Assembly of a guiding structure and a print head carriage

Described is an assembly of a guiding structure and a print head carriage, the print head carriage comprising a base carriage controllably movable relative to the guiding structure along a first horizontal axis, the print head carriage comprising a sub-carriage controllably movable relative to the base carriage along a second horizontal axis. The print head carriage comprises an intermediate carriage controllably movable relative to the base carriage along a vertical axis, the sub-carriage mounted on the intermediate carriage for moving together with the intermediate carriage relative to the base carriage, the sub-carriage controllably movable relative to the intermediate carriage along the second horizontal axis.

FIELD OF THE INVENTION

The present invention relates to an assembly of a guiding structure and a print head carriage.

BACKGROUND ART

A scanning-type inkjet printer comprises an inkjet print head mounted on a carriage guided to move along a certain axis by a guiding structure, to deposit swaths of ink droplets onto a recording medium moving relative to the guiding structure along an axis normal to the axis of carriage motion. By a recording medium being moved to advance over a certain distance in between different swaths, multiple swaths of ink droplets can be deposited side by side onto a recording medium so that the multiple swaths of ink droplets form a complete printed image.

In a known printer of the described type, the print head carriage comprises a base carriage controllably movable relative to the guiding structure along a first horizontal axis, wherein a print head is mounted on a sub-carriage controllably movable relative to the base carriage along a second horizontal axis. By a controlled motion of the sub-carriage relative to the base carriage, a position of the print head relative to the guiding structure can be adjusted, to correct for errors in the positioning of a recording medium relative to the guiding structure, or to compensate for inaccuracies in the guidance of the base carriage causing the base carriage to move to some extent along the axis of medium advance while moving along the axis of carriage motion.

The present invention aims to provide a more versatile assembly of a guiding structure and a print head carriage.

SUMMARY OF THE INVENTION

According to an aspect of the invention, in an assembly of a guiding structure and a print head carriage as described, the print head carriage comprises an intermediate carriage controllably movable relative to the base carriage along a vertical axis, the sub-carriage mounted on the intermediate carriage for moving together with the intermediate carriage relative to the base carriage, the sub-carriage controllably movable relative to the intermediate carriage along the second horizontal axis.

By the sub-carriage being mounted on an intermediate carriage, the intermediate carriage being controllably movable relative to the base carriage along a vertical axis and the sub-carriage being controllably movable relative to the intermediate carriage along the second horizontal axis, a print head mounted on the sub-carriage can be positioned not only at various distances from the guiding structure, but also at various heights above a supporting surface for supporting a recording medium. As a result, an assembly according to the invention can be used for printing on a range of recording media of various thicknesses, notably without the need of lifting a whole assembly of a guiding structure and a print head carriage to a certain height above a supporting surface as described.

DETAILED DESCRIPTION OF EMBODIMENTS

With reference toFIG. 1, a scanning-type inkjet printer comprises an inkjet print head3mounted on a print head carriage2arranged to move relative to a recording medium4along a first horizontal axis Y while being guided by a guiding structure1.

Either the guiding structure1or the recording medium4is movably arranged in order for the guiding structure1and the recording medium4to be moved relative to each other along a second horizontal axis X normal to the first horizontal axis Y.

In operation, a swath of ink droplets is deposited onto the recording medium4by the print head3ejecting sequences of ink droplets towards the recording medium4while the print head carriage2is moving along the first horizontal axis Y, guided by the guiding structure1.

In between the deposition of different swaths, the guiding structure1and the recording medium4are moved relative to each other along the second horizontal axis X, so that multiple swaths of ink droplets deposited onto the recording medium4can form a complete printed image.

In the shown embodiment, the guiding structure1comprises an elongated main part10, oriented to extend along the first horizontal axis Y.

The guiding structure1further comprises a pair of primary guidance rails20a,20b, mounted above each other on a front face11of the main part10oriented orthogonally with respect to the second horizontal axis X. The primary guidance rails20a,20bextend in parallel to each other along the first horizontal axis Y, spaced apart along the vertical axis Z.

