Table Spot Welder

Abstract

To provide a table spot welding machine capable of suppressing friction between a chain and a gun bracket by using a spring for absorbing vibration of the chain generated when pressure is applied, and enabling the spring to be used for a long period of time. [Solution] The device comprises a table electrode, a rod-shaped gun bracket, a pressure cylinder 82 whose piston rod 821 moves when air pressure is applied, a gun body supported at the tip of the gun bracket so that it can rotate freely in a direction perpendicular to the direction parallel to the table electrode, a chain 83 having one end connected to the pressure cylinder 82 and the other end connected to the gun body, and a coil spring 150 having an inner diameter large enough to allow the chain 83 to be inserted therein and having both ends connected to the chain 83 in a non-extendable state, the coil spring 150 being attached to the chain 83 with the chain 83 passing through the inside of the coil spring.

Description

[Technical Field]

[0001] The present invention relates to a table spot welder equipped with a flat table electrode on which an object to be welded, called a "workpiece," is placed, and a horizontal gun that can be moved in a horizontal position parallel to the table electrode. [Background technology]

[0002] The present inventors have previously proposed an example of the above-mentioned table spot welder (see Patent Document 1). Fig. 14 is a side view showing the horizontal gun 6 of the table spot welder described in Patent Document 1. Fig. 14 also shows the internal structures of the upper and lower ends of the horizontal gun 6. Fig. 15 is a side view showing the tip end of the horizontal gun 6.

[0003] The horizontal gun 6 includes a gun bracket 61, a pressure cylinder 62, a chain 63, and a gun body 64. The gun bracket 61 is formed in the shape of a long rectangular tube and supports the gun body 64. A lower end portion 61B (see FIG. 15) of the gun bracket 61 is formed in a bent, approximately L-shape. The rest of the gun bracket 61, excluding the lower end portion 61B, is formed in a cylindrical shape. An upper end portion 61A of the gun bracket 61 is attached to a rotation shaft 5D at the tip of a movable arm 5B of the table welding machine body (not shown). The rotation shaft 5D supports the gun bracket 61 so that it can rotate freely in the horizontal direction. A through-hole is formed in the rotation shaft 5D of the movable arm 5B along the axial direction, through which a piston rod 621 of the pressure cylinder 62 passes.

[0004] The pressure cylinder 62 is disposed directly above the rotation shaft 5D and rotates together with the gun bracket 61 via the rotation shaft 5D. The piston rod 621 of the pressure cylinder 62 is formed in a cylindrical shape with a length that reaches the upper end portion of the gun bracket 61. One end portion (upper end portion) of a chain 63 is connected to a tip portion 622 of the piston rod 621. The other end portion (lower end portion) of the chain 63 is connected to the gun main body 64 via a chain hook 65. Details of the chain 63 will be explained later. The chain hook 65 is connected to the gun main body 64 so that the gun main body 64 can rotate vertically.

[0005] The piston rod 621 of the pressure cylinder 62 is drawn into the pressure cylinder 62 when air pressure is applied inside the body of the pressure cylinder 62. When the piston rod 621 is drawn into the pressure cylinder 62, the chain 63 is pulled upward, causing the tip portion of the gun body 64 to rotate downward (the direction indicated by arrow Y3 in FIG. 15 ) and the rear end portion to rotate upward (the direction indicated by arrow Y4 in FIG. 15 ). In other words, since the position of the bolt 66 that rotatably attaches the gun bracket 61 and the gun body 64 is set closer to the tip portion of the gun body 64 than the position of the chain hook 65, pulling up the chain 63 causes the tip portion of the gun body 64 to rotate downward and the rear end portion to rotate upward, with the bolt 66 as a fulcrum.

[0006] A shank holder 71 is attached to the front end of the gun body 64, and a handle 74 is attached to the rear end. A shank 72 is attached to the tip of the shank holder 71, and a cap tip 73 is attached to the tip of the shank 72. The shank holder 71 is formed in a rod shape with the tip bent at a substantially right angle, and a flow path (not shown) is formed inside for circulating cooling water. The shank holder 71, shank 72, and cap tip 73 are made of a conductive material such as copper. The handle 74 is used to operate the gun body 64. A switch (not shown) for starting welding is attached to the handle 74.

