Printing System Having Four-Bar Linkage Mechanisms For Positioning Its Print Modules

Abstract

A printing system comprises a sub-frame (5), a print module (8) with printheads (27), a first support unit (30) that is connected to the sub-frame (5), in particular movable in a displacement direction (z) relative to the sub-frame, a substrate holder (2) for supporting a substrate (3), and a positioning mechanism for moving the print module relative to the first support unit to and from a print position. A set of positioning parts (34-36) and positioning references (14-16) is provided that form part of or are connected to the print module (8) respectively the sub-frame (5). The positioning parts (34-36) are engageable with corresponding ones of the positioning references (14-16) for aligning the print module (8) relative to the sub-frame (5) when moved into its print position. The positioning mechanism comprises one or more four-bar linkage mechanisms (32) acting between the print module (8) and the first support unit (30).

Claims

1. A printing system comprising: a sub-frame; a print module having a carrier with one or more printheads connected thereto; a first support unit that is connected to the sub-frame; a substrate holder for supporting a substrate to be printed on by the print module; and a positioning mechanism for moving the print module relative to the first support unit to and from a print position; wherein a set of positioning parts is provided that form part of or are connected to the print module, wherein in which a set of positioning references is provided that form part of or are connected to the sub-frame, wherein the positioning parts are engageable with corresponding ones of the positioning references for aligning the print module relative to the sub-frame when moved into its print position, wherein the positioning mechanism comprises one or more four-bar linkage mechanisms acting between the print module and the first support unit, and wherein the four-bar linkage mechanism is designed to move the print module to and from the positioning references while allowing the print module to move relative to the first support unit in six degrees of freedom when the positioning parts of the print module start engaging with the positioning references.

2. (canceled)

3. The printing system according to claim 1, wherein each four-bar linkage mechanism comprises arms that extend between the print module and the first support unit, wherein the arms are connected to the print module and the first support unit by means of hinge joints, and wherein at least one of the hinge joints of each arm comprises a slidable pen-slit connection.

4. The printing system according to claim 3, wherein the pen of the pen-slit connection is biased towards an intermediate position inside the slit by means of one or more springs.

5. A printing system comprising: a sub-frame; a print module having a carrier with one or more printheads connected thereto; a first support unit that is connected to the sub-frame and movable in a displacement direction relative to the sub-frame; a substrate holder for supporting a substrate to be printed on by the print module; and a positioning mechanism for moving the print module relative to the first support unit to and from a print position; wherein a set of positioning parts is provided that form part of or are connected to the print module, wherein a set of positioning references is provided that form part of or are connected to the sub-frame, wherein the positioning parts are engageable with corresponding ones of the positioning references for aligning the print module relative to the sub-frame when moved into its print position, wherein the positioning mechanism comprises one or more four-bar linkage mechanisms acting between the print module and the first support unit, wherein a second support unit is provided that is movable in the displacement direction relative to the sub-frame, wherein the first support unit is mounted to the second support unit via a first guiding mechanism allowing the first support unit to be moved relative to the second support unit in the displacement direction, and wherein a force actuator is provided between the second support unit and the print module such that a moving of the first and second support units to and from each other in the displacement direction causes the four-bar linkage mechanism to be operated.

6. The printing system according to claim 5, wherein the force actuator comprises an arm that extends between the print module and the second support unit, wherein the arm is connected to the print module and the second support unit by means of hinge joints, and wherein one of the hinge joints comprises a slidable pen-slit connection.

7. The printing system according to claim 5, wherein the force actuator operates a spring that is placed between the force actuator and the print module.

8. The printing system according to claim 5, wherein the second support unit is mounted to the sub-frame via a second guiding mechanism allowing the second support unit to be moved in a direction other than the displacement direction towards a maintenance position.

9. The printing system according to claim 1, wherein the four-bar linkage mechanism is a parallelogram four-bar linkage mechanism.

