PRINTING DEVICE, PREFERABLY A 3D PRINTER

Abstract

The present invention relates to a printing device (1), preferably a 3D printer (1), comprising at least one printing nozzle (3) which is designed to eject a flowable material through at least one ejection opening (32) in the direction of a work surface (11) which is preferably horizontal. The printing device (1) is characterized in that the printing nozzle (3) has a stationary printing nozzle frame (30) and a printing nozzle head (31) with the ejection opening (32), which printing nozzle head (31) can be moved, preferably in the vertical direction (Z), relative to the printing nozzle frame (30), wherein the printing nozzle (3) is designed to move the printing nozzle head (31) relative to the printing nozzle frame (30), preferably in the vertical direction (Z), between an open position, in which a flow of the flowable material through the ejection opening (32) is permitted, and a closed position, in which a flow of the flowable material through the ejection opening (32) is not permitted, by means of a drive, preferably by means of a piezoelectric or pneumatic drive, wherein the ejection opening (32) of the printing nozzle head (31) is spaced apart further from the work surface (11) in the closed position than in the open position.

Claims

1. A printing device comprising at least one printing nozzle which is designed to eject a flowable material through at least one ejection opening in the direction of a work surface, characterized in that the printing nozzle has a stationary printing nozzle frame and a printing nozzle head comprising the ejection opening, which printing nozzle head can be moved relative to the printing nozzle frame, wherein the printing nozzle is designed to move the printing nozzle head relative to the printing nozzle frame between an open position, in which a flow of the flowable material through the ejection opening is permitted, and a closed position, in which a flow of the flowable material through the ejection opening is not permitted, by means of a drive, wherein the ejection opening of the printing nozzle head is spaced apart further from the work surface in the closed position than in the open position.

2. Printing device according to claim 1, characterized in that the printing nozzle frame has at least one sealing surface and the printing nozzle head has at least one sealing surface, which are formed opposite one another such that, in the open position, the two sealing surfaces are spaced apart from one another and form a transition region therebetween, through which the flowable material is permitted to flow toward the ejection opening, and in the closed position, the two sealing surfaces form a seal together, so that the flowable material is not permitted to flow toward the ejection opening between the two sealing surfaces.

3. Printing device according to claim 2, characterized in that the two sealing surfaces are designed to touch one another in a planar or linear manner in the direction of movement or at an angle or at right angles to the direction of movement of the printing nozzle head relative to the printing nozzle frame.

4. Printing device according to claim 1, characterized in that the printing nozzle frame has at least two sealing surfaces and the printing nozzle head has at least two sealing surfaces, which are both formed opposite one another in pairs such that, in the open position, the one pair of sealing surfaces is spaced apart from one another and forms a transition region therebetween through which the flowable material is permitted to flow toward the ejection opening and the other pair of sealing surfaces forms a seal together so that the flowable material is not permitted to flow toward an outlet opening between the two sealing surfaces, and, in the closed position, the one pair of sealing surfaces forms a seal together so that the flowable material is not permitted to flow toward the ejection opening between the two sealing surfaces, and the other pair of sealing surfaces is spaced apart from one another and forms a transition region therebetween, through which the flowable material is permitted to flow toward the outlet opening.

5. Printing device according to claim 4, characterized in that the two pairs of sealing surfaces are each designed to touch one another in a planar or linear manner in the direction of movement or at an angle or at right angles to the direction of movement of the printing nozzle head relative to the printing nozzle frame.

6. Printing device according to claim 4, characterized by at least one receiving space which is designed to receive the flowable material from the outlet opening of the printing nozzle, and/or at least one return line, preferably of a printing head, which is designed to receive the flowable material from the outlet opening of the printing nozzle and to feed it to an inlet opening of the printing nozzle.

7. Printing device according to claim 4, characterized in that the transitions between the two pairs of sealing surfaces are each designed to keep the flow of the flowable material constant.

8. Printing device according to claim 4, characterized in that the printing nozzle frame and/or the printing nozzle head has/have at least substantially the same flow resistance for the flowable material between a transition region formed in the open position between the printing nozzle frame and the printing nozzle head and the outlet opening, and between a transition region formed in the closed position between the printing nozzle frame and the printing nozzle head and the ejection opening.

9. Printing device according to claim 1, characterized in that the ejection opening is designed to be narrowed.

10. Printing device according to claim 1, characterized by at least one metering pump which is designed to have the flowable material fed through an inlet opening and to feed it through an outlet opening to the printing nozzle, wherein the metering pump has at least a first chamber volume and a second chamber volume, each of which can be alternatively connected to the inlet opening or to the outlet opening to convey the flowable material.

11. Printing device according to claim 10, characterized in that the two chamber volumes are arranged in a straight line opposite one another, wherein the two chamber volumes face one another and are separated from one another by a valve element, wherein the two chamber volumes face away from one another and are each delimited by a corresponding piston, wherein the two pistons are fixedly connected to one another by means of a piston linkage in order to be translationally moved together in the same direction.

12. Printing device according to claim 11, characterized in that the two pistons are designed to be translationally moved together in the same translatory direction by means of a piston drive and by means of the pressure of the flowable material.

