JPH01266914A - Forming method in one stage for flanging and stepping pipe stock having swelled cylinder - Google Patents

Abstract

PURPOSE:To improve the forming efficiency and to reduce the cost by bulging a swelled pipe stock equipped with a leading hole at the side wall of the pipe stock, inserting the swelled pipe stock into a die and drawing a drawing tool for flanging upward. CONSTITUTION:The swelled cylindrical pipe 2 having the leading hole is formed on the pipe stock 1 by the bulging. A cylindrical projecting surface 7 with required length is notched at the inner surface of a cylindrical clearance 9 of the die 6, the cylindrical swelled pipe 2 of the pipe stock 1 is inserted into the clearance 9. Then, the drawing tool 5 for flanging is inserted from an opening part of the pipe stock 1 to set and the fool having an enlarged expanding part is strongly drawn upward is perform the drawing. By this method, the step 7 is formed the upper half part of the cylindrical pipe 2, simultaneously, the flanging is performed. Because the stepping 7 and flanging are performed in one stage, the forming efficiency of the product is improved and its cost is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for simultaneously machining a flange and a step in a bicycle component having a cylindrical projecting tube on the side wall of the tube material in one step.

As mentioned above, a formed tube having a cylindrical protruding tube on the side wall is generally widely used as a joint tube for assembling a bicycle frame. Although it is easy to obtain a cast product with a desired level difference on the outer periphery of the protruding tube, it has not been carried out due to manufacturing costs.

However, recently, bulge forming methods, whether hydraulic or rubber, have been widely used, and in the present invention, the side walls of pipe materials formed by the bulge forming method on raw pipes are also widely used. The starting material is one having a bulging cylindrical tube.

Furthermore, a pilot hole of an appropriate size is bored in the center of the tip of this bulging cylindrical tube as a preliminary step, and the raw material tube that has undergone this preliminary step is used as the starting material of the present invention.

In the present invention, the above-mentioned starting material is set and charged into the mold of the present invention, and a drawing tool or an extrusion tool is used to perform the first step.
At the same time as the first step is carried out, a required step is formed on the outer circumference of the cylindrical projection tube. This is the gist of the invention.

The invention will now be described with reference to the accompanying drawings.

FIG. 1 of the accompanying drawings is a sketch of an intermediate lug material tube 1 to be processed according to the present invention, and this intermediate lug material 1 has only one cylindrical protruding tube 2 on the tube side wall by bulge processing technology. The reason why the intermediate lug tube 1 having the - number of cylindrical projecting tubes 2 is shown here is to make the description of the embodiment of the present invention easier to understand and simpler.

Items that have a cylindrical protruding tube 2 on the side wall of the material tube and are used as bicycle parts include general head lugs, hanger lugs, and seats that have multiple cylindrical protruding tubes in addition to the intermediate lug mentioned above.・There are lags etc. It goes without saying that the method of the present invention can also be applied to any cylindrical protruding tubes in these lugs to process the "flange" and step.

Furthermore, FIG. 1 shows that a guide hole 3 is provided at the center of the tip of the cylindrical protruding tube 2, and this guide hole 3 engages with a gripping thread at the tip of an extraction tool 5 (described later). The cylindrical projection tube 2 is provided in order to be convenient and to facilitate the operation of opening the flange of the cylindrical projection tube 2.

FIG. 2 is a partially cross-sectional view showing an example of a known machining operation for protruding the tip of a tube, and shows a mold 4 having a cylindrical cavity 9 for accommodating a cylindrical protruding tube 2. This is a known example showing a situation in which the extraction tool 5 is introduced from the opening of the extraction tool 5, and the tip portion of the extraction tool 5 advances into the cylindrical projection tube 2 and passes through the guide hole 3. Since it is an enlarged extension field, the required protrusion is performed. Needless to say, the size of the enlarged portion of the extraction tool 5 is determined by the inner diameter of the tube to be machined.

Details regarding the driving method and device for the extraction tool 5 are disclosed in known documents such as Utility Model No. 10349/1983.

