Patent Publication Number: US-6705223-B2

Title: Inking unit for a printing machine

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The invention relates to an inking unit for a printing machine, including at least one roller, and a metering doctor blade disposed on an ink container and engageable with the roller. 
     Inking units of the hereinaforementioned type have become known heretofore. They include at least one roller, for example, a screen roller with cells located on the outer cylindrical or jacket surface thereof for accepting printing ink, and a metering doctor blade which, for example, is used for doctoring the printing ink off the roller jacket. The metering doctor blade is attached to an open ink container. During the operation of the inking unit, the level of the printing ink in the ink container lies above the tip and knife or cutting edge, respectively, of the metering doctor blade set against the roller jacket, so that, as the roller rotates, the roller jacket dips into the printing ink and is wetted thereby. It is then doctored off with the aid of the metering doctor blade. During an ink change, or in order to clean the ink container and the metering doctor blade, the container and the blade have to be dismantled and removed from the printing machine. A disadvantage regarding the heretofore known open metering doctor blades is that the level of the printing ink in the ink container must lie far above the tip of the metering doctor blade for attaining a reliable filling of the cells of the roller and, therefore, the ink container and the metering doctor blade cannot be dismantled without an at least brief flowing and dripping, respectively, of the printing ink out of the ink container over the tip of the metering doctor blade. Before the metering doctor blade can be lifted off the roller during dismantling, it is necessary, therefore, for the printing ink level in the ink container to be lowered below the tip of the metering doctor blade. 
     The published German Patent Document DE 297 18 387U1 reveals an ink fountain or duct with a metering doctor blade attached thereto which, during the operation of the inking unit, is located in a 12 o&#39;clock position with respect to the roller. In order to be able to dismantle the ink duct, it is pivoted through 90° into the 3 o&#39;clock position, as a result of which the printing ink stored in the ink duct runs into a channel in the ink duct and is collected therein. The printing ink level in the ink duct consequently falls below the highest point of the metering doctor blade, so that the ink duct can be dismantled without having printing ink run out over the tip of the metering doctor blade. 
     The published German Patent Document DE 43 37 386 A1 discloses a doctor blade device having an ink container and a metering doctor blade engageable with a roller. Arranged in the ink container are a number of sealing profile strips, which are arranged in an ink chamber containing printing ink, and are adjustable against the roller jacket. In this regard, all of the printing ink is displaced from the ink chamber into a residual space partitioned off from the roller. This occurs at the end of operations or when a temporary operational interruption of the inking unit occurs. The published European Patent Document EP 0 955 164 A1 reveals a similar doctor blade device wherein, in order to empty the ink chamber which is in contact with the outer jacket of the roller, a flexible diaphragm is pressed into the chamber and, in an end position, lies on the roller jacket. 
     The published German Patent Document DE 26 25 623 A1 discloses a device with an ink container having a wall which is movable linearly in a direction towards a roller and is used for the purpose of exerting pressure on the printing ink in order thereby to counteract the thixotropic behavior of the printing ink and also a nonuniform takeup of the ink from the roller. 
     SUMMARY OF THE INVENTION 
     It is accordingly an object of the invention to provide an inking unit of the type mentioned in the introduction hereto wherein the metering doctor blade can be arranged laterally on the roller, and wherein the ink container with the metering doctor blade attached thereto is removable from the roller by the shortest route, without allowing any printing ink to emerge from the ink container in the process. 
     With the foregoing and other objects in view, there is provided, in accordance with the invention, an inking unit for a printing machine, comprising at least one roller, an ink container adjacent to the roller, a metering doctor blade disposed on the ink container and being engageable with the roller, and a movable displacer element for setting a printing ink level in the ink container relative to the metering doctor blade. 
     In accordance with another feature of the invention, the displacer element is optionally adjustable into a first position, wherein the level of printing ink stored in the ink container lies above a highest point of the metering doctor blade, and into a second position, wherein the printing ink level in the ink container lies below the highest point of the metering doctor blade. 
     In accordance with a further feature of the invention, the displacer element is formed by an adjustable rear wall of the ink container. 
     In accordance with an added feature of the invention, the rear wall is pivotably mounted. 
     In accordance with an additional feature of the invention, the rear wall is pivotably mounted on a base body carrying the metering doctor blade. 
