Apparatus and method for screening powders

Abstract

To provide a device capable of preventing clogging during a screening process.SOLUTION: The device comprises a screening space comprising a first chamber 102 and a second chamber 103. These chambers are arranged adjacently and have a common partition wall 104. The device comprises a screen which is placed obliquely or vertically in a screening device 101, where the screen forms at least a part of the common partition wall. The first chamber comprises a raw material inlet 105, a drive gas inlet 106, a float gas unit 107, and a residual particle outlet 108. The second chamber comprises a product material outlet 109 and a rotatable blade, where the blade comprises nozzles configured for blowing gas at the screen.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a screening device and method for screening powders. [Background technology]

[0002] Japanese Patent Application Laid-Open Publication No. 2002 / 186908 discloses a sieving device in which a sieving space is formed within the device housing. The sieving space is divided into an upper space above the sieving device and a lower space below the sieving device. A horizontally disposed sieving screen is provided between the upper and lower spaces. A raw material inlet is provided above a lid that closes the upper surface of the sieving device, and a raw material distribution plate is provided below the raw material inlet. A product outlet is provided in the lower space below the sieving device, and a suction duct is connected to it. In addition, a nozzle is provided in the lower space below the sieving device that rotates below the sieving screen and blows air toward the sieve mesh. A residual particle outlet is provided on one side of the upper space of the sieving device to discharge residual particles that did not pass through the screen. A door is provided at this residual particle outlet so that it can be opened or closed.

[0003] During use, the residual particle discharge port can be closed when the amount of residual particles is small and does not interfere with the sieving process. The closed residual particle discharge port also prevents product particles from escaping. However, over time, the amount of residual particles in the upper space gradually increases to the point where it begins to interfere with the sieving process. When this occurs, the residual particle discharge port can be opened to discharge all the residual particles at once. Summary of the Invention

[0004] A drawback of known techniques is that residual particles accumulate on the screen and interfere with the sieving operation, gradually reducing the efficiency of the process over time.

[0005] In addition, when the residual particle discharge port is opened to discharge all the residual particles, it is not possible to prevent product particles that have not yet passed through the screen from being discharged through the residual particle discharge port.

[0006] It is an object of the present invention to at least partially obviate at least one of the problems of current sieving apparatus, or to provide at least an alternative device which preferably provides a more efficient screening process with better efficiency and / or can be substantially prevented from clogging during the screening process.

[0007] According to a first aspect, the present invention provides a new screening device, which comprises: a screening space comprising a first chamber and a second chamber, wherein the first chamber and the second chamber are adjacent and have a common partition wall; and a screen forming at least a portion of the partition; wherein the first chamber has a raw material inlet and a residual particle outlet; the second chamber having a product material outlet and a rotatable blade, the rotatable blade having one or more nozzles configured to blow gas against the screen; the screen is disposed diagonally or vertically, and the first chamber further comprises a float gas unit configured to, in use, provide an upward gas flow in a portion of the first chamber; The screening device is configured to provide a pressure differential between the first and second chambers such that, in use, the pressure in the second chamber is lower than the pressure in the first chamber.

[0008] According to the present invention, the screen is arranged on an inclined or vertical plane so that residual particles that do not pass through the screen slide off the screen and accumulate below the screen, and therefore the residual particles will not accumulate on the screen as they do on the sieves of prior art devices, and areas of the screen will not become clogged with residual particles.

[0009] Additionally, the screen is cleaned by gas from a rotating blade that blows gas against the screen through a nozzle. The rotatable blade is disposed within the second chamber, so that the nozzle is configured to blow gas against a side of the screen facing the second chamber. Thus, gas from the nozzle is blown at least partially from the second chamber into the first chamber.

[0010] Thus, with the screening device of the present invention, the efficiency and / or throughput of the screening process will not decrease substantially over time.

[0011] However, when the screen is positioned diagonally or vertically, most of the raw material, including particles that would normally pass through the screen, will slide off the screen. To assist in powder screening in the screening device of the present invention, the first chamber further includes a float gas unit configured to provide an upward gas flow in a portion of the first chamber during use. Thus, during use, the float gas unit is activated to provide an upward flow configured to at least partially suspend or suspend at least a portion of the powder particles within the first chamber, particularly in front of the screen, which assists in passing particles of the powder having dimensions smaller than the openings in the screen through the screen and into the second chamber. Additionally, during use, a pressure difference between the first and second chambers is provided such that the pressure in the second chamber is lower than the pressure in the first chamber, thereby generating a gas flow from the first chamber to the second chamber through the screen, which also assists in the screening process.

[0012] The screening device of the present invention also works with a screen made of mesh, particularly a metal mesh screen. However, in one embodiment, the screen has an array of openings with substantially the same dimensions, each of which is configured so that the diameter of the opening on the side of the screen facing the first chamber is smaller than the diameter of the opening on the side of the screen facing the second chamber. Therefore, the openings preferably taper toward the side of the screen facing the first chamber. Such a screen can be manufactured, for example, using 3D printing techniques. If particles can pass through the diameter of the opening on the side of the screen facing the first chamber, they will not be substantially clogged on their way to the second chamber.

[0013] It should be noted that the pressure differential may be established by increasing the pressure in the first chamber and / or decreasing the pressure in the second chamber. In one embodiment, the second chamber or product material outlet is configured to couple to a suction device or vacuum pump for decreasing the pressure in the second chamber in use. Thus, in use, a suction device or vacuum pump may be placed in fluid communication with the second chamber to decrease the pressure in the second chamber and establish a pressure differential between the first and second chambers.

[0014] In one embodiment, the feedstock inlet is located at or near the top of the first chamber, and the float gas unit is located at or near the bottom of the first chamber, such that, in use, the float gas unit is configured to provide a flow in a substantially counter-current direction relative to the flow of powder to be screened coming from the feedstock inlet, such that the counter-current flow is configured to at least partially levitate or suspend at least some of the particles of the powder within the first chamber, particularly in front of the screen.

