GB2448690A

GB2448690A - Inkjet printing apparatus having a docking station

Info

Publication number: GB2448690A
Application number: GB0707793A
Authority: GB
Inventors: Angela D Mcconnell
Original assignee: Seiko Epson Corp
Current assignee: Seiko Epson Corp
Priority date: 2007-04-23
Filing date: 2007-04-23
Publication date: 2008-10-29
Also published as: GB0707793D0; JP2008265340A

Abstract

An inkjet printing apparatus includes a print carriage 12, a docking station 14 and a number of printheads 18, 20. The carriage 12 and docking station 14 are driven by respective actuators and a control means 16 operates either or both of the two actuators, so as to transfer at least one of the printheads 18, 20 between the carriage 12 and docking station 14. Preferably each of the printheads 18, 20 is mounted on a carrier (40, Figs 2a and 2b), which is then transferred between carriage and docking station. The docking station 14 has a number of docking bays 30, 32 for respective printheads 18, 20 or printhead carriers (40, Figs 2a and 2b), and these docking bays 30, 32 are arranged either in a linear or a circular configuration.

Description

INKJET PRINTING APPARATUS

Several aspects of the present invention relate to an inkjet printing apparatus.

5!nkjet printing is a relatively mature technology, and many advanced products implementing inkjet printing already exist to suit a wide range of applications. However, there is an ongoing need to print substrates using multiple inks of different colors or types with higher speed and quicker turn-around time. Other important areas for continued improvement include reduced printer complexity and more efficient ink usage.

Printing with different types or colors of ink is conmion1y accomplished using an array of multiple printheads, with dedicated printheads for each ink. To avoid cross-contamination between differently colored inks, many inkjet printers include a separate wiper and capping system for each ink (see, e.g., US 5,585,826). Similarly, for printers that use multiple types of ink, such as dye-based and pigment-based, which require different wiping procedures to effectively clean the printheads, one approach is to use separate service stations that perform different maintenance tasks (see, e.g., US 6,203,135).

In most printer systems with multiple printheads and multiple service stations, the printheads are permanently fixed to the print carriage, so that all of the printheads are installed on the print carriage, even when not all of the printheads are needed for a particular printing job. This increases the weight and inertia of the print carriage assembly, which in turn can limit the speed of the actuator that positions the printheads. Also, printheads for infrequently used inks may well need periodic flushing to maintain their functionality.

Flushing is required with most types of ink (especially water-based and solvent-based inks), in order to prevent clogging of the nozzles, but it tends to use large amounts of ink. It is possible for flushing alone to consume an entire ink supply, which is therefore never available for printing.

Instead of mounting the printheads for all inks on the same print carriage, an alternative is to use a separate print carriage with a dedicated service station for each printhead (see, e.g., US 7,086,716). This design was originally intended to allow uninterrupted printing when the printheads are required to be serviced, but it can also be used for printing a single ink while other printheads are being stored and maintained at a service station. However, the use of separate print carriages for each printhead increases the overall size, complexity and cost of the printer, due to the extra actuator and associated components required for each additional print carriage.

Another option for printing with only the required printheads is to manually install printheads on the print carriage, as needed. There are many patents for interchangeable pnntheads to facilitate either multi-color printing or the replacement of worn-out printheads.

A typical design uses mechanical guide elements and couplings to enable an unskilled user to manually load printheads onto the print carriage (see, e.g., US 5,461,405). To avoid cross-contamination between different inks, service station components, such as the capping mechanism, can be exchanged along with the printhead (see US 6,520,621). However, in these designs there is no provision for maintaining printheads that have been unloaded from the printer. A more sophisticated approach is to transfer printheads from the print carriage directly to a service station, which both carries out maintenance tasks on printheads and stores printheads, which are not in use (US 2006,0 132534). A user decides when it is time to store or perform maintenance on a printhead and initiates and actuates the transfer of a printhead to the service station. However, for printing that requires frequent changes of ink-type or color, systems that rely on user intervention are impractical when turn-around time is a critical constraint.

In accordance with a first aspect of the present invention, there is provided an inkjet printing apparatus, comprising: a print carriage, which is movable by a first actuator; a docking station, which is movable by a second actuator; a plurality of printheads, and a control means; wherein the control means is arranged to operate the first actuator and/or second actuator, such that at least one of said priniheads can be transferred between said print carriage and said docking station.

A plurality of priffihead carriers.may be provided, upon which respective ones of said plurality of printheads are mounted, said printhead carriers being transferable between said print carriage and said docking station and being latchable to said docking station upon transferal of said at least one printhead from said print carriage to said docking station.

The docking station preferably has a plurality of docking bays to receive respective said printheads. There may be as many docking bays as there are printheads.

The docking bays may be arranged side-by-side in a linear configuration or in a circular configuration.

The inkjet printing apparatus may further comprise: a baseplate, upon which said print carriage, said docking station and said first and second actuators are mounted; said first actuator being arranged to move said print carriage linearly in a first direction parallel to a plane of said baseplate, and said second actuator being arranged to move said docking station linearly in a second direction orthogonal to the first direction and parallel to said plane of said baseplate. Alternatively, the second direction may be orthogonal to said plane of said baseplate.

The inkjet printing may further comprise: a baseplate, upon which said print carnage, said docking station and said first and second actuators are mounted; said first actuator being arranged to move said print carriage linearly in a first direction parallel to a plane of said baseplate, and said second actuator being arranged to rotate said docking station on an axis, which is orthogonal to said plane of said baseplate. Alternatively, said axis may be parallel to said plane of said baseplate.

The axis may be orthogonal to said first direction and it may intersect said first direction.

The control means may be arranged to operate said second actuator such as to rotate said docking station selectively in a clockwise or anticlockwise direction, thereby to locate a predetermined docking bay with minimum angular movement of said docking station.

The control means may be arranged to operate said second actuator so as to line up a predetermined docking bay with said print carriage, and to operate said first actuator so as to move said print carriage toward said docking bay.

The print carriage preferably comprises a frame for receiving one or more of said prinihead carriers.

