Cartridge for a stereolithographic machine

A cartridge for a stereolithographic machine, includes a body, which in turn, includes a container, delimited by walls, having a bottom, and an opposite access opening allowing access inside the container, inlet and outlet mouths for a photopolymerisable material, at least one tank for same. The tank includes a transit opening for a photopolymerisable material and an air passage opening communicating with the environment; and includes: circulation means to circulate the photopolymerisable material between the outlet mouth and the inlet mouth of the container. Between the circulation means and the inlet and outlet mouths, and between the circulation means and the transit and air passage openings, valve means are interposed, configured to alternatively allow various circulation configurations of the cartridge, either preventing or allowing passage of photopolymerisable material between the container and the tank; or allowing the passage of material between the outlet and inlet mouths of the same container.

The present invention relates to a cartridge for a stereolithographic machine. As is known, the stereolithographic technique envisages making a three-dimensional object by superimposing a plurality of layers of a liquid or pasty photopolymerisable material, which is solidified by exposure to predefined radiation, generally light.

One known type of stereolithographic machine comprises a container for containing the material and a modelling platform motorised in a vertical direction.

The machine further comprises emitting means for emitting the aforesaid predefined radiation, which are able to selectively solidify a layer of the material adjacent to the modelling platform.

Several photopolymerisable stereolithography materials are known which can be used to make the object, which mutually differ in colour, tonality, mechanical characteristics and other physical parameters.

A same stereolithographic machine can be used with any one of the different materials mentioned above, according to the requirements requested for each three-dimensional object to be made.

In US patent application US 2016/0288421 A1 a cartridge is described for a stereolithographic machine, comprising: a container provided with an access opening and a transparent bottom opposite the access opening, a tank for containing a base liquid or pasty material, irremovably associated with the container, and valve means for the passage of the base material from the tank to the container.

In this cartridge the valve means are configured to open when the difference between the pressure present in the tank and that present in the container is at least equal to a predefined value and to spontaneously close again when the pressure difference is lower than the predefined value; the tank comprises sealing means for the connection to an external air supply device.

In particular, during the execution of the stereolithographic process for the creation of a three-dimensional object, the need to refill the photopolymerisable material present in the container is known, so as to maintain its level constant. The refilling of the photopolymerisable material in the container where stereolithography is performed can be carried out automatically, providing the stereolithographic machine with a feeding device.

For example, Italian patent application no. 102017000015055 describes a cartridge for a stereolithography machine with an inclined tank, comprising a box-like body inside which a container and at least one tank for a photopolymerisable material are defined; the container is delimited by a containment wall, which has a bottom that is at least in part transparent, and an opposite access opening adapted to allow access inside the container; this container has an inlet mouth for introducing a photopolymerisable material and an outlet mouth for the release of the photopolymerisable material from the container.

The known cartridge also comprises:means for the transfer of a photopolymerisable material from the tank to the container, which are embodied in a plunger system,and means for the recirculation of a photopolymerisable material from the outlet mouth towards the inlet mouth of the container, which are embodied in a peristaltic-type pumping system.

Although this cartridge allows automatically refilling of photopolymerisable material and its recirculation, it has some perfectible aspects.

A first of these perfectible aspects resides in the relative complexity of components and construction of such known cartridge.

For example, this cartridge comprises both specific means for recirculating the photopolymerisable material, and specific means for transferring the photopolymerisable material from the tank to the container.

The preparation of both of these different means involves a certain burden in terms of components, assembly and actuator devices, since both of the aforementioned means require dedicated actuators for their operation.

Another limitation of the known cartridges is linked to the fact that if the photopolymerisable material transferred from the tank to the container for stereolithography operations is not completely used and remains in the container, it risks degrading and losing more or less important characteristics which are useful for its optimal use.

The aim of the present invention is to provide a cartridge for a stereolithographic machine capable of obviating the aforementioned drawbacks and limitations of the prior art.

In particular, an object of the invention is to provide a compact cartridge which is easier to manufacture and assemble than the known cartridges.