[0015] In one embodiment, the float gas unit comprises a fan and / or a float gas inlet. In the case where the float gas unit comprises a fan, the fan is activated in use to provide an upward flow in the first chamber for at least partially suspending or suspending at least a portion of the powder particles in the first chamber, particularly in front of the screen. Preferably, the fan provides gas turbulence and / or rotational motion in the first chamber. Additionally or alternatively, the float gas unit comprises a float gas inlet configured to introduce float gas into the first chamber in use to provide an upward flow configured to at least partially suspend or suspend at least a portion of the powder particles in the first chamber, particularly in front of the screen.

[0016] In one embodiment, the first chamber further comprises a drive gas inlet, which allows for the introduction of a drive gas into the first chamber to more easily regulate the gas flow from the first chamber to the second chamber, which assists particles of the powder having dimensions smaller than the openings in the screen to pass through the screen and into the second chamber.

[0017] In one embodiment, the drive gas inlet is located at or near the top of the first chamber. In an alternative embodiment, the drive gas inlet is located in a sidewall of the first chamber, preferably substantially opposite a partition or screen.

[0018] In one embodiment, the screening device is configured to introduce the raw material into the first chamber with a transport gas. The transport gas can assist in transporting the raw material into the first chamber. In addition, the transport gas can provide a gas flow support in addition to the drive gas to assist gas flow from the first chamber to the second chamber, thereby assisting particles of the powder having dimensions smaller than the openings in the screen to pass through the screen and into the second chamber.

[0019] In one embodiment, the retained particle outlet is located at or near the bottom of the first chamber, preferably adjacent to a partition or screen, such that large and / or heavy particles fall downward and are removed from the first chamber through the retained particle outlet.

[0020] In one embodiment, the angle of the screen relative to the horizontal plane is between 45 and 90 degrees, preferably between 80 and 90 degrees. In one embodiment, the device is configured with a vertical axis within the first chamber, where the vertical axis intersects with the screen at a position vertically below the screen and is spaced apart from the screen at a position vertically above the screen. This prevents particles from remaining on the screen and allows particles that do not pass through the screen to be easily transported to the residual particle outlet.

[0021] In one embodiment, the product material outlet is located at the bottom of the second chamber, so that removal of the product material from the second chamber is assisted by gravity.

[0022] In one embodiment, the screening device comprises an actuator configured to rotate a rotatable blade in front of the screen, hi one embodiment, the actuator comprises an electric motor for rotating the rotatable blade in front of the screen to clean at least a majority of the surface of the screen, or preferably the entire surface of the screen.

[0023] In one embodiment, the float gas, the gas for the rotatable blades, the drive gas, and / or the transport gas are inert gases, preferably argon or nitrogen. This substantially prevents corrosion of the particulate material in the screening device. If the powder material is not sensitive to corrosion, it is suitable to use air as the float gas, the gas for the rotatable blades, the drive gas, and / or the transport gas.

[0024] In one embodiment, the same gas is used as the float gas, the rotatable blade gas, the drive gas, and / or the transport gas, and therefore, in this embodiment, there is no need to provide multiple different gas sources, which makes the screening device of the present invention easier and more economical to use.

[0025] In one embodiment, the screening device further comprises a cyclone unit attached to the product material outlet, the cyclone unit being configured to substantially separate the screened particles from the gas flow. The gas introduced into the first chamber and a portion thereof flowing into the second chamber exit the screening device together with the product material through the product material outlet. To obtain the product material, it is necessary to separate the product material from the gas flow. This can be achieved by the cyclone unit.

[0026] In one embodiment, the cyclone unit comprises: a chamber for separating the screened particles from the gas stream; a gas outlet for the gas flow; and Cyclone material outlet.

[0027] According to a second aspect, the present invention provides a screen for use in the above-described screening device or embodiments thereof, wherein the screen comprises an array of openings having substantially the same dimensions, each of said openings configured such that the diameter of the opening on a side of the screen facing the first chamber is smaller than the diameter of said opening on a side of the screen facing the second chamber. In one embodiment, said screen is obtained by additive manufacturing, preferably by 3D printing.

[0028] According to a third aspect, the present invention provides an assembly for screening powders, said assembly comprising a first screening device according to the first aspect of the invention or an embodiment thereof as described above, and a second screening device according to the first aspect or an embodiment thereof as described above, the assembly further comprising a connection between a raw material inlet of the second screening device and a product material outlet of the first screening device.

[0029] Therefore, the first screening device and the second screening device are connected together. Such a connection of two screening devices is also referred to as a cascade system. In such a cascade system, the opening of the screen of the second screening device is preferably equal to or smaller than the opening of the screen of the first screening device. This cascade system can also be extended to three or more screening devices.

[0030] The assembly according to the invention is capable of separating the powdered raw material into at least three fractions: a first fraction of particles having dimensions larger than the openings of the screen of the first screening device; a second fraction of particles having a dimension smaller than the openings of the screen of the first screening device and larger than the openings of the screen of the second screening device; A third fraction of particles having dimensions smaller than the openings of the screen of the second screening device.

[0031] Larger fractions can be obtained by adding more screening devices with progressively smaller screen openings.

[0032] Thus, by selecting an appropriate screen with appropriate openings, a fraction of particles having a size within a desired range can be separated from the powder raw material.

[0033] In one embodiment, both the first chamber of the first screening device and the first chamber of the second screening device are equipped with a drive gas inlet. As described above, the drive gas inlet allows for the introduction of a drive gas into the first chamber to more easily adjust the gas flow from the first chamber to the second chamber, which helps particles of the powder having dimensions smaller than the openings in the screen to pass through the screen and enter the second chamber. By providing both the first screening device and the second screening device with their own drive gas inlet, the gas flow between the first and second chambers of the first screening device and the second screening device can be individually optimized.

[0034] In one embodiment, the connection between the product material outlet of the first screening device and the raw material inlet of the second screening device comprises a buffer device configured to collect the product material of the first screening device and to administer and transfer said product material to the second screening device. The buffer device allows the flow of material entering the second screening device to be substantially independent from the flow of material exiting the first screening device. Thus, the input and transfer of material to the second screening device can be optimized for screening of materials in the second screening device.

[0035] In one embodiment, the cyclone unit is disposed between the product material outlet of the first screening device and the buffer device, and preferably the cyclone material outlet is connected to the product material inlet of the buffer device. By disposing the cyclone unit between the first screening device and the buffer device, the gas flow from the product material outlet of the first screening device is separated from the product material, and the second screening device can operate substantially independently of the gas flow from the product material outlet of the first screening device.

