JPH04323015A - Manufacture of resin molded article - Google Patents

Abstract

PURPOSE:To make it possible to exactly divide liquid such as reagent of the like by a method wherein no longitudinal flash is developed on the inner peripheral edge of the tip of a chip, which is used for close examination or the like. CONSTITUTION:By inserting the tip 7a of the core member of a movable mold in a fixed mold 1 under the condition that the tip 8a of a tip core member 8 having a stepped part 8b is provided so as to project beyond the in-mold bottom of the fixed mold 1, the tip 9a of the core member is abutted against the tip 8a of the tip core member 8 so as to form a gap 3 in the molds in order to inject molten resin 4 in the gap, resulting in producing a chip 10.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a method for manufacturing resin molded products used mainly for dispensing liquids in the medical field and research fields such as biochemistry. The present invention relates to a method of manufacturing a resin molded product that prevents vertical burrs from forming on the peripheral edge.

0002

[Prior Art] Resin molded products have traditionally been used in various fields, one of which is the pipette tip for testing used for dispensing liquids in the medical field and research fields such as biochemistry. There is.

Therefore, in the following explanation, we will introduce a pipette tip that is used to collect a certain amount of liquid when testing liquids such as blood or conducting biochemistry research in hospital laboratories and laboratories. Let's explain with an example.

As shown in the front view of the chip in FIG.
The internal liquid is aspirated and discharged from the tip portion 10b using air pressure by operating a pipette. When manufacturing this chip 10, as shown in the enlarged view of the tip end of the chip and the mold in FIG.
A movable mold is attached to the joint surface 7a of the cylinder member 7 and the cylindrical member 7 (see Fig. 3).
By inserting the core member 9 and inserting the tip into the insertion hole 7b of the cylindrical member 7, the core member 9 is attached to the edge of the insertion hole 7b.
The outer shell member 1a and the joint surface 7a are brought into close contact with each other.
A gap 3 is formed and sealed between the core member 9 and the gap 3, and a chip 10 is molded by injecting molten resin 4 into the gap 3.

[0005] In this injection molding, when a synthetic resin such as polypropylene is molded using a general screw type injection molding machine, the resin temperature is 200 to 300°C.
Molding is performed at an injection pressure of 00 to 800 kg/cm2, and at this time, vaporized gas generated by the liquefaction of the air in the gap 3 and the molten resin 4 escapes by being discharged from the gap between the joint surfaces 7a in the Y direction. It looks like this. At this time, the molten resin as well as the gas flows out from the bonding surface 7a due to the high pressure described above, and the finished chip 10 has horizontal burrs 14 protruding from the outer peripheral edge 12.

[0006] As shown in the enlarged view of the chip tip and mold in FIG. 8, there is also a core member 9 whose tip 9a has a straight shape.

[0007]

[Problem to be Solved by the Invention] By the way, the amount of the above-mentioned chips used for inspection varies depending on the purpose of use and the place of use, but some places use hundreds of thousands of chips per month. Some of the liquids tested by these chips may be infectious, and the chips are generally thrown away rather than reused. Therefore, when manufacturing, it is necessary to mass produce and reduce costs.

On the other hand, when manufacturing resin molded products such as the above-mentioned chips, it is necessary to mold them using a precision mold.
When the mold is frequently moved and bonding and separation are repeated in an attempt to manufacture many chips in a short time in order to mass produce and reduce costs, the tip 9a of the core member 9 of the movable mold
The joint surface 7a of the cylindrical member 7 contacts frequently, and the core member 9
Alternatively, the cylindrical member 7 will wear out, resulting in a minute gap at this joint. In addition, the tip 9a
If it is made straight, a gap is provided for fitting at the time of manufacturing the mold, so there is always a gap.

As shown in FIG. 7, when a gap is created in the joint, air in the gap 3 and gas in the molten resin 4 flow from the outer peripheral edge 12 of the chip 10 to the joint surface 7 during injection molding.
Not only does it protrude in the Y direction through the gap a, but it also ends up being discharged in the X direction from the gap between the insertion hole 7b and the tip end 9a of the core member 9. When the gas is discharged in the X direction and the Y direction, a part of the molten resin protrudes together with the gas, forming vertical burrs 13 and horizontal burrs 14, as shown in the enlarged cross-sectional view of the chip tip in FIG. It will remain. In addition, Figure 8
When the tip is straight like this, there is always a gap, so a part of the molten resin always protrudes in the X and Y directions, causing a vertical burr 13 on the inner edge 11 and a vertical burr 13 on the outer edge 12. Lateral burrs 14 will always occur.

