Note: Descriptions are shown in the official language in which they were submitted.
CA 02459031 2004-11-03
HIGH TORQUE BATTERY TERMINAL AND METHOD OF MAKING
SAME
FIELD OF THE INVENTION
This invention relates generally to battery terminals and an improved method
of
making battery terminals by cold forming. Cold forming battery terminals is
disclosed
herein through the process of forming a lead slug into a cylindrical cup and
then
punching out the end of the lead slug while expanding the lead slug radially
outward
into a die having the shape of a finished battery terminal.
The present invention comprises improvements to the aforementioned process
by permitting one to cold form a battery terminal with a necked down region
extending
around the flanges of the battery terminal.
BACKGROUND OF THE INVENTION
The process of cold forming metals is well known in the art. Typically a
deformable or malleable metal is deformed at room temperature through a series
of
compression and/or expansion steps. Cold forming has been used to form various
articles including automotive items such as spark plug housings and battery
terminals.
Typically, spark plug housings are made of steel alloys and other articles,
including
battery terminals, are made of softer metals such as lead or lead alloys.
While cast
battery terminals have been used satisfactorily, cold formed battery terminals
may be
preferable since the working of the metals during the cold forming process
appears to
remove air pockets. The result is a more dense terminal that hinders
electrolyte from
escaping through the terminal. Although lead can be cold formed quite readily
the
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2
leak-proof sealing of lead terminals to battery containers after the terminal
has been
formed is difficult since the battery terminal also needs to have a leak-proof
seal
between the terminal and the battery wall. Sealants have now been developed
that
enable battery manufactures to seal cold formed battery terminals to the
battery
container in a leak-proof relationship.
The present invention provides a process for cold forming a lead slug into a
finished battery terminal with a necked down region that can be directly
inserted into a
battery container.
SUMMARY OF THE INVENTION
According to one aspect of the present invention there is provided a process
of
cold forming a finished battery terminal by:
placing a lead slug having a first end and a second end between two dies, one
of the two dies comprising at least two die segments;
forming a die chamber in the shape of a battery terminal around the lead slug
by radially closing said at least two die segments around the lead slug;
punching out the first end of the lead slug by forcing the end of a punch
through the end of the lead slug;
driving the end of the punch through the lead slug to force excess lead out of
the die chamber;
continuing to drive the punch through the first end of the lead slug until the
excess lead is sheared from the first end of the lead slug;
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deforming the lead slug into the shape of a finished battery terminal defined
by
the die chamber;
separating the die segments around the lead slug so that the die chamber is
free of the external features of the finished battery terminal; and
ejecting the finished battery terminal from the die chamber.
According to a second aspect of the present invention there is provided an
apparatus for forming a finished battery terminal comprising:
a first die having a cavity in the shape of one portion of a battery terminal;
a first stationary die case for supporting the first die;
a second segmented die having a cavity when closed in the shape of another
portion of a battery terminal;
an ejector sleeve having a central opening therein, said ejector sleeve
slidable
with respect to said first stationary die case for ejection of a finished
battery terminal
from said first die;
a stepped punch pin for forming a finished battery terminal when said second
segmented die is collapsed around a lead slug, said stepped punch pin having a
first
region for punching out the end of the lead slug located in said segmented
die, said
stepped punch pin having a second region for sealing one end of a chamber
containing the lead slug, and for severing waste material from the lead slug,
said
stepped punch pin including a third region for radially expanding the
remaining portion
of the lead slug into a finished battery terminal as said stepped punch pin is
driven
into said lead slug so that after said stepped punch pin forms the finished
battery
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4
terminal said stepped punch pin can be withdrawn from the finished battery
terminal
and said second segmented die can be expanded radially to allow said second
segmented die to move free of the finished battery terminal.
According to a further aspect of the present invention there is provided a
process of cold forming a finished battery terminal having a necked down
region on a
flange extending outward from the battery terminal comprising:
placing a lead slug having a central axis, a first end, and a second end,
between two dies having a die cavity in the shape of a semi-finished battery
terminal;
radially expanding the lead slug outward into the die cavity to partially fill
the
die cavity to thereby form a semi-finished cold formed battery terminal having
a
partially radially extending flange; and
driving a third die into the radially extending flange to complete formation
of the
flange with a necked down region comprising a groove in the flange to thereby
form a
finished battery terminal with a flange having a necked down region.
