Loop compensator for regulating the feed to a 3D printer

Abstract

The present invention relates to a feed device (1) for feeding a material in the form of a filament (3) to a three-dimensional printer, said feed device being provided with a compensator (4) which comprises: an inlet guide (5); a motorized drive system (6); an outlet guide (7); a guide receptacle (11) inside which the filament (3) coming from the inlet guide (5) forms a loop (13) on itself before re-emerging through the outlet guide (7), in such a way that the loop (13) constitutes a reserve of filament (3) and spontaneously adjusts its size in response to the deviations between the outflow speed (V_out) and the inflow speed (V_in) of the filament (3); a retaining member (15) which is placed inside the perimeter of the loop (13) to limit the extent of the overall shifting of the loop (13) when the loop (13) is subjected to a tensile stress (T_out), while allowing the loop (13) to freely adapt its size; and a regulation system (20) which adjusts the inflow speed (V_in) of the filament (3) according to the size of the loop (13).

Description

LOOP COMPENSATOR FOR REGULATING THE POWER SUPPLY OF A 3D PRINTER

[0001] The present invention relates to the general field of supplying raw material to an apparatus which consumes said raw material in the form of a wire, and more specifically to the regulation of the supply system which supplies such an apparatus with raw material in the form of a wire.

[0002] The present invention relates more specifically to the field of three-dimensional printing by fused deposition modeling (or "FDM" for "Fused Deposition Modeling" in English).

[0003] A fused deposition printer comprises a print head which is mounted movably opposite a printing support, such as a plate, and which incorporates a heating nozzle as well as a drive system, of the toothed roller drive type, which forces a thermoplastic material wire to pass through the nozzle, in order to melt said material and to be able to deposit it in successive layers on said support, according to a laying pattern which makes it possible to obtain the desired object.

[0004] One of the challenges of FDM printing is its industrial throughput, especially when you want to manufacture large parts or in large numbers, using a large surface area plate, typically a plate forming a square with sides of at least one meter.

[0005] Indeed, to obtain a high yield, it would be desirable for the print head carrying the nozzle to be able to move quickly from one point to another on the plate, in particular outside the printing phases, when said print head repositions itself after having deposited material at a first point, in order to resume the deposition of material at a second point, distant from the first point.

[0006] Since the print head naturally pulls the material strand along with it, it is necessary to be able to supply the necessary and sufficient length of strand into the printer at any time, at a speed that corresponds to the speed of movement of the print head.

[0007] However, when implementing rapid accelerations and high print head speeds over long strokes, sudden wire calls are generated, which known feeding systems struggle to manage.

[0008] In fact, known printers are generally powered by a wire which is stored on a reel which is simply mounted in passive rotation around its axis, so that the wire is unwound passively, under the effect of the traction exerted by the print head and its toothed roller drive.

[0009] Due to the inertia of the spool, we can then observe, at the beginning of the acceleration phases of the print head, the appearance of strong tensions in the wire, which tensions constitute a brake on the movement of the print head and can even, in certain cases, cause a breakage of the wire. Conversely, at the end of the movement of the print head, the spool, which has been launched into rotation and is not braked, releases a surplus of wire, which can create trajectory deviations that are difficult to control in the path of the wire, or even a jam.

[0010] Furthermore, it is difficult to envisage overcoming these difficulties by interposing, between the storage reel and the nozzle, a conventional regulator with pulleys and a puppet, such as is found for example in the textile industry, because the thermoplastic material threads used for the three-dimensional printing of large parts generally have a fairly large diameter, typically two to three millimeters, a fairly high bending rigidity, and in addition a persistent intrinsic curvature which results from their storage in a reel, so that such threads do not tolerate well, due to the lack of suitable flexibility, a forced path through pulleys which would impose on said threads small radii of curvature and / or changes, in particular multiple and close changes, in the sign of their curvature.

[0011] The objects assigned to the invention therefore aim to remedy the aforementioned drawbacks and to propose a supply device which makes it possible to supply wire to an apparatus, in particular a three-dimensional printer intended to produce a deposit of molten material from said wire, while being capable of reliably and efficiently managing sudden calls for long lengths of wire.

[0012] The objects assigned to the invention are achieved by means of a feeding device intended to convey to an apparatus, such as a three-dimensional printer, a material which is in the form of a wire, said feeding device being characterized in that it is provided with a compensator which comprises: - an entry guide which allows the wire to enter the compensator, - a motorized drive system, which is arranged to propel the wire entering through the entry guide at a chosen longitudinal speed, called the “entry speed”, - an exit guide which allows the wire to exit the compensator, towards the device, under the effect of a longitudinal traction force called "call traction" which is generated at the request of the device and which gives the wire exiting through the exit guide a longitudinal speed called "exit speed", - a guide receptacle which delimits a hollow space called a "travel space" inside which the wire coming from the entry guide forms a loop on itself before exiting through the exit guide, in such a way that the loop constitutes a reserve of wire and is able to spontaneously adjust its size, while remaining contained inside the travel space, alternately by tightening on itself under the effect of the take-up traction in order to reduce its perimeter and thus release a part of said reserve of wire to the device, when the exit speed resulting from said take-up traction exceeds the entry speed, and conversely by widening in order to increase its perimeter and thus reconstitute at least a part of said reserve of wire when the drive system generates an entry speed which exceeds the exit speed and therefore creates within the incoming wire which precedes the loop a longitudinal thrust force,called "supply push", which forces said incoming wire to join the loop and increase the perimeter of the loop, - a retaining member which is placed inside the perimeter of the loop, so as to be able to limit the extent of an overall movement of the loop within the clearance space, when the loop is subjected to a take-off pull, while allowing the loop to freely adapt its size, within the clearance space, in response to differences between the exit speed and the entry speed, - a regulation system which controls the drive system and which includes at least one measuring device making it possible to evaluate the size of the loop present within the clearance space, so that said regulation system can adjust the chosen input speed according to the size of the loop, wherein the guide receptacle comprises a guide track of cylindrical shape with a circular base, which delimits the clearance space in order to contain the centrifugal radial expansion of the loop within the limit of a maximum permitted diameter, as defined by said guide track.

