PRINTING ARRANGEMENT

Abstract: Printer unit comprising a printing arrangement (10) for printing out text or pictures onto paper, wherein the printing unit comprises a first storage vessel (70) comprising a fresh ink tank (80) and a first circuit (140) for transporting ink from the fresh ink tank to a shuttle (30) movable in relation to the paper and equipped with an inkjet print head (20). The inkjet print head (20) is arranged to controllably produce ink jets and thereby apply ink dots to the paper in accordance with a control signal. The first circuit (140) leads the ink from the fresh ink tank to a pressure wave damper (200) arranged on the shuttle (30) and a second circuit (294) leads the ink from the pressure wave damper (200) to the inkjet print head (20). The pressure wave damper is arranged to even out eventual pressure changes which occur in the ink as a consequence of the movement of the shuttle and to deliver ink to the inkjet print head (20) with an essentially even liquid pressure.

Description: Printing Arrangement The present invention concerns a printing unit of the type which is described in the introduction to Claim 1. A printing arrangement for an inkjet printer comprises an inkjet print head which is arranged to output ink against paper in accordance with control signals. The inkjet print head is movably arranged so that it can move in relation to the paper and produce text on different parts of the paper. In order to supply the inkjet print head v/ith ink there is an ink reservoir arranged in the printing unit. The nozzles in the inkjet print head occasionally need to be cleaned, for example in order to prevent the ink drying in or around the nozzle. In connection with the cleaning some ink is removed from the inkjet print head by suction and this waste ink must be stored somewhere. This problem has been solved in the prior art by providing a separate firmly mounted container for waste ink in the printing unit. A problem in the. prior art is that the operator often omits to empty or change the waste ink container, which can lead to an overfilled container and eventually to leakage of ink. Another problem with the prior art is how to supervise the amount of ink remaining in the fresh ink container. In many cases, in order to have an optimal print quality, the inkjet print head is dependent on the ink fulfilling certain performance requirements. If the wrong type of ink is deli-vered, it can in the worst case damage the inkjet print head. A problem with the prior art is that an operator can, by mis¬ take, mount a replacement ink container with ink which is of the wrong type for the inkjet print head comprised in the printer unit, which can lead to serious damage on certain components in the printing unit when the wrong type of ink is outputted in the ink system. The main object of the present invention is to produce a printer unit which is easy to use and which produces print¬ outs with a high performance. Another object of the present invention is to produce an ink container which in a reliable and simple manner can deliver fresh ink to an inkjet print head. Yet another object of the present invention is to produce a combined fresh ink container and waste ink container which is removably mounted in the printer unit. Yet another object of the present invention is to produce an ink conductor which is pliable and which can be bent with¬ out significantly influencing the liquid pressure in the ink. Yet another object of the present invention is to produce a status unit integrated with the fresh ink container, which registers how much ink has been used out of the fresh ink container. Yet another object of the present invention is to produce a unit, mounted on the moving shuttle, which can deliver ink to the inkjet print head with an even liquid pressure, essen¬ tially independent of the movement of the shuttle. Yet another object of the present invention is to produce a cleaning arrangement for efficient cleaning of the inkjet nozzles and for transporting the waste ink to a replaceable waste container. These and other objects which will be evident from the de¬ scription are achieved by the invention with an arrangement of the sort which is described in the characterizing part of claim 1. Other features and further developments of the arrangement according to the invention are given in the other claims. A brief description of the drawings In order to make the present invention simply understood and executed, it will be described by means of illustrative examples and with reference to the following drawings, in which: Fig. 1 shows a schematic general view of a printer unit, such as in a telefax machine or a printer for a personal computer, comprising a printing arrangement. Fig. 2 shows a schematic general view of a printing arrange¬ ment according to one embodiment of the invention. Fig. 3 shows a schematic general view of a part of an inkjet print head with inkjet nozzles. Fig. 4 shows a block diagram of an electronic status unit. Fig. 5A shows a schematic general view of an ink container unit according to a first embodiment of the invention, comprising an ink tank filled with fresh ink, a container for waste ink and the status unit shown in Fig. 4. Fig. 5B shows a schematic general view of an ink container unit according to a second embodiment of the invention, comprising an ink tank filled with fresh ink, a container for waste ink and the status unit shown in Fig. 4. Fig. 6A shows a schematic general view of an ink container unit according to a third embodiment of the invention, with an ink tank filled with fresh ink. Fig. 6B shows a schematic general view of an ink container unit according to Fig. 6A with the ink tank essentially emptied of ink. Fig. 7A shows an embodiment of a connection on an ink tank. Fig. 7B shows a second embodiment of a connection on an ink tank. Fig. 7C shows an embodiment of a cannula which can be con¬ nected to the connection shown in Fig. 7B. Fig. 8 shows a lateral view of an ink circuit according to one embodiment of the invention. Fig. 9 shows an enlarged portion of the ink circuit shown in Fig. 8. Fig. 10 is a sectioned