According to yet another aspect of the present invention there is provided an
apparatus for forming a finished battery terminal comprising:
a first die having a cavity in the shape of one portion of a semi-finished
battery
terminal;
a second die having a cavity in the shape of another portion of a battery
terminal, said second die being movable relative to said first die;
a step-punch for driving into a radially expanding a lead slug, said step-
punch
having a central axis, said step-punch having a first surface;
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a third die axially slidable with respect to said step-punch so that when said
step-punch is driven into the lead slug to form a semi-finished battery
terminal said
third die deforms the lead slug in an axial and radial direction to thereby
form a
finished battery terminal with a necked down flange.
A battery terminal is produced with high torque resistance utilizing three
sided
frusto-conical terminal recesses that coact with mating protrusions extending
from the
battery container. The method may comprise a horizontal cold forming process
to
form a finished battery terminal from a preworked lead slug by driving one end
of a
punch through the slug so that the one end forms an axial opening through the
slug
and removes excess material, a first and second portion of the punch closes
the die
chamber and a third portion of the punch radially expands the lead slug into a
completed or finished battery terminal. The dies for forming the battery
terminal
include a movable four-segmented die for collapsing radially inward around the
slug
and a frusto-conical die for forming the top portion of the battery terminal.
An ejector
sleeve may remove the finished battery terminal after the cold-forming process
is
completed. In addition the invention may include a cold-forming method of
making a
finished battery terminal with a necked down flange by first expanding the
metal
radially outward until the battery terminal the cavity is partially ~Iled with
metal and
then upsetting the metal to complete the deformation filling of the battery
terminal die
cavity and to simultaneously form a necked down region in the flange on the
battery
terminal.
BRIEF DESCRIPTION OF THE DRAWING
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Figure 1 shows a perspective view of a battery terminal inserted in a battery
cover;
Figure 2 is a cross-sectional view taken along lines 2-2 of Figure 1;
Figure 3 is a view taken along lines 2-2 of Figure 1 with the battery terminal
not
shown in section;
Figure 4 is a cross-sectional view taken along lines 4-4 of Figure 3;
Figure 5 shows a cylindrical metal slug for use to cold form into a battery
terminal in accord with the teaching of this invention;
Figure 6 shows the cylindrical slug of Figure 5 after its faces have been
squared off;
Figure 7 shows the cylindrical slug of Figure 6 with a cylindrical cavity or
recess
formed at one end;
Figure 8 is a cross-sectional view of a movable die case and a coacting
stationary die case for cold forming the slug into a battery terminal with the
dies
located in the open position;
Figure 8A is a view of the movable die case taken along lines 8A-8A of Figure
8;
Figure 9 is a view of the movable die case and the coacting stationary die
case
of Figure 8 in a partially closed position;
Figure 10 is a view of the movable die case and the coacting stationary die
case of Figure 8 in a further closed position;
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Figure 11 shows the movable die case and the coacting stationary die case of
Figure 8 in an open position after formation of a battery terminal;
Figure 12 shows the movable die case and the coacting stationary die case of
Figure 8 in the ejection position;
Figure 13 shows an enlarged view of the retaining lip for removing waste lead;
Figure 14 shows an enlarged view of the lead slug prior to final deformation;
Figure 15 shows the lead slug after final deformation just before the dies are
opened;
Figure 16 is a side view of the punch of the present invention;
Figure 17 is a cross sectional view of a lead slug cold formed in a shape of a
cylindrical cup,
Figure 18 is an enlarged sectional view showing a flash on a battery terminal;
Figure 19 is a cross sectional view illustrating transition zone forcing
excess
lead out of the die;
Figure 20 is a cross sectional view showing the punch forcing excess lead from
the die,
Figure 21 is a front view of a battery terminal having a flange with a necked
down region;
Figure 22 is a sectional view of the battery terminal of Figure 21 showing the
necked down region on the flange of the battery terminal;
Figure 23 is an enlarged view of a portion of Figure 22;
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Figure 24 shows two dies at the beginning of the stroke to cold form the
battery
terminal of Figure 21;
Figure 25 shows a die punch radialiy expanding the metal outward into a
flanged battery terminal cavity;
Figure 26 shows a slidable sleeve die at the beginning of the stroke to necked
down the flange on the battery terminal;
Figure 27 shows the slidable sleeve die at the bottom of its stroke; and
Figure 28 shows the slidable sleeve die in its retracted condition after
formation of the
finished battery terminal of Figure 27.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In Figure 1, reference numeral 10, generally identifies a cold formed high
torque lead battery terminal as it appears in a thermoplastic battery
container 11.
