Patent Publication Number: US-10328441-B2

Title: Nozzle unit and coating apparatus including the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     A claim for priority under 35 U.S.C. § 119 is made to Korean Patent Application No. 10-2016-0052936 filed on Apr. 29, 2016 and Application No. 10-2016-0065580 filed on May 27, 2016 in the Korean Intellectual Property Office, the entire contents of which are hereby incorporated by reference. 
     BACKGROUND 
     This disclosure relates to a nozzle unit where a fluid including a coating material is sprayed and a coating apparatus including the same. 
     Cold spray coating is one of a spray coating method which applies coating by spraying a powder which needs to be coated. Cold spray coating is a process of applying coatings to a material by spraying with high velocity using collision energy with basic material in a room temperature where the material reacts or its coordination does not change, or in a low temperature. 
       FIG. 1  is a lateral cross-sectional view briefly illustrating inside of a nozzle  1  of a conventional coating apparatus. Referring to  FIG. 1 , a cold spray coating apparatus supplies a powder and a gas to the nozzle  1 . The gas provides a pressure to spray powders. A flow velocity of the gas including powders is the highest in a center  2  of the nozzle  1  by its viscosity. The velocity of the gas decreases as moving to inner lateral wall  3  of the nozzle  1 , and gets close to 0 when the gas reaches an area adjacent to the inner lateral wall  3  of the nozzle  1 . Due to decrease in velocity, it requires a gas with higher pressure thereby lowering energy efficiency. Also, powder particles moving along the inner lateral wall  3  adjacently have lower momentum. Upon impact with a basic material, the particles experience elastic collision which occur no coatings or some coatings thereby causing a Void and losing the coating material. Therefore, cold spray coating requires long time to form a coating layer due to loss of the coating material and is not simple to form coating layer over certain thickness. 
     SUMMARY 
     An embodiment includes an apparatus to prevent decrease in a flow velocity in an area adjacent to an inner lateral wall of a nozzle. 
     An embodiment includes an apparatus to increase energy efficiency. 
     An embodiment includes an apparatus to minimize poor coating. 
     An embodiment includes an apparatus to minimize coating layer formation time. 
     An embodiment includes an apparatus to easily form thicker coating layer. 
     The objects of the inventive concept are not limited to the above mentioned disclosure. Other objects thereof will be understandable by those skilled in the art from the following descriptions and drawings. 
     Example embodiments of the inventive concept may provide a coating apparatus comprising: a support unit for supporting a coating object; and a spray assembly for spraying a fluid which includes a coating material to be coated by the coating object supported on the support unit. The spray assembly comprises: a nozzle unit where the fluid is sprayed; and a fluid supply unit for supplying the fluid to the nozzle unit. The nozzle unit comprises: a body including a passageway for the fluid therein and a dielectric unit provided with a dielectric material; and a plasma source for generating plasma from the fluid which flows to an area adjacent to inner lateral surface of the dielectric unit. The plasma source comprises: a power electrode applying a power; and a ground electrode to be grounded. 
     In example embodiments, the power electrode and the ground electrode are placed apart from each other in the dielectric unit. 
     In example embodiments, the power electrode may surround a center shaft of the body and may be a helical shape having a plurality of turns arranged along a lengthwise of the body. The ground electrode may surround a center shaft of the body and may be a helical shape having a plurality of turns arranged along a lengthwise of the body. 
     In example embodiments, when viewed from a lateral side, each of the turns of the power electrode and the turns of the ground electrode are departed from each other. 
     In example embodiments, the turn of the power electrode is provided closer to a turn which is closer to a spray hole where the fluid of the body is sprayed among the turns of the ground electrode. 
     In example embodiments, each distance between the turns close to each other of the power electrode may be the same, and each distance between the turns close to each other of the ground electrode may be the same. 
     In example embodiments, the distance between the turns close to each other of the power electrode and a distance between the turns close to each other of the ground electrode may be the same. 
     In example embodiments, the power electrode may surround a center shaft of the body and may be a plurality of rings arranged along a lengthwise of the body. The ground electrode may surround a center shaft of the body and may be a plurality of rings arranged along a lengthwise of the body. 
     In example embodiments, each ring of the power electrode and each ring of the ground electrode are arranged alternately, when viewed from a lateral side. 
     In example embodiments, the ring of the power electrode is provided closer to a ring which is closer to a spray hole where the fluid of the body is sprayed among the rings of the ground electrode. 
     In example embodiments, each distance between the rings close to each other of the power electrode may be the same, and each distance between the rings close to each other of the ground electrode may be the same. 
     In example embodiments, the distance between the rings close to each other of the power electrode and the distance between the rings close to each other of the ground electrode may be the same. 
     In example embodiments, the power electrode may be placed such that its outer lateral surface is further apart from the inner lateral surface of the dielectric unit with respect to the center shaft of the body. 
