Silk-screen printing apparatus

Abstract: Silk-Screen printing apparatus which includes a rack for a print frame (3) and a rack for an operation piece (17), the racks being engaged by gears attached to a print cylinder (2). During printing operations, the two racks are attached to one another rigidly. When printing operations cease, a camming arrangement (27, F) raises the operation piece to release the operation piece from the gears, so that the print frame can be pulled from the machine base (1), independently from the cylinder.

Description: This invention relates to silk-screen printing apparatus generally of the type which includes a rotatable cylinder and more particularly to such apparatus capable of moving a print frame independently from its cylinder. In cylinder type silk-screen printing devices, ink sticks on the silk-screen and the cylinder after repetitive printing operations. This sticking of the ink will degrade the quality of printing work. Because of this, it is frequently necessary to wipe ink from the silk-screen and cylinder and to keep them clean. A cleaning method for the purpose stated above is disclosed in U.S. Patent No. 4,448,124. According to this disclosed printing machine, a paper ejecting base 101 is installed in a swingable manner as shown in Fig. 6. During printing operations, the paper ejecting base 101 is held in a horizontal orientation as indicated by the two-dot chain. Thus, it feeds printing paper P sent by the rotation of cylinder 100 to a recovering device (not shown in the drawings). To clean the inside of the machine, the paper ejecting base 101 is swung in the direction indicated by the arrow in Figure 6 to the suspended position indicated by solid lines. This opens the space below the print frame 102. Thus an operator can lean into the printing machine to wipe ink from the bottom face of silk-screen 103 and the periphery of the cylinder 100. Since the print frame 102 is located at the rear of the cylinder 100 within the machine, the operator has to lean the upper portion of his body into the machine in order to wipe ink from the entire cylinder and silk-screen. However, gaining access to the limited space in the machine can be difficult. As a result, when a large operator tries to wipe ink from the inner parts, ink sometimes remains partially unremoved. The remaining ink sticks firmly on the rear face of silk-screen 103, thereby obstructing good printing operation thereafter. The present invention seeks to provide a silk-screen printing apparatus which is capable of assuring reliable cleaning of the cylinder regardless of the size of the operator. The invention seeks to provide silk-screen printing apparatus having a print frame that can be easily pulled from the machine base to provide a wide space inside the machine base. In one aspect, the invention provides silk-screen printing apparatus, which comprises a cylinder installed in a rotatable manner within a machine base, and a print frame which is located above the cylinder, the print frame being linked to the cylinder during printing so as to reciprocate in a horizontal direction in synchronisation with the rotation of the cylinder, and being capable of performing the printing work on paper held on the cylinder through a silk-screen provided in the print frame by means of a squeegee and a doctor, the apparatus being characterised in that it includes: (a) releasing members which permit the release of the linkage between the print frame and the cylinder during non-printing time, and which permit movement of the print frame independent of rotation of the cylinder; and (b) a tray for receiving ink, which is movable in synchronization with the releasing members between a position facing the cylinder and a position separated from the cylinder to one side thereof, the tray being provided in a space between the squeegee and the doctor and the silk screen on top of the machine base. Preferably, the silk-screen printing apparatus of the invention performs a printing operation by moving a silk-screen in synchronization with the rotation of a cylinder located inside a machine base. The printing apparatus includes a print frame located above the cylinder for carrying the silk-screen. The print screen is linked with the cylinder during printing and reciprocates in the horizontal direction in synchronization with the rotation of the cylinder. A releasing mechanism may be operable during non-printing times to release the linkage between the print frame and the cylinder, so as to allow movement of the print frame independent from the rotation of said cylinder. Preferably, the printing apparatus includes a paper ejecting base installed on the machine base in a swingable manner between a horizontal position and a suspended position. Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is an isometric view showing the silk-screen printing apparatus of the invention when the print frame is pulled to the outside of the machine base in a non-printing state. Figure 2 is a side view showing each operating mechanism of the silk-screen printing apparatus during a printing operation. Figure 3 is an isometric exploded view showing part of print frame. Figure 4 is a side view showing the print frame in pullable state during a non-printing time. Figure 5 is a side view showing the displacement of the ink-receiving tray during the non-printing time. Figure 6 is a partially enlarged side view indicating a conventional silk-screen printing machine in which the inside of the machine base can be cleaned. As shown in Figure 1 and Figure 2, a cylinder 2 is supported in a rotatable manner at the center in a machine base 1. As indicated in Figure 1, a horizontally extending rail 25 is mounted to the inner wall surface of the machine base 1 above the cylinder 2. A print frame 3 having a rectangular loop shape is located above the rail 25. A silk-screen 4 is located inside the loop of the print frame. A squeegee 6 and a doctor 5 are mounted on a mounting plate 7, which is fixed to the machine base 1 above the cylinder 2. The silk-screen 4 is located between the cylinder and the mounting plate. A paper ejecting plate 8 is provided at a paper ejecting side (at the left side in the figure) of the machine base 1 and can be swung between the horizontal position shown by the solid line in Figure 1 and the suspended position shown by the two-dot chain line. During printing operation, the paper ejecting plate 8 is in horizontal position. In this position, it feeds printing paper to a recovering device (not shown). During non-printing times, it is swung to the suspended position thereby widening the space at the paper ejecting side of the machine base 1. Drive gears 9 are fixed to opposing ends of said cylinder 2. The drive gears 9 have a diameter larger than that of the cylinder. These drive gears 9 are respectively engaged with racks 10 formed on the bottom faces of opposing sides of print frame 3. A driven gear 11 is fixed to the shaft of cylinder 2 at a position adjacent one of the drive gears 9. The driven gear 11 has a smaller diameter than cylinder 2 and engages a sector gear 12. Rotation of an electric motor 13 is transmitted as a reciprocating motion to the sector gear 12 through a motion conversion mechanism comprising two rods 15. The sector gear 12 makes reciprocating rotation within a prescribed range. Reciprocal rotation of said sector gear 12 drives the cylinder 2 in a reciprocating manner through the driven gear 11. The reciprocating rotation of the cylinder 3 is transmitted to the rack 10 through the drive gear 9, and the print frame 3 makes a reciprocating motion back and forth in synchronization with the cylinder 2. As shown in Figure 3, a recessed mounting portion 16 is formed in the length direction at a part of the bottom face of each side of the print frame 3. A channel-shaped mounting member 17 is attached to the recessed mounting portion 16. A pair of through holes 18 are made in the print frame 3 above the recessed mounting portion 16. Also a pair of supporting holes 19 are made in the print frame 3 adjacent the operation piece 17. A pair of washer-shaped guides 20a are supported in a rotatable manner by the print frame 3 by means of shafts 20. These guides are provided at both the ends of operation piece 17. At the bottom face of the operation piece 17, a rack 21 is formed throughout the whole length and width of the operation piece for engagement with the drive gear 5. A pair of holding walls 24 extend upward from the bottom at both sides of the operation piece 17. The operation piece 17 is attached to the print frame 3 in a manner such that the recessed mounting portion 16 can be covered by both the holding walls 24. Front and rear slots 22 are made in each holding wall 24. Pins 23 are inserted into both the slots 22 and supporting holes 18 in order to support the operation piece 17 in a vertically movable manner relative to the print frame 3. The operation piece 17 can move between an upper position (Figure 5) and a lower position (Figures 2 and 6). Each guide 20a contacts a face of the operation piece 17 and is rotated by the up-and-down motion of the operation piece 17. The guides thus ensure that the operation piece can be moved up and down smoothly. A pair of lift rollers 26 are rotatably attached to the holding walls 24. When the operation piece is at the lower position, the roller moves on the rail 25 and permits the movement of print frame 3. A pair of front and rear compression coil springs 13 are placed between the lower face of the recessed mounting portion 16 of print frame 3 and the inner bottom face of rack 21. These springs 13 always hold the operation piece 17 at the lower position and permit the absolute engagement of small rack 21 with the drive gear 9. As shown in Figure 2, an electric motor 32 is installed at the paper ejecting side of the cylinder 2 in the machine base 1. A sprocket 33 is fixed to the output shaft of the motor 32. An intermediate gear 29 is supported above the motor 29 in a rotatable manner relative to the machine base 1. The intermediate gear 29 and its shaft support a sprocket 30 and a toothed pulley (Figure 5). A chain 34 is attached between the sprockets 30 and 33. A gear 28 engages the intermediate gear 29 and is positioned above the gear 29. Gear 28 is mounted on the same shaft as a cam 27. At the machine base 1, a drive lever 35 is rotatably supported by a support shaft 36. One end of the drive lever 35 is fixed to the rail 25 by a pin while the