Filter wheel filtration system for high-pressure filtration of molten plastics

Abstract

A filter wheel filter device for high-pressure filtration of molten plastics, comprising at least a casing, which comprises at least: an inlet plate with at least one inlet passage, an outlet plate with at least one inlet and outlet passage, at least one spacer element arranged between the inlet and outlet plates, as well as a bearing ring (18) on which a filter wheel (20) arranged between the inlet and outlet plates is rotatably supported, and clamping pins (19.1) guided through the bearing ring (18), via which the inlet plate together with the outlet plate is clamped surrounding the bearing ring (18) inserted between the inlet and outlet plates, and the filter wheel (20) can be arranged between the inlet and outlet passages, respectively. a flow-through area is formed between the openings of the inlet and outlet passages facing the filter wheel (20), and the surfaces of all filter locations (22.1...22.13) which at least partially overlap this flow-through area (40), projected onto the inlet and outlet plates, together form an active pressure surface area (44), and a lubrication gap is formed between the sealing surfaces (23, 24, 25) of the filter wheel (20) and the inner surfaces of the inlet and outlet plates, respectively, a filter wheel filtration device (100), characterized in that: the cross-sectional area A2 of the bearing ring (18) is at least 9 times the cross-sectional area A1 of the central tensioning pin (19.1), and the cross-sectional area A1 of the central tensioning pin (19.1) is 0.1 to 0.4 times the area A3 of the active pressure surface area (44).

Description

Technical Field

[0001] The present invention relates to a filter wheel filtration device for high - pressure filtration of molten plastic, which has the characteristics of the superordinate concept of claim 1.

Background Technology

[0002] When filtering molten plastic, agglomerates or solid particles must be screened out, and then the melt can be supplied to a further processing device such as an extrusion device equipped with a nozzle. In order to enable uninterrupted production, various configurations of filtration devices are known in which a new, uncontaminated filter is provided in the flow path and the contaminated filter is removed from the flow path so that the filter can be replaced during continuous operation. A particularly difficult point in the filtration of molten plastic is that filtration must be carried out at high temperatures and at high pressures which are already 250 bar to 300 bar in normal use.

[0003] The type of filtration device described at the beginning is basically described in German Patent Publication No. 3302343 and European Patent Publication No. 0569866, and has been continuously improved upon therein. Such a filtration device can filter molten plastics and other medium to high viscosity fluids, in which case the limitation to low viscosity media is due to the structural form, as will be explained below. The filter wheel supporting the individual filter elements is positioned between two casing plates held at a predetermined distance from each other, so that on the one hand the filter wheel is still rotatable, and on the other hand the gap between the sealing surface of the filter wheel and the adjacent sealing surface of the casing plate is narrowed so that, in terms of the viscosity of the media being filtered, no leak flow is formed in the gap that opens outward. In short, the type of filter wheel filtration device described at the beginning cannot achieve an airtight seal to the outside, and rather the gap width is maintained so that the media, based on its viscosity, cannot flow to the outside along the gap that opens outward between the filter wheel and the casing. In contrast, low-viscosity aqueous media cannot be processed using the open structural form of a filter wheel filtration system because they may leak out at the edges.

[0004] German Patent Application Publication No. 3341508 describes another filtration device of the type described at the beginning, and further discloses a drive mechanism. The drive mechanism consists of a drive element in the form of a hydraulic cylinder attached to the side edge of the casing, a transmission lever, and a freewheel unit, the freewheel unit consisting of a pinion that meshes with the outer teeth of the filter wheel, and a freewheel that allows the transmission lever to return without moving the filter disc.

[0005] German Patent Application Publication No. 3522050 describes a filter wheel filtration device comprising a drive mechanism via a ratchet gear formed on the outer surface of the filter wheel and a feed rod that engages with the gear, for moving the filter wheel in steps.

[0006] German Utility Model No. 29908735 describes a filter wheel filtration system with a backwashing device. A device is provided to increase the pressure in the backwash conduit for backwashing. Means for operating the filtration system at high pressure and preventing leaks are not disclosed.

[0007] Similarly, German Patent Application Publication No. 3902061 describes a filter wheel filtration system with a backwashing device that does not have special suitability for high-pressure applications.

[0008] The filter wheel filtration system described in International Publication No. 2014 / 184220 is adjusted to minimize pressure fluctuations, but it is not explicitly specified for high-pressure applications and is therefore unsuitable.

[0009] The special advantage of the type of filtration device described at the beginning is that multiple individual filters can be arranged on the filter wheel, and these individual filters can be continuously passed through and easily moved to the opposite side of the flow path in the casing for cleaning purposes, or they can be replaced. The structure of the filtration device is also simple and inexpensive due to the layered structure of the casing.

