Apparatus for producing welded metallic can bodies

An improved apparatus for producing welded metallic can bodies is provided. The apparatus has two roll-like revolving electrodes and an elongate electrode, and the lap portions of two can bodies are disposed respectively between the two revolving electrodes and the elongate electrode. An alternating current flowing through these lap portions is supplied by coupling the two revolving electrodes to an ac power supply, or by dividing the elongate electrode into two electrically insulated portions and coupling these portions to the power supply.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to an apparatus for producing welded metallic can 
bodies, and particularly, to an apparatus comprising roll-like revolving 
electrodes and a linear elongate electrode for producing welded metallic 
can bodies by mash seam resistance welding. 
More specifically, this invention pertains to an apparatus for producing 
welded metallic can bodies, which comprises two revolving electrodes and 
an elongate electrode, and in which the lap portions of can bodies are 
adapted to be disposed respectively between the two revolving electrodes 
and the elongate electrode, and an alternating current flowing in these 
lap portions is supplied by coupling the two revolving electrodes to a 
power supply or by dividing the elongate electrode into two electrically 
insulated portions and coupling them to the power supply. 
The "revolving electrode", as used herein, denotes a type of electrode 
which rotates while moving in a predetermined direction. It should be 
understood therefore that the terms "revolving" as a qualifier and 
"revolve" as a verb are used in this sense in the present specification 
and the appended claims. 
2. Description of the Prior Art 
An apparatus for seam-welding the lap portion of a can body by inserting it 
between a pair of rotating roller electrodes disposed at fixed positions 
and applying an alternating current across the electrodes while moving the 
lap portion has been widely known for the production of welded metallic 
can bodies of cans for holding aerosols, beer, powdery coffee, etc. and 
18-liter cans. An apparatus comprising a roll-like revolving electrode and 
a linear elongate electrode has also been known widely. It is also well 
known that to avoid wear of the electrodes, seam welding is carried out 
while a wire-like electrode is interposed between the lap portion of the 
can body and the electrode. 
In a general apparatus for the production of a welded metallic can body 
using a revolving electrode and an elongate electrode, a can body is 
disposed so as to surround the elongate electrode provided fixedly, and a 
high-frequency voltage is applied across the elongate electrode and the 
revolving electrode. The revolving electrode moves with rotation. As a 
result, the lap portion of the can body is successively pressed by the 
elongate electrode and the revolving electrode, and a high-frequency 
current is passed through the lap portion, thereby welding the lap 
portion. 
The conventional apparatus, however, has the following problems. 
To increase the speed of production, it is necessary to increase the speed 
of welding, i.e. the revolving speed of the revolving electrode. For 
increasing the speed of welding and performing welding satisfactorily, it 
is necessary to increase the frequency of the current from an ac power 
supply to about 200 to 500 Hz. This in turn gives rise to the following 
problems. Firstly, flowing of the current becomes difficult. An ac current 
with an rms of 3 to 9 KA is required. This increase in frequency, however, 
results in difficulty in the flowing of the current. It is believed to be 
due mainly to the increase of the inductance L in the impedance Z. The 
magnitude of inductance L is markedly affected by the degree of opening of 
an electrical circuit on the secondary side of a transformer. The value of 
the inductance L becomes larger as the degree of opening of the electrical 
circuit becomes larger. For example, if the distance between two 
electrical paths from an ac power supply to the welding portion is large, 
the value of the inductance L becomes high. On the other hand, in the 
conventional apparatus described above, one of the electrical paths from 
the ac power supply to the welding portion is made up of a conductor 
leading up to the elongate electrode, and the other is a feeder leading to 
the revolving electrode. The revolving electrode moves relative to the 
elongate electrode. Accordingly, the two electrical paths cannot be caused 
to approach and the inductance L cannot be reduced. A second problem 
concerns the generation of heat at various parts. When a welding current 
having a relatively high frequency of about 200 to 500 Hz is used and, for 
example, a conductor exists in the secondary side circuit of the 
transformer, an eddy current occurs in the conductor to generate heat. 
This heat generation is particularly great in a magnetic material such as 
iron. In the prior art, therefore, it is necessary to limit the materials 
constituting various component parts, or a complex mechanism should be 
provided to cool these component parts. 
SUMMARY OF THE INVENTION 
It is an object of this invention to provide an apparatus for producing 
welded metallic can bodies, in which two electrical paths to a welding 
zone approximate each other, and therefore the restriction on the 
materials constituting these parts can be removed and the cooling 
mechanism can be markedly reduced in size as compared with the 
conventional apparatus. 
Another object of this invention is to provide an apparatus for producing 
welded metallic can bodies, which permits production speeds at least two 
times as fast as in the conventional apparatuses. 
Still another object of this invention is to provide an apparatus for 
producing welded metallic can bodies which can produce metallic can bodies 
of a small inside diameter. 
The above and other objects of this invention are achieved in accordance 
with this invention by an apparatus for producing a welded metallic can 
body by welding the lap portion of a metallic can body, said apparatus 
comprising an elongate electrode having an electrode surface of a shape 
corresponding to the shape of the lap portion of a can body, two revolving 
electrodes adapted to revolve on the lap portions of two can bodies 
disposed on the electrode surface of the elongate electrode while pressing 
said lap portions, means for revolving the two revolving electrodes on the 
lap portions of said can bodies, and feeder means for electrically 
coupling the two revolving electrodes respectively to an ac power supply, 
whereby when the two revolving electrodes are revolving on the lap 
portions of the two can bodies, one terminal of the ac power supply is 
electrically coupled to the other terminal of the ac power supply via the 
feeder means, one revolving electrode, the lap portion of one can body, 
the elongate electrode, the lap portion of the other can body, the other 
revolving electrode and again the feeder means. 
According to another aspect of this invention, the above and other objects 
are achieved by an apparatus for producing welded metallic can bodies by 
welding the lap portions of metallic can bodies, said apparatus comprising 
an elongate electrode having two electrode surfaces of a shape 
corresponding to the shape of the lap portions of the can bodies, two 
revolving electrodes adapted to revolve on the lap portions of two can 
bodies disposed on the two electrode surfaces of the elongate electrode 
while pressing said lap portions, and means for revolving the two 
revolving electrodes at the lap portions of the can bodies, said elongate 
electrode having two conductors electrically insulated from each other and 
electrically coupling the two electrode surfaces of the elongate electrode 
to an ac power supply, and said two revolving electrodes being 
electrically coupled to each other, whereby when the two revolving 
eletrodes are revolving on the lap portions of the two can bodies, one 
terminal of the ac power supply is electrically coupled to the other 
terminal of the ac power supply through one conductor and one electrode 
surface of the elongate electrode, one can body, one revolving eletrode, 
the other revolving electrode, the other can body, and the other electrode 
surface and the other conductor of the elongate electrode.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
First, with reference to FIGS. 1 and 2, a conventional apparatus for 
producing a welded metallic can body using a revolving electrode and an 
elongated electrode will be described. 
FIG. 1 is a partially cut-away front elevation showing the welding 
electrode portion of the conventional apparatus and its neighborhood, and 
FIG. 2 is a partially cut-away side elevation taken along line II--II of 
FIG. 1. 
An unwelded can body is shown at 10. It is fabricated by a can body maker 
(not shown) on the left side of FIG. 2 so that its lap portion 12 is 
directed downwardly. The can body maker is installed at the left end of a 
mandrel 14, and the lap, or overlapped portion is welded at the right end 
of the mandrel 14. The can body 10 is conveyed from left to right over the 
mandrel 14. A can body feeding rod 16 is inserted in a long channel 64 at 
the top portion of the mandrel 14. A plurality of claws 18 are provided on 
the feeding rod 16 at fixed intervals. When the feeding rod 16 moves to 
the right, the top portion of the rear end of the can body 10 engages the 
claws 18 and consequently the can body 10 is conveyed. The claws 18 are 
constructed such that they descend when pressed from above, and are 
returned to their original positions by a spring when the pressure is 
released. An elongate electrode 20 is disposed within a bottom channel at 
the right end portion of the mandrel 14. The elongate electrode 20 is 
composed of an elongate copper or copper alloy having a larger length than 
the length of the lap portion 12 (i.e., the height of the can body) at 
least at its electrode surface 22. The electrode surface 22 is a flat 
surface corresponding to the shape of the lap portion 12, or has a convex 
shape in the widthwise direction (the left-right direction in FIG. 1). 