Figure 2 shows terminal 10 with a central or axial through passageway or
opening 14
which will be subsequently filled with molten lead to form a mechanical and
electrical
connection to a battery grid within the battery container.
Figure 2, Figure 3 and Figure 4 show battery terminal 10 integrally formed or
secured to battery container 11 in a torque resistant relationship by the
coaction of
terminal torque lock regions forming recesses 15 and a moldable container
material
19 such as a thermoplastic resin. Annular rings 19a of the container material
19 fill a
set of annular openings located between parallel spaced acid-sealing rings 16,
17 and
18 which extend radially outward from terminal 10. Battery terminal 10 has a
frusto-
conical shaped hollow top portion 12 with an outer facing 13 for forming
electrical
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connection with a battery connector. As viewed in Figure 2, an inward
projecting
member 20 (or a protrusion member) has a massive base since the member extends
vertically upward from annular cover member 20a that abuts against acid ring
16.
The result is protrusion members or inward projecting members 20 that are
vertically
restrained in container 11 by terminal ring 13a, and acid ring 16.
Figure 3 shows an end view of torque locks that form a series of three-sided,
general pyramid-like, recesses 15 in the skirt of battery post 10. The
recesses 15 are
characterized in that they have a base dimension W~ which is substantially
larger than
the top dimension W2 so that the mating protrusions in battery container
material 19,
which fit into recesses 15, have a massive support base which tapers toward a
narrower top.
Figure 4 shows a sectional view taken along line 4-4 of figure 3 to
illustrates
how the battery container material, which forms three-sided, pyramid-like,
inward
projecting members 20, projects into torque locks 15 to thereby form
circumferentially
spaced retaining lugs for locking battery terminal 10 to container 11. Torque
locks 15
are located circumferentially around terminal 10. Torque locks 15 are equal
distance
from one another with center lines CX extending through each of the torque
locks to
intersect at a central point P. The use of the torque locks 15 in battery
terminal allows
one to provide a substantially strong and rigid torque resistant support
between
battery terminal 10 and container 11. That is, tests have shown that by using
torque
locks 15 and three-sided, inward projecting members 20 extending from the
molded
container into the torque locks of a positive battery terminal produces such
tenacious
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1~
and integral connection between the container and the positive battery
terminal that in
some cases, when the top portion 12 is subjected to a twisting high torque the
top
portion 12 of the battery terminal shears off before the terminal twists free
of the
container.
In the preferred embodiment the inward projecting members 20 are spaced
circumferentially around the periphery of the battery terminal 10 and project
inward.
Twelve, three sided, inward projecting members 20 are located around the
periphery
of battery terminal 10 to integrally engage twelve torque locks on terminal
10.
The terminal 10 is readily adaptable to forming through a horizontal cold
forming process that converts an extruded lead slug into a finished battery
terminal for
mounting in a battery container. Figure 5 shows a cylindrical lead slug 40
formed
through a conventional extrusion process. Lead slug 40 has a cylindrical outer
surface
42, a first end 43 and a second end 41. The diameter of the slug is designated
by D~
and the length of the slug is designed by L~. Prior to forming slug 40 into a
finished
battery terminal the slug is worked and shaped to square up the ends and the
diameter of the slug so that the cold forming of the battery terminal can be
performed
in a single cold forming operation. In addition the pre-working of the lead is
desirable
since the lead cold forms better if the lead has been pre-worked.