Another object of the invention is to provide a cartridge that allows for better preservation of the unused photopolymerisable material.

The aforesaid task and the aforementioned objects are achieved by a cartridge for a stereolithographic machine with an inclined tank according to claim1.

Further characteristics of the cartridge according to claim1are described in the dependent claims.

With reference to the aforementioned figures, a cartridge for a stereolithographic machine according to the invention is comprehensively indicated with the number10.

This cartridge10comprises:a box-like body11comprising in turn:a container12, delimited by containment walls13, having a bottom14, at least part of which is transparent, and an opposite access opening15, adapted to allow access inside the container12, an inlet mouth16, for the introduction of a photopolymerisable material, and an outlet mouth17for the photopolymerisable material to exit from the container12;a tank18for a photopolymerisable material, comprising a transit opening19for the photopolymerisable material and an air passage opening20, communicating with the environment.

This cartridge10also comprises circulation means21, for the circulation of a photopolymerisable material between the outlet mouth17and the inlet mouth16of the container12.

The cartridge10according to the present invention is characterised by the fact that between the circulation means21and the inlet16and outlet17mouths, and between the circulation means21and transit19and air passage20openings, valve means22and23are interposed as better described below, and configured to alternatively allow the following use configurations of the same cartridge10:a first configuration, shown inFIG. 2, for preventing the passage of photopolymerisable material between the container12and the tank18;a second configuration, shown inFIG. 3, allowing the passage of photopolymerisable material between the tank18and the container12;a third configuration, shown inFIG. 4, of circulation for the photopolymerisable material, allowing the passage of photopolymerisable material between the outlet mouth17of the container12and the inlet mouth16of the same container12.

In particular, in the embodiment described herein of the cartridge10according to the invention, but not limiting to the invention itself, the valve means22and23are configured to allow:a second configuration allowing the passage of photopolymerisable material from the tank18towards the container12;a third configuration allowing the passage of photopolymerisable material from the outlet mouth17of the container12towards the inlet mouth16of the same container12.

Still in particular, in the present embodiment which is exemplary but non-limiting to the invention, the valve means22and23are configured to allow a fourth use configuration of the cartridge10, allowing the passage of photopolymerisable material from the container12towards the tank18.

In the embodiment of the invention described herein, the perimeter containment walls13of the container12comprise a first wall24, on which the inlet mouth16is defined, an opposite second wall25, on which the outlet mouth17is defined, and two side walls26and27.

When the cartridge10is positioned in a position of use on a stereolithography machine with an inclined tank, the first wall24is placed at a greater height than the second wall25, with respect to a horizontal reference plane.

The tank18in turn also comprises a first wall32, on which the air passage opening20is defined, an opposite second wall33, on which the transit opening19is defined, and two side walls34and27.

The container12and the tank18are therefore separated by a wall, in the present embodiment this is wall27, which is shared between the two.

The circulation means21comprise a shaped tube28.

A section29of this shaped tube28is configured to surround at least in part a compression rotor30, defining with it a peristaltic pumping system31.

The compression rotor30and the peristaltic pumping system31are intended to be of a type known per se.

The shaped tube28has a first end35and a second opposite end36.

The valve means22and23comprise a first valve22configured to alternatively determine the following configurations:a first configuration of the first valve22, for the simultaneous closing of the transit opening19of the tank18and of the outlet mouth17of the container12, for the first use configuration of the cartridge10;a second configuration of the first valve22, connecting the first end35of the shaped tube28of the circulation means21and the transit opening19of the tank18, with the simultaneous closing of the outlet mouth17of the container12, for the second use configuration of the cartridge10;a third configuration of the first valve22, connecting the first end35of the shaped tube28of the circulation means21and the outlet mouth17of the container12, with the simultaneous closing of the transit opening19of the tank18, for the third use configuration of the cartridge10.

The first valve22is configured in such a way that its third configuration, connecting the first end35of the shaped tube28of the circulation means21and the outlet mouth17of the container12, with the simultaneous closing of the transit opening19of the tank18, cooperates in the fourth use configuration of the cartridge10.