The inkjet printing apparatus may comprise a holding means for retaining said one or more of said printhead carriers. The holding means may comprise one or more spring-loaded ball-bearings disposed on said frame and one or more recesses disposed on said printhead carrier, said recesses being for engagement with said ball-bearings. There may be as many recesses as there are ball-bearings.

The recesses may be constituted by a pair of grooves disposed on opposite sides of said printhead carrier. Each of said pair of grooves may have a groove depth, which is smaller than an amount of protrusion of said ball-bearings from said frame. Each of said pair of grooves may have a pair of recesses, which are of greater depth than the grooves and are disposed in spaced-apart manner along the printhead carrier, at locations corresponding to the locations of said ball-bearings in said frame.

The inkjet printing apparatus may further comprise a servicing means adjacent said docking station, said servicing means for performing servicing operations on printheads docked in said docking station. The servicing means may comprise one or more items from a group consisting of: a flushing means, a wiping means, a capping means, a priming means and an ink-degassing means.

The inkjet printing apparatus advantageously further comprises: a latching means for securing said at least one printhead to said docking station upon transferal of said at least one printhead from said print carriage to said docking station. The latching means may comprise: at least one latching member, which is pivotally attached to said docking station, such that the latching member has two degrees of freedoni of movement, and an associated groove arrangement provided in said printhead carrier. The groove arrangement may comprise: a latching portion, with which said latching member engages in order to secure said printhead carrier to said docking station, and a stepped portion, with which said latching member engages in order to allow said printhead carrier to be released from said docking station.

The latching portion may include a ramp portion, with which said latching member engages and against which said latching member moves in one of said two degrees of freedom, and the engagement of said latching member with said stepped portion involves movement of said latching member out of said latching portion into said stepped portion in the other of said two degrees of freedom.

The inkjet printing apparatus may further comprise: a bias means for urging said latching member into a starting position prior to engagement of the latching member with said groove arrangement.

The control means may be arranged to: (a) determine whether or not one of said printheads is to be used in a given printing operation: (b) if so, operate said second actuator, so as to bring said printhead into alignment with said print carriage; (c) operate said first actuator, so as to bring said print carriage toward said docking station; (d) operate said first actuator, so as to attach said printhead to said print carriage; (e) operate said first actuator, so as to move said print carriage to a desired position relative to a substrate, upon which printing is to take place, and (f) operate said printhead, so as to eject a printing medium onto said substrate in a predetermined manner.

The control means may be further arranged to: (g) operate said first actuator, so as to return said printhead to said docking station after printing with that printhead is completed; (h) determine whether or not another of said printheads is to be used in the given printing operation; (i) if so, repeat steps (b)4h) in respect of the other printhead.

The inkjet printing apparatus may further comprise: one or more reading heads for reading information on a substrate, upon which printing is performed by the inkjet printing apparatus, said control means being arranged to operate the first actuator and/or second actuator, such that at least one of said reading heads can be transferred between said print carriage and said docking station.

In a second aspect of the present invention an optical apparatus is provided, which comprises: a scanning carriage, which is movable by a first actuator; a docking station, which is movable by a second actuator; a plurality of reading heads, and a control means; wherein the control means is arranged to operate the first actuator and/or second actuator, such that at least one of said reading heads can be transferred between said scanning carriage and said docking station.

Embodiments of the invention will now be described, by way of example only, with the aid of the attached drawings, of which: Fig. I is a schematic block diagram of a first embodiment of an inkjet printing apparatus in accordance with the present invention; Figs. 2(a) and 2(b) are more detailed side and plan views, respectively, of part of an inkjet printing apparatus in accordance with said first embodiment.

Figs. 3(a) and 3(b) are side and plan views, respectively, of a latching arrangement employed in an embodiment of the present invention; Fig. 4 is a perspective view of a groove arrangement in a printhead carrier for use with the latching arrangement of Figs. 3(a) and 3(b); Fig. 5 is a perspective view of the first embodiment of the invention, and showing steps involved in the transferal of a printhead carrier from a print carriage to a docking station; Fig. 6 is a perspective view of the first embodiment of the invention, and showing steps involved in the transferal of a printhead carrier from a docking station to a print carriage; Fig. 7 is a flowchart showing the operations involved in a given control sequence in an embodiment according to the present invention; Fig. 8 is a plan view of part of a print carriage, as used in an embodiment of the present invention, and showing part of a holding means for retaining a printhead carrier in said carriage; Figs. 9(a) and 9(b) are side and plan views, respectively, of a first realization of a holding means incorporated into a printhead carrier and for use with the partial holding means of Fig. 8; Figs. 10(a) and 10(b) are side and plan views, respectively, of a second realization of a holding means incorporated into a printhead carrier and for use with the partial holding means of Fig. 8, and Figs. 11-14 are further embodiments of an inkjet printing apparatus in accordance the present invention.

Fig. I shows a first embodiment of an inkjet printing apparatus in accordance with the invention. The printing apparatus comprises a baseplate 10, upon which are mounted a print carriage 12, a docking station 14 and a controlling means 16. The print carriage 12 has a receiving means for receiving a printhead 18, 20 from the docking station 14 and is driven linearly in a direction shown by the arrow 22 by a first actuator 24. The printheads 18, 20 have, in common with all inkjet printheads, a series of nozzles (not shown), through which ink is ejected onto a print medium, or substrate 26. The substrate 26 is movable in a direction shown by the arrow 28, this direction being orthogonal to the first direction shown by the arrow 22. Thus, the printhead 18, 20 moves over the substrate in direction 22, while the substrate is advanced in direction 28.

The docking station 14 has a series of docking bays, one for each of the printheads in the arrangement. Thus, in the illustrated example, there are two docking bays 30, 32 for printheads 18 and 20 (designated in Fig. I as "printhead 1" and "printhead 2"), respectively.

The docking station 14 is driven by a second actuator (not shown) in a direction shown by the arrow 34. This direction is parallel to that shown by the arrow 28.

