Background Art A power plug for use in 200 to 250V has several shapes of electrode poles depending on the method of manufacturing the power plugs and their uses.

As shown in FIG. 1 to FIG. 3, an assembly type power plug 30 that is connected to a power supply line, is divided into an top end and a lower portion. The power plug 30 includes power plug bodies 31 and 31a that are coupled together by a screw 35, an electrode pole clamp unit 32 that is inserted with pressure between the bodies 31 and 31a, and two bar-shaped electrode poles 40 each having clamp screws 44 for clamping wires 50 formed at side ends of wire insert holes 43. At this time, the front side of each of the bar-shaped electrode poles 40 is supported by the electrode pole clamp unit 32, has a hemispherical front end 41 and is exposed toward the front of the bodies 31 and 31a. A wire insert hole 43 into which the wire 50 is inserted with it supported by the clamp unit 32, is formed in a given depth at the rear of each of the bar-shaped electrode pole 40.

FIG. 4 and FIG. 5 illustrate another types of the power plugs for use in 100 to 120V in which electrode poles have a piece shape. FIG. 4 and FIG. 5 illustrate the power plug 60 for an adaptor that is inserted into a receptacle for 200 to 250V having a bar-shaped insert member.

The power plug 60 includes two piece-shaped insert holes 63 the front sides of which are opened and into the rear sides of which two electrodes pieces 71 of a power plug 70 for 100 to 120V are inserted, a power plug body 61 having two electrode piece joint terminals 64 therein, electrode pole clamp units 62 that are inserted with pressure into the front side of the body 61 and then assembled by a screw 62a, and two circular bar-shaped electrode poles 65 supported by the clamp units 62 and having circular joint terminals 67 at its end into which the two electrode piece joint terminals 64 are inserted with pressure. At this time, the front side of each of the two bar-shaped electrode poles 65, having a hemispherical front end 66, is exposed toward the front side of the body 61. Further, the circular joint terminal 67 is inserted into the rear end of the clamp unit 62.

The construction of each of the two types of the bar- shaped electrode poles 40 and 65 used in the power plugs for common 200 to 250V will now be described.

The rear end of each of the bar-shaped electrode poles 40 and 65 has a construction in which the wire insert hole 43 into which the wire 50 is inserted is formed, or a construction in which a circular joint terminal 67 is formed. The shapes of the bar-shaped electrode poles may be different depending on their uses. In their entire shape, however, the front end of each of the bar-shaped electrode poles has a circular bar shape having a given diameter and length and the front end has a hemispherical or a shape

similar to the hemispherical shape that is inserted into the receptacle for use in 200 to 250V.

A common method of manufacturing the bar-shaped electrode pole for use in 200 to 250V includes a first cutting process of cutting a circular bar (brass bar) of a given diameter using a cutting machine such as a lathe, etc. , a second cutting process of cutting the front end of the bar to be hemispherical, a third process as a process of machining the rear end potion of the bar, of shaping a given wire insert hole using a boring or pressing process, or shaping a circular joint terminal, and a process of nickel-plating the surface of the electrode pole.

Further, in addition to the above manufacture method, another methods for manufacturing the electrode pole for a special use whose durability and functionality have been improved, may include a die-casting process using a die- casting mold, a stamping process using a stamping mold, and the like.

The above-mentioned methods for manufacturing the bar- shaped electrode pole have several advantages and disadvantages. Most bar-shaped electrode poles except for the electrode poles for a special use have been manufactured using a brass bar having a low manufacture cost as a material and using the cutting processes of several times as a main process.

However, the conventional methods for manufacturing the bar-shaped electrode pole using the brass bar as the material and employing the cutting processes of several times as the main process have a high material cost and are unsuitable for a mass production due to low production speed. Further, these methods require expensive manufacture equipments in case of automatic production.

Disclosure of Invention Accordingly, the present invention has been contrived to overcome the shortcomings of a conventional method for manufacturing a bar-shaped electrode pole for a power plug that uses a brass bar as a material and employs cutting processes of several times as a main process.

