Cooling device for spot welding machine, and method for replacing welding tips for spot welding machine

Abstract

This invention provides a cooling device for a spot welding machine and a method for replacing welding tips for a spot welding machine that can reduce cooling water leakage from the upper and lower shanks with a simple structure. [Solution] The cooling device 11 of the spot welding machine 10 includes a high-pressure side first passage 31 that sends cooling water from a cooling water supply source 12 to a high-pressure side manifold 34, a high-pressure side second passage 32 that sends cooling water from the high-pressure side manifold to the upper shank 23, a high-pressure side third passage 33 that sends cooling water from the high-pressure side manifold to the lower shank 24 located below the upper shank, a low-pressure side first passage 41 that returns cooling water from the low-pressure side manifold 44 to the supply source, a low-pressure side second passage 42 that returns cooling water from the upper shank to the low-pressure side manifold, and a low-pressure side third passage 43 that returns cooling water from the lower shank to the low-pressure side manifold. The cooling device also includes a first check valve 61 provided in the high-pressure side second passage and a second check valve 62 provided in the low-pressure side third passage.

Description

Technical Field

[0001] The present invention relates to a cooling device for a spot welder and a method for replacing a welding tip of a spot welder.

Background Art

[0002] A spot welder has an upper welding tip and a lower welding tip. The upper welding tip is detachably attached to an upper shank. The lower welding tip is detachably attached to a lower shank. The upper shank has a passage through which cooling water passes in order to cool the upper welding tip. The lower shank has a passage through which cooling water passes in order to cool the lower welding tip.

[0003] When the welding tip is consumed, it is replaced with a new welding tip. In the operation of replacing the welding tip, the upper welding tip is removed from the upper shank, and the lower welding tip is removed from the lower shank. At this time, cooling water drips from the upper shank and the lower shank.

[0004] Patent Document 1 discloses a spot welding robot having a cooling water discharge prevention unit at the tip of a welding gun actuator. The cooling water discharge prevention unit includes an on-off valve (solenoid valve) provided in the cooling water supply passage, a check valve provided in the cooling water passage on the supply side to the welding tip, a check valve provided in the cooling water passage on the discharge side from the welding tip, a flow rate sensor provided in the cooling water passage on the discharge side, and a control device that controls the opening and closing of the on-off valve.

[0005] When the welding tip is detached from the shank, this cooling water discharge prevention unit detects a decrease in the flow rate of the cooling water by the flow rate sensor, and the control device closes the on-off valve. As a result, the supply of the cooling water is stopped. The maximum amount of the leaking cooling water is equivalent to the sum of the remaining amount of the cooling water remaining in the passage between the welding tip and the check valve in the cooling water passage on the supply side and the remaining amount of the cooling water remaining in the passage between the welding tip and the check valve in the cooling water passage on the discharge side (see the description in paragraph "0055", FIGS. 8 and 9).

Prior Art Documents

[0006] [Patent Document 1] Japanese Patent Publication No. 2019-188404 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] Patent Document 1 does not describe at what point in the supply-side cooling water passage the cooling water supplied to the upper and lower welding tips is branched. Nor does it describe at what point in the discharge-side cooling water passage the cooling water discharged from the upper and lower welding tips is collected. If the cooling water is branched downstream of the check valve in the supply-side cooling water passage and collected upstream of the check valve in the discharge-side cooling water passage, cooling water will drip from the upper and lower shanks.

[0008] To minimize the maximum amount of cooling water leakage, check valves must be installed in both the supply and discharge cooling water passages to the upper shank, and in both the supply and discharge cooling water passages to the lower shank. Considering the system for cooling the transformer, a total of six check valves are required, resulting in a relatively complex device configuration.