13. Printing device according to claim 11, characterized in that the valve element is designed to be rotated by means of a valve drive perpendicular to the translatory direction of movement of the two pistons.

14. Printing device according to claim 11, characterized in that the piston linkage is arranged outside the two chamber volumes.

15. Printing device according to claim 1, characterized by at least one plasticizing unit, preferably at least one plasticizer, which is arranged stationary relative to the printing nozzle and is designed to produce the flowable material, wherein the plasticizing unit is connected to the printing nozzle by means of at least one material guide element which is designed to convey the flowable material, wherein the material guide element is preferably designed to be heatable.

16. The printing device of claim 1, comprising a 3D printer.

Description

[0065] A plurality of embodiments and further advantages of the invention are illustrated purely schematically and are explained in greater detail below in connection with the following drawings, in which:

[0066] FIG. 1 is a side view of a printing device according to the invention as a 3D printer;

[0067] FIG. 2 is a sectional view of a printing nozzle according to the invention according to a first embodiment in the open position;

[0068] FIG. 3 is the view of FIG. 2 in the closed position;

[0069] FIG. 4 is a sectional view of a printing nozzle according to the invention according to a second embodiment in the open position;

[0070] FIG. 5 is the view of FIG. 4 in the closed position;

[0071] FIG. 6 is a sectional view of a printing nozzle according to the invention according to a third embodiment in the open position;

[0072] FIG. 7 is the view of FIG. 6 in the closed position;

[0073] FIG. 8 is a sectional view of a printing nozzle according to the invention according to a fourth embodiment in the open position;

[0074] FIG. 9 is the view of FIG. 8 in the closed position;

[0075] FIG. 10 is a sectional view of a printing nozzle according to the invention according to a fifth embodiment in the open position;

[0076] FIG. 11 is the view of FIG. 10 in the closed position; and

[0077] FIG. 12 is a sectional view of a metering pump according to the invention.

[0078] The above figures are viewed in Cartesian coordinates. It extends in a longitudinal direction (not shown), which can also be referred to as depth or length. A transverse direction Y, which may also be referred to as the horizontal direction Y, extends perpendicularly to the longitudinal direction. A vertical direction Z, which may also be referred to as the height Z, extends perpendicularly to both the longitudinal direction and the transverse direction Y. The longitudinal direction and the transverse direction Y together form the horizontal, which may also be referred to as the horizontal plane.

[0079] FIG. 1 is a side view of a printing device 1 according to the invention as a 3D printer 1. The 3D printer according to the invention 1 has a frame 10, which may also be referred to as a rack 10. The frame 10 can be used to place the 3D printer 1 on a base (not shown) in order to be operated. Further components and elements of the 3D printer 1 are arranged on the frame 10.

[0080] For example, a plasticizing unit 16 in the form of a plasticizer 16 is arranged in a stationary manner on the frame 10, shown on the left in FIG. 1. A material to be plasticized can be fed from a material store 17 to the plasticizer 16 in the vertical direction Z from above, for example, as granulate or the like, by letting the granulate, e.g., a plastics material, fall into a funnel 16a of the plasticizer 16 and by it being able to be heated there inside the plasticizer 16 by means of a screw 16b by pressure and additional heating and thus be made flowable. The flowable material can then be discharged from the plasticizer 16 via an outlet opening 16c or via a nozzle opening 16c of the plasticizer 16.

[0081] On the right side of FIG. 1, a horizontal work surface 11 is arranged in the vertical direction Z on top of the frame 10, which horizontal work surface may also be referred to as a printing bed 11. Printing head kinematics 12 are arranged horizontally next to the printing bed 11 and consist of vertical and horizontal drive elements (not shown in detail) which can be moved vertically and horizontally with respect to the frame 10 and with respect to one another. A printing head holder 13 can be moved and positioned in the vertical direction Z above the printing bed 11 by means of the printing head kinematics 12. The printing head holder 13 is connected to the nozzle opening 16c of the plasticizer 16 by means of a hose-like, heatable material guide element 18 in the form of a heating hose 18 such that the flowable material can be dispensed from the plasticizer 16 via the heating hose 18 to the printing head holder 13.

[0082] A metering pump 2 according to the invention in the form of a piston conveyor 2, to which the flowable material can be fed by means of the heating hose 18, is arranged inside the printing head holder 13. The flowable material can be dispensed to a printing head 14 at a specified pressure by means of the metering pump 2, as will be described in more detail below with reference to FIG. 12. This can take place by means of the pressure of the flowable material itself as well as by means of the pressure which can be generated in the metering pump 2 by means of a piston drive 15 of the metering pump 2. The piston drive 15 is also arranged on the printing head holder 13.

[0083] The printing head 14 can output or eject the flowable material in the vertical direction Z downward onto the printing bed 11 in order to form a workpiece 4 on the printing bed 11 in the horizontal and in the vertical direction Z by printing upward and in layers. The flowable material is ejected by means of a printing nozzle 3 of the printing head 14 according to the invention, which can also be referred to as a nozzle 3 of the printing head 14. Various embodiments of the printing nozzle 3 will be explained in more detail below with reference to FIGS. 2 to 11.