exploded lateral view of a pressure wave damper according to one embodiment of the invention. Fig. 11 is a perspective view of a part of a shuttle com¬ prising a part of a pressure wave damper. Fig. 12 is a perspective view of the part of shuttle shown in Fig. 11, seen in the direction of arrow A. Fig. 13 is a perspective view of the part of shuttle shown in Fig. 12, seen in the direction of arrow B. Fig. 14 is a sectioned lateral view of a cleaning nozzle according to one embodiment of the invention. Fig. 15 is a lateral view of a cleaning nozzle and its sus- pension arrangement, seen in the direction of arrow C in Fig. 14. Fig. 16 is a lateral view of a cleaning nozzle and its suspension arrangement, seen in the direction of arrow C in Fig. 14. Fig. 17 shows the arrangement in Fig. 15, seen in the direc¬ tion of arrow E, and the shuttle with the inkjet head. Fig. 18 shows the arrangement from Fig. 17 when the shuttle with the inkjet print head is in the cleaning position. Fig. 19 shows a partially sectioned lateral view of a mem¬ brane pump for excess ink according to one embodiment of the invention. Fig. 20 shows an enlarged detail from Fig. 19. Summary A printing arrangement according to one embodiment of the present invention comprises a storage vessel for ink, a cir¬ cuit system for transporting ink to a shuttle with an inkjet print head and an arrangement for cleaning of the inkjet print head, and a vessel for collecting waste ink which arises during cleaning of the inkjet print head. The storage vessel for fresh ink is according to one embodiment of the invention integrated with the vessel for collecting waste ink. Description of a first embodiment of the invention The present invention concerns a printing arrangement 10, which can be included in a printer unit 15, as is illustrated in Fig. 1. The printer unit 15 can be a telefax machine, wherein the printing unit 10 carries out the printing of fax messages which the telefax machine receives. According to an alternative embodiment of the invention, the printer unit 15 can be a printer for a personal computer. The printing arrangement 10 comprises an inkjet print head 20 mounted in a shuttle unit 30, as illustrated schematically in Fig. 2. The shuttle unit 30 is arranged to be able to run backwards and forwards along a path essentially parallel with a paper surface during which the inkjet print head outputs ink in a manner such that the dots of ink are arranged on the paper in precise patterns. The inkjet print head 20 has 64 channels with inkjet nozzles, which can spray out ink, arranged essentially along one line. The distance from a nozzle to the paper is approximately 1 mm. The inkjet print head slopes in relation to a line of text on the paper, so that the line along which the nozzles are placed forms an angle α between 65 and 85 degrees to the path along which the shuttle runs. According to one embodi¬ ment of the invention, the angle α = 72.4 degrees. The path along which the shuttle runs is essentially parallel with a line of text produced on the paper, indicated by the x-axis in Fig. 3. By activating the ink nozzles, dots can be placed on the paper with a density of essentially 200 dpi. According to one embodiment, 204 dots per inch are achieved in the x- direction and 197 dots per inch in the y-direction (Fig. 3). Every third ink channel can be activated simultaneously according to one embodiment of the inkjet print head. The channels are divided into three groups A, B and C (Fig. 1). The resulting distance Δ in the height-direction (y- direction) between two adjacent dots of ink is approximately 1/200 of an inch. Activation of the inkjet print head 20 is controlled with signals which are delivered via a databus 40 from a proces- sing unit 45 in the printer unit 15. The databus 40 is made of a multiconductor flexible cable. The flexible cable 40 also delivers information to a first connector 50, which can be connected to a second connector 55 on a status unit 60. Figure 2 and Figure 4 The status unit is included in a replaceable ink refill unit 70. The ink refill unit further comprises an ink tank for new ink and a waste tank which will be described in more detail below. The tasks of the status unit are: 1. To calculate how much ink has been used from the ink tank. It keeps track of how many dots of ink have been ejected by the inkjet print head, by counting the number of ink dots ordered. These orders are delivered to both the inkjet print head 20 and status unit 60 via the flexible cable 40. Each ink dot corresponds essentially to a volume of 100 pico- liters. The tank has a volume of 33 ml which is enough for approximately 1500 pages of text with a 5% degree of coverage on the paper. 2. To store product information. The status unit has a memory unit which is equipped with a code which identifies the re¬ fill unit. When the refill unit is mounted in a printer or a fax machine, a processing unit in the printer or fax machine can ask the refill unit for its identity. This means that it becomes possible to programme the processing unit to only cooperate with the refill unit if the identification code delivered by the status unit corresponds with the criteria which are stored in the processing unit. Fig. 4 is a schematic view of the status unit. The status unit comprises a connector 55, through which it can be coup¬ led to the processing unit 45 of the printer/fax machine. A quantity of data is stored in the status unit and selected data blocks can be delivered to the processing unit after receipt of a corresponding command. Furthermore, the processing unit can deliver blocks of in¬ formation to the status unit and instruct the status unit to store these information blocks in a first memory means 70 comprised in the status unit. According to one embodiment of the invention, the first memory means is an EEPROM-chip. According to another embodiment, it is an EEPROM-capsule. Status unit 60 further comprises a processor 72 and a perma¬ nent memory means 74 in the form of ROM and a volatile memory means 76. Program code for execution by processor 72 is stored in per¬ manent memory means 74, and the volatile