An object of the present invention is to provide a method and mold apparatus for manufacturing a bar-shaped electrode pole for a power plug, in which the bar-shaped electrode pole are manufactured by means of a drawing process by a press using a pipe as a material, thereby lowering a material cost, reducing a material loss, being suitable for a mass production due to high production speed, and reducing an equipment cost and a manufacture cost.

To achieve the above objects, according to the present invention, there is provided a method of manufacturing a bar-shaped electrode pole for a power plug, including a pipe drawing setting step of inserting a cut raw material pipe into a drawing die having a hemispherical die head installed at a given press machine in an upright position ; a pre-drawing step of hammering a top end of the raw material pipe set in the drawing die, at a given stroke, by using a pre-drawing punch including a cylindrical punch groove having a gradient of an acute angle and an aperture larger than a hemispherical diameter of a front end of the given bar-shaped electrode pole, whereby a circumferential top end of the raw material pipe set in the drawing die is inwardly pleated at a given angle; a press drawing step of hammering the top end of the raw material pipe set in the drawing die, a portion of the top end is pleated by means of the pre-drawing step, by using the press drawing punch having a hemispherical punch groove same as the hemispherical diameter of the front end

of the given bar-shaped electrode pole, whereby the top end is hemispherically pressed on a hemispherical die head of the drawing die ; and a lapping step of finishing the top end of the pipe that is hemispherically pressed on the hemispherical die head of the drawing die by means of the press drawing process, by using a lapping punch having the hemispherical lapping groove same as the hemispherical diameter of the front end of the given bar-shaped electrode pole.

Further, the method further includes, between the pre- drawing process and the press drawing process, second drawing processes for hammering the top end of the raw material pipe a portion of which is pleated by the pre- drawing process, by using a second drawing punch including the hemispherical punch groove having a smooth gradient that is more similar to the hemispherical shape than the cylindrical punch groove of the pre-drawing punch, so that the top end of the raw material pipe is pleated to become more hemispherical.

Furthermore, the method further includes, between the press drawing process and the lapping process, a drawing junction welding process of spot-welding a top center of the raw material pipe that is pressed to be the hemispherical shape by the press drawing process, by using a punch having a spot welding head.

Brief Description of the Drawings Further objects and advantages of the invention can be more fully understood from the following detailed description taken in conjunction with the accompanying drawings in which: FIG. 1 is a cross-sectional view illustrating a power

plug according to one embodiment of the present invention; FIG. 2 is an assembled perspective view illustrating a bar-shaped electrode pole for a power plug according to one embodiment of the present invention; FIG. 3 is an exploded perspective view illustrating a bar-shaped electrode pole for a power plug according to one embodiment of the present invention; FIG. 4 is a cross-sectional view illustrating a power plug for an adaptor according to another embodiment of the present invention; FIG. 5 is an exploded perspective view illustrating a power plug for an adaptor according to another embodiment of the present invention; FIG. 6 is a cross-sectional view illustrating a pipe- shaped electrode pole for a power plug that will be shaped according to one embodiment of the present invention; FIG. 7 is a cross-sectional view illustrating a pipe- shaped electrode pole for a power plug that will be shaped according to another embodiment of the present invention ; FIG. 8 is a cross-sectional view illustrating a die in a mold apparatus for manufacturing the bar-shaped electrode pole for the power plug, which is viewed from one side, according to one embodiment of the present invention ; FIG. 9 is a cross-sectional view illustrating the die in the mold apparatus for manufacturing the bar-shaped electrode pole for a power plug, whish is viewed from another side, according to one embodiment of the present invention; FIG. 10 is a cross-sectional view illustrating the die taken along lines A to A in FIG. 8; FIG. 11 is a cross-sectional view illustrating the die taken along lines B to B in FIG. 9; FIG. 12 is a plane view illustrating a press drawing

