44,
retaining ring means 42 and pilot ring 32 move axially upward
against and thereby compress conical washers 46. Any elongation of
the can body wall due to reduction in diameter by inwardly
directing surface 22 and possibly due to the pressing of metal in
groove G, also aids in the compression of conical washers 46. As
outer reducing die 12 continues downward over the can body wall and
stationary die pilot 32, the can body wall metal is directed to lay
against the smaller diameters of pilot support surfaces 38 and 36.
As this occurs the can body wall shortens and conical washers 46
decompress to compensate for the shortening of the body wall. As
more fully explained later, this decompression is also believed to
aid in the initial bending and in the directing and the laying of
the can body metal inwardly against and along pilot ring supporting
surfaces 38 and 36. As outer reducing die 12 continues further
downwardly, somewhere between the stages of FIGS. 5 and 6 the can
body wall lengthens again and conical washers 46 compress to
accomodate the change in length. This compression remains until it
follows the can when the can is removed from die pilot 14. Thus, it
can be seen that conical washer spring means 46 are actively
compressing and decompressing throughout most if not all of the
necking-in operation. By doing so, they enable the die pilot to
accomodate and compensate for changes in body length occurring
during the necking-in operation as well as for cans of irregular
length.
There are several factors which are believed to account for the
fact the metal of can body C initially bends inwardly below pilot
ring step 40 and flows along and against the reduced diameter
supporting surfaces 38 and 36 of pilot ring 32. The factors are not
necessarily listed in their order of importance as it is believed
that they all cooperate to achieve the result. The most obvious
factor is that the metal is forced to go inwardly by the downward
movement of and the inward-angle of directing surface 22. Another
factor is that the directed metal tends to continue on its directed
path. Reducing the diameter of pilot ring surfaces below step 40
provides a clearance and a path of less resistance to the flow than
did step 40 and thereby permits the metal to proceed further and as
far as it can on its path. Other factors are the forces exerted on
the edges of the can body wall due to elongation of the can body
wall and the de-compressive force exerted by conical washers 46 at
both ends when both ends are being necked-in, and at one end when
one end is being necked-in and the other is being held steady by
some conventional resistive means. These forces are believed to
tend to aid the wall metal to initially bend inwardly toward
support surface 38 and to continue on its inwardly directed path
toward along support surface 36.
Because the method and die-pilot apparatus of this invention are
based on employing an induced natural flow of metal to greatly
reduce the amount of pressure and/or friction imposed upon the
necked-in surfaces of the can body by the die members, several
advantages are obtained. The necked-in can bodies are essentially
scratch and score free in their overall necked-in surface areas,
especially those surfaces not double seamed to an end closure. (The
overall necked-in can surface area just referred to is intended to
include rim-adjoining surface r, neck N and shoulder Sh). This is
because the overall necked-in wall surface area is not compressed
into a snug, approximately wall-thick area between two die surfaces
and because there is no rubbing of moving metal over or friction
occurring on the outer surface, and very little if any on the inner
surface of the overall necked-in wall area. There is little if any
relative movement or friction on the inside of the necked-in wall
surface because the metal is merely directed toward and laid
against and along the reduced diameter surfaces of the pilot ring
32. Relative movement between pilot ring 32 and the can body is
minimized because axial movement of the can body also moves control
surface 44 and pilot ring 32 tied thereto. Any friction during
removal of the necked-in can from the pilot is minimal since the
necked-in area fits loosely around the pilot ring. An additional
advantage of little compression and friction is increased operating
life of the die assembly.
Another advantage is that the length of the marginal edge portion
of can body C diameter that is initially reduced (see directing
surface 22 of FIG. 5) is shorter or less than that reduced in
conventional die necking-in operations. The length reduced is only
that which extends up to the opposing wide diameter surface of
pilot ring step 40. This means that the initial reduction in can
mouth circumference is also less than conventionally. Both of these
facts mean less bunching of metal around and adjacent the
circumference of the open end of the can body. Less compression
means less wrinkles when the cans are necked-in. It also means
substantially less wrinkles and cracks than usually occur during
flanging operations because the metal of the large diameter rim R
need not be bent and stretched as far outwardly as usual to form a
satisfactory flange. Less wrinkles and cracks result in a lower
incidence of can leakage.
The construction and operation of die assembly 10 compensates for
irregularities in can bodies that are to be necked-in. For example,
its spring means, allows it to accomodate irregularities in can
length due to a mislap of a side seam, and the clearance provided
between its rim-forming surface 24 and pilot ring supporting
surface 38 and 36 permits scratch-free necking-in despite portions
of can body walls being irregularly thick due to accumulations of
for example solder or enamel.
Tubular members constructed of any material which can be directed
to flow in the manner required of this invention, can be necked-in
in accordance with this invention. For example, metal cans can for
example be made of tin plate, tin free steel or aluminum, and may
have or not have any of the various hooked, soldered or
thermoplastically adhered or other type side seams. Materials and
can bodies of varying strengths can be necked-in by controlling
pressure, for example by varying the amount of pressure exerted by
conical washers 46. This can be done by raising or lowering
adjustable spring support means 48 and thereby respectively
applying less or more pressure upon the conical washers. Cans made
of hard materials such as steel require more tension than those
made of soft materials such as aluminum, and cans having side
seams, especially soldered or mira-seamed, i.e., thermo-plastically
adhered side seams require more than cans not having side seams.
The die assembly of this invention has been found especially
suitable for necking-in cans made of light weight low strength
materials such as aluminum because die assembly 10 does not tend to
cause such materials to collapse. Whereas conventional outer
reducing dies usually operate on an amount of pressure required to
force metal to bend around forming surfaces and to compress and rub
metal into and along narrow snug areas, reducing die 10 for the
most part only requires pressure sufficient to direct already
flowing material which flows through a clearance and rests on the
supporting surfaces of pilot ring 32. Also, little pressure is
required with die assembly 10 because, as previously mentioned,
little compression and friction of metal takes place.
From the foregoing description, it can be seen that the method of
necking-in a tubular member in accordance with this invention
basically involves bending the marginal edge portion of the tubular
member inwardly to initially reduce its diameter to a first
diameter, applying a restraining force to an end portion of the
inwardly bent marginal edge portion to form a rim out of the
restrained end portion, applying an exterior force to the initially
inwardly bent marginal edge portion, the force being sufficient to
direct the wall of the tubular member to flow further inwardly than
the diameter of the rim to obtain a wall having a second diameter
shorter than the initial diameter, and moving the exterior force
axially along and through a length of the tubular wall so that the
directing of the wall inwardly continues to occur throughout that
length and thereby forms a neck having the second diameter.
Desirably, an axial force is applied to both ends of the tubular
member to hold the tubular member steady while the rest of the
aforementioned steps are being carried out.
Thus it can be seen from the above description, and from the
appended claims, taken in conjunction with the drawings, that the
present invention provides a new and useful die necking assembly
and method for tubular can manufacture having a number of novel
advantages and characteristics, including those hereinbefore
pointed out and others which are inherent therein. It is
contemplated that certain changes and variations may be made by
those skilled in the art without departing from the spirit of the
invention or the scope of the appended claims.
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