Movement of the two actuators is controlled by the controlling means 16 under the control of a computing device, such as a PC, which interacts with the controlling means 16 by way of a user interface 36. The PC instructs the controller to perform a printing operation in accordance with a given printing pattern. This pattern comprises not only a set of instructions defining a particular configuration of ink dots on the substrate, but also a set of instructions defining which of the (in this case, two) printheads 18, 20 is to be used at any particular time. The two printheads may contain different types of ink or ink of the same type, but of a different color. Where different types of ink are used, these may be inks of a different formulation, such as by varying the solvents employed or using different concentrations of the same solvent. The two printheads may be brought into play one after the other, either in order to print traces on different parts of the substrate 26, or in order to print traces over already existing traces, or both. The different layers, which result from the second of these options, may relate to, for example, the manufacture of a semiconductor device consisting of consecutive semiconductor, dielectric and metal layers.

When a printhead is not in use, it is docked in one of the docking bays 30, 32 of the docking station 14. An advantage of this is that, since the docked printhead is not on the print carriage, the weight of the carriage is less than it would otherwise be and therefore has less inertia. It is therefore possible to move the printhead to the desired position on the substrate more quickly, leading to an enhanced print throughput. While in its docking bay, the docked printhead may be subjected to one or more maintenance operations. These include flushing of the ink through the printhead, wiping of the nozzles, priming of the printhead, capping of the nozzles and degassing of the ink. Capping involves covering up the nozzles in order to slow down the evaporation of the ink inside the printhead, and is advantageous in that it can greatly reduce the need for flushing, which uses large amounts of ink.

Figs. 2(a) and 2(b) show, in a side view and plan view, respectively, a situation in which the printhead is disposed on the carrier and has been offered up to a docking bay of the docking station. Subsequently the carriage will be moved away from the docking station, leaving the printhead behind in the docking bay. In Figs. 2(a) and 2(b) the printhead 18 is mounted on a printhead carrier 40, which is attached to a print carriage frame 42. The printhead carrier 40 has been moved by the carriage onto a docking-station platform 44, which includes a pair of latches 46. These latches engage with respective groove arrangements 48 formed in the printhead carrier 40 and prevent the carrier from being pulled away from the docking station when the carriage is finally moved away. The advantage of using a printhead carrier to interface between the printhead and the docking station is that it avoids the need to modify the prinihead, e.g. by forming grooves in the printhead itself. This allows standard printheads to be employed, which reduces the cost of theapparatus.

A suitable realization of the latches 46 is illustrated in Figs 3(a) and 3(b), which represent side and plan views of the latches, respectively. Each latch is formed as an elongate member 50, at one end of which is a pivot arrangement 52 for interfacing with the docking-station platform 44, while at the other end the elongate member 50 is continued as a hook member 54 for interfacing with the printhead carrier 40. The pivot arrangement 52 comprises two orthogonally disposed pivots 56, 58, which allow movement of the elongate member 50 in two planes, thereby providing the latch with two degrees of freedom. Thus, the elongate member 50 can swivel upwards perpendicular to the baseplate 10 (see Fig. 1) and also outwards parallel to the baseplate 10. A spring 55 is attached to the underside of the elongate member at some point intermediate the hook extension 54 and the pivot arrangement 52 and is attached at its other end to the docking-station platform 44. The spring is positioned so that it biases the elongate member 50 in a downward and inward direction. As an alternative to using just one spring, two springs, which bias the elongate member vertically and horizontally, may be used. This would normally only be necessary where the pivot arrangement was designed to provide the elongate member with more than two degrees of freedom. For example, instead of using two pivots, as shown in Figs. 3(a) and 3(b), it would be possible to use a ball-and-socket arrangement (not shown). Since this would allow an infinite number of degrees of freedom, it would be necessary to bias the elongate member with two orthogonally disposed springs, in order to limit the movement to just two degrees of freedom.

Fig. 4 shows a preferred realization of the groove arrangements 48 in the printhead carrier 40. Each groove arrangement comprises a ramp portion 60, a latching portion 62 and a stepped portion 64. In use, the printhead carrier 40 approaches the docking-station platform 44 in the direction shown by the arrow 66. Eventually, the hook ends 54 of the latches strike the lower part of the ramp portions 60 and begin to move up the ramp portions. When the hook ends reach the top of the ramp, continued movement of the printhead carrier in the direction shown causes the hook ends to drop down, under the action of the biasing spring 55, into the latching portion 62. At that point the printhead carrier is prevented from IS moving away from the docking station by the walls 68 of the groove arrangements 48.

When it is desired to reverse the process and transfer the printhead carrier back to the carriage, the printhead carrier is moved again in direction 66, so that the hook ends 54 strike a beveled part 70 of the latching portion 62, upon which the hook ends are urged outwards in the directions shown by the arrows 72, 74, against the biasing action of the spring 55.

Eventually the hook ends drop into the stepped portion 64. At that point the printhead carrier 40 is moved in the opposite direction to the arrow 66, causing the hook ends of the latches to slide along the lower level of the stepped portion 64 and out of the groove arrangements 48 altogether. The printhead carrier is now free from the latches.

A complete docking procedure is illustrated in Fig. 5. The procedure is shown as a number of consecutive stages (a)-(h). In stage (a) the docking-station platform 44 with its latches 46 is waiting to receive a printhead carrier, complete with printhead. The latches 46 are biased into their downward and inward position. In stage (b) the carriage frame 42 holding a printhead carrier 40 (the printhead itself is not shown) is positioned on the platform 44 and is moving toward the latches 46. In stage (c) the latches have started to strike the ramp portions and in stage (d) are moving up those ramp portions. In stage (e) the hook ends of the latches have dropped into the latching portions of the groove arrangements, the carriage frame 42 having slightly overshot on its travel toward the docking station in order to achieve this. Fig. 5(e) shows the frame starling to move away from the docking station. In stage (f) the inside surfaces of the latch hook ends 54 have engaged with the walls 68 of the latching arrangements, so that the printhead carrier is now retained by the docking station.

The carriage frame continues to move away from the docking station. In stage (g) the carriage frame continues to move still further along the platform 44 away from the docking station. Finally, in stage (h) the carriage frame has moved free from the docking-station platform, leaving the printhead carrier securely docked, and held, in its docking bay.