apparatus by a method and mold apparatus for manufacturing a bar-shaped electrode pole for a power plug according to one embodiment of the present invention; FIG. 13 is a cross-sectional view of the press drawing apparatus by the method and the mold apparatus for manufacturing the bar-shaped electrode pole for the power plug according to one embodiment of the present invention ; FIG. 14 is a cross-sectional view of the press drawing apparatus by the method and the mold apparatus for manufacturing the bar-shaped electrode pole for the power plug according to one embodiment of the present invention ; FIG. 15a to FIG. 15c illustrate pre-drawing processes by the method and the mold apparatus for manufacturing the bar-shaped electrode pole for the power plug according to one embodiment of the present invention; FIG. 16a to FIG. 16c illustrate press processes by the method and the mold apparatus for manufacturing the bar- shaped electrode pole for the power plug according to one embodiment of the present invention; FIG. 17a to FIG. 17c illustrate spot welding processes by the method and the mold apparatus for manufacturing the bar-shaped electrode pole for the power plug according to one embodiment of the present invention; FIG. 18a to FIG. 18b illustrate lapping processes by the method and the mold apparatus for manufacturing the bar-shaped electrode pole for the power plug according to one embodiment of the present invention ; FIG. 19 shows a state where the drawing machining has been completed by the method and the mold apparatus for manufacturing the bar-shaped electrode pole for the power plug according to one embodiment of the present invention; FIG. 20 is a plane view illustrating a press drawing apparatus by a method and a mold apparatus for

manufacturing a bar-shaped electrode pole for a power plug according to another embodiment of the present invention; FIG. 21a to FIG. 21c illustrate second pre-drawing processes by a method and a mold apparatus for manufacturing a bar-shaped electrode pole for a power plug according to another embodiment of the present invention ; and FIG. 22a to FIG. 22c illustrate press drawing processes by a method and a mold apparatus for manufacturing a bar-shaped electrode pole for a power plug according to another embodiment of the present invention.

Best Mode for Carrying Out the Invention A method of manufacturing a bar-shaped electrode pole and the construction of a mold apparatus thereof will now be described in detail in connection with preferred embodiments with reference to the accompanying drawings.

FIG. 6 is a cross-sectional view illustrating a pipe- shaped electrode pole 40a according to one embodiment of the present invention, which will substitute the conventional assembly type bar-shaped electrode pole 40 for the power plug 30.

The pipe-shaped electrode pole 40a to be shaped according to the present invention has the same diameter and length as the conventional bar-shaped electrode pole 40.

The pipe-shaped electrode pole 40a includes a front end 41a having the same diameter as the conventional front end 41 (see FIGS. 1 to 3). Further, an inner ring 45 for a wire insert member and a screw groove 46 for the clamp screw 44 (see FIGS. 2 and 3), are formed at the rear end of the pipe-shaped electrode pole 40a.

FIG. 8 to FIG. 19 illustrate processes of manufacturing the bar-shaped electrode pole for

manufacturing the pipe-shaped electrode pole 40a and the construction of a program-type drawing press mold apparatus thereof according to a preferred embodiment of the present invention.

Main constitutional elements of the press mold apparatus for implementing the method of manufacturing the bar-shaped electrode pole according to one embodiment of the present invention are as follows: a plurality of drawing dies 80a to 80f in which a raw material pipe P of a given thickness that has the same outer diameter as a given pipe-shaped electrode pole 40a to be shaped; a plurality of punches 90a to 90d mounted on a hammer apparatus (not shown) of a press machine, which are hammered into the plurality of the drawing dies 80a to 80f; a rotary feed stand 110 of a circular plate shape that rotatively supports the plurality of the drawing dies 80a to 80f to a bed 100 of the press machine; and a shaped product extraction unit formed at one sides of the plurality of the drawing dies 80a to 80f, the rotary feed stand 110 and the bed 100.

The number of the drawing dies 80a to 80f may be differently set depending on the number of a specific process of manufacturing the bar-shaped electrode pole. The drawing dies 80a to 80f are installed on a circumference around the top edge of the rotary feed stand 110. In one embodiment, six drawing dies referred to as first to sixth drawing dies 80a to 80f are radially installed at the same distance by 60 degree (see FIG. 12).