This first valve22is defined by a three-way valve with three positions.

In the embodiment of the invention described herein by way of non-limiting example of the invention itself, this first valve22consists of a slide-type valve. In particular, the first valve22comprises a tubular channel37in which a shaped slider rod38slides.

The tubular channel37extends in a straight line.

This tubular channel37is defined adjacent to the second wall25of the container12and to the second wall33of the tank18.

The outlet mouth17of the container12and the transit opening19of the tank18are open on this tubular channel37.

In the present embodiment, the tubular channel37is defined within the same box-like body11, adjacent to the second walls25and33.

The tubular channel37is positioned between these second walls25and33and a corresponding opposite perimeter wall40of the box-like body11.

The tubular channel37is connected to the first end35of the shaped tube28by a side through hole39defined on the perimeter wall40.

The shaped slider rod38of the first valve22comprises two blocking sections41and42and a transit section43, interposed between the blocking sections41and42.

The shaped slider rod38has a main extension axis X1.

With respect to this extension axis X1, the side through hole39is located on the perimeter wall40, between the transit opening19and the outlet mouth17. The transit section43consists of a section of transversal dimensions, with respect to the axis X1, smaller than the corresponding transversal dimensions of the blocking sections41and42, so that between this transit section43and the section of the tubular channel37occupied by the same, an annular conduit74is defined.

This transit section43extends in the direction of the axis X1for a length such to put in communication the side through hole39with the transit opening19of the tank18when the shaped slider rod38is in the second use configuration, and the side through hole39with the outlet mouth17of the container12in the third use configuration.

This transit section43extends in the direction of the axis X1for a length shorter than the minimum distance between the outlet mouth17and the transit opening19, so that they are never in communication via the transit section43. This transit section43is delimited in the direction of the axis X1by two opposite sealing rings71and72.

A first blocking section41is comprised between two sealing rings70and71. This first blocking section41extends along the axis X1for a length that completely obstructs the outlet mouth17both when the first valve22is in its first use configuration, with the simultaneous closing of the transit opening19of the tank18, and when the first valve22is in its second use configuration, with the first end35of the shaped tube28in connection with the transit opening19of the tank18through the transit section43.

A second blocking section42is comprised between two sealing rings72and73.

This second blocking section42extends along the axis X1for a length that completely obstructs the outlet mouth17both when the first valve22is in its first use configuration, with the simultaneous closing of the outlet mouth17of the container12, and when the first valve22is in its third use configuration, with the first end35of the shaped tube28in connection with the outlet mouth17of the container12through the transit section43.

The shaped slider rod38has two opposite end sections85and86, respectively.

These end sections85and86are respectively contiguous to the first41and second42blocking sections, and obviously externally to the latter.

These end sections85and86are available for connection with an actuator for the translation of the same shaped slider rod38and therefore for the operation of the first valve22.

In the particular embodiment described herein of the cartridge10according to the invention, the tank18comprises an auxiliary opening44for the passage of photopolymerisable material during the fourth use configuration of the cartridge10, allowing the passage of photopolymerisable material from the container12to the tank18.

The valve means22and23comprise a second valve23configured to alternatively determine the following configurations:a first configuration of the second valve23for the simultaneous closing of the air passage opening20and the auxiliary opening44of the tank18, for the first use configuration of the cartridge10;a second configuration of the second valve23of connection between the second end36of the shaped tube28of the circulation means21and the inlet mouth16of the container12, with the simultaneous opening of the air passage opening20of the tank18, for the second use configuration and the third use configuration of the cartridge10.

This second valve23is configured to determine, alternatively to its first configuration and second configuration, a third configuration connecting the second end36of the shaped tube28of the circulation means21and the auxiliary opening44of the tank18, with the simultaneous opening of the air passage opening20and the simultaneous closing of the inlet mouth16of the container12, cooperating in the fourth use configuration of the cartridge10.