memory means can be used as a working memory. Variables and protocols can be stored in the volatile memory means when the processor is computing. Communication between the processing unit 45 and the status unit takes place with half duplex. A clock signal is deliver¬ ed to the status unit from the processing unit via the flex¬ ible cable 40. A special communication protocol has been developed for this communication. A set of data is stored in the first memory means 70 with information on the total ink volume in the fresh ink tank. During use of the printer unit, the processing unit delivers at selectable moments updating information on the quantity of ink which has been used since the previous time this updating information was delivered. The processing unit can, for example, deliver volume updating information after every printed sheet of paper. The status unit performs a subtraction dependent on this up¬ dating information and calculates from it an estimation of the remaining volume of ink. Because each dot of ink which is printed corresponds to a predetermined volume of ink, this volume estimation can be calculated as a number of ink dots. At selectable moments the processing unit can send a question instruction to the status unit in order to request informa¬ tion. An example of such an instruction is "Query-Level" which means that the status unit shall deliver information on the ink volume condition in the ink tank. As a consequence of the instruction Query-Level, the status unit performs a logi¬ cal operation which can give one of the following three results: I. The status unit delivers the answer "not-empty" if the estimated remaining volume of ink is greater than 25% of the original volume. II. The status unit delivers the answer "soon-empty" if the estimated remaining volume of ink X is within the interval 0 < x < 25% of the original volume. III. The status unit delivers the answer "empty" if the estimated remaining volume of ink is zero. An instruction called "dot-count" means that the processing unit requests information on the amount of ink estimated re¬ maining. As a consequence of this instruction, the processor reads the count value stored in memory means 70, which corre- sponds to the number of dots of ink which it has been calcu¬ lated can still be printed, and delivers this value to the processing unit. The above described functions make it possible, in an advan- tageous manner, to arrange for example an alarm function for low ink level in the processing unit. As described above, the status unit can furthermore store production information. This can for example comprise a batch-number for the ink refill unit. The processing unit can store selected data in a data block in the memory means 70, and the processing unit can also request to read this data again at a later point of time. This makes it possible for the processing unit to find out if the ink refill unit has been removed and later replaced in the fax machine/printer. The processing unit can comprise a verifying procedure through which it, after it has communicated with the status unit, depending on the product information which has been read from the status unit, either accepts the ink refill unit or not. Supplying the processing unit with this product in- formation gives in this way a possibility to indicate, via a display connected to the processing unit, if an ink refill unit which has been mounted is of the type which is compa¬ tible with this printer, and contains an ink which is compa¬ tible with the inkjet print head. If the product information delivered from the status unit to the processing unit is not accepted during the verifying procedure, then in one embodi¬ ment of the invention the processing unit can place the printing means in a completely passive condition and in this way prevent the wrong type of ink being delivered from the ink container to the rest of the ink system. If the product information sent to the processing unit from the status unit is accepted by the verification procedure, according to one embodiment of the invention the processing unit can put the printing unit in a start-up condition, which will be described more closely with the description of a cleaning arrangement below. As the correct ink quality can be of great importance for the optimal functioning of the compo¬ nent items, such as the inkjet print head etc, and for the printing to be of optimal quality, it is advantageous to achieve in this way an automatic check that only ink of an improved quality is used in the printer. Figures 2, 5A, 5B. 6A and 6B The ink system comprises the above mentioned replaceable ink refill unit 70 as illustrated in Fig. 2 and 5A. The ink refill unit 70 comprises a tank space 80 which, when new, is essentially filled with liquid ink (Fig. 5A). The ink refill unit 70 further comprises a waste container 90 into which excess ink is delivered, for example during cleaning of the nozzle of the print head. The waste container 90 is completely or partially filled with a porous material 100, which is arranged to suck up and store the liquid ink which is delivered to the waste container 90. The porous material 100 comprises, according to one embodiment, a foamed porous material with open cells and which can be wetted by ink. Ink refill unit 70 comprises also the electronic status unit 60 which has the function, amongst others, to keep a check on how much ink remains in the tank space 80. When the ink refill unit 70 is replaced and a new ink refill unit 70 is fitted, the goals of, on the one hand, supplying a new supply of ink and, on the other hand, providing an empty waste container are thus achieved. This means that the operator cannot unintentionally equip the printing unit with a new supply of ink without at the same time equipping it with a new waste container, and in this way the risk of leakage of ink as a consequence of an overfilled waste container is eliminated. The refill unit 70 thus contains the following three compo¬ nents: 1. an ink tank 80 for fresh ink, 2. a waste tank 90 for receiving used waste ink, 3. an electronic status unit 60. The fresh ink tank 80 comprises