Powder conveying equipment, machine tools and screws

Abstract

To provide a powder conveying device, a machine tool, and a screw capable of preventing cold welding of powder. [Solution] The powder conveying device includes a screw (300) having a first thread portion (310) and rotatable about a rotation shaft (201), and a housing (210) that accommodates the screw (300). The housing (210) is provided with a first powder supply port (221) and a powder discharge port (231). The first thread portion (310) includes a first thread region (311) located between the first powder supply port (221) and the powder discharge port (231) in the axial direction of the rotation shaft (201) and from which the threads constituting the first thread portion (310) extend continuously, and a second thread region (312) located on the opposite side of the first powder supply port (221) from the powder discharge port (231) in the axial direction of the rotation shaft (201) and from which the threads constituting the first thread portion (310) extend intermittently.

Description

[Technical Field]

[0001] The present invention relates to a powder conveying device, a machine tool, and a screw. [Background technology]

[0002] For example, Japanese Patent Laid-Open Publication No. 2024-3370 (Patent Document 1) discloses a powder bed type three-dimensional additive manufacturing device. The three-dimensional additive manufacturing device has a powder supply device for supplying powder above a table in a chamber. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2024-3370 Summary of the Invention [Problem to be solved by the invention]

[0004] As disclosed in the above-mentioned Patent Document 1, a powder conveying device for conveying powder is used in an additive processing machine that performs additive manufacturing on a workpiece, etc. Among such powder conveying devices, there is one that conveys powder in the direction of the rotation axis of the screw by rotating the screw.

[0005] However, if the powder supplied to the screw enters a position different from the intended conveying path, the powder may become trapped in the gap between the screw and the inner wall of the housing that houses the screw. In this case, as the screw rotates, the powder trapped in the gap may be compressed and welded together (cold welding), which may hinder the screw's rotation. This concern becomes more pronounced when conveying powder such as aluminum, which has a low melting point.

[0006] An object of the present invention is to provide a powder conveying device, a machine tool, and a screw that are capable of preventing cold welding of powder to be conveyed. [Means for solving the problem]

[0007] A powder conveying device according to one aspect of the present invention includes a screw having a first thread portion and capable of conveying powder by rotating about a rotation axis, and a housing that accommodates the screw. The housing is provided with a first powder supply port for supplying powder toward the first thread portion, and a powder discharge port that is positioned offset from the first powder supply port in the rotation axis direction and for discharging the powder conveyed by the screw. The first thread portion includes a first thread region located between the first powder supply port and the powder discharge port in the rotation axis direction, and in which the threads constituting the first thread portion extend continuously about the rotation axis, and a second thread region located on the opposite side of the first powder supply port from the powder discharge port in the rotation axis direction, and in which the threads constituting the first thread portion extend intermittently about the rotation axis.

[0008] A machine tool according to the present invention includes the powder conveying device described above, and a machine tool body that performs additional machining on a workpiece using the powder conveyed by the powder conveying device.

[0009] A screw according to the present invention is capable of conveying powder by rotating about a rotation axis. The screw includes a first thread portion and a second thread portion, which is a reverse thread relative to the first thread portion and is located offset from the first thread portion in the direction of the rotation axis. The first thread portion includes a first thread region in which the threads constituting the first thread portion extend continuously about the rotation axis, and a second thread region located on the opposite side of the second thread portion in the direction of the rotation axis, with the threads constituting the first thread portion extending intermittently about the rotation axis. The second thread portion includes a third thread region in which the threads constituting the second thread portion extend continuously about the rotation axis, and a fourth thread region located on the opposite side of the first thread portion in the direction of the rotation axis, with the threads constituting the second thread portion extending intermittently about the rotation axis.

[0010] A powder conveying device according to another aspect of the present invention includes a screw capable of conveying powder by rotating about a rotation axis, and a housing that accommodates the screw. The housing is provided with a powder supply port for supplying powder toward the screw, and a powder discharge port that is positioned offset from the powder supply port in the rotation axis direction and for discharging the powder conveyed by the screw. The housing has an inner wall that faces the screw in the radial direction of the rotation axis and through which the powder supply port opens. The housing further includes a recess that is provided on the inner wall on the opposite side of the powder discharge port in the rotation axis direction, with the recess recessed radially outward from the rotation axis. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a powder transport device, a machine tool, and a screw that are capable of preventing cold welding of powder to be transported. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a perspective view showing a machine tool equipped with a powder conveying device in a first embodiment of the present invention. [Figure 2] FIG. 2 is a front view showing the powder conveying device in FIG. [Figure 3] FIG. 3 is a cross-sectional view partially showing the powder conveying device in FIG. 2. [Figure 4] FIG. 4 is a diagram showing the screw in FIG. 3. [Figure 5] 3 is a cross-sectional view showing the powder conveying device as seen in the direction of the arrows on line VV in FIG. 2. [Figure 6] FIG. 4 is a cross-sectional view showing the powder conveying device in FIG. 3. [Figure 7] FIG. 6 is a cross-sectional view showing a powder conveying device according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the accompanying drawings, in which the same or corresponding elements are designated by the same reference numerals.

[0014] (Embodiment 1) 1 is a perspective view showing a machine tool including a powder conveying device in accordance with a first embodiment of the present invention. Referring to FIG. 1, a powder conveying device 100 in the present embodiment is used in a machine tool 10.

[0015] The machine tool 10 is an additive manufacturing (AM) machine that uses a powder bed method in which metal powder is spread on a table and a laser is irradiated onto the powder to melt and solidify the required parts.

