JPH0353816Y2 - - Google Patents

Description

[Detailed explanation of the invention] [Industrial application field] This invention is for manufacturing can bodies of metal cans.
This invention relates to a device for welding circumferential edges of can bodies together by laser welding, and is intended to prevent damage to a condensing lens caused by spatter during welding.

[Conventional technology]

The edge welding of the can body is generally performed by a resistance welding method that utilizes electrical resistance heat. In the resistance welding method, pretreatment work is essential to remove oil, moisture, rust, or printed layers adhering to the welding area.

In order to omit such pre-treatment work and improve welding speed, it has been proposed to perform edge welding of can bodies by laser welding. For example, Japanese Patent Application Laid-open No. 76690/1983 by the present applicant is one of them.

The present inventor has been researching the practical application of can body edge welding using a carbon dioxide gas laser for several years, and has attempted to put edge welding to practical use under mass production conditions using a welding device with an output of 1KW as shown in Figure 8. This device includes a table 2 that supports a can body material 1, and a pair of rollers 45 that press and hold the can body edges 1a and 1b against the table 2.
and a processing head 3, and the can body material 1 is passed through rollers 45.
Welding is performed by irradiating a laser beam from the processing head 3 while holding the welding position in the welding position and moving it in the direction of arrow A. A condensing lens 5 is arranged inside the processing head 3, and a nozzle 7 for blowing out assist gas is provided at the lower end of the condensing lens 5. 8 is the air outlet.

In the above-mentioned welding apparatus, spatter is likely to scatter around the welding location, and the printed surface of the can body is likely to be scratched or foreign matter may adhere. In particular, can body materials 1 printed with inorganic paints containing pigments such as titanium and lead
When welding, spatter easily scatters, and the spatter jumps into the processing head 3 from the nozzle 7 and collides with and adheres to the surface of the condenser lens 5, causing a problem in that it degrades lens performance or destroys the lens. be. Since the oscillation wavelength of the carbon dioxide laser belongs to the infrared region, the condenser lens 5 is made of a material with high infrared transmission efficiency and is expensive, and repair costs such as wrapping and recoating are also expensive. Preventing performance deterioration and destruction of the condensing lens 5 is an unavoidable matter in realizing mass production.

In order to avoid damage to the condensing lens 5 as described above, conventionally the opening diameter of the outlet 8 of the nozzle 7 is set as small as possible to prevent spatter from jumping into the nozzle 7.

[Problem that the invention attempts to solve]

The trajectory of the spatter is basically an inverted truncated cone shape, but due to the influence of the assist gas and the secondary and tertiary scattering caused by the collision of the spattered spatters, spatters are blown away toward the air outlet 8, and this is the condensing lens. It is presumed that this is the cause of the destruction of 5.

Therefore, even if the aperture diameter of the air outlet 8 is made smaller as described above, the degree of damage to the condensing lens 5 will only be slightly reduced, but the damage will not be eliminated, and the lens life will be approximately two weeks. It stopped at . In other words, even if the opening diameter of the air outlet 8 is simply made smaller, the probability that spatter will fly into the nozzle 7 will only slightly decrease.

The present invention has been proposed based on the above knowledge, and its main purpose is to reliably prevent damage to the condenser lens and realize mass production of can bodies by laser welding.

[Means for solving problems]

The can body manufacturing apparatus of the present invention has a pressurized air in the vicinity of the condenser lens 5 between the condenser lens 5 that converges the laser beam and focuses it on the workpiece, and the outlet 8 of the nozzle 7 that blows out the assist gas. Supply source 33
Dust exhaust nozzle 3 that blows out pressurized gas supplied from
1 and a dust exhaust section 32 for discharging the pressurized gas thereof are arranged to face each other, and the dust exhaust nozzle 31 is set so that the gas blowing direction is substantially perpendicular to the optical axis center 30 of the light collecting path 29. Yes, it is required that the optical axis center 30 of the condensing path 29 be set at an angle of 10 degrees or more from the perpendicular to the workpiece surface.

