Abstract:
A tower type multi-color printing press has heating means which is constructed in compact and simple in structure to require lesser space for installation, to lower production cost, to facilitate inspection and maintenance and to reduce frequency of occurrence of failure. The tower type multi-color printing press includes a plurality of printing sections provided with stacking in vertical direction, and heating means provided on downstream side of each printing section and extending in a width direction of a paper web fed through a path across each printing section, for heating a printed surface of the paper web every time completing the printing in each printing section.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to a tower type multi-color printing press, in which a plurality of printing sections are stacked vertically and a paper web is passed through the printing sections in sequential order to print images on the paper web by the respective printing sections. More specifically, the invention relates to a tower type multi-color printing press having heating means for heating a printed image. 
     2. Description of the Related Art 
     A tower type multi-color printing press having means for drying a printed paper has been disclosed in Japanese Unexamined Patent Publication Nos. Heisei 7-285213, 8-66997 and 8-230138, for example. 
     Each the tower type multi-color printing press disclosed in these publications is provided with heating means or heating means and cooling means at a downstream position passed through all printing sections in a direction of feeding a paper web for drying a printed image after completion of printing by the respective printing sections. 
     The heating means is not clearly disclosed in Japanese Unexamined Patent Publication Nos. 7-285213 and 8-230138. However, if there are no indication of a special printing, such as printing using a UV ink and if no particular drying function is not clearly disclosed, it is typical to interpret that an apparatus disclosed as drying means for these publications is a heating means. 
     On the other hand, as a drying function of the ink printed on a paper surface, in addition to a drying function for evaporating a solvent by heating the ink and solidifying a thermoplastic material contained in the ink by cooling the ink, there is another well known drying function by penetrating a liquid component of the ink having high flowability in a paper fiber to leave solid component on the paper surface. 
     In the inventions disclosed in the foregoing publications, it is required to evaporate the solvent from a printed image after completion of printing by the respective printing sections, namely, in a relative thick ink layer, in which a plurality of inks are overlaid. Accordingly, it is required to elevate the entire thick ink layer in a short period. Also, in order to sufficiently evaporate the solvent from the entire thick ink layer, it is required to maintain high temperature for a relatively long period. Accordingly, a large heat amount is necessary. Also, in order to maintain high temperature over a relatively long period, the heating means inherently becomes quite bulky to the extent to be larger than a printing unit in the respective printing sections to require quite a large installation space. Furthermore, a mechanism inherently becomes quite complicated. 
     On the other hand, as heating means, a production cost becomes significantly large and inspection and maintenance require substantial period. Furthermore, due to complexity of the mechanism, and the possibility of occurrence of failure becomes relatively high. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide heating means of a tower type multi-color printing press which makes heating means compact and simplified to reduce a space required for installation of the heating means, to reduce production cost, to facilitate inspection and maintenance, and to reduce frequency of occurrence of failure. 
     In order to accomplish the above-mentioned object, according to one aspect of the present invention, a tower type multi-color printing press comprises: 
     a plurality of printing sections provided with stacking in a vertical direction; and 
     heating means provided on downstream side of each printing section and extending in a width direction of a paper web fed through a path across each printing section, for heating a printed surface of the paper web every time completing the printing in each printing section. 
     In the preferred construction, the tower type multi-color printing press further may comprise cooling means provided on downstream side of the heating means for cooling the printed surface, as required. 
     By passing the paper web through each printing section, multi-color printing is performed by each printing section. Each image printed by each printing section is individually heated by the heating means provided located on downstream side of the corresponding printing section for evaporating a solvent of the ink forming the image and/or softening and melting a thermoplastic material contained in the ink by heating to penetrate into a paper fiber. In case of the construction where the cooling means is provided on the downstream side of the heating means of each printing section, the image heated by the heating means is individually cooled to be hardened and set the thermoplastic material in the ink forming each image. 
     As set forth above, by implementing the present invention, in the tower type multi-color printing press, at every time of performing the printing the image by the printing section, heating is effected immediately after printing to evaporate the solvent in the ink forming the image and/or softening or melting a thermoplastic material to penetrate into the paper fiber. Accordingly, when an ink amount to be evaporated the solvent by the heating means and/or to be softened and molten the thermoplastic material into the paper fiber becomes small, the ink layer becomes thinner to be heated for a relatively short period to obtain a desired heating condition for evaporating the solvent and/or softening and melting the thermoplastic material. Thus, heating period can be short and a heating path of the paper web can be short. Namely, the heating means can be made compact and associating therewith, simplified in construction. 