[0084] In any case, the 3D printer 1 according to the invention makes it possible to dispense with moving the plasticizer 16 with the printing head 14 or with the printing head holder 13, which may significantly reduce the mass of the printing head holder 13 that the printing head kinematics 12 must support and move. Instead, the plasticizer 16 can be arranged in a stationary manner and the flowable material can be fed to the printing head 14 in a flowable manner by means of the heating hose 18. This can also make it possible to use granulate instead of wire-shaped materials, as a result of which the selection of materials that can be used can be increased and/or their costs can be reduced. Despite the comparatively long path of the flowable material through the heating hose 18, the pressure of the flowable material within the printing nozzle 2 that is required or optimal for printing can be ensured by the metering pump 2.

[0085] According to the invention, the flowable material can be ejected through the printing nozzle 3 of the printing head 14 such that the printing nozzle 3 consists substantially of a printing nozzle frame 30 as the nozzle body 30 and of a printing nozzle head 31 as the nozzle needle 31, see FIGS. 2 to 11. According to the invention, the printing nozzle frame 30 is arranged stationary on the printing head 14 and the printing nozzle head 31 is arranged so as to be moved relative to the printing nozzle frame 30 in the vertical direction Z. An ejection opening 32 of the printing head 14 as a nozzle opening 32 of the printing head 14 is formed by the movable printing nozzle head 31 so that the ejection opening 32 of the printing nozzle head 31 can be moved in the vertical direction Z relative to the stationary printing nozzle frame 30.

[0086] As a result, by moving in the vertical direction Z upward, the ejection opening 32 of the printing nozzle head 31 can be simultaneously changed from an open position— which allows the flowable material to be ejected in the vertical direction Z downward toward the printing bed 11 or toward the workpiece 4 to be printed and positions the ejection opening 32 of the printing nozzle head 31 in the vertical direction Z closer to the printing bed 11 or to the workpiece 4 to be printed—to a closed position of the ejection opening 32 of the printing nozzle head 31, which prevents the flowable material from being ejected in the vertical direction Z downward to the printing bed 11 or to the workpiece 4 to be printed and positions the ejection opening 32 of the printing nozzle head 31 further away from the printing bed 11 or from the workpiece 4 to be printed in the vertical direction Z. By moving the printing nozzle head 31 in the vertical direction Z relative to the printing nozzle frame 30 between the open position and the closed position, an enabling or preventing of the ejection of the flowable material at the height Z downward and a closer or further spacing apart of the ejection opening 32 of the printing nozzle head 31 to the printing bed 11 or to the workpiece 4 to be printed can occur together.

[0087] In the closed position of the ejection opening 32 of the printing nozzle head 31, the further spacing apart of the printing nozzle head 31 from the printing bed 11 or from the workpiece 4 to be printed can ensure that contact between the ejection opening 32 of the printing nozzle head 31 and the printing bed 11 or the workpiece to be printed 4, in particular during the displacement movement of the printing head 14 in the horizontal, can be reliably prevented without the printing head 14 having to be moved as a whole in the vertical direction Z for this purpose. This can avoid the corresponding effort and still protect the printing bed 11 or the workpiece 4 to be printed from colliding with the ejection opening 32 of the printing nozzle head 31. This movement of the printing nozzle head 31 in the vertical direction Z relative to the printing nozzle frame 30 can, for example, take place in a piezoelectric or pneumatic manner (not shown).

[0088] The mobility of the ejection opening 32 of the printing nozzle head 31 in the vertical direction Z in relation to the printing nozzle frame 30 arranged stationary on the printing head between the open position and the closed position can be structurally enabled in various ways, as is explained in more detail below by way of example:

[0089] FIG. 2 is a sectional view of a printing nozzle 3 according to the invention according to a first embodiment in the open position. FIG. 3 shows the view of FIG. 2 in the closed position.

[0090] In this case, the previously mentioned stationary printing nozzle frame 30 is arranged on the outside around the substantially cylindrical printing nozzle head 31 that is movable in the vertical direction Z relative to the printing nozzle frame 30. In the view of FIGS. 2 and 3 on the left, the printing nozzle frame 30 has an inlet opening 30a which can receive the flowable material from the metering pump 2, as previously described. A straight, cylindrical inlet channel 30b extends radially on the inside from the inlet opening 30a into the printing nozzle frame 30 and merges into an inlet ring 30c which extends in a closed ring shape around the printing nozzle head 31 and in the vertical direction Z on both sides beyond the inlet channel 30b. The upper and lower edges of the inlet ring 30c in the vertical direction Z each transition conically at an angle of 45° into the through-opening (not designated) of the printing nozzle frame 30 which accommodates the printing nozzle head 31. These two conical surfaces represent two sealing surfaces 30d of the printing nozzle frame 30.