Figure 6 shows lead slug 40 after further partial pre-working. Slug end faces
41
and 43 have been squared while the diameter D2 remains substantially the same
as
diameter D~. As a result of the end squaring process, the length L2 of slug 40
may be
slightly shorter than the length L~ of the slug prior to the pre-working step.
CA 02459031 2004-11-03
Figure 7 shows the cylindrical lead slug 40 after the final pre-working step
that
produces a slug for cold forming. During the final preworking step a
cylindrical punch
has been directed into a central portion of end 41 of slug 40 to produce a
cylindrical
cavity 43 that extends about half the depth of the lead slug with a diameter
D4. In this
step, slug 40 increases in length because the punch forces the lead in the
central
portion of the slug to flow onto the end of the slug as the lead slug is
confined by a
cylindrical chamber (not shown) of diameter D2. After the final pre-working
step slug
40 has an outer diameter of diameter D2 and a cavity of diameter D4. After the
final
preworking steps the slug is now ready for cold forming into a finished
battery
terminal. As pointed out the purpose of the preworking of the lead slug is to
prepare
the metal for cold forming since preworked metal is easier to cold form. In
addition the
cold forming produces suitable dimensions on the lead slug to permit the cold
forming
process through coaction of a die and punch. While slug 40 is shown with a
cavity 43
that extends about half way into slug 40, the cavity 43 may be formed in.
different
depths. In certain applications, cavity 43 could extend completely through the
lead
slug and in other applications lead slug 40 can be processed without any
cavity.
Figures 8 through 12 show the process of forming the pre-worked cylindrical
lead slug 40 into a battery terminal in greater detail. Reference numeral 50
identifies a
movable die case and reference numeral 70 identifies a stationary die case.
Reference numeral 49 identifies upper and lower members for moving movable die
case along central axis 48. Preworked lead slug 40 is shown located on end 57
of a
punch 52 which includes numerous cylindrical stepped sections as well as
frusto-
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12
conical connecting regions. Punch 52 includes a cylindrical end face 53, a
frusto-
conical connecting region 54, a cylindrical section 55, a further frusto-
conical
connecting region 56, a cylindrical section 57 having an end surface 58. The
diameter
of section 57 is slightly more than the diameter D4 so that lead slug 40 is
maintained
on punch section 57 through frictional engagement between slug 40 and punch
section 57. Punch 52 is powered by a source (not shown) and slides within a
sleeve
63 which sliding supports a four-part radially collapsible die section 50a
which is
axially displaceable in die case 50. Quadrant segments 60 and 61 of die
section 50a
are shown in figure 8. Figure 8A shows an end view of movable die 50 to
illustrate all
four segments 60, 61, 62 and 63. Die segments 60, 61, 62 and 63 slide on
frusto
conical surface 64 to permit each of the die segments to be displaced axially
and
radially around lead slug 40. A set of radial pins 50c, 50d, 50b, and 50e
extend inward
to act as stops for the die segments, a set of cross pins 60a, 61 a, 60b, and
61 b, act
as lateral guides to permit the die segments to move radially inward while
maintaining
alignment with each other. The front of movable die case 50 contains a frusto
conical
guide surface 64 so that die segments 60, 61, 62 and 63 can be collapsed
around
slug 40. While the die segments 60, 61, 62 and 63 can be collapsed around lead
slug
40 the die segments 60, 61, 62 and 63 do not do any deforming of the lead slug
40
during the collapsing step. That is the die segments 60, 61, 62 and 63
collapse to
form a die chamber having the shape of the lower portion of a battery terminal
which
contains the protrusions and recesses to form acid sealing rings 16, 17 and
18.
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13
The companion to movable die case 50 is stationary die case 70, which
includes an outer member 71 and a die 72 for forming the top portion 12 of a
battery
terminal. Die 72 contains a frusto-conical section 73 which forms the cavity
73 for
forming the top portion of a battery terminal. An ejector sleeve 74 slides
within die 72.
