JP2012006291A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus which hardly causes such a failure that peeling of paper from a plate cylinder is unstable to cause a curling-up phenomenon.SOLUTION: A stencil printing apparatus includes a compressed air generating means (20-26) discharging compressed air to the leading edge of the paper (27) pressed on an outer circumferential surface of the rotating plate cylinder (1), and a control means (28) controlling the compressed air generating means (20-26) such that discharge pressure of the compressed air may be constant regardless of printing speed. The compressed air generating means (20-26) is connected to a peeling pawl (14) through a hose (14a) in Fig.1.

Description

  The present invention relates to an image forming apparatus, and more particularly, to a paper discharge device of a stencil printing apparatus that peels a sheet pressed against a plate cylinder or the like.

  As related inventions of the present application that have been known prior to the filing of the present application, for example, there are inventions described in Patent Documents 1 and 2. As described in Patent Documents 1 and 2, the phenomenon of so-called roll-up, in which the paper pressed against the plate cylinder or the like remains stuck without peeling from the plate cylinder and becomes jammed without being peeled, has been a problem in the past. Known as.

  Paste a thermoplastic plate and a Japanese paper fiber or synthetic fiber of a porous support or a mixture of Japanese paper and synthetic fiber on a rotatable plate cylinder composed of a mesh screen of resin or metal mesh. Using a stencil master with a combined laminate structure, a master that has been punched and made in contact with a heating element of a thermal head is wound around a plate cylinder, and ink is supplied from an ink supply member provided inside the plate cylinder, 2. Description of the Related Art A thermal digital stencil printing apparatus that performs printing by continuously pressing a sheet of paper with a press roller or the like to cause ink to ooze out from a plate cylinder opening part or a master perforation part and transferring to a sheet is well known.

  The ink used in the stencil printing apparatus is a W / O type emulsion ink in which water or pigment is dispersed in oil so that it quickly permeates, decreases and dries when transferred to paper. . These inks have the characteristic that the fluidity changes depending on the temperature and the discharge amount from the opening through which the ink passes changes depending on the speed, and the amount of ink exuded when the temperature is high or when printing at low speed. In particular, with thin paper, peeling depends on the waist of the paper, so it sticks to the surface of the plate cylinder and the paper tip does not float, and the paper discharge claw of the peeling means is inserted between the paper and the plate cylinder. In this case, the paper peeling is unstable, and the paper is stuck in the gap between the peeling claw and the plate cylinder, which is slightly spaced from the master. There was a drawback that the phenomenon of rising was likely to occur.

  Therefore, a method is adopted in which air is discharged from the tip of the peeling claw for peeling the paper to improve the peeling of the paper (for example, Patent Document 1). Conventionally, a system has been adopted in which a piston and a cylinder, which are moved by the rotation of the main body, are discharged at a constant timing with a discharge pressure corresponding to the speed.

  The peak discharge pressure of the pump is set to a pressure that does not cause problems such as tearing of the thin film and soiling of the printing surface, and the discharge pressure varies depending on the speed as shown in FIG. If it is slow, the peeling force is weak, and even if it moves at a predetermined speed as the piston speed increases, there is a flow path resistance, etc., so even if it moves quickly, it is discharged while compressing the air confined inside strongly As the air pressure increases, the internal air is compressed and reduced, so that the air is discharged later than the moving speed of the piston. In some cases, the change in the discharge peak position with respect to the leading edge position of the paper becomes even larger, and the peeling ability of the leading edge of the paper from the plate cylinder is reduced.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an image forming apparatus in which problems such as paper peeling from a plate cylinder being unstable and winding up hardly occur.

  In order to achieve the above object, according to a first aspect of the present invention, there is provided, as a first aspect, compressed air generating means for discharging compressed air to the front end of a sheet pressed against the outer peripheral surface of a rotating plate cylinder, and printing speed. The image forming apparatus is characterized by comprising control means for controlling the compressed air generating means so that the discharge pressure of the compressed air becomes constant.

  According to the present invention, it is possible to provide an image forming apparatus in which problems such as unstable paper peeling from the plate cylinder and difficulty in winding up occur.

It is the schematic of the whole structure of embodiment (1st Embodiment) by this invention. It is a figure which shows the state at the time of paper (27) feeding in the apparatus of FIG. It is a figure which shows the structure of the means to generate | occur | produce compressed air in embodiment by this invention. It is a control block diagram of an embodiment according to the present invention. It is a figure which shows the discharge timing of the compressed air with respect to the rotational speed of the plate cylinder (1) in embodiment by this invention. It is the schematic of the whole structure of another embodiment (2nd Embodiment) by this invention. It is a figure for demonstrating the fluctuation | variation of the discharge pressure by speed, and the delay of the discharge timing accompanying it.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
1 and 2 are schematic views of the overall configuration of the stencil printing apparatus. FIG. 2 shows a state during feeding, and FIG. 1 shows other states.

