HONEYCOMB STRUCTURAL BODY EXTRUDING DIE APPARATUS

Abstract: A honeycomb structural body-extruding die apparatus which comprises an extruding die (1) and a die mask (7) around an outer peripheral portion of the extruding die (1) on an extruding material outlet side. The extruding die has extruding material-feeding holes (2) formed on the inlet side and shaping channels (3) communicating with each other in a lattice fashion on the outlet side. To make the rate of flow of extruding material more uniform, die apparatus is provided with an annular perforated plate (5) arranged concentrically with the extruding die on the inlet side. The perforated plate (5) has through holes (6) whose central axes are in conformity with those of the feeding holes (2).

Description: The present invention relates to a honeycomb structural body-extruding die apparatus which can produce honeycomb structures of a good quality. Heretofore, honeycomb structures have been produced by a honeycomb structural body-extruding die apparatus shown in Fig. 3, which comprises an extruding die 13 with holes 11 for feeding a material to be extrusion-shaped (hereinafter referred to as "extruding material-feeding holes), which holes are formed on the extruding material inlet side, as well as shaping channels 12 communicating with one another in a lattice fashion on the extruding material outlet side, and a die mask 14 provided around the outer periphery of an end face of the extruding die 13 on the extruding material outlet side. In the above-mentioned conventional apparatus, since an outer peripheral wall of the honeycomb body is formed by squeezing the extruding material having passed through the outer peripheral portion of the extruding die at a tapered inner peripheral wall of the die mask 14, the speed of discharging the extruding material through the shaping channels of the die is greater at the outer peripheral portion than at the central portion. Therefore, there is a drawback in that cell deformation is likely to appear in the honeycomb structural body near the outer peripheral wall thereof as seen at a portion "A" in Fig. 4. In order to eliminate such a drawback, Japanese patent publication No. 58-23,207 (U.S. Patent 4,368,025) discloses a honeycomb structural body-extruding die apparatus in which a plurality of grooves are opened at a small interval along an inner peripheral edge portion of a die mask in contact with an end face of a die for feeding an extruding material forcedly fed into shaping channels at the peripheral portion of the die to the inside of the die mask. However, since no attention is paid to a difference in a discharging speed of the fed extruding material between the central portion and the outer peripheral portion in the above die apparatus, either, deformation of cells cannot be completely removed. Further, in the case that a plurality of the openings are provided along the inner periphery of the die mask, the dimension of such openings of the die mask needs to be slightly varied depending upon a shrinkage factor of the extruding material. In addition, to determine where a plurality of such openings are to be provided in what direction for the extrusion of honeycomb structures is extremely troublesome. Mention is also made of EP-A-137572, Fig. 9 of which shows a perforated plate having holes aligned with the inlet feed holes of the die. This document is taken to disclose the features of claims 1 and 5 before the words "characterized in that". It is an object of the present invention to reduce or eliminate the above mentioned drawbacks, and to provide a honeycomb structural body-extruding die apparatus which can easily produce good quality honeycomb structures relatively free from troubles such as cell deformation. The honeycomb structural body-extruding die apparatus according to the present invention in one form is set out in claim 1. In the above construction, the speed of the extruding material discharged through the central portion and the peripheral portion of the extruding die is made at a desired constant value by the perforated plate arranged on the extruding material inlet side of the extruding die. Consequently, honeycomb structures of good quality can be obtained highly free from defects such as cell deformation. The invention also consists in the honeycomb structural body-extruding die apparatus set out in claim 5. For a better understanding of the invention, reference is made to the attached drawings, wherein: Fig. 1 is a sectional view of a principal portion of an embodiment of the honeycomb structural body-extruding die apparatus according to the present invention; Figs. 2(a) through (c) are sectional views illustrating other embodiments of perforated plates used in the present invention; Fig. 3 is a sectional view of a principal portion of a conventional honeycomb structural body-extruding die apparatus; and Fig. 4 is a plan view illustrating a defect possessed by a honeycomb structure. The feeding speed of an extruding material varies depending upon a size of a honeycomb structural body-extruding apparatus, a composition of the extruding material, etc. However, optimum extruding conditions may be selected to effect extruding operation by preliminarily preparing plural kinds of annular perforated plates for an extruding die and selectively attaching an appropriate perforated plate to the die. At that time, the feeding speed of the extruding material is finely adjusted by the perforated plate, preferably, according to a technique by which a diameter of holes of the perforated plate is varied, the inner diameter of the annular perforated plate is changed, or the thickness of the perforated plate is changed. The present invention will be explained in more detail with reference to the following specific embodiments. However, these embodiments are merely given in illustration of the invention, and should not be interpreted to limit the scope of the invention. Fig. 1 is a sectional view of a principal portion of an embodiment of the honeycomb structural body-extruding die apparatus according to the present invention. In the illustrated embodiment, the extruding die 1 is constituted by extruding material-feeding holes 2 formed on an extruding material inlet side and shaping channels 3 which communicate with one another in a lattice fashion on an extruding material outlet side. An annular perforated plate 5 is concentrically arranged inside a cylinder 4 on the extruding material inlet side of the extruding die 1. The perforated plate 5 is fixed to the extruding die 1 by means of screws or a jig (not shown) such that respective center axes of through holes 6 of the perforated plate 5 may be in conformity with those of the extruding material-feeding holes 2 of the extruding die 1. The honeycomb structural body-extruding die apparatus according to the present invention is constituted by the extruding die 1, the perforated plate 5, the cylinder 4 and the die mask 7. Figs. 2(a) through 2(c) are sectional views illustrating other embodiments of perforated plates 5 used in the present invention. In the embodiment of Fig. 2(a), the diameter of through holes 6 of the perforated plate 5 is made smaller toward the outer peripheral portion thereof so that the feeding speed of the extruding material is made greater at the inner peripheral portion of the perforated plate and smaller at the outer peripheral portion. In the embodiment illustrated in Fig. 2(b), the thickness of the perforated plate 5 is made larger toward the outer peripheral portion so that the feeding speed of the extruding material is made greater at the inner peripheral portion of the perforated plate and smaller at the outer peripheral portion. In the embodiment shown in Fig. 2(c), the perforated plate 5 is constituted by two perforated annular plate members 5-1 and 5-2 and the inner diameter of the annular perforated plate member 5-1 in contact with the extruding die is made smaller than that of the perforated plate member 5-2 so that the feeding speed of the extruding material is made greater at the inner peripheral portion of the perforated plate 5 and smaller at the outer peripheral portion. In the above-illustrated honeycomb structural body-extruding die apparatus of the present invention, the speed of the extruding material, such as a ceramic body, which is discharged through the shaping channels of the die, may be controlled to be constant at every location by passing the extruding material through the perforated plate, when the extruding material passes through the extruding die. That is, when optimum perforated plates 5 are preliminarily determined correspondingly to changes in conditions such as a composition and a viscosity of an extruding material used, an inner diameter of a cylinder 4, etc. and the perforated plate 5 is exchanged depending upon the extruding material, etc., the discharging speed of the extruding material through the extruding die 1 on the extruding material outlet side can always be made constant. Consequently, when the outer periphery of the ceramic structure is formed by using the die mask 7, defects such as the cell deformation do not occur and the thickness of the cells can be made smaller. The present invention will not be limited to the above-mentioned embodiments only, and various modifications, variations, and changes of the same could be made. For example, in the above mentioned embodiments, the outer walls of the honeycomb structures are formed by the die mask having a tapered portion. The outer walls may be formed by other appropriate conventional techniques. Although the perforated plates are exchangeably formed separatedly from the extruding die in the above embodiments, similar effects aimed at by the present invention may be obtained even when perforated plate may be integrally formed with the dies if exchange is unnecessary. As obvious from the foregoing detailed description, according to the honeycomb structural bodyextruding die apparatus of the present invention, even when the extruding material passing through the outer periphery of the extruding die is squeezed to form the outer peripheral wall, the feeding speed of the extruding material on the extruding material outlet side of the extruding die can be made constant by providing the perforated plate concentrically with the extruding die on the extruding material inlet side. Therefore, the good quality honeycomb structures can be obtained free from defects such as cell deformation. Further, since the speed at which an extruding material passes through the die may be easily varied by changing the shape or the like of the perforated plate, the extruding apparatus most suitable for the extruding material used can be obtained only by a simple operation of exchanging the perforated plate.

