Measuring and testing – Coating material: ink adhesive and/or plastic
Reexamination Certificate
2000-10-30
2001-11-20
Larkin, Daniel S. (Department: 2856)
Measuring and testing
Coating material: ink adhesive and/or plastic
C073S15000R, C073S064490, C101S349100
Reexamination Certificate
active
06318165
ABSTRACT:
BACKGROUND OF THE INVENTION
a) Field of the Invention
The invention relates to a device for measuring the stickiness of a flowable medium, in particular a printing ink, which is led as a layer between two surfaces that can be moved in the same direction, through a convergence zone, a pressure zone and a divergence zone, it being possible to use a measuring device to measure, as a measure of the stickiness, that force which is needed to separate the surfaces from each other.
In this case, the term stickiness is interned to include, in particular, the tack-and other rheological properties, such as viscosity.
b) Description of Related Art
In a device of this type disclosed by DE-A-19 00 328, the flowable medium to be tested is brought, in an accurately metered quantity, between two rotatable bodies, of which one is driven and the other is carried along by a frictional connection. In this case, a lever arrangement is used to measure the force which is necessary to separate the two bodies from each other. This device has the fundamental disadvantage that, as a result of driving only one rotatable body and carrying the second rotatable body along via the flowable medium to be measured, shear forces occur in this medium, which lead to a change in the rheological properties of the medium to be tested, which results in the set force for determining the tack which, during its measurement, is intended to be perpendicular to the two surfaces between which the medium to be measured is located, is falsified. A further disadvantage of this and other known devices is basically that, during the testing of printing inks and their lithographic properties, no account can be taken of those influences which result, for example, during the application of the flowable medium, for example a printing ink, to paper or other materials, since the device comprises two rotating bodies with metal and/or rubber surfaces but that, for example, the preconditions prevailing in a printing machine cannot be simulated with such a device. Furthermore, it is not possible either to determine the influence of the layer thickness of the applied medium as a function of the material of the surfaces on the tack value. Nor is there any possibility of establishing the superimposition, taking place during multicolor printing, of various flowable media, with regard to their influence on the tack. All such testing possibilities are impossible with this known device and also further devices which have been disclosed.
OBJECT AND SUMMARY OF THE INVENTION
The primary object of the invention is to configure a device of the type explained at the beginning in such a way that the stickiness values and, in particular, tack values and their changes which occur during the application, transfer, multiple covering, when being changed by the addition of further substances and during the preparation of flowable media, in various areas, for example in distributor mechanisms, on the impression cylinder or on the printing material of printing machines, can be measured in accordance with the relationships which actually occur.
In a device of the-type specified further above, according to the invention, this object is achieved in that at least one surface is led on a circularly cylindrical path, in that both surfaces can be driven positively in the same direction and at the same speed, in that both surfaces contain, at least in some sections, those materials of which the surfaces which are assigned to each other during the processing of the medium to be tested in intended devices, for example printing machines, are composed, in that at least one of the two surfaces used to transfer the measured value is arranged on a supporting body, directly or via a measured-value transmitter, has at least one area of set extensibility and is connected to measuring devices for establishing the magnitude and the direction of that force with which the surface is lifted off the supporting body, extending the extensible area, during the separation or splitting of the layer adhering to the surface, and in that the measuring devices can be moved synchronously together with the moving surface.
An important refinement of the device according to the invention is that the two surfaces can be driven in the same direction at the same speed, so that the flowable medium located between these surfaces and to be tested is not subjected to any significant shear forces which could lead to a change in the rheological properties of this flowable medium. In order to achieve these identical speeds, it is necessary for one of the surfaces to be led on a circularly cylindrical path, that is to say for this surface to be part of a circular cylinder. Although the second surface can be flat, it must also be able to be moved at the same speed, which corresponds to the circumferential speed of the circular cylinder. Of course, for the continuous measurement of the tack values, it is advantageous if both surfaces are led on circularly cylindrical paths, since in this way the interruption in time, needed to return the flat surface into the starting position without contact, is dispensed with.
A further decisive feature of the present invention is to be seen in the fact that the surfaces which are in contact with the flowable medium during the measuring operation correspond, with regard to the material selection, to those surfaces which are used in the devices in which the flowable medium to be measured is employed in the intended use. For example, one surface consists of the paper to be printed or another material to be printed, and the other surface consists of the material of which the press roll or other printing device also used in a printing machine consists. In this way, the conditions which are simulated are exactly those which are also present in the device in the intended application, that is to say in a printing machine. For those skilled in the art, it is necessary to know how a printing ink behaves during printing, where specific contents of these printing inks, for example oils, water, are picked up by the material to be printed, that is to say the paper, for example, as a result of which the rheological property of this printing ink is changed. In the previously usual measuring device, in which the materials present from the intended devices are not used, it is not possible either for these corresponding properties and changes in the flowable medium to be established. Thus, for example in the case of a measuring device which comprises a steel roll and a rubber roll, the effect will never occur such as occurs when a paper surface is used, to which the flowable medium to be tested adheres during the measuring operation.
Finally, it is also particularly significant that the measuring devices which are used to establish the magnitude and the direction of the forces occurring are moved together with the surfaces at which the forces occur. By this means, via the measuring transmitter on to [sic] the respectively associated measuring devices, the forces which, result from the medium to be tested adhering to the surface, and the forces resulting during the separation of the medium from this surface are registered at any point of the adhering area, so that the complete sequence of a separation or splitting operation can be registered with regard to the magnitude of the force and the direction of the force. Since the measuring devices are moved as well, they are able to transfer the sensed values continuously to evaluation devices, without any changes occurring in the medium to be tested as the result of any quiescent pauses, which are necessarily unavoidable in some known measuring devices. As a result of this configuration according to the invention, the measuring devices are, so to speak, always at the point of occurrence and are thus able to sense the entire range of the changes in the rheological properties during the splitting. Of course, during this measuring operation, it is necessary for the surface considered, to which the medium to be tested adheres, to be connected
Larkin Daniel S.
Politzer Jay L.
Reed Smith LLP
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