When the lap portion 12 of the can body 10 is not linear as in the case of 
a barrel-like can body, the electrode surface 22 has a curved surface 
corresponding to the shape of the lap portion in the longitudinal 
direction. The width of the electrode surface 22 is larger than the width 
of the lap portion 12. Usually, the electrode surface 22 exists on a plane 
extending from the mandrel 14. Within the elongate electrode 20 is 
provided a cooling hole 32 for passing cooling water, brine (for example, 
at -30.degree. C.), liquefied Freon, etc. therethrough so as to cool the 
surface of the can body welded portion sufficiently and thus prevent 
oxidation of such a part and wearing of the electrodes. The elongate 
electrode 20 is coupled to an ac power supply 34 (for example, having a 
commercial frequency, or a frequency of about 200 to about 500 Hz in the 
case of high-speed can making) by a feeder (not shown). 
A pair of holding wings 24 are disposed on the opposite sides of the 
electrode portion of the mandrel 14, and a supporting member 26 is 
disposed on the top of the mandrel 14. The holding wings 24 and the 
supporting member 26 can be moved laterally and vertically by a cam 
mechanism (not shown) which is in a synchronous relation to a driving 
mechanism for the feeding rod 16. Hence, prior to welding, these members 
can press the can body 10 against the mandrel 14 and fix it there. 
Beneath the elongate electrode 20 is disposed a revolving electrode 28. The 
revolving electrode 28 in the illustrated apparatus is disc-like and its 
electrode surface 30 is in the form of a short hollow cylinder. The width 
of the electrode surface 30 is larger than the width of the lap portion 
12. The revolving electrode 28 is supported by a bearing stand 36 through 
bearings and coupled to an ac power supply by a feeder 38. A supporting 
rod 40 is fixed to the bottom portion of the bearing stand 36, and the 
lower portion of the supporting rod 40 is slidably fitted in an aperture 
formed in a sliding plate 42. The bearing stand 36 is movable vertically 
with respect to the sliding plate 42. A pressing spring 44 surrounding the 
supporting rod 40 is provided between the lower surface of the bearing 
stand 36 and the upper surface of the supporting rod 40. At the time of 
welding, a pressure is applied to the lap portion 12 by means of the 
pressing spring 44. Both side portions of the sliding plate 42 slide 
longitudinally of the mandrel 14 along guide surfaces 50 of guides 48 
provided horizontally on the side inner surfaces of a supporting frame 46, 
and incident to this, the revolving electrode 28 revolves, or more 
specifically moves with rotation on the lap portion 12. Sliding of the 
sliding plate 42 is effected by rotating a rotating disc (not shown) 
through a pin 54 connecting the the sliding plate 42 to one end of a 
linking rod 52 with its other end being secured eccentrically to the 
rotating disc. Projecting portions (engaging portions) 56 are provided 
respectively on the inner upper end portions of both side plates of the 
supporting frame 46. When the upper surface of a bottom plate 58 of the 
bearing stand engages the lower surfaces of the projecting portions 56, 
the revolving electrode 28 is lowered to make the distance between the top 
surface of the revolving electrode 28 and the electrode surface of the 
elongate electrode 20 larger than the thickness of the lap portion or the 
welded portion. Hence, the revolving electrode 28 is prevented from 
hampering the feeding of the can body 10 into the electrode portion and 
the delivering of the welded can body. 
By the apparatus described above, the can body is welded by the following 
procedure. 
The unwelded can body 10 is sent to a predetermined position of the 
elongate electrode 20 by the feeding rod 16 and stopped there when the 
revolving electrode 28 is at the left end side (FIG. 2) of the supporting 
frame 46, the left projecting portion 56 is in engagement with the upper 
surface of the bottom plate 58 of the bearing stand 36, and the distance 
between the top surface of the revolving electrode 28 and the electrode 
surface 22 of the elongate electrode 20 is larger than the thickness of 
the lap portion. Simultaneously, the pair of holding wings 24 advance 
toward the mandrel 14 from left and right, and the supporting member 26 
from above, thereby pressing the can body 10 against the mandrel 14 and 
fixing it there. It is important that the entire width of the lap portion 
12 should contact the electrode surfaces 22 and 30 in this fixed state. 
This is for the purpose of mashing the entire lap portion 12 and reducing 
the thickness of the entire weld portion uniformly. If any part in the 
widthwise direction of the lap portion 12 is kept out of contact, this 
part is not mashed, and leaves a stepped portion corresponding to the 
thickness of the can blank. To achieve corrosion resistance by completely 
covering this stepped portion, a large amount of a protective lacquer is 
required. 
Then, the sliding plate 42 moves to the right to disengage the upper 
surface of the bottom plate 58 of the bearing stand 36 from the left 
projecting portion 56. The electrode surface 30 of the revolving electrode 
28 rotates on the electrode surface 22 of the elongated electrode 20 and 
moves to the right with rotation while pressing the lap portion 12 by the 
pressing spring 44. In the meantime, an electric current passes through 
the revolving electrode, the lap portion and the elongate electrode, and 
the lap portion is welded. Usually, when the revolving speed (i.e., the 
welding speed) is less than about 20 m/min., an alternating current having 
a frequency of 50 to 60 Hz is used. For higher welding speeds, an 
alternating current of a higher frequency is used. 
Alternating currents of various frequencies or wave forms may be applied. 
The conventional apparatus, however, has the disadvantage that the flowing 
of the current becomes difficult, and the various parts of the apparatus 
generate heat. 
Now, with reference to FIG. 3, a first embodiment of the apparatus of this 
invention will be described. 
The apparatus for producing welded metallic can bodies in accordance with 
the first embodiment of the invention includes a fixed elongate electrode 
120, a can body moving means 115, two revolving electrodes 128 and 129, a 
supporting means for supporting the two revolving electrodes 128 and 129, 
a revolving electrode moving means (not shown) and an ac power supply 134. 
The fixed elongate electrode 120 is constructed as part of a mandrel 114, 
and a can body maker (not shown) is provided at the left side portion in 
FIG. 3 of the mandrel 114. At least that portion of the mandrel 114 which 
constitutes the fixed elongate electrode 120 is formed of a conductor. A 
can body fixing device (not shown) cooperating with the mandrel 114 is 
provided so as to set the can body fixedly at a first position, a second 
position, etc. on the mandrel 114. In FIG. 3, a first unwelded can body 
110 is set at the first position and a second unwelded can body 111, at 
the second position. The can body fixing device may, for example, be 
holding wings and a supporting member as shown in FIGS. 1 and 2. The can 
bodies 110 and 111 are set such that when they are at the first and second 
positions, their lap portions 112 and 113 are located downwardly thereof 
in FIG. 3. An electrode surface, 122 similar to the electrode surface 22 
shown in FIGS. 1 and 2, is formed at the lower end (FIG. 3) of the fixed 
elongate electrode 120. 
The can body moving means 115 has a can body feeding rod 116 and a 
plurality of claws 118. The feeding rod 116 and the claws 118 have the 
same structure and function as the feeding rod 16 and the claws 18 in 
FIGS. 1 and 2. Specifically, the plurality of claws 118 are arranged on 
the feeding rod 116 at fixed intervals, and adapted to rise when pressed 
from below and elastically return to their original positions when 
released from pressure. Accordingly, the can bodies can be successively 
moved to the right in FIG. 3 by reciprocating the feeding rod 116 in the 
left-right direction in FIG. 3 and fixedly setting it intermittently at 
predetermined positions. 
