Multi-edge doctor blade, method for manufacturing a doctor blade, and method for manufacturing creped paper

Abstract

The present invention relates to a doctor blade (7, 8) comprising a plurality of working edges for the production of paper. The invention further relates to a method for manufacturing such a doctor blade having a plurality of working edges, as well as a method for producing paper using such doctor blades.

Description

Multi-edged scraper technical field

[0001] The present invention relates to a doctor blade for paper production, in particular a doctor blade having several working edges. The invention further relates to a method for manufacturing such a doctor blade. The invention also covers a method for manufacturing paper. State of the art

[0002] The production of crepe paper, widely used globally, involves a series of steps to create a final product with desirable characteristics such as softness, thickness, absorbency, strength, and elasticity. A crucial step in crepe paper manufacturing is the creping process, which gives the paper its distinctive texture. Creping occurs during the final stage of production on a rotating drying cylinder, commonly known as a "Yankee cylinder," where the paper is scraped and detached from the surface using a doctor blade, commonly called a "creping blade," resulting in a wrinkled, or "creped," structure. After creping, another doctor blade, commonly called a "cleaning blade," is often used to clean and level the surface of the drying cylinder, ensuring the uniformity and quality of the crepe paper produced.Traditional scrapers are made entirely or almost entirely of steel, meaning their chemical composition exceeds 95% steel by weight. Factors such as the scraper's angle of application, scraper pressure, temperature control, and chemical management play a vital role in achieving the desired quality of creped paper. The creping process fundamentally alters the paper's properties and characteristics, making it suitable for a variety of end-use applications, such as tissues, wipes, toilet paper, and paper towels for household or industrial use. AC2W-1-PCT

[0003] US patent application 2022 / 0379577 A1 describes the creping mechanism on a drying cylinder, by means of a creping blade whose field comprises several distinct surfaces having different coefficients of friction.

[0004] In the crepe paper manufacturing process, the scrapers, and in particular the creping blade, are crucial components. During the critical creping stage on the drying cylinder, the action of the scraper imparts the paper's properties and characteristics, or at least plays a significant role in them. Traditional scrapers typically have only one working edge, leading to frequent replacements, increased operating costs, and considerable waste. Given the high mechanical and thermal stresses, and the required quality specifications, the use of a traditional creping blade, even one made of hardened steel (for example, through quenching), is limited to approximately 3 to 6 hours before it needs replacing. To extend the product's lifespan, the scraper can be reinforced with a durable material on the wear-prone area, namely its working edge.This specific material is generally applied to the longitudinal edge of the doctor blade, typically on the part of the doctor blade, known as the "active zone", impacted by the paper and / or in contact with the rotating drying cylinder.

[0005] Patents GB 2,128,551 B and US 7,244,340 B2, and patent applications WO 2006 / 134208 A1, WO 2007 / 079731 A2, and WO 2021 / 121687 A1 are typical examples describing how a wear-resistant material can be applied to directly protect and extend the service life of a doctor blade used in the crepe paper manufacturing process. While these concepts are widely used in doctor blade manufacturing, these additional surface treatments are relatively complex and expensive. The use of more advanced materials combined with high-end surface treatment technologies leads to a rapid increase in the manufacturing costs of these solutions. This technological trend represents a significant drawback and necessitates finding more practical alternatives. AC2W-1-PCT

[0006] In addition to the solutions described above, specific designs and conceptions of the active area of ​​the scraper make it possible to stabilize the creping process for a longer period, thus indirectly extending the life of the scraper.

[0007] EP patent 0 906 472 B1 and US patent application 2021 / 0053311 A1 exemplify the operating principles of some of these doctor blade designs. While there are advantages to using these types of doctor blades in certain crepe paper manufacturing processes where quality requirements are specified within a narrow range, the manufacturing complexity of these designs limits their production and market development. Consequently, the multiple constraints and manufacturing costs of these solutions are further amplified, increasing interest in more practical alternatives.

[0008] In an economic environment where the cost of raw materials and transportation is rising and environmental concerns are significant, there is a need for new solutions that are simpler and less expensive to manufacture, and more sustainable and efficient in industrial applications. Paper manufacturers, aware of these economic and environmental challenges, are firmly committed to this approach, demanding higher-performing alternative options. Brief summary of the invention

[0009] One aim of the present invention is to provide a cheap and longer lasting scraper than those currently in use.

[0010] Another objective of the present invention is to provide a more versatile squeegee usable in the production of paper, in particular crepe paper. AC2W-1-PCT

[0011] Another objective of the present invention is to propose a method for manufacturing a more durable and / or more efficient squeegee than those currently used in the production of paper, such as crepe paper.

