Laser processing equipment

Abstract

To provide a laser beam machining apparatus capable of appropriately performing welding by a laser beam.SOLUTION: A laser beam machining apparatus is such that: Ar gas is discharged to a weld zone 12 of a workpiece 1 from an inert gas supply hole outlet of a first press jig 20 when irradiating the workpiece 1 supported by a receiving jig with a laser beam from a laser weld head 15; air supplied from a secondary air intake port 33 of a second press jig 30 forms a swirl flow of dust and air on a top face of the workpiece 1; a dust collection duct 39 for discharging dust and air after formation of a swirl flow to the outside is disposed; and a swirl flow of dust and air generated from the weld zone 12 of the workpiece is formed at an opposite gravity direction side of the workpiece so as to reduce the generation of fume and plume. Then, attenuation of a laser beam emitted to the workpiece is suppressed, and a weldment depth by a laser beam is prevented from becoming shallow to stabilize the quality of a laser welded product.SELECTED DRAWING: Figure 1

Description

Technical Field

[0005]

[0001] The present invention relates to a laser processing apparatus that processes a workpiece using a laser beam.

Background Art

[0002] When performing laser welding, fumes (smoke) are generated. If a fume accumulation occurs, due to the attenuation of the laser beam, the welding depth of the welded portion of the workpiece irradiated with the laser beam becomes shallower.

[0003] In Patent Document 1, as a method and apparatus for removing fumes generated during laser processing, there is provided a processing gas supply nozzle that supplies a processing gas toward the processing position, and a fume exhaust gas supply nozzle that supplies a fume exhaust gas above the processing gas atmosphere with respect to the fumes generated from the processing position while supplying the processing gas. This document discloses a technique of providing a gas jacket that rectifies the flow of the supplied gas downstream of the fume exhaust gas supply nozzle, or providing a side wall that guides the supplied fume exhaust gas flow in a certain direction.

[0004] In Patent Document 2, as a welding fume dust collection apparatus, there is provided a suction port that sucks air containing welding fumes F, a metal filter through which the inflowing air passes and removes the welding fumes F in the air, an electrostatic precipitator through which the air that has passed through the metal filter passes and removes the welding fumes F remaining in this air, an exhaust port that discharges the air that has passed through the electrostatic precipitator, a vibrator that vibrates the metal filter, an air nozzle that injects air into the electrostatic precipitator, and a welding fume storage portion that stores the welding fumes F collected by the metal filter and the electrostatic precipitator.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

[0006] Conventional laser welding equipment often welds horizontally (from the side) rather than in the direction of gravity, taking into account the attenuation of laser light by fumes and other factors. When welding is performed by irradiating with laser light from the side, the two workpieces to be welded, which are aligned horizontally, tend to become relatively eccentric, making it difficult to ensure coaxiality. Furthermore, the gap between the two workpieces being joined tends to become larger, which can easily lead to a decrease in the quality of the welded product. On the other hand, when a welding laser beam is shone onto a workpiece in the direction of gravity, the welding depth tends to become shallower due to the attenuation of the laser beam caused by the accumulation of fumes (smoke) and the attenuation of the laser beam caused by the generation of plumes (flames), resulting in unstable quality of the welded product.

[0007] Patent Document 1 does not explicitly describe a plurality of secondary air intake ports arranged to blow air that creates a spiral dust collection pattern upwards relative to the welding position of the workpiece. Patent Document 2 discloses a dust collector for collecting fumes, but this device discloses a method for removing welding fumes generated after welding, and does not disclose the relationship between the path of the laser beam during welding and the welding fumes.

[0008] The present invention has been made in view of the above, and its object is to provide a laser processing apparatus capable of performing welding by laser light appropriately. [Means for solving the problem]

[0009] The laser processing apparatus of the present invention is A laser processing apparatus that welds a workpiece by irradiating it with laser light, A support fixture (9) that supports the workpiece (1), The receiving jig has a first through-hole (25) through which welding laser light passes, and a first pressing jig (20) that holds the workpiece from the side opposite the receiving jig, A second pressing jig (30) has a second through hole (35) that communicates with the first through hole, and presses the first pressing jig against the receiving jig from the side opposite the receiving jig of the first pressing jig, The device comprises a laser beam path (41, 51) communicating with the first through hole and the second through hole, and a dust collection duct (39, 40, 50) communicating with the laser beam path and having an outlet (53) for discharging dust generated from the welded part (12) of the workpiece to the outside, The first pressing jig has inert gas supply port outlets (231, 232, 233, 234, 235) for supplying inert gas, The second pressing jig employs a configuration that includes secondary air intake ports (331, 332, 333, 334, 335, 336, 337, 338, 339) that draw in secondary air and generate a swirl-like swirling flow in the laser beam path. The laser processing apparatus of the present invention employs a configuration that eliminates factors that attenuate laser light.

