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(11) | EP 1 078 738 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Sheet-fed offset printing machine |
| (57) A sheet-fed printing machine in which a rotation brush (5) approaching the impression
cylinder (3) is disposed between the clamp arm (2) and the blanket cylinder (4), an
upstream wall (6) and a downstream wall (7) are disposed as to shield an upstream
side and a downstream side of the rotation brush (5) and end edge portions of the
upstream wall (6) and the downstream wall (7) are brought close to the impression
cylinder (3), an inside wall portion (8) shields the upstream wall (6) and the downstream
wall (7) tightly, and a suction slit (10) is formed on the inside wall portion (8)
connected to a vacuum passage (9) for sucking foreign matter (R) adhering to the rotation
brush (5) with the inside wall portion (8) approaching or touching an inside portion
of the rotation brush (5). |
[0002] In conventional sheet-fed offset printing apparatuses to print on paper (sheets), as shown in Figure 4, for example, paper 1 sent out of a feeding device (not shown in Figures) is held by a holding device 21 of a clamp arm 2 and fed to an impression cylinder 3. Then, the paper 1 is re-held by another holding device 31 on the impression cylinder 3, inserted between the impression cylinder 3 and a blanket cylinder 4 for printing.
[0003] An air nozzle 41 and a brush 42 for holding the paper are disposed right above the impression cylinder 3. The paper 1 transferred by the impression cylinder 3 is prevented from flapping by high-pressurized air. Further, the brush 42 removes foreign matter such as paper powder adhering to the surface of the paper 1 and holds the paper 1 to insert certainly between the blanket cylinder 4 and the impression cylinder 3. 43 is an air pipe for supplying compressed air to the air nozzle 41, and 44 is a supporting member for attachment of the brush 42 to the apparatus main body.
[0004] In the sheet-fed offset printing machine as described above, it is preferable to remove not only foreign matter on the paper such as paper powder, dust, etc. but all of adhesive foreign matter, foreign matter embedded in the paper 1, sticking foreign matter such as feather-like fiber on an edge of the paper before the printing to improve accuracy and clearness of the printing.
[0005] However, in dust removing by the brush 42, the foreign matter caught by the brush 42 may adhere to the paper 1, an apparatus for cleaning the brush 42 (a brush cleaner), which makes the construction complicated and the whole apparatus large, is necessary, and dust-removing ability is insufficient. And, the high-pressurized air blown to the paper 1 may put floating foreign matter onto or into the paper 1. The foreign matter causes degeneration of the accuracy and clearness of the printing. And the foreign matter may adhere to the blanket cylinder 4 for printing and reduce the accuracy and clearness of the printing further. To prevent this, the blanket cylinder 4 must be washed several times a month, and this causes much labor.
[0006] To solve the problems above, it is therefore an object of the present invention to provide a compact sheet-fed offset printing machine with which the paper can be cleaned before the printing, and prevented from flapping.
[0007] This object is solved according to the present invention by sheet-fed offset printing machine including features of claim 1.
[0008] The present invention will be described with reference to the accompanying drawings in which:
Figure 1 is a construction view of a principal portion showing a preferred embodiment of the sheet-fed offset printing machine of the present invention;
Figure 2 is an enlarged cross-sectional view of a principal portion;
Figure 3 is an enlarged view of a principal portion showing another preferred embodiment; and
Figure 4 is a construction view of a principal portion showing a conventional sheet-fed offset printing machine.
[0009] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings.
[0010] Figure 1 is a construction view of a principal portion showing a preferred embodiment of the sheet-fed offset printing machine of the present invention, and Figure 2 is an enlarged cross-sectional view of a principal portion. In these Figures, 1 is paper (a sheet) sent out of a feeding machine not shown in Figures and fed in an direction of an arrow A, and 2 is a clamp arm, of which end portion is provided with a holding device 21 for holding a forth end of the paper 1, driven rotationally clockwise as shown in Figure 1, and 3 is an impression cylinder on which a holding device 31 is disposed for, succeeding the holding device 21, re-holding the forth end of the paper 1 held and fed by the clamp arm 2.
[0011] 4 is a blanket cylinder pressed to contact the impression cylinder 3, supplied with ink by an ink supplying device (not shown in Figures), and the paper 1 is inserted between the impression cylinder 3 and the blanket cylinder 4 to print. And 5 is a rotating brush for removing foreign matter R such as paper powder, dust, etc. adhering to the paper 1 before the printing. The rotating brush 5 is disposed between the blanket cylinder 4 and the clamp arm 2, freely closed to and part from the impression cylinder 3, and rotated by a driving device not shown in Figures at about 1600 to 3000rpm.
