Bent honeycomb pipe assembly with central pipe

A bent honeycomb pipe includes an outer pipe section bent at a predetermined curvature, a bent central pipe section coaxial with the outer pipe section and a bent honeycomb-shaped section interposed between the outer and central pipe-sections, all three sections being simultaneously coextruded to form a single-piece construction.

FIELD OF THE INVENTION 
The present invention relates to a bent honeycomb pipe assembly with a 
central pipe and extruding apparatus for manufacturing the same. 
DESCRIPTION OF THE PRIOR ART 
Straight honeycomb pipe assemblies have been preferably used as pipes for 
joining with other parts, e.g., an exhaust gas combustor such as an 
automobile engine, but a bent honeycomb pipe assembly has not been 
realized because its manufacture was extremely troublesome and expensive, 
particularly in the case where it is made of an inflexible material such 
as cordierite porcelain or alumina. 
SUMMARY OF THE INVENTION 
It is therefore an object of the invention to provide a bent honeycomb pipe 
assembly with a central pipe particularly suitable for joining to such a 
straight honeycomb pipe assembly and providing extruding apparatus for 
manufacturing the same relatively simple and inexpensively utilizing any 
extrudable material. 
The preferred embodiment of the invention comprises a bent honeycomb pipe 
assembly having an outer pipe section bent at a substantial predetermined 
curvature, a bent central pipe section provided coaxially with the outer 
pipe section and a bent honeycomb-shaped pipe section interposed between 
the outer and central pipe sections, with the outer, central and 
honeycomb-shaped pipe sections being simultaneously coextruded to form a 
single piece construction. 
The invention is attained by provision of an extruding apparatus comprising 
a cylindrical metal-pattern body including a flange portion having at its 
center a hole and secured to the outlet end of an extrusion guide pipe 
into which a molding material to be shaped is inserted under a 
predetermined pressure, and a truncated conical portion formed integrally 
with the flange portion so as to project therefrom at the side opposite to 
the extrusion guide pipe and having at its center a hole communicating 
with the hole of the flange portion, the outer circumferential portion of 
the hole of the truncated conical portion being provided with a plurality 
of honeycomb-shaped grooves and those portions of the flange portion which 
face the respective intersecting points of the honeycomb-shaped grooves 
being provided with holes each having a larger diameter than that of each 
corresponding intersecting point of the honeycomb-shaped grooves, thereby 
to define first spaces acting as extruding passageways for shaping a 
honeycomb-shaped pipe section of the honeycomb pipe assembly; a core 
inserted coaxially into the central through holes of the flange and 
truncated conical portions of the metal-pattern body to define therearound 
a second space communicating with parts of the first spaces and acting as 
an extruding passageway for shaping a central pipe section of the 
honeycomb pipe assembly integral with the honeycomb-shaped pipe section 
thereof; a stopper ring securing the metal-pattern body through the flange 
portion thereof to the extrusion guide pipe, and having a truncated 
conical through hole disposed coaxially above the truncated conical 
portion of the metal-pattern body to define therewithin a third space 
communicating with parts of the first spaces and acting as an extruding 
passageway for shaping an outer pipe section of the honeycomb pipe 
assembly integral with the central and honeycomb-shaped pipe sections 
thereof; and means for gradually differing resistances of the molding 
material to be shaped passing through the first, second and third spaces 
from one diametric end of the metal-pattern body toward the other 
diametric end thereof, thereby successively to bend the central, 
honeycomb-shaped and outer pipe sections of the honeycomb pipe assembly at 
a desired curvature. 
Said means for gradually differing resistances of the molding material to 
be shaped may comprise gradually reducing the longitudinal lengths of the 
circumferential through holes provided in the flange portion of the 
metal-pattern body from its one diametric end toward the other diametric 
end, or may comprise differing the length of the projecting end of the 
truncated conical portion of the metal-pattern body gradually from its one 
diametric end toward the other diametric end. 
The extruding apparatus of the above-mentioned construction is capable of 
shaping any bent honeycomb pipe assembly with a central pipe comparatively 
easily and inexpensively by utilizing an extrudable material which may be 
a flexible material such as any plastics as well as an inflexible 
heat-resisting material such as cordierite, mullite, porcelain, alumina or 
the like particularly suitable for a pipe to join with an exhaust gas 
combustor such as an automobile engine. A plastic material containing 
ceramic powder may also be used to form a bent ceramic honeycomb pipe.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIG. 1, reference numeral 1 denotes an extruding cylindrical 
metal-pattern body before honeycomb-shaped grooves as hereinafter 
described are bored. Metal-pattern body 1 is made of a heat-resisting 
material such as cast iron and comprises a flange portion 2 and a 
truncated conical portion 3 projected coaxially from one surface of flange 
portion 2 so as to have a gradually smaller diameter. Truncated conical 
portion 3 is perforated at its center with a truncated conical hole 4 so 
as to have a gradually smaller diameter toward flange portion 2. A 
straight circular hole 5 is so bored as to pass through the center of 
flange portion 2 starting from the small diametric end, i.e., the 
truncated end of conical hole 4. The outer circumferential portion of 
truncated conical hole 4 is formed with honeycomb-shaped grooves 8 (FIGS. 