[0010] As described above, when vertical burrs 13 are formed in addition to horizontal burrs 14 on the tip 10b of the chip 10, for example, when testing or researching liquids such as blood or biochemistry at a hospital laboratory or laboratory, etc., and specify a precise fixed amount (e.g.
If the tip is used to collect a liquid of about 10 μl or 5 μl, the liquid discharged from the tip end will remain in the vertical burr 13, making it impossible to dispense the liquid accurately.

[0011] Particularly in the case of a very small amount of liquid, this results in a large error.

In view of the above problems, the present invention provides a method for manufacturing a resin molded product that does not cause vertical burrs on the inner peripheral edge of the tip of the resin molded product, thereby making it possible to accurately dispense liquids such as reagents. The purpose is to do so.

[0013]

[Means for Solving the Problems] In order to achieve the above object, the method for manufacturing a resin molded product according to the present invention includes inserting a core member of a movable mold into a stationary mold, thereby making the mold inside the mold. In the method for manufacturing a resin molded product, in which a cavity is formed in the cavity and a molten resin is injected into the cavity to manufacture the molded product, a tip core member having a step is protruded from the inner bottom of the stationary mold. By inserting the core member of the movable side mold into the fixed side mold, the tip of the core member is brought into contact with the tip of the tip core member, thereby creating a void in the mold. It is characterized by forming a part.

[0014]

[Operation] According to the manufacturing method having the above configuration, the core member of the movable mold is inserted into the fixed mold and the two molds are joined, thereby protruding from the inner bottom of the fixed mold. The tip of the tip core member having the stepped portion and the tip of the core member of the movable mold come into contact to form a gap in the mold. At this time,
The stepped portion of the tip core member forms the tip surface of the resin molded product, and the joint between the fixed side and the movable side is formed at a position spaced apart from the inner peripheral edge of the tip of the resin molded product.

By injecting molten resin into this gap, the stepped portion of the tip core member and the inner peripheral edge of the tip of the resin molded product are formed in the same shape, so that the inner peripheral edge of the tip of the resin molded product has a vertical It is possible to produce molded products without burrs.

[0016] As a result, liquid does not remain on the vertical burr portion formed at the inner circumferential edge of the tip of the resin molded product, unlike in the conventional case, and accurate dispensing becomes possible.

[0017]

Embodiments Hereinafter, embodiments of the present invention will be explained based on the drawings. Note that the same reference numerals will be used for the same configurations as in the prior art in the description.

First, the first embodiment will be explained with reference to FIG. 1, which is an enlarged cross-sectional view showing a first embodiment of a tip end and a mold according to the present invention, and FIG. 3, which is an overall view of a mold using the first embodiment. Explain an example.

As shown in the general view of FIG. 3, the mold K is composed of a fixed mold 1 and a movable mold 2, and the fixed mold 1 forms the outer shell of the resin molded product (chip). It is composed of the formed outer shell member 1a, a cylindrical member 7 provided at the tip of the resin molded product, and a tip core member 8 provided at the center of the cylindrical member 7, and the movable mold 2 is made of resin. It is composed of a core member 9 that forms the inner shape of the molded product, a support member 2a that supports the core member 9, and an extraction member 2b that separates the resin molded product from the core member 9. A cavity 3 is formed by inserting the core member 9 of the movable mold 2 into the mold 1 and sealing it. An injection port 5 for molten resin is provided above the cavity 3 (on the right side in the figure), and the injection port 5 is connected to a melting furnace (not shown) through a runner 6.
is connected to. Note that 2c is a cooling water passage for the movable mold 2.

To explain part A of the mold K in detail with reference to the enlarged sectional view shown in FIG. 1, the outer shell member 1a of the stationary mold 1
The joint surface 7a between the cylindrical member 7 and the cylindrical member 7 is on the same level as the step 8b of the tip core member 8, and from this step 8b to the tip 8a.
stands out. Then, the core member 9 of the movable mold 2 (
3) into the outer shell member 1a, the tip 9a and the tip 8a of the tip core member 8 are joined at a position spaced apart from the joining surface 7a of the cylindrical member 7.

When the molten resin 4 is injected in this state, the inner peripheral edge 11 of the chip 10 is formed to have the same shape as the step 8b of the tip core member 8, and the gas flows from the outer peripheral edge 12 of the chip 10 in the X direction. It will be discharged in the Y direction.

By cooling the mold K in this state, the molten resin 4 is solidified to form the chip 10, and the chip 10 is formed by separating the movable mold 2 from the stationary mold 1.
is pulled out from the fixed side mold 1, and further, by separating the support member 2a and the extraction member 2b of the movable side mold 2, the top of the chip 10 is pushed by the extraction member 2b, and the chip 10 is removed from the core member 9. separate.

