JP2007044761A - Method for manufacturing square pipe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for inexpensively manufacturing a square pipe with high precision. <P>SOLUTION: The invented method comprises a step of inserting a core material into a round pipe, a step of placing the round pipe with the core material inserted between an upper die in which an inverted V groove is formed and a lower die in which a V groove is formed, and a step of plastically deforming the round pipe into the square pipe by pressing the round pipe with the upper and the lower die in a manner satisfying the following formula: (A)+(B)=(K), where (K) is the outer diameter of the square pipe, (A) is the outer diameter of the core material and (B) is the wall thickness of the round pipe. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a metal square pipe used as a shaft member of office equipment such as a printer.

  Conventionally, a metal square pipe is used as a shaft member of office equipment such as a printer. The manufacturing method of this metal square pipe includes (1) a method of manufacturing a drawn square pipe with plastic deformation using a square die and a square plug (core metal) from a round pipe once formed, and (2) once forming. A method of manufacturing a round pipe that is not plastically deformed by pressing with a roller from a cross direction and deforming it into a square shape. A method of manufacturing while welding is employed.

JP-A-8-238520

However, the following problems occur depending on the above means.
B) In all of the above (1), (2), and (3), since the processed points are short and the processed products are continuously manufactured, bending and twisting occurs, and this measure requires a large cost.
B) In particular, since the principle of a general bend straightening machine is to straighten the roll by rotating the straightening roll around the outer circumference of the material or by rotating the material itself, the square shape is particularly difficult. Cost is high.
C) Of the manufacturing methods, (2) and (3) are easy in terms of manpower because they do not involve plastic deformation, but on the other hand, the material width before processing into a square shape (2 is a round pipe) Since the outer peripheral length of 3 cannot be made constant (the width of the hoop material), the four sides of the corner are deformed to the outside or the inside, and swelling and sagging occur.

Moreover, the following problems arise as problems of the current process manufacturing method during product processing.
B) The long material of the pipe manufactured as described above is cut into a certain length depending on the method of use, but the cut surface is chamfered and deburred, so the cut material is rotated and chamfered. Deburring is not possible and takes time,
B) When surface irregularity, surface roughness, etc. are required, flat polishing and buffing are required for each of the four surfaces, and high-efficiency methods such as center lace polishing and through buff polishing using rotation are used. I can't do it.
C) In order to remove the precise bend according to the product specifications, it takes time and effort to rotate the cut product through the inner and outer coaxial links and pressurize the dial gauge on the outer circumference of the ring to correct the bend.
Therefore, an object of the present invention is to solve the above-mentioned problems and to provide a member with low cost and high accuracy.

  Accordingly, in order to solve the above-mentioned problems, the invention of claim 1 includes a step of inserting a core material inside the round pipe, and an upper metal having a chevron groove formed inside the round pipe into which the core material is inserted. It comprises a step of placing between a die and a lower die having a valley groove, and a step of pressing the upper and lower dies to plastically deform the round pipe into a square square pipe, the outer diameter of the square pipe = ( K), when the outer diameter of the core material = (A) and the thickness of the round pipe = (B), the relationship of (A) + (B) = K is established.

As described above, according to the present invention, since there is a round metal core as compared with the conventional method, the accuracy is high. Since the front surface is processed at once, no twisting occurs. Bending does not occur due to processing stress dispersion during processing. Burr, chamfering, and 4-surface accuracy can be easily ensured. By the above, a much cheaper part can be made.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In the present invention, first, a metal round pipe 1 is prepared and cut into a necessary length, and after cutting, both ends are chamfered and subjected to a process for improving surface roughness by outer diameter polishing or the like.
Next, the core material 2 is inserted into the round pipe 1. The core material 2 is a hard member made of metal or the like, and can be a solid material having a circular cross section.