Claims: A honeycomb structural body-extruding die apparatus comprising an extruding die (1) and a die mask (7) provided against an outer peripheral portion of the end face of the extruding die (1) on the extruding material outlet side, said extruding die (1) having extruding material-feed holes (2) provided on the extruding material inlet side and shaping channels (3) communicating with one another in a lattice fashion on the extruding material outlet side, and a perforated plate (5) arranged against the extruding die on the extruding material inlet side, said perforated plate (5) having holes (6) of which respective center axes are aligned with those of the extruding material-feed holes (2), characterized in that said perforated plate (5) is an annular plate concentric with the die (1) and covering an outer peripheral portion of said die (1) while leaving free a more central portion thereof, so that the extruding material-feed holes (2) at said outer peripheral portion effectively have greater length than at said more central portion. A die apparatus according to claim 1, wherein the diameter of the holes (6) of the perforated plate is varied to control the amount of the extruding material to be fed to the extruding die. A die apparatus according to claim 1 or claim 2, wherein the inner diameter of the annular perforated plate (5) is selected to control the amount of the extruding material to be fed to the extruding die. A die apparatus according to any one of claims 1 to 3, wherein the thickness of the perforated plate (5) varies, to control the amount of the extruding material to be fed to the extruding die. A honeycomb structural body-extruding die apparatus comprising an extruding die (1) and a die mask (7) provided against an outer peripheral portion of an end face of the extruding die (1) on the extruding material outlet side, said extruding die (1) having extruding material-feed holes (2) provided on the extruding material inlet side and shaping channels (3) communicating with one another in a lattice fashion on the extruding material outlet side, characterized in that said extruding material-feed holes (2) have a greater length at a perhipheral region of said extruding die than at a central region thereof. A die apparatus according to claim 5 wherein said greater length of said feeding holes is provided by an annular perforated plate (5) on the inlet side of the die (1).

Inventors: HIGASHIZIMA, KOZO 102 PANA HEIGHTS OHE, INOUE, SATORU
Applicants: NGK INSULATORS, LTD.
Application year: 1988
Main classification: B28B3
IPC codes: B29C47, B32B3, B28B3