JP2004106345A - Device for preventing floating of paper, and recording apparatus with the device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a paper float preventing device for regulating floating of a paper when a paper rear end separates from a nip point. <P>SOLUTION: In a paper transfer mechanism, the nip point 33 between a paper feed driving roller 15 and a paper feed driven roller 17, and a platen 25 are positioned to bend the paper P downward into a projection state when the paper held at the nip point contacts the platen. A paper regulating device 35 is set between a lower face of a printing head 21 at the downstream side in a paper transfer direction from the nip point 33, and an upper face of the platen 25, which has a paper regulating face 37 for preventing a paper upper face from contacting the printing head 21 as a result of floating of the paper when the rear end P2 of the paper separates from the nip point 33. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sheet floating prevention device for preventing a sheet from coming into contact with a recording head during conveyance of the sheet in a recording apparatus such as an ink jet recording apparatus, and a recording apparatus including the apparatus.
[0002]
[Prior art]
In a conventional ink jet recording apparatus, a paper feed roller including a paper feed driving roller and a paper feed driven roller is provided to transport a paper between a recording head and a platen provided below the recording head. When the paper is transported by the paper feed roller at an angle close to parallel to the upper surface of the platen, the front end of the paper is lifted upward and comes into contact with the lower surface of the recording head, and the recording surface (printing surface) of the paper. It caused problems such as fouling.
[0003]
Therefore, conventionally, when the paper held at the nip point between the paper feed driving roller and the paper feed driven roller is in contact with the platen, the nip point and the platen are positioned so that the paper bends in a convex state downward. Thus, the problem of floating of the front end of the paper has been solved by pressing the front end of the paper against the upper surface of the platen.
[0004]
[Problems to be solved by the invention]
However, when the configuration as described above is adopted, the support on the rear end side of the paper (clamping by the paper feed roller) is lost at the moment when the rear end of the paper leaves the nip point. The sheet is lifted upward in an attempt to return the bent sheet to a nearly flat shape. The floating of the trailing edge of the paper causes the paper gap, which is the distance between the recording surface of the paper and the facing surface of the recording head (the lower surface of the head) to fluctuate, resulting in a decrease in recording quality. Caused the recording surface to get dirty due to contact with the recording head.
[0005]
SUMMARY OF THE INVENTION An object of the present invention is to provide a sheet lifting prevention device that restricts the lifting of the trailing edge of the sheet when the trailing edge of the sheet leaves (displaces) the nip point of the sheet feeding roller, and a recording apparatus including the apparatus. .
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the sheet lift prevention device according to the first aspect of the present invention is configured such that when the sheet held at the nip point between the sheet feed driving roller and the sheet feed driven roller is in contact with the platen. The nip point and the platen are positioned so that the paper bends in a downwardly convex state, and the back of the paper is between the lower surface of the recording head and the upper surface of the platen in the paper transport direction downstream from the nip point. A sheet regulating device having a sheet regulating surface for preventing the upper surface of the sheet from coming into contact with the recording head due to the floating of the sheet when the end leaves the nip point is provided. .
[0007]
When the sheet is nipped at the nip point, the leading edge of the sheet is pressed onto the platen, and the sheet is forcibly conveyed forward in a state of being curved downward and convex. When the trailing edge of the paper leaves the nip point, the force that forcibly curves the paper downward is released, so the trailing edge of the paper becomes free and the paper tries to return to its original shape from the curved state. Trying to float upward.
According to the first aspect of the present invention, when the trailing edge of the paper leaves the nip point, the paper tends to float, and at this time, the paper restricting surface of the paper restricting device contacts the upper surface of the paper. Therefore, the lifting of the paper is regulated, and therefore, the fluctuation of the paper gap and the upper surface of the paper can be prevented from coming into contact with the recording head.
[0008]
According to a second aspect of the present invention, there is provided the sheet lift preventing device according to the first aspect, wherein the sheet regulating device is a rotatable roller, and the circumferential surface of the roller is a sheet regulating surface. It is what. According to the present invention, since the roller is driven to rotate along with the conveyance of the paper, it is possible to realize a smooth conveyance of the paper.
[0009]
According to a third aspect of the present invention, there is provided the sheet lift preventing device according to the first aspect, wherein the sheet regulating device has the curved sheet regulating surface guided while the upper surface of the sheet is slidably contacted. It is a member. According to the present invention, the lifting of the trailing edge of the sheet can be regulated with a relatively simple structure.