[0013] Advantageously, the device according to the invention makes it possible to take advantage of the nervousness of the wire, that is to say the existence of a natural bend of said wire and a high modulus of elasticity in bending of said wire, to cause said wire to spontaneously form a loop within the compensator, a loop which is advantageously floating, that is to say the path and curvature of which are not imposed by pulleys and can therefore evolve freely within the clearance space, and self-supporting, to the extent that the rigidity of the wire is sufficient for said loop to exist and maintain itself in its curved, substantially circular form, without sagging or becoming tangled on itself.

[0014] Advantageously, the compensator can thus constitute and contain a reserve of wire, without forcing said wire to match the curvature of a pulley, in particular a small diameter pulley, nor forcing said wire to undergo changes in the sign of curvature.

[0015] The compensator can then advantageously use this reserve of wire as a buffer capable of rapidly delivering a length of outgoing wire in response to a sudden inrush pull, and therefore in response to a rapid increase in the output speed, without opposing any significant resistance to this inrush pull, and therefore in particular without creating any risk of breakage of the wire in traction, since the outgoing wire can freely operate a differential slip relative to the incoming wire, simply by adjusting the size of the loop thanks to the elasticity of the wire in bending, and without it being necessary to increase the input speed as suddenly as the output speed has increased.

[0016] Once the call pull has passed, and therefore once the output speed has dropped to a lower value, the compensator can advantageously gradually replenish the wire reserve by pushing the incoming wire towards the loop at a chosen input speed which is higher than the output speed, but which remains sufficiently moderate to be compatible, for example, with the unwinding of the wire from a spool placed upstream of the drive system.

[0017] Furthermore, the compensator according to the invention advantageously has a particularly simple and compact structure, in particular because it does not require any pulley or puppet transmission.

[0018] Other objects, characteristics and advantages of the invention will appear in more detail on reading the description which follows, as well as with the aid of the appended drawings, provided for purely illustrative and non-limiting purposes, among which:

[0019] Figure 1 illustrates, in a schematic front view, the operating principle of a feed device comprising a compensator according to the invention, which allows the wire loop to pass alternately from a wide configuration, shown in solid lines, to a reduced configuration, tightened on itself, shown in dotted lines.

[0020] Figure 2 illustrates, in an overall perspective view, the compensator of Figure 1.

[0021] Figure 3 illustrates, in an overall perspective view, the compensator of Figure 2 from the front side, one of the flanges of which forms a door which is in the open position to give an operator access to the clearance space and the wire loop.

[0022] Figure 4 illustrates, in an overall perspective view, the compensator of Figures 2 and 3, back side.

[0023] Figure 5 illustrates, in a perspective cutaway view, the compensator of Figure 4 within which a flange has been removed to reveal the clearance space.

[0024] The present invention relates to a feeding device 1 intended to convey to an apparatus 2, such as a three-dimensional printer, a material which is in the form of a wire 3.

[0025] Preferably, said material is a thermoplastic polymer, which is preferably intended to be melted within said device 2.

[0026] Said material may be chosen for example from: ABS (Acrylonitrile Butadiene Styrene), ASA (Acrylonitrile Styrene Acrylate), PLA (polylactic acid), BVOH (copolymer of butenediol and vinyl alcohol), PA6 / 66 (polyamide), PETG (polyethylene terephthalate glycol), TPU (thermoplastic polyurethane).

[0027] Said wire preferably has a section with a diameter between 1.5 mm and 4 mm, more preferably between 2 mm and 3 mm, for example equal to 2.85 mm.

[0028] The feed device 1 is provided with a compensator 4 which comprises: - an entry guide 5 which allows the wire 3 to enter the compensator 4, - a motorized drive system 6, which is arranged to propel the wire 3 which enters through the entry guide 5 at a chosen longitudinal speed V_in, called “entry speed” V_in, - an exit guide 7 which allows the wire 3 to exit the compensator 4, to the device 2, under the effect of a longitudinal traction force T out called “call traction” T out which is generated at the request of the device 2 and which gives the wire 3 which exits through the exit guide 7 a longitudinal speed V_out, called “exit speed” V_out.

[0029] The drive system 6 will preferably be integrated into the compensator 4, upstream of the entry guide 5 in the direction of introduction of the wire 3.

[0030] Said drive system 6 will comprise a motor 8, preferably an electric motor 8, which preferably drives in rotation a motor roller 9 against which a counter roller 10 pinches the wire 3. The motor roller 9 can preferably, for reasons of compactness, be mounted directly on the output shaft of the motor 8.

[0031] By convention, the notions of “upstream” and “downstream” will be understood in consideration of the direction in which the wire 3 moves longitudinally, in normal operation of the feed device 1, that is to say in consideration of the direction, here counter-clockwise in figure 1, in which the wire 3 enters through the input guide 5, then joins the output guide 7, then exits through said output guide 7.

[0032] Preferably, and as shown schematically in Figure 1, the supply device 1 comprises a coil 40 which is located upstream of the system motorized drive 6 and on which is stored the wire 3 intended to enter the compensator 4.

[0033] Preferably, said coil 40 is mounted in free rotation.

[0034] Thanks to this particularly simple, compact, and energy-efficient system, it is the traction exerted by the drive system 6 on the portion of wire between the spool 40, upstream, and the drive roller 9, downstream, which causes the passive spool 40 to rotate and the wire 3 to be unwound from said spool 40.

[0035] Furthermore, the storage in reel 40 will advantageously contribute to giving the wire 3 a certain bend, that is to say a certain persistent curvature at rest, which will be used by the compensator 4 to form a loop 13 of wire 3 in accordance with the invention.

[0036] The entry 5 and exit 7 guides will make it possible to fix obligatory passage points for the wire 3, and will preferably be in an elongated form, for example in the form of tubes or covered trenches which make it possible to give the wire 3 which passes through them a direction which corresponds substantially to the longitudinal direction of the guide 5, 7 concerned.

[0037] In a preferred example of application, the call traction T out will be generated by the movement, within the device 2, of a moving part, such as a print head, which directly pulls the wire 3 coming from the compensator 4.

