AU603270B2 - Method of forming window in electrolytic tank of storage battery for monitoring condition of electrolyte - Google Patents

Description

i_ _II COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 COMPLETE SPECIFICATION 7 0 NAME ADDRESS OF APPLICANT: Miyagawa Kasei Industry Co., Ltd.

16-25 Komatsu 1-chome Higashiyodogawa-ku Osaka Japan 4

I,

Yuasa Battery Co., Ltd.

6-6, Josai-cho Takatsuki-shi Osaka-fu Japan NAME(S) OF INVENTOR(S):

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K j~n~~~l3.i Shiro MIYAGAWA ADDRESS FOR SERVICE: DAVIES COLLISON Patent Attorneys 1 Little Collins Street, Melbourne, 3000.

COMPLETE SPECIFICATION FOR THE INVENTION ENTITLED: I I I Method of forming window in electrolytic conditon of electrolyte The following statement is a full description of this performing it known to me/us:tank of storage battery for monitoring invention, including the best method of a _i rp.- BACKGROUND OF THE INVENTION Field of the Invention This invention relates to a method of forming a window in the lateral wall of the electrolytic tank of a storage battery for monitoring the condition of the electrolyte such as the amount or specific gravity of the electrolyte.

Description of the Prior Art A storage battery is charged with an electrolyte, the amount of which has an important bearing on the performance of the storage battery and on the leakage of the electrolyte; therefore, the amount must be controlled so that it is within a given range. Generally, it is preferable that the electrolytic tank of a storage battery 1 be designed so that the liquid surface can be monitored from the outside.

The simplest method for making it possible to monitor the liquid surface from the outside is to make the electrolytic tank of the storage battery itself from a transparent or translucent material. In this case, however, not only the liquid surface but also the entire interior of the electrolytic tank can be seen through.

1A -UU I- Therefore, in the case of a storage battery which has been used for a long time, the interior of the electrolytic tank has been disfigured with the electrode plates being deteriorated or the active material falling off, and such ugly condition, which comes into view, detracts from the aesthetic value of the storage battery.

Under these circumstances, it has been usual practice for storage battery manufacturers to make transparent or translucent the region where the liquid surface is. to be observed, while leaving the other regions opaque.

For example, Japanese Utility Model Publication No.

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12442/1954 discloses a technique in which while the I 4 electrolytic tank is made from a transparent or 4 translucent synthetic resin, paint is applied to the electrolytic tank in order to make opaque the regions above and below the normal surface of the electrolyte.

r E However, according to the conventional technique described above, the step of applying paint to the predetermined regions is troublesome, and the paint applied often peels off during prolonged period of use of the storage battery or owing to rubbing against an object, thus detracting from the aesthetic value of the storage battery.

Japanese Patent Publication No. 27890/1965 discloses a technique in which the main portion of the storage 2 battery is made from an opaque region by injection molding, whereupon the molding is placed in a metal mold and then a transparent resin is poured into the metal mold to form the storage battery with a transparent portion.

This transparent portion makes it possible to see through the liquid surface from the outside.

However, according to the conventional technique described above, the interface between the transparent and opaque portions extends throughout the periphery of the electrolytic tank or over a relatively long distance, and the dissimilarity of the resins forming the respective portions weakens their joint, which, in turn, results in the lack of reliability of prevention of leakage of the electrolyte.

Japanese Utility Model Publication Nos. 2333/1963 and 6045/1963 disclose a construction in which an opaque electrolytic tank is formed in such a manner that a hole extending through the lateral wall is formed, and then a liquid surface seeing-through body having a transparent portion is fitted in said hole. In the conventional technique of the former, such liquid surface seeing-through body is fitted in the hole through a packing, while in the conventional technique of the latter, thread is utilized for fitting.

