JPH0999373A - Spot welding equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate the welding of a bottom surface of works including a long work and a high work with simple arrangement, to approach the pressing action of an upper electrode to the action intended by a worker, to stabilize the pressing force, to improve the welding quality, and to reduce the fatigue in the working. SOLUTION: A lower electrode 7 is provided before a frame 5 erected on a base 3, an upper electrode is corresponding to the lower electrode 7 is provided on an elevating base 23, the elevating base 23 is movable in the vertical direction relative to the frame 5, and the upper electrode 15 is provided in a freely displaceable manner to the welding position and the waiting position by operating an actuator 29. Both a long work and a high work can be worked by selecting the type of the electrode adapted to the work to be worked.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spot welding apparatus, and more particularly to a spot welding apparatus capable of welding a bottom surface of a work having a deep depth and a work having a height.

[0002]

2. Description of the Related Art Conventionally, stationary spot welding apparatuses are structurally classified into about four types. That is, there are a direct type of direct pressure application, an offset type direct type, a series type, and a rocker arm type.

The direct type of direct pressure application is a type in which a guide mechanism and a cylinder are installed above the electrodes.
There is little freedom, but there is little tilting or slipping of the electrode.

In the direct type of offset type, the upper electrode is offset through the horn and there is some degree of freedom, but tilting and slipping of the electrode occur correspondingly.

The series type is used when there is an insulator on the surface of the product and direct energization is not possible, or when projection welding is performed.

The rocker arm type has a low pressing force and a maximum short-circuit current, but can weld a panel-shaped or deep product, and has a high degree of freedom among stationary types.

[0007]

Among the above-mentioned conventional spot welding apparatuses, the direct-pressing, offset type spot welding apparatus has the problems as shown in FIGS. 17 to 19. That is, FIG. 17 and FIG.
In the directly-upward pressing type shown in FIG. 8, when the work W has an inverted U-shape, the flange portion W _F interferes with the bracket 203 supporting the upper electrode 201, and when the work W has a U-shape, The flange portion W _F interferes with the bracket 203 supporting the upper electrode 201. Reference numeral 205 is a lower electrode.

Further, the bracket 207 in the offset type, as shown in Figure 19, the workpiece W opposite U-shaped, the flange portion W _F is supporting the upper electrode 201
There was a problem of interfering with. In addition, this directly above pressurizing or offset type is mainly suitable for welding a panel-shaped work W.

Further, in the rocker arm type, FIG.
As shown in FIG. 21 and FIG. 21, there are a foot-operated type and a pneumatic type. In the foot-operated type shown in FIG. 20, the pedal arm 209 and the electrode arm 211 are connected by a connecting rod 215 having a spring 213. Is configured. Then, the pressing force is set by the elastic force of the spring 213. The upper electrode 201 is located on the lower electrode 205.

Since the pressing force is set by the spring 213 in the upper structure, there is a problem in that the pressing force varies and welding quality is deteriorated. Further, when the work W to be handled has an inverted U-shape, welding can be performed without causing any interference, but when welding a U-shape work W, the height of the flange W _F is restricted. Yes, if the height is high,
There is a problem that the flange portion W _F of the workpiece W comes into contact with the electrode arm 211 and welding cannot be performed.

As shown in FIG. 21, the pneumatic type is a system in which the electrode arm 211 is pressurized by a fluid pressure actuated cylinder 217. Also in this case, when welding a U-shaped work W, There is a restriction on the height of the flange portion W _F , and when the height is high, there is a problem that the flange portion W _F of the work W abuts on the electrode arm 211 and welding cannot be performed.

Further, in the pneumatic type, a large pressing force can be obtained, but since the working speed is high, it is difficult to align the upper electrode 201 with a target welding position.

On the other hand, a large pressure cannot be obtained in the foot-operated type, but in order to align the upper electrode 201 with the welding position, the clearance between the work W and the upper electrode can be obtained by adjusting the foot of the operator. There is an advantage that the positions can be easily adjusted.

