GB1604607A - Composite articles - Google Patents

Description

PATENT SPECIFICATION ( 11) 1604 607

L ( 21) Application No 26817/80 ( 22) Filed 30 May 1978 o ( 62) Divided out of No 1 604 606 ( 1 9 ( 31) Convention Application No 806 927 o ( 32) Filed 15 June 1977 in C ( 33) United States of America (US) ( 44) Complete Specification published 9 Dec 1981 ( 51) INT CL 3 B 29 F 1/00; H Oi M 4/73 ( 52) Index at acceptance B 5 A 1 R 314 CIC IR 314 C 1 D IR 314 C 6 1 R 439 A T 14 M B 3 F 11 G 11 J 16 A 10 16 B 2 C 1 16 B 4 16 D H 1 B 473 ( 54) IMPROVEMENTS IN OR RELATING TO COMPOSITE ARTICLES ( 71) We, GLOBE-UNION INC, a Corporation organized and existing under the laws of the State of Delaware, United States of America, of PO Box 591, Milwaukee, Wisconsin 53201, United States of America, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: -

This invention relates to the forming of composite artcles such as battery plate grids for secondary storage batteries.

Conventional lead-acid storage batteries comprise a plurality of alternating positive and negative battery plates which are stacked with interspersed nonconductive separators to form battery elements The battery elements are mounted in one or more individual cells of a storage battery case and electrically interconnected as is well known in the art Conventionally, each positive and negative plate comprises a supporting conductive grid structure which is normally made of lead or a lead alloy and which supports an electrochemically active paste material The lead grids serve the dual purpose of supporting the paste material as well as acting as electrical current conductors.

Over the years, the battery industry has endeavoured to reduce the amount of lead utilized in batteries A reduction in the amount of lead used not only reduces the weight of a battery but may also result in material cost savings as well Battery grids represent a potentially fruitful area of material reduction since conventional lead grids include much more material than is needed for the function of collecting and conducting electrical current.

Reduction of the amount of grid material has been limited, however, since the grids also serve as physical supports for the paste material and limitations on the ability to handle the pasted plates prior to combination into elements and installation in a storage battery have hampered efforts to reduce the grid thickness or the amount of lead utilized.

One particularly desirable method of reducing the amount of lead in battery grids lies in the area of combining less expensive, lightweight materials such as plastics with the lead Plastics are a particularly desirable class of materials since many types are available which are relatively insoluble in acid, are lightweight, yet strong enough to serve as supporting grid structures, and offer a reduction in cost as compared with lead Accordingly, many efforts have been directed toward forming composite plastic-lead battery grids Prior art efforts in this regard have centred on two basic approaches The first approach has been to utilize plastic alone to form the supporting grid structure For example, U S Patent No.

3,813,300, issued May 28, 1974 to Shunji Shima et al, shows a plastic grid in which the active paste material conducts electricity to a separately formed and attached conductive current collector Similarly, U S Patents Nos 3,516,863 and 3,516,864, both issued June 23, 1970 to Willmann, and British Patent No 1,240,672, published July 28, 1971, show plastic grids having lugs mechanically attached.

The plastic grids may be coated with a conductive material Finally, U S Patents No.

3,901,960, issued August 26, 1975, and No.

3,607,412, issued September 21, 1971, both to Holloway, show grids produced by placing a separately formed conductive lug in a mold and molding a plastic resin grid onto the lug.

These prior art techniques have several major disadvantages All involve separate handling of conductive lugs and plastic grids.

In Shunji Shima, the active material has low efficiency as a current conductor and collector, and loss of active material around the lug could render the plate useless Basically, in all cases, the savings in material costs and weight reduction would be offset by increased production costs as compared to conventional lead grid casting.

1,604,607 The second major approach to composite grid manufacture has been to combine lead and plastic to form a supporting grid structure U S Patent No 3,690,950, issued September 12, 1972 to Wheadon, shows a composite grid in which lead wires are heated and fused with a plastic grid Austrian Patent No 269,245, issued March 10, 1969, shows molding of plastic around preformed lead wires placed in a mold, and British Patent No.

1,007,497, published October 13, 1965, shows mechanical assembly of lead and plastic portions to form a battery grid.

While the second approach offers improved current carrying capabilities due to the use of lead wires, all prior art attempts again require separate handling of lead and plastic stages of assembly None of these techniques permit formation of a composite grid at a single station with minimal handling prior to complete fabrication.