[0038] The compensator 4 further comprises a guide receptacle 11 which delimits a hollow space 12 called the “deflection space” 12 inside which the wire 3 coming from the entry guide 5 forms a loop 13 on itself before exiting through the exit guide 7, and this in such a way that the loop 13 constitutes a reserve of wire 3 and is able to spontaneously adjust its size, while remaining contained inside the deflection space 12, alternately by tightening on itself under the effect of the take-up traction T out in order to reduce its perimeter and thus release a part of said reserve of wire for the device 2, when the exit speed V out resulting from said take-up traction T out exceeds the entry speed V in,and conversely by widening in order to increase its perimeter and thus reconstitute at least part of said wire reserve when the drive system 6 generates an input speed V in which exceeds the output speed V out and, therefore creates within the incoming wire 3 which precedes the loop 13 a longitudinal thrust force P in, called “supply thrust” P in, which forces said incoming wire 3 to join the loop 13 and to increase the perimeter of the loop 13.

[0039] Advantageously, the chosen wire 3 is on the one hand sufficiently flexible, and with a minimum of natural bend before entering the compensator 4, that is to say with a minimum of pre-existing curvature at rest, to be able to form a loop and be closed on itself, and on the other hand sufficiently rigid, and not very extensible as well as not very compressible longitudinally, so that the drive system can enlarge the loop 13 by pushing the incoming wire towards the loop 13, from a point located outside said loop 13, upstream of said loop 13 in the direction of longitudinal movement of the wire 3.

[0040] In this respect, the material constituting the wire 3 is preferably a polymer having a hardness greater than or equal to 60 Shore A. The device is then intended to convey to the apparatus 2 a wire 3 made of such a material.

[0041] This will help to give wire 3 a certain rigidity, and more generally the nervousness which will allow it to be configured as a floating loop within compensator 4.

[0042] Of course, the clearance space 12 is sufficiently clear to allow the loop 13 to freely modify its size, and more particularly to shorten then lengthen its perimeter, and to modify the curvature of the wire 3 inside said perimeter, to adapt almost instantly to the predictable differentials between the output speed V out and the input speed V in, while maintaining a curved trajectory of the wire 3 in the form of a loop.

[0043] In particular, it will be noted that the compensator 4 according to the invention is advantageously devoid of a pulley which would force the wire 3 to match the curvature of said pulley. More particularly, the wire 3 belonging to the perimeter of the loop 13 does not comprise any contact zone with a pulley which would be located inside the perimeter of the loop 13 and in which contact zone said wire 3 would have the same instantaneous center of rotation as that of said pulley. Thus, the loop 13 does not match, is not forced to match, the curvature of any element located inside said loop 13.

[0044] It will also be noted that the wire 3 forming the perimeter of the loop 13 preferably does not contain a rectilinear section, that is to say it has at every point of the perimeter of the loop 13 a curvature which directs said wire 3 towards the inside of the loop 13.

[0045] By convention and for convenience of description, it will be possible to associate with the compensator 4, and more particularly with the guide receptacle 11, a reference frame comprising a main axis Z and a reference plane PO normal to said main axis Z.

[0046] The main axis Z is such that the loop 13, whatever its size, forms a turn of wire 3 which winds around a central axis Z13 called the “loop axis” Z13 which is parallel to said main axis Z, and whose point of intersection with the reference plane PO moves as a function on the one hand of the overall position occupied by the loop 13 within the movement space 12 and on the other hand of the size of said loop 13 at the instant in question.

[0047] For convenience of description, we can designate as "axial" a direction parallel to the main axis Z, and more particularly parallel to the loop axis Z 13 at the instant considered, and by radial a direction perpendicular to the axis considered. Thus, the increase, respectively the decrease, of the perimeter of the loop 13 will result in a centrifugal radial increase, respectively by a centripetal radial reduction, of the loop relative to its loop axis Z13.

[0048] In practice, the loop 13 can be likened to a flat loop 13, which is contained, or substantially contained, in the reference plane PO.

[0049] In this respect, it will be noted that, preferably, the angle formed by the wire 3 constituting the loop 13 with respect to the reference plane PO, that is to say typically the helix angle of the turn of wire 3 which forms the loop 13, is, and remains during variations in the size of the loop 13, less than or equal to 10 degrees, more preferably less than or equal to 5 degrees, or even equal to or less than 2 degrees. The guide receptacle 11, and in particular the entry guide 5 and the exit guide 7, will preferably be arranged to limit the inclination of the wire 3 with respect to the reference plane PO in the aforementioned helix angle range, and thus maintain the loop 13 in its substantially flat configuration.

[0050] In projection in the reference plane PO, the loop 13 forms at least one complete turn on itself, around the loop axis Z13, that is to say that the wire 3 permanently travels at least 360 degrees around the loop axis Z13.

[0051] Said loop 13, however, forms less than two complete turns, that is to say that the wire travels less than 720 degrees around the loop axis Z13.

[0052] Preferably, the loop 13 may form between 1 turn and 1.5 turns, preferably between 1 turn and 1.25 turns, that is to say that the wire 3 will travel between 360 degrees and 540 degrees around the loop axis Z13, preferably between 360 degrees and 450 degrees around the loop axis Z13.

[0053] Such a configuration advantageously makes it possible to maintain the shape of the loop 13 and the capacity of the wire 3 to wind and close on itself to form said loop 13 in dynamic mode, whatever the respective variations in the output speed V_out and the input speed V_in.

[0054] This configuration may in particular be determined by the choice of the respective positions and orientations of the output guide 7 relative to the input guide 5.

[0055] The sector in which the wire 3 crosses itself, in projection in the reference plane PO, so as to close the loop, and more particularly the sector in which an incoming section of wire 3 runs along an outgoing section of wire 3 and thus closes the loop 13, is called the “overlapping sector” 14.

