HERMETICALLY SEALED LEAD STORAGE BATTERY

Abstract: Hermetically sealed lead storage battery comprises an electrode gp. (6) consisting of positive (2) and negative (3) electrode plates and a separator (4) which are set in a frame (1) of poly olefin resin and sandwiched between metal plates (7) whose inner sides are laminated with a sheet or film of polyolefin resin, and the frame and peripheral edges of the metal plates are heat fused. Lugs (5a) of the electrode plates (2,3) are each successively coated with epoxy resin and then polyolefin resin and sandwiched between a metal plate and the frame, and are fused simultaneously with the other elements. The battery has a vent valve (14) consisting of an outermost press plate (10), an intermediate cushion element (11) and an innermost flat rubber valve (12) adjacent a vent hole.

Description: FIELD OF TECHNOLOTY The present invention relates to the improvement of a sealed lead-acid storage battery being used as power source of portable apparatus or the like and provides a lead-acid storage battery that the assembling process is simple and is speedily completed, the cost is low, the reliability is high, and the volumetric efficiency is excellent. BACKGROUND TECHNOLOGY A conventional sealed lead-acid storage battery is constructed as shown in Fig. 2 which is used as power source of portable apparatus or the like. In Fig. 4, numeral 1 denotes a casing made of a thermoplastic resin and receiving a gorup of electrodes 6 composed of a positive electrode 2, a negative electrode 3, and a separator 4. An opening portion of a casing 1 surrounding the periphery of the group of the electrodes 6 is hermetically sealed, when the opening portion is thermally bonded to a periphery of a metal plate 7 for a battery casing, an inner surface of which metal plate has been already laminated with a polyethylene film or the like. Numeral 5 denotes a pole bar portion, and numeral 8 denotes a vent valve formed at the casing 1 and having the function of opening the valve with the increment of the inner pressure of the battery. The method for sealing completely the pole bar portion 5 will be described hereinbelow. One method is that an adhesive such as an epoxy resin is filled and hardened. The other method is that a sheet of lead alloy coated previously with the epoxy resin or a polyethylene resin is welded to a protruding portion of the electrode by TIG welding or the like to form a pole bar, and the resulting pole bar is thermally bonded between the casing and the metal plate for a battery casing. In such a conventional structure, the hardening of adhesive usually requires approximately one hour at 60 o C because the adhesive such as the epoxyresin or the like is used for sealing of the pole bar portion 5. As a result, it is impossible to improve production capacity in producing process. In the method that the sheet of lead alloy coated with the epoxy resin or the polyethylene resin is welded to the protruding portion, it was difficult to construct efficiently assembling line of sealed lead-acid storage battery at a high-speed and low cost, since there was a problem in reliability of welding and cost. DISCLOSURE OF THE INVENTION The present invention has been developed in view of the above-mentioned drawbacks and contemplates to provide an improved sealed lead-acid storage battery described hereinbelow. Owing to the fact that a protruding portion of an electrode is coated with an epoxy resin and a polyolefin resin and therefore it is possible to bond thermally the protruding portion with a casing and one surface of metal plate coated with a polyolefin film or the like, it is possible to make an assembling line for assembling the battery with efficiency at high-speed. As a result, the sealed lead-acid storage battery can be made which has a high volumetric efficiency and is of low cost. According to the present invention, the sealing structure of the pole bar portion is characterized in the next point described below. First, the protruding portion of each of the electrode is directly coated with the epoxy resin and the polyolefin resin, a group of electrodes is thereafter sandwiched between the casing made of a thermoplastic resin and surrounding the periphery of a group of electrodes and metal plate whose inner surface is laminated with a polyolefin film, and then, on thermal bonding of the casing and the metal plates, the protruding portions of electrodes are also thermally bonded to them for sealing the opening, instead of that conventionally, the above-mentioned epoxy resin adhesive is used for adhesion, and a sheet of lead alloy coated with the epoxy resin and the polyolefin resin is welded to the porotruding portion of the electrode, and then, the resulting part is thermally bonded to the casing. Since the process and installation for assembling the battery are simplified and it is possible to shorten largely the operation time of opening-sealing process by this structure, the battery can be assembled at a high-speed. As a result, the sealed lead-acid storage battery of low cost, high reliability, and excellent volumetric efficiency can be provided. Preferably, the casing of the battery casing and the pressing plate of the cushion are formed integrally, the joint portion of the pressing plate is formed such that the thickness of the joint portion is thinner than that of the pressing plate, thereby being easy to be bent by the function of the hinge, and the pressing plate fitting portion of the opening of the concave portion is provided with a concave portion and a convex portion. As a result, once the pressing plate is fitted, it is difficult to be disengaged. By this structure, the operation efficiency is largely improved and the products are stably obtained in quality in comparison with the conventional method. As a result, hereafter, even if sealed lead-acid storage battery is miniaturized, it is possible to design the structure in accordance with such trend. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view of the sealed lead-acid storage battery before assembling of the embodiment of the present invention; Fig. 2 is a perspective view showing the structure of the conventional sealed lead-acid storage battery. DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiment of the present invention will be described hereinbelow. Fig. 1 shows a sealed lead-acid storage battery of the present invention, and numeral 1 denotes a casing made of a polyolefin resin such as a polyethylene resin, which casing surrounds a periphery of a group of electrodes. A protruding portion of an electrode 5a is directly coated with an epoxy resin which is superior in heat resistance and adhesive property, the epoxy resin thereafter is hardened, and then the resulting surface is again coated with a modified-polyethylene solution. The group of electrodes 6 comprises a positive electrode 2 and a negative electrode 3 each having a protruding portion coated as described above, and a separator 4 made of nonwoven fabric mainly composed of glass fiber of diameter less than 5 µm, which separator 4 is superior in absorbing power of electrolyte. The group of electrodes 6 is received in the casing 1. As a metal plate 7 for a battery casing, is used an aluminium plate, a stainless steel plate, or a tinned steel plate. A thermally bondable polyethylene or polyester film is bonded, and especially, a thermally bondable film or sheet including one body with three layers consisting of an ethylene acrilic acid (EAA) layer, a polyethylene terephthalate (PET) layer, and another ethylene acrilic acid (EAA) layer, which film or sheet has been improved in acid resistance and strength on thermal bonding, is laminated to one surface of the metal plate by means of adhesion or bonding by fusion. The group of electrodes is sandwiched between two metal plates 7 with the resin film layer of each of the metal plates being opposed to the group of electrodes, and then the rim of the metal plates 7 and the rim of the opening of the casing 1 are thermally bonded each other. At the casing 1, are provided in advance, a shallow, slender and long concave portion 18 in which the protruding portion of the electrodes 5a is fitted on thermal bonding, and a vent valve 8 arranged to be opened when the inner pressure of the battery rises above a predetermined value. When the metal plates 7 for the battery casing are thermally bonded to the casing 1, the protruding portions 5a also are thermally bonded to the casing 1 and thermal bonding film on one side of the metal plates 7. The separator is impregnated with the electrolyte indispensable to the battery in advance before this thermal bonding. Before thermal bonding, an uncoated edge of the protruding portion of the electrode 5a arranged to be fitted in the concave portion 18 of the casing 1 made of a resin is spot-welded or the like to a film-removed portion of inner edge portion of the metal plate 7 for battery casing to connect each other electrically, so that the metal plate for battery casing 7 is used as an external terminal. According to the present invention as described above, the protruding portions 5a of the electrodes of the pole bar portions are directly coated with the epoxy resin in advance, and the surfaces coated with the epoxy resin are coated with the polyolefin resin having the property of thermal bonding. Therefore, the metal plates 7 for the battery casing and the pole bar portions can be thermally bonded to the casing 1 surrounding the periphery of the group of the electrodes in the same instant. As a result, the assembling process is simplified and is completed at a high-speed, and the sealed lead-acid storage battery of low cost, high reliability, and high volumetric efficiency can be made in comparison with the conventional method that adhesive is used and the pole bar treated by a resin is welded to the electrode. POSSIBILITIES OF INDUSTRIAL UTILIZATION According to the present invention described above, the number of parts to be used for the terminal portion decreases thereby reducing cost. Hereafter, the tendency of miniaturization of sealed lead-acid storage battery can be dealt with.