As the pressurized gas, in addition to air, an assist gas, a gas with a low vaporization temperature and excellent cooling properties, etc. can be used.

[Effect]

The flying energy of the spatter flying towards the condensing lens 5 becomes smaller as the flying distance becomes longer, that is, the closer it gets to the condensing lens 5. Therefore, by arranging the dust exhaust nozzle 31 and the dust exhaust section 32 facing each other near the condenser lens 5, the spatter flying towards the condenser lens 5 can be reliably blown away by pressurized gas. I can do it.

The reason why the gas blowing direction of the dust exhaust nozzle 31 is set to be almost perpendicular to the optical axis center 30 of the condensing path 29 is to make the path of spatter flying toward the condensing lens 5 the shortest distance and most efficient. change,
This is for discharging the dust through the dust removal section 32.

One reason why the optical axis center 30 of the condensing path 29 is set at an angle of 10 degrees or more from the perpendicular to the workpiece surface is because the main spatter scattering area is in the direction of the condensing lens 5. This is to prevent it from being included.

Further, by tilting the optical axis center 30, the shape of the beam spot of the laser beam on the workpiece surface is made into an ellipse, and a portion of the laser beam with low energy density can be created within the ellipse on the upper side in the feeding direction from the focal point center. This always ensures that there is a preheated area on the workpiece surface just before the center of focus of the beam spot hits, so it is effective in preventing sudden temperature changes on the workpiece surface and suppressing the occurrence of spatter to a minimum level.

[First Embodiment] FIGS. 1 to 6 show a first embodiment of the present invention.

In FIG. 2, a table 2 that supports a can body material 1 and a processing head 3 that irradiates a laser beam are arranged to face each other vertically.

The can body material 1 is made of a steel plate with a thickness of 0.1 to 0.4 mm, usually 0.2 mm, and is bent into a cylindrical shape in the previous process, and its circumferential edges 1a and 1b are guided by a jig (not shown). is polymerized and sent in the direction of arrow A. The can body material 1 sent out from the jig is supported by the table 2 and held in a welding position by workpiece pressing means 17 shown in FIG.

A condenser lens 5 is supported inside the processing head 3 via a cylindrical holder 4 and a lens mount 4a. A nozzle 7 for blowing out assist gas is attached to the lower end of the processing head 3 via a nozzle holder 6. The air outlet 8 of the nozzle 7 is surrounded by a cylindrical gas ring 9. A laser beam generated by a laser oscillation source (not shown) is guided to a processing head 3, focused by a condenser lens 5, and focused on the workpiece surface facing the air outlet 8.

The nozzle holder 6 includes a partition base 11 and a retaining ring 1 which are fastened together to the lower edge of the processing head 3.
2, and a holder cylinder 13 that is sandwiched and supported between the upper and lower surfaces of the base 11 and the retaining ring 12. Attach the nozzle 7 to the inner surface of the holder cylinder 13 with a screw 14.
Secure by screwing it in place. By operating adjustment screws 15 screwed into three locations on the circumferential surface of the retaining ring 12, the nozzle 7 can be positioned in the radial direction via the holder tube 13. In the installed state, the tip of the gas ring 9 is made to slightly protrude from the air outlet 8. In addition, from the work surface to the air outlet 8
The height was 8 mm.

In FIG. 3, the workpiece pressing means 17 consists of presser discs 18, 18 which are provided at two opposite locations perpendicular to the feeding direction A of the can body material 1 with the nozzle 7 interposed therebetween.
It consists of support shafts 19, 19 that rotatably support the disk 18, and an attitude changing member 20. The presser disk 18 is formed into a disk shape, preferably a flat inverted mortar shape, and presses the can body material 1 against the table 2 with the lower surface of its periphery while rotating together, so that the edges 1a and 1b of the can body are slightly pressed against each other. Hold in a wrap welding position. The support shafts 19, 19 rotatably support the presser disks 18, 18 so that the presser disks 18, 18 are inclined upwardly.

