PULP RESERVOIR FOR A FIBER MOLDING PLANT AND METHOD FOR SUCTIONING AND FORMING FIBERS OUT OF A PULP FROM A PULP RESERVOIR OF A FIBER MOLDING PLANT

TECHNICAL FIELD

[0001]Pulp reservoirs for a fiber molding plant and methods for suctioning and forming fibers out of a pulp from a pulp reservoir of a fiber molding plant are described.

DESCRIPTION OF RELATED ART

[0002]Fiber-containing materials are increasingly used, for example, to produce packaging for food (e.g., trays, capsules, boxes, etc.) and consumer goods (e.g., electronic devices, etc.) as well as beverage containers. Everyday items, such as disposable cutlery and tableware, are also made from fiber-containing material. Fiber-containing materials contain natural fibers or artificial fibers. Recently, fiber-containing material is increasingly used that has or is made of natural fibers that can be obtained, for example, from renewable raw materials or waste paper. The natural fibers are mixed in a so-called pulp with water and optionally further additives, such as starch. Additives can also have an effect on color, barrier properties and mechanical properties. This pulp can have a proportion of natural fibers of, for example, 0.1 to 10 wt. %. The proportion of natural fibers varies depending on the method used for the production of packaging etc. and the product properties of the product to be produced.

[0003]The production of fiber-containing products from a pulp generally takes place in several work steps. For this purpose, a fiber processing device has multiple stations. In a suctioning station, for example, fibers can be suctioned in a suction tool cavity of a suction tool, thus forming a preform. For this purpose, the pulp is provided in a pulp reservoir, and the suction tool is at least partially immersed in the pulp with at least one suction tool cavity whose geometry essentially corresponds to the product to be manufactured. During the immersion, suction takes place via openings in the suction tool cavity, which are connected to a corresponding suction device, where fibers from the pulp accumulate on the surface of the suction tool cavity. Usually, the suction tool cavity surface comprises a mesh. The suctioned fibers can subsequently be brought into a pre-pressing tool via the suction tool, and a preform is pre-pressed. For this purpose, for example, it is possible to use elastic mold bodies that are inflated in order to press and, in the process, exert pressure on the preforms. During this pre-pressing process, the fibers in the preform are compressed and the water content of the preform is reduced. After this, preforms are pressed in a hot press to form finished molded parts (hot pressing process). In this process, preforms are inserted into a hot press tool that has, for example, a lower tool half and an upper tool half that are heated. In the hot press tool, the preforms are pressed in a cavity under heat input, with residual moisture being removed by the pressure and heat so that the moisture content of the preforms is reduced from about 60 wt. % before hot pressing to, for example, 5-10 wt. % after hot pressing.

[0004]To provide products with high quality and material properties (e.g. oil and grease resistance (OGR), strength, wall thickness, etc.). several attempts have been made. One approach comprises the introduction of vibration during the suctioning of the fibers out of the pulp by means of a vibrator which is arranged on the suction tool (WO 2024/201096 A1).

[0005]However, a vibrator arranged on the suction tool has several disadvantages. Due to the connection with a moveable member of the plant, which is necessary for the transfer of the suction tool cavities in the pulp, the introduced vibrations are also transferred to the moveable member and other parts of the plant. This impairs the moveable member and the other parts. Thus, it will be necessary to adapt the control since the introduced vibration must be compensated. Furthermore, maintenance effort and downtime are increased. Integration of a damping member to avoid introduction of the vibration in the plant and the moveable member requires additional equipment and is also expensive. Moreover, vibration inside the suction tool causes loosening of screws and fittings. Thus, it is necessary to provide a special construction and additional parts to avoid loosening. Finally, since the suction tool is vibrating the orientation of the fibers in the pulp is not influenced which leads to poor product quality after forming.

SUMMARY

Object

[0006]In contrast thereto, it is an object of the present disclosure to specify a solution that solves the problems of the prior art and provides better material properties and decrease cycle time of a suctioning process.