First, the configuration of the plate making unit will be described.
The master (8) is wound around a roll (8a), and a roll core (8b) is rotatably supported by holder means provided on a plate making unit side plate (not shown). The master (8) is pressed against a platen roller (9) rotatably supported by a plate-making part side plate (not shown) by a thermal head (10) having an infinite number of heating elements, and a platen roller ( 9) is driven to rotate clockwise so that the master (8) is fed from the master roll (8a). The thermal head (10) is urged to the platen roller (9) by a spring member (not shown). On the downstream side of the platen roller (9), the upper and lower blades (guillotine type) or the rotary blade moving type cutter (11) for cutting the master (8) made into an appropriate length, and the plate making (not shown) A pair of transport rollers (12) rotatably supported while pressed against the side plate is provided, and the pair of transport rollers (12) is set at a speed higher than the peripheral speed of the platen roller (9), and the master (8). Appropriate tension is applied while sliding between the two. A master guide plate (13) for guiding the master (8) is provided between the plate making side plates (not shown) before and after the transport roller (12). These constitute the plate making section.

Next, the configuration of the plate cylinder (1) will be described.
On the lower right side of the plate-making part, a plate cylinder (1) constituted by winding a plurality of layers of a mesh screen made of a resin or metal mesh (not shown) covering the outer periphery of the porous support cylinder is provided with an ink pipe (5 ) Is fixed to a flange (not shown) rotatably supported by a support shaft, and a driving force is transmitted by a drive transmission means (gear or the like) (not shown) to be rotated in the clockwise direction. An ink roller (2) having an ink roller shaft rotatably supported by a side plate (not shown) fixed to the ink pipe (5) inside the plate cylinder (1) is provided with drive transmission means (gear, not shown). The belt) is driven to rotate in the same direction in synchronization with the plate cylinder (1). A doctor roller (3) is provided with a slight gap from the outer peripheral surface of the ink roller (2), and the ink in the ink reservoir (4) formed in the wedge-shaped space between the ink roller (2) and the doctor roller (3) A thin film is uniformly supplied to the outer surface of the ink roller (2). The ink in the ink reservoir (4) is sucked from an ink pack or the like provided outside the plate cylinder by an ink supply device (not shown), supplied to the ink reservoir (4) from the supply hole of the ink pipe (5), and kneaded. . A stage (6) made of a magnetic material is provided along the generatrix of the plate cylinder (1) on the surface of the non-opening portion of the plate cylinder (1). A clamper (7) is rotatably supported in parallel with the stage (6), and is opened and closed at a predetermined position by an opening / closing device (not shown). The plate cylinder (1) can be engaged and disengaged integrally with an ink pack or the like in its own axial direction.

Next, the structure of the means for pressing the paper (27) against the plate cylinder (1) will be described.
Under the plate cylinder (1), the shaft is rotated by a pair of an arm shaft (16a) rotatably supported by a housing side plate (not shown) and a press roller arm (16) fixed to the arm shaft (16a). A press roller (15) made of an elastic body as pressing means supported freely is provided. An arm (not shown) is fixed to the end of the arm shaft (16a). A rotatable cam follower is held by an arm (not shown), and is urged by a spring or the like to a cam that is rotatably supported by a housing side plate (not shown) and rotates in synchronization with the plate cylinder (1). The press roller (15) rotates while contacting the plate cylinder (1) when the paper (27) is fed (see FIG. 2). The press roller (15) is held at a position separated from the plate cylinder (1) by a locking means (not shown) except during feeding (see FIG. 1).

  On the right side of the press roller (15), there are a sheet feeding tray (not shown), a separation sheet feeding device for separating and feeding the stacked sheets (27) one by one, and a plate at the timing of the separated and fed sheets. A pair of registration rollers (17) is provided between the cylinder (1) and the press roller (15).

  On the left side of the plate cylinder (1), there is provided a peeling claw (14) that is pivotally supported and separates the paper (27) from the surface of the plate cylinder (1) in the vicinity of the plate cylinder (1). Yes. A nozzle portion (not shown) for ejecting compressed air is formed on the peeling claw (14), and a hose (14a) for introducing compressed air is connected thereto.