The two revolving electrodes 128 and 129 are disposed below the fixed 
elongate electrode. These revolving electrodes 128 and 129 are constructed 
in the same way as the revolving electrode 28 shown in FIGS. 1 and 2. In 
the illustrated embodiment, the revolving electrodes 128 and 129 are 
disc-like. Their shape, however, is not limited to this specific one, and 
may, for example, be a nearly fan-like shape. Generally, the revolving 
electrodes 128 and 129 have a radius of curvature of at least 40 mm. When 
can bodies are made of tin-free steel, these revolving electrodes 
preferably have a radius of curvature of at least 50 mm. 
The supporting device 135 has a bearing stand 136 for rotatably supporting 
shafts 160 and 161 of the revolving electrodes 128 and 129, respectively. 
The bearing stand 136 includes, for example, two bearing plates 162 and a 
supporting rod 165 for supporting the bearing plates 162 fixedly and 
parallel to each other. The revolving electrodes 128 and 129 and the 
shafts 160 and 161 are formed, for example, of metal as an integral unit 
respectively and are electricaly coupled to each other. However, a bearing 
(not shown) of the bearing plate 167 supporting the shaft 160 is 
electrically insulated from a bearing of the bearing plate 162 supporting 
the shaft 161, and therefore, the shaft 160 is electrically insulated from 
the shaft 161. 
The revolving electrode moving means (not shown) is connected to the 
bearing stand 136 so that the two revolving electrodes 128 and 129 can 
move toward and away from the electrode surface 122 of the fixed elongate 
electrode 120 and longitudinally of the fixed elongate electrode 120, i.e. 
in the left-right direction in FIG. 3. The revolving electrode moving 
means can be constructed, for example, of members similar to the 
supporting rod 40, the sliding plate 42, the pressing spring 44, the 
supporting frame 46, the guides 48, the linking rod 52, the pin 54, and 
the projecting portion 56 shown in FIGS. 1 and 2. 
The shafts 160 and 161 of the revolving electrodes 128 and 129 are 
connected respectively to the ac power supply 134. When the circuit is 
closed, one terminal of the ac power supply 134 is electrically coupled to 
the other terminal of the ac power supply 134 via the first shaft 160, the 
first revolving electrode 128, the lap portion 112 of the first can body 
110, the elongate electrode 120, the lap portion 113 of the second can 
body 111, the second revolving electrode 129 and the second shaft 161. 
Preferably, the current flowing in this circuit is an ac current having a 
rms value of 3 to 9 KA with a frequency of 200 to 500 Hz. The ac power 
supply 134 can be electrically coupled with the shafts 160 and 161 by 
using, for example, a feeder bearing which is adapted to electrically 
couple a member rotating while holding a conductive liquid such as mercury 
sealed therein to a non-rotatable member continuously. 
The operation of the apparatus in accordance with the first embodiment 
shown in FIG. 3 will be described. 
A thin can body blank, for example a tin-free steel plate (electrolytically 
chromate-treated steel plate), a tin plate or a nickel-plated steel plate 
having a thickness of 0.12 to 0.60 mm, preferably 0.15 to 0.40 mm is fed 
to a can body maker (not shown) disposed at the left side portion in FIG. 
3. By the can body maker, the metal blank is fabricated into a cylindrical 
form with the width of the lap portion being 0.1 to 1.0 mm, preferably 0.2 
to 0.8 mm. 
Can bodies so made are successively conveyed from left to right in FIG. 3 
by the can body moving means 115 comprised of the feeding rod 116 and the 
claws 118. When the feeding rod 116 moves from left to right, a first, a 
second and a third can body 110, 111 and 166 can freely move over the 
elongate electrode 120. By engagement of the claws 118 with the left ends 
of the can bodies 110, 111 and 166, respectively, these can bodies are 
moved to the right. The amount of movement corresponds to the distance 
from the the third position (i.e., the position at the left end portion of 
FIG. 3) at which the third can body 166 is located in FIG. 3 to the first 
position at which the first can body 110 is located in FIG. 3. When the 
feeding rod 116 moves from right to left, the can bodies 110, 111 and 166 
are set fixedly to the elongate electrode 120 by the can body fixing 
device (not shown). Thus, when the feeding rod 116 moves from right to 
left, the claws 118 are lifted by the can bodies 110, 111 and 166 and 
slide over the upper surfaces of the can bodies 110, 111 and 166. After 
the above movement, the can body fixing device (not shown) fixedly sets 
the first can body 110 at the first position, the second can body 111 at 
the second position, and the third can body 166 at the third position. 
Thereafter, by the revolving electrode moving means (not shown), the 
revolving electrodes 128 and 129 are moved to such positions that the 
upper end of the first revolving electrode 128 (FIG. 3) stands in 
proximity to the electrode surface 122 of the fixed elongate electrode 120 
and slightly on the left of the left side end of the first can body 110 
(FIG. 3) fixed as above, and the upper end of the second revolving 
electrode 129 (FIG. 3) stands in proximity to the electrode surface 122 of 
the fixed elongate electrode 120 and slightly left of the left side end of 
the second can body 111 (FIG. 3) fixed as above. As a result, one 
terminale of the power supply 134 is electrically coupled to the other 
terminal via the first shaft 160, the first revolving electrode 128, the 
elongate electrode 120, the second revolving electrode 129 and the second 
shaft 161. Then, the first and second revolving electrodes 128 and 129 are 
moved to the right in FIG. 3. 
This movement first electrically couples the left side end of the first can 
body 110 to the first revolving electrode 128, and simultaneously, the 
left side end of the second can body 111 to the second revolving electrode 
129. The first and second revolving electrodes 128 and 129 revolve on the 
lap portions 112 and 113 respectively. Consequently, one terminal of the 
ac power supply 134 is electrically coupled to the other terminal via the 
shaft 160 of the first revolving electrode 128, the first revolving 
electrode 128, the lap portion 112 of the first can body 110, the elongate 
electrode 120, the lap portion 113 of the second can body 111, the second 
revolving electrode 129 and the shaft 161 of the second revolving 
electrode 129. An ac voltage may be intermittently applied by the opening 
and closing of a switch (not shown). Application of the ac voltage is 
usually started slightly before the first and second revolving electrodes 
128 and 129 reach the left side ends of the first and second can bodies 
110 and 111 and contact them. When the circuit is closed, an ac current 
having a rms value of 3 to 9 KA with 200 to 500 Hz flows through the 
circuit. 
When the first and second revolving electrodes 128 and 129 further move to 
the right in FIG. 3, the distances from the tops of the first and second 
revolving electrodes 128 and 129 to the electrode surface 122 of the 
elongate electrode 120 become smaller than the thickneses of the lap 
portions 112 and 113 of the can bodies 110 and 111, respectively. Hence, 
the first and second revolving elecrodes 128 and 129 revolve while 
pressing the lap portions 112 and 113. The welding force so applied is 
generally 30 to 500 kg, preferably 40 to 200 kg. The speed of movement of 
the revolving electrodes 128 and 129 to the right in FIG. 3 is 30 to 70 
m/min. 
When the first and second revolving electrodes 128 and 129 further move to 
the right, the tops of the first and second revolving electrodes 128 and 
129 reach the right side ends of the can bodies 110 and 111 respectively 
and then move away therefrom. The moment the revolving electrodes 128 and 
129 leave the right side ends of the can bodies 110 and 111, the applied 
ac current is cut off by a switch (not shown). 