[0010]
In the paper lift prevention device according to the fourth aspect of the present invention, in the first aspect to the third aspect, the paper regulation surface is not in contact with the paper when the paper is held at the nip point. However, the rear end of the sheet is disposed at a height at which the sheet comes into contact when the sheet is lifted off the nip point.
[0011]
According to the present invention, when the sheet is held at the nip point, there is no difference from the conventional conveyance state, and stable sheet conveyance can be realized. On the other hand, when the trailing edge of the paper leaves (displaces) the nip point, the paper tries to return to its original shape from the curved state, but the paper tends to float upward. It stays in the gap with the paper transport path until then. Therefore, since it can be suppressed to the minimum paper lifting, it does not affect the paper gap fluctuation, and after the upper surface of the paper comes into contact with the paper regulation surface, further paper lifting is regulated. Contact of the upper surface of the sheet with the recording head is prevented.
[0012]
According to a fifth aspect of the present invention, there is provided a recording apparatus comprising the paper floating prevention device according to any one of the first to fourth aspects. According to the present invention, fluctuations in the paper gap and contact of the recording head on the upper surface of the paper can be prevented, so that high quality recording can be realized.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing an ink jet recording apparatus 1 which is one of recording apparatuses to which the paper floating prevention apparatus according to the present invention is applied, and FIG. 2 is a side sectional view of the ink jet recording apparatus 1. 3 is an enlarged perspective view of the main part of the ink jet recording apparatus, FIG. 4 is an enlarged plan view of the main part of the ink jet recording apparatus, and FIG. 5 is an enlarged perspective view of the main part of the ink jet recording apparatus. FIG. 6 is an enlarged side view of the main part of the ink jet recording apparatus, FIG. 7 is an explanatory view showing a paper transport state of the ink jet recording apparatus, and FIG. FIG. 7B shows the moment when the trailing edge of the sheet leaves the nip point.
[0014]
The ink jet recording apparatus 1 has a schematic configuration in which a paper feeding unit 5 is provided at the upper rear portion of the apparatus main body 3 and a paper discharge unit 7 is provided in front of the apparatus main body 3.
As shown in FIG. 2, a plurality of sheets P can be stacked on the sheet feeding tray 11 formed in the sheet feeding unit 5, and the sheet located at the top is provided immediately downstream of the sheet feeding tray 11. Since the outer peripheral surface of the paper feed roller 13 is in frictional contact, the sheet feeding roller 13 serves to feed out only one sheet in cooperation with the opposing separation pad.
[0015]
The paper fed from the paper feed tray 11 reaches a paper feed roller 19 composed of a lower paper feed drive roller 15 and an upper paper feed driven roller 17 provided for the main frame 9 of the printer body 3. The paper is fed toward the recording head 21 located downstream of the paper feed roller 19 while receiving a precise paper feed operation in the recording execution process by the drive system.
As shown in FIG. 3, the paper feed driven roller 17 is composed of eight roller elements 18 arranged at regular intervals in the present embodiment, and these roller elements 18 are placed on a holder 20 that tends to be biased downward. It is attached so that it can rotate freely.
[0016]
The recording head 21 is mounted on the carriage 23. The carriage 23 can reciprocate in a direction (main scanning direction) orthogonal to the paper feeding direction. A platen 25 is provided at a position facing the recording head 21, and the platen 25 is responsible for supporting the sheet from below when recording is performed on the sheet by the recording head 21.
[0017]
The distance between the recording head 21 and the sheet supported on the platen 25 from below, that is, the paper gap, is appropriately determined according to the thickness of the sheet by a conventionally known mechanism that moves the carriage 23 on which the recording head 21 is mounted. It can be adjusted. In a state where the paper gap is properly adjusted, the sheet passes through the platen 25 smoothly and high-quality recording is performed. The sheet that has been recorded by the recording head 21 is discharged. The paper is sequentially discharged by a paper discharge roller 27 provided in the section 7. The paper discharge roller 27 is composed of a lower paper discharge drive roller 29 and an upper paper discharge driven roller 31, and has a mechanism that the paper is pulled out and discharged by the rotational drive of the paper discharge drive roller 29. .
[0018]
The ink jet recording apparatus 1 has the above-described configuration, and the sheet floating prevention apparatus of the present invention will be specifically described below.
