US3587717A

US3587717A - Apparatus for producing grids of storage batteries

Info

Publication number: US3587717A
Application number: US769266A
Authority: US
Inventors: Shinya Yamauchi; Minoru Morita
Original assignee: Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Holdings Corp
Priority date: 1967-10-25
Filing date: 1968-10-21
Publication date: 1971-06-28
Anticipated expiration: 1988-06-28
Also published as: DE1805300A1; GB1243351A; DE1805300B2; FR1589916A

Abstract

AN APPARATUS FOR PRODUCING GRIDS OF STORAGE BATTERIES, WHEREIN A ROTARY MOLD, HAVING GRID CASTING GROOVES FORMED IN THE PERIPHERAL SURFACE THEREOF, AND A STATIONARY MOLD ARE ARRANGED IN CONFRONTING RELATION TO EACH OTHER AND MOLTEN LEAD OR A MOLTEN LEAD ALLOY IS POURED INTO A GAP DEFINED BETWEEN
SAID MOLDS, WHEREBY DEFECT-FREE, THIN, EXCELLENT GRIDS ARE OBTAINED.

D R A W I N G

Description

United States Patent inventors Shinya Yamauchi Osaka; Minoru Morita, Toyonaka-shi, Japan Appl. No. 769,266 Filed Oct. 21, 1968 Patented June 28, 1971 Assignee Matsushita Electric Industrial Co., Ltd.

Osaka, Japan Priority Oct. 25, 1967, Sept. 25, 1968 Japan 68486/67, 69487/67, 70658/68 and 70657/68 APPARATUS FOR PRODUCING GRIDS OF STORAGE BATTERIES 8 Claims, 16 Drawing Figs.

U.S. Cl 164/276, 164/88, 164/69, 164/283, 164/338, 164/348, 164/Dig.l Int. Cl B22d 11/06 Field of Search 164/88, 276

(Foreign & US), 278, 87, 281, 69, 70, (Battery Digest), 279, 283 (US) [56] References Cited UNITED STATES PATENTS 521,791 6/1894 Griscom 207/11 1,651,678 12/1927 Davis 164/283X 2,714,235 8/1955 Brennan 164/70 2,745,151 5/1956 Brennan l64/276X 2,787,816 4/1957 Brennan 164/278X 326,147 9/1885 Pielsticker et al. 164/276 Primary Examiner-J. Spencer Overholser Assistant Examiner-Vernon K. Rising Attorney- Stevens, Davis, Miller and Mosher ABSTRACT: An apparatus for producing grids of storage batteries, wherein a rotary mold, having grid casting grooves formed in the peripheral surface thereof, and a stationary mold are arranged in confronting relation to each other and molten lead or a molten lead alloy is poured into a gap defined between said molds, whereby defect-free, thin, excellent grids are obtained.

APPARATUS r011 rnonucmo cams or STORAGE BATTERIES This invention relates toan apparatus for producing grids of storage batteries, and more particularly to such an apparatus which is adapted to produce thin, defect-free, excellent grids in a large quantity.

An object of the present invention is to provide an apparatus for continuously producing thin, defect-free, excellent grids, comprising a rotary mold having a grid-molding groove formed in the peripheral surface thereof and a stationary mold located in confronting relation to said rotary mold so as to define a grid-molding cavity therebetween into which molten lead or a molten lead alloy is poured.

Another object of the invention is to provide an apparatus of the character described above, wherein a pouring basin is formed in the stationary mold in communication with an outlet for storing the molten lead or molten lead alloy and a damper is provided in said pouring basin to regulate the quantity and pressure of the molten lead or moltenlead alloy being poured into the grid-molding cavity.

Still another object of the invention is to provide an apparatus of the character described above, wherein said rotary mold and said stationary mold are connected with each other at their centers by a pair of arms and said stationary mold is provided with means for adjusting the angle of inclination thereof and elastic means for urging said stationary mold against said rotary mold; whereby variations in the space interval between said rotary mold and said stationary mold, caused by the pressure of the molten lead or molten lead alloy poured into the grid-molding cavity, are prevented.

