A rotary arc-welding apparatus which comprises: a rotatable nozzle having in its interior thereof a passage for directing a consumable welding electrode eccentrically from the center axis of the nozzle toward a groove formed between objects of welding; a consumable welding electrode feeding mechanism for continuously directing the consumable welding electrode toward the groove through the nozzle; a welding current feeding mechanism for feeding a welding current to the nozzle, which comprises a current receiving plate fixed to the top end of the nozzle, a brush having on the upper surface thereof a current feeding plate, the brush and the current receiving plate having a flat contact interface therebetween, a plurality of rods for stationarily holding the brush and the current feeding plate, and a plurality of springs for applying a pressure onto the contact interface between the brush and the current receiving plate; a nozzle rotating mechanism for rotating the nozzle about the center axis thereof at a high speed to cause a circular movement of an arc from the tip of the consumable welding electrode corresponding to the eccentricity thereof; and a shielding gas feeding mechanism for feeding a shielding gas toward the arc and a weld zone.

A prior art document pertinent to the present invention is Japanese Pat. 
Provisional Publication No. 133871/80 dated Oct. 18, 1980. 
The contents of the above-mentioned prior art document will be described 
hereafter under the heading of the "BACKGROUND OF THE INVENTION". 
FIELD OF THE INVENTION 
The present invention relates to a rotary arc-welding apparatus for welding 
objects to be welded (hereinafter referred to as "objects of welding") 
while causing a circular movement of an arc from the tip of a consumable 
welding electrode directed through a nozzle toward a groove formed between 
the objects of welding by rotating the nozzle about the center axis 
thereof at a high speed. 
BACKGROUND OF THE INVENTION 
As a method which permits efficient welding of objects of welding such as 
thick steel plates with uniform penetration of molten metal without 
causing welding defects, there is disclosed in Japanese Pat. Provisional 
Publication No. 133,871/80 an arc-welding method of a narrow groove, which 
comprises: 
directing a nozzle rotatable about the center axis thereof substantially 
vertically toward an I-shaped narrow groove formed between objects of 
welding; directing a consumable welding electrode through said nozzle 
eccentrically from the center axis of said nozzle toward said groove; 
feeding a welding current to said consumable welding electrode to produce 
an arc between said groove and the tip of said consumable welding 
electrode to weld said objects of welding with each other by means of heat 
from said arc; rotating said nozzle about the center axis thereof at a 
high speed of at least 120 r.p.m. to cause a circular movement of said arc 
from the tip of said consumable welding electrode corresponding to the 
eccentricity thereof; and feeding a shielding gas toward said arc and a 
weld zone to shield said arc and said weld zone from the open air 
(hereinafter referred to as the "prior art"). 
In the prior art described above, the welding current is fed to the 
consumable welding electrode by a welding current feeding mechanism 
provided on the tip portion of the nozzle or on a consumable welding 
electrode feeding mechanism located above the nozzle. However, the welding 
current feeding mechanism, if provided on the lower end portion of the 
nozzle, would be required to have a complicated construction because of 
the high-speed rotation of the nozzle and may be damaged by the arc heat 
or spatters produced during welding. Furthermore, when the groove width is 
very small, the welding current feeding mechanism may make it difficult to 
insert the nozzle into the groove. When the welding current feeding 
mechanism is provided on the consumable welding electrode feeding 
mechanism located above the nozzle, on the other hand, the considerable 
length of the consumable welding electrode between the tip thereof and the 
consumable welding electrode feeding mechanism leads to a larger electric 
resistance of the consumable welding electrode, thus resulting in a larger 
loss of the welding current. 
Under such circumstances, there is a strong demand for the devclopment of a 
rotary arc-welding apparatus which permits sure feeding of a welding 
current by a simple welding current feeding mechanism to a nozzle rotating 
about the center axis thereof at a high speed, without causing damages to 
the welding current feeding mechanism by the arc heat or spatters produced 
during welding, and gives only a small loss of the welding current, and 
furthermore, has a welding current feeding mechanism not hindering 
insertion of the nozzle into the groove even when the groove width is 
small, but such an apparatus is not as yet proposed. 
SUMMARY OF THE INVENTION 
An object of the present invention is therefore to provide, when welding 
objects of welding while causing a circular movement of an arc from the 
tip of a consumable welding electrode directed through a nozzle toward a 
groove formed between the objects of welding by rotating the nozzle about 
the center axis thereof at a high-speed, a rotary arc-welding apparatus 
which permits sure feeding of a welding current to the nozzle by a simple 
welding current feeding mechanism, without causing damages to the welding 
current feeding mechanism by the arc heat or spatters produced during 
welding, and gives only a small loss of the welding current. 
