Patent Publication Number: US-2023158746-A1

Title: Build material conveyors

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 16/074,502, titled BUILD MATERIAL CONVEYORS, filed on Aug. 1, 2018, which claims priority to PCT/US2017/025047, titled BUILD MATERIAL CONVEYORS, filed Mar. 30, 2017, to which all are incorporated herein in their entirety. 
    
    
     BACKGROUND 
     Many additive manufacture systems, commonly known as three-dimensional (3D) printers, enable objects to be generated on a layer-by-layer basis. Powder-based 3D printing systems, for example, form successive layers of a build material in a printer and selectively solidify portions of the build material to form layers of the object or objects being generated. 
     Before being sent to the printer for processing, build material can be stored in a container known as build unit and is transferred to the printer through a build material conveyor. 
     Build material is often either powdered or particulate type material or liquid material, at least, while it is stored in the build unit. 
    
    
     
       BRIEF DESCRIPTION 
       Examples will now be described, by way of non-limiting example only, with reference to the accompanying drawings. 
         FIG.  1    is a an example of conveyor to transport build material; 
         FIG.  2    is a longitudinal section of the example of  FIG.  1   ; 
         FIG.  3    is a transverse section view from the top of an example of conveyor; 
         FIG.  4    is a view of detail of a helicoidal element for a conveyor; 
         FIG.  5    is an example of conveyor with fingers as wall elements; 
         FIG.  6    is an example of conveyor with elastic strips as wall elements; 
         FIG.  7    is an example of conveyor with bristles as wall elements; 
         FIG.  8    is an example of conveyor with longitudinally movable paddles as wall elements; 
         FIG.  9    is a an example of conveyor with a complementary element as wall element; 
         FIG.  10    is a an example of conveyor with rotating paddles as wall elements 
     
    
    