Still another object of the invention is to provide an apparatus of the character described above, wherein heating means is provided to melt and remove thin films of lead and lead alloy when such thin films are formed in the spacings defined by the beams of the molded grid.

Still another object of the invention is to provide an apparatus of the character described above, wherein means is provided for cooling slowly the grid molded in the molding cavity in the rotary mold so as to enable a grid of uniform structure to be obtained.

Grids of storage batteries have generally be produced by a method wherein molten lead or molten lead alloy is poured into a molding cavity defined by a pair of openable planary casting molds. However, because of the fact that the grid has complicated structure comprising a number of longitudinally and laterally extending beams crossing each other, as shown in FIGS. and 16, and its size becomes large particularly when the thickness thereof, i.e. the thickness indicated by t in FIG. 16, is extremely small, eg 1 mm. or smaller, much difficulty has been encountered in the casting operation due to unsatisfactory flow of the molten lead or molten lead alloy, and even when the casting operation is accomplished satisfactorily, the grid molded has frequently had portions of the beams thereof missing. Thus, it has been difficult to produce an excellent grid by casting at high efficiency. On the other hand, storage batteries are desired to have better discharge characteristics from the standpoint of practical use and to meet such desire, there has been an increasing demand for thin grids.

The apparatus of the present invention is so designed that grids, which are sufficiently satisfactory to meet the aforesaid desire, can be produced continuously in large quantities.

The present invention will be described in detail hereinafter with reference to the accompanying drawings, which illustrate the invention by way of embodiment and in which:

FIG. 1 is a side elevational view showing an embodiment of an apparatus for producing grids of storage batteries according to the present invention;

FIG. 2 is a fragmentary side elevational view, partially in section, of a portion of the apparatus shown in FIG. 1;

FIG. 3 is a back elevational view showing means for retaining the stationary mold;

FIG. 4 is an illustrative view for explaining the pressure engagement between the rotary mold and the stationary mold;

FIG. 5 is a vertical sectional view showing the manner in which a grid is produced by casting;

FIG. 6 is a sectional view taken on the line VI-VI' of FIG. 5;

FIG. 7 is a vertical sectional view showing the manner in which a grid is produced by another embodiment of the apparatus of this invention;

FIG. 8 is a fragmentary top plan view showing the peripheral surface of the rotary mold;

FIG. 9 is a sectional view taken on the line IX-IX' of FIG. 8;

FIG. 10 is a side elevationalview of another form of the heating means for melting thin films of molten metal formed in the spacings defined by the grid beams;

FIG. 11 is a front elevational view, partially in section, of the heating means shown in FIG. 10;

FIG. 12 is a diagram showing the electric circuit of the heating rollers of the heating means shown in FIG. 10;

FIG. 13 is a diagram showing the electric circuit of the temperature detecting roller of the heating means;

FIG. 14 is a fragmentary sectional view of an incomplete grid, with thin films of lead or lead alloy formed in the spacings defined by the grid beams;

FIG. 15 is a top plan view ofa completed grid after the thin films have been melted away; and 7 FIG. 16 is a sectional view taken on the line XVI-XVI of FIG. 15.

Referring to the drawings, reference numeral 1 designates a stationary mold which has a pouring basin 3 formed therein in communication with a molten metal outlet 2. The stationary mold l is provided with a damper 7 to regulate the flow rate of a molten metal 5, i.e. molten lead or molten lead alloy, which is supplied into the pouring basin 3 through a supply tube 4. In the bottom wall of the pouring basin 3 is provided a heating tube 8 so as to prevent the molten metal 5 from solidifying in said pouring basin, while in the lower portion of the inside of a curved surface 11, confronting the rotary mold 10, is arranged a cooling tube 13 for circulating tepid water or the like therethrough, for thereby solidifying the molten metal 5 being poured from the outlet 2 into grid-molding grooves 12 formed in the peripheral surface of a rotary mold 10. The cooling tube 13 and the heating tube 8 are thermally isolated from each other by means of a heat insulation plate 14 embedded therebetween.

