Patent Application
20100230893
This invention relates to a sheet guide apparatus which is provided in a printing press (may hereinafter be referred to as the machine) for printing a sheet, or a coater for coating a sheet, and which transports, in a stable state, a sheet to be transported.
In a multicolor sheet-fed printing press for four colors, for example, a transfer cylinder (intermediate cylinder) 104 is disposed between respective printing units (103a to 103d) in a printing unit section 102 located between a feeder unit 100 and a delivery unit 101, as shown in
In recent years, there has been a demand for a printing press suitable for both of thin paper and thick paper, and a printing press of a skeleton configuration adaptable to both of thin paper and thick paper has appeared. As will be understood from what has been mentioned above, such a printing press is at a disadvantage against thin paper. Thin paper without toughness is not supported by a cylinder, and thus moves unstably, causing a printing trouble. The same holds true of coating on a sheet and, if the sheet is thin, a coating failure occurs. In order to stabilize the sheet being transported, thereby preventing the printing trouble or coating failure, therefore, it has been common practice to provide various sheet guide devices along the transfer cylinder, constructed as the skeleton shell, for passing the sheet on to the impression cylinder (see Patent Document 1 and Patent Document 2).
Moreover, Patent Document 3 discloses a printing press in which an air blowing means comprising a discharge duct and discharge nozzles is provided above a transfer position at which the sheet is passed from the skeleton shell on to the impression cylinder, and air is blown on the sheet received by the impression cylinder to suppress the unstable motion of the sheet.
[Patent Document 1] JP-A-2001-293843
[Patent Document 2] JP-A-2001-293844
[Patent Document 3] Japanese Patent No. 4061107
With the printing press of Patent Document 3 mentioned above, however, the unstable motion of the sheet is not similar depending on the type of the sheet, the size of the sheet, a printing image, etc. Thus, an operator has adjusted the flow rate of air by relying on the operator's experience and intuition.
Thus, a heavy burden is imposed on the operator, and a less experienced operator has difficulty in making adjustment and cannot suppress the unstable motion of the sheet. This has posed the problem that a printing trouble due to the unstable motion of the sheet cannot be prevented. As a result, the operation rate of the machine is low, and a waste sheet occurs.
Under these circumstances, it is an object of the present invention to provide a sheet guide apparatus which controls an air blowing means automatically without relying on the operator's experience and intuition, thereby sufficiently suppressing the unstable motion of the sheet, and which enables even an operator with a limited work experience in printing, etc. to do printing, etc. with a sense of security.
To solve the above-mentioned problems, the present invention provides a sheet guide apparatus including
a transport cylinder having holding means for holding a sheet and adapted to transport the sheet, and
air blowing means for blowing air on the sheet being transported by the transport cylinder,
the sheet guide apparatus, comprising:
detection means for detecting a distance to the sheet being transported by the transport cylinder; and
control means for controlling the air blowing means, based on detection results of the detection means, such that the distance between the sheet and the detection means becomes a distance which prevents an unstable motion of the sheet.
The sheet guide apparatus is also characterized in that the control means controls the air blowing means to adjust a flow rate of discharged air so that the distance between the sheet and the detection means becomes a set distance.
The sheet guide apparatus is also characterized in that the distance which prevents the unstable motion of the sheet differs according to whether the sheet is a thin sheet or a thick sheet.
The sheet guide apparatus is also characterized in that the distance, which prevents the unstable motion of the thick sheet when the sheet is the thick sheet, is shorter than the distance which prevents the unstable motion of the thin sheet when the sheet is the thin sheet.
The sheet guide apparatus is also characterized in that the detection means is provided on a downstream side in a sheet transport direction with respect to the air blowing means and on an upstream side in the sheet transport direction with respect to a cylinder in contact with the transport cylinder.
The sheet guide apparatus is also characterized in that the detection means is provided at a position opposing a surface of the sheet.
The sheet guide apparatus further comprises a sheet thickness input unit for inputting a thickness of the sheet, and wherein the control means judges the sheet as a thin sheet when the thickness of the sheet inputted by the sheet thickness input unit is less than a given value, and judges the sheet as a thick sheet when the thickness of the sheet inputted by the sheet thickness input unit is the given value or higher.
