Apparatus and method of forming battery parts

This application is a division, of application Ser. No. 09/706,376, filed Nov. 3, 2000 and now issued as U.S. Pat. No. 6,363,996 which is a continuation-in-part of Ser. No. 09/170,247 filed Oct. 13, 1998 and now abandoned titled APPARUTS FOR AND METHOD OF PRESSURE CASTING BATTERY TERMINALS.

FIELD OF THE INVENTION

This invention relates generally to pressure casting of battery terminals and, more specifically to pressure casting of lead and lead alloy battery terminals to inhibit the formation of cracks and tears during and after the solidification of the battery terminal.

BACKGROUND OF THE INVENTION

Battery parts such as terminals, which are typically made of lead or a lead alloy, are usually cold formed in order to produce a battery terminal that is free of voids and cracks. If lead or lead alloy battery terminals are pressure cast, air is left in the battery terminal cavity in the mold so that as the lead solidifies, the air bubbles prevent the battery terminal from cracking. That is, the air bubbles act as fillers so the lead remains distributed in a relatively uniform manner throughout the battery terminal. Unfortunately, air bubbles within the battery terminals cause the battery terminals to be rejects as the air bubbles can produce large voids in the battery terminal. In order to minimize the air bubbles in the battery terminal, a vacuum can be drawn in the battery terminal cavity mold; however, although the vacuum removes air from the mold and inhibits the forming of air bubbles in the battery terminal, the battery terminals cast with a vacuum in the battery terminal cavity oftentimes solidify in an uneven manner producing battery terminals with cracks or tears which make the battery terminals unacceptable for use. The present invention provides a method of forming a battery part during a pressure casting part through volume shrinkage of the mold during various phases of the solidification process.

In one embodiment of the invention, a battery terminal is cast which is substantially free of cracks and tears by pressure casting a lead alloy while a vacuum is being applied to the battery terminal cavity. At the moment when the lead in the battery terminal cavity reaches the liquid-to-solid transformation stage, a piston is driven into the mold to rapidly reduce the volume of the mold for solidification. By precisely controlling the time of application of an external compression force to the molten lead in the battery terminal cavity, and consequently, the time at which the volume of the battery terminal cavity is reduced, one can force the molten lead or lead alloy in the flowable state into a smaller volume where the pressure on the battery terminal cavity is maintained. By maintaining the pressure on the battery terminal cavity during the solidification process, the battery terminal can be cast in a form that is free of cracks and tears.

In another embodiment of the invention, the mold for forming the pressure cast battery part is sealed off while the molten lead is still in the molten state and before the molten lead can begin to solidify the supply of pressurized lead is shut off and at the same time the internal pressure of the molten lead is increased by driving a piston into the molten metal. This process is suited for those applications where the entire mold can withstand the higher pressures. That is, when the liquid metal is in a molten state an increase in pressure of the molten lead throughout the mold and the maintaining of the increased pressure during solidification can produce a battery part free of tears and cracks. This process allows one to obtain greater molding pressure than is available with conventional pressure casting techniques.

In another embodiment of the invention, the cast battery part is subjected to at least a partial cold forming during the volume contraction step by rapidly driving a piston into the solidified cast battery part with sufficient force to cold form a portion of the lead in the battery part to thereby produce a battery part that is free of cracks and tears. This method is more suitable for those battery parts where one does not want to subject the mold to excessively higher pressures than the die casting pressures.

SUMMARY OF THE INVENTION

Briefly, the system comprises an apparatus and method for pressure casting a battery terminal wherein the state of molten lead is monitored so that when the molten lead enters a transformation stage from liquid-to-solid, the volume of the mold available for the lead to solidify therein is quickly reduced to thereby cause the molten lead to flow into the remaining volume while one maintain pressures on the molten lead. As the molten lead solidifies under the reduced volume and pressure, it produces a battery terminal that is substantially free of both tears and cracks. In another embodiment of the pressure casting of a battery terminal, the battery terminal is allowed to solidify in the mold, but before removal of the battery terminal from the mold a piston is driven into the battery terminal with sufficient force so as to at least partially cold form a portion of the battery terminal to thereby produce a battery that is free of cracks and tears. In a further embodiment of the invention the mold is sealed off while the molten lead is in a molten state and the pressure of the molten lead is increased and maintained until the molten lead solidifies.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1

is a partial schematic of a system for pressure casting of a battery terminal to inhibit the cracking or tearing of the battery terminal during the solidification process;