Solution

[0007]The above-mentioned object is achieved by a pulp reservoir for a fiber molding plant, including a pulp basin for a fiber containing pulp, wherein the pulp basin comprises a bottom plate, side walls and an access portion via which a suction tool having at least one suction tool cavity is transferred in the pulp basin to suction fibers out of the pulp wherein the fibers are adsorbed at an suction tool cavity surface, further including at least one vibration element which is adapted to introduce vibration into the pulp contained in the pulp basin to provide an orientation of the fibers in the pulp for uniform distribution of the fibers over the suction tool cavity surface of the at least one suction tool cavity during suctioning.

[0008]The introduction of vibration in the pulp provides an orientation of the fibers in the pulp which are also adsorbed at the suction tool cavity tool surface in an orientated manner. Additionally, fibers already absorbed at the suction tool cavity surface (e.g. screen or mesh) are compacted. Thus, it is possible to increase the strength wherein the thickness of the preform and also the final molded product can be significantly reduced. In addition to having a increasing density, strength increase is also due to improving the formation of the parts. The fibers are now more evenly distributed.

[0009]Due to the vibration fibers and fine particles (fines) can be compacted so that the OGR is significantly increased.

[0010]A vibration element can include a motor with an unbalance which rotation causes vibrations.

[0011]In further embodiments the vibration element is arranged on an outer surface of a side wall of the pulp basin. This embodiment provides a subsequent integration of vibrator to improve the suctioning and forming process in existing pulp reservoirs. Moreover, the embodiment provides a simple integration of the vibration element wherein the walls of the basin transfer the vibration into the pulp.

[0012]In further embodiments the vibration element is connected to the outer surface via a vibration plate. A vibration plate can act as an amplifier. In further embodiments, the vibration plate can be connected to the wall on at least two connection regions wherein the introduced vibration causes vibrations which influences each other.

[0013]In further embodiments the vibration plate is made of metal. Metal comprises good vibration characteristics for introducing vibration in the walls and the pulp.

[0014]In further embodiments the vibration element includes a transmission element which is located inside the pulp. Thus, the vibration is directly introduced in the pulp which improves the process since the structural elements of the basin and other parts are not exposed to vibration. In further embodiments, the vibration is transferred by means of at least on rod so that the energy goes directly into the pulp. In further embodiments, the vibration element includes a submersible vibrator.

[0015]In further embodiments the side walls are metal side walls. Due to good vibration characteristics of metal the introduction of vibration is further improved.

[0016]In further embodiments at least one distribution plate is arranged in the pulp basin. In interaction with vibrations the distribution plate improves the distribution of fibers.

[0017]In further embodiments the distribution plate comprises open portions. The open portions provide deflection of fibers and fines in the pulp during the suctioning. Thus, it is possible to improve the fiber distribution over the suction tool cavity surface and a plane parallel to a suction tool plane or opening plane of the suction tool cavity/cavities. In further embodiments, at least one distribution plate is arranged at an angle inside the pulp basin wherein a flow of fibers, caused by a circulation means (e.g. a pump), is adapted so that fibers are deflected towards suction tool cavities. By means of that, a parallel flow of fibers which is often provided in conventional pulp basin is interrupted and fibers are deflected to the suction tool. Moreover, a diffuse distribution of the fibers is achieved by means of the deflector plate and the openings in the deflector plate. In contrast thereto, in a conventional pulp flow the fibers are orientated according to the flow so that the adsorbed fibers on the mesh of a suction tool also comprise the orientation of the fiber flow.

[0018]In further embodiments the vibration element is connected to the distribution plate. This embodiment reduces or eliminates the impact of the vibrations on components of the pulp reservoir and a molding plant.

[0019]In further embodiments the pulp reservoir includes a circulation element which is adapted to circulate the pulp in the pulp basin. In further embodiments, the circulation element comprises a pump.

