Grid base plate for an electrode plate for a storage battery and method of manufacture thereof

A grid base plate and its method of manufacture comprising intermittently conveying a thin elongated metallic sheet longitudinally in one direction through successive first, second and third stations, the sheet being stopped in each of the stations between successive conveying steps. In the first station, the sheet is bent to form a peripheral upwardly projecting portion in a frame region surrounding an inner grid region. In the second station, a plurality of openings are punched in the grid region and in the third station, the sheet is punched along an outer peripheral edge surface to separate the base plate from the sheet. The upwardly projecting portion forms a space with the grid region which is filled with an active material of a thickness determined by the height of the upwardly projecting portion. The upwardly projecting portion has an outer bend region with an end surface constituting a peripheral edge of the frame which faces laterally outwards and is disposed vertically. The outer bend region has a lower surface disposed in the same horizontal plane as a lower surface of an inner region in the vicinity of the juncture of the projecting portion and the grid region. Thereby, when the base plate is placed on a horizontal planar surface, the peripheral frame region will rest on the horizontal surface along two lines of contact respectively at the bottom of the edge surface and at the lower surface at the juncture of the frame region and the grid region.

FIELD OF THE INVENTION 
This invention relates to a press-punched type base plate for electrode 
plates for batteries, such as a lead storage battery or the like, which is 
improved in its paste filling property of active material and in its 
productivity. 
PRIOR ART 
The inventors have previously proposed, instead of a cast type grid base 
plate, a press-punched type grid base plate suitable for batteries, such 
as a lead storage battery or the like, in which a grid frame surrounding a 
grid surface region is formed, by bending, into a window frame so that an 
active material may be filled thickly therein. (Japanese Utility Model 
Registration No. 1,276,247 U.M. Publication No. 30979/Showa 53 (1978)). 
In the foregoing publication, there are disclosed three embodying examples 
of the punched type grid base plates of this kind having respective 
peripheral projecting frames which are varied in their sectional forms. It 
has been found that all of the grid base plates with those sectional forms 
of the respective peripheral projecting frames have deficiencies as will 
be described below with reference to FIGS. 1-3. 
Namely, the peripheral projecting frame A of the grid base plate shown in 
FIG. 1 comprises a bent portion a of arc sectional form projecting from 
the plane of one side of the plane of a grid surface region B. The portion 
a is formed by bending and an outer peripheral edge b thereof is extended 
to project towards the other side of the plane of the grid surface region 
B and beyond an inner peripheral base edge c of the projecting frame A, so 
that there is formed around the grid surface region B the peripheral 
projecting frame A of height T as determined by the distance between the 
bottom of the bent portion a and the end surface d of the outer peripheral 
edge b. Consequently, there is formed on the grid surface region a space f 
to be filled with an active material of a thickness corresponding to the 
height T. 
The peripheral projecting frame A of the grid base plate shown in FIG. 2 
comprises two bent portions a, a of arc sectional form defining an S shape 
on opposite sides of the plane of the grid surface region B. An end 
surface d of an outer peripheral edge b is directed upwards, so that the 
height T of the peripheral frame A is the distance between the crest of 
the upper and lower bent portions a, a, and consequently there is formed 
on the grid surface region B a space f to be filled with the active 
material of a thickness corresponding thereto. The grid base plate shown 
in FIG. 1 is a single point support type supported singly by either the 
bent portion a of the end surface d of the outer peripheral edge b. The 
grid base plate shown in FIG. 2 is also a single point support type which 
is supported singly by either of the two bent portions a, a. 
Consequently, each of the plates is deficient in that the peripheral 
projecting frame A is comparatively weak in withstanding pressure applied 
thereto at the time when the base plate is filled with an active material 
by an automatic active material paste-filling machine, and is subject to 
deformation, elongation, breakage or the like, resulting in a loss in 
manufacture of active material filled grid base plates. Additionally, 
there can be a change in the predetermined height T, and consequently 
there is brought about an inequality in the amount of filling of the 
active material. These unfavorable results are especially evident since 
the grid base plate is usually very thin and particularly when a soft 
metal, such as lead or lead alloy, is used as the plate material. 
Additionally, in the embodiment shown in FIG. 2, the outer peripheral edge 
b of the projecting frame A which is bent in the form of S, is directed 
upwards, so that on filling of the active material, a groove e in the form 
of U is subject to filling with active material resulting in waste 
thereof. 
