GB1604606A

GB1604606A - Manufacture of composite articles

Info

Publication number: GB1604606A
Application number: GB24090/78A
Authority: GB
Original assignee: Globe Union Inc
Current assignee: Globe Union Inc
Priority date: 1977-06-15
Filing date: 1978-05-30
Publication date: 1981-12-09
Also published as: DE2823871C2; GB1604607A; MX149348A; DE2823871A1; IT1158855B; IT7824588A0; CH634256A5; CH640368A5

Abstract

The composite body, for example an accumulator grid plate, is produced by means of two mould parts (130, 145) having a first and second mould cavity (135, 152) which are disposed one above the other. Displaceable means (140) can be moved between a first and second position and, in the first position, are connected to the second mould cavity (152) at the points at which it overlaps or intersects with the first mould cavity (135). Further means (148) which can be moved into a first and a second position serve, in one position, to separate the two mould cavities (135, 152) from one another. After the casting and solidification of a first material into the first mould cavities (135), the movable means (140, 148) are brought into their second positions, so that cavities (128) connected to the two mould cavities (135, 152) result. Then a flowable material is introduced into the mould cavities (152) of the second mould part (145), which material, after solidification, is interlocked with specific sections (128) of the first material. By means of this solution, the composite body can be produced in a simple manner by a mass-production process. <IMAGE>

Description

(54) IMPROVEMENTS IN OR RELATING TO THE MANUFACTURE OF COMPOSITE ARTICLES (71) We, GLOBEUNION 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 articles 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. Con ventionally, 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 aoting 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 a 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 particular desirable method of reducing the amount of lead in battery grids lies in the area of combining less expensive, light weight 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 centered 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 col lector, 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.

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 article comprising the steps of: providing two mold halves having first and second patterns formed therein, with at least one of said first and second patterns being in one of said mold halves, and said mold halves each including at least one type of movable means, with each said type of movable means being movable between a first position and a second position; placing said two mold halves together so that one of said patterns overlies at least one portion of the other of said patterns, with each said type of movable means being in its first position and being in communication with said first pattern, and with at least one said type of movable means separating said first pattern from said second pattern everywhere one of said patterns overlies the other of said patterns; introducing a first material in a liquid state into said first pattern, with said type of said movable means which separate said first and second patterns preventing entry of said first material into said second pattern and allowing said first material to at least partially solidify; moving each said type of movable means to its second position to form at least one vacated portion in communication with said first and second patterns and to remove the separation between said first and second patterns where one of said patterns overlies the other of said patterns; injecting a second fiowable material into said second pattern to cause said second material to liquify and flow into at ;cast one said vacated portion, where, upon solidifying, said second material engages said first material; allowing said second material to solidify; and removing the resulting molded article from said mold halves.

In carrying out one method according to the invention a composite article is produced by a method in which only two mold halves are employed which have first and second patterns formed therein. The second pattern overlies portions of the first pattern. Movable means are provided which are movable between a first position and a second position.

Such movable means, in their first position, are in communication with the first pattern at selected places where said second pattern overlies said first pattern; and at least one type of such movable means, in their first position, serves to separate the first and second patterns everywhere said second pattern overlies said first pattern. After molding and solidifying the first material in the first pattern, the movable means are positioned to create voids in communication with the first and second patterns and to remove the separation between the first and second patterns where the second pattern overlies the first pattern. Then the flowable material is injected into the second pattern and into the voids and is allowed to solidify to engage portions of the first material.

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; 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 Figure 1; Figure 4 is a sectional view of the portion of the first and second mold halves taken along line 13-13 of Figure 1 with two types of movable means in their first positions; and Figure 5 is a sectional view of the portion of the first and second mold halves taken along line 14--14 of Figure 1 and corresponds to Figure 4, except with the two types of movable means being in their second positions and plastic also being molded.

