Printing – Special article machines
Reexamination Certificate
1999-06-14
2001-07-24
Hilten, John S. (Department: 2854)
Printing
Special article machines
C101S022000
Reexamination Certificate
active
06263790
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a machine for the security printing of security paper, especially banknotes, comprising a paper sheet feed device, a device for transporting the paper and a unit for applying security images supported by at least one ribbon which is brought into contact with the paper such that these images are applied at determined points on the paper corresponding to the printing on the security paper, the application unit comprising an applicator cylinder fitted with pads arranged on the periphery of the applicator cylinder in register with said determined points, cooperating with an impression cylinder, between which cylinders the paper passes, said ribbon being mounted between two reels—for paying out the ribbon, and for winding up the ribbon—the ribbon passing parallel to the path of the paper.
It is already known practice to create security zones on security paper and in particular on banknotes, by applying images in the form of a film so as to make these papers difficult to falsify, particularly to reproduce by the use of photocopiers, the reproduction quality of which is ever increasing. These images are often optically variable images comprising either a kinegram or a hologram which have the property of changing appearance depending on the angle from which they are viewed. These images may be applied either hot or cold. In the European patent application No 0 625 466 A1, the content of which is incorporated by reference, by the same applicant, there is described an apparatus that allows such images to be applied cold using a two-part adhesive, the first part of the adhesive being applied at the desired point on the notes which have been partially or completely printed on a sheet and it is dried by passing the sheet past a catalyst. Thereafter, using an applicator cylinder and a press cylinder, the images, which have the second part of the adhesive, are applied to the previously chosen points, simply by the action of pressure.
In the abovementioned machine, the ribbon travels between two cassettes along a generatrix of the applicator cylinder. The applicator cylinder is fitted with a number of pairs of these cassettes to allow several images to be applied to several points of a sheet in a single pass.
There is also another type of apparatus which comprises a unit for applying an optically variable image borne by a ribbon of which there is one for each impression column and which is paid out between a paying-out reel and a winding-up reel. The path between the two reels comprises, apart from the guiding and tensioning rolls and rollers, a cylinder which has circumferential grooves, interrupted by bridges, said ribbon passing along said grooves. The sheets to be processed pass between said cylinder and press cylinders and image transfer occurs each time a bridge runs over the press cylinder. The applicator cylinder is heated to activate the adhesive borne by the image. In order that the adhesive should be heated sufficiently to obtain the desired effect, contact between the bridge of the applicator cylinder and the images must last for a certain length of time, which means that the dimensions of the applicator cylinder and those of the press rolls must always be tailored to the size of sheet and of the security papers partially or completely printed on said sheets. The ribbon carrying the images passes continuously and in synchronism with the sheets to which the images are to be applied. This apparatus produced by the applicant is satisfactory.
However, the obligation to maintain contact between the applicator cylinder and the image to be transferred for a period of time means that each time the paper format is changed, fundamental modifications have to be made to the applicator cylinder and to the press cylinder. Furthermore, the press cylinder used to keep the sheets in contact with the applicator cylinder prior to the transferring of the image, crushes the sheet along the entire length at the two ends of the sheet in the direction of travel of the paper. Specifically, for the sheet to remain in contact with the applicator cylinder, two small rollers press the sheet against the applicator cylinder near to the ends of the sheet before the sheet receives the images so that the bridge of the applicator cylinder is in close contact with the ribbon and allows the adhesive on the images to be applied to be brought up to the desired temperature, and afterwards, the sheet passes over a press cylinder which is the same width as the sheet, this allowing the images to be applied to the paper.
Thus, the pressure exerted by the two rollers which, from the outset, ensures that the sheet is pressed firmly against the applicator cylinder, leaves undesirable marks on the sheet.
The object of the present invention is to propose a machine similar to the one described earlier, but which does not have the aforementioned disadvantages.
SUMMARY OF THE INVENTION
The machine according to the present invention is one which is fitted with a device for preheating the ribbon upstream of the applicator cylinder so as to preheat the images which will be applied to the sheet of paper by simple contact of said pads with the images against the press cylinder.
The advantage of this machine lies in the fact that the preheating of the images that are to be applied to the sheet makes it possible to avoid the obligation of using press rollers pressing against the two longitudinal edges of the sheet to ensure good contact with the applicator cylinder and obtain the desired heating. Furthermore, the fact that simple contact between the pads on the applicator cylinder and the impression cylinder is enough to transfer the images from the ribbon onto the paper makes it possible not to have to modify the machine when the formats of the notes or of the sheets change, it simply being necessary for the pads to be moved both in the axial and in the peripheral directions, to suit the new dimensions of the sheet and notes to be printed, the ribbon with the images to be applied being prepared with the spacings that correspond to the new dimensions.
According to one alternative embodiment, the machine is one wherein, with a view to economizing on ribbon, the machine is fitted with means which allow the ribbon to be made to advance in synchronism with the sheet passing between the applicator cylinder and the press cylinder, to slow down the advance of the ribbon and to make it back up over a distance equal to approximately the length of a sheet, when the sheet has left the applicator cylinder while waiting for the arrival of the next sheet and to bring the ribbon into register with the next sheet.
Thus, by means of this device, it is possible to economize on the length of ribbon which in other apparatuses continues to turn even between the end of one sheet and the arrival of the next, which sheets are always separated by at least a few centimeters. These means take advantage of this space between the end of one sheet and the start of the next to slow down the advance of the ribbon and make it back up and bring it into register with the next sheet.
The means used to obtain these results are a pair of advance rollers arranged downstream of the applicator cylinder causing the ribbon to advance, a pair of backing-up rollers arranged upstream of the preheating device making it possible to slow down the ribbon and make it back up, a device for reading register marks already printed on the ribbon and controlling the aforementioned rollers, and devices for assisting the rollers at the time of abrupt changes in speed, these devices being arranged upstream of the backing-up rollers, and downstream of the advance rollers, respectively.
Said devices for assisting the rollers are advantageously two negative pressure boxes into which the ribbon is sucked, this making it possible to create a certain amount of slack in the travel of the ribbon which slack can thus be used to damp out abrupt changes in speed, as will be described later.
According to another preferred alternative embodiment of
Eitel Johann Emil
Nagler Kurt Georg
Schaede Johannes Georg
Wyssmann Hans
Bugnion S.A.
De La Rue Giori S.A.
Hilten John S.
Moetteli John
Nguyen Anthony H.
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