As best shown in FIG. 7A, the nip point 33 between the paper feed driving roller 15 and the paper feed driven roller 17 is 10 o'clock of the short hand of the watch as viewed from the center of rotation of the paper feed drive roller 15. Therefore, the sheet P is conveyed toward the recording head 21 while having a slightly downward component toward the tangential direction on the surface of the sheet feed driving roller 15 at the nip point 33. It is like that.
[0019]
Therefore, when the paper P is in contact with the upper surface 26 of the platen 25 in a state where the paper P is held at the nip point 33, the paper P is forcibly bent so as to protrude downward. As a result, the leading edge P1 of the sheet is always conveyed while being pressed against the upper surface 26 of the platen 25. This state continues until the trailing edge of the sheet comes off the nip point 33.
[0020]
A sheet regulating device 35 having a sheet regulating surface 37 is provided in the middle of the conveyance path of the sheet bent in a convex state in this way and downstream of the nip point 33 in the sheet conveyance direction. In the present embodiment, as shown in FIGS. 3 to 6, the paper regulating device 35 is in the form of a roller 36, and the roller 36 as the paper regulating device 35 is a roller element constituting the paper feed driven roller 17. It has the same length as the length of two of 18. The roller 36 is attached to a bearing (not shown) of the holder 20 in the same manner as the paper feed driven roller 17. That is, the roller 36 is held by the holder 20 so as to be rotatable around its rotation axis. Of the peripheral surface of the roller 36, the peripheral surface portion closest to the paper transport path functions as the paper regulating surface 37. In addition, since the roller 36 is rotatable, the entire circumferential surface of the roller 36 can actually be the sheet regulating surface 37.
[0021]
Such a sheet regulating surface 37 is located between the lower surface 22 of the recording head 21 and the upper surface 26 of the platen 25 on the downstream side in the sheet conveying direction from the nip point 33. Incidentally, the sheet regulating surface 37 of the sheet regulating apparatus 35 is preferably as close to the platen 25 side as possible and close to the upper surface 26 of the platen 25 in addition to such positional requirements. Is not essential in the present invention.
[0022]
The roller 36 is disposed at a position where the circumferential surface of the roller 36 is in contact with the upper surface of the sheet P bent in a convex state. The conveyance route to 26 is taken.
[0023]
FIG. 8 is a schematic side view of an essential part showing another embodiment of the present invention. The sheet restricting device 35 is not limited to the form of a roller, and may be a fixing member 39 having a sheet restricting surface 37 that smoothly curves downward toward the sheet conveyance path, for example, as shown in FIG. When the sheet regulating device 35 having such a form is employed, the upper surface of the sheet is guided to the platen 25 side while being in sliding contact with the sheet regulating surface 37. Note that the above-described roller 36 cannot be rotated, and the paper restricting device 35 having the paper restricting surface 37 in a fixed state can be provided.
[0024]
The sheet floating prevention device of the present invention has the above-described configuration, and its operation will be described below. In FIG. 6, the sheet P held at the nip point 33 is guided by the surface 37 after the leading end P <b> 1 abuts the vicinity of the sheet regulating surface 37 on the lower right side of the roller 36 in FIG. 6. Abuts on the upper surface 26. After that, since the paper P receives the forward driving force, the front end P1 of the paper P is curved in the horizontal direction on the upper surface 26 of the platen 25 as shown in FIG. It continues to be transported in a bent state. At this time, the upper surface of the paper P abuts on the paper regulation surface 37 of the roller 36, and the paper advances forward so as to be guided by the paper regulation surface 37 while rotating the roller 36 by friction with the paper. At this time, the paper P receives a biasing force that is forcibly pressed against the upper surface 26 of the platen 25.
[0025]
As shown in FIG. 7B, when the rear end P2 of the paper P is deviated from the nip point 33, the support on the rear end P2 side of the paper P is lost, so the bent paper P tries to return to the original state. The sheet tries to float upward. However, in the present invention, since the sheet regulating surface 37 of the roller 36 is in contact with the sheet P, the sheet P continues to be conveyed without being lifted.
As a result, since the fluctuation of the paper gap at the moment when the trailing edge P2 of the paper P deviates from the nip point 33 can be suppressed, the influence on the execution of recording can be minimized, and the upper surface of the paper P is the recording head 21. It is also possible to prevent contact with.