     In accordance with yet another feature of the invention, the pivotable mounting is on a pivot axis located below a highest point of the metering doctor blade. 
     In accordance with yet a further feature of the invention, the rear wall has a crank-shaped course. 
     In accordance with yet an added feature of the invention, in the first position thereof, the displacer element is at least partly immersed in the printing ink stored in the ink container, and in the second position thereof, is lifted completely out of the stored printing ink. 
     In accordance with yet an additional feature of the invention, the displacer element is pivotable about a pivot axis disposed above a bottom of the ink container. 
     In accordance with still another feature of the invention, the displacer element has an outer contour matched to an inner contour of the ink container so that a height of a gap formed between at least one of an ink container rear wall and an ink container bottom, on the one hand, and the displacer element moved into an end position, on the other hand, is very small. 
     In accordance with still a further feature of the invention, the metering doctor blade, in a position thereof wherein it is in engagement with the roller, is disposed, in relation to the roller, below an upper apex and above a lower apex of the roller. 
     In accordance with still an added feature of the invention, the metering doctor blade is disposed in a region of the roller between 7 o&#39;clock and 11 o&#39;clock positions thereon. 
     In accordance with still an additional feature of the invention, as viewed in the direction of rotation of the roller, at least one further doctor blade is disposed upline from the metering doctor blade, the further doctor blade being settable in engagement with the roller and serving as a wiper for at least one of air and printing ink. 
     In accordance with a concomitant feature of the invention, the ink container is trough-shaped, and a cover is disposed on the ink container for closing the ink container. 
     In order to attain the object of the invention, there is therefore provided an inking unit having a movable displacer element for setting the printing ink level in the ink container relative to the metering doctor blade. With the aid of the displacer element, it is readily possible, as required, to lower the level of the liquid or pasty printing ink in the ink container below the highest point of the metering doctor blade set against or in engagement with the roller. The ink container and the metering doctor blade can then be removed from the roller by a direct route, without allowing printing ink to flow or drip out of the ink container over the tip of the metering doctor blade. 
     In conjunction with the invention of the instant application, “setting the metering doctor blade” onto or into engagement with the roller is understood to mean that the metering doctor blade rests with the tip or cutting edge thereof on the roller cover or is pressed against the latter, so that printing ink located on the roller jacket can be doctored off, or that the metering doctor-blade tip/cutting edge is disposed at a short distance from the roller outer cylindrical or jacket surface, so that a printing ink film with a thickness defined by the gap remains on the roller jacket or a printing material transferred by the latter, for example, a sheet. 
     When installed in the inking unit, the ink container with the metering doctor blade attached thereto is preferably disposed laterally beside the roller, so that in order to make ready for removal of the ink container from the inking unit and the printing machine, respectively, it is necessary only for the printing ink level to be lowered below the tip of the metering doctor blade, it being possible to dispense with pivoting the ink container into a removal/emptying position, as required in heretofore known devices of this general type. A further advantage of the invention is that the ink container can be removed from the inking unit even with a full printing ink content, for example when production is interrupted, without allowing printing ink to run out in the process. The maximum filling quantity of the ink container, at least when the ink container is being removed, is therefore only sufficiently large so that, at the greatest possible volume of the ink container, which is provided by appropriately positioning the displacer element, the printing ink level lies below the tip of the metering doctor blade. 
     In a preferred embodiment, the displacer element can be adjusted optionally or selectively into a first position, wherein the level of the printing ink stored in the ink container lies above a highest point of the metering doctor blade, and into a second position, wherein the printing ink level in the ink container lies below the highest point of the metering doctor blade. The first and the second positions can be end positions, the displacer element preferably being adjustable into virtually any desired number of intermediate positions, i.e., infinitely or continuously, or into a limited number of intermediate positions, for example, in a fixed grid or pattern. The configuration according to the invention of the displacer element allows, at least approximately, emptying of the ink container completely, it being possible to ensure a desired inking of the roller even with a minimum quantity of ink in the ink container. 
     Other features which are considered as characteristic for the invention are set forth in the appended claims. 