The peripheral projecting frame A of the grid base plate shown in FIG. 3 
comprises a bent portion a in a semicircular sectional form and end 
surface d of the outer peripheral edge b thereof is positioned in the same 
horizontal plane as an inner peripheral edge base portion c. Accordingly, 
the filling of the active material is carried out under the condition that 
the grid base plate is supported by two point supports, that is, by the 
inner peripheral edge base portion c and the end surface d, and a 
deformation or the like of the peripheral projecting frame by the pressure 
applied thereto at the time of filling the active material can be 
prevented. However, from a practical point of view, it is difficult to 
obtain, by bending by means of a press machine, the peripheral projecting 
frame A in the semicircular sectional form as shown in FIG. 3, from a 
horizontal outer peripheral frame (shown by broken lines in FIG. 4) of a 
punched base plate, and it is inevitable in practice that the horizontal 
outer peripheral frame is usually bent into a shape in which the end 
surface d of the outer peripheral edge b thereof is positioned higher than 
the inner peripheral base edge c, that is, in a floated position as shown 
in solid lines in FIG. 4. Namely, the grid base plate becomes, in 
practice, a single support type as shown in FIG. 4, and in actual fact 
there is producted deformation, fluctuation in height, breakage or the 
like of the raised bent portion a by the pressure applied thereto during 
filling of the active material by the paste filling machine. Furthermore, 
the base plate with the projecting frame of the shape as shown in FIG. 1 
or 3 is such that the end surface d of the outer peripheral edge b is 
directed in the vertical direction, so that it has various disadvantages 
as described below. Namely, when the base plate is placed on a conveying 
belt, such as of woven fabric or the like, and is conveyed toward the 
automatic paste filling machine, it often happens that the base plate is 
caught in the belt and thus the conveying thereof is not carried out 
smoothly. Furthermore, the base plate is liable to be deformed by impact 
force imparted to the side surface thereof, and additionally, when the 
base plate and a separator are put upon one another at the time of 
assembling a group of electrode plates, the end surface d strikes against 
the separator and is liable to break the same. 
SUMMARY OF THE INVENTION 
An object of this invention is to provide a punched grid base plate for 
electrode plates for batteries, such as a lead storage battery or the 
like, by which the foregoing disadvantages of the conventional grid base 
plates are eliminated and especially variation in the filling amount of 
the active material is substantially decreased, and any deformation or 
breakage of the peripheral projecting frame is greatly overcome, and 
further, the productivity of acceptable electrode plates filled with 
active material is improved. 
According to this invention, in a grid base plate for an electrode plate 
for a battery of the type comprising a grid surface region having a large 
number of openings and a peripheral projecting frame which surrounds the 
grid surface region and is bent to project upwards in the form of an 
inverted U in section, there is produced, on the grid surface region 
surrounded by the peripheral projecting frame, a space to be filled with 
active material of a thickness determined by the height of the peripheral 
projecting frame, the improvement wherein the outer peripheral edge of the 
peripheral projecting frame is formed with a bent outer edge whose end 
surface is directed laterally outwards, the lower surface of the bent 
outer edge being positioned in the same horizontal plane as the lower 
surface of an inner peripheral base edge of the peripheral projecting 
frame.

DETAILED DESCRIPTION 
Referring to FIGS. 5 to 7, numeral 1 denotes a grid base plate of the 
invention for an electrode plate for a lead storage battery which is 
obtained, by pressing and punching, from a belt-shaped thin metallic 
sheet, namely, a belt shaped sheet of lead or lead alloy of a thickness in 
the range of from 0.3 mm to 2 mm and usually from 0.5 mm to 1.5 mm. The 
grid base plate 1 comprises a grid surface region 2 which is composed of a 
large number of longitudinal and transverse grid members 2b formed by 
punching a large number of holes 2a in the plate, and a peripheral 
projecting frame 3 which surrounds the grid surface region 2 and is 
formed, by bending, to project upwards by a press operation such as 
embossing, bending or the like. The base plate 1 has a tab 4 projecting 
horizontally outwards from the side thereof and formed by punching at a 
corner of the peripheral projecting frame 3. 
A predetermined height T of the base plate is obtained by the bent 
peripheral projecting frame 3, and thereby a space 2c to be filled with a 
pasty active material of a predetermined thickness is produced within the 
frame 3, that is, on the grid surface region 2. The formation of the grid 
base of FIGS. 5-7 is different from that of the conventional grid base 
plate. According to the invention, the sectional shape of the peripheral 
projecting frame 3 is formed as described below. Namely, as shown clearly 
in FIG. 6 and especially in FIG. 7, the peripheral projecting frame 3 is 
formed, at the middle portion in the width direction thereof and along the 
longitudinal direction thereof, with an upwardly projecting portion 3a 
which is generally characterized as being of inverted U-shape which is 
taken to include other inverted shapes such as V-shape. The inverted 
U-shape as shown in FIGS. 6 and 7 is rounded in cross-section and has an 
outer peripheral edge 3b joined to a short horizontal margin portion 3g 
formed with an outer end surface 3c directed laterally outwards and 
horizontally. The outer margin 3g has a short horizontal lower surface 3d 
which is disposed in the same horizontal plane as an inner peripheral edge 
of the peripheral projecting frame 3, i.e., horizontal lower surface 3f of 
inner peripheral base edge 3e which is adjacent the peripheral surface of 
the grid surface region 2. Thus, the peripheral projecting frame 3 of the 
invention is formed with two-point supports, namely, one support is at the 
horizontal lower surface 3d and the other support is at the horizontal 
lower surface 3f, and consequently, the frame 3 can sufficiently withstand 
the pressure applied thereto at the time of filling of the active material 
paste therein, and hence, will not undergo any fluctuation in height, 
deformation or breakage, whereby passage thereof through a paste filling 
machine can be carried out smoothly. Consequently, there can be obtained 
an excellent grid base plate correctly filled with active material of 
predetermined amount. 