Referring now to FIG. 8 to FIG. 14, the first to sixth drawing dies 80a to 80f have the same construction. Each of the drawing dies 80a to 80f includes a die base 81 fixed to the top of the rotary feed stand 110, a cylindrical die

body 82 extended upwardly from the die base 81 by a given height, a setting groove 83 of a given depth into which a given raw material pipe (P) is inserted in an upright position at the center of the die body 82, a plurality of discharge holes 85 that divide the circumference of a ring- shaped pipe abutment 84 formed at the bottom of the setting groove 83 at a constant distance and then penetrate the die base 81, and a die central stand 86 that is cylindrically formed at the center by the setting groove 83. At this time, the die central stand 86 has a hemispherical head 86a at its top end.

With reference to FIGS. 8 and 9, in the die central stand 86, the height (Ha) from the top end of the ring- shaped pipe abutment 84 being the bottom of the setting groove 83 to the aperture center of the hemispherical head 86a is same as the length (L) of the pipe-shaped electrode pole 40a shown in Fig. 6.

Furthermore, a radius of the hemispherical head 86a is same as the radius of the front end 41a of the pipe-shaped electrode pole 40a shown in FIG. 6 minus a thickness of the raw material pipe (P).

In addition, the height of a top end 82a in the cylindrical die body 82 is higher a little than the central line of the diameter of the hemispherical head 86a in the die central stand 86. The top end 82a is protruded about a half of a pleated member that will be drawn into the hemispherical head 86a of the die central stand 86 among the top end of the raw material pipe (P) inserted into the setting groove 83.

By reference to FIG. 12 to FIG. 14, the rotary feed stand 110 is rotatively mounted to a rotary axis 111 at the center of a rectangular press machine bed 100. At this time, the rotary axis 111 is connected to a driving motor (not

shown) installed at one lower side of the press bed 100 by means of a direct or indirect motor. Further, a plurality of bottom discharge holes 112 corresponding to the plurality of the discharge holes 85 formed in the die base 81 are formed at six location where the drawing dies 80a to 80f are installed.

Also, a discharge stand 120 being one of the constitutions of the shaped product discharge unit is installed in each of the bottom discharge hole 112 in the rotary feed stand 110, and supports the bottoms of the plurality of discharge rods 121.

In the above, the discharge stand 120 includes the plurality of the discharge rods 121 inserted into the plurality of the discharge holes 85 so as to extend from the bottom discharge hole 112 of the rotary feed stand 110 to the ring-shaped pipe abutment 84 being the bottom of the setting groove 83 in the drawing dies 80a to 80f, and a tension spring 123 installed between the top end of the outer circumference of the discharge stand 120 and the bottom end of the rotary feed stand 110, for downwardly resiliently supporting the discharge stand 120 (see FIG. 13 and FIG. 14).

The rotary feed stand 110 constructed above is controlled to rotate in six steps of a setting location D1, a pre-drawing location D2, a press drawing location D3, a spot welding location D4, a lapping location D5 and a discharge location D6, by means of a program-type drawing control circuit, at a constant angular velocity. At this time, the six locations are installed in an equal distance at a 60-degree distance on a circumference Further, a cylindrical discharge stand support wheel 124 of a given height is installed at the top of the press bed 100 that rotatively supports the rotary feed stand 110.

In the above, the support wheel 124 slidingly supports the bottom of the discharge stand 120 at a location corresponding to the remaining rotary trace of the discharge stand 120 except for the discharge location D6.

In addition, a discharge cylinder 126 having a working rod 125 connected to the bottom of the discharge stand 120 is installed at a portion corresponding to the discharge location D6 of the rotary feed stand 110. The discharge cylinder 126 is intermittently controlled to instantly upwardly hammer the working rod 125 when one of the drawing dies touches the discharge location D6 by a control device (see FIG. 13 and FIG. 14).

The plurality of the punches mounted on the hammer apparatus of the press machine are located vertically upwardly from the pre-drawing location D2, the press drawing location D3, the spot welding location D4 and the lapping location D5, of the setting location D1, the pre- drawing location D2, the press drawing location D3, the spot welding location D4, the lapping location D5 and the discharge location D6, along which the six drawing dies 80a to 80f installed at the rotary feed stand 110 are intermittently rotated. At this time, each punch includes a pre-drawing punch 90a, a press drawing punch 90b, a spot welding punch 90c and a lapping punch 90d (see FIG. 15 to FIG. 18).