     Although the invention is illustrated and described herein as embodied in an inking unit for a printing machine, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
     The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, wherein: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1 to  3 , respectively, are a fragmentary diagrammatic sectional view, in different operating phases, of an exemplary embodiment of the inking unit according to the invention, wherein a displacer element is shown moved into various positions; 
     FIGS. 4 to  6 , respectively, is a view like that of FIGS. 1 to  3  of another exemplary embodiment of the inking unit, in different operating phases, wherein the movable displacer element located in various positions is of different construction; 
     FIG. 7 is a view like those of FIGS. 1 to  3 , respectively, showing a further exemplary embodiment of the inking unit; and 
     FIG. 8 is a fragmentary diagrammatic sectional view of an exemplary embodiment of an ink receptacle or container having a metering doctor blade disposed thereon. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings and, first, particularly to FIGS. 1 to  7  thereof, there is shown therein an inking unit  1  such as has been described hereinabove, which can be used generally in conjunction with a printing machine, for example a rotary printing machine. The inking unit  1  includes at least one roller  3  which, in the exemplary embodiments illustrated in FIGS. 1 to  7 , is formed by a screen roller  5 . On the outer or jacket surface  7  thereof, the screen roller  5  is formed with depressions or cells  9  for holding printing ink therein. The construction and the function of the screen roller  5  are well known, so that they will not be discussed in any greater detail herein. 
     FIG. 1 shows a first exemplary embodiment of the inking unit  1  which, in addition to the screen roller  5 , includes a metering doctor blade  11 , which is disposed on or attached to an ink receptacle or container  13 . The metering doctor blade  11 , attached in a fixed position to the ink container  13 , is constructed like a knife and extends in the longitudinal direction of the screen roller  5 , as does the ink container  13 . In FIG. 1, the metering doctor blade  11  is set against the outer jacket surface  7  of the screen roller  5 , i.e., the tip  15  of the metering doctor blade  11  lies on the outer jacket surface  7  and doctors the printing ink off the screen roller  5 . The direction of movement of the outer jacket surface  7  of the screen roller  5  is represented by an arrow  17 . 
     The ink container  13  is of trough-type construction, i.e., it is open at the top and has a base body  19  which, as viewed in cross section, has a first wall  21  that is curved convexly with respect to an imaginary horizontal, and a second wall  23  which originates from the first wall  21  and extends in a direction towards the outer cylindrical or jacket surface  7  of the screen roller  5 . The first wall  21  forms the bottom  25 , and the second wall  23  forms the front wall  27  of the ink container  13 . The metering doctor blade  11  is disposed on the front wall  27  and, in effect, forms an extension thereof. The ink container  13  also has a rear wall  29 , which is somewhat crank-shaped. The ink container  13  also has side walls extending parallel to the plane of the drawings of the figures, but not illustrated therein. 
     In the exemplary embodiment shown in FIG. 1, the rear wall  29  is pivotable in and counter to the clockwise direction about a pivot axis  31  located on the base body  19 . Here, the pivot axis  31  runs at least approximately parallel to the longitudinal axis of the screen roller  5 . A sealing strip  33  prevents printing ink from emerging between the adjustable rear wall  29  and the stationary base body  19 . Also provided are non-illustrated lateral seals, which serve to seal off the gaps formed between the movable rear wall  29  and the non-illustrated stationary side walls. 
     The rear wall  29  is pivotable stepwise into various positions, for example, due to the latching of a non-illustrated latch pin into various holes, or else infinitely variably or continuously, the rear wall  29  being locked, for example, by a clamping fastening, in the case of an infinitely variable adjustment. The rear wall  29  is pivotable manually or by an actuating device having a drive. These aforementioned devices are not illustrated. 
     The respectively adjustable and pivotable rear wall  29  forms a displacer member  35 , by the aid of which the printing ink level in the ink container  13  can be set relative to the metering doctor blade  11 . In the case of a high printing-ink level, therefore, the depth of the printing-ink bath in the ink container  13  is greater than in the case of a comparatively lower printing-ink level. By pivoting the displacer elements  35  about the pivot axis  31 , the volume of the ink container  13  is changed, so that with a constant filling volume in the ink container  13 , the level of the ink container  13  changes, as will be explained in greater detail hereinbelow. 