The grid base plate of the invention is filled with the active material 
paste using a conventional automatic paste filling machine as shown in 
FIG. 8. Referring thereto, numeral 5 denotes a charging hopper for the 
active material paste, numeral 6 denotes a pair of paste applying rollers 
mounted within the hopper, numeral 7 denotes a stirrer, numeral 8 denotes 
an adjustable squeezing member, numeral 9 denotes an endless belt of woven 
fabric for conveying the grid base plates 1 in sequence below the charging 
hopper 5, numeral 10 denotes a supporting plate for supporting the upper 
run of the endless belt at the lower surface thereof, numeral 11 denotes a 
pair of guide rolls for supplying the grid base plates at the inlet end 
and numeral 12 denotes a group of conveying guide rolls on the delivery 
side for delivering the paste-filled grid base plates. 
In the case of the grid base plate of the invention, due to the particular 
shape of the projecting frame 3 thereof, in the course of the paste 
filling operation by the charging machine, the base plate will not become 
caught by the woven conveying belt 9 or by the squeezing member 8 or the 
like so that the conveying of the plates would become obstructed or the 
peripheral projecting frame 3 thereof strike the machine and thereby 
become deformed or broken. In contrast thereto, in the case of the 
conventional type base plate, due to the one point support of the 
projecting frame, the foregoing disadvantages, such as deformation or the 
like by the pressure or the like, frequently take place. 
The grid base plate and the conventional one point support type grid base 
plate were filled with the active material by the paste filling machine, 
and comparison tests were made in respect of variation in the amount of 
active material filled and in the frequency of deformation and the results 
are given in the following Table 1. 
A sample base plate was 0.8 mm in plate thickness, 1.2 mm in the height of 
its peripheral projecting frame and 3.5 mm in the width of its projecting 
frame, and a large number of the base plates were used. 
TABLE 1 
______________________________________ 
Variation in 
Frequency of 
filled amount 
deformation 
______________________________________ 
Base plates of the invention 
.+-.4% 0.01% 
Conventional products 
.+-.6% 0.3% 
______________________________________ 
The outer edge of the bent outer edge 3b of the grid base plate of the 
invention is the short horizontal margin 3g and is not bent back upwards, 
so that it can prevent the active material from accumulating on the upper 
surface thereof, thereby avoiding waste of active material. 
Additionally, the grid base plate of this invention is formed, as shown in 
FIG. 6 in which the crosswise grid members 2b are bent in zigzag form 
within the filling space 2c so as to improve its ability to hold the 
filled active material. 
The grid base plate of the invention can be formed with the particular 
shape of the peripheral projecting frame by the conventional process in 
which after a grid base plate of predetermined size and form is separated, 
by press punching, from a wide metallic material sheet, each of the 
punched grid base plates thus obtained is subjected one by one to press 
bending in a press machine so that the peripheral frame thereof may be 
given the particular shape. It is also possible to manufacture the grid 
base plates with the particular shaped peripheral frame continuously and 
directly from a belt-shaped metallic sheet by the process described below. 
Namely, the continuous method of manufacturing of this invention grid plate 
can be carried out using a progressive type press machine 13 as shown in 
FIG. 9. The machine 13 comprises a long upper movable base 13a and a long 
lower stationary base 13b which face one another. The upper base 13a is 
arranged to be opened and closed in relation to the lower base 13b. These 
upper and lower bases 13a, 13b are respectively provided with a set of 
upper and lower pressure dies 14a, 14b for forming the peripheral 
projecting frame, a set of upper and lower punching dies 15a, 15b for 
punching the window openings, and a set of upper and lower punching dies 
16a, 16b for punching dies 16a, 16b for punching the sheet at the 
surrounding edge of the peripheral projecting frame to obtain a 
predetermined shape of the punched grid base plate of the invention. 
The belt-shaped metallic sheet 17 is conveyed intermittently in the 
direction of the arrows in FIGS. 9 and 10 to pass between the upper and 
lower bases 13a, 13b and along the lower base 13b, the upper base 13a 
being arranged to be lowered to closed position on the lower base 13b each 
time when the sheet 17 is stopped. 