other end carries a rotatable cam foller F. A spring 37 biases the lever such that the cam follower F follows the movements of cam 27. At the paper feed side of the cylinder 2, the base end portion of a supporting lever 35a is supported in a rotatable manner by the frame of machine base 1. The tip portion of the supporting lever 35a is fixed to the rail 25 by a pin. Stepped pairs of notches 38 and 39 extend upward from the bottom face of rail 25 near the paper ejecting side of rail 25. Rotatable rail guides 40 are positioned within the notches 38, 39. When the cam 27 is rotated by motor 32, the drive lever 35 is rotated and the rail 25 is reciprocated up and down between the upper position (Figures 4 and 5) and lower position (Figure 2). Specifically, movement of the drive lever pushes the rails to the left as seen in Figure 2, causing the paper ejecting side of the rails to rise as the rail moves from notch 38 to 39. In the lifted position, the paper feed side is held by lever 35a. The paper ejecting side of the rail 25 is supported by rail guides 40 which rests in notches 39. Thus, the entire rail 25 is uniformly supported at both the upper and lower positions. When the rail 25 is moved to the upper position, the operation piece 17 is lifted by lift roller 26. This movement is against the force of spring 13. The upward movement of the operation piece 17 releases the engagement of gear 9 and rack 21. Because of this, the print frame 3 is supported by the lift rollers 26. In this state, if forces are applied to the print frame 3, the rollers 26 turn on the rail 25, thereby allowing the print frame 3 to be moved towards or away from the machine base 1. As shown in Figure 1, the ink-receiving tray 48 rests on the upper portion of the machine base 1. It may be moved longitudinally along the base. As shown in Figure 5, an endless timing belt 51 is extended between the pulley 31 attached to the intermediate gear 29 and a pulley 50 attached above the machine base 1. At the end portion of the feed side of the machine base 1, a pulley 52 is supported by bearings at the same height as pulley 50. A horizontal endless timing belt 53 is extends between pulleys 50 and 52. The ink-receiving tray 48 is attached at the upper side of the timing belt 53. Timing belts 51, 53 are turned by the sprockets 30, 33 which are rotated by the motor 32. Thus, the ink-receiving tray 48 is moved in synchronization with the movement of rail 25. That is, when the rail 25 is at the lower position, the ink-receiving tray 48 is held to the position indicated by the two-dot chain line in Figure 5. At the end of printing, the motor 32 is rotated forward a predetermined amount through the oepration of a manual switch (not shown). This moves the rail 25 to the upper position. At the same time, the ink-receiving tray 48 is moved to the position indicated by solid lines between the cylinder 2 and silk-screen 4. The action of the silk-screen printing apparatus will be explained hereinafter. As shown in Figure 2, the drive gear 9 is engaged with the rack 21 of the operation piece 17 during printing operations. When the motor 13 is rotated, the sector gear 12 is rotated through the rod 15, and the cylinder 2 is rotated through the driven gear 11. This rotation of cylinder 2 is transmitted to the print frame 3 through the engagement between the drive gear 9 and rack 10. Thus, the print frame 3 is moved back and forth in synchronization with the rotation of cylinder 2. When the cylinder 2 turns clockwise and reaches the paper feed position, a gripper (not shown) grips the printing paper. Thereafter, the cylinder 2 begins to rotate toward the paper ejecting side (counterclockwise). When the cylinder 2 reaches the printing start position, the paper it carries contacts the silk-screen 4. The squeegee 6 applies a pressure to the upper face of the silk-screen 4 and commences printing. Thereafter, when the cylinder 2 comes to the printing end position, the paper is separated from the silk-screen 4 and printing is completed. When the cylinder 2 turns further counter-clockwise and reaches the paper separating position, the gripper separates paper the paper from the cylinder. The printed paper is then sent to a recovering device (not shown) through the horizontally held paper ejecting plate 8, thereby completing printing. Thereafter, the cylinder 2 is reset and returned to the paper feed position and the above operation is repeated. When all the sheets of desired sheets have been printed, the rotation of the motor 13 is stopped, and the print frame 3 is held at the position indicated in Figure 2. Thereafter, the motor 32 is turned and the gear 28 is rotated through the sprocket 33, chain 34, sprocket 30 and intermediate gear 29. Thus, the cam 27 is rotated clockwise as shown in Figure 2, the rail 25 is raised by the rotation of the lever 35 clockwise, and an upward force will be applied to the roller 26 of the operation piece 17. Because of this, as indicated in Figure 4, the operation piece 17 is raised by a distance determined by the difference between the diamtere of pin 23 and the length of the slot 22. Additionally, the engagement between the rack 21 and drive gear 9 is released. As said motor 32 is rotated, the belt 53 is turned by