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DE-102024133166-A1 - Filter device for filtering fibers from a flow and method for its operation

DE102024133166A1DE 102024133166 A1DE102024133166 A1DE 102024133166A1DE-102024133166-A1

Abstract

A filter device (10) for filtering fibers from a flow for a feed device (20) for feeding the fibers in the production of fiber-reinforced plastics has at least one filter plate (52) which can be arranged in a housing recess (74) connected to a housing bore (76) of the feed device (20) and has a curvature (90) corresponding to the shape of the at least one housing bore (76). The filter plate (52) has at least one region (64) with several slit-shaped flow channels (58). At a predetermined flow rate in a flow direction (110) and at a Reynolds number below a critical Reynolds number, the flow channels generate laminar flows in the flow channels (58). These generate a homogeneous and uniform pressure distribution in the region (64) of the at least one filter plate (52). A method for operating the filter device (10) generates the flows accordingly.

Inventors

  • Jochen Brechenmacher

Assignees

  • ARBURG GMBH + CO KG

Dates

Publication Date
20260513
Application Date
20241113

Claims (20)

  1. Filter device (10) for filtering fibers from a flow, in particular from an airflow, configured for supplying the fibers in the production of fiber-reinforced plastics, with at least one filter element arranged in and transverse to the flow in a wall (51), characterized in that at least one filter plate (52) with a curvature (90) is provided as the filter element, which has at least one region (64) with several slit-shaped flow channels (58), which in the operating state at a predetermined or predeterminable flow rate have a Reynolds number (Re) with a value below a critical Reynolds number (Re<sub> crit</sub> ) and are thereby configured to form a laminar flow in the flow channels (58) and a homogeneous and uniform pressure distribution in the region (64).
  2. Filter system after Claim 1 , characterized in that the filter plate (52) has a closed comb (53) and that the slit-shaped flow channels (58) are several parallel slit-shaped flow channels (58) each with a constant flow cross-section and a predetermined ratio of length (l) to width (b).
  3. Filter system after Claim 1 or 2 , characterized in that the wall (51) is a cylindrical wall of a housing bore (76) with an inner radius for receiving a conveying means with a cylindrical cross-section, such as a screw shaft (80) of a feeding device (20) for feeding the fibers into a processing plant (40) and is designed to be preferably swept over without contact by the conveying means arranged in the at least one housing bore (76) during the removal of the filtered fibers, and that the filter element is pre-curved and has a curvature (90) corresponding to the shape of the housing bore (76).
  4. Filter device according to one of the preceding claims, characterized in that a radius of the curvature (90) of the filter plate (52) in the uninstalled state is larger than the inner radius of the wall (51).
  5. Filter device (10) according to one of the preceding claims, characterized in that the filter device (10) has a frame (50) or a receptacle which has at least one curvature (90) corresponding to the curvature (90) of the wall (51), on which the at least one filter plate (52) is replaceably mounted, wherein in the operating state the frame is preferably arranged in a housing recess (74) connected to the at least one housing bore (76).
  6. Filter device (10) after Claim 5 , characterized in that the at least one filter plate (52) has leaf spring-like properties and is pre-tensioned with its outer edges (57), which run along a preferably longer side (66) of the filter plate (52), being received in grooves (62) of the frame in a form-fitting and/or force-fitting manner.
  7. Filter device (10) after Claim 5 or 6 , characterized in that the filter device (10) has several filter plates (52) arranged side by side with bulges (90) which are mounted on several corresponding bulges (90) of the frame and which, in the operating state when using a multi-shaft screw machine (30) with several adjacent interpenetrating housing bores (76) with a screw shaft (80) arranged therein, can be arranged and that the frame (50) has at least one central web (60) with grooves (62) between the filter plates (52) which are designed to receive outer edges (57) of the filter plates (52) in a form-fitting and/or force-fitting manner.
