JPH08207078A - Plastic product and molding method thereof, and plastic radial impeller and molding method thereof - Google Patents

Abstract

PURPOSE: To provide a plastic product and a molding method thereof wherein deformation of a thin core which can be eluted and removed is prevented and a product having a highly precise shape can be molded at a low cost, and a plastic radial impeller and a molding method thereof. CONSTITUTION: Into a plastic product 10 molded by injecting a plastic material into a molding space formed between a mold face of a forming mold and a core, an insert member 17 ranging over the mold face of the forming mold and the surface of the core is embedded. As the insert member is embedded in the plastic product, the insert member works as a support and prevents deformation of the core, so that a product having a highly precise shape can be molded at a low cost. If the material of the insert member is selectively chosen, it can be a reinforcing material, so that mechanical strength of the product can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic product and a plastic centrifugal impeller injection-molded by using a mold and a core, and a molding method thereof.

[0002]

2. Description of the Related Art When a plastic product having a hollow structure is injection-molded, it is often difficult to integrally mold the plastic product if it has a three-dimensional shape. Therefore, a method is adopted in which the entire product is divided into a plurality of parts, these parts are partially molded, and then these are combined to form one product. For example, PP used for centrifugal pumps
When injection molding a centrifugal impeller made of general-purpose engineering plastics such as E, PPS, PA, etc., since many spiral blades have a three-dimensional shape, a back plate having many spiral blades is used. After separately molding the front plate, which is a constituent part of the front side, the back plate and the front plate are bonded or welded on the front surface of the blade to form a centrifugal impeller having a single structure as a whole. Was there.

However, the method of dividing a product into a plurality of parts and combining them to obtain one product requires respective molds for making the individual parts, which increases the cost of the mold and increases the cost of each part. Since each of them is individually manufactured, the number of steps is increased, and the work of combining these parts is required. Therefore, the labor is increased and the cost is increased. Furthermore, there are various problems such as variations in the molding dimensions for each component, and when these components are combined, their joints do not necessarily match.

Therefore, in the case of injection-molding a plastic product having such a complicated shape, a metal having a low melting point, for example, bismuth Bi / tin Sn is cast to mold a core, and the entire product is injection-molded with plastic. A method is used in which the unnecessary metal core is heated to the melting point of the metal and eluted. However, this method requires an expensive core, and in addition to the equipment for injection molding for molding plastic products, the equipment for casting the core and inside Equipment for eluting the baby is required, and equipment for the core is needed, which is not suitable for small-lot production of various types.

Because of this, recently, as a core,
A plastic member that can be eluted and removed by a solvent, for example,
Research is under way to form a core from a water-soluble resin member that dissolves in water, warm water or an alkaline aqueous solution, for example, a polymeric material such as PVA. If a core formed of such a water-soluble resin is used, after the product is molded, when the core is brought into contact with water or a solvent consisting of warm water or an alkaline aqueous solution, the core is dissolved and It is easily removed and the work of taking out the core becomes easy. In addition, since molding of such a core can be performed by injection molding, the core can be manufactured more easily than when the core is made of a low melting point metal, and the facility for manufacturing the core is omitted and is simple. Therefore, the cost can be reduced.
Therefore, as compared with the case of using a core made of a low melting point metal, it is advantageous for producing a small amount of various plastic products.

[0006]

However, a plastic material, such as PVA, which can be eluted and removed by a solvent, is used.
A polymer material such as is less rigid than a metal core, and may bend when subjected to the pressure of the plastic material during injection molding. That is, as shown in FIG. 11, at the time of injection molding, a high-temperature, high-pressure molding material is injected from the injection gate 22 of the molding die 100 into the molding space 6, but only slightly until the material wraps around the core 5. There is a stage where the pressure balance is not yet balanced in time, and at this time, a high injection pressure is applied to the core 5 from the injection gate 22 side,
Since the thin part has low rigidity, it is flexibly deformed.