[0010] According to the present invention, since the first and second pressing jigs press the workpiece from the side opposite the receiving jig that the receiving jig supports, it is easy to overlap the workpieces to be welded in the direction of gravity. As a result, the central axes of both workpieces are less likely to be eccentric, and it is easier to ensure coaxiality.

[0011] According to the present invention, when a laser beam is irradiated onto a workpiece from a laser welding head, an inert gas supply port outlet is provided that corresponds to an outlet for discharging an inert gas such as Ar gas toward the welding area of ​​the workpiece, and a dust collection duct is provided that discharges the dust and air supplied from a secondary air intake port, which forms a swirling flow of dust and air on the upper surface of the workpiece, to the outside after the swirling flow has been formed. This creates a swirling flow of dust and air generated from the weld area of ​​the workpiece on the anti-gravity side of the workpiece, thereby reducing the generation of fumes and plumes. Consequently, it suppresses the attenuation of the laser light irradiated onto the workpiece. This prevents the welding depth from becoming too shallow due to the laser light. Therefore, the quality of laser-welded products can be stabilized.

[0012] The laser processing method of the present invention is a laser processing method for irradiating a laser beam onto a welding portion (12) of an upper workpiece (2) to join the upper workpiece and a lower workpiece (3), and includes a step of irradiating a laser beam onto the welding portion of the upper workpiece, a step of supplying an inert gas and air to the welding portion of the upper workpiece, a step of sucking air on the upper surface side of the upper workpiece to the outside, a step of forming a swirling flow of dust and air above the upper surface side of the upper workpiece, and a step of discharging the air after the swirling flow to the outside.

Brief Description of the Drawings

[0013] [Figure 1] Cross-sectional view showing a laser processing apparatus according to an embodiment, [Figure 2] Partial cross-sectional view showing a workpiece and a laser welding apparatus according to an embodiment, [Figure 3] Schematic perspective view of a dust collection duct according to an embodiment, [Figure 4] Enlarged cross-sectional view taken along line IV-IV of FIG. 1, [Figure 5] Cross-sectional view showing a receiving jig, a workpiece, a first pressing jig, and a second pressing jig according to an embodiment, [Figure 6] Perspective view showing a first pressing jig and a second pressing jig according to an embodiment, [Figure 7] Plan view of the first pressing jig and the second pressing jig shown in FIG. 6, [Figure 8] Cross-sectional view taken along line VIII-VIII of FIG. 7, [Figure 9] Perspective view of a first pressing jig according to an embodiment, [Figure 10] Plan view of a first pressing jig according to an embodiment, [Figure 11] Cross-sectional view taken along line XI-XI of FIG. 10, [Figure 12] Perspective view of a second pressing jig according to an embodiment, [Figure 13] Plan view of a second pressing jig according to an embodiment, [Figure 14] Cross-sectional view taken along line XIV-XIV of FIG. 13, [Figure 15]A diagram showing the welding spots on the workpiece. [Figure 16] Enlarged cross-sectional view showing plume formation in the welded area. [Figure 17] An explanatory diagram showing the process during welding. [Figure 18] A comparative diagram of the comparative example and the experimental example. [Modes for carrying out the invention]

[0014] Hereinafter, a laser processing apparatus according to an embodiment of the present invention will be described with reference to the drawings. In addition, substantially identical components in multiple embodiments will be denoted by the same reference numerals, and their descriptions will be omitted. (First Embodiment) A first embodiment of the present invention will be described with reference to Figures 1 to 18. First, we will explain workpiece 1, which is to be welded by irradiating it with laser light, based on Figures 2 and 5. Workpiece 1 consists of a bottomed cylindrical upper workpiece 2 and a basic cylindrical lower workpiece 3. The lower workpiece 3 has a basic cylindrical shape with a disc-shaped flange 4 formed on its upper part. The lower surface 5 of the flange 4 is supported by the end surface 10 of a cylindrical support jig 9. The inner bottom surface 6 of the upper workpiece 2 covers the upper surface 7 of the flange 4 of the lower workpiece 3.

