Patent Description:
Fused filament fabrication (FFF) is an additive manufacturing process that typically uses a continuous filament of a thermoplastic material. The filament may be fed from a filament supply to a moving, heated print head, and may be deposited through a print nozzle onto an upper surface of a build plate. Further, the print head may be moved relative to the build plate under computer control to define a printed shape. In certain FFF devices, the print head may move in two dimensions to deposit one horizontal plane, or a layer, at a time. A work is therefore formed by the deposited layers. The work or the print head may then be moved vertically by a small amount to begin a new layer. In this manner, a 3D-object may be produced out of the thermoplastic material.

Some print heads may utilize multiple extruders to deposit different thermoplastic materials or a combination thereof. The ability to extrude different thermoplastic materials may allow selection and use of different thermoplastic materials based on desired physical properties and/or geometry of the 3D-object. The different thermoplastic materials may also be selected based on intended applications. For example, some print heads may utilize a pair of extruders that may selectively extrude a part material and a support material.

Conventional print heads utilizing multiple extruders require a separate motor and a corresponding drive for feeding the thermoplastic materials to each heated extruder. This may significantly increase the weight and size of the print head with each additional extruder, thereby degrading the overall performance of the print head and an additive manufacturing system utilizing the print head.

Some existing additive manufacturing systems may include feeders disposed outside the print head, for example, on a body of the additive manufacturing system. Such an arrangement may be complex in construction and reduces efficiency of the system since the feeders would be away from the print head. Current systems also use feeders that are typically disposed on the print head.

<CIT> discloses an extrusion head for an extrusion-based layered manufacturing system utilizing a single drive motor. The system includes an assembly positionable between a first state and a second state using a toggle-plate assembly. A first extrusion line engages a drive wheel while the assembly is positioned in the first state, and a second extrusion line engages the drive wheel while the assembly is positioned in the second state. The system may selectively extrude a pair of materials with the use of the single drive motor and the assembly. However, a single drive wheel is used for selectively engaging and feeding two different filaments. Therefore, a rotational direction of the motor needs to be changed when switching between the two filaments. Moreover, two separate wheels have to be moved relative to the drive wheel during switching between the two filaments. This may increase a complexity of the manufacturing system, thereby adversely impacting its reliability and cost.

The document <CIT> discloses a fused filament fabrication system comprising a drive gear coupling to a motor during operation; the drive gear selectively engages first or second sets of idler gears during operation of the system; a first filament is positioned between a shaft of said first idler gear and idler bearings and a second filament is positioned between a shaft of said second idler gear and idler bearings.

The aim of the present invention is to provide a new and improved dual filament feeder assembly for an additive manufacturing system and a dual extruder print head including the dual filament feeder assembly. The dual extruder print head may selectively extrude two materials while utilizing a single motor.

According to a first aspect of the present invention, there is provided a dual filament feeder assembly for an additive manufacturing system. The dual filament feeder assembly comprises a drive wheel. The dual filament feeder assembly further comprises a drive shaft connected to the drive wheel. The dual filament feeder assembly further comprises a first feeder wheel rotatably arranged around the drive shaft at a first side of the drive wheel. The dual filament feeder assembly further comprises a second feeder wheel rotatably arranged around the drive shaft at a second side of the drive wheel opposite to the first side. The dual filament feeder assembly further comprises a coupling member arranged to selectively couple the drive wheel with one of the first feeder wheel and the second feeder wheel. The dual filament feeder assembly further comprises a shifting member arranged to move the coupling member between a first position and a second position. The coupling member drivably couples the drive wheel with the first feeder wheel in the first position of the coupling member. The coupling member drivably couples the drive wheel with the second feeder wheel in the second position of the coupling member.

The dual filament feeder assembly of the present invention may allow selective feeding of two filaments based on the first position and the second position of the coupling member. Use of the shifting member to move the coupling member between the first position and the second position may allow selective coupling of the drive wheel with the first feeder wheel or the second feeder wheel. This may allow a single motor drive to be used, thereby reducing a weight and a size of the dual filament feeder assembly. The shifting member may be actuated mechanically, electrically, pneumatically, hydraulically, or any combinations thereof. Since only the coupling member is moved between the first position and the second position, instead of moving the first feeder wheel and the second feeder wheel, the dual filament feeder assembly of the present invention may have a simple design with improved performance and reliability. Moreover, a change in a rotational direction of the drive wheel may not be required during switching between the two filaments, leading to a simpler design and operation of the dual filament feeder assembly.

In an embodiment, the coupling member comprises a ring with a plurality of inner splines arranged on an inner surface of the ring. The first feeder wheel comprises a first splined portion that is at least partially engaged with the plurality of inner splines of the coupling member in the first position of the coupling member. The second feeder wheel comprises a second splined portion that is at least partially engaged with the plurality of inner splines of the coupling member in the second position of the coupling member. The drive wheel comprises a plurality of outer splines slidably and at least partially engaging with the plurality of inner splines of the coupling member. The coupling member is slidable over the drive wheel between the first position and the second position. The plurality of inner splines of the coupling member may always be at least partially engaged with the plurality of outer splines of the drive wheel. The inner splines and the outer splines may result in a reliable engagement between the coupling member and the drive wheel. Similarly, the inner splines and the first splined portion may result in a reliable engagement between the coupling member and the first feeder wheel while the coupling member is in the first position. Further, the inner splines and the second splined portion may result in a reliable engagement between the coupling member and the second feeder wheel while the coupling member is in the second position.

In an embodiment, the first feeder wheel further comprises a first roller portion for contact with a first filament. The second feeder wheel further comprises a second roller portion for contact with a second filament. The first and second roller portions may improve engagement of the first and second feeder wheels with the first and second filaments, respectively.

In an embodiment, the dual filament feeder assembly further comprises a support shaft arranged in parallel relative to the drive shaft. The shifting member comprises a sliding portion that receives the support shaft therethrough, such that the shifting member is slidable along the support shaft. The support shaft may enable the shifting member to move linearly and substantially parallel to the drive shaft.

In an embodiment, the coupling member further comprises a pair of end flanges. The shifting member further comprises an actuating portion extending from the sliding portion and received at least partially between the pair of end flanges of the coupling member, such that a linear movement of the shifting member along the support shaft causes a corresponding linear movement of the coupling member along the drive shaft. The pair of end flanges may restrict relative linear movement between the shifting member and the coupling member. Therefore, coupling between the shifting member and the coupling member may be improved. Further, the coupling member may also provide a bearing surface to allow relative rotational movement between the coupling member and the shifting member.

In an embodiment, the dual filament feeder assembly further comprises a mechanical switch that comprises an arm engaged with the shifting member, such that an actuation of the mechanical switch causes a linear movement of the shifting member and a corresponding movement of the coupling member between the first position and the second position. The mechanical switch may allow actuation of the shifting member and the coupling member based on a desired operation of the additive manufacturing system.

In an embodiment, the mechanical switch is rotatable about a vertical rotation axis. A rotation of the mechanical switch may result in the linear movement of the shifting member and the corresponding movement of the coupling member between the first position and the second position.

In an embodiment, the shifting member further comprises an engaging portion. The engaging portion comprises a lower surface, a first side surface extending from the lower surface, and a second side surface extending from the lower surface and spaced apart from the first side surface. The lower surface, the first side surface and the second side surface define a channel therebetween. The arm of the mechanical switch is at least partially and movably received within the channel. The channel and the arm may enable reliable engagement between the shifting member and the mechanical switch.

In an embodiment, the arm of the mechanical switch comprises an elongate portion and an end portion inclined to the elongate portion. The end portion is arranged to slide relative to the lower surface of the engaging portion prior to selectively engaging with one of the first side surface and the second side surface. The sliding movement of the end portion relative to the lower surface may allow a certain degree of play between the mechanical switch and the shifting member. Such play may improve an engagement between the coupling member and the first feeder wheel or the second feeder wheel.

In an embodiment, the end portion is disc-shaped. The disc-shaped end portion may allow smooth movement of the shifting member based on the movement of the mechanical switch. The disc-shaped end portion may also have less area of contact leading to reduced wear.

In an embodiment, the mechanical switch further comprises a curved wedge member configured to rotate about the vertical rotation axis. The curved wedge member is arranged to receive an upper part of a cylindrical extruder having a flange at a top end of the cylindrical extruder. The curved wedge member may allow the mechanical switch to move the cylindrical extruder based on a rotation about the vertical rotation axis. In this way, the mechanical switch both controls the suitable lifting of one of the extruders and at the same time, activates the driving of the correct feeder wheels.

In an embodiment, the dual filament feeder assembly further comprises an electrical motor for driving the drive shaft. The single electrical motor may selectively drive the first feeder wheel or the second feeder wheel via the drive wheel.

According to a second aspect, there is provided a dual extruder print head for an additive manufacturing system. The dual extruder print head comprises the dual filament feeder assembly of the first aspect. The print head may have reduced weight and size, while allowing dispensing of two filaments.

In an embodiment, the dual extruder print head further comprises a first dock for installing a first extruder that, at least in use, receives a first filament from the first feeder wheel, and a second dock for installing a second extruder that, at least in use, receives a second filament from the second feeder wheel. In some cases, the first and second extruders may be detachably received in the first and second docks, respectively, for facilitating replacement and/or maintenance.