[0020]In further embodiments the distribution plate is arranged parallel or at an angle to at least the bottom or an opening plane of the suction tool cavity.

[0021]In further embodiments at least two distribution plates are arranged parallel to each other.

[0022]In further embodiments the distribution plates have different designed open portions.

[0023]In further embodiments the orientation and dimension of the open portions of the at least one distribution plate are designed and orientated with regard to the at least one suction tool cavity.

[0024]In further embodiments the plate comprises at least one of a pattern of elongated openings or a pattern of circular openings.

[0025]The above-mentioned object is further achieved by a pulp reservoir for a fiber molding plant, including a pulp basin for a fiber containing pulp, wherein the pulp basin comprises a bottom plate, side walls and an access portion via which a suction tool having at least one suction tool cavity is transferred in the pulp basin to suction fibers out of the pulp wherein the fibers are adsorbed at a suction tool cavity surface, wherein at least one distribution plate is arranged in the pulp basin, wherein the at least one distribution plate comprises open portions, and wherein the open portions form a pattern of openings which provide an orientation of the fibers in the pulp for uniform distribution of the fibers over the suction tool cavity surface of the at least one suction tool cavity during suctioning.

[0026]The openings in the distribution plate provide deflection of fibers and fines in the pulp during the suctioning. Thus, it is possible to improve the fiber distribution over the suction tool cavity surface and a plane parallel to a suction tool plane or opening plane of the suction tool cavity/cavities.

[0027]In further embodiments the pulp reservoir includes a circulation element which is adapted to circulate the pulp in the pulp basin.

[0028]In further embodiments the distribution plate is arranged parallel or at an angle to at least the bottom or an opening plane of the suction tool cavity.

[0029]In further embodiments at least two distribution plates are arranged parallel to each other.

[0030]In further embodiments the distribution plates have different designed open portions.

[0031]In further embodiments the orientation and dimension of the open portions of the at least one distribution plate are designed and orientated with regard to the at least one suction tool cavity.

[0032]In further embodiments the plate comprises a pattern of elongated openings.

[0033]In further embodiments the plate comprises a pattern of circular openings.

[0038]The introduction of vibration during suctioning of fibers improves the distribution of the fibers wherein free spaces between fibers adsorbed at the suction tool cavity surface are at least reduced or eliminated to increase the properties of fiber molded products.

[0039]In further embodiments the vibration is introduced before suctioning. In this embodiment the vibration starts before the suction takes place so that the distribution of the fibers and fines is already improved before fibers are already adsorb on the suction tool cavity surface.

[0040]In further embodiments the vibration is introduced by a frequency between 50 Hz to 750 Hz. It has been found that good results are achieved within this frequency range.

[0041]In further embodiments the frequency of the introduced vibration is changed during suctioning. The distribution and compaction of fibers and fines can be controlled during the suctioning for example in relation to the thickness of a fiber layer already absorbed at the suction tool cavity surface.

[0042]In further embodiments, by means of at least one distribution plate a fiber flow caused by a circulating means, e.g. a pump, a deflection of fibers is achieved wherein fibers are deflected towards a suction tool in a diffuse manner.

[0043]Further features, embodiments and advantages result from the following illustration of exemplary embodiments with reference to the figures.

BRIEF DESCRIPTION OF THE FIGURES

[0044]In the drawings:

[0045]FIG. 1 depicts a schematic representation of a pulp reservoir and components of a fiber molding plant, according to some embodiments.

[0046]FIG. 2 depicts a schematic representation of various embodiments of a distribution plate, according to some embodiments.

[0047]FIG. 3 depicts a schematic representation of profiles of a distribution plate, according to some embodiments.

[0048]FIG. 4 depicts schematic representations of a fiber structure on a suction tool cavity surface according to the prior art and the inventive concept.

