[0001] Blades are often used to control the thickness of usually thin coatings applied to paper, rollers, plates and other substrates. Such blades are often referred to as "doctor" blades or "metering" blades. A liquid, powder or other blade-able material is applied to the substrate and bladed to the desired thickness. For example, a coating material may be dispensed on to the substrate in front of a doctor blade as the blade moves along the substrate or as the substrate moves past the blade. The material is bladed to the desire thickness according to the gap between the blade and the substrate.

DRAWINGS

[0002] Figs. 1 -3 illustrate one example of a blade to blade a coating material simultaneously to different thicknesses laterally across a substrate.

[0003] Figs. 4 and 5-6 illustrate other examples of a blade to blade a coating material simultaneously to different thicknesses laterally across a substrate.

[0004] Figs. 7 and 8 illustrate one example of an applicator for dispensing and blading a coating material on to a substrate.

[0005] Fig. 9 is a section showing the applicator of Figs. 7 and 8 dispensing and blading a coating material on to a substrate.

[0006] Fig. 10 is a detail of the material dispensing control cylinder in the applicator shown in Figs. 7 and 8.

[0007] Fig. 1 1 illustrates another example of an applicator for dispensing and blading a coating material on to a substrate.

[0008] The same part numbers designate the same or similar parts throughout the figures. The figures are not necessarily to scale.

DESCRIPTION

[0009] A new doctor blade has been developed to blade a substrate coating material simultaneously to different thicknesses laterally across the substrate. Examples of the new blade may be implemented in a coating material applicator that can dispense different coating materials individually across the substrate. Thus, the new applicator can function simultaneously both to dispense different coating materials laterally across the substrate and to blade those materials to different thicknesses. The coating thickness may be varied in a stepped configuration across the substrate for discrete changes in thickness or along a linear gradient for a continuum of changes in thickness (or a combination of both). Applying coatings in different thicknesses ("coat weights") in a single pass not only helps improve coating speed and versatility, it also simplifies trial and error processes used to determine optimum coat weights. Now multiple coat weights can be applied and tested simultaneously rather than one at a time.

[0010] As used in this document, the verb "blade" means to work a material with a blade, for example by spreading, reducing, or leveling the material; and a "datum" means something used as a basis for positioning, measuring or calculating.

[0011] Figs. 1 -3 illustrate one example of a blade to blade a substrate coating material simultaneously to different thicknesses laterally across the substrate. Fig. 2 is a section along the line 2-2 in Fig. 1 . Fig. 3 is a section along the line 3-3 in Fig. 2. Referring to Figs. 1 -3, a blade assembly 10 includes a holder 12 holding a blade 14 over a platen 16. A substrate 18 is supported on platen 16. Blade 14 and substrate 18 move with respect to one another. In the example shown in Figs. 1 -3, substrate 18 moves past a stationary blade 14, as indicated by arrows 20 in Figs. 1 and 3. Blade 14 includes parts 14A, 14B, 14C each spaced apart from platen 16 a distance 22A, 22B, 22C laterally across platen 16, as shown in Fig. 2. Accordingly, the gap between blade 14 and a substrate 18 on platen 16 varies laterally across the substrate, as indicted by gaps 24A, 24B, 24C between substrate 18 and blade parts 14A, 14B, 14C in Fig. 2. A coating material 26 dispensed on to substrate 18 is biaded to thicknesses 26A, 26B, 26C at blade parts 14A, 14B, 14C according to gaps 24A, 24B, 24C.

[0012] While three blade parts are shown, more or fewer blade parts are possible, in one example, each blade part is part of a single blade, as shown in Fig. 2. In another example, some or ail of the blade parts are themselves individual blades to blade the coating material to a respective thickness, in one example, the size of the gaps between blade 14 and platen 16 (and thus substrate 18) may be adjusted together by moving a single blade 14 in holder 12 toward and away from platen 16 to vary all of the gaps uniformly in one dimension (height in Fig. 2) across platen 16. In another example, the size of the gaps may be adjusted by replacing one blade 14 with another blade 14 having a different gap profile, in which case the gaps may be varied together or individually and in two dimensions - height and width in Fig. 2.

[0013] Although blade 14 is held over a flat platen 16 supporting a web or sheet substrate 18 in the example shown in Figs. 1 -3, other blading

configurations are possible. For another example, the blade could be positioned next to a rotating roller platen that carries a thin film of coating material past the blade to meter the thickness of the film. In this other configuration, the substrate may be a non-removable part integral to the roller platen or a discrete part applied to and removed from the platen.

[0014] In the example shown in Fig. 2, blade 14 is configured to blade coating material 28 to different thicknesses in steps laterally across substrate 18. In another example, shown in Fig. 4, blade 14 is configured to blade coating materia! 28 to different thicknesses along a linear gradient laterally across substrate 18.