However, as shown in FIGS. 22, 23 and 24, in the rocker arm type spot welding machine described in FIGS. 20 and 21, the upper electrode 201 is used.
The electrode arm 211 swings around a shaft 221 provided on the upper part of the frame 219 as a swing fulcrum, and the upper electrode 201 makes an arc motion (see FIG. 22). Therefore, the upper electrode 201
As shown in FIG.
It is difficult to aim the welding position at the position where is at the rising end. Also,
As shown in FIGS. 22 and 23, the lower electrode 205
Height, the work piece W has a small thickness t1 and the work piece has a large thickness t
2, the contact surface of the upper electrode 201 changes.

Therefore, as shown in FIG.
Adjustment such as lowering the lower electrode 205 is required, which requires a long setup time. Regarding the dressing of the electrode tip, the contact surface of the upper electrode 201 is different between when the work W is present between the lower electrode 205 and the upper electrode 201 and when the work W is not present. There was a problem that it was difficult.

The object of the present invention is to enable the welding of the bottom surface of a work having a height from a work having a large depth with a simple setup, and the operation of the upper electrode for applying a pressure to the operation intended by the operator. It is an object of the present invention to provide a spot welding apparatus which is brought closer to the welding machine to stabilize the applied pressure, improve the welding quality, and reduce the fatigue of work.

[0017]

In order to achieve the above object, the spot welding apparatus according to the present invention according to claim 1 is provided with a lower electrode at the front portion of a frame erected on a base and at the same time the lower electrode is provided. A corresponding upper electrode is provided on the elevating base, the elevating base is provided on the frame so as to be vertically movable by an actuator, and the upper electrode is displaceably provided between a welding position and a standby position. .

According to a second aspect of the spot welding apparatus of the present invention, in the spot welding apparatus of the first aspect, the upper electrode and the lower electrode are provided integrally with the upper electrode shank and the lower electrode shank, respectively. The upper electrode shank is detachably provided on the upper electrode horn provided on the elevating base, and the lower electrode shank is detachably provided on the lower electrode horn provided on the frame. is there.

Further, the spot welding apparatus of the present invention according to claim 3 is the spot welding apparatus according to claim 1, characterized in that the lifting base provided with the upper electrode is vertically pressed by an actuator. It is a thing.

With the spot welding apparatus according to the above-mentioned claims 1, 2 and 3, the lifting base provided with the upper electrode can be displaced between the welding position and the standby position by the actuator, thereby forming the electrode type. If is selected according to the product to be processed, both deep product and high product can be processed. Further, since the upper electrode shank including the upper electrode is detachably attached to the upper electrode horn, it can be easily replaced with various electrode types such as an L-shaped shank, and the lower electrode has the same structure. Thus, it is possible to easily replace the electrode with various electrode types such as a square electrode, and to reduce the setup time.

Further, by adopting a vertical pressing system in which the upper electrode is vertically pressed by the actuator, the contact of the upper electrode does not change with changes in the height of the lower electrode and the work plate thickness, so that the distance between the electrodes is changed. Setup adjustment is unnecessary.
When chip dressing is performed, a dressing material such as a file can be easily sandwiched between the electrodes, and dressing work is easier than in the conventional hinge rocker arm type.

Furthermore, the spot welding apparatus of the present invention according to claim 4 is the spot welding apparatus according to claim 1, wherein fluid pressure is used as a drive source of the actuator, and the working stroke of the upper electrode is made variable, and , A fluid pressure circuit having a stroke variable cylinder for stopping and holding the upper electrode at an arbitrary position.

Furthermore, the spot welding apparatus of the present invention according to a fifth aspect is the spot welding apparatus according to the first aspect, wherein the stroke variable cylinder is capable of moving back and forth by a moving amount of a piston rod provided in the stroke variable cylinder. It is characterized in that the position is adjusted by a stopper member.

With the spot welding apparatus according to the fourth and fifth aspects of the present invention, the fluid pressure is used as the drive source of the actuator, and the pressure is applied so that the actuator can be displaced between the welding position and the standby position by the stepping operation. The operation of the upper electrode to be performed can be approximated to the operation intended by the operator.
Also, since the working stroke can be changed by operating the stroke changing cylinder provided in the fluid pressure circuit, interference with the height of the work can be prevented as compared with the conventional fixed type. Furthermore, since it can be stopped and held at an arbitrary position, workability is improved.