[0007] Next, the chain 63 will be described. FIG. 16 is a diagram showing a portion of the chain 63. In the figure, the chain 63 is a type of link chain, and is formed by connecting a plurality of ring-shaped bodies 631 in series. In particular, adjacent ring-shaped bodies 631 are connected to each other at 90-degree angles. For example, ring-shaped body 631-1 is connected to ring-shaped body 631-2 and ring-shaped body 631-3 at 90-degree angles. The chain 63 is housed in the gun bracket 61, and its lower end is connected to a chain hook 65 and its upper end is connected to the tip of the piston rod 621 of the pressure cylinder 62. The chain 63 is mainly made of iron.

[0008] The table spot welder described in Patent Document 1 is configured as described above. During welding, the gun body 64 is operated to bring the cap tip 73 into contact with the workpiece 11, and in that state, the start switch (not shown) of the gun body 64 is operated. This operation applies air pressure to the pressure cylinder 62, causing the piston rod 621 to be retracted into the pressure cylinder 62. As the piston rod 621 is retracted into the pressure cylinder 62, the chain 63 is pulled up, and the gun body 64 is raised. As a result, the tip of the cap tip 73 attached to the gun body 64 comes into contact with and applies pressure to the workpiece 11. Then, a current flows between the horizontal gun 6 and the table electrode 10 via the workpiece 11, and welding is performed on the workpiece 11.

[0009] In the conventional table spot welding machine described above, when welding is performed using the horizontal gun 6, so-called "tip slippage" may occur, in which the tip of the cap tip 73 comes off the welding point on the workpiece 11. It has been found that this tip slippage is caused by vibrations generated in the chain 63 when the chain 63 is pulled up during pressure application. As a method for suppressing this tip slippage, for example, a method has been devised in which a coil spring ("coil spring") is connected in parallel to a portion of the chain 63 to absorb the vibrations generated in the chain 63.

[0010] Figure 17 shows an example in which a coil spring 150 is attached in parallel to a chain 63. In this figure, the coil spring 150 is attached to the chain 63 in a steady state where it is not stretched. When pressure is applied, the chain 63 is pulled up, causing the coil spring 150 to stretch and absorb vibrations generated in the chain 63. By having the coil spring 150 absorb the vibrations generated in the chain 63, slippage of the tip of the chain when pressure is applied can be suppressed. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Application Publication No. 2018-023984 Summary of the Invention [Problem to be solved by the invention]

[0012] However, although providing coil spring 150 parallel to chain 63 can absorb the vibration of chain 63 when pressure is applied, this means that coil spring 150 is always likely to come into contact with both the surface of chain 63 and the inner wall surface of gun bracket 61, which creates the problem that coil spring 150 is prone to breakage due to friction caused by repeated pressure application (i.e., friction between the surface of the spring and the surface of the chain, and friction between the surface of the spring and the inner wall surface of the gun bracket).

[0013] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a table spot welder having a horizontal gun that uses a coil spring to absorb chain vibrations that occur when pressure is applied, thereby minimizing friction between the chain and the gun bracket, thereby enabling long-term use of the coil spring. [Means for solving the problem]

[0014] The table spot welder of the present invention comprises a metal table electrode having a flat plate shape on which a workpiece is placed and connected to one electrode side of a power source, a gun bracket having a rod-like structure with a hollow interior, a piston rod, and a mechanism for moving the piston rod by application of air pressure, a pressure cylinder disposed at the rear end portion of the gun bracket, a shank holder attached to the front end, a handle attached to the rear end, and the portion between the front end and the rear end is the tip portion of the gun bracket, which is supported so as to be rotatable in a vertical direction perpendicular to a horizontal direction parallel to the table electrode, and is connected to the other electrode side of the power source. The gun body comprises: a chain having one end connected to the tip portion of the piston rod of the pressure cylinder and the other end connected to a position closer to the rear end of the gun body than the position of the rotation axis of the gun body; and a coil spring having an inner diameter large enough to allow the chain to be inserted therein and a length shorter than the overall length of the chain, the coil spring having both ends connected to the chain in a non-extendable state, the coil spring being attached to the chain with the chain passing through it, and the piston rod of the pressure cylinder moving to pull up the chain causes the front end of the gun body to rotate in a direction toward the table electrode.

