JPH0661790B2 - Method for manufacturing hinge part of plastic part - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a hinge portion of a plastic component.

(Prior Art) In order to attach a main body 11 to a plastic part, for example, a glove lid 1 as shown in FIG.
The hinge part 1 along the environmental line extending in the longitudinal direction with the mounting part 12 having the bolt holes 12a located at the widthwise end part.
3 is formed. This hinge is thin and
In order to withstand repeated use, a method has been widely used in which a portion corresponding to the hinge portion is internally provided with a polypropylene strip and molded. However, it is difficult to determine the interior position of the polypropylene strip used by the resin flow pressure during molding,
It may be exposed on the product surface and impair the appearance. Therefore, as means for holding the interior film, Japanese Patent Application Laid-Open No. 62-1
No. 19014, Japanese Utility Model Publication No. 52-199320 and Japanese Utility Model Publication No. 57-90817, the use of the method is proposed. However, simply holding both ends in the longitudinal direction of the strip with a pin or the like makes the strip long. The interior position is not determined by the flow of injection resin in the intersecting direction, and it is necessary to devise injection conditions such as lowering the injection pressure under the present circumstances, it is not possible to freely select the injection conditions, and the application of the above hinge structure is limited. Is occurring.

(Problems to be Solved by the Invention) Therefore, the present invention is a method for manufacturing a hinge part in which a polypropylene band is embedded in a part corresponding to the hinge part of a plastic part and molded, and the band-shaped body is formed on the product surface even under arbitrary injection conditions. It is an object to provide a manufacturing method that is not exposed.

(Means for Solving the Problems) In order to solve the above problems, the present invention sets a polypropylene strip to be installed inside a mold so as not to be exposed on the product surface side even under the influence of a resin flow pressure. It was made by paying attention to the fact that "the film strip of a material selected from a soft thermoplastic resin containing polypropylene is set in the hinge part of the plastic part in the mold so as to extend in the longitudinal direction of the hinge part. In order to discharge-mold a thermoplastic resin around the strip to mount the strip on the hinge part of the plastic part, the strip has a V-shaped or arc-shaped cross section, and the central portion in the width direction is raised. When the mold is opened, the above-mentioned strip is formed along the longitudinal direction at the part forming the hinge part on the side that forms the back surface of either the fixed type or the movable type when the mold is opened. Temporarily fix the strip body so that the raised center portion of its V-shaped or arc-shaped cross section faces the other die side, and when the die is clamped, the raised portion of the widthwise center portion of this strip body should be the Hinn part of the other die. It is set by pressing the convex part that forms the back side of the product so that both ends in the width direction press the mold surface on the side forming the back surface of the product, and the thermoplastic resin is injection-molded around the band-shaped body. " There is a method of manufacturing a hinge part of a plastic part.

(Operation) According to the present invention, the temporarily fixed band-shaped body is formed into a V shape or an arc shape in cross section, and the bulging portion at the center in the width direction thereof is used to press the convex portion that forms the hinge portion. Since the mold surface on the side forming the back surface is elastically pressed, it does not move even when the resin flow pressure acts, and it is not exposed on the product surface.

INDUSTRIAL APPLICABILITY The present invention is widely applied to a method of incorporating a polypropylene strip in order to impart durability to the hinge portion when integrally forming the hinge portion in a plastic part.

This strip is usually made of polypropylene,
Other soft thermoplastic resins such as polyethylene, which is another elastic material having excellent repeated bending durability, may be used.
The size is adjusted according to the size of the hinge and the weight of the parts to be opened and closed.

In the case of a long length of temporary fixing of the band-shaped body, a method of engaging and holding both ends by pins or the like provided in a fixed mold or a movable mold may be adopted, but if it has a function of holding until the mold is clamped. Well, for example, it may be temporarily fixed with an adhesive.

In order to suppress the widthwise ends of this strip at the mold surface on the side that forms the back surface of the product during mold clamping, make the strip bent in the width direction, such as a V-shaped cross section or an arc shape. Is preferably pressed by the mold surface on the side forming the product surface. At that time, a notch or notch is formed at the boundary between the interior part and the engagement holding part to prevent twisting due to the difference in deformation between the interior part and the engaging parts at both ends, and the occurrence of twisting is prevented. It is preferable to do so.

Hereinafter, the present invention will be described in detail based on specific examples shown in the additional drawings.

(Embodiment) FIG. 1 is a process explanatory view of each process in the case of manufacturing the globe lid shown in FIG. 7 using the manufacturing method according to the present invention.

In the drawing, reference numeral 3 denotes a movable die, which has a die surface that forms the back side of the product 1 and has a longitudinal direction of the hinge portion 31 sandwiched between the body portion die surface 32 and the attachment portion die surface 33, as shown in FIG. Engaging pins 34, 34 for temporarily fixing both ends of the belt-shaped body 4 to be described below are projected on both outer sides. On the other hand, 2 is a fixed die, which has a die surface that forms the front side of the product 1 as shown in FIG.
Is pressed along the longitudinal direction thereof, and the main body mold surface 22 and the mounting portion mold surface 23 are disposed with the ridge portion 21 forming a thin wall portion for the hinge portion on the front side of the product interposed therebetween. The locking portion 14 of the glove lid 1 is provided on the outer side of 22.
And a plurality of second protrusions 23a that form the engaging holes 12a of the mounting portion are formed on the mounting portion mold surface 23. Further, a pair of holes 24 into which the engaging pins 34 are inserted at the time of mold matching are formed on both sides of the protrusion 21 in the longitudinal direction.

