JPS6235373B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mold for injection molding a cylindrical plastic impeller used as, for example, a cylindrical fan.

As shown in Fig. 1, this type of impeller F has a complicated shape in which a large number of blades 2 with an arcuate cross section protrude from the back surface of a ring-shaped substrate 1, and therefore, it is injection molded. Conventional molds consist of a combination of many molds, and their molding requires special technology. However, as wire processing has become more uniform and it has become possible to form complex molds, it has become possible to obtain a desired complex mold even by combining a small number of molds. However, some difficult problems arose when combining a few types.

This will be explained later as an example in Figures 2 and 3.
Regarding the figure, the inventors constructed the main molding part of mold A by a combination of an inner mold 3, an outer mold 4, an upper mold 5, and a lower mold 6, but there is a slight gap between the inner and outer molds 3 and 4. However, a gap was created, and burrs inevitably occurred on the molded product f of the impeller F, and it was extremely difficult to extract the molded product f.

This invention has achieved its intended purpose as a result of numerous experiments and researches carried out to solve the above-mentioned problems.

That is, the present invention provides an injection mold for a cylindrical impeller in which a large number of blades having an arcuate cross section are protruded from the back surface of a ring-shaped substrate, and the blades are formed on the outer peripheral surface of the inner mold and the inner peripheral surface of the outer mold. Form the notch grooves by wire machining. The process is characterized by providing a draft angle and fitting the inner and outer molds closely together through a taper.

The draft angle and taper should be set to values close to the shrinkage allowance of the plastic molding material.
For example, if the shrinkage margin of a plastic molding material is 0.30%, the appropriate range is about 1/1000 to 5/1000.

Next, embodiments of the present invention will be described based on the drawings.

In the mold A, an inner mold 3 and an outer mold 4 are assembled between a lower mold 6 and an upper mold 5, and the inner mold 3 is centrally supported by the lower mold 6 by screws P.

The ring-shaped substrate 1 of the impeller F is mainly molded by an upper mold 5, and the blades 2 are mainly molded by an inner mold 3 and an outer mold 4. Therefore, a recessed part 7 for molding the ring-shaped substrate 1 is provided on the outer peripheral edge of the lower surface of the upper die 5, and a ring 8 is fitted on the outside thereof.

The outer diameter of the inner mold 3 and the inner diameter of the outer mold 4 are tapered so that they become smaller from the lower end to the upper end, and the inclination angle is set to about 3/1000 to match the shrinkage margin of the plastic molding material. be. The notch grooves 9 and 10 are also formed with a draft angle of about 3/1000. In the drawings, this angle of inclination is shown in an extreme manner for ease of understanding.

Further, an annular groove 11 is provided on the upper surface of the lower mold 6, protrusions 12 and 13 that fit into the annular groove 11 are provided on the lower surfaces of the inner mold 3 and outer mold 4, and the lower end of the blade 2 is located in the annular groove 11. It is now molded in

Further, the outer mold 4 and the lower mold 6 are provided with through holes 15 and 16 for ejecting pins 14, so that the ejecting pins 14 push up the bottom of the ring-shaped substrate 1 and the molded product f is extracted.

In the figure, 17 and 18 are protruding plates, 19 is a fixed side mounting plate, 20 is a runner protruding plate, 21 is a fixed side template, 22 is a movable side template, and 23 is a receiving plate.

As explained above, in the mold of this invention, the inner mold and the outer mold, which mainly mold the blades of the cylindrical impeller, are tapered and fit closely together, so there is no risk of creating a gap between them, and the blades It is possible to completely prevent the occurrence of burrs on the surface of the mold, allowing stable molding with less variation in product quality and dimensional accuracy.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of a cylindrical impeller molded by the mold of this invention, Fig. 2 is a vertical sectional view of the mold of this invention, and Fig. 3 is an enlarged view taken along the line X--X of Fig. 2. FIG. F... Cylindrical impeller, f... Cylindrical impeller molded product, A... Mold, P... Screw, 1... Ring-shaped substrate, 2... Vane, 3... Inner mold, 4... ...External mold, 5...
...Upper die, 6...Lower die, 7...Recessed portion, 8...Ring, 9, 10...Notch groove, 11...Annular groove, 1
2, 13...protrusion, 14...protrusion pin, 15,
16...Ejection pin through hole, 17, 18...Ejection plate, 19...Fixed side mounting plate, 20...Runner ejection plate, 21...Fixed side template, 22...Movable side template, 23... ...Receiver plate.

Claims (1)

[Claims] 1. In an injection mold for a cylindrical impeller in which a large number of blades with an arcuate cross section protrude from the back surface of a ring-shaped substrate, cutouts for blade molding are provided on the outer peripheral surface of the inner mold and the inner peripheral surface of the outer mold. A mold for injection molding a cylindrical impeller, characterized in that a groove is formed by wire processing, and an inner mold and an outer mold are closely fitted to each other by a taper.