Squeegee

Abstract

A doctor blade (100), in particular for doctoring off printing ink from an impression cylinder, comprises a doctor blade body (110) with a working edge (130) and a first doctor blade side (122) which faces the impression cylinder, in particular, during operation, and a second doctor blade side (121) which faces away from the impression cylinder, in particular, during operation. The doctor blade body (110) is provided with a coating (150) which comprises a polymer, wherein the coating (150) comprises particles (160) at least in one part region. The particles (160) are configured as hard material particles (160), and a mass proportion of the hard material particles (160) in the coating (150) on the first doctor blade side (122) is higher than a mass proportion of the hard material particles (160) in the coating (150) on the second doctor blade side (121).

Claims

1. A squeegee comprising a squeegee body having a working edge and a first squeegee side and a second squeegee side, where the squeegee body has been provided with a coating comprising a polymer, where the coating comprises particles at least in one subregion, whereby the particles take the form of hard material particles and in that a proportion by mass of the hard material particles in the coating on the first squeegee side is higher than a proportion by mass of the hard material particles in the coating on the second squeegee side, whereby the polymer in the coating forms a continuous phase and/or a dispersion medium for the hard material particles in the coating and the hard material particles are dispersed and/or embedded in the continuous phase of the polymer.

2. The squeegee as claimed in claim 1, wherein the coating of the first squeegee side comprises hard material particles and the coating of the second squeegee side is essentially free of hard material particles.

3. The squeegee as claimed in claim 2, wherein the coating of the second squeegee side does not comprise any particles.

4. The squeegee as claimed in claim 1, wherein the hard material particles comprise at least one of the following substances: a) metal oxides, especially aluminum oxide and/or chromium oxide; b) diamond; c) silicon carbide; d) metal carbide; e) metal nitride; f) metal carbonitride; g) boron carbide; h) cubic boron nitride; i) tungsten carbide.

5. The squeegee as claimed in claim 1, wherein the squeegee body has been formed from a metal or a metal alloy.

6. The squeegee as claimed in claim 5, wherein the squeegee body consists of steel.

7. The squeegee as claimed in claim 1, wherein the squeegee body has been formed from a plastic.

8. A process for producing a squeegee, where, in a squeegee body with a working edge, a first squeegee side and a second squeegee side is coated with a coating comprising a polymer and comprising particles at least in one subregion, wherein the particles take the form of hard material particles and in that a proportion by mass of the hard material particles in the coating on the first squeegee side is higher than a proportion by mass of the hard material particles in the coating on the second squeegee side.

9. The process as claimed in claim 8, wherein the squeegee body is heated prior to the coating.

10. The process as claimed in claim 8, wherein the squeegee body is roughened prior to the coating.

11. The process as claimed in claim 8, wherein the squeegee body is mechanically or electrolytically degreased prior to the coating.

12. The process as claimed in claim 10, wherein the squeegee is connected as the anode for electrolytic degreasing in order to remove grease from the squeegee body by means of cations.

13. The process as claimed in claim 8, wherein the coating of the squeegee body with the coating comprising a polymer is preceded by application of an adhesion coating.

14. The process as claimed in claim 13, wherein the application of the adhesion coating is followed and the coating of the squeegee body with the coating comprising a polymer is preceded by an intermediate drying step.

15. The process as claimed in claim 8, wherein the coating of the squeegee body is followed by a drying step.

16. The process as claimed in claim 15, where the drying step is followed by a hardening step.

17. The process as claimed in claim 16, wherein the hardening step is effected at a temperature of 150 C. to 350 C.

18. The squeegee as claimed in claim 1, wherein the coating comprising the polymer comprises more than 50% by weight of polymers.

19. The squeegee as claimed in claim 1, wherein the polymer is a thermoset.

20. The squeegee as claimed in claim 1, wherein the coating comprising the polymer includes a total of less than 5% by weight of nickel.

21. The squeegee as claimed in claim 1, wherein the coating comprising the polymer is free of nickel.

22. The squeegee as claimed in claim 1, wherein the coating comprising the polymer less than 5% by weight particulate polytetrafluoroethylene (PTFE).