[0010] However, the main challenge lies in the sealing between the outer casing plates and the filter wheel surrounded between them. The casing portions must be tightly compressed to surround the filter wheel, so that the flow pressure does not cause excessive expansion of the casing, thereby preventing the formation of significant leaks where the fluid would excessively flow out at the side edges of the casing. On the other hand, the filter wheel must remain movable and cannot rotate further if it is excessively clamped. In other words, under all operating conditions, a predetermined minimum gap width must exist between the sealing surface on the end face of the filter wheel and the opposing contact surfaces on the inlet and outlet plates of the casing. In this case, the required gap width depends on the fluid to be processed each time, its viscosity, processing temperature, and the flow pressure in the area of ​​the filter. While the basic effort of sealing against leakage flow toward the edges is achieved, a sufficient gap width is always required so that a very small amount of fluid leakage beyond the seal web is possible, and so that a kind of lubricating film is formed on both end faces of the filter wheel by the fluid itself.

[0011] By appropriately matching the height of the filter wheel with the height of the spacer element surrounding the filter wheel, positioned between the inlet and outlet plates, it is possible to adjust the specific gap width for the intended processing process. However, since this gap width is in the range of a few micrometers, the manufacturing of the spacer element and the filter wheel to which it belongs, forming a so-called inner pair fitted together between the inlet and outlet plates, is extremely difficult. In fact, it has been shown that even when the gap width is calculated and manufactured with great care, problems with the mobility of the filter wheel arise. This problem can only be solved by reducing the preload, but this also introduces a problem of non-sealing.

[0012] In the most recent known concepts of filter wheel filtration systems, at least two filter locations are simultaneously present in the flowing cross-section, hereafter referred to as the flow-through region. The flow-through region is the front-inflow surface region available for filtration. Typically, the first filter location partially overlaps the flow-through region, so that operating pressure is generated within the incoming filter cavity. Another filter location is located entirely or almost entirely inside the flow-through region. Part of the second or third filter location partially overlaps the flow-through region at its upper edge when viewed in the rotational direction. However, filter cavities that are separated from the flow-through region and move into or out of the flow-through region are under full operating pressure, even if the filter cavity overlaps the flow-through region over only a small area. Therefore, since there are no angular positions of the filter wheel where a pressure region wider than the flow-through region exists and the flow path is completely or substantially interrupted, it is possible for the filtration system to operate at a nearly constant pressure.

[0013] The plastic contained within such blocked filter locations remains under operating pressure of up to 500 bar. Therefore, not only are the directly flowing regions and the adjacent surface regions of the filter locations that partially overlap the flowing regions under pressure, but the filter cavities that have already been moved out of the actively flowing pressure regions are also under pressure. Assuming there are typically at least 10 filter locations on the filter wheel, and especially 13, the pressure-loaded region extends in the rotational direction from the first filter location that is just beginning to partially overlap the flowing region to the last filter location just before it enters the filter replacement position. Consequently, more than half of the filter locations on the filter wheel are under high internal pressure, contributing to the widening of the lubrication gap and causing leakage.

[0014] German Patent Application Publication No. 102017100032 describes the relationships that arise with respect to the geometric shape of the filter gap during operation. The gap width does not have a geometrically constant size during operation. This is because the gap expands due to the internal pressure during filtration operation, and by inserting a gap width adjustment layer between the spacer element and the adjacent casing plate, a predetermined operating point can be adjusted such that, on the one hand, the gap is large enough to fill with fluid that also functions as a lubricant and allow the movement of the filter wheel, and on the other hand, the gap width is limited to a width that does not cause large leakage flow with respect to the maximum internal pressure during operation. It is desirable to avoid uncontrolled leakage flow so that components located on the outer surface of the filtration device, such as measuring sensors, swivelable doors in the filter replacement station, or drive mechanisms for the step-like rotation of the filter wheel, are not damaged by the fluid that flows out and solidifies on the outer surface. Such adjustment of the operating point is easily possible for typical operating pressures of approximately 250 bar, up to a maximum of 300 bar, particularly by inserting a gap width matching layer. In this case, it is desirable that the filter wheel remains movable even under near-zero pressure conditions, and that leakage flow is blocked or reduced under maximum operating pressure.

[0015] The difficulty in adapting a filtration device for a given operating condition lies not in designing it for a certain high operating point within a narrow range, but rather in ensuring operation in near-zero pressure conditions as well as up to the maximum operating pressure. In this case, known concepts reach their limit at the aforementioned maximum pressure of 250 to 300 bar. [Overview of the project] [Problems that the invention aims to solve]

[0016] Therefore, the object of the present invention is to provide a high-pressure filter wheel filtration device in which the functionality of the filtration device in a no-pressure state is guaranteed as well as at other operating points in which a fluid with a high pressure of 500 bar or more is pressed through the filtration device, without individually adjusting the preload of the casing portion before or during operation. [Means for solving the problem]

[0017] This problem is solved by a filter wheel filtration apparatus for high-pressure filtration of molten plastic having the features of claim 1.