[0007] Such deformation causes a problem that the molded product cannot be molded into a predetermined product shape even if the material wraps around the core and the pressure balance is balanced.

The present invention has been made by paying attention to such a situation, and an object thereof is to prevent deformation of the core even by using a thin core which can be eluted and removed. It is intended to provide a plastic product having a highly accurate shape and a plastic product molding method capable of integrally molding the product at low cost, a plastic centrifugal impeller and a molding method thereof.

[0009]

In order to achieve the above object, the invention of claim 1 is a plastic molded by injecting a plastic material into a molding space formed between a molding surface of a molding die and a core. In the product, the plastic product is characterized in that an insert member extending over the molding surface of the molding die and the surface of the core is embedded in the plastic product.

According to a second aspect of the present invention, one or a plurality of cores are installed in a molding die having a molding surface corresponding to the outer shape of the plastic product, and at least a part of the cores is dissolved by a predetermined solvent. The material is formed by injecting a plastic material to be the product into a molding space between the molding surface and the core, molding the product with the plastic material, and after molding the core with the solvent. In the method for molding a plastic product, which is configured to be dissolved and removed by dissolving the soluble portion of the core by contacting with, in the molding space, between the molding surface and the surface of the core with the solvent. A method of molding a plastic product is characterized in that a support made of an insoluble material is provided, and a plastic material is injected into the molding space to integrally insert the support.

According to a third aspect of the present invention, in a plastic centrifugal impeller formed by injecting a plastic material into a molding space formed between a molding surface of a molding die and a core, the plastic centrifugal impeller is provided. In the plastic centrifugal impeller, an insert member is embedded in the molding surface of the molding die and the surface of the core.

According to a fourth aspect of the present invention, one or a plurality of cores are arranged in a molding die having a molding surface corresponding to the outer shape of the centrifugal impeller, and at least a part of the cores is dissolved by a predetermined solvent. A plastic material to be the impeller is injected into the molding space between the molding surface and the core, and the centrifugal impeller is molded from this plastic material. In a molding method of a plastic centrifugal impeller, in which the core is brought into contact with the solvent to dissolve and remove the soluble portion of the core, in the molding space, the molding surface and the surface of the core A support made of a material that does not dissolve in the solvent is provided over the space, and a plastic material is injected into this molding space so that the support is integrally inserted. It is a method of molding a heart impeller.

[0013]

According to the first aspect of the invention, since the insert member is embedded in the plastic product over the molding surface of the mold and the surface of the core, the insert member functions as a support and Prevent deformation. That is, when a high-temperature, high-pressure plastic material is injected into the molding space from the injection gate, even if a pressure balance imbalance occurs when the material wraps around the core, the insert member provided in the molding space is It serves as a support for holding the child, which prevents deformation of the core. Therefore, a highly accurate product can be molded at low cost. Then, when the plastic material is hardened, the insert member is integrally embedded in the product, so that it is not necessary to remove the insert member functioning as a support, and the labor for removing it can be saved.

According to the second aspect of the present invention, when the high temperature and high pressure plastic material is injected from the injection gate into the molding space, the support provided in the molding space holds down the core. It is possible to prevent the core from being deformed even if a pressure imbalance occurs when the material goes around. Therefore, a highly accurate product can be molded at low cost.
When the plastic material is hardened, the support is integrally inserted into the product, so that it is not necessary to remove the support, and the labor for removing the support is saved. Further, it is not necessary to change the conventional molding device.

