Patent Application
20230111746
The present teaching relates to an ink jet printer.
JP 2008-132628A, for example, discloses an ink jet printer that discharges ink onto a sheet-like medium for printing. The ink jet printer includes a platen, and a driving roller and a pinching roller that vertically sandwich a medium. When the driving roller rotates, the medium on the platen is thereby conveyed from an upstream side toward a downstream side in conveyance directions.
In the ink jet printer, ink is discharged onto the medium on the platen, and printing is performed. In this printing, to assure printing quality, the medium on the platen is preferably flat. In view of this, the driving roller and the pinching roller are disposed upstream of the platen, for example, and a tension bar is disposed downstream of the platen. A movable tension bar is disposed downstream of the tension bar. The movable tension bar applies a tension to the medium. Consequently, the medium on the platen can be made flat.
Media include relatively thin media. In conveying a thin medium in the conveyance directions, a center portion of the medium in a lateral direction orthogonal to the conveyance directions in a plan view is loosened. Consequently, the thin medium might float up from the platen in some cases. This floating of the medium leads to degradation of printing quality. The floating of the medium is more likely to occur as the thickness of the medium decreases. In addition, the floating of the medium is likely to occur in a configuration in which only both end portions of the medium in the lateral direction are pinched by the driving roller and the pinching roller. The floating of the medium is reduced by strictly adjusting parallelism between the driving roller and the tension bar, but it is difficult to suppress the occurrence of floating of the medium in some printing environments including humidity and temperature.
Preferred embodiments of the present invention provide ink jet printers capable of suppressing floating of a medium from a platen.
An ink jet printer according to a preferred embodiment of the present teaching includes a platen to support a medium, a conveyor, a tension bar, and a floating bar. The conveyor conveys the medium supported by the platen from an upstream side toward a downstream side in the conveyance direction. The tension bar is downstream of the platen in the conveyance directions and positioned such that a lower surface of the medium conveyed from the platen to the downstream side in the conveyance directions contacts the tension bar. The floating bar is downstream of the platen in the conveyance directions and upstream of the tension bar in the conveyance directions such that an upper surface of the medium located between the platen and the tension bar contacts the floating bar, the floating bar having a center axis that is freely movable by a predetermined degree.
In the ink jet printer, the floating bar is positioned on the medium located between the platen and the tension bar. At this time, the floating bar pushes the medium downward while freely moving in accordance with a tension exerted on the medium. Thus, the medium can be stretched by the floating bar so that floating of the medium from the platen can be reduced or prevented.
The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings.
Ink jet printers according to preferred embodiments of the present teaching will be described with reference to the drawings. The preferred embodiments described herein is, of course, not intended to particularly limit the present teaching.
The printer 10 is, for example, a large-size ink jet printer. As illustrated in
The apron 12 is disposed downstream of the platen 11 in the conveyance directions X. The apron 12 has an arc shape in cross section. The apron 12 is curved downward as the distance from the platen 11 increases. In this preferred embodiment, the platen 11 and the apron 12 are supported by a pair of left and right side frames 16.
The ink head 14 is configured to discharge ink onto the medium 5 supported by the platen 11. In this preferred embodiment, the ink head 14 is mounted on an unillustrated carriage. The ink head 14 is movable in the scanning directions Y together with the carriage.
The printer 10 includes a conveyance mechanism 20. The conveyance mechanism 20 conveys the medium 5 supported by the platen 11 from the upstream side toward the downstream side in the conveyance directions X (from the rear toward the front in this preferred embodiment). The conveyance mechanism 20 is disposed upstream of the platen 11 in the conveyance directions X. The conveyance mechanism 20 is not limited to a specific configuration.
In this preferred embodiment, the conveyance mechanism 20 includes driving rollers 21 and pinching rollers 22. The driving rollers 21 and the pinching rollers 22 are disposed upstream of the platen 11 in the conveyance directions X.
Although not shown, a driving motor is connected to the driving rollers 21. When the driving motor is driven, the driving rollers 21 are caused to rotate. Accordingly, the medium 5 sandwiched between the driving rollers 21 and the pinching rollers 22 is conveyed from the upstream side toward the downstream side in the conveyance directions X.