FIG. 2

is a diagram showing a portion of the mold and the piston that is driven into the runner of the mold;

FIG. 3

shows a portion of the system of

FIG. 1

with the piston in the extended position that produces a reduced volume for the solidification of a lead or lead alloy;

FIG. 4

shows an alternate system wherein a piston is maintained under pressure during the casting process;

FIG. 5

is a cross-sectional view showing a portion of a mold and a piston that is positioned having its end surface at the end surface of the mold cavity during the pressure casting process;

FIG. 6

is a cross-sectional view of

FIG. 5

showing the piston driven into the battery terminal to deform the metal into a shape free of cracks and tears;

FIG. 7

is a cross-sectional view showing a portion of a mold and a piston that is positioned having its end surface spaced from the end surface of the mold cavity during the pressure casting process;

FIG. 8

is a cross-sectional view of

FIG. 7

showing the end of the piston driven up to the end surface of the mold cavity to deform the metal into a shape free of cracks and tears;

FIG. 9

is a cross-sectional view showing a portion of a mold and a piston that is positioned having its end surface spaced from the end surface of the mold cavity during the pressure casting process;

FIG. 10

is a cross-sectional view of

FIG. 9

showing the end of the piston driven to a condition spaced from the end surface of the mold cavity to deform the metal into a shape free of cracks and tears;

FIG. 11

is a view of a battery terminal of

FIG. 10

with the pressure cast extension being sheared off;

FIG. 12

is a partial cross-sectional view of the piston of

FIG. 10

driving the sheared pressure cast extension from the mold cavity;

FIG. 13

is a front view of a two-metal battery connector;

FIG. 14

is a cross-sectional view taken along lines

14

—

14

of

FIG. 13

;

FIG. 15

is cross-sectional view of a mold and holding apparatus for pressure casting the battery connector of

FIG. 13

;

FIG. 16

is cross-sectional view of a mold and holding apparatus of

FIG. 15

with a pair of holding pins in the retracted position and the driving pins in the extended position;

FIG. 17

is a cross-sectional view of a pressure cast battery part with an extension pressure cast on the end of the battery with the length of the extension limited by the end of an annular drive punch;

FIG. 18

shows the battery part of

FIG. 17

with the annular drive punch driven into the extension to cold form the battery part free of cracks and voids; and

FIG. 19

shows a mold with a core pin and slidable collar for pressure casting a battery part and volume contraction of the battery part to provide a battery part free of cracks and tears.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to

FIG. 1

, reference numeral

10

generally identifies a system for pressure casting of a battery terminal or battery part to inhibit formation of cracks and tears in the pressure cast battery terminal or battery part. The system

10

incudes a source of pressurized molten lead

12

(which could be a source of pressurized alloy of lead) for directing molten lead under pressure into a mold

11

. Mold

11

has a battery terminal cavity

20

located therein with a runner

24

extending therefrom for supplying molten pressurized lead from pressurized lead source

12

to battery terminal cavity

20

.

System

10

includes a vacuum source

15

which is connected to a cold spot i.e. a spot that cools at a rapid rate and cools before the rest of the molten metal in the battery terminal cavity

20

. This enables the vacuum source

15

to evacuate the air from battery terminal cavity

20

through passage

21

prior to supplying molten lead to the battery terminal cavity

20

.

System

10

also includes a pressure sensor

16

having a probe

17

mounted in mold

11

with probe

17

mounted in position to form a portion of the mold surface surrounding the battery terminal cavity

20

. Pressure sensor probe

17

is preferably placed in a hot spot of the mold, i.e. a spot that cools at a slower rate. By placing the probe

17

in a portion of the mold that remains in a liquid state, one can monitor the pressure of the molten lead in the liquid state as the molten lead is supplied to battery terminal cavity

20

.

Located in slideable relationship in passage

25

is a cylindrical piston

23

for driving into runner passage

25

of mold

11

. A piston driver

13

, which carries piston

23

connects to mold

11

to hold piston

23

in an out of the way condition as molten lead is being forced into battery terminal cavity

20

. Piston

23

provides a mechanical means for reducing the volume available for solidification of the lead therein.