[0036] In one embodiment, the assembly further comprises a suction apparatus or vacuum pump disposed in fluid communication with the second screening device and / or the second chamber of the first screening device.

[0037] According to a fourth aspect, the present invention provides a method for screening powders using a screening device according to the first aspect of the invention or an embodiment thereof as described above, or an assembly according to the second aspect of the invention or an embodiment thereof as described above, the method comprising: providing a powder into the first chamber via a raw material inlet, wherein the powder is comprised of a collection of particles having various sizes; activating a float gas unit of the first chamber to provide a countercurrent flow configured to at least partially levitate or suspend at least a portion of the particles of the powder within the first chamber; blowing gas against the screen using one or more nozzles on a rotating blade; providing a pressure differential between the first chamber and the second chamber such that the pressure in the second chamber is lower than the pressure in the first chamber; and Allowing particles of the powder having dimensions smaller than the openings in the screen to pass through the screen and into a second chamber, wherein the particles arriving at the second chamber are part of the product material that exits the second chamber via the product material outlet.

[0038] The screen is thus cleaned by gas from a rotating blade which blows gas through a nozzle against the screen, the rotatable blade being powered by an actuator such as an electric motor to rotate in order to clean at least a majority of the surface of the screen, or preferably the entire surface of the screen.

[0039] In one embodiment, the screening device comprises a drive gas inlet and the method further comprises: Introducing a drive gas into the first chamber via the drive gas inlet to create or enhance a gas flow from the first chamber to the second chamber.

[0040] In one embodiment, the screening device comprises a cyclone unit and the method further comprises: Separating the product material from the gas stream using a cyclone unit, preferably wherein the product material exits the cyclone unit substantially via the cyclone material outlet, while the gas stream exits the cyclone unit via the gas outlet.

[0041] In an embodiment using an assembly according to the second aspect of the invention or an embodiment thereof described above, the product material of the first screening device is at least partially directed to the raw material inlet of the second screening device.

[0042] In one embodiment, the product material of the first screening device is at least partially collected in a buffer device, and the product material in the buffer device is introduced and transferred to the raw material inlet of the second screening device.

[0043] The various aspects and features described and illustrated in this specification may, whenever possible, be applied individually. These individual aspects, in particular those described in the accompanying dependent claims, may be the subject of divisional applications.

[0044] The invention will be elucidated on the basis of exemplary embodiments shown in the accompanying drawings. [Brief explanation of the drawings]

[0045] [Figure 1] 1 shows a schematic diagram of a first example of a screening device according to the present invention. [Figure 2A] 1 shows a schematic cross-sectional view of an example of a screening device according to the present invention. [Figure 2B] 2B shows a schematic cross-sectional view of the example of FIG. 2A along line IIB-IIB. [Figure 3] 1 shows a schematic process scheme of a first example of an assembly according to the invention. [Figure 4] 1 shows a schematic process scheme of a second example of an assembly according to the invention. [Figure 5] 1 shows a schematic example of the particle size distribution of powder particles obtained by the assembly of the present invention and of powder particle size distributions made using powders from different fractions than the original distribution. [Figure 6A] 1 shows a schematic top view of a first example of a screen for use in a screening device according to the invention. [Figure 6B]1 shows a schematic cross-sectional view of a first example of a screen for use in a screening device according to the invention; [Figure 7] 1 shows a schematic cross-sectional view of a second example of a screen for use in a screening device according to the invention. DETAILED DESCRIPTION OF THE INVENTION

[0046] FIG. 1 shows a schematic diagram of a first example of a screening device 101 according to the present invention. The screening device 101 comprises a first chamber 102 and a second chamber 103. The two chambers are adjacent to each other and share a common partition wall 104. At least a portion of the partition wall 104 is formed by a screen (not shown). In the example shown in FIG. 1, the first chamber 102 comprises a first flange 1041 on the side facing the second chamber 103, and the second chamber 103 comprises a second flange 1042 on the side facing the first chamber. The first chamber 102 and the second chamber 103 can be connected to each other by connecting the first flange 1041 to the second flange 1042. A screen (not shown) can then be fastened between the first flange 1041 and the second flange 1042 to form the partition wall 104.

[0047] The first chamber 102 comprises several inlets and outlets: a raw material inlet 105, a drive gas inlets 106, 106', a float gas inlet 107 and a residual particle outlet 108. It should be noted that in this example the float gas unit comprises only the float gas inlet 107.

[0048] 1, the raw material inlet 105 is located at or near the top side of the first chamber 102. At least in use, the raw material inlet 105 is coupled to a raw material supply (not shown), which is provided with a transport gas supply configured to allow a transport gas to assist in transporting raw material from the raw material supply to the first chamber 102 via the raw material inlet 105.

[0049] The residual particle outlet 108 is located at or near the bottom side of the first chamber 102. In particular, the bottom side of the first chamber 102 is configured to provide a substantially smooth transition to the residual particle outlet 108. The float gas inlet 107 is also located at or near the bottom side of the first chamber 102 and is preferably configured to direct a jet of float gas upwardly to provide a counterflow to the flow of raw material from the raw material inlet 105. Preferably, in use, the jet of float gas is configured to cause at least a portion of the raw material to be substantially suspended adjacent the partition 104 or screen.

[0050] To further aid in the screening of the raw material, the first chamber 102 further includes a drive gas inlet 106, 106'. The drive gas inlet 106 may be located on or near the top of the first chamber 102, or may be combined with the raw material inlet 105, and / or the drive gas inlet 106' may be located on a sidewall of the first chamber 102, preferably substantially opposite the partition wall 104 or screen. Adding a drive gas to the first chamber 102 increases the gas pressure in the first chamber 102. When the gas pressure in the first chamber 102 is greater than the gas pressure in the second chamber 103, a gas flow through the screen is established. This gas flow assists in the screening of the raw material by taking sufficiently small raw material particles from the first chamber 102 to the second chamber 103. This effect can be further enhanced by using a drive gas inlet 106' located opposite the screen. Using a drive gas inlet 106', the drive gas inlet 106' can be configured to provide a jet of drive gas that pushes the raw material towards the screen.