Referring to FIG. 15a to FIG. 15c, the pre-drawing punch 90a installed at the pre-drawing location D2 includes a cylindrical punch groove 91 having an entrance diameter larger than the hemispherical diameter of the front end of a given bar-shaped electrode pole and a gradient of an acute angle. The pre-drawing punch 90a hammers, at a given stroke, an upright top end (Pa) of a raw material pipe (P) set in each of the drawing dies 80a to 80f that are

sequentially moved onto the pre-drawing location D2, so that the upright top end (Pa) is inwardly pre-drawn to be a pleated type top end (Pb).

By reference to FIG. 16a to FIG. 16b, the press drawing punch 90b installed at the press drawing location D3 includes a hemispherical punch groove 92 having the same diameter as the hemispherical diameter of the front end 41a of a given pipe-shaped electrode pole to be shaped. The press drawing punch 90b hammers, at a given stroke, the pleated type top end (Pb) of the raw material pipe (P) the top of which was inwardly pleated at a given angle by the pre-drawing process, against each of the drawing dies 80a to 80f that are sequentially moved onto the press drawing location D3. Thus, the press drawing punch 90b presses the pleated type top end (Pb) of the raw material pipe (P) on the hemispherical die head 86a of each of the drawing dies 80a to 80f, so that the pleated type top end (Pb) is drawn to be a hemispherical front end (Pc).

With reference to FIG. 17a, the spot welding punch 90c installed at the. spot welding location D4 includes a sport welding head 93 at its bottom. The spot welding punch 90c controls the spot welding head 93 to access and then spot- weld the top center of the hemispherical front end (Pc), at a given stroke, when the raw material pipes (P) set in the respective drawing dies 80a to 80f are sequentially moved onto the spot welding location D4.

Referring to FIG. 18a, the lapping punch 90d installed at the lapping location D5 includes a hemispherical lapping groove 94 of the same diameter as the hemispherical diameter of the front end of a given bar-shaped electrode pole and rotates on its axis at a given number. The lapping punch 90d rotatively accesses and then finishes, at a given stroke, the top end of the hemispherical front end (Pc) of

the raw material pipe (P) set in the respective drawing dies 80a to 80f that are sequentially moved onto the lapping location D5.

In the above construction, the spot welding head 93 of the spot welding punch 90c and each of the drawing dies 80a to 80f are electrically connected to a spot welding machine.

The method of manufacturing the bar-shaped electrode pole by the press mold apparatus according to one embodiment of the present invention will now be described.

In the manufacture method of the bar-shaped electrode pole, raw material pipes (P) being metal material (brass) pipes that were cut by a given length and a given diameter required in order to shape the pipe-shaped electrode pole 40a of a given rule, is used as a shaping material.

The cut raw material pipes (P) are experienced by a pipe setting process. The pipe setting process includes inserting the pipes (P) into a material dispenser 130 formed around the pipe setting location Dl of the rotary feed stand 110, sequentially and consecutively dispensing the pipes (P) from the first drawing die 80a to the sixth drawing die 80f that are moved onto the pipe setting location Dl at a given angular velocity by means of the rotary feed stand 110 intermittently controlled by a control device, and inserting the pipes (P) into the setting groove 83 of each of the drawing dies 80a to 80f in an upright position.

The first drawing die 80a in which the raw material pipe (P) is set in the pipe setting location D1, is rotatively moved onto the pre-drawing location D2 by a rotary control of the rotary feed stand 110 (see FIG. 12).

If the first drawing die 80a in which the raw material pipe (P) is set is rotatatively moved onto the pre-drawing location D2, the first drawing die 80a is experienced by a

pre-drawing process. At this time, the pre-drawing process includes allowing the pre-drawing punch 90a in which the cylindrical punch groove 91 having an entrance diameter and a gradient of an acute angle larger than the hemispherical diameter of the front end of the pipe-shaped electrode pole 40a to hammer, at a given stroke, the upright top end (Pa) of the raw material pipe (P) set in the first drawing die 80a, so that the upright top end (Pa) is inwardly pleated at a given angle and then drawn to be the pleated type top end (Pb) (see FIG. 15a to FIG. 15c).

