JP2676563B2 - Injection Mold Structure of Push Button Panel Made of Thermoplastic Elastomer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a mold structure used in injection molding a push button panel using a thermoplastic elastomer.

[Prior Art] Generally, it is known that a thermoplastic elastomer has rubber-like elasticity at room temperature and is plasticized at a high temperature to become a property of a thermoplastic.

A conventional push button panel made of various kinds of rubber such as silicon rubber has a plate-shaped base portion, a thin skirt portion which bulges and rises from the base portion, and a thick wall portion which is supported on the upper portion of the skirt portion and has a conductive contact on the back surface. It is obtained by integrally molding the key top.

[Problems to be Solved by the Invention] However, since the rubber push button panel is molded by thermal vulcanization, there is a drawback that the molding time is long and the productivity is low.

Therefore, when injection molding is performed using a thermoplastic elastomer having a rubber-like property, the cavity of the mold is rapidly filled with molten plastic, so a gas vent can be formed in the peripheral portion of the top surface of the key top in the cavity of the mold, resulting in heat insulation. The compressed air causes a burn on the molded article, and the gas generated from the plastic causes a failure similar to that of the air, resulting in defective molding. Also, when molding is performed by locating the gate at the center of the back surface of the thick key top, sink marks or gate burrs can be formed on the gate mark part of the molded product, so conductive contacts are formed on the back surface of the key top by means such as printing or adhesion. At this time, there are drawbacks such as uneven sink marks and protruding gate burrs which obstruct the formation of the conductive contact and cause a malfunction of the contact when the contact is turned on / off after the contact is formed. Further, the thin skirt portion causes a click (buckling) on the way when the key top is pressed to perform the on / off operation, and the load for pushing the key top is adjusted by adjusting the thickness of the skirt portion. Therefore, when adjusting the load according to the wishes of the user, there is a drawback that an expensive mold must be remade in order to form the skirt portion according to the load each time. Furthermore, since the skirt portion has a thin wall structure, when the molten plastic is filled from the key top portion of the cavity through the skirt portion into the base portion, the molten resin in the skirt portion is rapidly solidified and is located on the base side of the skirt portion. There is a drawback that cracks are generated due to gas accumulation in the upper part of the thick base portion.

The present invention has been made in view of the above points, and an object thereof is to provide a peripheral edge of a key top in a cavity of a mold used for injection molding using a thermoplastic elastomer having a rubber-like property. Prevents burns from occurring in the molded product due to residual air and generated gas in the parts, eliminates the defective air by effectively removing the air and gas, and when forming the conductive contact on the back surface of the key top, the gate of the molded product In addition to eliminating the effects of sink marks and gate burrs on the base, it is possible to adjust the key load according to the user's wishes with only one mold without recreating an expensive mold. It is an object of the present invention to provide an injection molding die structure of a push button panel made of a thermoplastic elastomer in which cracks due to a gas pool are not generated in the upper part of the.

[Means for Solving the Problems] The injection molding die structure of a push button panel made of a thermoplastic elastomer according to the present invention has a cavity piece on a movable side mold plate.
Each core piece is formed on the fixed side template, and the gate formed on the core piece at the central portion corresponding to the central portion of the back surface of the key top is formed on the core piece at the central portion corresponding to the central portion of the rear surface of the key top so that a recess for sink mark escape and gate burr escape can be obtained. The cavity piece at the end of the rounded surface formed on the top edge of the key top is formed in a split mold.

In addition, a cavity piece is formed on the movable side mold plate, and a core piece is formed on the fixed side mold plate, and the gate formed on the core piece at the central portion corresponding to the back surface of the key top is formed so that it can be obtained from the sink recess and the gate burr escape recess. A protrusion is formed on the core piece in the central portion corresponding to the central portion of the back surface of the key top, and the cavity piece at the end portion of the rounded surface formed on the peripheral edge of the key top is formed in a split mold, and the lower peripheral edge of the key top and the base portion are formed. An injection molding die for a push button panel made of a thermoplastic elastomer in which a space is formed between the back surface of the cavity piece and the movable side mold plate so that the thickness of the skirt portion formed therebetween can be appropriately adjusted. It is a structure.

Further, the skirt portion formed between the peripheral portion of the lower portion of the key top and the base portion has an injection molding die structure of a push button panel made of a thermoplastic elastomer in which a cavity piece is formed so as to project the base portion from the lower portion of the base portion. It is a thing.

[Operation] Molten plastic is rapidly filled from the gate formed in the core piece in the central portion of the back surface of the key top toward the key top portion of the cavity of the mold, and the molten plastic fills the key top in the cavity of the mold. Air and gas flow along the rounded surface of the peripheral portion of the top surface and air and gas escape from the split surface at the terminal end of the rounded surface. In addition, since the molten plastic made of thermoplastic elastomer is filled in the key top part in the cavity, the molten plastic flows from the lower part of the base part through the skirt part, so there is no cracking due to gas accumulation in this part. A good molded product can be obtained.