[0051] 1, the partition 104 and the screen disposed therein are oriented substantially vertically. Preferably, the partition 104 and the screen are oriented at an angle of 80 to 90 degrees relative to the horizontal. Additionally, the screening device 101 is configured such that the vertical center axis of the raw material inlet 105 of the first chamber intersects with the screen at a position vertically below the first chamber 102 and is spaced apart from the screen at a position vertically above the first chamber 102, wherein the partition 104 and the screen are disposed between the vertical center axis and the second chamber 103, at least vertically above the first chamber 102.

[0052] The second chamber 103 includes a product material outlet 109. A rotatable blade is disposed within the second chamber, which will be described in more detail below with reference to Figure 2. The rotatable blade includes one or more nozzles directed toward the screen and configured to blow a stream of gas against the screen. In this example, the rotatable blade is mounted on a hollow shaft 115 that extends out of the second chamber 103 on the side facing away from the screen and away from the first chamber 102.

[0053] An actuator 113 is disposed outside the second chamber 103 for rotating a shaft 115. As the shaft 115 rotates, the rotatable blade also rotates in front of the screen to clean substantially the entire area of ​​the screen. The actuator 113 may be a pneumatically driven actuator, but preferably the actuator 113 comprises an electric motor 112.

[0054] Additionally, the hollow shaft 115 is coupled to a rotatable coupling 116 or swivel coupling for connecting a stationary gas supply tube 117 to the rotatable hollow shaft 115. Preferably, as shown in Figure 1, the rotatable coupling 116 is located at the distal end of the hollow shaft 115, on the side of the actuator 113 that faces away from the second chamber 103. The stationary gas supply tube 117 is, at least in use, in fluid communication with a screen cleaning gas supply.

[0055] 1, a cyclone separator 114 is connected to the product material outlet 109. The cyclone separator 114 includes a gas outlet 110 and a cyclone material outlet 111.

[0056] Thus, the screening device 101 can divide the raw material from the raw material inlet 105 into two fractions: residual material having dimensions larger than the openings in the screen, exiting the screening device 101 via residual material outlet 108 and into residual material container 118; Product material having dimensions smaller than the openings in the screen that exits the screening device 101 via the product material outlet 109 and the cyclone material outlet 111 into the product material container 119.

[0057] The operation of the screening device of the present invention is described below with reference to Figure 2A.

[0058] 2A shows a schematic cross-sectional view of an example of a screening device 201 according to the present invention. The screening device 201 comprises a first chamber 202 and a second chamber 203. The two chambers are adjacent and share a common partition wall 204. At least a portion of the partition wall 204 is formed by a screen 204'.

[0059] In this example, the float gas unit includes both a fan 207' and a float gas inlet 207, either or both of which may be used to provide an upward flow within the first chamber 202 to at least partially float or suspend at least some of the particles of powder within the first chamber 202, particularly in front of the screen 204'.

[0060] The first chamber 202 includes several inlets and outlets: a raw material inlet 205, a drive gas inlet 206′, a float gas inlet 207, and a residual particle outlet 208. The raw material inlet 205 is located at or near the top of the first chamber 202. The residual particle outlet 208 is located at or near the bottom of the first chamber 202.

[0061] Similarly, the float gas inlet 207 and fan 207' are located at or near the bottom side of the first chamber 202 and are both configured to provide a jet of float gas in an upward direction to provide a counterflow to the flow of raw material from the raw material inlet 205. Preferably, in use, the float gas introduced by the fan 207' and / or float gas inlet 207 is configured to cause at least a portion of the raw material to be substantially suspended adjacent the partition 204 or screen 204'.

[0062] To further assist in screening the raw material, the first chamber 202 further comprises a drive gas inlet 206' located in the sidewall of the first chamber 202 opposite the screen 204'.

[0063] 2A, the partition 204 and the screen 204' disposed therein are disposed at an angle of approximately 80 degrees relative to the horizontal. Additionally, the screening device 201 is configured such that the vertical central axis CA of the raw material inlet 205 of the first chamber 202 is disposed vertically below the first chamber 202 and spaced a distance d1 from the screen 204', and the vertical central axis CA is disposed vertically above the first chamber 202 and spaced a distance d2 from the screen 204', where the distance d2 is greater than the distance d1, and the screen 204' is disposed between the vertical central axis CA and the second chamber 203.

[0064] The second chamber 203 includes a product material outlet 209. A rotatable blade 210 is disposed within the second chamber. The rotatable blade 210 is directed toward the screen 204′ and includes one or more nozzles 211 configured to blow a gas stream against the screen 204′. The rotatable blade 210 is mounted on a hollow shaft 215 that extends out of the second chamber 203 on a side facing away from the screen 204′ and away from the first chamber 202.

[0065] An actuator 213 is disposed outside the second chamber 203 for rotating the shaft 215. As the shaft 215 rotates, the rotatable blade 210 also rotates in front of the screen 204' to clean substantially the entire area of ​​the screen 204'. As shown schematically in Figure 2B, the rotatable blade 210 includes a narrow beam with nozzles 211 extending in opposite radial directions from the shaft 215.

[0066] Additionally, the hollow shaft 215 is coupled to a rotatable coupling 216 or swivel coupling for connecting a stationary gas supply tube 217 to the rotatable hollow shaft 215. The rotatable coupling 216 is located at the distal end of the hollow shaft 215, on the side of the actuator 213 that faces away from the second chamber 203. The stationary gas supply tube 217 is, at least in use, in fluid communication with a screen cleaning gas supply.

[0067] The screening device 201 comprises one or more pressure sensors 219 configured to measure a difference in gas pressure dp between at least the first chamber 202 and the second chamber 203 .

[0068] In use, powder to be sieved is introduced into the screening device 201 via the raw material inlet 205. At the same time, pressurized float gas is introduced into the first chamber 202 via the float gas inlet 207. This pressurized float gas creates a gas flow that is directed upward and counter-flows against gravity. This counter-flow is configured so that at least a portion of the particles in the powder to be screened are lifted and float in front of the screen 204' in the first chamber 202. Particles that are too heavy will fall into the retained particle outlet 208 if the downward force is greater than the upward force.

