Laminated iron core assembling process

A process is provided for assembling a laminated iron core on a support structure about an electric coil from a plurality of laminations to form a shell-type transformer core. According to the process, the plurality of lamination sections are stacked in a staggered relationship to form a first core section which has joint ends to form overlapping joints between an adjacent core section. The first core section is stacked by placing a slider sheet of a low coefficient of friction on a first support member and stacking the lamination sections on the slider sheet. The first core section is then conveyed onto the support structure at which the iron core is to be assembled, and the slider sheet is pulled out to cause the first core section to directly sit on the support structure. The plurality of lamination sections are inserted between the joints on site to form a second core section which connects the joint ends of the first core section to define a magnetic circuit around the coil.

BACKGROUND OF THE INVENTION 
This invention relates to a process for assembling a laminated iron core 
and, more particularly, to a process for assembling a laminated iron core 
having overlapping joints on a support structure about an electric coil of 
a shell-type transformer core. 
FIGS. 1 and 2 illustrate a typical shell-type electrical transformer to 
which the present invention can be appplied. In the figure, the 
transformer comprises a lower tank 1 having a flange 2 at its upper open 
end. An electrical coil 3 having a coil window 4 is inserted at its bottom 
in the lower tank 1. The upper portion of the coil 3 projects and is above 
the lower tank 1. A support beam 5 having an inverted T-shaped cross 
section is mounted on the lower edge of the window 4 of the coil 3 and on 
the flange 2 of the lower tank 1. Lower spacers 6 are also mounted on the 
flange 2. 
The transformer further comprises two laminated iron cores 7 disposed on 
the support beam 5 and the spacers 6 around the legs of the coil 3. A 
wedge 8 is inserted between the top ends of the iron cores 7 and the upper 
edge of the window 4 of the coil 3. Upper spacers 9 are disposed between 
the top ends of the iron cores 7 and core support beams 11 disposed around 
the coil 3 and mounted to an upper tank 10. The upper tank 10 is attached 
to the flange 2 of the lower tank 1 by a flange 12. 
According to the conventional assembling process, the transformer thus 
constructed is assembled by first inserting the lower portion of the coil 
3 into the lower tank 1 with the coil legs protruding from the lower tank 
1. Then, the support beam 5 is placed on the lower edge of the coil window 
4 so that the opposite ends are mounted on the flange 2 of the lower tank 
1. The spacers 6 are placed on other portion of the flange 2 around the 
coil 3. 
A plurality of laminations or sheets of magnetic material 7a, 7b and 7c are 
placed and stacked on the spacers 6 and the support beam 5 one by one 
until the stack reaches a predetermined height to form a substantially 
rectangular iron core having overlapping joints 7d as shown in FIGS. 1 and 
2. During this process, since each of frame-shaped layers of the magnetic 
sheets is composed of four substantially trapezoidal sections of a 
magnetic sheet material, four trapezoidal sections must be precisely 
placed so that the slanted sides abut each other to form the first 
frame-shaped layer. The second layer is similarly prepared by arranging 
four trapezoidal sections on the first layer, but with the slanted sides 
of the trapezoidal sections of the second layer brought into an 
overlapping relationship with those of the first layer. As is well known 
this arrangement provides the overlapping joints in which the slanted 
sides of the sections are staggered by each sheet. 
Then, the wedge 8 is inserted between the top lamination of the iron cores 
and the upper edge of the coil window 4 of the coil 3 and the spacers 9 
are provided so that the assembled iron cores 7 are firmly held in their 
respective positions within the tank by the core support beams 11. 
According to the conventional assembling process as above described, each 
of a large number of the lamination sections are manually precisely 
positioned one by one with a great care so that the already stacked 
sections are not dislocated. Also, at each time the stacking of a single 
layer is finished, the stacked sections must be re-positioned. Therefore, 
stacking of the lamination sections into a laminated iron core is 
difficult and time-consuming. 
SUMMARY OF THE INVENTION 
Accordingly, one object of the present invention is to provide a process 
for assembling a laminated iron core for a static induction apparatus 
which can be simply and easily carried out. 
Another object of the present invention is to provide a process for 
assembling a laminated iron core for a static induction apparatus which 
allows the iron core to be assembled in a short time. 
Another object of the present invention is to provide a process for 
assembling a laminated iron core for a static induction apparatus which 
allows the assembled iron core to be precise. 