The reverse procedure, whereby a printhead carrier is transferred to the carriage, is shown in its various stages in Fig. 6. Stage (a) corresponds to stage (h) of Fig. 5, in which the printhead carrier 40 is docked in its docking bay secured by the latches 46. In stage (b) the carriage frame 42 is moving toward the docking bay and is receiving the printhead carrier 40. When the frame 42 has fully received the carrier, it moves with the carrier further toward the docking bay, so that the hook ends of the latches move toward the back of the latching portions of the latching arrangements (stage (c)). Eventually (stage (d)) the hook ends meet the beveled back-wall of the latching portions and are moved outwards. In stage (e) the hook ends drop into the stepped portion of the latching arrangements and the carriage starts to move away from the docking bay. The carriage with the printhead carrier continues to move away from the docking bay (stage (f)) until the hook ends of the latches drop Out of the stepped portion of the latching arrangements (stage (g)). Further movement of the carriage away from the docking bay leaves the latter empty (stage (h)).

The above-described transferal of a printhead carrier between the carriage and docking station involves movement of either the carriage toward the required docking bay, or movement of the docking station toward the carriage, or a combination of both. In the exemplary arrangement shown in Fig. I, the docking station is moved linearly upwardly toward the top edge of the baseplate 10, so that the required docking bay (dock 1 or dock 2) is lined up with the carriage. This is shown by the arrow 80 between the centerline 82 of the printhead and the centerline 84 of the first docking bay. When the two centerlines meet up, I' the carriage is then moved to the right in order to transfer the printhead carrier (not shown in Fig. 1) into the first docking bay. (Note that, in Fig. I, the printhead 18 is shown purely representationally and without its associated carrier. In practice, as shown in Figs. 5 and 6, the printhead and carrier will be held within the frame of the carriage, and it is this frame which is moved toward the docking bay.) An alternative arrangement to the one shown in Fig. I is to have the docking station 14 positioned so that the first docking bay 30 is already aligned with printhead I. This occurs when the distance represented by arrow 80 is reduced to substantially zero. This has the advantage that it reduces the response time of the printing system.

A flowchart depicting the flow of events in a typical printing routine involving two printheads is shown in Fig. 7. The flowchart starts by the inputting from the host computer of a new print pattern (step S 100). The pattern is inspected to see whether or not it contains an instruction to print with printhead 1 (step S 102). If so, the second actuator associated with the docking station moves the docking station so that docking bay 1 lines up with the print carriage. If no instruction to print with printhead I is found, a check is made as to whether or not there is an instruction to print with printhead 2 (step S 104). If so, the second actuator moves the docking station so that docking bay 2 is lined up with the print carriage.

If neither of these instructions is found, the routine passes back to step SI 00.

When one of the two printheads is specified, the first actuator is energized so as to bring the print carriage towards the relevant docking bay (step S106 or S 108) and the relevant printhead carrier is picked up, complete with its printhead (S 110). Once pickup has been completed, the print carriage is moved to its instructed position relative to the printing substrate 26 (see Fig. 1) and printing of the desired dot pattern takes place (step SI 12).

Upon completion of printing using this printhead, the printhead and its carrier are replaced in the empty docking bay (step S 114) and a check is made as to whether or not the other printheaci has also been specified in the print pattern (S 116). If so, the other printhead with its carrier is picked up by the carriage and printing using that printhead takes place. When that is completed, that printhead carrier is likewise placed back in its docking bay.

This routine can be extended to include any number of printheads and associated docking bays.

It was mentioned earl icr that, when the printhead carrier is picked up by the print carriage, it is held by the carriage so that the printhead can print at the required location on the substrate, as defined by the position of the carriage relative to the substrate. Figs. 8 and 9 show examples of a holding means suitable for securing the printhead carrier to the carriage.

As shown in Figs 2(a), 2(b), 5 and 6, the carriage comprises an open-ended frame 42, the open end at the right-hand side of the frame allowing entry of a printhead carrier into the frame. The frame comprises a number of spring-loaded elements, here ball-bearings 90 (see Fig. 8), disposed in spaced-apart manner along the inside of the frame and at opposite sides thereof. The spring-loading is achieved by means of coil springs 92, which are held in respective bores 94 in the frame. The bores 94 are blind at their outward ends, thereby to retain the springs within the bores. Thus the ball-bearings are urged against the printhead carrier, when it is received in the frame 42, and serve to restrain it from falling out of the frame, which could occur due to the movement of the carriage. The ball-bearings are restrained from falling out of the frame by some suitable means, for example by arranging for the holes, through which the ball-bearings protrude, to be slightly smaller than the diameter of the ball-bearings themselves. In that case, the ball-bearings may beintroduced into the bores 94 from the outside faces 96 of the frame 42, the springs 92 being then inserted and the openings of the bores on those outside faces being then blocked off, to prevent the ball-bearings and springs from falling out from that side.

In a preferred embodiment of the invention, recesses are provided in opposite sides of the printhead carrier, which engage with the ball-bearings. Figs. 9(a) and 9(b), which are partial side and plan views, respectively, of the printhead carrier, show one such arrangement, in which the recesses are a pair of grooves 98 formed in opposite sides of the carrier.

Reference numeral 100 represents the leading edge of the carrier, which becomes inserted into the carriage frame. Preferably the depth of the grooves is less than the amount of protrusion of the ball-bearings from the frame. This allows the ball-bearings to bear against the carrier, while also limiting the amount of movement of the carrier relative to the frame in a direction shown by the arrow 102.

A variant of this arrangement is shown in Figs. 10(a) and 10(b). In this variant the groove is preferably made a little shallower than that of Figs. 9(a) and 9(b). However, allocations along the length of the carrier corresponding to the locations of the ball-bearings in the sides of the carriage frame there are provided deeper recesses 106. In use, the carrier enters the carriage frame at the leading edge 100 of the carrier, so that the ball-bearings engage in the shallow grooves 104. When the carrier is fully home in the frame, the ball-bearings will relax into the deeper recesses 106. Either the recesses 106 can be deep enough, so that the ball-bearings are fully protruding when they engage these recesses, or they can be less deep, so that the ball-bearings are still urged by spring action against the recesses 106. Either way, the carrier will be discouraged from moving out of the hilly-home position by the presence of the ball-bearings in the recesses.

In a third variant (not shown), the grooves are dispensed with and only the recesses 106 are provided. This has the drawback, however, that the guiding action of the grooves on the ball-bearings is absent, which could make it more difficult to ensure that the carrier at all times assumes the correct position relative to the carrier frame.

