JPS6238078B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a can body having an improved weld seam.

Conventionally, as a method for manufacturing a welded can body, a method is known in which, as disclosed in US Pat. No. 3,102,945, the overlapping portions of both ends of a can material are continuously welded using an electrode equipped with a wire using an alternating current current. In this method, the overlapping parts at both ends of the can body are directly and continuously welded using alternating current, so the can bodies produced undergo thermal distortion at the welded parts, and the welded parts as a whole are arched (counter-curved).
bow), the diameter of the manufactured can body is not accurate, and the fitting condition with the can lid attached to the can body is not constant, making it difficult to seal completely. This caused micro-leakage of the product or a decrease in the degree of vacuum.

Furthermore, in order to keep the diameter of the welded can body constant, it has been known to spot-weld the overlapping parts on both sides of the can body material at several points using a spot welding roll electrode, and then to perform continuous welding using a continuous welding roll electrode. There is. However, with this method, thermal distortion occurs between spot welding locations, and when continuous welding is performed, the welding locations become wavy.
The diameter of the open end of the manufactured can bodies varied, resulting in the same drawbacks when tightening the can lid as in the above-mentioned method.
In addition, in order to reduce the polymerization stage of the weld, methods such as welding with a smaller polymerization width or polishing both edges of the can body material and polymerization welding have been adopted, but these methods have not solved the step difference. situation. The existence of these undulations and steps at the welded area, coupled with the fact that the surface of the welded area is generally rough, requires paint to be applied to the cut surface of the inner surface of the can body material to prevent corrosion or to prevent metal from leaching into the contents. This makes coating difficult, and even with electrostatic coating methods that can produce relatively thick coatings, it is difficult to ensure complete coverage. In particular, the presence of steps tends to create voids in the seamed portion, causing micro leaks or a decrease in the degree of vacuum.

Furthermore, when welding the overlapped parts at both ends of the can material, methods were used to either weaken the welding current or reduce the pressure during welding in order to prevent hardening due to overwelding, but this method is still insufficient. The opening ends on both sides of the can body are over-welded, and weld cracks are likely to occur in these areas during flanging and seaming of the can lid, resulting in micro-leakage or micro-leakage of the contents when filled as a can. This caused a decrease in the degree of vacuum. Furthermore, when the welding electrode is crimped with a constant pressure over the welding area of the can body, the can body material protrudes like a tongue at both open ends of the can body due to the pressure during welding, and the tongue pieces touch the can lid. This makes the sealing of the can unstable, causing micro-leakage of the contents or a decrease in the degree of vacuum, and the tongues damage the inner surface of the can lid, causing metal elution and corrosion.

The present invention eliminates the drawbacks of the conventional method, and when welding the overlapping parts at both ends of the can body material, the diameter of the opening end of the can body is made uniform, thereby eliminating the disadvantages caused by thermal distortion at the welding part. An object of the present invention is to provide a method for manufacturing a welded can body without causing significant deformation.

Another object of the present invention is to provide a can body that eliminates the level difference on the inner surface of the welded part of the can body, reduces the voids in the seamed part that cause micro leaks or a decrease in the degree of vacuum, and makes it easier to coat the inner surface of the welded part with paint. The purpose is to provide a manufacturing method. Still another object of the present invention is to provide a method for manufacturing a welded can body that does not cause weld cracks at the welded area at the open end of the can body during flanging of the welded can body and seaming of the can lid. A method for manufacturing a welded can body in which protruding tongues of the can material that can make the seaming of the can lid unstable and damage the inner surface of the can lid are not generated at the welded part of the open end of the can body. Our goal is to provide the following. A first aspect of the present invention is a method for manufacturing a can body by polymerizing and welding both side ends of a can body material, in which the can body material is formed into a substantially circular shape, the both side ends are polymerized, and then the periphery of a roll is A process of performing AC spot welding with a small welding area using a spot welding electrode with a wire attached to a groove provided along the roll, and then attaching a wire to a groove provided along the periphery of the roll at the overlapping area including the spot welding location. It is characterized by comprising a step of continuous AC welding using a continuous welding electrode. The second invention is a method of manufacturing a can body by polymerizing and welding both side ends of a can body material, in which the can body material is formed into a substantially circular shape. A process of AC spot welding with a small welding area using a spot welding electrode with a wire attached to a groove provided along the roll, and then AC using a continuous welding electrode with a wire attached to a groove provided along the periphery of the roll depending on the conveyance speed of the can body. It is characterized by comprising the steps of synchronizing the welding current and carrying out continuous AC welding so that the minimum value of the welding current is at the front and rear edges of the welded part of the can body to the overlapping part including the spot welded part. The third invention is a method for manufacturing a can body by polymerizing and welding both side ends of a can body material, in which overlapping points at both side ends of a can body formed from a can body material into a substantially circular shape are provided along the periphery of a roll. The process involves performing AC spot welding using a spot welding electrode with a wire attached to a groove provided in the roll, and then synchronizing the conveyance speed of the can body with the AC welding current of a continuous welding electrode with a wire attached to a groove provided along the periphery of the roll. Continuous AC welding to the overlapping part including the spot welding part so that the minimum value of welding current is at the front and rear edges of the can body, and at the same time reducing the pressing force of the continuous welding electrode at the front and rear edges of the can body. It is characterized by consisting of.