[0012] Another objective of the present invention is to provide a more efficient method for manufacturing paper, particularly crepe paper. The proposed method aims specifically to reduce the maintenance and / or replacement of wear parts such as doctor blades.

[0013] According to the invention, these goals are achieved in particular by means of the scrapers which are the subject of the main claim and the method which is the subject of claim 9, detailed in the claims which depend on it.

[0014] This solution offers a significant advantage over previous methods by limiting production interruptions, particularly those related to replacing doctor blades. Furthermore, the proposed solution minimizes paper production costs. Brief description of the figures

[0015] Examples of implementation of the invention are shown in the description illustrated by the following figures: • Figure 1: Schematic perspective view of the rotary drying cylinder on a crepe paper manufacturing machine, where the scrapers operate, • Figure 2: Schematic perspective view of a scraper, providing a basic geometric description and dimensional specifications, • Figure 3: Schematic side view of a scraper, showing the main variables involved in adjusting the scraper during its operation in the creping position, AC2W-1-PCT Figures 4A to 4H: Schematic side views of scrapers according to the present invention, manufactured from a single base material, • Figures 5A to 5D: Schematic side views of scrapers according to the present invention, comprising at least one additional surface treatment, • Figure 5E: Schematic perspective view of a scraper according to an embodiment of the present invention. • Figure 6: Flowchart of a method for manufacturing a scraper according to an embodiment of the present invention, • Figures 7A to 7F: Schematic side views of scrapers according to different embodiments of the present invention, including the corresponding production tools, The accompanying drawings are provided for illustrative purposes only and are not intended to limit the scope of the various embodiments described relating to the present invention. For simplicity and clarity, the elements shown in the drawings may not be to scale. Some dimensions may be enlarged relative to others to improve understanding. Example(s) of an embodiment of the invention

[0016] For the purposes of this description, the term "scraper" refers to a rigid blade designed to scrape the surface of a rotating cylinder or material wrapped around such a cylinder. Terms such as "blade," "scraper," and "scraper" may therefore be considered equivalent.

[0017] Figure 1 presents a schematic perspective view of the central part 1 of a crepe paper making machine, focusing on the rotating drying cylinder 2, and illustrating the AC2W-1-PCT The operation of the doctor blades is described according to the prior art. Characterized by a thickness of approximately 100 microns (0.1 mm), the sheet of paper being manufactured 3 moves in direction 4 towards the drying cylinder 2 at a speed of up to 2000 m / min. The sheet of paper being manufactured 3 is a continuous sheet whose width corresponds approximately to the length of the rotary drying cylinder 2, as well as to that of the other drive devices and the doctor blades. The sheet of paper undergoes various treatments, including several water removal and drying stages, before being pressed and transferred onto the drying cylinder 2 by a rotary pressure roller 5. A cutting doctor blade 6 is arranged transversely to the width of the paper being manufactured 3, near the drying cylinder 2. A creping doctor blade 7 is arranged parallel to the cutting doctor blade 6.The cutting blade 6 is generally positioned upstream of the creping blade 7, with upstream and downstream defined by the direction of travel 4 of the paper being manufactured 3. When activated, the cutting blade 6 cuts the continuous sheet of paper 3 to facilitate the winding process and ensure that individual rolls are produced with precise lengths. The creping blade 7 is used to scrape the partially dried sheet of paper 3 from the surface of the drying cylinder 2. This action creates the characteristic texture of creped paper 9, improving its softness, bulk, and absorbency. Finally, depending on specific practices, the cleaning blade 8 is used continuously or periodically to level the surface and remove contaminants, deposits, and residues from the surface of the rotary drying cylinder 2.This action helps maintain the cleanliness and efficiency of the drying process, and ensures consistent quality of the crepe paper. The scrapers are mounted on suitable supports that allow precise adjustment of their position and angle relative to the surface of the drying cylinder with which they interact. This adjustability ensures optimal performance and efficiency.

[0018] Figure 2 provides a perspective view of a scraper, highlighting its geometric specifications and basic quadrilateral shape in cross-section. Scrapers, particularly the creping blade 7 and cleaning blade 8, typically have geometric dimensions that AC2W-1-PCT These blades vary depending on the type of crepe paper and the specifications of the paper machine used. They measure up to 10 m (390 inches) in length and from 50 mm to 200 mm (2 to 8 inches) in width. Generally made from a strip of steel or cold-rolled metal, they are typically thin, with thicknesses ranging from 0.5 mm to 2.0 mm (0.02 to 0.08 inches). The average weight of a steel blade can be considered to be around 5 kg.