In this preferred embodiment, as illustrated in
The printer 10 includes a winding mechanism 30. The winding mechanism 30 is disposed downstream of the platen 11 in the conveyance directions X. The winding mechanism 30 includes a winding bar 31, a tension bar 32, and a movable tension bar 33.
The winding bar 31 extends in the scanning directions Y. The winding bar 31 is configured to wind the printed medium 5. The tension bar 32 extends in the scanning directions Y and is supported by the pair of left and right side frames 16. The tension bar 32 is configured to hold the medium 5 on the platen 11 in a flat state. The tension bar 32 is disposed above the winding bar 31. The upper end of the tension bar 32 is disposed at the same height as the upper surface of the platen 11 or at a position higher than the upper surface of the platen 11.
The movable tension bar 33 is configured to apply a tension to the medium 5. The movable tension bar 33 is disposed between the tension bar 32 and the winding bar 31. The movable tension bar 33 is disposed downstream of the tension bar 32. The movable tension bar 33 extends in the scanning directions Y.
The movable tension bar 33 is capable of swinging about the winding bar 31. In this preferred embodiment, the movable tension bar 33 is attached to the winding bar 31 with an arm 33a interposed therebetween. The arm 33a is integrated with the movable tension bar 33. The arm 33a is configured to swing about the rotation axis of the winding bar 31. The movable tension bar 33 is attached to be movable about the rotation axis of the winding bar 31 by swinging of the arm 33a. The movable tension bar 33 may be configured to be pivotable itself.
For example, a tension is applied to the medium 5 by forward and downward movement of the movable tension bar 33 by its own weight. The application of the tension to the medium 5 by the movable tension bar 33 stabilizes winding of the medium 5 by the winding bar 31. The tension applied to the medium 5 by the movable tension bar 33 is made uniform on the platen 11. Thus, the tension bar 32 functions as a bar that pulls the medium 5 between the driving rollers 21 and the movable tension bar 33.
As illustrated in
The floating bar 35 contacts the medium 5 across the entire width thereof. The floating bar 35 is configured to be pushed against the upper surface of the medium 5 by the weight of the floating bar 35. The floating bar 35 is rotatable with respect to the medium 5. In this preferred embodiment, the floating bar 35 does not have a biasing mechanism for pushing the floating bar 35 against the medium 5.
Although the configuration will be specifically described later, the floating bar 35 is attached to be swingable (i.e., rotatable) about the rotation axis of the tension bar 32. The floating bar 35 is configured such that the rotation axis (i.e., the center axis) of the floating bar 35 is freely movable by a predetermined degree.
The medium 5 is pushed slightly downward by bringing the floating bar 35 into contact with the upper surface of the medium 5 floating between the platen 11 and the tension bar 32. Accordingly, a tension of the medium 5 in the lateral direction is levelled as described later. Consequently, floating of the medium 5 from the platen 11 is reduced or prevented. The downward pushing of the medium 5 by the floating bar 35 causes the medium 5 to be pushed against the upper surface of the platen 11.
In
In this preferred embodiment, the medium 5 conveyed by the conveyance mechanism 20 to the downstream side of the conveyance directions X is guided from the platen 11 to the outer peripheral surface of the tension bar 32 with floating of the medium 5 adjusted by the floating bar 35. Thereafter, the movable tension bar 33 is brought into contact with the surface of the medium 5 opposite to the printing surface, that is, with the lower surface of the medium 5 on the platen 11. Subsequently, the medium 5 is wound around the outer peripheral surface of the winding bar 31.
Next, a structure in which the floating bar 35 is attached to the tension bar 32 will be described in detail.
In this preferred embodiment, the pair of left and right side frames 16 is disposed at the left and right ends of the tension bar 32. The tension bar 32 is bridged across the pair of left and right side frames 16. The tension bar 32 is rotatably supported on the pair of left and right side frames 16. Specifically, the pair of left and right support members 41 (see
The tension bar 32 includes a center axis member 32a projecting from left and right end portions of the tension bar 32 in the scanning directions Y. The center axis member 32a is tightly inserted in the bearing 42. In the manner described above, the tension bar 32 is rotatably supported on the pair of left and right side frames 16 with the support members 41 interposed therebetween.