[0012] The rotating brush 5 is having a width dimension same as or slightly larger than the width of the paper 1, extending in a vertical direction to the surface of Figure 1, and stored in a case 11. As the material of the bristle of the brush 5, for example, polyamide resin (nylon, etc.), acrylate resin, metal, conductive fiber, etc. are preferable. The holding device 31 outsizes the impression cylinder 3 for 5 to 6mm, contacts the rotating brush 5 in every rotation of the impression cylinder 3, and gives vibration to the rotating brush 5 and all parts connected to the rotating brush 5. Bristle size (length of the bristle) of the brush 5 is preferably (set to be long enough) 15mm to 20mm to absorb the vibration. The case 11 is provided with an upstream wall 6 and a downstream wall 7, of which end edges approach the above impression cylinder, to shield an upstream side and a downstream side of the rotation brush 5, and an inside wall portion 8 to tightly seal the upstream wall 6 and the downstream wall 7. Lower portions of the upstream wall 6 and the downstream wall 7 are bent toward inside, and lower bent portions 61 and 71 are formed approximately as to surround a lower portion of the rotation brush 5 from the both sides. And, upper portions of the upstream wall 6 and the downstream wall 7 are also bent toward inside to form upper bent portions 62 and 72, and upper space in the case 11 is narrowed upward by the upper bent portions 62 and 72.
[0013] A suction slit 10, which approaches or contacts an upper side of the rotation brush 5 to suck the foreign matter R adhering to the rotation brush 5, is formed in a direction parallel to the rotation brush 5 (a direction at right angles with the feeding direction of the paper 1). And, a vacuum duct 12 is attached to an upper portion of the inside wall portion 8, a vacuum passage 9 formed in the vacuum duct 12 is connected to the suction slit 10 formed on the inside wall portion 8 of the case 11. Further, a pipe 13 connected to the vacuum passage 9 for vacuumization is attached to the vacuum duct 12 and connected to a suction device provided with a vacuum pump not shown in Figures.
[0014] Current velocity V of the air passing through suction openings 14 formed between the lower bent portions 61 and 71 of the upstream wall 6 and the downstream wall 7 and the paper 1, may be set corresponding to operational conditions, is preferably set to be about 50 to 60m/sec. When the air is sucked at the velocity V, suction effect of the foreign matter R becomes remarkable, and the foreign matter R, once sucked off the paper 1, is certainly sucked into the vacuum passage 9 without falling off the brush and discharged to the outside from the suction device through the pipe 13. If the velocity is less than 50m/sec, the foreign matter R once swept by the rotation brush 5 may drop out of the case 11. On the other hand, the velocity over 60m/sec does not improve the foreign matter removing effect much.
[0015] Rotational frequency of the rotation brush 5 is, for example, preferably set to be about 1600 to 3000rpm. With this frequency, the foreign matter R adhering to the paper 1 can be effectively removed, and the paper 1 is prevented from being damaged. If the rotational frequency is less than 1600rpm, the foreign matter R firmly adhering to the paper 1 can not be removed. And, the rotational frequency over 3000rpm may cause flaws on the surface of the paper 1.
[0016] As described above, the vacuum duct 12, the pipe 13, and the case 11 are unified and supported by a supporting device 15 on the main body of the machine (not shown in Figures) as to be movable approximately in a vertical direction. The supporting device 15 is composed of an attachment member 151 attached to the main body of the machine with bolts, a cylinder 152 fixed to the attachment member 151, a piston rod 153, and an arm 154 attached to an end portion of the piston rod 153. The vacuum duct 12 and the pipe 13 are fixed to an end portion of the arm 154, and the rotation brush 5 is moved as to close to and part from the impression cylinder 3 by extension and contraction of the cylinder 152.
[0017] In a state shown in Figure 1, the cylinder 152 is extended, the rotation brush 5 is in a working position in which the brush 5 slightly contacts the surface of the impression cylinder 3, the rotation brush 5 is rotating in an arrow F direction at a predetermined rotation frequency, the inside of the case 11 is vacuumized by the suction device, and the velocity V of the air, passing through the suction openings 14 formed between the lower bent portions 61 and 71 of the upstream wall 6 and the downstream wall 7 and the paper 1, is set to be a predetermined velocity.
[0018] In this state, the paper 1 held and fed by the clamp arm 2 is re-held by the holding device 31 of the impression cylinder 3, and sent between the rotation brush 5 and the impression cylinder 3. And, the air of high velocity sucked through the suction openings 14 is sucked upward flowing along the surface of the paper 1, the foreign matter R biting into the surface of the paper 1 is effectively sucked up together with the foreign matter on the surface. And, the foreign matter R biting into the surface of the paper 1 is effectively swept off together with the foreign matter on the surface for the bristle 51 slightly curved (as not to cause flaws on the paper 1) and charged appropriately with elastic energy of which end portion certainly slides on the surface of the paper 1.
