EP4610054A1

EP4610054A1 - Image forming apparatus

Info

Publication number: EP4610054A1
Application number: EP25159025.3A
Authority: EP
Inventors: Shu Umehara; Masahiro Mizuno
Original assignee: Ricoh Co Ltd
Current assignee: Ricoh Co Ltd
Priority date: 2024-02-29
Filing date: 2025-02-20
Publication date: 2025-09-03

Abstract

An image forming apparatus (10) includes a head (20Y, 20M, 20C, 20Y) to discharge a liquid, in a discharge direction, onto a medium having a shape of a web paper to form an image on the medium, a conveyor (15, 16, 17, 18) including position shifters (15, 16) to shift a position of a part of the conveyor in the discharge direction, and a detector (19) disposed upstream from the recording region in the conveyance direction, to detect thickness of the medium. The position shifters (15, 16) are at each position upstream from and downstream from of the recording region, and shift the position of the part of the conveyor from a first position to a second position farther from the first position from the head in the discharge direction based on a detection of the detector.

Description

BACKGROUND

Technical Field

Embodiments of the present disclosure relate to an image forming apparatus.

Related Art

An image forming apparatus that forms an image by discharging a liquid from a head onto a medium while conveying the medium having a long belt shape (e.g., continuous sheet or web paper) in the longitudinal direction by a conveyor (e.g., rollers) has been known (see FIG. 1E). Such an image forming apparatus is used so that multiple independent images can be printed in order in the longitudinal direction of the sheet.
A post-processor that performs post-processing on the printed continuous sheet is often disposed downstream from the image forming apparatus that prints the continuous sheet. The post-processor may be, for example, another image recorder that records an image on the back side of the sheet, a cutter that cuts the sheet, a folder that folds the sheet, or a half-cutter that cuts only a seal layer of the sheet including a backing layer and the seal layer. In such an image forming apparatus, some technologies have been known that when a splice portion (i.e., thicker portion) of a sheet reaches a recording head, the recording head is moved to a retracted position away from the sheet to avoid collision of the splice portion with the recording head (see Japanese Unexamined Patent Application Publication No. 2002-046260 , Japanese Unexamined Patent Application Publication No. 2017-177059 , and Japanese Unexamined Patent Application Publication No. 2016-144895 ).

SUMMARY

An object of the present disclosure is to enable an image forming apparatus to print without moving a recording head even while a thicker portion of a recording medium passes the recording head.
According to an embodiment of the present disclosure, an image forming apparatus includes a head to discharge a liquid, in a discharge direction, onto a medium having a shape of a web paper to form an image on the medium, and a conveyor including position shifters to shift a position of a part of the conveyor in the discharge direction, and a detector, disposed upstream from the recording region in the conveyance direction, to detect thickness of the medium. The conveyor conveys the medium to a recording region of the conveyor in a conveyance direction orthogonal to the discharge direction. The recording region faces the head. The position shifters are at each position upstream from and downstream from of the recording region. The position shifters shift the position of the part of the conveyor from a first position to a second position farther from the first position from the head in the discharge direction based on a detection of the detector, while the conveyor conveys the medium, and the head discharges the liquid onto the medium conveyed by the conveyor.
According to the present disclosure, the image forming apparatus can print without moving the recording head even while a thicker portion of a recording medium passes the recording head.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of embodiments of the present disclosure and many of the attendant advantages and features thereof can be readily obtained and understood from the following detailed description with reference to the accompanying drawings, wherein:

FIG. 1A is a schematic diagram illustrating an image forming apparatus according to an embodiment of the present disclosure, in which a splice portion of a sheet is detected by a sensor;
FIG. 1B is a schematic diagram illustrating the image forming apparatus of FIG. 1A in a state in which a predetermined gap is formed between the splice portion and a recording head by lowering a position shifter;
FIG. 1C is a schematic diagram illustrating the image forming apparatus of FIG. 1A in a state in which a predetermined gap is formed between a sheet and the recording head by lifting the position shifter after the splice portion has passed the recording head;
FIG. 1D is a schematic diagram illustrating the image forming apparatus of FIG. 1A in a state in which the sensor detects a lowering of the position shifter;
FIG. 1E is a schematic diagram illustrating an image forming apparatus according to a comparative example;
FIG. 2A is a perspective view of a position shifter;
FIG. 2B is an elevation view of the position shifter of FIG. 2A, moving upward;
FIG. 2C is an elevation view of the moving unit of FIG. 2A, moving downward;
FIG. 3A is a plan view of a splice portion;
FIG. 3B is a cross-sectional view of the splice portion of FIG. 3A;
FIG. 4 is an elevation view of a sensor that detects a splice portion;
FIG. 5 is a perspective view of an image forming apparatus that prints an image on a fabric;
FIG. 6A is a schematic diagram illustrating an image forming apparatus according to an embodiment of the present disclosure, in which a splice portion of a sheet is detected by a sensor;
FIG. 6B is a schematic diagram illustrating the image forming apparatus of FIG. 6A, in a state in which a predetermined gap is formed between the splice portion and a recording head by lowering an abutment;
FIG. 6C is a schematic diagram illustrating the image forming apparatus of FIG. 6A, in a state in which a returning position of an elevating roller is set by operating an abutment while the splice portion passes the recording head; and
FIG. 6D is a schematic diagram illustrating the image forming apparatus of FIG. 6A, in a state in which the elevating roller has returned and is waiting for the following printing.

The accompanying drawings are intended to depict embodiments of the present disclosure and should not be interpreted to limit the scope thereof. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted. Also, identical or similar reference numerals designate identical or similar components throughout the several views.

DETAILED DESCRIPTION

In describing embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this specification is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that have a similar function, operate in a similar manner, and achieve a similar result.
Referring now to the drawings, embodiments of the present disclosure are described below. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.
The image forming apparatus proposed in Japanese Unexamined Patent Application Publication No. 2002-046260 , Japanese Unexamined Patent Application Publication No. 2017-177059 , or Japanese Unexamined Patent Application Publication No. 2016-144895 cannot print while the recording head is moved to the retracted position. Accordingly, there is a problem that the post-processor is affected by the delay, and productivity is lowered or a waste sheet is generated. Further, there is also a problem that a long time is required for a returning operation that positions the recording head with high accuracy when the recording head is returned from the retracted position to the printing position.
An image forming apparatus 10 according to an embodiment of the present disclosure will be described below with reference to the drawings. As illustrated in FIGS. 1A to 1D, 2A, and 2B, the image forming apparatus 10 according to the present embodiment includes a supply roll 11 that supplies a continuous sheet P having a long belt shape as a medium (e.g., web paper) and a winding roll 12 that winds the printed continuous sheet P.
A main body 13 of the image forming apparatus 10 is disposed between the supply roll 11 at the upstream side and the winding roll 12 at the downstream side. A conveyor of the continuous sheet P is disposed in the main body 13 and includes an inlet roller, two elevating roller pairs 15 and 16 (i.e., position shifters), a guide roller 17, and an outlet roller 18. A hot air heater 21 that dries the printed continuous sheet P may be disposed between the guide roller 17 and the outlet roller 18.
The conveyor may include, for example, a conveyance motor and multiple rollers. However, the elevating roller pairs 15 and 16 may or may not have driving force. The elevating roller pairs 15 and 16 may include a roller for supporting a sheet or a platen roller.
A detector 19 is disposed between the inlet roller and the elevating roller 15 as a detector that detects the thickness of the sheet. The detector 19 is a sensor that detects a thicker portion of the sheet having a thickness larger than other portions, and is configured to detect a splice portion Pa of the continuous sheet P in the present embodiment.