[0091] As already mentioned, the printing nozzle head 31 is of substantially cylindrical design and can be moved in the vertical direction Z relative to the printing nozzle frame 30, e.g., by means of a piezoelectric or pneumatic drive (not shown). The printing nozzle head 31 has a trapezoidal projection (not designated) approximately centered in the vertical direction Z, which points in the vertical direction Z conically at an angle of 45° each at the top and bottom toward the inlet ring 30c of the printing nozzle frame 30. These two conical surfaces represent two sealing surfaces 31d of the printing nozzle head 31 and correspond to the two sealing surfaces 30d of the printing nozzle frame 30, so that the upper and lower sealing surface 31d of the printing nozzle head 31 can each sealingly abut against and act sealingly in pairs against the corresponding upper and lower sealing surface 30d of the printing nozzle frame 30.

[0092] The sealing surface 31d of the printing nozzle head 31 which is on top in the vertical direction Z transitions upward in the vertical direction Z, facing away from the projection, into an inlet ring 31c of the printing nozzle head 31, which ring extends in a closed ring shape around the printing nozzle head 31 and in an open manner radially outward along the vertical direction Z beyond the upper sealing surface 31d of the printing nozzle head 31 facing away from the projection. The inlet ring 31c of the printing nozzle head 31 is connected at one point to an ejection channel 31h which initially extends obliquely to the central axis of the printing nozzle head 31 and from there in a straight line along the central axis of the printing nozzle head 31 in the vertical direction Z downward to the ejection opening 32. The ejection opening 32 of the printing nozzle head 31 is designed to be narrowed with respect to the ejection channel 31h, whereby an increase in pressure of the flowable material can be caused immediately before ejection.

[0093] Comparably, the sealing surface 31d of the printing nozzle head 31, which is on the bottom in the vertical direction Z, transitions downward in the vertical direction Z, away from the projection, into an outlet ring 31e of the printing nozzle head 31, which ring also extends in a closed ring shape around the printing nozzle head 31 and in an open manner radially outward in the vertical direction Z beyond the lower sealing surface 31d of the printing nozzle head 31, facing away from the projection. The outlet ring 31e of the printing nozzle head 31 is connected at one point to an outlet channel 31f, which initially extends obliquely to the central axis of the printing nozzle head 31 and from there in a straight line along the central axis of the printing nozzle head 31 in the vertical direction Z upward to an outlet opening 31g of the printing nozzle head 31. The outlet opening 31g of the printing nozzle head 31 can be connected to a receiving space (not shown) of the printing head 14, where the flowable material can be received and stored. Alternatively, the outlet opening 31g of the printing nozzle head 31 can be connected to a return line (not shown) in order to feed the flowable material to the metering pump 2 and from there back to the inlet opening 30a of the printing nozzle frame 30 and to reuse it.

[0094] Alternatively, the ejection channel 31h could also be Y-shaped in the upper region and connected to the inlet ring 31c of the printing nozzle head 31 at two diametrically opposite points. In this case, the outlet channel 31f of the printing nozzle head 31 would have to be arranged offset laterally or in the circumferential direction with respect to the ejection channel 31h of the printing nozzle head 31. If the outlet channel 31f of the printing nozzle head 31 is also designed to be Y-shaped, so that the outlet channel 31f of the printing nozzle head 31 is connected to the outlet ring 31e of the printing nozzle head 31 at two diametrically opposite points, the two Y-shaped portions of the ejection channel 31h of the printing nozzle head 31 could each be arranged so as to be offset by 90° relative to the two Y-shaped portions of the outlet channel 31f of the printing nozzle head 31.

[0095] If the flowable material is now to be ejected from the ejection opening 32 of the printing nozzle head 31, the printing nozzle head 31 is brought into the lower position as the open position, see FIG. 2. The flowable material can now flow in a flow direction A, fed by the metering pump 2 at a specified constant flow rate, through the inlet opening 30a via the inlet channel 30b into the inlet ring 30c of the printing nozzle frame 30 and spread out there in a ring shape. Since the upper pair of sealing surfaces 30d, 31d of the printing nozzle frame 30 and the printing nozzle head 31 are obliquely spaced apart from one another in the lower position, a ring-shaped, gap-like transition region 33 is formed here, through which the flowable material can get from the inlet ring 30c of the printing nozzle frame 30 into the Inlet ring 31c of the printing nozzle head 31. From the inlet ring 31c of the printing nozzle head 31, the flowable material can now get to the ejection opening 32 of the printing nozzle head 31 via the ejection channel 31h and in the vertical direction Z downward in a flow direction B from the ejection opening 32 of the printing nozzle head 31 to the printing bed 11 or to the workpiece 4 to be printed. The ejection opening 32 of the printing nozzle head 31 can be positioned by means of the printing head kinematics 12, in particular in the vertical direction Z, in relation to the printing bed 11 or in relation to the workpiece 4 to be printed, such that the 3D printing process can be carried out. In this process, the printing head 14 can also be moved horizontally while the flowable material is being ejected, in order to form or print the workpiece 4 in a planar manner.