10. A printing system comprising: a sub-frame; a print module having a carrier with one or more printheads connected thereto; a first support unit that is connected to the sub-frame and movable in a displacement direction relative to the sub-frame; a substrate holder for supporting a substrate to be printed on by the print module; and a positioning mechanism for moving the print module relative to the first support unit to and from a print position; wherein a set of positioning parts is provided that form part of or are connected to the print module, wherein a set of positioning references is provided that form part of or are connected to the sub-frame, wherein the positioning parts are engageable with corresponding ones of the positioning references for aligning the print module relative to the sub-frame when moved into its print position, wherein the positioning mechanism comprises one or more four-bar linkage mechanisms acting between the print module and the first support unit, wherein the sub-frame comprises a base plate with one or more openings for giving the one or more print heads of the print module access to the substrate in the print position, which base plate extends in a first and second direction that are perpendicular to each other and to the displacement direction, and wherein the set of positioning references comprises three positioning references, a first and second one of which are provided spaced from each other in the first direction at a same position in the displacement direction, and a third one 464 of which is provided at another position in the second direction than the first and second one at another position in the displacement direction than the first and second one.

11. The printing system according to claim 10, wherein the third one of the positioning references is provided at a center position in the first direction in between the first and second ones of the positioning references.

12. The printing system according to claim 10, wherein an adjustment mechanism is provided for adjusting a position of the third one of the positioning references in the first direction.

13. The printing system according to claim 12, wherein the third one of the positioning references is mounted with a connection organ to the base plate, which connection organ is elastically deformable in the first direction and rigid in the second direction and in the displacement direction.

14. A printing system comprising: a sub-frame; a print module having a carrier with one or more printheads connected thereto; a first support unit that is connected to the sub-frame; a substrate holder for supporting a substrate to be printed on by the print module; and a positioning mechanism for moving the print module relative to the first support unit to and from a print position; wherein a set of positioning parts is provided that form part of or are connected to the print module, wherein a set of positioning references is provided that form part of or are connected to the sub-frame, wherein the positioning parts are engageable with corresponding ones of the positioning references for aligning the print module relative to the sub-frame when moved into its print position, wherein the positioning mechanism comprises one or more four-bar linkage mechanisms acting between the print module and the first support unit, and wherein the sub-frame is a carriage that is movable back and forth in a transverse direction along the substrate holder during printing of a substrate.

15. The printing system according to claim 14, wherein the carriage comprises a plurality of print modules next to each other in the transverse direction, wherein for each print module an individually operable set of four-bar link mechanisms is provided.

16. The printing system of claim 1, wherein the first support unit is movable in a displacement direction relative to the sub-frame.

17. The printing system of claim 14, wherein the first support unit is movable in a displacement direction relative to the sub-frame.

Description

[0031] The invention will now be described in further detail below in a non-limiting way by reference to the accompanying drawing in which:

[0032] FIG. 1 shows a schematic perspective view of a scanning type printing system;

[0033] FIG. 1a shows an enlarged partial view of FIG. 1;

[0034] FIG. 2 shows a bottom part of the carriage of FIG. 1 seen from a back and front side and including a base plate with positioning references;

[0035] FIG. 3 shows a cut-away view of the carriage of FIG. 1 with print modules in various stages of movement between maintenance and print positions;

[0036] FIG. 4 shows an enlarged partial side view of FIG. 3;

[0037] FIG. 4a shows a further enlarged partial view of FIG. 4;

[0038] FIG. 5a, b show top and bottom perspective views of an assembly of one of the print modules connected to a set of first support units via a set of four-bar linkage mechanisms;

[0039] FIG. 6a, b, c show partial side views of the various stages of movement between the maintenance and print positions of FIG. 3; and

[0040] FIG. 7a, b, c show partially cut-away perspective views of FIGS. 6a, b and c.

[0041] In FIG. 1 a scanning printing system is shown which has a main frame 1 that can be placed on the ground. The system comprises an operable conveyor belt as substrate holder 2 that is designed for supporting, holding and transporting a substrate 3 to be printed on. The substrate 3 is supported in a horizontal plane by the substrate holder 2 and can be moved by it in a transportation direction x (first direction). A sub-frame 5 forms a carriage 6 that is reciprocatingly movable in a scanning direction y (second direction) relative to the main frame 1 and the substrate 3. The x- and y-directions are perpendicular to each other. The carriage 6 holds six print modules 8 that are positioned adjacent each other in the y-direction. Each print module 8 is connected via a flexible duct to its own ink reservoir that is filled with its own distinctive colour and that is provided on the main frame 1. The print modules 8 are individually movable up and down in a vertical displacement direction z that is perpendicular to the x- and y-directions. Thus the print modules 8 can be moved towards and away accurately aligned print positions and maintenance positions where they are easily accessible for having maintenance performed thereto.