[0069] Additionally or alternatively, the fan 207' is activated to provide an upward flow along the screen 204'. This upward flow is configured so that at least a portion of the particles in the powder to be screened are lifted and float in front of the screen 204' in the first chamber 202. Particles that are too heavy will fall into the residual particle outlet 208 if the downward force is greater than the upward force. It should be noted that when using the fan 207', the use of an additional float gas and / or float gas inlet 207 is not essential and may be omitted.

[0070] Applying a drive gas to the first chamber 202 increases the gas pressure in the first chamber 202. When the gas pressure in the first chamber 202 is higher than the gas pressure in the second chamber 203, a gas flow flows from the first chamber 202 through the screen 204' to the second chamber 203. This gas flow carries particles small enough to pass through the openings in the screen 204'. Larger particles remain in the first chamber 202 and exit the screening device 201 through the retained particle outlet 208. Particles that pass through the screen 204' reach the second chamber 203 and exit the screening device 201 through the product material outlet 209.

[0071] In the screening device 201 as shown in Figure 2, the drive gas inlet 206' is configured to direct a jet of drive gas from the drive gas inlet 206' towards the screen 204'. By using this jet of drive gas, the raw material is pushed towards the screen 204'.

[0072] The powder to be sieved is thus divided into two fractions: a residual material having dimensions larger than the openings in the screen, and a product material having dimensions smaller than the openings in the screen.

[0073] To control the transport of particles through the screen 204′, the pressure difference dp between the first chamber 202 and the second chamber 203 may be increased and / or controlled by introducing additional amounts of drive gas into the first chamber 202. Additionally or alternatively, the pressure difference dp between the first chamber 202 and the second chamber 203 may be increased and / or controlled by removing gas from the second chamber 203, for example, by connecting the product material outlet 209 to a suction device or vacuum pump.

[0074] Furthermore, to substantially prevent particles from clogging the screen 204′, the rotatable blade 210 includes one or more nozzles 211 that blow a gas flow against the surface of the screen 204′ facing the second chamber 203. The gas flow from the rotatable blade 210 is directed in a direction opposite to the gas flow from the first chamber 202 to the second chamber 203, which carries the particles through the screen 204′. Thus, at locations on the screen 204′ toward which the one or more nozzles 211 of the rotatable blade 210 are directed, the particles are blown back into the first chamber 202 to substantially remove the clogging particles. Note that the counterflow of gas from the rotatable blade 210 is substantially limited to locations on the screen 204′ toward which the one or more nozzles 211 of the narrow beam-shaped rotatable blade 210 are directed. In the remaining portion of the screen 204', the gas flow primarily flows from the first chamber 202 to the second chamber 203, carrying particles through the screen 204'. Thus, the screening device 201 of the present invention provides a continuous action of screening material through the screen 204' and cleaning the portion of the screen 204' toward which the rotatable blade 210 is directed.

[0075] 3 shows a schematic process scheme of an example of an assembly according to the invention, in which two screening devices are arranged in a cascade system. A powder buffer 301 provides powder consisting of fine particles with various particle sizes to a first screening device 302 via a dosing valve 303. A float gas supply 307 creates a countercurrent flow that lifts the particles in front of a screen 308. Particles that are too large and / or too heavy fall into a residual particle container 309 when the downward force (gravity) is greater than the upward force (jet of float gas).

[0076] The drive gas supply 304 introduces a drive gas into the first chamber 305 to create a higher pressure in the first chamber 305 than in the second chamber 306. This pressure difference dp1 creates a gas flow from the first chamber 305 to the second chamber 306, carrying particles smaller than the openings in the screen 308. Thus, the powder introduced into the first chamber 305 is separated into a fraction of particles smaller than the openings in the screen 308 that ultimately enter the second chamber 306, and a fraction of particles larger than the openings in the screen 308 that remain in the first chamber 305, exit the first screening device 302 via the retained particle outlet, and ultimately enter the retained particle container 309.

[0077] A rotatable blade 310 is disposed within the second chamber 306 to substantially prevent clogging of the screen 308. The rotatable blade 310 is provided with one or more nozzles which, in use, spray cleaning gas against the screen 308 to clean it. The gas nozzles of the rotatable blade 310 are connected to a compressed gas source 311. The rotatable blade rotates in front of the screen to clean it in stages, and its rotation is powered by an electric motor 312.

[0078] Particles that permeate the screen 308 exit the first screening device 302 via product material outlet 313. These particles, along with at least a portion of the gas that flowed from the first chamber of the first screening device to the second chamber, enter the second screening device 314 via particle inlet 324. By carefully selecting the combination of gas and particles from the first screening device 302 that enters the second screening device 314, as well as appropriate operating conditions for the first and second screening devices, the second screening device 314 can be operated without an additional drive gas supply in the first chamber 325 of the second screening device 314. However, if it proves difficult to obtain the required pressure difference dp2 between the first and second chambers in the second screening device 314, a drive gas supply is provided to the first chamber 325 of the second screening device 314 and / or the second chamber 326 of the second screening device 314 is arranged in fluid connection with the suction device 328 via a cyclone unit 317.

[0079] The procedure in the second screening device 314 follows the same principle as that of the first screening device 302, but preferably, only the openings of the screen 316 of the second screening device 314 are smaller than the openings of the screen 308 of the first screening device 302. The float gas supply 327 creates a counterflow against the downward-falling particles coming from the particle inlet 324, and the float gas provides lift to the particles in front of the screen 316. Therefore, particles that have a size smaller than the openings of the screen 308 of the first screening device 302 but larger than the openings of the screen 316 of the second screening device 314 remain in the first chamber 325 of the second screening device 314 and eventually enter the residual particle container 315 of the second screening device 314. Particles having a size smaller than the openings in screen 316 of second screening device 314 permeate screen 316 and exit second screening device 314 via a product material outlet and are directed to a cyclone unit 317 to separate the gas stream from the particles to be used as product material. The product material is stored in product material container 318, and the gas stream is then filtered by auto-cleaning filter 319 and HEPA filter 320 to remove residual particles and purify the gas. This clean gas is moved through blower 321 and stored in gas buffer 322.

