JP2017007134A - Inkjet printing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inkjet printing device that can reduce contact between an inkjet head and a sheet.SOLUTION: The inkjet printing device 1 includes: inkjet heads 61A to 61D for discharging ink to the transported sheet P; head lower support rollers 26 to 30 disposed on a lower side than the inkjet heads 61A to 61D along a sheet transportation direction while having an interval therebetween to support the sheet P; and a sheet pushing down part 5 for pushing down the sheet P downward between the head lower support rollers 26 to 30 during abnormal stop of sheet transportation.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an inkjet printing apparatus that prints by ejecting ink from an inkjet head.

  2. Related Art Inkjet printing apparatuses that perform printing by ejecting ink from an inkjet head while conveying a sheet of long continuous paper are known.

  In such an ink jet printing apparatus, when the paper sags or breaks, the paper may come into contact with the ink jet head. When the paper comes into contact with the inkjet head, the inkjet head may be damaged.

  On the other hand, techniques for reducing the occurrence of paper sagging and breakage have been proposed. For example, in Patent Document 1, when paper conveyance is stopped urgently, by controlling each roller or the like to stop in a predetermined order, the paper may sag or excessive tension may be applied to the paper. An image recording apparatus that prevents a sheet from being broken is disclosed.

JP 2009-249067 A

  However, in the technique of Patent Document 1, it is necessary to stop the sheet conveyance by controlling each roller and the like. For this reason, for example, when the sheet conveyance is stopped in a state where the operation of each roller or the like cannot be controlled due to the power interruption during the sheet conveyance, there is a possibility that the sheet may sag or break.

  The present invention has been made in view of the above, and an object of the present invention is to provide an ink jet printing apparatus that can reduce contact of paper with an ink jet head.

  In order to achieve the above object, a first feature of an ink jet printing apparatus according to the present invention is that an ink jet head that discharges ink onto a paper to be transported, and an interval along the paper transport direction below the ink jet head. It is provided with a plurality of support members that are disposed at intervals and support the paper, and a paper push-down unit that pushes the paper downward between the support members when the paper conveyance is abnormally stopped.

  A second feature of the ink jet printing apparatus according to the present invention is that the paper push-down unit pushes down the paper in a non-energized state.

  A third feature of the ink jet printing apparatus according to the present invention is that the paper push-down unit guides a plurality of rollers that rotate while being supported by the paper, and a plurality of guides that respectively guide the rotation shafts of the plurality of rollers to be movable up and down. A guide member having a hole, and the roller is lowered while the rotating shaft is guided by the guide hole in accordance with a decrease in the tension of the paper, whereby the roller pushes down the paper by its own weight.

  According to the first feature of the ink jet printing apparatus according to the present invention, the paper push-down unit pushes the paper downward between the support members when the paper conveyance is abnormally stopped. Accordingly, even when the paper is slack or broken due to abnormal stop of the paper conveyance, the approach of the paper to the inkjet head can be suppressed. As a result, the contact of the paper with the inkjet head can be reduced.

  According to the second feature of the inkjet printing apparatus according to the present invention, the paper push-down unit pushes down the paper in a non-energized state. For this reason, even when the control by the control unit of the ink jet printing apparatus cannot be performed due to power interruption, the push-down member can push down the paper.

  According to the third feature of the ink jet printing apparatus according to the present invention, the roller pushes down the paper by its own weight in accordance with the decrease in the tension of the paper. For this reason, the sheet can be pushed down without depending on the electrical mechanism. Accordingly, the roller can push down the paper even when the control by the control unit of the ink jet printing apparatus cannot be performed due to power interruption.

