JPH0361968B2 - - Google Patents

Description

[Detailed Description of the Invention] "Industrial Application Field" The present invention relates to a method of molding a casing of a switch used in various electrical devices, and particularly relates to a method of molding a casing in which a fixed contact piece is insert-molded. It is.

``Prior art and its problems'' FIG. 6 shows an example of a switch equipped with a housing 20 in which a fixed contact piece 10 is insert-molded. The pair of fixed contact pieces 10 each include a contact portion 12 and a terminal portion 14 that are integrally formed.
The contact portion 12 is exposed on the inner bottom surface of a recess 22 formed in the casing 20, and the tip of the terminal portion 14 is drawn out into the recess 22 of the casing 20. This switch is operated by the fact that when the push button 30 is pressed down, a movable contact 42 fixed to the underside of a flexible insulating dome 40 contacts the pair of contact portions 12, 12, causing them to conduct. It is a state.

When molding a housing 20 into which the fixed contact piece 10 is insert-molded, such as the housing 20 of this switch, a method as shown in FIG. 7, for example, has conventionally been used. In FIG. 7, 50 is the housing 2
0 is an upper mold having a downward protrusion 52 corresponding to the recess 22, and 60 is a lower mold having two upward protrusions 62. Both molds 50 and 60 sandwich and support the terminal portion 14 of the fixed contact piece 10, and at the same time support the contact portion 12 with the protruding portion 52 and two protrusions. In this state, when a synthetic resin is injected into the cavity 70 formed by both the molds 50 and 60 and molded, a casing 20 as shown in FIG. 8 is obtained.

However, in such a molding method, a hole 24 is created below the contact part 12 that corresponds to the protrusion 62 of the mold and reaches the contact part 12. Soldering flux penetrates through the hole 24 to the upper surface of the contact portion 12, causing malfunction of the switch. Therefore, in the past, it was necessary to fill the holes 24 with adhesive in order to prevent flux from entering.

"Means for Solving the Problems" The present invention provides a retractable support member inside the lower mold, and the contact part of the fixed contact piece is held between the support member and the upper mold in the cavity. Synthetic resin is injected into the cavity, and the pressure inside the cavity during this injection process causes the support member to retreat. By filling the synthetic resin below the contact area, there is no need to fill with adhesives, etc. This is what I did.

Embodiment FIG. 1 shows an embodiment of the molding method according to the present invention, and parts corresponding to those in FIG. 7 are designated by the same reference numerals. The upper mold 50 and the lower mold 60 are movable in the vertical direction in the figure, and a support member 80 is attached to the inside of the lower mold 60. Support member 8
0 is a piston 1 having two protrusions 82 at its upper end and whose lower end is slidable inside an air cylinder 90.
00 by known means, and is movable in the same direction as the molds 50 and 60, that is, in the vertical direction in the figure, within a hole 64 formed in the mold 60.

Next, a process for molding the above-mentioned casing 20 using the mold configured as described above will be described. First, as shown in FIG. 1, the terminal portion 14 of the fixed contact piece 10 is held between an upper mold 50 and a lower mold 60. Next, the piston 100 of the air cylinder 90 is driven to raise the support member 80, and the contact portion 12 is moved between the protrusion 52 of the upper mold 50 and the protrusion 8 of the support member 80.
2, and in this state, molten synthetic resin is injected into the cavity 70 from a runner (not shown). A few seconds after starting injection of synthetic resin,
When the inside of the cavity 70 is filled with synthetic resin, the support member 80 is pushed outward of the cavity 70, that is, downward, due to the pressure of the pressure part of the cavity 70 due to the injection, against the air pressure inside the air cylinder 90. Being pushed down. After that, the support member 8
0 descends until it hits the step part 66 of the lower mold as shown in FIG. 2, and a gap 72 is created between the contact part 12 and the protrusion 82, but at the same time as the support member 80 descends, the synthetic resin 110 fills this gap 72. flows into. At this time, a force equal to the pressing force acting on the support member 80 is applied to the contact portion 12 in the opposite direction, so that the contact portion 12 is strongly pressed against the protruding portion 52 of the upper mold 50. Therefore, the synthetic resin 110 does not wrap around the upper surface of the contact portion 12. The housing 20 formed in this manner is provided with a hole 26 that does not penetrate to the contact portion 12, as shown in FIG.