[0009] Therefore, the present invention aims to provide a cooling device for a spot welding machine that can reduce cooling water leakage from the upper and lower shanks with a simple structure, and a method for replacing welding tips for a spot welding machine. [Means for solving the problem]

[0010] One aspect of the present invention for achieving the above objective is a cooling device for a spot welding machine, comprising: a high-pressure side first passage, a high-pressure side second passage, a high-pressure side third passage, a low-pressure side first passage, a low-pressure side second passage, and a low-pressure side third passage. The high-pressure side first passage supplies cooling water from a cooling water supply source to a high-pressure side manifold. The high-pressure side second passage supplies cooling water from the high-pressure side manifold to the upper shank. The high-pressure side third passage supplies cooling water from the high-pressure side manifold to the lower shank, which is located below the upper shank. The low-pressure side first passage returns cooling water from the low-pressure side manifold to the supply source. The low-pressure side second passage returns cooling water from the upper shank to the low-pressure side manifold. The low-pressure side third passage returns cooling water from the lower shank to the low-pressure side manifold. The cooling device includes a first check valve provided in the high-pressure side second passage and a second check valve provided in the low-pressure side third passage.

[0011] Another aspect of the present invention for achieving the above objective is a welding tip replacement method for a spot welding machine having a cooling device for the spot welding machine described above, in which an upper welding tip attached to the upper shank and a lower welding tip attached to the lower shank are replaced. This replacement method involves stopping the supply of cooling water to the high-pressure side manifold through the high-pressure side first passage and stopping the return of cooling water to the supply source through the low-pressure side first passage. The upper welding tip and the lower welding tip are then removed simultaneously, or one welding tip and the other welding tip are removed with a time difference. [Effects of the Invention]

[0012] According to the present invention, the movement of cooling water caused by the height difference between the upper shank and the lower shank can be stopped with a simple structure, and leakage of cooling water from the upper and lower shanks can be reduced. [Brief explanation of the drawing]

[0013] [Figure 1] This is a side view showing the configuration of the cooling device for the spot welding machine in Embodiment 1. [Figure 2] This is a side view showing the configuration of the cooling system for the spot welding machine in Modification Example 1. [Figure 3] This is a side view showing the configuration of the cooling system for the spot welding machine in modified example 2. [Figure 4] This is a side view showing the configuration of the cooling system for the spot welding machine in modified example 3. [Figure 5] This is a side view showing the configuration of the cooling system for the spot welding machine in modified example 4. [Modes for carrying out the invention]

[0014] Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. The embodiments shown herein are illustrative examples to embody the technical idea of ​​the present invention and do not limit the present invention. Therefore, all other implementable forms, examples, and operational techniques that can be conceived by those skilled in the art without departing from the spirit of the present invention are included in the scope and spirit of the present invention, as well as in the claims and their equivalents.

[0015] Furthermore, the drawings attached to this specification may be schematically represented with changes to scale, aspect ratio, shape, etc., from the actual object for the sake of illustration and ease of understanding, but these are merely examples and do not limit the interpretation of the present invention.

[0016] In this specification, ordinal numbers such as "the first," "the second," etc., may be used. However, unless otherwise specified, these ordinal numbers are used for the purpose of identifying the constituent elements for the sake of explanation, and do not specify a number or order.

[0017] <Embodiment> As shown in FIG. 1, the spot welder 10 has an upper shank 23 to which an upper welding tip 21 is detachably attached, and a lower shank 24 to which a lower welding tip 22 is detachably attached. The upper shank 23 is disposed in a welding gun actuator 25, and the lower shank 24 is disposed in a gun arm 26. A transformer 27 is built into the welding gun actuator 25.

[0018] The spot welder 10 has a cooling device 11 that cools each of the upper welding tip 21 and the lower welding tip 22. The cooling device 11 has passages for supplying and discharging cooling water to and from each of the upper shank 23 and the lower shank 24.