According to the invention of claim 3, the advantages of the invention of claim 1 can be utilized in a plastic centrifugal impeller in which it is unavoidable to use a core having a complicated shape. It is possible to obtain a plastic centrifugal impeller having an accurate shape. According to the invention of claim 4, the manufacturing method of claim 2 can be utilized for a manufacturing method of a plastic centrifugal impeller having a complicated shape.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to FIGS. 1 to 8 as a first embodiment of an example of injection molding a plastic centrifugal impeller used for a centrifugal pump. First, the shape of a plastic centrifugal impeller as a product will be described with reference to FIGS. 5 and 6. This centrifugal impeller is indicated by reference numeral 10, and this impeller 10 is made of synthetic resin such as PPE, PPS, PA.
The impeller 10 includes a back plate 11 serving as a back wall, a front plate 12 serving as a front wall facing the back plate 11 with a space, and between the back plate 11 and the front plate 12. And a large number of blades 13 that are formed at intervals in the circumferential direction and are installed as main components. Each of the blades 13 has a spiral shape that gradually curves in the circumferential direction from the central portion of the centrifugal impeller 10 toward the outer diameter portion, and each of the blades 13 is positioned on the inner diameter side and has a spiral shape. A twisted blade portion 13a having a three-dimensional shape with a twisted shape while being curved, and a two-dimensional curved blade portion 13b located on the outer diameter side and curving and extending in a spiral shape are continuously formed. I am doing it. The blades 13 having such a shape are arranged in the circumferential direction with a space therebetween, and the space between the blades 13 is formed so as to gradually widen toward the outer diameter direction.

A mounting hole 14 for mounting a drive shaft (not shown) is formed at the center of the centrifugal impeller 10 at the axial center of the back plate 11. When this centrifugal impeller 1 is rotated in a pump casing (not shown), it sucks fluid from a blade inlet 15 opened in the center of the front plate 12 and passes the fluid through the gaps between the blades 13. It is pressurized by and is sent out from the blade outlets 16 ...

A plastic impeller 1 having such a structure
Insert member 17 ... Is embedded in 0. These insert members 17 ... Are provided on the front plate 12 at intervals. The insert members 17 are provided in the front plate 12 over the molding surface of the molding die and the surface of the core, which will be described later.

A plastic impeller 1 having such a structure
0 is integrally molded by an injection molding method. The injection molding device will be described. In FIG. 1 and FIG. 2, reference numeral 1 denotes a molding die of an injection molding machine, and the molding die 1 includes a main mold 2,
It is composed of a sub-mold 3 and a core assembly 4 which are attached to and detached from this.

On the inner surface of the main mold 2, there is formed a back plate molding surface 21 for molding the back plate 11 of the centrifugal impeller 10, and this back plate molding surface 21 is the above-mentioned. It has a molding surface that matches the outer shape of the back plate 11. Further, a front plate molding surface 31 for molding the front plate 12 and the blade inlet 15 of the centrifugal impeller 10 is also formed on the inner surface of the sub-mold 3, and the front plate molding surface 31 is the front plate molding surface 31 of the front plate 12. It has a molding surface that matches the outer shape.

Further, a gate 22 for plastic injection which communicates the molding space 6 with the outside is formed in the main mold 2 at the axial center portion, and the sub mold 3 further has a front plate molding. A mounting hole forming protrusion 32 for forming the mounting hole 14 of the centrifugal impeller 10 is formed at the axial center of the surface 31.

The core assembly 4 is incorporated in the molding die 1 between the back plate molding surface 21 and the front plate molding surface 31. The entire structure of the core assembly 4 is shown in FIG. 8, and includes a central circular portion 41 for forming the blade inlet 15 of the centrifugal impeller 10 and the adjacent blades 13 extending radially from the central circular portion 41. Has a curved portion 42 that bends in an arc shape so as to fill the space portion of the curved portion 42. The curved portions 42 that extend in the radial direction are, for example, six, and are arranged side by side at a predetermined interval in the circumferential direction. Has been formed. Also, the core assembly 4
As shown in FIG. 1, a holding portion 43 that is sandwiched between the main mold 2 and the sub mold 3 is formed at the outer diameter side end of the.

The core assembly 4 has a structure in which each blade 13 is divided as a device for easily constructing the core assembly 4 whose shape changes three-dimensionally. That is, there are a plurality of core assemblies 4, that is, six cores 5.
It is divided into ...