Claims: A sealed lead-acid storage battery comprising a group of electrodes consisting of a positive electrode, a negative electrode, and a separator is sandwiched between two metal plates laminated with a polyolefin resin film or sheet on one surface of said metal plate such that said polyolefin resin layer of said metal plate faces said group of electrodes, and said group of electrodes is sealed hermetically with a casing made of said polyolefin resin and surrounding a periphery of said group of electrodes and a peripheral rim of said metal plate being thermally bonded, and in that a protruding portion of a positive electrode and a negative electrode is coated with an epoxy resin and again coated with said polyolefin resin on said epoxy resin layer, said resulting protruding portion is sandwiched between said casing and said metal plate having said polyolefin layer so that said group of electrodes is hermetically sealed and said protruding portion is hermetically sealed between said casing and said resin layer surface of said metal plate. A sealed lead-acid storage battery as claimed in claim 1, wherein said separator is mainly composed of glass fiber of diameter less than 5 µm. A sealed lead-acid storage battery as claimed in claim 1, wherein said polyolefin resin film or sheet provided on one surface of said metal plate includes one body with three layers consisting of an ethylene acrilic acid layer, a polyethylene terephthalate layer, and another ethylene acrilic acid layer. A sealed lead-acid storage battery as claimed in claim 1, wherein said metal plate laminated with said film or sheet made of said polyolefin resin on one surface of said metal plate is a tinned steel plate. A sealed lead-acid storage battery as claimed in claim 1, wherein said protruding portion of said electrode is welded to a portion of a peripheral rim portion of one surface of said metal plate so that said metal plate is formed to be an external terminal. A sealed lead-acid storage battery as claimed in claim 1, wherein a concave portion is formed, for receiving said protruding portion of said electrode, in said casing to be sandwiched bewteen said metal plates and to be thermally bonded.

Inventors: KOIKE, KIICHI, MATSUO, KOUJIROU, SUGIMOTO, MANSAKU, SUZUKI, YOSHIE, YOSHINAKA, MINORU
Applicants: MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1987
Main classification: H01M2
IPC codes: H01M10, H01M2