[0019] More specifically, the basic shape of a scraper is characterized as follows: The scraper has two large flat surfaces, designated respectively by a first face 13 and a second face 13'. They are preferably of the same dimensions in terms of length and width. The length of these first 13 and second 13' faces corresponds approximately to the length 10 of the scraper. Their width corresponds approximately to the width 11 of the scraper. The first 13 and second 13' faces, opposite each other, are substantially parallel. The first face 13 can typically be designated as the one facing the drying cylinder 2. These two faces constitute the largest surfaces of the scraper. The scraper has two long, narrow surfaces, designated respectively by a first longitudinal field 14 and a second longitudinal field 14'. These two surfaces preferably have the same length and width. Their length corresponds approximately to the length 10 of the scraper. Their width corresponds to the thickness 12 of the scraper. The first 14 and second 14' longitudinal fields are preferably substantially parallel. The first longitudinal field 14 typically designates the one facing the drying cylinder 2. The second longitudinal field 14', on the opposite side, can then be placed in the scraper support 16. AC2W-1-PCT The doctor blade has two small lateral surfaces, designated respectively by a first lateral field 15 and a second lateral field 15'. They are the same width as the longitudinal fields 14, 14', corresponding to the thickness of the doctor blade, and their length roughly corresponds to the width of the doctor blade. The first lateral field 15 and second lateral field 15' are preferably substantially parallel; the first lateral field 15 typically designates the one facing the front side of the machine, called the "operator side," and the second is located on the opposite side, at the rear of the machine. These surfaces are commonly associated with the edge or border of the doctor blade, the paper, or the dryer cylinder.

[0020] The precise design of a squeegee ensures consistent contact, perfect positioning and efficient performance for tasks such as creping or cleaning in the crepe paper production process.

[0021] Figure 3 shows a side view of a creping blade 7 in contact with the rotating drying cylinder 2, illustrating in more detail how the blade is positioned to scrape the cylinder surface and properly detach the paper 3, in order to produce creped paper 9 with the required properties. In operation, the creping blade 7, positioned in its support 16, is applied precisely against the surface of the drying cylinder 2 to achieve the desired creping effect and, consequently, the quality, consistency, and uniformity of the produced creped paper 9. This requires careful control of the angles at which the blade meets the surface of the drying cylinder 2. The key angles to consider are the blade contact angle 17, the blade tip angle 18, and the pocket or opening angle 19. The sum of these three angles must equal 180 degrees. The contact angle 17, the tip angle 18 and the pocket angle 19 are defined as follows: Contact angle 17: It is defined as the angle between the tangent line 20 to the drying cylinder 2, at point 21 where the blade enters AC2W-1-PCT contact with the drying cylinder, and the first face 13 of the blade, facing the drying cylinder (figure 3). This angle, generally limited to 30°, is crucial for determining the efficiency with which the blade is positioned to effectively scrape and separate the paper from the drying cylinder 2. - Tip angle 18: This is defined as the angle formed between one of the first 13 and second 13' faces of the blade and the first 14 and second 14' longitudinal fields of the squeegee (Figure 3). The tip angle 18 is generally between 50° and 110°. Precisely adjusting the tip angle 18 according to the application requirements is essential in the creping process to control the texture and resulting properties of the creped paper. The tip angle 18 is particularly relevant for known squeegees where only one angle is used. In the context of the present invention, where the squeegee has several working edges 21, 21', the tip angle 18 can be considered equivalent to the angle formed by the working edges. The first 13 and second 13' faces, together with the first 14 and second 14' longitudinal fields of working edges 21, 21' subjected to the impact of the paper and / or in contact with the surface of the drying cylinder. - Pocket angle 19: It is defined as the angle formed between the first longitudinal field 14 of the squeegee and the tangent line 20 to the drying cylinder, determined at the point of contact of the squeegee and the drying cylinder 2. The point of contact corresponds in this case to the working edge 21. This opening angle, generally between 60° and 100°, also influences the creping process, the texture and the resulting properties of the creped paper 9.

[0022] The scraper is characterized by a basic quadrilateral shape in cross-section, often modified and provided with a beveled contact area, subsequently designated by the term "friction zone", which facilitates interaction with the surface of the drying cylinder 2, and consequently, AC2W-1-PCT the precise actions of creping, cleaning or cutting during their operation.