Each of the cores 5 has a semicircular arc-shaped curved portion 42 with the central circular portion 41 of the core assembly 4 as a core split surface and is divided into the number of blades. Is. That is, as shown in FIG. 7, each core 5 has a circular component 51 for forming the central circular portion 41 at one end on the inner diameter side, and the other end on the outer diameter side from this circular component 51. Has a circular arc-shaped portion 52, and the inner and outer surface shapes of the circular arc-shaped portion 52 are three-dimensionally bent torsion blades on the inner diameter side of the blades 13 of the centrifugal impeller 10. The shape is made to follow the shape of the inner and outer surfaces of the portion 13a and the two-dimensional curved blade portion 13b on the outer diameter side of the blade 13. The holding portion 43 is formed on the outer diameter side end of the arcuate portion 52.

Here, each core 5 ... Is a plastic member capable of being eluted and removed, specifically, a water-soluble resin member that is dissolved by a solvent such as water or warm water, alkaline water, for example PV.
It is formed of a polymer element such as A.

A total of six cores 5 ...
The core assembly 4 shown in FIG. In this assembly, the individual cores 5 ... Are arranged in the circumferential direction, and adjacent circular components 51 ...
Are in contact with each other, and arc-shaped portions 52 ... Extending from these circular components 51 are arranged at equal intervals. As a result, as shown in FIG. 7, blade forming portions 58 ... Which extend spirally from the axis toward the outer peripheral direction are formed between the arc-shaped portions 52.

The core assembly 4 assembled in this way is
As shown in FIG. 1, the molding die 1 is installed between the main die 2 and the sub die 3, and the holding portions 43 ... Of the outer peripheral portion are held between the main die 2 and the sub die 3.

When the core assembly 4 is attached, the supports 17 are provided in the molding space 6 formed between the front plate molding surface 31 and the cores 5. These supports 17 are made of a material different from that of the core 5, that is, a material that cannot be dissolved by a solvent that dissolves the core, such as resin, metal, or inorganic material. Has been done,
Each of the cores 5 forming the core assembly 4 is installed in a substantially middle portion in the circumferential direction from the central portion.

A method of injection-molding the plastic centrifugal impeller 10 using the molding die 1 having such a configuration will be described. As shown in FIG. 1, the core assembly 4 is incorporated between the main mold 2 and the sub mold 3, and the support 17 is provided in the molding space 6.
To place. Since these supports 17 abut on the cores 5, ..., The cores 5 ... are pressed and deformation is prevented. In this state, from the injection machine through the injection gate 22 into the molding space 6, the molding plastic material of the centrifugal impeller 1, for example, PP.
E, Molten metal such as PPS, PA is injected. As a result, the plastic material is injected into the molding space 6 formed in the molding die 1.

At the time of this injection, the molten material quickly circulates between the back plate molding surface 21 close to the injection gate 22 and the core 5, so that, as shown in FIG. It tries to bend and deform under the injection pressure of. However, in the case of the present invention, the support 1 provided in the molding space 6 on the opposite side
Since 7 ... Holds the core 5 ..., the core 5 is prevented from being deformed. In particular, since the core 5 receives the injection pressure in the molding space between the back plate molding surface 21 near the injection gate 22 and the core 5, ..., It tries to bend to the opposite side as shown in FIG. Since the support 17 is provided in the side molding space 6, deformation in the above-mentioned direction is prevented.

When the filled plastic material is cured, the supports 17 ... Are inserted into the solidified material and integrated with the product. After such solidification is completed, the main mold 2 and the sub mold 3 are separated, and the molded product inside is taken out. As shown in FIG. 3, this molded product has a centrifugal impeller 10 injection-molded from the injected plastic material, that is, a back plate 11, a front plate 12 into which supports 17 are inserted, and a large number of blades 13. , And the core assembly 4 including the cores 5 remains between the blades 13.