Ejector sleeve 74 includes an end surface 74a, a first inner surface 75 and a
second
inner surface 77 of slightly larger diameter. A waste retaining lip 76
connects first
inner surface 75 and second inner surface 77. Located to the right of ejector
sleeve
74 is a passage 78 for discharging lead removed during the cold working of the
lead
slug. The end of die 70 includes members 80 which abut against the closed four
split
die segments 60, 61, 62 and 63 when die 50 is moved axially against stationary
die
70. Figures 9 and 10 illustrate the cooperative relationship of die 50 and die
70.
Figure 9 shows lead slug 40 confined in the die segments 60, 61, 62 and 63 and
die
section 72. An end of slug 40 is shown partially displaced by end 58 of punch
section
57. Punch section 57 is completing the formation of a through hole in lead
slug 40 by
forcing a portion 40a of lead slug 40 through the interior of ejection sleeve
74. During
this first through hole punching phase with cylindrical punch section 57 lead
slug 40 is
not radially expanded outward although the die segments 60, 61, 62 and 63 and
die
section 72 do not prevent radially outward deformation of lead slug 40.
Figure 10 illustrates the cold forming process in a more advanced state with
slug 40 radially deformed and separated from excess lead 40a. Figure 10 shows
that
cylindrical punch section 55 has radially expanded the hollowed lead slug
radially
outward into die segments 60, 61, 62 and 63 and die section 72 to form a
finished
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14
battery terminal. Waste lead 40a is located on the inside of ejector sleeve 74
and
pushes waste lead slugs 40b located in ejector sleeve 74. In operation, waste
lead
40c is pushed out of ejector sleeve 74 by waste lead 40a and waste lead 40b as
shown in figure 10. Waste lead 40c falls out passage 78.
Figure 11 illustrates movable die 50 in a retracted position with lead slug 40
formed into a finished battery terminal which is frictionally held by the
sides of die
section 72 of die 70.
Figure 12 illustrates ejector sleeve 74 forcing finished battery terminal 40
out of
stationary die 70.
Thus, in the process of the present invention, a cylindrical cupped shaped
lead
slug is placed into a die and in a single operation a stepped punch forms a
through
opening in the lead slug, removes excess lead from the lead slug and radially
deforms
the remaining portion of the lead slug into a finished battery terminal ready
for
mounting into a battery container.
To understand the operation of the removal of waste lead 40a with ejection
sleeve 74, refer to Figure 13 which is an enlarged view of interior
cylindrical surfaces
74 and 75 which are connected by a cylindrical lip 76. The purpose of lip 76
is to
provide a means for catching the waste lead 40a so that as pin 57 is withdrawn
from
slug 40 lip 76 prevents waste slug 40a from being pulled back with punch 57.
During the cold forming process the punch and ejector sleeve coact so that the
proper amount of lead remains within the dies during the final cold forming
phase.
Figure 14 illustrate the final expansion of the lead slug as the first portion
of cylindrical
CA 02459031 2004-11-03
1S
punch 55 seals off one end of the die chamber around lead slug 40. Figure 14
shows
an enlarged view of lead slug 40 at the moment the die chamber for forming the
lead
slug into a battery post or terminal is completely confined. The cylindrical
punch
surface 55 has an outside diameter that closely fits within the opening of
ejector
sleeve 74 to seal off one end of the die chamber for the lead slug. That is,
when frusto
conical base surface 56 (region 56a) engages the inner surface 75 of ejector
74 it
completely seals off one end of the die chamber for lead slug 40 as well as
shears
waste lead 40a from slug 40. Similarly, punch face 53 completely seals off the
opposite end of the die chamber. Figure 14 shows that at the moment of
beginning
shear of the waste lead portion 40a , the base section 53 of punch pin 52 is
spaced a
distance x from the final position. That is, prior to the final expansion of
lead slug 40
waste lead 40a is separated from lead slug 40 and the die chamber is sealed at
both
ends. Even though the die chamber around the lead slug is sealed off there is
sufficient amount of punch pin travel left before the final radial expansion
and
deformation of lead slug 40 is completed. That is, the portion of lead slug 40
remaining in the chamber has in effect been measured for the proper amount of
lead
for the final compression phase. During the final compression phase punch face
53
may travel the complete or partial distance x to complete the final formation
of the
battery terminal. Since lead is relatively deformable but incompressible the
pressure
on the die dramatically increases when the lead fills the closed die chamber.