In an embodiment, the mechanical switch is coupled with the second extruder. The second extruder is in a raised position when the coupling member is in the first position. The second extruder is in a lowered position when the coupling member is in the second position. The single mechanical switch may therefore perform two operations simultaneously: a) actuating the coupling member between the first and second positions to switch between the two filaments; b) moving the second extruder between the raised position and the lowered position. Thus, the dual extruder print head including the mechanical switch may have a simpler design and operation. The first extruder may be active, and the second extruder may be idle in the raised position of the second extruder. Conversely, the second extruder may be active, and the first extruder may be idle in the lowered position of the second extruder. The raised and lowered positions of the second extruder may minimize interference between the first and second extruders when one of them is active and the other is idle.

According to a third aspect, there is provided an additive manufacturing system including the dual extruder print head of the second aspect. The additive manufacturing system may have an improved overall performance.

It should be noted that items which have the same reference numbers in different Figures, have the same structural features and the same functions, or are the same signals.

<FIG> schematically shows an embodiment of a dual extruder print head <NUM> for an additive manufacturing system. The dual extruder print head <NUM> may build parts/components in a layer-by-layer manner from a software model, such as a computer-aided design (CAD) model. In some embodiments, the dual extruder print head <NUM> may comprise a pair of extruders (not shown) that may receive a consumable material (e.g., a filament). As used herein, the term "consumable material" collectively refers to one or more consumable materials received by the dual extruder print head <NUM>. Each extruder may receive a corresponding consumable material. The consumable material may be melted by the pair of extruders and the molten consumable material may then be utilized to produce the parts/components.

The consumable material may be provided through a pair of guide tubes <NUM> corresponding to the pair of extruders. The guide tubes <NUM> may be utilized to support and guide the consumable material. In some embodiments, the dual extruder print head <NUM> may utilize other structures for guiding and supporting the consumable material. The dual extruder print head <NUM> further comprises adaptors <NUM> for receiving the respective guide tubes <NUM> and the associated consumable material. The dual extruder print head <NUM> may further comprise an inlet <NUM> for supplying power and control signals. In an example, power and control signal may be supplied to the dual extruder print head <NUM> using a cord running through the inlet <NUM>.

The dual extruder print head <NUM> further comprises a housing <NUM>. The housing <NUM> comprises an upper housing portion <NUM> and a lower housing portion <NUM> removably coupled to the upper housing portion <NUM>. In some embodiments, the upper housing portion <NUM> may further comprise sub-housing portions that may facilitate access to internal components.

The dual extruder print head <NUM> further comprises a rail carriage <NUM> disposed on the housing <NUM>. Specifically, the rail carriage <NUM> is disposed at a rear portion of the housing <NUM>. The rail carriage <NUM> allows the dual extruder print head <NUM> to be mounted on a guide rail <NUM> (shown in <FIG>) for appropriate movement of the dual extruder print head <NUM> in working directions.

<FIG> schematically shows an embodiment of the dual extruder print head <NUM> with the housing <NUM> omitted. The dual extruder print head <NUM> may further comprise a dual filament feeder assembly <NUM> for dispensing a first filament <NUM> and a second filament <NUM>. The dual filament feeder assembly <NUM> comprises a first feeder <NUM> for receiving the first filament <NUM> and a second feeder <NUM> for receiving the second filament <NUM>. The dual extruder print head <NUM> further comprises a first dock for installing a first extruder <NUM> that, at least in use, receives the first filament <NUM> from the first feeder <NUM>, and a second dock for installing a second extruder <NUM> that, at least in use, receives the second filament <NUM> from the second feeder <NUM>. In some embodiments, the first dock and the second dock may detachably receive the first extruder <NUM> and the second extruder <NUM>, respectively, in order to allow replacement and/or maintenance. The housing <NUM> (shown in <FIG>) at least partially encloses the dual filament feeder assembly <NUM>, the first extruder <NUM>, and the second extruder <NUM> therein.

The first and second filaments <NUM>, <NUM> may be provided through the guide tubes <NUM> (shown in <FIG>). In some embodiments, one of the first and second filaments <NUM>, <NUM> may comprise a consumable part material while the other filament may comprise a consumable support material. In some embodiments, the consumable part material and the consumable support material may differ in material properties. In some cases, the first filament <NUM> may comprise a thermoplastic polymer, such as Acrylonitrile Butadiene Styrene (ABS). Further, the second filament <NUM> may comprise a water-soluble material, such as Polyvinyl alcohol (PVA). In alternative embodiments, both the consumable part material and the consumable support material may be similar to each other. In some other embodiments, the first and second filaments <NUM>, <NUM> may comprise a similar build material with different cosmetic or aesthetic properties, such as different colours.

The dual filament feeder assembly <NUM> may engage with the consumable material (the first and second filaments <NUM>, <NUM>) and draw successive segments of the consumable material to be fed to the first extruder <NUM> or the second extruder <NUM>. In some embodiments, the dual filament feeder assembly <NUM> may engage with the first and second filament <NUM>, <NUM> without significantly deforming the filaments but such that the dual filament feeder assembly <NUM> feeds the filaments into the dual extruder print head <NUM> with a desired force.

In some embodiments, during a build operation, the successive segments of the consumable material may be heated by the first and second extruders <NUM>, <NUM>. Further, the melted consumable material may then be released from extruder tips (not shown) of the first and second extruders <NUM>, <NUM> and deposited in a layer-wise pattern to produce parts/components. In some embodiments, the dual filament feeder assembly <NUM> may selectively dispense only one of the first and second filaments <NUM>, <NUM> at a time, such that only one of the first and second extruders <NUM>, <NUM> may be operational at a time during the build operation.

The first and second feeders <NUM>, <NUM> are activated by a drive shaft <NUM>. The dual filament feeder assembly <NUM> further comprises an electrical motor <NUM> for driving the drive shaft <NUM>. The electrical motor <NUM> may rotate the drive shaft <NUM> through one or more gears <NUM>. During operation, the electrical motor <NUM> may selectively drive the first feeder <NUM> or the second feeder <NUM>. In some embodiments, the first feeder <NUM> and the second feeder <NUM> may be disposed adjacent to each other. In some embodiments, the first feeder <NUM> and the second feeder <NUM> may dispense the first filament <NUM> and the second filament <NUM> to the first extruder <NUM> and the second extruder <NUM>, respectively.

The dual extruder print head <NUM> may further comprise an electronic assembly <NUM> that monitors and/or controls the operation of the dual extruder print head <NUM>. In an example, the electronic assembly <NUM> may comprise a circuit board with printed circuits/components mounted thereon.

In some embodiments, separate heating units may be provided in heating engagement with the first and second extruders <NUM>, <NUM> so as to heat the first and second filaments <NUM>, <NUM> as the first and second filaments <NUM>, <NUM> travel through the first and second extruders <NUM>, <NUM>, respectively, during operation of the additive manufacturing system. The heating units may provide heat to the respective first and second extruders <NUM>, <NUM> for obtaining set point operating temperature(s) required to generate a desired thermal gradient for melting the consumable material. In some embodiments, the first and second extruders <NUM>, <NUM> may be cooled down from their respective operating temperatures after use to prevent the consumable material from thermally degrading, oozing, or dripping out. The heating and/or cooling of the first and second extruders <NUM>, <NUM> may be monitored by the electronic assembly <NUM> or by another controlling system arranged in the printing system.

<FIG> schematically shows an embodiment of the dual filament feeder assembly <NUM> for an additive manufacturing system. The dual filament feeder assembly <NUM> may be a part of a print head (e.g., the dual extruder print head <NUM> shown in <FIG>) of the additive manufacturing system. The dual filament feeder assembly <NUM> comprises a drive wheel <NUM>. The dual filament feeder assembly <NUM> further comprises the drive shaft <NUM> connected to the drive wheel <NUM>. The dual filament feeder assembly <NUM> further comprises the electrical motor <NUM> and the one or more gears <NUM> for driving the drive shaft <NUM>. The guide tubes <NUM> may provide the first filament <NUM> and the second filament <NUM> to the dual filament feeder assembly <NUM>. The guide tubes <NUM> may be supported by the adaptors <NUM> at least partially disposed in a housing (e.g., the housing <NUM> shown in <FIG>) of the print head.

The dual filament feeder assembly <NUM> further comprises a first feeder wheel <NUM> rotatably arranged around the drive shaft <NUM> at a first side X1 (also shown in <FIG>) of the drive wheel <NUM>. Specifically, the first feeder <NUM> comprises the first feeder wheel <NUM>. As used herein, the term "rotatably arranged" refers to configurations in which a first element may be directly coupled to a second element in a rotatable manner, for example, in a manner that allows for rotation of the first element with respect to the second element or vice versa. The term may also comprise configurations in which the first element may be indirectly coupled to a second element in a rotatable manner by affixing the first element to intermediate member(s) (e.g., bearings) that in turn are affixed to the second element.

In some embodiments, the first feeder wheel <NUM> may be selectively driven by the electrical motor <NUM>. The first feeder wheel <NUM> may comprise a first gear portion <NUM>. The first feeder <NUM> further comprises a third feeder wheel <NUM> having a third gear portion <NUM>. The first gear portion <NUM> of the first feeder wheel <NUM> meshes with and drives the third gear portion <NUM> of the third feeder wheel <NUM>. In some other embodiments, the first feeder wheel <NUM> and the third feeder wheel <NUM> may engage with each other by any other suitable means, such as a friction coupling.

The first feeder wheel <NUM> further comprises a first roller portion <NUM> for contacting the first filament <NUM>. The third feeder wheel <NUM> further comprises a third roller portion <NUM> that contacts the first filament <NUM> together with the first roller portion <NUM>. The first filament <NUM> may be received between the first roller portion <NUM> of the first feeder wheel <NUM> and the third roller portion <NUM> of the third feeder wheel <NUM>.

