JPS6242772B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for molding a two-layer molded body to serve as a casing for a wiring device such as an outlet, in which an inner shell 1 is primarily molded from a thermosetting synthetic resin, and then the inner shell 1 is When performing secondary molding in which the outer shell 2 of thermoplastic synthetic resin is attached to the inner shell 1 before the inner shell 1 hardens, the outer shell at this location is applied to the exposed portion 3 exposed to the outside of the inner shell 1. A protrusion 3a is formed that protrudes outward from the inner surface of the body 2, and a secondary mold 4 is pressed against the outer surface of the protrusion 3 to compress the outer surface of the inner shell 1 and mold the outer shell 2. The present invention relates to a method for forming a two-layer molded article, which is characterized by the following.

In general, thermosetting synthetic resin is used to manufacture parts for wiring devices such as table taps and exposed outlets from the standpoint of insulation performance and heat resistance.
They tend to break easily when dropped or hit by objects, and are unsafe because they are often used with the live parts exposed. Conventionally, as shown in FIGS. 1a and 1b, after assembling a blade holder 5 etc. inside an inner shell 1', an outer shell 2' made of rubber, soft vinyl chloride, etc.
was attached to the inner shell 1'. However, in this case, the molding process is a separate process, which increases the cost, and there is also the disadvantage that the cord 6 is integrated with the outer shell 2' and cannot be repaired.
Furthermore, when covering the outer shell 2', burrs of the resin of the outer shell 2' appear on the exposed portions of the inner shell 1'.

The present invention has been made in view of the above-mentioned points, and an object of the present invention is that the outer shell can be formed by secondary molding immediately after the inner shell is primarily molded, thereby reducing the number of steps. It is possible to reduce costs, and because the outer shell is molded with a secondary mold pressed against the outer surface of the protrusion of the inner shell and the outer surface of the protrusion is compressed, cracks in the inner shell are prevented. However, it is an object of the present invention to provide a method for molding a two-layer molded product in which no burrs of the outer shell appear on the upper surface of the protrusion.

The present invention will be explained in detail below with reference to Examples. This will be explained using a table tap as an embodiment of the present invention shown in FIG. The table tap consists of a base A for attaching a blade holder 5, a lid B that closes the opening of the base A, and a blade holder 5, and the base A has an inner shell 1.
and outer shell body 2. The inner shell 1 is molded from a thermosetting resin such as urea resin, melamine resin, or phenol resin, and has an approximately box-like shape with an open top. A partition wall 7 is erected over the entire length so as to be flush with the upper end surface of the inner shell body 1 from the bottom surface, and both sides of the partition wall 7 form blade holder insertion portions 8, respectively. A screw hole 9 is vertically bored in the approximate center of the partition wall 7, and press-fit parts 10 for fixing the blade holder 5 are provided on both sides of the screw hole 9. At the upper center of the side surface of the inner shell body 1 on the end side, there is provided an exposed portion 3 that protrudes and has a substantially rectangular cross section, and the exposed portion 3 has two plug blades for inserting the plug blades. A section 11 is bored. A cord insertion port 12 is bored in the upper center of the side surface of the inner shell body 1 opposite to the exposed portion 3, and the outer edge of the cord insertion hole 12 projects outward from the side surface of the inner shell body 1. This is the exposed part 3. An outer shell body 2 made of a thermoplastic synthetic resin with high impact resistance such as nylon resin is adhered to the outer surface of the inner shell body 1, and an exposed portion 3 of the inner shell body 1 where the plug blade insertion portion 11 is located; Cord insertion port 1
The exposed portion 3 with the screw hole 9 and the exposed portion 3 with the screw hole 9 are exposed to the outside. Like the base body A, the lid body B also consists of an inner shell body 1 made of a thermosetting synthetic resin and an outer shell body 2 made of a highly impact-resistant thermoplastic synthetic resin that covers the outer surface of the inner shell body 1. The exposed portion 3 of the plug blade insertion portion 11 on the side surface is exposed to the outside. A square hole 13 for inserting a press-fit part 10 is bored in the center of the blade holder 5, and a screw hole 14 is provided on the side of the square hole 13, so that both sides of the blade holder 5 in the longitudinal direction A blade receiving spring 15 is provided at each end. However, when assembling the table tap 13,
The square holes 13 are fitted into the press-fit portions 10 of the inner shell 1, and the two blade holder fittings 5 are respectively attached to the two blade holder insertion portions 8 facing each other via the partition wall 7, and the terminal screws 16 are inserted through the screw holes 14. Insert the blade holder 5 into the inner shell 1
Fix it to the bottom of the. Next, after connecting the cord 17 to one end of the blade holder 5, align the openings of the base A and the lid B, and insert the assembly screw 18 from the outer shell 2 into the screw hole 9 and the lid B side. The base A and the lid B are removably screwed together to form a tabel tap as shown in FIGS. 3a, b, and c.