[0019] The cooling device 11 of the spot welder 10 has a supply-side path for supplying cooling water to each of the upper shank 23 and the lower shank 24, and a discharge-side path for returning cooling water from each of the upper shank 23 and the lower shank 24. The supply-side path has a cooling water supply source 12, a high-pressure side manifold 34, a high-pressure side first passage 31, a high-pressure side second passage 32, and a high-pressure side third passage 33. The discharge-side path has a low-pressure side manifold 44, a low-pressure side first passage 41, a low-pressure side second passage 42, and a low-pressure side third passage 43. The cooling device 11 has a first check valve 61 provided in the high-pressure side second passage 32 and a second check valve 62 provided in the low-pressure side third passage 43.

[0020] The high-pressure side first passage 31 sends cooling water from the cooling water supply source 12 to the high-pressure side manifold 34. The high-pressure side second passage 32 sends cooling water from the high-pressure side manifold 34 to the upper shank 23. The high-pressure side third passage 33 sends cooling water from the high-pressure side manifold 34 to the lower shank 24 located below the upper shank 23.

[0021] The low-pressure side first passage 41 returns cooling water from the low-pressure side manifold 44 to the supply source 12. The low-pressure side second passage 42 returns cooling water from the upper shank 23 to the low-pressure side manifold 44. The low-pressure side third passage 43 returns cooling water from the lower shank 24 to the low-pressure side manifold 44.

[0022] The high-pressure side manifold 34 has a function of branching and sending out cooling water to a plurality of passages, and the low-pressure side manifold 44 has a function of merging the cooling water from the plurality of passages. As long as these functions are provided, the structure is not limited.

[0023] The high-pressure side on-off valve 30 is provided on the way of the high-pressure side first passage 31. When the high-pressure side on-off valve 30 is closed, the supply of cooling water to the high-pressure side manifold 34 through the high-pressure side first passage 31 is stopped. The low-pressure side on-off valve 40 is provided on the way of the low-pressure side first passage 41. When the low-pressure side on-off valve 40 is closed, the return of the cooling water to the supply source 12 through the low-pressure side first passage 41 is stopped.

[0024] The cooling device 11 of the embodiment further has a transformer cooling part 50 for cooling the transformer 27. The transformer cooling part 50 is provided on the way of the fourth passage 54 from the high-pressure side manifold 34 to the low-pressure side manifold 44. The cooling device 11 further has a third check valve 63 provided in the fourth passage 54. The transformer cooling part 50 has a cooler 51 through which the cooling water flows.

[0025] A check valve is a direction control valve that limits the flow of fluid to only one direction and stops the reverse flow. Generally, a check valve has a structure in which a spring is attached to the valve body and the valve body does not open unless a pressure greater than the elastic force of the spring acts.

[0026] The free flow direction of the first check valve 61 is, of course, the direction of sending the cooling water from the high-pressure side manifold 34 to the upper shank 23. The first check valve 61 blocks the flow of the cooling water from the upper shank 23 to the high-pressure side manifold 34.

[0027] The free flow direction of the second check valve 62 is, of course, the direction of sending the cooling water from the lower shank 24 to the low-pressure side manifold 44. The second check valve 62 blocks the flow of the cooling water from the low-pressure side manifold 44 to the lower shank 24.

[0028] The free flow direction of the third check valve 63 is, naturally, the direction in which cooling water is sent from the high-pressure side manifold 34 to the low-pressure side manifold 44. The third check valve 63 blocks the flow of cooling water from the low-pressure side manifold 44 to the high-pressure side manifold 34.

[0029] When the high-pressure side shut-off valve 30 and the low-pressure side shut-off valve 40 are closed, the supply and return of cooling water are stopped, and the flow of cooling water stops. For this reason, the first check valve 61 closes the high-pressure side second passage 32, the second check valve 62 closes the low-pressure side third passage 43, and the third check valve 63 closes the fourth passage 54.

[0030] For example, the first check valve 61, the second check valve 62, and the third check valve 63 can be low operating pressure check valves from the PCVLU series (manufactured by Nippon Pisco Co., Ltd.).