The attitude changing member 20 includes a first arm 21 that orthogonally supports the support shaft 19 and a second arm 22 that supports this arm 21. The first arm 21 is a dovetail-shaped slide groove 23 provided in the second arm.
It is supported in a vertically slidable manner and fixed at an arbitrary sliding position with a bolt 24. The second arm 22 is supported around a bolt 26 screwed into the fixed wall 25 so as to be able to swing up and down. By adjusting the postures of both arms 21 and 22, the pressing posture of the presser disk 18 against the can body material 1 can be changed, and compared to the conventional material holding structure using rollers, the can body edge 1a,
By holding down the approach position of 1b, the position of the can body material 1 can be held more accurately. Note that the can body edges 1a and 1b may be welded together in abutted state.

In this invention, in order to prevent damage to the condenser lens 5 caused by flying spatter in the can body manufacturing apparatus as described above, the following measures against spatter were taken.

First, the central axis of the processing head 3 is tilted so that the optical axis center 30 of the light collecting path 29 is aligned with respect to the work surface.
Tilt by angle θ. Inclination angle θ is 10 to 35
degree range, preferably 10 to 15 degrees. Due to the inclination of the optical axis center 30, the shape of the beam spot at the focal point on the workpiece surface becomes elliptical as shown in FIG. do. As already mentioned, when the optical axis center 30 is perpendicular to the workpiece surface, the spatter spreads out in an inverted truncated cone shape, but by tilting the optical axis center 30 as described above, the main scattering of the spatter is prevented. The areas can be concentrated on the feeding direction A side. This results in
By locating the area where the problematic secondary and tertiary scattering occurs on the feeding direction A side from the outlet 8 of the nozzle 7, it is possible to reduce spatter from flying into the processing head 3 from the outlet 8.

As the focus center P is biased toward the feed direction A side of the elliptical beam spot, the energy density of the laser beam in the beam spot region on the upper side in the feed direction than the focus center P decreases slightly;
This helps to preheat the can body material 1 that is continuously fed, and can alleviate explosive temperature changes on the surface of the workpiece, thereby suppressing the occurrence of spatter. That is, before the can body material 1 reaches the melting temperature, the printed layer, oil, etc. on the surface of the workpiece are vaporized in the preheating region. Well, with the inclination of the optical axis center 30, the gas ring 9
The protruding end face is inclined parallel to the work surface.

Second, the dust removal nozzle 3 is placed facing the condensing path 29 near the condensing lens 5 and perpendicular to the optical axis center 30.
1 is attached to the machining head 3, and a dust exhaust section 32 is defined opposite the dust exhaust nozzle 31 so as to communicate from the inside of the machining head 3 to the outside. The dust exhaust nozzle 31 blows out pressurized air supplied from a separately provided pressurized air supply source 33. A cylindrical protector 34 with a bottom is provided on the lower surface of the dust exhaust nozzle 31, and a light passing window 35 is provided on the upper bottom wall of the protector 34.
is installed as close as possible to the condensing path 29 to prevent spatter from jumping into the condensing lens 5 side. Spatter flying from the light passing window 35 towards the condensing lens 5 is discharged from the blowing hole 31a of the dust removal nozzle 31.
The dust is blown away by pressurized air blown from the dust removal section 32 and forced out of the processing head 3 through the dust removal section 32. What should be noted here is that the condensing lens 5 is cooled by the blown air, and this also effectively prevents the lens 5 from being damaged by adhesion of spatter. In FIG. 2, reference numeral 31b represents an air outlet for cooling the lens.

In FIGS. 2 and 6, a groove 37 is formed on the circumferential surface of the nozzle 7 in the middle of the threaded part, and gas passages 38 communicating with the groove 37 are vertically formed at six circumferential locations on the wall of the nozzle 7. It is formed through the nozzle 7 so that each gas passage 38 communicates with the inside of the nozzle 7 and the outer surface of the nozzle 7 facing the gas ring 9 near the lower end of the nozzle 7 . By supplying the assist gas to the groove 37 through the gas supply passage 39 penetrating the cylinder wall of the holder cylinder 13, the assist gas is blown out from the lower end opening of the guide passage 38 to both the inner and outer surfaces of the nozzle 7. Nozzle 7
The gas blown out is focused at the blow-off port 8 and sprayed onto the workpiece surface in the form of a beam. Due to the partitioning action of the gas ring 9, the gas blown out of the nozzle 7 covers the outer circumferential surface of the welded portion in a cloud shape.