Then, the can body fixing device is rendered inoperative, and the welded 
can bodies are moved a predetermined distance to the right in FIG. 3 by 
the feeding rod 116 and the claws 118. Consequently, the first and second 
welded can bodies 110 and 111 are removed from the right end of the 
mandrel 114, and the third unwelded can body 166 moves to the first 
position previously occupied by the first can body 110. A fourth unwelded 
can body (not shown) located to the left of the third can body 166 is 
moved to the second position previously occupied by the second can body 
111. 
Thereafter, by the procedure described above, the other unwelded can bodies 
are fixed to the elongate electrode 120, and their lap portions are 
welded. 
In the illustrated embodiment, the revolving electrodes 128 and 129 move to 
the right in FIG. 3 with rotation during welding. It is possible however 
to move them alternately to the right and to the left with rotation during 
the welding operation. 
In the apparatus in accordance with this invention, it is not necessary to 
pass an electric current through the mandrel. The shape and material of 
that portion of the mandrel which leads to the welding zone can be more 
freely chosen than in the conventional apparatus. Accordingly, it is easy 
to fabricate and weld metallic can bodies having a small inside diameter. 
Now, with reference to FIG. 4, a second embodiment of the apparatus of this 
invention will be described. 
The apparatus shown in FIG. 4 includes a mandrel 214, a can body moving 
means 215, holding wings 224, a supporting member 226, etc. which are 
similar to those shown in FIGS. 1 to 3 but are slightly modified. 
The mandrel 214 has cooling holes 232 extending therethrough so that a 
cooling liquid such as cooling water, brine (for example at -30.degree. 
C.) or liquefied Freon can be passed through it to cool an elongate 
electrode 220, can bodies 210 and 211, and other parts sufficiently and 
thereby to prevent oxidation and damage of these parts. 
The can body moving means 215 of the apparatus shown in FIG. 4 includes a 
can body feeding rod 216 disposed in each of long channels 264 formed on 
both side portions of the mandrel 214 and a plurality of claws 218 formed 
on the feeding rod 216, and functions in the same way as the can body 
moving means shown in FIGS. 1 to 3. 
Revolving electrodes 228 and 229 are formed as a unit with revolving 
electrode shafts 260 and 261, respectively, and the shafts 260 and 261 are 
rotatably supported on two bearing plates 262. Each of the bearing plates 
262 divided into a portion supporting the first shaft 260 and a portion 
supporting the second shaft 261 which are electrically isolated from each 
other by a first insulator 267. The two bearing plates 262 are fixed to 
the upper surface of a supporting stand 270 via a second insulator 268. As 
a result, the first revolving electrode 228 and the second revolving 
electrode 229 are not electrically coupled through the bearing plates. Two 
rail receiving members 272 are fixed to the under surface of the 
supporting stand 270, and two rails 276 fixed to a base stand 274 are 
received by the rail receiving members 272. The rail receiving members 272 
can move in the longitudinal direction with respect to the rails 276, but 
cannot move in other directions. The base stand 274 makes a controlled 
reciprocating motion in the vertical direction by a driving mechanism 278. 
The driving mechanism 278 is comprised of two rods 280 and 281 fixed to 
the base stand 274 and extending vertically, a sliding supporting portion 
284 fixed to a fixedly disposed frame 282, and a spring 286. The rod 281 
is adapted to move only in the vertical direction within the sliding 
supporting portion 284. As a result, during the vertical movement, the 
base stand 274 is maintained horizontal. The spring 286 is disposed around 
the other rod 280 and between the base stand 274 and the frame 282, and 
always urges the base stand 274 upwardly. The lower ends of the two rods 
280 and 281 are connected to a cam mechanism (not shown) so that the base 
stand 274 can make a controlled reciprocating motion vertically. When the 
base stand 274 is lifted by the cam mechanism, the revolving electrodes 
228 and 229 are brought into press contact with the elongate electrode 220 
through the lap portions 212 and 213 of the can bodies 210 and 211 by the 
urging force of the spring 286. On the other hand, the supporting stand 
270 is caused to make a controlled reciprocating motion longitudinally 
along the rails 276 by a driving mechanism not shown. 
In the apparatus of FIG. 4, a power supply 234 is electrically coupled to 
the revolving electrodes 228 and 229 by a feeder device to be described. 
The feeder device includes feeder rotors 288 and 289, a feeder plate 290 
and a feeder plate supporting member 292. The feeder rotors 288 are made 
of a material having a low electrical resistance, such as copper or a 
copper alloy, and are fixed respectively to the shafts 260 and 261. The 
feeder plate 290 has a first portion 172 and a second portion 173 which 
are electrically isolated from each other by an insulating portion 171. 
The feeder plate 290 is always urged downwardly as described below, 
whereby the feeder rotors 288 and 289 are electrically coupled to the 
first portion 172 and the second portion 173. The first portion 172 and 
the second portion 173 of the feeder plate 290 are connected to the power 
supply 234 through a flexible feeder 294. 
The feeder plate supporting member 292 has a top plate 174, two side plates 
175 (only one of which is shown), and a bottom plate 176, and is 
rectangular on the whole. The top plate 174 is formed of an insulator and 
fixedly supports the feeder plate 290. The side plate 175 is fixedly set 
on the bottom plate 176. An upwardly extending rod 177 is provided at the 
top surface of the side plate 175, and a projecting portion 178 is formed 
at the upper end of the rod 177. The rod 177 extends through a hole formed 
at the end portion of the top plate 174 so that the top plate 174 can move 
vertically with respect to the side plate 175. A compression spring 179 
always urging the top plate 174 downwardly is disposed around the rod 177 
and between the projecting portion 178 of the rod 177 and the top plate 
174. FIG. 4 shows only the right side plate 175, but the left side plate 
175 and other members attached thereto are constructed in the same way as 
described above. Four rail receiving members 183 (only one of which is 
shown in the drawing) are secured fixedly to the under surface of the 
bottom plate 176. Two rail receiving members 183 receive each of two rails 
180 fixed to the base stand 274. As a result, the feeder plate supporting 
member 292 can move longitudinally of the rail 180 parallel to the 
longitudinal direction of the elongate electrode 220, but cannot move in 
other directions, with respect to the base stand 274. 
The operation of the apparatus in accordance with the second embodiment of 
the invention described above will be described. 
In this apparatus, the right rear portion of the mandrel 214 in FIG. 4 
constitutes a can body maker (not shown) which fabricates a thin metal 
blank into can bodies. Can bodies so produced are successively moved 
forwardly to the left by the feeding rod 216 and the claws 218, and fixed 
at predetermined positions by the holding wings 224 and the supporting 
member 226. The revolving electrodes 228 and 229 are positioned such that 
their top portions stand respectively at longitudinal positions slightly 
on the left of the left ends of the first can body 210 and the second can 
body 211 fixed at predetermined positions as stated above and at vertical 
positions slightly below the lap portions 212 and 213 of the can bodies 
210 and 211. In this state, the first feeder rotor 288 is in press contact 
with the first portion 172 of the feeder plate 290, and the second feeder 
rotor 289, with the second portion 173 of the feeder plate 290. 
Then, the base stand 274 is moved upwardly by the driving mechanism 278, 
and the top portions of the revolving electrodes 228 and 229 stand in 
proximity to the electrode surface 222 of the elongate electrode 220. As a 
result, one terminal of the ac power supply 234 is electrically coupled 
with the other terminal via the feeder wire 294, the first portion of the 
feeder plate 290, the first feeder rotor 288, the shaft 260, the first 
revolving electrode 228, the elongate electrode 220, the second revolving 
electrode 229, the shaft 261, the second feeder rotor 289, the second 
portion of the feeder plate 290 and again the feeder wire 294, and thus an 
electric current flows. At this time, the feeder rotors 288 and 289 also 
ascend, but since the feeder plate supporting member 292 is also provided 
on the base stand 274, the positions of the feeder rotors 288 and 289 
relative to the feeder plate 290 remain unchanged. 