2 and 3) comprising a plurality of transversal grooves 6 each provided at 
a predetermined interval and a plurality of longitudinal grooves 7 each 
provided at a predetermined interval. Those portions of flange portion 2 
which face the respective intersecting points of transversal and 
longitudinal grooves 6 and 7 are perforated with circular holes 10 each 
having a larger diameter than that of each corresponding intersecting 
point of transversal and longitudinal grooves 6 and 7. Holes 10 are so 
formed to have their lengths reduced gradually from one diametric end 3b 
of truncated conical portion 3 toward the other diametric end 3a thereof. 
A reinforcing ring plate 11 is mounted on the surface of flange portion 2 
of metal-pattern body 1 opposite to truncated conical portion 3 thereof. 
Reinforcing ring plate 11 comprises a shallow annular ring section 11a 
having substantially the same diameter as that of flange portion 2 and a 
cross-shaped rib section 12 projected inwardly of annular ring section 11a 
integrally therewith slightly away from the surface of flange portion 2. 
The central intersecting portion of rib section 12 facing circular hole 5 
bored in flange portion 2 is formed with a circular hole 13. 
On the other hand, a core 14 is prepared which comprises a truncated 
conical head portion 14a formed to have an appropriately smaller diameter 
than truncated conical hole 4 provided in truncated conical portion 3, and 
an elongated rod-like portion 15 projected coaxially from the truncated 
end of head portion 14a and formed to have the same diameter as circular 
hole 5 of flange portion 2, a threading 16 being formed at the rear end 
peripheral surface of rod-like portion 15. Thus, core 14 is so inserted 
into truncated hole 4 and circular hole 5 with ring plate 11 disposed on 
flange portion 2 in a predetermined state that threading 16 passes through 
circular hole 13 of ring plate 11 and is then screwed by a nut 17. Thus, 
under this condition, an annular extruding passageway 18 for shaping an 
inner or central pipe section 104 (FIG. 9) of a desired honeycomb pipe 
assembly 101 to be described hereinafter is formed between the peripheral 
wall of truncated head portion 14a of core 14 and the wall surface 
defining truncated conical hole 4. 
On the other hand, a stopper ring member 22 (FIG. 4) is prepared which 
comprises a small ring section 22a having at its center a truncated 
conical through hole 23 formed to be arranged coaxially above truncated 
conical portion 3 of metal-pattern body 1 and to have an appropriately 
larger diameter than, and the same longitudinal length as, truncated 
conical portion 3, and a large ring section 22b projected integrally from 
the other peripheral end of small ring section 22a and having 
substantially the same diameter as flange portion 2 of metal-pattern body 
1, a female threading 22c being formed in the inner wall of large ring 
section 22b. Thus, under the condition where flange portion 2 of 
metal-pattern body 1 is contacted through reinforcing ring plate 11 with 
an extrusion guide pipe 21 having substantially the same diameter as 
reinforcing ring plate 11 and formed at its front peripheral wall portion 
with a male threading 21a, stopper ring member 22 is screwed to extrusion 
guide pipe 21 so as to press metal-pattern body 1 through reinforcing ring 
plate 11 toward extrusion guide pipe 21 and in the manner that small ring 
section 22a of stopper ring member 22 is disposed coaxially above 
truncated conical portion 3 of metal-pattern body 1. In this case, a 
positioning pin 19 may be disposed between stopper ring member 22 and 
flange portion 2 of metal-pattern body 1 in place of the aforesaid 
screwing. Thus, under this condition, an annular extruding passageway 24 
for shaping an outer pipe section 102 (FIG. 9) of the desired honeycomb 
pipe assembly is formed between the peripheral wall of truncated conical 
portion 3 of metal-pattern body 1 and the wall surface defining truncated 
conical hole 23 of stopper ring member 22. In this case, parts of the 
aforesaid honeycomb-shaped grooves 8 are formed to be communicated with 
extruding passageways 18 and 24. 