On the other hand, the rotary mold 10, as shown in FIGS. 1, 2 and 5, is formed into the shape of a drum and the gridshaped grooves 12 are formed in the peripheral surface thereof so as to define peripheral edges 15 as best shown in FIG. 8. As seen in FIG. .6, the rotary mold 10 engages the stationary mold 1 in confronting relation, defining a grid-molding cavity 12.

The stationary mold l and the rotary mold 10 are coupled by means of a pair of arms 19 each of which has one end pivotally connected to a bearing at the center of the rotary mold l0 and the other end to the center of the sidewall of the stationary mold 1 as shown in FIGS. 1 and 2. The stationary mold l is supported on a supporting frame 20 by four angle of inclination adjusting bolts 21 and four squarely arranged springs 22 engaging the back surface of said stationary mold, in such a manner as to hold said stationary mold in contact with the peripheral surface of the rotary mold 10. Each arm 19 is provided at the central portion thereof with a threaded rod 23 for adjusting the length of said arm. Namely, the length of the arm 19 is optionally adjusted by screw threading the threaded rod 23 into or from the arm.

The stationary mold I is connected to each one of the pair of arms 19 by a bolt 25, provided at the center of each side surface thereof, which extends through a slot 24 formed at one end of each arm 19 and is secured in position by a spring 27 which is pressed at one end by an adjusting screw 26.

Reference numeral 28 designates four bolts threadably extending through an upright wall 29, integral with the frame 20, to press and hold four springs 22 respectively which have one ends thereof received in holes 30 formed in the back surface of the stationary mold l. The rotary mold 10 is supported by wedge-shaped frames 31. The stationary mold l and the rotary mold 10 may be fixed in positions, with a predetermined gap, necessary for the casing of a grid, formed therebetween in the following manner:

First of all, the springs 27 disposed in the slots 24 of the respective arms 19 and the four springs 22 biasing the back surface of the stationary mold 1 are released and then the lengths of the arms 19 are adjusted by screw threading the adjusting threaded rods 23 into the respective arms. After a gap required for the casing of the grid has been secured between both molds l and 10, the threaded rods 23 are fixed in their positions and the four bolts 21 are also fixed by means of lock nuts 32.

Then, the adjusting screw 26, having its free end projecting into the slot 24 of each arm 19, is screw threaded against the force of the spring 27 thereby to impart an elastic force to said spring and simultaneously the four bolts 28 are screw threaded through the upright wall 29 of the frame 20 to press the respective springs 22 which in turn will urge the stationary mold 1 toward the rotary mold 10 from the back side thereof. The bolts 28 are fixed in position by respective lock nut 33.

The biasing forces of the

springs

27 and 22 are preferably such that the gap required for the casing of a grid therein can be maintained constantly even when the pressure of a riser head, etc. acting between the stationary mold 1 and the rotary mold 10 becomes large during operation of the apparatus. In this case, unnecessarily large biasing forces of these springs must be avoided because if the biasing forces are excessively large, the frictional resistance between the stationary mold I and the rotary mold 10 increases, with the result that a prescribed rate of rotation of the rotary mold 10 cannot be maintained and both molds will undergo wear.

As shown in FIG. 4, the stationary mold l is urged against the rotary mold 10 by the elastic force F of springs 27 acting on the bolts 25, a counterclockwise moment M developed by the upper two ones of four springs 22 urging the back surface of the stationary mold l and a clockwise moment M developed by the lower two ones of said springs. The upper two springs 22 and the lower two springs 22 are located such that the extensions of their axes pass above and below the bolts 25 on the sidewalls of the stationary mold 1 respectively. Normally, the moment M is made greater than the moment M because the thickness of the grid to be produced is deter mined by the spacing between the lower end of the curved surface 11 of the stationary mold 1 and the rotary mold 10.

