Filtermedium for resin extruders

Abstract: A filter member is provided including a breaker plate having an increased filtering area without any deterioration in screen back-up capability. This filter member (9) is adapted to filter off impurities of resin melt and is disposed in a resin passage. The filter member (9) comprises a screen (10) and a breaker plate (11) for backing up the screen (10). The breaker plate (11) has resin passageways in the form of elongated slits (14) extending as intersecting the flow direction of resin material.

Description: The present invention relates to a filter member according to the preambles of claims 1 and 5. From the document "KUNSTSTOFFBERATER", figure 5 on page 44, a screen changer is known into which a generic filter member is mountable. The filter member comprises a breaker plate (Siebstützplatte), a super plate or a wedge screen (Siebstützplatte "Super Plate") and two screens ("Siebe oder Siebpaket"). The super plate and the two screens are changeably mounted and the super plate is changed together with the two screen. Further, the super plate is different from the breaker plate in thickness. From the document US 2 661 497 another screen changer is known in which a filter member comprises a plurality of screens, a breaker plate and a retainer ring. From the document GB 2 073 038, figure 3, a screen changer is known in which the screen includes hollow cylindrical strainer elements. A filter member for filtering off impurities contained in a resin material is incorporated in the resin passage of resin extruders (inclusive of kneaders and molding machines) adapted to extrude resin materials such as polyolefins and compounds. A flat-type filter member is known comprising a screen for filtering off impurities and a breaker plate attached to the rear side of the screen for backing up the screen, as disclosed in JP-A-59-27698. Conventional breaker plates have a multiplicity of circular resin passageways, and the ratio of opening thereof is set to about 50% to maintain a strength sufficient to back-up the screen. For this reason, the filter member has a decreased effective filtering area within a limited area and hence tends to have a larger diameter. It is a general practice to provide a screen between the resin melt outlet of an extruder or the like and the inlet of a mold (hereby meant to include a granulating die) to filter off impurities contained in resin melt, and to provide a device for changing the used screen soiled by much accumulation of the impurities and the like on the mesh of the screen for a new screen without the need of stopping the operation of the extruder or the like. The object of the present invention is to provide a filter member which is mountable in a screen changer for use in an extruder and by which the productivity of the extruder can be enhanced, while at the same time its size can be minimized and its effective filtering area can be increased. Moreover, a filter member shall be provided which has an increased effective filtering area in a limited area and hence allowing for minimization of the size thereof by forming slit-like resin passageways in a breaker plate so as to ensure an increased ratio of opening (70% to 80%) without any deterioration in the back-up capability. The above-mentioned object is achieved by means of the combination of features as set forth in the independent claims 1 and 5. Preferred embodiments of the subject-matters of claims 1 and 5 are defined in the dependent claims. According to an aspect, a filter member comprises in combination a screen for filtering off impurities contained in a resin material flowing in an extruder and a breaker plate having a multiplicity of resin passageways and attached to the rear side of the screen for backing up the screen. According to another aspect, the resin passageways of the breaker plate are configured into elongated slits extending in a direction intersecting the flow direction of resin. According to the invention, the breaker plate comprise a first plate on the upstream side thereof and a second plate on the downstream side thereof which are mated to each other, the slits of one of the first and second plates being larger in width than those of the other plate and extending as intersecting those of the other plate. Alternatively, the breaker plate comprise a first plate on the upstream side thereof and a second plate on the downstream side thereof which are mated to each other, the resin passageways of the first plate being configured into elongated slits, and those of the second plate being configured into circular holes. Further, the face of the breaker plate defining the resin passageways may be configured circular or rectangular, and it is desired that the screen and the breaker plate respectively comprise curved surfaces having a single curvature which protrude in the extrusion direction or the direction opposite thereto. With the filter member according to the present invention, a resin material extruded from an extruder is filtered for its impurities by the screen of the filter member in the course of its flowing in the direction indicated by the arrow in Fig. 1(A). Since the resin passageways of the breaker plate in the filter member are configured into elongated slits extending as intersecting the direction of the arrow, the back-up capability of the breaker plate can be sufficiently ensured even when the ratio of opening of the slits is increased relative to that of circular holes. In the following, embodiments of the present invention are described in