To
prevent breaking of the dies pressurized chambers with a compressible gas (not
shown) are used to close segments 60, 61, 62, and 63 so that sufficient
pressure can
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16
be applied to pin 52 to produce the final deformation of lead slug 40.
Consequently,
this ensures that sufficient pressure is applied to lead slug 40 to completely
deform
slug 40 into a finished battery terminal.
While the present process is shown with regard to a cylindrical slug that is
formed into a cylindrical terminal the process is equally well suited for
forming battery
terminals with lateral extending members as shown in U.S. Patent 4,662,205.
Figure 16 reference numeral 52 identifies the improved step punch which is
generally shown in Figures 8-12. At the front portion of punch 52 is a frusto-
conical
section 56 which forms a transition section between and cylindrical section 57
and the
intermediate cylindrical section 55 of punch 52. It has been discovered that
controlling
the transition cone angle theta on punch 52 generally reduces the flash
present in the
finished part.
To illustrate flash in a battery terminal, refer to Figure 18 which shows an
enlarged portion of the battery terminal 12 with flash 101 extending outward
from the
inside comer of terminal 12. Typically, flash 101 comprises a thin section of
extruded
metal which extends radially inward a distance y and downward a distance x.
While
the size of the flash may vary, the typical flash may have an x dimension of
.005
inches and a y dimension of .005 inches with a thickness z of .0001 inches.
Since the
internal region 103 is to be filled with lead, the presence of flash 101 in
the interior
region normally causes no problems. However, if the terminals are handled
roughly,
flash 101 may flake off and fall into the plastic used to mold the battery
cover around
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17
the battery terminal, thereby creating the possibility for introducing a short
in the
battery.
The improvement in the process comprises a method and means for
eliminating the flash. One of the known ways to eliminate flash is to have the
exact
amount of lead necessary to expand into die 130. Another is to have the lead
positioned in the die so it uniformly fills the die during the cold forming
process.
Unfortunately, precisely controlling the amount of lead to fill up the die is
difficult to do
during a cold forming process.
An alternate approach is to form a lead slug with a known amount of excess
lead and then remove the excess lead during the cold fanning process. In the
present
process, excess lead is removed in two steps. First, the end of the
cylindrical lead
slug is punched out and then the remaining excess lead is forced out in an
annular
shaped member extending around pin 52. It should be pointed out that slug 100
(Figure 17) is shown having a bottom thickness designated by bt. The purpose
of
having a cylindrical bottom 100a is to facilitate handling of the lead slug
during the
forming steps; that is, the bottom section 100a of slug 100 allows end of pin
57 to
positively engage slug 100 and force the slug to seat against the end of
sleeve 74
(Figure 9 and 19). Once seated, the end 100a of slug 100 is removed as the end
of
pin 57 continues forward to remove the excess lead in the shape of a
cylindrical plug
100a (Figure 19). Thus, it is envisioned that if other means were used to seat
slug 100
in the die, one could use an annular slug rather than a cylindrical cup-shaped
slug for
radial deformation of a battery terminal in die 130.
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While flash is a problem in cold forming parts, one of the additional problems
in
closed cold deformation of a lead slug and particularly in high speed cold
forming of
parts is that air may not be completely purged from the die prior to closing
the die.
Consequently, local irregular deformation of the cold formed part may occur.
To
alleviate the problem of local deformation due to trapped air, we provide
peripheral
spaced elongated die vent holes proximate the end of the die where excess
material
is forced out Figure 19 shows die 130 and multi-step punch 52 coacting to
radially
expand lead slug 100 into a battery terminal. In Figure 19, punch 52 is shown
with a
portion of the forward travel of the punch yet to be completed, and Figure 20
shows
punch 52 with the forward travel completed. Figure 19 illustrates that during
the radial
expansion process, excess lead 101 extends in an annular shaped section 101
and is
forced forward of section 56 as punch 52 moves forward.