When, under this condition, a predetermined extrudable material to be 
shaped is successively introduced into extrusion guide pipe 21, then 
central pipe section 104 is shaped through extruding passageway 18, outer 
pipe section 102 is shaped through extruding passageway 24, and a 
honeycomb pipe section 103 (FIG. 9) integral with central and outer pipe 
sections 104 and 102 is shaped through honeycomb-shaped grooves 8. At this 
time, central, honeycomb-shaped and outer pipe sections 104, 102 and 103 
are each continuously bent at a predetermined curvature since the 
extruding speeds or resistances of the molding material to be shaped 
differs in response to the inclined angle defined by the longitudinal 
different ends of circular holes 10 from one diametric end of 
metal-pattern body 1 toward the other diametric end thereof. As is clearly 
shown in FIGS. 4, 8 and 9, the curvature of the resulting bent honeycomb 
pipe structure is substantial, i.e. it is more than an infinitesimal 
amount. Thus, a bent honeycomb pipe assembly of unitary construction is 
formed. As used here and in the appended claims, the term "unitary 
construction" describes a unit made of a single piece of material and 
having no adhesives or other fastening means. If a plastic material 
containing ceramic powders is used, the thus molded bent ceramic honeycomb 
pipe assembly is sintered to produce a final product. 
The embodiment according to FIGS. 5-8 has the same construction as the 
embodiment according to FIGS. 1-4, excepting that the inclination of the 
longitudinal lengths of circular holes 10 for differing the extruding 
speeds or resistances of the plastic molding material to be shaped from 
one diametric end of the metal-pattern body toward the other diametric end 
is replaced by the corresponding inclination of each of the extruding ends 
of a truncated conical portion 3' of a metal-pattern body 1', a truncated 
conical head portion 14'a of a core 14' and a small ring section 22'a of a 
stopper ring member 22'. Therefore, parts of FIGS. 5-8 corresponding to 
those of FIGS. 1-4 are designated by the corresponding symbols and the 
description is omitted. 
Thus, it will be understood to those skilled in the art that any desired 
bent honeycomb pipe assembly 101 as shown in FIG. 9 can be easily shaped 
according to the invention. If a molding material containing ceramic 
powders is used, the only necessary additional step is that the thus 
molded bent ceramic honeycomb pipe assembly must then be sintered to 
produce a final product. 
In this case, it is desired that the extruding ends of truncated conical 
portion 3 or 3' of the metal-pattern body, truncated conical head portion 
14a or 14'a of the core, and stopper ring member 22 or 22' each have a 
straightly extended portion, i.e., a constant diameter portion, of a 
predetermined length as shown in FIGS. 1, 2, 4, 5, 6 and 8. 
Bent honeycomb pipe assembly 101 manufactured in accordance with the 
invention is particularly suitable for a pipe, e.g., to join to any 
straight honeycomb pipe assembly such as a pipe used to join with any 
exhaust gas combustor including an automobile engine. In such as case, a 
plastic material containing ceramic powders such as cordierite, mullite, 
alumina or the like is used as the extrudable material. 
One concrete example of producing a bent ceramic honeycomb pipe assembly 
will be described in which a polyurethane resin predominently containing 
cordierite, mullite, alumina or the like is preferably usable as a plastic 
molding material to be shaped. 
EXAMPLE 
To 100 parts by weight of cordierite powders having an average particle 
size of 5.mu. was added 50 parts by weight of water insoluble water 
curing-type polyurethane resin, and the mixture was kneaded to obtain a 
plastic molding material using a vacuum kneader. The plastic molding 
material was extruded using the present apparatus to obtain a bent ceramic 
honeycomb pipe assembly, and then the extruded pipe assembly was immersed 
into a water to thereby harden it. The thus obtained bent ceramic 
honeycomb pipe assembly was subjected to a sintering treatment described 
below. 
(1) The pipe assembly is immediately dried. 
(2) The dried pipe assembly is heated to 800.degree. C. at a rate of 
50.degree. C./hour in reducing atmosphere. 
(3) After changing the atmosphere from a reducing atmosphere to a neutral 
atmosphere, the pipe assembly is then heated to 1000.degree. C. at a rate 
of 50.degree. C./hour therein. 
(4) Furthermore, the pipe assembly is heated to 1250.degree. C. at a rate 
of 50.degree. C./hour in an oxidizing atmosphere; and then it is 
continuously heated to maintain the temperature of 1250.degree. C. for two 
hours. As a result, the bent ceramic honeycomb pipe assembly can be 
obtained. 
In this case, the modulus of contraction which is caused by the sintering 
treatment was 12% of the whole volume, while the water absorption or was 
25%. 
According to the above treatment, it is possible to obtain a bent honeycomb 
pipe assembly made of cordierite as shown in FIG. 9. 
It will be apparent that various modifications in the above-described 
invention are possible without departing from the essential scope of the 
present invention as defined in the appended claims.