Reference numeral 4 denotes a strip-shaped body to be installed in the hinge portion, which is made of polypropylene and has a V-shape at the center line extending in the longitudinal direction located at the center in the width direction (folding angle 160 to 170).
Angle) and is adapted to respond to the elastic pressure at the time of mold clamping, and at both ends thereof, engaging holes 41, 41 for engaging the engaging pin 34 are formed, and a slightly inwardly cut portion. The notch 42 is formed. The cutout portion 42 is different in the deformation of the engaging portion on the outer side (see FIG. 5) and the deformation of the inner portion on the inner side (see FIG. 1). Let
If the notch portion does not exist, an unexpected shape (twisting or inclination) is generated in the boundary area, thereby preventing the flow and appearance of the injection resin from being adversely affected. Of course, the hinge portion also has a function of easily cutting off both end portions protruding after the interior.

Therefore, by engaging the strip-shaped body 4 with the engagement hole 41 of the strip-shaped body 4 along the hinge part die surface 31 of the movable die 3 in the die opening step, see FIG. 4 and FIG. The both ends in the width direction are temporarily fixed so as to project from the movable die surface (see FIG. 1).

When this is clamped, the protrusion 21 of the fixed mold 2 comes into contact with the center line of the belt-shaped body 4 temporarily fixed to the movable mold, and by pushing this, the belt-shaped body 4 becomes a shape that fits in the void, and
Both ends in the width direction of the band-shaped body 4 are set so as to elastically press the movable die surface and withstand the injection fluid pressure of the resin flowing into the void (see FIGS. 1 and 5).

Since the mold that has been clamped has the shape shown in FIG. 6,
When the resin is injected from the nozzle 5 on the stationary die side, the resin W is injected from the upper and lower ends of the space C and goes around the strip-shaped body 4, and both ends in the width direction thereof are opened slightly outward and are not exposed on the product surface. Will be decorated in. (See FIG. 1).

(Effects of the Invention) As is apparent from the above description, according to the present invention, a film strip of a soft thermoplastic resin typified by polypropylene is set in a mold, and a thermoplastic resin is injection-molded around the film strip. When the strip-shaped body is installed in the hinge, the strip-shaped body with a V-shaped cross section or a circular arc shape with a raised central portion in the width direction is used. Set the raised part by pressing the convex part that forms the hinge part of the other mold so that both widthwise ends press the mold surface on the side that forms the back surface of the product, and inject the thermoplastic resin around the band-shaped body. Since the hinge portion of the plastic part is manufactured as it is formed, the temporarily fixed band-shaped body is not exposed on the surface of the product even when the resin flow pressure acts. Therefore, it is possible to manufacture a product having a good appearance without restricting the injection conditions as in the conventional case.

[Brief description of drawings]

1 to 3 are process explanatory views showing a manufacturing process when the method of the present invention is applied to the manufacture of a globe rit, and FIG.
Fig. 3 is a perspective view of a movable mold used in the method shown in Fig. 3, Fig. 3 is a perspective view of a fixed mold used in the method shown in Fig. 1, and Fig. 4 is a perspective view showing details of corners of the movable mold shown in Fig. 3. 5 and FIG. 5 are cross-sectional views of a main part showing a state where the band-shaped body is temporarily fixed, and a cross-sectional view of a main part when the mold is clamped. FIG. 6 is a cross-sectional side view showing a mold assembled state in the mold clamped state. FIG. 7 is a perspective view showing the back surface of the globe lid to which the method of the present invention is applied. 1 ... Product (grove lid), 2 ... fixed type, 3 ...
Movable type, 4 band, 5 nozzle, 34 pin

Claims (1)

[Claims] 1. A film strip of a material selected from a soft thermoplastic resin containing polypropylene is set in the hinge part of a plastic part in a mold so as to extend in the longitudinal direction of the hinge part, and a thermoplastic resin is provided around this strip. When the above-mentioned strips are injection-molded and the above-mentioned strips are installed inside the hinges of plastic parts, use a strip-shaped or arcuate cross-section with a raised central portion in the width direction. In the part that forms the hinge part on the side that forms the product back surface of one of the movable dies, the above-mentioned strip-shaped body along the longitudinal direction of that part has the raised central part of the V-shaped or arc-shaped cross section on the other mold side. Temporarily fasten it so that when it is clamped, the raised portion in the center of the strip in the width direction is pressed against the protrusions that form the hinge of the other die so that both ends in the width direction are the back of the product. Set so as to repression the mold surface of the side forming the method of the hinge portion of the plastic part, characterized in that the thermoplastic resin formed by injection-molding around the strip.