Centrifugal impeller 10 as such a molded product
Is taken out by using a step of bringing the core assembly 4 into contact with water or a solvent such as hot water or alkaline water. In this step, for example, as shown in FIG. 4, the entire injection-molded article is immersed in a solvent, for example, warm water 70 filled in an immersion tank (not shown). As a result, the cores 5 formed of the water-soluble resin are dissolved from the contact surface with the hot water 70.

At this time, if a means such as rotating the centrifugal impeller 10 or stirring the hot water 70 is used, the core 5
Dissolution of… is promoted. When the cores 5 formed of the water-soluble resin are removed by such a melting operation, the centrifugal impeller 10 as shown in FIGS. 5 and 6 is completed.

According to the above manufacturing method, the core 5 ...
Since the centrifugal impeller 10 is molded, the core 5 is brought into contact with the solvent 70 to form the core 5 ...
Since it is solved, the core 5 is easily removed. Further, such molding of the cores 5 ... Can be performed by injection molding. Therefore,
Compared to the case where the cores 5 are formed of a low melting point metal such as bismuth or tin, the cores are easily manufactured, the facility for manufacturing the cores is omitted, and the cost can be reduced.

Further, the centrifugal impeller 10 having a three-dimensional shape and requiring the use of a large number of cores 5 is integrally formed while reducing the equipment required for manufacturing the cores 5 ... Therefore, it is possible to improve the productivity of various small quantities.

When such a meltable core 5 is used, the core 5 may be bent and deformed when receiving the injection pressure of the material, but in the above embodiment, the core 5 is deformed. Since 5 ... is pressed by the supports 17, the bending deformation of the cores 5 is prevented. Therefore, the product shape can be maintained with high accuracy, and the quality of injection molding is improved.

Moreover, since the supports 17 ... Are inserted into the product, it is not necessary to take out the supports, and the trouble of taking them out can be saved. And support (insert) 17
Since the core 5 is made of a material different from that of the core 5, it will not melt together when the core 5 is melted, and if it is made into a product that is harder than the plastic material, it will be a reinforcement of the product. , The strength is improved.

Further, according to the above method, it is not necessary to change the molding die 1 to the conventional molding die 100 shown in FIG.
The configuration of the device is simple. In the above-described embodiment, the supports (inserts) 17 are provided in the molding space 6 formed between the front plate molding surface 31 and the core 5, and are not used when the centrifugal impeller 10 is a product. The supports (inserts) 17 ... Are embedded and left in the face plate 12, but the present invention is not limited to this, and may be as in the second embodiment shown in FIGS. 9 and 10. That is, in the second embodiment, as shown in FIG. 9, the supports 17 are provided in the molding space 6 formed between the front plate molding surface 31 and the core 5.
Is installed, and other supports 18 are also installed in the molding space 6 formed between the back plate molding surface 21 and the core 5, and thus the centrifugal impeller 10 is manufactured. In this case, as shown in FIG. 10, the supports 17 ...
Support 18 is embedded in 1 and remains.
This further prevents the core 5 from being deformed, and if the materials of the supports (inserts) 17 and 18 are selected,
These serve as a reinforcing material and can improve the mechanical strength of the product.

In the above embodiment, the case where the centrifugal impeller 10 is molded as a plastic product has been described, but the present invention is not limited to this. That is, there are various types of plastic products that are injection-molded using a core, and in these manufacturing methods, when a molding method in which the core is brought into contact with a solvent to be dissolved and removed is adopted, the present invention is applied. Is possible. Further, in the above-mentioned embodiment, the core is divided into a plurality of pieces to form the core assembly 4, but the core may be an integrally molded product. Furthermore, the present invention can be variously modified without departing from the scope of the claims.

[0040]

As described above, according to the invention of claim 1, since the insert member is embedded in the plastic product over the molding surface of the molding die and the surface of the core, the insert member is used as a support. It works, prevents deformation of the core, and can form a highly accurate product at low cost. Then, if the material of the insert member is selected, it becomes a reinforcing material and the mechanical strength of the product can be improved.