23. The squeegee as claimed in claim 1, wherein the coating comprising the polymer comprises more than 50% by weight of polymers, and the polymer is a thermoset, and the coating comprising the polymer is free of nickel and free of particulate polytetrafluoroethylene (PTFE).

24. The squeegee as claimed in claim 19, wherein the thermoset comprises epoxy resins, phenolic resins, phenol-formaldehyde resins, melamine-formaldehyde resins, saturated and unsaturated polyester resins, or mixtures thereof.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The drawings used to elucidate the working example show:

(2) FIG. 1 a cross section through a first lamellar squeegee of the invention, wherein a working edge of the lamellar squeegee has been coated with a polymer-based coating and hard material particles dispersed therein;

(3) FIG. 2 a cross section through a second lamellar squeegee of the invention, wherein a working edge of the lamellar squeegee has been coated with a polymer-based coating and hard material particles dispersed therein;

(4) FIG. 3 a cross section through a third lamellar squeegee of the invention, which has been fully coated with a polymer-based coating and hard material particles dispersed therein;

(5) FIG. 4 a schematic diagram of a method of the invention for production of a squeegee.

(6) In principle, identical parts in the figures are given identical reference numerals.

WAYS OF EXECUTING THE INVENTION

(7) FIG. 1 shows an inventive lamellar squeegee 100 in contact with a printing roller 170 in cross section. The lamellar squeegee 100 comprises a main body 110 made of steel, which, on the left-hand side in FIG. 1, has a rear region 120 having an essentially rectangular cross section. The rear region 120 here has been provided as a securing region in order to hold the lamellar squeegee, for example, in a corresponding receiving apparatus of a printing machine. A squeegee thickness, measured from the top side 121 to the bottom side 122 of the rear region, is about 0.2 mm. A length of the main body 110 or of the lamellar squeegee 100 measured perpendicularly to the plane of the sheet is, for example, 1000 mm. The printing roller 170 may have a clockwise or counterclockwise direction of rotation 171. In the case of applications in flexographic printing, both directions of rotation are possible. In gravure printing, the printing roller in the present arrangement is rotated clockwise.

(8) On the right-hand side in FIG. 1, the main body 110 is tapered in stages from the top side 121 of the rear region 120 to form a working edge 130. A top side 131 of the working edge 130 lies in a plane beneath the plane of the top side 121 of the rear region 120, but is formed so as to be essentially parallel or plane-parallel to the top side 121 of the rear region 120. Between the rear region 120 and the working edge 130 there is a concave-shaped transition region 125. The bottom side 122 of the rear region 120 and the bottom side 132 of the working edge 130 are in a common plane, which is plane-parallel to the top side 121 of the rear region 120 and plane-parallel to the top side 131 of the working edge 130. A width of the main body 110, measured from the end of the rear region as far as the end face 140 of the working edge 130, measures 40 mm for example. A thickness of the working region 130, measured from the top side 131 to the bottom side 132 of the working region, is, for example, 0.060-0.150 mm, which corresponds to about half the squeegee thickness in the rear region 120. A width of the working region 130 measured at the top side 131 of the working region 130 from the end face 140 as far as the transition region 125 is, for example, 0.8-5 mm.

(9) A free end face 140 of the free end of the working edge 130 runs from the top side 131 of the working edge 130 obliquely downward to the bottom side 132 of the working edge 130. The end face 140, with respect to the top side 131 of the working edge 130 and with respect to the bottom side 132 of the working edge 130, has an angle of about 45 and 135 respectively. An upper transition region between the top side 131 and the end face 140 of the working edge 130 is rounded. Likewise rounded is a lower transition region between the end face 140 and the bottom side 132 of the working edge 130.

(10) The working edge 130 of the lamellar squeegee 100 is additionally surrounded by a coating 150. The coating 150 completely covers the top side 131 of the working edge 130, the transition region 125 and a subregion of the top side 121 of the rear region 120 of the main body 110 that adjoins said transition region 125. The coating 150 likewise covers the end face 140, the bottom side 132 of the working edge 130, and a subregion of the bottom side 122 of the rear region 120 of the main body 110 that adjoins the bottom side of the working edge 130.