Further, by using the fluid pressure, the pressing force becomes more stable as compared with the conventional rocker type, so that the welding quality is improved and the fatigue of the operator can be reduced.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings. Since the spot welding device has a known structure, the detailed structure is omitted.

With reference to FIGS. 1, 2 and 3, in the spot welding apparatus 1, a frame 5 is erected on a base 3. A lower electrode shank 9 integrally provided with a lower electrode 7 is provided on the front part of the frame 5 (on the left side in FIG. 1). The lower electrode shank 9 is not shown in the frame 5 but is interposed by an insulating plate. And is detachably mounted in a hole 13 provided in the lower electrode horn 11 which is integrally provided by a fastening member. An upper electrode 15 corresponding to the lower electrode 7 is integrally provided on the upper electrode shank 17 in the front portion of the frame 5, and the upper electrode shank 17 is attached to and detached from a hole 21 provided in the upper electrode horn 19. It is installed freely.

Although not shown, the upper electrode horn 19 is provided on an elevating base 23 which is movable in the vertical direction, and is integrally provided to a fastening member via an insulating plate.
Reference numeral 3 denotes a guide rail 25 extending vertically from the side surface of the frame 5, for example, an LM guide rail, and a plurality of guide members 27 provided so as to be vertically movable via, for example, an LM guide. A hydraulic cylinder, for example, is provided on the side surface of the frame 5 as an actuator 29 for moving the elevating base 23 up and down, and a tip of a piston rod 31 provided on the actuator 29 is attached to a bracket 33 provided on the elevating base 23. It has been concluded.

With the above structure, when the hydraulic cylinder, which is the actuator 29, is operated, the elevating base 23 moves up and down along the guide rail 25 via the guide member 27. Then, the vertical movement of the elevating base 23 causes the upper electrode 1 to pass through the upper electrode horn 19 and the upper electrode shank 17.
5, the work stroke S and the retract stroke R can be freely moved up and down, as shown by the solid line and the two-dot chain line in FIG. Further, the upper electrode shank 17 and the lower electrode shank 9 in which the upper electrode 15 and the lower electrode 7 are integrally provided are detachably attached to the upper electrode horn 19 and the lower electrode horn 11, respectively. It is possible to easily replace the electrode with a shape suitable for the shape. Furthermore, the upper and lower electrode shanks 9 of this type,
No. 17 is suitable for processing a deep product W _A.

A hydraulic pump 35 that drives a hydraulic cylinder as the actuator 29, and the hydraulic pump 35
A motor 37 for rotatively driving is provided on a hydraulic tank 39, and hydraulic pressure is supplied from a hydraulic pump 35 to an actuator 29 via piping materials and various piping accessories. Further, a raising switching valve 43 interlocking with a foot-operated lifting pedal 41 for switching the flow direction of the pressure oil and a lowering switching valve 47 interlocking with a foot-operated lowering pedal 45 are provided. Further, an electric operation panel 49 for hydraulic drive is provided, and a pressure reducing valve, a variable stroke cylinder, a drain switching valve, etc., which will be described later in detail, are provided in the electric operation panel 49 (see FIG. 3).

Further, a welding power source transformer 51 is provided on the side surface of the frame 5, and a conductor 53 is connected to the lower electrode horn 11 from the secondary side of the welding power source transformer 51.
And a conductor 55 and a cable 57 are welded to the upper electrode horn 19 to form a welding power source path.

In the embodiment shown in FIG. 4, an L-shaped shank 59 having the upper electrode 15 is integrated with an L-shaped electrode holder 61 instead of the upper electrode shank 17 having the upper electrode 15 described above. Of the L-shaped electrode holder 61
Was fixed to the upper electrode horn 19. Further, instead of the lower electrode shank 9 having the lower electrode 7 described above,
The rectangular lower electrode 63 is provided on the upper part of the hold part 65, and the water divider 67 is provided under the hold part 65, and the L-shaped electrode holder 69 integrally connected to the hold part 65 is provided on the lower electrode horn 11. Attached and fixed.

