NL2008068C2 - Substrate conveyor for an inkjet system and method for transferring a substrate to the substrate conveyor. - Google Patents

Description

P30976NL00/KHO

Title: substrate conveyor for an inkjet system and method for transferring a substrate to the substrate conveyor.

The present invention relates to a substrate conveyor for an inkjet system and a method for transferring a substrate to the substrate conveyor. In particular, the invention relates to the field of printing substrates with high accuracy like a printing of an integrated circuit. The invention relates to the field of printing printed circuit boards by using an inkjet 5 system. The substrate conveyor is suitable for use in an inkjet system for printing high accur A known inkjet system for printing substrates comprises several substrate conveyors for carrying and transporting substrates. A substrate is supported by a substrate conveyor during a printing operation and is transported through the inkjet system. At some places, the substrate has to be transferred from one substrate conveyor to another substrate conveyor. 10 Usually a robot arm is used to transfer the substrates. The robot arm comprises a suction gripper which includes a plurality of suction nozzles to engage the substrate at a flat top surface. The robot arm lifts the substrate from a first substrate conveyor to transfer the substrate to a second substrate conveyor.

A first drawback to the robot arm is that the handling of the substrate leaves residues 15 of silicon rubber or other contaminations on top of the substrate surface. These contaminations disturb the printing process.

Another drawback of the robot arm is that the accuracy of the transfer is not satisfying. The positioning of the substrate on top of the second substrate conveyor is inaccurate which leads to fall out and failures during the printing process.

20 The general object of the present invention is to at least partially eliminate the above mentioned drawbacks and/or to provide a useable alternative. More specific, it is an object of the invention to provide a transfer unit which allows an efficient and accurate transfer of a supported substrate from a first substrate conveyor to a second substrate conveyor.

According to the invention, this object is achieved by a substrate conveyor as defined 25 in claim 1.

According to the invention a substrate conveyor is provided for supporting and transporting a substrate in an inkjet system. A substrate is moved together with the substrate conveyor through the inkjet system in a conveyor direction. The substrate conveyor comprises a conveyor body including a conveyor support face for supporting the substrate. 30 The substrate conveyor comprises a conveyor guidance for guiding the conveyor body.

-2-

The substrate conveyor comprises further a substrate transfer unit for transferring the substrate to and fro the conveyor support face. The substrate transfer unit comprises at least one gripper for gripping the substrate. The substrate transfer unit further comprises a gripper holder for holding the at least one gripper and a transfer guidance for guiding the gripper 5 holder. Further, the transfer unit comprises a first holder actuator for driving the gripper holder along the transfer guidance in a transfer direction along the substrate conveyor.

The substrate conveyor according to the invention is improved in that the substrate transfer guidance is fixed to the conveyor body, such that during a movement of the 10 substrate conveyor body, the substrate transfer guidance moves together with the conveyor body.

Advantageously, a transferring and a subsequent positioning of a substrate onto the conveyor support face can be performed with high precision. Due to the fixation of the transfer guidance to the conveyor body, the substrate can be positioned more accurate on 15 the conveyor support face. Instead of a mounting of the transfer guidance to a frame of an inkjet system, the transfer unit according to the invention is mounted directly to the conveyor body. The transfer unit has a transfer unit reference which is located at the conveyor body which makes a high accuracy in positioning of the transfer unit possible. Deficiencies as a result of positioning tolerances build up during an assembly of the inkjet system which would 20 cause inaccuracies during a printing process can be reduced. Additionally, a more precise transferring of substrates reduce failures during operation and improves the reliability of the inkjet system.