This second valve23is defined by a five-way valve with three positions.

In the embodiment of the invention described herein by way of non-limiting example of the invention itself, this second valve23consists of a slide-type valve.

In particular, the second valve23comprises a tubular channel47in which a shaped slider rod48slides.

The tubular channel47extends in a straight line.

This tubular channel47is defined adjacent to the first wall24of the container12and the first wall32of the tank18.

The inlet mouth16of the container12, the air passage opening20and the auxiliary opening44of the tank18open directly on this tubular channel47.

In the present embodiment, the tubular channel47is defined within the same box-like body11, adjacent to the first walls24and32.

The tubular channel47is positioned between these first walls24and32and a corresponding opposite perimeter wall50of the box-like body11.

The tubular channel47is connected to the second end36of the shaped tube28through a side through hole49defined on the perimeter wall50.

The shaped slider rod48of the second valve23comprises four blocking sections51,52,53and54and three transit sections55,56and57, each interposed between two blocking sections51,52,53and54.

The shaped slider rod48has a main extension axis X2.

In a preferred embodiment of the cartridge10, this axis X2is parallel to the axis X1of the first valve22.

With respect to this extension axis X2, the side through hole49is located on the perimeter wall50, between the inlet mouth16and the auxiliary opening44. A first transit section55consists of a section of transversal dimensions, with respect to the axis X2, smaller than the corresponding transversal dimensions of the blocking sections51,52,53,54, so that between this first transit section55and the section of the tubular channel47occupied by the same, an annular conduit75is defined.

This first transit section55extends in the direction of the axis X2for a length such to put the side through hole49in communication with the inlet mouth16of the container12when the shaped slider rod48is in the second use configuration of the second valve23.

This first transit section55is interposed between a first blocking section51, outermost and comprising a first end of the shaped slider rod48, and a second blocking section52.

This first transit section55is delimited in the direction of the axis X2by two opposite sealing rings77and78.

A second transit section56consists of a section of transversal dimensions, with respect to the axis X2, smaller than the corresponding transversal dimensions of the blocking sections51,52,53,54, so that between this second transit section56and the section of the tubular channel47occupied by the same, an annular conduit76is defined.

This second transit section56extends in the direction of the axis X2for a length such to put the side through hole49in communication with the auxiliary opening44of the tank18when the shaped slider rod48is in the third use configuration of the second valve23.

This second transit section56is interposed between the second blocking section52and a third blocking section53.

This second transit section56is delimited in the direction of the axis X2by two opposite sealing rings79and80.

A third transit section57consists of a section of transversal dimensions, with respect to the axis X2, smaller than the corresponding transversal dimensions of the blocking sections51,52,53,54, so that between this third transit section57and the section of the tubular channel47occupied by the same, an annular conduit81is defined.

This third transit section57extends in the direction of the axis X2for a length such to put the air passage opening20of the tank18in communication with an external air passage hole82, open to the outside, defined on the perimeter wall50, when the shaped slider rod48is in the second use configuration and in the third use configuration of the second valve23.

This third transit section57is interposed between the third blocking section53and a fourth blocking section54, outermost and comprising a second end, opposite to the first end, of the shaped slider rod48.

This third transit section57is delimited in the direction of the axis X2by two opposite sealing rings83and84.

The second blocking section52is therefore comprised between two sealing rings78and79.

This second blocking section52extends along the axis X2for a length such to obstruct the auxiliary opening44when the second valve23is in its first use configuration, with the simultaneous closing of the air passage opening20by the third blocking section53.

The third blocking section53is comprised between two sealing rings80and83.

This third blocking section53extends along the axis X2for a length such to obstruct the air passage opening20and the air passage hole82when the second valve23is in its first use configuration, and such to at least partially open the air passage opening20and the air passage hole82both when the second valve23is in its second use configuration, and when the second valve23is in its third use configuration.

The first51and fourth54blocking sections, being positioned at opposite ends of the shaped slider rod48, can connect to an actuator for the translation of the same shaped slider rod48and therefore for the operation of the second valve23.

