JPH0413134Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to a composite structure, and more specifically, it prevents the foamable resin from leaking from the gap between the core material and the outer shell at the joint location when the foamable resin is foamed. The present invention relates to a seal structure for a composite structure for a piano, which prevents damage to the outer shell due to swelling of the core material.

Recently, as an alternative material to wood, a composite structure has been developed in which foamable resin is foam-filled between a core material made of wood etc. and a decorative outer shell made of plastic, metal etc. It is used for the gable base, legs, etc. that make up the body. In this case, especially for the composite structure used as the end base, one end of the core protrudes outward from a fitting opening provided on one side of the outer shell, and this protrusion is connected to the other end of the piano outer shell. It is joined to a component, such as a side plate. To manufacture such a composite structure, a core material is fitted through the opening at one end of the outer shell, and these are set in a mold, and a urethane resin or the like is filled in the gap between the core material and the outer shell. At the same time as the foamable resin is injected and filled, it is foamed.

However, in a deceptive composite structure, foaming pressure is generated when the foamable resin is foamed, resulting in high pressure inside the outer shell, and if there is a slight gap at the joint where the core material and the outer shell fit, this The foamable resin leaks into the mold through the gap, and the mold and the molded product are adhered to each other, making it difficult to take out the mold, and when the mold is taken out, the appearance of the molded product is spoiled.

Therefore, as a means to solve this inconvenience, the same applicant has already proposed a seal structure (see Japanese Utility Model Application Publication No. 140173/1983) in which a seal member made of soft foam is interposed at the mating location. There is.
However, even in such a composite structure, the gap at the joint where the core material and the outer shell fit together is set to almost zero in order to prevent leakage of the foamed resin, as described above. It was not possible to prevent the shell from being damaged.

In other words, the elongation of the outer shell is smaller than the expansion due to moisture absorption of the core material made of wood, so the outer shell is more likely to be damaged due to expansion due to moisture absorption of the core material after molding, resulting in a high rate of defective products. have.

This idea was made in view of the above-mentioned drawbacks, and includes a sealing member made of soft foam interposed at the joint between the core material and the outer shell, and a sealing member made of soft foam at the mating part to prevent swelling due to moisture absorption of the core material. The present invention provides a sealing structure for a composite structure for a piano that prevents leakage of foamed resin and damage to the outer shell by an extremely simple configuration of setting a gap.

This invention will be described in detail below based on embodiments shown in the drawings.

Fig. 1 is an exploded perspective view before foaming showing an example of applying the seal structure of the piano composite structure according to this invention to the end base of a piano, and Fig. 2 shows the incorporation of the core material before foaming. A side view showing the state, and FIG. 3 is a plan view after foaming. In these figures, the gable base, which is designated as a whole by reference numeral 1, has a core material 2 formed into a prismatic shape made of hard wood, and a tip part external shape of the gable base 1 made of plastic such as acrylic resin or SAN resin. It has a substantially box-shaped cosmetic outer shell 3. A fitting opening 4 that is somewhat larger than the cross-sectional shape of the core material 2 is formed on one side of the outer shell 3, and one end of the core material 2 is inserted into the outer shell 3 from this opening 4. is inserted into. In this case, there are predetermined gaps 8A and 8 between both side surfaces and the bottom surface of the core material 2 and the fitting opening 4, respectively.
B is maintained. These gaps 8A and 8B are set to dimensions that accommodate the expansion of the core material 2 due to moisture absorption, and although it varies slightly depending on the material, size, etc. of the core material 2 itself, the dimension of the gap 8A is △d ₁ =0.5~2
mm, and the dimension Δd ₂ of the gap 8B is set to be approximately 0.5 to 3 mm. The protruding end portion of the core material 2 that protrudes to the outside from the outer shell 3 constitutes a mounting base 2a by forming a mounting hole 5 for connection with another component, such as a piano side plate.

