JP2759118B2 - Method for producing sealing body for alkaline battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a sealed body for an explosion-proof battery in a sealed alkaline battery.

[0002]

2. Description of the Related Art In a sealed alkaline battery, abnormal gas may be generated due to sudden discharge or charging due to improper loading of equipment, and in the worst case, an explosion may occur. For this reason, a method of providing an explosion-proof valve is usually adopted. The present invention is directed to a sealing body in which a very thin part is provided in a sealing body made of a thermoplastic resin, and when the battery internal pressure exceeds a predetermined pressure, the thin part is broken and gas is discharged to the outside. is there. This resin-made sealing body has a thin portion of 0.
The gas discharge function does not work unless it is extremely thin, about 1 to 0.2 mm. The sealing body is usually manufactured by injection molding of a molten resin, but it has been extremely difficult to provide an excellent sealing body in the conventional manufacturing method due to the existence of an extremely thin portion. .

[0003] A method of manufacturing the resin sealing body will be described below. Conventionally, a method of manufacturing a resin sealing body having no thin portion and forming the thin portion by cutting or ultrasonic processing has been performed. I have. In this case, there is a problem that a large amount of capital investment is required for the post-processing, and the production cost becomes high when the post-processing labor is included. In order to solve the above difficulties, a method has been adopted in which a molten resin is injection-molded at a time with a thin portion provided from the beginning. In the case of this injection molding method, roughly two methods are employed at the position of the injection gate. One is a method of providing one or more gates on the outer wall for press-fitting. In this method, the resin flows into the thin portion after the outer wall is filled with the molten resin. It's easy to do. Further, since the gate is provided on the outer peripheral portion, the gate runner becomes large, and the material loss tends to increase.

Another method is to position the injection gate inside the thin portion. When the injection gate is provided on the boss portion for the current collecting shaft at the center of the sealing body, the distance from the gate to the thin portion is short, so that the molten resin is hardly cooled and solidified, and the molding of the thin portion is relatively good. Material loss by runners is also small.

[0005]

However, when the injection gate is provided on the boss for the current collecting shaft as described above, the injection molding is completed, the mold is opened, and a small crack is formed in the boss when the gate is cut. There is a problem that such cracks tend to occur and the cracks increase when the current collecting shaft is press-fitted.

The present invention has been made in order to solve such a problem, and an object of the present invention is to prevent a thin portion from having a weld line or a bonding defect, and to prevent a boss portion crack from occurring at the time of gate cutting. It is to provide a manufacturing method.

[0007]

In order to achieve the above-mentioned object, the present invention employs a means for connecting a boss provided with a hole for a current collecting shaft and a boss of a connecting portion connecting an outer wall to the boss. In the method for manufacturing a sealed body for an alkaline battery having an annular thin portion, an arc-shaped low-speed low-pressure
An injection molding gate having a moldable cross-sectional area is provided, and the connection region of the gate is arranged inside the inner and outer peripheral edges of the end face of the boss.

[0008]

[Function] In the resin-made sealing body, a thin portion requires a uniform thickness and strength in structure, and there is no weld line or joint failure, and a central boss portion is press-fitted with a current collecting shaft, so that it has high strength and no cracks. Is needed. In the present invention, since the gate is provided at the tip of the boss portion, the distance from the gate to the thin portion is short, and therefore the thin portion is filled in a state in which the molten resin has good fluidity, so that weld lines and poor joints occur. Very low.

The gate is formed in an arc shape and the gate cross section is
Expanding, and so is provided on the inside with spaced between inner and outer peripheral edge as the corner of the inner and outer periphery of the boss portion end surface remains, low speed and low
Press forming becomes possible, thereby avoiding a notch effect at the time of cutting the gate and preventing the occurrence of cracks. Traditional
Because the film gate or pin gate has a small cross-sectional area,
Even if it is annular or multiple points, the residual stress of the gate is large,
Cracks were easily generated in the boss when the gate was cut.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described based on embodiments. FIG. 1 is a sectional view of a molding die M according to one embodiment of the present invention. The sealing body 1 molded by the mold M has a cylindrical boss portion having a current collecting shaft hole 3 for press-fitting the current collecting shaft, and a cylindrical outer wall portion 5 for press-fitting the battery case. Disc-shaped connecting portion 9 for connecting boss portion 4 and outer wall portion 5
The joining portion between the connecting portion 9 and the boss portion 4 is formed in the annular thin portion 2. The gate 7 of the mold M is branched into two and connected to the end face of the boss 4.