With reference toFIG. 2, a pair of primary runner blocks120a,120bis arranged on each of the primary guidance rails20a,20b.

Each primary runner block120a,120bis configured to slide along a respective primary guidance rail20a,20b, thereby being able to translate along the first horizontal axis Y.

Each primary runner block120a,120bengages a primary guidance rail20a,20bin such a way, that the translational degrees of freedom of the primary runner block120a,120balong the second horizontal axis X and the vertical axis Z and the rotational degrees of freedom of the primary runner block120a,120babout all of the three axes X, Y, Z are constrained relative to the rail20a,20b.

With reference toFIG. 3, a base carriage100of the print head carriage2comprises a main plate110oriented orthogonally with respect to the second horizontal axis X, the main plate110having different plate sections111a,111beach positioned at a different one of the primary runner blocks120a,120b.

Each plate section111a,111bis connected to a main section112of the main plate110via one or more flexible bridges113,114, the flexible bridges113,114allowing for a certain motion of a connected plate section111a,111brelative to the main section112.

Each flexible bridge113,114comprises a section115of the main plate110having a middle portion115bof a certain width extending in between two end portions115a,115cof a reduced width. By the section115being able to flex about various axes, including an axis normal to the section115at each of the end portions115a,115c, a flexible bridge113,114constrains on a limited scale only a translational degree of freedom along an axis extending from the one end portion115ato the other end portion115c, allowing plate sections111a,111b,112connected to the respective end portions115a,115cto move relative to each other in all other degrees of freedom, both translational and rotational.

In the shown embodiment, the plate sections111apositioned at the primary runner blocks120aarranged on the bottom primary guidance rail20aare each connected to the main section112by a flexible bridge113extending along the first horizontal axis Y and a flexible bridge114extending along the vertical axis Z. A respective plate section111ais thereby constrained relative to the main section112in translational degrees of freedom along the first horizontal axis Y and the vertical axis Z, and allowed to move relative to the main section112along the second horizontal axis X, as well as in all rotational degrees of freedom.

The plate sections111bpositioned at the primary runner blocks120barranged on the top primary guidance rail20bare each connected to the main section112only by a flexible bridge113extending along the first horizontal axis Y. A respective plate section111bis thereby constrained relative to the main section.112in a translational degree of freedom along the first horizontal axis Y, and allowed to move relative to the main section112along the second horizontal axis X and the vertical axis Z, as well as in all rotational degrees of freedom.

With reference toFIG. 4, the base carriage100further comprises two pairs of secondary runner blocks130a,130b, each secondary runner block130a,130bmounted on one of the primary runner blocks120a,120b, and two secondary guidance rails140, each secondary guidance rail140arranged to be guided by a respective pair of the secondary runner blocks130a,130b.

Each pair of a secondary runner blocks130a,130bcomprises one runner block130amounted on a primary runner block120aarranged on, the bottom primary guidance rail20a, and one runner block130bmounted on a primary runner block120barranged on the top primary guidance rail20b.

Each secondary guidance rail140is oriented along the vertical axis Z, and configured to slide along said vertical axis Z relative to a respective pair of secondary runner blocks130a,130bengaging the rail140.

Each secondary runner block130a,130bengages a secondary guidance rail140in such a way, that the translational degrees of freedom of the guidance rail140along the two horizontal axes X, Y and the rotational degrees of freedom about all of the three axes X, Y, Z are constrained relative to the runner block130a,130b.

Each section111a,111bof the main plate110positioned at a respective primary runner block120a,120bis fixed to the secondary runner block130a,130bmounted on that primary runner block120a,120b. By the different plate sections111a,111bhaving a certain freedom to move relative to the main section112of the main plate110as described, the main plate110is not overly constrained by the plate sections111a,111bbeing fixed, despite any inaccuracies in the alignment of the two primary guidance rails20a,20b, or any different amounts of thermal expansion between the main plate110of the base carriage100and the main part10of the guiding structure1.