[0056] The compensator further comprises a retaining member 15 which is placed inside the perimeter of the loop 13, so as to be able to limit the extent of an overall displacement of the loop 13 within the clearance space 12, when the loop 13 undergoes a pull force T out, while allowing the loop 13 to freely adapt its size, and more particularly to freely adapt its perimeter and to elastically adapt the curvature of the wire 3 along this perimeter, inside the clearance space 12, in response to the differences between the output speed V out and the input speed V in.

[0057] Advantageously, the retaining member 15 makes it possible in particular to maintain the loop 13, and more particularly the loop exit point through which the wire 3 leaves the loop 13 to join the exit guide 7, in a position, and more generally in a range predefined number of possible positions, relative to the exit guide 7, which makes it possible to prevent incorrect positioning of the wire 3, and more particularly to prevent the outgoing wire 3 from forming an angular break between the loop exit point and the entrance to the exit guide 7 and from rubbing excessively against the entrance to the exit guide 7, regardless of the intensity of the call traction T out.

[0058] Thus, the retaining member 15 allows the loop 13 to retain at all times its capacity to release or accumulate wire 3, without being crushed or jammed within the guide receptacle 11, whatever the intensity or suddenness of variation of the call traction T out.

[0059] The compensator 4 also comprises a regulation system 20 which controls, for example by means of an electronic control unit, the drive system 6 and which comprises at least one measuring member 21 making it possible to evaluate the size of the loop 13 present within the travel space 12, so that said regulation system 20 can adjust the input speed V in chosen as a function of the size of the loop 13, as evaluated here by the measuring member 21.

[0060] The regulation system 20 is preferably arranged so as to converge the size of the loop 13 towards a predetermined nominal size, which corresponds to a nominal reserve of wire 3, which is preferably chosen to be equal to the maximum reserve of wire 3 which the compensator 4 can constitute and which is shown in solid lines in FIG. 1.

[0061] The regulation system 20 will therefore seek to establish a dynamic balance between the input speed V in, chosen, and the output speed V out, experienced according to the needs of the device 2, in order to maintain the wire reserve 3 at its nominal value, and to reconstitute said reserve after a sudden and high intensity inrush traction T out has temporarily reduced this wire reserve 3.

[0062] Advantageously, the compensator 4 makes it possible to dissociate, at least temporarily, the input speed setpoint V in, determined by the regulation system 20, from the instantaneous output speed V out generated by the needs of the device 2. It is thus possible to tolerate rapid and intense transient variations in the call traction T out and therefore in the output speed V out which results therefrom, without directly affecting these variations on the input speed V in, but on the contrary by allowing the system to regulation 20 to carry out a progressive catch-up of the wire reserve 3, by carrying out gentle variations in the input speed V in, which stress the coil 40 in a very smooth manner, without creating any risk of breakage of the wire 3 or inertial runaway of said coil 40, until finding, once the nominal size of the loop 13 has been restored, and therefore once the wire reserve 3 has been reconstituted, a stabilized regime according to which the input speed V in is substantially equal to the output speed V_out.

[0063] Preferably, the retaining member 15 has, opposite the internal face of the loop 13, a curved receiving surface 15A against which the wire 3 of the loop 13 comes to bear under the effect of the inrush traction T out, at least when the output speed V out resulting from said inrush traction T out exceeds the input speed V in.

[0064] It will be noted that it is not excluded that, in stabilized mode, when the loop 13 has its nominal size and the input speed V in is equal to the output speed V out, the loop 13 may, depending on the configuration of the compensator 4, not press, or at least not press permanently, against the retaining member 15 but float freely in the clearance space 12 near said retaining member 15, and that the loop 13 comes into contact with the receiving surface 15A temporarily, by inertia effect, when a sudden call of wire 3 causes the output speed V out to increase suddenly and exceed the input speed V in.

[0065] In this respect, when the apparatus 2 is in operation, and more particularly when a three-dimensional printing operation is in progress, the apparatus 2 will trigger frequent wire calls, so that the loop 13 will frequently come into contact with the retaining member 15.

[0066] Advantageously, the curvature of the receiving surface 15A of the retaining member 15 is of the same sign as the curvature of the wire 3 which comes to bear against said receiving surface 15A, but has a radius of curvature which is strictly less than the radius of curvature of the wire 3 which comes to bear against said receiving surface 15A.

[0067] More preferably, considering the loop 13 and the retaining member 15 in projection in the reference plane PO, normal to the loop axis Z 13, the respective curvatures of the wire 3 on the one hand and of the receiving surface 15A of the retaining member 15 on the other hand will be such that, at any point of contact between the wire 3 and the retaining member 15, here therefore at any point of contact between the wire 3 and the receiving surface 15A of said retaining member 15, the osculating circle of the wire 3 is larger, that is to say of larger diameter, than the osculating circle of the receiving surface 15A.

[0068] The rigidity of the wire 3 in fact advantageously allows said wire 3 to substantially tangent the receiving surface 15A of the retaining member 15 without having to exactly match its curvature, which facilitates the relative sliding of the wire 3 on the receiving surface 15A which allows, among other things, the dynamic adaptation of the size of the loop 13.

[0069] Preferably, the overlap sector 14, in which an incoming section of wire 3 runs along an outgoing section of wire 3 to close the loop 13, is between the receiving surface 15A of the retaining member 15 and the guide track 34. This arrangement makes it possible to leave a large free space to allow the top 17 of the loop 13, which is located opposite the overlap sector 14, to move radially and therefore to allow the loop 13 to tighten on itself. The retaining member 15 makes it possible to permanently maintain the overlap sector 14 in a position in which the wire 3 reaches the loop 13 from the entry guide 15 and then leaves said loop 13 to reach the exit guide 7 while being almost tangent to the loop 13, which promotes the smooth longitudinal advance movement of the wire 3, without the formation of angles which could slow down or damage the wire 3.Incorrect positioning of the wire 3 is avoided, and more particularly, it is avoided that the outgoing wire 3 forms an angular break between the loop 13 and the entry guide 5 or the exit guide 7.