sprocket 30, pulleys 31, t0 and belt 51, and the ink-receiving tray 48 is moved to the position indicated by solid lines in Figure 5. Then, if the print frame 3 is pulled toward the paper ejecting side of machine base 1, then th roller 26 turns on the rail 25, so that the print frame 3 is projected out to the paper ejecting side. Then, a large space is obtained below the paper ejecting side of silk-screen 4. Therefore, in cleaning the silk-screen 4, a worker is able to clean the rear surface of the silk-screen 4 easily from the bottom side without being obstructed by the machine base 1. When the paper ejecting plate 8 is swung into the suspended position indicated by the two-dot chain lines, a large space can be secured not only at the paper ejecting side but also as a whole below the silk-screen 4. Because of this, it becomes possible to clean the entire rear face of the silk-screen 4. Moreover the worker is able to perform the cleaning operation in a natural posture. In addition, ink dripping from the squeegee 6 and doctor 5 normally comes to the top face of the silk screen 4. However, at the time of cleaning said silk-screen 4, the print frame 3 is moved to the paper ejecting side and thus evacuated from the top portion of the cylinder 2. At that time, ink dripping down from the squeegee 6 and doctor 5 is recovered inside the ink-receiving tray 48 located at the position indicated by solid lines in Figure 2, so that ink will not drip down on the periphery of cylinder 4. This prevents the cylinder from being soiled. Moreover, the paper gripper on the periphery of the cylinder 2 can be easily checked and adjusted before printing is resumed. For this purpose, the print frame 3 should be moved to the paper ejecting side in the machine base 1 and the silk-screen 4 should be evacuated from the top of cylinder 2, and then the cylinder 2 should be kept still without being rotated. In another construction, a link mechanism or the like may be used instead of the cam 27 as a lifting device for the rail 25. This alternative mechanism may be moved in synchronization with the ink-receiving tray 48.

Claims: Silk-screen printing apparatus, which comprises a cylinder (2) installed in a rotatable manner within a machine base (1), and a print frame (3) which is located above the cylinder (2), the print frame (3) being linked to the cylinder (2) during printing so as to reciprocate in a horizontal direction in synchronisation with the rotation of the cylinder (2), and being capable of performing the printing work on paper held on the cylinder (2) through a silk-screen (4) provided in the print frame (3) by means of a squeegee (6) and a doctor (5), the apparatus being characterised in that it includes: (a) releasing members (28) which permit the release of the linkage between the print frame (3) and the cylinder (2) during non-printing time, and which permit movement of the print frame (3) independent of rotation of the cylinder (2); and (b) a tray (48) for receiving ink, which is movable in synchronization with the releasing members (28) between a position facing the cylinder (2) and a position separated from the cylinder (2) to one side thereof, the tray (48) being provided in a space between the squeegee (6) and the doctor (5) and the silk screen (4) on top of the machine base (1). Apparatus as claimed in claim 1, in which the cylinder (2) carries a gear (9), and in which the print frame (3) is formed with a first rack (10) at the base of the print frame (3) for engaging the gear (9) during printing. Apparatus as claimed in claim 2, in which the print frame (3) is equipped with a vertically displaceable operation piece (17) which has a second rack (21) with a pitch which is the same as that on the first rack (10), the second rack (21) of the operation piece (17) being pushed normally to a level which approximates to that of the first rack (10), and engaging the gear (9). Apparatus as claimed in claim 3, in which the releasing means (28) includes: (a) vertically moveable rails (25) which extend parallell to, and below the print frame (3); (b) rollers (26) attached to the vertically displaceable operation piece (17), and running along the vertically moveable rail (25); and (c) displacing member (27, F), for vertically displacing the rails (25) and then vertically displacing the operation piece (17) through the rollers (26). Apparatus as claimed in claim 4, in which the operation piece (17) is mounted on the print frame (3) with columnar pins (23) inserted into vertically extending slots (22) in the operation piece. Apparatus as claimed in claim 4 or claim 5, in which the displacing member comprises an eccentric cam (27) rotated by an electric motor, and a cam follower (F) which contacts the periphery of the cam (27), and in which the rails (25) are vertically displaced according to the profile of the cam (27) through the cam follower (F). Apparatus as claimed in any one of claims 1 to 6, in which the machine base (1) is equipped with a paper ejecting base (8) which is swingable between a horizontal position and a suspended position.

Inventors: NAGATANI KAZUO, NAGATANI, KAZUO
Applicants: SAKURA SEIKI CO LTD, SAKURA SEIKI CO., LTD.
Application year: 1990
Main classification: B41F15
IPC codes: B41F15