a cavity 110, in which an ink container 120 with flexible walls is arranged, according to one embodiment of the invention. The ink container 120 is according to the embodiment a bag filled with fresh ink 7 (Fig. 5A). As the ink is used, the volume of the bag shrinks. One of the stiff outer walls of the fresh ink tank 80 is equipped with an opening 130 through which air can come in, in order to fill the space which forms when the ink bag shrinks as the ink is used. According to a second embodiment of the fresh ink tank 80, the ink container 120 has a flexible wall 131, which sepa¬ rates the ink-filled space from an airfilled space 132 (Fig. 5B). The flexible wall 131 can be made from a pliable mate- rial which in its stretched condition has a shape which essentially corresponds to the shape of the inside of the bottom surface and the four stiff sidewalls of the ink con¬ tainer 120. The flexible wall 131 takes up an essentially extended condition when the ink container 120 is essentially emptied of ink. In Fig. 5B the ink container 120 is shown in a condition where it is approximately half-filled with ink. Because the ink container 120 has at least one flexible wall, ink can be delivered from the container without the liquid pressure being influenced appreciably and without the ink coming into contact with air. It is advantageous to hold the liquid pressure low in the ink in the inkjet print head, wherefore the fresh ink tank is ar- ranged so that the upper ink surface in the fresh ink tank is slightly lower than the horizontal plane in which, the inkjet print head lies. In order to achieve an ink level which is as low as possible, there is a third embodiment, wherein the fresh ink tank extends between all the outermost perpendicular walls of the refill unit, and the waste tank 90 is placed above the ink tank (see Fig. 6A and 6B). An air channel runs through the waste tank 90 in order to be able to supply the space 110 with air as the ink is used. In this third embodiment of the fresh ink tank, the ink is stored between five fixed walls and one flexible wall instead of in a bag. Figures 7A, 7B and 7C The bottom surface of the ink tank is equipped with a connec¬ tion coupling 134 comprising a puncturable membrane 136 (see Fig. 6B and Fig. 7A). Fig. 7B shows a sectioned sideview of a second embodiment of a connection coupling on an ink tank. According to this embodiment the connection coupling 134 comprises a plug 135 made of a sealing and compressible material. The plug 135 can for example be made of a rubber material. The plug is adapted to the shape of an orifice 137 in the bottom surface of the ink container. According to one embodiment, the plug is essentially cylindrically shaped and a peripheral part of the end surface, which faces towards the inside of the ink con- tainer, can rest against a shoulder 138 near the orifice 137. The plug 135 is equipped with a channel 135A, in which a cannula 139 can be inserted. In order to guide the cannula to the channel 135A, the plug is equipped with an essentially cylindrical indentation 135B which has a diameter which essentially corresponds to the diameter of the cannula 139. The connection coupling 134 further comprises a membrane 141 which can be sealed firmly against the outside of the connec¬ tion coupling. During connection of the cannula 139 to the connection coupling 134, the membrane 141 is punctured and thereafter, the cannula is steered by the indentation 135B to the originally squeezed closed and sealed channel 135A so that the cannula opens up the channel 135A, wherein the walls of the channel 135A lie sealingly against the periphery of the cannula 139. According to one embodiment the membrane 141 is made of aluminium. Ink circuit between fixed and movable container. Fig. 8 and 9 During insertion of the ink refill unit, coupling to an ink circuit 140, which delivers ink from the ink tank 80 to an intermediate storage tank 200 arranged on the shuttle 30 (see Fig. 2), takes place. Fig. 7C shows an embodiment of a cannula 139, which can be connected to the connection coupling 134. The cannula com¬ prises an essentially stiff and tube-shaped piece equipped with a point in a first end which is intended to penetrate the membrane and the plug. A hose 202 is threadable over the other end of the cannula 139, which is not intended to be inserted in the connection coupling 134. The cannula is bent so that the first end of the cannula and its point can be pointing vertically while the second part of the cannula tube is orientated horizontally. The printer unit comprises a holding arrangement for the ink refill unit and this holding arrangement comprises an attach¬ ment for the cannula. The attachment is arranged to orientate the cannula so that its first end and point are directed in the direction from which the connection coupling 134 approaches the cannula during mounting of a new ink refill unit. According to one embodiment of the invention, the first end and point of the cannula are directed vertically. The ink circuit 140 is subject to constant movement as its first end is attached to an intermediate storage tank 200 on the movable shuttle 30. The ink circuit 140 thus bends during use of the printer as the shuttle moves back and forth during printing. The ink circuit 140 between the ink tank 80 and the inter¬ mediate storage tank 200 comprises a flexible hose 202 (see Fig. 8) . A sleeve 204 is threaded around the hose 202 in order to minimize squeezing together of the hose. when the ink circuit bends. The sleeve 204 minimizes changes in the dia¬ meter of the hose and in this manner minimizes or prevents changes in the volume of the hose. In this way the problem of undesirable liquid pumping effects, which otherwise occur in flexible hoses which are subjected to bending, is avoided. Such undesirable pumping effects can lead to undesirable pressure changes in the ink at the inkjet print head 20, and thus to impaired print performance. The hose 202 is armoured by a helical spring which when straight is closely lapped in order to give the circuit a predetermined and unambiguous movement during movement of the shuttle. The