Abstract:
The density or size of an ink roll, which is formed in an ink fountain of a rotary printing press, is determined either directly or indirectly at several spaced locations. The measured values are then evaluated. A signal is generated to an ink feed device, or a warning signal can be transmitted in accordance with the size or density of the ink roll and its deviation from reference values.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a method for determining the presence of roll of ink in a pressureless ink fountain of a rotary printing press, as well as to several associated devices. 
     DESCRIPTION OF THE PRIOR ART 
     A device for inking a screen roller is known from EP 0 663 293 A1, wherein ink rotates around a longitudinal axis parallel with the screen roller in a filled ink chamber of circular cross section. 
     A negatively pitched working doctor blade and a positively pitched finishing doctor blade are provided. 
     U.S. Pat. No. 2,399,688 describes a device for maintaining the filling level in an ink fountain constant. 
     GB 2 299 546 shows a device for placing ink into an ink fountain, which can displaced in the longitudinal direction on a carriage. Sensors for monitoring the fill level of the ink in the ink fountain are fastened on the carriages. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is based on providing a method as well as a device, by means of which it can be determined whether build-up of ink forming a roll of ink is formed in an ink fountain in the course of the running of the press. 
     In accordance with the invention, this object is attained by measuring ink thickness values, the thickness of a rotating built-up roll of ink or the partial hydrostatic pressure exerted on a side wall of an ink fountain. The measured values are evaluated and are used to determine the presence of a built-up roll of ink and its size. 
     The advantages which can be achieved by means of the invention consist, in particular, in that the thickness of the built-up roll of ink being formed in the course of the running of the press is determined continuously or at intervals, and that an electrical, optical and/or acoustic signal is issued in case of a deviation from a nominal value. In accordance with the value and the direction of the deviation, either a signal for controlling the ink delivery device or a warning signal for the operator is issued. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Several preferred embodiments of the invention are represented in the drawings and will be described in greater detail in what follows. Shown are in: 
     FIG. 1, a schematic representation of a cross section through an ink fountain placed on a roller, which has a device in accordance with a first preferred embodiment; 
     FIGS. 2 to  9 , further embodiment variations of devices for executing the method; and 
     FIGS. 10,  11 , and  12  schematic representations of an ink fountain placed on a roller with further embodiments of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An ink fountain  1 , which is typically a pressureless ink fountain, open at the top, has a left and a right lateral wall  2 ,  3 , as well as two sealing front or end walls  6 ,  7 , which are matched to the periphery of a driven roller  4 . The ink fountain  1  extends over the entire length of the roller  4  which, for example, can be embodied as a screen roller or as a rotogravure cylinder. A working doctor blade  8  as well as a finishing doctor blade  9  are exchangeably attached at the bottom of the lateral walls  2 ,  3 . 
     In place of the doctor blades  8 ,  9  it is also possible to employ ink metering blades arranged next to each other over the length of the roller  4 . 
     Preferably highly viscous ink  11  having a viscosity greater than  60  poise is placed into the ink fountain  1 , which in the course of the operation of the press forms a build-up of ink forming a roll of ink  12  that rotates or rolls in accordance with the direction of rotation of the roller  4 , for example in a counterclockwise direction A and, which is in contact with the left inside  17  of the lateral wall  2  as well as the free width b as well as the length of the doctor blade  8 . The doctor blade edge of the doctor blade  8  removes ink from the surface  5  of the roller  4 . 
     At a defined position of its length, the rotating built-up roll of ink  12  has a nominal thickness d 1 , which is proportional to the used-up and replenished ink from the ink fountain  1 . Measurements are performed continuously or at intervals by means of a device  28 , which is directly or indirectly oriented toward the built-up roll of ink  12  and fixed in place on the lateral frame or on the ink reservoir, and the result of the measurements is evaluated. 
     The measurement of the distance takes place selectively by means of optical or acoustic means, for example laser beams or ultrasonics, which are emitted by the device  28  and impinge directly and contact-free on the surface  21  of the built-up roll of ink  12 . The thickness d 1  of the built-up roll of ink  12  is then determined on the basis of the known distance between the surface  5  of the roller  4  and the device  28 . 
     Because of the delivery of ink  11  from the ink fountain  1  to the ink roller  4  during the operation of the press, a built-up roll of ink  32  of a reduced thickness d 2  is formed—represented in dashed lines -. Thereupon the device  28  issues a signal which starts an ink pump, not represented, which supplies the ink fountain  1  with fresh ink via the ink delivery device  27 . 
     In case of a large negative deviation d 3  or a large positive deviation d 4  of the thickness of the built-up roll of ink  33 ,  34 —represented in dashed lines -, an optical or acoustic warning signal is emitted, which draws the attention of the operator to an error in the inking unit. 
     The device  28  is connected by means of an electrical or optical conductor  29  with the control post of the press. The time interval to be measured, as well as the fixed distance value, can be set by means of preselector switches  30 ,  31 . 