[0042] In FIG. 2 a bottom part of the carriage 6 is shown seen from a back side compared to FIG. 1. It comprises a base plate 10 with substantially rectangular openings 11, one for each print module 8. Long sides 11a of the openings 11 extend in the x-direction, short sides 11b extend in the y-direction. A first and second positioning ball 14, 15 are provided each along an opposing one of the short sides 11b. A third positioning ball 16 is provided at a center position along one of the long sides 11a. Thus the third positioning ball 16 lies spaced in both the x- and y-direction from the first and second positioning balls 14, 15. The first and second balls 14, 15 lie substantially in the plane of the base plate 10. The third ball 16 is provided on an upper part of a connection organ 18 that is mounted to the base plate 10, and lies at a higher level in the z-direction relative to the first and second balls 14, 15. The connection organ 18 comprises a number of elastic elements 19, for example leaf springs, which give flexibility in the x-direction, and rigidity in the y- and z-directions. The connection organ 18 is connected to an adjustment mechanism 20, here formed by a rod of which the x-position can be manually adjusted by means of a knob, via which the position of the third ball 16 can be adjusted in the x-direction.

[0043] In FIGS. 3 and 4 the base plate 10 with its six sets of positioning balls 14-16, one set for each opening 11, is shown together with the six print modules 8 in various stages of movement. Shown are a forwardly drawn maintenance position for the first and second print modules, a lifted position for the third print module, a coarsely lowered position for the fourth print module and an accurately aligned print position for the fifth and sixth print modules.

[0044] As can best be seen in FIG. 5a, each print module 8 comprises a plate-shaped carrier 25 that is provided with a number of holders 26 to which print heads 27 are mounted next to each other. At their outer ends the print heads 27 are bound by dummies or delimiters 28. Head ends of the carrier 25 are fixedly mounted to blocks 29. Each block 29 is connected to a first support unit 30 via a four-bar linkage mechanism 32.

[0045] The carrier 25 can best be seen in FIG. 5b. It comprises a first and second V-shaped groove 34, 35 that extend in the x-direction along opposing lower edge side parts of the carrier 25. A third V-shaped groove 36 that extends in the z-direction is provided at a center position at an upper part of a side surface of the carrier 25. The balls 14-16 that are actually connected to the base plate 10 of the carriage 6 are also schematically shown in FIG. 5b while lying in the grooves 34-36. This shows the form fit between the balls and the grooves as well as the ability of the balls to slide through their corresponding grooves towards their accurately aligned print position.

[0046] As can be seen in FIG. 3-7, each first position unit 30 is slideably connected to a second support unit 40 via a first guiding mechanism 41 that here is formed by two rods that extend in the z-direction. A spring 42 is provided over one the rods (see FIG. 5) which biases the first and second support units 30, 40 away from each other in the z-direction.

[0047] The second support unit 40 can be displaced up and down in the z-direction with a rack or spindle 44 that extends in the z-direction along one or more pinion or gear wheels. This displacement for example can be initiated by a manual operation of a crank handle 45 that rotates one of the pinion or gear wheels.

[0048] The pinion or gear wheels are mounted to a second guiding mechanism 47 that in turn is mounted to the carriage 6. The second guiding mechanism 47 here is formed by a rail that is telescopically extendable in the x-direction. The second support unit 40 can thus for example be manually pulled forward in the x-direction into its maintenance position.

[0049] Each four-bar linkage mechanism 32 comprises two rigid parallel guiding arms 50 that extend slanting upwards in the y-z plane between the block 29 of the print module 8 and the first support unit 30. Each arm 50 is connected to the first support unit 30 via a hinge joint 51 that comprises a substantially play-free pen-hole connection. Furthermore each arm 50 is connected to the block 29 via a hinge joint 52 that comprises a slidable pen-slit connection. The slidable pen-slit connection has a slit that extends in a longitudinal direction of the arm 50, and has a pen that is connected to the block 29 of the print module 8. The pen is able to rotate inside the slit as well as to slide through the slit in the longitudinal direction against a biasing force of a spring 55. The spring 55 is provided to bias the pen towards an intermediate position inside the slit.

[0050] A force actuator 60 that comprises a rigid operating arm 61 is active between the second support unit 40 and the block 29 of the print module 8. The arm 61 extends slanting downwards in the y-z plane between the second support unit 40 and the block 29 of the print module 8. With this the operating arm 61 extends substantially perpendicular to the guiding arms 50. The arm 61 is connected to the second support unit 40 via a hinge joint 62 that comprises a slidable pen-slit connection having a slit that extends in a longitudinal direction of the arm 61 and having a pen that is connected to the second support unit 40. The pen is able to slide through the slit in its longitudinal direction.