[0096] If the ejection of the flowable material from the ejection opening 32 of the printing nozzle head 31 to the printing bed 11 or to the workpiece 4 to be printed is to be interrupted, for example to move the printing head 14 in particular horizontally without ejecting material, the printing nozzle head 31 can be moved upward in the vertical direction Z into the closed position, see FIG. 3. During this movement, the transition region 33 between the upper pair of sealing surfaces 30d, 31d of the printing nozzle frame 30 and the printing nozzle head 31 is reduced to the same extent and finally closed, as simultaneously a corresponding transition region 33 between the lower pair of sealing surfaces 30d, 31d of the printing nozzle frame 30 and the printing nozzle head 31 is opened and increased. When the closed position is reached, the flowable material flows completely into the outlet ring 31e of the printing nozzle head 31 and from there via the outlet channel 31f and the outlet opening 31g of the printing nozzle head 31 in a flow direction C, for example into the previously described return line.

[0097] Due to the uniform transition of the two jointly closing and opening transition regions 33, the flow rate of the flowing material can be kept constant when changing between the open position and the closed position, and vice versa, thus avoiding pressure fluctuations in the flow of the flowing material, which, during the transition from the closed position to the open position, can ensure a uniform ejection of the flowable material from the ejection opening 32 of the printing nozzle head 31. This can prevent excessive ejection at the beginning of a printing operation, which might otherwise cause the workpiece 4 to be printed unevenly. The fact that both the ejection channel 31h and the outlet channel 31f of the printing nozzle head 31 have a comparable flow resistance for the flowable material may also facilitate this.

[0098] The movement of the printing nozzle head 31 in the vertical direction Z upward from the open position to the closed position not only causes the above-described interruption of the ejection of the flowable material from the ejection opening 32 of the printing nozzle head 31, but simultaneously causes the ejection opening 32 of the printing nozzle head 31 to be spaced apart from the printing bed 11 or from the workpiece 4 to be printed. In this way, in particular during the horizontal movement of the printing head 14, contact of the ejection opening 32 of the printing nozzle head 31 with the printing bed 11 or with the workpiece 4 to be printed can be avoided.

[0099] FIG. 4 shows a sectional view of a printing nozzle 3 according to the invention according to a second embodiment in the open position. FIG. 5 shows the view of FIG. 4 in the closed position. In this case, the printing nozzle head 31 is designed completely cylindrical. As a result, the two pairs of sealing surfaces 30d, 31d of the printing nozzle frame 30 and the printing nozzle head 31 are aligned perpendicular to one another, and the transition regions 33 are designed as passage openings instead of passage channels.

[0100] Considering the first embodiment of FIGS. 2 and 3 in comparison to the second embodiment of FIGS. 4 and 5, the two conical pairs of sealing surfaces 30d, 31d of the printing nozzle frame 30 and the printing nozzle head 31 of the first embodiment in FIGS. 2 and 3 can result in better sealing, since in the second embodiment of FIGS. 4 and 5 the sealing effect can be reduced in that a sealing effect can only be achieved by the fitting combination of the printing nozzle head 31 in relation to its receptacle in the printing nozzle frame 30. The opening and closing of the transition regions 33 in the two conical pairs of sealing surfaces 30d, 31d of the printing nozzle frame 30 and the printing nozzle head 31 of the first embodiment of FIGS. 2 and 3 can take place with a shorter movement than in the second embodiment of FIGS. 4 and 5, which can accelerate the opening and closing of the transition regions 33. Furthermore, the effort required to open and close the transition regions 33 can be lower with regard to the length of the movement required and/or the energy expenditure for this purpose.

[0101] However, a disadvantage of the first embodiment of FIGS. 2 and 3 compared to the second embodiment of FIGS. 4 and 5 can be considered that the arrangement of the trapezoidal projection of the printing nozzle head 31 within the printing nozzle frame 30 can require a multi-part design of the printing nozzle frame 30, which can result in increased manufacturing and assembly costs. Also, the closing of the upper pair of sealing surfaces 30d, 31d of the printing nozzle frame 30 and the printing nozzle head 31 in the first embodiment of FIGS. 2 and 3 can result in the flowable material located in the transition region 33 possibly being unintentionally ejected by the movement of the printing nozzle head 31 via its outlet channel 31h and its ejection opening 32 from this opening in the vertical direction Z downward in the direction of flow B, which can result, for example, in a change in the workpiece 4. This can be prevented by designing the transition regions 33 as passage openings instead of passage channels in the second embodiment in FIGS. 4 and 5.

[0102] FIG. 6 is a sectional view of a printing nozzle 3 according to the invention according to a third embodiment in the open position. FIG. 7 is the view of FIG. 6 in the closed position.

[0103] The third embodiment of FIGS. 6 and 7 corresponds to the first embodiment of FIGS. 2 and 3 with the difference that, in this case, the printing nozzle frame 30 has an outlet channel 30f which leads to an outlet opening 30g from which the flowable material can flow in the direction of flow C, e.g., into the previously described return line. The outlet channel 30f of the printing nozzle frame 30 is arranged pointing radially outward in the vertical direction Z at a point below the lower sealing surface 30d of the printing nozzle frame 30 such that, in the closed position of the printing nozzle head 31, the flowable material can get from the outlet ring 31e of the printing nozzle head 31 into the outlet channel 30f of the printing nozzle frame 30. This can represent an alternative variant for discharging the flowable material from the printing nozzle 3 in the closed position of the printing nozzle head 31.