With the above objects in view, the present invention provides a process 
for assembling a laminated iron core on a support structure about an 
electric coil from a plurality of laminations to form a magnetic core for 
a shell-type static induction apparatus. According to the process, the 
plurality of laminations are stacked in a staggered relationship to form a 
first core section which has joint ends to form overlapping joints between 
an adjacent core section. The first core section may be stacked by placing 
a slider sheet of a low coefficient of friction on a first support member 
and stacking the laminations on the slider sheet. The first core section 
is then conveyed onto the support structure at which the iron core is to 
be assembled. When the slider sheet is used, it is pulled out to cause the 
first core section to directly sit on the support structure. The plurality 
of laminations are inserted between the joints in site to form a second 
core section which connects the joint ends of the first core section to 
define a magnetic circuit around the coil.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
As best seen from FIG. 2, the magnetic core 7 of a shell-type transformer 
comprises a large number of substantially rectangular, frame-shaped 
laminations or layers of a magnetic material each including an inner leg 
section 7a, an outer leg section 7c and a pair of shorter yoke sections 
7b. The lamination sections 7a, 7b and 7c are substantially trapezoidal in 
shape and their sloped ends are arranged in an abutting relationship with 
the sloped ends of the adjacent lamination section so that four lamination 
sections 7a, 7b and 7c are all in the same plane to form a single 
frame-shaped lamination or layer jointed at each corner. In FIG. 2, it is 
seen that the topmost lamination has joints 7e and the second lamination 
under the topmost lamination has joints 7f staggered with respect to the 
joints 7e to form the overlapping joints 7d. 
According to the present invention, the laminated iron core 7 is assembled 
on the support structure of the static induction apparatus such as the 
support beam 5, the spacers 6 and the lower tank flange 2 about the 
electric coil 3 from a plurality of laminations to form a shell-type 
transformer core. 
The assembly is achieved by first stacking, as shown in FIGS. 3 and 4, the 
plurality of lamination sections 7a which are the trapezoidal sheets in a 
staggered relationship in the longitudinal direction to form a first core 
section 7A which has joint ends 7B for forming, at the later stage, the 
overlapping joints 7d shown in FIG. 2 between the adjacent core sections 
7A. In order to assemble iron core shown in FIGS. 1 and 2, four of these 
first iron core sections 7A are prepared. 
In the illustrated embodiments, since the iron core structure to be 
assembled by the present invention is the shell-type core, the stacked 
core section 7A is a leg of the iron core. Also, while FIG. 4 shows that 
each of the lamination sections 7a of the first core section 7A is 
staggered one by one in the longitudinal direction, any desired number of 
lamination sections 7a may be grouped and each of the groups of the 
lamination sections 7a can be arranged as a unit in the staggered 
relationship as shown in FIG. 5 in which the group contains two lamination 
sections 7a. 
In the preferred embodiment shown in FIG. 6, for the convenience of the 
following step, a support member 102 for supporting the stacked core 
section 7A is prepared and a slider sheet 100 of a low coefficient of 
friction is placed on the support member 102. Then, the lamination 
sections 7a are stacked on the slider sheet 100 until they form the 
stacked core section 7A. 
Then, as shown in FIG. 7, the support member 102 is carried together with 
the core section 7A on the slider sheet 100 by any suitable conveying 
means such as a table lift 32 to a position close to the support beam 5 on 
the flange 2 of the transformer tank 1. The slider sheet 100 is pulled by 
a winch wire 33 connected at 101 to the slider sheet 100 so that the 
slider sheet 100 as well as the first core section 7A is conveyed onto the 
support structure such as the flange 2 and the support beam 5 of the 
transformer. In order to stop the stacked core section 7A at the desired 
position on the support structure, a stopper 34 is provided to be 
relatively stationary with respect to the support structure. Therefore, 
when the slider sheet 100 is pulled even after the core section 7A on it 
abuts against the stopper 34, the slider sheet 100 can be further pulled 
to be removed from between the support member 102 and the stacked core 
section 7A. Thus, the first core section 7A can be precisely positioned on 
the support structure at positions at which they are finally mounted. 
Then, a plurality of sheets of the lamination sections 7b are manually 
inserted between two adjacent first core sections 7A so that the slanted 
joint ends of the respective lamination sections 7b are inserted into 
corresponding gaps defined between two protruding ends of the staggered 
overlapping joints. This inserting step is carried out until the joint 
ends of the first core sections 7A placed in position around the coil 3 
are magnetically connected to define a magnetic circuit around the coil 3. 
FIG. 8 illustrates a support member 110 which can be used in place of the 
support member 102 shown in FIGS. 6 and 7. The support member 110 is 
basically a framework comprising three parallel longitudinal members 110a 
and two transverse end members 111a assembled by pins 112a and bores 113a 
in a rectangular framework. With this arrangement, the outer dimensions of 
the framework can very easily be modified according to the dimension of 
the stacked core section 7A to be stacked and conveyed on the support 
member 110. 
FIGS. 9 and 10 show another method for conveying the stacked core section 
7A by first stacking the laminations 7a until the core section 7A is 
obtained on a second support member 20 as shown in FIG. 9. Then, the 
slider sheet 100 is placed on the stacked core section 7A and the first 
support member 102 is placed on the slider sheet 100 as shown in Fig. 10. 