[0080] Similarly, a rotatable blade 330 is disposed within the second chamber 326 of the second screening device 314 to substantially prevent clogging of the screen 316. The rotatable blade 330 is provided with one or more nozzles which, in use, spray cleaning gas against the screen 316 to clean it. The gas nozzles of the rotatable blade 330 are connected to a compressed gas source 331. The rotatable blade rotates in front of the screen to clean it in stages, and its rotation is powered by an electric motor 332.

[0081] The gas from the gas buffer 322 can then be reused as a float gas and / or drive gas in the first screening device and / or the second screening device. In addition, the gas from the gas buffer 322 is also used as a cleaning gas in the rotatable blades of the first screening device and the second screening device. If necessary, a compressor 323 can be used to increase the pressure of the cleaning gas to provide the desired pressure of the cleaning gas from the nozzles of the rotatable blades.

[0082] In addition, the gas buffer 322 is also connected to the powder buffer 301 via a transport gas supply pipe 340. The transport gas supply pipe 340 allows for the introduction of a transport gas into the powder buffer 301, which may assist in moving powder from the powder buffer 301 to the first chamber 305 of the first screening device 302.

[0083] For example, if the screen 308 of the first screening device 302 has 100 micron openings and the screen 316 of the second screening device 314 has 50 micron openings, the residual particle container 309 of the first screening device 302 will contain particles having dimensions of 100 microns or greater, the residual particle container 315 of the second screening device 314 will contain particles having dimensions of 50 to 100 microns, and the product material container 318 will contain particles having dimensions of less than 50 microns.

[0084] The operation of each of the first and second screening devices is preferably controlled by controlling the pressure differential dp1, dp2 across the corresponding screens 308, 316 and by controlling the amount of raw material flowing into the respective first chambers 305, 325 of the screening devices 302, 314.

[0085] 3, it should be noted that the amount of material flowing into the first chamber 325 of the second screening device 314 is equal to the amount of product material flowing out of the product material outlet 313 of the first screening device 302. Therefore, in this example, the amount of material flowing into the first chamber 325 of the second screening device 314 cannot be actively controlled.

[0086] Note that in this example, the float gas unit of each screening device 302, 314 includes only a float gas inlet 307, 327. However, in addition or alternatively, one or more of the float gas units of the screening devices 302, 314 may include a fan as described above with reference to FIG.

[0087] A second example of an assembly according to the invention, which allows for active control of the inflow of material into the first chamber 325 of the second screening device, is shown in Figure 4. Figure 4 shows a schematic representation of an alternative cascade system, in which the same features as those already described above in connection with the first example of the assembly according to the invention are given the same reference numerals. The product material outlet 313 of the first screening device 302 is connected to a cyclone unit 401, in which the particle and gas flows from the product material outlet 313 of the first screening device 302 are separated. The particles are directed to an intermediate buffer 402 for storage, and the gas is directed to an automatic cleaning filter 319. The particles from the intermediate buffer 402 are dosed and directed to the first chamber 325 of the second screening device 314 via a dosing valve 403. As shown in FIG. 4, the second screening device also includes a drive gas supply 404 configured to increase the pressure in the first chamber 325 of the second screening device 314 to obtain a desired pressure difference dp2 between the first chamber 325 and the second chamber 326 of the second screening device 314.

[0088] If it proves difficult to obtain the required pressure difference dp1 between the first and second chambers in the first screening device 302, the second chamber 306 of the first screening device 302 is arranged to be fluidly connected to the suction device 329 via a cyclone unit 401.

[0089] Because the screening device according to the invention is based on the principle of suspending particles in front of a screen, one might expect this technique to only work for particles with low density. However, the inventors have found that this technique also works very well with particles with relatively large densities, such as metal particles, particularly metal particles for use in three-dimensional printing of metallic objects.

[0090] By adding additional screening devices with screens having different opening sizes, the incoming raw material can be separated into different fractions. For example, as shown schematically in FIG. 5, if the raw material is composed of powder with a specific particle size distribution PD, this particle size distribution PD may not be suitable for use in, for example, a three-dimensional printing device. The example shown above illustrates an assembly for screening powder into different fractions F1, F2, and F3; the number of fractions can be increased by adding additional screening devices with appropriate screens. Thus, in one embodiment, an assembly for screening powder according to the present invention can separate a generated powder having powder particles with a specific particle size distribution PD into several different fractions F1, F2, F3, F4, and F5. By combining different amounts of powder from one or more of these several different fractions F1, F2, F3, F4, and F5, a powder with a particle size distribution equal to or close to the desired distribution DD can be obtained.

[0091] The screening device of the present invention also works with a screen composed of mesh, particularly a metal mesh screen, as shown schematically in FIG. 6A. The mesh screen comprises metal wires 601 arranged in an orthogonal array that define substantially rectangular openings 602 in the screen. As shown in the cross-sectional view of FIG. 6B, the rounded metal wires of the mesh screen cause the through openings to form a funnel-like shape, forming a narrow neck 603 with a minimum distance d3. This funnel-like shape can trap particles P1, P2, and P3 attempting to pass through the screen, preventing smaller particles from passing through the screen. Using a rotatable blade, as in the screening device of the present invention, where the rotatable blade comprises one or more nozzles configured to blow gas against the screen, trapped particles can be removed.

[0092] In the novel screen design according to the present invention, as shown schematically in the cross-sectional view of FIG. 7 , a screen 701 comprises an array of openings having substantially the same dimensions, each of which is configured such that the diameter d3 of the opening on a side 703 of the screen facing the first chamber is smaller than the diameter of the opening on a side 704 of the screen facing the second chamber. As shown in FIG. 7 , the openings 702 preferably taper in a direction toward the side 703 of the screen facing the first chamber. Such a screen can be manufactured, for example, using 3D printing techniques. If particles can pass through the diameter d3 of the opening on the side 703 of the screen facing the first chamber, they will not substantially become clogged on their way to the second chamber.

[0093] However, if opening 702' does not have a minimum diameter on side 703 but has rounded edges, particles P2 and P3 may still become trapped by the rounded edges. However, not only is the likelihood of particles P2 and P3 becoming trapped in such opening 702' significantly reduced compared to the mesh screen of Figure 6B, but these trapped particles may also be removed by the rotatable blades.