In order to control the operation of system

10

, a control unit

14

is included with system

10

. Control unit

14

connects to vacuum source

15

via electrical lead

14

a

and to pressure sensor

16

via electrical lead

14

b.

Similarly, control unit

14

connects to molten lead supply

12

through electrical lead

14

d

and to piston driver

13

through electrical lead

14

c.

The control unit

14

, which can be a computer with appropriate software, receives signals from pressure sensor

16

, which transmits the pressure of the molten lead in battery terminal cavity

20

. That is, as the molten lead from the pressurized lead source

12

fills the battery terminal cavity

20

, the pressure on probe

17

is continually transmitted to pressure sensor

16

and onward to control unit

14

. When the pressure in battery terminal cavity

20

reaches a predetermined level, control unit

14

sends a signal to piston driver

13

through electrical lead

14

c

which quickly drives piston

23

into passage

25

to simultaneously cutoff and seal passage

25

to prevent continued lead flow from runner

24

. As piston

23

plunges into the passage, it reduces the volume for the lead that is in the liquid-to-solid transformation stage. By reducing the volume of the lead during the liquid-to-solid transformation stage, one can compensate for the lead shrinking and contracting as the molten lead solidifies. Consequently, the finished cast product is free of the tears and cracks that would have a detrimental effect on the performance of the battery terminal.

The system of

FIG. 1

is described with respect to volume shrinkage during the liquid-to-solid transformation stage; however, the system of

FIG. 1

can also be used with the method of volume shrinkage when the molten lead is in the molten state. If the pressure of the molten lead is to be increased the vacuum source connected to the mold is sealed off while the lead is in the molten state. This leaves a closed mold with liquid molten metal having substantially the same pressure throughout the mold. Next, with the pressure of the molten lead being maintained by the source of pressurized lead

22

a piston

23

is driven inward to simultaneously shut off the supply of further molten lead while at the same time substantially increasing the liquid pressure throughout the mold. By increasing the pressure of the molten lead sufficiently the molten lead can solidify into a part free of cracks and tears. This process may not be used with all types of molds as it may not be feasible to build a mold to withstand the required high pressures throughout the mold. The required pressure of the molten lead to achieve a battery part free of cracks and tears will to a certain extend depend on the shape of the battery part and can be readily determined through trial and error.

Referring to

FIG. 2

, mold

11

has been opened to reveal a portion of mold

11

and piston

23

which are shown in perspective view in relation to a portion of battery terminal cavity

20

. Extending out of one side of mold

11

is piston

23

having a head

31

for engagement with a hydraulic cylinder or the like. Battery terminal cavity

20

is defined by a set of radial fins

34

that project into the battery terminal cavity

20

.

With system

10

one can pressure cast a lead battery terminal to inhibit formation of tears and cracks in the battery terminal. In order to inhibit the formation of tears and cracks in the cast battery terminal, the state of molten lead is continuously monitored so that when the molten lead enters the liquid-to-solid transformation stage, the volume of the mold available for the lead to solidify therein can be quickly reduced to force the lead, while it is still flowable, into the smaller volume. By rapidly reducing the volume and maintaining pressure on the molten lead during the critical liquid-to-solid transformation stage, one causes the molten lead to solidify as a solid terminal or battery part substantially free of tears and cracks. It should be pointed out that in the liquid-to-solid transformation stage, the lead is in a condition where it can flow and is sometimes referred to as a “mush”. Normally, as the molten lead goes through the liquid-to-solid transformation stage, the volume of lead contracts which results in a finished product that will have cracks or tears when it is completely solidified. The step of volume contraction at the moment when the lead is in the liquid-to-solid transformation stage produces a battery part when cooled that is substantially free of cracks and tears. This procedure is particularly useful where the battery cavity may have an unusual shape as the pressure produced by volume contraction can be transmitted throughout the part to produce sufficient pressure to prevent the formation of cracks and tears in the battery part.