[0051] Furthermore the arm 61 is connected via a hinge joint 63 to a piston 64 that is slidable in a cylinder opening 65 that is provided in the block 29. See FIG. 7 where the block 29 is partially cut-away for giving a good view on this biased piston-cylinder mechanism of the force actuator 60. The cylinder opening 65 here extends in a direction that is substantially perpendicular to the longitudinal direction of the arms 50 of the four-bar linkage mechanism 32. A spring 66 is provided between the piston 64 and the cylinder opening 65 for biasing the block 28 in a slanting downwards direction away from the second support unit 40 and thus force the carrier 25 downwards with its V-shaped grooves 34, 35 towards the first and second positioning balls 14, 15 as well as sideways with its V-shaped groove 36 towards the third positioning ball 16.

[0052] The positioning mechanism now can be operated as follows:

[0053] Starting from the maintenance position as shown for the first and second print modules in FIG. 3, the print module 8 can be pushed inwards along the second guiding mechanism 47. Thus the situation as shown for the third print module in FIG. 3 is obtained. Subsequently the second support units 40 can be lowered by means of operation of the crank handle 45 in the z-direction while taking the first support units 30, the four-bar linkage mechanisms 32 and the print module 8 held between them, along with it. This lowering can be continued until the first support unit 30 runs against the bottom plate 10. Thus the situation as shown for the fourth print module in FIG. 3 is obtained. A continuation of the operation of the crank handle 45 for moving the second support unit 40 further downwards then shall automatically cause the operating arm 61 of the force actuator 60 to start exerting a slanting downwardly directed pushing force onto the blocks 29 of the print module 8. The print module 8 then shall start to simultaneously translate and rotate downwards and sideways in such a way that substantially at a same time each of the V-shaped grooves 34-36 gets placed over and against its corresponding ball 14-16. With this the springs 55 of the four-bar linkage mechanism and the spring 66 of the force actuator 60 give the print module 8 compliance to freely find its accurately aligned print position and then be kept biased into that print position. Thus the situation as shown for the fifth and sixth print module in FIG. 3 is obtained.

[0054] For moving the print module 8 from its print position towards its maintenance position the above operation can be performed the other way around.

[0055] Besides the shown embodiment all kinds of variants are possible. For example the number and types of print heads can be varied. It is also possible to use the four-bar linkage mechanism as positioning mechanism in other types of printing systems, like in a single pass system. Instead of the parallelogram construction, the four-bar linkage mechanism can also be constructed with differently dimensioned, shaped or orientated arms in order to obtain another imaginary path along which the four-bar linkage mechanism then is able to guide the print module towards and away from its print position. Instead of having the displacement direction extending in the vertical direction, it is also possible to use the invention for displacements in other directions, like for example slanted ones along a curved path of a substrate to be printed, or even upside down when that is desired.

[0056] Instead of the four-bar linkage mechanism being connected to the first and second support unit that are movable relative to the sub-frame in the z-direction, it is noted that the four-bar linkage mechanism can also advantageously be used when the first and/or second positioning unit are fixedly connected to the sub-frame. The print module then gets solely moved relative to the sub-frame by means of the four-bar linkage mechanism. Furthermore it is noted that instead of using the force actuator between the second support unit and the print module for having the print module perform its alignment movements, it is also possible to have the print module forced to move in other ways. For example the force actuator can be provided between the sub-frame and the print module or between the sub-frame and the four-bar linkage mechanism and then be operated, for example electrically, pneumatically or hydraulically, to exert pulling or pushing forces onto the print module or onto the four-bar linkage mechanism. It is also possible to actuate the four-bar linkage mechanism to rotate clockwise or anti-clockwise by means of a controllable drive unit, like an electrically, pneumatically or hydraulically operable motor, that acts directly onto the four-bar linkage mechanism, and thus also have the print module forced to perform its alignment movements.

[0057] Thus according to the invention a printing system is provided with an optimized combination of a compliant and biased translational and rotational movement of print modules towards accurate aligned print positions while not having to make use of gravity forces and while at a same time preventing wear or damaging of the cooperating positioning references and positioning units that are critical to the accurate alignments of the print modules.