In an embodiment of the substrate conveyor according to the invention, the at least one gripper is movable along a gripper path. The gripper path extends over the conveyor 25 support face in a conveyor direction from a first position to a second position. The at least one gripper is movable from the first position to the second position with respect to the conveyor body. The first position is located in a front region of the substrate conveyor body and the second position is located in a back region of the substrate conveyor body. In an operation of the inkjet system, seen in the conveyor direction, the at least one gripper grips a 30 rectangular substrate at its front or back located edge instead of its lateral edges. Herewith, the least one gripper pulls or pushes the substrate to the conveyor support face during a transfer operation. Advantageously, especially when conveying relatively thin substrates, a one sided pulling or pushing transfer operation reduces a risk on damages due to bending to the substrate during a transfer operation. A double sided lateral engagement can damage 35 the thin substrate. Preferably, the at least one gripper pulls the substrate to the conveyor support face to prevent a buckling of the substrate during a transfer operation. To obtain a -3- pulling transfer operation, the at least one gripper of the transfer unit grips the substrate at a front or back edge.

In an embodiment of the substrate conveyor according to the invention, the gripper path of the at least one gripper is linear and extending across the substrates conveyor in the 5 conveyor direction.

In an embodiment of the substrate conveyor according to the invention, the gripper path of the at least one gripper comprises downwardly extending ends. The gripper path includes an downward extending gripper path section for sinking down the gripper with respect to the substrate conveyor support face. When the gripper moves along the gripper 10 path, the gripper moves down at the end of the gripper path. Herewith, the gripper sinks down with respect to the conveyor support face. The gripper sinks down under a height level of the conveyor support face, such that a substrate can pass above the gripper by a sliding movement.

In an embodiment of the substrate conveyor according to the invention, the at least 15 one gripper comprises a clamp element for clamping a substrate at an edge region. The clamp element includes a first and second clamping member, which are movable connected to each other for clamping an edge of substrate in between the first and second clamping member. Advantageously, the clamping element engages on a relatively small area at an edge of the substrate which reduces a risk on contaminations of the upper surface of the 20 substrate. In a printing operation, even minute residues of silicon or rubbers can drastically affect ink flow behavior. Additionally, the engagement with the clamping element provides a reliable engagement and reduces a risk on damages to the substrate which can further disturb a printing operation.

In an embodiment of substrate conveyor according to invention, the gripper holder 25 holds at least a pair of a first gripper and a second gripper, wherein the paired first and second gripper are oriented in opposite directions. Advantageously, the paired grippers allow a selection of a pushed or pulled transfer of a substrate to another conveyor body.

In an alternative embodiment of the substrate conveyor according to the invention, the at least one gripper comprises a suction head for engaging a substrate to the gripper by 30 a sucking force.

In an alternative embodiment of the substrate conveyor according to the invention, the at least one gripper comprises a electrostatic, magnetic or capacitive head for engaging a substrate to the gripper by respectively an electrostatic, magnetic or capacitive force.

35 In an embodiment of the substrate conveyor according to the invention, the gripper holder is elongated. The gripper holder may be beam shaped. The gripper holder extends in a transversal direction with respect to the conveyor direction across a full width of the -4- conveyor body. The transfer guidance includes two transfer rails which are each mounted at a lateral side of the conveyor body. The gripper holder is at both ends linearly movable, e.g. by ball bearings, connected to the transfer rails. Advantageously, herewith a rigid support is provided to obtain an accurate linear movement of the at least one gripper across the 5 conveyor support face.

In an embodiment of the substrate conveyor according to the invention, the transfer unit comprises a second holder actuator for acting the gripper holder in an up-down direction. In particular, the gripper holder is movable in substantially vertical direction. Preferably, the second holder actuator is a voice coil actuator. The transfer unit may further comprise a 10 gripper holder guidance for guiding the gripper holder in the up-down direction. Preferably, the gripper holder guidance is a resilient guidance, e.g. a spring leaf guidance including one or two parallel arranged spring leafs. Herewith, the gripper holder which positions the at least one gripper can be moved up and down with respect to the conveyor support face to sink the gripper holder under the height level of the conveyor support face, such that a substrate can 15 pass over the gripper holder.