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However, each of the conventional techniques described above involves the operation of fitting a liquid surface seeing-through body in the lateral wall of the electrolytic tank, and since the fitting condition has to be such that leakage can be perfectly prevented, the operation is troublesome, leading to a decrease in production efficiency. Further, the construction in which a separately prepared liquid surface seeing-through body is fitted in a hole in an electrolytic tank is low in reliability of prevention of leakage even if a packing or a thread is employed in the fitting portion, and the problem of leakage becomes noticeable particularly after the storage battery has been used for a long period of time.

In addition, the construction which allows the interior of the electrolytic tank to be seen through can be used as a construction for monitoring the condition of the electrolytic including not only the amount of electrolyte but also its specific gravity; therefore, all these constructions, whether they monitor the amount or the specific gravity of the electrolyte, encounter the <same problem.

SUMMARY OF THE INVENTION Accordingly, this invention is intended to provided a method of forming electrolyte condition monitoring windows 4 1 in the electrolytic tank of a storage battery, which method 2 is capable of solving the problem encountered by the various 3 conventional techniques described above.

4 Particularly, this invention is intended to 6 advantageously solve the problem of leakage occurring in the 7 interface between an electrolyte condition monitoring window 8 and another portion.

9 In accordance with the present invention there is 11 provided a method of forming a window in a storage battery 12 electrolytic tank having a lateral wall and a bottom wall, 13 said window being for monitoring the condition of the 14 electrolyte, comprising the steps of: preparing a storage battery electrolytic tank made t. 16 from an olefin resin and formed with a hole extending S 17 through said lateral wall, 18 disposing a pair of molds on opposite sides of 19 said lateral wall in such a manner as to form a cavity which includes said hole, said molds surrounding the peripheral 21 wall portion which defines said hole, 22 injecting into said cavity an olefin resin, which 23 has at least light-permeability and a higher transparency 24 than that of said olefin resin which forms said tank, to define the electrolyte condition monitoring window, and 26 separating said metal molds from said lateral wall 27 when said injected olefin resin has hardened.

28 29 31 32 33 34 36 37 'A8 4' a 90 0 8 1 6 dbwspe.012.miya.spe.5 t In thig inanion ftrj storage battery electrolytic tank having a hole in the lateral wall has been obtained, said hole is positioned within a cavity formed by a pair of metal molds placed on opposite sides of the lateral wall. And an olefin resin having at least light-permeability is injected into the cavity, so that an electrolyte condition monitoring window conforming to the shape of the cavity is formed by said olefin resin.

According to this invention, a storage battery electrolytic tank is formed from an olefin resin, and also an olefin resin is injected, so that electrolyte condition monitoring window is formed by the so-called "secondary" molding. Therefore, injection molding is applied to the "secondary" molding of the electrolyte condition monitoring window. As a result, the pressure for injection of the resin into the cavity defined by the molds can be fully increased and since both the electrolytic tank and the electrolyte condition monitoring window are made from olefin resins, they are advantageously integrated and the resulting joint portion is strong and reliable. Therefore, no problem of leakage will arise during a long period of use of the storage battery.

A -6i i. -i Further, the formation of an electrolyte condition monitoring window by "secondary" molding using metal molds can be efficiently performed.

In addition, if an electrolyte condition monitoring window is formed in such a manner that the resin forming the electrolyte condition monitoring window has a. contccct which eitats e- opposite surfaces of the peripheral wall portion defining the hole, then this is more effective in preventing leakage of the electrolyte.

Further, if a recess and ridge combination is formed on the interface where the resin forming the electrolyte condition monitoring window contacts the electrolytic tank, this is also effective in preventing leakage of the electrolyte.

Further, since the electrolyte condition monitoring window is formed by a step which is separate from the formation of the storage battery electrolytic tank and since the outer shape of said window is determined by the cavity formed by the metal molds, any desired shape can be ii given to the electrolyte condition monitoring window. For example, the setting of the thickness of the electrolyte condition monitoring window can be easily adjusted by the c, por-ior 0.fZ metal molds. For example, the thickness oflthe i electrolyte condition monitoring window can be made smaller than that of the lateral wall of the electrolytic l 7i tank. In the case where the electrolyte condition monitoring window is made thinner, as desired, the interior of the electrolytic tank can be made to be seen through even if use is made of a material of relatively low transparency.