[0031] In this embodiment, the third check valve 63 is positioned between the low-pressure side manifold 44 and the transformer cooling section 50 in the fourth passage 54. With this configuration, the position where the third check valve 63 is located is after the cooling water has passed through the transformer cooling section 50 while facing resistance, that is, in a position in the fourth passage 54 where the internal pressure is relatively low. When the high-pressure side on-off valve 30 and the low-pressure side on-off valve 40 are open, fluctuations may occur in the water pressure of the cooling water flowing in the forward direction. Even in such cases, the water pressure fluctuations of the cooling water flowing through the third check valve 63 are relatively suppressed. As a result, deterioration of the third check valve 63 due to physical input caused by water pressure fluctuations is suppressed.

[0032] The first check valve 61 is positioned closer to the high-pressure side manifold 34 than the upper shank 23. The second check valve 62 is positioned closer to the low-pressure side manifold 44 than the lower shank 24. With this configuration, both the first check valve 61 and the second check valve 62 are positioned relatively far from the upper shank 23 and lower shank 24, which become hot when energized. The temperature of the cooling water flowing through the first check valve 61 and the second check valve 62 is relatively low. As a result, thermal degradation of the first check valve 61 and the second check valve 62 caused by high temperatures is suppressed.

[0033] Furthermore, the positions where the first check valve 61 and the second check valve 62 are located are not visible from the upper shank 23 and the lower shank 24. During welding, spatter is scattered from the vicinity of the upper shank 23 and the lower shank 24. Spatter is scattered not only from the welding machine itself but also from welding machines installed in the surrounding area. Even in such cases, the first check valve 61 and the second check valve 62 are less susceptible to spatter scattering, making them less prone to damage such as melting of the surface or obscuration of markings on the surface. As a result, damage to the first check valve 61 and the second check valve 62 caused by spatter scattering is suppressed.

[0034] (action) Next, the operation of replacing the upper welding tip 21 and the lower welding tip 22 in the spot welding machine 10 of the embodiment will be explained.

[0035] First, the high-pressure side shut-off valve 30 is closed, stopping the supply of cooling water to the high-pressure side manifold 34 through the high-pressure side first passage 31.

[0036] Next, the low-pressure side shut-off valve 40 is closed, stopping the return of cooling water to the supply source 12 through the low-pressure side first passage 41.

[0037] As the flow of cooling water stops, the first check valve 61 closes the high-pressure side second passage 32, the second check valve 62 closes the low-pressure side third passage 43, and the third check valve 63 closes the fourth passage 54.

[0038] Then, the upper welding tip 21 is removed from the upper shank 23, and the lower welding tip 22 is removed from the lower shank 24. The upper welding tip 21 and the lower welding tip 22 may be removed at the same time. Alternatively, one welding tip may be removed with a time difference. For example, the lower welding tip 22 may be removed first, followed by the upper welding tip 21.

[0039] This section describes how to suppress cooling water leakage when removing the upper welding tip 21 and the lower welding tip 22.

[0040] When the upper welding tip 21 is removed from the upper shank 23 and the lower welding tip 22 is removed from the lower shank 24, the weight of the cooling water in the height difference h between the upper shank 23 and the lower shank 24 causes the cooling water to leak out from the upper shank 23 and the lower shank 24. This movement of cooling water can be stopped by the first check valve 61 to stop the flow of cooling water in the high-pressure side second passage 32, and by the second check valve 62 to stop the flow of cooling water in the low-pressure side third passage 43.

[0041] Furthermore, the third check valve 63 can stop the flow of cooling water in the high-pressure side third passage 33 and stop the flow of cooling water in the low-pressure side second passage 42.

[0042] These measures stop the movement of cooling water caused by the height difference h between the upper shank 23 and the lower shank 24, thereby reducing leakage of cooling water from both the upper shank 23 and the lower shank 24.