     In example embodiments, the power electrode may be provided to the inner lateral surface of the dielectric unit, and the ground electrode may be provided to an outer lateral surface of the dielectric unit. 
     In example embodiments, the dielectric unit may form a power electrode groove inserted with the power electrode in the inner lateral surface and may form a ground electrode groove inserted with the ground electrode in the outer lateral surface. 
     In example embodiments, the power electrode and the ground electrode may be provided in the outer lateral surface of the dielectric unit. 
     In example embodiments, the dielectric unit may include a power electrode groove inserted with the power electrode and a ground electrode groove inserted with the ground electrode in the outer lateral surface. 
     In example embodiments, the nozzle unit further comprises an insulator surrounding the outer lateral surface of the dielectric unit so that the power electrode and the ground electrode may not expose to outside. 
     In example embodiments, the fluid supply unit comprises: a coating material supply member for supplying the coating material; and a gas supply member for supplying a pressure gas for applying a power to spray the coating material. 
     In example embodiments, the coating material may be a powder form. 
     Example embodiments of the inventive concept may provide a nozzle unit where the fluid is sprayed which includes a coating material to be coated by the coating object. The nozzle unit comprising: a body including a passageway for the fluid therein and a dielectric unit provided with a dielectric material; and a plasma source for generating plasma from the fluid which flows to an area adjacent to inner lateral surface of the dielectric unit. The plasma source comprises: a power electrode applied with a power; and a ground electrode to be grounded. 
     In example embodiments, the power electrode and the ground electrode are placed apart from each other in the dielectric unit. 
     In example embodiments, the power electrode may surround a center shaft of the body and may be a helical shape having a plurality of turns arranged along a lengthwise of the body. The ground electrode may surround a center shaft of the body and may be a helical shape having a plurality of turns arranged along a lengthwise of the body. 
     In example embodiments, when viewed from a lateral side, each of the turns of the power electrode and the turns of the ground electrode are departed from each other. 
     In example embodiments, the turn of the power electrode is provided closer to a turn which is closer to a spray hole where the fluid of the body is sprayed among the turns of the ground electrode. 
     In example embodiments, the power electrode may surround a center shaft of the body and may be a plurality of rings arranged along a lengthwise of the body. The ground electrode may surround a center shaft of the body and may be a plurality of rings arranged along a lengthwise of the body. 
     In example embodiments, each ring of the power electrode and each ring of the ground electrode are arranged alternately, when viewed from a lateral side. 
     In example embodiments, the ring of the power electrode is provided closer to a ring which is closer to a spray hole where the fluid of the body is sprayed among the rings of the ground electrode. 
     Embodiments of the inventive concepts may provide an apparatus to prevent decrease in a flow velocity in an area adjacent to an inner lateral wall of a nozzle. 
     An embodiment may provide an apparatus to increase energy efficiency. 
     An embodiment may provide an apparatus to minimize poor coating. 
     An embodiment may provide an apparatus to minimize coating layer formation time. 
     An embodiment may provide an apparatus to easily form thicker coating layer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a lateral cross-sectional view briefly illustrating inside of a nozzle of a conventional coating apparatus. 
         FIG. 2  is a view illustrating a coating apparatus in accordance with an embodiment. 
         FIG. 3  is a perspective view of a part of a nozzle unit of  FIG. 2 . 
         FIG. 4  is a lateral cross-sectional view of a part of a nozzle unit of  FIG. 2 . 
         FIG. 5  is an enlarged view of a part of  FIG. 4 . 
         FIG. 6  is a lateral cross-sectional view of a part of a nozzle unit of  FIG. 2  in accordance with an embodiment. 
         FIG. 7  is a lateral view sectional view of a part of a nozzle unit of  FIG. 2  in accordance with another embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Embodiments will be described below in more detail with reference to the accompanying drawings. Embodiments may, however, take different forms and should not be constructed as limited to the particular embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope to those skilled in the art. In the drawings, shapes are exaggerated for clarity. 
     In example embodiments, a cold spray coating apparatus for spraying a coating material which needs to be coated with high velocity in a room temperature where the material reacts or its coordination does not change, or in a low temperature. However, the inventive concept is not limited hereinafter but may be applied to various apparatus including a nozzle where a material is sprayed. 
       FIG. 2  is a view illustrating a coating apparatus  10  in accordance with an embodiment. Referring to  FIG. 2 , the coating apparatus  10  includes a support unit  100  and a spray assembly  200 . 