[0094] In summary, the present invention relates to a screening device and method for screening powders. The device comprises a screening space including a first chamber and a second chamber, the chambers being adjacent to each other and sharing a common partition wall. The screening device comprises a screen disposed obliquely or vertically within the screening device, the screen forming at least a portion of the partition wall. The first chamber comprises a raw material inlet, a drive gas inlet, a float gas unit, and a residual particle outlet. The second chamber comprises a product material outlet and a rotatable blade, the blade comprising a nozzle configured to blow gas against the screen. Additionally, the present invention relates to an assembly comprising a first screening device and a second screening device, wherein the product material outlet of the first screening device is connected to the raw material inlet of the second screening device.

[0095] It should be understood that the above description is included to illustrate the operation of the preferred embodiment and is not intended to limit the scope of the invention. From the above description, many variations will become apparent to those skilled in the art which will in due course be encompassed by the scope of the invention as defined in the claims. The inventions described in the claims of the present application as originally filed are set forth below. [1] A screening device for screening powders, comprising: a screening space comprising a first chamber and a second chamber, wherein the first chamber and the second chamber are adjacent and have a common partition wall; a screen forming at least a portion of the partition; Equipped with the first chamber having a raw material inlet and a residual particle outlet; the second chamber having a product material outlet and a rotatable blade, the rotatable blade having one or more nozzles configured to blow gas against the screen; the screen is disposed diagonally or vertically, the first chamber further comprises a float gas unit configured to, in use, provide an upward gas flow in a portion of the first chamber, and the screening device is configured, in use, to provide a pressure differential between the first chamber and the second chamber such that the pressure in the second chamber is lower than the pressure in the first chamber. Screening devices. [2] The screening device described in [1], wherein the second chamber or the product material outlet is configured to connect to a suction device or vacuum pump for reducing the pressure in the second chamber during use. [3] A screening device described in [1] or [2], wherein the raw material inlet is located on or near the top side of the first chamber, and the float gas unit is located on or near the bottom side of the first chamber. [4] The screening device described in [1], [2], or [3], wherein the float gas unit includes a fan and / or a float gas inlet. [5] A screening device described in any one of [1] to [4], wherein the first chamber further comprises a drive gas inlet, the drive gas inlet being located on or near the top side of the first chamber, and / or the drive gas inlet being located on a side wall of the first chamber, preferably the drive gas inlet being located substantially opposite the partition wall or the screen. [6] A screening device described in any one of [1] to [5], wherein the screening device is configured to introduce raw material into the first chamber together with a transport gas. [7] A screening device described in any one of [1] to [6], wherein the residual particle outlet is located on or near the bottom side of the first chamber, preferably adjacent to the partition or the screen. [8] A screening device described in any one of [1] to [7], wherein the angle of the screen relative to the horizontal plane is between 45 and 90 degrees, preferably between 80 and 90 degrees. [9] A screening device described in any one of [1] to [8], wherein the screening device is configured to have a vertical axis within the first chamber, the vertical axis intersecting the screen at a position vertically below the screen, and the vertical axis being spaced apart from the screen at a position vertically above the screen.

[10] A screening device described in any one of [1] to [9], wherein the product material outlet is located on or near the bottom side of the second chamber.

[11] A screening device described in any one of [1] to

[10] , wherein the screening device comprises an actuator configured to rotate the rotatable blade in front of the screen.

[12] A screening device described in any one of [1] to

[11] , wherein the float gas, the gas for the rotatable blades, the drive gas, and / or the transport gas are an inert gas, preferably argon or nitrogen.

[13] The screening device of any one of [1] to

[12] , further comprising a cyclone unit attached to the product material outlet, the cyclone unit configured to substantially separate the screened particles from the gas flow.

[14] The cyclone unit comprises: a chamber for separating the screened particles from the gas stream; an inlet in fluid communication with the product material outlet; a gas outlet for said gas flow; Cyclone material outlet and The screening device according to

[13] , comprising:

[15] A screen for use in a screening device described in any one of [1] to

[14] , comprising an array of openings having substantially the same dimensions, each of the openings configured such that the diameter of the opening on the side of the screen facing the first chamber is smaller than the diameter of the opening on the side of the screen facing the second chamber.

[16] A screen according to

[15] , obtained by additive manufacturing, preferably by 3D printing.

[17] An assembly for screening powders, comprising a first screening device described in any one of [1] to

[13] and a second screening device described in any one of [1] to

[13] , the assembly further comprising a connection between the raw material inlet of the second screening device and the product material outlet of the first screening device.

[18] The assembly described in

[17] , wherein both the first chamber of the first screening device and the first chamber of the second screening device are provided with a drive gas inlet.

[19] The assembly described in

[17] or

[18] , wherein the connection between the product material outlet of the first screening device and the raw material inlet of the second screening device comprises a buffer device, the buffer device configured to collect the product material of the first screening device and to administer and transfer the product material to the second screening device.

[20] The assembly according to

[17] ,

[18] , or

[19] , dependent on

[13] or

[14] , wherein the cyclone unit is disposed between the first screening device and the buffer device, and preferably the cyclone material outlet is connected to the product material inlet of the buffer device.

[21] An assembly described in any one of

[17] to

[20] , further comprising a suction device or vacuum pump arranged in fluid connection with the second chamber of the second screening device and / or the first screening device.

[22] A method for screening powders using the screening device according to any one of [1] to

[14] or the assembly according to any one of

[17] to

[21] , comprising: providing a powder into the first chamber via the raw material inlet, wherein the powder is comprised of a collection of particles having various sizes; activating a float gas unit of the first chamber to provide a countercurrent flow configured to at least partially levitate or suspend at least some of the particles of the powder in the first chamber; blowing gas against the screen using one or more nozzles on the rotating blade; providing a pressure differential between the first chamber and the second chamber such that the pressure in the second chamber is lower than the pressure in the first chamber; allowing the particles of the powder having dimensions smaller than the openings in the screen to pass through the screen and into the second chamber, wherein the particles arriving at the second chamber are a portion of the product material exiting the second chamber via the product material outlet. A method for providing

[23] The method of

[22] dependent on [5], further comprising the step of introducing a drive gas into the first chamber through the drive gas inlet to create or enhance a gas flow from the first chamber to the second chamber.

