Multicolor stencil printer having pressing member holding devices

Abstract

A multicolor stencil printer including print drums each storing an ink of a particular color, pressing members each positioned and configured to move into contact with a particular one of the print drums to nip a recording medium for printing and move out of the contact to transport the recording medium toward downstream, and holding devices each assigned to a particular one of the pressing members for holding the particular one of the pressing members out of the contact with the particular one of the print drums, wherein in a color selective mode, the print drums and the pressing members selectively cooperate to nip the recording medium such that the holding devices assigned to unused pressing members hold the unused pressing members away from the print drums associated cooperatively with the unused pressing members.

Description

BACKGROUND OF THE INVENTION

The present invention relates to a stencil printer capable of printing a multicolor image on a paper or similar recording medium with a plurality of print drums.

A multicolor stencil printer of the type including a plurality of parallel print drums arranged in a direction of paper conveyance is conventional and taught in, e.g., Japanese Patent Laid-Open Publication No. 10-297073. In this type of printer, pressing members each are movable into and out of contact with a particular print drum. When each pressing member is pressed against the associated print drum with the intermediary of a paper or similar recording medium, the rotation of the print drum is transferred to a paper. As a result, an image is printed on the paper being conveyed by the print drum. The paper with the image is driven out to a print tray located at the most downstream side of the printer.

A problem with the above multicolor stencil printer is that even in a monocolor print mode, all the pressing members are pressed against the associated print drums and cause ink to be transferred from unused print drums to the corresponding pressing members and a paper. To solve this problem, it has been customary to wrap non-perforated stencils around the unused print drums and thereby prevent ink from depositing on the associated pressing members and paper. This is, however, undesirable from the cost standpoint because non-perforated stencils must be wrapped around the unused print drums every time the monocolor print mode is selected. Another problem is that because the print tray is located at the most downstream side in the direction of paper conveyance, sufficient conveying forces do not act on the paper when the pressing members are released from the print drums, resulting in defective paper conveyance.

Technologies relating to the present invention are also disclosed in, e.g., Japanese Patent Laid-Open Publication Nos. 1-290489, 3-55276, 6-32038, 7-17121, 10-305649, and 11-34467.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a multicolor stencil printer which does not require non-perforated stencils around unused print drums and thereby reducing the print cost.

It is another object of the present invention to provide a multicolor stencil printer capable of exerting a sufficient conveying force on a paper even when a pressing member does not press it and thereby obviating defective paper conveyance.

A multicolor stencil printer of the present invention includes a plurality of print drums each storing ink of particular color therein, a plurality of pressing members each being movable into and out of contact with a particular print drum, and a plurality of holding devices each being assigned to a particular pressing member. In a color selective print mode in which the print drums and pressing members selectively cooperate to nip a recording medium for printing an image, the holding devices associated with the pressing members unused in the above mode hold the pressing members at positions spaced from the associated print drums.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description taken with the accompanying drawings in which:

FIG. 1 is a view showing a multicolor stencil printer embodying the present invention;

FIG. 2 is an enlarged view showing a, pressing member, holding means and drive means included in the illustrative embodiment;

FIG. 3 is an enlarged view demonstrating the operation of the holding means and that of the pressing member;

FIG. 4 is an enlarged view showing the construction and operation of air sending means and a specific condition wherein a first drum is selected;

FIG. 5 is a block diagram schematically showing control means included in the illustrative embodiment;

FIG. 6 is a flowchart demonstrating a specific control procedure available with the control means;

FIG. 7 is an enlarged view showing another specific condition in which a second ink drum is selected;

FIG. 8 is a flowchart showing another specific control procedure available with the control means;

FIG. 9 is an enlarged view showing how the illustrative embodiment operates when one of the two print drums is absent;

FIG. 10 is a view showing an alternative embodiment of the present invention;

FIG. 11 is an enlarged view showing a pressing member, holding means and drive means assigned to each of a third and a fourth print drum included in the alternative embodiment;

FIG. 12 is an enlarged view showing arrangements around the first and second drums included in the alternative embodiment;

FIG. 13 is an enlarged view showing arrangements around the third and fourth drums included in the alternative embodiment;

FIG. 14 is a block diagram showing control means included in the illustrative embodiment;

FIGS. 15 through 19 are flowcharts demonstrating a specific control procedure available with the control means shown in FIG. 14 ; and

FIGS. 20 through 24 are flowcharts demonstrating another specific control procedure available with the control means shown in FIG. 14 .

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1 of the drawings, a multicolor stencil printer embodying the present invention is shown. As shown, the printer includes a printer body 100 accommodating first and second print drums 1 A and 1 B arranged in parallel in this order from the upstream side to the downstream side in a direction of paper conveyance X. The print drums 1 A and 1 B each store ink of a particular color thereinside. First and second press rollers 2 A and 2 B are also accommodated in the printer body 100 and movable into and out of contact with the print drums 1 A and 1 B, respectively. The printer is selectively operable in a multicolor mode or a color selective mode, as desired. In the multicolor mode, the print drum 1 A and press roller 2 A and the print drum 1 B and press roller 2 B each cooperate to nip a paper or similar recording medium 22 for printing a multicolor image thereon. In the color selective mode, either the print drum 1 A and press roller 2 A or the print drum 1 B and press roller 2 B nip the paper 22 for printing an image thereon in a desired color or colors. Control means 80 (see FIG. 5 ) sets up either the multicolor mode or color selective mode, as desired.

Conventional master making devices 3 A and 3 B, master discharging devices 4 A and 4 B, holding means 5 A and 5 B and air sending means 6 A, 6 B and 6 C are arranged around the print drums 1 A and 1 B, respectively. The holding means 5 A and 5 B respectively hold the press rollers 2 A and 2 B at positions spaced from the outer circumferences 1 a and 1 b of the print drums 1 A and 1 B (spaced positions hereinafter). Ink feeding means 7 A and 78 are arranged within the print drums 1 A and 1 B, respectively. The print drums 1 A and 1 B, press rollers 2 A and 2 B, master making devices 3 A and 3 B, master discharging devices 4 A and 4 B, holding means 5 A and 5 B, air sending means 6 A through 6 C and ink feeding means each are substantially identical in construction and operation and will be simply distinguished by the addition of suffices A, B and C.

The printer includes a scanner, not shown, mounted on the upper portion of the printer body 100 for reading a document. A CCD (Charge Coupled Device) image sensor or similar image sensor, not shown, photoelectrically transforms an imagewise reflection from the document to an electric image signal. An analog-to-digital converter, not shown, digitizes the electric image signal and selectively sends the resulting digital signal to the master making device 3 A or 3 B. The master making device 3 A or 3 B perforates a stencil with a conventional thermal head, not shown, in accordance with the digital image signal, thereby making a master 8 A or 8 B. The master 8 A and 8 B are conveyed toward the outer circumferences 1 a and 1 b of the print drums 1 A and 1 B, respectively. Clampers 9 A and 9 B are mounted on the outer circumferences 1 a and 1 b of the print drums 1 A and 1 B, respectively. The dampers 9 A and 9 B each clamp the leading edge of the respective master 8 A or 8 B. The print drum 1 A or 1 B is rotated to wrap the master 8 A or 8 B, respectively, around the outer circumference 1 a or 1 b . When a new master is to be made after the previous printing operation, the master discharging devices 4 A and 4 B respectively peel off the used masters 8 A and 8 B wrapped around the print drums 1 A and 1 B and collect them in boxes 4 A and 4 B. The control means 80 controls the various devices including the master making devices 3 A and 3 B and master discharging devices 4 A and 4 B via drive sections that will be described specifically later.

The print drums 1 A and 1 B each have a conventional porous, cylindrical configuration. The print drums 1 A and 1 B are rotatably mounted on drum shafts 35 A and 35 B, respectively. Frames 36 A and 36 B are removably mounted on the printer body 100 and support opposite ends of the drum shafts 35 A and 35 B, respectively. The print drums 1 A and 1 B are therefore removable from the printer body 100 . The print drums 1 A and 1 B are interconnected by a gear train, a belt and pulley device or similar conventional power transmission mechanism. A drum motor 68 (see FIG. 5 ) is drivably connected to the power transmission mechanism in order to cause the print drums 1 A and 1 B to rotate in the clockwise direction, as viewed in FIG. 1 , or printing direction. The control means 80 controls the print drum motor 68 in order to control the speed and direction of rotation of the print drums 1 A and 1 B. Specifically, the print drums 1 A and 1 B each are rotated clockwise at a higher speed during printing than during the interval between a master feeding operation and a master adhering operation.

Papers 22 are stacked on an elevatable tray 10 located at the most upstream side in the direction of paper conveyance X. A pickup roller 11 , a pair of separator rollers 12 and 13 and a separator plate 14 cooperate to pay out the top paper 22 from the tray 10 while separating it from the underlying papers 22 . The paper 22 paid out from the tray 10 is conveyed toward a registration roller pair 17 while being guided by guides 15 and 16 . The registration roller pair 17 conveys the paper 22 at a preselected timing. The press roller 2 A and print drum 1 A define a print position 18 therebetween while the press roller 2 B and print drum 1 B define a print position 19 therebetween. The paper 22 conveyed by the registration roller pair 17 is sequentially routed through the above print positions 18 and 19 to a print tray 20 located at the downstream side in the direction of paper conveyance X. The control means 80 causes the pickup roller 11 , separator rollers 12 and 13 and registration rollers 17 to rotate via drive sections that will be described specifically later. Particularly, after the master 8 A or 8 B has been wrapped around the print drum 1 A or 1 B, the control means 80 causes the above rollers to feed a single paper 22 in order to bring the master 8 A or 8 B into close adhesion to the drum 1 A or 1 B.

A conveyor 21 extends between the two print positions 18 and 19 and forms a paper conveyance path between the print drums 1 A and 1 B. Guides 23 and 24 respectively precede and follow the conveyor 21 . A paper discharging device 25 is positioned between the print position 19 and the tray 20 . The conveyor 21 includes a porous belt 28 passed over a drive roller 26 and a driven roller 27 , and a suction fan 29 positioned below the belt 28 . While the belt 28 is caused to turn counterclockwise, as viewed in FIG. 1 , the suction fan 29 exerts a sucking force on the upper surface of the belt 28 . The conveyor 21 is so configured as to convey the paper 22 coming out of the print position 18 to the downstream side in the direction X, i.e., the print position 19 while retaining the paper 22 on the belt 28 by suction.

The paper discharging device 25 includes a porous belt 32 passed over a drive roller 30 and a driven roller 31 , and a suction fan 33 positioned below the belt 32 . While the belt 32 is caused to turn counterclockwise, as viewed in FIG. 1 , the suction fan 33 exerts a sucking force on the upper surface of the belt 32 . The paper discharging device 25 is so configured as to convey the paper 22 coming out of the print position 19 toward the tray 20 while retaining the paper 22 on the belt 32 by suction. The control means 80 controls the operation of the conveyor 21 and paper discharging device 25 via drive sections that will be described specifically later.

Peelers 34 A and 34 B are respectively positioned above the conveyor 21 and paper discharging device 25 in order to remove the paper 22 from the print drums 1 A and 1 B. The peelers 34 A and 34 B each have a comb-like configuration and extend in the widthwise direction of the paper 22 . The air sending means 6 B and 6 C respectively send air toward positions around the print positions 18 and 19 .

The ink feeding means 7 A includes an ink roller 37 A and a doctor roller 38 A arranged within the print drum 1 A and forming an ink well 39 A therebetween. The rollers 37 A and 38 A are rotated to feed ink from the ink well 39 A to the inner periphery of the print drum 1 A while kneading it. Likewise, the ink feeding means 7 B includes an ink roller 37 B and a doctor roller 38 B arranged within the print drum 1 B and forming an ink well 39 B therebetween. The rollers 37 B and 38 B operate in the same manner as the rollers 37 A and 38 A except that they feed ink to the inner periphery of the print drum 1 B. The drum shafts 35 A and 35 B each are formed with a plurality of holes in the axial direction and communicated to a particular ink pack storing ink of a particular color via a respective ink pump. In this sense, the drum shafts 35 A and 35 B play the role of ink feed pipes. Ink of a particular color is fed from each of the drum shafts 35 A and 35 B to the ink well 39 A or 39 B, respectively. In the illustrative embodiment, black ink and red ink are respectively fed to the ink wells 39 A and 39 B when ink in the ink wells 39 A and 39 B is consumed.