[0104] In this case, inside the printing nozzle head 31, its ejection channel 31h may be formed in a Y-shape to connect the inlet ring 31c of the printing nozzle head 31 to the ejection opening 32 at two points. This can cause the flowable material to flow more uniformly toward the ejection opening 32 of the printing nozzle head 31. This also makes it possible to simplify the production of the printing nozzle head 31, in particular by reducing the number of bores.

[0105] FIG. 8 is a sectional view of a printing nozzle 3 according to a fourth embodiment in the open position. FIG. 9 is the view of FIG. 8 in the closed position.

[0106] In this case, the inlet channel 30b of the printing nozzle frame 30 protrudes in a trapezoidal manner toward the printing nozzle head 31, so that the sealing surfaces 30d of the printing nozzle frame 30 are formed in the vertical direction Z above and below the inlet channel 30b of the printing nozzle frame 30, each at a 45° angle. An outlet ring 30e of the printing nozzle frame 30 adjoins the upper sealing surface 30d of the printing nozzle frame 30, which extends in a closed ring shape and radially in an inwardly open manner around the printing nozzle head 31. In the view of FIGS. 8 and 9 on the right, the outlet ring 30e of the printing nozzle frame 30 transitions at one point into the outlet channel 30f of the printing nozzle frame 30, cf. the third embodiment in FIGS. 6 and 7. The lower sealing surface 30d of the printing nozzle frame 30 is correspondingly designed in a closed ring shape at a 45° angle below the trapezoidal projection of the printing nozzle frame 30.

[0107] The printing nozzle head 31 has a corresponding design and has the inlet channel 31c, which is connected to the ejection opening 32 of the printing nozzle head 31 via a T-shaped ejection channel 31h, as described above.

[0108] In this case, the flowable material can get into its inlet ring 30c via the inlet channel 30b of the printing nozzle frame 30, which is substantially formed by the surfaces of the printing nozzle head 31, but can be functionally assigned to the printing nozzle frame 30 for better comparison with the previous embodiments. In the open position of FIG. 8, the upper pair of sealing surfaces 30d, 31d of the printing nozzle frame 30 and the printing nozzle head 31 are in contact with one another in a planar and surface-sealing manner, and the lower pair of sealing surfaces 30d, 31d of the printing nozzle frame 30 and the printing nozzle head 31 form the transition region 33. Correspondingly, the flowable material can get from the inlet ring 30c of the printing nozzle frame 30 through the transition region 33 between the lower sealing surfaces 30d, 31d of the printing nozzle frame 30 and the printing nozzle head 31 into the inlet ring 31c of the printing nozzle head 31, which ring is not only formed in a closed ring shape around the printing nozzle head 31 but is also in the vertical direction Z between the printing nozzle frame 30 and the printing nozzle head 31. The flowable material can then get to the ejection opening 32 of the printing nozzle head 31 via the T-shaped ejection channel 31h of the printing nozzle head 31 and, as previously described, be ejected downward in the vertical direction Z.

[0109] If the printing nozzle head 31 is now moved upward in the vertical direction Z into the closed position, the transition region 33 between the lower sealing surfaces 30d, 31d of the printing nozzle frame 30 and the printing nozzle head 31, as described in the first embodiment in FIGS. 2 and 3, is reduced and finally closed to the same extent and at the same time as the transition region 33 between the upper sealing surfaces 30d, 31d of the printing nozzle frame 30 and the printing nozzle head 31 is opened and increased. When the closed position is reached, the flowable material can get to the outlet channel 30f of the printing nozzle frame 30 via the outlet ring 30e and be discharged from the printing nozzle 3.

[0110] The advantage of this fourth embodiment of FIGS. 8 and 9 is that in this case too a very effective seal can be achieved by the conical lower and upper sealing surfaces 30d, 31d of the printing nozzle frame 30 and the printing nozzle head 31, although this involves a higher design as well as manufacturing and assembly effort.

[0111] The advantage of the fourth embodiment of FIGS. 8 and 9 compared to the three embodiments of FIGS. 2 to 7 considered so far is that, by moving the printing nozzle head 31 in the vertical direction Z upward from the open position to the closed position, in addition to the closing of the transition region 33 between the lower sealing surfaces 30d, 31d of the printing nozzle frame 30 and the printing nozzle head 31, simultaneously an increase in the volume of the inlet ring 31c of the printing nozzle head 31 takes place. Thus, the flowable material, which during the closing movement from the open position to the closed position is pressed from the closing transition region 33 between the lower sealing surfaces 30d, 31d of the printing nozzle frame 30 and the printing nozzle head 31 into the inlet ring 31c of the printing nozzle head 31, can be at least partially or completely received by the simultaneously increasing volume of the inlet ring 31c of the printing nozzle head 31. This can reduce or even completely prevent an unwanted ejection of the flowable material during the closing movement. The increase of the inlet ring 31c of the printing nozzle head 31 can possibly be dimensioned such that the flowable material from the ejection channel 31h can even be partially suctioned back into the inlet ring 31c of the printing nozzle head 31, which can even more effectively prevent the flowable material from being ejected unintentionally during the closing movement.