[0023] In principle, depending on the crepe type, a lower tip angle (18) and a higher pocket angle (19) result in a finer, more delicate crepe texture, producing a softer-to-the-touch paper. This is desirable for premium products such as tissues, wipes, and high-quality toilet paper. Conversely, a higher tip angle (18) and a lower pocket angle (19) produce a coarser, more open crepe texture, resulting in a bulkier, stronger paper, typically suited for paper towels and absorbent materials for household or industrial use.

[0024] Figures 4A to 4H illustrate various embodiments of the scraper according to the present invention, in particular a creping blade 7 or a cleaning blade 8. A creping blade 7 or a cleaning blade 8 is preferably made from a single base material, forming the body of the scraper, usually steel.

[0025] The scraper according to the present invention is characterized in that it comprises at least two working edges 21, 21'. The working edges 21, 21' are parallel and extend along the length 10 of the scraper. They define the intersections between at least one of the first 14 and second 14' longitudinal fields and the first 13 and second 13' faces. When the point angle 18 is 90°, the corresponding longitudinal field can be a single flat surface. However, when the two opposite point angles 18 are not 90°, then the corresponding longitudinal field comprises two field surfaces 24, 24' arranged angularly with respect to each other. The point angle 18 is then defined by each of these field surfaces and the corresponding face 13.

[0026] According to one embodiment, the point angles 18 are less than 90° or 80° or 70° or between 50° and 89° or between 50° and 85°. AC2W-1-PCT

[0027] According to one embodiment, the point angles 18 are greater than 90° or 100° or 110° or between 91° and 160° or between 95° and 160°.

[0028] According to one embodiment, the field surfaces comprise a first field surface 24 and a second field surface 24' meeting at a field edge 210. The field edge 210 is typically parallel to the working edges 21, 21' and extends along the length 10 of the squeegee. The first 24 and second 24' field edges thus form a field angle 240°. The field angle can be 180° when the tip angle 18 is 90°. In other words, the longitudinal field 14 is planar. The field angle 240° can nevertheless be less than 180°, as illustrated, for example, in Figures 4A, 4B, 4D, 4E, 4F, 4G, and 4H. The field angle 240 can, for example, be between 179° and 60°, preferably between 175° and 100°, or for example a value of 160°, or 120°, or even 90°, 80°, 60° or any intermediate value. The longitudinal field 14, 14' takes on a concave shape in this case.Alternatively, the field angle 240 can be greater than 180°, specifically between 181° and 280°, preferably between 185° and 220°, with values ​​such as 190°, 210°, or even 230°, 240°, or any intermediate value. In this case, the longitudinal field takes on a convex shape.

[0029] According to a preferred embodiment, the two apex angles 18 pertaining to the same longitudinal field 14, 14' are identical. In other words, the first 24 and second 24' field surfaces are identical and symmetrical with respect to a plane of symmetry 25 parallel to the first 13 and second 13' faces and passing through the center of the squeegee. The field edge 210 is also coincident with this central vertical plane of symmetry 25, dividing the thickness 12 of the squeegee into two identical parts. Figure 4A shows a lateral view of the squeegee in this arrangement. Figures 4B and 4C show this same representation including a more specific apex angle 18 in accordance with the extreme specifications mentioned above. AC2W-1-PCT

[0030] According to another embodiment, the first 24 and second 24' field surfaces are not symmetrical. The field edge 210 they form is thus eccentric with respect to the central plane of symmetry 25. The point angles 18 relative to the first face 13 and the second face 13' differ from each other. This arrangement allows the scraper to be used in two different configurations depending on whether one or the other of the faces 13, 13' is positioned opposite the drying cylinder 2. Different creping qualities can thus be obtained with the same scraper. Alternatively, a scraper can be used as a creping scraper 7 with one of the point angles 18 and as a cleaning scraper 8 with the opposite point angle 18. Such an asymmetrical scraper can be adapted to other requirements.

[0031] In one embodiment, the field surfaces 24 and 24' are joined via one or more intermediate surfaces (not shown). In this case, the longitudinal field has more than one edge, for example, two edges: one at the junction of the first field surface 24 and an intermediate surface, and the other at the junction of the second field surface and an intermediate surface. Such an arrangement allows, for example, limiting the machining of the longitudinal field to the essential surfaces. The intermediate surface(s) can form a rounded shape. The important thing in all cases is to control the point angle.

