JPH10272680A - Die structure for blow molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide die structure for blow molding by which residual air is prevented from being generated between a die for blow molding and a parison and molding corresponding to the shape of the inner face of the die is enabled. SOLUTION: In the die structure for blow molding, a first air vent passage 8 for exhausting gas existing between the die and a parison is opened in the vertex position of a recessed part 6 in which a parison is swelled and entered. The second air vent passages 10 are opened in the vicinities of the vertex position to exhaust residual air remaining between the die and the parison after the parison reaches the vertex position of the recessed part 6 and closes the opening of the first air vent passage 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a mold structure for blow molding. More specifically, the present invention relates to a blow molding mold structure suitable for molding a product having a complicated uneven shape.

[0002]

2. Description of the Related Art In a mold for blow molding a product having a complicated uneven shape such as a CVJ boot, an air vent hole is opened in a concave portion into which a parison swells, that is, a concave portion forming a convex portion of the product. For example, as shown in FIG. 3, the air vent hole 101 is provided in the mold 1 with which the parison finally contacts.
03 is open at the deepest position of the concave portion 102, that is, at the position corresponding to the vertex of the convex portion of the molded product, and the parison 104 and the mold 103 remain Between the parison 1
The swelling of the recessed portion 102 of the portion 04 is enabled.

[0003]

However, when blow molding is performed using the above-described mold 103, the mold 1
There are cases where the 03 types of blow molding are hindered and a product having a desired shape cannot be obtained. For example, when blow molding a CVJ boot that covers a constant velocity joint of an automobile, as shown in FIG. A concave portion 107 may be formed near a boundary between an arc portion 106a corresponding to the top of the bellows of the bellows 106 and a slope portion 106b extending tangentially inward therefrom. The concave portion 107 is not preferable because it becomes a cause of generating a concave portion when the drive shaft on which the CVJ boot is mounted is largely steered, when the drive shaft extends outside the bending angle.

[0004] Accordingly, the present invention provides a method for manufacturing a mold having a cavity surface.
An object of the present invention is to provide a blow molding die structure that can be formed into a complete product shape along the inner surface shape of the die.

[0005]

As a result of various experiments and studies conducted by the present inventor to achieve the object, depending on the conditions of suction and exhaust at the air vent hole, as shown by the two-dot chain line in FIG. It has been found that the tip of the peak of the parison 104 reaches the apex of the concave portion 102 and blocks the air vent hole 101 before the air existing between the mold 104 and the mold 103 is exhausted. Parison 104 and mold 10
Since the air vent hole 101 is closed before the air between the mold 3 and the air has escaped, air remains near the apex position of the concave portion 102, and the molding of the mold 103 is obstructed to obtain a product having a desired shape. Came to know that it was not possible.

The present invention has been made based on this finding, and has a first gas vent passage for discharging gas existing between the parison and the parison at the apex of the concave portion into which the parison expands. In the blow molding die structure, the parison reaches the apex position of the concave portion near the apex position and closes the opening of the first degassing passage, and then discharges residual gas remaining between the parison and the parison. The second gas vent passage is opened.

Therefore, the blown and inflated parison is first discharged before exhausting all air between the parison and the mold.
Even if the gas vent passage is closed, the residual air remaining between the parison and the mold is exhausted from the second gas vent passage, and the parison can be in close contact with the inner surface of the mold.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below in detail based on the best mode shown in the drawings.

FIGS. 1 and 2 show an embodiment of the present invention applied to a press-blow mold as an example of an embodiment of a blow molding mold structure. FIG. 1 is an enlarged view of a portion indicated by an ellipse I in FIG. The blow molding die 1 is a press-blow mold for molding a CVJ boot, for example.
It is a split mold, for example, divided into two in the radial direction of the molded product, and is configured by combining the half-split sets 2 and 2. Each half-split set 2
Is a plurality of pieces 3,..., Further divided in the axial direction of the molded product.
4,... Are combined. Each piece 3 constitutes a convex portion 12. The division position between the pieces 4 is a concave portion 6. That is, by overlapping the pieces 3 and 4, the concave portions 6 and the convex portions 12 on the cavity 5 side corresponding to the peaks and valleys of the bellows of the CVJ boot are formed.

As shown in detail in FIG. 1, a first air vent passage (gas vent passage) 8 is opened at the apex position of each concave portion 6 over the entire circumference. That is, in the first air vent passage 8, a groove is formed on the circumference at the deepest position of each of the concave portions 6,... The air is easily blown into the first air vent passage 8 from the cavity 5 side at the time of blow molding, but the parison is difficult to enter. The first air vent passage 8 is
Grooves are formed in the divided surfaces of the pieces 4, 4 to be superimposed, and these grooves are combined to form a groove.

