JPH031237Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a mold for producing belts by injection molding of resin power transmission belts such as synthetic resin toothed belts and synthetic resin flat belts.

(Prior Art) Power transmission belts such as toothed belts and flat belts have excellent transmission efficiency and can be used up to relatively high speed rotation ranges. 2. Description of the Related Art Toothed belts made of rubber or polyurethane are often used as a power transmission member for various mechanical devices. Recently, attempts have been made to manufacture resin belts by injection molding in order to reduce the number of molding steps and manufacture power transmission belts within a relatively short period of time.

This molding method usually involves melting pellet-shaped thermoplastic elastomer or thermoplastic resin at a temperature of 180 to 230°C using an injection molding machine, as shown in Figure 6. Contact sprue 2, runner part 3, gate part 4
Formed between the inner and outer molds 6 and 7 of a mold consisting of a cylindrical outer mold 7 into which an inner mold 6 with a tensile member 5 spirally wound around the entire circumference is inserted concentrically. The molded belt 8 is injected into the annular gap and cured.
A power transmission belt is obtained by taking out the belt and cutting it into a predetermined belt width.

However, in manufacturing the power transmission belt by injection molding as described above, at the stage of taking out the product,
I saw a serious problem occur. That is, normally, to take out the product in injection molding, after the material has hardened, the mold is divided and a protruding pin provided at the bottom of the mold is used to remove the product.
The molded product was removed by pushing it out from the inside.

However, the power transmission belt, which is the target product of this invention, has an annular shape and a thin thickness of usually 0.5 to 3 mm, so it is difficult to push out the belt molded product with a protruding pin. , is very difficult. In particular, when a tensile material such as a rope is wound around the outer circumferential surface of the inner mold 6 with a tension of 5 to 15 kg, the winding tension between the tensile material and the inner mold is strong, and in practice, when the protruding pins are It was a very difficult task to push it out smoothly.

As a solution to this problem, as shown in FIG.
Attempts have been made to extract only the inner mold 6 leaving the belt molded body by using a tensile material 5 such as a rope.
Because the winding tension on the inner mold 6 is too strong,
The belt molded body 8 is pulled out together with the inner mold 6 while being attached to the inner mold 6.

Therefore, as shown in FIG. 7, it is necessary to press a cylindrical extracting jig 9a having an inner diameter slightly larger than the outer diameter of the inner die 6 and repeat the process of extracting the belt molded body 8 from the inner die 6 again. It didn't happen.

Furthermore, even in the case of a belt molded body lacking the tensile body 5, depending on the shape and roughness of the surface of the inner mold 6, and the condition of the mold release agent, the belt molded body 8 may become integral with the inner mold 6. In many cases, they were singled out.

(Problems to be solved by the invention) As mentioned above, the conventional technology requires many molding steps and requires man-hours to manufacture the power transmission belt. At present, the merits of adopting injection molding methods have been greatly reduced.

The present invention fully grasps these drawbacks of the conventional technology and provides a mold for manufacturing resin belts that is configured so that the belt molded body always adheres to the outer mold side when the inner mold is removed. The object of the present invention is to eliminate the time-consuming process of separating the belt molded body from the inner mold, thereby significantly improving the efficiency of manufacturing power transmission belts.

(Means for solving the problem) In order to achieve this object, the present invention has the following configuration. That is, injection molding in which an inner mold is inserted concentrically into a cylindrical outer mold to form an annular gap for injecting a synthetic resin material between the two molds, and one of the inner and outer molds is movable in the axial direction. A mold for manufacturing a resin belt according to the present invention is characterized in that a concave portion is provided in at least a part of the product molding surface of the outer mold.

(Function) When injecting into the gap between the inner and outer molds of resin materials,
A portion of the injected material is filled into the recesses provided on the product forming surface of the outer mold, hardens, and forms a protrusion on the outer periphery of the belt molding, and this protrusion of the belt molding and the outer mold Even when the inner and outer molds are separated, the concave portion maintains its engaged state and prevents the belt molded product from being separated from the outer molding surface, even when the inner mold is pulled out in the axial direction. always remains on the outer mold side.

(Example) Next, a specific example of the present invention will be described using the drawings.