[0015] According to the above configuration, friction between the coil spring and the chain, and friction between the coil spring and the gun bracket are reduced, allowing the coil spring to be used for a long period of time. In addition, the coil spring absorbs the vibrations of the chain that occur when pressure is applied, making it possible to prevent "tip slippage," a phenomenon that tends to occur during welding, in which the tip of the cap tip attached to the gun body comes off the welding point on the workpiece.

[0016] In the above configuration, the chain is a link chain in which multiple ring-shaped bodies are connected in series, and a pin is passed through the ring-shaped body located at the end of the coil spring on the gun body side and the other ring-shaped body connected to that ring-shaped body, thereby regulating the movement of the other ring-shaped body.

[0017] According to the above configuration, by passing a pin through the ring located at the end of the coil spring closer to the gun body and the other rings connected to that ring, the movement of the other rings can be restricted, and the other rings will not become fixed in a position where they are rotated to an angle of nearly 90 degrees. As a result, even if the chain below the lower end of the coil spring becomes slack when the pressure cylinder is switched from an activated state to an inactivated state, the ring adjacent to the lower end of the coil spring will not become fixed in a position where it is rotated to an angle of nearly 90 degrees. Therefore, even when the pressure cylinder is switched from an inactivated state to an activated state, no significant load is placed on the chain, and no loud noise is generated. [Effects of the Invention]

[0018] According to the present invention, vibration of the chain connecting the pressure cylinder and the gun body within the gun bracket can be suppressed when pressure is applied, thereby preventing "tip slippage" that often occurs during welding, i.e., the phenomenon in which the tip of the cap tip attached to the gun body comes off the welding point on the workpiece. In addition, by passing a coil spring through the chain to suppress vibration, it is possible to keep low friction between the coil spring and the chain and between the coil spring and the gun bracket, enabling the coil spring to be used for a long period of time. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a side view showing the appearance of a table spot welder according to an embodiment of the present invention. [Figure 2] A diagram showing the appearance of the horizontal gun of the table spot welding machine shown in Figure 1 and the internal structure of a part of it. [Figure 3] A diagram showing the connection relationship between the pressure cylinder, chain, and coil spring that constitute the horizontal gun of the table spot welding machine shown in Figure 1. [Figure 4] A diagram showing a portion of the chain and a portion of the coil spring that make up the horizontal gun of the table spot welding machine shown in Figure 1. [Figure 5] A diagram showing the connection state between the chain and coil spring that make up the horizontal gun of the table spot welding machine shown in Figure 1. [Figure 6] FIG. 2 is a perspective view showing the appearance of the pins that make up the horizontal gun of the table spot welding machine shown in FIG. [Figure 7] FIG. 7 is a perspective view showing the pin shown in FIG. 6 attached to a chain. [Figure 8] A diagram showing the pin shown in Figure 6 attached to the chain [Figure 9] A diagram showing the pin shown in Figure 6 attached to the chain [Figure 10] The figure shows the state in which the annular link adjacent to the lower end of the coil spring shown in Figure 4 is fixed in a state where it has rotated to an angle of nearly 90 degrees. [Figure 11] A diagram showing an example in which a pin is inserted into the annular link adjacent to the coil spring shown in Figure 4. [Figure 12] 12 is a plan view of the pin shown in FIG. 11. [Figure 13] A cross-sectional view showing a modified example of a mechanism for absorbing vibrations of the chain that occur when pressure is applied. [Figure 14] A side view showing the horizontal gun of a conventional table spot welding machine [Figure 15] A side view showing the tip portion of the horizontal gun shown in Figure 14. [Figure 16] A diagram showing a part of the chain that constitutes the horizontal gun shown in Figure 14. [Figure 17] A diagram showing an example in which a coil spring is attached in parallel to the chain that constitutes the horizontal gun shown in Figure 14. DETAILED DESCRIPTION OF THE INVENTION

