MXPA97008608A - Viscosi maintenance - Google Patents

Abstract

A device (18) for measuring the relative viscosity includes an apparatus (29) that can be movably mounted inside a container (12) and a detector system. The apparatus has two members (32, 34), with one member being more deformable than the other. When the apparatus moves, the sensing system detects a differential bending between the members, the differential bending being related to the viscosity of a fluid when the fluid is included in the fluid container in which the apparatus is movably mounted. The detection system includes two separate detectors (40, 42) which detect when the magnets (36, 38) on the members pass the detectors. A timer provides an elapsed time between the passage of a member passing a detector and the passage of the other member passing the other detector. The elapsed time is related to the viscosity of the fluid in the fluid container. A controller controls the addition of a solvent to the flui

Description

VISCOSITY MAINTENANCE Background of the Invention The invention relates to the measurement of viscosity. The desired viscosity of the ink in a gravure printing machine is a function of the substrate, the printing speed and the type of ink. The viscosity of the ink is affected by the evaporation of the solvent and the temperature of the environment.

Brief Description of the Invention In general, in one aspect, the invention features a device for measuring relative viscosity. The device includes a fluid container, a stirrer movably mounted within the fluid container and a detector system. The agitator has two members, with one member that is more deformable than the other, for example, one arm is rigid and one arm is flexible. When the agitator moves, a sensing system detects a differential bending between the members, the differential bending is related to the viscosity of a fluid in the fluid container. The implementations of the invention may include one or more of the following characteristics. The agitator rotates. The members are arms each with a magnet located at the end of the arm. The arms extend from a center of the rotation of the agitator. The detector system is a detector that detects when the magnets pass the detector. There are two separate detectors that detect when the magnets pass the detectors. A timer provides a time elapsed between the passage of one of the members passing a detector and the passage of the other member passing the other detector. The elapsed time is related to the viscosity of the fluid in the fluid container. An actuator coupled to the image moves the agitator. A controller automatically controls the addition of a solvent within a solvent container to a fluid within the fluid container. The addition of the solvent depends on the elapsed time that is related to the viscosity of the fluid. A conduit is directed from the solvent container to the fluid container. A flow controller, for example, a pump or a solenoid, controls the flow through the conduit. In general, in another aspect, the invention features a printing machine that includes an ink container, a gravure roll, a filler roller for transferring ink from the ink container to the gravure roll and a device for measuring the relative viscosity located in the ink container. Implementations of this aspect of the invention may include one or more of the following characteristics. The ink container is mounted for easy removal and cleaning. In general, in another aspect, the invention presents a method for measuring the relative viscosity. The method includes placing a fluid in a fluid container; moving an agitator mounted within the fluid container, the agitator including two members, one of which is more deformable than the other; and detecting a differential bending between the members when the agitator is moved, the differential bending being related to the viscosity of a fluid in the fluid container. Implementations of this aspect of the invention may include one or more of the following characteristics. The detection of differential bending includes counting the time elapsed between the passage of one of the members passing a detector and the passage of the other member passing a detector. The elapsed time is related to the viscosity of the fluid in the fluid container. The movement of the agitator includes the rotation thereof. The movement of the agitator includes providing an impeller coupled to a magnet. The detection of the bending differential includes counting the time elapsed between the passage of a magnet of one of the members passing the detector and the passage of a magnet of the other member passing the detector. In general, in another aspect, the invention presents a method of maintaining viscosity. The method includes automatically controlling the addition of a solvent from a solvent container to the fluid within a fluid container. In general, in another aspect, the invention presents a device for measuring the relative viscosity. The device includes an apparatus that can be movably mounted within a fluid container. The apparatus includes two members, one member being more deformable than the other member. A detector system detects a differential bending between the members when the apparatus moves. The differential bending is related to the viscosity of a fluid when the fluid is included in the fluid container in which the apparatus is movably mounted. Implementations of this aspect of the invention may include one or more of the following characteristics. The detector system includes a detector that detects when members pass the detector. The detector system includes two separator detectors that detect when the members pass the detectors. In general, in another aspect, the invention features a viscosity maintenance device that includes a first fluid container; a device for measuring the relative viscosity of a fluid in the first fluid container; a second fluid container; and a controller for controlling the addition of a second fluid from the second fluid container to the fluid within the first fluid container. In general, in another aspect, the invention presents a method for measuring the relative viscosity. The method includes moving an apparatus within a fluid, the apparatus including two members, one of which is more deformable than the other; and detecting a differential bending between the members when the apparatus moves, the differential bending being related to the viscosity of a fluid.