1 is a schematic configuration diagram of an inkjet printing apparatus according to a first embodiment. It is a principal part top view of the conveyance part under a head of the inkjet printing apparatus shown in FIG. It is a control block diagram of the inkjet printing apparatus shown in FIG. 2 is a flowchart for explaining the operation of the inkjet printing apparatus shown in FIG. 1. It is explanatory drawing of the operation | movement in which the paper pushing-down part of the inkjet printing apparatus shown in FIG. 1 pushes down a paper. It is a schematic block diagram of the inkjet printing apparatus which concerns on 2nd Embodiment. It is a top view of the pushing-down member of the inkjet printing apparatus shown in FIG. FIG. 7 is a control block diagram of the ink jet printing apparatus shown in FIG. 6. It is explanatory drawing of the operation | movement by which the paper pressing-down part of the inkjet printing apparatus shown in FIG. 6 pushes down a paper. It is a schematic block diagram of the inkjet printing apparatus which concerns on 3rd Embodiment. It is a principal part top view of the head lower conveyance part of the inkjet printing apparatus shown in FIG. It is the elements on larger scale of the inkjet printing apparatus shown in FIG. It is explanatory drawing of the operation | movement in which the paper pressing-down part of the inkjet printing apparatus shown in FIG.

  Embodiments of the present invention will be described below with reference to the drawings. Throughout the drawings, the same or equivalent parts and components are denoted by the same or equivalent reference numerals.

  The following embodiments exemplify devices for embodying the technical idea of the present invention, and the technical idea of the present invention is the material, shape, structure, arrangement, etc. of each component. Is not specified as follows. The technical idea of the present invention can be variously modified within the scope of the claims.

(First embodiment)
FIG. 1 is a schematic configuration diagram of an inkjet printing apparatus according to a first embodiment of the present invention. FIG. 2 is a plan view of the main part of the lower head transport section of the ink jet printing apparatus shown in FIG. FIG. 3 is a control block diagram of the inkjet printing apparatus shown in FIG. In the following description, the top, bottom, left, and right of the paper surface in FIG. Further, the direction orthogonal to the paper surface of FIG.

  As shown in FIG. 1, the ink jet printing apparatus 1 according to the first embodiment includes a delivery unit 2, an upstream buffer unit 3, a head lower transport unit 4, a paper pressing unit 5, a head unit 6, and a downstream unit. A side buffer unit 7, a winding unit 8, and a control unit 9 are provided.

  The delivery unit 2 sends out the paper P from the paper roll 10. The paper roll 10 is a roll of paper P, which is a long continuous paper. As shown in FIGS. 1 and 3, the delivery unit 2 includes a paper roll support shaft 11 and a delivery motor 12.

  The paper roll support shaft 11 rotatably supports the paper roll 10. The paper roll support shaft 11 is formed in a long shape extending in the front-rear direction.

  The feed motor 12 rotates the paper roll support shaft 11 clockwise in FIG. The rotation of the sheet roll support shaft 11 causes the sheet roll 10 to rotate in the same direction, and the sheet P is sent out to the downstream side (right side).

  The upstream buffer unit 3 absorbs the slack of the paper P between the sending unit 2 and the head lower conveyance unit 4. The upstream buffer unit 3 includes support rollers 16 and 17 and a dancer roller 18.

  The support rollers 16 and 17 support the paper P between the delivery unit 2 and the head lower conveyance unit 4. The support rollers 16 and 17 are spaced apart from each other by a predetermined distance in the left-right direction and are disposed at the same height.

  The dancer roller 18 pushes down the paper P by its own weight between the support rollers 16 and 17. As a result, the slack of the paper P generated between the delivery unit 2 and the head lower conveyance unit 4 is absorbed by the upstream buffer unit 3. The dancer roller 18 moves up and down according to the amount of slack of the paper P.

  The head lower transport unit 4 transports the paper P sent out by the sending unit 2 along a transport path below ink jet heads 61A to 61D described later. As shown in FIGS. 1 to 3, the head lower conveyance unit 4 includes upstream guide rollers 21 to 23, a tension applying roller 24, a brake 25, head lower support rollers 26 to 31, a drive roller 32, The head lower conveyance motor 33, a pair of support plates 34F and 34R, and downstream guide rollers 35 to 37 are provided.

  The upstream guide rollers 21 to 23 guide the paper P between the upstream buffer unit 3 and the head lower support roller 26.

  The tension applying roller 24 is for applying tension to the paper P. The tension applying roller 24 nips the paper P with the upstream guide roller 21 and rotates with the transported paper P. By applying the brake to the tension applying roller 24 by the brake 25, tension is applied to the paper P between the tension applying roller 24 and the driving roller 31, and the slack of the paper P during this time is prevented.