[0020] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0021] Fig. 1 is a side view showing the appearance of a table spot welder 1 according to one embodiment of the present invention. Fig. 2 is a view showing the appearance of a horizontal gun of table spot welder 1 according to this embodiment and the internal structure of a portion thereof. In Figs. 1 and 2, parts that are common to Figs. 14 and 15 described above are designated by the same reference numerals.

[0022] 1, a table spot welder 1 according to this embodiment includes a cooling unit 2, a power supply unit 3, a support post 4, a support arm (a cantilevered articulated arm) 5, a horizontal gun 8, a conductive cable 9, a flat table electrode 10, and a table drive unit 12. The cooling unit 2 supplies cooling water to cool the heat generated from the horizontal gun 8 during welding, and operates constantly while the power is on to circulate cooling water between the horizontal gun 8 and the cooling unit 2.

[0023] The power supply unit 3 converts three-phase AC power supplied from a power receiving facility (not shown) into DC using a rectifying element (not shown), and generates high-frequency AC from the converted DC. The support post 4 is installed vertically near the cooling unit 2 and the power supply unit 3, and supports the support arm 5 so that it can rotate horizontally. The support arm 5 includes horizontal arm portions 5A and 5B extending horizontally relative to the support post 4, a rotation shaft 5C that connects the horizontal arm portions 5A and 5B so that they can rotate horizontally, and a rotation shaft 5D that supports the horizontal gun 8 at the tip of the horizontal arm portion 5B so that it can rotate horizontally.

[0024] The gun bracket 81 of the horizontal gun 8 has a tip portion 81B bent into a generally L-shape, which supports the gun body 86. The gun bracket 81 has an upper end portion 81A attached to the rotation shaft 5D.

[0025] In addition to the above-mentioned gun bracket 81, the horizontal gun 8 also includes a pressure cylinder 82, a chain 83 (see FIG. 2), and a gun body 86. The pressure cylinder 82 lifts the gun body 86 via the chain 83. The pressure cylinder 82 is attached to the upper end of the rotation shaft 5D, and rotates together with the gun bracket 81 via the rotation shaft 5D. The chain 83 is housed within the gun bracket 81, with one end connected to the leading end of the piston rod 821 of the pressure cylinder 82 and the other end connected to the gun body 86 via a chain hook 85.

[0026] A spring coil ("coil spring", see FIG. 1) 92 is stretched between the rear end portion of the gun body 86 and the lower end portion of the gun bracket 81. The spring coil 92 urges the rear end portion of the gun body 86 to lift upward (in the height direction of the housing 1A of the table spot welder 1). The expansion and contraction of the spring coil 92 allows the gun body 86 to easily move up and down.

[0027] A handle 84 that is operated by an operator is attached to the rear end of the gun body 86, allowing the horizontal gun 8 to be moved up and down. A lever-type switch (not shown) for outputting welding commands is provided on the handle 84, and operating the lever turns the switch on, outputting a welding command. The welding command is taken into the power supply unit 3. The power supply unit (power source) 3 starts operating upon receiving the welding command and outputs high-frequency alternating current. The high-frequency alternating current output from the power supply unit 3 flows into the primary coil of a welding transformer (not shown). The table electrode 11 is connected to one electrode side of the power supply unit 3. The gun body 86 is connected to the other electrode side of the power supply unit 3.

[0028] In FIG. 1, a conductive cable 9 electrically connects the power supply unit 3 and the horizontal gun 8. High-frequency AC generated by the power supply unit 3 flows through the conductive cable 9 to the horizontal gun 8. The table electrode 10 is formed in a flat plate shape and serves to place the workpiece 11. A copper plate is typically used for the table electrode 10. The table electrode 10 is disposed in a portion of the housing 1A of the table spot welder 1 in a direction perpendicular to the height direction of the housing 1A (i.e., horizontal direction). A table drive unit (vertical movement mechanism) 12 moves the table electrode 10 up and down (i.e., vertical direction).