[0070] Preferably, the retaining member 15 is formed by a cylindrical pin or a roller, with a diameter which is preferably between 10 mm and 15 mm. The small size of the retaining member 15 makes it possible to leave a large free space within the clearance space 12, and in particular between the retaining member 15 and the top 17 of the loop 13 which is located opposite the overlap sector 14, so as to allow significant variations in the size of the loop 13, and in particular a significant reduction in the size of the loop 13 compared to its nominal size, since the retaining member 15 does not hinder the tightening of the loop 13 on itself.

[0071] The cylindrical shape of the retaining member 15, and more preferably the use of a roller, here the axis of which is normal to the reference plane PO and therefore parallel to the loop axis Z 13 at all times, makes it possible to implement a simple and compact retaining member 15, and furthermore facilitates the longitudinal movement of the wire 3 from upstream to downstream, and in particular the transfer of the wire 3 from the loop 13 to the output guide 7 under the effect of the call traction T out, by opposing very little resistance to the advance of the wire 3.

[0072] Preferably, as can be seen in particular in Figures 1, 4 and 5, the measuring member 21 of the regulation system 20 comprises a tilting follower arm 22 which is provided with a wire passage 23, for example formed by a pair of rollers 24, wire passage 23 through which passes a portion of the loop 13, so that a variation in the size of the loop 13 causes a movement of the tilting follower arm 22, which movement is measured by a sensor 25, such as an optical fork.

[0073] The rollers 24 carried by the follower arm 22 and forming the wire passage 23 may have a diameter between 10 mm and 15 mm.

[0074] Preferably, the follower arm 22 tilts about a horizontal axis, so as to be naturally pulled downwards by gravity when it accompanies an expansion of the loop 13, and conversely, to be lifted by a narrowing of the loop 13.

[0075] Any suitable sensor 25 may of course be used to detect and quantify the movements of the follower arm 22. However, an optical fork has the advantage of simplicity, compactness, and a short response time. The follower arm 22 is then arranged so that a portion of said follower arm 22 crosses the air gap delimited by the two branches of the fork, in order to cut the optical beam, when the loop 13 has its nominal size, here its maximum size, and to exit the air gap of the optical fork when the loop 13 shrinks by tightening on itself.

[0076] The tilting axis of the follower arm 22, as well as the central axes of the rollers 24 forming the wire passage 23 will advantageously be normal to the reference plane PO, and therefore parallel to each other and parallel to the loop axis Z 13.

[0077] It will be noted that the wire passage 23 materialized by the rollers 24 carried by the follower arm 22 thus forms a mobile point that the loop 13 will, when it modifies its size, move relative to the fixed point formed by the retaining member 15.

[0078] Preferably, the wire passage 23 of the follower arm 22 will cooperate with the wire 3 of the loop 13 substantially towards the apex 17 of the loop, in a sector of the perimeter of the loop 13 which is located substantially diametrically opposite the overlap sector 14, and therefore substantially diametrically opposite the retaining member 15. This will in particular allow good sensitivity of the detection, since the section of loop 13 which is located in the sector of the apex 17 is the one which makes the largest radial displacement when the loop 13 tightens, and respectively when the loop 13 extends.

[0079] Preferably, the guide receptacle 11 comprises a first flange 30 and a second flange 31, preferably flat, which laterally border the clearance space 12 in order to contain the loop 13 substantially flat between said first flange 30 and second flange 31.

[0080] Said first flange 30 and second flange 31 are preferably parallel to each other and parallel to the reference plane PO, and therefore normal to the loop axis Z 13.

[0081] Preferably, as can be seen in Figure 3, the first flange 30 forms a door which is mounted on a hinge 32 so as to be able to alternately adopt an open position, which gives access to the clearance space 12 located inside the guide receptacle 11 and to the wire 3 as well as to the loop 13, in particular to allow an operator to put the wire 3 in place, within the clearance space 12, by recovering the wire 3 which emerges through the entry guide 5 and by making the wire 3 describe a loop 13 before engaging the wire 3 in the exit guide 7, and a closed position in which the flat surface, preferably solid, of said door ensures the lateral guidance of the loop 13, by preventing the wire 3 from moving away axially beyond the limit formed by said door.

[0082] Preferably, as can be seen in Figures 2, 3 and 4, the second flange 31 is provided with a slot 33 in the shape of an arc of a circle which allows the rollers 24 forming the wire passage 23 of the follower arm 22 to penetrate inside the clearance space 12 delimited axially by the first and second flanges 30, 31, while said follower arm 22 is located and performs its tilting movements outside said clearance space 12, on the back of the second flange 31, so that said follower arm 22 does not risk interfering with the radial tightening and then expansion movements of the loop 13.

[0083] The first flange 30 can also be provided with a similar slot 33', which allows the rollers 24 forming the wire passage 23 to pass through said first flange 30 and to emerge outside the clearance space 12, so that the wire 3 is captive in the wire passage 3 thus closed, between the two rollers 24 on the one hand, and between the first flange 30 and the second flange 31 on the other hand.

[0084] Furthermore, the first flange 30 and / or the second flange 31 will preferably be made of a transparent material, so as to allow an operator to monitor the behavior of the wire 3, and of the loop 13, inside the guide receptacle 11, within the clearance space 12.

[0085] Preferably, the spacing distance W12 between the first flange 30 and the second flange 31, considered here of course in the working configuration, that is to say when the door forming the first flange 30 is in the closed position, which spacing distance W12 corresponds here to the axial width W12 of the clearance space 12, is between 2.1 times and 6 times the diameter D3 of the section of the wire.

[0086] Preferably, absolutely or in addition to the proportions indicated above, the spacing distance W12 between the first flange 30 and the second flange 31 is between 6 mm and 20 mm, in particular when the diameter D3 of the section of the wire 3 is between 1.5 mm and 4 mm, preferably between 2 mm and 3 mm, as indicated above.

[0087] Advantageously, this makes it possible to keep the loop 13 substantially flat, while leaving an axial clearance which is sufficient to allow two strands of wire 3, here the incoming strand which enters through the inlet guide 5 and arrives at the loop 13 and the outgoing strand which leaves the loop 13 to join the outlet guide 7, to cross by superimposing themselves axially, in the overlapping sector 14, and to slide relative to each other according to the longitudinal advance of the wire 3, consumed by the device 2, and the variations in size of the loop 13, without excessive friction, excessive heating or abrasion.