[0043] When the high-pressure side shut-off valve 30 and the low-pressure side shut-off valve 40 are closed while the cooling water is circulating, residual pressure is generated from the high-pressure side first passage 31 to the low-pressure side first passage 41. Residual pressure is also generated in the cooling water present in the transformer cooling section 50. Due to this residual pressure, when the upper welding tip 21 and the lower welding tip 22 are removed, cooling water tends to splash out from the upper shank 23 and the lower shank 24. The first check valve 61, the second check valve 62, and the third check valve 63 divide the length of the passage connected to the upper shank 23 and the length of the passage connected to the lower shank 24. As a result, compared to the case where the check valves 61, 62, and 63 are not provided, the residual pressure released from the upper shank 23 and the lower shank 24 is divided and weakened. As a result, splashing of cooling water due to residual pressure can be reduced, and leakage of cooling water from the upper shank 23 and the lower shank 24 can be reduced.

[0044] The cooling device 11 of this embodiment supplies cooling water to the upper shank 23, the lower shank 24, and the transformer cooling section 50 by branching the water supply. Three check valves, a first check valve 61, a second check valve 62, and a third check valve 63, reduce the leakage of cooling water from the upper shank 23 and the lower shank 24. Therefore, compared to the cooling water discharge prevention unit disclosed in Patent Document 1, it can reduce cooling water leakage with a simpler structure. In addition, there is no need to place on-off valves (solenoid valves) to block the flow of cooling water on the welding gun actuator 25 and the gun arm 26. Each of the check valves 61, 62, and 63 has a simpler structure than a solenoid valve and requires less maintenance. Therefore, it is possible to stably reduce the leakage of cooling water from the upper shank 23 and the lower shank 24 over a long period of time.

[0045] <Example 1> Figure 2 shows the configuration of the cooling device 11 of the spot welding machine 10 in Modification 1. Modification 1 differs from the embodiment in terms of the position of the third check valve 63. The other configurations are the same as in the embodiment.

[0046] In Modification 1, the third check valve 63 is positioned between the high-pressure side manifold 34 and the transformer cooling section 50. With this configuration, the third check valve 63 is positioned before the cooling water passes through the transformer cooling section 50, that is, at a position in the fourth passage 54 where the water temperature is relatively low. When the high-pressure side on-off valve 30 and the low-pressure side on-off valve 40 are open, the cooling water flowing in the forward direction becomes relatively hot by cooling the transformer 27, which becomes hot when energized. Even in such a case, the cooling water flowing through the third check valve 63 has a relatively low water temperature. As a result, deterioration of the third check valve 63 due to temperature input is suppressed.

[0047] <Modification 2> Figure 3 shows the configuration of the cooling device 11 of the spot welding machine 10 in Modification 2. Modification 2 differs from the embodiment in terms of the structure of the transformer cooling unit 50 and the position of the third check valve 63. Other configurations are the same as in the embodiment.

[0048] In Modification 2, the transformer cooling section 50 has a plurality of coolers 51. The fourth passage 54 includes a connecting passage 54a that connects the plurality of coolers 51 to each other. The third check valve 63 is located in the connecting passage 54a. With this configuration, the position where the third check valve 63 is located is not visible from the upper shank 23 and the lower shank 24. During welding, spatter is scattered from the vicinity of the upper shank 23 and the lower shank 24. The spatter is scattered not only from the machine itself but also from welding machines installed in the surrounding area. Even in such cases, the third check valve 63 is less susceptible to spatter scattering, so it is less likely to be damaged, such as its surface melting or the markings on its surface becoming unclear. As a result, damage to the third check valve 63 caused by spatter scattering is suppressed.

[0049] <Variation 3> Figure 4 shows the configuration of the cooling device 11 of the spot welding machine 10 in Modification 3. Modification 3 differs from the embodiment in terms of the height-direction arrangement of the upper shank 23 and the lower shank 24. The other configurations are the same as in the embodiment.

