US3368399A - Arrangement for measuring the ink pulling power on lithographic printing machines - Google Patents

Description

Feb. 13, 1968 wmz 3,368,399

B. ARRANGEMENT FOR MEASURING THE INK PULLING POWER 0N LITHOGRAPHIC PRINTING MACHINES Filed July 13, 1965 2 Sheets-Sheet 1 Inventor: 8UR/(HI9RDT' M 2 Feb. 13, 1968 B Wm 3,368,399

ARRANGEMENT FOR MEASURING THE INK PULLING POWER ON LITHOGRAPHIC PRINTING MACHINES Filed July 13, 1965 2 Sheets-Sheet 2 Fig. 4 ,/22 22 {7 o o 18 :r--=- p 1 I I l 1': L [i1 H I I L-U LP H lnvenfor.

' flunk mnor MR 2 1/19 United States Patent Ofitice 3,368,399 Patented Feb. 13, 1968 3,368,399 ARRANGEMENT FOR MEASURING THE INK PULLING POWER N LITHOGRAPHIC PRINT- ING MACHINES Burkhardt Wirz, Munich, Germany, assignor to Roland Olfsetmaschinenfabrik Faber & Schleicher AG. Filed July 13, 1965, Ser. No. 471,660 Claims priority, application Germany, July 15, 1964, R 38,380 6 Claims. (Cl. 73-150) ABSTRACT OF THE DISCLOSURE A device for measuring the pulling power of printing inks in which two rotatable measuring rollers with a nonelastic surface engage a non-elastic inking mechanism roller of a printing press. One of the measuring rollers is mounted radially resilient in reference to the inking mechanism roller and the other is mounted tangentially resilient in reference to the inking mechanism roller. Electric measuring means which are responsive to movements of the measuring rollers in radial and tangential direction respectively, as caused by the pulling power of the ink to be supervised, generate signals corresponding to the movements of the measuring rollers and these signals are used to control means for computing the pulling power of the printing inks.

The invention relates to an arrangement for measuring the ink pulling power on lithographic printing machines or presses.

It is known that in offset printing a high printing quality can only be achieved if the ink supply and also the water supply can be supervised and adjusted to a certain extent. This is true also for the running up of the machine, that is to say until the water and ink supply are in a state of balance, and also for the continuation of printing, in which the offset printer has to keep the water and ink continuously under control. Due to the mutual coaction of ink and water, the starting period, that is, the period during which the ink and the water are adjusted so that the density of the ink remains substantially constant on the sheets to be printed, may be a very prolonged one if the adjustment is not expertly effected. Furthermore, if on continuation of printing the ink-water balance necessary for the particular case is not supervised continuously with the necessary care, then ink fluctuations and quality fluctuations may occur which, especially in connection with multi-colour wet-in-wet printing may be so strong that they lie outside the allowable tolerance. Unfavourable water carrying conditions occur, for example when printing non-absorbent materials, and these can make still more difiicult the quality supervision.

The balance of ink and water in lithographic printing is more particularly determined by three factors: by the water amount present, on the printing plate, and by the thickness and pulling power of the ink layer on the Spreaders or application rollers. The printer understands pulling power to be the tackiness of the ink.

On the one hand, the ink pulling power influences the ink division and thus the reproduction of tone values. Thus, a good tone value reproduction can only be achieved with an ink which is only slightly emulsified and which has good pulling power, whereas an ink which has less pulling power is poorly transferred onto the plate. If the ink does not have a suflicient pulling power, then the printer must supply more ink in order to avoid the surface being too little saturated, so that the ink penetrates into the depth of screen parts and the reproduction becomes heavier. Furthermore, the ink pulling power, in wet-in-Wet printing, influences the ink acceptance of ink printed on a second region, with respect to the first, in such a manner. that according to experience the pulling power of the second ink should be lower than that of the first, so that a good acceptance of the second ink is obtained. Since the ink pulling power depends on the degree of emulsification, for achieving a good and constant ink acceptance, particular attention has to be given to the water-ink balance.

It is noteworthy that the layer thickness heavily influences the measuring value of the ink pulling power in the measuring method described further below. Values of ink pulling power can thus only be compared with each other for equal layer thicknesses, or possibly the influence of the layer thickness has to be allowed for by means of analogue calculation.

The pulling power arises from the cooperation of the water and ink quantities supplied. If for example more water is supplied than taken otf, then after a certain time a reduced pulling power occurs. A pulling power which is too high at constant layer thickness means an insufficient water supply. In practice, neither the ink pulling power nor the ink layer thickness are indicated on the printing machine. The printer accepts the fluctuations of quality as unavoidable for the offset process.