The foregoing and other objects, features, aspects and advantages of the present invention will become more p(reA~erre..c\ e bociiejs apparent from the following d-etail- description oft-he 1 present invention when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view showing the external appearance of a storage battery electrolytic tank 1 according to an embodiment of the invention; Fig. 2 is an enlarged sectional view taken along the line II-II in Fig. 1; Fig. 3 is a perspective view in which the portion S shown in Fig. 2 is shown partly broken away; "I iFig. 4 is an enlarged sectional view showing metal molds 11 and 12 for injection-molding a resin to form an electrolyte condition monitoring window 4, said metal molds being disposed on opposite sides of the lateral wall 2; 8 4 -i Fig. 5 is a view corresponding to Fig. 2, showing a portion of an electrolytic tank 1 obtained by performing another embodiment of the invention; Fig. 6 is a sectional view, showing enlarged a portion of the lateral wall 2 obtained by performing still another embodiment of the invention; Figs. 7 and 8 show a modified embodiment designed so that an electrolyte condition monitoring window 4c brings a float 18 into view; and Figs. 9 and 10 show a modified embodiment designed so that an electrolyte condition monitoring window 4d brings into view an indicating member 28 operatively connected to a float 2-4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Figs. 1 through 4 are views from explaining an embodiment of the invention. In Fig. I, the external appearance of a storage battery electrolytic tank obtained Sby an embodiment of the invention is shown. In addition, the embodiment to be described below is related to the case where a liquid surface indicating wiidow is formed as an electrolyte condition monitoring window.

As shown in Fig. 1, an electrolytic tank 1 has a lateral wall 2 and a bottom wall 3. As shown in dotted lines on the lateral wall 2, the electrolytic tank 1 is divided into 6 cells and for each cell there is formed a -9- 9liquid surface indicating window 4 to serve as an electrolyte condition monitoring window. The method of forming liquid surface indicating windows 4 will be later described with reference to Figs. 2 through 4.

The upper surface of the electrolytic tank 1 is closed by a cover 5. The cover 5 is formed with liquid ports 6 associated with the cells formed in the electrolytic tank i. Each liquid port 6 is used for pouring a liquid and is closed by an unillustrated electrolyte port plug except when pouring a liquid. Also, polar pillars 7 extend through the cover The electrolytic tank 1 and cover 5 are formed by injection molding using an olefin resin. Among the olefin resins, it is preferable to use a polypropylene-system copolymer for forming the electrolytic tank i. The reason is that this material has a high shock resistance and a relatively low transparency. In order to make the electrolytic tank 1 opaque or relatively low in transparency, a suitable pigment may be added to an olefin resin.

As shown in Figs. 2 through 4, the lateral wall 2 of the electrolytic tank 2 is formed with holes 8 extending therethrough. Such hole 8 can be formed by giving a corresponding shape to the metal mold used for injection-molding the electrolytic tank i. In this 10 -re ip i embodiment, as can be inferred from the shape of the window 4 shown in Fig. 3, the hole 8 is in the form of a vertically extending oval. However, the hole 8 may be any desired shape, such as a circle or quadrilateral. In addition, as can be seen from the following description, the hole 8 is formed at such a position and with such a size that when the liquid surface 10 of the electrolyte 9 is in the normal condition, the hole 8 covers the upper and lower limits of such liquid surface After the electrolytic tank 1 formed with holes 8 has been prepared, a pair of metal molds 11 and 12 are disposed on opposite sides of the lateral wall 2, as shown in an enlarged sectional view in Fig. 4. The metal molds 11 and 12 define a cavity 14 with the hole 8 positioned therein while surrounding a peripheral wall 13 defining the hole 8.

Subsequently, an olefin resin having at least light-permeability for forming a liquid surface indicating window 4 is injected into said cavity 14. The olefin resin thus injected flows into the cavity 14 via a sprue communicating with the cavity 14.