[0015] In this embodiment, the inner bottom surface 6 of the upper workpiece 2 and the upper surface 7 of the lower workpiece 3 are laser-welded at five welding points 12, as shown in Figure 15. The welding points 12, which correspond to the welding locations, are located at five equally spaced positions on the outer bottom surface 8 of the upper workpiece 2, around the coaxial center. The laser processing device 14 for welding the upper workpiece 2 and the lower workpiece 3 is equipped with a laser welding head 15 that irradiates laser light and a support jig 9 that supports the lower workpiece 3 at a position below it by gravity. The support jig 9 is cylindrical with an open top, and its upper end surface 10 supports the lower surface 5 of the flange 4 of the lower workpiece 3. The upper workpiece 2 has its inner bottom surface 6 in contact with the upper surface 7 of the flange 4 of the lower workpiece 3. The outer circumferential surface 131 of the flange 4 that forms the upper end surface 10 of the support jig 9 is in contact with the inner wall surface of the cylinder of the upper workpiece 2. This aligns the axes of the lower workpiece 3 and the upper workpiece 2, ensuring coaxiality during welding of the workpiece 1. The lower workpiece 3 and upper workpiece 2 are placed on the upper end surface 10 of the receiving jig 9, the first pressing jig 20 is pressed down on the upper workpiece 2 from above, and the second pressing jig 30 is pressed down on the first pressing jig 20 to temporarily fix the workpiece 1 in place.

[0016] The first pressing jig 20 will be described based on Figures 1, 2, 4, 5, and 6-11. The main body 21 of the first pressing jig 20 has an opening 25 that connects the upper surface and the lower surface, with the lower surface of the main body 21 in contact with the upper surface of the upper workpiece 2, exposing five welded joints 12 on the upper surface 7. The main body 21, which has an opening that exposes the welded joints 12, has inclined surfaces 221, 222, 223, 224, and 225 formed around the welded joints 12 so as to form an opening that allows laser light to pass through. As an example shown in Figure 5, the inert gas supply port is configured by connecting a hole 251 formed in the body 31 of the second pressing jig 30, a hole 252 formed in the body 21 of the first pressing jig 20, an air vent 253, and an inert gas supply port outlet 231. The distance (L) between each adjacent weld 12 and the five inert gas supply port outlets 231, 232, 233, 234, and 235 is set to 20 mm. The inert gas, such as Ar gas, supplied to the opening 25 from the inert gas supply port outlets 231, 232, 233, 234, and 235 of the inert gas supply port is supplied in the direction of the white arrow shown in Figure 5, and covers the five weld 12 locations. Note that the inert gas supply port outlets 231, 232, 233, 234, and 235 may be indicated as reference numeral 23 for convenience in this specification.

[0017] The second pressing jig 30 will be described based on Figures 1, 2, 4, 5, 6-8, and 12-14. The main body 31 of the second pressing jig 30 has an inner wall that forms an opening 35 connecting its upper and lower surfaces, and an outer wall that has a conical convex slope 32 that fits into the conical concave slope 22 of the main body 21 of the first pressing jig 20. This ensures coaxiality between the first pressing jig 20 and the second pressing jig 30. The secondary air intake ports 331, 332, 333, 334, 335, 336, 337, 338, and 339, formed at nine locations on the main body 31 of the second pressing jig 30, open with their central axis direction moving eccentrically from the center of the workpiece, and inclined upward as the central axis direction approaches the central axis of the workpiece. Note that, for convenience in this specification, the secondary air intake ports 331, 332, 333, 334, 335, 336, 337, 338, and 339 may be collectively referred to as the secondary air intake port 33. As shown in Figures 1 and 4, secondary air is supplied from the outside in the direction of the white arrow 34.

[0018] The dust collection duct 39 consists of a first dust collection duct 40 and a second dust collection duct 50. The first dust collection duct 40 has a basic cylindrical shape and contains a first dust collection chamber 41 through which laser light passes and exhaust gas flows. A swirling flow of exhaust gas is formed in this first dust collection chamber 41. The second dust collection duct 50 has the shape shown in Figure 3. Its basic form is cylindrical and it has an opening 54 through which the laser light emitted from the laser welding head 15 passes, a second dust collection chamber 51 that communicates with the first dust collection chamber 41, and a branch duct 52 that discharges dust generated from the welded part 12 during welding to the outside through an exhaust port 53. The branch duct 52, which has an exhaust port 53, is connected to an external suction device (not shown). When the suction device is activated during welding, dust generated from the weld 12 is carried by the secondary airflow in the openings 25, 35 and the first and second dust collection chambers 41 and 51 of the dust collection duct 39, and discharged to the outside through the exhaust port 53 of the branch duct 52.

[0019] The laser processing apparatus 14 described above has an opening 54 for passing welding laser light, a second dust collection chamber 51, a first dust collection chamber 41, and openings 35 and 25 on the non-joining surface side of the upper workpiece 2, and a first pressing jig 20 that presses the upper workpiece 2 and the lower workpiece 3 against the receiving jig 9 from the non-joining surface side of the upper workpiece 2, The system includes a second pressing jig 30 which presses the first pressing jig 20 against the receiving jig 9 from the opposite side of the first pressing jig 20. A dust collection duct 39 is provided on the upper surface of the second pressing jig 30. The dust collection duct 39 has an opening 54 corresponding to a hole through which laser light passes, a second dust collection chamber 51, and a first dust collection chamber 41.

[0020] The first pressing jig 20 has an inert gas supply hole 24 through which Ar gas, which is equivalent to an inert gas, passes. The outlet 23 of the inert gas supply hole is formed at a position spaced away from the welded portion 12, corresponding to the position where the laser beam is irradiated onto the upper workpiece 2. The distance between the outlet of the inert gas supply hole of the first pressing jig 20 and the welded portion 12 is set to be far enough to prevent overcooling, and short enough so that the inert gas concentration does not become diluted. The second pressing jig 30 has a secondary air intake port 33 that draws in secondary air and generates a spiral airflow at the opening 35. The air drawn in from the secondary air intake port 33 passes through the openings 25, 35 and the first and second dust collection chambers 41 and 51 of the dust collection duct 39, and is sucked into the suction device 60 along with the dust from the exhaust port 53.

[0021] The laser processing apparatus 14 described above has a large internal diameter for the dust collection chamber of the dust collection duct 39. The openings 25 and 35 that serve as the dust path, and the first and second dust collection chambers 41 and 51 of the dust collection duct 39, have large internal diameters. The maximum internal diameter rmax of the opening 35 of the second pressing jig 30 is larger than the outer diameter of the upper workpiece 2.

[0022] The secondary air intake ports 33 are located at multiple locations indicated by reference numerals 331, 332, 333, 334, 335, 336, 337, 338, and 339, and do not open near the welded area. The secondary air intake ports 33 function as secondary air intake ports, and in this case there are nine of them. When viewed from the inside, the direction of opening is such that the central axis direction is eccentric from the center of the workpiece, and the opening is inclined upward as the central axis direction approaches the central axis of the workpiece. Dust carried by the airflow from the openings 25 and 35 is uniformly scattered toward the first dust collection chamber 41 and the second dust collection chamber 51, and is discharged to the outside from the exhaust port 53, which corresponds to the suction port, and collected.

[0023] According to the laser processing apparatus 14 described above, the secondary air intake ports 331, 332, 333, 334, 335, 336, 337, 338, and 339 open eccentrically from the welding point in the center of the workpiece relative to the axis of the laser beam. The secondary air supplied from the secondary air intake ports 331, 332, 333, 334, 335, 336, 337, 338, and 339 to the opening 35 forms a spiral flow of secondary air within the relatively large dust collection duct 39. Dust carried by the rising airflow is quickly discharged from the exhaust port 53 without accumulating. Therefore, since fume buildup is less likely to occur, laser beam shielding is reduced, and the welding depth is stabilized.

[0024] Next, the plume generated during laser welding will be explained based on Figure 16. This diagram schematically illustrates the phenomenon of plume formation. Generally, when welding an upper workpiece 2 to a lower workpiece 3, if a laser beam is irradiated onto the welding spot 45 in the direction of gravity, a column-shaped plume 46 is likely to be generated in the anti-gravity direction of the welding spot 45.

[0025] In this embodiment, before the laser beam from the laser welding head 15 is irradiated onto the weld portion 12 of the workpiece, Ar gas is supplied from the inert gas supply port outlet 23 above the upper surface corresponding to the weld portion 12 of the upper workpiece 2, forming an Ar gas atmosphere above the upper surface of the weld portion 12 of the upper workpiece 2. Furthermore, since the secondary air intake port 33 opens in the anti-gravity direction and is inclined upwards compared to the inert gas supply port outlet 23, the secondary air is not directed towards the welding spot. Consequently, the welding spot is covered with Ar gas, and an inert atmosphere is formed at the welding spot, preventing the generation of a plume. This prevents attenuation of the laser beam, allows for proper laser welding, and enables stabilization without reducing the welding depth.

[0026] Since the secondary air intake port 33 is formed at a position away from the vicinity of the weld, an inert gas atmosphere is created near the weld, preventing the generation of a plume (flame column). Because a plume is less likely to occur, the laser beam is less likely to attenuate, and the welding depth is stabilized. Once laser processing is completed for one location of the weld 12, laser processing is started for the next location of the weld 12, and so on. When laser processing is completed for a total of five locations, the welding is completed.

[0027] Because a swirling flow is generated above the welding area (workpiece) by supplying secondary air, fume buildup is less likely to occur. As a result, dust is carried away by the swirling flow, reducing its influence on the laser beam and suppressing laser beam attenuation. Therefore, the welding depth can be stabilized without reducing the welding depth.

[0028] Furthermore, because a non-oxidizing region is formed by supplying an inert gas without excessive cooling, plume generation can be suppressed, laser light attenuation can be reduced, and the welding depth can be stabilized without reducing the welding depth. According to this embodiment, dust can be drawn in a spiral pattern towards the suction port by being carried by the secondary air supplied into the duct. Dust can be collected uniformly and quickly within the duct. Furthermore, according to this embodiment, since the components are divided into a first pressing jig and a second pressing jig, there are manufacturing advantages such as easier parts processing and assembly.

[0029] (Experimental Example 1) Experimental Example 1 and Comparative Example 1 will be explained in comparison. In Experimental Example 1, in the above embodiment, secondary air supplied to the opening 35 from multiple secondary air intake ports 33 generates a swirl-like swirling flow in the first dust collection chamber 41 and the second dust collection chamber 51, which have large inner diameters, dispersing the dust and rapidly discharging it from the exhaust port 53 as if blowing it upwards like a tornado. Flow analysis of the dust collection state of the CAD model revealed that, according to the improved simulation results from Experimental Example 1, dust was collected uniformly and quickly within the duct, as shown in Figure 18(B). In Figure 18, the arrows indicate the direction and velocity of the airflow within the dust collection duct.

[0030] Comparative Example 1 is the pre-improvement version, in which a jig (not shown) that holds the workpiece on its upper surface draws secondary air inward from the secondary air intake. When the dust collection state generated during welding is analyzed by flow analysis, the simulation results for Comparative Example 1, as shown in Figure 18(A), show that there are areas in the dust collection duct where down-blowing occurs in the airflow inside the duct, making it prone to fume buildup.

[0031] (Experimental Example 2) Experimental Example 2 and Comparative Example 2 will be explained in comparison. Experimental Example 2 is a configuration in the above embodiment in which Ar gas is evenly applied to multiple welds, covering the entire weld with Ar gas. Here, since Ar gas has a higher specific gravity than air, it is supplied from diagonally above toward the weld inside the opening 25. During laser welding, the weld is covered with an atmosphere filled with Ar gas to create a non-oxidizing region and prevent the generation of a plume. In Experimental Example 2, the separation distance (L) from the inert gas supply port outlet of the first clamping jig to the weld area was set to 20 mm. The separation distance (L) is set to be far enough to prevent overcooling of the weld area, but short enough to prevent the inert gas concentration from becoming too dilute. Ar gas is blown in from the inert gas supply port outlet to create an Ar gas-filled atmosphere around the weld area. This eliminates the formation of fume buildup through spiral dust collection and stabilizes the weld depth.