A measuring device for ink pulling power is known on a printing machine, in which however the ink layer thickness is not taken into account and the temperature is not held constant. With this device, an alteration of the ink layer thickness or the temperature means a different pulling power, it being known for example that draught in the printing machine room cools the ink layer by evaporation of moistening water from the roller surface, thus simulating a higher pulling power. A considerable disadvantage of this device is furthermore the necessity for standardizing by means of petroleum which is applied to the roller, and also that the indication is dependent on speed. These two difiiculties are based on the fact that the measuring roller on the one hand does not measure in a reproduceable manner, since the ink layer thickness and temperature are not allowed for, and on the other hand difiiculties of technical operation stand in the way of its practical use in the printing works.

Furthermore, a device for measuring the ink layer thickness on the machine is known, which however is not combined with a measuring device for ink pulling power, but simply serves for supervising the ink supply. In this known measuring device, only a single measuring roller cooperates with the inking mechanism roller. This can yield in the tangential direction against the action of a spring, the magnitude of this movement being intended to be a measure for the pulling power of the ink. Since however the absolute value of the occurring tangential force is dependent on the layer thickness of the ink, the known arrangement cannot give absolute values, but at the most can give comparison values. A further disadvantage of known devices is to be seen in that in each case an elastic and a non-elastic roller cooperate as inking roller and measuring roller, or vice versa. The occurring tangential forces, with otherwise equal conditions, are heavily dependent on the elastic nature of the covering of the elastic roller, and also on speed, temperature and measuring time, so that neither reproduceable nor absolute measuring values can be obtained.

Contrary to the above mentioned previously proposed devices, the present invention is characterised by the simultaneous sensing of the ink layer thickness, by means of two non-elastic measuring rollers which lie freely rotatably on a non-elastic inking mechanism roller, one of the two being radially resiliently mounted for the purpose of sensing the ink layer thickness and the other of the two being tangentially resiliently mounted relative to the their movements in the radial and tangential directions being sensed by an electrical measuring procedure known per se. Accordingly, the disadvantages of the known devices are avoided, the device being able to be standardised and delivering reproduceable values. On the other hand, it is constructed in such a manner that the measuring rollers run against a non-elastic roller so that standardising and servicing of the device is considerably simplified compared with known devices, and the device 15 thus the first usable for printing works. The device according to the invention considerably assists the printer to maintain the printing quality constant, since it indicates the condition of the ink, while allowing for the layer thickness. The printer can make comparisons for equal layer thicknesses with values known from experience, more particularly in connection with new prints using the same ink and the same paper.

It is provided according to the invention that the measuring rollers are arranged at a spacing from each other and act on the same peripheral zone of the sleeve of the inking mechanism roller. Since the measuring rollers preferably have only a fraction of the length of an inking mechanism roller, by this means the tangential forces caused by the ink separation forces are measured at the same region at which the ink layer thickness is determined by the radially movable roller. This is especially important in printing operations in which ink layers of different thicknesses over the breadth of the printing machine have to be supplied.

According to a further feature, the invention is characterised in that the temperature of the inking mechanism roller is maintained at a constant level by known means. Since the consistency of the ink is strongly dependent on temperature, and this changes with room temperature and also with the period of operation of the printing machine, faultless measuring values can only be achieved with this measure. The measuring device according to the invention for measuring the pulling power while allowing for the layer thickness can give the printer valuable information with regard to the ink being printed. With the machine cold, it indicates to him how strongly the ink has to be diluted; with reprints of the same work the earlier optimum consistency can be set and with multi-colour machines the correct sequences of pulling power. Comparative statements can however only be made for equal temperature and layer thicknesses.

If it is required to measure on an elastic inking mechanism roller, then according to the invention a non-elastic inking roller is provided in cooperation with the two measuring rollers, it having the length of the measuring rollers and bearing against the elastic inking mechanism roller as a supplementary roller. Thus, also in this case, the requirements for exact measurement exist.

The invention is furthermore characterised by a known mounting for resiliently carrying the two measuring rollers, which allows slight deviations from the axially parallel positions of the measuring and inking mechanism rollers. Localised inaccuracies of the non-elastic inking mechanism roller and tolerances in the mounting of the measuring rollers are accordingly compensated and the latter engage faultlessly over their entire length.