[0112] It is also advantageous in the fourth embodiment that the lower pair of sealing surfaces 30d, 31d of the printing nozzle frame 30 and the printing nozzle head 31 forms the transition region 33 in the open position, which transition region feeds the flowable material to the ejection opening 32 of the printing nozzle head 31. As a result, the path of the flowable material through the printing nozzle 3 to the ejection opening 32 of the printing nozzle head 31 can be shortened. This also reduces the volume of the flowable material between the transition region 33 or between the lower pair of sealing surfaces 30d, 31d of the printing nozzle frame 30 and the printing nozzle head 31 and its ejection opening 32 in the open position and thus also the influences of pressure changes and/or thermal expansions of the flowable material located there, which could also result in an unintentional ejection of the flowable material from the ejection opening 32 of the printing nozzle head 31 in the closed position.

[0113] FIG. 10 is a sectional view of a printing nozzle 3 according to the invention according to a fifth embodiment in the open position. FIG. 11 is the view of FIG. 10 in the closed position.

[0114] In contrast to the previous four embodiments, in the fifth embodiment in FIGS. 10 and 11, the stationary printing nozzle frame 30 is arranged on the inside and the printing nozzle head 31, which can be moved relative thereto in the vertical direction Z, is arranged on the outside and the printing nozzle frame 30 is arranged substantially cylindrically surrounding it. Correspondingly, the inlet channel 30b initially leads perpendicularly in the vertical direction Z from above into the printing nozzle frame 30 and then branches out in a T-shape in the horizontal direction Y. Parallel to this, the outlet channel 30f of the printing nozzle frame 30 extends upward in the vertical direction Z, said outlet channel being connected at one point to the outlet ring 30e of the printing nozzle frame 30 which is a closed ring shape and is open radially outward.

[0115] In the vertical direction Z downward, the printing nozzle frame 30 is designed conically and rounded at the tip (not designated). In the region of the rounded tip, the printing nozzle frame 30 is surrounded by the printing nozzle head 31 such that the inlet ring 31c of the printing nozzle head 31 is formed there. Near the rounded tip of the conical lower end of the printing nozzle frame 30, the lower pair of sealing surfaces 30d, 31d of the printing nozzle frame 30 and the printing nozzle head 31 are formed, which is followed by the ejection channel 31h of the printing nozzle head 31 and then, on the side of the printing nozzle head 31, the ejection opening 32. This results in a minimum volume of the ejection channel 31h of the printing nozzle head 31.

[0116] At the upper end of the inlet ring 31c of the printing nozzle head 31, the upper pair of sealing surfaces 30d, 31d of the printing nozzle frame 30 and of the printing nozzle head 31 is designed conically, comparable to the first, third, and fourth embodiments of FIGS. 2 and 3, FIGS. 6 and 7, as well as FIGS. 8 and 9 before.

[0117] In this case, the flowable material can flow through the inlet channel 30b of the printing nozzle frame 30 into the inlet ring 31c of the printing nozzle head 31 both in the open position of FIG. 10 and in the closed position of FIG. 11. In the open position of FIG. 10, the upper sealing surfaces 30d, 31d of the printing nozzle frame 30 and the printing nozzle head 31 are in planar, conical contact with one another and thereby close the outlet channel 30f of the printing nozzle frame 30. Simultaneously, the lower sealing surfaces 30d, 31d of the printing nozzle frame 30 and the printing nozzle head 31 are spaced apart from one another and form a transition region 33 that extends in a ring shape around the rounded cone tip of the printing nozzle frame 30 designed as a passage opening through which the flowable material can get to the ejection opening 32 of the pressure nozzle head 31 via the short ejection channel 31h, and can be ejected there as previously described.

[0118] In the closed position, the lower sealing surfaces 30d, 31d of the printing nozzle frame 30 and the printing nozzle head 31 are in contact with one another. Simultaneously, comparable to that described above, a transition region 33 is formed between the upper sealing surfaces 30d, 31d of the printing nozzle frame 30 and the printing nozzle head 31, so that the flowable material can flow via the outlet ring 30e into the outlet channel 30f of the printing nozzle frame 30.

[0119] The ejection channel 31h of the printing nozzle head 31 has such a small volume that the influence of pressure changes and/or thermal expansion on the flowable material located there can be so small that the flowable material is not expected to be unintentionally ejected from the ejection opening 32 of the printing nozzle head 31 in the closed position. Disadvantageously, however, the closing movement can result in an ejection of flowable material.

[0120] FIG. 12 shows a sectional view of a metering pump 2 according to the invention. The metering pump 2 is implemented as a piston conveyor 2. The metering pump 2 has an inlet opening 20a and an outlet opening 20b. The flowable material can get to the metering pump 2 from the heating hose 18 and from the return line (not shown) via the inlet opening 20a and be delivered to the printing nozzle 3 at a specified constant conveying speed via the outlet opening 20b.