detail with reference to the figures 3 to 5. Fig. 1 illustrates a first comparative example of a filter member, in which Fig. 1(A) is a sectional view of an extruder, and Fig. 1(B) is a front elevation of a breaker plate; Fig. 2 illustrates a second comparative example of a filter member, in which Fig. 2(A) is a front elevation thereof, and Fig. 2(B) is a sectional view thereof; Fig. 3 illustrates a first embodiment of a filter member according to the present invention, in which Fig. 3(A) is a front elevation of a first plate, Fig. 3(B) is a sectional view of the filter member, and Fig. 3(C) is a front elevation of a second plate; Fig. 4 illustrates a second embodiment of a filter member according to the present invention, in which Fig. 4(A) is a front elevation of a first plate, Fig. 4(B) is a sectional view of the filter member, and Fig. 4(C) is a front elevation of a second plate; Fig. 5 illustrates a third embodiment of a filter member according to the present invention, in which Fig. 5(A) is a front elevation of a first plate, Fig. 5(B) is a sectional view of the filter member, and Fig. 5(C) is a front elevation of a second plate. In Fig. 1(A) showing the first comparative example of a filter member, an extruder 1 (hereby meant to include a kneader and a molding machine) for extruding a resin material such as a polyolefin or a compound comprises an elongated cylindrical barrel 2 and a screw 3 inserted into the barrel 2 which, by its rotation, causes the resin material to flow in the direction indicated by an arrow T and extrudes it into a molding die (not shown) or the like. Between the extruder 1 and the molding die is interposed a filter device 4 including a first body 5 defining a passage 5A, a second body 6 defining a passage 6A which are mated together at their mating surfaces 7 and fastened with a plurality of bolts 8, and a filter member 9 disposed in the passage 6A of the second body 6. The filter member 9 comprises, in combination, a screen 10 made of a mesh material for filtering off the impurities of the resin material, and a breaker plate 11 attached to the rear side of the screen 10 for backing up the same. The screen 10 includes a plurality of mesh material layers superposed one on another. As shown in Fig. 1(B), the breaker plate 11 according to the first comparative example has a multiplicity of resin passageways 12 in a passageway defining face 13 shaped circular. The passageways are in the form of elongated slits 14 extending as intersecting the resin flow direction T. Rib portions 15 separating the slits 14 from each other ensures sufficient back-up capability even when they are formed very thin and this allows the resin passageways to have a ratio of opening of 70 to 80% relative to the passageway defining face 13. Figs. 2(A) and 2(B) show the second comparative example of a filter member. In contrast to the screen 10 and breaker plate 11 of the first comparative example being shaped circular, those of the second comparative example are shaped rectangular. By shaping them rectangular it is possible to increase the effective filtering area as compared with the circular configuration. It should be noted that like reference characters designate corresponding parts throughout the first and second comparative examples. Figs. 3(A), 3(B) and 3(C) show the first embodiment of a filter member according to the present invention in which breaker plate 11 attached to the rear side of screen 10 includes a first plate 111 and a second plate 211 which are mated together and assembled by means of a bolt 16. Slits 214 of the second plate 211 are made wider than slits 114 of the first plate 111, the slits 114 and 214 extending as intersecting each other. However, the width relation between the slits 114 and 214 may be converse to that shown in the drawings; i.e., the slits 114 may be made wider than the slits 214. Figs. 4(A), 4(B) and 4(C) show the second embodiment of a filter member according to the present invention which is basically the same as the first embodiment in arrangement. However, the second embodiment differs from the first embodiment in that, in contrast to the screen 10 and breaker plate 11 shaped circular in the first embodiment, those in the second embodiment are shaped rectangular to ensure a larger effective filtering area. It should be noted that like reference characters designate corresponding parts throughout the first and second embodiments. The first and second embodiments ensure a low pressure loss property by making the slits 214 of the second plate 211 wider than the slits 114 of the first plate 111. Figs. 5(A), 5(B) and 5(C) show the third embodiment of a filter member according to the present invention in which breaker plate 11 attached to the rear side of screen 10 includes first plate 111 and second plate 211 which are mated together and assembled by means of bolt 16. The first plate 111 defines slits 114, while on the other hand the second plate 211 defines circular holes 314, whereby the breaker plate 11 enjoys a low pressure loss property. Further, the slits 114 of the first plate 111 centrally have a partition wall 414 which is recessed on both the front side and rear side thereof to increase the net filtering area of the screen 10 and to ensure an sufficient passage area between the first plate 111 and the second plate 211. Although the screen 10 and the breaker plate 11 shown in Figs. 5(A), 5(B) and 5(C) are shaped rectangular, these may be shaped circular. Also, the partition wall 414 may be recessed on either one of the front and rear sides thereof.