Inkjet Head

A recording head includes four heads 20Y, 20M, 20C, and 20K (e.g., inkjet heads) disposed between the elevating roller pairs 15 and 16. These four heads 20Y, 20M, 20C, and 20K are arranged in a state where they are adjacent to each other in order from the upstream side to the downstream side in a conveyance direction of the continuous sheet P.
The order of the four heads 20Y, 20M, 20C, and 20K in the conveyance direction may be different from the order illustrated in FIG. 1A. A single monochrome printing head may be disposed in place of the four heads 20Y, 20M, 20C, and 20K.
The head 20Y is an inkjet head that discharges yellow ink. The head 20M is an inkjet head that discharges magenta ink. The head 20C is an inkjet head that discharges cyan ink. The head 20K is an inkjet head that discharges black ink.
When the four heads 20Y, 20M, 20C, and 20K are used, a full-color image can be recorded on a continuous sheet P. The four heads 20Y, 20M, 20C, and 20K have the same configuration.
The yellow ink, the magenta ink, the cyan ink, and the black ink are stored in a yellow ink tank, a magenta ink tank, a cyan ink tank, and a black ink tank, flow through a yellow ink flow path, a magenta ink flow path, a cyan ink flow path, and a black ink flow path, and are supplied to the head 20Y, the head 20M, the head 20C, and the head 20K, respectively. In FIG. 2A, the ink tanks and the ink flow paths for four colors are omitted.
Each of the heads 20Y, 20M, 20C, and 20K includes multiple nozzles. The multiple nozzles are disposed on a discharge surface, which is the lower surface, of each inkjet head.
The discharge surface is opposed to a conveyance surface of the continuous sheet P between the elevating roller pairs 15 and 16. The discharge surface is parallel to the conveyance surface.
The heads 20Y, 20M, 20C, and 20K are line-type inkjet heads. In the heads 20Y, 20M, 20C, and 20K of a line-type, multiple nozzles are arranged in the width direction of the continuous sheet P (i.e., the direction perpendicular to the plane on which FIG. 1A is illustrated).
The width direction is perpendicular to the conveyance direction. The width direction is perpendicular to the longitudinal direction of the continuous sheet P and coincides with the transverse direction of the continuous sheet P.
Multiple nozzle rows, each of which includes nozzles arranged in the width direction, may be arranged in the conveyance direction. The arrangement and number of the multiple nozzles can be appropriately determined in consideration of various conditions.

Elevating Rollers

Each of the elevating roller pairs 15 and 16 includes a pair of upper and lower rollers that put the continuous sheet P therebetween from above and below. The elevating roller pairs 15 and 16 support the continuous sheet P so as to be movable. As illustrated in FIG. 1E , roller pairs 15' and 16' of an image forming apparatus 10 according to a comparative example are not configured to be able to move up and down, but are configured to be able to retract the heads 20Y, 20M, 20C, and 20K above the continuous sheet P in order to avoid collision with the splice portion Pa.
Both ends of the shafts of the upper and lower rollers of the elevating roller pairs 15 and 16 are supported by four roller support plates 30 as illustrated in FIGS. 2A and 2B. The four roller support plates 30 are configured to simultaneously move up and down in synchronism with each other in the vertical direction (the direction of the arrow).
Accordingly, the continuous sheet P between the elevating roller pair 15 at the upstream side and the elevating roller pair 16 at the downstream side can move in parallel in up and down directions while the continuous sheet P is opposed to the lower surfaces (discharge surfaces) of the heads 20Y, 20M, 20C, and 20K.
The roller support plates 30 are coupled to an elevating unit such as a solenoid. The roller support plates 30 and the elevating roller pairs 15 and 16 are configured so as to move up and down in the arrow direction (i.e., vertical direction) in FIG. 2A based on the detection result of the detector 19.
In other words, the elevating roller pairs 15 and 16 are moving to an upper position (also referred to as normal position), which is an example of a first position, until the splice portion Pa of the continuous sheet P comes directly under the detector 19 as illustrated in FIG. 1A, and a predetermined gap suitable for flight of liquid droplets for printing is formed between the discharge surfaces of the heads 20Y, 20M, 20C, and 20K and the continuous sheet P. In this state, the recording region of the sheet is printed by the liquid droplets discharged from the heads 20Y, 20M, 20C, and 20K.
The splice portion Pa of the continuous sheet P passes just under the detector 19, and the elevating roller pairs 15 and 16 move to a lowered position (also referred to as separate position), which is an example of a second position, as illustrated in FIG. 1B. While the splice portion Pa passes through the heads 20Y, 20M, 20C, and 20K, the elevating roller pairs 15 and 16 are separated from the discharge surface of the heads 20Y, 20M, 20C, and 20K by the thickness of the splice portion Pa as an extra.
Even in this separate state, a predetermined gap suitable for the flight of liquid droplets is formed between the discharge surfaces of the heads 20Y, 20M, 20C, and 20K and the splice portion Pa of the continuous sheet P. Thus, the splice portion Pa of the continuous sheet P can be printed by the liquid droplets discharged from the heads 20Y, 20M, 20C, and 20K. Accordingly, while the elevating roller pairs 15 and 16 move to the separate position, the printing by the heads 20Y, 20M, 20C, and 20K can be continued while the continuous sheet P is conveyed at a constant speed.
The splice portion Pa of the continuous sheet P passes the heads 20Y, 20M, 20C, and 20K, and the elevating roller pairs 15 and 16 return to the upper position (also referred to as normal position), which is an example of the first position, as illustrated in FIG. 1C. Liquid droplets are discharged from the heads 20Y, 20M, 20C, and 20K on the continuous sheet P at the upstream side of the splice portion Pa, and the recording region of the sheet is printed.