     In FIG. 1, the displacer element  35  is in a first position, wherein the level of the printing ink stored in the ink container  13  is located above the highest point  37  of the metering doctor blade  11  lying against or in engagement with the outer jacket surface  7 . The highest point  37  here is formed by the tip  15  of the metering doctor blade  11 . To make ready for removing the ink container  13  from the inking unit  1  and from the printing machine, respectively, the displacer element  35  is moved in a counterclockwise direction into a second position illustrated in FIG. 2, due to which the volume of the ink container  13  increases, which causes the printing ink level in the ink container  13  to fall below the highest point  37  of the metering doctor blade  11 . Then, as represented by the arrow  39 , the ink container  13  can be taken directly out of the inking unit  1  laterally, i.e., parallel to the imaginary horizontal, without allowing printing ink to drip over the tip  15  of the metering doctor blade  11  into the inking unit  1  and the printing machine, respectively, in the process. Of course, it is also possible to remove the ink container  13  from the inking unit  1  in a vertical direction, downwardly or, if appropriate, upwardly. 
     As the printing ink level in the ink container  13  is lowered, the screen roller  5  preferably rotates further, so that the printing ink initially yet adhering to the outer jacket surface  7  of the screen roller  5  is wiped off on the metering doctor blade  11 . After the ink container  13  with the metering doctor blade  11  disposed thereon has been dismantled, the screen roller  5  is therewith also doctored off cleanly. There is still only printing ink in the cells  9 . Thus, at any time, for example, even after production has been interrupted, the ink container  13  can be dismantled with the complete printing-ink content thereof. It can be stored temporarily, just as it is, and if necessary can be inserted again later and reused. 
     If, towards the end of a production, it is desired to use up the printing ink supply in the ink container  13  as much as possible, the printing ink in the ink container  13  can be forced against the outer jacket surface  7  of the screen roller  5  by pivoting the displacer element  35  in the direction towards the screen roller  5 . In FIG. 3, the displacer element  35  is illustrated in a third position, which here is an end/stop position, wherein it tends to strike the front wall  27  of the ink container  13 . The volume of the container  13  is then a minimum. Because of the mutually matching shape of the rear wall  29  and of the front wall  27 , virtually all of the printing ink is displaced out of the ink container  13  into the space bounded or defined by the metering doctor blade  11 , the rear wall  29  and the outer jacket surface  7  of the screen roller  5 . It is believed to be apparent from FIG. 3 that, with the aid of the adjustable displacer element  35 , the printing ink level can be kept above the highest point  37  of the metering doctor blade  11  even with only very little printing ink in the ink container  13 , so that the screen roller  5  is inked in the desired way. It is thereby possible to ensure that only very little residual ink accumulates after the ink container  13  has been dismantled. 
     In the exemplary embodiment of the inking unit  1  described hereinbefore with respect to FIGS. 1 to  3 , a sensor  41  for registering the printing ink level and the filling height, respectively, of the ink container  13  is provided above the upwardly open ink container  13 , and a refilling device  43  for the automatic filling and refilling, respectively, of the ink container  13  is provided. The refilling device  43  can be formed, for example, by a cartridge. 
     FIGS. 4 to  6  show a further exemplary embodiment of the inking unit  1 . Identical parts have been identified by the same reference numerals, so that to this extent reference may be made to the description relating to the preceding FIGS. 1 to  3 . In the following text, only the differences will be described in greater detail. 
     As is apparent from FIG. 4, the rear wall  29 , the bottom  25  and the front wall  27  of the ink container  13  are formed in one piece. No movable seals for sealing off the ink container  13  with respect to the environment are therefore needed. However, seals are required between the non-illustrated side walls of the ink container and the rear wall, front wall and bottom, if the side walls do not have a material connection with the remaining container walls. 
     In the exemplary embodiment illustrated in FIGS. 4 to  6 , the displacer element  35 ′ is formed by a submersible or immersion element  45 , which is pivotably mounted. The pivot axis  47  extends parallel to the axis of rotation of the screen roller  5  and, with the aid of a non-illustrated holding device above the container bottom  25  and outside the printing ink bath, is held in a fixed location. 
     In the first position of the immersion element  45  illustrated in FIG. 4, it is partly submerged in the printing ink present in the ink container  13 , due to which a printing ink level is set which lies above the highest point  37  of the metering doctor blade  11 . By pivoting the immersion element  45  in clockwise direction about the pivot axis  47 , the immersion element  45  is moved into a second position illustrated in FIG. 5, wherein it is lifted completely out of the printing ink bath in the ink container  13 . The printing ink level in the ink container  13  consequently falls below the tip  15  of the metering doctor blade  11 , so that the ink container  13  can readily be dismantled without allowing printing ink to run out of the ink container  13  over the metering doctor blade  11  after the metering doctor blade  11  has been lifted off the roller jacket  7 . 