As shown in FIG. 3, the connection area of the gate 7 with the end face of the boss is arc-shaped and located inside the end face of the boss 4 at a distance from the inner and outer peripheral edges. The corners of the inner and outer peripheral edges of the boss 4 remain. Gate 7
The distance from the thin portion 2 to the thin portion 2 is less than half of the axial length of the boss portion 4 and is very short. Therefore, the molten resin injected from the gate is filled into the thin portion with good fluidity. Therefore, there is little possibility that a weld line or a bonding failure occurs in the thin portion.

FIGS. 2 and 3 show a state in which the sealing body 1 molded by the mold shown in FIG. 1 is taken out and its gate 7 is cut. Figure 3 shows that the relatively connection region Do gate <br/> over preparative 7 magnitude of the cross-sectional area is kept traces the end surface of the boss 4. The connection region of the gate 7 with the boss 4 has an arc shape with two concentrically divided central angles smaller than 180 degrees and is located slightly inside from the inner and outer peripheral edges of the boss end face.
The corners of the inner and outer peripheral edges of the boss 4 are sharp. Large cross section
Gate 7 having a lower speed and lower pressure than before.
Shape is made. Therefore, when the gate 7 is cut from the sealing body 1, a crack occurs in the boss portion 4, and when the current collecting shaft is later pressed into the current collecting shaft hole 3, the crack is formed in the thin portion 2 or the current collecting shaft. There is no possibility that the hole 3 may be defective. The sealing body 1 is injection-molded from a plastic resin such as polyamide, polyethylene, or polypropylene.

FIG. 4 is a sectional view of an essential part of the alkaline battery.
The outer wall 5 of the sealing body 1 is pressed into the battery case 8 and the sealing body 1 is pressed.
The current collecting shaft 6 is press-fitted into the current collecting shaft hole 3 of the boss 4. An annular thin portion 2 formed at a connection portion between the boss portion 4 of the connecting portion 9 connecting the boss portion 4 of the sealing body 1 and the outer wall portion 5.
Is a very thin film having a thickness of 0.1 to 0.15 mm, but is a uniform film having no weld line or poor bonding. When the internal pressure of the battery exceeds a predetermined pressure, the thin portion 2 is surely broken,
Functions as a safety valve. Since the corner of the inner peripheral edge of the boss portion 4 is apart from the gate, there is no possibility that a crack will be generated on the inner periphery of the boss portion 4 when the gate is cut. Therefore, even if the current collecting shaft 6 is pressed into the current collecting shaft boss hole 3, there is no possibility that the boss crack is enlarged and damaged.

In the embodiment, the gate is provided on the end surface of the boss portion so that the corners of the inner and outer peripheral edges of the boss portion remain. However, cracks when the gate is cut often occur on the inner peripheral surface of the boss portion. It may be merely provided so that the corner of the inner peripheral edge of 4 remains. That is, the gate may be in contact with the outer peripheral edge of the boss.

[0015]

According to the method of the present invention, since the ejection gate having a relatively large cross-sectional area is provided in an arc shape on the end face of the boss near the thin portion, even if the ejection pressure is lower than that of the conventional gate. Liquidity is
Good, resulting in internal stresses or residuals
Since the strain is small, there is no weld line or poor connection, and the explosion-proof function of the thin portion is not hindered, the safety of the battery is improved. Further, since the method of the invention provided with a Gate contact area as the corners of at least the inner peripheral edge of the boss end surface remains, advance also sealing member is damaged by press-fitting also collector shaft crack when at the gate cutting Can be prevented. Since the sealing body is an important component used for the alkaline battery and is produced in large quantities, the present invention has a great effect on improving the quality, yield and cost of the alkaline battery.

[Brief description of the drawings]

FIG. 1 is a sectional view of a mold according to the present invention;

FIG. 2 is a sectional view of a sealing body,

FIG. 3 is a plan view from the gate side of the sealing body,

FIG. 4 is a sectional view of a main part of an alkaline battery,

[Explanation of symbols]

1: sealing body, 2: thin part, 3: hole for current collecting shaft, 4:
Boss part, 5: outer wall part, 6: current collecting shaft, 7: gate,
8: Battery case, 9: Connection part

Claims (1)

(57) [Claims] 1. A cylindrical boss portion (4) through which a conductive shaft (6) is passed, a cylindrical outer wall portion (5) to be fitted into a battery case (8), and the boss portion and the outer wall portion. An annular thin portion (2) formed by thinning a connecting portion between the disc-shaped connecting portion (9) and the boss portion of the connecting portion.
A method for producing a thermoplastic resin sealing body made of a thermoplastic resin by injection molding, comprising: forming a circular arc-shaped low-speed low-pressure molding inside an end face of the boss portion;
Characterized in that an injection molding gate (7) having a large diameter is provided so that at least the corner of the inner peripheral edge of the end face of the boss remains.