As shown in the enlarged sectional view of FIG. 2, the tip of the tip 10 has an inner peripheral edge 11 formed in the same shape as the step 8b of the tip core member 8, and a vertical burr extending from the outer peripheral edge 12. 13 and the horizontal burr 14 become protruding.

In addition to the above-mentioned embodiment, as shown in the enlarged sectional view of FIG. 4 showing a second embodiment of the chip tip and mold, the joint surface 7a of the columnar member 7 and the outer shell member 1a is spaced apart from the stepped portion 8b. By forming the gas at the outer peripheral edge 1 of the chip 10,
2, it can be discharged only in the X direction, and it can be made to protrude in the Y direction from the joint surface 7a of the mold. in this case,
A vertical burr 13 protrudes from the outer peripheral edge 12, and a horizontal burr 14 protrudes from the joint surface 7a spaced apart from the tip of the chip 10. Even in this case, no vertical burr 13 is produced on the inner peripheral edge portion 11, as in the chip 10 shown in the first embodiment described above.

[0025] Furthermore, the tip end of the tip and the third part of the mold shown in FIG.
As shown in the enlarged cross-sectional view showing the embodiment, a convex portion 8 is formed on the distal end portion 8a of the distal end core member 8 that protrudes from the inner bottom of the stationary mold 1.
b, and a recess 9b is formed in the tip 9a of the core member 9 protruding from the movable mold 2, so that the fixed mold 1 and the movable mold 2 are fitted together when they are joined. By aligning the centers of the cavity 3, the tip 8a of the tip core member 8 and the tip 9a of the core member 9 will always be in the same position, making it possible to mold the tip 10 without misalignment. can.

As mentioned above, in any of the embodiments, the chip 1
Since the stepped portion 8b of the tip core member 8 is present on the inner peripheral edge portion 11 of 0, no gas is discharged and no vertical burr 13 is formed.

[0027] In the above-mentioned embodiments, a pipette tip was used as an example of a resin molded product, but the present invention can achieve the same effect with any resin molded product that would be inconvenient if vertical burrs were formed on the inner peripheral edge of the tip. be able to. Particularly, when disposable molded products (disposable plastics) are manufactured, it is more effective because no burrs are generated on the inner peripheral edges of the tips of all resin molded products.

In addition, in the above embodiment, a configuration in which one chip is molded was explained for the sake of explanation, but a configuration in which multiple chips are molded at the same time, which is commonly used in the past, is used to mold a large number of chips. There is no particular limitation, as long as it is manufactured.

[0029]

[Effects of the Invention] According to the present invention, since the inner peripheral edge of the tip of the resin molded product is formed in the same shape as the stepped portion of the tip core member, vertical burrs are not generated on the inner peripheral edge when injection molding is performed. Furthermore, even if the mold is used frequently, the part that forms the inner peripheral edge of the tip of the resin molded product will not wear out, so it is possible to always produce resin molded products without vertical burrs on the inner peripheral edge. can.

[0030] As a result, no liquid remains on the inner peripheral edge of the tip of the resin molded product, and an accurate amount of liquid can be dispensed.

[Brief explanation of the drawing]

FIG. 1 is an enlarged sectional view showing a first embodiment of a tip end portion and a mold according to the present invention.

FIG. 2 is an enlarged sectional view showing the tip end portion of the tip according to the present invention.

FIG. 3 is an overall view of a resin molding die using the present invention.

FIG. 4 is an enlarged sectional view showing a second embodiment of a tip end portion and a mold according to the present invention.

FIG. 5 is an enlarged sectional view showing a third embodiment of a tip end portion and a mold according to the present invention.

FIG. 6 is a front view showing a conventional chip.

FIG. 7 is an enlarged sectional view showing a conventional tip end portion and a mold.

FIG. 8 is an enlarged sectional view showing another example of a conventional tip end portion and a mold.

FIG. 9 is an enlarged cross-sectional view showing the tip of a conventional tip.

[Explanation of symbols]

1... Fixed side mold 2...Movable side mold 3...Void part 4...Melted resin 5...Ejection port 6…Yudo 7...Cylindrical member 8...Tip core member 8a...Tip 8b...Stepped part 9... Core member 9a...Tip 10...chip 11...Inner peripheral edge 12...Outer periphery 13...Vertical burr 14...Horizontal burr K...Mold

Claims (1)

[Claims] Claim 1: A resin for producing a molded product by inserting a core member of a movable mold into a stationary mold to form a void in the mold, and injecting molten resin into the void. In the method for manufacturing a molded product, a tip core member having a stepped portion is provided protruding from the inner bottom of the mold on the fixed side mold, and the core member of the movable side mold is inserted into the fixed side mold. . A method for manufacturing a resin molded product, comprising: bringing the tip end of the core member into contact with the tip end of the tip core member to form a void in a mold.