The dual filament feeder assembly <NUM> further comprises a second feeder wheel <NUM> rotatably arranged around the drive shaft <NUM> at a second side X2 (also shown in <FIG>) of the drive wheel <NUM> opposite to the first side X1. Specifically, the second feeder <NUM> comprises the second feeder wheel <NUM>. In some embodiments, the second feeder wheel <NUM> may be selectively driven by the electrical motor <NUM>. The second feeder wheel <NUM> comprises a second gear portion <NUM>. The second feeder <NUM> further comprises a fourth feeder wheel <NUM> having a fourth gear portion <NUM>. The second gear portion <NUM> of the second feeder wheel <NUM> meshes with and drives the fourth gear portion <NUM> of the fourth feeder wheel <NUM>. In some other embodiments, the second feeder wheel <NUM> and the fourth feeder wheel <NUM> may engage with each other by any other suitable means, such as a friction coupling.

The second feeder wheel <NUM> further comprises a second roller portion <NUM> for contacting the second filament <NUM>. The fourth feeder wheel <NUM> further comprises a fourth roller portion <NUM> that contacts the second filament <NUM> together with the second roller portion <NUM>. The second filament <NUM> may be received between the second roller portion <NUM> of the second feeder wheel <NUM> and the fourth roller portion <NUM> of the fourth feeder wheel <NUM>. The third feeder wheel <NUM> and the fourth feeder wheel <NUM> are arranged around an idle shaft <NUM>. In some embodiments, the third feeder wheel <NUM> and the fourth feeder wheel <NUM> are rotatably arranged around the idle shaft <NUM>, such that the third feeder wheel <NUM> and the fourth feeder wheel <NUM> rotate relative to the idle shaft <NUM>. In some other embodiments, the idle shaft <NUM> may rotate along with the third feeder wheel <NUM> and the fourth feeder wheel <NUM>.

In some embodiments, the electrical motor <NUM> may be arranged to selectively drive one of the first feeder wheel <NUM> and the second feeder wheel <NUM>. It should be appreciated that any type of prime mover may be utilized for driving the first feeder wheel <NUM> and/or the second feeder wheel <NUM> without departing from the scope of this disclosure.

The dual filament feeder assembly <NUM> further comprises a coupling member <NUM> arranged to selectively couple the drive wheel <NUM> with one of the first feeder wheel <NUM> and the second feeder wheel <NUM>. Specifically, the electrical motor <NUM> may be arranged to drive either the first feeder wheel <NUM> or the second feeder wheel <NUM> based on selective coupling of the drive wheel <NUM> with the corresponding first feeder wheel <NUM> or the second feeder wheel <NUM>. As used herein, the term "selectively couple" means removably coupled wherein a first element may be coupled to a second element under one or more conditions and the first element may be detached from the second element under one or more conditions.

The dual filament feeder assembly <NUM> further comprises a shifting member <NUM> arranged to move the coupling member <NUM> between a first position P1 (shown in <FIG>) and a second position P2 (shown in <FIG>). In some embodiments, the shifting member <NUM> may be coupled to the coupling member <NUM>. Further, in some embodiments, the shifting member <NUM> may be coupled to the coupling member <NUM>, such that the coupling member <NUM> may be arranged to move along with the shifting member <NUM>. In some embodiments, the shifting member <NUM> may be arranged to move the coupling member <NUM> for selectively coupling the drive wheel <NUM> with one of the first feeder wheel <NUM> and the second feeder wheel <NUM>.

The dual filament feeder assembly <NUM> further comprises a mechanical switch <NUM> engaged with the shifting member <NUM>. In some embodiments, the mechanical switch <NUM> may move the shifting member <NUM> to allow the shifting member <NUM> to move the coupling member <NUM> between the first position P1 and the second position P2. The coupling member <NUM> drivably couples the drive wheel <NUM> with the first feeder wheel <NUM> in the first position P1 of the coupling member <NUM>. The coupling member <NUM> drivably couples the drive wheel <NUM> with the second feeder wheel <NUM> in the second position P2 of the coupling member <NUM>. When the coupling member <NUM> drivably couples the drive wheel <NUM> with one of the first feeder wheel <NUM> and the second feeder wheel <NUM>, the rotation of the drive wheel <NUM> may be transmitted to the first feeder wheel <NUM> or the second feeder wheel <NUM>.

As used herein, the term "drivably couple" refers to a state in which two rotary elements are coupled to each other in such a way that allows transfer of a drive force, which comprises a state in which the two rotary elements are coupled to each other to rotate together with each other, or a state in which the two rotary elements are coupled to each other via one or two or more transmission members in such a way that allows transfer of the drive force. Examples of such transmission members may comprise various members that transfer rotation at a substantially equal speed or a changed speed, such as a gear mechanism, a belt mechanism, and a chain mechanism. Additional examples of such transmission members may comprise engagement elements that selectively transfer rotation and the drive force, such as a friction engagement element and a meshing-type engagement element.

In some embodiments, the mechanical switch <NUM> may rotate between a first switch position S1 (shown in <FIG>) and a second switch position S2 (shown in <FIG>), such that the shifting member <NUM> moves the coupling member <NUM> to couple the drive wheel <NUM> with one of the first feeder wheel <NUM> and the second feeder wheel <NUM>. The electrical motor <NUM> may drive the drive wheel <NUM> through the drive shaft <NUM> and the one or more gears <NUM>. The first switch position S1 may correspond to the first position P1 of the coupling member <NUM> and the second switch position S2 may correspond to the second position P2 of the coupling member <NUM>. In some embodiments, the mechanical switch <NUM> may be actuated automatically. However, in some embodiments, the mechanical switch <NUM> may be manipulated manually as well.

The selective coupling of the first feeder wheel <NUM> or the second feeder wheel <NUM> with the electrical motor <NUM> allows either the first filament <NUM> or the second filament <NUM> to be dispensed accordingly based on the position of the mechanical switch <NUM> and the coupling member <NUM>. Further, referring to <FIG>, the dual extruder print head <NUM> may extrude either the first filament <NUM> or the second filament <NUM> after being processed by the first extruder <NUM> or the second extruder <NUM>, respectively.

It should be understood that the selective coupling of the electrical motor <NUM> with the first feeder wheel <NUM> or the second feeder wheel <NUM> by the coupling member <NUM> through movement of the mechanical switch <NUM> is incorporated in the present disclosure by way of example only, and the actuation of the coupling member <NUM> for selective engagement of the electrical motor <NUM> with the first feeder wheel <NUM> or the second feeder wheel <NUM> may be realized by any other means as well without limiting the scope of the present disclosure. For example, the mechanical switch <NUM> may be replaced with any suitable electrical actuator, hydraulic actuator, pneumatic actuator, mechanical actuator, and/or the like.

<FIG> schematically show a left perspective view and a right perspective view, respectively, of an embodiment of the electrical motor <NUM> and the one or more gears <NUM> of the dual filament feeder assembly <NUM>. Referring now to the illustrated embodiment of <FIG>, the one or more gears <NUM> comprise a first gear 238A, a second gear 238B meshed with the first gear 238A, a third gear 238C, and a fourth gear 238D meshed with the third gear 238C. The first gear 238A is mounted on a motor shaft <NUM> of the electrical motor <NUM> and is driven by the electrical motor <NUM>. The first gear 238A drives the second gear 238B. The third gear 238C is coupled to the second gear 238B, such that the second and third gears 238B, 238C rotate together at a same speed. In some embodiments, the second and third gears 238B, 238C may be fixedly coupled with each other. The third gear 238C drives the fourth gear 238D. The fourth gear 238D is coupled to the drive shaft <NUM>, such that the fourth gear 238D and the drive shaft <NUM> rotate together at a same speed. The first and second gears 238A, 238B may form a first reduction stage, while the second and third gears 238C, 238D may form a second reduction stage. The first, second, third and fourth gears 238A-D may reduce a rotational speed provided by the electrical motor <NUM> to a desired speed of the drive shaft <NUM>.

The electrical motor <NUM> may drive the drive wheel <NUM> through the one or more gears <NUM>. Specifically, the electrical motor <NUM> may rotate the drive shaft <NUM> that drives the drive wheel <NUM>. In some embodiments, the drive wheel <NUM> may be fixedly or removably coupled with the drive shaft <NUM>, for example, through welding, interference fit or keyed coupling. In the examples shown in <FIG>, the one or more gears <NUM> are illustrated as spur gears, however, any other suitable type of gear may be utilized without limiting the scope of the present disclosure. Further, in some embodiments, the one or more gears <NUM> may comprise one or more idle gears as well.

In some embodiments, the electrical motor <NUM> may be monitored and controlled by a controller (not shown) during operation of the additive manufacturing system. For example, the controller may control stop, start and a change in direction of rotation of the electrical motor <NUM> when required. Referring now to <FIG>, <FIG>, in some embodiments, the electrical motor <NUM> may be momentarily stopped before the coupling member <NUM> drivably couples the drive wheel <NUM> with the second feeder wheel <NUM> from the first feeder wheel <NUM> and vice versa. Further, in some embodiments, the electrical motor <NUM> may first operate in a reverse direction before the coupling member <NUM> shifts between the first position P1 (shown in <FIG>) and the second position P2 (shown in <FIG>) for substantially pulling a corresponding filament (e.g., the first filament <NUM> or the second filament <NUM>) out from a corresponding extruder (e.g., the first extruder <NUM> or the second extruder <NUM>). However, the reverse operation of the electrical motor <NUM> may be momentary or for a predetermined angle/number of rotations of the motor shaft <NUM>.