After the above pre-drawing process is completed, the first drawing die 80a is rotatively moved onto the press drawing location D3 by a rotary control of a given angle by the rotary feed stand 110.

If the first drawing die 80a is rotatively moved onto the press drawing location D3, the first drawing die 80a is experienced by a press drawing process. At this time, the press drawing process includes allowing the press drawing punch 90b having the hemispherical punch groove 92 of the same diameter as the hemispherical diameter of the front end of a given pipe-shaped electrode pole 40a to hammer, at a given stroke, the pleated type top end (Pb) of the raw material pipe (P) that was inwardly pleated at a given angle by the pre-drawing process, so that the pleated type top end (Pb) of the raw material pipe (P) is pressed on the hemispherical die head 86a of the first drawing die 80a and is then drawn to be the hemispherical front end (Pc) (see FIG. 16a to FIG. 16c).

After the press drawing process is completed, the first drawing die 80a is rotatively moved onto the spot welding location D4 by a rotary control of a given angle by the rotary feed stand 110.

If the first drawing die 80a is rotatively moved onto

the spot welding location D4, the first drawing die 80a is experienced by a spot welding process. At this time, the spot welding process includes allowing the spot welding punch 90c having the sport welding head 93 to access, at a given stroke, and then spot-weld the top center of the hemispherical front end (Pc) of the raw material pipe that was pressed on the hemispherical die head 86a by the press drawing process (see FIG. 17a to FIG. 17c).

After the mentioned drawing junction welding process is completed, the first drawing die 80a is moved onto the lapping location D5 by a rotary control of a given angle by the rotary feed stand 110.

If the first drawing die 80a is moved onto the lapping location D5, the first drawing die 80a is experienced by a lapping process. At this time, the lapping process includes allowing the lapping punch 90d having the hemispherical lapping groove 94 of the same diameter as the hemispherical diameter of the front end of the given pipe-shaped electrode pole 40a to rotatively access, at a given stroke, and then finish the welded portion of the top center of the hemispherical front end (Pc) that was welded by the sport welding process (see FIG. 18a and FIG. 18b).

Through the pre-drawing process, the press drawing process and the lapping process, the raw material pipe (P) that was set in the first drawing die 80a in an upright position, is shaped to be a shaping pipe P40 having the hemispherical front end (Pd) the top end of which is smooth like the front end 41a of a given pipe-shaped electrode pole 40a to be shaped (see FIG. 19).

After the lapping process is completed, the first drawing die 80a is moved onto the pipe discharge location D6 by a rotary control of a given angle by the rotary feed stand 110 along with the shaping pipe P40 the hemispherical

front end (Pd) of which is shaped.

If the first drawing die 80a is moved onto the pipe discharge location D6, the first drawing die 80a is experienced by a shaping pipe discharge process. At this time, the shaping pipe discharge process includes allowing the bottom of the discharge stand 120 of the first drawing die 80a to access the top of the working rod 125 of the discharge cylinder 126 out of a sliding contact with the cylindrical discharge stand support wheel 124, and instantly upwardly hammering the discharge rod 125 of the first drawing die 80a by means of a hammering force of the working rod 125 that is instantly upwardly hammered at a given height under the control of the discharge cylinder 126 while hammering the bottom of the shaping pipe P40 inserted into the setting groove 83, so that the shaping pipe P40 is outwardly discharged in one direction from the first drawing die 80a.

If the process of discharging the shaping pipe (P40) from the first drawing die 80a is completed, the process of shaping the bar-shaped electrode pole by a series of the first drawing dies 80a is completed. The first drawing die 80a is again moved onto the pipe setting location D1 by an intermittent rotation control of a given angle by the rotary feed stand 110.