The sheet guide apparatus further comprises a sheet thickness input unit for inputting a thickness of the sheet, and wherein the control means judges the sheet as a thin sheet when the thickness of the sheet inputted by the sheet thickness input unit is a given value or lower, and judges the sheet as a thick sheet when the thickness of the sheet inputted by the sheet thickness input unit exceeds the given value.
The sheet guide apparatus is also characterized in that the air blowing means includes an air discharge duct having discharge holes, and discharge nozzles, and the control means exercises control such that air is discharged from the discharge holes of the air discharge duct and the discharge nozzles when the sheet is a thick sheet, and exercises control such that air is discharged only from the discharge holes of the air discharge duct when the sheet is a thin sheet.
The sheet guide apparatus is also characterized in that the distance which prevents the unstable motion of the sheet when the sheet is a thick sheet is a distance from a position between a sheet motion instability position and an improper position to the detection means, the sheet motion instability position being a position at which the sheet is excessively separated from the transport cylinder, and the improper position being a position at which the sheet is excessively close to the transport cylinder.
The sheet guide apparatus is also characterized in that the detection means is a displacement gauge.
According to the present invention, the unstable motion of the sheet is detected, and the air blowing means is controlled automatically, whereby the flow rate of air can be adjusted appropriately. Thus, the unstable motion of the sheet can be fully suppressed, and the sheet can be transported stably. Hence, even a little experienced operator can perform an operation, such as printing, with a sense of security. Since a printing trouble due to the unstable motion of the sheet does not occur, moreover, the rate of operation of the machine is increased, and waste sheets are also decreased.
a) to 6(c) are explanation drawings of the structure of a guide plate,
A sheet guide apparatus according to the present invention will be described in detail by an embodiment with reference to the accompanying drawings.
In a printing unit section of a multicolor sheet-fed printing press for four colors, etc., an upstream-side impression cylinder 3a and a downstream-side impression cylinder (transport cylinder) 3b are rotatably supported between right and left frames 2 erected on a bed 1, and a transfer cylinder 4 comprising a skeleton shell is likewise rotatably supported between these impression cylinders 3a and 3b, as shown in
A first guide device 7A, which guides the printing sheet being transported in a region ranging between transfer positions P1 and P2 of the printing sheet on the upstream and downstream sides in the flow direction of the printing sheet, is provided below the transfer cylinder 4. Moreover, a second guide device 7B, which guides the printing sheet transported by the downstream-side impression cylinder 3b, is provided above the transfer position P2 of the printing sheet on the downstream side.
The first guide device 7A, as shown in
The air discharge ducts 8a, 8b are supported, on their outer end sides, by stays 10a, 10b spanning the right and left frames 2 via holders 11a, 11b and blocks 12a, 12b, and have their inner ends bound together by bolts 14 between their bars 13a and 13b, as shown in
The guide plates 15a, 15b each comprise an arcuate plate extending along the movement trajectory S of the gripper device 5 of the transfer cylinder 4, and each have many air jet holes 16 formed to be open so that air flows rightward and leftward symmetrically with respect to the machine center along their guide surfaces (i.e., air flows in the sheet width direction of the printing sheet), as shown in
The interior of the air discharge ducts 8a, 8b is supplied with pressurized air from a blower pump 19 outside the machine via pipings 17a, 17b and collecting piping 18.
Between the forward and rearward stays 10a and 10b as a pair, subframes 20a and 20b located on both sides of the guide plates 15a and 15b are installed to span the stays 10a and 10b. Bars 21a and 21b are installed to span the front ends and rear ends of the subframes 20a and 20b.
The plate-shaped guide 22a extending in the sheet width direction of the printing sheet is fixed to an upper surface part of the bar 21a on the upstream side in the transport direction of the printing sheet with respect to the transfer position P2 of the printing sheet so as to become as close as possible to the transfer position P2 of the printing sheet. An end of the plate-shaped guide 22a facing the transfer position P2 of the printing sheet is formed in the shape of a comb (comb-shaped) to have notches 27a at predetermined intervals in the sheet width direction of the printing sheet. The notches 27a are arranged parallel in the axial direction of the gripper device 5 of the downstream-side impression cylinder 3b, and are provided at positions corresponding to grippers so that a plurality of the grippers protruding from the circumferential surface of the impression cylinder 3b can pass without interfering with the plate-shaped guide 22a.