Located peripherally around die 130 are a series of narrow, elongated vent
passages 120 and 121. Vent passage 121 connects to a larger discharge passage
123, and vent passage 120 connects to a larger discharge passage 122. The vent
passages are narrow to allow air to escape and are placed at the end of the
die to
prevent the vent passage from acting as a die cavity. Typically, vent passages
120
and 121 may have a width of up to 0.125-inches but have a depth dX of only
about
0.0005-inches. The small depth vent passages allow air to escape and thus
avoid
local deformation as a result of air trapped within the die. While only two
vent
passages are shown, one may prefer to radially space more or less vent
passages.
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19
Typically, four to six vent passages radially spaced around die 130 provide
means for
removing trapped air from the die.
Figure 19 illustrates another feature of the process. Note, end plug 100a
located on the end of pin 57. End plug 100a was forced out of the bottom of
slug 100
(Figure 17) to provide an annular slug 100 for radially expansion within die
130. Due
to the rapid forward motion (indicated by arrows) of pin 52, end plug 100a is
forced
outward of ejector sleeve 74 and drops off the end of pin 57 (Figure 20) as
pin 52
reaches the end of its forward travel. Thus, a first portion of excess lead
100a is
removed from slug 100 by pin 57 with a shearing or punching process. The
second
portion of excess lead removed from slug 100 comprises annular lead member 101
(Figure 19) which is being formed around transition section 56 as lead is
being forced
radially outward and forward in front of section 56. As punch 52 continues its
forward
journey, annular waste lead member 101 is sheared from the end of slug 100 by
co-
action of punch section 55 with die 130 and the end of sleeve 74. Extending
centrally
through punch 52 is a central axis 110. Central axis 110 is concentric with
die 130 and
sleeve 74. Figure 19 shows frusto-conical transition section 56 located
between and
smoothly connecting cylindrical pin sections 55 and 57 to each other. The
transition
zone 56 is maintained at an angle theta which is less than 15 degrees.
Preferably an
11 degree transition angle is preferred.
It has been discovered that the larger the angle theta, the greater the
pressure
build-up in the die and the great the chances for flash occurring during the
cold
forming of the terminal through a radial expansion process. On the other hand,
the
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20
less the transition angle, the longer the transition zone 56. To avoid the
transition
zone from extending too far and consequently extending the required length of
travel
of pin 52, it is preferred to have the transition angle theta a minimum of
about 8
degrees.
It has been found that with a transition zone 56 of about 11 degrees, the
excess metal 101 is sheared from the end of terminal 101 without creating
excess
deformation forces that force metal in the form of a flash between the outside
of a die
section 55 and the interior sleeve 74. While the optimal transition zone angle
may
vary with different components, one can readily determine the proper angle by
observing the finished part. If the finished put is not completely filled out,
the transition
angle may be too shallow. Conversely, if the transition angle is too high,
excessive
deformation pressure is provided in the die forcing flash from parting
surfaces
between die 130 and sleeve 74.
While cold forming of battery terminals is preferred, there are certain
battery
terminal configurations which can not be cold formed to the proper dimensions.
This is
particularly true of battery terminals which have an outer flange with some
type of a
groove or acid-sealing ring located on the underside of the flange. Figures 21
and 22
illustrate such a battery terminal which is difficult to cold form. Figure 21
shows a side
view of such a battery terminal, and Figure 22 shows a cross sectional view of
the
terminal.
Figure 21 shows the battery terminal 150 having a frusto-conical top 151, a
radially extending cylindrical flange 152 with a radial extending cylindrical
skirt 153
CA 02459031 2004-11-03
21
located therearound. A series of rectangular shaped lugs 154 extend downward
from
flange 152 and radially outward from lower terminal section 155.
Figure 22 shows a V-shaped groove 156 extending completely around the
underside of flange 152. The presence of the V-shaped groove 156 creates
problems
in conventional cold forming of battery terminals. That is, in the process of
cold
forming battery terminals, the lead is deformed radially outward by a punch
until a die
cavity is completely filled, thereby forming the finished battery terminal.