Description has been made hereinabove with reference to the case when the pressure acting between the molds 1 and 10 during pouring ofa molten metal into the molding'cavity 12 is large. When the riser head is small, the biasing force F of the springs 27 is not necessarily required and the arms 19 may be connected directly to the bolts on the sidewalls of the stationary mold l at one end thereof.

Reference numeral 34 designates a heating belt provided beneath the stationary mold l in such a manner as to contact the grooved portion 12 on the peripheral surface of the rotary mold 10. The heating belt 34 is formed out of an endless stainless steel plate or the like and trailed around two driving

drums

35, 36 to be driven thereby in the direction of arrow A while being heated to elevated temperature by heating tubes 37, 38 arranged inside and outside of the loop of belt respectively. A support roller 39 is provided at the bottom of the rotary mold 10 for rotation in the direction of arrow B.

Between the supporting roller 39 and the rotary mold I is provided a knife-shaped separator 40 which has a sharp edge and by which a web of solidified lattice mold being delivered continuously in contact with the peripheral surface of the rotary mold is separated therefrom. The web of grid 42 of lead or lead alloy, having been separated from the rotary mold 10, is sent'forwardly of the molding apparatus by means of a pair of pinch rollers 41 which are positioned one on each side of the grid 42 and rotating in opposite directions to each other as indicated by arrow C.

A cooling tube 43 provided exterior of the rotary mold 10, from which tepid water or the like is sprayed to prevent excessive heating of the rotary mold, while heating tube 43' is provided to preheat the peripheral surface of the rotary mold.

Next, the operation of the apparatus, constructed as described above, for the production of a grid of the type shown in FIG. 15, will be explained hereunder.

First of all, a gap necessary for the casing of the grid 44 is defined between the stationary mold 1 and the rotary mold 10 to be rotated in the direction of arrow D, and then the stationary mold 1 is urged toward the rotary mold 10 by the

springs

27 and 22. Molten lead or molten lead alloy 5 is introduced into the pouring basin 3 through the molten metal supply tube 4 and the damper 7 is moved vertically to regulate the flow rate and the pressure at which the molten metal 5 is poured. The molten metal 5 is poured into the molding cavity 12 formed in the peripheral surface of the rotary mold 10 through the inlet 2 with no head. In the pouring basin 3, the molten metal 5 is not solidified and has a suitable fluidity by virtue of the heat from the heating tube 8, but when poured into the molding cavity in the peripheral surface of the rotary mold 10 it begins to solidify by being cooled by said cold rotary mold. The grid 42 thus molded has its thickness adjusted during its passage through between the rotary mold l0 and the lower edge of the curved portion 11 of stationary mold 1. In this case, the grid is also cooled from the surface by the cooling tube 13 provided interior of the curved portion 11. The web of continuous grid 42 thus molded in the molding cavity 12 in the peripheral surface of the rotary mold is subjected to a spray of tepid water or the like from the cooling tube 43, whereby it is further cooled without undergoing an abrupt structural change.

As stated previously and shown in FIG. 6, the rotary mold 10 and the stationary mold 1 form therebetween under the biasing forces of the

springs

27 and 22 only that amount of a gap which is needed for the casting of the grid. In practice, however, a thin film oflead or lead alloy is formed on the surface of the grid 42, particularly in the space defined by the grid beams 54, integrally therewith on account of a pressure, such as the riser head of the molten metal 5, and the extremely high fluidity of said molten metal. Such thin film 46 is melted away by the heat of the heating belt 34 when the surface of the grid 42 is brought into contact therewith. The heating belt 34 can be used continuously repeatedly because the lead attached thereto is cleared therefrom during its rotation.