In this preferred embodiment, the pair of left and right support members 41 is provided with a pair of left and right brackets 50. The brackets 50 are rotatably attached to the support members 41. The floating bar 35 is bridged over the pair of left and right brackets 50. The floating bar 35 is rotatably supported on the brackets 50.
The brackets 50 are formed by bending plate-shaped members (e.g., metal plate members). The brackets 50 are not limited to a specific configuration. In this preferred embodiment, as illustrated in
In this preferred embodiment, the floating bar 35 includes the center axis members 35a projecting from the left and right end portions of the floating bar 35 in the scanning directions Y. The center axis members 35a integrally project from the left and right end portions of the floating bar 35 toward the outside in the axial direction. As illustrated in
The extending portion 53 is provided in a portion of the bracket 50 located at an outer side of the tension bar 32 relative to the body portion 51 when seen from an end of the tension bar 32 (e.g., in the right side view) and upstream of the floating bar 35 in the conveyance directions X. The extending portion 53 projects toward the outside of the outer peripheral surface of the tension bar 32 (i.e., the outer peripheral surface of the floating bar 35) from the upstream end of the body portion 51 in the conveyance directions X. The extending portion 53 projects along the tension bar 32. The extending portion 53 is formed by bending.
The body portion 51 of the bracket 50 extends along the radial direction of the tension bar 32. The floating bar 35 is swingably supported on the front end of the bracket 50 in the extension directions of the tension bar 32. The brackets 50 are configured to restrict a swing of the floating bar 35 toward the medium 5 by contact of the extending portions 53 of the brackets 50 (specifically cushioning members 53a described later) with the apron 12. The brackets 50 restrict a swing of the floating bar 35 in a direction away from the medium 5 by contact of the restricting portions 54 of the brackets 50 with the stoppers 45 provided on the support members 41.
In this preferred embodiment, as illustrated in
In this preferred embodiment, a groove 35b extends along the circumferential direction in a portion of the center axis member 35a projecting from the bush 60. A retaining member 38 including, for example, a clip is inserted in the groove 35b. With the configuration described above, the floating bar 35 is supported to be rotatable with respect to the brackets 50.
In this preferred embodiment, a predetermined gap is provided between the inner hole 63 of the bush 60 and the center axis member 35a of the floating bar 35. In addition, a predetermined gap is also provided between the cylindrical portion 61 of the bush 60 and the insertion hole 51a of the bracket 50. In this manner, the floating bar 35 is freely fitted onto the brackets 50. In the floating bar 35, a center axis C35 of the floating bar 35 freely moves by a predetermined degree with respect to the brackets 50 or the tension bar 32. Although specifically described later, free movement of the floating bar 35 levels a tension on the medium 5 in the lateral direction. Consequently, floating of the medium 5 from the platen 11 is reduced or prevented.
In this preferred embodiment, gaps are preferably provided in both a space between the inner hole 63 of the bush 60 and the center axis member 35a and a space between the cylindrical portion 61 of the bush 60 and the insertion hole 51a of the bracket 50, but a gap may be provided in only one of these spaces.
The extending portions 53 are provided with the cushioning members 53a. The cushioning members 53a are attached to portions of the extending portions 53 that face the apron 12 and are to contact the apron 12. The cushioning members 53a are made of, for example, rubber. Each of the cushioning member 53a has a pad shape. When the brackets 50 and the floating bar 35 swing toward the medium 5, the brackets 50 might contact the apron 12. The cushioning members 53a are used to reduce an impact occurring when the brackets 50 contact the apron 12.
As illustrated in
The projecting portions 52 define and function as operation portions to be used to cause the floating bar 35 to swing. The projecting portions 52 are disposed radially outside not to overlap with the tension bar 32 and downstream of the floating bar 35 in the conveyance directions X, when seen in the rotation axis of the tension bar 32. The projecting portions 52 are located at the opposite side to the extending portions 53 with respect to the floating bar 35. The projecting portions 52 extend in parallel with the rotation axis of the tension bar 32. The projecting portions 52 extend toward the floating bar 35 from the body portions 51. The projecting portions 52 are formed by bending portions of metal plates defining the brackets 50 toward the floating bar 35. A predetermined gap is provided between each projecting portion 52 and the floating bar 35. The predetermined gap is large enough to allow an operator to insert his/her finger.
