JPS6241029A - Preparation of toothed belt made of synthetic resin - Google Patents

Abstract

PURPOSE:To prepare a voidless belt molding by discharging completely an air remaining in a mold and between tensile members, by vacuum-sucking through deaeration concave part and vacuum-sucking hole when an elastomer flows into the product cavity portion formed by both inner and outer molds, fills there and is molded under curing. CONSTITUTION:O-rings 10, 11, 11' are mounted separately to the parting line 9b of a gate 8 between inner and outer molds M1, M2, and O-rings 12, 12' are mounted to the joint surface 13 between these two molds and retaining plate M5 for retaining them. At the joint surface 13, a deaeration concave part 14 leading to product cavity portion 5 is provided to the retaining plate M5 between both inner and outer O-rings 12, 12'. When at the preset place they are led to vacuum-sucking hole 15 penetrated in the retaining plate M5 and outer vacuum system is actuated, each parting line are completely closed by O-rings. Additionally air existing inside is sucked and air contained in tensile members wound on the outer periphery of the inner mold M1 is discharged, so voids occurring at belt tooth parts, stretching parts, back parts, etc. disappear to offer a product having good quality.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an improvement in a method for manufacturing a synthetic resin toothed belt by injection molding.

(Prior Technology) Because toothed belts can transmit rotation without slipping, they are of interest as power transmission parts for precision machinery, and toothed belts made of rubber or polyurethane are used in various applications. However, recently, attempts have been made to make toothed belts made of resin using injection molding machines in order to obtain toothed belts in a shorter time with fewer molding steps.

As shown in Figure 1, this method usually involves putting a thermoplastic elastomer or thermoplastic resin in the form of a pellet into an injection molding machine and melting it at a temperature of 180 to 230°C.
) is applied to the sprue (2a) of the sprue bush (2) and injected and flows into the mold (M), from the center hole (3a) of the runner (3) in Fig. 3 to the radial groove (3b), then the circumference. Circumferential groove (3C) for flow in direction 1 (3c)
From there, it flows into a vertical runner (3d) formed vertically in a comb-like shape along the circumference. The elastomer that has passed through the vertical runner (3d) and exited to the gate (8) is then transferred to the inner mold (H6) and the outer mold (1) wrapped with the tensile member (4) as shown in FIG. A belt tension section (22) as shown in FIG.

The protrusions (23) and the voids (5) formed in the shape of the teeth (21) are filled, and after filling, they harden in about 30 seconds to form a toothed belt molded body, and this is internally molded. It is taken out from the mold (Ml) and manufactured as a predetermined toothed belt.

(Problems to be Solved by the Invention) However, in the process of manufacturing the toothed belt by injection molding as described above, it has been found that there are the following problems. That is, when producing a toothed belt by injection molding, in order to improve the strength and creep resistance of the belt, if various tensile ropes are wrapped around the inner mold (core) of a mold and molded with an injection molding machine, the rope becomes The remaining air forms voids in the toothed belt, making it impossible to produce a complete product.

The present invention has focused on this problem, and by providing a vent for the air between the ropes and directly connecting it to an external vacuum line system, the product forming section is reliably vacuumed, and a void-free resin toothed belt is produced. The purpose is to obtain.

(Means for Solving the Problems) A feature of the manufacturing method of the present invention that satisfies the above object is the nozzle touch portion that comes into contact with the nozzle of the sprue in the injection mold.

Parting line between each plate that forms the inner and outer molds (Ml) (M2), sprue, and runner.

O-rings are installed on both the inner and outer sides of the product gap at the joint surface between the product part formed by both the inner and outer molds and its holding plate (Mi), and the 0.0 between the O-rings and communicating with the product gap
In addition to providing an annular air vent recess with a depth of 3 to 0.2 m,
A vacuum suction hole that communicates with the external vacuum system from the recess is provided through the holding plate at a position offset from the product cavity in the air release recess, and during injection molding, suction is drawn from the vacuum suction hole into the product cavity. The purpose of molding is to exhaust the air and create a vacuum in the turning section.