The present invention consists in a method of forming a composite battery grid comprising the steps of:

providing a first mold half having a portion of a first pattern formed therein, said portion including a lug portion and finger portions connected to the lug portion and diverging therefrom; providing a second mold half having the remaining portion of said first pattern formed therein, said remaining portion including a second lug portion corresponding to the lug portion in said first mold half and a plurality of mold cavities; placing said first and second mold halves together in such a manner that said portions of said first pattern in said first and second mold halves are in communication with each other; injecting a molten metal into said first pattern to form a lug and a plurality of interconnected runners, each of said runners having at least one integral rod formed in one of said mold cavities in said second mold half, and allowing said metal to at least partially solidify therein; removing said second mold half while retaining said metal in said portion of said first pattern in said first mold half; placing a third mold half adjacent said first mold half, said third mold half having a second pattern formed therein defining a supporting grid into which extend said rods and the portion of said lug formed in said portion of said first pattern in said second mold half; injecting a plastics material into said second pattern to form a supporting grid and to cause said plastics material to flow around said rods; allowing said plastics material to solidify whereupon it engages said rods; and removing the resulting composite grid from said first and third mold halves.

In carrying out one method according to the invention a first pattern is located in each of the first and second mold halves After molding and solidifying the metal in the first pattern, the second mold half is withdrawn with the molded metal being retained in the first mold half A third mold half is moved into 70 engagement with the first mold half for injection of the plastics material The third mold half has a second pattern formed therein into which extends a portion of the metal which was molded in the portion of the first pattern 75 in the second mold half The plastics material is injected into the second pattern and flows around the portion of the molded metal which extends into the second pattern and is allowed to solidify to engage portions of the metal 80 The invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a battery plate grid according to the present invention; 85 Figure 2 is a top view of a first mold half for forming the battery plate grid of Figure 1; Figure 3 is a top view of a second mold half for forming the battery plate grid of 90 Figure 1;_ Figure 4 is a top view of a third mold half for forming the battery plate grid of Figure 1; Figure 5 is a sectional view of the portion 95 of the first and second mold halves taken along line 19-19 of Figure 1; and Figure 6 is a sectional view of the portion of the first and third mold halves taken along line 20-20 of Figure 1 and corresponds to 100 Figure 5, except for the third mold half replacing the second mold half and plastic also being molded.

Referring to Figure 1, grid 210 is an embodiment of a composite grid according to this 105 invention With reference to Figures 1, 5 and 6, a battery grid 210 according to this embodiment of the invention comprises a molded supporting grid 212 with which a fan-like conductive member 214 is in engagement 110 The molded supporting grid 212 comprises peripheral sides 215 and top and bottom members 216 and 217, respectively, defining a generally rectangular boundary Within the sides 215 and top and bottom members 216 115 and 217, respectively, are a plurality of interconnected spaced runners 220, having generally cylindrically shaped cavities 221 which are formed in the surface thereof In engagement with the supporting grid 212 is the fan-like 120 conductive member 214 comprising a terminal lug 222 having a plurality of divergent conductive runners 224 extending therefrom.

Each of the conductive runners 224 has at least one generally cylindrically shaped rod 125 225 integrally formed thereon and extending laterally therefrom and into the generally cylindrically shaped cavities 221 formed in the conductive runners 224 The cylindrically shaped rods 225 and cylindrically shaped cavi 130 1,604,607 ties 221 are so located and formed that each of the rods 225 fits into a hollow cavity 221 and is engaged and supported therein by the molded material of the supporting grid 212.

In the preferred embodiment, a conductive grid 214 is formed of lead or a lead alloy, and the molded supporting grid is formed from a suitable acid resistant moldable plastic material such as polypropylene, polyethylene, polycarbonate, polystyrene, or filled versions of the same.

Manufacture of the grid 210 is effected through the use of three mold halves shown in Figures 2 through 4 With reference to Figure 2, the first mold half 230 is shown which has a planar top surface 231 A pattern 235 includes an area 236 conforming to the lug portion 222 and divergent finger portions 237 which define the conductive runners 224.

As shown in Figures 3 and 5 a second mold half 245 is provided which has a generally planar top surface 246 in which is formed a mold cavity 247 which generally defines one-half of the lug portion 222 of the conductive grid 214 and mold cavities 248 which define the generally cylindrically shaped rods 225 formed in the conductive runners 224.

The mold cavities 248 are located at desired connection points between the lead runners 224 and plastic grid runners 220 and thus are located where portions of the non-conductive grid defining pattern 252 overlie the lead runner grooves 237.