  The brake 25 brakes the tension applying roller 24. The brake 25 is a powder brake, for example.

  The head lower support rollers 26 to 31 support the paper P below the ink jet heads 61A to 61D. A path connecting the highest points of the head lower support rollers 26 to 31 is a conveyance path of the paper P below the ink jet heads 61A to 61D. The head lower support rollers 26 to 31 are arranged at the same height at intervals along the paper transport direction (left-right direction). In the head lower support rollers 26 to 31, the respective rotation shafts 26 a to 31 a are supported by the support plates 34 </ b> F and 34 </ b> R. The head lower support rollers 26 to 30 correspond to support members in claims.

  The head lower support roller 26 is disposed in the vicinity of the upstream side of the ink jet head 61A in the paper transport direction. The head lower support rollers 27, 28, and 29 are disposed between the inkjet heads 61A and 61B, between the inkjet heads 61B and 61C, and between the inkjet heads 61C and 61D, respectively, in the paper transport direction. In other words, the head lower support rollers 27, 28, and 29 are disposed in the vicinity of the downstream side of the inkjet heads 61A, 61B, and 61C and in the vicinity of the upstream side of the inkjet heads 61B, 61C, and 61D, respectively. The head lower support roller 30 is disposed in the vicinity of the downstream side of the ink jet head 61D in the paper transport direction. The head lower support roller 31 is disposed on the downstream side of the head lower support roller 30 in the paper transport direction.

  The driving roller 32 conveys the paper P in the right direction by rotating while niping the paper P with the lower support roller 31. The drive roller 32 has a rotating shaft 32a supported by support plates 34F and 34R.

  The under-head transport motor 33 rotates the drive roller 32.

  The support plates 34F and 34R rotatably support the rotation shafts 26a to 31a of the head lower support rollers 26 to 31 and the rotation shaft 32a of the drive roller 31. The support plates 34F and 34R are spaced apart from each other in the front-rear direction across the transport path of the paper P.

  The downstream guide rollers 35 to 37 guide the paper P between the head lower support roller 31 and the downstream buffer unit 7.

  The paper push-down unit 5 is disposed between the head lower support rollers 26 and 27, between the head lower support rollers 27 and 28, between the head lower support rollers 28 and 29, and between the head lower support rollers 29 and 30 when the paper conveyance is abnormally stopped. The paper P is pushed down. The abnormal stop of the paper transport is a stop other than the normal stop of the paper transport operation performed at the end of printing. The abnormal stop of the sheet conveyance includes an emergency stop due to the occurrence of an emergency of the ink jet printing apparatus 1 and a stop due to power interruption of the ink jet printing apparatus 1.

  As shown in FIGS. 1 to 3, the sheet pressing portion 5 includes pressing members 41 to 48 and solenoids 51 to 58.

  The push-down members 41 to 48 are members that push down the paper P downward. The push-down members 41 to 48 are formed in a long shape extending in the front-rear direction.

  The push-down members 41 and 42 are disposed between the head lower support roller 26 and the ink jet head 61A and between the ink jet head 61A and the head lower support roller 27, respectively, in the paper transport direction. The push-down members 43 and 44 are disposed between the head lower support roller 27 and the ink jet head 61B and between the ink jet head 61B and the head lower support roller 28, respectively, in the paper transport direction. The push-down members 45 and 46 are disposed between the head lower support roller 28 and the ink jet head 61C and between the ink jet head 61C and the head lower support roller 29, respectively, in the paper transport direction. The push-down members 47 and 48 are disposed between the head lower support roller 29 and the ink jet head 61D and between the ink jet head 61D and the head lower support roller 30, respectively, in the paper transport direction.

  The solenoids 51 to 58 move the push-down members 41 to 48 up and down, respectively. When the solenoids 51 to 58 are on (energized state), the push-down members 41 to 48 are disposed at the standby position. The standby positions of the push-down members 41 to 48 are above the conveyance path of the paper P. When the solenoids 51 to 58 are off (non-energized state), the push-down members 41 to 48 become free and descend from the standby position, and push down the paper P by its own weight.