Implementations of this aspect of the invention may include one or more of the following characteristics. The detection of differential bending includes counting the time elapsed between the passage of one of the members passing a first detector and the passage of the other member passing a second detector. The elapsed time is related to the viscosity of a fluid. One of the members is rigid and one of the members is flexible. The advantages of the invention may include one or more of the following. The viscosity measuring device is located in the ink container itself and therefore measures the viscosity of the ink near the point of transfer of the ink from the gravure roller to the printing roller. This provides high quality, consistent printed images. The viscosity of the ink is maintained continuously by the addition of solvent. Other advantages and features will become apparent from the following description and from the claims.

Brief Description of the Drawings Fig. 1 is a diagrammatic representation of the gravure printing machine with a viscosity maintenance device; Fig. 2 is a perspective view of the ink container including a viscosity measuring device; Fig. 2A is a top view of a stirrer of the viscosity measuring device; Fig. 2B is an exploded view of an agitator coupling assembly; Fig. 3 is a block diagram of the control system; Fig. 4 is a block diagram of the control algorithm of the viscosity maintenance device; and Fig. 5 shows a representation of the relative viscosity of the ink under the control of the control maintenance device.

Description of the Preferred Modalities Referring to Fig. 1, a rotary rotogravure printing machine 10 includes an ink container 12 supported by a base 13, a gravure roller 14, a filler roller 16 for transferring the ink from the ink container 12 to the ink roller. gravure 14 and, a relative viscosity measuring device 18 located in the ink container 12. A printing roller 20 having elastomeric holders 21 collects the inked image from the engraving cells (not shown) of the gravure roller 14 for printing on a substrate (not shown). The viscosity of the ink located in the ink container 12 is adjusted by the addition of a solvent. A solvent container 24 and conduit 26 are provided for solvent addition. The solvent container 24 includes a flow controller 64, for example, a pump or solenoid, for controlling the flow of solvent in the conduit 26. A cover 28, shown here in its open position, can be included to prevent spillage of the solvent. ink from the ink container 12, to minimize the evaporation of solvent from the container and, to keep the foreign waste out of the container. With reference to Figs. 2-2A, a rotary agitator 29 located in the ink container 12 serves the dual purpose of mixing the ink and measuring the viscosity as it rotates. The agitator 29 includes a coupling assembly 30, a rigid blade 32 and a flexible blade 34. The blades help to mix the ink by agitation and the rigid blade 32 includes holes 33 which aid mixing by creating a shearing action instead of a wave like the palette that goes through the ink. The filler roller 16 also helps to mix the ink, being particularly useful for mixing the solvent with the ink. The blades 32, 34 include magnets 36, 38, respectively, located at the ends of the blades and 180 ° apart. The flexible vane 34 is approximately 0.95 cm longer than the rigid vane 32 resulting in a 0.95 cm shifting between the magnet locations. The detectors 40, 42 of the viscosity measuring device 18, for example, Omni-Polar Hall Effect Detectors, from Microswitch, Freeport, Illinois, part # SR4P2-A1, which have a sensitivity scale below about seven gauss and wired in parallel , they are adjustable approximately 160 ° apart, mounted with a 0.95 cm phase shift and, located at a distance of approximately 0.29-0.63 cm from the magnets 36, 38 when the magnets are placed on the detectors. The sensors 40, 42 transmit a signal when a magnet crosses over the detector. Although shown in Fig. 2 for clarity, the sensors 40, 42 are preferably mounted on the base 13. The detector 42, or alternatively the detector 40 or both detectors, are adjustably mounted in a slot 41. The position of the detector 40 it is such that the time delay between the crossing, for example, of the rigid vane 32 on the detector 40, is 50 m ahead of the junction, for example, of the flexible vane 34 on the detector 42, when the agitator 29 is rotated dextrorotatory in a dry container. The rotation of the agitator 29 within an ink volume causes the blade 34 to flex while the blade 32 remains rigid. The amount of flexure of the flexible vane 34 is indicative of the viscosity of the ink. The time delay between the crossing of the rigid pallet 32 on one of the detectors and the crossing of the flexible pallet 34 on the other detector, for example, for right-handed rotation, the crossing of the rigid pallet 32 on the detector 40 and the Subsequent crossing of the flexible vane 34 on the detector 42, gives a measure of the relative viscosity of the ink, the greater the time delay the higher the viscosity. The rigid blade 32 is made, for example, of stainless steel and the flexible blade 34 is made of one or more flexible materials, for example, spring steel. The thickness of the flexible vane 34 depends on the expected viscosity scale of the ink, for example, 1-3000 centipoise the thickness is 0.012 cm, 3000-5000 centipoise the thickness is 0.017 cm and >; 5000 centipoise thickness is 0.025 cm. The thickness of the rigid blade 32, for example, 0.152 cm, is selected to avoid any bending of the blade in all viscosities encountered in the use of the device. The pallets generally have heights of approximately 0.95 cm with the rigid pallet 32 having a length of approximately 6.66 cm and the flexible pallet 34 having a length of approximately 7.62 cm. The magnets 36, 38, for example, samarium cobalt magnets with nickel plating for chemical resistance, having a diameter of approximately 0.31 cm and 0.63 cm in length, are mounted with their north poles facing towards the detectors 40, 42. The magnets they are selected to be sufficiently powerful to be detected through the container 12 as sufficiently small to provide good sensitivity and accuracy. Referring to FIG. 2B, the coupling assembly 30 includes an agitator housing 50, made of, for example. Delrin®, a slotted pin 52, a washer 54, samarium cobalt magnets 56 and a magnet holder 58. A magnet driver, as taught in US Patent No. 3,677,070 to Norcross, incorporating a motor 62 (see Fig. 3), for example, a stepper motor operating at 18 rpm, can be used to activate the drive coupling assembly 30. The magnetic coupling allows the ink container 12 to be easily removed from the machine 10 for cleaning. The ink container 12 is made of a non-magnetic, chemical resistant material, for example, preferably aluminum, although delrin, polypropylene, stainless steel or ceramic can be used. The ink container 12 includes a raised projection (not shown) on which a hole 59 of the magnet holder 58 is placed to place the coupling assembly 30 in the container. The agitator 29 can be easily moved from the container 12 for cleaning by lifting it on the pin 52. Referring to FIG. 3, a controller 60 controls the stepper motor 64 to rotate the agitator 29. The detectors 40, 42 are measured twice for each revolution if the magnets and detectors are not mounted with a phase shift. If the measured viscosity (Fig. 5) is above the desired viscosity scale, that is, the ink is too thick, at 86, the solvent is added at 88. After the set number of ink is added to the ink jets, there is a time delay at 90 before the next addition of solvent is made. During this time delay, the additional solvent is mixed into the ink by the action of the agitator and the filler roller. Fig. 5 shows a typical output of the measured relative viscosity 87 compared to the desired relative viscosity 100 and the acceptable scale 102 during the addition of the solvent to reduce the viscosity of the ink. In an alternative scheme, the automatic control of the solvent addition can be eliminated and the controller 60 can provide a signal to the operator indicating that the viscosity of the ink is high and the operator can add the solvent manually. Other embodiments are within the scope of the following claims. The separation of the magnets 36, 38 and the detectors 40, 42 may be different from the 180 ° separation. A detector can be used instead of two detectors. The principle in essence is the same as that of the two-detector system, although here a detector detects when each vane crosses the position of the detector with the time delay being related again to the viscosity.