[0018] The concept of the present invention stipulates that, although the configuration of the filter wheel filtration device is fundamentally unchanged, the casing tightening pins supporting the bearing ring, the bearing ring itself, the area of ​​the filter portion through which the flow passes, and adjacent pressure-loaded filter portions are coordinated with each other in a special manner.

[0019] In general, such adjustments for high-pressure filtration of at least 500 bar result in the outer diameter of the filter wheel, which defines the filter cavity and forms the starting point of the ring-shaped outer sealing surface, being approximately the same size as that of conventional filter wheel filtration devices. Consequently, the casing is also approximately the same size.

[0020] However, in the prior art, the diameter of the inner ring-shaped sealing surface defining the filter cavity is selected to be as small as possible in order to increase the radial extension and thus the filter area available for filtration, whereas in the present invention, the filter portion is pushed aside by the outer edge of the filter wheel. In this case, the inner bearing ring and / or the inner sealing surface on the filter wheel appear as a large, seemingly wasted surface area. That is, the present invention deliberately avoids the obvious approach of increasing the filter area available for filtration in the filter wheel under a given configuration size of the filtration device casing, or decreasing the configuration size of the filtration device casing under a given filter area. Placing a relatively small filter portion further out on the outer edge of a large-diameter filter wheel, as defined by the present invention, may be mistakenly perceived as irrational and economically disadvantageous at first glance.

[0021] The present invention specifies special geometric adjustments for the bearing ring, casing tightening pin, and so-called active pressure surface area. The active pressure surface area includes the entire area of ​​the filter portion that is simultaneously under operating pressure. The active pressure surface area is the surface projected onto the inlet and outlet plates, that is, the surface that, in relation to the operating internal pressure, applies an expanding force to the casing, and consequently expands the lubrication gap between the filter wheel and adjacent surfaces of the casing.

[0022] Since the filter area where the flow-through region and its area partially overlap are still under full operating pressure, the area of ​​the active pressure surface region is usually larger than that of the flow-through region. - The cross-sectional area A2 of the bearing ring is at least 9 times, and especially 9 to 13 times, the cross-sectional area A1 of the central tightening pin. - The cross-sectional area A1 of the central tightening pin is 0.1 to 0.4 times the area A3 of the active pressure surface region. It is stipulated that...

[0023] Preferably, a predetermined aspect ratio of the active pressure surface region having the area A3 is defined, and in this case, the central length of the arc-shaped active pressure surface region is 1.9 to 2.5 times the radial width. For this purpose, the length is measured along the middle pitch circle passing through the center of the filter location. If the filter location does not have a symmetric contour, instead, the surface centroid of the filter location is selected as the reference point for the pitch circle. Thereby, in addition to other geometric criteria, the active area is defined to be long and narrow rather than short and wide.

[0024] In consideration of the high preloading force and the resulting surface pressure, in a preferred embodiment, the thicknesses of the inlet block and the outlet block are each defined to be at least 2.5 to 3.5 times the thickness of the bearing ring and / or spacer element inserted therebetween.

[0025] The active pressure surface region is preferably limited to the region adjacent to the openings of the inlet passage and the outlet passage. After the filter cavity is moved outside the through-flow region, at least one pressure relief hole is provided in the casing to avoid remaining under pressure. This pressure relief hole opens into the orbit described by the filter location during the rotation of the filter wheel and is advantageously connected via a flow path to conduct the fluid to the outer surface of the casing. Thus, the region of the pressure relief hole forms a pressure drop and provides a tangential flow path extending in the rotational direction from the substantially closed filter cavity under pressure.

[0026] Thereby, the pre-permeated filter cavity still under pressure is suddenly depressurized when it is moved outside the through-flow region. As a result, only the expansion of the casing and the widening of the gap between the filter wheel and the adjacent casing plate are caused by the directly permeated filter location. However, there is no longer a filter chamber under pressure that contributes to the expansion of the casing outside the pressure region and can only be depressurized gradually by leakage flow. <-

[0027] The tangential pressure relief defined by this invention is achieved when the filter portion, located forward and upward in the rotational direction, aligns with the opening of the pressure relief hole when the filter portion is completely separated from the pressure region and there is no further flow connection with the region through which the fluid is flowing. Furthermore, the pressure relief hole is geometrically defined to open in the trajectory traced by the filter portion as the filter wheel rotates, and to be connected to guide fluid to the outer surface of the casing via a flow path. In this case, it is important that the distance between the opening of the pressure relief hole and the forward and upward edges of the funnel-shaped openings of the inlet and outlet passages, as viewed in the rotational direction, is always greater than the maximum arc length of the filter portion. As a result, the filter cavity is first completely separated from the region through which the fluid is flowing, and then the filter wheel must rotate some further until a flow connection can be established between the closed, but still under pressure, filter cavity and the pressure relief hole.