An example of the implementation of the present invention will be explained with reference to FIGS. 1 to 9.

In the present invention, in order to prevent micro-leakage or a decrease in the degree of vacuum and to facilitate coating of the paint on the inner surface of the weld, the can body material is modified as described below in order to eliminate the step at the overlapping part on the inner surface of the weld. Apply pressure.

Figure 1a shows a can material 1 used for carrying out the present invention.
Since there are cutbacks 2 at both ends of the can body when cutting, the cutbacks 2 are pressed with a forming roll and processed sequentially as shown in a, b, c, and d in Figure 1b to obtain the thickness H of the can body material 1. Use by press molding to about 1/3.
In FIG. 1b, only the cutback 2 located on the inside of the can body material 1 is shown processed, but it is preferable that the cutback 2 located on the outside of the other end is also processed in the same manner.

Figure 2 schematically shows the entire main part of the embodiment of the present invention when a roll form type can making machine is used, but the same process can also be adopted in an inverted type can making machine. obtain. That is, the can material 1 is formed into a substantially circular can body 4, and then bent by a bending device 5 in order to facilitate overlapping of both ends of the can body 4 and to reduce the overlapped inner surface difference, and then spot welded. It is transported to machine 6. The spot welding wire machine 6 includes a spot welding roll group 7 provided on the lower surface of a can body forming cylinder (not shown) and a spot welding roll group 7' that is intermittently pressed against the spot welding roll group 7 via a crank 8. Be prepared. Each of the upper spot welding roll groups 7 is provided with a copper wire electrode wire holding groove 8, and a forming roll group 12 in which the copper wire electrode wire 11 is formed into an elliptical cross-sectional shape from a wire drum 10 for the spot welding roll is formed in the holding groove 8. The wire 11 is supplied to the lower spot welding roll via the wire correction roll group 13 which corrects the cross section of the wire 11 into an elliptical shape in the same manner as described above. The wire 11 is supplied to the wire holding groove 8' of the group 7' so that the long diameter end thereof is the welding surface, and is wound up by the winding drum 14. When the copper electrode wire is fed to the lower spot welding roll, it is inverted so that the wire is always clean during welding. The wires 11 supplied to both spot welding roll groups 7 and 7' are pulled out by a step motor 15 with a pitch equal to or slightly longer than the length of the spot welding part, and the wires 11 are pulled out by a step motor 15 whose pitch is equal to or slightly longer than the length of the spot welding part. The parts used for welding of groups 7 and 7' are always new end faces 7'. If the length of the small pitch pullout exceeds the distance between the rolls of spot welding, the wire fed by the next small pitch pullout is already used, and the small pitch drawer must feed a new end face. When this becomes impossible, the variable step motor 16 pulls out and supplies a pitch equal to the distance between the spot welding rolls multiplied by the number of spot welding rolls, and the length is equal to or slightly less than the length of the weld point. A long pitch of wire is drawn out, and this process is repeated to constantly supply new wire.

The can body 4 thus transferred to the spot welding machine 6 undergoes the outward expansion movement of the side block 17 of the cylinder and the closing mold 18 as shown in FIGS. 2 and 3.
The both ends of the can body 4 are overlapped by the closing movement of the can body 4, and the wires 11, 11 of the spot welding roll group 7' moved upward via the crank 8 and the spot welding roll group 7 of the cylinder are overlapped. The wires 11 are pressed together and an alternating current is applied to the wires 11 to locally spot weld within 1 mm at the long diameter ends of the wires 11 having an elliptical cross section as shown in the fourth figure.

The spot-welded can body 4 is fed to a continuous welding machine 19 by a continuous feed chain 20. As shown in FIGS. 2 and 5, the continuous welding machine 19 has a hammer 22 that moves up and down via the lower part of the cylinder and a cam 21.
A pair of welding rolls 23, 23' are provided in the cylinder, and the welding roll 23 in the cylinder is provided with a copper electrode wire holding groove 24, into which the wire is fed from a wire drum 26 for continuous welding rolls. A copper wire electrode wire 27 is supplied through a group of forming rolls 28 that shape the wire 27 into an elliptical cross-section so that the short diameter end of the wire 27 is the welding surface.
7 is again supplied to the wire holding groove 24' of the welding roll 23' on the hammer 22 side via the wire correction roll group 29 that corrects the cross section of the wire 27 to an elliptical shape in the same manner as described above, and is wound up by the winding drum 30. . In this case as well, as with spot welding wire, the wire is fed inverted to the lower welding roll so that the welding is always carried out on a new side of the wire.

