Note: Descriptions are shown in the official language in which they were submitted.
11~7799
This invention relates to a battery grid casting
machine and method, and, more particularly, to a machine
and method for casting battery grids in a continuous
manner.
~t the present time battery grids are normally
cast individually in molds having separable mold sections,
the grid pattern cavity being machined as shallow grooves
in the opposed faces of the mold sections. The mold faces
in which the grid cavity is machined are periodically coat-
ed with a thin layer of powdered cork or acetylene smoke
which acts as an insulator to prevent the lead from chill-
ing before all of the grooves definig the grid pattern
are completely filled. The production of individual
battery grids in this manner is a relatively slow process
and requires a considerable amount of skill on the part
of the operator.
In recent years attempts have been made to cast
battery grids in a more rapid, continuous manner utiliz-
ing a rotary drum having the desired battery grid pattern
cavity machined into the outer peripheral surface of the
drum. Such continuous casting machines have presented
numerous problems, especially with respect to the diffi-
culty in obtaining complete filling of the shallow grooves
forming the grid cavity with molten lead while rotating
the drum at a reasonably rapid rate. Because of this
~ 4t7799
and other problems encountered, continuous casting of
battery grids with such drums has not enjoyed wide
commercial use at the present time.
The primary object of the present invention is
to provide a machine and method for casting battery grids
in a continuous manner which overcomes the problems here-
tofore encountered with such methods and machines.
More specifically, it is an object of this in-
vention to provide a machine and method for continuously
casting battery grids which utilize a rotary drum having
the grid cavity machined in the outer peripheral surface
thereof and in which complete and rapid filling of the
grid cavity is assured by directing the lead thereto
under substantial pre~sure and in an amount greatly in
excess of that required to fill the grid cavity as the
drum rotates.
The machine of the present invention includes
a shoe having a smooth arcuate surface conforming closely
to the outer cylindrical surface of the drum. The shoe is
held in fixed position against the outer periphery of the
drum while the drum is rotating so as to provide a smooth
sliding engagement therewith. An internal passageway in
the shoe extends to the surface of the drum and is connect-
ed to a source of molten lead under pressure and the out-
let is restricted by suitable means to maintaio the molten
1~4t77~9
metal flowing through the passageway under superatmos-
pheric pressure. This arrangement produces several
desirable advantages discussed hereinafter.
Other objects, features and advantages of the
present invention will become apparent from the follow-
ing description and accompanying drawings, in which:
FIG. 1 is a vertical sectional view of a battery
grid casting machine according to the present invention
taken on a plane transverse to the axis of rotation of
the casting drum;
. FIG. 2 is a plan view of a portion of the con-
: tinuous battery grid strip cast in the machine;
FIG. 3 is a sectional view taken along the line
3-3 in FIG. l;
FIG. 4 is a sectional view generally along the
line 4-4 in FIG. 3;
FIG. 4a is an enlarged view of a portion of the
arrangement shown in FIG. 4;
FIG. S is an enlarged sectional view of a por-
tion of the machine shown in FIG. l;
FIG. 6 is a fragmentary sectional view taken
along the line 6-6 in FIG. 5;
FIG. 7 is a sectional view of a modified form
of shoe on the machine;
FIG. 8 is a sectional view taken along the line
8-8 in FIG. 7; and
~4'77~9
FIG. 9, which is on the same sheet of drawings
as FIGS. 1 and 2, is a fragmentary side elevational view,
partly in section, of another modification of the machine.
Referring first to FIGS. 1 and 3, the machine
comprises a supporting frame 10 by means of which it is
mounted on the supporting structure 12 of a heated lead
pot 14. Frame 10 can be of any suitable construction
and, in the arrangement shown, includes a pair of spaced
channels 16 supported at their opposite ends for vertical
adjustment on upright threaded rods 18. A pair of pillow
blocks 20 on channels 16 support a shaft 22 to which a
ca~ting drum 24 is keyed. A suitable drive 26 is connect-
ed to shaft 22 for rotating drum 24 at the desired speed.
In the arrangement shown in FIG. 1 drum 24 is rotated in
a counterclockwise direction.