sleeve comprises, according to one embodiment of the invention, a helical spring with metal wires which are close¬ ly lapped, as is shown schematically in Fig. 9. The wires are so closely lapped that, when the sleeve is completely strai¬ ghtened out, they lie against the next and preceding turn of wire. The hose 202 has an inner diameter in the range from 0.3 to 3.0 mm, and preferably in the range from 1.0 to 2.0 mm. The sleeve and the hose are adapted tp one another so that the outer diameter of the hose essentially corresponds with the inner diameter of the sleeve so that the underside of the hose has radial support along the whole of the part of the circuit which is bent as a consequence of the movement of the shuttle. In order to further minimize the risk that possible pressure changes in the circuit 140 influence the ink pressure at the inkjet print head 20, there is an intermediate storage tank 200 arranged between circuit 140 and the inkjet print head 20. The intermediate storage tank 200 is mounted on the movable shuttle 30. Ink container on movable shuttle. Figures 10. 11. 12 and 13 An advantage which is achieved through the combination of a fixed mounted ink tank 80 and the intermediate storage tank 200 mounted on the shuttle is that the printer can have access to a large quantity of ink without the movable shuttle being loaded with a large quantity of ink. In this way pro¬ blems, which otherwise could arise as a consequence of a large mass in the shuttle with corresponding large shuttle 30 inertia, are avoided. The ink circuit 140 from the main tank 80 leads ink to an inlet opening 205 in the intermediate storage tank, as illu¬ strated in Fig. 10. The intermediate storage tank 200 com¬ prises a cavity 210. The cavity is divided into two subspaces by means of a flexible and stretchable membrane 220. The ink from the main tank is led into one of the subspaces 230, also known as the ink chamber 230. The ink chamber 230, which is delimited by the five stiff walls 232,233,234 and the flexible membrane 220, is completely filled with ink during normal function of the printer. The flexible membrane 220 dampens any possible pressure waves which come from the inlet opening 205 or which occur as a consequence of the movement of the shuttle. According to this embodiment of the intermediate storage tank, the membrane 220 is stretchable and essentially flat in the state where the ink chamber has its minimal volume. A number of ribs 250 are arranged on an inside 240 of a stiff wall 233 of the ink chamber 230. These ribs form a support for the membrane 220 and thereby these ribs 250 help to define the minimum volume which the ink chamber can have. The ink chamber 230 has an essentially minimal volume when the membrane lies against the outer end surface 260 on each of the ribs 250. According to one embodiment of the inven¬ tion, the height of the ribs from the bottom surface is somewhat higher than that of the side walls 232 and 234, respectively, which means that the flexible and stretchable membrane can be stretched over the ribs and in this way pre- tensioned to a predetermined value. The height difference is illustrated by the dimension β in Fig. 10. A lid 270 is arranged to form a limit to the cavity 210 on the side opposite to the fastening surface of the ribs. The lid is in sealing contact against an end surface 280 of the walls 232. The lid is equipped with one or more openings 272 which can let in air in the second subspace in the cavity 210. According to one embodiment of the invention, the membrane 220 is fastened by being clamped between the peripheral surface of the lid 270 and the end surface 280. The absolute maximum volume of the ink chamber 230 is achiev¬ ed when the membrane 220 is forced to lie against the inner surface 282 of the lid 270. As described above, ink is inputted into the ink chamber 230 via an inlet opening 205, which inlet opening can be arranged on a side wall 232. As illustrated in Fig. 10, an outlet opening 290 is placed in a position corresponding to that of the inlet opening 205, but by the opposing side wall 234. The outlet opening 290 is thus arranged on the opposite end of the ink chamber 230. The outlet opening is connected to the inkjet print head 20 by means of an ink circuit 294 (Fig. 2). The ink which is transported out through the outlet opening 290 is thus delivered to the inkjet print head. Between the outlet 290 and the inkjet print head, the ink passes through a filter. Fig. 11 is a perspective view of a shuttle piece 296 compris¬ ing a part of a pressure wave damper. During the printing function the shuttle is movable along the line X in Fig. 11. When the printing unit is placed on a flat horizontal surface, the line of movement X is horizontal. Fig. 12 is a perspective view of the shuttle piece 296 in Fig. 11, seen in the direction of arrow A. The inkjet print head 20 is mounted on the side of shuttle piece 296 shown in Fig. 12. Fig. 13 is a perspective view of the shuttle piece in Fig. 12, seen in the direction of arrow B. The axis Z in Fig. 13 illustrates a direction which can be vertical when axis X is horizontal. When the X-axis in Fig. 13 is horizontal and the Z-axis is vertical, a lower stiff side wall 300 in the ink chamber 230 forms a horizontally orientated surface. A side wall 300 opposite the bottom side wall 300 is then orientated so that its surface inclines somewhat so that the outlet 290 is posi¬ tioned a bit higher than the inlet 205. The outlet 290 is arranged in the upper left corner of the surface 240, as shown in Fig. 13. Cleaning station for inkjet print head. Figures 14 - 20 The printer arrangement 10 further comprises a cleaning station for cleaning the ink nozzles of the inkjet print head 20. After a certain amount of text has been printed, for example when a sheet of A4-paper has been printed out, a cleaning procedure is performed. During this cleaning procedure, the shuttle moves to an end position at which a cleaning nozzle 410 is caused to lie against the inkjet print head 20 (see Fig. 2 and 14, respectively). The cleaning nozzle 410 comprises a sealing ring 412 made of rubber which, when in