Referring to

FIG. 1

to illustrate the operation of system

10

, the mold

11

is assembled with the battery terminal cavity

20

located within the mold. One end of a vacuum conduit

21

is attached to vacuum source

15

, and the other end of vacuum conduit

21

is attached to a location on the mold

11

which is referred to as a “cold spot”. That is, the lead in this portion of the mold is referred to as a “cold spot” as the molten lead in this region will solidify sooner than the molten lead being fed into the mold through runner passage

25

. Consequently, as the lead begins to solidify in the “cold spot” the solidified lead immediately closes the end of conduit

21

which prevents molten lead from being drawn into the vacuum source

15

. The location of a cold spot or cold spots will vary depending on the shape and size of the casting. For any particular shape battery casting, one can generally determine the cold spots by determining the regions of the mold that are less massive than others. If needed, one can also determine the cold spot through trial and error.

In addition to the position of a vacuum passage in mold

11

, one places a pressure probe

17

on the surface boundary of the battery mold cavity

20

in order to determine when the molten lead is in the liquid-to-solid transformation stage. While the temperature could be measured to determine when the lead reaches the liquid-to-solid transformation stage, the time lag between the actual temperature of the lead and the measured temperature may be sufficiently long so that the actual temperature of the molten lead may have cooled sufficiently so the lead is no longer in the liquid-to-solid transformation stage even though the temperature probe indicates that the temperature of the lead is in the liquid-to-solid transformation stage. However, by measuring the pressure using a pressure probe, one is able to obtain a pressure reading which can more quickly determine when the molten lead enters the liquid-to-solid transformation stage. By being able to more quickly determine the molten state of the lead, one still has sufficient time to active the piston driver

13

to drive the piston

23

into the molten lead and force the molten lead to flow into a reduced volume before the molten lead passes completely through the liquid-to-solid transformation stage.

With the system

10

in the condition shown in

FIG. 1

, the control unit

14

can activate the molten lead supply to deliver molten lead under pressures of 40,000 psi or higher to deliver molten lead to pipe

22

which delivers the molten lead under pressure to runner

24

. The molten lead flows in the directions indicated by the arrows in runners

24

and

25

. Note, in this condition piston

23

is located behind runner

24

so that molten lead flows from runner

24

to runner

25

and into battery terminal cavity

20

. While the molten lead is flowing into battery terminal cavity

20

, the vacuum source is removing air from battery terminal cavity

20

with the air flowing through vacuum source

15

as indicated by arrow in conduit

21

. As previously mentioned, air evacuation conduit

21

terminates at a cold spot indicated by reference numeral

29

while the molten lead enter battery terminal cavity at what is considered a hot spot

28

, i.e. an area where the lead solidifies last.

Once the molten lead enters the battery terminal cavity

20

, the molten lead fills up the battery terminal cavity and the lead in the cold spot

29

begins to solidify thereby preventing further molten lead from being drawn out of the mold and into conduit

21

. It should be pointed out that the size of the opening in the cold spot is kept sufficiently small so that the molten lead will solidify and quickly fill the open end of conduit

21

, yet the conduit

21

is sufficiently large so that the air can quickly be evacuated from the battery terminal cavity

20

.

As the vacuum passage

21

is sealed off, the pressure in the battery terminal cavity

20

begins to rise under the pressure of the molten lead supply. When the pressure reaches a predetermined level, which can be determined by the shape and size of the battery terminal being cast, the control unit

14

senses the pressure and sends a signal to piston driver

13

. Piston driver

13

includes a quick action hydraulic cylinder or the like which quickly fires piston

23

foreword, which simultaneously cuts off the supply of additional molten lead from runner

24

, while reducing the volume in which the lead will solidify.

If desired, the decrease in volume can be determined based on trial and error. That is, by observing the finished product for cracks and tears, one can determine if more volume reduction is necessary as insufficient volume reduction of the lead or lead alloy leaves cracks and tears in the finished battery terminal.

FIG. 3

shows a portion of system

10

with mold

11

. In the condition shown in

FIG. 3

the piston

23

has been driven into the passage

25

thereby cutting off the flow of additional molten lead through runner

24

. At the same time the end of piston

23

has forced the molten lead in passage

25

into the mold by pushing the molten lead ahead of end

23

a

of piston

23

. Thus the volume for molten lead to solidify therein has been decreased by forcing the piston end

23

a

proximate the battery terminal cavity

20

. In the preferred method, the piston end

23

a

is driven to the outer confines of the battery terminal cavity

20

thereby eliminating a protrusion on the battery casting. That is, the end

23

a,

when in the piston shown in

FIG. 3

defines the end of a portion of the battery terminal being cast therein.