[0032] According to one embodiment, the scraper according to the present invention comprises at least one friction surface 26, 26', 26", 26'". As such, at least one of the first 13 and second 13' faces is beveled near the working edges 21, 21', 21", 21'" so as to produce such friction surfaces 26, 26', 26", 26'". The friction surface(s) form a bevel angle 27 with the corresponding face 13, 13'. Figure 4D provides a side view showing the friction surfaces 26 and 26', specifically designed to accommodate contact between the scraper and the surface of the drying cylinder 2 and to facilitate sliding during operation. The friction surface 26 or 26' is important for the positioning and overall operation of the scraper, and to ensure that the scraper maintains proper contact with the drying cylinder 2 without excessive pressure that could cause damage or premature wear. By definition, the AC2W-1-PCT The friction surface extends along the length 10 of the scraper. The bevel angle 27, measured between the friction surface 26 and the corresponding face 13 of the scraper, is limited to 30°. The bevel angle 27 can, for example, be between 1° and 25°, more particularly between 2° and 20°, and preferably between 3° and 15°. The width 28 of the friction surface 26, separating the working edge 21 from the corresponding face 13, is limited to 5 mm. It can, for example, be less than 3 mm or, preferably, between 0.1 and 2.5 mm. The tip of the scraper can be considered to extend approximately 5 mm across the width of the scraper.

[0033] Regardless of the arrangement of the first 24 and second 24' surfaces of the fields, the friction surfaces 26, 26' can be symmetrical with respect to the central plane of symmetry 25, as illustrated in Figure 4D. The bevel angle 27 can correspond to the contact angle 17.

[0034] According to another embodiment, the friction surfaces 26, 26', 26", 26'" can be designed asymmetrically. In this case, the bevel angle 27 differs depending on which of the first 13 and second 13' faces it relates to. The bevel angles 27 and the point angles 18 can thus be adapted independently of each other for greater flexibility in the use of the scraper.

[0035] The presence of a friction surface does not, by definition, alter the tip angle of the scraper. Figures 4E and 4F show a more specific bevel angle 27 in accordance with the extreme specifications mentioned previously. Unlike the prior art, Figures 4A to 4F offer the advantageous alternative of providing a scraper with two active working edges 21 and 2T. In this case, the present invention offers the opportunity to use the scraper a second time, potentially increasing its lifespan by 100%.

[0036] According to one embodiment, the two longitudinal fields 14, 14' each have two working edges 21, 21', 21", 21'". Figure 4G provides a side view illustrating such an arrangement, according to which the AC2W-1-PCT The first longitudinal field 14 comprises a first field edge 210, and the second longitudinal field 14' comprises a second field edge 210', obeying the characteristics described previously. The second longitudinal field 14' then comprises a first field surface 24" and a second field surface 24'". As indicated previously, more than one field edge can be considered, in the case where the field surfaces are separated by one or more intermediate surfaces.

[0037] The first 14 and second 14' longitudinal fields can be designed symmetrically with respect to a central symmetry plane 29, orthogonal to the symmetry plane 25 described previously. The second symmetry plane 29 divides the scraper along both its thickness 12 and its length 10. In this case, the scraper has four identical point angles 18 and can thus be used more intensively or for longer periods for the same application.

[0038] Alternatively, the second longitudinal field 14' may have two field surfaces that are not symmetrical to those of the first longitudinal field 14 with respect to the second plane of symmetry 29. Alternatively, or in addition, the field surfaces of the second longitudinal field 14' may not be symmetrical with respect to the first plane of symmetry 25. One of the two longitudinal fields may be concave while the other is convex. As a result, the point angles 18 may be different for the four working edges 21, 21', 21", 21'". Such an arrangement multiplies the possible applications of a scraper according to the present invention.

[0039] According to one embodiment, the scraper according to the present invention comprises more than two friction surfaces as described above. Friction surfaces can be considered between the first 13' and second 13' faces and the first 14' and second 14' longitudinal fields. Figure 4H illustrates such an arrangement. AC2W-1-PCT

[0040] As indicated above, the friction surfaces 26", 26"' relating to the second longitudinal field 14' can be symmetrical with respect to the first plane of symmetry 25 or asymmetrical. They can alternatively or in addition be symmetrical to those relating to the first longitudinal field 14 along the second plane of symmetry 29 or asymmetrical.

[0041] Unlike the prior art, Figures 4G and 4H offer the advantageous alternative of providing a scraper with four active working edges 21, 2T, 21", and 2T". Consequently, the present invention offers the possibility of using the scraper four times, potentially increasing its service life by 300%. In this latter case, however, it should be noted that specific protection must be provided for the scraper tip 14' to prevent damage when the scraper is inserted into its holder 16 and subsequently during operation.