Each secondary runner block130a,130bis connected to a respective primary runner block120a,120bvia a flexible structure150, the flexible structure150allowing for a certain motion of the secondary runner block130a,130brelative to the primary runner block120a,120b.

With reference toFIG. 5, each flexible structure150comprises a pair of flexing plates151oriented orthogonally with respect to the first horizontal axis Y, each flexing plate151having a relatively thin middle portion151bextending along the second horizontal axis X in between two wider end portions151a,151c. Each flexing plate151being able to flex about the first horizontal axis Y at the middle portion151b, the pair of flexing plates151, arranged on opposite sides of a secondary runner block130balong the first horizontal axis Y, constrains such a secondary runner block130brelative to the connected primary runner block120bin respect of a translational degree of freedom along the second horizontal axis X while providing a rotational degree of freedom about the first horizontal axis Y.

One end portion151aof each flexing plate151is connected to a primary runner block120bvia a pair of flexing plate sections152arranged at a top end and a bottom end of the end portion151a, each flexing plate section152oriented orthogonally with respect to the vertical axis Z. Each flexing plate section152being able to flex about the first horizontal axis Y, each pair of flexing plate sections152connected to a flexing plate151allows a secondary runner block130bfixed to the other end portion151bof the flexing plate151to translate to a limited extent along the vertical axis Z relative to the primary runner block120b.

The one end portion151aof each flexing plate151being able to flex about the vertical axis Z relative to the flexing plate sections152arranged at the top end and the bottom end, a secondary runner block130bfixed to the other end portion151bis also allowed to rotate to some extent about the vertical axis Z relative to the primary runner block120b.

The one end portion151aof each flexing plate151being able to flex about the first horizontal axis X, a secondary runner block130bfixed to the other end portion151bis also allowed to translate to some extent along the first horizontal axis Y relative to the primary runner block120b, and to rotate to some extent about the second horizontal axis X relative to the primary runner block120b.

In summary, each flexible structure150constrains a secondary runner block130a,130brelative to a primary runner block120a,120bin respect of a translational degree of freedom along the second horizontal axis X, and provides the secondary runner block130a,130bwith translational degrees of freedom relative to the primary runner block120a,120balong the first horizontal axis Y and the vertical axis Z, and rotational degrees of freedom relative to the primary runner block120a,120babout all three axes X, Y, Z.

By each flexible structure150allowing for a certain motion between a secondary runner block130a,130band a respective primary runner block120a,120b, the secondary guidance rails140are not overly constrained by the secondary runner blocks130a,130beach being mounted on a respective primary runner block120a,120b, despite any inaccuracies in the mutual alignment of the two primary guidance rails20a,20band/or the two secondary guidance rails140.

With further reference toFIG. 4, the two secondary guidance rails140are mutually connected by a driving plate160extending in parallel to the main plate110.

The base carriage100comprises a first pair of linear motors170each connected to a different end163of the driving plate160for driving said end163to move along the vertical axis Z relative to the main plate110, the two linear motors170thereby being able also to drive the two secondary guidance rails140to move along the vertical axis Z relative to the main plate110together with the driving plate160.

The two linear motors170having different positions along the first horizontal axis Y allows the two linear motors170also to tilt the driving plate160to some extent about the second horizontal axis X, by the linear motors170driving the different ends163of the driving plate160towards different positions along the vertical axis Z.

Limited tilting of the driving plate160about the second horizontal axis X is enabled by each secondary guidance rail140being connected to a main section162of the driving plate160by a flexible section161allowing the main section162to tilt about the second horizontal X relative to the respective guidance rail140.

With further reference toFIG. 5as well asFIG. 6, each secondary guidance rail140carries a pair of mounting elements180a,180benabling an intermediate carriage300to be mounted onto the pair of secondary guidance rails140, the mounting elements180a,180bspaced apart on each guidance rail140along the vertical axis Z.