FIG. 3 shows a configuration of means for generating compressed air from the peeling claw (14).
A crank gear (23) is rotatably supported on a shaft implanted in a side plate or the like (not shown), and a drive gear (24) fixed to a shaft end of the pump drive motor (25) is engaged. A link (26) rotatably supported by the rotatable crank gear (23) is connected to a piston (21) moving inside the cylinder (20), and the piston (21) reciprocates inside the cylinder (20). The compressed air is discharged by moving. The piston (21) is provided with a known seal (22) that closes the cylinder (20) wall surface. Although not shown, a one-way valve for sucking into the cylinder when the piston (21) moves to the left side is provided on either the piston (21) or the cylinder (20).

Control of the means for generating compressed air shown in FIG. 3 will be described with reference to the control block diagram of FIG.
The pump drive motor (25) is operated by the control means (28) while rotating and stopping at every rotation of the plate cylinder at the maximum discharge pressure that does not damage the film surface of the master (8). Is driven to discharge at a predetermined position in synchronization with the rotation (printing speed). In the present embodiment, the rotational speed of the plate cylinder (1) is 30 rpm when the master (8) is wound around the plate cylinder (1) and is filled with ink immediately after being wound on the plate cylinder (1). It is set to a plurality of stages of 150 rpm. The compressed air is controlled at a predetermined leading end position of the sheet (27) conveyed from the nip portion between the plate cylinder (1) and the press roller (15) based on the control by the control means (28) of the pump drive motor (25). In response to this, it is ejected from the peeling claw (14). Further, the ejection of the compressed air is controlled so as to be blown into the gap between the plate cylinder (1) and the paper (27) by the control of the control means (28). In addition, the ejection position (at the peak pressure) is linked with the movement of the front end position of the paper cylinder (1) by moving the paper position in the front-rear direction of the image (referred to as printing position movement or vertical movement). It is controlled to be in the same position.

  The control means (28) receives a detection result by a plate cylinder position sensor (not shown), that is, information indicating which position the plate cylinder (1) has rotated. In addition, a detection result by a crank gear position sensor (not shown), that is, information indicating which position the crank gear (23) has rotated is input.

Refer to FIGS. 1 and 2 again.
The other end of the hose (14a) connected to the peeling claw (14) is connected to the cylinder (20). A peeling fan (19) for blowing air toward the paper (27) is provided above the peeling claw (14). A discharge tray (18) for discharging and stacking discharged sheets (27) is provided on the lower left side of the press roller (15).

Next, the operation of the stencil printing apparatus of this embodiment will be described.
A manuscript is set in a manuscript reading unit (not shown), and the plate cylinder (1) is rotated and used when an operator sets a speed, the number of sheets to be printed, and the top / bottom movement amount from an operation panel (not shown) and the start button is pressed The master is peeled off from the surface of the plate cylinder (1) and discarded, and is rotated and stopped until the clamper (7) is positioned almost directly above, and the clamper (7) is released to enter a plate feed standby state. The master (8) is sent by the thermal head (10) while the original is sent to the original reading unit and is transported by the platen roller (9) and the transport roller (12) via the plate making control device. Heat drilling is performed and plate making is performed.

  At this time, the drive timing per rotation of the plate cylinder (1) of the pump drive motor (25) is set by the control means (28) according to the input information from the panel described above. As shown in FIG. 5, for example, the maximum speed is continuously driven in synchronism with the rotation of the plate cylinder (1), and when the speed is low, the plate cylinder (1) is driven intermittently. It is controlled so as to be discharged. Further, the number of pulses for the sheet position with respect to the plate cylinder (1) is calculated from a plate cylinder pulse generating means (not shown) according to the printing position movement amount, and the discharge timing is controlled based on the calculation result.

  The master (8) made by plate making is guided between the stage (6) and the clamper (7) by the guide plate (13), and the clamper (7) is closed to sandwich the tip of the master (8). Winding is performed in such a manner that the rear end of the master (8) made by rotating the cylinder (1) is pulled out. When the winding of the master (8) of the plate cylinder (1) is completed, one sheet of paper (27) loaded by the paper feeder is fed and timed by the registration roller (17), It is conveyed toward (1) and the press roller (15). When the paper sensor (not shown) detects the passage of the paper (27), the locking means (not shown) is released, and the press roller (15) is rotated clockwise by the biasing force of the spring by a cam and a cam follower (not shown). Then, printing is performed by filling the master (8) support body with ink through the plate cylinder opening (1a) while also printing while continuously pressing the paper (27) against the plate cylinder (1).

  The paper (27) printed by being pressed against the plate cylinder (1) is moved away from the plate cylinder (1) by a peeling claw (14) and air discharged from a nozzle provided on the peeling claw (14). Continuously by a peeling fan (19) that floats from the surface of the cylinder (1) and blows in cooperation with the peeling claw (14) inserted into the gap between the floated paper (27) and the plate cylinder (1). The plate is peeled off from the surface of the plate cylinder (1), discharged and stacked on the discharge tray (18), and the master (8) is filled with ink.