The grid 42 having the thin film 46 eliminated therefrom in the manner described is further carried on the rotary mold 10 while being attached to the peripheral surface thereof, and reaches the bottom portion of said rotary mold where the supporting roller 39 is provided. At this portion, the knife-shaped separator 40 is inserted between the grid 42 and the rotary mold 10, so that the grid 42 is separated from the rotary mold l0 and delivered by the pinch rollers 41 in a direction tangentially of said rotary mold.

The web of grid thus obtained may be cut into a suitable length at a point past the pinch rollers 41, whereby a piece of grid 44 is obtained as shown in FIG. 15. Thereafter, the grid 44 is filled with an active substance and subjected to a suitable chemical treatment, to be used as an electrode plate. Alternatively, the web of grid may be cut into a suitable length after it is filled with the paste and subjected to the chemical treatment.

Beside the foregoing, the present inventors have confirmed through many experiments that the grid 44 as shown in FIG. 15 may also be produced in a large quantity by a simple apparatus as shown in FIG. 7.

In the apparatus shown in FIG. 7, an arcuate stationary mold l is held opposite to the rotary mold 10, having the gridmolding cavity formed in the peripheral surface thereof, by means of springs as those mentioned in the preceding embodiment or by an elastic mechanism making use of pneumatic or hydraulic pressure, with only that much of gap therebetween which is needed for the formation of the grid 44, and molten lead or molten lead alloy is poured into said gap directly from the molten metal supply tube 4 in an amount sufficient to form the grid 44.

In this case, since the molten metal 5 is supplied through the supply tube 4 in an amount just sufficient for the formation of the grid 44 and not in excess thereto, the molten metal can be poured into the molding cavity in the peripheral surface of the rotary mold 10, with no portion thereof flowing down through between said rotary mold and the lower edge of stationary mold 1', even though a pouring basin or a flow rate regulating damper is not provided in the stationary mold.

The stationary mold 1' preferably has a heating tube or other heading means embedded in the upper portion thereof so as to prevent rapid cooling and solidification of the molten metal poured, and has a cooling tube or other cooling means embedded in the lower portion thereof to solidify the molten metal. The molten metal 5 poured into the gap between the rotary mold l0, rotating in the direction of arrow D, and the stationary mold l, is cooled and solidified slowly, and is subjected to a spray of tepid water or the like from the cooling tube 43 at a lower point past the stationary mold 1', whereby the solidification of molten metal is further promoted. The web of grid thus formed is separated from the rotary mold by the separator at the position of the supporting roller 39 an sent into the pinch roller 41. By cutting the web of grid 42 into a predetermined length, a grid unit 44 as shown in FIG. 15 is obtained.

In this case also, a thin film 46 or lead or lead alloy is formed over the grid beams 45 in the stage of formation of the web of grid. Therefore, it is necessary to provide the heating belt 34 to eliminate the thin film as in the preceding embodiment.

The depth of the molding grooves 12, particularly the grooves 18, formed in the peripheral surface of the rotary mold 10 must be determined in accordance with the desired thickness of grid since the thickness 1 of the grid web 42 or the grid 44 depends upon such depth.

It is of course possible to cast continuously grids of thickness ranging from large thickness to very thin thickness by the selective use of rotary molds having varying depth of the grooves 12, particularly the grooves 18, but the present invention is highly variable in that grids of particularly small thickness, that is, a thickness of 1 mm. or smaller, can be formed satisfactorily with no portions of the beams missing.

Although in the embodiments described above, use is made, for melting oh the thin film 46 formed over the mesh of the grid 44, of heating means which comprises an endless stainless steel plate engaged around two driving drums to be rotated thereby in contact with the web of grid 42, one shown in FIGS. 10 and 11 may also be used.

