Metal deforming – By relatively movable offset tool-faces – With tool motion in fixed path
Reexamination Certificate
2000-11-20
2002-09-17
Jones, David (Department: 3725)
Metal deforming
By relatively movable offset tool-faces
With tool motion in fixed path
C072S389300, C072S383000, C072S387000
Reexamination Certificate
active
06450001
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method and an apparatus for manufacturing a thick-walled bent pipe.
BACKGROUND ART
As for a metal elbow for piping, one with an elbow body
111
being attached to a piping block
113
or the like with a fastening nut
112
as shown in
FIG. 8
, is used conventionally. Both ends of the elbow body
111
are threaded, and one thread is screwed into the piping block
113
or the like and fastened with the nut
112
, while a pipe not shown is attached to the other thread. The elbow body
111
can be freely oriented to the piping and fixed by being fastened with the nut
112
. The elbow body
111
is provided with parallel plane portions
111
s
and
111
s
so that the elbow body
111
can be fixed with a spanner or the like when it is attached. Further, the elbow body
111
is bent at almost the right angle, which reduces the protruding amount from the piping block
113
or the like, thus requiring less piping space.
In a section of the elbow body
111
, two fluid paths
111
d
and
111
d
cross each other at almost the right angle as shown in FIG.
9
. Further, since the elbow needs to be threaded, a margin to cut needs to be secured, which makes a material for the elbow thick-walled. In addition, it is necessary to secure pressure resistance of an elbow in order to respond to high-pressurization of the fluid devices in recent years, and the wall thickness of the elbow body
111
after being worked becomes larger.
Accordingly, it is difficult to manufacture the elbow body
111
as shown in
FIG. 9
by bending a thick-walled metal pipe at a small radius, since the pipe is crushed or the wall thickness of the pipe is reduced. Thus, a material of the elbow is made by cutting out a thick metal plate and forming it into a right-angle elbow, then the material is drilled from both end sides thereof to make the fluid passages
111
d
and
111
d
crossing each other at almost the right angle, and thereafter screw thread cutting is performed for both ends to thereby manufacture the elbow body
111
.
However, in the above manufacturing method, the process of cutting the material includes two drilling operations and two screw thread cutting operations, which results in too many working steps, and thus the number of steps of preparing the material is large. Further, burrs caused by drilling occur at a crossing portion of the fluid passages
111
d
and
111
d
crossing each other at almost the right angle, which are made by drilling. Thus, an operation for removing the burrs that have occurred has to be performed, and the deburring operation is not easy and takes time, since burrs in the small holes have to be removed. Further, many cutting operations increase cutting amount of the material, thus reducing yields. Consequently, manufacturing cost is increased.
In order to eliminate the above disadvantages, a method for manufacturing a curved pipe material described in Japanese Patent Laid-open No. 59-163024 as shown in
FIG. 10
to
FIG. 12B
is proposed. An apparatus thereof has a presser die A and press bearer dies B and C for supporting guide shafts b and c symmetrically positioned and respectively attached below the presser die A so as to be rotatable and horizontally slidable by inserting though and supporting them by horizontally long holes p and q provided in corresponding support frames P and Q. Bearing portions
2
b
and
3
c
for securely supporting both end portions of a straight pipe-shaped semiprocessed product N, which is formed by performing predetermined forging or grinding for a round metal bar, are respectively formed on the press bearing dies B and C. With the apparatus as described above, a thick-walled curved pipe can be manufactured by placing the straight pipe-shaped semiprocessed product N on the press bearing dies B and C, and lowering the press presser die A to thereby press and bend the straight pipe-shaped semiprocessed product N.
However, the method of manufacturing the curved pipe material described in Japanese Patent Laid-open No. 59-163024 has the following disadvantages.
The straight pipe-shaped semiprocessed product N is provided with a pipe hole
1
and bulging parts for connection at both ends as shown in
FIG. 12A. A
pipe part
4
is provided with uneven wall thickness on an upper side and an lower side with wall thickness being made smaller on the upper side and larger on the lower side as shown in FIG.
12
B. Accordingly, forging or grinding, and boring are performed to form the round bar-shaped material into the straight pipe-shaped semiprocessed product N as described above, thus requiring plenty of time to perform the working.
Further, when the straight pipe-shaped semiprocessed product N is pressed and bent, the press bearing dies B and C are moved transversely within the ranges of the horizontally long holes p and q to widen a space between them following the deformation of the straight pipe-shaped semiprocessed product N, while rotating as shown in FIG.
11
. The moving amount is determined by an outer shape dimension and wall thickness dimension of the straight pipe-shaped semiprocessed product N, and the aforesaid moving amount varies according to the variations in the outer shape dimension and the wall thickness dimension of the straight pipe-shaped semiprocessed product N. Accordingly, the dimension of the straight pipe-shaped semiprocessed product N in a longitudinal direction thereof, that is, a dimension in the left and right direction in
FIG. 11
varies within the range of the horizontally long holes p and q in which the dies B and C move transversely to widen the space between them. Specifically, the longitudinal dimension of the straight pipe-shaped semiprocessed product N changes and varies. If the dimension of the straight pipe-shaped semiprocessed product N varies, positioning becomes difficult when machining is performed in the next process, which is not preferable.
SUMMARY OF THE INVENTION
The present invention is made in view of the above disadvantages, and its object is to provide a method and an apparatus for manufacturing a thick-walled bent pipe capable of manufacturing an elbow material for piping with higher size accuracy with use of a thick-walled pipe material.
In order to attain the above object, a method for manufacturing a thick-walled bent pipe according to the present invention has a configuration including the steps of:
placing a thick-walled metal pipe material of a predetermined length on a lower die including a pair of bottom dies having sliding surfaces each in a circular arc form and placed on slide surfaces of a lower guide;
pressing a middle portion in a longitudinal direction of the thick-walled metal pipe material by means of an upper die including an upper guide having a guide surface in a circular arc form for guiding the lower die, and a presser die;
rotating the bottom dies respectively while they are facing to each other, by lower end portions of the bottom dies respectively abutting to and sliding along the slide surfaces at the same time when the sliding surfaces abut to and slide along the guide surface in the circular arc form to thereby bend the thick-walled metal pipe material.
According to the above configuration (a first configuration of the method), a pair of bottom dies of the lower die rotate along the guide surface in the circular arc form of the upper die having a center of rotation while they are facing to each other. Thereby, changes in the distances between both the end surfaces of the thick-walled pipe material and the center of rotation at the start of bending and at the completion of bending are reduced, thus making it possible to form a thick-walled elbow material with less variations in size.
As a result, an elbow material can be provided by cutting the thick-walled pipe, thus making it unnecessary to prepare a forged material. Further, since a thick-walled pipe can be used, drilling for making small holes to form fluid passages is unnecessary, and deburring at the crossing portion of the drilled holes, which is conventionally perform
Armstrong Westerman & Hattori, LLP
Jones David
Tokiwa Seiki Co., Ltd.
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