After the olefin resin charged into the cavity 14 is hardened, the metal molds 11 and 12 are separated from the lateral wall 2. Thereby, a liquid surface indicating window 4 is formed to close the hole 8, as shown in Figs.

11 c 2 and 3 and also in Fig. 1. The olefin resin forming the liquid surface indicating window 4 is advantageously integrated with the olefin resin which forms the lateral wall 2 of the electrolvtic tank 1.

When a second member is added to a premolded first member, as in the case of forming said liquid surface indicating window 4, by the so-called "secondary" molding, it has been found that if both of said first and second members are formed of olefin resins, the joint strength is very high. Such joint strength cannot be obtained at present by other resins than the olefin resins.

Therefore, as described above, the olefin resin which forms the liquid surface indicating window 4 is advantageously integrated with the olefin resin which forms the electrolytic tank 1, whereby high reliability of prevention of leakage can be attained.

o .As can be seen from Figs. 2 and 3, the thickness of the liquid surface indicating window 4 is less than that of the lateral wall 2. Such control of the thickness can be effected as desired by the shape of the metal molds.

The fact that the thickness of the liquid surface indicating window 4 is small means that light-transparency is ensured even if the material has low transparency.

Therefore, even if the liquid surface indicating window 4 is formed of the same olefin resin as that of the 12 I-a electrolytic tank 1, it is possible to ensure that the interior can be seen through more easily at the liquid surface indicating window 4.

The olefin resin forming the liquid surface indicating window 4 may not be the same as the olefin resin forming the electrolytic tank 1. For example, if the electrolytic tank 1 is made from a copolymer 0. containing polypropylene, it is preferable that the liquid ;i surface indicating window 4 be made from a homoploymer or random copolymer of polypropylene. The reason is that these polymers are more transparent than usual copolymers.

o t* Further, as random copolymers are also superior in shock resistance, they may be said to be more desirable.

4 Fig. 5 is a view for explaining another embodiment of 15 the invention.

The embodiment shown in Fig. 5 is characterized in a a that the olefin resin which forms the liquid surface o indicating window 4a has a portion which contacts the 0 4a a: opposite surfaces of the peripheral wall portion 13 de.ining the hole 8. The shape of the metal molds for forming such liquid surface indicating window 4a could be easily inferred from the shape of the liquid surface indicating window 4a and hence it is omitted from illustration.

-13- According to the liquid surface indicating window 4a integrated with the lateral wall 2 in the manner described above, since the area of the interface between the liquid surface indicating window 4a and the lateral wall 2 is increased, higher performance for prevention of leakage of the electrolyte can be expected.

Fig. 6 is a view for explaining a further embodiment of the invention.

In the embodiment shown in Fig. 6, the liquid surface indicating window 4b has substantially the same shape as that of the liquid surface indicaeing window 4a of Fig. This embodiment is characterized in that a recess and ridge combination is formed in the interface between the olefin resin forming the liquid surface indicating window 4b and the lateral wall 2. That is, in Fig. 6, the opposite sides of the peripheral wall portion 13 defining the hole 8 are formed with roughened surfaces 16. Such roughened surfaces 16 can be easily formed by, for example, the sand blast method. Further, the inner peripheral surface defining the hole 8 is formed with a groove 17 which is, for example, V-shaped. The presence of such recess and ridge combination provided by the roughened surfaces 16 and groove 17 promotes the integration between the liquid surface indicating window 4b and the lateral wall 2.

14 In addition, only one of the two features, the roughened surface 16 or groove 17, will suffice and their respective positions of formation may be reversed. As for the means for forming the recess and ridge combination, other mechanical and chemical methods may be employed.

In the embodiments described so far, it has been intended to monitor the amount of the electrolyte 9 by directly bringing into view the liquid surface 10 of the electrolyte 9 through the liquid surface indicating window 4, as shown in Fig. 2, for example. However, as shown in phantom lines in Fig. 2, a float 33 which floats on the liquid surface 10 may be installed so that it can be seen through the electrolyte indicating window 4. In this case, the float 33 may be colored to provide indication which is easier to see than directly seeing the liquid surface 10 of the colorless electrolyte 9. In addition, the float 33 may be arranged so that it is vertically movable while being guided by a guide rod 34 vertically extending therethrough.

