Seam welding machine

Details Seam welding machine Seam welding machine

1999-08-05

2001-07-31

Shaw, Clifford C. (Department: 1725)

Electric heating

Metal heating

For bonding with pressure

C219S089000

Reexamination Certificate

active

06268581

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a seam welding machine for welding flat plates, etc., by seam welding using electrical resistance, and in particular relates to a construction and control configuration for a circular electrode pressure cylinder and pressure roller cylinder.
2. Description of the Related Art
FIGS.
8
(A) and
8
(B) show a conventional seam welding machine such as that disclosed in Japanese Patent No. HEI 4-72638, for example. As shown in
FIG. 8
(A), the conventional seam welding machine comprises:
a pair of upper and lower circular electrodes
104
,
105
for applying pressure from above and below to an overlapping portion
103
where edges of two flat plate-shaped members being welded
101
,
102
overlap and welding the members by imparting an electric current thereto while moving;
a circular electrode pressure cylinder
106
for generating a force for pressing the upper circular electrode
104
against the overlapping portion
103
of the members being welded
101
,
102
;
a pair of upper and lower pressure rollers
108
,
109
for compressing the weld
107
welded by the upper and lower circular electrodes
104
,
105
by applying additional pressure thereto from above and below; and
a pressure roller cylinder
110
for generating a force for pressing the upper pressure roller
108
against the weld
107
.
Electric current is supplied to the upper and lower circular electrodes
104
,
105
from a welding transformer
141
. These devices are mounted on a C-shaped frame
140
.
As shown in FIG.
8
(B), the members being welded
101
,
102
are held by clamps
111
,
112
in order to secure them against the separating forces generated in the weld
107
during welding. The lower circular electrode
105
and the lower pressure roller
109
are adjusted to the level of the clamps.
As shown in detail in
FIG. 9
, the circular electrode pressure cylinder
106
is provided with a freely reciprocating piston
113
having a piston rod
114
projecting downwards from the lower end of the circular electrode pressure cylinder
106
, and the piston rod
114
is connected to a circular electrode pressure shaft
115
on the upper circular electrode
104
. The circular electrode pressure shaft
115
is supported so as to freely reciprocate and is guided in the direction of application of pressure by means of circular electrode guide bearings
116
.
Furthermore, the pressure roller cylinder
110
is provided with a freely reciprocating piston
117
. The piston
117
comprises an upper piston rod
118
projecting upwards from the upper end of the pressure roller cylinder
110
and a lower piston rod
119
connected to the upper pressure roller
108
projecting downwards from the lower end of the pressure roller cylinder
110
. A stopper
120
for limiting the descent of the upper pressure roller
108
is disposed on the upper end of the upper piston rod
118
. The stopper
120
is designed to contact a gauge
121
whose position is adjustable from above, and the position of the gauge
121
is set so that the spacing between the upper pressure roller
108
at its limit of descent and the lower pressure roller
109
is a value corresponding to the final thickness of the finished plate at the weld
107
.
Next, the control circuit of the above circular electrode pressure cylinder
106
will be explained with reference to FIG.
9
.
The circular electrode pressure cylinder
106
is divided into a pressure chamber
122
on the opposite side of the piston
113
from the upper circular electrode
104
(the head side) and a back pressure chamber
123
on the same side as the upper circular electrode
104
. The control circuit comprises:
a pressure-side direction-switching electromagnetic valve
125
for controlling the inflow and outflow of pressure fluid from a pressure source
124
to the pressure chamber
122
;
a back pressure-side direction-switching electromagnetic valve
126
for controlling the inflow and outflow of pressure fluid from the pressure source
124
to the back pressure chamber
123
; and
a pressure-side pressure-releasing valve
127
and a back pressure-side pressure-releasing valve
128
disposed in each of the circuits.
Furthermore, the pressure-side direction-switching electromagnetic valve
125
comprises an inflow-side coil
125
B for switching the direction of flow of pressure fluid so that fluid flows into the pressure chamber
122
, and an outflow-side coil
125
A for switching the direction of flow of pressure fluid so that fluid flows out of the pressure chamber
122
. Furthermore, the back pressure-side direction-switching electromagnetic valve
126
comprises an inflow-side coil
126
B for switching the direction of flow of pressure fluid so that fluid flows into the back pressure chamber
123
, and an outflow-side coil
126
A for switching the direction of flow of pressure fluid so that fluid flows out of the back pressure chamber
123
.
When low pressure output is required such as in cases where the members
101
,
102
being welded are thin plates, the inflow-side coil
125
B of the pressure-side direction-switching electromagnetic valve
125
is energized allowing pressure fluid to flow into the pressure chamber
122
and the outflow-side coil
126
A of the back pressure-side direction-switching electromagnetic valve
126
is energized allowing pressure fluid to flow out of the back pressure chamber
123
, allowing the upper circular electrode
104
to descend, then pressure fluid is introduced to the back pressure chamber
123
of the circular electrode pressure cylinder
106
by re-energizing the inflow-side coil
126
B of the back pressure-side direction-switching electromagnetic valve
126
. The downward output (pressure output) of the circular electrode pressure cylinder
106
can be freely set if the pressure is low by means of the set value of the pressure-side pressure-releasing valve
127
and the back pressure-side pressure-releasing valve
128
in each of the circuits and by the pressure-receiving surface areas of the pressure chamber
122
and the back pressure chamber
123
in the circular electrode pressure cylinder
106
. The above circuit is usually adopted because of problems such as poor performance of the pressure-releasing valves in the low pressure region when only the pressure of the pressure chamber
122
is being controlled which make it impossible to set the pressure at less than the weight of the moving portion of the circular electrode pressure cylinder
106
.
Another plausible method of changing the pressure output of the circular electrode pressure cylinder
106
is a construction in which two cylinder portions having different pressure-receiving surface areas are disposed in series.
FIG. 10
shows a construction of a pressure cylinder
131
in which two cylinders
129
,
130
are joined and a control system therefor such as that disclosed in Japanese Patent Laid-Open No. HEI 9-295159, for example.
In this conventional example, in addition to disposing the two cylinders
129
,
130
on the longitudinal axis of a cylinder rod
132
, two pistons
133
,
134
inserted into each of the cylinders
129
,
130
are formed integrally with the cylinder rod
132
. The pressure output can be varied by changing the pressure-receiving surface areas of the two cylinders
129
,
130
. In other words, the overall pressure output of the pressure cylinder
131
is set by introducing compressed gas into a cylinder chamber
129
a
in one of the cylinders
129
by means of direction control valves
138
,
139
as shown in FIG.
10
(A) or by introducing compressed gas into a cylinder chamber
130
a
in the other cylinder
130
by means of the direction control valves
138
,
139
as shown in FIG.
10
(B).
However, when used in a seam welding machine, a conventional circular electrode pressure cylinder
106
such as that shown in
FIG. 9
suffers from the problems described below.
It is necessary to set the pressure output of the upper circular electrode
104
at a value suited to the thickne

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