Thus, there is provided a sub-assembly of the first core section 7A and 
the slider sheet 100 sandwiched between the first and the second support 
members 102 and 20. The first and the second support members 102 and 20 
are fastened together by suitable fastening means such as bolts and nuts. 
The entire structure thus fastened is then turned upside down so that the 
first support member 102 and the slider sheet 100 support the bottom 
surface of the stacked core section 7A and the second support member 20 
support the top surface of the stacked core section 7A. 
The second support member 20 on the top of the stacked core section 7A can 
be removed from the stacked core section 7A so that the same assembly as 
shown in FIG. 6 is obtained. This assembly may be conveyed onto the 
support structure of the transformer in the same way as explained in 
connection with the embodiment shown in FIG. 7. 
FIG. 11 illustrates another example of conveying the stacked core section 
7A onto the support structure of the transformer. In this example, the 
stacked core section 7A is sandwiched between the first and the second 
support members 5a and 21 and is clamped between them by bolts 22. The 
bolts 22 extend through the second support member 21 and screwed into the 
first support member 5a to form a rigid assembly. The first support member 
5a in this embodiment can also be used as the spacer such as the support 
beam 5 shown in FIG. 1 after the stacked core section 7A is placed on the 
transformer support structure. The second support member 21 of the 
assembly is attached by bolts 24 to support plate 23 secured to an 
elongated beam 25. The elongated beam 25 is supported at its one end by a 
frame 25a so that the beam 25 can be inserted, together with the stacked 
core section 7A attached thereto, within the window 4 of the coil 3 so 
that the stacked core section may be conveyed and placed onto the support 
structure of the transformer by moving the elongated beam 25. The frame 
25a is supported from a crane (not shown). 
The beam 25 together with the stacked core section 7A is then inserted into 
the coil window 4 as shown by an arrow A and lowered on the support 
structure including the first support member 5a on the position at which 
they are to be mounted. After the elongated beam 25, together with the 
upper, second support member 21, is removed from the stacked core section 
7A seated on the transformer support structure, additional laminations 7a 
are stacked on the stacked core section 7A until the overall height of the 
stacked core section 7A reached a predetermined dimension and 
substantially fill the coil window 4. Then, after the yoke section 7b is 
assembled by inserting the laminations one by one into the gaps in the 
overlapping joints 7d, the spacers 9 and the wedge 8 are inserted between 
the top lamination 7a of the core section 7A and the upper edge of the 
coil window 4 to firmly secure the iron core with respect to the tank 1 
and the coil 3. 
FIG. 12 shows another example of conveying the stacked core section 7A onto 
the support structure of the transformer, in which the elongated beam 25 
is extended at both ends to have extentions 25b supported by wire ropes 
25d connected to a crane (not shown). The length of the extention 25b is 
larger than the width of the coil 3 so that the beam extention 25b can be 
first inserted into the coil window 4 and suspended by the wire ropes 25d 
and still the beam 25 projects from the coil 3 with sufficient length for 
mounting the stacked core section 7A. 
In this embodiment, it is seen that the lower ends of the fastening bolts 
22 are screwed into the support beam 5 so that the latter serves as the 
first support member 5a shown in FIG. 11 during the conveying step. 
According to this embodiment, the support beam should not be removed and 
should be assembled in the transformer. In other respects, the steps and 
the arrangement are the same as those explained in the conveying step 
explained in conjunction with FIG. 11. 
In FIG. 13, an example of the method for conveying the stacked core section 
7C to be mounted on the flange 2 of the tank 1 extending outside of the 
coil 3 is illustrated. It is seen that the spacer 6 having grooves 26 for 
allowing insulating oil to flow in the transformer tank is placed under 
the stacked core section 7C. This sub-assembly is suspended by wire ropes 
25e from an unillustrated hoist so that the sub-assembly can be easily 
conveyed and placed at the desired precise position on the support 
structure of the transformer. 
As has been described, according to the present invention a process for 
assembling a laminated iron core on a support structure about an electric 
coil from a plurality of laminations to form a magnetic core for a 
shell-type static induction apparatus is provided. According to the 
process, the plurality of laminations are stacked in a staggered 
relationship to form a first core section which has joint ends to form 
overlapping joints between an adjacent core section, and the first core 
section is then conveyed onto the support structure at which the iron core 
is to be assembled. Then a plurality of laminations are inserted between 
the joints in site to form a second core section which connects the joint 
ends of the first core section to define a magnetic circuit around the 
coil. 
Accordingly, the process for assembling a laminated iron core for a static 
induction apparatus can be simply and easily carried out. Also, the 
assembly of a laminated iron core for a static induction apparatus can be 
assembled in a short time with precision.