Similarly, as seen in Figure 4, a third mold half 250 is provided which has a generally planar top surface 251 and a mold pattern 252 in the shape of the plastic supporting grid 212, plus a clearance area 253 to accommodate the lug portion 222.

Figures 5 and 6 show a cross-sectional view of a portion of mold halves 230 and 245 and 250 for forming a grid 210 according to this embodiment of the invention As seen in Figure 5 initially the first and second mold halves 230 and 245, respectively, are brought together so that each of the cavities 248 is in communication with a lead runner groove 237.

Lead is injected under pressure or fed by gravity into the mold cavities to form the lug portion 222, lead runners 224 and the rods 225 The lead injection point and gating may be provided by conventional techniques.

Referring to Figure 6, after the lead portion has been cast and solidified, the second mold half 245 is removed while retaining the lead in the first mold half 230, and the third mold half 250 is brought into contact with the first mold half 230 so that the rods 225 extend into the mold pattern 252 The plastic is then injected to form the grid portions including the bottom member 217 and runners 220.

Additionally, the plastic will pass around the perimeter of each of the rods 225 to form the cavities 221 Upon solidfication of the plastic, the rods 225 fit snugly into the cavities 221 65 and are engaged and supported therein by the molded plastic supporting grid 212 Again, conventional injection and gating may be provided, After solidification of the plastic, the mold halves 250 and 230 may be separated 70 and the grid 210 ejected in a conventional manner.

While the present invention has been described as applied to the manufacture of a composite battery grid for a lead acid storage 75 battery, those skilled in the art will appreciate that numerous other applications are possible.

For example, the invention will find equal application to the production of composite grids for other types of batteries such as alka 80 line storage batteries Those skilled in the art will appreciate that the temperatures and pressures of the injected materials may be varied depending upon the materials and the shape of the article to be molded Furthermore, 85 the time required to permit solidification of the materials in the molds will also vary depending upon the external environment conditions, whether or not artificial cooling is provided to the mold, and the shape and design of 90 the mold pattern and molds themselves.

Further, while a particular embodiment of the present invention is shown and described above, it will be understood, of course, that the invention is not to be limited thereto, since 95 many modifications may be made, but is to be taken solely from an interpretation of the claims which follow.

For example, the rods 225 can have a wide variety of shapes other than that of a cylin 100 drical ro dand can extend laterally from the lead runners 224 at any angle necessary to permit effective engagement of the conductive member 214 and supporting grid 212.

Claims (4)

WHAT WE CLAIM IS: 105

1 A method of forming a composite battery grid comprising the steps of:

providing a first mold half having a portion of a first pattern formed therein, said portion including a lug portion and finger portions 110 connected to the lug portion and diverging therefrom; providing a second mold half having the remaining portion of said first pattern formed therein, said remaining portion including a i 15 second lug portion corresponding to the lug portion in said first mold half and a plurality of mold cavities; placing said first and second mold halves together in such a manner that said portions 120 of said first pattern in said first and second mold halves are in communication with each other; injecting a molten metal into said first pattern to form a lug and a plurality of inter 125 connected runners, each of said runners having at least one integral rod formed in one 4 1,604,607 4 of said mold cavities in said second mold half, and allowing said metal to at least partially solidify therein; removing said second mold half while retaining said metal in said portion of said first pattern in said first mold half; placing a third mold half adjacent said first mold half, said third mold half having a second pattern formed therein defining a supporting grid into which extend said rods and the portion of said lug formed in said portion of said first pattern in said second mold half; injecting a plastics material into said second pattern to form a supporting grid and to cause said plastics material to flow around said rods; allowing said plastics material to solidify whereupon it engages said rods; and removing the resulting composite grid from said first and third mold halves.

2 A method as claimed in Claim 1, wherein said metal is an alloy of lead.

3 A method as claimed in Claim 1 or 2, wherein said plastics material is selected from the group consisting of polypropylene, polyethylene, polycarbonate and polystyrene.

4 A method of forming a composite battery grid substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.

A composite battery grid formed by the method as claimed in any one of the preceding claims.

MATHYS & SQUIRE, Chartered Patent Agents, Fleet Street, London EC 4 Y l AY, Agents for the Applicants.

Printed for Her Majesty's Stationery Office by the Courier Press, Leamington Spa, 1981.

Published by the Patent Office, 25 Southampton Buildings, London, WC 2 A l AY, from which copies may be obtained.

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