Method of injection molding a skin layer around a core resin

Details Method of injection molding a skin layer around a core resin Method of injection molding a skin layer around a core resin

2000-04-11

2003-04-29

Ortiz, Angela (Department: 1732)

Plastic and nonmetallic article shaping or treating: processes

Mechanical shaping or molding to form or reform shaped article

To produce composite, plural part or multilayered article

C264S328800, C264S328120, C264SDIG005, C425S130000

Reexamination Certificate

active

06555041

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a multilayer injection molding machine capable of press fitting resins from a plurality of injection units to a cavity part within a metal mold, respectively, an injection unit connecting device therefor, and an injection molding method thereby.
In the manufacture of a molded product formed of a plurality of layers of resins or colors, an injection molding machine for press fitting the resin of each layer into a metal mold in order is generally adapted, but in recent years, a multilayer injection molding machine capable of press fitting the resins of all the layers into the metal mold by one operation has been developed and adapted so that the molding time can be shortened to improve the productivity.
The conventional multilayer injection molding machine is constituted, as shown in
FIG. 6
, by juxtaposing, every resin of each layer, a plurality of (for example, two) injection units
53
,
53
each of which has a heating cylinder
51
capable of raising the internal temperature to a prescribed temperature or more and an extruding screw
52
provided rotatably within the heating cylinder
51
, and connecting and integrating the injection units
53
,
53
together through a nozzle member
54
. In injection molding, the tip of the nozzle member
54
is brought into contact with the spool hole of a metal mold
55
, and the resin from each injection unit,
53
,
53
is then collected together in the nozzle member
54
and discharged through the tip, whereby the resin of each layer is simultaneously press fitted into the metal mold
55
.
However, since the above-mentioned conventional structure having all the injection units
53
,
53
connected and integrated to the nozzle member
54
is intended for an exclusive machine for a molded product having the number of layers corresponding to the number of units of the injection units
53
,
53
, it is required to introduce and a set a multilayer injection molding machine for every molded product having each number of layers. Thus, even if a single-layer injection molding machine, for example, was introduced, new introduction of a two-layer injection molding machine is necessary in addition to this machine when a two-layer molded product is required. Therefore, existing facility equipments such as an injection molding machine, carrying device, and the like can not be effectively utilized. In a factory having no sufficient setting space, particularly, the introduction is extremely difficult since an action such as layout change of each equipment or disposal of the existing injection molding machine with the lowest frequency of use is required in order to ensure the setting space.
In recent years, it is also desired, from the view point of material cost or effective use of resources, to manufacture a molded product in which a core layer resin of low quality or low cost is thoroughly or partially covered with a desired skin layer resin. Thus, the multilayer injection molding machine having the structure described above is used also to cover such a core layer resin with the skin layer resin. However, this molding machine has a problem in that it is difficult to more surely cover the core layer resin with the skin layer resin because the core layer resin is likely to be included to the skin layer resin at the start of press fitting.
Thus, an object of the present invention is to easily manufacture a molded product having an optional number of layers by use of existing facility equipments.
Further, another object of the present invention is to surely cover a core layer resin with a skin layer resin in the manufacture of a molded product having the core layer resin covered with the skin layer resin.
SUMMARY OF THE INVENTION
The present invention involves an injection unit connecting device for a multilayer injection molding machine capable of press fitting resins from a plurality of injection units to a cavity part formed by clamping metal mold, and this injection unit connecting device comprises a connecting device body provided on the metal mold, and a resin passage means provided on the connecting device body and having a plurality of resin passages allowing the cavity part to communicate with each injection unit described above.
Since the number of injection units can be optionally changed by changing the number of passages of the resin passages of the injection unit connecting device, a multilayer injection molding machine capable of forming a molded product having an optional number of layers can be provided. The design specifications of the connecting device body and the resin passage means are matched to an existing metal mold or injection molding machine, whereby the existing metal mold or injection molding machine can be utilized as it is to form a multilayer injection molding machine. Thus, a multilayer injection molding machine for an optional number of layers can be provided while existing facility equipments are effectively utilized.
The above-mentioned resin passage means has a first resin passage formed in the clamping direction of the metal mold and a second resin passage formed in the direction crossing the clamping direction.
Since the second resin passage is formed so as to cross the first resin passage formed in the clamping direction of the metal mold, the second resin passage can be determined toward, for example, a setting space having a vertical or horizontal room according to the equipment layout around the injection unit to be connected to the first resin passage. Thus, the existing injection molding machine can be changed into a multilayer injection molding machine for an optional number of layers without moving existing facility equipments.
The above-mentioned resin passage means also has a passage opening and closing means for opening and closing the resin passages. Since the opening and closing timing of the resin passages can be optionally set by the passage opening and closing means, the timings of start and termination of press fitting of each resin to the cavity part can be optionally set, and resin leakage can be also surely prevented.
The injection unit connecting device is integrated into a multilayer injection molding machine having an injection unit arranged in the clamping direction of the metal mold and an injection unit arranged in the direction orthogonal to the clamping direction. Thus, a multilayer injection molding machine having the structure in which each injection unit is arranged in the least obstructive orthogonal direction can be provided.
Further, the injection unit connecting device is integrated into an injection molding machine for forming a single-layer molded product so as to provide it with a plurality of injection units. Since the multilayer injection molding machine is formed by use of an existing single-layer injection molding machine, the introduction cost can be reduced.
The injection unit connecting device is also preliminarily provided on the metal mold. When a metal mold is newly manufactured, the injection unit connecting device is provided on the metal mold in advance, whereby the metal mold can be preliminarily manufactured in the state integrated with the injection unit connecting device. Therefore, only by replacing the metal mold, an existing single-layer injection molding machine or multilayer injection molding machine, for example, can be switched to a multilayer injection molding machine according to metal mold.
The present invention also involves a multilayer injection molding machine for forming a molded product having a core layer resin covered with a skin layer resin, and this multilayer injection molding machine comprises a metal mold for forming a cavity part, a core layer injection unit for press fitting the core layer resin to the cavity part through a core layer passage, a skin layer injection unit for press fitting the skin layer resin to the cavity part through a skin layer passage, and a passage opening and closing means for opening and closing the core layer passage.
The resin passage for the cor

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