[0028] Since the molten plastic is compressible, pressure relief occurs independently by the outflow and discharge of a small amount of molten plastic through the pressure relief holes. Once pressure compensation is complete, the outflow of molten plastic from the filter cavity abruptly stops again, meaning the filter cavity remains filled.

[0029] According to the present invention, the number of filter cavities that are pressure-loaded can be limited to a maximum of three during a single intentional pressure release at each contaminated filter location, at least two of which partially overlap the flow-through region during operation, and one which is moved toward the pressure release port.

[0030] To release pressure, it is necessary to discharge a small amount of the plastic fluid compressed at the filter. Preferably, this discharge is carried out through a pressure relief passage that starts from the pressure relief hole and leads mainly to a backwash area located on the underside of the filter wheel filtration device. The backwash device can remove contaminating particles adhering to the filter element. Since this requires the discharge of molten plastic containing contaminating particles, the underside of the filtration device is separated from other devices, and a suitable collection device can be prepared there.

[0031] In particular, the pressure relief port is located on the inlet plate side. In this case, it is desirable that the backwash passage and the pressure relief passage end in as close to the same region as possible within the filtration device, i.e., in the lower region. This is because, in this case, the material can be directly guided by gravity to the collection container located below the filtration device.

[0032] At least one pressure relief hole is provided on the outlet plate side, where cleaned molten material is present, and this pressure relief hole can be directly connected to the unpressurized portion of the backwash passage in the outlet plate of the casing. This allows for at least partial backwashing of the filter insert elements in the filter cavity, which is necessary anyway, by the amount of molten plastic discharged through the tangential flow path for pressure relief. Thus, an additional function can be added by the intermittently flowing fluid for pressure relief, and the output of the backwashing device's drive mechanism, such as moving a piston to perform backwashing, can be reduced. Furthermore, less molten material needs to be diverted from the production flow for backwashing.

[0033] In other words, in any case, in a filter wheel filtration system equipped with a backwashing device, the pressure relief according to the present invention does not result in a significant loss of filtered media in terms of net balance.

[0034] Another preferred embodiment of the present invention is assumed to additionally allow for at least one radial pressure relief channel.

[0035] In this sense, "radial direction" refers to the flow that originates from the position of the filter cavity in the filter wheel and flows inward towards the center or outward towards the outer surface; the flow direction does not necessarily have to be strictly radial in a geometric sense.

[0036] In particular, the bearing ring on which the filter wheel is supported by a sliding bearing can be utilized for further pressure relief. Molten plastic flowing through the filter gap, which expands near the pressure region, reaches the bearing ring, which is essentially intended for the purpose of forming a sliding bearing. However, under high-pressure operation, more molten plastic than is needed for lubrication locally reaches the area of ​​the bearing ring. To prevent the formation of axial leakage flow along the bearing ring that flows out in front of the casing inlet or outlet plate, preferably, at least one additional pressure relief hole is provided, located at an angular position laterally to the flow region or below the flow region, reaching up to the lowest point of the bearing ring. If the top surface of the casing is at 12 o'clock and the bottom surface of the casing is at 6 o'clock, and the filter portion to be passed through is located, for example, at the 3 o'clock position, then the radial pressure relief hole is preferably located between 2 o'clock and 6 o'clock.

[0037] In a more advantageous embodiment, it is envisioned that leakage flow generated from the pressure range toward the outer circumference of the filter wheel is also captured and diverted. This leakage flow reaches the region of the outer teeth of the filter wheel necessary for driving. If molten plastic solidifies there and is transported to the outer surface of the casing, the molten plastic may solidify, which may damage the drive mechanism after several rotations of the filter wheel. To prevent this, according to the present invention, it is envisioned that another pressure relief opening be provided in the gap between the teeth on the outer surface of the filter wheel and an adjacent spacer element, which may allow molten material that has entered the gap to be guided outward by gravity, in particular to the lower region of the casing, from where the molten material can flow out into a collection container installed below it.

[0038] It is advantageous to provide at least one tangential pressure relief passage on the side of the inlet plate. This is because, on the side of the inlet plate, there is free access to the filter cavity, whereas on the opposite side, i.e., the back of the filter wheel, the opening is partially covered by a perforated plate that supports the actual filter element inserted into the filter cavity.