Namely, referring to FIGS. 10 and 11, a driving roller 47 mounted on a rotary shaft 49 is rotatably supported by a pair of bearings 48, 48 and one end of the rotary shaft 49 is extended outwardly through one of the bearings 48' with the driving chain gearing 50 mounted thereon. The bearings 48, 48 are supported on a vertical, inverted U-shaped arm 51. The arm 51 is provided at the central portion thereof with a cylindrical member 52 in which is received a supporting column 58 with a spring 57 disposed in a cavity 56 in the lower end thereof. The supporting column 52 is rotatably mounted on a bearing member which supports a heating roller 53 and a temperature detecting roller 54. A supporting rod 59 extends through upright portions 60, 60' of the bearing member 55 and also through the top end of the supporting column 58. The bottom plate 61 of the bearing member 55 has an opening 62 formed in the center thereof to provided for rotation of the supporting column 58.

The heating roller 53 is rotatably mounted on one end ofthe upright portions 60, 60' of bearing member 55, while the temperature detecting roller 54 is rotatably mounted on hearing blocks which are slidably disposed in slots 63 formed in the walls of the upright portions 60, 60' respectively while being biased by springs 64.

The endless heating belt 34 of stainless steel plate is engaged around the three rollers, i.e. the driving roller 47, the heating roller 53 and the temperature detecting roller 54, and held in contact with the grooved portion 12 of the peripheral surface of rotary mold 10 at a portion between the heating roller 53 and the temperature detecting roller 54 under the biasing force of the spring 57. These

rollers

47, 53 and 54 rotate in the direction of arrow E to drive the belt 34 at the same speed as the peripheral speed of the rotary mold 10. Reference numeral 66 designates a heating tube to heat the belt 34 before the heating roller 53 and 67 designates a wire brush to remove lead or lead alloy from the belt 34 which is attached to said belt upon melting.

The heating roller 53 has a plurality of rod-shaped heaters 68 embedded therein at the same circular pitch and these heaters are connected to a power source through slip rings 70 and a brush 71, mounted on an end of a rotary shaft 69, as shown in FIG. 12. A current conducted through the rodshaped heaters 68 from the power source is controlled by a temperature switch 74 which is connected to a thermocouple 72 along with a thermoelectric thermometer 73, and thermocouple 72 being disposed within the temperature detecting roller 54 for detecting the temperature of the belt 34 as shown in FIG. 13. Namely, the temperature switch operates in such a manner that the current passing through the rod-shaped heaters 68 in the heating roller 53 in interrupted when the when the temperature detected by the thermocouple 72 is higher than a predetermined value,while the current is conducted through the rod-shaped heaters 68 to heat the roller 53 when said temperature is lower than the predetermined value, thereby heating the heating belt 34 to the predetermined temperature.

Thus, the heating belt 34 is maintained in a certain temperature range in the proximity of the predetermined temperature. Reference numeral 75 designates slip rings electrically connected to the thermocouple 72, 76 a brush and 77 a rotary shaft of the temperature detecting roller.

It is to be understood that the positions of the heating roller 53 and the temperature detecting roller 54 may be changed with each other as desired. It is also to be understood that where the quantity of heat required for heating the belt 34 is relatively small, a single roller may be used with the heaters and the temperature detecting means disposed therein or further a roller having the heaters and the temperature detecting means mounted therein may be contacted directly with the grooved portion 12 of the rotary mold 10, without using the belt 34.

The temperature to which the heating belt 34 is heated for the melt-removing the thin film 46 formed over the mesh of grid web 42 is variable depending upon whether the molten metal 5 consists of lead only or a lead alloy. In the case, for example, of a lead-antimony alloy containing 5 percent of antimony, the heating belt 34 is preferably maintained in the temperature range from 295 C. to about 320 C. as the melting point of said alloy is 295 C. Overheating of the heating belt will provide the danger of the grid beams 45 being melted. It will be appreciated, therefore, that the temperature detecting means in the temperature detecting roller 54 is set such that the rod-shaped heaters 68 in the heating roller 53 are deenergized when the temperature of the heating belt detected has reached 320 C. and are energized when said temperature has dropped to a level immediately above 295 C.