In the vicinity of the apex of each recess 6, a second air vent passage (gas vent passage) 10 is open all around. This will be described more specifically with reference to FIG. Now, regarding the cross section of the concave portion 6, the contour shape on the cavity 5 side is changed to the arc portion 1 including the position of the deepest vertex of the concave portion 6.
1 and each of the slope portions 13 extending from both ends in the tangential direction of the arc portion 11 toward the convex portion (corresponding to a valley portion of the product shape) 12, the arc portion 11 and each of the slope portions 13, Residual air during blow molding is likely to be generated in the vicinity of the boundary portions 14 and 14 between them. The second air vent passage 10 opens at each of these boundary portions 14.

Like the first air vent passage 8, the second air vent passage 10 has a circumferential groove formed over the entire periphery of each boundary portion 14. The air is easily blown into the second air vent passage 10 from the cavity 5 side at the time of blow molding, but the parison is difficult to flow. Each of the second air vent passages 10 is formed by forming a groove on the divided surface of each of the pieces 3 and 4 to be overlapped, and by combining these grooves. That is, the boundary portions 14, 14 where the respective second air vent passages 10 are formed are divided surfaces of the pieces 3, 4.

The first and second air vent passages 8, 10 are
The air is exhausted to the outside of the mold through a flow path formed on the division surface of each half-split set 2 and communicating with the outside of the mold. That is, grooves of a predetermined shape are formed on the divided surface of each half-split set 2, and by combining these grooves, the air vent passages 8 and 10 can be formed in the mold 1.
An air passage communicating outside is formed. Then, through the air passages, the air vent passages 8 and 10 are connected to suction means as a negative pressure source. The suction means operates at the time of blow molding, and assists blow molding and bulging of the parison.

When blow molding is performed using the blow molding die 1 configured as described above, even if the blown parison swells and closes each of the recesses 6, the parison thereafter becomes the first and second parisons. It continues to expand while discharging air existing between the mold 1 and the air vent passage 10.

The parison expands mainly at a portion not in contact with the cavity surface of the mold 1, that is, at a portion stretched across the space of the concave portion 6. Therefore,
Even if the parison reaches the apex position of the concave portion 6 before closely contacting the entire cavity surface of the concave portion 6 and blocks the first air vent passage 8 before bleeding all air between the mold 1 and
Residual air remaining between the mold 1 and the parison is discharged from the second air vent passage 10 by the second air vent passage 10 at each boundary portion 14 near the vertex position on the near side. Therefore, each of the boundary portions 14, 14 near the apex position of the concave portion 6, that is, the contour shape of the cavity 5.
No air remains in the vicinity of. Therefore, the blown parison is in close contact with the entire cavity surface of the concave portion 6, and a desired shape is obtained.

The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the gist of the present invention. For example, in the above description, the mold 1 in which a large number of pieces 3 and 4 are overlapped to further form the half-split sets 2 and 2 is taken as an example. May be applied to a mold that divides the mold in the radial direction.

In the above description, the first and second air vent passages 8 and 10 are formed in a circumferential groove shape over the entire circumference. However, it is not always necessary to form the passages 8 and 10 over the entire circumference. . For example, each of the passages 8 and 10 may be a hole that is opened at a plurality of locations at predetermined intervals in the circumferential direction.

Furthermore, although the mold for blow molding the CVJ boot has been described as an example, it is needless to say that the present invention may be applied to a mold for other molded products.

[0019]

As described above, according to the present invention, the parison reaches the vertex position of the concave portion near the vertex position where the first gas vent passage for discharging gas between the parison and the first gas vent passage opens. Since the second gas vent passage for discharging the residual gas remaining between the parison and the parison after closing the opening of the gas vent passage is opened, all the air between the parison and the mold is exhausted to remove the cavity. The parison can be adhered to the entire surface. For this reason, a desired shape can be obtained and the quality of the molded article can be stabilized. In addition, when applied to a mold for a CVJ boot having a complex uneven shape, it is possible to prevent the occurrence of a dent due to residual air near the apex of the bellows peak, and to operate as designed. And durability can be obtained. In addition, the number of routes for degassing between the parison and the mold will increase, and even if one degassing passage is clogged, a route for degassing is secured. Even if blow molding is performed, the occurrence of blow shortage can be delayed.

[Brief description of the drawings]

FIG. 1 is an enlarged cross-sectional view showing an example of an embodiment of a blow molding mold structure according to the present invention.

FIG. 2 is a cross-sectional view showing an example of a blow molding die to which the present invention is applied.

FIG. 3 is a sectional view showing a conventional blow molding die structure.

FIG. 4 is a cross-sectional view of a molded product using a conventional blow molding mold structure.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 blow molding die 6 recess 8 first air vent passage (gas vent passage) 10 second air vent passage (gas vent passage)

Claims (1)

[Claims] 1. A blow molding die structure in which a first gas vent passage for discharging gas existing between the parison and the parison is opened at a vertex position of a concave portion into which the parison bulges and enters, in the vicinity of the vertex position. And a second gas venting passage for discharging residual gas remaining between the parison and the opening.