[0042] According to one embodiment, one or more of the scraper surfaces, including the first 14' and second 14' longitudinal fields, the friction surfaces 26, 26', 26", 26'", and the first 13 and second 13' faces in whole or in part, may be subjected to a special treatment to modify their mechanical properties. Figures 5A to 5E illustrate a creping blade 7 or a cleaning blade 8, modified by at least one surface treatment 30. Any type of surface treatment may be applicable. The term "surface treatment" refers to a variety of processes applied to the surface of a material to obtain a specific desired property or characteristic. These processes may improve appearance, surface properties, corrosion resistance, chemical resistance, wear resistance, and mechanical properties.Examples of surface treatments include chemical, electrochemical, electroplating, coating, heat treatment, hardening, and laser surface treatments. While some of these treatments modify or transform the surface to varying depths without adding any specific material, others add a few microns to several hundred microns of a specific material. Preferred surface treatments are those in the field of... AC2W-1-PCT Coatings, which include thermal spraying and vacuum deposition techniques, involve the application of ceramic or ceramic-based materials. The term "ceramic" refers to inorganic, non-metallic materials that are generally produced by the application of heat. These specific materials are typically characterized by their high hardness, brittleness, thermal resistance, and chemical stability. Preference is given to technical ceramics, which include oxides, carbides, and nitrides. It is understood that, when at least one surface treatment is applied, the scraper according to the invention can benefit from the addition of one or more coating materials and / or one or more surface modifications.Although all possible embodiments described in Figures 4A to 4H could benefit from the addition of at least one surface treatment, Figures 5A to 5C focus on the preferred embodiment, which corresponds to the embodiment shown in Figure 4D. Figures 5D and 5E refer to the embodiment illustrated in Figure 4H. While the entire scraper can be modified by a surface treatment, depending on the manufacturing technique and certain technical and / or economic constraints, it is advisable to modify only the necessary portion. Figure 5A provides an example where the treated portion is focused on the first longitudinal field 14, including the first 24 and second 24' field surfaces. Figure 5B provides an example where the treated portion is extended to the friction surfaces adjacent to the first longitudinal field 14.Depending on the product design specifications, the friction surfaces can be treated in whole or in part, i.e., over the entire surface or a limited portion. Figure 5C shows an example where the treated area extends to part of the first 13' and second 13' faces. This latter area can be more or less extended in the direction of the width of the scraper, thus covering a narrower, wider, or even the entire surface of the first 13' and second 13' faces. In all Figures 5A to 5C, the working edges 21' and 21' are treated, thus leading to the modification or protection of the active edges by at least one surface treatment. Figure 5D shows a side view of this latter embodiment with a treated surface on the opposite side of the scraper, relative to the second longitudinal field 14'. AC2W-1-PCT A modification of the four possible working edges 21, 21', 21" and 21"' allows the scraper to be used a maximum of four times for a given application. FIG. 5E provides a perspective view of this latter embodiment for clarity, adding the third dimension along the longitudinal axis 31 of the scraper, thus revealing the characteristic of the ultimate product of the scraper according to the present invention.

[0043] The present invention further covers a method or process for manufacturing a scraper according to the present invention.

[0044] Figure 6 describes the manufacturing steps, in the form of a flow diagram, for the production of a scraper, i.e., a creping blade 7 or a cleaning blade 8, according to the invention. Starting from a raw material, or raw product, defined as a thin metal strip, having a quadrilateral shape in cross-section (width x thickness) and characterized primarily by three dimensional specifications (length x width x thickness). The present process comprises one or more of the following steps:

[0045] A preforming step P1 of at least one first longitudinal field 14 of the squeegee. This preforming step includes, where applicable, the production of the first 24 and second 24' field surfaces. Preferably, the first 24 and second 24' field surfaces are produced in a single operation.

[0046] A step P2 of preforming the two friction surfaces 26 and 26' related to the longitudinal field preformed in step P1. Preferably, the two friction surfaces 26 and 26' related to a given longitudinal field are produced in a common operation.

[0047] A P3 surface treatment step 30. The surface treatment step can be applied to the longitudinal fields preformed during the P1 step, and / or to the friction surfaces preformed during the P2 step or to other surfaces such as the first 13 and the second 13' faces. AC2W-1-PCT

[0048] A step F1 of forming at least one longitudinal field 14 of the squeegee. Step F1 may, if necessary, include forming the first 24 and second 24' field surfaces. The forming of the first 24 and second 24' field surfaces is preferably carried out by a single operation.

[0049] A step F2 of forming the friction surfaces 26 and 26' preferably carried out by a common operation.