[0121] The metering pump 2 has a metering pump housing 20, which extends substantially in the horizontal direction Y and has the outlet opening 20b pointing downward in the vertical direction Z. Two through-openings (not designated) are formed laterally in the horizontal direction Yin the metering pump housing 20, which each receive a piston 23, 24 movable in the horizontal direction Y from the outside. Centered in the horizontal direction Y, and in the vertical direction Z from above, the metering pump housing 20 accommodates a cylindrical valve element 26 in the form of a rotary valve 26 which can be rotated back and forth about its vertical axis by at least 180° . A first chamber volume 21 is enclosed within the metering pump housing 20 by the valve element 26 and the left piston 23, and a second chamber volume 22 is enclosed by the valve element 26 and the right piston 24.

[0122] The valve element 26 has the inlet opening 20a on the top in the vertical direction Z, which is followed by an inlet channel 26a extending first perpendicularly downward and then, in the view of FIG. 12, to the right. An outlet channel 26b extends, in the view of FIG. 12, first horizontally and then downward in the vertical direction Z, where the outlet channel 26b merges into the outlet opening 20b. In the view of FIG. 12, the first chamber volume 21 is connected to the outlet opening 20b of the metering pump 2 via the outlet channel 26b of the valve element 26, so that flowable material received there can be released from the metering pump 2 to the printing nozzle 3. Simultaneously, the second chamber volume 22 is connected to the inlet opening 20a of the metering pump 2 via the inlet channel 26a of the valve element 26, so that flowable material can get from the heating hose 18 into the second chamber volume 22 and be received there. By turning the valve element 26 by means of a valve drive 27, this can be done in reverse with regard to the two chamber volumes 21, 22.

[0123] The two pistons 23, 24 are connected to one another in a fixed manner outside the two chamber volumes 21, 22 by means of a piston linkage 25 in the form of a tie rod 25, so that the two pistons 23, 24 can only be moved jointly in the same direction in the horizontal direction Y. The sum of the two chamber volumes 21, 22 is therefore constant. The two coupled pistons 23, 24 can be moved by means of the piston drive 15 already mentioned. On the other hand, the flowable material flowing into the second chamber volume 22, for example, can additionally push the corresponding piston 24 outward or in the horizontal direction Y to the right, so that the piston drive 15 is partially relieved by this force. Both forces pull the opposite piston 23 of the first chamber volume 21 toward the valve element 26, as a result of which the flowable material located in the first chamber volume 21 is conveyed into the outlet channel 26b.

LIST OF REFERENCE SIGNS (PART OF THE DESCRIPTION)

[0124] A Flow direction of the inflowing flowable material

[0125] B Flow direction of the outflowing flowable material

[0126] C Flow direction of the returning flowable material

[0127] Y Horizontal direction;

[0128] Z Vertical direction;

[0129] 1 Printing device; 3D printer

[0130] 10 Frame; rack

[0131] 11 (horizontal) work surface; printing bed

[0132] 12 Printing head kinematics

[0133] 13 Printing head holder

[0134] 14 Printing head

[0135] 15 Piston drive of the metering pump 2

[0136] 16 Plasticizing unit; plasticizer

[0137] 16a Funnel of the plasticizing unit 16

[0138] 16b Screw of the plasticizing unit 16

[0139] 16b Ejection opening or nozzle opening of the plasticizing unit 16

[0140] 17 Material store

[0141] 18 (Hose-like) material guide element; heating hose

[0142] 2 Metering pump; piston conveyor

[0143] 20 Metering pump housing

[0144] 20a Inlet opening of the metering pump 2

[0145] 20b Outlet opening of the metering pump 2

[0146] 21 First chamber volume

[0147] 22 Second chamber volume

[0148] 23 Piston of the first chamber volume 21

[0149] 24 Piston of the second chamber volume 22

[0150] 25 Piston linkage; tie rod

[0151] 26 Valve element; rotary valve

[0152] 26a Inlet channel of the valve element 26

[0153] 26b Outlet channel of the valve element 26

[0154] 27 Valve drive

[0155] 3 Printing nozzle; nozzle

[0156] 30 Printing nozzle frame; nozzle body

[0157] 30a Inlet opening of the printing nozzle frame 30

[0158] 30b Inlet channel of the printing nozzle frame 30

[0159] 30c Inlet ring of the printing nozzle frame 30

[0160] 30d Sealing surfaces of the printing nozzle frame 30

[0161] 30e Outlet ring of the printing nozzle frame 30

[0162] 30f Outlet channel of the printing nozzle frame 30

[0163] 30g Outlet opening of the printing nozzle frame 30

[0164] 31 Printing nozzle head; nozzle needle

[0165] 31c Inlet ring of the printing nozzle head 31

[0166] 31d Sealing surfaces of the printing nozzle head 31

[0167] 31e Outlet ring of the printing nozzle head 31

[0168] 31f Outlet channel of the printing nozzle head 31

[0169] 31g Outlet opening of the printing nozzle head 31

[0170] 31h Ejection channel

[0171] 32 Ejection opening; nozzle opening

[0172] 33 Transition region

[0173] 4 Workpiece