The plate-shaped guide 22b extending in the sheet width direction of the printing sheet is fixed to an upper surface part of the bar 21b on the downstream side in the transport direction of the printing sheet with respect to the transfer position P1 of the printing sheet so as to become as close as possible to the transfer position P1 of the printing sheet, as is the plate-shaped guide 22a fixed to the upper surface part of the bar 21a. An end of the plate-shaped guide 22b facing the transfer position P1 of the printing sheet is formed in the shape of a comb (comb-shaped) to have notches 27b at predetermined intervals in the sheet width direction of the printing sheet. The notches 27b are arranged parallel in the axial direction of the gripper device 5 of the upstream-side impression cylinder 3a, and are provided at positions corresponding to grippers so that a plurality of the grippers protruding from the circumferential surface of the impression cylinder 3a can pass without interfering with the plate-shaped guide 22b.
The second guide device 7B, as shown in
The air discharge duct 31 and the air discharge pipe 32 are supplied with pressurized air from a blower pump 35 outside the machine via pipings 34a and 34b. This pressurized air is blown via the discharge holes 31a and the discharge nozzles 33 toward the circumferential surface of the downstream-side impression cylinder 3b located on the downstream side in the flow direction of the printing sheet with respect to the transfer position P2 of the printing sheet, the directions of blowing being a direction nearly perpendicular to the printing surface of the printing sheet and a direction opposite to the flowing direction of the printing sheet.
In
A displacement gauge (detection means) 42, which is located at an intermediate part in the sheet width direction of the printing sheet for detecting the distance to the printing sheet being transported by the impression cylinder 3b, is installed on the upper surface of the air discharge duct 31. A detection signal of the displacement gauge 42 (i.e., floating amount of the printing sheet) is inputted to a control device (control means) 40 (to be described later). The displacement gauge 42 is provided at a position opposed to the printing surface of the printing sheet.
That is, as shown in
Because of the above features, when the printing sheet is transported from the impression cylinder 3a of the preceding printing unit to the transfer cylinder 4, and then to the impression cylinder 3b of the succeeding printing unit via the gripper devices 5, pressurized air gushing from the air jet holes 16 of the guide plates 15a, 15b and flowing in the sheet width direction while being directed from the center toward both side edges of the printing sheet (see arrows in
In leading end portions of the plate-shaped guides 22a, 22b provided to be continuous with the guide plates 15a, 15b, moreover, the many notches 27a, 27b are formed at predetermined intervals in the sheet width direction of the printing press to avoid interference with the grippers of the gripper devices 5 of the impression cylinders 3a, 3b. Thus, the leading end portions of the plate-shaped guides 22a, 22b not corresponding to the grippers can be extended all the more to sites near the transfer positions P1, P2 of the printing sheet. As a result, the zones where the printing sheet is not guided by the guide plates 15a, 15b are rendered as narrow as possible, and the printing sheet is transported in a stable state.
In the present embodiment, when the printing sheet passes the transfer position P2 of the printing sheet, pressurized air gushed with a predetermined length in the flow direction of the printing sheet from the discharge holes 31a of the air discharge duct 31 and the discharge nozzles 33 of the air discharge pipe 32 in the air blowing device of the second guide device 7B brings the printing sheet into intimate contact with the circumferential surface of the impression cylinder 3b to suppress its fluttering or unstable motion, thus preventing a printing trouble.
In detail, the air blowing device is controlled by the control device 40 in the following manner:
When the thickness of the thin sheet Wa (see
That is, in accordance with the distance to the thin sheet Wa measured by the displacement gauge 42 (indicating the amount of floating of the sheet), the pump drive motor 43 for the blower pump 35 is drivingly controlled, and the frequency to the pump drive motor 43 is boosted to increase the flow rate of air so that the thin sheet Wa is moved, for example, from a sheet motion instability position (NG position) indicated by a long dashed double-dotted line to a proper position (OK position) indicated by a solid line in
In the case of the thin sheet Wa, as seen above, pressurized air is gushed only from the discharge holes 31a of the air discharge duct 31. Thus, the thin sheet Wa is pressed uniformly against the circumferential surface of the impression cylinder 3b and transported in a stable state. In other words, wrinkles or the like due to local pressurization by an air jet from the discharge nozzles 33 do not occur.