     As a result, space saving of the heating means, lowering of production cost and facilitating of inspection and maintenance can be achieved. Also, for simplified construction of the heating means, frequency of occurrence of failure can be reduced. Also, for short period required for heating, a heat amount to be accumulated in the entire paper web becomes small. Thus, cooling means can be compact and simplified associating with compact construction. Accordingly, similar to the heating means, space saving of the cooling means, lowering of production cost and facilitating of inspection and maintenance can be achieved. Also, for simplified construction of the cooling means, frequency of occurrence of failure can be reduced. 
     On the other hand, in the construction of the shown embodiment where the cooling means for cooling the printed surface is provided on the downstream side of the heating means, the ink forming the image printed by each printing section can be positively cooled every time heating the ink instead of expecting the cooling effect of the dampening water in the downstream side printing section. Also, by providing each cooling means individually corresponding to each printing section, the simple and compact cooling means can be satisfactory. 
     It should be noted that owing to down-sizing and simplification of both the heating means and the cooling means, as the overall device stabilizing the ink, space saving, lowering of production cost and facilitating of inspection and maintenance can be achieved. Furthermore, associating with simplification, frequency of occurrence of failure can be reduced. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be understood more fully from the detailed description given herebelow and from the accompanying drawings of the preferred embodiment of the invention, which, however, should not be taken to be limitative to the present invention, but are for explanation and understanding only. 
     In the drawings: 
     FIG. 1 is a side elevation showing an internal layout of a preferred embodiment of a tower type multi-color printing press according to the present invention; 
     FIG. 2 is a side elevation showing an internal layout of another embodiment of the tower type multi-color printing press according to the present invention, different from the embodiment shown in FIG. 1; 
     FIG. 3 is a perspective view showing an embodiment of a heating means which can be implemented in the embodiments shown in FIGS. 1 and 2; 
     FIG. 4 is a partially cut perspective view showing another embodiment of the heating means which can be implemented in the embodiments shown in FIGS. 1 and 2 and different from the embodiment shown in FIG. 3; 
     FIG. 5 is a perspective view showing an embodiment of a cooling means which can be implemented in the embodiments shown in FIGS. 1 and 2; and 
     FIG. 6 is a side elevation showing an internal layout of a further embodiment of the tower type multi-color printing press according to the present invention, different from the embodiment shown in FIGS.  1  and  2 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be obvious, however, to those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known structures are not shown in detail in order to avoid unnecessarily obscuring the present invention. 
     FIG. 1 is a side elevation showing an internal layout of a preferred embodiment of a tower type multi-color printing press according to the present invention. A tower type multi-color printing press TC has four printing sections, i.e. first, second, third and fourth printing sections P 1 , P 2 , P 3  and P 4  stacked in a vertical direction. A paper web W is guided to pass these four printing sections P 1 , P 2 , P 3  and P 4  from lower side to upper side in sequential order. 
     On the other hand, the tower type multi-color printing press TC also includes first, second, third and fourth heating means H 1 , H 2 , H 3  and H 4  provided on the respective downstream sides of the respective printing sections P 1 , P 2 , P 3  and P 4  and opposing to a path to pass the paper web  W , over the entire width of the paper web  W . 
     The first, second, third and fourth printing sections P 1 , P 2 , P 3  and P 4  have blanket cylinders  2  contacting with the paper web  W  to perform printing on both sides of the paper web  W , simultaneously, and thus constructing so-called BB (blanket-to-blanket) type offset printing sections. Namely, in each printing section, two blanket cylinders  2  respectively provided with plate cylinders  1  are located adjacent to each other across a guide path of the paper web  W  guided to be fed in a vertical direction. Then, these two blanket cylinders  2  contact with each other interpositioning the paper web  W  therebetween in a condition respectively contacted with respectively corresponding plate cylinders  1  to perform printing operation. 
     In each plate cylinder  1  of each printing section P 1 , P 2 , P 3  and P 4 , an inking unit  3  and a dampening unit  4  are provided for supplying an ink and a dampening water to a plate (not shown) mounted on the peripheral surface of the plate cylinder  1 . The ink and the dampening water supplied on the plate reach the paper web  W  via blankets (not shown) mounted on the peripheral surfaces of the blanket cylinders  2 . Thus, printing is performed. 
     Each of the first, second, third and fourth heating means H 1 , H 2 , H 3  and H 4  is an infrared ray irradiation type heating mechanism  10 , in which an elongated infrared ray lamp  11  and a reflection plate  12  are combined as shown in FIG. 3, for example. A reflection surface of a reflection plate  12  is opposed to the paper web  W . The elongated infrared ray lamp  11  positioned between the paper web W and the reflection plate  12  at a position inclined toward the reflection plate  12 , is constructed in parallel to the width direction of the paper web  W . 