In the can body manufacturing apparatus as described above, can body edges 1a, 1
By performing the welding step b, it was possible to prevent the condenser lens 5 from being damaged by secondary or tertiary spatter.

[Modification example]

In the above embodiment, the optical axis center 30 is located at the can body material 1.
However, if only the jumping of spatter into the nozzle 7 is considered, it is not necessary to do so. It may be inclined either to the left or right with respect to A. Of course, it is also possible to make a compound inclination in the front-rear direction and the left-right direction. Further, the table 2 side may be inclined with respect to the optical axis center 30.

In the first embodiment, a dust suction pipe to which a vacuum pressure is applied may be placed adjacent to the nozzle 7 on the downstream side in the material feeding direction to prevent spatter from scattering.

The workpiece pressing means 10 can also be replaced with a conventional roller type one.

The laser oscillation method may be pulsed or continuous.

In both of the above embodiments, the laser beam is focused using a lens, but in some cases, the present invention may be applied to a concave mirror that focuses the laser beam. It is desirable that the shaft center 30 be inclined to the workpiece surface.

[Effect of idea]

In the present invention, first, the optical axis center 30 of the condensing path 29 is set at an angle of 10 degrees or more from the vertical to the workpiece surface, so that the occurrence of spatter can be minimized. However, regarding the spatter that did occur, the main scattering area did not include the direction of the condenser lens 5, so the amount of spatter flying toward the condenser lens 5 could be further reduced. Ta.

Furthermore, regarding spatter that flies toward the condenser lens 5 due to secondary scattering, tertiary scattering, etc., the spatter is removed by the pressurized gas blown out from the dust removal nozzle 31 just before the condenser lens 5, where the flying energy is the minimum. Since the dust is blown off in a direction substantially perpendicular to the optical axis center 30 of the light collecting path 29 and discharged through the dust removal section 32, almost no spatter can reach the light collecting lens 5.

That is, according to the present invention, damage to the condensing lens 5 caused by spatter can be reliably prevented, the life of the condensing lens 5 can be extended, and can bodies can be mass-produced by laser welding at low cost.

[Brief explanation of the drawing]

1 to 6 show a first embodiment of the present invention, FIG. 1 is a principle explanatory diagram illustrating the gist of the present invention, and FIG. 2 is a longitudinal sectional side view of a processing head in a can body manufacturing apparatus. , FIG. 3 is a longitudinal sectional front view showing the workpiece pressing means, FIG. 4 is an explanatory diagram showing the detailed shape of the beam spot, FIG. 5 is a sectional view taken along the line A-A in FIG. 2, and FIG. FIG. FIG. 7 is a schematic vertical sectional view of a processing head showing a second embodiment of the present invention. FIG. 8 is a longitudinal sectional view of a processing head showing a conventional example. 1... Can body material, 2... Table, 3... Processing head, 5... Condensing lens, 7... Nozzle, 8...
...Air outlet, 17... Work pressing means, 29... Light collection path, 30... Optical axis center, 31... Dust removal nozzle,
33...Pressure air supply source, A...Material feeding direction.

Claims (1)

[Claims for Utility Model Registration] Pressurized air is supplied to the vicinity of the condenser lens 5 between the condenser lens 5 that focuses the laser beam onto the workpiece and the outlet 8 of the nozzle 7 that blows out the assist gas. A dust exhaust nozzle 31 that blows out pressurized gas supplied from a source 33 and a dust exhaust section 32 that exhausts the pressurized gas are arranged to face each other, and the dust exhaust nozzle 31 is arranged so that its gas blowing direction is in the direction of the light collecting path 29. It is set to be almost perpendicular to the optical axis center 30, and the optical axis center 30 of the light collecting path 29 is set to form an angle of 10 degrees or more with respect to the perpendicular to the workpiece surface. Can body manufacturing equipment.