An alternative to the use of ball bearings and associated coil springs is to use leaf springs secured to the inside faces of the carriage frame. The leaf springs may be secured at one end thereof to the frame, the other end being free in cantilever style and protruding into the inner space of the frame. The free end may engage with grooves and/or recesses as described in connection with the ball-bearings. Instead of securing the springs at one end only, they may be secured at both ends to the inner frame faces, the central portion of the springs midway between the two secured ends then protruding into the inner frame space and engaging with the grooves/recesses. To allow the central protruding portion to be urged toward the inner frame faces when the printhead carrier enters the carriage, it may be necessary to provide one end of the leaf springs with an elongated hole, so that that end can slide against the inner frame face.

Further embodiments of the present invention are illustrated in Figs 11-14.

Whereas in Fig. I the docking station 14 is shown as moving linearly in direction 34 parallel to the baseplate 10, in Fig. I I, which is a side view of the printing apparatus, it moves orthogonally to the baseplate 10. Thus, in this embodiment the docking station 114 is moved so that the required docking bay 130, 132 is in alignment with the print carriage 42 and printhead carrier 40, so that the latter can be transferred to that docking bay. As with the first embodiment, this embodiment also employs suitable latching means for securing the carrier 40 to the docking station 114.

A third embodiment is illustrated in Fig. 12, which is a plan view of the printing apparatus.

In this embodiment the linear arrangement of the docking bays 30, 32 in Fig. I is replaced by a circular arrangement. In the illustrated example, there are four docking bays 230, 232, 234, 236 in the docking station 214 serving four printheads. This configuration is particularly useful where there is a large number of printheads to be accommodated, since such a circular arrangement can make for a more compact docking arrangement than a linear arrangement. The docking station rotates about an axis 240, which is perpendicular to the baseplate (not shown) upon which the various components are mounted.

Fig. 13 shows a fourth embodiment of an inkjet printing apparatus in accordance with the invention, in which the circular docking-bay configuration is configured to rotate about an axis, which is parallel to the baseplate. Thus Fig. 13 represents a side view of the printing apparatus of this embodiment. As with the third embodinient, a docking station 314 comprises four docking bays 330, 332, 334 and 336, which rotate about an axis 340, which this time lies parallel to the baseplate JO.

A fifth embodiment of the inkjet printing apparatus is illustrated in Fig. 14. in Fig. 14, which is a plan view of the printing apparatus, a docking station 414 has its axis of rotation 440 parallel to the baseplate and also parallel to the direction of linear travel of the printhead-carriage frame 42 shown by the arrow 43. There are three docking bays 430,432, 434 and a further bay hidden from view. The docking station 414 is rotated until the required docking bay is aligned with the arrow 43, so that transfer of a printhead, or printhead carrier, can take place between the carriage and the docking bay.

In the third, fourth and fifTh embodiments rotation of the docking station occurs, in order to bring a required docking bay into alignment with the printhead carrier and carriage. In these configurations, care must be taken to ensure that any conduits, which connect the docking station to maintenance, or other, apparatus situated near the docking station, are not damaged by the rotational movement of the docking station. This can be achieved by limiting the angle of rotation of the docking station. In order to be able to locate any of the docking bays with the least rotation, it is necessary to make the docking station rotatable in either direction, clockwise or anti-clockwise. This has the advantage that it at the same time reduces the "seek" time of the required docking bay, which enhances the overall responsiveness of the printing apparatus.

The number of actuators in the present invention is not limited to two, as described above (or three, if an actuator for moving the substrate relative to the print carriage is included), but may include other actuators for achieving other measures common to modem printing techniques. One example is the use of a further actuator to rotate the printhead relative to the carnage and therefore relative to the main scanning direction of the printhead over the substrate. Such rotation can be useful not only in achieving fine control of print alignment in the normal main-scanning direction orthogonal to the direction of feed of the substrate through the printing apparatus, but also in achieving a deliberately skewed alignment of print across the substrate. This can be desirable, where it is necessary to enhance the print density of the apparatus, since such skewing reduces the effective distance between the nozzles in the afore-mentioned orthogonal direction. However, along with such skewing comes the need for modified timing of ink release from the various nozzles, which increases the complexity of the control arrangement.

Although, iii connection with the flowchart of Fig. 7, it has been assumed that the second actuator will be operated to drive first the docking station to its required position, after which the first actuator will be operated to drive the print carriage toward the selected docking bay, in practice both these events may occur simultaneously. This has the advantage of saving time, which further increases the responsiveness of the printing apparatus. Furthermore, it may be arranged for only one of the first and second actuators to be driven in order to perform a printhead transfer. Thus, either the second actuator alone may be arranged to both move the docking station into alignment with the print carriage, after which the same actuator moves the docking station toward the print carriage in order to effect the transfer, or the carriage alone may be moved by way of the first actuator. The first of these two alternative arrangements has the advantage that the first actuator only has to deal with strictly printing matters, i.e. moving the printhead over the substrate. Thus it is possible to simplify the first actuator arrangement, though of course the second actuator arrangement is rendered more complex.

In a preferred embodiment of the invention, only one printhead will be present on the print carriage at any one time, the remaining printheads being parked in the docking bays of the docking station. This reduces the mass, and therefore inertia, of the print carriage, allowing for faster printing and therefore higher print throughput. However, it is within the scope of the invention to allow two or even more printheads to be picked up by the carnage. This nullifies somewhat the weight advantage gained by the single-printhead-only arrangement, but has the benefit that fewer movements are necessary between the carriage and docking station in order to print with different printheads, since it is not necessary for the carriage and docking station to be brought near each other each time.

Whereas it has been assumed that a pair of latches will be employed, in order to secure the printhead or printhead carrier to the docking station, in practice more than two may be employed or, conversely, only one. Where only one latch is used, this is best located centrally across the width of the docking-station platform, i.e. midway between the positions shown in Figs. 5 and 6. The same applies, of course, to the associated groove arrangement, with which the latch engages.