  The head unit 6 prints on the paper P conveyed on the lower head support rollers 26 to 31. The head unit 6 has four inkjet heads 61A to 61D. In addition, the alphabetic suffixes (A to D) in the reference numerals of the ink jet heads 61A to 61D may be omitted and collectively described.

  The ink jet heads 61 </ b> A to 61 </ b> D discharge ink onto the conveyed paper P. The inkjet heads 61 </ b> A to 61 </ b> D are arranged in parallel along the conveyance direction (left-right direction) of the paper P. The inkjet heads 61A to 61D eject inks of different colors (for example, black, cyan, magenta, and yellow). Each of the inkjet heads 61 </ b> A to 61 </ b> D has six head modules 66.

  In the inkjet head 61, the head modules 66 are arranged in a staggered manner. That is, the ink jet head 61 is formed by arranging two head rows composed of three head modules 66 arranged at equal intervals in the front-rear direction so as to be shifted by a half pitch in the front-rear direction. .

  The head module 66 has a plurality of nozzles (not shown) arranged along the front-rear direction, and ejects ink from the nozzles.

  The downstream buffer unit 7 absorbs the slack of the paper P between the lower head transport unit 4 and the winding unit 8. The downstream buffer unit 7 includes support rollers 71 and 72 and a dancer roller 73.

  The support rollers 71 and 72 support the paper P between the head lower conveyance unit 4 and the winding unit 8. The support rollers 71 and 72 are arranged at the same height and spaced apart from each other by a predetermined distance in the left-right direction.

  The dancer roller 73 pushes down the paper P by its own weight between the support rollers 71 and 72. Thereby, the slack of the paper P generated between the head lower conveyance unit 4 and the winding unit 8 is absorbed by the downstream buffer unit 7. The dancer roller 73 moves up and down according to the amount of slack of the paper P.

  The winding unit 8 winds the printed paper P. The winding unit 8 includes a winding shaft 76 and a winding motor 77.

  The take-up shaft 76 takes up and holds the paper P. The winding shaft 76 is formed in a long shape extending in the front-rear direction.

  The winding motor 77 rotates the winding shaft 76 in the clockwise direction in FIG. The sheet P is wound around the winding shaft 76 by the rotation of the winding shaft 76.

  The control unit 9 controls the operation of each unit of the printing apparatus 1. The control unit 9 includes a CPU, a RAM, a ROM, a hard disk, and the like.

  Next, the operation of the inkjet printing apparatus 1 will be described with reference to the flowchart of FIG.

  First, in step S1 of FIG. 4, the control unit 9 determines whether or not a print job has been input. If it is determined that no print job has been input (step S1: NO), the control unit 9 waits until a print job is input.

  If it is determined that a print job has been input (step S1: YES), in step S2, the control unit 9 starts a printing operation.

  Specifically, the control unit 9 activates the feed motor 12, the under-head transport motor 33, the brake 25, and the take-up motor 77. As a result, the paper P is transported from the delivery unit 2 toward the winding unit 8. In the lower head transport unit 4, the tension is applied to the tension applying roller 24 by the brake 25, whereby the sheet P is transported while tension is applied to the sheet P.

  After the conveyance speed of the paper P reaches a predetermined speed, the control unit 9 starts printing by the head unit 6. Specifically, the control unit 9 controls the ink jet heads 61 </ b> A to 61 </ b> D based on the print job to eject ink onto the paper P.

  Here, in the inkjet printing apparatus 1, the solenoids 51 to 58 are turned on when the power is turned on. For this reason, at the start of the printing operation, the solenoids 51 to 58 are on, and the push-down members 41 to 48 are disposed at the standby position.

  After the start of the printing operation, in step S <b> 3, the control unit 9 determines whether an emergency has occurred in the inkjet printing apparatus 1. For example, when the meandering of the paper P is detected by a sensor (not shown), the control unit 9 determines that an emergency has occurred.

  If it is determined that an emergency has not occurred (step S3: NO), in step S4, the control unit 9 determines whether printing by the head unit 6 based on the print job is finished. If it is determined that printing has not ended (step S4: NO), the control unit 9 returns to step S3.