According to the second aspect of the present invention, when the high temperature and high pressure plastic material is injected from the injection gate into the molding space, the support provided in the molding space holds down the core. It is possible to prevent the core from being deformed even if a pressure imbalance occurs when the material goes around. Therefore, a highly accurate product can be molded at low cost.
When the plastic material is hardened, the support is integrally inserted into the product, so that it is not necessary to remove the support, and the labor for removing the support is saved. Further, it is not necessary to change the conventional molding device.

According to the invention of claim 3, the advantages of the invention of claim 1 can be utilized in a plastic centrifugal impeller using a core with a complicated shape, and a plastic with a high precision shape. A centrifugal impeller manufactured can be easily obtained. According to the invention of claim 4, the manufacturing method of claim 2 can be utilized for a manufacturing method of a plastic centrifugal impeller having a complicated shape.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a molding die used for molding a centrifugal impeller according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing different working states of the molding die.

FIG. 3 is a cross-sectional view showing a molded product injection-molded using the molding die.

FIG. 4 is a cross-sectional view for explaining a step of dissolving the molded product in a solvent.

FIG. 5 is a cross-sectional view showing the manufactured centrifugal impeller.

6 is a sectional view taken along line VI-VI of FIG.

FIG. 7 is a plan view showing a single core.

FIG. 8 is a plan view showing a state where cores are combined to form a core assembly.

FIG. 9 is a cross-sectional view of a molding die used in molding a centrifugal impeller according to the second embodiment of the present invention.

FIG. 10 is a sectional view showing a manufactured centrifugal impeller.

FIG. 11 is a cross-sectional view illustrating a case where injection molding is performed using a conventional molding die.

[Explanation of symbols]

1 ... Mold 2 ... Main mold 3 ... Sub mold 4 ... Core assembly 5 ... Core 6 ... Molding space 10 ... Centrifugal impeller 11 ... Rear plate 12 ... Front plate 13 ... Blade 14 ... Mounting hole 15 ... Blade inlet 16 ... Blade outlet 17, 18 ... Support (insert member) 21 ... Rear plate molding surface 31 ... Front plate molding surface 22 ... Injection gate

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location // B29K 105: 20 B29L 31:08

Claims (4)

[Claims] 1. A plastic product molded by injecting a plastic material into a molding space formed between a molding surface of a molding die and a core, wherein the molding product has a molding surface and a core. A plastic product in which an insert member is embedded over the surface of the plastic product. 2. One or a plurality of cores are installed in a mold having a molding surface corresponding to the outer shape of a plastic product, and at least a part of the cores is made of a material which is dissolved by a predetermined solvent. A plastic material to be the product is injected into a molding space between the molding surface and the core, and the product is molded with this plastic material, and after the molding, the core is brought into contact with the solvent to In a method for molding a plastic product, in which a soluble portion of a core is dissolved and removed, in the molding space, a material which is insoluble in the solvent is formed between the molding surface and the surface of the core. A method of molding a plastic product, comprising providing a support, and injecting a plastic material into the molding space to integrally insert the support. 3. A plastic centrifugal impeller formed by injecting a plastic material into a molding space formed between a molding surface of a molding die and a core, wherein the plastic centrifugal impeller is formed with the molding die. A plastic centrifugal impeller having an insert member embedded between the molding surface and the surface of the core. 4. One or a plurality of cores are arranged in a molding die having a molding surface corresponding to the outer shape of a centrifugal impeller, and at least a part of the cores is made of a material which is dissolved by a predetermined solvent. The plastic material to be the impeller is injected into the molding space between the molding surface and the core, the centrifugal impeller is molded from this plastic material, and after this molding, the core is used in the solvent. In a method for molding a plastic centrifugal impeller, which is brought into contact with a core to dissolve and remove a soluble portion of the core, in the molding space, the solvent is applied between the molding surface and the surface of the core. Molding of a plastic centrifugal impeller characterized in that a support made of a material that does not dissolve in is provided, and a plastic material is injected into this molding space so that the support is integrally inserted. Law.