In an embodiment of the substrate conveyor according to the invention, the conveyor support face of the conveyor body comprises a plurality of gas openings for keeping a substrate in abutting engagement with the conveyor support face by sucking or for releasing a substrate from the conveyor support face. Preferably, during a conveyance of the 20 substrate, the substrate is engaged to the conveyor support face by a sucking force, which is generated by sucking a gas, in particular air, through the gas openings. In such a manner it is possible to keep, in particular light weighted substrates in position on top of the conveyor body. When the substrate has to be transferred from the conveyor support face, the sucking force can be cancelled and instead of sucking now a blowing force can be generated by 25 blowing a gas, in particular air, through the gas openings of the conveyor body. The substrate is raised by the blowing force away from the conveyor support face. Subsequently, the transfer unit engages to the substrate to transfer the substrate away from the conveyor body. Advantageously, the gas overpressure allows a contactless substrate transport through an inkjet system.

30 In an embodiment of the substrate conveyor according to the invention, the conveyor support face of the conveyor body is subdivided in a plurality of engagement zones. An amount of engagement zones can be operated in dependence of outer dimensions of a particular substrate. Advantageously, the engagement zones in the conveyor body allow a handling of substrates in a variety of sizes.

35 In an embodiment of the substrate conveyor according to the invention the substrate conveyor is arranged as a printing conveyor of an inkjet system for conveying a substrate during a printing operation relative to a printing head. The printing conveyor comprises a -5- conveyor body which supports a substrate and moves together with the substrate during a printing operation.

In a particular embodiment of the printing conveyor according to the invention, the conveyor body of the printing conveyor comprises a substrate positioning stage for moving a 5 supported substrate in a printing direction with respect to the print head holder during the printing operation. Further, the conveyor body of the printing conveyor comprises a stage positioning device for positioning the substrate positioning stage with respect to a frame of the inkjet system. Further, the conveyor body of the printing conveyor comprises a substrate holder connected to the substrate positioning stage for holding a substrate.

10 In an embodiment of the printing conveyor according to the invention, the substrate transfer unit is connected to the substrate holder. The substrate holder may be movable connected in at least one degree of freedom with respect to the substrate positioning stage.

A holder positioning device may be provided for positioning the substrate holder with respect to the substrate positioning stage in the at least one degree of freedom. In particular, the 15 transfer guidance is fixedly connected to the substrate holder.

In an alternative embodiment of the printing conveyor according to the invention, the substrate transfer unit is connected to substrate positioning stage. The transfer guidance of the subject transfer unit is fixedly connected to the substrate positioning stage. The substrate holder is movable in at least one degree of freedom with respect to the transfer guidance.

In an embodiment of the substrate conveyor according to invention, the substrate conveyor is arranged as a station conveyor for handling a substrate. The inkjet system may comprise a station for handling the substrate. The station is for example a supply station for supplying substrates to a print area of the inkjet system. The station may be a buffer station 25 for temporarily storing a substrate in the inkjet system. The station may be a discharge station for discharging substrates after being processed in the printing area of the inkjet system.

Further, the invention relates to an inkjet system for printing an ink pattern on a substrate. The inkjet system comprises a substrate conveyor in an embodiment as described 30 above. The inkjet system further comprises a frame for holding components of the inkjet system and a printhead holder for holding at least one printhead, which printhead holder is connected to frame. The substrate conveyor has a conveyor body which is movable relative to the frame. The substrate transfer unit is connected to the substrate conveyor, such that during the movement of the substrate conveyor body, the substrate transfer unit moves 35 together with the conveyor body.

-6-

In an embodiment of the inkjet system according to the invention, the inkjet system comprises a substrate conveyor according to the invention as a printing conveyor for transporting a substrate in a printing area during a printing operation.

In an embodiment of the inkjet system according to the invention, the inkjet system 5 comprises a handling station for handling a substrate, wherein the handling station comprises a substrate conveyor as a station conveyor for conveying a substrate, wherein the station conveyor comprises a transfer unit which is arranged to transfer a substrate from the station conveyor to the printing conveyor.