  When it is determined that the printing has been completed (step S4: YES), in step S5, the control unit 9 performs a normal stop of the sheet transport operation. Specifically, the control unit 9 stops the feed motor 12, the under-head transport motor 33, the brake 25, and the take-up motor 77. Here, the control unit 9 stops the feed motor 12, the under-head transport motor 33, the brake 25, and the take-up motor 77 in order to prevent sagging or breakage of the paper P, the feed motor 12, and the under-head transport. The deceleration acceleration of the motor 33 and the winding motor 77 is controlled. As a result, when the paper transport operation is completed, a series of operations are completed.

  If it is determined in step S3 that an emergency has occurred (step S3: YES), in step S6, the controller 9 urgently stops the operation of the ink jet heads 61A to 61D and the sheet transport operation.

  Here, also in this emergency stop, the control unit 9 stops the paper transport operation by the same control as in the normal stop by the end of printing (step S5). However, since an emergency situation has occurred in the inkjet printing apparatus 1, the behavior of the paper P is disturbed when the paper transport operation is stopped, which may cause the paper P to sag or break.

  Therefore, in step S6, the control unit 9 turns off the solenoids 51 to 58 together with the emergency stop of the sheet transport operation. As a result, the push-down members 41 to 48 are lowered from the standby position. As a result, as shown in FIG. 5, the push-down members 41 to 48 allow the head lower support rollers 26, 27, the head lower support rollers 27, 28, the head lower support rollers 28, 29, the head lower support rollers 29, The sheet P is pushed downward between 30.

  Here, FIG. 5 is a diagram illustrating a state in which the push-down members 41 to 48 are lowered when the paper P is slack. By the lowering of the push-down members 41 to 48, the paper P is moved away from the ink jet heads 61A to 61D, and the contact of the paper P with the ink jet heads 61A to 61D is suppressed.

  Even when the paper P is broken between the head lower support rollers 26 to 30, the push-down members 41 to 48 are lowered to push the paper P, so that the paper P is moved away from the ink jet heads 61 </ b> A to 61 </ b> D. The contact of the sheet P with the heads 61A to 61D can be reduced.

  Returning to FIG. 4, when the operations of the ink jet heads 61 </ b> A to 61 </ b> D and the paper transport operation are urgently stopped and the solenoids 51 to 58 are turned off in step S <b> 6, the series of operations is completed.

  Next, the operation of the paper push-down unit 5 when the power is shut off during the printing operation of the inkjet printing apparatus 1 will be described.

  For example, the power supply may be interrupted during the printing operation of the inkjet printing apparatus 1 due to an erroneous operation by the user. When the power is shut off, the operation of the entire inkjet printing apparatus 1 is stopped. At this time, the feed motor 12, the under-head transport motor 33, the brake 25, and the take-up motor 77 are stopped without being controlled by the control unit 9. For this reason, there is a possibility that the paper P may sag or break.

  On the other hand, when the power is cut off, the solenoids 51 to 58 are turned off in the paper push-down unit 5 and the push-down members 41 to 48 are lowered from the standby position. Thus, as in the case of the emergency stop described above, the push-down members 41 to 48 allow the head lower support rollers 26, 27, the head lower support rollers 27, 28, the head lower support rollers 28, 29, and the head lower support. The sheet P is pushed downward between the rollers 29 and 30.

  As described above, in the ink jet printing apparatus 1, the paper push-down unit 5 has the head lower support rollers 26, 27, the head lower support rollers 27, 28, the head lower support rollers 28, 29, the paper P is pushed downward between the head lower support rollers 29 and 30. Thereby, even when the paper P is slackened or broken due to the abnormal stop of the paper conveyance, the approach of the paper P to the inkjet heads 61A to 61D can be suppressed. As a result, the contact of the paper P with the inkjet heads 61A to 61D can be reduced.

  In addition, since the paper push-down unit 5 pushes down the paper P in a non-energized state, the push-down members 41 to 48 can push down the paper P even in a state where the control by the control unit 9 cannot be performed due to power interruption.

(Second Embodiment)
FIG. 6 is a schematic configuration diagram of an ink jet printing apparatus according to the second embodiment. FIG. 7 is a plan view of a push-down member of the inkjet printing apparatus shown in FIG. FIG. 8 is a control block diagram of the inkjet printing apparatus shown in FIG.