FIG. 1 is a central vertical sectional view of a mold for manufacturing a resin belt according to the present invention, in which an inner mold 12 is inserted concentrically into a cylindrical outer mold 10. A plurality of guide bars 13 are implanted in the bottom wall 11 of the outer mold 10 with central angles at equal intervals, and the group of guide bars 13 aligns with the axial direction of the outer mold 10 and is inserted into the outer mold 10. elongation (the details of which are shown in FIG. 2), the inner mold 1
2, guide bars 13 are inserted into elongated holes (not shown) drilled in advance in the axial direction of the body of the inner mold 12, and the outer mold 1 is guided by the group of guide bars 13.
It is inserted in parallel state inside 0, and both inside and outside type 1
An annular interval 14 is formed between 0 and 12, which corresponds to the thickness of the resin belt to be molded.

Further, a runner plate 16 is disposed on the opening side of the outer mold 10 to close the opening, and the runner plate 16 serves as a communication port with a nozzle 17 that supplies a material such as thermoplastic elastomer or thermoplastic resin. A spool 18 is provided, and the runner plate 16 contacts the outer mold 10 and closes the opening of the outer mold 10, so that the narrow gate portion 20 of the runner plate 16 and the runner portion 19
and the annular gap 14 of the mold are in continuous communication.

Reference numeral 22 denotes an ejection mechanism for the inner mold 12 disposed on the bottom side of the outer mold 10, and a frame body 2 integrally formed with the outer mold 10.
A push rod 25 having a rectangular plate 24 fixed to the end thereof is housed in the interior of the outer mold 10 through a through hole 26 provided in the bottom wall 11 of the outer mold 10.
protrude inward. This protruding movement of the push rod 25 is caused by the frame 2
A long protruding rod 28 fixed to an injection molding machine (not shown) enters from the end wall 27 of the outer mold 10.
As the push rod 25 moves backward, it comes into contact with the plate 24 fixed to the end of the push rod 25, and as the push rod 25 protrudes into the outer mold 10, the inner mold 12 moves in the axial direction of the outer mold 10, and both the inner and outer molds 12, The 10 combinations are dismantled.

The illustrated inner mold 12 is for manufacturing flat belts, but in the case of manufacturing toothed belts, grooves of the same pitch extending in the axial direction are carved on the surface of the inner mold 12, and the cross section thereof is The inner mold is gear-shaped.

In the mold having the above configuration, the main component of the present invention is the presence of the recess 29 formed on the product molding surface 15 of the outer mold 10.

The concave portion 29 illustrated in FIG. 1 is shown as having an annular groove provided over the entire circumference of the product molding surface 15 that is in contact with the part farthest from the resin material injection portion, that is, the bottom wall 11 of the outer mold 10. There is. This annular groove, which is a concave part, has a width of 0.5 to 5.0 mm and a height of 0.5 to 5.0 mm, and is designed to improve the engagement strength with the outer mold 10 of the completed belt molded body, the economical efficiency of the resin material used in this part, The shape, size, number, and location of the recessed portions 29 are appropriately selected based on the roughness of the inner mold surface and comprehensive consideration from various other aspects. The annular concave portion 29 extending over the entire circumference of the outer mold product forming surface 15 illustrated in FIG. 1 is one of the desirable shapes from the viewpoint of ensuring a strong engagement between the outer mold and the belt molded body.

A rope tensile body 30 is spirally wound around the outer peripheral surface of the inner mold 12, and the inner mold 12 is connected to the outer mold 10.
The annular gap 1 of both the inner and outer molds 12 and 10 is
A resin material is injected into the belt 4, and as a result, a belt molded body 32 is produced between the inner and outer dies, with an outward annular protrusion 31 integrally protruding from its end.
After the belt molded body 32 has hardened, the outer mold 10 is moved back to the left by an appropriate means, and the plate 2 fixed to the end of the push rod 25 is removed, as shown in FIG.
4, a protruding rod 28 that is fixed to the injection molding machine and secures a fixed position comes into contact with it, and as the outer mold 10 retreats, the tip of the push rod 25 pushes the end wall surface of the inner mold 12.
During this removal work of the outer mold 10 and the inner mold 12, the outward annular protrusion 31 integrally provided on the belt molded body 32 is still fitted and locked in the recessed part 29 of the outer mold 10, and the belt The molded body is attached to the product molding surface 15 of the outer mold 10. In this way, the inner mold 12 is pulled out with the push rod 25 and the group of guide bars 13 as a guide, leaving the belt molded body 32 in the outer mold 10.