FIG. 4

shows an alternate embodiment of my system that uses a piston

41

that is maintained under a predetermined pressure. The components of system

50

that are identical to the components in system

10

are shown with identical numbers. System

50

includes a housing

40

which is secured to mold

11

. Housing

40

includes a cylinder

42

that has a slidable piston

41

located therein. A chamber

43

is located above the top end of piston

41

. A high pressure source

45

connects to chamber

43

though conduit

46

. The control for high pressure

45

source comes from control unit

14

and through lead

14

e.

Piston

41

is shown in the slightly elevated condition and during the course of its operation the lower end

41

a

of piston

41

will move from a position flush with the surface of the battery terminal casting

20

to a position above the battery terminal casting

20

(shown in

FIG. 4

) and eventually again to a position where end

41

a

is flush with the surface of the lead battery terminal casting

20

.

In the embodiment shown in

FIG. 4

, the piston

41

is positioned in a hot spot in the mold. The lead is then injected under pressure into mold

28

though runner

24

. During this stage of the molding process the injection pressure of the lead builds to a level where the pressure of the lead in the mold is sufficient to force piston

41

upward as shown in FIG.

4

. As the mold begins to cool and the supply of lead to the battery terminal cavity is terminated, the pressure in the battery terminal cavity

20

begins to decrease. As the pressure in the mold decreases, it reaches a point where the pressure forces on the top end of piston

41

become greater than the pressure forces on the bottom end

41

a

of piston

41

. In this condition piston

41

is driven downward by the pressurized air in chamber

43

causing the volume available for the lead to solidify in to be reduced. As long as the piston

41

is located in a hot spot on the mold, the lead is forced into a smaller volume as it solidifies. Consequently, the reduction of volume causes the battery casting formed therefrom to be formed substantially free of cracks. If desired, one can ensure that the lead does not solidify in the area where the piston contacts the molten the piston by maintaining a temperature of the piston in excess of the molten lead in the mold.

FIG. 5

is a cross-sectional view showing a portion of a mold

50

in cross section. A battery terminal cavity

51

is shown therein having an upper cylindrical electrical contact surface

51

a

and a lower non-electrical contact surface

51

b.

The electrical contact surface is defined as the surface of the battery terminal that is mechanically clamped to a battery cable to transmit electrical energy from the battery terminal to the battery cable. The non-electrical contact surface

51

b

is the surface of the battery terminal that is either connected to the battery casing, remains free of contact with another part or is fused to another battery part Generally, the electrical contact surface should have a smooth and continuous finish for mechanically engaging a battery clamp thereto while smoothness and continuous of the non-electrical contact surface is less critical because there are no mechanical connections thereto. Mold

50

includes a blow hole or vent passage

56

for removing air from the battery mold cavity. Depending upon the conditions of molding, a vacuum source could be connected thereto to remove air more rapidly. A cylindrical piston

54

is positioned in a cylindrical passage with the piston

54

having an end source

51

b

flush with the surface of the non-electrical contact surface of the mold cavity during the pressure casting process. A piston driver

53

is positioned proximate the mold

50

and includes therein means (not shown) for driving the piston

54

toward the battery terminal cavity

51

or for retracting the piston

54

away from the battery terminal cavity.

FIG. 6

is a cross-sectional view of the mold in

FIG. 5

showing a solidified battery terminal

60

located in battery cavity

51

. The piston

54

has been driven into the solidified battery terminal

60

with sufficient force so as to at least partially cold form the solidified lead into a battery terminal which is free of cracks and tears. That is, the end of piston

54

a

is shown penetrating into the batter terminal to decrease the volume of the battery terminal cavity while at the same time mechanically deforming at a least a portion of the battery terminal

60

located therein. In the embodiment shown, the mechanical pressure is sufficient to force solidified lead through passage

56

and out of mold

50

as indicated by solidified lead

60

a

extending from vent passage

56

. Thus, one can pressure cast a battery part and allow the pressure cast battery part to solidify and while the battery part is still in the mold but in the solidified state a piston can be driven into the solidified part to mechanically deform the lead which will remove cracks or tears in the battery terminal that occur as a result of the pressure casting process.