  When the printing is completed, control is performed so as to have a predetermined discharge timing according to the speed information and the top-and-bottom movement information, and printing of the number of sheets is continuously performed.

  In this embodiment, in order to prevent a delay in internal compression at the rotational speed or a loss of the connecting portion, the rotation is stopped at every cycle at a predetermined rotational speed, and continuously according to the speed. Or, it is configured to be intermittently rotated and discharged from the nozzle at a constant discharge pressure regardless of the printing speed, so when the speed is low as in the past, only a low discharge pressure can be generated, so the peeling force cannot be gained Or, conversely, the discharge timing may be delayed as the speed increases, so that the disadvantage that the peeling point deviates from the optimum position and the peelability from the plate cylinder deteriorates is improved. . That is, it is difficult for problems such as paper peeling from the plate cylinder (1) to become unstable and roll up.

  In addition, since the discharge position is controlled to be the same according to the change in the front end position of the paper due to vertical movement or the like, the paper is delayed even though the paper comes out from the nip earlier than the conventional paper. In spite of this, there is no possibility that the ink is discharged early, even though it comes out late, so that the disadvantage that the peelability from the plate cylinder is lowered is improved.

(Second Embodiment)
In the first embodiment, the compressed air is discharged from the peeling claw (14), but the present invention is not limited to this. A specific other configuration will be disclosed as a second embodiment.

  FIG. 6 shows that the front and back side first and second side images are made in half before and after the plate cylinder (1), and after the first side printing of the paper (27), the switching guide (34) is turned counterclockwise. The front end of the paper (30) is guided by swinging, and the front end is guided by a moving guide (44) reciprocating near the press roller (15). 15) and the roller roller (45) are conveyed to the vicinity of the nip, and the paper (27) on which the first surface is printed is sent out at a predetermined timing, and the roller (45) presses the paper (27) against the press roller (15). The sheet is conveyed while returning the switching guide (34) to the initial position, and the sheet (27) on which the second surface that has passed through the nip portion between the press roller (15) and the plate cylinder (1) is printed is ejected. (30-33) Is another embodiment in which a similar air discharging unit to the switching claw (34) of the printing apparatus for printing on both sides. Also in this embodiment, the discharge timing is a predetermined position when the sheet (27) that has passed through the nip portion between the plate cylinder (1) and the press roller (15) is guided downward, as in the first embodiment. It is controlled to discharge.

  According to the second embodiment, the same effect as that of the first embodiment can be obtained.

DESCRIPTION OF SYMBOLS 1 Plate cylinder 1a Opening part 2 Ink roller 3 Doctor roller 4 Ink reservoir 5 Ink pipe 6 Stage 7 Clamper 8 Master 8a Master roll 8b Roll core 9 Platen roller 10 Thermal head 11 Cutter 12 Conveying roller 13 Guide plate 14 Peeling claw 14a Hose 15 Press roller 16 Press roller arm 16a Arm shaft 17 Registration roller 18 Paper discharge tray 19 Peeling fan 20 Cylinder 21 Piston 22 Seal 23 Crank gear 24 Drive gear 25 Pump drive motor 26 Link 27 Paper 28 Control means 30 Before paper discharge roller 31 Paper discharge After roller 32 Paper discharge belt 33 Paper discharge suction fan 34 Switching guide 40 Before transport roller 41 After transport roller 42 Transport belt 43 Transport suction fan 44 Movement guide 45 Roller roller 46 Bow guide

JP 2006-212982 A JP 2009-113458 A

Claims (4)

Compressed air generating means for discharging compressed air to the front end of the paper pressed against the outer peripheral surface of the rotating plate cylinder;
Control means for controlling the compressed air generating means so that the discharge pressure of the compressed air is constant regardless of the printing speed;
An image forming apparatus comprising:   The control means controls the compressed air generating means so that the discharge pressure becomes constant by driving the compressed air generating means continuously or intermittently according to the printing speed. The image forming apparatus according to claim 1. The compressed air generating means includes a piston that reciprocates in a cylinder, and generates the compressed air by pushing the air in the cylinder by the piston.
The image forming apparatus according to claim 1, wherein the control unit makes the discharge pressure constant by making a moving speed of the piston constant.   The control unit controls the discharge position so that the discharge position of the compressed air by the compressed air generation unit becomes appropriate with respect to a leading end portion of the paper. 4. The image forming apparatus according to any one of items 1 to 3.

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