Another object of the present invention is to provide, when welding objects 
of welding while causing a circular movement of an arc from the tip of a 
consumable welding electrode directed through a nozzle toward a narrow 
groove formed between the objects of welding by rotating the nozzle about 
the center axis thereof at a high speed, a rotary arc-welding apparatus 
which has a welding current feeding mechanism not hindering insertion of 
the nozzle into the narrow groove. 
In accordance with one of the features of the present invention, there is 
provided a rotary arc-welding apparatus which comprises: 
a nozzle rotatable about the center axis thereof at a high speed, said 
nozzle having in the interior thereof a passage for directing a consumable 
welding electrode eccentrically from the center axis of said nozzle toward 
a groove formed between objects of welding; 
a consumable welding electrode feeding mechanism, provided above said 
nozzle, for continuously directing said consumable welding electrode 
toward said groove through said nozzle; 
a welding current feeding mechanism for feeding a welding current to said 
nozzle to produce an arc between said groove and the tip of said 
consumable welding electrode passing through said nozzle; 
a nozzle rotating mechanism for rotating said nozzle about the center axis 
thereof at a high speed to cause a circular movement of said arc from the 
tip of said consumable welding electrode corresponding to the eccentricity 
thereof, said nozzle rotating mechanism comprising a motor fixed to a 
carriage, gears for transmitting the rotation of said motor to said 
nozzle, and a gear box for housing said gears, said gear box rotatably 
supporting said nozzle passing therethrough; and 
a shielding gas feeding mechanism for feeding a shielding gas toward said 
arc and a weld zone to shield said arc and said weld zone from the open 
air; 
characterized in that: 
said welding current feeding mechanism (8) comprises: 
a circular current receiving plate (9), which is fixed to the upper end of 
said nozzle (1) and rotates together with said nozzle (1), said current 
receiving plate (9) having at the center thereof a passage (10) for said 
consumable welding electrode (4); 
a circular brush (11), having substantially the same diameter as that of 
said current receiving plate (9), for feeding said welding current to said 
current receiving plate (9), said brush (11) having on the upper surface 
thereof a current feeding plate (13), the lower surface of said brush (11) 
and the upper surface of said current receiving plate (9) having a flat 
contact interface (12) therebetween, and said brush (11) and said current 
feeding plate (13) having at the center thereof a passage (23) for said 
consumable welding electrode (4); 
a plurality of rods (19) for stationarily holding said brush (11) and said 
current feeding plate (13) so as to prevent same from rotating together 
with said nozzle (1) and said current receiving plate (9), the lower 
halves of said plurality of rods (19) being inserted into said brush (11) 
and said current feeding plate (13), and the upper end portions of said 
plurality of rods (19) being secured to a supporting plate (21) fixed to 
said carriage; 
a plurality of springs (22) for applying a pressure onto said contact 
interface (12) between the lower surface of said brush (11) and the upper 
surface of said current receiving plate (9), said plurality of springs 
(22) being provided between said supporting plate (21) and said current 
feeding plate (13); and 
said pressure applied by said plurality of springs (22) onto said contact 
interface (12) between the lower surface of said brush (11) and the upper 
surface of said current receiving plate (9) being such that, when 
actuating said nozzle rotating mechanism (5), said nozzle (1) and said 
current receiving plate (9) rotate whereas said brush (11) and said 
current feeding plate (13) do not rotate, and said welding current 
smoothly flows from said brush (11) to said current receiving plate (9).

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
From the aforementioned point of view, the present inventors carried out 
extensive studies to develop a rotary arc-welding apparatus which permits 
sure feeding of a welding current by a simple welding current feeding 
mechanism to a nozzle rotating about the center axis thereof at a high 
speed, without causing damages to the welding current feeding mechanism by 
the arc heat or spatters produced during welding, and gives only a small 
loss of the welding current, and furthermore, has a welding current 
feeding mechanism not hindering insertion of the nozzle into the groove 
even when the groove width is small. 
As a result, we found that it is possible to solve the above-mentioned 
problems by adopting a welding current feeding mechanism for feeding a 
welding current to a nozzle which comprises: a current receiving plate 
fixed to the upper end of the nozzle and rotating together with the 
nozzle, and a brush having on the upper surface thereof a current feeding 
plate, and stationarily held so as not to rotate together with the nozzle 
and the current receiving plate, for feeding the welding current to the 
current receiving plate. 
The present invention was made on the basis of the above-mentioned finding, 
and the rotary arc-welding apparatus of the present invention is described 
below with reference to the drawings. 