[0016] The machine tool 10 has a machine tool main body 21 and a powder conveying device 100. The machine tool main body 21 is the main body part of the machine tool 10, and performs additional machining.

[0017] The machine tool body 21 has a cover body 31, a door 33, a processing chamber 50, a table (not shown) placed in the processing chamber 50 and on which powder is spread, and a laser irradiation device (not shown) that irradiates a laser onto the powder spread on the table.

[0018] The cover body 31 covers the processing chamber 50 and defines the outer appearance of the machine tool 10. The processing chamber 50, together with the door 33, defines a space where additional processing is performed. The processing chamber 50 is filled with an inert gas such as argon to prevent oxidation of the powder.

[0019] The door 33 is attached to the processing chamber 50 so as to be rotatable about a rotation center axis extending in the vertical direction. By rotating the door 33, the processing chamber 50 is isolated from the outside space or opened to the outside space.

[0020] Fig. 2 is a front view showing the powder conveying device in Fig. 1. With reference to Figs. 1 and 2, powder conveying device 100 conveys powder used for additional machining in machine tool main body 21. Powder conveying device 100 is disposed outside processing chamber 50. Cover body 31 defines and forms accommodation space 60. Powder conveying device 100 is accommodated in accommodation space 60.

[0021] The powder conveying device 100 includes a tank 110 , a powder conveying section 130 , a pipe 140 , and a powder sending section 150 .

[0022] Powder is stored in tank 110. Tank 110 has a bottom surface 121, a side surface 126, and a top surface 128. An opening 122 is provided in bottom surface 121. Side surface 126 rises from the edge of opening 122 in bottom surface 121. A storage space 116 for storing powder is formed on the opening surface formed by opening 122 in bottom surface 121, at a position surrounded by side surface 126. Top surface 128 faces the opening surface formed by opening 122 in the vertical direction. Top surface 128 is connected to the upper end of side surface 126.

[0023] The tank 110 is provided with a powder recovery port 111 and a powder supply port 112. The powder recovery port 111 and the powder supply port 112 open to the top surface 128 and communicate with the storage space 116. Powder that has not been used for additional machining in the machine tool body 21 is transported from the processing chamber 50 toward the powder transport device 100 and collected into the storage space 116 through the powder recovery port 111. When the amount of powder stored in the storage space 116 becomes insufficient, new powder is replenished into the storage space 116 through the powder supply port 112.

[0024] The powder conveying unit 130 conveys the powder from the tank 110. The powder conveying unit 130 conveys the powder stored in the tank 110 toward the piping 140 and the powder delivery unit 150, which will be described later. The powder conveying unit 130 is disposed below the tank 110. The top of the powder conveying unit 130 is connected to the bottom surface 121 of the tank 110.

[0025] The powder from the powder conveying section 130 flows through the piping 140. The powder from the powder conveying section 130 to the powder delivery section 150 flows through the piping 140. The piping 140 is made of a tubular member and extends in the vertical direction. The piping 140 extends between the powder conveying section 130 and the powder delivery section 150. The upper end of the piping 140 is connected to the bottom of the powder conveying section 130. The lower end of the piping 140 is connected to the powder delivery section 150.

[0026] The powder delivery unit 150 mixes the powder with gas from the piping 140 and delivers it. The powder delivery unit 150 mixes the powder with gas from the piping 140 and delivers it towards the processing chamber 50.

[0027] Fig. 3 is a cross-sectional view partially showing the powder conveying device in Fig. 2. Fig. 4 is a view showing the screw in Fig. 3. With reference to Figs. 3 and 4, powder conveying device 100 (powder conveying section 130) has a screw 300, a housing 210, a first bearing 261 and a second bearing 262.

[0028] The screw 300 extends around a rotation axis 201. The rotation axis 201 is an imaginary straight line corresponding to the central axis of rotation of the screw 300. The screw 300 as a whole is made of a shaft body whose center is the rotation axis 201. The screw 300 is made of, for example, steel.

[0029] The housing 210 accommodates the screw 300. The housing 210 is a cylinder extending along the rotation shaft 201. The housing 210 is made of, for example, aluminum. The housing 210 has an inner wall 216. The inner wall 216 faces the screw 300 with a gap in the radial direction of the rotation shaft 201. The size of the gap may be in the range of 0.1 mm to 1.0 mm in diameter, or in the range of 0.2 mm to 0.5 mm in diameter.

[0030] The screw 300 is supported in a position where the rotation axis 201 extends horizontally. The tank 110 is disposed above the screw 300. The piping 140 is disposed below the screw 300. The powder delivery unit 150 is disposed below the screw 300.

[0031] The first bearing 261 and the second bearing 262 are provided at a distance from each other in the axial direction of the rotating shaft 201. The screw 300 is supported by the first bearing 261 and the second bearing 262 so as to be rotatable around the rotating shaft 201.

[0032] The powder conveying device 100 (powder conveying section 130) further includes a motor 271. An output shaft 271p of the motor 271 is connected to the screw 300 via a coupling 266. The screw 300 rotates about the rotation shaft 201 by the rotation from the motor 271 being transmitted thereto.

[0033] The screw 300 is capable of conveying powder by rotating around the rotation shaft 201. The screw 300 is capable of conveying powder in the axial direction of the rotation shaft 201 while rotating around the rotation shaft 201.