Each upper mounting element180bserves to hold a top end of a respective first leaf spring (not shown) connecting the intermediate carriage300to the base carriage100, the first leaf spring having at least a portion extending along the vertical axis Z oriented orthogonally with respect to the first horizontal axis Y to allow a bottom end of the first leaf spring, fixed to a part of the intermediate carriage300, to move along the first horizontal axis Y while a translation along the vertical axis Z is constrained.

Each lower mounting element180aserves to hold a back end of a respective second leaf spring181aconnecting the intermediate carriage300to the base carriage100, the second leaf spring181ahaving at least a portion extending along the second horizontal axis X oriented orthogonally with respect to the vertical axis Z as well as a portion extending along the second horizontal axis X oriented orthogonally with respect to the first horizontal axis Y, to allow a front end of the second leaf spring,181a, fixed to another part of the intermediate carriage300, to move along both the first horizontal axis Y and the vertical axis Z while a translation along the second horizontal axis X is constrained.

A translation of the intermediate carriage300as a whole relative to the base carriage100along the first horizontal axis Y is constrained by a rod (not shown) connecting yet another part of the intermediate carriage300to the base carriage100, extending along the first horizontal axis Y.

Being mounted as described, the intermediate carriage300is minimally constrained with respect to translations relative to the base carriage100along the first horizontal axis Y and the vertical axis Z, which allows for the intermediate carriage300and the base carriage100to be subject to different amounts of thermal expansion. At the same time, the intermediate carriage300is fixedly constrained with respect to a translation relative to the base carriage100along the second horizontal axis X, which allows for horizontal reaction forces resulting from the sub-carriage200being driven to move relative to the intermediate carriage300along the second horizontal axis X to be transferred, via the pair of secondary guidance rails140, the secondary runner blocks130a,130b, the flexible structures150, and the primary runner blocks120a,120b, to the guidance rails20a,20band the main part10of the guiding structure1.

With reference toFIG. 7, a sub-carriage200mounted on the intermediate carriage300comprises a support plate210for supporting at least one print head, or a sub-structure carrying at least one print head, with a portion of the print head facing a recording medium4, the support plate210horizontally oriented and arranged at a bottom of the sub-carriage200.

The support plate210is connected to a main structure310of the intermediate carriage300via a pair of leaf spring structures220,230extending along the vertical axis Z, the leaf spring structures220,230spaced apart along the first horizontal axis Y and fixed to the support plate210at opposite ends211,212thereof, on opposite sides of an area213for receiving a print head.

A leaf spring structure220connecting a first end211of the support plate210to the main structure310comprises a pair of leaf springs221oriented in parallel to each other orthogonally with respect to the first horizontal axis Y, and two leaf spring sections222oriented orthogonally with respect to the second horizontal axis X, each leaf spring section222connecting the pair of leaf springs221to one of the support plate210and the main structure310. The pair of leaf springs221is configured to flex about the second horizontal axis X, providing the first end211of the support plate210with a translational degree of freedom relative to the main structure310along the first horizontal axis Y, thereby enabling the support plate210and the main structure310to be subject to different amounts of thermal expansion. The two leaf spring sections222are each configured to flex about the first horizontal axis Y, enabling the first end211of the support plate213to be moved along the second horizontal axis X.

A leaf spring structure230connecting the second end212of the support plate210to the main structure310comprises a relatively stiff middle section231, and two leaf springs232oriented orthogonally with respect to the second horizontal axis X, each leaf spring232connecting the middle section231to one of the support plate210and the main structure310. Each leaf spring232is configured to flex about the first horizontal axis Y, enabling also the second end212of the support plate210to be moved along the second horizontal axis X. The relatively stiff middle section231keeps the second end212of the support plate210fixed relative to the main structure310along the first horizontal axis Y.

The leaf spring structures220,230together constrain a rotational degree of freedom of the support plate210about the second horizontal axis X.