FIG. 6

shows that the piston can be driven into the battery terminal

60

to leave a recess within the battery terminal. As the piston is driven into the portion of the battery terminal that contains the non-electrical contact surface, a feature such as a recess can be tolerated thereon without adverse conditions for operation of the battery terminal. This procedure of volume contraction is suitable when the battery part has a shape so that the volume contraction can cause the deformation of the lead in remote portions of the battery part. That is, in some battery parts the configuration of the battery part may be such that a volume reduction in one region produces only partial cold deformation or reworking the battery part thereby leaving a battery part with a crack or tear. However, in those battery parts where the cold deformation can effectively move metal throughout the battery cavity the volume contraction can be performed after the solidification of the battery part. The advantage of this method is that the internal pressure within the mold is increased locally but not throughout the mold as the solidified battery part does not transmit pressure forces in the same manner as if it were a liquid.

FIG. 7

is a cross-sectional view showing a portion of a mold

50

and a piston

54

that is positioned having its end surface

54

a

spaced from the non-electrical contact surface

51

b.

A pressure cast solidified battery terminal

65

is shown therein with a solidified extension

65

a

extending outward from the battery terminal

65

to the end surface

54

a

of piston

54

. In this condition, the extension

65

a

has solidified as an integral part of the battery terminal. Battery terminal

65

having been formed by a pressure cast process can include cracks and tears. In order to remove any tears or cracks the piston

54

is driven toward battery terminal post

65

with sufficient force to force the material in extension

65

a

into the battery terminal and thereby mechanically deform the battery terminal to a condition wherein the tears and cracks are removed.

FIG. 8

illustrates the driving of the piston to a condition flush with the surface of the battery terminal. By driving the piston end

54

a

to a condition flush with the battery terminal

65

, the battery terminal is provided with a continuous surface. Consequently, the method illustrated by

FIG. 8

can be used on either the non-electrical contact surface or the electrical contact surface as the finished surface remains flush with the adjacent surface.

FIG. 9

is a cross-sectional view showing a portion of a mold

55

with a solidified battery terminal

66

therein. A piston

54

is positioned having its end surface

54

a

spaced from the mold cavity end surface

51

b.

In the condition shown, a solidified cylindrical extension of length L

1

extends from battery terminal

66

.

FIG. 10

is a cross-sectional view of the mold in

FIG. 9

showing the end of the piston driven to a condition which is also spaced from the end surface of the mold cavity. That is the piston has been driven in passage

55

until the extension

66

b

has been shortened to length L

2

. The purpose of mechanically reducing the volume of the solidified battery terminal

66

is to cold form at least a portion of the metal in the battery terminal to thereby relieve any cracks or tears in the pressure cast battery terminal. The method illustrated in

FIGS. 9 and 10

requires less precession in the piston movement to deform the metal into a shape free of cracks and tears. For example, the amount of force applied to piston

53

could be the determining factor of the travel of the piston rather than the length of piston travel determining the pressure of deformation on the battery terminal.

FIG. 11

is a view of a battery terminal of

FIG. 10

with the pressure cast extension

66

b

being schematically shown as being sheared off. In practice the removal of the battery terminal

66

from the mold may cause the extension

66

b

to shear off and remain in cylindrical passage

55

. That is, the extension

66

b

is sufficiently small in diameter so that the extension can be broken with the battery terminal removal force.

To illustrate the removal of the extension

66

b

from the mold, reference should be made to

FIG. 12

which is a partial cross-sectional view of the piston of FIG.

10

. Piston

53

is shown driving the pressure cast extension

66

b

from the passage

55

. Thus with the method illustrated in

FIGS. 9-12

one can leave an extension on the cast battery terminal and then break the extension off during the removal of the battery terminal. The use of the piston

54

allows one to clear the passage

55

for the next casting.

FIG. 13

is a front view of a two-metal battery connector

70

having an intermediate member

73

with a first connector end

71

having an opening

71

a

and a second connector end

72

having an opening

72

a

therein. The exterior of connector

70

is lead.