[24] Separating the product material from the gas stream using a cyclone unit, preferably wherein the product material exits the cyclone unit substantially via the cyclone material outlet, but the gas stream exits the cyclone unit via the gas outlet. The method according to

[22] or

[23] , which is dependent on

[13] or

[14] , further comprises:

[25] A method for screening powders according to any one of

[22] ,

[23] or

[24] , which is dependent on any one of

[17] to

[21] , wherein the product material of the first screening device is at least partially guided to the raw material inlet of the second screening device.

[26] A method for screening powders as described in

[25] , wherein the product material of the first screening device is at least partially collected in a buffer device, and the product material in the buffer device is introduced and transferred to the raw material inlet of the second screening device.

Claims

1. 1. A screening device for screening powders, comprising: A screening space including a first chamber and a second chamber, wherein the first chamber and the second chamber are adjacent to each other and have a common partition wall. a screen forming at least a portion of the partition; Equipped with the first chamber having a raw material inlet and a residual particle outlet; the second chamber having a product material outlet and a rotatable blade, the rotatable blade having one or more nozzles configured to blow gas against the screen; the screen is disposed diagonally or vertically, the first chamber further comprises a float gas unit configured to, in use, provide an upward gas flow in a portion of the first chamber, and the screening device is configured, in use, to provide a pressure differential between the first chamber and the second chamber such that the pressure in the second chamber is lower than the pressure in the first chamber; the raw material inlet is located at or near the top of the first chamber, and the float gas unit is located at or near the bottom of the first chamber; Screening devices.

2. 10. The screening device of claim 1, wherein the second chamber or the product material outlet is configured to connect to a suction device or vacuum pump for reducing the pressure in the second chamber in use.

3. 3. The screening device of claim 1 or 2, wherein the float gas unit comprises a fan and / or a float gas inlet.

4. A screening device as described in any one of claims 1 to 3, wherein the first chamber further comprises a drive gas inlet, the drive gas inlet being located on or near the top side of the first chamber, or the drive gas inlet being located on a side wall of the first chamber, the drive gas inlet being located opposite the partition wall or the screen.

5. The screening device of claim 1 , wherein the screening device is configured to introduce raw material into the first chamber together with a transport gas.

6. 6. The screening device of claim 1, wherein the residual particle outlet is located adjacent to or near a bottom side of the first chamber.

7. 7. The screening device of claim 1, wherein the angle of the screen relative to the horizontal plane is between 45 and 90 degrees.

8. A screening device as described in any one of claims 1 to 7, wherein the screening device is configured to have a vertical axis within the first chamber, the vertical axis intersecting the screen at a position vertically below the screen and the vertical axis being spaced apart from the screen at a position vertically above the screen.

9. 9. The screening device of claim 1, wherein the product material outlet is located at or near a bottom side of the second chamber.

10. 10. The screening device of claim 1, wherein the screening device comprises an actuator configured to rotate the rotatable blade in front of the screen.

11. 11. The screening device of claim 1, wherein the float gas, the gas for the rotatable blades, the drive gas, and the transport gas are inert gases.

12. 12. The screening device of claim 1, further comprising a cyclone unit attached to the product material outlet, the cyclone unit configured to separate screened particles from the gas flow.

13. The cyclone unit comprises: a chamber for separating the screened particles from the gas stream; an inlet in fluid communication with the product material outlet; a gas outlet for said gas flow; Cyclone material outlet and Equipped with 13. The screening device of claim 12, wherein the gas outlet is connected to a HEPA filter configured to remove residual particles and purify the gas.

14. 14. A screening device as described in any one of claims 1 to 13, comprising an array of openings having the same dimensions, each of the openings configured so that the diameter of the opening on the side of the screen facing the first chamber is smaller than the diameter of the opening on the side of the screen facing the second chamber.

15. 15. An assembly for screening powders, comprising: a first screening device that is a screening device described in any one of claims 1 to 14; and a second screening device that is a screening device described in any one of claims 1 to 14, the assembly further comprising a connection between the raw material inlet of the second screening device and the product material outlet of the first screening device.

16. The assembly of claim 15, wherein the connection between the product material outlet of the first screening device and the raw material inlet of the second screening device comprises a buffer device, the buffer device configured to collect the product material of the first screening device and to administer and transfer the product material to the second screening device.

17. the second screening device further comprising a cyclone unit attached to the product material outlet, the cyclone unit configured to separate screened particles from the gas stream; or 17. The assembly of claim 15 or 16, wherein the first screening device and the second screening device further comprise a cyclone unit attached to the product material outlet, the cyclone unit configured to separate screened particles from the gas flow.

18. The cyclone unit comprises: a chamber for separating the screened particles from the gas stream; an inlet in fluid communication with the product material outlet; a gas outlet for said gas flow; Cyclone material outlet and Equipped with 18. The screening device of claim 17, wherein the gas outlet is connected to a HEPA filter configured to remove residual particles and purify the gas.

19. 19. A method for screening powders using a screening device according to any one of claims 1 to 14 or an assembly according to any one of claims 15 to 18, comprising the steps of: providing a powder into the first chamber via the raw material inlet, wherein the powder is comprised of a collection of particles having various sizes; activating a float gas unit of the first chamber to provide a countercurrent flow configured to at least partially levitate or suspend at least some of the particles of the powder in the first chamber; blowing gas against the screen using one or more nozzles on a rotating blade; providing a pressure differential between the first chamber and the second chamber such that the pressure in the second chamber is lower than the pressure in the first chamber; allowing the particles of the powder having dimensions smaller than the openings in the screen to pass through the screen and into the second chamber, wherein the particles arriving at the second chamber are a portion of the product material exiting the second chamber via the product material outlet. A method for providing the above.

20. separating the product material from the gas stream using a cyclone unit, wherein the product material exits the cyclone unit via a cyclone material outlet, while the gas stream exits the cyclone unit via a gas outlet; using the HEPA filter connected to the gas outlet to remove residual particles and purify the gas; 20. The method of claim 19 when dependent on claim 13, further comprising:

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