[0049]FIG. 5 depicts a schematic representation of a method for suctioning fibers according to some embodiments.

DETAILED DESCRIPTION

[0050]Various embodiments of the technical teaching described herein are shown below with reference to the figures. Identical reference signs are used in the figure description for identical components, parts and processes. Components, parts and processes that are not essential to the technical teachings disclosed herein or that are obvious to a person skilled in the art are not explicitly reproduced. Features specified in the singular also include the plural unless explicitly stated otherwise. This applies in particular to statements such as “a” or “one.”

[0051]FIG. 1 depicts a schematic representation of a pulp reservoir 100 and components of a fiber molding plant, according to some embodiments. The pulp reservoir 100 comprises a pulp basin 110 with a housing. The housing comprises side walls 114 and a bottom 112. The pulp basin 110 is open at the top so that access to the pulp basin 110 is provided. The bottom 112 and side walls 114 are made of metal in the depicted embodiment. In other embodiments, the bottom 112 and the side walls 114 are made of non-metal materials, for example composite materials or plastic materials.

[0052]The pulp basin 110 contains a pulp 200 comprising water, fibers and fines. In further embodiments, additives can be contained in the pulp 200. The content of fibers and fines in the pulp 200 is 0,1-10 wt-%.

[0053]FIG. 1 depicts the pulp reservoir 100 during a suctioning process wherein a suction tool 140 is immersed in the pulp 200. The suction tool 140 comprises suction tool cavities 142 wherein FIG. 1 depicts only four suction tool cavities 142. In further embodiments, a suction tool 140 can have less or more suction tool cavities 142. The suction tool cavities 142 comprise a screen 146 (e.g. mesh) with a suction tool cavity surface 144 on which fibers and fines are adsorbed during suctioning. During suctioning, a vacuum is provided so that pulp 200 is suctioned over the screen 146 which comprises small openings (<1 mm). Fibers and fines in the pulp 200 are deposited on the suction tool cavity surface 144. Water penetrates the openings in the screen 146 and is drained of over channels in the suction tool 140 and a transfer device 150. The transfer device 150 serves to transfer the suction tool 140 to the pulp reservoir 100 and the pulp 200 in the pulp basin 110 for suctioning fibers. After suctioning the transfer device 150 moves the suction tool 150 together with fibers adsorbed at the screen 146 to a pre-pressing station or a mold station. The transfer device 150 in the depicted embodiment is a robot arm.

[0054]FIG. 1 depicts various embodiments wherein at least one vibrator 120 can be arranged at least on an outer surface of a side wall 114, on an outer surface of the bottom 112 and on a surface of a distribution plate 130.

[0055]In an embodiment, the vibrator 120 is connected to the side wall 114 via a vibration plate 122. The vibration plate 122 comprises a great extend over the surface of the side wall 114 to increase the connection area between the vibrator 120 and the side wall 114.

[0056]In a further embodiment, a vibrator 120 is connected to a distribution plate 130 inside the pulp basin 110 and the pulp 200.

[0057]The vibrator 120 and the distribution plate 130 each provide a better distribution of fibers and fines of the pulp 200 during suctioning. Thus, a vibrator 120 and a distribution plate 130 are alternatives in further embodiments wherein FIG. 1 depicts an embodiment with a vibrator 120 and a distribution plate 130. In further embodiments, the number and location of vibrators 120 and distribution plates 130 are different to the depicted embodiment of FIG. 1.

[0058]The pulp reservoir 100 comprises a pump 118 for circulation fibers and fines in the pulp 200 during suctioning. The pump 118 can provide a circulation in a direction parallel to the bottom 112 or the side walls 114. FIG. 1 depicts a schematic representation of the pulp stream by the curved arrow. In other embodiments, the pulp stream returns below the surface of the pulp 200. By way of example, the pulp stream can be deflected after returning to the side wall 114 of the pump 118 by means of a deflection plate. In further embodiments, the side walls 114 and the bottom 112 have deflecting means causing a diffuse fiber flow.