What has been described is an inkjet printing apparatus, which enables printing on a substrate to be easily achieved using one or more of a number of resident printheads. The printheads are docked in respective docking bays of a docking station, which supplies the printheads with ink (e.g. using a central ink reservoir) and also enables various maintenance procedures to be carried out on the printheads. These procedures include flushing, wiping and capping of the printhead nozzles. Hence, by the time a particular printhead is required for printing purposes, it can be fully charged with ink and be immediately ready for action, having been flushed, wiped, primed or capped, as needed. The default action for storing printheads is capping, since this minimizes evaporation of ink from the nozzles and thus reduces the frequency with which a printhead needs to be flushed.

The apparatus hereinbefore described is readily scalable. Thus, although only two pnntheads are shown in some of the drawings, many more than two may be employed (see, e.g., the four printheads provided for in Figs. 12-14). Likewise, the control sequence for driving the second actuator is easily extended to accommodate more than two printheads.

Referring to Fig. 7, for example, more steps than just the steps SI 02 and SI 04 may be included in the decision as to which of the printheads is to be printed with. This involves simply using an appropriate number of steps in the series "Print with printhead 1, 2,..." and a corresponding number of steps in a series "Move printhead service station to dock 1, 2...".

The output of each of this latter series of steps will be OR-ed in block S 109.

The ability, created by the present invention, to use many different inks quickly in succession allows for greater printing flexibility. For example, this could facilitate the testing of different ink formulations, such as varying solvents or concentrations of one solvent, on a single substrate. Also, it is possible to mix inks on a substrate in order to form complex patterns or structures, which may be useful in printing biological materials in lab-on-a-chip applications.

Storing unused printheacis at the docking station results in more efficient ink usage, which is particularly relevant for research and industrial printing applications. In many research applications often only small amounts of ink material are available, or the materials are very valuable or costly. Having the unused printheads docked in the docking station allows them to be capped, which helps to maintain nozzle functionality between printing runs. This greatly reduces the amount of ink lost in the flushing process, which would othenvise be required much more frequently in the docked state of the printheads. (It is assumed that flushing may well be required even when the printheads are in use, since the nozzles can also become clogged during normal printing). Capping also reduces the need for priming of a printhead, since less evaporation, and therefore drying, takes place within the printhead.

For industrial printing applications, less wasted ink reduces production costs, and continuously maintained printheads result in quicker turn-around times.

The advantages of this invention can benefit many different applications. One example is the printing of electronic devices comprising multiple layers -e.g. semiconductor, dielectric and metal layers. Separate layers of each material can be printed in any order with minimal waste of the other materials, and the use of dedicated printheads for each material avoids the cross-contamination that might otherwise occur where the same printhead is used to dispense different types or colors of ink.

Printing with only one printhead at a time also makes it easier to accurately align the printhead relative to the substrate, whether that involves the normal alignment orthogonal to the feed direction of the substrate through the printing apparatus, or the more specialized skewed alignment which enables a greater number of dots-per-inch of print density to be achieved.

With only one printhead installed on the carriage, the printhead assembly has low mass and inertia, which gives rise to improved acceleration and more precise positioning movements of the printhead relative to the substrate.

Finally, whereas the invention has been described in connection with inkjet printing, it is also applicable to other systems, such as scanning, faxing, copying or image-analysis systems. In these cases the printheads will be replaced by two or more scanning heads to read an image or other information on the substrate, Indeed, it is envisaged that both printheads and scanning heads may be employed in the same apparatus. Thus, for example, the apparatus may enable inkjet printing to take place on a substrate, after which the printed information on the substrate may be read, in order to assess the accuracy and quality of the printed result.