Referring to Figure 1, grid 110 is a first embodiment of a composite grid according to this invention. Manufacture of the grid 110 can be effected through the use of only two mold halves shown in Figures 2-5. With reference to Figures 1, 4 and 5, the battery plate grid 110, according to this embodiment of the invention, comprises a molded supporting grid 112 to which a fan-like conductive member 114 is attached. The molded supporting grid 112 comprises peripheral sides 115 and top and bottom members 116 and 117, respectively, defining a generally rectangular boundary. Within the sides 115 and top and bottom members 116 and 117, res pectively, are a plurality of interconnected spaced runners 120. Attached to the supporting grid 112 is the fan-like conductive member 114 comprising a terminal lug 122 having a plurality of divergent conductive runners 124 extending therefrom. Each of the conductive runners 124 has at least one generally disc-shaped portion 125 formed therein, each of which has a central aperture 126 formed therein. The disc-shaped portions 125 are located at points where the molded runners 120 overlie the conductive runners 124 and are mechanically locked to the sup porting grid 112 at such points by molded material extending from the runners 120 through the apertures 126 to form generally circular retaining heads 128. In the preferred embodiment, the conductive grid 114 is formed of lead or a lead alloy, and the molded supporting grid 112 is formed from a suitable acid resistant moldable plastic material such as polypropylene, polyethyene, polycarbonate, polystyrene, or filled versions of the same.

With reference to Figure 2, the first mold half 130 is shown which has a planar top surface 131. A first pattern 135 defines the conductive member 114 including the portion 136 which conforms to the lug portion 122 and divergent finger portions 137 which define the conductive runners 124 including the disc-shaped portions 125 formed therein.

Referring now to Figures 2, 3, 4 and 5, it will be seen that the mold half 130 includes a plurality of a first type of retractable pins 140 which are movable in a direction perpendicular to the planar top surface 131.

The pins 140 are placed at desired connection points between the lead runners 124 and plastic grid runners 120 and thus are located at selected points where portions of a nonconductive grid defining pattern 152 overlie the lead runner grooves 137. The end portions of the pins 140 are provided with a generally frustoconical upraised portion 141 which is of reduced diameter from the diameter of the pins 140. The generally planar end surface 143 of the frustoconical portion 141 is coplanar with the plane 131 when the pin 140 is in an extended position and is movable to a point indicated by the phantom lines 142 in Figure 4 when the pins 140 are retracted.

As shown in Figures 3 and 4, a second mold half 145 is provided which has a generally planar top surface 146 in which is formed a mold cavity 147 which generally defines one-half of the lug portion 122 of the conductive grid 114. The second mold half 145 also is provided with a second mold pattern 152 in the shape of the plastic sup porting grid 112. The mold cavity 147 and second mold pattern 152 are separated so that lead injected into the mold cavity 147 does not enter the second mold pattern 152.

The second mold half 145 also is provided with a second type of retractable pins 148 which are movable in a direction perpendicular to the planar top surface 146. The pins 148 are placed at the above-mentioned desired connection points-that is, where the nonconductive grid defining portions 152 overlie the lead runner grooves 137 and opposite from the retractable pins 140-as well as at all other points where the nonconductive grid defining portions 152 overlie the lead runner grooves 137. The pins 148 are pr vided with a generally planar end surface 149. The end surface 149 is coplanar with the plane 146 when the pin 148 is in an extended position and is movable to a point indicated by phantom lines 150 in Figure 3 when the pins 148 are retracted.

Figures 4 and 5 show a cross-sectional view of a portion of the mold halves 130 and 145 for forming a grid 110 according to this embodiment of the invention. As seen in Figure 4, initially the first and second mold halves 130 and 145, respectively, are brought together with the retractable pins 140 and 148 in their extended positions. In their extended positions, both types of the pins 140 and 148 are in communication with the first pattern 135, and the pins 148 prevent entry of lead into the second mold pattern 152.

Lead is injected under pressure or fed by gravity into the mold cavities to form the lug portion 122 and the lead runners 124 including the disc portions 125 having the apertures 126 formed therein. The lead injection point and gating may be provided by conventional techniques.