When the thickness of the thick sheet Wb (see
That is, in accordance with the distance to the thick sheet Wb measured by the displacement gauge 42 (indicating the amount of floating of the sheet), the pump drive motor 43 for the blower pump 35 is drivingly controlled, and the frequency to the pump drive motor 43 is boosted or lowered to increase or decrease the flow rate of air so that the thick sheet Wb is moved, for example, from a sheet motion instability position (NG position excessively separated from the impression cylinder 3b) indicated by a long dashed double-dotted line or an improper position (NG position excessively close to the impression cylinder 3b) indicated by another long dashed double-dotted line to a proper position (OK position) indicated by a solid line in
In detail, when the thick sheet Wb is located at the NG position excessively separated from the impression cylinder 3b, the frequency to the pump drive motor 43 is boosted to increase the flow rate of air. When the thick sheet Wb is located at the NG position excessively close to the impression cylinder 3b, by contrast, the frequency to the pump drive motor 43 is lowered to decrease the flow rate of air. The reason why NG is given when the thick sheet Wb becomes too close to the impression cylinder 3b is as follows: When the thick sheet Wb passes the air blowing device and is freed from the gush of the pressurized air, the thick sheet Wb has a possibility to rebound greatly because of its own elasticity, eventually causing the same state as the unstable motion of the sheet. To avoid this situation, a position which enables the above rebound to be suppressed as much as possible and which fits the contour of the impression cylinder 3b as much as possible is set as the above-mentioned proper position (OK position). The distance defined by the above proper position (OK position) of the thick sheet Wb, namely, the distance for preventing the unstable motion of the thick sheet Wb, is shorter than the distance defined by the aforementioned proper position (OK position) of the thin sheet Wa, namely, the distance for preventing the unstable motion of the thin sheet Wa.
Because of the above features, for the thick sheet Wb, a combination of pressurized air from the discharge holes 31a of the air discharge duct 31 and pressurized air from the discharge nozzles 33 of the air discharge pipe 32 presses the thick sheet Wb against the circumferential surface of the impression cylinder 3b as strongly as possible, and can thereby suppress the fluttering or unstable motion of the sheet. The control device 40 may judge the sheet as the thin sheet Wa when the thickness of the sheet inputted by the sheet thickness input unit 41 is the given value or higher, and may judge the sheet as the thick sheet Wb when the thickness of the sheet inputted by the sheet thickness input unit 41 exceeds the given value.
According to the present embodiment, as described above, the unstable motion of the sheet is detected by the displacement gauge 42, and the air blowing device is controlled automatically, whereby the flow rate of air can be adjusted appropriately. Thus, the unstable motion of the sheet can be fully suppressed, and the printing sheet can be transported stably. Hence, even a little experienced operator can do printing with a sense of security. Since a printing trouble due to the unstable motion of the sheet does not occur, the rate of operation of the machine is increased, and waste sheets are also decreased.
It goes without saying that the present invention is not limited to the above-described embodiment, and various changes and modifications may be made without departing from the gist of the present invention. For example, even for the thin sheet Wa, pressurized air may be gushed from the nozzles 33, depending on the paper quality of the sheet or the like. Nor is it necessary to gush pressurized air from the nozzles 33 toward the thick sheet Wb, depending on its paper quality or the like. Moreover, the blower pump 35 may be provided for each of the pipings 34a and 34b, and the respective blower pumps 35 may be controlled independently.
Furthermore, the plate-shaped guides 22a, 22b may each be configured to have a flat leading end surface without the notches 27a, 27b over the sheet width direction of the printing sheet. Alternatively, there may be a configuration in which a plurality of rod-shaped guides are arranged parallel in the sheet width direction of the printing sheet, instead of the plate-shaped guides 22a, 22b. There may also be a configuration in which the plate-shaped guides 22a, 22b or the rod-shaped guides each have the front extremity in a semispherical or arcuate shape. The plate-shaped guides 22a, 22b may each be composed of a plurality of plates each having a strip-shaped leading end portion, rather than a one-piece plate having the notches 27a, 27b. The transport cylinder is not limited to the impression cylinder, and may be a blanket cylinder having a means for holding a sheet, such as a gripper device. The means for holding the sheet is not limited to the gripper, and may be a suction-attracting pad.
The sheet guide apparatus according to the present invention can be applied even to a sheet which is not a printing sheet, but a film, and can also be applied to a coater for coating the sheet.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009-057284 | Mar 2009 | JP | national |
