The object of this invention is a filament feeding mechanism for a 3D printer head. Invention is applicable to printing heads of 3D printers adopted to supply at least two different filaments in a sequence.

In fused deposition modelling technology called 3D printing different types of utilities and prototypes, are made out of plastic filament. 3D printers uses single or multiple head mechanism which provides to obtain complex shapes and apply materials with different properties. Depending on project, the filament feeding system changes type of extruded material and/or printing nozzle without interrupting printing.

Document PL226634B1 discloses a method and filament feeding system attached to 3D printer. The feeding system comprises a lever connected to the shaft of a centrally located servomotor. Switching between different types of the filament is effected by a lever movement and pressing filament by a pinch roller to the motor wheel. Rotation of the motor wheel pushes the filament into the nozzle of a single printer head.

Document CN205631393U discloses a lifting system of dual head extrusion mechanism of a 3D printer. The lifting system comprises frame with center drive gear of servomotor fixed in the bottom of the frame and tooth belts connected to the gear and a printing head. As a consequence of changing rotation of a servomotor, lifting of the printing heads is provided.

Document US9469071 B2 discloses a filament feeding system adapted to single or multiple head 3D printer. The feeding system according to US Ό92 comprises centrally located servomotor connected with a drive gear. Switching between different types of filament is effected by changing rotation of the servomotor and meshing gears connected to the fixed printer head.

Document CN105538730A discloses a method and a filament changing system for 3D printing. The changing system comprises two separate gears mechanisms connected to the single servomotor. By changing rotation of the servomotor, lifting of the printing heads and filament feeding is affected.

Document CN205097553U discloses a printing heads changing mechanism of dual head 3D printer. The mechanism comprises a bracing arm connected with servomotor fixed on the symmetry axis and fixed printing nozzles in V-arrangement on the both ends. Rotation of the servomotor provides positioning one of the printing nozzles in perpendicular to the printing surface. Document CN103465633B discloses a filament switching system for dual head extrusion 3D printer. The system comprises the motor shaft tripod meshing with gears connected to filament feeding system. Changing one of the position, left, right or idle of the motor shaft provides switching between filament feeding systems of printing nozzles.

The gist of the invention is a filament feeding mechanism for a 3D printer head for selectively feeding filaments, comprising a motor wheel for feeding filaments, and a set of pinch rollers mounted on a rocker arm. Mechanism according to the invention is characterised in that it further comprises a pushrod connected to the rocker arm, and the rocker arm is pivotably mounted with the axis of rotation and adopted to rotate by lateral motion of the pushrod to press one of the pinch rollers to the respective filament.

Preferably the mechanism according to the invention is characterized in that the rocker arm has a leading wheel and pushrod has an opening guiding the leading wheel of the rocker arm to rotate the rocker arm by lateral motion of the pushrod.

Preferably the mechanism according to the invention is characterized in that the rocker arm is adopted to be actuating by the tooth wheel arrangement.

Preferably the mechanism according to the invention is characterized in that the rocker arm comprises an U-type groove for a motor wheel, and pinch rollers are mounted on both sides of motor wheel on the U- type groove arms.

Preferably the mechanism according to the invention is characterized in that the rocker arm comprises an oval opening for a motor wheel and filament guiding channels creating a pinching volume where filaments are pressed to the motor wheel by the pinch rollers.

Preferably the mechanism according to the invention is characterized in that at least one pinch roller is spring loaded.

Preferably the mechanism according to the invention is characterized in that the pushrod is provided with pressing element for lowering the printing nozzle arrangement when the respective filament is fed to the nozzle.

Preferably the mechanism according to the invention is characterized in that the nozzle arrangement is further provided with a rest spring for lifting the nozzle arrangement when nozzle is not fed with the filament.

Preferably the mechanism according to the invention is characterized in that the rocker arm is a modular assembly.

Advantageously the present invention solves the problem of switching filaments fed to a printing head of a 3D printer with a compact and elegant solution. Providing such effective mechanism allows to increase a speed of printing, reduce a risk of affecting already placed layers of filament. Further mechanism according to the invention is compact in size and therefore it can increase the working area of the 3D printer and is cheap in manufacturing.