[0026]
Next, another embodiment of the sheet floating prevention device of the present invention will be described with reference to FIG. In the present embodiment, as in the above embodiment, a paper regulating device 35 in the form of a roller 36 is provided, and the paper regulating device 35 has a paper regulating surface 37 on its peripheral surface. In the present embodiment, the sheet regulating surface 37 (the circumferential surface portion of the circumferential surface of the roller 36 closest to the sheet conveyance path) is also downstream of the nip point 33 and the lower surface 22 of the recording head 21. Although positioned between the upper surface 26 of the platen 25, the sheet regulating surface 37 in this embodiment does not contact the sheet P when the sheet P is held at the nip point 33, but the sheet P This is different from the above-described embodiment in that the end P2 is disposed at a height at which the sheet P comes into contact when the sheet P is lifted off the nip point 33.
[0027]
According to such an embodiment, when the paper P is nipped at the nip point 33, it does not come into contact with the paper regulating surface 37, so that it is possible to realize a transport state that is not different from the conventional one and realize stable paper transport. can do. On the other hand, when the rear end P2 of the paper P leaves the nip point 33, the paper P is lifted upward in an attempt to return to the original shape from the bent state. However, since the sheet lifting distance is limited to the gap between the sheet regulating surface 37 and the sheet conveyance path up to that time, the sheet lifting can be suppressed to a minimum. Therefore, also in the present embodiment, there is no influence on the fluctuation of the paper gap. Further, after the upper surface of the paper P comes into contact with the paper regulation surface 37 due to the lifting, the further lifting of the paper is restricted, so that the contact of the upper surface of the paper with the recording head 21 is prevented.
[Brief description of the drawings]
FIG. 1 is a perspective view of an ink jet recording apparatus according to the present invention.
FIG. 2 is a side view of the ink jet recording apparatus.
FIG. 3 is an overall perspective view around a paper feed roller of the recording apparatus.
FIG. 4 is a plan view around a paper feed roller of the recording apparatus.
FIG. 5 is an enlarged perspective view around a paper feed roller of the recording apparatus.
FIG. 6 is a side view of the periphery of the paper feed roller of the recording apparatus.
FIGS. 7A and 7B are explanatory diagrams illustrating a sheet conveyance state of the recording apparatus, where FIG. 7A illustrates the start of conveyance of the leading edge of the sheet, and FIG. 7B illustrates a moment when the trailing edge of the sheet leaves the nip point.
FIG. 8 is a side view showing another embodiment of the sheet regulating device.
FIG. 9 is a side view showing another embodiment in which the position of the sheet regulating device is changed.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Inkjet type recording apparatus, 3 Apparatus main body, 5 Paper feed part 7 Paper discharge part, 9 Main frame, 11 Paper feed tray, 13 Paper feed roller 15 Paper feed drive roller, 17 Paper feed driven roller, 18 Roller element,
19 paper feed roller, 20 holder, 21 print head,
22 lower surface of print head, 23 carriage, 25 platen,
26 upper surface of platen, 27 paper discharge roller, 29 paper discharge drive roller,
31 Paper discharge serrated roller, 33 Nip point, 35 Paper restricting device, 36 roller, 37 Paper restricting surface, 39 Fixing member, P paper, P1 Front edge of paper,
Rear edge of P2 paper

Claims (5)

The nip point and the platen are positioned so that the paper is bent downwardly when the paper held at the nip point between the paper feed driving roller and the paper feed driven roller is in contact with the platen. At the same time, between the lower surface of the print head and the upper surface of the platen downstream of the nip point in the sheet transport direction, the print head on the upper surface of the sheet is caused by the floating of the sheet when the rear end of the sheet leaves the nip point. A paper lifting prevention device, characterized in that a paper regulation device having a paper regulation surface for preventing contact is provided. 2. The paper lifting prevention apparatus according to claim 1, wherein the paper restricting device is a rotatable roller, and a peripheral surface of the roller is a paper restricting surface. 2. The sheet lifting prevention apparatus according to claim 1, wherein the sheet regulating device is a fixed member having the curved sheet regulating surface guided while the upper surface of the sheet is in sliding contact. 4. The paper regulation surface according to claim 1, wherein the paper does not come into contact with the paper regulating surface when the paper is nipped at the nip point, but the rear edge of the paper leaves the nip point and the paper is lifted. A device for preventing paper floating, which is arranged at a height at which the paper sometimes contacts. A recording apparatus comprising the sheet lifting prevention device according to claim 1.

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