<FIG> further illustrate the first side X1 of the drive wheel <NUM> and the second side X2 of the drive wheel <NUM>. The first side X1 and the second side X2 are opposing sides that correspond to opposing axial faces of the drive wheel <NUM>. Referring to <FIG>, <FIG>, the first feeder wheel <NUM> and the second feeder wheel <NUM> are disposed at the first side X1 and the second side X2, respectively, of the drive wheel <NUM>, such that the drive wheel <NUM> is disposed between the first and second feeder wheels <NUM>, <NUM> along a length of the drive shaft <NUM>.

<FIG> illustrates the dual filament feeder assembly <NUM> in the first position P1 of the coupling member <NUM>. The first position P1 of the coupling member <NUM> may correspond to the first switch position S1 of the mechanical switch <NUM>. In the first position P1 of the coupling member <NUM>, the coupling member <NUM> drivably couples the drive wheel <NUM> with the first feeder wheel <NUM>, such that power from the electrical motor <NUM> (shown in <FIG>) may be transmitted to the first feeder wheel <NUM>. <FIG> schematically shows the dual filament feeder assembly <NUM> in the second position P2 of the coupling member <NUM>. The second position P2 of the coupling member <NUM> may correspond to the second switch position S2 of the mechanical switch <NUM>. In the second position P2 of the coupling member <NUM>, the coupling member <NUM> drivably couples the drive wheel <NUM> with the second feeder wheel <NUM> such that power from the electrical motor <NUM> may be transmitted to the second feeder wheel <NUM>. Some of the parts of the dual filament feeder assembly <NUM> in <FIG> are not shown for clarity.

Referring now to <FIG>, the dual filament feeder assembly <NUM> comprises the first feeder wheel <NUM> and the second feeder wheel <NUM> rotatably arranged around the drive shaft <NUM>. The dual filament feeder assembly <NUM> further comprises the third feeder wheel <NUM> and the fourth feeder wheel <NUM> arranged around the idle shaft <NUM>. The dual filament feeder assembly <NUM> further comprises the coupling member <NUM> for selectively coupling the drive wheel <NUM> (shown in <FIG>) with the first feeder wheel <NUM> or the second feeder wheel <NUM>. In the illustrated embodiment, the coupling member <NUM> comprises a ring <NUM> (shown in <FIG>) with a plurality of inner splines <NUM> arranged on an inner surface <NUM> of the ring <NUM>. The dual filament feeder assembly <NUM> further comprises the drive wheel <NUM> coupled to the drive shaft <NUM> and receiving power from the electrical motor <NUM> through the one or more gears <NUM> (shown in <FIG>, <FIG>).

The first feeder wheel <NUM> and the second feeder wheel <NUM> may receive the drive shaft <NUM> therethrough, such that each of the first feeder wheel <NUM> and the second feeder wheel <NUM> may rotate relative to the drive shaft <NUM>. In some embodiments, the first feeder wheel <NUM> and the second feeder wheel <NUM> may be mounted on the drive shaft <NUM> through any suitable bearing, such as a roller bearing or a journal bearing. The third feeder wheel <NUM> and the fourth feeder wheel <NUM> may receive the idle shaft <NUM> therethrough, such that each of the third feeder wheel <NUM> and the fourth feeder wheel <NUM> may rotate relative to the idle shaft <NUM>. In some embodiments, the third feeder wheel <NUM> and the fourth feeder wheel <NUM> may be mounted on the idle shaft <NUM> through any suitable bearing, such as a roller bearing or a journal bearing.

The dual filament feeder assembly <NUM> further comprises the shifting member <NUM> arranged to move the coupling member <NUM> between the first position P1 (shown in <FIG>) and the second position P2 (shown in <FIG>). The dual filament feeder assembly <NUM> further comprises a support shaft <NUM> arranged in parallel relative to the drive shaft <NUM>. The shifting member <NUM> comprises a sliding portion <NUM> (shown in <FIG>) that receives the support shaft <NUM> therethrough, such that the shifting member <NUM> may be slidable along the support shaft <NUM>. Further, the sliding portion <NUM> may slide relative to the support shaft <NUM> along a longitudinal axis A. The longitudinal axis A is defined along a length of the support shaft <NUM>. Further, the drive shaft <NUM> and the idle shaft <NUM> may be disposed substantially parallel to the longitudinal axis A. The shifting member <NUM> may be coupled to the coupling member <NUM>, such that the coupling member <NUM> also moves along the drive shaft <NUM> with the movement of the shifting member <NUM> along the longitudinal axis A. In some embodiments, the shifting member <NUM> may be mounted on the support shaft <NUM> through any suitable bearing, such as a roller bearing or a journal bearing.

The shifting member <NUM> can move the coupling member <NUM> between the first position P1 and the second position P2. In other words, the shifting member <NUM> can move the coupling member <NUM> from the first position P1 to the second position P2, and back from the second position P2 to the first position P1. A linear movement of the coupling member <NUM> from the first position P1 to the second position P2 along the longitudinal axis A is indicated by an arrow A1 in <FIG>. Further, a linear movement of the coupling member <NUM> from the second position P2 to the first position P1 along the longitudinal axis A is indicated by an arrow A2 in <FIG>.

The mechanical switch <NUM> can move the shifting member <NUM> which in turn moves the coupling member <NUM> between the first position P1 and the second position P2. The mechanical switch <NUM> can rotate between the first switch position S1 and the second switch position S2. In other words, the mechanical switch <NUM> can rotate from the first switch position S1 to the second switch position S2, and back from the second switch position S2 to the first switch position S1. A rotational movement of the mechanical switch <NUM> from the first switch position S1 to the second switch position S2 is indicated by an arrow A3 in <FIG>. Further, a rotational movement of the mechanical switch <NUM> from the second switch position S2 to the first switch position S1 is indicated by an arrow A4 in <FIG>. The coupling member <NUM> is in the first position P1 when the mechanical switch <NUM> is in the first switch position S1. Conversely, the coupling member <NUM> is in the second position P2 when the mechanical switch <NUM> is in the second switch position S2.

<FIG> schematically shows the dual filament feeder assembly <NUM> where the coupling member <NUM> and the shifting member <NUM> are omitted. Referring now to <FIG>, the drive wheel <NUM> may comprise a plurality of outer splines <NUM> slidably and at least partially engaging with the plurality of inner splines <NUM> (shown in <FIG>) of the coupling member <NUM>. The coupling member <NUM> may be slidable over the drive wheel <NUM> between the first position P1 and the second position P2. Further, the coupling member <NUM> may be slidable relative to the drive wheel <NUM> for selectively coupling the drive wheel <NUM> with one of the first feeder wheel <NUM> and the second feeder wheel <NUM>. The drive wheel <NUM> is disposed between the first feeder wheel <NUM> and the second feeder wheel <NUM>. Further, each of the first feeder wheel <NUM>, the drive wheel <NUM>, and the second feeder wheel <NUM> are rotatably arranged around the drive shaft <NUM>. In some embodiment, the plurality of inner splines <NUM> (shown in <FIG>) of the coupling member <NUM> may be permanently and at least partially engaged with the plurality of outer splines <NUM> of the drive wheel <NUM>. In other words, the plurality of inner splines <NUM> may always be at least partially engaged with the plurality of outer splines <NUM> irrespective of a position of the coupling member <NUM>.

The first feeder wheel <NUM> further comprises a first splined portion <NUM> that may be at least partially engaged with the plurality of inner splines <NUM> (shown in <FIG>) of the coupling member <NUM> in the first position P1 (shown in <FIG>) of the coupling member <NUM>. The first roller portion <NUM> of the first feeder wheel <NUM> is disposed between the first gear portion <NUM> and the first splined portion <NUM>.

In the first position P1 of the coupling member <NUM>, the coupling member <NUM> may couple the first splined portion <NUM> with the plurality of outer splines <NUM> of the drive wheel <NUM>, such that the rotation of the drive wheel <NUM> may be transmitted to the first feeder wheel <NUM> through the coupling member <NUM>. Thus, the coupling member <NUM> drivably couples the drive wheel <NUM> with the first feeder wheel <NUM> in the first position P1 of the coupling member <NUM>. The first feeder wheel <NUM> and the drive wheel <NUM> may then rotate at substantially the same speed. In other words, power from the electrical motor <NUM> may be transmitted to the first feeder wheel <NUM> through the one or more gears <NUM>, the drive shaft <NUM>, the drive wheel <NUM> and the coupling member <NUM>. In the first position P1 of the coupling member <NUM>, the mechanical switch <NUM> is in the first switch position S1.

The first feeder wheel <NUM> may drive the third feeder wheel <NUM>. The first filament <NUM> may then be pulled between the first roller portion <NUM> of the first feeder wheel <NUM> and the third roller portion <NUM> of the third feeder wheel <NUM>. Hence, the first filament <NUM> may be dispensed by the dual filament feeder assembly <NUM> as the electrical motor <NUM> drives the first feeder wheel <NUM>. Each of the first roller portion <NUM> and the third roller portion <NUM> may be at least partially concave. The concave surface may conform with an outer surface of the first filament <NUM> and may allow appropriate engagement of the first filament <NUM> with the first roller portion <NUM> and the third roller portion <NUM>.

The second feeder wheel <NUM> further comprises a second splined portion <NUM> that may be at least partially engaged with the plurality of inner splines <NUM> (shown in <FIG>) of the coupling member <NUM> in the second position P2 of the coupling member <NUM> (shown in <FIG>). The second roller portion <NUM> of the second feeder wheel <NUM> is disposed between the second gear portion <NUM> and the second splined portion <NUM>.