[0059]The distribution plate 130 is connected by means of support elements 134 to the housing of the pulp basin 110, for example to the bottom 112. The distribution plate 134 runs parallel to the bottom 112 and an opening plane 148 of the suction tool 140. The opening plane 148 defines a surface of the suction tool 140 in which openings of the suction tool cavities 142 extend. The support elements 134 comprise damping elements in further embodiments to prevent vibration of the housing of the pulp basin 110.

[0060]In further embodiments, at least two distribution plates 130 form a unit and such a unit is arranged inside the pulp basin 110. The distance between the distribution plates 130 depends on at least one of the size of openings 132 in the distribution plates 130, the pump speed for circulating the pulp 200 inside the pulp basin 110, the pulp composition and the characteristics of the fibers.

[0061]In further embodiments, at least one distribution plate 130 is arranged at an angle. The distribution plate 130 can be arranged between 15-60 degrees to the bottom 114, in particular at an angle between 35-50, more particular at an angle of 45 degrees.

[0062]A fiber molding plant comprises further components. Reference is made to US-patent application US 2023-0313458 which discloses a process of forming products from a fiber containing material and a structure of a fiber molding plant the disclosure of which is incorporated by reference herein.

[0063]FIG. 2 depicts a schematic representation of various embodiments of a distribution plate 130, according to some embodiments. FIG. 2 depicts a first surface 136 of different embodiments of distribution plates 130. The distribution plates 130 comprise a pattern of openings 132. In FIG. 2a) the pattern includes circular openings 132. For example, the openings 132 of FIG. 2a) have a diameter of 5-30 mm, in particular 10-25 mm, more particular 15-20 mm. In FIG. 2 b) the pattern includes longitudinal openings 132. For example, the openings 132 of FIG. 2b) have a width of 5-30 mm, in particular 10-25 mm, more particular 15-20 mm. The closed areas between the openings 132 in the depicted embodiments may a have an extension between 5-30 mm, in particular 10-25 mm, more particular 15-20 mm.

[0064]In further embodiments, a pattern of openings 132 comprises different designed openings 132 which incorporates the structure and design of the suction tool cavities 142.

[0065]The openings 132 of the distribution plate 130 provide a distribution of fibers in the pulp 200 during suctioning. In combination with a pulp flow caused by the circulation of pulp 200 through a pump 118 orientation of fibers is influenced. The orientation of fibers during circulation by means of a pump 118 leads to a length wise orientation of the fibers. This also affects the orientation of the fibers adsorbed on the suction tool cavity surface 144. The distribution plate 130 affects the orientation of the fibers during suctioning so that the length wise orientation caused by the pump 118 is disrupted. Fibers then penetrate the openings 132 in different orientations wherein opening surfaces of the openings 132 serve as deflectors. Thus, the orientation of fibers is improved so that the compaction of fibers on the suction tool cavity surface 144 is increased.

[0066]FIG. 3 depicts a schematic representation of profiles of a distribution plate 130, according to some embodiments. FIG. 3a) depicts openings 132 with a straight profile. FIG. 3b) depicts openings 132 with a funnel-shaped profile wherein the openings 132 increase from a second surface 138 to a first surface 136. The first surface 136 of the distribution plate 130 is directed to the opening plane 148. The second surface 138 of the distribution plate 130 is directed to the bottom 112. In further embodiments. The profile of FIG. 3b) is reverse. In further embodiments, a distribution plate 130 has different profiles.

[0067]The dimension of the distribution plates 130 is adapted to the size of the pulp basin 110 depending on the orientation of the distribution plates 130 to the bottom 114 (inclined or parallel) and the position of the at least one pump 118 as well as the direction of the pulp stream. Since the openings 132 affects the distribution and orientation of fibers in the pulp 200 and affects the pulp flow stream, distribution plates 130 with openings 132, especially longitudinal openings 132, are positioned in order to achieve desired and required fiber distributions for suctioning.