Then, the supporting stand 270 supporting the revolving electrodes is moved 
rearwardly to the right along the rails 276 by a driving mechanism. As a 
result, the revolving electrodes 228 and 229 move with rotation while 
standing in proximity to the elongate electrode 220, and the feeder rotors 
288 and 289 move with rotation while standing in proximity to the feeder 
plate 290. 
When the revolving electrodes 228 and 229 and the feeder rotors 288 and 289 
are further moved, the revolving electrodes 228 and 229 contact the left 
front ends of the can bodies 210 and 211. Consequently, one terminal of 
the ac power supply 234 is electrically coupled to the other terminal of 
the ac power supply 234 via the feeder 294, the first portion 172 of the 
feeder plate 290, the first feeder rotor 288, the shaft 260, the first 
revolving electrode 228, the lap portion 212 of the first can body 210, 
the elongate electrode 220, the lap portion 213 of the second can body 
211, the second revolving electrode 229, the shaft 261, the second feeder 
rotor 289, the second portion 173 of the feeder plate 290 and again the 
feeder 294. Thus, an electric current flows and welding of the lap 
portions 212 and 213 is started. 
On further movement, the first revolving electrode 228 moves with rotation 
while being in contact with the lap portion 212 of the first can body; the 
second revolving electrode 229, while being in contact with the lap 
portion 213 of the second can body 211; the first feeder rotor 288, while 
being in contact with the first portion 172 of the feeder plate 290; and 
the second feeder rotor 289, while being in contact with the second 
portion 173 of the feeder plate 290. As a result, the lap portion 212 of 
the first can body 210 and the lap portion 213 of the second can body 211 
are welded. 
To prevent slippage between the revolving electrodes 228 and 229 and the 
lap portions 212 and 213, it is necessary that the diameter of the first 
revolving electrode 228 should be equal to that of the second revolving 
electrode 229. Likewise, to prevent slippage between the feeder rotors 288 
and 289 and the feeder plate 290, the diameter of the first feeder rotor 
288 should be equal to that of the second feeder rotor 289. 
When the diameters of the revolving electrodes 228 and 229 are equal 
respectively to those of the feeder rotors 288 and 289, the feeder plate 
290 is kept from moving longitudinally, no slippage occurs between the 
revolving electrodes 228 and 229 and the lap portions 212 and 213, and 
between the feeder rotors 288 and 289 and the feeder plate 290, and 
therefore, the electrical connection is not interrupted during the welding 
operation. Even when the revolving electrodes and the feeder rotors are 
designed such that the diameters of the revolving electrodes 228 and 229 
are equal to those of the feeder rotors 288 and 289, it is preferred to 
make the feeder plate 290 movable longitudinally by the structure shown in 
FIG. 4 or by simply supporting the feeder plate 290 elastically, so that 
no slippage occurs between the feeder rotors 288 and 289 and the feeder 
plate 290 over a long period of time. 
On the other hand, let us assume that the radii of the revolving electrodes 
228 and 229 are different from those of the feeder rotors 288 and 289. In 
order to avoid slippage between the feeder rotors 288 and 289 and the 
feeder plate 290 during movement in this case, the feeder plate 290 should 
be constructed such that it can be moved longitudinally. 
In this case, the amount, X, of movement of the feeder plate 290 in the 
longitudinal direction is given by the following equation. 
EQU X=[(R.sub.o -R)/R.sub.o ]S 
wherein 
R.sub.o : the radius of each of revolving electrodes 228 and 229, 
R: the radius of each of the feeder rotors 288 and 289, 
S: the stroke of the revolving electrode in the welding direction (the 
longitudinal direction of the mandrel 214). 
When the supporting stand 270 is moved through the stroke S in the 
longitudinal direction, the revolving electrodes 228 and 229 move in a 
straight line through the stroke S relative to the lap portions 212 and 
213 respectively. During this time, the revolving electrodes 228 and 229 
rotate through an angle .omega..sub.o (=S/R.sub.o), and the feeder rotors 
288 and 289 also rotate through the same angle .omega..sub.o (=S/R.sub.o). 
If there is no slippage between the feeder rotors 288 and 289 and the 
feeder plate 290, the feeder rotors 288 and 289 and the feeder plate 290 
move the distance S'=.omega..sub.o R relatively and in a straight line as 
a result of the aforesaid rotation. The difference X between the amount 
(stroke) of movement, S, of the revolving electrodes 228 and 229 relative 
to the lap portions 212 and 213 and the amount of movement, S', of the 
feeder rotors 288 and 289 relative to the feeder plate 290 is given by the 
following equation. 
EQU X=S-S'=[(R.sub.o -R)/R.sub.o ]S 
Accordingly, if the feeder plate 290 is moved by this difference X with 
respect to the lap portions 212 and 213, and therefore the feeder plate 
supporting member 292, with respect to the base stand 274, the feeder 
rotors 288 and 289 and the feeder plate 290 do not slide, and therefore, 
the electrical connection is not interrupted. In the feeder device shown 
in FIG. 4, the feeder plate supporting member 292 can freely move 
longitudinally of the base stand 274. Accordingly, by a frictional force 
between the feeder rotors 288 and 289 and the feeder plate 290, the feeder 
plate supporting member 292 and the feeder plate 290 are automatically 
moved longitudinally. 
The lap portions 212 and 213 of the can bodies 210 and 211 are welded as 
stated above. The revolving electrodes 228 and 229 leave the right rear 
ends of the lap portions 212 and 213, and the welding is completed. The 
revolving electrodes 228 and 229 are further moved a little rearwardly to 
the right, and then the distance between each of the revolving electrodes 
228 and 229 and the elongate electrode 220 is increased. The movement of 
the revolving electrodes 228 and 229 in this process is the same as the 
aforesaid movement before the starting of welding. 
The removal of the welded can bodies 210 and 211 from the mandrel 214 and 
the movement of the revolving electrodes 228 and 229 can be carried out, 
for example, in the same way as described with regard to the embodiment 
shown in FIG. 3. 
Preferably, in order to supply the electrical current properly, a switch 
(not shown) is provided between the flexible feeder 294 and the ac power 
supply 234. This switch is controlled such that it is turned on 
immediately upon or before the contacting of the revolving electrodes 228 
and 229 with the lap portions 212 and 213 of the can bodies 210 and 211, 
and turned off as soon as, or immediately after, the revolving electrodes 
228 and 229 leave the lap portions 212 and 213 after completion of the 
welding operation. 
A third embodiment of the apparatus of this invention will be described 
below in detail with reference to FIGS. 5 and 6. 
The third embodiment differs from the second one mainly in the use of a 
wire electrode, and the following description is directed mainly to this 
difference. 
In the apparatus of the third embodiment, can bodies 310, 311 and 366 are 
fabricated by a can body maker (not shown) located at the left side 
portion of a mandrel 314, welded by an elongate electrode 320 and 
revolving electrodes 328 and 329, and taken out from the right end of the 
mandrel 314. 
The can bodies 310, 311 and 366 are moved on the mandrel 314 by three sets 
of a combination of a can body feeding rod 316 and a claw 318, and fixed 
by holding wings 324 and a supporting member 326. A cooling hole 332 is 
formed within the mandrel 314. 
The mandrel 314 includes a first guide roll 504, a lower guide channel 506, 
a second guide roll 508 and an upper guide channel 510 for a wire 
electrode 502. The wire electrode 502 is obtained, for example, by 
flattening a round copper or tin-plated copper wire having a diameter of 
about 1.5 mm. The first guide roll 504 and the second guide roll 508 are 
rotatably supported by the mandrel 314. The wire electrode 502 is moved a 
predetermined distance in the longitudinal direction by a driving 
mechanism (not shown) when the two revolving electrodes 328 and 329 are at 
positions away from the elongate electrode 320. 