  As shown in FIGS. 6 and 8, the inkjet printing apparatus 1 </ b> A according to the second embodiment has a configuration in which the sheet pressing unit 5 of the inkjet printing apparatus 1 of the first embodiment described above is replaced with a sheet pressing unit 5 </ b> A. .

  The paper push-down unit 5A includes push-down members 81A to 81D and solenoids 82A to 82D. In addition, the alphabetic suffixes (A to D) in the symbols of the push-down members 81A to 81D and the solenoids 82A to 82D may be omitted and collectively described.

  The push-down members 81A to 81D are members that push down the paper P downward. The push-down members 81A to 81D are respectively arranged between the head lower support rollers 26, 27, between the head lower support rollers 27, 28, between the head lower support rollers 28, 29, and under the head lower support rollers 29, in the paper transport direction (left-right direction). It is arranged between 30. As shown in FIG. 7, the push-down member 81 is formed in a shape that can be fitted to each head module 66 of the inkjet head 61. Specifically, the push-down member 81 is formed in a shape in which portions having a shape that goes around the side surface of each head module 66 are integrated.

  The solenoids 82A to 82D move the push-down members 81A to 81D up and down, respectively. When the solenoid 82 is on, the push-down member 81 is disposed at the standby position. At this standby position, the push-down member 81 is fitted to the lower end of each head module 66. For this reason, the push-down member 81 does not prevent the ink ejected from the head module 66 during printing. When the solenoid 82 is off, the push-down member 81 becomes free and descends, and the paper P is pushed downward by its own weight.

  Also in the second embodiment, similarly to the first embodiment, when an emergency occurs during the printing operation, the control unit 9 turns off the solenoids 82A to 82D together with the emergency stop of the sheet transport operation. As a result, the push-down members 81A to 81D are lowered from the standby position. As a result, as shown in FIG. 9, the pressing members 81 </ b> A to 81 </ b> D allow the head lower support rollers 26, 27, the head lower support rollers 27, 28, the head lower support rollers 28, 29, the head lower support rollers 29, The sheet P is pushed downward between 30.

  Here, FIG. 9 is a diagram illustrating a state in which the push-down members 81A to 81D are lowered when the paper P is slack. By the lowering of the pressing members 81A to 81D, the paper P is moved away from the ink jet heads 61A to 61D, and the contact of the paper P with the ink jet heads 61A to 61D is suppressed.

  Even when the paper P is broken between the head lower support rollers 26 to 30, the push-down members 81 </ b> A to 81 </ b> D are lowered to push the paper P, so that the paper P is moved away from the ink jet heads 61 </ b> A to 61 </ b> D. The contact of the sheet P with the heads 61A to 61D can be reduced.

  When the power is shut off during the printing operation of the ink jet printing apparatus 1A, the solenoids 82A to 82D are turned off in the paper push-down unit 5A, and the push-down members 81A to 81D are lowered from the standby position. As a result, as in the case of the emergency stop described above, the pressing members 81A to 81D allow the head lower support rollers 26, 27, the head lower support rollers 27, 28, the head lower support rollers 28, 29, and the head lower support. The sheet P is pushed downward between the rollers 29 and 30.

  As described above, in the ink jet printing apparatus 1A, when the sheet conveyance is abnormally stopped, the sheet pressing portion 5A is located between the head lower support rollers 26 and 27, between the head lower support rollers 27 and 28, and between the head lower support rollers 28 and 29. Then, the paper P is pushed downward between the head lower support rollers 29 and 30. Thereby, similarly to 1st Embodiment, the contact of the paper P to the inkjet heads 61A-61D can be reduced.

  Similarly to the paper push-down unit 5 of the first embodiment, the paper push-down unit 5A pushes down the paper P in a non-energized state, and therefore the push-down member 81A is in a state where control by the control unit 9 is not possible due to power interruption. ˜81D can push down the paper P.

(Third embodiment)
FIG. 10 is a schematic configuration diagram of an ink jet printing apparatus according to the third embodiment. FIG. 11 is a plan view of the main part of the lower head transport section of the ink jet printing apparatus shown in FIG. 12 is a partially enlarged view of the ink jet printing apparatus shown in FIG.