In order to prevent the measuring device having any action on the inking, for example by forming bands or stripes running in the peripheral direction of the roller, according to a further feature of the invention a known mechanism is provided for moving the two measuring rollers axially to and fro. Even a slight axial movement is sufficient to avoid the above mentioned disadvantage.

A further feature of the invention is the provision of a known analogue computer which converts the movements obtained by the two measuring value generators into a single indication which is dependent on the pulling power of the printing ink while allowing for its layer thickness. Accordingly, it is possible to combine the two measuring values into a single magnitude and all calculations for allowing for the influence of the layer thickness become unnecessary.

The above features and advantages of the invention will be clear from the following description, taken with reference to the accompanying drawings, which are given by way of example and in which:

FIG. 1 is an end view of a measuring device for measing ink pulling power;

FIG. 2 is a front view of the measuring device of FIG. 1;

FIG. 3 is an end view of a modified measuring device; and

FIG. 4 is a front view of the device of FIG. 3.

Referring to FIGS. 1 and 2, on a non-elastic inking mechanism roller 1, for example a rubbing roller, the metal rollers 2, 3 engage, which are mounted in a holder 4 which for its part is clamped on the traverse 5. After loosening the clamping screws 6, the entire measuring device can be pushed along the roller 1. The measuring roller 2 is mounted by means of roller bearings in two holders 7 each of which is connected by means of a flat spring 8 with a respective arm 9. By means of this elastic mounting, the roller 2 bears in all cases on the roller 1. According to the ink layer thickness on the roller 1, the roller 2 is more or less lifted and this movement can be measured by means of a strain gauge 10 in known manner stuck on each of the flat springs 8. The measuring roller 3 is mounted in a bracket or frame 11 which is fixed by means of the fiat springs 12 on the arms 13. The frame 11 is provided with slots 14 so that the roller 3 can lift to a greater or lesser extent depending on the ink layer thickness. The tangential forces occurring on rotation of the roller 1 cause a tangential movement of the roller 3, 'which is taken up by the strain gauges and converted in known manner into an electric value. To prevent oscillations, an oscillation damper 16 is arranged between the frame 11 and the arm 15. Instead of the two holders 7, alternatively a closed frame corresponding to frame 11 can be used.

. roller 18 on the holder 20 correspond precisely to the arrangement of the roller 2 according to FIGS. 1 and 2, and accordingly the same reference numerals are used. The roller 19 is mounted in a frame 21 which is fixed by means of two flat springs 22 onto the frame 24 which is rotatable about the traverse 5 by the eyes 23. The basic setting of the frame 24 is effected by the stop screw 25, a tension spring 26 ensuring contact of the screw 25 with the arm 15. The movement of the roller 19 radially to the rubbing roller 17 causes bending of the flat springs 22, which by means of the strain gauges 27 is converted into an electric value.

I claim:

1. A device for measuring the pulling power of a printing ink, said device comprising in combination:

two freely rotatable measuring rollers having a substantially non-elastic surface and arranged to engage an inking mechanism roller of a printing press also having a substantially non-elastic surface; mounting means mounting one of said measuring rollers resiliently in radial direction in reference to the inking mechanism roller and mounting the other measuring roller resiliently in tangential direction in reference to the inking mechanism roller; electric measuring means responsive to movements of said measuring rollers in radial and tangential direction respectively, as caused by the pulling power of the ink to be measured for generating signals corresponding to said movements; and means responsive to said signals for computing the pulling power of said printing ink. 2. A device according to claim 1 wherein said mounting means mount said measuring rollers spaced apart in a side-by-side relationship, and support means extending parallel to the rotational axis of the inking mechanism roller and slidably supporting said mounting means.

3. The device according to claim 1 wherein said mounting means mount said measuring rollers in circumferentially spaced relationship in reference to said inking mechanism roller, and support means supporting said mounting means.

4. The device according to claim 3 wherein said support means extend parallel to the rotational axis of the inking mechanism roller and support said mounting means lengthwise slidable in reference to the inking mechanism roller.

5. The device according to claim 1 wherein said mounting means comprise support means for each of said measuring rollers, each of said support means including a flexible portion to permit said radial and tangential movements of the measuring rollers in reference to the inking mechanism roller, the flexing of said flexible portions controlling said electric measuring means.

6. A device according to claim 5 wherein said electric measuring means are strain gauges.

References Cited UNITED STATES PATENTS LOUIS R. PRINCE, Primary Examiner.

J. N-OLTON, Assistant Examiner.

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