If the first drawing die 80a is again moved onto the pipe setting location D1, a new raw material pipe (P) is dispensed into the first drawing die 80a from the material dispenser 130 and is then set in the setting groove 83 in an upright position. The process of shaping the bar-shaped electrode pole is then repeatedly performed by the series of the above processes.

The series of the processes for shaping the bar-shaped electrode pole by the first drawing die 80a are

sequentially and consecutively carried out in the same process, by the remaining five second to sixth drawing dies 80b to 80f radially installed in the rotary feed stand 110 while being sequentially moved onto the corresponding shaping locations.

The raw material pipes (P) that were dispensed into and set in the six drawing dies 80a to 80f from the material dispenser 130 at the setting location D1, are consecutively shaped to be the shaping pipes (P40) having the same hemispherical front end (Pd) as the hemispherical diameter of the front end of the pipe-shaped electrode pole 40a while passing through the discharge location D6.

The shaping pipes (P40) having the hemispherical front end (Pd) that was formed by the press mold apparatus and method for manufacturing the bar-shaped electrode pole, are shaped to have the rear ends of various shapes necessary for various kinds of the bar-shaped electrode poles by means of several post-machining apparatus and post- machining methods.

For example, when the shaping pipe (P40) is to be made to be used for the bar-shaped electrode pole 40 for the assembly type power plug 30 as shown in FIG. 1 to FIG. 3, the inner ring 45. is formed into a given depth to form the wire insert hole 43a at the rear end of the shaping pipe (P40) since the rear end of the shaping pipe (P40) is already empty. Next, the screw groove 46 having the clamp screw 44 for clamping the wire is formed at the side of the shaping pipe (P400, thus completing the pipe-shaped electrode pole 40a being a substitution of the bar-shaped electrode pole 40 (see FIG. 6).

As another example, when the shaping pipe (P40) is to be made to be used for the bar-shaped electrode pole 65 that has the hemispherical front end 66 for another kind of

the power plug 60 for an adaptor as shown in FIG. 4 to FIG.

5 and has the circular joint terminal 67 at its rear end, a joint hoop 67a the rear end of the shaping pipe (P40) is outwardly pleated at a given width is formed, thus completing the pipe-shaped electrode pole 65a being a substitution of the bar-shaped electrode pole 65 (see FIG.

7).

Further, in addition to the above construction, even in a construction of a bar-shaped electrode pole for a so called mold-shaped power plug that is formed by inserting the wire and the bar-shaped electrode pole into a mold and then pressing the body of the power plug using a synthetic resin, a rib for a mold insert or a concaved groove for a synthetic resin mold may be formed at the rear end of the bar-shaped electrode pole.

In implementing this present invention, the above- mentioned press mold apparatuses and the manufacture methods are only illustrative but not limited to them. In order to increase drawing efficiency of the hemispherical front end (Pd) of the shaping pipe (P40), the press mold apparatuses and the manufacture methods may be modified in part.

FIG. 20 to FIG. 22 illustrate a press mold apparatus and a manufacture method for a method of manufacturing the bar-shaped electrode pole according to another embodiment of the present invention.

In the construction of the press mold apparatus for the method of manufacturing the bar-shaped electrode pole according to another embodiment of the present invention, the plurality of the drawing dies 80a to 80f, the rotary feed stand 110 and the discharge units are same as those in the one embodiment. However, some of the plurality of the punches 90a to 90d that are mounted on the hammer units of

the press machine and hammered to the plurality of the drawing dies 80a to 80f, are same to those in the one embodiment but some of the plurality of the punches 90a to 90d have modified punch grooves.

In the construction of the punches according to another embodiment of the present invention, the pre- drawing punch 90a, the press drawing punch 90b and the lapping punch 90d are same as those in the one embodiment.

However, a second pre-drawing punch 90e is further installed between the pre-drawing punch 90a and the press drawing punch 90b. A press drawing punch 90b is then installed. Next, the spot welding punch 90c is removed from the present embodiment and a lapping punch 90d is further installed.