  As shown in FIGS. 10 to 12, the ink jet printing apparatus 1 </ b> B according to the third embodiment has a configuration in which the paper pressing unit 5 of the ink jet printing apparatus 1 of the first embodiment described above is replaced with a paper pressing unit 5 </ b> B. .

  Further, in the ink jet printing apparatus 1B, guide holes 86A to 86D and 87A to 87D are formed in the support plate 34F. Similarly, guide holes 86A to 86D and 87A to 87D are formed in the support plate 34R. In the ink jet printing apparatus 1B, the support plates 34F and 34R constitute a part of the sheet pressing portion 5B. The support plates 34F and 34R correspond to the guide plates in the claims.

  The sheet pressing unit 5B includes pressing rollers 91A to 91D and 92A to 92D. The pressing rollers 91 </ b> A to 91 </ b> D and 92 </ b> A to 92 </ b> D are members that press the paper P downward as the tension of the paper P decreases. The push-down rollers 91A to 91D and 92A to 92D are formed in a long shape extending in the front-rear direction. The pressing rollers 91A to 91D and 92A to 92D correspond to the rollers in the claims.

  In addition, the alphabetic suffixes (A to D) in the reference numerals of the guide holes 86A to 86D, 87A to 87D, and the push-down rollers 91A to 91D and 92A to 92D may be omitted and collectively described.

  The push-down rollers 91A to 91D are arranged in the vicinity of the upstream side of the ink jet heads 61A to 61D, respectively, in the paper transport direction. In the push-down rollers 91A to 91D, the front end portion of the rotation shaft 91a is inserted into the guide holes 86A to 86D of the support plate 34F, respectively, and the rear end portion of the rotation shaft 91a is inserted into the guide holes 86A to 86D of the support plate 34R, respectively. It is inserted.

  The push-down rollers 92A to 92D are disposed in the vicinity of the downstream side of the inkjet heads 61A to 61D, respectively, in the paper transport direction. In the push-down rollers 92A to 92D, the front end portions of the rotation shaft 92a are respectively inserted into the guide holes 87A to 87D of the support plate 34F, and the rear end portions of the rotation shaft 92a are respectively inserted into the guide holes 87A to 87D of the support plate 34R. It is inserted.

  The guide holes 86 and 87 are for guiding the rotary shafts 91a and 92a of the push-down rollers 91 and 92, respectively, so as to be movable up and down.

  The guide holes 86A to 86D are formed between the rotation shaft 26a of the head lower support roller 26 and the ink jet head 61A, between the rotation shaft 27a of the head lower support roller 27 and the ink jet head 61B, and below the head support roller. 28 between the rotary shaft 28a and the inkjet head 61C, and between the rotary shaft 29a of the head lower support roller 29 and the inkjet head 61D. The guide hole 86 is formed in an arc shape that curves toward the inkjet head 61.

  The guide holes 87A to 87D are formed between the inkjet head 61A and the rotation shaft 27a of the head lower support roller 27, between the inkjet head 61B and the rotation shaft 28a of the head lower support roller 28, and between the inkjet head 61C and the paper transport direction. They are disposed between the rotary shaft 29a of the head lower support roller 29 and between the inkjet head 61D and the rotary shaft 30a of the head lower support roller 30, respectively. The guide hole 87 is formed in an arc shape that curves toward the inkjet head 61.

  The guide holes 86 and 87 guide the push-down rollers 91 and 92 between the normal position and the lower limit position, respectively.

  The normal positions of the push-down rollers 91 and 92 are the positions of the push-down rollers 91 and 92 indicated by solid lines in FIG. The normal positions of the push-down rollers 91 and 92 are positions of the push-down rollers 91 and 92 when normal tension is applied to the paper P. The lowest point of the push-down rollers 91 and 92 in the normal position and the highest point of the head lower support rollers 26 to 30 are the same height.

  The lower limit position of the push-down rollers 91 and 92 is the position of the push-down rollers 91 and 92 indicated by a two-dot chain line in FIG. The lower limit positions of the push-down rollers 91 and 92 are below the normal position, and are closer to the inkjet head 61 than the normal position in the paper transport direction (left-right direction).