Further, the vertical dimension of each of the liquid surface indicating windows 4, 4a and 4b in the illustrated embodiments has been selected so that at least the upper and lower limits of the liquid surface 10 can be brought into view. However, it is not absolutely necessary to select said vertical dimension in such a manner as to 15 cover the upper and lower limits of the liquid surface.

For example, as in an embodiment to be described with reference to Figs. 7 et seq., in the case where a float is used, the normal and abnormal conditions of the liquid surface can be indicated even if the vertical dimension of the liquid surface indicating window is made less than the distance between the upper and lower limits of the liquid surface.

Referring to Figs. 7 and 8, a vertically elongated float 18 which floats on the electrolyte is installed within the liquid surface indicating window 4c and inside the electrolytic tank 1. The float 18 is placed in free condition in a guide member 19 which defines the upper and lower limits of the float 18. The upper half of the float 18 is a red colored region 20 while the lower half is a green colored region 21. In Figs. 7 and 8, of two horizontal dot-and-dash lines, the upper one denotes the upper limit liquid surface 22 and the lower one the lower limit liquid surface 23.

Fig. 7 shows the position of the float 18 when the electrolyte assumes the upper limit liquid surface 23. In this condition, the green colored region 21 can be seen through the liquid surface indicating window 4c. On the other hand, Fig. 8 shows the position of the float 18 established when the electrolyte assumes the lower limit 16 liquid surface 23. In this condition, the red colored region 20 can be seen through the liquid surface indicating window 4c.

In the condition intermediate between the conditions of Figs. 7 and 8, there is a time when both of the read and green colored regions 20 and 21 are seen through the liquid surface indicating window 4c, so that the decrease of the electrolyte can be recognized by the position of the boundary line between the two colored regions 20 and 21. Further, even if the electrolyte is decreased further from the lower limit liquid surface 23 of the electrolyte, the presence of the guide member 19 maintains the float 18 in the condition shown in Fig. 8, so that the red colored region 20 can continue to be indicated through the liquid surface indicating window 4c.

When the distance between the upper and lower limit liquid surfaces 22 and 23 shown in Figs. 7 and 8 is compared with the vertical dimension of the liquid surface indicating window 4c, it is seen that the vertical dimension of the liquid surface indicating window 4c is less than the distance between the upper and lower limit liquid surfaces 22 and 23.

In an embodiment shown in Figs. 9 and 10, the float 24 installed so that it is rotatable around the axis of a fixed shaft 25. In addition, the range of rotation of the 17 float 24 is limited to a predetermined range by upper and lower limit stoppers 26 and 27. Opposei to the float 24, an arcuately extending indicating member 28 is installed on the opposite side of the fixed shaft 25. The indicating member 28 has a green colored region 29 formed in the upper portion and a red colored region 30 in the lower portion thereof. In Figs. 9 and 10, the numeral 31 denotes the upper limit liquid surface and 32 denotes the lower limit liquid surface.

In the condition shown in Fig. 9, the electrolyte assumes the upper limit liquid surface 31. At this time, the float 24 abuts against an upper limit stopper 26, while the indicating member 28 directs the green colored reyion 29 to the liquid surface indicating window 4d.

Therefore, the green indication can be seen through the liquid surface indicating window 4d. On the other hand, in Fig. 10, the electrolyte assumes the lower limit liquid surface 32, with the float 24 abutting against the lower limit stopper 27. At this time, the indicating member 28 directs the red colored region 30 to the liquid surface indicating window 4d; therefore, the red indication appears in the liquid surface indicating window 4d.