[0034] The screw 300 has a first axial end portion 340, a first threaded portion 310, a axial intermediate portion 350, a second threaded portion 320, and a second axial end portion 330. The first axial end portion 340, the first threaded portion 310, the axial intermediate portion 350, the second threaded portion 320, and the second axial end portion 330 are arranged in the axial direction of the rotation shaft 201 in the listed order.

[0035] The first threaded portion 310 extends around the rotation shaft 201. The second threaded portion 320 extends around the rotation shaft 201. The second threaded portion 320 is provided at a position offset from the first threaded portion 310 in the axial direction of the rotation shaft 201. Each of the first threaded portion 310 and the second threaded portion is composed of a shaft body (cylindrical body) centered on the rotation shaft 201, and a screw thread extending helically around the rotation shaft 201 along the outer circumferential surface of the shaft body. The second threaded portion 320 is a reverse thread to the first threaded portion 310. The first threaded portion 310 is either a right-handed thread or a left-handed thread, and the second threaded portion 320 is the other of the right-handed thread and the left-handed thread.

[0036] The shaft intermediate portion 350 is made of a shaft body centered on the rotary shaft 201. The shaft intermediate portion 350 is located between the first threaded portion 310 and the second threaded portion 320 in the axial direction of the rotary shaft 201. The diameter of the shaft intermediate portion 350 is larger than the diameter of the first shaft end portion 340 and is larger than the diameter of the second shaft end portion 330.

[0037] The first shaft end portion 340 consists of a shaft body centered on the rotary shaft 201. The first shaft end portion 340 is located at one end of the screw 300 in the axial direction of the rotary shaft 201. The first threaded portion 310 is located between the first shaft end portion 340 and the shaft intermediate portion 350 in the axial direction of the rotary shaft 201. The first bearing 261 is fitted onto the outer periphery of the first shaft end portion 340.

[0038] The second shaft end portion 330 comprises a shaft body centered on the rotary shaft 201. The second shaft end portion 330 is located at the other end of the screw 300 in the axial direction of the rotary shaft 201. The second threaded portion 320 is located between the shaft intermediate portion 350 and the second shaft end portion 330 in the axial direction of the rotary shaft 201. The second bearing 262 is fitted onto the outer periphery of the second shaft end portion 330. The output shaft 271p of the motor 271 is connected to the second shaft end portion 330 via a coupling 266.

[0039] The first thread portion 310 includes a first thread region 311 and a second thread region 312. The first thread region 311 and the second thread region 312 are aligned in the axial direction of the rotation shaft 201. The first thread region 311 is located between the second thread region 312 and the shaft intermediate portion 350 in the axial direction of the rotation shaft 201. The first thread region 311 is located between the second thread region 312 and the second thread portion 320 in the axial direction of the rotation shaft 201.

[0040] The second thread region 312 is located between the first shaft end portion 340 and the first thread region 311 in the axial direction of the rotating shaft 201. The second thread region 312 is located on the opposite side of the second thread portion 320 across the first thread region 311 in the axial direction of the rotating shaft 201. The length of the first thread region 311 in the axial direction of the rotating shaft 201 is greater than the length of the second thread region 312 in the axial direction of the rotating shaft 201.

[0041] In the first thread region 311, the threads that make up the first thread portion 310 extend continuously around the rotation shaft 201. In the second thread region 312, the threads that make up the first thread portion 310 extend intermittently around the rotation shaft 201. The second thread region 312 is provided with a plurality of first cutout portions 313. The plurality of first cutout portions 313 cut out the threads that make up the first thread portion 310 at positions spaced apart from one another in the circumferential direction of the rotation shaft 201.

[0042] The height of the thread at a position where the first cutout portion 313 is provided may be zero, or may be smaller than the height of the thread at a position where the first cutout portion 313 is not provided. The multiple first cutout portions 313 may be provided at equal intervals (for example, at intervals of 60°) in the circumferential direction of the rotating shaft 201. The multiple first cutout portions 313 may also be provided at unequal intervals in the circumferential direction of the rotating shaft 201. As shown in Fig. 4, the intervals between the multiple first cutout portions 313 may be determined so that the positions where the first cutout portions 313 are provided are aligned in the axial direction of the rotating shaft 201.

[0043] The second thread portion 320 includes a third thread region 321 and a fourth thread region 322. The third thread region 321 and the fourth thread region 322 are aligned in the axial direction of the rotation shaft 201. The third thread region 321 is located between the fourth thread region 322 and the shaft intermediate portion 350 in the axial direction of the rotation shaft 201. The third thread region 321 is located between the fourth thread region 322 and the first thread portion 310 in the axial direction of the rotation shaft 201.

[0044] The fourth thread region 322 is located between the second shaft end portion 330 and the third thread region 321 in the axial direction of the rotating shaft 201. The fourth thread region 322 is located on the opposite side of the third thread region 321 from the first thread portion 310 in the axial direction of the rotating shaft 201. The length of the third thread region 321 in the axial direction of the rotating shaft 201 is greater than the length of the fourth thread region 322 in the axial direction of the rotating shaft 201.

[0045] In the third thread region 321, the threads that make up the second thread portion 320 extend continuously around the rotation shaft 201. In the fourth thread region 322, the threads that make up the second thread portion 320 extend intermittently around the rotation shaft 201. A plurality of second cutout portions 323 are provided in the fourth thread region 322. The plurality of second cutout portions 323 cut out the threads that make up the second thread portion 320 at positions that are spaced apart from one another in the circumferential direction of the rotation shaft 201. The plurality of second cutout portions 323 are provided in the same manner as the plurality of first cutout portions 313.