FIG. 4 shows another embodiment of the present invention, and in this figure as well, parts corresponding to those in FIG. 1 are designated by the same reference numerals. Since the casing formed by the mold in this case is provided with three contact portions 12, the support member 80 is also provided with three protrusions 82 corresponding to the respective contact portions 12. Reference numeral 120 denotes a plate fixed to the lower side of the lower mold 60, and a protrusion 122 for a stopper that limits the amount of movement of the support member 80 is provided on the upper surface of the plate so as to protrude into the hole 64. ing. A spring 130 is attached between the support member 80 and the plate 120, and constantly urges the support member 80 toward the contact portion 12. Note that the strength of the spring 130 is
This pressure is set lower than the internal pressure of the cavity 70 when the synthetic resin is injected.

The molding process using a mold having such a configuration is also carried out in substantially the same manner as in the above case. That is,
When the inside of the cavity 70 is filled with the injected synthetic resin 110, the support member 80 is strongly pressed downward by the internal pressure of the cavity 70. For this reason,
The support member 80 descends against the elasticity of the spring 130 and stops when it hits the protrusion 122 as shown in FIG. After cooling in this way, the molds 50, 60
When opened, a switch housing in which the gap 72 below the contact portion 12 is also filled with the synthetic resin 110 is obtained. The contact portion 12 is connected to the spring 13 until the inside of the cavity 70 is filled with the synthetic resin 110.
The support member 80 is pressed against the protrusion 52 of the upper mold 50 with a strong elastic force of 0, and after the support member 80 starts to descend, it is strongly pressed upward by the pressure inside the cavity 70, so that the composite Resin 11
0 does not wrap around the upper surface of the contact portion 12.

Note that the spring 130 attached between the support member 80 and the plate 130 is not limited to a coiled spring, and may be replaced with an elastic body such as rubber, for example. Alternatively, a spring may be attached between the support member 80 and the air cylinder 90 in FIG. 1, so that the support member 80 can be biased upward by both the air cylinder and the spring. For convenience of explanation, the upper mold is shown as the upper mold in the figure, but it goes without saying that the positional relationship between the upper mold and the lower mold may be reversed in the actual configuration.

As described above, in the method for molding a switch housing according to the present invention, a supporting member movable along the moving direction of the mold is provided inside the lower mold, and the terminal portion of the fixed contact piece to be insert-molded is attached to the upper and lower sides. The contact part is held in the cavity formed by the two molds, and the contact part is held between the support member and the upper mold, and molten synthetic resin is injected into the cavity. This is characterized in that the support member is separated from the contact portion during this injection process, so that the space between the support member and the contact portion is also filled with the synthetic resin.

"Effects of the Invention" According to the present invention, it is possible to reliably prevent flux from infiltrating when a switch, which is completed by incorporating push buttons and movable contacts into a molded housing, is attached to a printed circuit board using automatic soldering. . In addition, the contact part remains in close contact with the upper mold until the synthetic resin injection is completed, so even if the contact part has a complicated shape, the resin will not adhere to the top surface of the contact part. Can be molded with high precision.

[Brief explanation of drawings]

Figures 1 to 5 are related to the present invention; Figures 1 and 2 are explanatory diagrams of the molding method, Figure 3 is a front sectional view of the switch housing, and Figures 4 and 5 are the molding method. An explanatory diagram showing another example of the method, FIG. 6 is a front cross-sectional view showing an example of the structure of the switch, FIG. 7 is an explanatory diagram of the conventional molding method, and FIG. 8 is a diagram showing a switch molded by the same method. FIG. 3 is a front sectional view of the housing. 10...Fixed contact piece, 12...Contact part, 14...
Terminal part, 20... Housing, 50... Upper mold, 60...
... lower mold, 70 ... cavity, 80 ... support member, 110 ... synthetic resin.

Claims (1)

[Claims] 1. In a method for molding a switch housing in which a fixed contact piece having a contact part and a terminal part is implanted, the first
It comprises a second mold and a support member movably attached inside the first mold, the terminal portion is held between the two molds, and the terminal portion is held in the cavity formed by the two molds. While accommodating the contact part, molten synthetic resin is injected into the cavity with the contact part being sandwiched between the support member and the second mold, and during the injection process, the support member is 1. A method for molding a switch casing, characterized in that the space between the support member and the contact portion is also filled with synthetic resin by separating the support member from the contact portion.