Preferred embodiments of the invention have been described in more detail in reference to the figures of drawing :

Fig. 1 shows the first embodiment of the printing head mechanism according to the invention; Fig. 2 shows the second embodiment of the printing head mechanism according to the invention;

Fig. 3 shows section view of the second embodiment of the invention from Fig. 2.;

Fig.4 shows the third embodiment of the printing head mechanism according to the invention;

Fig. 5 shows the forth embodiment of the printing head mechanism according to the invention;

Fig. 6 shows section view of the fifth embodiment of the printing head mechanism according to the invention;

Fig. 1 shows the first embodiment of a printing head mechanism according to the invention. In this embodiment, the printing head mechanism comprises substantially a motor wheel 1 for feeding filaments, a pinch roller 2, a pinch roller 3, a rocker arm 4, a rocker arm's axis 5„ a leading wheel 7, a leading wheel's pin 6, a pushrod 8 and a pushrod lever 9. The motor wheel 1 is preferably a bi-directional servomotor. The rocker arm 4 is pivotably mounted with the axis of rotation 5. In this embodiment of the invention the rocker arm 4 has a U-type groove arms in the upper-middle part, where the motor wheel 1 is located. On the both sides of the groove of the rocker arm 4, are mounted symmetrically the pinch roller 2 and the pinch roller 3. In this embodiment of the invention the bottom part of the rocker arm 4 is connected to the pushrod 8, through the leading wheel's pin 6 and the pushrod 8 and is able to do side-to-side movements. The printing head mechanism according to this embodiment of the invention, comprises moreover two hotend radiator adapters 11 A, 11 B connecting the bottom of the filament guiding tubes with respective hotend 12 ended with a nozzle 14 and a hotend 13 ended with a nozzle 15. The hotend 13 is movable, while the hotend 12 is stationary.

As shown in Fig. 1 , a rest spring 16 is fixed between the hotend radiator adapter 11 B and the hotend 13. The pushrod 8 via pushrod lever 9 pushes down hotend radiator adapter 11 B to activate the nozzle 15.

In this embodiment of the invention, as a consequence of the finished work of the nozzle 15, the pushrod 8 moves to the left. It results in the clockwise rotational movement of the rocker arm 4 and the pinch roller 2 movement from the left side to the right side. At the same time the pushrod lever 9 stops pressing the hotend radiator adapter 11 B and the rest spring 16 causes the hotend13 and the nozzle 15 to move upward. Once the movement is completed the nozzle 15 is above the level of the nozzle 14. To activate the nozzle 15, the pushrod 8 moves to the right side, resulting in counter - clockwise rotational movement of the rocker arm 4 and the pinch roller 3 movement from the right side to the left side.

In the second embodiment of the invention shown in Fig.2 and Fig.3, the material switching mechanism comprises a rocker arm 4 with oval openings and a pushrod 8 with a pushrod lever 9. In this embodiment of the invention the rocker arm 4 is mounted to a mechanism block 17 on a rocker arm's axis 5 and the bottom part of the rocker arm 4 is connected to the pushrod 8 through a leading wheel's pin 6 and a leading wheel 7. A pinch roller 2 and a pinch roller 3 in this embodiment of the invention are mounted on both sides of the oval opening of the rocker arm 4 and a motor wheel 1 is arranged in the oval opening between them. The pushrod bearings 10 in this embodiment of the invention, as shown in Fig.3, rotates freely enabling therefore the pushrod 8, to do side-to-side movements. When the nozzle 15 starts working, the pushrod 8 moves to the right side resulting in counter-clockwise rotational movement of the rocker arm 4 and the pinch roller 3 movement from the right to the left side. The pushrod 8 movement to the right further causes that the pushrod 9 starts pushing the hotend radiator adapter 11 B and the hotend 13 ended with nozzle 15 moving downward. Once the movement is completed, the nozzle 15 is below the level of the nozzle 13 and the pinch roller 3 together with the rotating motor wheel 1 are pushing the filament directly into the filament guiding tube causing extrusion of the filament through the nozzle 15. In this embodiment of the invention when the nozzle 15 finishes work, the pushrod 8 moves to the left, resulting in the clockwise rotational movement of the rocker arm 4 and pinch roller 2 movement from the left to the right side. At the same time the pushrod lever 9 stops pressing the hotend radiator adapter 11 B and the rest spring 16 fixed to the hotend mounting block 18 causes the hotend 13 and the nozzle 15 to move upward.

Fig. 3 shows section view of second embodiment of the invention from Fig. 2.;in particular details of the pushrod 8. The pushrod 8 is placed between a set of pushrod bearings 10. The pushrod bearings 10 are grouped in two pairs however a different placement resulting in a stable positioning of the pushrod 8 can be applied. With four pushrod bearings applied, the pushrod 8 is firmly positioned laterally. Such arrangement provides a directional stability and yet introduce a low friction to the lateral motion. In that respect grease media is applied.

The pushrod 8 is provided with a guiding opening for holding a leading wheel 7. The shape of the opening provides side-to-side movement of the leading wheel 7 and respective rotation of the rocker arm 4.

Fig. 4 shows third embodiment of the invention where the pinch roller 2 is spring loaded. In this embodiment The pinch roller 2, and the pinch roller 3 are mounted to the rocker arm 4 symmetrically on both sides of the motor wheel opening.