[0039] The cross-section preferably widens in the flow direction, i.e., from the pressure relief hole to the discharge opening on the underside of the housing, rather than narrowing along the extension of the flow path. This prevents foreign matter or plastic plugs, or degraded material, accumulated from residual material from a previous production cycle, from causing stagnation in the passage that could hinder pressure relief. Such a configuration with a widening passage cross-section preferably applies to all passages for leading material from the casing to the collection tank.

[0040] The present invention will be described in detail below with reference to the illustrated embodiments. The drawings are shown in detail. [Brief explanation of the drawing]

[0041] [Figure 1] This is a plan view showing the intermediate plane of a conventional filter wheel filtration system. [Figure 2] This is a plan view showing the filter wheel of the filter wheel filtration apparatus according to the present invention. [Figure 3] This is a perspective view showing the casing of a filter wheel filtration system. [Figure 4] Figure 1 is a perspective view showing the casing with the inlet plate removed. [Figure 5] This is a perspective view showing a filter wheel filtration system without the filter wheel, in the mid-plane. [Figure 6] This is a perspective view showing a filter wheel filtration system with an inlet plate partially cut out and shown in a transparency diagram. [Figure 7] This is a perspective view showing a filter wheel filtration system along with the filter wheel in the intermediate plane. [Figure 8] This is a perspective view showing a cross-section through the rotation axis of the filter wheel. [Figure 9] This is a detailed enlarged view of Figure 8. [Figure 10] This is a tension graph related to a part of a filtration system. [Modes for carrying out the invention]

[0042] Figure 1 is a plan view showing the intermediate plane of a conventional filter wheel filtration device 100'. In this case, the inlet plate that guides fluid to the filter locations 21' on the rotatable filter wheel 20' has been removed. Behind it, an outlet plate 12' is positioned to guide fluid out from each filter location 21' to the outside. Each filter location 21' is defined by a ring-shaped inner sealing surface 23', a ring-shaped outer sealing surface 24', and a web 25' extending between the inner sealing surface 23' and the outer sealing surface 24'. The filter wheel is surrounded by two relatively small intermediate plates 13', 14' on the left and one relatively large intermediate plate 15' on the right. Within the area of ​​intermediate plate 15', there is a pressure-loaded active pressure surface area 44', which is roughly indicated on the filter wheel 20' by a dashed line. A bearing ring 18' is further positioned on the intermediate plane, and a casing tightening pin 19 is guided through this bearing ring. A filter wheel 20' is supported by a bearing ring 18', and a sliding bearing is formed between them.

[0043] Figure 2 shows a plan view of the optimal filter wheel 20 according to the present invention, which has a total of 13 filter locations 21. The outer diameter 3 of the outer edge of the outer seal area 24 and simultaneously the outer edge of the filter locations 21 remain unchanged compared to the filter wheel 20' in Figure 1.

[0044] The outer diameter of the bearing ring 18 has been significantly increased. For comparison, circumference 1 shows the outer circumference of the bearing ring 18' in Figure 1. According to this, the inner sealing surface 23 and the inner demarcation lines of the filter area 21 have also been shifted outward. For comparison, circumference 2 shows the corresponding circumference in Figure 1.

[0045] Figure 10 shows the force F with respect to strain ε in the system, with the casing tightening pin-bearing ring-casing plate plotted as a tension graph. This is a qualitative figure, not to scale, and the following example of the design of a filter wheel filtration device according to the present invention will be explained based on this figure.

[0046] The area A3 of the active pressure surface region associated with the three filter locations 21 is defined as A3 = 100 cm². 2 The design for high-pressure filtration assumes a maximum operating pressure of 500 bar. This pressure generates an expanding force of 500 kN, equivalent to approximately 50 tons, in the active pressure surface region, causing the filter gap to widen between the filter wheel 20 and the inlet plate 11, or between the filter wheel 20 and the outlet plate 12, and resulting in an enhanced leak flow. The slope of line 5 in Figure 10 corresponds to the spring constant of the tightening pin 19 guided through the bearing ring 18.

[0047] The package, consisting of an inlet plate 11, a bearing ring 18, and an outlet plate 12, which is preloaded by a casing tightening pin 19, can be considered as a single flange having the cross-section of the bearing ring 18 with sufficient precision. This is because the inlet plate 11 and the outlet plate 12 are extremely rigid, especially when the thicknesses of the inlet plate 11 and the outlet plate 12 are set to 2.5 to 3.5 times the height of the bearing ring 18, i.e., its axial extension.

[0048] For example, if the area of ​​the fastening pin is A1 = 33 cm² 2 Therefore, the ring area is A2 = 357 m². 2 Therefore, the cross-sectional area of ​​the bearing ring 18, i.e., the ring surface A2 obtained by subtracting the central hole for the tightening pin, is preferably about 10 times the cross-sectional area A1 of the tightening pin 19, so the spring constant becomes about 10 times larger. The slope of line 6 corresponds to this spring constant, although this is qualitative and not to scale.