[0050] Step P1 or F1, relating to the production of the two working edges, constitutes a minimum requirement for validating the specific criteria of the scraper according to the invention. Although the main possibilities are shown in the flow diagram in Figure 6, alternative manufacturing methods exist. By way of example, the following three preferred manufacturing flows are proposed:

[0051] Option 1: - E1: Preforming of a longitudinal field 14 of the squeegee and of the two field surfaces 24 and 24', in a single production step. - E2: Surface treatment 30 comprising a coating with a material covering the whole surface of a longitudinal field 14 and at least part of the first 13 and second 13' adjacent faces, in a single production step. - E3: Forming of a longitudinal field 14 of the squeegee and field surfaces 24 and 24', characterized by the presence of at least one field edge 210 and a field angle 240 different from 180°, in a single production step. E4: Forming of friction surfaces 26 and 26', in a single production step. AC2W-1-PCT

[0052] Steps E3 and E4 above can be reversed, so as to produce the two working edges 21 and 2T with precision and quality.

[0053] Option 2: - F1: Surface treatment 30: a coating of a material covering the entire surface of a longitudinal field 14 and at least part of the first 13 and second 13' adjacent faces, in a single production step. - F2: Forming of a longitudinal field 14 of the squeegee and of the first 24 and second 24' field surfaces, characterized by the presence of at least one field edge 210 and a field angle 240 different from 180°, in a single production step. - F3: Forming of friction surfaces 26 and 26', in a single production step.

[0054] Steps F2 and F3 above can be reversed to produce both working edges 21 and 2T with precision and quality. Without the preliminary preforming, this second option eliminates one production step but requires more effort during the final forming. The choice of the most effective and efficient manufacturing option depends on the selected surface treatment and the type and specifications of the associated coating material. A surface engineer will have no difficulty making this technical decision.

[0055] Option 3: - G1: Preforming of a longitudinal field 14 of the squeegee and the first 24 and second 24' field surfaces, in a single production step. AC2W-1-PCT - G2: Surface treatment 30: a coating of a material covering the entire surface of a longitudinal field 14 and at least part of the first 13 and second 13' adjacent faces, in a single production step. - G3: Forming of the two friction surfaces 26 and 26', in a single production step.

[0056] Figures 7A to 7F illustrate the fabrication of at least two working edges, a critical aspect of the invention, corresponding to the preferred embodiment of the scraper shown in Figure 5A. However, the present method applies to all embodiments covered by the present invention. A circular tool 34, rotating about an axis 35 transverse to the longitudinal field 14 of the scraper, is used to shape the longitudinal field 14 and simultaneously produce the two field surfaces 24 and 24'. The passage of the first tool 34 along the longitudinal field 14 allows the two field surfaces to be shaped in a single operation. The machining surface 340 of the tool 34 comprises two machining surfaces arranged angularly with respect to each other at an angle corresponding to the field angle 240 required for the scraper. Depending on the requirements, the machining surfaces may be symmetrical or asymmetrical.

[0057] Figure 7B shows how to form the two sliding surfaces 26 and 26' in a single step, using another circular tool 36, rotating about an axis of rotation 35 orthogonal to the longitudinal surface 14. The second tool 36 has two machining surfaces 360 arranged opposite each other at a distance approximately corresponding to the thickness 12 of the scraper and oriented at an angle corresponding to the required bevel angle 27. Passing the second tool 36 along the longitudinal surface 14 allows the two opposing friction surfaces to be shaped in a single operation. At least one of the two manufacturing operations described above results in the production and sharpening of at least two working edges 21 and 21', according, for example, to the procedures defined as "Option 1" or "Option 2" illustrated in Figures 6, 7C, and 7D. Figure 7E proposes AC2W-1-PCT An alternative form of tool 36, used to manufacture a scraper according to the design shown in Figure 4A, whether or not it is modified by surface treatment. In this case, even if the two sliding surfaces 26 and 26' are not required, the sliding surface and working edges must conform to specifications to ensure effective use of the scraper, regardless of the application. In all cases, the manufacturing principle and associated method remain the same, even if the two sliding surfaces 26 and 26' are not present. Figure 7F shows an alternative form of tool 34, used to form a higher point angle 18, typically above 90°, for example 91°, 95°, 100°, 105°, or 110°, or between 91° and 160°. The forming on the second longitudinal field 14' of the squeegee, and the adjacent surfaces can be done in a similar manner.

[0058] Forming a longitudinal field 14, 14', while allowing simultaneous formation of the first 24 and second 24' field surfaces of the scraper, may involve several steps to ensure a functional and efficient working edge 21, 21', 21" or 21'", free from defects such as microscopic chips. A grinding step may be followed by a polishing step, resulting in improved surface quality. Proceeding in this manner guarantees a perfect intersection between the elements defining the angle between adjacent surfaces of the working edge, along the entire active length of the scraper. These grinding or polishing tools, familiar to surface finishing specialists, are rotary. Preferred abrasive tools are those made of diamond grains and preformed according to a precise design, so as to reproduce the field angles described above.These manufacturing steps can be carried out continuously, with a moving scraper and a fixed rotating abrasive tool; or "piece by piece", with a fixed scraper and a moving rotating abrasive tool.