[0046] The first thread region 311 and the second thread region 312, and the third thread region 321 and the fourth thread region 322 may be provided symmetrically across the axial intermediate portion 350 (powder discharge port 231, which will be described later).

[0047] 3, the housing 210 is provided with a first powder supply port 221, a second powder supply port 226, and a powder discharge port 231. The first powder supply port 221, the second powder supply port 226, and the powder discharge port 231 open to the inner wall 216.

[0048] The first powder supply port 221 and the second powder supply port 226 open to the inner wall 216 above the powder discharge port 231. The second powder supply port 226 is provided at a position shifted from the first powder supply port 221 in the axial direction of the rotation shaft 201. The powder discharge port 231 is located between the first powder supply port 221 and the second powder supply port 226 in the axial direction of the rotation shaft 201. The first powder supply port 221 and the second powder supply port 226 may be provided symmetrically with the powder discharge port 231 in between.

[0049] The first powder supply port 221 and the second powder supply port 226 communicate with the storage space 116 via an opening 122. The opening 122 opens directly above the first powder supply port 221 and the second powder supply port 226. The powder discharge port 231 communicates with a pipe 140.

[0050] The first powder supply port 221 opens into the inner wall 216, facing the first screw portion 310. The first powder supply port 221 defines a first opening edge 221j and a second opening edge 221k on the inner wall 216. The first opening edge 221j is the closest to the powder discharge outlet 231 in the axial direction of the rotation shaft 201 among the edge parts of the opening surface that the first powder supply port 221 forms in the inner wall 216. The second opening edge 221k is the farthest from the powder discharge outlet 231 in the axial direction of the rotation shaft 201 among the edge parts of the opening surface that the first powder supply port 221 forms in the inner wall 216.

[0051] Second powder supply port 226 opens into inner wall 216, facing second screw portion 320. Second powder supply port 226 defines third opening edge 226j and fourth opening edge 226k on inner wall 216. Third opening edge 226j is the closest edge of the opening surface formed by second powder supply port 226 in inner wall 216 to powder discharge outlet 231 in the axial direction of rotation shaft 201. Fourth opening edge 226k is the farthest edge of the opening surface formed by second powder supply port 226 in inner wall 216 from powder discharge outlet 231 in the axial direction of rotation shaft 201.

[0052] Powder discharge port 231 opens into inner wall 216, facing shaft middle portion 350. Powder discharge port 231 defines a fifth opening edge 231s and a sixth opening edge 231t on inner wall 216. Of the edges of the opening surface formed by powder discharge port 231 in inner wall 216, fifth opening edge 231s is closest to first powder supply port 221 in the axial direction of rotation shaft 201. Sixth opening edge 231t is closest to second powder supply port 226 in the axial direction of rotation shaft 201 among the edges of the opening surface formed by powder discharge port 231 in inner wall 216.

[0053] The first thread region 311 is located between the first powder supply port 221 and the powder discharge port 231 in the axial direction of the rotating shaft 201. The first thread region 311 is located in a range from the fifth opening edge 231s, through the first opening edge 221j, to the second opening edge 221k in the axial direction of the rotating shaft 201. The second thread region 312 is located on the opposite side of the first powder supply port 221 from the powder discharge port 231 in the axial direction of the rotating shaft 201. The second opening edge 221k forms a boundary between the first thread region 311 and the second thread region 312 in the axial direction of the rotating shaft 201.

[0054] The boundary between the first thread region 311 and the second thread region 312 in the axial direction of the rotation shaft 201 may be shifted from the second opening edge 221k toward the first opening edge 221j. In this case, the boundary between the first thread region 311 and the second thread region 312 in the axial direction of the rotation shaft 201 is preferably located closer to the second opening edge 221k than to the first opening edge 221j. The amount of deviation of the boundary between the first thread region 311 and the second thread region 312 from the second opening edge 221k may be 5 mm or less, 3 mm or less, or 1 mm or less.

[0055] The boundary between the first thread region 311 and the second thread region 312 in the axial direction of the rotating shaft 201 may be shifted from the second opening edge 221k toward the first shaft end 340. In this case, the amount of deviation of the boundary between the first thread region 311 and the second thread region 312 from the second opening edge 221k may be 1 mm or less, or 0.5 mm or less. The amount of deviation of the boundary between the first thread region 311 and the second thread region 312 from the second opening edge 221k may be equal to or less than the pitch of the threads that form the first thread portion 310, or may be equal to or less than ½ the pitch of the threads that form the first thread portion 310.

[0056] The third thread region 321 is located between the second powder supply port 226 and the powder discharge port 231 in the axial direction of the rotating shaft 201. The third thread region 321 is located in a range from the sixth opening edge 231t, through the third opening edge 226j, to the fourth opening edge 226k in the axial direction of the rotating shaft 201. The fourth thread region 322 is located on the opposite side of the second powder supply port 226 from the powder discharge port 231 in the axial direction of the rotating shaft 201. The fourth opening edge 226k forms a boundary between the third thread region 321 and the fourth thread region 322 in the axial direction of the rotating shaft 201.

[0057] The boundary between the third thread region 321 and the fourth thread region 322 in the axial direction of the rotation shaft 201 may be shifted from the fourth opening edge 226k toward the third opening edge 226j. In this case, the boundary between the third thread region 321 and the fourth thread region 322 in the axial direction of the rotation shaft 201 is preferably located closer to the fourth opening edge 226k than to the third opening edge 226j. The amount of deviation of the boundary between the third thread region 321 and the fourth thread region 322 from the fourth opening edge 226k may be 5 mm or less, 3 mm or less, or 1 mm or less.