In the second position P2 of the coupling member <NUM>, the coupling member <NUM> may couple the second splined portion <NUM> with the plurality of outer splines <NUM> of the drive wheel <NUM>, such that the rotation of the drive wheel <NUM> may be transmitted to the second feeder wheel <NUM> through the coupling member <NUM>. Thus, the coupling member <NUM> drivably couples the drive wheel <NUM> with the second feeder wheel <NUM> in the second position P2 of the coupling member <NUM>. The second feeder wheel <NUM> and the drive wheel <NUM> may then rotate at substantially the same speed. In other words, power from the electrical motor <NUM> may now be transmitted to the second feeder wheel <NUM> through the one or more gears <NUM>, the drive shaft <NUM>, the drive wheel <NUM> and the coupling member <NUM>. In the second position P2 of the coupling member <NUM>, the mechanical switch <NUM> is in the second switch position S2.

The second feeder wheel <NUM> may further drive the fourth feeder wheel <NUM>. The second filament <NUM> may now be pulled between the second roller portion <NUM> of the second feeder wheel <NUM> and the fourth roller portion <NUM> of the fourth feeder wheel <NUM>. Hence, the second filament <NUM> may now be dispensed by the dual filament feeder assembly <NUM> as the electrical motor <NUM> drives the second feeder wheel <NUM>. Each of the second roller portion <NUM> and the fourth roller portion <NUM> may be at least partially concave. The concave surface may conform with an outer surface of the second filament <NUM> and may allow appropriate engagement of the second filament <NUM> with the second roller portion <NUM> and the fourth roller portion <NUM>.

<FIG> schematically shows a perspective view of an embodiment of the coupling member <NUM>, the drive wheel <NUM>, and the shifting member <NUM> of the dual filament feeder assembly <NUM>. <FIG> illustrates an exploded view of the coupling member <NUM>, the drive wheel <NUM>, and the shifting member <NUM>. Referring now to <FIG>, the coupling member <NUM> comprises the plurality of inner splines <NUM> that at least partially engage with the plurality of outer splines <NUM> of the drive wheel <NUM>. The coupling member <NUM> comprises the ring <NUM> having the inner surface <NUM>. The plurality of inner splines <NUM> are disposed on the inner surface <NUM> of the coupling member <NUM>. The coupling member <NUM> further comprises a pair of end flanges <NUM>. The pair of end flanges <NUM> may protrude from the edges of the ring <NUM>, such that the pair of end flanges <NUM> may provide an engagement surface therebetween.

Referring now to <FIG>, <FIG>, the shifting member <NUM> may be arranged to slide along the longitudinal axis A. The shifting member <NUM> further comprises an actuating portion <NUM> extending from the sliding portion <NUM> and received at least partially between the pair of end flanges <NUM> of the coupling member <NUM>, such that a linear movement of the shifting member <NUM> along the support shaft <NUM> causes a corresponding linear movement of the coupling member <NUM> along the drive shaft <NUM>. Specifically, a linear movement of the shifting member <NUM> along the longitudinal axis A causes a corresponding linear movement of the coupling member <NUM> along the longitudinal axis A. The sliding portion <NUM> comprises an aperture <NUM> for receiving the support shaft <NUM> therethrough. Further, the coupling member <NUM> can linearly move between the first position P1 (shown in <FIG>) and the second position P2 (shown in <FIG>). The pair of end flanges <NUM> may restrict relative linear movement between the shifting member <NUM> and the coupling member <NUM>. Therefore, the coupling member <NUM> may move linearly along with the shifting member <NUM>. Further, the ring <NUM> of the coupling member <NUM> may also provide a bearing surface to allow the coupling member <NUM> to rotate relative to the actuating portion <NUM> of the shifting member <NUM>. This may enable the coupling member <NUM> to rotate along with the drive wheel <NUM>. In some embodiments, the actuating portion <NUM> may comprise two parts that are angularly separated from each other and engage an outer surface of the ring <NUM>. However, the actuating portion <NUM> may have any number of parts that engage with the ring <NUM>.

The shifting member <NUM> further comprises an engaging portion <NUM>. The engaging portion <NUM> comprises a lower surface <NUM>, a first side surface <NUM> extending from the lower surface <NUM>, and a second side surface <NUM> extending from the lower surface <NUM> and spaced apart from the first side surface <NUM>. The lower surface <NUM>, the first side surface <NUM> and the second side surface <NUM> define a channel <NUM> therebetween. The channel <NUM> may be substantially U-shaped. A rear surface <NUM> of the engaging portion <NUM> may limit a length of the channel <NUM>. It is noted that the lower surface <NUM> may be absent, since only the side surfaces <NUM>, <NUM> are needed to make the coupling between the shifting member <NUM> and the mechanical switch <NUM> operational. Nevertheless, the lower surface <NUM> forms a connection between the two side walls (i.e. the side surfaces) which makes the design more stiff, which avoids unwanted play.

<FIG> schematically shows a perspective view of an embodiment of the mechanical switch <NUM>. The mechanical switch <NUM> comprises an arm <NUM> engaged with the shifting member <NUM> (shown in <FIG> and <FIG>), such that an actuation of the mechanical switch <NUM> may cause a linear movement of the shifting member <NUM> and a corresponding movement of the coupling member <NUM> between the first position P1 and the second position P2. The first position P1 and the second position P2 may correspond to the first switch position S1 and the second switch position S2, respectively. In some embodiments, the mechanical switch <NUM> is rotatable about a vertical rotation axis B which in practice resembles the axis of the feed channel of the second extruder. The mechanical switch <NUM> may be supported by surrounding structures (not shown) arranged in the print head to enable rotation of the mechanical switch <NUM> around the upper part <NUM> (see <FIG>) of the second extruder. The mechanical switch <NUM> may be arranged to rotate about the vertical rotation axis B for movement between the first switch position S1 and the second switch position S2. In some embodiments, the rotation of the mechanical switch <NUM> about the vertical rotation axis B causes the linear movement of the shifting member <NUM>.

In the example of <FIG>, the arm <NUM> of the mechanical switch <NUM> comprises an elongate portion <NUM> and an end portion <NUM> inclined to the elongate portion <NUM>. In some examples, an angle between the elongate portion <NUM> and the end portion <NUM> may be in a range from about <NUM> degrees to about <NUM> degrees. In some embodiments, the end portion <NUM> of the mechanical switch <NUM> is received in the channel <NUM> (shown in <FIG>) of the engaging portion <NUM> of the shifting member <NUM>. In the illustrated embodiment, the end portion <NUM> of the mechanical switch <NUM> is disc-shaped. Due to the inclination, the top and bottom of the disc-shaped end portion <NUM> lie in a plane perpendicular to the axis B and parallel to the surface <NUM>. The disc shape of the end portion <NUM> of the mechanical switch <NUM> may allow smooth movement of the shifting member <NUM> along the longitudinal axis A with the rotation of the mechanical switch <NUM> about the vertical rotation axis B. However, the end portion <NUM> may be realized in any shape without limiting the scope of the present disclosure.

The mechanical switch <NUM> further comprises a curved wedge member <NUM> configured to rotate about the vertical rotation axis B. The elongate portion <NUM> of the arm <NUM> extends from the curved wedge member <NUM>. It is noted that the elongated portion <NUM> may radially extend from the curved wedge member <NUM>. In that case, the end portion <NUM> lies in the same plane as the elongated portion <NUM> and there is no need to incline the end portion <NUM> relative to the elongated portion <NUM>. The curved wedge member <NUM> comprises a plurality of ramp sections <NUM> that extend from a base surface <NUM> of the curved wedge member <NUM>. In some embodiments, the plurality of ramp sections <NUM> may be provided on both sides of the base surface <NUM> (top and bottom). The mechanical switch <NUM> further comprises a lever portion <NUM> extending from the curved wedge member <NUM> and angularly spaced apart from the arm <NUM>. In some embodiments, the curved wedge member <NUM> may be arranged to receive an upper part of a cylindrical extruder (e.g., the second extruder <NUM> shown in <FIG>) having a flange at a top end of the cylindrical extruder. The curved wedge member <NUM> may comprise an opening for receiving the upper part of the cylindrical extruder.

<FIG> schematically shows an embodiment of the coupling member <NUM>, the drive wheel <NUM>, the shifting member <NUM>, and the mechanical switch <NUM> of the dual filament feeder assembly <NUM> in the first position P1 on the coupling member <NUM>. The first position P1 of the coupling member <NUM> may correspond to the first switch position S1. <FIG> illustrates the coupling member <NUM>, the drive wheel <NUM>, the shifting member <NUM>, and the mechanical switch <NUM> in the second position P2 on the coupling member <NUM>. The second position P2 of the coupling member <NUM> may correspond to the second switch position S2.

The arm <NUM> of the mechanical switch <NUM> is at least partially and movably received within the channel <NUM>. Specifically, the end portion <NUM> of the arm <NUM> is at least partially and movably received within the channel <NUM>. In some embodiments, the end portion <NUM> is arranged to slide relative to the lower surface <NUM> of the engaging portion <NUM> prior to selectively engaging with one of the first side surface <NUM> and the second side surface <NUM>.

Referring now to <FIG>, the actuation of the mechanical switch <NUM> causes a linear movement of the shifting member <NUM> along the longitudinal axis A relative to the support shaft <NUM> (shown in <FIG>). In the first switch position S1 of the mechanical switch <NUM> (shown in <FIG>), the end portion <NUM> may engage with the first side surface <NUM> of the engaging portion <NUM>. As the mechanical switch <NUM> moves from the first switch position S1 to the second switch position S2, the arm <NUM> of the mechanical switch <NUM> may rotate about the vertical rotation axis B causing the end portion <NUM> to engage with the second side surface <NUM>. Engagement of the arm <NUM> with the second side surface <NUM> and further movement of the mechanical switch <NUM> may cause the shifting member <NUM> to move along the longitudinal axis A. Thus, the rotational movement of the mechanical switch <NUM> causes the linear movement of the shifting member <NUM>.