A pair of support bars 28 is mounted on shaft
22 at opposite sides of drum 24 by means of pillow blocks
30. Each support bar 28 has one end ~hereof fixed to its
adjacent channel 16 at a desired angle of inclination by
a screw 32. A pair of laterally spaced guide bars 34 is
mounted on support bars 28 by screws 36,38 which enable
the guide bars 34 to be adjusted toward and away from
support bars 28. Between guide bars 34 there is mounted
a shoe 40.
~ ~ .
~ a~
1~47~9
The desired pattern of the battery grid cavity
42 is machined in the smooth outer cylindrical surface of
drum 24. This grid pattern comprises a plurality of cir-
cumferentially extending grooves 44 and a plurality of
~, 5 transversely extending grooves 46. Grooves 44 are adapt-
ed to form the longitudinally extending wires 44a,44b and
the transverse grooves 46 are adapted to form the trans-
verse wires 46a,46b of the finished grid shown in FIG. 2.
The wires 44b and 46b are normally wider than the wires
44a and 46a and form the outer framework of the finished
grid. At one side of the grid the groove 44 is enlarged
to form the conventional solder lug 44c adjacent one end
of each grid. At each side thereof the grid cavity
terminates inwardly from the side edges of drum 24 so
that the laterally outer edge portions 48 of the drum 24
are in the form of smooth, continuous, cylindrical sur-
faces which lie in the same cylindrical surface as the
pads 48a bounded by grooves 44,46. In the embodiment
illustrated the drum 24 comprises a central web 50 with
a cylindrical flange 52 extending around the periphery
thereof. The grid cavity 42 is machined around the outer
face of flange 52.
~i:47799
Shoe 40 is in the form of a block of metal
having a smooth curved surface 54 which conforms closely
to and which i8 in sliding engagement with the outer
cylindrical surface portions 48,48a of drum 24. A smooth
sliding engagement between the curved surface 54 of shoe
40 and the outer peripheral surface of the drum 24 is ob-
tained by the adjustment of screws 36,38. In the embodi-
ments illustrated in FIGS. 1 through 6 and 9 shoe 40 has
an inlet 56 at one side thereof and an outlet 58 at the
opposite side thereof. An internal orifice slot 60 ex-
tending transver6ely acro6s shoe 40 and open at the
curved surface 54 thereof extends between inlet 56 and
outlet 58. Orifice slot 60 is of smaller cross section
than the inlet and the outlet and is connected thereto
at its OppO9 ite ends by upwardly angled passageways 62.
As shown in FIG. 6, the orifice slot 60 is co-extensive
in a direction transversely of drum 24 with the grid
cavity 42 therein. As shown in FIG. 3, a conduit 64 ex-
tends downwardly from inlet 56 into the molten lead in
pot 14 and is connected with the outlet of a pump 66.
A suitable drive shaft 68 extending upwardly from the
pump is provided for driving the pump at the desired
speed. A similar conduit 70 extends downwardly into the
lead pot 14 from outlet 58 and discharges into the lead
pot through a restricting valve 72, the amount of restric-
tion provided by valve 72 being adjustable by control rod
~147799
74. Valve 72 allows adjustment of the rate of lead flow
and back pressure in orifice slot 60.
The liquid level in lead pot 14 is designated
by the broken line 76. It will be noted that the lower
5 portion of drum 24 is spaced above the lead level 76 and
that the shoe 40 is partially submerged within the lead
in pot 14. Shoe 40 is provided with a plurality of cool-
ant passageways 78, each of which is located above the
lead level 76. In the arrangement shown three such
10 passageways 78 extend transversely through shoe 40 down-
stream of orifice slot 60 and one such passageway 78 ex-
tends transversely through shoe 40 upstream of orifice
slot 60. The upstream coolant passageway 78 is provided
to prevent molten lead from flowing in a clockwise direc-
15 tion from orifice slot 60 and di~charging from betweenthe drum and the upstream end of shoe 40O The terms
"upstream" and "downstream" are used with reference to
the direction of rotation of drum 24. Passageways 78
are connected by suitable piping 80 for conducting cool-
20 ant (such as water) through shoe 40. A thermocouple isalso preferably located in shoe 40 within a thermocouple
recess 82.
In operation drum 24 is rotated at a desired
speed and pump 66 is operated to provide a continuous
supply of molten lead alloy (for example at 70Q-800 F.)