In an embodiment of the inkjet system according to invention, the handling station is a 10 supply station for supplying a substrate to the printing conveyor, a buffer station for temporary storing a substrate or a discharge station for discharging a substrate away from the printing conveyor.

Further, the invention relates to a method of transferring a substrate from a first 15 substrate conveyor to a second substrate conveyor of an inkjet system. The method comprises a step of providing a first and second substrate conveyor and at least one transfer unit. The at least one transfer unit is connected to at least the first or second substrate conveyor. Only one or both substrate conveyors can be provided with a transfer unit. The transfer unit is mounted to the first or/and second substrate conveyor. The transfer unit 20 comprises a gripper holder including at least one gripper which is movable along a gripper path from a first position at a front region of the substrate conveyor to a second position at a back region of the substrate conveyor.

The method according to the invention comprises a step of providing a substrate on a conveyor support face of the first conveyor. Further, the method according to invention 25 comprises a step of positioning the second substrate conveyor adjacent the first substrate conveyor. In dependence of a situation, the first substrate conveyor can be positioned in front of the second substrate conveyor or vice versa. In dependence of the situation, a substrate can be transferred in a forward or backward transfer direction. The substrate can be pulled or pushed onto the second substrate conveyor. The first and second substrate 30 conveyor in the adjacent position are aligned with respect to their conveyor support face.

The method according to the invention comprises a step of positioning the gripper holder to the respectively the first position or second position, such that the at least one gripper is able to grip the substrate at the first conveyor at an edge region. The at least one gripper grips the substrate in a small area at the front or back edge of the substrate.

35 Subsequently, the substrate at the first substrate conveyor is gripped at an edge region. The gripper holder is moved to the respectively second or first position while gripping the substrate and moving the substrate from the first substrate conveyor to the second substrate -7- conveyor. After positioning the substrate onto the second substrate conveyor, the substrate is released from the transfer unit.

In an embodiment of the method according to the invention, the substrate is transferred in a floating condition from the first substrate conveyor to the second substrate 5 conveyor. The floating condition is provided by generating an gas film underneath a supported substrate. The floating condition is obtained by supplying gas to the substrate conveyor support face underneath the supported substrate. Advantageously, the substrate is transferred without contact with the substrate conveyor which reduces a risk on damages to the substrate and reduces a necessary transfer energy.

10 In an embodiment of the method according to the invention a calibration is performed in a preparing step for positioning the second substrate conveyor adjacent the first substrate conveyor. The calibration is performed by docking the first and second substrate conveyor to each other. The first substrate conveyor is mechanically docked to the second substrate conveyor. A pin and socket structure may be provided for mechanically docking the first and 15 second substrate conveyor. A docking position of the first and second substrate conveyor may be stored by a control electronics of the inkjet system, wherein during a printing process the first and second substrate conveyor may return to the stored docking position for transferring a substrate. Advantageously, the stored docking position may increase an accuracy during the printing process which may reduce a risk of transfer-failure or damages 20 to the substrate during a transfer.

In an embodiment of the method according to the invention, the first or second substrate conveyor is a printing conveyor, wherein the at least one gripper is sunken with respect to a conveyor support face of the printing conveyor after transferring a substrate onto a printing conveyor. Advantageously, a printing process may be performed without an 25 interference with the transfer unit.

Further preferred embodiments are defined in the subclaims.

The invention will be explained in more detail with reference to the appended drawings. The drawings show a practical embodiment according to the invention, which may 30 not be interpreted as limiting the scope of the invention. Specific features may also be considered apart from the shown embodiment and may be taken into account in a broader context as a delimiting feature, not only for the shown embodiment but as a common feature for all embodiments falling within the scope of the appended claims, in which: 35 Fig. 1a shows in a top view an embodiment of the substrate conveyor according to the invention;

Fig. 1b shows in a front view the substrate conveyor as shown in figure 1a; -8-

Fig. 2a shows in a side view a transfer unit in a lower position;

Fig. 2b shows in a side view the transfer unit in an upper position;

Fig. 3a shows in a perspective view a gripper of the transfer unit; and

Fig. 3b shows in a perspective view the gripper of Fig. 3a mounted to a transfer unit.