     As represented by dashed lines in the drawings, the device  28  can be arranged projecting past the upper edge  38  of the ink fountain  1 . It is also possible to provide measurements by means of a device operating on a capacitive basis. 
     Moreover, the device  28  can also be arranged over the length of the ink fountain  1  on a guide rail, which is fastened parallel with the roller, and can be displaced manually or by means of a motor. 
     In accordance with another preferred embodiment of the present invention, as depicted in FIG. 10, a built-up roll of ink sensing lever  23  is hinged on a bearing  18  fastened on the inside  17  of the left lateral wall  2 , whose underside  36  rests tangentially on the periphery  21  of the built-up roll of ink  12 . In this way, a distance between the top  37  of the sensing lever  23  and the device  28  is measured indirectly and by contact, so that it is possible by taking into consideration the thickness of the material of the sensing lever  23 , to determine the various thicknesses d 1  to d 4  of the built-up roll of ink  12 ,  32 ,  33 ,  34 . 
     In accordance with a third preferred embodiment, as seen in FIG. 11, the sensing lever  23  can be part of a double-armed sensing lever assembly  16 , whose second arm  22  points in the direction toward the opening of the ink fountain  1  and which joins the first arm  23  in the bearing  18  at an angle ∝, for example of 130° to 140°. A device  39 , that is the same as device  28 , is arranged on the upper edge  38  of the right lateral wall  3  and measures a horizontal distance between the device  39  and the second arm  22 , again in an indirect and contacting manner, while the underside  36  of the first arm  23  rests against the periphery  21  of the built-up roll of ink  12 . 
     The position of the two-armed sensing lever assembly  16  changes as a function of the thickness d 1  to d 4  ofthe built-up roll of ink  12 ,  32 ,  33 ,  34 , so that the device  39 ,  16  determines the thickness of the built-up roll of ink. The device  39  can be designed in the same way as the device  28 . 
     In accordance with a fourth preferred embodiment, depicted in FIG. 12, the two-armed sensing lever assembly  16  has a vane  24  at the end of its second arm  22 , which is in contactless connection with an inductive device  13 , for example. The vane  24  can be made of sheet metal. The underside  36  of the first arm  23  of the two-armed sensing lever  16  rests tangentially against the built-up roll of ink  12  of a thickness d 1 , so that the sensing lever  16  is in a first, solid line position. The amount of ink is reduced in the course of the operation of the press, so that a resultant built-up roll of ink  32  now has a reduced thickness d 2 . In this case, the sensing lever  16  is in second position—represented by dashed lines -. A signal for the control of the ink delivery device  27  is emitted by the device  13 , so that the built-up roll of ink again attains the nominal thickness d 1 . 
     The device  13  is arranged fixed in place on the lateral frame or on the ink fountain and is connected via an electrical conductor  26  with the control post of the press. 
     Of course, the device can also be set in such a way that a short turn-on of the ink delivery device  27  can immediately take place with even a lesser reduction of the nominal thickness d 1 . The thickness of the built-up roll of ink is preferably scanned continuously or at preselectable time intervals. 
     The number of intervals d 1 , d 2 , d 1  occurring in the course of a correct printing operation—taking into consideration the ink surface portion of the material to be printed as well as the number of revolutions of the press—is advantageously determined during a preselected length of time, for example of five minutes, by means of a known evaluation circuit. For example, five intervals are created within a preselected length of time of five minutes. 
     If the preselected number of intervals falls below this, this is a sign for the wrong formation of the built-up roll of ink and therefore a sign for an erroneous delivery of the amount of ink. In this case an additional alarm signal is emitted. 
     The principle of the methods of the present invention lies in that the ink fountain  1  is filled with ink, for example highly viscous ink, in such a way that during the operating stage a part of the lower ink fountain  1  is free of ink, while a built-up roll of ink  12  is formed in the other lower part of the ink fountain  1 . This status is determined by means of further exemplary embodiments and is evaluated. 
     In accordance with a fifth preferred embodiment, as seen in FIG. 2, a measuring device  39 , for example an ultrasonic sensor or a running time sensor, is arranged above the ink fountain  1 , which measuring device  39  can be pivoted over an angle βof approximately 20° in the circumferential direction of the roller  4 , for the contactless measurement of the thickness d 1  of the, built-up roll of ink  12  in a continuous manner or at intervals. This measuring device  39  measures the distance from the planes C and E. Based on a preselected nominal difference between both planes C, E, it is possible to determine whether sufficient ink  11  is present, or respectively whether a built-up roll of ink  12  has been formed at all. 
     In accordance with a sixth preferred embodiment, as seen in FIG. 3, a measuring device  39  is arranged above the ink fountain  1 , and which device  39  can be displaced in the circumferential direction of the roller  4  by an amount f, for example corresponding to half the width of the ink fountain  1 . The measuring device  39  operates as described in connection with the fifth preferred embodiment, and can be moved back and forth on a rail fixed in place on the lateral frame by means of a linear drive which is not represented. 