The holding means 5 A includes an arm 40 A supporting the press roller 2 A such that the roller 2 A is movable into and out of contact with the print drum 1 A. A stop 41 A is engagable with the arm 40 A. A tension spring or biasing means 42 A constantly biases the stop 41 A in a direction in which the stop 41 A engages with the arm 40 A. A first electromagnetic solenoid or actuator 43 A moves the stop 41 A away from the arm 40 A. Likewise, the holding means 5 B includes an arm 40 B supporting the press roller 2 B such that the roller 2 B is movable into and out of contact with the print drum 1 B. A stop 41 B is engageable with the arm 40 B. A tension spring or biasing means 42 B constantly biases the stop 41 B in a direction in which the stop 41 B engages with the arm 40 B. A second electromagnetic solenoid or actuator 43 B moves the stop 41 B away from the arm 40 B.

As shown in FIG. 2 , the arms 40 A and 40 B each are generally L-shaped and pivotally supported by a shaft 44 A or 44 B at its bend portion. The shafts 44 A and 44 B are affixed to the printer body 100 . The press rollers 2 A and 2 B are respectively rotatably supported by one end 401 A and 401 B of the arms 40 A and 40 B via shafts 45 A and 45 B. Rollers 46 A and 46 B are respectively rotatably mounted on the other ends 402 A and 402 B of the arms 40 A and 40 B. Tension springs 47 A and 47 B are respectively anchored to the above ends 402 A and 402 B at one end thereof, constantly biasing the arms 40 A and 40 B clockwise and exerting pressures on the print drums 1 A and 1 B, respectively. The other ends of the tension springs 47 A and 47 B are anchored to the printer body 100 .

The rollers 46 A and 46 B are respectively pressed against the contours of cams 48 A and 48 B. The cams 48 A and 48 B respectively move the outer circumferences 2 a and 2 b of the press rollers 2 A and 2 B into and out of contact with the outer circumferences 1 a and 1 b of the print drums 1 A and 1 B. The cams 48 A and 48 B are respectively rotated in synchronism with the print drums 1 A and 1 B via link mechanisms not shown. The cam 48 A has a profile configured such that when the damper 9 A passes the print position 18 , the circumference 2 a of the press roller 2 A is spaced from the circumference 1 a of the print drum 1 A. The cam 48 B has the same profile as the cam 48 A except that it releases the circumference 2 b of the press roller 2 B from the circumference 1 b of the print drum 1 B when the damper 9 B passes the print position 19 . More specifically, the arm 40 A is mounted on the shaft 44 A in such a manner as to move the press roller 2 A between a position where the roller 2 A is spaced from the print drum 1 A ( FIG. 2 ; spaced position hereinafter) and a position where the former is pressed against the latter (solid line in FIG. 3 ). Likewise, the arm 40 B is mounted on the shaft 44 B in such a manner as to move the press roller 2 B between a position where the roller 2 B is spaced from the print drum 1 B ( FIG. 2 ) and a position where the former is pressed against the latter (solid line in FIG. 3 ). The press rollers 2 A and 2 B each press the paper 22 against the associated print drum 1 A or 1 B in order to transfer an image to the paper 22 .

Pins 49 A and 49 B are studded on the arms 40 A and 40 B, respectively. As shown in FIG. 2 , the stops 41 A and 41 B are located in the vicinity of the arms 40 A and 40 B, respectively, with their base ends 41 a and 41 b respectively angularly movably supported by the printer body 100 . The stops 41 A and 41 B have free ends 41 c and 41 d thereof bent at substantially right angle. When the arms 40 A and 40 B move to release the press rollers 2 A and 2 B from the print drums 1 A and 1 B, respectively, the stops 41 A and 41 B abut against the pins 49 A and 49 B, respectively. A tension spring 42 A is anchored at one end to the printer body 100 and at the other end to the stop 41 A, constantly biasing the stop 41 A toward the pin 49 A. Likewise, a tension spring 42 B is anchored at one end to the printer body 100 and at the other end to the stop 41 B, constantly biasing the stop 41 B toward the pin 49 B.

The first and second solenoids 43 A and 43 B have plungers 50 A and 50 B, respectively, pinned to the stops 41 A and 41 B, respectively. The solenoids 43 A and 43 B are of the type pulling the plungers 50 A and 50 B, respectively, when energized. Specifically, when the solenoids 43 A and 43 B each are energized, it pulls the stop 41 A or 41 B against the action of the associated tension spring 42 A or 42 B from a catch position indicated by a dash-and-dots line in FIG. 3 to a release position indicated by a solid line in FIG. 3 .

As shown in FIG. 2 , pulleys 51 A and 51 B are respectively mounted on one side of the press rollers 2 A and 2 B via one-way clutches 69 A and 69 B. The one-way clutches 69 A and 69 B transfer rotation only from the pulleys 51 A and 51 B to the press rollers 2 A and 2 B, respectively. Double pulleys 52 A and 52 B are rotatably mounted on the shafts 44 A and 44 B, respectively. Belts 53 A and 53 B are respectively passed over the pulleys 51 A and 51 B and double pulleys 52 A and 52 B. A first and a second drive motor or drive means 54 A and 54 B have output shafts 55 A and 55 B, respectively, on which drive pulleys 56 A and 56 B are mounted. Drive belts 57 A and 57 B are respectively passed over the double pulleys 52 A and 52 B and drive pulleys 56 A and 56 B. The output shafts 55 A and 55 B of the drive motors 54 A and 54 B each are rotatable counterclockwise, as viewed in FIG. 2 , under the control of the control means 80 .

In the above construction, when the drive motor 54 A or 54 B is driven, it causes the associated press roller 2 A or 2 B to rotate counterclockwise, i.e., in a direction opposite from the direction in which the print drum 1 A or 1 B rotates during printing. When the press roller 2 A or 2 B is brought into contact with the associated print drum 1 A or 1 B while the drive motor 54 A or 54 B is deenergized, the press roller 2 A or 2 B is caused to rotate by the print drum 1 A or 1 B via the associated one-way clutch 69 A or 69 B.

Referring again to FIG. 1 , the air sending means 6 A is positioned at the right-hand side of the first print drum 1 A. The air sensing means 6 B is positioned between the first print drum 1 A and the second print drum 1 B. Further, the air sending means 6 C is positioned at the left-hand side of the second print drum 1 B. The air sending means 6 A, 6 B and 6 C respectively have fans 58 A, 58 B and 58 C for generating air streams, fan motors 59 A, 59 B and 59 C, and paths 60 A, 60 B and 60 C for respectively guiding air streams generated by the fans 58 A, 58 B and 58 C to the vicinity of the print positions 18 and 19 .

As best shown in FIG. 4 , the path 60 A is formed by a duct 62 A extending from a case 61 A accommodating the fan 58 A toward the print position 18 . The duct 62 A has an air outlet 63 A at its lower end. This air outlet 63 A faces a paper conveyance path 64 intervening between the registration roller pair 17 and the print position 18 . Therefore, the air stream generated by the fan 58 A is sent to the range between the above path 64 and the print position 18 from the upstream side in the direction of paper conveyance X. The path 60 A has a sectional area sequentially decreasing toward the air outlet 63 A in order to increase the flow rate of air around the air outlet 63 A.

The path 60 C is formed by a duct 62 C extending from a case 61 C accommodating the fan 58 C toward the print position 19 . The duct 62 C has an air outlet 63 C at its lower end. The air outlet 63 C faces the upper surface of the peeler 34 B and sends the air stream generated by the fan 58 C to the range between a paper conveyance path 65 underlying the peeler 34 B and the print position 19 from the downstream side. The path 60 C also has a sectional area sequentially decreasing toward the air outlet 63 C in order to increase the flow rate of the air stream around the air outlet 63 C.

The path 60 B is formed by a duct 62 B extending from a case 61 B accommodating the fan 58 B toward the belt 28 of the conveyor 21 . The duct 62 B is bifurcated and has two air outlets 63 B a and 63 B b at its lower end. The air outlet 63 B a faces the upper surface of the peeler 34 A and sends the air stream generated by the fan 58 B to the range between a paper conveyance path 66 extending between the peeler 34 A and the belt 28 and the print position 18 from the downstream side. The other air outlet 63 B b faces a paper conveyance path 67 formed by the belt 28 and guide 24 and sends the air stream generated by the fan 58 B to the range between the above path 67 and the print position 19 from the upstream side in the direction X.

The ducts 62 A through 62 C are affixed to the printer body 100 , and each has a width slightly greater than the axial length of associated one of the print drums 1 A and 1 B. The ducts 62 A through 62 C each are curved along the contours 1 a or 1 b of the adjoining print drum 1 A or 1 B and so positioned as not to contact the damper 9 A or 9 B when the print drum 1 A or 1 B rotates.

As shown in FIG. 5 , the illustrative embodiment includes a control panel 70 on which the following keys and display are arranged. Numeral keys 71 are used to input a desired number of prints. A print start key 72 is pressed to start producing a desired number of prints. A perforation start key 73 is pressed to start a sequence of steps of document reading, master making, master feeding, and master adhering. A color selective mode key 74 and a multicolor mode key 75 , constituting print mode selecting means in combination, are pressed to select the color selective mode and multicolor mode, respectively. A first drum key 76 and a second drum key 77 , constituting drum selecting means in combination, are pressed to select the first print drum 1 A and second print drum 1 B, respectively. A display 78 , which is implemented by an LCD (Liquid Crystal Display), displays the number of prints input on the numeral keys 71 , the number of remaining prints, drum selection information, print mode, and so forth.

The control means 80 is implemented by a conventional microcomputer including a CPU (Central Processing Unit) 81 , a ROM (Read Only Memory) 82 and a RAM (Random Access Memory) 83 connected by a signal bus not shown. The various keys and display of the control panel 70 are connected to the CPU 81 . Also connected to the CPU 81 are power supply 79 , a perforation driver 84 for driving the master making devices 3 A and 3 B, a master discharge driver 85 for driving the master discharging devices 4 A and 4 B, a paper feed driver 86 for driving the pickup roller 11 and separator rollers 12 and 13 , a conveyor driver 87 for driving the conveyor 21 , and a paper discharge driver 88 for driving the paper discharging device 25 . Further connected to the CPU 81 are the drum motor 68 , first and second solenoids 43 A and 43 B, first and second drive motors 54 A and 54 B and fan motors 59 A through 59 C as well as a first and a second drum sensor or drum sensing means 89 and 90 .

As shown in FIG. 1 , the first and second drum sensors 89 and 90 are implemented by switches mounted on the print body 100 and facing the first and second print drums 1 A and 1 B, respectively. When the print drums 1 A and 1 B are mounted to the printer body 100 , the sensors 89 and 90 , respectively, turn on.

The ROM 82 stores the color selective mode, the multicolor mode, a first color mode and a second color mode belonging to the color selective mode, and a master making program beginning with the perforation of the stencil and ending with the adhesion of the master and triggered by the perforation start key 73 . In addition, the ROM 82 stores a printing program triggered by the print start key 72 for repeating a printing cycle a number of times corresponding to the desired number of prints, a control program for controlling, based on the print modes, the positions and drive of the press roller 2 A and 2 B, the positions of the print drums 1 A and 1 B, and the air sending means 6 A through 6 C.

In the color selective mode, the printer executes the discharge of a used master and the feed of a new master with only one of the print drums 1 A and 1 B selected and executes printing with the drum 1 A or 1 B selected. Specifically, in the illustrative embodiment, when the color selective mode is selected, monocolor printing is effected by using either the print drum 1 A or the print drum 1 B. In the multicolor mode, the discharge of a used master and the feed of a new master are effected with both of the two print drums 1 A and 1 B, and multicolor printing is executed by using the two print drums 1 A and 1 B. Further, in the first color mode, the discharge of a used master and the feed of a new master are effected with the print drum 1 A only, so that monocolor printing is performed with the print drum 1 A. This is also true with the second color mode except that only the print drum 1 B is used.

Reference will be made to FIGS. 6 and 8 for describing a specific operation of the above printer, particularly control over the press rollers 2 A and 2 B and air sending means 6 A through 6 B executed by the controller 80 in each of the print modes.