5

Identical reference numbers in the drawings are used for identical or similar components.

Fig. 1a shows in a top view an embodiment of the substrate conveyor 1 according to the invention. The substrate conveyor 1 is arranged for moving a substrate in an inkjet 10 system. The substrate conveyor comprises a conveyor body 10 and a conveyor guidance 19. The conveyor body 10 comprises a conveyor support face 15 for supporting a substrate during a movement of the conveyor body 10. The conveyor guidance 19 is arranged for guiding the conveyor body 10. In particular, the conveyor guidance 19 is arranged for a linear or rotational guidance of the conveyor body 10.

15 The substrate conveyor 1 can be arranged as a printing conveyor to transport a substrate through a printing area of the inkjet system. The substrate can be linearly moved by the printing conveyor along a printhead for depositing an ink onto the substrate. Alternatively, the substrate conveyor 1 can be arranged as a station conveyor for handling a substrate in a station. The station can be a buffer station, a supply station, an exit station, a 20 turnover station etc. The station conveyor can be included in a buffer station for buffering substrates or in a turnover station for turning a substrate upside down.

The conveyor body 10 has a rectangular shape. The conveyor body 10 has four side faces 11,12,13,14, a top face 15 and a bottom face.

The conveyor body 10 has a front side face 11, a back side face 12 and two lateral 25 side faces 13,14. The conveyor body has a longitudinal axis L which extends from the front side face 11 to the back side face 12. A transversal axis can be defined in a direction perpendicular to the longitudinal axis L. A substrate can be transferred in a transfer direction T to or away from the conveyor body 10 by passing the front or back side face 11, 12. A double sided arrow is shown in figure 1 to indicate the transfer direction T. The transfer 30 direction T is in parallel with the longitudinal axis L of the conveyor body 10.

The top face 15 is arranged as a conveyor support face. The conveyor support face 15 is a flat surface to support a flat substrate. The conveyor support face 15 is subdivided into at least one engagement zone. A plurality of engagement zones allow an engagement with a variety of substrate sizes. The conveyor support face 15 comprises at least one gas 35 opening 151 which is in fluid communication with at least one gas channel for conducting gas to or from the conveyor support face. The at least one gas opening 151 can be used to engage with the substrate on the conveyor support face of the conveyor body. The conveyor -9- support face 15 comprises a plurality of gas openings 151 to keep a substrate in an abutting engagement with the conveyor support face by sucking through the gas openings 151. A plurality of gas openings is positioned in a raster. During a movement of the conveyor body, a substrate can be engaged with the conveyor support face 15 by a sucking force by sucking 5 gas from the gas openings. During a transfer, a substrate can be brought in a floating condition with respect to the conveyor support face by supplying gas through the gas openings.

The conveyor body 10 is supported by a conveyor guidance 19. The conveyor guidance 19 is provided at the bottom face of the conveyor body 10. Here, the conveyor 10 guidance is a linear guidance for a linear movement of the conveyor body. Here, the conveyor guidance defines a conveyor direction of the conveyor body which is in parallel with the longitudinal axis L and with the transfer direction T.

Further, the substrate conveyor 1 comprises a transfer unit 20. The transfer unit 20 comprises at least one gripper 22 which is arranged to engage an edge of a substrate. The 15 gripper is shown in further detail in Fig. 3. The transfer unit 20 comprises two grippers 221, 222. The two grippers grip the substrate at two positions at the edge of the substrate. Advantageously, the two grippers prevent a rotational movement of the substrate during a transfer movement.

