MXPA99005511A - Doctor blade for wiping away excess printing ink from the surface of a printing form - Google Patents

Abstract

The inventive doctor blade for wiping away excess printing ink from the surface of a printing form (10) has a front section in the form of a blade (3) which interacts with the surface of the printing form (10). In order to avoid the surface of the printing form from being worn away or damaged by the pressure exerted on it by the blade (3), said blade (3) is provided with a coating (5) over the entire length of the doctor blade. Said coating (5) consists of a lubricant or contains particles of lubricant (8). As a result, there is considerably less friction between the blade and the printing form surface and the doctor blade wears less quickly and therefore lasts for longer.

Description

SCRAPER TO CLEAN THE EXCESS INK PRINT OF THE SURFACE IN A PRINTED SHAPE. DESCRIPTION OF THE INVENTION: The invention relates to a scraper blade for cleaning excess ink or printing color from the surface in a printed form according to the main idea of claim 1. A scraper blade of that type, "which can be used for example for the engraved gap known from US-4,184,429. The scraper blade consists of a rear part, • which is installed in a handle or retention, and a front lamella, which with some pressure rests on the surface of the printed form. The lamella is essentially thinner than the rear scraper part (its thickness is about half the thickness of the rear scraper part). The advantage of this scraping blade is that when the front contact area acting together with the surface of the printed form is worn, that contact area remains in its geometry or magnitudes necessary for the quality of the print without variation, or influence, until the entire width of the lamella has been worn or used. The constant geometrical relationships in the contact area and with this the constant scraping pressure makes a consistent regulation of the applied pressure unnecessary and allows a constant print quality. However, also in this scraper blade is REF .: 30450 presents the danger that the surface of the printed form, when the chromatic supreme layer is etched, will be damaged or worn by the scraper blade. In addition, the doctor blade sharpens. The tribology with reference to the scraper blade steel / chromatic layer was always problematic. To eliminate this problem a proposal is known from DE-A 28 17964, which is in the scraper blade itself stuffing a lubricating agent, in one the contact area come to protrude and decreases the friction between the scraper blade and the surface of the printed form. This solution has the disadvantage that the embossing lubricant influences the properties of the doctor blade, for example in its elastic behavior. In addition this solution is difficult to manufacture and expensive. In order to reduce the wear or filament of the scraper blade, it is also known to coat the scraper blade in the area of the lamella with a wear-resistant material. This solution, however, increases the danger of damaging the surface of the printed form. The same problem occurs with narrow scrapers, which consist of a thin sheet fixed between two sheets of support and has a constant thickness throughout the width of the scraper blade. The present invention proposes the task of creating a scraper blade, in which the wear of the surface of the printed form and the sharpening of the scraper blade are considerably reduced without. that influences the properties of the. scraper blade. This task is solved according to the invention by a scraper blade with the features indicated in claim 1. The scraper blade according to the invention has the advantage that the coating that decreases the wear of the surface of the printed form is applicable to the scraper blade hitherto used, which is essentially easier to manufacture technically and of better pressure than the solution mentioned in DE-A-26 17 964. It is especially advantageous that the lubricant particle is installed in a layer, in the one that already exists a particle of a resistant material to the wear that diminishes the wear of the scraper blade. Such coating causes an effective decrease in wear or sharpening of the doctor blade and an increase in the service life of the doctor blade, and yet protects the surface of the printing form against wear. Other advantageous configurations of the doctor blade according to the invention form the subject matter of the dependent claims. The invention will now be described with reference to the drawings DESCRIPTION OF THE DRAWINGS The following is shown in a purely schematic manner: FIG. 1 shows an embodiment on an enlarged scale of a scraper blade in cross section; and Figure 2 a coated part of the doctor blade according to Fig. i in cross section, strongly enlarged. According to Figure 1 there is a scraper blade of a rear scraper blade part 2 and a front section in the form of a one-piece blade 3, which is thinner than the rear part of the scraper blade 2. eg thick Di from the back of the scraper blade 2 measures aprsx. I50μ, that of the foil 3 (D12) approx. 50 μ. The upper side of the foil 3 is indicated in Figure 1 with 3a the lower side with 3b. The width of the wiper blade Bl can, depending on the need, measure for example 8-80 mm, where the width of the lamella B2 is approximately 1 mm. The scraper blade may, depending on the application, have different scraper blade lengths, measured in a plane perpendicular to the plane of the drawing. The scraper blade is installed with its scraper blade rear part 2 in a retainer not shown in the drawing, possibly together with a scraper blade. The foil 3 is pressed under a determined pressure on the surface of a printing form 10, indicated by stripes in a schematic manner in the drawing, for example an engraved hollow cylinder, for cleaning the excess printing color. The direction of rotation of the printing form 10 is indicated by an arrow D. The front contact area of the foil 3 which comes to be placed next to the printing form is indicated by the figure 4. The exact geometry of the blade scraper, its position with respect to the printing form and its advantages are known for example from US 4, 184, 429 and will not be described here. In order to avoid as much as possible the wear of the surface of the printed form 10, which is in contact with the scraper blade 1, for example the chromatic bed of a printing hole cylinder, the foil 3 is provided according to the invention. and also the connecting area with the foil at the rear of the doctor blade 2 over the entire length of the doctor blade with a coating 5, which consists of a lubricating material or at least has particles of lubricant material. By means of the lubricant material existing in the contact area, the friction between the doctor blade 1 and the surface of the printing form 10 is markedly reduced, and thus the wear of the surface of the printing form is reduced. As shown by the example according to Figure 2, the covering 5 can advantageously include a material 7, in which both particles 8 of lubricant material 8 and particles 9 of a wear-resistant material are embedded (particles 8 and 8). 9 are indicated in Figure 2 in a purely schematic manner). Insofar as the finally mentioned particle 9 reduces the wear of the scraper blade 1 or of the lamella 3 and increases its service length, the particles of lubricating material 8 take care of the wear of the surface of the printing form - to weight of the presence of the particle 9 which increases in itself the danger of damage to the surface of the printing form, but which reduces the wear of the doctor blade - is essentially diminished. The coating 5 has a thickness of some microns, the particles of lubricant material 8 as well as the particles 9 of a wear-resistant material are less than one miera. The coating 5 can be applied to the scraping blade already finished in different shapes and manners, for example chemically, galvanically, by spraying, glueing, etc. In the illustrated embodiment, both sides 3 a, 3 b of the front section or of the foil 3 are covered. However, only one side 31, 3 b, preferably according to the invention, could be covered on the side 3 b opposite the direction of rotation D of the shape printed 10 But it would also be possible to cover one side with the coating containing the lubricant material or lubricant particles and the other side with a coating containing the particles of a wear resistant material. The coating according to the invention also finds application in doctor blades, which for example are known from US Pat. No. 5,638,751. In these doctor blades is disposed an intermediate particle (reference figure in that patent 16) between the section front that acts with the surface of the printed form (reference figure 18 according to that patent) and the rear rascadsra blade part (reference figure 14 of that patent 5, 638,751), intermediate part that is thicker than the front section and thinner than the back of the scraper blade. Also in these doctor blades the front section can be coated in the manner and manner that has been described. While in the drawing (and also in US 5,638,751) the rear part of the scraper blade and the front section (or also the intermediate part 16 according to US 5,638,751) are constructed in one piece, the rear part of the scraper blade can be according to the invention, it consists of two or more parts or layers one on top of the other and joined together. Also narrow doctor blades, consisting of two thin fixed support sheets and laminate having the same thickness over the entire width of the doctor blade, can be equipped with the coating according to the invention.