[0049] At the operating point B, the preload force F that results in the compression of the package described above occurs. V The maximum expanding force F formed during operation is added. A This partially reduces the load on the compressed package, but in this case, the preload is never completely eliminated.

[0050] The downward-sloping lines along the horizontal axis show, on the one hand, the deformation when a preload force is applied (when there is no expanding force due to pressure flow), and on the other hand, the deformation when pressure is applied during operation.

[0051] The preload is adjusted so that the lubrication gap between the inlet plate 11 and the filter wheel 20, and between the outlet plate 12 and the filter wheel 20, is minimized, or even so that there is no lubrication gap at all.

[0052] As can be seen from the schematic diagram in Figure 10, the change in deformation during operation is extremely small. This is because the area relationship between areas A1 and A2 defined by the present invention is selected to be clearly different from a ratio of 1:9 to 1:13. This results in a change in strain during operation that is small enough to avoid the remarkably high slope of line 6 in the diagram, excessive gap widening, and the resulting significant leakage flow.

[0053] In this case, this calculated design results in the structural configuration described above for comparison between Figures 1 and 2. In this case, the filter portion according to the present invention is thinner and visually further to the outer edge compared to the prior art, and in the center there is a bearing ring that appears to be oversized, which contradicts the usual efforts to maximize the filter area.

[0054] Figure 3 shows a perspective view of the casing 10 of the filter wheel filtration device 100, specifically a view of the inlet plate 11 with an inlet passage 13. The outlet plate 12 is connected to the inlet plate 11 via spacer elements 15 and 16, forming an intermediate space between the inlet and outlet plates where the filter wheel is supported. All three adjacent elements of the casing 10—the inlet plate 11, the spacer elements 15 and 16, and the outlet plate 12—are screw-fastened to each other via a total of seven casing fastening pins 19.1, 19.2, and 19.3, and are fastened to each other by a preload designed for the intended operating pressure. The central axis of the casing fastening pins 19.1 at the center of the casing simultaneously forms the axis of rotation of the filter wheel. The drive unit 30 for the filter wheel is located on the outer surface of the casing 10.

[0055] Figure 4 is a perspective view of a filter wheel filtration device 100 similar to Figure 1, but the inlet plate has been removed so that the internally located filter wheel 20 can be seen. Furthermore, another spacer element 17 can be seen at the upper casing edge, which connects the two lateral spacer elements 15, 16 to each other without gaps. As a result, the filter wheel 20 is almost completely surrounded on its outer circumference. Therefore, the opening in the casing 10 is present only in the lower region in the form of a discharge opening 48, which serves to allow the intentional outflow of molten material into a collection container located below the filtration device. In the illustrated embodiment, the filtration device has a drive mechanism that acts on the annular gear row 21 via a drive pinion 31. In the case of an alternative drive mechanism via a ratchet that engages with the appropriate gear row on the outer circumference, the casing has at least one additional opening in the upper region at the engagement point of the drive mechanism.

[0056] The filter wheel 20 is provided with a plurality of filter locations 22.1...22.13 in a known form, and 13 filter locations in the illustrated embodiment. Each filter location 22.1...22.13 is defined by an inner ring-shaped seal web 23 and an outer ring-shaped seal web 24 provided on the surface of the filter wheel 20, and an inner-to-outer seal web 25 extending between these seal webs. A stationary bearing ring 18 is positioned in the center, and the filter wheel 20 is supported by this bearing ring. A sliding bearing is formed between the outer surface of the bearing ring and the inner surface of the central hole of the filter wheel 20. An annular tooth row 21 is formed on the outer circumferential surface of the filter wheel 20.

[0057] The casing fastening pins 19.1, 19.2, and 19.3 compress the spacer elements 15, 16, and 17 that are fastened between the outer casing plates on the inside of the preloaded surface, thereby reducing the gap between the inlet plate 11 and the outlet plate 12 and the filter wheel 20 surrounded between these plates.

[0058] The dotted lines correspond to the contours of the funnel-shaped openings of the inlet and outlet passages of the filter wheel 20, indicating the flow-through region 40 available for filtration. The filter wheel 20 rotates counterclockwise. At the angular position of the filter wheel 20 shown in Figure 2, filter section 22.1 partially overlaps the flow-through region 40. This creates an operating pressure throughout filter section 22.1. Filter section 22.2 is entirely located in the flow-through region 40. Filter section 22.3 also partially overlaps the flow-through region 40, so an operating pressure is also created here. Filter section 22.4 is rotated outside the flow-through region 40, in which case the fluid stored here is still under operating pressure.