The can body 4 is sent to a continuous welding machine 19 by a continuous feed chain 20, and while being conveyed, a hammer 22 is moved upward by a cam 21, and an inert gas is sprayed from an adjacent inert gas blowing nozzle 31 while the can body 4 is welded by a welding roll. 23, 23' wire 27, 2
7, continuous welding is performed overlapping the overlapping portion including the spot welding portion. At this time, as shown in FIG.
2 is moved upward by the cam 21 and the welding roll 2 is attached to the can body 4.
Motors M1, M2, M
3 to control and synchronize. The cam 21 moves the hammer 22 upward and welds the welding roll 2 as shown in FIG.
The can body 4 is brought into pressure contact with the welded portion of the can body 4 that is being conveyed synchronously, and the front and rear ends of the can body 4 have cam profiles that reduce the pressing force.

A pulse generator 32 built into the cam 21 is designed to generate two pulses per one cycle of welding current frequency when the cam 21 makes one revolution, and to generate a pulse at the same time as the cam 21 starts pressing. Set to .

On the other hand, a pulse generator 33a detects the welding current generated by the frequency converter 36 and generates a pulse at the peak of the welding current;
a pulse comparator 33b that compares the pulses of the pulse generator 3a with the pulses of the pulse generator 32 and calculates a difference between the two pulses based on the pulses of the pulse generator 32; and a time period for generating an analog voltage according to the difference. A phase detection circuit 33 comprising a voltage converter 33c changes the time constant in a phase control circuit 34 using the analog voltage to change the phase of the welding current waveform.
By continuously changing the phase of the welding current waveform in this way, the minimum value (0 point) of the actual welding current in FIG. 8 comes to the front and rear ends of the can body 4. 35
is the power source. Therefore, the can body 4 is continuously welded.
are welded so that the minimum value of the welding current is at the front and rear edges, and the pressing force of the welding rolls 23, 23' is reduced at the front and rear edges, so that the does not over-weld, and the pressing force is also reduced, so the metal does not protrude like a tongue.

The continuously welded can body 4 is welded so that the minimum value of the welding current is at the front and rear edges of the can body 4, and the welding rolls 23, 2 are welded at the front and rear edges.
Since the pressing force 3' is reduced, the front and rear edges of the can body will not protrude like a tongue due to the pressing force during welding. In this embodiment, the welded portion of the can body 4 creates a gap at the seamed portion with the can lid due to the difference in level formed by the thickness of the overlapping side ends of the can body material. In order to prevent micro-leakage from occurring through the can body material 1 and to facilitate coating of the inner surface of the welded part of the can body 4 by the paint jetting nozzle 36 shown in FIG.
The can body material 1 is made by pressing the cutbacks 2 on both sides of the can body material 1.
Then, as shown in FIGS. 5 and 6, the continuous welding roll 23' on the hammer 22 side of the continuous welding rolls 23, 23' is Pressure forming was carried out in the same manner as continuous welding using the attached bend rolls 34, eliminating the level difference on the inner surface of the welded part, and producing a can body with a good seaming condition of the can lid a shown in FIG. 9.

Thus, according to the first aspect of the present invention, since AC spot welding with a small welding area is performed using a spot welding electrode with a wire attached to a spot welding roll, thermal strain occurring at the spot welding location can be suppressed as much as possible. Therefore, it is possible to reduce waving due to thermal distortion, and since AC continuous welding is performed using a continuous welding electrode with a wire attached to a roll next to the overlapping part including the spot welded part, it is possible to prevent the entire welding part from bowing. Since the caliber of the can body can be made uniform without causing any difference in caliber from the can lid, it is possible to manufacture a can body that can be sufficiently tightened with the can lid. In addition, spot welding and continuous welding are performed using an electrode with a wire attached to a roll, so even if the wire becomes deformed or damaged during welding, you can always weld with a new wire end of the desired diameter by simply replacing the wire. In particular, when spot welding is performed using a wire attached to a spot welding roll, the cross section of the wire should be formed into an elliptical shape and welding should be carried out at the long diameter end of the wire in order to enable spot welding with a small desired welding area. Furthermore, in the case of continuous welding using a wire attached to a continuous welding roll, continuous welding of the desired width can be achieved by forming the cross section of the wire into an elliptical shape and welding at the short diameter end of the wire. . Furthermore, we plastically deformed the ends of the material located at least on the inside of both sides of the can body material to the extent that the cut edges during cutting were completely eliminated to within the range where the material ends exhibited a sloped shape, so that the ends of the material were deformed to the extent that the ends of the material were sloping. It is possible to manufacture a can body that reduces the level difference at the welded part of the can body that occurs during seaming and improves the seaming state with the can lid. Second aspect of the present invention
According to the invention, in the first invention, the conveyance speed of the can body in the continuous welding process and the alternating current welding current of the wire electrode of the welding roll are synchronized so that the minimum value of the welding current is at the front and rear edges of the can body. Since AC continuous welding is performed on the front and rear edges of the can body, unnecessary over-welding of the front and rear edges of the can body is prevented. It is possible to manufacture a can body that does not protrude from the edges.