With the above structure, the electrodes can be easily replaced, the bottom of the work W _B having a deep depth can be welded, and the work W _B can be stably held by the rectangular lower electrode 63. .

Next, the fluid pressure circuit 71 for driving the hydraulic cylinder which is the actuator 29 provided in the spot welding apparatus 1 will be described in detail.

Referring to FIG. 5, the fluid pressure circuit 71 is provided with the hydraulic pump 35 driven by the motor 37 via a strainer 73 hanging in the hydraulic tank 39. The discharge side of the hydraulic pump 35 is connected via a check valve 75 to the P port of the descending switching valve 47 whose flow path can be switched by the foot descending pedal 45, and the A port of the descending switching valve 47 is a foot operated type. It communicates with the up / down switching valve 43 whose flow path can be switched by the up pedal 41, and also with the left oil chamber 79 of the variable stroke cylinder 77. The check valve 75 and the lowering switching valve 47
A relief valve 76 is provided between the pressure valve and the pressure valve so that the pressure oil is returned to the hydraulic tank 39 when the pressure becomes equal to or higher than a predetermined line pressure.

For details of the variable stroke cylinder 77, referring to FIG. 6, the variable stroke cylinder 77 is provided on a base plate 81, and end plates 85 and 87 are fastening members at the left and right ends of the outer cylinder 83. A piston 91, which is integrally provided and has a piston rod 89, is provided in the outer cylinder 83 so as to be movable in the left-right direction.
A spring 93 is mounted between the piston 91 and the end plate 87, and the piston 91 is constantly attached to the end portion of FIG.
Is biased to the left at. A pressure oil inlet 95 is provided in the end plate 85, and a pressure oil outlet 97 is provided near the right side of the outer cylinder 83. The left oil chamber 79 is formed on the left side of the variable stroke cylinder 77,
A right oil chamber 99 is formed on the right side.

Further, a stopper member 101 with which the tip of the piston rod 89 abuts is provided on a vertical portion 81A formed on the base plate 81, and the stopper member 101 is screwed on the vertical portion 81A. Screw part 103
It is composed of a screw member 105 that is screwed into the screw member and a nut 107 that fixes the position of the screw member 105.

With the above structure, the screw member 1 serving as the stopper member 101 is provided in a state where the piston rod 89 is contracted.
05, and the tip of the piston rod 89 and the screw member 1
After adjusting the position so that the distance between the tips of 05 becomes the desired work stroke S, the screw member 105 is fixed by the nut 107 so as not to move.

As shown in detail in FIGS. 7 and 8, the construction of the lifting switching valve 43 operated by the foot-operated lift pedal 41 is such that the valve body 109 penetrates through the lift-operated lift pedal 41. A rotary shaft 111 that rotates in conjunction with stepping is mounted. And the rotating shaft 1
A seal member 113 is mounted between the valve body 109 and the valve body 109 to prevent pressure oil outflow, and snap rings 115 are provided on both sides of the valve body 109 to prevent the rotation shaft 111 from coming off. .

A half-moon shaped notch 11 is formed on the rotating shaft 111.
7 is formed, and a hard sphere 1 rolling on the surface of the notch 117
Ball 12 provided on check valve 121 through 19
3 is in contact. In the check valve 121, a valve seat 127 is provided below the check valve body 125, and the ball 123 is provided on the valve seat 127 so as to be separable, and the ball 123 is always in contact with the valve seat 127 by a spring 129. Are urged to do so.

A pressure oil inlet 131 and a pressure oil outlet 133 are provided in the valve body 109, and a seal member 135 is provided between the valve body 109 and the check valve body 125 to prevent pressure oil outflow. It is installed in place.

With the above configuration, the raising switching valve 43
In the state shown by the solid lines in FIGS. 7 and 8, the ball 123 provided on the check valve 121 abuts on the valve seat 127, passes through the lowering switching valve 47, and is sent to the pressure oil inlet 131. The pressure fluid is not sent to the pressure oil outlet 133 side.