The at least one gripper is connected to a gripper holder 21. The gripper holder 21 is 20 arranged for holding the at least one gripper 22. The gripper holder is beam shaped. The gripper holder 21 is elongated. The gripper holder 21 extends over the whole width of the conveyor body 10. At both lateral side faces of the conveyor body 10, the gripper holder 21 is supported by a transfer guidance 23. The transfer guidance 23 is provided for guiding the gripper holder 21. The transfer guidance 23 provides a linear movement to the gripper holder 25 21 in the transfer direction T. The transfer guidance 23 is mounted to the conveyor body 10. The transfer guidance 23 comprises two transfer rails 231, 232. The two transfer rails 231, 232 extent along a longitudinal axis of the conveyor body 10. The two transfer rails extent along the lateral side faces of the conveyor body 10. A first transfer rail 231 is connected at one lateral side face of the conveyor body 10. The second transfer rail 232 is connected to 30 an opposite lateral side face of the conveyor body 10.

Fig. 2a and Fig. 2b show in a schematic side view a more detailed view of the transfer unit 20. The transfer unit comprises a transfer guidance 23 for guiding a gripper holder 21. The gripper holder 21 comprises a slidable gripper holder part 21a which is slidable in a transfer direction T and a dynamic gripper holder part 21b which is movable in an upwards 35 direction U. The slidable gripper holder part 21a has a bearing house 213 to bear the gripper holder 21 to the transfer guidance 23.

The gripper holder part 21a comprises a first and second holder actuator 211. The - 10- first holder actuator (not shown) is provided for moving the gripper holder 21 along the transfer guidance 23. The first holder actuator comprises for example an electrical motor with a belt gear or a rack and pinion drive.

The second holder actuator 211 is provided for moving the dynamic gripper holder 5 part 21b from a lifted position to a sunken position. Fig. 2a shows the transfer unit 20 in the sunken, also called lowered position. Fig. 2b shows the transfer unit 20 of in the lifted position. In the sunken position, the transfer unit is positioned below a height level which is defined by the conveyor support face of the conveyor body. In the lifted position, the gripper 22 of the transfer unit reaches above the height level to be able to grip a substrate end to 10 pass over the conveyor support face. The movement of the gripper holder part 21b from the lifted to the sunken position defines an up-down direction which is indicated with a double sided arrow U. The up-down direction is a substantially vertical direction. The up-down direction is directed substantially perpendicular to the longitudinal axis and perpendicular to the transversal axis. The movement of the gripper holder 21 in the up-down direction has a 15 stroke of at least 3 millimetres, in particular at least 5 millimetres, more in particular at least 8 millimetres.

The second holder actuator 211 includes a voice coil actuator for actuating the dynamic holder part 21b and a gripper holder guidance 212 for guiding the dynamic gripper holder part 21b in the up-down direction. The gripper holder guidance 212 comprises at least 20 one spring leaf for a resilient coupling of the dynamic gripper holder part 21b with the slidable gripper part 21a. In this case, the resilient coupling is provided with two parallel arranged spring leafs at both ends of the gripper holder 21. Advantageously, the resilient coupling by spring leafs may provide a hysteresis free coupling which has a relatively fast dynamic behaviour.

25 Fig. 3a shows the gripper 22 in further detail. The gripper 22 has a gripper outer contour which is elongated and beam shaped. The elongated outer contour defines a length direction. The gripper 22 is suitable to be positioned in length direction in parallel with the elongated gripper holder 21. As shown in Fig. 3b, the gripper 22 can be positioned in a sunken position with respect to an upper surface of the gripper holder 21. Due to its oblong 30 geometry, the gripper 22 can be nested into the gripper holder 21 to obtain a compact configuration. In particular, the gripper holder 21 holds two grippers 22 as shown in Fig. 3b, wherein the grippers 22 are aligned to each other in length direction.