contact with the inkjet print head, prevents ink from leaking and prevents air from being intro- duced into the inkjet head nozzles. Inside the sealing ring the cleaning nozzle comprises an absorption element 414 which has ink ab-sorbing properties in combination with ink perme¬ ability. The surface of the absorption element facing towards the inkjet print head during the cleaning phase is placed at a predetermined distance from the inkjet print head. The dis¬ tance between the absorption element and the inkjet head can be from approximately 1 to 2 mm. A circuit 440 is connected to the cleaning nozzle 410 and is connected to a pump 450, which is arranged to suck out a certain quantity of ink from the nozzles in the inkjet print head 20. This means, amongst others, that any possible small air bubbles, which possibly could be stuck in any of the narrow ink channels or nozzles in the inkjet print head, are sucked out via the cleaning nozzle to circuit 440 for transportation further to the waste tank 90. This means that after cleaning, all the ink channels in the inkjet print head are comp-letely filled with fresh ink and equally that the porous absorption element in the cleaning nozzle is saturated with ink in liquid form. The rubber sealing of the cleaning nozzle prevents air from coming into contact with the nozzles of the inkjet print head, and in this way retains the fresh properties of the ink even if the shuttle remains in the idle position for a long time. The sucked-out ink is to be treated as waste and is delivered via a waste circuit 460 from the pump 450 to the waste tank 90 (see Fig. 2). When the printer unit remains in the idle position, i.e. when no printing is being performed, then the inkjet print head 20 is placed at the cleaning station. This occurs in the following manner: The shuttle and the head move to the cleaning position. The shuttle then presses against a mechanical position sensor which causes the cleaning nozzle to be pushed out and lie in contact with the inkjet print head. A suction phase is performed, as described above. This suc¬ tion phase continues for a predetermined time in order to achieve the above described objects. This means that the absorption element 414, which is in the cleaning nozzle, becomes completely soaked with ink. This means that the ink in the accessible volume in the cleaning nozzle in front of the inkjet print head cannot dry out, and in this way the problems with plugging of the inkjet nozzles, which otherwise could occur, are avoided. In this state the shuttle can remain in the rest position until the next printout is ordered. After the above described cleaning procedure or rest phase, the inkjet print head passes a wiper blade 470, which wipes off the surface where the ink nozzles are placed. This means that possible particles of rubbish or excess ink, which may have stuck to the surface of the inkjet print head, are removed. Fig. 15 is a view of a cleaning nozzle and its suspension arrangement 475, seen in the direction of arrow C in Fig. 14. Cleaning nozzle 410 is shaped so as to cover the whole of the surface of the inkjet print head which has openings for ink. Since the inkjet print head is arranged to be inclined, the nozzle 410 is mounted so that its opening 480 is orientated in a corre¬ sponding manner. Wiper blade 470 is arranged just to the left of the cleaning nozzle 410. Fig. 17 shows the arrangement in Fig. 15, shown in the direc¬ tion of arrow E, and the shuttle 30 with the inkjet print head 20. The shuttle 30 comprises an activating detail 490 which is arranged to cooperate with a number of sensor bosses in the suspension arrangement 475. Fig. 17 shows the shuttle in the right turning position where it normally stops and changes direction of travel during con¬ tinued printing. The point of the arrow 500 indicates the position for the right edge of a sheet of paper, on which the inkjet print head produces text according to one embodiment of the invention. The shuttle 30 is movable in a direction parallel with the X-axis in Fig. 17 and anti-parallel with the X-axis. When the shuttle is in the position shown in Fig. 17 and when it, during normal printing function, is further to the left on the shuttle path, then the suspension arrange- ment 475 is in the stable rest position as illustrated in Fig. 17. Cleaning nozzle 410 is in the retracted position and is fastened to a cam element 510, which is shown with dashed lines in Fig. 17. The cam element 510 is rotatably suspended and is rotatable about a point of rotation 520. When the shuttle moves from the position shown in Fig. 17 to the cleaning position, the activating detail 490 meets a first activating lip 530 on an L-shaped link element 540. The link element 540 is rotatable around an axis of rotation 550. Fig. 18 shows the arrangement with the shuttle placed in the cleaning position. By a comparison of Fig. 17 and 18, it can be seen that the movement of the shuttle from the turning position (Fig. 17) to the cleaning position (Fig. 18) causes link element 540 to press a lip 560 in a direction essential- ly towards the shuttle 30. The lip 560 is attached to a link element 570, which is rotatable around the axis of rotation 520. The link element 570 cooperates with an intermediate link 580 and a link element 590 and forms in cooperation with a helical spring 600 a toggle-joint arrangement 610. Cam element 510 and the cleaning nozzle 410 are movable in direct dependence on the movements of the link element 570, and this means that the nozzle 410 moves from its rest posi¬ tion (Fig. 17) to its position against the inkjet print head (Fig. 18), when the activating detail 490 moves the activa¬ ting lip 530 to the right, as shown in the arrangement in Fig. 17. Note lines 620 and 625. The line 620 runs between the point of rotation 520 and the hinged point 630 where the link element 570 is rotatably fixed to the intermediate link 580. The line 625 runs between the axis of rotation 630 and an axis of rotation 640, on which the intermediate link 580 is rotatably fastened to the link element 590. Toggle-joint arrangement 610 has two stable positions, where- of the