     The support unit  100  supports a coating object  20 . The support unit  100  may support the coating object  20  in various ways. For example, the support unit  100  may support the coating object  20  by mechanical clamping or by vacuum lift. Also, the support unit  100  may support the coating object  20  in various angles. In an embodiment, the support unit  100  may support the coating object  20  such that a surface of the coating object  20  which will be coated may be vertical to a plane. However, the support unit  100  may support the coating object  20  such that the surface of the coating object  20  which will be coated may be parallel to the plane. The support unit  100  may selectively support the coating object  20  in various angles. 
     The spray assembly  200  sprays a fluid to the coating object  20  supported on the support unit  100 . In an embodiment, the spray assembly  200  includes a nozzle unit  1000  and a fluid supply unit  2000 . 
     A fluid is sprayed through the nozzle unit  1000 .  FIG. 3  is a perspective view of a part of the nozzle unit  1000  of  FIG. 2 .  FIG. 4  is a lateral cross-sectional view of a part of the nozzle unit  1000  of  FIG. 2 . Referring to  FIGS. 3 and 4 , the nozzle unit  1000  includes a body  1100  and a plasma source  1200 . 
     The body  1100  includes a passageway therein. The body  1100  includes a dielectric unit  1110  provided with a dielectric material. The entire body  1100  may be the dielectric unit  1110 . However, some part of the body  1100  may be the dielectric unit  1110 . In this case, an area of the body  1100  which corresponds to an area surrounding a power electrode  1210  and a ground electrode  1220  may be the dielectric unit  1110 . 
       FIG. 5  is an enlarged view of a part of  FIG. 4 . Referring to  FIGS. 3 to 5 , the plasma source  1200  generates plasma  30  from a fluid which flows to an area adjacent to an inner lateral surface of the dielectric unit  1110 . In an embodiment, the plasma source  1200  includes a power electrode  1210  and a ground electrode  1220 . The power electrode  1210  and the ground electrode  1220  are placed apart from each other in the dielectric unit  1110 . The power electrode  1210  may be placed such that its outer lateral surface is further apart from the inner lateral surface of the dielectric unit  1110  with respect to a center shaft of the body  1100 . 
     In the power electrode  1210 , a power is applied to form an electric filed from the power electrode  1210  to the ground electrode  1220 . In an embodiment, the power electrode  1210  surrounds the center shaft of the body  1100  and has a helical shape having a plurality of turns arranged along a lengthwise of the body  1100 . A distance between the turns close to each other of the power electrode  1210  may be the same. 
     The ground electrode  1220  is grounded. In an embodiment, the ground electrode  1220  surrounds the center shaft of the body  1100  and has a helical shape having a plurality of turns arranged along a lengthwise of the body  1100 . A distance between the turns close to each other of the ground electrode  1220  may be the same. 
     When viewed from a lateral side, each of the turns of the power electrode  1210  and the turns of the ground electrode  1220  are departed from each other. The turn of the power electrode  1210  is provided closer to a turn which is closer to a spray hole where the fluid of the body  1100  is sprayed among the turns of the ground electrode  1220 . Therefore, a direction of the electric field looks toward the spray hole from each turn of the power electrode  1210 . And accelerates a positive ion  31  of plasma  30  toward the spray hole. 
     The distance between the turns close to each other of the power electrode  1210  and the distance between the turns close to each other of the ground electrode  1220  may be the same. The power electrode  1210  may be provided to the inner lateral surface of the dielectric unit  1110 , and the ground electrode  1220  may be provided to an outer lateral surface of the dielectric unit  1110 . As the power electrode  1210  is provided in the inner lateral surface of the dielectric unit  1110 , it may generate a stronger electric field than provided in the outer lateral surface of the dielectric unit  1110 . Therefore, the power electrode  1210  is provided in the inner lateral surface of the dielectric unit  1110  may accelerate the positive ion  31  of the plasma  30  more effectively. As the ground electrode  1220  provided in the outer lateral surface of the dielectric unit  1110 , and the both of the power electrode  1210  and the ground electrode  1220  are provided in the inner lateral surface, an arcing may be prevented which may generated in the inner lateral surface of the dielectric unit  1110 . 
     A power electrode groove  1111  where the power electrode  1210  is inserted is formed in the inner lateral surface of the dielectric unit  1110 . A ground electrode groove  1112  where the ground electrode  1220  is inserted is formed in the outer lateral surface of the dielectric unit  1110 . It is not easy to fixedly connect the power electrode  1210  and the ground electrode  1220  to the inner lateral surface or the outer lateral surface of the dielectric unit  1110 . The power electrode  1210  and ground electrode  1220  may be easily fixedly connected to the dielectric unit  1110  by forming the power electrode groove  1111  and the ground electrode groove  1112  in the dielectric unit  1110  and inserting the power electrode  1210  and the ground electrode  1220 , respectively. When the power electrode  1210  is inserted in the dielectric unit  1110 , a surface of the power electrode  1210  which faces a center of the body  1100  is exposed. Therefore, it may generate a stronger electric field than totally inserting the power electrode  1210  in the dielectric unit  1110 . 