[Embodiment] An embodiment of the present invention will be specifically described below with reference to the drawings.

As described above, the thermoplastic elastomer used in the present invention has rubber elasticity at room temperature, is plasticized at high temperature, and has the properties of a thermoplastic. In this thermoplastic elastomer, the portion exhibiting rubber elasticity is called a soft phase, and the constrained portion is called a hard phase. For example, in the polystyrene system, the soft phase is polybutadiene, polyisoprene or polyolefin and the hard phase is polystyrene. In the polyolefin system, the soft phase is EPDM or EPM and the hard phase is polypropylene. In the polyurethane system, the soft phase is polyether or polyester and the hard phase is urethane structure. In the polyester system, the soft phase is polyether and the hard phase is polyester. In polyamide systems, the soft phase is polyester or polyether and the hard phase is polyamide. In the fluororesin system, the soft phase is fluororubber and the hard phase is fluororesin. In any case, any thermoplastic elastomer having the above properties and used for injection molding may be used.

Reference numeral 1 denotes a movable side mold plate, which is attached to a mounting plate 2 via a spacer block 3. Reference numeral 4 denotes an ejector pin for projecting a product, which is provided so as to penetrate the movable side mold plate 1. 5
Is a cavity piece formed in the movable mold plate 1 in a nested structure. The cavity piece 5 and a core piece 6 described later form a cavity 7 for obtaining a push button panel molded product. The push button panel includes a plate-shaped base portion 8a and the base portion 8a.
It is composed of a thin skirt portion 8b that bulges out of the skirt and rises, and a thick key top 8c supported on the upper portion of the skirt portion 8b. A rounded surface 9 is formed on the periphery of the key top top surface 8c 'in the cavity 7 of the cavity piece 5, and the cavity piece 5 at the terminal end of the rounded surface 9 is formed on the cavity pieces 5a and 5b of the split mold structure. Only the adiabatically compressed air and the generated gas of plastic are allowed to escape from the boundary surface of the split mold cavity pieces 5a and 5b.

Reference numeral 10 denotes a fixed-side template, which is attached to a mounting plate 11 via a stripper plate 12. Reference numeral 6 is a core piece formed in a fixed side template 10 in a nested structure. Thick key tops
8c A gate 13 is formed at a position corresponding to the central portion of the back surface of the core piece 6. By forming the gate 13 in the thick central portion, the molten plastic flows from the thick key top 8c to the thin skirt portion 8b in a well-balanced manner, and sink marks etc. do not occur. The gate 13 formed on the core piece 6 is formed with a protrusion 15 on the core piece 6 at the central portion on the back surface of the key top 8c so that the recess 14 for sink relief and gate burr escape can be obtained. Concavity 4 for sink escape and gate burr escape
The depth of the sink mark and the gate burr 16 are conductive contacts (not shown)
The depth is set so as not to protrude from the key top back surface 8c ″ that forms the groove (see FIG. 3 (a)). As shown in FIG. 3 (b), when the recess 14 for sink mark escape and gate burr escape is shallow,
As shown in Fig. 3 (c), the gate burr 16 is the back surface 8 of the key top.
The conductive contact 19 protruding from the c "and formed on the back surface 8c" is not flat, and that portion becomes bulged, which causes a trouble such as a malfunction when the contact is turned on / off.

FIG. 2 shows a mold structure in which the thickness of the skirt portion can be adjusted appropriately.

As shown in FIG. 5, the relationship between the load variation of pushing the key top 8c and the stroke is a curved line that is bent in the middle, and the bending point is where the so-called click motion of the base portion 8a is performed. The load variation can be a desired load by appropriately changing the wall thickness of the base portion 8a. Usually, the load can be changed by changing the wall thickness of the base portion 8a from several microns to several tens of microns. Therefore the key top
In order to properly adjust the thickness of the skirt portion 8b formed between the lower peripheral edge of 8c and the base portion 8a, the thickness between the back surface of the cavity piece 5 and the movable side template 1 is about several to several tens of microns. Of the skirt portion 8b so that a load according to a user's request can be obtained by providing one or a plurality of spacers 18 made of a heat-resistant material, for example, phosphor bronze, in a laminated manner in the void 17 of the skirt 8b. Adjust the thickness.

FIG. 4 is a cross-sectional view of the base portion of the skirt formed so as to rise from the lower peripheral edge of the base portion.