Lower Stopper and Upper Stopper

As illustrated in FIGS. 2A and 2B, a lower stopper 40 as an example of a first stopper is disposed below the roller support plate 30, and an upper stopper 41 as an example of a second stopper are disposed above the roller support plate 30. In FIG. 2A, the lower stopper 41 is omitted.
The height positions of the lower stopper 40 and the upper stopper 41 can be determined in accordance with the thickness of the splice portion Pa. The roller support plate 30 abuts against the lower stopper 40 and the upper stopper 41 so that the elevating position of the roller support plate 30 is restricted.
In other words, in FIG. 1B, the lower position (also referred to as separate position) of the elevating roller pairs 15 and 16 is restricted by the lower stopper 40. Further, in FIG. 1C, the upper position (also referred to as normal position) of the elevating roller pairs 15 and 16 after the returning operation is restricted by the upper stopper 41.
In this way, the elevating positions of the elevating roller pairs 15 and 16 are restricted by the lower stopper 40 and the upper stopper 41 that are mechanical abutments, so that the elevating position of the elevating roller pairs 15 and 16 can be quickly positioned with high accuracy. In addition, the lower stopper 40 and the upper stopper 41 have a simple structure and can be disposed at a low cost.
According to the present embodiment, the retracting time of the elevating roller pairs 15 and 16 when the splice portion Pa passes the heads 20Y, 20M, 20C, and 20K can be shortened, and the productivity can be increased and the waste sheet can be reduced.
Further, since the heads 20Y, 20M, 20C, and 20K are not retracted in the configuration, printing can be continued even while the conveying roller pairs 15 and 16 are retracted, and, for example, a distinction marker of the post-processor can be printed on the splice portion Pa. In other words, as illustrated in FIGS. 3A and 3B, a sort mark SM and a cut mark CM can be printed on or near the splice portion Pa, and the post-processing such as sorting and sheet cutting is not affected by the delay.

Splice Portion

As illustrated in FIGS. 3 and 4, a splice portion Pa may be formed in a part of the long continuous sheet P along the conveyance direction. The splice portion Pa is a portion at which a seam between a rear end portion of the continuous sheet P1 at the downstream side and a front end portion of the continuous sheet P2 at the upstream side are connected by using an adhesive tape C.
Since the splice portion Pa is formed by attaching the adhesive tapes C on both sides of a pair of main surfaces of the continuous sheet P as illustrated in FIG. 4, the thickness Ts of the splice portion Pa is larger than the thickness Tp of the other portion (i.e., unspliced portion) of the continuous sheet P by the thickness of the adhesive tapes C. The image forming apparatus 10 according to the present embodiment is applied to an image forming apparatus using a continuous sheet P having such a splice portion Pa (i.e., seam) as a print medium.
In other words, when the splice portion Pa passes under the heads 20Y, 20M, 20C, and 20K, the splice portion Pa may rub and damage the heads 20Y, 20M, 20C, and 20K if the thickness Ts of the splice portion Pa in FIG. 4 is larger than the distance between the continuous sheet P and any one of the heads 20Y, 20M, 20C, and 20K. Thus, in the present embodiment, before the splice portion Pa passes under the heads 20Y, 20M, 20C, and 20K, the splice portion Pa is detected by the detector 19, and the position of the continuous sheet P is moved from the normal position in FIG. 1A to the separate position in FIG. 1B.