     DETAILED DESCRIPTION 
     Powder or liquid based 3D printing systems generate objects by forming successive layers of build material on a movable support platform. Portions of each layer are selectively solidified using any suitable technique, and a support platform may be lowered into a build chamber (also known as a build volume) to enable the next layer of build material to be formed. Suitable selective solidification systems include, for example, laser sintering systems, chemical binder systems, and fusing agent and fusing energy systems. 
     In such 3D printing systems, the time it takes to generate an object or objects may be, to a certain extent, dependent on the speed to convey material from the build unit to the printer. Also, it may be desirable that the flow rate of material being fed to the printer is as high and repeatable as possible. 
       FIG.  1    shows an example of build material conveyor  1  to transport build material from a storage container  2  to an outlet  3  that can be connected to another module within, e.g., a 3D printer, such as a build unit or a printing module.  FIG.  1    shows an example wherein the conveyor comprises a helicoidal element  11  such as an auger wherein, as this elements rotates in a defined direction, build material is transported following the travel path of the crests. Also,  FIG.  1    shows an example wherein the conveyor further comprises a set of wall elements  12  located as to selectively cover parts of the conveyor as will be explained in more detail below. 
       FIG.  2    shows a longitudinal section wherein the helicoidal element  11  can be seen in more detail as can the interaction with the wall elements  12 . Also, it can be seen that build material passes from the storage container  2  to the conveyor  1  through an inlet  21  that, in this case, it is an opening that communicates with the storage container  2  and the conveyor  1 . Also, with reference to  FIG.  2    it can be seen that the helicoidal element is substantially vertical, the conveyor may work with a tilt of around 20 degrees from the vertical or around 10 degrees and even with no tilt, as in the example shown in  FIG.  2   . 
       FIG.  3    shows an example that illustrates the transportation process of build material within the conveyor. As the helicoidal element is rotated build material  4  passes from a build material storage container  2  through the inlet  21 , and reaches the upper surface of the helicoidal element  1  wherein the rotational movement of this helicoidal element  1  transports the material following a spiral movement until it reaches a wall element  12 , the wall element  12  eliminates the rotational component of such spiral movement so that material is moved mostly upwards. Additionally, the wall element  12  stacks the build material  4  thereby increasing the flow build material that reaches the output and making the flow more repetitive, i.e., the amount of build material that reaches the output is substantially more constant that in the case wherein no wall element  12  is put in place. In the case of free flowing powder type materials travelling in an upward travel direction the wall element prevent build material  4  from flowing or falling back to the storage container  2  or the inlet  21 . 
     In the example of  FIG.  3   , the wall element  12  is an elastic element which is pivotally attached to an auxiliary structure  120 , the elastic element being biased in a direction opposite to the rotation direction of the helicoidal element  11 . 
       FIG.  4    shows the helicoidal element  11  in more detail. In this figure, it can be seen that the helicoidal element comprises a shaft  110  and crests  111 . As mentioned above, transportation of build material is made by the upper surface of the crest. Consequently, the larger the area of the crest (or, in other words, the transversal length of the helicoidal element), the more material that can transported. By locating a wall element between at least one pair of crests  111  the stacking of material increases the volume of material that can be transported on each full rotation of the helicoidal element, in essence, the effective area  112  of the helicoidal element  11  that can be used for transportation is defined by the transversal length of the helicoidal element  11 , the width of the shaft  110  and the distance between crests, i.e., the effective area  112  of the helicoidal element  11  is the area between each pair of adjacent crests  111  of the helicoidal element and transversely between the edge of the adjacent crests  111  and the shaft  110 . 
     In an example, the wall elements are located between at least one pair of crests, nonetheless, such wall elements can be located between some or even all pairs of crests. 
       FIG.  5    shows an example of wall element  12 . In this example the wall elements  12  are a set of fingers which are biased to the effective area by means of elastic or spring-compliant members  121 . In a particular example, the elastic members  121  can be replaced by a spring or even be replaced by electrically activated members such as solenoids. In this example, a clockwise rotation of the helicoidal element  11  moves some fingers in a clockwise direction thereby moving them outside the effective area so that the crests are allowed to move as the helicoidal element is rotated. The elements that are in the effective area work as stops preventing the material from moving in directions other than the conveying direction, in the case wherein the conveyor is used for vertical transport (such as in  FIGS.  1  and  2   ) the conveying direction would be a substantially upwards direction. 
       FIGS.  6  and  7    show two further examples of wall elements wherein the wall elements can be, e.g., elastic elements such as flexible elements or elements pivotably attached to an auxiliary structure  120 . In the case of  FIG.  6    the elastic elements are flexible strips and in the case of  FIG.  7    bristles can also be used as wall elements  12 . Such strips or bristles can be made of any flexible material, e.g., plastics or thin metal. 
     In this example, the elastic elements are attached to the auxiliary structure so that they protrude from such auxiliary structure in a substantially perpendicular direction. As the helicoidal element  11  rotates in order to convey build material, the crests of the helicoidal element push on some of the elastic elements in the rotating direction of such helicoidal element, the elastic elements are attached to the auxiliary structure in such way that they are biased in the opposite rotation direction so that they allow the crests to pass but once the crests has passed the elastic elements are biased to return to their original position thereby returning to a position occupying at least part of the effective area. 