     In accordance with a seventh preferred embodiment, as seen in FIG. 4, spaced measuring devices  39  are arranged fixed in place above the ink fountain  1 , and which are spaced from each other by an amount f. The left measuring device  39  determines the distance from the plane C, and the right measuring device  39  determines the distance from the plane E. The measuring method operates as described in connection with the fifth preferred embodiment. 
     In accordance with an eighth preferred embodiment, as seen in FIG. 5, a CCD camera  41  is arranged above the ink fountain  1 , by means of which the actual formation of the built-up roll of ink  12  is detected, which is compared with a nominal formation of the built-up roll of ink stored in a computer. In case of deviations outside of the tolerance range, appropriate signals are emitted, the same as in connection with the previous exemplary embodiments. 
     In accordance with a ninth preferred embodiment, as seen in FIG. 6, a measuring device  39  is arranged on a plane G located above the ink fountain  1 , and which works together with a pivotable mirror  42  located above the ink fountain  1 . The mirror  42  can be pivoted around an angle β, of approximately 20°, for example by means of an electromagnet which is not represented, which can be returned into the initial position by a spring force. The mirror  42  selectively directs the measuring beam on the surface  21  of the built-up roll of ink  12  (plane C) or on the plane E. 
     In accordance with a tenth preferred embodiment, as seen in FIG. 7, a measurement at intervals of the thickness d 1  of the built-up roll of ink  12  in a plane C takes place by means of an angled lever  43 , which is fixed in place on the ink fountain and touches the surface  21  of the built-up roll of ink  12  in a radial direction. The angled lever  43  is designed in an L-shape, for example. A first leg  46  of the angled lever  43  is fastened on the surface of the lateral wall  2  and has a wire strain gauge  44 . The second leg  47  extends vertically and parallel with the lateral wall  2 . The plane C is at an approximate distance from the surface of the roller  4  which corresponds to the diameter d 1  of a built-up roll of ink  12 , as seen in FIG.  7 . It is furthermore possible to also arrange the wire strain gauge  44  on the second leg  47  of the angled lever  43 . 
     In accordance with an eleventh preferred embodiment, as seen in FIG. 8, the lateral walls  2  and/or  3  are set back in the direction toward the interior of the ink fountain  1 . The depression created by this is covered by a flexible piece of sheet metal  48 . It is fastened, at an upper portion, to the lateral wall  2 , or respectively  3 , and with its lower end either cooperates with the inside of the doctor blades  8  and  9  to form a very narrow gap, or rests on them. At least one wire strain gauge  49  has been applied on the inside of the flexible piece of sheet metal  48 , which projects into the depression. A bending moment is generated by the contact of the rotating built-up roll of ink  12  with the flexible piece of sheet metal  48 , which bending is detected by the wire strain gauge  49 , which emits a corresponding signal, which is evaluated. It is also possible to detect oscillations by means of the wire strain gauge, which are evaluated and are used as an indicator of a rotating movement of the ink roll  12 . 
     The distance h can be up to several millimeters. 
     However, it is also possible to arrange an elastic material, for example silicon caoutchouc, between the support  48  and the lateral wall  2 . 
     In accordance with another embodiment which is not specifically represented, at least one of the lateral walls has a pressure-measuring pickup. A signal is emitted when the ink roll  12  comes into contact with the pressure-measuring pickup. 
     With the preferred embodiment in accordance with FIG. 9, the device operates the same as with the subject of FIG.  8 . In place of a flexible piece of sheet metal  48  with a lower free end, a flexible piece of sheet metal  51  is now used, which is fastened on the top and bottom on the lateral wall  2  and/or  3  and in this way covers a depression or opening  52  in them—sealed against the entry of ink. 
     The “flexible piece of sheet metal” can, as shown in FIG. 9, also be created by the removal of material from the lateral wall  2  and/or  3  from the outside. Because of this, the lateral wall  2 ,  3  can be stressed by bending because of the hydrodynamic forces generated by the rotating built-up roll of ink  12 . These generated bending stresses can be detected by means of wire strain gauges  49  and evaluated. They are a measurement for determining whether the built-up roll of ink  12  rotates. This can also be determined in another way by means of the wire strain gauges  49 . It is possible to electronically evaluate the oscillations, by means of which the rotating built-up roll of ink  12  excites the flexible piece of sheet metal  51 , from the signals of the wire strain gauges. 
     While preferred embodiments of an ink fountain in accordance with the present invention have been set forth and completely hereinabove, it will be apparent to one of the skill in the art that a number of changes in, for example the specific printing press, the ink supply device and the like could be made without departing for the true spirit and scope of the present invention which is accordingly to be limited only by the following claims.