Metal deforming – Process – Tube making or reshaping
Reexamination Certificate
2001-02-02
2003-08-05
Larson, Lowell A. (Department: 3725)
Metal deforming
Process
Tube making or reshaping
C072S051000
Reexamination Certificate
active
06601427
ABSTRACT:
TECHNICAL FIELD
The present invention relates to manufacture a pipe body by performing a bending operation on a metal plate.
BACKGROUND OF THE INVENTION
Conventionally, there is disclosed a technique by which a pipe body, for example, a prism pipe body is made by bending a metal plate, such as in Japanese Patent Laid-Open No. Hei 11-290940.
In Japanese Patent Laid-Open No. Hei 11-290940, a prism pipe body is manufactured by using a rectangular metal plate as a material by means of pressing.
The method of manufacturing prism pipe body includes a first bending step, a second bending step, and a re-striking step. In the first bending step, a primary intermediate product is formed of a metal plate. In the second bending step, the primary intermediate product is processed to form a secondary intermediate product. In the re-striking step, the secondary intermediate product is processed to form a prism pipe body as a final product.
In the first bending step, both width direction sides of the metal plate are bent at the right angle in length direction. Accordingly, the primary intermediate product which includes flanges and a bottom plate is formed. The flanges face to each other. The bottom plate connects the flanges to each other.
In the second bending step, a concave surface having a predetermined width is formed on the bottom plate of the primary intermediate product lengthwise, and at the same time, both ends of the concave surface is bent at the right angle to inside. Accordingly, the second intermediate product is formed. The secondary intermediate product includes a pair of side walls which facing to each other. The cross section of the secondary intermediate product is U shape.
In the re-striking step, edges of a pair of flanges (seam) are contacted together by pressing a pair of side walls of the secondary intermediate product inside. Accordingly, a prism pipe body as a final product is formed.
According to this method of manufacturing the prism pipe body, the concave surface which is formed on bottom plate of secondary intermediate product, has a function to restrict a spring back force generated by pressing the pair of side walls together to inside. Accordingly a prism pipe body with square cross section, in which edges of the flanges closely contact together, can be manufactured only by pressing without welding edges of the flanges.
PROBLEMS TO BE SOLVED
However, in this conventional method of manufacturing prism pipe body, even though the concave surface of secondary intermediate product has a function to restrict spring back force, spring back force which tends to open to outside still remains at the pair of side walls. Accordingly, it is difficult to stably manufacture without deflection the prism pipe body whose edges of flange (wall including the seam) closely contacts for mass production.
When testing a prism pipe body manufactured by the conventional working method, if edges of flanges are contacted each other or not, some are closely contacted each other, but many of them have gaps in the seam due to the spring back force appearing at the pair of side walls.
It is an object of the present invention to solve the above mentioned problems and to provide an method of manufacturing pipe body and pipe body manufactured by the method having capability of manufacturing pipe body stably without deflection in which a seam tightly contacted by pressing when mass production the pipe body.
SUMMARY OF THE INVENTION
In order to achieve the above objects, according to one aspect of the present invention, a method of manufacturing a metal pipe body by bending a flat metal plate at predetermined angles, comprising the steps of bending a portion near at least one end of the plate along an axis of the completed metal pipe body so as to have a predetermined angle of a corner of the completed metal pipe body; bending the same side as said bent portion of said metal plate at points which correspond to some integer times of one side of the completed metal pipe body in the same bending direction as said bent portion along the axis of completed metal pipe with an angle more than said predetermined angle; making one of the portion made by said second bending, concave toward the center of completed metal pipe body; pressing portions including edges of the plate towards the center of completed metal pipe body along the bottom surface of said portions including edges so as for said edges to get close contact and at the same time modifying said angles more than the predetermined angle into said predetermined angle; generating a modifying operation of said concave portion into convex form toward outside against center of the completed metal pipe accompanied with said angle modifying operation; accumulating inner stress for said concave portions tending back to said convex form through said modifying operation by making said concave portion flat thereby making a close contacting operation of said portion including edges by operation for all sides other than said convex portion and portions including edges enforcing towards the center of completed metal pipe; and maintaining said edges contacting together and said originally concave portion flat, is provided.
According to another aspect of the present invention, a method of manufacturing a metal pipe body by bending a flat metal plate at an angle, comprising the steps of bending a portion of the flat metal plate near at least one end of the flat metal plate along an axis of the completed metal pipe body so as to have a predetermined angle of a corner of the completed metal pipe body; bending the same side as said bent portion of said metal plate at points which correspond to some integer times of one side of the completed metal pipe body in the same bending direction as said bent portion along the axis to be completed metal pipe with an obtuse angle more than said predetermined angle; making one of the portion made by said second bending, concave toward the center portion of completed metal pipe body; pressing portions including edges of the plate towards center of the completed metal pipe body along the bottom surface of said portions including edges so as to get close contact of said edges and at the same time modifying said angles more than predetermined angle into said predetermined angle; modifying said concave portion into convex form toward outside against center of the completed metal pipe accompanied with said angle modifying operation; modifying said convex portion into flat by pressing said bottom surface and the surface facing to said surface with convex form towards center of completed metal pipe body with said portions including edges contacting together; accumulating inner stress for said concave portions tending back to said convex form through said modifying operation by making said concave portions flat thereby making close contacting operation of said portions including edges; and maintaining said edges contacting together and said originally concave portion flat, is provided.
According to other aspect of the present invention, a method of manufacturing pipe body having a seam and circular shaped cross section made of a rectangular metal plate, comprising the steps of: by bending said metal plate, forming a curved pipe-like intermediate product of oval-like cross section in which a pair of edges of said metal plate to be a seam of said pipe is still not contacted and located at one end of longer axis of said oval and extending along the axis of the completed pipe; and modifying the curved intermediate product by applying a force along the longer axis of said oval so as to force said edges contacted tightly with spring back force tending to return to the original oval shape, is provided.
According to still other aspect of the present invention, a method for manufacturing pipe body having a seam and polygonal cross section made of a rectangular metal plate, comprising the steps of: by bending said plate at plurality of points along its edge direction, forming a pipe-like intermediate product in which a pair of edges of said metal
Ishino Keiji
Kondou Takafumi
Cooper & Dunham LLP
Larson Lowell A.
Ricoh & Company, Ltd.
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