[0029] Next, the horizontal gun 8 will be described in detail. Figure 3 is a diagram showing the connection state between the pressure cylinder 82, the chain 83, and the spring coil 150, which will be described later. As shown in the figure, the pressure cylinder 82 has a piston rod 821 that protrudes from inside the body to outside the body when air pressure is applied. Air pressure is applied to the pressure cylinder 82 during welding and stops when welding is completed.

[0030] One end of the chain 83 is connected to the tip of the piston rod 821 of the pressure cylinder 82, and the other end is connected to a chain hook 85. When the horizontal gun 8 is attached to the body of the table spot welder 1, the chain 83 is suspended from the pressure cylinder 82. Details of the chain 83 will be described later. The chain hook 85 is connected to the gun body 86 with a bolt 88 (see FIG. 2). In this case, the chain hook 85 is connected to a position closer to the rear end than the center of gravity of the gun body 86. The chain hook 85 is also rotatable vertically relative to the gun body 86.

[0031] By positioning the attachment position of chain hook 85 closer to the rear end than the center of gravity of gun body 86, when chain 83 is pulled up, the gun body 86 rotates so that the front end side of bolt 88 of gun body 86 faces downward and the rear end side of bolt 88 faces upward. In other words, pulling up chain 83 rotates gun body 86 toward table electrode 10. Here, "upward" refers to the height direction of housing 1A of table spot welder 1 (see FIG. 1), and "downward" refers to the opposite direction from the height direction of housing 1A of table spot welder 1.

[0032] During welding, the workpiece 11 is placed on the table electrode 10, and the gun body 86 rotates toward the table electrode 10, causing the cap tip 73 of the gun body 86 to come into contact with and apply pressure to the workpiece 11. During welding, the cap tip 73 is pressed against the workpiece 11, but the cap tip 73 is pressed against the workpiece 11 just before welding starts (i.e., just before welding current is supplied), and is released just after welding is completed.

[0033] In addition to the cap tip 73, the shank holder 71 and the shank 72 are connected to the gun body 86. In this case, the shank holder 71, shank 72, and cap tip 73 are connected to the gun body 86 in this order. The shank holder 71 is formed in a rod shape with the tip bent at a substantially right angle, and a flow path (not shown) for flowing cooling water is formed inside.

[0034] Similar to the chain 63 described above, the chain 83 has a structure in which multiple ring-shaped bodies 831 are connected in series. FIG. 4 shows a portion of the chain 83 and a portion of the coil spring 150. As shown in the figure, each ring-shaped body 831 constituting the chain 83 has a nearly elliptical shape consisting of two opposing straight portions 831a and 831b, a U-shaped portion 831c connecting one side of the straight portions 831a and 831b, and a U-shaped portion 831d connecting the other side of the straight portions 831a and 831b. The chain 83 is housed in the gun bracket 81, and its lower end is connected to a chain hook 85 and its upper end is connected to the tip of the piston rod 821 of the pressure cylinder 82. The chain 83 is primarily made of iron.

[0035] Returning to FIG. 3, a coil spring 150 is attached to a portion of the chain 83. The total length of the coil spring 150 is shorter (about 1 / 5) than the total length of the chain 83, and the inner diameter is slightly larger than the outer diameter of the chain 83. To attach the coil spring 150 to the chain 83, the coil spring 150 is passed through the chain 83 and locked to the chain 83 at a desired position. Note that the attachment position of the coil spring 150 is preferably closer to the gun body 86. In FIG. 3, the coil spring 150 is attached between the ninth annular body 831-8 and the seventeenth annular body 831-17 from the bottom.

