JPH0558378B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a molding method for increasing the bonding strength between a first injection molded product and a second injection molded product in double injection molding.

(Prior art) For example, in automotive parts such as timing gear covers, cylinder head covers, and oil pans, the main body must be made of hard material, and the sealing parts and soundproofing parts must be made of soft material. , Double injection molding method is adopted. That is, in the first step, for example, after injection molding the hard material as the first material into the spaces between the fixed mold and the first movable mold, the first injection molded product and the second movable mold remaining in the fixed mold are A soft material, which is a second material, is injection molded into the space between the two, and the molded product made of the hard material and the soft material is joined together at the same time as the molding.

However, in order to fuse the joining surfaces of the first molded product and the second molded product during double molding, it is necessary to select materials of the same type, and there is a problem in that there are restrictions on the use from the material standpoint. . On the other hand, when attempting to physically bond the two, it is necessary to design the mold to have an undercut so that the second material meshes with the joint surface of the first molded product, which increases mold manufacturing costs.
In addition, the basic problem remains that it is easy to break down.

(Problems to be Solved by the Invention) Therefore, the present invention provides a double injection molding method capable of physically joining a first molded product and a second molded product without using an undercut in the mold. That is the issue.

(Means for Solving the Problems) In the first step of the present invention, a protrusion is formed in the die cutting direction so that there is no problem in die cutting, but such a protrusion does not physically engage with the second molded product as it is. Since it has no function, it is tilted from the mold removal direction using the next mold clamping process to engage with the second molded product so as to prevent it from coming off, and the second molded product is molded so as to be entangled with this. This was done with the focus on the fact that the above problems could be solved by doing this, and when molding plastic by opening and closing a male mold and a female mold, one type of one mold and one type of the other mold were used. A first step of preparing two types and injection molding the first material into the spaces between one mold and the first other mold, and the first injection molded product remaining in one mold and the second other mold. In carrying out double injection molding by a second step of injection molding a second material into the void space between the mold and the mold, in the first step, the second material of the first injection molded product is
A protrusion is formed in the mold removal direction on the joint surface with the injection molded product, and in the mold clamping process before the second process, the protrusion is removed from the mold by a slope provided on the protrusion side and/or the second other mold side. In the second step, a second material is injected around the inclined protrusion.

The present invention uses either the male type or the female type as one
It can be widely applied to a double molding method in which two types of molds are prepared and the two types are recombined to perform two steps, and various methods can be used for moving the molds at that time.

For example, two molds of one type (rotating fixed mold) are rotated, and the other two molds (movable molds) are slid on both sides of the fixed mold to combine the molds. Method of combining molds by moving one mold into a U-shape, fixed one
A system in which two types of molds move in an L-shape and replace each type of mold, or various combinations in which three or four molds are moved vertically, horizontally, rotated, etc. may be adopted. In the present invention, the shape of the protrusion formed in the die-cutting direction is not particularly limited, but at least in the mold-clamping process, the protrusion may come into contact with the other mold, for example, a movable die, and deviate from the die-cutting direction, resulting in a second molded product. It is necessary to deform the protrusion into a form that can be engaged with the protrusion, and a slope is formed on the protrusion side and/or the second, for example, movable mold side, so that the protrusion is deformed when the two come into contact. When two or more protrusions are formed, it is preferable that the deformation directions of the protrusions are alternately directed in opposite directions, since this strengthens the physical bond with the second molded product.

According to the present invention, the protrusion is formed in the die cutting direction,
Since this is transformed into a form that allows physical connection in the mold clamping process, the second molded product molded around the protrusion is physically combined with the first molded product by the protrusion.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.

(Example) In the drawings, FIGS. 1 a to d show a process of molding a soft sealing member 2 on the back surface of a hard molded product 1 by a double injection molding method. In the first step a, a rotating fixed mold 3 and a first movable mold 4 that moves with respect to the fixed mold 3, a hard plastic H, which is a first material, is injection molded into the cavity of the mold combination. The first movable mold 4 has a convex portion 41 and a notch 42 around it, forming a concave portion 11 to which the second injection molded product 2 is joined to the first injection molded product 1, and an edge of the concave portion. A pair of protrusions 1 that protrude from the part in the die cutting direction and have an upright slope with a triangular cross section.
2, 12 are formed.

Next, in the mold clamping step b, when the second movable mold 5 is brought into contact with the first injection molded product 1 on the fixed mold 3, the second movable mold 5 is brought into contact with the pair of protrusions 12 of the first injection molded product 1. Since it has arcuate slopes 51, 51 that come into contact with the slope 12a of the projection 12 in the die cutting direction,
will curve into the space 6 between the second movable mold 5 and the first injection molded product 1 from both sides.

Therefore, in the second step c, the void space 6
When the soft plastic S is injected, the soft plastic S of the second material is injected around the inclined protrusion 12.
is injection molded, and this inclined protrusion 12 physically connects the first injection molded product 1 and the second injection molded product 2 (see FIG. 1d).