       FIG.  8    shows an example wherein the wall elements  12  are a set of paddles configured to move longitudinally along the helicoidal element  11  in the travel direction of the build material, wherein a paddle is provided between at least some pairs of crests  111 . The paddles may be rotatably attached together by means of joints. 
     This example may be configured so that the rotation of the helicoidal element  11  causes a movement of the wall elements in the conveying direction, for example, upwards. The paddles may be arranged in a guiding mechanism or be attached to a rotating mechanism around an axis substantially orthogonal to the shaft. 
     In this example the rotating mechanism causes less wear on the helicoidal element given that there is no or little friction between the wall elements  12  and the crests  111 . Furthermore, the movement of the paddles can also be performed by motor means so that the helicoidal element does not have to act on the wall elements  12  thereby further reducing its wear. 
       FIG.  9    shows an example wherein the wall element  12  can be a complementary helicoidal element rotating in a direction opposite to the helicoidal element  11  the complementary helicoidal element  11  may be dimensioned so that each of its crests has approximately the width of the effective area, i.e., the pitch of the helicoidal element  11 . This width can be of around 90% or 80% the effective width to avoid wear of the elements. 
     The complementary helicoidal element can also be seen as a slotted cylinder wherein the slots are configured so that the crests of the helicoidal element go through such slots. The complimentary element may rotate in a direction opposite to the rotating direction of the helicoidal element  11 . 
     Another example that could have a similar functionality to that of the complementary helicoidal element is shown in  FIG.  10    wherein the wall elements  12  are a set of rotating paddles. Such paddles are attached to an auxiliary structure  122  that work as an axis for their rotation, the paddles can also be made of elastic material to have a sweeping effect on the upper surface of the crests. 
     Several examples of wall elements  12  have been shown above, however, the wall elements can be any element configured to move from a position wherein they cover less of the effective area (or even outside the effective area) of a helicoidal element to a position wherein they function as active wall elements and occupy more of the effective area thereby achieving a stacking function on the build material  4 . 
     In essence, the examples show a build material conveyor comprising: an inlet defining a passage between a build material container and the conveyor; an outlet located remote from the inlet, and a helicoidal element between the inlet and the outlet, the helicoidal element surrounding a central axis defined by its shaft; wherein the build material conveyor transports build material using at least part of an effective area of the helicoidal element defined as the area between each pair of adjacent crests of the helicoidal element and transversely between the edge of the adjacent crests and the central axis and wherein the build material conveyor further comprises a set of wall elements configured to selectively cover, at least partially the effective area of the helicoidal element. 
     Furthermore, it is disclosed that the wall elements may be movable between a first position, wherein the walls are located as to at least partially cover the effective area, and a second position wherein the wall elements are located outside the effective area. 
     In an example, the wall elements comprise an elastic mechanism to move the elements between the first and the second position. In this case, the wall elements may be elastic elements, such as, a set of fingers rotatably attached to an auxiliary structure and biased towards the effective area, a set of flexible strips, and/or a set of flexible bristles. In any case, the wall elements may be biased to cover the effective area and moved to a second position outside the effective area by means of the crests of the helicoidal element. 
     In the case of elastic elements, they may be attached to an auxiliary structure and biased to cover the effective area. 
     In another example, it is disclosed an auger to transport build material in a substantially vertical direction wherein the conveyor further comprises a set of wall elements selectively positioned to, in a first position occupy part of the volume of the auger. The transportation can be completely vertical or tilted around 20 degrees. The wall elements of this example may be selectively positioned to occupy the volume of the auger in a plane parallel to the helicoidal element&#39;s axis. 
     The wall elements are movable from the first position wherein the elements occupy, at least partially the volume of the auger and a second position wherein the wall elements are outside the volume of the auger. 
     One use of the conveyor can be in a 3D printing system comprising an storage module and another module, the 3D printing system comprising a build material conveyor to transport material from the storage module to the another module comprising:
         an inlet defining a passage between a build material container and the conveyor;   an outlet located remote from the inlet, and   a helicoidal element between the inlet and the outlet, the helicoidal element surrounding a central axis;
 
wherein the build material conveyor transports build material using an effective area of the helicoidal element defined as the area between each pair of adjacent crests of the helicoidal surface and transversely between the edge of the adjacent crests and the central axis and wherein the build material conveyor further comprises a set of wall elements configured to selectively cover, at least partially the effective area of the helicoidal element.
       

     Furthermore a method is discussed for conveying build material from a build material container to another 3D printing module by using a conveyor comprising a helicoidal element, the method comprising: 
     rotating the helicoidal element so that the helicoidal element transports build material using an effective area of the helicoidal element, the effective area being defined as the area between each pair of adjacent crests of the helicoidal surface and transversely between the edge of the adjacent crests and the central axis; and 
     selectively setting a set of wall elements to cover, at least partially the effective area of the helicoidal element. 
     The wall elements may be set to cover the effective area in a plane parallel to the helicoidal element&#39;s axis. Also, the wall elements may be movable from a first position wherein the elements cover, at least partially the effective area of the helicoidal element and a second position wherein the wall elements are outside the effective area of the helicoidal element.