According to the third aspect of the present invention, in the second aspect, the pressing force of the wire electrode against the welding roll is reduced at the front and rear ends of the can body, so that the heated welded portion to which the pressing force is applied during continuous welding is on the can body. It is possible to manufacture a can body that is not pressed to the extent that it protrudes from the front and rear ends, and therefore, there is no risk of tongue protrusions occurring at the front and rear ends of the can body.

[Brief explanation of the drawing]

The illustrations show an example of the implementation of the present invention, and FIG. 1a is a front view showing the sheared state of the can material;
Fig. 1b is an explanatory diagram showing changes in the edge of the material, Fig. 2 is a schematic diagram of an apparatus for carrying out the present invention, and Fig. 3 is an explanatory diagram showing changes in the edge of the material.
Fig. 4 is an enlarged view of the spot welded part in Fig. 3, Fig. 5 is a cut sectional view taken along the line V-V in Fig. 2, and Fig. 6 is a continuous welded part in Fig. 5. Fig. 7 is an explanatory diagram of the continuous welding machine shown in Fig. 2, Fig. 8 shows the position of the can body in the example, the pressure of the welding roll,
FIG. 9 is an explanatory diagram of the relationship between the welding current, the actual welding current, and the welding surface of the can body, and FIG. 9 is a cut-away sectional view of the can body manufactured according to this embodiment with a can lid tightened. 1... Can body material, 7, 7'... Spot welding roll,
11... Wire, 23, 23'... Welding roll, 8, 8', 24, 24'... Wire holding groove.

Claims (1)

[Scope of Claims] 1. A method of manufacturing a can body by polymerizing and welding both ends of a can body material, in which the can body material is formed into a substantially circular shape, the both ends of the can body are polymerized, and then the rolls are welded. A process of performing AC spot welding with a small welding area using a spot welding electrode with a wire attached to a groove provided along the periphery of the roll, and then inserting a wire into a groove provided along the periphery of the roll to remove the overlapping area including the spot welding area. A method for producing a welded can body, comprising the step of continuous AC welding using an attached continuous welding electrode. 2. The method of manufacturing a welded can body according to claim 1, wherein the cross section of the wire attached to the spot welding electrode is formed into an elliptical shape, and AC spot welding is carried out at the longer diameter end of the wire. 3. The method of manufacturing a welded can body according to claim 2, characterized in that the cross section of the wire attached to the continuous welding electrode is formed into an elliptical shape, and AC continuous welding is performed at the short diameter end of the wire. 4. The material ends located at least on the inside of both side ends of the can body material are plastically deformed to the extent that the cutbacks during cutting are completely eliminated to within the range where the material ends exhibit a sloped shape. A method for manufacturing a welded can body according to claim 1. 5 In a method of manufacturing a can body by polymerizing and welding both side ends of the can body material, the can body material is formed into a substantially circular shape.After polymerizing both side ends of the can material, a can body is provided along the periphery of the roll. The process of performing AC spot welding with a small welding area using a spot welding electrode with a wire attached to the groove, and then the conveyance speed of the can body and the AC welding current of a continuous welding electrode with a wire attached to the groove provided along the periphery of the roll. and performing continuous AC welding so that the minimum value of welding current is at the front and rear edges of the welded part of the can body to the overlapped part including the spot welded part. How to manufacture the torso. 6 In a method of manufacturing a can body by polymerizing and welding both ends of the can material, the can material is formed into a substantially circular shape, the both ends of the can material are polymerized, and then the can body is provided along the periphery of the roll. The process of performing AC spot welding with a small welding area using a spot welding electrode with a wire attached to the groove, then the conveyance speed of the can body and the AC welding current of a continuous welding electrode with a wire attached to the groove provided along the periphery of the roll. AC continuous welding is carried out so that the minimum value of the welding current is at the front and rear edges of the can body to the overlapping part including the spot welding point, and at the same time, the pressing force of the continuous welding electrode is applied to the front and rear edges of the can body. A method for producing a welded can body, comprising the steps of: