Nozzle body

Abstract

A nozzle body for ejecting a slurry is provided, the nozzle body being capable of having reduced air consumption and improving processing speed. The nozzle body comprises: a slurry introduction port for introducing a slurry obtained by mixing abrasive grains and a liquid; a pressurized-air introduction port for introducing pressurized air for ejecting the slurry from an ejection port; an air jet disposed at the fore end of the pressurized-air introduction port; a mixing chamber which communicates with the slurry introduction port and in which the air jet is disposed; and a cylindrical nozzle main body which has the ejection port formed in the leading end thereof and in which the other end faces the air jet inside the mixing chamber. The mixing chamber has a circular shape in a cross section orthogonal to the extension direction of the nozzle main body. The slurry introduction port is disposed offset from the center of the circular shape in the cross section orthogonal to the extension direction.

Description

Nozzle body

[0001] The present invention relates to a nozzle body that sprays an abrasive (e.g., a slurry made by mixing abrasive grains with a liquid such as water) onto a workpiece, and in particular to a nozzle body for wet blasting that uses an abrasive made by mixing slurry and air as the abrasive.

[0002] Conventionally, wet blasting, also known as wet blasting or liquid honing, involves preparing a slurry made by mixing liquid and abrasive grains, and spraying this slurry onto the workpiece using compressed air to treat the surface of the workpiece.

[0003] Here, wet blasting is used in various processes, and is carried out, for example, to remove oxide films (scales) formed on the surface of special steels during the hot rolling process before wire drawing and forging, and to remove fine scratches and surface layers formed on the surface of products after forging.

[0004] Various configurations of nozzle bodies for performing such wet blasting are known, and for example, a nozzle body (slurry jetting body) described in Patent Document 1 is known.

[0005] The nozzle body described in Patent Document 1 has a slurry passage section through which a slurry made by mixing abrasive grains with a liquid passes, and a compressed air passage section through which compressed air passes, the slurry discharged from the slurry passage section and the compressed air discharged from the compressed air passage section being mixed in a mixing chamber communicating with the compressed air passage section, and the slurry mixed with the compressed air is sprayed onto the workpiece from an end opening of an injection section connected to the mixing chamber, and the end opening of the compressed air passage section located within the mixing chamber is composed of a plurality of small holes.

[0006] The nozzle body described in Patent Document 1 has an end opening of the compressed air passage portion that is composed of multiple small holes, making it extremely practical, as it can quickly and effectively wet blast the surface of the object to be treated.

[0007] JP 2017-18329 A

[0008] However, although conventional nozzle bodies are capable of quickly and effectively wet-blasting the surface of workpieces and are highly practical, as the types and numbers of workpieces to be treated increase, further improvements in processing performance are required, such as reducing air consumption and improving processing speed.

[0009] Regarding such a demand, the inventors of the present invention have conducted extensive research and have found the following: In a conventional nozzle body, as shown in Figure 10(a), a pressurized air inlet 120 and a slurry inlet 130 are each connected to a mixing chamber 140, and the slurry inlet 130 opens toward an air jet 121 disposed in the mixing chamber 140, and as shown in Figure 10(b), the slurry introduced from the slurry inlet 130 collides with the air jet 121 within the mixing chamber 140. At this time, the flow of the slurry is distributed to the left and right of the air jet 121, and is dispersed within the mixing chamber 140, causing turbulence in the flow of the slurry within the mixing chamber 140, and this turbulence has led to the finding that the pressure loss of the slurry is increased.

[0010] Therefore, we have come to the conclusion that by preventing such turbulence in the slurry flow within the nozzle body 100 and optimizing the dimensions of the pressurized air and slurry flow paths in the nozzle body, it may be possible to solve the problems of further reducing air consumption and improving processing speed.

[0011] The present invention has been made to solve the above-mentioned problems, and aims to provide a nozzle body that can reduce the amount of air consumed by the nozzle body that sprays slurry and improve the processing speed, and a blasting method using this nozzle body.

[0012] The nozzle body of the present invention, which solves the above-mentioned problems, comprises a slurry inlet through which a slurry of abrasive grains and a liquid is introduced, a pressurized air inlet through which pressurized air is introduced to inject the slurry from an injection port, an air jet arranged at the tip of the pressurized air inlet, a mixing chamber connected to the slurry inlet and in which the air jet is arranged, and a cylindrical nozzle body having the injection port formed at its tip and the other end facing the air jet within the mixing chamber, wherein the mixing chamber is formed in a circular shape in a cross section perpendicular to the extension direction of the nozzle body, and the slurry inlet is arranged offset from the center of the circle in the cross section perpendicular to the extension direction.

[0013] In the nozzle body according to the present invention, it is preferable that the slurry inlet is disposed on the base side of the air jet disposed in the mixing chamber.

[0014] In the nozzle body according to the present invention, it is preferable that the pressurized air inlet is disposed approximately coaxially with the nozzle main body.

[0015] In the nozzle body according to the present invention, it is preferable that the ratio of the inner diameter of the injection port to the distance from the other end of the nozzle body to the tip of the air jet is 0.75 to 1.25.

[0016] In the nozzle body according to the present invention, it is preferable that the other end side of the nozzle main body has a nozzle angle forming portion that is inclined so as to reduce in diameter along the extension direction of the nozzle main body.

[0017] In the nozzle body according to the present invention, it is preferable that the inclination angle of the nozzle angle forming portion is 10° to 30°.

[0018] According to the nozzle body and the blasting method using this nozzle body of the present invention, the slurry inlet is positioned offset from the center of the circular cross-sectional shape of the mixing chamber. Therefore, the slurry introduced from the slurry inlet swirls around the inner wall of the mixing chamber before being sprayed from the spray nozzle. This prevents the slurry from directly colliding with the air jet, causing turbulence in the flow within the mixing chamber. This reduces the pressure loss of the slurry, making it possible to reduce air consumption, shorten processing time, and improve the uniformity of processing quality.

[0019] 1 is a perspective view of a nozzle body according to an embodiment of the present invention; an A-A cross-sectional view in FIG. 1; a B-B cross-sectional view in FIG. 2; a graph showing air consumption and machining time for a nozzle body according to an embodiment of the present invention; a graph showing the effect of the ratio of nozzle position and nozzle diameter on performance for a nozzle body according to an embodiment of the present invention, where (a) shows the air consumption ratio and (b) shows the machining time ratio for a conventional nozzle body; a graph showing the effect of nozzle angle on performance for a nozzle body according to an embodiment of the present invention, where (a) shows the air consumption ratio and (b) shows the machining time ratio for a conventional nozzle body; a graph showing the amount of scraping, air consumption, and machining time depending on the ratio of air flow rate and slurry flow rate for a nozzle body according to an embodiment of the present invention; a graph showing the performance of a nozzle body according to an embodiment of the present invention and a conventional nozzle body; a graph showing the scraping depth and uniformity for a nozzle body according to an embodiment of the present invention, where (a) shows an example (nozzle body according to the present embodiment) and (b) shows a comparative example (conventional nozzle body); a cross-sectional view of a conventional nozzle body.

[0020] Preferred embodiments for carrying out the present invention will be described below with reference to the drawings. Note that the following embodiments do not limit the inventions according to the claims, and not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[0021] FIG. 1 is a perspective view of a nozzle body according to an embodiment of the present invention, FIG. 2 is a cross-sectional view taken along line A-A in FIG. 1, FIG. 3 is a cross-sectional view taken along line B-B in FIG. 2, FIG. 4 is a graph showing the air consumption and machining time of the nozzle body according to an embodiment of the present invention, FIG. 5 is a graph showing the effect of the ratio of the nozzle position and the nozzle diameter of the nozzle body according to an embodiment of the present invention on performance, where (a) is a graph showing the air consumption ratio and (b) is a graph showing the machining time ratio compared to a conventional nozzle body, and FIG. 6 is a graph showing the effect of the nozzle angle of the nozzle body according to an embodiment of the present invention on performance, where (a) is a graph showing the air consumption ratio and (b) is a graph showing the machining time ratio. 7 is a graph showing the amount of scraping, air consumption, and processing time depending on the ratio of air flow rate to slurry flow rate of the nozzle body according to the embodiment of the present invention; FIG. 8 is a graph showing the performance of the nozzle body according to the embodiment of the present invention and a conventional nozzle body; FIG. 9 is a graph showing the scraping depth and uniformity of the nozzle body according to the embodiment of the present invention, where (a) is a graph showing an example (the nozzle body according to the present embodiment) and (b) is a graph showing a comparative example (the conventional nozzle body); and FIG. 10 is a cross-sectional view of the conventional nozzle body.

[0022] As shown in Figure 1, a nozzle body 10 according to this embodiment is suitable for use in a wet blasting treatment apparatus (not shown). The wet blasting treatment apparatus sprays abrasives S onto the surface of a workpiece held in a treatment tank to perform surface treatment on the workpiece. The nozzle body 10 sprays the abrasives S from a spray nozzle 13 formed at the tip of a nozzle body 12. During wet blasting, the nozzle body 10 and the workpiece can move relative to each other, making it possible to perform wet blasting on the entire surface of the workpiece.

[0023] It is preferable to use a slurry, which is a mixture of liquid and abrasive grains, as the abrasive material S. The liquid contained in the slurry serves to transport the abrasive grains, which will be described later, to the surface of the workpiece. Therefore, any liquid can be used as long as it can fulfill this role, except for flammable substances. Specifically, it is preferable to use water from the viewpoints of environmental considerations and cost.

[0024] The abrasive grains are carried to the surface of the workpiece by the liquid and serve to perform the desired processing on the surface of the workpiece, so any abrasive grains can be used as long as they can perform this function.

[0025] Specifically, the material of the abrasive grains can be ceramic, resin, metal, etc., and more specifically, alumina, glass, zirconia, stainless steel, etc. The shape of the abrasive grains can be polygonal, spherical, true spherical, etc. The size of the abrasive grains can be appropriately selected from about 1 μm to about 300 μm.

[0026] The proportion of abrasive grains in the entire slurry is not particularly limited and can be appropriately designed depending on the material and processing area of ​​the workpiece, as well as the desired degree of processing. For example, a high concentration of 30 vol% (72 wt%) or more of the total volume of the slurry is preferable. In this case, stress can be applied to the workpiece more effectively and efficiently.

[0027] In addition to the liquid and abrasive grains, the slurry may contain additives with various functions, such as a rust inhibitor. By including a rust inhibitor in the slurry used in the wet blasting method, it is possible to impart rust prevention effects to the surface of the workpiece while simultaneously subjecting it to conventional wet blasting. Instead of the rust inhibitor, various additives may be added to the slurry to the extent that they do not impair the effects of the other components.

[0028] The nozzle body 10 according to this embodiment includes a housing 11 in which a pressurized air inlet 20 and a slurry inlet 30 are formed, and a nozzle main body 12 fixed to the lower end of the housing 11 via fixing means 16. The fixing means 16 is a member that is screwably attached to the lower end of the housing 11, and fixes the housing 11 and the nozzle main body 12 by clamping a flange 17 formed on the outer periphery of the nozzle main body 12. A spacer 18 is interposed between the housing 11 and the flange 17, and by changing the thickness of the spacer 18, it is possible to change the nozzle position L, which will be described later.

[0029] The pressurized air inlet 20 is formed above the housing 11 so that pressurized air is introduced in a direction substantially parallel to the direction of injection of the abrasives S injected from the injection port 13 formed at the tip of the nozzle body 12, and the slurry inlet 30 is formed on the side surface of the housing 11 so that slurry is introduced in a direction substantially perpendicular to the pressurized air inlet 20. In other words, it is preferable that the pressurized air inlet 20 is disposed substantially coaxially with the nozzle body, which will be described later.

[0030] The pressurized air inlet 20 and the slurry inlet 30 are each formed in a cylindrical shape, and a pressurized air inlet hose and a slurry inlet hose (not shown) are attached to them. In this embodiment, the pressurized air inlet 20 and the slurry inlet 30 are described as openings that are formed in the housing 11 and communicate with a mixing chamber 40 (described later).

[0031] 2, a mixing chamber 40 is formed within the housing 11, and an air jet 21 attached to the tip of a pressurized air inlet 20 is disposed in the mixing chamber 40. A nozzle body 12 is attached to the tip of the mixing chamber 40 so as to face the air jet 21, and a slurry inlet 30 opens into the inner wall of the mixing chamber 40.

[0032] The nozzle body 12 is a roughly cylindrical member with an injection passage 14 penetrating therethrough, with an injection port 13 formed at the tip end and a funnel-shaped nozzle angle forming portion 15 formed at the base end that is inclined so that its diameter decreases in the extension direction of the injection passage 14. The inclination angle of the nozzle angle forming portion 15 (hereinafter referred to as the "nozzle angle θ") is preferably set to 10° to 30°.

[0033] Furthermore, it is preferable that the distance between the air jet 21 and the base end face of the nozzle body 12 (hereinafter referred to as the "nozzle position L") is positioned so that the ratio to the nozzle diameter φ, which is the inner diameter of the injection port 13, is 0.75 to 1.25.

[0034] 3, mixing chamber 40 is formed in a circular shape in a cross section perpendicular to the extension direction of nozzle body 12, and slurry inlet 30 is disposed on its inner wall, offset from the center of the circle. It is preferable that slurry inlet 30 is disposed so that the inflow direction of the slurry introduced from slurry inlet 30 coincides with the tangent direction of the circle of mixing chamber 40.

[0035] As shown in FIG. 2, the slurry inlet 30 is preferably disposed close to the base of the air jet 21 disposed in the mixing chamber 40 (the left end side of the mixing chamber 40 in FIG. 2).

[0036] Furthermore, pressurized air injection ports 22, 23 for injecting pressurized air are formed at the tip of the air jet 21, and the air jet 21 has a first hole portion 22 arranged in the center of the air jet 21 and a plurality of second hole portions 23 arranged circumferentially of the first hole portion 22.

[0037] In the nozzle body 10 configured in this manner, the slurry introduced into the mixing chamber 40 swirls along the inner wall of the mixing chamber 40, so that the flow within the mixing chamber 40 is not disturbed and the pressurized air injected from the air jet 21 can efficiently inject the abrasives S from the injection port 13. Furthermore, because the slurry inlet 30 opens at the base side of the air jet 21 arranged in the mixing chamber 40, the slurry can swirl along the axial direction from the base end to the tip end within the mixing chamber 40, so that the flow of the slurry is not disturbed.

[0038] Furthermore, the nozzle body 10 according to this embodiment is set so that the ratio between the nozzle angle θ and the nozzle position L and the nozzle diameter φ is optimal, which makes it possible to improve processing performance, such as reducing the amount of pressurized air consumed and processing time, and improving the processing quality of the sprayed abrasive material S.

[0039] [Examples] Next, the present invention will be described in more detail with reference to examples. First, using the nozzle body 10 according to this embodiment, a wet blasting treatment was performed by spraying abrasives S onto stainless steel (SUS304) as a workpiece under the following experimental conditions. Note that, as a comparative example, a conventional nozzle body 100 shown in Figure 10 was used and experiments were performed under the same experimental conditions.

[0040] [Experimental Conditions] The abrasive shot material used was a polygonal stainless steel shot material with a particle diameter of 140 μm. The slurry concentration was 15 vol%, the slurry pressure was 0.20 MPa, the pressurized air pressure was 0.40 MPa, the shot distance from the nozzle body to the workpiece was 100 mm, the shot angle was 90°, and the nozzle body and the workpiece were stopped relative to each other during the stop process. The shot duration was 30 seconds. The workpiece was a 3 mm thick, 50 mm square plate made of stainless steel (SUS304) as described above.

[0041] 4, when the nozzle body 10 according to this embodiment is projected, the air consumption ratio is 0.90 and the processing time ratio is 0.75, where the conventional nozzle body is set to 1, and it was confirmed that the air consumption and processing time were reduced. This is because, whereas conventionally, pressure loss occurs due to a sudden change in the flow direction of the slurry when the slurry collides with the air jet, the nozzle body 10 according to this embodiment generates a swirling flow of the slurry within the mixing chamber 40, thereby reducing pressure loss.

[0042] Next, the effect of the nozzle position L was confirmed. The effect of the nozzle position L was confirmed by setting the nozzle angle θ to 15° and the nozzle diameter φ to 12.5 mm, and adjusting the position of the nozzle body 12 to measure the relationship between the ratio of the nozzle position / nozzle diameter and the ratio of the air consumption amount and the processing time.

[0043] As shown in Figure 5, when comparing the air consumption and processing time with the comparative example, it was confirmed that the air consumption and processing time were shorter when the nozzle position / nozzle diameter was in the range of 0.16 to 1.36. It was also confirmed that processing performance was improved particularly in the range of 0.75 to 1.25.

[0044] Next, the effect of the nozzle angle θ was confirmed. To confirm the effect of the nozzle angle θ, the nozzle diameter was set to φ12.5 mm, the nozzle position L was set to 12 mm, which was the optimal range confirmed by the nozzle position L described above, and the nozzle angle θ was adjusted to measure the relationship between the nozzle angle θ and the ratio of air consumption to processing time.

[0045] As shown in Figure 6, when comparing the air consumption and processing time with the comparative example, it was confirmed that the air consumption and processing time were shorter when the nozzle angle was in the range of 15° to 80°. This is thought to be due to the effect of the swirling flow in the mixing chamber 40. It was also confirmed that processing performance was further improved, especially in the small angle range, preferably in the range of 10° to 30°.

[0046] Next, the trends of the air flow rate of the pressurized air introduced through the pressurized air inlet 20 and the slurry flow rate of the slurry introduced through the slurry inlet 30 were measured. These measurements were carried out with the nozzle diameter φ set to 12.5 mm, the nozzle position L set to 12 mm, and the nozzle angle θ set to 15°, which are the ranges considered optimal for the nozzle position L and nozzle angle θ described above, and by adjusting the flow path cross-sectional area ratio by increasing or decreasing the opening diameters of the pressurized air inlet 20 and the slurry inlet 30. Note that in this example, the air flow rate and the slurry flow rate were changed by changing the opening diameters of the pressurized air inlet 20 and the slurry inlet 30, but similar effects can be confirmed by changing the pressurized air pressure or the slurry pressure.

[0047] As shown in Figure 7, in terms of the tendency according to the flow rate ratio, it was confirmed that the amount of removal, which measured how much of the workpiece was removed per minute, was greatest when the flow rate ratio was around 320. It was also confirmed that the air consumption and processing time were minimum when the flow rate ratio was around 320, and when air consumption and processing time were taken into consideration, it was confirmed that processing performance improved when the flow rate ratio was around 320. It was also confirmed that when the flow rate ratio was set to 280 to 370, wet blasting processing could be performed with the best amount of removal, air consumption, and processing time.