1147799
to inlet 56. The interior of the drum flange 52 is
preferably cooled by air nozzles 84 so that the casting
surface of the drum will be maintained at a temperature
(for example 400-500~ F.) substantially below the solidi-
fication temperature of the alloy being cast. Thus, themolten lead directed into orifice slot 60 through inlet
56 from pump 66 is quickly chilled as it comes into con-
tact with the surfaces 48,48a and the grooves 44,46 on
the outer surface of drum 24. Since the drum is rotat-
ing in a counterclockwise direction, the lead which tendsto solidify on the surfaces 48,48a is scraped off of these
surfaces by the downstream edge 86 of orifice slot 60 and
tends to accumulate along this edge. However, since the
molten lead directed through the orifice slot 60 by pump
66 is far in excess of that required to fill the adjacent
portion of the rotating cavity, the continuous stream of
lead flowing through orifice slot 60 i8 maintained at a
relatively high temperature sufficient to melt, break-up
or remove the solidified lead scraped from the surface
of the drum. This rapid and continuous flow of high
temperature molten lead through the orifice slot 60 thus
prevents the solidified lead from building up along the
edge 86 and thereby prevents clogging of the orifice
slot 60. In addition, since valve 72 provides a restric-
tion for the free flow of lead back to the lead pot through
outlet 58, the lead in orifice slot 60 is maintained ata desirably high, superatmospheric pressure. This pres-
sure is sufficient to continuously feed and force molten
lead into the portions of grooves 44,46 that have rotated
upwardly past orifice slot 60. This assures a final and
complete filling of the grooves 44,46 even if the grooves
have voids therein after they rotate past the orifice
slot 60. Thus, the combination of the excessive lead
flow and the superatmospheric pressure on the lead being
directed into the grid cavity assures complete filling
of the successive portions of the grid cavity while still
maintaining a very rapid chill within the grooves. The
rapid chill results in a very fine and uniform grain struc-
ture in the lead alloy. This ~ery fine grain structure
is excellent in cast battery grids because of its resis-
tance to corrosion.
As the filled portions of grooves 44,46 rotate
upwardly in a counterclockwise direction they advance
along the portion of shoe 40 cooled by the coolant passage-
ways 78 on the downstream side of orifice slot 60. Thus,the temperature of the lead in these groove~ is progres-
sively lowered such that, aq it emerges from the down-
stream end of the shoe, the lead has solidified into a
continuous strip having the battery grid pattern. The
strip S is preferably stripped from the top side of the
77~
drum so that it will have cooled to a sufficiently low
temperature to assume a sufficiently rigid condition to
permit easy handling. The grid strip is cooled substan-
tially after it emerges from between the shoe and drum
by the nozzles 84 which direct streams of air against
the interior and exterior surfaces of flange 52 as these
surfaces rotate past the shoe and before the grid is
stripped therefrom. Thereafter, strip S is advanced to
a die (not illustrated) which shears it into individual
battery grids.
In a typical machine according to the present
invention the drum has a diameter of about 18 inches, a
width of about 3-1/4 inches and is rotated at about 20
R.P.M. to produce a lineal speed of 94 feet per minute.
The battery grids are cast from a lead alloy containing
about .0~/O Ca and .3% Sn and have a length of 5-1/2
inches, a width of 2 inches and a thickness of .035
inches. Each grid weighs about 18 grams and the grid
strip weighs about .085 pounds per foot. At a lineal
speed of 94 feet per minute the grid strip uses about
8 pounds of alloy per minute. Pump 66 has a capacity
of about 45 pounds per minute and can be operated at
full capacity or its inlet can be adjusted so that the
pump delivers somewhat less than its full capacity de-
pending upon the setting of restrictor valve 72. Theshoe 40 has a length of about 4 inches and a width of
10 .
1~t7799
about 3-1/4 inches. The orifice slot 60 has a width of
about 3/8 inches, a depth of about 5/16 inches and is
located about 1 inch from the upstream end of the shoe.
The lead pot is heated to a temperature of be-
tween 750 to 800 F. With cooling water at about 70 F.
and the air nozzles as shown, the temperature of the shoe
stabilizes at about 575 F. and at the outer surface of
the drum at about 450 F.
