Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to ~lash butt welding~ and
particularl~ to apparatu~ Por program control of flash butt
.velding.
Most efficientl~ the invention can be used in simultaneous-
1~ welding several join-ts, as well as in welding articles having
long seams to be formed, such a , for example~ metal s~eets measu-
ring several meters in width and pipes of large diameters.
'~here is known a program control device ~or controlling a
~lash bu-tt welding process (cf. U~SR Author's Certi~icate
~o. 557~889) comprising welding culren-t pick-ups switched into
each welding circuit, and a welding program controlling unit
havin~ a power suppl~ circuit and being connec-ted through its
output with a drive for moving workpieces being welded. ~his
device ~ur-ther includes a peak s;Lgnal de-tector having inpu-ts
connected to outputs o~ the welding current pick-ups and an out-
put connected, through a parallel-connected proportional and
r~al dif~eren-tiating elemen-ts, to a comparator unit.
This prior art device opera-t;es as ~ollows. A preset
current magnitude ~rom a pic~-up~ an actual current magnitude,
and a time deri~ative thereo~ ara applied to the comparator unit.
'~he ampli~ied signal from the comparator unit is fed to the
: welding program con~rol unit controlling the drive ~or moving the
woxkpieces being welded. It is to be noted that the speed of
approach o~ the wor~pieces is propor-tional to the said signal.
Thus, t~e operation o~ the above device consis-ts in detect-
ing a maximal magnitude o~ the current densi-ty in one of t~e
parallel circuits, and in controlling the welding process to
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maintain s-tability thereof bas-ing on the said maximal
magnitude of the current density.
However, in the case of using the prior art
device, a starting flashing allowance has to be increased.
Moreover the welding time has also to be increased to
compensate for an irregular preparation of abutting ends
of the workpieces to be welded together, which in the
end brings down the efficiency of the welding process.
In addition non-uniform heating of individual joints
being welded affects the quality of the resulting weld
joints.
The principal object of the invention is
to provide a program control device for controlling
flash butt welding, which due to analizing signals
received from each joint in the course of flashing of
abutting ends being joined, ensures a higher efficiency
of the welding process and a better quality of the
resulting weld joints.
Another object of the invention is to reduce
a flashing allowance for the workpieces being welded.
Yet another object of the invention is to
decrease that portion of welding time which is caused by
an irregular preparation of workpiece edges before weld-
ing.
In accordance with a particular embodiment of
the invention there is provided a program control device
for controlling flash butt welding of several joints
~- simultaneously. The device includes welding circuits,
welding current pick-ups connected in each welding cir-
cuit, and a logical coincidence means which has inputs
to which are applied signals from the outputs of the
welding current pick-ups with an output signal of the
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logical coincidence means being produced when the signals
are applied to all its inputs. A welding program con-
trol means has a power supply circuit which is switched
on at the moment when there appears an output signal on
the logical coincidence means. A drive means moves the
workpieces being welded and being controlled by the
welding program control means.
It is expedient that the logic coincidence
unit include a logic NAND-gate, a flip-flop, a logic
AND-gate, and a relay whose contact which is a control
input of the welding program control unit is connected
in the power supply circuit thereof, and the winding
of which is connected, through the logic AND-gate and
the flip-flop, to the output of the logic NAND-gate
having inputs connected to the outputs of the welding
current pick-ups.
Such embodiment of the invention ensures a
high efficiency of the welding process and better quality
of the resulting weld joints.
The nature of the invention will be clear
from the following description of a specific embodiment
thereof taken in conjunction with the accompanying draw-
ings~ wherein:
Fig. 1 represents a block diagram of the device
of the invention'
Fig. 2 represents one of the possible embod-
iments of a logical coincidence unit according to the
invention.
Workpieces 1 and 2 to be welded together by
flash butt welding are clamped by current-carrying jaws
- 3 and 4 whereto, through several parallel circuits, is
applied voltage from transformers 5. The number of the
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transformers 5 depends on the length of seams to be
formed ana, as practice shows, may reach 10-12. Conn-
ected in the welding circuit of each transformer 5 are
welding current pick-ups 6.
The welding current pick-ups are intended for
producing signals in the presence of a certain current
magnitude in a welding circuit. The welding current
pick-ups 6 are current transformers having their
OUtptlts connected to inputs of rectifiers 8. The rec-
tifiers 8 outputs which are the outputs of the welding
current pick-ups 6, are connected to inputs of a logical
coincidence unit 9 whose output is connected to a con-
trol input of a program control unit 10. The device
9 is adpated to start the unit 10 at the moment when
along the whole welding circuit the current will reach a
certain level.