Referring to Figure 5, after the lead portion has been cast and solidified, the pins 140 and 148 are retracted. Retraction of the pins 140 and 148 produces the voids 126 which are in communication with both the first and second patterns 135 and 152, respectively, and retraction of the pins 148 also removes the separation between the first and second patterns 135 and 152, respectively, and permits plastic to flow into the voids 126. The plastic is then injected to form the grid portions including the bottom member 117 and runners 120. Additionally, the plastic will pass through the apertures 126 formed in the lead disc portions 125 to form the disc-like heads 128 which lock the lead disc portions 125 to the supporting grid 112.

Again, conventional injection and gating may be provided. After solidification of the plastic, the mold halves 130 and 145 may be separated and the grid 110 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 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 alkaline storage batteries. Furthermore, the teachings of the invention may be applied to the production of other articles of manufacture wherever it is desired to join two materials at a single molding station. Preferably, the first material injected will be of a relatively higher melting point followed by injection of the second material having a lower melting point. However, those skilled in the art will appreciate that such a limitation is not absolutely necessary. The materials may vary from two metals, a metal and a plastic, two plastic materials, or other moldable materials. 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, 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 the mold pattern and molds themselves.

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

For example, the retractable pins 140 could each be replaced by movable pins which move from first, retracted positions to second, extended positions when plastic is being injected, in order to push the molded discshaped portions 125, at least partially out of finger-defining portions 137 and into second mold patterns 152. Thus, voids are formed around the outside walls of the disc-shaped portions 125, into which the plastic can flow and engage the conductive members 114 along the exterior of the fingers 124. The retractable pins 140 could also each be replaced by retractable pins which are so constructed as to abut the outside wall of the conductive runners 124 when in their first, extended positions, and to create voids along such walls, when in their second, retracted positions, so that plastic can flow into such voids and engage the conductive members 114 along the exterior of the conductive runners 124.

In short, the particular number, configuration or combination of movable pins and the manner and direction in which they are moved can be varied greatly and still serve the function of the movable pins in making the integrally formed plastic support grids and the integrally formed conductive members of this invention as described hereinabove.

WHAT WE CLAIM IS:- 1. A method of forming a composite article comprising the steps of: providing two mold halves having first and second patterns formed therein, with at least one of said first and second patterns being in one of said mold halves, and said mold halves each including at least one type of movable means, with each said type of movable means being movable between a first position and a second position; placing said two mold halves together so that one of said patterns overlies at least one portion of the other of said patterns, with each said type of movable means being in its first position and being in communication with said first pattern, and with at least one said type of movable means separating said first pattern from said second pattern everywhere one of said patterns overlies the other of said patterns; introducing a first material in a liquid state into said first pattern, with said type of said movable means which separate said first and second patterns preventing entry of said first material into said second pattern and allowing said first material to at least partially solidify; moving each said type of movable means to its second position to form at least one vacated portion in communication with said first and second patterns and to remove the separation between said first and second patterns where one of said patterns overlies the other of said patterns; injecting a second flowable material into said second pattern to cause said second material to liquify and flow into at least one said vacated portion, where, upon solidifying, said second material engages said first material; allowing said second material to solidify; and removing the resulting molded articles from said mold halves.

2. A method as claimed in Claim 1, wherein said first pattern is in one mold half and said second pattern is in the other mold half.