The shifting member <NUM> may correspondingly move the coupling member <NUM> along the drive shaft <NUM> via the actuating portion <NUM>. When the mechanical switch <NUM> moves from the first switch position S1 to the second switch position S2, the shifting member <NUM> may move relative to the support shaft <NUM>, such that the coupling member <NUM> disengages from the first splined portion <NUM>, slides with respect to the drive wheel <NUM>, and engages with the second splined portion <NUM>, while being at least partially engaged with the plurality of outer splines <NUM> of the drive wheel <NUM> at all times. Specifically, the coupling member <NUM> slides relative to the plurality of outer splines <NUM> of the drive wheel <NUM> to engage with the second splined portion <NUM>. Therefore, the coupling member <NUM> drivably couples the drive wheel <NUM> with the second splined portion <NUM> of the second feeder wheel <NUM> in the second position P2 of the coupling member <NUM>. In the second position P2 of the coupling member <NUM>, the end portion <NUM> may engage with the second side surface <NUM> of the engaging portion <NUM>, as shown in <FIG>.

In the second position P2, the coupling member <NUM> may couple the second feeder wheel <NUM> with the drive wheel <NUM> for drivably coupling the electrical motor <NUM> (shown in <FIG>) with the second feeder wheel <NUM>. The second feeder wheel <NUM> may then rotate the fourth feeder wheel <NUM> causing the second filament <NUM> (shown in <FIG>) to be pulled between the second feeder wheel <NUM> and the fourth feeder wheel <NUM>.

Similarly, movement of the mechanical switch <NUM> from the second switch position S2 (shown in <FIG>) to the first switch position S1 (shown in <FIG>) may cause rotation of the arm <NUM> about the vertical rotation axis B to engage with the first side surface <NUM> of the engaging portion <NUM>. Engagement of the arm <NUM> with the first side surface <NUM> and further movement of the mechanical switch <NUM> may cause the shifting member <NUM> to move along the longitudinal axis A.

The movement of the shifting member <NUM> and the coupling member <NUM> may be reversed when the mechanical switch <NUM> is moved from the second switch position S2 to the first switch position S1. The shifting member <NUM> may move the coupling member <NUM> along the drive shaft <NUM> via the actuating portion <NUM>. The shifting member <NUM> may move relative to the support shaft <NUM>, such that the coupling member <NUM> disengages from the second splined portion <NUM>, slides with respect to the drive wheel <NUM>, and engages with the first splined portion <NUM>. Therefore, the coupling member <NUM> couples the drive wheel <NUM> with the first splined portion <NUM> of the first feeder wheel <NUM> in the first position P1. In the first position P1 of the coupling member <NUM>, the end portion <NUM> may engage with the first side surface <NUM> of the engaging portion <NUM>. In some embodiments, the electrical motor <NUM> may be stopped momentarily to allow movement of the coupling member <NUM> between the first position P1 and the second position P2. In other words, the electrical motor <NUM> may be inactive for the time duration during which the coupling member <NUM> moves between the first position P1 and the second position P2.

In the first position P1, the coupling member <NUM> may couple the first feeder wheel <NUM> with the drive wheel <NUM> for drivably coupling the electrical motor <NUM> (shown in <FIG>) with the first feeder wheel <NUM>. The first feeder wheel <NUM> may then rotate the third feeder wheel <NUM> causing the first filament <NUM> (shown in <FIG>) to be pulled between the first feeder wheel <NUM> and the third feeder wheel <NUM>.

The sliding movement of the end portion <NUM> of the arm <NUM> relative to the lower surface <NUM> of the engaging portion <NUM> may allow a certain degree of play between the mechanical switch <NUM> and the shifting member <NUM>. Such play may improve an engagement between the coupling member <NUM> and the first feeder wheel <NUM> or the second feeder wheel <NUM>. However, in some other embodiments, the arm <NUM> may be fixedly coupled to the engaging portion <NUM>, such that a rotation of the arm <NUM> causes a simultaneous linear movement of the shifting member <NUM> without any play.

It should be understood that the linear movement of the shifting member <NUM> along the longitudinal axis A may be achieved without utilizing the mechanical switch <NUM> as well. For example, any suitable drive may be utilized to move the shifting member <NUM> along the longitudinal axis A. In some examples, a rotating geared drive shaft may be engaged with the shifting member <NUM>. The geared drive shaft may be received by the sliding portion <NUM>, such that the sliding portion <NUM> moves relative to the longitudinal axis A with the rotation of the geared drive shaft.

In some embodiments, the linear movement of the shifting member <NUM> along the longitudinal axis A may be achieved without the rotation of the mechanical switch <NUM>. For example, in such cases, a (non-rotational) mechanical switch may be arranged fixedly on or coupled directly to the shifting member <NUM>, and may be actuated appropriately to move the shifting member <NUM> along the longitudinal axis A. Actuation may be achieved by pulling or pushing a lever arm arranged on the switch, which lever arm extends out of the housing of the print head. It is also conceivable that actuation of the switch is achieved in an electrical way by using e.g. an electrical actuator coupled to the switch. The also account for the rotational switch mentioned above.

The first feeder wheel <NUM> may not receive any power from the electrical motor <NUM> in the second position P2 of the coupling member <NUM>. Thus, the first feeder wheel <NUM> may not dispense the first filament <NUM> to the first extruder <NUM> (shown in <FIG>) in the second position P2 of the coupling member <NUM>. Similarly, the second feeder wheel <NUM> may not receive any power from the electrical motor <NUM> in the first position P1 of the coupling member <NUM>. Therefore, the second feeder wheel <NUM> may not dispense the second filament <NUM> (shown in <FIG>) to the second extruder <NUM> (shown in <FIG>) in the first position P1 of the coupling member <NUM>. Consequently, the first filament <NUM> and the second filament <NUM> may be selectively dispensed by the dual filament feeder assembly <NUM> based on the position of the coupling member <NUM>.

<FIG> schematically shows an embodiment of a front view of the dual extruder print head <NUM> in the first position P1 of the coupling member <NUM>. The dual extruder print head <NUM> comprises the dual filament feeder assembly <NUM>. Some of the components of the dual extruder print head <NUM> are not shown in <FIG> for clarity.

The dual extruder print head <NUM> comprises the first extruder <NUM> and the second extruder <NUM>. The first extruder <NUM> and the second extruder <NUM> may extrude a molten material after heat processing a consumable material (e.g., the first filament <NUM> or the second filament <NUM> shown in <FIG>) during an additive manufacturing cycle. The first extruder <NUM> and the second extruder <NUM> may comprise separate heating units in heating engagement with the respective extruders so as to heat the consumable material as the consumable material passes through the first extruder <NUM> and the second extruder <NUM>. In some embodiments, the heating units may comprise a conductive ceramic or a wire, such as an alloy of nickel, chromium, and iron. The first and second extruders <NUM>, <NUM> comprise first and second extrusion outlets <NUM>, <NUM>, respectively, through which the molten consumable material may be released.

The dual extruder print head <NUM> further comprises the dual filament feeder assembly <NUM> having the first feeder <NUM> and the second feeder <NUM>. The dual filament feeder assembly <NUM> further comprises the electrical motor <NUM> and the drive wheel <NUM> driven by the electrical motor <NUM> through the one or more gears <NUM>. The dual filament feeder assembly <NUM> further comprises the coupling member <NUM> arranged to selectively couple the drive wheel <NUM> with the first feeder wheel <NUM> (shown in <FIG>) or the second feeder wheel <NUM> (shown in <FIG>). In the configuration shown in <FIG>, the coupling member <NUM> drivably couples the drive wheel <NUM> with the first feeder wheel <NUM> in the first position P1 of the coupling member <NUM>. In the first position P1 of the coupling member <NUM>, the dual filament feeder assembly <NUM> may dispense the first filament <NUM> to the first extruder <NUM>.

The dual extruder print head <NUM> further comprises the mechanical switch <NUM> coupled with the second extruder <NUM>. Further, the mechanical switch <NUM> comprises the curved wedge member <NUM> arranged to receive an upper part <NUM> of the second extruder <NUM>. The second extruder <NUM> comprises a flange <NUM> at a top end of the second extruder <NUM>. The first position P1 of the coupling member <NUM> may correspond to the first switch position S1. The mechanical switch <NUM> engages with the shifting member <NUM>.

The second extruder <NUM> is in a raised position RP when the coupling member <NUM> is in the first position P1. In the raised position RP of the second extruder <NUM>, the second extruder <NUM> may be positioned higher than the first extruder <NUM> by a distance L1. Such an arrangement may avoid interference between the first and second extruders <NUM>, <NUM> when one of the extruders may be actively extruding material while the other extruder may be momentarily idle. In the raised position RP of the second extruder <NUM>, the mechanical switch <NUM> is in the first switch position S1.

The mechanical switch <NUM> may rest on a base member <NUM> and may support a lift member <NUM>. In some embodiments, the base member <NUM> may be fixed while the lift member <NUM> may be movable with respect to the base member <NUM>. The lift member <NUM> comprises a lower end <NUM> and an upper end <NUM>. The lower end <NUM> of the lift member <NUM> may be in wedging engagement with the curved wedge member <NUM> of the mechanical switch <NUM>. The curved wedge member <NUM> comprises the plurality of ramp sections <NUM> extending from the base surface <NUM> of the mechanical switch <NUM>. In some embodiments, the vertical rotation axis B of the mechanical switch <NUM> (shown in <FIG>) may coincide with a central axis of the second extruder <NUM>.