While these relative dimensions and other para-
meters are given by way of example and are not critical,
several basic considerations are important. For example,
it is very important to maintain a close sliding fit be-
tween the curved surface 54 of the shoe 40 and the outer
peripheral surface of the drum. Since the temperature of
the shoe differs substantially from the temperature of
the drum and since the temperatures o each vary somewhat
at different sections thereof, the length of shoe 40
should be maintained at a minimum consistent with rela-
tively fast solidification of the grid strip in order to
assure close sliding contact between them. Furthermore,
a longer shoe requires the application of a greater clamp-
ing force to the drum to obtain the proper close fit
therebetween and results in excessive friction. A rela-
tively narrow orifice slot is also desirable to prevent
- 25 the temperature of the drum from becoming excessively
11 47799
high at the section thereof contacting the shoe. Further-
more, it is important that the upstream end of the shoe
and the portion of the drum in contact therewith be main-
tained at temperatures sufficiently low to prevent the
pressurized molten lead from leaking out therebetween.
The amount of molten lead delivered by the pump must be
sufficiently in excess of the amount required to fill the
grid cavity to maintain the temperature of the lead in
the orifice slot sufficiently high to melt and wash away
the lead that solidifies against the outer smooth sur-
face portions of the drum. In addition, the pressure on
the molten lead in the orifice slot must be sufficiently
high to force the lead up into any voids or past any
lead blockages that might occur in the cavity grooves
44,46 as they rotate upwardly past the orifice slot.
The shoe 88 shown in FIGS. 7 and 8 differs
only slightly from shoe 40 previously described. In
shoe 88 two molten lead passageways 90,92 extend trans-
versely through the shoe. At one end these passageways
are plugged. At the opposite end one of these passage-
ways is connected to an inlet pipe extending from pump
66 and the other passageway is connected to an outlet
pipe extending to the restriction valve 72. At the
curved surface 94 of the shoe 88 an orifice slot 96
similar to orifice slot 60 is machined. However, orifice
~147~9
slot 96 is closed at its opposite ends. A plurality of
two sets of oppositely inclined passageways 98,100 ex-
tend, respectively, from passageways 90,92 to the ori-
fice slot 96. Thus, referring to FIG. 8 and assuming
that passageway 90 is the inlet passageway and passage-
way 92 is the outlet passageway, the molten lead is
directed as a continuous stream which flows upwardly
through the inclined passageways 98 into the orifice
slot 96 and then downwardly from orifice slot 96 into
the discharge passageway 92 and back to the lead pot
through the restriction valve 72. It will be observed
that, whether the lead passageways through the shoe are
formed in the manner illustrated in FIGSo 1 through 6
or in the manner illustrated in FIGS. 7 and 8, the ori-
fice slot is connected in series relation with the in-
let and the outlet of the lead recirculation path. Thu~,
the hot molten lead continuously recirculates throughout
the entire length of the orifice slot. This constant
flow of molten lead at high temperature and superatmos-
pheric pressure prevents e~cessive chilling and leadbuild up on the locali~ed surfaces of the drum against
which the molten lead is directed. It also insures that
the solidified lead scraped off the drum by the down-
stream edge of the orifice slot will be melted, broken
up or otherwise removed to prevent clogging of the
13,
~1477~9
orifice slot and incomplete filling of the grooves form-
ing the battery grid cavity.
The arrangement shown in FIG. 9 differs from
that shown in FIG. 1 in that the shoe 40a is located at
the top side of drum 24 rather than at the bottom side
thereof. When the shoe is located so that it is not
partially submerged in the molten lead in pot 14, the
temperature thereof is maintained at the relatively high
value required by means of auxiliary heaters 102. In
other respects the construction and operation of the
modification shown in FIG. 9 are substantially the same
as in the embodiments previously described.
In each of the embodiments illustrated it will
be noted that the drum is located out of contact with the
molten lead in the lead pot. This is desirable not only
from the standpoint of maintaining the drum at a desir-
ably low temperature to produce rapid solidication, but
also because, if the drum is wetted by the lead bath,
oxides and other contaminants form, collect or build up
on the outer peripheral surface of the drum. It will
also be noted that the lead flows between the lead pot
and the orifice slot in the completely closed path. This
substantially completely eliminates the tendency for the
formation and entrainment of oxide films and particles
in the molten metal being cast.
lA