Claims: A filter member for use in a resin extruder (1) comprising in combination a screen (10) for filtering off impurities contained in a resin material flowing in the extruder (1) and a breaker plate (11) having a multiplicity of resin passageways (12) and attached to the downstream side of the screen (10) for backing up the screen (10), the resin passageways (12) of the breaker plate (11) are configured into elongated slits (14) extending in a direction intersecting the flow direction (T) of the resin material, characterized in that the breaker plate (11) comprises a first plate (111) on the upstream side thereof and a second plate (211) on the downstream side thereof which are mated to each other, the slits (214) of one (211) of the first and second plates (111, 211) being larger in width than those (114) of the other plate (111) and extending so as to intersect those (114) of the other plate (111). The filter member as set forth in claim 1, wherein the face of the breaker plate (11) defining the resin passageways (12) is configured circular or rectangular. The filter member as set forth in claim 1, wherein the screen (10) and the breaker plate (11) respectively comprise curved surfaces having a single curvature which protrude in the resin extrusion direction (T) or the direction opposite thereto. The filter member as set forth in claim 2, wherein the screen (10) and the breaker plate (11) respectively comprise curved surfaces having a single curvature which protrude in the resin extrusion direction (T) or the direction opposite thereto. A filter member for use in a resin extruder (1) comprising in combination a screen (10) for filtering off impurities contained in a resin material flowing in the extruder (1) and a breaker plate (11) having a multiplicity of resin passageways (12) and attached to the downstream side of the screen (10) for backing up the screen (10), characterized in that the breaker plate (11) comprises a first plate (111) on the upstream side thereof and a second plate (211) on the downstream side thereof which are mated to each other, the resin passageways (12) of the first plate (111) being configured into elongated slits (114), and those of the second plate (211) being configured into circular holes (314). The filter member as set forth in claim 5, wherein the face of the breaker plate (11) defining the resin passageways (12) is configured circular or rectangular. The filter member as set forth in claim 5, wherein the screen (10) and the breaker plate (11) respectively comprise curved surfaces having a single curvature which protrude in the resin extrusion direction (T) or the direction opposite thereto.

Inventors: FUKUMIZU SHINICHI, IKEDA OSAMU, NAGAMI NOBUKI, NAKATA YOSHIAKI, YAMASAKI NOBUHIRO, YOSHII YASUO, FUKUMIZU, SHINICHI, IKEDA, OSAMU, NAGAMI, NOBUKI, NAKATA, YOSHIAKI, YAMASAKI, NOBUHIRO, YOSHII, YASUO, FUKUMIZU, Shinichi Takasago Works Kabushiki Kaisha, IKEDA, Osamu Takasago Works, Kabushiki Kaisha,, NAGAMI, Nobuki Takasago Works, Kabushiki Kaisha,, NAKATA, Yoshiaki Takasago Works, Kabushiki Kaisha, YAMASAKI, Nobuhiro Takasago Works,Kabushiki Kaisha, YOSHII, Yasuo Takasago Works, Kabushiki Kaisha,
Applicants: KOBE STEEL LTD, KABUSHIKI KAISHA KOBE SEIKO SHO
Application year: 1995
Main classification: B29C47
IPC codes: B29C47