The second pre-drawing punch 90e includes a punch groove 95 having a vertex bar 95a and a vertex groove 95b at its center. Thus, the pleated type top end (Pb) of the raw material pipe (P) that was pleated by the pre-drawing punch 90a is pleated to become more a hemispherical shape and the top end (Pb) is simultaneously upwardly protruded in part to form a vertex portion (Pe) (see FIG. 21).

The plurality of the punches constructed above are installed in the rotary feed stand 110, as shown in FIG. 20.

In the punches 90a to 90d according to another embodiment, at the top end of the rotary feed stand 110, the pre-drawing punch 90a is installed using the pre- drawing location D2a as a next location of the pipe setting location Dla, the second pre-drawing location the punch 90e is installed using the second pre-drawing location D3a as a next location, the press drawing punch 90b is installed using the press drawing location D4a as a next location, the lapping punch 90c is installed using the lapping location D5a as a next location, and the discharge cylinder

126 is installed using the discharge location D6a as a next.

The method of manufacturing the pipe-shaped electrode pole 40a by the punches 90a to 90d according to another embodiment will now be described.

Similar to the drawing process by the punches 90a to 90d according to the one embodiment, if the top end of the raw material pipe (P) is firstly drawn to be the pleated type top end (Pb) that was inwardly pleated at a given angle and is then moved onto the second pre-drawing location D3a by means of the pre-drawing process at a pre- drawing location D2a, the second pre-drawing punch 90e including the punch groove 95 having the vertex bar 95a and the vertex groove 95b at its center hammers the pleated type top end (Pb). Thus, the pleated type top end (Pb) of the raw material pipe (P) is pleated to become more a hemispherical shape while its top end is upwardly protruded thereby forming the vertex portion (Pe) (see FIG. 21a to FIG. 21c).

Next, at a press drawing location D4a, the press drawing process is performed. The press drawing process includes allowing the press drawing punch 90b to hammer the pleated type top end (Pb) of the raw material pipe (P) having the vertex portion (Pe) at a given stroke, thus pressing the pleated type top end (Pb) of the raw material pipe (P) and the vertex portion (Pe) on the hemispherical die head 86a and then drawing the pleated type top end (Pb) to become the hemispherical front end (Pc) (see FIG. 22a to FIG. 22b).

The lapping process at the lapping location D5a, and the process of discharging the shaping pipe (P40) shaped at the discharge location D6a are implemented in the same manner as the one embodiment.

In the method of manufacturing the pipe-shaped

electrode pole 40a according to another embodiment of the present invention, the vertex portion (Pe) is formed at the pleated type top end (Pb) of the raw material pipe (P) in the second pre-drawing process by the second pre-drawing punch 90e. Due to this, in the press process of making the pipe-shaped electrode pole 40a hemispherical by the press drawing punch 90b, a junction state of the center junction becomes good compared to the one embodiment. Accordingly, the spot welding process may be omitted from the present embodiment.

In the method of manufacturing the bar-shaped electrode pole according to one embodiment, depending on the level of the quality required for the bar-shaped electrode pole to be manufactured, the spot welding process or the lapping process might be omitted for the hemispherical front end (Pc) shaped by the pressure process.

Further, second and third drawing processes for more smoothly pleating the pleated portion may be further carried out between the pre-drawing process and the press drawing process.

Furthermore, in the method of manufacturing the bar- shaped electrode pole according to another embodiment of the present invention, depending on the level of the quality required for the bar-shaped electrode pole to be manufactured, a third drawing process of more smoothly pleating the pleated portion may be further carried out between the second pre-drawing process and the press drawing process. Also, the lapping process might be omitted for the hemispherical front end (Pc) shaped by the pressure process. The spot welding process may be further implemented between the press drawing process and the lapping process.

As described above, according to a mold apparatus and

a method for manufacturing a bar-shaped electrode pole for a power plug, the electrode pole is manufactured using a pipe as a material by means of a drawing process. Therefore, the present invention has new effects that it can lower material cost, reduce a material loss, reduce equipment cost and significantly reduce manufacture cost, and is suitable for a mass production due to a rapid production speed.

While the present invention has been described with reference to the particular illustrative embodiments, it is not to be restricted by the embodiments but only by the appended claims. It is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and spirit of the present invention.