Apparatus for feeding wire over large distances

Apparatus for feeding wire at great distances, as in feeding electrode wire in electric welding. A plurality of wire-feeding mechanisms are disposed in tandem, each of such mechanisms being coupled to a DC motor, the DC motors being connected in parallel through individual back-polarizing diodes. The first or leading DC motor is connected via a speed stabilizer in a generator for switch-on impulses to a thyristor rectifier, the outputs of a rectifier being connected to the first DC motor. Each of the remaining DC motors is connected to the outputs of the thyristor rectifier, the connection of all DC motors to the thyristor rectifier being effected via a respective separating diode. The apparatus of the invention is particularly characterized by its simplified structure, while it still preserves all functional possibilities of prior art systems for feeding wire over large distances.

This invention relates to an apparatus for feeding wire over large 
distances, and is particularly adapted for feeding electrode wire in 
electric welding. 
A known apparatus, disclosed in U.S. Pat. No. 4,305,537 for feeding wire at 
great distances comprises wire-feeding mechanisms disposed in tandem, each 
of such mechanisms being coupled to a DC motor. In parallel to each motor 
there is connected one individual back-polarizing diode. The first or 
leading DC motor is connected via a speed stabilizer and a generator of 
ignition pulses to a thyristor rectifier, the outputs of the rectifier 
being connected such DC motor. The remaining DC motors, for the following 
wire-feeding mechanisms, are each connected individually via a respective 
thyristor rectifier to a respective genertor for ignition pulses. The 
output of the generators of switch-on impulses of the first DC motor is 
connected via common synchronizing conductors or bus bars to the inputs of 
the generators for switch-on impulses of the remaining DC motors. 
The drawback of the afore-described known apparatus lies in the fact that 
the circuit system is quite complicated. 
It therefore the general object of the present invention to provide an 
apparatus for feeding wire over large distances which has a simplified 
circuit system. 
The above object is achieved by apparatus of the invention for feeding wire 
over large distances. In the disclosed, preferred embodiment of such 
apparatus, there are employed tandemly arranged wire-feeding mechanisms, 
each of which is coupled to its individual DC motor. Each motor has a 
parallel connected polarizing diode. The first DC motor, for the leading 
wire-feeding mechanism, is connected via a speed stabilizer and a 
generator for ignition pulses to a thyristor rectifier, the outputs of 
such rectifier being connected to the first DC motor. A distinguishing 
feature of the apparatus of the invention lies in the fact that each of 
the remaining DC motors, for successive wire-feeding mechanisms, is 
connected to the outputs of this thyristor rectifier, and the connection 
of all motors to the thyristor rectifier is effected via a respective 
separating diode. 
The advantage of the invention lies in the simplified structure of the 
apparatus, while all functional possibilities of the above-described prior 
art apparatus are preserved. 
For a better understanding of the invention, reference should be had to the 
accompanying drawing, in which:

Referring now to the drawing, the apparatus comprises a plurality of 
tandemly arranged mechanisms (three shown) for feeding a wire 9 in the 
direction from right to left. the first or leading wire-feeding mechanism 
is designated 8.sub.a, whereas the succeeding two such mechanisms are 
designated 8.sub.b,8 .sub.c respectively. The first or leading 
wire-feeding mechanism 8.sub.a is driven by a DC motor 1, whereas each of 
the succeeding mechanisms 8.sub.b and 8.sub.c is driven by its individual 
DC motor 6. The first DC motor 1 is connected by a speed stabilizer 2 and 
a generator 3 for ignition pulse s to a thyristor rectifier 4 of known 
design. The rectifier 4 has two outputs which are connected respectively 
to conductors or bus bars 10 and 11. One terminal of each of motors 1 and 
6 is connected to the conductor 10 by its individual separating diode 5 
which passes current to the respective motor from the conductor 10 but 
prevents passage of such current in the reverse direction. The same one 
terminal of each of motors 1 and 6 is also connected to the conductor 11 
through a back-polarizing diode 7 which blocks the flow of current 
therethrough from said one terminal of motors 1 and 6 to the conductor 11 
the second terminals of each of motors 1 and 6 are directly connected to 
the conductor 11. The thyristor rectifier 4 is supplied with alternating 
current, as shown at U. 
The above-described apparatus operates as follows. 
The thyristor rectifier 4 feeds feeding DC current impulses to the motors 1 
and 6. In the interval between successive DC current impulses there is 
formed an electromotive voltage in the motors 1 and 6, such voltage being 
proportional to the speed of revolution of each of the motors and to a 
proportionality factor, which can be different for each of the motors 
because of production tolerances. It is also possible that at any given 
moment the motors 1 and 6 do not rotate at the same speed. Because of such 
two possible conditions, it may occur that the electromotive voltages 
which drive each of the motors 1 and 6 are different. The separating 
diodes 5 make it possible for these different voltages in each motor to 
exist simultaneously and independently of each other; only the 
electromotive voltage of the first motor 1 is fed to the speed stabilizer 
2 to give information as to the speed of such motor 1. This would be 
impossible if the motors 1 and 6 were connected directly parallel without 
the separating diodes 5. Moreover, an undesired electromechanical 
interaction would occur, if the separating diodes were not employed, 
during the pauses between the feeding DC current impulses: The motors with 
higher electromotove voltage would operate in a generator mode and, hence 
in a braking condition, while the other motors would operate, 
respectively, in a driving condition. 
Although the invention is illustrated and described with reference to one 
preferred embodiment thereof, it is to be expressly understood that it is 
in no way limited to the disclosure of such a preferred embodiment, but is 
capable of numerous modifications within the scope of the appended claims.