[0088] Preferably, the guide receptacle 11 comprises a guide track 34, preferably of cylindrical shape with a circular base, which delimits the clearance space 12 in order to contain the centrifugal radial expansion of the loop 13 within the limit of a maximum diameter D34 permitted, as defined by said guide track 34.

[0089] In practice, the maximum diameter, radially external, of the loop 13 may thus be equal to the diameter D34 of the guide track 34.

[0090] The central axis Z34 of the guide track 34 is preferably coincident, by convention, with the main axis Z, and therefore normal to the reference plane PO, and consequently parallel to the loop axis Z 13 and normal to the first and second flanges 30, 31.

[0091] Likewise, the generatrices of said guide track 34 will therefore be parallel to the loop axis Z13 and normal to the first and second flanges 30, 31.

[0092] Such a circular guide track 34, in addition to protecting the loop 13 from external disturbances and making it possible to limit the size of said loop 13 while keeping said loop 13 in a controlled manner in a predefined space, advantageously offers curved guidance which promotes the curvature of the wire 3 which enters the clearance space 12 via the entry guide 5, and therefore the maintenance of said wire 3 in the form of a loop 13.

[0093] Preferably, the diameter D34 of the guide track 34 is between 200 mm and 600 mm, preferably between 250 mm and 400 mm, for example equal to 300 mm.

[0094] Such dimensions make it possible in particular to constitute a sufficient reserve of wire 3 within the loop 13 to cover sudden calls of a length of wire 3 between 300 mm and 900 mm, for example between 350 mm and 500 mm.

[0095] As a first approximation, we can consider that the reserve of wire 3 that can be mobilized for a sudden call represents approximately half the perimeter of the maximum loop 13.

[0096] As an indicative example, we could have a loop 13 which has a maximum diameter of 270 mm, corresponding to a full reserve, and which can shrink without damage to reach a minimum diameter of 120 mm, corresponding to an exhausted reserve, so that the length of wire released will be 471 mm = Pi x (270 mm - 120 mm).

[0097] According to a particularly simple preferred arrangement, the guide track 34 forms a spacer which connects the first flange 30 to the second flange 31, and which maintains between said first flange 30 and second flange 31, parallel to each other, a spacing distance W12 which is equal to the width W34 of said guide track 34.

[0098] The width W34 of the guide track 34 will thus be adapted, as explained above, to provide sufficient space axially, transversely to the longitudinal advance direction of the wire 3, to allow the wire 3 to travel and to overlap axially on itself in the overlap sector 14, by distributing itself along the loop axis Z13, without risk of heating, blocking or abrasion.

[0099] Preferably, the guide track 34 may form the internal hollowed-out portion of a frame 35, preferably metallic, which serves as a support for various members of the compensator, including: the drive system 6, and more particularly the motor 8, the drive roller 9 and the counter-roller 10, the first flange 30 which is articulated here on said frame 35 by means of the hinge 32, the second flange 31, here fixed in an invariant position on the frame 35, for example by means of screws, and the tilting follower arm 22 which is pivotally articulated on said frame 35.

[0100] It will be noted that the guide track 34 preferably comprises a notch 36 which allows one of the rollers 24 of the wire passage 23 of the follower arm 22 to retract radially beyond the surface of the guide track 34 so that the wire 3 passes naturally through the wire passage 23, between the two rollers 24, when said wire travels in contact with the guide track 34, and therefore here forms the loop 13 of larger size which corresponds to the nominal, and maximum, reserve of wire 3.

[0101] The input guide 5 and the output guide 7 are preferably formed by grooves hollowed out from a face of the frame 35 which is then covered by one of the first and second flanges 30, 31 so that the guides 5, 7 each have a closed section around the wire 3.

[0102] In projection in the reference plane PO normal to the central axis Z34 of the guide track 34, the input guide 5 opens onto said guide track 34 at a first point M5, located at a first azimuth around the central axis Z34 of the guide track 34, while the output guide 7 definitively leaves the guide track 34 at a second point M7, located at a second azimuth distinct from the first azimuth. Preferably, the receiving surface 15A, and more preferably the entirety of the retaining member 15, is included in the circular segment defined by the guide track 34 between this first point M5 and this second point M7, that is to say in the domain which corresponds to the portion of disk which is delimited on the one hand by the arc chord which corresponds to the straight line segment which connects the first point M5 to the second point M7 and on the other hand by the arc of a circle which corresponds to the portion of the guide track 34 which extends from the first point M5 to the second point M7.

[0103] Thus, not only will the retaining member 15 leave a large free space to allow the top 17 of the loop 13 to move radially and therefore to allow the loop 13 to tighten on itself, but in addition said retaining member 15 will make it possible to permanently maintain the overlap sector 14 in a position in which the wire 3 reaches the loop 13 from the entry guide 15 then leaves said loop 13 to reach the exit guide 7 while being almost tangent to the loop 13, which promotes the smooth longitudinal advance movement of the wire 3, without the formation of angles which could slow down or damage the wire 3.

[0104] Preferably, the retaining member 15 will be located in an angular sector S15, considered in azimuth around the central axis Z34 of the guide track 34, which is located between the first point M5 and the second point M7, and more preferably substantially at an equal distance from the first point M5 and the second point M7, for example centered on the bisector of the angle formed, in the reference plane PO, by the half-lines originating perpendicularly from the central axis Z34 and passing respectively through the first point M5 and the second point M7.

[0105] More generally, considering that the input guide 5 opens onto the guide track 34 via an input mouth 5A and the output guide 7 opens onto the guide track 34 via an output mouth 7A, then the retaining member 15 is preferably contained in an angular sector S 15, considered in azimuth around the central axis Z34 of the guide track 34, which is between the input mouth 5A, upstream, and the output mouth 7A, downstream.

[0106] Preferably, the retaining member 15 will be contained within an angular sector S15, considered around the central axis Z34 of the guide track 34, in the reference plane PO, here more particularly the aforementioned angular sector S15 between the inlet mouth 5A and the outlet mouth 7A, which extends over less than 30 degrees, preferably over less than 20 degrees, more preferably over less than 10 degrees, for example over 5 degrees.