The pinch roller 2 is mounted on one end of a pinch roller arm 20. The pinch roller arm 20 is pivotably mounted to the construction of the rocker arm 4. On the other end of the pinch roller arm 20 a loading spring 19 is provided, which is connected to the rocker arm 4 with its other end. Such an arrangement enables regulation of the pressing force produced by the pinch roller 2 on the filament by regulation of the tension force of the spring 19.

When the left nozzle starts working the spring 19 pushes the pinch roller lever 20 which pushes the pinch roller 2 to the filament. To deactivate the nozzle 14 the rocker arm 4 starts rotating counter-clockwise due to pushrod 8 lateral motion. The spring 19 keeps pushing the pinch roller 2 until the pinch roller lever 20 rests on a rocker arm inset 21. The movement continues until the moment when filament stops touching the motor wheel 1. A similar arrangement is applied to the pinch roller 3.

Figure 5 shows the forth embodiment of the present invention where the pushrod 8 is adopted to be actuating by the tooth wheel arrangement 22, 23. The pushrod 8 can be actuated by any suitable actuation means that generates lateral motion of the pushrod 8. In the preferred embodiment the tooth wheel arrangement 22, 23 is applied as it has a better control properties over other means as linear electromagnetic motor, hydraulic or pneumatic systems.

According to this embodiment the pushrod 8 is firmly positioned laterally by a set of pushrod bearings 10 as described in relation to figure 3.

The tooth wheel arrangement 22,23 comprises a toothed wheel or gear 22 and notched linear path or gear rack 23 provided on the upper edge of the pushrod 8. Rotation of the toothed wheel 22 in clockwise direction on fig. 5, translates into linear motion of the pushrod 8 to the left of fig. 5. A counter-clockwise rotation of toothed wheel 22 translates into linear motion of the pushrod 8 to the right of fig. 5. One can easily notice the placement of the tooth wheel arrangement 22, 23 below the pushrod 8 is also possible, in a such a case notched linear path 23 would be placed on a lower edge of the pushrod 8, and directional effects described above would be reversed. The tooth wheel 22 can be powered by any suitable motor for example a an electric servomotor that provides full control over the translation, speed, momentum or acceleration of the pushrod 8. Such means greatly improves keeping a control over the print head mechanism.

Figure 6 shows the fifth embodiment of the invention where the rocker arm has a modular construction. The rocker arm comprising two major parts: main part of the rocker arm 4A as in the previous embodiments and additional upper part 4B containing short filament tunnels leading the filament to both sides of the motor wheel 1. The rocker's arm upper part 4B is placed above the rocker arm's axis 5. Below the rocker arm's axis 5 and above the rocker arm 4A there is provided a filament guiding block 26 containing filament channels 24 and 25 fixed to the mechanism block 17. Rocker arm 4A and rocker arm's upper part 4B are connected with each other by any suitable means as threaded bolts or adhesive. A connection made between the parts of the rocker arm A, 4B fixes the position of the respective part with others and has a required mechanical strength appropriate to transmit the loads that can be expected in the mechanically moving assembly of this type.

The modular construction of rocker arm facilitates manufacturing process of rocker arm and assembling process of the mechanism according to the invention. The rocker arm's upper part 4B can be made using conventional milling techniques instead of directional drilling or 3d printing using plastic or metal powder than can be used in a cased a rocker arm made of one solid object.

Assembly process of the mechanism according to the invention is much facilitated by introduction of modular design of the rocker arm. Mounting pinching rollers 2, 3 is much easier when main parts of the rocker arm 4A and 4B can be joined after placing respective pinch rollers 2, 3 in place.

Further, a modular construction of this embodiment facilitates and makes much easier an introduction of more sophisticated mechanism within the rocker arm, as for example a spring loading mechanism used for regulation of the pressure applied by pinching rollers to the filament as described above in relation to one of the preferred embodiments.

As a general remark it shall be noted, the preferred embodiments of the invention as described above can be joined in any feasible combination as in general they contributes to different aspects of the invention.

List of reference numbers:

1 - motor wheel

2 - pinch roller A

3 - pinch roller B

4 - rocker arm

4A, 4B - parts of modular rocker arm

5 - rocker arm's axis

6 - leading wheel's pin

7 - leading wheel

8 - pushrod

9 - pushrod lever 10 - pushrod bearing

11 A, 11 B - hotend radiator adapters

12 - hotend A

13 - hotend B

14 - nozzle A

15 - nozzle B

16 - rest spring

17 - mechanism block

18 - hotend mounting block

19 - spring

20 - pinch roller lever

21 - rocker arm inset

22 - pushrod gear

23 - pushrod gear rack

24 - filament guiding tube A

25 - filament guiding tube B

26 - filament guiding block