     In FIG. 6, the immersion element  45  is shown in a third position, wherein it is completely submerged in the ink container  13 . Because of the arrangement and shape of the immersion element  45 , the major part of the printing ink is displaced out of the ink container  13  onto the screen roller  5  by the immersion element  45 . The ink container  13  can also be emptied virtually forcibly in this exemplary embodiment. 
     It is apparent from FIG. 6 that the outer contour of the immersion element  45  is matched to the inner contour of the ink container  13  in a manner that the height of the gap formed between the rear wall  29  and the bottom  25  of the ink container  13 , on the one hand, and the immersion element  45  moved into an end position, on the other hand, is only very small. 
     FIG. 7 shows a further exemplary embodiment of the inking unit  1 , which differs from the inking unit described hereinbefore with regard to FIGS. 1 to  3  only in that the metering doctor blade  11  has a further doctor blade  49  disposed upline therefrom in the direction of rotation of the screen roller  5 , the further doctor blade  49  serving for wiping or stripping off the air layer entrained by the screen roller surface at high machine speeds, before the outer jacket surface  7  of the screen roller  5  enters the printing ink, so that this air layer is not concomitantly entrained with the printing ink, which could lead to a disruption of the inking of the cells  9 . The air layer  51  that is wiped off is represented by curved arrows. If printing ink on the outer jacket surface  7  of the screen roller  5  is also doctored off by the doctor blade  49 , this ink can drip back into the ink container  13 , which is directly under the doctor blade  49 . The doctor blade  49  is held in the position illustrated in FIG. 7 by non-illustrated holding elements. 
     In the exemplary embodiment shown in FIG. 7, the ink container  13  is partly covered on the open side thereof by the doctor blade  49 . The remaining part of the ink container  13  is open at the top. In order to be able to close the ink container in the dismantled state, in the exemplary embodiment shown in  8 , a cover  53  is provided which, by a hinge  55  provided on the ink container  13 , can be folded over the open side of the ink container  13 . The ink container  13  closed in this way, together with the printing ink remaining therein, can then be stored without allowing any dirt to fall into it. In addition, the cover  53  projecting beyond the tip  15  of the metering doctor blade  11  also protects the metering doctor blade  11 , in particular, the tip  15  thereof, against damage. When it is installed in the inking unit  1 , the cover  53  is folded away, so that it does not disrupt the printing operation. The cover  53  in the folded-away condition is illustrated in FIG. 8 with broken lines. 
     A common factor in all of the various constructions of the displacer element  35  or  35 ′ is that it can extend over the entire width of the metering doctor blade  11 . Alternatively, provision is made for the displacer element to extend over part of the length of the metering doctor blade  11 . 
     The displacer elements described with regard to FIGS. 1 to  8  are, respectively, pivotably mounted and can be pivoted manually and/or by a suitable actuating device. Alternatively, in a non-illustrated exemplary embodiment, provision can be made for the displacer elements  35 ,  35 ′ to be constructed so that they can be adjusted linearly. For this purpose, for example, a rectilinear guide can be used. The shape of the ink container  13  is appropriately adapted to the linear adjustment of the displacer element. 
     In summary, it remains to be noted that, by using the displacer element  35  or  35 ′, the volume of the ink container can be changed specifically, so that a desired printing ink level in the ink container is set, and can be raised and lowered with respect to the tip  15  of the metering doctor blade  11 , with the same printing ink filling quantity, by an adjustment of the displacer element. 
     In the exemplary embodiments of the inking unit  1  described with regard to FIGS. 1 to  8 , when the ink container  13  is installed and during the operation of the inking unit  1 , respectively, the metering doctor blade  11  is located in the region between the 7 o&#39;clock position and the 11 o&#39;clock position, namely, in approximately the 9 o&#39;clock position, in relation to the screen roller  5 . The ink container  13  and the metering doctor blade  11  are thus arranged laterally beside the screen roller  5 . 
     The inking unit  1  according to the invention offers the advantage, amongst others, that, in order to dismantle the ink container  13  and the metering doctor blade  11 , the ink container  13  does not have to be moved into a removal position, as is contemplated or provided for in the case of heretoforeknown devices of this general type.