First, the operator of the printer presses the color selective mode key 74 or the multicolor mode key 75 to select desired one of the color selective mode and multicolor mode. The operator then presses the first drum-key 76 or the second drum key 77 to designate the print drum 1 A or 1 B to use, and then presses the perforation start key 73 . In response, the master making program starts to execute the master discharging, master making and master adhering steps. After the master adhering step, the operator presses the print start key 72 , so that the printing program starts.

A procedure shown in FIG. 6 starts in parallel with the master making program or the printing program when the key 73 or 72 , respectively, is pressed. As shown, the controller 80 reads print mode information input by the operator (step A 1 ) and then determines a print mode (step A 2 ). If the color selective mode is selected on the key 74 (Yes, step A 2 ), the controller 80 advances to a step A 3 the answer of the step A 2 is No, the controller 80 ends the procedure, determining that the multicolor mode is selected.

The controller 80 determines the statuses of the first drum key 76 and second drum key 77 (steps A 3 and A 4 ). If the first drum key 76 is in an ON state (Yes, step A 3 ), the controller 80 determines that the first print drum 1 A is selected, turns on the first solenoid 43 A (step A 5 ), turns on the second drive motor 54 B (step A 6 ), turns on the fan motors 59 A through 59 C (step A 7 ), and ends the procedure.

When the solenoid 43 A is energized, the stop 41 A is brought to the release position shown in FIG. 4 and allows the arm 40 A to rotate clockwise due to the action of the tension spring 47 A. As a result, the press roller 2 A is brought to the contact position where it is pressed against the print drum 1 A. When the second drive motor 54 B is turned on, the press roller 2 B rotated counterclockwise, as viewed in FIG. 4 . The fan motors 59 A through 59 C respectively cause the fans 58 A through 58 C to rotate when turned on, thereby generating air streams. The air streams from the fans 58 A through 58 C are respectively sent to the vicinity of the print positions 18 and 19 via the paths 60 A through 60 C and air outlets 63 A, 63 B a , 63 B b and 63 C.

On the other hand, when the second drum key 77 is pressed (Yes, step A 4 ), the controller 80 advances to step A 8 , determining that the second print drum 1 B is selected. The controller 80 turns on the second solenoid 43 B (step A 8 ), turns on the first drive motor 54 A (step A 9 ), and turns on the fan motors 59 A through 59 C (step A 7 ).

When the solenoid 43 B is energized, the stop 41 B is brought to the release position shown in FIG. 7 and allows the arm 40 B to rotate clockwise due to the action of the tension spring 47 B. As a result, the press roller 2 B is pressed against the print drum 1 B. When the first drive motor 54 A is turned on, the press roller 2 A rotated counterclockwise, as viewed in FIG. 7 . The fan motors 59 A through 59 C respectively cause the fans 58 A through 58 C to rotate when turned on, thereby generating air streams. The air streams from the fans 58 A through 58 C are respectively sent to the vicinity of the print positions 18 and 19 via the paths 60 A through 60 C and air outlets 63 A, 63 B a , 63 B b and 63 C.

More specifically, when the print drum 1 A is selected, the holding means 5 B holds the press roller 2 B associated with the other print drum 1 B in the spaced position spaced from the drum 1 B. When the print drum 1 B is selected, the holding means 5 A holds the press roller 2 A associated with the other print drum 1 A in the spaced position spaced from the drum 1 A. It is therefore not necessary to wrap a non-perforated stencil around the print drum 1 A or 1 B not selected, so that the print cost is reduced. In addition, the printer allowing the operator to select desired one of the print drums 1 A and 1 B is convenient to use.

Assume that the print drum 1 A is selected. Then, when the printing program starts and causes the paper 22 to be fed in FIG. 4 , the press roller 2 A presses the paper 22 being conveyed via the print position 18 . As a result, an image is transferred from the master 8 A wrapped around the print drum 1 A to the paper 22 . When the leading edge of the paper 22 arrives at the paper conveyance path 66 , the fan 58 B sends an air stream toward the leading edge of the paper 22 from above via the air outlet 63 B a . The air stream, coupled with the stiffness of the paper 22 , causes the paper 22 to separate from the circumference 1 a of the print drum 1 A before reaching the peeler 34 A. This successfully prevents the paper 22 from noticeably rolling up. The air stream being sent via the air outlet 63 B a guides the leading edge of the paper 22 separated from the print drum 1 A toward the belt 28 . The belt 28 conveys the paper 22 toward the print position 19 while retaining it thereon by suction. Even when the paper 22 is not stiff or when ink is deposited on the paper 22 in an excessive amount and causes the paper 22 to closely adhere to the print drum 1 A, the peeler 34 A and air stream being sent via the air outlet 63 B a cooperate to separate the leading edge of the paper 22 from the drum 1 A.

When the paper 22 being conveyed by the belt 28 in the direction X approaches the print position 19 , an air stream being sent from the air outlet 63 B b forces the paper 22 against the press roller 2 B that is rotating at the spaced position. Further, an air stream is sent via the air outlet 63 C in the vicinity and downstream of the print position 19 , forcing the paper 22 against the press roller 22 even after the paper 22 has moved away from the print position 19 .

In the above condition, the rotation of the press roller 2 B is successfully transferred to the paper 22 despite that the paper 122 is not nipped between the press roller 2 B and the print drum 1 B. The paper 22 can therefore be conveyed by a sufficient force without defective conveyance or a jam. The paper 22 moved away from the print position 19 is conveyed by the belt 32 to the tray 20 , FIG. 1 , while being subjected to the air stream being sent via the air outlet 63 C.

Assume that the second print drum 1 B is selected. Then, at positions upstream and downstream of the print position 18 , the air streams being sent via the air outlets 63 A and 63 B a , respectively, act on the paper 22 being conveyed via the print position 18 . As a result, the paper 22 is forced against the press roller 2 A rotating at the spaced position. It follows that the rotation of the press roller 2 A is transferred to the paper 22 despite that the press roller 2 A and print drum 1 A do not nip the paper 22 . This is successful to obviate defective conveyance and jam ascribable to a short conveying force.

The belt 28 conveys the paper 22 moved away from the print position 18 to the print position 19 . At the print position 19 , the press roller 2 B presses the paper 22 with the result that an image is transferred from the master 8 B wrapped around the print drum 18 to the paper. The paper 22 moved away from the print position 19 is sucked onto the belt 32 while being subjected to the air stream being sent from the air outlet 63 C and driven out to the tray 20 , FIG. 1 .

On the other hand, in the multicolor mode, the press rollers 2 A and 2 B press the paper 22 at the print positions 18 and 19 , respectively. Consequently, images are transferred from the masters 8 A and 8 B wrapped around the print drums 1 A and 1 B, respectively, to the paper 22 one above the other. The paper 22 with the resulting multicolor image is driven out to the tray 20 .

In the illustrative embodiment, automatic print mode switching is also available on the basis of the presence/absence of the print drums 1 A and 1 B, as will be described with reference to FIGS. 8 and 9 hereinafter. As shown in FIG. 8 , the controller 80 reads information output from the first and second drum sensors 89 and 90 (step B 1 ). If the drum sensor 89 is in an ON state (Yes, step B 2 ), the controller 80 determines that the print drum 1 A is present on the printer body 100 , and then determines the status of the drum sensor 90 (step B 3 ). If the answer of the step B 2 is No, the controller 80 determines that the print drum 1 A is not mounted to the printer body 100 , and then determines the status of the drum sensor 90 (step B 4 ).

If the answer of the step B 4 is Yes, the controller 80 determines that only the print drum 1 B is present on the printer body 100 , and advances to step B 5 . In the step B 5 , the controller 80 automatically selects the second color mode for printing an image with the print drum 1 B and then executes the master making program and printing program in response to the operation of the perforation start key 73 and print start key 72 . Subsequently, the controller 80 energizes the second solenoid 43 B (step B 6 ), energizes the first drive motor 54 A (step B 7 ), energizes the fan motors 59 A through 59 C (step B 12 ), and ends the control.

If the drum sensor 90 is in an OFF state (No, step B 4 ), the controller 80 determines that neither the print drum 1 A nor the print drum 1 B is present on the printer body 100 . The controller 80 then informs the operator of the absence of the print drums 1 A and 1 B via the display 78 (step B 8 ). In this case, the controller 80 does not execute the master making program or the printing program, i.e., stops the entire operation even when the operator presses the perforation start key 73 or the print start key 72 .

If the drum sensor 90 is in an ON state (Yes, step B 3 ), the controller 80 determines that both the print drum 1 A and print drum 1 B are present on the printer body 100 , and then automatically selects the multicolor mode (step B 13 ). The controller 80 then turns on the first and second solenoids 43 A and 43 B (step B 14 ) while executing the master making program and printing, program. In the multicolor mode, the press rollers 2 A and 2 B are brought into contact with the print drums 1 A and 1 B, respectively. In this condition, images are transferred from the masters 8 A and 8 B wrapped around the print drums 1 A and 1 B, respectively, to the paper 22 fed from the tray 10 at the print positions 18 and 19 . As a result, a multicolor image is printed on the paper 22 .

If the drum sensor 90 is in an OFF state (No, step B 3 ), the controller 80 determines that only the print drum 1 A is present on the printer body 100 . The controller 80 then selects the first color mode (step B 9 ) and executes the master making program and printing program in response to the operation of the perforation start key 73 and print start key 72 . Further, the controller 80 turns on the solenoid 43 A (step B 10 ), turns on the drive motor 54 B (step B 11 ), and turns on the fan motors 59 A through 59 C (step B 12 ).

In the first color mode, the press roller 2 B cooperative with the unused print drum, i.e., the print drum 1 B absent on the printer body 100 is held at the spaced position by the holding means 5 B while being rotated. The air streams being generated by the fans 58 A through 58 C are sent to the vicinity of the print positions 18 and 19 via the paths 60 A through 60 C and air outlets 63 A through 63 C.

In the second color mode, the press roller 2 A cooperative with the unused print drum, i.e., the print drum 1 A absent on the printer body 100 is held at the spaced position by the holding means 5 A while being rotated. The air streams being generated by the fans 58 A through 58 C are sent in the same manner as in the first color mode.

FIG. 9 shows a specific condition wherein the second print drum 1 B is absent on the printer body 100 . In this condition, the first color mode is automatically selected. If the first print drum 1 A is absent, the second color mode is automatically selected. The operator therefore does not have to care whether or not the print drums 1 A and 1 B are present on the printer body 100 . This successfully obviates the operator's erroneous operation.

In the first color mode, the paper 22 with an image printed thereon at the print position 18 is conveyed to the downstream side. In the vicinity of the print position 19 , the air streams being sent via the air outlets 63 B b and 63 C force the paper 22 against the press roller 2 B being rotated. This insures a sufficient conveying force despite the absence of the print drum 1 B and thereby surely obviates defective conveyance and jam ascribable to a short conveying force.

In the second color mode, in the vicinity of the print position 18 , the air streams being sent via the air outlets 63 A and 63 B a force the paper 22 against the press roller 2 A being rotated. This also insures a sufficient conveying force despite the absence of the print drum 1 A and thereby surely obviates defective conveyance and jam ascribable to a short conveying force.

Referring to FIG. 10 , an alternative embodiment of the multicolor stencil printer in accordance with the present invention will be described. As shown, the printer includes four parallel print drums, i.e., first to fourth print drums 1 A, 1 B, 1 C and 1 D arranged in parallel in this order from the upstream side to the downstream side in the direction of paper conveyance X within a printer body 1000 . The print drums 1 A through 1 D each store ink of a particular color thereinside. Four press rollers 2 A, 2 B, 2 C and 2 D are also accommodated in the printer body 1000 and movable into and out of contact with the print drums 1 A through 1 D, respectively. The printer is selectively operable in a multicolor mode or a color selective mode, as desired. In the multicolor mode, the print drums 1 A through 1 D and press drums 2 A through 2 D respectively cooperate to nip the paper 22 for printing a multicolor image thereon. In the color selective mode, the print drum 1 A and press roller 2 A, the print drum 1 B and press roller 2 B, the print drum 1 C and press roller 2 C or the print drum 1 D and press roller 2 D nip the paper 22 for printing an image thereon in a desired color. Control means 80 (see FIG. 14 ) sets up either the multicolor mode or the color selective mode, as desired.