[0068]FIG. 4 depicts schematic representations of a fiber structure 300 on a suction tool cavity surface 144 according to the prior art and the inventive concept.

[0069]FIG. 4a) depicts the fiber structure 300 according to the prior art wherein vibration is introduced via a suction tool. Thus, during suctioning, fibers are adsorbed at the suction tool cavity surface wherein fibers are high compacted. However, after a first layer 310 of fibers is adsorbed on the suction tool cavity surface of a screen 146 the vibration effect decreases so that the fibers of a second layer 312 are compacted less compared to the first layer 310. The fibers of a third layer 314 are compacted less compared to the second layer 312.

[0070]FIG. 4a) depicts a schematic illustration wherein the structure of the layers 310, 312, 314 is illustrated not in detail. Thus, the transition between the layers 310, 312, 314 can be smooth. Also, the number of layers 310, 312, 314 can vary. The effect of introducing vibration via the suction tool results in a decreasing compaction of fibers and an increase in the thickness to provide a fiber structure with sufficient strength. However, OGR suffers in such fiber structures 300 since oil and grease can enter at least an outer layer (for example a third layer 314) of the fiber structure 300 and weakens the hole fiber structure 300. Also, a middle or second layer 312 may be not able to resist the oil, wherein the thickness of a last layer, for example layer 310, is not thick enough to provide sufficient resistance.

[0071]FIG. 4b) depicts a schematic illustration wherein a fiber structure 300 has a thickness which is less compared to the thickness of the fiber structure 300 according to FIG. 4a) since the fiber structure 300 is highly compacted. The substantially uniform compaction is achieved by means of vibration introduced from the pulp side. Thus, all fibers are adsorbed to the same extend since the vibration is not damped through layers 310, 312, 314 of already adsorbed fibers.

[0072]FIG. 5 depicts a schematic representation of a method 400 for suctioning fibers according to some embodiments.

[0073]In a first step 410, a pump 118 is activated to start circulation of pulp 200 inside a pulp basin 110 of a pulp reservoir 100.

[0074]In a second step 420, a suction tool 140 is transferred to the pulp basin 110 by means of a transfer device 150 and the suction tool 140 is immersed in the pulp 200 until all suction tool cavities 142 are immersed in the pulp 200.

[0075]In a third step 430, vibration is introduced in the pulp 200 by means of at least one vibrator 120. After that, suctioning 440 is started wherein fibers are adsorbed on a suction tool cavity surface 144 of a screen 146. Due to the vibration, the fibers are highly compacted so that the thickness of a fiber structure 300 is reduced and the fiber structure of a final fiber molded part (product) has a high strength.

[0076]In further embodiments, at least one distribution plate 130 is arranged in the pulp basin 110 to affect orientation of the fibers in the pulp 200 and improve the characteristics of the fiber structure 300. In further embodiments, a vibrator 120 is connected to a distribution plate 130 and the vibrations are introduced via the distribution plate 130 further improving the orientation and compacting of fibers.

[0077]After that, the suction tool 140 is transferred 450 out of the pulp 200 and the pulp basin 110 when the fiber structure 300 has reached the necessary thickness. Since the fibers are compacted and the thickness is decreased the suctioning time is also decreased improving the total cycle time of a fiber molding process.

[0078]The vibration is stopped when the fiber structure 300 has reached its final thickness or after transferring the suction tool 140 out of the pulp 200.

[0079]The fiber structures 300 adsorbed in the cavities 144 are then molded 460 to form fiber products.

[0080]The embodiments and methods disclosed herein provide improvements in fiber molding wherein the strength and OGR of fiber molded parts are increased due to high compaction of fibers. Moreover, the thickness of fiber molded parts and the process time (suctioning time) are decreased.

LIST OF REFERENCE SIGNS