  8. Filter device (10) after one of the Claims 5 until 7 , characterized in that the at least one filter plate (52) has symmetrical properties and is thereby designed to allow installation in the frame (50) rotated by 180°, and that the frame (50) and the at least one filter plate (52) are designed to allow replacement or rotation of the at least one filter plate (52) by means of a sliding removal mechanism.
  9. Filter device (10) after one of the Claims 5 until 8 , characterized in that the filter device (10) has symmetrical properties and is therefore designed to be installed rotated by 180° into the housing recess (74).
  10. Filter device (10) after one of the Claims 5 until 9 , characterized in that the at least one filter plate (52) on the frame (50) is secured against displacement in the grooves (62) by two locking plates (54) which are arranged at the front of the frame (50) and are detachably attached thereto.
  11. Filter device (10) according to one of the preceding claims, characterized in that the at least one filter plate (52) has several substantially rectangular separated areas (64) arranged along a preferably longer side of the filter plate (52) with several slit-shaped flow channels (58).
  12. Filter device (10) according to one of the preceding claims, characterized in that the flow channels (58) are configured to generate a pressure drop (Δp) in a range around 50 mbar.
  13. Filter device (10) according to one of the preceding claims, characterized in that the at least one filter plate (52) has a thickness between 0.5 mm and 2 mm.
  14. Filter device (10) after one of the Claims 5 until 13 , characterized in that the frame (50) has at least one space (49) with a cross-section that remains constant in the direction of flow downstream of the filter plate (52) and following the filter plate.
  15. Filter device (10) after one of the Claims 5 until 14 , characterized in that the frame (50) is arranged in the housing recess (74) in a substantially airtight or flow-tight manner.
  16. Feeding device (20) for feeding fibers in the production of fiber-reinforced plastics, comprising at least one screw machine (30) for feeding fibers into a processing plant (40) with a housing (70) having at least one housing bore (76), a screw shaft (80) arranged concentrically in the at least one housing bore (76) and driven about an associated axis of rotation, and a feed opening (72) for feeding the fibers into the at least one housing bore (76), wherein the feeding device (20) has a suction device for drawing the fibers through the feed opening (72) into the at least one housing bore (76) by means of a flow, in particular an airflow, with a predetermined flow rate, and with a filter device (10) arranged between the suction device and the at least one housing bore (76) for filtering the fibers out of the flow, characterized by a filter device (10) according to one of the preceding claims.
  17. Method for operating a filter device (10) for filtering fibers from a flow, in particular from an airflow, for supplying the fibers in the production of fiber-reinforced plastics with at least one filter element arranged in and transverse to the flow in a wall (51), characterized in that at least one filter plate (52) with a curvature (90) is used as the filter element, which has at least one region (64) with several slit-shaped flow channels (58) which, in the operating state at a predetermined or predeterminable flow rate, generate a laminar flow in the flow channels (58) and a homogeneous and uniform pressure distribution in the region (64) with a Reynolds number (Re) with a value below a critical Reynolds number (Re <sub>crit </sub>).
  18. Procedure according to Claim 17 , characterized in that the flow channels (58) generate a pressure drop (Δp) in a range around 50 mbar.
  19. Procedure according to Claim 17 or 18 , characterized in that the at least one filter plate (52) is mounted interchangeably on a curvature of a frame (50), wherein the curvature of the frame corresponds approximately to the curvature (90) of the at least one filter plate (52), and that the at least one filter plate (52) is received in a leaf spring-like and pre-tensioned manner with its outer edges (66) in grooves (62) of the frame (50) in a form-fitting and/or force-fitting manner, and that the at least one filter plate (52) can be replaced without tools by sliding it in the grooves (62) by means of another filter plate (52) identical to the at least one filter plate (52), which engages on a side (68) of the at least one filter plate (52).
  20. Procedure according to one of the Claims 17 until 19 characterized in that an ionized airflow is used as the flow.