[0107] The small angular size of the retaining member 15 will, here again, optimize the capacity of the loop 13 to tighten to release a reserve of wire 3.

[0108] Preferably, the retaining member 15, and more particularly its receiving surface 15A, will be contained radially inside a fictitious crown which is centered on the central axis Z34 of the guide track 34 and of which: - the internal radius represents between 60% and 85% of the radius of the guide track 34, so that a large central space is kept completely clear to allow the tightening of the loop 13, - and the external radius, strictly greater than the internal radius, represents between 70% and 97% of the radius of the guide track 34, such that the retaining member 15 will be sufficiently far from the guide track 34 to allow the wire 3 to travel freely between the receiving surface 15A and the guide track 34, without the longitudinal movement of the wire 3 being hindered, while being sufficiently close to the guide track 34 to act quickly on the loop 13 in order to limit the overall movement of the loop 13 in the event of sudden and intense pull-out traction, and in particular to ensure that at all times the overlap sector 14 remains correctly positioned with respect to the entry 5 and exit 7 guides so that the longitudinal advance movement of the wire 3 remains fluid.

[0109] For information purposes, the retaining member 15 may be positioned relative to the guide track 34 in such a way that, considered in the reference plane PO, the smallest distance separating the retaining member 15, and more particularly its receiving surface 15A, from the surface of the guide track 34, and which therefore provides a passage for the wire 3 and more particularly for the overlap sector 14, is equal to or greater than 4 times the diameter D3 of the section of the wire 3.

[0110] Preferably, the input guide 5 opens onto the guide track 34 at a first azimuth which is located upstream of the azimuth at which the retaining member 15 is located in the direction of arrival of the wire 3, and in a first direction L5, called the “input direction” L5, which is tangent to said guide track 34, while the output guide 7 leaves the guide track 34 at an azimuth which is located downstream of the azimuth at which the retaining member 15 is located, and in a second direction L7, called the “output direction” L7, which is tangent to the guide track 34.

[0111] Here again, this arrangement, considered in the reference plane PO, normal to the central axis Z34 of the guide track 34, promotes the longitudinal advance movement of the wire 3, both to enter the loop 13 and to exit the loop 13, and allows the wire 3 to make a complete turn on itself, to form the loop 13, and to cross over itself in an overlapping sector 14 which is located in the vicinity of, and preferably bearing against, the retaining member 15.

[0112] Preferably, the output guide 7 leaves the guide receptacle 11 in a direction L7 called the “output direction” L7 which deviates from the direction L5 called the “input direction” L5, in which the input guide 5 opens onto the guide receptacle 11, by an angle A_5_7 called the “deviation angle” A_5_7 which is between zero degrees and 180 degrees, for example equal to 90 degrees.

[0113] The deflection angle A_5_7 may be chosen depending on the location of the compensator 4 relative to the coil 40 and the apparatus 2. A deflection angle of zero degrees will correspond to an output guide 7 placed in alignment with the input guide 5, so that the wire 3 makes exactly one turn on itself. A deflection angle of 180 degrees will mean that the wire 3 leaves the compensator 4 in a direction parallel but opposite to the direction in which it entered, i.e., it makes 1.5 turns on itself and takes an output guide 7 which is diametrically opposite to the input guide 5. A deflection angle A_5_7 of 90 degrees indicates that the wire makes 1.25 turns and is returned to the output of the compensator 4 at a right angle to its input direction, as illustrated in Figures 1, 2, 3 and 5.

[0114] These values, considered in the reference plane PO, advantageously make it possible to easily create and maintain a loop 13 of wire which covers at least one turn but less than two turns, typically between 1.1 turns and 1.5 turns, for example 1.25 turns as indicated above.

[0115] Of course, the invention also relates as such to any device 2 provided with a power supply device 1 according to the invention.

[0116] In particular, the invention relates to a three-dimensional printer which is equipped with a feed device 1 according to the invention to ensure the supply of said printer with a thermoplastic material in the form of a wire 3.

[0117] As indicated in the preamble, said printer will preferably be an “FDM” type printer and will include a heating nozzle 50 making it possible to melt the wire 3 in order to deposit the material in successive layers on a support, such as a tray.

[0118] Said heating nozzle 50 may belong to a print head mounted to move relative to the support, under the control of a motorized positioning system. In a manner known per se, said print head will preferably include a pulley straightener making it possible to reduce or even eliminate the curvature of the wire 3, followed by a toothed roller driver which pulls the wire 3 coming from the compensator 4 to force it to pass through the heating nozzle 50, at the speed required by the deposition of molten material.

[0119] Of course, the invention is in no way limited to the embodiment variants described above, the person skilled in the art being able to isolate or freely combine the above-mentioned characteristics or to substitute equivalents for them.