In this state, when the foot-operated lift pedal 41 is depressed, the rotary shaft 111 rotates, and the cutout 117 formed on the rotary shaft 111 moves, whereby the cutout 117 is formed.
The ball 123 provided on the check valve 121 is lifted up against the repulsive force of the spring 129 via the hard ball 119 that abuts on the ball 123, and the ball 123 is separated from the valve seat 127 and flows through the pressure oil inlet 131. Oil is sent to the outlet 133.

Referring again to FIG. 5, the pressure oil discharged from the pressure oil outlet 133 of the ascending switching valve 43 flows into the right side oil chamber 99 of the variable stroke cylinder 77, and at the same time, in the hydraulic cylinder which is the actuator 29. Lower oil chamber 139
Flow into. Then, the oil in the upper oil chamber 141 of the hydraulic cylinder which is the actuator 29 is returned to the hydraulic tank 39 through the pressure reducing valve 143, the B port of the lowering switching valve 47. Reference numeral 145 is a gauge cock, and reference numeral 147 is a pressure gauge. In addition, the lift switching valve 43 and the right side oil chamber 99 of the variable stroke cylinder 77.
The pipe communicated with is provided with a tip-dress switching valve 137 as shown in FIG. 9 in a branched manner, and the tip-dress switching valve 137 is provided with a lifting switching pedal 138. .

Further, a tip dressing switching valve 137.
And a pipe 149 communicating with the tank 39 and the upper oil chamber 14
1 is connected by a pipe 151, and a check valve 153 is provided in the middle of the pipe 151. The tip-dress switching valve 137 and the lifting switching valve 4
3 and the middle of the pipe communicating with the right oil chamber 99 of the variable stroke cylinder 77 are connected by a pipe 155.

With the above construction, the operation is that when the motor 37 for rotating the hydraulic pump 35 is driven, the hydraulic oil in the hydraulic tank 39 is discharged from the hydraulic pump 35, and at the pressure set by the relief valve 76. As shown in FIG. 10, it flows from the P port of the lowering switching valve 47 to the A port and is sent to the left oil chamber 79 side of the variable stroke cylinder 77. Then, the piston rod 89 provided integrally with the piston 91 projects, and the piston rod 89 contacts the stopper member 101 to move forward by a desired stroke. Since the rising switching valve 43 is blocked, pressure oil does not flow.

The flow rate corresponding to the forward movement of the piston 91 provided in the variable stroke cylinder 77 is determined by the actuator 29.
Is sent to the lower oil chamber 139 of the hydraulic cylinder, and the piston rod 31 rises accordingly, and the lift base 23 having the upper electrode 15 fastened to the piston rod 31 rises and stops. Since the stroke of the variable stroke cylinder 77 can be changed by operating the stopper member 101, the stroke by which the elevating base 23 equipped with the upper electrode 15 rises can also be changed.

The hydraulic oil on the side of the upper oil chamber 141 of the hydraulic cylinder which is the actuator 29 is pushed by the ascent of the piston rod 31, and passes through the pressure reducing valve 143 to the oil tank 39 from the port B of the lowering switching valve 47. Will be returned.

When the work W is placed between the lower electrode 7 and the upper electrode 15 for welding, the foot-operated lowering pedal 4 is used.
Step 5 is performed to switch the flow direction of the pressure oil in the lowering switching valve 47, and the lifting base 23 having the upper electrode 15 is lowered via the pressure reducing valve 143 and the hydraulic cylinder that is the actuator 29.

That is, when the foot-operated lowering pedal 45 is stepped on the lowering switching valve 47, each port is switched as shown in FIGS. 11, 12 and 13.

When the foot-operated lowering pedal 45 is not depressed, as shown in FIG. 11, the spool 47A provided on the lowering switching valve 47 is in the position as shown in the drawing, and the hydraulic oil is in the P port. From A port to B port B
It communicates with the port.