Claims

I. An inkjet printing apparatus, comprising: a print carriage, which is movable by a first actuator; a docking station, which is movable by a second actuator; a plurality of printheads, and a control means; wherein the control means is arranged to operate the first actuator and/or second actuator, such that at least one of said printheads can be transferred between said print carriage and said docking station.
2. An inkjet printing apparatus as claimed in claim I, further comprising: a plurality of printhead carriers, upon which respective ones of said plurality of printheads are mounted, said printhead carriers being transferable between said print carriage and said docking station and being latchable to said docking station upon transferal of said at least one printhead from said print carriage to said docking station.
3. An inkjet printing apparatus as claimed in any one of the preceding claims, wherein: said docking station has a plurality of docking bays to receive respective said printheads.
4. An inkjet printing apparatus as claimed in claim 3, wherein: there are as many docking bays as there are printheads.
5. An inkjet printing apparatus as claimed in claim 4, wherein: said docking bays are arranged side-by-side in a linear configuration.
6. An inkjet printing apparatus as claimed in claim 4, wherein: said docking bays are arranged side-by-side in a circular configuration.
7. An inkjet printing apparatus as claimed in claim 5, further comprising: a baseplate, upon which said print carriage, said docking station and said first and second actuators are mounted; said first actuator being arranged to move said print carriage linearly in a first direction parallel to a plane of said baseplate, and said second actuator being arranged to move said docking station linearly in a second direction orthogonal to the first direction and parallel to said plane of said baseplate.
8. An inkjet printing apparatus as claimed in claim 5, further comprising: a baseplate, upon which said print carriage, said docking station and said first and second actuators are mounted; said first actuator being arranged to move said print carriage linearly in a first direction parallel to a plane of said baseplate, and said second actuator being arranged to move said docking station linearly in a second direction orthogonal to the first direction and orthogonal to said plane of said baseplate.
9. An inkjet printing apparatus as claimed in claim 6, further comprising: a baseplate, upon which said print carriage, said docking station and said first and second actuators are mounted; said first actuator being arranged to move said print carriage linearly in a first direction parallel to a plane of said baseplate, and said second actuator being arranged to rotate said docking station on an axis, which is orthogonal to said plane of said baseplate.
10. An inkjet printing apparatus as claimed in claim 6, further comprising: a baseplate, upon which said print carriage, said docking station and said first and second actuators are mounted; said first actuator being arranged to move said print carriage linearly in a first direction parallel to a plane of said baseplate, and said second actuator being arranged to rotate said docking station on an axis, which is parallel to said plane of said baseplate.
II. An inkjet printing apparatus as claimed in claim 10, wherein: said axis is orthogonal to said first direction.
12. An inkjet printing apparatus as claimed in claim 9 or claim II, wherein: said axis intersects said first direction.
13. An inkjet printing apparatus as claimed in any one of claims 9 to 12, wherein: said control means is arranged to operate said second actuator such as to rotate said docking station selectively in a clockwise or anticlockwise direction, thereby to locate a predetermined docking bay with minimum angular movement of said docking station.
14. An inkjet printing apparatus as claimed in any one of claims 7 to 13, wherein: said control means is arranged to operate said second actuator so as to line up a predetermined docking bay with said print carriage, and to operate said first actuator so as to move said print carriage toward said docking bay.
15. An inkjet printing apparatus as claimed in claim 2, wherein: said print carriage comprises a frame for receiving one or more of said printhead carriers.
16. An inkjet printing apparatus as claimed in claim 15, wherein: said inkjet printing apparatus comprises a holding means for retaining said one of more of said printhead carriers.
17. An inkjet printing apparatus as claimed in claim 16, wherein: said holding means comprises one or more spring-loaded ball-bearings disposed on said frame and one or more recesses disposed on said printhead carrier, said recesses being for engagement with said ball-bearings.
18. An inkjet printing apparatus as claimed in claim 17, wherein: there are as many recesses as there are ball-bearings.
19. An inkjet printing apparatus as claimed in claim 17, wherein: said recesses are constituted by a pair of grooves disposed on opposite sides of said printhead carrier.
20. An inkjet printing apparatus as claimed in claim 19, wherein: each of said pair of grooves has a groove depth, which is smaller than an amount of protrusion of said ball-bearings from said frame.
21. An inkjet printing apparatus as claimed in claim 20, wherein: each of said pair of grooves has a pair of recesses, which are of greater depth than the grooves and are disposed in spaced-apart manner along the printhead carrier at locations corresponding to the locations of said ball-bearings in said frame.
22. An inkjet printing apparatus as claimed in any one of the preceding claims, further comprising: a servicing means adjacent said docking station, said servicing means for perfoming servicing operations on printheads docked in said docking station.
23. An inkjet printing apparatus as claimed in claim 22, wherein: said servicing means comprises one or more items from a group consisting of: a flushing means,a wiping means, a capping means, a priming means and an ink-degassing means.
24. An inkjet printing apparatus as claimed in any one of the preceding claims, further comprising: a latching means for securing said at least one printhead to said docking station upon transferal of said at least one printhead from said print carriage to said docking station.
25. An inkjet printing apparatus as claimed in claim 24, wherein: said latching means comprises: at least one latching member, which is pivotally attached to said docking station, such that the latching member has two degrees of freedom of movement, and an associated groove arrangement provided in said printhead carrier.
26. An inkjet printing apparatus as claimed in claim 25, wherein: said groove arrangement comprises: a latching portion, with which said latching member engages in order to secure said printhead carrier to said docking station, and a stepped portion, with which said latching member engages in order to allow said printhead carrier to be released from said docking station.
27. An inkjet printing apparatus as claimed in claim 26, wherein: said latching portion includes a ramp portion, with which said latching member engages and against which said latching member moves in one of said two degrees of freedom, and the engagement of said latching member with said stepped portion involves movement of said latching member out of said latching portion into said stepped portion in the other of said two degrees of freedom.
28. An inkjet printing apparatus as claimed in any one of claims 25 to 27, further comprising: a bias means for urging said latching member into a starting position prior to engagement of the latching member with said groove arrangement.
29. An inkjet printing apparatus as claimed in any one of the preceding claims, wherein: said control means is arranged to: (a) determine whether or not one of said printheads is to be used in a given printing operation: (b) if so, operate said second actuator, so as to bring said printhead into alignment with said print carriage; (c) operate said first actuator, so as to bring said print carriage toward said docking station; (d) operate said first actuator, so as to attach said printhead to said print carriage; (e) operate said first actuator, so as to move said print carriage to a desired position relative to a substrate, upon which printing is to take place, and (f) operate said printhead, so as to eject a printing medium onto said substrate in a predetermined manner.
30. An inkjet printing apparatus as claimed in claim 29, wherein: said control means is further arranged to: (g) operate said first actuator, so as to return said printhead to said docking station after printing with that printhead is completed;.

(h) determined whether or not another of said printheads is to be used in the given printing operation; (1) if so, repeat steps (b)-(h) in respect of the other printhead.
31. An inkjet printing apparatus as claimed in any one of the preceding claims, further comprising: one or more reading heads for reading information on a substrate, upon which printing is *, performed by the inkjet printing apparatus, said control means being arranged to operate the first actuator and/or second actuator, :" * such that at least one of said reading heads can be transferred between said print carriage and * said docking station. * ** * S S S...

S

* ** I.. S *

31. An inkjet printing apparatus as claimed in any one of the preceding claims, further comprising: one or more reading heads for reading information on a substrate, upon which printing is performed by the inkjet printing apparatus, said control means being arranged to operate the first actuator and/or second actuator, such that at least one of said reading heads can be transferred between said print carriage and said docking station.

32. An optical apparatus, comprising: a scanning carriage, which is movable by a first actuator; a docking station, which is movable by a second actuator; a plurality of reading heads, and a control means; wherein the control means is arranged to operate the first actuator and/or second actuator, such that at least one of said reading heads can be transferred between said scanning carriage and said docking station.

mendments to the claims have been filed as follows

1. An inkjet printing apparatus, comprising: a print carriage, which is movable by a first actuator; a docking station, which is movable by a second actuator; a plurality of printheads, and a control means; wherein the control means is arranged to operate the first actuator and/or second actuator, such that at least one of said printheads can be transferred between said print carriage and said docking station.

2. An inkjet printing apparatus as claimed in claim I, further comprising: a plurality of printhead carriers, upon which respective ones of said plurality of printheads are mounted, said -printhead carriers being transferable between said print carriage and said docking station and being latchable to said docking station upon transferal of said at least one printhead from said print carriage to said docking station.

3. An inkjet printing apparatus as claimed in any one of the preceding claims, wherein: said docking station has a plurality of docking bays to receive respective said prirnheads.