The lower end <NUM> of the lift member <NUM> further comprises a rim <NUM> that selectively engages with the flange <NUM> disposed at the top end of the second extruder <NUM>. The rim <NUM> of the lift member <NUM> may protrude inwardly from a circumference of the lower end <NUM> of the lift member <NUM> and may encircle, at least in part, the upper part <NUM> of the second extruder <NUM>. In some embodiments, the flange <NUM> of the lift member <NUM> may be larger in diameter than a diameter of an inner end <NUM> of the rim <NUM> of the lift member <NUM>.

<FIG> schematically shows an embodiment of a front view of the dual extruder print head <NUM> in the second position P2 of the coupling member <NUM>. The second extruder <NUM> is in a lowered position LP when the coupling member <NUM> is in the second position P2. In the lowered position LP, the second extruder <NUM> may be positioned lower than the first extruder <NUM> by a distance L2. In some embodiments, the distance L1 may be equal to the distance L2. In other embodiments, the distance L1 may be less than or greater than the distance L2.

In the second position P2 of the coupling member <NUM>, the mechanical switch <NUM> may be in the second switch position S2. Further, the coupling member <NUM> drivably couples the drive wheel <NUM> with the second feeder wheel <NUM> (shown in <FIG>) in the second position P2 of the coupling member <NUM>. In the second position P2 of the coupling member <NUM>, the dual filament feeder assembly <NUM> may dispense the second filament <NUM> (shown in <FIG>) to the second extruder <NUM>. Therefore, the second extruder <NUM> may actively extrude material.

Referring now to <FIG> and <FIG>, as the mechanical switch <NUM> moves from the first switch position S1 (shown in <FIG>) to the second switch position S2 (shown in <FIG>), the coupling member <NUM> may move from the first position P1 to the second position P2. The second extruder <NUM> may move from the raised position RP to the lowered position LP along a vertical axis Y1 as the coupling member <NUM> moves from the first position P1 to the second position P2. The movement of the mechanical switch <NUM> from the first switch position S1 to the second switch position S2 may cause a linear movement of the shifting member <NUM> and a corresponding movement of the coupling member <NUM> from the first position P1 to the second position P2.

As the mechanical switch <NUM> moves from the second switch position S2 back to the first switch position S1, the coupling member <NUM> may move from the second position P2 to the first position P1. Further, the coupling member <NUM> may move between the first position P1 and the second position P2 based on movement of the mechanical switch <NUM> between the first switch position S1 and the second switch position S2. The position of the coupling member <NUM> may determine the operation of the first extruder <NUM> and the second extruder <NUM>. In some embodiments, heating of the first extruder <NUM> and the second extruder <NUM> may be controlled and monitored by the electronic assembly <NUM> (shown in <FIG>) based on the position of the mechanical switch <NUM> and/or the position of the coupling member <NUM>.

<FIG> schematically show the lift member <NUM> and the mechanical switch <NUM> in the first switch position S1 and the second switch position S2, respectively. In some embodiments, the mechanical switch <NUM> may be arranged to rotate with respect to the base member <NUM> and the lift member <NUM>. The curved wedge member <NUM> of the mechanical switch <NUM> may be in wedging engagement with the lower end <NUM> of the lift member <NUM>. Further, the curved wedge member <NUM> may comprise the plurality of ramp sections <NUM> in sliding engagement with the lower end <NUM> of the lift member <NUM>. The curved wedge member <NUM> may be arranged to receive the upper part <NUM> of the second extruder <NUM> (shown partially). The second extruder <NUM> further comprises the flange <NUM> at the top end of the second extruder <NUM>. The first switch position S1 and the second switch position S2 may correspond to the raised position RP (shown in <FIG>) and the lowered position LP (shown in <FIG>), respectively, of the second extruder <NUM>.

The lift member <NUM> may receive the flange <NUM> of the second extruder <NUM>. The rim <NUM> of the lift member <NUM> may protrude inwardly from the circumference of the lower end <NUM> of the lift member <NUM>. The flange <NUM> of the lift member <NUM> may be larger in diameter than the diameter of the inner end <NUM> of the rim <NUM> of the lift member <NUM>.

Referring now to <FIG>, as the mechanical switch <NUM> moves from the first switch position S1 (shown in <FIG>) to the second switch position S2 (shown in <FIG>), the lower end <NUM> of the lift member <NUM> may slide down the plurality of ramp sections <NUM>. Further, the rim <NUM> of the lift member <NUM> may move down and disengage from the flange <NUM> of the second extruder <NUM> allowing the lift member <NUM>, and thus, the upper part <NUM> of the second extruder <NUM> to be lowered as the lower end <NUM> slides down the plurality of ramp sections <NUM>. The plurality of ramp sections <NUM> may allow the lift member <NUM> to be lowered and raised along the vertical axis Y1 based on movement of the mechanical switch <NUM>. It should be understood that corresponding ramp sections may also be provided at the lower end <NUM> of the lift member <NUM> for a smooth engagement of the lower end <NUM> with the plurality of ramp sections <NUM>.

Referring to <FIG>, the curved wedge member <NUM> may comprise a plurality of ramp sections <NUM> extending from a base surface <NUM> and opposite to the plurality of ramp sections <NUM>. The plurality of ramp sections <NUM> may engage with a plurality of ramp sections <NUM> disposed on the base member <NUM> to further raise the upper part <NUM> of the second extruder <NUM>. In some embodiments, the base member <NUM>, the lift member <NUM> and the mechanical switch <NUM> may comprise multiple ramp sections with varying heights.

The upper end <NUM> of the lift member <NUM> comprises a resilient biasing member <NUM> in downward biasing engagement with the lift member <NUM> with respect to the vertical axis Y1. In some embodiments, the resilient biasing member <NUM> may comprise a spring element for continuously pushing the lift member <NUM> downward, and thus, biasing the second extruder <NUM> downward. When the lift member <NUM> and the second extruder <NUM> are moved to the raised position RP, the resilient biasing member <NUM> may store potential energy which may be released when the lift member <NUM> and the second extruder <NUM> are restored to the lowered position LP.

Referring now to <FIG>, the dual extruder print head <NUM> may extrude either the first filament <NUM> or the second filament <NUM> based on the position of the coupling member <NUM>. In some embodiments, during the additive manufacturing cycle, molten material may be extruded from the first and second extrusion tips <NUM>, <NUM> to be deposited in a layer-by-layer manner on a build platform. In some embodiments, the dual extruder print head <NUM> may operate based on inputs from a controller (not shown). The build platform may define a start-print plane or surface.

In some embodiments, the dual extruder print head <NUM> may first utilize the first filament <NUM> for a first layer in the additive manufacturing cycle. In such an embodiment, the second extruder <NUM> may be in the raised position RP (shown in <FIG>), such that the second extrusion outlet <NUM> is positioned higher than the first extrusion outlet <NUM> by the distance L1. Further, the coupling member <NUM> may be in the first position P1 and the mechanical switch <NUM> may be in the first switch position S1. The dual filament feeder assembly <NUM> may dispense the first filament <NUM> through the first feeder <NUM>. The first extruder <NUM> may receive the first filament <NUM> from the first feeder <NUM> and may deposit the extruded material on the build platform to form a layer of the extruded material. Further, the dual extruder print head <NUM> may move relative to the build platform to generate the layer.

In some embodiments, the dual extruder print head <NUM> may utilize the second filament <NUM> for one or more subsequent layers during the additive manufacturing cycle. As the dual extruder print head <NUM> may be switched from first extruder <NUM> to the second extruder <NUM>, the mechanical switch <NUM> may move from the first switch position S1 to the second switch position S2. The end portion <NUM> of the mechanical switch <NUM> may disengage from the first side surface <NUM> of the engaging portion <NUM> and move relative to the lower surface <NUM> to engage with the second side surface <NUM>. Further movement of the end portion <NUM> may cause the shifting member <NUM> to move relative to the support shaft <NUM> along the longitudinal axis A. The movement of the shifting member <NUM> may cause a corresponding linear movement of the coupling member <NUM> along the drive shaft <NUM>. The shifting member <NUM> actuates the coupling member <NUM> via the actuating portion <NUM>. The coupling member <NUM> further linearly moves relative of the plurality of outer splines <NUM> of the drive wheel <NUM>. Thus, the coupling member <NUM> may disengage from the first splined portion <NUM> of the first feeder wheel <NUM> and engage with the second splined portion <NUM> of the second feeder wheel <NUM>. Therefore, the coupling member <NUM> may now drivably couple the second feeder wheel <NUM> with the drive wheel <NUM> in the second position P2 of the coupling member <NUM>.

The movement of the mechanical switch <NUM> from the first switch position S1 to the second switch position S2 may also cause the lower end <NUM> of the lift member <NUM> to slide down the plurality of ramp sections <NUM> of the mechanical switch <NUM>. The lift member <NUM> may be pushed down due to the biasing force of the resilient biasing member <NUM> causing the flange <NUM> at the top end of the upper part <NUM> of the second extruder <NUM> to be lowered till the second extrusion outlet <NUM> may be positioned lower than the first extrusion outlet <NUM> of the first extruder <NUM> by the distance L2 (shown in <FIG>). In the second position P2 of the coupling member <NUM>, the electric motor <NUM> may drive the second feeder wheel <NUM> allowing the second filament <NUM> to be dispensed to the second extruder <NUM>. Further, the second extruder <NUM> may extrude molten material through the second extrusion outlet <NUM>.