From this state, as shown in FIG. 12, when the foot-operated lowering pedal 45 is stepped on, the spool 47A provided on the lowering switching valve 47 moves to the position as shown in the drawing, and the port P It is possible to block entry from the port A to the elevation base 23, that is, to stop the upper electrode 15.

When the foot-operated lowering pedal 45 is further depressed, as shown in FIG.
, And port A communicates with port T. For this reason,
As shown in FIG. 14, the upper oil chamber 14 of the hydraulic cylinder, which is the actuator 29, passes through the pressure reducing valve 143.
1, the pressure oil flows into the replenishment valve 142 and the piston 1, and the piston rod 31 is pushed down to raise and lower the base 23 having the upper electrode 15.
To lower.

Referring again to FIG. 5, as the elevating base 23 descends, the upper electrode 15 comes into contact with the work W and welding is performed by pressurizing the lower electrode 7 with the pressure set by the pressure reducing valve 143. Be done. The hydraulic oil sent to the supply valve 142 and the hydraulic oil in the lower oil chamber 139 of the hydraulic cylinder, which is the actuator 29, enter the right side oil chamber 99 of the stroke variable cylinder 77, and the stroke variable cylinder 7
Replenish the hydraulic oil of No. 7 and the surplus oil is the switching valve 4 for rising.
3 through the check valve 121 provided in the hydraulic tank 3
Returned to 9.

When the welding operation is completed, the operator releases his foot from the foot-operated lowering pedal 45, and then the lowering switching valve 47.
5, the pressure oil flows from the P port to the A port to raise the piston rod 31 of the hydraulic cylinder that is the actuator 29 through the stroke variable cylinder 77, and the upper electrode 15 again has a constant stroke. Rise and stop.

Loading / unloading of work W and L-shaped shank 59
15 is used, when the foot-operated lift pedal 41 is depressed, the lift switching valve 43 is lifted.
The pressure oil flows into the right side oil chamber 99 of the variable stroke cylinder 77 and the lower oil chamber 139 of the actuator 29, and the piston rod 31 rises to raise the elevating base 23 including the upper electrode 15. When the foot is lifted from the foot-operated lifting pedal 41, the lifting switching valve 43
And the lifting base 23 stops at an arbitrary position.

When chip dressing is performed, the process shown in FIG.
6, the tip dressing switching valve 137 is switched to return the hydraulic oil to the hydraulic tank 39, and the lifting base 23 is dropped by its own weight. And the lifting base 2
A dressing material is sandwiched between the lower electrode 7 and the upper electrode 15 using the weight of 3 as the chip dressing pressure.

After the tip dressing work, in order to raise the upper electrode 7 by the working stroke, the raising switching pedal 138 is used.
When stepping is performed, the tip dressing switching valve 137 is switched, and the flow path to the tank 39 is blocked.

The present invention is not limited to the above-described embodiments, but can be implemented in other modes by making appropriate changes.

[0060]

As can be understood from the above description of the embodiments, the present invention according to claims 1 and 2 makes it possible to set the lifting base having the upper electrode to the welding position via the actuator. Displaceable to the standby position. Therefore, by selecting the type of electrode as the product to be processed, it is possible to process either a deep product or a high product.

Further, since the upper electrode shank having the upper electrode can be easily exchanged and the lower electrode can be easily exchanged by the same structure, the setup can be simplified.

According to the third aspect of the present invention, by adopting the vertical pressing method, the contact of the upper electrode does not change with respect to the change of the height of the lower electrode and the plate thickness of the work. No adjustment is required, tip dressing can be performed easily, and the welding position can be aimed more easily than in the conventional hinge rocker arm type.

According to the fourth and fifth aspects of the present invention, by using the fluid pressure as the drive source of the actuator, the applied pressure is stabilized and the welding quality is improved, and the fatigue of the operator can be reduced and the stepping operation is performed. Is operated so that it can be displaced between the welding position and the standby position. Therefore, the operation of the upper electrode for applying pressure can be approximated to the operation intended by the operator.

Further, since the work stroke can be varied, interference with the height of the work can be prevented, and the upper electrode can be stopped and held at an arbitrary position, so that workability can be improved.