In the present embodiment of a cartridge10according to the invention, the inlet mouth16for the introduction of a photopolymerisable material is constituted by a plurality of inlet through holes, of which three holes16a,16b,16care indicated in the figures by way of example, defined in a row along the first wall24of the container12, so as to substantially occupy this first wall24throughout its length.

These inlet holes16a,16b,16chave a diameter which increases starting from a first hole with a smaller diameter16a, which is closest to the side through hole49of connection with the shaped tube28of the circulation means21, towards a last, opposite inlet hole16zwith the largest diameter.

Thanks to this inlet mouth16, a better distribution of the photopolymerisable material entering the container12is obtained, since the increasing diameter inlet holes allow the progressive filling of the tubular conduit75little by little as the photopolymerisable material enters the shaped conduit28; this progressive filling allows the photopolymerisable material to pass through more and more inlet holes as the tubular conduit75fills up, with the consequent passage of photopolymerisable material in the container12of better and more widespread distribution compared to what has been achieved with the known type inlet mouths with a single hole.

The second wall25of the container12is shaped in such a way as to direct the photopolymerisable material which encounters it towards the outlet mouth17. In particular, in the present embodiment, obviously to be understood as a non-limiting example of the invention, the outlet mouth17is defined near a side wall27of the container12, and the second wall25is inclined to descend towards the outlet mouth17starting from the opposite side wall26.

The operation of the cartridge10according to the invention is described below. Preferably, this cartridge10is designed to be set up on a stereolithographic machine, not illustrated for purposes of simplicity, so that the first walls24and32are higher than the second walls25and33.

In particular, this cartridge10according to the invention is adapted to being positioned on the stereolithographic machine with an inclination greater than or equal to 20° with respect to a horizontal reference plane, and less than 90°, or rather nearing verticality.

FIG. 2shows the first use configuration of the cartridge10.

In this first use configuration, to prevent the passage of photopolymerisable material between the container12and the tank18:the first valve22is in its first configuration, simultaneously closing the transit opening19of the tank18and the outlet mouth17of the container12for the first use configuration of the cartridge10;the second valve23is in its first configuration, simultaneously closing the air passage opening20and the auxiliary opening44of the tank18.

In this first use configuration of the cartridge10, the photopolymerisable material is closed inside the tank18and the photopolymerisable material possibly present in the container12is held in the same container12.

In this first use configuration of the cartridge10, the photopolymerisable material is substantially sealed closed in the tank18since all the openings19,20and44of the latter are completely blocked; this first use configuration therefore lends itself to the shipping and transport phases of the cartridge10.FIG. 3shows the second use configuration of the cartridge10.

In this second use configuration, to allow the passage of photopolymerisable material between the container18and the tank12:the first valve22is in its second configuration, connecting the first end35of the shaped tube28of the circulation means21and the transit opening19of the tank18, with the simultaneous closing of the outlet mouth17of the container12;the second valve23is in its second configuration, connecting the second end36of the shaped tube28of the circulation means21and the inlet mouth16of the container12, with the simultaneous opening of the air passage opening20of the tank18, and impeding the passage of photopolymerisable material from the second end36to the auxiliary opening44.

In this second use configuration of the cartridge10, the diffuse distribution of the photopolymerisable material in the container12is allowed through the row of inlet holes16a,16b,16c,16zof the inlet mouth16.

The opening of the air passage opening20, and obviously of the external air passage hole82, allows the emptying of the tank18, avoiding the ‘air pocket’ effect.

FIG. 4shows the third use configuration of the cartridge10.

In this third use configuration of circulation for the photopolymerisable material:the first valve22is in its third configuration, connecting the first end35of the shaped tube28of the circulation means21and the outlet mouth17of the container12, with the simultaneous closing of the transit opening19of the tank18, for the third use configuration of the cartridge10;the second valve23is in its second configuration, as described above.

In this third use configuration of the cartridge10, the recirculation of the photopolymerisable material from the outlet mouth17directly to the inlet mouth16is allowed.