A foamable resin 6 such as a hard foamed urethane resin is injected into the inside of the outer shell 3, and is foamed and hardened with a foaming agent to form the core material 2.
and the outer shell body 3 are integrally coupled. When foaming the foamable resin 6, there is a risk that the resin 6 will leak into the mold from the gaps 8A and 8B, and to prevent this, the seal member 7 is interposed inside the fitting opening 4. The sealing member 7 that closes the gaps 8A and 8B is required to have a gas releasing function when the foamable resin 6 is foamed in addition to the sealing function, so it is made of a low-density soft foam such as a soft urethane foam. It is formed into a substantially U-shape and is fitted and fixed to the outer periphery of the core material 2 from below. When the core material 2 is inserted into the outer shell 3, the lower surface of the seal member 7 comes into contact with the internal surface of the outer shell 3, thereby causing the lower surface of the core material 2 and the lower edge of the fitting opening 4 to A gap 8B between the two is set and maintained.

When injecting and foaming the foamable resin 6 into the outer shell 3, the core material 2 is inserted into the outer shell 3 together with the seal member 7, and the core material 2 is pulled toward the mounting base 2a to seal. The member 7 is pressed into close contact with the inner wall of the fitting opening 4, and while this state is maintained, these are set in the mold 10 shown by the chain line in FIG. 4. When the foamable resin 6 is injected into the outer shell 3 and foamed, the resin 6 foams toward the opening 4 as shown by arrows A and B in FIG. Press the sides. Foaming resin 6
is a cream-like liquid at the time of injection, but since the sealing member 7 has a bubble structure, it exhibits a sealing effect even at the beginning of injection. Therefore, leakage of the resin 6 is reliably prevented. In addition, at the initial stage of foaming,
Since the foaming pressure is low, the sealing member 7 is not strongly compressed, and therefore the gas generated during foaming passes through the sealing member 7 and enters the mold 10 from the gaps 8A and 8B.
exit to the outside. Therefore, the gas release function is also good,
This can prevent cracking of the outer shell 3 due to residual gas.

As the foaming progresses, the foamable resin 6 expands and grows into a foamy substance. As the foaming pressure increases, the sealing member 7 moves in the direction of arrow A (the fifth
The foaming pressure in the figure) compresses the inner wall of the outer shell 3, and a part of it protrudes into the gaps 8A, 8B to seal the gaps 8A, 8B, and at the same time, the foaming pressure in the direction of arrow B causes the outer periphery of the core material 2 compressed into Therefore, in the late stage of foaming, the arrow A of the sealing member 7
The air permeability in this direction becomes poor and leakage of the foamable resin 6 is prevented. Furthermore, when the core material 2 absorbs moisture and expands, the amount of expansion is absorbed by the gaps 8A and 8B, so the outer shell 3
No stress is generated at all, thus preventing the outer shell 3 from cracking or breaking.

In the above embodiment, the seal member 7 is fitted to the outer periphery of the core member 2, but it may be fixed to the inner wall around the fitting opening 4.

As explained above, the sealing structure of the piano composite structure according to the present invention includes interposing a sealing member made of a soft foam with a cellular structure at the joint between the core material made of wood and the outer shell made of plastic. Since a gap is provided in the mating part of the core material to accommodate the moisture absorption of the core material, leakage of foamed resin during foam molding can be reliably prevented, and the sealing effect is great. It is possible to prevent damage to the outer shell due to moisture absorption and expansion, and reduce the defective rate of molded products.

[Brief explanation of the drawing]

Fig. 1 is an exploded perspective view before foaming showing an example of applying the seal structure of the piano composite structure according to this invention to the end base of a piano, and Fig. 2 shows the incorporation of the core material before foaming. FIG. 3 is a side view showing the state, FIG. 3 is a plan view after foaming, FIG. 4 is a perspective view for explaining the molding of the end base, and FIG. 5 is a diagram for explaining the foaming of the foamable resin. 1... End base, 2... Core material, 3... Outer shell, 4
...Fitting opening, 6...Foamable resin, 7...Sealing member, 8A, 8B...Gap.

Claims (1)

[Scope of utility model registration request] A core material made of wood is fitted into the opening at one end of the outer shell made of plastic, a part of this core material is made to protrude from the inside of the outer shell, and a foamed resin is injected into the space formed between the two. In a composite structure for a piano formed by integrally forming both the core material and the outer shell, a sealing member made of a soft foam is interposed inside the outer shell at a joint between the core material and the outer shell, and A seal structure for a composite structure for a piano, characterized in that a gap is provided at a fitting portion between an outer shell and a core material to absorb expansion due to moisture absorption of the core material.