On the other hand, when the molten metal 5 consists solely of lead, the heating belt 43 is preferably maintained in the temperature range from about 327 C. to about 340 C. for the same reason as mentioned above, in consideration of the fact that the melting point of pure lead is 327.4 C.

Upon melt-removing the thin film 46 from the web of grid 42 by the heated belt 34 in the manner described, the resultant molten lead or lead alloy is attached to the belt. However, the molten lead or lead alloy is brushed off the belt by the wire brush 67 so that the belt may be used continuously.

As will be understood from the foregoing description, it is possible according to the present invention to produce excellent, defectnfree, thin grid in'a large quantity by pouring molten lead or molten lead alloy into the gap formed between the rotary mold, having agrid molding grooves formed in the peripheral surface thereof, and the stationary mold located in confronting relation to said rotary mold.

We claim:

1. An apparatus for producing grids for storage batteries, comprising a rotary mold part provided with gridlike grooves in the peripheral surface. thereof, a stationary mold disposed in confronting relationship to the peripheral surface of said rotary mold part to cooperate with said gridlike grooves to define therebetween a grid casting cavity, said stationary mold part comprising a molten metal outlet positioned in opposite relationship to said gridlike grooves in the periphery of said rotary mold part, a reservoir for a molten metal in communication with said molten metal outlet, a stopper movable up and down for regulating the flow rate and the pressure of said molten metal contained in said reservoir, heating tubes adjacent the bottom of said reservoir for circulating a heating medium therethrough, cooling tubes adjacent said curved concave surface for circulating a coolant therethrough, and a heat insulating plate thermally separating said heating tubes apart from said cooling tubes.

2. An apparatus according to claim 1 further comprising a pair of arms for interconnecting said rotary and stationary mold parts substantially at their central points, means for resiliently urging said stationary mold part against said rotary mold part and leg members for adjusting the inclination of said stationary mold part with respect to said rotary mold part.

3. An apparatus according to claim 1 further comprising means for melting off thin films of metal closing the openings of the mesh as said gridlike cast is continuously delivered from said casting cavity, said film being formed by the narrow gap defined between the confronting peripheral surfaces of said stationary and rotary mold parts, said melting means comprising a heated endless belt movable in contact with the peripheral surface of said rotary mold part at the portion downstream of said stationary mold part, at least a pair of drums for supporting said endless belt, at least one of said drums being power-driven to move .said endless belt, and means for heating said endless belt.

4. An apparatus according to claim 3 in which said means for heating said endless belt comprises heating tubes disposed adjacent the run of said endless belt on opposite sides thereof.

5. An apparatus according to claim 3 in which said means for heating said endless belt comprises heating tubes disposed adjacent the run of said endless belt on the outer side thereof and heater means disposed within at least one of said drums.

6. An apparatus according to claim 5 further comprising a temperature detecting roller having a thermocouple disposed therein and mounted in rolling contact with said endless belt, at least one of said drums having heater means disposed therein and means responsive to said thermocouple for controlling said heaters.

7. An apparatus according to claim 1 in which said coolant is tepid water for slowly cooling the cast metal within said grid casting cavity.

8. An apparatus according to claim 1 in which said molten metal is selected from a group including lead and lead alloys.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 587, 717 Dated June 28, 1971 Inventor(s) Shinya YAMAUCHI et al It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

The first Japanese application number should read -6 9 486/67-- and not "6g486/6'7 Signed and sealed this 11th day of January 1972.

(SEAL) Attest:

EDWARD M.FLETGHER,JR. ROBERT GO'I'TSCHALK Attesting Officer Acting Commissioner of Patents FORM P0405) "069) uscoMM-Dc wave-P09 3 U 5 GOVERNMENY PRINTI'; OFFICE 9Q, 0-165-334