The gripper 22 has a gripper mouth 223 which extends in a direction transversal the length direction. The gripper mouth has an upper gripper mouth part 223b and a lower 35 gripper mouth part 223a. The lower gripper mouth part 223a is connected to a first gripper subframe 224a. The upper gripper mouth part 223a is connected to a second gripper subframe 224b. The second gripper subframe 224b is movable connected to the first gripper -11 - subframe 224a by a subframe guidance 225. The subframe guidance is resilient and comprises two leaf springs which are arranged in parallel. In an assembly of the gripper 22 to the gripper holder 21, the lower gripper mouth part 223a is mounted stationary and the upper gripper mouth part 223a is mounted movable with respect to the lower gripper mouth part 5 223b. In an assembly of the gripper 22 to the gripper holder 21, the first subframe 224a is mounted to the gripper holder 21.

The gripper 22 comprises a gripper actuator 226 for actuating the gripper mouth. In assembly with the gripper holder 21, the gripper actuator is stationary mounted to the gripper holder by a third gripper subframe 224c. The gripper actuator includes a cylinder, in 10 particular a pneumatic cylinder. The cylinder comprises a piston rod 2261 which is linearly movable from a returned to an extended position and v.v.. At least one gripper runner 2262 is connected to the end of the piston rod. The gripper runner 2262 is movable along a runner surface 2242. The second gripper subframe 224b comprises a wedge element 2241. The runner surface 2242 is provided onto the wedge element 2241. The wedge element is fixedly 15 connected to the upper mouth part 223b. Here, the gripper comprises two parallel arranged wedge elements. Two gripper runners are connected to the piston rod. The upper mouth part 223b can be move towards the lower mouth part by moving the piston rod to the extended position. By moving the piston rod to the extended position, the gripper runner 2262 runs along the running surface 2242. During the movement, the gripper runner 2262 presses onto 20 the runner surface 2242 and hence moves the upper mouth part 223b in a direction towards the lower mouth part 223a. The subframe guidance is resilient to return the upper mouth part 223b away from the lower mouth part when the gripper runner moves back to the returned position.

Although the invention has been disclosed with reference to particular embodiments, 25 from reading this description those of skilled in the art may appreciate a change or modification that may be possible from a technical point of view but which do not depart from the scope of the invention as described above and claimed hereafter. It will be understood by those of skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention.

30 Modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention is not limited to the particular embodiments disclosed in the above detailed description, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims (17)