first one is shown in Fig. 17 and the second in Fig. 18. When lines 620 and 625 are parallel, the toggle-joint arrangement 610 is in an instable balance position (not shown), and this instable balance position is passed each time the arrangement 610 moves between the stable positions. The distance from the shuttle's turning position (Fig. 17) to its cleaning position (Fig. 18) is greater than 0.3 mm and preferably in the range 0.8 to 10 mm. According to one embo¬ diment of the invention, the distance is approximately 1 mm. As described above, the nozzle 410 is made to come into con¬ tact against the inkjet print head 20 in the cleaning position. When the nozzle 410 has taken up the position shown in Fig. 18, the pump 450 is activated and it then sucks so that a fixed amount of ink is sucked out through the ink nozzles of the inkjet print head. According to one embodiment, the pump is a membrane pump which is powered electromechanically and is capable, when activated, to produce a pump stroke which sucks a volume in the range of between 3 mm 3 to 30 mm"3. According to one embodiment of the invention, the pump sucks a volume of approximately 10 mirr per pump stroke. Fig. 19 shows a pump 450 according to one embodiment of the invention. The waste ink circuit 440 is connected to an inlet opening 700 in a bottom part 710. The inlet opening 700 leads to a first non-return valve 720, which is arranged only to conduct fluid from the inlet 700 to a pump chamber 730 (see Fig. 19 and 20). Pump chamber 730 is limited by, amongst others, a casing 740 and a movable membrane 750. The membrane 750 is fixed to an axle 755, which is displaceably arranged on a solenoid 760. When the solenoid is activated, the axle 755 is subjected to a force which tries to remove the membrane 750 from the non¬ return valve 720. In this way an underpressure is formed in the pump chamber 730, and the non-return valve then opens a channel 770 and lets in waste ink or other fluids, e.g. air, to chamber 730 (Fig. 20). The part 780 circled in Fig. 19 is shown in an enlargement in Fig. 20. The non-return valve 720 can be made of a flexible and elastic piece of material, which comprises a foot 790 and lip elements 800,810 which are fixed to the foot. The lips 800,810 can lie against each other and in this manner seal in the back direction of the valve. When the valve conducts in the forward direction, the lips 800 and 810 separate. Pump 450 comprises a second non-return valve 820 which when it conducts fluid in its forward direction connects pump chamber 730 with an outlet opening 830. The ink circuit 460 described in connection with Fig. 2 is coupled to the outlet opening 830. According to one embodiment, the membrane 750 has its peripheral part introduced between an end surface of the housing 740 and a heel plate 840. The membrane pump 450 further comprises an electronic temperature regulator 850. When an operator fits in a new ink-containing vessel 70 and the processing unit 45 by means of the above described veri¬ fication procedure accepts the new vessel, the printing unit is put into a start condition. In the start condition, an initiation procedure is run through, which means that the shuttle 30 goes to the cleaning position (Fig. 18) and that the pump 450 is activated to carry out an adjustable number of pump strokes. This number of pump strokes is adapted according to the para- meters of the ink system, e.g. the volume in circuits 140, 294 and 440, and intermediate storage tank 200 and cleaning nozzle 410, and has the purpose of insuring that all the air, which possibly could come into the circuit 140 during re¬ placement of the ink tank, is sucked out through the above mentioned part of the ink system so that the inkjet print head is certain to receive ink during the coming printing phase. Thereby the initiation procedure is finished and the shuttle idles in a condition which is equivalent to the condition which is taken up when a normal cleaning cycle has gone through the earlier described steps and the pump 450 has pumped one pump stroke. The printing unit is then at idle and the sealing ring 412 of the cleaning nozzle ensures that the environment around the nozzles of the inkjet print head is saturated with ink solvent so that drying out is prevented. When the processing unit then sends a control signal to print, a motor is activated which moves the shuttle so that activating detail 490 moves away from the activating lip 530 (Fig. 18). Link element 570 comprises a first return lip 850 and when the shuttle leaves the position shown in Fig. 18, the activating detail 490 meets the first return lip 850, which causes the link element 570 to rotate anti-clockwise around the rotation axis 520. The toggle-joint arrangement, however, does not come past the instable balance position because the return lip 850 has a height adjusted for this purpose, which means that the spring power of spring 600 presses the lip 850 and edge 860 of the link element against the activating detail 490. When the link element is rotated anti-clockwise as described above, the cleaning nozzle 410 also moves from the inkjet print head 20 so that the sealing ring 412 no longer lies against the head 20. The shuttle now moves a bit in the direction of arrow F (Fig. 18) whereby the wiper blade 470, which is arranged by the nozzle 410, comes into contact with the surface on the inkjet print head which is equipped with ink openings. The inkjet print head goes past the wiper blade 470 and when the wiper blade 470 has passed over all of the inkjet nozzles, the activating detail 490 comes into contact with a second return lip 900 on the link element 570. The activating detail 490 then forces the link element to be rotated a further bit anti-clockwise, and the toggle-joint arrangement 610 passes the instable balance position, whereafter the spring 600 forces the toggle-joint arrangement 610 to the stable position shown in Fig. 17. In this position, both the nozzle 410 and the wiper blade 470 are in a retracted position so that they do not come into contact with the head 20 during printing. Printing arrangement 10 is then ready for printing.