[0032] Comparative Example 2, although not shown in the figure, is an example in which a jig is provided to directly blow Ar gas onto the weld area from near the weld area of ​​the workpiece. Although Ar gas is supplied from the inert gas supply port of the jig, in Comparative Example 2 there were areas where the Ar gas contact was weak. A plume was generated in those areas. Here, a plume refers to a column of fire indicated by reference numeral 46 that is generated in a cylindrical shape above the weld area, as shown in Figure 16. When a plume 46 is generated, it attenuates the laser light irradiated onto the welding spot 45, resulting in a shallower weld depth.

[0033] (Other embodiments) The workpiece shown in the above embodiment is merely an example, and the shape of the workpiece may, of course, be anything else. In the present invention, the shape of the workpiece irradiated with laser light is not limited to the form shown in the above embodiment. In the above embodiment, the jig for temporarily fixing the workpiece to the receiving jig was composed of a first pressing jig and a second pressing jig, but of course, in the present invention, these first pressing jig and second pressing jig may be integrated into a single jig. In the above embodiment, nine secondary air intake ports were provided, but in the present invention, the number of secondary air intake ports is not limited. In the above embodiment, five inert gas supply holes were provided, but in the present invention, the number of inert gas supply holes is not limited. The shape and structure of the receiving jig of the present invention are not limited to those of the embodiments described above. As shown in Figure 17, the spiral dust collection function according to the present invention can be applied when it is desired to uniformly collect dust that is swirled in the airflow by swirling the airflow inside the duct 391, which corresponds to the dust collection duct 39.

[0034] As stated above, the present invention is not limited to the embodiments described above, and can be implemented in various forms without departing from its essence. [Explanation of symbols]

[0035] 1 work, 2. Upper work, 3. Lower work, 9. Receiving fixture, 12 Welded joints, 14. Laser processing equipment, 15 laser welding heads, 20 First pressing jig, 23 Inert gas supply port outlet, 24 Inert gas supply port, 25 opening (first hole), 30. Second pressing jig, 33 Secondary air intake, 35 opening (second through hole), 39 Dust collection duct, 40. First dust collection duct, 41. First dust collection chamber (laser beam passage), 50. Second dust collection duct, 51. Second dust collection chamber (laser beam passage), 53 Exhaust vent, 54 Aperture (laser beam path), 60 suction device, 251 holes (inert gas supply holes), 252 holes (inert gas supply holes), 253 air vents, 231-235 Inert gas supply port outlet, 331-339 Secondary air intake.

Claims

1. A laser processing apparatus that welds a workpiece by irradiating it with laser light, A support fixture (9) that supports the workpiece (1), The receiving jig has a first through-hole (25) through which welding laser light passes, and a first pressing jig (20) that holds the workpiece from the side opposite the receiving jig, A second pressing jig (30) has a second through hole (35) that communicates with the first through hole, and presses the first pressing jig against the receiving jig from the side of the first pressing jig opposite the receiving jig, The device comprises a laser beam path (41, 51) communicating with the first through hole and the second through hole, and a dust collection duct (39, 40, 50) communicating with the laser beam path and having an outlet (53) for discharging dust generated from the welded part (12) of the workpiece to the outside, The first pressing jig has inert gas supply port outlets (231, 232, 233, 234, 235) for supplying inert gas, The second pressing jig is a laser processing apparatus having secondary air intake ports (331, 332, 333, 334, 335, 336, 337, 338, 339) that draw in secondary air and generate a swirl-like swirling flow in the laser beam path.

2. The laser processing apparatus according to claim 1, wherein the distance (L) between the outlet of the inert gas supply hole of the first pressing jig and the welded portion is set to a distance that is far enough to prevent overcooling and short enough to prevent the inert gas concentration from becoming too dilute.

3. The laser processing apparatus according to claim 1 or 2, wherein the second pressing jig has the secondary air intake port whose central axis direction opens eccentrically from the center of the workpiece.

4. The laser processing apparatus according to claim 1 or 2, wherein the secondary air intake port of the second pressing jig opens with an inclination toward the sky as the central axis direction approaches the central axis of the workpiece.

5. The laser processing apparatus according to claim 1 or 2, further comprising a laser welding head (15) that emits laser light on the side of the dust collection duct opposite the pressing jig.

6. The laser processing apparatus according to claim 1 or 2, further comprising a suction device (60) on the discharge port side of the dust collection duct.

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