Next, an upper die 3 and a lower die 4 having a valley groove 4a formed therein are prepared on the inner side. The angle groove 3a and the valley groove 4a are formed such that the outer diameter of the square pipe is K. When the hypotenuse dimension is K and the target square pipe is square, the groove angle α = 45 degrees forms a substantially equilateral triangle.
Between the upper mold 3 and the lower mold 4, the round pipe 1 in which the intermediate core material 2 is inserted is disposed and pressed by a press machine.
When the press of the press machine is started, first, the inner wall surfaces of the angle groove 3a and the valley groove 4a contact the surface of the round pipe, and the position of the center of the slope of the angle groove 3a and the valley groove 4a becomes the contact point. , T1, t2, t3, and t4 are contact points, respectively.

When the press is further pressed, the metal pipe starts plastic deformation around t1 which is the contact point, and it forms a flat surface along the inner side of the groove, at t2, t3 and t4. Works the same way.
This action is such that the upper mold t1 and the lower mold t3 facing each other just press the round pipe 1 from above and below, and acts as a force that deforms the circular round pipe 1 into an elliptical shape. And since it works also between the other t2 and t4, it does not become an ellipse but becomes a shape approaching a quadrilateral.

  In the process of deforming the pipe to form a flat surface along the inside of the groove, between the contact points t1, t2, t3, and t4, for example, between t1 and t2, the pipe is t1 and t2. A force in the direction of pushing the material to the top of the middle mountain-shaped groove peak will work. Between t2 and t3, a force that pushes the material into the intermediate gap between the upper mold and the lower mold works. Similarly, a force acts on the bottom of the trough at t3 and t4, and on the intermediate gap between t1 and t4.

Eventually, when the upper and lower molds approached and approached the final point, the force that went toward the peak, valley bottom, and left and right intermediate gaps reached the end and approached the corner. May be warped as a reaction in the opposite direction. For example, there are variations in the outer diameter of the round pipe 1, and this possibility arises when the diameter is larger than a predetermined dimension.
Then, the reaction force returned from the corner may collide in the vicinity of t1, t2, t3, and t4, and may act as a force that bends t1, t2, t3, and t4 inward.

  However, since there is an inner core material on the inner side, the bending force to the inner side is suppressed, and the outer diameter of the square pipe = (K), the outer diameter of the inner core material = (A), When the thickness dimension = (B), the relationship of (A) + (B) = K is established, so that the upper and lower molds match and the deformation of the round pipe has just approached the shape of the intended square pipe. At that point, each other's action ends.

That is, even if a force for bending inward is applied to t1, t2, t3, t4, the presence of the core material 2 suppresses this, and they are adjusted to each other as described above. It becomes the appearance which suppresses the reaction force, and can be brought close to the size and form of the target square pipe.
The forces that cause the t1, t2, t3, and t4 to bend inwardly acting on the middle core material 2 are generated simultaneously and in opposite directions, so that each force collides via the middle core material 2 to generate a reaction force, It acts to suppress the bending force.
At this time, since the intermediate core material is an intervening point where the mutual force acts, it is not necessary to accurately fix the position, and an appropriate position can be maintained by balancing the opposing forces.

  The shape of the square pipe can be applied to a square such as a rectangle in addition to the regular square. The core material 2 is preferably circular considering the ease of drawing after molding with a mold, but is not limited to this, and includes a deformation type that performs the same function.

  The present invention can be used in a method of manufacturing a metal square pipe used as a shaft member of office equipment such as a printer.

It is a whole perspective view when the round pipe and middle core material of this invention are inserted in the metal mold | die. It is the front and side view figure of a round pipe same as the above. It is an enlarged front view of a round pipe. It is an expansion front when a round pipe and a core material are inserted in a metal mold. It is an enlarged front view in the middle of pressing with a mold. It is an enlarged front view when the pressing of the mold enters the final stage. It is an expansion front of the formed square pipe.

Explanation of symbols

1 Round pipe
2 Core material 3 Upper mold 3a Angle groove 4 Lower mold 4a Valley groove

Claims (1)

The step of inserting the core material inside the round pipe, and the round pipe into which the core material is inserted are arranged between the upper mold having the inner groove formed therein and the lower mold having the valley groove formed therein. And a step of pressing the upper and lower molds to plastically deform the round pipe into a square pipe,
When the outer diameter of the square pipe = (K), the outer diameter of the core material = (A), and the wall thickness of the round pipe = (B), the relationship of (A) + (B) = K holds. The manufacturing method of the square pipe characterized by these.