Description

Field of invention The present invention relates to a filter device for filtering fibers from a flow, which is configured for feeding the fibers in the production of fiber-reinforced plastics, having the features according to the preamble of claim 1, a corresponding feeding device for feeding fibers with a filter device having the features according to the preamble of claim 16 and a method for operating a filter device for filtering fibers from a flow for such a feeding device having the features according to the preamble of claim 17. State of the art In the production of fiber-reinforced plastics, fibers such as glass fibers, carbon fibers, or fibers from renewable resources are incorporated into the plastics to increase their strength and stability. For this purpose, bundles of fibers are fanned out and cut into fiber pieces of the desired length in a shredding device. These pieces are then transported by a feeding device, such as a screw extruder, to a unit where raw materials, such as plastic granules, are plasticized. In this plasticizing unit, the molten plastics are mixed with the fiber pieces. Such a feeding device typically consists of a screw conveyor through which the fiber pieces are transported towards the plasticizing unit. During the comminution of the fibers, waste products such as fiber dust or very short fiber fragments are generated. Both the fiber fragments and the waste products are drawn into the screw conveyor by the comminution device via a flow, such as an airflow, generated by a suction device. The fiber fragments are also drawn to the underside of the screw conveyor or the side opposite the fiber feed point, thus achieving a uniform distribution within a housing bore of the screw conveyor, particularly around the at least one conveying element located therein. The waste products, on the other hand, are removed from the airflow in the housing bore by a filter device located between the housing bore and the suction device. A disadvantage of this prior art is that the waste products lead to clogging of the filter device after a relatively short time, resulting in increased maintenance requirements. Previous solutions for filter systems use, for example, filter fleeces with fine-mesh filter structures, filters with perforations, or filters with filter lamellae. In the EP 2 218 568 A1 A screw machine for processing at least partially powdered bulk material is disclosed, comprising a housing with at least one housing bore and a screw arranged in the housing bore. A vacuum housing section is provided, designed as a detachably mounted vacuum housing insert in which a metal fleece is interchangeably held as a gas-permeable wall section on a base body. The WO 2014/048667 A1 Disclosure reveals a feeding device for fibers using a multi-screw machine for the lateral feeding of fibers into a processing plant for the production of fiber-reinforced plastics. The multi-screw machine comprises a housing, several intersecting housing bores, rotatably driven screw shafts arranged therein, and a feed opening. A suction device is provided for drawing the fibers through the feed opening into the housing bores, generating an airflow that draws the fibers in. The fibers are filtered out of the airflow by means of a filter device. To ensure a long service life, the filter device has several flow channels with a cross-section that widens abruptly in one direction of flow. The filter system of the WO 2014/048667 A1 It consists of a series of interconnected metallic lamellae, between which flow channels form. These channels abruptly widen in cross-section and, in particular, in width in the direction of flow towards the underside of the filter assembly. This abrupt change affects the flow parameters, leading to vortex formation, turbulence, backflow at the separation point/area, and sudden pressure changes. The effect is comparable to flow resistance. Due to the inconsistent cross-sections, inconsistent pressure conditions or pressure differences arise within the flow channels. These promote fiber accumulation and clogging. Clogging of the filter assembly. The special geometry of the filter pack, constructed from lamellae, with its inconsistent cross-sections in the flow direction and inconsistent pressure conditions, also promotes the lamellae from opening or separating, a so-called fanning effect, which also leads to fiber accumulation and clogging. To counteract this, a high tightening torque is used when assembling the lamellae, which can, conversely, lead to distortion or deflection of the lamellae and thus to inconsistent cross-sections between them. During assembly, especially after maintenance of the filter assembly, contamination or soiling can occur in the flow channels and between the contact surfaces of the spacer plates between the lamellae, leading to assembly inaccuracies. These inaccuracies accumulate with each spacer plate. All of this can lead to unfavorable flow conditions. Similarly, assem