Claims (36)

1. A device for measuring relative viscosity comprising: a fluid container, a movably mounted agitator mounted within the fluid container, the agitator including two members, one member being more deformable than the other member, and a sensing system that detects a differential bending between the members when the agitator is moved, the differential bending being related to the viscosity of the fluid when the fluid is included in the fluid container.

2. The device of claim 1, wherein the agitator rotates.

3. The device of claim 1, wherein each member includes a magnet.

4. The device of claim 3, wherein each member comprises an arm, the magnet being positioned at one end of the arm.

5. The device of claim 3, wherein the detector system comprises a detector, the detector detects when the magnet passes the sensor.

The device of claim 5, wherein the detector system comprises two separate detectors, the detectors detect when the magnets pass the detectors.

7. The device of claim 6, further including a timer that provides a time elapsed between the passage of one of the members passing one of the detectors and the passage of the other of the members passing the other of the detectors, the elapsed time being related to the viscosity of the fluid when the fluid is included in the fluid container.

The device of claim 1, further comprising a magnet coupling driver for moving the agitator.

The device of claim 1, wherein one of the members is rigid and one of the members is flexible.

The device of claim 1, further including a solvent container, and a controller for controlling the addition of a solvent within the solvent container to a fluid within the fluid container.

The device of claim 10, wherein the controller automatically controls the addition of the solvent, the addition of the solvent being dependent on the elapsed time.

12. A device for measuring the relative viscosity, comprising: a fluid container, a stirrer rotatably mounted within the fluid container, the agitator having first and second arms extending from a center of rotation of the agitator, one of the arms being more deformable than the other of the arms, each arm including a magnet mounted on one end of the arm, two sensors mounted on the device to detect when the magnets pass the detectors when the agitator rotates, a timer that provides the time elapsed between the passage of one of the members passing one of the detectors and the passage of the other member passing the other detector, the elapsed time that is related to the viscosity of a fluid when the fluid is included in the container of fluid.