FIGS. 2a to 2d show a process of molding a soft member 2 having a chevron-shaped cross section on the back surface of a hard molded product 1 by a double injection molding method. In the first step a, a fixed mold 3 and a first movable mold 4 are formed. A hard plastic H, which is the first material, is injection molded into the empty space. A pair of notches 42 are formed at regular intervals in the first movable mold 4, and protrude in the mold removal direction where the second injection molded product 2 is joined to the first injection molded product 1. A pair of protrusions 12, 12 having slopes are formed. Next, in the mold clamping step b, the first
When the second movable mold 5 is brought into contact with the injection molded product 1, the second movable mold 5 forms an arcuate convex portion 52 that comes into contact with the notched tips of the pair of protrusions 12 of the first injection molded product 1.
Therefore, the protrusion 12 oriented in the die cutting direction comes into contact with the convex portion 52 of the second movable die 5 and is curved so that its tips open outwards opposite to each other.
Therefore, in the second step c, when the soft plastic S is injected into the space 7, the second material soft plastic S is injection molded around the inclined protrusion 12, and this inclined protrusion 12 is injected into the first injection molded part. The molded product 1 and the second injection molded product 2 are physically joined (see FIG. 2d).

FIGS. 3a to 3d show a process of fitting and molding a soft lid member 2 having a soundproofing function into a circular opening 13 of a timing gear cover 1, which is a hard molded product, by a double injection molding method. In the first step a, A hard plastic H, which is a first material, is injection molded into the space between the fixed mold 3 and the first movable mold 4. A plurality of notches 42 are formed in the first movable mold 4 at regular intervals in the circumferential direction, and around the circular opening 13 where the second injection molded product 2 is joined to the first injection molded product 1, A plurality of protrusions 12, 12 are formed that protrude in the die cutting direction at regular intervals and have cutout slopes facing outward or inward alternately at their tips.

Next, in the mold clamping step b, when the second movable mold 5 is brought into contact with the first injection molded product 1 on the fixed mold 3, the second movable mold 5 is brought into contact with the tip of the protrusion 12 of the first injection molded product 1. When the cutout slope 12a faces inward, the convex portion 53 having an outward slope comes into contact with it and curves the protrusion 12 outward. (Figure 3 b-1). On the other hand, when the slopes 12b of the protrusions 12 face outward, they come into contact with the convex portions 54 having inward slopes, causing the protrusions 12 to curve inward (FIG. 3b-2), thereby curving alternately. Therefore, in the second step c, when the soft plastic S is injected into the space 8, the second material soft plastic S is injection molded around the inclined protrusion 12, and this inclined protrusion 12 is formed by the first injection molding. The molded product 1 and the second injection molded product 2 are physically joined (see FIG. 3d).
In addition, in the second step c, the first injection molded product 1 is pressed against the fixed mold 3 by the protrusion 12, so that
The second injection molded product 2 can be molded without generating burrs.

(Effects of the Invention) As is clear from the above description, according to the present invention, in the first step, protrusions are formed in the die-cutting direction so as to cause no problem in die-cutting. Since it does not have a physical engagement function with the molded product, it is tilted from the mold removal direction using the next mold clamping process to engage with the second molded product in a manner that prevents it from coming off. By molding the two molded products so that they intertwine, the first and second molded products can be physically combined. Therefore,
There is no longer a restriction on the material of the first and second molded products to be of the same type of material, and both the hard and soft members can be made of different types of materials. In addition, even if the materials are of the same type, if there is a concern about the adhesion strength or the bonding part may be incomplete due to molding conditions, the method of the present invention can be adopted to more reliably join the two. can.

Furthermore, since the hard molded product is pressed against the fixed mold with a light force during mold clamping in the second step, there is no movement of the hard molded product within the mold, and the resin can flow stably in the second step. Furthermore, if there is a risk of burrs occurring, the above pressing force can prevent burrs from occurring.

[Brief explanation of the drawing]

Figures 1, 2, and 3 are process diagrams for double injection molding using the method of the present invention, and Figure 4 shows the second movable mold used in the double injection molding in Figure 3. FIG. 3 is a plan view showing a part of the inner surface. DESCRIPTION OF SYMBOLS 1...First injection molded product, 2...Second injection molded product, 3...Fixed mold, 4...First movable mold, 5...Second movable mold, 12...Protrusion.

Claims (1)

[Claims] 1. When molding plastic by opening and closing a male mold and a female mold, one type of one mold and two types of the other mold are used.
A first step of preparing a type and injection molding a first material into a space between one mold and a first other mold; In performing double injection molding by a second step of injection molding a second material into the space between the mold and the second material, in the first step, the second material of the first injection molded product is
A protrusion is formed in the mold removal direction on the joint surface with the injection molded product, and in the mold clamping process before the second process, the protrusion is molded by a slope provided on the protrusion side and/or the second other mold side. A double injection molding method, characterized in that the second material is injected around the inclined protrusion in the second step, the second material being inclined from the punching direction.