[0036] A pin 300 (see FIG. 5) is used to connect the coil spring 150 to the chain 83. FIG. 5 is a diagram showing the connection between the chain 83 and the coil spring 150. As shown in the figure, one end 150a of the coil spring 150 is engaged with the pin 300 that is passed through approximately the third annular body 831 from the one end 150a side. The other end side of the coil spring 150 is also engaged with a pin (not shown) that is passed through approximately the third annular body 831 from the other end, similar to the one end 150a side. FIG. 6 is a perspective view showing the appearance of the pin 300. As shown in the figure, the pin 300 is formed in a T-shape, and a through-hole 302 is formed in a support portion 301. One end 150a of the coil spring 150 is passed through the through-hole 302. Figures 7 to 9 show the state in which pin 300 is attached to ring-shaped body 831 of chain 83, Figure 7 is an oblique view showing the state in which pin 300 is inserted into ring-shaped body 831 of chain 83, Figure 8 is a view from the direction of arrow Y5 in Figure 7, and Figure 9 is a view from the direction of arrow Y6 in Figure 7.

[0037] By passing the coil spring 150 through the chain 83, it is less likely to come into contact with the chain 83 and also with the gun bracket 81. This reduces friction between the coil spring 150 and the chain 83, and between the coil spring 150 and the gun bracket 81, allowing the coil spring 150 to be used for a longer period of time than with conventional technology. In addition, because the coil spring 150 absorbs the vibration of the chain 83 that occurs when pressure is applied, it is possible to prevent "tip slippage," which tends to occur during welding, in which the tip of the cap tip 73 attached to the gun body 86 comes off the welding point on the workpiece 11.

[0038] In the table spot welder 1 configured as described above, during welding, the gun body 86 is operated to bring the tip of the cap tip 73 into contact with the workpiece 11, and in that state, the start switch (not shown) of the gun body 86 is operated. This activates the pressure cylinder 82, which pulls up the chain 83 and raises the gun body 86. This causes the tip of the cap tip 73 attached to the gun body 86 to come into contact with and apply pressure to the workpiece 11. Then, current flows between the horizontal gun 8 and the table electrode 10 via the workpiece 11, and welding of the workpiece 11 is performed.

[0039] In the table spot welding machine 1, by passing the coil spring 150 through the chain 83, the friction between the coil spring 150 and the chain 83 and the friction between the coil spring 150 and the gun bracket 81 can be significantly reduced, allowing the coil spring 150 to be used for a long period of time.

[0040] Furthermore, since the coil spring 150 absorbs vibrations of the chain 83 that occur when pressure is applied, slippage of the tip end when pressure is applied can be suppressed.

[0041] When the pressure cylinder 82 changes from an activated state to a deactivated state, the chain 83 descends due to its own weight. At this time, the portion of the chain 83 below the lower end of the coil spring 150 becomes loose. In this loosened portion, the ring-shaped body 831 adjacent to the lower end of the coil spring 150 may occasionally become fixed in a state rotated nearly 90 degrees. FIG. 10 shows a state in which the ring-shaped body 831-9 adjacent to the lower end of the coil spring 150 is fixed in a state rotated nearly 90 degrees. As shown in the figure, the ring-shaped body 831-9 has rotated nearly 90 degrees, making contact with the coil spring 150 at the point indicated by arrow Y7 and with the adjacent ring-shaped body 831-7 at the point indicated by arrow Y8. When this state occurs, it is difficult to immediately return the ring-shaped body 831-9 to its original state even by manually pulling it.

[0042] Since a large amount of air pressure is applied from the pressure cylinder 82, it is possible to return the ring-shaped body 831-9 to its original state by using this air pressure. However, when the ring-shaped body 831-9 returns to its original state, a large load (load due to the air pressure) is applied to the chain 83 itself, which may cause a loud noise.

[0043] In the portion of the chain 83 above the lower end of the coil spring 150, particularly in the portion corresponding to the length of the coil spring 150, the coil spring 150 restricts the ring-shaped bodies 831 to be aligned in series, so that the ring-shaped body 831-9 does not become fixed in a state where it has rotated to an angle of nearly 90 degrees. Furthermore, in the portion of the chain 83 above the portion corresponding to the length of the coil spring 150, the coil spring 150 also restricts the ring-shaped body 831-9 in this portion, so that the ring-shaped body 831-9 does not become fixed in a state where it has rotated to an angle of nearly 90 degrees. In contrast, in the portion of the chain 83 below the lower end of the coil spring 150, the coil spring 150 does not restrict the ring-shaped body 831-9, so that the ring-shaped body 831-9 may become fixed in a state where it has rotated to an angle of nearly 90 degrees. When this happens, it is not easy to forcefully return it to its original state.