In the illustrative embodiment, holding means 5 A, 5 B, 5 C and 5 D and air sending means 6 A, 6 B, 6 C, 6 D and 6 E are arranged around the first to fourth print drums 1 A through 1 D, respectively. The holding means 5 A through 5 D respectively hold the press rollers 2 A through 2 D at spaced positions spaced from the outer circumferences 1 a through 1 d of the print drums 1 A through 1 D. Ink feeding means 7 A, 7 B, 7 C and 7 D are arranged within the print drums 1 A through 1 D, respectively. The illustrative embodiment, like the previous embodiment, additionally includes conventional master making devices and master discharging devices although not shown specifically.

The print drums, press rollers, holding means, air sending means and ink feeding means of the illustrative embodiment are substantially identical in construction and operation with those of the previous embodiment and simply distinguished by suffixes A, B, C, D and E. The following description will concentrate mainly on arrangements relating to the third and fourth print drums 1 C and 1 D and configurations unique to this embodiment in order to avoid redundancy.

Yellow ink and magenta ink are respectively fed to the drums 1 A and 1 B from respective ink packs, not shown, via the drum shafts 35 A and 35 B. Likewise, cyan ink and black ink are respectively fed to the drums 1 C and 1 D from respective ink packs, not shown, via drum shafts 35 C and 35 D.

The third and fourth print drums 1 C and 1 D are rotatably mounted on the drum shafts 35 C and 35 D, respectively. Frames 36 C and 36 D are removably mounted on the printer body 100 and support opposite ends of the drum shafts 35 C and 35 D, respectively. The print drums 1 C and 1 D are interconnected by a gear train, a belt and pulley device or similar conventional power transmission mechanism. A drum motor 68 (see FIG. 14 ) is drivably connected to the power transmission mechanism in order to cause the print drums 1 C and 1 D to rotate in the clockwise direction, as viewed in FIG. 10 , or printing direction in synchronism with the print drums 1 A and 1 B. The control means 280 controls the drum motor 68 in order to control the speed and direction of rotation of the print drums 1 A through 1 D. Specifically, the print drums 1 C and 1 D each are rotated clockwise at a higher speed during printing than during the interval between the master feeding operation and the master adhering operation. Masters 8 C and 8 D are wrapped around the print drums 1 C and 1 D, respectively.

The press roller 2 C and print drum 1 C define a print position 180 therebetween while the press roller 2 D and print drum 1 D define a print position 190 therebetween. A conveyor 21 B identical with the conveyor 21 extends between the two print positions 19 and 180 and forms a paper conveyance path between the print drums 1 B and 1 C. Guides 23 B and 24 B respectively precede and follow the conveyor 21 B. Also, a conveyor 21 C identical with the conveyor 21 extends between the two print positions 180 and 190 and forms a paper conveyance path between the print drums 1 C and 1 D. Guides 23 C and 24 C respectively precede and follow the conveyor 21 C. In the illustrative embodiment, the paper discharging device 25 is interposed between the print position 190 and the print tray 20 .

The conveyors 21 B and 21 C respectively include belts 28 B and 28 C and suction fans 29 B and 29 C positioned below the belts 28 B and 28 C, respectively. The conveyors 21 B and 21 C are respectively configured to convey the paper 22 coming out of the print position 19 and 180 to the downstream side in the direction X, i.e., the print positions 180 and 190 while retaining the paper 22 on the belts 28 B and 280 by suction.

Peelers 34 C and 34 D are respectively positioned above the conveyor 21 C and paper discharging device 25 in order to remove the paper 22 from the circumferences 1 c and 1 d of the print drums 1 C and 1 D. The peelers 34 C and 34 D each have a comb-like configuration and extend in the widthwise direction of the paper 22 . The air sending means 6 E and 6 C respectively send air toward positions around the print positions 180 and 190 .

The holding means 5 C includes an arm 40 C supporting the press roller 2 C such that the roller 2 C is movable into and out of contact with the print drum 1 C. A stop 41 C is engageable with the arm 40 C. A tension spring or biasing means 42 C constantly biases the stop 41 C in a direction in which the stop 41 C engages with the arm 40 C. A third electromagnetic solenoid or actuator 43 C moves the stop 41 C away from the arm 40 C. Likewise, the holding means 5 D includes an arm 40 D supporting the press roller 2 D such that the roller 2 D is movable into and out of contact with the print drum 1 D. A stop 41 D is engageable with the arm 40 D. A tension spring or biasing means 42 D constantly biases the stop 41 D in a direction in which the stop 41 D engages with the arm 40 D. A fourth electromagnetic solenoid or actuator 43 D moves the stop 41 D away from the arm 40 D.

As shown in FIG. 11 , the arms 40 C and 40 D each are generally L-shaped and pivotally supported by a shaft 44 C or 44 D at its bend portion. The shafts 44 C and 44 D are affixed to the printer body 1000 . The press rollers 2 C and 2 D are respectively rotatably supported by one end 401 C and 401 D of the arms 40 C and 40 D via shafts 45 C and 45 D. Rollers 46 C and 46 D are respectively rotatably mounted on the other ends 402 C and 402 D of the arms 40 C and 40 D. Tension springs 47 C and 47 D are respectively anchored to the above ends 402 C and 402 D at one end thereof, constantly biasing the arms 40 C and 40 D clockwise and exerting pressures on the print drums 1 C and 1 D, respectively. The other ends of the tension springs 47 C and 47 D are anchored to the printer body 1000 .

The rollers 46 C and 46 D are respectively pressed against the contours of cams 48 C and 48 D. The cams 48 C and 48 D respectively move the outer circumferences 2 c and 2 d of the press rollers 2 C and 2 D into and out of contact with the outer circumferences 1 c and 1 d of the print drums 1 C and 1 D. The cams 48 C and 48 D are respectively rotated in synchronism with the print drums 1 C and 1 D via link mechanisms not shown. The cam 48 C has a profile configured such that when a damper 9 C passes the print position 180 , the circumference 2 c of the press roller 2 C is spaced from the circumference 1 c of the print drum 1 C. The cam 48 D has the same profile as the cam 48 C except that it releases the circumference 2 d of the press roller 2 D from the circumference 1 d of the print drum 1 D when a clamper 9 D passes the print position 190 . More specifically, the arm 40 C is mounted on the shaft 44 C in such a manner as to move the press roller 2 C between the spaced position spaced from the print drum 1 C and the contact position contacting the print drum 1 C. Likewise, the arm 40 D is mounted on the shaft 44 D in such a manner as to move the press roller 2 D between the spaced position spaced from the print drum 1 D and the contact position contacting the drum 1 D. The press rollers 2 C and 2 D each press the paper 22 against the associated print drum 1 C or 1 D in order to transfer an image to the paper 22 .

Pins 49 C and 49 D are studded on the arms 40 C and 40 D, respectively. As shown in FIG. 11 , the stops 41 C and 41 D are located in the vicinity of the arms 40 C and 40 D, respectively, with their base ends 41 e and 41 f respectively angularly movably supported by the printer body 1000 . The stops 41 C and 41 D have free ends 41 g and 41 h thereof bent at substantially right angle. When the arms 40 C and 40 D move to release the press rollers 2 C and 2 D from the print drums 1 C and 1 D, respectively, the stops 41 C and 41 D abut against the pins 49 C and 49 D, respectively. A tension spring 42 C is anchored at one end to the printer body 1000 and at the other end to the stop 41 C, constantly biasing the stop 41 C toward the pin 49 C. Likewise, a tension spring 42 D is anchored at one end to the printer body 1000 and at the other end to the stop 41 D, constantly biasing the stop 41 D toward the pin 49 D.

The third and fourth solenoids 43 C and 43 D have plungers 50 C and 50 D, respectively, pinned to the stops 41 C and 41 D, respectively. The solenoids 43 C and 43 D are of the type pulling the plungers 50 C and 50 D, respectively, when energized. Specifically, when the solenoids 43 C and 43 D each are energized, it pulls the stop 41 C or 41 D against the action of the associated tension spring 42 C or 42 D from the catch position to the release position.

As shown in FIG. 11 , pulleys 51 C and 51 D are respectively mounted on one side of the press rollers 20 and 2 D via one-way clutches 69 C and 69 D. The one-way clutches 690 and 69 D transfer rotation only from the pulleys 51 C and 51 D to the press rollers 2 C and 2 D, respectively. Double pulleys 52 C and 52 D are rotatably mounted on the shafts 44 C and 44 D, respectively. Belts 53 C and 53 D are respectively passed over the pulleys 51 C and 51 D and double pulleys 52 C and 52 D. A third and a fourth drive motor or drive means 54 C and 54 D have output shafts 55 C and 55 D, respectively, on which drive pulleys 56 C and 56 D are mounted. Drive belts 57 C and 57 D are respectively passed over the double pulleys 52 C and 52 D and drive pulleys 56 C and 56 D. The output shafts 55 C and 55 D of the drive motors 54 C and 54 D each are rotatable counterclockwise, as viewed in FIG. 11 , under the control of the control means 280 .

In the above construction, when the drive motor 54 C or 54 D is driven, it causes the associated press roller 2 C or 2 D to rotate counterclockwise, i.e., in a direction opposite to the direction in which the print drum 1 C or 1 D rotates during printing. When the press roller 2 C or 2 D is brought into contact with the associated print drum 1 C or 1 D while the drive motor 54 C or 54 D is deenergized, the press roller 2 C or 2 D is caused to rotate by the print drum 1 C or 1 D via the associated one-way clutch 69 C or 69 D.

Referring again to FIG. 10 , the air sending means 6 D is positioned between the second and third print drums 1 B and 1 C while the air sending means 6 E is positioned between the third and fourth drums 1 C and 1 D. The air sending means 6 C is positioned at the left-hand side of the print drum 1 D. The air sending means 6 D, 6 E and 6 C respectively have fans 58 D, 58 E and 58 C for generating air streams, fan motors 59 D, 59 E and 59 C, and paths 60 D, 60 E and 60 C for respectively guiding air streams generated by the fans 58 D, 58 E and 58 C to the vicinity of the print positions 19 , 180 and 190 .

As shown in FIGS. 12 and 13 , the path 60 D is formed by a duct 62 D extending from a case 61 D accommodating the fan 58 D toward the belt 28 B of the conveyor 21 B. The conveyor 21 B includes a drive roller 26 B and a driven roller 27 B. The duct 62 D is bifurcated and has two air outlets 63 D a and 63 D b at its lower end. The air outlet 63 D a faces the upper surface of the peeler 34 B and sends the air stream generated by the fan 58 D to the range between a paper conveyance path 65 extending between the peeler 34 B and the belt 28 B and the print position 19 from the downstream side. The other air outlet 63 D b faces a paper conveyance path 164 formed by the belt 28 B and guide 24 B and sends the air stream generated by the fan 58 D to the range between the above path 164 and the print position 180 from the upstream side in the direction X.

The path 60 E is formed by a duct 62 E extending from a case 61 E accommodating the fan 58 E toward the belt 28 C of the conveyor 21 C. The conveyor 21 C includes a drive roller 26 C and a driven roller 27 C. The duct 62 E is bifurcated and has two air outlets 63 E a and 63 E b at its lower end. The air outlet 63 E a faces the upper surface of the peeler 340 and sends the air stream generated by the fan 58 E to the range between a paper conveyance path 166 extending between the peeler 34 C and the belt 28 C and the print position 180 from the downstream side. The other air outlet 63 E b faces a paper conveyance path 167 formed by the belt 28 C and guide 24 C and sends the air stream generated by the fan 58 E to the range between the above path 167 and the print position 190 from the upstream side in the direction X.

The path 60 C is formed by a duct 62 C extending from a case 61 C accommodating the fan 58 C toward the print position 190 . The duct 62 C has an air outlet 63 C at its lower end. The air outlet 63 C faces the upper surface of the peeler 34 D and sends the air stream generated by the fan 58 C to the range between a paper conveyance path 165 below the peeler 34 D and the print position 190 from the downstream side. The duct 60 C has a cross-sectional area sequentially decreasing toward the air outlet 63 in order to increase the flow rate of air around the air outlet 63 .

The ducts 62 D, 62 E and 62 C are affixed to the printer body 1000 , and each have a width slightly greater than the axial length of associated one of the print drums 1 B, 1 C and 1 D. The ducts 62 D, 62 E and 62 C each are curved along the contours 1 b , 1 c or 1 d of the adjoining print drum 1 B, 1 C or 1 D and so positioned as not to contact the clamper 9 B, 9 C or 9 D when the print drum rotates.