4. An inkjet printing apparatus as claimed in claim 3, wherein: there are as many docking bays as there are printheads.

5. An inkjet printing apparatus as claimed in claim 4, wherein: said docking bays are arranged side-by-side in a linear configuration.

6. An inkjet printing apparatus as claimed in claim 4, wherein: said docking bays are arranged side-by-side in a circular configuration.

7. An inkjet printing apparatus as claimed in claim 5, further comprising: a baseplate, upon which said print carriage, said docking station and said first and second actuators are mounted; said first actuator being arranged to move said print carriage linearly in a first direction parallel to a plane of said baseplate, and said second actuator being arranged to move said docking station linearly in a second direction orthogonal to the first direction and parallel to said plane of said baseplate.

8. An inkjet printing apparatus as claimed in claim 5, further comprising: a baseplate, upon which said print carriage, said docking station and said first and second actuators are mounted; said first actuator being arranged to move said print carriage linearly in a first direction parallel to a plane of said baseplate, and said second actuator being arranged to move said docking station linearly in a second direction orthogonal to the first direction and orthogonal to said plane of said baseplate.

9. An inkjet printing apparatus as claimed in claim 6, further comprising: a baseplate, upon which said print carriage, said docking station and said first and second actuators are mounted; said first actuator being arranged to move said print carriage linearly in a first direction parallel to a plane of said baseplate, and said second actuator being arranged to rotate said docking station on an axis, which is orthogonal to said plane of said baseplate.

10. An inkjet printing apparatus as claimed in claim 6, further comprising: a baseplate, upon which said print carriage, said docking station and said first and second actuators are mounted; said first actuator being arranged to move said print carriage linearly in a first direction parallel to a plane of said baseplate, and said second actuator being arranged to rotate said docking station on an axis, which is parallel to said plane of said baseplate.

11. An inkjet printing apparatus as claimed in claim 10, wherein: said axis is orthogonal to said first direction.

12. An inkjet printing apparatus as claimed in claim 9 or claim 11, wherein: said axis intersects said first direction.

13. An inkjet printing apparatus as claimed in any one of claims 9 to 12, wherein: said control means is arranged to operate said second actuator such as to rotate said docking station selectively in a clockwise or anticlockwise direction, thereby to locate a predetermined docking bay with minimum angular movement of said docking station.

14. An inkjet printing apparatus as claimed in any one of claims 7 to 13, wherein: said control means is arranged to operate said second actuator so as to line up a predetermined docking bay with said print carriage, and to operate said first actuator so as to move said print carriage toward said docking bay.

15. An inkjet printing apparatus as claimed in claim 2, wherein: said print carriage comprises a frame for receiving one or more of said printhead carriers.

16. An inkjet printing apparatus as claimed in claim 15, wherein: said inkjet printing apparatus comprises a holding means for retaining said one of more of said printhead carriers.

17. An inkjet printing apparatus as claimed in claim 16, wherein: said holding means comprises one or more spring-loaded ball-bearings disposed on said frame and one or more recesses disposed on said printhead carrier, said recesses being for engagement with said ball-bearings.

18. An inkjet printing apparatus as claimed in claim 17, wherein: there are as many recesses as there are ball-bearings.

19. An inkjet printing apparatus as claimed in claim 17, wherein: said recesses are constituted by a pair of grooves disposed on opposite sides of said printhead carrier.

20. An inkjet printing apparatus as claimed in claim 19, wherein: *each of said pair of grooves has a groove depth, which is smaller than an amount of protrusion of said ball-bearings from said frame.

21. An inkjet printing apparatus as claimed in claim 20, wherein: each of said pair of grooves has a pair of recesses, which are of greater depth than the grooves and are disposed in spaced-apart manner along the printhead carrier at locations corresponding to the locations of said ball-bearings in said frame.

22. An inkjet printing apparatus as claimed in any one of the preceding claims, further comprising: a servicing means adjacent said docking station, said servicing means for performing servicing operations on printheads docked in said docking station.

23. An inkjet printing apparatus as claimed in claim 22, wherein: said servicing means comprises one or more items from a group consisting of: a flushing means, a wiping means, a capping means, a priming means and an ink-degassing means.

24. An inkjet printing apparatus as claimed in any one of the preceding claims, further comprising: a latching means for securing said at least one printhead to said docking station upon transferal of said at least one printhead from said print carriage to said docking station.

25. An inkjet printing apparatus as claimed in claim 24, wherein: said latching means comprises: at least one latching member, which is pivotally attached to said docking station, such that the latching member has two degrees of freedom of movement, and an associated groove arrangement provided in said printhead carrier.

26. An inkjet printing apparatus as claimed in claim 25, wherein: said groove arrangement comprises: a latching portion, with which said latching member engages in order to secure said printhead carrier to said docking station, and a stepped portion, with which said latching member engages in order to allow said printhead carrier to be released from said docking station.

27. An inkjet printing apparatus as claimed in claim 26, wherein: said latching portion includes a ramp portion, with which said latching member engages and against which said latching member moves in one of said Iwo degrees of freedom, and the engagement of said latching member with said stepped portion involves movement of said latching member out of said latching portion into said stepped portion in the other of said two degrees of freedom.

28. An inkjet printing apparatus as claimed in any one of claims 25 to 27, further comprising: a bias means for urging said latching member into a starting position prior to engagement of the latching member with said groove arrangement.

29. An inkjet printing apparatus as claimed in any one of the preceding claims, wherein: said control means is arranged to: (a) determine whether or not one of said printheads is to be used in a given printing operation: (b) if so, operate said second actuator, so as to bring said printhead into alignment with said print carriage; (c) operate said first actuator, so as to bring said print carriage toward said docking station; (d) operate said first actuator, so as to attach said printhead to said print carriage; (e) operate said first actuator, so as to move said print carriage to a desired position relative to a substrate, upon which printing is to take place, and (f) operate said printhead, so as to eject a printing medium onto said substrate in a predetermined manner.

30. An inkjet printing apparatus as claimed in claim 29, wherein: said control means is further arranged to: (g) operate said first actuator, so as to return said printhead to said docking station after printing with that printhead is completed; (h) determined whether or not another of said printheads is to be used in the given printing operation; (i) if so, repeat steps (b)-(h) in respect of the other printhead.