       FIG. 6  is a lateral cross-sectional view of a part of a nozzle unit  1000   a  of  FIG. 2  in accordance with an embodiment. Referring to  FIG. 6 , the power electrode  1210  and the ground electrode  1220  may be provided in the outer lateral surface of the dielectric unit  1110 . The power electrode groove  1111  and the ground electrode groove  1112  may be formed in the outer lateral surface of the dielectric unit  1110 . When the power electrode  1210  and the ground electrode  1220  are provided in the inner lateral surface of the dielectric unit  1110 , or when the power electrode  1210  is provided in the inner lateral surface of the dielectric unit  1110  and the ground electrode  1220  is provided in the outer lateral surface of the dielectric unit  1110 , the electric field may become weaker and the arcing may be prevented. When the both of the power electrode  1210  and the ground electrode  1220  are provided in the outer lateral surface of the dielectric unit  1110 , an arcing may happen in the outer lateral surface of the dielectric unit  1110 . Therefore, the nozzle unit  1000  may further comprise an insulator  1300 . The insulator  1300  surrounds the outer lateral surface of the dielectric unit  1110  so that the power electrode  1210  and the ground electrode  1220  do not expose to outside. To prevent the arcing from the outer lateral surface of the dielectric unit  1110 , a surface of the power electrode  1210  and the ground electrode  1220  which is exposed to outside is insulated with the insulator  1300 . It is easier to form the power electrode groove  1111  and to install the power electrode  1210  than installing the power electrode  1210  by forming the power electrode groove  1111  in the inner lateral surface therein. A composition, structure, shape, and function of the nozzle unit  1000   a  are similar to the nozzle unit  1000  of  FIG. 5 . 
       FIG. 7  is a lateral view sectional view of a part of a nozzle unit  1000   b  of  FIG. 2  in accordance with another embodiment. Referring to  FIG. 7 , the power electrode  1210  may surround a center shaft of the body  1100  and may be a plurality of rings arranged along a lengthwise of the body  1100 . The rings of the power electrode  1210  are electrically connected. A distance between the rings close to each other of the power electrode  1210  may be the same. 
     The ground electrode  1220  may surround a center shaft of the body  1100  and may be a plurality of rings arranged along a lengthwise of the body  1100 . The rings of the ground electrode  1220  are electrically connected. A distance between the rings close to each other of the ground electrode  1220  may be the same. 
     Each ring of the power electrode  1210  and each ring of the ground electrode  1220  are arranged alternately, when viewed from a lateral side. The ring of the power electrode  1210  is provided closer to a ring which is closer to a spray hole where the fluid of the body is sprayed among the rings of the ground electrode  1220 . The distance between the rings close to each other of the power electrode  1210  and the distance between the rings close to each other of the ground electrode  1220  may be the same. A composition, structure, shape, and function of the nozzle unit  1000   b  are similar to the nozzle unit  1000  of  FIG. 5 . 
     Except in case of  FIGS. 5 to 7 , the nozzle unit may be provided with various compositions to accelerate the positive ion  31  of plasma  30  toward the spray hole of the body  1100 . 
     As described above, with the power electrode  1210  and the ground electrode  1220 , the fluid adjacent to the inner lateral surface of the dielectric unit  1110  is applied to the plasma  30 . And, an electric field is formed along the rings or turns closer to the spray hole of the ground electrode  1220  in respective to the turns or rings of the power electrode  1210 . Therefore, the positive ion  31  of the plasma  30  which is generated from the fluid close to the inner lateral surface of the dielectric unit  1110  by the electric field is accelerated. As the above positive ion  31  of the plasma  30  is accelerated, a decrease in a flow velocity in an area adjacent to an inner lateral surface of the body  1100  may be prevented. Therefore, an additional pressure energy is not needed to prevent decrease in a flow velocity, thereby energy efficiency may be increased. Also, a velocity needed for a coating material to collide with the coating objects  20  is provided, thereby minimize poor coating and easily form thicker coating layer. 
     Again referring to  FIG. 2 , the fluid supply unit  2000  supplies the fluid to the nozzle unit  1000 . In an embodiment, the fluid supply unit  2000  includes a coating material supply member  2100  and a gas supply member  2200 . The fluid may include a pressure gas applying a power to spray the coating material and a coating material to be coated. 
     The coating material supply member  2100  supplies a coating material through the passageway in the body  1100 . The coating material may be a powder form. For example, the coating material may include Y 2 O 3 , Al 2 O 3 , or SiO 2 . 
     The gas supply member  2200  supplies a pressure gas through the passageway in the body  1100 . The pressure gas may be inert gas. For example, the pressure gas may be He, Ar, N 2 , or H 2 .