As shown in FIG. 14 , the illustrative embodiment also includes the control panel 70 on which a third drum key 176 and a fourth drum key 177 are additionally arranged.

The control means 280 is implemented by a conventional microcomputer including the CPU 81 , ROM 182 and RAM 83 . The various keys and display of the control panel 70 described in relation to the previous embodiment are connected to the CPU 81 . In the illustrative embodiment, additionally connected to the CPU 81 are third and fourth solenoids 43 C and 43 D, third and fourth drive motors 54 C and 54 D, and fan motors 59 D through 59 E as well as third and fourth drum sensors or drum sensing means 189 and 290 . In the illustrative embodiment, the drivers 84 and 85 assigned to the master making devices and master discharging devices, respectively, function to drive master making devices and master discharging devices associated with the third and fourth print drums 1 C and 1 D at the same time. The driver 87 for paper conveyance functions to drive the conveyors 21 B and 21 C also.

As shown in FIG. 10 , the third and fourth drum sensors 189 and 290 are implemented by switches mounted on the print body 1000 and facing the third and fourth print drums 1 C and 1 D, respectively. When the print drums 1 C and 1 D are mounted to the printer body 1000 , the sensors 189 and 290 , respectively, turn on.

The ROM 182 stores the color selective mode, multicolor mode, a first color mode to a third color mode belonging to the color selective mode, the master making program, and printing program. Further, the ROM 182 stores a control program for controlling the positions and drive of the press rollers 2 A through 2 D and the drive of the air sending means 6 A through 6 E.

In the color selective mode, the printer executes the discharge of a used master and the feed of a new master with only one of the print drums 1 A through 1 D selected and executes printing with the drum selected. Specifically, in the illustrative embodiment, when the color selective mode is selected, monocolor printing is effected by using one of the print drums 1 A through 1 D. In the multicolor mode, the discharge of a used master and the feed of a new master are effected with all of the print drums 1 A through 1 D, and multicolor printing is executed by using the print drums 1 A through 1 B.

Reference will be made to FIGS. 15 through 24 for describing a specific operation of the illustrative embodiment, particularly control over the press rollers 2 A through 2 D and air sending means 6 A through 6 E executed by the controller 280 in each of the print modes.

First, the operator of the printer presses the color selective mode key 74 or the multicolor mode key 75 to select desired one of the color selective mode and multicolor mode. The operator then presses any one of the first to fourth drum keys 76 through 177 to designate one of the print drums 1 A through 1 D to use, and then presses the perforation start key 73 . In response, the master making program starts to execute the master discharging, master making and master adhering steps. After the master adhering step, the operator presses the print start key 72 , so that the printing program starts.

A procedure shown in FIG. 15 starts in parallel with the master making program or the printing program when the key 73 or 72 , respectively, is pressed. As shown, the controller 280 reads print mode information input by the operator (step E 1 ) and then determines a print mode (step E 2 ). If the color selective mode is selected on the key 74 (Yes, step E 2 ), the controller 280 advances to step E 5 . If the answer of the step E 2 is No, the controller 280 sets up the multicolor mode (step E 3 ), then drives all of the first to fourth solenoids 43 A through 43 D (step E 4 ), and then ends the program.

When the solenoids 43 A through 43 D are energized, the stops 41 A through 41 D are brought to the releases position shown in FIG. 10 and allow the arms 40 A through 40 D to rotate clockwise due to the action of the tension springs 47 A through 47 D. As a result, the press rollers 2 A through 2 D are respectively pressed against the print drums 1 A through 1 D (contact position). In this condition, multicolor printing using the four print drums 1 A through 1 D is effected.

The controller 280 determines the statuses of the first to third drum keys 76 , 77 and 176 (steps E 5 , E 6 and E 7 ). If all the answers of the steps E 5 through E 7 are Yes, the controller 280 determines that the first to third drums 1 A through 1 C are selected, and then sets up a tricolor mode (step E 8 ). Subsequently, the controller 280 turns on the solenoids 43 A through 43 C (step E 9 ), energizes the fourth motor 54 D (step E 10 ), and turns on all of the fan motors 59 A through 59 C (step E 11 ).

In the steps E 5 through E 11 , the solenoids 43 A through 43 C energized pull the stops 41 A through 41 C, respectively, to their release positions, so that the arms 40 A through 40 C rotate clockwise. As a result, the press rollers 2 A through 2 C are pressed against the print drums 1 A through 1 C, effecting tricolor printing. When the fourth drive motor 54 D is energized, the press roller 2 D is rotated counterclockwise. When all the fan motors are turned on, the fans 58 A, 58 B, 58 D, 58 E and 58 C rotate to generate air streams. The air streams from the fans 58 A, 58 B, 58 D, 58 E and 58 C are respectively sent to the vicinity of the print positions 18 , 19 , 180 and 190 via the paths 60 A, 60 B, 60 D, 60 E and 60 C and air outlets 63 A, 63 B a , 63 B b , 63 D a , 53 D b , 63 E a , 63 E b and 63 C.

If the drum keys 76 , 77 and 176 each are in an OFF state (No, steps E 5 , E 6 and E 7 ), the controller 280 advance to a step E 12 shown in FIG. 16 from the step E 5 , to a step E 40 shown in FIG. 18 from the step E 6 , or to step E 55 shown in FIG. 19 from the step E 7 .

In the step E 12 shown in FIG. 16 , the controller 280 determines the status of the second drum key 77 . If the key 77 is in an ON state (Yes, step E 12 ), the controller 280 determines whether or not the third drum key 176 is in an ON state (step E 13 ). (f the answer of the step E 12 is No, the controller 280 advances to step E 28 shown in FIG. 17 . If the answer of the step E 13 is Yes and if the answer of step E 14 is also Yes, meaning that the fourth drum key 177 is in an ON state, the controller 280 advances to step E 15 , determining that the second to fourth drums 1 B through 1 D are selected. The controller 280 sets up the tricolor mode (step E 15 ) and turns on the second to fourth solenoids 43 B through 43 D (step E 16 ). Subsequently, the controller 280 turns on the first drive motor 54 A (step E 17 ) and turns on all the fan motors (step E 11 , FIG. 15 ).

In the steps E 12 through E 17 executed via the step E 11 , the solenoids 43 B, 43 C and 43 D energized pull the stops 41 B, 41 C and 42 D, respectively, to their release positions, so that the arms 40 B, 40 C and 40 D rotate clockwise. As a result, the press rollers 2 B, 2 C and 2 D are pressed against the print drums 1 B, 1 C and 1 D, effecting tricolor printing. When the first drive motor 54 A is energized, the press roller 2 A is rotated counterclockwise. When all the fan motors are turned on, the fans rotate to generate air streams. The air streams are sent to the vicinity of the print positions 18 , 19 , 180 and 190 via the respective paths and air outlets.

If the answer of the step E 13 is No, the controller 280 determines the status of the fourth drum key 177 (step E 18 ). If the key 177 is in an ON state (Yes, step E 18 ), the controller 280 determines that the second and fourth drums 1 B and 1 D are selected, and then sets up a bicolor mode (step E 19 ). Subsequently, the controller 280 turns on the second and fourth solenoids 43 B and 43 D (step E 20 ), turns on the first and third drive motors 54 A and 54 C (step E 21 ), and turns on all the fan motors (step E 11 , FIG. 15 ).

In the steps E 18 through E 11 executed via the step E 21 , the second and fourth solenoids 43 B and 43 D energized pull the stops 41 B and 41 D, respectively, to their release positions, so that the arms 40 B and 40 D rotate clockwise. As a result, the press rollers 2 B and 2 D are pressed against the print drums 1 B and 1 D, effecting bicolor printing. When the first and third drive motors 54 A and 54 C are energized, the press rollers 2 A and 2 C are rotated counterclockwise. When all the fan motors are turned on, the fans rotate to generate air streams. The air streams are sent to the vicinity of the print positions 18 , 19 , 180 and 190 via the respective paths and air outlets.

If the answer of the step E 18 is No, the controller 280 determines that only the second drum 1 B is selected, and then sets up a monocolor mode (step E 22 ). The controller 280 then turns on the second solenoid 43 B (step E 23 ), turns on the first, third and fourth drive motors 54 A, 54 C and 54 D (step E 24 ), and turns on all the fan motors (step E 11 , FIG. 15 ).

In the steps E 18 through E 11 executed via the step E 24 , the second solenoid 43 B energized pulls the stop 41 B to its release position, so that the arm 40 B rotates clockwise. As a result, the press roller 2 B is pressed against the print drum 1 B, effecting monocolor printing. When the first, third and fourth drive motors 54 A, 54 C and 54 D are energized, the press rollers 2 A, 2 C and 2 D are rotated counterclockwise. When all the fan motors are turned on, the fans rotate to generate air streams. The air streams are sent to the vicinity of the print positions 18 , 19 , 180 and 190 via the respective paths and air outlets.

If the answer of the step E 14 is No, the controller 280 determines that the second and third drums 1 B and 1 C are selected, and then sets up the bicolor mode (step E 25 ). The controller 280 then turns on the second and third solenoids 43 B and 430 (step E 26 ), turns on the first and fourth drive motors 54 A and 54 D (step E 27 ), and turns on all the fan motors (step E 11 , FIG. 15 ).

In the steps E 14 through E 11 executed via the step E 27 , the second and third solenoids 43 B and 43 C energized pull the stops 41 B and 41 C, respectively, to their release positions, so that the arms 40 B and 40 C rotate clockwise. As a result, the press rollers 2 B and 2 C are pressed against the print drums 1 B and 1 C, effecting bicolor printing. When the first and fourth drive motors 54 A and 54 D are energized, the press rollers 2 A and 2 D are rotated counterclockwise. When all the fan motors are turned on, the fans rotate to generate air streams. The air streams are sent to the vicinity of the print positions 18 , 19 , 180 and 190 via the respective paths and air outlets.

If the third drum key 176 is in an ON state (Yes, step E 28 , FIG. 17 ), the controller 280 determines whether or not the fourth drum key 177 is in an ON state (step E 29 ). If the answer of the step E 28 is No, the controller 280 advances to step E 36 . If the answer of the step E 29 is Yes, the controller 280 sets up the bicolor mode (step E 30 ), determining that the third and fourth drums 1 C and 1 D are selected. Subsequently, the controller 280 turns on the third and fourth solenoids 43 C and 43 D (step E 31 ), turns on the first and second motors 54 A and 54 B (step E 32 ), and turns on all of the fan motors (step E 11 , FIG. 15 ).

In the steps E 28 through E 11 executed via the step E 32 , the third and fourth solenoids 43 C and 43 D energized pull the stops 41 C and 41 D, respectively, to their release positions, so that the arms 40 C and 40 D rotate clockwise. As a result, the press rollers 2 C and 2 D are pressed against the print drums 1 C and 1 D, effecting bicolor printing. When the first and second drive motors 54 A and 54 B are energized, the press rollers 2 A and 2 B are rotated counterclockwise. When all the fan motors are turned on, the fans rotate to generate air streams. The air streams are sent to the vicinity of the print positions 18 , 19 , 180 and 190 via the respective paths and air outlets.

If the fourth drum key 177 is in an ON state (Yes, step E 36 ), the controller 280 determines that only the fourth drum 1 D is selected, and then sets up the monocolor mode (step E 37 ). Subsequently, the controller 280 executes step E 38 . If the answer of the step E 36 is No, the controller 280 returns to the step E 5 , FIG. 15 , determining that not all the print drums have been selected yet. In the step E 38 , the controller 280 turns on only the fourth solenoid 43 D. The controller 280 then turns on the first, second and third motors 54 A, 54 B and 54 C (step E 39 ) and turns on all the fan motors (step E 11 , FIG. 15 ).

In the steps E 36 through E 11 executed via the step E 39 , the fourth solenoid 43 D energized pulls the stop 41 D to its release position, so that the arm 40 D rotates clockwise. As a result, the press roller 2 D is pressed against the print drum 1 D, effecting monocolor printing. When the first, second and third drive motors 54 A, 54 B and 54 C are energized, the press rollers 2 A, 2 B and 2 C are rotated counterclockwise. When all the fan motors are turned on, the fans rotate to generate air streams. The air streams are sent to the vicinity of the print positions 18 , 19 , 180 and 190 via the respective paths and air outlets.