The belt molded body 32 still attached to the outer mold 10 from which the inner mold 12 has been completely removed is the product forming surface 1 of the outer mold 10.
It is peeled off and taken out from 5. Additionally, the belt molded body 32
has good inward flexibility, so it can be easily peeled off from the outer mold (see Figure 4).

In the above explanation, the push rod 25 is provided to improve the compatibility of molds, but
If compatibility of molds is not so important, a configuration may be adopted in which the tip of the protruding rod 28 of the injection molding machine is brought into direct contact with the end wall of the inner mold.

FIG. 5 shows a structure in which the inner mold 12 is fixed to the runner plate 16 by screws 21 or the like, and the movement of the runner plate 16 is directly connected to the extraction operation of the inner mold 12. If a long movement distance is possible, or by rotating one side of the mold while fixing the inner mold 12 to the runner plate 16, the rope tensile body 30 can be spirally wrapped around the inner mold 12 using a single mechanism. This is particularly effective when performing work, injecting resin materials, and cutting the width of belt molded bodies.

In the present invention, it is important that the surface of the inner mold 12 constituting the molding die be smoothly separated from the belt molded body 32.

Therefore, it is desired that the surface of the inner mold is as smooth as possible, and for this purpose, applying hard chrome plating to the surface of the inner mold is also effective in enhancing the effects of the present invention.

(Effects of the invention) The present invention uses recesses formed at appropriate locations on the product molding surface of the outer mold to form protrusions integrally with the belt molding during the manufacturing process of the belt molding, and after curing. This projecting piece of the belt molded body still fits into the recessed part of the outer mold and maintains the locked state, which is actively used to remove the inner mold from the outer mold. The belt molded body remains stuck to the product molding surface of the outer mold, making it easy to separate from the inner mold, and after the inner mold is removed from the outer mold, the belt molded body has good inward flexibility. By utilizing this, the separation of the belt molding from the outer mold becomes simple, and the workability is significantly improved compared to the conventional work of removing the belt molding that adheres to the inner mold surface. The manufacturing efficiency of resin belts can be dramatically improved by this method, and the easy removal of the belt molding from the molding die eliminates the risk of damaging the belt molding, making it possible to mass-produce high-quality resin belts. This is a major contribution.

[Brief explanation of the drawing]

Fig. 1 is a central longitudinal sectional view of a belt molding die implementing the present invention, Fig. 2 is an enlarged detailed view of a portion of Fig. 1,
FIG. 3 is a diagram corresponding to FIG. 1 showing the state in which the inner mold is pulled out from the outer mold after the belt molded body has hardened, FIG. 4 is a cross-sectional explanatory diagram showing the separation of the belt molded body from the outer mold, and FIG. is a diagram corresponding to FIG. 1 showing another belt mold, FIG. 6 is a diagram corresponding to FIG. 1 of this conventional belt mold, and FIG. 7 is a state in which the belt molded body is removed from the conventional inner mold. FIG. In the figure, 10 is a cylindrical outer mold, 12 is an inner mold, 14 is an annular gap, 15 is a product forming surface of the outer mold, 22 is an extraction mechanism, 25 is a push rod, 29 is a recessed part, 31 is a protruding piece, 3
2 shows a belt molded body.

Claims (1)

[Claims for Utility Model Registration] (1) An inner mold is inserted concentrically into a cylindrical outer mold, an annular gap for injection of synthetic resin material is formed between the two molds, and one of the inner and outer molds is 1. A mold for manufacturing a resin belt, which is movable in the axial direction and is characterized in that the mold is provided with a concave portion in at least a part of the product molding surface of the outer mold. (2) The mold for manufacturing a resin belt according to claim 1, wherein the recessed portion has an annular groove. (3) The mold for manufacturing a resin belt according to claim 1 or 2 of the utility model registration claim, wherein the surface of the inner mold is coated with hard chrome plating.