[0050] In Modification 3, the upper shank 23 and the lower shank 24 are positioned higher than the components constituting the cooling device 11 (such as the high-pressure side manifold 34, the low-pressure side manifold 44, and the transformer cooling unit 50). Even in this positional relationship, similar to the embodiment, the flow of cooling water in the high-pressure side second passage 32 can be stopped by the first check valve 61, and the flow of cooling water in the low-pressure side third passage 43 can be stopped by the second check valve 62. Furthermore, the flow of cooling water in the high-pressure side third passage 33 can be stopped by the third check valve 63, and the flow of cooling water in the low-pressure side second passage 42 can be stopped. By doing so, the movement of cooling water caused by the height difference h between the upper shank 23 and the lower shank 24 can be stopped, and leakage of cooling water from the upper shank 23 and the lower shank 24 can be reduced.

[0051] <Modification 4> Figure 5 shows the configuration of the cooling device 11 of the spot welding machine 10 in Modification 4. Modification 4 differs from the embodiment in that it has an added release section 80 for discharging residual pressure present in the low-pressure side first passage 41. The other configurations are the same as in the embodiment.

[0052] The cooling device 11 of the modified example 4 further includes a release section 80 provided in the low-pressure side first passage 41 for discharging residual pressure present in the low-pressure side first passage 41.

[0053] The release section 80 has an introduction pipe 81 connected to the low-pressure side first passage 41 and a cylinder 82 connected to the introduction pipe 81. The introduction pipe 81 is connected between the low-pressure side manifold 44 and the low-pressure side on-off valve 40 of the low-pressure side first passage 41. The cylinder 82 sucks in or discharges cooling water in the low-pressure side first passage 41 via the introduction pipe 81. The cylinder 82 has a movable piston 83 and a chamber 84 into which the sucked-in cooling water flows. The piston 83 is driven by an air cylinder 85. The air cylinder 85 has a first air pipe 86 and a second air pipe 87 for supplying or exhausting working air. The first air pipe 86 and the second air pipe 87 are each provided with speed controllers 86a and 87a. When sucking in cooling water, the piston 83 is driven in the suction direction 88 and when discharging cooling water, it is driven in the discharge direction 89. The air that operates the air cylinder 85 is supplied by branching off from the air piping through which the air that operates the high-pressure side shut-off valve 30 and the low-pressure side shut-off valve 40 flows.

[0054] When drawing in coolant, the working air enters the air cylinder 85 from the first air pipe 86, is affected by the adjusted speed controller 87a, and is discharged into the second air pipe 87. When discharging coolant, the working air enters the air cylinder 85 from the second air pipe 87, is affected by the adjusted speed controller 86a, and is discharged into the first air pipe 86.

[0055] When the high-pressure side shut-off valve 30 and the low-pressure side shut-off valve 40 are closed while the cooling water is circulating in order to replace the upper welding tip 21 and the lower welding tip 22, residual pressure is generated from the high-pressure side first passage 31 to the low-pressure side first passage 41. Residual pressure is also generated in the cooling water present in the transformer cooling section 50. In such cases, after stopping the supply and return of cooling water, and before removing the upper welding tip 21 and the lower welding tip 22, the residual pressure present in the low-pressure side first passage 41 is discharged by the release section 80.

[0056] When releasing residual pressure, the release section 80 operates as follows: Operating air enters the air cylinder 85 from the first air pipe 86 and is discharged from the second air pipe 87 at a speed adjusted by the speed controller 87a. The operation of the air cylinder 85 drives the piston 83 of the cylinder 82 in the suction direction 88. As the piston 83 is driven, cooling water is drawn in from the low-pressure side first passage 41 through the introduction pipe 81 and flows into the chamber 84. This releases the residual pressure present in the low-pressure side first passage 41. Furthermore, all residual pressure of the cooling water present in the low-pressure side second passage 42, the low-pressure side third passage 43, the high-pressure side second passage 32, the high-pressure side third passage 33, and the transformer cooling section 50 is released.

[0057] Since the residual pressure of the cooling water inside the cooling device 11 becomes virtually zero, when the upper welding tip 21 and the lower welding tip 22 are removed, no cooling water will splash out from the upper shank 23 and the lower shank 24. As a result, in addition to reducing cooling water leakage caused by the height difference h between the upper shank 23 and the lower shank 24, splashing out due to residual pressure is eliminated, resulting in virtually zero cooling water leakage from the upper shank 23 and the lower shank 24.