[0015] Coating material 28 may be any blade-able material including, for example, liquids and powders. Substrate 18 may be any substrate suitable for receiving the blade-able material.

[0016] Figs. 5 and 8 illustrate another example of a blade assembly 1 (3 to blade a coating material simultaneously to different thicknesses laterally across a substrate, in this example, and referring to Figs. 5 and 6, blade assembly 10 includes replaceable subassemblies 28A, 28B, 28C each with a holder 12A. 12B, 12C holding a respective blade 14A, 14B, 14C. Holders 12A, 12B, 12C are mounted to a rod 30 side-by-side and secured, for example, with end caps 32 held with screws or another suitable fastener. Each blade 14A. 14B, 14C is spaced apart from datum surfaces 34 on the respective holder a distance 22A, 22B, 22C. Thus, the gap between blades 14A, 14B, 14C and a substrate referenced to datum surfaces 34 will vary laterally across the substrate according to distances 22A, 22B, 22C.

[0017] in this example, each blade 14A, 14B, 14C contacts the coating material along a blunt edge 38. In other examples, the blades may have a sharp edge. The holders may be mounted in a fixed orientation with respect to connection rod 30, if desired, for example using keys 38 on mounting rod 30 and keyways 40 on holders 12A, 12B, 12C,

[0018] The use of replaceable blade subassemblies such as those shown in Figs. 5 and 6 facilitates changing the blades for different gap sizes. More or fewer subassemblies 28A, 28B, 26C may be used to fit different width substrates or to blade more or less of a substrate. Other subassembly configurations and combinations are possible. For example, the width of one blade subassembly may be different from the width of another blade

subassembly. For another example, the sequence of gap variations may differ from the uniform progression shown in Figs. 5 and 6 (and in Fig. 2 for blade parts 14A-14C).

[0019] Figs. 7 and 8 illustrate one example of an applicator 42 for dispensing and blading coating material on to a substrate. Fig. 9 is a section showing applicator 42 applying coating material 26 on to a substrate 18. Referring to Figs. 7-9, applicator 42 includes two reservoirs 44A, 44B for holding coating material 26. Material 26 is omitted from Figs. 7 and 8 for clarity. Reservoirs 44A, 44B may hold the same coating material or different coating materials. Fig. 9 shows a liquid coating material 26 in reservoir 44A. Coating material is dispensed from each reservoir 44A, 44B on to a substrate 18 through openings 46A, 46B at the bottom of each reservoir.

[0020] The flow of material from each reservoir 44A, 44B on to substrate 18 is controlled by valves 48A, 48B. In the example shown, each flow control valve 48A, 48B is configured as a manually operated cylinder 50A, SOB with slots 51 A, 51 B at the bottom of each reservoir 44A, 44B. Cylinders 50A and SOB are shown in detail in Fig. 10. Each cylinder 50A, 50B may be rotated between open and closed positions to dispense coating material from one or the other or both reservoirs 44A, 44B. Although two separate cylinders are shown, more or fewer cylinders are possible. For example, it may be desirable in some implementations to integrate the control valve functions into a single cylinder.

[0021] Referring specifically to Fig. 9, with control valve 48A in the open position, liquid coating material 26 flows through slot 51 A in cylinder 50A to opening 46A and on to substrate 18 upstream from blade 14A. In this example, applicator 42 and thus blade 14A move over substrate 18, as indicated by arrows 52, to blade coating material 26 to a thickness 26A Coating material thickness 26A is determined by gap 24A between blade 14A and substrate 18. The liquid coating material 26 may be contained in a chamber 54 at the forward part of applicator 42 just upstream from blade 14A to help form a more uniform coating on substrate 18.

[0022] Although only one side of applicator 42 is shown in Fig. 9, the blading operation is the same for both sides of the applicator. The gap 24A, 24C between each blade 14A, 14B and substrate 18 may be set to achieve the desired coating thicknesses. While the position of each blade 14A, 14B is fixed in the example of applicator 42 shown in Figs. 7-9, adjustable gap blades are also possible. For example, and referring to Fig. 1 1 , applicator 42 may include lead screws 56A, 56B or another suitable mechanism to adjust the gap for each blade 14A, 14B. Each lead screw 56A, 56B is operativeiy connected between a stationary frame 58 and a movable internal housing 60A, 60B that hold blades 14A, 148, reservoirs 44A, 44B, and control valves 48A, 48B. (Reservoirs 44A, 44B and valves 48A, 48B are not visible in Fig. 1 1 .) Turning each lead screw 56A, 56B raises and lowers the corresponding housing 60A, 60B and, thus, blade 14A, 14B affixed to housing 60A, 60B.

[0023] The examples shown in the figures and described above illustrate but do not limit the claimed subject matter. Other examples are possible.

Therefore, the foregoing description should not be construed to limit the scope of the following claims.