As described above, when the floating bar 35 and the brackets 50 are caused to swing toward the medium 5 to place the floating bar 35 on the medium 5, the floating bar 35 is located between the tension bar 32 and the platen 11. As illustrated in
The operator puts his/her fingers on the projecting portions 52 to move the floating bar 35 and the brackets 50 so that the floating bar 35 and the brackets 50 can be caused to swing in a direction away from the medium 5 placed on the platen 11 and the apron 12. In addition, the operator puts his/her fingers on the projecting portions 52 to move the floating bar 35 and the brackets 50 to cause the floating bar 35 and the brackets 50 to swing toward the medium 5. Since the brackets 50 include the projecting portions 52 as described above, the floating bar 35 can be caused to swing smoothly. The extending portions 53 or the projecting portions 52 may be disposed at the opposite side to the floating bar 35 with respect to the body portions 51.
In the case of printing with the printer 10 according to this preferred embodiment, as indicated by chain double-dashed lines in
Thereafter, the operator puts his/her fingers on the projecting portions 52 of the brackets 50 to pull down the brackets 50 rearward (toward the platen 11 in this preferred embodiment). Then, the brackets 50 are rotated down toward the platen 11 so that the floating bar 35 is brought into contact with the upper surface of the medium 5 as illustrated in
As described above, in this preferred embodiment, the printer 10 includes the platen 11 that supports the medium 5, the conveyance mechanism 20 that conveys the medium 5 supported by the platen 11 from the upstream side toward the downstream side in the conveyance directions X, the tension bar 32, and the floating bar 35, as illustrated in
In this manner, the floating bar 35 comes to be situated on the medium 5 located between the platen 11 and the tension bar 32. At this time, the floating bar 35 is allowed to push the medium 5 downward while freely moving, in accordance with a tension occurring in the medium 5. Accordingly, the medium 5 can be remain stretched by the floating bar 35, and thus, floating of the medium 5 from the platen 11 can be reduced or prevented.
Specifically, in this preferred embodiment, the floating bar 35 is brought into contact with the medium 5 floating between the platen 11 and the tension bar 32 while the floating bar 35 is placed on the medium 5 due to the weight of the floating bar 35. At this time, the medium 5 is pushed down, and the center axis C35 of the floating bar 35 freely moves by a predetermined degree. In this preferred embodiment, the movable tension bar 33 applies a tension to the medium 5.
In this preferred embodiment, in a case where parallelism between the tension bar 32 and the driving roller 21 is extremely high, the tension on the medium 5 is substantially uniform in the lateral direction. On the other hand, in a case where parallelism between the tension bar 32 and the driving roller 21 is not high, the tension on the medium 5 varies in the lateral direction. Parallelism between the tension bar 32 and the driving roller 21 is supposed to vary depending on the temperature. Elongation of the medium 5 is supposed to vary depending on the humidity. For this reason, even in a case where parallelism between the tension bar 32 and the driving roller 21 is simply increased, it is difficult to make uniform the tension on the medium 5 in the lateral direction. This variation in tension on the medium 5 in the lateral direction causes the elongation degree of the medium 5 in the conveyance directions X to vary so that the medium 5 warps. Consequently, the platen 11 easily floats. Floating of the medium 5 from the platen 11 is more conspicuous as the medium 5 becomes thinner (i.e., the medium 5 is more easily elongated). In addition, in a case where the driving rollers 21 and the pinching rollers 22 sandwich only both lateral ends of the medium 5, floating of the medium 5 tends to occur easily.
On the other hand, as described in this preferred embodiment, when the floating bar 35 whose center axis C35 is freely movable is placed on the upper surface of the medium 5 floating between the platen 11 and the tension bar 32 as a result of the weight of the floating bar 35, the medium 5 does not significantly warp in a portion of the medium 5 subjected to a large tension, whereas the medium 5 significantly warps in a portion of the medium 5 subjected to a small tension. Accordingly, variations in elongation degree of the medium 5 in the lateral direction are absorbed, and the tension on the medium 5 is levelled in the lateral direction. Thus, floating of the medium 5 from the platen 11 can be reduced or prevented. Since floating of the medium 5 is reduced or prevented, printing quality can be obtained.