[0058] The boundary between the third thread region 321 and the fourth thread region 322 in the axial direction of the rotating shaft 201 may be shifted from the fourth opening edge 226k toward the second shaft end 330. In this case, the amount of deviation of the boundary between the third thread region 321 and the fourth thread region 322 from the fourth opening edge 226k may be 1 mm or less, or 0.5 mm or less. The amount of deviation of the boundary between the third thread region 321 and the fourth thread region 322 from the fourth opening edge 226k may be equal to or less than the pitch of the thread that constitutes the second thread portion 320, or may be equal to or less than ½ the pitch of the thread that constitutes the first thread portion 310.

[0059] 2 to 4, the powder stored in tank 110 flows by gravity into first powder supply port 221 and second powder supply port 226 through opening 122. The powder that has entered first powder supply port 221 is supplied to first screw portion 310 that rotates around rotation axis 201.

[0060] The powder is transported from the first powder supply port 221 toward the powder discharge port 231 by a first screw region 311 in which the threads constituting the first screw portion 310 extend continuously around the rotation axis 201 (the movement of the powder is indicated by arrow 202 in FIG. 3 ). The powder that has entered the second powder supply port 226 rotates around the rotation axis 201 and is supplied to a second screw portion 320 that has a reverse thread to the first screw portion 310. The powder is transported from the second powder supply port 226 toward the powder discharge port 231 by a third screw region 321 in which the threads constituting the second screw portion 320 extend continuously around the rotation axis 201 (the movement of the powder is indicated by arrow 203 in FIG. 3 ). The powder transported by the screw 300 is discharged toward the pipe 140 through the powder discharge port 231.

[0061] On the other hand, some of the powder from the first powder supply port 221 may enter a region on the opposite side of the powder discharge port 231 in the axial direction of the rotation shaft 201, across the first powder supply port 221 (powder movement indicated by arrow 204 in FIG. 3 ). Also, some of the powder from the second powder supply port 226 may enter a region on the opposite side of the powder discharge port 231 in the axial direction of the rotation shaft 201, across the second powder supply port 226 (powder movement indicated by arrow 205 in FIG. 3 ). In these regions, no powder flow toward the powder discharge port 231 occurs throughout the entire interior of the housing 210, and the powder accumulates in the gap between the screw 300 and the inner wall 216 of the housing 210. In this case, the accumulated powder is compressed and welded (cold welded) as the screw 300 rotates, which may hinder the rotation of the screw 300.

[0062] In contrast to this, in the present embodiment, first screw portion 310 is located on the opposite side of powder discharge port 231 in the axial direction of rotation shaft 201, across first powder supply port 221, and has second screw region 312 in which the threads constituting first screw portion 310 extend intermittently around rotation shaft 201. With this configuration, powder remaining in the gap between screw 300 and inner wall 216 of housing 210 is released into notch portion 313 of the threads in second screw region 312, and the released powder can be transported toward first screw region 311 by the threads in second screw region 312.

[0063] Additionally, second screw portion 320 is located on the opposite side of powder discharge port 231 in the axial direction of rotation shaft 201, with second powder supply port 226 in between, and has fourth screw region 322 in which the threads constituting second screw portion 320 extend intermittently around rotation shaft 201. With this configuration, powder remaining in the gap between screw 300 and inner wall 216 of housing 210 can be released into notch portion 323 of the threads in fourth screw region 322, and the released powder can be transported toward third screw region 321 by the threads in fourth screw region 322.

[0064] For the above reasons, cold welding of powder can be prevented from occurring in the area opposite the powder discharge outlet 231 across the first powder supply port 221 in the axial direction of the rotating shaft 201, and in the area opposite the powder discharge outlet 231 across the second powder supply port 226 in the axial direction of the rotating shaft 201.

[0065] Fig. 5 is a cross-sectional view showing the powder conveying device as seen in the direction of the arrows on line VV in Fig. 2. With reference to Figs. 2, 3, and 5, side surface 126 of tank 110 has first side surface portion 126A and second side surface portion 126B. Second side surface portion 126B faces first side surface portion 126A in the axial direction of rotation shaft 201. Opening 122 opens between first side surface portion 126A and second side surface portion 126B in the axial direction of rotation shaft 201.

[0066] The angle that first side surface portion 126A makes with respect to the vertical direction is larger than the angle that second side surface portion 126B makes with respect to the vertical direction. First side surface portion 126A has a sloped shape that extends obliquely with respect to the vertical direction. The length of first side surface portion 126A in the axial direction of rotation shaft 201 is larger than the length of second side surface portion 126B in the axial direction of rotation shaft 201.

[0067] 5, in a top view, the first powder supply port 221 is disposed at a position closer to the first side surface portion 126A than to the second side surface portion 126B in the axial direction of the rotating shaft 201. A distance B1 between the first side surface portion 126A and the first powder supply port 221 in the axial direction of the rotating shaft 201 is smaller than a distance B2 between the first powder supply port 221 and the second side surface portion 126B in the axial direction of the rotating shaft 201 (B1 <B2)。

[0068] When viewed from above, second powder supply port 226 is disposed at a position closer to second side surface portion 126B than to first side surface portion 126A in the axial direction of rotation shaft 201. The distance between second side surface portion 126B and second powder supply port 226 in the axial direction of rotation shaft 201 is smaller than the distance between first side surface portion 126A and second powder supply port 226 in the axial direction of rotation shaft 201.