In the embodiment shown in Figs. 9 and 10, the vertical dimension of the liquid surface indicating window 4d is less than in the embodiment shown in Figs. 7 and 8 18 i described above. When it is desired to decrease the vertical dimension of the liquid surface indicating window 4d in this manner, this can be attained by simply increasing the distance between the float 24 and the fixed shaft As in the embodiment shown in Figs. 7 and 8 and the embodiment shown in Figs. 9 and 10, the fact that the liquid surface indicating window 4c or 4d is small-sized is advantageous in that even if a homopolymer of 10 polyproplylene which, through having a low resistance to 44 shock, is highly transparent, is used as a material for the liquid surface indicating window, a decrease in the t strength of the entire electrolytic tank can be minimized.

In the various embodiments described so far, the through-holes 8 for forming the liquid surface indicating windows 4, 4a, 4b, 4c and 4d can be formed simultaneously 4 with the injection molding of the electrolytic tank 1 by imparting the corresponding shape to the metal mold to be used in injection-molding the electrolytic tank 1.

However, after an electrolytic tank 1 has been formed without having holes 8, such holes 8 may be formed in the lateral wall 2 by machining such as punching and cutting.

When hole 8 are to be formed after such electrolytic tank 1 has been obtained in this manner, the following advantage can be expected.

19 First, since there is no need to consider formation of holes, the metal mold for molding the electrolytic tank may be simple in construction. Further, when a shape necessary for forming holes in a metal mold used to mold an electrolytic tank is imparted to the metal mold, during injection molding the resin will not smoothly flow in the region where said holes are formed. Particularly, in the usual injection molding, the gate for injecting resin is located on the bottom surface of the electrolytic tank, while the holes are formed generally in a relatively upper region, with the result that the flow path extending from sit Sthe gate to each hole tznds to be relatively long.

'It' Therefore, coupled with the poor flow of resin in the hole-forming regions, the removal of heat by the metal mold results in premature hardening of resin, likely to raise a problem of formation of weld lines or the like.

However, in the case of forming holes after an i electrolytic tank has been obtained, as described above, the problem of formation of weld lines related to the fluidity of resin can be advantageously solved. Further, since the operation involved in forming holes after an electrolytic tank has been obtained is easier than the operation involved in forming such holes at the stage of forming an electrolytic tank, the shape, size and position of such holes can be more easily selected as desired.

20 In addition, while the embodiments described so far refer to the case of forming a liquid surface indicating window which serves as an electrolyte condition monitoring window, the invention is equally applicable to a method of forming a window for monitoring another condition of the electrolyte, for example specific gravity.

Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of the present invention being limited only by the terms of the appended claims.

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Claims (4)

1. 2. A method of forming a window in a storage battery electrolytic tank as set forth in claim 1, wherein said electrolyte condition monitoring window includes a portion which has a thickness less than that of said lateral wall.
2. 3. A method of forming a window in a storage battery electrolytic tank as set forth in claim 1 or 2, wherein said olefin resin forming said electrolyte condition monitoring window has portions contacting opposite surfaces of said peripheral wall portion hole.
3. 4. A metbod of forming a window in a storage battery electrolytic tank as set forth in claim 1 or 2, wherein the interface between said olefin resin forming said electrolyte condition monitoring window and said storage battery electrolytic tank is formed with a recess and ridge combination. 4 /F* I Vp~? 900 8
4. 16.dbwspe.012,miya. spe. 22 L_ 1 23 A method of forming a window in a storage battery electrolytic tank as set forth in claim 1 or 2, wherein said olefin resin forming said storage battery electrolytic tank and said olefin resin forming said electrolyte condition monitoring window are of the polypropylene type. 6. A method of forming a window in a storage battery electrolytic tank substantially as hereinbefore described with reference to the accompanying drawings. 11 12 13 14 16 17 18 19 21 22 23 24 26 27 28 L29 31 32 33 34 36 37 38 DATED this 16th day of August, 1990. MIYAGAWA KASEI INDUSTRY CO., LTD. and YUASA BATTERY CO., LTD. By their Patent Attorneys DAVIES COLLISON 960~S bwspe.012.miya.spe,23 C 1 i