Claims

CLAIMS 1. Feeding device (1) intended to convey to a device (2), such as a three-dimensional printer, a material which is in the form of a wire (3), said feeding device being characterized in that it is provided with a compensator (4) which comprises: - an entry guide (5) which allows the wire (3) to enter the compensator (4), - a motorized drive system (6), which is arranged to propel the wire (3) which enters through the entry guide (5) at a chosen longitudinal speed, called “entry speed” V_in, - an exit guide (7) which allows the wire to exit the compensator (4), to the device (2), under the effect of a longitudinal traction force called “call traction” (T out) which is generated at the request of the device (2) and which gives the wire (3) which exits through the exit guide (7) a longitudinal speed called “exit speed” (V_out), - a guide receptacle (11) which delimits a hollow space called "clearance space" (12) inside which the wire (3) coming from the entry guide (5) forms a loop (13) on itself before exiting through the exit guide (7), in such a way that the loop (13) constitutes a reserve of wire (3) and is able to spontaneously adjust its size, while remaining contained inside the clearance space (12), alternatively by tightening on itself under the effect of the take-up traction (T out) in order to reduce its perimeter and thus release a part of said reserve of wire for the device (2), when the exit speed (V out) resulting from said take-up traction (T out) exceeds the entry speed (V in),and conversely by widening in order to increase its perimeter and thus replenish at least part of said reserve of wire (3) when the drive system (6) generates an input speed (V in) which exceeds the output speed (V out) and therefore creates within the incoming wire (3) which precedes the loop (13) a longitudinal thrust force, called “supply thrust” (P_in), which forces said incoming wire (3) to join the loop (13) and to increase the perimeter of the loop (13), - a retaining member (15) which is placed inside the perimeter of the loop (13), so as to be able to limit the extent of an overall displacement of the loop (13) within the clearance space (12), when the loop (13) undergoes a pull-up (T out), while allowing the loop (13) to freely adapt its size, within the clearance space (12), in response to the differences between the output speed (V out) and the input speed (V_in), - a regulation system (20) which controls the drive system (6) and which comprises at least one measuring member (21) making it possible to evaluate the size of the loop (13) present within the clearance space (12), so that said regulation system (20) can adjust the input speed (V in) chosen according to the size of the loop (13), characterized in that the guide receptacle (11) comprises a guide track (34) of cylindrical shape with a circular base, which delimits the clearance space (12) in order to contain the centrifugal radial expansion of the loop (13) within the limit of a maximum authorized diameter (D34), as defined by said guide track (34).

2. Device according to claim 1 characterized in that the retaining member (15) has, opposite the internal face of the loop (13), a curved receiving surface (15A) against which the wire (3) of the loop (13) comes to bear under the effect of the inrush traction (T out), at least when the output speed (V out) resulting from said inrush traction (T out) exceeds the input speed (V in), and in that the curvature of said receiving surface (15 A) is of the same sign as the curvature of the wire (3) which comes to bear against said receiving surface (15 A), but has a radius of curvature which is strictly less than the radius of curvature of the wire (3) which comes to bear against said receiving surface (15A).

3. Device according to claim 1 or 2 characterized in that the retaining member (15) is formed by a cylindrical pin or a roller, with a diameter between 10 mm and 15 mm.

4. Device according to one of the preceding claims, characterized in that the measuring member (21) of the regulation system (20) comprises a tilting follower arm (22) which is provided with a wire passage (23), for example formed by a pair of rollers (24), through which a portion of the loop (13) passes, so that a variation in the size of the loop (13) causes a movement of the tilting follower arm (22), which movement is measured by a sensor (25), such as an optical fork.

5. Device according to one of the preceding claims, characterized in that the guide receptacle (11) comprises a first flange (30) and a second flange (31), preferably flat, which laterally border the clearance space (12) in order to contain the loop (13) substantially flat between said first flange (30) and second flanges (31).

6. Device according to claim 5 characterized in that the spacing distance (W12) between the first flange (30) and the second flange (31) is between 2.1 times and 6 times the diameter (D3) of the section of the wire (3), and / or between 6 mm and 20 mm.

7. Device according to one of claims 5 or 6, characterized in that the guide track (34) forms a spacer which connects the first flange (30) to the second flange (31), and which maintains between said first flange (30) and second flange (31) a spacing distance (W12) equal to the width (W34) of said guide track (34).

8. Device according to any one of the preceding claims, in which the retaining member (15) has, opposite the internal face of the loop (13), a curved receiving surface (15A) against which the wire (3) of the loop (13) comes to bear under the effect of the inrush traction (T out), at least when the output speed (V out) resulting from said inrush traction (T out) exceeds the input speed (V in), and an overlap sector (14), in which an incoming section of wire (3) runs along an outgoing section of wire (3) to close the loop (13), is between the receiving surface (15A) of the retaining member (15) and the guide track (34).

9. Device according to any one of the preceding claims, in which the input guide (5) opens onto the guide track (34) at a first azimuth around the central axis (Z34) of the guide track (34) which is located upstream of the azimuth at which the retaining member (15) is located in the direction of arrival of the wire (3), and the output guide (7) leaves the guide track (34). guide (34) at an azimuth which is downstream of the azimuth at which the retaining member (15) is located.

10. Device according to claim 9, characterized in that the input guide (5) opens onto the guide track (34) in a first direction (L5), called the “input direction” (L5), which is tangent to said guide track (34), and in that the output guide (7) leaves the guide track (34) in a second direction (L7), called the “output direction” (L7), which is tangent to the guide track (34).

11. Device according to one of claims 9 to 10, characterized in that the input guide (5) opens onto the guide track (34) via an input mouth (5A) and the output guide (7) opens onto the guide track (34) via an output mouth (7A), in that the retaining member (15) is contained in an angular sector (S15), considered in azimuth around the central axis (Z34) of the guide track (34), which is between the input mouth (5A) and the output mouth (7A), in that said angular sector (S15) extends over less than 30 degrees, preferably over less than 20 degrees, more preferably over less than 10 degrees, for example over 5 degrees, and in that the retaining member (15) is contained radially inside a fictitious crown which is centered on the central axis (Z 34) of the guide track (34) and of which: - the internal radius represents between 60% and 85% of the radius of the guide track (34), - and the external radius, strictly greater than the internal radius, represents between 70% and 97% of the radius of the guide track (34).

12. Device according to one of the preceding claims, characterized in that the output guide (7) leaves the guide receptacle (11) in a direction (L7) called the “output direction” (L7) which deviates from the direction (L5) called the “input direction” (L5), in which the input guide (5) opens onto the guide receptacle (11), by an angle called the “deviation angle” (A_5_7) which is between zero degrees and 180 degrees, for example equal to 90 degrees.

13. Device according to one of the preceding claims, characterized in that the device is intended to convey to the apparatus (2) a wire (3) whose constituent material is a polymer having a hardness greater than or equal to 60 Shore A.

14. Device according to one of the preceding claims, characterized in that it comprises a reel (40) which is located upstream of the motorized drive system (6) and mounted in free rotation, and on which is stored the wire (3) intended to enter the compensator (4).

15. Three-dimensional printer equipped with a supply device (1) according to any one of the preceding claims to ensure the supply of said printer with a thermoplastic material in the form of a wire (3).

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