As shown in FIGS. 5 and 6, a bearing stand 336 of a supporting device 335 
supporting the two revolving electrodes 328 and 329 has a first portion 
512 supporting the first revolving electrode 328 and a second portion 514 
supporting the second revolving electrode 329 whch are insulated from each 
other by an insulating portion 516. A third guide roll 518 is rotatably 
provided on the first portion 512, and a fourth guide roll 520 is 
supported by a bearing on the insulating portion 516. A fifth guide roll 
522 is displosed on the second portion 514. Guide channels for guiding the 
wire electrode 524 are formed in the revolving electrodes 328 and 329, 
respectively. As shown in FIG. 5, the wire electrode 524 extends via the 
third guide roll 518, the first revolving electrode 328, the fourth guide 
roll 520, the second revolving electrode 329 and the fifth guide roll 522, 
and is moved a predetermined amount in the longitudinal direction by a 
driving mechanism (not shown) when the two revolving electrodes 328 and 
329 are at positions spaced away from the elongate electrode 320. 
Preferably, the wire electrode 502 for the elongate electrode 320 is the 
same as the wire electrode 524 for the revolving electrodes 328 and 329. 
For example, the wire electrode 524 may be caused to extend from the fifth 
guide roll 522 supported on the bearing stand 336 to the first guide roll 
504 supported on the mandrel 314 via some guide rolls (not shown). 
Rail receiving members 372 are provided through an insulator 368 on the 
bottom surface of the bearing stand 336 of the supporting device 335. Two 
rail receiving members 372 are provided on each of the two sides of the 
bottom surface of the bearing stand 336, and receive rails 376 provided on 
the upper surface of the base stand 374. One end of a driving rod is 
connected to the right side portion in FIG. 5 of the supporting device 
335, and the other end of the driving rod 530 is linked to a driving 
device (not shown). As a result, the supporting device 335, and therefore 
the revolving electrodes 328 and 329, make a controlled reciprocating 
motion longitudinally, namely in the left-right direction in FIG. 5. 
Four vertically extending rods 381 are fixed to the bottom surface of the 
base stand 374. These rods 381 are fitted in four sliding supporting 
portions 384 provided on a fixedly disposed frame 382, and as a result, 
maintain the base stand 374 horizontal when it moves vertically. One end 
of a driving rod 380 is further fixed to the base stand 374, and its other 
end is linked to a driving device (not shown). A spring 386 is disposed 
around the driving rod 380 and between the base stand 374 and the frame 
382. Consequently, the base stand 374 makes a controlled vertical 
movement, and during welding, a pressure is generated by the action of the 
spring 386 between the elongate electrode 320 and the revolving electrodes 
328 and 329. 
The shafts 360 and 361 of the revolving electrodes 328 and 329 are 
connected respectively to an ac power supply through a feeder bearing (not 
shown), for example. 
The apparatus in accordance with the third embodiment operates in the same 
way as the first and second embodiments described hereinabove. However, 
when the welding is carried out while the revolving electrodes 328 and 329 
move along the elongate electrode 320, the lap portions 312 and 313 of the 
can bodies 310 and 311 are pressed between the wire electrodes 502 and 
524. This serves to prevent damage to the elongate electrode 320 and the 
revolving electrodes 328 and 329 and to avoid poor welding which is due to 
the surface unevenness of these electrodes. 
Now, with reference to FIG. 7, a fourth embodiment of the apparatus of this 
invention will be described below in detail. This apparatus differs from 
the third embodiment in the manner of supplying the wire electrode. The 
following description, therefore, is directed mainly to this difference. 
The apparatus in accordance with the fourth embodiment includes a wire 
electrode feed roll 532 rotatably mounted on a fixed frame. The feed roll 
532 holds and feeds a wire electrode 534. The wire electrode 534 extends 
upwardly from the feed roll 532 through a first hole 536 provided in the 
mandrel 414, advances along a long channel 540 formed in the upper portion 
of the mandrel 414 via a first roll 538 rotatably mounted on the mandrel 
414, and further advances into a gap between a first portion 547 of an 
electrode surface 422 of an elongate electrode 420 and the lap portion 412 
of a first can body 410 via a second roll 542, a second hole 544 and a 
third roll 546. Then, it advances upwardly via a fourth roll 548 rotatably 
mounted on the mandrel 414, goes along the long channel 540, and advances 
between the second portion 549 of the electrode surface 422 of the 
elongate electrode 420 which is electrically coupled to the first portion 
547 and the lap portion 413 of a second can body 411 via a fifth roll 550, 
the second hole 544 and a sixth roll 552. Finally, it reaches two driving 
rollers 556 via a roller 554 rotatably mounted on a fixed frame. The 
driving rollers 556 move the wire electrode 534 a distance slightly larger 
than the length of each of the lap portions 412 and 413 of the can bodies 
410 and 411 (i.e., the height of the can body) while there is a clearance 
between the elongate electrode 420 and the revolving electrodes 428 and 
429. 
Likewise, a wire electrode 558 extends from a feed roll 560 to two driving 
rolls 576 via a first roll 561 mounted rotatably on a fixed frame, a 
second roll 562, over the second revolving electrode 429 adjacent the lap 
portion 413, between the revolving electrodes 428 and 429 and a third roll 
564 mounted rotatably on a bearing stand 462, a fourth roll 566 and a 
fifth roll 568 rotatably mounted on a fixed frame, a sixth roll 570, over 
the first revolving electrode 428 adjacent the lap portion 412, between 
the revolving electrodes 428 and 429 and a seventh roll 572 rotatably 
mounted on the bearing stand 462, and an eighth roll 574 rotatably mounted 
on a fixed frame. This wire electrode 558 is driven in the same way as the 
aforesaid wire electrode 534. 
In the apparatus in accordance with the fourth embodiment, the surface of 
each of the wire electrodes 534 and 558 which stands in proximity to the 
lap portion 413 of the second can body 411 differs from that surface which 
stands in proximity to the lap portion 412 of the first can body 410. For 
this reason, even when during welding of one can body, the facing surfaces 
of the wire electrodes 534 and 558 undergo deformation, this deformation 
can be prevented from affecting the welding of the other can body. 
In the apparatus shown in FIG. 5, every time the welding is performed, the 
wire electrode should be moved by a length corresponding to the sum of the 
lengths of the two can bodies and the distance between the two can bodies, 
and that part of the wire electrode which is located between the two can 
bodies is not utilized. In contrast, in the apparatus in accordance with 
the fourth embodiment, the wire electrodes are moved by a length slightly 
larger than the length of the can body every time the welding is 
performed. Thus, almost all of both surfaces of the wire electrodes can be 
effectively used. 
Now, referring to FIGS. 8 and 9, a fifth embodiment of the apparatus of 
this invention will be described in detail. 
The apparatus in accordance with the fifth embodiment includes a fixed 
elongate electrode 632, two revolving electrodes 634 and 636, a bearing 
stand 638 supporting the two revolving electrodes 634 and 636, and an ac 
power supply 640. 
The fixed elongate electrode 632 is constructed as part of a mandrel 642, 
and the left side portion of the mandrel in FIG. 8 constitutes a can body 
maker (not shown). The fixed elongate electrode 632 includes a first 
conductor 644 and a second conductor 646. The first conductor 644 has 
formed therein a channel having a nearly rectangular cross section as 
shown in FIG. 9, and the second conductor 646 is fixedly disposed in this 
channel through an insulator 647. Accordingly, the first conductor 644 is 
electrically insulated from the second conductor 646. Furthermore, a can 
body fixing means (not shown) cooperating with the fixed elongate 
electrode 632 is provided so as to fixedly dispose can bodies at a first 
position, a second position, etc. on the fixed elongate electrode 632. In 
FIG. 8, a first can body 648 is set at a first position, and a second can 
body 650, at a second position. The can body fixing means may be 
constructed of the holding wings 24 shown in FIG. 1 or the like. The can 
bodies 648 and 650 are so arranged that when they are set at the first and 
second positions, their lap portions 652 and 654 are directed downwardly 
in FIG. 8. A first electrode surface 656 and a second electrode surface 
658 are formed respectively on the lower ends (FIG. 8) of the first 
conductor 644 and the second conductor 646, respectively. These electrode 
surfaces 656 and 658 are formed as in the case of the electrode surface 22 
shown in FIGS. 1 and 2. 