[0069] In FIG. 2, the state of the powder stored in tank 110 is indicated by dotted line Fa (when the storage amount is large) and dotted line Fb (when the storage amount is small). When the storage amount of powder is large, the height of the powder from bottom surface 121 is approximately uniform. On the other hand, because a relatively large frictional force is generated between the powder supplied to powder conveying section 130 and first side surface 126A, which has a sloped shape, when the storage amount of powder decreases, the height of the powder from bottom surface 121 becomes higher on the side of first side surface 126A and lower on the side of second side surface 126B. In this case, first powder supply port 221 is positioned closer to first side surface 126A than to second side surface 126B in the axial direction of rotation shaft 201, and therefore the amount of powder supplied to screw 300 through first powder supply port 221 increases. Therefore, a phenomenon that some of the powder from the first powder supply port 221 falls to the area on the opposite side of the powder discharge port 231 across the first powder supply port 221 in the axial direction of the rotation shaft 201 easily occurs.

[0070] From this perspective, in the powder conveying device 100 of this embodiment, the first screw portion 310 may be provided with a first screw region 311 and a second screw region 312, and the second screw portion 320 may be provided with only a third screw region 321.

[0071] Fig. 6 is a cross-sectional view showing the powder conveying device in Fig. 3. Fig. 6 shows a cross section of the housing 210 and the screw 300 taken along a plane perpendicular to the rotation axis 201.

[0072] 3 and 6, housing 210 has a circular opening surrounded by inner wall 216. Screw 300 is arranged concentrically with the circular opening formed in housing 210. First powder supply port 221 opens into inner wall 216 near top 217u of gap 217. The rotation direction of screw 300 is counterclockwise in FIG. 6.

[0073] In this case, the powder supplied to the screw 300 through the first powder supply port 221 takes two paths: one that falls directly from the first powder supply port 221 toward the bottom 217v of the gap 217 (the path indicated by arrow 207 in Figure 6), and the other that follows the rotation direction of the screw 300 and passes through the top 217u of the gap 217 toward the bottom 217v of the gap 217 (the path indicated by arrow 206 in Figure 6).

[0074] The structures of powder conveying device 100, machine tool 10, and screw 300 in the first embodiment of the present invention described above will be summarized below. Powder conveying device 100 in the present embodiment includes screw 300 having a first screw portion 310 and capable of conveying powder by rotating about a rotation shaft 201, and housing 210 that accommodates screw 300. Housing 210 is provided with a first powder supply port 221 for supplying powder toward first screw portion 310, and a powder discharge port 231 that is positioned offset from first powder supply port 221 in the axial direction of rotation shaft 201 and is used to discharge powder conveyed by screw 300. The first screw portion 310 includes a first screw region 311 located between the first powder supply port 221 and the powder discharge port 231 in the axial direction of the rotating shaft 201, in which the threads constituting the first screw portion 310 extend continuously around the rotating shaft 201, and a second screw region 312 located on the opposite side of the powder discharge port 231 in the axial direction of the rotating shaft 201, across the first powder supply port 221, in which the threads constituting the first screw portion 310 extend intermittently around the rotating shaft 201.

[0075] With this configuration, as the screw 300 rotates, powder supplied to the first screw portion 310 through the first powder supply port 221 can be transported by the first screw region 311 toward the powder discharge port 231. Furthermore, powder that has entered a region on the opposite side of the powder discharge port 231 across the first powder supply port 221 in the axial direction of the rotation shaft 201 can be released in the second screw region 312 in which the threads that make up the first screw portion 310 extend intermittently around the rotation shaft 201. This makes it possible to prevent cold welding of the powder supplied through the first powder supply port 221.

[0076] The screw 300 further has a second screw portion 320 having a reverse thread to the first screw portion 310. The housing 210 is further provided with a second powder supply port 226, which is disposed on the opposite side of the powder discharge port 231 from the first powder supply port 221 in the axial direction of the rotation shaft 201, and which is used to supply powder toward the second screw portion 320.

[0077] With this configuration, the powder supplied to the second screw portion 320 through the second powder supply port 226 can be transported toward the powder discharge port 231 as the screw 300 rotates.

[0078] In addition, the second screw portion 320 includes a third screw region 321 located between the second powder supply port 226 and the powder discharge port 231 in the axial direction of the rotating shaft 201, and in which the threads constituting the second screw portion 320 extend continuously around the rotating shaft 201, and a fourth screw region 322 located on the opposite side of the powder discharge port 231 in the axial direction of the rotating shaft 201, across the second powder supply port 226, and in which the threads constituting the second screw portion 320 extend intermittently around the rotating shaft 201.

[0079] With this configuration, powder that has entered a region on the opposite side of the powder discharge port 231 across the second powder supply port 226 in the axial direction of the rotating shaft 201 can be released in the fourth thread region 322 where the threads that make up the second threaded portion 320 extend intermittently around the rotating shaft 201. This makes it possible to prevent cold welding of the powder supplied through the second powder supply port 226.

[0080] The powder conveying device 100 further includes a tank 110 arranged above the screw 300 for storing powder to be supplied to the first powder supply port 221, a powder conveying section 130 having the screw 300 for conveying powder from the tank 110, a pipe 140 arranged below the screw 300 through which powder from the powder discharge port 231 flows, and a powder delivery section 150 arranged below the pipe 140 for mixing the powder from the pipe 140 with gas and delivering it.