[0059] The present invention also covers a method for manufacturing paper, in particular crepe paper, comprising the steps of passing a strip of paper being manufactured 3 around a drying cylinder 2, and of scraping the surface of the drying cylinder 2 with a scraper. AC2W-1-PCT The process may involve a creping 7 and / or a cleaning squeegee 8 comprising more than one working edge, and, when one of the working edges is worn, reversing the squeegee to use a second working edge. Reversing the squeegee may be manual or automated. For this purpose, the squeegee support 16 may have lateral rotating attachment points (not shown) allowing, for example, the squeegee to be rotated about its longitudinal axis 31 so as to position the second longitudinal field 14' opposite the drying cylinder 2. Alternatively, or in addition, the process may include a step of transferring the creping squeegee 7 into the position of a cleaning squeegee 8 so as to use it as a cleaning squeegee with the same or a different working edge. AC2W-1-PCT Reference numbers used in the figures Central part of a paper production machine Rotary drying cylinder Tangent line to the drying cylinder, 21', 21", 21" Blade working edge First field area ' Second field area First plane of symmetry, 26', 26", 26" Sliding / friction surfaces Bevel angle Width of the friction surface Second plane of symmetry Paper in the process of being made Paper transfer direction in manufacturing. Rotary pressure roller. Cutting scraper Creping scraper Cleaning scraper Crepe paper Blade length, blade width, blade thickness, first blade face, second blade face First longitudinal field 'Second longitudinal field First side field ' Second side field Blade support Blade contact angle Blade tip angle Blade pocket angle Surface treatment AC2W-1-PCT Longitudinal axis, 36 Circular tools Rotation axis 0, 360 Machining surfaces 0, 210' Field edges 0 Field angle AC2W-1-PCT

Claims

Demands 1. Scraper (7, 8) comprising a first face (13) and a second face (13'), connected by a first longitudinal field (14) and a second longitudinal field (14') characterized in that the scraper comprises at least two working edges (21, 21', 21", 21'") at the base of the point angles (18) formed by the first (13) and second (13') faces and the first (14) and second (14') longitudinal fields.

2. Scraper according to claim 1, wherein at least one of said first (14) and second (14') longitudinal fields comprises a first field surface (24, 24") and a second field surface (24', 24'") arranged between them at a field angle (240).

3. Scraper according to any one of claims 1 and 2, wherein said point angles (18) are less than 90° or 80° or 70° or between 50° and 89°.

4. Scraper according to any one of claims 1 and 2, wherein said point angles (18) are greater than 90° or 100° or 110° or between 91° and 160°.

5. Squeegee according to any one of claims 2 to 4, wherein the field angle (240) is less than 180°, or between 179° and 60°.

6. Squeegee according to any one of claims 2 to 4, wherein the field angle (240) is greater than 180°, or between 181° and 280°.

7. Scraper according to any one of claims 1 to 6, wherein the first (13) and second (13') faces comprise at least one friction surface (26, 26', 26", 26'") forming a bevel angle (27) between said faces (13, 13') and said friction surfaces less than 30° or between 1° and 25°. AC2W-1-PCT 8. Scraper according to any one of claims 1 to 7, wherein said first (14) and second (14') longitudinal fields comprise a ceramic-based surface coating.

9. Method of manufacturing a scraper according to any one of claims 1 to 8 comprising a step of forming said first (14) and second (14') longitudinal fields simultaneously so as to produce at least two working edges (21, 21', 21", 21'").

10. A method according to claim 9, when it depends on claims 7 or 8, further comprising a step of forming the friction surfaces (26, 26', 26", 26'") so as to produce two of these friction surfaces simultaneously by forming a bevel angle (27) between said faces (13, 13') and said friction surfaces less than 30° or between 1° and 25°.

11. Process for manufacturing crepe paper 9 from a sheet of linear paper 3, comprising the steps of: - to rotate the paper strip 3 around a drying cylinder 2, - scraping the surface of the drying cylinder 2 with a creping scraper 7 and / or a cleaning scraper 8 comprising more than one working edge, according to any one of claims 1 to 8 and, - when one of the working edges is worn, turn the scraper over so as to use a second working edge. AC2W-1-PCT

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