FIG. 3 is a sectional view of a mold 6 for carrying out the method of the present invention, and the differences from the known mold 4 shown in FIG. 2 are as follows. In order to add a step 7 that is lower than the lower outer circumferential portion to the part, a circumferential convex surface 7 corresponding to the step of a required length is carved on the inner surface of the cylindrical cavity 9 of the mold 6.

This cylindrical convex surface reaches the upper opening of the cylindrical cavity 9.

As shown, the rear part of the extraction tool 5 consists of an enlarged extension, and the wall of the cylindrical projecting tube 2, i.e. the thick wall of the tube, lies between the circumferential convex surface 7 of the mold 6 and the enlarged extension of the extraction tool 5. Since the extraction tool 5 is held in place, the extraction tool 5 is pulled upward with a strong extraction force, and the upper half of the cylindrical protruding tube 2 becomes thinner and slightly elongated, thus forming the required step 7. is formed.

As the extraction tool 5 rises, a step 7 is created on the outer periphery of the upper wall of the cylindrical projection tube 2, and at the same time, the upper end of the projection tube 2 is also removed by the tool 5.
The required expansion is achieved by the enlarged extension.

After completing its work, the extraction tool 5 escapes from the upper opening of the cylindrical cavity 9 of the mold 6.

As described above, according to the method of the present invention, it has become possible to form an overhang and a step on the side wall of the material tube with a bulging cylindrical body in the same process.

Fig. 4 shows the situation where both the work of flange and adding the step 7 to the bulging cylindrical pipe 2 of the material pipe 1 has been completed, and shows the cross section of the mold 6 and the workpiece set inside it. This indicates that the workpiece can now be removed from the mold.

FIG. 5 is a side view of a molded article, ie, an intermediate lug, obtained by the method of the present invention, showing that the outer diameter of the upper outer circumference of the cylindrical projection tube 2 is smaller than that of the lower outer circumference. In other words, the difference in level can be said to be that the inner diameters of the main tubes are the same but the outer diameters are different.

FIG. 6 shows a cylindrical projecting tube 2 in which the boundary line of the step is made into a curved line 8 for decorative purposes.

Data obtained when the method of the present invention was carried out using an aluminum pipe as a material pipe are shown below.

Aluminum tube body Outer diameter 36mm Inner diameter 26mm 1 bulging protruding tube Outer diameter 32mm Inner diameter 24mm Leading hole Size Diameter 16 Trunk step Difference Small diameter 2 9
mm Large diameter 33mm

[Brief explanation of the drawing]

Figure 1 shows a material tube with a bulging cylindrical tube on the side wall, Figure 2 is a partial cross-sectional view of the bulging cylindrical tube of the material tube inserted into a mold, and Figure 3 shows the inside of the mold of the present invention being pulled out. Figure 4 is a diagram showing how the tool works, Figure 4 is a diagram of the extraction tool being removed from the mold, Figure 5 is a side view of the molded product obtained by the present invention, and Figure 6 is a diagram showing the step boundary line of the present invention being curved. Indicates a molded product with . 1: Material tube 2: Swelling cylindrical tube 3: Leading hole
4: Conventional mold 5; Drawing tool 6: Mold of the present invention 7: Step and convex surface on which the step is to be formed 8: Curved step boundary line 9: Cylindrical gap of the mold

Claims (1)

[Claims] The starting material is a raw material tube with one bulging tube body on the side wall and a guide hole of any size drilled in the center of the tip of the bulging tube body by bulge forming method, and the material is tightly attached to the bulging tube body. The tube is charged into a mold having a cylindrical gap with an open upper end, and the cylindrical gap is divided into upper and lower parts, and a step is formed on the inner surface of the upper cylinder around the upper outer periphery of the expanded tube. A circumferential protrusion is carved into the material tube, a flange extraction tool is inserted from the open end of the material tube, and the tool is set inside the bulge tube, grasping the upper grip of the tool and firmly pulling it upward. A method for forming a flange of the bulging tube and a step on the upper outer periphery of the bulging tube in one step, characterized by a drawing step.