Detector of Thicker Portion

In the present embodiment, the detector 19 is disposed as a detector that detects a portion thicker than other portions of the sheet (i.e. thicker portion). The detector 19 is disposed upstream from the heads 20Y, 20M, 20C, and 20K. In the present embodiment, the detector 19 is disposed between the inlet roller 14 and the elevating roller 15.
The detector 19 may include, for example, a transmitter 19a and a receiver 19b that put the continuous sheet P therebetween from above and below as illustrated in FIG. 4. The splice portion Pa formed on the continuous sheet P can be detected in a non-contact manner by the transmitter 19a and the receiver 19b.
In other words, a signal such as a laser beam or an ultrasonic wave is transmitted from the transmitter 19a to the receiver 19b, and the thickness of the continuous sheet P intervening between the transmitter 19a and the receiver 19b can be detected in accordance with the reception state of the receiver 19b.
When the detector 19 detects the splice portion Pa, since the seam of the continuous sheet P is stuck with, for example, the adhesive tape C as illustrated in FIG. 4, a difference occurs between the thickness Tp of the normal portion (i.e., non-splice portion) of the continuous sheet P and the thickness Ts of the splice portion Pa. As a result, the difference between these thicknesses is detected as the splice portion Pa.
The detector 19 may be an optical sensor in addition to a sensor that detects the thickness of the continuous sheet P by the transmittance of a laser beam or an ultrasonic wave. In the case of an optical sensor, the thicker portion of the continuous sheet P is indirectly detected by detecting a splice mark printed in advance on the surface of the splice portion Pa with a reflective optical sensor.
Embodiments of the present disclosure have been described in detail above, but embodiments of the present disclosure are not limited to the embodiments described above, and various modifications may be made within the scope of the technical ideas described in the claims. For example, in order to confirm the completion of the elevation of the elevating roller pairs 15 and 16, the sensor 22 for measuring distance may be disposed as illustrated in FIG. 1D. The sensor 22 for measuring distance can reliably detect that the elevating roller pairs 15 and 16 are lowered to the separate position and are elevated to the normal position. When the completion of the elevation of the elevation roller pairs 15 and 16 cannot be confirmed, the sensor 22 for measuring distance generates an error signal, and image forming apparatus 10 can stop printing. Accordingly, the occurrence of waste sheet due to an error can be prevented.
The medium may be, for example, a fabric other than the continuous sheet P. FIG. 5 is a diagram illustrating an example of an image forming apparatus that forms an image on a fabric F as a medium. The heads 20Y, 20M, 20C, and 20K that are fixedly disposed on a horizontal base 53 can form a pattern Fa in the recording region on the upper surface of the fabric F.
The fabric F is conveyed in the conveyance direction indicated by the arrow by a pair of rollers 50 and 51 as a conveyor, a motor 52 that drives the roller 51, and a belt B wound around the rollers 50 and 51. The elevating roller pairs 15 and 16 are disposed on both sides of the heads 20Y, 20M, 20C, and 20 K in the conveyance direction. The belt B at the upper side and the fabric F are put between the elevating roller pairs 15 and 16 from above and below so that the belt B at the upper side and the fabric F are supported so as to be movable in the vertical direction.