The two revolving electrodes 634 and 636 are disposed below the fixed 
elongate electrode 632, and constructed in the same way as in the case of 
the revolving electrode 28 shown in FIGS. 1 and 2. 
The two revolving electrodes 634 and 636 are rotatably mounted on the 
bearing stand 638, and are electrically coupled to each other through the 
bearing stand 638. 
In this specific embodiment, the revolving electrodes 634 and 636 are 
disc-like. But their shape is not limited to this shape, and may, for 
example, be a part of a disc-like shape. The revolving electrodes 634 and 
636 have a radius of curvature of at least 40 mm, and in particular, when 
can bodies made of tin-free steel are to be produced, their radius of 
curvature is preferably at least 50 mm. 
A revolving electrode moving means (not shown) is linked to the bearing 
stand 638, and consequently, the two revolving electrodes 634 and 636 are 
adapted to move toward and away from the two electrode surfaces of the 
fixed elongate electrode 632 and longitudinally of the fixed elongate 
electrode 632, i.e. the left-right direction in FIG. 8. The revolving 
electrode moving means may be constructed of members similar to the bottom 
plate 58 of the bearing stand 36, the supporting rod 40, the sliding plate 
42, the pressing spring 44, the guide 48, the linking rod 52, the pin 54, 
and the projecting portion 56 shown in FIGS. 1 and 2. 
An ac power supply 640 is electrically coupled to the first conductor 644 
and the second conductor 646 of the fixed elongate electrode 632. When the 
circuit is closed, this ac power supply 640 feeds an ac current having a 
rms value of 3 to 9 KA with a frequency of 200 to 500 Hz. 
The apparatus in accordance with the fifth embodiment further includes a 
can body moving means 660 having a feeding rod 662 and claws 664. The 
feeding rod 662 and the claws 664 function in the same way as the feeding 
rod 16 and the claws 18 shown in FIGS. 1 and 2. The claws 664 are adapted 
to be lifted when pressed from below, and return elastically to their 
original positions when released from pressure. Can bodies can therefore 
be moved successively to the right in FIG. 8 by reciprocating the feeding 
rod 664 in the left-right direction in FIG. 8 and intermittently fixing 
the can bodies at predetermined positions. 
The operation of the apparatus in accordance with the fifth embodiment will 
be described. 
First, a thin can body blank, for example a tin-free steel 
(electrolytically chromate-treated steel plate), a tin plate or a 
nickel-plated steel plate having a thickness of 0.12 to 0.6 mm, preferably 
0.15 to 0.4 mm, is fed to a can body maker disposed on the left hand side 
in FIG. 8. By the can body maker, this thin meal blank is fabricated into 
a cylindrical form having a lap portion width of 0.1 to 1.0 mm, preferably 
0.2 to 0.8 mm. 
Can bodies so made are moved successively from left to right in FIG. 8 by 
means of the feeding rod 662, etc. The can bodies 648, 650 and 666 are in 
condition for free movement over the fixed elongate electrode 632. By the 
engagement of the claws 664 with the left ends of the can bodies 648, 650 
and 666, these can bodies are moved to the right. The amount of movement 
of these can bodies corresponds to the distance which the third can body 
666 at the left end in FIG. 8 travels until it reaches the position of the 
first can body 648 at the right end in FIG. 8. When the feeding rod 662 
moves from right to left, the can bodies 648, 650 and 666 are fixedly set 
at the fixed elongate electrode 632 by the can body fixing means (not 
shown). Thus, when the feeding rod 662 moves from right to left, the claws 
664 are lifted by the can bodies 648, 650 and 666 and slide over the upper 
surfaces of these can bodies. After movement as described above, the first 
can body 648 is fixed set at a first position, and the second can body 650 
at a second position, as shown in FIG. 8, by the can body fixing means 
(not shown). 
Thereafter, the revolving electrodes 634 and 636 are moved by the revolving 
electrode moving means (not shown) from positions away from the fixed 
elongate electrode 632 to such positions that the upper end 668 of the 
first revolving electrode 634 (FIG. 8) is located in proximity to the 
first electrode surface 656 of the fixed elongate electrode 632 and 
slightly on the left of the left side end 672 of the first can body 648 
(FIG. 8), and the upper end 670 of the second revolving electrode 636 
(FIG. 8) is located in proximity to the second electrode surface 658 of 
the fixed elongate electrode 632 and slightly to the left of the left side 
end 674 of the second can body 650 (FIG. 8). Then, the first and second 
revolving electrodes 634 and 636 are moved to the right in FIG. 8. 
AS a result of this movement, the left side end 672 of the first can body 
648 is electrically coupled to the first revolving electrode 634, and 
simultaneously, the left side end 674 of the second can body 650 is 
electrically coupled to the second revolving electrode 636. Thus, one 
terminal of the ac power supply 640 is electrically coupled to the other 
terminal of the ac power supply 640 via the first conductor 644 and the 
first electrode surface 656 of the fixed elongate electrode 632, the first 
can body 648, the first revolving electrode 634, the second revolving 
electrode 636, the second can body 650 and the second electrode surface 
658 and the second conductor 646 of the fixed elongate electrode 632. An 
ac current is intermittently applied by the opening and closing of a 
switch (not shown). Application of the ac current is usually started just 
before the revolving electrodes 634 and 636 reach the left side ends 672 
and 674 of the can bodies 648 and 650. As a result, an ac current having a 
rms value of 3 to 9 KA with a frequency of 200 to 500 Hz flows. 
When the first and second revolving electrodes 634 and 636 further move to 
the right in FIG. 8, the distance between the top portion 668 of the first 
revolving electrode 634 and the first electrode surface 656 of the 
elongate electrode and the distance between the top portion 670 of the 
second revolving electrode 636 and the second electrode surface 658 of the 
elongate electrode become smaller than the thicknesses of the lap portions 
652 and 654 of the can bodies 648 and 650, respectively. Accordingly, the 
first and second revolving electrodes 634 and 636 rotate while pressing 
the lap portions 652 and 654. The welding force applied by the revolving 
electrodes is generally 30 to 500 kg, preferably 40 to 200 kg. The speed 
of moving of the revolving electrodes 634 and 638 to the right is 30 to 70 
m/min. 
When the first and second revolving electrodes 634 and 636 further moves to 
the right, their top portions 634 and 636 reach the right side ends of the 
can bodies 648 and 650, respectively, and then leave there. The moment the 
revolving electrodes 634 and 636 have left the right side ends of the can 
bodies 648 and 650, the applied ac current is cut off by a switch (not 
shown). 
The can body fixing means is then rendered inoperative, and the can bodies 
are moved a predetermined distance to the right in FIG. 8 by the feeding 
rods 662 and the claws 664. Specifically, the first and second can bodies 
648 and 650 are removed from the right ends of the fixed elongate 
electrode 632, and the third can body 666 is moved to the position 
previously occupied by the first can body 648, and a fourth can body (not 
shown) located to the left of the third can body 666 is moved to the 
position previously occupied by the second can body 650. Thereafter, by 
the procedure described hereinabove, the third and fourth can bodies are 
fixedly set on the fixed elongate electrode 632 and their lap portions are 
welded. 
In the fifth embodiment, the revolving electrodes 634 and 636 revolve in 
the right hand direction in FIG. 8. It is possible, if desired, to 
construct them so that they can revolve alternately in the right hand 
direction and the left hand direction. 
Now, a sixth embodiment of the apparatus of this invention will be 
described with reference to FIGS. 10 to 12. 