     In the alternative, each of the first, second, third and fourth heating means H 1 , H 2 , H 3  and H 4  is constructed with a hot air blowing type heating mechanism  20  which is constructed by a combination of an elongated heating box  22  having an appropriate heating portion  21  and a blowing mechanism  23  as shown in FIG. 4, for example. A slit  22   a  provided in the heating box  22  is opposed to the paper web  W  with an appropriate angle orienting the heating box  22  in parallel to the width direction of the paper web  W . 
     In the further alternative, both the infrared ray irradiation type heating mechanism  10  and the hot air blowing type heating mechanism  20  may be juxtaposed (not shown) with each other relative to feeding direction of the paper web  W . 
     On the downstream side of the first, second, third and fourth heating means H 1 , H 2 , H 3  and H 4 , appropriate first, second, third and fourth cooling means C 1 , C 2 , C 3  and C 4  are provided as required, as shown in FIG.  2 . Each of these cooling means C 1 , C 2 , C 3  and C 4  is adapted to cure the ink which is heated by each heating means H 1 , H 2 , H 3  and H 4  to soften the thermoplastic component of the ink and thus becomes unstable on the web  W  by drying. Accordingly, upon printing, for example, the solvent of the ink is evaporated by heating with the heating means H 1 , H 2 , H 3  and H 4 , if the ink becomes stable on the paper web  W  and the thermoplastic component is softened by heating with the heating means H 1 , H 2 , H 3  and H 4  to penetrate into the paper web  W  to be stable thereon, the cooling means C 1 , C 2 , C 3  and C 4  are not necessary. 
     On the other hand, as will be explained later, if there is some component serving as replacement of the cooling means C 1 , C 2 , C 3  and C 4 , the cooling means C 1  C 2 , C 3  and C 4  are unnecessary. 
     Each of the first, second, third and fourth cooling means C 1 , C 2 , C 3  and C 4  is constructed with a cool air blowing type cooling mechanism  30  comprising an elongated cooling box  32  having an appropriate coolant flow path portion  31  and a blower mechanism  33  as shown in FIG. 33, for example. A slit  32   a  provided in the cooling box  32  is opposed in opposition to the paper web  W  with an appropriate angle relative to the paper web  W . The cooling box  32  is oriented in parallel to the width direction of the paper web  W . The respective first, second and third cooling means C 1 , C 2  and C 3  are positioned in the vicinity of the respective two blanket cylinders  2  of the printing sections P 2 , P 3  and P 4  located downstream side of the respective first, second and third heating means H 1 , H 2  and H 3 . The uppermost cooling means C 4  is located at an appropriate position on the downstream side of the uppermost heating means H 4 . 
     Next, operation and effect of the shown embodiment constructed as set forth above will be discussed hereinafter. Associating with initiation of printing operation or in advance of initiation of printing operation, the heating means or in case that the cooling means is also provided, the heating means and the cooling means are actuated. 
     At first, discussion will be given for the tower type multi-color printing press TC employing only heating means as shown in FIG.  1 . Printing operation is initiated and the paper web  W  is fed and the respective images are printed on both surfaces of the paper web  W  by the respective first, second, third and fourth printing sections P 1 , P 2 , P 3  and P 4 . Also, the paper web  W  passes through the respective first, second, third and fourth heating means H 1 , H 2 , H 3  and H 4  provided on downstream side of the respective printing sections P 1 , P 2 , P 3  and P 4 . 
     Accordingly, the image printed in each printing section P 1 , P 2 , P 3  and P 4  is heating in advance of being fed into the next printing section. Then, the solvent of the ink forming the printed image is evaporated immediately after printing by the corresponding printing section and/or the thermoplastic material of the ink is softened and molten to increase flowability to be penetrated into paper fiber and then dried. At this time, heating of the paper web  W  by the respective heating means H 1 , H 2 , H 3  and H 4  is performed to sufficiently elevate the temperature of the paper web surface for evaporating the solvent of the ink forming the image printed by one printing section and for softening and melting the thermoplastic material of the ink. The temperature is in a range of 90° C. to 200° C. 
     When the heating means H 1 , H 2 , H 3  and H 4  is the infrared ray irradiating type heating mechanism  10  shown in FIG. 3, an electric power is supplied to the infrared ray lamp  11  for generating the infrared ray. The infrared ray thus generated is directly irradiated or reflected by the reflection plate  12  to be irradiated to the paper web  W  for heating the latter. 