Continuous Printing of Multiple-Type Sheets Having Different Thicknesses

In the case of continuous printing of a continuous sheet P in which multiple-type sheets (paper types) having different thicknesses are connected (i.e., spliced), the gaps between the continuous sheet P and the heads 20Y, 20M, 20C, and 20K (i.e., head gap) are adjusted so as to be an appropriate distance with the splice portion Pa of the sheet as a boundary. Thus, in the image forming apparatus 10 according to a comparative example illustrated in FIG. 1E, when different-type sheets (i.e., different splice portions Pa) arrive at the image forming apparatus 10, the continuous printing is once stopped, and the type of the sheet having arrived at the image forming apparatus 10 is again set as a new sheet type on the operation panel by a user (i.e., head gap readjustment).
However, in such a manner that adjustment is operated on an operation panel by a user one by one in accordance with the thickness of the new-type sheet, the printing stop time becomes longer and the productivity is lowered. Further, the operation panel may be mistakenly operated by a user.
In a modification of the above-described embodiment of the present disclosure, as illustrated in FIGS. 6A to 6D, a sheet thickness sensor 60 that continuously (i.e., online) detects the thickness of the sheet is disposed immediately upstream from the detector 19, in addition to the detector 19 that detects the splice portion Pa of the continuous recording sheet P. Further, the abutments 71 and 72 are disposed to be movable up and down with respect to the elevating roller pairs 15 and 16.
The abutments 71 and 72 may include, for example, a lower stopper 40 as an example of the first stopper and an upper stopper 41 as an example of the second stopper as illustrated in FIGS. 2A and 2B. The lower stopper 40 and the upper stopper 41 may be separately disposed in each of the abutments 71 and 72.
When the splice portion Pa of the continuous sheet P arrives at the position of the detector 19, the thickness of the splice portion Pa is detected by the detector 19, and the thickness of the continuous sheet P is also detected by the sheet thickness sensor 60. Various types of sensors can be used as the sheet thickness sensor 60. For example, as a non-contact type sensor, a capacitance-type sheet thickness sensor using a flat plate of a flat plate capacitor as a thickness detection sensing element, or a light-transmission-type sheet thickness sensor that measures the sheet thickness by the transmittance of light transmitted in the vertical direction through the continuous sheet P can be used.
As a contact-type sensor, a pair of conveying rollers that put the continuous sheet P therebetween from above and below can be used. One of the pair of conveying rollers is a driving roller whose shaft height is fixed, and the other is a driven roller whose shaft height varies according to the sheet thickness. The thickness of the continuous sheet P can be detected online by detecting the up-and-down movement of the driven roller with a displacement sensor.
The positions of the detector 19 and the sheet thickness sensor 60 may be reversed, so that the detector 19 may be disposed on the upstream side and the sheet thickness sensor 60 may be disposed on the downstream side. The detector 19 that detects the splice portion Pa of the continuous sheet P may be combined with (also used as) the sheet thickness sensor 60. As a result, the image forming apparatus 10 can reduce the size and cost.
When the splice portion Pa is approaching the head 20Y disposed at the most upstream side, the elevating roller pairs 15 and 16 are retracted in a direction father from the heads 20Y, 20M, 20C, and 20K (i.e., downward) as illustrated in FIGS. 6B and 6C. At the same time of the retraction of the elevating roller pairs 15 and 16, the abutments 71 and 72 can move up and down so that the head gap becomes constant in accordance with the thickness of the following sheet having a different thickness. For example, when the following new sheet has a thickness thicker than the previous sheet, the elevating roller pairs 15 and 16 can be lowered in the direction in which the distance between the heads 20Y, 20M, 20C, and 20K and the continuous sheet P is increased.
In typical, the adjustment of the head gap requires high-precision positioning using an encoder. According to the present embodiment, the elevating roller pairs 15 and 16 are retracted as illustrated in FIGS. 6B and 6C so that the returning positions of the elevating roller pairs 15 and 16 can be set quickly by operating the abutments 71 and 72 while the splice portion Pa passes the heads 20Y, 20M, 20C, and 20K.
Accordingly, as illustrated in FIG. 6D, the return operation of the elevating roller pairs 15 and 16 after the splice portion Pa has passed the heads 20Y, 20M, 20C, and 20K becomes faster, and the following printing can be resumed quickly. Thus, even when multiple sheets having different thicknesses are spliced together to form a continuous sheet P, the productivity of the image forming apparatus 10 is not reduced (i.e., downtime is reduced).

ASPECT

Aspects of the present disclosure are, for example, as follows.

First Aspect

An image forming apparatus that conveys a medium having a long belt shape in a longitudinal direction by a conveyor and forms an image on the medium includes a head disposed opposed to a recording region of the medium on a conveyance path, to form an image by discharging a liquid onto the medium reaching the recording region, a detector disposed upstream from the recording region, to detect a thicker portion of the medium than other portions, position shifters that are parts of the conveyor, are disposed upstream and downstream from the recording region, hold the medium movable, and are movable in a direction the medium and the head are opposed. The position shifters move from a first position (e.g., an upper position or normal position) to a second position (e.g., a lower position or separate position) away from the head by a thickness of the thicker portion while the thicker portion passes the recording region based on a detection result of the thicker portion by the detector, the head continues an image formation while the position shifters are at the second position, and the position shifters return from the second position to the first position after the thicker portion passes the recording region.

Second Aspect

The image forming apparatus according to the first aspect includes a first stopper disposed at the second position of the position shifters. When the position shifters move from the first position to the second position, the position shifters abut against the first stopper so that the second position of the position shifters is determined.

Third Aspect

The image forming apparatus according to the first or second aspect includes a second stopper disposed at the first position of the position shifters. When the position shifters move from the second position to the first position, the position shifters abut against the second stopper so that the first position of the position shifters is determined.

Fourth Aspect

The image forming apparatus according to any one of the first to third aspects includes a post-processor disposed downstream from the recording region in the longitudinal direction, and a distinction marker as a reference of post processing of the post-processor is formed by the head on the medium while the position shifters are at the second position.

Fifth Aspect

The image forming apparatus according to any one of the first to fourth aspects includes a sensor to detect the movement of the position shifters to the second position.

Sixth Aspect

The image forming apparatus according to any one of the first to fifth aspects includes a sensor to detect the returning of the position shifters to the first position.