[0059] Figure 5 is a perspective view of the filter wheel filtration apparatus 100, similar to Figures 1 and 2, but with the filter wheel removed. Only the annular teeth 21 of the filter wheel are shown to indicate the position of the filter wheel. The contour of the funnel-shaped opening 14.1 of the outflow passage 14 corresponds to the flow-through region 40. The backwash passage begins from the lateral opening 12.2 of the outflow plate 12, and this backwash passage opens into an elongated slit-shaped backwash nozzle 49 in the lower region of the filter wheel. The fluid generated during backwashing flows out from the casing opening 48.

[0060] Figure 6 shows the filtration device 100 including all the casing elements 11, 12, 15, 16, 17 and the filter wheel 20, where the right side of the inlet plate 11 of the casing, where the inlet passage 13 is located, is partially cut out and shown in a transparency view. A filter replacement position 10.1 is provided on the left side of the casing, where the inlet plate 11 is open, allowing for the replacement of the filter elements. The filter replacement position 10.1 can be closed by a door (not shown). The inlet passage 13 can be clearly seen to have expanded into a funnel-shaped opening 13.1. The position and shape of this funnel-shaped opening are the same as the funnel-shaped opening 14.1 in the outlet plate 12 (see Figure 3). Between these funnel-shaped openings, a flow-through region 40 is formed, outlined by a dotted line, within which the molten plastic flows through the filter elements installed in the filter locations 22.1...22.13.

[0061] At the position of the filter wheel 20 in Figure 6, filter location 22.5 is precisely aligned with the pressure relief hole 41, which is connected to the filter wheel 20 laterally and continues downward in the pressure relief passage 41.1. Therefore, the filter cavity at filter location 22.5 is already pressure-free. When rotating counterclockwise, the subsequent filter location 22.4 is still under high internal pressure. Filter location 22.4 is no longer aligned with the flow-through region 40 and is completely isolated from the next subsequent filter location 22.3 by the seal web 25. Filter locations 22.2 and 22.3 are completely located in the flow-through region 40. Filter location 22.1 is just beginning to align with the flow-through region 40. If a filter replacement has been performed beforehand, pre-injection is carried out at this position and internal pressure is formed.

[0062] Another pressure relief hole 42 leads directly from the side into the sliding bearing surface between the inner circumferential surface of the bearing hole of the filter wheel 20 and the bearing ring 18 which is tightly fastened to the casing. This pressure relief hole continues downward to another pressure relief passage 42.1.

[0063] Figure 7 shows a vertical cross-sectional view of the casing 10 showing the filter wheel 20, where the cutting plane is in the mid-plane where the lubrication gap is formed and extends parallel to the plane of the filter wheel 20. The dotted arrows indicate the approximate flow direction of the molten plastic from the filter locations 22.2, 22.3 in or near the through-flow region 40 toward the pressure relief holes 41, 42. These flow directions differ in that the flow toward the upper first pressure relief hole 41 travels within the trajectory of the filter locations 22.1...22.13 of the filter wheel and is therefore approximately "tangential," while the flow toward the lower second pressure relief hole 42 crosses the inner ring-shaped seal web 23 of the filter wheel and is therefore called "radial."

[0064] Figure 8 is a perspective view showing a cross-section of the filter wheel 20 passing through the rotation axis, which is the same as the central axis of the casing tightening pin 19.1 and the central axis of the bearing ring 18. The lower pressure relief hole 42 is located in the cross-sectional plane, and this pressure relief hole continues downward in the pressure relief passage 42.1.

[0065] Important details regarding the pressure relief generated by the second pressure relief hole 42, the so-called "radial" pressure relief, are revealed for the first time in the enlarged view of a portion of Figure 8, shown in Figure 9. Where the bearing ring 18 and the hole in the filter wheel 20 come into contact with each other to form a sliding bearing, the bearing ring 18 and the filter wheel 20 are provided with chamfered edges, so that the adjacent chamfered edges form a ring passage 43 with a triangular cross-section. The volume of this ring passage is significantly larger than the ring gap of the sliding bearing 26, allowing molten plastic to be discharged for pressure relief without the need to modify the casing portion or other parts of the filter wheel 20 and bearing ring 18 pair. [Explanation of Symbols]

[0066] 100,100' filter wheel filtration system 10,10' casing 10.1 Filter replacement location 11,11' Inflow plate 12,12' Outflow Plate 13,13' Inflow passage 13.1 Funnel-shaped opening 14,14' Outflow passage 14.1 Funnel-shaped opening 15,16,17; 15',16',17' Spacer element 18,18' bearing ring 19, 19', 19.1...19.3 Casing tightening pins 20,20' filter wheel 21,21' Circular dentition 22',22,22.1···22.13 Filter locations 23,23' Inner seal web 24,24' Outer seal web 25,25' Seal Web 26,26' Plain bearing 30 Drive unit 40 Through-flow area 41 Pressure relief holes 41.1 Pressure relief passage 42 Pressure relief holes 42.1 Pressure relief passage 43 Ring passage 44,44' Active pressure surface region 48 Release aperture 49 Backwash nozzle