As shown in FIG. 4, in order to form the skirt portion 8b, the cavity piece 5 is formed to project so that the base portion of the skirt portion 8b rises from the lower peripheral edge of the base portion 8a. As a result, the molten plastic causes the thick key tops 8c in the cavity 7 to
When flowing from the portion to the thin skirt portion 8b, the generation of cracks due to gas accumulation is eliminated.

[Effects of the Invention] As can be seen from the above description, the present invention provides a gate formed on the core piece of the central portion corresponding to the central portion of the back surface of the key top so that a recess for sink mark escape and a gate burr escape can be obtained. The core piece has a protrusion, and the cavity piece at the end of the rounded surface formed on the peripheral edge of the key top is formed in a split mold, so when using a thermoplastic elastomer that is close to rubber, injection molding As a result that only residual air and generated gas in the peripheral portion of the top surface of the key top in the cavity of the mold used for escape from the split mold portion of the cavity piece,
Burning does not occur in the peripheral portion of the top surface of the key top, and molding defects are eliminated. Further, by forming a protrusion on the core piece in the central portion corresponding to the center of the back surface of the key top so that a recess for sink mark escape and a gate burr escape can be obtained in the gate portion, the sink mark and the gate burr can be inserted into the recess. When a conductive contact is formed on the back surface, there is no influence of sink marks or gate burrs formed on the gate part of the molded product, and there is no malfunction in the on / off operation of the contacts.

Further, according to the present invention, a gap is provided between the back surface of the cavity piece and the movable side mold plate so that the thickness of the skirt portion formed between the lower edge of the key top and the base portion can be adjusted appropriately.
Since the spacer is provided in the gap, when adjusting the load according to the user's wish, the thickness of the skirt portion can be easily changed by adjusting the thickness of the spacer without remaking an expensive mold, It can be manufactured at low cost.

Further, since the skirt portion formed between the lower peripheral edge of the key top and the base portion has the cavity piece projectingly formed so that the base portion thereof is raised from the lower peripheral edge of the base portion, the molten plastic is formed by the key top of the cavity as in the conventional case. When filling the base part from the part through the skirt part, the molten resin of the skirt part solidifies quickly and cracks due to gas accumulation occur at the top of the thick base part located on the base side of the skirt part. It is solved all at once, and a good molded product without cracks can be obtained.

[Brief description of the drawings]

FIG. 1 is a structural diagram of a mold showing an embodiment of the present invention, FIG. 2 is a structural diagram of a mold in which the thickness of a skirt portion is appropriately adjustable, and FIG. 3 (a) is a main part of a push button panel. Sectional view, FIG. 3 (b) Sectional view of a principal part showing an example of bad molding of a push button panel, FIG.
Figure (c) is a schematic view showing a bad molding example in which the gate burr protrudes from the back surface of the key top, FIG. 4 is a cross-sectional view in which the base of the skirt is raised from the lower peripheral edge of the base, and FIG. 5 is the key. It is a relationship diagram of a load variation pushing the top and a stroke. 1 ... Movable mold plate, 5 ... Cavity piece, 5a, 5b ... Split mold cavity piece, 6 ... Core piece, 7 ... Cavity, 8a ... Base portion, 8b ... Skirt portion, 8c. Key top, 9 ... R-side, 10 ... Fixed side template, 13 ... Gate, 14 ... Recess for sink and gate burr escape, 15 ... Projection, 17 ... Void, 18 ... Spacer.

Claims (3)

(57) [Claims] 1. A cavity piece is formed on the movable side mold plate, and a core piece is formed on the fixed side mold plate. The gate formed on the core piece at the central portion corresponding to the center of the back surface of the key top has recesses for sink mark escape and gate burr escape. As described above, a thermoplastic resin is characterized in that a protrusion is formed on the core piece in the central portion corresponding to the back surface of the key top, and a cavity piece at the end portion of the rounded surface formed on the peripheral edge of the key top is formed in a split mold. Injection mold structure of push button panel made of elastomer. 2. A cavity piece is formed on the movable side mold plate, and a core piece is formed on the fixed side mold plate. The gate formed on the core piece at the central portion corresponding to the center of the back surface of the key top has recesses for sink mark escape and gate burr escape. As described above, a protrusion is formed on the core piece at the central portion corresponding to the back surface of the key top, and the cavity piece at the end of the rounded surface formed on the peripheral edge of the key top is formed in a split mold, and the lower peripheral edge of the key top and the base are formed. A space is provided between the back surface of the cavity piece and the movable side mold plate so that the thickness of the skirt portion formed between
An injection mold structure for a push button panel made of a thermoplastic elastomer, characterized in that a spacer is provided in the void. 3. The skirt portion formed between the lower peripheral edge of the key top and the base portion has a cavity piece projectingly formed so as to raise the base portion from the lower peripheral edge of the base portion. An injection-molding die structure for a push-button panel made of the thermoplastic elastomer described.