(11) The coating 150 is a polymer-based coating; for example, the coating comprises epoxy resin, where the epoxy resin content in the ready-to-use coating is, for example, about 70% or 80% by weight, according to the squeegee side (see below). Dispersed therein are hard material particles 160, for example of silicon carbide (SiC). An average particle size of the hard material particles 160 is about 0.8 m. The layer thickness of the first coating 150 in the region of the working edge 130 measures 15 m for example. In the region of the top side 121 and the bottom side 122 of the rear region 120, the layer thickness of the first coating 150 decreases continuously, such that the first coating 150 tapers in a wedge-like manner in a direction away from the working edge 130.

(12) The proportion by mass of hard material particles 160 in the coating of the first side of the squeegee 100 facing the printing roller is higher than in the coating of the second side of the squeegee facing away from the printing roller. The first side comprises the end face 140 and the bottom side 132 of the working edge 130. The second side comprises the top side 131 of the working edge 130. The proportion by mass of hard material particles 160 in the coating of the first side is, for example, 20% by weight, and the proportion by mass of epoxy resin in the coating of the same side is, for example, 70% by weight. The proportion by mass of hard material particles 160 in the coating of the second side is, for example, 10% by weight, and the proportion by mass of epoxy resin in the coating of the same side is, for example, 80% by weight. Thus, the second side of the squeegee 100 has a lower content of hard material particles 160 than the first side of the squeegee 100.

(13) The first side, i.e. the side facing the printing roller 170, thus includes the contact region between squeegee 100 and printing roller 170, namely the end face 140. Moreover, the first side also includes that surface 122 of the squeegee which forms an angle of less than 90 with a tangent in the contact region of the squeegee. The same interpretation also applies to FIGS. 2 and 3 which follow.

(14) FIG. 2 shows a second inventive lamellar squeegee 200 in cross section. The second lamellar squeegee 200 has a main body 210 with a rear region 220 and a working edge region 230, and is essentially of the same design as the first lamellar squeegee 100 from FIG. 1. In the case of the second lamellar squeegee 200, the top side 231 of the working edge 230, the transition region 225, and a subregion of the top side 221 of the rear region 220 of the main body 210 that adjoins said transition region 225, and also the end face 240, the bottom side 232 of the working edge 230, and a subregion of the bottom side 222 of the rear region 220 of the main body 210 that adjoins the bottom side 232 of the working edge 230 are likewise coated with a coating 250.

(15) The coating 250 again consists of a polymer-based coating, for example phenol-formaldehyde resin. The coating of the first side of the squeegee 200 facing the printing roller comprises hard material particles 260, while the coating of the second side of the squeegee facing away from the printing roller comprises no or essentially no hard material particles. The first side here again includes the end face 240 and the bottom side 232 of the working edge 230. The second side comprises the top side 231 of the working edge 230. The hard material particles are cubic B.sub.4O for example.

(16) On the first side of the squeegee 200, the ready-to-use coating has a content of phenol-formaldehyde resin of, for example, 80% by weight. The coating of the first side further includes a content of cubic B.sub.4O of 15% by weight. The second side of the squeegee 200 has a content of phenol-formaldehyde resin of, for example, 95% by weight. The second side of the squeegee 200 is essentially free of particles.

(17) An average particle size of the hard material particles 260 is about 0.6 m. The layer thickness of the first coating 250 in the region of the working edge 230 measures 17 m for example.

(18) FIG. 3 shows a third inventive lamellar squeegee 300 in cross section. The third squeegee 300 has a main body 310 coated in the region of the working edge 330 with a coating 350 in the same way as the first squeegee from FIG. 1. Correspondingly, the top side 331 of the working edge 330, the transition region 325, and a subregion of the top side 321 of the rear region 320 of the main body 310 that adjoins said transition region 325, and also the end face 340, the bottom side 332 of the working edge 330 and a subregion of the bottom side 322 of the rear region 320 of the main body 310 that adjoins the bottom side 332 of the working edge 330 have been covered with the coating 350.