As shown in FIG. 1, a nozzle 1 rotatable about the center axis thereof at a 
high speed has in the interior thereof a passage 3 for directing a 
consumable welding electrode 4 eccentrically from the center axis of the 
nozzle 1 toward a groove formed between objects of welding. The lower end 
portion 1a of the nozzle 1 has a diameter smaller than that of the other 
portion thereof, and a tip member 2 is replaceably fitted to the lower end 
of the nozzle 1. As shown in FIGS. 3(a) and 3(b), the passage 3, provided 
through the nozzle 1 and the tip member 2, for directing the consumable 
welding electrode 4 may be eccentric from the center axis of the nozzle 1 
at the tip member 2, or as shown in FIG. 3(c), may be eccentric from the 
center axis of the nozzle 1 throughout the entire passage 3 of the nozzle 
1 and the tip member 2. 
In FIG. 1, a nozzle rotating mechanism 5 comprises a motor 6 fixed to a 
carriage (not shown), gears (not shown) for transmitting the rotation of 
the motor 6 to the nozzle 1, and a gear box 7 for housing the gears. The 
gear box 7 supports the nozzle 1 passing through the gear box 7 through an 
insulator (not shown) rotatably about the center axis of the nozzle 1. 
A welding current feeding mechanism 8 is provided at the upper end of the 
nozzle 1, for feeding a welding current to the nozzle 1 to produce an arc 
between the tip of the consumable welding electrode 4 passing through the 
nozzle 1 and the groove formed between the objects of welding. Now, the 
welding current feeding mechanism 8 is described with reference to FIGS. 1 
and 2. A circular current receiving plate 9 is secured for example by 
driving to the upper end of the nozzle 1. The current receiving plate 9 
has at the center thereof a passage 10 for the consumable welding 
electrode 4. 
A circular carbonaceous brush 11, which has a diameter substantially equal 
to that of the current receiving plate 9, for feeding the welding current 
to the current receiving plate 9, is provided on the upper surface of the 
current receiving plate 9. The lower surface of the brush 11 and the upper 
surface of the current receiving plate 9 have a flat contact interface 12 
therebetween. A current feeding plate 13 having a diameter substantially 
equal to that of the brush 11 is secured by means of a plurality of bolts 
14 onto the upper surface of the brush 11. The current feeding plate 13 is 
connected with the end of a cable 15 connected to an electric power source 
(not shown) with a terminal 16. In FIG. 2, 17 is a terminal fitting bore 
provided in the current feeding plate 13. A guide pipe 18 described later, 
which serves as the passage for the consumable welding electrode 4, is 
provided through the brush 11 and the current feeding plate 13 at their 
centers. 
The lower halves of a plurality of rods 19 for stationarily holding the 
brush 11 and the current feeding plate 13 are inserted into a plurality of 
holes 20 provided in the brush 11 and the current feeding plate 13 so as 
not to rotate together with the nozzle 1 and the current receiving plate 
9. The upper end portions of the plurality of rods 19 are secured for 
example by driving to a supporting plate 21 fixed to the carriage. A 
plurality of coil-shaped springs 22 for applying a pressure onto the 
contact interface 12 between the lower surface of the brush 11 and the 
upper surface of the current receiving plate 9 are provided between the 
supporting plate 21 and the current feeding plate 13. The plurality of 
rods 19 are inserted into the plurality of coil-shaped springs 22. The 
pressure applied by the plurality of springs 22 onto the contact interface 
12 between the lower surface of the brush 11 and the upper surface of the 
current receiving plate 9 is such that, when the nozzle rotating mechanism 
5 is actuated, the nozzle 1 and the current receiving plate 9 rotate 
whereas the brush 11 and the current feeding plate 13 do not rotate, and 
the welding current smoothly flows from the brush 11 to the current 
receiving plate 9. 
The middle portion of the guide pipe 18 having in the interior thereof a 
passage 23 for directing the consumable welding electrode 4 toward the 
nozzle 1 is secured to the supporting plate 21 for example by driving. The 
lower half of the guide pipe 18 passes through the current feeding plate 
13 and the brush 11, and the passage 23 provided in the guide pipe 18 
communicates with the passage 10 provided in the current receiving plate 
9. 
As shown in FIG. 1, a consumable welding electrode feeding mechanism 24 for 
continuously directing the consumable welding electrode 4 toward the 
groove formed between the objects of welding is provided above the guide 
pipe 18. The consumable welding electrode feeding mechanism 24 comprises a 
pair of rollers 25 and 25' and a motor 26 for rotating the pair of rollers 
25 and 25'. The consumable welding electrode 4 is continuously directed 
toward the above-mentioned groove through the passage 23 in the guide pipe 
18, the passage 10 in the current receiving plate 9 and the nozzle 1, by 
means of the pair of rollers 25 and 25' driven by the motor 26. 
