Electric heating – Metal heating – For bonding with pressure
Reexamination Certificate
2000-08-03
2002-09-03
Shaw, Clifford C. (Department: 1725)
Electric heating
Metal heating
For bonding with pressure
Reexamination Certificate
active
06444942
ABSTRACT:
FIELD OF THE INVENTION
The present application relates to welding control systems. More particularly, it relates to welding control systems that can be produced, operated and maintained at a low cost.
BACKGROUND OF THE INVENTION
Welding apparatus are frequently utilized together with robots, workpiece transferring systems, and workpiece positioning jigs to automate the welding process. In such cases, it is necessary to synchronize the operation of, for instance, the robot and the welding apparatus. Normally, when the workpiece has been moved by the workpiece transferring system to a prescribed position and/or the workpiece positioning jig has reached at a prescribed position in which welding can be performed, a signal to start welding is sent to the welding control apparatus. Hereinafter, the apparatus that sends the signal to start welding to the welding apparatus will be called the “upper control apparatus.”
The optimum welding conditions, such as the magnitude of the welding current, the time variation of the current magnitude, the duration of the current flow, and the pressure applied to the workpiece by the pair of welding guns and other welding parameters, will vary. The welding conditions depend, for example, on the type of material that is being welded, its thickness, surface treatment and welding position. Therefore, a plurality of welding sequence data, which correspond to the various types of welding operations, are stored in the welding apparatus. After accessing the specific welding sequence data that correspond to the type of welding to be performed, the prescribed welding process is initiated.
As shown in
FIG. 1
, a known welding control system includes upper control apparatus
102
, welding control apparatus
122
, and a set of cables
100
connecting the two apparatus.
The upper control apparatus
102
controls the robot, workpiece transferring system, positioning jig for the workpiece, and the time to start the welding. Upper control apparatus
102
comprises CPU
106
, memory unit
108
, and input/output interface (I/O)
110
. A teaching apparatus
104
for the upper control apparatus
102
is connected to the upper control apparatus
102
. The program and data necessary for the upper control apparatus
102
to control the robot, workpiece transferring system, and workpiece positioning jig are sent to the upper control apparatus
102
from the teaching apparatus
104
. Timing data for the welding control apparatus
122
to start the welding, and data instructing the type of welding to be performed at the prescribed time, are also sent to the upper control apparatus
102
from the teaching apparatus
104
. These instruction data are stored in the memory unit
108
.
The welding control apparatus
122
controls the welding apparatus by controlling the welding transformer
136
and a set of valves
138
that controls the opening and closing of a pair of welding guns (not shown). The welding control apparatus
122
comprises CPU
126
, memory unit
128
, No.
1
I/O
124
, No.
2
I/O
130
, and a switching element
132
. The switching element
132
is placed between the welding power supply
134
and welding transformer
136
and controls the effective welding current by intermittently turning on and off the connection of the welding power supply
134
and welding transformer
136
. The welding transformer supplies current to the pair of welding guns.
A teaching apparatus
105
is provided for the welding control apparatus and is connected to the welding control apparatus
122
. The pertinent data necessary for the control of the welding operation is transmitted to the welding control apparatus
122
from the teaching apparatus
105
, and stored in memory unit
128
. The welding sequence data, which is transmitted from the teaching apparatus
105
, is stored in memory unit
128
of the welding control apparatus
122
.
In order to achieve satisfactory welding results, various welding conditions, such as the magnitude of the welding current, the time variation of the current magnitude, the duration of the current flow, and the pressure applied to the workpiece by the pair of welding guns and other welding parameters, must be adjusted to optimum values. However, these optimum values differ for different types of welding conditions. For example, a lower welding current is preferred when welding thin iron plates as compared to thick iron plates, because the heat dissipated to the area surrounding the welding point is less. Similarly, a lower welding current is preferred when welding the comer of iron plates as compared to the center of iron plates, because the heat dissipated to the area surrounding the welding point is less. Thus, welding control apparatus
122
must be capable of welding using optimum conditions that are suitable for each different type of welding environment, such as thick iron plates, thin iron plates and welding the comers or the center of the plates. Therefore, teaching apparatus
105
is utilized to instruct the welding control apparatus
122
to use the appropriate set of data corresponding to the type of welding to be performed. The welding sequence data stored in memory unit
128
provides the data necessary to adjust the welding conditions to the optimum values for each type of welding. For example, welding sequence data
1
indicates the optimum welding conditions, such as the magnitude of the welding current, the time variation of the current magnitude, the duration of the current flow, and the pressure applied to the workpiece by the pair of welding guns and other welding parameters, for welding type
1
, which may be for instance, comer welding of thin iron plates.
As described above, the upper control apparatus
102
is programmed to control the robots and other apparatus. At the appropriate time for the robot to start welding, upper control apparatus
102
outputs a signal to the welding control apparatus
122
to start the welding. The upper control apparatus
102
not only outputs the signal to start welding, but also outputs a signal to indicate the type of welding. Therefore, appropriate welding conditions for different types of welding can be provided.
At I/O
110
of the upper control apparatus
102
, a number of separate output ports are provided to accommodate a corresponding number of welding types. Therefore, the signal indicating the welding type as well as the signal indicating the start of welding can be transmitted from the upper control apparatus
102
to the welding control apparatus
122
. Similarly, a corresponding number of input ports are provided at I/O
124
of the welding control apparatus
122
. Cable group
100
connects the corresponding ports. For example, when welding type
1
is to begin, the No.
1
port of I/O
110
is set high. This high signal is transmitted to the No.
1
input port of I/O
124
via one of the cables in the cable group
100
. Then, instructions to start the welding using welding type
1
conditions are provided to the welding control apparatus
122
.
Additionally, an output port is provided at I/O
124
so that a signal indicating the completion of the welding operation can be transmitted from the welding control apparatus
122
to the upper control apparatus
102
. Similarly, an input port is provided at I/O port
110
. The two ports are connected by cable
110
so that the welding complete signal can be transmitted from the welding control apparatus
122
to the upper control apparatus
102
.
In this welding control system, a number of I/O ports corresponding to the number of welding types that can be performed by the welding control apparatus is required for each I/O port
110
and
124
of the upper control apparatus
102
and welding control apparatus
122
. In addition, a number of cables corresponding to at least the number of welding types accommodated are required between the upper control apparatus
102
and the welding control apparatus
122
. Furthermore, it is necessary to transmit a welding completion signal from the welding control apparatus
122
to the upper contro
Kawai Shingo
Kawamatsu Satoru
Lyon & Lyon LLP
Nadex Co. Ltd
Shaw Clifford C.
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