[0044] In the table spot welding machine 1 of this embodiment, a pin is passed through the ring-shaped body 831 to prevent the ring-shaped body 831-9 from rotating even if the chain 83 becomes loose. FIG. 11 is a diagram showing an example in which a pin 900 is passed through the ring-shaped body 831-9 adjacent to the coil spring 150. As shown in the figure, the pin 900 is passed through the ring-shaped body 831-9 adjacent to the coil spring 150. FIG. 12 is a plan view showing the pin 900. In the figure, the pin 900 is formed in an annular shape with a circular cross section and consists of two parts 900a and 900b so that it can be attached to and detached from the ring-shaped body 831-9. The two parts 900a and 900b can be attached and detached using two screws 901. Of course, the pin 900 can also be attached and detached to other parts than the ring-shaped body 831-9.

[0045] Furthermore, a structure such as a "set collar" is suitable for the pin 900. By passing the pin 900 through the ring-shaped body 831-9, the movement of the ring-shaped body 831-9 can be restricted, and the ring-shaped body 831-9 will not become fixed in a state where it has rotated to an angle of nearly 90 degrees. As a result, even if the chain 83 below the lower end of the coil spring 150 becomes loose when the pressure cylinder 82 is switched from an activated state to an inactivated state, the ring-shaped body 831 adjacent to the lower end of the coil spring 150 will not become fixed in a state where it has rotated to an angle of nearly 90 degrees. Therefore, even when the pressure cylinder 82 is switched from an inactivated state to an activated state, no significant load is placed on the chain 83, and no loud noise is generated.

[0046] Although the present invention has been described with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.

[0047] For example, the following can be considered as a modified example of a mechanism in which a coil spring absorbs vibrations of a chain that occur when pressure is applied (hereinafter referred to as a "vibration absorbing mechanism"). 13 is a cross-sectional view showing the same modified example, in which the chain 83 and the coil spring 1004 are not shown in cross section. The vibration absorbing mechanism 1000 includes a casing member 1001 , a stopper member 1002 , a T-shaped member 1003 , and a coil spring 1004 .

[0048] The casing member 1001 has a hollow cylindrical shape and houses a stopper member 1002, a T-shaped member 1003, and a coil spring 1004. The casing member 1001 consists of two parts (a first part 1001a and a second part 1001b). The first part 1001a has an opening in a part of its side and a through-hole in the center of its top surface. The second part 1001b closes the opening of the first part 1001a and is attached to the first part 1001a with screws or the like (not shown). Since the shape of the casing member 1001 is cylindrical, the cross section of the second part 1001b is crescent-shaped.

[0049] The stopper member 1002 has a cylindrical shape with an outer diameter approximately the same as the inner diameter of the casing member 1001, and is attached to the upper part of the casing member 1001 (the side where the through-hole 1001d is formed). The stopper member 1002 is formed to a size that allows the locking portion 1003b of the T-shaped member 1003 to come into contact with it. The stopper member 1002 is attached to the casing member 1001 with screws or the like (not shown). The inner diameter of the stopper member 1002 is slightly larger than the outer diameter of the coil spring 1004.

[0050] The T-shaped member 1003 is composed of a rod-shaped portion 1003a having a diameter smaller than that of the coil spring 1004, and a locking portion 1003b having a diameter larger than that of the through-hole 1001d of the casing member 1001. The locking portion 1003b is formed in a disk shape. The through-hole 1001d of the casing member 1001 is for passing the rod-shaped portion 1003a of the T-shaped member 1003 through. Bushings 1005 made of rubber, resin, or metal are fitted into the outside and inside of the through-hole 1001d of the casing member 1001.