The apparatus in accordance with the fixth embodiment differs from the 
apparatus of the fifth embodiment in that it uses wire electrodes and a 
mechanism for cooling the elongate electrode similar to the embodiment of 
FIGS. 5 and 6. The following description is directed mainly to these 
different features. 
A fixed elongate electrode 732 used in this embodiment includes a first 
guide roll 684 for a wire electrode 682, a lower guide channel 686, a 
second guide roll 688 and an upper guide channel 690. The wire electrode 
682 is obtained, for example, by flattening a round copper or tin-plated 
copper wire having a diameter of about 1.5 mm. The first guide roll 684 is 
rotatably supported on a second conductor 746, and the second guide roll 
688 is rotatably supported by a first conductor 744. The wire electrode 
682 is moved a predetermined amount in the longitudinal direction by a 
driving mechanism (not shown) when two revolving electrodes 734 and 736 
are at positions spaced away from the fixed elongate electrode 732. 
As FIG. 10 shows, a supporting device 738 supporting the two revolving 
electrodes 734 and 736 further rotatably supports a third guide roll 694, 
a fourth guide roll 696 and a fifth guide roll 698 for another electrode 
wire 692. The revolving electrodes 734 and 736 have formed therein a guide 
channel for guiding the wire electrode 692. Thus, as shown in FIG. 10, the 
wire electrode 692 extends via the third guide roll 694, the first 
revolving electrode 734, the fourth guide roll 696, the second revolving 
electrode 736 and the fifth guide roll 698, and is moved a predetermined 
amount in the longitudinal direction when the two revolving electrodes 734 
and 736 are located at positions spaced away from the fixed elongate 
electrode 732. 
Preferably, the wire electrode 682 for the fixed elongate electrode 732 is 
the same as the wire electrode 692 for the revolving electrodes 734 and 
736. Specifically, the wire electrode 692 may be constructed such that it 
extends from the fifth guide roll 698 supported on the supporting device 
738 to the first guide roll 684 supported on the first conductor 744 via 
some guide rolls (not shown). 
In the sixth embodiment, the apparatus further comprises a cooling hole 700 
for conducting a cooling fluid which is formed in the fixed elongate 
electrode 732. As FIGS. 10 and 11 show, the cooling hole 700 extends 
through the first conductor 744 and the second conductor 746. The cooling 
fluid may, for example, be cooling water, brine (for example, at 
-30.degree. C.), or liquefied Freon. 
Furthermore, as shown in FIG. 11, can bodies 748, 750 and 766 are moved on 
the fixed elongate electrode 732 in the longitudinal direction (the right 
hand direction in FIG. 10) by three can body moving means 760 each 
consisting of a feeding rod 762 and claws 164, and are fixed at 
predetermined positions by three holding wings 709. 
The revolving electrode moving device 739 illustrated in FIGS. 10 and 11 
includes a lever 802 for lateral movement, two rails 804 having a nearly 
circular cross section, four rail-receiving members 806, a supporting 
plate 808, four projecting rods 810, four projecting rod receiving members 
812, a supporting stand 814, a driving rod 816 and a coil spring 818. 
The lateral movement lever 802 is connected to the supporting device 738 
supporting the revolving electrodes 734 and 736 and to a driving device 
(not shown), and moves the supporting device 738, and therefore the 
revolving electrodes 734 and 736, in the lateral direction (the left-right 
direction in FIG. 10). 
The four rail-receiving members 806 are fixed to the supporting device, and 
the two rails 804 are fixed to the supporting plate 808. Thus, the 
supporting device 738 can move longitudinally of the rails 804 with 
respect to the supporting plate 808. 
The four projecting rods 810 which extend downwardly are secured to the 
supporting plate 808, and the four projecting rod-receiving members 812 
are fixed to the supporting stand 814. The projecting rods 810 are fitted 
respectively in the corresponding projecting rod-receiving members 812. 
With this structure, the supporting plate 808 can move in the longitudinal 
direction (the up-and-down direction in FIG. 10) while being maintained 
parallel to the supporting stand 814. 
The driving rod 816 is connected to the supporting plate 808 and a driving 
device (not shown), and moves the supporting plate 808 longitudinally. The 
coil spring 818 is disposed around the driving rod 816 and between the 
supporting plate 808 and the supporting stand 814, and urges the 
supporting plate 808 upwardly in FIG. 10. 
Because of the aforesaid structure, the revolving electrode moving device 
739 can be moved along a desired path by the lateral movement of the lever 
802 and the longitudinal movement of the driving rod 816, while the 
supporting device 738 is maintained parallel to the fixed elongate 
electrode 732. As a result, as in the aforesaid embodiment, the revolving 
electrodes 734 and 736 can be moved with respect to the fixed elongate 
electrodes 732. 
The apparatus in accordance with the sixth embodiment operates in the same 
way as the apparatus in accordance with the fifth embodiment. But as shown 
clearly in FIG. 12, when the welding is performed while the revolving 
electrodes 734 and 736 are in proximity to the fixed elongate electrode 
732, the lap portions 752 and 754 of the can bodies 748 and 750 are 
pressed between the wire electrodes 682 and 692. Accordingly, the 
apparatus of the sixth embodiment can avoid poor welding ascribed to 
damages or depressions in the electrodes more effectively than the 
apparatus in accordance with the fifth embodiment. 
In the first to sixth embodiments described hereinabove, the elongate 
electrode is fixed and disposed inwardly of the can bodies, and the 
revolving electrodes which revolve with the movement of their axes of 
rotation are disposed outwardly of the can bodies. If desired, it is 
possible to make the elongate electrode movable and dispose it outwardly 
of the can bodies, and to rotate the revolving electrodes without movement 
of their axes of rotation and dispose them inwardly of the can bodies. 
In the above embodiments, the first and second revolving electrodes are 
fixed to each other, and adapted to exert a welding force by one 
pressurizing system such as a spring. If desired, welding forces can be 
separately applied to the first and second can bodies by providing one 
pressurizing system for each of the two revolving electrodes. For example, 
by providing two parallel-laid sets of the revolving electrode 28 and the 
pressing spring 44 shown in FIG. 2 and using the sliding plate 42 in 
common, welding forces can be exerted on the first and second can bodies 
by separate springs. By providing one pressurizing system for each 
revolving electrode, the welding forces on the first and second can bodies 
can be made more uniform, and the welded states of the two can bodies can 
be made uniform. 
According to the apparatus of this invention, two can bodies can be welded 
by using two revolving electrodes. For rapid welding, it may be possible 
to weld one can body using two revolving electrodes. With this method, 
however, the welded state of that part of the lap portion of the can body 
which first comes into contact with the revolving electrode becomes 
different from the welded states of the other parts, and poor welding 
results. When the welded can body is taken out, the revolving electrodes 
must be kept away from the elongate electrode, and when the can body is 
welded, the revolving electrodes should be kept in proximity to the 
elongate electrode. In the welding of one can body by using two revolving 
electrodes, one of the revolving electrodes is necessarily located over 
the lap portion of the can body when the two revolving electrodes are kept 
in proximity to the elongate electrode. The welding force becomes unstable 
in this positional relationship. If a welding current is passed when the 
welding force is unstable, the welded state of that part becomes unstable, 
and poor welding tends to result with the occurrence of splashes, 
weakening of the weld strength, etc. Conversely, if no welding current is 
passed when the welding force is unstable, that part of the lap portion is 
deformed by the welding force. When, thereafter, the other revolving 
electrode welds that part, the welded state of that part becomes different 
from the other part, and poor welding tends to result. 
According to this invention, when two revolving electrodes are maintained 
in proximity to the elongate electrode prior to welding two can bodies at 
the same time, the lap portions of the can bodies do not exist between the 
revolving electrodes and the elongate electrode. Hence, the poor welding 
can be avoided.