Thus, as will be clear from FIG. 10, the plate can be manufactured by a 
sequential process in which the sheet 17 is first subjected to a press 
operation to form the peripheral projecting frame 3 by the press dies 14a, 
14b, and then the grid surface region 2 is formed by punching a large 
number of window openings 2a in the surface region within the projecting 
frame 3 by the punching dies 15a, 15b, and then the sheet 17 is subjected 
to a punching operation by the punching dies 16a, 16b such that an outer 
peripheral edge of the peripheral projecting frame 3a is separated from 
the sheet in a region spaced slightly outwards from the inverted U-shaped 
portion 3a of the projecting frame 3 so that outer margin 3g remains 
around the projection 3a of the frame 3 and, at the same time, integral 
tab 4 projects at a corner of the frame 3. These operations are effected 
continuously in sequence and there can be obtained a large number of grid 
base plates of this invention with high efficiency and accuracy. Stated 
otherwise, punched grid base plates with the bent outer edge 3b thereround 
can be separated from the sheet 17 continuously with high efficiency and 
accuracy. 
In the illustrated process, in order to produce a pair of grid base plates 
of this invention at one time as shown in FIG. 10, respective additional 
sets of metallic dies 14a, 14b, metallic dies 15a, 15b and metallic dies 
16a, 16b are provided on the upper and lower dies 13a, 13b so that each 
pair of dies are arranged side by side, in sequence. With this 
arrangement, the sheet 17 is first formed by the press dies with a pair of 
peripheral projecting frames 3, leaving a space 18 therebetween, then a 
pair of grid surface regions 2, are simultaneously formed in the frames by 
the punching dies. At this time, openings 20 are punched in the space 18 
at predetermined intervals, so that left and right leg portions 19 are 
formed in the space 18. Thereafter, the sheet 17 is subjected to a 
punching operation by the punching dies 16a, 16b for removing the entire 
region surrounding the two frames 3 the punching being carried out in the 
region surrounding the outline of the two formed plates as shown in FIG. 
10, so that two punched grid plates are separated from the sheet 17 and 
remain interconnected by the leg portions 19. Thereafter, the resultant 
punched plates are separated at the center of the leg portions 19 in a 
cutting machine (not illustrated), whereby there are obtained two grid 
base plates of the invention each having a pair of left and right legs 19. 
This constructive arrangement is advantageous in respect of the 
manufacturing efficiency of the products according to the invention. 
It has been found that if the formation of the grid surface region 2 is 
carried out before the forming of the peripheral projecting frame 3, 
deformations at or near the intersections of the peripheral projecting 
frame 3 and the grid forming members 3b are produced and thus the 
resultant product has lowered mechanical strength and increased 
susceptability to corrosion. 
In FIG. 10 are shown pin holes 21 made a predetermined regular intervals in 
the sheet 17 along both side edges thereof, and each time when the 
conveyed sheet 17 is stopped, fixing pins 22 provided along both side 
edges of the upper base 13a corresponding to respective pin holes 21 are 
tightly inserted into the pin holes 21, whereby the sheet is fixed at a 
predetermined position at the time of the working operations and thus 
accurate pressing and punching can be effected. Numeral 23 (FIG. 9) 
denotes pin holes provided in the respective dies of the lower base 13b so 
that the lower ends of the fixing pins 22 may enter therein. There may be 
additionally provided, on the upper base 13a and the lower base 13b, a 
male punching die 24a and a female punching die 24b for producing the pin 
holes 21 in the sheet 17 as shown in phantom lines in FIG. 9. 
If each of the metallic dies 14a, 14b for pressing the sheet is modified so 
that both side surfaces of the inverted U-shape are formed with straight 
sides as shown in FIG. 11, release of the sheet 17 from the dies can be 
carried out favorably. 
Thus, according to this invention, the outer peripheral edge of the 
peripheral projecting frame of the grid base plate is formed with its end 
surface facing laterally outwards and horizontally and with its lower 
surface positioned in the same hoirzontal plane as the lower surface of 
the inner peripheral base edge. Consequently, the obtained grid base plate 
is stable as a result of its two-point support and it has improved 
dimensional precision and significantly decreased in fluctuation in height 
and deformation of the peripheral projecting frame by the pressure at the 
time of filling of the active material and accordingly in variation in the 
filled amount of the active material as compared to the conventional grid 
base plates. Furthermore, the manufacturing loss of filled base plates is 
decreased, and additionally it becomes possible to manufacture a number of 
grid base plates continuously directly from a long metallic sheet. Thus, 
there is higher mass productivity of the grid base plate and improved 
battery performance, productivity and reduced manufacturing costs 
especially when the invention is applied to base plates for lead storage 
batteries for motorcars which are thin and are mass produced.