A shielding gas feeding mechanism 27 for feeding a shielding gas toward the 
arc produced between the tip of the consumable welding electrode 4 passing 
through the nozzle 1 and the above-mentioned groove and a weld zone to 
shield the arc and the weld zone from the open air is provided on the 
lower surface of the gear box 7. The shielding gas feeding mechanism 27 
comprises a pair of opposing gas nozzles 28 and 28' which eject a 
shielding gas toward the arc and the weld zone and a substantially 
horizontal gas nozzle support 29 for securing the pair of gas nozzles at a 
predetermined position. The nozzle support 29 is fitted to the lower 
surface of the gear box 7 by means of a fitting piece 30. The nozzle 1 
passes, through an insulator (not shown), through the nozzle support 29 
and the fitting piece 30 at the center portions thereof. In FIG. 1, 31 is 
a detector for detecting the deviation of the tip of the consumable 
welding electrode 4, which projects from the lower end of the nozzle 1 and 
rotates, from the center line of the groove. 
By means of the rotary arc-welding apparatus of the present invention 
having the construction as described above, welding of the objects of 
welding is conducted as follows. The nozzle 1 is directed toward the 
groove formed between the objects of welding, and the consumable welding 
electrode 4 is directed by the consumable welding electrode feeding 
mechanism 24, through the nozzle 1, eccentrically from the center axis of 
the nozzle 1 toward the groove. The nozzle 1 is rotated about the center 
axis thereof at a high speed by the nozzle rotating mechanism 5, and a 
welding current is fed to the nozzle 1 by the welding current feeding 
mechanism 8 provided at the upper end portion of the nozzle 1. As a 
result, an arc is produced between the tip of the consumable welding 
electrode 4 directed toward the groove eccentrically from the center axis 
of the nozzle 1 and the groove, and the arc shows a circular movement 
corresponding to the eccentricity mentioned above caused by the rotation 
of the nozzle 1. The shielding gas is fed by the shielding gas feeding 
mechanism 27 toward the arc and the weld zone to shield the arc and the 
weld zone from the open air. Thus, the objects of welding are efficiently 
welded with each other without the occurrence of welding defects caused by 
the heat of the rotating arc as mentioned above. 
In the rotary arc-welding apparatus of the present invention, the welding 
current feeding mechanism 8 for feeding the welding current to the nozzle 
1 comprises, as described above, the current receiving plate 9 fixed to 
the upper end of the nozzle 1, the brush 11 having on the upper surface 
thereof the current feeding plate 13, the lower surface of the brush 11 
and the upper surface of the current receiving plate 9 having the flat 
contact interface 12 therebetween, the plurality of rods 19 for 
stationarily holding the brush 11 and the current feeding plate 13, and 
the plurality of springs 22 for applying a pressure onto the contact 
interface 12 between the lower surface of the brush 11 and the upper 
surface of the current receiving plate 9 in such a manner that the nozzle 
1 and the current receiving plate 9 rotate whereas the brush 11 and the 
current feeding plate 13 do not rotate and the welding current smoothly 
flows from the brush 11 to the current receiving plate 9. 
It is therefore possible to ensure feeding of the welding current to the 
nozzle 1 rotating at a high speed by a simple construction without 
disturbing the rotation of the nozzle 1. The welding current feeding 
mechanism 8, being provided at the upper end of the nozzle 1, is not 
damaged by the arc heat or spatters produced during welding, and does not 
hinder, even when welding the objects of welding along a narrow groove, 
the insertion of the nozzle 1 into the groove. In addition, since the 
welding current flows through a shorter length of the consumable welding 
electrode than in the case of the welding current feeding mechanism 
provided on the consumable welding electrode feeding mechanism 24, the 
electric resistance of the consumable welding electrode 4 is smaller, thus 
resulting in a relatively small loss of welding current. 
According to the rotary arc-welding apparatus of the present invention, as 
described above in detail, it is possible, when welding objects of welding 
while causing a circular movement of an arc from the tip of a consumable 
welding electrode directed through a nozzle toward a groove formed between 
the objects of welding by rotating the nozzle about the center axis 
thereof at a high speed, to ensure feeding of a welding current to the 
nozzle by a simple welding current feeding mechanism without damages to 
the welding current feeding mechanism by the arc heat or spatters produced 
during welding, to give only a small loss of the welding current, and 
furthermore, to prevent the welding current feeding mechanism from 
hindering the insertion of the nozzle into the groove even when the groove 
width is small, thus providing industrially useful effects.