1. Substrate conveyor for supporting a substrate during a movement in an inkjet system, wherein the substrate conveyor comprises a conveyor body with a conveyor support surface for supporting the substrate, and a conveyor guide for guiding the conveyor body in a transport direction, wherein the substrate conveyor further comprises a substrate transfer unit for transferring the substrate from and to the conveyor support surface, the substrate transfer unit comprising: at least one gripper for gripping the substrate; a gripper holder holding the at least one gripper; 10 a transfer guide for guiding the gripper holder; a first holder actuator for driving the gripper over the transfer guide in a transfer direction along the substrate conveyor; wherein the substrate transfer guide is fixedly connected to the conveyor body, such that during a movement of the substrate conveyor body, the substrate transfer guide moves together with the conveyor body. 2. Substrate transport according to claim 1, wherein the at least one gripper is movable over the conveyor support surface over a gripper path from a first to a second position, wherein the first position is located in a front area of the substrate conveyor body and wherein the second position is in a rear area of the substrate conveyor body. 3. Substrate conveyor as claimed in claim 1 or 2, wherein the gripper pad comprises a downwardly extending gripper pad section for lowering the at least one gripper relative to the substrate conveyor supporting surface. The substrate conveyor according to any of claims 1-3, wherein the at least one gripper comprises a clamping element for clamping a substrate on an edge portion. The substrate conveyor of any one of claims 1-4, wherein the grab holder holds at least a pair of a first grab and a second grab, the paired first and second grab being oriented in opposite directions. - 13- A substrate conveyor according to any of claims 1-5, wherein the conveyor support surface comprises a variety of gas openings for keeping a substrate abutting with the conveyor support surface by suction. A substrate conveyor according to any of the preceding claims, wherein the substrate conveyor is a print conveyor for transporting a substrate during a printing operation, the print conveyor comprising: a substrate positioning carriage for moving a substrate in a printing direction relative to a printhead holder during the printing operation; 10 a slide positioning device for positioning the substrate positioning slide relative to the frame; and a substrate holder connected to the substrate positioning carriage for holding a substrate; wherein the substrate holder is movably connected in at least a degree of freedom with respect to the substrate positioning carriage, wherein a holder positioning device is provided for positioning the substrate holder with respect to the substrate positioning carriage in the at least one degree of freedom, wherein the conveyor guide of the substrate transfer unit is fixedly connected to the substrate holder. A substrate conveyor according to any of claims 1-6, wherein the substrate is a station conveyor of a processing station for processing a substrate in the processing station. 9. An inkjet system for printing an ink cartridge on a substrate comprising a substrate conveyor according to any of the preceding claims, and further comprising: a frame for holding components of the inkjet system; a print head holder for holding at least one print head, which print head holder is connected to the frame; Wherein the substrate conveyor has a conveyor body movable with respect to the frame, the substrate transfer unit being connected to the conveyor body such that during a movement of the conveyor body, the substrate transfer unit together with the conveyor body moves. The inkjet system of claim 9 comprising a substrate conveyor as a print conveyor for moving a substrate in a print area during a printing operation. - 14- 11. Ink-jet system as claimed in claim 9 or 10, wherein the ink-jet system comprises a processing station for processing a substrate, wherein the processing station comprises a substrate conveyor as a station conveyor for moving a substrate, the station conveyor comprising a transfer unit which is adapted to transfer a substrate from the station conveyor to the print conveyor. 12. Ink-jet system according to claim 11, wherein the processing stations is a supply station for supplying a substrate to the print conveyor, a buffer station for temporarily storing a substrate or a discharge station for discharging a substrate from the print conveyor. 13. Method for transferring a substrate from a first substrate conveyor to a second substrate conveyor of an inkjet system comprising the steps of: - providing a first and second substrate conveyor, wherein at least one of the first and second substrate conveyor comprises a transfer unit, the transfer unit being connected to the substrate conveyor, the transfer unit comprising a gripper holder with at least one gripper which is movable over a gripper path from a first position in a front area of the substrate conveyor to a second position in a rear area of the substrate conveyor; - providing a substrate on a conveyor support surface of the first conveyor; - positioning the second substrate conveyor adjacent to the first substrate conveyor; - positioning the gripper holder at the first or second position, respectively, such that the at least one gripper can grip the substrate on the first conveyor on an edge portion; - grasping the substrate on the first substrate conveyor on the edge portion; 30. moving the gripper holder to the second or first position, respectively, while the substrate is gripped and moving the substrate from the first substrate conveyor to the second substrate conveyor; - releasing the substrate when the substrate is positioned on the second substrate conveyor. 35 A method according to claim 13, wherein the substrate is transferred from the first substrate conveyor to the second substrate conveyor in a floating condition, which floating condition is obtained by supplying gas to the support surface under a supported substrate. 15. Method as claimed in claim 13 or 14, wherein the substrate is held in position on the second substrate conveyor by a suction force on the substrate conveyor support surface. 16. Method as claimed in any of the claims 13-15, wherein a calibration for positioning the second substrate conveyor adjacent to the first substrate conveyor is performed by mechanically coupling the first and second substrate conveyors to each other, the calibration being a step of storing electronics by a docking position in which the first substrate conveyor is coupled to the second substrate conveyor. A method according to any of claims 13-16, wherein the first or second substrate conveyor is a print conveyor, wherein the at least one gripper is recessed relative to a conveyor support surface of the print conveyor after transferring a substrate to the print conveyor.