For the lead to
be deformed radially outward for forming the battery terminal shown in Figures
21 and
22, the lead must not only flow radially outward but it must flow backward
around the
narrowed portion of the V-shaped groove 156. The V-shaped groove is shown in
greater detail in Figure 22. Note that flange 152 extends radially outward
with a skirt
153 located radially outward of groove 156. The arrows indicate the general
radial
outward flow of metal during the cold forming process. If the V-groove 156 is
not
present, the metal can be radially formed outward as illustrated in Figures 8-
12.
However, the deformation of metal around the apex of 156 in order to form
skirt 153
becomes difficult since excessive pressures are required which may cause
flashing
between the dies and, in certain instances, voids may be left in the cavity
resulting in
a defective battery terminal.
The present process provides a method and apparatus for cold forming battery
terminals which have a narrowed neck or necked down region located in the
flange of
the battery terminal. To appreciate the process of applicant's apparatus for
forming a
CA 02459031 2004-11-03
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battery terminal flange with a necked down region, reference should be made to
Figures 24-28.
Figure 24 shows a movable die 200 and a stationary die 201. Die 201 is similar
to die 70 and includes a die cavity 220 having a frusto-conical recess 221 for
forming
the top portion of a battery terminal. An injector sleeve 223, similar to
injector sleeve
79, is located in die 201 for injecting the finished part. Movable die 200
includes a
slidable punch 202. Punch 202 includes an annular end face 213, a cylindrical
section
203, a frusto-conical connecting region 205, a further frusto-conical region
206, and a
cylindrical section 207 having an end surface 216.
The diameter of section 207 is slightly larger than the inside diameter of the
lead slug 150 so the lead slug is maintained in frictional contact on punch
section 207
through frictional engagement between slug 150 and punch section 207. Punch
202 is
powered by a source not shown and slides within a sleeve 263.
Located on pin 202 is a sleeve die 204 for forming the annular V-shaped
groove in the underside of the battery terminal flange as well as the locking
lugs
located around the periphery of the battery terminal shown in Figures 21 and
22.
To understand the process of forming a finished battery terminal in a two-step
operation, reference should be made to Figures 24-28. Figure 24 shows lead
slug 150
held on pin 207 in a position between die 200 and 201. In this position, the
slug is
ready to begin the process of deformation.
Figure 25 shows the die 200 abutting against die 201 with punch 202 extending
inta and through lead slug 150. Figures 25 shows lead slug 150 being forced
radially
CA 02459031 2004-11-03
23
outward into the cavity 221 a. The end of slug 175 is shown being forced out
of die
201. In the condition shown in Figure 25, the end of die sleeve 204 rests
against
punch end face 213 through the action of a compression spring 215 located in
annular
chamber 216. Note that in the position shown in Figure 25, the metal 150a only
partially fills the battery terminal cavity 221 a.
Figure 26 illustrates the beginning of the formation of the neck in the flange
area of a battery terming. Note that die sleeve 204 is moved forward a
distance xp by
cylindrical end face 213. Spring 215 compresses to allow forward motion of die
sleeve
204. The lead 150b located radially outward forms flange 152 with the slidable
die 204
axially slidable along pin 202 to form the V-groove in the underside of flange
152.
Figure 27 shows pin 202 at the bottom of its stroke with sleeve 204 extending
a
distance noted by xf. Note that spring 15 is fully compressed in annular
chamber 216.
This is in a later portion of the stroke. The opposite end of sleeve 202
actually
deforms and necks down the flange 152 to form the V-shaped groove or acid ring
on
the underside of flange 152. With the die sleeve in the position shown in
Figure 27,
the battery terminal 150 is in the finished condition and is ready for use.
Figure 28 shows the dies 200 and 201 separated with the finished battery
terminal 150 ready for removal by ejector sleeve 223. Note that die sleeve 204
returns
to its retracted condition with compression spring 215 expanding to displace
die
sleeve 204 to the left into a position for forming another battery terminal.