[0048] 8, the flow paths were configured with the opening diameter of the pressurized air inlet 20 set to φ10 mm, the opening diameter of the slurry inlet 30 set to φ12 mm, and a cross-sectional area ratio of 0.69, and the results of wet blasting were shown, where processing was performed under the above-mentioned experimental conditions of pressurized air pressure and slurry pressure, resulting in a flow rate ratio of 327. In this case, it was confirmed that the amount of removal was improved by 53%, air consumption was reduced by 23%, and processing time was reduced by 35%, demonstrating a significant improvement in processing performance compared to the comparative example.

[0049] Thus, it was confirmed that the wet blasting method using the nozzle body 10 according to this embodiment provides the most excellent processing performance when the flow rate ratio is set to 280 to 370.

[0050] Furthermore, as shown in FIG. 9, when the difference in the amount of scraping in the X direction (horizontal direction) and Y direction (vertical direction) of the processing surface of the workpiece was examined, it was confirmed that in the comparative example, as shown in (b), there was a deviation in the scraping depth in the X direction and the Y direction from the center (directly below the injection nozzle) toward the radial direction, whereas, as shown in (a), with the nozzle body 10 according to this embodiment, there was no deviation in the X direction and the Y direction, and it was possible to perform uniform processing in a state close to a perfect circle in the radial direction from the center of the workpiece.

[0051] It was confirmed that the nozzle body 10 according to this embodiment configured in this manner has improved processing performance, such as an improved amount of scraping, reduced air consumption, and reduced processing time, compared to conventional nozzle bodies.

[0052] Furthermore, the nozzle body 10 according to this embodiment has been described as having a pressurized air outlet for the air jet with the first hole portion 22 and the second hole portion 23, but the pressurized air outlet for the air jet is not limited to this, and various conventionally known air jets can be used.

[0053] Furthermore, the nozzle body 10 according to this embodiment has been described with the pressurized air introduced from the pressurized air inlet 20 arranged in a direction substantially parallel to the injection direction of the abrasives S, but the direction of the pressurized air introduction is not limited to this and may be introduced in a direction intersecting the injection direction. Furthermore, in the examples, the flow rate ratio trend has been described with an air pressure of 0.4 MPa and a slurry concentration of 15 vol%, but the optimal flow rate ratio may be changed depending on the injection pressure and concentration. It is clear from the claims that such modified or improved embodiments are also included within the technical scope of the present invention.

[0054] REFERENCE SIGNS LIST 10 nozzle body, 11 housing, 12 nozzle main body, 13 injection port, 14 injection passage, 15 nozzle angle forming portion, 16 fixing means, 20 pressurized air inlet, 21 air jet, 22 first hole portion, 23 second hole portion, 30 slurry inlet, 40 mixing chamber, S injection material.

Claims

1. A nozzle body comprising: a slurry inlet through which a slurry of abrasive grains and liquid is introduced; a pressurized air inlet through which pressurized air is introduced to inject the slurry from an injection port; an air jet located at the tip of the pressurized air inlet; a mixing chamber connected to the slurry inlet and in which the air jet is located; and a cylindrical nozzle body at the tip of which the injection port is formed and at the other end of which faces the air jet within the mixing chamber, wherein the mixing chamber is formed in a circular shape in a cross section perpendicular to the extension direction of the nozzle body, and the slurry inlet is located offset from the center of the circle in the cross section perpendicular to the extension direction.

2. A nozzle body according to claim 1, characterized in that the slurry inlet is arranged on the root side of the air jet arranged in the mixing chamber.

3. A nozzle body according to claim 1, characterized in that the pressurized air inlet is arranged approximately coaxially with the nozzle main body.

4. A nozzle body as described in claim 1, characterized in that the ratio of the inner diameter of the injection port to the distance from the other end of the nozzle body to the tip of the air jet is 0.75 to 1.

25.

5. A nozzle body as set forth in claim 4, characterized in that the other end of the nozzle body has a nozzle angle forming portion that is inclined so as to reduce in diameter along the extension direction of the nozzle body.

6. A nozzle body according to claim 5, characterized in that the inclination angle of the nozzle angle forming portion is 10° to 30°.

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