[0081] With this configuration, the powder can be transported through the tank 110, the powder transport section 130, the piping 140 and the powder delivery section 150 in this order by gravity acting on the powder and the rotation of the screw 300.

[0082] The machine tool 10 includes a powder conveying device 100 and a machine tool main body 21 that performs additional machining of a workpiece using the powder conveyed by the powder conveying device 100.

[0083] This configuration can prevent cold welding of the powder used in additional processing of the workpiece.

[0084] The screw 300 in this embodiment is capable of conveying powder by rotating about the rotation axis 201. The screw 300 includes a first threaded portion 310 and a second threaded portion 320 that is reverse-threaded relative to the first threaded portion 310 and is disposed at a position offset from the first threaded portion 310 in the axial direction of the rotation axis 201. The first threaded portion 310 includes a first thread region 311 in which the threads constituting the first threaded portion 310 extend continuously about the rotation axis 201, and a second thread region 312 that is located on the opposite side of the first threaded region 311 from the second threaded portion 320 in the axial direction of the rotation axis 201 and in which the threads constituting the first threaded portion 310 extend intermittently about the rotation axis 201. The second screw portion 320 includes a third screw region 321 in which the threads constituting the second screw portion 320 extend continuously around the rotation axis 201, and a fourth screw region 322 located on the opposite side of the first screw portion 310 in the axial direction of the rotation axis 201, across the third screw region 321, in which the threads constituting the second screw portion 320 extend intermittently around the rotation axis 201.

[0085] According to this configuration, by rotating the screw 300 in a predetermined direction around the rotation axis 201, the powder supplied to the first screw portion 310 can be transported by the first screw region 311 in a direction approaching the second screw portion 320 in the axial direction of the rotation axis 201, and the powder supplied to the second screw portion 320 can be transported by the third screw region 321 in a direction approaching the first screw portion 310 in the axial direction of the rotation axis 201.

[0086] Furthermore, when powder enters a region on the opposite side of the second screw portion 320 across the first screw region 311 in the axial direction of the rotating shaft 201, the powder can be released in the second screw region 312 where the threads that make up the first screw portion 310 extend intermittently around the rotating shaft 201. Furthermore, when powder enters a region on the opposite side of the first screw portion 310 across the third screw region 321 in the axial direction of the rotating shaft 201, the powder can be released in the fourth screw region 322 where the threads that make up the second screw portion 320 extend intermittently around the rotating shaft 201. This makes it possible to prevent cold welding of the powder.

[0087] The powder conveying device and screw of the present invention may be used in additive manufacturing machines (3D printers) of a type other than the powder bed type. The present invention is suitable for conveying metal powders such as aluminum having a low melting point, but may also be used for conveying metal powders such as stainless steel and Inconel having a high melting point. The present invention may also be used for conveying resin powder.

[0088] (Embodiment 2) Fig. 7 is a cross-sectional view showing a powder conveying device according to a second embodiment of the present invention. Fig. 7 shows a powder conveying device corresponding to the area surrounded by two-dot chain line VII in Fig. 3. The powder conveying device according to this embodiment has a basically similar structure to powder conveying device 100 according to the first embodiment. Hereinafter, description of the overlapping structure will not be repeated.

[0089] 3 and 7, in the present embodiment, a recess 291 is further provided in housing 210. Recess 291 is provided so as to be continuous with first powder supply port 221 in the axial direction of rotating shaft 201. Recess 291 is provided on the opposite side of powder discharge port 231 in the axial direction of rotating shaft 201, with first powder supply port 221 in between. Recess 291 has a concave shape in inner wall 216 that is concave outward in the radial direction of rotating shaft 201.

[0090] The recess 291 has the function of releasing powder (the function of the first cutout portion 313 in the second screw region 312 described in embodiment 1) when the powder from the first powder supply port 221 enters the region on the opposite side of the powder discharge port 231 in the axial direction of the rotation shaft 201, across the first powder supply port 221.

[0091] The depth of the recess 291 from the inner wall 216 may be greater than the gap between the inner wall 216 and the screw 300. The depth of the recess 291 from the inner wall 216 may be greater than the height of the threads that make up the first screw portion 310 (the length between the top and bottom of the threads in the radial direction of the rotation shaft 201). The depth of the recess 291 from the inner wall 216 may be in the range of 1 mm or more and 20 mm or less, or in the range of 3 mm or more and 10 mm or less.

[0092] The width of the recess 291 in the axial direction of the rotating shaft 201 may be larger than the pitch of the threads that form the first screw portion 310. The width of the recess 291 in the axial direction of the rotating shaft 201 may be larger than twice the pitch of the threads that form the first screw portion 310, or may be larger than three times the pitch of the threads that form the first screw portion 310.

[0093] Note that a recess having the same configuration as recess 291 may also be provided in second powder supply port 226. This recess is provided on the opposite side of powder discharge port 231 across second powder supply port 226 in the axial direction of rotation shaft 201.

[0094] In this embodiment, the first thread portion 310 of the screw 300 may be composed of only the first thread region 311, and the second thread portion 320 of the screw 300 may be composed of only the third thread region 321.