If the answer of the step E 29 is No, the controller 280 determines that only the third print drum 1 C is selected, and then sets up the monocolor mode (step E 33 ). The controller 280 then turns on the third solenoid 43 C (step E 34 ), turns on the first, second and fourth drive motors 54 A, 54 B and 54 D (step E 35 ), and turns on all the fan motors (step E 11 , FIG. 15 ).

In the steps E 29 through E 11 executed via the step E 35 , the third solenoid 43 C energized pulls the stop 41 C to its release position, so that the arm 40 C rotates clockwise. As a result, the press roller 2 C is pressed against the print drum 1 C, effecting monocolor printing. When the first, second and fourth drive motors 54 A, 54 B and 54 D are energized, the press rollers 2 A, 2 B and 2 D are rotated counterclockwise. When all the fan motors are turned on, the fans rotate to generate air streams. The air streams are sent to the vicinity of the print positions 18 , 19 , 180 and 190 via the respective paths and air outlets.

If the third drum key 176 is in an ON state (Yes, steep E 40 , FIG. 18 ), the controller 280 advances to step E 41 . If the answer of the step E 40 is No, the controller 280 executes step E 45 . If the fourth drum key 177 is in an ON state (Yes, step E 41 ,), the controller 280 sets up the tricolor mode (step E 42 ), determining that the first, third and fourth drums 1 A, 1 C and 1 D are selected. Subsequently, the controller 280 turns on the first, third and fourth solenoids 43 A, 43 C and 43 D (step E 43 ), turns on only the second drive motor 54 B (step E 44 ), and turns on all the fan motors (step E 11 , FIG. 15 ).

In the steps E 40 through E 11 executed via the step E 44 , the first, third and fourth solenoids 43 A, 43 C and 43 D energized pull the stops 41 A, 41 C and 41 D, respectively, to their release positions, so that the arms 40 A, 40 C and 40 D rotate clockwise. As a result, the press rollers 2 A, 2 C and 2 D are pressed against the print drums 1 A, 1 C and 1 D, effecting tricolor printing. When the second drive motor 54 B is energized, only the press roller 2 B is rotated counterclockwise. When all the fan motors are turned on, the fans rotate to generate air streams. The air streams are sent to the vicinity of the print positions 18 , 19 , 180 and 190 via the respective paths and air outlets.

If the fourth drum key 177 is in an ON state (Yes, step E 45 ), the controller 280 determines that the first and fourth drum 1 A and 1 D are selected, and then sets up the bicolor mode (step E 46 ). Subsequently, the controller 280 executes step E 47 . In the step E 47 , the controller 280 turns on the first and fourth selenoids 43 A and 43 D. The controller 280 then turns on the second and third motors 54 B and 54 C (step E 48 ) and turns on all the fan motors (step E 11 , FIG. 15 ).

In the steps E 45 through E 11 executed via the step E 48 , the first and fourth solenoids 43 A and 43 D energized pull the stops 41 A and 41 D, respectively, to their release positions, so that the arms 40 A and 40 D rotate clockwise. As a result, the press rollers 2 A and 2 D are pressed against the print drums 1 A and 1 D, effecting bicolor printing. When the second and third drive motors 54 B and 54 C are energized, the press rollers 2 B and 2 C are rotated counterclockwise. When all the fan motors are turned on, the fans rotate to generate air streams. The air streams are sent to the vicinity of the print positions 18 , 19 , 180 and 190 via the respective paths and air outlets.

If the fourth drum key 177 is in an OFF state (No, step E 45 ), the controller 280 determines that only the first drum 1 A is selected, and then sets up the monocolor mode (step E 49 ). Subsequently, the controller 280 executes step E 50 . In the step E 50 , the controller 280 turns on only the first solenoid 43 A. The controller 280 then turns on the second, third and fourth motors 54 B, 54 C and 54 D (step ES 1 ) and turns on all the fan motors (step E 11 , FIG. 15 ).

In the steps E 45 through E 11 executed via the step E 51 , the first solenoid 43 A energized pulls the stop 41 A to its release position, so that the arm 40 A rotates clockwise. As a result, the press roller 2 A is pressed against the print drum 1 A, effecting monocolor printing. When the second, third and fourth drive motors 54 B, 54 C and 54 D are energized, the press rollers 2 B, 2 C and 2 D are rotated counterclockwise. When all the fan motors are turned on, the fans rotate to generate air streams. The air streams are sent to the vicinity of the print positions 18 , 19 , 180 and 190 via the respective paths and air outlets.

If the answer of the step E 41 is No, the controller 280 determines that the first and third print drum 1 A and 1 C are selected, and then sets up the bicolor mode (step E 52 ). The controller 280 then turns on the first and third solenoids 43 A and 43 C (step E 53 ), turns on the second and fourth drive motors 54 B and 54 D (step E 54 ), and turns on all the fan motors (step E 11 , FIG. 15 ).

In the steps E 41 through E 11 executed via the step E 54 , the first and third solenoids 43 A and 43 C energized pull the stops 41 A and 41 C, respectively, to their release positions, so that the arms 40 A and 40 C rotate clockwise. As a result, the press rollers 2 A and 2 C are pressed against the print drums 1 A and 1 C, effecting bicolor printing. When the second and fourth drive motors 54 B and 54 D are energized, the press rollers 2 B and 2 D are rotated counterclockwise. When all the fan motors are turned on, the fans rotate to generate air streams. The air streams are sent to the vicinity of the print positions 18 , 19 , 180 and 190 via the respective paths and air outlets.

If the fourth drum key 177 is in an ON state (Yes, step E 55 , FIG. 19 ), the controller 280 determines that the first, second and fourth drums 1 A, 1 B and 1 D are selected, and then sets up the tricolor mode (step E 56 ). Subsequently, the controller 280 executes step E 57 . In the step E 57 , the controller 280 turns on the first, second and fourth solenoids 43 A, 43 B and 43 D. The controller 280 then turns on the third motors 54 C (step E 58 ) and turns on all the fan motors (step E 11 , FIG. 15 ).

In the steps E 55 through E 11 executed via the step E 58 , the first, second and fourth solenoids 43 A, 43 B and 43 D energized pull the stops 41 A, 41 B and 41 D, respectively, to their release positions, so that the arms 40 A, 40 B and 40 D rotate clockwise. As a result, the press rollers 2 A, 2 B and 2 D are pressed against the print drums 1 A, 1 B and 1 D, effecting tricolor printing. When the third drive motor 54 C is energized, only the press roller 2 C is rotated counterclockwise. When all the fan motors are turned on, the fans rotate to generate air streams. The air streams are sent to the vicinity of the print positions 18 , 19 , 180 and 190 via the respective paths and air outlets.

If the fourth drum key 177 is in an OFF state (No, step E 55 ), the controller 280 determines that the first and second drums 1 A and 1 B are selected, and then sets up the bicolor mode (step E 59 ). Subsequently, the controller 280 executes step E 60 . In the step E 60 , the controller 280 turns on the first and second solenoids 43 A and 43 B. The controller 280 then turns on the third and fourth motors 54 C and 54 D (step E 61 ) and turns on all the fan motors (step E 11 , FIG. 15 ).

In the steps E 55 through E 11 executed via the step E 61 , the first and second solenoids 43 A and 43 B energized pull the stops 41 A and 41 B, respectively, to their release positions, so that the arms 40 A and 40 B rotate clockwise. As a result, the press rollers 2 A and 2 B are pressed against the print drums 1 A and 1 B, effecting bicolor printing. When the third and fourth drive motors 54 C and 54 D are energized, the press rollers 2 C and 2 D are rotated counterclockwise. When all the fan motors are turned on, the fans rotate to generate air streams. The air streams are sent to the vicinity of the print positions 18 , 19 , 180 and 190 via the respective paths and air outlets.

As stated above, the press roller corresponding to the print drum not selected via associated one of the first to fourth print keys 76 through 177 is held in the spaced position by associated one of the holding means 5 A through 5 D. It is therefore not necessary to wrap a non-perforated stencil around the unused print drum, so that the print cost is reduced. In addition, the printer allowing the operator to select desired one of the print drums is convenient to use.

Assume that three print drums 1 B, 1 C and 1 D are selected. Then, when the printing program starts and causes the paper 22 to be fed in FIG. 12 , the press roller 2 A rotates in the direction indicated by an arrow while being held at the spaced position by the holding means 5 A. The fan 58 A sends an air stream toward the paper 22 from above via the air outlet 63 A, forcing the paper 22 against the press roller 2 A. Further, the air stream being sent via the air outlet 63 B a at the print position 18 forces the paper 22 against the press drum 12 A even after the paper 22 has moved away from the print position 18 . In this condition, the rotation of the press roller 2 A is successfully transferred to the paper 22 despite that the paper 22 is not nipped between the press roller 2 A and the print drum 1 A. The paper 22 can therefore be conveyed by a sufficient force without defective conveyance or a jam.

The paper 22 moved away from the print position 18 is conveyed toward the belt 28 while being subjected to the air stream being sent via the air outlet 63 B a . The belt 28 conveys the paper 22 toward the print position 19 in the direction X while retaining it thereon by suction. When the paper 22 arrives at the print position 19 , the press roller 2 B presses it with the result that an image is transferred from the master 8 B wrapped around the drum 1 B to the paper.

When the leading edge of the paper 22 moved away from the print position 19 reaches the path 65 , the air stream being sent from the fan 58 D via the air outlet 63 D a acts on the paper 22 from above. This, coupled with the stiffness of the paper 22 , separates the paper 22 from the print drum 1 B before the paper 22 reaches the peeler 34 B and thereby prevents the paper 22 from rolling up. The air stream being sent via the air outlet 63 D a guides the leading edge of the paper 22 toward the belt 28 B. The belt 28 B conveys the paper 22 toward the print position 180 while retaining it thereon by suction, as shown in FIG. 13 . Even when the paper 22 is not stiff when ink is deposited on the paper 22 in an excessive amount and causes the paper 22 to closely adhere to the print drum 1 B, the paper 22 is desirably separated from the print drum 1 B by the peeler 34 B and the air stream being send via the air outlet 63 D a.

When the paper 22 being conveyed by the belt 28 B approaches the print position 180 , the press roller 2 C pressed against the print drum 1 C by the cam 48 C presses the paper 22 . At this instant, the air stream being sent via the air outlet 63 D b acts on the paper 22 . In this condition, an image is transferred from the master 8 C wrapped around the print drum 1 C to the paper 22 . When the leading edge of the paper 22 moved away from the print position 180 arrives at the path 166 , the air stream being sent via the air outlet 63 E a acts on the leading edge of the paper 22 from above. This, coupled with the stiffness of the paper 22 , separates the paper 22 from the print drum 1 C before the paper 22 reaches the peeler 34 C and thereby prevents it from rolling up. The air stream being sent via the air outlet 63 E a guides the leading edge of the paper 22 separated from the print drum 1 C toward the belt 28 C. The belt 28 C conveys the paper 22 toward the print position 190 while retaining it thereon by suction.

When the paper 22 being conveyed by the belt 28 C approaches the print position 190 , the press roller 2 D pressed against the print drum 1 D by the cam 48 D presses the paper 22 with the result that an image is transferred from the master 8 D wrapped around the print drum 1 D to the paper. When the leading edge of the paper 22 moved away from the print position 190 arrives at the path 165 , the air stream being sent via the air outlet 63 C acts on the leading edge from above. This, coupled with the stiffness of the paper 22 , separates the paper 22 from the print drum 1 D before the paper 22 reaches the peeler 34 D and thereby prevents it from rolling up. Finally, the belt 32 conveys the paper 22 peeled off by the peeler 34 D to the print tray 20 (see FIG. 10 ) while retaining it thereon by suction.

In the illustrative embodiment, too, automatic print mode switching is also available on the basis of the presence/absence of the print drums 1 A through 1 D, as will be described with reference to FIGS. 20 through 24 hereinafter. As shown in FIG. 20 , the controller 280 reads information output from the first to fourth drum sensors 89 , 90 , 189 and 290 (step D 1 ). If all the drum sensors are in an ON state (Yes, step D 2 ), the controller 280 determines that all the print drums are present on the printer body 1000 . The controller 280 then sets up the multicolor mode (step D 3 ) and energizes the first to fourth solenoids (step D 4 ).

When the solenoids are turned on, the stops 41 A through 41 D are brought to their release positions. As a result, the arms 40 A through 40 D shown in FIG. 10 are rotated clockwise by the tension springs 47 A through 47 D, respectively. Consequently, the press rollers 2 A through 2 D are pressed against the print drums 1 A through 1 D, respectively, effecting multicolor printing.