Note that the depth of the air vent recess is set at 0.03 to 0.0.
There is no particular critical meaning in setting it as 20, but it is 0.03m.
If it is less than m, it is too shallow and the vacuum suction effect cannot be obtained practically.
．． Further, if Q is 2 mm or more, many burrs will occur on the belt side portions, so this is because it is suitable as a depth that has a vacuum suction effect and does not cause burrs.

(Function) Thus, according to the above method, in injection molding of a toothed belt, the elastomer flows into the product void formed by both the inner and outer molds, fills the void, and when hardening and molding is performed, air is removed from the holding plate. By vacuum suctioning through the recesses and vacuum suction holes, air remaining in the mold and between the tensile members can be completely released, resulting in a void-free belt molded product.

(Example) Hereinafter, specific implementation B of the above method of the present invention will be sequentially explained with reference to the accompanying drawings.

Figure 1 shows an injection mold (M
), and in the figure, (1) is a nozzle of an injection molding machine (not shown) for injecting molten thermoplastic elastomer or thermoplastic resin into the mold; The molten molding material is injected into the sprue (2a) provided on the sprue bush (2).

The molding material used here is urethane-based.

Thermoplastic elastomers such as polyester (for example, DuPont brand name: Hytrel or Toyobo brand name: Pelprene, etc.), polyamide-based (for example, Daicel brand name: Diaamide-PAE), and flexible thermoplastic resins, such as polyamide with a Shore hardness of 10 to 100. -11, polyamide-12
Examples include.

These thermoplastic elastomers and thermoplastic resins are then supplied to an injection molding machine in the form of pellets and heated to a temperature of 180 to 230°C.
in? Contained.

The injected molten molding material is then sprued (
2a) and the center hole (
Radial grooves (3b) formed radially from 3a).

A vertical runner (3d) then flows into the circumferential groove (3C) and further extends vertically from the circumferential groove (3c).
).

Note that the vertical runner (3d) usually has a circumferential groove (
From 3c), a large number of comb teeth are formed along the circumference, and the number is usually 50 to 60, although it varies depending on the belt size.

The molding material passing through this vertical runner (3d) then reaches the gate (8) and exits from this to the tensile body (4).
Flows into the product gap (5) formed between the wrapped inner mold (Ml) and the outer mold (M2) surrounding the inner mold, fills the core part (5), and 30 seconds after filling. After this period, the molding material hardens and is formed into a toothed belt molded body.

Note that this toothed belt molded body has a cylindrical shape, and is therefore manufactured into a desired toothed belt by taking it out from the inner mold (Ml) and cutting it to a predetermined width.

Therefore, the shapes of the inner mold (Ml) and the outer mold (Myo) are formed to match the shape of the toothed belt. Gotoku inner type (core)
A convex strip having a nose (N) at the tip is provided on the outer periphery of the mold (Ml), while a concave strip is provided on the inner periphery of the outer mold (M2) with a required space. Therefore, the toothed belt (20) is made of steel cord, aromatic polyamide (trade name: Kevlar), and polyester as shown in FIG.

A low-elongation, high-strength rope tensile body made of glass fiber or the like is embedded, and the teeth (21), protrusions (23), and tension parts (2) are embedded.
2) is obtained.

Therefore, in the injection mold CM) as described above,
In the case of the method of the present invention, the outer periphery of the nozzle touch part (7) of the sprue (2a) of the sprue bush (2) fitted with the locator ring (6), the plate (touch part) holding the sprue bush (2), ) and the plate (M4) forming the runner (3).
a), O-rings (10) are installed at the parting line (9b) of the gate (8) between the play (L-) and both the inner and outer molds (Ml) (FIz) forming the product cavity.
(11) (11) is installed, and an O-ring (12) is further installed on the joint surface (13) between the inner and outer molds (MlXMz) and the holding plate (M,) that holds them.
(12') is installed.