[0058] The cooling device 11 of the spot welding machine 10 and the welding tip replacement method for the spot welding machine 10 of the present invention have been described above. However, the present invention is not limited to the configurations described in the embodiments and modifications described above, and can be modified as appropriate based on the claims.

[0059] The following embodiments are also included in the scope of the present invention: a cooling device 11 for a spot welding machine 10 according to any one of claims 2 to 5, having the features of claim 6. [Explanation of Symbols]

[0060] 10 Spot Welding Machines 11 Cooling device 12 Source 21 Upper welding tip 22 Lower welding tip 23 Upper shank 24 Lower shank 25 Welding Gun Actuator 26 Gun Arm 27 Transformers 30 High-pressure side shut-off valve 31 High-voltage side first passage 32 High-voltage side second passage 33 High-voltage side third passage 34 High-pressure side manifold 40 Low-pressure side on / off valve 41 Low-pressure side first passage 42 Low-pressure side second passage 43 Low-pressure side third passage 44 Low-pressure side manifold 50 Transformer Cooling Section 51 Cooler 54 4th aisle 54a Connecting passage 61 First check valve 62. Second check valve 63. Third check valve 80 Liberation Department h: Height difference between the upper shank and the lower shank

Claims

1. A high-pressure side first passage that sends cooling water from the cooling water supply source to the high-pressure side manifold, A high-pressure side second passage that supplies cooling water from the high-pressure side manifold to the upper shank, A high-pressure side third passage that supplies cooling water from the high-pressure side manifold to the lower shank located below the upper shank, A low-pressure side first passage that returns cooling water from the low-pressure side manifold to the supply source, The low-pressure side second passage returns cooling water from the upper shank to the low-pressure side manifold, A third low-pressure passage that returns cooling water from the lower shank to the low-pressure manifold, The first check valve provided in the high-pressure side second passage, The second check valve provided in the third passage on the low-pressure side, A cooling device for a spot welding machine.

2. A transformer cooling unit is provided in the middle of the fourth passage between the high-pressure side manifold and the low-pressure side manifold, for cooling the transformer. The cooling device for a spot welding machine according to claim 1, further comprising a third check valve provided in the fourth passage.

3. The cooling device for a spot welding machine according to claim 2, wherein the third check valve is disposed between the low-pressure side manifold and the transformer cooling section.

4. The cooling device for a spot welding machine according to claim 2, wherein the third check valve is disposed between the high-pressure side manifold and the transformer cooling section.

5. The transformer cooling section has a plurality of coolers, The fourth passage includes a connecting passage that connects the multiple coolers to each other, The cooling device for a spot welding machine according to claim 2, wherein the third check valve is located in the connecting passage.

6. The first check valve is positioned closer to the high-pressure side manifold than the upper shank. The cooling device for a spot welding machine according to claim 1, wherein the second check valve is positioned closer to the low-pressure side manifold than the lower shank.

7. A cooling device for a spot welding machine according to any one of claims 1 to 6, further comprising a release section provided in the low-pressure side first passage for discharging residual pressure present in the low-pressure side first passage.

8. A spot welding machine having a cooling device for the spot welding machine as described in claim 1, a method for replacing the welding tip of the spot welding machine, wherein the upper welding tip attached to the upper shank and the lower welding tip attached to the lower shank are replaced, The supply of cooling water to the high-pressure side manifold through the high-pressure side first passage is stopped. The return of cooling water to the supply source through the low-pressure side first passage is stopped. A method for replacing welding tips in a spot welding machine, comprising removing the upper welding tip and the lower welding tip simultaneously, or removing one welding tip and the other welding tip with a time difference.

9. A method for replacing welding tips in a spot welding machine according to claim 8, wherein, after stopping the supply and return of cooling water, the residual pressure present in the low-pressure side first passage is discharged before removing the upper welding tip and the lower welding tip.

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