The cartridge10, or the stereolithographic machine in which the cartridge is mounted, comprises level sensor means for monitoring the recirculation of the photopolymerisable material, so as to detect a possible lowering of the photopolymerisable material level below a threshold which requires refilling the photopolymerisable material in the container12.

The level signal detected by the level sensor means is adapted, via an electronic control and management unit of the stereolithographic machine, to operate the first valve22in order to bring the cartridge10to its second use configuration, thus determining a transfer of photopolymerisable material from the tank18to the container12until the optimal level of photopolymerisable material in the container12is restored.

FIG. 5shows the fourth use configuration of the cartridge10.

In this fourth use configuration allowing the passage of photopolymerisable material from the container12towards the tank18:the first valve22is in its second configuration, as described above;the third valve23is in its third configuration, connecting the second end36of the shaped tube28of the circulation means21and the auxiliary opening44of the tank18, with the simultaneous opening of the air passage opening20and the respective external air passage hole82, and the simultaneous closing of the inlet mouth16of the container12.

In this fourth use configuration of the cartridge10, the first22and second23valves assume respective configurations such as to allow the recovery of photopolymerisable material from the outlet mouth17of the container12for its reintroduction into the tank18through the auxiliary opening44.

In doing so, the unused photopolymerisable material is returned to the optimal storage conditions in the tank18.

In the refilling phase of the tank18, the air passage opening20is open to prevent the formation of overpressure inside the same tank18.

Once all the photopolymerisable material has been recovered, the first22and second23valves are actuated to return the cartridge10to its first use configuration.

A cartridge as described above is to be understood as included in the invention, whose tank18does not have an auxiliary opening44for the reintroduction of the photopolymerisable material.

It is therefore to be understood that a cartridge10is included in the invention wherein the valve means22and23are configured for the implementation of the first three use configurations of the cartridge10and not also for the implementation of the fourth use configuration of the same cartridge10.

A variant of this cartridge10is to be understood as included in the invention, not shown for purposes of simplicity, whose tank18does not have an auxiliary opening44for the reintroduction of the photopolymerisable material, and whose valve means22and23are configured to allow the reintroduction of the photopolymerisable material from the container12to the tank18through the same transit opening19.

It is therefore to be understood that a cartridge10is included in the invention whose valve means22and23are configured to allow the reintroduction of the photopolymerisable material from the container12to the tank18by passing the photopolymerisable material from the outlet mouth17of the container12directly to the transit opening19of the tank18.

It is also therefore to be understood that a cartridge10is included in the invention whose valve means22and23are configured to allow the reintroduction of the photopolymerisable material from the container12to the tank18by passing the photopolymerisable material from the inlet mouth16of the container12towards the transit opening19of the tank18.

It has in practice been established that the invention achieves the intended task and objects.

In particular, a compact cartridge has been developed with the invention which is simpler to manufacture and assemble with respect to the cartridges of a known type, thanks to the valve means which allow the use of a single pumping system, for example a peristaltic pumping system, to create both an optimal conservation phase of the photopolymerisable material, a refilling phase of the moulding container and possible refilling phases of the same container, a recirculation phase of the photopolymerisable material and a reintroduction phase of the unused photopolymerisable material from the container to the tank.

Moreover, a cartridge has been developed with the invention which allows for better preservation of the unused photopolymerisable material.

Moreover, a cartridge has been developed with the invention which can be used on stereolithography machines with an inclined tank of a known type.

The invention thus conceived is susceptible to many modifications and variants, all falling within the same inventive concept; furthermore, all details can be replaced by equivalent technical elements.

In practice, any components and materials can be used according to requirements and the prior art, as long as they are compatible with the specific use, the dimensions and the contingent shapes.

Where the characteristics and techniques mentioned in any claim are followed by reference signs, such reference signs should be intended as having been added for the sole purpose of increasing the intelligibility of the claims and consequently such reference signs have no limiting effect on the interpretation of each element identified by way of example by such reference signs.