The dual extruder print head <NUM> may be switched back to the first extruder <NUM> from the second extruder <NUM> by actuating the mechanical switch <NUM> back to the first switch position S1. The end portion <NUM> of the mechanical switch <NUM> may engage with the first side surface <NUM> of the engaging portion <NUM> to cause movement of the shifting member <NUM> relative to the support shaft <NUM> along the longitudinal axis A. The movement of the shifting member <NUM> may cause a corresponding movement of the coupling member <NUM> to the first position P1 and may lift the second extruder <NUM> again to the raised position RP (shown in <FIG>).

<FIG> schematically shows a front view of an embodiment of an additive manufacturing system <NUM>. The additive manufacturing system <NUM> comprises a chamber <NUM>, which may be an enclosed environment that comprises a build plate and assemblies for manufacturing parts/components (e.g., 3D parts). The additive manufacturing system <NUM> further comprises the dual extruder print head <NUM> supported on the guide rail <NUM> and disposed inside the chamber <NUM>. The dual extruder print head <NUM> has been described in detail above with reference to <FIG>. The dual extruder print head <NUM> may build parts/components on a build plate <NUM> in a layer-by-layer manner from a software model, such as a computer-aided design (CAD) model.

In some embodiments, the guide rail <NUM> together with other parts of a gantry <NUM>, may allow movement of the dual extruder print head <NUM> along an x-y plane within the chamber <NUM> based on inputs provided by a controller (not shown). Further, the print plate <NUM> may be movable along a vertical z-axis by the gantry <NUM> based on commands provided by the controller. Alternatively, the additive manufacturing system <NUM> may allow movement of the dual extruder print head <NUM> along the x, y, and z axis through one or more of the guide rails <NUM>. The guide rail <NUM> may utilize any suitable bridge-type gantry or robotic mechanism for moving the dual extruder print head <NUM> that may comprise one or more motors (e.g., stepper motors and encoded DC motors), gears, pulleys, belts, screws, robotic arms, and/or the like. In some embodiments, the print plate <NUM> may alternatively move in the x-y plane while the dual extruder print head <NUM> moves along the z-axis. Other similar arrangements may also be utilized such that either or both of the print plate <NUM> and the dual extruder print head <NUM> may be moveable relative to each other. In some embodiments, the print plate <NUM> and/or the dual extruder print head <NUM> can be aligned at an angle with respect to the x, y, or z axis.

As described above with reference to <FIG>, the dual extruder print head <NUM> comprises the first and second extruders <NUM>, <NUM> arranged to receive a consumable material, for example, the first and second filaments <NUM>, <NUM>, respectively. The consumable material may be melted by the first and second extruders <NUM>, <NUM> to produce a molten material, and the molten material may then be deposited (or extruded) on the print plate <NUM>.

The consumable material may be provided by material storage assemblies (not shown) mounted on the additive manufacturing system <NUM> or otherwise accessible to the additive manufacturing system <NUM>. The material storage assemblies may supply the consumable material to the dual extruder print head <NUM> while allowing the consumable material to be loaded, replaced, or removed. For example, the material storage assemblies may retain the consumable material on a wound spool, a spool-less coil, or any other suitable supply arrangement.

In some embodiments, one of the first and second extruders <NUM>, <NUM> may supply a consumable part material while the other extruder <NUM> or <NUM> may supply a consumable support material. In some embodiments, the consumable part material and the consumable support material may be mounted on separate material storage assemblies. In some embodiments, the consumable part material and the consumable support material may differ in material properties.

In some embodiments, the chamber <NUM> may be heated (e.g., by circulating heated air) to reduce a rate at which the manufactured parts/components and support materials solidify after being extruded or deposited (e.g., to reduce distortions and curling), or otherwise maintained in a temperature-controlled environment. In some embodiments, the chamber <NUM> may be omitted and/or replaced with other types of heated, cooled, and/or ambient build environments.

The chamber <NUM> may be a part of a casing <NUM> having multiple sub-structural components, such as support frames, housing walls, and/or the like that support the dual extruder print head <NUM> and the guide rail <NUM>. In some embodiments, the casing <NUM> may comprise arrangements for receiving the material storage assemblies.

The additive manufacturing system <NUM> may further comprise a user input <NUM>, such as a button, a switch, a touch-type graphical user interface, etc. The user input <NUM> may be used to control an operational status of the additive manufacturing system <NUM> or operational parameters thereof. The additive manufacturing system <NUM> further comprises a user interface <NUM> arranged to output one or more operational parameters of the additive manufacturing system <NUM>. Further, the additive manufacturing system <NUM> may comprise an input port for receiving power. Additional ports may also be provided for data communication.

In some embodiments, the controller may be arranged to monitor and control one or more components or operations of the additive manufacturing system <NUM>. Further, the controller may comprise one or more control circuits and/or one or more computers for carrying out the intended functions. The controller may be embodied in a number of different ways. For example, the controller may be embodied as various processing means, such as one or more of a microprocessor or other processing elements, a coprocessor, or various other computing or processing devices including integrated circuits, such as an ASIC (application specific integrated circuit), an FPGA (field programmable gate array), or the like.

In some embodiments, the controller may be arranged to execute instructions stored in a memory or otherwise accessible to the controller. As such, whether configured by hardware or by a combination of hardware and software, the controller may represent an entity capable of performing operations according to some embodiments while configured accordingly. For example, one or more of control functions performed by the controller may be implemented in hardware, software, firmware, and the like, or a combination thereof. The controller may comprise computer-based hardware, such as data storage devices, processors, memory modules, and/or the like, which may be external and/or internal to the additive manufacturing system <NUM>. In some embodiments, the controller may communicate with the dual extruder print head <NUM> and/or other components (e.g., the guide rail <NUM>, one or motors of the gantry <NUM>, various sensors, calibration devices, user interfaces, and/or user input devices) of the additive manufacturing system <NUM> through a wired or wireless communication interface.

<FIG> schematically shows an embodiment of the dual extruder print head <NUM> disposed inside the chamber <NUM> of the additive manufacturing system <NUM>. The dual extruder print head <NUM> may be supported on the guide rail <NUM> disposed inside the chamber <NUM> that allows movement of the dual extruder print head <NUM> in operational directions. The dual extruder print head <NUM> further comprises the guide tubes <NUM> for providing consumable materials. The dual extruder print head <NUM> further comprises the inlet <NUM> for providing power to the dual extruder print head <NUM>.

Referring to <FIG>, the dual extruder print head <NUM> further comprises the first and second extruders <NUM>, <NUM>. The first and second extruders <NUM>, <NUM> may be arranged to receive the consumable material which may be melted by the first and second extruders <NUM>, <NUM> to produce a molten material. The dual extruder print head <NUM> further comprises the mechanical switch <NUM> (partly shown in <FIG>) having the lever portion <NUM> that may be moved between the first switch position S1 and the second switch position S2 to allow selective operation of one of the first and second extruders <NUM>, <NUM>. The dual extruder print head <NUM> may operate one extruder at a time during an additive manufacturing cycle.

The mechanical switch <NUM> may be selectively movable between the first switch position S1 and the second switch position S2 by a switch bay <NUM> through the lever portion <NUM> of the mechanical switch <NUM>. In some embodiments, the switch bay <NUM> may be fixedly coupled to the casing <NUM> (shown in <FIG>) of the additive manufacturing system <NUM>. The lever portion <NUM> of the mechanical switch <NUM> may be received in a slot <NUM> disposed on the switch bay <NUM> such that the mechanical switch <NUM> may move between the first switch position S1 and the second switch position S2 based on forward and reverse movements of the dual extruder print head <NUM>.

During an additive manufacturing cycle, the dual extruder print head <NUM> may move towards the switch bay <NUM> along the guide rail <NUM>, such that the lever portion <NUM> of the mechanical switch may be received in the slot <NUM> of the switch bay <NUM>. Subsequently, forward or reverse movements of the dual extruder print head <NUM> may cause the lever portion <NUM> to rotate about a vertical rotation axis (e.g., the vertical rotation axis B) so as to shift the mechanical switch <NUM> between the first switch position S1 and the second switch position S2. In some embodiments, the lever portion <NUM> of the mechanical switch <NUM> may be manually movable between the first switch position S1 and the second switch position S2. In some embodiments, the movement of the lever portion <NUM> of the mechanical switch <NUM> may be automatically controlled by a controller (not shown) through an actuator mounted on the dual extruder print head <NUM>.

Claim 1:
A dual filament feeder assembly (<NUM>) for an additive manufacturing system (<NUM>), the dual filament feeder assembly (<NUM>) comprising:
a drive wheel (<NUM>);
a drive shaft (<NUM>) connected to the drive wheel (<NUM>);
a first feeder wheel (<NUM>), a second feeder wheel (<NUM>), a coupling member (<NUM>) arranged to selectively couple the drive wheel (<NUM>) with one of the first feeder wheel (<NUM>) and the second feeder wheel (<NUM>), characterised in that the first feeder wheel (<NUM>) is rotatably arranged around the drive shaft (<NUM>) at a first side (X1) of the drive wheel (<NUM>);
that the second feeder wheel (<NUM>) is rotatably arranged around the drive shaft (<NUM>) at a second side (X2) of the drive wheel (<NUM>) opposite to the first side (X1); and
that the dual filament feeder assembly (<NUM>) additionally comprises a shifting member (<NUM>) arranged to move the coupling member (<NUM>) between a first position (P1) and a second position (P2), such that:
the coupling member (<NUM>) drivably couples the drive wheel (<NUM>) with the first feeder wheel (<NUM>) in the first position (P1) of the coupling member (<NUM>); and
the coupling member (<NUM>) drivably couples the drive wheel (<NUM>) with the second feeder wheel (<NUM>) in the second position (P2) of the coupling member (<NUM>).