[0051] In this vibration absorbing mechanism 1000, the lower end 83a of the upper chain 83 is connected to the tip of the rod-shaped portion 1003a of the T-shaped member 1003, and the central portion of the lower part of the first part 1001a of the casing member 1001 is connected to the upper end 83b of the lower chain 83. In this way, the vibration absorbing mechanism 1000 is interposed in series with the chain 83. It goes without saying that the central axis of the upper chain 83 and the central axis of the lower chain 83 are positioned so as to be on the same line.

[0052] By installing the vibration absorption mechanism 1000 in series with the chain 83, the upper and lower chains 83 are connected via the coil spring 1004. When the pressure cylinder 82 is operated in this state, the gun body 86 is pulled upward via the chain 83. As a result, the tip of the cap tip 73 attached to the gun body 86 presses the workpiece 11. Current then flows between the horizontal gun 8 and the table electrode 10 via the workpiece 11, welding the workpiece 11. Even if the chain 83 vibrates during pressure application, the coil spring 1004 absorbs the vibration until the T-shaped member 1003 abuts against the stopper member 1002, thereby suppressing tip slippage during pressure application. Once the T-shaped member 1003 abuts against the stopper member 1002, the upper and lower chains are directly connected, preventing the coil spring 1004 from collapsing, ensuring reliable pressure application.

[0053] In this vibration absorbing mechanism 1000, the coil spring 1004 is connected in series with the chain 83, so that no friction occurs between the coil spring 1004 and the chain 83, and no friction occurs between the coil spring 1004 and the gun bracket 81, so that the coil spring 1004 can be used for a longer period of time. [Industrial Applicability]

[0054] The present invention can be applied to a table spot welding machine that includes a table electrode on which a workpiece is placed and a horizontal gun that is movable in a horizontal position parallel to the table electrode. [Explanation of symbols]

[0055] 1 Table Spot Welder 1A Table Spot Welder Housing 2 Cooling Unit 3 Power Supply Unit 4 support posts 5 Support Arm 8 Horizontal Gun 9 Conductive Cable 10 Table Electrodes 11 Work 71 Shank holder 72 Shank 73 Cap Tip 81 Gun bracket 82 Pressure Cylinder 83 Chain 85 Chain Hook 86 Gun body 88 volts 150,1004 Coil spring Coil spring 300,900 pins 821 Piston rod 831,831-7,831-8,831-9,831-10 Ring-shaped body 1000 vibration absorption mechanism 1001 Casing member 1002 Stopper member 1003 T-shaped member 1003b Locking part 1005 Bush

Claims

1. a metal table electrode having a flat plate shape on which the workpiece is placed and connected to one electrode side of the power source; a gun bracket having a hollow rod-like structure; a pressure cylinder having a piston rod and a mechanism for moving the piston rod by application of air pressure, the pressure cylinder being disposed at a rear end portion of the gun bracket; a gun body having a shank holder attached to a front end and a handle attached to a rear end, the portion between the front end and the rear end being a tip portion of the gun bracket, the gun body being supported so as to be rotatable in a vertical direction perpendicular to a horizontal direction parallel to the table electrode, and the gun body being connected to the other electrode side of the power source; a chain having one end connected to a tip end portion of the piston rod of the pressure cylinder and the other end connected to a position closer to the rear end portion of the gun body than the position of the rotation axis of the gun body; a coil spring having an inner diameter large enough to allow the chain to be inserted therein, a length shorter than the entire length of the chain, and both ends connected to the chain in a non-stretched state; Equipped with The coil spring is attached to the chain with the chain passing through the coil spring, When the piston rod of the pressure cylinder moves and the chain is pulled up, the front end of the gun body rotates in a direction toward the table electrode. Table spot welding machine.

2. The chain is a link chain in which a plurality of ring-shaped bodies are connected in series, a pin is passed through the annular body located at the end of the coil spring on the gun body side and another annular body connected to the annular body, thereby restricting the movement of the other annular body; 2. The table spot welder according to claim 1.

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