13. A device for maintaining viscosity, comprising: a fluid container, a stirrer movably mounted within the fluid container, the agitator including two members, one member being more flexible than the other member, a sensing system which detects a differential bending between the members when the agitator is moved, the differential bending being related to a viscosity of a fluid when the fluid is included in the fluid container, a solvent container, and a controller to control the addition of a solvent within the solvent container to a fluid within the fluid container.

14. The device of claim 13, wherein each member includes a magnet.

15. The device of claim 14, wherein the detection system comprises two separate detectors, the detectors detect when the magnets pass the detectors.

16. The device of claim 15, which also includes a timer that provides a time elapsed between the passage of one of the members that passes a detector and the passage of the other member passing the other of the detectors, the time elapsed being related to the viscosity of the detector. fluid when the fluid is included in the fluid container.

The device of claim 16, wherein the controller automatically controls the addition of the solvent, the addition of the solvent being dependent on the elapsed time.

18. The viscosity maintenance device of claim 13, further including a conduit guiding from the solvent container to the fluid container.

The viscosity maintenance device of claim 18, further including a flow controller for controlling the flow of the solvent in the conduit.

20. A printing machine comprising an ink container, a gravure roller, a filler roller for transferring the ink from the ink container to the gravure roller, and a device for measuring the relative viscosity located in the ink container.

21. The printing machine of claim 19, wherein the ink container is mounted for easy removal.

22. A method for measuring the relative viscosity comprising: placing a fluid in a fluid container, moving an agitator mounted within the fluid container, the agitator including two members, one member being more deformable than the other, detecting a differential bending between the members when the agitator is moved, the differential bending being related to a viscosity of a fluid when the fluid is included in the fluid container.

The method of claim 22, wherein the detection of differential bending includes counting the time elapsed between the passage of one of the members passing a detector and the passage of the other member passing the detector, the elapsed time being related to a viscosity of a fluid when the fluid is included in the fluid container.

24. A method for maintaining viscosity comprising placing a fluid in a fluid container, moving an agitator mounted within the fluid container, the agitator including two members, one member being more deformable than the other member, detecting differential bending between the members when the agitator is moved, differential bending being related to a viscosity of a fluid when the fluid is included in the fluid container, and controlling the addition of solvent from a solvent container to a fluid within of the fluid container.

25. The method of claim 24, wherein the detection of differential bending includes counting the time elapsed between the passage of one of the members passing a detector and the passage of the other member passing the detector, the elapsed time being related to a viscosity of a fluid when the fluid is included in the fluid container.

26. The method of claim 25, wherein the addition of the solvent is automatically controlled and depends on the elapsed time.

27. A device for measuring relative viscosity comprising: an apparatus that can be movably mounted within a fluid container, the apparatus including two members, one member being more deformable than the other member, and a sensing system which detects a differential bending between the members when the apparatus is moved, the differential bending being related to a viscosity of a fluid when the fluid is included in the fluid container in which the apparatus is movably mounted.

28. A device for maintaining viscosity, comprising: a first fluid container, a device for measuring the relative viscosity of a fluid in the first fluid container, a second fluid device, and a controller for controlling the addition of a fluid. second fluid from the second fluid container to the fluid within the first fluid container.

29. A method for measuring the relative viscosity comprising: moving an apparatus of a fluid, the apparatus including two members, one of the members being more deformable than the other of the members, and detecting a differential bending between the members when moves the apparatus, the differential bending being related to a viscosity of a fluid.

30. The device of claim 1 or 27, wherein the detector system comprises a detector, the detector that detects when the members pass the detector.

The device of claim 30, wherein the detector system comprises two separate detectors, the detectors that detect when the members pass the detectors.

32. The method of claim 22, wherein the movement of the agitator includes rotating the agitator.

The method of claim 22, wherein the movement of the agitator includes providing an impeller coupled to a magnet.

34. The method of claim 23, wherein the detection of the differential bending includes counting the time elapsed between the passage of a magnet of one of the members passing the detector and the passage of one magnet of the other of the members passing the detector.

35. The method of claim 22 or 29, wherein the detection of differential bending includes counting the time elapsed between the passage of one of the members passing a first detector and the passage of the other member passing a second detector , the elapsed time being related to a viscosity of the fluid.

36. The method of claim 22 or 29, wherein one of the members is rigid and one of the members is flexible.