[0095] To summarize the configuration of the powder conveying device in the second embodiment of the present invention described above, the powder conveying device in the present embodiment includes a screw 300 that can convey powder by rotating about a rotation axis 201, and a housing 210 that accommodates the screw 300. The housing 210 is provided with a first powder supply port 221 as a powder supply port for supplying powder toward the screw 300, and a powder discharge port 231 that is positioned offset from the first powder supply port 221 in the axial direction of the rotation axis 201 and for discharging the powder conveyed by the screw 300. The housing 210 faces the screw 300 in the radial direction of the rotation axis 201 and has an inner wall 216 into which the first powder supply port 221 opens. The housing 210 further has a recess 291 on the inner wall 216, which is located on the opposite side of the powder discharge port 231 in the axial direction of the rotating shaft 201, across the first powder supply port 221, and which is recessed radially outward from the rotating shaft 201.

[0096] With this configuration, powder that has entered a region on the opposite side of powder discharge port 231 across first powder supply port 221 in the axial direction of rotating shaft 201 can be released in recess 291 that is recessed toward the outside in the radial direction of rotating shaft 201 in inner wall 216. This makes it possible to prevent cold welding of powder supplied through first powder supply port 221.

[0097] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0098] 10 machine tool, 21 machine tool body, 31 cover body, 33 door, 50 processing chamber, 60 storage space, 100 powder conveying device, 110 tank, 111 powder recovery port, 112 powder supply port, 116 storage space, 121 bottom surface, 122 opening, 126 side surface, 126A first side surface portion, 126B second side surface portion, 128 top surface, 130 powder conveying section, 140 piping, 150 powder delivery section, 201 rotating shaft, 210 housing, 216 inner wall, 217 gap, 217u top portion, 217v bottom portion, 221 first powder supply port, 221j first opening edge, 221k second opening edge, 226 second powder supply port, 226j third opening edge, 226k Fourth opening edge, 231 powder discharge port, 231s fifth opening edge, 231t sixth opening edge, 261 first bearing, 262 second bearing, 266 coupling, 271 motor, 271p output shaft, 291 recess, 300 screw, 310 first threaded portion, 311 first threaded region, 312 second threaded region, 313 first notch portion, 320 second threaded portion, 323 second notch portion, 321 third threaded region, 322 fourth threaded region, 330 second shaft end, 340 first shaft end, 350 shaft intermediate portion.

Claims

1. a screw having a first screw portion and capable of conveying powder by rotating about a rotation axis; a housing that accommodates the screw, The housing includes: a first powder supply port for supplying powder toward the first screw portion; a powder discharge port that is disposed at a position shifted from the first powder supply port in the rotation axis direction and that discharges the powder transported by the screw, The first screw portion is a first thread region located between the first powder supply port and the powder discharge port in the rotation axis direction, in which a thread constituting the first thread portion extends continuously around the rotation axis; a second thread region located on the opposite side of the powder discharge port with the first powder supply port in between in the rotation axis direction, in which the threads constituting the first thread portion extend intermittently around the rotation axis, The screw further has a second threaded portion having a reverse thread to the first threaded portion, the housing is further provided with a second powder supply port, the second powder supply port being disposed on an opposite side of the first powder supply port with respect to the rotation axis direction, with the powder discharge port interposed therebetween, for supplying powder toward the second screw portion; The second screw portion is a third thread region located between the second powder supply port and the powder discharge port in the rotation axis direction, in which the threads constituting the second thread portion extend continuously around the rotation axis; a fourth screw region located on the opposite side of the powder discharge port across the second powder supply port in the rotation axis direction, in which the threads constituting the second screw portion extend intermittently around the rotation axis.

2. a tank having a bottom surface that opens directly above the housing and a side surface that rises from the bottom surface, the tank forming a space for storing powder on the bottom surface and surrounded by the side surfaces; the side surface includes a first side surface portion and a second side surface portion facing the first side surface portion in the rotation axis direction, and an angle formed by the first side surface portion with respect to the vertical direction is larger than an angle formed by the second side surface portion with respect to the vertical direction, The powder conveying device according to claim 1 , wherein, when viewed from above, the first powder supply port is positioned closer to the first side surface portion than the second side surface portion in the rotation axis direction.

3. a tank disposed above the screw and configured to store powder to be supplied to the first powder supply port; a powder conveying unit having the screw and conveying the powder from the tank; a pipe disposed below the screw and through which the powder from the powder discharge port flows; The powder conveying device according to claim 1 , further comprising a powder delivery unit disposed below the pipe, which mixes the powder with a gas and delivers the powder from the pipe.

4. the housing has an inner wall that faces the screw in a radial direction of the rotation shaft and through which the first powder supply port opens, 2. The powder conveying device according to claim 1, wherein the housing further has a recess on the inner wall on the opposite side of the powder discharge port across the first powder supply port in the rotation axis direction, the recess being recessed radially outward of the rotation axis.

5. The powder conveying device according to claim 1; a machine tool body that performs additional processing on a workpiece using the powder transported by the powder transport device.

6. A screw capable of conveying powder by rotating around a rotation axis, A first threaded portion; a second thread portion that is reverse-threaded relative to the first thread portion and is provided at a position shifted from the first thread portion in the rotation axis direction, The first screw portion is a first thread region in which the threads constituting the first thread portion extend continuously around the rotation axis; a second thread region located on the opposite side of the second thread portion with the first thread region interposed therebetween in the rotation axis direction, in which the threads constituting the first thread portion extend intermittently around the rotation axis, The second screw portion is a third thread region in which the threads constituting the second thread portion extend continuously around the rotation axis; and 、 a fourth thread region located on the opposite side of the first thread portion with respect to the third thread region in the rotation axis direction, in which the threads constituting the second thread portion extend intermittently around the rotation axis.

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