Seventh Aspect

A image forming apparatus that conveys a medium connecting multiple-type sheets having different thicknesses in a long belt shape and forms an image on the medium includes a head disposed opposed to a recording region of the medium on a conveyance path, to form an image by discharging a liquid onto the medium reaching the recording region, a detector disposed upstream from the recording region, to detect a thickness of the medium, position shifters that are parts of the conveyor, are disposed at upstream and downstream from the recording region, hold the medium movable, and are movable in a direction in which the medium and the head are opposed. The head forms an image while the position shifters cause a gap between the head and the medium to be constant based on a detection result of the detector.

Eighth Aspect

The image forming apparatus according to the seventh aspect includes a first stopper to restrict a position at which the medium is farther from the head and a second stopper to restrict a position at which the medium is closing to the head.

Ninth Aspect

In the image forming apparatus according to the eight aspect, the first stoper and the second stopper are disposed to be movable in a direction in which the medium and the head are opposed, based on a detection result by the detector.

Tenth Aspect

In the image forming apparatus according to any one of the seventh to ninth aspects, the detector according to the seventh aspect to detect a thickness of the medium is combined with the detector according to the first aspect to detect the thicker portion.
The above-described embodiments are illustrative and do not limit the present invention. Thus, numerous additional modifications and variations are possible in light of the above teachings. For example, elements and/or features of different illustrative embodiments may be combined with each other and/or substituted for each other within the scope of the present invention. Any one of the above-described operations may be performed in various other ways, for example, in an order different from the one described above.

Claims

An image forming apparatus (10) comprising:
a head (20Y, 20M, 20C, 20K) to discharge a liquid, in a discharge direction, onto a medium having a shape of a web paper to form an image on the medium;

a conveyor (15, 16, 17, 18) including position shifters (15, 16) to shift a position of a part of the conveyor in the discharge direction, the conveyor to convey the medium to a recording region of the conveyor in a conveyance direction orthogonal to the discharge direction, the recording region facing the head; and

a detector (19), disposed upstream from the recording region in the conveyance direction, to detect thickness of the medium,
wherein the position shifters (15, 16) are at each position upstream from and downstream from of the recording region,
the position shifters shift the position of the part of the conveyor from a first position to a second position farther from the first position from the head in the discharge direction based on a detection of the detector,

while the conveyor conveys the medium, and

the head (20Y, 20M, 20C, 20K) discharges the liquid onto the medium conveyed by the conveyor.
The image forming apparatus (10) according to claim 1, further comprising:
a first stopper (40) at the second position on the position shifters (15 16), wherein the first stopper (40) contacts the part of the conveyor shifted from the first position to the second position to position the part of the conveyor at the second position.
The image forming apparatus (10) according to claim 1, further comprising:
a second stopper (41) at the first position on the position shifters (15, 16) wherein the second stopper (40) contacts the part of the conveyor shifted from the second position to the first position to position the part of the conveyor at the first position.
The image forming apparatus (10) according to claim 1, further comprising:
a post-processor downstream from the recording region in the conveyance direction to perform a post-processing on the medium,
wherein the head (20Y, 20M, 20C, 20Y) forms a distinction marker on the medium as a reference for the post-processing when the part of the conveyor is at the second position.
The image forming apparatus (10) according to claim 1,
wherein the position shifters includes:
a sensor (22) to detect that the part of the conveyor shifts to the second position.
The image forming apparatus (10) according to claim 5,
wherein the sensor (22) detects that the part of the conveyor returned to the first position from the second position.
The image forming apparatus (10) according to claim 1,
wherein the detector (19) detects a thicker portion of the medium than other portions of the medium.
The image forming apparatus (10) according to claim 7,
wherein the position shifters (15, 16) moves to a second position from the head (20K, 20C, 20M, 20Y) by the thicker portion from the first position based on a detection result of the thicker potion by the detector (19),
the head (20Y, 20M, 20C, 20Y) continues an image formation while the position shifters (15, 16) moves to the second position, and

the position shifters (15, 16) returns to the first position from the second position after the thicker portion passes the recording region.
The image forming apparatus (10) according to claim 1,
wherein the position shifters (15, 16) includes:
a first stopper (40) to restrict a position at which the medium is away from the head (20Y, 20M, 20C, 20K); and

a second stopper (41) restrict a position at which the medium is closing to the head (20Y, 20M, 20C, 20K),

the first stopper (40) and the second stopper (41) are disposed movable in a direction that the medium and the head are opposite.