Next, a method of molding the two-layer molded body of the base body A and the lid body B constructed as described above will be explained. Figure 4 1
Reference numeral 9 denotes a rotating mold that rotates by 90 degrees, and has a primary core 20 protruding from each of its four sides, and a primary mold 21 is disposed to face the first stage A for primary molding. . In the third stage C, secondary molds 4 are arranged to face each other. In the first step A, the primary mold 21 is fitted to the primary core 20, thermosetting synthetic resin is injected into the cavity to form the inner shell 1, and the primary mold 21 is released to form the rotary mold 19. is rotated, adhesive is applied to the inner shell 1 as required in the second step (B), and the inner shell body 1 is further rotated by 90 degrees, and the secondary mold 4 is fitted in the third step (C). At this time, the outer surface of the exposed portion 3 of the inner shell 1 is pressed with the secondary mold 4 to
The outer surface of is compressed by an amount δ. The outer surface of the exposed portion 3 on the upper surface is compressed by pressing the inner upper surface of the secondary mold 4 downward as shown in FIG. 5a, and the exposed portion 3 on the side surface is compressed as shown in FIG. Inner slope 23 of mold 4
It is compressed by . In this state, a thermoplastic synthetic resin is injected into the cavity to form the outer shell 2. In other words, a protrusion 3 that protrudes outward from the inner surface of the outer shell 2 at this location is located at an exposed portion 3 of the inner shell 1 molded from thermosetting synthetic resin.
a, and a secondary mold 4 is formed on the outer surface of this protrusion 3a.
The outer shell 2 is molded from thermoplastic synthetic resin while the inner shell 1 is compressed by pressing. Thereafter, the secondary mold 4 is released, the rotary mold 19 is rotated, and in the fourth step D, the knockout pin 24 is driven to take out the two-layer molded product. Here, reference numeral 25 in the figure is a leg for preventing peeling of the outer shell 2. In the two-layer molded product thus formed, no burrs appear on the outer surface of the protrusion 3 from the outer shell 2 as shown in FIGS. 6a and 6b.

As described above, the present invention forms a two-layer molded product by secondly molding the outer shell immediately after the primary molding of the inner shell, so it is possible to reduce costs by reducing the number of steps compared to the conventional method. Moreover, a protrusion that protrudes outward from the inner surface of the outer shell at this location is formed in the exposed part of the inner shell, and a secondary mold is pressed against the outer surface of this protrusion to form the inner shell. Since the outer shell is molded in a compressed state, there is no need for resin to enter between the outer surface of the protrusion and the secondary mold due to the pressure of injection molding the outer shell, resulting in a beautiful two-layer structure with no burrs. Since a molded body can be formed and the outer shell is molded on top of the inner shell in a compressed state, the adhesion strength between the inner shell and the outer shell after molding can be greatly increased.
Because the inner shell and the outer shell are in close contact with each other without creating a gap between them, the material is made of thermosetting synthetic resin and has excellent electrical insulation performance and heat resistance. However, even if an impact is applied to the exposed parts of the inner shell, which has poor impact resistance, the inner shell is made of thermoplastic synthetic resin and is in close contact with the outer shell, which has high impact resistance. This prevents the inner shell from cracking or chipping.

[Brief explanation of the drawing]

1a and 1b are a partially cutaway front view and a partially cutaway side view of a conventional example, FIG. 2 is an exploded perspective view of an embodiment of a two-layer molded product obtained by the method of the present invention, and FIGS. 3a, b and c are a half-sectional view, a left side view, and a half-sectional view seen from the right side after assembly of the same as above; FIG. 4 is a sectional view of the device used in the method of the present invention; FIGS.
b is an explanatory view of the state in which the protruding portion of the inner shell body as described above is pressed with a secondary mold, and FIGS. 6 a and b are partially cutaway sectional views of the vicinity of the exposed portion of the two-layer molded product molded by the method of the present invention. 1 is an inner shell, 2 is an outer shell, 3 is a protrusion, and 4 is a secondary mold.

Claims (1)

[Claims] 1 Primary molding of the inner shell with thermosetting synthetic resin,
Next, when performing secondary molding to cover the inner shell with an outer shell made of thermoplastic synthetic resin before the inner shell hardens, the outer shell at this location is applied to the exposed portion of the inner shell that is exposed to the outside. Two-layer molding characterized by forming a protrusion that protrudes outward from the inner surface of the body, and pressing a secondary mold against the outer surface of this protrusion to compress the inner shell and molding the outer shell. How to shape your body.