It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects or products to which it refers.

Claims (1)

1. REI NDICACTONES Having described the invention, as above, the content of the following claims is claimed as property: 1. - Scraping blade for cleaning the excess or spill of the dye or ink from the surface of a printing form, characterized by the front section which locks together with the surface of the printing form is provided over the entire length of the doctor blade at least on one side with a coating containing lubricant or particles of lubricant material. 2. - Scraping blade according to claim 1, characterized in that for the reduction of the sharpening wear of the scraper blade the coating contains particles of a wear resistant material. 3. Scraping blade according to claim 2, characterized in that the coating includes a carrier material, where particles of lubricant material and particles of a wear-resistant material are embedded. 4. - Scraper blade according to claim 1, characterized in that one side of the front section is provided with the coating that contains lubricant or particles of lubricant material and the other is provided with a coating that has a wear resistant materi. 5. - Scraping blade according to one of claims 1-4 characterized in that the front section is thinner than the rear one, to be installed in a scraper blade part provided with a retention 6. - Scraping blade according to the claim 5, characterized in that, the rear part of the scraper blade and a lamella forming the front section are constructed in one piece. 7. - Scraping blade according to the claim 6, characterized in that an intermediate part, which is thicker than the foil and thinner than the rear part of the scraper blade, is disposed between the foil and the rear part of the scraper blade. 8. - Scraping blade according to claim 6 or 7, characterized in that the rear part of the scraper blade consists of two or more parts placed one on top of the other and joined together. . - Scraping blade according to the claim 6 or 7, characterized in that the coating extends outside the foil, in the border area of the scraper blade with that. 10. Scraping blade according to one of claims 1-3, characterized in that the coating is applied only on one side, preferably on the side of the front section that faces the direction of rotation of the printing form.