Claims

1. A filter wheel filter (100) for high-pressure filtration of molten plastic, comprising at least a casing (10), the casing comprising at least, - An inlet plate (11) having at least one inlet passage (13), - An outflow plate (12) having at least one outflow passage (14), - At least one spacer element (15, 16, 17) positioned between the inlet plate (11) and the outlet plate (12), and a bearing ring (18) on which a filter wheel (20) positioned between the inlet plate (11) and the outlet plate (12) is rotatably supported, - A central tightening pin (19.1) guided through the bearing ring (18), through which the inlet plate (11) is tightened together with the outlet plate (12) while surrounding the bearing ring (18) inserted between the inlet plate and the outlet plate, It has, - The filter wheel (20) has a plurality of filter locations (22.1...22.13) that can be positioned and through which flow can pass between the inlet passage (13) and the outlet passage (14), - A flow-through region (40) is formed between the openings (13.1, 14.1) of the inflow passage (13) and the outflow passage (14) that face the filter wheel (20), - All filter locations (22.1...22.13) that at least partially overlap the flow-through region (40) have surfaces projected onto the inlet plate (11) and the outlet plate (12) that together form a single active pressure surface region (44). - A lubrication gap is formed between the sealing surfaces (23, 24, 25) of the seal web of the filter wheel (20) and the inner surfaces of the inlet plate (11) and the outlet plate (12), respectively. In a filter wheel filtration device (100), - The cross-sectional area A2 of the bearing ring (18) is at least 9 times the cross-sectional area A1 of the central tightening pin (19.1), - The cross-sectional area A1 of the central tightening pin (19.1) is 0.1 to 0.4 times the area A3 of the active pressure surface region (44). A filter wheel filtration device (100) characterized by the following features.

2. The filter wheel filtration apparatus (100) according to claim 1, characterized in that the central length of the arc-shaped active pressure surface region (44) is 1.9 to 2.5 times the radial width of the active pressure surface region (44).

3. The filter wheel filtration apparatus (100) according to claim 1 or 2, characterized in that the thickness of the inlet plate (11) and the outlet plate (12) is at least 2.5 to 3.5 times the thickness of the bearing ring (18) and / or the spacer elements (15, 16, 17), respectively.

4. - The inlet plate (11) and / or the outlet plate (12) are provided with at least one pressure relief hole (41), which opens in the trajectory traced by the filter locations (22.1...22.13) when the filter wheel (20) rotates, and is connected to guide fluid to the outer surface of the casing (10) via a pressure relief passage (41.1). - When one filter location (22.1...22.13) overlaps with at least one pressure relief hole (41), the one filter location (22.1...22.13) does not overlap with the flow-through region (40). A filter wheel filtration apparatus (100) according to claim 1, characterized in that...

5. The filter wheel filtration apparatus (100) according to claim 4, characterized in that at least one tangential pressure relief channel is formed inside at least one lubrication gap, extending between one of the openings (13.1) of the inflow passage (13) or the outflow passage (14).. and at least one pressure relief hole (41) that opens in front of the through-flow region (40) in the rotational direction of the filter wheel (20).

6. The filter wheel filtration device (100) according to claim 5, characterized in that the distance between the opening of the pressure relief hole (41) and the front edge of the flow-through region (40) in the rotational direction of the filter wheel (20) is greater than the maximum extension of the filter portion (22.1...22.13) in the rotational direction of the filter wheel (20).

7. The filter wheel filtration device (100) according to claim 1, characterized in that at least one radial pressure relief channel is formed inside at least one lubrication gap, the radial pressure relief channel extends between the through-flow region (40) and at least one pressure relief hole (42) provided in the inlet plate (11) and / or the outlet plate (12), the pressure relief hole (42) opens into the bearing ring (18) and is connected to guide fluid to the outer surface of the casing (10) via a pressure relief passage (42.1) formed in the casing (10).

8. The filter wheel filtration device (100) according to claim 7, characterized in that a ring passage (43) is formed by a chamfered portion on the outer circumferential surface of the bearing ring (18) and on the inner circumferential surface of the hole in the filter wheel (20) that houses the bearing ring (18).

9. The filter wheel filtration device (100) according to claim 8, characterized in that the ring passage is flow-connected to a ring-shaped sliding bearing (26) formed between the bearing ring (18) and the filter wheel (20).

10. The filter wheel filtration device (100) according to claim 1, characterized in that the cross-sectional area A2 of the bearing ring (18) is at most 13 times the cross-sectional area A1 of the tightening pin (19.1).

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