In particular, at the joint surface (13) between both the inner and outer molds and the holding plate (M,) that form the latter product gap, that is, the parting line of the core, there are zero
It is essential that the ring (12) (12) is installed.

Then, as shown in an enlarged view in FIG. 2, the joint surface (13
) has an air vent recess (14) connected to the product cavity (5).
are provided on the inner and outer O-rings (12) (holding plate 0+s between ii).

This air vent recess (14) usually has a depth of 0°03
~0.2ml, and the holding plate (M
It communicates with a vacuum suction hole (15) provided through s) and is connected to an external vacuum system such as a vacuum pump.

In the figure, (16) indicates a protruding rod of the mold.

Thus, the vacuum suction hole (15
) is connected to an external vacuum system and activated, the O-ring (1
0) (11011) (11) (12) By installing (12), each parting line is completely sealed, and the air existing inside is sucked through the vacuum suction hole (15), and the outer periphery of the inner mold (Ml) is The air between the tensile members (4) wrapped around the belt is released to the outside, and the belt teeth, tension parts,
The voids generated on the back surface, etc. disappear, and a synthetic resin toothed belt of good quality as shown in FIG. 5 can be obtained.

In addition, the mold is, for example, Utility Model Publication No. 58-320943! I
G is generally divided into four parts as disclosed.

(Effects of the Invention) The present invention provides a nozzle touch portion of a molding die in the production of a toothed belt by injection molding.

Two O-rings are installed on the runner parting line, the gate bartering line, and the core parting line, and O-rings are installed at the required locations on the holding plate where the inner and outer molds that form the product gap come into contact. 0.03~0,
It is designed so that it can be molded by providing a double-shaped air vent recess and a vacuum suction hole at a predetermined position in this recess to connect it to an external vacuum system. By creating a vacuum inside the mold and performing injection molding, the air remaining between the tensile material wrapped around the inner mold can be completely released to the outside, eliminating voids that were previously considered difficult. The remarkable effect of solving this problem and obtaining a void-free resin toothed belt of good quality is achieved.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing an example of an injection mold used for carrying out the method of the present invention, Fig. 2 is an enlarged view of part A in Fig. 1, and Fig. 3 is an enlarged view of part A in Fig.
The figure is a side view of the runner of the same mold in Figure 1, Figure 4 is an explanatory view of the main parts of the same mold in Figure 1 at the joint surface between the product cavity forming mold and the holding plate, and Figure 5 is It is a sectional view showing one example of the toothed belt which can be obtained. (1)...Nozzle, (2)...Sprue bush. (2a)...Sprue, (3)...Runner. (4)...Tensile body, (5)...Product void. (7)...Nozzle touch part, (8)...Gate. (9a) (9b) ... Parting line. (10) (11) (11) (12) (12)・
...0 ring. (13)...Joint surface, (14)...Air vent recess (15)...Vacuum suction hole, (ML)...
Internal mold. (M2)... Outer mold, (MS) (M4)... Plate. (MS) ・・Holding plate. Rod frfJ

Claims (1)

[Claims] 1. Melt a thermoplastic elastomer or thermoplastic resin, inject it from a sprue through a runner into the product gap formed between the inner mold around which the tensile material is wound and the outer mold, and In the injection molding method for manufacturing toothed belts made of synthetic resin, the parts are filled and hardened to form a toothed belt molded product. O-rings are installed on both the inner and outer sides of the product gap at the joint surface between the inner and outer molds and the holding plate that form the parting line and the product gap, and the inner and outer parts that form the product gap An annular air vent recess with a depth of 0.03 to 0.2 mm is provided in the holding plate between the inner and outer O-rings at the joint surface between the two molds and the holding plate, and communicates with the product gap, and A vacuum suction hole communicating with an external vacuum system from the recess is provided through the holding plate at a location offset from the product gap in the air vent recess,
A method for manufacturing a toothed belt made of synthetic resin, which is characterized by injection molding and forming a product by evacuating the voids of the product by suctioning through a vacuum suction hole.