Claims: Claims 1. Printer unit comprising a printing arrangement for print¬ ing of text or pictures on a sheet of paper, wherein the printing unit comprises a first storage vessel (70) com¬ prising a fresh ink tank (80) and a first circuit (140) for transporting ink from the fresh ink tank to a shuttle (30) movable in relation to the paper, equipped with an inkjet print head (20), which is arranged to controllably produce ink jets under the control of a control signal and in this way apply dots of ink to the paper, characterized in that the first circuit (140) leads ink from the fresh ink tank to a pressure wave damper (200) arranged on the shuttle (30) and that a second circuit (294) leads the ink from the pressure wave damper (200) to the inkjet head (20), wherein the pressure wave damper is arranged to even out possible pressure changes which occur in the ink as a consequence of the movement of the shuttle, and to deliver ink to the inkjet print head (20) with an essentially even liquid pressure. 2. Printer unit according to Claim 1, characterized in that the pressure wave damper comprises a cavity (210), which by means of a flexible membrane (220) is divided into two sub¬ spaces, wherein the first ink circuit is coupled to an end of the first subspace and the second circuit for transport of ink to the inkjet print head (20) is connected to an opposite end of the first subspace, and that the first subspace com¬ prises a plurality of ribs positioned transversely in rela¬ tion to the flow of ink. 3. Printer unit according to Claim 2, characterized in that the membrane is elastic and pretensioned between surfaces on the walls which form the rigid innersides of the first sub¬ space, and where the second subspace is air-filled. 4. Printer unit according to any of the previous claims, characterized in that a status unit is arranged near the replaceable first storage vessel (70) and connectable to the printer unit; and that the status unit comprises a processor unit (72) and a first permanent memory means (71,74), and that the status unit is functionally connectable with a processing unit (45). 5. Printer unit according to Claim 4, characterized in that the first permanent memory means (71) is read- and writable and that the status unit changes a count value in the first permanent memory means (71) under the influence of a control signal, and in this way produces a level value which corre- sponds to the quantity of ink taken out of the fresh ink tank. 6. Printer unit according to Claim 3 or 4, characterized in that the first permanent memory means (74) of the status unit comprises a data field, which is equipped with an identifica¬ tion code which depends on the ink stored in the fresh ink tank. 7. Printer unit according to any of the previous claims, characterized in that the processing unit (45), depending on the identification code, determines the function of the printing unit. 8. Printer unit according to any of the previous claims, characterized by an ink circuit arranged to deliver ink from the ink container to the movable shuttle unit which comprises an inkjet print head, wherein the ink circuit is movably arranged in the printing unit and is bendable and that a first end is connected to the movable shuttle unit and that the second end of the ink circuit is connectable to a remov¬ able firmly mounted ink container in the printing arrange¬ ment; and that the circuit comprises a flexible hose around which a helical spring element is threaded, which minimizes radial changes in the hose when the circuit is bent during movement of the shuttle and thereby minimizes or eliminates the production of pressure changes in the ink. 9. Printer unit according to any of the previous claims, characterized by a cleaning arrangement for ink nozzles on the inkjet print head, comprising a cleaning nozzle (410) which is arranged to move in accordance with the position of the shuttle against the inkjet print head and lie in contact with the inkjet head essentially sealingly by means of a sealing rim (412); that the cleaning nozzle (410) is connected to a pump (450) arranged to suck, in accordance with a second control signal, a predetermined quantity of fluid from the cleaning nozzle (410). 10. Printer unit according to Claim 9, characterized in that the pump (450) is a membrane pump, which in cooperation with a return valve arrangement is arranged, in accordance with the second control signal, to either perform one pump stroke or an adjustable number of pump strokes. 11. Intermediate storage tank, characterized in that it is arranged on a movable shuttle in a printing arrangement and that it comprises a cavity (210) which is divided into two subspaces by a flexible membrane (220) where a first ink circuit, which delivers ink to the intermediate storage tank, is connected to one end of the first subspace; that a second circuit, which transports ink to the inkjet print head (20), is connected to an opposite end of the first subspace; and that the first subspace comprises a plurality of ribs positioned transversely in relation to the flow of ink which, in cooperation with the membrane (220), dampens possible pressure waves in the ink. 12. Status unit, characterized in that it is arranged in a removable ink storage vessel (70,80) connectable to a printer unit; and that the status unit comprises a processor unit (72) and a permanent memory means (70) and that the status unit is functionally connectable to a processing unit (45 ) . 13. Ink container unit, characterized in that the ink con¬ tainer unit (70) is removably mounted in a printing arrange¬ ment, and that the ink container unit comprises an ink tank (80) intended to store ink, a waste tank for collecting waste ink and an electronic status unit comprising a memory means; where the ink tank comprises at least one flexible wall allowing volume changes in the ink tank with essentially unchanged pressure in the ink. 14. Ink circuit for transporting ink, characterized in that it is arranged to deliver ink from an ink container to a mov¬ able shuttle unit, which comprises an inkjet print head in a printing arrangement, where the ink circuit is movably ar¬ ranged in the printer unit and is bendable and that one end is connected to the movable shuttle element and that the other end of the ink circuit is connectable to the removable ink container firmly mounted in the printing arrangement; and that the circuit comprises a flexible hose around which a helical spring element is threaded, which minimizes radial changes in the hose when the circuit is bent during movement of the shuttle and thereby minimizes or eliminates the occurrence of pressure changes in the ink. 15. Cleaning arrangement for ink nozzles on an inkjet print head, comprising a cleaning nozzle (410) which is arranged in accordance with the position of the shuttle to move against the inkjet print head and lie in contact with the inkjet print head essentially sealingly by means of a sealing rim (412), characterized in that the cleaning nozzle (410) is connected with a pump (450) arranged, in accordance with a second control signal, to suck out a predetermined quantity of fluid from the cleaning nozzle (410). 16. Cleaning arrangement according to Claim 15, characterized in that the pump (450) is a membrane pump, which in coopera¬ tion with a non-return valve arrangement is arranged, in accordance with a second control signal, to either produce one pump stroke or an adjustable number of pump strokes. 17. Cleaning arrangement for an inkjet print head with inkjet nozzles, characterized in that the cleaning nozzle comprises an ink-permeable absorption element (414).

Inventors: BOSTROEM CHRISTER, MOLIN ALF, WENNERGRUND GOERAN, BOSTROEM, CHRISTER, MOLIN, ALF, WENNERGRUND, GOERAN
Applicants: BOSTROEM CHRISTER, MIT MODULAR INK TECHNOLOGY I S, MOLIN ALF, WENNERGRUND GOERAN, BOSTROEM, CHRISTER, MIT MODULAR INK TECHNOLOGY I STOCKHOLM AB, MOLIN, ALF, WENNERGRUND, GOERAN
Application year: 1995
Main classification: B41J2
IPC codes: B41J2