  Next, the operation of the paper push-down unit 5B will be described.

  During the paper transport operation, the push-down rollers 91 and 92 of the paper push-down unit 5B are arranged at the normal position by the tension of the paper P and rotate while being supported by the paper P.

  When the normal stop of the sheet conveyance is performed, the sheet P is stopped while maintaining a normal tension similar to that during the conveyance. For this reason, the push-down rollers 91 and 92 remain in the normal position.

  On the other hand, when the paper conveyance is abnormally stopped (emergency stop or stop due to power interruption) and the tension of the paper P is lower than that at the time of conveyance, as shown in FIG. The lowering rollers 91 and 92 are lowered while 91a and 92a are guided by the guide holes 86 and 87, respectively. As a result, the press-down rollers 91 and 92 are under their own weight between the head lower support rollers 26 and 27, between the head lower support rollers 27 and 28, between the head lower support rollers 28 and 29, and between the head lower support rollers 29 and 30. Press down. Here, as the case where the tension of the paper P is lowered, there are a case where the paper P is slack and a case where the paper P is broken.

  As described above, also in the third embodiment, the sheet push-down portion 5B has the lower head support rollers 26, 27, the lower head support rollers 27, 28, the lower head support rollers 28, 29, the lower head support rollers 29, 29. By pressing down the paper P between 30, the contact of the paper P with the ink jet heads 61 </ b> A to 61 </ b> D can be reduced.

  Further, since the push-down rollers 91 and 92 push down the paper P by its own weight according to the decrease in the tension of the paper P, the paper P can be pushed down regardless of the electrical mechanism. For this reason, the push-down rollers 91 and 92 can push down the paper P even in a state where the control by the control unit 9 is not possible due to power interruption.

(Other embodiments)
As described above, the present invention has been described according to the first to third embodiments. However, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  In the first embodiment described above, the push-down members 41 to 48 have a long shape. In the second embodiment, the push-down member 81 has a shape that can be fitted to each head module 66 of the inkjet head 61. However, the shape of the push-down member in the first and second embodiments is not limited to these. The push-down member in the first and second embodiments may have any shape that can push down the paper P by its own weight by lowering without hindering the flying of ink from the head module 66 at the standby position.

  In the third embodiment described above, the guide holes 86 and 87 are arcuate, but the shape is not limited to this. The guide hole may have any shape that guides the rotary shafts 91a and 92a of the push-down rollers 91 and 92 so as to be movable up and down.

  As described above, the present invention naturally includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

DESCRIPTION OF SYMBOLS 1 Inkjet printing apparatus 2 Sending part 3 Upstream buffer part 4 Head lower conveyance part 5 Paper pushing down part 6 Head unit 7 Downstream buffer part 8 Winding part 9 Control part 21-23 Upstream side guide roller 24 Tension applying roller 25 Brake 26 -31 Head lower support roller 32 Drive roller 33 Head lower transport motor 34F, 34R Support plate 35-37 Downstream guide roller 41-48 Depressing member 51-58 Solenoid 61, 61A-61D Inkjet head 66 Head module 1A Inkjet printing apparatus 5A Paper pressing part 81, 81A-81D Pushing member 82, 82A-82D Solenoid 1B Inkjet printer 5B Paper pressing part 86, 86A-86D, 87, 87A-87D Guide hole 91, 91A-9 D, 92,92A~92D depressed roller

Claims (3)

An inkjet head that ejects ink onto the conveyed paper;
Below the inkjet head, a plurality of support members arranged at intervals along the paper transport direction and supporting the paper,
An ink jet printing apparatus comprising: a paper pressing unit that presses the paper downward between the support members when the paper conveyance is abnormally stopped.   The inkjet printing apparatus according to claim 1, wherein the paper push-down unit pushes down the paper in a non-energized state. The paper pressing portion is
A plurality of rollers that rotate while being supported by the paper;
A guide member having a plurality of guide holes that respectively guide the rotation shafts of the plurality of rollers in a vertically movable manner,
The inkjet printing apparatus according to claim 1, wherein the roller is pushed down by its own weight when the roller is lowered while the rotating shaft is guided by the guide hole in accordance with a decrease in the tension of the paper.