The program control unit 10 having a power
supply circuit 11 is connected through its OlltpUt with
a drive 12 adapted for moving the workpieces 1 and 2.
- 20 According to one embodiment of the invention the pro-
gram control unit is a multicircuit time relay, and
the drive 12 includes an electronic or electromechanical
booster, a d.c. motor, a reduction gear, a control
sliding valve and a hydraulic cylinder (cf. ~S Patent
No. 3,335,257).
In the preferred emhodiment of the invention
the logical coincidence unit 9 includes a logic NAND-
~` gate 13, a flip-flop 14, a logic A~D-gate 15, and a
relay 16 whose contact 17 being a control input of the
welding program control unit 10 is connected in the
power supply circuit 11 of the unit 10, and whose wind-
ing, through the logic AND-gate 15 and the flip-flop
14, is connected to the output of the logic NAND-gate
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13 having its outputs connected to the outputs of the
welding current pick-ups 6.
The logic NAND-gate 13 is intended for deliv-
ering all the input signals, and the flip-flop 14 is
adapted for storing a signal at its output in the
absence of a signal at the output of the logic NAND-
gate 13.
The logic AND-gate 15 having a high load cap-
acity serves as a decoupling network in the case of
switching-on of the relay 16.
Such construction of the logical coincidence
unit 9 provides for that the moment of the simultaneous
arrival of signals at its input is determined with a
high precision and the power supply circuit of the unit
10 is switched on at a right moment.
The logical coincidence unit 9 features a
high noise immunity since the switching-on of the power
supply circuits is effected directly through the output
contact of the relay.
The logical coincidence unit 9 may be variously
otherwise embodied. It may have, for example, multiple
input logic NAND-gate having its output connected to
the flip-flop. In this case however, the output of
the flip-flop is connected directly to the control
input of the program control unit 10 whose construction
is based on logic elements, which complicates to a
great extent the unit 10, thereby making the unit more
costly~
The welding program control device operates as
follows. Welding voltage from the transformer 5 is
applied, through the current-carrying jaws 3 and 4 to
the workpieces 1 and 2. The workpieces 1 and 2 are
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moved towards each other by the drive 12, with the
approach speed being controlled by the welding program
control unit 10. Starting speed of approach of the
workpieces is selected so as to ensure a more rapid
flashing of the workpiece butt end irregularities without
causing the already flashed parts thereof to be heated
until the flashing process takes place along the whole
line of the seam to be formed.
In the course of upsetting of the workpieces
1 and 2 the abutting ends thereof begin to fuse down at
their different portions, which is caused by irregular-
ities resulting from inadequate preparation of the edges
i.e. abutting ends of the workpieces 1 and 2, and
~ uneven clamping thereof by the jaws 3 and 4. In this
:~ 15 case the welding current will flow in the circuits of
only those transformers 5 at the sections of which there
takes place contacting and flashing of the abutting edges
of the workpieces 1 and 2. As a result, signals in-
dicative of the presence of the welding current in a
: 20 respective welding circuit are fed to the corresponding
inputs of the logical coincidence unit 9, in which case
a signal at the output of the unit 9 does not appear.
As indicated above, the logical coincidence unit 9 is
constructed so that the output signal is generated only
in thé case of presence of signals at all its inputs
the number of which is determined by the number of the
welding current pick-ups 6.
As the abutting edges of the workpieces 1 and
2 fuse down their edges become more even, and at the
moment when the welding current rlows in each circuit
of the transformers 5, to all the inputs of the unit 9
will be fed signals from the welding current pick-ups 6,
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in which case at the output of the unit 9 there appears
a signal to start the welding program control unit 10.
Thus, a program controlled welding begins at
the moment when the workpieces being welded begin to
flash off over the whole length of the seam to be formed.
The logical coincidence unit 9 shown in Fig.
2 operates as follows. When signals are applied
to all the inputs of the logic NAND-gate 13, at the
output thereof there appears a fixed signal which,
being applied to the input of the logic AND-gate 15,
causes the relay 16 to operate and through its contact 17
to energize the welding program control unit 10.
Beginning from this moment the welding process proceeds
under the control of the unit 10.
The proposed device allows the flashing allow-
ance to be considerably reduced and the efficiency
and quality of welding to be irnproved.
This invention may be variously otherwise
embodied withln the scope of the appended claims.
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