JP2003053441A - Bulging method for cylindrical body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily obtain a curved hollow body whose middle part in the longitudinal direction is bent downward and/or upward by bulging. SOLUTION: A cylindrical body (1) is covered with a plastics film (2) in the outer circumference and held between an upper and lower dies (6, 7) through the plastics film (2); and then, liquid is force-fed into the cylindrical body (1), deforming the external form into a contour corresponding to the forming faces (6b, 7b) of the upper and lower dies (6, 7).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for bulging a tubular body such as a round pipe, an elliptic pipe or a square pipe which is bulged to transform its cross-sectional shape into a predetermined shape.

[0002]

2. Description of the Related Art Conventionally, when a cylinder made of an aluminum alloy is sandwiched between upper and lower molds and bulge processing (molding), a lubricant such as grease, oil or soapy water is conventionally applied to the molding surfaces of the upper and lower molds.
The upper and lower molds sandwich the cylinder through the lubricant, and the liquid is pressed into the cylinder to deform the outer shape of the cylinder into a shape corresponding to the molding surface of the upper and lower molds.

[0003]

The above-mentioned conventional ones have a limit in the lubricity of repetitive operation, so that every predetermined number of machining operations,
Alternatively, it is necessary to confirm the consumption state of the lubricant on the molding surface and apply the lubricant regularly to the molding surface. For this reason, in the above-mentioned conventional products, the lubricant may adhere to hands, clothes, etc., resulting in unsanitary conditions, or the lubricant may be delayed in application timing to cause scratches on the molded product. It is an object of the present invention to obtain a method for bulging a cylindrical body that solves the above problems.

[0004]

The present invention is configured as follows to achieve the above object. That is, in the invention according to claim 1, the outer periphery of the cylinder is covered with a plastic film, and the cylinder is sandwiched by the upper and lower molds with the plastic film interposed therebetween. The outer shape is transformed into a shape corresponding to the molding surfaces of the upper and lower dies. The invention according to claim 2 is
The material of the cylinder is aluminum alloy, and the plastic film is polyethylene film. Claim 3
In the invention according to (1), the plastic film is formed in a tube shape that is fitted into the outer periphery of the cylindrical body in a removable manner.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. 1 to 6 show a bulging process of a cylinder according to the present invention, FIG. 1 is a perspective view of the cylinder, FIG. 2 is a perspective view of a plastic film, and FIG. 3 is FIG.
III-III enlarged cross-sectional view of FIG. 4, FIG. 4 is a partial cross-sectional side view of a cylinder whose outer periphery is covered with a plastic film, and FIG.
6 is an enlarged cross-sectional view of the VV of FIG. 6, FIG. 6 is a cross-sectional view showing a bulging state of the cylindrical body, FIG. 7 is an enlarged cross-sectional view of a portion A of FIG. 6, and FIG. 8 is a perspective view of a hollow body bulged by the present invention.

First, as shown in FIG. 1, an aluminum alloy cylinder 1 (pipe) is formed by drawing or extruding. As shown in FIG. 5, the tubular body 1 is an uneven-walled tubular body in which the wall thickness T1 of the left and right peripheral walls 1a, 1a is thinner than the wall pressure T2 of the upper and lower walls 1b, 1b. The thin portion (left and right walls 1a, 1a) and the thick portion (upper and lower walls 1) of the cylindrical body 1
The position b, 1b), that is, the wall thickness changing portion corresponds to the wall thickness changing portion of the peripheral wall required for the molded product. Further, the amounts of the thin wall portion and the thick wall portion of the cylindrical body 1 are appropriately set according to the strength, rigidity, etc. required of the molded product. The cylindrical body 1 may have a uniform wall pressure on the peripheral wall.

In FIG. 2, reference numeral 2 is a plastic film which covers the outer circumference of the cylindrical body 1. The plastic film 2 has a lubricating function between the mold and the cylinder 1 during bulging. In this example, the plastic film 2 is formed of a polyethylene film having a thickness of 10 to 50 μm in a tube shape, and its diameter is the same as that of the cylinder. The diameter is set so that the body 1 can be loosely fitted, and the length thereof is slightly longer than the length of the cylindrical body 1. The left end (one end) of the plastic film (tube) 2 is shown in FIG.
As shown in FIG. 3, the upper half is removed stepwise so that the left end 2a of the upper half is shorter than the left end 2b of the lower half, facilitating manual opening of the left ends 2a, 2b. . This facilitates the work of fitting the plastic film 2 into the cylindrical body 1.

As shown in FIGS. 4 and 5, the plastic film 2 is fitted to the cylindrical body 1 to cover the entire circumference thereof, as shown in FIGS. It is bent in one direction and accommodated in both ends of the tubular body 1. Then, the cylindrical body 1 covered with the plastic film 2 is expanded into a predetermined shape by the bulge processing machine 5 shown in FIG.