(19) In the case of the third lamellar squeegee, there is a coating 350 which completely surrounds the lamellar squeegee 300. In other words, the coating 350 completely covers both the top side 321 and the bottom side 322 of the rear region 320 of the main body 310.

(20) The coating 350 in turn consists of a polymer-based coating, for example polyamide. The coating of the first side of the squeegee 300 facing the printing roller comprises hard material particles 360, while the coating of the second side of the squeegee facing away from the printing roller comprises no or essentially no hard material particles. The first side here again includes the end face 340 and the bottom side 332 of the working edge 330. The second side comprises the top side 331 of the working edge 330. The hard material particles are tungsten particles for example.

(21) On the first side of the squeegee 300, the ready-to-use coating has a content of polyamide of 85% by weight for example. The coating of the first side further comprises a content of tungsten particles of 8% by weight. The second side of the squeegee 300 has a content of phenol-formaldehyde resin of 93% by weight for example. The second side of the squeegee 200 is in turn essentially free of particles.

(22) An average particle size of the hard material particles 360 is about 0.3 m. The layer thickness of the first coating 350 in the region of the working edge 330 measures 12 m for example.

(23) The above-described lamellar squeegees shown in FIGS. 1-3 should be regarded merely as illustrative examples for a multitude of implementable embodiments.

(24) FIG. 4 illustrates a process 400 for production of a lamellar squeegee as depicted, for example, in FIG. 1. In this process, in a first step 401, the squeegee is electrolytically degreased. This is done by connecting the squeegee 100 as the anode for electrolytic degreasing, in order to remove grease from the squeegee body 110. The anodic electrolytic degreasing avoids hydrogen embrittlement. Subsequently, the squeegee body 110 is heated. In a second step 402, coating with the polymer-based coating material is effected, in which the hard material particles and any further particles have been dispersed and/or other auxiliaries have been introduced. In the last step 403, a drying and hardening step is effected.

(25) However, the above-described embodiments and the production process should be regarded merely as illustrative examples which can be modified as desired in the context of the invention.

(26) For instance, the main bodies 110, 210, 310 of the squeegees from FIGS. 1-3 may also have been manufactured from a different material, for example stainless steel or a carbon steel. 3 In principle, the main bodies of the squeegees from FIGS. 1-3 may alternatively consist of a nonmetallic material, for example plastics. This may be advantageous particularly for applications in flexographic printing.

(27) It is also possible, rather than the main bodies shown in FIGS. 1-3, to use main bodies having a different shape in each case. More particularly, the main bodies may have a wedge-shaped working edge or a non-tapering cross section with a rounded working edge. The free end faces 140, 240, 3403 of the working edges 130, 230, 330 may, for example, also have a fully rounded shape.

(28) In addition, the inventive squeegees from FIGS. 1-3 may also have different dimensions. For example, the thicknesses of the working regions 130, 230, 330, measured from the respective top sides 131, 231, 331 to the respective bottom sides 132, 232, 332, may vary within a range of, for example, 0.040-0.200 mm.

(29) The coatings of the squeegees from FIGS. 1-3 may likewise contain further coating components and/or additional substances, for example metal atoms, nonmetal atoms, inorganic compounds and/or organic compounds. More particularly, it is possible to provide different lubricants or substances which affect the hardness of the coating. The additional substances may also be particulate.

(30) All the squeegees shown in FIGS. 1-3 may be coated, for example, with one or more further coatings. The further coatings may be present in the region of the working edges and/or the rear regions and, for example, improve the wear resistance of the working edges and/or protect the rear region from influences by aggressive chemicals. Any further coating is preferably likewise polymer-based. In variants, it is alternatively possible to use other coating types.

(31) In summary, it can be stated that novel squeegees have been created which feature good wear resistance and enable homogeneous and streak-free stripping-off of printing ink over their entire lifetime and are additionally inexpensive to produce. At the same time, the squeegees of the invention can be implemented in a wide variety of different embodiments, and so they can be adapted in a controlled manner to specific end uses.