A rotation of the sub-carriage200relative to the intermediate carriage300about the first horizontal axis Y is constrained by a flexible rod240connecting the support plate210to the main structure310, extending along the vertical axis Z, positioned in between the two leaf spring structures220,230along the first horizontal axis Y, and spaced apart with respect to the two leaf spring structures220,230along the second horizontal axis X.

A top end241of the rod240is connected to a lever250mounted on the main structure310of the intermediate carriage300, the lever250operable for accurately adjusting a position of said top end241along the vertical axis Z in order to control a rotational position of the support plate210about the first horizontal axis Y, the support plate210connected to the other end of the rod240.

A position of each end211,212of the support plate210along the second horizontal axis X can be adjusted by a second pair of linear motors260, each linear motor260positioned on the main structure310and connected to one of the ends211,212for driving the respective end211,212to move relative to the main structure310along said axis X.

The two linear motors260having different positions along the first horizontal axis Y allows the two linear motors260also to rotate the support plate210to some extent about the vertical axis Z, by the linear motors260driving the different ends211,212of the support plate210towards different positions along the second horizontal axis X.

Each linear motor170,260may comprise a voice coil.

The translational degree of freedom along the vertical axis Z of the intermediate carriage300relative to the base carriage100allows an assembly1,2as described to be used for printing on recording media of various thicknesses.

Before printing, by control of the first pair of linear motors170, the intermediate carriage300is moved relative to the base carriage100in order to set a print head mounted on the sub-carriage200at a suitable height above a supporting surface for supporting a recording medium4.

By control of the same motors170, before printing, the sub-carriage200may also be tilted to some extent about the second horizontal axis X, in order to compensate for any inaccuracies in the assembly1,2causing the print head not to be appropriately aligned with the supporting surface.

Aligning the sub-carriage200before printing may also comprise the tilting of the sub-carriage200about the first horizontal axis Y by control of the lever250.

The translational degree of freedom along the second horizontal axis X of the sub-carriage200relative to the intermediate carriage300allows the position of a print head relative to the guiding structure1to be continuously corrected in order for the print head to follow a straight path. In parallel to the guiding structure1, despite any inaccuracies in the main part10of the guiding structure1causing the guidance rails20a,20bnot to be perfectly straight or aligned within a perfectly flat, vertical plane, oriented orthogonally with respect to the second horizontal axis X.

During printing, while the base carriage100moves along the guiding structure1, the position of a print head mounted on the sub-carriage200is continuously adjusted by the second pair of linear motors260driving the sub-carriage200to move in a certain direction along the second horizontal axis X, enabled by the flexibility of the leaf spring structures220,230connecting the sub-carriage200to the intermediate carriage300.

A rotational position of the print head about the vertical axis Z may be adjusted at the same time, by the two linear motors260being controlled independently, for driving the two ends211,212of the sub-carriage200to move at different speeds or in different directions along the second horizontal axis X.

In summary, in an assembly1,2according to the invention, the base carriage100, the sub-carriage200and the intermediate carriage300are constrained relative to each other in respect of some degrees of freedom, and configured to translate and/or rotate relative to each other in respect of other degrees of freedom. By operation of certain actuators170,250,260, the position and/or orientation of certain carriages100,200,300relative to each other can be adjusted, in order to properly align a print head3with a recording medium4and/or with an axis of carriage motion Y. This enables certain parts of the assembly1,2, such as the main part10of the guiding structure1, parts of the sub-carriage200, and the main structure310of the intermediate carriage300, to be assembled from relatively inaccurately shaped, but light-weight, and low-cost materials, such as sheet metal parts. Any inaccuracies can then be compensated for by appropriate adjustment of a relative position and/or orientation as described.

It is to be understood that the disclosed embodiments are merely exemplary of the invention, which can be embodied in various forms. Specific structural and functional details are not to be interpreted as limiting, but merely as a basis for the claims and as a teaching for one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. In particular, features presented and described in separate dependent claims may be applied in combination, and any advantageous combination of such claims is herewith disclosed.