FIG. 14

is a cross-sectional view taken along lines

14

—

14

of

FIG. 13

showing the extension connector

73

of lead and the inner core

75

which is a different metal such as copper. Core

75

is surrounded by a lead sheathing that has been pressure cast thereon.

To illustrate the pressure casting of the battery part of

FIG. 13

, reference should be made to

FIG. 15

which is a cross-sectional view of a mold

80

and a holding apparatus for pressure casting the battery connector of FIG.

13

. Holding apparatus comprises a pair of retractable members

82

and

83

that are oppositely disposed with the core

75

being supported therebetween in a condition that leaves an envelope of space

86

around core

75

to allow for molten metal to flow therein. Retractable members

82

and

83

are held in pressure contact with core

75

through means not shown. A source of pressured lead

81

is located in fluid communication with mold cavity

86

through feed runner

82

. In the condition shown, the mold

80

is ready to receive molten lead. In the condition to receive molten lead a first piston

84

is located in a retracted condition to provide a mold space

84

a

in front of the end of piston

84

and similarly, piston

85

is located in a retracted condition to provide mold space

85

a

in front of the end of piston

85

. During the pressure casting of connector

70

, the molten lead will be forced into void

86

and into the space

85

a

and

84

a.

Once the lead in the mold has solidified to support core therein, the retractable members

82

and

83

are retracted leaving the pressure cast lead to support the core therein. The withdrawn of the retractable members

82

and

83

will leave a void in the solidified material in mold

80

. In order to fill the voids produced by retraction of retractable members

82

and

83

, the pistons

84

and

85

are driven inward to a condition flush with the exterior of the remaining portion of the mold.

FIG. 16

is cross-sectional view of a mold and holding apparatus of

FIG. 15

with a pair of retractable members

82

and

83

in the retracted position and the driving pistons

84

and

85

in the extended position. In this condition, the metal present in region

85

a

and

84

a

of

FIG. 14

has been forced into the voids produced by the withdrawal of retractable members

82

and

83

. Consequently, the connector

70

can be formed in a pressure cast process with the completion of the battery connector accomplished with a deformation of the pressure cast lead to thereby produce a finished product.

FIG. 17

is a cross-sectional view of an alternate embodiment of a pressure cast part

91

that has formed a cylindrical extension

91

a

thereon. The length of the cylindrical extension

91

a

is limited by the end of an annular drive punch

95

.

FIG. 18

shows the battery part of

FIG. 17

with the annular drive punch

95

driven into the solidified extension

91

a

to cold form the battery part

91

free of cracks and voids. Thus with the present process, one can pressure cast a variety of battery parts and through a process of decreasing the volume during either the pre-solidification state or the solidified state, one can produce a battery terminal that is free of tears and cracks.

FIG. 19

shows a mold

100

with a core pin

101

and slidable collar

108

for pressure casting a battery part which is defined by cavity

110

which includes the annular cavity surrounding core pin

101

. In operation of the mold of

FIG. 19

, molten lead under pressure enters runners

103

to fill the battery part cavity

110

. A slidable collar

108

is located within fixed collar

109

with the end of collar

108

and the inner portion of collar

109

defining a portion of the battery part. Casting of the battery part with the collars in the position shown produces an annular extension of the battery part in the battery cavity portion defined by

110

a.

In order to provide the volume contraction of the battery part to provide a battery part free of cracks and tears, there is included a piston

106

that is slidable in chamber

107

. A first port

104

receives a first fluid and a second port

105

receives a second fluid. When the pressure in port

105

is increased rapidly, it forces piston

106

upward which drives collar

108

upward into the battery cavity region

110

a

which compresses the annular lead extension located therein by reducing the volume available for the lead extension. In the mold shown in

FIG. 19

, the collar

108

can be driven upward to reduce the volume while the lead is in the transition state between liquid and solid or when the lead has cooled. If the lead has cooled to solid state before the slideable collar

108

is driven upward the lead is cold formed into a battery part. The piston

106

can be lowered again by increasing the pressure in port

104

and reducing the pressure in port

105

, thus withdrawing the piston

106

from the drive collar

108

.