3. A method as claimed in Claim 2, wherein said type of movable means in said mold half containing said first pattern is retractable means which are movable between an extended position as their first position and a retracted position as their second position, which are located within at least one portion of said first pattern, and which are moved to a retracted position to form at least one vacated portion in said first pattern; and wherein said type of movable means in said mold half containing said second pattern is means which are movable between an extended position as their first position and a retracted position as their second position and which in their extended position separate said first pattern from said second pattern everywhere

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. application to the production of composite grids for other types of batteries such as alkaline storage batteries. Furthermore, the teachings of the invention may be applied to the production of other articles of manufacture wherever it is desired to join two materials at a single molding station. Preferably, the first material injected will be of a relatively higher melting point followed by injection of the second material having a lower melting point. However, those skilled in the art will appreciate that such a limitation is not absolutely necessary. The materials may vary from two metals, a metal and a plastic, two plastic materials, or other moldable materials. 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, 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 the mold pattern and molds themselves. Further, while particular embodiments of the present invention are shown and described above, it will be understood, of course, that the invention is not to be limited thereto, since many modifications may be made, but is to be taken solely from an interpretation of the claims which follow. For example, the retractable pins 140 could each be replaced by movable pins which move from first, retracted positions to second, extended positions when plastic is being injected, in order to push the molded discshaped portions 125, at least partially out of finger-defining portions 137 and into second mold patterns 152. Thus, voids are formed around the outside walls of the disc-shaped portions 125, into which the plastic can flow and engage the conductive members 114 along the exterior of the fingers 124. The retractable pins 140 could also each be replaced by retractable pins which are so constructed as to abut the outside wall of the conductive runners 124 when in their first, extended positions, and to create voids along such walls, when in their second, retracted positions, so that plastic can flow into such voids and engage the conductive members 114 along the exterior of the conductive runners 124. In short, the particular number, configuration or combination of movable pins and the manner and direction in which they are moved can be varied greatly and still serve the function of the movable pins in making the integrally formed plastic support grids and the integrally formed conductive members of this invention as described hereinabove. WHAT WE CLAIM IS:-

1. A method of forming a composite article comprising the steps of: providing two mold halves having first and second patterns formed therein, with at least one of said first and second patterns being in one of said mold halves, and said mold halves each including at least one type of movable means, with each said type of movable means being movable between a first position and a second position; placing said two mold halves together so that one of said patterns overlies at least one portion of the other of said patterns, with each said type of movable means being in its first position and being in communication with said first pattern, and with at least one said type of movable means separating said first pattern from said second pattern everywhere one of said patterns overlies the other of said patterns; introducing a first material in a liquid state into said first pattern, with said type of said movable means which separate said first and second patterns preventing entry of said first material into said second pattern and allowing said first material to at least partially solidify; moving each said type of movable means to its second position to form at least one vacated portion in communication with said first and second patterns and to remove the separation between said first and second patterns where one of said patterns overlies the other of said patterns; injecting a second flowable material into said second pattern to cause said second material to liquify and flow into at least one said vacated portion, where, upon solidifying, said second material engages said first material; allowing said second material to solidify; and removing the resulting molded articles from said mold halves.

one of said patterns overlies the other of said patterns and prevent entry of said first material into said second pattern.

4. A method as claimed in any one of the preceding claims, wherein said first material is injected under pressure into said first pattern.

5. A method as claimed in Claim 4, wherein said first material is fed by gravity into said first pattern.

6. A method as claimed in any one of the preceding claims, wherein said first material has a higher melting point than said second material.

7. A method as claimed in Claim 6, wherein said first material is a metal and said second material is a plastics.

8. A method as claimed in Claim 7, wherein said article is a battery grid and said first material is an alloy of lead.

9. A method as claimed in Claim 7 or 8, wherein said plastics is selected from the group consisting of polypropylene, polyethylene, polycarbonate and polystyrene.

10. A composite article formed by a method as claimed in any one of the preceding claims.

11. A composite battery grid made by a method as claimed in any one of Claims 1 to 9 and comprising: an injection molded plastic support; and an injection molded electrically conductive member; said support mechanically engag ing said conductive member at a region of said conductive member at which a por tion of said plastic has been caused to flow during injection molding thereof and, upon solidification thereof, engages said conductive member.

12. A composite battery grid as claimed in Claim 11, wherein said conductive member comprises a lug having a plurality of interconnected fingers and said support has a grid-like structure.

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

14. A composite article formed by the method as claimed in Claim 13.