As described above, in this preferred embodiment, in the state where a tension is applied by the movable tension bar 33 to the medium 5, the floating bar 35 rotates while applying tension to the upper surface of the medium 5 floating between the platen 11 and the tension bar 32 due to the weight of the floating bar 35 (predetermined weight in this preferred embodiment). At this time, the center axis C35 freely moves in the floating bar 35. A tension to be applied to the medium 5 by the movable tension bar 33 varies in the lateral direction of the medium 5 as long as the tension bar 32 and the driving rollers 21 are not parallel. In addition, as the medium 5 becomes thinner or is more easily elongated, the elongation degree in the conveyance directions X is more likely to vary in the lateral direction. Such a difference in elongation degree of the medium 5 can cause floating of the medium 5 from the platen 11.
On the other hand, as described in this preferred embodiment, when the floating bar 35 that is freely movable applies tension to the medium 5 floating between the platen 11 and the tension bar 32 due to the weight of the floating bar 35, the floating bar 35 pushes the medium 5 downward while freely moving, in accordance with a balance of a tension on the medium 5. Accordingly, a difference in elongation degree of the medium 5 in the conveyance directions X is absorbed so that a balance of tension on the medium 5 is levelled in the lateral direction. As a result, floating of the medium 5 from the platen 11 is reduced or prevented.
In this preferred embodiment, as illustrated in
In this preferred embodiment, the floating bar 35 includes the center axis member 35a projecting from the floating bar 35 in the axial direction (the scanning directions Y in this preferred embodiment). The center axis member 35a is freely fitted into the brackets 50 to be freely movable with respect to the brackets 50. Accordingly, the floating bar 35 is freely movable with a simple configuration so that tension balance of the medium 5 can be levelled.
In this preferred embodiment, the brackets 50 include the body portions 51 supported by the tension bar 32, and the restricting portions 54 provided in portions of the brackets 50 located at outer sides of the tension bar 32 relative to the body portions 51 when seen from an end of the tension bar 32 and downstream of the floating bar 35 in the conveyance directions X. The printer 10 includes the stoppers 45 disposed in rotation orbits of the restricting portions 54 at positions outside the tension bar 32 when seen from an end of the tension bar 32. The stoppers 45 are configured to contact the restricting portions 54 when the floating bar 35 and the brackets 50 rotate about the tension bar 32 and move in a direction away from the platen 11. Accordingly, even in a case where the brackets 50 and the floating bar 35 swing excessively, the contact of the restricting portions 54 with the stoppers 45 can restrict movement of the brackets 50 and the floating bar 35. The stoppers 45 are provided on the support members 41 in this preferred embodiment, but may be disposed at any location. For example, the stoppers 45 may be provided on portions of the printer 10, such as on the side frames 16.
In this preferred embodiment, as illustrated in
The printer 10 according to this preferred embodiment has been described above. The present teaching is not limited to the preferred embodiments disclosed herein, and various changes and modifications may be made within the gist of the present teaching. For example, in the preferred embodiments described above, the floating bar 35 rotates while being put on and contacting the upper surface of the medium 5 floating between the platen 11 and the tension bar 32. Alternatively, a biasing mechanism with which the floating bar 35 is pushed against the medium 5 may be provided. The biasing mechanism is capable of adjusting a weight under which the floating bar 35 pushes the medium 5 downward.
In the preferred embodiments described above, the restricting portions 54 of the brackets 50 are provided closer to the tension bar 32 than the projecting portions 52 in the radial direction of the tension bar 32, and project toward the stoppers 45 relative to the projecting portions 52. Alternatively, the restricting portions 54 may be disposed inside the projecting portions 52 as long as the restricting portions 54 are provided at the downstream side in the conveyance directions X. Alternatively, the projecting portions 52 may be used as the restricting portions 54, namely, the projecting portions 52 may contact the stoppers 45. In this case, the projecting portions 52 have both the operation function and the restriction function. As a result, the shape of the brackets 50 can be simplified.
While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.