[Brief description of drawings]

FIG. 1 is a side view of a spot welding apparatus showing a main part of the present invention.

FIG. 2 is a plan view of FIG.

FIG. 3 is a front view as viewed from the left side in FIG. 1;

FIG. 4 is a side view of a spot welding device in which an L-shaped electrode is replaced.

FIG. 5 is a hydraulic circuit diagram of the present invention.

FIG. 6 is a sectional view of a variable stroke cylinder.

FIG. 7 is a cross-sectional view of a rising switching valve.

8 is a cross-sectional view taken along the line VIII-VIII in FIG.

FIG. 9 is a cross-sectional view of a tip dressing switching valve.

FIG. 10 is an operation explanatory view of the hydraulic circuit in a state where the hydraulic pump is turned on.

FIG. 11 is an explanatory view of the operation of the lowering switching valve.

FIG. 12 is an explanatory view of the operation of the lowering switching valve.

FIG. 13 is an explanatory view of the operation of the lowering switching valve.

FIG. 14 is an operation explanatory view of the hydraulic circuit when the foot-operated lowering pedal is depressed.

FIG. 15 is an operation explanatory view of the hydraulic circuit when the foot-operated lift pedal is depressed.

FIG. 16 is an operation explanatory view of the hydraulic circuit when the tip dressing pedal is depressed.

FIG. 17 is a diagram for explaining the operation of the direct-on-pressurization type stationary spot welding apparatus, showing a conventional example.

FIG. 18 is an operation explanatory view of a directly above pressure type stationary spot welding apparatus showing a conventional example.

FIG. 19 is a view for explaining the operation of the offset type stationary spot welding apparatus showing a conventional example.

FIG. 20 is a view for explaining the operation of the rocker arm stepping type stationary spot welding apparatus showing a conventional example.

FIG. 21 is a view for explaining the operation of a rocker arm pneumatic type stationary spot welding apparatus, showing a conventional example.

FIG. 22 is a view for explaining the action of the upper and lower electrodes, showing a conventional example.

FIG. 23 is a view for explaining the action of the upper and lower electrodes, showing a conventional example.

FIG. 24 is a view for explaining the action of the upper and lower electrodes, showing a conventional example.

FIG. 25 is an explanatory view showing a conventional example and showing the relationship between the work stroke and the height of the work.

[Explanation of symbols]

 1 Spot Welding Equipment 3 Base 5 Frame 7 Lower Electrode 9 Lower Electrode Shank 11 Lower Electrode Horn 15 Upper Electrode 17 Upper Electrode Shank 19 Upper Electrode Horn 23 Lifting Base 29 Actuator 71 Fluid Pressure Circuit 77 Stroke Variable Cylinder 89 Piston Rod 101 Stopper S Working stroke

Claims (5)

[Claims] 1. A lower electrode is provided on a front portion of a frame erected on a base, and an upper electrode corresponding to the lower electrode is provided on an elevating base, and the elevating base is vertically movable on the frame by an actuator. A spot welding apparatus, wherein the upper electrode is provided so as to be displaceable between a welding position and a standby position. 2. The upper electrode and the lower electrode are integrally provided on the upper electrode shank and the lower electrode shank, respectively, and the upper electrode shank is detachably provided on the upper electrode horn provided on the elevating base. The spot welding apparatus according to claim 1, wherein the lower electrode shank is detachably provided on a lower electrode horn provided on a frame. 3. The spot welding apparatus according to claim 1, wherein the elevating base having the upper electrode is vertically pressed by an actuator. 4. A fluid pressure circuit comprising a stroke variable cylinder that uses fluid pressure as a drive source of the actuator, makes the working stroke of the upper electrode variable, and stops and holds the upper electrode at an arbitrary position. The spot welding apparatus according to claim 1, wherein the spot welding apparatus is provided. 5. The spot welding apparatus according to claim 4, wherein the stroke variable cylinder is configured such that a movement amount of a piston rod provided in the stroke variable cylinder is positionally adjusted by a stopper member which can be moved forward and backward.