If one or more of the drum sensors are in an OFF state (No, step D 2 ), the controller 280 determines the statuses of the first, second and third drum sensors 89 , 90 and 189 (steps D 5 , D 6 and D 7 ). If all the drum sensors 89 , 90 and 189 are in an ON state, (Yes, steps D 5 through D 7 ), the controller 280 determines that the print drums 1 A, 1 B and 1 C are present on the printer body 1000 , and then sets up the tricolor mode (step D 8 ). Subsequently, the controller 280 turns on the first to third solenoids 43 A, 43 B and 43 C (step D 9 ), turns on the fourth drive motor 54 D (step D 10 ), and turns on all the fan motors (step D 11 ).

By the steps D 5 through D 11 , the solenoids 43 A, 43 B and 43 C energized locate the associated stops at their release positions, causing the arms 40 A, 40 B and 40 C to rotate clockwise. As a result, the press rollers 2 A, 2 B and 2 C are respectively pressed against the print drums 1 A, 1 B and 1 C, effecting tricolor printing. When the fourth drive motor 54 D is energized, only the press roller 2 D is rotated counterclockwise. Further, all the fan motors are turned on to generate air streams, as stated earlier.

Assume that the answer of any one of the steps D 5 through D 7 is No. Then, the controller 280 advances from the step D 5 to step D 12 shown in FIG. 21 , or from the step D 6 to step D 41 shown in FIG. 23 , or from the step D 7 to step D 56 shown in FIG. 24 .

In the step D 12 , FIG. 21 , the controller 280 determines whether or not the drum sensor 90 is in an ON state. If the answer of the step D 12 is Yes, the controller 280 advances to step D 13 ; otherwise, (No, step D 12 ), the controller 280 advances to step D 28 shown in FIG. 22 . If the third drum sensor 189 is in an ON state (Yes, step D 13 ) and if the fourth drum sensor 290 is in an ON state (Yes, step D 14 ), the controller 280 sets up the tricolor mode (step D 15 ), determining that the second, third and fourth print drums 1 B, 1 C and 1 D are present on the printer body 1000 . Subsequently, the controller 280 turns on the second, third and fourth solenoids 43 B, 43 C and 43 D (step D 16 ), turns on the first drive motor 54 A (step D 17 ), and turns on all of the fan motors (step D 11 , FIG. 20 ).

In the steps D 12 through D 11 executed via the step D 17 , the second, third and fourth solenoids 43 B, 43 C and 43 D energized locate the associated stops at their release positions, causing the arms 40 B, 40 C and 40 C to rotate clockwise. As a result, the press rollers 2 B, 2 C and 2 D are respectively pressed against the print drums 1 B, 1 C and 1 D, effecting tricolor printing. When the first drive motor 54 A is energized, only the press roller 2 A is rotated counterclockwise. Further, all the fan motors are turned on to generate air streams, as stated earlier.

If the third drum sensor 189 is in an OFF state (No, step D 13 ), the controller 280 determines whether or not the fourth drum sensor 190 is in an ON state (step D 18 ). If the answer of the step D 18 is Yes, the controller 280 sets up the bicolor mode (step D 19 ), determining that the second and fourth print drums 1 B and 1 D are present on the printer body 1000 . Subsequently, the controller 280 turns on the second and fourth solenoids 43 B and 43 D (step D 20 ), turns on the first and third drive motors 54 A and 54 C (step D 21 ), and turns on all the fan motors (step D 11 , FIG. 20 ).

In the steps D 18 through D 11 executed via the step D 21 , the second and fourth solenoids 43 B and 43 D energized locate the stops 41 B and 41 D, respectively, at their release positions, causing the arms 40 B and 40 D to rotate clockwise. As a result, the press rollers 2 B and 2 D are respectively pressed against the print drums 1 B and 1 D, effecting bicolor printing. When the first and third drive motors 54 A and 54 C are energized, the press rollers 2 A and 2 C are rotated counterclockwise. Further, all the fan motors are turned on to generate air streams, as stated earlier.

If the fourth drum sensor 190 is in an OFF state (No, step D 18 ), the controller 280 sets up the monocolor mode (step D 22 ), determining that only the second print drum 1 B is present on the printer body 1000 . Subsequently, the controller 280 turns on only the second solenoid 43 B (step D 23 ), turns on the first, third and fourth drive motors 54 A, 54 C and 54 D (step D 24 ), and turns on all the fan motors (step D 11 , FIG. 20 ).

In the steps D 18 through D 11 executed via the step D 24 , the second solenoid 43 B energized locates the stop 41 B at its release position, causing the arm 40 B to rotate clockwise. As a result, the press roller 2 B is pressed against the print drum 1 B, effecting monocolor printing. When the first, third and fourth drive motors 54 A, 54 C and 54 D are energized, the press rollers 2 A, 2 C and 2 D are rotated counterclockwise. Further, all the fan motors are turned on to generate air streams, as stated earlier.

If the fourth drum sensor 190 is in an OFF state (No, step D 14 ), the controller 280 sets up the bicolor mode (step D 25 ), determining that the second and third print drums 1 B and 1 C are present on the printer body 1000 . Subsequently, the controller 280 turns on the second and third solenoid 43 B and 43 C (step D 26 ), turns on the first and fourth drive motors 54 A and 54 D (step D 27 ), and turns on all the fan motors (step D 11 , FIG. 20 ).

In the steps D 14 through D 11 executed via the step D 27 , the second and third solenoids 43 B and 43 C energized locate the stops 41 B and 41 C, respectively, at their release positions, causing the arms 40 B and 40 C to rotate clockwise. As a result, the press rollers 2 B and 2 C are respectively pressed against the print drums 1 B and 1 C, effecting bicolor printing. When the first and fourth drive motors 54 A and 54 D are energized, the press rollers 2 A and 2 D are rotated counterclockwise. Further, all the fan motors are turned on to generate air streams, as stated earlier.

If the third drum sensor 189 is in an ON state (Yes, step D 28 ), the controller 280 advances to step D 29 ; otherwise (No, step D 28 ), the controller 280 advances to step D 36 . If the fourth drum sensor 290 is in an ON state (Yes, step D 29 ), the controller 280 sets up the bicolor mode (step D 30 ), determining that the third and fourth print drums 1 C and 1 D are present on the printer body 1000 . Subsequently the controller 280 turns on the third and fourth solenoids 43 C and 43 D (step D 31 ), turns on the first and second drive motors 54 A and 54 B (step D 32 ), and turns on all the fan motors (step D 11 , FIG. 20 ).

In the steps D 28 through D 11 executed via the step D 32 , the third and fourth solenoids 43 C and 43 D energized locate the stops 41 C and 41 D, respectively, at their release positions, causing the arms 40 C and 40 D to rotate clockwise. As a result, the press rollers 2 C and 2 D are respectively pressed against the print drums 1 C and 1 D, effecting bicolor printing. When the first and second drive motors 54 A and 54 B are energized, the press rollers 2 A and 2 B are rotated counterclockwise. Further, all the fan motors are turned on to generate air streams, as stated earlier.

If the fourth drum sensor 290 is in an ON state (Yes, step D 36 ), the controller 280 sets up the monocolor mode (step D 37 ), determining that only the fourth print drum 1 D is present on the printer body 1000 . If the answer of the step D 36 is No, the controller 280 ends the control, determining that none of the print drums is present on the printer body 1000 (step D 40 ). Subsequently the controller 280 turns on only the fourth solenoid 43 D (step D 38 ), turns on the first, second and third drive motors 54 A, 54 B and 54 C (step D 39 ), and turns on all the fan motors (step D 11 , FIG. 20 ).

In the steps D 36 through D 11 executed via the step D 39 , the fourth solenoid 43 D energized locates the stop 41 D at its release position, causing the arm 40 D to rotate clockwise. As a result, the press roller 2 D is pressed against the print drums 1 D, effecting monocolor printing. When the first, second and third drive motors 54 A, 5 B and 54 C are energized, the press rollers 2 A, 2 B and 2 C are rotated counterclockwise. Further, all the fan motors are turned on to generate air streams, as stated earlier.

If the fourth drum sensor 290 is in an OFF state (No, step D 29 ), the controller 280 sets up the monocolor mode (step D 33 ), determining that only the third print drum 1 C is present on the printer body 1000 . Subsequently, the controller 280 turns on only the third solenoid 43 C (step D 34 ), turns on the first, second and fourth drive motors 54 A, 54 B and 54 D (step D 35 ), and turns on all the fan motors (step D 11 , FIG. 20 ).

In the steps D 29 through D 11 executed via the step D 35 , the third solenoid 43 C energized locates the stop 41 C at its release position, causing the arm 40 C to rotate clockwise. As a result, the press roller 2 C is pressed against the print drums 1 C, effecting monocolor printing. When the first, second and fourth drive motors 54 A, 5 B and 54 D are energized, the press rollers 2 A, 2 B and 2 D are rotated counterclockwise. Further, all the fan motors are turned on to generate air streams, as stated earlier.

If the third drum sensor 189 is in an ON state (Yes, step D 41 ), controller 280 advances to step D 42 ; otherwise, (No, step D 41 ), the controller 280 advances to step D 46 . If the fourth drum sensor 290 is in an ON state (Yes, step D 42 ), the controller sets up the tricolor mode (step D 43 ), determining that the first, third and fourth print drums 1 A, 1 C and 1 D are present on the printer body 1000 . Subsequently, the controller 280 turns on the first, third and fourth solenoids 43 A, 43 C and 43 D (step D 44 ), turns on only the second motor 54 B (step D 45 ), and turns on all the fan motors (step D 11 , FIG. 20 ).

In the steps D 41 through D 11 executed via the step D 45 , the first, third and fourth solenoids 43 A, 43 C and 43 D energized locate the stops 41 A, 41 C and 41 D, respectively, at their release positions, causing the arms 40 A, 40 C and 40 D to rotate clockwise. As a result, the press rollers 2 A, 2 C and 2 D are respectively pressed against the print drums 1 A, 1 C and 1 D, effecting tricolor printing. When the second drive motor 54 B is energized, only the press roller 2 B is rotated counterclockwise. Further, all the fan motors are turned on to generate air streams, as stated earlier.

If the fourth drum sensor 290 is in an ON state (Yes, step D 46 ), the controller 280 sets up the bicolor mode (step D 47 ), determining that the first and fourth print drums 1 A and 1 D are present on the printer body 1000 . Subsequently the controller 280 turns on the first and fourth solenoids 43 A and 43 D (step D 48 ), turns on the second and third drive motors 54 B and 54 C (step D 49 ), and turns on all the fan motors (step D 11 , FIG. 20 ).

In the steps D 46 through D 11 executed via the step D 49 , the first and fourth solenoids 43 A and 43 D energized locate the stops 41 A and 41 D, respectively, at their release positions, causing the arms 40 A and 40 D to rotate clockwise. As a result, the press rollers 2 A and 2 D are respectively pressed against the print drums 1 A and 1 D, effecting bicolor printing. When the second and third drive motors 54 B and 54 C are energized, the press rollers 2 B and 2 C are rotated counterclockwise. Further, all the fan motors are turned on to generate air streams, as stated earlier.

If the fourth drum sensor 290 is in an OFF state (No, step D 46 ), the controller 280 sets up the monocolor mode (step D 50 ), determining that only the first print drum 1 A is present on the printer body 1000 . Subsequently, the controller 280 turns on only the first solenoid 43 A (step D 51 ), turns on the second, third and fourth drive motors 548 , 54 C and 54 D (step D 52 ), and turns on all the fan motors (step D 11 , FIG. 20 ).

In the steps D 46 through D 11 executed via the step D 52 , the first solenoid 43 A energized locates the stop 41 A at its release position, causing the arm 40 A to rotate clockwise. As a result, the press roller 2 A is pressed against the print drums 1 A, effecting monocolor printing. When the second, third and fourth drive motors 54 B, 5 C and 5 D are energized, the press rollers 2 B, 2 C and 2 D are rotated counterclockwise. Further, all the fan motors are turned on to generate air streams, as stated earlier.