     On the other hand, when the heating means H 1 , H 2 , H 3  and H 4  is the hot air blowing type heating mechanism  20  as shown in FIG. 4, an appropriate energy is supplied to a heat generating portion  21  provided in the heating box  22 . For example, when the heating generating portion  21  is an electric heating type, an electric power is supplied to the heat generating portion  21 . Also, within the heating box  22 , in which the heating generating portion  21  is heated, an air is blown by the blower mechanism  23 . Then, the air is heated by the heat generating portion  21  to be blown as a hot air through the slit  22   a  of the heating box  22  to heat the paper web W by this hot air. 
     On the other hand, when the heating means H 1 , H 2 , H 3  and H 4  is constructed by combination of the infrared ray irradiating type heating mechanism  10  and the hot air blowing type heating mechanism  20 , operations of both mechanisms are performed to attain the effects of both mechanisms. 
     In the embodiment shown in FIG. 1, the solvents of the inks forming the image printed by the respective printing sections P 1 , P 2 , P 3  and P 4  are heated and evaporated individually by the heating means H 1 , H 2 , H 3  and H 4 . Certain kind of inks forming the image is half softened the thermoplastic component contained in the ink not to lower viscosity thereof and thus not to penetrate into the paper fiber to be unstable on the paper web W to possibly deposit or stain other substances. 
     However, in this embodiment, the printing sections P 1 , P 2 , P 3  and P 4  are provided with the dampening units  4  respectively to constantly transfer the dampening water to the blanket cylinders  2  via the plate cylinders  1  for printing by the first, second and third printing sections P 1 , P 2  and P 3 . The image individually heated on the downstream side respectively is appropriately and abruptly cooled by the dampening water on the peripheral surface of the blanket cylinders  2  upon passing through the downstream side printing sections, namely the second, third and fourth printing sections P 2 , P 3  and P 4 . 
     As a result, the images printed by the first, second and third printing sections P 1 , P 2  and P 3  except for the fourth printing section P 4  located on the most downstream side, are individually heated by the heating means and cooled by respective printing sections. Thus, the solvent of the ink forming the image is evaporated and cooled to be cured. 
     At this time, the image printed by the fourth printing section P 4  on the most downstream side cannot pass other printing sections and thus cannot be cooled by the dampening water of the printing section. Therefore, as shown in FIG. 6, the cooling means C 4  shown in FIG. 5 are provided on both sides of the path of the paper web  W  on the downstream side of the printing section P 4  for cooling. 
     Next, discussion will be given for the tower type multi-color printing press TC employing the heating means and the cooling means as shown in FIG.  2 . In the shown embodiment, instead of expecting the cooling effect of the dampening water in the printing section on the downstream side as in the embodiment shown in FIG. 1, the image printed by each printing section is positively cooled by the cooling means every time heating the ink. 
     Namely, the image printed in each printing section P 1 , P 2 , P 3  and P 4  is heated by the heating means before passing through another printing portion to evaporate the solvent contained in the ink for forming each image and then cooled by the cooling means. 
     Accordingly, when the solvent is evaporated by heating the ink forming the image, if the thermoplastic component contained in the ink is half softened, the viscosity of the thermoplastic component as half softened by heating can be lowered by hardening as cooled by the cooling means and thus set so as not to deposit or stain on other substances. 
     At this time, cooling the paper web  W  by the respective cooling means C 1 , C 2 , C 3  and C 4  is performed to sufficiently cool the thermoplastic component of the ink forming the image down to the temperature of the paper web surface for setting the thermoplastic component. Namely, the thermoplastic component is cooled to be lower than or equal to about 30° C. 
     On the other hand, when each cooling means C 1  C 2 , C 3  and C 4  is the cool air blowing type cooling mechanism as shown in FIG. 5, a cool water, for example, passes through the coolant flow path portion  31  provided in the cooling box  32 . Also, within the cooling box  32  passed through the cooling water in the coolant flow path portion  31 , air is blown by the blower mechanism  33  to be cooled by the coolant flow path portion  31 . Then, the cool air is blown through the slit  32   a  of the cooling box  32  to cool the paper web  W  by the cool air. 
     Although the invention has been illustrated and described with respect to the exemplary embodiment thereof, it should be understood by those skilled in the art that the foregoing and various other changes, omissions and additions may be made therein and thereto, without departing from the spirit and scope of the present invention. Therefore, the present invention should not be understood as limited to the specific embodiment set out above but to include all possible embodiments which can be embodied within a scope encompassed and equivalents thereof with respect to the feature set out in the appended claims.