In FIG. 6, 5 is a bulge processing machine, 6, 7
Is its upper and lower type. The lower die 7 is fixed to the base side, and the upper die 6 is vertically moved by a ram. Upper and lower molds 6, 7
Has punch fitting grooves 6a, 7a having an arcuate cross section at both left and right ends of the mating surface portion, and arcuate groove-shaped forming surfaces 6b, 7b having a gradually increasing diameter at the left and right center portions therebetween. Further, the stepped punches 8 and 8 are fitted and arranged in the punch fitting grooves 7a and 7a of the lower die 7, and the molding surface 7b of the lower die 7 is covered with the above-mentioned plastic film 2 to form the cylindrical body 1.
Is fitted and placed. The cylindrical body 1 is composed of the upper and lower walls 1 on the compression wall side.
The b and 1b are arranged so as to be vertically arranged and fitted and mounted on the molding surface 7b.

As shown in FIG. 7, in the stepped punches 8 and 8, the large diameter portion 8a is located outside and the small diameter portion 8b is located inside, and the outer peripheral surface 8b-1 of the small diameter portion 8b is formed. The outer peripheral surface 8 has a curved conical surface having an axial center outward in the radial direction on the inner end side, and the outer peripheral edge portion 8b-2 at the inner end has a smooth arc surface.
By press-fitting b-1 (small diameter portion 8b) into the end portion 1c of the cylindrical body 1 described above, the sealing function of this portion is enhanced without damaging the end portion 1c.

In this state, the upper die 6 is lowered to surround the punches 8 and 8 and the upper half of the cylindrical body 1, and then each punch 8,
While pressurizingly supplying the molding oil from the oil passages 9 formed through the axial center of the cylinder 8, the punches 8 are moved in the approaching direction to compress the cylinder 1 in the axial direction. The hollow part (molded product) 3 as shown in FIG. 8 is formed by bulging the middle part of the body 1 into a shape along the molding surfaces 6b, 7b of the upper and lower molds 6, 7. This hollow body 3 is thin in the left and right walls of the middle part and thicker in the upper and lower walls, and is bulging-molded into an elliptical shape whose cross section is long in the vertical direction. It forms the main arm of the rear arm. The above-mentioned cylinder 1 is a cylinder (square pipe) having a rectangular cross section, the outer periphery of the cylinder is covered with a plastic film and attached to a predetermined bulge processing machine, and the outer shape is transformed into a predetermined shape by the bulge processing machine. You may allow it.

[0012]

As is apparent from the above description, according to the present invention, the outer periphery of the cylinder is covered with a plastic film,
Since the tubular body is attached to the upper and lower molds via the plastic film, the plastic film prevents direct contact between the tubular body and the upper and lower molds, and fulfills a lubricating function between the two during bulging. . Also,
Since the plastic film also covers the outer periphery of the molded product after molding, it is possible to prevent damage due to contact of the molded product with obstacles. Further, since the plastic film is a solid material, it does not adhere to the hands of workers, clothes, etc., and is easily peeled off from the molded product, which improves the working environment.

[Brief description of drawings]

FIG. 1 is a perspective view of a cylinder according to the present invention.

FIG. 2 is a perspective view of a plastic film according to the present invention.

FIG. 3 is an enlarged sectional view taken along the line III-III in FIG.

FIG. 4 is a partial cross-sectional side view of a cylindrical body whose outer periphery is covered with a plastic film.

5 is an enlarged sectional view taken along line VV of FIG.

FIG. 6 is a cross-sectional view showing a bulging state of a cylinder according to the present invention.

FIG. 7 is an enlarged cross-sectional view of a portion A of FIG.

FIG. 8 is a perspective view of a hollow body bulged according to the present invention.

[Explanation of symbols]

1 cylinder (pipe) 1a Left and right side walls 1b Surrounding walls 1c end 2 plastic film 3 hollow body 5 Bulge processing machine 6 Upper mold 6a Punch fitting groove 6b Molding surface 7 Lower mold 7a Punch fitting groove 7b Molding surface 8 punches 8a Large diameter part 8b small diameter part 8b-1 outer peripheral surface 8b-2 outer peripheral edge 9 oilways

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yuji Mizuno             10 stock associations at 1417 Kinoricho, Hamamatsu City, Shizuoka Prefecture             Shakyoei Factory F-term (reference) 4E050 HA06

Claims (3)

[Claims] 1. A cylindrical body (1) is covered with a plastic film (2) on its outer periphery, and the cylindrical body (1) is sandwiched by upper and lower molds (6, 7) with the plastic film (2) interposed therebetween. A cylinder characterized in that a liquid is press-fitted into the cylindrical body (1) to deform the outer shape of the cylindrical body (1) into a shape corresponding to the molding surfaces (6b, 7b) of the upper and lower molds (6, 7). How to bulge your body. 2. The method of bulging a cylinder according to claim 1, wherein the material of the cylinder (1) is an aluminum alloy, and the plastic film (2) is a polyethylene film. 3. A plastic film (2) is a cylindrical body (1).
3. The method for bulging a tubular body according to claim 1, wherein the tubular body is formed in a tubular shape that is fitted into the outer periphery of the tube so as to be detachable.