If the fourth drum sensor 290 is in an OFF state (No, step D 42 ), the controller 280 sets up the bicolor mode (step D 53 ), determining that the first and third print drums 1 A and 1 C are present on the printer body 1000 . Subsequently, the controller 280 turns on the first and third solenoids 43 A and 43 C (step D 54 ), turns on the second and fourth drive motors 54 B and 54 D (step D 55 ), and turns on all the fan motors (step D 11 , FIG. 20 ).

In the steps D 42 through D 11 executed via the step D 55 , the first and third solenoids 43 A and 43 C energized locate the stops 41 A and 41 C, respectively, at their release positions, causing the arms 40 A and 40 C to rotate clockwise. As a result, the press rollers 2 A and 2 C are respectively pressed against the print drums 1 A and 1 C, effecting bicolor printing. When the second and fourth drive motors 54 B and 54 D are energized, the press rollers 2 B and 2 D are rotated counterclockwise. Further, all the fan motors are turned on to generate air streams, as stated earlier.

If the fourth drum sensor 290 is in an ON state (Yes, step D 56 , FIG. 24 ), the controller 280 sets up the tricolor mode (step D 57 ), determining that the first, second and fourth print drums 1 A, 1 B and 1 D are present on the printer body 1000 . Subsequently the controller 280 turns on the first, second and fourth solenoids 43 A, 43 B and 43 D (step D 58 ), turns on only the third drive motor 54 C (step D 59 ), and turns on all the fan motors (step D 1 , FIG. 20 ).

In the steps D 56 through D 11 executed via the step D 59 , the first, second and fourth solenoids 43 A, 43 B and 43 D energized locate the stops 41 A, 41 B and 41 D, respectively, at their release positions, causing the arms 40 A, 40 B and 40 D to rotate clockwise. As a result, the press rollers 2 A, 2 B and 2 D are respectively pressed against the print drums 1 A, 1 B and 1 D, effecting tricolor printing. When the third drive motor 54 C is energized, only the press roller 2 C is rotated counterclockwise. Further, all the fan motors are turned on to generate air streams, as stated earlier.

If the fourth drum sensor 290 is in an OFF state (No, step D 56 ), the controller 280 sets up the bicolor mode (step D 60 ), determining that the first and second print drums 1 A and 1 B are present on the printer body 1000 . Subsequently, the controller 280 turns on the first and second solenoids 43 A and 43 B (step D 61 ), turns on the third and fourth drive motors 54 C and 54 D (step D 62 ), and turns on all the fan motors (step D 11 , FIG. 20 ).

In the steps D 56 through D 11 executed via the step D 62 , the first and second solenoids 43 A and 43 B energized locate the stops 41 A and 41 B, respectively, at their release positions, causing the arms 40 A and 40 B to rotate clockwise. As a result, the press rollers 2 A and 2 B are respectively pressed against the print drums 1 A and 1 B, effecting bicolor printing. When the third and fourth drive motors 54 C and 54 D are energized, the press rollers 2 C and 2 D are rotated counterclockwise. Further, all the fan motors are turned on to generate air streams, as stated earlier.

For example, when the first and second print drums 1 A and 1 B shown in FIG. 10 are absent on the printer body 1000 , the controller 280 automatically sets up the bicolor mode using the third and fourth print drums 1 C and 1 D. When the first print drum 1 A is absent, the controller 280 automatically selects the tricolor mode using the second, third and fourth print drums 1 B, 1 C and 1 D. This makes it needless for the operator to care whether or not the print drums are present on the printer body 100 . This is extremely advantageous when it comes to a multicolor printer including four print drums as in the illustrative embodiment.

Of course, the illustrative embodiment, like the previous embodiment, causes the press roller corresponding to the print drum absent on the printer body 1000 to rotate at the spaced position and sends air to the consecutive print positions. Therefore, even when the paper 22 passes any one of the print positions where the print drum is absent, the air streams force the paper 22 against the above press roller. This guarantees a sufficient conveying force and thereby surely obviates defective transfer and jam ascribable to a short conveying force.

In the embodiments shown and described, all the air sending means 6 A, 6 B, 6 D, 6 E and 6 C are driven at the same time in order to send air to the vicinity of the print positions 18 , 19 , 180 and 190 . This prevents the paper 22 from rolling up together with the print drums 1 A through 1 D. Alternatively, the control means 80 or 280 may control the fan motors 59 A, 59 B, 59 D, 59 E and 59 C such that air is sent only to the vicinity of the press rollers spaced from the associated print drums, which may even be absent, neglecting the roll-up problem. With this control, it is possible to reduce noise ascribable to air streams and the operation ratio of the motors, i.e., to enhance silent operation and durability of the printer.

If desired, the bifurcated air sending means 6 B, 6 D and 6 E each may be replaced with two discrete paths, in which case a particular drive motor will be assigned to each of the discrete paths.

While each illustrative embodiment is implemented as a stencil printer including a thermal digital master making device, the master making devices and master discharging devices do not have to be arranged on the printer body 100 or 1000 . For example, masters made by master making devices independent of the printer body 100 or 1000 may be wrapped around the print drums, and used masters may be peeled off after the printing operation. As for image data for making masters, the scanner shown and described may be replaced with a computer or similar data input/output unit independent of the printer. It is to be noted that the color selective mode includes a mode in which one of a plurality of print drums to be used for printing is simply selected.

In summary, it will be seen that the present invention provides a multicolor stencil printer having various unprecedented advantages, as enumerated below.

(1) When a color selective mode is selected, holding means assigned to a pressing member, which corresponds to a print drum unused in the above mode, holds the pressing member at a spaced position spaced from the print drum. This prevents the unused print drum and the associated pressing member from contacting each other and thereby makes it needless to wrap a non-perforated stencil around the unused print drum. The printer therefore reduces the print cost.

(2) When desired one of a plurality of print drums is selected in the color selective mode, control means energizes an electromagnetic actuator so as to bring the pressing member corresponding to the above print drum to a contact position contacting the print drum. Printing can therefore be effected with the print drum selected. Further, the holding means assigned to the pressing members associated with the unused print drums hold the pressing members at the spaced positions. This allows a desired print drum to be selected in the color selective mode while preventing the unused print drums and pressing members associated therewith from contacting each other. It follows that non-perforated stencils do not have to be wrapped around the unused print drums. The printer therefore reduces the print cost and is convenient to use.

(3) The printer automatically sets up the color selective mode or a multicolor mode on the basis of the presence/absence of the print drums. In the color selective mode, the control means energizes the electromagnetic actuator so as to bring the pressing member corresponding to the print drum sensed by drum sensing means into contact with the print drum. Printing can therefore be effected with the print drum selected. Further, the holding means assigned to the pressing members associated with the print drums not sensed hold the pressing members at the spaced positions. This makes it needless to wrap non-perforated stencils around the unused print drums and therefore reduces the print cost while preventing the unused print drums and pressing members associated therewith from contacting each other. In addition, the printer is convenient to use and reduces operator's mishandling to thereby enhance reliable operation.

(4) Drive means causes the pressing member to rotate in a direction opposite to a direction in which the associated print drum rotates during printing. Therefore, even the pressing member held at the spaced position can exert a sufficient conveying force on a paper. This also makes it needless to wrap non-perforated stencil is around the unused print drums and therefore reduces the print cost. In addition, a paper can be desirably conveyed even if it is not pressed by the pressing member.

(5) An air stream source sends air toward a paper around a print position where the print drum and associated pressing member face each other from the print drum side. Therefore, even when the holding means holds the pressing member at the spaced position, the air stream forces the paper against the pressing member rotating in the previously stated direction and allows the rotation of the pressing member to be efficiently transferred to the paper. It follows that the conveying force to act on the paper is increased and obviates defective conveyance.

(6) Because desired one of the multicolor mode and color selective mode can be selected, prints matching a desired application can be produced.

Various modifications will become possible for those skilled in the art after receiving the teachings of the present disclosure without departing from the scope thereof.

Claims

1. A multicolor stencil printer comprising:a plurality of print drums each storing an ink of a particular color therein; a plurality of pressing members each positioned and configured to move into contact with a particular one of said print drums to nip a recording medium for printing an image and move out of the contact with the particular one of said print drums to transport the recording medium toward downstream; and a plurality of holding devices each configured to hold a particular one of said pressing members out of the contact with said particular one of said print drums; wherein: when the printer is operated in a color selective mode, said print drums and said pressing members selectively cooperate to nip the recording medium for printing such that at least one of the pressing members is held out of contact with a corresponding one of the print drums by a corresponding one of said holding devices; and said plurality of holding devices each comprise an arm rotatably supporting a respective one of said pressing members and configured to move said respective one of said pressing members between a contact position where a circumference of said respective one of said pressing members is pressed against a circumference of a respective one of the print drums therewith and a spaced position where the circumference of said respective one of said pressing members is spaced from the circumference of said respective one of said print drums, a stop configured to engage with said arm to hold said arm at said spaced position, biasing means for biasing said stop toward said arm, and an electromagnetic actuator configured to move said stop away from said arm.

2. The multicolor stencil printer as claimed in claim 1, further comprising;drum selecting means for selecting a desired one of said print drums; and driving means for driving, in said color selective mode, said electromagnetic actuator to move said stop away from said arm such that the respective one of said pressing members associated with the respective one of said print drums selected by said drum selecting means is brought to said contact position.

3. The multicolor stencil printer as claimed in claim 1, further comprising:a plurality of drum sensing means each for sensing whether a particular one of said print drums is present; and setting means for setting up, based on an output from said drum sensing means, one of said color selective mode and a multicolor mode in which said print drums and said pressing members all cooperate to nip the recording medium for printing.

4. The multicolor stencil printer as claimed in claim 3, wherein said setting means sets up one of said color selective mode when at least one of said drum sensing means senses an associated one of said print drums and said multicolor mode when all of said drum sensing means sense associated ones of said print drums.

5. The multicolor stencil printer as claimed in claim 3, further comprising print mode selecting means for selecting one of said multicolor mode and said color selective mode.

6. The multicolor stencil printer as claimed in claim 1, further comprising rotating means for rotating a respective one of said pressing members in a direction opposite to a direction in which an associated one of said print drums rotates during printing.

7. The multicolor stencil printer as claimed in claim 6, further comprising air sending means comprising an air stream generator for generating an air steam and a guide for guiding said air stream to the vicinity of a location where a respective one of print drums and a respective one of the pressing members face each other.

8. A multicolor stencil printer comprising:a plurality of print drums each storing an ink of a particular color therein; a plurality of pressing devices each positioned and configured to move into contact with a particular one of said print drums to nip a recording medium for printing an image and move out of the contact with the particular one of said print drums to transport the recording medium toward downstream, said pressing devices each including a holding device configured to hold a respective one of said pressing devices out of the contact with said particular one of said print drums; and a print mode selecting device configured to select one of a multicolor mode in which said print drums and said pressing devices nip the recording medium for printing and a color selective mode in which said print drums and said pressing devices selectively cooperate to nip the recording medium for printing; wherein said holding device comprises an arm rotatably supporting a respective one of said pressing members and configured to move said respective one of said pressing members between a contact position where a circumference of said respective one of said pressing members is pressed against a circumference of a respective one of the print drums therewith and a spaced position where the circumference of said respective one of said pressing members is spaced from the circumference of said respective one of said print drums, a stop configured to engage with said arm to hold said arm at said spaced position, biasing means for biasing said stop toward said arm, and an electromagnetic actuator configured to move said stop away from said arm.

9. A multicolor stencil printer comprising:a plurality of print drums each storing an ink of a particular color therein; a plurality of pressing devices each positioned and configured to move into contact with a particular one of said print drums and move out of the contact with the particular one of said print drums to transport the recording medium toward downstream, said pressing devices each including a holding device configured to hold a respective one of said pressing devices out of the contact with said particular one of said print drums; and print mode selecting means for selecting one of a multicolor mode in which said print drums and said pressing devices nip the recording medium for printing and a color selective mode in which said print drums and said pressing devices selectively cooperate to nip the recording medium for printing; wherein said holding device comprises an arm rotatably supporting a respective one of said pressing members and configured to move said respective one of said pressing members between a contact position where a circumference of said respective one of said pressing members is pressed against a circumference of a respective one of the print drums therewith and a spaced position where the circumference of said respective one of said pressing members is spaced from the circumference of said respective one of said print drums, a stop configured to engage with said arm to hold said arm at said spaced position, biasing means for biasing said stop toward said arm, and an electromagnetic actuator configured to move said stop away from said arm.