[0019] Further, the rotating brush 5 is always kept cleaned because the foreign matter R caught by the rotating brush 5 is sucked into the suction slit 10. Therefore, the device for cleaning the rotating brush 5 is unnecessary. As described above, the foreign matter R is efficiently removed without causing flaws on the surface of the paper 1 by sweeping function of the rotating brush 5 with vacuumization.
[0020] To describe in further details, the closer the air comes to the suction openings 14, the larger the velocity of the air becomes, and the suction effect to the paper 1 is improved and the removing effect of the foreign matter R becomes remarkable because the lower bent portions 61 and 71 are formed by bending the lower portions of the upstream wall 6 and the downstream wall 7 of the case 11. Further, the upper parts of the upstream wall 6 and the downstream wall 7 are bent inside to form the upper bent portions 62 and 72, and upper space in the case 11 is narrowed upward. The velocity of the air in the upper space is increased, suction effect to the upper part of the rotating brush 5 touching the suction slit 10 is improved, and the foreign matter R adhering to the rotating brush 5 is effectively sucked and removed.
[0021] Even in the vacuumization state as described above, the paper 1 is prevented from raising and flapping, and transferred in tight contact with the impression cylinder 3 because the paper 1 is pressed to the surface of the impression cylinder 3 by elasticity of the bristle 51 of the rotation brush 5. Therefore, the paper 1 is certainly inserted between the blanket cylinder 4 for printing and the impression cylinder 3, and a clear image of high accuracy is printed on the paper 1 without blur and bleeding. That is to say, conventional prevention of flapping by the air nozzle 41 and paper holding and removing the foreign matter by the brush 42 are conducted together by the one rotating brush 5 with vacuumization, and the foreign matter R is removed far more efficiently than the conventional printing machine.
[0022] And, the whole apparatus can be formed far more compact than the conventional machine because the rotating brush 5 is stored in the compact case 11. To describe in further details, in a conventional turbo cleaner, a nozzle is attached right below a vacuum passage, and an end portion of the nozzle is disposed close to a rotating brush. In the embodiments of the present invention, however, height dimension of the apparatus is greatly diminished and remarkable compactification can be achieved because the nozzle is omitted and the end portion of the rotating brush 5 is closed directly to the suction slit 10 of the vacuum duct 12.
[0023] Figure 3 shows another embodiment. In this case, the downstream wall 7 (and the upstream wall 6) is bent plural times (twice) as to form lower bent portions 71a and 71b (61a and 61b) gradually approach the lower peripheral portion of the rotating brush 5. That is to say, minimum opening dimensions T1, T2, and T3 gradually diminish toward the suction opening 14 side. With this construction, the air velocity increases as becomes close to the suction opening 14, and further remarkable suction effect against the paper 1 can be demonstrated. And, the upstream wall 6, not shown in Figure 3, is constructed to be symmetric to the downstream wall 7.
[0024] And, the minimum opening dimension T1 may be set to have different values between the upstream wall 6 and the downstream wall 7. For example, the minimum opening dimension T1 on the downstream wall 7 may be smaller than that on the upstream wall 6 to make the suction effect high and volume on a sucking-up side of the foreign matter R (the upstream side) large to effectively deal with a case that the adhesion of the foreign matter R is relatively excessive. And, the upper parts of the upstream wall 6 and the downstream wall 7 may be attached to the inside wall portion 8 with hinges or bolts as to be position-adjustable for arranging appropriately the interval between the upstream wall 6 and the downstream wall 7.
[0025] According to the sheet-fed offset printing machine, foreign matter adhering onto the paper 1 is effectively sucked and removed by the rotating brush 5 with vacuumization, and foreign matter adhering to the rotating brush is also removed by the vacuumization. And, the paper 1 is prevented from raising and flapping by the rotating brush 5 pushing the paper 1 to the impression cylinder 3. Therefore, a clear and highly accurate image is printed on the paper 1, and the whole apparatus is formed to be compact.
1. A sheet-fed printing machine in which paper (1) sent out of a feeding machine is held
by a clamp arm (2), sent to an impression cylinder (3), and pressed by the impression
cylinder (3) to be printed by cooperation of the impression cylinder (3) and a blanket
cylinder (4) for printing, comprising:
a rotation brush (5) approaching the impression cylinder (3) and disposed between the clamp arm (2) and the blanket cylinder (4);
an upstream wall (6) and a downstream wall (7), shielding an upstream side and a downstream side of the rotation brush (5), of which end edge portions are brought close to the impression cylinder (3);
an inside wall portion (8) which shields the upstream wall (6) and the downstream wall (7) tightly; and
a suction slit (10) formed on the inside wall portion (8) connected to a vacuum passage (9) for sucking foreign matter (R) adhering to the rotation brush (5) with the inside wall portion (8) approaching or touching an inside portion of the rotation brush (5).